The production of PCBs is a highly intricate process, encompassing various disciplines such as fluid mechanics, polymers, and photochemistry. It also requires careful consideration of equipment stability and material performance to avoid PCB defects. Meeting these requirements depends on the expertise of experienced engineers. Additionally, the rising demand for high-quality products has resulted in increasingly stringent quality standards, leaving little room for even minor defects. In this article, TechSparks will highlight several common PCB problems and offer effective solutions to help you avoid potential failures.
How to diagnose circuit board problems
This simple and straightforward method of diagnosing circuit board problems involves using the naked eye or a magnifying glass to inspect the board’s surface. This technique can detect fundamental issues such as faulty boards, components, and solder joints, as well as identify abnormalities like cracks, burns, or corrosion. During the inspection process, be sure to check for the following:
- Correct wiring
- Proper component installation and any missing components
- High-quality pin soldering
- Smooth surfaces and the absence of scratches or cracks
- Complete PCB silkscreens with clear graphics and text
Functional testing is a critical method of detection that ensures software, hardware, or systems perform their intended functions according to regulations. It helps to identify defects and errors early in the development cycle, reducing the risk of costly product recalls and other failures. Aspects that can be detected through testing include:
- Short circuits and open circuits
- Voltage levels that are incorrect or related to circuit function or signal transmission
- Improperly functioning circuit boards
- Components that are not performing as expected
- Output signals that do not meet specifications
Thermal Imaging Technology
Thermal imaging technology is a non-destructive testing method that relies on infrared thermal radiation images to observe and measure temperature distribution on the surface of a target object, such as a PCB. This technology can quickly and accurately locate overheating or thermal imbalances on the board, which can speed up the repair and maintenance process. By using this technology, many problems can be uncovered, such as:
- Monitoring component heating during operation to rule out component malfunctions
- Identifying thermal imbalances on the board, which is the most intuitive way to diagnose this problem
- Detecting abnormal temperatures that may indicate a malfunction, whether they are too high or too low.
List of Common PCB Problems and Solutions
Substrate Dimensional Shrinkage Problem
- Residual stress in the base material can be caused by not considering the fiber direction during the manufacturing process;
- Incomplete solidification of the resin can also lead to substrate dimensional shrinkage;
- Due to the poor stability of the substrate material, shrinkage is caused by high temperature pressing during the manufacturing process;
- Inadequate compensation for film magnification in internal graphic transfers;
- Asymmetric structural panel design due to insufficient design experience can also contribute to substrate dimensional shrinkage;
- Recognize the patterns of weft and warp variation through film shrinkage compensation and trimming based on fiber processing direction;
- Determine the magnification of the first board through first-article inspection, and use it as a reference for determining the transfer magnification of the first inner layer pattern of the production board, usually controlled within +/-0.025%;
- Optimize substrate material formulation and improve the manufacturing process by controlling temperature, time, and pressure;
- Adopt a symmetrical structural design to avoid unbalanced internal forces;
Circuit Board Deformation
- Deformation problems with circuit boards are often caused by temperature fluctuations. High temperatures can cause expansion, while low temperatures can cause shrinkage;
- Humidity can also lead to board deformation. When the board is exposed to a humid environment, it may absorb or release moisture, causing it to warp or bend;
- Inappropriate combination of material properties and lamination methods during the design phase can result in uneven board thickness, leading to deformation;
- Failure to enforce strict manufacturing standards, such as applying excessive pressure during brushing, can also cause deformation issues with circuit boards;
- To achieve optimal results in the PCB manufacturing process, it is essential to understand the brush plate process parameters and use brushes that match them. For thinner substrates, TechSparks recommends using chemical cleaning technology or electrolytic processes;
- During PCB design, Design for Manufacturing (DFM) rules must be strictly enforced to ensure the appropriate combination of material properties and lamination methods;
- During Surface Mount Technology (SMT), set the pick-up strength of the machine and pay attention to the strength during DIP plug-in;
- It is essential to provide enterprise training to cultivate high-quality technical personnel who can execute various operations accurately;
- To reduce the impact of thermal expansion and moisture absorption and release, control the temperature and humidity of the environment during the production and use of PCB boards;
- Reinforce the four corners of the board using the anti-deformation process to keep the board flat;
Solder Ball Defects
- The defect occurs due to violation of the minimum electrical clearance requirement, as the distance between the solder ball and the trace is too close, less than 0.13mm.
- According to IPC’s A610 standard, a maximum of 5 solder balls per 600 square millimeters is acceptable. If more than that, the PCB is considered bad.
- Improper operation or incorrect printing machine settings can cause uneven application of solder paste, resulting in inconsistent size and shape of solder balls.
- Excessive solder paste leads to the formation of solder balls during soldering.
- If the board is not cleaned before soldering, pollutants may fuse with the solder, resulting in weak solder joints.
- Failure to check the instructions for the use of the solder paste may result in incomplete volatilization of volatile components in the solder paste, causing the solder balls to burst after formation.
- Poor quality substrate material, uneven surfaces, or potholes can cause welding quality problems.
- Follow the DFM design rules to check the minimum electrical clearance requirements provided by the manufacturer and avoid a distance between the solder ball and the wire that is too close.
- Adjust the welding parameters according to specific conditions such as temperature, time, air volume, etc.
- Select components and PCB boards with matching thermal expansion and contraction coefficients to reduce the stress generated by solder balls.
- Optimize the welding process to ensure uniform deposition of solder paste.
- Verify that the composition of the solder paste meets the standards, and completely volatilize the volatile components in the solder paste through proper baking and drying to prevent solder balls from bursting after formation.
- Address unexpected solder ball issue promptly.
- Use high-quality solder paste to ensure soldering quality.
Solder bridging issues
- There is no solder mask between adjacent pads, resulting in a lack of isolation between the pads;
- Excessive solder or inexperienced manual soldering techniques result in a longer soldering time, causing the solder to flow to adjacent pads and create a bridge;
- Improper placement of the solder joint or insufficient distance between pads prevents the solder from flowing correctly, leading to bridging between adjacent pads;
- Incorrect soldering parameters, such as excessively high temperature or time, can cause excessive liquefaction of the solder, resulting in bridging between adjacent pads;
- The solder tip used is excessively worn, preventing the solder from flowing to the correct position;
- Contaminants on the surface of the board obstruct the flow of solder;
- To avoid bridging, proper control and adjustment of welding parameters (such as soldering temperature and time) and size of pads and stencil apertures are necessary;
- When designing the layout of the pads, adequate spacing between the components should be considered;
- During the manufacturing process, it is crucial to ensure that both the components and pads’ surfaces are clean;
- Regular maintenance and inspection of welding equipment are recommended to ensure proper functionality;
- Adding a solder mask between the pads can prevent bridging;
- It’s essential to avoid mixing old and new fluxes, as well as different types of fluxes;
- Adjusting the pressure for solder paste printing and nozzle pick and place can improve the welding process and prevent bridging;
Damaged circuit board components
- Components are relatively fragile and can be damaged even by the static electricity generated by the human body;
- Component failure can also occur due to excessive current or voltage. It is important to consider undervoltage and overcurrent protection in the design;
- High temperature can damage components due to poor welding, material defects, or inadequate heat dissipation design;
- Incorrect installation of components, such as not following component directions, can result in component damage or circuit failure;
- Take necessary measures to protect components from static electricity, such as using electrostatic wristbands and implementing electrostatic discharge control measures during PCB assembly.
- Keep the working temperature within the specified range to prevent component damage due to overheating. This can be achieved through proper welding, material selection, and heat dissipation design.
- Avoid subjecting components to excessive vibration or mechanical stress during transport and assembly.
- Control humidity levels in storage and operating environments to prevent moisture-related damage to components.
- Ensure that components are properly installed and used according to the manufacturer’s specifications to avoid damage or circuit failure.
- Prevent environmental pollution and contamination during manufacturing and use to maintain component integrity.
- The power cord may be poorly connected or damaged due to various reasons, such as rusted plugs or damaged power cord cores.
- Insufficient power supply can be caused by current overload, a power supply with insufficient capacity, or external interference.
- Vibration during transportation, installation, or use, or the use of defective products can lead to power filter capacitor failure.
- Poor grounding may result from poor contact in the grounding line or the presence of common mode noise in the system.
- Check and repair the power line to ensure proper connection and no damage.
- Verify and adjust the power supply to meet the requirements of the device.
- Install protective devices, such as fuses, surge protectors, or voltage regulators, to prevent overvoltage or current overload.
- Replace any damaged power filter capacitors or transformers.
- Ensure a proper ground connection and eliminate ground interference.
- Replace any damaged power modules or ICs.
Signal Transmission Problem
- Signal interference can be caused by external sources such as electromagnetic waves, nearby equipment, or power sources.
- Poor signal routing can also contribute to interference, including long or improperly routed traces, vias, or connectors.
- Incompatible or improperly matched impedance between the source and receiver can weaken the signal.
- Signal attenuation can occur due to the distance traveled or when passing through lossy materials.
- Crosstalk between signals can happen due to their proximity or shared transmission lines.
- Signal reflections can occur when there are impedance mismatches or sudden changes in the transmission medium.
- Shield the affected area or device with grounded conductive material.
- Ensure proper signal routing by using short, straight traces, differential pairs, and avoiding sharp bends or vias.
- Use impedance matching or filtering techniques such as termination resistors, ferrite beads, or low-pass filters.
- Combat attenuation with signal boosters or repeaters.
- Reduce crosstalk by using shielding, separating or twisting cables, or crosstalk elimination techniques.
- Design transmission lines for impedance matching and to reduce reflections.
Circuit Board Overheating
- High current flowing through the PCB.
- Inadequate heat dissipation due to poor design or insufficient cooling.
- Overvoltage or short circuits.
- Improve the design of the PCB to ensure adequate heat dissipation, such as adding heat sinks or thermal vias.
- Reduce the current flowing through the PCB by optimizing the circuit design or using higher rated components.
- Ensure that the operating environment of the PCB is within the recommended temperature range.
- Add cooling components such as fans or heat pipes to dissipate excess heat.
- Improve the quality of components used in the PCB to prevent short circuits and overvoltage.
How to Avoid PCB Failures
- Follow DFM rules: Design for Manufacturability (DFM) rules ensure that the PCB design is compatible with the manufacturing process and that the end product is reliable and of high quality.
- Choose reliable suppliers: Select suppliers with a good reputation for producing quality materials, components, and equipment.
- Implement quality control: Establish a quality control process that checks and verifies the quality of materials, components, and equipment, as well as the finished product.
- Train personnel: Train personnel to follow best practices when handling materials, components, and equipment to avoid damaging them during the manufacturing process.
- Maintain equipment: Regularly maintain and calibrate equipment to ensure that it is functioning correctly and producing high-quality products.
- Use proper storage and handling: Proper storage and handling of materials, components, and equipment can prevent damage or degradation that could lead to circuit board problems.
- Conduct regular testing: Regularly test finished circuit boards to ensure that they meet the required standards and specifications.
- Implement ESD protection: Incorporate electrostatic discharge (ESD) protection measures to prevent damage to sensitive components from static electricity.
- Ensure proper ventilation: Proper ventilation can prevent the accumulation of dust, debris, or fumes that could interfere with the manufacturing process or damage components.
- Address problems immediately: Immediately address any problems that arise during the manufacturing process to prevent them from causing further issues or defects in the finished product.