Mechanical stress reduction in heat sink bond layers-a numerical feasibility study

Abstract

High interfacial thermal stresses in the adhesive layer used to bond heat sinks to chips and IC packages threaten the integrity of the bond layer and have been implicated in packaging failures, associated with both rapid delamination and progressive bond layer fatigue. It has been proposed to take advantage of a mechanical edge restraint on the heat sink base to reduce these thermal stresses and dramatically improve bond layer fatigue life. The present study explores the feasibility of this approach. Nomenclature 1 : Characteristic length, m a : Thermal expansion coefficient ( U T ) E: Modulus of elasticity (Pa) k : Thermal conductivity, WImK Nf : Number of cycles to failure f : Cycling frequency (Hz) ?: : shear stress (Pa) r s : Axial stress (Pa) ~~d h : Adhesion strength (Pa)

Performance of Solder Bond on Thermal Mismatch Stresses in Electronic Packaging Assembly

“…The CTE difference might cause unsynchronized geometrical shrinkage and expansion upon thermal loading, resulting in bending of the assembly. Consequently, the thermal mismatch resulted from temperature change generates interfacial stresses in the assembly [3]. These interfacial stresses might lead to structural failure in electronic packaging, mainly delamination and crack.…”