PCB Testing: A Focus on In-Circuit and Functional Testing

PCB Testing: A Focus on In-Circuit and Functional Testing

Apr 07,2020

A printed circuit board (PCB) contributes to the current-carrying capacity of various electronic and electrical devices by connecting different electronic components. The connection is made through fine elements such as pads, conductive tracks, and so on. A sudden malfunction of any of these elements may lead to a drop in efficiency or a sudden breakdown of a device, where it is being used. This is why PCBs are meticulously tested for functionality and performance before their integration in devices, where they are supposed to be used. It is a common practice among PCB manufacturers to test PCBs in different conditions before delivering them. It is observed that most of them prefer In-circuit testing and functional testing over other forms of testing. This post discusses, why these types are preferred over others.

Therefore, they are certainly demanded to be meticulously tested for functionality. There are many techniques of PCB testing yet in order to test PCB assemblies, In-circuit Testing & Functional Testing are the most preferred ones.

In-Circuit Testing and Functional Testing: Why They Are 

There are two broad categories of PCB testing- bare-board testing and assembly level testing. Assembly level testing is conducted to ensure the proper functioning of PCBs. Let’s discuss the most popular assembly-level PCB testing methods that are in-circuit testing & functional testing.

    1. In-Circuit Testing (ICT):

    In-circuit testing (ICT) for PCB is the technique that uses a probe to test the functionality of assembled PCBs. This ICT testing is performed to check shortages or open connections in an assembled electronic circuit like PCBs. This technique also helps determine the functionality of the PCB by verifying factors current, voltage, resistance, temperature, with the calculated design values. It ensures that the functional values of these factors do match with the calculated ones, this ensures the proper functionality.

    In-circuit testing (ICT) is also called a “bed of nails test” because it uses a traditional device called the “bed of nails”. Bed of Nails is a device made of pogo pins lying on a surface, where each pogo pin makes contact with the specific node of the device under test, in this case, the PCB. The pogo pins are set on the bed/surface of this device to compliment the design of the PCB. Different nodes signify different factors like the current, voltage, etc. The interconnection between pogo pins and PCB nodes helps keep a record of its functionality.

    ICT is the technique that is often used for circuits with complex ball grid arrays. This technique is expected to be 100% complimentary to the device to be tested, otherwise, you cannot perform it.

    Since the technique is complex, expensive and sometimes critical, it is preferred for matured and precisely manufactured PCBs.

    2. Functional Testing:

    Functional testing is a type of assembly-level testing that is performed post-manufacturing. This testing is performed on the PCBs to ensure that its functionality matches the calculated specifications. It tests the presence of the components on PCB, the precise location of the components, and its function. There are different types of functional tests for PCB, all are specified for different purposes. The list of different functional tests is given as follows.

    • X-ray inspection/test
    • Micro-sectioning test
    • Contamination test
    • Solderability test
    • Time-domain reflectometer test (TDR)
    • Peel test

Functional tests are preferred for inexpensive testing requirements. Specific tests can be used for specified purposes like X-ray inspection is performed to test complex PCBs with several hidden components.

Since in-circuit testing & functional testing play a key role in analyzing the performance of PCBs, they need to be performed meticulously. You can be assured of performance-driven PCBs when you buy them from trusted PCB manufacturers like Creative Hi-Tech. This company has been working with clients across critical industries such as medical, military, aerospace and electronics. The company possesses extensive testing capabilities that enable them to meet extensive testing requirements of demanding PCB assemblies across the aforementioned industries.

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