Rate controlled sintering: A novel approach to improve quality and yield of die-attach interconnects

Silver (or copper) sintering is nowadays the best choice for power electronics systems with high requirements on reliability, lifetime and application temperature. Especially SiC power modules can only achieve a peak performance together with sintered interconnects. Due to the higher melting temperature and better mechanical properties of silver or copper compared to soft-solder alloys, sintering is used as interconnect material in power modules. But the sintering process itself requires a high pressure up to 30 MPa onto the devices and the process itself is more cost-intensive. To achieve an economical process and make sintering worthwhile to invest, a high yield as a result of a stable process is needed. The idea of rate-controlled sintering (RCS) is a novel approach to make the sintering process robust and profitable. It improves the mechanical properties of sintered die-attach interconnects and decrease their deviation by using vacuum and nitrogen to control the different stages of the sintering reaction. Within this paper the mechanisms of sintering will be introduced, on which the idea of RCS is founded on. A case-study will be presented to demonstrate how rate-controlled sintering works, how it can improve the shear-values of die-attaches and lower die shear deviation.