Process factors affecting adhesion of encapsulation molding compounds

Purpose: The purpose of this paper is to determine the key process factors which affect the adhesion strength of encapsulation molding compounds (EMCs) to leadframes to obtain reliable components without any need to pretreat the leadframe surface. Design/methodology/approach: EMCs were molded to Cu leadframes to experimentally quantify the effect of mold temperature, resin viscosity, leadframe oxidation and powder moisture on the adhesion force. Component reliability was assessed by PCT. Findings: A higher mold temperature result in a larger adhesion force. The mold temperature of 175°C provides the largest process window. Leadframe oxidation can increase adhesion first, but then decrease it drastically with further oxidation. The powder moisture content has mixed effect on adhesion. Practical implications: By molding at 175°C, limiting the wire bonding time and minimizing the powder moisture content, reliable components can be obtained without any need for leadframe surface pretreatment such as plasma cleaning or surface coating. Originality/value: Quantify the key process factors which affect the adhesion of EMCs and reveal reason behind the current industrial practice of using the mold temperature of 175°C.