This paper introduces a test methodology to examine the durability of surface mount interconnects under impact loading when a portable electronic product is dropped. Conventional testing approaches that consider loading (total impact energy, orientation and number of impacts) as the governing criterion for failure, typically report difficulties in correlating with impact durability under field conditions. This study considers damage accumulated in the interconnects in terms of local flexural strain, strain rate and acceleration. The advantage is that the results are less dependant on structure and loading, because damage is quantified in terms of specimen response rather than the loading. An instrumented, repeatable impact test setup is developed. The test matrix covers the design space in terms of specimen styles, impact orientation, loading and boundary conditions. The entire test matrix is replicated twice for proof of consistency of the test data. A finite element model of the transient impact is developed. Results indicate that number of impacts to failure is a good damage metric for constrained impacts. The same damage metric may not be applicable for unconstrained (free) impacts because the strain signatures are more complex. A comparative analysis of the experimental and numerical data indicates a good correlation between the two. The end goal is to develop a consistent, accurate and generic methodology for ranking the impact durability of different surface mount interconnects technologies.

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This paper characterizes the fatigue failure envelopes for solder damage in Printed Wiring Assemblies (PWAs) subjected to dynamic loading. An empirical, rate-dependent, power-law durability model, motivated by mechanistic considerations, is used to characterize the failure envelopes in terms of PWA flexural strain and strain rate. Explicit nonlinear finite element analysis (FEA) is used to make the damage constants independent of the specimen geometry and characterize the durability in terms of the ratio of solder plastic strain to its failure strain. A case study, using a simple PWA specimen containing a single area array component, is presented to demonstrate the proposed approach.