PURPOSE: To facilitate a soldering work, and to prevent a conductive piece from floating from a circuit board formed by so integrally filling and molding with insulating synthetic resin as to expose parts of conductive pieces from both upper and lower faces by forming the exposing area of the piece with the soldering face side to be wider than the area exposed with a component placing side.
CONSTITUTION: A circuit board 51 to be contained in a body case, and a component to be placed thereon are provided. The board 51 is so buried and covered with insulating synthetic resin as to expose parts of conductive pieces 73 from both upper and lower faces. The component is placed on a land 51a of one face of the board 51, leads l extended from the component are inserted to the exposed part of the piece 73 to protrude to the side of a face 51b to be soldered of the other face of the board 51, and the protrusion end is soldered to the piece 73. The piece 73 is so formed that the exposed area with the side of the face 51b ls wider than the exposed area with the side of the face 51a.