Electroless nickel-plating solution

The present invention relates to an electroless nickel plating solution and a stabilizer for an electroless nickel plating solution.

Electroless nickel plating has excellent film characteristics and good uniform precipitation, and is widely used in various fields such as electronic parts and automobile parts.

One of the problems with electroless nickel plating is that during long-term continuous use, due to poor liquid control and the inclusion of impurities, plating precipitation on parts other than the object to be plated and sudden abnormal precipitation phenomenon, so-called Decomposition of the plating solution may occur.

Therefore, usually, a stabilizer is added to the electroless nickel plating solution so that the decomposition of the plating solution can be suppressed and the plating solution can be used stably for a long period of time. For example, in Patent Document 1 below, Pb²⁺, Cd²⁺, CN^-Etc. have been reported to be effective as stabilizers for electroless nickel plating, and these stabilizers have been widely put into practical use. Further, Non-Patent Document 1 below reports that heavy metals are effective as stabilizers for electroless nickel plating solutions.

However, the Pb reported in the above literature²⁺, Cd²⁺, CN^-, Heavy metals, etc. are known to have an adverse effect on the human body and the environment, and in recent years, movements to eliminate such harmful substances have become active.

For this reason, stabilizers that can replace these are desired, but stabilizers made of highly safe substances that do not adversely affect the precipitation property of the plating solution and the film characteristics have not been found. Is the current situation.<patcit num="1"><text>U.S. Pat. No. 2,762,723</text></patcit><nplcit num="1"><text>J. Elze, J. Metall 14, 1960 2, 104</text></nplcit>

<p> The present invention has been made in view of the current state of the prior art described above, and its main object is to be able to impart good stability without impairing the precipitation property of the electroless nickel plating solution. To provide a stabilizer for electroless nickel plating made of a highly safe substance.</p>

<p> As a result of intensive studies to achieve the above object, the present inventor has found that a phosphine compound represented by a specific general formula has excellent performance as a stabilizer for an electroless nickel plating solution. The present invention has been completed.</p><p> That is, the present invention provides the following electroless nickel plating solution and electroless nickel plating stabilizer. 1. The following general formula:</p><p><chemistry num="1"><img file="JP2005290414A_D0001.tif" /></chemistry>(In the formula, R₁, R₂And R₃Is the same or different, a monovalent aliphatic hydrocarbon group that may have a substituent, an aryl group that may have a substituent, or a heterocyclic group that may have a substituent). A non-electrolytic nickel plating solution containing the phosphine compound to be used as a stabilizer. 2. The electroless nickel plating solution according to Item 1 above, wherein the electroless nickel plating solution is an aqueous solution containing a water-soluble nickel compound, a complexing agent and a reducing agent in addition to the phosphine compound. 3. The following general formula:</p><p><chemistry num="2"><img file="JP2005290414A_D0002.tif" /></chemistry>(In the formula, R₁, R₂And R₃Is the same or different, a monovalent aliphatic hydrocarbon group that may have a substituent, an aryl group that may have a substituent, or a heterocyclic group that may have a substituent). Stabilizer for electroless nickel plating solution, which is composed of a phosphine compound. The stabilizer to be blended in the electroless nickel plating solution of the present invention has the following general formula.</p><p><chemistry num="3"><img file="JP2005290414A_D0003.tif" /></chemistry>It is a phosphine compound represented by.</p><p> In the above general formula, R₁, R₂And R₃Is the same or different monovalent aliphatic hydrocarbon group that may have a substituent, an aryl group that may have a substituent, or a heterocyclic group that may have a substituent.</p><p> Examples of the monovalent aliphatic hydrocarbon group include a linear or branched aliphatic hydrocarbon group having about 1 to 8 carbon atoms and an alicyclic group having about 4 to 10 carbon atoms. Both of these aliphatic hydrocarbon groups and alicyclic groups may contain one or two or more unsaturated bonds such as double bonds and triple bonds.</p><p> Among these monovalent aliphatic hydrocarbon groups, specific examples of the linear or branched aliphatic hydrocarbon group include methyl group, ethyl group, n-propyl group, isopropyl group and n-butyl. Alkyl groups such as groups, sec.-butyl groups, tert.-butyl groups, pentyl groups, hexyl groups, heptyl groups, octyl groups; vinyl groups, propenyl groups, propazienyl groups, butenyl groups, butazienyl groups, pentenyl groups, pentadienyl groups. , Hexenyl group, hexadienyl group, hexatrienyl and other hydrocarbon groups containing one or more double bonds; ethynyl group, propynyl group, propadinyl group, butynyl group, butadynyl group, pentynyl group, pentadiynyl group, hexynyl group. , A hydrocarbon group containing one or more triple bonds such as a hexadiynyl group and a hexatrienyl group can be exemplified. Examples of the alicyclic group include a cyclopentyl group, a cyclohexyl group, a cyclooctyl group, and perhydronaphthalene.</p><p> Examples of the aryl group include a phenyl group and a naphthyl group.</p><p> Examples of the heterocyclic group include a sulfur-containing heterocyclic group such as a thienyl group and a benzothienyl group; an oxygen-containing heterocyclic group such as a frill group, a benzofuranyl group, a pyranyl group, a benzopyranyl group and a chromenyl group; a pyrrolyl group and an imidazolyl group. , Pyrazolyl group, pyridyl group, pyrazinyl group, pyrimidyl group, pyridadinyl group, indridinyl group, indolyl group, indazolyl group, prynyl group, quinolyl group, quinolidienyl group, quinolyl group, phthalazienyl group, naphthidinyl group, quinoxanyl group, quinazolinyl group, cinnolinyl group. A nitrogen-containing heterocyclic group such as a group or a pteridinyl group; a heterocyclic group containing a plurality of heteroatoms such as a thiazolyl group and a benzothiazole group can be exemplified.</p><p> The above-mentioned aliphatic hydrocarbon group, aryl group and heterocyclic group may all contain one or more substituents. Examples of such a substituent include an alkyl group, a phenyl group, a hydroxyl group, a nitro group, a thiol group, a carbonyl group, a carboxyl group, an amino group, a nitrile, a nitro group, a sulfone group, a methoxy group and an ethoxy group.</p><p> Specific examples of the phosphine compound represented by the above general formula include trimethylphosphine, triethylphosphine, tri-n-butylphosphine, tri-tert-butylphosphine, tricyclohexylphosphine, tris (p-methoxyphenyl) phosphine, and tri-. O-trilphosphine, tri-2,4-kisilylphosphine, tribenzylphosphine, triphenylphosphine, diphenylphosphinestyrene, diphenyl-2-pyridylphosphine, tris (3-sulfonatophenyl) phosphine, bis (m-sulfo) Natophenyl) phenylphosphine, 3-sulfotriphenylphosphine, diphenylcyclohexylphosphine, tri (1-naphthyl) phosphine, tris (2-cyanoethyl) phosphine, tris (4,6-dimethyl-3-sulfanatophenyl) phosphine, Examples thereof include methyldiphenylphosphine and diethylphenylphosphine.</p><p> In the present invention, the phosphine compound can be used alone or in combination of two or more.</p><p> The electroless nickel plating solution of the present invention may have the same composition as the known electroless nickel plating solution except that the above-mentioned phosphine compound is contained as a stabilizer.</p><p> Specifically, the electroless nickel plating solution composed of an aqueous solution containing a water-soluble nickel compound, a complexing agent and a reducing agent may be used as a basic bath, and the above-mentioned phosphine compound may be added thereto.</p><p> The concentration of the phosphine compound in the plating solution is preferably about 0.01 mg / l to 100 g / l, and more preferably about 0.02 mg / l to 10 g / l. If the concentration of the phosphine compound is too low, sufficient stability cannot be imparted and the plating solution is easily decomposed, which is not preferable. On the other hand, if the concentration is too high, the precipitation rate of the plating film is lowered and the precipitation reaction may not occur, which is not preferable.</p><p> The water-soluble nickel compound is not particularly limited, and examples thereof include water-soluble nickel inorganic salts such as nickel sulfate, nickel chloride and nickel hypophosphite, and water-soluble nickel organic salts such as nickel acetate and nickel malate. Can be used. These nickel compounds can be used alone or in admixture of two or more.</p><p> The concentration of the water-soluble nickel compound is preferably about 0.001 to 1 mol / l, more preferably about 0.01 to 0.3 mol / l. If the concentration of the water-soluble nickel compound is too low, the deposition rate of the film becomes very slow and it takes a long time to form the film, which is not preferable. On the other hand, if the concentration of the water-soluble nickel compound is too high, the viscosity of the plating solution becomes high, the fluidity of the solution decreases, the uniform precipitation property is adversely affected, and the cost increases, which is not preferable.</p><p> The complexing agent is an effective component for preventing the precipitation of nickel compounds and further accelerating the precipitation reaction of nickel at an appropriate rate, and is a variety of complexing agents used in known electroless nickel plating solutions. Can be used. Specific examples of such complexing agents include dicarboxylic acids such as oxalic acid and adipic acid, soluble salts thereof; oxycarboxylic acids such as malic acid and tartaric acid, soluble salts thereof; aminocarboxylic acids such as glycine and alanine, and the like. Soluble salts; ethylenediamine derivatives such as ethylenediaminetetraacetic acid, versenol (N-hydroxyethylethylenediamine N, N', N'-triacetic acid), quadrol (N, N, N', N'-tetrahydroxyethylethylenediamine), Soluble salts; phosphonic acids such as 1-hydroxyethane-1,1-diphosphonic acid and ethylenediaminetetramethylenephosphonic acid, soluble salts thereof and the like can be mentioned. These complexing agents can be used alone or in admixture of two or more.</p><p> The concentration of the complexing agent varies depending on the type and is not particularly limited, but is usually preferably about 0.001 to 2 mol / l, and more preferably about 0.002 to 1 mol / l. If the concentration of the complexing agent is too low, nickel hydroxide is likely to precipitate, and further, the redox reaction is too fast, so that the plating solution is easily decomposed, which is not preferable. On the other hand, if the concentration of the complexing agent is too high, the precipitation rate of the plating film becomes very slow, and the viscosity of the plating solution becomes high, so that the uniform precipitation property is lowered, which is not preferable.</p><p> As the reducing agent, various reducing agents used in known electroless nickel plating solutions can be used. Specific examples thereof include hypophosphorous acid compounds such as sodium hypophosphate and potassium hypophosphite; boron borohydride compounds such as sodium borohydride, potassium borohydride and dimethylamine borane; hydrazines and the like. Be done.</p><p> The concentration of the reducing agent varies depending on the type and is not particularly limited, but is usually preferably about 0.001 to 1 mol / l, and more preferably about 0.002 to 0.5 mol / l. If the concentration of the reducing agent is too low, the reduction of nickel ions in the plating solution is delayed and it takes time to form a film, which is not preferable. On the other hand, if the concentration of the reducing agent is too high, the plating solution is likely to be decomposed, which is not preferable.</p><p> Further, various known additives contained in the electroless nickel plating solution can be added to the electroless nickel plating solution of the present invention, if necessary. Further, if necessary, the electroless nickel plating solution may be stirred.</p><p> The electroless nickel plating solution of the present invention preferably has a pH of about 3 to 12, more preferably about 4 to 10. If the pH is too low, the smooth progress of the reduction reaction is hindered, the reducing agent is decomposed, the precipitation property of the plating is lowered, and the plating solution may be decomposed, which is not preferable. On the other hand, if the pH is too high, the stability of the plating solution tends to decrease, which is not preferable.</p><p> The liquid temperature for electroless nickel plating varies depending on the specific composition of the plating solution, but is usually preferably about 25 ° C or higher, more preferably about 40 to 100 ° C. .. If the temperature of the plating solution is too low, the plating precipitation reaction becomes slow, and the nickel plating film is likely to be unprecipitated or have a poor appearance. On the other hand, if the temperature of the plating solution is too high, the plating solution evaporates violently, making it difficult to maintain the plating solution composition within a predetermined range, and further, decomposition of the plating solution is likely to occur, which is not preferable.</p><p> The type of the object to be plated is not particularly limited, and the same object as the object of ordinary electroless nickel plating can be used as the object to be plated. Further, for an object to be plated having no catalytic activity such as plastics, electroless nickel plating may be performed after applying a catalyst such as palladium according to a conventional method.</p>

<p> The stabilizer for electroless nickel plating solution of the present invention contains a substance having higher safety than the conventional stabilizer for electroless nickel plating as an active ingredient, and is extremely adverse to the human body and the environment. It is highly useful.</p><p> The electroless nickel plating solution of the present invention containing such a stabilizer can be used stably for a long period of time without causing decomposition or abnormal precipitation of the plating solution, and there is no significant decrease in the precipitation rate, and the electroless nickel plating solution is formed. The appearance of the nickel plating film is also good.</p>

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 Using the electroless nickel plating solution having the following composition as a basic bath, an electroless nickel solution was prepared by adding the additives shown in Table 1 below.

Basic bath composition Nickel sulfate 20g / l Sodium hypophosphate 24g / l Malic acid 16g / l Succinic acid 18g / l

<tables num="1"><img file="JP2005290414A_D0004.tif" /></tables> Samples (5 x 5 cm) of 96% alumina ceramics, mild steel plate (JIS-SPCC SB), and rolled copper plate (JIS-1020 p) using each electroless nickel plating solution containing the additives shown in Table 1. Was used as an object to be plated, and electroless nickel plating was performed at pH 5.2 and a bath temperature of 95 ° C for 1 hour to form an electroless nickel plating film.

The pretreatment process and chemicals used are as follows. 1.96% Alumina Ceramics (1) Solvent degreasing (Trademark name: OPC-370 Condiclean M, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) (2) Catalysis (trade name: OPC-80 catalystist, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) (3) Activation (Trademark name: OPC-505 Accelerator, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) 2. Mild steel plate (1) Immersion degreasing (Trademark name: Ascreen 801, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) (2) Electrolytic degreasing (trade name: Top Cleaner E, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) (3) Acid activity (trade name: Top Acid, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) 3. Rolled copper plate (1) Immersion degreasing (trade name) : Ascreen 801, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) (2) Electrolytic degreasing (trade name: Top Cleaner E, manufactured by Okuno Pharmaceutical Industry Co., Ltd.) (3) Activation (trade name: ICP Axela, Okuno Pharmaceutical Industry Co., Ltd.) Made by Co., Ltd.) The characteristics of each electroless nickel plating film formed by the above method were evaluated by the following method. The results are shown in Table 1 below. 1. Plating deposition rate and phosphorus content Measured using a fluorescent X-ray film thickness meter. 2. Film stress Measured using an electrodeposition strip stress meter. 3. Appearance of film The plating test piece was visually observed and evaluated according to the following criteria. Good: There is no abnormality in the appearance of the plating film, and a uniform plating film is formed on the entire surface. Zara: A state in which a large number of protrusions are confirmed on the surface of the plating film. Non-uniformity: A state in which the plating film is not precipitated or the film thickness is extremely thin for a specific part. 4. Bath stability After the plating treatment was completed, the plating solution was kept at the same temperature as the plating treatment temperature for 3 hours, and then the state of the plating solution was observed.

<tables num="2"><img file="JP2005290414A_D0005.tif" /></tables> As is clear from the above results, the plating solutions 1 to 7 of the present invention containing the phosphine compound can form an electroless nickel plating film having a good appearance without significantly reducing the precipitation rate, and the plating solution is stable. The sex was also very good.

On the other hand, in the comparative plating solution 1 containing no stabilizer, the surface of the electroless nickel plating film to be formed has roughness, and the plating solution is decomposed after the plating is completed, resulting in inferior bath stability. there were. Further, in the comparative plating solution 2 containing lead nitrate as a stabilizer, the electroless nickel plating film formed becomes a non-uniform precipitation state depending on the type of material, and abnormal precipitation occurs when left to stand after the completion of plating. It occurred and was inferior in stability.

Example 2 Using the electroless nickel plating solution having the following composition as a basic bath, an electroless nickel solution to which the additives shown in Table 3 below were added was prepared.

Basic bath composition Nickel sulfate 26.3g / dimethylamine borane 1.5g / l Trisodium citrate 25.8g / l

<tables num="3"><img file="JP2005290414A_D0006.tif" /></tables> Samples (5 x 5 cm) of 96% alumina ceramics, mild steel plate (JIS-SPCC SB), and rolled copper plate (JIS-1020 p) using each electroless nickel plating solution containing the additives shown in Table 3. Was used as an object to be plated, and electroless nickel plating was performed at pH 8.0 and a bath temperature of 70 ° C for 1 hour to form an electroless nickel plating film.

The pretreatment method and the evaluation method are the same as in Example 1. The results are shown in Table 4 below.

<tables num="4"><img file="JP2005290414A_D0007.tif" /></tables> As is clear from the above results, the plating solutions 8 to 14 of the present invention containing the phosphine compound can form an electroless nickel plating film having a good appearance without a significant decrease in the precipitation rate, and have good bath stability. Met.

On the other hand, the comparative plating solution 3 containing no stabilizer was extremely inferior in bath stability because the plating solution was decomposed during electroless plating. Further, in the comparative plating solution 4 containing lead nitrate as a stabilizer, the surface of the electroless nickel plating film to be formed had roughness, and the plating solution was decomposed after the plating was completed, resulting in poor bath stability. ..