Bonding strengths at plastic encapsulant-gold-plated copper leadframe interface

The effect of plasma treatment on the adhesion strength of a moulding compo und to a leadframe is evaluated on the basis of leadframe pull-out tests. T he contact angle measurement method and atomic force microscopy are employe d to quantitatively characterise the modified surface so as to correlate wi th the bond strength measurements. Process parameters including the type of gases used and the duration exposed in air before moulding are specificall y studied. The results indicate that plasma treatments of leadframe have th ree major ameliorating effects, namely, clean surface due to the removal of organic contaminants, enhanced chemical compatibility with moulding compou nd and rough surface with associated larger surface contact area for better mechanical interlocking. Exposure of plasma treated leadframes in air befo re moulding is found detrimental to interface bond quality, recommending mo ulding operations immediately after treatment. It is also shown that roughn ess on the nanoscale is an important surface characteristic that has a stro ng correlation with the interface bond strength. (C) 2000 Elsevier Science Ltd. All rights reserved.