Assessment of thermo-mechanical stresses in Low Temperature Joining Technology

The Low Temperature Joining Technology (LTJT) creates silver joints by a sintering process. It is an alternative die-attach technology to soldering. To initiate the sintering process the temperature has to be raised above ~ 215°C. The quality of a sintered joint is strongly enhanced by applying pressure to the specimen during the process, thus reducing the porosity in the sintered material. After the interconnect process, residual stresses occur in the sintered material, as well as in the joined parts. The examined specimen was a silicon MOSFET attached to a copper substrate at a sintering pressure of 50 MPa. The scope of this paper is to provide information about residual stress after production and thermo-mechanical stresses during thermal cycling. The focus is put on the investigation of the reliability of sintered silver by simulation.