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Browse Prior Art Database

Method of Detecting Missing Metallization Layers in Evaporated C-4 Structure

IP.com Disclosure Number: IPCOM000061039D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Henry, BC: AUTHOR

Abstract

In the semiconductor manufacturing process it is vital that layers be properly soldered. In many instances, solder will adhere well enough to pass visual and electrical tests, but be unreliable in the machine environment. This article describes a method to provide a reliable indication of missing CrCuAu underneath a solder pad, so the defective pads will be rejected. In the desire to improve C-4 (controlled collapse chip connector) fatigue life, solder volume of the C-4's is increased to make them taller. However, the use of the thicker masks during evaporation results in unacceptable levels of solder pull-out during mask removal.

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Method of Detecting Missing Metallization Layers in Evaporated C-4 Structure

In the semiconductor manufacturing process it is vital that layers be properly soldered. In many instances, solder will adhere well enough to pass visual and electrical tests, but be unreliable in the machine environment. This article describes a method to provide a reliable indication of missing CrCuAu underneath a solder pad, so the defective pads will be rejected. In the desire to improve C-4 (controlled collapse chip connector) fatigue life, solder volume of the C-4's is increased to make them taller. However, the use of the thicker masks during evaporation results in unacceptable levels of solder pull-out during mask removal. The most practical way to increase solder volume is by using two mask sets: one for the CrCuAu ball limiting metallurgy (BLM) evaporation and a second one with larger openings for the solder evaporation. During solder reflow after evaporation, the solder retracts from the non- wettable glass surface around the BLM pads, thereby giving a taller C-4. The use of a single mask for both the CrCuAu deposition and the solder deposition is advantageous in that a plugged hole in the mask will result in an easily detectable missing C-4. This may be determined either visually or electrically. With two mask sets, a plugged hole in the first will prevent deposition of the CrCuAu, which is essential for reliable solder adhesion to the chip. The solder will be deposited throu...