Electrolytic silver germanium alloy plating solution

Abstract

To provide an electrolytic silver germanium alloy plating solution capable of codepositing a sufficient amount of germanium in a film, having good liquid stability, and hardly causing foaming.SOLUTION: The problem is solved by an electrolytic silver germanium alloy plating solution containing a silver source and a germanium source characterized by containing a nitrogen-containing coordination compound having a molecular weight of 500 or less. Specific examples of the nitrogen-containing coordination compound include N,N-di(2-hydroxyethyl)glycine, diethanolamine, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, triethylenetetramine, glycine, tris(hydroxymethyl) aminomethane, N-methylglucamine, bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane, tricin, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, and salts of these compounds.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an electrolytic silver germanium alloy plating solution. Furthermore, the present invention relates to a germanium eutectic accelerator for such an electrolytic silver germanium alloy plating solution, a composition for preparing such an electrolytic silver germanium alloy plating solution, and a method for manufacturing such an electrolytic silver germanium alloy plating solution.

Background Art

[0002] In recent years, the popularity of electric vehicles, plug-in hybrid vehicles, etc. has been progressing, and there is a demand for plating films having characteristics such as large area, high hardness, and low electrical resistance value, mainly for in-vehicle connector applications. And, the development of a plating solution capable of stably producing such a plating film over a long period of time is desired.

[0003] The silver plating film has the lowest electrical resistance value compared to other metal films, and has the merit of being low cost compared to the gold plating film that is often used for electronic components even when used in a large area.

[0004] The silver plating film has the drawback of relatively low hardness. However, by making the silver plating film an alloy plating film with another metal added to the silver plating film, the hardness can be improved, and this drawback can be covered.

[0005] As an example of a silver alloy plating film used for connector applications, a silver antimony alloy plating film is known (for example, Patent Document 1 and Patent Document 2). By eutecticizing antimony with silver, the crystal grains can be made smaller, and a silver plating film with high hardness (silver antimony alloy plating film) is formed.

[0006] However, like other silver plating films, the silver antimony alloy plating film may cause crystal grain growth due to recrystallization by heat, resulting in a decrease in hardness. As a result, the wear resistance when used for connector applications deteriorates in a high-temperature environment such as when a large current is applied. Furthermore, there is a drawback that due to heat, antimony atoms segregate on the surface of the silver plating layer and are oxidized, deteriorating the contact resistance of the surface.

[0007] In addition, since antimony is toxic to the human body, regulations have become stricter, and the establishment of alternative technologies is urgently needed.

[0008] As an alternative element to antimony, germanium has been studied. The silver plating film (silver-germanium alloy plating film) obtained by eutecticizing germanium with silver has high hardness. And the obtained silver-germanium alloy plating film is less likely to experience a decrease in hardness and deterioration of contact resistance even when heated.

[0009] However, it is not easy for an electrolytic silver-germanium alloy plating solution for obtaining a silver-germanium alloy plating film to succeed industrially. The reason for this is that it is not easy to eutecticize germanium in the silver plating film, and the germanium source dissolved in the plating solution is likely to precipitate. Several electrolytic silver-germanium alloy plating solutions capable of eutecticizing germanium in the silver plating film have been proposed.

[0010] Patent Document 3 discloses an electrolytic silver-germanium alloy plating solution containing a coordinating polymer additive such as polyethyleneimine or polyacrylic acid. However, Patent Document 3 does not discuss the solution stability when using a coordinating polymer additive at all. According to the follow-up tests (Examples described later) by the present inventors, in the electrolytic silver-germanium alloy plating solution described in Patent Document 3, a compound expected to be an electrolytic polymer derived from the coordinating polymer adheres to the electrode. Also, in the plating solution of Patent Document 3, germanium in the plating solution is unstable, and it has been found that the dissolved germanium precipitates when the plating solution is left standing. In addition, when the polymer is contained in the plating solution, foaming occurs, and in an industrial hoop plating line, there are problems such as the plating solution overflowing from the plating tank and the amount of the plating solution taken out to the subsequent stage increasing.

[0011] Patent Document 4 discloses a silver / germanium alloy plating solution containing a specific conductive salt, a soluble silver compound, and a specific soluble germanium compound and having a pH of 10 or more. In addition, Patent Document 5 discloses an electrolytic solution for forming a germanium-containing thin film, which is prepared by dissolving germanium dioxide in an alkaline solution, adding a free acid to prepare an acidic germanium solution, and further dissolving silver. Neither Patent Document 4 nor Patent Document 5 mentions anything about the above problems.

[0012] As described above, there is an expectation for the demand for silver alloy plating films with an alloy added to silver for uses such as connectors. Development of a silver germanium alloy plating solution that can solve the drawbacks of the known technologies described above and stably produce a silver alloy plating film over a long period of time is desired.

Prior Art Documents

Patent Documents

[0013]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0014] The present invention has been made in view of the above background art. An object of the present invention is to provide an electrolytic silver-germanium alloy plating solution capable of eutectically depositing a sufficient amount of germanium in a film, having good solution stability and being less likely to foam.

Means for Solving the Problems

[0015] As a result of intensive studies to solve the above problems, the present inventors have found the following facts and have completed the present invention.

[0016] That is, an electrolytic silver-germanium alloy plating film formed by an electrolytic silver-germanium alloy plating solution containing a compound containing a nitrogen atom in the molecule and coordinating to germanium in the plating solution (nitrogen-containing coordinating compound) contains a sufficient amount of germanium and is excellent in mechanical properties, electrical properties, etc. Further, in such an electrolytic silver-germanium alloy plating solution, the nitrogen-containing coordinating compound does not precipitate with changes during the plating operation, so such an electrolytic silver-germanium alloy plating solution exhibits good solution stability and is less likely to foam.

[0017] The present invention thus completed is as follows.

[0018] An electrolytic silver-germanium alloy plating solution containing a silver source and a germanium source, characterized by containing a nitrogen-containing coordinating compound having a molecular weight of 500 or less.

[0019] A germanium eutectic promoting agent for an electrolytic silver-germanium alloy plating solution containing a silver source and a germanium source, characterized by containing a nitrogen-containing coordinating compound having a molecular weight of 500 or less as a main component.

[0020] A composition for preparing an electrolytic silver-germanium alloy plating solution by adding a silver source to prepare the above electrolytic silver-germanium alloy plating solution, characterized by containing the germanium source and the nitrogen-containing coordinating compound.

[0021] A method for manufacturing an electrolytic silver-germanium alloy plating solution, characterized by mixing a silver source, a germanium source, and the germanium eutectic promoter described above.

[0022] A method for manufacturing an electrolytic silver-germanium alloy plating solution, characterized by mixing a silver source and the composition for preparing the electrolytic silver-germanium alloy plating solution described above.

Advantages of the Invention

[0023] The electrolytic silver-germanium alloy plating solution of the present invention can eutectic a sufficient amount of germanium in the film, so that a high-hardness electrolytic silver-germanium alloy plating film can be manufactured. The present invention can be applied to the manufacture of films that require hardness, such as electronic components like connectors.

[0024] The electrolytic silver-germanium alloy plating solution of the present invention is less likely to cause precipitation and exhibits good liquid stability. Therefore, in the present invention, compared with the prior art, the renewal cost of the electrolytic silver-germanium alloy plating solution can be significantly suppressed.

[0025] The electrolytic silver-germanium alloy plating solution of the present invention is less likely to foam. Therefore, it is possible to mass-produce products using the electrolytic silver-germanium alloy plating film with high productivity.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0027] Hereinafter, the present invention will be described, but the present invention is not limited to the following embodiments and can be arbitrarily modified and implemented.

[0028] [Electrolytic silver-germanium alloy plating solution] The present invention relates to an electrolytic silver-germanium alloy plating solution containing a silver source and a germanium source, characterized by containing a nitrogen-containing coordination compound having a molecular weight of 500 or less.

[0029] [Silver source] The silver source contained in the electrolytic silver-germanium alloy plating solution of the present invention is reduced by a plating reaction and deposited as silver on an object to be plated.

[0030] Specific examples of the silver source include silver cyanide, silver nitrate, silver sulfate, silver oxide, silver phosphate, silver chloride, silver bromide, silver iodide, and silver carbonate. Further, salts of these silver compounds (for example, lithium salt, sodium salt, potassium salt, rubidium salt, cesium salt, beryllium salt, magnesium salt, calcium salt, strontium salt, barium salt, ammonium salt) can also be used as the silver source.

[0031] Among the specific examples of the above silver source, silver cyanide salt is particularly suitable as the silver source in the electrolytic silver-germanium alloy plating solution of the present invention because it is particularly stable in an aqueous solution.

[0032] Among the silver cyanide salts, an alkali metal silver cyanide is desirable as the silver source in the electrolytic silver-germanium alloy plating solution of the present invention.

[0033] Specific examples of such an alkali metal silver cyanide include sodium silver cyanide and potassium silver cyanide. Among these, potassium silver cyanide is particularly desirable as the silver source in the electrolytic silver-germanium alloy plating solution of the present invention from the viewpoints of plating performance such as silver deposition efficiency, cost, and ease of availability.

[0034] The electrolytic silver-germanium alloy plating solution of the present invention may contain only one kind of silver source or two or more kinds of silver sources. When the electrolytic silver-germanium alloy plating solution of the present invention contains a silver cyanide salt as a silver source, the electrolytic silver-germanium alloy plating solution may contain only one kind of silver cyanide salt or two or more kinds of silver cyanide salts.

[0035] There is no particular limitation on the concentration of the silver source in the electrolytic silver-germanium alloy plating solution of the present invention (when two or more kinds of silver sources are used in combination, the total concentration). This concentration is preferably 0.5 g / L or more, more preferably 5 g / L or more, and particularly preferably 10 g / L or more in terms of silver conversion. Further, this concentration is preferably 200 g / L or less, more preferably 150 g / L or less, and particularly preferably 100 g / L or less in terms of silver conversion.

[0036] When the concentration of the silver source is equal to or higher than the above lower limit, the supply amount of silver ions becomes sufficient, and appearance defects such as burning are less likely to occur. With the plating operation, the silver source is consumed and the concentration of the silver source in the electrolytic silver-germanium alloy plating solution decreases. Therefore, when the concentration falls below the above lower limit, it is desirable to replenish the silver source to the electrolytic silver-germanium alloy plating solution.

[0037] On the other hand, when the concentration of the silver source is equal to or lower than the above upper limit, it is economically preferable because the loss amount of the silver source due to the carry-out of the electrolytic silver-germanium alloy plating solution can be suppressed.

[0038] In the present invention, instead of previously adding a silver source to the plating solution, a soluble silver anode may be used during electrolytic plating. In this case, when a voltage is applied, silver dissolves from the silver anode and is supplied into the plating solution as a silver source.

[0039] <Germanium source> The electrolytic silver-germanium alloy plating solution of the present invention contains a germanium source. Germanium supplied from the germanium source eutectifies in the plating film.

[0040] Specific examples of germanium sources include germanium dioxide, germanium inorganic acids and their salts, germanium organic acids and their salts, germanic acid and its salts, tetraalkoxygermanium, germanium halides, germanium sulfide, and elemental germanium (metallic germanium).

[0041] Specific examples of germanium inorganic acids include germanium sulfonate, germanium phosphate, germanium pyrophosphate, germanium sulfate, and germanium nitrate.

[0042] Specific examples of germanium organic acids include germanium citrate, germanium lactate, and poly-trans-[(2-carboxyethyl)germanium sesquioxide].

[0043] Even more specific examples of salts of germanium inorganic acids, germanium organic acids, and germanic acid include their lithium salts, sodium salts, potassium salts, rubidium salts, cesium salts, beryllium salts, magnesium salts, calcium salts, strontium salts, barium salts, and ammonium salts.

[0044] Among the above-mentioned germanium sources, germanium dioxide, sodium germanate, and potassium germanate are particularly desirable as germanium sources in the electrolytic silver-germanium alloy plating solution of the present invention from the viewpoints of stability in aqueous solution and ease of availability.

[0045] The electrolytic silver-germanium alloy plating solution of the present invention may contain only one type of germanium source or may contain two or more types of germanium sources.

[0046] The concentration of the germanium source in the electrolytic silver-germanium alloy plating solution of the present invention (total concentration when using two or more germanium sources in combination) is not particularly limited. In terms of germanium conversion, the concentration is preferably 0.05 g / L or more, more preferably 0.1 g / L or more, and particularly preferably 0.2 g / L or more. Further, in terms of germanium conversion, the concentration is preferably 200 g / L or less, more preferably 150 g / L or less, and particularly preferably 100 g / L or less.

[0047] When the concentration of the germanium source is at or above the above lower limit, a sufficient amount of germanium is likely to eutectify in the plating film. With the plating operation, the germanium source is consumed and the concentration of the germanium source in the electrolytic silver-germanium alloy plating solution decreases. Therefore, when the concentration falls below the above lower limit, it is desirable to replenish the germanium source to the electrolytic silver-germanium alloy plating solution.

[0048] On the other hand, when the concentration of the germanium source is at or below the above upper limit, germanium is less likely to precipitate in the electrolytic silver-germanium alloy plating solution.

[0049] In the electrolytic silver-germanium alloy plating solution of the present invention, the content ratio of silver to germanium is preferably 0.03 or more, more preferably 0.05 or more, and particularly preferably 0.1 or more in terms of germanium when silver is taken as 1. Further, in terms of germanium when silver is taken as 1, the content ratio is preferably 0.5 or less, more preferably 0.3 or less, and particularly preferably 0.2 or less. When the lower limit of the content ratio is at or above the above value, a sufficient amount of germanium is likely to eutectify in the plating film. Also, when the upper limit of the content ratio is at or below the above value, the electrical resistance value of the plating film tends to be good.

[0050] <Nitrogen-containing coordination compound> The electrolytic silver-germanium alloy plating solution of the present invention contains a nitrogen-containing coordination compound having a molecular weight of 500 or less. Unless otherwise specified, in this specification, the "nitrogen-containing coordinating compound with a molecular weight of 500 or less" is simply referred to as the "nitrogen-containing coordinating compound".

[0051] The nitrogen-containing coordinating compound contained in the electrolytic silver-germanium alloy plating solution of the present invention is a compound containing a nitrogen atom in its molecule. By containing the nitrogen-containing coordinating compound, germanium is stabilized in the electrolytic silver-germanium alloy plating solution and is less likely to precipitate. Therefore, it is presumed that a sufficient amount of germanium will eutectify in the plating film formed by the electrolytic silver-germanium alloy plating solution of the present invention. The nitrogen-containing coordinating compound contained in the electrolytic silver-germanium alloy plating solution of the present invention is not a polymer, and deposits on the electrode are less likely to form during the plating operation.

[0052] There is no particular limitation on the number of nitrogen atoms in the molecule of the nitrogen-containing coordinating compound contained in the electrolytic silver-germanium alloy plating solution of the present invention. The nitrogen-containing coordinating compound has, for example, 1, 2, 3, 4, or 5 nitrogen atoms in its molecule.

[0053] Examples of the nitrogen-containing coordinating compound contained in the electrolytic silver-germanium alloy plating solution of the present invention include compounds represented by the following general formula (1), compounds represented by the following general formula (2), and salts of these compounds.

[0054]

Chemical formula

[0055] [R 1 , R 2 , R 3 and R 4 are each a hydrogen atom or a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms. R 5 is a direct bond or a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms. Also, R 1 , R 2 , R3 and R 4 Among them, any two of them may be bonded to form a ring. In that case, the ring is a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms.

[0056] [Chemical formula]

[0057] [R 6 and R 7 are each a hydrogen atom, or a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms. R 8 is a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms. Also, R 6 , R 7 and R 8 Among them, any two of them may be bonded to form a ring. In that case, the ring is a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms.

[0058] Specific examples of R 1 ~R 8 in the general formula (1) and the general formula (2) are described below.

[0059] R 1 When it is a hydrocarbon group, specifically, an aliphatic saturated hydrocarbon group, an aliphatic unsaturated hydrocarbon group, and an aromatic hydrocarbon group can be mentioned.

[0060] R 1 When it is an aliphatic saturated hydrocarbon group, specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a neopentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and a cyclohexylmethyl group.

[0061] R 1When it is an aliphatic unsaturated hydrocarbon group, specific examples thereof include a vinyl group, an allyl group, an ethynyl group, and a propargyl group.

[0062] R 1 When it is an aromatic hydrocarbon group, specific examples thereof include a phenyl group, a tolyl group, a xylyl group, a benzyl group, a naphthyl group, a biphenyl group, an anthryl group, and a phenanthryl group.

[0063] R 1 When it is a hydrocarbon group, the number of carbon atoms in the hydrocarbon group is 1 or more and 18 or less, preferably 1 or more and 12 or less, more preferably 1 or more and 10 or less, and particularly preferably 1, 2, 3, 4, 5, 6, 7, or 8.

[0064] In the present specification, the "substituted hydrocarbon group" refers to a group that satisfies any one of the conditions that a hydrogen atom of the hydrocarbon group is substituted with a substituent or a substituent is inserted (substituted) into a carbon-carbon bond of the hydrocarbon group.

[0065] R 1 When it is a substituted hydrocarbon group, examples of the substituent include a sulfo group, a sulfoalkyl group, a carboxy group, a hydroxy group, an alkyl group, a hydroxyalkyl group, an alkenyl group, an alkynyl group, an amino group, an alkylamino group, a dialkylamino group, a cyano group, a nitro group, a halogen group, a carbonyl group, an imino group, an amide group, a sulfonyl group, and an ester group.

[0066] When the substituent is an alkyl group, a hydroxyalkyl group, an alkenyl group, an alkynyl group, an amino group, an alkylamino group, or a dialkylamino group, the substituent may be linear or branched. Further, the number of carbon atoms contained in the substituent is, for example, 1, 2, 3, 4, 5, 6, 7, or 8.

[0067] When the substituent is a halogen group, more specific examples of the substituent include a fluoro group, a chloro group, a bromo group, and an iodo group.

[0068] R 1 When is a substituted hydrocarbon group, the number of substituents may be 1 or may be 2 or more. When the substituted hydrocarbon group has two or more substituents, the respective substituents may be the same or different.

[0069] R 1 When is a substituted hydrocarbon group, specific examples thereof include the above-mentioned hydrocarbon groups (unsubstituted hydrocarbon groups) substituted with the above-mentioned substituents.

[0070] R 1 When is a substituted hydrocarbon group, the substituted hydrocarbon group has 1 or more and 18 or less carbon atoms, preferably 1 or more and 12 or less, more preferably 1 or more and 10 or less, and particularly preferably 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms. The number of carbon atoms included in the substituents is also counted.

[0071] R 2 , R 3 , R 4 , R 6 and R 7 Specific examples of R 1 This is similar to the specific example above.

[0072] R 5 When is a hydrocarbon group, specific examples include a saturated aliphatic hydrocarbon group, an unsaturated aliphatic hydrocarbon group, and an aromatic hydrocarbon group.

[0073] R 5 When is an aliphatic saturated hydrocarbon group, specific examples thereof include a methylene group, an ethylene group, an ethylidene group, a trimethylene group, a propylene group, a propylidene group, a tetramethylene group, a pentamethylene group, and a hexamethylene group.

[0074] R 5 When is an aliphatic unsaturated hydrocarbon group, specific examples thereof include a vinylene group and a vinylidene group.

[0075] R5 When it is an aromatic hydrocarbon group, specific examples thereof include a phenylene group, a naphthylene group, and a biphenylene group.

[0076] R 5 When it is a hydrocarbon group, the number of carbon atoms of the hydrocarbon group is 1 or more and 18 or less, preferably 1 or more and 12 or less, more preferably 1 or more and 10 or less, and particularly preferably 1, 2, 3, 4, 5, 6, 7, or 8.

[0077] R 5 When it is a substituted hydrocarbon group, specific examples of the substituent are the same as the specific examples of the substituent in the above-mentioned R 1 described above.

[0078] R 5 When it is a substituted hydrocarbon group, the number of substituents may be 1 or may be 2 or more. When the substituted hydrocarbon group has 2 or more substituents, the respective substituents may be of the same kind or of different kinds.

[0079] R 5 When it is a substituted hydrocarbon group, specific examples thereof include groups in which the hydrocarbon group (unsubstituted hydrocarbon group) exemplified above is substituted with the above-mentioned substituent.

[0080] R 5 When it is a substituted hydrocarbon group, the number of carbon atoms of the substituted hydrocarbon group is 1 or more and 18 or less, preferably 1 or more and 12 or less, more preferably 1 or more and 10 or less, and particularly preferably 1, 2, 3, 4, 5, 6, 7, or 8. Note that the number of carbon atoms described above also includes the carbon atoms contained in the substituent.

[0081] R 8 Specific examples of R are the same as the specific examples of R 5 when R is a hydrocarbon group or a substituted hydrocarbon group described above. 5

[0082] R 1 R 2 R​3 and R 4 When any two of them are combined to form a ring, or R 6 , R 7 and R 8 When any two of them are combined to form a ring, these rings are hydrocarbon groups or substituted hydrocarbon groups having 1 to 18 carbon atoms. Specific examples of these rings are the same as the specific examples of R 5 when R 5 is a hydrocarbon group or a substituted hydrocarbon group.

[0083] For reasons such as good solution stability and easy availability, in the general formula (1), a compound in which R 5 is an ethylene group, in the general formula (2), a compound in which R 8 is an ethylene group, and salts of these compounds are particularly desirable as the nitrogen-containing coordinating compounds to be contained in the electrolytic silver-germanium alloy plating solution of the present invention.

[0084] When the nitrogen-containing coordinating compound contained in the electrolytic silver-germanium alloy plating solution of the present invention is a salt of the compound represented by the above general formula (1) or the compound represented by the general formula (2), specific examples of the salt include lithium salt, sodium salt, potassium salt, rubidium salt, cesium salt, beryllium salt, magnesium salt, calcium salt, strontium salt, barium salt, ammonium salt.

[0085] As examples of the specific compound names of the nitrogen-containing coordinating compounds contained in the electrolytic silver-germanium alloy plating solution of the present invention, N,N-di(2-hydroxyethyl)glycine, diethanolamine, triethanolamine, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, triethylenetetramine, glycine, N,N,N’,N’-tetrakis(2-hydroxypropyl)ethylenediamine, N,N,N’,N’-tetrakis(2-hydroxyethyl)ethylenediamine, iminodiacetic acid, 1,3-diamino-2-propanol-N,N,N’,N’-tetraacetic acid, N,N’-bis(2-hydroxyethyl)ethylenediamine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, 1-(2-hydroxyethyl)piperazine, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, 4-(2-hydroxyethyl)-1-piperazinepropanesulfonic acid, N-(2-acetamido)iminodiacetic acid, N-(2-acetamido)-2-aminoethanesulfonic acid, bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane, tricine (alias: N-[tris(hydroxymethyl)methyl]glycine), 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxypropanesulfonic acid, 4-(2-hydroxyethyl)piperazine-1-(2-hydroxypropane-3-sulfonic acid), N-tris(hydroxymethyl)methyl-2-aminoethanesulfonic acid, N-tris(hydroxymethyl)methyl-3-aminopropanesulfonic acid, 3-[N,N-bis(2-hydroxyethyl)amino]-2-hydroxypropanesulfonic acid, guanidine, 1,1,3,3-tetramethylguanidine, piperazine-1,4-bis(2-hydroxypropanesulfonic acid), 2-hydroxy-3-morpholinopropanesulfonic acid, tris(hydroxymethyl)aminomethane, 2-(carbobenzoxyamino)-2-hydroxyacetic acid, trimethylurea, trimethylthiourea, tetramethylurea, N,N,N’,N’-tetramethyldiaminomethane, 1,3-propanediamine, 1,3-diamino-2-propanol, 1,4-butanediamine, 3-aminopropanoic acid, 4-aminobutyric acid, hydrazine, methylhydrazine, 1,1-dimethylhydrazine, formohydrazide, imidazole, N,N'-diacetyl ethylenediamine, 2-amino-1,3-propanediol, DL-serine, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol, and salts of these compounds (lithium salt, sodium salt, potassium salt, rubidium salt, cesium salt, beryllium salt, magnesium salt, calcium salt, strontium salt, barium salt, ammonium salt) are included.

[0086] The electrolytic silver-germanium alloy plating solution of the present invention may contain only one kind of nitrogen-containing coordination compound, or may contain two or more kinds of nitrogen-containing coordination compounds.

[0087] There is no particular limitation on the concentration of the nitrogen-containing coordination compound in the electrolytic silver-germanium alloy plating solution of the present invention (total concentration when two or more nitrogen-containing coordination compounds are used in combination). The concentration is preferably 0.1 g / L or more, more preferably 1 g / L or more, and particularly preferably 10 g / L or more. Also, the concentration is preferably 1000 g / L or less, more preferably 700 g / L or less, and particularly preferably 500 g / L or less. When the concentration of the nitrogen-containing coordination compound is not less than the above lower limit, germanium precipitation in the electrolytic silver-germanium alloy plating solution can be sufficiently suppressed. Also, when the concentration of the nitrogen-containing coordination compound is not more than the above upper limit, it is easy to suppress the cost (even if a nitrogen-containing coordination compound is added exceeding the above upper limit, the liquid stability does not improve).

[0088] <Other Components> In addition to the above-mentioned components, other components can be added to the electrolytic silver-germanium alloy plating solution of the present invention as needed. Specific examples of other components include a buffer for keeping the pH of the electrolytic silver-germanium alloy plating solution constant, a conductive salt for improving the conductivity of the electrolytic silver-germanium alloy plating solution, a surfactant for improving the defoaming of the electrolytic silver-germanium alloy plating solution, and a brightener for imparting luster to the appearance of the plating film.

[0089] There are no particular limitations on the buffer agent added to the electrolytic silver-germanium alloy plating solution of the present invention, and known ones can be used.

[0090] Specific examples of the buffer agent include carboxylic acids such as adipic acid, benzoic acid, citric acid, malic acid, succinic acid, formic acid, acetic acid, lactic acid, malonic acid, phthalic acid, oxalic acid, tartaric acid, glycine, glutamic acid, glutaric acid, iminodiacetic acid, dehydroacetic acid, maleic acid, fumaric acid, and salts thereof; inorganic acids such as boric acid, phosphoric acid, pyrophosphoric acid, phosphorous acid, thiosulfuric acid, sulfurous acid, nitric acid, sulfuric acid, hydrochloric acid, thiocyanic acid, and salts thereof; ammonia; amine compounds such as 1,2-ethylenediamine, hydroxyamine, ethanolamine, diethanolamine, triethanolamine, and salts thereof.

[0091] More specific examples of the salts of the above-mentioned carboxylic acids and inorganic acids include lithium salts, sodium salts, potassium salts, rubidium salts, cesium salts, beryllium salts, magnesium salts, calcium salts, strontium salts, barium salts, and ammonium salts of the above-mentioned carboxylic acids and inorganic acids.

[0092] More specific examples of the salts of the above-mentioned amine compounds include hydrochlorides, hydrobromides, hydroiodides, sulfates, nitrates, citrates, and lactates of the above-mentioned amine compounds.

[0093] The electrolytic silver-germanium alloy plating solution of the present invention may contain only one kind of buffer agent or may contain two or more kinds of buffer agents.

[0094] There is no particular limitation on the concentration of the buffer agent in the electrolytic silver-germanium alloy plating solution (total concentration when two or more are used in combination). The concentration is preferably 1 g / L or more, more preferably 3 g / L or more, and particularly preferably 10 g / L or more. Also, the concentration is preferably 500 g / L or less, more preferably 300 g / L or less, and particularly preferably 100 g / L or less. When the concentration of the buffer is at or above the above lower limit, a sufficient buffering effect is likely to be exhibited. Also, when the concentration of the buffer is at or below the above upper limit, costs can be suppressed (even if a buffer is added beyond the above upper limit, the buffering effect does not improve).

[0095] The pH of the electrolytic silver-germanium alloy plating solution of the present invention is preferably 6 or higher, more preferably 8 or higher, and particularly preferably 10 or higher. Also, there is no particularly preferred upper limit value for the pH. When the pH of the electrolytic silver-germanium alloy plating solution is at or above the above lower limit, the generation of hydrogen cyanide derived from silver cyanide salt is likely to be suppressed. By appropriately selecting a buffer, the pH of the electrolytic silver-germanium alloy plating solution can be made at or above the above lower limit.

[0096] There are no particular limitations on the conductive salt added to the electrolytic silver-germanium alloy plating solution of the present invention, and known ones can be used. Also, the conductive salt may be the same component as the buffer.

[0097] Specific examples of the conductive salt include cyanide salts; inorganic acids such as phosphoric acid, pyrophosphoric acid, sulfuric acid, thiosulfuric acid, nitric acid, nitrous acid, boric acid, and salts thereof; carboxylic acids such as oxalic acid, succinic acid, glutaric acid, malonic acid, citric acid, tartaric acid, malic acid, and salts thereof; ammonia; amine compounds such as 1,2-ethylenediamine, hydroxyamine, ethanolamine, diethanolamine, triethanolamine, and salts thereof.

[0098] More specific examples of the above-mentioned cyanide salts, carboxylate salts, and inorganic acid salts include lithium salts, sodium salts, potassium salts, rubidium salts, cesium salts, beryllium salts, magnesium salts, calcium salts, strontium salts, barium salts, and ammonium salts.

[0099] More specific examples of the salts of the above-mentioned amine compounds include hydrochloride salts, hydrobromide salts, hydroiodide salts, sulfate salts, nitrate salts, citrate salts, and lactate salts of the above-mentioned amine compounds.

[0100] The electrolytic silver-germanium alloy plating solution of the present invention may contain only one kind of conductive salt or may contain two or more kinds of conductive salts.

[0101] There is no particular limitation on the concentration of the conductive salt in the electrolytic silver-germanium alloy plating solution (the total concentration when two or more kinds are used in combination). The concentration is preferably 1 g / L or more, more preferably 3 g / L or more, and particularly preferably 10 g / L or more. Also, the concentration is preferably 500 g / L or less, more preferably 300 g / L or less, and particularly preferably 100 g / L or less. When the concentration of the conductive salt is at or above the above lower limit, a sufficient conductivity effect is likely to be exhibited. Also, when the concentration of the conductive salt is at or below the above upper limit, the cost can be suppressed (even if the conductive salt is added exceeding the above upper limit, the conductivity effect does not improve).

[0102] There is no particular limitation on the surfactant added to the electrolytic silver-germanium alloy plating solution of the present invention, and known surfactants can be used. Also, any of nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants can be used as the surfactant added to the electrolytic silver-germanium alloy plating solution of the present invention.

[0103] Specific examples of nonionic surfactants include ester-type nonionic surfactants such as sorbitan fatty acid esters and sucrose fatty acid esters; ether-type nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene polyoxypropylene glycols; ether-ester type nonionic surfactants such as polyoxyethylene glycerin fatty acid esters, polyoxyethylene castor oil, polyoxyethylene hydrogenated castor oil, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene sorbitol fatty acid esters, and polyoxyethylene hexitan fatty acid esters; amide-type nonionic surfactants such as lauric acid diethanolamide, oleic acid diethanolamide, and stearic acid diethanolamide.

[0104] Specific examples of the anionic surfactant include sulfonate-type anionic surfactants such as sodium 1-hexanesulfonate, sodium 1-octanesulfonate, sodium 1-decanesulfonate, sodium 1-dodecanesulfonate, sodium toluenesulfonate, sodium octylbenzenesulfonate, and sodium polyoxyethylene alkylphenol sulfonate; carboxylate-type anionic surfactants such as sodium laurate, sodium myristate, sodium palmitate, and sodium stearate; sulfate ester salt-type anionic surfactants such as sodium lauryl sulfate, sodium myristyl sulfate, and ammonium lauryl sulfate; and phosphate ester salt-type anionic surfactants such as sodium lauryl phosphate and potassium lauryl phosphate.

[0105] Specific examples of the cationic surfactant include amine salt-type cationic surfactants such as monomethylamine hydrochloride, dimethylamine hydrochloride, and trimethylamine hydrochloride; quaternary ammonium salt-type cationic surfactants such as tetramethylammonium chloride, tetrabutylammonium chloride, dodecyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, benzalkonium chloride, benzethonium chloride, dialkyldimethylammonium chloride, didodecyldimethylammonium chloride, alkyltrimethylammonium bromide, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, and benzalkonium bromide; and pyridinium salt-type cationic surfactants such as butylpyridinium chloride, dodecylpyridinium chloride, and cetylpyridinium chloride.

[0106] Specific examples of the amphoteric surfactant include betaine-type amphoteric surfactants such as lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, dodecylaminomethyldimethylsulfopropyl betaine, octadecyldimethylaminomethyldimethylsulfopropyl betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine; amino acid-type amphoteric surfactants such as sodium lauroyl glutamate, potassium lauroyl glutamate; amine oxide-type amphoteric surfactants such as lauryldimethylamine N-oxide, oleoyldimethylamine N-oxide; and the like.

[0107] The electrolytic silver-germanium alloy plating solution of the present invention may contain only one kind of surfactant or two or more kinds of surfactants.

[0108] There is no particular limitation on the concentration of the surfactant in the electrolytic silver-germanium alloy plating solution (total concentration when two or more are used in combination). The concentration is preferably 0.01 g / L or more, more preferably 0.03 g / L or more, and particularly preferably 0.1 g / L or more. Also, the concentration is preferably 20 g / L or less, more preferably 10 g / L or less, and particularly preferably 5 g / L or less.

[0109] There is no particular limitation on the brightener added to the electrolytic silver-germanium alloy plating solution of the present invention, and known brighteners can be used. Also, both organic brighteners and inorganic brighteners can be used as the brightener added to the electrolytic silver-germanium alloy plating solution of the present invention.

[0110] Specific examples of the brightening agent include 2-thiophenemethanol, triphenylphosphine, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, phenylpropionic acid, phenylpropionamide, sulfonamide, cysteine, methionine, triaminotriphenylmethane, 1-(p-aminophenyl)-3-methylpyrazole, stearamidopropyldimethyl-(β-hydroxyethyl)ammonium dihydrogen phosphate, 1,5-diphenylcarbazide, chloral hydrate, allyl isothiocyanate, carbon disulfide, thiourea, allyl thiourea, ethylene thiourea, polyethylene glycol, 2-mercaptobenzothiazole, 2-mercapto-1-methylimidazole, 2-mercaptobenzimidazole, zinc 2-mercaptobenzothiazole, 5-chloro-2-mercaptobenzothiazole, 6-amino-2-mercaptobenzothiazole, 6-nitro-2-mercaptobenzothiazole, 2-mercapto-5-methoxybenzothiazole, benzotriazole, β-indolylalanine, α-aminoglutaric acid, phenylalanine, pyridine-3-carboxylic acid, polyethylene glycol, alkylphenol polyoxyethylene ether, aliphatic amine polyoxyethylene ether, L-methionine, β-hydroxyalanine, pyridine-4-carboxylic acid, polypropylene imine, α-aminoindolepropionic acid, polyethanolamine, α-amino-β-imidazolylpropionate acid, polyvinyl alcohol, lysine, γ-methyl-α-aminovaleric acid, β-phenyl-α-alanine, polyethyleneimine, α-aminoacetic acid, α-aminovaleric acid, 1-pyridine-4-piperidine-4-carboxylic acid, α-amino-β-hydroxybutyric acid, α-tetrahydropyrrolephosphoric acid, α-alanine, 4-(4-piperidine)benzoic acid, 2-pyridylacetic acid, 2,6-pyridinedicarboxylic acid, 3,4-pyridinedicarboxylic acid, naphthol, sodium polydithiodipropanesulfonate, thiosemicarbazide, D-lyxosylamine, thiouracil, propylthiouracil, 3-ethoxy-4-hydroxybenzaldehyde, 1,4-Butynediol, 4-formyl-2-methoxyphenyl acetate, 4-hydroxy-3-methoxy-5-nitrobenzaldehyde, 3-methoxy-4-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 3-hydroxycoumarin, 2-(2-pyridyl)benzimidazole, benzotriazole, imidazole, 2-hydroxypyridine, 2,2-bipyridine, 4,4-diamino-2,2-bipyridine, bis(1-benzyl-3-carboxydihydropyridyl) ether sodium salt, methylbenzotriazole, 2-imidazole formaldehyde, isothiazole, sodium selenite, selenium oxide are exemplified.,

[0111] The electrolytic silver-germanium alloy plating solution of the present invention may contain only one kind of brightener or may contain two or more kinds of brighteners.,

[0112] There is no particular limitation on the concentration of the brightener in the electrolytic silver-germanium alloy plating solution (total concentration when two or more kinds are used in combination). The concentration is preferably 0.01 g / L or more, more preferably 0.03 g / L or more, and particularly preferably 0.1 g / L or more. Also, the concentration is preferably 20 g / L or less, more preferably 10 g / L or less, and particularly preferably 5 g / L or less.,

[0113] <Conditions for electrolytic silver-germanium alloy plating> There is no particular limitation on the film thickness of the electrolytic silver-germanium alloy plating film obtained by performing electrolytic plating using the electrolytic silver-germanium alloy plating solution of the present invention. The film thickness is preferably 0.01 μm or more, more preferably 0.03 μm or more, and particularly preferably 0.1 μm or more. Also, the film thickness is preferably 50 μm or less, more preferably 20 μm or less, and particularly preferably 10 μm or less.,

[0114] There is no particular limitation on the temperature of the electrolytic silver-germanium alloy plating solution when forming an electrolytic silver-germanium alloy plating film with the electrolytic silver-germanium alloy plating solution of the present invention. The temperature is preferably 15 °C or higher, more preferably 20 °C or higher, and particularly preferably 30 °C or higher. Also, the temperature is preferably 90 °C or lower, more preferably 80 °C or lower, and particularly preferably 70 °C or lower.

[0115] There is no particular limitation on the time (plating time) when forming an electrolytic silver-germanium alloy plating film with the electrolytic silver-germanium alloy plating solution of the present invention. The time is preferably 1 second or more, more preferably 5 seconds or more, and particularly preferably 10 seconds or more. Also, the time is preferably 60 minutes or less, more preferably 30 minutes or less, and particularly preferably 15 minutes or less.

[0116] When the temperature of the electrolytic silver-germanium alloy plating solution and the plating time are within the above ranges, it is easy to make the film thickness within the above-mentioned range.

[0117] The electrolytic silver-germanium alloy plating solution of the present invention preferably has 0.1% by mass or more of germanium eutectic in the electrolytic silver-germanium alloy plating film when forming an electrolytic silver-germanium alloy plating film by electrolytic plating. That is, the germanium eutectic rate of the electrolytic silver-germanium alloy plating film is preferably 0.1% by mass or more. The germanium eutectic rate is more preferably 0.2% by mass or more, and particularly preferably 0.5% by mass or more. By setting the content ratio of silver and germanium in the electrolytic silver-germanium alloy plating solution within the above range and making the electrolytic silver-germanium alloy plating solution contain a nitrogen-containing coordination compound with a molecular weight of 500 or less, it becomes easy to make the germanium eutectic rate not less than the above lower limit.

[0118] The germanium eutectic rate is more preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 3% by mass or less. For the purpose of obtaining a silver-germanium alloy film with high hardness, it is not necessary to make the germanium eutectic rate higher than the above upper limit.

[0119] Before forming the electrolytic silver-germanium alloy plating film, in order to improve the adhesion between the electrolytic silver-germanium alloy plating film and the base metal, a thin film with a thickness of about 0.01 μm to 0.05 μm may be formed on the base metal. Such a thin film is a film of gold, silver, etc., called a flash plating film. The electrolytic silver-germanium alloy plating solution of the present invention can be used to form an electrolytic silver-germanium alloy plating film on such a flash plating film.

[0120] The electrolytic silver-germanium alloy plating solution of the present invention can be used for in-vehicle contact members and the like. Such applications can be said to make use of the features of the electrolytic silver-germanium alloy plating solution of the present invention. When using the electrolytic silver-germanium alloy plating solution of the present invention for such applications, it is generally desirable to form a nickel plating film on a base such as copper in advance.

[0121] There is no particular limitation on the type of nickel plating solution used when forming the nickel plating film, and generally used nickel plating solutions can be used. Examples of such nickel plating solutions include Watts bath, sulfamin bath, and nickel bromide bath.

[0122] A pitting inhibitor, a primary brightener, a secondary brightener, etc. may be added to the nickel plating solution used when forming the nickel plating film as needed. There is no particular limitation on the method of using the nickel plating solution, and the nickel plating solution can be used according to a conventional method.

[0123] There is no particular limitation on the film thickness of the nickel plating film. The film thickness is preferably 0.1 μm or more, more preferably 0.3 μm or more, and particularly preferably 0.5 μm or more. Also, the film thickness is preferably 20 μm or less, more preferably 10 μm or less, and particularly preferably 5 μm or less.

[0124] [Germanium eutectic accelerator] The present invention also relates to a germanium eutectic accelerator for an electrolytic silver germanium alloy plating solution containing a silver source and a germanium source, which is characterized in that a nitrogen-containing coordinating compound having a molecular weight of 500 or less is the main component.

[0125] It may not be appropriate to store the electrolytic silver germanium alloy plating solution of the present invention in the form of a solution in which all components are dissolved for a long time in terms of storage stability. Therefore, when storing for a long time, each component in the electrolytic silver germanium alloy plating solution of the present invention may be stored separately, and the electrolytic silver germanium alloy plating solution of the present invention may be prepared immediately before plating. The germanium eutectic accelerator of the present invention is a raw material for preparing the electrolytic silver germanium alloy plating solution of the present invention.

[0126] It is presumed that the nitrogen-containing coordinating compound, which is the main component of the germanium eutectic accelerator of the present invention, coordinates with germanium in the electrolytic silver germanium alloy plating solution of the present invention to stabilize germanium, prevent precipitation of germanium, and enable a sufficient amount of germanium to eutectify in the electrolytic silver germanium alloy plating film.

[0127] Specific examples of the nitrogen-containing coordinating compound, which is the main component of the germanium eutectic accelerator of the present invention, are the same as those listed in the section of [electrolytic silver germanium alloy plating solution]. The germanium eutectic accelerator of the present invention may contain only one kind of nitrogen-containing coordinating compound or may contain two or more kinds of nitrogen-containing coordinating compounds.

[0128] The germanium eutectic accelerator of the present invention may contain components other than the nitrogen-containing coordinating compound. Hereinafter, components other than the nitrogen-containing coordinating compound and the silver source in the germanium eutectic accelerator of the present invention may be referred to as "other components".

[0129] Specific examples of the other components include a buffer, a conductive salt, a surfactant, and a brightener described in the section of [electrolytic silver germanium alloy plating solution].

[0130] Since the germanium eutectic accelerator of the present invention desirably has good storage stability, among other components, components that are incompatible with nitrogen-containing coordinating compounds are preferably not included in the germanium eutectic accelerator of the present invention. Also, since the silver source is expensive and is usually added to the plating solution by the user of the plating solution immediately before plating, it is desirable that the silver source is not included in the germanium eutectic accelerator of the present invention.

[0131] There is no particular limitation on the form of the germanium eutectic accelerator of the present invention. For example, the germanium eutectic accelerator of the present invention may be in powder form or in liquid form. The germanium eutectic accelerator of the present invention in liquid form may be an aqueous solution.

[0132] When the germanium eutectic accelerator of the present invention is an aqueous solution, components for an electrolytic silver-germanium alloy plating solution such as a silver source may be directly added to the germanium eutectic accelerator (aqueous solution) to produce the electrolytic silver-germanium alloy plating solution of the present invention, or when adding a silver source etc. to the germanium eutectic accelerator (aqueous solution), water may be further added (diluted) to produce the electrolytic silver-germanium alloy plating solution of the present invention. In the latter case, the concentration of the germanium eutectic accelerator in the germanium eutectic accelerator (aqueous solution) needs to be made higher than the concentration of the germanium eutectic accelerator desired in the electrolytic silver-germanium alloy plating solution.

[0133] [Composition for preparing electrolytic silver-germanium alloy plating solution] The present invention also relates to a composition for preparing an electrolytic silver-germanium alloy plating solution for preparing the above-mentioned electrolytic silver-germanium alloy plating solution by adding a silver source, which is characterized by containing a germanium source and a nitrogen-containing coordinating compound having a molecular weight of 500 or less.

[0134] The composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention can be said to essentially contain a germanium source with respect to the germanium eutectic accelerator of the present invention described above. Similar to the germanium eutectic accelerator of the present invention described above, the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention is a raw material for preparing the electrolytic silver-germanium alloy plating solution of the present invention.

[0135] Specific examples of the germanium source contained in the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention are the same as those listed in the section of [electrolytic silver-germanium alloy plating solution] above. The composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention may contain only one type of germanium source or may contain two or more types of germanium sources.

[0136] Specific examples of the nitrogen-containing coordination compound contained in the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention are the same as those listed in the section of [electrolytic silver-germanium alloy plating solution] above. The composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention may contain only one type of nitrogen-containing coordination compound or may contain two or more types of nitrogen-containing coordination compounds.

[0137] The composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention may contain components other than the germanium source and the nitrogen-containing coordination compound. Specific examples of such components include the buffer, the conductive salt, the surfactant, and the brightener described in the section of [electrolytic silver-germanium alloy plating solution] above.

[0138] Since it is desirable that the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention has good storage stability, among the components described above, it is desirable not to include components that have poor compatibility with the nitrogen-containing coordination compound in the germanium eutectic accelerator of the present invention. Further, the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention does not contain a silver source.

[0139] There is no particular limitation on the form of the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention. For example, the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention may be in powder form or in liquid form. The composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention in liquid form may be an aqueous solution.

[0140] When the composition for preparing an electrolytic silver-germanium alloy plating solution of the present invention is an aqueous solution, components for an electrolytic silver-germanium alloy plating solution such as a silver source may be directly added to the composition for preparing an electrolytic silver-germanium alloy plating solution (aqueous solution) to produce the electrolytic silver-germanium alloy plating solution of the present invention, or when adding a silver source etc. to the composition for preparing an electrolytic silver-germanium alloy plating solution (aqueous solution), water may be further added (diluted) to produce the electrolytic silver-germanium alloy plating solution of the present invention. In the latter case, it is necessary to make the concentrations of the germanium source and the nitrogen-containing coordination compound in the composition for preparing an electrolytic silver-germanium alloy plating solution (aqueous solution) higher than their desired concentrations in the electrolytic silver-germanium alloy plating solution.

[0141] [Method for manufacturing an electrolytic silver-germanium alloy plating solution] The present invention also relates to a method for manufacturing an electrolytic silver-germanium alloy plating solution, which is characterized by mixing a silver source, a germanium source, and the germanium eutectic accelerator described above. The present invention also relates to a method for manufacturing an electrolytic silver-germanium alloy plating solution, which is characterized by mixing a silver source and the composition for preparing an electrolytic silver-germanium alloy plating solution described above.

[0142] In the method for manufacturing an electrolytic silver-germanium alloy plating solution of the present invention, an electrolytic silver-germanium alloy plating solution is prepared using a germanium eutectic accelerator or a composition for preparing an electrolytic silver-germanium alloy plating solution as raw materials.

[0143] The manufacturing method of the electrolytic silver-germanium alloy plating solution of the present invention is preferably carried out immediately before using the electrolytic silver-germanium alloy plating solution. By doing so, the storage stability of each component of the electrolytic silver-germanium alloy plating solution is improved, and the electrolytic silver-germanium alloy plating solution can exhibit its performance without regret.

[0144] In the manufacturing method of the electrolytic silver-germanium alloy plating solution of the present invention, the electrolytic silver-germanium alloy plating solution is manufactured by mixing a silver source, a germanium source, and a germanium eutectic accelerator, or by mixing a silver source and a composition for preparing an electrolytic silver-germanium alloy plating solution. When manufacturing the electrolytic silver-germanium alloy plating solution, components other than the above components may be mixed. For example, when the germanium eutectic accelerator or the composition for preparing the electrolytic silver-germanium alloy plating solution is in powder form, it is necessary to mix water. Also, when manufacturing the electrolytic silver-germanium alloy plating solution, a buffer, a conductive salt, a surfactant, a brightener, etc. may be mixed. The above "water" does not mean only pure water, but also an "aqueous solution" in which the solute is already dissolved is included in the category of the above "water".

Examples

[0145] Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded.

[0146] In the examples and comparative examples, the following coordination compounds were used.

[0147] (Nitrogen-containing coordination compound used in the example (molecular weight 500 or less)) ·N,N-di(2-hydroxyethyl)glycine ·Diethanolamine ·N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid ·Triethylenetetramine ·Glycine ·Tris(hydroxymethyl)aminomethane ·N-methylglucamine · Bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane · Tris[hydroxymethyl]aminomethane · N,N,N’,N’-tetrakis(2-hydroxypropyl)ethylenediamine

[0148] (Complexing compounds used in comparative examples) · Polyacrylic acid (average molecular weight: 5000) · Polyethyleneimine (average molecular weight: 600)

[0149] (Measurement of germanium concentration after bath preparation and heating and standing of electrolytic silver-germanium alloy plating bath) Example 1 The following components were dissolved in water to the following concentrations, and the pH was adjusted to 12 to prepare (bath preparation) an electrolytic silver-germanium alloy plating bath.

[0150] (a) Potassium silver cyanide: 50 g / L (as silver) (b) Potassium cyanide: 100 g / L (c) N,N-di(2-hydroxyethyl)glycine: 200 g / L (d) Germanium dioxide: 5.5 g / L (as germanium) (e) Conductive salt (f) Buffer

[0151] After bath preparation, the electrolytic silver-germanium alloy plating bath was heated and allowed to stand at 40 °C for 1 week. Then, the electrolytic silver-germanium alloy plating bath was sampled with a 0.22-μm syringe filter, and the germanium concentration in the solution was quantified using a high-frequency inductively coupled plasma optical emission spectrometer ICPS-7510 (manufactured by Shimadzu Corporation). The measured germanium concentration after heating and standing is shown in Table 1.

[0152] Examples 2 to 10, Comparative Examples 1 to 4 An electrolytic silver-germanium alloy plating solution was prepared in the same manner as in Example 1, except that the type and concentration of the component (c) (coordination compound) and the concentration of the component (d) were changed as shown in Table 1. In Comparative Example 1, the component (c) (coordination compound) was not added to the electrolytic silver-germanium alloy plating solution. Also, in the same manner as in Example 1, the electrolytic silver-germanium alloy plating solution after bath formation was allowed to stand heated, and the germanium concentration after standing was measured.

[0153]

Table 1

[0154] <(2) Measurement of the eutectic ratio of germanium in the electrolytic silver-germanium alloy plating film> A 15 mm × 25 mm copper plate was used as a plating sample. Electrolytic nickel strike plating, electrolytic nickel plating, electrolytic gold strike plating, and electrolytic silver-germanium alloy plating were performed on the copper plate in the steps shown in Table 2.

[0155]

Table 2

[0156] "Electrolytic nickel strike plating A" used in the electrolytic nickel strike plating step is an electrolytic nickel strike plating solution containing nickel chloride at a concentration of 240 g / L and hydrochloric acid at a concentration of 125 mL / L.

[0157] "Electrolytic nickel plating B" used in the electrolytic nickel plating step is an electrolytic nickel plating solution containing nickel sulfate at a concentration of 240 g / L, nickel chloride at a concentration of 45 g / L, boric acid at a concentration of 30 g / L, and additive SN-2000 (manufactured by Murata Co., Ltd.) at a concentration of 1 mL / L.

[0158] The electrolytic silver-germanium alloy plating solution used in the electrolytic silver-germanium alloy plating step is the same as that prepared in (1) above. However, the concentration of the added (d) germanium dioxide was not the concentration at the time of bath formation in the above (1), but was set to be the germanium concentration measured after heating and leaving standing (the concentration shown in the rightmost column of Table 1).

[0159] The process of electrolytic silver-germanium alloy plating was carried out using a jet-stream plating apparatus (manufactured by Nippon High Purity Chemical Co., Ltd.) under the following conditions.

[0160] · Jet orifice: circular (diameter 10 mm) · Flow rate of the electrolytic silver-germanium alloy plating solution: 18 L / min · Temperature of the electrolytic silver-germanium alloy plating solution: 30 °C · Current density: 25 A / dm 2 · Plating time: 30 seconds

[0161] The plated sample was put into a mixed solution of 15 mL of an aqueous sodium cyanide solution at 50 g / L and 0.8 mL of hydrogen peroxide solution and stirred to dissolve the electrolytic silver-germanium alloy plating film.

[0162] This dissolution solution was filled into a volumetric flask and diluted to 20 mL to obtain a measurement sample. Then, it was analyzed with a high-frequency inductively coupled plasma optical emission spectrometer ICPS-7510 (manufactured by Shimadzu Corporation) to quantify the concentrations of silver and germanium.

[0163] The percentage value obtained by dividing the content of germanium in the measurement sample by the sum of the contents of silver and germanium was calculated as the germanium eutectic ratio. When the germanium eutectic ratio was 0.1 mass% or more, it was judged as "good", and when the germanium eutectic ratio was less than 0.1 mass%, it was judged as "bad". The results are shown in Table 3.

[0164] <(3) Measurement of the hardness of the electrolytic silver-germanium alloy plating film> In the same manner as in the above (2), electrolytic nickel strike plating, electrolytic nickel plating, electrolytic gold strike plating, and electrolytic silver-germanium alloy plating were carried out on the sample to be plated (15 mm × 25 mm copper plate). However, in the process of electrolytic silver-germanium alloy plating, the plating time was changed to 3 minutes.

[0165] The plated sample was heated on a hot plate at 260 °C for 90 seconds. For the silver-germanium alloy plating film after heating, resin embedding was carried out using cold embedding resin 105NSP (manufactured by Stoeras) and hardener 105MZAI (manufactured by Stoeras), and processing was carried out using a polishing machine.

[0166] Using a microhardness tester MVK-H300 (manufactured by Mitutoyo Corporation), the micro-Vickers hardness obtained when the surface of the electrolytic silver-germanium alloy plating film was held at a test force of 10 g for 10 seconds was measured. The measurement was carried out 3 times, and the average value was calculated. The results are shown in Table 3.

[0167] <(4) Foaming property of electrolytic silver-germanium alloy plating solution> In the process of electrolytic silver-germanium alloy plating, when the phenomenon that it foamed during operation and spilled out of the jet spray type plating apparatus was confirmed, it was judged as "defective", and when such a phenomenon was not confirmed, it was judged as "good". The results are shown in Table 3.

[0168] <(5) Liquid stability of electrolytic silver-germanium alloy plating solution> Current density 25 A / dm 2 , at a plating solution temperature of 30 °C, the electrolytic silver-germanium alloy plating solution was run for 15.5 hours. The bath load (plating area (dm 2 ) / capacity (L) of the plating bath) was 0.011 dm 2 / L. When the occurrence of precipitation was confirmed, it was judged as "defective", and when the occurrence of precipitation was not confirmed, it was judged as "good". The results are shown in Table 3.

[0169]

Table 3

[0170] <(6) Presence or absence of deposits on the electrode after running> In (5) above, the state of the electrode was observed after running the electrolytic silver-germanium alloy plating solution for 15.5 hours.

[0171] In Comparative Example 4, as shown in Fig. 1, the platinum anode (the cylindrical protruding portion in the center of Fig. 1) was discolored black. Fig. 2 shows the platinum anode before running. In contrast, in Examples 1 to 10, the appearance of the platinum anode after running was unchanged from that before running.

[0172] In Comparative Example 4, it is presumed that the platinum anode was discolored black because the electrolytic polymer derived from the complexing polymer (polyethyleneimine) in the electrolytic silver-germanium alloy plating solution adhered to the platinum anode.

Industrial Applicability

[0173] The electrolytic silver-germanium alloy plating solution of the present invention can produce an electrolytic silver-germanium alloy plating film having high hardness and maintains good solution stability, so it is used for manufacturing silver alloy plating films in the electronic industry field and the like. The electrolytic silver-germanium alloy plating solution of the present invention is particularly suitable for the hard silver alloy plating which has been put into practical use in the manufacture of in-vehicle contact members (connectors) and the like.

Claims

1. 1. An electrolytic silver-germanium alloy plating solution containing a silver source and a germanium source, the electrolytic silver-germanium alloy plating solution comprising a nitrogen-containing coordinating compound having a molecular weight of 500 or less.

2. The electrolytic silver-germanium alloy plating solution according to claim 1, wherein the nitrogen-containing coordinating compound is one or more compounds selected from the group consisting of compounds represented by the following general formula (1) and compounds represented by the following general formula (2) and salts of these compounds: 【Chemical 1】 [R １ , R ２ , R ３ and R ４ is each a hydrogen atom, or a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms. R ５ is a direct bond or a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms. Further, any two of R １ , R ２ , R ３ and R ４ may be bonded to each other to form a ring, and in that case, the ring is a hydrocarbon group or a substituted hydrocarbon group having 1 or more and 18 or less carbon atoms.] 【Chemical formula 2】 [R ６ and R ７ is each a hydrogen atom or a hydrocarbon group or substituted hydrocarbon group having from 1 to 18 carbon atoms. R ８ is a hydrocarbon group or substituted hydrocarbon group having from 1 to 18 carbon atoms. Further, any two of R ６ , R ７ and R ８ may combine to form a ring, in which case the ring is a hydrocarbon group or substituted hydrocarbon group having from 1 to 18 carbon atoms.]

3. The electrolytic silver-germanium alloy plating solution according to claim 2, wherein the nitrogen-containing coordinating compound is one or more compounds selected from the group consisting of N,N-di(2-hydroxyethyl)glycine, diethanolamine, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, triethylenetetramine, glycine, tris(hydroxymethyl)aminomethane, N-methylglucamine, bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane, tricine, and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, and salts of these compounds.

4. wherein the nitrogen-containing coordinating compound, R in the general formula (1) ５ is a compound in which is an ethylene group and R in the general formula (2) ８ is an electrolytic silver-germanium alloy plating solution according to claim 2, which is at least one compound selected from the group consisting of a compound in which is an ethylene group and salts of these compounds.

5. 2. The electrolytic silver-germanium alloy plating solution according to claim 1, wherein said silver source is a silver cyanide salt.

6. 2. The electrolytic silver-germanium alloy plating solution according to claim 1, wherein the germanium source is one or more germanium sources selected from the group consisting of germanium dioxide, germanic acid and its salts, tetraalkoxygermanium, germanium halides, germanium sulfide, and germanium elements.

7. 2. The electrolytic silver-germanium alloy plating solution according to claim 1, wherein when an electrolytic silver-germanium alloy plating film is formed by electrolytic plating, 0.1% by mass or more of germanium is co-deposited in the electrolytic silver-germanium alloy plating film.

8. A germanium co-deposition accelerator for an electrolytic silver-germanium alloy plating solution containing a silver source and a germanium source, the germanium co-deposition accelerator being characterized in that it comprises, as a main component, a nitrogen-containing coordinating compound having a molecular weight of 500 or less.

9. The germanium co-deposition accelerator according to claim 8, wherein the nitrogen-containing coordinating compound is one or more compounds selected from the group consisting of one or more compounds selected from the group consisting of compounds represented by the following general formula (1) and compounds represented by the following general formula (2) and salts of these compounds: 【Chemical Formula 3】 [R １ , R ２ , R ３ and R ４ is each a hydrogen atom or a hydrocarbon group or a substituted hydrocarbon group having from 1 to 18 carbon atoms. R ５ is a direct bond or a hydrocarbon group or a substituted hydrocarbon group having from 1 to 18 carbon atoms. Further, any two of R １ , R ２ , R ３ and R ４ may be bonded to each other to form a ring, and in that case, the ring is a hydrocarbon group or a substituted hydrocarbon group having from 1 to 18 carbon atoms.] 【Chemical Formula 4】 [R ６ and R ７ are each a hydrogen atom or a hydrocarbon group or a substituted hydrocarbon group having 1 to 18 carbon atoms. R ８ is a hydrocarbon group or a substituted hydrocarbon group having 1 to 18 carbon atoms. Further, any two of R ６ , R ７ and R ８ may be bonded to each other to form a ring, and in that case, the ring is a hydrocarbon group or a substituted hydrocarbon group having 1 to 18 carbon atoms.]

10. The germanium eutectic accelerator according to claim 9, wherein the nitrogen-containing coordinating compound is one or more compounds selected from the group consisting of N,N-di(2-hydroxyethyl)glycine, diethanolamine, N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid, triethylenetetramine, glycine, tris(hydroxymethyl)aminomethane, N-methylglucamine, bis(2-hydroxyethyl)aminotris(hydroxymethyl)methane, tricine and N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine and salts of these compounds.

11. The nitrogen-containing coordination compound, wherein R in the general formula (1) ５ is an ethylene group, the compound wherein R in the general formula (2) ８ is an ethylene group, and at least one compound selected from the group consisting of salts of these compounds; the germanium eutectic accelerator according to claim 9

12. A composition for preparing an electrolytic silver-germanium alloy plating solution for preparing an electrolytic silver-germanium alloy plating solution according to any one of claims 1 to 7 by adding a silver source, characterized by containing the germanium source and the nitrogen-containing coordinating compound.

13. A method for producing an electrolytic silver-germanium alloy plating solution, characterized by mixing a silver source, a germanium source, and the germanium eutectic accelerator according to any one of claims 8 to 11.

14. A method for producing an electrolytic silver-germanium alloy plating solution, characterized by mixing a silver source and the composition for preparing an electrolytic silver-germanium alloy plating solution according to claim 12.

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