Herbert D Miller

US Patent:

48458422, Jul 11, 1989

Filed:

Nov 25, 1987

Appl. No.:

7/125428

Inventors:

Herbert Miller - San Jose CA
Richard D. Harline - San Jose CA

Assignee:

National Semiconductor Corporation - Santa Clara CA

International Classification:

H01R 4300

US Classification:

29827

Abstract:

A metal sheet (58) to be etched into lead frames has an emulsion coating (60) on its top and bottom. A bottom glass plate (56) has a mask pattern (64) defining the pattern of metal from the sheet (58) that is to remain after etching to form the lead frame. The pattern (64) has a first line width d1. A top glass plate (62) has a corresponding mask pattern (66) also defining the pattern of metal from the sheet (58) that is to remain after etching to form the lead frame. The mask pattern (66) has a second line width d2 that is less than the first line width. The emulsion coating (60) on the sheet (58) is exposed through the mask plates (56) and (62), and the emulsion coating is developed in a conventional manner to give photoresist patterns (64a) and (b 66a) or (64b) and (66b) on the metal sheet (58). The patterns (64a ) and (66a) are produced when the mask plates (56) and (62) are in exact registration with each other, and the patterns (64b) and (66b) are produced when the mask plates (56) and (62) are misaligned to the greatest extent permissible while avoiding lead sweep. The metal sheet (58) with the photoresist patterns (64a) and (66a) or (64b) and (66b) in place is then etched in a convention etching process to produce a lead frame and the photoresist patterns are stripped from the resulting etched lead frame.