JP6544792B2 - Method of selecting a stabilizer for electroless platinum plating solution and electroless platinum plating solution - Google Patents
Method of selecting a stabilizer for electroless platinum plating solution and electroless platinum plating solution Download PDFInfo
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- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 title claims description 244
- 229910052697 platinum Inorganic materials 0.000 title claims description 122
- 238000007747 plating Methods 0.000 title claims description 108
- 239000003381 stabilizer Substances 0.000 title claims description 44
- 238000000034 method Methods 0.000 title claims description 21
- 239000000243 solution Substances 0.000 claims description 120
- 230000010287 polarization Effects 0.000 claims description 43
- 150000003464 sulfur compounds Chemical class 0.000 claims description 42
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 21
- 239000003638 chemical reducing agent Substances 0.000 claims description 20
- 239000012279 sodium borohydride Substances 0.000 claims description 16
- 229910000033 sodium borohydride Inorganic materials 0.000 claims description 16
- 229910021607 Silver chloride Inorganic materials 0.000 claims description 15
- HKZLPVFGJNLROG-UHFFFAOYSA-M silver monochloride Chemical compound [Cl-].[Ag+] HKZLPVFGJNLROG-UHFFFAOYSA-M 0.000 claims description 15
- 150000003057 platinum Chemical class 0.000 claims description 14
- 239000012085 test solution Substances 0.000 claims description 12
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims description 10
- 239000007864 aqueous solution Substances 0.000 claims description 7
- 238000002360 preparation method Methods 0.000 claims description 7
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 5
- 238000005259 measurement Methods 0.000 claims description 5
- 238000007772 electroless plating Methods 0.000 claims description 4
- GTKRFUAGOKINCA-UHFFFAOYSA-M chlorosilver;silver Chemical compound [Ag].[Ag]Cl GTKRFUAGOKINCA-UHFFFAOYSA-M 0.000 claims description 3
- DHCDFWKWKRSZHF-UHFFFAOYSA-N sulfurothioic S-acid Chemical compound OS(O)(=O)=S DHCDFWKWKRSZHF-UHFFFAOYSA-N 0.000 claims description 3
- 230000006866 deterioration Effects 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 26
- 238000011156 evaluation Methods 0.000 description 13
- 230000015572 biosynthetic process Effects 0.000 description 10
- -1 alkali metal salts Chemical class 0.000 description 9
- 230000008021 deposition Effects 0.000 description 7
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 6
- 239000002253 acid Substances 0.000 description 6
- 239000012490 blank solution Substances 0.000 description 6
- CLSUSRZJUQMOHH-UHFFFAOYSA-L platinum dichloride Chemical compound Cl[Pt]Cl CLSUSRZJUQMOHH-UHFFFAOYSA-L 0.000 description 6
- 238000006722 reduction reaction Methods 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000010187 selection method Methods 0.000 description 3
- LMPMFQXUJXPWSL-UHFFFAOYSA-N 3-(3-sulfopropyldisulfanyl)propane-1-sulfonic acid Chemical compound OS(=O)(=O)CCCSSCCCS(O)(=O)=O LMPMFQXUJXPWSL-UHFFFAOYSA-N 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- PIICEJLVQHRZGT-UHFFFAOYSA-N Ethylenediamine Chemical compound NCCN PIICEJLVQHRZGT-UHFFFAOYSA-N 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000008139 complexing agent Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
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- KGRJUMGAEQQVFK-UHFFFAOYSA-L platinum(2+);dibromide Chemical compound Br[Pt]Br KGRJUMGAEQQVFK-UHFFFAOYSA-L 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- AKHNMLFCWUSKQB-UHFFFAOYSA-L sodium thiosulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=S AKHNMLFCWUSKQB-UHFFFAOYSA-L 0.000 description 2
- 235000019345 sodium thiosulphate Nutrition 0.000 description 2
- FRTIVUOKBXDGPD-UHFFFAOYSA-M sodium;3-sulfanylpropane-1-sulfonate Chemical compound [Na+].[O-]S(=O)(=O)CCCS FRTIVUOKBXDGPD-UHFFFAOYSA-M 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerol Natural products OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229920003171 Poly (ethylene oxide) Polymers 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- YTGJWQPHMWSCST-UHFFFAOYSA-N Tiopronin Chemical compound CC(S)C(=O)NCC(O)=O YTGJWQPHMWSCST-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 150000005215 alkyl ethers Chemical class 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- IXSUHTFXKKBBJP-UHFFFAOYSA-L azanide;platinum(2+);dinitrite Chemical compound [NH2-].[NH2-].[Pt+2].[O-]N=O.[O-]N=O IXSUHTFXKKBBJP-UHFFFAOYSA-L 0.000 description 1
- 239000003788 bath preparation Substances 0.000 description 1
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- 239000002932 luster Substances 0.000 description 1
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- 238000007254 oxidation reaction Methods 0.000 description 1
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- 229910052700 potassium Inorganic materials 0.000 description 1
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- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052979 sodium sulfide Inorganic materials 0.000 description 1
- GRVFOGOEDUUMBP-UHFFFAOYSA-N sodium sulfide (anhydrous) Chemical group [Na+].[Na+].[S-2] GRVFOGOEDUUMBP-UHFFFAOYSA-N 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- UVZICZIVKIMRNE-UHFFFAOYSA-N thiodiacetic acid Chemical group OC(=O)CSCC(O)=O UVZICZIVKIMRNE-UHFFFAOYSA-N 0.000 description 1
- 229960004402 tiopronin Drugs 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
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Description
本件出願は、無電解白金めっき液用安定剤の選定方法及び無電解白金めっき液に関する。 The present application relates to a method of selecting a stabilizer for an electroless platinum plating solution and an electroless platinum plating solution.
従来から、白金めっきは、耐腐食性に優れ、良好な電気伝導度を示し、美麗な金属光沢をもつため、配線基板の端子めっき、触媒の表面被覆、装飾品の表面修飾等に広く利用されてきた。そして、この白金めっきを行うにあたり、無電解白金めっき法が使用されてきた。 Conventionally, platinum plating has excellent corrosion resistance, exhibits good electrical conductivity, and has a beautiful metallic luster, so it is widely used for terminal plating of wiring boards, surface coating of catalysts, surface modification of decorative articles, etc. It has And in performing this platinum plating, the electroless platinum plating method has been used.
この無電解白金めっき法は、白金塩と還元剤とによる化学的な還元反応を利用して、被めっき対象物表面に白金被膜を形成させるものである。このときの無電解白金めっき液に含有させる還元剤として、ヒドラジンが用いられてきたが、ヒドラジンは環境及び人体に影響を与えると言われ、作業環境及び排水処理負荷が大きくなるという問題がある。 In this electroless platinum plating method, a platinum film is formed on the surface of an object to be plated by utilizing a chemical reduction reaction between a platinum salt and a reducing agent. Hydrazine has been used as a reducing agent to be contained in the electroless platinum plating solution at this time, but hydrazine is said to affect the environment and the human body, and there is a problem that the working environment and waste water treatment load become large.
そこで、この問題を解決するために、特許文献１及び非特許文献１に開示されているような、無電解白金めっき液の還元剤として水素化ホウ素ナトリウムを用いた無電解白金めっき液が検討されている。そして、このような無電解白金めっき液においては、溶液の長期安定性に欠けるため、安定剤として硫黄化合物を用いている。 Therefore, in order to solve this problem, an electroless platinum plating solution using sodium borohydride as a reducing agent for the electroless platinum plating solution as disclosed in Patent Document 1 and Non-patent Document 1 is studied. ing. And, in such an electroless platinum plating solution, a sulfur compound is used as a stabilizer because the solution lacks long-term stability.
しかしながら、市場において知られている水素化ホウ素ナトリウムを用いた無電解白金めっき液の溶液寿命は依然として短いと言われている。また、無電解白金めっき液に安定剤として含有させた硫黄化合物は、白金表面における還元剤の酸化反応を抑制するように機能して、被めっき対象物表面への白金の析出速度が低下することがある。 However, the solution life of electroless platinum plating solutions using sodium borohydride known in the market is said to be still short. In addition, the sulfur compound contained as a stabilizer in the electroless platinum plating solution functions to suppress the oxidation reaction of the reducing agent on the platinum surface, and the deposition rate of platinum on the surface of the object to be plated is reduced. There is.
上述のことから理解できるように、市場では、溶液寿命が長く、被めっき対象物表面への白金の析出速度の速い水素化ホウ素ナトリウムを用いた無電解白金めっき液が望まれてきた。 As understood from the above, in the market, an electroless platinum plating solution using sodium borohydride having a long solution life and a high deposition rate of platinum on the surface of the object to be plated has been desired.
そこで、本件出願の発明者等は、無電解白金めっき液の安定剤として使用する最適な硫黄化合物に関する研究を、鋭意実施している中で安定剤として硫黄化合物を用いる無電解白金めっき液の分極特性に着目して、以下の発明に想到した。 Therefore, the inventors of the present application are keenly carrying out research on an optimum sulfur compound to be used as a stabilizer for the electroless platinum plating solution, and the polarization of the electroless platinum plating solution using the sulfur compound as a stabilizer. Focusing on the characteristics, the following invention was conceived.
＜無電解白金めっき液用安定剤の選定方法＞
本件出願に係る無電解白金めっき液用安定剤の選定方法は、白金塩と還元剤と安定剤とを含有する無電解白金めっき液に用いる安定剤の選定方法であって、以下の手順で安定剤としての硫黄化合物の適否を判断することを特徴とする。
<Method of selecting a stabilizer for electroless platinum plating solution>
The method of selecting a stabilizer for an electroless platinum plating solution according to the present application is a method of selecting a stabilizer used for an electroless platinum plating solution containing a platinum salt, a reducing agent and a stabilizer, and is stabilized by the following procedure It is characterized by judging the propriety of the sulfur compound as an agent.
選定試験溶液の調製： 水酸化ナトリウム濃度が０．２５ｍｏｌ／ｄｍ３，水素化ホウ素ナトリウム濃度が０．１ｍｏｌ／ｄｍ３の基本混合水溶液とし、ここに選定する硫黄化合物を０．００５×１０−３ｍｏｌ／ｄｍ３〜０．０５０×１０−３ｍｏｌ／ｄｍ３の濃度となるように添加し、溶液ｐＨは１３．５，溶液温度２５℃の選定試験溶液を調製する。
分極電位測定： 作用電極として白金円板、補助電極として白金線、参照電極として銀−塩化銀電極を用い、これらを当該選定試験溶液中に配置して、参照電極に対する作用電極の電位を自然電位から貴な電位方向へ０．００２Ｖ／ｓｅｃ．の速度で電位走査し、所定の測定電位における作用電極と補助電極間の電流を測定し、分極曲線（電位−電流曲線）を得る。
安定剤としての適否判断： 前記選定試験溶液の分極曲線において、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備え、、かつ、当該硫黄化合物を用いて無電解白金めっき液を調製した場合に無電解めっき液が溶液変質無く４週間以上保管可能な硫黄化合物を無電解白金めっき液に使用可能と判断する。
Preparation of selected test solution: A basic mixed aqueous solution with a sodium hydroxide concentration of 0.25 mol / dm 3 and a sodium borohydride concentration of 0.1 mol / dm 3 is used, and the sulfur compound to be selected here is 0.005 × 10 −3 It was added at a concentration of mol / dm 3 ~0.050 × 10 -3 mol / dm 3, the solution pH is 13.5, the preparation of a selected test solution having a temperature of 25 ° C..
Polarization potential measurement: A platinum disk as a working electrode, a platinum wire as an auxiliary electrode, and a silver-silver chloride electrode as a reference electrode, which are disposed in the selected test solution to make the potential of the working electrode relative to the reference electrode a natural potential From the potential to 0.002 V / sec. The potential scan is performed at the speed of, the current between the working electrode and the auxiliary electrode at a predetermined measured potential is measured, and a polarization curve (potential-current curve) is obtained.
Judgment of suitability as a stabilizer: In the polarization curve of the selected test solution, it has a polarization characteristic in which the potential at 0.25 A / dm 2 falls within the range of −0.7 V to −0.8 V vs Ag / AgCl , and When the electroless platinum plating solution is prepared using the sulfur compound, it is judged that the electroless plating solution can use a sulfur compound which can be stored for 4 weeks or more without deterioration of the solution , as the electroless platinum plating solution.
＜無電解白金めっき液＞
本件出願に係る無電解白金めっき液は、白金塩と還元剤と安定剤とを含有する無電解白金めっき液であって、当該還元剤が、水素化ホウ素ナトリウムであり、当該安定剤が、上述の無電解白金めっき液用安定剤の選定方法で選ばれた硫黄化合物であるチオプロニン、チオ尿素、チオ硫酸のいずれかを０．００５×１０−３ｍｏｌ／ｄｍ３〜０．０５０×１０−３ｍｏｌ／ｄｍ３濃度の範囲で含有し、分極曲線において、０．２５Ａ／ｄｍ ２ における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備えることを特徴とする。
<Electroless platinum plating solution>
The electroless platinum plating solution according to the present application is an electroless platinum plating solution containing a platinum salt, a reducing agent and a stabilizer, wherein the reducing agent is sodium borohydride, and the stabilizer is the above-mentioned. The sulfur compounds selected by the method of selecting a stabilizer for electroless platinum plating solution of any of thioproine, thiourea and thiosulfuric acid are 0.005 × 10 −3 mol / dm 3 to 0.050 × 10 −3 It is characterized by including polarization characteristics in the concentration range of mol / dm 3 and having a potential at 0.25 A / dm 2 in the range of −0.7 V to −0.8 V vs Ag / AgCl in the polarization curve. Do.
無電解白金めっき液用安定剤の選定方法： 本件出願に係る無電解白金めっき液用安定剤の選定方法を用いて、無電解白金めっき液に用いる安定剤として機能する硫黄化合物を選定する。そして、この硫黄化合物を安定剤として用いた無電解白金めっき液は、溶液寿命が長く、被めっき対象物表面への白金の析出速度が速いものとなる。 Method of Selecting Stabilizer for Electroless Platinum Plating Solution: Using the method of selecting a stabilizer for electroless platinum plating solution according to the present application, a sulfur compound which functions as a stabilizer used in the electroless platinum plating solution is selected. And, the electroless platinum plating solution using this sulfur compound as a stabilizer has a long solution life and a high deposition rate of platinum on the surface of the object to be plated.
以下、発明の実施の形態に関して述べるが、説明の都合上、後述する実施例及び比較例の評価結果を利用する場合がある。 Hereinafter, although an embodiment of the invention is described, evaluation results of examples and comparative examples described later may be used for convenience of explanation.
＜無電解白金めっき液用安定剤の選定方法の形態＞
本件出願に係る無電解白金めっき液用安定剤の選定方法は、白金塩と還元剤と安定剤とを含有する無電解白金めっき液に用いる安定剤の選定方法である。以下、選定するための手順に従って説明する。
<Form of selection method of stabilizer for electroless platinum plating solution>
The method of selecting a stabilizer for an electroless platinum plating solution according to the present application is a method of selecting a stabilizer used in an electroless platinum plating solution containing a platinum salt, a reducing agent and a stabilizer. Hereinafter, description will be made according to the procedure for selecting.
選定試験溶液の調製： ここでいう無電解白金めっき液用安定剤とは硫黄化合物のことであり、後述する分極電位測定を選定に用いる。従って、所定の溶液中に当該硫黄化合物を含ませた溶液を調製する必要がある。このとき、水に対して、水酸化ナトリウム濃度が０．２５ｍｏｌ／ｄｍ３、水素化ホウ素ナトリウム濃度が０．１ｍｏｌ／ｄｍ３の基本混合水溶液とし、ここに選定する硫黄化合物を０．００５×１０−３ｍｏｌ／ｄｍ３〜０．０５０×１０−３ｍｏｌ／ｄｍ３の濃度となるように添加し、溶液ｐＨは１３．５，溶液温度２５℃の選定試験溶液を調製する。ここで硫黄化合物の濃度が０．００５×１０−３ｍｏｌ／ｄｍ３未満の場合には、硫黄化合物が少なすぎて、硫黄化合物の安定剤としての効果が期待できないからである。一方、硫黄化合物の濃度が０．０５０×１０−３ｍｏｌ／ｄｍ３を超えても特段の問題はないが、これ以上の濃度の安定剤添加を必要とする要請がない。 Preparation of Selection Test Solution: The stabilizer for an electroless platinum plating solution as referred to herein is a sulfur compound, and the polarization potential measurement described later is used for selection. Therefore, it is necessary to prepare a solution in which the sulfur compound is contained in a predetermined solution. At this time, a basic mixed aqueous solution containing sodium hydroxide at a concentration of 0.25 mol / dm 3 and sodium borohydride at a concentration of 0.1 mol / dm 3 with respect to water is used, and the sulfur compound selected here is 0.005 × 10. was added such that the -3 mol / dm 3 ~0.050 concentration of × 10 -3 mol / dm 3, the solution pH is 13.5, the preparation of a selected test solution having a temperature of 25 ° C.. Here, when the concentration of the sulfur compound is less than 0.005 × 10 −3 mol / dm 3 , the amount of the sulfur compound is too small, and the effect of the sulfur compound as a stabilizer can not be expected. On the other hand, there is no particular problem if the concentration of the sulfur compound exceeds 0.050 × 10 −3 mol / dm 3 , but there is no request for the addition of a stabilizer at a concentration higher than this.
分極電位測定： 作用電極として白金円板、補助電極として白金線、参照電極として銀−塩化銀電極を用い、これらを当該選定試験溶液中に配置して、参照電極に対する作用電極の電位を自然電位から貴な電位方向へ０．００２Ｖ／ｓｅｃ．の速度で電位走査し、所定の測定電位における作用電極と補助電極間の電流を測定する。図１に示した分極曲線（電位−電流曲線）を得る。 Polarization potential measurement: A platinum disk as a working electrode, a platinum wire as an auxiliary electrode, and a silver-silver chloride electrode as a reference electrode, which are disposed in the selected test solution to make the potential of the working electrode relative to the reference electrode a natural potential From the potential to 0.002 V / sec. The potential scan is performed at the speed of, and the current between the working electrode and the auxiliary electrode at a predetermined measurement potential is measured. The polarization curve (potential-current curve) shown in FIG. 1 is obtained.
安定剤としての適否判断： 前記選定試験溶液の分極曲線において、０．２５Ａ／ｄｍ２（図１の電流軸においては約１８０μＡに相当）における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備える硫黄化合物を無電解白金めっき液に使用可能と判断する。無電解白金めっき液に添加する添加剤の濃度を調整することで、この範囲に入れることが可能である。しかしながら、単にこの範囲に入れることと、添加した成分が無電解白金めっき液中で安定に存在するか否かは別の問題となる。この点に関しては後述する。 Judgment of suitability as a stabilizer: In the polarization curve of the selected test solution, the potential at 0.25 A / dm 2 (corresponding to about 180 μA in the current axis of FIG. 1) is −0.7 V to −0.8 V vs Ag / It is judged that a sulfur compound having polarization characteristics falling within the range of AgCl can be used for the electroless platinum plating solution. It is possible to enter this range by adjusting the concentration of the additive added to the electroless platinum plating solution. However, simply putting in this range and whether or not the added component is stably present in the electroless platinum plating solution is another problem. This point will be described later.
＜無電解白金めっき液＞
本件出願に係る無電解白金めっき液は、白金塩と還元剤と安定剤とを含有する無電解白金めっき液であって、当該還元剤が、水素化ホウ素ナトリウムであり、当該安定剤として上述の無電解白金めっき液用安定剤の選定方法で選ばれた硫黄化合物を０．０１５×１０−３ｍｏｌ／ｄｍ３〜０．０５０×１０−３ｍｏｌ／ｄｍ３濃度の範囲で含有することを特徴とする。本件出願に係る無電解白金めっき液は、当該還元剤として「水素化ホウ素ナトリウム」を用いることを前提としている。
<Electroless platinum plating solution>
The electroless platinum plating solution according to the present application is an electroless platinum plating solution containing a platinum salt, a reducing agent and a stabilizer, wherein the reducing agent is sodium borohydride, and the above-mentioned as the stabilizer. A sulfur compound selected by the method of selecting a stabilizer for an electroless platinum plating solution is contained in a range of 0.015 × 10 −3 mol / dm 3 to 0.050 × 10 −3 mol / dm 3 concentration. I assume. The electroless platinum plating solution according to the present application is premised on using “sodium borohydride” as the reducing agent.
本件出願に係る無電解白金めっき液において、白金塩として、塩化白金（ＩＶ）酸、塩化白金（ＩＩ）酸、臭化白金（ＩＶ）酸、臭化白金（ＩＩ）酸、ヘキサヒドロオクソ白金（ＩＶ）酸、ジニトロジアンミン白金（ＩＩ）及びこれらのアルカリ金属塩（カリウム、ナトリウム等のアルカリ金属塩）またはアンモニウム塩を用いることができる。しかし、溶液としての安定性を考慮すると、塩化白金（ＩＶ）酸アンモニウムを用いることが好ましい。そして、本件出願に係る無電解白金めっき液において、白金塩を０．００１ｍｏｌ／ｄｍ３〜０．０５０ｍｏｌ／ｄｍ３濃度の範囲で含有することが好ましい。白金塩の濃度が０．００１ｍｏｌ／ｄｍ３未満の場合には、白金めっき皮膜の形成速度が低くなるため工業的使用が困難となる。白金塩の濃度が０．０２０ｍｏｌ／ｄｍ３を超えると、形成する白金めっき皮膜の表面が粗くなるため好ましくない。 In the electroless platinum plating solution according to the present application, as a platinum salt, platinum chloride (IV) acid, platinum chloride (II) acid, platinum bromide (IV) acid, platinum bromide (II) acid, hexahydrooxoplatinum (platinum chloride (II) IV) Acid, dinitrodiammine platinum (II) and alkali metal salts thereof (alkali metal salts such as potassium and sodium) or ammonium salts can be used. However, in view of the stability as a solution, it is preferable to use ammonium chloroplatinate (IV). And, in the electroless platinum plating solution according to the present application, it is preferable to contain a platinum salt in the range of 0.001 mol / dm 3 to 0.050 mol / dm 3 concentration. When the concentration of the platinum salt is less than 0.001 mol / dm 3 , the rate of formation of the platinum plating film is low, which makes industrial use difficult. When the concentration of the platinum salt exceeds 0.020 mol / dm 3 , the surface of the platinum plating film to be formed becomes unfavorably roughened.
本件出願に係る無電解白金めっき液において、上述の白金塩濃度の範囲を考えると、白金塩から供給される白金イオンを還元するための還元剤である水素化ホウ素ナトリウムは、０．００４ｍｏｌ／ｄｍ３〜０．０５０ｍｏｌ／ｄｍ３濃度の範囲で含有させることが好ましい。還元剤である水素化ホウ素ナトリウムが０．００４ｍｏｌ／ｄｍ３未満の場合には、還元速度が遅く、且つ、白金イオンの十分な還元ができないため好ましくない。一方、還元剤である水素化ホウ素ナトリウムが０．０５０ｍｏｌ／ｄｍ３を超えるようにしても、還元効率が飽和し、白金めっき皮膜の形成速度も向上しないからである。 In the electroless platinum plating solution according to the present application, considering the above range of platinum salt concentration, sodium borohydride which is a reducing agent for reducing platinum ions supplied from the platinum salt is 0.004 mol / dm it is preferably contained in 3 ~0.050mol / dm 3 concentration ranging. If the reducing agent sodium borohydride is less than 0.004 mol / dm 3 , the reduction rate is slow and the platinum ion can not be sufficiently reduced. On the other hand, even if sodium borohydride which is a reducing agent is made to exceed 0.050 mol / dm 3 , the reduction efficiency is saturated, and the formation rate of the platinum plating film is not improved.
そして、無電解白金めっき液用安定剤の選定方法で選ばれた硫黄化合物として、チオプロニン、チオ尿素、チオ硫酸ナトリウムのいずれかを用いることが好ましい。この研究において、ＭＰＳ（３−メルカプト−1−プロパンスルホン酸 ナトリウム）、ＳＰＳ（ビス（３−スルホプロピル）ジスルフィド）は、無電解白金めっき液中で分解しめっき液性状が変化するため、安定しためっき性能が発揮できないと考えられ好ましくない。これらを用いた無電解白金めっき液が、後述する適正な分極曲線を示すからである。これらの無電解白金めっき液用安定剤としての硫黄化合物は、無電解白金めっき液中に０．００５×１０−３ｍｏｌ／ｄｍ３〜０．０５０×１０−３ｍｏｌ／ｄｍ３濃度の範囲で含有することが好ましい。この硫黄化合物濃度が０．００５×１０−３ｍｏｌ／ｄｍ３未満の場合には、安定剤としての機能を果たさず、溶液寿命が短くなるため好ましくない。一方、硫黄化合物濃度が０．０５０×１０−３ｍｏｌ／ｄｍ３を超える場合には、過剰に無電解白金めっき液の溶液特性が安定化するため、白金の無電解析出速度が遅くなるため好ましくない。 And as a sulfur compound chosen by the selection method of the stabilizer for non-electrolytic platinum plating solutions, it is preferable to use either thioproin, thiourea, or sodium thiosulfate. In this study, MPS (sodium 3-mercapto-1-propanesulfonate) and SPS (bis (3-sulfopropyl) disulfide) were stabilized in the electroless platinum plating solution and changed in the plating solution properties, so they were stable. It is considered that the plating performance can not be exhibited, which is not preferable. It is because the electroless platinum plating solution using these exhibits the suitable polarization curve mentioned later. The sulfur compound as a stabilizer for these electroless platinum plating solutions has a concentration of 0.005 × 10 −3 mol / dm 3 to 0.050 × 10 −3 mol / dm 3 in the electroless platinum plating solution. It is preferable to contain. If the concentration of the sulfur compound is less than 0.005 × 10 −3 mol / dm 3 , it does not function as a stabilizer and the solution life is shortened, which is not preferable. On the other hand, when the concentration of the sulfur compound exceeds 0.050 × 10 −3 mol / dm 3 , the solution characteristics of the electroless platinum plating solution are excessively stabilized, and the rate of electroless deposition of platinum is slow, which is preferable. Absent.
その他、本件出願に係る無電解白金めっき液の場合、錯化剤としてエチレンジアミン、平滑化剤としてポリオキシエチレンアルキルエーテル、ポリアルキルフェニルエーテル、グリセリンエステル、ポリグリセリンエステル、ソルビタンエステル等を含ませることも好ましい。錯化剤としての濃度は、０．０５ｍｏｌ／ｄｍ３〜０．５ｍｏｌ／ｄｍ３、平滑化剤としての濃度は１ｐｐｍ〜１００ｐｐｍの範囲が好ましい。また、ｐＨ調整剤としては、水酸化ナトリウムを用いることが好ましい。 In addition, in the case of the electroless platinum plating solution according to the present application, ethylenediamine as a complexing agent, polyoxyethylene alkyl ether as a leveling agent, polyalkylphenyl ether, glycerin ester, polyglycerin ester, sorbitan ester, etc. may also be included. preferable. Concentration as complexing agent, 0.05mol / dm 3 ~0.5mol / dm 3, the concentration of the leveling agents in the range of 1ppm~100ppm is preferred. Moreover, it is preferable to use sodium hydroxide as a pH adjuster.
以上に述べてきた無電解白金めっき液は、溶液ｐＨ＝９〜１３、溶液温度＝４０℃〜７０℃の範囲で用いることが好ましい。この溶液ｐＨの調製には、水酸化ナトリウム、水酸化カリウム等を用いることが好ましい。溶液ｐＨが８未満では白金めっき皮膜の形成が困難である。一方、溶液ｐＨが１３を超えても、特段の問題はないが、白金めっき皮膜の形成速度が飽和するため不経済である。そして、溶液温度が４０℃未満になると無電解白金めっき皮膜の形成が極度に遅くなるため好ましくない。一方、溶液温度が７０℃を超えると、水分蒸発が顕著になり、溶液性状が短時間で変動するため、溶液管理が煩雑となり好ましくない。 The electroless platinum plating solution described above is preferably used in the range of solution pH = 9 to 13, solution temperature = 40 ° C. to 70 ° C. Sodium hydroxide, potassium hydroxide or the like is preferably used to adjust the solution pH. If the solution pH is less than 8, formation of a platinum plating film is difficult. On the other hand, even if the solution pH exceeds 13, there is no particular problem, but it is uneconomical because the formation rate of the platinum plating film is saturated. When the solution temperature is less than 40 ° C., the formation of the electroless platinum plating film becomes extremely slow, which is not preferable. On the other hand, when the solution temperature exceeds 70 ° C., evaporation of water becomes remarkable, and the solution property fluctuates in a short time, so that solution management becomes complicated, which is not preferable.
実施例１では、塩化白金（ＩＶ）酸アンモニウム（０．００５ｍｏｌ／ｄｍ３），水素化ホウ素ナトリウム（０．０１３ｍｏｌ／ｄｍ３），水酸化ナトリウム（０．２５ｍｏｌ／ｄｍ３），エチレンジアミン（０．１７ｍｏｌ／ｄｍ３）の基本混合水溶液に、硫黄化合物であるチオプロニンを０．０３１×１０−３ｍｏｌ／ｄｍ３濃度となるように添加して、０．２５Ａ／ｄｍ２における電位が−０．７５Ｖ ｖｓ Ａｇ／ＡｇＣｌの分極特性を示す無電解白金めっき液を調製した。図１において符号１（図面中では○で囲んだ数字で示している。）で示したのが実施例１における無電解白金めっき液の分極曲線である。 In Example 1, chloroplatinic (IV) ammonium (0.005 mol / dm 3), sodium borohydride (0.013 mol / dm 3), sodium hydroxide (0.25 mol / dm 3), ethylenediamine (0. Thiopronin, which is a sulfur compound, is added to a basic mixed aqueous solution of 17 mol / dm 3 ) so as to have a concentration of 0.031 × 10 −3 mol / dm 3, and the potential at 0.25 A / dm 2 is −0.75 V The electroless platinum plating solution which shows the polarization characteristic of vs. Ag / AgCl was prepared. The polarization curve of the electroless platinum plating solution in Example 1 is shown in FIG. 1 by reference numeral 1 (indicated by a circled number in the drawing).
そして、被めっき対象物として銅板（１０ｍｍ×１０ｍｍ）を用い、浸漬脱脂（５０℃，４分）、ソフトエッチング（３０℃，１分）、酸洗浄（３０℃，１分）、白金触媒付与（５０℃，３分）の順で前処理した後、溶液温度６０℃とした無電解白金めっき液（溶液ｐＨ＝１２．３）に１０分間浸漬し、無電解白金めっきを行った。種々の評価に関しては、以下の表１に示す。 Then, using a copper plate (10 mm × 10 mm) as an object to be plated, immersion degreasing (50 ° C., 4 minutes), soft etching (30 ° C., 1 minute), acid cleaning (30 ° C., 1 minute), platinum catalyst application ( After pre-treating in the order of 50 ° C., 3 minutes), the substrate was immersed in an electroless platinum plating solution (solution pH = 12.3) at a solution temperature of 60 ° C. for 10 minutes to perform electroless platinum plating. The various evaluations are shown in Table 1 below.
実施例２では、実施例１の基本混合水溶液に、硫黄化合物であるチオ尿素を０．０１３×１０−３ｍｏｌ／ｄｍ３濃度となるように添加して、０．２５Ａ／ｄｍ２における電位が−０．７５Ｖ ｖｓ Ａｇ／ＡｇＣｌの分極特性を示す無電解白金めっき液を調製した。その他の条件等は実施例１と同様であり、重複した説明は省略する。なお、この分極曲線は、実施例１に近似しており、掲載を省略した。評価に関しては、以下の表１に示す。 In Example 2, thiourea which is a sulfur compound is added to the basic mixed aqueous solution of Example 1 so as to have a concentration of 0.013 × 10 −3 mol / dm 3, and the potential at 0.25 A / dm 2 is An electroless platinum plating solution having polarization characteristics of -0.75 V vs Ag / AgCl was prepared. The other conditions and the like are the same as in the first embodiment, and duplicate explanations are omitted. The polarization curve is similar to that of Example 1, and the description is omitted. The evaluation is shown in Table 1 below.
実施例３では、実施例１の基本混合水溶液に、硫黄化合物であるチオ硫酸を０．００６２×１０−３ｍｏｌ／ｄｍ３濃度となるように添加して、０．２５Ａ／ｄｍ２における電位が−０．７５Ｖ ｖｓ Ａｇ／ＡｇＣｌの分極特性を示す無電解白金めっき液を調製した。その他の条件等は実施例１と同様であり、重複した説明は省略する。なお、この分極曲線は、実施例１に近似しており、掲載を省略した。評価に関しては、以下の表１に示す。 In Example 3, thiosulfuric acid which is a sulfur compound is added to the basic mixed aqueous solution of Example 1 so as to have a concentration of 0.0062 × 10 −3 mol / dm 3, and the potential at 0.25 A / dm 2 is An electroless platinum plating solution having polarization characteristics of -0.75 V vs Ag / AgCl was prepared. The other conditions and the like are the same as in the first embodiment, and duplicate explanations are omitted. The polarization curve is similar to that of Example 1, and the description is omitted. The evaluation is shown in Table 1 below.
［比較例１］
実施例１の硫黄化合物をＳＰＳ（ビス（３−スルホプロピル）ジスルフィド）に代え、０．２５Ａ／ｄｍ２における電位が−０．７５Ｖ ｖｓ Ａｇ／ＡｇＣｌの分極特性を示す無電解白金めっき液を調製した。その他の条件等は実施例１と同様であり、重複した説明は省略する。図１において符号２（図面中では○で囲んだ数字で示している。）で示したのが比較例１における無電解白金めっき液の分極曲線である。評価に関しては、以下の表１に示す。
Comparative Example 1
The sulfur compound of Example 1 was replaced with SPS (bis (3-sulfopropyl) disulfide) to prepare an electroless platinum plating solution exhibiting a polarization characteristic of −0.75 V vs Ag / AgCl at a potential of 0.25 A / dm 2 did. The other conditions and the like are the same as in the first embodiment, and duplicate explanations are omitted. The polarization curve of the electroless platinum plating solution in Comparative Example 1 is shown by reference numeral 2 (indicated by a circled number in the drawing) in FIG. The evaluation is shown in Table 1 below.
［比較例２］
実施例１の硫黄化合物を２，２’−チオ二酢酸に代え、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備えていない無電解白金めっき液を調製した。その他の条件等は実施例１と同様であり、重複した説明は省略する。図１において符号ａで示したのが比較例２における無電解白金めっき液の分極曲線である。評価に関しては、以下の表１に示す。
Comparative Example 2
The sulfur compound of Example 1 is replaced with 2,2′-thiodiacetic acid, and the polarization characteristic is obtained such that the potential at 0.25 A / dm 2 falls within the range of −0.7 V to −0.8 V vs Ag / AgCl. An electroless platinum plating solution was prepared. The other conditions and the like are the same as in the first embodiment, and duplicate explanations are omitted. The polarization curve of the electroless platinum plating solution in Comparative Example 2 is shown by symbol a in FIG. The evaluation is shown in Table 1 below.
［比較例３］
実施例１の硫黄化合物をチオ硫酸ナトリウムに代え、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備えていない無電解白金めっき液を調製した。その他の条件等は実施例１と同様であり、重複した説明は省略する。図１において符号ｂで示したのが比較例３における無電解白金めっき液の分極曲線である。評価に関しては、以下の表１に示す。
Comparative Example 3
Electroless platinum plating which does not have polarization characteristics in which the sulfur compound of Example 1 is replaced with sodium thiosulfate and the potential at 0.25 A / dm 2 falls within the range of −0.7 V to −0.8 V vs Ag / AgCl. The solution was prepared. The other conditions and the like are the same as in the first embodiment, and duplicate explanations are omitted. The polarization curve of the electroless platinum plating solution in Comparative Example 3 is shown by symbol b in FIG. The evaluation is shown in Table 1 below.
［比較例４］
実施例１の硫黄化合物をチオ尿素に代え、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備えていない無電解白金めっき液を調製した。その他の条件等は実施例１と同様であり、重複した説明は省略する。図１において符号ｃで示したのが比較例４における無電解白金めっき液の分極曲線である。評価に関しては、以下の表１に示す。
Comparative Example 4
Electroless platinum plating solution having no polarization characteristic in which the sulfur compound of Example 1 is replaced with thiourea and the potential at 0.25 A / dm 2 falls within the range of −0.7 V to −0.8 V vs Ag / AgCl Was prepared. The other conditions and the like are the same as in the first embodiment, and duplicate explanations are omitted. The polarization curve of the electroless platinum plating solution in Comparative Example 4 is shown by symbol c in FIG. The evaluation is shown in Table 1 below.
［比較例５］
実施例１の硫黄化合物を硫化ナトリウムに代え、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備えていない無電解白金めっき液を調製した。その他の条件等は実施例１と同様であり、重複した説明は省略する。図１において符号ｄで示したのが比較例５における無電解白金めっき液の分極曲線である。評価に関しては、以下の表１に示す。
Comparative Example 5
Electroless platinum plating solution having no polarization characteristic in which the sulfur compound of Example 1 is replaced with sodium sulfide and the potential at 0.25 A / dm 2 falls within the range of −0.7 V to −0.8 V vs Ag / AgCl Was prepared. The other conditions and the like are the same as in the first embodiment, and duplicate explanations are omitted. The polarization curve of the electroless platinum plating solution in Comparative Example 5 is shown by symbol d in FIG. The evaluation is shown in Table 1 below.
［ブランク溶液］
このブランク溶液は、上述した硫黄化合物を含んでいない「基本混合水溶液」であり、水酸化ナトリウムおよび水素化ホウ素ナトリウムのみを含むものである。図１において符号Ｂｌで示したのがブランク溶液の分極曲線である。評価に関しては、以下の表１に示す。
[Blank solution]
This blank solution is a "basic mixed aqueous solution" which does not contain the above-mentioned sulfur compound, and contains only sodium hydroxide and sodium borohydride. The polarization curve of the blank solution is shown by the symbol Bl in FIG. The evaluation is shown in Table 1 below.
＜実施例と比較例との対比＞
以下に述べる実施例と比較例との対比を行うにあたり、対比結果の理解を容易とするため表１を示す。
<Comparison between Example and Comparative Example>
Table 1 is shown in order to facilitate understanding of the comparison result when performing comparison between the example described below and the comparative example.
表１に示す溶液安定性評価は、無電解白金めっき液をポリプロピレン製容器に入れ、室温環境下で白金が還元析出するまでの時間を計ることを基本とした。但し、無電解白金めっき液の調製途中、液温調整過程で不具合が生じた場合には溶液安定性がないと判断した。そこで、表１の溶液安定性評価をみると、実施例１〜実施例３の無電解白金めっき液は、ポリプロピレン製容器に入れ、室温環境下で白金が還元析出することなく４週間以上保管できている。しかし、比較例１の無電解白金めっき液は、建浴直後においては何ら問題が無いが、数日以内にＳＰＳが分解して溶液の性状が変化していく。そして、比較例２の無電解白金めっき液とブランク溶液とは、非常に不安定な溶液であり、無電解めっき処理を行おうとして加温する途中で、めっき槽内に白金が還元析出している。また、比較例３〜比較例５の無電解白金めっき液の場合、加温途中で白金が還元析出するという不具合は生じないが、無電解白金めっき皮膜の形成が困難であったため、溶液安定性評価の対象としていない。 The solution stability evaluation shown in Table 1 was based on putting the electroless platinum plating solution in a polypropylene container and measuring the time until the platinum was reduced and deposited under a room temperature environment. However, during the preparation of the electroless platinum plating solution, it was determined that there was no solution stability if a problem occurred in the process of adjusting the solution temperature. Therefore, looking at the solution stability evaluation in Table 1, the electroless platinum plating solutions of Examples 1 to 3 can be placed in a polypropylene container and stored for at least 4 weeks without reduction precipitation of platinum in a room temperature environment. ing. However, although the electroless platinum plating solution of Comparative Example 1 has no problem immediately after the bath preparation, SPS is decomposed within several days to change the property of the solution. The electroless platinum plating solution and the blank solution of Comparative Example 2 are very unstable solutions, and platinum is reduced and precipitated in the plating tank during heating to perform electroless plating. There is. Moreover, in the case of the electroless platinum plating solutions of Comparative Example 3 to Comparative Example 5, although the problem that platinum is reduced and deposited during heating does not occur, the formation of the electroless platinum plating film is difficult, so the solution stability Not considered for evaluation.
次に、白金めっき皮膜の目視による形成状況を観察している。表１には、「白金皮膜形成状況」として結果を掲載している。表１から分かるように、確実に無電解白金めっきが可能なのは、実施例１〜実施例２及び比較例１のみである。但し、比較例１に関しては、建浴直後からＳＰＳの分解が進行して溶液性状が変化していくため、析出速度も遅く実用上使用が困難と判断できる。よって、図１の符号２として示した分極曲線は、建浴直後のものである。そして、比較例３〜比較例５の無電解白金めっき液の場合、使用した硫黄化合物の無電解白金めっき液用安定剤としての効果が過剰であるため、無電解白金めっき皮膜の形成が困難であると考えられる。そのため無電解白金めっき皮膜の形成ができないと推測できる。なお、比較例２及びブランク溶液の場合は、無電解白金めっき液を加温する途中で、めっき槽内に白金が還元析出したので、無電解めっき処理を行わなかった。そして、実施例１〜実施例３で銅板上に形成した白金めっき皮膜は，蛍光Ｘ線膜厚計で膜厚を測定し，膜厚と浸漬時間との関係から析出速度を換算している。 Next, the formation condition by visual observation of the platinum plating film is observed. Table 1 shows the results as "the state of platinum film formation". As can be seen from Table 1, it is only Examples 1 to 2 and Comparative Example 1 that the electroless platinum plating can be reliably performed. However, with regard to Comparative Example 1, since decomposition of SPS proceeds immediately after construction and the solution properties change, the deposition rate is slow and it can be determined that it is practically difficult to use. Therefore, the polarization curve shown as symbol 2 in FIG. 1 is the one immediately after bathing. In the case of the electroless platinum plating solutions of Comparative Examples 3 to 5, the effect of the used sulfur compound as a stabilizer for an electroless platinum plating solution is excessive, so that formation of an electroless platinum plating film is difficult. It is believed that there is. Therefore, it can be inferred that formation of an electroless platinum plating film can not be performed. In the case of Comparative Example 2 and the blank solution, platinum was reduced and precipitated in the plating tank during heating of the electroless platinum plating solution, so the electroless plating treatment was not performed. And the platinum plating film formed on the copper plate in Example 1- Example 3 measures a film thickness with a fluorescent-X-ray film thickness meter, and has converted the deposition rate from the relationship between a film thickness and immersion time.
ここで、図１をみると、実施例１〜実施例３の分極曲線は、ブランク溶液と比較例２との分極曲線グループと、比較例３〜比較例５の分極曲線グループとの間に位置している。即ち、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備えている。 Here, referring to FIG. 1, the polarization curves of Example 1 to Example 3 are positioned between the polarization curve group of the blank solution and Comparative Example 2 and the polarization curve group of Comparative Examples 3 to 5. doing. That is, it has a polarization characteristic in which the potential at 0.25 A / dm 2 falls within the range of -0.7 V to -0.8 V vs Ag / AgCl.
更に、「実施例２と比較例４」、「実施例３と比較例３」との対比から、使用する硫黄化合物の種類が同じでも、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を発揮する量を含まなければ良好な無電解白金めっき液が得られないことが理解できる。 Furthermore, from the comparison between “Example 2 and Comparative Example 4” and “Example 3 and Comparative Example 3”, the potential at 0.25 A / dm 2 is −0.7 V even when the type of sulfur compound to be used is the same. It can be understood that a good electroless platinum plating solution can not be obtained if it does not contain an amount that exhibits polarization characteristics falling within the range of -0.8 V vs Ag / AgCl.
本件出願に係る無電解白金めっき液用安定剤の選定方法は、溶液寿命が長く、被めっき対象物表面への白金の析出速度が速い無電解白金めっき液の安定剤（硫黄化合物）選定に効果を発揮する。そして、この選定方法で得られた硫黄化合物は、環境及び人体に影響を与える還元剤であるヒドラジンに代えて水素化ホウ素ナトリウムを還元剤として用いる無電解白金めっき液に有用である。無電解白金めっきは、プリント配線板、チップ部品端子等の電子部品材料、装飾品の表面修飾等に有用である。 The method for selecting a stabilizer for an electroless platinum plating solution according to the present application is effective in selecting a stabilizer (sulfur compound) for an electroless platinum plating solution which has a long solution life and a high deposition rate of platinum on the surface of the object to be plated. Demonstrate. The sulfur compound obtained by this selection method is useful for an electroless platinum plating solution which uses sodium borohydride as a reducing agent in place of hydrazine which is a reducing agent that affects the environment and human body. Electroless platinum plating is useful for surface modification of electronic component materials such as printed wiring boards, chip component terminals, etc., decorative articles, and the like.
Claims (2)
以下の手順で安定剤としての硫黄化合物の適否を判断することを特徴とする無電解白金めっき液用安定剤の選定方法。
選定試験溶液の調製： 水酸化ナトリウム濃度が０．２５ｍｏｌ／ｄｍ３，水素化ホウ素ナトリウム濃度が０．１ｍｏｌ／ｄｍ３の基本混合水溶液とし、ここに選定する硫黄化合物を０．００５×１０−３ｍｏｌ／ｄｍ３〜０．０５０×１０−３ｍｏｌ／ｄｍ３の濃度となるように添加し、溶液ｐＨは１３．５，溶液温度２５℃の選定試験溶液を調製する。
分極電位測定： 作用電極として白金円板、補助電極として白金線、参照電極として銀−塩化銀電極を用い、これらを当該選定試験溶液中に配置して、参照電極に対する作用電極の電位を自然電位から貴な電位方向へ０．００２Ｖ／ｓｅｃ．の速度で電位走査し、所定の測定電位における作用電極と補助電極間の電流を測定し、分極曲線（電位−電流曲線）を得る。
安定剤としての適否判断： 前記選定試験溶液の分極曲線において、０．２５Ａ／ｄｍ２における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備え、、かつ、当該硫黄化合物を用いて無電解白金めっき液を調製した場合に無電解めっき液が溶液変質無く４週間以上保管可能な硫黄化合物を無電解白金めっき液に使用可能と判断する。 A method of selecting a stabilizer used in an electroless platinum plating solution containing a platinum salt, a reducing agent and a stabilizer,
A method of selecting a stabilizer for an electroless platinum plating solution, which comprises determining the suitability of a sulfur compound as a stabilizer according to the following procedure.
Preparation of selected test solution: A basic mixed aqueous solution with a sodium hydroxide concentration of 0.25 mol / dm 3 and a sodium borohydride concentration of 0.1 mol / dm 3 is used, and the sulfur compound to be selected here is 0.005 × 10 −3 It was added at a concentration of mol / dm 3 ~0.050 × 10 -3 mol / dm 3, the solution pH is 13.5, the preparation of a selected test solution having a temperature of 25 ° C..
Polarization potential measurement: A platinum disk as a working electrode, a platinum wire as an auxiliary electrode, and a silver-silver chloride electrode as a reference electrode, which are disposed in the selected test solution to make the potential of the working electrode relative to the reference electrode a natural potential From the potential to 0.002 V / sec. The potential scan is performed at the speed of, the current between the working electrode and the auxiliary electrode at a predetermined measured potential is measured, and a polarization curve (potential-current curve) is obtained.
Judgment of suitability as a stabilizer: In the polarization curve of the selected test solution, it has a polarization characteristic in which the potential at 0.25 A / dm 2 falls within the range of −0.7 V to −0.8 V vs Ag / AgCl , and When the electroless platinum plating solution is prepared using the sulfur compound, it is judged that the electroless plating solution can use a sulfur compound which can be stored for 4 weeks or more without deterioration of the solution , as the electroless platinum plating solution.
当該還元剤が、水素化ホウ素ナトリウムであり、
当該安定剤が、請求項１に記載の無電解白金めっき液用安定剤の選定方法で選ばれた硫黄化合物であるチオプロニン、チオ尿素、チオ硫酸のいずれかを０．００５×１０−３ｍｏｌ／ｄｍ３〜０．０５０×１０−３ｍｏｌ／ｄｍ３濃度の範囲で含有し、
分極曲線において、０．２５Ａ／ｄｍ ２ における電位が−０．７Ｖ〜−０．８Ｖ ｖｓ Ａｇ／ＡｇＣｌの範囲内になる分極特性を備えることを特徴とする無電解白金めっき液。 An electroless platinum plating solution comprising a platinum salt, a reducing agent and a stabilizer,
The reducing agent is sodium borohydride,
The stabilizer is any one of thioproine, thiourea and thiosulfuric acid which is a sulfur compound selected by the method of selecting a stabilizer for an electroless platinum plating solution according to claim 1 at 0.005 × 10 -3 mol / Containing in the range of dm 3 to 0.050 × 10 -3 mol / dm 3 concentration ,
An electroless platinum plating solution having polarization characteristics in which a potential at 0.25 A / dm 2 falls within a range of -0.7 V to -0.8 V vs Ag / AgCl in a polarization curve .
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