Method of making plastic sealed cavity molded type semi-conductor devices

Claim 1

In a method of making a plastic sealed cavity molded type semi-conductor device wherein a molded plastic header having an external lead frame molded therein is provided with an internal cavity housing the semi-conductor element which is electrically connected to the internal end of the external leads by way of internal lead wires within the cavity and wherein a cap is heat and pressure sealed to the header to seal the cavity from ambient atmosphere, the improvement comprising the steps of: a. forming the external lead frame from a metal having a composition of Copper (89.6-98.97%), Phosphor (0.03-0.4%) and Tin (1-10%); b. heating the external lead frame to 80°C prior to embedding it in the header; c. molding said header by injection molding an epoxy resin powder at a temperature of 150°C, a pressure of 70kg/cm 2 and a plunger injection rate of 10 mm/sec such that said external lead frame is embedded therein and internal ends thereof protrude into the cavity; and d. honing the internal ends of the external lead frame by subjecting the surfaces to a liquid stream of water and aluminum oxide of 20 to 30 micron grain size in a mixture ratio of 2 parts water to 1 part abrasive material by volume at a flow rate of 1 sec/cm 2 and under 3kg/cm 2 pressure.