LT6547B - The solution of chemical platinum deposition and the method of continuous platinum coating formation - Google Patents

Abstract

This invention relates to chemical (autocatalytic) metal deposition processes, particularly chemical deposition of platinum. The invention may be applied for the deposition of platinum coatings on dielectrics, semiconductors, or conductors of complex configurations. This invention aims to reduce the toxicity of chemical platinum deposition solution, simplify and cheapen the method of continuous platinum coating formation. According to the invention continuous platinum coating formation method comprises the surface sensitisation using SnCl2 solution, activation using PdCl2 solution and immersion in a bath with a chemical deposition solution comprising 0.003 to 0.03 M Na2Pt(OH)6 as a platinum (IV) ion source, 0.015 to 0.25 M diisopropanolamine (Dipa) as a ligand, 0.01 to 0.1 M N2H4 hydrazine as a reducer and concentrated acetic acid CH3COOH as pH adjuster to the mixture pH 10.

Description

Technical field

The present invention relates to a platinum coating method using a chemical (direct current) deposition method based on autocatalytic metal ion reduction reactions where the electrons formed during the anodic oxidation of the reducing agent reduce the Pt ⁴⁺ ions to a metal Pt and a platinum chemical deposition solution for this method. The invention can be applied to the deposition of platinum coatings on dielectrics, semiconductors or conductors of complex configuration, e.g., in the manufacture of electronic devices and components, by chemically plating platinum on natural or already coated layers of other materials as a barrier layer, using platinum coatings for effective corrosion protection. , as well as the deposition of the platinum layer as a catalyst for the combustion of propellants on complex configurations and natures in the manufacture of aerospace engines.

State of the art

Currently known solutions of platinum chemical precipitation can be divided into alkaline and acidic.

US 3486928 (30.12.1969) describes a chemical platinum bath using a hexahydroxy platinum (IV) complex as the source of Pt (IV) and hydrazine as a reducing agent. Disadvantages of this solution: above room temperature (35 ° C), carcinogenic ethylenediamine used as a stabilizer in the solution, the hydrazine content of the solution should be constantly added, since at higher hydrazine concentrations Pt (IV) is reduced throughout the solution.

US 3698939 (October 17, 1972) also describes an alkaline solution of platinum chemical precipitation. Disadvantages: temperature above room temperature, strong evaporation of ammonia to maintain pH, solution with at least three different stabilizing additives capable of sorption into a platinum precipitate, addition of hydrazine to solution as Pt (IV) occurs at higher hydrazine concentrations reduction throughout the solution volume.

The acidic solution of platinum chemical precipitation in U.S. Pat. No. 3,562,911 (February 16, 1971) is acidified with hydrochloric acid. The disadvantages of this type of solution are similar to those of alkaline platinum chemical precipitation solutions: the temperature is significantly higher than room temperature, a strong evaporating hydrochloric acid solution is used to maintain the pH, and the solution uses at least four different stabilizing and wetting additives to sorpate the platinum precipitate.

DE 2607988 (11.08.1977) selected cisdiamine Pt (IV) dinitrite as the source of platinum (IV) and sodium nitrite and disodium hydrogen phosphate as stabilizers. In addition to the use of stabilizers, the drawbacks include the high working temperature of the solution (60-95 ° C) and the way in which hydrazine is added in drops rather than all the required amount at once.

JPS 59336667 (08.08.1984) also used cis-diamine Pt (IV) dinitrate as well as hydrazine in the choice of varnish ammonia as the ligand. Hydroxylamine hydrochloride was used as a stabilizer and the working temperature was higher than room temperature (40-50 ° C).

US 6391477 (21.05.2002) used diamine Pt (IV) dinitrite or potassium tetranitroplatinate as the source of Pt (IV). The temperature of this solution was also higher than room temperature and equal to 50 ° C.

In addition to the reducer used in the patents mentioned above, other reducers have been proposed.

The authors of JP 09287078 (04.11.1997) used hydrogen as a reducing agent, borohydride, in the same way as hydrazine. The disadvantages of the proposed platinum chemical precipitation solution relate to the use of carcinogenic amines such as ethylenediamine, ethyleneamine, methylamine, piperidine as ligands and the use of various additives including sulfur.

JP 201037612 (22.03.2016) also used borohydride as a reducing agent and toxic polyethyleneamine as the ligand. It should be noted that, as in the above patent, the main disadvantage is that the resulting coatings necessarily contain elemental boron or boron compounds adsorbed to the reduced platinum, which affects the purity of the platinum coating.

US 9499913 (22.11.2016) A charge transfer reducing agent, the Co (III) / Co (II) redox pair, was used to reduce Pt (IV) in platinum chemical precipitation solutions.

US 9469902 (18.10.2016) also used a charge transfer reducing agent, another redox pair Ti (IV) / Ti (III), for the reduction of Pt (IV) in platinum chemical precipitation solutions. A major disadvantage of the latter two patents is that the processes must take place in an oxygen-free atmosphere, since Co (II) and Ti (III) are readily oxidized to, respectively, Co (III) and Ti (IV). Ensuring such conditions requires a large amount of additional equipment and funds.

Resolving a technical issue

The purpose of the invention is to reduce the toxicity of a platinum chemical deposition solution, to simplify and reduce the cost of forming a continuous platinum coating that allows the deposition of continuous and compact platinum coatings at room temperature and without the additive reduction process and the use of relatively expensive additives.

Disclosure of Invention

According to the present invention, the platinum chemical precipitation solution comprises: 0.0030.03 M Na2Pt (OH) ₆ as a source of platinum (IV) ions, 0.015-0.25 M diisopropanolamine (Dipa) as a ligand, 0.01-0 , 1M hydrazine N2H4 as reducing agent, concentrated acetic acid CH3COOH as pH adjuster to pH 10 of the mixture.

Said solution is from 0.015 M Na2Pt (OH) 6, 0.03 M Dipa, 0.056 M N2H4 and CH3COOH to pH 10.

A method of forming a platinum continuous coating comprising sensitizing a coating surface in a SnCk solution, activating it in a PdCl ₂ solution, and immersing in a bath with a chemical precipitation solution according to any one of claims 1-2.

The concentration of the SnCI ₂ solution used for sensitization is in the range of 0.1-1.0 g / l and the concentration of PdCfe solution used for activation is in the range of 0.05-1.0 g / l. The temperature of said solution during chemical deposition of platinum does not exceed 20 ° C.

The process of chemical precipitation of platinum occurs by passing nitrogen through the solution, which serves as a stirring function and stabilizes the solution.

Utility of the invention

According to the present invention, the platinum chemical precipitation solution is non-toxic because of the use of organic and non-carcinogenic Pt (IV) ligand, and the solution does not contain additional additives which can sorpate into the platinum precipitates.

According to the present invention, the method of forming a platinum coating allows for the deposition of a continuous and compact platinum coating at room temperature and without the addition of a reducer during the process, i. i.e., by chemical precipitation of platinum from the stock solution without the addition of reactive solution components.

When using hydrazine as a reducing agent, which produces only gaseous products in the anodic oxidation reaction and does not contaminate the resulting reduced metallic platinum coatings, the environmentally safe and non-carcinogenic ligand diisopropanolamine (Dipa) was used as Pt (IV) ligand:

HO,, OH (1)

Formula (1). Structural formula of diisopropanolamine (Dipa)

According to the invention, the use of an optimized composition of a platinum chemical precipitation solution employing hydrazine as a reducing agent and diisopropanolamine as a ligand at room temperature provides greater volumetric stability of the solution and prevents the addition of higher hydrazine to the platinum chemical precipitate.

The invention will be explained in more detail by the following drawings, which do not limit the scope of the invention, and which show:

Fig.1 Photograph of SEM (scanning electron microscope) chemically deposited on coarse glass. Coating Deposition Conditions: 0.015 M Na ₂ Pt (OH) ₆ , 0.03 M Dipa, 0.056 MN ₂ H ₄ , CH ₃ COOH to pH 10; 20 ° C, 90 min.

Fig.2 Kinetics of platinum chemical deposition.

Example of embodiment of the invention

Prepare a platinum chemical precipitation solution containing 0.015 M Na ₂ Pt (OH) ₆ , 0.03 M Dipa, 0.056 MN ₂ H ₄ , CH ₃ COOH to pH 10; 20 ° C. Then prepare a coarse glass plate as follows: plate for 1 min. immersed in 0.5 g / l SnCl ₂ sensitization solution, rinsed with deionized water, followed by 1 min. immersed in 0.5 g / l PdCI ₂ activation solution, rinsed with deionized water and immersed in platinum chemical precipitation solution, where the coating is deposited for 90 minutes, allowing nitrogen (bubbling) to act as a stirring solution while stabilizing the solution. there are no additional accessories for this. In 90 minutes remove the coating plate from the solution, rinse with deionized water and dry. A continuous platinum coating is obtained (Fig. 1) and the amount of deposited platinum is about 0.25 mg / cm ² (Fig. 2).

Claims (6)

DEFINITION OF INVENTION 1. A platinum chemical precipitation solution comprising a platinum (IV) ion source, a ligand, a reducing agent and a pH regulator, characterized in that said chemical precipitation solution comprises: - 0.003-0.03 M Na ₂ Pt (OH) ₆ as a source of platinum (IV) ions; - diisopropanolamine Dipa 0.015-0.25 M as ligand; - hydrazine N ₂ H _{4 in a} concentration of 0.01-0.1 M as a reducing agent; - concentrated acetic acid CH ₃ COOH as pH adjuster up to pH 10. 2. A solution according to claim 1, wherein said solution is from 0.015 M Na ₂ Pt (OH) ₆ , 0.03 M Dipa, 0.056 MN ₂ H ₄ and CH ₃ COOH to pH 10. A method of forming a platinum continuous coating comprising sensitizing a coating surface in a SnCI ₂ solution, activating it in a PdCl ₂ solution, and immersing in a bath with a chemical precipitation solution, wherein said chemical precipitation solution is as claimed in any one of claims 1-2. 4. The method of claim 3, wherein the concentration of the SnCl ₂ solution used for sensitization is in the range of 0.1 to 1.0 g / L and the concentration of the PdCl ₂ solution used for activation is in the range of 0.05 to 1.0 g / L. A process according to any one of claims 3 to 4, wherein the temperature of said solution during chemical deposition of platinum does not exceed 20 ° C. 6. A process according to any one of claims 3 to 5, wherein the platinum chemical precipitation process is effected by passing nitrogen through a solution which performs a mixing function and stabilizes the solution.