U.S. patent application number 10/772595 was filed with the patent office on 2005-08-11 for electroplated quaternary alloys.
Invention is credited to Bokisa, George, Eckles, William E., Frischauf, Robert E..
Application Number | 20050173255 10/772595 |
Document ID | / |
Family ID | 34826619 |
Filed Date | 2005-08-11 |
United States Patent
Application |
20050173255 |
Kind Code |
A1 |
Bokisa, George ; et
al. |
August 11, 2005 |
Electroplated quaternary alloys
Abstract
Disclosed are methods of electroplating a quaternary alloy
containing nickel, cobalt, and at least two metal alloys involving
providing an electroplating bath comprising ionic nickel, ionic
cobalt, at least two ionic alloy metals, and at least one
brightener; and applying a current to the electroplating bath
whereby a quaternary alloy forms.
Inventors: |
Bokisa, George; (North
Olmsted, OH) ; Eckles, William E.; (Cleveland Hts.,
OH) ; Frischauf, Robert E.; (Lakewood, OH) |
Correspondence
Address: |
AMIN & TUROCY, LLP
1900 EAST 9TH STREET, NATIONAL CITY CENTER
24TH FLOOR,
CLEVELAND
OH
44114
US
|
Family ID: |
34826619 |
Appl. No.: |
10/772595 |
Filed: |
February 5, 2004 |
Current U.S.
Class: |
205/255 |
Current CPC
Class: |
C25D 3/562 20130101 |
Class at
Publication: |
205/255 |
International
Class: |
C25D 003/56 |
Claims
What is claimed is:
1. A method of electroplating a quaternary alloy comprising nickel
and cobalt, comprising: providing an electroplating bath comprising
an anode, a cathode, water, ionic nickel, ionic cobalt, at least
two ionic alloy metals, and at least one brightener selected from
the group consisting of sulfur containing brighteners and organic
brighteners; and applying a current to the electroplating bath
whereby the quaternary alloy comprising nickel, cobalt, and at
least two alloy metals forms on the cathode.
2. The method of claim 1, wherein the at least two ionic alloy
metals comprise at least two selected from the group consisting of
aluminum, antimony, bismuth, boron, copper, gallium, germanium,
gold, indium, iridium, iron, lead, manganese, molybdenum, niobium,
osmium, rhodium, ruthenium, scandium, silver, palladium, platinum,
tantalum, thallium, tin, titanium, tungsten, vanadium, yttrium,
zirconium, and zinc in ionic form.
3. The method of claim 1, wherein the electroplating bath comprises
at least one organic brightener selected from the group consisting
of acetylenic alcohols, ethylenic alcohols, acetylenic amines,
acetylenic esters, acetylenic sulfonic acids and sulfonates,
alkoxylated acetylenic alcohols, acetylenic carboxylic acids,
coumarins, aldehydes, compounds containing a C.ident.N linkage, and
N-hetercyclics.
4. The method of claim 1, wherein the electroplating bath comprises
at least one sulfur containing brightener selected from the group
consisting of sulfinic acids, sulfonic acids, aromatic sulfonates,
aromatic sullfinates, sulfonamides, sulfonimides, sulfimides, and
sulfo-betaines.
5. The method of claim 1, wherein the electroplating bath has a pH
from about 2 to about 6 and a temperature from about 10.degree. C.
to about 90.degree. C., and a current density of about 1 ASF or
more and about 500 ASF or less is applied to the electroplating
bath.
6. The method of claim 1, wherein the electroplating bath comprises
about 10 g/l or more and about 150 g/l or less of ionic nickel,
about 0.5 g/l or more and about 70 g/l or less of ionic cobalt,
about 0.01 g/l or more and about 20 g/l or less of each of the
ionic alloy metals, and from about 0.001% to about 5% by weight of
at least one brightener.
7. The method of claim 1, wherein the anode comprises at least one
of nickel, cobalt, at least one alloy metal, iridium oxide,
platinum, titanium, graphite, carbon, and platinum-titanium.
8. The method of claim 1, wherein the quaternary alloy comprises
about 2% by weight or less of components other than nickel, cobalt,
and at least two alloy metals.
9. A method of forming an alloy comprising nickel, cobalt, and at
least two alloy metals, comprising: providing an electroplating
bath comprising an anode, a cathode, water, about 40 g/l or more
and about 100 g/l or less of ionic nickel, about 1 g/l or more and
about 30 g/l or less of ionic cobalt, and about 0.05 g/l or more
and about 10 g/l or less of each of at least two ionic alloy
metals, and from about 0.005% to about 2.5% by weight of at least
one brightener selected from the group consisting of sulfur
containing brighteners and organic brighteners; and applying a
current to the electroplating bath whereby the alloy comprising
nickel, cobalt, and at least two alloy metals forms on the
cathode.
10. The method of claim 9, wherein the electroplating bath has a pH
from about 3 to about 5 and a temperature from about 30.degree. C.
to about 80.degree. C., and a current density of about 10 ASF or
more and about 200 ASF or less is applied to the electroplating
bath.
11. The method of claim 9, wherein the electroplating bath
comprises at least one sulfur containing brightener selected from
the group consisting of sulfinic acids, sulfonic acids, aromatic
sulfonates, aromatic sullfinates, sulfonamides, sulfonimides,
sulfimides, and sulfo-betaines.
12. The method of claim 9, wherein the electroplating bath
comprises at least one organic brightener selected from the group
consisting of acetylenic alcohols, ethylenic alcohols, acetylenic
amines, acetylenic esters, acetylenic sulfonic acids and
sulfonates, alkoxylated acetylenic alcohols, acetylenic carboxylic
acids, coumarins, aldehydes, compounds containing a C.ident.N
linkage, and N-hetercyclics.
13. The method of claim 9, wherein the electroplating bath
comprises a sulfo-betaine brightener.
14. The method of claim 9, wherein the electroplating bath
comprises an acetylenic brightener.
15. The method of claim 9, wherein the electroplating bath
comprises an N-hetercyclic brightener.
16. The method of claim 9, wherein the at least two ionic alloy
metals comprise at least two selected from the group consisting of
aluminum, antimony, bismuth, boron, copper, gallium, germanium,
gold, indium, iridium, iron, lead, manganese, molybdenum, niobium,
osmium, rhodium, ruthenium, scandium, silver, palladium, platinum,
tantalum, thallium, tin, titanium, tungsten, vanadium, yttrium,
zirconium, and zinc in ionic form.
17. The method of claim 9, wherein the at least two ionic alloy
metals comprise iron and boron in ionic form.
18. A method of plating a substrate with an alloy comprising
nickel, cobalt, and at least two alloy metals, comprising:
providing an electroplating bath comprising an anode, a cathode
substrate, water, ionic nickel, ionic cobalt, at least two ionic
alloy metals, and at least two brighteners selected from the group
consisting of sulfur containing brighteners and organic
brighteners; and applying a current to the electroplating bath
whereby the alloy comprising nickel, cobalt, and at least two alloy
metals forms on the cathode substrate.
19. The method of claim 18, wherein the at least two ionic alloy
metals comprise at least two selected from the group consisting of
aluminum, antimony, bismuth, boron, copper, gallium, germanium,
gold, indium, iridium, iron, lead, manganese, molybdenum, niobium,
osmium, rhodium, ruthenium, scandium, silver, palladium, platinum,
tantalum, thallium, tin, titanium, tungsten, vanadium, yttrium,
zirconium, and zinc in ionic form.
20. The method of claim 18, wherein at least one of the two
brighteners is selected from the group consisting of acetylenic
alcohols, ethylenic alcohols, acetylenic amines, acetylenic esters,
acetylenic sulfonic acids and sulfonates, alkoxylated acetylenic
alcohols, acetylenic carboxylic acids, coumarins, aldehydes,
compounds containing a C.ident.N linkage, and N-hetercyclics.
21. The method of claim 18, wherein at least one of the two
brighteners is selected from the group consisting of sulfinic
acids, sulfonic acids, aromatic sulfonates, aromatic sullfinates,
sulfonamides, sulfonimides, sulfimides, and sulfo-betaines.
22. The method of claim 18, wherein the electroplating bath further
comprises at least one conductivity salt.
23. The method of claim 22, wherein the conductivity salt is
selected from the group consisting of boric acid, sodium sulfate,
sodium chloride, potassium sulfate, and potassium chloride.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to quaternary alloys
containing at least nickel and cobalt that may be employed in place
of chrome and chrome alloys and methods of making the quaternary
alloys.
BACKGROUND OF THE INVENTION
[0002] Chromium is steel-gray, lustrous, hard, metallic, and takes
a high polish. Chromium is a naturally occurring element present in
the environment in several different forms. The most common forms
are chromium (0), chromium (III), and chromium (VI). The metal
chromium, which is the chromium (0) form, is used for making steel.
Chromium (VI) and chromium (III) are often used for chrome plating.
Chromium (VI) is used as an anti-corrosion treatment and as an
electrical shielding material for certain sheet metals. There are
many desirable characteristics associated with chromium
plating.
[0003] However, the use of chromium (VI) and its compounds are
restricted in certain applications in some areas, primarily in the
European Union. Broad legislative restrictions such as the
Restriction of Hazardous Substances in the United States are
expected to eliminate the use of chromium (VI) compounds in
electronic products by 2006. Substitutes for chromium, especially
in the plating industry, are therefore desired.
SUMMARY OF THE INVENTION
[0004] The following presents a simplified summary of the invention
in order to provide a basic understanding of some aspects of the
invention. This summary is not an extensive overview of the
invention. It is intended to neither identify key or critical
elements of the invention nor delineate the scope of the invention.
Rather, the sole purpose of this summary is to present some
concepts of the invention in a simplified form as a prelude to the
more detailed description that is presented hereinafter.
[0005] The present invention provides quaternary alloys containing
at least nickel and cobalt that have a mirror bright deposit and a
hardness on par with chrome. At least two of many other alloy
metals, such as iron and boron, are also contained in the
quaternary alloys. In this context, the quaternary alloys contain
at least four metal components. The desirable characteristics of
the quaternary alloys made in accordance with the present invention
are, at least in part, attributable to the use of certain
brighteners in the electroplating bath. The brighteners facilitate
deposition of metal ions on the cathode in such a manner as to
result in electroplated nickel cobalt quaternary alloys having
numerous desirable properties. For example, the brighteners
facilitate deposition of metal ions at relatively low current
densities, thereby increasing the bright plating range.
Consequently, the nickel cobalt quaternary alloys may take the
place of electroplated chrome and chromium alloys, thereby
providing potential environmental benefits.
[0006] One aspect of the invention relates to methods of
electroplating a quaternary alloy containing nickel cobalt
involving providing an electroplating bath containing an anode, a
cathode, water, ionic nickel, ionic cobalt, at least two ionic
alloy metals, and at least one brightener selected from the group
consisting of sulfur containing brighteners and organic
brighteners; and applying a current so that the quaternary alloy
forms on/at the cathode.
[0007] To the accomplishment of the foregoing and related ends, the
invention comprises the features hereinafter fully described and
particularly pointed out in the claims. The following description
and the annexed drawings set forth in detail certain illustrative
aspects and implementations of the invention. These are indicative,
however, of but a few of the various ways in which the principles
of the invention may be employed. Other objects, advantages and
novel features of the invention will become apparent from the
following detailed description of the invention when considered in
conjunction with the drawings.
BRIEF SUMMARY OF THE DRAWINGS
[0008] FIG. 1 illustrates a schematic diagram of a nickel cobalt
boron alloy electroplating system in accordance with one aspect of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The present invention provides quaternary alloys made by
electroplating that exhibit two or more of high brightness, high
luster, level/smoothness, uniform thickness, high hardness, high
reflectivity, ductile, high density, resistant to corrosion,
resistant to heat, and resistant to wear. Typically, the quaternary
alloys made in accordance with the present invention have a mirror
bright deposit and a hardness on par with chrome. Electroplating
involves metal in ionic form migrating in solution from a positive
electrode (anode) to a negative electrode (cathode). The anode and
cathode are connected to a power source and an electrical current
is passed through the electroplating bath or solution causing
substrates at the cathode to be coated by the metal (nickel,
cobalt, and at least two alloy metals) in solution. In most
embodiments, the substrate to be plated is the cathode.
[0010] The cathodes are any electrically conductive material that
can accommodate a nickel cobalt quaternary alloy plating while
resisting degradation by the acidic nature of the catholyte. The
cathode substrates include metal structures and non-metal
structures. Metal structures, or structures with a metal surface
contain surfaces of one or more of aluminum, bismuth, cadmium,
chromium, copper, brass, gallium, germanium, gold, indium, iridium,
iron, lead, magnesium, nickel, palladium, platinum, silver, steel,
stainless steel, tin, titanium, tungsten, zinc, alloys thereof, and
the like. Non-metal structures include plastics, circuit board
prepregs (including materials such as glass, epoxy resins,
polyimide resins, Kevlar.RTM., Nylon.RTM., Teflon.RTM., etc.),
ceramics, metal oxides, and the like.
[0011] The electroplating bath is typically an aqueous solution. In
addition to water, the electroplating bath (or the catholtye and
anolyte if a separator is employed) may optionally contain one or
more co-solvents. Such co-solvents include water-miscible solvents
such as alcohols, glycols, alkoxy alkanols, ketones, and various
other aprotic solvents. Specific examples of co-solvents include
methanol, ethanol, propanol, ethylene glycol, 2-ethoxy ethanol,
acetone, dimethyl formamide, dimethyl sulfoxide, acetonitrile, and
the like.
[0012] Prior to placing the substrate/cathode in the electroplating
bath, it may be optionally pretreated, washed and/or activated.
Pretreatment may include cleaning with alcohol and/or with an
anionic solution. Washing may include an anodically cleaning in an
alkaline solution in the presence of a negative current, rinsing in
hot or cold distilled or deionized water, and/or immersing in an
acid bath. Activation includes one or both of anodically activating
by passing a negative current through an acidic activator bath and
cathodically activating by passing a positive current through an
acidic activator bath. An advantage of the cleaning process is that
the substrate is free of contaminant, such as oxides when placed in
the plating bath eliminating the possible need for sequestering
agents to prevent precipitation or the formation of sludge in the
electroplating bath.
[0013] In the electroplating bath, platable nickel, cobalt, and at
least two alloy metals are present in ionic form, and in
embodiments where one of the two alloy metals is boron, platable
boron is present in ionic form or in an ionic complex. Although
platable boron may be present in ionic form or in an ionic complex,
it is henceforth referred to as ionic boron for brevity. Sources of
ionic nickel, cobalt, and alloy metals are typically the
corresponding nickel, cobalt, and alloy metal salts and optionally
an anode that contains one or more of nickel, cobalt, and/or one or
more of the alloy metals.
[0014] Examples of nickel and cobalt salts include nickel acetate,
nickel acetylacetonate, nickel ethylhexanoate, nickel carbonate,
nickel formate, nickel nitrate, nickel oxalate, nickel sulfate,
nickel sulfamate, nickel sulfide, nickel chloride, nickel fluoride,
nickel iodide, nickel bromide, nickel oxide, nickel
tetrafluoroborate, nickel phosphide, cobalt acetate, cobalt
acetylacetonate, cobalt ethylhexanoate, cobalt carbonate, cobalt
nitrate, cobalt oxalate, cobalt sulfate, cobalt chloride, cobalt
fluoride, cobalt hydroxide, cobalt iodide, cobalt bromide, cobalt
oxide, cobalt boride, cobalt tetrafluoroborate, and hydrates
thereof.
[0015] The two or more alloy metals are any metals that can be
electroplated in a compatible manner with nickel and cobalt
generally include transition metals. Examples of transition metals
include aluminum, antimony, bismuth, boron, copper, gallium,
germanium, gold, indium, iridium, iron, lead, manganese,
molybdenum, niobium, osmium, rhodium, ruthenium, scandium, silver,
palladium, platinum, tantalum, thallium, tin, titanium, tungsten,
vanadium, yttrium, zirconium, zinc, and the like.
[0016] Examples of alloy metal salts include aluminum salts such as
aluminum acetate, aluminum bromide, aluminum chloride, aluminum
fluoride, aluminum iodide, aluminum nitrate, aluminum oxide,
aluminum phosphate, and aluminum sulfate; antimony salts such as
antimony acetate, antimony bromide, antimony chloride, antimony
fluoride, antimony iodide, antimony oxide, and antimony sulfide;
bismuth salts such as bismuth chloride, bismuth fluoride, bismuth
nitrate, bismuth acetate, bismuth methanesulfonate, bismuth
oxychloride, and bismuth citrate; copper salts such as copper
sulfate, copper polyphosphate, copper sulfamate, copper chloride,
copper formate, copper fluoride, copper nitrate, copper oxide,
copper tetrafluoroborate, copper trifluoromethanesulfonate, and
copper trifluoroacetate; gold salts such as gold bromide, gold
chloride, gold iodide, gold oxide, and gold sulfide; indium salts
such as indium acetate, indium sulfate, indium phosphide, indium
chloride, indium fluoride, indium bromide, indium nitrate, indium
oxide, indium methanesulfonate, and indium
trifluoromethanesulfonate; iridium salts such as iridium bromide,
iridium chloride, and iridium oxide; iron salts such as iron
acetate, iron citrate, iron sulfate, iron chloride, iron fluoride,
iron bromide, iron nitrate, iron oxide, iron tetrafluoroborate,
iron phosphate, iron oxalate, and iron iodide; molybdenum salts
such as molybdenum acetate, molybdenum bromide, molybdenum
chloride, molybdenum fluoride, molybdenum oxide, and molybdenum
sulfide; niobium salts such as niobium bromide, niobium chloride,
niobium fluoride, niobium nitride, and niobium oxide; palladium
salts such as palladium acetate, palladium bromide, palladium
chloride, palladium iodide, palladium nitrate, palladium oxide, and
palladium sulfate; platinum salts such as platinum bromide,
platinum chloride, platinum iodide, platinum oxide, and platinum
sulfide; silver salts such as tin salts such as silver acetate,
silver carbonate, silver sulfate, silver phosphate, silver
chloride, silver bromide, silver fluoride, silver citrate, silver
nitrate, silver methanesulfonate, silver tetrafluoroborate, and
silver trifluoroacetate; tantalum salts such as tantalum chloride,
citrate, tantalum fluoride, tantalum nitride, and tantalum oxide;
tin salts such as tin acetate, tin ethylhexanoate, tin sulfate, tin
chloride, tin fluoride, tin iodide, tin bromide, tin
methanesulfonate, tin oxide, tin tetrafluoroborate, tin
trifluoromethanesulfonate, tin pyrophosphate, titanium salts such
as titanium bromide, titanium chloride, titanium fluoride, titanium
iodide, titanium nitride, titanium oxide, and titanium sulfide;
tungsten salts such as tungsten bromide, tungsten chloride,
tungsten fluoride, tungsten oxide, and tungsten sulfide; and tin
sulfide; zinc salts such as zinc acetate, zinc citrate, zinc
sulfate, zinc chloride, zinc fluoride, zinc bromide, zinc nitrate,
zinc oxide, zinc tetrafluoroborate, zinc methanesulfonate, zinc
trifluoromethanesulfonate, and zinc trifluoroacetate; and hydrates
thereof.
[0017] Specific examples of boron salts and boron containing
compounds include boron nitride, boron trichloride, boron
trifluoride, boron triiodide, boron tribromide, boron oxide, boron
phosphate, dimethylamine borane, morpholine borane, dimethylamino
borane, dimethylsufide borane, t-butylamine borane, ammonia borane,
N,N-diethylaniline borane, diphenylphosphine borane,
dimethylaminopyridine borane, ethylmorpholine borane,
methylmorpholine borane, 2,6-lutidine borane, morpholine borane,
oxathiane borane, phenylmorpholine borane, pyridine borane,
tetrahydrofuran borane, tributylphosphine borane, triethylamin
borane, trimethylamine borane, borax, and hydrates thereof. Boron
may alternatively be introduced into the electroplating bath by a
boron containing acid, an amino-borane compound, and/or an
amine-borane compound (collectively referred to as boron containing
compounds). The boron containing acid does not include boric acid,
as boric acid improves conductivity and/or is used as a pH
adjuster. It is noted that the boric acid does not provide a
significant portion of platable boron, although in some instances
it may provide minor amounts of platable boron.
[0018] The anodes are electrically conductive materials, and
optionally contain materials that can deliver one or more of
nickel, cobalt, and/or one or more of the alloy metal ions into the
electroplating solution. Accordingly, in one embodiment, the anode
contains at least one or more of nickel, cobalt, any of the alloy
metals, and optionally other materials. In this embodiment, the
anode is a working anode. There is an economic advantage associated
with generation of the quaternary metal alloy ions from the working
anodes. In particular, compared to providing metal ions from a
liquid concentrate (such as a nickel salt), the cost of one or more
of nickel, cobalt, and the alloy metals via an anode is a fraction
of that from the liquid concentrate (such as about one-quarter of
the cost or less including about one-eight of the cost). Solid
working anodes are also advantageous in that they are markedly
easier to handle, store, and transport, compared with liquid
concentrates of one or more of nickel, cobalt, and alloy metal
salts. In another embodiment, the anode is an inert anode
containing materials such as iridium oxide, platinum, titanium,
platinum-titanium, graphite, carbon, and the like.
[0019] The electroplating bath contains an amount of ionic nickel,
cobalt, and at least two alloy metals to facilitate electroplating
the quaternary alloy, typically, on the cathode. In one embodiment,
the electroplating bath contains about 10 g/l or more and about 150
g/l or less of ionic nickel, about 0.5 g/l or more and about 70 g/l
or less of ionic cobalt, and about 0.01 g/l or more and about 20
g/l or less of each of at least two ionic alloy metals. In another
embodiment, the electroplating bath contains about 40 g/l or more
and about 100 g/l or less of ionic nickel, about 1 g/l or more and
about 30 g/l or less of ionic cobalt, and about 0.05 g/l or more
and about 10 g/l or less of each of at least two ionic alloy
metals. In yet another embodiment, the electroplating bath contains
about 50 g/l or more and about 70 g/l or less of ionic nickel,
about 3 g/l or more and about 6 g/l or less of ionic cobalt, and
about 0.1 g/l or more and about 6 g/l or less of each of at least
two ionic alloy metals.
[0020] In some instances, the ratio of one of the alloy metals to
cobalt and/or the ratio of cobalt to nickel in solution is set to
facilitate an orderly and high quality deposition of the quaternary
alloy on the substrate. For instance, in one embodiment, the ratio
of one of the alloy metals to cobalt is from about 1:4 to about 3:1
while the ratio of cobalt to nickel is from about 1:20 to about
1:5. In another embodiment, the ratio of one of the alloy metals to
cobalt is from about 1:3 to about 2:1 while the ratio of cobalt to
nickel is from about 1:15 to about 1:10.
[0021] In order to obtain a nickel cobalt quaternary alloy with
desirable properties, it is necessary to employ at least one
brightener. Two or more brighteners can be used. Although not
wishing to be bound by any theory, it is believed that the active
deposition of nickel, cobalt, and alloy metal species
simultaneously is complex, due to differences in characteristics
between these metals, and that the presence of at least one
brightener as described herein facilitates the orderly plating of
the metals on a substrate such that beneficial properties are
realized.
[0022] The brighteners that may be employed in the nickel cobalt
quaternary alloy electroplating bath include sulfur containing
brighteners and organic brighteners. In one embodiment, the
electroplating baths contain from about 0.001% to about 5% by
weight of at least one brightener. In another embodiment, the
electroplating baths contain from about 0.005% to about 2.5% by
weight of at least one brightener. In yet another embodiment, the
electroplating baths contain from about 0.01% to about 1% by weight
of at least one brightener.
[0023] In one embodiment, the quaternary alloy electroplating baths
contain an effective amount of at least one sulfur containing
brightener to improve the quality of the alloy deposit.
Improvements in the alloy deposit include improving such
characteristics such as one or more of the brightness of the
deposited alloy, the luster of the deposited alloy, the levelness
of the deposited alloy, the hardness of the deposited alloy, the
reflectivity of the deposited alloy, and the similarity in
appearance to a high quality chromium deposit. General examples of
sulfur containing brighteners include sulfinic acids, sulfonic
acids, aromatic sulfonates, aromatic sullfinates, sulfonamides,
sulfonimides, sulfimides, sulfo-betaines, and the water-soluble
salts of these materials. Examples sulfur containing brighteners
include the alkyl naphthalene and benzene sulfonic acids, the
benzene and naphthalene di- and trisulfonic acids, benzene and
naphthalene sulfonamides, and sulfonimides such as saccharin, vinyl
and allyl sulfonamides and sulfonic acids.
[0024] Specific examples of sulfur containing brighteners include
sodium saccharinate; trisodium 1,3,6-naphthalene trisulfonic acid;
trisodium 1,3,7-naphthalene trisulfonic acid; benzene sulfinic
acid; sodium styrene sulfonate; p-toluene sulfinic acid; p-toluene
sulfonic acid; propyl sulfonic acid; beta-hydroxy propyl sulfonic
acid; ditolylsulfimide; sodium salt of di-o-tolyl disulfimide;
sodium salt of dibenzene disulfimide; pyridine-3-sulfonic acid;
p-vinylbenzene sulfonic acid; sodium allyl sulfonate; sodium vinyl
sulfonate; sodium propargyl sulfonate; sodium o-sulfobenzimide;
disodium 1,5-naphthalene disulfonate; sodium benzene monosulfonate;
dibenzene sulfonimide; sodium benzene monosulfinate; sodium allyl
sulfonate; sodium 3-chloro-2-butene-1-sulfona- te; monoallyl
sulfamide; diallyl sulfamide; 1(gamma-sulfopropoxy)-2-butyn-- 4-ol;
1,4-di(beta-hydroxy-gamma-sulfonic propoxy)-2-butyne; allyl
sulfonamide; quinaldyl-N-propanesulfonic acid betaine; quinaldine
dimethyl sulfate; isoquinaldyl-N-propanesulfonic acid betaine;
isoquinaldine dimethyl sulfate; disulfonated
1,4-di(beta-hydroxyethoxy)-2- -butyne; and sulfonated
1-(beta-hydroxyethoxy)-2-propyne. Many sulfur containing
brighteners are described in U.S. Pat. Nos. 3,922,209; 4,036,709;
4,053,373; and 4,421,611 which are hereby incorporated by
reference.
[0025] Sulfo-betaines are heterocyclic compounds having Formula
I:
RN.sup.+R'SO.sub.3.sup.- I
[0026] wherein RN is an aromatic heterocyclic nitrogen-containing
group, and R' is an alkylene or hydroxy alkylene group. Generally,
the RN group is an aromatic nitrogen-containing group such as
pyridine, substituted pyridines, quinoline, substituted quinolines,
isoquinoline, substituted isoquinolines, benzimidazoles, and
acridines. Various substituents can be incorporated into the
aromatic nitrogen-containing groups specified above, and the
substituent may be attached to the various positions of the
aromatic group. Examples of substituents include hydroxy, alkoxy,
halide, lower alkyl, lower alkenyl, amino alkyl, mercapto, cyano,
hydroxyalkyl, acetyl, benzoyl, etc.
[0027] The sulfo-betaine compounds can also be characterized by
Formulae II, III, and IV: 1
[0028] wherein R.sup.1 is hydrogen, benzo(b), or one or more lower
alkyl, halide, hydroxy, lower alkenyl or lower alkoxy groups;
R.sup.2 is an alkylene or hydroxy alkylene group containing three
or four carbon atoms in a straight chain; R.sup.3 is an alkylene or
hydroxy alkylene group containing two or three carbon atoms in a
straight chain; and R.sup.4 is a hydrogen or a hydroxyl group.
[0029] As indicated in Formulae II, III, and IV, the sulfobetaines
contain a pyridinium portion which may be an unsubstituted pyridine
ring or a substituted pyridine ring. Thus, R.sup.1 may be one or
more lower alkyl groups, halogen groups, lower alkoxy groups,
hydroxy groups or lower alkenyl groups.
[0030] Examples of the pyridine groups which may be included in the
above Formulae II-IV include pyridine, 4-methylpyridine (picoline),
4-ethyl pyridine, 4-t-butyl pyridine, 4-vinyl pyridine, 3-chloro
pyridine, 4-chloro pyridine, 2, 3 or 2,4 or 2, 6 or
3,5-di-methylpyridine, 2-methyl-5-ethyl pyridine, 3-methylpyridine,
3-hydroxy pyridime, 2-methoxy pyridine, and 2-vinyl pyridine.
[0031] In Formula II, R.sup.2 can be an alkylene or hydroxy
alkylene group containing three or four carbon atoms in a straight
chain which may contain alkyl substituents which may be represented
by Formula V 2
[0032] wherein R.sup.5 is hydrogen or a lower alkyl group, one X is
hydrogen, hydroxy or a hydroxy methyl group, the remaining X is
hydrogen and a is 3 or 4.
[0033] The preparation of the sulfo-betaines of Formula II wherein
R.sup.2 is an alkylene radical is described in, for example, U.S.
Pat. No. 2,876,177, which is hereby incorporated by reference.
Briefly, the compounds are formed by reaction of pyridine or a
substituted pyridine with lower 1,3- or 1,4-alkyl sultones.
Examples of such sultones include propane sultone and 1,3- or
1,4-butane sultone. The reaction products formed thereby are
internal salts of quaternary ammonium-N-propane-omega-- sulfonic
acids or the corresponding butane derivative, depending on the
alkyl sultone used.
[0034] Examples of sulfo-betaines of Formula II wherein R.sup.2 is
an alkylene group may be represented by Formula VI: 3
[0035] wherein R.sup.5 is hydrogen, one or more lower alkyl groups
or a benzo(b) group, and x is 3 or 4.
[0036] The preparation of the sulfo-betaine of Formula II wherein
R.sup.2 is a hydroxy alkylene group is described in, for example,
U.S. Pat. No. 3,280,130, which is hereby incorporated by reference.
The method involves a first reaction step wherein pyridine is
reacted with epichlorohydrin in the presence of hydrochloric acid,
and, thereafter, in a second reaction step, the quaternary salt
formed thereby is reacted with sodium sulfite.
[0037] Examples of the sulfo-betaines wherein R.sup.2 is a hydroxy
alkylene group including pyridine compounds of the Formula VII:
4
[0038] wherein R.sup.5 is hydrogen, one or more lower alkyl groups
or a benzo(b) group, a is 3 or 4, one X substituent is a hydroxyl
group and the other are hydrogen. In an alternative embodiment, two
of the X groups could be hydrogen and the third X group can be a
hydroxy alkyl group, such as a hydroxy methyl group.
[0039] The sulfo-betaines include the type represented by Formula
III above wherein R.sup.1 is defined as in Formula I, and R.sup.3
is an alkylene or hydroxy alkylene group containing two or three
carbon atoms in a straight chain and optionally pendant hydroxyl
groups, hydroxyl alkyl groups or alkyl groups containing one or two
carbon atoms. Examples of the betaines represented by Formula III
are those wherein R.sup.1 includes pyridine compounds of Formula
VIII: 5
[0040] wherein R.sup.1 is hydrogen, a lower alkyl group or a
benzo(b) group, and both X groups are hydrogen or one X is hydrogen
and the other is a hydroxyl group.
[0041] The preparation of the sulfo-betaines of the type
represented by Formulae III and VIII which are known as
pyridinium-alkane sulfate betaines is known in the art. For
example, the sulfate betaines can be prepared by reacting a
pyridine compound with an alkanol compound containing a halogen
atom to form an intermediate hydroxylalkyl pyridinium-halide which
is thereafter reacted with the corresponding halosulfonic acid to
form the desired betaine. Specifically, pyridinium-(ethyl
sulfate-2) betaine can be prepared by reacting ethylene
chlorohydrin with pyridine followed by reaction with chlorosulfonic
acid. The details of the procedure are described in U.S. Pat. No.
3,314,868 which is hereby incorporated by reference. Other alkanol
compounds containing a halogen which can be reacted with pyridine
to form the desired betaines include 1-chloro-2-propanol,
3-chloro-1-propanol, etc.
[0042] Betaines also include those represented by Formula IV given
above which may be obtained by reacting, for example, o-chloro
benzyl chloride (prepared from o-chloro benzaldehyde) with pyridine
or a substituted pyridine followed by replacement of the o-chloro
group with a sulfonic acid group. Although a similar reaction can
be conducted with the corresponding meta and para chloro compounds,
the ortho derivative tend to perform better in the electroplating
baths of the present invention.
[0043] In another embodiment, the quaternary alloy electroplating
baths contain an effective amount of at least one organic
brightener to improve the quality of the alloy deposit. General
examples of organic brighteners include acetylenic alcohols,
ethylenic alcohols, acetylenic amines, acetylenic esters,
acetylenic sulfonic acids and sulfonates, alkoxylated acetylenic
alcohols such as ethoxylated and propoxylated acetylenic alcohols,
acetylenic carboxylic acids such as 3-(2-propynoxy)-2-propenoic
acid, coumarins, aldehydes, compounds containing the C--N linkage,
and N-hetercyclics.
[0044] Specific examples of organic brighteners include ethoxylated
butynediol; 2-butyne-1,4-diol; propargyl alcohol;
thiodipropionitrile; ethoxylated propargyl alcohol; hydroxyethyl
propynyl ether; beta-hydroxypropyl, propynyl ether;
gamma-propynoxy, gamma-propynoxy, bis-beta-hydroxyethyl ether
2-butyn-1,4-diol; bis-beta-hydroxypropyl ether 2-butyn-1,4-diol;
1,4-di-(beta-hydroxyethoxy)-2-butyne;
1,4-di-(beta-hydroxy-gamma-chloropropoxy)-2-butyne;
1,4-di-(beta-gamma-epoxypropoxy)-2-butyne;
1,4-di-(beta-hydroxy-gamma-but- enoxy)-2-butyne;
1,4-di-(2'-hydroxy-4'-oxa-6'-heptenoxy)-2-butyne;
N-(2,3-dichloro-2-propenyl)-pyridinium chloride; 2,4,6-trimethyl
N-propargyl pyridinium bromide; N-allylquinaldinium bromide;
2-methyl-3-butyn-2-ol; N-allypyridinium bromide;
N-allylisoquinaldine bromide; 1-(beta-hydroxyethoxy)-2-propyne;
1-(beta-hydroxypropoxy)-2-prop- yne; phenosafranin; and fuchsin.
Many acetylenic derivatives that may be employed as organic
brighteners in the quaternary alloy electroplating baths include
those described in the U.S. Pat. Nos. 3,133,006; 3,140,988;
3,152,975; 3,160,574; 3,170,853; 3,305,462; 3,366,557; 3,699,016;
3,378,470; 3,502,550; 3,515,652; 3,711,384; 3,719,568; 3,723,260;
3,759,803; 3,795,592; 3,860,638; 3,862,019; 3,844,773; 3,898,138;
3,907,876; 3,969,198; 4,036,709; 4,054,495; 4,062,738; and
4,421,611, which are hereby incorporated by reference.
[0045] The electroplating baths may optionally contain one or more
of a number of additives. Such additives include complexing agents,
chelating agents, surfactants, wetting agents, hardening agents, pH
adjusters, leveling agents, reducing agents, antipitting agents,
promoters, antioxidants, stress relief agents, conductivity salts,
and the like. In one embodiment, the electroplating baths contain
from about 0.001% to about 5% by weight of each of the
additives.
[0046] In embodiments where the quaternary alloy contains iron, the
electroplating bath optionally contains one or more bath-soluble
complexing agents for iron. Such complexing agents may be
amine-containing complexing agents or aliphatic carboxylic acids
containing from about 1 to about 3 carboxyl groups and from about 1
to about 6 hydroxyl groups. The carboxyl group may be present as
--COOH, as the anion --COO.sup.- in solution, or in the form of an
internal lactone such as present in the sugars. Examples of
complexing agents in the hydroxy substituted lower aliphatic
carboxylic acids having from about two to about eight carbon atoms
include ascorbic acid, isoascorbic acid, citric acid, malic acid,
glutaric acid, gluconic acid, muconic acid, glutamic acid,
glycollic acid, aspartic acid, dextrose, sucrose, and the like.
Examples of amine-containing complexing agents include
nitrilotriacetic acid and ethylene diamine tetra-acetic acid.
Alternative complexing agents include water soluble salts of
ammonium, alkali metal, and iron salts.
[0047] The complexing agents facilitate keeping the metal ions,
particularly the ferrous and ferric ions, in solution thereby
preventing precipitation of iron as ferric hydroxide. In one
embodiment, the electroplating bath contains from about 5 to about
100 grams/liter of the complexing agent to provide a mole ratio of
complexing agent to iron ions in the bath of from about 1:1 to
about 50:1.
[0048] The optional incorporation of wetting or surface active
agents (surfactants) and particularly anionic wetting agents into
the electroplating baths of the invention sometimes results in a
ternary alloy plating with improved leveling and brightness, and/or
the electroplating baths exhibit improved stability compared to an
electroplating bath without wetting or surface active agents. The
incorporation of surfactants may in some instances mitigate gas
streaking and pitting.
[0049] Wetting agents promote leveling and brightening, as well as
promoting bath stability. Examples of wetting agent include
polyoxyalkylated naphthols; ethylene oxide/polyglycol compounds;
sulfonated wetting agents; carbowax type wetting agents; and the
like.
[0050] Surfactants contribute to the overall stability of the bath
and improve various properties in the resultant tin alloy layer.
General examples of surfactants include one or more of a nonionic
surfactant, cationic surfactant, anionic surfactant, and amphoteric
surfactant. Specific examples of surfactants include nonionic
polyoxyethylene surfactants; alkoxylated amine surfactants;
ethylene oxide-fatty acid condensation products; polyalkoxylated
glycols and phenols; betaines and sulfobetaines; amine ethoxylate
surfactants; quaternary ammonium salts; pyridinium salts;
imidazolinium salts; sulfated alkyl alcohols; sulfated lower
ethoxylated alkyl alcohols; sodium lauryl sulfonate; sodium sulfate
derivative of 2-ethyl-1-hexanol and sodium dialkyl sulfosuccinates
such as the dihexyl ester of sodium sulfosuccinic acid; and the
like.
[0051] The optional incorporation of leveling agents in some
instances promotes the formation of a smooth surface of the
electroplated tin alloy layer, even if the cathode surface on which
the tin alloy layer is formed is not smooth. Examples of leveling
agents include the condensation products of thiourea and aliphatic
aldehydes; thiazolidinethiones; imidazolidinethiones; quaternized
polyamines; and the like. Specific examples of leveling agents
include 1-(sulfopropyl)pyridinium hydroxide and
(1-sulfo-2-hydroxypropyl)pyridinium hydroxide.
[0052] Suitable hardening agents include 2-butyne-1,4-diol,
phenylpropiolic acid, 2-butyne-1,4-disulfonic acid,
3-dimethylamino-1-propyne and
bis(trimethylamine)-1,2-diphenyl-1,2-bis(di- chloroboryl)ethylene.
The hardener effectively makes grain size more fine and slows down
the rate at which the nickel, cobalt, and at least two alloy metal
ions reach the substrate. This thereby provides a more uniform
deposition of the coating on the substrate.
[0053] The optional incorporation of one or more conductivity salts
in some instances enhances the conductivity of the electroplating
solution, such as by varying the chloride content or by the
addition of conductivity salts. In one embodiment, such
conductivity salts are added during make up of the electroplating
bath. Examples of conductivity salts include boric acid, sodium
sulfate, sodium chloride, potassium sulfate, potassium chloride,
and the like. Higher conductivity generally means that lower
operating electrical costs are realized. It also may allow the
application of more current from rectifiers with lower voltage
maximums. Finally, higher conductivity may allow for improved
current carrying capacity into confined plating spaces. In one
embodiment, the electroplating bath contains from about 5 g/L to
about 200 g/L of a conductivity salt. In another embodiment, the
electroplating bath contains from about 10 g/L to about 150 g/L of
a conductivity salt.
[0054] In one embodiment, a catalyst is not included in the
electroplating bath. In another embodiment, a chromium compound is
not included in the electroplating bath. In yet another embodiment,
a cyanide compound is not included in the electroplating bath. In
still yet another embodiment, a lead compound is not included in
the electroplating bath. In these embodiments, the electroplating
bath is environmentally friendly.
[0055] The pH of the electroplating bath is maintained to promote
the efficient plating of the quaternary alloy on the
substrate/cathode. In one embodiment, the pH of the electroplating
bath is about 2 or more and about 6 or less. In another embodiment,
the pH of the electroplating bath is about 3 or more and about 5 or
less. In yet another embodiment, the pH of the electroplating bath
is about 3.5 or more and about 4.5 or less. The pH of the
electroplating bath may be adjusted using additions of the acid or
a base compound. The acids are relatively strong acids that are not
oxidizing acids. Examples of acids include sulfuric acid,
trifluoroacetic acid, phosphoric acid, polyphosphoric acid,
fluoboric acid, hydrochloric acid, acetic acid, alkane sulfonic
acids, and alkanol sulfonic acids. Bases include hydroxide
compounds, such as ammonium hydroxide, tetraalkylammonium
hydroxide, sodium hydroxide, potassium hydroxide, sodium carbonate,
potassium carbonate, sodium bicarbonate, potassium bicarbonate,
lithium carbonate, nickel carbonate, cobalt carbonate, lithium
bicarbonate, nickel bicarbonate, cobalt bicarbonate, and the
like.
[0056] The temperature of the electroplating bath is maintained to
promote the efficient plating of the quaternary alloy on the
substrate/cathode. In one embodiment, the temperature of the
electroplating bath, during plating, is about 10.degree. C. or more
and about 90.degree. C. or less. In another embodiment, the
temperature of the electroplating bath is about 30.degree. C. or
more and about 80.degree. C. or less. In yet another embodiment,
the temperature of the electroplating bath is about 40.degree. C.
or more and about 70.degree. C. or less.
[0057] Any suitable source of power is connected to the electrodes,
such as direct current, alternating current, pulsed current,
periodic reverse current, or combinations thereof. A current
density is imposed from an energy source through the electrodes
causing nickel, cobalt, and at least two alloy metal ions from the
electroplating bath to migrate towards and attach to the
substrate/cathode forming a layer of a nickel, cobalt, and at least
two alloy metals thereon. In one embodiment, current densities of
about 1 ASF or more and about 500 ASF or less are employed. In
another embodiment, current densities of about 5 ASF or more and
about 200 ASF or less are employed. In yet another embodiment,
current densities of about 10 ASF or more and about 100 ASF or less
are employed. In still yet another embodiment, current densities of
about 2 ASF or more and about 40 ASF or less are employed. In still
yet another embodiment, current densities of about 4 ASF or more
and about 35 ASF or less are employed.
[0058] Circulation of the bath in the tank is optionally provided
by any suitable means, such as a filtration system and/or air
agitation system. Circulation and agitation facilitates keeping the
anodes active, and provides benefits to the quaternary alloy
forming reaction by keeping ion concentrations substantially equal
in all areas of the electroplating bath, and in some instances
contributes to the resultant brilliant appearance of the alloys.
For example, a pump may continuously or intermittently, as needed,
pump the electroplating bath through a filter to provide the
circulation and to remove contaminates and any other particles
which may undesirably precipitate out of the electroplating bath.
An air agitation system also may operate to circulate the solution
in the electroplating bath. The components of the electroplating
bath may be replenished as necessary to facilitate the
electroplating process.
[0059] The length of time that the substrate/cathode is in contact
with the electroplating bath under a specified current density
depends upon the desired thickness of the resultant quaternary
alloy layer and the concentrations of the electroplating bath
components. In one embodiment, the substrate/cathode is in contact
with the electroplating bath (period of time from the when the
nickel, cobalt, and at least two alloy metals begin to form until
the quaternary alloy is removed from the bath) under a specified
current density for a time of about 1 second or longer and about
120 minutes or shorter. In another embodiment, the
substrate/cathode is in contact with the electroplating bath (under
plating conditions) under a specified current density for a time of
about 5 seconds or longer and about 60 minutes or shorter. In yet
another embodiment, the substrate/cathode is in contact with the
electroplating bath (under plating conditions) under a specified
current density for a time of about 10 seconds or longer and about
30 minutes or shorter.
[0060] The quaternary alloy electroplating bath optionally contains
at least one selective membrane, such as ionic and nonionic
selective membranes, positioned between the anode and cathode. The
membranes may function as diffusion barriers. The presence of a
selective membrane forms a catholyte around the cathode and an
anolyte around the anode, where the catholyte is typically the
electroplating bath. Selective membranes may have one or more of
the following properties: permit the passage therethrough of
certain ionic species while preventing the passage therethrough of
other ionic species; permit the passage therethrough of nonionic
species while preventing the passage therethrough of ionic species;
prevent or mitigate the migration of additives of the catholyte to
the anode; and/or prevent substantial amounts of metal cations from
migrating from the catholyte to the anolyte. For example, the
selective membrane may permit the flow of water therethrough, for
instance osmotically, while preventing the passage of metal ions
therethrough. In some instances, the migration of additives of the
catholyte to the anode may produce undesirable species at the
anode.
[0061] The electroplating bath, and valves that permit components
to enter the electroplating bath may be equipped with flow meters
and/or flow controllers to measure and control the amount of
components entering into the electroplating bath. The flow meter
and/or a flow controller may be connected to a computer/processor
including a memory to facilitate measuring and controlling the
amount of individual components that flow into the electroplating
bath and/or for automated process control of the ternary alloy
electroplating method. The computer/processor may be further
coupled to sensors in the electroplating bath to measure one or
more of pH, species concentration, volume, and the like. The
computer/processor may be coupled to control valves that permit
introduction of additional water, metals, anode replacement, acid,
and/or base, into the electroplating bath.
[0062] Referring to FIG. 1, an exemplary arrangement of a method
and nickel cobalt quaternary alloy plating system are described.
The quaternary alloy plating system 100 includes a power source
(not shown) for providing current to an electrochemical cell 102
containing an aqueous bath. The electrochemical cell 102 may
contain an optional selective membrane 106, which subdivides the
bath into a catholyte or electroplating bath 108 and an anolyte 110
(and this general arrangement may be repeated one or more times in
an adjacent fashion to provide multiple electrochemical cells with
a plurality of anolytes 110, catholytes 108, and selective
membranes 106). The catholyte or electroplating bath 108 contains
the ionic metals as described above while the anolyte 110 contains
any acidic, basic, or neutral solution that can carry a current.
The quaternary alloy plating system 100 also contains an anode 112
and a cathode 114. Current is run through the electrochemical cell
102 inducing the deposition or plating of a nickel cobalt
quaternary alloy at the cathode 110. If the optional selective
membrane 106 is not present, which occurs in a more traditional
set-up, there is no separate anolyte and catholyte, but only an
electroplating bath in the electrochemical cell 102.
[0063] Optionally, after the quaternary alloy is formed, the
quaternary alloy may be heat treated to improve its hardness. For
example, the nickel cobalt quaternary alloy may be heated from
about 200.degree. C. to about 700.degree. C., and more specifically
from about 250.degree. C. to about 550.degree. C., for a sufficient
period of time to improve hardness.
[0064] The quaternary alloys formed in accordance with the present
invention contain a major amount of nickel and cobalt and minor
amount of at least two alloy metals. Major amounts include at least
50% by weight whereas minor amounts include less than 50% by
weight.
[0065] Examples of quaternary alloys that may be formed in
accordance with the present invention include nickel cobalt boron
iron alloys, nickel cobalt bismuth iron alloys, nickel cobalt tin
iron alloys, nickel cobalt copper iron alloys, nickel cobalt silver
iron alloys, nickel cobalt bismuth boron alloys, nickel cobalt tin
boron alloys, nickel cobalt copper boron alloys, nickel cobalt
silver boron alloys, nickel cobalt boron iron silver alloys, and
the like. In one embodiment, the quaternary alloys contain at least
four metals. In another embodiment, the quaternary alloys contain
at least five metals.
[0066] The quaternary alloy formed in accordance with the present
invention mainly contains nickel, cobalt, and at least two alloy
metals. In one embodiment, the quaternary alloy contains from about
30% to about 80% by weight of nickel, from about 30% to about 80%
by weight of cobalt, and from about 0.001% to about 10% by weight
of each of at least two alloy metals. In another embodiment, the
quaternary alloy contains from about 40% to about 70% by weight of
nickel, from about 40% to about 70% by weight of cobalt, and from
about 0.01% to about 5% by weight of each of at least two alloy
metals.
[0067] While the quaternary alloy formed in accordance with the
present invention mainly contains nickel, cobalt, and at least
alloy metals, other components may be present including small
amounts (such as less than about 2% by weight) of other compounds.
For example, the quaternary alloy may contain small amounts of one
or more of the additives to the bath, contaminants, or another
metal. In another embodiment, the quaternary alloy formed in
accordance with the present invention contains less than about 1%
by weight of other components (not nickel, cobalt, or at least two
alloy metals). In yet another embodiment, the quaternary alloy
formed in accordance with the present invention contains less than
about 0.1% by weight of other components.
[0068] The nickel cobalt quaternary alloy formed in accordance with
the present invention, can have a thickness as small as about 0.5
.mu.m with substantially no pores. In another embodiment, the
thickness of the quaternary alloy formed in accordance with the
present invention can be as small as about 1 .mu.m with
substantially no pores.
[0069] The nickel cobalt quaternary alloys formed in accordance
with the present invention may have high hardness values, when
measured using a Vickers hardness measuring device having 100 gm
loads. In one embodiment, the hardness of the quaternary alloy
formed in accordance with the present invention is at least about
600 as deposited, and at least about 900 after optional heat
treatment. In another embodiment, the hardness of the quaternary
alloy formed in accordance with the present invention is at least
about 1,000 as deposited, and at least about 1300 after optional
heat treatment. In yet another embodiment, the hardness of the
quaternary alloy formed in accordance with the present invention is
at least about 1,050 as deposited, and at least about 1400 after
optional heat treatment.
[0070] The resultant nickel cobalt quaternary alloy layer
electroplated in accordance with the present invention has many
desirable characteristics including one or more of high brightness,
high hardness, excellent lubricity, corrosion resistance, uniform
thickness, excellent leveling, excellent ductility, lack of
pinholes, environmentally friendly processing, and controllable
thickness.
[0071] Uniform thickness means uniform in two senses. First, a
uniformly thick quaternary alloy layer results when electroplating
a smooth or curvilinear surface cathode and the nickel cobalt
quaternary alloy layer has substantially the same thickness in any
location after removal from the surface of the cathode. This
uniformly thick quaternary alloy layer is smooth and flat when the
surface of the cathode is smooth while the uniformly thick
quaternary alloy layer may have an uneven surface mimicking the
uneven contours of the underlying cathode surface. Second, a
uniformly thick quaternary alloy layer results when electroplating
an uneven cathode surface so that the resultant nickel cobalt
quaternary alloy layer appears smooth and the quaternary alloy
layer has substantially the same thickness within locally smooth
regions on the surface of the cathode. This second sense also
refers to excellent leveling.
[0072] While the invention has been explained in relation to
certain embodiments, it is to be understood that various
modifications thereof will become apparent to those skilled in the
art upon reading the specification. Therefore, it is to be
understood that the invention disclosed herein is intended to cover
such modifications as fall within the scope of the appended
claims.
* * * * *