U.S. patent application number 16/473764 was filed with the patent office on 2021-04-01 for cyanide-free liquid composition for immersion gold plating.
The applicant listed for this patent is Kanto Kagaku Kabushiki Kaisha. Invention is credited to Takuo OHWADA, Kazutaka SENDA, Tomoaki TOKUHISA, Takahiro TSUDA.
Application Number | 20210095378 16/473764 |
Document ID | / |
Family ID | 1000005315049 |
Filed Date | 2021-04-01 |
United States Patent
Application |
20210095378 |
Kind Code |
A1 |
TSUDA; Takahiro ; et
al. |
April 1, 2021 |
CYANIDE-FREE LIQUID COMPOSITION FOR IMMERSION GOLD PLATING
Abstract
A gold deposition accelerator for electroless gold plating
comprising one or more alkali metal compound(s), wherein said
alkali metal compound is not a compound comprising only sodium as
an alkali metal, and said alkali metal compound is not only halide,
only potassium sulfite, or only potassium sodium tartrate of an
alkali metal, an electroless gold plating solution comprising said
gold deposition accelerator, a gold plating method and a gold
deposition accelerating method using the same and the like are
provided.
Inventors: |
TSUDA; Takahiro; (Saitama,
JP) ; TOKUHISA; Tomoaki; (Saitama, JP) ;
OHWADA; Takuo; (Saitama, JP) ; SENDA; Kazutaka;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kanto Kagaku Kabushiki Kaisha |
Tokyo |
|
JP |
|
|
Family ID: |
1000005315049 |
Appl. No.: |
16/473764 |
Filed: |
December 27, 2016 |
PCT Filed: |
December 27, 2016 |
PCT NO: |
PCT/JP2016/089007 |
371 Date: |
June 26, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 18/42 20130101;
C09D 5/24 20130101 |
International
Class: |
C23C 18/42 20060101
C23C018/42 |
Claims
1. A gold deposition accelerator for electroless gold plating
comprising one or more alkali metal compound(s), wherein said
alkali metal compound is not a compound comprising only sodium as
an alkali metal, and said alkali metal compound is not only halide,
only potassium sulfite, or only potassium sodium tartrate of an
alkali metal.
2. An electroless gold plating solution comprising the gold
deposition accelerator of claim 1, a water-soluble source of gold
and a complexing agent.
3. The electroless gold plating solution of claim 2, wherein the
concentration of the alkali metal compound is 0.001 to 5 M on an
alkali metal ion basis other than sodium.
4. A gold deposition accelerator comprising a rubidium compound
and/or cesium compound.
5. An electroless gold plating solution comprising the gold
deposition accelerator of claim 4, a water-soluble source of gold
and a complexing agent.
6. The electroless gold plating solution of claim 5, further
comprising a sodium compound.
7. The electroless gold plating solution of claim 5, comprising no
cyanide compound.
8. The electroless gold plating solution of claim 5, comprising an
acid or a base as a pH regulator.
9. A method of forming a gold plating film comprising a step of
applying the electroless gold plating solution of claim 5 on a
surface of an electronic industrial component.
10. A method of accelerating gold deposition in electroless gold
plating comprising adding one or more alkali metal compound(s) in
an electroless gold plating solution, wherein said alkali metal
compound is not a compound comprising only sodium as an alkali
metal, and said alkali metal compound is not only halide, only
potassium sulfite, or only potassium sodium tartrate of an alkali
metal.
11. The method of claim 10, wherein the concentration of the alkali
metal compound is 0.001 M to 5 M on an alkali metal ion basis other
than sodium.
12. A method of accelerating gold deposition in electroless gold
plating by adding a rubidium compound and/or cesium compound.
13. The method of claim 12, wherein the concentration of the
rubidium compound and/or cesium compound is 0.001 M to 5 M on a
rubidium ion and/or cesium ion basis.
14. The electroless gold plating solution of claim 2, further
comprising a sodium compound.
15. The electroless gold plating solution of claim 2, comprising no
cyanide compound.
16. The electroless gold plating solution of claim 2, comprising an
acid or a base as a pH regulator.
17. A method of forming a gold plating film comprising a step of
applying the electroless gold plating solution of claim 2 on a
surface of an electronic industrial component.
Description
[0001] This application is a U.S. National Phase application under
35 U.S.C. .sctn. 371 of PCT/JP2016/089007, filed Dec. 27, 2016. The
entire disclosure content of this application is herewith
incorporated by reference in its entirety into the present
application.
TECHNICAL FIELD
[0002] The present invention relates to a gold deposition
accelerator for use in formation of a gold plating film on an
electronic industrial component such as a printed wiring board, an
electroless gold plating solution comprising said gold deposition
accelerator, and a plating method and a gold deposition
accelerating method using said electroless gold plating
solution.
BACKGROUND ART
[0003] A printed board has a metal circuit pattern on and/or within
the board. For the circuit, a metal with a low electrical
resistance such as copper is used, and further, a barrier metal
layer is provided for preventing an oxidation, corrosion of the
circuit and/or preventing a migration with gold. As a metal used as
the barrier metal layer, palladium, platinum, silver, cobalt, and
an alloy thereof can be used, as well as nickel or a nickel alloy.
There is also a technique of forming a palladium layer on a nickel
layer in order to prevent a diffusion of nickel due to a thermal
treatment. After these substrate metal layers are formed, they are
further covered with a gold film to be a complete circuit. However,
a gold film is, in general, used for preventing corrosion of a
circuit and/or is used as a contact, thus a film with a high
porosity is not preferable and a surface with few gaps is
required.
[0004] As a gold plating method, electrolytic gold plating,
autocatalytic electroless gold plating, substrate-catalytic
(surface-catalytic) gold plating, and immersion gold plating and
the like are known. Autocatalytic electrolytic gold plating
performs gold deposition by a reducing agent of which gold is a
catalyst. Substrate-catalytic (surface-catalytic) gold plating
performs gold deposition by a reducing agent of which a substrate
metal is a catalyst. Immersion gold plating performs gold
deposition by an electrical displacement reaction between a
substrate metal on a surface to be plated and a gold ion and/or a
gold ion complex. These plating methods may also be used in
combination of two or more kinds.
[0005] Although, as for an electroless gold plating solution, many
plating solutions containing a cyanide compound as a source of gold
have been reported, there are storage and management issues, safety
issues during various treatments, as well as a cost issue for a
waste liquid treatment. Because of this, a development of an
electroless gold plating solution containing no cyanide compound
has been desired. Patent Literature 1 describes an electroless
plating solution containing two types of reducing agents using
water-soluble gold salts such as gold sodium sulfite in place of
cyanide compounds, and considers using ethylenediamine tetraacetic
acid (EDTA), and oxocarboxylic acids such as tartaric acid and the
like, which are generally used as complexing agents, as reaction
accelerators. Patent Literature 2 similarly describes an
electroless plating solution that uses gold sodium sulfite as a
source of gold, and considers using potassium sulfite to improve
the gold deposition speed, while the concentration of potassium
sulfite is described to be limited to equal to or less than 500
mg/L, since the plating solution becomes unstable and causes
self-decomposition when the concentration of potassium sulfite is
too large. In Patent Literature 3, a compound which releases a
halogen ion having a strong action of promoting an anode reaction
is considered as a gold deposition accelerator of an electroless
gold plating solution. Patent Literature 4 uses a heavy metal such
as thallium salt as a gold deposition accelerator.
PRIOR ART LITERATURES
Patent Literatures
[0006] [PATENT LITERATURE 1] JP, A, 2003-221674 [0007] [PATENT
LITERATURE 2] JP, B, 4758470 [0008] [PATENT LITERATURE 3] JP, A,
2010-209415 [0009] [PATENT LITERATURE 4] JP, A, 2007-308796
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0010] The conventional methods using complexing agents such as
oxocarboxylic acids and potassium sulfite as reaction accelerators
were to anticipate in the accelerating effect in gold deposition by
interfacial complexation in which a complex ion coordinates to a
metal ion. However, it was difficult to obtain the desired gold
deposition speed only by a complexing agent. This was because a
complexing agent, depending on its amount to be added, has a
problem of erosion to a substrate, and due to decomposition of the
complexing agent itself, makes a plating solution unstable and
induces the self-decomposition of the plating solution, thus the
amount of the complexing agent to be added needs to be controlled.
Also, when reducing agents and stabilizers are included, one must
consider the interaction with such ingredients. On the other hand,
a gold deposition accelerator using heavy metals such as thallium
has an issue with an impact on the environment.
[0011] Thus, the present invention is to provide a gold deposition
accelerator which readily improves the gold deposition speed of an
electroless gold plating solution and enables to form a uniform
gold film, an electroless gold plating solution containing said
gold deposition accelerator, a gold plating method and a gold
deposition accelerating method etc., using the same.
Means to Solve the Problem
[0012] While considering a method to accelerate gold deposition
without depending on complexing agents, the present inventors found
that alkali metal ions influence a gold deposition speed, and as a
result of further proceeding of the research, the present invention
has been accomplished.
[0013] That is, the present invention relates to the following:
[1] A gold deposition accelerator for electroless gold plating
comprising one or more alkali metal compound(s), wherein said
alkali metal compound is not a compound comprising only sodium as
an alkali metal, and said alkali metal compound is not only halide,
only potassium sulfite, or only potassium sodium tartrate of an
alkali metal. [2] An electroless gold plating solution comprising
the gold deposition accelerator according to [1], a water-soluble
source of gold and a complexing agent. [3] The electroless gold
plating solution according to [2], wherein the concentration of the
alkali metal compound is 0.001 to 5 M on an alkali metal ion basis
other than sodium. [4] A gold deposition accelerator comprising a
rubidium compound and/or cesium compound. [5] An electroless gold
plating solution comprising the gold deposition accelerator
according to [4], a water-soluble source of gold and a complexing
agent. [6] The electroless gold plating solution according to [2],
[3] or [5] further comprising a sodium compound. [7] The
electroless gold plating solution according to [2], [3], [5] or [6]
comprising no cyanide compound. [8] The electroless gold plating
solution according to [2], [3], [5], [6] or [7] comprising an acid
or a base as a pH regulator. [9] A method of forming a gold plating
film comprising a step of applying the electroless gold plating
solution according to [2], [3], [5], [6], [7] or [8] on a surface
of an electronic industrial component. [10] A method of
accelerating gold deposition in electroless gold plating comprising
adding one or more alkali metal compound(s) in an electroless gold
plating solution, wherein said alkali metal compound is not a
compound comprising only sodium as an alkali metal, and said alkali
metal compound is not only halide, only potassium sulfite, or only
potassium sodium tartrate of an alkali metal. [11] The method
according to [10], wherein the concentration of the alkali metal
compound is 0.001 to 5 M on an alkali metal ion basis other than
sodium. [12] A method of accelerating gold deposition in
electroless gold plating by adding a rubidium compound and/or
cesium compound. [13] The method according to [12], wherein the
concentration of the rubidium compound and/or cesium compound is
0.001 M to 5 M on a rubidium ion and/or cesium ion basis.
Effects by the Invention
[0014] According to the present invention, it can readily improve
the gold deposition speed of an electroless gold plating solution,
thus, it can realize a sufficient gold deposition speed even in an
electroless gold plating solution which does not have a cyanide
compound as a source of gold and has a slow deposition speed. Also,
since the gold deposition speed can be regulated only by regulating
the concentration of alkali metal ions other than sodium, a
regulation by many ingredients is possible as compared to when gold
deposition is accelerated depending only on a complexing agent,
thus being able to provide a more stable electroless gold plating
solution. Furthermore, since the deposition speed can be improved
without increasing the concentration of gold, an inexpensive
plating solution can be provided.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a FIGURE comparing gold deposition speeds when
alkali metal ions are changed.
EMBODIMENTS FOR CARRYING OUT INVENTION
[0016] The gold deposition accelerator of the present invention
comprises an alkali metal compound.
[0017] The gold deposition accelerating action of the gold
deposition accelerator of the present invention is of an alkali
metal ion, and the alkali metal compound comprised in the gold
deposition accelerator of the present invention may be anything
that dissociates to generate an alkali metal ion. Surprisingly,
although it is the same alkali metal ion, a sodium ion does not
accelerate the gold deposition reaction. Thus, the alkali metal
compound comprised in the gold deposition accelerator of the
present invention is not a compound comprising only sodium as an
alkali metal, but may comprise sodium as long as an alkali metal
other than sodium is present. Such compounds include, for example,
potassium sodium tartrate.
[0018] The alkali metal compound comprised in the gold deposition
accelerator of the present invention is preferably one or more
selected from the group consisting of a potassium compound,
rubidium compound and cesium compound, and more preferably, in
terms of deposition accelerativity, a rubidium compound and/or
cesium compound. In terms of cost, a potassium compound is also
preferable.
[0019] The alkali metal compound comprised in the gold deposition
accelerator of the present invention includes, but not limited to
the following compounds. For example, carbonates such as potassium
carbonate, rubidium carbonate, cesium carbonate; nitrates such as
cesium nitrate, rubidium nitrate, cesium nitrate; sulfates such as
potassium sulfate, rubidium sulfate, cesium sulfate; halides are
included, and as halides, fluorides such as potassium fluoride,
rubidium fluoride, cesium fluoride; chlorides such as potassium
chloride, rubidium chloride, cesium chloride; bromides such as
potassium bromide, rubidium bromide, cesium bromide; iodides such
as potassium iodide, rubidium iodide, cesium iodide are included.
These compounds may be used alone or in combination of two or
more.
[0020] A counterion to an alkali metal ion in said compound is not
particularly limited. As said counterion, carbonate ion, nitrate
ion, sulfate ion, sulfite ion, phosphate ion, borate ion, halide
ion; carbonate ion such as formate ion, acetate ion, propionate
ion, butanoate ion, pentanoate ion, hexanoate ion, heptanoate ion,
octanoate ion; hydroxy acid ions such as glycolate ion, lactate
ion, malate ion, citrate ion, tartrate ion, isocitrate ion,
salicylate ion; aromatic carboxylate ions such as benzoate ion,
phthalate ion; dicarboxylate ions such as oxalate ion, malonate
ion, succinate ion, glutarate ion, adipate ion, fumarate ion,
maleate ion are included, for example. These compounds may be used
alone or in combination of two or more.
[0021] Alkali metal compounds other than compounds having the
above-mentioned counterion include, but not limited to, the
following compounds. For example, oxide, peroxide, hydroxide,
chromic acid compound, tungstic acid compound, selenic acid
compound, molybdic acid compound, orthomolybdic acid compound,
niobic acid compound, permanganic acid compound, azide compound,
amide compound, toluene sulfonic acid compound, hydride, picric
acid compound, tetrahydroboric acid compound, hexafluorosilicic
acid compound, perrhenic acid compound, periodic acid compound,
iodic acid compound, nitrous acid compound, phosphinic acid
compound, nitrobenzene sulfonic acid compound, benzenesulfonic acid
compound, alkoxide compound, hydrogen carbonate compound,
methacrylic acid compound etc. of alkali metals are included. These
compounds may be used alone or in combination of two or more.
[0022] As such, the gold deposition accelerator of the present
invention may be an alkali metal compound itself, or may be a
composition comprising said compound. The composition may be a
mixture consisting of two or more alkali metal compounds. Also, the
composition may comprise water, a solvent such as organic solvent,
in addition to one or more alkali metal(s).
[0023] In the gold deposition accelerator of the present invention,
the alkali metal compound comprised in the gold deposition
accelerator is not only halide, only potassium sulfite, or only
potassium sodium tartrate of an alkali metal.
[0024] In one embodiment of the gold deposition accelerator of the
present invention, the alkali metal compound comprised in the gold
deposition accelerator is not only sulfite.
[0025] In one embodiment of the gold deposition accelerator of the
present invention, the alkali metal compound comprised in the gold
deposition accelerator is not only tartrate.
[0026] In one embodiment of the gold deposition accelerator of the
present invention, when the gold deposition accelerator comprises
only a potassium compound as an alkali metal compound, it comprises
a potassium compound other than potassium compounds selected from
potassium halide, potassium sulfite, and potassium sodium
tartrate.
[0027] The gold deposition accelerator of the present invention, in
the plating solution comprising said gold deposition accelerator,
can use an alkali metal compound comprising an alkali metal other
than sodium by regulating the concentration on an alkali metal ion
basis other than sodium to equal to or more than 0.001 M,
preferably equal to or more than 0.01 M, more preferably equal to
or more than 0.02 M. In terms of deposition accelerativity, said
concentration may be regulated to 0.001 M to 5 M, more preferably
0.01 M to 2 M, particularly preferably 0.02 M to 0.5 M. Since a
concentration dependency is also recognized for the gold deposition
speed, the desired gold deposition speed can be regulated by
regulating the concentration.
[0028] In one embodiment of the present invention, the gold
deposition accelerator of the present invention does not comprise
potassium sodium tartrate.
[0029] In one embodiment of the present invention, when the gold
deposition accelerator of the present invention comprises potassium
sodium tartrate or tartrate, it is preferable to use potassium
sodium tartrate in the plating solution by regulating the
concentration thereof to equal to or more than 0.11 M, preferably
more than 0.11 M, more preferably equal to or more than 0.2 M. In
terms of deposition accelerativity, said concentration is
preferably 0.11 M to 5 M, more preferably 0.11 M to 2 M,
particularly preferably 0.11 M to 0.5 M.
[0030] In one embodiment of the present invention, the gold
deposition accelerator of the present invention does not comprise
potassium sulfite.
[0031] In one embodiment of the present invention, when the gold
deposition accelerator of the present invention comprises potassium
sulfite or sulfite, it is preferable to use potassium sulfite in
the plating solution by regulating the concentration thereof to
equal to or more than 0.004 M. In terms of deposition
accelerativity, said concentration is preferably 0.004 M to 5 M,
more preferably 0.01 M to 2 M, particularly preferably 0.02 M to
0.5 M.
[0032] The present invention also relates to an electroless gold
plating solution comprising the above-mentioned gold deposition
accelerator of the present invention, a water-soluble source of
gold and a complexing agent.
[0033] In the electroless gold plating solution comprising the gold
deposition accelerator of the present invention, the concentration
of the alkali metal compound is preferably equal to or more than
0.001 M, more preferably equal to or more than 0.01 M, particularly
preferably equal to or more than 0.02 M on an alkali metal ion
basis other than sodium. In terms of deposition accelerativity,
said concentration is preferably 0.001 M to 5 M, more preferably
0.01 M to 2 M, particularly preferably 0.02 M to 0.5 M. Since a
concentration dependency to a certain extent is also recognized for
the gold deposition speed, the desired gold deposition speed can be
regulated by regulating the concentration.
[0034] As a source of gold used for the present invention,
water-soluble gold salts such as a gold sulfite salt and a
chloroauric acid salt can be used, in particular. It is preferable
to use a source of gold comprising no cyanide in terms of safety
and waste water treatment issues. The concentration of the source
of gold is preferably 0.1 to 10 g/L, even preferably 0.5 to 5 g/L.
When sodium gold sulfite is used for example, its concentration
range is preferably 0.1 to 10 g/L, even preferably 0.5 to 5 g/L on
a gold concentration basis, considering the property of the
deposition film. In one embodiment of the present invention, the
source of gold does not comprise any alkali metal other than
sodium. Also, in one embodiment of the present invention, the gold
deposition accelerator of the present invention comprises an alkali
metal compound comprising no gold.
[0035] In one embodiment of the present invention, when the source
of gold comprises an alkali metal other than sodium, the
electroless gold plating solution of the present invention further
comprises an alkali metal compound comprising no gold, and in this
case, the concentration of the alkali metal ion other than sodium
in the electroless gold plating solution is preferably equal to or
more than 0.001 M, more preferably equal to or more than 0.01 M,
particularly preferably equal to or more than 0.02 M. In terms of
deposition accelerativity, said concentration is preferably 0.001 M
to 5 M, more preferably 0.01 M to 2 M, particularly preferably 0.02
M to 0.5 M. The concentration of said alkali metal ion is the
combined concentration of the alkali metal ion derived from the
source of gold and the alkali metal ion derived from the
above-mentioned alkali metal compound comprising no gold (not
including sodium ion).
[0036] The complexing agent used for the present invention is not
particularly limited, but include, for example in particular, a
compound capable of forming a complex with a monovalent or
trivalent gold ion such as sulfite, thiosulfite, and the like. The
concentration of the complexing agent is preferably 0.001 M to 5 M,
even preferably 0.01 M to 0.5 M, and when sodium sulfite is for
example used as a complexing agent, its concentration range is
preferably 0.001 to 5 M, even preferably 0.01 to 0.5 M.
[0037] As a pH regulator, various acids such as sulfuric acid,
hydrochloric acid, phosphoric acid; hydroxide salts such as
potassium hydroxide; and amines such as NR.sub.4OH (R: hydrogen or
alkyl) with a restriction and the like can be used for example.
When a phosphate buffer is used for example as a pH regulator, it
is preferable to perform by phosphoric acid and sodium hydroxide or
potassium hydroxide.
[0038] pH is preferably in the range of 5 to 11, even preferably 6
to 10, depending on its composition.
[0039] While the gold deposition accelerator of the present
invention can be added to a plating solution for electroless gold
plating, said plating solution can also be used for any of the
methods of autocatalytic electroless gold plating,
substrate-catalytic (surface-catalytic) gold plating, immersion
gold plating and plating in combination thereof. Particularly, in
terms of deposition accelerativity, it is preferable to be used for
immersion gold plating.
[0040] The plating solution of the present invention may or may not
comprise a reducing agent. The reducing agent includes ascorbates
such as sodium ascorbate; hydroxylamine or salts of hydroxylamine
such as hydroxylamine hydrochloride, hydroxylamine sulfate;
hydroxylamine derivatives such as hydroxylamine-O-sulfonic acid;
hydrazine; amine borane compounds such as dimethylamine borane;
boron hydride compounds such as sodium boron hydride, sugars such
as glucose; hypophosphites, etc. These reducing agents may be used
alone or in combination of two or more. Furthermore, any compound
judged to be capable of depositing gold by reduction from gold ions
or gold complexes according to the Nernst equation may be used, but
is used in consideration of the reactivity toward other bath
components, the bath stability, etc.
[0041] The plating solution of the present invention can use other
additives such as grain-shape regulator, brightener in an
appropriate range of concentration. Other additives are not
particularly limited, and additives that have conventionally been
used can be used for example. Namely, grain-shape regulators such
as polyethylene glycol, brighteners such as thallium, copper,
antimony, lead are included. Any other additives besides these
additives can be used as long as they meet the above-mentioned
condition.
[0042] In one embodiment of the present invention, the electroless
gold plating solution of the present invention does not comprise
potassium sodium tartrate.
[0043] In one embodiment of the present invention, when the
electroless gold plating solution of the present invention
comprises potassium sodium tartrate or tartrate, it is preferable
to use potassium sodium tartrate in the plating solution by
regulating the concentration thereof to equal to or more than 0.11
M, preferably more than 0.11 M, more preferably equal to or more
than 0.2 M on an alkali metal ion basis other than sodium. In terms
of deposition accelerativity, said concentration is preferably 0.01
M to 5 M, more preferably 0.01 M to 2 M, particularly preferably
0.01 M to 0.5 M.
[0044] In one embodiment of the present invention, the electroless
gold plating solution of the present invention does not comprise
potassium sulfite.
[0045] In one embodiment of the present invention, when the
electroless gold plating solution of the present invention
comprises potassium sulfite, it is preferable to use potassium
sulfite in the plating solution by regulating the concentration
thereof to equal to or more than 0.004 M. In terms of deposition
accelerativity, said concentration is 0.004 M to 5 M, more
preferably 0.01 M to 2 M, particularly preferably 0.02 M to 0.5
M.
[0046] In one embodiment of the electroless gold plating solution
of the present invention, when the electroless gold plating
solution comprises only a potassium compound as an alkali metal
compound, it comprises a potassium compound other than potassium
compounds selected from potassium halide, potassium sulfite and
potassium sodium tartrate.
[0047] The present invention also relates to a gold deposition
accelerator comprising a rubidium compound and/or cesium compound.
Gold deposition is accelerated by a rubidium ion and cesium ion.
The concentration of the rubidium ion is preferably 0.001 to 5 M,
more preferably 0.01 to 2M, particularly preferably 0.02 to 0.5 M.
The concentration of the cesium ion is preferably 0.001 to 5 M,
more preferably 0.01 to 2 M, particularly preferably 0.02 to 0.5 M.
Examples of rubidium compounds and/or cesium compounds include the
similar compounds included as the examples for the above-mentioned
alkali metal compounds.
[0048] The gold deposition speed of the electroless gold plating
solution comprising the gold deposition accelerator of the present
invention may be equal to or more than 0.003 .mu.m/min, preferably
equal to or more than 0.004 .mu.m/min, more preferably equal to or
more than 0.005 .mu.m/min on 4 cm.sup.2 Ni substrate at pH 7, bath
temperature of 80.degree. C.
[0049] The present invention also relates to a method of forming a
gold plating film comprising a step of applying the electroless
gold plating solution of the present invention on a surface of an
electronic industrial component. In terms of deposition speed, the
operating temperature of the electroless gold plating solution in
said step is preferably 20 to 90.degree. C., more preferably 40 to
70.degree. C. In terms of the liquid stability and deposition
speed, pH is preferably 5 to 11, more preferably 6 to 10. The
electronic industrial component is not particularly limited, but
typically includes electrodes, wirings, etc.
[0050] The present invention also relates to a method of
accelerating gold deposition in electroless gold plating comprising
adding one or more alkali metal compound(s) in an electroless gold
plating solution, wherein said alkali metal compound is not a
compound comprising only sodium as an alkali metal, and said alkali
metal compound is not only halide, only potassium sulfite, or only
potassium sodium tartrate of an alkali metal.
[0051] The concentration of said alkali metal compound in the
method of accelerating gold deposition of the present invention may
be 0.001 to 5 M, preferably 0.01 to 2 M, more preferably 0.02 to
0.5 M on an alkali metal ion basis other than sodium.
[0052] In one embodiment of the present invention, the method of
accelerating gold deposition of the present invention does not
comprise potassium sodium tartrate.
[0053] In one embodiment of the present invention, when the method
of accelerating gold deposition of the present invention comprises
potassium sodium tartrate, it is preferable to use potassium sodium
tartrate in the plating solution by regulating the concentration
thereof to equal to or more than 0.11 M, preferably more than 0.11
M, more preferably equal to or more than 0.2 M on a potassium ion
basis. In terms of deposition accelerativity, said concentration is
preferably 0.11 M to 5 M, more preferably 0.11 M to 2 M,
particularly preferably 0.11 M to 0.5 M.
[0054] In one embodiment of the present invention, the method of
accelerating gold deposition of the present invention does not
comprise potassium sulfite.
[0055] In one embodiment of the present invention, when the method
of accelerating gold deposition of the present invention comprises
potassium sulfite, it is preferable to use potassium sulfite in the
plating solution by regulating the concentration thereof to equal
to or more than 0.004 M. In terms of deposition accelerativity,
said concentration is preferably 0.004 M to 5 M, more preferably
0.01 M to 2 M, particularly preferably 0.02 M to 0.5 M.
[0056] The present invention also relates to a method of
accelerating gold deposition in electroless gold plating by adding
a rubidium compound and/or cesium compound. Preferably, the total
concentration of the rubidium compound and/or cesium compound is
preferably 0.001 M to 5 M, more preferably 0.01 M to 1 M on a
rubidium ion and/or cesium ion basis. When only a rubidium compound
is added, its preferable concentration is 0.001 M to 5 M, more
preferably 0.01 M to 1 M on a rubidium ion basis. When only a
cesium compound is added, a preferable concentration is 0.001 M to
5 M, more preferably 0.001 M to 1 M on a cesium ion basis.
[0057] The present invention also relates to, in another
embodiment, a method of accelerating gold deposition in electroless
gold plating, wherein the concentration of an alkali metal ion in
an electroless gold plating solution is regulated to regulate a
gold deposition speed.
[0058] The concentration of the total alkali metal ions in the
electroless gold plating solution is regulated to be 0.001 M to 5
M, preferably 0.01 M to 2 M, more preferably 0.02 M to 0.5 M.
WORKING EXAMPLES
[0059] The electroless gold plating solution of the present
invention is explained further in detail below by reference to
working examples and comparative examples, which however are not to
limit the present invention in any way. A copper plate was used as
a plating sample, and this was subjected to Ni alloy plating by the
procedure below and used for testing.
Comparative Examples 1-3
[0060] The sources of gold, the complexing agents in Table 1 were
mixed in the concentrations in Table 1 to prepare gold plating
solutions, and pH of the gold plating solutions were regulated to
pH 7.0 by using phosphoric acid as a pH regulator. A 4 cm.sup.2 Ni
rolling plate was used, plating was performed for 10 minutes at
80.degree. C., the film thickness was measured, and the deposition
speed was calculated.
Working Examples 1-6
[0061] The sources of gold, the complexing agents, the deposition
accelerators in Table 1 were mixed in the concentrations in Table 1
to prepare gold plating solutions, and pH of the gold plating
solutions were regulated to pH 7.0 by using phosphoric acid as a pH
regulator. A 4 cm.sup.2 Ni rolling plate was used, plating was
performed for 10 minutes at 80.degree. C., the film thickness was
measured, and the deposition speed was calculated. For the gold
plating film thickness, "FT-9500X", X-ray fluorescence film
thickness meter by Hitachi was used.
TABLE-US-00001 TABLE 1 Composition of plating solutions and plating
conditions Comparative Working Working Working Working example 1
example 1 example 2 example 3 example 4 Substrate Ni Ni Ni Ni Ni
Source of Sodium gold mol/L 0.005 0.005 0.005 0.005 0.005 gold
sulfite as Au Sodium mol/L -- -- -- -- -- chloroaurate as Au
Complexing Sodium mol/L 0.1 0.1 0.1 0.1 0.1 agent sulfite Sodium
mol/L -- -- -- -- -- thiosulfate Potassium mol/L -- 0.05 -- -- --
carbonate Deposition Rubidium mol/L -- -- 0.05 -- -- accelerator
carbonate Cesium mol/L -- -- -- 0.05 -- carbonate Cesium mol/L --
-- -- -- 0.1 chloride pH regulator Phosphoric Phosphoric Phosphoric
Phosphoric Phosphoric acid acid acid acid acid pH 7.0 7.0 7.0 7.0
7.0 Bath 80.degree. C. 80.degree. C. 80.degree. C. 80.degree. C.
80.degree. C. temperature Deposition 0.03 0.05 0.06 0.08 0.05
speed(.mu.m/ 10 min) Comparative Working Comparative Working
example 2 example 5 example 3 example 6 Substrate Ni Ni Ni Ni
Source of Sodium gold mol/L 0.005 0.005 0.005 0.005 gold sulfite as
Au Sodium mol/L 0.005 0.005 -- -- chloroaurate as Au Complexing
Sodium mol/L 0.1 0.1 -- -- agent sulfite Sodium mol/L -- -- 0.05
0.05 thiosulfate Potassium mol/L -- -- -- -- carbonate Deposition
Rubidium mol/L -- -- -- -- accelerator carbonate Cesium mol/L --
0.05 -- 0.005 carbonate Cesium mol/L -- -- -- -- chloride pH
regulator Phosphoric Phosphoric Phosphoric Phosphoric acid acid
acid acid pH 7.0 7.0 7.0 7.0 Bath 80.degree. C. 80.degree. C.
80.degree. C. 80.degree. C. temperature Deposition 0.02 0.05 0.24
0.41 speed(.mu.m/ 10 min)
[0062] FIG. 1 is of a comparison of deposition speeds when an
alkali metal ion is changed based on the results of comparative
example 1, working examples 1-3 of Table 1. It was recognized that
a gold deposition speed improves by adding an alkali metal ion. In
addition, it was recognized that a gold deposition speed depends on
an alkali metal ion, since working example 1, working example 2 and
working example 3 have different gold deposition speeds in spite of
them all comprising a carbonate ion in the same concentration.
[0063] It was recognized that, for an electroless gold plating
solution containing a gold deposition accelerator comprising at
least one or more alkali metal ion(s) other than a sodium ion, the
gold deposition speed is large as compared to an electroless gold
plating solution comprising no gold deposition accelerator, even
after changing the kinds of cesium salt, source of gold and
complexing agent.
INDUSTRIAL APPLICABILITY
[0064] By the present invention, a sufficient gold deposition speed
can be realized even in electroless plating using an electroless
gold plating solution which does not have cyanide compound as a
source of gold and has a slow deposition speed.
* * * * *