Title :
Creep strains in an elongated bond layer
Author :
Mirman, B. ; Knecht, S.
Author_Institution :
Digital Equipment Corp., Andover, MA, USA
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;
Conference_Titel :
Thermal Phenomena in Electronic Systems, 1990. I-THERM II., InterSociety Conference on
Conference_Location :
Las Vegas, NV
DOI :
10.1109/ITHERM.1990.113307
