Effect of oxidation on mold compound-copper leadframe adhesion

The effect of oxidation on adhesion between a mold compound and copper leadframe material was investigated for OCN and DCP molding compounds and one copper alloy. The oxidation temperatures selected were 175 and 200/spl deg/C and the bake times were varied between 5 minutes and 118 hours. Adhesion strength results obtained by the button shear test method indicated that the DCP mold compound-Cu adhesion was virtually unaffected by oxidation of the Cu at both 175 and 200/spl deg/C for exposure times up to 50 minutes. The adhesion in the case of the OCN mold compound was lower and exhibited a sharp decrease with increasing bake time at both temperatures. The degradation in adhesion strength was attributed primarily to the low cohesive strength of the copper oxide layer.