JP5452458B2 - Nickel plating solution and nickel plating method - Google Patents

Description

  The present invention relates to a nickel plating solution and a nickel plating method using the nickel plating solution. In particular, the present invention relates to a nickel plating solution that does not contain boric acid and carboxylic acid strong organic acid and has a solution pH in a weakly acidic to neutral range.

  Nickel plating film is used in the field of daily necessities that require decorativeness, the field of industrial products that require functions such as rust prevention and gloss, and the field of electronic components that require functions such as conductivity and solder wettability. It is used in a wide range of fields.

  For the formation of the nickel plating film, an acidic nickel plating solution such as a watt bath or a sulfamic acid bath is mainly used. Here, in the acidic nickel plating solution, boric acid has been used as a pH buffering agent for suppressing pH fluctuation in order to form a stable plating film by suppressing erosion of the object to be plated. However, boric acid was specified as a regulated substance in the revised Water Pollution Control Law that came into effect on July 1, 2001. Therefore, a technique using organic acids has been developed as a substitute for boric acid.

  For example, Patent Document 1 does not contain boric acid, which is difficult to treat waste water, and aims to provide a nickel plating bath that does not adversely affect the working environment. A nickel plating bath to which 5 mol / L aliphatic dicarboxylic acid is added is disclosed. As the aliphatic dicarboxylic acid, malonic acid, succinic acid, glutaric acid, and adipic acid are preferable, and the aliphatic dicarboxylic acid is preferably mixed with an aqueous nickel salt solution in advance.

  In Example 1 of Patent Document 1, a nickel plating bath having a solution pH of 4.8 containing nickel sulfate 280 g / L, nickel chloride 50 g / L, malonic acid 5.0 g / L, and nickel carbonate 2.0 g / L is prepared. In addition, as a result of performing nickel plating for 10 minutes at a temperature of 50 ° C. and a current of 2 A in a hull cell tank using a 70 × 100 mm brass plate as the cathode and a nickel plate as the anode, the object to be plated is glossy. It is described that a smooth nickel-plated film with a large thickness was obtained and there was almost no pH fluctuation of the plating bath.

  Patent Document 2 discloses nickel chloride and / or nickel sulfate as a nickel ion source for the purpose of providing a nickel plating bath that is excellent in throwing power, does not use boron, and has a low plating cost. 1 g / L to 20 g / L in terms of nickel ion concentration, citric acid to 50 g / L to 300 g / L in terms of citric acid monohydrate, and the solution pH is adjusted to 6.5 to 10 with ammonia. A technique using a nickel plating bath is disclosed.

  In Examples of Patent Document 2, citric acid monohydrate is 200 g / L in water, nickel chloride hexahydrate is 10 g / L, 20 g / L, 40 g / L, 60 g / L, and 80 g / L. , 100 g / L, and warm to dissolve. Then, concentrated ammonia water was added while measuring the pH of the solution with a pH meter, a hull cell test was carried out using a nickel plating solution whose pH was adjusted to 8.0, and three points were measured with a fluorescent X-ray film thickness meter. The thickness of the plating film is measured. As a result, it is described that the example of Patent Document 2 is more excellent in throwing power as compared with nickel plating using a Watt bath containing boric acid having a solution pH of 4.0.

JP 2001-107284 A JP 2009-62577 A

  However, in the market, nickel plating solutions containing carboxylic acid-based strong organic acids such as malonic acid and citric acid as disclosed in Patent Document 1 and Patent Document 2 are said to have large variations in the quality of the resulting plating film. It has been broken. That is, like the nickel plating solutions disclosed in Patent Document 1 and Patent Document 2, even if a carboxylic acid strong organic acid such as malonic acid or citric acid is contained as a pH buffer, the plating solution is stable for a long time. Thus, it has been difficult to form a stable plating film.

  On the other hand, in the case of a nickel plating solution containing a carboxylic acid strong organic acid as disclosed in Patent Document 1 and Patent Document 2, depending on the solution pH of the prepared nickel plating solution, an object to be plated, particularly ceramics In the case of a material, the surface sometimes eroded and sometimes caused damage.

  From the above, it is possible to suppress the fluctuation of the plating solution pH stably for a long time in the market, and it is possible to obtain a nickel plating film with the same productivity and the same appearance and characteristics as before. In addition, there has been a demand for a nickel plating solution that does not contain a regulated substance in the Water Pollution Control Law and a nickel plating method using the nickel plating solution.

  Therefore, as a result of earnest research, the inventors of the present invention, by using the following nickel plating solution, stable from long acidity to neutrality without containing not only boric acid but also carboxylic acid strong organic acid. It was conceived that nickel plating can be formed while suppressing fluctuations in solution pH between regions.

Nickel plating solution according to the present invention: The nickel plating solution according to the present invention is a nickel plating solution for electroplating containing one or more nickel salts as a source of nickel ions and a pH buffer, and the pH The buffering agent is aminoalkanesulfonic acid or a derivative thereof, and the solution pH is 4.0 to 6.5.

  In the nickel plating solution according to the present invention, the nickel salt is preferably nickel sulfate and nickel chloride, and the content of the nickel salt and aminoalkanesulfonic acid or a derivative thereof is preferably in the following range.

Nickel sulfate hexahydrate: 120 g / L to 480 g / L
Nickel chloride hexahydrate: 15 g / L to 70 g / L
Aminoalkanesulfonic acid or derivative thereof: 30 g / L to 100 g / L

  In the nickel plating solution according to the present invention, the nickel salt is preferably nickel sulfamate and nickel chloride, and the content of the nickel salt and aminoalkanesulfonic acid or a derivative thereof is preferably in the following range.

Nickel sulfamate tetrahydrate: 200 g / L to 600 g / L
Nickel chloride hexahydrate: 1 g / L to 6 g / L
Aminoalkanesulfonic acid or derivative thereof: 30 g / L to 100 g / L

  In the nickel plating solution according to the present invention, the aminoalkanesulfonic acid or a derivative thereof is preferably taurine.

  In addition, the nickel plating solution according to the present invention preferably contains a stress adjusting agent.

  In the nickel plating solution according to the present invention, it is also preferable that the stress adjusting agent is o-sulfobenzoimide and the concentration of o-sulfobenzoimide is 0.1 g / L to 5 g / L.

Nickel plating method according to the present invention: The nickel plating method according to the present invention uses any of the nickel plating solutions described above, the liquid temperature is set to 40 ° C to 60 ° C, and the cathode current density is 0.05 A / dm ^{2 to} 10 A /. Electrolysis is performed at dm ² to form a nickel plating film on the surface of the object to be plated.

Plating product according to the present invention: The plated product according to the present invention is characterized in that a nickel plating film is formed using the nickel plating method described above.

  The nickel plating solution according to the present invention does not contain any substances regulated by the Water Pollution Control Law. Moreover, the nickel plating solution according to the present invention can stably suppress the fluctuation of the solution pH of the plating solution for a long time, and has productivity, plating appearance, and various characteristics comparable to those of the conventional nickel plating solution. A nickel plating film can be formed.

  Further, the nickel plating solution according to the present invention has a solution pH in a weakly acidic to neutral range and does not contain boric acid or a carboxylic acid strong organic acid. For this reason, when a nickel plating film is formed on a chip part, erosion of the ceramic part of the chip part can also be suppressed, and even a chip part having a protective coating layer made of ceramics can be directly plated with nickel. Is possible.

  Furthermore, the nickel plating method according to the present invention does not need to be operated with a reduced current density as compared with the conventional nickel plating method. Therefore, the productivity of the plating film is also improved. Therefore, the nickel plating method using the nickel plating solution according to the present invention is suitable for nickel plating on all objects to be plated that are uneasy about corrosion resistance in addition to chip parts.

It is an observation image (x10,000) by the scanning electron microscope of the nickel plating film obtained in Example 1 and Comparative Example 1. It is an observation image (x10,000) by the scanning electron microscope of the nickel plating film obtained in Example 2 and Comparative Example 2. It is an observation image (x10,000) by the scanning electron microscope of the nickel plating film obtained in Example 3 and Comparative Example 3. It is an observation image (x10,000) by the scanning electron microscope of the nickel plating film obtained in Example 4 and Comparative Example 4. It is an observation image (x10,000) by the scanning electron microscope of the nickel plating film obtained in Example 5 and Comparative Example 5.

1. 1. Form of nickel plating solution according to the present invention 1-1. Technical thought relating to nickel plating solution according to the present invention The nickel plating solution according to the present invention is a nickel plating solution for electroplating containing one or more nickel salts that are nickel ion supply sources and a pH buffer, The pH buffer is aminoalkanesulfonic acid or a derivative thereof, and the solution pH is 4.0 to 6.5.

  In the nickel plating solution according to the present invention, it is a common feature that “aminoalkanesulfonic acid or a derivative thereof” is used as a pH buffer. Aminoalkanesulfonic acid and its derivatives are aminosulfonic acids having a cation center and an anion center in the molecule, and are compounds that exist in a zwitterionic state in a neutral solution pH range. The zwitterion becomes an anion when the contained solution becomes acidic, and becomes a cation when the solution becomes alkaline, thereby exhibiting an effect of buffering the pH of the solution containing itself.

  Here, the content of “aminoalkanesulfonic acid or a derivative thereof” as a pH buffer in the nickel plating solution according to the present invention will be described first. In the nickel plating solution according to the present invention, the content of aminoalkanesulfonic acid or a derivative thereof is preferably 30 g / L to 100 g / L. If the content of aminoalkanesulfonic acid or a derivative thereof is less than 30 g / L, setting the solution pH of the nickel plating solution to around 6.0 is not preferable because the pH buffering effect may not be sufficiently exhibited. On the other hand, even if aminoalkanesulfonic acid or a derivative thereof is contained in excess of 100 g / L, the buffering effect of the solution pH has already reached saturation, and no further effect is observed, which is a waste of resources. Absent. From the above, the content of “aminoalkanesulfonic acid or a derivative thereof” as a pH buffer is determined.

  Furthermore, it is preferable to use taurine among the “aminoalkanesulfonic acids or derivatives thereof” for the nickel plating solution according to the present invention. This taurine has excellent stability in nickel plating solution among “aminoalkanesulfonic acid or its derivatives”, has excellent ability to stabilize solution quality over a long period of time, and has little change in solution pH during plating operation. It is an additive suitable for obtaining a good nickel plating film. Further, taurine is used as an orally administered drug for the human body, has no toxicity, has an advantage of being a compound that is easy to procure on the market and does not increase the load of wastewater treatment.

  In the nickel plating solution according to the present invention, the nickel salt used as a nickel ion supply source is not particularly limited, and the nickel plating film formed by electroplating is nickel sulfamate so that the required characteristics can be satisfied. Selected from nickel chloride, nickel sulfate, nickel acetate and the like, and can be used alone or in combination.

  Furthermore, the nickel plating solution according to the present invention preferably has a solution pH of 4.0 to 6.5. If the solution pH of the nickel plating solution is in a strong acid region of less than 4.0, ceramics may be eroded, which is not preferable because it cannot be used for chip component plating. On the other hand, if the solution pH of the nickel plating solution exceeds 6.5 and becomes alkaline, nickel hydroxide may be generated, and it is difficult to obtain a nickel plating solution having excellent solution stability, which is not preferable.

1-2. Specific Composition of Nickel Plating Solution According to the Present Invention As described above, the nickel plating solution according to the present invention contains aminoalkanesulfonic acid or a derivative thereof as a pH buffer, and “a nickel salt containing nickel sulfate and nickel chloride. The watt bath type nickel plating solution containing "and the" sulfamic acid bath type nickel plating solution containing nickel sulfamate and nickel chloride as nickel salts ". Hereinafter, each nickel plating solution will be described in detail. Regarding the content of “aminoalkanesulfonic acid or a derivative thereof” as a pH buffering agent, the above concept can be applied to any nickel plating solution.

1-2-1. Watt bath type nickel plating solution The Watt bath type nickel plating solution contains 120 g / L to 480 g / L of nickel sulfate hexahydrate and 15 g / L to 70 g / L of nickel chloride hexahydrate. Is preferred. Use as a watt bath-type nickel plating solution within this range is preferable from the viewpoints of current efficiency, film properties, solution stability for long-term storage, sludge is not easily generated, and the like. As far as the blending balance of nickel sulfate hexahydrate and nickel chloride hexahydrate is concerned, there is no particular problem within the above range. The reason why the contents of nickel sulfate hexahydrate and nickel chloride hexahydrate are limited will be described below.

  When the content of nickel sulfate hexahydrate is less than 120 g / L in the watt bath type nickel plating solution, nickel chloride hexahydrate is used to ensure an appropriate nickel concentration as the plating solution. This increases the content ratio of chlorine ion and excessively increases the chlorine ion concentration. This is not preferable because a tendency to obtain a brittle nickel plating film having high internal stress and large lattice distortion is not preferable. On the other hand, when nickel sulfate hexahydrate exceeds 480 g / L, nickel hydroxide is likely to be precipitated at a solution pH of around 6.5, so that the solution stability is lacking, which is not preferable.

  When the nickel chloride hexahydrate is less than 15 g / L in the watt bath type nickel plating solution, the function as a depolarizer cannot be exhibited, and gas is generated from the anode during the plating operation. This is not preferable because the pH of the solution becomes remarkable. On the other hand, when nickel chloride hexahydrate exceeds 70 g / L, the chlorine ion concentration becomes excessive, the internal stress is high, and the tendency to obtain a brittle nickel plating film having a large lattice strain is unfavorably increased.

1-2-2. Nickel plating solution of sulfamic acid bath type Nickel plating solution of sulfamic acid bath type is 200 g / L to 600 g / L of nickel sulfamate tetrahydrate and 1 g / L to 6 g / L of nickel chloride hexahydrate. It is preferable to contain. In the case of a sulfamic acid bath-based nickel plating solution within this range, current efficiency, film properties, solution stability against long-term storage, and sludge are not easily generated, as with the above-described watt bath-based nickel plating solution. From the viewpoint of the above. Moreover, as far as the blending balance of nickel sulfamate tetrahydrate and nickel chloride hexahydrate is concerned, there is no particular problem within the above range. The reason why the contents of nickel sulfamate tetrahydrate and nickel chloride hexahydrate are limited will be described below.

  In a sulfamic acid bath-based nickel plating solution, when the content of nickel sulfamate tetrahydrate is less than 200 g / L, the current efficiency is remarkably lowered, and it is difficult to form a stable nickel plating film. Therefore, it is not preferable. On the other hand, even when nickel sulfamate tetrahydrate exceeds 600 g / L, effects such as improvement of current efficiency and improvement of stability of plating operation cannot be obtained. Rather, the solution viscosity of the plating solution increases, the amount of the plating solution adhering to the object to be plated increases, management of the amount of nickel in the nickel plating solution becomes complicated, and the load of wastewater treatment increases, which is not preferable.

  When the content of nickel chloride hexahydrate is less than 1 g / L in a sulfamic acid bath-based nickel plating solution, it cannot function as a depolarizer, and gas is generated from the anode during the plating operation. However, it is not preferable because a change in solution pH is observed. On the other hand, when nickel chloride hexahydrate exceeds 6 g / L, the chlorine ion concentration becomes excessive, the internal stress is high, and the tendency to obtain a brittle nickel plating film having a large lattice strain is unfavorable. .

1-2-3. Other Additives for Nickel Plating Solution Generally, a plating film obtained by the electrolytic plating method has an internal stress in the lattice of the precipitated crystal. With respect to the nickel plating film obtained under the predetermined electrolytic conditions using the nickel plating solution according to the present invention, internal strain is generated inside the precipitated crystal, and as a result, internal stress is generated. This internal stress is influenced by the components of the plating solution, the solution temperature, the electrolysis conditions, etc., and becomes tensile stress or compressive stress. However, from the viewpoint of improving the adhesion of the nickel plating film to the object to be plated, the nickel plating film preferably has an internal stress in the range of stress-free to compressive stress.

  That is, in the case of a nickel plating solution, when the solution pH and the chlorine ion concentration increase, the internal stress of the nickel plating film tends to shift to the tensile stress side. In such a case, it is preferable to add a stress adjusting agent to the nickel plating solution according to the present invention. This stress modifier is said to be included in the nickel plating film that is adsorbed on the cathode surface and deposited by electrolysis. In particular, in the case of a watt bath type nickel plating solution, it is said that the tensile stress of the nickel plating film tends to increase. Therefore, it is preferable to improve the adhesion between the nickel plating film and the object to be plated by adding a stress adjusting agent to the Watt bath nickel plating solution to adjust the internal stress of the nickel plating film to be formed.

  As such a stress adjusting agent, a sulfur-containing organic compound such as o-sulfobenzoic imide, p-toluenesulfoamide, benzenesulfonic acid or naphthalenetrisulfonic acid can be used. Among these, in the case of the nickel plating solution according to the present invention, it is preferable to use o-sulfobenzoic imide as the stress adjusting agent. This is because o-sulfobenzoimide is easily obtained as a sodium salt among the above-described sulfur-containing organic compounds, has good solubility in water, and has the greatest stress adjustment effect.

  The o-sulfobenzoic acid imide at this time is added so that it may become a density | concentration range of 0.1g / L-5g / L in a nickel plating solution. When the concentration of this o-sulfobenzoic imide is less than 0.1 g / L, the amount of adsorption to the cathode is small, and the effect as a stress adjusting agent cannot be exhibited. On the other hand, when the concentration of o-sulfobenzoimide exceeds 5 g / L, the compressive stress contained in the nickel plating film gradually increases, but improves the adhesion between the nickel plating film and the object to be plated. The effect saturates and does not improve.

  And in the nickel plating solution according to the present invention, in consideration of the effect of the bath composition on the stress of the nickel plating film, the “watt bath type nickel plating solution” and the “sulfamic acid bath type nickel plating solution” The range of the appropriate amount of stress modifier is different. That is, in the case of the Watt bath type nickel plating solution, the concentration of the stress adjusting agent is preferably set in the range of 1 g / L to 5 g / L. In the case of a sulfamic acid bath-based nickel plating solution, the concentration of the stress adjusting agent is more preferably 0.1 g / L to 5 g / L.

Nickel plating form according to the present invention: In the nickel plating method according to the present invention, any of the nickel plating solutions described above is used, the liquid temperature is set to 40 ° C to 60 ° C, and the cathode current density is 0.05 A / dm ^{2 to} 10 A /. Electrolysis is performed at dm ² to form a nickel plating film on the surface of the object to be plated. In this nickel plating method, electrolysis at a higher current density is possible with a sulfamic acid bath-based nickel plating solution than with a Watt bath-based nickel plating solution. However, in order to fully exhibit the characteristics of each nickel plating solution, the watt bath type nickel plating solution is electrolyzed at a cathode current density of 0.05 A / dm ^{2 to} 5 A / dm ² at a liquid temperature of 40 ° C. to 60 ° C. In the sulfamic acid bath-based nickel plating solution, it is more preferable to perform electrolysis at a cathode current density of 0.05 A / dm ^{2 to} 10 A / dm ² at a liquid temperature of 40 ° C. to 60 ° C.

2. Form of plated product according to the present invention The nickel plating solution according to the present invention does not select the type of the object to be plated. Therefore, in the field of various electric nickel plating such as decorative nickel plating applied to automobile parts, nickel plating for forming resistance circuits on conductors of printed wiring boards, and nickel plating applied to chip parts which are electronic parts. Can be used. Therefore, the nickel-plated product according to the present invention means all products in which a nickel plating film is formed using the nickel plating solution and the nickel plating method according to the present invention described above.

  Furthermore, the nickel plating solution according to the present invention has a feature that the solution pH is in a neutral region of 4.0 to 6.5. Therefore, the surface is hardly damaged regardless of the material of the surface of the object to be plated. In consideration of this point, the nickel plating solution according to the present invention is preferably used for an electronic component including a ceramic material that is easily damaged in the case of a strongly acidic or strongly alkaline plating solution. That is, when plating is applied to chip parts that are easily damaged in the case of strong acids or strong alkalis in the field of electronic parts, there is little damage to the ceramic and its protective coating layer, and a good nickel plating film on the conductive parts Can be formed.

  Hereinafter, examples and comparative examples will be shown so that the above-mentioned contents can be understood in more detail. Before describing the examples and comparative examples, the evaluation methods common to all will be described. The nickel plating solution was evaluated based on “change in solution pH before and after electrolysis” and “characteristics of the nickel plating film obtained by electroplating”. Specifically, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were evaluated. At this time, the film stress was measured with a spiral stress meter manufactured by Yamamoto Metal Testing Co., Ltd., and the film hardness was measured with a micro hardness meter (model: MVK-E) manufactured by Akashi Seisakusho. The pinhole is subjected to a ferroxyl test on a nickel plating film having an area of 5 cm × 5 cm, converted to an area of 1 cm × 1 cm, and the uniform electrodeposition is determined by a Haring cell manufactured by Yamamoto Kakin Tester Co., Ltd. evaluated. Further, the surface of the nickel plating film was observed using a scanning electron microscope (hereinafter referred to as “SEM”) at a tilt angle of 0 ° and a magnification of 10,000 times.

Preparation of Nickel Plating Solution: In Example 1, a Watt bath type nickel plating solution (TW1 bath) was prepared. This watt bath type nickel plating solution (TW1 bath) is nickel salt, nickel sulfate hexahydrate concentration of 240 g / L, nickel chloride hexahydrate concentration of 45 g / L, taurine as pH buffering agent. The concentration is 60 g / L, and the solution pH is 4.50 using sulfuric acid or sodium hydroxide solution. Accordingly, the TW1 bath is a watt bath-based nickel plating solution that does not contain a stress modifier. The composition of the TW1 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in other examples and comparative examples.

Preparation and Evaluation of Nickel Plating Film: Electrolysis was carried out at a cathode current density of 5 A / cm ² for 10 minutes using a TW1 bath with a liquid temperature of 45 ° C., a metal nickel plate as the anode and a copper hull cell plate as the cathode. A nickel plating film having a thickness of 2 μm was formed. The solution pH of the TW1 bath after electrolysis for 10 minutes was 4.52. The obtained nickel plating film had a stress of 119 Pa, a hardness of Hv221, a pinhole of 3.3 holes / cm ² , and a uniform electrodeposition of 3.5% for 1: 3 and 5.2 for 1: 5. %Met. The evaluation results of the solution pH of the TW1 bath after electrolysis and the properties of the nickel plating film are shown in Table 2 together with Examples and Comparative Examples. Moreover, the SEM observation image on the surface of the nickel plating film is shown in FIG. 1A together with the SEM observation image on the surface of the nickel plating film obtained in Comparative Example 1.

Preparation of nickel plating solution: In Example 2, the TW1 bath prepared in Example 1 was further added with 1 g / L of a sodium salt of o-sulfobenzoimide as a stress adjusting agent, and a Watt bath having a solution pH of 4.50. It was prepared as a nickel plating solution (TW2 bath). The composition of the TW2 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in other examples and comparative examples.

Preparation and Evaluation of Nickel Plating Film: Electrolysis was performed in the same manner as in Example 1 using a TW2 bath to form a nickel plating film having a thickness of 2 μm. The solution pH of the TW2 bath after electrolysis for 10 minutes was 4.53. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was −94 Pa, the hardness was Hv451, the pinholes were 1.9 pieces / cm ² , and the uniform electrodeposition was 4.2% for 1: 3 and 5.5% for 1: 5. Table 2 summarizes the evaluation results of the solution pH of the TW2 bath after electrolysis and the properties of the nickel plating film. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 2A together with the SEM observation image of the nickel plating film surface obtained in Comparative Example 2.

Preparation of Nickel Plating Solution: In Example 3, sodium naphthalene trisulfonate was added instead of the sodium salt of o-sulfobenzoimide used as a stress adjusting agent in the TW2 bath prepared in Example 2, and a solution pH of 4. Prepared as a 50 watt bath nickel plating solution (TW3 bath). The composition of the TW3 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in other examples and comparative examples.

Preparation and Evaluation of Nickel Plating Film: Electrolysis was performed in the same manner as in Example 1 using a TW3 bath to form a nickel plating film having a thickness of 2 μm. The solution pH of the TW3 bath after electrolysis for 10 minutes was 4.53. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was 111 Pa, the hardness was Hv452, the pinholes were 2.2 holes / cm ² , and the uniform electrodeposition was 4.6% for 1: 3 and 6.3% for 1: 5. Table 2 shows the evaluation results of the solution pH of the TW3 bath and the properties of the nickel plating film after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 3A together with the SEM observation image on the surface of the nickel plating film obtained in Comparative Example 3.

Preparation of Nickel Plating Solution In Example 4, nickel sulfamate tetrahydrate 450 g / L, nickel chloride hexahydrate 3 g / L as nickel salt, taurine 60 g / L as pH buffer, solution pH 4 .50 sulfamic acid bath nickel plating solution (TS4 bath). Therefore, the TS4 bath is a nickel plating solution of a sulfamic acid bath system that does not contain a stress adjusting agent. The solution pH was adjusted using a sulfamic acid solution or a sodium hydroxide solution. The composition of the TS4 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in other examples and comparative examples.

Preparation and evaluation of nickel plating film: Using a TS4 bath, electrolysis was performed in the same manner as in Example 1 to form a nickel plating film having a thickness of 2 μm. The solution pH of the TS4 bath after 10 minutes of electrolysis was 4.53. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was 31.8 Pa, the hardness was Hv228, the pinhole was 1.1 pieces / cm ² , and the throwing power was 4.4% for 1: 3 and 7.1% for 1: 5. . Table 2 shows the evaluation results of the solution pH and nickel plating film characteristics of the TS4 bath after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 4A together with the SEM observation image on the surface of the nickel plating film obtained in Comparative Example 4.

Evaluation of erosion property: TS4 bath evaluated the erosion property of the chip parts. Evaluation was performed using a chip part varistor and a low-temperature co-fired ceramic (hereinafter referred to as “LTCC”), and the amount eroded by immersion in a TS4 bath was evaluated.

  The amount of erosion of the chip parts was measured by a change in mass before and after being immersed in a 45 ° C. TS4 bath for 5 hours. Specifically, about 10 g of a varistor having been weighed and LTCC were separately immersed for 5 hours in a stirring TS4 bath with a liquid volume of 100 ml. After 5 hours, the entire amount of each chip part was pulled up from the TS4 bath, washed with water, drained with a paper towel, and dried at 60 ° C. for 30 minutes using a circulation oven. As a result of measuring the mass of the dried chip part, the mass reduction rate of the varistor was 0.9%, and the mass reduction rate of LTCC was 0.1% or less. The erosion amount of the chip component is shown in Table 2 together with the evaluation result in Comparative Example 4.

Preparation of Nickel Plating Solution: In Example 5, a sulfamic acid bath having a solution pH of 4.50 containing 1 g / L of a sodium salt of o-sulfobenzoic acid imide as a stress modifier with respect to the TS4 bath prepared in Example 4. A nickel plating solution (TS5 bath) was prepared. The composition of the TS5 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in other examples and comparative examples.

Preparation and Evaluation of Nickel Plating Film: Using a TS5 bath, electrolysis was performed in the same manner as in Example 1 to form a nickel plating film having a thickness of 2 μm. The solution pH of the TS5 bath after electrolysis for 10 minutes was 4.53. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was 124 Pa, the hardness was Hv 492, the pinholes were 1.1 pieces / cm ² , and the uniform electrodeposition was 2.8% for 1: 3 and 3.7% for 1: 5. Table 2 shows the evaluation results of the solution pH of the TW5 bath and the properties of the nickel plating film after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 5A together with the SEM observation image on the surface of the nickel plating film obtained in Comparative Example 5.

Comparative example

<Comparative Example 1>
Preparation of nickel plating solution: In Comparative Example 1, in place of 60 g / L of taurine as a pH buffer contained in the TW1 bath prepared in Example 1, 30 g / L of boric acid and a Watt bath system having a solution pH of 4.50 A nickel plating solution (CW1 bath) was prepared. Therefore, the CW1 bath is a conventional Watt bath type nickel plating solution that does not contain a stress modifier. The composition of the CW1 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in the examples and other comparative examples.

Preparation and Evaluation of Nickel Plating Film: Using a CW1 bath, electrolysis was performed in the same manner as in Example 1 to form a nickel plating film having a thickness of 2 μm. The solution pH of the CW1 bath after electrolysis for 10 minutes was 4.57. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was 114 Pa, the hardness was Hv 227, the pinhole was 2.7 pieces / cm ² , and the throwing power was 4.1% for 1: 3 and 4.5% for 1: 5. Table 2 shows the evaluation results of the solution pH and nickel plating film characteristics of the CW1 bath after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG.1 (b) together with the SEM observation image of the nickel plating film surface obtained in Example 1. FIG.

<Comparative example 2>
Preparation of nickel plating solution: In Comparative Example 2, the Watt bath system having a solution pH of 4.50 further containing 1 g / L of sodium salt of o-sulfobenzoimide as a stress adjusting agent with respect to the CW1 bath prepared in Comparative Example 1. A nickel plating solution (CW2 bath) was prepared. The composition of the CW2 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in the examples and other comparative examples.

Preparation and Evaluation of Nickel Plating Film: Electrolysis was performed in the same manner as in Example 1 using a CW2 bath to form a nickel plating film having a thickness of 2 μm. The solution pH of the CW2 bath after electrolysis for 10 minutes was 4.55. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was −92 Pa, the hardness was Hv453, the pinhole was 2.4 holes / cm ² , and the throwing power was 4.4% for 1: 3 and 7.1% for 1: 5. Table 2 shows the evaluation results of the solution pH and nickel plating film characteristics of the CW2 bath after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 2B together with the SEM observation image of the nickel plating film surface obtained in Example 2.

<Comparative Example 3>
Preparation of nickel plating solution: In Comparative Example 3, a Watt bath having a solution pH of 4.50 containing 1 g / L of sodium naphthalene trisulfonate instead of the sodium salt of o-sulfobenzoimide in the CW2 bath prepared in Comparative Example 2 A nickel plating solution (CW3 bath) was prepared. The composition of the CW3 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in the examples and other comparative examples.

Preparation and Evaluation of Nickel Plating Film: Electrolysis was carried out in the same manner as in Example 1 using a CW3 bath to form a nickel plating film having a thickness of 2 μm. The solution pH of the CW3 bath after electrolysis for 10 minutes was 4.55. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was 110 Pa, the hardness was Hv455, the pinhole was 2.7 pieces / cm ² , and the uniform electrodeposition was 3.8% for 1: 3 and 6.2% for 1: 5. Table 2 shows the evaluation results of the solution pH and nickel plating film characteristics of the CW3 bath after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 3B together with the SEM observation image of the nickel plating film surface obtained in Example 3.

<Comparative Example 4>
Preparation of nickel plating solution: In Comparative Example 4, instead of 60 g / L of taurine as a pH buffer contained in the TW4 bath prepared in Example 4, sulfamine having a solution pH of 4.50 so that boric acid is 30 g / L An acid bath nickel plating solution (CS4 bath) was prepared. The composition of the CS4 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in the examples and other comparative examples.

Preparation and Evaluation of Nickel Plating Film: Using a CS4 bath, electrolysis was performed in the same manner as in Example 1 to form a nickel plating film having a thickness of 2 μm. The solution pH of the CS4 bath after electrolysis for 10 minutes was 4.55. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was 30.0 Pa, the hardness was Hv210, the pinhole was 1.3 pieces / cm ² , and the throwing power was 3.9% for 1: 3 and 7.2% for 1: 5. . Table 2 shows the evaluation results of the solution pH and nickel plating film characteristics of the CW4 bath after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 4B together with the SEM observation image of the nickel plating film surface obtained in Example 4.

Evaluation of erosion property: In the same manner as in Example 4, the erosion property of the chip part by the TS4 bath was evaluated. As a result, the mass reduction rate of the varistor was 6.6%, and the mass reduction rate of LTCC was 0.2%. Table 2 shows the amount of erosion of the chip parts together with the evaluation results in Example 4.

<Comparative Example 5>
Preparation of nickel plating solution: In Comparative Example 5, in place of 60 g / L of taurine as a pH buffer contained in the composition of the TS5 bath prepared in Example 5, solution pH 4.50 so that boric acid was 30 g / L. A sulfamic acid bath nickel plating solution (CS5 bath) was prepared. The composition of the CS5 bath is shown in Table 1 together with the compositions of the nickel plating solutions prepared in the examples and other comparative examples.

Preparation and Evaluation of Nickel Plating Film: Electrolysis was performed in the same manner as in Example 1 using a CS5 bath to form a nickel plating film having a thickness of 2 μm. The solution pH of the CS5 bath after electrolysis for 10 minutes was 4.54. Further, the stress, hardness, pinhole and uniform electrodeposition of the obtained nickel plating film were measured in the same manner as in Example 1. As a result, the stress was 99.2 Pa, the hardness was Hv 432, the pinhole was 0.9 pieces / cm ² , and the throwing power was 2.9% for 1: 3 and 3.2% for 1: 5. . Table 2 shows the evaluation results of the solution pH and nickel plating film characteristics of the CW5 bath after electrolysis. Furthermore, the surface of the nickel plating film was observed by SEM in the same manner as in Example 1. This SEM observation image is shown in FIG. 5B together with the SEM observation image of the nickel plating film surface obtained in Example 5.

<Contrast between Example and Comparative Example 1: Change in pH of solution before and after electrolysis>
As shown in Table 2, the solution pH of the nickel plating solution after electrolysis increased by 0.02 to 0.03 in the examples, and increased by 0.04 to 0.07 in the comparative examples. Moreover, when the rise degree of solution pH is contrasted between the same bath compositions, the comparative example is 0.01-0.05 higher than the example. Therefore, a nickel plating solution containing aminoalkanesulfonic acid or a derivative thereof as a pH buffering agent has a smaller change in solution pH when the same electrolysis conditions are employed than when a conventional nickel plating solution is used. That is, it can be determined that the nickel plating solution containing aminoalkanesulfonic acid or a derivative thereof as a pH buffer is a nickel plating solution capable of stable nickel plating over a long period of time.

<Contrast between Example and Comparative Example 2: Film Characteristics>
First, in FIGS. 1-5, the SEM photograph (a) of the nickel plating film surface obtained by the Example and the SEM photograph (b) of the nickel plating film surface obtained by the comparative example are contrasted. 1 to 5, there is no significant difference in appearance between the case where taurine is used as the pH buffering agent and the case where boric acid is used. In addition, as shown in Table 2, there is no significant difference in film characteristics and throwing power. On the other hand, the film characteristics are greatly influenced by the stress modifier in both the Watt bath system and the sulfamic acid bath system. Therefore, even when aminoalkanesulfonic acid or a derivative thereof is used instead of boric acid as a pH buffer, a nickel plating film having the same film characteristics as when a conventional nickel plating solution is used can be obtained. I can judge.

<Contrast of Example and Comparative Example 3: Erosion>
The erodibility of the nickel plating solution to the chip parts is compared in the sulfamic acid baths of Example 4 and Comparative Example 4. However, in Comparative Example 4 containing boric acid as a pH buffering agent, the varistor was 6.6% and LTCC was 0.2% eroded, whereas the erosion amount of Example 4 containing taurine as a pH buffering agent The varistor is 0.9% and the LTCC is 0.1% or less. Therefore, considering that the erosion power of the carboxylic acid system is stronger than that of boric acid, the nickel plating solution of the embodiment containing aminoalkanesulfonic acid or a derivative thereof as a pH buffer is boron-free and at the same time, It can be determined that the nickel plating solution exhibits a great effect in preventing erosion.

  The nickel plating solution according to the present invention does not contain any substances regulated by the Water Pollution Control Law. Therefore, it is a plating solution with very little environmental load / drainage load. In addition, the nickel plating solution according to the present invention can be used for a long period of time and has excellent cost performance because it can stably suppress fluctuations in the pH of the plating solution for a long time.

  This nickel plating solution can be used in all technical fields that require nickel plating. And since the nickel plating liquid which concerns on this invention is a solution pH from weakly acidic to neutral area | region, even if it uses it for nickel plating film formation of the chip components provided with a ceramic site | part, the erosion of the ceramic site | part of a chip component can also be suppressed. .

  In addition, the nickel plating method according to the present invention can be implemented using existing existing equipment and does not require new equipment investment, so that the existing equipment can be used effectively.

Claims (8)

A nickel plating solution containing at least one nickel salt that is a source of nickel ions and a pH buffer,
The nickel plating solution, wherein the pH buffer is aminoalkanesulfonic acid or a derivative thereof, and the solution pH is 4.0 to 6.5. The nickel plating solution according to claim 1, wherein the nickel salt is nickel sulfate and nickel chloride, and the content of the nickel salt and aminoalkanesulfonic acid or a derivative thereof is in the range shown below.
Nickel sulfate hexahydrate: 120 g / L to 480 g / L
Nickel chloride hexahydrate: 15 g / L to 70 g / L
Aminoalkanesulfonic acid or derivative thereof: 30 g / L to 100 g / L The nickel plating solution according to claim 1, wherein the nickel salt is nickel sulfamate and nickel chloride, and the content of the nickel salt and aminoalkanesulfonic acid or a derivative thereof is in the range shown below.
Nickel sulfamate tetrahydrate: 200 g / L to 600 g / L
Nickel chloride hexahydrate: 1 g / L to 6 g / L
Aminoalkanesulfonic acid or derivative thereof: 30 g / L to 100 g / L The nickel plating solution according to any one of claims 1 to 3, wherein the aminoalkanesulfonic acid or a derivative thereof is taurine. The nickel plating solution according to any one of claims 1 to 4, comprising a stress adjusting agent. The nickel plating solution according to claim 5, wherein the stress adjusting agent is o-sulfobenzoic imide, and the concentration of the o-sulfobenzoic imide is 0.1 g / L to 5 g / L. Using the nickel plating solution according to any one of claims 1 to 6, the solution temperature is set to 40 ° C to 60 ° C, and electrolysis is performed at a cathode current density of 0.05 A / dm ^{2 to} 10 A / dm ² to be plated. A nickel plating method comprising forming a nickel plating film on a surface of an object. A plated product, wherein a nickel plating film is formed using the nickel plating method according to claim 7.