U.S. patent application number 16/561407 was filed with the patent office on 2020-03-26 for electrolytic tin plating solution.
The applicant listed for this patent is C. Uyemura & Co., Ltd.. Invention is credited to Daisuke HASHIMOTO, Masayuki KISO, Akira OKADA, Keita TANIGUCHI.
Application Number | 20200095698 16/561407 |
Document ID | / |
Family ID | 69885359 |
Filed Date | 2020-03-26 |
United States Patent
Application |
20200095698 |
Kind Code |
A1 |
HASHIMOTO; Daisuke ; et
al. |
March 26, 2020 |
ELECTROLYTIC TIN PLATING SOLUTION
Abstract
An electrolytic tin plating solution contains a compound serving
as a source of supply of tin ions and an unsaturated aldehyde
compound having a heterocyclic group.
Inventors: |
HASHIMOTO; Daisuke; (Osaka,
JP) ; OKADA; Akira; (Osaka, JP) ; TANIGUCHI;
Keita; (Osaka, JP) ; KISO; Masayuki; (Osaka,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
C. Uyemura & Co., Ltd. |
Osaka |
|
JP |
|
|
Family ID: |
69885359 |
Appl. No.: |
16/561407 |
Filed: |
September 5, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C25D 3/32 20130101 |
International
Class: |
C25D 3/32 20060101
C25D003/32 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 2018 |
JP |
2018-177797 |
Claims
1. An electrolytic tin plating solution comprising: a compound
serving as a source of supply of tin ions; and an unsaturated
aldehyde compound having a heterocyclic group.
2. The electrolytic tin plating solution of claim 1, wherein the
heterocyclic group is a five- or six-membered heterocyclic group
containing at least one of an oxygen atom, a nitrogen atom, or a
sulfur atom.
3. The electrolytic tin plating solution of claim 1, wherein a
content of the unsaturated aldehyde compound having the
heterocyclic group in the electrolytic tin plating solution is from
0.01 mmol/L to 10 mmol/L.
4. The electrolytic tin plating solution of claim 1, wherein grains
to be deposited have a maximum grain size of 10 um or smaller.
5. The electrolytic tin plating solution of claim 1, wherein the
heterocyclic group is one, two, or more groups selected from a
pyrrolidine group, a pyrrole group, a tetrahydrofuran group, an
oxolane group, a furan group, a tetrahydrothiophene group, a
thiolane group, a thiophene group, an imidazole group, a pyrazole
group, an imidazoline group, an oxazole group, a thiazole group, a
thiazolidine group, a triazole group, a tetrazole group, a
dioxolane group, an oxadiazole group, a thiadiazole group, a
piperidine group, an azinane group, a tetrahydropyran group, an
oxane group, a tetrahydrothiopyran group, a pyridine group, a
pyrane group, a thiopyran group, a pyrimidine group, a pyrazine
group, a pyridazine group, a thiazine group, a morpholine group, a
dioxane group, a dithiin group, a thiomorpholine group, a trithiane
group, a dithiazine group, a thiazepine group, an indole group, an
isoindole group, an indolizine group, a benzimidazole group, a
benzotriazole group, a purine group, a quinoline group, an
isoquinoline group, a quinazoline group, a quinoxaline group, a
cinnoline group, a phthalazine group, a chromene group, an
isochromene group, a benzodioxole group, a benzodioxan group, a
benzoxazole group, a benzothiazole group, a pteridine group, a
phenothiazine group, a phenanthridine group, and a thianthrene
group.
6. The electrolytic tin plating solution of claim 1, wherein the
unsaturated aldehyde compound having the heterocyclic group is one,
two, or more selected from 3 -(2-furyl)acrolein,
2-methyl-3-(2-furyl)propenal, 3-(5-nitro-2-furyl)acrolein,
(4-pyridyl)acrolein, 1,3-benzodioxole-5-acrolein,
3-[3-(4-fluorophenyl)-1-isopropylindol-2-yl]acrolein,
5-hydroxytetrahydrofuran-2-acrolein, 5-(2-furyl)-2,4-pentadienal,
2-formyl-3-(2-furyl)propenenitrile, 2-cyano-3-(2-furyl)propenal,
3-(4-pyridyl)propenal, pyridine-3-propenal,
3-(1H-indole-3-yl)propenal, 3-(3,4-diethyl-2-pyrrolyl)propenal,
3-(2-thienyl)acrolein, and 3-(isoindoline-2-yl)propenal.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Japanese Patent
Application No. 2018-177797 filed on Sep. 21, 2018, the entire
disclosure of which is incorporated by reference herein.
BACKGROUND ART
[0002] The present disclosure relates to an electrolytic tin
plating solution, and more particularly relates to an electrolytic
tin plating solution which can reduce voids formed after reflow and
which is suitable for forming a bump.
[0003] A connection bump is provided on a semiconductor chip. A
solder ball or any other suitable structure is used as a connection
bump. However, miniaturization of semiconductor chips increases the
difficulty in using a known solder ball as the connection bump.
Although microballs having a diameter of about 100 .mu.m may also
be used, finer design rules have been required. Attention has been
given to the formation of a bump plated with tin (Sn) or a Sn alloy
(see, for example, Japanese Unexamined Patent Publication No.
2016-106181).
[0004] If a minute bump is formed by plating, a plurality of films
having a thickness of several tens of micrometers and independent
of one another need to be uniformly deposited in the
several-tens-of-micrometer range. To improve the joint reliability,
voids to be formed need to be reduced. Furthermore, even if a step
is present on a BVH (blind via hole) forming part of a film, a
uniform film needs to be deposited.
SUMMARY OF THE INVENTION
[0005] However, an electrolytic tin plating solution suitable for
forming a minute bump has not been present yet. In particular, even
if a step is formed on the BVH, a uniform bump needs to be formed
without any void.
[0006] The present disclosure attempts to provide an electrolytic
tin plating solution suitable for forming, e.g., bumps.
[0007] An electrolytic tin plating solution according to one aspect
of the present disclosure contains a compound serving as a source
of supply of tin ions and an unsaturated aldehyde compound having a
heterocyclic group. Since the electrolytic tin plating solution
according to the aspect contains the unsaturated aldehyde compound
having the heterocyclic group, a uniform film containing grains
having a small grain size can be formed.
[0008] In the electrolytic tin plating solution according to the
aspect, the heterocyclic group may be a five- or six-membered
heterocyclic group containing at least one of an oxygen atom, a
nitrogen atom, or a sulfur atom.
[0009] In the electrolytic tin plating solution according to the
aspect, a content of the unsaturated aldehyde compound having the
heterocyclic group may be from 0.01 mmol/L to 10 mmol/L.
[0010] In the electrolytic tin plating solution according to the
aspect, grains to be deposited may have a maximum grain size of 10
.mu.m or smaller.
[0011] An electrolytic tin plating solution according to an aspect
of the present disclosure allows a uniform film containing grains
having a small grain size to be formed.
DESCRIPTION OF EMBODIMENTS
[0012] An electrolytic tin plating solution according to an
embodiment contains an unsaturated aldehyde compound having a
heterocyclic group (hereinafter referred to as a
heterocycle-containing unsaturated aldehyde compound). The
heterocycle-containing unsaturated aldehyde compound functions as a
crystal regulator, which reduces the grain size of Sn deposit by
electrolytic plating. Reducing the grain size allows for formation
of a dense Sn deposit having less voids. Further, the electrolytic
tin plating solution containing the heterocycle-containing
unsaturated aldehyde compound allows for formation of a Sn deposit
having a uniform thickness also on a BVH having a step.
[0013] The unsaturated aldehyde is aldehyde having a straight chain
or a branched chain of molecules each having one or more
unsaturated bonds, and may have a group other than a heterocyclic
group. Examples of the unsaturated aldehyde include acrolein,
methacrolein, crotonaldehyde, 2-methylcrotonaldehyde,
2-ethylcrotonaldehyde, 2-ethylacrolein, 2-ethyl-2-hexenal,
citronellal, 2,3-dimethyl-2-propenal, undecylenic aldehyde,
4-heptenal, 2-hexenal, 2-undecenal, 2-nonenal,
2-formylpropenenitrile, 3-ethoxy-2-methyl-2-propenal,
4-hydroxy-2-nonenal, citronellyloxyacetaldehyde, 2-heptenal,
2-octenal, 2-decenal, 2,4-nonadienal, 2,6-nonadienal,
2,4-octadienal, 2,4-decadienal, and farnesal. The unsaturated
aldehyde may include a stereoisomer, which may be any stereoisomer
or include various stereoisomers.
[0014] The heterocyclic group should not be specifically limited,
but may be a five-, six-, or seven-membered nitrogen-, oxygen-, or
sulfur-containing heterocyclic group, or a nitrogen-, oxygen-, or
sulfur-containing polycyclic group. Examples of the heterocyclic
group or the polycyclic group include a five-membered ring
heterocyclic group, such as a pyrrolidine group, a pyrrole group, a
tetrahydrofuran group, an oxolane group, a furan group, a
tetrahydrothiophene group, a thiolane group, a thiophene group, an
imidazole group, a pyrazole group, an imidazoline group, an oxazole
group, a thiazole group, a thiazolidine group, a triazole group, a
tetrazole group, a dioxolane group, an oxadiazole group, and a
thiadiazole group, a six-membered ring heterocyclic group, such as
a piperidine group, an azinane group, a tetrahydropyran group, an
oxane group, a tetrahydrothiopyran group, a pyridine group, a
pyrane group, a thiopyran group, a pyrimidine group, a pyrazine
group, a pyridazine group, a thiazine group, a morpholine group, a
dioxane group, a dithiin group, a thiomorpholine group, a trithiane
group, and a dithiazine group, a seven-membered ring heterocyclic
group, such as a thiazepine group, and a polycyclic group, such as
an indole group, an isoindole group, an indolizine group, a
benzimidazole group, a benzotriazole group, a purine group, a
quinoline group, an isoquinoline group, a quinazoline group, a
quinoxaline group, a cinnoline group, a phthalazine group, a
chromene group, an isochromene group, a benzodioxole group, a
benzodioxan group, a benzoxazole group, a benzothiazole group, a
pteridine group, a phenothiazine group, a phenanthridine group, and
a thianthrene group. The heterocyclic group may include a
constitutional isomer and a stereoisomer, which may be any isomer
or include various isomers.
[0015] These unsaturated aldehydes and these heterocyclic groups
may be optionally combined together. Examples of the resultant
compound include 3-(2-furyl)acrolein, 2-methyl-3-(2-furyl)propenal,
3-(5-nitro-2-furyl)acrolein, (4-pyridyl)acrolein,
1,3-benzodioxole-5-acrolein,
3-[3-(4-fluorophenyl)-1-isopropylindol-2-yl]acrolein,
5-hydroxytetrahydrofuran-2-acrolein, 5-(2-furyl)-2,4-pentadienal,
2-formyl-3-(2-furyl)propenenitrile, 2-cyano-3-(2-furyl)propenal,
3-(4-pyridyl)propenal, pyridine-3-propenal,
3-(1H-indole-3-yl)propenal, 3-(3,4-diethyl-2-pyrrolyl)propenal,
3-(2-thienyl)acrolein, and 3-(isoindoline-2-yl)propenal. In
particular, (2-furyl)acrolein, (4-pyridyl)acrolein, and
1,3-benzodioxole-5-acrolein are preferably used for reasons such as
cost, ease of availability, and stability. The
heterocycle-containing unsaturated aldehyde compound may include a
constitutional isomer and a stereoisomer, which may be any isomer
or include various isomers. One or more types of the
heterocycle-containing unsaturated aldehyde compound may be
contained in the plating solution.
[0016] The concentration of the heterocycle-containing unsaturated
aldehyde compound in the electrolytic tin plating solution
according to this embodiment is preferably from 0.01 mmol/L to 10
mmol/L and more preferably from 0.1 mmol/L to 1 mmol/L, to maintain
a small grain size and to make the film deposited on the step
uniform.
[0017] To reduce the formation of voids, the grain size of a
maximum one of grains forming the Sn deposit formed using the
electrolytic tin plating solution according to this embodiment is
preferably 10 .mu.m or smaller and more preferably 9 .mu.m or
smaller. The maximum one of the grains preferably has a smaller
grain size. However, an actually possible grain size range of the
maximum grain is preferably 0.1 .mu.m or larger, more preferably
0.5 .mu.m or larger, still more preferably 1 .mu.m or larger, and
yet more preferably 3 .mu.m or larger. A minimum one of the grains
preferably has a smaller grain size. However, an actually possible
grain size range of the minimum grain is, but not limited to,
preferably 0.1 .mu.m or larger, more preferably 0.5 .mu.m or
larger, and still more preferably 1 .mu.m or larger.
[0018] The electrolytic tin plating solution according to this
embodiment contains a compound serving as a source of supply of tin
(Sn) ions, in addition to the heterocycle-containing unsaturated
aldehyde compound. Examples of the compound serving as the source
of supply of Sn ions include a tin salt. In particular, a first tin
salt (tin salt (II)) and a second tin salt (tin salt (IV)) are
preferably used.
[0019] Non-limiting examples of the first tin salt (tin salt (II))
include tin (II) alkanesulfonate, such as tin (II)
methanesulfonate, organic tin (II) sulfonate, such as tin (II)
alkanolsulfonate such as tin (II) isethionate, tin (II) sulfate,
tin (II) fluoroborate, tin (II) chloride, tin (II) bromide, tin
(II) iodide, tin (II) oxide, tin (II) phosphate, tin (II)
pyrophosphate, tin (II) acetate, tin (II) citrate, tin (II)
gluconate, tin (II) tartrate, tin (II) lactate, tin (II) succinate,
tin (II) sulfamate, tin (II) formate, and tin (II)
silicofluoride.
[0020] Non-limiting examples of the second tin salt (tin salt (IV))
include sodium stannate and potassium stannate.
[0021] In particular, tin (II) alkanesulfonate, such as tin (II)
methanesulfonate, and organic tin (II) sulfonate, such as tin (II)
alkanolsulfonate such as tin (II) isethionate are preferably
used.
[0022] To reduce burning, the concentration of tin salt as
Sn.sup.2+ is preferably 5 g/L or higher and more preferably 10 g/L
or higher. To improve the stability of plating solution and reduce
precipitation, the concentration of the tin salt is preferably 120
g/L or lower and more preferably 90 g/L or lower. This
concentration also helps reduce cost.
[0023] Tin salt having a low lead (Pb) concentration of 1.0 ppm or
lower may be used as the tin salt. Using tin salt having a low Pb
concentration allows the plating solution to have a lower Pb
concentration.
[0024] The electrolytic tin plating solution according to this
embodiment may contain any one of an inorganic acid, an organic
acid, and soluble salts of these acids. Adding the acid or the
soluble salt to the plating solution allows the pH of the surface
of a plated object and the pH of the surface of Sin forming the Sn
deposit to be kept constant, thus providing a uniform surface
potential. This can retard the eutectoid reaction of Pb.
[0025] Non-limiting examples of the acid or the soluble salt of the
acid include a sulfuric acid, a hydrochloric acid, a nitric acid, a
phosphoric acid, a sulfamic acid, an organic sulfonic acid (an
alkanesulfonic acid, such as a methanesulfonic acid, or an
alkanolsulfonic acid, such as an isethionic acid), and a carboxylic
acid (an aromatic carboxylic acid, an aliphatic saturated
carboxylic acid, or an amino carboxylic acid). If necessary, a
neutralized salt of any one of these soluble salts may be used. In
particular, a methanesulfonic acid is preferably used for ease of
handling.
[0026] To improve the stability of the plating solution and reduce
the precipitation, the concentration of the acid or the soluble
salt of the acid is preferably 50 g/L or higher and more preferably
100 g/L or higher. This concentration also helps substantially
prevent an appropriate Pb deposition potential. To reduce cost, the
concentration of the acid or the soluble salt is preferably 500 g/L
or lower, more preferably 300 g/L or lower, and still more
preferably 200 g/L or lower.
[0027] The electrolytic tin plating solution according to this
embodiment may contain a surfactant. One or more selected from an
anionic surfactant, a cationic surfactant, and a nonionic
surfactant may be used as the surfactant. In particular, a nonionic
surfactant is preferably used, and an alkylene oxide-based
surfactant is more preferably used. Adding the surfactant to the
plating solution allows the surface of a plated object and the
surface of a Sn crystal forming a film to have a uniform current
density, thus maintaining a uniform deposition potential at the
surface. This can retard the eutectoid reaction of Pb.
[0028] Non-limiting examples of the alkylene oxide-based surfactant
include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl
ether, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide,
polyoxyethylene fatty acid ester, polyoxyethylene polyhydric
alcohol ether, an ethylene oxide-propylene oxide block copolymer
compound, an ethylene oxide-propylene oxide random copolymer
compound, and a propylene oxide polymer compound. In particular,
polyoxyethylene alkyl phenyl ether is preferably used.
[0029] The concentration of the surfactant is preferably 0.05 g/L
or higher, and more preferably 0.5 g/L or higher. Even if plating
is performed at a high current density to shorten the plating time,
the surfactant having such a concentration or higher can reduce
burning at an area having a high current density. To reduce color
irregularities arising from blackening of the Sn deposit, the
concentration of the surfactant is preferably 100 g/L or lower.
[0030] The electrolytic tin plating solution according to this
embodiment contains an acid or a soluble salt thereof and a
surfactant. The acid or the soluble salt thereof is more preferably
one or more acids or soluble salts thereof selected from a sulfuric
acid, a hydrochloric acid, a nitric acid, a phosphoric acid, a
sulfamic acid, an organic sulfonic acid, a carboxylic acid, or
salts of these acids. The surfactant is more preferably selected
from one or more surfactants selected from an anionic surfactant, a
cationic surfactant, and a nonionic surfactant.
[0031] The electrolytic tin plating solution according to this
embodiment may contain an organic solvent, an antioxidant, and a
chelating agent. Non-limiting examples of the organic solvent
include monohydric alcohols, such as methanol and 2-propanol, and
dihydric alcohols, such as ethylene glycol, diethylene glycol, and
triethylene glycol. Non-limiting examples of the antioxidant
include catechol, hydroquinone, 4-methoxyphenol, and ascorbic acid.
Non-limiting examples of the chelating agent include oxalic acid,
succinic acid, malonic acid, glycolic acid, gluconic acid,
gluconolactone, glycine, ethylenediamine-acetic acid,
pyrophosphoric acid, and tripolyphosphoric acid.
[0032] To form a Sn deposit using the electrolytic tin plating
solution according to this embodiment, the pH of the plating
solution is preferably strongly acidic. The temperature at which
the Sn deposit is formed should not be specifically limited.
However, the temperature is preferably from 25.degree. C. to
40.degree. C. The current density at which the Sn deposit is formed
is preferably from 1 A/dm.sup.2 to 20 A/dm.sup.2, and more
preferably from 2 A/dm.sup.2 to 6 A/dm.sup.2.
[0033] The electrolytic tin plating solution according to the
present disclosure can be used, for example, to form plated bumps
on a semiconductor chip. To form a plated bump, a Sn deposit having
a predetermined size is formed at a predetermined position, and
then a reflow process is performed. The reflow process should not
be specifically limited, but may be performed using a known reflow
apparatus.
EXAMPLES
[0034] The electrolytic tin plating solution according to the
present disclosure will now be described in more detail with
reference to examples. The following examples are illustrative, and
are not intended to limit the present disclosure.
Formation of Sn Deposit
[0035] A substrate was electrolytically plated with Ni (an
electrolytic nickel plating solution: Thru-Nic AMT, manufactured by
C. Uyemura & Co., Ltd., liquid temperature: 50.degree. C.,
current density: 1 A/dm.sup.2, plating time: 10 min). A Sn deposit
was formed on the Ni surface, where an electrolytic tin plating
solution having a predetermined composition was set to have a
liquid temperature of 30.degree. C. and a current density of 4
A/dm.sup.2.
Estimation of Grain Size
[0036] The grain size of Sn grains forming the resultant Sn-plated
film was measured by an electron emission scanning electron
microscope (JSM-7800F, manufactured by JEOL Ltd.). An IPF mapping
image obtained under conditions of an accelerating voltage of 20 kV
and an illumination current of 13 nA was analyzed to calculate a
distribution range of the grain sizes of the Sn grains.
Evaluation of Void
[0037] The obtained Sn deposit was reflowed at 260.degree. C., and
then the presence or absence of a void was evaluated by an X-ray
nondestructive testing system (XD7600NT Diamond FP, manufactured by
Nordson DAGE). The X-ray nondestructive testing system had a tube
voltage of 60 kV and an output of 1.5 W.
First Example
[0038] As a heterocycle-containing unsaturated aldehyde compound,
3-(2-furyl)acrolein was used. The concentration of the
heterocycle-containing unsaturated aldehyde compound was 0.2
mmol/L. Tin (II) alkanesulfonate as a tin salt, methanesulfonic
acid as an orgainc acid, and polyoxyethylene bisphenol A ether as a
surfactant were added. The Tin (II) alkanesulfonate was added such
that the concentration thereof was 70 g/L as Sn(Sn.sup.2+), and the
methanesulfonic acid, and the polyoxyethylene bisphenol A ether in
the compound were respectively 100 g/L, and 50 g/L. The resultant
plating solution was set to have a liquid temperature of 30.degree.
C. and a current density of 4 A/dm.sup.2.
[0039] Grain size of Sn deposit obtained had a maximum grain size
of 8 .mu.m and a minimum grain size of 1 .mu.m. No voids were
observed in the Sn deposit after reflow.
Second Example
[0040] A second example was similar to the first example except
that (4-pyridyl)acrolein was used as a heterocycle-containing
unsaturated aldehyde compound and that the concentration of the
(4-pyridyl)acrolein was 0.8 mmol/L.
[0041] Grain size of Sn deposit obtained had a maximum grain size
of 7 .mu.m and a minimum grain size of 1 .mu.m. No voids were
observed in the Sn deposit after reflow.
Third Example
[0042] A third example was similar to the first example except that
1,3-benzodioxole-5-acrolein was used as a heterocycle-containing
unsaturated aldehyde compound and that the concentration of the
1,3-benzodioxole-5-acrolein was 0.4 mmol/L.
[0043] Grain size of Sn deposit obtained had a maximum grain size
of 6 .mu.m and a minimum grain size of 1 .mu.m. No voids were
observed in the Sn deposit after reflow.
First Comparative Example
[0044] A first comparative example was similar to the first example
except that no heterocycle-containing unsaturated aldehyde compound
was added.
[0045] Grain size of Sn deposit obtained had a maximum grain size
of 12 .mu.m and a minimum grain size of 4 .mu.m. Voids were
observed in the Sn deposit after reflow.
Second Comparative Example
[0046] A second comparative example was similar to the first
example except that 1.0 mmol/L of benzaldehyde was added instead of
a heterocycle-containing unsaturated aldehyde compound.
[0047] Grain size of Sn deposit obtained had a maximum grain size
of 12 .mu.m and a minimum grain size of 3 .mu.m. Voids were
observed in the Sn deposit after reflow.
Third Comparative Example
[0048] A third comparative example was similar to the first example
except that 1.0 mmol/L of cinnamaldehyde was added instead of a
heterocycle-containing unsaturated aldehyde compound.
[0049] Grain size of Sn deposit obtained had a maximum grain size
of 12 .mu.m and a minimum grain size of 3 .mu.m. Voids were
observed in the Sn deposit after reflow.
Fourth Comparative Example
[0050] A fourth comparative example was similar to the first
example except that 0.4 mmol/L of acrylic acid was added instead of
a heterocycle-containing unsaturated aldehyde compound.
[0051] Grain size of Sn deposit obtained had a maximum grain size
of 12 .mu.m and a minimum grain size of 3 .mu.m. Voids were
observed in the Sn deposit after reflow.
Fifth Comparative Example
[0052] A fifth comparative example was similar to the first example
except that 0.8 mmol/L of acrolein was added instead of a
heterocycle-containing unsaturated aldehyde compound.
[0053] Grain size of Sn deposit obtained had a maximum grain size
of 12 .mu.m and a minimum grain size of 3 .mu.m. Voids were
observed in the Sn deposit after reflow.
TABLE-US-00001 TABLE 1 Examples Comparative Examples 1 2 3 1 2 3 4
5 Heterocycle- 3-(2-furyl) (4-pyridyl) 1,3-benzodioxole- None
(benz- (cinnam- (acrylic (acrolein) containing acrolein acrolein
5-acrolein aldehyde) aldehyde) acid) Unsaturated Aldehyde Compound
(mmol/L) 0.2 0.8 0.4 -- 1.0 1.0 0.4 0.8 Grain Size 1-8 1-7 1-6 4-12
3-12 3-12 3-12 3-12 (.mu.m) Void None None None Formed Formed
Formed Formed Formed
[0054] Table 1 summarizes the conditions and result of each of the
examples and comparative examples. Using the electrolytic tin
plating solution containing the heterocycle-containing unsaturated
aldehyde compound reduced the grain size, and allowed for formation
of uniform bumps without any void.
[0055] The electrolytic tin plating solution according to the
present disclosure allows for formation of a Sn deposit having a
uniform and small grain size, and is useful for forming bumps, for
example.
* * * * *