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New Immersion (Nickel) Plating Formulation for Copper and Its Alloys

IP.com Disclosure Number: IPCOM000120283D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 33K

Publishing Venue

IBM

Related People

Mahmoud, IS: AUTHOR

Abstract

Copper and its alloys are widely used in first and second level packaging. Since copper corrodes readily, it is normally plated with nickel metallurgy. In the case of electroless nickel plating, it is difficult to initiate the reaction which results in poor yields.

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New Immersion (Nickel) Plating Formulation for Copper and Its Alloys

      Copper and its alloys are widely used in first and second level
packaging.  Since copper corrodes readily, it is normally plated with
nickel metallurgy.  In the case of electroless nickel plating,  it is
difficult to initiate the reaction which results in poor yields.

      Disclosed is a new immersion nickel plating bath, which is
based on a displacement reaction mechanism.  In this reaction,
displacement of copper atoms by nickel continues as long as exposed
copper is available. Once copper is depleted, the reaction terminates
wherein a pore-free layer of nickel is formed.  This layer serves as
an ideal surface for subsequent electroless plating.

      The new immersion bath has the following composition:
           Distilled Water              1000 ml (1 liter)
           Nickel Sulfate               200 - 225 g/liter
           Sulfuric Acid                 10 -  20 ml/liter
           Sodium Thiosulfate           140 - 160 g/liter
           Asorbic Acid                  10 - 15  g/liter

      The reagents are added in the manner they are listed in above.
A sufficient amount of ammonium hydroxide is added to adjust the pH
of the solution to 7.0.  The parts are plated at room temperature for
20 to 25 minutes.

      Disclosed anonymously.