Troubleshooting PCB Faults: Best Practices for Repairing Electronics
PCB faults are a common problem with every electrical appliance and device. With extended lifetime, improper handling, and external factors, we can face issues in the functional operation of the electronics. PCB troubleshooting and repair work is an important skill for beginners. Following a correct approach to find the root cause of the PCB fault, we can foresee future issues in the PCB supply. Debugging a PCB opens the door to understanding the circuit components. Engineers can use the practical knowledge of electronic components in building new circuits. We can inspect the PCB with the help of basic measuring tools like a multimeter, hand microscope and a soldering station. However, for the complex boards, we need a few other high-end machines.
This article will focus on the PCB repair and rework steps that are a path to failure diagnosis. Manual and automation processes demand many steps to follow in the PCB repair stage. Major and minor reasons for PCB faults will be discussed too. Let us begin.
Why does a PCB Failure Occur?
Having clarity on multiple reasons why a PCB can get damaged should be known. It will help to speed up the troubleshooting process. When we begin to identify the exact problem in the PCB, it will take up a lot of time. The process has various stages. It becomes easier next time to skip a few steps if the cause is known before. Below we will learn about a few causes of PCB faults occurrence.
Some of the external factors like crashes, accidents, and device falling cannot be predicted and controlled. It will definitely damage the outer cover and internal PCBs. Physical damage during testing, vibration and shock lead to major causes of PCB faults. It will make the traces get short with each other and the PCB will fail.
PCB layout is not easy. Layout routing in an unorganised format will lead to PCB failure. To avoid known PCB faults, design rules should be set according to calculations of the power supply voltage. Ignoring clearance and creepage rules will not allow heat to pass, driving other nearby parts into thermal runaway failure.
Some errors and issues arise after improper soldering of components in the assembly process. The supplier can misread the assembly drawings or the in-house production team. Component placement, direction, and soldering quality are the primary factors causing PCB fault chances.
The product’s field of application can be in extremely dry, dusty, moist, and humid areas. These factors can lead to PCB malfunctioning. Some foreign particles can enter the PCB and spoil the board’s features. Shorting occurs if water and chemicals enter. The conductive parts get rusted, reducing the product’s lifetime. All these factors would result in PCB faults and affect the overall PCB performance.
Electrostatic discharge is very high voltage. Electronic components are sensitive to ESD transients. During board assembly, holding the board with bare hands transfers static charge to the semiconductor parts. This should be avoided at all times during the manufacturing process to avoid PCB faults.
Testing Tools Required to Repair PCBs
Simple PCB faults of double-sided boards can be fixed and diagnosed with basic lab tools. But for multi-layered high-density complex boards. We require high-end automation machines to help with PCB repair work. Let us check the list of tools necessary for debugging.
Steps to follow for PCB Repair
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Outsourcing PCB repair work to external suppliers is a risky task. The design will be copied easily and they will launch their product at a cheaper price. Such instances can be avoided by taking the matter in the electronics lab. It will be a time-consuming process. It involves a lot of patience and understanding of the circuit flow. Engineers who will undertake the method and actions to identify and fix the PCB faults will benefit a lot. We will learn about the best practices to begin with to avoid basic PCB faults.
Setup the Board:
ESD workbenches with intense lights should be used as furniture to lay out the repair tools first. Wear the anti-static bands, use a PCB stand to fix the position of the board, and keep the board under a magnifying lamp. These basic setup actions are manageable with every engineer and professional. Irrespective of the work environment office or home lab.
Begin with a Visual Inspection:
A few major PCB fault detections can be caught with a thorough visual checkup of the faulty board.
Working PCB Comparison:
Based on the availability of quality pass boards. It is a good practice to compare the bad board with the good board. Engineers can scan the board parts through clear visual inspection, measure the power supply, test the component’s functionality, and compare the output values of the circuit for PCB fault finding. This will allow easier access to faulty areas considering the type of issue observed. Signal attenuation error requires more analysis in the bad PCB.
Test for Shorting:
Keeping the power away from the board, probe the input section of the PCB. If the multimeter makes a buzzer sound, we have found the power supply section of the board is defective. Test the individual components of the supply section like a resistor, transistor, and didoes. The specification should match the datasheet values. Any mismatch found requires replacing those parts with new ones to avoid the potential PCB faults.
Power up the Board:
Once the visual inspection is completed and no issue can be encountered, we move to powering the board. Assuming you have the schematic diagram handy, engineers can identify the main power supply section of the board. Now it is time to use an external power supply to power the board and measure the power rails voltage. Variation in the correct voltage (zero voltage, fluctuating voltage, higher voltage)indicates a problem in the related parts. Due to overheating or voltage transients, some PCB faults would arise during the final product testing.
Fixing Broken Traces/pads:
The current capacity of a trace depends on the trace width. Traces are scraped off if the current exceeds the limit. A cracked trace will stop the conductive path in the circuit. We can fix these traces by soldering them or by using a thin wire strand. If the gap is small, clean the trace and fill the gap with solder to fix the PCB faults.
Verify ICs:
An integrated circuit is used for various operations on a circuit board. DC-DC converters, flash memory storage ICs, analog and digital sensors, isolators, microcontrollers, communications ICs (CAN bus) etc. It is a tedious task to determine which IC is not working properly. Engineers should have the skills to use an oscilloscope to test the ICs for PCB fault detection. Input and output signals have to be probed. It is better to analyze the waveforms with a working board. Functionality and IC behaviours can be rectified with this method.
Testing Systems:
Automated test systems are another option to fix faulty boards. These test instruments have information on IC pins. We get the details about the VI curve and active and passive components functionality. Companies can buy these systems and perform the analysis internally. In-circuit testing (ICT) and functional circuit testing (FCT) can be done for complex multilayered boards. These ATEs can be handled by staff members who are also not very trained.ABI Electronics System 8 is an example of ATE.
Summary
We should remember that PCB faults can occur in any electronic device. But some measures can be undertaken to avoid the faults repeatedly. PCB repair work puts a lot of pressure on the engineers if the failure rate is high in a product. All these techniques are guided principles that will allow engineers to gain knowledge on the circuit and component level. Cost replacement of the component should be considered because the major ICs are expensive. If the EMI shields are broken we can fix them by using conductive paints.