Browse Prior Art Database

Dual Metal Thickness Tape Automated Bonding Leadframe

IP.com Disclosure Number: IPCOM000035722D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bickford, HR: AUTHOR [+2]

Abstract

One approach to the interconnection of electrical devices, such as silicon chips, is the use of tape automated bonding (TAB), in which leads ("inner leads") are bonded to the silicon device. These leads are part of an overall package structure which allows bonding of the package (using the "outer leads") to a circuit board or other second level packaging substrate. At the present time, the TAB industry places a rough, practical lower limit on the width and spacing of inner lead bonds at .002" (i.e., .002" wide beams spaced on .004" centers). This limit is coupled with a beam thickness of roughly .001".

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Dual Metal Thickness Tape Automated Bonding Leadframe

One approach to the interconnection of electrical devices, such as silicon chips, is the use of tape automated bonding (TAB), in which leads ("inner leads") are bonded to the silicon device. These leads are part of an overall package structure which allows bonding of the package (using the "outer leads") to a circuit board or other second level packaging substrate. At the present time, the TAB industry places a rough, practical lower limit on the width and spacing of inner lead bonds at .002" (i.e., .002" wide beams spaced on .004" centers). This limit is coupled with a beam thickness of roughly .001". Disclosed is a tape automated bonding leadframe structure that allows more finely spaced inner lead bonds than current industry practice, thus extending the applicability of TAB packaging to the interconnection of high I/O count VLSICs. A relatively thinner layer of metal conductor is provided in the area of the inner leads so that fine pitch spacing may be accomplished; while rugged, thicker metal conductors are provided in the area of the outer leads which must withstand mechanical stresses associated with a variety of card assembly operations: excising, forming, placing, and bonding.

The leadframe is fabricated by commonly known lithographic, plating and etching techniques. To achieve the desired dual metal thickness structure, an initial metal layer (perhaps one half of the usual thickness) is deposited thro...