Methods of cleaning copper surfaces in the manufacture of printed circuit boards
View Patent ↗The present invention sets forth an improved method of microetching a metal substrate by contacting the substrate with an aqueous composition comprising a sodium persulfate or hydrogen peroxide oxidizing agent, acid, and one or more additives. When the oxidizing agent is sodium persulfate, the one or more additives generally comprise an aliphatic saturated dicarboxylic acid. When the oxidizing agent is hydrogen peroxide, the one or more additives generally comprise a stabilizer and amino tris(methylene phosphonic acid).
1. A process for the manufacture of a printed circuit board comprising conductors comprised of copper and non-conducting material, said process comprising:
(a) contacting said printed circuit board with a dispersion comprising carbon particles; and
(b) contacting the printed circuit board with an aqueous microetchant comprising:
(i.) sodium persulfate;
(ii.) acid; and
(iii.) one or more aliphatic saturated dicarboxylic acids; such that the carbon particles are substantially removed from the conductors but the carbon particles substantially remain as a coating on the non-conducting material.
2. The process according to claim 1 , wherein the aliphatic saturated dicarboxylic acid is selected from the group consisting of malonic acid, succinic acid, and glutaric acid.
3. The process according to claim 2 , wherein the aliphatic saturated dicarboxylic acid comprises glutaric acid.
4. The process of claim 1 , wherein the etch of the surface is controlled to less than about 40 microinches.
5. The process according to claim 1 , wherein the etch of the surface is controlled to less than about 25 microinches.
6. The process according to claim 1 wherein the etch of the surface is controlled to less than about 15 microinches.
7. A method of microetching a metal substrate by contacting the substrate with an aqueous composition consisting essentially of:
(a) sodium persulfate;
(b) an acid; and
(c) an aliphatic saturated dicarboxylic acid; and
(d) copper sulfate.
8. The method according to claim 7 , wherein the aliphatic saturated dicarboxylic acid is selected from the group consisting of malonic acid, succinic acid, and glutaric acid.
9. The method according to claim 7 , wherein the aliphatic saturated dicarboxylic acid comprises glutaric acid.
10. The method according to claim 7 , wherein the aliphatic saturated dicarboxylic acid is present in said composition in an amount of about 1 to 5 grams/liter.
11. The method of claim 7 , wherein the surface is etched to a depth of less than about 40 microinches.
12. The method according to claim 7 , wherein the surface is etched to a depth of less than about 25 microinches.
13. The method according to claim 7 , wherein the surface is etched to a depth of less than about 15 microinches.