Composition, Method for Producing Composition, and Method for Producing Silver Film

The present invention relates to a composition including compounds each having a specific structure and a silver compound, a method of producing the composition, and a method of producing a silver film through use of the composition.

A silver film has been used for a fine wiring of an electronic circuit, an imaging apparatus, a reflective material, or the like because the silver film is a useful member exhibiting a high reflectance and high conductivity among metal films. Silver plating is one typical method of producing the silver film. In the formation of the silver film through silver plating, it is required that a silver film having satisfactory adhesiveness and satisfactory surface flatness be formed in order to obtain high connection reliability.

As a composition used as a silver plating solution, many and various compositions have been reported. For example, in Patent Document 1, there is disclosed a non-silver cyanide plating bath containing a silver hydroxyalkanesulfonate, potassium iodide, and sulfanilic acid. In Patent Document 2, there is disclosed a silver plating bath containing silver isethionate, isethionic acid, and 3-aminopyrazole. In Patent Document 3, there is disclosed an electroless tin-silver alloy plating bath containing tin 2-hydroxyethanesulfonate, silver methanesulfonate, 2-hydroxyethanesulfonic acid, and thiourea.

Patent Document 1: JP H05-075837 B2

Patent Document 2: JP 2007-327 127 A

Patent Document 3: JP 2009-155703 A

However, when silver plating is performed trough use of each of silver plating solutions described in Patent Documents 1 to 3 above, there has been a problem in that a silver film excellent in adhesiveness and surface flatness cannot be obtained.

Accordingly, an object of the present invention is to provide a composition capable of providing a silver film excellent in adhesiveness and surface flatness.

The inventors of the present invention have repeated investigations, and as a result, have found that the above-mentioned object can be achieved by using a composition including compounds each having a specific structure and a silver compound. Thus, the inventors have reached the present invention.

That is, according to one embodiment of the present invention, there is provided 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:

In addition, according to one embodiment of the present invention, there is provided a method of producing the above-mentioned composition, including a step of mixing the component (A), the component (B), the component (C), and a solvent.

In addition, according to one embodiment of the present invention, there is provided a method of producing a silver film, including a step of forming a silver film through use of the above-mentioned composition.

According to the present invention, the composition capable of providing a silver film excellent in adhesiveness and surface flatness can be provided.

Embodiments of the present invention are described in detail below.

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)”).

In the general formula (), Rand Reach 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 Rand Rmay 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. Rand Reach 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 Rand Rrepresent methyl groups.

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.

In the general formula (2), Rand Reach 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 Rand Rmay 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. Rrepresents 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. Rrepresents 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 SiOsubstrate, a SiN substrate, a Ni substrate, a NiB substrate, a Co substrate, a CoB substrate, a resist substrate, a TiOsubstrate, 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.

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/dmto 30 A/dm, and is preferably from 0.05 A/dmto 10 A/dm, more preferably from 0.1 A/dmto 5 A/dm. 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.

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.

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.

In this disclosure, the following aspects are given.

A composition, including: