Firstly, as shown in FIG. 11-a and in FIG. 11-b, the first, the second and a third set of lead frames 11 a, 11 a???, 11 b, 11 b??? and 11 c, 11 c???, which are formed in a predetermined shape and at a predetermined interval by pressing and etching a conductive plate made of such a metal material as Al or Cu with all of the flames being united with each other (not shown) at their end portions initi