Reliability of Sn based LT-TLPS Joints for High Temperature Electronic Systems

Inhalt:
Sinter pastes for Low Temperature Transient Liquid Phase Sintering (LT-TLPS) of electronic interconnects have been developed. Sn3.5Ag is used as low temperature alloy forming the transient liquid phase during processing which is consumed and transformed to intermetallic phases with high melting temperatures. Ni, Cu, and combinations of both elements are used as high melting temperature constituents. LT-TLPS enables the joining of metallic systems pressure-less or with the application of low pressures (< 0.5 MPa) without vacuum or reducing atmosphere. Joint composition was analysed by optical microscopy, SEM, and EDS analyses. It was demonstrated that the pastes show good wetting be-haviour to common metallization types such as Cu, Ni, or Ag. Shear tests at temperatures of 25°C, 400°C, and 600°C have been performed. Depending on paste composition the joints showed no reduction of shear strength up to 600°C. Failure analyses for sheared specimen have been performed. The joint softening behaviour is compared to that of a Pb5.0Sn2.5Ag high temperature solder. It is demonstrated that the paste based LT-TLPS process can be facilitated as interconnect technology for high power and high temperature systems.