LEADFRAME FOR MULTIPLE LEAD-COUNTS FROM SINGLE TRIM AND FORM TOOL
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2002-Jun-13
This concept is for a leadframe design that allows a number of different lead-counts of a partic- ular device type to be manufactured from a single set of trim and form punches. This concept would include dejunk, dambar trim, lead length trim, lead form operations and singulation. (Singulation not applicable to TSSOP example illustrated.) DESCRIPTION The leadframe is designed around the largest lead-count to be produced. The appropriate pitch between devices and between rows of devices is determined based on the largest lead-count package. Once these two pitches are determined, they are fixed and all smaller lead-counts use the same spac- ing. Accordingly, the centerpoint of the largest lead- count package becomes the centerpoint for all lead-counts. The smaller lead-count packages are produced by shortening the largest device from both ends towards the fixed centerpoint. As the lead- count is reduced (from the largest), the leads on the leadframe that are not required when producing a smaller lead-count are replaced by a through hole in the leadframe. The smaller the lead-count, the larger the through hole becomes (See Figure I).