All You Need to Know About How to Check If a PCB Is Working

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A PCB that works as the brain of several electronics is made from several components. It is a complex structure, and everything needs to be perfect for the PCB to work properly. Even if one small component stops functioning properly, there will be performance issues, or in the worst case, the circuit may stop working. Knowing how to check if a PCB is working is essential.

Here we will take you through different automated ways of checking PCB along with the manual way of checking whether it is working.

How to check if a PCB is working or not? Top eight methods you can try.

Automated methods are better when you want to know how to check if a PCB is working or not for batches. Once set up, these offer quicker results with higher efficiency. Here are the details about different ways you can check PCBs in batches to check if they are working correctly or not.

In-circuit testing

It is the most robust type of PCB testing that we use today. It powers up the PCB and checks everything on the circuit for perfect performance. Including the performance metrics, this testing method also checks the physical solder connections using a bed of probes.

ICT is an efficient testing method if your PCB has ball grid arrays that make manual testing difficult. It is a rather costly testing method and only good for mature units instead of the ones in the development phase.

AOI

AOI stands for Automated Optical Inspection, which uses cameras to take PCBs photos in 2D and 3D planes. After taking pictures, the circuitry is compared with a schematic to see if it has any issues. AOI checking is useful for detecting issues in the PCB in its early production stages.

It may be cheaper and quicker, but the results are unreliable as you have to use it in combination with other testing methods like ICT, flying probe, or functional testing.

Flying probe testing

It is a less expensive testing method than ICT, and it works with the help of an ECM, where coordinates are programmed to match the right points on your circuit. There are several needles attached to a prob on the x-y grid. It tests different aspects of a circuit, including inductance, resistance, shorts, opens, capacitance, and diode issues. Flying probe testing can be cheaper but is not as quick as the much better ICT.

Burn-in testing

Burn-in testing is used for detecting issues in PCBs in the early stages, and it is good if you want to test the load capacity of a PCB. Due to its way of working with higher intensity, this testing method may end up burning certain parts of a PCB, but the remaining ones can be verified as being able to bear the load capacity. The PCB stays under continuous stress for 2 to 7 days in this testing method.

It may not be a good choice for every type of PCB, but this testing can prevent users from dangerous and embarrassing situations after the early launch of the product.

PCB

Functional testing

Functional testing is a traditional method of testing PCBs, and the main goal here is to verify if the PCB powers up and works as intended or not. Functional testing may need external equipment and an ECM to develop tests specifically for the PCB.

Functional testing is cheap and tells about every functionality of a PCB, but it can also take a longer time for results depending on the complexity of the circuits.

Xray inspection

X-ray inspection is also known as AXI, which is practical for hidden components. This testing method uses 2D and 3D X-ray tests to see the parts of a PCB, like ball solder joints that go under an IC. Many testing methods, including ICT, visual testing, and flying probe testing, cannot see those hidden components and internal defects, while X-ray inspection is efficient for testing those.

Solderability

Solderability testing ensures that the surface of the PCB is sturdy enough to house all the components. Additionally, it ensures that there could be reliable solder joints for all the components on your PCB. However, this testing does not work for any circuit schematic functionality or technicalities.

Contamination

Contamination testing is about detecting Ionics in the PCB that may contaminate the soldering points. This testing can prevent the PCB against corrosion and other similar issues by taking the right prevention measures.

Manual checking of a circuit board that stopped working

Automated ways for how to check if a PCB is working are better for batch testing. However, manual checking is the most effective way if you have one PCB that you need to test. It provides an in-depth look at the PCB and all its components, but there are several components of the PCB that you need to check.

Although this method may take longer, it can help you track down the issue with a PCB, which will be vital if you want to repair the PCB.

Tools needed for testing

For manual testing, you will need certain tools and equipment, including the following:

  • Magnifying glass
  • Multimeter
  • Solder and desoldering station
  • Variable power supply
  • A pair of tweezers, etc.

These tools will be helpful in different steps of manually checking a PCB for different components. Below are the steps you may follow for manual PCB testing.

Visual inspection

The first step in the manual testing of a PCB is visual inspection. It is efficient in checking if there are:

  • Liquid damages
  • Burnt or blown components
  • Cracked or broken circuit traces

These are the most common reasons why PCBs stop working sometimes, and these are also easy to detect. Even if these aspects are smaller, you can get assistance from a magnifying glass in a well-lit area. The burnt components will show structural damage and dark areas near them, which will be the aftereffects of burning.

In case of liquid damage, there may be corrosion in different colors (commonly white or green). There could be longer cracks for the cracks and broken traces, while shorter ones, generally near the corner or edge, can also make the PCB malfunction. Cracks in most PCBs are generally thinner and undetectable with the naked eye.

Checking power module

After your PCB passes visual inspection, you must look at the power module. A part of the PCB is always dedicated to converting the input power to the desired power ranges for efficient performance. Some circuits may have separate power modules, while the power modules are built within the circuit in most compact circuits.

It is the part where you need to use your multimeter. Start by checking the input voltage and verify if the PCB is getting the correct amount of input voltage. Next, you need to check the output voltage of your power module. That must also be within the working range of the power module.

When you are checking the power module, and you find a 0 voltage reading at the regulator, then one of the components of your PCB is short. A common indication of this happening has a frequently breaking fuse.

Checking input and output values of the circuit

Next, you need to check the input and output values of the actual circuit, and checking I/O ports is an important part of this step. Damaged ports can result in the circuit shutting down as it creates anomalies in the circuit. If your I/O ports are protected by fuses, varistors, or Zener diodes, and they are working perfectly, then there are chances that the microcontroller of the circuit is damaged.

The only way to verify that microcontroller is good or bad is by replacing it with a known good replacement. Alternatively, using a multimeter, you can also check the circuit diagram and verify the microcontroller according to its internal circuit. Although it will take a very long time, it can be a good choice if you don’t have a replacement readily available.

Detailed inspection with a multimeter

If you haven’t found any issues, you need to do a detailed inspection. Detailed inspection means checking every component and circuit trace to track the issue. The multimeter will be your best friend here as you can verify the perfect working of all the tiny components like resistances, capacitors, inductors, transistors, etc.

A multimeter can also make detecting any short circuits and broken circuit paths on your PCB easier. Using these steps, you can manually check the PCB to see if it is working and verify it is working perfectly.

Conclusion

Quality checking and testing are one of the most important things about a PCB. Mass production testing ensures that there are no problems with a PCB. Similarly, knowing how to check if a PCB is working can help you resolve issues with your PCBs, especially the ones that stopped working. Depending on certain requirements, you can choose any automated or manual way to check the performance of a PCB.

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