JP4605359B2 - Lead-free acid tin-bismuth alloy electroplating bath - Google Patents

Description

  The present invention relates to acidic tin-bismuth alloy electroplating baths that are lead-free (thus, lead-containing tin-bismuth alloy plating baths such as tin-bismuth-lead alloy baths are excluded). By effectively preventing the precipitation of substitution, it is possible to suppress excessive consumption of bismuth in the plating bath and to stabilize the bath composition.

In recent years, there has been a concern about the influence of lead on the human body and the environment. Since pure tin plating may cause whisker, development of solder plating that does not contain lead is desired.
Tin-silver alloys and tin-bismuth alloys have been studied as lead-free solders. However, in the case of tin-silver alloy plating, the plating bath is easy to decompose, the bath stability is low, and the cost is high. Of the tin alloys, whiskers are relatively likely to occur.
In contrast, tin-bismuth alloys are attracting attention as leading candidates for lead-free solder in that whiskers are less likely to occur and costs can be reduced compared to tin-silver alloys.

Patent documents 1-5 are mentioned as conventional technology of the electroplating bath of the above-mentioned tin-bismuth system alloy.
Patent Document 1 contains a complexing agent composed of a predetermined aminocarboxylic acid such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), triethylenetetraminehexaacetic acid (TTHA), and gluconic acid, Is a tin-lead-bismuth alloy plating bath containing surfactants and / or brighteners such as polyoxyethylene laurylamine, polyoxyethylene alkylpropylene diamine (claims, column 5, lines 35 to 5). In column 6 line 8), Examples 1 to 7 describe a tin-lead-bismuth alloy plating bath containing DTPA and TTHA (pages 3 to 5).

The above Patent Document 2 is a tin-bismuth alloy plating bath using methanesulfonic acid at a specific concentration or more for the purpose of suppressing hydrolytic precipitation of bismuth, and chelated with nitrilotriacetic acid (NTA) or DTPA as a bismuth ion source. It is described that a bismuth compound can be used (see column 4, line 13 to line 15, column 8, line 15 to line 28, page 5).
In the examples of the document 2, there is no specific description using a bismuth compound chelated with NTA or DTPA.

  Patent Document 3 discloses that 2-mercaptobenzimidasol-S-methanesulfonic acid sodium salt is used for the purpose of easy formulation of a bath and improvement of film appearance and solderability in a wide current density range. It is a tin alloy plating bath containing a tin-bismuth alloy containing a specific benzoazole-based sulfonic acid compound (claims, paragraphs 1, 4, and 17), and the plating bath includes EDTA, DTPA, citric acid, It is described that a complexing agent such as gluconic acid can be contained (paragraph 41).

  The above Patent Document 4 contains a nonionic surfactant in the tin-copper ternary alloy for the purpose of eutecting tin with a high composition ratio together with a third component metal such as copper and bismuth. And a tin-copper-based alloy plating bath containing a tin-copper-bismuth alloy that can contain a complexing agent such as EDTA, NTA, DTPA, TTHA, citric acid, and gluconic acid (claims, paragraph 23, paragraph 36, paragraphs 40-41), Example 6 describes a tin-copper-bismuth alloy plating bath containing an amphoteric surfactant and NTA (paragraph 56).

  Patent Document 5 discloses a tin-bismuth alloy plating bath containing at least one kind of anionic, cationic and amphoteric surfactants together with a nonionic surfactant for the purpose of obtaining a dense and good film appearance. (Claims, paragraphs 1, 19).

Japanese Patent No. 2819180 Japanese Patent No. 2983548 Japanese Patent Laid-Open No. 10-25595 JP 2001-172791 A JP-A-8-260186

The above-mentioned Patent Document 1 is a tin-lead-bismuth alloy plating bath, which contains tin and bismuth, but is not a lead-free plating bath, and is intended to eliminate lead and contribute to environmental conservation. Contrary to
Moreover, in actual tin-bismuth alloy electroplating, tin or tin alloy is used for the anode from the viewpoint of productivity due to cost reduction. However, since the electrode potential of bismuth is noble with respect to tin, When the anode is immersed in a bath without current, tin is dissolved from the anode and bismuth is substituted and deposited on the anode surface. As bismuth consumption due to this substitution proceeds, the bismuth concentration in the plating bath decreases, the plating bath composition changes, the alloy composition of the electrodeposits changes, and the cost increases. Furthermore, when bismuth is substituted and deposited on the object to be plated, it also adversely affects the solder wettability and bonding strength of the electrodeposited film.

  The tin-bismuth alloy plating baths of Patent Documents 2 and 5 above, the tin alloy plating bath containing the tin-bismuth alloy of Patent Literature 3, or the tin-copper alloy plating bath containing the tin-copper-bismuth alloy of Patent Literature 4 In this case, the purpose is not to prevent substitution deposition of bismuth on the anode surface, and therefore the prevention function cannot be expected or very insufficient.

  The present invention relates to a technology for stabilizing a bath composition by effectively preventing substitution deposition of bismuth on the surface of tin or a tin alloy anode during plating in a lead-free acidic tin-bismuth alloy electroplating bath. Let it be an issue.

The inventors of the present invention have disclosed a group of compounds listed in the same row as stabilizers, complexing agents and the like in Patent Documents 1 to 5, for example, EDTA, NTA, DTPA, TTHA, and the like. As a result of intensive studies on the influence of bismuth on the surface and precipitation, among compounds belonging to aminocarboxylic acids, DTPA, TTHA, N, N-dicarboxymethyl-L-glutamic acid, N, N-dicarboxymethyl- It has been found that certain species such as L-alanine have a clear difference in the anti-substitution function compared to others.
That is, the aminocarboxylic acids of a specific type selected from DTPA, TTHA, N, N-dicarboxymethyl-L-glutamic acid, N, N-dicarboxymethyl-L-alanine and the like have a unique effect of preventing this substitutional precipitation. Large, showing significant advantages over other aminocarboxylic acids, stabilizing the bismuth composition of the plating bath, preventing displacement precipitation of bismuth, and improving bismuth by electroplating It was found that it is important to add these specific species in an appropriate range for electrodeposition. Furthermore, among the compounds belonging to polyphosphonic acids, phosphonopolycarboxylic acids or mercaptocarboxylic acids, specifics such as nitrilotris (methylenephosphonic acid), hydroxyethylaminodimethylenephosphonic acid, phosphonobutanetricarboxylic acid, mercaptosuccinic acid, etc. The seeds were found to be excellent in the function of preventing substitution of bismuth in the same manner as the above-mentioned specific kinds of aminocarboxylic acids, and the present invention was completed.

That is, the present invention 1 provides at least one acid selected from a soluble stannous salt, a soluble bismuth salt, an inorganic acid composed of hydrochloric acid, sulfuric acid, borohydrofluoric acid, an organic sulfonic acid, and an organic acid composed of a carboxylic acid. In an acidic tin-bismuth alloy electroplating bath containing
Diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid, N, N-dicarboxymethyl-L-glutamic acid, nitrilotris (methylenephosphonic acid), phosphonobutanetricarboxylic acid, hydroxyethylaminodimethylenephosphonic acid, Complexes selected from diethylenetriaminepentamethylenephosphonic acid, N, N-dicarboxymethyl-L-alanine, hydroxyethyliminodiacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, mercaptosuccinic acid, and salts thereof Lead-free acidic tin-, characterized in that at least one of the agents is added in an amount of 1.5 to 12 moles relative to bismuth ions to prevent displacement precipitation of bismuth on the anode surface made of tin or tin alloy Bismuth alloy A plating bath.

  The present invention 2 is characterized in that in the present invention 1, it further comprises at least one of a surfactant, a semi-gloss agent, a brightener, a smoothing agent, an auxiliary complexing agent, a hiding complexing agent and an antioxidant. This is a lead-free acidic tin-bismuth alloy electroplating bath.

In the present invention 3, when the anode and the cathode are immersed in a lead-free acidic tin-bismuth alloy plating bath, tin or tin alloy is used as an anode, and electroplating is performed using an object to be plated as a cathode,
Containing a soluble stannous salt, a soluble bismuth salt, and at least one acid selected from inorganic acids consisting of hydrochloric acid, sulfuric acid, borohydrofluoric acid, organic sulfonic acids, and organic acids consisting of carboxylic acids, Diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid, N, N-dicarboxymethyl-L-glutamic acid, nitrilotris (methylenephosphonic acid), phosphonobutanetricarboxylic acid, hydroxyethylaminodimethylenephosphonic acid, Complexes selected from diethylenetriaminepentamethylenephosphonic acid, N, N-dicarboxymethyl-L-alanine, hydroxyethyliminodiacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, mercaptosuccinic acid, and salts thereof At least of the agent Lead that is characterized in that a bismuth ion is prevented from being deposited on the anode surface by using a tin-bismuth alloy plating bath in which one kind is added in an amount of 1.5 to 12 moles per mole of bismuth ions. This is a free acidic tin-bismuth alloy electroplating method.

  The present invention 4 is an electronic component in which a lead-free acidic tin-bismuth alloy film is formed on a substrate using the acidic tin-bismuth alloy electroplating bath of the present invention 1 or 2.

In Patent Documents 1 to 6, compounds having complexing action such as various aminocarboxylic acids are listed, but as shown in the test examples described later, ordinary aminocarboxylic acids that are not appropriate selected species Even if it is contained in the plating bath, substitution deposition of bismuth on the surface of the tin or tin alloy anode cannot be effectively prevented.
Further, if the complexing agent of the present invention is not added to the bismuth ions at a predetermined concentration, substitutional precipitation of bismuth on the surface of the tin or tin alloy anode is effectively prevented, and bismuth is deposited on the object to be plated. The required amount cannot be electrodeposited. Incidentally, Patent Documents 1 to 6 have no quantitative disclosure of a complexing agent for bismuth ions, from the viewpoint of prevention of substitution deposition of the bismuth and good electrodeposition of bismuth on the object to be plated. There is no suggestion to the complexing agent concentration.
On the other hand, in the present invention, the tin-bismuth alloy bath is selected from DTPA, TTHA, N, N-dicarboxymethyl-L-alanine, N, N-dicarboxymethyl-L-glutamic acid, etc. Add specific amino carboxylic acids or specific polyphosphonic acids selected from nitrilotris (methylenephosphonic acid), phosphonobutane tricarboxylic acid, mercaptosuccinic acid, etc., phosphonopolycarboxylic acids or mercaptocarboxylic acids at a predetermined concentration Therefore, substitutional precipitation of bismuth on the anode surface made of tin or tin alloy can be effectively prevented. For this reason, during electroplating, excessive consumption of bismuth in the plating bath can be eliminated, and fluctuations in the plating bath composition can be suppressed and stabilized, so that there is no unevenness in color tone with excellent denseness and smoothness. A tin-bismuth alloy electrodeposition film having a good appearance can be obtained.
In addition, since the substitutional precipitation of bismuth on the anode surface can be effectively prevented, there is no need to clean the anode each time the plating operation is performed, and the plating operation can be simplified.

The present invention is primarily directed to DTPA, TTHA, N, N-dicarboxymethyl-L-glutamic acid, N, N-dicarboxymethyl-L-alanine, nitrilotris (methylenephosphonic acid), hydroxyethylaminodimethylenephosphone. It is a lead-free acidic tin-bismuth alloy electroplating bath containing a specific kind of aminocarboxylic acid selected from acids, mercaptosuccinic acid, etc., polyphosphonic acids, phosphonopolycarboxylic acids, and mercaptocarboxylic acids as a complexing agent. Second, there is a lead-free acidic tin-bismuth alloy electroplating method that prevents substitution deposition of bismuth on the anode surface by using this electroplating bath, and thirdly, by this plating bath. This is an electronic component in which a tin-bismuth alloy film is formed on the substrate.
In the lead-free acidic tin-bismuth alloy electroplating bath or plating method of the present invention, from the viewpoint of productivity, the anode is made of tin or a tin alloy instead of an insoluble material such as platinum (therefore, Prevention of substitutional precipitation of bismuth is a problem).

The tin-bismuth alloy that is the subject of the present invention is not limited to a binary alloy of tin-bismuth alloy, but tin-bismuth-silver alloy, tin-bismuth-copper alloy, tin-bismuth-indium alloy, tin-bismuth- Including ternary alloys such as zinc alloy, tin-bismuth-nickel alloy, tin-bismuth-cobalt alloy, tin-bismuth-antimony alloy, or other multi-component alloys containing tin and bismuth, but lead-free In addition, tin-bismuth-lead alloys are excluded.
In the plating bath, a metal source such as tin or bismuth is contained in an arbitrary form depending on the type of the bath as a metal compound that dissolves in acidic, neutral or alkaline water, and generally in the form of a soluble salt of the metal. Take.
Therefore, the basic composition of a tin-bismuth alloy electroplating bath (binary alloy bath) is described, which is composed of a soluble stannous salt, a soluble bismuth salt, and a base acid.
Examples of the soluble stannous salt include stannous salts of organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, p-phenolsulfonic acid, stannous borofluoride, sulfosuccinic acid Examples include stannous, stannous sulfate, stannous oxide, and stannous chloride.
Examples of the soluble bismuth salt include bismuth salts of the above organic sulfonic acids, bismuth salts of sulfosuccinic acid, bismuth sulfate, bismuth oxide, bismuth nitrate, bismuth chloride, and bismuth bromide.

Further, in the case of a ternary alloy electroplating bath such as tin-bismuth-silver alloy, each soluble salt such as silver, copper, and indium is further contained.
Examples of the soluble silver salt include silver sulfate, silver sulfite, silver carbonate, silver nitrate, silver oxide, silver sulfosuccinate, silver salts of the above organic sulfonic acids, silver citrate, silver tartrate, silver gluconate, silver oxalate, and the like. It is done.
Examples of the soluble copper compound include copper salts of the above organic sulfonic acids, copper sulfate, copper chloride, copper oxide, copper carbonate, copper acetate, copper pyrophosphate, and copper oxalate.
Examples of the soluble indium salt include indium sulfamate, indium sulfate, indium borofluoride, indium oxide, indium methanesulfonate, and indium 2-hydroxypropanesulfonate.
Examples of the soluble salt of zinc include zinc sulfate, zinc nitrate, zinc chloride, zinc pyrophosphate, zinc cyanide, zinc methanesulfonate, zinc 2-hydroxyethanesulfonate, and zinc 2-hydroxypropanesulfonate.
Examples of the soluble salt of nickel include nickel sulfate, nickel formate, nickel chloride, nickel sulfamate, nickel borofluoride, nickel acetate, nickel methanesulfonate, nickel 2-hydroxypropanesulfonate.
Examples of the soluble salt of cobalt include cobalt sulfate, cobalt chloride, cobalt acetate, cobalt borofluoride, cobalt methanesulfonate, and cobalt 2-hydroxypropanesulfonate.
Examples of the soluble salt of antimony include antimony borofluoride, antimony chloride, antimony potassium tartrate, potassium pyroantimonate, antimony tartrate, antimony methanesulfonate, and antimony 2-hydroxypropanesulfonate.
Each of the above-mentioned soluble metal salts can be used alone or in combination, and the total concentration of the soluble salt in the bath relative to the plating bath is 0.05 to 300 g / L, preferably 10 to 180 g / L in terms of metal salt. Moreover, the mixing ratio of tin and other metals is appropriately determined according to the desired composition ratio of the tin alloy plating film.
Specifically, the content of the soluble stannous salt is suitably 1 to 290 g / L, preferably 5 to 200 g / L.
Moreover, 0.05-50 g / L is suitable for content of soluble bismuth salt, Preferably it is 0.5-20 g / L.
The content of the soluble copper salt is suitably 0.01 to 30 g / L, preferably 0.05 to 5 g / L.
The content of the soluble silver salt is suitably 0.01 to 10 g / L, preferably 0.05 to 5 g / L.

  Examples of the base acid include organic acids such as organic sulfonic acid and aliphatic carboxylic acid, inorganic acids such as borofluoric acid, silicofluoric acid, sulfamic acid, hydrochloric acid, sulfuric acid, and perchloric acid, and salts thereof. Can also be used. These acids can be used singly or in combination, and the acid content is 5 to 400 g / L, preferably 20 to 300 g / L.

Among the above base acids, organic sulfonic acids are preferable from the viewpoint of solubility of tin and ease of wastewater treatment.
Examples of the organic sulfonic acid include alkane sulfonic acid, alkanol sulfonic acid, and aromatic sulfonic acid, and the alkane sulfonic acid is represented by a chemical formula C _n H _{2n + 1} SO ₃ H (for example, n = 1 to 11). Specifically, methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, Examples include decane sulfonic acid and dodecane sulfonic acid.

Examples of the alkanol sulfonic acid include chemical formula C _m H _{2m + 1} —CH (OH) —C _p H _2p —SO ₃ H (for example, m = 0 to 6, p = 1 to 5).
In particular, 2-hydroxyethane-1-sulfonic acid (isethionic acid), 2-hydroxypropane-1-sulfonic acid (2-propanolsulfonic acid), 2-hydroxybutane-1 -In addition to sulfonic acid, 2-hydroxypentane-1-sulfonic acid, etc., 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxy Examples include hexane-1-sulfonic acid.

The aromatic sulfonic acid is basically benzene sulfonic acid, alkyl benzene sulfonic acid, phenol sulfonic acid, naphthalene sulfonic acid, alkyl naphthalene sulfonic acid, naphthol sulfonic acid, etc., specifically, 1-naphthalene sulfonic acid, 2 -Naphthalenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, diphenylamine-4-sulfonic acid and the like.
Among the organic sulfonic acids, methanesulfonic acid, ethanesulfonic acid, 2-propanolsulfonic acid, 2-hydroxyethanesulfonic acid, phenolsulfonic acid, cresolsulfonic acid and the like are preferable.

As the aliphatic carboxylic acids can be used carboxylic acid C ₁ -C _6, specifically, acetic acid, propionic acid, acetic acid, citric acid, tartaric acid, gluconic acid, sulfosuccinic acid, such as trifluoroacetic acid.

The acidic tin-bismuth alloy-based electroplating bath of the present invention effectively prevents plating substitution deposition of bismuth on the surface of the tin or tin alloy anode, and forms a plating film having an excellent appearance by stabilizing the plating bath composition. Therefore, it is necessary to add a complexing agent selected from specific types of aminocarboxylic acids, polyphosphonic acids, phosphonopolycarboxylic acids or mercaptocarboxylic acids.
The specific types of aminocarboxylic acids, polyphosphonic acids, phosphonopolycarboxylic acids or mercaptocarboxylic acids are DTPA, TTHA, hydroxyethylethylenediaminetriacetic acid (HEDTA), N, N-dicarboxymethyl-L-glutamic acid, nitrilotris ( Methylenephosphonic acid), phosphonobutanetricarboxylic acid, hydroxyethylaminodimethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, N, N-dicarboxymethyl-L-alanine, hydroxyethyliminodiacetic acid, 1,3-diamino-2 -Hydroxypropanetetraacetic acid, mercapsuccinic acid, or salts thereof.
The complexing agent is in a specific range selected from compounds exhibiting a complexing action. For example, EDTA and NTA described in the patent document belong to the same aminocarboxylic acids as DTPA and TTHA. It deviates from the complexing agent of the present invention, and oxycarboxylic acids such as gluconic acid, tartaric acid and citric acid also deviate.
Examples of salts of the above-mentioned specific types of aminocarboxylic acid, polyphosphonic acid, phosphonopolycarboxylic acid or mercaptocarboxylic acid include salts such as sodium, potassium, magnesium, calcium, ammonium, triethylamine, monoethanolamine, diethanolamine, and triethanolamine. Can be mentioned.
The complexing agent can be used alone or in combination, but as described above, in order to prevent substitution deposition of bismuth on the surface of the tin or tin alloy anode and to deposit bismuth, the content of the complexing agent is: It is necessary to be 1.5 to 12 moles relative to bismuth ions. A preferable content is 2.5 to 10 times mol, more preferably 3.0 to 6 times mol for the bismuth ion. If the content of the complexing agent is less than 1.5 times mol, substitution deposition of bismuth on the anode surface cannot be effectively prevented. On the other hand, if the content is more than 12 times mol, bismuth is deposited smoothly when electroplating. Therefore, a tin-bismuth alloy plating film cannot be formed.

In addition, the above-mentioned specific types of aminocarboxylic acids, polyphosphonic acids, phosphonopolycarboxylic acids, or mercaptocarboxylic acids are added to the acidic tin-bismuth alloy electroplating bath, and further, a predetermined HLB or cloud point is obtained. Addition of at least one specific kind of nonionic surfactant promotes the effect of preventing substitution deposition of bismuth on the anode surface.
Specific types of nonionic surfactants having a predetermined HLB or cloud point are as follows (a) to (j).
(a) a distyrenated phenol polyalkoxylate having an HLB of 7.3 to 15.6
(b) Tristyrenated phenol polyalkoxylate having an HLB of 7.8 to 15.3
(c) a distyrenated cresol polyalkoxylate having an HLB of 8.2 to 15.6
(d) a tristyrenated cresol polyalkoxylate having an HLB of 7.7 to 15.2.
(e) dodecylamine polyalkoxylate having an HLB of 3.8 to 16.2.
(f) tetradecylamine polyalkoxylate having an HLB of 3.4 to 16.1
(g) Hexadecylamine polyalkoxylate having an HLB of 3.1 to 15.7
(h) Octadecylamine polyalkoxylate having an HLB of 2.8 to 15.3
(i) cis-9-octadecenylamine polyalkoxylate having an HLB of 2.8 to 15.4
(j) Polyalkoxylate of ethylenediamine having a cloud point of 15 ° C. to 30 ° C. The nonionic surfactants (a) to (j) are all alkylene oxide adducts, and the alkylene oxide to be added is C _{2 to} C ₄ Alkylene oxides are suitable, preferably ethylene oxide (EO) and / or propylene oxide (PO).

Generally, as the number of EO added increases, hydrophilicity increases and HLB increases, and as the number of PO added increases, lipophilicity increases and HLB decreases. Further, the HLB of polyoxyethylene alkyl ether can be usually expressed by HLB = E / 5 (E: weight fraction (%) of ethylene oxide). Therefore, in the nonionic surfactants (a) to (i), from the viewpoint of effectively ensuring an emulsifying action in an aqueous system, the addition number of EO and PO, or a styrene group, based on the above formula By adjusting the added number, the HLB of the predetermined area can be adjusted.
In addition, in the case of a nonionic surfactant, once the type is specified, it is not so difficult to obtain an equivalent product whose HLB is specified within a desired range from the manufacturer.
Therefore, specific examples for each of the specific species are listed individually. For example, distyrenated phenol polyethoxylate (EO4 mol) belongs to a specific region of HLB = 7.3 to 15.6, and distyrenated cresol polyethoxylate. (EO12 mol) belongs to a specific region of HLB = 8.2 to 15.6. In addition, dodecylamine polyethoxylate (EO 20 mol) belongs to a specific region of HLB = 3.8 to 16.2, and octadecylamine polyethoxylate (EO 10 mol) belongs to a specific region of HLB = 2.8 to 15.3. Belongs.

On the other hand, when the number of EO added increases, the cloud point becomes higher. When the EO chain is constant, the cloud point becomes lower when the lipophilic group such as PO becomes larger. Therefore, in the nonionic surfactant (j), Further, the low temperature solubility is ensured by appropriately adjusting the cloud point range by the addition number of hydrophilic EO and lipophilic PO. The surfactant (j) is preferably a compound represented by the following general formula (1).
H (B) _Y- (A) _X (A) _X- (B) _YH
｜ ｜
N—CH ₂ CH ₂ —N (1)
｜ ｜
H (B) _Y- (A) _X (A) _X- (B) _YH
(In the formula (1), A and B are either oxyethylene groups or oxypropylene groups; X and Y are each an integer of 1 to 100)
Specific examples of the compound belonging to the general formula (1) include ethylenediamine polypropoxylate (P050 mol) and polyethoxylate (EO5 mol). The cloud point of the compound is a specific value of 15 to 30 ° C. Belongs to the region.
By the way, when the type of nonionic surfactant is specified, it is not so difficult to obtain an equivalent product with a cloud point designated within a desired range from the manufacturer, as with the HLB. .
The nonionic surfactants (a) to (j) can be used singly or in combination, and the content relative to the plating bath is suitably 3 to 300% by weight, preferably 10 to 100% by weight of the bismuth amount.

In the present invention, the inclusion of the nonionic surfactant in the lead-free acidic tin-bismuth alloy electroplating bath contributes to promoting the prevention of bismuth substitution deposition at the anode. Other types of nonionic surfactants and surfactants such as amphoteric, anionic and cationic other than nonionic surfactants may coexist (see Invention 2).
When surfactants other than these specific types are added, it contributes to improving the appearance, denseness, smoothness, adhesion, and throwing power of the plating film.
As the surfactant, various surfactants such as nonionic, anionic, cationic, and amphoteric can be used singly or in combination, and the addition amount is preferably about 0.01 to 100 g / L with respect to the plating bath. About 0.1-50 g / L is preferable.

The nonionic surfactant, C ₁ -C ₂₀ alkanols, phenol, naphthol, styrenated phenol, styrenated cresol, cumylphenol, bisphenol, C ₁ -C ₂₅ alkyl phenol, C ₁ -C ₂₅ alkyl naphthol, C _{1 to} C ₂₅ alkoxylated phosphoric acid (salt), sorbitan ester, polyalkylene glycol, alkylene diamine, C _{1 to} C ₂₂ aliphatic amide, sulfonamide, phosphoric acid, polyhydric alcohol, glucoside, ethylene oxide (EO) and propylene An alkylene oxide adduct obtained by addition condensation of 2 to 300 mol of at least one alkylene oxide selected from oxides (PO).
Therefore, any of the above alkanols, phenols, naphthols and other EO single adducts, PO single adducts, or EO and PO coexisting adducts may be used. Specifically, α-naphthol or β-naphthol ethylene oxide adduct (that is, α-naphthol polyethoxylate or the like) is preferable.

Examples of the C _{1 to} C ₂₀ alkanol for addition condensation of the alkylene oxide include octanol, decanol, dodecanol, tetradecanol, hexadecanol, octadecanol, eicosanol, cis-9-octadecenol, docosanol and the like.

  Bisphenol A, bisphenol B, bisphenol F, etc. are mentioned as bisphenols which carry out addition condensation of the said alkylene oxide.

Examples of the C ₁ -C ₂₅ alkylphenol for addition condensation of the alkylene oxide include mono, di, or trialkyl substituted phenols such as p-butylphenol, p-isooctylphenol, p-nonylphenol, p-hexylphenol, 2,4- Examples include dibutylphenol, 2,4,6-tributylphenol, p-dodecylphenol, and p-octadecylphenol.

Examples of the alkyl group of the C ₁ -C ₂₅ alkyl naphthol for addition condensation of the alkylene oxide include methyl, ethyl, propyl, butyl, hexyl, octyl, decyl, dodecyl, octadecyl, etc., and can be located at any position of the naphthalene nucleus. Good.

The C ₁ -C ₂₅ alkoxylated phosphoric acid (salt) for addition condensation of the alkylene oxide is represented by the following general formula (a).
Ra · Rb · (MO) P = O (a)
(In the formula (a), Ra and Rb are the same or different C ₁ -C ₂₅ alkyl, provided that one is better even H .M represents H or an alkali metal.)

  As the sorbitan ester for addition condensation of the alkylene oxide, mono-, di- or triesterized 1,4-, 1,5- or 3,6-sorbitan, specifically, sorbitan monolaurate, sorbitan monopalmitate Sorbitan distearate, sorbitan dioleate, sorbitan mixed fatty acid ester and the like.

Examples of the C _{1 to} C ₂₂ aliphatic amide for addition condensation of alkylene oxide include amides such as propionic acid, butyric acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid.

Examples of the cationic surfactant include a quaternary ammonium salt represented by the following general formula (b) and a pyridinium salt represented by the following general formula (c).
_{(R 1 · R 2 · R} 3 · R 4 N) + · X - ... (b)
(In the formula (b), X is halogen, hydroxy, C ₁ -C ₅ alkanesulfonic acid or sulfuric acid, R ₁ , R ₂ and R ₃ are the same or different C ₁ -C ₂₀ alkyl, and R ₄ is C ₁ -C _{10 represents} alkyl or benzyl.)
R _6- (C ₆ H ₄ N-R ₅ ) ⁺ · X ⁻ (c)
(Wherein (in c), X is a halogen, hydroxy, C ₁ -C ₅ alkane sulfonic acid or sulfuric acid, R ₅ is C ₁ -C ₂₀ alkyl, R ₆ is H or C ₁ -C ₁₀ alkyl.)

  Examples of the cationic surfactant in the form of the salt include dodecyltrimethylammonium salt, octadecyltrimethylammonium salt, dodecyldimethylethylammonium salt, octadecyldimethylethylammonium salt, dimethylbenzyldodecylammonium salt, hexadecyldimethylbenzylammonium salt, Examples include octadecyldimethylbenzylammonium salt, trimethylbenzylammonium salt, triethylbenzylammonium salt, hexadecylpyridinium salt, dodecylpyridinium salt, dodecylamine acetate, octadecylamine acetate and the like.

Examples of the anionic surfactant include alkyl sulfates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl phenyl ether sulfates, alkyl benzene sulfonates, (mono, di, tri) alkyl naphthalene sulfonates, and the like. It is done.
Examples of the alkyl sulfate include sodium dodecyl sulfate and sodium cis-9-octadecenyl sulfate.
Examples of the polyoxyethylene alkyl ether sulfate include sodium polyoxyethylene (EO12) nonyl ether sulfate and sodium polyoxyethylene (EO15) dodecyl ether sulfate.
Examples of the polyoxyethylene alkylphenyl ether sulfate include polyoxyethylene (EO15) nonylphenyl ether sulfate.
Examples of the alkylbenzene sulfonate include sodium dodecylbenzenesulfonate.
Examples of the (mono, di, tri) alkyl naphthalene sulfonate include sodium dibutyl naphthalene sulfonate.

  Examples of the amphoteric surfactant include carboxybetaine, imidazoline betaine, sulfobetaine, and aminocarboxylic acids. Further, sulfated or sulfonated adducts of condensation products of ethylene oxide and / or propylene oxide with alkylamines or diamines can also be used.

  Representative carboxybetaines or imidazoline betaines include dodecyldimethylaminoacetic acid betaine, tetradecyldimethylaminoacetic acid betaine, octadecyldimethylaminoacetic acid betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, 2-undecyl-1-carboxymethyl-1 -Hydroxyethyl imidazolinium betaine, 2-octyl-1-carboxymethyl-1-carboxyethyl imidazolinium betaine, etc. are mentioned. Examples of sulfated or sulfonated adducts include sulfated adducts of ethoxylated alkylamines, sulfonated lauric acid derivative sodium salts, and the like.

  Examples of the sulfobetaines include coconut oil fatty acid amidopropyldimethylammonium-2-hydroxypropanesulfonic acid, N-cocoylmethyl taurine sodium, and N-palmitoylmethyl taurine sodium.

  Examples of the aminocarboxylic acids include dioctylaminoethylglycine, N-dodecylaminopropionic acid, and octyldi (aminoethyl) glycine sodium salt.

As shown in the present invention 2, the acidic tin-bismuth alloy electroplating bath further includes a semi-brightening agent, a brightening agent, a smoothing agent, an auxiliary complexing agent, a hiding complexing agent, an antioxidant, if necessary. Various additives such as an antifoaming agent can be contained.
The above-mentioned antioxidant is for the purpose of preventing the oxidation of Sn ^{2+ in} the bath. Ascorbic acid or a salt thereof, hydroquinone, catechol, resorcin, phloroglucin, cresolsulfonic acid or a salt thereof, phenolsulfonic acid or a salt thereof, catechol Examples include sulfonic acid or a salt thereof, hydroquinone sulfonic acid or a salt thereof, hydroxynaphthalene sulfonic acid or a salt thereof, and hydrazine.

Examples of the smoothing agent include β-naphthol, β-naphthol-6-sulfonic acid, β-naphthalenesulfonic acid, m-chlorobenzaldehyde, p-nitrobenzaldehyde, p-hydroxybenzaldehyde, (o-, p-) methoxybenzaldehyde, Vanillin, (2,4-, 2,6-) dichlorobenzaldehyde, (o-, p-) chlorobenzaldehyde, 1-naphthaldehyde, 2-naphthaldehyde, 2 (4) -hydroxy-1-naphthaldehyde, 2 ( 4) -Chloro-1-naphthaldehyde, 2 (3) -thiophenecarboxaldehyde, 2 (3) -furaldehyde, 3-indolecarboxaldehyde, salicylaldehyde, o-phthalaldehyde, formaldehyde, acetaldehyde, paraaldehyde, butyraldehyde , Isobutyraldehyde, propi Onaldehyde, n-valeraldehyde, acrolein, crotonaldehyde, glyoxal, aldol, succindialdehyde, capronaldehyde, isovaleraldehyde, allylaldehyde, glutaraldehyde, 1-benzylidene-7-heptanal, 2,4-hexadienal, Cinnamaldehyde, benzylcrotonaldehyde, amine-aldehyde condensate, mesityl oxide, isophorone, diacetyl, hexanedione-3,4, acetylacetone, 3-chlorobenzylideneacetone, sub.pyridylideneacetone, sub.furfuridineacetone, sub. Tenylideneacetone, 4- (1-naphthyl) -3-buten-2-one, 4- (2-furyl) -3-buten-2-one, 4- (2-thiophenyl) -3-butene-2- On, Kurkumi Benzylideneacetylacetone, benzalacetone, acetophenone, (2,4-3,4-) dichloroacetophenone, benzylideneacetophenone, 2-cinnamylthiophene, 2- (ω-benzoyl) vinylfuran, vinylphenylketone, acrylic acid, Methacrylic acid, ethacrylic acid, ethyl acrylate, methyl methacrylate, butyl methacrylate, crotonic acid, propylene-1,3-dicarboxylic acid, cinnamic acid, (o-, m-, p-) toluidine, (o-, p-) aminoaniline, aniline, (o-, p-) chloroaniline, (2,5-3,4-) chloromethylaniline, N-monomethylaniline, 4,4'-diaminodiphenylmethane, N-phenyl- (α-, β-) naphthylamine, methylbenztriazole, 1,2,3-triazine, 1,2,4-triazine 1,3,5-triazine, 1,2,3-benztriazine, imidazole, 2-vinylpyridine, indole, quinoline, reaction product of monoethanolamine and o-vanillin, polyvinyl alcohol, catechol, hydroquinone, resorcin, polyethylene Examples include imine, disodium ethylenediaminetetraacetate, and polyvinylpyrrolidone.
Gelatin, polypeptone, N- (3-hydroxybutylidene) -p-sulfanilic acid, N-butylidenesulfanilic acid, N-cinnamoylidenesulfanilic acid, 2,4-diamino-6- (2'-methylimidazolyl) (1 ′)) ethyl-1,3,5-triazine, 2,4-diamino-6- (2′-ethyl-4-methylimidazolyl (1 ′)) ethyl-1,3,5-triazine, 2, 4-Diamino-6- (2'-undecylimidazolyl (1 ')) ethyl-1,3,5-triazine, phenyl salicylate or benzothiazoles are also effective as a smoothing agent.
Examples of the benzothiazoles include benzothiazole, 2-methylbenzothiazole, 2-mercaptobenzothiazole, 2- (methylmercapto) benzothiazole, 2-aminobenzothiazole, 2-amino-6-methoxybenzothiazole, and 2-methyl. -5-chlorobenzothiazole, 2-hydroxybenzothiazole, 2-amino-6-methylbenzothiazole, 2-chlorobenzothiazole, 2,5-dimethylbenzothiazole, 6-nitro-2-mercaptobenzothiazole, 5-hydroxy -2-methylbenzothiazole, 2-benzothiazolethioacetic acid and the like.

  As the above-mentioned brightener or semi-brightener, there are some overlaps with the above-mentioned smoothing agent, but benzaldehyde, o-chlorobenzaldehyde, 2,4,6-trichlorobenzaldehyde, m-chlorobenzaldehyde, p-nitrobenzaldehyde, p-hydroxy. Benzaldehyde, furfural, 1-naphthaldehyde, 2-naphthaldehyde, 2-hydroxy-1-naphthaldehyde, 3-acenaphthaldehyde, benzylideneacetone, pyridideneacetone, furfurylideneacetone, cinnamaldehyde, anisaldehyde, salicylaldehyde, Various aldehydes such as crotonaldehyde, acrolein, glutaraldehyde, paraaldehyde, vanillin, triazine, imidazole, indole, quinoline, 2-vinylpyridine, aniline, phena Toroline, neocuproine, picolinic acid, thioureas, N- (3-hydroxybutylidene) -p-sulfanilic acid, N-butylidenesulfanilic acid, N-cinnamoylidenesulfanilic acid, 2,4-diamino-6- ( 2'-methylimidazolyl (1 ')) ethyl-1,3,5-triazine, 2,4-diamino-6- (2'-ethyl-4-methylimidazolyl (1')) ethyl-1,3,5 -Triazine, 2,4-diamino-6- (2'-undecylimidazolyl (1 ')) ethyl-1,3,5-triazine, phenyl salicylate, or benzothiazole, 2-mercaptobenzothiazole, 2- Methylbenzothiazole, 2-aminobenzothiazole, 2-amino-6-methoxybenzothiazole, 2-methyl-5-chlorobenzothiazole, 2-hydroxybenzothiazo 2, 2-amino-6-methylbenzothiazole, 2-chlorobenzothiazole, 2,5-dimethylbenzothiazole, 5-hydroxy-2-methylbenzothiazole, benzothiazoles such as 2-benzothiazolethioacetic acid, etc. It is done.

The complexing agent acts on bismuth to smoothly eutect tin with bismuth, and to stably promote the dissolution of metals other than bismuth, such as copper and silver, in a bath.
Specific examples of the complexing agent include gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptlactone, oxalic acid, malonic acid, succinic acid, glycolic acid, malic acid, tartaric acid, diglycolic acid, Examples thereof include lactic acid, salts thereof, ethylenediamine, EDTA, NTA, iminodiacetic acid (IDA), iminodipropionic acid (IDP), Rochelle salt, thiourea or derivatives thereof, and aliphatic sulfide compounds.

  Examples of the antifoaming agent include pluronic surfactants, higher aliphatic alcohols, acetylene alcohols and polyalkoxylates thereof.

In the plating bath of the present invention, the concentration of the various additives may be appropriately selected according to the method of use such as barrel plating, rack plating, high-speed continuous plating, rackless plating and the like.
When electroplating using the plating bath of the present invention, the bath temperature is preferably about 0 ° C. or higher, more preferably about 10 to 50 ° C. Cathode current density is preferably about 0.01~150A / dm ^2, about 0.1~30A / dm ² is more preferable.

  The present invention 3 is a method of electroplating using the lead-free acidic tin-bismuth alloy plating bath of the present invention 1 or 2, wherein the anode and the cathode are immersed in the tin-bismuth alloy plating bath, Alternatively, when electroplating is performed using a tin alloy as an anode and an object to be plated as a cathode, a surface of the anode is obtained by using a tin-bismuth alloy plating bath containing a complexing agent such as the specific type of aminocarboxylic acid as an essential component. This is a lead-free acidic tin-bismuth alloy electroplating method that prevents bismuth from being deposited by substitution.

The electroplating method using the acidic tin-bismuth alloy plating bath of the present invention can form a plating film with excellent solderability, particularly when an electrical component or an electronic component is to be plated. It is also useful because it is excellent.
There are no particular limitations on the electrical parts or electronic parts as the objects to be plated, but specific examples thereof include semiconductor devices, printed boards, flexible printed boards, film carriers, ICs, connectors, switches, resistors, variable resistors, capacitors. , Filters, inductors, thermistors, crystal resonators, lead wires, and the like (see Invention 4).
Moreover, there is no restriction | limiting in particular also about the film thickness of a plating film, Usually, about 1-20 micrometers is preferable.

Hereinafter, examples of the lead-free acidic tin-bismuth alloy electroplating bath of the present invention, bath compositions when electroplating using the plating bath, particularly observation test examples of bismuth concentration, and similarly when electroplating Examples of evaluation tests for prevention of bismuth substitution deposition on the anode surface will be sequentially described.
The present invention is not limited to the following examples and test examples, and it is needless to say that arbitrary modifications can be made within the scope of the technical idea of the present invention.

<< Example of tin-bismuth electric alloy plating bath >>
Among Examples 1 to 22 below, Example 3 is an example of a tin-bismuth-silver alloy plating bath, Example 5 is an example of a tin-bismuth-copper alloy plating bath, and all other examples are tin-bismuth alloys. It is an example of a gold plating bath. Example 6 is an example in which the complexing agent of the specific type of the present invention is used in combination, Example 3, Example 5, and Examples 12 to 13 are both the complexing agent of the specific type of the present invention and the complexing function other than the present invention. Examples of the combined use of certain compounds and other examples are all single use examples of the complexing agent of the specific type of the present invention. Example 21 is an example in which the complexing agent was added at the lower limit (1.5 times mole) of the appropriate concentration range with respect to bismuth ions.
On the other hand, Comparative Example 1 and Comparative Example 4 below are blank examples that do not use the specific type of complexing agent of the present invention, and Comparative Examples 2-3 and Comparative Examples 5-6 are aminocarboxylic acids other than the specific type of the present invention. In this example, EDTA, NTA and IDA, which are acids, are used as complexing agents, and Comparative Example 7 is an example in which oxycarboxylic acids having a complexing action other than the present invention are used. Comparative Example 8 is an example in which the specific type complexing agent of the present invention was added in less than the lower limit (1.5 times mole) of the proper concentration range of the present invention.
In the leftmost column of FIG. 1, the concentration of complexing agent with respect to bismuth ions in each example and comparative example (unit: times mole) is shown.

(1) Example 1
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Diethylenetriaminepentaacetic acid 9.4 g / L

(2) Example 2
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Diethylenetriaminepentaacetic acid / pentammonium salt 27.5 g / L

(3) Example 3
A tin-bismuth-silver alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Silver methanesulfonate (as Ag ⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L
Diethylenetriaminepentaacetic acid 37.6 g / L
3,6-dithia 1,8-octanediol 12g / L

(4) Example 4
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 40g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 8g / L
Methanesulfonic acid (as free acid) 120g / L
Triethylenetetramine hexaacetic acid 75.7 g / L

(5) Example 5
A tin-bismuth-copper alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺⁾ 20g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Copper methanesulfonate (as Cu ²⁺ ) 1g / L
Methanesulfonic acid (as free acid) 120g / L
Triethylenetetramine hexaacetic acid, hexapotassium salt 83.7 g / L
3,6-dithia 1,8-octanediol 15g / L
Bisphenol A polyethoxylate (EO15 mol) 2g / L
2-mercaptobenzothiazole 0.2 g / L

(6) Example 6
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 40g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 8g / L
Methanesulfonic acid (as free acid) 120g / L
Diethylenetriaminepentaacetic acid 45.2 g / L
Triethylenetetramine hexaacetic acid 37.9 g / L

(7) Example 7
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 60g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 12g / L
Methanesulfonic acid (as free acid) 130g / L
Diethylenetriaminepentaacetic acid 79.1 g / L
β-Naphthol polyethoxylate (EO10 mol) 5g / L

(8) Example 8
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 60g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 12g / L
Methanesulfonic acid (as free acid) 130g / L
Diethylenetriaminepentaacetic acid 79.1 g / L
Octylphenol polyethoxylate (EO15 mol) 5g / L

(9) Example 9
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 60g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 12g / L
Methanesulfonic acid (as free acid) 130g / L
Diethylenetriaminepentaacetic acid 79.1 g / L
Cumylphenol polyethoxylate (EO8mol) 5g / L

(10) Example 10
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 60g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 12g / L
Methanesulfonic acid (as free acid) 130g / L
Diethylenetriaminepentaacetic acid 79.1 g / L
Bisphenol A polyethoxylate (EO 17.5 mol) 12g / L
Naphthalenesulfonic acid 1g / L

(11) Example 11
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 60g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 12g / L
Methanesulfonic acid (as free acid) 130g / L
Diethylenetriaminepentaacetic acid 79.1 g / L
Polypropoxylate (PO50 mol)
-Polyethoxylate (EO8 mol) block copolymer 7g / L

(12) Example 12
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 40g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 8g / L
Methanesulfonic acid (as free acid) 120g / L
Diethylenetriaminepentaacetic acid 52.7g / L
Citric acid monohydrate 16.1 g / L

(13) Example 13
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 40g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 8g / L
Methanesulfonic acid (as free acid) 120g / L
Triethylenetetramine hexaacetic acid 66.3 g / L
Sodium gluconate 16.9g / L

(14) Example 14
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 60g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 12g / L
Methanesulfonic acid (as free acid) 130g / L
Diethylenetriaminepentaacetic acid 79.1 g / L
Nonylphenol polyethoxylate (EO15 mol) 5g / L
Hydroquinone 1g / L
Methacrylic acid 0.5g / L
Betaine dodecyldimethylaminoacetate 0.8g / L

(15) Example 15
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 60g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 12g / L
Methanesulfonic acid (as free acid) 130g / L
Diethylenetriaminepentaacetic acid 79.1 g / L
α-Naphthol polyethoxylate (EO12 mol) 5g / L
2-mercaptobenzothiazole 0.3 g / L
Acrylic acid 0.5g / L
Dodecyldimethylethylammonium chloride 0.2g / L

(16) Example 16
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Hydroxyethylethylenediaminetriacetic acid, trisodium salt 9.9 g / L

(17) Example 17
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
N, N-dicarboxymethyl-L-glutamic acid 10.1 g / L

(18) Example 18
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Phosphonobutanetricarboxylic acid 7.8 g / L

(19) Example 19
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Hydroxyethylaminodimethylenephosphonic acid 7.2g / L

(20) Example 20
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
N, N-dicarboxymethyl-L-alanine 5.9 g / L

(21) Example 21
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Diethylenetriaminepentaacetic acid 5.7 g / L

(22) Example 22
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Mercaptosuccinic acid 4.3g / L

(23) Comparative Example 1
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 9g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L

(24) Comparative Example 2
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 9g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L
Ethylenediaminetetraacetic acid disodium dihydrate 6.25g / L

(25) Comparative Example 3
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 9g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L
Nitrilotriacetic acid trisodium monohydrate 4.6 g / L

(26) Comparative Example 4
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 9g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L
Nonylphenol polyethoxylate (EO15 mol) 5g / L

(27) Comparative Example 5
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 9g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L
Ethylenediaminetetraacetic acid disodium dihydrate 8.9g / L

(28) Comparative Example 6
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 9g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L
Iminodiacetic acid 2.25g / L

(29) Comparative Example 7
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Stannous methanesulfonate (as Sn ²⁺ ) 9g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 1g / L
Methanesulfonic acid (as free acid) 100g / L
Citric acid monohydrate 3.6g / L

(30) Comparative Example 8
A tin-bismuth alloy electroplating bath was constructed with the following composition.
Tin methanesulfonate (as Sn ²⁺ ) 18g / L
Tin methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Diethylenetriaminepentaacetic acid 3.76 g / L

Then, the tin anode was immersed in each of the tin-bismuth alloy plating baths of Examples 1 to 22 and Comparative Examples 1 to 8, and the degree of prevention of substitution precipitation of bismuth on the tin anode and the stability of the plating bath composition were evaluated. A test was conducted.
<< Evaluation Test Example A of Substrate Deposition Prevention on Anode and Stability of Plating Bath Composition When Anode is Dipped in Plating Bath >>
After immersing a tin electrode plate (60 mm × 20 mm) in 100 mL of each of the tin-bismuth alloy plating baths of Examples 1 to 22 and Comparative Examples 1 to 8 heated to 50 ° C. without stirring for 2 hours, the appearance of the tin anode Was visually observed, and the bismuth concentration in the plating bath at the time point of 2 hours was measured by atomic absorption spectrometry and converted into a residual ratio relative to the initial bismuth concentration.
In addition, Example 11 was tested at a plating bath temperature of 25 ° C.

FIG. 1 shows the result.
According to FIG. 1, in Comparative Example 1 of the blank example that does not contain the complexing agent of the present invention, the tin anode was turned to black due to substitution deposition of bismuth. Similarly, in Comparative Example 4 of the blank example, substitution deposition of bismuth was It turned black over a wide part of the anode, and only a part of the anode retained the metallic luster.
Further, in Comparative Examples 2-3 (EDTA, NTA) and Comparative Examples 5-7 (EDTA, IDA, citric acids) to which aminocarboxylic acids or oxycarboxylic acids different from the specific type complexing agent of the present invention are added, A wide part of the anode maintained a metallic luster, but substitutional precipitation of bismuth was observed in part, and it turned black. The bismuth residual rate in the plating bath after 2 hours was only 23 to 27% in Comparative Example 1 and Comparative Example 4, confirming that bismuth was rapidly consumed by substitutional precipitation. Further, Comparative Examples 2 to 3 and Comparative Examples 5 to 7 remained at a residual rate of 41 to 61%. And although the specific kind of complexing agent of this invention was used, in the comparative example 8 whose content is less than 1.5 times mole with respect to bismuth ion, a part of anode surface was changed to black. This was confirmed by the fact that the residual bismuth was 68%.
On the other hand, in Examples 1 to 22 , substitutional precipitation of bismuth was well prevented, and the anode maintained the entire metallic luster of tin. This point is also supported by the fact that the bismuth residual rate in the plating bath after 2 hours in Examples 1 to 22 showed a high ratio of 74 to 95%.

More specifically for the Examples 1 22 to be excellent in ability to prevent DTPA and / or Examples 1 to 15 in a high residual ratio of bismuth the bath was added TTHA, substitution precipitation of bismuth in the anode Is recognized. HEDTA, N, N-dicarboxymethyl-L-glutamic acid, N, N-dicarboxymethyl-L-alanine, which is a specific type of aminocarboxylic acid other than DTPA and TTHA, or a specific type of phosphonopolycarboxylic acid Examples 16 to 20 and 22 to which phosphonobutanetricarboxylic acid such as acid or mercaptocarboxylic acid, mercaptosuccinic acid, and the like were added showed the bismuth residual rate according to Examples 1 to 15 described above, and the effect of preventing substitution precipitation of bismuth. Was confirmed to have worked effectively. In Example 21 where the concentration of the complexing agent with respect to bismuth ions was the lower limit (1.5 times mole) of the proper range of the present invention, the bismuth residual rate maintained a high level.
Thus, in the tin-bismuth binary alloy plating bath that occupies most of the examples, the bismuth residual rate in the bath can be kept high, and substitution precipitation of bismuth at the anode can be effectively prevented. As seen in the bismuth-silver alloy plating bath (Example 3) and the tin-bismuth-copper alloy plating bath (Example 5), even in the ternary alloy plating bath of tin and bismuth, the specific species of the present invention is used. It has been clarified that the addition of a complexing agent exhibits an excellent effect of preventing substitution precipitation of bismuth as supported by a high bismuth residual ratio of 93 to 94%.

As described above, when Examples 1 to 22 are compared with Comparative Example 1 or 4, in the tin-bismuth alloy electroplating bath, in order to effectively prevent substitution deposition of bismuth at the tin or tin alloy anode, the present invention is used. It has become clear that it is important to add certain complexing agents to the plating bath.
Furthermore, when comparing the Examples 1 22 Comparative Example 2-3 or relatively 5-7, be a compound with a complexing action, tin EDTA, NTA, IDA, citric acid - bismuth alloy electroplating bath When added to the above, the function of preventing displacement precipitation of bismuth at a tin or tin alloy anode cannot be sufficiently expected. Therefore, in order to effectively prevent the displacement precipitation, certain kinds of aminocarboxylic acids are used. It has become clear that it is necessary to select polyphosphonic acids, phosphonopolycarboxylic acids, or mercaptocarboxylic acids.
Furthermore, when Examples 1 to 22 are compared with Comparative Example 8, even when the specific type of complexing agent of the present invention is added to the plating bath, the complexing agent is not less than a specific concentration in order to prevent displacement precipitation on the tin anode. It became clear that it was necessary to use in.
As described above, in the examples containing a complexing agent such as a specific type of aminocarboxylic acid, even when the tin or tin alloy anode is immersed in the bath, substitution deposition of bismuth at the anode can be effectively prevented, and the plating bath The composition of can be stabilized. And when the tin-bismuth system alloy electroplating was performed using the plating bath of the said Example, the plating film of the outstanding external appearance was able to be obtained. This point will be described, for example, by using the above-mentioned Example 5 as a representative. The tin-bismuth alloy electrodeposition film obtained from the plating bath of Example 5 by electroplating is excellent in denseness, smoothness, etc. Excellent plating appearance with no unevenness was exhibited.

Next, an electrodeposition film obtained when electroplating is performed using a tin-bismuth alloy plating bath having a common composition of the plating bath excluding the complexing agent and having a different content of the complexing agent with respect to bismuth ions. The composition of was investigated.
<< Evaluation Test Example B for Composition of Electrodeposition Film Obtained from Bath by Electroplating When Concentration of Complexing Agent is Changed >>
First, as shown below, a tin-bismuth alloy electroplating bath in which only the content of the complexing agent for bismuth ions among the components of the plating bath was Xg / L was hypothesized. Then, the complexing agent concentration was specified within and outside the proper range of the present invention, and the following Example 23 and Comparative Example 9 were constructed.
Stannous methanesulfonate (as Sn ²⁺ ) 18g / L
Bismuth methanesulfonate (as Bi ³⁺ ) 0.5g / L
Methanesulfonic acid (as free acid) 120g / L
Distyrenated cresol polyethoxylate (HLB13.6) 4g / L
Nonylphenol polyethoxylate (HLB15) 4g / L
Sodium dipentylnaphthalenesulfonate 1g / L
Diethylenetriaminepentaacetic acid Xg / L
2-mercaptobenzothiazole 0.3 g / L
Hydroquinone 0.8g / L

(1) Example 23
A tin-bismuth alloy electroplating bath was constructed with the content (Xg / L) of the complexing agent in the virtual plating bath being 4.7 g / L. In this case, the concentration of the complexing agent was 5 times mol with respect to bismuth ions.

(2) Comparative Example 9
A tin-bismuth alloy electroplating bath was constructed with the complexing agent content of the virtual plating bath being 14.1 g / L. In this case, the concentration of the complexing agent was 15 times mol with respect to bismuth ions.

Therefore, electroplating was performed under the following conditions using the tin-bismuth alloy electroplating baths of Example 23 and Comparative Example 9, and the bismuth composition of the obtained electrodeposition coating was examined.
[Conditions for electroplating]
Cathode current density: 2 A / dm ²
Bath temperature: 25 ° C
Stirring: Cathode locker (1m / min)
Plating time: 10 minutes

As a result, the bismuth composition of the electrodeposition film obtained from the plating bath of Example 23 was 2.0% by weight, and the film exhibited a uniform mat-like dense appearance.
On the other hand, the bismuth composition of the electrodeposition film obtained from the bath of Comparative Example 9 was 0% by weight, a tin-bismuth alloy film could not be formed, and only a tin film was obtained.
In view of the above, in order to effectively prevent substitution deposition of bismuth on the tin or tin alloy anode, it is important to select a specific kind of complexing agent of the present invention. In order to deposit bismuth smoothly when electroplating is performed (to form a tin-bismuth-based alloy film), it is not sufficient to select this specific type of complexing agent. It was revealed that it was necessary to add the complexing agent in an inhibitory manner without exceeding a specific concentration.

Finally, in addition to the complexing agent of the present invention, when a specific kind of nonionic surfactant having the predetermined HLB or cloud point is added to the plating bath, the effect of preventing substitution precipitation of bismuth on the tin anode Was evaluated how it changed.
<< Evaluation Test Example C for Preventing Displacement Precipitation on the Anode when a Nonionic Surfactant of Specific Kind is Added in Combination >>
First, using Example 1 as a basic composition, a specific type of nonionic surfactant was added in combination, and new tin-bismuth alloy electroplating baths ( Examples 24 to 25 ) were respectively constructed.

(1) Example 24
A tin-bismuth electroalloy plating was constructed with the following composition.
Tin methanesulfonate (as Sn ²⁺ ) 18g / L
Tin methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Distyrenated cresol polyethoxylate (HLB 13.6 mol) 2g / L
Diethylenetriaminepentaacetic acid 11.3 g / L

(2) Example 25
A tin-bismuth electroalloy plating was constructed with the following composition.
Tin methanesulfonate (as Sn ²⁺ ) 18g / L
Tin methanesulfonate (as Bi ³⁺ ) 2g / L
Methanesulfonic acid (as free acid) 100g / L
Ethylenediamine polypropoxylate
-Polyethoxylate (cloud point: 18 ° C) 4g / L
Bisphenol A polyethoxylate (HLB15.5) 2g / L
Diethylenetriaminepentaacetic acid 11.3 g / L

Then, using each of the plating baths of Examples 24 to 25 , an immersion test of the tin anode in the plating bath (accordingly, the immersion time was 2 hours) under the same conditions as in the evaluation test A, the test of FIG. The result was obtained.
That is, the residual ratio of bismuth ions in the plating bath was 87% in Example 1 in which only the complexing agent was used, but Example 24 in which a specific kind of nonionic surfactant having a predetermined HLB was used in combination. It increased to 98%. The same high numerical value (98%) was also shown in Example 25 in which a specific kind of nonionic surfactant having a predetermined cloud point was used in combination. In Examples 24 to 25 , the anode appearance was entirely metallic because there was no bismuth substitution.
Therefore, in a tin-bismuth alloy electroplating bath, in addition to the complexing agent of the present invention, the addition of a specific type of nonionic surfactant further enhances the effect of preventing the precipitation of bismuth on the tin anode. It became clear.

First, the evaluation test results of the appearance of the tin anode and the bismuth residual rate of the bath when the tin anode was immersed in each tin-bismuth alloy plating bath of Examples 1 to 22 and Comparative Examples 1 to 8 for a predetermined time, Second, the same appearance and bismuth residual ratio when the tin anode is immersed in the baths of Examples 24 to 25 , in which the complexing agent of the present invention is added with a specific kind of nonionic surfactant having a predetermined HLB or cloud point. It is a chart which shows the evaluation test result.

Claims (4)

Acidic tin containing a soluble stannous salt, a soluble bismuth salt, and at least one acid selected from inorganic acids consisting of hydrochloric acid, sulfuric acid, borohydrofluoric acid, organic sulfonic acids, and organic acids consisting of carboxylic acids In bismuth alloy electroplating bath,
Diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, triethylenetetraminehexaacetic acid, N, N-dicarboxymethyl-L-glutamic acid, nitrilotris (methylenephosphonic acid), phosphonobutanetricarboxylic acid, hydroxyethylaminodimethylenephosphonic acid, Complexes selected from diethylenetriaminepentamethylenephosphonic acid, N, N-dicarboxymethyl-L-alanine, hydroxyethyliminodiacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, mercaptosuccinic acid, and salts thereof Lead-free acidic tin-, characterized in that at least one of the agents is added in an amount of 1.5 to 12 moles relative to bismuth ions to prevent displacement precipitation of bismuth on the anode surface made of tin or tin alloy Bismuth alloy Plating bath.   The lead-free acid according to claim 1, further comprising at least one of a surfactant, a semi-brightener, a brightener, a smoothing agent, an auxiliary complexing agent, a hiding complexing agent and an antioxidant. Tin-bismuth alloy electroplating bath. When an anode and a cathode are immersed in a lead-free acidic tin-bismuth alloy plating bath, and electroplating is performed using tin or a tin alloy as an anode and an object to be plated as a cathode, a soluble stannous salt and a soluble bismuth salt And at least one acid selected from inorganic acids consisting of hydrochloric acid, sulfuric acid, borohydrofluoric acid, organic sulfonic acids, and organic acids consisting of carboxylic acids, and diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid, Triethylenetetramine hexaacetic acid, N, N-dicarboxymethyl-L-glutamic acid, nitrilotris (methylenephosphonic acid), phosphonobutanetricarboxylic acid, hydroxyethylaminodimethylenephosphonic acid, diethylenetriaminepentamethylenephosphonic acid, N, N- Dicarboxymethyl At least one complexing agent selected from ru-L-alanine, hydroxyethyliminodiacetic acid, 1,3-diamino-2-hydroxypropanetetraacetic acid, mercaptosuccinic acid, and salts thereof is 1. A lead-free acidic tin-bismuth-based alloy electric characterized in that, by using a tin-bismuth-based alloy plating bath added 5 to 12 times in mole, bismuth is prevented from being deposited on the anode surface. Plating method.   An electronic component in which a lead-free acidic tin-bismuth-based alloy film is formed on a substrate using the acidic tin-bismuth-based alloy electroplating bath according to claim 1 or 2.

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