| 摘要 |
PURPOSE:To make partial plating only on necessary tops at accurate dimensions and positions without generation of stepwise differences, by a method wherein a stripe of metal is previously punched out only at the part except the part which needs partial plating, partially plated at the part not punched out, and then molded into the final form by another press punching. CONSTITUTION:The roots of inner leads are punched out with guide holes 8, outer leads 5, and parts 9 larger than the outer periphery which needs partial plating in the product left flat in a lead frame stripe of metal. Next, required parts are subjected to partial plating 10 by a continuous partial plating device. Finally, this stripe is molded into the final form of lead frame by punching out the chip mount and inner lead tips by the second press punching. This manner allows no deformation of leads because of the joint of the chip mount to the inner lead tips in the plating process even when continuous plating is made, and produces no lead stepwise differences. Since the strip of metal is stronger against deformation than the material fully punched out, the positions and dimensions of partial plating by masking can be accurately made. |
