US3634207A

US3634207A - Nickel etching and plating bath

Info

Publication number: US3634207A
Application number: US855420A
Authority: US
Inventors: Emil Toledo
Original assignee: US Department of Navy
Current assignee: US Department of Navy
Priority date: 1969-09-04
Filing date: 1969-09-04
Publication date: 1972-01-11
Anticipated expiration: 1989-01-11

Abstract

A process for plating nickel onto a nickel surface comprising first etching said nickel surface by anodic treatment in a bath, and then electroplating in the same bath. The bath is comprised of nickel chloride, nickel sulfate and boric acid to which are added small amounts of a brightener and a wetting agent.

Description

United States Patent Emil Toledo Natick, Mass.

Sept. 4, 1969 Jan. 11, 1972 The United States of America as represented by the Secretary of the Navy Inventor Appl. No. Filed Patented Assignee NICKEL ETCHING AND PLATING BATH 2 Claims, No Drawings US. Cl 204/32 R, 204/49 Int. Cl C23b 3/02 Field of Search 204/32 R, 33, 49,141, 325, 34, 20, 30

References Cited UNITED STATES PATENTS 6/1942 Wesley et al 204/34 4/1940 Lindetal 2,198,268 204/49 2,299,054 10/1942 Harshaw et al. 204/14] 2,702,785 2/1955 Eyerund 204/33 OTHER REFERENCES Smith, R. S. Nickel Plating Directly onto Aluminum, IBM Technical Disclosure Bulletin. Vol. 9, No. 8, January 1967.

Primary Examiner-John H. Mack Assistant Examiner-W. l. Solomon Att0rneys- Edgar J. Brower, H. H. Losche and Paul S.

Collignon ABSTRACT: A process for plating nickel onto a nickel surface comprising first etching said nickel surface by anodic treatment in a bath, and then electroplating in the same bath. The bath is comprised of nickel chloride, nickel sulfate and boric acid to which are added small amounts of a brightener and a wetting agent.

NICKEL ETCI-IING AND PLATING BATH BACKGROUND OF THE INVENTION The present invention relates to a process for electroplating nickel onto a nickel surface and has particular utility in applying a nickel coating onto a nickel coated printed circuit board.

One of the major problems that must be overcome to obtain good adhesion on a nickel coated printed circuit board is the removal of its passive nickel oxide coating in a manner which will not affect its thin nickel coating. Most mild-cleaning methods, such as a HCl dip, do not completely remove the oxide coating and more active cleaning methods, such as electroetching and electropolishing can damage the thin nickel coating on the printed circuit board.

Conventional baths and processes for electroplating nickel are described in Principles of Electroplating and Electroforming, by Blum and Hogaboom, pages 362-381, revised third addition, 1949, McGraw-Hill Book Co., Inc., New York; and in Modern Electroplating," edited by A. G. Gray, the Electrochemical Society, 1953, pages 299-355. Almost all baths for electroplating nickel contain nickel sulfate, a chloride, such as nickel chloride, a buffering agent, such as boric acid, and a wetting agent such as sodium lauryl sulfate, sodium lauryl ether sulfate or sodium 7-ethyl-2-methyl-4-undecanol sulfate. Such baths include the well-known Watts bath and other baths containing, as the source of the nickel, a combination of nickel fluoborate with nickel sulfate and nickel chloride, or a combination of nickel fluoborate with nickel chloride.

Various methods have been employed in the past to cleanse the nickel oxide film from a part which is to receive subsequent plating. In U.S. Pat. No. 2,299,054, which was issued Oct. 13, 1942, to William J. Harshaw and Kenneth E. Long, there is described an anodic-cathodic treatment for preparing a nickel plated article for chromium plating. The nickel plated article is placed in an aqueous solution of sodium cyanide and connected as an anode while passing an electric current therethrough as a voltage of from 2 to 10 volts for a period of about 1 second. The current is then reversed, by connecting the piece as a cathode for a few seconds.

Another anodic method for cleaning nickel is described in U.S. Pat. No. 3,362,894, which issued Jan. 9, 1968, to William A. Pennington and Stephen D. Cramer. In this patent, a cleaning method for nickel is described wherein a metal substrate is given an anodic treatment in a concentrated aqueous solution of a lithium halide. The metal substrate is then rinsed and plated in a conventional plating bath.

SUMMARY OF THE INVENTION The present invention provides an improved process for plating nickel onto a nickel surface by providing a bath which serves as both a cleaning bath and a plating bath. The article is first reverse plated, that is, the article is immersed as anode in the bath and, after about 1 minute of current application, the

current flow is reversed and the article is connected as cathode in the bath. Plating is accomplished in the normal manner. The bath is a nickel sulfate-nickel chloride bath to which a buffering agent, a brightener, and a wetting agent are added.

DESCRIPTION OF THE PREFERRED EMBODIMENT ticing the present invention.

EXAMPLE I A nickel coated printed circuit board having an area of 1.7 square inches was prepared for plating by first cleaning. The article was degreased in a methanol rinse and then dipped in an acid bath (50 percent I-ICI dip at about F The plating bath was comprised as follows:

Nickel chloride 10 ozJgal. Nickel sulfate 30 oz./gal. Boric acid 5 oz./gal. Saccharine 0.1 oz./gal. Sodium lauryl sulfate 0.0] oz./gal. Temperature I60 F.

A nickel coated printed circuit board was reverse plated for 1 minute at 500 ma. in the plating bath and then plated at 500 ma. for 1 hour without removing the circuit board from the plating bath after reverse plating.

Bend tests and metallurgical examinations revealed the plated product had excellent adhesion. Leads were welded to the plated product and pull tests were conducted by pulling on the leads both parallel and perpendicular to the surface. Metallographic examination revealed that adhesion between nickel layers was satisfactory.

I claim:

1. A process for electroplating nickel onto a thin nickelcoated surface on a printed circuit board comprising first removing oxide coating from said nickel-coated surface by reverse plating in a bath with said nickel-coated surface being connected as anode and then plating in the same bath with said nickel-coated surface being connected as cathode, said bath consisting of about 10 oz./gal. of nickel chloride, about 30 oz./gal. of nickel sulfate, about 5 oz./gal. of boric acid, about 0.1 oz./gal. of saccharine, about 0.0l oz./gal. of sodium lauryl sulfate and the balance of water.

2. The process as set forth in claim I wherein said reverse plating is carried on for about 1 minute and said plating is carried on for about 60 minutes.

Claims

2. The process as set forth in claim 1 wherein said reverse plating is carried on for about 1 minute and said plating is carried on for about 60 minutes.