To reduce air enclosed in a gap between a circuit board and a semiconductor component by a cover when the component is solder mounted on a surface of the board and the component is sealed with the cover made of a synthetic resin.

A method for mounting and sealing the semiconductor component comprises a step of filling a sheet-like filler 7 made of a heat resistant insulator in the gap between a bottom of a package 3 of the component 1 and the surface of the circuit board 4 for mounting the package. Since the board 4 is previously coated with a solder paste, when the board 4 after the package 3 is mounted is introduced into a heating furnace, the board 4 is soldered to the package 3. The method further comprises the steps of coating a liquid heat resistant synthetic resin on the entire package 3 and the board after soldering, and curing the resin.