JP2017179515A - Plating solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tin or tin alloy plating solution that is excellent in uniform electrodeposition property and that suppresses, when a bump electrode or the like is formed, the generation of voids.SOLUTION: Provided is a plating solution containing (A) a soluble salt containing at least a stannous salt, (B) an acid selected from an organic acid and an inorganic acid or a salt thereof, and (C) an additive. The additive contains a quaternary ammonium salt, a surfactant and a crystal refining agent, the surfactant containing a nonionic surfactant having a predetermined structure, and furthermore the crystal refining agent containing a low molecular weight compound having a predetermined structure.SELECTED DRAWING: None

Description

  The present invention relates to a plating solution of tin or tin alloy that has excellent throwing power and suppresses generation of voids when a bump electrode or the like is formed.

  Conventionally, a lead-tin alloy solder plating solution comprising an aqueous solution containing at least one selected from acids and salts thereof, a soluble lead compound, a soluble tin compound, a nonionic surfactant and a formalin condensate of naphthalenesulfonic acid or a salt thereof Is disclosed (for example, see Patent Document 1). In this plating solution, a formalin condensate of naphthalenesulfonic acid or a salt thereof as an additive contains 0.02 to 1.50% by mass with respect to lead ions. Patent Document 1 states that even if plating is performed with this plating solution at a high current density, a lead-tin alloy protruding electrode having a small surface height variation, a smooth surface, and a small lead / tin composition ratio can be formed. Have been described.

  Further, (A) a soluble salt composed of any of a tin salt and a mixture of a tin salt and a predetermined metal salt such as silver, copper, bismuth, lead, etc., (B) an acid or a salt thereof, and (C) a specific A tin or tin alloy plating bath containing a phenanthrolinedione compound is disclosed (for example, see Patent Document 2). In Patent Document 2, since this plating bath contains a specific phenanthrolinedione compound as an additive, the plating bath can have excellent uniform electrodeposition and a good film appearance in a wide range of current densities. It is described that a uniform synthetic composition can be obtained in the current density region.

  Furthermore, a tin plating solution containing a tin ion source, at least one nonionic surfactant, and imidazoline dicarboxylate and 1,10-phenanthroline as additives is disclosed (for example, see Patent Document 3). ). Patent Document 3 states that this tin plating solution does not cause discoloration even in the plating of highly complicated printed circuit boards, has excellent uniformity of in-plane film thickness distribution, and excellent uniformity of through-hole plating. Has been.

JP 2005-290505 A (Claim 1, paragraph [0004]) Japanese Patent Laying-Open No. 2013-044001 (Summary, paragraph [0010]) JP 2012-087393 A (Abstract, paragraph [0006])

  Although the conventional electrodeposition described in the above-mentioned Patent Documents 1 to 3 has improved the uniform electrodeposition of the plating solution of tin or tin alloy, in recent years, the demand for the quality of the plating film has increased, and the uniformity has further increased. There is a need for improved electrodeposition. In addition, when a bump electrode provided on a substrate for connecting a semiconductor device in flip chip mounting is formed by a plating method, a void called a void may be formed inside the bump after the reflow process. If voids are formed inside the bumps, there is a risk of poor bonding, and there is a need to suppress this. However, there is a contradictory relationship between improving the throwing power and suppressing the generation of voids. That is, the throwing power is improved by increasing the polarization resistance of the electrode surface, while the generation of voids is suppressed by reducing the overvoltage of the cathode. In recent years, additives for plating solutions that satisfy both characteristics have been demanded.

  An object of the present invention is to provide a tin or tin alloy plating solution that is excellent in throwing power and suppresses generation of voids when a bump electrode or the like is formed.

  A first aspect of the present invention is (A) a soluble salt containing at least a stannous salt, (B) an acid selected from organic acids and inorganic acids or salts thereof, and (C) a plating solution containing an additive. The additive includes a quaternary ammonium salt, a surfactant, and a crystal refining agent, the surfactant includes a nonionic surfactant represented by the following formula (1), and the crystal refining agent is It includes a low molecular compound represented by the following formula (2).

但し、式（１）中、Ｒ₁、Ｒ₂は、下記の式（Ａ）で示される基であり、 Ｙ₁、Ｙ₂は、単結合、−Ｏ−、−ＣＯＯ−及び−ＣＯＮＨ−から選ばれる基であり、 Ｚはベンゼン環又は２，２−ジフェニルプロパンを表す。

In the formula _{(1), R 1, R} 2 is a group represented by the following formula _{(A), Y 1, Y} 2 is a single bond, -O -, - COO- and from -CONH- And Z represents a benzene ring or 2,2-diphenylpropane.

但し、式（Ａ）中、ｎは２又は３を示す。ｍは１〜１５の整数を示す。

However, in formula (A), n represents 2 or 3. m shows the integer of 1-15.

但し、式（２）中、Ｒ₃は水素、ハロゲン原子、置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基、Ｃ₂−Ｃ₂₀アルケニル基、Ｃ₄−Ｃ₂₀ジエニル基、Ｃ₃−Ｃ₂₀シクロアルキル基、Ｃ₃−Ｃ₂₀シクロアルケニル基及びＣ₄−Ｃ₂₀シクロジエニル基並びに式−ＮＲ₇Ｒ₈（式中Ｒ₇、Ｒ₈はそれぞれ独立に水素又は置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基である）で表されるアミノ基からなる群より選択され、Ｒ₄〜Ｒ₆はそれぞれ独立に、水素、ハロゲン原子、置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基、Ｃ₂−Ｃ₂₀アルケニル基、Ｃ₄−Ｃ₂₀ジエニル基、Ｃ₃−Ｃ₂₀シクロアルキル基、Ｃ₃−Ｃ₂₀シクロアルケニル基及びＣ₄−Ｃ₂₀シクロジエニル基からなる群より選択され、Ｒ₄とＲ₆又はＲ₃とＲ₅は結合して環を形成してもよく、形成された環は１以上の二重結合を有していてもよく、ここでＲ₃が上記式−ＮＲ₇Ｒ₈で表されるアミノ基である場合に上記環はＲ₇若しくはＲ₈がＲ₅と結合した複素環であり、またＲ₃が置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基、Ｃ₂−Ｃ₂₀アルケニル基又はＣ₄−Ｃ₂₀ジエニル基の場合に上記環は、カルボニル炭素とＲ₃の間に１つの酸素原子を有する複素環であってもよい。

In the formula (2), R ₃ is hydrogen, halogen atom, substituted or unsubstituted C ₁ -C ₂₀ alkyl group, C ₂ -C ₂₀ alkenyl group, C ₄ -C ₂₀ dienyl groups, C ₃ -C ₂₀ A cycloalkyl group, a C ₃ -C ₂₀ cycloalkenyl group and a C ₄ -C ₂₀ cyclodienyl group and a formula —NR ₇ R ₈ (wherein R ₇ and R ₈ are each independently hydrogen or substituted or unsubstituted C ₁ -C is selected from the group consisting of amino group represented by a is) ₂₀ alkyl group, the R ₄ to R ₆ are each independently, hydrogen, halogen atom, substituted or unsubstituted C ₁ -C ₂₀ alkyl group, C ₂ - C ₂₀ alkenyl group, C ₄ -C ₂₀ dienyl groups, C ₃ -C ₂₀ cycloalkyl group, it is selected from the group consisting of C ₃ -C ₂₀ cycloalkenyl group, and C ₄ -C ₂₀ cyclodienyl group, R ₄ and R ₆ or R ₃ and R ₅ may form a ring, form Been ring may have one or more double bonds, wherein said ring when R ₃ is an amino group represented by the formula -NR ₇ R ₈ is R ₇ or R ₈ is R ₅ and a bound heterocycles, also the ring in the case of R ₃ is substituted or unsubstituted C ₁ -C ₂₀ alkyl radical, C ₂ -C ₂₀ alkenyl or C ₄ -C ₂₀ dienyl groups, carbonyl carbon And a heterocycle having one oxygen atom between R ₃ and R ₃ .

  A second aspect of the present invention is an invention based on the first aspect, wherein the additive further includes at least one of a complexing agent or an antioxidant.

  The plating solution of the first aspect of the present invention includes (A) a soluble salt containing at least a stannous salt, (B) an acid selected from organic acids and inorganic acids or salts thereof, and (C) an additive. The additive includes a quaternary ammonium salt, a surfactant, and a crystal refining agent, and the surfactant includes the nonionic surfactant represented by the general formula (1), and crystal The finer includes a low molecular compound represented by the general formula (2). Thus, by including the quaternary ammonium salt, the surfactant having a specific structure, and the crystal refining agent having a specific structure as essential components, uniform electrodeposition can be achieved over a wide current density range. Can be remarkably improved. In addition, it is possible to form a highly reliable plating film with a good appearance and very few voids. As a result, a high-quality product that can cope with a narrow pitch or a complicated wiring pattern can be manufactured.

  In the plating solution according to the second aspect of the present invention, the following effects can be obtained by further including at least one of a complexing agent or an antioxidant as an additive. By including the complexing agent, in particular, in a plating solution containing a noble metal such as silver, noble metal ions and the like are stabilized in the bath, and the precipitated alloy composition is easily uniformized. Moreover, oxidation to the stannic salt of soluble stannous salt is prevented by containing antioxidant.

  Next, the form for implementing this invention is demonstrated.

  The plating solution of the present invention is a plating solution of tin or a tin alloy, (A) a soluble salt containing at least a stannous salt, (B) an acid selected from an organic acid and an inorganic acid or a salt thereof, (C ) Contains additives.

<Soluble salt (A)>
The soluble salt (A) comprises any one of a stannous salt and a mixture of the stannous salt and a metal salt selected from the group consisting of silver, copper, bismuth, nickel, antimony, indium, and zinc. . The tin alloy constituting the plating film is an alloy of tin and a predetermined metal selected from silver, copper, bismuth, nickel, antimony, indium, and zinc. For example, tin-silver alloy, tin-copper alloy, tin -Binary alloys such as bismuth alloy, tin-nickel alloy, tin-antimony alloy, tin-indium alloy or tin-zinc alloy, and ternary alloys such as tin-copper-bismuth, tin-copper-silver alloy .

Therefore, the above-mentioned soluble salts contained in the plating solution are Sn ²⁺ , Ag ⁺ , Cu ⁺ , Cu ²⁺ , Bi ³⁺ , Ni ²⁺ , Sb ³⁺ , In ³⁺ , Zn ^{2 in the} plating solution. Meaning any soluble salt producing various metal ions such as ⁺ , for example, the metal salt of the metal oxide, halide, inorganic acid or organic acid.

  Examples of metal oxides include stannous oxide, copper oxide, nickel oxide, bismuth oxide, antimony oxide, indium oxide, and zinc oxide. Metal halides include stannous chloride, bismuth chloride, and bromide. Examples thereof include bismuth, cuprous chloride, cupric chloride, nickel chloride, antimony chloride, indium chloride, and zinc chloride.

  Metal salts of inorganic or organic acids include copper sulfate, stannous sulfate, bismuth sulfate, nickel sulfate, antimony sulfate, bismuth nitrate, silver nitrate, copper nitrate, antimony nitrate, indium nitrate, nickel nitrate, zinc nitrate, copper acetate , Nickel acetate, nickel carbonate, sodium stannate, stannous borofluoride, stannous methanesulfonate, silver methanesulfonate, copper methanesulfonate, bismuth methanesulfonate, nickel methanesulfonate, indium metasulfonate, bismethane Examples include zinc sulfonate, stannous ethanesulfonate, and bismuth 2-hydroxypropanesulfonate.

  The soluble salt (A) can be used alone or in combination, and the content in the plating solution is preferably 30 to 100 g / L. When there is too little content of soluble salt (A), productivity may fall. On the other hand, if the content of the soluble salt (A) is too large, the cost of the plating solution may increase. Among these, it is especially preferable that content of soluble salt (A) is 40-60 g / L. The content (addition concentration) of each component in the plating solution includes plating methods such as barrel plating, rack plating, high-speed continuous plating, rackless plating, and bump plating, including components other than the soluble salt (A) described below. It will be arbitrarily adjusted and selected according to the situation.

<Acid or its salt (B)>
The acid or salt (B) is selected from organic acids and inorganic acids, or salts thereof. Examples of the organic acid include organic sulfonic acids such as alkane sulfonic acid, alkanol sulfonic acid, and aromatic sulfonic acid, and aliphatic carboxylic acids. Inorganic acids include borohydrofluoric acid, silicofluoric acid, and sulfamine. Examples include acid, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid and the like. The salts are alkali metal salts, alkaline earth metal salts, ammonium salts, amine salts, sulfonates, and the like. The component (B) is preferably an organic sulfonic acid from the viewpoint of the solubility of the metal salt and the ease of wastewater treatment.

As the alkane sulfonic acid, those represented by the chemical formula C _n H _{2n + 1} SO ₃ H (for example, n = 1 to 5, preferably 1 to 3) can be used. Specifically, methanesulfonic acid, ethane In addition to sulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid and the like, hexanesulfonic acid, decanesulfonic acid, dodecanesulfonic acid and the like can be mentioned.

As the alkanol sulfonic acid, the formula _{C m H 2m + 1 -CH (} OH) -C p H 2p -SO 3 H ( e.g., m = 0~6, p = 1~5 ) represented by those can be used in Specifically, in addition to 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, etc. -Hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, 2 -Hydroxydodecane-1-sulfonic acid and the like.

  The aromatic sulfonic acid is basically benzene sulfonic acid, alkylbenzene sulfonic acid, phenol sulfonic acid, naphthalene sulfonic acid, alkyl naphthalene sulfonic acid, etc., specifically, 1-naphthalene sulfonic acid, 2-naphthalene. Examples include sulfonic acid, toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, diphenylamine-4-sulfonic acid, and the like.

  Examples of the aliphatic carboxylic acid include acetic acid, propionic acid, butyric acid, citric acid, tartaric acid, gluconic acid, sulfosuccinic acid, and trifluoroacetic acid.

  These acids or salts (B) thereof can be used alone or in combination, and the content in the plating solution is preferably 80 to 300 g / L. When there is too little content of an acid or its salt (B), electrical conductivity may be low and a voltage may rise. On the other hand, if the content of the acid or its salt (B) is too large, the viscosity of the plating solution may increase and the stirring rate of the plating solution may decrease. Among these, it is especially preferable that content of an acid or its salt (B) is 100-200 g / L.

<Additive (C)>
The additive (C) contains a quaternary ammonium salt, a surfactant, and a crystal refining agent as essential components, and may further contain a complexing agent or an antioxidant.

  Although it does not specifically limit as a quaternary ammonium salt, For example, cetyltrimethylammonium hydroxide, tetrabutylammonium hydroxide, tris (2-hydroxyethyl) methylammonium hydroxide, benzyltrimethylammonium hydroxide, benzylcetyldimethylammonium hydroxide, Examples thereof include benzethonium hydroxide, cetyltrimethylammonium chloride, benzyldimethyltetradecylammonium chloride, and benzyltrimethylammonium chloride. By including a quaternary ammonium salt as an essential component, there is a tendency that uniform electrodeposition, etc., particularly when electrodepositing at a high current density is improved.

  The quaternary ammonium salt can be used alone or in combination, and its content in the plating solution is preferably 0.01 to 10 g / L. If the content of the quaternary ammonium salt is too small, the effect of remarkably improving the throwing power by adding three components (the quaternary ammonium salt, a surfactant having a specific structure described later and a crystal refining agent) can be obtained. There are cases where problems such as insufficient availability may occur. On the other hand, if the content of the quaternary ammonium salt is too large, foamability is increased and a defect may occur during plating. Among these, the content of the quaternary ammonium salt is particularly preferably 0.1 to 5 g / L.

  Surfactants are generally used to improve the appearance, denseness, smoothness, adhesion and the like of the plating film. Examples of general surfactants include various surfactants such as nonionic, anionic, amphoteric, or cationic. In the plating solution of the present invention, nonionic compounds represented by the following general formula (1) are used. A surfactant is included as an essential component. By including the nonionic surfactant represented by the general formula (1) as an essential component, there is a tendency to improve the uniformity of electrodeposition particularly when electrodeposition is performed at a low current density.

但し、式（１）中、Ｒ₁、Ｒ₂は、下記の式（Ａ）で示される基であり、 Ｙ₁、Ｙ₂は、単結合、−Ｏ−、−ＣＯＯ−及び−ＣＯＮＨ−から選ばれる基であり、 Ｚはベンゼン環又は２，２−ジフェニルプロパンを表す。

In the formula _{(1), R 1, R} 2 is a group represented by the following formula _{(A), Y 1, Y} 2 is a single bond, -O -, - COO- and from -CONH- And Z represents a benzene ring or 2,2-diphenylpropane.

但し、式（Ａ）中、ｎは２又は３を示す。ｍは１〜１５の整数を示す。

However, in formula (A), n represents 2 or 3. m shows the integer of 1-15.

Specific examples of the nonionic surfactant represented by the above formula (1) include the following nonionic surfactants 1 and 2, for example. Nonionic surfactant 1 is polyoxyethylene bisphenol ether. In this polyoxyethylene bisphenol ether, in the above formula (1), the substituent R ₁ is H— (CH ₂ —CH ₂ —O) _p (p is an integer of 2 to 10), Y ₁ is —O—, Z in There _{(C 6 H 10) C 3} H 4 (C 6 H 10), Y 2 is -O-, R ₂ is _{H- (CH 2 -CH 2 -O)} p (p is 2-10 integer) Yes, specifically represented by the following formula (1-1).

Further, the nonionic surfactant 2 is polyoxyethylene phenyl ether. In this polyoxyethylene phenyl ether, in the above formula (1), the substituent R ₁ is H— (CH ₂ —CH ₂ —O) _q (q is an integer of 2 to 15), and Y ₁ is —O. -, Z is C ₆ H _10, Y ₂ is a single bond, R ₂ is CH ₂ -CH ₂ -OH, as represented by the following formula (1-2).

The nonionic surfactant represented by the general formula (1) can be used alone or in combination, and the content in the plating solution is preferably 1 to 20 g / L. If the content of the nonionic surfactant is too small, there may be a problem that the remarkable improvement effect of the uniform electrodeposition due to the addition of the three components cannot be sufficiently obtained. On the other hand, if the content of the nonionic surfactant becomes too large, there may be a problem in solubility. Among these, the content of the nonionic surfactant represented by the general formula (1) is particularly preferably 3 to 10 g / L. In addition, in this invention, the nonionic surfactant represented by the said General formula (1) should just be included as surfactant, and the structure which further contains other nonionic surfactant etc. is not prevented. As other surfactants in this case, for example, nonionic surfactants include sugar esters, fatty acid esters, C ₁ -C ₂₅ alkoxyl phosphoric acid (salts), sorbitan esters, C ₁ -C ₂₂ aliphatic amides, and the like. Ethylene oxide (EO) and / or propylene oxide (PO) 2-300 mol addition-condensed, silicon-based polyoxyethylene ether, silicon-based polyoxyethylene ester, fluorine-based polyoxyethylene ether, fluorine-based polyoxyethylene ester And sulfated or sulfonated adducts of condensation products of ethylene oxide and / or propylene oxide and alkylamines or diamines. Anionic surfactants include polyoxyethylene (ethylene oxide: containing 12 mol) nonyl ether sulfate polyoxyalkylene alkyl ether sulfate such as sodium sulfate, polyoxyethylene (ethylene oxide: containing 12 mol) dodecyl phenyl ether sodium sulfate, etc. Polyoxyalkylene alkylphenyl ether sulfates, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, naphthol sulfonates such as 1-naphthol-4-sulfonic acid sodium, 2-naphthol-3,6-disulfonic acid disodium salt, (Poly) alkylnaphthalene sulfonates such as sodium diisopropyl naphthalene sulfonate and sodium dibutyl naphthalene sulfonate, sodium dodecyl sulfate, sodium oleyl sulfate They include alkyl sulfates of. Examples of amphoteric surfactants include betaine, carboxybetaine, imidazolinium betaine, sulfobetaine, and aminocarboxylic acid.

  The low molecular weight compound contained as the crystal refining agent is a compound represented by the following general formula (2).

但し、式（２）中、Ｒ₃は水素、ハロゲン原子、置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基、Ｃ₂−Ｃ₂₀アルケニル基、Ｃ₄−Ｃ₂₀ジエニル基、Ｃ₃−Ｃ₂₀シクロアルキル基、Ｃ₃−Ｃ₂₀シクロアルケニル基及びＣ₄−Ｃ₂₀シクロジエニル基並びに式−ＮＲ₇Ｒ₈（式中Ｒ₇、Ｒ₈はそれぞれ独立に水素又は置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基である）で表されるアミノ基からなる群より選択され、Ｒ₄〜Ｒ₆はそれぞれ独立に、水素、ハロゲン原子、置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基、Ｃ₂−Ｃ₂₀アルケニル基、Ｃ₄−Ｃ₂₀ジエニル基、Ｃ₃−Ｃ₂₀シクロアルキル基、Ｃ₃−Ｃ₂₀シクロアルケニル基及びＣ₄−Ｃ₂₀シクロジエニル基からなる群より選択され、Ｒ₄とＲ₆又はＲ₃とＲ₅は結合して環を形成してもよく、形成された環は１以上の二重結合を有していてもよく、ここでＲ₃が上記式−ＮＲ₇Ｒ₈で表されるアミノ基である場合に上記環はＲ₇若しくはＲ₈がＲ₅と結合した複素環であり、またＲ₃が置換若しくは非置換のＣ₁−Ｃ₂₀アルキル基、Ｃ₂−Ｃ₂₀アルケニル基又はＣ₄−Ｃ₂₀ジエニル基の場合に上記環は、カルボニル炭素とＲ₃の間に１つの酸素原子を有する複素環であってもよい。

In the formula (2), R ₃ is hydrogen, halogen atom, substituted or unsubstituted C ₁ -C ₂₀ alkyl group, C ₂ -C ₂₀ alkenyl group, C ₄ -C ₂₀ dienyl groups, C ₃ -C ₂₀ A cycloalkyl group, a C ₃ -C ₂₀ cycloalkenyl group and a C ₄ -C ₂₀ cyclodienyl group and a formula —NR ₇ R ₈ (wherein R ₇ and R ₈ are each independently hydrogen or substituted or unsubstituted C ₁ -C is selected from the group consisting of amino group represented by a is) ₂₀ alkyl group, the R ₄ to R ₆ are each independently, hydrogen, halogen atom, substituted or unsubstituted C ₁ -C ₂₀ alkyl group, C ₂ - C ₂₀ alkenyl group, C ₄ -C ₂₀ dienyl groups, C ₃ -C ₂₀ cycloalkyl group, it is selected from the group consisting of C ₃ -C ₂₀ cycloalkenyl group, and C ₄ -C ₂₀ cyclodienyl group, R ₄ and R ₆ or R ₃ and R ₅ may form a ring, form Been ring may have one or more double bonds, wherein said ring when R ₃ is an amino group represented by the formula -NR ₇ R ₈ is R ₇ or R ₈ is R ₅ and a bound heterocycles, also the ring in the case of R ₃ is substituted or unsubstituted C ₁ -C ₂₀ alkyl radical, C ₂ -C ₂₀ alkenyl or C ₄ -C ₂₀ dienyl groups, carbonyl carbon And a heterocycle having one oxygen atom between R ₃ and R ₃ .

  Among the low molecular weight compounds represented by the formula (2), there are those used as a brightener for imparting luster to the plating film. However, in the plating solution of the present invention, these are described above. By including it as an essential component together with the quaternary ammonium salt and the nonionic surfactant having the above-mentioned specific structure, particularly, the effect of greatly improving the throwing power is obtained. Examples of the low molecular weight compound represented by the above formula (2) include 4-hexen-3-one, acetophenone, propiophenone, benzalaldehyde, cinnamaldehyde, and β-ionone.

  The low molecular weight compound contained as a crystal refining agent can be used alone or in combination, and the content in the plating solution is preferably 0.001 to 0.3 g / L. When the content of the crystal refining agent is too small, there may be a problem that the effect of significantly improving the throwing power due to the addition of the three components cannot be sufficiently obtained. On the other hand, if the content of the crystal refining agent is too large, the solubility becomes a problem, and there may be a problem that the uniform electrodeposition is impaired. Among these, the content of the crystal refining agent is particularly preferably 0.003 to 0.1 g / L.

  The complexing agent is used to stabilize noble metal ions and the like in a bath with a plating solution containing a noble metal such as silver and to make the precipitated alloy composition uniform. Examples of the complexing agent include oxycarboxylic acid, polycarboxylic acid, and monocarboxylic acid. Specifically, gluconic acid, citric acid, glucoheptonic acid, gluconolactone, glucoheptlactone, formic acid, acetic acid, propionic acid, butyric acid, ascorbic acid, oxalic acid, malonic acid, succinic acid, glycolic acid, malic acid, Tartaric acid, diglycolic acid, thioglycolic acid, thiodiglycolic acid, thioglycol, thiodiglycol, mercaptosuccinic acid, 3,6-dithia-1,8-octanediol, 3,6,9-trithiadecane-1,11 -Disulfonic acid, thiobis (dodecaethylene glycol), di (6-methylbenzothiazolyl) disulfide trisulfonic acid, di (6-chlorobenzothiazolyl) disulfide disulfonic acid, gluconic acid, citric acid, glucoheptonic acid, gluco Nolactone, glucoheptlactone, dithiodianiline, dipyridi Disulfide, mercaptosuccinic acid, sulfite, thiosulfate, ethylenediamine, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (NTA), iminodiacetic acid (IDA), iminodipropionic acid (IDP), Hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetramine hexaacetic acid (TTHA), ethylenedioxybis (ethylamine) -N, N, N ', N'-tetraacetic acid, glycines, nitrilotrimethylphosphonic acid, or salts thereof Etc. Further, there are sulfur-containing compounds such as thioureas, and phosphorus compounds such as tris (3-hydroxypropyl) phosphine. Examples of the conductive salt include sulfuric acid, hydrochloric acid, phosphoric acid, sulfamic acid, sodium salt of sulfonic acid, potassium salt, magnesium salt, ammonium salt, and amine salt. The complexing agent can be used alone or in combination, and its content in the plating solution is preferably 0 to 100 g / L. Even if the complexing agent is added too much, no further increase in the effect is observed and it is uneconomical, so excessive addition is not desirable.

  Antioxidants are used to prevent oxidation of soluble stannous salts to stannic salts. Antioxidants include hypophosphorous acid, ascorbic acid or a salt thereof, phenolsulfonic acid (Na), cresolsulfonic acid (Na), hydroquinonesulfonic acid (Na), hydroquinone, α or β-naphthol, catechol, Examples include resorcin, phloroglucin, hydrazine, phenolsulfonic acid, catecholsulfonic acid, hydroxybenzenesulfonic acid, naphtholsulfonic acid, and salts thereof. The antioxidant can be used alone or in combination, and the content in the plating solution is preferably 0 to 3 g / L. Even if the antioxidant is added too much, no further increase in the effect is observed and it is uneconomical. Therefore, excessive addition is not desirable. )

<Preparation of plating solution>
In order to prepare a plating solution using each of the above-mentioned components, first, after weighing so that the content of each component in the plating solution becomes the above-mentioned preferred ratio, these are sequentially added into the reaction vessel, Mix.

<Applications>
As described above, the plating solution of the present invention can be used as a plating solution for forming a plating film of tin or a tin alloy on an electronic component that is an object to be plated. Excellent wearability. Moreover, generation of voids can be suppressed when bump electrodes or the like are formed. Examples of the electronic component include a printed board, a flexible printed board, a film carrier, a semiconductor integrated circuit, a resistor, a capacitor, a filter, an inductor, a thermistor, a crystal resonator, a switch, and a lead wire. Further, a coating can be formed by applying the above plating solution to a part of an electronic component such as a bump electrode of a wafer.

  Next, examples of the present invention will be described in detail together with comparative examples.

<Examples 1-6 and Comparative Examples 1-3>
The types of soluble salt (A), acid or salt (B), and additive (C) contained in the plating solution, and their content (concentration) are changed or adjusted as shown in Table 2 and Table 3 below. Then, a plating solution was prepared for each example or comparative example. In Table 2, quaternary ammonium salts represented by classifications (i) to (vi), surfactants represented by classifications (i) and (ii), and fine crystals represented by classifications (i) to (vi) Details of the agent are shown in Table 1 below.

<Comparison test and evaluation>
About the plating solution obtained in Examples 1-6 and Comparative Examples 1-3, the hull cell test and the plating test were done, and the uniform electrodeposition property and void generation rate of each plating solution were evaluated. The results are shown in Table 4.

(A) Hull cell test In the hull cell test, a commercially available hull cell tester (manufactured by Yamamoto Kakin Tester Co., Ltd.) is used, and a copper hull cell plate (length 70 mm, width 100 mm, thickness 0.3 mm) is used as a substrate to be plated. used. The plating solution was put into a Hull cell tester, the solution temperature was 25 ° C., and the energization current was 2A. The plating treatment time was 5 minutes, and the plating solution was not stirred during the plating treatment. The hull cell evaluation was performed based on the presence or absence of burns on the plated hull cell plate.

(B) Plating test
(b-1) Variation in plating film thickness In the first plating test, a copper substrate (10 cm long, 10 cm wide, 0.3 mm thick) was immersed in a plating solution at a liquid temperature of 25 ° C. and a current of 5 A / dm ² . By energizing for 1 minute at a density, a plating film was formed on the substrate. The film thickness of ten places of the obtained plating film was measured with the fluorescent X-ray film thickness measuring device (made by SII nanotechnology Co., Ltd.). The standard deviation (3σ) of film thickness at 10 locations was calculated, and it was evaluated whether the plating film thickness variation, that is, electrodeposition was performed uniformly.

(b-2) Void generation rate of plating film In the second plating test, a copper substrate (10 cm long, 7 cm wide, 0.3 mm thick) was immersed in a plating solution at a liquid temperature of 25 ° C. and 3 A / dm ² A current was applied at a current density for 13 minutes to form a plating film having a thickness of 20 μm on the substrate. The center of the substrate with the plating film is cut into square pieces of 10 mm in length and 10 mm in width, and these pieces are heated on a hot plate in a nitrogen atmosphere until the surface temperature of the substrate reaches 270 ° C., resembling reflow treatment. Then, after holding at that temperature for 20 seconds, it was rapidly cooled. Evaluation of the void was performed by observing the plated film after reflowing with transmission X-ray, and dividing the area occupied by the void by the area of small pieces of 10 mm in length and 10 mm in width to calculate the void area ratio. Whether or not voids were generated was defined as void generation when the void area ratio was 0.1% or more.

  As is apparent from Table 4, when Examples 1 to 6 and Comparative Examples 1 to 3 are compared, a quaternary ammonium salt, a nonionic surfactant represented by the above general formula (1), and the above general formula Of the three components of the low molecular weight compound (crystal refining agent) represented by (2), Comparative Example 1 that does not contain the low molecular weight compound has relatively good results in the hull cell test and evaluation of the void generation rate. Although obtained, in the evaluation of film thickness variation, the standard deviation (3σ) value was larger than the values of Examples 1 to 6, and the result was poor uniform electrodeposition.

  Moreover, in the comparative example 2 which does not contain a quaternary ammonium salt among the three components, and the comparative example 3 which does not contain a nonionic surfactant, generation of burns was confirmed in a hull cell test. Moreover, both the variation in film thickness and the evaluation of the void generation rate were significantly worse than those in Examples 1-6.

  On the other hand, in Examples 1 to 6, good results were obtained in all evaluations of the hull cell test, film thickness variation, and void generation rate.

  The plating solution of the present invention includes printed circuit boards, flexible printed circuit boards, film carriers, semiconductor integrated circuits, resistors, capacitors, filters, inductors, thermistors, crystal resonators, switches, lead wires and other electronic components, wafer bump electrodes, etc. It can be used for some electronic components.

Claims (2)

(A) a soluble salt containing at least a stannous salt,
(B) an acid selected from organic acids and inorganic acids or salts thereof,
(C) a plating solution containing an additive,
The additive includes a quaternary ammonium salt, a surfactant, and a crystal refining agent,
The surfactant includes a nonionic surfactant represented by the following formula (1),
The plating solution, wherein the crystal refining agent contains a low molecular compound represented by the following formula (2).

In the formula _{(1), R 1, R} 2 is a group represented by the following formula _{(A), Y 1, Y} 2 is a single bond, -O -, - COO- and from -CONH- And Z represents a benzene ring or 2,2-diphenylpropane.

However, in formula (A), n represents 2 or 3. m shows the integer of 1-15.

In the formula (2), R ₃ is hydrogen, halogen atom, substituted or unsubstituted C ₁ -C ₂₀ alkyl group, C ₂ -C ₂₀ alkenyl group, C ₄ -C ₂₀ dienyl groups, C ₃ -C ₂₀ A cycloalkyl group, a C ₃ -C ₂₀ cycloalkenyl group and a C ₄ -C ₂₀ cyclodienyl group and a formula —NR ₇ R ₈ (wherein R ₇ and R ₈ are each independently hydrogen or substituted or unsubstituted C ₁ -C is selected from the group consisting of amino group represented by a is) ₂₀ alkyl group, the R ₄ to R ₆ are each independently, hydrogen, halogen atom, substituted or unsubstituted C ₁ -C ₂₀ alkyl group, C ₂ - C ₂₀ alkenyl group, C ₄ -C ₂₀ dienyl groups, C ₃ -C ₂₀ cycloalkyl group, it is selected from the group consisting of C ₃ -C ₂₀ cycloalkenyl group, and C ₄ -C ₂₀ cyclodienyl group, R ₄ and R ₆ or R ₃ and R ₅ may form a ring, form Been ring may have one or more double bonds, wherein said When R ₃ is an amino group represented by the formula -NR ₇ R ₈ ring R ₇ or R ₈ is R ₅ and a bound heterocycles, also the ring in the case of R ₃ is substituted or unsubstituted C ₁ -C ₂₀ alkyl group, C ₂ -C ₂₀ alkenyl or C ₄ -C ₂₀ dienyl groups, carbonyl carbon And a heterocycle having one oxygen atom between R ₃ and R ₃ .   The plating solution according to claim 1, wherein the additive further contains at least one of a complexing agent or an antioxidant.