COMPOSITION, METHOD FOR PRODUCING COMPOSITION, AND METHOD FOR PRODUCING SILVER FILM

Abstract

Provided is a composition, including: (A) a compound represented by the following general formula (1); (B) a compound represented by the following general formula (2); and (C) a silver compound:

##STR00001## where R.sup.1 and R.sup.2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms;

##STR00002## where R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 5 carbon atoms, and n represents 1 or 2.

Claims

1. A composition, comprising: (A) a compound represented by the following general formula (1); (B) a compound represented by the following general formula (2); and ##STR00011## (C) a silver compound: where R.sup.1 and R.sup.2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms; where R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 5 carbon atoms, and n represents 1 or 2. ##STR00012##

2. The composition according to claim 1, wherein the component (C) is at least one kind selected from the group consisting of: silver isethionate; histidine silver; hydantoin silver; and dimethylhydantoin silver.

3. The composition according to claim 1, further comprising (D) an amine compound.

4. The composition according to claim 1, further comprising (E) a reducing agent.

5. The composition according to claim 1, wherein the composition is a silver plating solution.

6. The composition according to claim 5, wherein the composition is an electroless silver plating solution.

7. The composition according to claim 5, wherein a concentration of the component (A) is from 1 g/L to 500 g/L, a concentration of the component (B) is from 0.1 g/L to 100 g/L, and a concentration of the component (C) is from 0.04 g/L to 400 g/L.

8. A method of producing the composition of claim 1, comprising of mixing the component (A), the component (B), the component (C), and a solvent.

9. A method of producing a silver film, comprising forming a silver film through use of the composition of claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0016] FIG. 1 is a schematic sectional view of a substrate to be plated after the formation of a silver film on the surface of the substrate to be plated by a silver plating method in an evaluation test.

DESCRIPTION OF EMBODIMENTS

[0017] Embodiments of the present invention are described in detail below.

Composition

[0018] A composition of the present invention includes, as essential components: (A) a compound represented by the general formula (1) (hereinafter also referred to as component (A)); (B) a compound represented by the general formula (2) (hereinafter also referred to as component (B)); and (C) a silver compound (hereinafter also referred to as component (C)).

[0019] In the general formula (1), R.sup.1 and R.sup.2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group having 1 to 5 carbon atoms that is represented by each of R.sup.1 and R.sup.2 may include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, a secondary butyl group, a tertiary butyl group, a pentyl group, and a neopentyl group. R.sup.1 and R.sup.2 each independently represent preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, particularly preferably a methyl group, because a silver film more excellent in adhesiveness and surface flatness can be obtained. In addition, it is most preferred that both R.sup.1 and R.sup.2 represent methyl groups.

[0020] Preferred specific examples of the compound represented by the general formula (1) include Compounds No. 1 to No. 15 below. In the following compounds, the symbol Me represents a methyl group, the symbol Et represents an ethyl group, the symbol nPr represents a normal propyl group, and the symbol nBu represents a normal butyl group.

##STR00005## ##STR00006##

[0021] In the general formula (2), R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group having 1 to 5 carbon atoms that is represented by each of R.sup.3 and R.sup.4 may include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, a normal butyl group, an isobutyl group, a secondary butyl group, a tertiary butyl group, a pentyl group, and a neopentyl group. R.sup.3 represents preferably a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom, a sodium atom, or a potassium atom, particularly preferably a hydrogen atom or a sodium atom because a silver film more excellent in adhesiveness and surface flatness can be obtained. R.sup.4 represents preferably a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, particularly preferably a hydrogen atom, because a silver film more excellent in adhesiveness and surface flatness can be obtained.

[0022] In the general formula (2), n represents 1 or 2. n preferably represents 2 because a silver film more excellent in adhesiveness and surface flatness can be obtained.

[0023] Preferred specific examples of the compound represented by the general formula (2) include Compounds No. 16 to No. 27 below. In the following compounds, the symbol Me represents a methyl group, the symbol Et represents an ethyl group, and the symbol iPr represents an isopropyl group.

##STR00007## ##STR00008##

[0024] Any silver compound serving as a supply source for a silver ion may be used as the silver compound serving as the component (C), and for example, silver isethionate, histidine silver, hydantoin silver, dimethylhydantoin silver, silver citrate, silver nitrate, or silver oxide may be used. Those silver compounds each serving as the component (C) may be used alone or in combination thereof. Silver isethionate, histidine silver, hydantoin silver, or dimethylhydantoin silver is preferably used as the component (C), silver isethionate or dimethylhydantoin silver is more preferably used as the component (C), and silver isethionate is most preferably used as the component (C), because a silver film more excellent in adhesiveness and surface flatness can be obtained.

[0025] The content of the component (B) is preferably from 0.1 part by mass to 20 parts by mass, more preferably from 0.3 part by mass to 10 parts by mass, particularly preferably from 1 part by mass to 5 parts by mass with respect to 100 parts by mass of the component (A) in the composition, because a silver film excellent in adhesiveness and surface flatness can be obtained.

[0026] The content of the component (C) is preferably from 0.2 part by mass to 30 parts by mass, more preferably from 0.5 part by mass to 20 parts by mass, particularly preferably from 2 parts by mass to 10 parts by mass with respect to 100 parts by mass of the component (A) in the composition, because a silver film excellent in adhesiveness and surface flatness can be obtained.

[0027] The concentration of the component (A) in the composition is not particularly limited, but is preferably from 1 g/L to 500 g/L, more preferably from 5 g/L to 200 g/L, particularly preferably from 10 g/L to 100 g/L, most preferably from 20 g/L to 60 g/L, because a silver film excellent in adhesiveness and surface flatness can be obtained.

[0028] The concentration of the component (B) in the composition is not particularly limited, but is preferably from 0.1 g/L to 100 g/L, more preferably from 0.3 g/L to 50 g/L, particularly preferably from 0.5 g/L to 10 g/L, most preferably from 0.5 g/L to 3 g/L, because a silver film excellent in adhesiveness and surface flatness can be obtained.

[0029] The concentration of the component (C) in the composition is not particularly limited, but is preferably from 0.04 g/L to 400 g/L, more preferably from 0.4 g/L to 40 g/L, particularly preferably from 0.8 g/L to 20 g/L, most preferably from 2 g/L to 10 g/L, because a silver film excellent in adhesiveness and surface flatness can be obtained.

[0030] The composition of the present invention may include, as components except the above-mentioned components (A) to (C), for example, an amine compound (D), a reducing agent (E), a stabilizer, a polymeric surfactant, and a pH adjuster.

[0031] For example, an alkylamine compound or an alkanolamine compound may be used as the amine compound (D). Specific examples of the alkylamine compound include tetramethylammonium hydroxide and ethylenediamine. Specific examples of the alkanolamine compound include ethanolamine, 2-methylaminoethanol, diethanolamine, and diisopropanolamine. Of those, tetramethylammonium hydroxide, 2-methylaminoethanol, and diisopropanolamine are preferred, and diisopropanolamine is more preferred, from the viewpoint of easily controlling a plating rate. Those amine compounds each serving as the component (D) may be used alone or in combination thereof. From the same viewpoint, the concentration of the component (D) in the composition is preferably from 0.1 g/L to 200 g/L, more preferably from 1 g/L to 200 g/L, particularly preferably from 10 g/L to 100 g/L, most preferably from 10 g/L to 70 g/L. The compound represented by the general formula (1) is not encompassed in the component (D).

[0032] Any reducing agent capable of reducing a silver ion to form a silver film may be used as the reducing agent (E), and for example, a hydrazine compound, an aldehyde compound, a hypophosphorous acid salt, a hydroxylamine compound, a polyhydric phenol compound, or a borane compound may be used. A specific example of the hydrazine compound is hydrazine. Specific examples of the aldehyde compound include formaldehyde and glyoxylic acid. A specific example of the hypophosphorous acid salt is sodium hypophosphite. A specific example of the hydroxylamine compound is hydroxylamine sulfate. A specific example of the polyhydric phenol compound is hydroquinone. A specific example of the borane compound is dimethylamine borane. Of those, the hydrazine compound and the aldehyde compound are preferred, hydrazine, formaldehyde, and glyoxylic acid are more preferred, and glyoxylic acid is most preferred, from the viewpoint of easily controlling the plating rate. Those reducing agents each serving as the component (E) may be used alone or in combination thereof. From the same viewpoint, the concentration of the component (E) in the composition is preferably from 0.1 g/L to 100 g/L, more preferably from 1 g/L to 50 g/L, particularly preferably from 5 g/L to 20 g/L.

[0033] Any compound capable of preventing a silver ion from undergoing undesired reduction owing to the influence of, for example, light or addition of the reducing agent, and enabling staying as the silver ion in a plating solution may be used as the stabilizer, and for example, a thiosulfuric acid salt, a thiocyanic acid salt, an iodide salt, a cyanide compound, a heterocyclic amine compound, a polyvalent carboxylic acid and salts thereof, or a polyvalent phosphonic acid and salts thereof may be used. Specific examples of those compounds include sodium thiosulfate, potassium thiocyanate, potassium iodide, potassium cyanide, imidazole, pyrazole, triazole, benzotriazole, ethylenediamine tetraacetic acid, ethylenediamine tetramethylene phosphonic acid. Those stabilizers may be used alone or in combination thereof. The concentration of the stabilizer in the composition varies depending on the kind of the stabilizer, but is preferably set to from about 1 g/L to about 100 g/L. When the stabilizer is blended at an appropriate concentration, a plating solution that makes adhesiveness and surface flatness more satisfactory, and besides, is excellent in stability can be provided.

[0034] For example, an oxygen-containing high-molecular weight organic compound may be used as the polymeric surfactant. Specific examples of the oxygen-containing high-molecular weight organic compound include polyethylene glycol, polypropylene glycol, a polyoxyethylene-polyoxypropylene random copolymer, a polyoxyethylene-polyoxypropylene block copolymer, a polyoxyethylene alkyl ether, and a polyoxyethylene alkyl phenyl ether. Of those, polyethylene glycol and a polyoxyethylene alkyl phenyl ether are preferred. From the viewpoint of further improving the effect of the present invention, the weight-average molecular weight of the oxygen-containing high-molecular weight organic compound is preferably from 300 to 100,000, more preferably from 500 to 10,000. In particular, polyethylene glycol or a polyoxyethylene alkyl phenyl ether having a weight-average molecular weight of from 500 to 5,000 is most preferred. From the same viewpoint, the concentration of the oxygen-containing high-molecular weight organic compound in the composition is preferably from 0.05 g/L to 50 g/L, more preferably from 0.5 g/L to 10 g/L. The weight-average molecular weight may be measured with a GPC (Tosoh HLC-8320GPC) or the like.

[0035] For example, potassium hydroxide, sodium hydroxide, sulfuric acid, hydrochloric acid, phosphoric acid, or sulfurous acid may be preferably used as the pH adjuster. Those pH adjusters may be used alone or in combination thereof so that the plating solution achieves a desired pH.

[0036] The composition of the present invention may include a solvent. A solvent well-known in a plating solution may be used as the solvent. Herein, the solvent is defined as a substance that is a liquid at 25 C. under an atmospheric pressure. Examples of the solvent include: water; alcohols, such as methanol, ethanol, isopropyl alcohol, n-butanol, ethylene glycol, 1,3-butanediol, and glycerin; acetic acid esters, such as ethyl acetate, butyl acetate, and methoxyethyl acetate; ethers, such as tetrahydrofuran, tetrahydropyran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, dibutyl ether, and dioxane; ketones, such as methyl butyl ketone, methyl isobutyl ketone, ethyl butyl ketone, dipropyl ketone, diisobutyl ketone, methyl amyl ketone, cyclohexanone, and methylcyclohexanone; and hydrocarbons, such as hexane, cyclohexane, methylcyclohexane, dimethylcyclohexane, ethylcyclohexane, heptane, octane, toluene, and xylene. Those solvents may be used alone or in combination thereof. Of those, water is preferred. The concentration of the solvent in the composition is preferably from 700 g/L to 990 g/L, more preferably from 800 g/L to 970 g/L, most preferably from 850 g/L to 950 g/L.

[0037] Any other additive known to be capable of being added to a plating solution may be optionally used in the composition of the present invention to the extent that the effect of the present invention is not inhibited.

[0038] Examples of the other additive include an anthraquinone derivative, a cationic surfactant, a nonionic surfactant, an anionic surfactant, an amphoteric surfactant, an alkanesulfonic acid, an alkanesulfonic acid salt, an alkanesulfonic acid ester, a hydroxyalkanesulfonic acid ester, and a hydroxyalkanesulfonic acid organic acid ester (provided that a compound corresponding to the component (B) is excluded). The concentration of such other additive in the composition is preferably from 0.1 mg/L to 500 mg/L, more preferably from 0.5 mg/L to 100 mg/L.

[0039] The pH of the composition of the present invention is not particularly limited, but is preferably an alkaline condition of 7.5 or more, more preferably an alkaline condition of 8 or more, particularly preferably an alkaline condition of 8.5 or more. The upper limit of the pH of the composition of the present invention is not particularly limited, but is preferably 13 or less. For the measurement of the pH, a PH meter LAQUA F-70 manufactured by HORIBA, Ltd. or the like may be used. A temperature at the time of the measurement of the pH may be about room temperature.

[0040] The composition of the present invention can be preferably used as a silver plating solution, and can be more preferably used as an electroless silver plating solution.

[0041] A method of producing the composition of the present invention only needs to include a step of mixing the component (A), the component (B), the component (C), and the solvent, and if necessary, the amine compound (D), the reducing agent (E), the stabilizer, the polymeric surfactant, the pH adjuster, and other additives. The mixing ratios of the respective components may be appropriately adjusted so that the above-mentioned preferred concentrations of the components are obtained.

Method of producing Silver Film

[0042] Next, as an example of a method of producing a silver film through use of the composition of the present invention, a method of producing a silver film by a silver plating method is described. The method of producing a silver film of the present invention may be performed in the same manner as a conventional silver plating method except that the composition of the present invention is used as a silver plating solution. Herein, a case of forming a silver film on a substrate to be plated is described.

[0043] For example, a paddle stirring-type plating apparatus may be used as a silver plating apparatus. The plating tank of the silver plating apparatus is filled with the composition of the present invention, and the substrate to be plated is immersed in the composition. As the substrate to be plated, there may be used, for example, a Si substrate, a SiO.sub.2 substrate, a SiN substrate, a Ni substrate, a NiB substrate, a Co substrate, a CoB substrate, a resist substrate, a TiO.sub.2 substrate, a TiN substrate, a TiAl substrate, a TaN substrate, a Cu substrate, a Ru substrate, a W substrate, a Ge substrate, Group III-V compound substrates, and composite substrates thereof.

[0044] The temperature of the composition during the formation of the silver film may be, for example, from 10 C. to 70 C., and is preferably from 20 C. to 60 C. When the composition of the present invention is used as an electrolysis silver plating solution, a current density may be, for example, from 0.01 A/dm.sup.2 to 30 A/dm.sup.2, and is preferably from 0.05 A/dm.sup.2 to 10 A/dm.sup.2, more preferably from 0.1 A/dm.sup.2 to 5 A/dm.sup.2. In addition, for example, air stirring, quick liquid current stirring, or mechanical stirring with a stirring blade or the like may be used as a stirring method for the composition.

[0045] In the method of producing a silver film of the present invention, a silver film excellent in adhesiveness and surface flatness can be formed on the substrate to be plated under such conditions as described above.

[0046] A product having a silver film formed thereon, which is manufactured by using the composition of the present invention, is not particularly limited, and examples thereof include a wide range of products, such as materials for automobile industry (such as a heat sink, a carburetor part, a fuel injector, a cylinder, various valves, and an inner part of an engine), materials for electronic industry (such as contact, a circuit, a semiconductor package, a printed board, a film resistor, a capacitor, a hard disk, a magnetic material, a lead frame, a nut, a magnet, a resistor, a stem, a computer part, an electronic part, a laser oscillation device, an optical memory device, an optical fiber, a filter, a thermistor, a heater, a heater for high temperature, a varistor, a magnetic head, various sensors (gas, temperature, humidity, light, speed, and the like), and MEMS), precision instruments (such as a copying machine part, an optical instrument part, and a timepiece part), aviation or ship materials (such as an instrument of a hydraulic system, a screw, an engine, and a turbine), materials for chemical industry (such as a ball, a gate, a plug, and a check), various dies, a machine tool part, and a vacuum apparatus part. The method of producing a silver film of the present invention is preferably used for the materials for electronic industry, in which a particularly fine pattern is required, is more preferably used in the manufacture of, among the materials, an optical instrument part, and is particularly preferably used in a sensor device.

Others

[0047] In this disclosure, the following aspects are given. [0048] [1]

[0049] A composition, including: [0050] (A) a compound represented by the following general formula (1); [0051] (B) a compound represented by the following general formula (2); and [0052] (C) a silver compound:

##STR00009## [0053] where R.sup.1 and R.sup.2 each independently represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms;

##STR00010## [0054] where R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a sodium atom, a potassium atom, or an alkyl group having 1 to 5 carbon atoms, and n represents 1 or 2. [0055] [2]

[0056] The composition according to Item [1], wherein the component (C) is at least one kind selected from the group consisting of: silver isethionate; histidine silver; hydantoin silver; and dimethylhydantoin silver. [0057] [3]

[0058] The composition according to Item [1]or [2], further including (D) an amine compound. [0059] [4]

[0060] The composition according to any one of Items [1]to [3], further including (E) a reducing agent. [0061] [5]

[0062] The composition according to any one of Items [1]to [4], wherein the composition is a silver plating solution. [0063] [6]

[0064] The composition according to Item [5], wherein the composition is an electroless silver plating solution. [0065] [7]

[0066] The composition according to Item [5]or [6], wherein a concentration of the component (A) is from 1 g/L to 500 g/L, a concentration of the component (B) is from 0.1 g/L to 100 g/L, and a concentration of the component (C) is from 0.04 g/L to 400 g/L. [0067] [8]

[0068] A method of producing the composition of any one of Items [1]to [7], including a step of mixing the component (A), the component (B), the component (C), and a solvent. [0069] [9]

[0070] A method of producing a silver film, including a step of forming a silver film through use of the composition of any one of Items [1]to [7].

[0071] This disclosure is not limited to the above-mentioned embodiments. The above-mentioned embodiments are illustrative, and any embodiment having substantially the same configuration as that of the technical idea described in Claims of this disclosure and exhibiting an action and effect similar thereto is encompassed in the technical scope of this disclosure.

EXAMPLES

[0072] The present invention is described in more detail below by way of Examples and Comparative Examples. However, the present invention is by no means limited by the following Examples and the like.

[0073] The components (A) used in Examples and Comparative Examples and comparative components thereof are described below. [0074] a-1: Compound No. 6 [0075] a-2: Compound No. 1 [0076] a-3: imidazole [0077] a-4: pyrazole

[0078] The components (B) used in Examples and Comparative Examples and comparative components thereof are described below. [0079] b-1: Compound No. 22 [0080] b-2: Compound No. 23 [0081] b-3: citric acid [0082] b-4: methanesulfonic acid

[0083] The components (C) used in Examples and Comparative Examples are described below. [0084] c-1: silver isethionate [0085] c-2: dimethylhydantoin silver

[0086] The components (D) used in Examples and Comparative Examples are described below. [0087] d-1: diisopropanolamine [0088] d-2: tetramethylammonium hydroxide [0089] d-3:2-methylaminoethanol

[0090] The components (E) used in Examples and Comparative Examples are described below. [0091] e-1: glyoxylic acid [0092] e-2: formaldehyde

Examples 1 to 10

[0093] The component (A), the component (B), the component (C), the component (D), the component (E), additives, and water were mixed so as to give compositions shown in Table 1. Thus, silver plating solutions of Examples 1 to 10 were obtained. As the additives, imidazole and ethylenediamine tetramethylene phosphonic acid were each added at 10 g/L in each of the silver plating solutions. The balance in the composition of each of the silver plating solutions shown in Table 1 was water, and the concentration of each component was adjusted with water.

TABLE-US-00001 TABLE 1 Example Silver plating Component (A) Component (B) Component (C) Component (D) Component (E) solution Concentration (g/L) Concentration (g/L) Concentration (g/L) Concentration (g/L) Concentration (g/L) Example 1 a-1 b-1 c-1 d-1 e-1 50 g/L 1 g/L 4.31 g/L 25 g/L 10 g/L Example 2 a-1 b-1 c-1 d-1 e-1 30 g/L 1 g/L 4.31 g/L 25 g/L 10 g/L Example 3 a-1 b-1 c-1 d-1 e-1 50 g/L 2 g/L 4.31 g/L 25 g/L 10 g/L Example 4 a-1 b-1 c-1 d-1 e-1 50 g/L 1 g/L 2.15 g/L 25 g/L 10 g/L Example 5 a-2 b-1 c-1 d-1 e-1 50 g/L 1 g/L 4.31 g/L 13 g/L 10 g/L Example 6 a-1 b-2 c-1 d-1 e-1 50 g/L 1 g/L 4.31 g/L 50 g/L 10 g/L Example 7 a-1 b-1 c-2 d-1 e-1 70 g/L 1 g/L 4.35 g/L 25 g/L 5 g/L Example 8 a-1 b-1 c-1 d-2 e-1 50 g/L 1 g/L 1.08 g/L 25 g/L 10 g/L Example 9 a-1 b-1 c-1 d-3 e-1 50 g/L 1 g/L 4.31 g/L 25 g/L 10 g/L Example 10 a-1 b-1 c-1 d-1 e-2 50 g/L 0.5 g/L 4.31 g/L 50 g/L 5 g/L

Comparative Examples 1 to 7

[0094] The component (A), the component (B), the component (C), the component (D), the component (E), additives, and water were mixed so as to give compositions shown in Table 2. Thus, silver plating solutions of Comparative Examples 1 to 7 were obtained. As the additives, imidazole and ethylenediamine tetramethylene phosphonic acid were each added at 10 g/L in each of the silver plating solutions. The balance in the composition of each of the silver plating solutions shown in Table 2 was water, and the concentration of each component was adjusted with water.

TABLE-US-00002 TABLE 2 Comparative Example Silver plating Component (A) Component (B) Component (C) Component (D) Component (E) solution Concentration (g/L) Concentration (g/L) Concentration (g/L) Concentration (g/L) Concentration (g/L) Comparative b-1 c-1 d-1 e-1 Example 1 1 g/L 4.31 g/L 10 g/L 10 g/L Comparative a-1 c-1 d-1 e-1 Example 2 50 g/L 4.31 g/L 10 g/L 10 g/L Comparative a-1 b-1 d-1 e-1 Example 3 50 g/L 1 g/L 10 g/L 10 g/L Comparative a-3 b-1 c-1 d-1 e-1 Example 4 10 g/L 1 g/L 4.31 g/L 10 g/L 10 g/L Comparative a-4 b-1 c-1 d-1 e-1 Example 5 50 g/L 1 g/L 4.31 g/L 10 g/L 10 g/L Comparative a-1 b-3 c-1 d-1 e-1 Example 6 50 g/L 1 g/L 4.31 g/L 10 g/L 10 g/L Comparative a-1 b-4 c-1 d-1 e-1 Example 7 50 g/L 1 g/L 4.31 g/L 10 g/L 10 g/L

Evaluation Examples 1 to 10 and Comparative Evaluation Examples 1 to 7

[0095] A paddle stirring-type plating apparatus was used as a silver plating apparatus, and the plating tank of the paddle stirring-type plating apparatus was filled with each of the silver plating solutions of Examples 1 to 10 and Comparative Examples 1 to 7. A substrate to be plated was immersed in each of the silver plating solutions. A product obtained by forming a NiB layer on a Si substrate having a SiO.sub.2 layer on its surface was used as the substrate to be plated. Next, a silver film was formed on the substrate to be plated by an electroless silver plating method under the following plating conditions.

(Plating Conditions)

[0096] (1) Liquid temperature: 25 C. [0097] (2) Plating time: 3 minutes

[0098] In Evaluation Examples 1 to 10 and Comparative Evaluation Examples 1 to 7, as illustrated in FIG. 1, the surface of a silver film 1 formed on the surface of a substrate 2 to be plated was observed with a scanning probe microscope (manufactured by BRUKER, model number: MultiMode 8). Thus, the roughness Ra of the surface of the silver film 1 was measured. In addition, the presence or absence of peeling of the resultant silver film was visually observed. The results are shown in Table 3.

TABLE-US-00003 TABLE 3 Silver Presence or plating Ra absence of solution (nm) peeling Evaluation Example 1 Example 1 1.0 Absent Evaluation Example 2 Example 2 1.3 Absent Evaluation Example 3 Example 3 1.3 Absent Evaluation Example 4 Example 4 1.4 Absent Evaluation Example 5 Example 5 1.4 Absent Evaluation Example 6 Example 6 1.2 Absent Evaluation Example 7 Example 7 1.5 Absent Evaluation Example 8 Example 8 1.1 Absent Evaluation Example 9 Example 9 1.5 Absent Evaluation Example 10 Example 10 1.8 Absent Comparative Evaluation Comparative 3.5 Present Example 1 Example 1 Comparative Evaluation Comparative 2.2 Present Example 2 Example 2 Comparative Evaluation Comparative Fails to form Example 3 Example 3 silver film Comparative Evaluation Comparative 2.6 Present Example 4 Example 4 Comparative Evaluation Comparative 2.9 Present Example 5 Example 5 Comparative Evaluation Comparative 4.0 Present Example 6 Example 6 Comparative Evaluation Comparative 3.7 Present Example 7 Example 7

[0099] A lower value of the Ra of the silver film indicates that a silver film more

[0100] excellent in surface flatness was able to be formed. In addition, a case in which the peeling of the silver film is absent indicates that a silver film excellent in adhesiveness was able to be formed. It was found from the results of Table 3 that, in each of Evaluation Examples 1 to 10, the peeling of the silver film was absent, and the silver film excellent in surface flatness was able to be formed as compared to each of Comparative Evaluation Examples 1 to 7. In particular, it was found that, in each of Evaluation Example 1, Evaluation Example 6, and Evaluation Example 8, the silver film particularly excellent in surface flatness was able to be formed.

[0101] As described above, it was found that the silver film excellent in adhesiveness and surface flatness was able to be formed on the substrate to be plated by the silver plating method using the composition of the present invention.

EXPLANATION ON NUMERALS

[0102] 1 silver film [0103] 2 substrate to be plated