Posts Tagged ‘pcb design’

Monday, August 26th, 2024

PCB (Printed Circuit Board) boards can be classified according to their constituent materials and characteristics. PCBs are classified into single-sided boards, double-sided boards, and multi-layer boards according to board applications. They are classified into flexible PCB boards (flexible boards), rigid PCB boards, rigid-flexible PCB boards (rigid-flexible boards) according to materials, etc.

PCB is an important electronic component, a support for electronic components, and a provider of electrical connections for electronic components. Since it is made using electronic printing technology, it is also called a printed circuit board. PCB is simply a thin board with integrated circuits and other electronic components.

1. Single-sided board:

On the most basic printed circuit board, parts are concentrated on one side and wires are concentrated on the other side. Because wires only appear on one side, this type of printed circuit board is called a single-sided board. Because single-sided boards have many strict restrictions on designing circuits (because there is only one side, wiring cannot cross and must go around a separate path), early circuits used this type of circuit board.

2. Double-sided board

This type of circuit board has wiring on both sides. In order to connect the wires on both sides, there must be a proper circuit connection between the two sides. This connection between the circuits is called a guide hole. A guide hole is a small hole filled or coated with metal on a printed circuit board, which can be connected to the wires on both sides. Because the area of a double-sided board is doubled that of a single-sided board, and the wiring can be interlaced (can go around to the other side), double-sided boards can be used on more complex circuits than single-sided boards.

3. Multilayer board:

In order to increase the area that can be wired, multilayer boards use more single- or double-sided wiring boards. Multilayer boards use several double-sided boards, and put an insulating layer between each layer of boards and glue them firmly. The number of layers of the circuit board represents how many independent wiring layers there are, usually an even number of layers, and includes the two outermost layers.

4. Flexible PCB board

Flexible PCB board is a printed circuit board made of a flexible substrate. Its advantage is that it can be bent, which is convenient for the assembly of electrical components. Flexible circuit board, flexible PCB, flexible circuit and multi-function printed circuit are other names for these circuit boards. These printed circuit boards are made using the same components as rigid printed circuit boards. The main difference is that the circuit board is designed to bend to the desired shape throughout the application process. These PCBs are available in single-sided, double-sided, and multi-layer configurations. This helps reduce the complexity of unit assembly.

5. Rigid PCB Board

Rigid PCB is a circuit board that cannot be twisted or folded. The base material of the board is a rigid substrate, which gives the board rigidity and strength. They are composed of multiple layers, including substrate layers, copper layers, solder mask layers, and silk screen layers, which are bonded together by adhesives and heat. While some circuit boards are single-sided, double-sided, or multi-layered, rigid PCBs can be any of these as needed. However, once made, they cannot be modified or changed.

6. Rigid-Flex Board

Rigid-Flex Board is a hybrid circuit board that combines elements of flexible and rigid circuit boards to form a foldable or continuously bendable circuit board, which is usually molded into a curved shape or curve during the manufacturing process.

The flexible portion of the circuit board is often used for interconnections between rigid circuit boards, allowing narrower wires to take up less space, thereby reducing the size of the circuit board. Using flexible PCBs for interconnections often eliminates the need for bulky and heavy connectors, making rigid-flex boards lighter. The design of rigid-flex boards is slightly more complicated because these boards are 3D constructed, allowing the board to be folded or twisted to produce the shape required for the product.

7. High-frequency PCB board

High-frequency circuits refer to the overall circuit board design, not the other types of circuit board structures we described earlier. These PCBs are designed to conduct signals over 1 GHz.

High-frequency boards mostly use FR4-grade glass-reinforced epoxy boards, polyphenylene ether (PPO) resins, and Teflon, but Teflon has a low and stable Dk value, low dielectric loss, low hygroscopicity, and is slightly more expensive.

When designing high-frequency circuits, various factors must be considered, such as Dk value, dissipative loss, and dielectric thickness. The DK value of the substrate is an important factor to remember. Substrates with a higher probability of Dk value changes usually experience impedance changes, which affects the harmonics that make up the electrical signal, resulting in poor signal integrity.

8. Copper substrate

Copper substrate is a metal substrate with high thermal conductivity, suitable for high-frequency circuits and areas with large high and low temperature changes and heat dissipation and architectural decoration industries for precision communication equipment.

The copper substrate circuit layer requires a large current carrying capacity, and a thicker copper foil should be used, with a thickness of generally 35μm~280μm. The thermal conductive insulation layer is the core technology of the copper substrate. It is composed of core thermal conductive components and high molecular polymers, with low thermal resistance (0.15), excellent viscoelastic properties, resistance to thermal aging, and the ability to withstand mechanical and thermal stress.

The copper substrate metal base is the supporting member of the copper substrate, which is required to have high thermal conductivity. It is generally a copper plate, and a copper plate can also be used (where the copper plate can provide better thermal conductivity). It is suitable for conventional mechanical processing such as drilling, punching and cutting.

9. Aluminum-based PCB board

The design of aluminum-based PCB circuits is similar to that of copper-based PCBs, but the substrate material of aluminum-based PCBs is aluminum metal, rather than the standard glass fiber used in most circuits.

The aluminum layer is reinforced with the least heat-resistant insulation material, which means less heat is transferred from the insulation material to the backing. After applying the insulation layer, another layer of copper is required.

10. High Density Interconnect (HDI) PCB

Among the many types of PCBs, HDI PCB is a circuit with multiple interconnections that takes up very little space. HDI components are mounted close to each other, minimizing PCB space while maintaining high functionality. Boards containing 120-160 pins per square inch are classified as HDI PCBs.

HDI designs integrate dense device mounting and multi-purpose wiring. With the help of microvias, buried vias, and blind vias, compact circuits can be made, minimizing drilling to copper. For the electrical requirements of high-speed signals, HDI PCBs must have high-frequency conduction capabilities, impedance control, and minimal redundant radiation.

11. Thick Copper PCB

Thick copper PCB is also called heavy copper PCB. Basically, it contains more than 2 ounces of copper in the inner and outer layers of the board. Heavy copper transmitters significantly increase the overall thickness of the board; thick copper boards are known for supporting high currents, high temperatures, and cyclical thermal cycles.

12. High TG PCB

Among various types of PCBs, high Tg PCBs are circuit boards designed to work at high temperatures. Glass transition temperature (Tg) is an essential element of any epoxy resin. It is basically the temperature point at which the polymer changes from a hard glass substrate to a soft rubber substrate. The substrates used to make high Tg circuit boards must be flame retardant, which means that they soften instead of burning at the glass transition point (Tg).

The higher the Tg value, the higher the temperature requirement during lamination. Under such conditions, the PCB will become hard and brittle, affecting the aperture size and related electrical properties. Standard boards will soften, deform and melt under such conditions, and their mechanical and electrical properties will be significantly reduced.

Standard FR-4 Tg is between 130-1400C, medium Tg is between 150-1600C, and high Tg is above 1700C. The higher the Tg value, the better the board’s heat, moisture and chemical resistance.

Conclusion:

PCB board types are updated and iterated with the rapid development of the industry, and various types of PCB boards have gradually evolved to cope with various application scenarios, adding corresponding materials according to the required performance. BEST Technology has various PCB types of manufacturing technology, which can meet your any type of PCB needs.

PCB Stack-up Parameter

Internal Copper Thickness After Processing

Base Foil	Min. After Processing
18um (1/2oz)	11.4um
35um (1oz)	24.9um
70um (2oz)	55.7um
105um (3oz)	86.6um
140um (4oz)	117.5um

External Copper Thickness After Plating

Base Foil	Min. Class 2	Min. Class 3
12um (3/8oz)	29.3um	34.3um
18um (1/2oz)	33.4um	38.4um
35um (1oz)	47.9um	52.9um
70um (2oz)	78.7um	83.7um
105um (3oz)	108.6um	113.6um
140um (4oz)	139.5um	144.5um

Common Prepreg (PP) Properties

Type	Thickness (mm)	Resin (%)
106	0.05	65
1080	0.075	65
2116	0.12	55
7628	0.2	46

Common Material List

Medium Tg	Shengyi S1000-H
	ITEQ IT-158
	Elite EMC-825
High Tg	Shengyi S1000-2M
	ITEQ IT-180A
	Elite EMS-827

Common Core Thickness

PCB Stack-up and Impedance Control Guidelines

Design Tips – Stack-up

1. Ensure the stack-up remains symmetric.

2. Typically, a foil build is recommended. Special core builds, like those with Rogers, are possible but less common.

3. For boards thicker than 1mm, the standard thickness tolerance is +/-10%. For 1mm boards, the standard tolerance is +/-0.1mm. Any board with a thickness ≤1mm requires approval from Best Tech.

4. The minimum dielectric thickness will be 90µm, according to IPC standards, unless otherwise specified by the FAB drawing and there are no micro vias.

5. Use a maximum of three sheets of prepreg to bond the layers.

6. While the stack-up used in production may differ slightly from the specified one, an Engineering Query (EQ) will be sent for confirmation.

7. Variations can occur due to factors like copper distribution and available materials.

8. Thicker copper foils require thicker dielectrics between layers, and the foil thickness after processing differs from the base foil thickness.

9. Additionally, variations in resin percentage for the same prepreg type can impact the final prepreg thickness.

10. When incorporating micro vias, consider the aspect ratio—recommended at 0.8:1 and advanced at 1:1—when selecting prepreg.

If you need special materials, thickness tolerances, or stack-ups, contact Best Technology for guidance. Below are some suggested stack-ups for different layers PCB.

Impedance Parameters Needed for Calculation

Symbol	Feature
H1, H2, H3..	Dielectric thickness between copper layers after pressing
Er1	Dielectric constant of prepreg or core used between copper layers.
W1	The bottom width od impedance lines, which is the customer required impedance trace width.
W2	The top width of impedance lines.
S1	The space between two differential impedance traces.
T1	Finished copper thickness, which is different with our normal definition.
C1	Solder mask thickness on material.
C2	Solder mask thickness on copper.
C3	Solder mask thickness on material between traces (C1 = C3).
CEr	Dielectric constant of solder mask. Normally use 3.4 to calculate.

Tolerance of Impedance Control

Type of Impedance	Common Requested Value	Tolerance of Impedance Control
Type of Impedance	Common Requested Value	General	Moderate	Advanced
Single/Single Coplanar	40Ω/510Ω/75Ω	+/-10%	+/-8%	+/-5%
Differential/Differential Coplanar	90Ω/100Ω/120Ω	+/-10%	+/-8%	+/-5%

Relationship between Parameters and Impedance Value

Parameters Modification		Effect on Impedance Value
Parameters	Increase/Reduce	Impacts on impedance	Impedance value increase/reduced
H (dielectric thickness)	Increase	Big	Increase
W (trace width)	Increase	Big	Reduced
S (trace space)	Increase	Big	Increase
T (copper thickness)	Increase	Low	Reduced
C (solder mask thickness)	Increase	Low	Reduced

Design tips – Impedance

When signal speeds exceed 2 GHz and timing is critical, consider using better materials such as medium, high, or ultra-high-speed options, along with flat glass styles. To ensure a reliable lamination process and prevent resin starvation, allow the factory to select the number of prepregs, prepreg styles, and resin content in the stack-up.

Key factors influencing impedance signal losses include:

1. Line Length: Signal losses are directly proportional to the line length—shorter lines result in fewer losses, while longer lines lead to greater losses.

2. Dielectric Loss: These losses can be minimized by selecting appropriate materials.

3. Copper Loss: This includes losses from the cross-sectional area (affected by stack-up design) and surface roughness, which can be reduced through material selection and proper stack-up configuration.

If you require impedance tolerances tighter than +/-10%, discuss your design possibilities with the Best Technology team.

When designing rigid-flex boards, note that separate calculations are necessary for both the rigid and flex sections of the same signal. Manufacturers will adjust the thickness and dielectric constant of the solder mask based on their solder mask properties and printing method. Variations in resin content for the same prepreg type can also affect impedance. For assistance with impedance calculations, contact Best Technology for support.

Checklist of Necessary Information for Impedance Calculations

1. Specify the type, value, and tolerance of impedance control.

2. Ensure you define the width and space of impedance traces, as well as the layers where these traces will be present, along with the layers to be considered as reference points.

3. Identify the type of material and final board thickness, and provide a reference stack-up for the design.

4. Confirm the finished copper thickness on external and internal layers, and note if any special type of solder mask is required.

5. Always request Best Technology’s stack-up before starting the routing design.

What is the standard for PCB assembly?

The standards for PCB assembly mainly include PCB panel specifications, ISO standards, IPC standards, JEDEC standards, and ROHS standards. ‌

‌PCB panel specifications‌ involve the width, shape, frame design, center distance between small boards, setting of positioning holes, arrangement of reference symbols, and positioning of large components of the panel. The panel frame should adopt a closed-loop design to ensure that the panel is fixed on the fixture without deformation.

‌ISO standards‌ emphasize key factors such as fit tolerance, surface roughness, contact area, and tightening force in PCB tight-fit installation to ensure the accuracy and stability of installation‌.

‌IPC standards‌ include IPC-7711 and IPC-A-600E, the former provides basic recommendations and guidelines for the design and manufacture of printed boards, and the latter provides acceptable conditions and practice guidelines for printed boards.

‌JEDEC standards‌ provide specifications for circuit board materials, dimensions, interfaces, etc., including material selection, dimension design, interface specifications, test methods and quality assurance.

‌ROHS standard‌ is a directive on the restriction of the use of hazardous substances, aimed at reducing the impact on the environment and human health. It stipulates the use restrictions of hazardous substances such as lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls and polybrominated diphenyl ethers.

Compliance with these standards ensures the quality, safety and environmental friendliness of PCB products, and also provides clear guidance and specifications for the design, manufacture and assembly of PCBs.

Why is PCB assembly so expensive?

The high cost of PCB assembly is mainly due to the combined influence of multiple factors. ‌

First, the production cost of PCB boards is affected by materials, design and manufacturing complexity, precision and quality, and supply chain and regional differences. PCB boards are mainly made of materials such as copper, fiberglass and epoxy resin, and the cost of these materials directly affects the price of PCB boards.

The complexity of the design and manufacturing process, including pre-processing, image transfer, electroplating, etching, inspection and trimming, and post-processing, requires precise tools and professional skills, which will also be reflected in the cost. High-precision PCB boards require higher manufacturing costs because they require more precise tools and more stringent manufacturing processes.

Details in the PCB assembly process, layer selection, and the application of HDI technology will all have an impact on the cost. Every small change may cause the cost to plummet, so if you want to save money without losing performance, you need to consider these factors comprehensively.

In addition, the welding process is also a costly link. Soldering is a key step in fixing electronic components to PCBs. This process requires heating each joint separately for welding, which is a slow and laborious process.

Finally, the price of PCBs is also affected by factors such as materials, surface processing, design standards, copper foil thickness, quality acceptance standards, and mold fees and test frames. For example, different materials, surface processing, and copper foil thickness will lead to price differences.

In summary, the high cost of PCB assembly is mainly due to the combined effect of multiple factors such as material cost, manufacturing complexity, precision and quality requirements, production needs, and specific design and quality requirements.

What does PCB stand for?

PCB stands for Printed Circuit Board. ‌

Printed circuit board (PCB), also known as printed circuit board, is an indispensable component in electronic engineering. It is the support of electronic components and also the carrier of electrical connection of electronic components.

Printed circuit boards are widely used in various electronic devices. Printed circuit boards can be divided into single-sided boards, double-sided boards, multi-layer boards, etc. according to the number of layers of circuit boards. Among them, multi-layer boards refer to printed boards with more than two layers. It consists of connecting wires on several layers of insulating substrates and pads for assembling and welding electronic components. It has the function of conducting each layer of circuits and insulating each other.

The wide application of printed circuit boards makes it possible to miniaturize and visualize the circuits of electronic devices, which plays an important role in the mass production of fixed circuits and optimizing the layout of electrical appliances. This type of circuit board uses polyimide or polyester film as the substrate, and has the characteristics of high wiring density, light weight, thin thickness and good bendability.

What is the difference between PCB and PCBA?

The main difference between PCB and PCBA lies in their definition, function, application and manufacturing process. ‌

Definition:

PCB (printed circuit board) is a basic electronic component made by electronic printing, mainly used as a support for electronic components, and does not contain any active or passive components.

PCBA (printed circuit board assembly) is a circuit board assembly with specific functions formed by soldering electronic components to PCB through processes such as SMT (surface mount technology) or THT (through-hole mounting technology). PCBA contains PCB and all necessary electronic components, which work together to realize the preset functions of the circuit board.

‌Function and application‌:

The main function of PCB is to support and connect electronic components, while PCBA integrates electronic components into a complete circuit system, which can be used in the manufacture of various electronic products.

PCBA is the core part of electronic products and directly determines the performance and function of the product.

‌Manufacturing process‌:

The manufacturing process of PCB includes circuit design, PCB board design, PCB template production, copper foil etching, drilling, tin spraying and board making.

The production of PCBA requires component mounting, welding, testing and other processes.

In summary, the main difference between PCB and PCBA lies in their definition, function, application and manufacturing process. PCB is a basic electronic component, mainly used to support and connect electronic components, while PCBA is a finished product formed by welding electronic components to PCB. It has specific circuit functions and is an indispensable part of electronic products.

What is the difference between PCB manufacturing and assembly?

The main difference between PCB manufacturing and assembly is that they involve different processes and focuses. ‌

‌PCB manufacturing‌ mainly involves the process of converting raw materials into printed circuit boards through a series of process flows, including design, layout, etching, lamination, drilling, welding and other steps, and finally forming a complete and usable printed circuit board.

‌PCB assembly‌ is the process of soldering electronic components to the printed circuit board according to the design requirements after the PCB is manufactured. The focus of assembly is to ensure that all components are in the correct position and direction, the pins of each component are fully soldered to the designated pads, and there is no excess solder or other excess materials to ensure the normal operation and reliability of the circuit board.

In short, ‌manufacturing‌ covers the entire production process from raw materials to finished products, including design, production and testing, while ‌assembly‌ is a link in the manufacturing process that focuses on accurately mounting electronic components on printed circuit boards to ensure the final function and performance of the product.

Conclusion:

PCB assembly is an important part of manufacturing and affects the quality of the final product. Therefore, choosing the right manufacturer becomes particularly important. BEST Technology is committed to becoming the world’s most trusted one-stop electronic circuit solution provider, while focusing on PCBA prototyping and small batch production. Choosing us will get the best quality products.

Is PCB design hard to learn?

PCB design is not difficult to learn. The key lies in mastering the relevant basic knowledge and practical experience.

PCB design mainly involves electronic circuit knowledge and software operation skills. For people with electronic circuit foundation, it is relatively easy to learn the use of PCB design software. It is important that learners should use their spare time to learn and practice at the same time. They can assist in learning by watching video tutorials. These resources can help understand the basic concepts and skills of circuit design and software operation.

In addition, the difficulty of PCB design lies mainly in the design of wiring rules, which is the most complex and critical part of PCB design. Beginners should pay attention to the design of conventional constraint rules, such as the size of vias, line width and line spacing, etc., which need to be mastered through practical operation and practice. Just reading materials is not enough. Practical operation and practice are the key to improving PCB design capabilities.

In general, although PCB design involves certain technical difficulties, it can be gradually mastered through systematic learning and practice.

What should I learn before PCB design?

Before PCB design, you need to learn the following key knowledge and skills:

1. Basic knowledge reserve: First of all, you need to understand various electronic components, such as resistors, capacitors, inductors, diodes, triodes, integrated circuits, etc. You also need to be familiar with common circuit topologies, such as amplifier circuits, filter circuits, oscillation circuits, and their functions and representation methods in circuits.

2. PCB design software: Be proficient in at least one PCB design software for schematic design, component layout, wiring, and generation of PCB production files, such as Altium Designer, EAGLE, PADS, OrCAD, etc.

3. Circuit board manufacturing process: Understand the manufacturing process of PCB circuit boards, including substrate material selection, circuit pattern transfer, etching, drilling, welding, assembly, etc.

4. Component packaging: Familiar with the packaging types and sizes of various components, such as DIP, SOP, QFP, BGA, etc., as well as their characteristics and usage scenarios.

5. Basic terms and concepts: Master some basic PCB terms, such as microstrip, stripline, differential line, via, solder mask, silk screen, structural diagram, etc.

6. Circuit function and signal flow: Understand the function and signal flow of the circuit, and be able to distinguish between digital circuits and analog circuits, as well as places with large and small currents.

By mastering the above knowledge and skills, you can better design and layout circuits, improve the performance and reliability of circuit boards,

Which software is used for PCB design?

1. Altium Designer is a powerful PCB design software that provides a wealth of tools and libraries to quickly create complex circuit board designs. This software has an intuitive interface and powerful simulation functions to help designers quickly verify the correctness of the design. It also supports multiple design file formats, which is convenient for collaboration with other design tools.

2. Cadence Allegro is a comprehensive circuit board design software with powerful layout and routing tools, as well as multiple simulation and verification tools to ensure the correctness of the design. It also supports multiple design file formats for team collaboration.

3. Mentor Graphics DesignX is also a powerful PCB design software that provides a variety of tools and libraries to help designers quickly create complex circuit board designs. It also has an intuitive interface and powerful simulation functions, and supports multiple design file formats.

4. PADS is a professional circuit board design software with powerful layout, routing, simulation and verification functions, which can quickly complete complex PCB design work. It also supports multiple design file formats, which is convenient for collaboration with other design tools.

These software are all commonly used PCB design tools with powerful layout, routing, simulation and verification functions, which can help designers quickly complete complex PCB design work.

What is the basic rule of PCB design?

The basic rules of PCB design involve many aspects, including layout, routing, power and ground design, signal integrity, etc.

1. Layout design:

Follow the design principle of placing in a straight line along the signal flow direction to avoid the signal from circling back and forth to reduce the impact of direct signal coupling.

The filtering, protection and isolation devices of the interface circuit should be placed close to the interface to achieve effective protection, filtering and isolation effects.

For high-speed signals or high-current signals, multi-layer board design should be considered to control the signal loop area.

2. Wiring rules:

Control the length of the trace, especially for important signal lines, such as clock signals, the trace length should be shortened as much as possible to reduce unnecessary interference.

Avoid forming self-loop traces to reduce radiation interference.

Follow the principle of minimum ground loop, design the signal line and its loop to form the smallest possible loop area to reduce external radiation and external interference.

3. Power and ground design:

The power plane should be retracted a certain distance relative to its return ground plane to effectively suppress edge radiation problems.

Avoid overlapping of different power layers in space to reduce interference between different power supplies.

4. Drawing:

When drawing the board frame, a specific line width should be used to ensure that the error between the board frame size and the assembly size is within the allowable range.

Set a reasonable origin to ensure that the coordinates of the SMT original are within the first quadrant.

Set a prohibited area, especially prohibiting routing and placing components within a certain range around the mounting hole.

Following these basic rules can ensure the effectiveness and reliability of PCB design, while improving product performance and user experience.

How long does it take to design a PCB board?

It takes about 1-2 days to design a PCB board, and the specific time depends on multiple factors, including the number of layers of the PCB, design complexity, etc.

‌Number of layers and complexity‌: The more layers the PCB has, the more complicated the design process is, and more time and delicate work are required to ensure the correctness and performance of the circuit.

‌Design stage‌: PCB design includes multiple steps such as design layout, schematic drawing, and PCB design conversion.

The time to design a PCB board is a comprehensive estimate involving multiple stages and factors.

What is the proper PCB layout?

Proper PCB layout involves many aspects, including structural requirements, heat dissipation considerations, component spacing, routing rules, etc. ‌

‌Structural requirements‌: First, the PCB layout must meet the structural requirements, including the location arrangement of structural components such as power sockets and DVI interfaces.

‌Heat dissipation considerations‌: The distribution of heat sinks should be even to ensure good ventilation of the air path. Avoid heat sinks blocking the air path to avoid affecting the heat dissipation effect‌.

‌Component spacing‌: Capacitors, ICs, etc. should be kept away from thermal components to avoid being affected by heat.

‌Routing rules‌: The design of the current loop should consider the convenience of threading, and the lead hole spacing should not be too far or too close. The layout of input/output and AC/socket should meet the consistency of the length of the two lines, leaving a certain space margin, and pay attention to the position of the plug wire buckle and the convenience of plugging and unplugging‌.

‌Special component layout‌: For high-frequency components and components with high potential difference, the distance between them should be increased to avoid electrical interference and damage.

Wiring design parameters‌: including the line width of the copper trace, the minimum gap between the copper foil traces, the minimum distance between the copper foil traces and the edge of the PCB board, etc. ‌ .

In summary, the correct PCB layout is a process that comprehensively considers the structure, heat dissipation, component spacing, routing rules and wiring design parameters, aiming to optimize the performance and reliability of the circuit board.

Conclusion:

Designing a PCB board is a complex and meticulous process involving multiple steps and considerations. Systematically complete the design process of a PCB board. Each step requires careful operation and multiple checks to ensure the quality and reliability of the final product. ‌ BEST Technology’s PCB designers have many years of design experience and are far ahead in the industry design. We can meet any PCB design you need.

What is the glass transition temperature and Its Significance?

The glass transition temperature (Tg) refers to the temperature corresponding to the transition from the glass state to the high elastic state. The glass transition is an inherent property of amorphous polymer materials and a macroscopic manifestation of the transformation of the polymer motion form. It directly affects the performance and process performance of the material. Therefore, it has long been the main content of polymer physics research.

The glass transition temperature is of great significance to the application of polymers. Above this temperature, polymers show elasticity; below this temperature, polymers show brittleness. This characteristic must be considered when used as plastics, rubber, synthetic fibers, etc.

The glass transition temperature of mainstream FR-4 boards is approximately between 130-140℃. In the PCB manufacturing process, the temperature needs to be strictly controlled to avoid exceeding the glass transition temperature to ensure the quality of the product.

Is higher glass transition temperature better?

In PCB manufacturing, the higher the glass transition temperature (Tg), the better. ‌

The glass transition temperature is an important performance indicator of polymer materials, which determines the changes in the physical and chemical properties of the material at a specific temperature. When the temperature of the polymer is lower than its glass transition temperature, the material exhibits hard and brittle characteristics, similar to the glass state; when the temperature is higher than the glass transition temperature, the material becomes soft and exhibits elasticity similar to rubber or leather. This state change has a direct impact on the performance during PCB manufacturing and use.

1. ‌ Temperature deformation resistance ‌:

The higher the Tg value, the stronger the material’s temperature deformation resistance. This means that in a high temperature environment, such as during SMT welding, the PCB substrate is not easy to deform, thereby maintaining dimensional stability, which is crucial to ensure the reliability and long-term use of the circuit board.

2. ‌ Electrical performance and mechanical strength: ‌

The high or low Tg value directly affects the electrical performance and mechanical strength of the PCB. High Tg materials can maintain good physical and chemical stability at high temperatures, thereby maintaining the electrical properties and mechanical strength of the circuit board, which is crucial to improving the quality and reliability of the product.

3. Safety:

PCB materials with high Tg values are not easy to soften or melt at high temperatures, thereby improving the safety and durability of the circuit board and reducing the risk of short circuits or other damage caused by high temperatures.

In summary, choosing PCB materials with higher Tg values is one of the key factors to ensure that the circuit board maintains stable performance and safety in complex manufacturing and use environments.

What is glass transition temperature vs melting temperature?

In PCB manufacturing, glass transition temperature and melting temperature are two different physical properties that describe the state changes of materials under different conditions. ‌

The glass transition temperature (Tg) mainly involves amorphous materials or amorphous regions in partially crystalline materials. At this temperature, the physical state of the material changes from glass to highly elastic.

The melting temperature (melting point) mainly involves the melting process of crystalline materials. For crystalline polymers, the melting point marks the temperature at which the molecular chain begins to move, that is, the material changes from solid to liquid. The melting point is related to the crystallinity and lattice structure of the material and is a physical property unique to crystalline materials.

In short, the glass transition temperature mainly affects the amorphous region in amorphous or partially crystalline materials, while the melting temperature mainly affects crystalline materials and involves the melting process of the entire crystal. These two temperatures reflect the different physical state changes of different materials when heated.

How do you determine the glass transition temperature?

Expansion method, thermomechanical method, differential scanning calorimetry (DSC), DTA method, dynamic mechanical property analysis (DMA) method, nuclear magnetic resonance method (NMR).

Differential scanning calorimetry (DSC) is the most traditional and commonly used measurement method. It measures the relationship between the power difference (heat flow rate) and temperature between the sample and the reference material, and then obtains the glass transition temperature of the material;

Dynamic mechanical analysis (DMA) is the most sensitive method. It measures the sinusoidal alternating stress of constant amplitude applied to the sample, observes the change of strain with temperature or time, and calculates the mechanical parameters to characterize the elastomer;

Thermomechanical analysis (TMA): Use a probe with good sensitivity to measure the expansion coefficient of the material, and measure the glass transition temperature of the material based on this change.

What is the difference between TM and Tg?

In the PCB industry, TM and Tg are two different parameters, representing two different physical properties.

Tm: melting point; m is the melting point of crystalline polymers, that is, the temperature at which crystalline polymers melt. It is the highest use temperature of crystalline polymers when used in plastics and fibers, and it is also their heat resistance temperature and the lowest temperature for molding processing.

What is the Tg of polyurethane?

The glass transition temperature (Tg) of polyurethane is not a fixed value, but a physical quantity determined by the type of resin.

‌There are many types of polyurethane, including polyether, polyester, polyimide, polyurea, etc. Each type of polyurethane has its own specific glass transition temperature.

Shape memory polyurethane has a small volume expansion rate at temperatures below Tg, but increases at temperatures above Tg, which shows the characteristics of its glass transition temperature. Therefore, to determine the glass transition temperature of a specific polyurethane, its specific chemical structure and application field need to be considered.

What is Tg for epoxy?

The Tg value of PCB epoxy resin is usually between 130℃ and 170℃. ‌

The Tg value (glass transition temperature) of PCB (printed circuit board) epoxy resin is an important performance indicator, which reflects the change in the physical state of the material when heated. According to different application requirements, the Tg value of PCB epoxy resin can be divided into several grades:

‌TG130‌: The temperature resistance of this type of board is about 140℃. Common Tg value boards of this type are Shengyi S1141 and Jiantao KB-6164F.

TG150: A medium Tg board with a temperature range of 150°C to 170°C. Common boards with this type of Tg include Shengyi S1141 150 and Jiantao KB-6165F.

TG170: A high Tg board with a temperature range of over 170°C. Common boards with this type of Tg include Shengyi S1170 and Jiantao KB-6167F.

Selecting the right Tg value is critical to ensuring the performance and reliability of the PCB. Although boards with high Tg values are relatively expensive, their superior temperature resistance is indispensable in applications that require higher temperatures, such as aerospace. In addition to Tg values, other factors should be considered when selecting PCB boards, such as thermal decomposition temperature (Td), which is another important indicator for evaluating the stability of boards at high temperatures.

Conclusion:

High Tg represents high heat resistance. Electronic products represented by computers are developing towards high functionality and high multi-layer, which requires higher heat resistance of PCB substrate materials as an important guarantee. BEST Technology focuses on manufacturing high-performance PCB circuit boards and is far ahead in the industry. It has professional production equipment and 18 years of design experience, and has high quality requirements for products.

PCB Line Width and Flow Current Comparison Table Chart

PCB Line Width and Flow Current Comparison Table Chart
Line width (mm)	Current (A)	Line width (mm)	Current (A)	Line width (mm)	Current (A)
0.15	0.2	0.15	0.5	0.15	0.7
0.2	0.55	0.2	0.7	0.2	0.9
0.3	0.8	0.3	1.1	0.3	1.3
0.4	1.1	0.1	1.35	0.4	1.7
0.5	1.35	0.5	1.7	0.5	2.0
0.6	1.6	0.6	1.9	0.6	2.3
0.8	2.0	0.8	2.4	0.8	2.8
1.0	2.3	1.0	2.6	1.0	3.2
1.2	2.7	1.2	3.0	1.2	3.6
1.5	3.2	1.5	3.5	1.5	4.2
2.0	4.0	2.0	4.3	2.0	5.1
2.5	4.5	2.5	5.1	2.5	6.0
Copper thickness 1OZ (0.035mm)		Copper thickness 1.5OZ (0.05mm)		Copper thickness 2OZ (0.7mm)

From the chart as above:

35um copper thickness and 0.4mm line width, the current is 1.1A;

50um copper thickness and 0.4mm line width, the current is 1.35A;

70um copper thickness and 0.4mm line width, the current is 1.7A.

Best Technology PCB Line Width and Flow Current Calculator

When using copper foil as a conductor for large currents, the width of the copper foil should be selected by reducing the current-carrying capacity values from the reference table by 50%. However, there are other methods to address this. In some power circuits, due to PCB constraints, the current-carrying paths are designed as long pads, and solder is added on top of them to form a thick current path. Besides adding tin to the copper foil to increase the current capacity, you can also consider using multiple PCB layers to increase the current. For instance, placing the same circuit on both the top and bottom layers or using short jumper wires can also help increase the current capacity.

How Wide Should the Trace be If Current is 1A?

1. Due to the limited thickness of the copper foil on the copper-clad board, the current-carrying capacity of the copper foil needs to be considered for strip-shaped copper foil that needs to carry a large current. Taking the typical thickness of 0.03mm as an example, if the copper foil is used as a strip-shaped conductor with a width of W (mm) and a length of L (mm), its resistance is 0.0005 L / W ohms. Additionally, the current-carrying capacity of the copper foil is related to the types of components installed on the PCB, their quantity, and the heat dissipation conditions. Under safe conditions, the current-carrying capacity can generally be calculated using the empirical formula: 0.15 W (A).

2. The calculation method is as follows: First, calculate the cross-sectional area of the track. Most PCBs have a copper foil thickness of 35μm (if unsure, you can ask the PCB manufacturer). Multiply this by the trace width to get the cross-sectional area, making sure to convert to square millimeters. There’s an empirical value for current density, which is 15-25 amperes per square millimeter. Multiply this by the cross-sectional area to get the current capacity.

3. I = K T^0.44 A^0.75, where K is a correction factor (0.024 for internal copper traces, 0.048 for external copper traces), T is the maximum temperature rise in degrees Celsius (copper’s melting point is 1060°C), A is the copper cross-sectional area in square mils (not square millimeters, so be mindful of the conversion), and I is the allowable maximum current in amperes (amps). Typically, 10 mil = 0.010 inches = 0.254 mm, which can carry 1A. Therefore, 250 mil = 6.35 mm can carry 8.3A.

4. The calculation of PCB current-carrying capacity has long lacked authoritative technical methods and formulas. Experienced CAD engineers can make accurate judgments based on personal experience. However, for CAD novices, this can be quite a challenge.

5. PCB current-carrying capacity depends on the following factors: trace width, trace thickness (copper foil thickness), and allowable temperature rise. As we all know, the wider the PCB trace, the greater the current-carrying capacity. Under the same conditions, a 10mil trace can carry 1A, but can a 50mil trace carry 5A? The answer is, of course, no.

Current-Carrying Capacity of External PCB Traces (1mil = 0.0254mm)

Line length – current carrying data chart (unit: A)

Line width (mil)	Line length 5cm	Line length 10cm	Line length 15cm	Line length 20cm	Line length 25cm	Line length 30cm	Line length 35cm	Line length 40cm
4	0.403	0.201.	0.134	0.101	0.081	0.067	0.058	0.050
6	0.604	0.302	0.201	0.151	0.121	0.101	0.086	0.075
8	0.753	0.403	0.268	0.201	0.161	0.134	0.115	0.101
10	0.886	0.503	0.336	0.252	0.201	0.168	0.144	0.126
12	1.011	0.604	0.403	0.302	0.242	0.201	0.173	0.151
16	1.245	0.805	0.537	0.403	0.322	0.268	0.230	0.201
20	1.464	1.007	0.671	0.503	0.403	0.336	0.288	0.252
30	1.964	1.510	1.007	0.755	0.604	0.503	0.431	0.378
40	2.419	2.013	1.342	1.007	0.805	0.671	0.575	0.501
50	2.844	2.517	1.678	1.258	1.007	0.839	0.719	0.629
60	3.246	3.020	2.013	1.510	1.208	1.007	0.862	0.755
80	3.999	3.999	2.684	2.013	1.611	1.342	1.150	1.007
100	4.701	4.701	3.356	2.517	2.013	1.678	1.438	1.258
120	5.365	5.365	4.027	3.020	2.413	2.013	1.726	1.510
160	6.610	6.610	5.369	4.027	3.221	2.684	2.301	2.013
200	7.770	7.770	6.711	5.033	4.027	3.355	2.876	2.517
240	8.868	8.868	8.053	6.040	4.832	4.027	3.451	3.020
280	9.917	9.917	9.395	7.047	5.637	4.698	4.027	3.523
320	10.925	10.925	10.738	8.053	6.443	5.369	4.602	4.027
360	11.899	11.899	11.899	9.060	7.248	6.040	5.177	4.530
400	12.844	12.844	12.844	10.067	8.053	6.711	5.752	5.033

For low-frequency, low-current PCB designs, the general trace width is around 10 mil, and for more compact designs, 6 mil may be used. The key factor in determining PCB trace width is the current: higher currents require wider traces, while lower currents can use narrower traces. The operating frequency also plays a role in determining the width.

Ideally, the width of the PCB power trace should be at least 40 mil, with a minimum of 25 mil when conditions allow. Always opt for the widest trace possible to accommodate the current.
Consider the actual current flow. Typically, a 10 mil trace can carry a maximum of 1A, so adjust the width according to the current requirements.
The ground trace should be wider than the V+ trace and should surround the V+ trace to reduce interference and power ripple.
When converted to millimeters, the positive power trace should be no less than 0.6mm wide, while the negative power trace should be wider than the positive trace and surround it.

How Are Multilayer Boards Constructed?

The multi-layer board is composed of several single sided PCB for the outer layer and some double-sided PCBs for the inner layer.

l Single-Sided Boards

In the most basic PCB design, components are placed on one side of the board, and the wiring is on the other. This is called a single-sided board. Due to strict routing limitations (since traces cannot cross each other), single-sided boards are mostly used in simpler circuits.

l Double-Sided Boards

Double-sided boards have wiring on both sides. To connect the circuits on both sides, vias (small holes filled or coated with metal) are used. The larger area and ability to route traces through both sides make double-sided boards more suitable for complex circuits compared to single-sided boards.

l Multilayer Boards

To increase routing space, multilayer boards are created by combining multiple layers of single-sided or double-sided boards. For example, a four-layer or six-layer PCB might consist of a double-sided board as the core with single-sided boards on either side, all bonded together. Multilayer boards allow more complex designs, and while most modern PCBs use between 4 to 8 layers, designs with up to 100 layers are possible for advanced computing needs, though they are increasingly rare due to advances in other technologies.

The number of layers doesn’t always indicate the number of wiring layers—some layers may be added purely to adjust board thickness. Most motherboard designs consist of 4 to 8 layers, and while extremely complex multilayer boards were once used in supercomputers, they are now often replaced by clusters of standard machines.

Trace Width and Copper Pour Guidelines

When designing PCBs, a general rule is to use thicker traces for high-current areas (e.g., 50 mil or more) and thinner traces for low-current signals (e.g., 10 mil). In some electromechanical control systems, the instantaneous current through a trace can exceed 100A, in which case thin traces would fail.

An empirical rule of thumb is that 10A can safely pass through 1 square millimeter of trace cross-section. If the trace is too thin, it may burn out under high current. This phenomenon follows the energy equation: Q = I^2*t. For example, a trace designed for 10A can likely handle a sudden current spike of 100A for microseconds, but beyond that, other factors like stray inductance in the trace could generate strong counter-electromotive forces, potentially damaging other components. Longer and thinner traces have higher stray inductance, so their length must also be considered.

Copper Pouring on Vias and Pads

Most PCB design software offers options for how to connect vias or pads to copper planes, such as direct pour, orthogonal spokes, or 45-degree angled spokes. While many designers select based on aesthetics, these choices affect both current capacity and heat dissipation.

l Direct Pour: This method provides the strongest current-carrying capacity for pads or vias, making it ideal for high-power circuits. However, direct pours also enhance heat conduction, which, while beneficial for cooling components, can complicate soldering by rapidly dissipating heat, requiring higher soldering temperatures and larger soldering irons, which may reduce production efficiency.

l Orthogonal and 45-Degree Spokes: These methods reduce the contact area between the pad or via and the copper, slowing heat dissipation and making soldering easier. For low-power signal traces, orthogonal or 45-degree spokes are recommended, while direct pour is necessary for pads carrying high currents. The choice between orthogonal and 45-degree spokes is mainly aesthetic.

What is a High Speed Circuit PCB?

High-speed PCB is a circuit board that can support signal transmission. High-speed signals usually refer to signals with frequencies higher than 50MHz, such as high-speed digital signals, high-speed analog signals, etc. These fast transitions can introduce challenges like signal reflections, electromagnetic interference (EMI), and crosstalk, which can disrupt performance if not properly managed.

Additionally, these signals will be affected by board materials, layout, wiring and other factors during transmission. Therefore, a specially designed circuit board is required to ensure the integrity and reliability of the signal. Here is a 4 layers high speed PCB for Iradar device with 50ohm single-ended impedance control.

Features of High-Speed PCB

High frequency

Low permittivity and low loss factor

Multilayer design

Strict impedance control

High-precision manufacturing

Low noise characteristic

High density circuit layout (micro-vias)

High performance

What is Considered High-Speed PCB Design?

High-speed PCB design focuses on managing the complexities that come with high-frequency signals and fast switching. Key considerations include:

– Signal Integrity: Ensuring signals travel without distortion or loss.

– Power Management: Distributing power effectively to minimize noise and voltage drops.

– Heat Handling: Managing heat from high-speed components to prevent overheating.

– Impedance Matching: Keeping impedance consistent to reduce signal reflections and loss.

– Differential Pair Routing: Reducing EMI and crosstalk by routing complementary signal pairs together.

This type of high speed pcb design requires a solid understanding of electromagnetic principles, advanced simulation tools, and precise manufacturing techniques. For those new to high-speed PCB design, Best Technology offers expert guidance and solutions.

What’s the Best Material for High-Speed PCB Design?

Choosing the right material for high speed pcb is vital for maintaining signal integrity and achieving optimal performance. The material impacts the board’s dielectric constant (Dk), loss tangent, and overall signal quality. Common materials include:

– FR4: Widely used but not ideal for very high frequencies due to higher loss tangent.

– Rogers (RO4000 series): Preferred for high-speed designs thanks to its low dielectric constant and loss tangent.

– Teflon: Excellent for high-frequency applications but more expensive and harder to process.

Selecting the appropriate material ensures the PCB can handle high-speed signals without compromising performance.

Where is the High-Speed PCB Commonly Used in?

High-speed circuit boards are widely used in signal transmission applications, the typical fields are including:

1. Communication equipment – such as 5G base stations, optical fiber communication equipment, etc.

2. Data center – like high-performance computing, storage servers, etc.

3. Consumer electronics in our daily life – high-end smartphones, tablets, gaming devices, etc.

4. Aerospace and military – high speed are always used in high-end devices. For example, radar, navigation systems and other equipment with high reliability requirements.

What is the 3H Rule in High Speed PCB Design?

The 3H rule is a guideline suggesting that signal traces should be spaced at least three times the height of the dielectric (3H) between the signal layer and the adjacent ground or reference layer. This helps minimize crosstalk and maintain signal integrity, particularly for high-speed digital signals with rise times of 1 ns or less. Key aspects include:

– Trace Spacing: Keeping traces apart by at least 3H reduces electromagnetic coupling and interference.

– Signal Integrity: Adequate spacing helps maintain clear signals in high-speed circuits.

– Effectiveness: This rule is especially beneficial for fast digital signals, reducing the risk of crosstalk and interference.

For instance, if the dielectric height between the signal layer and the reference layer is 0.2 mm, traces should be at least 0.6 mm apart to follow the 3H rule.

How to Design a High-Speed Board?

Designing a high-speed PCB involves several strategies to ensure effective signal transmission, power distribution, and minimal EMI. Here’s a step-by-step approach:

Component Placement and Layer Stack-Up

Place high-speed components to minimize signal paths and interference. Group related components to simplify routing. In addition, create a layer stack-up that supports controlled impedance and reduces signal loss. Use ground planes between layers for a return path for high-frequency currents.

Trace Routing and Impedance Control

Keep high-speed traces short and direct, avoiding right-angle bends. Use microstrip or stripline configurations for controlled impedance and minimal noise. For impedance control, calculate and ensure consistent impedance for traces. Use differential pair routing for high-speed signals to reduce EMI and crosstalk.

Power Distribution and EMI Mitigation

Use decoupling capacitors near high-speed components to filter noise and stabilize the power supply. Design a robust power distribution network to minimize impedance and ensure stable voltage. And employ proper grounding and shielding techniques. Route high-speed signals on inner layers between ground planes to reduce EMI and provide a consistent return path.

Simulation and Testing

Use signal integrity analysis tools like SI or PI to simulate the PCB layout, predicting signal behavior and identifying potential issues. Analyze aspects like eye diagrams to assess signal quality.

High-speed PCB design is a complex but rewarding endeavor that ensures your electronics perform efficiently in high-frequency environments. By understanding the fundamentals and applying the right techniques and materials, you can create robust, high-speed boards. Best Technology is here to assist you with expert advice and solutions for your high-speed PCB needs.

PICE card

[1]: Main chip: XCKU11P

[2]: 30A maximum current

[3]: Single pair differential line, 10G optical network

[4]: 14 layers PCB

If you need a custom industrial PCB design, please feel free to contact us.

Video decoder

[1]: Xlinx: XC7K325T, Hisilicon: HI3521DV100_VI

[2]: Single pair differential line, 10G optical network, memory of DDR4

[3]: 12 layers PCB

Why choose us?

We are a China based fabricator with over 17 years experience, what we provide not only including PCB design service, but also PCB fabricating, PCB duplicating and component sourcing and so on. Choose Best Technology you can enjoy:

Professional engineer evaluation

DFM analysis

One-time successully on prototyping

SI analysis of signal integrity

Electromagnetic compatibility (EMC) analysis

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3. Multilayer board:

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7. High-frequency PCB board

8. Copper substrate

9. Aluminum-based PCB board

10. High Density Interconnect (HDI) PCB

11. Thick Copper PCB

12. High TG PCB

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