Study of intermetallics formation in thick film solder joints

Intermetallics formation between metallization conductor Pd–Ag and solder 62Sn–36Pb–2Ag has been investigated by transmission electron microscopy (TEM) and X-ray diffraction. Energy-dispersive X-ray (EDX) analysis and Selected Area Electron Diffraction (SAED) analysis reveals the formation of the intermetallic compounds Ag5Sn, Ag3Sn, Pd2Sn, PdSn2, PdSn4, and PbPd3. X-ray diffraction results further confirm the coexistence of the above phases and additional intermetallic compounds including Pd3Sn2, PdSn and Pb3Pd5. Evident single phase intermetallic compound (IMC) layer structure is not observed. The different intermetallic phases coexist near the metallization/solder interface. Silver–tin intermetallic compounds are also observed in the solder.