The invention uses a high Sb soldering materials to weld the insulation circuit basal plate and the semiconductor chip and obtains the welding method achieving a good connection state in which the gaps are fewer. For the Sn-high Sb soldering materials, the oxidized films of which are relatively thick and invasion is bad, the U-shaped soldering tin plate which can reduce the superficial area to perform welding by tin between the insulation circuit board and the semiconductor chip, so that the formation of the oxidized films is less and the welding tin connection surface in which the gaps are to produce can be generated. Furthermore, the semiconductor chip is laminated on the U-shaped welding tin plate, and the gaps are positioned in the welding tin center of the connection surface of the semiconductor chips and the circuit substrate, so that the contact area with the hydrogen is increased and the cleaning effects for the welding tin connection surface by the reduction reaction.