WO2002046492A1

WO2002046492A1 - Process for producing plating solution for electroless platinum plating, plating solution for electroless platinum plating, and method of electroless platinum plating

Info

Publication number: WO2002046492A1
Application number: PCT/JP2001/010608
Authority: WO
Inventors: Katsutsugu Kitada
Original assignee: Tanaka Kikinzoku Kogyo K.K.
Priority date: 2000-12-05
Filing date: 2001-12-05
Publication date: 2002-06-13
Also published as: JP2002173780A; TW538133B; JP4463972B2

Abstract

A process for producing from a hexaaminoplatinum complex salt a plating solution for electroless platinum plating which contains the hexaaminoplatinum complex, characterized by including a process for hexaaminoplatinum complex purification which comprises (a) a step in which an aqueous solution of a hexaaminoplatinum complex salt as a starting material is prepared and carbon dioxide is passed through the aqueous solution to produce the carbonate of the hexaaminoplatinum complex and (b) a step in which the hexaaminoplatinum complex carbonate is dissolved with an acid.

Description

Specification

Method for producing electroless platinum plating liquid, electroless platinum plating liquid and electroless platinum plating method

TECHNICAL FIELD The present invention relates to an electroless plating solution having excellent stability and capable of producing a high-quality platinum thin film. The present invention also relates to a method for plating platinum using the electroless platinum plating solution. Background art

Several electroless platinum plating solutions have been known so far, but many of them have problems with stability and do not have sufficient potential for practical use. In addition, few provide solutions to this stability problem but disclose enough. For example, Japanese Patent Publication No. Sho 59-33667 discloses an electroless method in which a nitro complex or a nitroamine ammine complex is contained as a platinum ion, hydrazine is added as a reducing agent, and a hydroxylamine salt is added as a stabilizer. A platinum plating liquid is disclosed. This electroless platinum plating solution focuses on the disadvantage of reducing the stability of the liquid composition while hydrazine has an excellent reducing action, and as a measure to improve the stability, hydroxylamine salt is used as a stabilizer. Was selectively added.

Although this electroless platinum plating solution has a certain effect due to its stabilizer, the plating solution containing such a stabilizer has the problem that decomposition occurs when the plating solution is replenished during the plating operation. There is. Therefore, the plating operation using this plating solution is based on a batch process, which is not suitable for a continuous plating operation, but this does not allow efficient plating.

On the other hand, one having better stability than the above electroless platinum plating liquid is electroless platinum plating described in JP-A-5-222543. This The plating solution is mainly composed of a tetravalent platinum amine salt represented by the general formula [Pt (NH ₃ ) ₆ X], and is used for continuous plating without a stabilizer. It is disclosed that platinum plating can be performed stably. According to this plating liquid, it is possible to produce a high-quality platinum thin film, and it is also applicable to the plating of decorative articles because of its good gloss. However, the stability of the electroless platinum plating solution described in Japanese Patent Application Laid-Open No. 5-222543 is not always sufficient, and the present inventor conducted preliminary tests. It was confirmed that decomposition could not be completely suppressed and that deposition of platinum on the plating tank wall surface made it difficult to control the film thickness. Therefore, this electroless platinum plating solution is considered to be unsuitable for the production of a platinum thin film requiring strict thickness control. In recent years, applications of precious metals such as platinum have been expanding, and they are expected to be used in advanced fields such as capacities of semiconductor devices, instead of decorative articles, catalysts, and heat-resistant materials. In order to produce a platinum thin film used in such fields by electroless plating, a conventional electroless plating solution cannot be applied as it is, and the more stable electroless platinum is used. The development of plating liquid is desired. The present invention has been made in view of the above background, and has extremely high stability, enables continuous plating operation, and has an electroless platinum plating solution capable of producing a high-quality thin film. The purpose is to provide. And it aims at providing the plating method using this plating solution. Disclosure of the invention

The present inventor evaluated the stability of the electroless platinum plating solution containing the above hexaminoplatinum complex ([Pt (NH ₃ ) ₆ X]) as a main component, After a detailed study to improve the stability, it was found that this plating solution contained the following impurities, although it contained a tetravalent hexaaminoplatinum complex as a main component. Equation 1

[P t CI (a) ₅ 3 3 +

[P t C (a) J

[P t C (a) ₃ ] +

[P t (a) ₄ ] 2 +

Such impurities are considered to be generated in the process of preparing the plating solution during the production of the hexaminoaminoplatinum complex salt used as the raw material, but are less stable than the hexaminoplatinum complex as the main component. It decomposes in the solution to produce platinum fine particles that easily adhere to the plating tank wall and the adherend. Then, the catalytic action of the platinum fine particles promotes the deposition of platinum on portions other than the plating tank wall surface and the plated portion of the adherend. Therefore, the present inventor has determined that in order to improve the stability of the plating solution, it is necessary to eliminate the above-mentioned impurities, and for that purpose, in the production process of the plating solution, a hexaminoplatinum complex was used. It was considered appropriate to purify in advance. As a specific method, a hexaneaminoplatinum complex salt as a raw material is made into an aqueous solution, and carbon dioxide gas is blown into the aqueous solution. A technique for extracting platinum complexes was found. Here, the reason for once reacting with the carbon dioxide gas is that the carbonate ions have excellent reactivity and selectivity with respect to the tetravalent hexaminoaminoplatinum complex to be purified. This is based on the idea that the hexaminoaminoplatinum complex can be extracted with high purity. That is, the present invention provides a method for producing an electroless platinum plating solution containing a hexaminoplatinum complex using a salt of the hexaminoplatinum complex represented by the following general formula as a raw material, A method for producing an electroless platinum plating solution, which comprises a step of purifying a complex. Equation 2

[P t (a) J 4 +

(Wherein, a _{_{is, C n H 2 n + 1}} NH 2 (n is an amino group represented by 0 to 1 0 integer).)

(a) a step of producing a hexaminoplatinum complex carbonate by converting a hexaminoplatinum complex salt as a raw material into an aqueous solution, and passing carbon dioxide gas through the aqueous solution;

(b) Step of Dissolving the Hexamino Platinum Complex Carbonate with Acid Hereinafter, the purification step which is a feature of the present invention will be described. In the purification step of the present invention, first, a hexaminoplatinum complex salt is converted into an aqueous solution. Here, it is preferable to use a hydroxide as the hexamino platinum complex salt. This is because coprecipitation of impurities is the least in the subsequent step of reacting with carbon dioxide to form carbonate. On the other hand, the amount of the hexaaminoplatinum complex salt dissolved in the aqueous solution is preferably 1 g / L to 20 gZL in terms of platinum. If the amount is less than 1 gZL, a sufficient amount of carbonate cannot be purified, and the efficiency is low. Also, if it exceeds 20 gZL, the salt will not be dissolved. Then, carbon dioxide gas is blown into the aqueous solution to precipitate carbonates. The amount of carbon dioxide gas passing here depends on the concentration of the hexaminoplatinum complex salt solution in the aqueous solution. As a guide, it is better to blow carbon dioxide gas until the solution becomes neutral.

By the above operation, the hexaminoaminoplatinum complex in the aqueous solution precipitates as a carbonate. This carbonate is a high purity hexaaminoplatinum complex carbonate that does not contain the above-mentioned impurities.

Next, the carbonate is dissolved with an acid in order to extract the hexaminoplatinum complex for platinum plating from the carbonate. Here, as an acid for dissolving the carbonate, a halogen acid such as hydrochloric acid can also dissolve the carbonate. However, when these acids are used, the halogen remains in the dissolution solution, and this is fixed. The thin film is adsorbed on the thin film, thereby decreasing the deposition rate and darkening the appearance of the thin film. Similarly, sulfuric acid generates sulfate, and nitric acid has a problem that the appearance of the thin film is deteriorated.

Thus, as the acid used in the present invention, it is preferable to use an organic sulfonic acid such as methanesulfonic acid or ethanesulfonic acid, or a low molecular weight organic carboxylic acid such as acetic acid or propionic acid. These acids are added in the form of an aqueous solution. In addition, since carbonate ions remain in the solution after the addition of the acid, it is desirable to remove the carbonate ions when producing the plating solution. The method of this carbonate removal, since co ₂ a carbonate in which dissolve in an acid such as an organic sulfonic acid or organic carboxylic acids described above can be foamed easily carbonate by to Rukoto reduced pressure atmosphere solution upon dissolution The ions are removed.

The aqueous solution after these purification steps is a high-purity hexaaminoplatinum complex solution. The hexaminoplatinum complex solution can be used as it is as an electroless platinum plating solution, but it may be appropriately diluted to bring the concentration of the platinum complex to a predetermined concentration. It can be a platinum plating liquid.

Here, regarding the electroless platinum plating liquid according to the present invention, It is preferred to add a reducing agent. As this reducing agent, phosphinic acid, phosphonic acid, hydrazine, boron hydride, formalin, L-ascorbic acid, formic acid and the like are applicable. The concentration of these reducing agents is preferably 1 to 10 times the platinum ion concentration (molar concentration) in the plating solution.

Further, the plating solution according to the present invention enables the production of a high-precision thin film. However, in order to produce a platinum thin film having excellent morphology and no pits, it is necessary to further add a leveling agent. preferable. Here, the leveling agent may be applied to a general electroless plating solution other than platinum. In this case, a cationic surfactant is applied. However, the platinum thin film intended for the production of the present invention tends to adsorb the organic substances in these surfactants, so that the deposition rate is reduced and, in some cases, the deposition reaction is interrupted. When these surfactants are added, insoluble precipitates may be formed. Therefore, as the leveling agent for the electroless plating solution of the present invention, polyoxyethylene alkyl ether, polyalkylphenyl ether, polyoxyethylene polyoxypropyl alkyl ether, dalyserine ester, polyglycerin ester, sorbitan ester It is preferable to use a nonionic surfactant such as ester. The concentration of these leveling agents is preferably 0.1 to 100 ppm. ADVANTAGE OF THE INVENTION According to the electroless platinum plating solution which concerns on this invention, a stable platinum plating process is possible without decomposing | disassembling a plating solution, and it is excellent in step coverage and can manufacture a highly precise platinum thin film. . The conditions for performing platinum plating using the electroless platinum plating solution according to the present invention are as follows: pH is set to 8 to 12, and the liquid temperature is set to 40 to 80 ° C. It is good. This is because, when the pH is less than pH 8, precipitation of platinum does not occur, and when the pH exceeds pH 12, the working environment deteriorates. In addition, when the liquid temperature is lower than 40 ° C, platinum does not precipitate, and when the liquid temperature is higher than 80 ° C, evaporation of amine in the plating liquid becomes remarkable. When adjusting the pH of this plating solution, add acid or aluminum to the plating solution. When adding the alkali, it is necessary to apply an alkali having the same amino group as the amino group (a in Chemical formula 3) coordinated to platinum in the hexamino platinum complex. Is preferred.

In addition, in this plating process, it is preferable to perform a catalyst application process of depositing platinum as a growth source on a portion where a thin film is to be formed. At this time, the platinum deposited by the catalyst application treatment may be extremely thin. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described together with comparative examples. First Embodiment: 5 L of a “Pt (NH ₃ ) ₆ ] (OH) 4 solution having a platinum concentration of 10 gZL was prepared, and carbon dioxide gas was blown into the solution for 3 hours. The carbonate was weighed so that the amount of platinum contained was 30 g, and 45 mL of acetic acid was added thereto to dissolve the carbonate, and further water was added. Then, the solution after dissolution was reduced in pressure to remove carbonic acid.

This way Kisaamino platinum complex solution to the purified _{([P t (NH 3)} 6] (CH 3 COO) 4 solution) was taken platinum amount 3 g portion of the solution (1 0 OML), reduced to this Add 3 mL of hydrazine monohydrate as an agent, add 7 O mL of 28% aqueous ammonia so that the pH of the solution becomes pH 11, and then add deionized water so that the volume becomes 1 L. Was added, and glycerin ester (20 ppm) was further added as a leveling agent.

The electroless platinum plating solution produced as described above was heated to a temperature of 60 ° C., and an alumina plate treated with a catalyst was immersed in the solution to perform platinum plating. As a result, platinum with good gloss was deposited at a deposition rate of 1: 8 mZh. The plating solution after the plating treatment was left for one week, but it was confirmed that the plating solution did not decompose. Second _{Embodiment: [P t (NH 3)} 6] in 1 0 GZL platinum concentration (OH) ₄ Was prepared, and carbon dioxide gas was blown into the solution for 3 hours. The precipitated carbonate was collected by filtration, washed, and dried. Next, 50 mL of maleic sulfonic acid was added to the carbonate to dissolve the carbonate, and water was further added to make the volume 1 L, and then the carbonic acid was removed from the solution.

Then, a solution (100 mL) of 3 g of platinum was collected from the platinum complex solution, and 3 mL of hydrazine monohydrate was added as a reducing agent to adjust the solution pH to pH 10.5. After 70 mL of 28% aqueous ammonia was added, deionized water was added so as to have a liquid volume of 1 L, and polyoxyethylene dodecyl ether 20 ppm as a leveling agent was further added. As in the case of the first embodiment, a platinum plating treatment was performed on an alumina plate at a liquid temperature of 60 ° C. As a result, platinum with good gloss was deposited at a deposition rate of 1.3 zm / h. It was also confirmed that the plating solution after the plating treatment did not decompose after leaving it for one week. Third Embodiment: In this embodiment, as in the second embodiment, a carbonate is produced using an aqueous solution of [Pt (NH ₃ ) ₆ ] (OH) ₄ as a raw material. In place of the acid, 6 OmL of ethanesulfonic acid was added to dissolve the carbonate, and a reducing agent was added to adjust the pH and the volume of the solution to produce a plating solution. Here, other conditions such as the concentration of [Pt (NH ₃ ) ₆ ] (OH) ₄ are the same as in the second embodiment.

Again, at a liquid temperature of 60 ° C., platinum plating was performed on the alumina plate, and as a result, platinum with a good gloss was deposited at a deposition rate of 1.1 mZh. It was also confirmed that the plating solution after the plating treatment did not decompose after leaving it for one week. Fourth Embodiment: In this embodiment, instead of [Pt (NH ₃ ) ₆ ] (OH) ₄ in the second embodiment, as a hexaminoplatinum complex salt, a platinum concentration l O gZL of [P t (CH ₃ NH ₂₎ _6] (OH) was used ₄ 5 L. Then, carbon dioxide gas is blown under the same conditions as in the second embodiment, and ethane ethane is added to the collected carbonate. Rubonic acid was added to dissolve the carbonate, 100 mL of this solution was sampled, and a reducing agent was added to adjust the pH and the volume of the solution to produce a plating solution. The conditions such as the amount of the reducing agent are the same as in the second embodiment.

Then, at a liquid temperature of 60 ° C., platinum plating was performed on the alumina plate, and as a result, platinum with a good gloss was deposited at a deposition rate of 1.0 mZh. It was also confirmed that the plating solution after the plating treatment did not undergo decomposition of the plating solution after standing for one week. Fifth Embodiment: In the present embodiment, the purification is performed in the fourth embodiment.

After adding 20 g of phosphinic acid as a reducing agent to 10 OmL of the noplatinum complex solution, adjust the solution pH to pH 8.0, and add deionized water so that the solution volume becomes 1 L. Furthermore, 20 ppm of polyoxyethylene blended ether was added as a leveling agent.

Then, the alumina plate was subjected to a platinum plating treatment at a liquid temperature of 80 ° C. using this plating solution. As a result, platinum having a good gloss was deposited at a deposition rate of 0.95 zmZh. It was also confirmed that the plating solution after the plating treatment did not decompose after leaving for one week. Comparative Example: As a comparative example with respect to the above-described embodiment, the same [Pt (NH ₃ ) ₆ ] (OH) ₄ as in the first embodiment was used as a raw material, and the plating solution was directly used without going through a purification step. It was manufactured and its stability was studied. In this comparative example, ₃ mL of hydrazine monohydrate and 0.2 g of glycine were used as reducing agents in 1 L of a [Pt (NH ₃ ) 6] (OH) ₄ solution having a platinum concentration of 10 g ZL. In addition, 0.2 mg of lead monoxide was added as a stabilizer. Then, the solution volume was adjusted, and the pH was adjusted to pH 12 to obtain a plating solution.

The plating rate was 2.0 m_ / h, which was not inferior to those of the first to fifth embodiments. Deposition speed was obtained, but when the plating solution after the plating treatment was allowed to stand, platinum was deposited on the bottom and wall of the plating tank one day later. Was confirmed. This is because, although the stabilizer was added in the comparative example, the raw material [Pt (NH ₃ ) ₆ ] (OH) ₄ was not purified, and the impurities contained therein caused the purification. It is considered that the plating liquid was decomposed. Industrial applicability

As described above, the present invention aims to further improve the stability of a conventional electroless platinum plating solution containing a hexaminoaminoplatinum complex as a main component, and to improve the stability of an electroless platinum plating solution for purifying a hexaminoplatinum complex. This is a method of producing an electroless platinum plating solution, which does not contain impurities and does not decompose the composition of the solution during the plating operation. According to the electroless platinum plating solution of the present invention, a high-quality platinum thin film can be produced from its stability.

Claims

The scope of the claims

1. A method for producing an electroless platinum plating solution containing a hexaminoplatinum complex, using a salt of a hexaminoplatinum complex represented by the following general formula as a raw material,

Equation 1

[P t (a) ₆ ] 4 +

(Wherein, a _{_{is, C n H 2 n + 1}} NH 2 (n is an amino group represented by 0-1 0 integer).)

A method for producing an electroless platinum plating solution, comprising a step of purifying a hexaaminoplatinum complex shown in the following step.

(a) a step of producing a hexaminoplatinum complex carbonate by converting a hexaminoplatinum complex salt as a raw material into an aqueous solution and passing carbon dioxide gas through the aqueous solution;

(b) dissolving the hexaminoplatinum complex carbonate with an acid

2. The method for producing an electroless platinum plating liquid according to claim 1, wherein a hydroxide is used as the hexaminoaminoplatinum complex salt in the step (a).

3. The method for producing an electroless platinum plating liquid according to claim 1, wherein an organic sulfonic acid or an organic carboxylic acid having a molecular weight of 300 or less is used as the acid in the step (b).

4. An electroless platinum plating liquid produced by the method according to claim 1.

5. The electroless platinum plating solution according to claim 4, wherein the reducing agent contains at least one of phosphinic acid, phosphonic acid, hydrazine, boron hydride, formalin, L-ascorbic acid, and formic acid.

6. The electroless platinum plating liquid according to claim 4, which contains a nonionic surfactant as a leveling agent.

7. A method for plating electroless platinum, which comprises bringing the electroless platinum plating liquid according to claim 4 into contact with an object to be plated,

An electroless platinum plating method in which the pH of the electroless platinum plating liquid is set at pH 8 to l2 and the temperature of the liquid is 40 to 80 ° C, and the substance is brought into contact with the object to be plated.