Abstract: In a plastic encapsulated semiconductor device, a part of wire piece may break down due to thermal fatigue, which positioned adjacent to a bonding portion of the wire piece connected to a chip. This is caused by that wire piece moves relative to plastic encapsulating the chip and the wire piece, and a strain in the wire piece due to thermal deformation of the device concentrates on one portion of the wire piece. Accordingly, a rugged portion is formed on a surface of a part of wire piece subjected to a breakdown to thermal fatigue. The plastic bites recesses of the rugged portion to prevent the wire piece from moving relative to the plastic, thereby preventing the wire piece from breaking down due to thermal fatigue.

Abstract: A lead frame and a semiconductor device wherein a through hole is formed in the center of a semiconductor chip-mounting surface of a chip pad at the center of the lead frame, the through hole being tapered or being one which corresponds to a surface area that is greater on the surface of the chip-mounting surface of the chip pad than on the surface of the side opposite to the chip-mounting surface thereof. This prevents the occurrence of cracks in the sealing plastic portion in the step of reflow soldering of the lead frame to the substrate.