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LEADFRAME FOR MULTIPLE LEAD-COUNTS FROM SINGLE TRIM AND FORM TOOL

IP.com Disclosure Number: IPCOM000008431D
Original Publication Date: 1997-Dec-01
Included in the Prior Art Database: 2002-Jun-13
Document File: 2 page(s) / 101K

Publishing Venue

Motorola

Related People

Larry Boughter: AUTHOR [+2]

Abstract

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).

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MOTOROLA Technical Developments

LEADFRAME FOR MULTIPLE LEAD-COUNTS FROM SINGLE TRIM AND FORM TOOL

by Larry Boughter and Doug Cotney

OVERVIEW

  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).

Trim and form tooling is then designed and

built with all the necessary punches to accommo- date the largest lead-count package. These punches are permanently installed in the die set. As the l...