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C4 Implant Stand-Off Technique for Mass Bonding to Film Circuits

IP.com Disclosure Number: IPCOM000037643D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Honeycutt, JO: AUTHOR [+4]

Abstract

A method is described which provides a precise C4 chip height thus allowing TAB & C4ATAB bonding directly to Sn/Pb pads. The method prevents bridging while allowing thermode planarity variations.

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C4 Implant Stand-Off Technique for Mass Bonding to Film Circuits

A method is described which provides a precise C4 chip height thus allowing TAB & C4ATAB bonding directly to Sn/Pb pads. The method prevents bridging while allowing thermode planarity variations.

This method employs a technique of thermosonic, ultrasonic, or thermocompression automatic high speed plunge insertion bonding of typically copper balls into selected Sn/Pb pads, followed by mechanical wire abrasion above the ball, precisely locating the fracture site during wire clamp/bond tool lift, creating an intrinsic solder pad stand-off, providing a TAB/ C4ATAB thermode self-leveling mechanism during bond cycle reflow.

Prior art TAB/C4ATAB bonding techniques to C4 solder pad structures utilize Au, Sn, or 63/37 Sn/Pb tape lead fingers or pads requiring very narrow parameter windows and precise pad height control to ensure total bonding to all pads without complete reflow of the C4 structures. Complete reflow results in pad bridging, zero chip to tape height, and potential chip edge/lead finger shorts.

This method provides implanted C4/solder alloy metallic ball stand-offs allowing complete reflow of C4 structures with precise chip to tape pad or lead finger height control for mass thermode bonding. High speed automatic ball wire bonders form, a controlled size ball on wire ends, fed through bonding capillaries. The implant is formed as capillaries insert these balls into selected C4 pads.

Capillaries...