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A Methodology for Reliability Assessment of Non-Ductile Encapsulants

Published online by Cambridge University Press:  26 February 2011

Boon Wong
Affiliation:
Hughes Aircraft Company, El Segundo, California 90245
David C. Sandkulla
Affiliation:
Hughes Aircraft Company, El Segundo, California 90245
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Abstract

This paper presents a probabilistic fracture-mechanics based methodology for the reliability assessment of non-ductile encapsulants. The study used an alumina-epoxy encapsulant as a working example and assessed the reliability in terms of (1) fast fracture and (2) delayed failure behavior of the material.

Applying the Weibull probabilistic model to flexural strength data, survival probabilities and strength requirements against fast fracture of the encapsulant under various stress states were quantified. Unifying the probabilistic concept and linear elastic fracture mechanics (LEFM), the probabilistic lifetime of the encapsulant was predicted as a function of stress magnitude, stress state, and material size. Merging the results obtained from this study with the mechanical response results independently acquired from finite element analysis (FEA) one may then establish conservative design margins for the encapsulant used in various electronic assemblies.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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