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Protocol Development for Testing Solder Reliability
Analysis Lab |
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Authored By:John McMahon, Polina Snugovsky, Jeffrey Kennedy, Subramaniam Suthakaran, Russell Brush Celestica Joseph Juarez, Milea Kammer Honeywell Ivan Straznicky Curtiss Wright David Hillman, David Adams Rockwell Collins Stephan Meschter BAE Systems Doug Perovic University of Toronto SummaryThis paper updates progress in the development of methods for investigating solder joint reliability in a combined environment of vibration and thermal cycle testing. Since combined environmental testing is an evolving concept, no default approach or standard test protocol currently exists. The need to develop such a protocol arises from the fact that materials may behave differently under combined stress conditions; exhibit different failure modes and impact the overall reliability. Combined environmental testing would therefore provide the closest approximation to actual field conditions and the best means of evaluating the performance capability of solder joints. In developing this protocol, consideration was given to obtain relevant information from both a reliability perspective (number of cycles to failure) as well as micro-structural stand point (at time of failure). Further, in combining the two conditions, time to failure had to be weighed against the overall expected time of the test; when performed alone, vibration testing is often completed within a single day, while thermal cycle testing can take up to six months to complete. Phase 1A of this project is complete and results will be presented to compare the performance of SAC305 alloy on ENIG and OSP solder pad surface coatings. Phase 1B which is in progress will involve isothermal vibration life testing over the range of alloys and temperatures. Phase 2 will then use the information to evaluate, characterize and compare various lower melt, high reliability, Bi-containing alloys against currently used SAC305 and Sn-Pb solders under combined environmental stresses. ConclusionsTest procedures and data collection systems for isothermal step stress testing have been validated and refined for longer term testing. Step stress testing of units with resonance frequencies near 50 Hz can generate solder fatigue failure modes at a step length of 100K cycles and step increments of 1G. Test temperature is the dominant factor in determining expected lifetime under sine wave vibration. Technology Type is also a significant factor. Surface Finish is not a significant factor over the range of this testing but the Interaction between Surface finish and test temperature is significant, affects the basic microstructure and deserves more investigation. The interaction between test temperature and technology type is dependent on the geometry and mechanical properties of the various components but may also be impacted by the microstructural changes associated with device types. Initially Published in the SMTA Proceedings |
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