WO2019176049A1 - Electrolytic rhodium plating solution - Google Patents

Electrolytic rhodium plating solution Download PDF

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Publication number
WO2019176049A1
WO2019176049A1 PCT/JP2018/010208 JP2018010208W WO2019176049A1 WO 2019176049 A1 WO2019176049 A1 WO 2019176049A1 JP 2018010208 W JP2018010208 W JP 2018010208W WO 2019176049 A1 WO2019176049 A1 WO 2019176049A1
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Prior art keywords
rhodium
plating
phosphite
plating solution
electrolytic
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PCT/JP2018/010208
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French (fr)
Japanese (ja)
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宏治 片倉
理恵 菊池
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日本エレクトロプレイテイング・エンジニヤース株式会社
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Priority to KR1020197017863A priority Critical patent/KR102549660B1/en
Priority to PCT/JP2018/010208 priority patent/WO2019176049A1/en
Priority to CN201880005951.4A priority patent/CN110494596B/en
Priority to JP2018536208A priority patent/JP6474536B1/en
Priority to TW108107690A priority patent/TWI794440B/en
Publication of WO2019176049A1 publication Critical patent/WO2019176049A1/en

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/567—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of platinum group metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/50—Electroplating: Baths therefor from solutions of platinum group metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys

Definitions

  • the present invention relates to an electrolytic rhodium plating solution, and more particularly to an electrolytic rhodium plating solution that forms an amorphous structure of rhodium phosphorus.
  • Rhodium metal is widely used for optical components such as reflectors because of its excellent reflectance. Furthermore, excellent properties such as high hardness, high wear resistance, low contact resistance, oxidation resistance in air, and stability against sparks due to a high melting point, which are characteristics of rhodium metal, are used in the industrial field. Rhodium metal is extremely chemically stable among platinum group metals and does not dissolve in aqua regia. In addition, rhodium metal has the highest reflectance among platinum group metals, and the color tone has a beautiful white gloss, the Vickers hardness of the precipitate is as high as 800 to 1,000 Hv, and has excellent corrosion resistance. In order to show the characteristics, it has gained popularity as a plating material for decorative articles and has been widely used.
  • Rhodium metal Since rhodium metal is expensive, its use as a bare metal is rare. Rhodium metal is used as a contained alloy, or as a deposit for electrolytic plating of parts for electrical, electronic and communication industries, electrolytic plating of optical equipment parts, electrolytic plating for electrodes, electrolytic plating of precision equipment parts, etc. Diluted rhodium metal is widely used in various industrial fields, and is used extensively in platinum ring ornaments.
  • the rhodium electrolytic plating solution is roughly classified into a sulfuric acid plating solution and a phosphoric acid plating solution.
  • Table 4.86 of “4.11.2 Rhodium plating” of “Plating Technology Handbook” includes “metal rhodium (as sulfate or phosphate) 1 to 4 g / L and Electroplating baths of “phosphoric acid 40-80 mL / L” and “metal rhodium (as sulfate or phosphate) 4 g / L and sulfuric acid 20-40 mL / L” are shown.
  • various compounds have been studied in “Development research of rhodium plating bath for thickening” (Non-patent Documents 2 and 3 described later).
  • Japanese Patent Laid-Open No. 52-014538 discloses that a rhodium phosphate plating bath composed of 0.1 to 10 g / L of rhodium as metal rhodium and 30 to 1000 g / L of phosphoric acid has an alkaline phosphate, that is, ammonium. Further, a phosphate rhodium plating bath characterized by adding 0.1 to 10 g / L of any one of potassium, sodium, calcium and magnesium phosphates is disclosed. Japanese Patent Application Laid-Open No.
  • 54-158340 discloses “rhodium ion 0.1 g / L to 30 g / L, polycarboxy organic carboxylic acid 0.1 g / L to 20 g / L containing at least one amino group, and ortholine.
  • An acidic rhodium plating bath comprising acid groups 10 g / L to 100 g / L and having a bath pH of 0 to 2.0 is disclosed.
  • Patent Document 1 Japanese Patent Laid-Open No. 58-048688 (Patent Document 1 to be described later) describes “a black rhodium plating bath characterized by containing hypophosphite as an additive in an acidic rhodium plating bath. Is disclosed.
  • a titanium plate plated with platinum in a plating bath obtained by mixing rhodium sulfate (rhodium: 8 g / L), sodium hypophosphite (1 g / L) and sulfuric acid (free 10 g / L) was used as an anode.
  • the brass plate was placed as a cathode, and electroplated on the brass plate for 10 minutes under the conditions of a bath temperature of 25 ° C. and a current density of 3 A / dm 2.
  • the obtained deposit was specularly glossy and black.
  • the thickness was 0.3 ⁇ m and the adhesion was good.
  • This electroplated rhodium deposit has a black color that includes rhodium black and therefore cannot be used for industrial purposes.
  • an industrial product in which a gold plating film is formed on the rhodium plating film has a poor color tone as viewed from the surface and is considered to be defective in plating.
  • this rhodium plating film had a high porosity, and in the corrosion test with the potential applied, the corrosion was severe.
  • the rhodium electroplating solution containing a rhodium salt and a free acid further contains sulfur or a sulfur-containing substance.
  • the low stress rhodium electroplating solution is disclosed in Example 1.
  • Example 1 “Rh concentration 5 g / L, T—H 2 SO 4 80 g / L, current density 1 A / dm 2 , bath temperature 60 ° C., plating
  • the plating film obtained for 90 minutes was excellent without any cracks even in a corrosive atmosphere.
  • Example 35 in paragraph 0114 of Japanese Patent Laid-Open No. 11-050295 includes “adding 0.3 g / L of surfactant polystar OM to the plating solution of Comparative Example 35”.
  • Comparative Example 35 of paragraph 0113 “Rhodium Phosphate 2 g / L, Sulfuric Acid 30 mL / L, Bath Temperature 45 ° C., Electric Density 4 A / dm” is described. 2 "plating conditions are described.
  • the plating solution of Comparative Example 35 of JP-A No. 11-050295 can be obtained by referring to the plating bath composition described in “Handbook of Plating Technology” (Non-Patent Document 1 described later). Pure rhodium precipitates are obtained rather than alloys. If an electroplating solution bathed with phosphoric acid is used, cracks are more likely to occur than an electroplating bath bathed with sulfuric acid. It seems that rhodium precipitation efficiency in phosphoric acid is worse than the precipitation efficiency in sulfuric acid.
  • the rhodium precipitate plated from the rhodium sulfate plating solution forms an interface structure of the rhodium precipitate according to the form of the underlying surface.
  • the crystal grains of the rhodium plating film have a characteristic characteristic of rhodium plating that internal stress is high. For this reason, as the rhodium plating film increases in thickness, there is a problem that peeling from the base material and generation of cracks are recognized due to internal stress.
  • Satoshi Aoya “Development of rhodium plating bath for thickening (“ Report 1 ”, Plating and Coating, Vol. 8, No. 3, pp.143-152, 1988) Satoshi Aoya, “Development and research of rhodium plating bath for thickening”, Plating and coating, Vol. 9, No. 2, pp. 88-96, 1989
  • the corrosion resistance of the connection terminals is also tested for the corroded cord test in which a voltage is applied from the porosity test in the atmosphere and the salt spray test (NaCl 5%, 20% ⁇ 35 ° C). Strict corrosion testing standards such as accelerated sulfur dioxide testing have begun to be applied.
  • base materials used for rhodium plating have begun to be incorporated into products under conditions that are thin and easily deformed. In such a recent inexpensive electric / electronic component, the application range of the conventional robust rhodium film is narrowed, and it has become difficult to adopt the conventional rhodium plating film.
  • the present invention has been made in order to address the above-described problems, and provides a rhodium plating solution capable of obtaining a plating film having a dense amorphous structure of rhodium phosphorus. That is, the present invention provides various rhodium in the plating solution by at least one compound selected from the group consisting of phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite. The main point is to keep the ionic species in a state of being easily reduced as a rhodium phosphorus amorphous plating film.
  • Phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite is used in the rhodium plating solution rather than the rhodium atom-rhodium atom metal bond. This is to give priority to the metal bond.
  • rhodium plating solution if rhodium atom-phosphorus atom bonds are formed before plating deposits are formed, rhodium phosphorus atomic groups in which phosphorus atoms are incorporated during electroplating will accumulate. . Therefore, a rhodium phosphorus precipitate formed with a dense amorphous structure of rhodium phosphorus atomic groups having low internal stress can be obtained.
  • the present inventors examined the ionic state of various rhodium complexes present in the sulfuric acid solution.
  • the following large rhodium complex ions are known in the sulfuric acid solution.
  • [Rh (H 2 O) 2 (SO 4 ) 2 ] ⁇ species and [Rh (H 2 O) 4 SO 4 ] + species exist, and [Rh n ( ⁇ -OH) 2 (SO 4 ) 2 (H 2 O) 4 ] 0 species and [Rh n ( ⁇ -SO 4 ) ( ⁇ -OH) (SO 4 ) 2 (H 2 O) 4 ] — species.
  • the present inventors have added alkali metal phosphites, alkaline earth metal phosphites or ammonium phosphites such as phosphorous acid and disodium hydrogen phosphite (Na 2 HPO 3 ) salt in sulfuric acid solution. It has been found that when it coexists with the above, it becomes a deposit of an amorphous structure of rhodium phosphorus by electroplating. The large ion population is decomposed, and low-melting phosphorus atoms and rhodium atoms seem to be combined in the plating solution.
  • sodium dihydrogen phosphate (NaH 2 PO 4 ) salt or sodium hypophosphite (NaH 2 PO 2 ) salt may coexist,
  • the plating solution could be discolored and the rhodium phosphorous amorphous structure as in the present invention could not be obtained.
  • the present inventors diligently studied the rhodium phosphorous plating film having an amorphous structure, and the present invention compared with the cross section of the rhodium plating film obtained by the prior art (see FIG. 3 described later). It turned out that the crystal grain of the cross section (refer FIG. 2 mentioned later) of this rhodium phosphorus plating film becomes fine. As a result of further research on this film, it was found that the interface of the rhodium-phosphorus plating film of the present invention is not influenced by the form of the base surface of the base material or the intermediate layer, and an unprecedented dense amorphous structure can be obtained. The present invention has been completed.
  • One of the electrolytic rhodium plating solutions of the present invention is 1-20 g / L of metal rhodium (as sulfate or phosphate), 10-100 mL / L of sulfuric acid and phosphorous acid, alkali metal phosphite, phosphorous acid It contains 0.001 to 10 g / L of at least one compound selected from the group consisting of alkaline earth metal salts or ammonium phosphite salts.
  • electrolytic rhodium plating solutions of the present invention include metal rhodium (as sulfate or phosphate) 1 to 20 g / L, sulfuric acid 10 to 100 mL / L, phosphorous acid, alkali metal phosphite, phosphorous acid 0.001 to 10 g / L of at least one compound selected from the group consisting of acid alkaline earth metal salts or ammonium phosphite salts, and alkali metal sulfates, alkaline earth metal sulfates or ammonium sulfate salts It contains 0.001 to 30 g / L of at least one compound selected from the group consisting of:
  • electrolytic rhodium plating solutions of the present invention include 1 to 20 g / L of metal rhodium (as sulfate or phosphate), 10 to 100 mL / L of phosphoric acid, phosphorous acid, alkali metal phosphite, It contains 0.001 to 10 g / L of at least one compound selected from the group consisting of alkaline earth metal phosphates or ammonium phosphite salts.
  • electrolytic rhodium plating solutions of the present invention include 1 to 20 g / L of metal rhodium (as sulfate or phosphate), 10 to 100 mL / L of phosphoric acid, phosphorous acid, alkali metal phosphite, 0.001 to 10 g / L of at least one compound selected from the group consisting of alkaline earth metal phosphates or ammonium phosphite salts, and alkali metal phosphates, alkaline earth metal phosphates or It contains 0.001 to 30 g / L of at least one compound selected from the group consisting of ammonium phosphates.
  • the alkaline earth metal salt means beryllium salt, magnesium salt, calcium salt and barium salt. Practically, magnesium salt and calcium salt are preferable. This is because magnesium phosphite salt or the like becomes phosphite ion in sulfuric acid or phosphoric acid solution. From the above, practically preferred phosphites are lithium phosphite, sodium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite and ammonium phosphite. .
  • rhodium phosphate lowers the cathode deposition efficiency of the electrolytic rhodium plating solution, so the rhodium sulfate salt is preferred in the industrial field from the viewpoint of productivity.
  • a silver-white plating film having a brighter color tone than rhodium sulfate salt can be obtained by using phosphate, rhodium phosphate salt is preferred in the decorative field from the viewpoint of decoration.
  • the rhodium-phosphorous plating film of the present invention has an average rhodium crystal grain size of less than 0.01 ⁇ m when a cross section by a focused ion beam is observed with a scanning electron microscope. Say. That is, it refers to a state of compartments that are too finely divided and cannot be observed with a normal scanning electron microscope.
  • Various effects of the present invention are brought about by such a dense amorphous structure.
  • the metal rhodium concentration is set to 1 to 20 g / L for the following reason. That is, when the metal rhodium concentration is less than 1 g / L, the deposition efficiency of the electrolytic rhodium plating solution is lowered. Further, when the concentration of metal rhodium exceeds 20 g / L, the amount of unused rhodium is excessively increased and the maintenance cost of the plating solution is increased. In addition, the management aspects such as recovery of metal rhodium from an aged rhodium plating bath and treatment of waste liquid are considered.
  • the concentration of metal rhodium is preferably in the range of 2 to 10 g / L, particularly preferably in the range of 2 to 6 g / L. This is because a desired thick plating film can be obtained in a short time.
  • the maximum thickness of the dense amorphous structure is 20 ⁇ m.
  • the concentration of metal rhodium is preferably in the range of 2 to 10 g / L, particularly preferably in the range of 2 to 4 g / L. This is because if a dense amorphous film is obtained, a corrosion-resistant gold plating film, rhodium plating film, or platinum plating film can be formed on the dense surface layer.
  • the concentration of metal rhodium is preferably in the range of 1 to 5 g / L, particularly preferably in the range of 2 to 4 g / L. This is because the ultra-thin and dense amorphous structure prevents the surface form of the base material from reaching the deposited shape of the coating layer and avoids alloying of the base material and the surface layer.
  • the concentration of sulfuric acid is 10 to 100 mL / L for the following reason. That is, when the concentration of sulfuric acid is less than 10 mL / L, the rhodium compound may be hydrolyzed. Further, when the concentration of sulfuric acid exceeds 100 mL / L, the rhodium compound is difficult to move, and the deposit of rhodium phosphorus may cause burn plating.
  • the concentration of sulfuric acid is preferably 10 to 50 mL / L, more preferably 10 to 20 mL / L.
  • the phosphoric acid concentration is set to 10 to 100 mL / L for the following reason. That is, if the concentration of phosphoric acid is less than 10 mL / L, the rhodium compound may be hydrolyzed. Further, when the concentration of phosphoric acid exceeds 100 mL / L, the rhodium compound is difficult to move, and the deposit of rhodium phosphorus may cause burn plating.
  • the concentration of phosphoric acid is preferably 10 to 50 mL / L, more preferably 10 to 20 mL / L.
  • 0.001 to 0.001 to at least one compound selected from the group consisting of phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite The reason for containing 10 g / L is that these compounds form an amorphous structure with rhodium in the precipitate. If the concentration of the compound is less than 0.001 g / L, the rhodium precipitate cannot be formed amorphous. On the other hand, if the concentration of the compound exceeds 10 g / L, a rhodium precipitate may be formed in the electroplating solution.
  • rhodium phosphorus The formation of an amorphous structure of rhodium phosphorus can be understood as follows. Generally, if a phosphorus compound can enter the rhodium plating film, the rhodium precipitate becomes finer. However, rhodium deposited from various rhodium species during electroplating has very strong internal stress. This means that even if the amount of the phosphorus compound increases in the liquid, the phosphorus compound cannot enter the precipitated rhodium, and the rhodium precipitate is not refined. When rhodium is deposited by electroplating, it seems that a huge network of various rhodium complexes is formed in the plating solution. When there is no phosphorus compound inside the rhodium crystal grains and phosphorus is co-deposited at the grain boundaries of the crystal grains, the rhodium crystal grains become strong and peel off.
  • phosphorus compounds such as sodium phosphite described above lead to various rhodium species in the plating solution to be easily decomposed in advance before rhodium crystal grains are deposited by electroplating. It is thought that an atomic group in which phosphorus is bonded is formed. For this reason, when electrolytic rhodium plating is performed, the rhodium phosphorus deposit has a dense structure in which the following rhodium phosphorus atomic groups are stacked like snow on a small rhodium phosphorus atomic group. Each rhodium phosphorus atomic group having such a dense amorphous structure is an aggregate of rhodium metal atoms and phosphorus metal atoms. This rhodium phosphorus plating deposit has no crystal orientation, and the rhodium phosphorus plating film has no orientation.
  • the compound containing 0.001 to 10 g / L of a compound such as sodium phosphite cannot be made amorphous at less than 0.001 g / L, This is because if it exceeds 10 g / L, the melting point of the rhodium phosphorus plating film becomes too low.
  • the compound such as sodium phosphite is preferably contained in an amount of 0.05 to 5.0 g / L, more preferably 1.0 to 3.0 g / L. In particular, an amount of less than 1/10 is preferable and an amount of less than 1/20 is particularly preferable with respect to the metal rhodium concentration.
  • the electrolytic rhodium plating solution of the present invention does not contain hypophosphite such as sodium hypophosphite (NaH 2 PO 2 .H 2 O) salt. This is because the deposited rhodium film turns black, is not stable, or cannot be made amorphous.
  • hypophosphite such as sodium hypophosphite (NaH 2 PO 2 .H 2 O) salt.
  • NaH 2 PO 2 .H 2 O sodium hypophosphite
  • various rhodium species in the electrolytic rhodium plating solution may be decomposed and deposited on the anode.
  • electrolytic rhodium plating solution of the present invention additives such as organic sulfur compounds and surfactants used in general electrolytic rhodium plating solutions can also be used. This is because the effect of the electrolytic rhodium plating solution of the present invention is exhibited as long as the amorphous structure of the present invention is not broken.
  • the present inventors have found that the above phosphorus compounds such as sodium phosphite tend to have a certain precipitation ratio with rhodium precipitates. That is, when the concentration of rhodium metal is fixed and the concentration of the compound such as sodium phosphite is appropriately changed every 1/10 unit, the concentration of the compound such as sodium phosphite is rhodium in weight ratio. : Phosphorus ⁇ 4: 1, 9: 1, 20: 1, etc. This makes it speculated that a predetermined rhodium phosphorus atomic group is formed in the electroplating solution.
  • the concentration of metal rhodium and phosphorous acid, alkali metal phosphite such as sodium phosphite, alkaline earth metal phosphite or ammonium phosphite is reduced.
  • alkali metal phosphite such as sodium phosphite, alkaline earth metal phosphite or ammonium phosphite
  • the deteriorated electrolytic rhodium plating solution can be recovered, and the number of turnovers of the electrolytic rhodium plating solution can be dramatically improved as compared with the conventional case.
  • “sodium phosphite salt” means sodium phosphite pentahydrate, which has a composition formula of HNa 2 O 3 P ⁇ 5H 2 O or Na 2 HPO 3 ⁇ 5H 2 O. .
  • the electrolytic rhodium plating solution of the present invention contains 0.001 to 30 g / L of at least one compound selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates or ammonium sulfates. This is because these inorganic compounds are conductive salts.
  • the conductive salt stabilizes the electrolytic rhodium plating solution of the present invention, but if it exceeds 30 g / L, it is necessary to increase the amount of metal rhodium. In particular, when the content is 0.001 to 30 g / L, stable plating deposits can be obtained when a large plating bath is used.
  • Sodium salt, potassium salt, magnesium salt, calcium salt and ammonium salt are preferred, and sodium salt, potassium salt and ammonium salt are particularly preferred.
  • the concentration is preferably 20 to 30 g / L.
  • the sulfuric acid bath and the phosphoric acid bath preferably have a pH of 1 or less. This is because a dense amorphous rhodium-phosphorous plating film can be obtained.
  • the temperature of the solution is preferably 40 to 70 ° C. in both the sulfuric acid bath and the phosphoric acid bath. This is because the hardness of the rhodium phosphorous plating film is lowered and the flexibility of the rhodium phosphorous plating film is increased.
  • the lowermost layer of the dense amorphous structure has an amorphous structure regardless of the form of precipitation on the underlying surface.
  • the intermediate layer having a dense amorphous structure has no crystal grains and low internal stress. For this reason, even if a dense amorphous structure is formed by thick plating, it does not peel off from the surface layer.
  • a dense amorphous structure is used for the intermediate layer, even in an ultrathin intermediate layer such as strike plating, the precipitation structure of the noble metal plating on the surface layer is affected by the intermediate layer and has an effect of becoming dense.
  • the concentration ratio and the film thickness are appropriately selected in accordance with the required characteristics of electrical parts such as electrical contacts, electronic parts such as connectors, and automobile parts such as corrosion resistance.
  • a rhodium phosphorous plating film having a crystalline structure can be provided. For example, since a uniform smooth surface can be obtained, the contact point area becomes large when applied to a contact. Moreover, when the rhodium concentration is high, the hardness of the rhodium phosphorous plating film is high as before, and stable wear characteristics are obtained. In addition, the rhodium precipitates on the rhodium-phosphorous plating film do not have strong internal stress and do not easily generate wear powder as in the past.
  • the appearance of the obtained rhodium phosphorus plating test pieces was in a silver-white amorphous state.
  • the rhodium phosphorus plating test piece was used as an anode, a 40 mm ⁇ 20 mm copper test piece was used as a cathode, a low voltage of 0.74 V was applied, and the porosity was measured for 20 minutes in a 5% sulfuric acid solution. The result was obtained.
  • the porosity when the test piece not subjected to rhodium phosphorus plating was used as an anode was defined as 100%.
  • the rhodium (as rhodium sulfate) was 3 g / L
  • the phosphorus concentration (as sodium hypophosphite) was 0.05 g / L and 1.0 g / L.
  • a 20 mm ⁇ 20 mm copper test piece was electroplated to a thickness of 0.10 ⁇ m at a current density of 4 A / dm 2 .
  • the appearance of the obtained rhodium phosphorus plating test piece was a black precipitate.
  • a 40 mm ⁇ 20 mm copper test piece as a cathode
  • a low voltage of 0.74 V was applied, and the porosity was measured for 20 minutes in a 5% sulfuric acid solution.
  • the results of 12.0% and 8% in the column were obtained.
  • the effectiveness 12.0% of the trial number 07 is compared with the effectiveness 4.1% of the trial number 04. That is, it can be seen that the black rhodium precipitate film has a porosity that is twice or more worse than the rhodium phosphorus amorphous structure film of the present invention.
  • FIG. 1 shows a scanning electron microscope image (30,000 times) obtained by applying gold strike plating to the surface of the nickel coating. It can be seen that a wavy pattern is formed on the surface form of the nickel coating whose contrast is enhanced by gold strike plating.
  • rhodium phosphorus strike plating of 10 V ⁇ 10 seconds was performed on this nickel coating in a rhodium phosphorus strike bath with rhodium (as rhodium sulfate) at 1 g / L and phosphorus concentration (as calcium phosphite) at 1 g / L.
  • the rhodium (as rhodium sulfate) concentration was 4.0 g / L
  • sulfuric acid was 50 mL / L
  • the pure rhodium coating was electroplated to a thickness of 0.5 ⁇ m at a current density of 4 A / dm 2 .
  • a test piece electroplated with this pure rhodium film was subjected to a defect detection test at a voltage of 5 V ⁇ 10 minutes in a 5% sodium chloride aqueous solution using a 20 mm ⁇ 20 mm stainless steel piece as a cathode. Corrosion defects were detected.
  • Comparative Example 3 A sample of Comparative Example 3 was prepared except for rhodium phosphorus strike plating, and a corrosion resistance test was performed. Corrosion defects were detected at the first time.
  • a 20 mm ⁇ 20 mm copper test piece was plated with nickel of 5 ⁇ m with an electrolytic nickel plating solution of nickel sulfate salt 300 g / L, sodium chloride salt 20 g / L and phosphoric acid 0.30 mL / L.
  • a rhodium phosphorus amorphous film having a rhodium concentration (as rhodium sulfate) of 10 g / L and a phosphorus concentration (as sodium phosphite salt) of 1 g / L was deposited on this nickel film by 4.5 ⁇ m. This scanning ion microscope image is shown in FIG.
  • the white portion at the top of FIG. 2 is a rhodium phosphorous amorphous film with enhanced contrast.
  • this surface morphology is compared with the surface morphology of the nickel coating in FIG. 1, it can be seen that the presence of crystal grains is not confirmed.
  • the black part of the middle stage of FIG. 2 is an amorphous structure of rhodium phosphorus. In the middle black portion of FIG. 2, no crystal structure is found.
  • the crystal grains of the nickel plating shown in FIG. 1 are not formed at the interface between the black portion in the middle stage of FIG. 2 and the nickel plating in the lower stage. That is, it can be seen that the precipitation form of the base does not reach the amorphous structure of rhodium phosphorus just above.
  • rhodium (as rhodium sulfate) concentration was kept constant at 2.0 g / L
  • the sulfuric acid concentration was 30 mL / L
  • the phosphorus concentration (sodium phosphite) was as shown in the left column of Table 3.
  • a 20 mm ⁇ 20 mm copper test piece was electroplated in the same manner as in Test No. 14 except that sodium phosphite was not added. This was designated as trial number 19.
  • the film thicknesses at the four corners and the center of the test piece 19 were measured, the results in the right column of Table 3 were obtained. From this result, it can be seen that the pure rhodium film is an unstable precipitate with large variations.
  • a 20 mm ⁇ 20 mm copper test piece was electroplated in the same manner as in Test No. 17 except that 1 g / L of hypophosphite sodium salt was added. This was designated as trial number 20.
  • the film thicknesses at the four corners and the center of the copper test piece of sample number 20 were measured, the results in the right column of Table 3 were obtained. From this result, it can be seen that the rhodium phosphorous film deposited by sodium hypophosphite is an unstable precipitate with large variations.
  • the ratio of the rhodium phosphorus amorphous coating was determined by an energy dispersive X-ray analyzer (X-max N manufactured by Horiba, Ltd.), it was 92% rhodium and 8% phosphorus. Further, in the intensity analysis using an X-ray diffractometer, no diffraction image specific to Rh metal was observed. The melting point of the rhodium-phosphorus 8.2% eutectic alloy is 1,255 ° C.
  • a pure rhodium electrolytic plating film was deposited on the nickel film in a thickness of 4.5 ⁇ m in the same manner as in Example 4 except that the phosphorus concentration (as sodium hypophosphite salt) was changed to 0 g / L.
  • the crystal structure of this robust rhodium coating is shown in FIG.
  • the electrolytic rhodium plating solution of the present invention can obtain a rhodium phosphorous plating film in a fine amorphous state, so that it can be used as an alternative to conventional thick / thin rhodium plating products, or as a substrate and other noble metal plating surface layers. It can be used as an intermediate layer for connecting, and as a strike-plated product for applications such as electrical parts, electronic parts, automobile parts, catalyst / sensor parts, and decorative products.

Abstract

In order to addresses the problem regarding generation of cracks and detachment from a substrate due to internal stress associated with an increase in the thickness of a conventional rhodium plating film, the present invention provides a rhodium plating solution from which a dense amorphous rhodium-phosphorus plating film is obtained. This electrolytic rhodium plating solution is characterized by containing 1-20 g/L of metal rhodium (in the form of a sulfate or a phosphate), 10-100 mL/L of sulfuric acid or phosphoric acid, and 0.001-10 g/L of at least one compound selected from the group consisting of phosphorous acid, alkali metal salts of phosphorous acid, alkaline-earth metal salts of phosphorous acid, or ammonium salts of phosphorous acid.

Description

電解ロジウムめっき液Electrolytic rhodium plating solution
本発明は、電解ロジウムめっき液に関し、更に詳しくは、ロジウムリンの非晶質構造を形成する電解ロジウムめっき液に関する。 The present invention relates to an electrolytic rhodium plating solution, and more particularly to an electrolytic rhodium plating solution that forms an amorphous structure of rhodium phosphorus.
ロジウム金属はその優れた反射率から、反射鏡等の光学部品に多く利用されている。更には、ロジウム金属の特性である、高い硬度、大きな摩耗抵抗、低い接触抵抗、空気中での酸化耐性、高い融点による対スパーク安定性等の優れた諸性質が工業分野で利用されている。また、ロジウム金属は白金族金属の中でも化学的に極めて安定であり、王水にも溶解しない。また、ロジウム金属は、反射率が白金族金属中で最も優れ、且つその色調も白色の美麗な光沢を有し、析出物のビッカース硬さは８００～１，０００Ｈｖと高く、耐食性にも優れた特性を示すため、装飾用品のめっき材料として好評を得て広範囲に使用されている。 Rhodium metal is widely used for optical components such as reflectors because of its excellent reflectance. Furthermore, excellent properties such as high hardness, high wear resistance, low contact resistance, oxidation resistance in air, and stability against sparks due to a high melting point, which are characteristics of rhodium metal, are used in the industrial field. Rhodium metal is extremely chemically stable among platinum group metals and does not dissolve in aqua regia. In addition, rhodium metal has the highest reflectance among platinum group metals, and the color tone has a beautiful white gloss, the Vickers hardness of the precipitate is as high as 800 to 1,000 Hv, and has excellent corrosion resistance. In order to show the characteristics, it has gained popularity as a plating material for decorative articles and has been widely used.
ロジウム金属は高価であるため、そのままの地金としての利用はまれである。ロジウム金属は含有合金として利用されたり、電気・電子・通信工業用部品の電解めっき、光学機器部品の電解めっき、電極用の電解めっき、精密機器部品の電解めっき等の析出物として使用されたりして、希釈したロジウム金属が様々な工業分野で幅広く、また、プラチナ指輪の装飾品などで重用されている。 Since rhodium metal is expensive, its use as a bare metal is rare. Rhodium metal is used as a contained alloy, or as a deposit for electrolytic plating of parts for electrical, electronic and communication industries, electrolytic plating of optical equipment parts, electrolytic plating for electrodes, electrolytic plating of precision equipment parts, etc. Diluted rhodium metal is widely used in various industrial fields, and is used extensively in platinum ring ornaments.
ロジウム電解めっき液には、硫酸めっき液とリン酸めっき液とに大別されている。例えば、『めっき技術便覧』（後述する非特許文献１）の「４．１１．２ロジウムめっき」の表４．８６には「金属ロジウム（硫酸塩またはリン酸塩として）１～４ｇ／Ｌおよびリン酸４０～８０ｍＬ／Ｌ」の電気めっき浴や「金属ロジウム（硫酸塩またはリン酸塩として）４ｇ／Ｌおよび硫酸２０～４０ｍＬ／Ｌ」の電気めっき浴が示されている。また、「厚付け用ロジウムめっき浴の開発研究」（後述する非特許文献２，３）では、様々な化合物が検討されている。 The rhodium electrolytic plating solution is roughly classified into a sulfuric acid plating solution and a phosphoric acid plating solution. For example, Table 4.86 of “4.11.2 Rhodium plating” of “Plating Technology Handbook” (non-patent document 1 described later) includes “metal rhodium (as sulfate or phosphate) 1 to 4 g / L and Electroplating baths of “phosphoric acid 40-80 mL / L” and “metal rhodium (as sulfate or phosphate) 4 g / L and sulfuric acid 20-40 mL / L” are shown. In addition, various compounds have been studied in “Development research of rhodium plating bath for thickening” (Non-patent Documents 2 and 3 described later).
また、特開昭５２－０１４５３８号公報には「金属ロジウムとしてロジウム０．１～１０ｇ／Ｌと、リン酸３０～１０００ｇ／Ｌとよりなるリン酸ロジウムめっき浴に、アルカリリン酸塩即ち、アンモニウム、カリウム、ナトリウム、カルシウム、マグネシウムの各々のリン酸塩の内の何れか１種を０．１～１０ｇ／Ｌ添加したことを特徴とするリン酸系ロジウムめっき浴」が開示されている。また、特開昭５４－１５８３４０号公報には「ロジウムイオン０．１ｇ／Ｌないし３０ｇ／Ｌと、少なくとも１個のアミノ基を含むポリカルボキシ有機カルボン酸０．１ｇ／Ｌないし２０ｇ／Ｌおよびオルトリン酸根１０ｇ／Ｌないし１００ｇ／Ｌから成り、浴のｐＨが０ないし２．０であるような酸性ロジウムメッキ浴」が開示されている。 Japanese Patent Laid-Open No. 52-014538 discloses that a rhodium phosphate plating bath composed of 0.1 to 10 g / L of rhodium as metal rhodium and 30 to 1000 g / L of phosphoric acid has an alkaline phosphate, that is, ammonium. Further, a phosphate rhodium plating bath characterized by adding 0.1 to 10 g / L of any one of potassium, sodium, calcium and magnesium phosphates is disclosed. Japanese Patent Application Laid-Open No. 54-158340 discloses “rhodium ion 0.1 g / L to 30 g / L, polycarboxy organic carboxylic acid 0.1 g / L to 20 g / L containing at least one amino group, and ortholine. An acidic rhodium plating bath comprising acid groups 10 g / L to 100 g / L and having a bath pH of 0 to 2.0 is disclosed.
上記の文献や特許に記載のリン酸系電解めっき液では、電気めっきの際にリン酸中のリンは析出せず、純粋なロジウム金属の頑強な結晶粒が析出される。しかし、リン酸電解めっき液では金属ロジウム析出物の陰極析出効率が低いため、工業分野の市場では硫酸電解めっき液が一般的であった。 In the phosphoric acid-based electroplating solution described in the above-mentioned documents and patents, phosphorus in phosphoric acid does not precipitate during electroplating, and robust rhodium metal crystal grains are precipitated. However, since the cathode deposition efficiency of the metal rhodium deposit is low in the phosphoric acid electroplating solution, the sulfuric acid electroplating solution is common in the industrial field.
例えば、特開昭５８－０４８６８８号公報（後述する特許文献１）には「酸性ロジウムメッキ浴において、該メッキ浴に添加剤として、次亜燐酸塩を含有することを特徴とする黒色ロジウムメッキ浴」が開示されている。その実施例１には「硫酸ロジウム（ロジウム：８ｇ／Ｌ）、次亜燐酸ナトリウム（１ｇ／Ｌ）および硫酸（遊離１０ｇ／Ｌ）を混合して得られるメッキ浴に白金メッキしたチタン板を陽極とし、黄銅板を陰極として配置し、浴温２５℃、電流密度３Ａ／ｄｍ２の条件下に１０分間黄銅板に電気メッキを行った。得られた析着物は鏡面光沢を有し黒色を呈していた。厚みは０．３μであり、密着性は良好であった。」ことが記載されている。 For example, Japanese Patent Laid-Open No. 58-048688 (Patent Document 1 to be described later) describes “a black rhodium plating bath characterized by containing hypophosphite as an additive in an acidic rhodium plating bath. Is disclosed. In Example 1, a titanium plate plated with platinum in a plating bath obtained by mixing rhodium sulfate (rhodium: 8 g / L), sodium hypophosphite (1 g / L) and sulfuric acid (free 10 g / L) was used as an anode. The brass plate was placed as a cathode, and electroplated on the brass plate for 10 minutes under the conditions of a bath temperature of 25 ° C. and a current density of 3 A / dm 2. The obtained deposit was specularly glossy and black. The thickness was 0.3 μm and the adhesion was good. ”
この電気めっきされたロジウム析出物は、ロジウムブラックを含むような黒色を呈するので、工業用には利用することができなかった。例えば、このロジウムめっき被膜の上に金めっき被膜を形成した工業製品は、表面から見た色調が悪く、めっき不良とされるためである。また、このロジウムめっき被膜は有孔度も高く、電位を印加した腐食試験では腐食が激しいものであった。 This electroplated rhodium deposit has a black color that includes rhodium black and therefore cannot be used for industrial purposes. For example, an industrial product in which a gold plating film is formed on the rhodium plating film has a poor color tone as viewed from the surface and is considered to be defective in plating. Moreover, this rhodium plating film had a high porosity, and in the corrosion test with the potential applied, the corrosion was severe.
また、特開平０１－２９０７８８号公報（後述する特許文献２）の特許請求の範囲には「ロジウム塩と遊離酸とを含むロジウム電気めっき液において、硫黄又は硫黄含有物質を更に含有させることを特徴とする低応力ロジウム電気めっき液」が開示され、その実施例１には「Ｒｈ濃度５ｇ／Ｌ、Ｔ－Ｈ２ＳＯ４８０ｇ／Ｌ、電流密度１Ａ／ｄｍ２、浴温度６０℃、…めっき時間９０分得られためっき皮膜は腐食性雰囲気においても全くクラックを生じない優れたものであった。」ことが記載されている。 Further, in the claims of Japanese Patent Laid-Open No. 01-290788 (Patent Document 2 to be described later), the rhodium electroplating solution containing a rhodium salt and a free acid further contains sulfur or a sulfur-containing substance. The low stress rhodium electroplating solution is disclosed in Example 1. In Example 1, “Rh concentration 5 g / L, T—H 2 SO 4 80 g / L, current density 1 A / dm 2 , bath temperature 60 ° C., plating The plating film obtained for 90 minutes was excellent without any cracks even in a corrosive atmosphere. "
なお、特開平１１－０５０２９５号公報（後述する特許文献３）の明細書０１１４段落の実施例３５には「比較例３５のめっき液に０．３ｇ／Ｌの界面活性剤ポリスターＯＭを添加して比較例３５と同条件でめっきを施した。」ことが記載され、同０１１３段落の比較例３５には「リン酸ロジウム２ｇ／Ｌ、硫酸３０ｍＬ／Ｌ、浴温４５℃、電気密度４Ａ／ｄｍ２」のめっき条件が記載されている。 In addition, Example 35 in paragraph 0114 of Japanese Patent Laid-Open No. 11-050295 (Patent Document 3 to be described later) includes “adding 0.3 g / L of surfactant polystar OM to the plating solution of Comparative Example 35”. In Comparative Example 35 of paragraph 0113, “Rhodium Phosphate 2 g / L, Sulfuric Acid 30 mL / L, Bath Temperature 45 ° C., Electric Density 4 A / dm” is described. 2 "plating conditions are described.
しかし、特開平１１－０５０２９５号公報（後述する特許文献３）の比較例３５のめっき液は、上述した『めっき技術便覧』（後述する非特許文献１）のめっき浴組成を参照すると、ロジウムリン合金ではなく純粋なロジウム析出物が得られる。なお、リン酸で建浴した電気めっき液を用いると、硫酸で建浴した電気めっき液よりもクラックが発生しやすくなる。リン酸中でのロジウムの析出効率が硫酸中での析出効率より悪いことに起因するようである。 However, the plating solution of Comparative Example 35 of JP-A No. 11-050295 (Patent Document 3 described later) can be obtained by referring to the plating bath composition described in “Handbook of Plating Technology” (Non-Patent Document 1 described later). Pure rhodium precipitates are obtained rather than alloys. If an electroplating solution bathed with phosphoric acid is used, cracks are more likely to occur than an electroplating bath bathed with sulfuric acid. It seems that rhodium precipitation efficiency in phosphoric acid is worse than the precipitation efficiency in sulfuric acid.
硫酸ロジウムめっき液からめっきされたロジウム析出物は、後述する図３に示すように、下地表面の形態に従ってロジウム析出物の界面組織が形成される。また、ロジウムめっき被膜の結晶粒は内部応力が高いというロジウムめっき特有の性質を有する。このためロジウムめっき被膜が厚みを増すに従い、内部応力によって基材からの剥離やクラックの発生が認められるようになるという課題を有する。 As shown in FIG. 3 to be described later, the rhodium precipitate plated from the rhodium sulfate plating solution forms an interface structure of the rhodium precipitate according to the form of the underlying surface. In addition, the crystal grains of the rhodium plating film have a characteristic characteristic of rhodium plating that internal stress is high. For this reason, as the rhodium plating film increases in thickness, there is a problem that peeling from the base material and generation of cracks are recognized due to internal stress.
特開昭５８－０４８６８８号公報Japanese Patent Laid-Open No. 58-048688 特開平０１－２９０７８８号公報Japanese Patent Laid-Open No. 01-290788 特開平１１－０５０２９５号公報Japanese Patent Laid-Open No. 11-050295
最近では、電気・電子部品の小型化や高密度化が進展してきた結果、高価なロジウムめっき製品も薄い被膜で厚い膜厚に相当する特性が求められるようになってきた。また、内部応力の低いロジウムめっき被膜も求められるようになってきた。しかし、従来の非特許文献１～３および特許文献１～３に記載されたようなこれまでのロジウムめっき被膜は、個々のロジウム結晶粒が強固で頑強であるものの、その内部応力によってロジウム析出物の被膜中にクラックが発生しやすく、昨今の厳しい環境基準に耐えることが困難になってきた。 Recently, as electric and electronic parts have been miniaturized and densified, expensive rhodium plated products have been required to have characteristics corresponding to a thick film with a thin film. Further, a rhodium plating film having a low internal stress has been demanded. However, the conventional rhodium plating films as described in the conventional Non-Patent Documents 1 to 3 and Patent Documents 1 to 3 have rhodium precipitates due to their internal stress although individual rhodium crystal grains are strong and robust. Cracks are likely to occur in the coating film, and it has become difficult to withstand the recent strict environmental standards.
すなわち、貴金属価格の高騰が進行する昨今、接続端子の耐食性も大気雰囲気下での有孔度試験や塩水噴霧試験（ＮａＣｌ　５％、２０％×３５℃）から電圧を印加したコロードコード試験や加速亜硫酸ガス試験などの厳しい腐食試験の基準が適用され始めてきた。また、ロジウムめっきに使用される基材も薄く変形しやすい条件で製品に組み込まれ始めてきた。このような最近の安価な電気・電子部品では、これまでの頑強なロジウム被膜の適用範囲が狭まり、従来のロジウムめっき被膜の採用が困難になってきた。 In other words, as the price of precious metals continues to rise, the corrosion resistance of the connection terminals is also tested for the corroded cord test in which a voltage is applied from the porosity test in the atmosphere and the salt spray test (NaCl 5%, 20% × 35 ° C). Strict corrosion testing standards such as accelerated sulfur dioxide testing have begun to be applied. In addition, base materials used for rhodium plating have begun to be incorporated into products under conditions that are thin and easily deformed. In such a recent inexpensive electric / electronic component, the application range of the conventional robust rhodium film is narrowed, and it has become difficult to adopt the conventional rhodium plating film.
本発明は、上記の課題に対応するためになされたものであり、ロジウムリンの緻密な非晶質構造のめっき被膜が得られるロジウムめっき液を提供するものである。すなわち、本発明は、亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物によってめっき液中の様々なロジウムイオン種を、ロジウムリン非晶質のめっき被膜として還元しやすい状態にしておくことを要点とする。 The present invention has been made in order to address the above-described problems, and provides a rhodium plating solution capable of obtaining a plating film having a dense amorphous structure of rhodium phosphorus. That is, the present invention provides various rhodium in the plating solution by at least one compound selected from the group consisting of phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite. The main point is to keep the ionic species in a state of being easily reduced as a rhodium phosphorus amorphous plating film.
亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩を用いるのは、ロジウムめっき液中でロジウム原子－ロジウム原子の金属結合よりもロジウム原子－リン原子の金属結合が優先するようにしておくためである。ロジウムめっき液中で、めっき析出物が形成される前にロジウム原子－リン原子の結合があらかじめ形成されていると、電気めっきの際にリン原子が組み込まれたロジウムリンの原子団が積み重なっていく。よって、内部応力の低いロジウムリンの原子団の緻密な非晶質構造で形成されたロジウムリンの析出物が得られる。 Phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite is used in the rhodium plating solution rather than the rhodium atom-rhodium atom metal bond. This is to give priority to the metal bond. In rhodium plating solution, if rhodium atom-phosphorus atom bonds are formed before plating deposits are formed, rhodium phosphorus atomic groups in which phosphorus atoms are incorporated during electroplating will accumulate. . Therefore, a rhodium phosphorus precipitate formed with a dense amorphous structure of rhodium phosphorus atomic groups having low internal stress can be obtained.
本発明者らは、硫酸液中に存在する様々なロジウム錯体のイオン状態を検討した。硫酸液中では次のような大きなロジウム錯体イオンが知られている。例えば、［Ｒｈ（Ｈ２Ｏ）２（ＳＯ４）２］－化学種や［Ｒｈ（Ｈ２Ｏ）４ＳＯ４］＋化学種が存在し、［Ｒｈｎ（μ－ＯＨ）２（ＳＯ４）２（Ｈ２Ｏ）４］０化学種や［Ｒｈｎ（μ－ＳＯ４）（μ－ＯＨ）（ＳＯ４）２（Ｈ２Ｏ）４］－化学種が存在する。さらには、［Ｒｈ２（μ－ＳＯ４）２（Ｈ２Ｏ）８］２＋や［Ｒｈ２（μ－ＳＯ４）（μ－ＯＨ）（Ｈ２Ｏ）８］３＋等も存在する。これらの化学種は硫酸液中でさらに大きな大集団のイオンを形成していくものと考えられる。電気めっきによりこの大きなイオン集団からロジウムイオンが抜けると、次のロジウムイオンの補充が困難になる。このため内部応力の高いロジウムめっきが形成されると予想される。 The present inventors examined the ionic state of various rhodium complexes present in the sulfuric acid solution. The following large rhodium complex ions are known in the sulfuric acid solution. For example, [Rh (H 2 O) 2 (SO 4 ) 2 ] − species and [Rh (H 2 O) 4 SO 4 ] + species exist, and [Rh n (μ-OH) 2 (SO 4 ) 2 (H 2 O) 4 ] 0 species and [Rh n (μ-SO 4 ) (μ-OH) (SO 4 ) 2 (H 2 O) 4 ] — species. Furthermore, [Rh 2 (μ-SO 4 ) 2 (H 2 O) 8 ] 2+ and [Rh 2 (μ-SO 4 ) (μ-OH) (H 2 O) 8 ] 3+ exist. These chemical species are thought to form larger groups of ions in sulfuric acid solution. If rhodium ions are removed from this large ion population by electroplating, it becomes difficult to replenish the next rhodium ions. For this reason, rhodium plating with high internal stress is expected to be formed.
本発明者らは、亜リン酸、亜リン酸水素二ナトリウム（Ｎａ２ＨＰＯ３）塩等の亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩を硫酸液中に共存させると、電気めっきによってロジウムリンの非晶質構造の析出物となることを知得した。上記の大きなイオン集団が分解され、低融点のリン原子とロジウム原子とがめっき液中で結びつくようである。なお、亜リン酸水素二ナトリウム（Ｎａ２ＨＰＯ３）塩の代わりに、リン酸二水素ナトリウム（ＮａＨ２ＰＯ４）塩や次亜リン酸ナトリウム（ＮａＨ２ＰＯ２）塩を共存させても、めっき液が変色したりして本願発明のようなロジウムリンの非晶質構造とすることはできなかった。 The present inventors have added alkali metal phosphites, alkaline earth metal phosphites or ammonium phosphites such as phosphorous acid and disodium hydrogen phosphite (Na 2 HPO 3 ) salt in sulfuric acid solution. It has been found that when it coexists with the above, it becomes a deposit of an amorphous structure of rhodium phosphorus by electroplating. The large ion population is decomposed, and low-melting phosphorus atoms and rhodium atoms seem to be combined in the plating solution. In place of disodium hydrogen phosphite (Na 2 HPO 3 ) salt, sodium dihydrogen phosphate (NaH 2 PO 4 ) salt or sodium hypophosphite (NaH 2 PO 2 ) salt may coexist, The plating solution could be discolored and the rhodium phosphorous amorphous structure as in the present invention could not be obtained.
これらの知見をもとに、本発明者らが非晶質構造のロジウムリンめっき被膜を鋭意検討したところ、従来技術により得たロジウムめっき被膜の断面（後述する図３参照）に比べて本発明のロジウムリンめっき被膜の断面（後述する図２参照）の結晶粒子が微細となっていることがわかった。この被膜をさらに研究した結果、本発明のロジウムリンめっき被膜の界面は基材や中間層の下地表面の形態に左右されず、これまでにない緻密な非晶質構造が得られることが突き止められ、本発明を完成させるに至った。 Based on these findings, the present inventors diligently studied the rhodium phosphorous plating film having an amorphous structure, and the present invention compared with the cross section of the rhodium plating film obtained by the prior art (see FIG. 3 described later). It turned out that the crystal grain of the cross section (refer FIG. 2 mentioned later) of this rhodium phosphorus plating film becomes fine. As a result of further research on this film, it was found that the interface of the rhodium-phosphorus plating film of the present invention is not influenced by the form of the base surface of the base material or the intermediate layer, and an unprecedented dense amorphous structure can be obtained. The present invention has been completed.
本発明の電解ロジウムめっき液の一つは、金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、硫酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ含有することを特徴とする。 One of the electrolytic rhodium plating solutions of the present invention is 1-20 g / L of metal rhodium (as sulfate or phosphate), 10-100 mL / L of sulfuric acid and phosphorous acid, alkali metal phosphite, phosphorous acid It contains 0.001 to 10 g / L of at least one compound selected from the group consisting of alkaline earth metal salts or ammonium phosphite salts.
また、本発明の他の電解ロジウムめっき液は、金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、硫酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ、およびアルカリ金属の硫酸塩、アルカリ土類金属の硫酸塩または硫酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～３０ｇ／Ｌ含有することを特徴とする。 Other electrolytic rhodium plating solutions of the present invention include metal rhodium (as sulfate or phosphate) 1 to 20 g / L, sulfuric acid 10 to 100 mL / L, phosphorous acid, alkali metal phosphite, phosphorous acid 0.001 to 10 g / L of at least one compound selected from the group consisting of acid alkaline earth metal salts or ammonium phosphite salts, and alkali metal sulfates, alkaline earth metal sulfates or ammonium sulfate salts It contains 0.001 to 30 g / L of at least one compound selected from the group consisting of:
また、本発明の他の電解ロジウムめっき液は、金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、リン酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ含有することを特徴とする。 Other electrolytic rhodium plating solutions of the present invention include 1 to 20 g / L of metal rhodium (as sulfate or phosphate), 10 to 100 mL / L of phosphoric acid, phosphorous acid, alkali metal phosphite, It contains 0.001 to 10 g / L of at least one compound selected from the group consisting of alkaline earth metal phosphates or ammonium phosphite salts.
また、本発明の他の電解ロジウムめっき液は、金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、リン酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ、およびアルカリ金属のリン酸塩、アルカリ土類金属のリン酸塩またはリン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～３０ｇ／Ｌ含有することを特徴とする。 Other electrolytic rhodium plating solutions of the present invention include 1 to 20 g / L of metal rhodium (as sulfate or phosphate), 10 to 100 mL / L of phosphoric acid, phosphorous acid, alkali metal phosphite, 0.001 to 10 g / L of at least one compound selected from the group consisting of alkaline earth metal phosphates or ammonium phosphite salts, and alkali metal phosphates, alkaline earth metal phosphates or It contains 0.001 to 30 g / L of at least one compound selected from the group consisting of ammonium phosphates.
本発明の電解ロジウムめっき液において、アルカリ金属塩とは、リチウム塩、ナトリウム塩、カリウム塩、ルビジウム塩、セシウム塩およびフランシウム塩をいう。実用的には、リチウム塩、ナトリウム塩およびカリウム塩が好ましく、ナトリウム塩およびカリウム塩がより好ましい。すなわち、より好ましくは、亜リン酸ナトリウム（亜りん酸水素二ナトリウム五水和物）塩および亜リン酸カリウム（亜りん酸二水素=カリウム）塩である。 In the electrolytic rhodium plating solution of the present invention, the alkali metal salt refers to lithium salt, sodium salt, potassium salt, rubidium salt, cesium salt and francium salt. Practically, lithium salt, sodium salt and potassium salt are preferable, and sodium salt and potassium salt are more preferable. More specifically, sodium phosphite (disodium hydrogen phosphite pentahydrate) salt and potassium phosphite (dihydrogen phosphite = potassium) salt are more preferable.
本発明の電解ロジウムめっき液において、アルカリ土類金属塩とは、ベリリウム塩、マグネシウム塩、カルシウム塩およびバリウム塩をいう。実用的には、マグネシウム塩およびカルシウム塩が好ましい。亜リン酸マグネシウム塩等は硫酸またはリン酸液中で亜リン酸イオンとなるからである。
以上のことから、実用的に好ましい亜リン酸塩は、亜リン酸リチウム塩、亜リン酸ナトリウム塩、亜リン酸カリウム塩、亜リン酸マグネシウム塩、亜リン酸カルシウム塩および亜リン酸アンモニウム塩となる。 In the electrolytic rhodium plating solution of the present invention, the alkaline earth metal salt means beryllium salt, magnesium salt, calcium salt and barium salt. Practically, magnesium salt and calcium salt are preferable. This is because magnesium phosphite salt or the like becomes phosphite ion in sulfuric acid or phosphoric acid solution.
From the above, practically preferred phosphites are lithium phosphite, sodium phosphite, potassium phosphite, magnesium phosphite, calcium phosphite and ammonium phosphite. .
本発明の電解ロジウムめっき液において、リン酸ロジウムは、電解ロジウムめっき液の陰極析出効率を低くするので、生産性の観点から工業分野は硫酸ロジウム塩のほうが好ましい。他方、リン酸塩を用いたほうが硫酸ロジウム塩よりも色調は明るい銀白色のめっき被膜が得られるので、装飾性の観点から装飾分野はリン酸ロジウム塩のほうが好ましい。 In the electrolytic rhodium plating solution of the present invention, rhodium phosphate lowers the cathode deposition efficiency of the electrolytic rhodium plating solution, so the rhodium sulfate salt is preferred in the industrial field from the viewpoint of productivity. On the other hand, since a silver-white plating film having a brighter color tone than rhodium sulfate salt can be obtained by using phosphate, rhodium phosphate salt is preferred in the decorative field from the viewpoint of decoration.
本発明の非晶質構造のロジウムリンめっき被膜は、後述する図２に示すように、集束イオンビームによる断面を走査型電子顕微鏡で観察した時のロジウムの平均結晶粒が０．０１μｍ未満のものをいう。すなわち、微細に区画されすぎて通常の走査型電子顕微鏡では観察できない区画の状態をいう。このような緻密な非晶質構造によって本発明の種々の効果がもたらされる。 As shown in FIG. 2 described later, the rhodium-phosphorous plating film of the present invention has an average rhodium crystal grain size of less than 0.01 μm when a cross section by a focused ion beam is observed with a scanning electron microscope. Say. That is, it refers to a state of compartments that are too finely divided and cannot be observed with a normal scanning electron microscope. Various effects of the present invention are brought about by such a dense amorphous structure.
本発明の電解ロジウムめっき液において、金属ロジウムの濃度を１～２０ｇ／Ｌとしたのは、次の理由による。すなわち、金属ロジウムの濃度が１ｇ／Ｌ未満では、電解ロジウムめっき液の析出効率が低くなるからである。また、金属ロジウムの濃度が２０ｇ／Ｌを超えると、未使用のロジウム量が多くなりすぎてめっき液の維持費用がかさむからである。また、老化したロジウムめっき浴からの金属ロジウムの回収や廃液の処理等の管理面を考えてのことである。 In the electrolytic rhodium plating solution of the present invention, the metal rhodium concentration is set to 1 to 20 g / L for the following reason. That is, when the metal rhodium concentration is less than 1 g / L, the deposition efficiency of the electrolytic rhodium plating solution is lowered. Further, when the concentration of metal rhodium exceeds 20 g / L, the amount of unused rhodium is excessively increased and the maintenance cost of the plating solution is increased. In addition, the management aspects such as recovery of metal rhodium from an aged rhodium plating bath and treatment of waste liquid are considered.
本発明の電解ロジウムめっき液における一般的な厚付けでは、金属ロジウムの濃度は２～１０ｇ／Ｌの範囲が好ましく、２～６ｇ／Ｌの範囲が特に好ましい。短時間で所望の厚めっき被膜が得られるからである。緻密な非晶質構造の最大厚さは２０μｍである。 In general thickening in the electrolytic rhodium plating solution of the present invention, the concentration of metal rhodium is preferably in the range of 2 to 10 g / L, particularly preferably in the range of 2 to 6 g / L. This is because a desired thick plating film can be obtained in a short time. The maximum thickness of the dense amorphous structure is 20 μm.
本発明の電解ロジウムめっき液における一般的な薄付けでは、金属ロジウムの濃度は２～１０ｇ／Ｌの範囲が好ましく、２～４ｇ／Ｌの範囲が特に好ましい。緻密な非晶質の膜が得られれば緻密な表面層の上に耐食性のある金メッキ被膜やロジウムめっき被膜や白金めっき被膜が可能だからである。 In general thinning in the electrolytic rhodium plating solution of the present invention, the concentration of metal rhodium is preferably in the range of 2 to 10 g / L, particularly preferably in the range of 2 to 4 g / L. This is because if a dense amorphous film is obtained, a corrosion-resistant gold plating film, rhodium plating film, or platinum plating film can be formed on the dense surface layer.
本発明の電解ロジウムめっき液によるストライクめっきでは、金属ロジウムの濃度は１～５ｇ／Ｌの範囲が好ましく、２～４ｇ／Ｌの範囲が特に好ましい。極薄の緻密な非晶質構造によって基材の表面形態が被覆層の析出形状に及ぶのを防ぐとともに、基材と表面層との合金化を避けることができるからである。 In strike plating with the electrolytic rhodium plating solution of the present invention, the concentration of metal rhodium is preferably in the range of 1 to 5 g / L, particularly preferably in the range of 2 to 4 g / L. This is because the ultra-thin and dense amorphous structure prevents the surface form of the base material from reaching the deposited shape of the coating layer and avoids alloying of the base material and the surface layer.
本発明の電解ロジウムめっき液において、硫酸の濃度を１０～１００ｍＬ／Ｌとしたのは次の理由による。すなわち、硫酸の濃度が１０ｍＬ／Ｌ未満では、ロジウム化合物が加水分解するおそれがあるからである。また、硫酸の濃度が１００ｍＬ／Ｌを超えると、ロジウム化合物の移動が困難となってロジウムリンの析出物が焼けめっきを生じることがあるからである。硫酸の濃度は、好ましくは１０～５０ｍＬ／Ｌで、より好ましくは１０～２０ｍＬ／Ｌである。 In the electrolytic rhodium plating solution of the present invention, the concentration of sulfuric acid is 10 to 100 mL / L for the following reason. That is, when the concentration of sulfuric acid is less than 10 mL / L, the rhodium compound may be hydrolyzed. Further, when the concentration of sulfuric acid exceeds 100 mL / L, the rhodium compound is difficult to move, and the deposit of rhodium phosphorus may cause burn plating. The concentration of sulfuric acid is preferably 10 to 50 mL / L, more preferably 10 to 20 mL / L.
本発明の電解ロジウムめっき液において、リン酸の濃度を１０～１００ｍＬ／Ｌとしたのは次の理由による。すなわち、リン酸の濃度が１０ｍＬ／Ｌ未満では、ロジウム化合物が加水分解するおそれがあるからである。また、リン酸の濃度が１００ｍＬ／Ｌを超えると、ロジウム化合物の移動が困難となってロジウムリンの析出物が焼けめっきを生じることがあるからである。リン酸の濃度は、好ましくは１０～５０ｍＬ／Ｌで、より好ましくは１０～２０ｍＬ／Ｌである。 In the electrolytic rhodium plating solution of the present invention, the phosphoric acid concentration is set to 10 to 100 mL / L for the following reason. That is, if the concentration of phosphoric acid is less than 10 mL / L, the rhodium compound may be hydrolyzed. Further, when the concentration of phosphoric acid exceeds 100 mL / L, the rhodium compound is difficult to move, and the deposit of rhodium phosphorus may cause burn plating. The concentration of phosphoric acid is preferably 10 to 50 mL / L, more preferably 10 to 20 mL / L.
本発明の電解ロジウムめっき液において、亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ含有することとしたのは、これらの化合物が析出物中でロジウムと非晶質構造を形成するからである。化合物の濃度が０．００１ｇ／Ｌ未満では、ロジウム析出物を非晶質に形成することができない。他方、化合物の濃度が１０ｇ／Ｌを超えると電気めっき液中にロジウムの沈殿物ができてしまうおそれがあるためである。 In the electrolytic rhodium plating solution of the present invention, 0.001 to 0.001 to at least one compound selected from the group consisting of phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite The reason for containing 10 g / L is that these compounds form an amorphous structure with rhodium in the precipitate. If the concentration of the compound is less than 0.001 g / L, the rhodium precipitate cannot be formed amorphous. On the other hand, if the concentration of the compound exceeds 10 g / L, a rhodium precipitate may be formed in the electroplating solution.
ロジウムリンの非晶質構造の形成は次のように理解することができる。一般的にリン化合物がロジウムめっき被膜中に入ることができれば、ロジウム析出物は微細化する。しかし、電気めっきの際に様々なロジウム化学種から析出したロジウムはその内部応力が極めて強い。このことは、リン化合物の量が液中で増えても析出したロジウムの内部にリン化合物が入り込めず、ロジウム析出物は微細化しない。電気めっきでロジウムが析出する際にめっき液中では様々なロジウム錯体の巨大なネットワークが形成されているようである。ロジウム結晶粒の内部にリン化合物がなく、結晶粒の粒界にリンが共析している場合にはロジウム結晶粒が頑強になって剥離する現象が起きる。 The formation of an amorphous structure of rhodium phosphorus can be understood as follows. Generally, if a phosphorus compound can enter the rhodium plating film, the rhodium precipitate becomes finer. However, rhodium deposited from various rhodium species during electroplating has very strong internal stress. This means that even if the amount of the phosphorus compound increases in the liquid, the phosphorus compound cannot enter the precipitated rhodium, and the rhodium precipitate is not refined. When rhodium is deposited by electroplating, it seems that a huge network of various rhodium complexes is formed in the plating solution. When there is no phosphorus compound inside the rhodium crystal grains and phosphorus is co-deposited at the grain boundaries of the crystal grains, the rhodium crystal grains become strong and peel off.
これに対して、上記の亜リン酸ナトリウム塩等のリン化合物は、電気めっきでロジウム結晶粒が析出される前にめっき液中で様々なロジウム化学種をあらかじめ分解しやすい状態へ導いてロジウムとリンが結合した原子団を形成していると考えられる。このため電解ロジウムめっきを行うと、ロジウムリン析出物は微小なロジウムリン原子団の上に次のロジウムリン原子団が雪のように積み重なる緻密な構造をとる。このような緻密な非晶質構造の個々のロジウムリン原子団はロジウム金属原子とリン金属原子の集合体である。このロジウムリンのめっき析出物は結晶方位を持たず、ロジウムリンめっき被膜は配向性もない。 In contrast, phosphorus compounds such as sodium phosphite described above lead to various rhodium species in the plating solution to be easily decomposed in advance before rhodium crystal grains are deposited by electroplating. It is thought that an atomic group in which phosphorus is bonded is formed. For this reason, when electrolytic rhodium plating is performed, the rhodium phosphorus deposit has a dense structure in which the following rhodium phosphorus atomic groups are stacked like snow on a small rhodium phosphorus atomic group. Each rhodium phosphorus atomic group having such a dense amorphous structure is an aggregate of rhodium metal atoms and phosphorus metal atoms. This rhodium phosphorus plating deposit has no crystal orientation, and the rhodium phosphorus plating film has no orientation.
このため本発明の電解ロジウムめっき液で厚付けめっきしても、ロジウムリンの平滑性は保たれ、応力が高くなることはなく、クラックの発生が無い銀白色の光沢被膜が得られる。また、中間めっきに用いても非晶質構造なので他の貴金属めっきを確実に積層することができる。また、フラッシュメッキの膜厚が０．０１μｍ以下のストライクめっきであっても、ロジウムリンのめっき被膜は非晶質構造なので、基材とめっき層との間を確実に区画することができる。ロジウムリンの非晶質構造が介在すると、基材上面の結晶組織が上層のめっき組織に影響することが無い。 For this reason, even if thick plating is performed with the electrolytic rhodium plating solution of the present invention, the smoothness of rhodium phosphorus is maintained, the stress does not increase, and a silver-white glossy coating free from cracks is obtained. Further, even when used for intermediate plating, since it has an amorphous structure, other noble metal plating can be reliably laminated. Moreover, even if the flash plating has a thickness of 0.01 μm or less, the rhodium phosphorous plating film has an amorphous structure, so that the substrate and the plating layer can be reliably partitioned. When the amorphous structure of rhodium phosphorus is present, the crystal structure on the upper surface of the substrate does not affect the upper plating structure.
本発明の電解ロジウムめっき液において、亜リン酸ナトリウム塩等の化合物を０．００１～１０ｇ／Ｌ含有することとしたのは、０．００１ｇ／Ｌ未満では非晶質とすることができず、１０ｇ／Ｌを超えるとロジウムリンめっき被膜の融点が低くなりすぎるからである。亜リン酸ナトリウム塩等の化合物は０．０５～５．０ｇ／Ｌ含有することが好ましく、１．０～３．０ｇ／Ｌ含有することがより好ましい。特に金属ロジウムの濃度に対して、１／１０未満の量が好ましく、１／２０未満の量が特に好ましい。 In the electrolytic rhodium plating solution of the present invention, the compound containing 0.001 to 10 g / L of a compound such as sodium phosphite cannot be made amorphous at less than 0.001 g / L, This is because if it exceeds 10 g / L, the melting point of the rhodium phosphorus plating film becomes too low. The compound such as sodium phosphite is preferably contained in an amount of 0.05 to 5.0 g / L, more preferably 1.0 to 3.0 g / L. In particular, an amount of less than 1/10 is preferable and an amount of less than 1/20 is particularly preferable with respect to the metal rhodium concentration.
本発明の電解ロジウムめっき液において、次亜リン酸ナトリウム（ＮａＨ２ＰＯ２・Ｈ２Ｏ）塩等の次亜リン酸塩は含まれない。析出したロジウム被膜が黒く変色したり、安定しなかったり、非晶質とすることができなかったりするからである。また、電解ロジウムめっき液中の様々なロジウム化学種が分解して陽極に析出することがある。 The electrolytic rhodium plating solution of the present invention does not contain hypophosphite such as sodium hypophosphite (NaH 2 PO 2 .H 2 O) salt. This is because the deposited rhodium film turns black, is not stable, or cannot be made amorphous. In addition, various rhodium species in the electrolytic rhodium plating solution may be decomposed and deposited on the anode.
他方、本発明の電解ロジウムめっき液においては、一般的な電解ロジウムめっき液に用いられる有機硫黄化合物や界面活性剤などの添加剤も用いることができる。本発明の非晶質構造が壊れない限り、本発明の電解ロジウムめっき液の効果が発揮されるからである。 On the other hand, in the electrolytic rhodium plating solution of the present invention, additives such as organic sulfur compounds and surfactants used in general electrolytic rhodium plating solutions can also be used. This is because the effect of the electrolytic rhodium plating solution of the present invention is exhibited as long as the amorphous structure of the present invention is not broken.
本発明の電解ロジウムめっき液において、上記の亜リン酸ナトリウム塩等のリン化合物は、ロジウム析出物と一定の析出割合をもつ傾向にあることが本発明者らによって知見された。すなわち、金属ロジウムの濃度を固定したとき、亜リン酸ナトリウム塩等の化合物の濃度を適当に１／１０単位ごとに変動すると、亜リン酸ナトリウム塩等の化合物の濃度は、重量比で、ロジウム：リン≒４：１、９：１、２０：１などの分布傾向を示すことがわかった。このことは電気めっき液中で所定のロジウムリン原子団が形成されていることを推測させるものである。 In the electrolytic rhodium plating solution of the present invention, the present inventors have found that the above phosphorus compounds such as sodium phosphite tend to have a certain precipitation ratio with rhodium precipitates. That is, when the concentration of rhodium metal is fixed and the concentration of the compound such as sodium phosphite is appropriately changed every 1/10 unit, the concentration of the compound such as sodium phosphite is rhodium in weight ratio. : Phosphorus ≈4: 1, 9: 1, 20: 1, etc. This makes it speculated that a predetermined rhodium phosphorus atomic group is formed in the electroplating solution.
本発明の電解ロジウムめっき液において、金属ロジウム、および亜リン酸、亜リン酸ナトリウム塩等の亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩の濃度が低下すると、必要成分を補充することができる。これにより、劣化した電解ロジウムめっき液を回復させ、電解ロジウムめっき液のターンオーバー数を従来よりも飛躍的に向上させることができる。なお、例えば「亜リン酸ナトリウム塩」とは、亜リン酸ナトリウム五水和物を意味し、組成式がＨＮａ２Ｏ３Ｐ・５Ｈ２ＯまたはＮａ２ＨＰＯ３・５Ｈ２Ｏのものをいう。 In the electrolytic rhodium plating solution of the present invention, the concentration of metal rhodium and phosphorous acid, alkali metal phosphite such as sodium phosphite, alkaline earth metal phosphite or ammonium phosphite is reduced. Can be replenished with necessary ingredients. Thereby, the deteriorated electrolytic rhodium plating solution can be recovered, and the number of turnovers of the electrolytic rhodium plating solution can be dramatically improved as compared with the conventional case. For example, “sodium phosphite salt” means sodium phosphite pentahydrate, which has a composition formula of HNa 2 O 3 P · 5H 2 O or Na 2 HPO 3 · 5H 2 O. .
本発明の電解ロジウムめっき液において、アルカリ金属の硫酸塩、アルカリ土類金属の硫酸塩または硫酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～３０ｇ／Ｌ含有することとしたのは、これらの無機化合物は導電塩だからである。導電塩は本発明の電解ロジウムめっき液を安定化させるが、３０ｇ／Ｌを超えると金属ロジウム量を多くする必要がある。特に、０．００１～３０ｇ／Ｌ含有すると、大型のめっき浴を用いた場合に安定なめっき析出物が得られる。ナトリウム塩、カリウム塩、マグネシウム塩、カルシウム塩およびアンモニウム塩が好ましく、特にナトリウム塩およびカリウム塩およびアンモニウム塩がより好ましい。また、その濃度は２０～３０ｇ／Ｌ含有することが好ましい。 The electrolytic rhodium plating solution of the present invention contains 0.001 to 30 g / L of at least one compound selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates or ammonium sulfates. This is because these inorganic compounds are conductive salts. The conductive salt stabilizes the electrolytic rhodium plating solution of the present invention, but if it exceeds 30 g / L, it is necessary to increase the amount of metal rhodium. In particular, when the content is 0.001 to 30 g / L, stable plating deposits can be obtained when a large plating bath is used. Sodium salt, potassium salt, magnesium salt, calcium salt and ammonium salt are preferred, and sodium salt, potassium salt and ammonium salt are particularly preferred. The concentration is preferably 20 to 30 g / L.
本発明の電解ロジウムめっき液において、硫酸浴およびリン酸浴はｐＨが１以下であることが好ましい。緻密な非晶質状態のロジウムリンめっき被膜が得られるからである。また、本発明の電解ロジウムめっき液において、硫酸浴およびリン酸浴のいずれの場合でも液温が４０～７０℃であることが好ましい。ロジウムリンめっき被膜の硬度が低くなり、ロジウムリンめっき被膜の柔軟性を増すからである。 In the electrolytic rhodium plating solution of the present invention, the sulfuric acid bath and the phosphoric acid bath preferably have a pH of 1 or less. This is because a dense amorphous rhodium-phosphorous plating film can be obtained. In the electrolytic rhodium plating solution of the present invention, the temperature of the solution is preferably 40 to 70 ° C. in both the sulfuric acid bath and the phosphoric acid bath. This is because the hardness of the rhodium phosphorous plating film is lowered and the flexibility of the rhodium phosphorous plating film is increased.
本発明によれば、緻密な非晶質構造のロジウムリンめっき被膜が得られる効果がある。すなわち、緻密な非晶質構造の最下層は、下地表面の析出形態に左右されず、非晶質構造となる。このことは、後述する図２と図3との接合界面を比較すると、よく理解される。また、緻密な非晶質構造の中間層は結晶粒がなく、内部応力が低いことがわかる。このため緻密な非晶質構造を厚めっきとしても表層からはがれることが無い。また、緻密な非晶質構造を中間層に用いた場合、ストライクめっきのような極薄中間層でも、表層の貴金属めっきの析出構造が中間層の影響を受け、緻密になる効果がある。 According to the present invention, there is an effect that a rhodium phosphorus plating film having a dense amorphous structure can be obtained. That is, the lowermost layer of the dense amorphous structure has an amorphous structure regardless of the form of precipitation on the underlying surface. This is well understood by comparing the junction interface between FIG. 2 and FIG. 3 described later. It can also be seen that the intermediate layer having a dense amorphous structure has no crystal grains and low internal stress. For this reason, even if a dense amorphous structure is formed by thick plating, it does not peel off from the surface layer. Further, when a dense amorphous structure is used for the intermediate layer, even in an ultrathin intermediate layer such as strike plating, the precipitation structure of the noble metal plating on the surface layer is affected by the intermediate layer and has an effect of becoming dense.
本発明の電解ロジウムめっき液によれば、電気接点等の電気部品やコネクター等の電子部品や耐食性等の自動車部品等の工業製品の必要特性に合わせて、濃度比や膜厚を適宜選択した非晶質構造のロジウムリンめっき被膜を提供することができる。例えば、均一な平滑面が得られるので、接点に応用した際、接触点面積が大きくなる。また、ロジウム濃度が高い場合は、これまでと同様にロジウムリンめっき被膜の硬度が高く、安定した摩耗特性が得られる。また、ロジウムリンめっき被膜のロジウム析出物は内部応力が強くなく、これまでのように摩耗粉を生じやすくなることはない。 According to the electrolytic rhodium plating solution of the present invention, the concentration ratio and the film thickness are appropriately selected in accordance with the required characteristics of electrical parts such as electrical contacts, electronic parts such as connectors, and automobile parts such as corrosion resistance. A rhodium phosphorous plating film having a crystalline structure can be provided. For example, since a uniform smooth surface can be obtained, the contact point area becomes large when applied to a contact. Moreover, when the rhodium concentration is high, the hardness of the rhodium phosphorous plating film is high as before, and stable wear characteristics are obtained. In addition, the rhodium precipitates on the rhodium-phosphorous plating film do not have strong internal stress and do not easily generate wear powder as in the past.
従来のニッケルめっき被膜の表面走査電子顕微鏡像（約３万倍）である。It is the surface scanning electron microscope image (about 30,000 times) of the conventional nickel plating film. 本発明のロジウムリン非晶質めっき被膜の断面走査イオン顕微鏡像である。It is a cross-sectional scanning ion microscope image of the rhodium phosphorus amorphous plating film of this invention. 従来のロジウム被膜の断面走査イオン顕微鏡像である。It is a cross-sectional scanning ion microscope image of the conventional rhodium film.
以下、本発明について実施例および比較例を挙げて説明するが、本発明は以下の実施の形態に限定されるものではなく、任意に変形して実施することができる。 Hereinafter, although an example and a comparative example are given and explained about the present invention, the present invention is not limited to the following embodiments and can be carried out arbitrarily changing.
ロジウム（硫酸ロジウムとして）濃度とリン濃度（亜リン酸ナトリウム塩として）を表１左欄の試番０１～０６にした電解ロジウムめっき液（硫酸４０ｍＬ／Ｌ、ｐＨ＝０．６、浴温６０℃）を用い、２０ｍｍ×２０ｍｍの銅テストピースに４Ａ／ｄｍ２の電流密度で０．１０μｍの厚さまで電気めっきした。 Electrolytic rhodium plating solution (sulfuric acid 40 mL / L, pH = 0.6, bath temperature 60) having rhodium (as rhodium sulfate) and phosphorus concentrations (as sodium phosphite) as test numbers 01 to 06 in the left column of Table 1 And 20 mm × 20 mm copper test piece at a current density of 4 A / dm 2 to a thickness of 0.10 μm.
得られたロジウムリンめっき試験片の外観はいずれも銀白色の非晶質状態であった。このロジウムリンめっき試験片を陽極とし、４０ｍｍ×２０ｍｍの銅テストピースを陰極とし、０．７４Ｖの低電圧をかけ、５％硫酸液中にて２０分間有孔度を測定して表１右欄の結果を得た。なお、ロジウムリンめっきを行わなかった試験片を陽極とした場合の有孔度を１００％と定義した。 The appearance of the obtained rhodium phosphorus plating test pieces was in a silver-white amorphous state. The rhodium phosphorus plating test piece was used as an anode, a 40 mm × 20 mm copper test piece was used as a cathode, a low voltage of 0.74 V was applied, and the porosity was measured for 20 minutes in a 5% sulfuric acid solution. The result was obtained. In addition, the porosity when the test piece not subjected to rhodium phosphorus plating was used as an anode was defined as 100%.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
これらの結果から、同一膜厚の場合はリン濃度が高いほど有効度が低くなることがわかる。つまり、本ロジウムリンめっき液中ではリン濃度が高いほどロジウム金属原子に及ぼす亜リン酸ナトリウム塩の還元効果が高くなることが示された。なお、リン濃度を９．５ｇ／Ｌまで増加した場合も有孔度はすべて８％以下であった。 From these results, it can be seen that the effectiveness decreases as the phosphorus concentration increases in the case of the same film thickness. That is, in this rhodium phosphorus plating solution, it was shown that the reduction effect of sodium phosphite on rhodium metal atoms increases as the phosphorus concentration increases. Even when the phosphorus concentration was increased to 9.5 g / L, the porosity was 8% or less.
比較例１Comparative Example 1
ロジウム（硫酸ロジウムとして）を３ｇ／Ｌとし、リン濃度（次亜リン酸ナトリウム塩として）を０．０５ｇ／Ｌおよび１．０ｇ／Ｌとし、表１左欄の試番０７および試番０８にした電解ロジウムめっき液（ｐＨ＝０．６、浴温２５℃）を用い、２０ｍｍ×２０ｍｍの銅テストピースに４Ａ／ｄｍ２の電流密度で０．１０μｍの厚さまで電気めっきした。 The rhodium (as rhodium sulfate) was 3 g / L, the phosphorus concentration (as sodium hypophosphite) was 0.05 g / L and 1.0 g / L. Using an electrolytic rhodium plating solution (pH = 0.6, bath temperature 25 ° C.), a 20 mm × 20 mm copper test piece was electroplated to a thickness of 0.10 μm at a current density of 4 A / dm 2 .
得られたロジウムリンめっき試験片の外観は黒色の析出物であった。このロジウムリンめっき試験片を陽極とし、４０ｍｍ×２０ｍｍの銅テストピースを陰極とし、０．７４Ｖの低電圧をかけ、５％硫酸液中にて２０分間有孔度を測定したところ、表１右欄の１２．０％および８％の結果を得た。この試番０７の有効度１２．０％は、上記試番０４の有効度４．１％と対比される。すなわち、黒色のロジウム析出物の被膜は、本発明のロジウムリン非晶質構造の被膜よりも有孔度が２倍以上悪い結果となったことがわかる。 The appearance of the obtained rhodium phosphorus plating test piece was a black precipitate. When this rhodium phosphorus plating test piece was used as an anode, a 40 mm × 20 mm copper test piece as a cathode, a low voltage of 0.74 V was applied, and the porosity was measured for 20 minutes in a 5% sulfuric acid solution. The results of 12.0% and 8% in the column were obtained. The effectiveness 12.0% of the trial number 07 is compared with the effectiveness 4.1% of the trial number 04. That is, it can be seen that the black rhodium precipitate film has a porosity that is twice or more worse than the rhodium phosphorus amorphous structure film of the present invention.
次に、ロジウム（リン酸ロジウムとして）濃度を４．０ｇ／Ｌとし、リン酸濃度を４０ｍＬ／Ｌ、リン濃度（亜リン酸カリウム塩）を表２左欄のようにした試番０９～１２の電解ロジウムめっき液（ｐＨ＝０．６、浴温６０℃）を用い、２０ｍｍ×２０ｍｍの銅テストピースに４Ａ／ｄｍ２の電流密度で０．１０μｍの厚さまで電気めっきした。 Next, rhodium (as rhodium phosphate) concentration of 4.0 g / L, phosphoric acid concentration of 40 mL / L, and phosphorus concentration (potassium phosphite) as shown in the left column of Table 2 Was electroplated to a thickness of 0.10 μm at a current density of 4 A / dm 2 on a copper test piece of 20 mm × 20 mm using an electrolytic rhodium plating solution (pH = 0.6, bath temperature 60 ° C.).
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
これらの結果から、ロジウム（リン酸ロジウム）濃度が４．０ｇ／Ｌの場合はリン濃度（亜リン酸カリウム塩）のロジウム金属に対する割合が１／１００以上になれば、有効度が極端に低くなることがわかる。なお、リン濃度を９．５ｇ／Ｌまで増加した場合も有孔度はすべて１０％以下であった。 From these results, when the rhodium (rhodium phosphate) concentration is 4.0 g / L, if the ratio of phosphorus concentration (potassium phosphite) to rhodium metal is 1/100 or more, the effectiveness is extremely low. I understand that Even when the phosphorus concentration was increased to 9.5 g / L, the porosity was all 10% or less.
比較例２Comparative Example 2
ロジウム（リン酸ロジウムとして）濃度を４．０ｇ／Ｌとし、リン濃度（亜リン酸ナトリウム塩）を０ｇ／Ｌとした試番１３の電解ロジウムめっき液（ｐＨ＝０．６、浴温６０℃）を用い、２０ｍｍ×２０ｍｍの銅テストピースに４Ａ／ｄｍ２の電流密度で０．１０μｍの厚さまで電気めっきした。頑強なロジウム析出物にもかかわらず、このロジウムめっき試験片の有効度は１４．５％であった。 Test No. 13 electrolytic rhodium plating solution (pH = 0.6, bath temperature 60 ° C.) having a rhodium (as rhodium phosphate) concentration of 4.0 g / L and a phosphorus concentration (sodium phosphite) of 0 g / L. ) Was electroplated to a 20 mm × 20 mm copper test piece at a current density of 4 A / dm 2 to a thickness of 0.10 μm. Despite the robust rhodium deposits, the effectiveness of this rhodium plated specimen was 14.5%.
２０ｍｍ×２０ｍｍの銅のテストピースに、硫酸ニッケル２００ｇ／Ｌ、塩化ナトリウム塩１５ｇ／Ｌおよびリン酸０．１５ｍＬ／Ｌの電解ニッケルめっき液で８μｍめっきした。このニッケル被膜の表面に金ストライクめっきを施した走査電子顕微鏡像（３万倍）を図１に示す。金ストライクめっきによりコントラストを強調したニッケル被膜の表面形態はうねった模様が形成されていることがわかる。 A 20 mm × 20 mm copper test piece was plated with an electrolytic nickel plating solution of nickel sulfate 200 g / L, sodium chloride salt 15 g / L and phosphoric acid 0.15 mL / L at 8 μm. FIG. 1 shows a scanning electron microscope image (30,000 times) obtained by applying gold strike plating to the surface of the nickel coating. It can be seen that a wavy pattern is formed on the surface form of the nickel coating whose contrast is enhanced by gold strike plating.
その後、このニッケル被膜上にロジウム（硫酸ロジウムとして）を１ｇ／Ｌとし、リン濃度（亜リン酸カルシウム塩として）を１ｇ／Ｌとしたロジウムリンストライク浴で、１０Ｖ×１０秒間のロジウムリンストライクメッキを施した後、ロジウム（硫酸ロジウムとして）濃度を４．０ｇ／Ｌとし、硫酸を５０ｍＬ／Ｌとし、４Ａ／ｄｍ２の電流密度で０．５μｍの厚さまで純ロジウム被膜を電気めっきした。 Thereafter, rhodium phosphorus strike plating of 10 V × 10 seconds was performed on this nickel coating in a rhodium phosphorus strike bath with rhodium (as rhodium sulfate) at 1 g / L and phosphorus concentration (as calcium phosphite) at 1 g / L. After that, the rhodium (as rhodium sulfate) concentration was 4.0 g / L, sulfuric acid was 50 mL / L, and the pure rhodium coating was electroplated to a thickness of 0.5 μm at a current density of 4 A / dm 2 .
次に、この純ロジウム被膜を電気めっきしたテストピースにつき、２０ｍｍ×２０ｍｍのステンレス鋼片を陰極にして５％塩化ナトリウム水溶液中に電圧５Ｖ×１０分間の欠陥検出試験を行ったところ、６回目で腐食欠陥が検出された。 Next, a test piece electroplated with this pure rhodium film was subjected to a defect detection test at a voltage of 5 V × 10 minutes in a 5% sodium chloride aqueous solution using a 20 mm × 20 mm stainless steel piece as a cathode. Corrosion defects were detected.
比較例３Comparative Example 3
ロジウムリンのストライクメッキを除いて比較例3のサンプルを作成し、耐食性試験を行ったところ、１回目で腐食欠陥が検出された。 A sample of Comparative Example 3 was prepared except for rhodium phosphorus strike plating, and a corrosion resistance test was performed. Corrosion defects were detected at the first time.
２０ｍｍ×２０ｍｍの銅のテストピースに、硫酸ニッケル塩３００ｇ／Ｌ、塩化ナトリウム塩２０ｇ／Ｌおよびリン酸０．３０ｍＬ／Ｌの電解ニッケルめっき液で５μｍのニッケルめっきをした。このニッケル被膜にロジウム（硫酸ロジウムとして）を１０ｇ／Ｌとし、リン濃度（亜リン酸ナトリウム塩として）を１ｇ／Ｌとしたロジウムリン非晶質被膜を４．５μｍ析出させた。この走査イオン顕微鏡像を図２に示す。 A 20 mm × 20 mm copper test piece was plated with nickel of 5 μm with an electrolytic nickel plating solution of nickel sulfate salt 300 g / L, sodium chloride salt 20 g / L and phosphoric acid 0.30 mL / L. A rhodium phosphorus amorphous film having a rhodium concentration (as rhodium sulfate) of 10 g / L and a phosphorus concentration (as sodium phosphite salt) of 1 g / L was deposited on this nickel film by 4.5 μm. This scanning ion microscope image is shown in FIG.
図２の上段の白い部分はコントラストが強調されたロジウムリン非晶質被膜である。この表面形態を図１のニッケル被膜の表面形態と比較すると、結晶粒の存在が確認されないことがわかる。また、図２の中段の黒い部分はロジウムリンの非晶質構造である。図２の中段の黒い部分は結晶組織が見当たらない。さらに、図２の中段の黒い部分と下段のニッケルめっきの界面には図１に示されるニッケルめっきの結晶粒が形成されていない。すなわち、下地の析出形態が直上のロジウムリンの非晶質構造に及んでいないことがわかる。 The white portion at the top of FIG. 2 is a rhodium phosphorous amorphous film with enhanced contrast. When this surface morphology is compared with the surface morphology of the nickel coating in FIG. 1, it can be seen that the presence of crystal grains is not confirmed. Moreover, the black part of the middle stage of FIG. 2 is an amorphous structure of rhodium phosphorus. In the middle black portion of FIG. 2, no crystal structure is found. Furthermore, the crystal grains of the nickel plating shown in FIG. 1 are not formed at the interface between the black portion in the middle stage of FIG. 2 and the nickel plating in the lower stage. That is, it can be seen that the precipitation form of the base does not reach the amorphous structure of rhodium phosphorus just above.
図２から、下段のニッケルめっきの結晶粒界は観察されるが、中段のロジウムリン非晶質構造の結晶粒界は観察できないことがわかる。さらに、図２のロジウムリン非晶質構造の平均結晶粒を走査電子顕微鏡で１万倍に拡大して観察したが、微細に区画されすぎて区画がまったく観察できなかった。０．０１μｍ未満の状態であるといえる。なお、上記ロジウムリン非晶質被膜上にさらに純ロジウムめっきを施すことができた。 From FIG. 2, it can be seen that the grain boundary of the lower nickel plating is observed, but the grain boundary of the rhodium phosphorus amorphous structure in the middle stage cannot be observed. Further, the average crystal grains of the rhodium phosphorus amorphous structure in FIG. 2 were observed with a scanning electron microscope at a magnification of 10,000 times, but were too finely sectioned so that the section could not be observed at all. It can be said that it is in a state of less than 0.01 μm. Further, pure rhodium plating could be applied on the rhodium phosphorus amorphous coating.
次に、ロジウム（硫酸ロジウムとして）濃度を２．０ｇ／Ｌと一定にし、硫酸濃度を３０ｍＬ／Ｌ、リン濃度（亜リン酸ナトリウム塩）を表３左欄のようにした試番１４～１８の電解ロジウムめっき液（ｐＨ＝０．５、浴温５５℃）を用い、２０ｍｍ×２０ｍｍの銅テストピースに４Ａ／ｄｍ２の電流密度で０．２μｍの厚さを目標に電気めっきした。 Next, test numbers 14 to 18 in which the rhodium (as rhodium sulfate) concentration was kept constant at 2.0 g / L, the sulfuric acid concentration was 30 mL / L, and the phosphorus concentration (sodium phosphite) was as shown in the left column of Table 3. Was electroplated on a 20 mm × 20 mm copper test piece at a current density of 4 A / dm 2 with a target thickness of 0.2 μm using the electrolytic rhodium plating solution (pH = 0.5, bath temperature 55 ° C.).
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
リンの共析量を測定したところ表３中欄の結果を得た。さらに、２０ｍｍ×２０ｍｍの銅テストピースの４隅と中央部の膜厚を測定したところ、表３右欄の結果を得た。これらの結果から、ロジウムリンの非晶質被膜はばらつきがなく、付きまわり性が良好であることがわかる。 When the amount of eutectoid of phosphorus was measured, the results in the column of Table 3 were obtained. Furthermore, when the film thickness of the 4 corners and the center part of a 20 mm x 20 mm copper test piece was measured, the result of the right column of Table 3 was obtained. From these results, it can be seen that the amorphous coating of rhodium phosphorus has no variation and good throwing power.
比較例４Comparative Example 4
亜リン酸ナトリウム塩を添加しなかった以外は、試番１４と同様にして２０ｍｍ×２０ｍｍの銅テストピースに電気めっきした。これを試番１９とした。この試番１９の銅テストピースの４隅と中央部の膜厚を測定したところ、表３右欄の結果を得た。この結果から、純ロジウム被膜はばらつきが大きく不安定な析出物であることがわかる。 A 20 mm × 20 mm copper test piece was electroplated in the same manner as in Test No. 14 except that sodium phosphite was not added. This was designated as trial number 19. When the film thicknesses at the four corners and the center of the test piece 19 were measured, the results in the right column of Table 3 were obtained. From this result, it can be seen that the pure rhodium film is an unstable precipitate with large variations.
比較例５Comparative Example 5
また、次亜リン酸ナトリウム塩を１ｇ／Ｌ添加した以外は試番１７と同様にして２０ｍｍ×２０ｍｍの銅テストピースに電気めっきした。これを試番２０とした。この試番２０の銅テストピースの４隅と中央部の膜厚を測定したところ、表３右欄の結果を得た。この結果から、次亜リン酸ナトリウム塩により析出したロジウムリン被膜は、ばらつきが大きく不安定な析出物であることがわかる。 Further, a 20 mm × 20 mm copper test piece was electroplated in the same manner as in Test No. 17 except that 1 g / L of hypophosphite sodium salt was added. This was designated as trial number 20. When the film thicknesses at the four corners and the center of the copper test piece of sample number 20 were measured, the results in the right column of Table 3 were obtained. From this result, it can be seen that the rhodium phosphorous film deposited by sodium hypophosphite is an unstable precipitate with large variations.
エネルギー分散型Ｘ線分析装置（堀場製作所製 Ｘ－ｍａｘＮ）により、ロジウムリン非晶質被膜の割合を求めたところ、ロジウム９２％、リン８％であった。また、Ｘ線回折装置による強度解析では、Ｒｈ金属固有の回折像は全くみられなかった。なお、ロジウム－リン８．２％共晶合金の融点は１，２５５℃である。 When the ratio of the rhodium phosphorus amorphous coating was determined by an energy dispersive X-ray analyzer (X-max N manufactured by Horiba, Ltd.), it was 92% rhodium and 8% phosphorus. Further, in the intensity analysis using an X-ray diffractometer, no diffraction image specific to Rh metal was observed. The melting point of the rhodium-phosphorus 8.2% eutectic alloy is 1,255 ° C.
比較例６Comparative Example 6
リン濃度（次亜リン酸ナトリウム塩として）を０ｇ／Ｌとした以外は実施例４と同様にして、ニッケル被膜上に純粋なロジウム電解めっき被膜を４．５μｍ析出させた。この頑強なロジウム被膜の結晶構造を図３に示す。 A pure rhodium electrolytic plating film was deposited on the nickel film in a thickness of 4.5 μm in the same manner as in Example 4 except that the phosphorus concentration (as sodium hypophosphite salt) was changed to 0 g / L. The crystal structure of this robust rhodium coating is shown in FIG.
図３中段のロジウム被膜の接合界面付近は、下段のニッケル被膜の表面形態の影響を受けて析出物が形成されていることがわかる。さらにその上方のロジウム被膜は不規則な析出構造をしていることがわかる。さらに図３上段のロジウム被膜の表面形態は、凹凸が激しくなっている。これはめっき液中のロジウムイオンが供給不足になった様子を現すものである。 It can be seen that precipitates are formed near the bonding interface of the rhodium film in the middle of FIG. 3 due to the influence of the surface morphology of the lower nickel film. Further, it can be seen that the rhodium film above it has an irregular precipitation structure. Furthermore, the surface form of the rhodium film in the upper part of FIG. This shows that the rhodium ions in the plating solution are insufficiently supplied.
また、ロジウム被膜のＸ線回折装置による強度解析（図は省略）では、Ｒｈ（１１１）、Ｒｈ（２００）、Ｒｈ（２２０）、Ｒｈ（３１１）などのロジウム金属固有の方向性を持つ回折像が現れた。これは本発明のロジウムリン非晶質被膜と明確な相違を示すものである。 In addition, in the intensity analysis (illustration is omitted) of the rhodium coating by a X-ray diffractometer, a diffraction image having directivity inherent to rhodium metal such as Rh (111), Rh (200), Rh (220), Rh (311) Appeared. This is a clear difference from the rhodium phosphorus amorphous coating of the present invention.
本発明の電解ロジウムめっき液は、微細な非晶質状態のロジウムリンめっき被膜を得ることができるので、これまでの厚・薄ロジウムめっき製品の代替品として、あるいは基材と他の貴金属めっき表層をつなぐ中間層として、さらにはストライクめっき品として、電気部品、電子部品、自動車部品や触媒・センサー部品、装飾品などの用途に利用することができる。
  The electrolytic rhodium plating solution of the present invention can obtain a rhodium phosphorous plating film in a fine amorphous state, so that it can be used as an alternative to conventional thick / thin rhodium plating products, or as a substrate and other noble metal plating surface layers. It can be used as an intermediate layer for connecting, and as a strike-plated product for applications such as electrical parts, electronic parts, automobile parts, catalyst / sensor parts, and decorative products.

Claims (6)

  1. 金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、硫酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ含有することを特徴とする電解ロジウムめっき液。 From metal rhodium (as sulfate or phosphate) 1-20 g / L, sulfuric acid 10-100 mL / L and phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite An electrolytic rhodium plating solution containing 0.001 to 10 g / L of at least one compound selected from the group consisting of:
  2. 金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、硫酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ、およびアルカリ金属の硫酸塩、アルカリ土類金属の硫酸塩または硫酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～３０ｇ／Ｌ含有することを特徴とする電解ロジウムめっき液。 From metal rhodium (as sulfate or phosphate) 1-20 g / L, sulfuric acid 10-100 mL / L and phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite 0.001 to 10 g / L of at least one compound selected from the group consisting of, and 0.001 to at least one compound selected from the group consisting of alkali metal sulfates, alkaline earth metal sulfates or ammonium sulfates. An electrolytic rhodium plating solution characterized by containing 001-30 g / L.
  3. 上記アルカリ金属の硫酸塩、アルカリ土類金属の硫酸塩または硫酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物が上記亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物と同一の化合物であることを特徴とする請求項２に記載の電解ロジウムめっき液。 At least one compound selected from the group consisting of the alkali metal sulfate, alkaline earth metal sulfate or ammonium sulfate is the alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite. The electrolytic rhodium plating solution according to claim 2, wherein the electrolytic rhodium plating solution is the same as at least one compound selected from the group consisting of salts.
  4. 金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、リン酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ含有することを特徴とする電解ロジウムめっき液。 Metal rhodium (as sulfate or phosphate) 1-20 g / L, phosphoric acid 10-100 mL / L and phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite An electrolytic rhodium plating solution containing 0.001 to 10 g / L of at least one compound selected from the group consisting of:
  5. 金属ロジウム（硫酸塩またはリン酸塩として）１～２０ｇ／Ｌ、リン酸１０～１００ｍＬ／Ｌおよび亜リン酸、亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～１０ｇ／Ｌ、およびアルカリ金属のリン酸塩、アルカリ土類金属のリン酸塩またはリン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物を０．００１～３０ｇ／Ｌ含有することを特徴とする電解ロジウムめっき液。 Metal rhodium (as sulfate or phosphate) 1-20 g / L, phosphoric acid 10-100 mL / L and phosphorous acid, alkali metal phosphite, alkaline earth metal phosphite or ammonium phosphite 0.001 to 10 g / L of at least one compound selected from the group consisting of: and at least one selected from the group consisting of alkali metal phosphates, alkaline earth metal phosphates or ammonium phosphates An electrolytic rhodium plating solution containing 0.001 to 30 g / L of the above compound.
  6. 上記アルカリ金属のリン酸塩、アルカリ土類金属のリン酸塩またはリン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物が上記亜リン酸アルカリ金属塩、亜リン酸アルカリ土類金属塩または亜リン酸アンモニウム塩からなる群より選ばれる少なくとも１種類の化合物と同一の化合物であることを特徴とする請求項５に記載の電解ロジウムめっき液。 At least one compound selected from the group consisting of the alkali metal phosphate, alkaline earth metal phosphate or ammonium phosphate is the alkali metal phosphite, alkaline earth metal phosphite or 6. The electrolytic rhodium plating solution according to claim 5, wherein the electrolytic rhodium plating solution is the same compound as at least one compound selected from the group consisting of ammonium phosphite salts.
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