Surface chemical characterization of copper oxide and its relationship to adhesion in formed epoxy/copper interfaces

Experiments have been performed to comprehensively analyze copper oxides formed from a chlorite oxidation bath on copper bar stock and to measure the adhesion of an epoxy casting resin to the corresponding oxidized surfaces. Temperature conditions for the bath ranged from 25 to 90 degrees C with oxidation times between 0.25 and 20 minutes. Adhesion testing of the epoxy/copper systems was performed using a 3-point bend testing rig and measuring the ultimate force and displacement at the moment of sample failure near the epoxy/substrate interface. The flexure testing configuration used the resin as a stiffening rib which created a deviation in the force-deflection curve from that of the originally-oxidized copper bar stock. As the oxidation temperature increased above 50 degrees C, there was higher cohesion of the oxide layer formed on the copper and that led to a higher measured force at failure. On copper samples oxidized at lower temperatures, failure occurs within the oxide as a part of the latter remains on the resin side and lower adhesion was measured.