SMTA International Conference Proceedings


UNIFIED FINITE ELEMENT MODEL FOR PREDICTION OF SOLDER JOINT FATIGUE UNDER THERMAL, POWER, AND VIBRATION ENVIRONMENTS FOR CERAMIC AREA ARRAY ELECTRONIC PACKAGES

Authors: Andrew Perkins and Suresh K. Sitaraman
Company: Georgia Institute of Technology
Date Published: 10/11/2007   Conference: SMTA International


Abstract: The majority of research on solder joint reliability of electronic packages has focused on reliability under a single environment without consideration of the effects of multiple environments. In space, automotive, and military applications an electronic component is subject to a combination of thermal-mechanical, power cycling, and dynamic mechanical loading such as shock/vibration. A design that is optimal for one environment may not be optimal in another. Competing effects may exist which make it difficult to optimize fatigue life simultaneously for all three environments. For example, decreasing the board thickness may improve solder joint fatigue life for thermal and power cycling environments. However, in a vibration environment, a thinner board results in a more compliant system, which can result in greater board displacements and ultimately lower solder joint fatigue life due to higher strains in the solder to account for the increased board curvature. There is a need to develop a tool that can assess solder joint reliability under multiple environments in order to determine the best design when there are competing effects.

Numerical Finite Element Models (FEM) have been successfully used in the past to determine solder joint reliability for a variety of environments. However, separate models are typically constructed for each loading environment due to variations in element types and capabilities of the software for each environment. Calculation and comparison of damage parameters may be inconsistent between models as mesh, boundary conditions, and element types change between models. A single FEM for all environments will enable consistent calculation of damage under each environment.

Therefore, this study aims to develop a unified FEM for predicting solder joint fatigue of a Ceramic Column Grid Array (CCGA) under thermal, power cycling, and vibration modeling. The FEM is validated against experimental data from ATC tests, power cycling tests, harmonic vibration testing, and dye-n-pry failure analysis. The developed methodology can be used for ‘what-if’ scenarios to determine fatigue life under multiple environments and look for competing design effects.

Key words: Finite Element Method, solder joint reliability, Ceramic Column Grid Array, CCGA



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