TW202227672A - Platinum electroplating bath and platinum-plated product wherein the platinum electroplating bath is a plating bath that further contains an anionic surfactant in an acidic platinum plating bath containing a divalent platinum (II) complex and free sulfuric acid or sulfamic acid - Google Patents

Abstract

The present invention provides an acidic platinum electroplating bath that is extremely stable, has a long bath life, little impurity accumulation, and can be plated thickly, and uses the acidic platinum electroplating bath to produce a platinum-plated product having a dense, high-hardness, low-stress, glossy and good corrosion resistance platinum-plated coating. The platinum electroplating bath is a plating bath that further contains an anionic surfactant in an acidic platinum plating bath containing a divalent platinum (II) complex and free sulfuric acid or sulfamic acid. In addition, a platinum-plated product is produced by using this platinum electroplating bath.

Description

Platinum Electroplating Baths and Platinum-Plated Products

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

In platinum electroplating baths, divalent platinum (II) complexes are often used as platinum compounds. The divalent platinum (II) complex is preferably used by synthesizing various platinum compounds using tetravalent chloroplatinum (IV) salt as a raw material. Inorganic platinum (II) complexes include compounds such as hydrochloric acid, nitric acid, sulfuric acid, and phosphoric acid. For example, there are platinum chloride (PtCl ₂ ), platinum nitrate (Pt(NO ₃ ) ₂ ), platinum dichlorodiammine (Pt(NH ₃ ) ₂ Cl ₂ , trichloramine platinic acid (HPtCl ₃ (NH ₃ )) ) or its salt (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 represents an alkali metal element, The second main group element or ammonium. In addition, there are tetravalent platinum (IV) complexes as platinum compounds. The tetravalent platinum (IV) complexes include hexahydroxyplatinic acid (H ₂ Pt(OH) ₆ ) or its salt (M' ₂ Pt(OH) ₆ ), etc. Here, M' represents an alkali metal element, a second main group element, or ammonium.

The divalent platinum(II) complexes preferably used in the electroplating bath are known as dinitrodiammine platinum (Pt( _NH3 ) ₂ (NO2 _{)2 ,} so-called p-salt), dinitrodihydrate dihydrate Ammonium platinum (Pt(NH ₃ ) ₂ (H ₂ O) ₂ (NO ₂ ) ₂ ), nitrohydroxyplatinum diammine (Pt(NH ₃ ) ₂ (H ₂ O)(OH)(NO ₂ ) ), platinum nitrohydroxydiamine (Pt(NH ₃ ) ₂ (OH)(NO ₂ )), platinum diammonium dinitrate (Pt(NH ₃ ) ₂ (NO ₃ ) ₂ ), platinum dinitro sulfate ( [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 ), tetraammine platinum hydrogen phosphate (Pt(NH ₃ ) ₄ (HPO ₄ ), so-called Q salt), and the like.

Platinum electroplating baths using these divalent platinum (II) complexes or tetravalent platinum (IV) complexes have been known since ancient times. For example, the platinum electroplating baths using dinitrodiammine platinum, dinitroplatinum sulfate, or the like include the following platinum electroplating baths.

For example, Japanese Patent Publication No. Sho 36-19658 (Patent Document 1 to be described later) discloses an invention of an electrolytic solution for platinum plating comprising an aqueous solution containing nitrosobisulfuric acid heated in an aqueous solution of sulfamic acid. A composition obtained from ammonia platinum". The specification states that the P salt [Pt(NH ₃ ) ₂ (NO ₃ ) ₂ ] was found to decompose in an aqueous solution of sulfamic acid, and platinum could be electroplated in this diluted solution. However, when the electroplating operation is performed at a temperature of 70 to 80° C. using this platinum electroplating bath, sulfamic acid is decomposed and a platinum salt precipitates.

In addition, Japanese Patent Publication No. Sho 36-19812 (Patent Document 2 to be described later) discloses an invention of an electrolytic solution for platinum plating comprising a solution containing 10 to 100 cc of concentrated sulfuric acid and 10 to 100 cc of water and water. It is obtained by heating a composition containing nitrosodiammine platinum at a ratio of 10 to 40 g per liter in about 200 cc of an aqueous mixture of 100 cc of concentrated phosphoric acid. However, when the electroplating operation is continued using this electrolytic solution for platinum plating, phosphoric acid is accumulated in the solution, and the corrosion resistance of the platinum plating film may be inhibited. In addition, in the electrolytic solution for platinum plating in which phosphoric acid is accumulated, it is difficult to reliably obtain plating of 5 μm or more with stable adhesion in one plating operation. In addition, there is a disadvantage of preventing the recovery of platinum from the waste liquid of the electrolytic solution for platinum plating.

After that, Japanese Patent Publication No. Sho 49-21018 (Patent Document 3 to be described later) discloses “dissolving diammine in a solution containing (specific) ammonium salt 0.05 to 2 mol/L and sulfuric acid 0.05 to 1 mol/L The invention of the electrolytic platinum plating bath made of platinum nitrate. In the examples, a bath temperature of 70 to 90°C was used. This specification states that "(1) The stability of the bath is high. ... (3) The bath life is long and has the characteristics of an industrial plating bath."

In addition, the following invention is disclosed in claim 4 of Japanese Patent Application Laid-Open No. 08-319595 (Patent Document 4 to be described later), "a platinum bath for electroplating, characterized in that: Electroplating of Ammine Sulfamato complex platinum (Ammine Sulfamato) complex, which is the product of the reaction of molar dinitrodiammine platinum (II) with 4 to 6 molar sulfonamides, and the pH value is less than 1 In a platinum bath, the electrolyte contains a maximum of 5 g/l of free sulfonamides and 20 to 400 g/l of a strong acid with a pH value of less than 1, and 0.01 to 0.2 g/l of a fluorosurfactant as a wetting agent.” . In the examples the operation was carried out at a bath temperature of 80°C. The description of the invention states that "the object is to provide a platinum bath for electroplating that can precipitate smoothly and shiny without cracks even when the layer thickness is greater than 100 μm, and is stable even when not in use for a while". It should be noted that "sulfamic acid" is another name for sulfamic acid.

In addition, US Pat. No. 3,206,382 (Patent Document 5 to be described later) discloses a method for electrodepositing platinum, that is, a method of electrodepositing platinum by forming an aqueous solution of a predetermined nitroso compound complex of platinum with a pH value of less than 2. electrolyte for electrolysis. This Example 1 discloses a method of reacting potassium tetranitroplatinum (II) acid with sulfuric acid and adjusting potassium dinitroplatinum (II) sulfate according to the following formula. K ₂ Pt(NO ₂ ) ₄ + H ₂ SO ₄ → K ₂ Pt(NO ₂ ) ₂ SO ₄ This specification discloses that the plating bath of the invention is stable, giving consistent results, and does not deteriorate even when left to stand.

When a platinum electroplating bath is used to manufacture a platinum-plated product, a layer of nickel, copper, palladium, etc. is provided as an intermediate layer of the object to be plated. An acidic plating bath is usually used to form the intermediate layer, but when an acidic plating bath is used to form the intermediate layer, platinum plating is performed using an acidic plating bath. This is because if an alkaline platinum plating bath is used, the acid solution in the previous stage is brought into the platinum plating bath, and the pH of the alkaline bath is easily changed.

prior art literature [Patent Literature] Patent Document 1 : Japanese Patent Publication No. 36-19658 Patent Document 2 : Japanese Patent Publication No. 36-19812 Patent Document 3 : Japanese Patent Publication No. 49-21018 Patent Document 4 : Japanese Patent Application Laid-Open No. 08-319595 Patent Document 5 : Specification of US Patent No. 3206382

[Problems to be Solved by Invention]

As described in Japanese Patent Publication No. Sho 36-19658 (Patent Document 1 mentioned above), conventional platinum films plated from acidic platinum plating baths (platinum plating solutions) have problems of high stress and easy generation of pinholes and cracks. Although the platinum film of Japanese Patent Laid-Open No. 08-319595 (Patent Document 4 mentioned above) does not have pinholes and cracks in appearance, when the porosity is measured, it is found that the value of the porosity is very poor, and the platinum film remains on the platinum film. There are pinholes and cracks.

The poor porosity of the platinum film is caused by platinum particles electrolytically precipitated by electroplating. That is, one factor is that the stable platinum complex becomes an unstable compound in the platinum electroplating bath due to the extraction of platinum ions from the stable platinum complex in the platinum electroplating bath. For example, when the nitro group contained in p-salt, DNS salt, etc. is coordinated to platinum, it is extremely stable, but when platinum metal is precipitated from the complex by electroplating, the remaining nitro group forms various nitrogens in the platinum electroplating bath oxide (NOx) ions. The complex nitrogen oxide (NOx) ions act on the platinum complexes in the platinum electroplating bath, destabilizing the particles of the precipitated platinum metal.

Specifically, tetranitroplatinic acid (H ₂ Pt(NO ₂ ) ₄ ) may form Pt(NO ₂ ) ₃ (H ₂ O) ⁻ , Pt(NO ₂ ) ₂ (H 2 O) ₂ , Pt( NO ₂ ) (H ₂ O) ₃ ⁺ , Pt(H ₂ O) ₄ ^{2 +} and other complexes. In addition, it is known that a nitro group has a property of easily generating a complex compound of nitrogen and oxygen such as [Pt(NH ₃ ) ₂ (NO ₃ ) ₂ ] in addition to the above-mentioned compounds in an aqueous solution. For example, it is known that the color tone of the platinum electroplating bath changes when the nitro group remaining in the platinum electroplating bath is excessively concentrated. From this, it can also be understood that the nitro group of the platinum complex has the property of easily generating a complex compound. In addition, it is known that in an acidic platinum electroplating bath, sulfur oxide (SOx) ions released from platinum complexes are not as active as nitrogen oxide (NOx) ions, but have the property of easily generating complex compounds. Electrolytic deposits can be affected by changes in such platinum complexes in the platinum electroplating bath. As described above, in an acidic platinum electroplating bath, the electrolytic deposit tends to fluctuate easily during the electroplating operation. In particular, when continuous plating is continued under high current density conditions such as spray plating, the bath temperature rises, and new unstable compounds such as nitrogen oxide (NOx) ions and sulfur oxide (SOx) ions are easily formed.

Microscopic observation of the electrolytically precipitated platinum particles found that the crystal grains were large and unstable. In addition, an acidic platinum electroplating bath tends to dissolve metals, so platinum-plated products tend to be easily affected by metal impurities. When the metal impurities are accumulated and concentrated, the plating conditions of the platinum plating bath are easily changed, and the failure of the platinum-plated product is likely to occur. In addition, when halide ions coexist in such a platinum plating bath, free nitrogen oxide (NOx) ions and sulfur oxide (SOx) ions further undergo complicated reactions. The platinum ions electrolytically precipitated near the cathode are affected in various ways by these complex compounds and ligands. The precipitation conditions are therefore constantly changing when platinum ions become the nucleus of new platinum particles. Since the precipitation conditions of platinum particles on the cathode are different even if the plating conditions are the same, the platinum electrolytic precipitate may become unstable. From this, it can be speculated that the electroplated platinum film has high stress and large crystal grains, and pinholes and cracks are generated.

To sum up, in the conventional platinum electroplating bath, nitrogen oxide (NOx) ions, sulfur oxide (SOx) ions, etc. of stable platinum complexes are released, which makes the platinum electroplating bath unstable, and these ions and the like accumulate, concentrate. When these ions and the like are present in a large amount in the platinum electroplating bath, the conditions for the precipitation of platinum particles from the aqueous solution during electroplating become unstable. In addition, the platinum particles deposited on the deposited platinum particles are affected by these ions and the like. Therefore, the stress of the electrolytically deposited platinum precipitate is high, and crystal grains grow irregularly. Therefore, the obtained platinum-plated product has the problem of many microscopic cracks and pinholes. In addition, when copper is used for electroplating as a metal substrate, copper may be eluted at the ppm level in an acidic platinum electroplating bath. The same applies to the plating treatment of the intermediate layer of nickel, palladium, or the like. Such metallic impurities may negatively affect platinum-coated products.

However, in the conventional platinum electroplating baths, the influence of other metal impurities has not been considered. In addition, microscopic cracks and pinholes in conventional platinum-plated products have not been a problem. This is because the platinized product has a high stress and has chemical properties that are not easily corroded even if the platinized product is immersed in an aqueous solution of acid and alkali. However, in applications such as connectors, porosity, ie, corrosion resistance, caused by microscopic cracks, pinholes, and the like in platinum-plated products has become a problem. Because when a platinum-coated product is touched with bare hands, there is a risk that components such as sweat will penetrate the platinum film and corrode the metal substrate. In such applications, sometimes ppm-level metal impurities also affect platinum-coated products. Consequently, dense high-purity platinum-plated products and high-purity platinum electroplating baths were subsequently required. In particular, silicon is abundant in nature and is a metal element that is easily involved as an impurity in platinum electroplating baths. For example, precious metals are also produced as by-products of the electrorefining of copper. Referring to the twelfth embodiment of Japanese Patent Laid-Open No. Sho 50-116326, it is described that a platinum-containing alloy containing silicon is produced in the electrolytic refining of copper. Silicon readily enters platinum plating baths, so special care is required in high-purity platinum plating baths.

The present invention has been made in view of the above-mentioned problems, and an object thereof is to provide a platinum electroplating bath that is extremely stable and has a long bath life. In particular, it is possible to provide a high-purity platinum precipitate that is dense and has an amorphous crystal structure even in an acidic platinum plating solution containing a large amount of platinum (II) complexes that are easily decomposable ligands such as nitro groups. platinum electroplating baths.

Another object of the present invention is to provide a platinum-coated product having a platinum coating whose stress is small and is so dense that the grain boundaries of platinum particles cannot be observed under a scanning electron microscope. Another object of the present invention is to provide a platinum-plated product having a high-purity platinum film that can be thick-plated. In particular, a platinum-plated product with small porosity and good corrosion resistance is provided. [means to solve the problem]

The inventors of the present invention studied the porosity of platinum-plated products that are not easy to corrode and found that the smaller the porosity of the platinum film, the better the corrosion resistance of the platinum-plated products. In addition, it is known that when metal impurities are present in platinum-plated products, a dense platinum film may not be obtained depending on the type and content of the metal. For example, when a specific metal impurity on the ppm level is contained in a conventional acidic platinum electroplating bath, the porosity of the electrolytically deposited platinum precipitate sometimes deteriorates remarkably. Observing the platinum-plated product, surface defects such as cracks and pinholes occurred on the platinum film.

An investigation into the source of silicon contained in the platinum electroplating bath found that, like the by-products of the above-mentioned copper electrolytic refining, the platinum matrix, which is nominally 99.9% or more, sometimes contains metal impurities such as silicon at the level of several tens of ppm. In addition, distilled water also contains silicon. Therefore, metal impurities such as silicon may accidentally accumulate when preparing a platinum-plating bath and replenishing evaporated water. In addition, it is known that metal impurities such as silicon are sometimes contained in gold plating baths, palladium plating baths, and nickel plating baths as pretreatment plating liquids, or in cleaning liquids such as dragout tanks and water washing apparatuses.

The present inventors first studied platinum electroplating baths under conditions where silicon was removed. It has been found that in the conventional acidic platinum electroplating bath based on the sulfate or sulfamic acid salt of divalent platinum (II) complex and free sulfuric acid or sulfamic acid, even if the platinum precipitate is of high purity, its crystalline The grains are also larger. That is, in a platinum electroplating bath that does not contain metal impurities other than platinum, only platinum is electrolytically precipitated. Electrolytically precipitated platinum is high-purity platinum, and its film properties can be accurately understood.

The present inventors have studied various additives in such a high-purity platinum electroplating bath. Furthermore, it was found that when an anionic surfactant with both a hydrophilic group and a hydrophobic group in one molecule was added, the platinum particles precipitated on the cathode were dense and uniform in shape. Explain its function. That is, in the anionic surfactant having both a hydrophilic group and a hydrophobic group, the periphery of the divalent platinum complex is surrounded by one group. When energized in the platinum electroplating bath, the anionic surfactant maintains the state surrounding the divalent platinum complex and transports the platinum complex to the cathode surface. On the cathode surface, the 2-valent platinum complex becomes zero-valent platinum metal. When the divalent platinum complex contacts the cathode surface on the solution side of the cathode surface, the ligands of the platinum complex become nitrogen oxide (NOx) ions or the like, and are freed in the platinum electroplating bath. In this process, anionic surfactants replace nitrogen oxide (NOx) ions, etc., surrounding platinum metal. Free nitrogen oxide ions are no longer accessible to platinum metal due to the hindrance of anionic surfactants. When the platinum metal on the cathode is reduced to platinum particles, the platinum particles are absorbed by the platinum crystal particles, and the platinum crystal particles on the cathode grow. On the other hand, the anionic surfactant surrounding the platinum metal in the platinum electroplating bath is separated from the cathode surface and freed again in the platinum electroplating bath.

The action of this anionic surfactant will be explained easily using FIG. 1 . FIG. 1 is a schematic diagram of a platinum plating solution to which a p-salt of sodium lauryl sulfate as an anionic surfactant is added. For convenience, the ligand of platinum ion is labeled as sulfate ion (SO ₄ ) ^2- . As shown on the left side of FIG. 1 , in the platinum plating solution, sodium lauryl sulfate, which is an anionic surfactant, surrounds the Pt(II) complex. The Pt(II) complex is transported to the cathode by external electrical energy. As shown in the center of Figure 1, the 2-valent Pt(II) complex transported to the cathode surface gains two electrons from the cathode and is reduced to zero-valent Pt(0) metal surrounded by anionic surfactants. On the plating bath side on the cathode, the anionic surfactant of the zero-valent Pt(0) metal and the anionic surfactant of the Pt(II) complex repelled each other. In addition, they also repel each other with hydroxide ions (not shown) and sulfur oxide (SOx) ions (not shown) generated by electrolysis. Therefore, the interaction between the zero-valent Pt(0) metal and the platinum atoms in the 2-valent Pt(II) complex is suppressed.

Next, as shown on the right side of FIG. 1 , the zero-valent Pt(0) metal is reduced to platinum particles (not shown) and absorbed by the platinum crystal particles. On the cathode, platinum crystal grains grow to form a platinum-plated film. On the other hand, the anionic surfactant surrounding the platinum metal is separated from the cathode and freed again in the platinum plating solution. By the action of such an anionic surfactant, the platinum particles can suppress the interaction of other platinum atoms, so that the platinum particles can always be precipitated under constant conditions. When homogenized crystalline particles are layered on the cathode surface, a seamless electrolytic deposit is formed. As a result, a dense platinum film having an amorphous crystal structure was obtained on the cathode.

On the other hand, such anionic surfactants are known to be ineffective against metallic impurities in platinum electroplating baths. The role of anionic surfactants is effective for the ligands of platinum complexes, but not for metal impurities in platinum electroplating baths. When metal impurities such as silicon are contained in the platinum electroplating bath of the present invention, these metal impurities are eutectically deposited on the platinum plating film. Conversely, if these metal impurities are not contained in the platinum electroplating bath, a high-purity platinum electrolytic precipitate can be obtained. It is known that a high-purity platinum-plated film that does not contain metal impurities is an electrolytic deposit that has a low tensile stress, is dense, and has a low porosity even if its hardness is high.

Scanning electron microscope images of the surface and cross section of the platinum electrolytic precipitate of the present invention are shown in FIG. 2 . This figure is a photograph obtained by photographing the surface (the upper part of the photograph demarcated by the white horizontal line) and the cross-section (the lower part of the photograph) of a thickness of 4 μm of a platinum electrolytic deposit having a purity of 99% or more from an obliquely above 45 degrees. As can be seen from this figure, the crystal grains of the platinum electrolytic precipitate are as dense as in an amorphous state.

The gist of the platinum plating bath of the present invention capable of solving the above-mentioned problems is to include an anionic surfactant in an acidic platinum plating bath containing a divalent platinum (II) complex and free sulfuric acid or sulfamic acid.

In addition, the gist of the platinum electroplating bath of the present invention capable of solving the above-mentioned problems is that an anionic surfactant and an anionic surfactant and Metal salts of elements of the second main group or metal salts of alkali metal elements. Here, the second main group element refers to elements such as beryllium, magnesium, calcium, strontium and the like. In addition, the said alkali metal element means elements, such as lithium, sodium, potassium, and rubidium.

In addition, the main points of the platinum electrolytic precipitate of the platinum electroplating bath of the present invention that can solve the above problems are 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 100 MPa or less. Less than or equal to 30%. [Inventive effect]

By containing an anionic surfactant, the platinum plating bath of the present invention has a crystal structure like an amorphous state even in an acidic platinum plating bath, and has the effect that a dense platinum electrolytic deposit can be obtained. That is, the platinum electrolytic precipitate of the present invention is characterized by being shiny, and having extremely low stress even if it is hard and dense. In particular, in a high-purity platinum electroplating bath that does not contain metal impurities such as silicon, the above-mentioned effects are enhanced.

The platinum electroplating bath of the present invention has the effect that the amount of anionic surfactant used can be reduced by permeating the metal salts containing alkali metal elements, second main group elements, or these metal elements. That is, it is known that the same effect can be obtained even if the content of the anionic surfactant is small by containing an alkali metal element, a second main group element, or a metal salt of these metal elements in addition to the anionic surfactant. In addition, the platinum electroplating bath of the present invention has the effect of reducing the accumulation of anionic surfactant even when electroplating is continued for a long time. There is also an effect that the platinum electroplating bath of the present invention can be continuously operated for a long period of time even if the anionic surfactant is deteriorated and the surfactant concentration is substantially lowered.

In addition, according to the platinum electroplating bath of the present invention, even if it is a thin plating film of 1 μm or less, it is dense and has an amorphous crystal structure, so that a plating film having a low porosity and excellent corrosion resistance can be obtained. Effect. Furthermore, when a high-purity platinum plating bath is used, the purity of the platinum electrolytic deposit is high and the quality of the platinum film is stabilized.

In addition, according to the platinum electroplating bath of the present invention, since the plating quality is stable, there is an effect that the bath temperature can be set to a relatively low temperature. When the bath temperature of the platinum electroplating bath of the present invention is lowered, there is an effect that the management of the plating solution becomes easy. In addition, the platinum electroplating bath of the present invention has less accumulation of impurities, so there is also an effect of eliminating the need to install expensive equipment such as filtration and separation of the plating solution.

The crystal grains of the platinum coating of the platinum-plated product including the platinum electrolytic deposit of the platinum electroplating bath of the present invention are dense and have a crystal structure such as an amorphous state. Such a platinum film has a low porosity and is therefore excellent in corrosion resistance. In particular, there is an effect that a platinum-plated product with high corrosion resistance can be obtained even in a thin plating of 1 μm or less. The corrosion resistance of the platinum-plated product of the present invention includes not only static corrosion resistance against corrosion liquids, but also dynamic corrosion resistance in the case of flowing a weak current or the like. In addition, since the platinum-plated product of the present invention is hard and dense, when used as a connector or the like, it has the effect of being excellent in insertion/extraction durability and wear resistance. Since the stress of the platinum coating of the present invention is extremely low, the adhesiveness is strong, the coating does not peel off, and pinholes, cracks, etc. do not appear in the coating.

In addition, the high-purity platinum-plated product of the present invention has the effect that the temperature coefficient of resistance is stable and an equal resistance value can be obtained. In addition, the platinum-plated product of the present invention is a platinum electrolytic deposit that is shiny and corrosion-resistant even at high purity, and thus has the effect of being suitable as a decorative item. In particular, the porosity shows a more stringent corrosion resistance standard than sweat resistance, and it has the effect of being suitable for use in jewelry such as bracelets and earrings.

In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solutions of the present invention are now described in detail below, but should not be construed as limiting the scope of implementation of the present invention. Hereinafter, embodiments of the platinum electroplating bath of the present invention and the platinum-plated product including the platinum electrolytic deposit produced using the platinum electroplating bath will be described. ＜Platinum plating bath＞ (Divalent platinum (II) complex)

In the platinum electroplating bath of the present invention, the divalent platinum (II) complex which is preferably used in a conventional electroplating bath can be used as the divalent platinum (II) complex. The divalent platinum (II) complex preferably has a nitro group (NO ₂ ), a nitric acid group (NO ₃ ), a sulfate group (SO ₄ ) or a sulfo group (SO ₃ ), an amino group (NH ₃ ), an oxonium ( Inorganic platinum complexes of at least one or more ligands selected from H ₂ O) or hydroxyl (OH). Divalent platinum (II) complexes more preferably used in the electroplating 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 electroplating bath of the present invention, an aqueous solution obtained by dissolving a divalent platinum (II) complex in free sulfuric acid or sulfamic acid is used. For example, when a bivalent platinum complex powder such as a p-salt or DNS salt is dissolved in a sulfuric acid solution or a sulfamic acid solution, it becomes a brown or pale yellow liquid. In the platinum electroplating bath of the present invention, the divalent platinum solution may be used as it is, or the divalent platinum solution may be diluted and used. In the platinum electroplating bath of the present invention, the so-called "sulfuric acid or sulfamic acid" means that sulfuric acid or sulfamic acid may be used alone or in combination.

The concentration of platinum (the total content when two or more platinum salts are used in combination) is preferably 1 to 20 g/L, more preferably 2.5 to 15 g/L as the platinum (Pt) content. When the concentration of platinum is less than 1 g/L, the precipitation rate may become slow, but when there is a metal salt, the retardation of the precipitation rate is alleviated. In addition, when the concentration of platinum is less than 1 g/L in visual observation, abnormal precipitation such as an overfired layer and unevenness may be found in the plating film. On the other hand, even if the concentration of platinum is more than 20 g/L, the effect of platinum plating is hardly changed. Therefore, when the concentration of platinum(II) ions is greater than 20 g/L, the cost of the substrate increases. Continuous plating can be performed stably as long as the concentration of platinum is in the range of 2.5 to 15 g/L. It should be noted that the amount of phosphoric acid contained in platinum complexes such as Q salts can be appropriately adjusted by passing through other platinum complexes that do not contain phosphorus.

The content of free sulfuric acid or sulfamic acid in the platinum electroplating bath of the present invention is preferably 30 to 600 g/L, more preferably 50 to 400 g/L, regardless of whether it is used alone or in combination of two or more. If the total content of free sulfuric acid or sulfamic acid is less than 30 g/L, although it also depends on the content of other auxiliary conductive salts, etc., abnormal precipitation such as overfired coating and unevenness may be found on the plating film. On the other hand, when the total content of free sulfuric acid or sulfamic acid exceeds 600 g/L, the concentration of free sulfate may become too high due to the evaporation loss of water during the plating operation, and the balance of the platinum plating solution will be lost. risks of. (anionic surfactant)

The platinum electroplating bath of the present invention contains an anionic surfactant. As the anionic surfactant in the platinum electroplating bath of the present invention, generally known anionic surfactants such as sulfonic acid type, sulfate type, and fatty acid type can be used. However, the phosphate ester type surfactant is not suitable as the anionic surfactant of the present invention because the phosphate ester salt as a component may inhibit the corrosion resistance of the platinum electrolytic deposit. Specifically, the following anionic surfactants can be exemplified, but not limited to these, as long as they are sold as anionic surfactants, they can be used without problems except for phosphate ester type anionic surfactants. Sulfonic acid-type anionic surfactants include alkylated sulfonates such as sodium undecylsulfonate, sodium octadecylsulfonate, alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate, dioxane, etc. Sulfosuccinates such as sodium sulfosuccinate, etc. Sulfate-type anionic surfactants include sodium lauryl sulfate, ammonium lauryl sulfate, and the like. Fatty acid type anionic surfactants include sodium laurate, sodium stearate, etc., as well as amino acid decanoyl groups such as sodium N-decanoyl sarcosinate, N-lauroyl-N-methyl-β-alanine, etc. Amino acid substances such as sodium sarcosinate, etc.

The above-mentioned anionic surfactants are preferably alkylated sulfuric acid or its salt and alkylbenzenesulfonic acid or its salt, stearic acid or its salt, sulfonic acid or its salt, or an alkali metal element salt of lauryl sulfuric acid, the second main Group element salts, ammonium salts, etc. Because these anionic surfactants are incorporated into the sulfate or sulfamate of the divalent platinum(II) complex, the electrolytic precipitate is dense. A small amount of anionic surfactant acts on the platinum electrolytic precipitate and has the property of turning crystal grains into an amorphous state. In addition, since the anionic surfactant is not easily evaporated from the platinum electroplating bath, it stably acts on the platinum electrolytic precipitate in the platinum electroplating bath for a long period of time. The anionic surfactant is not limited to use of one type, and two or more types may be used in combination. Non-foaming anionic surfactants are preferred because the platinum electroplating bath is sometimes pumped to circulate.

The small amount of the anionic surfactant in the platinum electroplating bath of the present invention is preferably in the range of 5 to 500 mg/L. When the content of the anionic surfactant is less than 5 mg/L, the stress of the platinum electrolytic deposit increases, and the effect of improving corrosion resistance cannot be exhibited in many cases. The lower limit of the total amount of the anionic surfactant is preferably 20 mg/L, more preferably 50 mg/L. When the salt of the alkali metal element or the second main group element is contained, the content of the anionic surfactant of 50 mg/L can be relatively reduced to less than 15 mg/L. When the salt of the alkali metal element or the second main group element is contained, the content of the anionic surfactant of 5 mg/L can be relatively reduced to less than 3 mg/L. On the other hand, when the content of the anionic surfactant is more than 500 mg/L, abnormal precipitation such as an overfired layer and unevenness is often observed on the plated film by visual observation. In addition, the upper limit is preferably 300 mg/L, more preferably 200 mg/L. The content of anionic surfactants can likewise be relatively reduced when salts of alkali metal elements or elements of the second main group are contained. (metal salt)

It is known that in the platinum electroplating bath of the present invention, when a metal salt of a second main group element or a metal salt of an alkali metal element is present, the content of anionic surfactant can be reduced. In the platinum electroplating bath of the present invention, the metal salt of the second main group element or the metal salt of the alkali metal element has a high ionization tendency, and therefore these metals do not eutect into 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 anionic surfactants. Among the metal salts of the second main group element or the metal salts of alkali metal elements, magnesium salts are more preferred. Examples of the magnesium salt include magnesium sulfate, magnesium sulfite, magnesium nitrate, and their water mixtures. Magnesium acetate, magnesium citrate, magnesium lactate, magnesium stearate and the like can also be used. Moreover, the thing which forms a salt in the platinum electroplating bath of this invention like magnesium oxide and magnesium hydroxide can also be used as a raw material. Since the platinum electroplating bath of the present invention contains free sulfuric acid or sulfamic acid, it is preferable to use an inexpensive metal sulfate as the metal salt of the second main group element or the metal salt of the alkali metal element.

If metal impurities such as silicon other than the metal salt of the second main group element and the metal salt of the alkali metal element are present in the platinum electroplating bath, these impurity metals tend to eutect in the platinum electrolytic precipitate. Eutectoid of these metal impurities in the platinum electrolytic precipitate may adversely affect the porosity of the platinum film, that is, the corrosion resistance of platinum-plated products, although it also depends on the type and content of these metal impurities. Therefore, in order to obtain 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 easily enters the platinum electroplating bath of the present invention. In the case of obtaining a high-purity platinum electrolytic deposit, silicon can be used as an index of impurities. Silicon is preferably 1 ppm or less. In addition, the metal salt of the second main group element or the metal salt of the alkali metal element does not contain a halogen element. Because the halogen element will have a negative effect on the platinum electrolytic precipitate. These metal salts also do not contain phosphates. Because platinum electroplating baths containing a large amount of phosphate will deteriorate the corrosion resistance of platinum electrolytic deposits. Phosphorus has the effect of densifying the platinum precipitate, but phosphate has the property of being difficult to evaporate. If phosphate is used as the metal salt of the second main group element or the metal salt of the alkali metal element, it will concentrate and thus contain phosphorus in the platinum electrolytic precipitate, with the risk of negatively affecting the platinized product. (other additives)

Known additives such as pH buffers can be used in the platinum plating bath of the present invention. The pH buffer is not particularly limited as long as it is a known pH buffer. Preferable buffering agents include inorganic salts such as potassium hydroxide, sodium hydroxide, magnesium hydroxide, and calcium hydroxide, or acetic acid, boric acid, tetraboric acid, citric acid, malic acid, succinic acid, malonic acid, horse Acid, fumaric acid, glycine or its compounds (potassium salt, sodium salt, ammonium salt, etc.), etc. These pH buffers can be added in a concentration range of 0.1 to 100 g/L. In addition, the platinum electroplating bath of the present invention may contain functional additives such as complexing agents, bath stabilizers, speed modifiers, leveling agents, crystallization modifiers, stress relaxation agents, and physical property improvers as necessary. However, functional additives that cannot maintain a high purity of 99% or more of the platinum electrolytic precipitate, and functional additives that deteriorate the porosity are excluded. (plating conditions, etc.)

In the platinum electroplating bath of the present invention, pH is preferably 2 or less, more preferably 1.5 or less. This is because an anionic surfactant is contained. It is also because the sulfate or sulfamate of the divalent platinum (II) complex is stable in electroplating operations. The pH is usually in the range of 0.2 to 1.0. In order to control pH within a predetermined range, a pH buffer can be used. The pH buffer may be used alone or in combination of two or more. In addition, the bath temperature can be appropriately determined according to the surrounding environment of the plating work. Preferably it is the range of 30-90 degreeC, More preferably, it is the range of 35-70 degreeC, More preferably, it is the range of 40-60 degreeC. The higher the bath temperature, the faster the precipitation rate of the platinum electrolytic precipitate, but the greater the evaporation of the plating solution. The bath temperature can be appropriately determined according to the metal substrate used and the application of the platinum product. In addition, the application range of the cathode current density is large, and the optimal current density can be selected in combination with the plating area of the metal substrate, the selection of the immersion and spray coating equipment, and the flow rate of the plating solution. <Platinum electrolytic deposit>

The object to be plated in the platinum electroplating bath of the present invention is used as a metal substrate. The metal substrate is not limited as long as it can be electroplated on its surface, even if the substrate is an insulating material such as plastic and ceramics. The surface of the metal base is appropriately selected from metals or alloys according to the application. In the application of electrical and electronic components such as connectors, metals such as iron, nickel, and chromium, and alloys thereof are generally used in addition to copper metal and copper alloy. In addition, the surface of the metal substrate can also be a surface subjected to electroless plating or electroplating of nickel, palladium, gold, or the like. In addition, for electrode applications, refractory metals such as titanium and tantalum are used. For jewelry and decorative purposes, metals such as stainless steel, nickel, silver alloys, and gold alloys are used. In addition, the platinum electrolytic deposit subjected to thick plating can also be used for ornaments and ornaments.

The platinum electrolytic deposit of the present invention is dense, and no cracks and pinholes are seen. The porosity test, which is one of the corrosion resistance tests shown in Examples, was performed on the platinum electrolytic deposit of the present invention. This is because it is difficult to evaluate the difference in corrosion even if the artificial sweat test (JIS B 7285) and the accelerated corrosion test (JIS H 8502) are carried out. In addition, the platinum electrolytic deposit of the present invention has low internal stress, and enables thick plating with a thickness of 10 μm or more. In addition, even when the platinum film was peeled off from the metal substrate, the platinum film of the present invention was not seen to be bent or curled.

In the platinum-plated product of the present invention, a two-layer structure of a metal substrate and a platinum electrolytic deposit is preferred. In this way, the cost of expensive platinum substrates can be saved. As described above, the metal base is appropriately selected according to the application. The metal matrix can be either a single metal or a laminated metal. Single metal and laminated metal also include metals clad in plastics, ceramics, etc. In addition, the platinum-plated product of the thin plating film of the present invention is more preferably a connector. The platinum electrolytic precipitate of the present invention has a crystal structure such as an amorphous state, low porosity, high hardness and corrosion resistance. Therefore, even if the surface of the thin platinum electrolytic deposit is touched with bare hands, it will not corrode. It should be noted that although the porosity also depends on the film thickness of the plating film, it is preferably 25% or less, and more preferably 20% or less. Example

Hereinafter, the present invention will be specifically described using Examples and Comparative Examples, but the present invention is not limited to these Examples unless the gist of the present invention is exceeded. (Example) (Example 1)

The platinum stock solution of Example 1 was a sulfuric acid solution containing DNS, and the DNS contained 11 g/L as platinum. Sulfuric acid and sulfamic acid were respectively added in equal amounts to this platinum stock solution, and a total of 160 g/L was added to prepare a basic bath. To this basic bath, 60 mg/L of sodium lauryl sulfate ("Emal (registered trademark) 0" manufactured by Kao Corporation) was added as an anionic surfactant, and the pH was adjusted to 0.4 to prepare a platinum plating bath. (Example 2)

The platinum stock solution of Example 2 was a sulfamic acid solution containing 15 g/L of p salt in terms of platinum. To this platinum stock solution, 70 g/L of sulfuric acid was added to prepare a basic bath. 70 mg/L of sodium dodecylbenzenesulfonate ("Neopelex (registered trademark) G-15" manufactured by Kao Corporation) was added to this basic bath, and the pH was adjusted to 0.4 to prepare a platinum plating bath. (Example 3)

The platinum stock solution of Example 3 was a sulfamic acid solution containing DNS of 17 g/L in terms of platinum. Sulfuric acid and sulfamic acid were respectively added to this platinum stock solution in equal amounts to a total of 150 g/L to prepare a basic bath. 180 mg/L of N-laurel sarcosine sodium salt (purity 95.5% or more) was added to this basic bath, and the pH was adjusted to 0.4 to prepare a platinum plating bath. (Example 4)

The platinum stock solution of Example 4 was a mixed solution of sulfuric acid and sulfamic acid containing DNS at 16 g/L in terms of platinum. To this platinum stock solution, 60 g/L of sulfamic acid was added to prepare a basic bath. 400 mg/L of alkylallyl sulfonate/alkylammonium salt ("VISCO TOP (registered trademark of the company) 200LS-2" manufactured by Kao Corporation) was added to this basic bath, and the pH was adjusted to 0.4. A platinum electroplating bath is made. (Example 5)

The platinum stock solution of Example 5 was a mixed solution of sulfuric acid and sulfamic acid containing DNS at 5 g/L in terms of platinum. To this platinum stock solution, 80 g/L of sulfuric acid was added to prepare 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 to adjust the pH to 0.4 to prepare a platinum plating bath. (Example 6)

The platinum stock solution of Example 6 was a sulfamic acid solution containing DNS at 3 g/L in terms of platinum. To this platinum stock solution, 180 g/L of sulfamic acid was added to prepare a basic bath. 90 mg/L of sodium stearate was added to this basic bath, and the pH was adjusted to 0.4 to prepare a platinum plating bath. (Example 7)

The platinum stock solution of Example 7 was a sulfuric acid solution containing 13 g/L of p-salt in terms of platinum. To this platinum stock solution, 110 g/L of sulfamic acid was added to prepare a basic bath. 160 mg/L of linear sodium alkylbenzene sulfonate (“Newrex (registered trademark) Soft Type 30” manufactured by NOF Corporation) was added to this basic bath, and the pH was adjusted to 0.4 to prepare platinum plating. bath. (Example 8)

The platinum stock solution of Example 8 was a mixed solution of sulfuric acid and sulfamic acid containing DNS at 1 g/L in terms of platinum. Sulfuric acid and sulfamic acid were respectively added in equal amounts to this platinum stock solution, and a total of 80 g/L was added to prepare a basic bath. To this basic bath, 10 mg/L of ammonium lauryl sulfate ("Emal (registered trademark of the company) AD-25R" manufactured by Kao Corporation) and 15 g/L of magnesium sulfate were added to adjust the pH to 0.4 to prepare platinum electroplating bath. (Example 9)

The platinum stock solution of Example 9 was a sulfamic acid solution containing 18 g/L of p salt in terms of platinum. To this platinum stock solution, 190 g/L of sulfamic acid was added to prepare a basic bath. To this basic bath, 140 mg/L of potassium lauryl sulfate manufactured by Tokyo Chemical Industry Co., Ltd. and 6 g/L of magnesium sulfate were added, and the pH was adjusted to 0.4 to prepare a platinum plating bath. (Example 10)

The platinum stock solution of Example 10 was a sulfuric acid solution containing DNS of 8 g/L in terms of platinum. To this platinum stock solution, 130 g/L of sulfuric acid was added to prepare a basic bath. 200 mg/L of sodium linear alkyl benzene sulfonate (“Neogen (registered trademark) AS-20” manufactured by Daiichi Kogyo Co., Ltd.) and 2 g/L of magnesium sulfate were added to the basic bath, and the pH was adjusted to Adjusted to 0.4, a platinum plating bath was prepared. (Example 11)

The platinum stock solution of Example 11 was a mixed solution of sulfuric acid and sulfamic acid containing 14 g/L of p-salt in terms of platinum. To this platinum stock solution, 200 g/L of sulfuric acid was added to prepare 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 prepare a platinum plating bath. (Example 12)

The platinum stock solution of Example 12 was a mixed solution of sulfuric acid and sulfamic acid containing DNS at 6 g/L in terms of platinum. Sulfuric acid and sulfamic acid were respectively added to this platinum stock solution in equal amounts to a total of 140 g/L to prepare a basic bath. To this basic bath, 80 mg/L of "sodium 1-octadecylsulfonate" manufactured by Tokyo Chemical Industry Co., Ltd. and 20 g/L of magnesium sulfate were added to adjust the pH to 0.4 to prepare a platinum plating bath. (Example 13)

The platinum stock solution of Example 13 was a sulfamic acid solution containing DNS at 7 g/L in terms of platinum. To this platinum stock solution, 120 g/L of sulfuric acid was added to prepare a basic bath. To this basic bath, 5 mg/L of "dimethyl isophthalate-5-sodium sulfonate" 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 prepare platinum plating. bath.

In the platinum electroplating baths of Examples 1 to 13 described above, p-salt or DNS was dissolved in a sulfuric acid solution or a sulfamic acid solution to prepare a platinum concentrate containing a divalent platinum complex. Then, a sulfuric acid solution, a sulfamic acid solution, or a mixed solution thereof was added to the platinum concentrated solution to prepare a platinum basic bath. Then, a predetermined surfactant was added to this basic bath, and this was used as the platinum electroplating bath of Examples 1-13. In addition, sulfate was added as a metal salt to the platinum electroplating baths of Examples 8 to 13. The components of the platinum electroplating baths of these Examples 1 to 13 are extracted and shown in Table 1. In addition, the pure water used for dilution is deionized water processed by an ion exchange resin apparatus. In any of the platinum electroplating baths in Examples 1 to 13, silicon as an impurity was 0.1 ppm or less.

[Table 1] Basic bath (as Pt) (g/L) Anionic surfactant (mg/L) Metal sulfate (g/L) Implementation 01 DNS・Sulfuric acid 11 Sodium Lauryl Sulfate 60 none - Implementation 02 p-salt・Sulfamic acid 15 Sodium dodecylbenzenesulfonate 70 none - Implementation 03 DNS・Sulfamic acid 17 Sodium N-Lauryl Sarcosine 180 none - Implementation 04 DNS・Sulfuric acid・Sulfamic acid 16 Alkyl allyl sulfonate + alkyl ammonium salt 400 none - Implementation 05 p-salt, sulfuric acid, sulfamic acid 5 Ammonium Lauryl Sulfate 500 none - Implementation 06 DNS・Sulfamic acid 3 Sodium Stearate 90 none - Implementation 07 p-salt・sulfuric acid 13 Sodium Alkylbenzene Sulfonate 160 none - Implementation 08 DNS・Sulfuric acid・Sulfamic acid 1 Ammonium Lauryl Sulfate 10 Na ₂ (SO ₄ ) 15 Implementation 09 p-salt・Sulfamic acid 18 Potassium Lauryl Sulfate 140 MgSO ₄ 6 Implementation 10 DNS・Sulfuric acid 8 Sodium Alkylbenzene Sulfonate 200 MgSO ₄ 2 Implementation 11 p-salt, sulfuric acid, sulfamic acid 14 Sodium Stearate 300 CaSO ₄ 4 Implementation 12 DNS・Sulfuric acid・Sulfamic acid 6 Sodium 1-octadecylsulfonate 80 MgSO ₄ 20 Implementation 13 DNS・Sulfamic acid 7 Dimethyl 5-sulfophthalate 5 Na ₂ (SO ₄ ) 1

All the metal substrates to be electroplated use the same copper test piece (a test piece with a wire fused to a 20mm × 40mm × 0.1mm thick sheet). Degreasing and pickling pretreatments were performed on the test piece. After that, using the platinum electroplating baths of Examples 1 to 13, a current (0.32 A) with a cathodic current density of 2 A/dm 2 was applied to the pretreated test pieces at a bath temperature of 55° C., directly from each platinum electroplating bath. The test piece was electroplated with platinum.

In this way, the platinum electrolytic deposit was deposited by 0.8 μm from the platinum electroplating baths of Examples 1 to 13, and the platinum films of Examples 01 to 13 were prepared. The platinum purity of the platinum films of Examples 01 to 13 was all 99%, and these platinum films were all glossy. Then, the porosity of the platinum films of Examples 01 to 13 was measured, and the hardness and internal stress were measured. The results are shown in Table 2.

[Table 2] Porosity(%) Hardness (Hv) Stress (MPa) luster Film thickness (μm) Implementation 01 9.5 470 40 Have 0.8 Implementation 02 10.5 480 70 Have 0.8 Implementation 03 10.8 480 50 Have 0.8 Implementation 04 10.9 480 40 Have 0.8 Implementation 05 11.4 470 60 Have 0.8 Implementation 06 12.2 480 20 Have 0.8 Implementation 07 12.5 450 50 Have 0.8 Implementation 08 8.5 480 80 Have 0.8 Implementation 09 9.5 460 20 Have 0.8 Implementation 10 11 480 20 Have 0.8 Implementation 11 12.5 470 80 Have 0.8 Implementation 12 13.2 480 50 Have 0.8 Implementation 13 13.5 480 80 Have 0.8

Here, the porosity test is a test used because platinum electrolytic deposits do not corrode in a normal corrosion test. In this porosity test, a low voltage of 0.74 V was applied to a 5% sulfuric acid electrolyte at 50° C., and the platinum film of the example was used as an anode for electrolysis for 20 minutes. On the electrolyzed platinum film, the copper surface is exposed. The exposed copper was measured with the current value of the rectifier, and the ratio of copper exposed on the surface of the platinum film was estimated from the numerical change of the current value, which was defined as "porosity". That is, the porosity of 100% is the current value in the state in which copper is exposed on the entire surface of the platinum film, and the porosity of 0% is the current value in the state in which copper is not exposed at all. The porosity of the platinum films of Examples 01 to 13 is a percentage assigned according to the ratio of the current values of the porosity of 100% and the porosity of 0%. The smaller the numerical value of the porosity, the better the corrosion resistance.

As shown in the above test results, the platinum films of Examples 01 to 13 of the present invention were glossy even when the film thickness was as thin as 0.8 μm. The Vickers hardness of these platinum films is 450 to 480 Hv, which is relatively hard, the porosity is also in the range of 8.5 to 13.5%, and the corrosion resistance is excellent. In addition, the purity of platinum in these platinum films was all 99%. It was also found that the internal stress of these platinum films was extremely low in the range of 20 to 80 MPa.

On the other hand, no correlation was found between the porosity and stress of the platinum films of Examples 01 to 13 of the present invention. Therefore, an attempt was made to compare Example 09 and Example 10 with Example 05 and Example 07 individually. The platinum electroplating 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 plating bath of Example 05 contained 500 mg/L of ammonium lauryl sulfate and did not contain magnesium sulfate. The platinum electroplating bath of Example 10 contained 200 mg/L of sodium alkylbenzene sulfonate and 2 g/L of magnesium sulfate. On the other hand, the platinum electroplating bath of Example 07 contained 160 mg/L of sodium alkylbenzenesulfonate and did not contain magnesium sulfate.

Comparing the porosity of the platinum film, Example 09 was 9.5%, while Example 05 was 11.4%. In addition, Example 10 was 11%, while Example 07 was 12.5%. That is, it can be seen that the platinum coatings of Example 09 and Example 10 containing metal sulfate have lower porosity and corrosion resistance than the platinum coatings of Example 05 and Example 07 containing no metal sulfate, regardless of the type of platinum compound. high. In addition, when comparing the stress of the platinum film, the stress of Example 09 was 20 MPa, and the stress of Example 05 was 60 MPa. In addition, the stress of Example 10 was 20 MPa, while that of Example 07 was 50 MPa. That is, it can be seen that the stress of the platinum coating of Example 09 and Example 10 containing metal sulfate is lower than the internal stress of the platinum coating of Example 05 and Example 07 containing no metal sulfate, regardless of the type of platinum compound. In addition, the hardness of the platinum film|membrane of Example 05, Example 07, Example 09, and Example 10 was 450 Hv or more.

FIG. 2 shows a scanning electron microscope photograph of 4 μm of platinum electrolytic precipitate precipitated from the platinum electroplating bath of Example 1. FIG. As shown in the photograph of FIG. 2 , there is no difference in the size of the crystal grains between the surface and the cross section of the particles of the platinum electrolytic precipitate, and the platinum film is so dense that the grain boundaries of the platinum particles cannot be observed even with a scanning electron microscope. . When this platinum film was subjected to X-ray diffraction, the crystal orientation of platinum was observed. In this specification, such a precipitation form of the platinum electrolytic precipitate is referred to as "a crystal structure such as an amorphous state". It can be seen that the particles of the platinum electrolytic precipitate of Example 1 have a crystal structure such as an amorphous state, and are very fine and dense. Therefore, the plated product of the present invention is excellent in corrosion resistance such as sweat resistance. In addition, even when 10 micrometers or more of platinum electrolytic deposits were deposited from the platinum electroplating bath of Example 1, the platinum film maintained the crystal structure as an amorphous state. (Example 14)

The platinum stock solution of Example 14 was a sulfamic acid solution containing 4 g/L of Q salt in terms of platinum. 70 g/L of sulfuric acid was added to this platinum stock solution to prepare a basic bath. To this basic bath, 250 mg/L of N-laurel-N-methyl-β-alanine (“ALANON ALA” manufactured by Kawaken Fine Chemical Co., Ltd.) was added as an anionic surfactant, and 5 g/L of The pH was adjusted to 0.5 with magnesium sulfate to prepare a platinum plating bath. (Example 15)

The platinum stock solution of Example 15 was a sulfamic acid solution containing 8 g/L of Q salt in terms of platinum. To this platinum stock solution, 70 g/L of sulfamic acid was added to prepare a basic bath. To this basic bath, 250 mg/L of polycarboxylate (“CARRYBON L-400” manufactured by Sanyo Chemical Industry Co., Ltd.) was added as an anionic surfactant, and the pH was adjusted to 1.5 to prepare a platinum plating bath. (Example 16)

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

The components of the platinum electroplating baths of these Examples 14 to 16 are extracted and shown in Table 3. It should be noted that in any platinum plating bath, silicon as an impurity was 0.1 ppm or less.

[table 3] Basic bath (as Pt) (g/L) Anionic surfactant (mg/L) Metal sulfate (g/L) Implementation 14 Q Salt・Sulfamic acid 4 N-laurel-N-methyl-beta-alanine 250 MgSO ₄ 5 Implementation 15 Q Salt・Sulfamic acid 8 Polycarboxylic acid 250 none - Implementation 16 Q Salt・Sulfamic acid 10 Sodium Dialkyl Sulfosuccinate 100 none - Comparison 01 DNS・Sulfuric acid・Sulfamic acid 11 none - none - Comparison 02 Tetraammine platinum hydrogen phosphate・disodium hydrogen phosphate dihydrate 5 none - none - Comparison 03 DNS・Sulfuric acid 11 Sodium Lauryl Sulfate 600 none -

As in Example 1, using the same copper test piece (a test piece in which a lead wire was welded to a sheet of 20 mm×40 mm×0.1 mm thickness), platinum electrolytic deposits of 0.8 μm were deposited at the same cathode current density. All of the platinum electrolytic precipitates of Examples 14 to 16 had a platinum purity of 99%, and these platinum electrolytic precipitates were all glossy. In addition, the porosity of the platinum electrolytic deposits of Examples 14 to 16 was measured, and the hardness and internal stress were measured.

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

[Table 4] Porosity(%) Hardness (Hv) Stress (MPa) luster Film thickness (μm) Implementation 14 11.5 470 40 Have 0.8 Implementation 15 13.8 465 80 Have 0.8 Implementation 16 10.2 480 20 Have 0.8 Comparison 01 30.6 400 450 Have 0.8 Comparison 02 35.1 420 550 Have 0.8 Comparison 03 33.5 410 510 Have 0.8 (Comparative Example) (Comparative Example 1)

Comparative Example 1 is the same as Example 1 except that it does not contain an anionic surfactant, and contains DNS of 11 g/L in terms of platinum, and is a platinum electroplating bath in which sulfuric acid and sulfamic acid are respectively added in equal amounts and added in a total of 160 g/L. . (Comparative Example 2)

Comparative Example 2 is a platinum electroplating bath in which 5 g/L of platinum (II) tetraammine hydrogen phosphate (5 g/L in terms of platinum) and disodium hydrogen phosphate dihydrate were added and adjusted to pH 10.5 using a sodium hydroxide solution. (Comparative Example 3)

Comparative Example 3 was the same platinum electroplating bath as 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, using the same copper test piece (a test piece in which a lead wire was welded to a sheet with a thickness of 20 mm×40 mm×0.1 mm), a platinum electrolytic deposit of 0.8 μm was deposited. All of the platinum electrolytic precipitates of Comparative Products 01 to 03 had a platinum purity of 99%, and these platinum electrolytic precipitates were all glossy. In addition, the porosity of the platinum electrolytic precipitates of Comparative Products 01 to 03 was measured, and the hardness and internal stress were measured.

The porosity, hardness and internal stress of Comparative Product 01 were 30.6%, 400 Hv and 450 MPa. In addition, the porosity, hardness, and internal stress of Comparative Product 02 were 35.1%, 420 Hv, and 550 MPa. In addition, the porosity, hardness, and internal stress of Comparative Product 03 were 33.5%, 410 Hv, and 510 MPa. The results are shown in Table 3.

As shown in the above test results, the platinum electrolytic precipitates of Examples 14 to 16 of the present invention were glossy despite their thin film thickness of 0.8 μm. In addition, it can be seen that the Vickers hardness of the platinum electrolytic precipitates of Examples 14 to 16 of the present invention is 465 to 480 Hv, which is relatively hard, the porosity is also in the range of 10.2 to 13.8%, and the corrosion resistance is excellent. In addition, the purity of platinum is all 99%. In addition, it can be seen that the internal stress of Examples 14 to 16 of the present invention is in the range of 20 to 80 MPa, which is extremely low. On the other hand, the porosity of the platinum electroplating bath of Comparative Product 01 is 30.6%, the platinum electroplating bath of Comparative Product 02 is 35.1%, and the platinum electroplating bath of Comparative Product 03 is also 33.5%, which are all extremely high. It is also found that the internal stress of the platinum electrolytic precipitates of Comparative Products 01 to 03 is 450 to 550 MPa, which is extremely high. Even though the porosity of Comparative Products 01 to 03 was inferior, no cracks or pinholes were found in appearance.

On the other hand, the Hall cell test was performed on the platinum electroplating bath of Comparative Example 3 and the platinum electroplating bath of Example 1. The platinum electroplating bath of Example 1 contained 60 mg/L of sodium lauryl sulfate, and the platinum electroplating bath of Comparative Example 3 contained 600 mg/L of sodium lauryl sulfate. Visual observation of the area of the Hall cell sample where amorphous plating was performed revealed that the platinum electroplating bath of Comparative Example 3 was inferior to the platinum electroplating bath of Example 1 by about 50% on the high current density side.

As described above, it can be seen that the platinum electroplating bath of the present invention can obtain a high-purity platinum film, but has a low porosity and is excellent in corrosion resistance. In addition, the platinum-plated product of the present invention is dense, low in stress, and glossy, so it can be applied not only to electrical components such as connectors, printed circuit boards, but also to seawater electrolysis electrodes, insoluble anodes for electroplating, jewelry, and other aspects. use.

none

FIG. 1 is an explanatory diagram explaining the principle of the platinum plating bath of the present invention. Fig. 2 is a scanning electron microscope photograph of the platinum electrolytic precipitate of the present invention.

none

Claims (10)

A platinum electroplating bath comprising an anionic surfactant in an acidic platinum plating bath comprising a divalent platinum(II) complex and free sulfuric or sulfamic acid. A platinum electroplating bath comprising an anionic surfactant and a metal salt or alkali metal element of a second main group element in an acidic platinum plating bath comprising a divalent platinum(II) complex and free sulfuric or sulfamic acid of metal salts. The platinum electroplating bath according to claim 1 or 2, wherein the divalent platinum (II) complex has a nitro group (NO ₂ ), a nitric acid group (NO ₃ ), a sulfate group (SO ₄ ) or a sulfo group ( SO ₃ ) and at least one ligand selected from amino group (NH ₃ ), oxonium (H ₂ O) or hydroxyl group (OH). The platinum electroplating bath according to claim 1 or 2, wherein the anionic surfactant is at least one compound selected from the group consisting of stearic acid or a salt thereof, a sulfonic acid or a salt thereof, and a sulfate ester or a salt thereof. The platinum electroplating bath according to claim 1 or 2, wherein the anionic surfactant is at least one compound of alkylated sulfuric acid or a salt thereof, and alkylbenzenesulfonic acid or a salt thereof. The platinum electroplating bath according to claim 1 or 2, characterized by containing 5 to 500 mg/L of the anionic surfactant. The platinum electroplating bath according to claim 1 or 2, wherein silicon as an impurity is 1 ppm or less. The platinum electroplating bath according to claim 1 or 2, wherein the pH of the platinum electroplating bath is 2 or less. A platinized product comprising a platinum electrolytic precipitate obtained by using the platinum electroplating bath described in claim 1 or 2, the purity of platinum is 99% by weight or more, the Vickers hardness is 450-500Hv, the stress is equal to or less than 100 MPa, and the porosity is equal to or less than 30%. The platinum-plated product according to claim 9, wherein the silicon content of the platinum-plated product is 1 ppm or less, and the remainder is platinum electrolytic precipitate.

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