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What Causes Intermittent Failure in Cable Assemblies?

March 26, 2016

What Causes Intermittent Failure in Cable Assemblies?

In the earlier blog post, we explored the testing processes for intermittent failure. The two main types of test equipment discussed were PC-based and those operated via microprocessors. In this post, we will explore the causes for intermittent failure.

Contact-to-Contact Failure

The following contact-to-contact failures can be seen in cable assemblies:

  1. When tin or lead contacts are used, a common problem that occurs is micro fretting. Here, oxides are formed when the two metals come in contact with each other. When testing for electrical conductivity or performing other regular tests, this problem will not be detected. Hence, cable assembly manufacturers need to take additional care to avoid micro fretting.
  2. When an incorrect force mates with the contacts, an intermittent failure can occur. This could be for several reasons like contaminated contacts, wear and tear of contacts, etc. The same problem could occur if there are some manufacturing defects with the contacts. For example, insufficient locking of crimped pins.

Contact-to-Wire Failure

Below are some of the contact-to-wire failures that can occur:

  1. Cable assemblies featuring crimped connections can suffer from manufacturing defects. Hence, it is important to test the crimped connections using crimp pull testing, or any other relevant test.
  2. Improper soldering processes can be a major cause for intermittent failure. Proper soldering processes have to be followed to ensure reliable connections.

Contact-to-Contact & Contact-to-Wire Failure

If the cable assembly witnesses mating or bonding between two contacts or contacts and wires, respectively, then the assembly will experience weak or no electrical connection. This leads to an intermittent failure.

Cable assemblies and wire harnesses are tested thoroughly to ensure smooth functioning. If an assembly shows repetitive failures, it is easy for cable assembly test equipment to detect it. However, if the problem lies in intermittent failures, then it might be a little more challenging. Finding out the root cause for intermittent failure will allow you to eliminate them altogether.

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