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Viscosity Stabilizer for High Adhesion Metallizing Pastes

IP.com Disclosure Number: IPCOM000087530D
Original Publication Date: 1977-Feb-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Gorton, DL: AUTHOR [+3]

Abstract

Metallizing conductive pastes are commonly used in the fabrication of semiconductor packaging structure. It has been noted that when metallizing pastes which embody alumina and a vehicle containing ethyl cellulose as a resin, the viscosity of the paste increases rapidly and drastically in a few days, making the paste too viscous to use. This behavior necessitates either immediate use of the paste, which is inconvenient and often wasteful, or rework of the paste immediately before use, which is also inconvenient and costly.

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Viscosity Stabilizer for High Adhesion Metallizing Pastes

Metallizing conductive pastes are commonly used in the fabrication of semiconductor packaging structure. It has been noted that when metallizing pastes which embody alumina and a vehicle containing ethyl cellulose as a resin, the viscosity of the paste increases rapidly and drastically in a few days, making the paste too viscous to use. This behavior necessitates either immediate use of the paste, which is inconvenient and often wasteful, or rework of the paste immediately before use, which is also inconvenient and costly.

It is believed that the reason for this behavior is that alumina is a basic oxide and also a good catalyst for several types of organic reactions involving OH groups. Ethyl cellulose has several free OH groups. It is postulated that the alumina causes cross-linking among the ethylcellulose chains, increasing the effective chain length and thus the viscosity.

The solution to the viscosity problem consists of adding molybdenum trioxide (MoO(3)) to the conductive metal formulation. Since the MoO(3) is an acid oxide, it is postulated that it, in effect, neutralizes the alumina, preventing it from promoting the cross-linking of the ethyl cellulose chains. The solution proposed is particularly applicable to conductive pastes utilizing Mo as the conductive element. While other acid oxides could possibly be used to obtain the same effect, the MoO(3) is particularly attractive in a Mo paste since...