Interface adhesion between copper lead frame and epoxy mouldingcompound: effects of surface finish, oxidation and dimples

摘要

A comprehensive study is made of the effects of dimple andfinishing material of copper alloy lead frame on interface adhesion withepoxy moulding compound. The surface plating materials studied includecopper alloy, microetched copper, Ag, black oxide coating, Ni, Pd/Ni andAu/Ni plating. Special emphasis was placed on the effects of variousstages in manufacturing processes, including post mould cure, thermalcycling, IR reflow and temperature and humidity storage, on the changesin interface adhesion. The interface bond strength was measured usingthe lead pull test. The lead frame surface was characterized usingvarious techniques, such as atomic force microscopy, X-ray photoelectronspectroscopy, ellipsometry, Raman spectroscopy and contact anglemeasurements, to correlate the measured interface bond strength with thesurface characteristics of various types. It was confirmed that dimplesetched on the lead frame surface offered several mechanical anchoringmechanisms and much improved interface bond with moulding compound. Theinterface bond strength and the number of dimples exhibited roughly alinear relationship. The black oxide and Pd coated surfaces were shownto provide the strongest interface adhesion, with the highestwettability amongst various surface finishes studied. The measurement ofcontact angle is proved to be an efficient method of evaluating themetal surface quality for interface adhesion with polymer resin