Catalyst solution for electroless plating

Abstract

To provide catalyst solution for electroless plating that is low-cost yet useful.SOLUTION: Catalyst solution for electroless plating contains nickel alloy nanoparticles having a hexagonal closest packing structure. Preferably, the nickel alloy nanoparticles are at least one kind selected from a group consisting of Ni-B alloy nanoparticles and Ni-C alloy nanoparticles.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a catalyst solution for electroless plating and the like.

Background Art

[0002] In recent years, resin molded bodies have been used as automotive parts for the purpose of reducing the weight of automobiles. For such purposes, as the resin molded body, for example, acrylonitrile-butadiene-styrene copolymer (ABS) resin, polycarbonate (PC) / ABS resin, polyphenylene ether (PPE) resin, polyamide resin, etc. are used, and plating such as copper and nickel is applied to impart a sense of luxury and aesthetics. Furthermore, even when imparting conductivity to a resin substrate to form a conductor circuit, a plating film such as copper is formed on the resin substrate.

[0003] As a general method for forming a plating film on a resin material, after roughening the surface of the resin material by etching treatment with chromic acid, neutralization and pre-dip are performed as necessary, and then a catalyst for electroless plating is applied using a colloidal solution containing a tin compound and a palladium compound, and then an activation treatment (accelerator treatment) for removing tin is performed, and a method of sequentially performing electroless plating and electroplating is performed.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above plating method, there is a problem that the cost is high because a catalyst solution for electroless plating containing an expensive palladium compound is used.

[0005] The main problem of the present invention is to provide a useful catalyst solution for electroless plating at low cost.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the inventors have found that nickel alloy nanoparticles having a hexagonal close-packed structure are useful as a catalyst for electroless plating while being low-cost. The present invention has been completed through further studies based on this finding.

[0007] The present invention includes the following aspects. Item 1. An electroless plating catalyst solution containing nickel alloy nanoparticles having a hexagonal close-packed structure. Item 2. The electroless plating catalyst solution according to Item 1, wherein the nickel alloy nanoparticles are at least one selected from the group consisting of Ni-B alloy nanoparticles and Ni-C alloy nanoparticles. Item 3. The electroless plating catalyst solution according to Item 1 or 2, wherein the average particle diameter of the nickel alloy nanoparticles is 1 to 200 nm. Item 4. The electroless plating catalyst solution according to any one of Items 1 to 3, wherein the content of the nickel alloy nanoparticles is 0.1 to 80% by mass with respect to 100% by mass of the electroless plating catalyst solution. Item 5. The electroless plating catalyst solution according to any one of Items 1 to 4, containing at least one solvent selected from the group consisting of water, alcohol, glycol ether, alicyclic hydrocarbon, amide, and sulfoxide. Item 6. A pretreatment method for electroless plating, including a step of bringing an object to be plated into contact with the electroless plating catalyst solution according to any one of Items 1 to 5.

Advantages of the Invention

[0008] According to the present invention, an electroless plating catalyst solution that is useful while being low-cost is provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0010] 1. Catalyst solution for electroless plating The electroless plating catalyst solution of the present invention (hereinafter simply referred to as "catalyst solution") contains nickel alloy nanoparticles having a hexagonal close-packed (hcp) structure.

[0011] Nickel and nickel alloys usually have a face-centered cubic lattice (fcc) structure. When nickel or a nickel alloy having an fcc structure is used as an electroless plating catalyst, its activity is lower compared to conventional palladium. Therefore, among those skilled in the art, nickel and nickel alloys have been recognized as having low activity as electroless plating catalysts. However, as a result of intensive studies, the present inventors have found that nickel alloy nanoparticles having an hcp structure unexpectedly exhibit activity equivalent to or higher than that of conventional palladium.

[0012] (Nickel alloy nanoparticles) In this specification, "nanoparticles" refer to particles with an average particle diameter on the order of nm, that is, particles with a diameter of less than 1 μm. The "average particle diameter" refers to a value calculated by randomly selecting 50 particles in a transmission electron microscope (TEM) photograph, measuring their particle diameters, and averaging them.

[0013] Nickel alloy nanoparticles are not particularly limited as long as they have an hcp structure. Examples of nickel alloy nanoparticles include Ni-B alloy nanoparticles, Ni-C alloy nanoparticles, Ni-N alloy nanoparticles, Ni-S alloy nanoparticles, and the like. The nickel alloy nanoparticles may be used alone or in combination of two or more.

[0014] The average particle diameter of the nickel alloy nanoparticles is preferably 1 to 200 nm. When the average particle diameter is within this range, aggregation of the nanoparticles can be prevented, the stability of the catalyst solution is excellent, and the catalytic activity is even more excellent. The average particle diameter of the nickel alloy nanoparticles is more preferably 1 to 150 nm, still more preferably 2 to 100 nm, and particularly preferably 5 to 50 nm.

[0015] Examples of the method for producing nickel alloy nanoparticles include the following steps A and B: (A) Step A of dissolving nickel chloride hydrate (e.g., hexahydrate, tetrahydrate) and, if necessary, a dispersant in a solvent, and (B) Step B of adding a material for forming an alloy (e.g., sodium borohydride for forming a Ni-B alloy, hydrazine hydrate for forming a Ni-C alloy) to the solution obtained in Step A A method including these steps can be mentioned.

[0016] The solvent and dispersant used in Step A are not particularly limited, and examples include the same ones as those contained in the catalyst solution described later. The concentration of nickel chloride hydrate is not particularly limited, but is, for example, 1 to 50 g / L.

[0017] The addition amount of the alloy-forming material used in Process B is not particularly limited. The addition amount may be, for example, an amount that results in a concentration of 1 to 50 g / L. The conditions of Process B are not particularly limited as long as an alloy can be formed. However, the liquid temperature of the dissolution solution can be selected, for example, from within the range of 1 to 250 °C according to the type of solvent, the type of alloy-forming material, etc.

[0018] The content of the nickel alloy nanoparticles is preferably 0.1 to 80% by mass, more preferably 0.2 to 40% by mass, still more preferably 0.5 to 30% by mass, and particularly preferably 1 to 20% by mass with respect to 100% by mass of the catalyst solution. As the content increases, the catalyst adsorption amount also increases, and sufficient plating precipitation properties can be obtained. On the other hand, as the content is reduced, the catalyst usage amount is also reduced, and the cost can be reduced.

[0019] (Solvent) The catalyst solution usually contains a solvent. The solvent is not particularly limited as long as it can disperse the nickel alloy nanoparticles. Examples of the solvent include water, alcohol, glycols, alicyclic hydrocarbons, amides, sulfoxides, etc. The solvent may be a single type or a combination of two or more types.

[0020] The alcohol is not particularly limited. For example, C 1-4 alcohols such as methanol and ethanol can be mentioned.

[0021] The glycols are not particularly limited. For example, polyalkylene glycol or its alkyl ether can be mentioned. Specifically, (poly)C 2-4 alkylene glycols such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, etc. or their mono-C 1-4 alkyl ethers, etc. can be mentioned.

[0022] The alicyclic hydrocarbon is not particularly limited, and examples thereof include cyclopropane, cyclobutane, cyclopentane, housane, cyclohexane, cycloheptane, cyclooctane, cubane, basketane, cyclopropene, cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctyne, etc. C 5-10 Examples thereof include cycloalkanes or cycloalkenes.

[0023] The amide is not particularly limited, and examples thereof include formamide, acetamide, benzamide, N,N-dimethylformamide (DMF), acetanilide, etc.

[0024] The sulfoxide is not particularly limited, and examples thereof include dimethyl sulfoxide (DMSO), diethyl sulfoxide, disulfoxide, methyl-phenyl-sulfoxide, 4-chlorophenyl sulfoxide, etc.

[0025] (Dispersant) The catalyst solution may further contain a dispersant. The dispersant is not particularly limited, and examples thereof include polyvinylpyrrolidone, polyvinyl alcohol, carboxymethyl cellulose, gelatin, etc. The dispersant may be used alone or in combination of two or more. The content of the dispersant is preferably 0.01 to 40% by mass, more preferably 0.02 to 20% by mass, and still more preferably 0.05 to 10% by mass with respect to 100% by mass of the catalyst solution.

[0026] (pH) The pH of the catalyst solution at 25 °C is not particularly limited and is usually in the range of 2 to 9. The higher the pH, the less concern there is about the dissolution and ionization of nickel alloy nanoparticles, and the lower the pH, the better the bath stability of the catalyst solution.

[0027] 2. Pretreatment method for electroless plating The pretreatment method for electroless plating of the present invention includes a step of bringing an object to be plated into contact with a catalyst solution (hereinafter referred to as "catalyst application step").

[0028] (Catalyst solution) As the catalyst solution, the catalyst solution described in the above 1 can be used.

[0029] (Object to be plated) The object to be plated is not particularly limited with respect to its shape, size, etc., as long as it is an object for electroless plating. Typical examples of the object to be plated include resin molded articles. By performing pretreatment with the catalyst solution of the present invention, a good plating film excellent in decorativeness, physical properties, etc. can be formed even on a resin molded article having a large surface area. Examples of such resin molded articles include automotive-related parts such as radiator grills, wheel caps, medium and small emblems, and door handles; exterior parts in the electric and electronic fields; faucet fittings used in water-related areas; and gaming machine-related parts such as pachinko parts.

[0030] The resin material of the resin molded article is not particularly limited either. For example, styrene-based resins such as acrylonitrile-butadiene-styrene copolymer (ABS) resin, resin (AAS resin) in which the butadiene rubber component of ABS resin is replaced with an acrylic rubber component, and resin (AES resin) in which the butadiene rubber component of ABS resin is replaced with an ethylene-propylene rubber component can be mentioned. Alloy resins of the above styrene-based resins and polycarbonate (PC) resins (for example, alloy resins in which the mass ratio of the above styrene-based resin to PC resin is about 30 / 70 to 70 / 30) can also be preferably used. Furthermore, polyamide resins, polyphenylene ether (PPE) resins, polyphenylene oxide (PPO) resins, etc. excellent in heat resistance and physical properties can be used in the same manner. The resin material may be a single type or a combination of two or more types.

[0031] (Degreasing process) The pretreatment method for electroless plating of the present invention preferably includes a step of subjecting the object to be plated to a degreasing treatment (hereinafter simply referred to as the "degreasing step") before the catalyst application step. The degreasing treatment can remove the dirt on the surface of the object to be plated.

[0032] The degreasing treatment can be carried out by a known method, for example, a method of bringing the object to be plated into contact with or immersing it in a degreasing solution. The degreasing solution is not particularly limited, and examples thereof include a degreasing solution containing water, an alkali metal salt, and a surfactant. Examples of the alkali metal salt include sodium hydroxide, sodium metasilicate, sodium carbonate, sodium phosphate, sodium pyrophosphate, and the like. Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ether.

[0033] The degreasing treatment conditions are not particularly limited regardless of the degreasing solution used. The treatment temperature (for example, the liquid temperature of the degreasing solution) can be about 40 to 70°C, and the treatment time (for example, the contact or immersion time in the degreasing solution) can be about 1 to 20 minutes.

[0034] (Etching step) The pretreatment method of electroless plating of the present invention preferably includes a step of etching the object to be plated (hereinafter simply referred to as the "etching step") before the catalyst imparting step. By appropriately roughening the surface of the object to be plated by etching, the adhesion of the plating film can be improved.

[0035] Etching can be carried out by a known method, for example, a method of bringing the object to be plated into contact with or immersing it in an etching solution. The etching solution is not particularly limited, and examples thereof include an etching solution containing chromic acid and sulfuric acid, and an etching solution containing permanganate. Examples of the former include an etching solution having a composition of chromic anhydride; 400 g / L, sulfuric acid; 400 g / L, trivalent chromium; 10 g / L. Examples of the latter include an etching solution described in International Publication No. 2015 / 060196 containing 0.2 mmol / L or more of permanganate ions and having a total acid component concentration of 10 mol / L or more.

[0036] The etching treatment conditions are not particularly limited regardless of the etching solution used. The treatment temperature (for example, the liquid temperature of the etching solution) can be about 30 to 80 °C, and the treatment time (for example, the contact or immersion time in the etching solution) can be about 3 to 30 minutes.

[0037] (Reduction step) In addition to the etching step, the pretreatment method of electroless plating of the present invention preferably includes a step of subjecting the object to be plated to a reduction treatment (hereinafter simply referred to as the "reduction step") in order to remove etching residues (chromic acid, permanganic acid, etc.) on the surface of the object to be plated.

[0038] The reduction treatment can be carried out by a known method, for example, a method of bringing the object to be plated after the etching step into contact with or immersing it in an aqueous solution containing a reducing agent. Examples of the reducing agent include inorganic acids having reducing properties, hydrazine, hydroxylamine, etc. The concentration of the reducing agent is not particularly limited, but can be, for example, about 1 to 100 g / L.

[0039] The reduction treatment conditions are not particularly limited. The treatment temperature (for example, the liquid temperature of the aqueous solution containing the reducing agent) can be about 20 to 40 °C, and the treatment time (for example, the contact or immersion time in the aqueous solution containing the reducing agent) can be about 30 seconds to 3 minutes.

[0040] (Catalyst application step) Nickel alloy nanoparticles can be applied to the surface of the object to be plated by the catalyst application step. In order to apply the catalyst uniformly, catalyst solution flow using a pump, rocking of the object to be plated in the catalyst solution, etc. may be performed.

[0041] The processing conditions of the catalyst application step are not particularly limited. The processing temperature (for example, the liquid temperature of the catalyst solution) is preferably 20 to 80 °C. The higher the temperature, the better the catalyst adsorption property, and the lower the temperature, the better the liquid stability. The processing temperature is more preferably 30 to 70 °C, and even more preferably 40 to 60 °C. The processing time (for example, the immersion time in the catalyst solution) is preferably 1 second to 60 minutes. The longer the processing time, the better the catalyst adsorption property, and the shorter the processing time, the more the amount of catalyst used can be suppressed, and the cost can be reduced. The processing time is more preferably 1 to 30 minutes, and even more preferably 2 to 15 minutes.

[0042] (Electroless plating) Electroless plating can be carried out by contacting or immersing the object to be plated, which has been pretreated by a known method, for example, a pretreatment method including a catalyst application step, with an electroless plating solution.

[0043] The electroless plating solution is not particularly limited. For example, an autocatalytic electroless plating solution can be used. Examples of the electroless plating solution include electroless nickel plating solution, electroless nickel - copper alloy plating solution, electroless nickel - cobalt alloy plating solution, electroless cobalt plating solution, electroless gold plating solution, etc.

[0044] The electroless plating solution preferably contains a reducing agent. Examples of the reducing agent include sodium hypophosphite, dimethylamine borane, sodium borohydride, etc. From the viewpoint of bath stability, it is preferable to use sodium hypophosphite as the reducing agent.

[0045] The content of the reducing agent in the electroless plating solution is not particularly limited, but is preferably 0.01 to 100 g / L, more preferably 0.05 to 50 g / L, and even more preferably 0.1 to 10 g / L. By setting the lower limit of the content of the reducing agent to the above value, the deposition property of the plating is further improved, and by setting the upper limit of the content of the reducing agent to the above value, the bath stability is further improved.

[0046] The processing conditions for electroless plating are not particularly limited. The processing temperature (for example, the liquid temperature of the electroless plating solution) can be about 20 to 70°C, and the processing time (for example, the contact or immersion time in the electroless plating solution) can be about 3 to 30 minutes.

[0047] 3. Electroless plating method The present invention includes an electroless plating method including a step of bringing an object to be plated into contact with a catalyst solution (catalyst application step) and a step of bringing the object to be plated that has undergone the step into contact with an electroless plating solution (electroless plating step).

[0048] As the catalyst solution, the catalyst solution described in 1 above can be used, and as the object to be plated, those described in "Object to be plated" in 2 above can be used. The catalyst application step and the electroless plating step can be the steps described in "Catalyst application step" and "Electroless plating" in 2 above, respectively.

[0049] The electroless plating method of the present invention preferably includes the "degreasing step", "etching step", and "reduction step" described in 2 above.

[0050] The electroless plating method of the present invention may repeat the electroless plating step two or more times. By repeating the electroless plating step two or more times, two or more electroless plating films can be formed.

[0051] 4. Plating method The present invention includes a plating method including a step of bringing an object to be plated into contact with a catalyst solution (catalyst application step), a step of bringing the object to be plated that has undergone the step into contact with an electroless plating solution (electroless plating step), and a step of bringing the electroless plated object that has undergone the step into contact with an electroplating solution (electroplating step).

[0052] As the catalyst solution, the catalyst solution described in 1 above can be used, and as the object to be plated, those described in the "object to be plated" of 2 above can be used. The catalyst application step and the electroless plating step can each be the steps described in the "catalyst application step" and "electroless plating" of 2 above.

[0053] The plating method of the present invention preferably includes the "degreasing step", "etching step", and "reduction step" of 2 above.

[0054] The plating method of the present invention may repeat the electroless plating step two or more times. By repeating the electroless plating step two or more times, two or more electroless plating films can be formed.

[0055] The plating method of the present invention may include a step of activating the electroless plating object before the electroplating step. As the activation method, known methods such as contacting or immersing the electroless plating object in an aqueous solution such as an acid or an alkali can be mentioned.

[0056] The electroplating step can be carried out by a known method.

Examples

[0057] Examples and comparative examples are shown below to specifically explain the present invention. However, the present invention is not limited to the examples.

[0058] (Production of electroless plating film) As a resin molded body to be plated, a flat plate (10 cm × 5 cm × 0.3 cm, surface area of about 1 dm 2 ) of ABS resin (manufactured by UMG ABS Co., Ltd., trade name: UMG ABS3001M) was prepared, and an electroless plating film was formed by the following method.

[0059] As a first step, the resin molded body was immersed in an alkaline degreasing solution (Ace Clean A-220 bath manufactured by Okuno Pharmaceutical Co., Ltd.) at 40 ° C for 5 minutes and then washed with water.

[0060] As the second step, the resin molded body after the first step was immersed in an etching solution having a composition of chromic anhydride; 400 g / L, sulfuric acid; 400 g / L, trivalent chromium; 10 g / L at 67°C for 10 minutes.

[0061] As the third step, the resin molded body after the second step was immersed in a catalyst solution prepared with the formulations shown in Tables 1 and 2 at 50°C for 10 minutes.

[0062] The method for producing Ni alloy nanoparticles contained in the catalyst solutions of the examples and comparative examples is as follows. (1) The Ni alloy nanoparticles contained in the catalyst solutions of Examples 1, 3, 5, and 12 were obtained by dissolving 40.5 g of nickel chloride hexahydrate and 100 g of polyvinylpyrrolidone per liter of solvent (water), maintaining the liquid temperature at 25°C ± 3°C, adding 30 g of sodium borohydride all at once while stirring, stirring for 1 hour, and then centrifuging. (2) The Ni alloy nanoparticles contained in the catalyst solutions of Examples 7 and 8 were obtained by dissolving 40.5 g of nickel chloride hexahydrate and 100 g of polyvinylpyrrolidone per liter of solvent (water), maintaining the liquid temperature at 40°C ± 3°C, adding 30 g of sodium borohydride all at once while stirring, stirring for 1 hour, and then centrifuging. (3) The Ni alloy nanoparticles contained in the catalyst solution of Example 10 were obtained by dissolving 40.5 g of nickel chloride hexahydrate and 100 g of polyvinylpyrrolidone per liter of solvent (water), maintaining the liquid temperature at 7°C ± 3°C, adding 30 g of sodium borohydride all at once while stirring, stirring for 1 hour, and then centrifuging. (4) The Ni alloy nanoparticles contained in the catalyst solutions of Examples 2, 4, and 6 were obtained by dissolving 4.5 g of nickel chloride tetrahydrate, 2.5 g of polyvinylpyrrolidone, and 4 g of NaOH per liter of solvent (triethylene glycol), maintaining the liquid temperature at 230°C ± 3°C, adding 4.5 g of hydrazine monohydrate all at once while stirring, stirring for 1 hour, and then centrifuging. (5) The Ni alloy nanoparticles contained in the catalyst solution of Example 9 were obtained by dissolving 4.5 g of nickel chloride tetrahydrate, 2.5 g of polyvinylpyrrolidone, and 4 g of NaOH per 1 L of the solvent (triethylene glycol), maintaining the liquid temperature at 180°C ± 3°C, adding 4.5 g of hydrazine monohydrate all at once while stirring, stirring for 1 hour, and then performing centrifugation. (6) The Ni alloy nanoparticles contained in the catalyst solution of Example 11 were obtained by dissolving 4.5 g of nickel chloride tetrahydrate, 0.5 g of polyvinylpyrrolidone, and 4 g of NaOH per 1 L of the solvent (triethylene glycol), maintaining the liquid temperature at 180°C ± 3°C, adding 4.5 g of hydrazine monohydrate all at once while stirring, stirring for 1 hour, and then performing centrifugation. (7) The Ni alloy nanoparticles contained in the catalyst solution of Comparative Example 1 were obtained by calcining the Ni alloy nanoparticles of Examples 1, 3, 5, and 12 at 250°C for 10 minutes in a hydrogen atmosphere. (8) The Ni alloy nanoparticles contained in the catalyst solution of Comparative Example 2 were obtained by calcining the Ni alloy nanoparticles of Examples 2, 4, and 6 at 250°C for 10 minutes in a hydrogen atmosphere.

[0063] EtOH described in Tables 1 and 2 represents ethanol, and EG represents ethylene glycol.

[0064]

Table 1

[0065]

Table 2

[0066] As the fourth step, the resin molded body after the third step was immersed in an electroless nickel plating solution (manufactured by Okuno Pharmaceutical Co., Ltd., Chemical Nickel RS bath) using sodium hypophosphite as a reducing agent at 40°C for 5 minutes to form an electroless nickel plating film.

[0067] The coverage rate of the electroless nickel plating film formed by the above method was evaluated by the following method.

[0068] Coating rate The ratio of the area where the electroless plating film was formed on the surface of the resin molded body was evaluated as the coating rate. When the entire surface of the resin molded body was coated, the coating rate was defined as 100%.

[0069] In addition, the bath stability of the catalyst solutions prepared with the formulations shown in Tables 1 and 2 was evaluated by the following method.

[0070] Bath stability The prepared catalyst solution was left at room temperature for 10 days, and the liquid state after standing was visually confirmed. If no change was observed compared to the state immediately after preparation, it was marked as ○, and if precipitates or aggregates were formed, it was marked as ×.

[0071] The results of the coating rate and bath stability are shown in Table 3.

[0072]

Table 3

[0073] From the results in Table 3, it was found that the catalyst solution containing nickel alloy nanoparticles having an hcp structure was excellent in bath stability, and after immersing the object to be plated in the catalyst solution and then in the electroless plating solution, the electroless plating film formed had a high coating rate. On the other hand, when the catalyst solutions of Comparative Example 1 and Comparative Example 2 having an fcc structure were used, it was found that the coating rate of the formed electroless plating film was inferior.

Claims

1. An electroless plating catalyst solution containing nickel alloy nanoparticles having a hexagonal closest-packed structure.

2. The electroless plating catalyst solution according to Claim 1, wherein the nickel alloy nanoparticles are at least one selected from the group consisting of Ni-B alloy nanoparticles and Ni-C alloy nanoparticles.

3. The electroless plating catalyst solution according to Claim 1 or 2, wherein the average particle diameter of the nickel alloy nanoparticles is 1 to 200 nm.

4. The electroless plating catalyst solution according to any one of Claims 1 to 3, wherein the content of the nickel alloy nanoparticles is 0.1 to 80% by mass based on 100% by mass of the electroless plating catalyst solution.

5. The electroless plating catalyst solution according to any one of Claims 1 to 4, containing at least one solvent selected from the group consisting of water, alcohol, glycol ether, alicyclic hydrocarbon, amide, and sulfoxide.

6. A pretreatment method for electroless plating, including the step of bringing an object to be plated into contact with the electroless plating catalyst solution according to any one of Claims 1 to 5.

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