U.S. patent application number 14/911442 was filed with the patent office on 2016-07-07 for galvanic bath.
The applicant listed for this patent is HARTING KGaA. Invention is credited to Frank Brode, Alexander Meyerovich.
Application Number | 20160194775 14/911442 |
Document ID | / |
Family ID | 51383525 |
Filed Date | 2016-07-07 |
United States Patent
Application |
20160194775 |
Kind Code |
A1 |
Meyerovich; Alexander ; et
al. |
July 7, 2016 |
GALVANIC BATH
Abstract
The invention relates to a galvanic bath for depositing a
nickel-molybdenum alloy which consists of an aqueous solution of
amine complexes and/or ammonium complexes in each case of nickel
and/or molybdenum, the galvanic bath containing citric acid and/or
citrate ions and/or oxidation products of the citric acid and/or
the citrates, and molybdenum being present in different oxidation
stages, in particular as Mo(V) and Mo(VI), in the galvanic
bath.
Inventors: |
Meyerovich; Alexander;
(Espelkamp, DE) ; Brode; Frank; (Berlin,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HARTING KGaA |
Espelkamp |
|
DE |
|
|
Family ID: |
51383525 |
Appl. No.: |
14/911442 |
Filed: |
July 15, 2014 |
PCT Filed: |
July 15, 2014 |
PCT NO: |
PCT/DE2014/100258 |
371 Date: |
February 10, 2016 |
Current U.S.
Class: |
205/50 ;
205/255 |
Current CPC
Class: |
C25D 3/56 20130101; C25D
3/562 20130101; C25D 7/00 20130101 |
International
Class: |
C25D 3/56 20060101
C25D003/56; C25D 7/00 20060101 C25D007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2013 |
DE |
10 2013 110 263.8 |
Claims
1. An electroplating bath for depositing a nickel-molybdenum alloy,
said bath comprising an aqueous solution of amine complexes and/or
ammonium complexes, in each case of nickel and/or molybdenum,
wherein the electroplating bath contains a citric acid and/or
citrate ions and/or oxidation products of citric acid and/or of
citrates, and wherein molybdenum is present in different oxidation
states, in the electroplating bath.
2. The electroplating bath as claimed in claim 1, wherein the
concentration of the citric acid and/or of the citrate ions and/or
the oxidation products of citric acid and/or of citrates is in the
range from 0.1 to 0.6 mol/l, in particular from 0.1 to 0.4
mol/l.
3. The electroplating bath as claimed in claim 1, wherein the
electroplating bath contains a proportion of molybdenum of at least
15% by weight.
4. The electroplating bath as claimed in claim 1, wherein the
concentration of nickel is in the range from 0.20 to 0.35 mol/l, in
particular from 0.22 to 0.3 mol/l.
5. The electroplating bath as claimed in claim 1, wherein the
electroplating bath contains an ammonium concentration in the range
from 0.20 mol/l to 0.40 mol/l, preferably from 0.25 to 0.35
mol/l.
6. The electroplating bath as claimed in claim 1, wherein the
concentration of molybdenum is in the range from 0.01 to 1 mol/l,
in particular from 0.02 to 0.06 mol/l.
7. The electroplating bath as claimed in claim 1, wherein the
molybdenum/nickel ratio is in the range from 1:10 to 1:4.
8. The electroplating bath as claimed in claim 1, wherein the
electroplating bath contains further salts of alloy-forming metals,
for example salts of nickel and/or cobalt and/or iron and/or
phosphorus and/or rhenium and/or palladium and/or platinum, and
where the individual metals are preferably present in a
concentration in the range from 0.1 to 5% by weight.
9. The electroplating bath as claimed in claim 1, wherein the bath
contains organic additives such as stabilizers, wetting agents and
brighteners.
10. The electroplating bath as claimed in claim 1, wherein the
electroplating bath contains at least one additive selected from
the following group or a mixture thereof: brighteners, preferably
in a concentration in the range from 0.01 to 5% by weight, wetting
agents, preferably in a concentration in the range from 0.05 to
0.5% by weight, electrolyte salts, preferably in a concentration in
the range from 0.2 to 0.8 mol/l, particularly preferably in a
concentration in the range from 0.3 to 0.6 mol/l, sulfur-containing
additives, preferably in the concentration range from 0.1 mg/l to
4.0 g/l, particularly preferably in the concentration range from
0.2 mg/1 to 2.0 g/l.
11. The electroplating bath as claimed in claim 1, wherein
electrolyte salts such as sodium salts and potassium salts are
present in the electroplating bath.
12. The electroplating bath as claimed in claim 1, wherein the
concentration of the electrolyte salts is in the range from 0.2 to
0.8 mol/l, but preferably in the range from 0.3 to 0.6 mol/l.
13. The electroplating bath as claimed in claim 1, wherein the
electrolyte salt is an inorganic electrolyte salt, in particular
from the group consisting of sulfates and chlorides, or an organic
electrolyte salt, in particular from the group consisting of
citrates.
14. The electroplating bath as claimed in claim 1, wherein the
electroplating bath contains ketoglutaric acid and/or aconitic acid
and/or ketoglutarates and/or aconitates, and where the
concentration of these materials is preferably in the range from
0.1 to 0.6 mol/l, particularly preferably from 0.1 to 0.4
mol/l.
15. The electroplating bath as claimed in claim 1, wherein the
electroplating bath contains gluconates, tartrates or
hydroxycarboxylic acids.
16. The electroplating bath as claimed in claim 1, wherein
sulfur-containing additives such as sulfanilamides, sulfonimides,
sulfonic acids or sulfonates have been added to the electroplating
bath, and where the concentration of these sulfur-containing
additives is preferably in the range from 0.1 mg/l to 4.0 g/l, in
particular from 0.2 mg/l to 2.0 g/l.
17. The electroplating bath as claimed in claim 1, wherein at least
one surfactant from the group consisting of cationic, anionic,
nonionic, amphoteric surfactants, or mixtures of the abovementioned
surfactants, is present as wetting agent in the electroplating
bath.
18. The electroplating bath as claimed in claim 1, wherein the pH
of the electroplating bath is in the range from 4 to 11, but
particularly preferably in the range from 7.5 to 9.5.
19. The electroplating bath as claimed in claim 1, wherein the
electroplating bath contains alkali metal hydroxide for adjusting
pH.
20. The electroplating bath as claimed in claim 1, wherein the
electroplating bath has a temperature in the range of from 20 to
85.degree. C., in particular from 50.degree. C. to 75.degree.
C.
21. An object, preferably a contact element of a plug connector,
the surface of which has been coated with a nickel-molybdenum alloy
using an electroplating bath as claimed in claim 1.
22. The electroplating bath as claimed in claim 1, wherein the
molybdenum is present as Mo(V) and Mo(VI).
Description
[0001] The invention relates to an electroplating bath for
depositing nickel-molybdenum alloys on a surface of an object.
[0002] Contact elements of plug connectors, for example, can be
coated with such nickel-molybdenum alloys. Further layers, for
example consisting of silver/silver alloys or gold/gold alloys or
copper/copper alloys, can be applied to a nickel-molybdenum
alloy.
PRIOR ART
[0003] Electroplating baths based on ammonium-nickel and
ammonium-molybdenum complexes are generally considered to have low
stability in the prior art. In the baths studied, insoluble
molybdenum compounds, for example MoO(OH).sub.3
(trihydroxomolybdenum monoxide) are formed, as a result of which
the electrolyte becomes unusable.
[0004] DE 121664 B, JP 2005-082856 A, JP 04124293 A disclose
electroplating baths for depositing a nickel-molybdenum alloy. The
electroplating baths additionally contain ammonium and/or citrate
ions.
[0005] A disadvantage of these baths is considered to be that the
current yield and the composition of the layer change continually
during the coating process and the process becomes virtually
uncontrollable as a result. Molybdenum oxides are included in the
layer and coatings having only low shine are deposited. For these
reasons, the baths having this composition have hitherto been
without industrial importance.
FORMULATION OF PROBLEM
[0006] The problem addressed by the present invention is to provide
a stable alloy bath which makes it possible to deposit
nickel-molybdenum alloys having a high molybdenum content.
[0007] The problem is solved by an electroplating bath as claimed
in claim 1.
[0008] Advantageous embodiments of the invention are indicated in
the dependent claims.
[0009] The electroplating bath of the invention can be produced in
a simple way. In addition, it is environmentally friendly.
[0010] An electroplating bath can consist of an aqueous, preferably
alkaline (basic), solution of amine complexes and/or ammonium
complexes, in each case of nickel and/or molybdenum, for example
[Ni(NH.sub.3).sub.6].sup.2+ or (NH.sub.4).sub.6Mo.sub.7O.sub.24,
and many salts of the corresponding alloy-forming metals. These
baths display long-term stability and can be used for the
electrolytic deposition of nickel-molybdenum alloys.
[0011] The addition of a citrate prevents the electroplating bath
from becoming unusable as a result of the above-described
precipitation of insoluble molybdenum compounds. The citrate
suppresses the disportionation reaction of the molybdenum
complexes.
[0012] Instead of citric acid and/or citrates, it is also possible
to use their oxidation products which are formed by thermal and/or
anodic oxidation of the citric acid/citrates. As oxidation
products, the bath contains, for example, ketoglutaric acid and/or
aconitic acid and/or .alpha.-ketoglutarates and/or
.beta.-ketoglutarates and/or aconitates. The abovementioned
materials preferably have a concentration in the range from 0.1 to
0.6 mol/l, particularly preferably from 0.1 to 0.4 mol/l, in the
bath.
[0013] It is particularly advantageous for molybdenum to be present
in different oxidation states in the electroplating bath.
[0014] The soluble complexes of molybdenum can be, before being
used according to the invention, prepared by, for example, reacting
molybdenum salts in which the molybdenum is present in different
oxidation states in aqueous solution at room temperature with a
complexing agent in a molar ratio of 1 mol of molybdenum to from
four to 10 mol of complexing agent. However, it is also possible to
add the molybdenum salts and complexing agents directly to the bath
solution.
[0015] The molybdenum in different oxidation states is generated by
chemical and/or electrochemical reduction of molybdate ions. After
reduction, molybdenum ions in the oxidation states +3, +4, +5 and
+6, preferably +5 and +6, are present in the solution.
[0016] Salts of nickel and/or cobalt and/or iron and/or phosphorus
and/or rhenium and/or palladium and/or platinum, which in
combination with molybdenum salts allow various alloy compositions
of the layer, are advantageously used as electrolyte. Up to 50% by
weight of molybdenum can be deposited in this way.
[0017] The molybdenum content of the alloy matrix exercises a
substantial influence on the structure of a metal coating. Thus,
for example, scanning electromicrographs (SEM) have shown that a
layer having a molybdenum content of from 20 to 40 percent by
weight (% by weight) has finely crystalline to amorphous
structures.
[0018] The bath can advantageously contain organic additives such
as stabilizers, wetting agents and brighteners. The customary
wetting agents are nonionic, cationic or anionic in nature. These
materials can also act as brighteners in concentrations of from
0.01 to 20 g/liter.
[0019] The electroplating bath advantageously contains at least one
additive from the following group or a mixture thereof: [0020]
brighteners, preferably in a concentration in the range from 0.01
to 5 percent by weight (% by weight), [0021] wetting agents,
preferably in a concentration in the range from 0.05 to 0.5% by
weight. The customary wetting agents are nonionic, cationic or
anionic in nature. [0022] electrolyte salts, preferably in a
concentration in the range from 0.2 to 0.8 mol/l, particularly
preferably in a concentration in the range from 0.3 to 0.6
mol/l.
[0023] As wetting agents, it is advantageous to use lauryl sulfate,
lauryl ether sulfate or acrylamido sulfonates or a mixture of the
above-mentioned wetting agents. These wetting agents greatly reduce
the surface tension of the bath. Visually defect-free and
high-quality coatings can be achieved by means of these
additives.
[0024] Sulfonimides, sulfonamides, alkylsulfonic acids
(sulfonates), arylsulfonic acids (sulfonates) or a mixture thereof
are ideal as brighteners for the nickel-containing baths.
[0025] As electrolyte salts, it is advantageous to use sodium and
potassium salts. The preferred concentrations of these materials
are in the range from 0.2 to 0.8 mol per liter (mol/l), but
preferably in the range from 0.3 to 0.6 mol/l.
[0026] The pH of the electroplating bath is advantageously in the
range from 4 to 11, but particularly preferably in the range from
7.5 to 9.5. The pH is advantageously set by addition of alkali
metal hydroxide, for example NaOH. It has been found that the
abovementioned citrate is particularly well suited to suppressing
disproportionation in these pH ranges.
[0027] The electroplating bath is advantageously operated in a
temperature range from 20 to 85 degrees Celsius (.degree. C.), in
particular from 50.degree. C. to 75.degree. C.
[0028] Current densities in the range from 0.1 to 3 ampere per
square decimeter (A/dm.sup.2) are preferably employed in the
coating operation.
[0029] Ketoglutaric acid and/or aconitic acid and/or
.alpha.-ketoglutarates and/or .beta.-ketoglutarates and/or
aconitates are particularly preferably present in the
electroplating bath, here the concentration of these materials is
preferably in the range from 0.1 to 0.6 mol/l, particularly
preferably from 0.1 to 0.4 mol/l.
[0030] The electroplating bath of the invention is outstandingly
suitable for depositing silver-colored nickel-molybdenum alloys on
industrial objects, for example abrasion-resistant and
corrosion-resistant coatings on electronic components. Contact
elements of plug connectors can particularly advantageously be
coated therewith. The electrolytically deposited coating is
particularly corrosion- and wear-resistant.
[0031] The electroplating bath of the invention displays long-term
stability and can be used for the electrolytic deposition of
nickel-molybdenum alloys. Such a result was not able to be achieved
by the known baths having a similar composition.
[0032] In the following, the essence of the electroplating bath of
the invention will be summarized once more. It is provided as an
aqueous solution of salts or oxides of nickel and/or of molybdenum
and further additives. Furthermore, many alloy-forming metals can
be added in ionic form. The pH of the bath is set to the weakly to
strongly alkaline region. Since nickel and molybdenum should be
present in the form of amine or ammonium complexes, amine- or
ammonium-containing compounds are added to the bath. An example is
[Ni(NH.sub.3).sub.n].sup.2+ where n=1-6.
[0033] Further suitable nickel sources are nickel (II) sulfate,
nickel sulfate hexahydrate or nickel chloride. The nickel
concentration in the bath is advantageously in the range from 0.20
to 0.35 mol/l, particularly preferably from 0.22 to 0.3 mol/l.
* * * * *