JP2017075379A5 - - Google Patents

Description

Electroless platinum plating solution

  The present invention relates to an electroless platinum plating solution.

Conventionally, an electroless platinum plating solution, containing a Jinitoroji ammine platinum or dinitro tetraamine platinum as platinum salt, and ethylenediamine or ammonia as a complexing agent and hydrazine monohydrate or sodium borohydride as a reducing agent Is known (see, for example, Patent Documents 1 to 4).

Jinitoroji ammine platinum and dinitro tetraamine platinum is poorly soluble in water. Therefore, by adding ethylenediamine or ammonia as a complexing agent to the electroless platinum plating solution, a platinum complex in which ethylenediamine or ammonia is coordinated to platinum is formed and dissolved in water.

  In general, by adding a reducing agent to the electroless platinum plating solution, metal ions or metal complexes can be reduced on the surface of the plating substrate to deposit a metal. Since the platinum complex in which ethylenediamine or ammonia is coordinated to platinum is not easily reduced, hydrazine monohydrate or sodium borohydride having a strong reducing action is added to the electroless platinum plating solution as a reducing agent. However, since hydrazine monohydrate and sodium borohydride have too much reducing power, there is a problem that platinum is precipitated in the plating solution due to the reduction of the platinum complex and hydrogen is generated in accordance with the reduction reaction. .

  Therefore, in order to solve the above problems, in the electroless platinum plating solution, the stability of the solution is improved by adding heavy metal ions such as lead and thallium and thiol compounds as stabilizers.

JP-A-5-222543 Japanese Patent Laid-Open No. 9-287078 International Publication No. 2014/162935 International Publication No. 2013/094544

  However, since the concentration management of the heavy metal ions and thiol compounds is necessary, the operation of the plating solution is complicated. In addition, the heavy metal ions are harmful to the human body and may be co-deposited on the deposited platinum film to lower the film purity. Moreover, since ammonia gas is generated from the plating solution with use, the working environment is lowered by the odor accompanying the generation of ammonia gas.

  Accordingly, an object of the present invention is to provide an electroless platinum plating solution that can obtain excellent solution stability without using heavy metal ions or thiol compounds and can prevent generation of ammonia gas. There is.

As a result of intensive studies, the inventors of the present invention have found that the conventional electroless platinum plating solution decreases the stability of the solution for the following reason. That is, in a conventional electroless platinum plating solution, a platinum complex is formed by coordination of ethylenediamine or ammonia used as a complexing agent to platinum ions. Since ethylenediamine or ammonia forms a strong complex with platinum ions, a reducing agent with a strong reducing action is required to reduce the platinum complex and deposit it on the surface of the plating substrate. As a result, the electroless platinum plating solution is reduced and decomposed by the reducing power of the reducing agent having a strong reducing action.
Therefore, the present inventors have achieved the above problem by employing the following electroless platinum plating solution.

Electroless platinum plating solution of the present invention, a water-soluble platinum compounds, formalin, glucose, formic acid, see contains the one or more reducing agents selected from the group consisting of formic acid salt, the water-soluble platinum compounds, hexa It is one or more water-soluble platinum compounds selected from the group consisting of hydroxoplatinum (IV) acid, hexahydroxoplatinum (IV) acid salt, and dichlorotetraammineplatinum (II) .

  The electroless platinum plating solution according to the present invention preferably contains an organic acid as a complexing agent. The organic acid is preferably one or more compounds selected from aliphatic hydroxy acids having a molecular weight of 90 to 500.

In the electroless platinum plating solution according to the present invention, since a water-soluble platinum compound is used, the platinum compound generates a platinum complex even if it does not contain a complexing agent that strongly forms a complex with platinum ions such as ethylenediamine and ammonia. Easily dissolved in water. A platinum complex produced from a water-soluble platinum compound is easily reduced as compared with a platinum complex in which ethylenediamine or ammonia is coordinated to platinum produced by a conventional electroless platinum plating solution. For this reason, even if formalin, glucose, formic acid, and formate having a weak reducing action are used as the reducing agent, the platinum complex can be easily reduced.

  In addition, formalin, glucose, formic acid, and formate as reducing agents all have a weaker reducing action than hydrazine monohydrate and sodium borohydride. For this reason, the electroless platinum plating solution is not decomposed by the reducing agent. Therefore, the electroless platinum plating solution can obtain excellent solution stability as compared with the conventional electroless platinum plating solution without using heavy metal ions or thiol compounds. Also, formalin, glucose, formic acid, and formate are all suitable in that the amount of hydrogen generation is small compared to hydrazine monohydrate and sodium borohydride as conventional reducing agents.

  Furthermore, since the electroless platinum plating solution does not contain a compound capable of generating ammonia gas such as ethylenediamine and ammonia, generation of ammonia gas can be prevented.

It is a graph which shows the precipitation characteristic by the electroless platinum plating solution of this embodiment. 2 is an SEM image of a platinum electroless coating obtained by electroless plating treatment with an electroless platinum plating solution of Example 1. FIG. 3 is an SEM image of a platinum electroless coating obtained by electroless plating treatment with an electroless platinum plating solution of Example 2. FIG.

  Hereinafter, embodiments of the electroless platinum plating solution according to the present invention will be described.

[1. (Electroless platinum plating solution)
The electroless platinum plating solution of the present invention is an aqueous solution containing a water-soluble platinum compound and one or more reducing agents selected from the group consisting of formalin, glucose, formic acid, and formate.

  Examples of the water-soluble platinum compound include platinum (II) chloride, platinum (II) chloride, platinum (II) chloride, platinum (IV) chloride, platinum (IV) acid, and platinum chloride (IV). ) Acid salt, hexahydroxoplatinum (IV) acid, hexahydroxoplatinum (IV) acid salt, one or more water-soluble platinum compounds selected from the group consisting of dichlorotetraammineplatinum (II).

  The electroless platinum plating solution preferably contains the water-soluble platinum compound in the range of 0.0005 mol / L to 0.05 mol / L, and in the range of 0.0025 mol / L to 0.01 mol / L. It is more preferable to contain. If the content of the water-soluble platinum compound in the electroless platinum plating solution is less than 0.0005 mol / L, it may be difficult to form a platinum electroless coating or the plating rate may be reduced. When L is exceeded, although the plating itself can be performed satisfactorily, the economic efficiency decreases.

  Platinum chloride (IV) is easily dissolved in the electroless platinum plating solution to form a platinum complex represented by the following formula (1).

  Dichlorotetraammineplatinum (II) is easily dissolved in the electroless platinum plating solution to form a platinum complex represented by the following formula (2).

  The platinum complexes represented by the above formulas (1) and (2) are more susceptible to reduction as compared with platinum complexes in which ethylenediamine is coordinated to platinum produced by a conventional electroless platinum plating solution. . For this reason, the electroless platinum plating solution does not need to use a reducing agent having a strong reducing action, and even if a reducing agent having a weak reducing action is used, the platinum complex can be easily reduced.

  One or more reducing agents selected from the group consisting of formalin, glucose, formic acid, and formate all reduce the platinum complex represented by the above formulas (1) and (2), although the reducing action is small. It is possible to make it easy to do. In any of the above reducing agents, the decomposition products generated in the reduction reaction are mainly carbon dioxide and water, and there is an advantage that the amount of hydrogen generation is small compared to hydrazine monohydrate or sodium borohydride. Moreover, although the said electroless platinum plating solution is adjusted to the range of pH 6.5-12.0 so that it may mention later, the said reducing agent can be used over this whole pH range.

The electroless platinum plating solution preferably contains the reducing agent in a range of 0.1 mol / L to 1.0 mol / L, and in a range of 0.2 mol / L to 0.8 mol / L. More preferably. If the content of the reducing agent in the electroless platinum plating solution is less than 0.1 mol / L , an undeposited part may occur. If the content exceeds 1.0 mol / L, the reducing agent has an excessive reducing action. And solution stability may be impaired.

  As formate, sodium formate, potassium formate, and ammonium formate can be used. Sodium formate is preferred in terms of easy water solubility and ease of handling.

  Since the electroless platinum plating solution uses a water-soluble platinum compound, a complexing agent is not necessarily required to dissolve the platinum compound in water. However, the electroless platinum plating solution can be further stabilized by adding a complexing agent.

  An organic acid is preferably used as the complexing agent. The organic acid is preferably one or more compounds selected from aliphatic hydroxy acids having a molecular weight of 90 to 500, such as lactic acid, malic acid, citric acid, trisodium citrate, ammonium citrate, glycine, One or more compounds selected from the group consisting of gluconic acid, malonic acid, oxalic acid, succinic acid, acetic acid, maleic acid, and fumaric acid can be used. The complexing agent also acts as a pH buffer material.

  The electroless platinum plating solution preferably contains the organic acid in a range of 0.01 mol / L to 0.5 mol / L, and in a range of 0.02 mol / L to 0.3 mol / L. More preferably. If the content of the organic acid in the electroless platinum plating solution is less than 0.01 mol / L, it may not act as a complexing agent, and if it exceeds 0.5 mol / L, the plating itself can be performed satisfactorily. Decreases.

  The electroless platinum plating solution may further include various components such as a surfactant, a stress relaxation agent, and a pH adjuster.

  As the surfactant, polyethylene glycol can be used, and various conventionally known surfactants can be used. When polyethylene glycol is used as a surfactant, it improves the wettability of the surface of the plating substrate, and when bubbles are generated on the surface of the plating substrate, the bubbles can be easily separated from the surface of the plating substrate. it can.

As a stress relaxation agent, saccharin, 1, 4-butynediol, benzenesulfonic acid, addition can be used naphthalene disulfonic acid, can be used various known stress relaxation agent.

  As a pH adjuster, sodium hydroxide, sulfuric acid, or the like can be used. The electroless platinum plating solution is preferably adjusted to a pH range of 6.5 to 13.0 by adding a pH adjuster. If the pH in the electroless platinum plating solution is less than 6.5, the reducing action of the reducing agent may be reduced. Even if the pH of the electroless platinum plating solution exceeds 13.0, no particular problem occurs, but it is preferably 13.0 or less from the viewpoint of workability such as pH adjustment and bath management.

  Moreover, the said electroless platinum plating liquid can change the external appearance of the platinum electroless membrane | film | coat obtained by adjusting pH in the said range. For example, when the pH of the electroless platinum plating solution is 7, a gray platinum electroless coating can be obtained, and when the pH is 12, a white platinum electroless coating can be obtained.

  According to the electroless platinum plating solution of this embodiment, a water-soluble platinum compound such as platinum (II) chloride, platinum (IV) chloride, hexahydroxoplatinum (IV), dichlorotetraammine platinum (II), etc. Therefore, even if it does not contain a complexing agent, this platinum compound forms a platinum complex and can be easily dissolved in water. Moreover, the platinum complex produced | generated from the said water-soluble platinum compound is easy to receive a reduction | restoration compared with the platinum complex which ethylenediamine coordinated to the platinum produced | generated with the conventional electroless platinum plating solution. For this reason, even if formalin, glucose, formic acid, and formate having a weak reducing action are used as the reducing agent, the platinum complex can be easily reduced.

  In addition, formalin, glucose, formic acid, and formate as reducing agents all have a weaker reducing action than hydrazine monohydrate and sodium borohydride. For this reason, the electroless platinum plating solution is not decomposed by the reducing agent. Therefore, the electroless platinum plating solution can obtain excellent solution stability as compared with the conventional electroless platinum plating solution without using heavy metal ions or thiol compounds. Also, formalin, glucose, formic acid, and formate are all suitable in that the amount of hydrogen generation is small compared to hydrazine monohydrate and sodium borohydride as conventional reducing agents.

  Furthermore, since the electroless platinum plating solution does not contain a compound capable of generating ammonia gas such as ethylenediamine, generation of ammonia gas can be prevented.

[2. (Electroless plating treatment with electroless platinum plating solution)
An example of the plating method using the electroless platinum plating solution of this embodiment will be described below. Here, the case where the plating base material which formed the copper membrane | film | coat and the nickel membrane | film | coat in order on the surface of the insulating base material by the electroless-plating process as a plating base material which is to-be-plated object is demonstrated. A plating base material is not limited to the above-mentioned thing, A conventionally well-known plating base material can be used.

  First, a platinum film (platinum electrolytic film) is formed on the surface of the nickel film by performing electrolytic plating on the plating substrate.

  Then, the electroless-plating process is performed by immersing the plating base material in which the platinum electrolytic film was formed on the surface of the nickel film in the electroless platinum plating solution of this embodiment. The platinum complex in the electroless platinum plating solution is reduced and deposited on the surface of the platinum electrolytic film, whereby a platinum film (platinum electroless film) can be formed on the surface of the platinum electrolytic film.

Electroless plating using an electroless platinum plating solution of this embodiment, the deposition rate is 1 to 2 [mu] m / time, the deposition rate comparable to an electroless platinum plating solution containing conventional Jinitoroji ammine platinum or dinitro tetraamine platinum Can be obtained.

  The operating temperature of the electroless platinum plating solution is preferably in the range of 40 to 90 ° C. If the temperature is lower than 40 ° C., the plating rate may be slow, and if it exceeds 90 ° C., the amount of water evaporation increases and the composition variation may increase.

  The plating time with the electroless platinum plating solution depends on the thickness of the platinum electroless film to be formed. For example, in the case of an electroless platinum plating solution containing 1.05 mol / L of dichlorotetraammineplatinum (II) as a water-soluble platinum compound (1.0 g / L in terms of platinum), by setting the plating time to 30 minutes A platinum electroless film having a thickness of 0.5 μm can be formed.

  The said reducing agent mainly produces | generates a carbon dioxide and water with a reductive reaction. Since carbon dioxide and water do not accumulate in the electroless platinum plating solution, the electroless platinum plating solution is not altered and can be used for a long time.

[3. (Use of electroless platinum plating solution)
The electroless platinum plating solution of this embodiment is suitable for plating of electronic parts made of metal, electrode materials, synthetic resins such as ABS resin, polyamide resin, polycarbonate resin, non-conductive ceramics such as alumina and zirconia. It is. In particular, it can be suitably used for applications of oxygen sensor electrodes made of ceramics such as zirconia, and various jewelry.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, it is needless to say that the present invention is not limited to the following examples.

[Creation of plating substrate]
First, a nickel film having a thickness of 3 μm was formed on a copper plate by electrolytic plating. Next, a plating base material was prepared by forming a platinum film (platinum electrolytic film) having a thickness of 0.1 μm on the surface of the nickel film by electrolytic plating.

[Preparation of electroless platinum plating solution]
In this example, dichlorotetraammineplatinum (II) 0.005 mol / L (1.0 g / L in terms of platinum) as a water-soluble platinum compound, sodium formate 0.5 mol / L as a reducing agent, complexed with water, As an agent, 0.1 mol / L of malic acid was dissolved to prepare an electroless platinum plating solution. Subsequently, the pH (temperature: 25 ° C.) of the electroless platinum plating solution was adjusted to 7.0 using sodium hydroxide and sulfuric acid as pH adjusting agents.

[Electroless plating treatment]
The obtained electroless platinum plating solution is heated to a temperature of 70 ° C., and the plating base material on which the platinum electrolytic film is formed is immersed in the electroless platinum plating solution to perform the electroless plating treatment, thereby obtaining a platinum electrolytic film. A platinum film (platinum electroless film) was formed on the surface.

  At this time, the thickness of the platinum electroless coating was measured every 10 minutes until the immersion time reached 60 minutes. The results are shown in FIG. From FIG. 1, it was confirmed that the deposition rate in the electroless plating process was 1.0 μm / hour.

  In addition, a platinum electroless coating having a thickness of 0.5 μm was formed by performing electroless plating treatment for 60 minutes. It was visually confirmed that the obtained platinum electroless coating was gray. Further, when the surface of the obtained platinum electroless coating was observed with a scanning electron microscope (SEM) at a magnification of 30,000 times, as shown in FIG. Met.

  Next, the temperature of the electroless platinum plating solution is changed to 50 ° C., 60 ° C., 70 ° C., and 80 ° C., and the plating base material on which the platinum electrolytic film is formed is immersed in the electroless platinum plating solution for 2 hours. The electroless plating process was performed. At this time, the presence or absence of decomposition | disassembly of the said electroless platinum plating solution was determined by observing whether the platinum deposit produced in the said electroless platinum plating solution. Table 1 shows the results. In Table 1, “X” means that the electroless platinum plating solution was decomposed within 1 hour, “Δ” means that it was decomposed within 2 hours, and “◯” indicates that it was completely decomposed after 2 hours. It means no.

  Next, after the above electroless platinum plating solution kept at a temperature of 50 to 80 ° C. for 2 hours is naturally cooled, it is heated again to the same temperature the next day, and the plating base material is immersed for 2 hours to be electroless. Plating treatment was performed. Even when the electroless platinum plating solution was heated to any temperature, the electroless plating treatment could be normally performed. From this, it is clear that the electroless platinum plating solution can be used continuously.

  In this example, an electroless platinum plating solution was prepared in the same manner as in Example 1 except that the pH (temperature 25 ° C.) was adjusted to 11.0.

  The obtained electroless platinum plating solution is heated to a temperature of 70 ° C., and the plating base material on which the platinum electrolytic film is formed is immersed in the electroless platinum plating solution for 60 minutes to perform the electroless plating treatment. A platinum electroless film having a thickness of 0.5 μm was formed on the surface of the electrolytic film. It was confirmed visually that the obtained platinum electroless coating had a white glossy appearance. Further, when the surface of the obtained platinum electroless coating was observed with an SEM at a magnification of 30,000, the surface shape of the platinum particles was small and smooth as shown in FIG.

  Next, the presence or absence of decomposition of the electroless platinum plating solution was determined using the obtained electroless platinum plating solution exactly as in Example 1. Table 1 shows the results.

  Next, the electroless platinum plating solution kept at a temperature of 50 to 80 ° C. for 2 hours was made exactly the same as in Example 1, and an electroless plating treatment was performed the next day. Even when the electroless platinum plating solution was heated to any temperature, the electroless plating treatment could be normally performed. From this, it is clear that the electroless platinum plating solution can be used continuously.

[Comparative Example 1]
In this comparative example, an electroless platinum plating solution was prepared in exactly the same manner as in Example 2 except that hydrazine monohydrate 0.5 mol / L was used instead of sodium formate as the reducing agent. The pH (temperature 25 ° C.) was adjusted to 11.0. Next, the presence or absence of decomposition of the electroless platinum plating solution was determined using the obtained electroless platinum plating solution exactly as in Example 1. Table 1 shows the results.

[Comparative Example 2]
In this comparative example, an electroless platinum plating solution was prepared in exactly the same manner as in Example 2 except that sodium borohydride 0.5 mol / L was used instead of sodium formate as the reducing agent. The pH (temperature 25 ° C.) was adjusted to 11.0. Next, the presence or absence of decomposition of the electroless platinum plating solution was determined using the obtained electroless platinum plating solution exactly as in Example 1. Table 1 shows the results.

[Comparative Example 3]
In this comparative example, it was completely the same as Comparative Example 1 except that 0.005 mol / L (1.0 g / L in terms of platinum) of dinitrodiammine platinum (II) was used as the platinum compound instead of dichlorotetraammine platinum (II). An electroless platinum plating solution was prepared in the same manner, and then the pH (temperature 25 ° C.) was adjusted to 11.0. Next, the presence or absence of decomposition of the electroless platinum plating solution was determined using the obtained electroless platinum plating solution exactly as in Example 1. Table 1 shows the results.

[Comparative Example 4]
This comparative example is exactly the same as Comparative Example 2 except that 0.005 mol / L of dinitrodiammine platinum (II) (1.0 g / L in terms of platinum) was used as the platinum compound instead of dichlorotetraammine platinum (II). An electroless platinum plating solution was prepared in the same manner, and then the pH (temperature 25 ° C.) was adjusted to 11.0. Next, the presence or absence of decomposition of the electroless platinum plating solution was determined using the obtained electroless platinum plating solution exactly as in Example 1. Table 1 shows the results.

  As shown in Table 1, the electroless platinum plating solutions of Example 1 and Example 2 in which the platinum compound is dichlorotetraammineplatinum (II) and the reducing agent is sodium formate are both 50 to 80 ° C. It is clear that it does not decompose even after 2 hours in the range and has excellent solution stability. On the other hand, the electroless platinum plating solutions of Comparative Examples 1 to 4 in which the reducing agent is hydrazine monohydrate or sodium borohydride are all decomposed within one hour in the temperature range of 70 to 80 ° C. It is apparent that the solution decomposes within 2 hours even in the temperature range of 50-60 ° C. and the solution stability is poor.

  As described above, the electroless platinum plating solution of the present invention has excellent solution stability and can withstand long-term use. Further, since the electroless platinum plating solution does not contain a compound capable of generating ammonia gas such as ethylenediamine and ammonia, generation of ammonia gas can be prevented. For this reason, it is possible to prevent the work environment from being deteriorated due to the odor accompanying the generation of ammonia gas. In addition, the electroless platinum plating solution does not use a complexing agent that forms a strong complex with platinum ions such as ethylenediamine and ammonia, so use a reducing agent with a weak reducing action such as formalin, glucose, formic acid, and formate. can do. Moreover, these reducing agents can reduce the generation amount of hydrogen gas compared with hydrazine monohydrate and sodium borohydride.

Further, the electroless platinum plating solution of the present embodiment is suitable for plating of electronic parts made of metal or the like, electrode materials, various synthetic resins, ceramics, and the like. In particular, it can be suitably used for applications of oxygen sensor electrodes made of ceramics such as zirconia, and various jewelry.

Claims (3)

A water-soluble platinum compounds, formalin, glucose, formic acid, and one or more reducing agents selected from the group consisting of formic acid salts seen including,
The water-soluble platinum compound is one or more water-soluble platinum compounds selected from the group consisting of hexahydroxoplatinum (IV) acid, hexahydroxoplatinum (IV) acid salt, and dichlorotetraammineplatinum (II). Electroless platinum plating solution. The electroless platinum plating solution according to claim 1 containing an organic acid as a complexing agent. The electroless platinum plating solution according to claim 2 , wherein the organic acid is at least one compound selected from aliphatic hydroxy acids having a molecular weight of 90 to 500.