U.S. patent application number 12/456077 was filed with the patent office on 2010-01-07 for electrolytic tin plating solution and electrolytic tin plating method.
This patent application is currently assigned to Rohm and Haas Electronic Materials LLC. Invention is credited to Masaaki Imanari, Yasuo Ohta, Motoya Shimazu, Fai Lung Ting.
Application Number | 20100000873 12/456077 |
Document ID | / |
Family ID | 41334608 |
Filed Date | 2010-01-07 |
United States Patent
Application |
20100000873 |
Kind Code |
A1 |
Imanari; Masaaki ; et
al. |
January 7, 2010 |
Electrolytic tin plating solution and electrolytic tin plating
method
Abstract
A plating solution and a plating method, which does not use a
complexing agent and which provides favorable solder wetting
properties and an extremely low coupling rate when electrolytic tin
plating is performed, and particularly when electrolytic tin
plating is performed using a barrel plating method.
Inventors: |
Imanari; Masaaki;
(Misato-city, JP) ; Ting; Fai Lung; (New
Territories, CN) ; Shimazu; Motoya; (Saitama-city,
JP) ; Ohta; Yasuo; (Tokyo, JP) |
Correspondence
Address: |
John J. Piskorski;Rohm and Haas Electronic Materials LLC
455 Forest Street
Marlborough
MA
01752
US
|
Assignee: |
Rohm and Haas Electronic Materials
LLC
Marlborough
MA
|
Family ID: |
41334608 |
Appl. No.: |
12/456077 |
Filed: |
June 11, 2009 |
Current U.S.
Class: |
205/304 |
Current CPC
Class: |
C25D 3/30 20130101; C25D
7/12 20130101; C25D 17/16 20130101 |
Class at
Publication: |
205/304 |
International
Class: |
C25D 3/32 20060101
C25D003/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 12, 2008 |
JP |
2008-154461 |
Claims
1. An electrolytic tin plating solution for chip components,
comprising: (A) stannous ions, (B) acid, (C)
N,N-dipolyoxyalkylene-N-alkyl amine, an amine oxide, or a blend
thereof, and (D) an anti-sticking agent; wherein the pH is 1 or
lower.
2. The electrolytic tin plating solution for chip components
according to claim 1, further comprising: (E) a plating uniformity
improver.
3. The electrolytic tin plating solution for chip components
according to claim 1, further comprising: (F) one or more acrylic
acid or acrylic acid derivative as expressed by the following
General Formula (1); and (G) an antioxidant. ##STR00012## where R
represents hydrogen or an alkyl group containing between 1 and 3
carbon atoms
4. The electrolytic tin plating solution for chip components
according to claim 1, wherein the aforementioned
N,N-dipolyoxyalkylene-N-alkyl amine is one or more compounds
expressed by the following General Formula (2). ##STR00013##
wherein R represents an alkyl group with between 6 and 28 carbon
atoms, and w, x, y, and z each represent an integer between 0 and
30. However, the sum of w, x, y, and z is not 0.
5. The electrolytic tin plating solution for chip components
according to claim 1, wherein the aforementioned amine oxide is one
or more compounds expressed by the following General Formula (3).
##STR00014## where R represents an alkyl group, cycloalkyl group,
or aryl group, and R' represents a hydrogen atom, alkyl group, or
cycloalkyl group.
6. The electrolytic tin plating solution for chip components
according to claim 1, wherein the (D) anti-sticking agent is one or
more compound selected from a group consisting of aromatic
aldehydes and aromatic ketones.
7. A method of plating chip components, comprising electrolytically
tin plating chip components using an electrolytic tin plating
solution comprising (A) stannous ions, (B) acid, (C)
N,N-dipolyoxyalkylene-N-alkyl amine, an amine oxide, or a blend
thereof, and (D) an anti-sticking agent; wherein the pH is 1 or
less.
Description
[0001] The present invention relates to a tin plating solution and
an electrolytic tin plating method; and in further detail relates
to an electrolytic tin plating solution and plating method for
plating chip components such as ceramic capacitors.
[0002] Chip components are metal plated with tin, copper, silver,
gold, nickel, palladium, or an alloy thereof, or the like, using a
plating method such as barrel plating, plating with a flow-through
plater, or the like, depending on the shape of the chip and the
construction of the regions to be plated. The purpose for tin
plating is to provide solderability to the electrode parts of the
chip component.
[0003] However, with tin plating, and particularly barrel plating,
there is a problem where the chip components will stick to each
other (hereinafter also referred to as aggregation, sticking, and
coupling). Chips that stick together become defective products, and
reduce the yield of the product. The ratio of chip components that
stick together from the total number of chip components is referred
to as the coupling rate, and in severe cases, the coupling rate can
exceed 90%.
[0004] Coupling is known to occur when chip components are plated
in a barrel using a conventional plating bath with a sulfuric acid
or methanesulfonic acid as a base. In order to resolve this
problem, Japanese unexamined patent application 2003-82492
discloses a method of forming an electrode on chip-type ceramic
electronic components using a tin electroplating bath containing
stannous sulfonate as a stannous salt, a complexing agent such as
citric acid, gluconic acid, or pyrophosphoric acid, or the like,
and a glossing agent.
[0005] However, with the plating solution of Japanese unexamined
patent application 2003-82492, a complexing agent is included, so
wastewater processing of the plating solution and wash water is
difficult. Therefore, a low pH tin plating bath that does not
contain a complexing agent is preferable from the perspective of
protecting the environment.
[0006] Furthermore, a tin plating bath with excellent solder
wetting properties is important for tin plating to provide
solderability to the chip components, or the like. The present
inventors have previously improved on this point, and have
discovered that specific naphthol compounds are useful as an
additive for electrolytic tin plating that can form a tin film with
uniform appearance, and the deposited tin film will have favorable
solder wetting properties, and have also discovered that the
solderability can be improved using specific naphthol
compounds.
[0007] Therefore, an objective present invention is to provide a
plating solution for chip components and a plating method for chip
components, which does not use a complexing agent, and which
provides favorable solder wetting properties and an extremely low
coupling rate when electrolytic tin plating is performed, and
particularly when electrolytic tin plating is performed using a
barrel plating method.
[0008] As a result of diligent research to achieve the
aforementioned objectives, the present inventors have discovered
that a smooth tin plating film with higher film surface hardness
than a conventional film and which can minimize sticking between
plated substrates can be achieved by using specific compounds in a
strongly acidic (pH of 1 or lower) tin plating bath, and
particularly in a barrel tin plating bath that does not contain a
complexing agent.
[0009] In other words, one aspect of the present invention provides
an electrolytic tin plating solution for chip components,
comprising (A) stannous ions, (B) acid, (C)
N,N-dipolyoxyalkylene-N-alkyl amine, amine oxide, or blend thereof,
and (D) an anti-sticking agent; wherein the pH is 1 or lower.
[0010] Furthermore, one aspect of the present invention provides an
electrolytic tin plating solution for chip components, further
containing (E) a plating uniformity improver in addition to the
components (A) through (D).
[0011] Furthermore, one aspect of the present invention provides an
electrolytic tin plating solution for chip components, further
containing (F) an acrylic acid or acrylic acid derivative expressed
by the following General Formula (1) and (G) an antioxidant, in
addition to the components of (A) through (E).
##STR00001##
[0012] In the above formula, R represents a hydrogen atom or an
alkyl group containing between 1 and 3 carbon atoms.
[0013] Furthermore, one aspect of the present invention provides an
electrolytic tin plating solution for chip components, wherein the
aforementioned N,N-dipolyoxyalkylene-N-alkyl amine is one or more
compounds expressed by the following General Formula (2).
##STR00002##
[0014] In the above formula, R represents an alkyl group with
between 6 and 28 carbon atoms, and w, x, y, and z each represent an
integer between 0 and 30. However, the sum of w, x, y, and z is not
0.
[0015] Furthermore, one aspect of the present invention provides an
electrolytic tin plating solution for chip components, wherein the
aforementioned amine oxide is one or more compound expressed by the
following General Formula (3).
##STR00003##
[0016] In the above formula, R represents an alkyl group,
cycloalkyl group, or aryl group, and R' represents a hydrogen atom,
alkyl group, or cycloalkyl group.
[0017] Furthermore, one aspect of the present invention provides an
electrolytic tin plating solution for chip components, wherein the
aforementioned (D) anti-sticking agent is one or more compound
selected from a group consisting of aromatic aldehydes and aromatic
ketones.
[0018] Furthermore, one aspect of the present invention provides a
method of plating chip components, comprising electrolytically tin
plating chip components using an electrolytic tin plating solution
comprising (A) stannous ions, (B) acid, (C)
N,N-dipolyoxyalkylene-N-alkyl amine, amine oxide, or blend thereof,
and (D) an anti-sticking agent; wherein the pH is 1 or lower.
[0019] The plating solution of the present invention is very
effective at preventing substrates from sticking together and can
minimize plating defects so the product yield increases when a
plurality of substrates such as chip components, or the like, are
electrolytically tin plated, and particularly when electrolytically
tin plated using a barrel plating method. In other words, making
the tin plating film smooth can reduce the sticking phenomenon that
occurs when substrates come in contact with each other, where
substrates lock together and physically cannot be peeled apart,
similar to mat plating. Furthermore, increasing the film surface
hardness can prevent tin plating films from deforming when
substrates come in mutual contact, caused by the film surface being
soft such as with mat plating, and can minimize the occurrence of
tin plating films sticking together. Furthermore, the plating
solution of the present invention does not include a complexing
agent, so wastewater treatment is easier than with a convention
plating solution for barrel plating.
[0020] The abbreviations used in this specification have the
following meanings unless otherwise noted.
g=grams; mg=milligrams; .degree. C.=degrees Celsius; min=minutes;
m=meters; cm=centimeters; L=liters; mL=milliliters; A=amperes; and
dm.sup.2=square decimeters. All of the number ranges include the
boundary points, and can be combined in any arbitrary order. The
terms "plating solution" and "plating bath" used in this
specification have exactly the same meaning and are used
interchangeably.
[0021] The electrolytic tin plating solution of the present
invention is an electrolytic tin plating solution for chip
components, containing: (A) stannous ions, (B) acid, (C)
N,N-dipolyoxyalkylene-N-alkyl amine, amine oxide, or blend thereof,
and (D) an anti-sticking agent; wherein the pH is 1 or lower. The
components are described below in order.
[0022] (A) Stannous Ion
[0023] The plating bath of the present invention contains stannous
ions as an essential component. Stannous ions are bivalent tin
ions. Any compound that can provide stannous ions to the plating
bath can be used. Generally, the tin salt of an inorganic acid or
an organic acid is preferable. Examples of tin salts of inorganic
acids include the stannous salt of sulfuric acid or hydrochloric
acid; and examples of tin salts of organic acids include the
stannous salt of substituted or unsubstituted alkanesulfonic acids
or alkanolsulfonic acids, such as methanesulfonic acid,
ethane-sulfonic acid, propanesulfonic acid,
2-hydroxyethane-1-sulfonic acid, 2-hydroxypro-pane-1-sulfonic acid,
and 1-hydroxypropane-2-sulfonic acid, and the like. Particularly
preferable sources of stannous ions are stannous sulfate for salts
of inorganic acids and stannous methane-sulfonate for salts of
organic acids. The compounds which can provide these ions can be
used individually, or as a blend of 2 or more types.
[0024] The amount of stannous ion added to the plating bath is, for
example, between 1 g/L and 150 g/L, preferably between 5 g/L and 50
g/L, and more preferably between 8 g/L and 20 g/L.
[0025] (B) Acid
[0026] The acid can be any arbitrary acid that can adjust the pH to
1 or lower and can provide conductivity to the plating bath. The
acid can be any inorganic or organic acid. Examples of organic
acids include substituted or unsubstituted alkanesulfonic acids or
alkanolsulfonic acids, such as methanesulfonic acid, ethanesulfonic
acid, propanesulfonic acid, 2-hydroxyethane-1-sulfonic acid,
2-hydroxypropane-1-sulfonic acid, and 1-hydroxypropane-2-sulfonic
acid. Methanesulfonic acid is preferable. Examples of inorganic
acids include sulfuric acid and hydrochloric acid, and sulfuric
acid is preferable. These acids that can adjust the pH to 1 or
lower and can provide conductivity to the plating bath can be used
individually, or as a blend of 2 or more types.
[0027] The amount of acid in the plating bath solution is
preferably at least stoichiometically equivalent to the amount of
bivalent tin ions in the plating bath. The amount of free acid in
the plating bath is, for example, between 10 g/L and 500 g/L,
preferably between 30 g/L and 300 g/L, and more preferably between
50 g/L and 200 g/L.
[0028] (C) N,N-dipolyoxyalkylene-N-alkyl Amine or Amine Oxide
[0029] The plating bath of the present invention contains
N,N-dipolyoxyalkylene-N-alkyl amine, amine oxide, or blend thereof
as an essential component. The present inventors have evaluated
various nonionic surfactants, and have discovered that uniform
plating at the required plating film thickness can be achieved by
using N,N-dipolyoxyalkylene-N-alkyl amine or amine oxides which are
specific anionic surfactants.
[0030] N,N-dipolyoxyalkylene-N-alkyl amine is preferably a
polyoxypropylene polyoxyethylenealkylamine expressed by the
following General Formula (2).
##STR00004##
[0031] In the aforementioned formula, R represents a straight or
branched alkyl group with between 6 and 26 carbon atoms, and w, x,
y, and z each represent an integer between 0 and 30. However, the
sum of w, x, y, and z is not 0. Preferably, R represents a straight
chain alkyl group with between 8 and 18 carbon atoms, and the sum
of w, x, y, and z is between 10 and 20.
[0032] The amine oxide is one or more compound expressed by the
following General Formula (4).
##STR00005##
[0033] In the aforementioned formula, R.sup.1, R.sup.2, and R.sup.3
each represent an alkyl group, a cycloalkyl group, or an aryl
group, which may have a substitution group. Examples include a
methyl group, ethyl group, propyl group, butyl group, pentyl group,
hexyl group, phenyl group, tolyl group xylyl group and naphthyl
group, and the like.
[0034] In particular, the amine oxide of the present invention is
preferably one or more amine oxides with a structure as expressed
by General Formula (3).
##STR00006##
[0035] In the aforementioned formula, R represents an alkyl group,
cycloalkyl group or aryl group, and R' represents an alkyl group or
a cycloalkyl group.
[0036] N,N-dipolyoxyalkylene-N-alkyl amine or amine oxide can act
as a film modifying agent in the plating bath of the present
invention. In other words, smoothing the plating film with
N,N-dipolyoxyalkylene-N-alkyl amine or amine oxide can minimize the
sticking phenomenon where substrates lock together and physically
cannot be peeled apart, similar to mat plating, which occurs when
substrates come in contact with each other.
[0037] The concentration of N,N-dipolyoxyalkylene-N-alkyl amine or
amine oxide in the plating bath is suitably between 0.01 g/L and
100 g/L, preferably between 0.1 g/L and 50 g/L, and more preferably
between 1 g/L and 25 g/L.
[0038] (D) Anti-Sticking Agent
[0039] The plating bath of the present invention contains an
anti-sticking agent as an essential component. The anti-sticking
agent acts to prevent the plated chip components from agglomerating
(sticking) together in the plating bath of the present invention.
The anti-sticking agent is useful for preventing the chip
components from agglomerating together, or in other words,
preventing the chip components from sticking together, particularly
during barrel plating. Examples of anti-sticking agents include
aromatic aldehydes and aromatic ketones. Examples of preferable
anti-sticking agents include benzaldehyde and benzylidene acetone.
These compounds act to increase the film surface hardness in
particular. In other words, increasing the film surface hardness
can prevent tin plating films from deforming when substrates come
in mutual contact, which is caused by the film surface being soft
such as with mat plating, and can minimize the occurrence of tin
plating films sticking together.
[0040] The aforementioned preferable anti-sticking agents are
particular effective when used in combination with the
aforementioned (C) N,N-dipolyoxyalkylene-N-alkyl amine or amine
oxide. The concentration of anti-sticking agent in the plating bath
is suitably between 1 mg/L and 50 g/L, preferably between 5 mg/L
and 10 g/L, and more preferably between 10 mg/L and 5 g/L.
[0041] (E) Plating Uniformity Improver
[0042] The plating bath of the present invention preferably
contains a plating uniformity improver as an arbitrary component in
addition to the aforementioned components (A) through (D). The
plating uniformity improver of the present invention is a compound
that improves the plating uniformity particularly in areas of low
current density. With barrel plating in particular, the object to
be plated is placed in a barrel and electroplating is performed
while rotating the barrel with the parts immersed in the plating
solution, and therefore variation in the current density will
occur, the current density range of the object to be plated will
vary widely from a high current density region to a low current
density region, and in the low current density region, there will
be problems with lower plating uniformity, and therefore the
plating film will have variation. By adding a plating uniformity
improver, the plating can be uniformly performed even in the low
current density regions.
[0043] Examples of plating uniformity improvers include
2-naphthol-7-sulfonic acid and compounds (I) with the structural
formula shown below. 2-naphthol-7-sulfonic acid can be either in
the form of a free acid or as a salt. Suitable salts of
2-naphthol-7-sulfonic acid include water soluble salts such as
potassium, sodium, ammonium, and tin, or the like, but potassium
and sodium salts are preferable, and sodium 2-naphthol-7-sulfonate
is even more preferable. These salts can be used individually, or
as a blend of two or more types. As shown in patent document 2,
specific naphtholsulfonic acids where a sulfonic acid group is
bonded to a hydroxyl group in specific positions on a naphthalene
ring, and specifically 2-naphthol-7-sulfonic acid or alkali salt
thereof is remarkably more effective than other naphtholsulfonic
acids or salts thereof. Other positional isomers such as
2-naphthol-6-sulfonic acid and 1-naphthol-4-sulfonic acid have
almost no effect, and are not preferable.
##STR00007##
[0044] The amount of 2-naphthol-7-sulfonic acid or salt thereof
added to the plating bath is between 0.01 g/L and 20 g/L,
preferably between 0.1 g/L and 10 g/L, and more preferably between
0.2 g/L and 5 g/L.
[0045] On the other hand, if the aforementioned compound (I) is
used, the concentration used in the plating solution is suitably
between 0.1 mg/L and 10 g/L, preferably between 1 mg/L and 1 g/L,
and more preferably between 5 mg/L and 100 mg/L. These plating
uniformity improvers can be used individually or blended
together.
[0046] (F) Acrylic Acid or Acrylic Acid Derivative
[0047] The plating bath of the present invention preferably
contains one or more acrylic acid or acrylic acid derivative
expressed by the following General Formula (1) as an arbitrary
component. In particular, acrylic acid and methacrylic acid are
preferable.
##STR00008##
[0048] In the formula, R represents a hydrogen atom or an alkyl
group containing between 1 and 3 carbon atoms. The methacrylic acid
or acrylic acid is preferably added to the plating solution of the
present invention as an auxiliary anti-sticking agent that supports
the aforementioned (D) anti-sticking agent. The methacrylic acid or
acrylic acid can further increase the component anti-sticking
effect of the (D) anti-sticking agent, and in particular has the
effect of increasing the film surface hardness, and can increase
the sustainability of the anti-sticking effect, by being used in
combination with the (D) anti-sticking agent.
[0049] The amount of acrylic acid or acrylic acid derivative
expressed by the aforementioned General Formula (1) in the plating
solution is suitably such that the concentration is between 0.1 g/L
and 100 g/L, preferably between 0.1 g/L and 50 g/L, more preferably
between 0.5 g/L and 10 g/L.
[0050] (G) Antioxidant
[0051] An antioxidant can arbitrarily be used in the plating
solution of the present invention. The antioxidant is used to
prevent oxidation of the bivalent tin ions to tetravalent tin ions,
and examples include hydroquinone, catechol, resorcin,
phloroglucin, pyrogallol, hydroquinonesulfonic acid, and salts
thereof.
[0052] The concentration of antioxidant in the plating bath is
suitably between 10 mg/L and 100 g/L, preferably between 100 mg/L
and 50 g/L, more preferably between 0.5 g/L and 5 g/L.
[0053] Furthermore, other commonly known additives can be added to
the plating bath of the present invention, if necessary, such as
glossing agents, smoothing agents, conductivity agents, and anode
dissolving agents, and the like.
[0054] The order when adding the various components when making the
plating bath is not restricted in particular, but from the
perspective of safety, the acid is added after adding the water,
and after sufficiently mixing, the tin salt is added, and after
sufficiently mixing, the other required chemicals are added in
order.
[0055] Examples of the chip components that can be plated using the
plating solution of the present invention include electronic
components such as resistors, capacitors, inductors, variable
resistors, variable capacitors, and other passive components,
quartz oscillator, LC filter, ceramic filter, delay lines, SAW
filters, and other functional components, switches, connectors,
relay fuses, optical components, and other contact components.
[0056] Plating Method
[0057] The electroplating method that is used with the plating
solution of the present invention can be a commonly known plating
method such as barrel plating, and plating using a flow-through
plater, or the like. The concentration of the various components
(A) through (F) in the plating solution can be arbitrarily selected
based on the forgoing descriptions for each of the components.
[0058] The electroplating method that is used with the plating
solution of the present invention can be performed at a bath
temperature between 10.degree. C. and 50.degree. C., preferably
between 15.degree. C. and 30.degree. C.
[0059] Furthermore, the cathode current density is suitably
selected within a range between 0.01 and 5 A/dm.sup.2, preferably
between 0.05 and 3 A/dm.sup.2.
[0060] During the plating process, the plating bath may be left
without stirring, or can be stirred using a stirrer, or the like,
or re-circulated using a pump, or the like.
EXAMPLE 1
[0061] A bath was formed using the tin plating solution with the
following composition.
TABLE-US-00001 (A) Stannous methanesulfonate (as tin ion): 12 g/L
(B) (A) Methanesulfonic acid (as free acid): 50 g/L (C) Amine
oxide: oxirane, methyl-, polymer with oxirane, 10 g/L ether with
2,2'-(oxidoimino)bis[ethanol] (2:1) N-[3-(C9-11-
isoalkyloxy)propyl] derives (D) Benzylidene acetone: 0.4 g/L (E)
Methacrylic acid: 2 g/L (F) Sodium 2-naphthol-7-sulfonate: 0.5 g/L
(G) Potassium hydroquinonesulfonate: 2 g/L (H) Distilled water:
balance
[0062] Barrel tin plating was performed on chip resistors that had
been nickel plated using a 1 L tin plating solution at the
conditions shown below, and then various evaluations were
performed. The results are shown in Table 1.
[0063] Barrel Plating
Object for plating: chip resistor, barrel: Yamamoto minibarrel
(volume: 140 mL) Rotational speed: 20 rpm Nickel plating: 2.4 A--60
minutes Tin plating: 2 A--90 minutes Chip R resistor (size 1608):
4.7 k.OMEGA. 15 mL/barrel Steel ball: 1 mm o 30 mL/barrel
[0064] Evaluation Items
Plating Thickness
[0065] After barrel plating, the plating thickness on the front
surface, back surface, and on the left and right sides was measured
using a fluorescent light x-ray film thickness meter, and the
thickness and the plating thickness various between each point were
evaluated.
Coupling Rate
[0066] The barrel-plated chip components were sorted into chips
which were stuck together and chips that were not stuck together,
and the coupling rate was calculated as a ratio (%) with the weight
of chips that stuck together in the numerator and the weight of all
of the chips in the denominator (stuck chips/(stuck chips+unstuck
chips).times.100).
[0067] Solder Wetting Test
[0068] One liter of each of the plating solutions of the
embodiments and comparative examples were prepared, and tin
electroplating was performed for 90 minutes at a current of 2 A and
a bath temperature of 20.degree. C. Each of the tin plated films
obtained was subjected to humidity resistance testing at
105.degree. C. and 100% RH, for 8 hours, and then the solder
wetting properties of the humidity resistance tested plated films
were evaluated by measuring the zero cross time ("ZCT") using the
solder paste equilibrium method using a Multi Solderability Tester
SWET-2100 manufacturer by TARUTIN. The measurement conditions were
as shown below.
[0069] Zero Cross Time Measurement Conditions
Solder paste: Sn:Ag:Bi:Cu=96:2.5:1:0.5 Bath temperature:
245.degree. C. Immersion depth: 0.25 mm Immersion speed: 2 mm/sec
Immersion time: 8 sec
[0070] The zero cross time was measured and a value of 3.0 seconds
or less was considered a PASS. The pass rate was calculated as a
percentage using the number of samples with a zero cross time of 3
seconds or less in the numerator, and the total number of samples
measured (10 samples) in the denominator.
EXAMPLES 2 THROUGH 11 AND COMPARATIVE EXAMPLES 1 THROUGH 7
[0071] Tin plating baths were created at the ratios shown in Table
1 and Table 2 in a similar manner to Example 1, and the various
tests were performed similar to Example 1. The results are also
shown in Table 1 and Table 2. Note, the symbols related to the
evaluation of the plating thickness are as shown below.
[0072] Plating thickness is uniform on the front surface, back
surface, and on the left and right sides: O
Plating is not uniform: .DELTA. Plating is not formed: X
TABLE-US-00002 TABLE 1 (Values in the table are express in g/L.
However values for compound (I) are expressed as mg/L) Embodiment 1
2 3 4 5 6 7 8 9 10 11 Tin salt Tin methanesulfonate (as tin) 12 12
12 12 15 15 0 0 12 12 12 Stannous sulfate (as tin) 0 0 0 0 0 0 10
10 0 0 0 Acid Methanesulfonic acid 50 50 50 50 50 50 0 0 50 50 50
Sulfuric acid 0 0 0 0 0 0 50 50 0 0 0 Surfactant Amine oxide 10 1
10 5 5 5 15 15 0 0 10 N,N-dipolyoxyalkylene-N-alkyl 0 0 0 0 0 0 0 0
5 1 0 amine.sup.Note 1) Anti-sticking Benzylidene acetone 0.4 0.4
0.05 0.2 0.2 0.2 0 0 0.4 0.4 agent Benzaldehyde 0.4 Auxillary
Acrylic acid 0 0 0 0 0 0 5 2 0 0 0 anti-sticking agent Methacrylic
acid 2 2 2 2 2 2 0 0 2 2 2 Plating uniformity Sodium
2-naphthol-7-sulfonate 0.5 0.5 0.5 0.25 0.25 0.25 0 0 0.5 0.5 0.5
improver Compound (I) 0 0 0 0 10 15 20 20 0 0 0 Antioxidant
Potassium hydroquinone sulfonate 2 2 2 2 2 2 2 2 2 2 2 pH 1 or 1 or
1 or 1 or 1 or 1 or 1 or 1 or 1 or 1 or 1 or lower lower lower
lower lower lower lower lower lower lower lower Plating thickness
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle.
.largecircle. .largecircle. .largecircle. Coupling rate 0 0 0 0 0 0
0 0 0 0 0 ZCT (average) 2.5 2.7 2.2 2.1 2.8 2.8 2.3 2.9 2.8 2.6 2.5
sec sec sec sec sec sec sec sec sec sec sec Pass rate 100 100 100
100 100 100 100 100 100 100 100 .sup.Note
1)N,N-dipolyoxyalkylene-N-alkyl amine is expressed by the following
structural formula (2), and in the formula, w + x + y + z = 16.
##STR00009##
TABLE-US-00003 TABLE 2 (In the table, values are expressed as g/L)
Comparative Examples 1 2 3 4 5 6 7 Tin salt Tin methanesulfonate
(as tin) 12 12 12 0 12 12 12 Stannous sulfate (as tin) 0 0 0 10 0 0
0 Acid Methanesulfonic acid 50 50 50 0 50 50 50 Sulfuric acid 0 0 0
50 0 0 0 Surfactant Amine oxide 0 0 10 0 0 0 0 Surfactant
1.sup.Note 1 10 10 0 10 0 0 0 Surfactant 2.sup.Note 2 0 0 0 0 10 10
0 Surfactant 3.sup.Note 3 0 0 0 0 0 10 0 Surfactant 4.sup.Note 4 0
0 0 0 0 0 10 Anti-sticking agent Benylidene acetone 0.4 0.4 0 0.4
0.4 0.4 0.4 Glutaraldehyde 0 0 2 0 0 0 0 Auxiliary Methacrylic acid
2 2 2 2 2 2 2 anti-sticking agent Plating uniformity Sodium 0.5 0
0.5 0.5 0.5 0.5 0.5 improver 2-naphthol-7-sulfonate Compound (I) 0
0 0 0 0 0 0 Sodium 0 0.5 0 0 0 0 0 1-naphthol-6-sulfonate
Antioxidant Potassium 2 2 2 2 2 2 2 hydroquinonesulfonate pH 1 or 1
or 1 or 1 or 1 or 1 or 1 or lower lower lower lower lower lower
lower Plating thickness X X .DELTA. X X .largecircle. X Coupling
rate (%) 0 0 50 0 1 50 30 ZCT (average) 5 sec or 5 sec 5 sec or 5
sec or 5 sec 4.5 sec 4.5 sec more or more more more Pass rate (%) 0
0 0 0 0 10 10 .sup.Note 1)surfactant 1 is: In the formula, X.sup.I
through X.sup.III are approximately 13, Y.sup.I through Y.sup.III
are approximately 11, and the molecular weight is approximately
800. ##STR00010## .sup.Note 2)Surfactant 2 is: ##STR00011## R:
polyoxyalkene .sup.Note 3)Surfactant 3: polyoxyethylene allyl
phenyl ether .sup.Note 4)Surfactant 4: lauryl dimethyl betaine
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