Common PCB Failures and Troubleshooting Techniques
Managing a PCB assembly process can be an intimidating task. It does not matter if you outsource production or manage it in-house; numerous factors go into designing a functional product. A critical element of your design is the circuit board itself. The biggest problem with preventing or identifying PCB failures is the lack of information on the subject.
However, there are a lot of techniques you can apply to ensure that your PCBs are built to the highest quality standard. To lead you through this maze, we have included the most common failure points you should keep an eye out for. Through these methods, you will be able to troubleshoot any issues that you may come across. In addition, it will help you in knowing where to go for your next potential PCB job as well.
Demystifying PCB Troubleshooting
Bad Solder Joint
A solder joint is often the cause of many problems in electronics. For instance, if you have a solder joint that is not properly soldered or if it has come loose from its position on the board, it can cause several issues like poor performance or complete failure of the circuit.
To troubleshoot this problem, you need to check for corrosion or other damage that may have occurred during manufacturing, shipping, or handling. You should also check for loose connections where two components meet on the board through soldering joints.
Electrical shorting is the most common problem with PCBs. It can occur in any area of the board, including through-hole (TH) components, surface mount (SMT) components, capacitors, and resistors. Short circuits usually occur when two trace layers come into contact. This can be caused by poor manufacturing practices or improper handling during assembly.
One way to detect this failure is by using an ohmmeter, which measures the resistance between two points in a circuit. If you find no resistance between two points, your board may have an issue. Another way to test for shorts is by using ultraviolet light. A board damaged by an electrical short will show up as bright under UV light since it contains no copper traces or solder mask paint.
A short circuit or excess resistance causes a PCB failure that is easily spotted or overheated. You can use a multimeter to test for this type of failure. If you suspect your PCB is overheating, check the location of your components and see if any are damaged or broken. If they are, replace them. If none of your components are damaged, you might need to add more heat sinks to dissipate heat from your board.
Cracked coatings can be caused by excessive thermal shock or exposure to high temperatures. This can occur when a component requires a large amount of heat or has a poor thermal track. The best way to avoid this is to use components with proper thermal channels and provide adequate ventilation within your enclosure.
Component Stress and Fatigue
Printed circuit boards make them susceptible to stress from electrostatic discharge (ESD), mechanical shock, and thermal cycling. These stresses can cause fatigue, which results in cracks that lead to open circuits. Particularly vulnerable areas include connections between layers where traces are thin, such as microvias or small through-hole vias, and connections with large pad sizes.
The best way to protect against fatigue is to design boards that can withstand the maximum anticipated ESD and mechanical shock without fail. This typically involves using plated through-holes rather than surface-mount components, providing adequate board spacing and routing clearances between traces and components, using flexible materials for signal traces such as FR4 instead of Rogers 4350, and using conformal coating on the entire board surface.
Acid traps are used to remove impurities from the etchant. If the acid trap is clogged up, it will not be able to remove all of the impurities, and you will end up with a lousy quality board. To keep your boards clean and free of defects, you should ensure that your acid traps are free of debris or other particles that may clog them up.
To clean an acid trap, pour some fresh etchant into your etching tank and add some baking soda. This will help neutralize any remaining acids in the tank and prevent further corrosion.
Broken tracks happen when a conductive material is ripped off the board during assembly or due to an electrical short. They can also occur if a component was soldered incorrectly. To troubleshoot this failure, you will want to start by checking for broken tracks using a continuity tester or multimeter. If you find any broken tracks, try re-soldering the broken track back onto the board. If that does not work, it is time to consider replacing the entire PCB.
Chemical leakage is one of the most common types of PCB failure, especially in older devices. The chemical used to etch the circuit board may leak out over time, causing corrosion on nearby components and sometimes even destroying them entirely.
The best way to fix this problem is to remove all affected components from the board and replace them with new ones that do not contain corrosive chemicals or materials such as lead. If you are unsure whether or not there is damage caused by chemical leakage, test each component individually using an ohmmeter before installing it back onto your board.
Delamination is the separation of layers in a multi-layer PCB. This failure occurs when there is an electrostatic discharge or a burn-through on one board layer. A burn-through means that one layer has been completely burned through and has come into contact with another layer, causing it to overheat and melt. The best way to address this problem is by using a repair kit that contains conductive epoxy, which helps conduct electricity away from damaged areas so that they do not cause more damage.
Plating voids are small holes in the copper caused by a chemical reaction between the copper and the plating bath. This can happen when an operator leaves a component in the etching solution for too long or if you use a dirty etch tank. Voids can also be caused by poor plating technique or improper board layout.
The most common way to fix this type of failure is to re-plate the area with copper, but this may not be possible if there are too many voids around your board. You could also try spot soldering a jumper wire over each void and removing it with a solder wick once everything is working. Another option would be to use a solder mask to cover up any remaining voids on your board and then solder jumpers over these areas.
Electromagnetic Interference (EMI)
Electromagnetic interference is any signal that interferes with the operation of electronic devices. EMI is caused by external sources such as radio waves, microwaves, and power lines. Most modern circuits use shielding and filtering to reduce their exposure to EMI; however, there are still ways for these signals to reach your circuit boards and interfere with their operation.
To prevent EMI from interfering with your circuit boards, you must use active and passive shielding techniques depending on your application's requirements. Active shielding involves using an electronic circuit or device such as an op-amp to block out incoming signals. In contrast, passive shielding involves using an enclosure or barrier around sensitive circuits to prevent outside interference from entering sensitive areas.
Insufficient Pad to Hole Size Ratio
This is one of the most common problems with PCBs. An insufficient pad-to-hole size ratio means there is not enough copper surface area on the pad or hole where solder is supposed to flow. This can lead to poor solder joints and high failure rates.
A good rule of thumb is to use at least 1 square millimeter of copper on each pad and hole or 2 square millimeters if you use leaded solder. If your design needs to use smaller pads or holes, consider increasing their size by adding copper or making them larger by moving traces off-board.
This is by far the most common type of failure concerning PCBs. The problem arises when the adhesive used to attach components to the board is not strong enough or when components are not adequately prepared beforehand.
The best way to avoid this problem is by researching and choosing an adhesive that has been proven effective for your specific application. You should also ensure all your components have been appropriately cleaned before putting them on the board, as any residue left behind can cause problems later on down the line.
There are numerous failures associated with PCBs. They can either be due to defects in the manufacturing process or external factors. Many companies have adopted newer and better techniques to create a high quality products. However, there is still some leeway for failure in these techniques, which is why troubleshooting techniques are used.
Ultimately, the manufacturer is what matters, as the final PCB quality is most of the time-dependent on them. Finding a reputable PCB manufacturer like HemeixinPCB would not let you down. Over the years, we have seen all manner of circuit board failures. We have worked on products that have lasted decades, and we have seen almost every type of PCB failure imaginable in our day-to-day work and know all the troubleshooting techniques to ensure that your final product is reliable.