Accelerated Life Testing Solder Reliability in Combined Environments: Isothermal Conditions with Harmonic Vibration
Authors: Ivan Tan, Joseph Juarez, Polina Snugovsky, Jeffrey Kennedy, Milea Kammer, Ivan Straznicky, David Hillman, David Adams, Stephan Meschter, Subramaniam Suthakaran, Russell Brush, Doug Perovic Company: Celestica, Honeywell, Curtiss Wright, Rockwell Collins, BAE Systems, University of Toronto Date Published: 1/30/2018
Abstract: This paper updates progress in the development of methods for investigating solder joint reliability in a combined environment for 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 because materials fatigue earlier under combined stress conditions than separate exposure to the same levels of thermal and vibration. 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 have been published in (McMahon, Juarez, et al, 2016)14. They compare the performance of SAC305 alloy on ENIG and OSP solder pad surface coatings. Phase 1b failure results presented here for isothermal harmonic vibration life testing for SAC305, Sn-Pb, and Violet each at 25C, 75C, and 125C for various strain levels suggest a thermal cycling protocol with injection of vibration at 75C. Phase 2 will then use this protocol to evaluate, characterize, and compare various lower melt, high reliability, Bi-containing alloys against currently used SAC305 and Sn-Pb solders under the same combined environmental conditions.