Research of vacuum soldering on 10# steel 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. 10 steel and thick film substrates have been widely used in power circuits to achieve miniaturization and high thermal conductivity. At present, most of the military enterprises adopt the method of reflow soldering to realize the interconnection between the thick film substrate and 10 steel, as well as the thick film substrate and the components with the same soldering paste. The efficiency of this method is high due to the simple process, while the void rate of the interface is high, which affects the heat dissipation. So it is important to reduce the void rate of the interface between the thick film substrate and 10 steel. Vacuum soldering can effectively reduce the void rate of the interface. In this study, we reflowed the Ni-plated 10 steel and thick film hybrid circuit coated palladium silver slurry by vacuum brazing furnace with the solder piece, Sn-3.0Ag-0.5Cu. The effect of the thermal shock resistance of the Pd-Ag coat on the thick film ceramic substrate and the Ni film on 10 steel was determined by the water quenching method. The microstructure of the joint was observed by SEM. And the shear strength of the joints was tested by the material testing machine.