To provide a lead frame having a heat sink which is free from deformation at a thick plate part and a thin plate part during the rolling, and excellent in pitch precision of the thick plate part by repeatedly feeding and rolling the stock between a die and a flat roll using the die and the flat roll in which a plurality of grooves of the same size as that of the thick plate part are provided on the lead frame with the prescribed pitch.
A thin plate part 3b and a thick plate part 3a are simultaneously formed on a lead frame by relatively moving a flat roll 1 and a die 4 while keeping the clearance therebetween. When the flat roll 1 is moved from the forward tip of the die 4 to the rear tip, the die 4 and the flat roll 1 are opened, i.e., the flat roll 1 is moved upward, and returned to the tip of the die 4. A stock 5 is fed therebetween, and the next working is started to manufacture the long lead frame. The feed of the stock 5 is the length of the rolling pitch of the thick plate part 3a multiplied by the number of the groove of the die 4. The thick plate part 3a which is worked twice by the die 4 may be present.
OBA MAKOTO
HAGIWARA NOBORU
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