Low Temperature Sinter-Able Silver Paste For High Power Die Attach ApplicationAuthors: Sihai Chen, Christine LaBarbera and Ning-Cheng Lee
Company: Indium Corporation
Date Published: 6/6/2017 Conference: ICSR (Soldering and Reliability)
Ag joints having no or less than 1% voids have been generated on 3mm x 3mm and 10mm x 10mm Ag-die/Au-Si3N4 AMB combination under optimized sintering conditions. Methods including changing the die surface finish and varying aging temperature (250 or 300C) and time (1 to 6 hours) have been tried to improve the joint quality. It is found that the aging indeed increase the joint shear strength. The increased inter-diffusion of elements between substrate and sintered silver is the reason for bonding enhancement. Inter-diffusion between surface Au finish and sintered Ag promotes the formation of an Ag dense layer at interface.
Long term stability of the sintered joints was studied by aging at 250oC with different dies including Au and Ag finished silicon dies and Cu dies. Experiments show that both Au and Ag finished dies show an enhancement in shear strength, with Ag showing a steady shear strength increase. In contrast, Cu dies result in a quick decrease in shear strength even after one day of aging, the failure points are located between the sintered Ag and Cu surface, presumably due to the formation of copper oxide on top of the Cu die surface.
Silver sintering paste, pressure-less, die-attach, porosity, high temperature aging, surface finish
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