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A Comprehensive Analysis of Soldering Defects

Friday, November 15th, 2024

PCB assembly involves mounting electronic components onto bare PCB boards to create semi-finished devices. In this process, soldering is the initial and essential step. Today, we’ll discuss the common soldering issues that arise during PCB assembly and how to prevent them.

Soldering Defects

Soldering defects are issues that arise when joints do not meet the expected quality standards. These defects can impact the functionality, reliability, and longevity of a product.

Some typical issues include software design flaws, overheating, incorrect component placement, and power supply issues. Every manufacturer should be aware of these potential pitfalls to ensure reliable and efficient PCB assembly.

A Comprehensive Analysis of Soldering Defects

Why Soldering Defects Occur?

Soldering defects can occur during the assembly process, potentially leading to wasted resources, damaged reputation, product malfunctions, and most critically, loss of time—frustrating both manufacturers and clients. However, by understanding common PCB failure causes, you can address them quickly and effectively.

‌‌Poor Solderability of Holes Vias

Poor solderability of holes can lead to soldering defects, affecting the parameters of components in the circuit and causing unstable connections between components and inner layers in multilayer boards. This can result in the failure of the entire circuit.

Soldering Temperature

The soldering temperature, whether too high or too low, and inadequate surface cleanliness can affect the soldering quality. When the temperature is too high, the solder spreads quickly and is prone to oxidation, leading to defects. When the temperature is too low, the solder may not fully melt, resulting in weak joints.

Flux Issues

The quality and application of flux also impact soldering quality. Insufficient or poor-quality flux can cause poor wetting, resulting in weak and dull solder joints. Excessive flux may lead to overheating, causing rough joint surfaces.

Solder Issues

The quality and fluidity of the solder directly affect the soldering outcome. Poor-quality solder or solder with low fluidity can lead to weak and dull joints, or defects where the solder covers less than 80% of the pad.

PCB Design Issues

Poor PCB design can also result in soldering defects. For example, excessively long traces can increase impedance and noise, affecting soldering quality. Components generating heat without proper heat dissipation can also lead to soldering issues.

Operational Issues During Soldering

Problems such as insufficient soldering time, improper temperature control, or loose component leads during soldering can all result in defects.

How many types of soldering defects are there?

There are several types of soldering defects that can occur during the PCB assembly process. Here is a list of common soldering defects:

Cold Joints
Bridging
Insufficient Solder
Solder Balls
Voids
Cracked Joints
Non-wetting
Tombstoning
Pin Holes or Blow Holes
Oxidation Defects
De-wetting
Component Misalignment
Solder Splashes
Excessive Solder

How Do You Troubleshoot Soldering? -One by One

Cold Joints

Cold joints occur when the solder doesn’t heat properly, resulting in weak, dull, and rough connections. To prevent this, use a soldering iron with adequate power and maintain the correct soldering temperature (typically between 350°C to 400°C for leaded solder). Ensure that both the pad and component lead are evenly heated before applying solder. The solder should flow smoothly around the joint. Using a clean, well-tinned soldering iron tip ensures efficient heat transfer. Additionally, avoid moving the joint before the solder has fully solidified.

Bridging

Bridging happens when excess solder connects adjacent leads, creating shorts. To avoid this, apply an appropriate amount of solder paste using a stencil with the right thickness. Use a fine-tipped soldering iron or a hot air rework tool to apply heat precisely. If bridging occurs, use a desoldering braid or a vacuum desoldering tool to remove excess solder. Practice steady hand movements when applying solder manually and avoid dragging the soldering tip across pads.

Insufficient Solder

Insufficient solder leads to weak joints that can easily break. To fix this, ensure that enough solder paste is applied during the assembly process. Check that the soldering tip transfers enough heat to allow solder to flow adequately across the pad and component lead. If needed, reflow the joint by reheating and adding a small amount of solder to improve coverage and strength.

Solder Balls

Solder balls are tiny spherical particles that can detach and create shorts. To prevent this, maintain a proper reflow profile that allows gradual heating and cooling. Ensure that the solder paste is of high quality and free from contamination. Clean the PCB surface thoroughly to remove dust and oil. Control the application of solder paste to prevent excessive paste that could splatter during heating.

Voids

Voids are gaps in the solder joint caused by trapped gas or flux residue. To minimize voids, pre-bake PCBs to remove moisture that can turn into steam during soldering. Use high-quality, low-residue flux and ensure even application. Adjust the reflow profile to give enough time for gases to escape before the solder solidifies. This reduces the chances of void formation.

Cracked Joints

Cracked joints can form due to rapid cooling or mechanical stress. Allow the solder joint to cool naturally without sudden air exposure. Ensure the PCB is not moved or subjected to vibrations while the solder is cooling. Choose solder materials with good thermal expansion properties to withstand temperature changes. For wave soldering, ensure that components are secure on the PCB before the process starts.

Non-wetting

Non-wetting occurs when the solder does not adhere properly to the pad or lead. This issue is often due to surface contamination or oxidation. Clean the board thoroughly with isopropyl alcohol or a PCB cleaner to remove oils, oxidation, or other contaminants. Use high-quality flux that promotes wetting and re-tin oxidized component leads before soldering. Ensure that the soldering temperature is within the recommended range for proper flow and adhesion.

Tombstoning

Tombstoning happens when one side of a component lifts off the PCB due to uneven heating. This can be addressed by ensuring an even reflow profile where both sides of the component are heated simultaneously. Verify that the solder paste deposit is balanced on each pad to prevent uneven solder melting. Additionally, using smaller components with balanced thermal mass can help prevent tombstoning.

Pin Holes or Blow Holes

Solution: Pin holes or blow holes result from gas escaping during soldering. To reduce this, pre-bake PCBs at a low temperature (e.g., 100°C for one hour) to remove moisture. Use flux that contains fewer volatile components. Optimize the reflow profile to allow flux and trapped gases to escape before the solder solidifies. Ensure that the soldering environment has low humidity to further minimize gas formation.

Oxidation Defects

Oxidation occurs when solder joints are exposed to air for too long before the soldering process. To prevent oxidation, apply flux shortly before soldering to create a barrier against air. Use a nitrogen atmosphere in reflow ovens to reduce oxidation. Regularly clean the soldering tip and apply fresh solder to prevent oxidation on the tip itself.

De-wetting

De-wetting occurs when the solder initially wets the pad but retracts, leaving an uneven surface. This can be caused by contamination or poor-quality solder. Ensure the soldering surface is free from contaminants and oxides by cleaning it with an appropriate cleaner. Use high-quality solder and maintain an optimal soldering temperature to allow proper wetting without over-stressing the solder.

Component Misalignment

Misaligned components can lead to poor connections and defects. Use automated pick-and-place machines for accurate component positioning. Check component alignment manually before reflow if placing by hand. During reflow, use alignment aids or fixtures to ensure components stay in place. Verify that the solder paste stencil and reflow settings are precise for even solder distribution.

Solder Splashes

Solder splashes are small splatters of solder that can lead to shorts or contamination. To prevent this, maintain a consistent reflow profile and avoid sudden movements during the soldering process. Check that solder paste is applied evenly, without excess. Ensure that the soldering environment is stable and free of vibrations.

Excessive Solder

Excessive solder can create thick joints or bridges between pads. Apply solder paste using a stencil with an appropriate aperture size for precise control. Train operators to apply the right amount of solder during manual soldering. Use a fine-tipped soldering iron for better control and to prevent large, excessive solder deposits.

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Definition of Solder Paste Flux

Solder paste flux ‌ is a material used in the field of electronic welding, usually consisting of tin, silver, copper, nickel and other metal powders as well as flux and solvent components. It divided into clean flux and no clean flux. It can form a thin layer of solder paste on the surface of the circuit board, which has strong adhesion and electrical conductivity, and can make electronic components and circuit boards quickly welded together. The ingredients of solder paste flux include:

Solvent: Used to dissolve solid or liquid components and regulate uniformity.
Resin: Increase the adhesion of solder paste, prevent PCB reoxidation after welding.
Activator: Remove oxidized substances from the through hole surface layer of PCB copper film and parts SMT patch, reduce the liquid surface tension of tin and lead.
Thixotropic agent: Adjust the viscosity of solder paste to prevent tailing and adhesion.

There are two common solder paste flux types used in the PCB assembly:

Water-soluble flux: large solubility, strong activity, residue after welding can be cleaned with water. It also called cleaned flux.
No-cleaning flux: little residue after welding, non-toxic and tasteless, does not pollute the environment.

No Clean Flux vs. Clean Flux

When working with PCBs, the choice between no clean flux and clean flux can greatly impact the quality, reliability, and cost of the final product. Understanding their properties, benefits, and appropriate use cases helps in making informed decisions for different soldering scenarios.

Composition and Characteristics

Clean Flux: This type of flux contains active ingredients designed to ensure thorough cleaning during the soldering process. Its composition includes stronger activators that effectively remove oxides and contaminants from the metal surfaces being soldered. However, the resulting residue left behind is often corrosive or conductive. Thus, it must be cleaned after soldering to prevent damage to the circuit or degradation of electrical performance.

No Clean Flux: As its name implies, no clean flux is formulated to leave minimal, non-corrosive, and non-conductive residue. The formulation uses milder activators that still assist in the soldering process but are designed to burn off or remain as safe deposits. These residues do not interfere with the circuit’s electrical properties, allowing the assembly to be used without further cleaning. The residue left is typically clear and dry, posing minimal risk under normal conditions.

Performance and Suitability

Clean Flux is ideal for applications that demand high reliability and minimal contamination. Examples include:

High-frequency circuits: Residue from clean flux can interfere with signal integrity. Removing these residues ensures optimal performance.
Sensitive electronic devices: Medical devices or aerospace electronics that operate in critical conditions benefit from using clean flux due to the necessity of pristine circuit conditions.

No Clean Flux, on the other hand, is suited for:

Consumer electronics: Phones, computers, and household gadgets that do not operate under extreme conditions.
Cost-sensitive production: Mass production benefits from the time and expense saved by eliminating the cleaning step.
Environmentally conscious manufacturing: With no post-soldering cleaning required, the use of chemical solvents is minimized.

Clean Flux Advantages:

Superior Cleanliness: Ensures there is no residue to attract moisture or create pathways for current leakage.

Reliability in Critical Applications: Guarantees circuits remain in top condition, preventing issues in high-risk environments.

Certification Compliance: Many stringent industry standards and certifications require flux to be cleaned for safety and performance assurance.

Disadvantages of Clean Flux:

Additional Steps: Post-soldering cleaning adds time, labor, and costs.

Environmental Impact: Cleaning often involves chemical solvents that must be disposed of properly.

Equipment Needs: Special machinery like ultrasonic cleaners may be required to remove flux residues effectively.

No Clean Flux Advantages:

Time and Cost Savings: Speeds up the production process by eliminating the need for cleaning.

Reduced Chemical Use: Contributes to a cleaner manufacturing process by avoiding harsh cleaning agents.

Simplified Workflow: Reduces the complexity of production lines by removing an extra step.

Disadvantages of No Clean Flux:

Limited High-Reliability Use: In high-frequency or high-voltage circuits, even minimal residue could pose potential risks.

Residue Visibility: While safe, residues can still be visible, which might not be acceptable for circuits requiring visual inspection.

Selective Suitability: Not ideal for all applications, especially those where long-term exposure to various environmental factors could react with even benign residues.

Application Considerations

Clean Flux is the better choice when:

The circuit board is part of a medical device, aerospace system, or any application where safety and precision are crucial.

The project involves sensitive circuits that cannot tolerate any contaminants, no matter how minimal.

Certification bodies require absolute cleanliness for approval.

No Clean Flux is more suitable when:

Production efficiency is a priority, as in consumer electronics manufacturing.

The board does not require visual perfection or meets the tolerance for low-level residues.

Environmental policies favor reduced chemical use and waste.

Why is it Called No Clean Flux?

The term no clean flux reflects its primary feature: no mandatory post-soldering cleaning. This type of flux is made with a formulation that leaves behind minimal, safe residues. The composition typically includes a mix of weak organic acids and solvents that burn off or leave a thin, inert layer during the soldering process. This layer is non-conductive and won’t affect the circuit’s performance, eliminating the need for additional cleaning steps.

This type of flux gained popularity as manufacturing practices evolved to become faster and more cost-efficient. The avoidance of cleaning also means fewer chemicals are used, supporting environmentally friendly production lines. The convenience of no clean flux does not compromise soldering quality in most cases, making it a go-to choice for many electronics manufacturers.

What Happens if You Don’t Clean Flux on a PCBA?

Not cleaning the flux on the PCBA can cause a range of problems including reduced electrical performance, corrosion, leakage, short circuit, etc. ‌

First of all, incomplete flux cleaning can significantly reduce the electrical performance of the circuit. Residual flux may cause resistance to increase, capacitance to decrease, and in severe cases, complete circuit failure. In addition, residual flux may cause metal corrosion and leakage, increasing the risk of circuit damage and short circuit. Improper cleaning will also affect the insulation performance of the circuit, resulting in reduced insulation impedance, which may cause leakage or more serious circuit failure.

When the temperature changes, the flux residue may also cause the thermal expansion mismatch between the solder joint and the circuit board, causing the solder joint to crack or fall off, and eventually lead to circuit failure. In addition, the residual flux may form electron movement during electrification, resulting in short circuit and product failure ‌. Especially in modern electronic products, the pad spacing is getting smaller and smaller, and the presence of residue increases the possibility of short circuit.

When to Use No Clean Flux?

No clean flux fits well with everyday consumer electronics, where quick production and cost savings are key. It is useful for circuits where non-conductive residue won’t impact performance, like in standard home appliances or low-sensitivity equipment. Some typical situations are suitable to use no-clean flux, like:

Environment with very low requirements for residue after soldering: no-clean flux has very little residue after welding, and can reach the standard of ionic cleanliness without cleaning. It is suitable for environments with very high requirements for residue after welding.
Occasions with high environmental requirements ‌ : no-cleaning flux does not contain halide active agent, no need to clean, reduce the discharge of waste gas and wastewater, in line with the requirements of environmental protection.
Project requires high economic benefit: the use of no-cleaning flux can reduce the input of cleaning equipment and cleaning solvent, reduce the production cost.
Low odor requirements situation: the traditional loose-scented flux has a larger odor, while the no-clean flux has a smaller odor. It is suitable for the environment with low odor requirements.

How to Use No Clean Flux Paste?

‌The basic steps for using no-clean flux are as follows‌:

‌1. Clean the welding part‌: Before using the flux, clean the welding part to ensure that there is no oil, degreaser or moisture on the surface to avoid affecting the welding effect and welding strength‌

‌2. Apply flux‌: After stirring the no-clean flux evenly, apply the flux on the welding part by brushing or dripping, and ensure that the coverage area is sufficient‌

‌3. Welding‌: After waiting for a while, you can perform normal welding. The function of the flux is to improve the welding quality and make the contact surface of the electronic components easy to melt during the welding process.

‌Precautions during use‌:

‌1. Environmental requirements‌: No-clean flux is a flammable chemical material. It should be operated in a well-ventilated environment, away from fire and avoid direct sunlight‌

‌2. Storage and replacement‌: The opened flux should be sealed before storage. Do not pour the used flux back into the original packaging to ensure the cleanliness of the original liquid. The flux should be replaced with new liquid after 50 hours of use to prevent contamination, aging and degradation that affect the work effect and quality.

3. Safe handling: The scrapped flux must be handled by a dedicated person and must not be dumped at will to pollute the environment. If it is accidentally contaminated on your hands and feet, rinse it immediately with soap and water; if it is contaminated on your face, rinse it immediately with soap and water. If the situation is serious, seek medical treatment.

Best Technology engaging in PCB and PCBA assembly industry for more than 18 years. We have professional engineering team to offer one-to-one technical support. And all of our core members have over 10 years experience in PCB industry, we are so confident that we can serve you perfect! Contact us for more!

What is the Fiducial Mark?

Fiducial marks are small, round copper pads on a PCB. They serve as reference points to guide automated assembly machines. Usually circular and made of copper, it serves as a visual cue that tells machines where the board is located on the assembly line. In the PCB manufacturing industry, fiducial marks play an important role in improving production efficiency and quality and reducing manual errors.

What is the Purpose of Fiducial Marks?

The fiducial marks on PCB plays a vital role in the manufacturing industry, mainly used to assist equipment or systems in the production process of PCB automatic positioning, alignment error detection, size measurement, lead inspection and other operations. Specifically, the role of fiducial marks includes the following:

Accurate positioning

Fiducial marks can provide high-precision positioning information, so that the PCB components can be accurately aligned and installed.

Automated assembly

Through the use of machine vision system, fiducial marks can be automatically identified and positioned to achieve automated PCB assembly process, improve production efficiency and reduce manual errors.

Quality control

Fiducial marks can be used to detect the position and condition of PCB components for quality control and defect detection to ensure product compliance with specifications.

Accurate calibration

Fiducial marks can be used to calibrate measuring equipment or machine vision systems to ensure their accuracy and stability.

Design update and repair

Fiducial marks can be used as markers or reference points for positioning and adjusting the PCB during design iteration, troubleshooting, and repair.

What are the Different Types of Fiducial Marks in PCB?

Fiducial marks are not one-size-fits-all. Depending on the PCB design and complexity, different types of fiducials come into play:

Global Fiducials: These marks are used to align the entire board. They’re usually placed on the corners or designated locations on the PCB to help machines recognize the board’s overall position.
Local Fiducials: When certain areas of the PCB require high precision—especially spots with tight component layouts—local fiducials come into play. They’re placed near these critical sections to ensure parts like chips and connectors are placed with pinpoint accuracy.
Panel Fiducials: If multiple PCBs are organized into a single panel for manufacturing, panel fiducials are added to align the entire panel. This ensures that each section of the panel stays in place during assembly.

Each type of fiducial has its job, guiding machines from broad alignment down to component-specific positioning.

What is the Size of the Fiducial Marks on a PCB?

The dimensions of the optical points on the PCB are usually circular pads of 1mm to 3mm diameter, plus a solder shield of twice or more the pad size‌. Specifically, the size of the optical points can be adjusted according to different needs, and common sizes include:

1mm diameter round pad ‌ with a 0.6mm radius solder mask.
‌2mm diameter round pad ‌ with a 1mm radius solder mask.

These sizes are chosen to ensure that the optical points can be accurately identified and positioned by the mounter during the SMT production process, especially when dealing with dense pin components, improving the mounting accuracy.

In addition, the shape of the optical point is generally round, because the circular object is easier to be positioned by the machine, and the machine vision system can find the center of the reference point ‌2 more accurately.

What are Fiducial Marks Used For?

Fiducial marks have a straightforward yet essential purpose. They act as guideposts for automated assembly, ensuring the board is positioned and oriented correctly. Their main uses include:

Aligning the Board: Fiducials tell the machines where the board starts and ends, helping them align it for each production step.
Orientation Control: They guide machines to understand how the board is placed on the assembly line, preventing flipped or rotated placement.
Component Precision: Especially with advanced and densely packed PCBs, fiducials ensure that each component is placed where it belongs.

Fiducial Marks vs. Positioning Holes

Fiducial marks and positioning holes are both used for alignment, but they serve different roles. Fiducial marks are visual reference points that automated machines read optically. They tell the machine where the board is and ensure accurate component placement. On the other hand, positioning holes are physical features. They’re used to mount the board securely onto a frame or machine bed, ensuring that it stays put during the assembly or manual handling.

Think of fiducial marks as the eyes of the process and positioning holes as the hands. Fiducial marks guide precision and accuracy, while positioning holes provide stability and physical anchoring.

1+N+1 Stack Up

1. Here, “1” (including the following “1”) refers to the layer number of blind holes (Blind via/ micro-via). And one layer blind hole always called a first step.

N refers to the number of non-blind hole layers in the inner layer (not necessarily just the Core), such as 4 layers, combined with 1, which is a 1-4-1 stacked structure. At the same time, if the N-layer is laminated, then this 1-4-1 laminated structure is called first-step-second-lamination (1 times N-layer lamination + 1 times outer layer lamination = 2 times, so it is called second lamination).

Does it make sense? If you have any questions, feel freely to leave a message or contact us at sales@bestpcbs.com.

2. Typical 1+N+1 stack-up

This kind of stack up shown as following is made by laminate a CCL sheet into 4 layers firstly and then laminate into 6 layers. It is also a common product on the market at present.

2+N+2 Stack Up

1. Here, 2 and N have the same meaning as 1-N-1, it will not be repeated again.

2. Typical 2+N+2 stack-up:

There are two types of second-step stack-up: stacked via and staggered via, which have different levels in difficulty, cost, and process.

2.1 Staggered via

Here is a stack-up of a staggered vias, this kind of structure has relatively lower cost and good reliability.

2.2 Stacked via

From the stack-up, it is not difficult to see the difference with staggered vias. This stacking structure requires drilling another blind hole on top of the blind hole, and the previous blind hole needs to be filled with copper or a material that can conduct electricity and resist laser drilling. This gives a rise to another technology, we will introduce in the later HDI electroplating process.

N+N Stack Up

1. Here, the “N” and the “N” in 1-N-1 or 2-N-2 have the same meaning.

2. Typical N+N stack-up

Although N+N stacking may not have blind holes, due to the special process and strict registration requirements, the actual production difficulty is no less than HDI technology.

Anylayer for Any Interconnection

1. The Any-layer means it can conduct at any layer, so how to achieve it?

2. Typical stack-up of Any-layer

From the section of the PCB as following, it can also be seen that how to stack each layer together to form a straight line is also a challenge, so the Anylayer process good or not depends on the registration ability of the manufacturer. Of course, the circuit uses this technology will definitely be very dense and fine, which gives rise to an advanced PCB process called MSAP.

So in summary, despite facing many challenges, HDI’s stacked design has become a key part of high-end electronic products. From smartphones to wearable devices, from high-performance computers to advanced communication systems, HDI technology is playing a crucial role. With the continuous advancement of technology and the increasing demand from consumers, we have reason to believe that HDI’s stacking will continue to lead the innovation trend in the field of electronic manufacturing.

What is 1st Article Inspection For?

First Article Inspection (FAI) refers to the inspection of the first or several products produced at the beginning of production (such as every day, every shift or the beginning of each production batch) to confirm whether the production conditions (such as equipment, process, materials, environment, etc.) meet the technical and quality requirements. This is a preventive quality control measure designed to prevent batch defects by early detection of possible problems in the production process.

The first inspection usually includes the following steps:

1. Preparation stage: clear inspection standards, inspection methods, inspection tools and equipment, and prepare relevant inspection records and forms.

2. Production preparation: Check whether the production equipment is in good condition, whether the process parameters are set correctly, and whether the raw materials or parts meet the requirements.

3. Production of the first piece: Start production according to the production plan, and make the first piece or the first few products as the first piece.

4. First inspection: Detailed inspection of the first product, including inspection of appearance, size, performance, function, etc., to ensure that the product meets the design requirements and quality standards.

5. Result judgment: According to the inspection results, determine whether the first piece is qualified. If qualified, mass production can continue; If it is not qualified, it is necessary to analyze the cause, adjust the production conditions, and re-make the first part for inspection until it is qualified.

6. Record and feedback: Record the results of the first inspection, and feedback the results to relevant departments and personnel in order to take timely measures to solve the problem.

Why Need to Perform a FAI?

◆ The first inspection in the production process is mainly to prevent the product from a batch of out-of-quality, repair, scrap. It is a means to control the product production process in advance, is an important method of product process quality control. It is an effective and essential method for enterprises to ensure product quality and improve economic efficiency.

◆ The first inspection is to find the factors affecting product quality in the production process as early as possible to prevent bad batch or scrap.

◆ The first piece can be entered into formal production after passing the inspection, mainly to prevent the occurrence of batch unqualified products.

◆ Long-term practical experience has proved that the first inspection system is an effective measure to detect problems as early as possible and prevent products from being scrapped in batches. Through the first piece inspection, it can be found that systematic causes such as severe wear of the fixture or installation positioning errors, poor accuracy of the measuring instrument, incorrect reading of the drawing, feeding or formulation errors exist, so that corrective or improvement measures can be taken to prevent the occurrence of batch nonconforming products.

What Happens if a Component Passes or Fails the FAI?

If a component passes the FAI, full-scale production can proceed to next stage. Because knowing that the process yields parts that match design criteria. Meanwhile, it builds confidence and reduces the likelihood of future issues.

If a component fails, corrective action is necessary. This means process, parameters, or used tools, materials are not suitable or with poor quality. After modifications, a new FAI may be needed to verify the adjustments work as expected.

When Should a First Article Inspection Occur?

Knowing the right time for a 1st article inspection is crucial to avoid production issues and ensure highest quality. But when exactly should this process take place? Let me tell you:

Initial Production Run

Picture this – you’re ready to kick off a new product line or start manufacturing a brand-new part. This is the perfect time for an FAI. Performing it at this stage helps catch any potential problems right from the start. It’s like giving your process a test drive before you commit to full-scale production.

Process Changes

Changes are inevitable in manufacturing. Maybe there’s an upgrade to your equipment or you’re switching up the method used to produce parts. Any significant change to the process means it’s time for a new FAI. Why? Because even small adjustments can lead to unexpected differences in the final product.

Supplier Changes

If you decide to switch to a different supplier for critical components, you shouldn’t skip an FAI. Even if the new supplier promises the same specifications, differences in materials or production methods can impact the final product. An FAI here ensures that what you’re getting from the new supplier matches your quality expectations.

Design Modifications

Tweaking a design might seem minor, but it can change everything from part fit to performance. Any time there’s an update or redesign, running an FAI confirms that the modified product still aligns with the original quality standards.

What is the Difference Between PPAP and First Article Inspection?

You might hear the terms PPAP (Production Part Approval Process) and FAI thrown around in manufacturing discussions. While they share a goal of ensuring quality, they are different in their approach, scope, and where they are commonly used.

1. Industries and Common Use

FAI is used across various industries, and it especially popular in fields like aerospace and defense. It’s typically a requirement when introducing a new part or process. PPAP, on the other hand, is most commonly linked to the automotive industry. It’s a standard method required by major automotive manufacturers to ensure that their suppliers can consistently meet production quality standards.

2. Range and Detail

FAI is about confirming that one specific piece meets all the design and specification requirements. The process involves checking the dimensions, materials, and other key aspects to ensure everything matches up before moving forward with full-scale production.

PPAP, however, takes a broader approach. Instead of just focusing on one component, PPAP is like an in-depth audit of the entire production process. It includes elements like process flow diagrams, control plans, and even failure mode and effects analysis (FMEA). PPAP doesn’t just ask, “Does this part meet the specs?” but goes further to check if the entire production line can consistently produce parts that meet quality requirements over time. A PPAP file like as below:

3. Level of Documentation

FAI has its documentation, but it’s more straightforward. You get a detailed report of the inspected part, including dimensions and results from any tests performed. With PPAP, the documentation is more comprehensive and multi-layered. It often involves around 18 sheets, including a sample production run, process validation reports, and customer-specific requirements.

First Article Inspection in Best Technology

At Best Technology, we believe that FAI is more than a formality—it’s a guarantee of reliability and quality. So, we pay more attention to the first article inspection, from every step, every operator, every report. We have a 1st article inspection tester in our factory, for each prototype, we can finish the FAI inspection quickly and effectively.

As an advanced PCB and PCBA manufacturer, we have more than 18 years experiences in this industry. We have served over 5000 customers with 98% satisfied comments. All of them are amazed with our one-stop service and quick delivery.

What is Gold Plating in PCB?

Firstly, let’s know what is a gold plating. Gold plating on PCBs refers to a layer of gold applied over specific areas of a circuit board. This gold coating is typically applied on the connectors, pads, and edge contacts of a PCB to improve electrical conductivity and provide better resistance against wear and oxidation. Gold plating protects these sensitive areas, which are critical for the performance and reliability of the PCB.

The principle of gold plating is to dissolve nickel and gold (commonly known as gold salt) in the chemical solution. And then the circuit board is immersed in the electroplating cylinder and the current is passed on the copper foil surface of the circuit board to generate nickel gold coating. Due to the electric nickel gold has good hardness, wear resistance, and not easy to oxidization, it is widely used in the electronics.

Does Gold Plating Process Use Real Gold?

‌The gold plating in PCB is not really pure gold, but a gold alloy (has gold and some other metals in it). ‌

In PCB manufacturing, gold-plating is usually not done using pure gold, but by compression and treatment of gold alloys. Such alloys often contain small amounts of metals such as silver, nickel, and copper to reduce costs and meet specific performance requirements.

The role of gold plating in PCB is mainly to enhance electrical conductivity and chemical stability. Gold has good electrical conductivity and oxidation resistance, which can provide stable signal transmission and reliable connections in electronic devices. In addition, gold does not discolor or corrode, making it an ideal material for electronic applications.

In general, there are two main gold-plating processes: electrolytic gold-plating and brush gold-plating. Electrolytic gold plating is the deposition of metal on the circuit board through chemical bath and electrolytic process, which has higher cost but better quality. Brush gold plating, by depositing metal particles onto a conductive substrate via electronic devices, is cheaper but of poorer quality.

Why Use Gold in PCB?

May somebody curious about why use gold in PCB? To make the PCB surface more beautiful? Let me tell you why.

1. Improve electrical conductivity

Metals such as gold have good electrical conductivity. Through gold plating, a metal conductive layer can be formed at the circuit connection of the PCB board, thus significantly improving the electrical conductivity of the circuit. This helps to reduce the resistance at the circuit connection, reduce signal loss.

2. Prevent oxidation and corrosion

The gold coating has excellent chemical stability and can resist oxidation and corrosion. This can protect the PCB board from the erosion of harmful substances in the external environment, such as humidity, salt spray, chemical gases, etc., thereby extending its service life.

3. Improve welding performance

Oxidized layer may be formed on the metal surface during welding, affecting welding quality. The gold coating can reduce the thickness of the surface oxide layer, thereby improving the reliability and robustness of the welding. In addition, gold plating can also provide better welding contact, reduce thermal stress during welding, and reduce the occurrence of welding defects.

4. Enhance the appearance

Gold plating can give the PCB surface metallic luster, improve the appearance texture and product grade, and increase the market competitiveness of the product. To be honest, gold appearance indeed gives a better appearance.

5. Meet specific needs

In some high-end electronic products, there are higher requirements for the electrical conductivity, corrosion resistance, welding performance and appearance texture of PCB boards. Gold plating, as an effective surface treatment technology, can meet these specific needs.

6. Meet welding quality challenges

With the improvement of integration of electronic products, IC feet are becoming more and more dense, and traditional vertical tin injection technology is difficult to meet the welding challenges of thin pads. Gold plating technology can provide better welding performance and reliability, and reduce the occurrence of welding quality problems such as virtual welding.

How Thick is Gold Plating on Circuit Boards?

The thickness of gold plating on PCBs depends on the type and application. Generally, PCB gold plating thickness ranges from 0.1-1.27um. For standard PCBs, a gold layer thickness of 0.03 to 0.05 microns is common, especially for immersion gold. However, thicker plating is applied for connectors or contacts exposed to frequent wear and tear, as these areas need more protection.

Hard gold, used for high-wear applications like edge connectors, typically has a greater thickness than immersion gold. The thickness is carefully controlled because too thin a layer might fail to provide effective protection, while an excessively thick layer could lead to wasted materials and unnecessary expense. The goal is to strike a balance that delivers durability without incurring excessive costs.

What is the Difference Between Immersion Gold and Hard Gold PCB?

Hard gold plating ‌is by electroplating, so that the gold particles are attached to the ‌PCB board, so it is also called electric gold. Because of its strong adhesion, hard gold plating is also called hard gold, which is often used for ‌ memory bar ‌ gold finger and other parts that need wear-resistant.

‌Immersion gold ‌ is through the ‌ chemical reaction, the gold particles crystallization and attached to the PCB ‌ pad, so it is also known as ‌ soft gold. Due to the weak adhesion, the sinking gold is mainly used for the surface treatment of the pad, and the weldability is good. The difference between hard gold plating and immersion gold are including:

Color: Immersion gold is more yellow, while gold plating is more white.
Crystal structure: Immersion gold has a denser crystal structure.
Thickness: Immersion gold has a thicker layer of gold.
Wear resistance: Gold plating is harder and more resistant to wear and tear.
Solderability: Immersion gold is easier to solder.
Short circuits: Gold plating is more likely to cause short circuits.
Oxidation resistance: Immersion gold is less prone to oxidation.
Cost: Immersion gold is more expensive.
Deposition process: Gold plating uses an external electric current, while immersion gold is a chemical process.
Suitability: Gold plating is better for environments with high mechanical stress, while immersion gold is better for movable contacts.

PCB Applications of Gold Plating

Gold-plated PCBs are popular in industries where reliability and durability are essential. Some typical applications include:

Aerospace and Defense
Medical Devices
Telecommunications
Consumer Electronics
High power electronics
High current electronics
Low voltage digital logic electronics

As a PCB and PCBA manufacturer, we provide various surface treatment options for customers, including: ENIG, ENEPIG, OSP, HASL-LF, Immersion gold, hard gold (up to 50u’’). We offer customized PCB service tailored to customer’s requirements, we will try our best to meet the demands of surface treatment. Welcome to contact us if you have any questions.

What is a PCB Antenna?

A PCB antenna is an antenna built directly onto the printed circuit board, often as a conductive trace or embedded component. By integrating it directly onto the PCB, the antenna becomes a seamless part of the overall design, eliminating the need for separate antennas. The design principle of PCB antenna is based on electromagnetic field theory. By arranging a specific metal conductor pattern on the PCB board, an effective electromagnetic radiation and receiving structure can be formed, so as to achieve the transmission and reception of wireless signals.

This antenna uses PCB as the medium, through the PCB process to achieve, no need to assemble the antenna separately, testing and use are very convenient. PCB antenna can be directly integrated on the circuit board, easy to touch and damage, and easy to assemble.

PCB Antenna Types

PCB antennas come in different types, each suited to specific applications and requirements. The most common types include:

Monopole Antennas

These antennas are simple, consisting of a single conductor. They’re straightforward to design and offer decent performance for applications with limited space. Monopole antennas are ideal for Bluetooth and Wi-Fi applications, where simplicity is needed without compromising basic functionality.

Dipole Antennas

Known for their balanced design, dipole antennas use two conductors, often resulting in improved radiation patterns. They are commonly used in environments where the antenna needs to work effectively in multiple directions. Dipole antennas are popular in high-frequency applications.

Inverted-F Antennas (IFA)

This type features a ground plane and a radiating element shaped like an “F.” IFAs are compact and provide a stable, omnidirectional pattern, making them suitable for Wi-Fi and cellular applications. The structure of IFA antennas helps achieve good efficiency even in confined spaces.

Patch Antennas

These antennas are flat and rectangular, making them excellent for devices with strict space limitations. Often used in GPS and RFID applications, patch antennas offer directional radiation patterns, allowing them to focus energy toward specific areas, enhancing range and strength.

Slot Antennas

Slot antennas consist of a slot cut out of a conductive surface, with electromagnetic fields radiating from the slot. They are typically more directional, so they are suitable for specific point-to-point applications or where the signal needs to be targeted.

What is the Frequency Range of a PCB Antenna?

The frequency range of a PCB antenna depends on the design and intended application. Most PCB antennas operate within common wireless communication bands, such as 2.4 GHz for Wi-Fi, Bluetooth, and other short-range communications. However, they can be designed for various ranges, including sub-1 GHz bands (for long-range IoT applications) and frequencies as high as 5 GHz for Wi-Fi 6 and other high-speed networks.

Higher frequencies typically require smaller antennas, which aligns well with compact devices but may also affect range. Low-frequency antennas, on the other hand, are larger but provide greater coverage and are less affected by obstacles.

PCB antenna’s Basic Formulas

1. Wavelength Calculation

The wavelength (λ) of the signal is an essential parameter in designing antennas, especially for determining the length of a PCB trace antenna.

Where:

c = Speed of light (approximately 3×10^8m/s)

f = Frequency in Hz

For example, at 2.4 GHz (a common frequency for Wi-Fi and Bluetooth), the wavelength is around 12.5 cm.

2. Length of a Monopole Antenna

For a monopole antenna on a PCB, the length (L) of the antenna is typically set to one-quarter of the wavelength. This is known as a quarter-wave monopole antenna, which is commonly used in PCB designs.

This length provides a good balance of efficiency and compact size.

3. Length of a Dipole Antenna

A dipole antenna is usually designed to have a length of half the wavelength. The total length L for a dipole is:

Each “arm” of the dipole would then be a quarter-wavelength. This structure is well-suited for many applications due to its balanced design.

4. Inverted-F Antenna (IFA) Length Calculation

For an Inverted-F Antenna, the length of the main resonant arm is usually close to a quarter of the wavelength. This helps the IFA to maintain a compact form while still achieving effective performance:

Since IFAs often include a grounding element, they may be slightly shorter than traditional quarter-wave monopoles.

5. Impedance Matching

The impedance (Z) of the antenna needs to match the transmission line (typically 50 ohms) to maximize power transfer. For a basic dipole or monopole antenna, the impedance can be approximated with empirical formulas. For instance, a free-space dipole impedance is around 73 ohms, but this value changes on a PCB.

To achieve matching, adjustments can be made by changing the length or width of the antenna trace or by using matching networks with inductors or capacitors.

6. Resonant Frequency Calculation

The resonant frequency (f) of a PCB trace antenna depends on its physical length. Rearranging the wavelength formula allows you to solve for f if you know the length:

Where L would typically be one-quarter of the wavelength for a monopole or half for a dipole.

7. Effective Dielectric Constant Adjustments

PCB antennas are affected by the PCB material’s dielectric constant (ϵr). This changes the effective wavelength (λ):

Using this adjusted wavelength improves accuracy in trace length calculations for PCB antennas, especially when working with substrates with a high dielectric constant.

8. Bandwidth Calculation

The bandwidth of a PCB antenna can be approximated using the Quality Factor (Q) of the antenna:

Where Q is influenced by factors such as antenna length, material, and layout. Lower Q values usually provide broader bandwidth, which can be achieved through specific design choices like wider traces or shorter antennas.

9. Gain Estimation

The gain of a PCB antenna depends on its radiation pattern and efficiency. Although gain is typically measured rather than calculated, some estimates can be made based on the type of antenna and its efficiency. For simple PCB antennas, a rough gain value might range from 0 dBi (isotropic) for omnidirectional designs to 3–5 dBi for directional designs.

Are PCB Antennas Directional?

PCB antennas can be directional or omnidirectional, depending on their type and design. Directional antennas focus the energy in a specific direction, which increases range in that direction while reducing it in others. Omnidirectional antennas, in contrast, distribute the signal evenly in all directions, which is beneficial for applications where the device orientation may vary.

Patch antennas and slot antennas are generally more directional, suitable for point-to-point communication or when a targeted signal path is needed. Monopole and dipole antennas, however, are typically omnidirectional, making them ideal for devices like smartphones and IoT gadgets, where a consistent signal is required from various angles.

The choice between directional and omnidirectional antennas should align with the specific needs of the application. For example, in a warehouse, an omnidirectional antenna might be preferred for broad coverage, while a directional antenna could be beneficial for a remote control application.

What Are the Applications of PCB Antenna?

PCB antennas are used in a wide range of applications, including:

Consumer Electronics: PCB antennas are essential in smartphones, tablets, and laptops for Wi-Fi, Bluetooth, and cellular connectivity.
IoT Devices: Many IoT devices use PCB antennas for wireless data transmission, making them integral in smart homes, agriculture, and industrial monitoring.
Automotive: In vehicles, PCB antennas enable GPS, remote keyless entry, and other connectivity features, enhancing both functionality and user experience.
Medical Devices: PCB antennas are used in medical equipment for wireless communication, which enables real-time monitoring and diagnostics.
Wearables: PCB antennas are commonly found in wearable tech like fitness trackers and smartwatches, where compactness is a priority.
Industrial Equipment: Many industrial machines rely on PCB antennas for remote monitoring and control, helping to streamline operations and improve efficiency.

When choosing a PCB antenna, consider the application requirements, including size constraints, frequency range, and directional needs. PCB antennas bring numerous advantages to electronics, from consumer gadgets to industrial equipment. With the right antenna, you can achieve reliable wireless communication, keeping your designs efficient and effective in today’s connected world.

What is an AOI Machine in PCB?

AOI machine is a kind of inspection equipment based on optical principle, mainly used to detect various defects on a PCB board. The AOI device automatically scans the PCB through a high-definition CCD camera, acquires images, and compares the tested solder joints with qualified parameters in the database. After image processing, the defects on the PCB are checked, and the defects are displayed through the display or automatic signs for repair personnel to correct.

AOI detection is mainly composed of light source and its control subsystem, digital imaging and its control subsystem (including CCD/CMOS camera, image acquisition), image scanning motion mechanism and its control subsystem, image processing and optimization subsystem, image feature recognition and defect recognition subsystem, HMI and main control subsystem. These subsystems work together to scan the PCB and obtain the PCB image by controlling the light source, digital imaging, scanning and other subsystems, and then register the processed PCB image with the PCB standard image, extract features and compare and analyze the processed PCB image to determine whether the PCB has defects and the type of defects, and identify the location of defects.

What is the Basic Principle of AOI?

The principle behind AOI is quite straightforward: it illuminates the PCB through the light source, uses the optical lens to collect the reflected light of the PCB into the computer, and analyzes the color difference or gray ratio of the PCB information through the computer software, so as to judge the solder paste printing on the PCB, component placement, solder joint welding quality and so on. The AOI system can also analyze and count the defects to provide a basis for adjusting the process parameters of the manufacturing process.

In another word, it relies on optical imaging and pattern recognition to detect defects. AOI machines are programmed with reference images of a perfect PCB layout. They then scan each PCB, capturing images and comparing them pixel-by-pixel to the reference model. Variations between the scanned image and the reference indicate potential defects, prompting the machine to flag these areas for further review.

What are the Benefits of an AOI Machine?

1. Accuracy in Detection

AOI machines can identify defects that might be overlooked by manual inspection. The precision with which they analyze each PCB ensures high-quality output, reducing errors in the final product.

2. Speed and Efficiency

Automated inspection greatly speeds up the inspection process, especially valuable in large-scale manufacturing. With AOI, hundreds of PCBs can be checked in a fraction of the time required for manual inspection.

3. Cost Reduction

Early detection of defects prevents costly rework or scrap, saving both time and resources. By addressing issues during the early stages, AOI contributes to a smoother production process.

4. Consistency and Reliability

Unlike human inspection, which can vary, AOI provides consistent results every time. It applies the same criteria to every PCB, ensuring uniformity and quality across all batches.

5. Enhanced Quality Control

In a competitive market, high-quality products build trust with clients. AOI enables manufacturers to deliver high-standard PCBs, maintaining quality and reducing potential returns.

What Kinds of Defects Can Be Checked During AOI?

1. Soldering Issues

AOI machines are highly effective in identifying soldering defects, such as insufficient solder, excess solder, or bridging, which can interfere with connectivity.

2. Misalignment of Components

AOI can detect misaligned components or misplaced parts, which might cause issues in functionality or even physical interference on the PCB.

3. Component Presence and Orientation

The machine checks if all components are present and correctly oriented. Missing or rotated parts can lead to non-functioning circuits.

4. Short Circuits and Opens

AOI identifies unwanted connections (shorts) and incomplete circuits (opens), ensuring each connection is accurate and functional.

5. Surface Defects

Surface issues, including scratches, contamination, or other irregularities, are also detectable through AOI, contributing to the visual quality of the board.

6. Polarity and Value Verification

Some AOI systems can check component polarity and values, confirming that each component matches the required specifications for the PCB design.

AOI Applications

1. Consumer Electronics Manufacturing

Given the high volume of consumer electronics, AOI’s speed and accuracy are essential for maintaining efficiency without sacrificing quality. It is used for inspecting products like smartphones, laptops, and household appliances.

2. Automotive Industry

In automotive electronics, reliability is critical. AOI helps ensure that safety and performance-related components are defect-free, such as sensors, control units, and in-car entertainment systems.

3. Medical Devices

Medical equipment relies on precision and reliability. AOI in PCB inspection for medical devices ensures that these life-saving tools meet strict standards, minimizing risks in critical applications.

4. Aerospace and Defense

For aerospace and defense, where reliability and durability are paramount, AOI supports quality assurance in sensitive equipment, such as navigation systems and communication devices.

5. Telecommunications

In telecommunications, AOI assists in inspecting high-frequency PCBs, ensuring that communication devices remain operational and effective over long periods.

To ensure high quality of PCBA, Best Technology equipped with 3D online AOI to detect PCB defectives from all aspects. Contact us if you have any questions.

What is the Process of PCB Rework?

The process of PCB rework generally follows a series of careful steps. Technicians start by inspecting the board to identify the defective areas. For rework, precise tools like soldering irons, hot air rework stations, or BGA rework machines are typically used.

Once heated, damaged or defective components are removed. A flux application ensures that the solder flows cleanly, which reduces the risk of bridging or insufficient connections. The next step is carefully placing a new component in place, using a microscope to ensure accuracy, particularly for small parts like surface-mount components. Finally, the connections are resoldered, and the board undergoes cleaning and testing.

What is the Difference Between Repair and Rework in PCB?

PCB repair and rework, though closely related, serve unique purposes within electronics manufacturing and servicing. Rework refers specifically to correcting issues in a PCB due to assembly errors or modifications required before the board is shipped to the customer. This process should be operated very carefully, including during removing, adjusting, or replacing components. For instance, rework might be needed if components were placed incorrectly, solder joints are weak, or the board has minor assembly defects.

Repair, however, addresses boards that have become faulty or non-functional after use. Repair focuses on bringing a board back to working condition, whether due to physical damage, such as broken traces or burnt components, or due to environmental factors like corrosion. While rework ensures the board meets its initial design intent, repair aims to recover a board’s functionality after it has failed. Both repair and rework require precise techniques and skilled technicians, but repair can be more complex due to the nature of post-production or operational damages.

In summary:

Rework: Fixing pre-delivery assembly issues to align the board with its intended design.
Repair: Restoring functionality to a damaged or non-functional board, often due to wear, damage, or environmental exposure.

How Many Times Can You Rework a PCB?

The number of rework attempts a PCB can safely endure depends on factors like the materials used in the board, the board’s structure (e.g., number of layers), and the rework methods applied. Typically, each rework cycle subjects the board to a heating process, which can wear down solder joints and laminate strength over time. For most PCBs, rework should be limited to two or three cycles to avoid degradation, as repeated heating can lead to pad lifting, warping, or delamination of the substrate, especially with multi-layer boards.

Multilayer PCBs with multiple embedded connections are particularly sensitive, as excessive heating can damage internal layers. High-temperature cycles weaken solder joints, increasing the risk of electrical faults. Some high-quality boards, particularly those designed for critical applications like aerospace or medical devices, may tolerate additional rework if built with durable materials, but general guidance suggests minimal rework attempts. Careful planning and accurate diagnostics are essential for minimizing rework cycles, ensuring the board’s lifespan is preserved.

Can a Damaged PCB Be Repaired?

Yes, in many cases, a damaged PCB can be repaired.

It depends on the type and extent of the damage. For example, broken traces, lifted pads, and minor component failures are often fixable. Using epoxy, technicians can repair lifted pads, while trace repair kits can restore broken connections. However, severe burns or extensive damage to multiple layers can make repairs impractical or costly. The best approach is to assess each situation individually and determine if repair is viable.

What Wire is Best for PCB Rework?

Using the right wire during PCB rework is crucial for achieving reliable connections. For rework, thin, lead-free solder wire with a flux core is often recommended. A wire diameter of 0.5mm to 0.8mm provides better control and precision, making it suitable for both small and large components. Lead-free solder is preferred in many industries due to environmental regulations, but it requires higher temperatures than traditional lead-based solders, so it’s essential to have proper temperature control.

Flux-core solder wire is essential as it allows for smoother, more reliable connections by promoting better solder flow and reducing oxidation at solder joints. Rosin-core flux is commonly used because it provides a strong bond and requires minimal cleaning. Additionally, if jumper wires are needed to bridge broken traces, insulated 30 AWG wire is ideal due to its fine gauge.

What is the IPC Standard for PCB Rework?

The IPC standards for PCB rework and repair are widely recognized and adhered to within the electronics industry to ensure quality and reliability. IPC-7711 and IPC-7721 specifically address rework, modification, and repair of printed circuit boards.

IPC-7711 provides guidelines for reworking and modifying electronic assemblies. This includes instructions on tools, temperature control, and safety practices necessary for removing and replacing components while preserving the board’s structure. It offers details on soldering and desoldering techniques that ensure high-quality connections after rework.
IPC-7721 focuses on the repair aspect, covering methods for handling damaged components and structural faults like broken traces, lifted pads, and substrate repair. This standard is critical for technicians performing repairs, as it outlines best practices for restoring physical and electrical integrity without compromising board function.

What is the Main Cause of PCB Failure?

PCB failures may cause from a variety of factors, with design flaws, manufacturing errors, and environmental stresses among the primary culprits. Here’s a closer look at some of the main causes:

Design Flaws: Poorly optimized PCB layouts can lead to issues like excessive heat buildup, inadequate trace width for current capacity, or improper component spacing.
Manufacturing Errors: Mistakes during the assembly process, such as improper soldering temperatures or placement inaccuracies, can lead to weak solder joints or misaligned components. These issues may not be apparent initially but can result in premature board failure.
Environmental Stress: PCBs exposed to extreme temperatures, humidity, or corrosive environments are at risk of damage. Moisture can cause short circuits or corrosion on solder joints and traces, while high temperatures may warp the board or degrade the substrate. Boards used in outdoor or industrial settings are especially vulnerable.
Electrostatic Discharge (ESD): Sensitive components can fail if exposed to static electricity.
Aging and Wear: Over time, boards and components naturally wear out. Solder joints may crack, components degrade, and thermal cycles lead to material fatigue.

If your PCB or PCBA can’t work, and don’t know where is the problem. You can contact Best Team to ask for help, we are professional in this industry.

‌What is Laser Direct Imaging?

Laser Direct Imaging (LDI) is a technology that uses a laser beam emitted by an ultraviolet laser to image directly on a PCB (printed circuit board). Compared to traditional exposure techniques, LDI has higher image quality, precision traces and real-time adjustment.

The LDI technology achieves pattern transfer by projecting the line image directly onto the PCB coated with photoresist through the laser beam emitted by the laser diode. This method eliminates the use of negatives in the traditional exposure process, reduces the time and cost of loading and unloading negatives, and avoids deviations caused by negative growing. The image resolution of LDI technology is high, and the fine wire can reach about 20um, which is suitable for the production of fine wire and improves the yield of PCB production.

What is Laser Direct Imaging in PCB Manufacturing?

Working Principle of LDI Technology

The principle of laser imaging is to acquire and present images based on the characteristics of laser beam. As we know, a laser is a highly focused, high-brightness, monochromatic beam that can therefore produce high-quality images. The laser imaging system mainly consists of laser, lens, scanning device and receiver. The laser is used to generate the laser beam, the lens is used to focus the beam, the scanning device is used to change the path of the beam on the object, and the receiver is used to receive the light signal and convert it into an image.

In the imaging process, the laser beam is focused from the laser through the lens, and then the path of the beam on the object is controlled by the scanning device. When the laser beam hits the surface of an object, it interacts with the surface. This interaction causes light to scatter and reflect, with scattered light diffusing in different directions and reflected light remaining in its original direction of propagation. The receiver receives the light scattered and reflected by the object and converts it into an electrical signal. The receiver converts the signal into a digital image signal, which is then processed and displayed on the screen to form an image. In the processing process, the received signal can be filtered, amplified and other operations to improve the quality and clarity of the image.

As PCB manufacturing processes continue to advance, LDI technology is also evolving. At present, the mainstream light source in the industry is the 405nm laser diode produced by Nichiya, Panasonic, and it is expected that the optical power requirements for exposure will be further improved in the future, and the optical power of a single device may develop to 100W. Nowadays, LDI technology is not only used in PCB manufacturing process, but also in high-end applications like medical imaging, industrial detection, remote sensing.

Advantages of Laser Direct Imaging Over Photo Exposure

The advantages of laser direct imaging (LDI) compared with traditional exposure machines mainly include the following aspects:

1. Eliminating the negative process in the exposure process

The LDI technology eliminates the step of making the negative in the traditional exposure process, thereby saving the time and cost of loading and unloading the negative, and reducing the deviation caused by the negative growth and contraction.

2. High resolution

The image resolution of LDI technology is very high, which is suitable for some very fine line production, especially for multi-layer PCB, which greatly improves the yield of PCB production.

3. High quality and precision

LDI is contactless operation, reducing the chance of miscontact, the closed operating environment reduces the influence of temperature and humidity, the image quality is high and fine, eliminating many defects in the traditional process.

4. Reduce errors and improve alignment

LDI technology improves alignment by eliminating alignment problems that often exist in photographic plates, especially the anisotropic movement of photographic plates caused by changes in temperature and humidity. High-precision alignment is achieved by using a charge-coupled device (CCD) camera system and a reference target to line up printed images and panels.

5. Shorten the production process and reduce costs

Because there is no need to have a negative production process, LDI technology shortens the production process, reduces the call of personnel, and reduces the production cost. In addition, the LDI system can lay more devices in the same environment, enabling two-way scanning and further savings.

6. Adapt to a variety of production needs

LDI technology has a flexible manufacturing route, which can meet various production needs without affecting the output. Once the data is delivered to the engineering department, production can begin, reducing product delivery time.

The image quality of LDI technology is clearer than that of traditional exposure technology, and it has obvious advantages in mid-to-high-end PCB manufacturing. With the transfer of global PCB production capacity to China and the high-end development of the electronics industry, the demand for LDI equipment continues to grow, and it is expected that the future will gradually replace traditional exposure equipment in the field of low-end PCB.

What is the Process of Direct Imaging?

Direct imaging with LDI involves several steps that ensure precise layer creation:

Design Preparation: The digital circuit design is prepped for imaging, with adjustments made to accommodate laser processing specifics.

Photoresist Coating: The PCB is coated with a light-sensitive photoresist material, which reacts chemically when exposed to the laser.

Laser Imaging: The laser projects the circuit pattern directly onto the photoresist. Adjustments can be made mid-process, allowing for precise alignment.

Developing: After exposure, the board is treated with a developer to reveal the circuit paths. Unexposed areas are removed, leaving only the intended design.

Etching or Plating: Depending on the PCB type, the board undergoes etching or plating to define the copper traces, completing the imaging process.

Difference Between Positive and Negative Images in PCB

In PCB photo exposure, the terms “positive” and “negative” refer to how the photoresist reacts to the laser exposure:

Positive Image: Here, the laser exposes areas intended to be removed. During development, the exposed regions dissolve, leaving behind the unexposed areas as the design.

Negative Image: In a negative image process, the laser exposes the regions meant to remain on the board. These exposed parts resist the developer, protecting the underlying material, while unexposed regions dissolve away.

The choice between positive and negative imaging depends on the photoresist type and the specific design requirements. Both methods offer high accuracy, but each has unique benefits based on the intended application.

Why LDI Process Less Cost-effective than Phototool?

While LDI offers many advantages, it often requires a higher initial investment than phototools:

1. Equipment Costs: LDI machines are sophisticated and costly, requiring a significant investment in laser technology and imaging systems.

2. Maintenance: High-precision lasers and optics demand regular maintenance and calibration to ensure consistent performance, which adds to operational costs.

3. Speed on Larger Runs: For high-volume production, phototools may still be more cost-effective. Phototools offer rapid replication without the need for repeated laser exposure, lowering costs for large-scale production.

These cost factors make LDI more suitable for specialized, lower-volume, or high-precision applications rather than large-batch productions.

How is Layer Registration in LDI?

Layer registration is crucial in PCB manufacturing, especially for multilayer boards where each layer must align precisely. LDI excels in this aspect:

1. Automated Alignment: LDI systems come with advanced alignment software that adjusts each laser exposure to match the existing layer positions.

2. Reduced Human Error: Since the process is largely automated, human handling is minimal, reducing the risk of alignment issues.

3. Dynamic Adjustment: With real-time feedback systems, LDI machines adjust alignment during the process, maintaining tight registration tolerances.

If you’re seeking high-quality PCB manufacturing, consider choosing a provider skilled in LDI processes like Best Technology. Our company combines expertise with cutting-edge technology to ensure your boards are produced to exact specifications, delivering the durability and performance you need in today’s advanced electronics.

Archive for the ‘best pcb’ Category

Soldering Defects

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