PURPOSE: To realize effective sealing without using flux by a method wherein a cap is placed on a substrate with the intermediary of solder layer and then pressed to the substrate by a cyclically vibrating heat column in a reducing atmosphere, when a metal cap is soldered to a thick-film integrated-circuit substrate for hermetic seal.

CONSTITUTION: Ag/Pd conductors 2 to constitute an electric circuit are printed on a substrate 1 made of insulating material such as alumina and then subjected to baking. In the same way, a connecting conductor 3 is provided at a prescribed location on the substrate 1 with the intermediary of an insulating dielectric body 4 and then subjected to baking. Next, a solder layer 6 is formed on the conductor 3, flux is removed therefrom, and an element 7 is bonded with adhesive 8 to the exposed part between the conductors 2. Terminals belonging in the element 7 are then bonded to the conductors 2 with wires 9. A process follows wherein the lower flange of a metal-made cap 5 is pressed to the solder layer 6 and is in turn abutted against from above by the lower end of a heat column 10 including a heater 11. Cyclic vibration is applied in a reducing atmosphere for the integration of the abutting parts.