SMTA International Conference Proceedings

Microstructurally Adaptive Constitutive Relations and Reliability Assessment Protocols for Lead Free Solder

Authors: P. Borgesen, Ph.D., E. Cotts, Ph.D., and I. Dutta
Company: Binghamton University, Washington State University
Date Published: 9/28/2014   Conference: SMTA International

Abstract: Typical SnAgCu solder joints are extremely anisotropic although an interlaced twinning structure, which is much less anisotropic, can be achieved for small solder volumes and pad sizes under specific conditions. Aside from that, the joint properties are dominated by the distributions of the secondary precipitates, which vary with design, composition, process and subsequent thermo-mechanical history. Together, these factors lead to strong variations in life in accelerated tests, acceleration factors, and sensitivity to aging.

A major systematic research effort has led to a quantitative understanding of the initial microstructure and its subsequent evolution, as well as the resulting deformation properties and damage evolution, in thermal and isothermal cycling. Constitutive relations were developed that predict the evolution of properties during thermal cycling and aging. Approaches to reliability testing and the interpretation of test results in terms of life in service will be outlined and discussed.

Key Words: 

Pb-free, solder, reliability, constitutive relations

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