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Dual Material Cu Bond Stitch On Bump Process

IP.com Disclosure Number: IPCOM000234047D
Publication Date: 2014-Jan-08
Document File: 2 page(s) / 160K

Publishing Venue

The IP.com Prior Art Database

Abstract

Bond stitch on bump offers a wire bond alternative whenever an interconnect is required on two sensitive, fragile surfaces using a wire bond process or low loop wire bond application. The process however is challenging when using Cu wire due to instant bump oxidation before the stitch attach on its surface. This problem has resulted second bond non stick, short tail and low wire peel strength problems. In this paper we provide an effective solution to resolve the second bond non stick, short tail and low peel strength issues due to bump oxidation during Cu wire bond stitch on bump process.

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Document Title 

Dual Material Cu Bond Stitch On Bump Process

Abstract 

Bond stitch on bump offers a wire bond alternative whenever an interconnect is required on two sensitive, fragile surfaces using a wire bond process or low loop wire bond application. The process however is challenging when using Cu wire due to instant bump oxidation before the stitch attach on its surface. This problem has resulted second bond non stick, short tail and low wire peel strength problems.  In this paper we provide an effective solution to resolve the second bond non stick, short tail and low peel strength issues due to bump oxidation during Cu wire bond stitch on bump process.

Background

Semiconductor device assembly plants have performed Copper Ball on Gold Bump (COG) at least since 2009 with 1 mil gold and copper wires. The process is to bond a gold bump on an Al bond pad first, then wire bond a copper ball on the gold bump using conventional copper wire-bonding. The pre-bonded gold bump serves as a cushion to absorb most of the mechanical stress from copper wire bonding by its body deformation. The Al bond pad only receives the remaining mechanical stress, which is no more than its sustaining capability.  The COG bonding was successfully performed using a conventional wire bonder with an add-on system copper kit.  No degradation of electrical performance before and after reliability tests was observed as compared with Au wire bonding, nor was there any difference in package integrity throughout ICs’ lifetime between with the COG bonding and Au wire bonding....