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Thick Conductor Stencil

IP.com Disclosure Number: IPCOM000061048D
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+2]

Abstract

This article relates generally to integrated circuit fabrication and, more particularly, to the formation of thick metal pads and lines from a thin organic photoresist stencil. Thin conducting contacts and lines can be coated simply with thick metal by dipping in a solder bath, thus eliminating extensive evaporation or plating time to form thick circuit conductors. A thin layer of photoresist 1-2 microns thick is coated over conducting pads or lines, exposed and developed to form the desired stencil of conductor. The substrate with photoresist is dipped in a solder flux bath and then in a hot solder bath. Molten metal wets the exposed conductor, but not the stencil, resulting in a much thicker metal layer than the stencil. A solvent is used to then remove the photoresist pattern.

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Thick Conductor Stencil

This article relates generally to integrated circuit fabrication and, more particularly, to the formation of thick metal pads and lines from a thin organic photoresist stencil. Thin conducting contacts and lines can be coated simply with thick metal by dipping in a solder bath, thus eliminating extensive evaporation or plating time to form thick circuit conductors. A thin layer of photoresist 1-2 microns thick is coated over conducting pads or lines, exposed and developed to form the desired stencil of conductor. The substrate with photoresist is dipped in a solder flux bath and then in a hot solder bath. Molten metal wets the exposed conductor, but not the stencil, resulting in a much thicker metal layer than the stencil. A solvent is used to then remove the photoresist pattern. A variation of this technique is to first oxidize the metal conductor prior to forming the photoresist pattern, such as by heating. This method avoids wetting by the solder through pinholes in the photoresist since subsequent immersion in solder flux is not as effective in removing oxidation in pinholes as in the pattern openings. After solder dipping and removal of the resist layer, the oxidation remaining on conductors not soldered can be removed by again dipping in the solder flux or other etchant.

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