Immersion plating of silver
AssigneeAtotech Deutschland GmbH
InventorsHans-Jürgen Schreier, Hartmut Mahlkow
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Abstract
The problem in forming solderable and bondable layers on printed circuit boards is that the surfaces tarnish after storage of the boards prior to further processing (mounting of the electrical components), thus affecting solderability and bondability. In order to overcome this problem it is suggested to deposit, in a first method step, a first metal which is more noble than copper to the printed circuit board and to plate silver in a second method step with the proviso that the first metal be deposited at a rate that is at most half the rate of silver in the second method step when the first metal is silver.
Claims15
A method of plating silver on a substrate by a displacement plating reaction provided with a copper surface comprising:
- a) depositing silver on the substrate in a first method step, and
- b) plating silver on said substrate in a second method step,
- wherein silver is deposited in the first method step at a rate that is at most half the rate of plating of silver in the second method step, and
- wherein the rate of silver deposition from a silver deposition bath in the first method step is regulated by adjusting at least one deposition parameter and/or by adjusting the composition of the silver bath.
The method according to 9, wherein the at least one Cu(II) complexing agent is selected from the group consisting of ethylene diamine, alanin diacetic acid, amino trimethylene phosphonic acid, diethylene triamine pentamethylene phosphonic acid and 1-hydroxyethylene-1,1-diphosphonic acid.
Dependencies are inferred from the claim text.