Characteristics of silver-plated film on the second wire bondability

Strong bond between the gold wire and the silver-plated leadframe is significantly crucial for maintaining either bondability or reliability during IC (integrated circuit) 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, hardness measurement and grain structure by transmission electron microscopy (TEM). The characteristics of the silver-plated film surface and structure, e.g., surface roughness, hardness, 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 softer crystal surface and fewer grain boundaries of silver-plated film provided the higher pull strength which improved the yield of wedge bondability and reliability.