LEAD FRAME FOR SEMICONDUCTOR

摘要

PURPOSE:To produce a lead frame for semiconductor improving both heat resistance of silver plated layer and resin sealing property by a method wherein a lead frame substrate is provided with Ni-Sn alloy or Co-Sn alloy layer while element fixing part and inner terminal part is also provided with copper or copper alloy layer and further with silver layer thereon. CONSTITUTION:An Ni-Sn alloy provided on a lead frame substrate shall contain around 70wt% of Sn while Co-Sn alloy shall contain around 75wt% of Sn. A frame is produced by means of stamping a substrate 10 made of Co-Sn alloy into specified pattern to form a semiconductor element fixing part 5, an inner lead 6 and an outer lead 7. Firstly after preliminary treatment such as degreasing and pickling operations, overall substrate is provided with Ni-Sn alloy plated layer 2 as base metal layer after pyrophosphoric acid bath utilizing electroplating process. Secondly a copper plated layer 4 is formed after copper cyanide bath as an intermediate plated layer and then element fixing part 5 and the inner lead terminal part 6 are provided with a partial silver plated layer 6. Finally a copper plated layer of a part not covered with silver layer is removed by means of anodically resolving process during copper cyanide bath to produce a lead frame.