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Electronics Failure Analysis Case Study from ITRI Innovation

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This Electronics Failure Analysis Case Study highlights how ITRI Innovation (a leading electronics testing laboratory) helped a leading assembler of electronics components for the automotive sector.
The failure of a chip component was found to be caused by the encapsulation process. The case study explains the process that enabled this conclusion to be reached and the recommendations that were made to improve long term reliability. Feel free to call +44 1727 871328 to discuss your electronics failure analysis requirements.

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Electronics Failure Analysis Case Study from ITRI Innovation

  1. 1. FAILURE ANALYSIS OF SURFACE MOUNT CHIP COMPONENTS How a failure of a chip component was found to be caused by the encapsulation process and the recommendations made to improve long term reliability
  2. 2. The Client The client is a major assembler of electronic parts for the automotive sector.
  3. 3. The challenge Certain surface mount chip-type components soldered to the printed circuit board were not functioning correctly. The initial suspicion was the quality of the soldered joints. At the outset, the aim of the investigation was to suggest possible modifications to the soldering process in order to improve the longevity of the solder joints.
  4. 4. The problem The chip components are critical to the functionality of the PCB and proper operation of the vehicle would not be possible without resolution of the issue. On closer inspection of the solder joints, the wetting and contact angles seemed fine. The ceramic component body has a different thermal expansion coefficient to the other materials present, so suspicion then shifted to thermal fatigue in the joint
  5. 5. The Solution Through cross-sectional analysis and high magnification electron microscopy, ITRI Innovation was able to identify that the soldering and the joint was fine, but that there was a clear crack within the ceramic body of the component that would account for the issues encountered. The PCB is encapsulated in a potting compound during assembly, and examining pre- and post-potted samples revealed that the cause of the issue was not the soldering process or in-service conditions of the product, but rather the curing action of the potting compound which caused the board to bow slightly, thereby introducing mechanical stresses to the component.
  6. 6. The Outcome The replacement of the potting compound with one that had different curing characteristics eliminated the mechanical stresses applied to the board and the solder joints.  A benchmarking exercise was carried out to identify a potting compound that exhibited less shrinkage  Soldered joints from chip components on assembled boards produced with the different potting material were assessed to find presence of the component body cracking  Once candidate potting compounds were shortlisted, the assembled parts were then environmentally tested through thermal cycling, salt spray and vibration to ensure that the potting compounds also provided adequate in-service protection to the board The use of the new potting compound has meant that chip capacitors now continue to work on the board, with no reported failures since.

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