WO2019082884A1 - Tin or tin alloy plating solution - Google Patents

Abstract

A tin or tin alloy plating solution containing (A) a soluble salt including at least a first tin salt, (B) an acid selected from an organic acid and an inorganic acid or a salt thereof, (C) a phenyl-type surfactant comprising a polyoxyethylene bisphenol ether represented by general formula (1) and (D) a leveling agent. In formula (1), X represents CaH2a (a = 1 or 3) and m represents 2 to 12.

Description

Tin or tin alloy plating solution

The present invention relates to a tin or tin alloy plating solution for producing a bump serving as a bump electrode of tin or tin alloy on a substrate when the semiconductor integrated circuit chip is mounted on a circuit board. More specifically, the present invention relates to a tin or tin alloy plating solution which is excellent in via filling property to vias on a substrate and in which the height of the formed bumps is uniform, even for patterns having different bump diameters.
Priority is claimed on Japanese Patent Application No. 2017-205203 filed on Oct. 24, 2017, and Japanese Patent Application No. 2018-197082 filed on Oct. 19, 2018, the contents of which are incorporated herein by reference. Is incorporated herein by reference.

In a circuit board on which a semiconductor integrated circuit chip (hereinafter referred to as a semiconductor chip) is mounted, CSP (Chip Size / CSP) in which the package substrate area is reduced to approximately the same size as the semiconductor chip mounted on the substrate. At present, semiconductor devices of the scale package type are mainly manufactured. In order to connect the circuit board and the semiconductor chip, the via opening which is a via body on the substrate side is filled with tin or tin alloy to form a bump which is a protruding electrode of a protruding metal terminal, and this bump Is loaded with semiconductor chips.

Conventionally, in order to form a bump by filling the tin or tin alloy material, a conductive paste such as tin-based solder paste or a tin-based solder ball is filled in a via body portion, or a tin or tin alloy plating solution is used. After using the electroplating method to form a tin plating deposition layer in the via, heat treatment is performed to melt the conductive paste, the solder ball or the tin plating deposition layer.

A general method of forming bumps by electroplating will be described with reference to FIG. As shown in FIG. 1A, a solder resist pattern having an opening is formed on the surface of the substrate 1 to which wiring and the like have been applied. Next, electroless plating is performed on the surface of the solder resist layer 2 to form a copper seed layer 3 for feeding. 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 connected to the opening of the solder resist layer 2. Next, electric tin plating is performed inside the via 6 of the dry film resist pattern by feeding power through the copper seed layer 3, and a tin plating deposition layer 7 (tin plating film is formed in the via 6 on the copper seed layer 3. Form). Next, after the dry film resist layer and the copper seed layer are sequentially removed, the remaining tin plating deposition layer is melted by a reflow process to form tin bumps 8 as shown in FIG. 1 (b).

Until now, when forming a tin or tin alloy bump using electroplating, the composition of the tin or tin alloy plating solution is changed to suppress the via filling property to the via on the substrate or the void in the bump. Improvements have been made (see, for example, Patent Documents 1, 2, 3, 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. According to this patent document 1, this plating solution has a high via fill effect, and if this plating solution is used, tin plating is selectively deposited in the recess, so that a tin plating deposit substantially free of voids can be obtained. It is described that since there is no burnt or abnormal deposition on the surface of the formed tin-plated film, a tin-plated film having a practical and good appearance excellent in solderability, discoloration resistance and the like can be obtained.

Patent Document 2 contains (a) a carboxyl group-containing compound and (b) a carbonyl group-containing compound, and the component (a) is 1.3 g / L or more and the component (b) is 0.3 g / L. The tin or tin alloy plating solution which is the above is disclosed. In this patent document 2, this plating solution can be filled with blind vias or through holes with high reliability and in a short time by electroplating on an object to be plated having blind vias or through holes, and three-dimensional mounting of semiconductors. It is described that it can be used in the process of filling blind vias or through holes in printed wiring boards and in the formation of silicon through electrodes.

Patent Document 3 discloses a tin or tin alloy plating solution containing an inorganic acid and an organic acid, and a water-soluble salt thereof, a surfactant, and a leveling agent. Here, the surfactant is at least one nonionic surfactant selected from the group consisting of polyoxyalkylene phenyl ether or a salt thereof, and polyoxyalkylene polycyclic phenyl ether or a salt thereof, and polyoxyalkylene phenyl The phenyl constituting the ether and the polycyclic phenyl constituting the polyoxyalkylene polycyclic phenyl ether may be substituted with an alkyl group having 1 to 24 carbon atoms or a hydroxy group, and the leveling agent is an aliphatic aldehyde, And at least one member selected from the group consisting of aromatic aldehydes, aliphatic ketones, and aromatic ketones; α, β-unsaturated carboxylic acids or their amides, or salts thereof. Since this patent document 3 contains a specific nonionic surfactant and two specific types of leveling agents, it is excellent in recess fillability and can suppress the generation of voids, which makes it possible It is described that if a plating solution is used, it is possible to provide a good bump which has no recess, is smooth, and does not generate a void after reflow.

Further, Patent Document 4 discloses a soluble salt comprising either (A) a stannous salt and a mixture of a stannous salt and a salt of a metal selected from silver, copper, bismuth, nickel, indium, and gold. (B) an acid or a salt thereof, and (C) a filling organic compound selected from the group consisting of aromatic and aliphatic aldehydes, aromatic and aliphatic ketones, unsaturated carboxylic acids, and aromatic carboxylic acids; D) A galvanic tin or tin alloy plating solution for forming a bump electrode containing a nonionic surfactant is disclosed. In this patent document 4, since this plating solution is used by combining the component (D) with the specific compound (C) which suppresses the precipitation of the tin-based material, the precipitation of the upper portion of the via is effectively suppressed. The deposition of the base material can be advanced from the bottom of the via preferentially toward the upper side of the via, and the via can be filled smoothly while preventing the generation of the void, and as a result, the reflow or reflow is not performed. It is described that the protruding electrodes can be formed well and the bonding strength and the electrical characteristics are excellent.

JP-A-2014-125662 (claim 2, paragraph [0020]) JP, 2015-007276, A (claim 1, paragraphs [0011] and [0012]) JP, 2015-193916, A (claim 1, paragraph [0019]) JP, 2016-074963, A (claim 1, paragraph [0019])

In recent years, wiring patterns having different bump diameters and bump pitches are mixed on one circuit board. In such a complicated wiring pattern, it is required to form all the bumps with uniform height even when the bump diameter and the bump pitch are different. According to the tin or tin alloy plating solution of Patent Documents 1 to 4, the generation of voids in the bumps is suppressed, and the vias on the substrate can be reliably filled in a short time, and the features are excellent in via filling property and appearance. is there. However, the substrate plating solution in these documents does not have the problem of achieving height uniformity of the bumps.

Specifically, as shown in FIG. 2, in the case of patterns having different bump diameters, plating using a conventional tin or tin alloy plating solution improves the via filling property of either the small diameter or the large diameter. Is possible, but the via filling of the other is reduced. That is, in a substrate in which both small diameter and large diameter vias are present, it is difficult to plate both vias with good via filling when plating both vias simultaneously. As described above, when there are vias with different via filling properties (FIG. 2B), the height variation of the bumps after reflow becomes large, and the height uniformity of the bumps can not be achieved (FIG. 2). (D)). Therefore, in order to achieve bump height uniformity (FIG. 2C), as shown in FIG. 2A, it is necessary to improve the via filling property to both the small diameter and large diameter vias.

An object of the present invention is to provide a tin or tin alloy plating solution which is excellent in via filling property to vias on a substrate and in which the height of the formed bumps is uniform, even in the case of patterns having different bump diameters.

According to a first aspect of the present invention, there is provided (A) a soluble salt containing at least a stannous salt, (B) an acid selected from organic and inorganic acids or a salt thereof, (C) a surfactant, D) A tin or tin alloy plating solution containing a leveling agent, wherein the surfactant comprises a phenyl surfactant and the phenyl surfactant is represented by the following general formula (1): It is characterized by being an ether.

However, in the formula (1), X is C _a H _2a (a = 1 or 3), and m is 2 to 12.

A second aspect of the present invention is the invention based on the first aspect, further comprising two of a surfactant other than a phenyl surfactant, an antioxidant and an alcohol having 1 to 3 carbon atoms. It is characterized by further including the above.

According to a third aspect of the present invention, after a tin or tin alloy plating deposition layer is formed on a substrate using the tin or tin alloy plating solution described in the first or second aspect, a reflow process is performed to form bumps. Is a method of forming

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

In the tin or tin alloy plating solution according to the first aspect of the present invention, the phenyl surfactant has a specific phenyl structure in which a of X in the general formula (1) and m of a polyoxyethylene group are each in a predetermined range. By suppressing the deposition of Sn ions during plating, it becomes possible to well plate the surface to be plated. In particular, according to this plating solution, in the case of a pattern having different bump diameters, the polarization resistance is large regardless of whether the bump diameter is large or small, so that the via filling property to the via on the substrate is excellent and the formed bumps The height of the

The tin or tin alloy plating solution according to the second aspect of the present invention further comprises two or more of a surfactant other than a phenyl surfactant, an antioxidant, and an alcohol having 1 to 3 carbon atoms. The following effects are achieved. Surfactants other than phenyl surfactants exhibit effects such as stabilization of the plating solution and improvement of solubility. Antioxidants also prevent the oxidation of soluble stannous salts to stannic salts. Furthermore, the alcohol is effective in improving the solubility of the surfactant.

In the bump forming method according to the third aspect of the present invention, a tin or tin plating deposition layer is formed on a substrate using the above-mentioned tin or tin alloy plating solution, and then reflow treatment is performed to form bumps. Even if the patterns have different bump diameters, bumps having a uniform height can be formed.

In the method of manufacturing a circuit board according to the fourth aspect of the present invention, a highly reliable semiconductor device free of electrical connection defects is manufactured by manufacturing a circuit board using the bumps formed according to the method according to the third aspect. Can be made.

(A) is a cross-sectional block diagram in which the plating deposition layer was formed in the via | veer of this invention, (b) is a cross-section block diagram after peeling a dry film and a copper seed layer and heating a plating deposition layer. . (A) is a cross-sectional view showing an example in which the plating deposition layer is uniformly formed in patterns different in bump diameter (via diameter), (b) is a plating deposition layer in a pattern different in bump diameter (via diameter) It is a cross-sectional block diagram which shows the example formed unevenly, (c) peels a dry film and a copper seed layer in (a), and after heating a plating deposition layer, the height of the formed bump is uniform. (D) is an example in which the height of the bumps formed varies after peeling the dry film and copper seed layer in (b) and heating the plating deposition layer. It is a cross-sectional block diagram which shows.

Next, an embodiment of the present invention will be described.

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 selected from organic acids and inorganic acids, or a salt thereof, and (C) a surfactant. And (D) a leveling agent. This surfactant contains a phenyl surfactant, and the phenyl surfactant is a polyoxyethylene bisphenol ether represented by the above general formula (1).

The soluble salt comprises any of a stannous salt and a mixture of a stannous salt and a salt of a metal selected from the group consisting of silver, copper, bismuth, nickel, antimony, indium and zinc.

The tin alloy of the present invention is an alloy of tin and a predetermined metal selected from silver, copper, bismuth, nickel, antimony, indium and zinc, and for example, tin-silver alloy, tin-copper alloy, tin-bismuth Alloys, tin-nickel alloys, tin-antimony alloys, tin-indium alloys, binary alloys of tin-zinc alloys, ternary alloys of tin-copper-bismuth, tin-copper-silver alloys and the like can be mentioned.

Therefore, the soluble salt (A) of the present invention can form any metal ion such as Sn ²⁺ , Ag ⁺ , Cu ⁺ , Cu ²⁺ , Bi ³⁺ , Ni ²⁺ , Sb ³⁺ , In ³⁺ , Zn ^{2+ in the} plating solution. And soluble salts of the metal, such as oxides, halides of the metal, metal salts of the inorganic acid or the organic acid, and the like.

Examples of metal oxides include stannous oxide, copper oxide, nickel oxide, bismuth oxide, antimony oxide, indium oxide, zinc oxide and the like, and metal halides include stannous chloride, bismuth chloride, bromide Bismuth, cuprous chloride, cupric chloride, nickel chloride, antimony chloride, indium chloride, zinc chloride and the like can be mentioned.

As metal salts of inorganic acids or organic acids, 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 And zinc sulfonate, stannous ethane sulfonate, bismuth 2-hydroxypropane sulfonate and the like.

The acid or salt (B) of the present invention is selected from organic and inorganic acids or salts thereof. Examples of the organic acids include organic sulfonic acids such as alkanesulfonic acids, alkanolsulfonic acids and aromatic sulfonic acids, and aliphatic carboxylic acids. Examples of inorganic acids include borohydrofluoric acid, silicofluoric acid and sulfamine. Acid, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid and the like can be mentioned. The salts are salts of alkali metals, salts of alkaline earth metals, 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 waste water treatment.

As the alkanesulfonic acid, those represented by a 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 and ethanesulfonic acid Other than 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 p H 2p + 1 -CH (} OH) -C q H 2q -SO 3 H ( e.g., p = 0 ~ 6, q = 1 ~ 5) shown are those can be used in, particularly In particular, 2-hydroxyethane-1-sulfonic acid, 2-hydroxypropane-1-sulfonic acid, 2-hydroxybutane-1-sulfonic acid, 2-hydroxypentane-1-sulfonic acid, etc., 1-hydroxy Propane-2-sulfonic acid, 3-hydroxypropane-1-sulfonic acid, 4-hydroxybutane-1-sulfonic acid, 2-hydroxyhexane-1-sulfonic acid, 2-hydroxydecane-1-sulfonic acid, 2-hydroxy And dodecane-1-sulfonic acid.

The aromatic sulfonic acid is basically benzenesulfonic acid, alkylbenzenesulfonic acid, phenolsulfonic acid, naphthalenesulfonic acid, alkylnaphthalenesulfonic acid, etc. Specifically, 1-naphthalenesulfonic acid, 2-naphthalene And sulfonic acid, toluene sulfonic acid, xylene sulfonic acid, p-phenol sulfonic acid, cresol sulfonic acid, sulfosalicylic acid, nitrobenzene sulfonic acid, sulfobenzoic acid, diphenylamine-4-sulfonic acid and the like.

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

The phenyl surfactant contained in the surfactant of the present invention is a polyoxyethylene bisphenol ether represented by the following general formula (1).

However, in the formula (1), X is C _a H _2a (a = 1 or 3), and m is 2 to 12. Here, if m is less than 2, there is a problem that dissolution in the plating solution is difficult or abnormal appearance of plating occurs, and if it exceeds 12, the via filling property is inferior or abnormal appearance of plating is There is a problem that occurs. M is preferably 5 to 10. The polyoxyethylene bisphenol ether represented by the above general formula (1) may contain ortho, meta and para isomers, and mixed isomers thereof.

The leveling agent (D) of the present invention is a first leveling agent in order to form a plating film uniformly and densely and to make the plating film smooth, in addition to enhance the via filling property and to suppress the generation of voids. Two types of (D-1) and a second leveling agent (D-2) are used. As the first leveling agent (D-1), one or more selected from the group consisting of aliphatic aldehydes, aromatic aldehydes, aliphatic ketones and aromatic ketones may be mentioned, and the second leveling agent (D As -2), α, β-unsaturated carboxylic acids or their amides, or salts thereof can be mentioned.

The first leveling agent (D-1) is a carbonyl compound containing an aldehyde and 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 aliphatic aldehydes include formaldehyde, acetaldehyde and allyl aldehyde. Also, as the aromatic aldehyde, benzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-chlorobenzaldehyde, 2,4-dichlorobenzaldehyde, 2,6-dichlorobenzaldehyde, 2,4,6-trichlorobenzaldehyde, 1- Naphthaldehyde, 2-naphthaldehyde, 2-hydroxy benzaldehyde, 3-hydroxy benzaldehyde, 4-hydroxy benzaldehyde, 2-methyl benzaldehyde, 3-methyl benzaldehyde, 4-methyl benzaldehyde, m-anisaldehyde, o-anisaldehyde, p- Anisaldehyde etc. are mentioned. Moreover, as aliphatic ketone, acetylacetone etc. are mentioned. Further, as the aromatic ketone, benzylideneacetone (equivalent to benzalacetone), 2-chloroacetophenone, 3-chloroacetophenone, 4-chloroacetophenone, 2,4-dichloroacetophenone, 2,4,6-trichloroacetophenone, etc. It can be mentioned. These may be used alone or in combination of two or more. The preferred content of the first leveling agent (D-1) in the electroplating bath (it is a single amount when it is contained alone, and the total amount of these when it contains 2 or more types) is 0.001 g / L It is ̃0.3 g / L, more preferably 0.01 g / L ̃0.25 g / L. If the content of the above component is small, the effect of the addition is not sufficient. On the other hand, if the content of the above component is too large, there is a possibility that the smoothing of the plating film is inhibited.

As the second leveling agent (D-2), acrylic acid, methacrylic acid, picolinic acid, crotonic acid, 3-chloroacrylic acid, 3,3-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-hydroxy methacrylate Dimethylaminoethyl methacrylate, methacrylic anhydride, methyl methacrylic acid and the like can be mentioned. Further, as the second leveling agent (D-2), an amide of α, β-unsaturated carboxylic acid (eg, acrylamide etc.) or a salt of α, β-unsaturated carboxylic acid (eg, potassium, sodium, ammonium) Etc.) are also included. The preferred content of the second leveling agent (D-2) in the electroplating bath (it is a single amount when it is contained alone, and the total amount of these when it contains 2 or more types) is 0.01 g / L It is ̃50 g / L, more preferably 0.05 g / L to 30 g / L, still more preferably 0.05 g / L to 10 g / L. If the content of the above component is small, the effect of the addition is not sufficient. On the other hand, if the content of the above component is too large, there is a possibility that the smoothing of the plating film is inhibited.

In the tin or tin alloy plating solution of the present invention, two of a surfactant (E) other than a phenyl surfactant, an antioxidant (F) and an alcohol having 1 to 3 carbon atoms (G) It is preferable to further include the above.

Examples of other surfactants (E) in this case include usual anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants.

Examples of anionic surfactants include polyoxyalkylene alkyl ether sulfates such as polyoxyethylene (ethylene oxide: 12 mol content) nonyl ether sodium sulfate, polyoxyethylene (ethylene oxide: 12 mol content) sodium dodecyl phenyl ether sulfate, etc. Of alkylbenzene sulfonates such as polyoxyalkylene alkyl phenyl ether sulfates and sodium dodecylbenzene sulfonate, naphthol sulfonates such as sodium 1-naphthol-4-sulfonate and disodium 2-naphthol-3,6-disulfonate , (Poly) alkyl naphthalene sulfonates such as sodium diisopropyl naphthalene sulfonate, sodium dibutyl naphthalene sulfonate, sodium dodecyl sulfate, oleyl sulfate nato Alkyl sulfates such as Um like.

As a cationic surfactant, mono- to trialkylamine salts, dimethyldialkylammonium salts, trimethylalkylammonium salts, dodecyltrimethylammonium salts, hexadecyltrimethylammonium salts, octadecyltrimethylammonium salts, dodecyldimethylammonium salts, octadecenyl Dimethylethyl ammonium salt, dodecyl dimethyl benzyl ammonium salt, hexadecyl dimethyl benzyl ammonium salt, octadecyl dimethyl benzyl ammonium salt, trimethyl benzyl ammonium salt, triethyl benzyl ammonium salt, hexadecyl pyridinium salt, dodecyl pyridinium salt, dodecyl picolinium salt, dodecyl imidazo Rhinium salt, oleylimidazolinium salt, octadecylamine acetate DOO, and the like dodecylamine acetate.

Examples of nonionic surfactants include sugar esters, fatty acid esters, C ₁ -C ₂₅ alkoxyl phosphate (salts), sorbitan esters, C ₁ -C ₂₂ fatty amides, etc. ethylene oxide (EO) and / or propylene oxide (PO 4) 2) to 300 mol of addition-condensed silicone), silicon-based polyoxyethylene ether, silicon-based polyoxyethylene ester, fluorine-based polyoxyethylene ether, fluorine-based polyoxyethylene ester, ethylene oxide and / or propylene oxide and alkyl oxide with alkylamine Or sulfated or sulfonated adducts of condensation products with diamines.

Amphoteric surfactants include betaine, carboxybetaine, imidazolinium betaine, sulfobetaine, aminocarboxylic acid and the like.

The antioxidant (F) is used to prevent the oxidation of soluble stannous salts to stannic salts. As the antioxidant, hypophosphorous acids and the like, ascorbic acid or a salt thereof, phenolsulfonic acid (Na), cresol sulfonic acid (Na), hydroquinone sulfonic 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 alcohol (G) having 1 to 3 carbon atoms is used to improve the solubility of the surfactant. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol and the like. The alcohol can be used singly or in combination of two or more.

The content of the phenyl surfactant (C) in the plating solution is 0.5 g / L to 50 g / L, preferably 1 g / L to 5 g / L. If the content is less than the lower limit value, plating defects such as dendrite occur due to excessive supply of Sn ions. If the upper limit value is exceeded, it is difficult for Sn ions to reach the surface to be plated and the via filling property is inferior (deteriorated).

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

The inorganic acid, the organic acid or the salt thereof (B) can be used singly or in combination, and the content in the plating solution is 80 g / L to 300 g / L, preferably 100 g / L to 200 g / L. If the content is less than the appropriate range, the conductivity is low and the voltage is increased, and if the content is large, the viscosity of the plating solution is increased and the stirring speed of the plating solution is decreased.

On the other hand, the temperature of the electroplating solution of the present invention is generally 70 ° C. or less, preferably 10 to 40 ° C. The current density at the time of plating film formation by electroplating is in the range of 0.1 A / dm ^{2 to} 100 A / dm ² , preferably in the range of 0.5 A / dm ^{2 to} 20 A / dm ² . If the current density is too low, productivity will deteriorate, and if it is too high, the height uniformity of the bumps will deteriorate.

The plating solution of tin or tin alloy containing the phenyl surfactant (C) of the present invention can be applied to a circuit board which is an object to be plated to form a predetermined metal film on the circuit board. As the circuit board, a printed circuit board, a flexible printed circuit board, a semiconductor integrated circuit board and the like can be mentioned.

Next, an example of the present invention will be described in detail along with a comparative example.

(Phenyl-based surfactant (C) used in Examples and Comparative Examples)
Tables 1 and 2 show structural formulas of polyoxyethylene bisphenol ether which is a phenyl surfactant (C) used in Examples 1 to 7 and Comparative Examples 1 and 2.

Example 1
(Building bath of Sn plating solution)
A homogeneous solution is prepared by mixing an aqueous solution of methanesulfonic acid, methanesulfonic acid as a free acid, hydroquinone as an antioxidant, 1-naphthaldehyde as a first leveling agent, and methacrylic acid as a second leveling agent. After reaching the above, the polyoxyethylene bisphenol ether (weight average molecular weight: about 600 g / mol) of the above (C-1) was further added as a surfactant. Finally, ion exchange water was added, and a Sn plating solution of the following composition was prepared. In addition, the methanesulfonic acid Sn aqueous solution was prepared by electrolyzing a metal Sn plate in the methanesulfonic acid aqueous solution.

(Composition of Sn plating solution)
Methanesulfonic acid Sn (as Sn ²⁺ ): 50 g / L
Potassium methanesulfonate (as free acid): 100 g / L
Phenyl surfactant (C-1): 2 g / L
Hydroquinone (as antioxidant (F)): 1 g / L
1-naphthaldehyde (as a first leveling agent (D-1)): 0.1 g / L
Methacrylic acid (as a second leveling agent (D-2)): 2 g / L
Ion exchange water: balance

Examples 2 to 8 and Comparative Examples 1 to 2
In Examples 2 to 8 and Comparative Examples 1 to 2, polyoxyethylene bisphenol ethers ((C-2) to (C-10) having the structural formulas shown in Tables 1 to 2 as phenyl surfactants (C). Was used. The Sn plating solutions of Examples 2 to 8 and Comparative Examples 1 and 2 were assembled in the same manner as Example 1 except for the above. In Example 3 and Comparative Example 2, Ag is contained as a metal other than Sn (1.0 g / L as Ag ⁺ ), and in Example 5, Cu is contained as a metal other than Sn (0 2 as Cu ^2+. .5 g / L).

<Comparison test and evaluation>
Using the plating solutions prepared in 10 types of baths of Examples 1 to 8 and Comparative Examples 1 to 2, a substrate having patterns with different bump diameters is plated at a current density of 2 ASD, and tin or tin in a via is formed. An alloy plating deposited layer was formed. And it heated to 280 degreeC using the reflow apparatus, the plating deposition layer was fuse | melted, and the bump was formed. These plating deposited layers and bumps were evaluated.
In addition, “the via filling property of the tin or tin alloy plating deposition layer in the via” and the “appearance of the tin or tin alloy plating deposition layer in the via” described later are measured for the plating deposition layer before reflow. The height variation "and" voiding potential "are measured for the bumps formed after reflow of the plated deposit. The results are shown in Table 3.

(1) Via Filling Property of Tin or Tin Alloy Plating Deposited Layer in Via Using a laser microscope, observing the tin or tin alloy plated deposition in the via, the height from the highest point to the lowest point of the plated deposited layer Difference was measured. The case where the difference in height exceeds 5 μm is regarded as “defective”, and the case where the difference in height is 5 μm or less is judged as “good”, and is shown in the “via filling property” column of Table 3.

(2) Appearance of Plating Deposit Layer The tin or tin alloy plating deposition layer in the via was observed using a laser microscope to measure the surface roughness Ra. The case where the surface roughness Ra of the plating deposition layer exceeded 2 μm was regarded as “defective”, and the case of 2 μm or less was considered “good”, and it is shown in the “appearance of plating deposition layer” column of Table 3.

(3) Variation of Bump Height The height of the bumps on the substrate was measured using an automatic visual inspection apparatus. Height variation σ (standard deviation) was calculated from the measured bump height. The case where height variation σ is 3 or less is considered as “uniform”, and the case where height variation σ exceeds 3 is determined as “non-uniform”, and the result is the column of “bump height variation σ” in Table 3. It was shown to.

(4) Ease of Void Generation Transmission X-ray images were taken of bumps (2000 in total) arranged at pitches of 180 μm, 250 μm and 360 μm and having a diameter of 70 μm, 90 μm and 120 μm. The photographed image was visually observed, and when one or more voids having a size of 1% or more were observed with respect to the size of the bumps, "NG" was determined, and when no voids were observed, "OK" . The results are shown in the "void" column of Table 3.

As apparent from Table 3, compound nos. In Comparative Example 1 using C-9, since m in the general formula (1) was too small at 1, the via filling property is good, no void is observed in the bump, and the ease of occurrence of the void is also OK. However, the appearance of the plating deposition layer was poor, and the bump height variation was also uneven. Moreover, as a phenyl surfactant, the compound No. 1 is used. In Comparative Example 2 using C-10, m in the general formula (1) was too large to be 15, and no void was observed in the bump, and the void generation probability was OK, but via filling property and The appearances of the plated deposition layers were all poor, and the height variations of the bumps were also uneven.

On the other hand, compound nos. In Examples 1 to 8 in which C-1 to C-8 were used, m in the general formula (1) was in the appropriate range (2 to 12), so that the via filling property and the plating deposited layer The appearance was all good, the height variations of the bumps were all uniform, and no voids were observed in the bumps, and the tendency to generate voids was also OK.

Examples 9 to 18
In Examples 9 to 18, the weight average molecular weight of any of the first leveling agent (D-1), the second leveling agent (D-2) or a metal other than Sn and the phenyl surfactant is shown in Table 4. The Sn plating solution was built up in the same manner as in Example 1 except that it was changed to In the first leveling agent (D-1) in Table 4, D1A is benzaldehyde, D1B is 4-chlorobenzaldehyde, and D1C is 1-naphthoaldehyde. Further, in the second leveling agent (D-2) in Table 4, D2A is methacrylic acid, D2B is acrylic acid, and D2C is acrylamide.

<Comparative test 2 and evaluation>
In the same manner as in Comparative Test 1, a substrate having patterns with different bump diameters is plated under the conditions of current density 2ASD using the 10 kinds of plating solutions prepared in Examples 9 to 18 and tin or in the vias A tin alloy plating deposited layer was formed. Then, it is heated to 280 ° C. using a reflow apparatus, and the plating deposition layer is melted to form a bump, “via filling property of tin or tin alloy plating deposition layer in via”, “tin or tin in via The appearance of the alloy plating deposited layer, the "variation in bump height" and the "probability of void generation" were evaluated. The results are shown in Table 4.

As apparent from Table 4, the first leveling agent (D-1) is changed to either benzaldehyde, 4-chlorobenzaldehyde or 1-naphthaldehyde, and the second leveling agent (D-2) is methacrylic acid, acrylic In Examples 9 to 12 in which either acid or acrylamide was changed, both the via filling property and the appearance of the plating deposited layer were good, the variation in bump height was uniform, and voids were observed in the bumps. The void generation tendency was OK.

Also, change the first leveling agent (D-1) to benzaldehyde or 1-naphthaldehyde, change the second leveling agent (D-2) to methacrylic acid or acrylamide, and further add Cu or Ag as a metal other than Sn. In Examples 13 to 14 in which the additive was added, both of the via filling property and the appearance of the plating deposition layer were good, the variation in the height of the bumps was uniform, and no voids were observed in the bumps and the voids were easily generated. Was ok.

Furthermore, Examples 15 to 16 in which the concentration of the first leveling agent (D-1) was changed to 0.001 g / L and 0.3 g / L, respectively, and the concentration of the second leveling agent (D-2) were adjusted to 0. In Examples 17 to 18 which are respectively changed to 05 g / L and 30 g / L, both the via filling property and the appearance of the plating deposited layer are good, the bump height variation is also uniform, and voids are formed in the bumps. It was not seen and the possibility of void generation was OK.

The tin or tin alloy plating solution of the present invention can be used for circuit boards such as printed circuit boards, flexible printed circuit boards, and semiconductor integrated circuits.

1 substrate 2 solder resist layer 3 copper seed layer 4 dry film resist layer 6 via 7 tin plating deposition layer (tin plating film)
8 tin bumps

Claims (4)

1. (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 surfactant,
   (D) A tin or tin alloy plating solution comprising: a leveling agent;
   The surfactant comprises a phenyl surfactant,
   The tin or tin alloy plating solution, wherein the phenyl surfactant is a polyoxyethylene bisphenol ether represented by the following general formula (1).
   

   

   However, in the formula (1), X is C _a H _2a (a = 1 or 3), and m is 2 to 12.
2. The tin or tin alloy plating solution according to claim 1, further comprising two or more of a surfactant other than the phenyl surfactant, an antioxidant, and an alcohol having 1 to 3 carbon atoms.
3. A method for forming a bump by reflow processing after forming a tin or tin alloy plating deposition layer on a substrate using the tin or tin alloy plating solution according to claim 1 or 2.
4. A method of manufacturing a circuit board using bumps formed by the method according to claim 3.

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