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MULTI-METAL BALL BUMPS FOR INTEGRATED CIRCUIT FLIP CHIP INTERCONNECTIONS

IP.com Disclosure Number: IPCOM000006285D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-20
Document File: 1 page(s) / 69K

Publishing Venue

Motorola

Related People

Thomas A. Scharr: AUTHOR

Abstract

Multi-metal bumps bonded to integrated circuit chip bond pads will facilitate the interconnection of the cir- cuits to multi-chip module substrates. A multi-metal bump is comprised of a tin-lead bump which is bonded on top of either a copper or gold bump on an aluminum metal bond pad of the circuit. The copper or gold and the solder bumps are bonded to the chips with an auto- matic wire bonder. The chips with the multi-metal bumps are "flip-chip" bonded to the multi-chip module using a standard solder reflow process.

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MOTOROLA INC. Technical Developments Volume 14 December 1991

MULTI-METAL BALL BUMPS FOR INTEGRATED CIRCUIT

FLIP CHIP INTERCONNECTIONS

by Thomas A. Scharr

   Multi-metal bumps bonded to integrated circuit chip bond pads will facilitate the interconnection of the cir- cuits to multi-chip module substrates. A multi-metal bump is comprised of a tin-lead bump which is bonded on top of either a copper or gold bump on an aluminum metal bond pad of the circuit. The copper or gold and the solder bumps are bonded to the chips with an auto- matic wire bonder. The chips with the multi-metal bumps are "flip-chip" bonded to the multi-chip module using a standard solder reflow process.

  Established processes for forming solder bumps on chips involve evaporating or plating of adhesion, barrier and solderable metal layers followed by evaporation or plating of the tin-lead solder bumps. With the advent of a technique to form solder bumps from 45~ diameter solder wire using an automatic thermosonic wire bonder the bump forming process has become more flexible. Using the wire bonder the solder bumps can be put down without the masking, plating or evaporation processes previously needed. Bond pad location can be programmed in the wire bonder and single chips can be bumped using this process. The one draw back is that

thin metal adhesion, and solder wettable layers are still required on top of the bond pads since it is diicult for solder to form a metallurgical bond or wet directly to the...