Research of reflow soldering on Al-SiC composite material and thick film ceramic substrates

With the high speed development of information technology, the circuit assembly density becomes higher, which caused that the power density and the demand for heat dissipation increase. The traditional packaging metals such as copper, aluminum play a good performance on the heat conduction, but a higher heat mismatch stress is caused by the difference of the thermal expansion coefficient between packing metals and ceramic materials. Kolar alloy can solve the problem, but its thermal conductivity is to low (less 20 times than Cu). W/Cu, Mo/Cu alloy could meet the demand for high fever guide and low inflation, but they have large density (> 8.9 g/cm3). So a new type of material with a low inflation, high thermal conductivity and light is demanded in the aerospace field. Al/SiC composites materials is expected to replace the first and the second generation special electronic packaging alloy because of the low density, low inflation and high thermal conductivity. Therefore, the reflow soldering between the Al-SiC composites materials for heat sink and ceramic substrates have extensive significance[1,2]. In this paper, we reflowed the 63Sn37Pb/Ni-plated Al-SiC carrier and thick film hybrid circuit coated palladium silver slurry with two kinds of solder paste ,63Sn37Pb and 62Sn36Pb2Ag. The effect of the thermal shock resistance of the Pd-Ag coat on the thick film ceramic substrate and the 63Sn37Pb/Ni film on Al-SiC was determined by the water quenching method. The microstructure of the joint was observed by SEM. The thickness of the PdAg film was bigger with SnPbAg solder paste than SnPb, which meaned that the element Ag made a effect on coating corrosion resistance. After a long time about 400 hours of the heat cycle test, no cracks were found by SEM and the joint microstructure remained relatively uniform.