Browse Prior Art Database

No Bump Beam Tape

IP.com Disclosure Number: IPCOM000050135D
Original Publication Date: 1982-Sep-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Edwards, JC: AUTHOR

Abstract

In traditional tape automated bonding (TAB), it is necessary to provide for some kind of stand off between the chip surface and the beam lead to prevent a short circuit. This is done with either gold bumps on the wafer or with gold plated copper bumps on the tape. The configuration disclosed here utilizes photo definable polyimide and planar (no bumps) tape.

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No Bump Beam Tape

In traditional tape automated bonding (TAB), it is necessary to provide for some kind of stand off between the chip surface and the beam lead to prevent a short circuit. This is done with either gold bumps on the wafer or with gold plated copper bumps on the tape. The configuration disclosed here utilizes photo definable polyimide and planar (no bumps) tape.

The tape is manufactured using rolled/annealed copper coated with photo definable polyimide (less than .0005 inches). In a mask exposure step, the standard beam lead layout is defined on one side while on the reverse side a rectangle is exposed in the polyimide slightly smaller (approximately 1 mil on each side) than the chip itself. This results in only the tips of the beam leads being exposed. These tips are then gold plated using the polyimide as a mask.

Bonding to the chip is accomplished with a standard thermo compression tool slightly smaller than the polyimide window (also approximately 1 mil). The chip is brought up against the polyimide side of the tape. As the tool pushes the polyimide/copper laminate against the chip, the undersized polyimide catches on the edge of the chip. The tool continues down, deforming the copper lead over the edge of the polyimide and bonding the tip of the beam lead to the chip pad.

In Fig. 1, the parts are shown aligned before the bonding cycle. In Fig. 2, the thermo compression tool is shown causing initial contact of the polyimide and the chip edge. Fi...