Surface treatment of copper for the adhesion improvement to epoxy mold compounds

This paper is related to the surface treatment of a copper leadframe to improve the adhesion of copper to mold compounds and die attach adhesives in IC packages. The surface treatment includes the initial roughening of Cu surface by Cu electrodeposition and electroless Cu plating, followed by an electrolytic chemical treatment in a chemical solution. The adhesion of treated Cu to mold compound and die attach adhesive, after surface treatment, is proven to be considerably increased. The oxygen-deficit silicon oxide is detected by XPS, Auger and FTIR to have formed on the treated Cu surface by the chemical treatment, thereby increasing adhesion by forming the chemical bonding between Cu and epoxy adhesive. The surface roughening of Cu is important in maintaining the high adhesion of Cu after temperature/humidity exposure by providing a mechanical interlock structure which impedes or prevents the ingress of moisture into the interface. The integration of surface roughening and chemical treatment of the Cu leadframe significantly increases the adhesion of Cu to epoxy compounds even after thermal simulation and temperature/humidity exposure. As a result, TQFP packages with treated leadframes passed the IPC level 1 moisture sensitivity test