JP2001049447A - Aqueous solution of nickel hypophosphite with high concentration and electroless nickel plating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a satisfactory plating film and to prolong the life of a plating soln. by adding an aq.soln. contg. nickel hypophosphite hydrate salt of specified concn. with an complexing agent and increasing the solubility of the nickel hypophosphite hydrate salt. SOLUTION: The aq.soln. of nickel hypophosphite with high concn. is the one contg. nickel hypophosphite hydrate salt and a complexing agent as effective components, and nickel hypophosphirte is contained by the high concn. of>=22 wt.% at the temp. of 25 deg.C. As the nickel hypophosphite hydrate salt, hydrate salt crystallized products such as nickel hypophosphite are given, where nickel hypophosphite expressed by [Ni(H2PO2)2.6H2O and excellent in solubility is preferable. As the complexing agent, glycine, tartaric acid, glycollic acid and EDTA are preferable. The amt. of the complexing agent to be added is controlled to 7-30 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a highly concentrated hypophosphorous acid.
Nickel aqueous solution and electroless nickel plating
Method, more specifically, plating of electroless nickel plating solution.
Metal ion Ni ²⁺And hypophosphite ion as reducing agent
H_TwoPO_Two ^-High concentration, useful as the main drug supply for
Using an aqueous solution containing nickel phosphite and the aqueous solution
And an electroless nickel plating method.

[0002]

2. Description of the Related Art Conventionally, the basic composition of an electroless nickel plating solution is generally a combination of nickel sulfate as a nickel source and sodium hypophosphite as a reducing agent. Sodium hydroxide or ammonium hydroxide is added to maintain the pH. When electroless nickel plating is performed using a plating solution having such a composition, the plating solution contains sodium phosphite, an oxidation product from sodium hypophosphite, and sulfate from nickel sulfate, a nickel source. And sodium sulfate is produced and accumulated with time. For this reason, phenomena such as a decrease in plating speed, abnormal deposition and deterioration of film physical properties are induced, and the plating solution ages. Therefore, the plating solution used for a certain period of time is periodically replenished with insufficient chemical solution, renewed and used repeatedly, but finally the working solution containing high concentrations of sodium sulfate and sodium phosphite is reused as an aging solution. It is disposed of in the ocean without being used. However,
Since 1995, the London Dumping Treaty has banned the disposal of such plating aging solution from the ocean to protect the global environment. Therefore, development of an electroless plating solution capable of extending the life of the electroless plating solution or environmentally friendly disposal is desired.

The present inventors have previously proposed a recyclable electroless nickel plating solution which has a long service life of the plating solution, facilitates disposal of the plating aging solution, and is recyclable.
147882). Such an electroless nickel plating solution contains nickel hypophosphite hexahydrate and nickel hypophosphite pentahydrate as a main supply agent of plating metal ion Ni ²⁺ and hypophosphite ion H ₂ PO ₂ ⁻ as a reducing agent. A hydrated salt crystal of a salt is used. Such a supply form of the nickel hypophosphite hydrate crystal is supplied as a powder as a manufacturer. However, the nickel hypophosphite hydrate crystal has a problem that the composition changes due to the amount of water of crystallization contained or changes over time with the amount of water of crystallization, causing discoloration. The problem becomes an important issue for manufacturers.

[0004]

However, the problem of discoloration can also be solved if the nickel phosphite hydrate crystals can be supplied to the user in a liquid state in which water is dissolved at a high concentration. However, since the solubility of the nickel hypophosphite hydrate crystal is usually as low as 20% by weight at 25 ° C., supply in a liquid form is as follows.
The cost is considerably higher than the powder supply, which is economically disadvantageous.

Japanese Patent Application Laid-Open No. H11-12752 discloses Ni (MS) containing a nickel cation and a hypophosphite anion, wherein the concentration of the nickel cation is 36 g / L or more.
A) and Ni (H ₂ PO ₂₎ nickel hypophosphite solution having a nickel concentration increased with ₂ has been proposed. However, the method of increasing the solubility of an aqueous solution of nickel hypophosphite in this method is simply to an aqueous solution of nickel phosphite obtained by adding nickel carbonate to an aqueous solution of hypophosphorous acid.
Furthermore, the solubility of only the nickel cation is increased by the addition of alkylsulfonic acid, and it does not improve the solubility of the nickel hypophosphite compound itself as in the present invention.

In view of the above problems, the present inventors have studied a method for increasing the solubility of nickel hypophosphite, and as a result, have found that adding a complexing agent to an aqueous solution containing nickel hypophosphite hydrate. As a result, the solubility of the nickel hypophosphite hydrate increases, and even with this high-concentration nickel hypophosphite aqueous solution, a good plating film is formed even when electroless nickel plating is performed, and the plating life is further extended. The inventors have found that the present invention can be performed, and have completed the present invention.

That is, the present invention provides a high-concentration nickel hypophosphite aqueous solution containing nickel hypophosphite to a practical level and an electroless nickel plating method having a long plating solution life and a good plating film. The purpose is to provide.

[0008]

The high-concentration aqueous solution of nickel hypophosphite to be provided by the present invention is an aqueous solution containing a hydrated nickel hypophosphite and a complexing agent as active ingredients. The constitution is characterized in that the concentration of the nickel phosphate hydrate is at least 22% by weight at a temperature of 25 ° C. Further, the electroless nickel plating method provided by the present invention includes a plating metal ion Ni ²⁺ of an electroless nickel plating solution and a hypophosphite ion H ₂ PO ₂ as a reducing agent.
^- characterized in construction to be used as the main supply agent.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The high-concentration nickel hypophosphite aqueous solution of the present invention is an aqueous solution containing a nickel phosphite hydrate and a complexing agent as active ingredients, and has a nickel hypophosphite concentration of 2%.
It is dissolved at a temperature of 5 ° C. at a high concentration of 22% by weight or more.

The hydrated nickel hypophosphite used in the present invention includes hydrated crystals such as pentahydrate and hexahydrate of nickel hypophosphite. The chemical formula [Ni
_{(H 2 PO 2) 2 ·} 6H 2 O] hypophosphite nickel hexahydrate salt represented by are preferred. The method of producing such a nickel hypophosphite hydrate may be in accordance with a known method.For example, a nickel source and a hypophosphorous acid source are reacted in an aqueous system, and the resulting hydrated crystals are separated by crystallization and dried. It should be processed. As a specific example, nickel hypophosphite
A hydrated crystal of hexahydrate can be obtained.

The complexing agent serving as another component includes malic acid, citric acid, glycine, acetic acid, tartaric acid, glycolic acid, EDTA and alkali metal salts thereof. Among these complexing agents, glycine , Tartaric acid, glycolic acid and EDTA are particularly preferred. In addition, one or more of these complexing agents may be used. The addition amount of such a complexing agent is usually 7 to 30% by weight, preferably 7 to 15% by weight. The reason for this is that if the amount of the complexing agent is less than 7% by weight, the effect of increasing the solubility of the nickel hypophosphite hydrate by the addition of the complexing agent is small, while if it is more than 30% by weight, the effect of increasing the solubility is also reduced. It is not preferable because it saturates.

The solubility of the nickel hypophosphite hydrate in the high-concentration nickel hypophosphite aqueous solution of the present invention is usually 22% by weight or more, preferably 25 to 30% by weight at 25 ° C.

Here, the solubility (%) in the present invention means the following general formula:

(Equation 1) It is represented by

Further, as another component, a hypophosphorous acid source such as hypophosphorous acid and sodium hypophosphite can be added. In this case, the molar ratio of H ₂ PO ₂ ⁻ / Ni ²⁺ is usually 2
It is preferable to add them so as to be in the range of ~ 4.

The high-concentration nickel hypophosphite aqueous solution of the present invention is formed by plating metal ions Ni ²⁺ of an electroless nickel plating solution.
And hypophosphite ion H ₂ PO ₂ as a reducing agent ^- useful as primary supply drugs. Here, the metal ion Ni
The main supply agent of ²⁺ and hypophosphite ion H ₂ PO ₂ ⁻ as a reducing agent is a Ni ²⁺ source and a H ₂ PO ₂ ⁻ source used in preparation of a plating bath, and plating during continuous plating. auxiliary supplies the bath Ni ^{2 +} source and H ₂ PO ₂ ^- means a supply drugs both sources, high-concentration hypophosphite aqueous nickel of the present invention is either diluted to the desired concentration, also used as it is be able to.

The composition of the electroless nickel plating solution is as follows:
In a steady state, Ni ²⁺ is in the range of 0.017 to 0.34 mol / liter, H ₂ PO ₂ ⁻ is in the range of 0.017 to 1.0 mol / liter, and H ₂ PO ₂ ⁻ / Ni ²⁺ Is preferably in the range of 2.5 to 4. Also, 80
If the temperature bath to a plating treatment at ℃ above, Ni ²⁺ is 0.
From 017 to 0.085 mol / l, H ₂ PO ₂ ^- 0.
In the case of a low-temperature bath for plating at room temperature to about 60 ° C., Ni ²⁺ is 0.095 to 0.34 mol / L and H ₂ PO ₂ ⁻ is 0.095 to 0.25 mol / L. In the range of 1.0 mol / liter, it is preferable that the bath is controlled within the above molar ratio.

The above-mentioned steady state does not necessarily mean the basic solution composition at the time of building the bath, but refers to a stable state including adjustment of replenishment and recycling of the treatment solution after plating aging.

The electroless nickel plating solution preferably contains, in addition to the above essential components, at least one selected from a chelating agent, a buffer, a pH adjuster and a stabilizer. Examples of the chelating agent include malate, lactate, citrate, tartrate, and amino acid salt.
Used in species or two or more. Examples of the buffer include acetate, succinate, malonate, and the like,
These are used alone or in combination of two or more. Further stabilizers include, for example, acetates such as lead, bismuth and thallium, nitrates and certain sulfur compounds,
These are used alone or in combination of two or more.

The pH of the electroless nickel plating solution is as follows:
It can be adjusted by a pH adjuster, and is 4.5 to 5.5 in an acidic bath.
5. In an alkaline bath, the concentration may be adjusted to 8 to 10 with an alkali agent such as ammonia, an amine compound and caustic.

The electroless nickel plating solution may further contain, if necessary, auxiliary agents used in ordinary electroless nickel plating solutions such as brighteners and surfactants.

[0021]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

<Nickel Hypophosphite Hydrous Crystal> Ni
_{(H 2 PO 2) 2 ·} 6H 2 O} Preparation of> reaction vessel into water 18
5.1 g, 60.7 g of nickel chloride hexahydrate and 54.2 g of sodium hypophosphite monohydrate were charged, and the mixture was heated to 60 ° C. with stirring to react. The total amount of water is 48 times the molar amount of nickel chloride (in terms of anhydrous salt). In about 30 minutes, the reaction end point was reached when all of the raw material nickel chloride had dissolved, and the reaction was continued at 20 ° C.
And crystallized for 2 hours. The obtained crystals were separated by filtration. Next, the obtained crystal in a wet state is dried at 30 ° C. for 2 hours at a degree of vacuum of 0.006 kg / cm ² , and nickel hypophosphite hydrated crystal {Ni (H ₂ PO ₂ ) ₂ .6H ₂ O}
I got

Examples 1 to 6 Nickel hypophosphite hexahydrate prepared as above was treated with water 200
g, to prepare a saturated aqueous solution at 25 ° C., and further, tartaric acid and nickel hypophosphite at the ratios shown in Table 1.
Hexahydrate was added alternately, and the solubility of nickel hypophosphite / hexahydrate at 25 ° C. was measured.

[0024]

[Table 1]

Examples 7-11 Nickel hypophosphite hexahydrate was dissolved in 200 g of water to prepare a saturated aqueous solution at 25 ° C. in the same manner as in Examples 1-6. Glycolic acid and nickel hypophosphite hexahydrate were alternately added at the above ratio, and the solubility of nickel hypophosphite hexahydrate at 25 ° C was measured.

[0026]

[Table 2]

Examples 12 to 13 In the same manner as in Examples 1 to 6, nickel hypophosphite hexahydrate was dissolved in 200 g of water to prepare a saturated aqueous solution at 25 ° C. EDTA and nickel hypophosphite hexahydrate were alternately added at the above ratio, and the solubility of nickel hypophosphite hexahydrate at 25 ° C was measured.

[0028]

[Table 3]

Examples 14 to 16 Nickel hypophosphite hexahydrate was dissolved in 200 g of water in the same manner as in Examples 1 to 6 to prepare a saturated aqueous solution at 25 ° C. Malic acid, citric acid, glycine and nickel hypophosphite hexahydrate were alternately added at the above ratio, and the solubility of nickel hypophosphite hexahydrate at 25 ° C was measured.

[0030]

[Table 4]

Example 17 Nickel hypophosphite hexahydrate 305 g and tartaric acid 225
g was dissolved in 500 ml of water to prepare a 29.6% by weight aqueous solution of nickel hypophosphite having high concentration, which was used as stock solution A, and allowed to stand at room temperature for 30 days. At this time, no crystals were precipitated in the storage solution A, and the state of the solution was extremely stably maintained. In another beaker, 4800 ml of water, 79.2% 50% hypophosphorous acid
g, 50 mg of lead nitrate, 100 g of sodium malate and 100 g of sodium succinate were used as solution B. 500 ml of stock solution A was added to solution B (molar ratio of H ₂ PO ₂ ⁻ / Ni ²⁺ 3.2), the pH was adjusted to 4.5, and the electroless nickel plating solution was placed in a 1 liter glass beaker. . Next, after the temperature was raised to 90 ° C., ten degreased and acid-washed iron plates (5 cm × 10 cm × 0.2 mm) were immersed at once, and electroless nickel plating was performed for 30 minutes. Then
The same process was repeated seven times while replacing the iron plate. In addition,
During the plating operation, a chemical consumed by the plating reaction was supplied by the storage solution A every 30 minutes. Also, adjust the pH of the solution
An aqueous sodium hydroxide solution was constantly replenished to maintain 4.5, and demineralized water was added to replenish evaporating water. By this electroless nickel plating, the iron plate has a thickness of 10.5 μm, a minimum thickness of 9.3 μm, and an average thickness of 9.8.
A μm nickel plating film was deposited, and the formed plating layers were all smooth and exhibited excellent metallic luster. Further, even if the number of times of plating treatment was increased, the deposition rate of plating did not decrease, and the reactivity was good.

Example 18 305 g of nickel hypophosphite hexahydrate and 275 g of glycolic acid were dissolved in 500 ml of water to prepare a 28.2% by weight aqueous solution of nickel hypophosphite having a high concentration.
It was left at room temperature for 30 days. At this time, no crystals were precipitated in the storage solution A, and the state of the solution was extremely stably maintained.
In another beaker, 4800 ml of water, 50% hypophosphorous acid 7
9.2 g, lead nitrate 50 mg, sodium malate 100
g and 100 g of sodium succinate were used as solution B.
Charge 500 ml of stock solution A to solution B (H ₂ PO ₂ ⁻ / Ni
The molar ratio of ²⁺ 3.2) pH was adjusted to 4.5, and the electroless nickel plating solution was placed in a 1-liter glass beaker. Next, after the temperature was raised to 90 ° C., ten degreased and acid-washed iron plates (5 cm × 10 cm × 0.2 mm) were immersed at once, and electroless nickel plating was performed for 30 minutes. Next, the same process was repeated seven times while replacing the iron plate.
During the plating operation, the chemical consumed by the plating reaction was supplied from the storage solution A every 30 minutes. Further, an aqueous sodium hydroxide solution was constantly replenished to maintain the pH of the solution at 4.5, and demineralized water was added to replenish the evaporating water. By this electroless nickel plating treatment, a nickel plating film having a thickness of 10.5 μm, a minimum thickness of 9.3 μm, and an average thickness of 9.8 μm is deposited on the iron plate, and the formed plating layers are all smooth and have excellent metallic luster. Was something. Further, even if the number of times of plating treatment was increased, the deposition rate of plating did not decrease, and the reactivity was good.

Example 19: 230 g of nickel hypophosphite hexahydrate and EDTA12
5 g was dissolved in 500 ml of water to prepare a 26.9% by weight aqueous solution of nickel hypophosphite having high concentration, which was used as a stock solution A, and allowed to stand at room temperature for 30 days. At this time, no crystals were precipitated in the storage solution A, and the state of the solution was extremely stably maintained. In another beaker, 4800 ml of water, 50% hypophosphorous acid
2 g, lead acetate 50 mg, sodium malate 100 g,
100 g of sodium succinate was charged to prepare solution B. The solution B was charged with 500 ml of the stock solution A (the molar ratio of H ₂ PO ₂ ⁻ / Ni ²⁺ was 3.5), the pH was adjusted to 4.5, and the electroless nickel plating solution was placed in a 1-liter glass beaker. .
Next, after the temperature was raised to 90 ° C., ten degreased and acid-washed iron plates (5 cm × 10 cm × 0.2 mm) were immersed at once, and electroless nickel plating was performed for 30 minutes. Next, the same process was repeated seven times while replacing the iron plate. During the plating operation, the chemical consumed by the plating reaction was supplied from the storage solution A every 30 minutes. Also, the p
An aqueous sodium hydroxide solution was constantly replenished to maintain H at 4.5, and demineralized water was added to replenish the evaporating water. By this electroless nickel plating treatment, a nickel plating film having a thickness of 10.2 μm, a minimum thickness of 9.1 μm, and an average thickness of 9.6 μm is deposited on the iron plate, and the formed plating layers are all smooth and have excellent metallic luster. Was something. Further, even if the number of times of plating treatment was increased, the deposition rate of plating did not decrease, and the reactivity was good.

Comparative Example 1 Nickel hypophosphite hexahydrate (200 g) was dissolved in water (800 ml) to prepare a 20.0% by weight aqueous solution of nickel hypophosphite. In another beaker, water 4800m
1, 50% hypophosphorous acid 60.2 g, lead nitrate 50 mg, sodium malate 100 g, sodium succinate 100
g was used as preparation B liquid. The solution B was charged with 500 ml of the stock solution A (the molar ratio of H ₂ PO ₂ ⁻ / Ni ²⁺ was 3.3), and the pH was adjusted to 4.
The bath was adjusted to 5 and the electroless nickel plating solution was placed in a 1-liter glass beaker. Then, after the temperature was raised to 90 ° C., the iron plate (5 cm * 10 cm *) was degreased and acid washed.
(0.2 mm) were immersed at one time, and electroless nickel plating was performed for 30 minutes. Next, the same process was repeated seven times while replacing the iron plate. During the plating operation,
The chemical consumed by the plating reaction was supplied from the storage solution A every 30 minutes. In addition, an aqueous sodium hydroxide solution was constantly replenished to maintain the pH of the solution at 4.5, and demineralized water was added to replenish evaporating water. By this electroless nickel plating treatment, a nickel plating film having a thickness of 10.2 μm, a minimum thickness of 9.1 μm, and an average thickness of 9.6 μm is deposited on the iron plate, and the formed plating layers are all smooth and have excellent metallic luster. Was something. Further, even if the number of times of plating treatment was increased, the deposition rate of plating did not decrease, and the reactivity was good.

As described above, it became possible to increase the concentration of the storage as an aqueous solution of nickel hypophosphite, and it became clear that the performance of the plating solution was not inferior to that of the storage solution of nickel hypophosphite alone. In addition, the electroless nickel plating method using the high-concentration nickel hypophosphite aqueous solution of the present invention is equivalent to the conventional method using nickel hypophosphite hexahydrate previously proposed by the present inventors. It can be seen that a plating film having a good quality can be obtained.

[0036]

As described above, the aqueous solution of nickel hypophosphite of the present invention contains hydrated nickel hypophosphite to a practical level and is stable even when stored for a long period of time. Nickel acid can be supplied to the user in liquid form. Further, the aqueous solution of nickel hypophosphite contains a plating metal ion Ni ²⁺ of an electroless nickel plating solution and a hypophosphite ion H ₂ PO ₂ ⁻ as a reducing agent.
According to the electroless nickel plating method of the present invention which is used as a main supply chemical of the present invention, the life of the plating solution is long and a better plating film can be obtained.

Claims (5)

[Claims] 1. An aqueous solution containing nickel hypophosphite hydrate and a complexing agent as active ingredients, wherein the concentration of nickel hypophosphite is 22% by weight or more at a temperature of 25 ° C. A high-concentration nickel hypophosphite aqueous solution, characterized in that: 2. The nickel hypophosphite hydrate salt is Ni (H ₂
PO ₂₎ nickel hypophosphite represented by ₂ · 6H ₂ O ·
The high-concentration nickel hypophosphite aqueous solution according to claim 1, which is a hexahydrate. 3. The high-concentration nickel hypophosphite aqueous solution according to claim 1, wherein the complexing agent is at least one selected from glycine, tartaric acid, glycolic acid, and EDTA. 4. A highly concentrated aqueous solution of nickel hypophosphite according to claim 1, wherein the amount of the complexing agent is in the range of 7 to 30% by weight. 5. The high concentration nickel hypophosphite aqueous solution according to claim 1, wherein the metal ion Ni ²⁺ of the electroless nickel plating solution and the hypophosphite ion H ₂ as a reducing agent are used.
PO ₂ ^- electroless nickel plating method, which comprises using as the main supply agent.