Surface topographical characterization of silver-plated film on the wedge bondability of leaded IC packages

Strong bond between gold wire and silver-plated leadframe is significantly crucial for maintaining either bondability or reliability during integrated circuit (IC) manufacturing process and IC application in the fields. This study investigated the surface and grain structure of the silver-plated film on the copper leadframe in terms of surface roughness test by atomic force microscopy (AFM), thickness measurement by nano-indentation, and grain structure by transmission electron microscopy (TEM). The characteristics of the silver-plated film surface and structure, e.g., surface roughness, film thickness and grain structure impacted the bonding quality which was verified by the full factorial design of experiment (DOE) wedge pull test. Implications of AFM, TEM and DOE results showed that more smooth and soft crystal surface topography and fewer grain boundaries of silver-plated film provided the higher pull strength which could improve the yield of wedge bondability. (C) 2003 Elsevier Science Ltd. All rights reserved.