PURPOSE:To prevent the generation of positional deviation between a metal base and an external outgoing lead as well as to reduce assembling manhours by a method wherein the metal base and the external lead-out lead are integrally formed in advance, and after they have been brazed to the bottom part of the side face member, they are separated with each other. CONSTITUTION:An external outgoing lead part 26 and a base part 2a are formed with the frame 2 of single part which is integrally formed using a tie-bar from the same element and material (plate material) such as a copper alloy by performing a press-cutting method and the like. The frame 2 is fixed by brazing to the bottom part of a side wall member l. Then, the metal plating such as nickel plating, gold plating and the like is performed. Subsequently, the lead part 2b and the base part 2a are separated by cutting. As a result, the positional deviation between the lead part 2b and the base part 2a is prevented, and the manhours of assembling can also be reduced.