BATH AND PROCESS FOR HIGH SPEED NICKEL ELECTROPLATING

BAIN ET METHODE DE NICKELAGE ELECTROLYTIQUE RAPIDE

English Abstract

ABSTRACT
An electroplating bath suitable for use with insolu-
ble anodes in the electrodeposition of nickel comprising a
nickel salt, and electrolyte selected from the group consis-
ting of boric acid and citric acid, ortho formyl benzene
sulfonic acid as a brightener, and a wetting agent comprising
a blend of potassium perfluoroalkyl sulfonates. The elec-
troplating bath of the invention can be operated at relatively
high speeds to produce nickel deposits which are semi-bright,
ductile and relatively stress-free.

Claims

The embodiments of the present invention in which an
exclusive property or privilege is claimed are defined as
follows:


1. An electroplating bath suitable for use with insolu-
ble anodes in the electrodeposition of semi-bright, ductile
and stress-free nickel deposits, said bath comprising a
nickel salt; an electrolyte selected from the group consisting
of boric acid and citric acid; ortho formyl benzene sulfonic
acid as a brightener, and a wetting agent comprising a blend
of potassium perfluoroalkyl sulfonates.


2. The electroplating bath of claim 1 wherein the nickel
salt is nickel sulfate.


3. The electroplating bath of claim 1 wherein the
electrolyte is boric acid.


4. The electroplating bath of claim 1 having a pH of
2.5 to 4.5.


5. A method for electrodepositing nickel on a substrate
which comprises passing an electric current between a cathode
and an insoluble anode through an electroplating bath as de-
fined in claims 1, 2 or 3, for a period of time sufficient
to deposit the desired thickness of nickel.

Description

677

BACKGROI~ND OF THE INVENTION
It is well known in the art pertaining to electro-
lytic nickel systems to utilize soluble anodes. The use of
soluble anodes was prescribed because experience has shown
that organic additives in the bath break down in the presence
of insoluble anodes. Furthermore, it is known that the stress
of the nickel deposit is increased by the insoluble anodes and
thus adversely affected. For various commercial reasons it
would be highly desirable to use insoluble anodes in a nickel
electroplating system without encountering additive break down
or stressed nickel deposits.
Typical United States patents relating to nickel
plating include U.S. Patents 2,228,991 (Freed), 2,409,119
(Freed), 2,409,120 (Freed et al), 2,485,149 (Freed et al); and
2,998,360 (Castellano). As far as can be determined, these
patents involve the use of a conventional or modified consuma-
ble anode. See, for example, page 2, column 2, lines 53 to 64,
of U.S. Patent 2,228,991.
SUMMARY OF THE INVE~TIO~
The present invention relates to a new and improved
electroplating bath for use with insoluble anodes and can be
operated at relatively high speeds to produce nickel deposits
which are also relatively stress-free. The insoluble anodes
which can be employed in the process of this invention are,
for example, platinized titanium, platinized tantalum,
platinized columbium (niobium) as well as a platinum metal
anode itself. Additionally, titanium anodes having mixed oxide
coatings, such as ruthenium dioxide - titanium dioxide coatings,
may also be used.

The electroplating bath of this invention contains
certain prescribed additives which do not break down during
operations carried out in the presence of insoluble anodes. In
addition to a conventional nickel source, e.g. nickel sulfate,
and a conducting agent such as boric acid, the electroplating
bath will contain ortho-formyl ~enzene sulfonic acid as the
brightener and a blend of potassium perfluoroalkyl sulfonates
sold under the tradename designation of FC 98 as the wetting
agent.
In accordance with the present invention, there is
thus provided an electroplating bath suitable for use with
insoluble anodes in the electrodeposition of semi-bright,
ductile and stress-free nickel deposits, which bath comprises
a nickel salt, an electrolyte selected from the group consis-
ting of boric acid and citric acid, ortho formyl benzene sul-
fonic acid as a brightener, and a wetting agent comprising a
blend of potassium perfluoroalkyl sulfonates.
DETAILED DESCRIPTION OF T~E INVE~TIO~
In general, the electroplating baths of the present
20 invention will be formulated as follows:
Component Concentration (q/l)
~ickel Salt 30 to 105 tas ~i)
Electrolyte 20 to 100
O-formyl benzene sulfonic acid 0.25 to 3.0
FC 98 0.02 to 0.2
The preferred sources of the nickel metal are nickel
sulfate, nickel citrate, nickel carbonate, and the like. These
salts are preferably employed in an amount of from about 135
to 470 g/l to provide the desired nickel metal concentration.
Electrolytes which are most useful for the prèsent
purpose are boric acid, citric acid, and the like. The prefer-
red amounts used in preparing the electroplating baths of this


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6~7

invention will range from about 22.5 to 45 g/l~ The use of
boric acid is especially preferred.
The organic components of the bath are usually the
brighteners and the wetting agents. In formulating the
special electroplating bath of this invention the specific
brightener employed is ortho-formyl benæene sulfonic acid. The
required wetting agent is FC 98, a tradenamed product marketed
by the Minnesota Mining & Manufacturing Company.
For most purposes the pH of the electroplating bath
is adjusted to a range of about 2 to 5, preferably 2.5 to 4.5.
The compounds used to effect the pH adjustment include nickel
carbonate, sulfuric acid, potassium citrate, or citric acid.
The baths of the present invention are operated at
temperatures of about 46 to 57C and at a relatively high cur-
rent density of up to about 1000 ASF, and preferably about 100
to 600 ASF. The ability to use such high current densities is
another important advantage of the electroplating baths of the
present invention.
Nickel deposited on various substrates when utilizing
the baths of this invention is characterized by being semi-
bright, ductile, and low-stressed. Heretofore the obtention
of such properties required consumable anodes in nic~el elec-
troplating systems.
The invention will be more fully understood by
reference to the following illustrative embodiment.




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i7~

` EY~ PLE
An electroplating bath was formulated from the following
ingredients:
Components Concentration ~/1
~ickel Sulfate 75 (as Ni)
Boric Acid 40
O-formyl benzene sulfonic acid 1.5
FC 98* 0.1
*Blend of potassium perfluoroalkyl sulfonates.Prior to use
sufficient nickel carbonate was added to the ba.h to adjust
'the pH to about 2.5. The bath was used in a conventional
electroplating bath with platinized titanium anodes to coat
;copper at 55C. and 500 ASF. The resulting nickel deposit
was semi-bright and ductile. Further analysis indicated low-stre~
,;In utilizing this bath subs.antially no break down of the organic
additives present in the bath was noted.
It will be understood that the illus~rative embodiment
set forth above is subject to variations and modifications
without departing from the broader aspects of the present
invention.