Guideline

Guide to Testing PCB Boards: Everything You Need to Know

PCB Test and AOI

PCB manufacturers set a lot of various quality control checks and perform PCB testing as they acknowledge that PCB goes through a lot during its fabrication. To ensure the high quality and reliability of PCB, these checks and tests proved beneficial in many perspectives. Pre-established guidelines regarding PCB requirements and functions are being directed to manufacturers by designers, and to achieve a functional and reliable PCB, it is important to perform comprehensive mechanical and electrical testing on the PCB. This guide covers all the perspectives on why testing is important, what is being tested, and how to test a PCB board.

Why is PCB Testing Important?

Before we dive into how to test a PCB, we will talk about why PCB testing is important first. Some of the top benefits of PCB testing are jotted down.

  • Keet Good Quality:

Although most times, PCBs will be produced correctly, no one can ensure no mistakes in PCB production. So a lot of tests are done during or after PCBs are finished. For example, E-test will help PCB manufacturers to defect the circuit boards with open or short circuits.

  • Meet Industrial Standards:

Almost all industrial areas have their acceptance standards. In the PCB production industry, the most widely acceptable standard is the IPC standard, such as IPC-A-600. PCB manufacturers will do many tests to ensure the PCBs are produced and meet the standard, such as copper thickness, plating thickness, defects., etc.

  • Meet Customers’ Demands:

Except for industrial standards in PCB production like IPC standards, many PCBs have their own requirements. For example, PCBs with impedance traces need to do a TDR test, to make sure the impedance value can meet customers’ requirements.

  • Troubleshooting And Bug Detection:

One major advantage of PCB testing is, that it helps to find a bug in the final PCB whether the bug is related to mechanical or electrical functionality which eventually helps in troubleshooting of malfunctioned PCB.

  • Save Cost:

Although extra testing will need more time and investment in PCB production, and any serious defects may bring extremely big losses to PCB manufacturers and customers. So comparing this loss, PCB testing can save a lot of money.

  • Increased Safety:

As PCBs are becoming essential for every electronic device ranging from daily usage devices to health and safety devices, failures in such devices can result in serious consequences due to failures of PCB. For example, a PCB with a short circuit may cause fire or very serious accidents. Testing in the early stages of manufacturing such devices reduces PCB failure and eventually reduces the potential damage caused by faulty devices, thus improving safety.

PCB Dimension Test

What is Being Tested?

Before going to how to test PCB board, we will check about what will be tested first. PCBs undergo different testing phases during fabrication and also after completion to ensure the final PCB satisfies reliability and durability standards. Overall PCB testing is divided into the following major categories.

1. Mechanical Testing:

To check durability, PCBs undergo different mechanical testing, some are jotted down below.

  • Physical Inspection: This test is performed either manually or with the help of an automated machine to check for delamination, insufficient solder mask, cracked PCB, or other physical defects.
  • Peel Test: after stacking up PCB laminates, this test is performed to check how much force is required to peel the PCB laminates apart.
  • Solder Pot: This test is performed to check the sustainability of pads, especially the plated through-hole solderability.
    Ionic Contamination Test: This test is used to check the ionic residues in the PCB production process.

2. Electrical Testing:

Electrical testing is performed to check the fabricated PCB concerning its electrical requirements, like connectivity, impedance matching, and conductive residue. Some of the electrical tests are:

  • Continuity Test: This test is mandatory and generally performed to check the short traces and open points that are meant to be short and open respectively, in the fabricated PCB.
  • Hi-Potential Test: While performing this test, the newly fabricated PCB undergoes high potential to check the insulation between unconnected nets in the PCB. This test is highly recommended for PCBs with dielectric layers or high-voltage PCBs.
  • Impedance Test: An impedance test is performed to check the impedance of different traces from single-ended traces to differential pair traces. It is always needed in high-speed or high-frequency PCBs.

PCB Open and Short Test

PCB Testing Methods

How to test a PCB? Generally, PCB fabricators offer different PCB testing methods to their customers while placing PCB fabrication orders, some of them are highlighted below.

Visual Inspection:

This inspection is performed manually by the trained operator simply with the help of a microscope or simple magnifier glass and is considered one of the most widely used testing methods. There are many reasons why this testing method is considered a widely used method like low operational cost and, the test procedures may change flexibly according to PCB.

In-Circuit Testing (ICT):

ICT proved a very powerful tool in PCB testing, as it covers a vast range of fault detection and verification for electronic circuits as well as electronic components like short circuits, open circuits, and wrong component placement. This test can be performed with the help of a bed of nails to check different electronic parameters such as inductance, resistance, and capacitance, in newly fabricated PCB.

Flying Probe Testing:

Flying probe testing is considered cheaper than ICT and is generally performed without powering up the PCB. This testing helps to check for open or short circuits, capacitance, inductance, and resistance. This is performed with the help of probes with needles. This testing is slower and more prone to error than ICT yet cheaper.

X-Ray Inspection:

X-ray testing is performed to check for PCB defects that are hidden from the naked eye such as defects in inner layers of PCB, solder voids, solder joints under BGA or other IC packages, insufficient solder, components misalignment, and inner layer misalignment. X-Ray testing is beneficial for complex multi-layered densely packed PCBs.

Functional Testing:

To check if the fabricated PCB performs the intended functions correctly, functional testing plays a part. This testing varies for different PCBs. A predefined testing procedure with relevant equipment is required to perform the functional testing by simulating operating conditions like in the real world.

Environmental Testing:

This testing procedure is performed to check the reliability of the fabricated PCB by subjecting it to extreme environmental conditions like high temperature, low temperature, humidity, shock, vibration, and even extreme temperatures in an operational state. This reliability test allows to access the durability and long-term performance of the PCB.

Conclusion

PCB testing is very important in the electronics manufacturing industry to ensure that the fabricated PCB meets the highest standards of functionality, reliability, durability, and quality. No matter if you are a PCB designer or buyer, it is important to know the PCB testing and how to test PCBs. By performing different sets of testing procedures PCB fabricators can detect problems and address the defects more efficiently which eventually aids in maintaining OpEx and TAT and in enhancing overall customer satisfaction.

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