Microstructural evolution in Sn/Pb solder and Pd/Ag thick filmconduction metallization

摘要

Intermetallic compound formation between thick-film mixed bondedconductor and Sn/Pb solder is investigated. Microstructural evolution ofthe interfacial morphology, and elemental and phase distribution areprobed with the aid of electron microscopy and X-ray diffraction.Mechanical interlocking between the conductor and the substrate is shownto exist. Penetration of Bi element into the substrate is observed.Decrease in adhesion strength occurs when the sample is aged at130° C for a long period of time. Microstructural analysis revealsthe formation of the intermetallic compounds Pd₃Sn, Pd₂Sn, Pd₃Sn₂, PdSn, Pd₃Pb, Ag₅Sn, and Ag₃Sn. The grain growth of the compounds afteraging is also observed. It is argued that conductor swelling caused bytin diffusion into the conductor film and volume change caused by theintermetallic formation are the major reasons for the degradation of thepeel strength