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In-Circuit Testing: The Best Technique to Detect Manufacturing Faults

 Jan 08, 2018

PCBs can be designed to various specifications as per the application requirements in varied industries. There are simple designs with a single layer, as well as complex designs with multiple layers that are assembled using hundreds of components and solder connections. Hence, there are more chances of defects, and component-level faults. Here is where the importance of testing comes in. Testing ensures the overall quality of the PCBs by detecting defects such as wrong or missing components, solder bridges and short circuits, among several others. Amongst the several PCB testing techniques, the most popular and commonly used method is In-Circuit Testing (ICT). Let us understand in-circuit testing in this post.

In-Circuit Testing: Cost-Effective Method for Medium and High Volume PCBs

In-circuit testing is widely recognized as the cost-effective method to test PCBs. This is owing to the fact that its test time is typically less than one minute and cost per unit is less. Compared to other testing methods, ICT provides more reliable results as it individually tests PCB components one at a time to detect:

  • Wrong or missing components
  • Solder bridges
  • Short circuits
  • Shorts, opens, resistance, and capacitance

ICT can be performed with a bed-of-nails test fixture or with a flying probe set up to detect individual defects.

Power-On and Power-Off ICT

The test is commonly performed in two parts namely; power-off tests and power-on tests. The power-off test is performed to detect shorts between traces and component leads, values of resistors in the circuit, presence/absence of passive and analog components. This test also ensures the correct setting of jumpers/switches. On the other hand, power-on test is executed to detect wrong or miss-aligned analog and digital component, capacitance and inductance values, transistor beta, and digital component timing. Besides these, power-on test also performs all the other tests aforementioned for power-off test.

ICT Advantages

As you can see, ICT checks individual components and the components’ interconnections to a substrate and identify potential defects. Also, the test can be conducted without power being applied to the unit under test, which adds to its popularity. Once the test is completed, a report is generated including points pertaining to coverage report listing tested, partially tested and untested components, details of fixture wiring, details of probe types used, and the Software employed. The PCB fabricator can closely analyze the report after the testing and make appropriate changes accordingly. Accelerated Assemblies is one of the reputed PCB manufacturers and suppliers in the USA.