Silver sinter paste for SiC bonding with improved mechanical properties

Abstract

Silver sintering become a mature interconnection technology for high reliability or high temperature electronic devices. Different sintering processes are applied depending upon application requirements, for instance pressure sintering process is optimized for elevated life time power modules. The pressure of the sintering process can be adjusted in order to modify the properties of the sinter layer. In general, higher pressure or temperature leads to higher Young’s modulus. With respect to the lifetime of an interconnection, the Young’s modulus, the dimension of the connected area and the CTE mismatch of the joint materials play an important role in temperature cycling. Thermo-mechanical tension might not be reduced easily by the interconnection material if the Young’s modulus of the material itself is high. A brittle die attach material might crack due to the bending of the package caused by the CTE mismatch of the used materials. This leads to a degradation of thermal conductivity and a reduced life time of the components, particularly on components which are operated at above 175°C. Silver sinter material with a reduced Young’s modulus as well as an adjusted CTE is desired to avoid crack, especially for the interconnection of large areas. This paper shows the result of silver sinter paste with improved mechanical properties. By adding non-silver particles to the sinter paste the Young’s modulus became independent of process parameters and became stable against further thermal exposure. This investigation is part of the public project HHK funded by BMBF.