ABSTRACT
Abstract-Adhesion strength of a novo lac epoxy-based mold compound to nickel leadframes was investigated. Surface energetics and wettabilities of untreated, thermally treated and Ar-plasmaetched leadframes were studied via the contact-angle approach. Surprisingly, both the most (plasmatreated) and the least (untreated) wettable nickel surfaces, as ascertained by the water contact angle, offered very low adhesion to the mold compound. Only thermally treated leadframes with modest wettability gave high adhesion. X-Ray photoelectron spectroscopy (XPS) data and scanning electron microscopy (SEM) micrographs suggest that the surface oxide layer thickness and its integrity on thermally treated leadframes are the most important factors in determining the adhesion of mold compounds to nickel leadframe surfaces. The study shows that a thermally treated nickel surface with an oxide thickness of 3.5-5.0 nm and free of organic contamination is most likely to offer high adhesion to epoxy mold compounds.
