SMTA International Conference Proceedings

Strain Energy Model for Underfill

Authors: Michael Bodendorfer, Reza Ghaffarian
Company: Jet Propulsion Laboratory, California Institute of Technology
Date Published: 10/14/2018   Conference: SMTA International

Abstract: Predicting solder joint fatigue failure under thermal cycling has been one of the challenging problems for microelectronics packaging and assembly. Numerous models including Coffin-Manson and more recently energy methods in conjunction with finite element analysis (FEA) have been developed to project reliability. However, there exist no simple projection methods for reliability of underfill/adhesive, even though there are numerous research activities on developing stresses/strains distribution methods.

A new strain energy model based on adhesive material for bond/underfill was developed to estimate the mean-time-to-failure (MTTF) under accelerated thermal cycle testing. To reduce the complexity of analysis, the strain-energy model concentrated on the assumption that the test data generated under laboratory accelerated thermal cycle condition is need to be projected for an application cycle condition. The paper presents details of this energy model approach and provides an example for an adhesive that its characteristics behavior with temperature was derived from dynamic mechanical analysis (DMA) plots.

Key Words: 

underfill, adhesive bond, potting, strain energy, solder joint reliability, thermal cycle, DMA

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