Damage Progression Using Speckle-Correlation and High-Speed Imaging for Survivability of Leadfree Packaging Under Shock

摘要

In this paper, a methodology to predict failure of electronics under shock and vibration loads has been investigated. Reliability prediction models have been developed using optical feature extraction techniques for 6-leadfree solder alloy systems. Solder alloy systems investigated include, Sn1Ag0.5Cu, Sn3Ag0.5Cu, Sn0.3Ag0.7Cu, Sn0.3Ag0.7Cu0.1Bi, Sn0.2Ag.7Cu0.1Bi-0.1 Ni, 96.5Sn3.5Ag. Previously, Digital Image Correlation (DIC) has been used for measurement of thermally-induced deformation and material characterisation. In this paper, DIC has been used for transient dynamic measurements, and optical feature extraction. Board assemblies have been subjected to shock-impact in various orientations including the zero-degree JEDEC drop and the vertical free-drop. Transient deformation has been measured using both DIC and the strain gages. Measurements have been taken on both the package and the board side of the assemblies. Accuracy of high-speed optical measurement has been compared with that from discrete strain gages. Package architectures examined include-flex ball-grid arrays, tape-array ball-grid arrays, and metal lead-frame packages. Explicit finite-element models have been developed and correlated with experimental data. Three models were developed: smeared property models: Timoshenko-beam models: and explicit sub-models. The potential of damage identification and tracking for various solder alloys has been investigated. Data on the identification of damage proxies for competing failure mechanisms at the copper-to-solder, solder-to-printed circuit board, and copper-to-package substrate has been presented. Design envelopes have been developed based on Statistical Pattern Recognition (SPR). The design-envelope is intended for component integration to ensure survivability in shock and vibration environments at a user-specified confidence level.