The role of plastic package adhesion in IC performance

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Abstract
The author examines the relationship between plastic package adhesion and semiconductor device performance. It is a general belief that better adhesion between the encapsulant, lead frame, and silicon chip will result in improved reliability, resistance to package cracking and reduced line movement due to thermal stresses. The multifacets of adhesion are considered from the viewpoints of thermodynamics, rheology, and processing conditions. The relationship between adhesion characteristics and copper oxide morphological structures as well as copper chemical treatments is investigated. Adhesion influences the integrity of IC packages, as evidenced by aluminium line movement tests and highly accelerated stress test (HAST) results. Adhesion is directly influenced by the viscosity of the molding compound. Metallurgical properties of the lead frame are as important as epoxy molding compound (EMC) properties. Strong oxide layers are required for good adhesion. The peel test is the most sensitive of the methods studied and provides an accurate measure of adhesion.