Adhesion improvement of epoxy resin to alloy 42 lead frame by silane coupling agents

Three different silane coupling agents were used to improve the adhesion between epoxy resin and alloy 42 lead frame. The adhesion strength and durability of epoxy resin/silane coupling agent-treated alloy 42 joints were investigated. The highest initial adhesion strength, 200 N/m, was obtained with gamma-aminopropyltrimethoxysilane (gamma-APS), but durability in a high humidity environment was best with N-beta-(aminoethyl)-gamma-aminopropyltrimethoxysilane (AAMS). An optimum concentration of the silane coupling agent was determined and thermal stability was studied by thermogravimetric analysis (TGA). Vapor phase deposition of the AAMS silane coupling agent was also employed and compared with dipping of the lead frame in the silane coupling agent solution. Moisture absorption behavior was examined for different silane coupling agents and for different geometries of the joints to resolve the moisture absorption path of joints. The improvement in adhesion obtained by applying a silane coupling agent to the lead frame can prevent the penetration of water via the interface between the epoxy resin and alloy 42 and the accumulation of water in the interfaces. Therefore, the cracking of the EMC package can be diminished and the existing 'popcorn' problem can be suppressed by applying a silane coupling agent to the lead frame.