U.S. patent application number 16/481959 was filed with the patent office on 2019-12-26 for tin alloy plating solution.
The applicant listed for this patent is MITSUBISHI MATERIALS CORPORATION. Invention is credited to Takuma Katase, Kouji Tatsumi, Tsukasa Yasoshima.
Application Number | 20190390357 16/481959 |
Document ID | / |
Family ID | 63110055 |
Filed Date | 2019-12-26 |
United States Patent
Application |
20190390357 |
Kind Code |
A1 |
Tatsumi; Kouji ; et
al. |
December 26, 2019 |
TIN ALLOY PLATING SOLUTION
Abstract
A tin alloy plating solution comprising a soluble tin salt, a
soluble salt of a metal nobler than tin, and a sulfide compound
represented by general formula (I). In formula (I), n is 1 to 3.
The metal nobler than tin is preferably silver, copper, gold, or
bismuth.
Inventors: |
Tatsumi; Kouji; (Sanda-shi,
JP) ; Yasoshima; Tsukasa; (Sanda-shi, JP) ;
Katase; Takuma; (Sanda-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI MATERIALS CORPORATION |
Tokyo |
|
JP |
|
|
Family ID: |
63110055 |
Appl. No.: |
16/481959 |
Filed: |
December 13, 2017 |
PCT Filed: |
December 13, 2017 |
PCT NO: |
PCT/JP2017/044668 |
371 Date: |
July 30, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 3/56 20130101; C25D
3/60 20130101; C25D 7/12 20130101; C25D 3/32 20130101 |
International
Class: |
C25D 3/56 20060101
C25D003/56; C25D 3/32 20060101 C25D003/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 31, 2017 |
JP |
2017-015219 |
Nov 20, 2017 |
JP |
2017-222433 |
Claims
1. A tin alloy plating solution comprises a soluble tin salt, a
soluble salt of a metal nobler than tin, and a sulfide compound
represented by general formula (1), wherein a metal nobler than tin
is at least 1 or 2 or more kinds of metals selected from silver,
copper, gold and bismuth, in general formula (1), n is from 1 to 3
HO--CH.sub.2CH.sub.2--S--(CH.sub.2CH.sub.2--O--CH.sub.2CH.sub.2--S).sub.n-
--CH.sub.2CH.sub.2--OH (1)
2. The tin alloy plating solution according to claim 1, further
comprising at least 1 or 2 or more surfactants selected from
anionic surfactants, cationic surfactants, nonionic surfactants,
and amphoteric surfactants.
3. (canceled)
4. The tin alloy plating solution according to claim 1, further
comprising an antioxidant.
5. The tin alloy plating solution according to claim 1, further
comprising a complexing agent for tin.
6. The tin alloy plating solution according to claim 1, further
comprising a pH adjusting agent.
7. The tin alloy plating solution according to claim 1, further
comprising a brightening agent.
8. The tin alloy plating solution according to claim 2, further
comprising an antioxidant.
9. The tin alloy plating solution according to claim 2, further
comprising a complexing agent for tin.
10. The tin alloy plating solution according to claim 4, further
comprising a complexing agent for tin.
11. The tin alloy plating solution according to claim 8, further
comprising a complexing agent for tin.
12. The tin alloy plating solution according to claim 2, further
comprising a pH adjusting agent.
13. The tin alloy plating solution according to claim 4, further
comprising a pH adjusting agent.
14. The tin alloy plating solution according to claim 5, further
comprising a pH adjusting agent.
15. The tin alloy plating solution according to claim 8, further
comprising a pH adjusting agent.
16. The tin alloy plating solution according to claim 2, further
comprising a brightening agent.
17. The tin alloy plating solution according to claim 4, further
comprising a brightening agent.
18. The tin alloy plating solution according to claim 5, further
comprising a brightening agent.
19. The tin alloy plating solution according to claim 6, further
comprising a brightening agent.
20. The tin alloy plating solution according to claim 8, further
comprising a brightening agent.
21. The tin alloy plating solution according to claim 9, further
comprising a brightening agent.
Description
TECHNICAL FIELD
[0001] The present invention relates to a tin alloy plating
solution for forming a tin alloy plating film by electroplating
method. More specifically, it relates to a tin alloy plating
solution suitable for forming solder bumps for semiconductor wafers
and printed circuit boards. This international application claims
priorities based on Japanese Patent Application No. 15219 (Japanese
Patent Application No. 2017-15219) filed on Jan. 31, 2017 and
Japanese Patent Application No 222433 (Japanese Patent Application
No. 2017-222433) filed on Nov. 20, 2017, and the entire contents of
Japanese Patent Application No. 2017-15219 and Japanese Patent
Application No. 2017-222433 are incorporated into this
international application.
BACKGROUND ART
[0002] In a tin alloy plating bath (liquid) to be used for forming
a tin alloy plating film, for example, a tin-silver alloy plating
film on a conductive object, when oxidation reduction potentials of
tin ions and other metal ions (for example, silver ions) in the
bath are significantly different from each other, it has been known
that metal ions nobler than tin tend to form an insoluble salt or a
metal simple substance and precipitate in the plating bath, whereby
making it difficult to stably maintain the plating bath. Therefore,
for example, a plating solution containing a cyan compound has
conventionally been used as a tin-silver alloy plating solution.
However, this bath contains a toxic cyan compound, so that it is
extremely high toxic and causes various problems in handling.
[0003] As a tin alloy plating bath containing no cyan compound,
various plating baths (liquids) have conventionally been proposed
(for example, see Patent Documents 1 to 4.). Patent Document 1
shows a non-cyanide type stable silver and silver alloy plating
bath, and the silver and silver alloy plating bath comprises (A) a
soluble salt comprising any of a silver salt, and a mixture of a
silver salt and a salt of a metal such as tin, bismuth, indium,
lead and the like, (B) a specific sulfide-based compound having 1
or more basic nitrogen atoms in the molecule such as
2,2'-dipyridylsulfide, 2,2'-dipiperadinyldisulfide and the like, or
a specific thiocrown ether compound such as
1-aza-7-oxa-4,10-dithiacyclododecane and the like. Due to inclusion
of these specific compounds, this plating bath is said to be
excellent in temporal stability of the plating bath,
coprecipitation of silver with various metals, appearance of the
electrodeposited film and the like, as compared with the bath
containing other sulfur-based compound such as thioglycolic acid
and the like.
[0004] Patent Document 2 shows a non-cyanide type stable silver and
silver alloy plating bath, and this silver and silver alloy plating
bath comprises (A) a soluble salt comprising any of a silver salt,
and a mixture of a silver salt and a salt of a metal such as tin,
bismuth, indium, lead and the like, (B) a specific aliphatic
sulfide-based compound which contains one or more ethereal oxygen
atom(s), 1-hydroxypropyl group(s) or hydroxypropylene group(s), and
does not contain a basic nitrogen atom in the molecule such as
thiobis(diethylene glycol), dithiobis(triglycerol),
3,3'-thiodipropanol, thiodiglycerin and the like. According to this
plating bath, due to inclusion of these specific compounds, it is
said to be excellent in temporal stability of the plating bath,
coprecipitation of silver with various metals, appearance of the
electrodeposited film and the like, as compared with the bath
containing thiodiglycolic acid or .beta.-thiodiglycol which is an
aliphatic monosulfide compound containing no ethereal oxygen
atom(s), a 1-hydroxypropyl group nor a hydroxypropylene group.
[0005] Patent Document 3 shows a non-cyanide type tin-silver alloy
plating bath, and the tin-silver alloy plating bath contains (a) at
least one kind of an aliphatic amino acid and a nitrogen-containing
aromatic carboxylic acid, and (b) at least one kind of an aliphatic
sulfide and an aliphatic mercaptan. As the (a) aliphatic amino
acid, glycine and the like may be mentioned, as the (a)
nitrogen-containing aromatic carboxylic acid, picolinic acid,
3-aminopyrazine-2-carboxylic acid and the like may be mentioned, as
the (b) aliphatic sulfide, 4,7-dithiadecane-1,10-diol and the like
may be mentioned, and as the aliphatic mercaptan, thioglycol and
the like may be mentioned. In this plating bath, the sulfur
compound of the component (b) is used as a stabilizer for silver,
and further, by using the component (a) such as glycine, picolinic
acid and the like in combination, it is said that solder
wettability and appearance of the tin-silver alloy film can be well
improved.
[0006] Patent Document 4 shows a silver-based plating bath
containing no cyanide, and the plating bath contains a soluble salt
including a silver salt, and one kind or more of sulfide-based
compounds selected from the group consisting of compounds
represented by a specific general formula. According to the plating
bath, it is said that stability of silver ions in the bath is
improved, a sufficient complexing power can be obtained, the
production cost can be reduced, and practicality is excellent.
PRIOR ART DOCUMENTS
Patent Documents
[0007] Patent Document 1: JP Hei.11-269691A (Abstract) [0008]
Patent Document 2: JP 2000-192279A (Abstract) [0009] Patent
Document 3: JP 2006-265572A (Abstract) [0010] Patent Document 4: JP
2007-046142A (Abstract)
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0011] In the plating baths of the above-mentioned Patent Documents
1 to 4, various kinds of complexing agents for complexing silver
are contained for stability of silver ions in a plating bath or
temporal stability of the plating bath. However, the complexing
agents shown in Patent Documents 1 to 4 involve the problems that
these are decomposed when the plating bath is used for a long term
or the plating solution is stored for a long period of time, and
silver tends to precipitate. Further, when the complexing agent
exhibits high stability in the plating bath, it exerted bad
influences on appearance of a plating film and uniformity of a film
thickness in some cases.
[0012] An object of the present invention is to provide a tin alloy
plating solution which is excellent in electrolytic stability and
temporal stability, and appearance of a plating film and uniformity
of a film thickness are good.
Means to Solve the Problems
[0013] The present inventors have conducted intensive studies to
solve the above-mentioned problems, and as a result, they have
found that when a specific sulfide compound is contained in a tin
alloy plating solution, a complex of a metal nobler than tin in the
plating bath is stabilized without decomposition both during use
and during storage, and good appearance of a plating film and
uniformity of a film thickness can be obtained, whereby reached the
present invention.
[0014] A first aspect of the present invention is a tin alloy
plating solution containing a soluble tin salt, a soluble salt of a
metal nobler than tin, and a sulfide compound represented by the
following formula (1). In the formula (1), n is 1 to 3.
[Formula 1]
HO--CH.sub.2CH.sub.2--S--(CH.sub.2CH.sub.2--O--CH.sub.2CH.sub.2--S).sub.-
n--CH.sub.2CH.sub.2--OH (1)
[0015] A second aspect of the present invention is the invention
according to the first aspect, which is the tin alloy plating
solution further comprising at least one kind or two or more kinds
of surfactants selected from an anionic surfactant, a cationic
surfactant, a nonionic surfactant and an amphoteric surfactant.
[0016] A third aspect of the present invention is the invention
according to the first or second aspect, which is the tin alloy
plating solution wherein the metal nobler than tin is at least one
kind or two or more kinds of metals selected from silver, copper,
gold and bismuth.
[0017] A fourth aspect of the present invention is the invention
according to any one of the first to third aspects, which is the
tin alloy plating solution further comprising an antioxidant.
[0018] A fifth aspect of the present invention is the invention
according to any one of the first to fourth aspects, which is the
tin alloy plating solution further comprising a complexing agent
for tin.
[0019] A sixth aspect of the present invention is the invention
according to any one of the first to fifth aspects, which is the
tin alloy plating solution further comprising a pH adjusting
agent.
[0020] A seventh aspect of the present invention is the invention
according to any one of the first to sixth aspects, which is the
tin alloy plating solution further comprising a glossing agent.
Effects of the Invention
[0021] In the tin alloy plating solution of the first aspect of the
present invention, the sulfide compound contains an oxygen atom
"--O--" in the molecule in the above-mentioned general formula (1),
so that there is an effect of increasing water-solubility by the
hydrogen bond with water. In addition, by presenting an ether bond
"C--O--C" between S atoms, it is excellent in stability of the
compound itself, and by containing 2 to 4 S atoms, the S atom
sufficiently complexes a metal ion nobler than tin in the plating
bath and stabilized. According to this constitution, the tin alloy
plating solution is excellent in electrolytic stability and
temporal stability during use and storage over a long period of
time. In addition, since adsorption of the sulfide compound on the
surface of the plating electrode is appropriately performed, when a
surfactant is used in combination as a smoothening agent, the
action of the surfactant is not inhibited, and appearance of a
plating film and uniformity of a film thickness are good.
[0022] In the tin alloy plating solution according to the second
aspect of the present invention, it further contains a surfactant
such as an anionic surfactant, a cationic surfactant, a nonionic
surfactant, an amphoteric surfactant, and the like, so that there
is an effect of making the appearance of a plating film and
uniformity of a film thickness better.
[0023] In the tin alloy plating solution according to the third
aspect of the present invention, a metal nobler than tin is at
least one kind or two or more kinds selected from silver, copper,
gold and bismuth, so that there are effects that it is excellent in
solder wettability, mounting strength, bendability and
reflowability, whisker is difficultly formed, and the like.
[0024] In the tin alloy plating solution according to the fourth
aspect of the present invention, it further contains an
antioxidant, so that there is an effect of preventing oxidation of
Sn.sup.2+ in the tin alloy plating solution.
[0025] In the tin alloy plating solution according to the fifth
aspect of the present invention, it further contains a complexing
agent for tin, so that when the tin alloy plating solution is
applied to the tin plating bath near neutrality, there is an effect
of stabilizing Sn.sup.2+ ions.
[0026] In the tin alloy plating solution according to the sixth
aspect of the present invention, it further contains a pH adjusting
agent, so that there is an effect of adjusting the tin alloy
plating solution to an arbitrary pH range such as acidic, weakly
acidic, neutral and the like.
[0027] In the tin alloy plating solution according to the seventh
aspect of the present invention, it further contains a glossing
agent, so that there is an effect of making the crystal grains of
the tin alloy in tin alloy plating film fine.
EMBODIMENTS TO CARRY OUT THE INVENTION
[0028] In the following, a tin alloy plating solution according to
an embodiment of the present invention will be described. The tin
alloy plating solution is utilized as a material for forming a
plating film of a tin alloy used as a solder bump for a
semiconductor substrate (wafer), a printed circuit board, or the
like.
[0029] The tin alloy plating solution of the present embodiment
contains a soluble tin salt, a soluble salt of a metal nobler than
tin, and a sulfide compound represented by the following formula
(1). In the formula (1), n is 1 to 3.
[Formula 2]
HO--CH.sub.2CH.sub.2--S--(CH.sub.2CH.sub.2--O--CH.sub.2CH.sub.2--S).sub.-
n--CH.sub.2CH.sub.2--OH (1)
[Tin Alloy]
[0030] A tin alloy produced by the tin alloy plating solution of
the present embodiment is an alloy of tin (Sn), and a predetermined
metal selected from silver (Ag), copper (Cu), gold (Au) and bismuth
(Bi), and include, for example, a binary alloy such as an SnAg
alloy, an SnCu alloy, an SnAu alloy, an SnBi alloy and the like,
and a ternary alloy such as an SnCuAg alloy and the like.
[Soluble Tin Salt]
[0031] A soluble tin salt used in the tin alloy plating solution of
the present embodiment is a salt that forms divalent tin ions by
dissolving in water. Examples of the soluble tin salt include
halides, sulfates, oxides, alkane sulfonates, aryl sulfonates and
alkanol sulfonates. Specific examples of the alkane sulfonates
include methane sulfonate and ethane sulfonate. Specific examples
of the aryl sulfonate include benzene sulfonate, phenol sulfonate,
cresol sulfonate and toluene sulfonate. Specific examples of the
alkanol sulfonates include isethionate.
[0032] The soluble tin salt may be used one kind alone or in
combination of two or more kinds. A content of the soluble tin salt
in the tin alloy plating solution of the present embodiment is
preferably in the range of 5 g/L or more and 200 g/L or less, and
more preferably in the range of 20 g/L or more and 100 g/L or less
in terms of tin. If the content of the soluble tin salt is
excessively little, precipitation of tin does not normally occur in
the range of 1 to 20 ASD (amperes per square decimator) generally
used in bump plating, and there is a fear that formation of good
bump cannot be performed. On the other hand, if the content of the
soluble tin salt is excessively high, formation of bump becomes
difficult due to increase in the viscosity of the plating solution,
and tin is contained more than necessary, so that there is a fear
that the cost of the plating bath becomes high.
[Soluble Salt of Metal Nobler than Tin]
[0033] The soluble salt of a metal nobler than tin to be used in
the tin alloy plating solution of the present embodiment is a salt
soluble in water. Examples of the metal nobler than tin include at
least one kind or two or more kinds of metals selected from silver,
copper, gold and bismuth. Examples of the soluble salt of these
metals are the same as the examples of the soluble tin salt. Among
these metals, silver or copper is preferably contained. An alloy of
tin and silver (SnAg alloy) has a low melting point as a melting
point at a eutectic composition (Sn-3.5 wt % Ag) of 221.degree. C.,
and an alloy of tin and copper (SnCu alloy) has a low melting point
as a melting point at a eutectic composition (Sn-1.7 wt % Cu) of
227.degree. C., so that these have advantages such as excellent in
solder wettability, mounting strength, bendability and
reflowability, and whisker is difficultly formed and the like. The
soluble salt of the metal nobler than tin may be used one kind
alone or in combination of two or more kinds. A content of the
soluble salt of the metal nobler than tin in the plating solution
of the present embodiment is preferably in the range of 0.01 g/L or
more and 10 g/L or less, and more preferably in the range of 0.1
g/L or more and 2 g/L or less in terms of the amount of the metal.
If the content of the soluble salt of the metal nobler than tin is
excessively little or excessively high, the composition of the
deposited solder alloy cannot be made a eutectic composition, and
the characteristics as a solder alloy cannot be obtained.
[Sulfide Compound]
[0034] The sulfide compound to be used in the tin alloy plating
solution of the present embodiment is represented by the
above-mentioned general formula (1), and can be obtained by
subjecting to dehydration condensation of thiodiethanol (n=0) in a
strong acid having a dehydrating action such as concentrated
sulfuric acid, alkylsulfonic acid and the like. By changing the
reaction temperature, reaction time and purification conditions at
this time, the value of n in the general formula (1) can be
controlled. If the n exceeds 3, the sulfide compound is not water
soluble and becomes hydrophobic. In order to dissolve the sulfide
compound in an aqueous solution, n is required to be 3 or less. As
described above, since the sulfide compound contains an oxygen atom
"--O--" in the molecule in the general formula (1) described above,
there is an effect of increasing water solubility by the hydrogen
bond with water. In addition, by being present an ether bond
"C--O--C" between S atoms, stability of the compound itself is
excellent, and by containing 2 to 4 S atoms in one molecule, the S
atoms can be sufficiently complexing the metal ions nobler than tin
in the plating bath and stabilized. The structure of the sulfide
compound can be analyzed by using analytical instruments such as
high performance liquid chromatography (HPLC), high performance
liquid chromatography mass spectrometer (LC-MS), Fourier-transform
infrared spectroscopy (FT-IR), nuclear magnetic resonance apparatus
(NMR), and the like, in combination.
[Additive]
[0035] The tin alloy plating solution of the present embodiment may
further contain an additive such as an acid electrolyte (free
acid), a surfactant, an antioxidant, a complexing agent for tin, a
pH adjusting agent, a glossing agent and the like.
(Acid Electrolyte)
[0036] As the acid electrolyte, hydrogen chloride, hydrogen
bromide, sulfuric acid, an alkanesulfonic acid, an arylsulfonic
acid or an alkanolsulfonic acid can be mentioned. Specific examples
of the alkanesulfonic acid include methanesulfonic acid or
ethanesulfonic acid. Specific examples of the arylsulfonic acid
include benzenesulfonic acid, phenolsulfonic acid, cresol sulfonic
acid or toluenesulfonic acid. Specific examples of the alkanol
sulfonic acid include isethionic acid. The acid electrolyte has the
effect of enhancing conductivity of the tin alloy plating
solution.
[0037] The acid electrolyte may be used one kind alone or in
combination of two or more kinds. A content of the acid electrolyte
in the tin alloy plating solution of the present embodiment is
preferably in the range of 5 g/L or more and 500 g/L or less, and
more preferably in the range of 30 g/L or more and 300 g/L or
less.
(Surfactant)
[0038] The tin alloy plating solution of the present embodiment
preferably contains a surfactant. The surfactant has a function of
enhancing affinity between the tin alloy plating solution and the
object to be plated, and functions of improving appearance of a
plating film, improving adhesiveness with the object to be plated,
and making the film thickness uniform and the like by adsorbing to
the surface of the plating film at the time of forming the tin
alloy plating film, thereby suppressing crystal growth of the tin
alloy in the plating film and making the crystals fine. As the
surfactant, various kinds of the surfactants such as an anionic
surfactant, a cationic surfactant, a nonionic surfactant and an
amphoteric surfactant, and the like can be used.
[0039] Specific examples of the anionic surfactant include alkyl
sulfate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl
phenyl ether sulfate, alkyl benzene sulfonate, alkyl naphthalene
sulfonate and the like. Specific examples of the cationic
surfactant include mono- to trialkylamine salts, dimethyldialkyl
ammonium salts, trimethylalkyl ammonium salts and the like.
Specific examples of the nonionic activating agent include
materials in which 2 to 300 mol of ethylene oxide (EO) and/or
propylene oxide (PO) is subjected to addition condensation to
alkanols having 1 to 20 carbon atoms, phenol, naphthol, bisphenols,
alkylphenols having 1 to 25 carbon atoms, arylalkylphenols,
alkylnaphthols having 1 to 25 carbon atoms, alkoxyl phosphoric
acids (salts) having 1 to 25 carbon atoms, sorbitan esters,
polyalkylene glycols, aliphatic amides having 1 to 22 carbon atoms,
and the like. Specific examples of the amphoteric surfactant
include carboxybetaine, imidazoline betaine, aminocarboxylic acid,
and the like.
[0040] The surfactant may be used one kind alone or in combination
of two or more kinds. An amount of the surfactant to be added in
the tin alloy plating solution of the present embodiment is
generally in the range of 0.01 g/L or more and 50 g/L or less,
preferably in the range of 0.1 g/L or more and 20 g/L or less, and
more preferably in the range of 1 g/L or more and 10 g/L or
less.
(Antioxidant)
[0041] The tin alloy plating solution of the present embodiment may
contain an antioxidant, if necessary. The antioxidant is intended
to prevent oxidation of Sn.sup.2+ in the tin alloy plating
solution. Examples of the antioxidant include ascorbic acid or a
salt thereof, pyrogallol, hydroquinone, phloroglucinol,
trihydroxy-benzene, catechol, cresol sulfonic acid or a salt
thereof, catechol sulfonic acid or a salt thereof, hydroquinone
sulfonic acid or a salt thereof or the like. For example, in an
acidic bath, hydroquinone sulfonic acid or a salt thereof are
preferable, and in a neutral bath, ascorbic acid or a salt thereof,
and the like are preferable.
[0042] The antioxidant may be used one kind alone or in combination
of two or more kinds. An amount to be added of the antioxidant in
the tin alloy plating solution of the present embodiment is
generally in the range of 0.01 g/L or more and 20 g/L or less,
preferably in the range of 0.1 g/L or more and 10 g/L or less, and
more preferably in the range of 0.1 g/L or more and 5 g/L or
less.
(Complexing Agent for Tin)
[0043] The tin alloy plating solution of the present embodiment can
be applied to a tin alloy plating bath in an optional pH range such
as acidic, weakly acidic, neutral, and the like. Sn.sup.2+ ions are
stable at strong acidity (pH: <1), but tend to form white
precipitates from acidity to near neutrality (pH: 1 to 7). For this
reason, when the tin alloy plating solution of the present
embodiment is applied to the tin plating bath near neutrality, it
is preferable to add a complexing agent for tin for the purpose of
stabilizing the Sn.sup.2+ ions.
[0044] As the complexing agent for tin, oxycarboxylic acids,
polycarboxylic acids and monocarboxylic acids can be used. Specific
examples thereof include gluconic acid, citric acid, glucoheptonic
acid, gluconolactone, acetic acid, propionic acid, butyric acid,
ascorbic acid, oxalic acid, malonic acid, succinic acid, glycolic
acid, malic acid, tartaric acid, or salts thereof, and the like. It
is preferably gluconic acid, citric acid, glucoheptonic acid,
gluconolactone, glucoheptolactone, or salts thereof, and the like.
In addition, it is also effective as a complexing agent such as
polyamines including ethylenediamine, ethylenediamine tetraacetic
acid (EDTA), diethylenetriaminepentaacetic acid (DTPA),
nitrilotriacetic acid (NTA), iminodiacetic acid (IDA),
iminodipropionic acid (IDP), hydroxyethylethylene-diaminetriacetic
acid (HEDTA), triethylenetetramine hexaacetic acid (TTHA),
ethylenedioxybis(ethylamine)-N,N,N',N'-tetraacetic acid,
mercaptotriazoles, mercaptotetrazoles, glycines,
nitrilotrimethylphosphonic acid, 1-hydroxyethane-1,1-diphosphonic
acid, or salts thereof, and the like, or aminocarboxylic acids.
[0045] The complexing agent for tin may be used one kind alone or
in combination of two or more kinds. An amount to be added of the
complexing agent for tin in the tin alloy plating solution of the
present embodiment is generally in the range of 0.001 mol or more
and 10 mol or less, preferably in the range of 0.01 mol or more and
5 mol or less, and more preferably in the range of 0.5 mol or more
and 2 mol or less based on 1 mol of tin in the soluble tin salt
compound contained in the tin alloy plating solution.
(pH Adjusting Agent)
[0046] The tin alloy plating solution of the present embodiment can
contain a pH adjusting agent, if necessary. Examples of the pH
adjusting agent include various kinds of acids such as hydrochloric
acid, sulfuric acid, and the like, and various kinds of bases such
as aqueous ammonia, potassium hydroxide, sodium hydroxide, sodium
hydrogen carbonate, and the like. In addition, as the pH adjusting
agent, it is also effective including monocarboxylic acids such as
acetic acid, propionic acid, and the like, boric acids, phosphoric
acids, dicarboxylic acids such as oxalic acid, succinic acid, and
the like, and oxycarboxylic acids such as lactic acid, tartaric
acid, and the like.
(Glossing Agent)
[0047] The tin alloy plating solution of the present embodiment can
contain a glossing agent, if necessary. As the glossing agent, an
aromatic carbonyl compound is effective. The aromatic carbonyl
compound has a function of refining the crystal particles of the
tin alloy in the tin alloy plating film. The aromatic carbonyl
compound is a compound in which a carbonyl group (--CO--X: wherein
X means a hydrogen atom, a hydroxyl group, an alkyl group having a
number of the carbon atoms in the range of 1 to 6 or an alkoxy
group having a number of the carbon atoms in the range of 1 to 6)
is bonded to the carbon atom of the aromatic hydrocarbon. The
aromatic hydrocarbons include a benzene ring, a naphthalene ring
and an anthracene ring. The aromatic hydrocarbons may have a
substituent(s). Examples of the substituent(s) include a halogen
atom, a hydroxyl group, an alkyl group having a number of the
carbon atoms in the range of 1 to 6 or an alkoxy group having a
number of the carbon atoms in the range of 1 to 6. The carbonyl
group may be directly bonded to the aromatic hydrocarbon, or may be
bonded via an alkylene group having a number of the carbon atoms in
the range of 1 or more and 6 or less. The aromatic carbonyl
compound includes benzalacetone, cinnamic acid, cinnamaldehyde and
benzaldehyde.
[0048] The aromatic carbonyl compound may be used one kind alone or
in combination of two or more kinds. An amount to be added of the
aromatic carbonyl compound in the tin alloy plating solution of the
present embodiment is generally in the range of 0.01 mg/L or more
and 500 mg/L, preferably in the range of 0.1 mg/L or more and 100
mg/L or less, and more preferably in the range of 1 mg/L or more
and 50 mg/L or less.
[0049] The tin alloy plating solution of the present embodiment can
be prepared by, for example, mixing a soluble tin salt, a soluble
salt of a metal nobler than tin, the sulfide compound represented
by the general formula (1) described above and other components
with water. In order to suppress oxidation of Sn.sup.2+ ions and
reduction reaction of a metal ion nobler than tin, it is preferable
that the soluble salt of a metal nobler than tin is mixed after
introducing the sulfide compound.
[0050] As a method of forming a plating film using the plating
solution of the present embodiment, electroplating is used as
described above. A current density at the time of forming a plating
film by electroplating is in the range of 0.1 A/dm.sup.2 or more
and 100 A/dm.sup.2 or less, and preferably in the range of 0.5
A/dm.sup.2 or more and 20 A/dm.sup.2 or less. The liquid
temperature is in the range of 10.degree. C. or higher and
50.degree. C. or lower, and more preferably in the range of
20.degree. C. or higher and 40.degree. C. or lower.
EXAMPLES
[0051] Next, Examples of the present invention will be described in
detail along with Comparative Examples.
(Bath Preparation of SnAg Plating Solution)
Example 1
[0052] With an aqueous tin methanesulfonate solution were mixed
methanesulfonic acid as a free acid, a sulfide compound wherein n=1
of the general formula (1) as a complexing agent, and a nonionic
surfactant (polyoxyethylene and polyoxypropylene were added to
ethylenediamine with a ratio of 50:50) and dissolved, and a silver
methanesulfonate liquid was further added and mixed. And finally,
ion exchange water was added to prepare a bath of an SnAg plating
solution having the following composition. Incidentally, the
aqueous tin methanesulfonate solution was prepared by electrolyzing
a metal tin plate and the aqueous silver methanesulfonate solution
was prepared by electrolyzing a metal silver plate, both in an
aqueous methanesulfonic acid solution, respectively.
(Composition of SnAg Plating Solution)
[0053] Tin methanesulfonate (as Sn.sup.2): 50 g/L
[0054] Silver methanesulfonate (as Ag.sup.+): 0.5 g/L
[0055] Methanesulfonic acid (as free acid): 150 g/L
[0056] Sulfide compound (n=1): 5 g/L
[0057] Nonionic surfactant: 5 g/L
[0058] Ion exchange water: balance
Example 2
[0059] An SnAg plating solution was prepared as a bath in the same
manner as in Example 1 except that a sulfide compound wherein n=2
of the general formula (1) was used as a complexing agent.
Example 3
[0060] An SnAg plating solution was prepared as a bath in the same
manner as in Example 1 except that a sulfide compound wherein n=3
of the general formula (1) was used as a complexing agent.
Example 4
[0061] An aqueous tin methanesulfonate solution was mixed with
methanesulfonic acid as a free acid and a sulfide compound wherein
n=2 of the general formula (1) as a complexing agent and dissolved,
and an aqueous copper methanesulfonate solution was further added
and mixed. After making the solution uniform by mixing, a nonionic
surfactant was further added thereto. And finally, ion exchange
water was added to the mixture to prepare a bath of an SnCu plating
solution having the following composition. Incidentally, the
aqueous tin methanesulfonate solution was prepared by electrolyzing
a metal tin plate, and the aqueous copper methanesulfonate solution
was prepared by electrolyzing a metal copper plate in an aqueous
methanesulfonic acid solution, respectively.
(Composition of SnCu Plating Solution)
[0062] Tin methanesulfonate (as Sn.sup.2+): 50 g/L
[0063] Copper methanesulfonate (as Cu.sup.2+): 0.3 g/L
[0064] Methanesulfonic acid (as free acid): 150 g/L
[0065] Sulfide compound (n=2): 5 g/L
[0066] Nonionic surfactant: 5 g/L
[0067] Ion exchange water: balance
Example 5
[0068] An aqueous tin methanesulfonate solution was mixed with
methanesulfonic acid as a free acid, a sulfide compound wherein n=1
of the general formula (1) as a complexing agent and a nonionic
surfactant (20 mol of polyoxyethylene was added to 1 mol of
bisphenol A) to dissolve these materials, then, sodium gluconate as
a complexing agent of tin and mercaptotetrazole were added, and
benzalacetone was mixed as a glossing agent. Further, a silver
methanesulfonate solution was added and mixed. And finally, ion
exchange water was added to prepare a bath of an SnAg plating
solution having the following composition.
(Composition of SnAg Plating Solution)
[0069] Tin methanesulfonate (as Sn.sup.2+): 80 g/L
[0070] Silver methanesulfonate (as Ag.sup.+): 1.0 g/L
[0071] Methanesulfonic acid (as free acid): 100 g/L
[0072] Sulfide compound (n=1): 3 g/L
[0073] Nonionic surfactant: 8 g/L
[0074] Sodium gluconate: 10 g/L
[0075] Mercaptotetrazole: 1 g/L
[0076] Benzalacetone: 0.01 mg/L
[0077] Ion exchange water: balance
Comparative Example 1
[0078] An SnAg plating solution was prepared as a bath in the same
manner as in Example 1 except that a sulfide compound wherein n=0
of the general formula (1) was used as a complexing agent.
Comparative Example 2
[0079] An SnAg plating solution was prepared as a bath in the same
manner as in Example 1 except that a sulfide compound wherein n=4
of the general formula (1) was used as a complexing agent.
Comparative Example 3
[0080] An SnAg plating solution was prepared as a bath in the same
manner as in Example 1 except that 3,6-dithia-1,8-octanediol was
used as a complexing agent.
Comparative Example 4
[0081] An SnAg plating solution was prepared as a bath in the same
manner as in Example 5 except that a sulfide compound wherein n=4
of the general formula (1) was used as a complexing agent.
<Comparative Test and Evaluation>
[0082] By using nine kinds of the prepared baths of the plating
solutions in Examples 1 to 5 and Comparative Examples 1 to 4,
stability and plating performance of the tin alloy plating solution
were evaluated. Stability of the tin alloy plating solution was
evaluated by performing an electrolytic stability test and a
temporal stability test. The plating performance was evaluated by
performing Hull cell test and a plating test.
(a) Electrolytic Stability Test
[0083] Nine kinds of the prepared baths of the tin alloy plating
solutions were used as an electrolyte, a copper plate was located
as a cathode and a platinum plate as an anode in the electrolyte,
nine kinds of the prepared baths of the tin alloy plating solutions
were performed to electroplating each separately at a bath
temperature of 25.degree. C. and a cathode current density of 10
ASD. Since metal components in the plating solution were consumed
by electroplating, while powders of stannous oxide (SnO) and silver
oxide (Ag.sub.2O) were added to, mixed with and dissolved in the
plating solution every 5 Ah/L of electroplating to supply the metal
components to the plating bath, electroplating was performed up to
200 Ah/L. A concentration of the sulfide compound which is a
complexing agent remaining in the tin alloy plating solution after
electroplating was quantitatively analyzed by the following HPLC
(High Performance Liquid Chromatography) method. The tin alloy
plating solution was filtered with a disposable syringe, and
analysis was performed using L-Column ODS kept at 40.degree. C.
using an HPLC apparatus (Model No.: Prominence) manufactured by
Shimadzu Corporation and making a mobile phase MeOH (methanol). The
concentration of the complexing agent immediately after preparation
of the bath was made 100%, and a remaining ratio (%) of the
complexing agent after electroplating was evaluated as the
remaining amount of the complexing agent.
(b) Temporal Stability Test
[0084] Nine kinds of the prepared baths of the tin alloy plating
solutions were separately charged in a sealed bottle made of a
glass, and stored in a clean oven manufactured by Panasonic
Corporation at 50.degree. C. for 6 months. Using an ICP Automatic
Emission Spectrometer (ICP-AES, Model No.: ICPE-9800) manufactured
by Shimadzu Corporation, metal concentrations other than Sn in the
tin alloy plating solution immediately after preparation of the
bath, that is, in the case of the SnAg alloy plating solution, the
Ag concentration, and in the case of the SnCu plating solution, the
Cu concentration was made 100%, respectively, and metal
concentrations other than Sn remained after storage of 6 months,
that is, in the case of the SnAg alloy plating solution, the Ag
concentration, and in the case of the SnCu plating solution, the Cu
concentration was measured and the remaining ratio (%) thereof was
each calculated.
(c) Hull Cell Test
[0085] Nine kinds of the prepared baths of the tin alloy plating
solutions were each separately placed in a hull cell tank
manufactured by Yamamoto-MS Co., Ltd., and a hull cell plate made
of copper was arranged in the liquid as a cathode and a platinum
plate as an anode, respectively, to perform the Hull cell test. The
plating conditions were such that the liquid temperature was
25.degree. C., the applied current was 3 A, and the plating
processing time was 5 minutes. During the plating processing, the
plating solution was stirred by a cathode rocker. The hull cell
evaluation was performed by observing the film appearance of a
plating film on the hull cell plate subjected to plating treatment
confirming with naked eyes using a current density quick reference
plate, and evaluated with three judgement criteria that the film
with gloss or semi-gloss was regarded as "good", the film without
gloss or cloudy was regarded as "acceptable" and the film with
scorching or burning was regarded as "poor".
(d) Plating Test
[0086] Nine kinds of the prepared baths of the tin alloy plating
solutions were used as electrolytes and a plating test was carried
out separately. The electrolyte was adjusted to a liquid
temperature of 25.degree. C., and a substrate made of copper (10 cm
in length, 10 cm in width and 0.3 mm in thickness) was immersed in
the electrolyte and subjected to 10 minutes at a current density of
5 A/dm.sup.2. The film thickness of ten portions of the obtained
plating film was measured by a fluorescent X-ray film thickness
measuring device (manufactured by Hitachi High-Technologies
Corporation). The maximum value (T.sub.max) the minimum value
(T.sub.min) and the average value (T.sub.average) of the film
thickness at the 10 portions were obtained, and uniformity of a
film thickness was calculated by the following equation (2) to
evaluate whether electrodeposition was uniformly performed or not.
The test results as above are shown in Table 1.
Uniformity of film
thickness=(T.sub.max-T.sub.min)/(2.times.T.sub.average).times.100(%)
(2)
TABLE-US-00001 TABLE 1 Plating characteristics Tin alloy plating
solution of plating Complexing agent solution Compound Stability of
Hull cell Plating other Metal plating solution test test than other
Electrolytic Temporal (plating (film Sulfide sulfide than stability
stability film thickness compound compound Sn test test appearance)
uniformity) Example 1 n = 1 -- Ag 90% 93% Good 2.1% Example 2 n = 2
-- Ag 92% 84% Good 3.3% Example 3 n = 3 -- Ag 95% 97% Acceptable
4.0% Example 4 n = 2 -- Cu 88% 89% Good 3.2% Example 5 n = 1 -- Ag
91% 92% Good 4.2% Comparative n = 0 -- Ag 86% 27% Good 2.7% Example
1 Comparative n = 4 -- Ag 98% 98% Poor 15.8% Example 2 Comparative
-- 3, 6-Di- Ag 21% 9% Good 3.1% Example 3 thia- 1,8- octane- diol
Comparative n = 4 -- Ag 93% 92% Poor 24.6% Example 4
[0087] As clearly seen from Table 1, in the case of Examples 1 to 5
using the sulfide compound represented by n=0 to 3 in the general
formula (1), even after electrolytic plating, the complexing agent
remained with a high ratio as 90% to 95% in the SnAg plating
solution and as 88% in the SnCu plating solution, and even after
lapse of time, the remaining ratio of Ag or Cu in the solution was
as high as 84% to 97% in the SnAg plating solution, and 89% in the
SnCu plating solution, and in the plating performance, appearance
of the film was good and uniformity of a film thickness was as good
as 2.1% to 4.2% in the SnAg plating solution and 3.2% in the SnCu
plating solution. On the other hand, in Comparative Example 1,
while electrolytic stability and plating performance were good, the
residual ratio of Ag decreased after lapse of time. This is
considered that the compound of n=0 used in Comparative Example 1
has one S atom in one molecule, so that an ability of forming a
complex with Ag ion is not sufficient, and Ag was reduced and
deposited. Also, in Comparative Example 2 and Comparative Example
4, while stability of the plating solution was good, the plating
performance worsened. This is presumed that the compound of n=4 has
high hydrophobicity and is strong in adsorbing power to the surface
of the electrode, so that it interfered with the smoothening action
of the surfactant used in combination. Further, in Comparative
Example 3, while the plating performance was good, the sulfide
compound of the present invention as a complexing agent was not
contained in the tin alloy plating solution, so that a
concentration of the complexing agent was lowered after the
electrolytic plating.
UTILIZABILITY IN INDUSTRY
[0088] The plating solution of the present invention can be
utilized for forming a part of an electronic component such as a
bump electrode of a semiconductor wafer or a printed circuit
board.
* * * * *