阅读说明：本技术 锡或锡合金电镀液、凸点的形成方法及电路基板的制造方法 (Tin or tin alloy plating solution, method for forming bump, and method for manufacturing circuit board ) 是由 渡边真美 薄京佳 中矢清隆 于 2019-03-19 设计创作，主要内容包括：本发明的锡或锡合金电镀液含有：(A)至少含有亚锡盐的可溶性盐；(B)选自有机酸及无机酸中的酸或其盐；(C)表面活性剂；(D)流平剂；及(E)添加剂,所述表面活性剂为由以下通式(1)表示的化合物(C1)和/或由通式(2)表示的化合物(C2)。式(1)、(2)中,R为碳原子数7～13的烷基,m为5～11,n为1～3,m与n不同。<Image he="361" wi="700" file="DDA0002650647470000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>(The tin or tin alloy plating solution of the present invention comprises: (A) a soluble salt containing at least a stannous salt; (B) an acid or a salt thereof selected from an organic acid and an inorganic acid; (C) a surfactant; (D) leveling agent; and (E) an additive, wherein the surfactant is a compound (C1) represented by the following general formula (1) and/or a compound (C2) represented by the general formula (2). In the formulas (1) and (2), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 1 to 3, and m and n are different.)

1. A tin or tin alloy electroplating bath comprising:

(A) a soluble salt containing at least a stannous salt;

(B) an acid or a salt thereof selected from an organic acid and an inorganic acid;

(C) a surfactant;

(D) leveling agent; and

(E) an additive agent is added to the mixture,

the surfactant is a compound C1 represented by the following general formula (1) and/or a compound C2 represented by the general formula (2),

[ chemical formula 1]

In the formula (1), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 0 to 3, m and n are different,

[ chemical formula 2]

In the formula (2), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 1 to 3, and m and n are different.

2. The tin or tin alloy plating solution as set forth in claim 1,

the additive contains two or more selected from a surfactant, an antioxidant and an alcohol having 1-3 carbon atoms, and the surfactant is different from the surfactant C1 and the surfactant C2.

3. A method for forming a bump, comprising the steps of:

forming a tin or tin alloy plating deposit on a substrate using the tin or tin alloy plating solution according to claim 1 or 2; and

then, reflow processing is performed to form bumps.

4. A method of manufacturing a circuit board, characterized in that the circuit board is manufactured by using the bump formed by the method of claim 3.

Technical Field

The present invention relates to a tin or tin alloy plating solution for forming a bump to be a tin or tin alloy bump electrode on a circuit board when a semiconductor integrated circuit chip is mounted on the circuit board, a method for forming a bump using the tin or tin alloy plating solution, and a method for manufacturing a circuit board. More particularly, the present invention relates to a tin or tin alloy plating solution which has excellent via filling properties into a via hole on a substrate even in a pattern having a different bump diameter or bump pitch, and which can form bumps having a uniform height.

The present application claims priority based on patent application nos. 2018-52012, 2018-57551, 2018-26, 2019-40216, 2018-20, 2018-26, and 2019-40216, 2019-6, and the contents thereof are incorporated herein.

Background

In order to cope with the reduction in thickness and Size (weight, thickness, and Size) of a circuit board on which a semiconductor integrated circuit Chip (hereinafter referred to as a semiconductor Chip) is mounted, a CSP (Chip Size/scale Package) type semiconductor device in which the area of a Package substrate is reduced to approximately the same Size as that of the semiconductor Chip mounted on the substrate has been mainly manufactured. In order to connect the circuit board and the semiconductor chip, a bump of a protruding electrode as a metal terminal is formed by filling a via opening as a via main body on the substrate side with tin or a tin alloy, and the semiconductor chip is mounted on the bump.

Conventionally, in order to form a bump by filling the tin or tin alloy material, a conductive paste such as a tin-based solder paste or a tin-based solder ball is filled in a via main body, or a tin plating deposit layer is formed in a via by a plating method using a tin or tin alloy plating solution, and then the conductive paste, the solder ball or the tin plating deposit layer is melted by heat treatment.

A general method of forming a bump by electroplating will be described with reference to fig. 1. As shown in fig. 1 (a), a solder resist pattern having an opening is formed on the surface of a substrate 1 on which wiring and the like are provided by photolithography using a solder resist. Next, a copper seed layer 3 for supplying power is formed on the surface of the solder resist layer 2 by electroless plating. Next, a dry film resist layer 4 is formed on the surface of the copper seed layer 3, and a dry film resist pattern having an opening is formed so as to be bonded to the opening of the solder resist layer 2. Then, by supplying electricity through the copper seed layer 3, electrolytic tin plating is performed inside the via hole 6 of the dry film resist pattern, and a tin plating deposition layer 7 (tin plating film) is formed in the via hole 6 on the copper seed layer 3. Next, the dry film resist layer 4 and the copper seed layer 3 are removed in this order, and then the remaining tin electroplating deposition layer 7 is melted by a reflow process, thereby forming a tin bump 8 as shown in fig. 1 (b).

Heretofore, when a tin or tin alloy bump is formed by a plating method, improvement has been made in terms of via hole filling properties to a via hole on a substrate and suppression of voids in the bump by changing the content of a tin or tin alloy plating solution (see, for example, patent documents 1, 2,3, and 4).

Patent document 1 discloses a tin or tin alloy plating solution containing a specific α, β -unsaturated aldehyde or a specific α, β -unsaturated ketone compound. Patent document 1 describes the following matters.

The plating solution has high via filling ability, and tin plating is selectively deposited in the concave portion by using the plating solution, so that tin plating deposits substantially free of voids can be obtained.

Since scorching or abnormal precipitation does not occur on the surface of the formed tin electroplated coating, a tin electroplated coating having excellent practical properties such as weldability and discoloration resistance and having a good appearance can be obtained.

Since the plating solution has high via hole filling properties, a columnar tin plating deposit (bump) substantially free of voids can be formed.

Patent document 2 discloses a tin or tin alloy plating solution containing (a) a carboxyl group-containing compound and (b) a carbonyl group-containing compound, wherein the component (a) is 1.3g/L or more and the component (b) is 0.3g/L or more. Patent document 2 describes the following.

By using this plating solution, a plated object having blind holes or through holes can be plated to fill the blind holes or through holes reliably in a short time.

The present invention can be used for three-dimensional mounting of semiconductors, a process for filling blind holes or through holes in printed circuit boards, and formation of through-silicon via electrodes.

Patent document 3 discloses a tin or tin alloy plating solution containing an inorganic acid, an organic acid, a water-soluble salt thereof, a surfactant, and a leveling agent. Wherein the surfactant is at least one nonionic surfactant selected from polyoxyalkylene phenyl ether or salts thereof and polyoxyalkylene polycyclic phenyl ether or salts thereof. The phenyl group constituting the polyoxyalkylene phenyl ether and the polycyclic phenyl group constituting the polyoxyalkylene polycyclic phenyl ether may be substituted with an alkyl group having 1 to 24 carbon atoms or a hydroxyl group. The leveling agent is at least one selected from aliphatic aldehyde, aromatic aldehyde, aliphatic ketone and aromatic ketone; and an α, β -unsaturated carboxylic acid or an amide thereof or a salt thereof. Patent document 3 describes the following.

Since the composition contains a specific nonionic surfactant and two specific leveling agents, the composition is excellent in the filling property of the grooves and can suppress the generation of voids. Thus, by using this plating solution, it is possible to provide a good bump which is smooth without a groove and which does not generate a void after reflow.

Patent document 4 discloses a tin or tin alloy plating solution for forming a bump electrode, the tin or tin alloy plating solution including: (A) a soluble salt consisting of any one of stannous salt and a mixture of stannous salt and a salt of a metal selected from silver, copper, bismuth, nickel, indium and gold; (B) an acid or salt thereof; (C) a filling organic compound selected from aromatic and aliphatic aldehydes, aromatic and aliphatic ketones, unsaturated carboxylic acids, and aromatic carboxylic acids; and (D) a nonionic surfactant. Patent document 4 describes the following.

In this plating solution, since the specific compound (C) for suppressing the deposition of the tin-based material and the component (D) are used in combination, the deposition of the upper portion of the via hole can be effectively suppressed, and the deposition of the tin-based material can be preferentially performed from the bottom portion of the via hole toward the upper portion of the via hole. Therefore, via hole filling can be smoothly performed while preventing generation of voids. As a result, the bump electrode can be formed well with or without reflow, and the bonding strength and the electrical characteristics are excellent.

In recent years, wiring patterns having different bump diameters or different bump pitches are mixed on one circuit board. In such a complicated wiring pattern, it is required to form all bumps at a uniform height even when the bump diameter or the bump pitch is different. The tin or tin alloy plating solutions according to patent documents 1 to 4 are characterized in that the occurrence of voids in the bumps is suppressed, the via holes on the substrate can be filled with high reliability in a short time, and the via hole filling property and the appearance are excellent. However, the plating solutions for substrates in these patent documents 1 to 4 do not have the problem of achieving high uniformity of bumps.

Specifically, as shown in fig. 2, in the case of a pattern having bumps of different diameters, when plating is performed using a conventional tin or tin alloy plating solution, the via hole filling property of either the small diameter or the large diameter can be improved, but the via hole filling property of the other is lowered. That is, when two via holes 6 are plated simultaneously on a substrate having both small-diameter and large-diameter via holes 6, it is difficult to plate both via holes 6 with good via hole filling properties. If there are via holes 6 having different via hole filling properties (fig. 2 (b)), the bumps 8 after reflow have large height variations, and the bumps 8 cannot have uniform height (fig. 2 (d)). Therefore, in order to achieve the height uniformity of the bump 8 (fig. 2 c), it is necessary to improve the via filling performance for the two vias 6 having a small diameter and a large diameter as shown in fig. 2 a.

Patent document 1: japanese patent laid-open No. 2014-125662 (claim 2, paragraph [0020 ])

Patent document 2: japanese patent laid-open publication No. 2015-007276 (claims 1, paragraphs [0011] and [0012 ])

Patent document 3: japanese patent laid-open publication No. 2015-193916 (claim 1, paragraph [0019 ])

Patent document 4: japanese laid-open patent publication No. 2016-074963 (claim 1, paragraph [0019 ])

Disclosure of Invention

The purpose of the present invention is to provide a tin or tin alloy plating solution which has excellent via hole filling properties for via holes in a substrate even in patterns having different bump diameters, and in which the height of bumps to be formed is uniform.

A first aspect of the present invention is a tin or tin alloy plating solution containing: (A) a soluble salt containing at least a stannous salt; (B) an acid or a salt thereof selected from an organic acid and an inorganic acid; (C) a surfactant; (D) leveling agent; and (E) an additive, wherein the surfactant is a compound (C1) represented by the following general formula (1) and/or a compound (C2) represented by the general formula (2).

In the formula (1), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 0 to 3, and m and n are different. In the formula (2), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 1 to 3, and m and n are different.

[ chemical formula 1]

[ chemical formula 2]

A second aspect of the present invention is the tin or tin alloy plating solution of the first aspect, wherein the additive contains two or more selected from the group consisting of a surfactant, an antioxidant, and an alcohol having 1 to 3 carbon atoms, and the surfactant is different from the two surfactants (C1, C2).

A third aspect of the present invention is a method for forming a bump, including the steps of:

forming a tin or tin alloy plating deposit layer on the substrate using the tin or tin alloy plating solution of the first or second mode; and then performing a reflow process to form a bump.

A fourth aspect of the present invention is a method for manufacturing a circuit board using the bumps formed by the method of the third aspect.

In the tin or tin alloy plating solution according to the first aspect of the present invention, since the surfactant (C1, C2) has a specific nonionic (Non-ionic) structure in which the number m of polyoxypropylene alkyl groups and the number n of polyoxyethylene groups in the general formulae (1) and (2) are respectively set to predetermined ranges, it is possible to suppress the deposition of Sn ions during plating and to perform good plating on the surface to be plated. In particular, according to this plating solution, in the case of a pattern having different bump diameters, even if the bump diameter is large or small, the via hole filling property to the via hole on the substrate is excellent, and the height of the formed bump becomes uniform. This is considered to be because the polarization resistance becomes large.

The tin or tin alloy plating solution of the second aspect of the present invention further contains two or more selected from the group consisting of a surfactant different from the two surfactants (C1 and C2), an antioxidant, and an alcohol having 1 to 3 carbon atoms, whereby the following effects are exhibited. The surfactants different from the two surfactants (C1, C2) exert effects such as stabilization of the plating liquid and improvement of solubility. Also, antioxidants prevent the oxidation of soluble stannous salts to tin salts. Furthermore, the alcohol exerts an effect of improving the solubility of the surfactant.

In the method of the third aspect of the present invention, a tin or tin alloy plating layer is formed on a substrate using the tin or tin alloy plating solution of the first or second aspect, and then reflow processing is performed to form a bump. Thus, even in a pattern having different bump diameters, bumps having a uniform height can be formed.

In the method of the fourth aspect of the present invention, the circuit substrate is manufactured using the bump formed by the method of the third aspect. Thus, a highly reliable semiconductor device without electrical connection failure can be manufactured.

Drawings

Fig. 1 (a) is a cross-sectional view of a substrate in which a plating layer is formed in a via hole of the present embodiment. (b) Is a cross-sectional view of the substrate after stripping the dry film and the copper seed layer and heating the electroplated deposition layer.

Fig. 2 (a) is a cross-sectional view of a substrate showing an example in which via hole filling properties of a plating layer are good in patterns having different bump diameters (via hole diameters). (b) The cross-sectional structure of the substrate shows an example in which via hole filling properties of the plating layer are poor in patterns having different bump diameters (via hole diameters). (c) The cross-sectional structure of the substrate shows an example in which the dry film and the copper seed layer are peeled off and the deposited layer is heated and electroplated in (a), and the height of the bump formed is uniform. (d) The cross-sectional structure of the substrate shows an example of the state after the dry film and the copper seed layer are peeled off and the deposited layer is heated and electroplated in (b), and the height of the formed bumps is not uniform.

Detailed Description

Next, a mode for carrying out the present invention will be described.

The tin or tin alloy plating solution of the present embodiment includes: (A) a soluble salt containing at least a stannous salt; (B) an acid or a salt thereof selected from an organic acid and an inorganic acid; (C) a surfactant; (D) leveling agent; and (E) an additive. The remainder being water of the solvent. The surfactant is a compound (C1) represented by the above general formula (1) and/or a compound (C2) represented by the above general formula (2).

The soluble salt is composed of any one of a stannous salt and a mixture of a stannous salt and a salt of a metal selected from silver, copper, bismuth, nickel, antimony, indium, and zinc.

The tin alloy of the present embodiment is an alloy of tin and a predetermined metal selected from silver, copper, bismuth, nickel, antimony, indium, and zinc, and examples thereof include ternary alloys such as tin-silver alloy, tin-copper alloy, tin-bismuth alloy, tin-nickel alloy, tin-antimony alloy, tin-indium alloy, and tin-zinc alloy, and tin-copper-bismuth and tin-copper-silver alloy.

Therefore, the soluble salt (A) of the present embodiment means that Sn is generated in the plating solution²⁺、Ag⁺、Cu⁺、Cu²⁺、Bi³⁺、Ni^{2 +}、Sb³⁺、In³⁺、Zn²⁺And any soluble salt of various metal ions, for example, oxides, halides, inorganic acids, or organic acids of the metal ions.

Examples of the metal oxide include stannous oxide, copper oxide, nickel oxide, bismuth oxide, antimony oxide, indium oxide, and zinc oxide, and examples of the metal halide include stannous chloride, bismuth bromide, cuprous chloride, copper chloride, nickel chloride, antimony chloride, indium chloride, and zinc chloride.

Examples of the metal salt of the inorganic acid or organic acid 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 carbonate, sodium stannate, stannous fluoroborate, stannous methanesulfonate, silver methanesulfonate, copper methanesulfonate, bismuth methanesulfonate, nickel methanesulfonate, indium methanesulfonate, zinc methanesulfonate, stannous ethanesulfonate, bismuth 2-hydroxypropanesulfonate, and the like.

The acid or salt thereof (B) of the present embodiment is selected from organic acids and inorganic acids or salts thereof. Examples of the organic acid include organic sulfonic acids such as alkanesulfonic acid, alkanesulfonic acid and aromatic sulfonic acid, and aliphatic carboxylic acids. Examples of the inorganic acid include fluoroboric acid, fluorosilicic acid, sulfamic acid, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, and the like. The salt is alkali metal salt, alkaline earth metal salt, ammonium salt, amine salt, sulfonate, etc. From the viewpoint of solubility of the metal salt and easiness of drainage treatment, the component (B) is preferably an organic sulfonic acid.

As the above-mentioned alkanesulfonic acid, those of the formula C_nH_2n+1SO₃Examples of alkanesulfonic acids represented by H (e.g., n-1 to 5, preferably 1 to 3) include methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 2-propanesulfonic acid, 1-butanesulfonic acid, 2-butanesulfonic acid, pentanesulfonic acid, etc., and hexanesulfonic acid, decanesulfonic acid, dodecanesulfonic acid, etc.

As the above-mentioned alkanol sulfonic acid, a compound represented by the formula C_pH_2p+1-CH(OH)-C_qH_2q-SO₃Examples of the alkanol sulfonic acid represented by H (e.g., p ═ 0 to 6, and q ═ 1 to 5) include, for example, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, and 2-hydroxypentane-1-sulfonic acid, and 1-hydroxypropane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, and 2-hydroxydodecane-1-sulfonic acid.

The aromatic sulfonic acid is basically benzenesulfonic acid, alkylbenzenesulfonic acid, phenolsulfonic acid, naphthalenesulfonic acid, alkylnaphthalenesulfonic acid, and the like, and specific examples thereof include 1-naphthalenesulfonic acid, 2-naphthalenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid, p-phenolsulfonic acid, cresolsulfonic acid, sulfosalicylic acid, nitrobenzenesulfonic acid, sulfobenzoic acid, and diphenylamine-4-sulfonic acid.

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

The nonionic surfactant (C1) contained in the surfactant (C) of the present embodiment is a condensate of polyoxyethylene and polyoxypropylene alkyl ether represented by the following general formula (1) or polyoxyethylene alkyl ether.

[ chemical formula 3]

In the formula (1), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 0 to 3, and m and n are different. The alkyl group of R may be linear or branched. If the number of carbon atoms of R is less than 7, the appearance of plating may be deteriorated. If the number of carbon atoms of R is greater than 13, the following disadvantages may occur: the plating solution is difficult to dissolve, the via hole filling property is poor, and the plating appearance is abnormal. The number of carbon atoms of R is preferably 10 to 12. And if m is less than 5, there are the following disadvantages: are difficult to dissolve in the plating solution, or cause plating appearance abnormality. If m is larger than 11, the via hole filling property may be poor. Preferably, m is 6 to 10. If n is greater than 3, the following disadvantages occur: are difficult to dissolve in the plating solution, or cause plating appearance abnormality. In addition, n is preferably 0 to 2.

The nonionic surfactant (C2) contained in the surfactant (C) of the present embodiment is a condensate of polyoxypropylene and polyoxyethylene alkyl ether represented by the following general formula (2).

[ chemical formula 4]

In the formula (2), R is an alkyl group having 7 to 13 carbon atoms, m is 5 to 11, n is 1 to 3, and m and n are different. The alkyl group of R may be linear or branched. If the number of carbon atoms of R is less than 7, the appearance of plating may be deteriorated. If the number of carbon atoms of R is greater than 13, the following disadvantages may occur: the plating solution is difficult to dissolve, the via hole filling property is poor, and the plating appearance is abnormal. The number of carbon atoms of R is preferably 10 to 12. And if m is less than 5, there are the following disadvantages: are difficult to dissolve in the plating solution, or cause plating appearance abnormality. If m is larger than 11, the via hole filling property may be poor. Preferably, m is 6 to 10. If n is greater than 3, the following disadvantages occur: are difficult to dissolve in the plating solution, or cause plating appearance abnormality. In addition, n is preferably 1 to 2.

The leveling agent (D) of the present embodiment is contained in order to form a plating film uniformly and densely and to smooth the plating film. In addition, in order to improve via hole filling performance and suppress the occurrence of voids, both the first leveling agent (D-1) and the second leveling agent (D-2) are used. The first leveling agent (D-1) may be one or two or more selected from the group consisting of an aliphatic aldehyde, an aromatic aldehyde, an aliphatic ketone and an aromatic ketone, and the second leveling agent (D-2) may be an α, β -unsaturated carboxylic acid, an amide thereof or a salt thereof.

The first leveling agent (D-1) is a carbonyl compound containing an aldehyde or a ketone, and does not contain the α, β -unsaturated carboxylic acid of the second leveling agent (D-2). Specifically, the following are exemplified. Examples of the aliphatic aldehyde include formaldehyde, acetaldehyde, and allyl aldehyde. Examples of the aromatic aldehyde include benzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-chlorobenzaldehyde, 2, 4-dichlorobenzaldehyde, 2, 6-dichlorobenzaldehyde, 2,4, 6-trichlorobenzaldehyde, 1-naphthaldehyde, 2-hydroxybenzaldehyde, 3-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, m-anisaldehyde, o-anisaldehyde, p-anisaldehyde, and the like. Further, examples of the aliphatic ketone include acetylacetone. Examples of the aromatic ketone include benzalacetone (synonymous with mesityl oxide), 2-chloroacetophenone, 3-chloroacetophenone, 4-chloroacetophenone, 2, 4-dichloroacetophenone, and 2,4, 6-trichloroacetophenone. These may be used alone or in combination of two or more. The preferable content (amount may be a single one, or a total amount of two or more types) of the first leveling agent (D-1) in the plating bath is 0.001g/L to 0.3g/L, and more preferably 0.01g/L to 0.25 g/L. If the content of the above component is small, the effect of addition thereof is insufficient, while if the content of the above component is too large, the smoothing of the plated film may be inhibited.

Examples of the second leveling agent (D-2) include acrylic acid, methacrylic acid, picolinic acid, crotonic acid, 3-chloroacrylic acid, 3-dimethylacrylic acid, 2, 3-dimethylacrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl methacrylate, methacrylic anhydride, and methyl methacrylate. Also, the second leveling agent (D-2) includes an amide of an α, β -unsaturated carboxylic acid (e.g., acrylamide, etc.) and a salt of an α, β -unsaturated carboxylic acid (e.g., potassium, sodium, ammonium, etc.). The preferable content (amount may be a single one, or a total amount of two or more kinds) of the second leveling agent (D-2) in the plating bath is 0.01 to 50g/L, and more preferably 0.05 to 10 g/L. If the content of the above component is small, the effect of addition thereof is insufficient, while if the content of the above component is too large, the smoothing of the plated film may be inhibited.

The additive (E) in the present embodiment is various additives added to the tin or tin alloy plating solution. The additive (E) preferably contains two or more selected from the group consisting of a surfactant different from the two surfactants (C1, C2), an antioxidant, and an alcohol having 1 to 3 carbon atoms.

Examples of the other surfactants in this case include common anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

Examples of the anionic surfactant include polyoxyalkylene alkyl ether sulfates such as sodium nonyl ether sulfate (polyoxyethylene (1 mol containing ethylene oxide in the molecule: 12 mol)); polyoxyalkylene alkyl phenyl ether sulfates such as sodium dodecylphenyl ether sulfate, polyoxyethylene (1 mol of which contains ethylene oxide in the molecule: 12 mol); alkyl benzene sulfonates such as sodium dodecylbenzenesulfonate; naphthol sulfonates such as sodium 1-naphthol-4-sulfonate and disodium 2-naphthol-3, 6-disulfonate; (poly) alkylnaphthalene sulfonates such as sodium diisopropylnaphthalene sulfonate and sodium dibutylnaphthalene sulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium oleyl sulfate.

Examples of the cationic surfactant include monoalkylamine salts, dialkylamine salts, trialkylamine salts, dimethyldialkylammonium salts, trimethylalkylammonium salts, dodecyltrimethylammonium salts, hexadecyltrimethylammonium salts, octadecyltrimethylammonium salts, dodecyldimethylammonium salts, octadecenyldimethylethylammonium salts, dodecyldimethylbenzylammonium salts, hexadecyldimethylbenzylammonium salts, octadecyldimethylbenzylammonium salts, trimethylbenzylammonium salts, triethylbenzylammonium salts, hexadecylpyridinium salts, dodecylpyridinium salts, dodecylpicolinium salts, dodecylimidazolinium salts, oleylimidazolinium salts, octadecylamine acetate, dodecylamine acetate, and the like.

Examples of the nonionic surfactant include sugar esters, fatty acid esters, and C₁～C₂₅Alkoxy phosphoric acid (salts), sorbitan esters, silicon-based polyoxyethylene ethers, silicon-based polyoxyethylene esters, fluorine-based polyoxyethylene ethers, fluorine-based polyoxyethylene esters, sulfated or sulfonated adducts of ethylene oxide and/or propylene oxide with alkylamines or diamines, polyoxyethylene cumyl phenyl ethers (wherein the EO chain is 10 to 14), and the like.

Examples of the amphoteric surfactant include betaine, carboxybetaine, imidazolinebetaine, sulfobetaine, and aminocarboxylic acid.

The above-mentioned antioxidant is used for preventing the soluble stannous salt from being oxidized into a tin salt.

Examples of the antioxidant include hypophosphorous acids, ascorbic acid or a salt thereof, phenolsulfonic acid (Na), cresolsulfonic acid (Na), hydroquinone sulfonic acid (Na), hydroquinone, α -naphthol or β -naphthol, catechol, resorcinol, phloroglucinol, hydrazine, phenolsulfonic acid, catechol sulfonic acid, hydroxybenzenesulfonic acid, naphthol sulfonic acid, or a salt thereof.

The alcohol having 1 to 3 carbon atoms is used to improve the solubility of the surfactant. Examples of the alcohol include methanol, ethanol, 1-propanol, and 2-propanol. The alcohol may be used singly or in combination of two or more.

When the nonionic surfactant (C1 or C2) of the present embodiment is used alone, the content of the nonionic surfactant (C1 or C2) in the plating solution is 0.5 to 50g/L, preferably 1 to 5 g/L. If the content is less than the lower limit, plating defects such as dendrites occur due to excessive supply of Sn ions. If the content is greater than the upper limit, Sn ions are less likely to reach the surface to be plated, and the via hole filling property is poor. In the case where both the nonionic surfactant (C1) and the nonionic surfactant (C2) are used, the total amount of the content of the nonionic surfactant (C1) and the content of the nonionic surfactant (C2) may be within the above range.

One or more of the above compounds can be used as the soluble metal salt (A), and the content in the plating solution is 30 to 100g/L, preferably 40 to 60 g/L. If the content is less than the appropriate range, the productivity is lowered, and if the content is more than the appropriate range, the cost of the plating solution is increased.

As the inorganic acid, the organic acid or the salt thereof (B), only one or two or more of the above-mentioned compounds can be used, and the content in the plating solution is 80 to 300g/L, preferably 100 to 200 g/L. If the content is less than the appropriate range, the conductivity is low and the voltage rises. When the content is increased, the viscosity of the plating liquid increases and the stirring speed of the plating liquid decreases.

The content of the additive (E) in the plating solution is 0.5 to 50g/L, preferably 1 to 5 g/L.

On the other hand, the plating liquid of the present embodiment has a liquid temperature of usually 70 ℃ or lower, preferably 10 to 40 ℃. The current density at the time of formation of the plating film by electroplating was 0.1A/dm²Above and 100A/dm²The range below is preferably 0.5A/dm²Above 20A/dm²The following ranges. If the current density is too low, the productivity is lowered, and if it is too high, the height uniformity of the bump is lowered.

When a tin or tin alloy plating solution containing the nonionic surfactant (C1 and/or C2) of the present embodiment alone or containing both the nonionic surfactant (C1) and the nonionic surfactant (C2) as the surfactants is applied to a circuit board as an object to be plated, and the solution temperature and the current density are set to the above ranges, a predetermined metal film (tin or tin alloy plating layer) can be formed on the circuit board. Subsequently, when reflow processing is performed, bumps are formed.

When the bumps thus formed are loaded with a semiconductor chip, a circuit board on which the semiconductor chip is mounted is manufactured.

Examples of the circuit board include a printed circuit board, a flexible printed circuit board, and a semiconductor integrated circuit board.