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Role of Functional Testing in PCB Assembly

 Sep 13, 2022

PCB Assembly

Printed circuit boards (PCBs) have significantly surged the growth of the electronics industry for many years, and this trend is set to continue for the next few years. They are the backbone of several electrical, electronics, or electromechanical devices. Advancements in electronics and technology have led PCBs to their way in several critical applications. PCB design, fabrication, and assembly are all important aspects of the process, and it is crucial to have no errors in these stages. Also, it is crucial to meet the functional requirements based on the application and check how it works for the final product. This is why PCBs undergo different testing and inspection methods during each step of the manufacturing process. There are different PCB testing and inspection methods used today, and they may be used at different levels or stages. Of all these, functional testing is a popular testing technique that guarantees the functionality of circuit boards. Although it comes at a much later stage, it is extremely important as a functional test verifies the component's functionality, parametric values, and other important aspects of circuit boards in detail. Functional testing is done close to the real environment and tested with the actual product. Are you intrigued to know more about the PCB functional test?

Details About Functional Testing

Being a final step in the process, functional testing validates that the PCB is free of defects and functions well at all levels. While the PCB design is already tested at this stage, the functionality of the circuit board is checked at various levels to understand how the final product will be in the real environment. Simply, a functional test of PCB provides pass or fail determination to proceed with further processes. Functional testing stands out among other PCB testing techniques. For instance, in-circuit testing examines each component after being soldered in the circuit board. However, the entire board is checked in functional testing to ensure its flawless performance. As a result, it gives a green single before the assembled PCBs are shipped. The below section describes the benefits of this PCB testing technique.

How Does Functional Testing Improve PCB Quality?

Functional testing can detect defects in PCB manufacturing and assemblies. Aside from helping with fault detection, this technique analyzes a detailed root cause. The process of identifying and fixing the faulty components or circuitry is documented, ensuring a laid down guideline for improving PCB quality in the long run. The following benefits of functional testing also help improve PCB quality. So, let’s take a look at them.

  • A functional test detects inappropriately placed or missing components. The operating environment of the device under test (DUT) is stimulated, eliminating the need to buy testing equipment.
  • It is considered a cost-effective and more straightforward testing technique than others.
  • It is possible to document the entire process. This acts as a reference to improve the PCB quality. The documented material also serves as a guideline for future versions and developments.
  • The functional test ensures zero errors as the whole circuit board is tested.
  • This testing method operates simultaneously with other testing methods, such as flying probes and in-circuit testing.
  • The tester or engineer can test 50% to 100% of the final product being shipped. This eliminates the efforts and time required for an OEM to test and debug.

PCB Functional Inspection and Testing Techniques Adopted by OEMs

Most OEMs find it challenging to develop compact-sized circuit boards with many solder connections. Due to the high density of connections, there is a possibility of misplaced components, wrong orientations, open wires, and more. This is where the following inspections and testing methods come to the rescue. Functional testing checks include:

  • X-ray Inspection: It is mainly employed to identify several complexities which are not visible to human eyes. Also called automated x-ray inspection (AXI), it can penetrate solder joints and capture their images. Experts compare these images to identify defects, such as missing balls, inappropriate placement of components, solder disposition, and more.
  • PCB Solderability: It is another important functional test method. Testing PCB pad and component solderability help minimize several PCB assembly problems, ensure the sturdiness of the surface, and more.
  • PCB Contamination Test: PCBs may be contaminated due to various reasons. This may include flux residue, reaction byproducts, and more, resulting in degradation, metallization, and corrosion. Therefore, a contamination test is performed to ensure the flawless performance of components.
  • Micro-sectioning Analysis: It checks the inner workings of PCBs. Popularly called metallographic or cross-sectioning, it helps identify shorts, open wires, solder reflow, faulty components, and much more.
  • Peel Test: It is designed to determine the adhesive strength required to peel the laminate from the board.

By now, you may have got an idea regarding the significance of functional testing in PCB manufacturing and assembly. The better the PCB quality, the better the product will perform. The quality of circuit boards depends on two important aspects, namely precision, and accuracy. So, it is important to test these aspects throughout PCB manufacturing and testing. Being one of the leading industry players, Accelerated Assemblies offers PCB manufacturing, assembly, and testing services. Over the years, the company has served clients across industries.

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