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Process for Removing Flux Residue

IP.com Disclosure Number: IPCOM000085027D
Original Publication Date: 1976-Feb-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Schiller, JM: AUTHOR

Abstract

In the packaging of integrated circuit semiconductor devices, particularly where devices are joined to a substrate by solder bonding, it is necessary to remove the rosin flux used in the solder bonding process. Experience has shown that no one organic solvent, such as hydrocarbons, ketones, acetates, ethers, alcohols, and the like, fully removes all rosin flux residues. In addition, chlorinated solvents frequently degrade to form chloride ions which are detrimental to the ultimate package, particularly in a liquid cooled package, since they contribute to corrosion and have other detrimental effects.

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Process for Removing Flux Residue

In the packaging of integrated circuit semiconductor devices, particularly where devices are joined to a substrate by solder bonding, it is necessary to remove the rosin flux used in the solder bonding process. Experience has shown that no one organic solvent, such as hydrocarbons, ketones, acetates, ethers, alcohols, and the like, fully removes all rosin flux residues. In addition, chlorinated solvents frequently degrade to form chloride ions which are detrimental to the ultimate package, particularly in a liquid cooled package, since they contribute to corrosion and have other detrimental effects.

It has been noted that there is a difference in flux solubility for flux reacted with the metal oxide as compared with flux residing on the alumina substrate. The metal oxide reacted flux may form compounds such as chelates, whereas the flux on the substrate may oxidize and/or polymerize. In order to have an effective flux removal process, the sequence of solvents must be compatible and not insolubilize any flux fragment on the various parts of the package.

An example of this process would be the following for flux removal from a substrate and device package: (1) immerse in xylene at 25 to 95 degrees C for one to ten minutes. This step can be repeated as often as necessary. Xylene effectively removes flux interacted with the metal oxide. (2) Follow with immersion in CELLOSOLVE* acetate at 25 to 95 degrees C for one to ten minutes (to...