Abstract
Intermetallic formation between thick film mixed bonded conductor and Sn/Pb solder is investigated. Microstructural evolution of the interfacial morphology, elemental and phase distribution is probed with the aid of electron microscopy and X-ray diffraction. There exists mechanical interlocking between conductor and substrate. Penetration of a Bi element into the substrate is observed. A decrease in adhesion strength occurs when the sample is aged at 130°C for a long period of time. Microstructural analysis reveals the segregation of Pb-rich and Sn-rich phases in aged samples and formation of intermetallic compounds Pd 3 Sn 2 , Pd 2 Sn, Pd 3 Sn 2 , PdSn, Ag 5 Sn, and Ag 3 Sn. It is argued that conductor swelling caused by tin diffusion into the conductor film and volume change resulting from the intermetallic formation are major factors in the degradation of the peel strength. © 1990 IEEE