Adhesion strengths of epoxy molding compounds to gold-plated copper leadframes

In the present study, the effects of plasma cleaning on the adhesion streng th of molding compounds to gold-plated copper leadframes are presented. Imp ortant process parameters such as the type of gasses used and the time expo sed in air before molding are specifically evaluated. The leadframe pullout test is performed to measure interfacial bonding strengths. The liquid dro plet test is used to measure contact angles and atomic force microscope (AF M) is employed to characterize quantitatively the roughness of modified sur faces to correlate with the bond strength measurements. The results indicat e that plasma cleaning of leadframes has three major ameliorating effects, namely, surface cleaning due to the removal of contaminants, enhanced chemi cal compatibility with molding compounds and surface roughening with associ ated larger surface contact area for better mechanical interlocking. Exposu re of plasma-cleaned leadframes in air before molding is detrimental to int erface bond quality, a finding suggesting that molding operations should be carried out immediately after cleaning. The experimental results show that roughness on the nano-scale is an important surface characteristic that ha s a strong correlation with interface bonding strengths.