Guideline

Troubleshooting PCB: Identifying and Resolving Common Faults

PCBs are considered the backbone of almost every electronic device. With the advent of electronics, PCBs are nowadays becoming more complex which means the probability of having faulty PCBs is increasing with increasing complexity. PCB troubleshooting extends the lifespan of PCBs, there are different ways to repair and troubleshoot faulty PCBs, but each PCB board troubleshooting method requires a different expertise level. This guide covers almost every aspect of troubleshooting faulty PCBs, from why PCB malfunctions to how to troubleshoot faulty PCBs. 

In this article, we will talk about the main causes of PCB failure and how to troubleshoot a PCB. 

Causes of PCB Malfunctioning

Before troubleshooting PCB circuits, we need to know the reasons for faulty PCBs first. There are various reasons why a PCB may malfunction, and some of them are jotted down.

  • Design Shortcomings: It include incorrect PCB routing, minimum clearance violence between components and traces, improper grounding and power plans, and not taking care of signal integrity.
  • Defective Electronics Components: Some components have inherent manufacturing faults, components whenever used in any PCB, may lead to malfunctioning PCB.
  • Design flaws: Design flaws are considered one of the primary reasons which lead to PCB failure. It includes almost every aspect like PCB routing, inadequate component placement, power distribution, signal integrity problems, and thermal management. Such flaws can be mitigated by comprehensive collaborations between PCB design engineers and PCB fabricators. 
  • Lack of ESD Protection: During PCB’s stuffing, failure to incorporate appropriate ESD protection leads to damaged sensitive components on the PCB and eventually leads to PCB failure.
  • Environmental Factors: Different PCBs are meant to be designed to operate in different environmental conditions and stuffed components must qualify accordingly. For example, if a certain PCB has to operate in extremely high temperatures or extremely low temperatures then sourced components for that PCB must have the capacity to operate in such extreme environmental conditions, if not then the final PCB will malfunction. This could be achieved by thoroughly going through the component datasheet before sourcing it.

There are many other reasons for PCB failure like manufacturing errors, soldering issues, physical damage, ageing, wear and tear of components, power mismanagement, and sourced under-rated components than required. To understand these reasons is helpful to know how to troubleshoot PCB.

How to Troubleshoot PCB Board

PCB troubleshooting is a hectic job and sometimes a challenging job to do. Here, we will talk about how to troubleshoot PCB in details. A step-by-step guide to performing PCB troubleshooting is shown in Figure 1. Before starting PCB troubleshooting, it is important to keep safety measures intact to avoid health-related problems. 

  • Before starting PCB troubleshooting, it is mandatory to turn off all power sources.
  • Use anti-ESD straps, gloves, and other personal safety equipment.
  • Make sure there is no shortage of jumping wires, then turn on the power sources.
  • It is important to work in properly ventilated areas so there is no accumulation of cleansing chemical fumes or soldering smoke.
PCB Troubleshooting Steps

Figure 1: Flow diagram showing step-by-step guide for troubleshooting faulty PCB.

1. Visual Inspection:

Visual inspection is very important in PCB board troubleshooting. It’s the first step after having a faulty PCB. Generally burning out of electronic components is the major cause of PCB failure which can be easily spotted by visual inspection (refer to figure 2), and then strategies of how to troubleshoot PCB board. Other faults like cold joints, excessive solder, missing pads, and the polarity of polar components can also be detected and resolved by naked-eye visual inspection. Some errors are not detected by the naked eye, for those errors AOI or x-ray inspection can be beneficial. After detecting and replacing the defective component check for PCB functionality if the PCB is troubleshot successfully or not, if not then move to the next step of troubleshooting a PCB (refer to Figure 1).

Burnt out Components on PCBs

Figure 2: showing how burnt-out components look alike in PCB.

2.  Check out Schematic Design:

As discussed earlier, a PCB comprises different electronic components connected to form a closed-loop circuit. A good PCB designer makes different sections in the PCB like the power supply region comprised of capacitors with high ratings, sometimes a bridge rectifier, and voltage divider, other sections for sensitive components, and an operational amplifier for easy debugging and clarity. Schematic checking is very helpful in PCB board troubleshooting.

By good luck, if the schematic diagram is available then with a good understanding of electronics, PCB debugging becomes easier but if there is no schematic diagram then it is good practice to have one by simply reverse engineering the PCB to have better insights. 

3. Power Up the PCB:

It is important to check whether while troubleshooting PCB can be powered up or not. There are different methods to troubleshoot the PCB for each case. Both cases are jotted down.

  • Case 1: when PCB can be powered up:

In this case, simply power up the PCB. Different PCB requires different powering-up procedures for example some PCB requires simple DC power and can easily powered up by using DC power supplies, some PCB requires AC power and for such PCB function generators may be used.

After powering up the PCB, look for the hotspots and check whether any component has a heating-up issue or not. If any component has a heating problem, then check its input and output. If, for required input that component does not provide the required output then by replacing that malfunctioned component the faulty PCB is successfully troubleshooted.

If there is no hotspot, then check different circuits’ input vs output parameters with the help of DMM and Oscilloscope. This requires extensive electronics experience and knowledge to troubleshoot such PCBs. This method is most commonly used and most effective in troubleshooting faulty PCBs.

  • Case 2: When PCB cannot be powered up:

It is recommended to consult the schematic diagram and with good knowledge of electronics make the faulty PCB power up, but if this isn’t the option then look for a reference PCB that is working fine and start a thorough comparison to spot if any component is different in both PCBs. If there is a different component, then replace that and check if the faulty PCB is successfully troubleshooted or not. In this case, powering up different small circuits in a PCB may sometimes prove beneficial making troubleshooting easier, but this requires a very high level of electronics knowledge so that powering up small circuits doesn’t affect other circuits in the PCB.

Conclusion

PCB troubleshooting is an essential task to not only detect why PCB malfunctions but also mitigate the problem which requires extensive knowledge, and experience. By systematically analyzing the options and applying the corresponding techniques mentioned above, PCB board troubleshooting becomes easier and more effective, saving time and cost as well. 

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