Effect of Sintering Time on Silver-Aluminium Nanopaste for High Temperature Die Attach Applications

Abstract

Nanoscale materials, primarily metallic elements have been proven as suitable solutions for interconnect technology on power semiconductor devices. Nanoscale materials possess high surface energies thus enabling them to be processed at lower temperatures for high temperature applications of more than 500°C. This literature work aims to present a novel silver-aluminium (Ag-Al) nanoalloy die attach paste solution for power semiconductor devices. Ag and Al nanoparticles were pre-mixed into an organic paste system using binders and a surfactant. Viscosity tests concluded that the Ag-Al nanopaste is suitable for mass manufacturing dispensing and screen printing with an average value of 47,800 cps. Thermogravimetric analysis was used to design the sintering profile at 380°C from 10 to 30 minutes. X-ray diffraction analysis detected the formation of Ag2Al and Ag3Al compounds in the post-sintered nanopaste. Scanning electron microscopy and Energy-dispersive X-ray spectroscopy showcased larger grains in the nanopaste microstructure with the passage of sintering time. The electrical conductivity of the Ag-Al nanopaste decreased as the stencil printed paste thickness increased between 25.4-101.6 microns. This was due to the much larger pore formation in the thicker nanopaste layers during sintering and organics burn off.