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Browse Prior Art Database

Method of Forming a Solder Barrier

IP.com Disclosure Number: IPCOM000083856D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Ameen, JG: AUTHOR [+5]

Abstract

This is a method of applying an improved material composition to exposed circuit metals so as to form a simple, adherent, and effective solder barrier. The composition is as follows: 2.5 grams per liter of sodium sulfide solution Na(2)S 9H(2)O and 2.5 grams per liter of sodium hydroxide NaOH. This formulation is particularly compatible with the immersion tin coatings.

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Method of Forming a Solder Barrier

This is a method of applying an improved material composition to exposed circuit metals so as to form a simple, adherent, and effective solder barrier. The composition is as follows: 2.5 grams per liter of sodium sulfide solution Na(2)S 9H(2)O and 2.5 grams per liter of sodium hydroxide NaOH. This formulation is particularly compatible with the immersion tin coatings.

Starting with a circuitized board, the application of the solder barrier is as follows:
1. Apply KPR* photoresist or equivalent, expose, develop, and

post bake the barrier pattern.
2. Immersion tin dip the entire panel.
3. Strip the KPR material resist from the panel.
4. Bake the panel assembly for approximately 5 minutes at a

temperature of about 165 degrees C.
5. Immerse the panel for approximately 1 minute in the sulfide

solution formulation outlined above.
6. Remove the panel from the solution and permit it to stand for

approximately 4 minutes in the air, to accelerate the reaction

and enhance the coating characteristics.
7. Rinse the panel and dry it.
8. Solder as required.

The coating, as applied, has been empirically found very effective as a solder barrier and can survive a plurality of passes through a solder-fall process with no visible signs of degradation. * Trademark of Eastman Kodak Company.

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