What are the Main Techniques for PCB Inspection?

No matter the type of PCB you are creating or building, or the device they are intended for, your printed circuit board needs to work correctly.

This is because these boards are important for the effective functioning of many products. Also, malfunctions can lead to serious issues.

This is why we have come up with this article. Here, we will be discussing why PCB inspection is important, as well as the various PCB inspection techniques you can use for the process. Please read on as we explain the concept of PCB inspection further.

What is PCB Inspection?

PCB Inspection is a very important element during the manufacturing process of any electronics. With PCB inspection, it allows the manufacturer to detect faults much easier and quickly after the process of manufacturing. This is why PCB inspection is very important.

Inspecting printed circuit boards all through the design, the manufacturing process, as well as PCB assembly process, is important in ensuring the product meets the quality standards, and that it operates properly.

Today, printed circuit boards are complex. However, this complexity allows new capabilities as well as creates possibilities for more failures.

As printed circuit boards become more advanced, the inspection technologies and techniques used have also become advanced to ensure they are of quality.

You can select from the different methods or techniques of PCB inspection. This type of PCB will decide the best technique to make use of. It also has to do with the present stage in the process of production, as well as the faults that you wish to test.

Basis of PCB inspection

During the early periods of PCB manufacturing, or the manufacturing of electronics equipment, the inspection was a manual process. Back then, it was the best option, but with limited value. The nature of this manual process was repetitive.

This means that many faults were not discovered and were passed to the next production stage without being detected.

Below are methods through which manufacturers can achieve PCB inspection.

Methods of PCB Inspection

In this section, we will be discussing the 7 main inspection methods.

Manual Visual Inspection

From the name, manual visual inspection deals with individual inspectors that are searching for boards as well as other assemblies to check them for issues. Visual inspection is expensive and yields poor results. However, before automation, this was the only available way to carry out PCB inspection.

Automated Optical Inspection

Automatic or automated optical inspection is among the best inspection methods for PCBs. It makes use of an optical system, which captures the image of well-completed PCB assemblies or assembly, and then compares both images to help detect faults as well as other issues.

This PCB Inspection method is widely acceptable and it has been well perfected to ensure it operates more reliably.

AXI PCB Inspection or X-Ray Inspection

With PCB density increasing, and the use of newly developed technologies for IC mounting, you may not be able to see all the solder joints. Most especially, during the manufacturing of new boards as well as the use of new set ups, it is necessary to verify that the solder joints on some packages like the ball grid array (BGA) have been properly soldered.

You cannot achieve this with optical inspection because the solder joints cannot be seen. The options available are using the x-ray system, AXI, automated x-ray inspection, which can check underneath the chips to view and check the solder joints. Though it is expensive and can only be used for a little proportion of solder joints, they play a significant role in many ways or instances.

For production in high volumes today, the majority of manufacturers make use of the AOI system to handle PCB inspection. As the number of ball grid arrays increases, as well as the BGA packages used, the use of the AXI inspection also increases.

In-Circuit Testing

This PCB testing is known as the most robust testing method in existence. Its high cost reveals that about thousands of dollars via the cost depends on fixture and board size, coupled with other factors.

This test has to do with the use of fixed probes, which are laid out in such a way that it has a match with the PCB design. This checks the solder connection’s integrity.

Functional Testing

Some customers will prefer to have an old-fashioned, good functional test. This is used by the electronic contract manufacturer to verify the powering up of the product. This test requires some things:

  • Fixtures
  • External test equipment
  • Requirements for MSHA, UL, as well as other standards

The customer usually provides the functional test with its parameters. Furthermore, some ECMs offer the service of developing and designing this test.

Burn-In Testing

This PCB testing type is a more intense testing method. It helps in detecting failures early as well as establishes the capacity of the load. Due to the intensity, this testing method could bring destruction to the tested parts.

Though burn-in testing isn’t meant for all projects, there are projects where this test is very useful. It could prevent dangerous or embarrassing product launches even before they get to the customers.

Flying Probe Testing

This is a tested option which is less expensive compared to in-circuit testing. This test is non-powered and it checks for diode issues, inductance, capacitance, resistance, shorts, and opens.

Flying probe test functions using needles, which are attached to the probe on the x-y grid that has been obtained from the basic CAD. The ECM program helps in coordinating to match the printed circuit boards and then helps in running the program.

Note that the flying probe testing isn’t responsible for powering up the board.

PCB Inspection During the Process of ManufacturingPCB inspection has two major usesManufacturing defects

Notably, the most important and obvious function of PCB inspection is to help in highlighting defects. This is to make sure that they are corrected before moving on to the next stage of production.

Finding faults quickly and earlier during production is important because the costs involved in finding and fixing faults increase by about 10x as you pass each stage of production.

Provides feedback of the process

Another significant function of PCB inspection is providing feedback about the process of manufacturing. Using this system on the process of soldering can allow the manufacturer to see any pattern faults. This process will then be corrected immediately to eliminate or reduce this problem from happening again.

Furthermore, the PCB production process allows you to detect boards having failures coupled with feedback to aid the production.


Here is the end of our article on PCB inspection. Kindly check our blog for more information on PCB-related topics.

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