Creep strains in an elongated bond layer

Author

Mirman, B. ; Knecht, S.

Author_Institution

Digital Equipment Corp., Andover, MA, USA

fYear

1990

fDate

23-25 May 1990

Firstpage

21

Lastpage

32

Abstract

Thermally induced shear stresses and strains in a bimaterial assembly are studied as functions of two variables, position and time. It is shown that the initial uneven distribution of shear stress will first relax such that stresses are distributed uniformly along the bond without change of total shear force; during this initial stress redistribution, a significant magnitude of creep may occur in the region of high stresses. Numerical procedures for calculating possible failure indicators, including peeling stresses and several kinds of creep strain, are developed. For some of these failure indicators, approximate formulas are presented. The results are applicable to any bimaterial assembly, but particular examples from electronic packaging applications are used. Detailed numerical results are presented for an example case of the `lead-foot´ structure

Keywords

creep; reliability; surface mount technology; approximate formulas; bimaterial assembly; creep strain; electronic packaging applications; elongated bond layer; failure indicators; functions of two variables; initial stress redistribution; initial uneven distribution of shear stress; lead foot structure; numerical results; peeling stresses; position; time; Assembly; Bonding forces; Building materials; Capacitive sensors; Creep; Electronics packaging; Lead; Tensile stress; Thermal expansion; Thermal stresses;

fLanguage

English

Publisher

ieee

Conference_Titel

Thermal Phenomena in Electronic Systems, 1990. I-THERM II., InterSociety Conference on

Conference_Location

Las Vegas, NV

Type

conf

DOI

10.1109/ITHERM.1990.113307

Filename

113307