Archive for the ‘HDI PCB’ Category

Tuesday, December 3rd, 2024

PCB Full Form

PCB stands for Printed Circuit Board. It is a crucial part of nearly all modern electronic devices. It acts as a physical base for electronic components while also providing the pathways to connect them electrically. Without PCBs, electronic devices would rely on cumbersome wiring that is prone to failure. With PCBs, electronics are compact, efficient, and highly reliable.

What Is a PCB?

A PCB (Printed Circuit Board), also known as a printed wiring board, is one of the most essential components in the electronics industry. It is used in almost every electronic device, from small gadgets like digital watches and calculators to large systems such as computers, communication equipment, and military weaponry. Wherever electronic components like integrated circuits are present, PCBs are necessary to electrically connect them.

In the early stages, paper-based copper-clad PCBs were commonly used. However, with the introduction of semiconductor transistors in the 1950s, the demand for PCBs skyrocketed. The rapid development and widespread use of integrated circuits (ICs) further increased the need for smaller and more densely packed circuit boards. This has driven continuous advancements in PCB technology.

What Is a PCB Made Of?

PCBs consist of multiple layers, each serving a distinct purpose. Here’s a breakdown of the common layers:

1. Substrate

The substrate is the core material that provides mechanical strength to the PCB. The most common material is FR4, a fiberglass-reinforced epoxy resin. It provides mechanical support and offers good heat resistance. For flexible PCBs, materials like polyimide are used, allowing the board to bend without breaking.

‌2. Copper Layer

This is a thin sheet of copper laminated onto the substrate. It forms the conductive pathways that carry electrical signals. Depending on the PCB’s design, there may be one or more copper layers. Single-layer boards have copper on one side, while multilayer boards have copper on multiple layers.

3. Solder Mask

Solder mask is a layer of polymer coated on copper foil to protect unused copper tracks. It prevents oxidation and helps prevent solder bridges during assembly. It also adds an aesthetic touch to the PCB. It is usually green, hence the name “green oil”. While green is the most common color, solder masks can be blue, red, black, white or even transparent.

4. Silkscreen

Screen printing is a layer of paint, applied to a solder resistance film. The silkscreen layer contains printed information, such as component labels, polarity markings, and company logos. It helps technicians and engineers identify components and troubleshoot the board. The silkscreen is usually white but can be in other colors.

‌5. Through-holes and via holes‌

Through holes are used to mount components and vias to connect the layers of the board together for electrical interconnection and thermal management.

‌6. Component

Electronic components, such as resistors, capacitors and integrated circuits (IC), mounted on the PCB, secured in place using soldering.

Types of PCB

PCB can be classified according to the number of circuit layers and hardness of the board.

1. According to the number of layers, a PCB can be divided into single sided PCB, double

sided PCB and multi-layer PCB. The common multi-layer board is generally 4-layer or 6-layer, and the complex multi-layer board can reach dozens of layers. PCB board has the following three main types of division:

Single-sided PCB

This type has copper tracks on only one side of the board. It is the simplest and most cost-effective type of PCB. Single-sided PCBs are used in low-complexity devices like calculators, LED lighting, and simple power supplies.

Double-Sided PCB

In double-sided PCBs, copper tracks are present on both sides of the board. They allow for more complex circuits compared to single-sided boards. They are commonly used in power supplies, audio systems, and industrial equipment.

Multilayer PCB

Multilayer PCBs consist of three or more layers of copper and insulating material stacked together. They are ideal for complex circuits requiring high density and performance. Applications include computers, smartphones, and aerospace systems.

2. According to the hardness, a PCB can be divided into rigid PCB, flexible PCB and rigid-

flex PCB. Generally, the PCB shown in the left side below is rigid PCB, and the right side is flexible PCB (or short for FPC). The main difference between a rigid PCB and a flexible PCB is that a flexible PCB can be bent.

The common thickness of rigid PCB is 0.2mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 1.2mm, 1.6mm, 2.0mm and so on. The common thickness of flexible PCB is 0.2mm. Since it has thinner thickness, the place where the parts are to be soldered will add a thick layer behind it (generally PI, FR4, stainless stiffeners), and the thickness of the thick layer is 0.2mm and 0.4mm. Common rigid PCB materials include: phenolic paper laminate, epoxy paper laminate, polyester glass felt laminate, epoxy glass cloth laminate. Flexible PCB materials commonly include: polyester film, polyimide (PI) film, fluorinated ethylene propylene film.

What Is the Difference Between PCB and PCBA?

Many people confuse PCB with PCBA, but they are not the same.

A PCB is the bare board with copper traces and no components attached. It provides the framework for electronic connections.
A PCBA (Printed Circuit Board Assembly) is a PCB with all components soldered and assembled onto it. It is a fully functional electronic circuit ready for integration into a device. In short, PCBA is the finished product, while PCB is the base.

In simple terms, a PCB is the blank canvas, while a PCBA is the finished painting.

What File Type Is Used for PCB?

When designing a PCB, specific file types are needed for manufacturing. The most commonly used file is the Gerber file. It contains all the information required to fabricate the PCB, including:

Copper layer data: Specifies the layout of copper traces.
Solder mask data: Indicates where the solder mask should be applied.
Silkscreen data: Provides details for component labels and markings.
Drill files: Indicate the size and location of holes.

Additional files used in PCB manufacturing include:

Netlist files: Define the electrical connections between components.
BOM (Bill of Materials): Lists all components required for assembly.
Pick-and-Place files: Provide coordinates for placing components during assembly.

How Do You Know if Your PCB Is Damaged?

Detecting a damaged PCB early can prevent device failure. Here are some common signs of a damaged PCB.

Physical Damage: Cracks, burns, or broken traces are visible on the board.
Overheating: Discoloration or burnt areas indicate overheating issues.
No Power: The device fails to power on, which could point to a short circuit or broken trace.
Malfunctioning Components: Components behave erratically or fail to function.
Unusual Odor: A burning smell may indicate a serious short circuit.

How to Fix a PCB Board?

Repairing a PCB depends on the nature and extent of the damage. Here are some common repair techniques:

1. Visual Inspection

Examine the PCB for visible damage, such as cracks, broken traces, or burnt components. Use a magnifying glass for a closer look.

2. Soldering Repairs

Resolder loose or broken connections using a soldering iron. Ensure the solder joints are clean and secure.

3. Trace Repair

For broken traces, use a conductive pen or solder a thin copper wire to bridge the gap.

4. Component Replacement

Identify and replace faulty components like resistors, capacitors, or ICs. Ensure the replacement components match the original specifications.

5. Testing

After repairs, use a multimeter to check for continuity and verify that the circuit functions correctly.

In some cases, especially with extensive damage, it may be more practical to replace the PCB rather than repair it.

Where Is PCB Used?

PCBs are used in nearly every industry, powering devices and systems that drive modern life. Some common applications include:

1. Consumer electronics – smartphones, tablets, laptops, televisions, and gaming consoles.

2. Automotive – engine control units, infotainment systems, sensors, and lighting.

3. Medical devices – diagnostic equipment, monitoring systems, pacemakers, and imaging devices like MRI machines.

4. Aerospace – navigation systems, communication devices, and flight control systems.

5. Industrial equipment – automation systems, machinery control, power supplies, and sensors used in industrial environments.

FAQs about PCB

1. Why Is a PCB Important in Electronics?

PCBs offer a reliable and efficient way to connect electronic components, enabling compact and functional devices.

2. Can a PCB Be Recycled?

Yes, PCBs can be recycled to recover valuable metals like copper, gold, and silver, reducing electronic waste.

3. How Long Does a PCB Last?

The lifespan of a PCB is around 50-70years, but it depends on its quality and usage conditions. High-quality PCBs can last for decades with proper care.

4. What Are Common PCB Defects?

Common defects include open circuits, short circuits, and misaligned layers, which can affect performance.

5. How Do You Test a PCB?

Testing methods include Automated Optical Inspection (AOI), In-Circuit Testing (ICT), and functional testing.

Choosing a reliable PCB manufacturer ensures you receive high-quality boards tailored to your needs. A trusted supplier like Best Technology can provide durable, efficient, and custom-designed PCBs that meet your project requirements, ensuring long-term success.

What Are PCB Designs Called?

PCB designs are often referred to by different names depending on the context or the stage of the design process. Let’s explore the most common terms:

1. PCB Layout

This is probably the most frequently used term. When someone mentions a PCB layout, they’re talking about the physical arrangement of components and the routing of electrical connections (also called traces) on the board.

Think of it like designing the floor plan of a house. The layout ensures that everything fits within the available space and that all the rooms (or in this case, components) are connected in the right way.

2. Circuit Board Design

Sometimes, you’ll hear people refer to the process as circuit board design. This term emphasizes the broader design aspect, from planning the circuit to placing components and routing connections. It’s a more general term that covers everything from the initial schematic to the final layout.

3. PCB Schematic

While the schematic is technically just one part of the design process, some people refer to the entire design as the schematic. This is more common among those who focus on the circuit’s logic rather than its physical structure.

4. Gerber Files

Once the design is complete, it’s converted into a set of files called Gerber files. These files contain all the information needed to manufacture the PCB. Sometimes, people use the term Gerber files to refer to the finished design, even though it’s technically just the output.

5. EDA (Electronic Design Automation) File

In professional environments, PCB designs are often called EDA files. These are the files created by design software like Altium Designer, KiCad, or Eagle. They contain all the details of the design, including the schematic, layout, and design rules.

What Is the Difference Between a PCB Design and a Schematic Design?

Many people use the terms PCB design and schematic design interchangeably, but they serve different purposes in the design process.

Schematic Design

Represents the electrical connections between components.
Focuses on the logic and functionality of the circuit.
Uses symbols to represent components like resistors, capacitors, and transistors.
Helps engineers understand how the circuit works.

PCB Design

Translates the schematic into a physical layout.
Focuses on the placement of components and routing of traces.
Considers factors like board size, layer count, and thermal performance.
Ensures the circuit can be manufactured and assembled.

In summary, the schematic shows what the circuit does, while the PCB design shows how it does it physically.

PCB Schematics Elements

A schematic is the starting point for any PCB design. It provides a clear visual representation of the circuit’s functionality. Here are the key elements of a schematic:

1. Component Symbols

Each component in the circuit is represented by a symbol. For example, a resistor is usually shown as a zigzag line, while a capacitor is two parallel lines.

2. Nets (Connections)

Lines connecting the symbols represent electrical connections, known as nets. These nets define how components interact with each other.

3. Reference Designators

Lines connecting the symbols represent electrical connections, known as nets. These nets define how components interact with each other.

4. Values and Ratings

The schematic also shows the values and ratings of components, such as the resistance of a resistor or the capacitance of a capacitor.

5. Power and Ground Symbols

Every circuit needs power and ground connections. These are represented by standard symbols, ensuring the circuit has a common reference point for voltage.

Common Terms in PCB Design

1. Silkscreen Layer

The silkscreen layer contains text, logos, and symbols printed on the surface of the PCB to help identify components and guide assembly. It can also include part numbers, component values, and polarity markings.

2. Via

A via is a hole in the PCB that allows electrical connections between different layers. Vias are often used in multi-layer PCBs to route signals between the top and bottom layers or inner layers.

3. Copper Pour

A copper pour is a large, solid region of copper that is poured over areas like ground or power planes. It helps reduce noise, increase current-carrying capacity, and improve thermal dissipation.

4. Trace Width

Trace width refers to the thickness of the copper traces used to connect components. The width of a trace must be designed to carry the required amount of current without overheating.

5. Drill Hole

A drill hole is a hole that is made in the PCB to accommodate components with leads or for vias. The size and placement of drill holes are critical to the assembly process.

6. Solder Mask

The solder mask is a protective layer applied over the PCB to prevent solder from bridging between pads. It also helps prevent oxidation of the copper traces and improves the board’s overall durability.

7. Pad

Pads are small copper areas on the PCB where components are mounted or soldered. Pads can be through-hole or surface-mount, depending on the type of component.

8. Bill of Materials (BOM)

The BOM is a comprehensive list of all the components required for the assembly of a PCB. It includes details like part numbers, quantities, and specifications for each component.

9. Impedance Control

Impedance control is the process of ensuring that the impedance of the PCB traces matches the requirements of the signals that will travel through them. This is important for high-speed and RF circuits.

10. Stack-up

Stack-up refers to the arrangement of layers in a multi-layer PCB. It defines how the copper, dielectric, and other materials are stacked to create the board.

11. Daisy-Chaining

Daisy-chaining is a method of connecting multiple components or pins in a series, often used in signal or power distribution systems within the PCB design.

12. Overcurrent Protection

Overcurrent protection refers to circuits designed to prevent excessive current from flowing through the PCB traces, often by using fuses or resistors that limit the current flow.

13. Design for Manufacturability (DFM)

DFM refers to designing the PCB in a way that makes it easier and more cost-effective to manufacture. This includes factors like trace width, pad size, and component placement.

14. Routing

Routing is the process of designing the electrical paths that connect the components on a PCB. Proper routing ensures that signals are carried efficiently with minimal interference.

15. Thermal Via

Thermal vias are specially designed vias used to transfer heat away from high-heat components to other parts of the PCB or a heat sink.

16. Electromagnetic Interference (EMI) Shielding

EMI shielding involves using design techniques, such as grounding and the use of shielding components, to protect sensitive parts of the PCB from electromagnetic interference.

17. Differential Pair

A differential pair is a set of two traces that carry complementary signals, often used in high-speed designs like USB or Ethernet to minimize noise and improve signal integrity.

18. Power Distribution Network (PDN)

The PDN refers to the system of traces and planes that deliver power to various components on the PCB. Proper PDN design is crucial to ensure reliable power delivery and minimize voltage drops.

19. Electrical Rule Check (ERC)

ERC is a process that checks the schematic design for electrical issues like unconnected nets, incorrect component connections, or incorrect power supply connections.

20. Multi-layer PCB

A multi-layer PCB contains more than two layers of conductive material and is used for more complex designs that require high-density circuits, especially in smaller devices.

21. Surface-Mount Technology (SMT)

SMT is a method for mounting components directly onto the surface of the PCB, rather than inserting them through holes. This allows for smaller, more compact designs.

22. Through-Hole Technology

Through-hole technology involves inserting component leads through holes in the PCB and soldering them on the opposite side. It’s commonly used for components that require strong mechanical bonds.

23. Hot Air Soldering

A method of soldering components onto the PCB using hot air, often used in reflow soldering processes for surface-mount components.

24. Trace Routing

Trace routing is the process of laying out the paths that the electrical signals will take through the PCB. Good trace routing ensures efficient and reliable signal transmission.

25. Tenting

Tenting refers to the process of covering the vias with a layer of solder mask, leaving the pad open. It helps prevent solder from flowing into vias during soldering.

PCB Design vs. PCB Layout

Although often used interchangeably, PCB design and PCB layout have different meanings:

PCB Design: Refers to the entire process, from schematic creation to generating manufacturing files.

PCB Layout: Specifically focuses on the physical arrangement of components and routing of traces on the board.

In simple terms, PCB layout is a part of the overall PCB design process.

PCB Design Process

Designing a PCB is a multi-step process that requires careful planning and attention to detail.

1. Schematic Capture

The process starts with creating a schematic diagram that defines the circuit’s functionality and connections.

2. Component Selection

Next, components are selected based on the circuit requirements. Factors like size, power rating, and cost are considered.

3. PCB Layout

Components are placed on the board, and traces are routed to connect them. This step requires balancing electrical performance with physical constraints.

4. Design Rules Check (DRC)

The layout is checked for errors or violations of design rules to ensure it meets manufacturing standards.

5. Gerber File Generation

Once the design is complete, Gerber files are generated. These files are used by manufacturers to produce the PCB.

6. Fabrication and Assembly

The PCB is fabricated, and components are assembled to create the final product.

FAQs

Q: What software is used for PCB design?

A: Popular software includes Altium Designer, Eagle, KiCad, and OrCAD.

Q: How many layers can a PCB have?

A: PCBs can have anywhere from one to 16 or more layers, depending on complexity.

Q: Why is trace width important?

A: Trace width affects the current-carrying capacity and signal integrity of the circuit.

Q: What is a multilayer PCB?

A: A multilayer PCB has multiple layers of copper separated by insulating material, allowing for more complex designs.

Q: How long does it take to design a PCB?

A: The time varies based on complexity. Simple designs may take a few days, while complex designs can take weeks.

What is Via in Pad?

With the improvement of the integration of electronic products, the package of components is getting smaller and smaller, and the pin spacing is also getting smaller and smaller. In complex PCB design, the signal cannot be fanned out without punching the disc hole, and the signal must be drawn from the next layer through the disc hole. Especially in the miniaturization applications of ‌BGA (Ball Grid Array) and ‌SMD (Surface Mount Device) chips, the process of disc holes has been widely used.

Via in pad is a design methodology in PCB manufacturing where vias are directly embedded in the pads of surface-mount devices (SMDs). Traditional vias are placed near the components with traces connecting them to the pads. However, in via-in-pad designs, the vias and pads are combined, which saves space and shortens trace lengths. This approach is particularly useful in HDI PCBs, where board real estate is limited, and signal integrity is critical.

What is Via-in-Pad Plating?

Via-in-pad plating refers to a specialized manufacturing process where vias embedded in pads are filled and plated over to form a smooth, conductive surface. This process involves:

Via Filling: The via hole is filled with a material, often epoxy or a conductive paste, to eliminate voids and provide structural stability.
Copper Plating: The filled via is then plated with copper to create a uniform and conductive layer.
Surface Finish: A finish such as ENIG (Electroless Nickel Immersion Gold) or HASL (Hot Air Solder Leveling) is applied to ensure solderability.

Proper via-in-pad plating prevents solder wicking, a phenomenon where solder flows into the via during reflow, causing insufficient solder on the component leads.

Is Via-in-Pad Expensive?

Via-in-pad designs are undeniably more expensive than traditional vias. The additional manufacturing steps, such as via filling, plating, and the need for precise alignment, contribute to the higher costs. Moreover, the advanced equipment and materials required for this process add to the overall expense.

However, for designs that demand high performance, such as smartphones, medical devices, and aerospace electronics, the benefits of via in pad often outweigh the cost. It allows for compact layouts, improved performance, and better thermal management, making it indispensable for cutting-edge applications.

What Size is a Via-in-Pad?

The size of a via-in-pad is influenced by the PCB’s application, layer count, and the size of the components used. In HDI PCBs, via sizes typically range from 0.15 mm to 0.4 mm in diameter. Microvias, often used in via-in-pad designs, can be as small as 0.1 mm.

The diameter must align with the pad size to avoid compromising the pad’s mechanical and electrical integrity. Designers also need to consider the PCB manufacturer’s capabilities when selecting via sizes, as extremely small vias may require advanced fabrication techniques.

What are the Drawbacks of Via in Pad?

While via in pad offers several advantages, it also comes with notable challenges:

Higher cost
Soldering defects
Complex manufacturing
Thermal stress risks
Complex manufacturing process

Can You Put Vias Under Components?

Yes, placing vias under components is common in advanced PCB designs, particularly with via in pad. This technique is often used for BGAs, QFNs, and other fine-pitch components.

However, proper design and manufacturing practices must be followed to prevent defects. Filling and plating the vias ensure they do not interfere with soldering. Additionally, simulations and testing are essential to validate the design and ensure reliability.

Traditional Vias vs. Via-in-Pad Design

Traditional vias are placed outside the component pad, with traces connecting them to the pads. While this approach is cost-effective, it consumes more space and may result in longer trace lengths, increasing parasitic effects.

Via-in-pad designs embed the vias directly within the component pads, reducing trace lengths and optimizing space. They enhance signal integrity, thermal performance, and overall board aesthetics but at a higher cost and complexity.

When to Use Via-in-Pad Design?

Via-in-pad designs are not always necessary, but they are indispensable in specific scenarios where performance, space optimization, and thermal management are critical. Below are the situations where via-in-pad designs are most appropriate:

1. High-Density Interconnect (HDI) PCBs

When designing HDI PCBs with compact layouts and high layer counts, via-in-pad is essential. This design technique optimizes the limited space available, allowing for more components and connections on the board. It is particularly useful for devices like smartphones, wearables, and IoT devices where miniaturization is key.

2. Fine-Pitch Components

Via-in-pad designs are commonly used for components with fine pitches, such as:

BGA chips: BGAs have numerous pins closely spaced, leaving minimal room for traditional routing. Via in pad provides a clean solution to connect signals directly.
QFNs: QFNs require vias under the pads for effective routing and thermal management.

3. High-Speed and RF Applications

In high-speed and RF circuits, signal integrity is paramount. Via-in-pad designs minimize trace lengths, reducing parasitic inductance and impedance mismatches. This makes them ideal for applications like:

5G communication systems
High-frequency radar systems
Advanced networking equipment

4. Improved Thermal Management Needs

For power components or heat-sensitive devices, via in pad aids in efficient thermal dissipation. By directly connecting the pads to thermal vias leading to internal or external layers, heat is transferred away from the components. This is critical for:

High-power LEDs
Voltage regulators
Power amplifiers

5. Limited PCB Real Estate

In designs with severe space constraints, via in pad maximizes usable board area. This allows for additional routing space and supports high component density without sacrificing performance. Applications like medical implants and aerospace electronics greatly benefit from this approach.

6. Double-Sided Component Placement

When components are placed on both sides of the PCB, traditional vias can interfere with the routing on the opposite side. Via in pad eliminates this issue by embedding the vias within the pads, simplifying double-sided designs.

7. High-Performance Computing Systems

For processors, GPUs, and other high-speed ICs, via in pad ensures reliable power delivery and signal integrity. It is frequently used in:

Data centers
High-performance workstations
AI hardware

Guidelines for Via-in-Pad Design

Via-in-pad designs require meticulous attention to detail to ensure reliability and performance.

1. Decide on the most suitable via type based on your design requirements:

Microvias: Ideal for high-density designs due to their small size.
Blind/Buried Vias: Useful for connecting internal layers without penetrating through the entire board.
Through-Hole Vias: Less common in via-in-pad but may be necessary for specific designs.

2. Fill the vias with appropriate materials to ensure mechanical stability and prevent solder wicking:

Non-Conductive Epoxy Fill: Provides a reliable, flat surface for soldering.
Conductive Fill: Used when electrical connectivity through the via is needed.

3. The plating over the filled vias should be smooth and flat to avoid soldering issues. Use a high-quality copper plating process to enhance electrical and thermal conductivity.

4. Collaborate with your PCB manufacturer early in the design process to align on their capabilities. This includes:

Minimum via diameter and pad size.
Spacing requirements between vias and traces.
Maximum number of vias that can be placed in pads.

5. Ensure the via size is proportionate to the pad size. A via that is too large can compromise the pad’s structural and electrical integrity, while a too-small via may not provide the necessary connectivity or thermal performance.

6. For high-power applications, incorporate thermal relief patterns or thermal vias.

7. Maintain sufficient spacing between vias and other components or traces to prevent electrical interference or thermal stress.

8. To avoid solder flowing into the via during reflow soldering:

Use filled and capped vias.
Employ surface finishes like ENIG (Electroless Nickel Immersion Gold) or OSP (Organic Solderability Preservative) for enhanced soldering reliability.

9. When using via in pad for power components or ground connections, thermal relief patterns help prevent excessive heat buildup. These are especially important in high-current designs.

Need assistance in designing via-in-pads in your PCB design? Leave your comments on below, our design experts will help to solve them.

What is the standard thickness of a PCB core?

The standard thickness of PCB core boards usually includes the following specifications: 0.5mm, 0.7mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.6mm, 2.0mm, 2.4mm, 3.2mm, 6.4mm. These thickness specifications are widely used in different electronic products and circuit board designs.

The thickness of PCB includes not only the thickness of the core board, but also the total thickness of all layers such as copper layer, solder mask layer and silk screen. The standard thickness ranges widely, from thinner 0.5mm to thicker 6.4mm, suitable for different application requirements.

Choosing the right PCB thickness is essential to ensure the performance and reliability of the circuit board. Thicker PCBs have higher mechanical strength and load-bearing capacity, and are suitable for products with high power and large electronic components, such as industrial, automotive, aerospace and military applications.

Ultra-thin PCBs are suitable for small electronic products such as smartphones, smart wearable devices and laptops due to their lightweight characteristics.

What is the thickness tolerance of a PCB core?

The thickness tolerance of a PCB core varies according to different thickness ranges.

For PCBs with a thickness of less than or equal to 1mm, the board thickness tolerance is ±10% of the board thickness. For example, a PCB with a thickness of 0.5mm has a tolerance of ±0.05mm; a PCB with a thickness of 0.8mm has a tolerance of ±0.08mm.

For PCBs with a thickness greater than 1mm and less than or equal to 1.6mm, the tolerance is ±0.14mm.

For PCBs with a thickness greater than 1.6mm and less than or equal to 2.0mm, the tolerance is ±0.18mm.

For PCBs with a thickness greater than 2.0mm and less than or equal to 2.4mm, the tolerance is ±0.22mm.

For PCBs with a thickness greater than 2.4mm and less than or equal to 3.0mm, the tolerance is ±0.25mm.

For PCBs with a thickness greater than 3.0mm, the tolerance is ±10%.

These tolerance standards apply to most PCB manufacturing processes, ensuring the stability and reliability of the PCB.

What is the difference between HDI and non-HDI PCB?

The main differences between HDI PCB and non-HDI PCB are their line density, size, production process and electrical performance. HDI PCB (High Density Interconnect PCB) has higher line density, smaller size and better electrical performance, while ordinary PCBs are lacking in these aspects.

First of all, the design and structure of HDI PCB are significantly different from ordinary PCBs. HDI PCB adopts higher line density and more complex circuit layout, which enables smaller size and lighter design. In contrast, ordinary PCBs have lower line density and are suitable for some application scenarios that do not require high line density.

In terms of production process, the manufacturing process of HDI PCB is relatively complex, including laser drilling, stacked copper plates, etching technology, etc., to achieve high-density interconnection and complex circuit wiring. The manufacturing process of ordinary PCB is relatively simple, generally using photolithography, etching process, etc.

In terms of electrical performance, HDI PCB uses technologies such as blind holes and buried holes to reduce signal transmission paths and improve the transmission rate and stability of electrical signals. In addition, HDI PCB also has better radio frequency interference, electromagnetic wave interference, electrostatic discharge and thermal conductivity performance.

Finally, the cost of HDI PCB is relatively high, mainly due to its complex manufacturing process and high technical requirements. The manufacturing cost of ordinary PCB is low, which is suitable for some application scenarios with low requirements for line density and technology.

How thick is a 2 layer PCB core?

The thickness of a 2-layer PCB core is usually 0.4mm.

PCB core is a base material composed of copper foil, solid resin material and glass fiber, with a certain hardness and thickness. Common PCB core thickness specifications include 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, 1.6mm, 2.0mm, 2.4mm, etc.

Among the common specifications of Shengyi core boards, the thickness of 0.4mm is widely used. In addition, the performance of multi-layer PCBs does not directly depend on the number of layers, but more reflects the space requirements during design.

Are HDI PCB reliable?

HDI PCBs are reliable. HDI PCBs are manufactured using high-density and high-reliability interconnection technology, with higher line density and more complex circuit layout, which can achieve smaller and lighter electronic devices.

Compared with ordinary PCBs, HDI PCBs perform well in anti-interference ability and electromagnetic compatibility, and can effectively reduce the impact of external interference on signal transmission, while having higher reliability and longer service life.

The reliability of HDI PCBs is due to the high-quality substrates, solder mask and copper foil materials used, as well as strict manufacturing processes and quality control. These characteristics enable HDI PCBs to maintain stable performance and quality in various harsh environments.

In addition, the development trend of HDI PCBs is towards higher integration, higher signal transmission rate, better electromagnetic compatibility and optimized thermal management capabilities, which further enhances its application value in high-performance and high-density integration requirements.

What are the benefits of HDI PCB?

The main benefits of HDI PCB include high-density wiring, high-performance signal transmission, adaptability to high-frequency applications, miniaturization, and thinness. These characteristics make HDI PCB play a vital role in electronic devices, especially in high-end electronic products such as smartphones, tablets, and high-end computers.

First, HDI PCB has the characteristics of high-density wiring, which can achieve more circuit connections in a smaller space. This allows the design of electronic products to be more compact and meet application scenarios with extremely high space requirements.

Secondly, HDI PCB excels in high-performance signal transmission, can provide better signal transmission quality and electrical performance, and is particularly suitable for processing high-speed and high-frequency signals.

In addition, HDI PCB also has the advantages of miniaturization and thinness, which contributes to the thinness and miniaturization of electronic products, making the equipment more portable while maintaining high performance.

These benefits of HDI PCB are due to its advanced manufacturing process and technology. By adopting finer line widths and smaller apertures, HDI PCB achieves higher wiring density and signal transmission speed.

At the same time, by optimizing material selection and circuit design, HDI PCB can reduce the loss and reflection during signal transmission and improve the integrity and accuracy of the signal. In addition, HDI PCB also has better anti-interference ability and electromagnetic compatibility, which can effectively reduce the impact of external interference on signal transmission.

The application range of HDI PCB is very wide, including smart phones, tablets, laptops, medical equipment and communication equipment. Due to its high-density interconnection and excellent electrical performance, HDI PCB plays an important role in these fields, promoting the development of the PCB industry, so that more dense components can be arranged more closely on HDI boards.

What are the disadvantages of HDI PCB?

The main disadvantages of HDI PCB include high cost, complex production process, environmental sensitivity and possible quality problems.

First, the cost of HDI PCB is relatively high. This is because high-precision manufacturing technology and special materials are required in its manufacturing process, which all lead to its cost increase.

In addition, HDI PCB is usually used in high-performance equipment, and the value of these equipment itself is also high, which further pushes up the price of HDI PCB.

Second, the production process of HDI PCB is very complicated. Due to its high density of lines and components, the manufacturing of HDI PCB requires highly precise processes and equipment. This not only increases the difficulty of production, but may also lead to a longer production cycle, further increasing costs.

In addition, HDI PCB has certain requirements for the environment. Due to its delicate structure, HDI PCB is very sensitive to humidity and temperature changes in the environment. Improper storage or transportation conditions may cause the PCB to become damp or deformed, affecting its performance and reliability.

Finally, HDI PCB may have some quality problems. Due to the complexity of the production process, HDI PCB may have problems such as poor solderability, delamination, short circuit, open circuit, etc. These problems may need to be avoided through strict quality control and testing.

The core thickness of HDI PCB is an important parameter, which is directly related to the performance and application of PCB. When choosing the core thickness of HDI PCB, factors such as application requirements, design requirements and manufacturing process need to be considered comprehensively to select the appropriate core thickness.

Is the circuit board DC or AC?

Circuit boards can transmit both direct current and alternating current. In modern electronic products, we use alternating current for power supply, so most circuit boards are also designed to transmit alternating current. Of course, in some special application scenarios, some circuit boards also need to transmit direct current. Whether transmitting direct current or alternating current, the circuit board needs to meet the requirements of the transmitted current.

What is the PCB in AC?

The alternating current in PCB refers to the current whose direction changes periodically, that is, alternating current (AC). The application of alternating current in PCB is mainly reflected in power conversion and power transmission. PCB power supply usually converts AC into stable direct current (DC) output to meet the demand of electronic equipment for stable power supply. PCB power supply converts AC into the required DC through components such as transformers, rectifiers, filters and voltage regulators, and provides stable power output.

How to calculate the bandwidth of AC in PCB traces

The calculation of AC PCB trace width can be performed by the following formula: W = (I / J) * K, where W represents the trace width, I represents the current, J represents the current density, and K represents a coefficient related to materials and processes. ‌This formula shows that the trace width is related to the current, current density, and material properties‌.

AC in PCB Design Guide

Current Carrying Capacity: The width of a trace directly affects its ability to handle current without exceeding temperature limits or causing excessive voltage drop.
‌Impedance Control: In high-frequency applications, maintaining controlled impedance is critical for signal integrity. Trace width, trace spacing, and dielectric properties affect the characteristic impedance of the transmission line.
‌Heat Dissipation: Adequate trace width helps to effectively dissipate heat, preventing thermal issues such as trace delamination or solder joint failure.
‌Voltage Drop: Narrower traces exhibit higher resistance, resulting in increased voltage drop along the length of the trace. By adjusting the trace width, the voltage drop can be minimized.
‌Manufacturability: The PCB manufacturing process imposes restrictions on the minimum trace width, and designers must balance performance requirements with manufacturability constraints. ‌2.
‌Minimum Trace Width: Most manufacturers have a minimum trace width of 6mil or 0.152mm, and typically use traces of 0.254-0.3mm.
‌Material and Process Deviations: Due to the possibility of material and process deviations in the actual PCB manufacturing process, a certain margin needs to be left when calculating the line width.
‌Signal Integrity Simulation‌: Perform signal integrity simulations to ensure impedance is controlled and signal degradation due to reflections, crosstalk, or transmission line effects is minimized‌

AC in PCB wiring

The current trend is that the power supply voltage is getting lower and lower (especially for highly integrated digital devices), the space occupied is getting smaller and smaller, the weight is getting lighter and lighter, and the efficiency is getting higher and higher, which requires the precise design of the power supply circuit starting from the PCB.

Safety distance includes electrical clearance (spatial distance), creepage distance (surface distance) and insulation penetration distance…

Electrical clearance: the shortest distance between two adjacent conductors or one conductor and the adjacent motor housing surface measured along the air.
Creepage distance: the shortest distance between two adjacent conductors or one conductor and the adjacent motor housing surface measured along the insulation surface.

Determination of electrical clearance:

The distance can be determined according to the measured working voltage and insulation level

The electrical clearance size requirements of the primary side line are shown in Table 3 and Table 4

The electrical clearance size requirements of the secondary side line are shown in Table 5

But usually: Primary side AC part: L-N ≥ 2.5mm before the fuse, L.N PE (earth) ≥ 2.5mm, no requirements are made after the fuse is installed, but a certain distance should be maintained as much as possible to avoid short circuit damage to the power supply.

Primary side AC to DC part ≥2.0mm

Primary side DC ground to earth ≥2.5mm (primary side floating ground to earth)

Primary side to secondary side ≥4.0mm, components connected between primary and secondary sides

Secondary side gap ≥0.5mm

Secondary side ground to earth ≥1.0mm

Note: Before determining whether it meets the requirements, the internal parts should be applied with a force of 10N and the outer shell with a force of 30N to reduce the distance so that the space distance still meets the requirements under the worst case.

Determination of creepage distance:

Based on the working voltage and insulation level, the creepage distance can be determined by looking up Table 6

But usually: (1), primary side AC part: L-N ≥2.5mm before the fuse, L.N earth ≥2.5mm, no requirement is required after the fuse, but try to keep a certain distance to avoid short circuit damage to the power supply.

(2) Primary side AC to DC part ≥2.0mm

(3) Primary side DC ground to ground ≥4.0mm such as primary side ground to earth

(4) Primary side to secondary side ≥6.4mm, such as optocoupler, Y capacitor and other components, the foot spacing ≤6.4mm needs to be slotted.

(5) Secondary side parts ≥0.5mm

(6) Secondary side ground to earth ≥2.0mm or more

(7) Transformer two-stage ≥8.0mm or more

Insulation penetration distance:

It should meet the following requirements according to the working voltage and insulation application:

For working voltage not exceeding 50V (71V AC peak or DC value), there is no thickness requirement;
The minimum thickness of additional insulation should be 0.4mm;
When the reinforced insulation is not subjected to any mechanical stress that may cause deformation or performance degradation of the insulating material at normal temperature, the minimum thickness of the reinforced insulation should be 0.4mm. If the insulation provided is used in the protective casing of the equipment and will not be bumped or scratched during maintenance by the operator, and any of the following conditions apply, the above requirements do not apply to thin insulating materials regardless of their thickness;
For additional insulation, at least two layers of material are used, each of which can pass the dielectric strength test for additional insulation; or:
For additional insulation composed of three layers of material, any combination of two layers of material can pass the dielectric strength test for additional insulation; or:
For reinforced insulation, at least two layers of material are used, each of which can pass the dielectric strength test for reinforced insulation; or:
For reinforced insulation composed of three layers of insulating material, any combination of two layers of material can pass the dielectric strength test for reinforced insulation.

Points to note about wiring process:

Flat components such as capacitors must be flat without glue.

If the distance between two conductors can be shortened by applying a force of 10N, which is less than the safety distance requirement, glue can be used to fix the part to ensure its electrical clearance.

When laying PVC film inside some shell equipment, attention should be paid to ensuring the safety distance (pay attention to the processing technology).

When fixing the parts with glue, be careful not to leave foreign matter such as glue wire on the PCB board.

When processing parts, insulation damage should not be caused.

Requirements for flame-proof materials:

Heat shrink tubing V-1 or VTM-2 or above; PVC tubing V-1 or VTM-2 or above

Teflon tubing V-1 or VTM-2 or above; plastic materials such as silicone sheets, insulating tape V-1 or VTM-2 or above

PCB board 94V-1 or above

Regarding insulation level

(1) Working insulation: insulation required for normal operation of equipment

(2) Basic insulation: insulation that provides basic protection against electric shock

(3) Supplementary insulation: independent insulation applied in addition to basic insulation to protect against electric shock in case of basic insulation failure

(4) Double insulation: insulation consisting of basic insulation plus supplementary insulation

(5) Reinforced insulation: a single insulation structure that provides the same level of protection against electric shock as double insulation under the conditions specified in this standard

The applicable situations of various insulation are as follows:

A. Operational insulation

a. Between parts with different voltages

b. Between ELV circuits (or SELV circuits) and grounded conductive parts.

B. Basic insulation

a. Between parts with dangerous voltages and grounded conductive parts;

b. Between SELV circuits with dangerous voltages and grounding-dependent;

c. Between the primary power conductor and the grounded shield or the core of the main power transformer;

d. As part of double insulation.

C. Supplementary insulation.

a. Generally speaking, between accessible conductive parts and parts that may carry dangerous voltages after basic insulation is damaged, such as:

Ⅰ. Between the surface of handles, knobs, handles or similar objects and their ungrounded axis.

Ⅱ. Between the metal casing of the second category equipment and the outer skin of the power cord passing through this casing.

Ⅲ. Between the ELV circuit and the ungrounded metal casing.

b. As part of double insulation

D. Double insulation

Double insulation Reinforced insulation

Generally speaking, between the primary circuit and

a. between accessible ungrounded conductive parts, or

b. between floating SELV circuits, or

c. between TNV circuits

Double insulation = basic insulation + supplementary insulation

Note: ELV circuit: extra low voltage circuit

Under normal working conditions, the AC peak value between conductors or between any conductors does not exceed 42.4V or the DC value does not exceed 60V.

SELV circuit: safety extra low voltage circuit.

A properly designed and protected secondary circuit so that under normal conditions or single fault conditions, the voltage between any two accessible parts, and between any accessible parts and the protective grounding terminal of the equipment (only for Class I equipment) will not exceed the safety value.

TNV: communication network voltage circuit

Under normal working conditions, the circuit carrying communication signals

Difference between direct current and alternating current

‌The main differences between DC and AC include direction and polarity, voltage change, current loss, transformer use, and application scenarios.

‌Direction and polarity:

DC: The direction of the current remains unchanged, and the electrons flow from the positive electrode to the negative electrode.

AC: The direction of the current changes periodically, and the electrons flow back and forth between the positive and negative electrodes. ‌
‌Voltage change:

DC: The voltage remains constant and does not change over time.

AC: The voltage magnitude and direction change periodically over time. For example, the mains is an AC with a sine waveform.

‌Current loss:

DC: Fault losses are relatively small.

AC: There is capacitive current, and there is capacitive current in the transmission line. ‌
‌Transformer use:

DC: The voltage cannot be changed using a transformer.

AC: The voltage can be changed using a transformer, which is suitable for boosting voltage to reduce losses during long-distance transportation.

‌Application scenarios:

DC: Suitable for low-voltage electrical appliances and occasions that require stable current.
‌Alternating current‌: Suitable for household and industrial use, using transformers to change voltage to suit different needs.‌

FAQ About AC in PCB

FAQ About AC in PCB

Q: The relationship between PCB current and line width. Is the current divided into AC or DC?
A: The relationship between PCB current and line width is not divided into AC or DC. In terms of the nature of the lines on the PCB, the lines are all made of copper materials, and both AC and DC can pass. However, how much current can pass depends on the cross-sectional area of the line on your PCB. That is, line width x thickness of the copper foil of the line. If the cross-sectional area of the line is small, only small current signals can pass, and if the cross-sectional area is large, large current signals can pass. This signal can be AC or DC.
Not just 1mm, any line width can pass DC or AC signals.

Q: There is a packaged device, and there are 2 pins in the device that need to be connected to the live wire and neutral wire of 220V AC respectively. So how to deal with this power line when drawing the PCB? Are there any size requirements for pads, wires, etc.? Are there any protective measures required? Is it not possible to directly add pads to connect to the pin pads of the device?
A: It is best to mill a groove between the neutral wire and the live wire, and choose the thickness of the wire according to the current. When the current is large, you can put a tin layer on the wire, and the pad should be slightly larger.

Q: The grounding of the PCB circuit board design is also the negative pole. What is the difference between the grounding here and the AC grounding?

A: The concept of the circuit board ground is somewhat different from that of the power supply system. The power supply system refers to the earth, that is, the terminal with the same potential as the earth.

The ground in the circuit board is just a common terminal of a potential, which can be positive or negative, depending on the needs of the designer. It’s just that everyone is used to and assumes that the negative pole is the common terminal, that is, the ground. The circuit board ground is not necessarily connected to the earth.

But it must be connected to the earth when EMI filtering is required.

Q: Should all GNDs on the PCB board be connected? There is a terminal (screw type) with two terminals marked as V1+ and V1- on the PCB schematic. Should V1- be connected to the power supply ground? But I used a multimeter to measure why V3- is not connected to other GNDs on the board?

So how do you connect the ground and 10V of the power supply to the V1+ and V1- ends of the terminal?

A: Not all ground wires on the board are connected together. The ground wires are divided into analog ground and digital ground, just like the ground wire in DC and the ground wire in AC cannot be connected together. That is to say, there is a ground wire that is specifically used for power supply, and there is a ground wire that is specifically used for signals (shielding signal interference). These two ground wires cannot be connected together.
In addition, you mentioned V1+ and V1-, and V1- should not be considered a ground wire. Generally, the signal represented by this method is a differential signal, that is, the V1 signal is differentially divided into V1+ and V1-, which can reduce external interference and transmit farther. Finally, V1+ and V1- are integrated into the V1 signal.
You need to figure out whether the V1+ and V1- of the terminal are used for power supply. If they are used for power supply, then V1+ is the positive pole. V1- is the negative pole. Since you didn’t show us the picture, you can’t just connect it randomly. The circuit board needs to connect not only power but also signals, depending on how your board is made.

What are high density interconnects?

High-density interconnect (HDI) is a printed circuit board (PCB) manufactured using higher-density wiring technology. Compared with traditional PCB, HDI board achieves miniaturization, lightweight and higher wiring density of circuit board through smaller aperture, finer line width/spacing and more layers of blind and buried hole technology to adapt to Electronic devices, especially mobile devices, require efficient space utilization and high-performance transmission.

The core of HDI technology lies in its high-density wiring design. By increasing the number of PCB layers, reducing wire width and spacing, and using micro-hole (such as laser drilling) processes, HDI technology significantly increases circuit complexity and wiring density. This technology is often used in electronic products such as smartphones, tablets, and smart wearable devices, meeting the needs of these devices for efficient space utilization and high-performance transmission.

What is the difference between PCB and HDI?

The main differences between PCB and HDI boards lie in wiring density, manufacturing process, size and cost. HDI boards use high-density interconnection technology, with higher wiring density and more complex circuit layouts, while ordinary PCBs are relatively simple and suitable for some application scenarios that do not require high line density.

There are significant differences between HDI boards and ordinary PCBs in terms of wiring density, manufacturing process, size and cost. HDI boards use high-density interconnection technology, with higher wiring density and more complex circuit designs, enabling smaller size and lighter design requirements. In comparison, the wiring density of ordinary PCB is low, which is suitable for some application scenarios that do not require high line density.

In terms of manufacturing process, HDI boards use more advanced manufacturing processes, including laser drilling, stacked copper plates and etching technology, to achieve high-density interconnection and complex circuit wiring. In comparison, the manufacturing process of ordinary PCBs is relatively simple, usually using photolithography and etching processes.

Because HDI boards have higher circuit density and complex circuit layouts, their size and thickness are usually smaller, making them suitable for applications that require compact packaging and space constraints. Ordinary PCBs do not have these restrictions and are suitable for more diverse application scenarios.

In terms of cost, since the manufacturing process of HDI boards is more complex and has higher technical requirements, its manufacturing cost is relatively high. In comparison, ordinary PCBs have lower manufacturing costs and are suitable for some application scenarios that do not have high circuit density and technical requirements.

What is the structure of HDI PCB?

The structure of HDI PCB mainly includes inner laminate, outer laminate, gaskets, blind and buried vias and other components. ‌

The inner laminate is the core part of the HDI circuit board. It is composed of multiple layers of conductive materials and insulating materials alternately stacked. It mainly realizes the transmission and control of circuit signals. The number of layers of the inner laminate can be very high. It uses microporous technology to achieve a high-density circuit layout and has excellent electrical performance and stability‌.

The outer laminate is located on the outside of the inner laminate and is also composed of multiple layers of conductive materials and insulating materials alternately stacked. Its main function is to protect the internal circuit from the influence of the external environment, such as humidity, temperature, mechanical stress, etc. The outer laminate can also provide additional grounding and shielding to improve circuit performance and reliability‌.

The gasket is an insulating material used to connect the inner laminate and the outer laminate. Its main function is to isolate the inner and outer laminates, prevent electrical interference, and provide certain mechanical support to ensure the stability of the circuit board.

A blind buried via is a non-penetrating through hole located inside the inner laminate. It is not directly connected to the outer laminate and mainly realizes the electrical connection between the inner laminates. Blind and buried vias do not penetrate the entire circuit board, which can effectively reduce the thickness and weight of the circuit board and improve the circuit board’s thermal resistance and mechanical stress resistance.

What are the advantages of HDI PCB?

The main advantages of HDI PCB include high-density interconnection, optimized wiring design, good signal transmission performance, high reliability and stability, smaller size and weight, and higher production efficiency. ‌

First, HDI PCB achieves higher line density by using higher-level packaging technology and smaller apertures. This means that under the same board size, HDI PCB can accommodate more electronic components and complex circuit designs, thereby improving the performance of the product. ‌

Second, the design of HDI PCB is more compact. Through multi-layer wiring and micro-via technology, the size and weight of the circuit board can be greatly reduced, adapting to the trend of modern electronic devices to pursue thinness and shortness.

Finally, the production process of HDI PCB is more efficient, and advanced technologies such as laser opening, thin film transformer, and cover packaging are used to achieve high-efficiency production.

What are the disadvantages of HDI PCB?

1. Difficulty in impedance control: The complexity of pattern transfer and electroplating processes increases production difficulty, which may lead to unstable impedance values.

2. Complex production cost control: The high-density circuit part of HDI PCB has a slow etching speed, which leads to excessive etching of isolation lines and increases production costs.

‌3. Environmental impact‌: During the electroplating and etching process, a large amount of copper ions enter the waste liquid, causing environmental pollution and difficulty in recycling.

4. High difficulty in design and manufacturing: HDI PCB is manufactured using micro-blind buried via technology and built-up method. The technical requirements are high and the process is complex, which increases the difficulty of design and manufacturing.

‌5. High material costs‌: The materials used in HDI PCB, such as PI and other high-performance materials, are more expensive, increasing manufacturing costs‌.

6. Quality issues: HDI PCB is prone to problems such as poor solderability and delamination during the manufacturing process. These problems may require higher process capabilities and quality control to avoid.

What are the applications of HDI PCB?

HDI PCB (High Density Interconnect PCB) can greatly reduce the size and weight without sacrificing performance by using microvias and tiny line widths and spacing, and is particularly suitable for portable electronic devices.

The main application areas of HDI PCB include:

‌Communication field‌: HDI PCB can achieve higher data transmission rates and lower energy consumption by increasing the number of tiny components.

‌Automotive Electronics‌: HDI PCB reduces product volume and production costs in the high integration of automotive electronic products, ensuring the stable operation of automotive electronic products.

‌Medical Equipment‌: HDI PCB is widely used in high-precision and high-stability medical equipment, improving the accuracy, sensitivity and stability of the equipment‌.

‌Mobile Communication‌: HDI PCB supports high-speed data transmission, maintains stable signal transmission, and supports a variety of wireless communication technologies‌.

‌High Performance Computing (HPC)‌: HDI PCB provides efficient interconnection channels, significantly improving computing performance and response speed‌.

In short, high-density interconnection circuit boards, as an important embodiment of high-density interconnection technology, play an irreplaceable role in the development of modern electronic technology. With the continuous advancement of technology, its future development prospects are still very broad, and it will continue to promote the development of electronic devices in the direction of smaller, stronger, and smarter.

What are the holes in a PCB called?

What are the holes on PCB called? What are the holes in the circuit? The holes on PCB can be roughly divided into 3 types, screw holes (mounting holes), conductive holes (vias), and plug-in holes.

Screw holes: Screw holes are used for fixing.

Conductive holes: Conductive holes (also called vias) are used for conducting electricity just like circuits.

Plug-in holes: Plug-in holes are of course used to plug in various parts, such as diodes, transistors, capacitors, inductors, etc.

What is a through hole

What is a through hole? Through holes, also known as perforations, are holes in a PCB that go all the way through the board. Their main purpose is to provide electrical connections for component pins while allowing soldering on both sides of the board.

1.A via is a special through hole whose wall is metallized to achieve electrical connection between different layers on a circuit board. This type of hole is usually used to connect component pins to internal circuits, or to achieve electrical connection between different layers in a multi-layer PCB. Vias need to be metallized during the PCB manufacturing process, which usually includes drilling, desmearing, chemical copper plating, and electroplating.

2.Non-conducting holes are the opposite of through holes. Their hole walls are not metallized, so they do not have electrical connection functions. These holes are mainly used for mechanical fixation, heat dissipation or identification purposes. Non-conducting holes are relatively simple in the PCB manufacturing process, and only drilling operations are required.

What is a blind via?

A blind via is a hole that extends from one side of a PCB to a certain internal layer without penetrating the entire board. The emergence of blind vias is mainly due to the development of HDI technology, which provides circuit designers with greater flexibility and more compact layout. Blind vias are usually used to connect surface mount components (SMD) to internal circuit layers, or to connect circuits between different internal layers.

What are buried vias?

Buried vias are holes located inside the PCB that do not penetrate any side of the board. They are completely hidden inside the board and are used to connect circuits between different internal layers. Buried vias are especially useful in HDI boards because they can reduce the overall thickness of the board while maintaining electrical connections between internal circuits.

What is a microvia?

Microvia refers to a hole with a smaller diameter, usually at the micron level. The emergence of microvia technology enables PCB designers to achieve more complex circuit layouts in a smaller space. Microvias are often used in high-density, high-reliability electronic devices such as mobile phones and tablets. The manufacture of microvias requires high-precision drilling equipment and technology to ensure the accuracy and reliability of the holes.

What are Mounting holes？

What are Mounting holes?Locking holes are auxiliary holes used in the PCB manufacturing and assembly process to accurately locate and fix the circuit board. They are usually located at the edge or specific position of the PCB to ensure that the circuit board can be accurately aligned and fixed during manufacturing, testing and assembly. The locating holes do not participate in the connection of the circuit, but are essential to ensure the quality and performance of the circuit board.

What are Mounting holes？

What are thermal vias?

Thermal vias are holes designed specifically for heat dissipation, usually large and can run through the entire PCB or multiple layers. Their role is to reduce heat buildup on the circuit board by increasing surface area and air flow, thereby improving the stability and reliability of the device. Thermal vias are particularly important in high-performance, high-power electronic devices.

FAQ About board electronics with holes

How to solve the contradiction between manual routing and automatic routing of high-speed signals?

Most of the current powerful routing software’s automatic routing tools have set constraints to control the routing method and the number of vias. The routing engine capabilities and constraint setting items of various EDA companies are sometimes very different. For example, whether there are enough constraints to control the winding method of the serpentine, whether the routing spacing of the differential pair can be controlled, etc. This will affect whether the routing method generated by automatic routing can meet the designer’s ideas. In addition, the difficulty of manually adjusting the routing is also related to the capabilities of the routing engine. For example, the pushing ability of the routing, the pushing ability of the via, and even the pushing ability of the routing pair copper. Therefore, choosing a routing tool with strong routing engine capabilities is the solution.

Will adding test points affect the quality of high-speed signals?

As for whether it will affect the signal quality, it depends on the method of adding test points and how fast the signal is. Basically, the additional test points (not using the existing vias (via or DIP pins) as test points) may be added to the line or a small section of wire may be pulled out from the line. The former is equivalent to adding a very small capacitor to the line, while the latter is an additional branch. Both of these situations will have some impact on high-speed signals, and the extent of the impact is related to the frequency speed of the signal and the edge rate of the signal. The magnitude of the impact can be learned through simulation. In principle, the smaller the test point, the better (of course, it must meet the requirements of the test equipment) and the shorter the branch, the better.

Can you introduce some foreign technical books and data on high-speed PCB design?

Now the application of high-speed digital circuits includes communication networks and calculators and other related fields. In the communication network, the operating frequency of PCB boards has reached around GHz, and the number of layers is as many as 40 layers as far as I know. Due to the advancement of chips, the operating frequency of calculator-related applications, whether it is a general PC or server, has reached 400MHz (such as Rambus) or above. In response to the demand for high-speed and high-density routing, the demand for blind/buried vias, mircrovias and build-up process technology is gradually increasing. These design requirements can be mass-produced by manufacturers.

Does the design of rigid-flexible boards require special design software and specifications? Where can I undertake the processing of such circuit boards in China?

Can I use general PCB design software to design flexible printed circuits (Flexible Printed Circuit). The Gerber format is also used for FPC manufacturers to produce. Since the manufacturing process is different from that of general PCBs, each manufacturer will have its own restrictions on line width, line spacing, and aperture (via) based on their manufacturing capabilities. In addition, some copper foil can be laid at the turning point of the flexible circuit board for reinforcement. As for the manufacturer, you can search for “FPC” as a keyword on the Internet and you should be able to find it.

If the size of the circuit board is fixed, if the design needs to accommodate more functions, it is often necessary to increase the routing density of the PCB, but this may lead to increased mutual interference between the routings, and at the same time, the impedance cannot be reduced if the routing is too thin. Please introduce the techniques in the design of high-speed (>100MHz) high-density PCBs?

When designing high-speed and high-density PCBs, crosstalk interference does need to be paid special attention to because it has a great impact on timing and signal integrity. Here are a few things to note:

Control the continuity and matching of the characteristic impedance of the trace.

The size of the trace spacing. The spacing commonly seen is twice the line width. Through simulation, you can know the impact of trace spacing on timing and signal integrity and find the tolerable spacing. The results of different chip signals may be different.

Choose an appropriate termination method.

Avoid the same routing direction of the upper and lower adjacent layers, or even have traces overlapped up and down, because this kind of crosstalk is greater than the case of adjacent traces on the same layer.

Use blind/buried vias to increase the trace area. However, the production cost of the PCB board will increase. It is indeed difficult to achieve complete parallelism and equal length in actual implementation, but it should be done as much as possible.

In addition, differential termination and common mode termination can be reserved to mitigate the impact on timing and signal integrity.

The RF part, IF part, and even the low-frequency circuit part of the outdoor unit are often deployed on the same PCB. What are the material requirements for such PCB? How to prevent interference between RF, IF, and even low-frequency circuits?

Hybrid circuit design is a big problem. It is difficult to have a perfect solution.

Generally, RF circuits are laid out and wired as an independent single board in the system, and there will even be a special shielding cavity. Moreover, RF circuits are generally single-sided or double-sided boards, and the circuits are relatively simple. All of these are to reduce the impact on the distributed parameters of RF circuits and improve the consistency of RF systems. Compared with general FR4 materials, RF circuit boards tend to use high-Q substrates. The dielectric constant of this material is relatively small, the distributed capacitance of the transmission line is small, the impedance is high, and the signal transmission delay is small. In hybrid circuit design, although RF and digital circuits are made on the same PCB, they are generally divided into RF circuit area and digital circuit area, and laid out and wired separately. Shielding is used between ground vias and shielding boxes.

‌What is a high frequency pcb communication circuits

High frequency pcb communication circuits to a circuit board with an operating frequency in the high frequency band (usually greater than 300MHz or a wavelength less than 1 meter), which is mainly used to transmit high-frequency signals and data. ‌ This type of circuit board is widely used in radio frequency (RF) and microwave fields, such as communication equipment, radar systems, satellite communications, and high-speed data transmission systems.

What is a high frequency pcb communication circuits

The characteristics of high-frequency circuits include challenges such as transmission line effects, signal integrity issues, and electromagnetic interference (EMI). Due to the short wavelength of high-frequency signals, traditional low-frequency circuit design methods are no longer applicable, and special design and processing methods are required to ensure the performance and stability of the circuit.

High-frequency circuit boards are produced on microwave substrate copper-clad boards using ordinary rigid circuit board manufacturing methods or special processing methods. They need to have high-quality electrical properties and chemical stability to meet the requirements of high-frequency signal transmission.

Definition of high frequency pcb communication circuits

High-frequency circuit board, as a special circuit board, is mainly suitable for occasions with high electromagnetic frequency, especially in the fields of high frequency (frequency greater than 300MHz or wavelength less than 1 meter) and microwave (frequency greater than 3GHz or wavelength less than 0.1 meter).

It is a circuit board made on a microwave substrate copper-clad board by adopting some manufacturing processes or special processing methods of ordinary rigid circuit boards. Generally speaking, when the frequency of the circuit board reaches above 1GHz, it can be defined as a high-frequency board.

With the rapid development of science and technology, more and more equipment designs have begun to involve microwave frequency bands (>1GHz) and even expanded to the millimeter wave field (such as 77GHz), especially in popular applications such as 77GHz millimeter wave antennas on vehicles.

This trend not only promotes the continuous increase in frequency, but also puts higher requirements on the substrate of the circuit board.

For example, the substrate material needs to have excellent electrical properties, stable chemical properties, and as the frequency of the power signal increases, the loss on the substrate must be extremely small. Therefore, the importance of high-frequency boards is becoming more and more prominent.

Advantages of high frequency pcb communication circuits

The main advantages of high frequency pcb communication circuits include efficient data transmission, strong anti-interference ability, high-frequency bandwidth and high reliability. ‌

high frequency pcb communication circuits can achieve efficient data transmission. High-frequency signals have a short cycle and can transmit more information per unit time, so they have the advantage of large-capacity transmission. In addition, high-frequency signals can achieve fast signal processing and are suitable for application scenarios that require high-speed data transmission and high real-time requirements.
high frequency pcb communication circuits have strong anti-interference capabilities. Due to the short wavelength of high-frequency signals, they can better avoid external interference and attenuation and have strong anti-interference capabilities. This makes high-frequency signals have advantages in fields such as wireless communications and radar systems, and can achieve stable signal transmission and reception. ‌
high frequency pcb communication circuits also have the advantage of high-frequency bandwidth. High-frequency signals correspond to a larger frequency range and can provide higher bandwidth than low-frequency signals. This means that more data can be transmitted, thereby supporting higher data rates and richer media content. ‌
High reliability of high frequency pcb communication circuits is also one of its advantages. The use of high-quality materials and manufacturing processes can effectively resist external interference and oxidation corrosion, ensure stable performance in high temperature environments, and thus extend the service life of the circuit board.

Classification of high frequency pcb communication circuits

Classification by material:

Organic materials: including phenolic resin, glass fiber/epoxy resin, Polyimide, BT/Epoxy (bismaleimide triazine/epoxy resin), etc.
Inorganic materials: mainly including aluminum, copper-invar-copper, ceramic, etc. These materials are mainly selected for their excellent heat dissipation function.

Classification by the hardness of the finished product:

Rigid PCB: has a solid structure and stable performance.
Flexible PCB: has flexibility and bendability, suitable for occasions requiring flexible wiring.
Rigid-Flex PCB: It combines the characteristics of rigid and flexible boards, and has higher design flexibility and wide application.

Classification by structure:

Single-sided board: A circuit board with a conductive layer on only one side.
Double-sided board: Both sides are coated with conductive layers, separated by insulating materials in the middle.
Multilayer board: It is composed of multiple conductive layers and insulating layers, and has higher circuit integration and reliability.

Classification by use:

Communication board: It is used in various communication equipment and systems.
Consumable electronic board: It is commonly found in consumer electronic products.
Military board: A circuit board that meets special requirements in the military field.
Computer board: A circuit board used in computer hardware.
Semiconductor board: A circuit board used in the manufacturing and testing process of semiconductors.
Electrical test board: A circuit board used in electronic testing and measurement equipment.

How to choose high-frequency circuit board high-speed board

When choosing PCB board, you must find a balance between meeting design requirements, mass production and cost. In short, the design requirements cover two aspects: electrical performance and structural reliability. Especially when designing ultra-high-speed PCB (frequency greater than GHz), the choice of board is particularly important. For example, the commonly used FR-4 material will have a significantly increased dielectric loss (Df, i.e., Dielectric Loss) at a frequency of several GHz, and may no longer be applicable.

Taking the 10Gb/S high-speed digital signal as an example, this signal can be regarded as the superposition of multiple sinusoidal wave signals of different frequencies. Therefore, the 10Gb/S signal contains multiple components of different frequencies: such as a 5GHz fundamental signal, a 3rd-order 15GHz signal, a 5th-order 25GHz signal, and a 7th-order 35GHz signal. In order to ensure the integrity of digital signals, maintain the steepness of the upper and lower edges of the signals, and be compatible with the low-loss, low-distortion transmission of RF microwaves (the high-frequency harmonic part of the digital signal reaches the microwave frequency band), the selection of materials for high-speed digital circuit PCBs has many similarities with the needs of RF microwave circuits.

In actual engineering operations, the selection of high-frequency boards seems simple, but the factors that need to be considered are quite complex. Through the introduction of this article, PCB design engineers or high-speed project leaders can have a deeper understanding of the characteristics and selection of boards. Understand the electrical properties, thermal properties, reliability and other characteristics of the board, and use the stacking design reasonably to create products with high reliability and excellent processability, and achieve the best balance of various factors.

Composition and key components of high frequency pcb communication circuits

High frequency pcb communication circuits are basically composed of passive components, active devices and passive networks. Passive components include resistors, capacitors and inductors, which mainly exhibit resistance characteristics at low frequencies, but also exhibit reactance characteristics at high frequencies. Active devices such as high-frequency triodes have the characteristics of high gain, high frequency response and low noise, and are widely used in television, radio communication, radar and other fields.

Application of high frequency pcb communication circuits

High frequency pcb communication circuits are widely used in long-distance communication systems, with a communication distance of up to thousands of kilometers, and are often used to maintain communication between aircraft and bases. It occupies a high-frequency band of 2~30MHz, uses skywave propagation, and can propagate over long distances. Modern airborne high-frequency communication systems usually use single-sideband communication systems, which can greatly compress the occupied frequency band and save transmission power. However, high-frequency communication is also susceptible to electrical interference such as ionospheric disturbances and lightning, generating radio background noise, and there is fading, and the signal is sometimes strong and sometimes weak.

Design Guidelines for High Frequency PCB Communication Circuits

Design Guidelines

High Frequency PCB Communication Circuits

How to avoid high-frequency interference?

The basic idea of avoiding high-frequency interference is to minimize the interference of the electromagnetic field of high-frequency signals, which is the so-called crosstalk. You can increase the distance between high-speed signals and analog signals, or add ground guard/shunt traces next to analog signals. Also pay attention to the noise interference of digital ground to analog ground.

How to solve the signal integrity problem in high-frequency communication PCB design?

Signal integrity is basically an impedance matching problem. The factors that affect impedance matching include the architecture and output impedance of the signal source, the characteristic impedance of the trace, the characteristics of the load end, and the topology of the trace. The solution is to rely on termination and adjust the topology of the trace.

How is the differential wiring method implemented?

There are two points to note when wiring differential pairs. One is that the length of the two lines should be as equal as possible, and the other is that the spacing between the two lines (this spacing is determined by the differential impedance) should remain unchanged, that is, they should be kept parallel. There are two parallel methods, one is that two lines run on the same routing layer (side-by-side), and the other is that two lines run on two adjacent layers (over-under). Generally, the former side-by-side (side by side, shoulder to shoulder) is more commonly used.

How to implement differential routing for clock signal lines with only one output end?

To use differential routing, it must be meaningful if both the signal source and the receiving end are differential signals. Therefore, differential routing cannot be used for clock signals with only one output end.

Can a matching resistor be added between the differential line pairs at the receiving end?

The matching resistor between the differential line pairs at the receiving end is usually added, and its value should be equal to the value of the differential impedance. This will improve the signal quality.

Why should the routing of differential pairs be close and parallel?

The routing method of differential pairs should be appropriately close and parallel. The so-called appropriate proximity is because this spacing will affect the value of differential impedance, which is an important parameter for designing differential pairs. Parallelism is also required because the consistency of differential impedance must be maintained. If the two lines are sometimes far away and sometimes close, the differential impedance will be inconsistent, which will affect the signal integrity and timing delay.

How to deal with some theoretical conflicts in actual wiring?

Basically, it is right to separate the analog/digital ground. It should be noted that the signal routing should try not to cross the split place (moat), and the return current path of the power supply and signal should not be too large.

The crystal oscillator is an analog positive feedback oscillation circuit. To have a stable oscillation signal, the loop gain and phase specifications must be met. The oscillation specification of this analog signal is easily interfered. Even if ground guard traces are added, it may not be possible to completely isolate the interference. Moreover, if it is too far away, the noise on the ground plane will also affect the positive feedback oscillation circuit. Therefore, the distance between the crystal oscillator and the chip must be as close as possible.

It is true that there are many conflicts between high-speed wiring and EMI requirements. But the basic principle is that the resistors, capacitors or ferrite beads added due to EMI cannot cause some electrical characteristics of the signal to not meet the specifications. Therefore, first use the techniques of arranging routing and PCB stacking to solve or reduce EMI problems, such as routing high-speed signals on the inner layer. Only then use resistors, capacitors or ferrite beads to reduce damage to the signal.

How to solve the contradiction between manual routing and automatic routing of high-speed signals?

Most of the current powerful routing software’s automatic routing tools have set constraints to control the winding method and the number of vias. The winding engine capabilities and constraint setting items of various EDA companies are sometimes very different. For example, whether there are enough constraints to control the winding method of the serpentine, whether the routing spacing of the differential pair can be controlled, etc. This will affect whether the routing method generated by automatic routing can meet the designer’s ideas. In addition, the difficulty of manually adjusting the routing is also related to the ability of the winding engine. For example, the pushing ability of the routing, the pushing ability of the via, and even the pushing ability of the routing to the copper plating, etc. Therefore, choosing a routing tool with a strong winding engine capability is the solution.

About test coupon.

The test coupon is used to measure the characteristic impedance of the produced PCB board with TDR (Time Domain Reflectometer) to see if it meets the design requirements. Generally, the impedance to be controlled is single line and differential pair. Therefore, the trace width and line spacing (when there is a differential pair) on the test coupon should be the same as the line to be controlled. The location of the ground point during measurement is important. In order to reduce the inductance of the ground lead, the grounding point of the TDR probe is usually very close to the probe tip, so the distance and method between the point where the signal is measured on the test coupon and the ground point should be consistent with the probe used.

In high-speed PCB design, the blank area of the signal layer can be copper-plated, and how should the copper of multiple signal layers be distributed in grounding and power supply?

Generally, the copper plating in the blank area is mostly grounded. However, when plating copper next to high-speed signal lines, pay attention to the distance between the copper plating and the signal line, because the copper plating will reduce the characteristic impedance of the trace a little. Also be careful not to affect the characteristic impedance of other layers, such as in the dual strip line structure.

Can the signal line on the power plane be calculated using the microstrip line model? Can the signal between the power and ground planes be calculated using the stripline model?

Yes, both the power plane and the ground plane must be considered as reference planes when calculating the characteristic impedance. For example, a four-layer board: top layer-power layer-ground layer-bottom layer. At this time, the model of the characteristic impedance of the top layer routing is a microstrip line model with the power plane as the reference plane.

Can the automatic generation of test points on high-density printed circuit boards by software generally meet the test requirements of mass production?

Whether the test points automatically generated by general software meet the test requirements depends on whether the specifications for adding test points meet the requirements of the test equipment. In addition, if the routing is too dense and the specifications for adding test points are strict, it may not be possible to automatically add test points to each line. Of course, the places to be tested need to be filled manually.

Will adding test points affect the quality of high-speed signals?

As for whether it will affect the signal quality, it depends on the way of adding test points and how fast the signal is. Basically, the additional test point (without using the existing via or DIP pin as the test point) may be added to the line or a short line may be pulled out from the line. The former is equivalent to adding a very small capacitor to the line, and the latter is an additional branch. Both situations will have some impact on the high-speed signal, and the degree of impact is related to the frequency speed of the signal and the edge rate of the signal. The magnitude of the impact can be known through simulation. In principle, the smaller the test point, the better (of course, it must meet the requirements of the test equipment) and the shorter the branch, the better.

How should the ground wires between the boards of a system be connected when several PCBs are connected to each other?

When the signals or power supplies between the PCB boards are in operation, for example, when the power supply or signal from board A is sent to board B, there will be an equal amount of current flowing back from the ground layer to board A (this is Kirchoff current law). The current on the ground layer will flow back to the impedance. Therefore, at each interface where the power supply or signal is connected to each other, the number of pins allocated to the ground layer should not be too small to reduce the impedance, so as to reduce the noise on the ground layer. In addition, the entire current loop can be analyzed, especially the part with larger current, and the connection method of the ground layer or ground wire can be adjusted to control the flow of current (for example, create low impedance at a certain place to let most of the current flow through this place) to reduce the impact on other more sensitive signals.

What is High Density Interconnect PCB?

High density Interconnect (HDI) PCB is a printed circuit board designed to meet the growing needs of modern electronic products. It allows for higher component density due to the use of thinner lines, smaller through-holes, and precise component placement. These boards are particularly popular in industries where miniaturization is key, such as smartphones, medical devices, and military equipment.

The HDI board uses the micro-blind hole technology to realize the circuit board design with high line distribution density, which is especially suitable for applications requiring high performance and high reliability. Compared with traditional PCBs, HDI boards have significant advantages in terms of volume, weight, wiring density and electrical performance, which can meet the electrical requirements of high-speed signals, provide impedance control of alternating current characteristics, high-frequency transmission capacity and reduce unnecessary radiation (EMI).

HDI PCBs use a combination of advanced technologies such as laser drilling and sequential lamination to enable denser wiring without compromising performance. By integrating smaller, more efficient through-holes, HDI boards offer greater functionality on a smaller footprint than traditional PCBs.

What is the Difference Between Connect and Interconnect?

The terms “connect” and “interconnect” may seem similar but serve distinct functions in electronics. “Connect” typically refers to the linking of two points, components, or circuits. This could be as simple as joining a wire to a terminal.

On the other hand, “interconnect” deals with more complex connections, usually involving the linking of multiple circuits or components within a system. In the context of HDI PCBs, interconnectivity is crucial because it defines how different layers and components of the board communicate. HDI technology optimizes these interconnections to make the board more efficient in terms of space and performance.

What is HDI PCB Stackup?

The stackup in HDI PCBs refers to how the multiple layers of the board are arranged. Stackups are critical in determining the board’s performance, particularly when it comes to signal integrity, power delivery, and heat dissipation. HDI stackups often involve intricate configurations that vary depending on the design’s complexity and purpose. Here are the most common types:

HDI PCB (1+N+1)

This is one of the simplest forms of HDI stackups, where “1+N+1” means there are two layers of high-density interconnect (one on each side) sandwiching N layers of traditional PCB. This structure is often used in applications where moderate complexity is required, providing a balance between performance and cost.

HDI PCB (2+N+2)

In this configuration, there are two HDI layers on each side of the N traditional layers. This setup allows for greater flexibility in routing, especially for complex designs requiring more components. The additional HDI layers enhance the board’s ability to manage signal transmission efficiently, making it suitable for high-performance applications.

ELIC (Every Layer Interconnection): Most Complex HDI

ELIC takes HDI technology to the next level. In this configuration, every layer of the PCB can interconnect directly with any other layer. This is the most advanced form of HDI stackup, offering unparalleled design flexibility and performance. However, it is also the most complex and expensive option. ELIC is often used in cutting-edge technology applications such as aerospace and military equipment.

Other HDI Stackups

What are the Advantages of HDI PCB?

The main advantage of the HDI board is its high-density interconnect design, through the use of micro lines and highly compact layout, can achieve higher interconnection density, thereby accommodating more electronic components in a limited space, improving the performance and function of the board. This design makes HDI boards particularly suitable for applications requiring high performance and high functional density, such as high performance computing, data centers, and mobile communication equipment, to support high-speed data transmission and processing.

The design of the HDI board also focuses on improving the anti-interference ability and reliability of the circuit board, by using better signal integrity and power management technology, effectively reduce the impact of electromagnetic interference and power noise on the circuit.

However, HDI boards also have some limitations. First of all, compared with other advanced boards, the cost of HDI boards is usually lower, because HDI manufacturing technology helps to use advanced packaging technology, but its processing is more difficult, higher requirements for technology and equipment, which may increase a certain cost. In addition, the material choice of HDI board will also affect its performance and cost, such as FR4, PI and BT materials have advantages and disadvantages, need to be weighed according to the specific application needs.

5 Types of Vias in HDI PCB

HDI PCBs rely on several types of vias to achieve their high-density interconnections. Each type of via has its specific role in the design and manufacturing process.

Blind Vias

Blind vias connect an outer layer of the PCB to one or more inner layers but do not extend through the entire board. These vias allow for complex routing without using unnecessary space on the PCB’s inner layers.

Buried Vias

Buried vias are located entirely within the board, connecting internal layers without appearing on the outer surfaces. This is ideal for designs where surface area needs to be preserved for components, while still allowing inter-layer connectivity.

Microvias

Microvias are tiny vias, typically created using laser drilling, that connect adjacent layers of the PCB. These are essential for HDI designs as they save space while maintaining high-density connections. They can be used in stacked or staggered configurations to optimize space and signal flow.

Staggered Vias

Staggered vias are microvias that are offset from each other across layers. This design allows for more flexibility in routing and avoids overlapping, making it a popular choice for HDI PCBs that require complex routing.

Through Hole Vias

Though not exclusive to HDI designs, through-hole vias extend through the entire PCB, connecting all layers. While these vias occupy more space, they are sometimes necessary for power connections or when working with thicker boards.

What is the Difference Between PCB and HDI PCB?

The key difference between a traditional PCB and an HDI PCB lies in the design and manufacturing process. Traditional PCBs use through-hole technology and thicker traces, limiting the board’s ability to accommodate high-density components. HDI PCBs, by contrast, use finer lines, smaller vias, and advanced interconnect techniques to maximize component density. Here are some key differences between them:

Manufacturing Processes

The embedded via and blind via technologies used in the manufacturing process of HDI (High-Density Interconnect) boards allow for the addition of more layers without increasing the thickness of the board, thereby improving space utilization. In contrast, the drilling process for standard PCBs is relatively simple, but as the number of layers increases, the board thickness also increases accordingly. This difference means that HDI boards require more advanced equipment and higher technical requirements during production.

Space Constraints

In space-constrained devices, such as smartphones and portable electronics, HDI boards are the ideal choice because they can integrate more functions within a smaller size. HDI boards can achieve a line width of 2/2 mil and a 10-layer board thickness of below 0.8mm. Standard PCBs, due to their larger size and lower integration, may not be suitable for these applications. The line width and spacing of regular PCBs are generally limited to 3/3 mil, and their thickness also has certain restrictions.

Performance Requirements

For high-end electronic products that require high-speed signal processing and complex circuit designs, HDI boards offer better performance. Due to their high density and efficiency, HDI boards can meet the high-performance demands of modern electronic devices. Standard PCBs, on the other hand, may not be suitable for these applications because of their lower signal transmission quality and higher latency.

Different Layering Methods

HDI boards are created through continuous stacking and lamination, resulting in advantages such as being “light, thin, short, and small.” Electrical interconnections between layers are achieved through conductive vias, embedded vias, and blind vias, making the structure different from standard multilayer boards. Most HDI boards are laminated two or more times (except for special structures), while standard boards are typically laminated once.

PTH vs. HDI PCB

Plated Through Hole (PTH) technology is commonly used in traditional PCBs and involves drilling holes through the entire board to connect different layers. This method, while reliable, is limited in terms of design flexibility and component density.

HDI PCBs, on the other hand, use smaller vias such as microvias, blind vias, and buried vias. These allow for more efficient use of space, making HDI technology the go-to solution for high-density, multi-layer designs.

High Density Interconnect PCB Applications

Communication equipment
Computers and servers
Automotive electronics
Medical equipment
Industrial control equipment
Consumer electronics
ADAS system
Wireless connection module

For nearly 20 years, Best Technology have always been committed to providing overseas customers High Mixed, Low Volume products with Reliable Quality and Quick Delivery, and are determined to become one of most trusted partners in the field of printed circuit boards and PCBA. As an expert of HDI PCB manufacturer, we are so confident that we can provide the highest quality product that highly meet your specifications.

What is hdi pcb?

HDI stands for High Density Interconnect, which refers to high-density interconnect technology. HDI circuit board is a high-end printed circuit board with very high circuit density and complexity, which can achieve high-speed signal transmission and reliability design. The main features of HDI circuit board are multi-layer circuit, thin plate, small aperture, dense wiring and fine circuit. It is widely used in mobile phones, computers, network communications, automotive electronics and other fields. Bestpcb is a professional HDI manufacturer with 18 years of HDI manufacturing experience.

What are the advantages of hdi pcb

Higher line density: HDI PCB can support more circuit tracks, arrange more electronic components in a limited space, and achieve high-density interconnection.
Smaller device spacing: The micro-hole technology of HDI PCB allows smaller spacing between components, which is suitable for compact design.
Improve signal integrity: The advanced stacking layer structure is adopted to provide better signal transmission quality and reduce signal interference.
Improve reliability: The manufacturing process of HDI PCB improves the mechanical strength of the board, making it more durable and suitable for demanding application environments.
Improve circuit integration: More line connections and component arrangements are achieved in a limited circuit board space to meet the needs of modern products that are thin and compact.
Enhance signal transmission efficiency: The use of advanced wires and connection methods can increase the operating speed of electronic devices and reduce energy consumption.
Support more complex system design: High-density connection capabilities provide support for complex system design and give full play to the performance of electronic devices. ‌
Promote innovation in the electronics industry: The application of HDI technology has promoted the innovation and development of the electronics industry, making electronic equipment more intelligent and efficient. ‌
Smaller size: It can complete a large number of circuit connections in a smaller space, meeting the needs of electronic products for lightness and portability. ‌
Higher signal transmission speed: The high-density line design allows signals to be transmitted quickly in a short time, improving the system operation speed and response speed.

Why does HDI PCB need via filling and plating?

‌Via filling plating plays a vital role in ‌HDI PCB manufacturing, with the main purpose of improving ‌electrical performance, connection reliability, operating frequency, and avoiding electromagnetic interference. This technology fills the blind holes of HDI PCB with conductive materials through the electroplating process to form a conductive path, which improves the performance and reliability of electronic equipment.

Improve electrical performance: Via filling plating can improve the electrical performance of HDI PCB, especially in high-frequency circuit board design, which is crucial for improving connection reliability, operating frequency and avoiding electromagnetic interference.
Via plugging and electrical interconnection in one step: Via filling plating technology combines via plugging and electrical interconnection, avoiding the defects caused by resin via filling, and also avoiding the CTE difference caused by other materials via filling.
Improve efficiency: Compared with resin via filling or other materials via filling, via filling plating has a simpler process and higher efficiency.
Process flow and technical challenges of via filling plating
Process flow: including steps such as tank preparation, setting of electroplating process control parameters, and analysis of potion addition.
Technical challenges: including positioning accuracy issues and electroplating quality issues, which need to be solved by strictly controlling parameters such as electroplating time and current density.

Application scenarios of hole filling electroplating

First-order HDI: Suitable for electronic devices with less complex circuits.
Second-order and above blind hole electroplating copper filling: Suitable for more complex electronic devices, such as mobile phones, laptops, etc.
Comparison between hole filling electroplating and full-board electroplating
Full-board electroplating: Although it can provide a uniform surface copper thickness distribution, it may encounter the problem of residual dry film on the board surface or in the hole during pre-treatment, resulting in some areas unable to be plated with copper. In addition, the etching process after full-board electroplating may cause quality defects such as side etching and fine lines.
Hole filling electroplating: Compared with full-board electroplating, hole filling electroplating is more accurate in filling blind holes, avoiding the problems that may be encountered in full-board electroplating, while simplifying the process and improving efficiency.

Materials of HDI PCB

The materials of HDI PCB mainly include coated copper foil (RCC), prepreg, copper foil, etc.

Resin-coated copper foil (RCC): This is a material that coats a special resin film layer on electroplated copper foil, used for HDI insulation layer. The characteristics of RCC include no glass dielectric layer, easy laser and plasma micro-hole forming, extremely high peel strength and good toughness, suitable for micro-narrow line etching. Laser drilling is performed on RCC, and the aperture shape formed is an inverted trapezoid, and the general aperture size is 0.076-0.10 mm. The use of RCC makes HDI PCB more widely used in small portable products, such as mobile phones, digital cameras, laptops, etc.

Prepreg and copper foil: These are basic materials in HDI PCB manufacturing, there are no special requirements, and they are suitable for different types of HDI PCB structures. The inner layer circuits are generally 1 ounce copper thick, while the outer layer circuits are plated with half an ounce of base copper to 1 ounce of finished copper thickness. The thickness of the board is usually thinner to meet the miniaturization requirements of HDI PCB.

Other materials: In addition to the main materials mentioned above, the manufacture of HDI PCBs may also involve other materials, such as FR4, PI (polyimide), BT, etc. These materials are selected according to specific application requirements. For example, FR4 has good electrical and mechanical properties and is suitable for most general applications; PI has higher heat resistance and chemical corrosion resistance, and is suitable for high temperature, high humidity and strong acid and alkali environments, but it is more expensive and difficult to process; BT combines good electrical properties, mechanical properties and thermal stability, and is suitable for application scenarios that require higher heat resistance.

Classification of HDI circuit boards

HDI circuit boards are mainly divided into first-order, second-order, third-order, high-order (including fourth-order and above) and Anylayer HDI. ‌

First-order HDI circuit boards mainly include single-sided or double-sided micro-hole processes, and the circuit layer has only one layer. ‌This type of HDI circuit board is suitable for applications with high requirements on cost and space, such as consumer electronics. ‌
Second-order HDI circuit boards contain two circuit layers, which are more complex but also more powerful than first-order HDI circuit boards. They can handle higher signal frequencies and are suitable for applications that require high performance, such as high-end communication equipment and computer hardware. ‌
Third-order HDI circuit boards contain three circuit layers. They are the most complex type at present. They can handle the highest signal frequency and the maximum data transmission rate. They are usually used in applications that require the highest performance, such as aerospace and military equipment. ‌
High-order HDI (including fourth-order and above) The applications of third-order or fourth-order HDI in electronic terminal products are more, while those above fourth-order are mostly converted to Anylayer structure. ‌
Anylayer HDI refers to HDI of any order/any layer. Compared with PCB boards with traditional lamination processes, HDI can reduce costs to a lower level when the stacking density exceeds eight layers. It also has higher electrical performance and signal accuracy, and significantly improves the performance of electromagnetic waves and radio frequency interference, electrostatic discharge and heat conduction in interconnection and relay transmission.

HDI PCB Process Flow

The process flow standards of HDI PCB mainly involve the application and processing technology of high-density interconnection technology (High Density Interconnection Technology, HDI for short), including first-order, second-order and third-order processes. Specifically, the HDI PCB process flow includes the following key steps and characteristics:

First-order process (1+N+1): This is a basic high-density interconnection technology that manufactures multi-layer boards through build-up and micro-blind via technology.

Second-order process (2+N+2): Further development on the basic technology, adding more layers and complexity.

Third-order process (3+N+3): Represents the highest stage of HDI technology, with extremely high layers and interconnection density

Differences between HDI PCB and ordinary PCBs

Differences in circuit design:
HDI PCB adopts a more sophisticated circuit design, with smaller line width and spacing, and smaller aperture, which can integrate more electronic components and realize more complex circuit functions. ‌
The blind, buried and stacked hole designs of HDI PCB greatly improve the utilization rate and signal transmission performance of the circuit board.
Differences in manufacturing process:
The manufacturing process of HDI PCB is more complicated, requiring high-precision processes such as laser drilling technology, hole filling electroplating technology and photolithography technology.
The manufacturing cost of HDI PCB is relatively high, but the performance and reliability are also higher. ‌
Differences in application:
Due to its high density and high performance, HDI PCB is widely used in high-end electronic products, such as smartphones, tablets, high-end communication equipment, etc.
Ordinary PCB is mainly used in low-end electronic products and general electronic equipment.
Characteristics and application scenarios of HDI PCB:
HDI PCB has high-density wiring, multi-layer structure, high-precision manufacturing process and excellent electrical performance, which can meet the extremely high requirements of high-end electronic products for size, weight, performance and reliability.
HDI PCB is widely used in smart phones, tablet computers, high-end communication equipment and other fields, promoting the continuous development and upgrading of electronic products.

Application of HDI PCB

HDI PCB (High Density Interconnection Printed Circuit Board) is widely used in multiple industries, including medical equipment, mobile phones, laptops, automotive electronics, computer industry, and future 5G technology fields

Medical equipment: The application of HDI PCB in medical equipment, such as sphygmomanometers and ultrasonic imaging systems, achieves accurate measurement of blood pressure and high-definition imaging of the internal structure of the body, providing patients with timely and accurate diagnosis and treatment information. ‌
Mobile phone industry: With the increasingly miniaturized design of mobile phones, HDI PCB is widely used in transceiver modules, motherboards, SIM card interfaces, fingerprint recognition modules and other parts of mobile phones due to its high density, high quality and high reliability. ‌
Computer industry: In the computer industry, the application of HDI PCB improves the performance of computers, especially in the fields of high-speed algorithms and multimedia applications, and adapts to the miniaturization trend of computer equipment2. ‌
Automotive electronics: HDI PCB has broad application prospects in the field of automotive electronics. In addition to the dominant mobile phone market, it also involves multiple fields such as automobiles, modules and artificial intelligence, demonstrating its key role in complex electronic systems. ‌
Future development trends: With the advent of 5G technology, the demand for HDI PCB will continue to increase, requiring higher speeds and frequencies while adapting to smaller and thinner device designs. Research new micro HDI PCB boards to adapt to future development trends. ‌

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What is the structure of HDI PCB?

What are the advantages of HDI PCB?

What are the disadvantages of HDI PCB?

What are the applications of HDI PCB?

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What are the holes in a PCB called?

What is a through hole

What is a blind via?

What are buried vias?

What is a microvia?

What are Mounting holes？

What are thermal vias?

FAQ About board electronics with holes

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‌What is a high frequency pcb communication circuits

Definition of high frequency pcb communication circuits

Advantages of high frequency pcb communication circuits

Classification of high frequency pcb communication circuits

How to choose high-frequency circuit board high-speed board

Composition and key components of high frequency pcb communication circuits

Application of high frequency pcb communication circuits

Design Guidelines for High Frequency PCB Communication Circuits

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What is High Density Interconnect PCB?

What is the Difference Between Connect and Interconnect?

What is HDI PCB Stackup?

What are the Advantages of HDI PCB?

5 Types of Vias in HDI PCB

What is the Difference Between PCB and HDI PCB?

PTH vs. HDI PCB

High Density Interconnect PCB Applications

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