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Low Cyanide Electroless Plating

IP.com Disclosure Number: IPCOM000039201D
Original Publication Date: 1987-May-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Kaschak, RA: AUTHOR [+2]

Abstract

An additive plating bath uses sodium cyanide as a brightener, which increases the ductility of the deposited copper. This is achieved by reducing hydrogen embrittlement at the grain boundaries. Sodium cyanide in sufficient quantities has been used a a stabilizer of Cu+1 to Cu0, but it has the tendency to form extraneous copper (nodules) in the solution bulk. In the presence of both high cyanide, >8 ppm NaCN, and high disolved oxigen concentration, 2.5 ppm, a dissolution of a copper bondable catalytic surface will occur in the additive bath and takeability will be very negatively affected. In order to minimize the negative impact of both high cyanide and high dissolved oxygen, a number of techniques are possible.

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Low Cyanide Electroless Plating

An additive plating bath uses sodium cyanide as a brightener, which increases the ductility of the deposited copper. This is achieved by reducing hydrogen embrittlement at the grain boundaries. Sodium cyanide in sufficient quantities has been used a a stabilizer of Cu+1 to Cu0, but it has the tendency to form extraneous copper (nodules) in the solution bulk. In the presence of both high cyanide, >8 ppm NaCN, and high disolved oxigen concentration, 2.5 ppm, a dissolution of a copper bondable catalytic surface will occur in the additive bath and takeability will be very negatively affected. In order to minimize the negative impact of both high cyanide and high dissolved oxygen, a number of techniques are possible. One, a dual-bath concept, to get take on a catalytic substrate in one bath and transfer into another, uses one bath with a high cyanide concentration (>4 ppm) and low dissolved oxygen concentration (<1.5 ppm) to achieve take followed by a transfer of the substrate to another bath with both a high cyanide concentration and high dissolved oxygen concentration to minimize nodule formation, is outlined in U.S. Patent 4,525,390. Another way to plate on a catalytic substrate uses the dual-bath concept with low CN- (<3 pp,) and a high dissolved oxygen 2.5 - 3.5 ppm, in one bath followed by high CN- (>8 ppm) and high DO2 (2.5 - 3.5 ppm) in another bath also requires transfer of the substrate from the first bath to the second bath. This transfer step, although done under controlled conditions, c...