Interpreting Accelerated Test Results for Lead Free Solder JointsAuthors: P. Borgesen, S. Hamasha, L. Wentlent, D. Watson, and C. Greene
Company: Binghamton University and Rose-Hulman Institute of Technology
Date Published: 1/25/2016 Conference: Pan Pacific Symposium
In general, reliability engineers need to know when ‘best in test’ is unlikely to mean ‘best in service’, how large deviations may be, and which comparisons can be counted on to be conservative. This includes cases where acceleration factors vary with solder volume, pad sizes, pad finishes or process parameters. A mechanistically justified model for the fatigue of lead free solder joints does allow for the generalization of observed trends and should be considered when formulating test protocols and guidelines. Another concern is the effects of the ongoing variations in cycling amplitude common under realistic service conditions. These are not appropriately accounted for in accelerated test protocols. A dependence of the effects on the solder alloy suggests that the sensitivity to these will vary with assembly process parameters and subsequent thermal history as well. The behavior is explained by the effects of cycling on the deformation properties of the solder joints, and recommendations can be made with respect to reliability assessment/optimization and Environmental Stress Screening (ESS). This includes guidelines for vibration testing and combinations of vibration and thermal cycling.
Solder, Reliability, Accelerated Test, Thermal Cycling, Vibration, ESS
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