JP3466824B2 - Tin-silver alloy plating bath - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tin-silver alloy electroplating bath, and in particular, to obtain a smooth and dense electrodeposit from a bath stabilized with a non-cyan complexing agent, nitrate ion and And / or a tin-silver alloy electroplating bath to which amine alcohols and / or oximes or sulfamic acids are added.

[0002]

2. Description of the Related Art Joining with a solder having a basic composition of tin-lead is widely used in the electronic industry as an indispensable technique. In order to perform soldering quickly and reliably, it is necessary to apply a film with good solderability to the parts to be soldered in advance.As this solderability film, a tin-lead alloy plating film is generally used. It's being used.
However, in recent years, there is concern about the effects of lead on health and the environment, and the idea of controlling tin-lead solder containing harmful lead is rapidly spreading. From the viewpoint of industrial production conditions and usage conditions, there is no lead-free solder that has characteristics that can substitute for tin-lead solder, and research and development is being conducted mainly in Japan, Europe and the United States. As a substitute for tin-lead solder, binary or multi-component alloys of tin and silver, bismuth, copper, indium, antimony, zinc, etc. are listed as candidates, and tin-silver alloy is also a promising alternative alloy of solder. Is one. In response to alternative solder, it is necessary to change the plating film for soldering to one that does not contain lead. On the contrary,
Although the plating bath for obtaining a tin-silver alloy plating film has silver as a main component for a long time, the non-cyan tin-silver alloy plating bath containing tin as a main component has not been industrially performed.
As a plating bath containing only silver, a cyan bath has been used for a long time. Although silver nitrate bath, sulfamic acid bath, silver chloride bath, thiocyanic acid bath, thiosulfuric acid bath, etc. have been studied in place of the cyanide bath, which is not preferable in terms of pollution prevention, silver complexing agents other than cyan have stability constants. Since it was small, the crystals of the precipitate were coarser than those in the cyan bath, and the performance was not satisfactory for industrial application. Recently, as a bath in which a precipitate of finer particles than these is obtained, a bath prepared by adding a sulfanilic acid derivative to a plating bath containing a silver salt of organic sulfonic acid and potassium iodide is disclosed in JP-A-2-290993. A bath containing succinimide or a derivative thereof as a complexing agent is disclosed in JP-A-7-16.
No. 6391, but the possibility of alloy plating with tin is not described.

[0003]

It has been known for a long time that tin-silver alloys can be obtained by electroplating, and it has been obtained from a cyan bath. However, the use of cyan is also effective for environmental hygiene, pollution and pollution. Not preferable from the viewpoint of poisonous and deleterious substance management. As a tin-silver alloy plating bath other than the cyan bath, 1
In 1997, Matsushita used a cyan-pyrophosphoric acid mixed bath (Metal surface technology 22 , 60 (1971)), and 1983.
In the year, Kubota et al. Obtained a tin-silver alloy coating from a pyrophosphoric acid bath (Metal Surface Technology 34 , 37 (1983)) as a non-cyan bath. However, these have been developed and researched mainly for the purpose of substituting for silver plating or improving the performance of silver plating, and are baths for obtaining a silver-tin alloy electroplating film containing silver as a main component, and tin is When it becomes the main component,
It was not possible to obtain smooth and dense plating. Tin
In the tin-silver alloy plating film as an alternative to lead solder, it is preferable that the silver content is as low as possible from the viewpoint of cost, as long as it contains silver in a sufficient ratio to suppress the generation of whiskers, it is generally It is considered that a composition having a content of 20% or less, particularly a composition centered on a eutectic composition of Sn-3.5% Ag will be used.

As a bath for obtaining a tin-silver alloy plating film having such a composition, potassium stannate has recently been used by Ise et al.
Silver Nitrate Bath (Surface Technology Association 93rd Lecture Meeting Preliminary Collection 20
5 (1996)), and by Arai et al.
Iodide Bath (Preliminary Collection of 93rd Lecture Meeting of Surface Technology Association 1
95 (1996)). However,
Since the former does not contain a complexing agent, silver is likely to be preferentially deposited, and in order to obtain a tin-silver plating film having a content of several%,
The silver ratio in the plating solution must be extremely low, and industrial operations are difficult to manage. Further, the latter is considered to be a more advanced bath than the former in terms of suppressing the preferential deposition of silver from the viewpoint of a complexing agent for silver ions, but it is involved in the electrodeposition reaction near the electrode surface and the metal Since it does not contain an additive that suppresses precipitation and refines the electrodeposited alloy crystals, the current density dependence of the alloy ratio in the electrodeposit is large, leaving a problem in this regard. At the same time, it is not a smooth and dense plating film having crystals that are sufficiently fine for industrial use.

The inventors have found a surfactant and an additive for obtaining a good plating film in order to solve the problem, and have already applied for a patent (Japanese Patent Application No. 8-1434).
No. 81) had a problem that when an object having a complicated shape was plated, the edge portion of the object was slightly lacking in smoothness.

[0006]

The inventor of the present invention comprises a complexing agent containing divalent tin ions and monovalent silver ions, and further for stably dissolving and retaining the divalent tin ions in a bath. As a solution containing one or more of pyrophosphate ion, gluconate ion, and citrate ion as a complexing agent for stably dissolving monovalent silver ion in a bath, and By adding one or more compounds selected from nitrate ions and / or amine alcohols and / or oximes or sulfamic acids, the smoothness of the plating film, especially the smoothness of the edge portion of the plating object. It has been found that the performance can be improved, and it is possible to put into practical use non-cyan tin-silver alloy plating that replaces tin-lead solder, which has environmental, sanitary, and pollution problems.
We have solved the alternative soldering problem.

SUMMARY OF THE INVENTION Namely, the present invention contains a divalent tin ions and monovalent silver ion, further pyrophosphate ions, gluconate ions, divalent one or more of citrate ion A solution containing a tin ion complexing agent and an iodine ion as a monovalent silver ion complexing agent was further added with a nitrate ion and / or the following general formula (I).

[Chemical 3] [Here, R ₁ , R ₂ and R ₃ are each independently hydrogen, a methyl group, an ethyl group or (CH ₂ ) _n- CH (R
₄ ) represents (OH), and at least one of R ₁ , R ₂ and R ₃ is (CH ₂ ) _n —CH (R ₄ ) (OH). R ₄ represents hydrogen or a methyl group, and n represents an integer of 1 or 2. ] And / or the following general formula (II)

[Chemical 4] [Here, R ₁ is a phenyl group, a pyridyl group, a styryl group, an alkyl group (C _{1 to} C ₅ ), an acyl group (C _{1 to} C 5
₅₎ or -C (CH ₃₎ = represents NOH, said phenyl group, hydrogen hydroxyl groups of a pyridyl group and styryl group, a carboxyl group, an aldehyde group, may be substituted with a methoxy group or a nitro group. R ₂ is hydrogen, an alkyl group (C _{1 to} C ₅ ), or φ-C (OH) H- (here, φ
Represents a phenyl group). X represents a hydroxyl group or a sulfonic acid group. ] The non-cyantin-silver alloy plating bath which adds 1 type, or 2 or more types of the compound selected from the oxime or sulfamic acid represented by these.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the non-cyan type tin-silver alloy electroplating bath of the present invention, any known divalent tin compound can be used, and examples thereof include tin oxide, tin sulfate, tin chloride, and tin chloride. Tin borofluoride, tin fluorosilicate, tin sulfamate, tin oxalate, tin tartarate, tin gluconate, tin sulfosuccinate, tin pyrophosphate, 1-hydroxyethane-1,1
-Tin bisphosphonate, tin tripolyphosphate or tin salt of aliphatic sulfonic acid represented by the general formulas (i) and (ii),
For example, tin methanesulfonate, tin methanedisulfonate, tin methanetrisulfonate, tin trifluoromethanesulfonate, or a tin salt of an aromatic sulfonic acid represented by the general formula (iii), such as tin phenolsulfonate and sulfobenzoic acid. Tin or the like can be used alone or in an appropriate mixture.

General formula (i)

[Chemical 5] [Wherein R represents a C ₁ -C ₅ alkyl group, X represents a hydrogen, a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, a carboxyl group or a sulfonic acid group, and at any position of the alkyl group. It may be present, and n is an integer of 0 to 3. ] General formula (ii)

[Chemical 6] [Here, R ₁ represents a C ₁ -C ₃ alkyl group, and R ₂
Represents a C ₁ -C ₃ alkylene group, the hydroxyl group may be at any position of the alkylene group, X represents halogen of chlorine and fluorine, and chlorine or fluorine substituted with hydrogen of the alkyl group and alkylene group. The number of substitutions is from 1 to a saturated substitution of all hydrogens coordinated to an alkyl group or an alkylene group, the number of substituted halogen species is one or two, and the substituent of chlorine or fluorine is arbitrary. Can be in position. Y represents hydrogen or a sulfonic acid group, and the substitution number of the sulfonic acid group represented by Y is in the range of 0 to 2. ] General formula (iii)

[Chemical 7] [Where X represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, an aldehyde group, a carboxyl group, a nitro group, a mercapto group, a sulfonic acid group or an amino group, or two Xs together with a benzene ring Can form a naphthalene ring, and m is an integer of 0 to 3. ].

The tin compound is used in an amount of 5 to 50 as tin.
g / l is suitable, preferably 10-30 g / l
The degree.

As the monovalent silver compound, any known compounds can be used, and examples thereof include silver oxide, silver nitrate, silver sulfate, silver chloride, silver bromide, silver iodide, silver benzoate, silver sulfamate, and citric acid. Acid silver, silver lactate, silver mercaptosuccinate, silver phosphate, silver trifluoroacetate, silver pyrophosphate, silver 1-hydroxyethane-1,1-bisphosphonate, or represented by the general formulas (i) and (ii) Aliphatic sulfonic acid silver salt,
For example, silver methanesulfonate, silver sulfosuccinate, silver trifluoromethanesulfonate, or a silver salt of an aromatic sulfonic acid represented by the general formula (iii), such as silver p-toluenesulfonate, silver sulfobenzoate, etc., alone or It can be used by appropriately mixing.

General formula (i)

[Chemical 8] [Wherein R represents a C ₁ -C ₅ alkyl group, X represents a hydrogen, a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, a carboxyl group or a sulfonic acid group, and at any position of the alkyl group. It may be present, and n is an integer of 0 to 3. ] General formula (ii)

[Chemical 9] [Here, R ₁ represents a C ₁ -C ₃ alkyl group, and R ₂
Represents a C ₁ -C ₃ alkylene group, the hydroxyl group may be at any position of the alkylene group, X represents halogen of chlorine and fluorine, and chlorine or fluorine substituted with hydrogen of the alkyl group and alkylene group. The number of substitutions is from 1 to a saturated substitution of all hydrogens coordinated to an alkyl group or an alkylene group, the number of substituted halogen species is one or two, and the substituent of chlorine or fluorine is arbitrary. Can be in position. Y represents hydrogen or a sulfonic acid group, and the substitution number of the sulfonic acid group represented by Y is in the range of 0 to 2. ] General formula (iii)

[Chemical 10] [Where X represents a hydroxyl group, an alkyl group, an aryl group, an alkylaryl group, an aldehyde group, a carboxyl group, a nitro group, a mercapto group, a sulfonic acid group or an amino group, or two Xs together with a benzene ring Can form a naphthalene ring, and m is an integer of 0 to 3. ].

The amount of silver compound used is 0.05 in terms of silver content.
Approximately 10 g / 1 is suitable, and preferably 0.1-5.
It is about g / l. However, when a tin-silver alloy plating film having a high silver content is to be obtained, the silver concentration is not limited to this, and the silver concentration can be about 50 g / l.

As the complexing agent for divalent tin ion, one or more of pyrophosphate ion, gluconate ion and citrate ion can be used alone or in admixture. Iodine ions are used as a complexing agent for monovalent silver ions. Any of known compounds can be used to supply the pyrophosphate ion, gluconate ion, or citrate ion, which is a complexing agent for tin ion, and an acid, an alkali metal salt, an ammonium salt, a tin salt, a silver salt, or the like can be used alone or as appropriate. It can be mixed and added. The amount of them used is appropriately selected according to the kind of the complexing agent, but is appropriately about 1 to 20 mol, preferably 2 to 1 mol of tin content in the bath.
It is about 15 mol. As for the supply of iodide ion which is a complexing agent for silver ion, any known one can be used, and alkali metal salt, ammonium salt, tin salt, silver salt, hydroiodic acid or the like can be used alone or in an appropriate mixture. Can be added. The amount used is 5 to 1 of silver ion.
000-fold is used, preferably 10-600-fold.

The electroplating bath of the present invention contains the above solution,
Furthermore, nitrate ions and / or the following general formula (I)

[Chemical 11] [Here, R ₁ , R ₂ , and R ₃ are each independently hydrogen, a methyl group, an ethyl group, or (CH ₂ ) _n- CH (R
₄ ) represents (OH), and at least one of R ₁ , R ₂ and R ₃ is (CH ₂ ) _n —CH (R ₄ ) (OH). R ₄ represents hydrogen or a methyl group, and n represents an integer of 1 or 2. ] And / or the following general formula (II)

[Chemical 12] [Here, R ₁ is a phenyl group, a pyridyl group, a styryl group, an alkyl group (C _{1 to} C ₅ ), an acyl group (C _{1 to} C 5
₅₎ or -C (CH ₃₎ = represents NOH, said phenyl group, hydrogen hydroxyl groups of a pyridyl group and styryl group, a carboxyl group, an aldehyde group, may be substituted with a methoxy group or a nitro group. R ₂ is hydrogen, an alkyl group (C _{1 to} C ₅ ), or φ-C (OH) H- (here, φ
Represents a phenyl group). X represents a hydroxyl group or a sulfonic acid group. ] A non-cyantin-silver alloy plating bath, characterized in that one or more compounds selected from oximes or sulfamic acids are added.

As the supply of nitrate ions, any known one can be used, and nitric acid, alkali metal salts, ammonium salts,
A silver salt or the like can be added alone or in an appropriate mixture. The amount used is 1 g / 1-200 as nitrate ion
g / l is used, preferably 3 g / 1 to 100 g / 1
To use. The amine alcohols are the same as those in (I) above.
Can be used, and specifically, N-methylethanolamine, 2-diethylaminoethanol, 3-diethylamino-1-propanol, 1- (dimethylamino) -2-propanol, 3- (dimethylamino)- Two
-Propanol, monoethanolamine, diethanolamine, triethanolamine and the like can be added alone or in an appropriate mixture. The amount used is 10 to 1000 times that of silver ions, preferably 30 times.
Use ~ 600 times. For both nitrate ion and amine alcohol, excessive addition exceeding the above range darkens the appearance of the precipitate, while when insufficient, it does not achieve the intended purpose of smoothing and densifying the precipitate at the edge part. . Further, with respect to nitrate ions, excessive use exceeding this range may cause a new problem of corroding the copper-based substrate. Further, as the oxime or sulfamic acid, those represented by the above formula (II) can be used, and specifically, benzaldehyde oxime, acetophenone oxime, salicylaldehyde oxime, benzoin-α-oxime, 2-pyridinecarbaldehyde oxime, Acetaldehyde oxime, propionaldehyde oxime, acetoxime, pyrvaldehyde-1-oxime, dimethylglyoxime, reaction product of benzaldehyde and sulfamic acid, reaction product of cinnamic aldehyde and sulfamic acid, etc., alone or in admixture as appropriate. You can The amount used is 0.005 to 5 g / l, more preferably 0.01 to 3 g / l. Excessive addition results in a kogation-like appearance, while insufficient addition does not achieve the intended purpose of smoothing and densifying the precipitates at the edges.

In the plating bath of the present invention, a conductive salt can be added in order to improve the electric conductivity of the plating solution and lower the bath voltage. As the conductive salt, known salts can be used, for example, potassium chloride, ammonium chloride and the like can be used alone or in an appropriate mixture. The amount of the conductive salt used is suitably about 5 to 50 g / l, preferably 10
~ 20 g / l is added.

Further, in the plating bath of the present invention, the pH of the bath is
A pH buffer can be added to reduce variability. As the buffer, a known one can be used, for example,
In the case of sodium, potassium and ammonium salts of phosphoric acid, acetic acid, boric acid and tartaric acid, and in the case of a polybasic acid, an acid salt containing hydrogen ions and the like can be used alone or in an appropriate mixture. The amount of pH buffer used is 5 to 50 g /
About 1 is suitable, and preferably about 10 to 20 g / l is added. Since the pH buffer is of course an electrolyte,
The addition of a buffer may serve as a conductive salt.

In the plating bath of the present invention, an antioxidant can be added in order to suppress natural oxidation of divalent tin ions. Known antioxidants can be used, and for example, resorcinol, pyrocatechol, hydroquinone, phlorogricinol, pyrogallol, hydrazine, ascorbic acid and the like can be used alone or in an appropriate mixture. The amount of the antioxidant used is appropriately about 0.05 to 50 g / l, and preferably 0.1 to 10 g / l is added. The concentration of each component of the plating bath of the present invention can be arbitrarily selected within the above range, corresponding to barrel plating, rack plating, continuous plating and the like.

[0020]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples, and the composition of the plating bath and the plating conditions are appropriately set in accordance with the above-mentioned object. It can be changed arbitrarily. As a comparative example, a tin-silver alloy plating bath having the following composition containing no amine alcohol or nitrate ion was prepared. The obtained bath was used for plating at a current density of 2.0 A / dm ² , a plating time of 5 minutes, and a temperature of 25 ° C. Sample is 0.3 × 30
A copper plate of 25 mm × 25 mm, buffed → benzine degreasing → electrolytic degreasing → water washing → 5% sulfuric acid immersion → water washing → tin-silver alloy plating →
Plating was performed in the steps of washing with water and drying to evaluate the appearance of the plating.

Comparative Example 1 Stannous chloride 0.195 mol / l Silver iodide 0.005 mol / l Potassium pyrophosphate 0.55 mol / l Potassium iodide 2.0 mol / l pH 9 Comparative Example 2 Chloride chloride Stannous 0.18 mol / l Silver iodide 0.02 mol / l Potassium pyrophosphate 0.55 mol / l Potassium iodide 2.0 mol / l pH 9 Comparative Example 3 Tin methanesulfonate 0.195 mol / l Silver iodide 0.005 mol / l Potassium pyrophosphate 0.6 mol / l Potassium iodide 2.0 mol / l Surfactant (dimethyl coconut oil alkyl betaine) 10 g / l pH 5

As an example, a tin-silver alloy plating bath having the following composition containing amine alcohol or / and nitrate ions was prepared. The plating conditions and process were the same as in the comparative example, and after plating, the appearance of the plating was evaluated.

Example 1 Tin methanesulfonate 0.195 mol / l Silver iodide 0.005 mol / l Potassium pyrophosphate 0.6 mol / l Potassium iodide 2.0 mol / l Triethanolamine 0.4 mol / L pH 5

Example 2 Tin sulfate 0.20 mol / l Silver sulfate 0.02 mol / l Potassium pyrophosphate 0.4 mol / l Potassium iodide 1.5 mol / l Potassium nitrate 20 g / l pH 4.5

Example 3 Tin chloride 0.15 mol / l Silver chloride 0.003 mol / l Sodium gluconate 0.9 mol / l Potassium iodide 1.5 mol / l Triethanolamine 0.15 mol / l Nitric acid 100 g / l pH 4.5

Example 4 Tin methanesulfonate 0.195 mol / l Silver iodide 0.005 mol / l Potassium pyrophosphate 0.6 mol / l Potassium iodide 2.0 mol / l Triethanolamine 0.39 mol / L ammonium nitrate 1 g / l salicylaldehyde oxime 0.01 g / l hydroquinone 0.05 g / l pH 5

Example 5 Tin pyrophosphate 0.30 mol / l Silver pyrophosphate 0.005 mol / l Potassium pyrophosphate 0.30 mol / l Potassium iodide 2.0 mol / l N-methylethanolamine 0.3 mol / l potassium nitrate 10 g / l salicylaldehyde oxime 3 g / l ascorbic acid 10 g / l pH 5

Example 6 Tin methanesulfonate 0.15 mol / l Silver methanesulfonate 0.005 mol / l Potassium citrate 0.6 mol / l Potassium iodide 1.0 mol / l 2-Diethylaminoethanol 0. 15 mol / l potassium nitrate 10 g / l potassium chloride 20 g / l pH 5

Example 7 Tin methanesulfonate 0.10 mol / l Silver methanesulfonate 0.001 mol / l Potassium pyrophosphate 1.0 mol / l Potassium iodide 0.8 mol / l Triethanolamine 0.6 mol / l sodium nitrate 1 g / l dihydrogen phosphate monosodium 10 g / l pH 5

The appearances of the plating films obtained from the plating baths of the above Comparative Examples and Examples were as follows. In Comparative Examples 1 and 2, a plating film having an off-white appearance was obtained at the center of the sample, but bump-like or needle-like precipitates were observed at the edge. In Comparative Example 3, the appearance of the central portion of the sample was superior to that of Comparative Examples 1 and 2 due to the addition of the surfactant, but the edge portion had a bump-like or needle-like shape as in Comparative Examples 1 and 2. -Like precipitates were observed. On the other hand, in the samples plated with the baths shown in Examples 1 to 6, no bump-shaped or needle-shaped deposits were observed even at the edge portion, and the entire surface of the plated object was excellent. It could be coated with a plating film.

[0031]

The tin-silver alloy plating bath according to the present invention comprises:
Compared with conventional baths, a smooth and dense tin-silver alloy plating film is obtained from a non-cyan bath over the entire surface of the object to be plated, including tin-silver, which replaces tin-lead solder. It is intended to provide a surface treatment applicable to solder.

Continuation of the front page (56) Reference JP-A-7-252684 (JP, A) JP-A-8-13185 (JP, A) JP-A-49-22342 (JP, A) JP-A-49-20035 (JP , A) JP-A-49-20036 (JP, A) JP-A-2-290993 (JP, A) JP-A-7-166391 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB) Name) C25D 3/56

Claims (4)

(57) [Claims] 1. A divalent tin ion containing a divalent tin ion and a monovalent silver ion, wherein one or more ions selected from pyrophosphate ion, gluconate ion and citrate ion are divalent tin ions. A solution containing iodine ions as a complexing agent for monovalent silver ions as a complexing agent is further added with nitrate ions and / or the following general formula (I): [Here, R ₁ , R ₂ and R ₃ are each independently hydrogen, a methyl group, an ethyl group or (CH ₂ ) _n- CH (R
₄ ) represents (OH), and at least one of R ₁ , R ₂ and R ₃ is (CH ₂ ) _n —CH (R ₄ ) (OH). R ₄ represents hydrogen or a methyl group, and n represents an integer of 1 or 2. ] And / or the following general formula (II): [Here, R ₁ is a phenyl group, a pyridyl group, a styryl group, an alkyl group (C _{1 to} C ₅ ), an acyl group (C _{1 to} C 5
₅₎ or -C (CH ₃₎ = represents NOH, said phenyl group, hydrogen hydroxyl groups of a pyridyl group and styryl group, a carboxyl group, an aldehyde group, may be substituted with a methoxy group or a nitro group. R ₂ is hydrogen, an alkyl group (C _{1 to} C ₅ ), or φ-C (OH) H- (here, φ
Represents a phenyl group). X represents a hydroxyl group or a sulfonic acid group. ] The non-cyan tin-silver alloy plating bath which adds 1 type (s) or 2 or more types of the compound selected from the oxime or sulfamic acid represented by these. 2. The non-cyan tin-silver alloy plating bath according to claim 1, further comprising a conductive salt. 3. The non-cyan tin-silver alloy plating bath according to claim 1, further comprising a pH buffering agent. 4. The non-cyan tin-silver alloy plating bath according to claim 1, further comprising an antioxidant.