Effects of oxidation treatments on the fracture toughness of leadframe/epoxy interfaces

A copper-based leadframe is oxidized in two types of alkaline solutions; one forming brown oxide and the other forming black oxide, and molded with epoxy. SEM and X-ray studies on the surfaces of oxidized leadframe and fracture-toughness measurements by using sandwiched double-cantilever beam (SDCB) specimens showed that the interfacial fracture toughness is directly related to the formation of acicular CuO precipitates at the interface. However, once a continuous layer of CuO precipitates formed on the leadframe (brown oxide) or the underlying Cu2O layer (black oxide), interfacial fracture toughness saturated regardless of further oxide thickening. The size of the acicular precipitates was found to have secondary effects on the interfacial fracture toughness.