Copper alloys are widely used as a leadframe (chip carrier) material in plastic packaged semiconductor devices. The oxidation of Cu leadframes during the assembly process can result in poor adhesion between the moulding compound and the die-pad. This often leads to interfacial delamination and contributes to popcorn cracking during the component-board attachment process. The main cause of poor adhesion has been attributed to the weak Cu oxide(s) layer on the leadframe surface. Studies have shown that the moulding compound/leadframe adhesion decreases with increasing oxide thickness.

The aim of this investigation is to give a detailed analysis of the phase formation of a CuNiSi alloy during oxidation and to identify the locus of failure for the interfacial delamination. The Cu leadframes were oxidized in an air oven at 240° C for up to 200 min exposures before encapsulation. A scanning acoustic microscope was used to locate delamination regions along the moulding compound/leadframe interface.