A Single Step Process for Die-Attach and Substrateattach with Pressure Assisted Sintering to Face Harsh Conditions

With increased demand for power electronics, silicon devices are progressively substituted by Wide Bandgap semiconductors (WBG) like SiC or GaN.. WBG imposes harsher conditions to actual power modules working environment due to higher electric breakdown field, therefore high thermal expansion exposes microelectronic packages to high mechanical stress and jeopardize their lifetime. Providing interconnection material with high electric and thermal conductivity could remove one of WBG bottlenecks. by replacing the cheapest Sn-solders thermal interface materials and common epoxy-silver compounds. which are inappropriate as they might not be able to withstand the higher temperature and prolonged mission profiles. Numerous industries including automotive, downhole drilling, aeronautics, space exploration, nuclear environment, radars, could benefit from silver sintering increased bonding performance as it provides the highest electrical and thermal conductivity. and much higher reliability up to$400^{\circ} \mathrm{C}$. This paper presents novel silver sinter-bonding including material and process which allows us to fulfil harsh electronic conditions by improving joint mechanical strength through a new all-in-one pressure-assisted packaging step. By combining sintering of both die-level and substrate-level in a single step, this process made affordable a twofold productivity increase while holding high-quality uniformed silver layers. The attach process takes advantage of great sintering homogeneity to be able within the same flow to sinter dies just as well as large surface substrates (3000 mm2) to attach DBC or AMB to copper heat-spreader. Focusing on the atmosphere control, temperature, pressure and cooling rate was key to ensure consistent quality. Successful sustainability versus thermal expansion is confirmed by C-SAM with no visible voiding and just slightly delamination under 5 percent occurring after 1000 cycles of thermal shock cycles at the die-DBC and DBC-copper heatspreader interconnects. This paper demonstrated easy transposable one step solution to tackle harsh environment's challenge. In parallel thanks to the versatility of this silver sintering technology, a pressure less version has been developed to ensure high performance die-attach where processes avoid pressure assistance. To investigate sintered silver joints with advanced characterization techniques, die-shear test, microscopy and spectroscopy are carried out. Sintered silver interconnect for copper-to-copper showed strength above 30 MPa with mixed adhesive bond fracture offering high performance material able to sustain harsh conditions.