KR102575117B1 - Platinum electrolytic plating bath and platinum plated product - Google Patents

Abstract

(Problem) An acidic platinum electrolytic plating bath that is extremely stable, has a long bath life, and is capable of thick plating with little accumulation of impurities, and a dense, high hardness, low stress, and luster using this acidic platinum electrolytic plating bath A platinum-plated product having a high-purity platinum-plated film having good corrosion resistance is provided.
(Means for solution) The platinum electrolytic plating bath is an acidic platinum plating bath composed of a divalent platinum (II) complex and liberated sulfuric acid or sulfamic acid, and further contains an anionic surfactant. Moreover, a platinum-plated product is manufactured by processing using this platinum electrolytic plating bath.

Description

Platinum electrolytic plating bath and platinum plating product {PLATINUM ELECTROLYTIC PLATING BATH AND PLATINUM PLATED PRODUCT}

The present invention relates to an acidic platinum electrolytic plating bath and a platinum plated product electroplated from the plating bath.

In platinum electrolytic plating baths, many divalent platinum (II) complexes are used as platinum compounds. Divalent platinum (II) complexes are synthesized from various platinum compounds using tetravalent chloroplatinum (IV) acid salts as raw materials, and are preferably used. Inorganic platinum (II) complexes include compounds such as hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid. For example, platinum chloride (PtCl ₂ ), platinum nitrate (Pt(NO ₃ ) ₂ ), diaminedichloroplatinum (Pt(NH ₃ ) ₂ Cl ₂ , trichloroamineplatinic acid (HPtCl ₃ (NH ₃ ))) or salts thereof. (MPtCl ₃ (NH ₃ )), tetrachloroplatinic acid (H ₂ PtCl ₄ ) or its salt (M ₂ PtCl ₄ ), tetranitroplatinic acid (H ₂ Pt(NO ₂ ) ₄ ) or its salt (M ₂ Pt(NO ₂ ) ₄ ), tetrasulfoplatinic acid (H ₆ Pt(SO ₃ ) ₄ ) or its salt (M ₆ Pt(SO ₃ ) ₄ ), etc. Here, M is an alkali metal element, a Group 2 element or ammonium In addition, as a platinum compound, there is also a tetravalent platinum (IV) complex. The tetravalent platinum (IV) complex includes hexahydroxoplatinic acid (H ₂ Pt(OH) ₆ ) or its salt (M' ₂ Pt(OH) ) ₆ ) etc. Here, M' represents an alkali metal element, a Group 2 element or ammonium.

Examples of divalent platinum (II) complexes preferably used in the electrolytic plating bath include dinitrodiammine platinum (Pt(NH ₃ ) ₂ (NO ₂ ) ₂ , so-called p-salt), dinitrodiaquadiammine platinum (Pt (NH ₃ ) ₂ (H ₂ O) ₂ (NO ₂ ) ₂ ), nitratohydroxoaquadiammine platinum (Pt(NH ₃ ) ₂ (H ₂ O)(OH)(NO ₂ )), nitratohydride Loxodiammine platinum (Pt(NH ₃ ) ₂ (OH)(NO ₂ )), dinitratodiammine platinum (Pt(NH ₃ ) ₂ (NO ₃ ) ₂ ), dinitrosulfato platinum ([Pt(NO ₂ ) ) ₂ (SO ₄ )] ^2- , so-called DNS salt), dichlorotetraammine platinum (Pt(NH ₃ ) ₄ Cl ₂ ), dichlorodiammine platinum (Pt(NH ₃ ) ₂ Cl ₂ ), hydrogen tetraammine platinum phosphate (Pt(NH ₃ ) ₄ (HPO ₄ ), so-called Q-salt) and the like are known.

Platinum electrolytic plating baths using these divalent platinum (II) complexes or tetravalent platinum (IV) complexes have been known for a long time. For example, there are the following types of platinum electrolytic plating baths using dinitrodiammine platinum, dinitrosulfato platinum, or the like.

For example, in Japanese Patent Publication No. 36-19658 (patent document 1 described later), there is an invention of "an electrolyte solution for platinum plating comprising an aqueous solution containing a composition obtained by heating platinum diammonium dinitrate in an aqueous solution of sulfamic acid". has been initiated. This specification shows that P salt [Pt(NH ₃ ) ₂ (NO ₃ ) ₂ ] dissolves in an aqueous solution of sulfamic acid, and that platinum can be electroplated with this diluted solution. However, when the electroplating operation was performed at a temperature of 70 to 80° C. using this platinum electrolytic plating bath, there was a drawback that sulfamic acid was decomposed and platinum salt was precipitated.

Further, in Japanese Patent Publication No. 36-19812 (Patent Document 2 described later), diammonium platinum diammonium nitrate is added to about 200 cc of an aqueous mixture of 10 to 100 cc of concentrated sulfuric acid and 10 to 100 cc of concentrated phosphoric acid for every liter. Disclosed is an invention of an electrolyte solution for platinum plating comprising water and a solution obtained by heating a composition containing the composition in an amount of 10 to 40 g. However, when the electroplating work is continued with this electrolytic solution for platinum plating, phosphoric acid is accumulated in the solution and the corrosion resistance of the platinum plating film is deteriorated. In addition, in the electrolyte solution for platinum plating in which phosphoric acid is accumulated, it becomes difficult to reliably obtain a plating having a thickness of 5 μm or more having strong adhesion in one plating operation. In addition, there is a drawback of inhibiting the recovery of platinum from the waste liquid of this electrolytic solution for platinum plating.

Then, in Japanese Patent Publication No. 49-21018 (patent document 3 described later), a specific "dissolving diaminodinitroplatinum in a solution containing 0.05 to 2 mol/L of an ammonium salt and 0.05 to 1 mol/L of sulfuric acid" The invention of the "electrolytic platinum plating bath formed" is disclosed. In the examples, a bath temperature of 70 to 90°C is employed. In this specification, “(1) The stability of the bath is high. … (3) It has characteristics as an industrial plating bath, such as a long bath life.”

In addition, in Japanese Unexamined Patent Publication No. Hei 08-319595 (Patent Document 4 described later), "Ammin alcohol using a product derived from the reaction of 1 mole of diamminodinitritoplatinum (II) and 4 to 6 moles of amide sulfuric acid" In a platinum bath for electroplating containing 5 to 30 g/l of platinum as a pamato-complex and having a pH-value lower than 1, the electrolytic solution contains at most 5 g/l of free amide sulfuric acid and 1 The invention of a platinum bath for electroplating, characterized by containing 20 to 400 g/l of a strong acid having a lower pH value and containing 0.01 to 0.2 g/l of a fluorosurfactant as a wetting agent, is claimed in claim 4. has been initiated. In the examples, it is operated at a bath temperature of 80°C. This invention is described in the specification as "an object of the present invention is to provide a platinum bath for electroplating that does not have cracks even when the layer thickness exceeds 100 μm, is smooth, can deposit with gloss, and is stable even when not in use." there is. In addition, "amide sulfuric acid" is another name for sulfamic acid.

Further, in the specification of U.S. Patent No. 3206382 (Patent Document 5 described later), as a method of electrodepositing platinum, the pH value is less than 2, and a method of electrolyzing an electrolyte essential from an aqueous solution of a predetermined nitrito compound complex of platinum This is disclosed. This Example 1 discloses a method for preparing dinitrosulfatoplatinum (II) potassium by the following formula by reacting potassium tetranitroplatinum (II) with sulfuric acid.

K ₂ Pt(NO ₂ ) ₄ +H ₂ SO ₄ → K ₂ Pt(NO ₂ ) ₂ SO ₄

It is disclosed that the plating bath of this invention is stable, produces consistent results, and does not deteriorate even when left alone.

In applying a platinum electrolytic plating bath to the production of platinum-plated products, a layer of nickel, copper, palladium, or the like is formed as an intermediate layer of the material to be plated. Although an acidic plating bath is generally used for forming the intermediate layer, when an acidic electrolytic plating bath is used for forming the intermediate layer, an acidic plating bath is used for platinum electroplating. This is because when an alkaline platinum electrolytic plating bath is used, the acidic liquid in the previous step is carried into the platinum electrolytic plating bath, and the pH of the alkaline bath tends to fluctuate.

Japanese Patent Publication No. 36-19658 Japanese Patent Publication No. 36-19812 Japanese Patent Publication No. 49-21018 Japanese Unexamined Patent Publication No. 08-319595 Specification of US Patent No. 3206382

Until now, platinum coatings electroplated from an acidic platinum electrolytic plating bath (platinum electrolytic plating solution) have high stress and generate pinholes and cracks, as in Japanese Patent Publication No. 36-19658 (patent document 1 described above). There was a task that was easy to do. In the platinum coating of Japanese Unexamined Patent Publication No. 08-319595 (Patent Document 4 described above), pinholes and cracks are not visible on the appearance, but when the porosity is measured, the value of the porosity is very poor, and the platinum coating is still intact. It was found that pinholes and cracks existed.

Thus, the subject that the porosity of a platinum film is bad originates in platinum particle electrolytically deposited by electroplating. That is, one factor is that the stable platinum complex changes into an unstable compound in the platinum electrolytic plating bath due to the release of platinum ions from the stable platinum complex in the platinum electrolytic plating bath. For example, nitro groups contained in p-salt, DNS salt, etc. are very stable when coordinated with platinum, but when platinum metal is precipitated from the complex by electroplating, the remaining nitro groups form various nitrogen oxides (NOx) in the platinum electrolytic plating bath. ) to form ions. This complex nitrogen oxide (NOx) ion acts on the platinum complex in the platinum electrolytic plating bath to make the precipitated platinum metal particles unstable.

Specifically, tetranitroplatinic acid (H ₂ Pt(NO ₂ ) ₄ ) is Pt(NO ₂ ) ₃ (H ₂ O) ^- , Pt(NO ₂ ) ₂ (H ₂ O) ₂ , Pt(NO ) in an aqueous solution. Complexes such as ₂ )(H ₂ O) ₃ ⁺ and Pt(H ₂ O) ₄ ²⁺ can be formed. It is also known that the nitro group has the property of easily forming complex compounds of nitrogen and oxygen such as [Pt(NH ₃ ) ₂ (NO ₃ ) ₂ ] in addition to the above compounds in an aqueous solution. For example, it is known that the color tone of the platinum electrolytic plating bath changes when nitro groups remaining in the platinum electrolytic plating bath are excessively concentrated. From this point as well, it can be understood that the nitro group of the platinum complex has a property that makes it easy to form a complex compound. Further, in an acidic platinum electrolytic plating bath, sulfur oxide (SOx) ions released from platinum complexes are not as vigorous as nitrogen oxide (NOx) ions, but it is known that they tend to form complex compounds. The electrolytic precipitate is affected by such a change in the platinum complex in the platinum electrolytic plating bath. In such an acidic platinum electrolytic plating bath, there is a tendency for electrolytic precipitates to fluctuate easily during the electroplating operation. In particular, if continuous plating is continued under high current density conditions such as jet plating, the temperature of the bath rises and new unstable compounds such as nitrogen oxide (NOx) ions and sulfur oxide (SOx) ions are easily formed.

When the electrolytically deposited platinum particles were observed microscopically, it was found that the crystal grains were large and unstable. In addition, since metal is easily dissolved in an acidic platinum electrolytic plating bath, platinum-plated products tend to be easily affected by metal impurities. When metal impurities are accumulated or concentrated, the plating conditions of the platinum electrolytic plating bath tend to fluctuate, and problems tend to occur in platinum-plated products. Further, when halogen ions coexist in such a platinum electrolytic plating bath, the released nitrogen oxide (NOx) ions and sulfur oxide (SOx) ions undergo a more complex reaction. Platinum ions electrolytically deposited in the vicinity of the cathode are affected in various ways by these complex compounds and ligands. For this reason, the precipitation conditions when platinum ions become nuclei of new platinum particles change constantly. Even if the plating conditions are the same, since the conditions for depositing platinum particles on the cathode are different, the platinum electrolytic precipitate becomes unstable. It is thought that the electroplated platinum film had high stress and large crystal grains, and thus pinholes and cracks were generated.

In summary, in conventional platinum electrolytic plating baths, nitrogen oxide (NOx) ions and sulfur oxide (SOx) ions of stable platinum complexes are released and become unstable, and these ions and the like accumulate and become concentrated. When these ions and the like are present in a large amount in the platinum electrolytic plating bath, conditions for precipitation of platinum particles from the aqueous solution during electroplating become unstable. In addition, platinum particles to be deposited next on the precipitated platinum particles are affected by these ions and the like. For this reason, the electrolytically deposited platinum precipitate has a high stress, and crystal grains grow irregularly. For this reason, the obtained platinum-plated product had the problem that microscopic cracks and pinholes increased. In addition, when electroplating is performed using a copper metal substrate, copper may be eluted in the ppm order in an acidic platinum electrolytic plating bath. The same applies even if plating treatment of an intermediate layer such as nickel or palladium is performed. Such metallic impurities may adversely affect platinum-plated products.

However, the influence of other metallic impurities has not been considered in conventional platinum electrolytic plating baths. In addition, microscopic cracks or pinholes in platinum-plated products have not been a problem so far. This is because platinum-plated products have high stress and exhibit chemical properties that make them difficult to corrode even when immersed in an acid or alkali aqueous solution. However, in applications such as connectors, porosity due to microscopic cracks or pinholes of platinum-plated products, that is, corrosion resistance, is a problem. This is because there is a risk that if a platinum-plated product is touched with bare hands, components such as sweat penetrate the platinum film and corrode the metal body. In such applications, metal impurities on the order of ppm may also affect platinum-plated products. For this reason, a precise high-purity platinum plating product and a high-purity platinum electrolytic plating bath are required. In particular, since silicon is abundant in nature, it is one of the metal elements that are easily mixed as an impurity even in a platinum electrolytic plating bath. For example, precious metals are also produced as a by-product of electrolytic refining of copper. Referring to embodiment (12) of Japanese Laid-open Patent Publication No. 50-116326, it is described that electrolytic refining of copper yields a platinum-containing alloy containing silicon. Since silicon easily enters a platinum electrolytic plating bath, special care is required in a high-purity platinum electrolytic plating bath.

The present invention has been made in view of the above problems, and its object is to provide a platinum electrolytic plating bath that is very stable and has a long bath life. In particular, to provide a platinum electrolytic plating bath in which a high-purity platinum precipitate having a dense and amorphous crystal structure can be obtained even in an acidic platinum electrolytic plating solution of a platinum (II) complex containing a large amount of a ligand that is easily decomposed such as a nitro group. .

Another object of the present invention is to provide a platinum-plated product having a platinum coating film that is less stressed and is so dense that grain boundaries of platinum particles cannot be observed with a scanning electron microscope. Another object of the present invention is to provide a platinum-plated product having a high-purity platinum coating capable of thick plating. In particular, it is to provide a platinum-plated product having a small porosity and good corrosion resistance.

As a result of examining the porosity of a platinum-plated product that is less likely to corrode, the inventors of the present invention found that the smaller the porosity of the platinum film, the better the corrosion resistance of the platinum-plated product. In addition, it was found that, when metal impurities are present in a platinum-plated product, a dense platinum coating cannot be obtained depending on the type or content of the metal. For example, when a specific metal impurity is contained on the order of ppm in a conventional acidic platinum electrolytic plating bath, the porosity of the electrolytically deposited platinum precipitate may significantly deteriorate. When this platinum-plated product was observed, surface defects such as cracks and pinholes had occurred on the platinum film.

When investigating the source of silicon contained in the platinum electrolytic plating bath, metal impurities such as silicon may be contained on the order of several tens of ppm even in platinum of nominal 99.9% or more, as by-products of electrolytic refining of copper described above. In addition, it was found that silicon was also contained in distilled water. For this reason, even when drying the platinum plating bath or replenishing evaporated water, metal impurities such as silicon may accumulate unintentionally. Further, it has been found that metal impurities such as silicon may be contained in a gold plating bath, a palladium plating bath, a nickel plating bath, or a cleaning liquid such as a drag-out tank or a water washing device as a pretreatment plating solution.

The present inventors first examined a platinum electrolytic plating bath under conditions in which silicon was removed. In an acidic platinum electrolytic plating bath in which sulfate or sulfamate of a conventional divalent platinum (II) complex and liberated sulfuric acid or sulfamic acid are used as a base liquid, it has been found that the crystal grains of the platinum precipitate become large even though the platinum precipitate is of high purity. there was. That is, in a platinum electrolytic plating bath containing no metal impurities other than platinum, only platinum is electrolytically deposited. Electrolytically deposited platinum is high-purity platinum, and its film properties can be properly understood.

The present inventors studied various additives in such a high-purity platinum electrolytic plating bath. Then, it was found that when an anionic surfactant having both a hydrophilic group and a hydrophobic group is added in one molecule, the platinum particles precipitated on the cathode become dense and the shape thereof becomes homogeneous. explain this action. That is, the anionic surfactant having both a hydrophilic group and a hydrophobic group surrounds the divalent platinum complex with one of the groups. When an electric current is passed through the platinum electrolytic plating bath, the anionic surfactant transfers the platinum complex to the surface of the cathode while surrounding the divalent platinum complex. On the surface of the cathode, the divalent platinum complex changes to zero-valent platinum metal. When the divalent platinum complex comes into contact with the cathode surface from the solution side of the cathode surface, the ligand of the platinum complex is changed into nitrogen oxide (NOx) ions and the like, and is liberated in the platinum electrolytic plating bath. In this process, the anionic surfactant is converted into nitrogen oxide (NOx) ions and the like, surrounding the platinum metal. Once liberated, the nitrogen oxide ions are unable to re-access the platinum metal because the anionic surfactant is in the way. When the platinum metal on the cathode is reduced to platinum particles, the platinum particles are absorbed into the platinum grains, and the platinum grains on the cathode grow. On the other hand, the anionic surfactant that surrounded the platinum metal in the platinum electrolytic plating bath was separated from the surface of the cathode and released again into the platinum electrolytic plating bath.

The action of this anionic surfactant is explained using FIG. 1 in an easy-to-understand manner. 1 is a schematic diagram of a p-salt platinum electrolytic plating solution to which sodium lauryl sulfate is added as an anionic surfactant. For convenience, the platinum ion ligand was expressed as sulfate ion (SO ₄ ) ^2- . As shown in the left figure of FIG. 1, in the platinum electroplating solution, sodium lauryl sulfate, an anionic surfactant, surrounds the Pt(II) complex. This Pt(II) complex is transferred onto the cathode by external electrical energy. As shown in the central figure of FIG. 1, the divalent Pt(II) complex transferred to the surface of the cathode receives two electrons from the cathode and is reduced to zero-valent Pt(0) metal, surrounded by an anionic surfactant. there is. On the side of the plating solution on the cathode, the anionic surfactant of the zero-valent Pt(0) metal repells the anionic surfactant of the Pt(II) complex. In addition, hydroxide ions (not shown) and sulfur oxide (SOx) ions (not shown) generated by electrolysis also repel each other. For this reason, the interaction between the zero-valent Pt(0) metal and the platinum atom in the divalent Pt(II) complex is suppressed.

Subsequently, as shown in the right diagram of FIG. 1, the zero-valence Pt(0) metal is reduced to platinum particles (not shown) and absorbed into platinum crystal grains. On the cathode, platinum crystal grains grow to form a platinum plating film. On the other hand, the anionic surfactant surrounding the platinum metal moves away from the cathode phase and is released into the platinum electrolytic plating solution again. Since the interaction of other platinum atoms can be suppressed by the action of such an anionic surfactant, platinum particles can always be deposited under certain conditions. When the homogenized crystal grains are stacked on the surface of the cathode, an electrolytic precipitate without gaps is formed. As a result, a dense platinum coating film having a crystal structure similar to that of an amorphous state is obtained on the cathode.

On the other hand, it has been found that such an anionic surfactant has no effect on metal impurities in a platinum electrolytic plating bath. The anionic surfactant acts on the ligand of the platinum complex, but does not act on the metal impurities in the platinum electrolytic plating solution. When metal impurities such as silicon are contained in the platinum electrolytic plating bath of the present invention, these metal impurities are deposited in the platinum plating film. Conversely, if these metallic impurities are not contained in the platinum electrolytic plating bath, a highly pure platinum electrolytic precipitate can be obtained. It was found that the high-purity platinum plating film containing no metallic impurities had a low tensile stress despite its high hardness, and was a dense, low-porosity electrolytic precipitate.

Fig. 2 shows scanning electron microscope images of the surface and cross section of the platinum electrolytic precipitate of the present invention. This figure is a photograph of the surface of a platinum electrolytic precipitate having a purity of 99% or more (upper photograph divided by white horizontal lines) and a cross section (lower photograph) having a thickness of 4 μm from above at an angle of 45 degrees. From this figure, it can be seen that the crystal grains of the platinum electrolytic precipitate are dense like an amorphous state.

The platinum electrolytic plating bath of the present invention that has been able to solve the above problems is an acidic platinum plating bath composed of a divalent platinum (II) complex and free sulfuric acid or sulfamic acid, and the gist is that an anionic surfactant is included.

In addition, the platinum electrolytic plating bath of the present invention that has been able to solve the above problems is an acidic platinum plating bath composed of a divalent platinum (II) complex and free sulfuric acid or sulfamic acid, an anionic surfactant, and a metal salt of a group 2 element Or it makes it a summary to contain the metal salt of an alkali metal element. Here, Group 2 elements refer to elements such as beryllium, magnesium, calcium, and strontium. Moreover, an alkali metal element means elements, such as lithium, sodium, potassium, and rubidium.

In addition, the platinum electrolytic precipitate obtained from the platinum electrolytic plating bath of the present invention, which can solve the above problems, has a platinum purity of 99% by weight or more, a Vickers hardness of 450 to 500 Hv, a stress of 100 Mpa or less, and It is a gist that the porosity is 30% or less.

By containing an anionic surfactant, the platinum electrolytic plating bath of the present invention has an effect of obtaining a dense platinum electrolytic precipitate having a crystal structure similar to that of an amorphous state even in an acidic platinum plating bath. That is, the platinum electrolytic precipitate of the present invention is characterized by very low stress despite being shiny, hard and dense. In particular, the above effect is increased in a high-purity platinum electrolytic plating bath containing no metal impurities such as silicon.

The platinum electrolytic plating bath of the present invention contains an alkali metal element, a Group 2 element, or a metal salt of these metal elements, so that the amount of anionic surfactant used can be reduced. That is, it turned out that the content of anionic surfactant at least equivalent effect is acquired by including an alkali metal element, a Group 2 element, or a metal salt of these metal elements in addition to anionic surfactant. In addition, the platinum electrolytic plating bath of the present invention has an effect of reducing the accumulation of anionic surfactant even when electroplating is performed continuously for a long time. In addition, even if the anionic surfactant deteriorates and the surfactant concentration substantially decreases, the platinum electrolytic plating bath of the present invention has an effect of enabling continuous operation for a long period of time.

In addition, according to the platinum electrolytic plating bath of the present invention, even a thin plating film of 1 μm or less has an effect of obtaining a plating film having a dense and amorphous crystal structure, so that the porosity is low and the plating film excellent in corrosion resistance is obtained. In addition, when a high-purity platinum electrolytic plating bath is used, the platinum electrolytic precipitate is high in purity and has an effect of stabilizing the quality of the platinum film.

In addition, since the plating quality is stable according to the platinum electrolytic plating bath of the present invention, there is an effect that the bath temperature can be set to a relatively low temperature. When the bath temperature of the platinum electrolytic plating bath of the present invention is lowered, there is an effect of facilitating management of the plating solution. In addition, since the platinum electrolytic plating bath of the present invention has little accumulation of impurities, there is also an effect that there is no need to install expensive equipment such as filtration and separation of the plating solution.

A platinum-plated product composed of platinum electrolytic precipitates obtained from the platinum electrolytic plating bath of the present invention has a crystal structure in which the crystal grains of the platinum film are dense and are in an amorphous state. Since such a platinum film has a low porosity, it is excellent in corrosion resistance. In particular, there is an effect that a platinum-plated product having high corrosion resistance can be obtained even with thin plating of 1 µm or less. Corrosion resistance of the platinum-plated product of the present invention includes not only static corrosion resistance to corrosive liquid, but also dynamic corrosion resistance to a case where a weak current is applied. In addition, since the platinum-plated product of the present invention is hard and dense, there is an effect of being excellent in insertion/extraction durability and wear resistance in connectors and the like. In addition, since the platinum film of the present invention has very low stress, the adhesion is strong, and there is an effect that the film is not peeled off or pinholes or cracks are not generated in the film.

In addition, the high-purity platinum-plated product of the present invention has a stable temperature coefficient of resistance and has an effect of obtaining a uniform electrical resistance value. In addition, since the platinum-plated product of the present invention is a platinum electrolytic precipitate that is shiny even at high purity and has corrosion resistance, there is an effect that it is suitable for decoration. In particular, since porosity represents a stricter corrosion resistance standard than cold resistance, there is an effect suitable for use as accessories such as bracelets or earrings.

1 is a diagram explaining the principle of a platinum plating bath of the present invention.
2 is a scanning electron micrograph of the platinum electrolytic precipitate of the present invention.

Hereinafter, an embodiment of the platinum electrolytic plating bath of the present invention and a platinum-plated product composed of a platinum electrolytic precipitate produced using the platinum electrolytic plating bath will be described.

<Platinum Electrolytic Plating Bath>

(divalent platinum (II) complex)

In the platinum electrolytic plating bath of the present invention, as the divalent platinum (II) complex, a divalent platinum (II) complex preferably used in a conventional electrolytic plating bath can be used. A divalent platinum (II) complex contains a nitro group (NO ₂ ), a nitrate group (NO ₃ ), a sulfate group (SO ₄ ) or a sulfo group (SO ₃ ), an ammine group (NH ₃ ), and an aquo group. An inorganic platinum complex having at least one ligand of (H ₂ O) or hydroxyl group (OH) is preferred. Divalent platinum (II) complexes particularly preferably used in the electrolytic plating bath include p-salts, DNS salts, and the like. These platinum (II) complexes may be used alone or in combination of two or more.

In the platinum electrolytic plating bath of the present invention, an aqueous solution in which a divalent platinum (II) complex is dissolved in liberated sulfuric acid or sulfamic acid is used. For example, when divalent platinum complex powder such as p-salt or DNS salt is dissolved in sulfuric acid or sulfamic acid, it becomes a brown or pale yellow liquid. The platinum electrolytic plating bath of the present invention may use this divalent platinum solution as it is or after dilution. In the platinum electrolytic plating bath of the present invention, "sulfuric acid or sulfamic acid" means that sulfuric acid or sulfamic acid may be used alone or in combination.

The platinum (Pt) concentration is preferably 1 to 20 g/L, more preferably 2.5 to 15 g/L, as the platinum (Pt) content. If the concentration of platinum is less than 1 g/L, the precipitation rate may slow down, but the delay in the precipitation rate is alleviated by the presence of a metal salt. In addition, when visually observed, if the concentration of platinum is less than 1 g/L, precipitation abnormalities such as soot and unevenness may be observed in the plated film. On the other hand, even if the concentration of platinum exceeds 20 g/L, the effect of platinum electrolytic plating hardly changes. Therefore, if the concentration of platinum (II) ions exceeds 20 g/L, the cost now becomes high. If the concentration of platinum is in the range of 2.5 to 15 g/L, continuous plating can be performed stably. In addition, the amount of phosphoric acid contained in platinum complexes such as Q-salt can be appropriately adjusted by using it together with other platinum complexes that do not contain phosphorus.

The content of liberated sulfuric acid or sulfamic acid in the platinum electrolytic plating bath of the present invention is preferably 30 to 600 g/L, more preferably 50 to 400 g/L, either alone or in combination of two or more. do. When the total content of free sulfuric acid or sulfamic acid is less than 30 g/L, precipitation abnormalities such as soot and unevenness may be observed in the plated film, depending on the content of other auxiliary conductive salts, etc. On the other hand, if the total content of liberated sulfuric acid or sulfamic acid exceeds 600 g/L, there is a risk that the concentration of liberated sulfate becomes too high due to evaporation loss of water during the plating operation, and the balance of the platinum electrolytic plating solution is disturbed. .

(anionic surfactant)

The platinum electrolytic plating bath of the present invention contains an anionic surfactant. As the anionic surfactant in the platinum electrolytic plating bath of the present invention, generally known anionic surfactants such as sulfonic acid type, sulfate ester type, and fatty acid type can be used. However, phosphoric acid ester type surfactant is not preferable as an anionic surfactant of the present invention because the phosphoric acid ester salt as a component may inhibit the corrosion resistance of platinum electrolytic precipitate. Specific examples include the following, but are not limited thereto, and any commercially available anionic surfactant can be used without problems, except for phosphoric acid ester type surfactants.

As the sulfonic acid type anionic surfactant, alkylsulfonates such as sodium undecanesulfonate and sodium octadecanesulfonate, alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, and sulfosuccinates such as sodium dialkylsulfosuccinate.

Examples of sulfuric acid ester type anionic surfactants include sodium lauryl sulfate and ammonium lauryl sulfate.

Examples of fatty acid type anionic surfactants include sodium laurate and sodium stearate, and amino acid decanoylsarcosine such as sodium N-decanoylsarcosine and N-lauroyl-N-methyl-β-alanine. Amino acid-type things, such as sodium, etc.

The above anionic surfactants include alkyl sulfuric acid or a salt thereof, alkylbenzenesulfonic acid or a salt thereof, stearic acid or a salt thereof, sulfonic acid or a salt thereof, or alkali metal element salt, group 2 element salt, ammonium salt of lauryl sulfate, etc. this is preferable This is because these anionic surfactants dissolve in the sulfate or sulfamate of the divalent platinum (II) complex and make the electrolytic precipitate dense. The anionic surfactant has a property of acting on the platinum electrolytic precipitate in a small amount to make the crystal grains in an amorphous state. In addition, since the anionic surfactant does not easily evaporate from the platinum electrolytic plating bath, it acts stably on the platinum electrolytic deposit in the platinum electroplating bath for a long period of time. Anionic surfactant is not limited to 1 type of use, You may use 2 or more types together. Since the anionic surfactant may be circulated through a platinum electrolytic plating bath with a pump, it is preferable that no bubbles are generated.

It is preferable to contain 5-500 mg/L of an anionic surfactant in the platinum electrolytic plating bath of this invention. If the content of the anionic surfactant is less than 5 mg/L, the stress of the platinum electrolytic precipitate increases, and the effect of improving corrosion resistance cannot be exhibited in many cases. 20 mg/L is preferable and, as for the lower limit of the total amount of anionic surfactant, 50 mg/L is more preferable. When an alkali metal element or a salt of a Group 2 element is included, the content of the anionic surfactant of 50 mg/L can be relatively low to less than 15 mg/L. When an alkali metal element or a salt of a Group 2 element is included, the content of the anionic surfactant of 5 mg/L can be relatively low to less than 3 mg/L. On the other hand, when the content of the anionic surfactant exceeds 500 mg/L, precipitation abnormalities such as soot and unevenness are often observed in the plated film when visually observed. Moreover, as for an upper limit, 300 mg/L is preferable and 200 mg/L is more preferable. When an alkali metal element or a salt of a Group 2 element is included, the content of the anionic surfactant can be made relatively low in the same way.

(metal salt)

In the platinum electrolytic plating bath of the present invention, it was found that the content of the anionic surfactant can be reduced if a metal salt of a Group 2 element or a metal salt of an alkali metal element is present. In the platinum electrolytic plating bath of the present invention, since metal salts of Group 2 elements or metal salts of alkali metal elements have a high ionization tendency, these metals do not precipitate in the platinum electrolytic precipitate even when electroplating is performed. In addition, these metal salts do not have the effect of inhibiting the growth of platinum particles like an anionic surfactant. Among metal salts of Group 2 elements or metal salts of alkali metal elements, magnesium salts are particularly preferred. Examples of magnesium salts include magnesium sulfate, magnesium sulfite, magnesium nitrate, and hydrates thereof. Magnesium acetate, magnesium citrate, magnesium lactate, magnesium stearate and the like can also be used. In addition, those that form salts in the platinum electrolytic plating bath of the present invention, such as magnesium oxide and magnesium hydroxide, can also be used as raw materials. Since the platinum electrolytic plating bath of the present invention contains free sulfuric acid or sulfamic acid, it is preferable to use a cheap metal sulfate metal salt for the metal salt of a Group 2 element or metal salt of an alkali metal element.

When metal impurities such as silicon other than metal salts of Group 2 elements and metal salts of alkali metal elements are present in the platinum electrolytic plating bath, these impurity metals are likely to precipitate in the platinum electrolytic precipitate. When these metallic impurities precipitate in the platinum electrolytic precipitate, the porosity of the platinum film, that is, the corrosion resistance of the platinum-plated product may be adversely affected, depending on the type and content of these metallic impurities. For this reason, when obtaining a high-purity platinum electrolytic precipitate, it is necessary to remove these impurity metals as much as possible. In particular, silicon is an impurity element that tends to be mixed in the platinum electrolytic plating bath of the present invention. In the case of obtaining a high-purity platinum electrolytic precipitate, silicon can be used as an indicator as an impurity. Silicon is preferably 1 ppm or less. In addition, a metal salt of a Group 2 element or a metal salt of an alkali metal element does not contain a halogen element. This is because the halogen element has an adverse effect on the platinum electrolytic precipitate. Moreover, phosphate is not included in these metal salts. This is because a platinum electrolytic plating bath containing a large amount of phosphate deteriorates the corrosion resistance of the platinum electrolytic precipitate. Phosphorus has the effect of densifying the platinum precipitate, but phosphate does not evaporate well. When a phosphate is used for a metal salt of a Group 2 element or a metal salt of an alkali metal element, there is a risk that phosphorus will be concentrated and contained in the platinum electrolytic precipitate, adversely affecting the platinum-plated product.

(other additives)

Known additives such as pH buffering agents can be used for the platinum electrolytic plating bath of the present invention. The pH buffering agent is not particularly limited as long as it is a known pH buffering agent. Preferably, an inorganic salt such as potassium hydroxide, sodium hydroxide, magnesium hydroxide, calcium hydroxide, or acetic acid, boric acid, tetraboric acid, citric acid, malic acid, succinic acid, malonic acid, maleic acid, fumaric acid, glycine, or a compound thereof (potassium salt , sodium salt, ammonium salt, etc.) and the like. These pH buffering agents can be added in a concentration range of 0.1 to 100 g/L. In addition, the platinum electrolytic plating bath of the present invention may contain functional additives such as complexing agents, bath stabilizers, rate regulators, leveling agents, crystal regulators, stress relievers, and physical property improvers as needed. However, functional additives that prevent the platinum electrolytic precipitate from maintaining a high purity of 99% or more or functional additives that deteriorate porosity are excluded.

(plating conditions, etc.)

In the platinum electrolytic plating bath of the present invention, the pH is preferably 2 or less, more preferably 1.5 or less. This is because it contains an anionic surfactant. Also, it is because the sulfate or sulfamate of the divalent platinum (II) complex is stable during the electroplating operation. The pH is usually in the range of 0.2 to 1.0. A pH buffer may be used to control the pH within a predetermined range. A pH buffer may be used individually by 1 type, and may mix and use 2 or more types. In addition, the bath temperature can be appropriately determined according to the surrounding environment of the plating operation. It is preferably in the range of 30 to 90°C, more preferably in the range of 35 to 70°C, and still more preferably in the range of 40 to 60°C. As the bath temperature increases, the deposition rate of the platinum electrolytic precipitate increases, but the amount of evaporation of the plating solution increases. The bath temperature can be appropriately determined according to the purpose of the metal substrate or platinum product to be used. In addition, the application range of the cathode current density is wide, and the optimum current density can be selected in accordance with conditions such as the plating area of the metal substrate, selection of immersion/spray plating equipment, and flow rate of plating solution.

<Platinum Electrolytic Precipitate>

The object to be plated in the platinum electrolytic plating bath of the present invention is applied to a metal substrate. The metal substrate is not limited even if the base is an insulating material such as plastic or ceramic, as long as the surface thereof can be electroplated. The surface of the metal substrate is appropriately selected from a metal or an alloy depending on the application. In applications of electric/electronic components such as connectors, metals such as iron, nickel, chromium, and alloys thereof in addition to copper metal and copper alloys are usually used. In addition, electroless plating or electroplating of nickel, palladium, gold, or the like can be used for the surface of the metal substrate. In addition, for electrode applications, refractory metals such as titanium and tantalum are used. Metals such as stainless steel, nickel, silver alloys, and gold alloys are used for ornaments and decorations. In addition, thick-plated platinum electrolytic precipitates can also be used for ornaments and decorations.

The platinum electrolytic precipitate of the present invention is dense and shows no cracks or pinholes. The platinum electrolytic precipitate of the present invention was subjected to a porosity test, which is one type of corrosion resistance test as shown in Examples. This is because it is difficult to evaluate the difference in corrosion even if an artificial perspiration test (JIS B 7285) or an accelerated corrosion test (JIS H 8502) is conducted. In addition, the platinum electrolytic precipitate of the present invention has low internal stress and can be plated with a thickness of 10 µm or more. Moreover, even if the platinum film is peeled off from the metal base, neither warp nor curl is seen in the platinum film of the present invention.

In the platinum-plated product of the present invention, it is preferable to have a two-layer structure of a metal substrate and a platinum electrolytic precipitate. This is because it can save expensive platinum bullion. As described above, the metal substrate is appropriately selected depending on the use. The metal substrate may be a single metal or a laminated metal. Single metals and laminated metals also include metals coated with plastics or ceramics. Moreover, it is more preferable that the platinum-plated product with a thin plated film of this invention is a connector. The platinum electrolytic precipitate of the present invention has a crystal structure like an amorphous state, has low porosity and high hardness, and has corrosion resistance. For this reason, even if the surface of the thin platinum electrolytic precipitate is touched with bare hands, it does not corrode. Further, the degree of porosity varies depending on the film thickness of the plated film, but is preferably 25% or less, and more preferably 20% or less.

[Example]

Hereinafter, the present invention will be specifically described by examples and comparative examples, but the present invention is not limited to these examples unless departing from the gist thereof.

(Example)

(Example 1)

The platinum stock solution of Example 1 is a sulfuric acid solution containing 11 g/L of DNS as platinum. Equal amounts of sulfuric acid and sulfamic acid were added to this platinum stock solution in a total amount of 160 g/L to prepare a basic bath. To this basic bath, 60 mg/L of sodium lauryl sulfate (“Emal (registered trademark) 0” manufactured by Kao Co., Ltd.) was added as an anionic surfactant, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 2)

The platinum stock solution of Example 2 is a sulfamic acid solution containing 15 g/L of p-salt as platinum. 70 g/L of sulfuric acid was added to this platinum stock solution to make a basic bath. To this basic bath, 70 mg/L of sodium dodecylbenzenesulfonate (“Neopelex (registered trademark) G-15” manufactured by Kao Corporation) was added, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 3)

The platinum stock solution of Example 3 is a sulfamic acid solution containing 17 g/L of DNS as platinum. Equal amounts of sulfuric acid and sulfamic acid were added to this platinum stock solution in an amount of 150 g/L in total to obtain a basic bath. 180 mg/L of N-lauroylsarcosine sodium salt (purity 95.5% or higher) was added to this basic bath, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 4)

The platinum stock solution of Example 4 is a mixed solution of sulfuric acid and sulfamic acid containing 16 g/L of DNS as platinum. 60 g/L of sulfamic acid was added to this platinum stock solution to make a basic bath. To this basic bath, 400 mg/L of an alkylallylsulfonate/alkylammonium salt (“Visco Top (registered trademark) 200LS-2” manufactured by Kao Corporation) was added, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 5)

The platinum stock solution of Example 5 is a mixture of sulfuric acid and sulfamic acid containing 5 g/L of DNS as platinum. 80 g/L of sulfuric acid was added to this platinum stock solution to make a basic bath. To this basic bath, 500 mg/L of ammonium lauryl sulfate ("Emal (registered trademark) AD-25R" manufactured by Kao Corporation) was added, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 6)

The platinum stock solution of Example 6 is a sulfamic acid solution containing 3 g/L of DNS as platinum. 180 g/L of sulfamic acid was added to this platinum stock solution to make a basic bath. 90 mg/L of sodium stearate was added to this basic bath, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 7)

The platinum stock solution of Example 7 is a sulfuric acid solution containing 13 g/L of p-salt as platinum. 110 g/L of sulfamic acid was added to this platinum stock solution to make a basic bath. To this basic bath, 160 mg/L of sodium linear alkylbenzenesulfonate (Neurex (registered trademark) Soft Type 30 manufactured by Nichiyu Co., Ltd.) was added, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath. .

(Example 8)

The platinum stock solution of Example 8 is a mixture of sulfuric acid and sulfamic acid containing 1 g/L of DNS as platinum. Equal amounts of sulfuric acid and sulfamic acid were added to this platinum stock solution in a total amount of 80 g/L to obtain a basic bath. To this basic bath, 10 mg/L of ammonium lauryl sulfate ("Emal (registered trademark) AD-25R" manufactured by Kao Co., Ltd.) and 15 g/L of magnesium sulfate were added, the pH was adjusted to 0.4, and platinum electrolytic plating was performed. made it an insult

(Example 9)

The platinum stock solution of Example 9 is a sulfamic acid solution containing 18 g/L of p-salt as platinum. 190 g/L of sulfamic acid was added to this platinum stock solution to make a basic bath. To this basic bath, 140 mg/L of potassium lauryl sulfate and 6 g/L of magnesium sulfate, manufactured by Tokyo Chemical Industry Co., Ltd., were added, the pH was adjusted to 0.4, and a platinum electrolytic plating bath was obtained.

(Example 10)

The platinum stock solution of Example 10 is a sulfuric acid solution containing 8 g/L of DNS as platinum. 130 g/L of sulfuric acid was added to this platinum stock solution to make a basic bath. To this basic bath, 200 mg/L of sodium linear alkylbenzenesulfonate (“Neogen (registered trademark) AS-20” manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) and 2 g/L of magnesium sulfate were added, and the pH was adjusted to 0.4. was adjusted to make a platinum electrolytic plating bath.

(Example 11)

The platinum stock solution of Example 11 is a mixture of sulfuric acid and sulfamic acid containing 14 g/L of p-salt as platinum. 200 g/L of sulfuric acid was added to this platinum stock solution to make a basic bath. 300 mg/L of sodium stearate and 4 g/L of calcium sulfate were added to this basic bath, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 12)

The platinum stock solution of Example 12 is a mixture of sulfuric acid and sulfamic acid containing 6 g/L of DNS as platinum. Equal amounts of sulfuric acid and sulfamic acid were added to this platinum stock solution in a total amount of 140 g/L to obtain a basic bath. To this basic bath, 80 mg/L of "sodium 1-octadecanesulfonate" manufactured by Tokyo Chemical Industry Co., Ltd. and 20 g/L of magnesium sulfate were added, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

(Example 13)

The platinum stock solution of Example 13 is a sulfamic acid solution containing 7 g/L of DNS as platinum. 120 g/L of sulfuric acid was added to this platinum stock solution to make a basic bath. To this basic bath, 5 mg/L of "dimethylsodium 5-sulfoisophthalate" manufactured by Tokyo Chemical Industry Co., Ltd. and 1 g/L of sodium sulfate were added, and the pH was adjusted to 0.4 to obtain a platinum electrolytic plating bath.

In the platinum electrolytic plating baths of Examples 1 to 13, p-salt or DNS was dissolved in sulfuric acid or sulfamic acid to prepare a platinum concentrate containing a divalent platinum complex. Thereafter, a sulfuric acid solution, a sulfamic acid solution, or a mixture thereof was added to the platinum concentrated solution to obtain a basic platinum bath. Then, a platinum electrolytic plating bath of Examples 1 to 13 was obtained by adding a predetermined surfactant to this basic bath. In addition, sulfate was added as a metal salt to the platinum electrolytic plating baths of Examples 8 to 13. The compositions of the platinum electrolytic plating baths of Examples 1 to 13 are extracted and shown in Table 1. In addition, pure water used for dilution is deionized water passed through an ion exchange resin device. In any of the platinum electrolytic plating baths of Examples 1 to 13, the amount of silicon as an impurity was 0.1 ppm or less.

For the metal substrate to be electroplated, all the same copper test pieces (20 mmХ40 mmХ0.1 mm thick foil with lead wire welded) were used. This test piece was subjected to pretreatment of degreasing and pickling. Thereafter, a current (0.32 A) of a cathode current density of 2 A/dm ² was applied to the pretreated test piece using the platinum electrolytic plating bath of Examples 1 to 13 at a bath temperature of 55° C., and each platinum electrolytic plating was performed. Platinum electrolytic plating was applied directly onto this test piece from the bath.

In this way, 0.8 μm of platinum electrolytic precipitate was precipitated from the platinum electrolytic plating bath of Examples 1 to 13, and it was set as the platinum coating of Examples 01 to 13. The platinum purity of the platinum coatings of Examples 01 to 13 was all 99%, and these platinum coatings were all glossy. In addition, the porosity of the platinum coatings of Examples 01 to 13 was measured, and hardness and internal stress were measured together. The results are shown in Table 2.

Here, the porosity test is a test employed because the platinum electrolytic precipitate is not corroded in a normal corrosion test. In this porosity test, a low voltage of 0.74 V was applied to a 5% sulfuric acid electrolyte solution at 50°C, and electrolysis was performed for 20 minutes using the platinum film of the working product as an anode. A copper surface was exposed on the platinum film after electrolysis. This exposed copper was measured by the current value of the rectifier, and the ratio of copper exposed to the surface of the platinum film was estimated by the numerical change of the current value, and it was defined as "porosity". That is, a porosity of 100% is a current value in a state in which copper is exposed on the entire surface of the platinum film, and a porosity of 0% is a current value in a state in which copper is not exposed at all. The porosity of the platinum coatings of Examples 01 to 13 is a percentage proportionally distributed from the current values of 100% porosity and 0% porosity. The smaller the porosity value, the more corrosion resistance there is.

As is clear from the above test results, the platinum coatings of Examples 01 to 13 of the present invention are glossy, although the film thickness is as thin as 0.8 µm. In addition, these platinum coatings are hard with a Vickers hardness of 450 to 480 Hv, and have a porosity in the range of 8.5 to 13.5%, indicating that they are excellent in corrosion resistance. In addition, the purity of platinum in these platinum films is all 99%. In addition, it can be seen that the internal stress of these platinum coatings is in the range of 20 to 80 Mpa and is very low.

On the other hand, no correlation was found between the porosity and stress of the platinum coatings of Examples 01 to 13 of the present invention. Therefore, samples 09 and 10 were individually compared with samples 05 and 07. The platinum electrolytic plating bath of Example 09 contained 140 mg/L of potassium lauryl sulfate and 6 g/L of magnesium sulfate. On the other hand, the platinum electrolytic plating bath of Example 05 contained 500 mg/L of ammonium lauryl sulfate and no magnesium sulfate. The platinum electrolytic plating bath of Example 10 contained 200 mg/L of sodium alkylbenzenesulfonate and 2 g/L of magnesium sulfate. On the other hand, the platinum electrolytic plating bath of Example 07 contained 160 mg/L of sodium alkylbenzenesulfonate and no magnesium sulfate.

Comparing the porosity of the platinum coating, Example 09 is 9.5%, whereas Example 05 is 11.4%. In addition, Example 10 is 11%, whereas Example 07 is 12.5%. That is, the platinum film of Example 09 and Example 10 containing metal sulfate has a lower porosity than the platinum film of Example 05 and Example 07 that does not contain metal sulfate, regardless of the type of platinum compound, and has excellent corrosion resistance. It can be seen that this increases Further, comparing the stress of the platinum film, the stress of Example 09 is 20 Mpa, whereas the stress of Example 05 is 60 Mpa. Further, the stress of Example 10 is 20 Mpa, whereas the stress of Example 07 is 50 Mpa. That is, the stress of the platinum film of Example 09 and Example 10 containing metal sulfate is lower than that of the platinum film of Example 05 and Example 07 not containing metal sulfate, regardless of the type of platinum compound. can know that In addition, the hardness of the platinum film was 450 Hv or more in all of Example 05, Example 07, Example 09, and Example 10.

Fig. 2 shows a scanning electron micrograph in which 4 µm of platinum electrolytic precipitate was deposited from the platinum electrolytic plating bath of Example 1. As is evident from the photograph of FIG. 2, the platinum electrolytic precipitate particles have a platinum coating film so dense that no difference in crystal grain size can be seen on both the surface and cross section, and no grain boundaries of the platinum particles can be observed with a scanning electron microscope. Have. When this platinum film was subjected to X-ray diffraction, the crystal orientation of platinum was observed. In this specification, the precipitation form of such a platinum electrolytic precipitate is called "crystal structure like an amorphous state". It is understood that the particles of the platinum electrolytic precipitate in Example 1 have a crystal structure similar to that of an amorphous state and are very fine and dense. For this reason, the plated product of this invention is excellent in corrosion resistance, such as cold resistance. Further, even when a platinum electrolytic precipitate was precipitated from the platinum electrolytic plating bath of Example 1 to a thickness of 10 μm or more, the platinum film maintained a crystal structure similar to that of an amorphous state.

(Example 14)

The platinum stock solution of Example 14 is a sulfamic acid solution containing 4 g/L of Q salt as platinum. 70 g/L of sulfuric acid was added to this platinum stock solution to make a basic bath. To this basic bath, 250 mg/L of N-lauroyl-N-methyl-β-alanine ("Alanone ALA" manufactured by Kawaken Fine Chemical Co., Ltd.) was added as an anionic surfactant, and 5 g/L of magnesium sulfate was added. Then, the pH was adjusted to 0.5 to obtain a platinum electrolytic plating bath.

(Example 15)

The platinum stock solution of Example 15 is a sulfamic acid solution containing 8 g/L of Q salt as platinum. 70 g/L of sulfamic acid was added to this platinum stock solution to make a basic bath. To this basic bath, 250 mg/L of a polycarboxylic acid salt (“Caribone L-400” manufactured by Sanyo Chemical Industry Co., Ltd.) was added as an anionic surfactant, and the pH was adjusted to 1.5 to obtain a platinum electrolytic plating bath.

(Example 16)

The platinum stock solution of Example 16 is a sulfamic acid solution containing 10 g/L of Q salt as platinum. 50 g/L of sulfamic acid was added to this platinum stock solution to make a basic bath. To this basic bath, 100 mg/L of sodium dialkyl sulfosuccinate (Pelex OT-P, manufactured by Kao Co., Ltd.) was added as an anionic surfactant, and the pH was adjusted to 1.5 to obtain a platinum electrolytic plating bath.

The compositions of the platinum electrolytic plating baths of Examples 14 to 16 are extracted and shown in Table 3. In addition, the amount of silicon as an impurity in any platinum electrolytic plating bath is 0.1 ppm or less.

In the same manner as in Example 1, using the same test piece made of copper (a lead wire welded to a thin piece having a thickness of 20 mmХ40 mmХ0.1 mm), a platinum electrolytic precipitate of 0.8 µm was deposited at the same cathode current density. All platinum electrolytic precipitates of Examples 14 to 16 had a purity of 99%, and all of these platinum electrolytic precipitates were glossy. Further, the porosity of the platinum electrolytic precipitates of Examples 14 to 16 was measured, and hardness and internal stress were measured together.

Porosity, hardness and internal stress of Example 14 were 11.5%, 470 Hv and 40 Mpa. Further, the porosity, hardness, and internal stress of Example 15 were 13.8%, 465 Hv, and 80 Mpa. Further, the porosity, hardness, and internal stress of Example 16 were 10.2%, 480 Hv, and 20 Mpa. The results are shown in Table 4.

(Comparative example)

(Comparative Example 1)

Comparative Example 1 was the same as in Example 1 except that the anionic surfactant was not included, including 11 g/L of DNS as platinum, and adding sulfuric acid and sulfamic acid in equal amounts to a total of 160 g/L Platinum electrolysis it's a bath of gold

(Comparative Example 2)

Comparative Example 2 is a platinum electrolytic plating bath adjusted to pH 10.5 with a sodium hydroxide solution by adding platinum (II) hydrogen phosphate tetraamine (5 g/L as platinum) and 5 g/L of disodium disodium hydrogen phosphate. am.

(Comparative Example 3)

Comparative Example 3 is a platinum electrolytic plating bath carried out in the same manner as in Example 1, except that 600 mg/L of sodium lauryl sulfate (“Emal (registered trademark) 0” manufactured by Kao Corporation) was added.

In the same manner as in Example 1, a platinum electrolytic precipitate of 0.8 µm was deposited using the same test piece made of copper (a lead wire welded to a thin piece having a thickness of 20 mmХ40 mmХ0.1 mm). All platinum electrolytic precipitates of Comparative Products 01 to 03 had a purity of 99%, and all of these platinum electrolytic precipitates were shiny. In addition, the porosity of the platinum electrolytic precipitates of Comparative Products 01 to 03 was measured, and hardness and internal stress were measured together.

The porosity, hardness and internal stress of Comparative Product 01 were 30.6%, 400 Hv and 450 Mpa. Further, the porosity, hardness, and internal stress of Comparative Product 02 were 35.1%, 420 Hv, and 550 Mpa. Further, the porosity, hardness, and internal stress of Comparative Product 03 were 33.5%, 410 Hv, and 510 Mpa. The results are shown in Table 4.

As is clear from the above test results, the platinum electrolytic precipitates of Examples 14 to 16 of the present invention are shiny despite having a thin film thickness of 0.8 µm. In addition, the platinum electrolytic precipitates of Examples 14 to 16 of the present invention are hard with a Vickers hardness of 465 to 480 Hv and have a porosity in the range of 10.2 to 13.8%, indicating that they are excellent in corrosion resistance. In addition, the purity of all platinum is 99%. Further, the internal stress of Examples 14 to 16 of the present invention is in the range of 20 to 80 Mpa, which is very low. In contrast, the porosity of the platinum electrolytic plating bath of Comparative Product 01 was 30.6%, the platinum electrolytic plating bath of Comparative Product 02 was 35.1%, and the platinum electrolytic plating bath of Comparative Product 03 was 33.5%, respectively. In addition, it was found that the internal stress of the platinum electrolytic precipitates of Comparative Products 01 to 03 was also very high at 450 to 550 Mpa. Although the porosity of Comparative Products 01 to 03 was all poor, no apparent cracks or pinholes were observed.

On the other hand, the Hersel test was conducted on the platinum electrolytic plating bath of Comparative Example 3 and the platinum electrolytic plating bath of Example 1. The platinum electrolytic plating bath of Example 1 contained 60 mg/L of sodium lauryl sulfate, and the platinum electrolytic plating bath of Comparative Example 3 contained 600 mg/L of sodium lauryl sulfate. As a result of visual observation of the amorphous plated region of the Hussel test piece, the platinum electrolytic plating bath of Comparative Example 3 was inferior to the platinum electrolytic plating bath of Example 1 by about 50% in terms of high current density.

As described above, it can be seen that the platinum electrolytic plating bath of the present invention has a low porosity and excellent corrosion resistance even though a high-purity platinum film is obtained. In addition, since the platinum-plated product of the present invention is dense, has low stress, and is glossy, it can be applied not only to electrical parts such as connectors and printed circuit boards, but also to seawater electrolysis electrodes, insoluble anodes for electroplating, and accessories. It can.

Claims (10)

A platinum-plated product comprising a platinum electrolytic precipitate obtained by using a platinum electrolytic plating bath comprising a divalent platinum (II) complex and liberated sulfuric acid or sulfamic acid and containing an anionic surfactant, wherein the platinum has a purity of 99% by weight or more; A platinum-plated product characterized in that the Vickers hardness is 450 to 500 Hv, the stress is 100 Mpa or less, and the porosity is 30% or less. A platinum-plated product comprising a platinum electrolytic precipitate obtained by using a platinum electrolytic plating bath comprising a divalent platinum (II) complex and free sulfuric acid or sulfamic acid and containing an anionic surfactant, free sulfuric acid and sulfamic acid, comprising: A platinum-plated product characterized in that the purity is 99% by weight or more, the Vickers hardness is 450 to 500 Hv, the stress is 100 Mpa or less, and the porosity is 30% or less. consisting of a platinum electrolytic precipitate obtained by using a platinum electrolytic plating bath comprising a divalent platinum (II) complex and liberated sulfuric acid or sulfamic acid and containing an anionic surfactant and a metal salt of a Group 2 element or an alkali metal element; A platinum-plated product, characterized in that the purity of platinum is 99% by weight or more, the Vickers hardness is 450 to 500 Hv, the stress is 100 Mpa or less, and the porosity is 30% or less. Using a platinum electrolytic plating bath consisting of a divalent platinum (II) complex and free sulfuric acid or sulfamic acid and containing an anionic surfactant, free sulfuric acid, sulfamic acid, and a metal salt of a Group 2 element or a metal salt of an alkali metal element A platinum-plated product made of platinum electrolytic precipitate obtained by, characterized in that the purity of platinum is 99% by weight or more, the Vickers hardness is 450 to 500 Hv, the stress is 100 Mpa or less, and the porosity is 30% or less. Platinum plated products. delete delete delete delete delete delete