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Undercoat to Prevent Underplating in Electrolytic Processing

IP.com Disclosure Number: IPCOM000077415D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Bakos, P: AUTHOR [+2]

Abstract

This process provides a method of preparing circuitized substrates, where excessive electrolytic platings are required. The electrolytic depositions are performed through thick (dry) film photoresists. The photoresists, although exhibiting adequate adhesion to the substrate, are unable to prevent underplatings.

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Undercoat to Prevent Underplating in Electrolytic Processing

This process provides a method of preparing circuitized substrates, where excessive electrolytic platings are required. The electrolytic depositions are performed through thick (dry) film photoresists. The photoresists, although exhibiting adequate adhesion to the substrate, are unable to prevent underplatings.

To eliminate this problem, a specially formulated undercoat is applied prior to the dry-film photoresist lamination. The function of the undercoat is to provide maximum adhesion between substrate and dry-film photoresist. Furthermore, to ensure simultaneous photoprocessing the undercoat must contain at least 70% w/w of the same polymeric structure as the dry-film photoresist. The undercoat is prepared as follows: 1) Dissolve 1% w/w - 25% w/w of a commercially available light-sensitive polymer into a suitable solvent or combination of solvents, such as aromatic hydrocarbons or halogenated hydrocarbons. 2) Dissolve a selected dry film photoresist 75% w/w - 99% w/w into the solvent described above. 3) Add an antioxidant within the range from 0.01% w/w - 2.0% w/w. 4) Add a suitable plasticizer 9.1% w/w - 6.0% w/w. 5) If required, a suitable sensitizer can then be added within a range of 0.5% w/w - 10% w/w.

Use of this specially formulated undercoat allows for substantially increased circuit densities, because of the absence of underplatings.

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