Failure-Envelope Approach to Modeling Shock and Vibration Survivability of Electronic and MEMS Packaging

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Abstract
Product level assessment of drop and shock reliability relies heavily on experimental test methods. Prediction of drop and shock survivability is largely beyond the state-of-art. However, the use of experimental approach to test out every possible design variation, and identify the one that gives the maximum design margin is often not feasible because of product development cycle time and cost constraints. Presently, one of the primary methodologies for evaluating shock and vibration survivability of electronic packaging is the JEDEC drop test method, JESD22-B111 which tests board-level reliability of packaging. However, packages in electronic products may be subjected to a wide-array of boundary conditions beyond those targeted in the test method. In this paper, a failure-envelope approach based on wavelet transforms and damage proxies has been developed to model drop and shock survivability of electronic packaging. Data on damage progression under transient-shock and vibration in both 95.5Sn4.0Ag0.5Cu and 63Sn37Pb ball-grid arrays has been presented. Component types examined include flex-substrate and rigid substrate ball-grid arrays. Dynamic measurements like acceleration, strain and resistance are measured and analyzed using highspeed data acquisition system capable of capturing in-situ strain, continuity and acceleration data in excess of 5 million samples per second. Ultra high-speed video at 150,000 fps per second has been used to capture the deformation kinematics. The concept of relative damage index has been used to both evaluate and predict damage progression during transient shock. The failure-envelope provides a fundamental basis for development of component integration guidelines to ensure survivability in shock and vibration environments at a user-specified confidence level. The approach is scalable to application at system-level. Explicit finite-element models have been developed for prediction of shock survivability based on the failure envelope. Model predictions have been correlated with experimental data for both leaded and leadfree ball-grid arrays

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