PURPOSE: To improve the electric characteristics and to contrive to cut down the cost of material, the cost of processing and the like of the title transformer by a method wherein the structure of a bobbin is divided into two parts, one of them is formed into a thermoplastic resin part, the other part is formed into a thermosetting resin part, and then they are coupled together, thereby enabling to thin off the thickness of the bobbin.

CONSTITUTION: A pin terminal 7 is buried in the flange 8 consisting of thermosetting resin, and a lead wire lead-out groove 9 is provided between pin terminals 7. The flange 8, consisting of thermoplastic resin, has the structure wherein a metal mold 2-directions forming can be performed, a hole 15 where a pin is buried is provided thereon, and the lead wire lead-out groove 9 corresponding to the lead wire lead-out groove 4 of a bobbin 13 is provided thereon. A guide protrusion 10 and a mating protrusion 11 are provided on the flanges 8. The completed flanges 8 are press-fitted in the guide 5 provided on the lower end flange 3 of the bob- bin 13 respectively. The guide protrusion 10 provided on the side face of the flange 8 is press-fitted in the guide groove 5 provided in the lower end flange 3 of the bobbin 13, and the protrusion 10 is inserted as far as to the point where the mating protrusion 11 provided on the lower face of the flange 8 is caught by the stepped part 6 provided on the lower end flange 3 of the bobbin 13.