PCB Testing Methods

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Apr 9, 2020|Quality and Testing

When it comes to electronics, there’s a relatively high chance of a designer finding something wrong, such as a faulty wire or a bug. Printed circuit board (PCB) testing methods are crucial in ensuring a product is working correctly. Using PCB methods, including Automated Optical Inspection (AOI) and X-Ray Inspection, can help identify problems early on, saving both time and money. 

Why PCB Testing is Required

It is absolutely necessary that any designer or builder performs PCB testing methods if they want to achieve ultimate success. By testing your circuit boards, you can minimize significant issues, identify minor bugs, save time, and reduce overall costs. 

PCB testing primarily serves to mitigate issues both throughout the manufacturing process and during the final production run. These kinds of tests can also be used on prototypes or small-scale assemblies, which help single out potential issues that the final product might have.  

What is Being Tested in PCB Testing

Various components of a circuit board can be tested during the various PCB testing methods. 

Lamination

The quality of lamination in a PCB is a crucial component. Testing your lamination’s resistance to peeling using force or heat application. Peeling can cause significant issues surrounding a PCB’s final functionality. 

Copper Plating

It’s essential to test the copper plating of a PCB board, which is a copper foil laminated to the board. This covering delivers conductivity and should be tested for quality, tensile strength, and elongation in great detail. 

Solderability

Solderability testing means analyzing the material on a circuit board to ensure that other components can be attached securely. If a board proves to not be solderable, a designer cannot confidently connect other necessary components to it. This testing is done using wetting. 

Hole Wall Quality

Using hole wall quality testing, a professional can determine whether or not the hole walls will crack or delaminate while the PCB is in use. This testing typically involves quick temperature changes to gauge how the PCB will react to thermal stress environments.  

Electrical

In order for any PCB to function appropriately, it has to have stable electrical conductivity. An electrical test will determine this by passing electric currents with minimal leakage through the board. 

Environment

Because PCBs often work in humid climates, designers have to test them for water absorption. Experts will weigh the PCB both before and after its introduction to a moist environment. If there are major changes in weight, the PCB has failed. 

Cleanliness

Finally, a PCB needs to be able to withstand all kinds of corrosion, humidity, dirt, and other outside factors while still operating properly. Experts will test a PCB and its resistance to a wide range of potential environmental conditions, analyzing the before and after of each. 

PCB Testing Methods

If you’re wondering how to test a circuit board, you may not realize that there are actually several PCB testings methods. The following circuit board testing methods can help you discover various issues, and all serve as essential processes. 

In-Circuit Testing

In-circuit testing requires the use of an in-circuit tester, a fixture, and specialized software. This equipment is used together to interact directly with the board that is being tested, while the software instructs the system and delivers the tests for each type of board. 

This method is prevalent because it is capable of identifying 98% of faults and can test individual components, regardless of any others that are attached to it. 

Flying Probe Testing

The Flying Probe Test, also known as the Fixtureless In-Circuit Test, operates without using any of the custom fixtures. Its main benefit is that it minimizes the overall costs of the test, but it’s also very simple.

This test uses one fixture to hold the board so that test pins can move around and analyze various points, all controlled by software. It’s very versatile and adapts to new boards quickly and easily. 

Automated Optical Inspection (AOI)

An AOI test will use either a 2D camera to two 3D cameras to capture photos of the PCB. Then, the program will compare these pictures to a detailed schematic and look for flaws or mismatches. 

AOIs are useful in detecting early issues to halt production and save time and money. However, experts will never rely solely on an AOI simply because it doesn’t power up the board and can’t test all part types. 

X-Ray Inspection

Technicians use X-Ray Inspections (AXI) to locate defects in solder connections, internal traces, and barrels. With both 2D and 3D AXI tests available, designers can take their pick depending on the board on hand – though 3D testing is typically faster. 

Functional Testing

Functional testing is pretty straightforward, as it simply tests the functionality of a circuit. Used at the end of a manufacturing plan, functional testing simulates the final environment of the PCB by interfacing with it via test-probe points or edge connectors. 

Design for Manufacturing (DFM)

DFM arranges a PCB topology concerning the manufacturing process. It tests for silvers and islands, solder bridges, and copper to edge – all things that can cause shorts, corrosion, and interference within a circuit board. 

DFM tests are typically used early on in the process to help reduce overall costs and timelines. They use various software programs to maintain success. 

Solderability Testing

As we mentioned earlier, solderability is crucial to the building process of a PCB. A solderability test will ensure that the surface of a PCB is ready and sturdy enough to form a strong, reliable solder joint. 

PCB Contamination Testing

This test locates bulk ionics that might contaminate a PCB board. These contaminants can cause major issues like corrosion and should be found and eliminated as soon as possible. 

Micro-Sectioning Analysis

A micro-sectioning test will have a professional look into defects, opens, shorts, and any other kind of failure. 

Other Functional Tests

Other functional tests will determine a PCB’s behavior during the product’s end-use environment. 

Time-Domain Reflectometer

Also referred to as a TDR, this test locates failures within a high-frequency board. 

Peel Test

The peel test analyzes the strength and resilience of the laminate used on the board. It will determine the amount of force needed to peel the laminate. 

Solder Float Test

A solder float test measures the level of thermal stress that a PCB’s holes can withstand, using extreme temperatures to do so. 

Conclusion

Printed circuit board failure analysis testing is crucial to the success of any product using a PCB. PCB performance testing methods, PCB assembly testing methods, and PCB functional testing methods are all ways to ensure your circuit boards and materials are working properly.