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.

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. The Client
The client is a major assembler of electronic
parts for the automotive sector.

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. 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. 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. 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.