JPH10195669A - System for circulating electroless nickel plating solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively reutilize an exhausted electroless nickel plating soln. by removing the HPO3 <2-> and salts from the exhausted soln. consisting essntially of nickel hypophosphite and circulating and returning the treated soln. to the original plating soln. SOLUTION: The exhausted electroless nickel plating soln. contg. nickel hyporphosphite contg. nickel ion and the hypophospite ion as the reducing agent for the nickel ion, chelating agent, buffer, pH regulator, stabilizer, etc., is controlled to pH 6 to 9 by adding Ca(OH)2 , etc., and the HPO3 <2-> is precipitated as calcium phosphate and removed. The soln. remaining after the precipitate is filtered off is passed through an electrodialytic tank, cation-exchange resin, reverse-osmosis membrane, etc., to remove the Na ion, NH4 ion, etc., in the soln. The deficiency of the nickel hypophosphite and other assistants in the soln. obtained is supplied, if necessary, and the soln. is returned to the original electroless nickel plating soln. and recycled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system for circulating an electroless nickel plating solution capable of reusing a plating aging solution.

[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 replenishes the insufficient chemical solution, renews it and uses it repeatedly, but the working solution containing high concentrations of sodium sulfate and sodium phosphite is not finally reused as an aging solution. It is disposed of in the ocean etc. However, in 1995
The London Dumping Treaty has been banning the disposal of such plating aging solutions from the ocean for the protection of 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.

Various attempts have been made to remove sodium phosphite and sodium sulfate accumulated in the course of the above-described electroless nickel plating operation, but none of them has been industrially put to practical use. For example, as a method for removing the sodium phosphite or sodium sulfate, a method using an electrolytic diaphragm, an aluminum plate or an aluminum foil is put into an alkaline plating aging solution to precipitate nickel, and the mother liquor is recovered with nitric acid. A method of adsorbing nickel remaining in a chelate resin (Japanese Patent Laid-Open No. 51-61)
No. 36), nickel ions and sodium ions are separated from the plating solution with an ion exchange resin in advance, adsorbed on the ion exchange resin to separate and desorb sodium and nickel, and then only nickel is returned to the plating solution for reuse. Methods have been proposed. On the spot, a method of discarding a part of the aged plating solution and replenishing a new solution to extend the life is also adopted.

[0004] However, although these methods have elements that are evaluated as partially rational processes, they have not been put into practical use because they have many economic and technical problems. Also, the method of partially discarding the plating aging solution and replenishing the new solution is not a fundamental solution.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an industrially advantageous method capable of reusing an electroless nickel plating aging solution as a plating solution. An object of the present invention is to provide a circulation system for an electrolytic nickel plating solution.

[0006]

Under such circumstances, the present inventors have made intensive studies and as a result, specified the aging solution of a plating solution containing a nickel source and a hypophosphorous acid source in which sulfate does not accumulate. processing steps and specific if the order processing HPO ₃ ^{2 -,} Na ^2+, and NH ₄ ⁺ ions can effectively separated and removed, and also, if recycling the treatment liquid, very efficiently aging solution Was found to be recyclable as a plating solution, and the present invention was completed.

That is, the present invention relates to (A) plating metal ion Ni ²⁺ and hypophosphite ion H ₂ PO ₂ as a reducing agent.
De HPO ₃ for processing the plating aging solution from (B) the step (A); ^- ₂ electroless nickel plating treatment step of the plating solution to plating treatment using a containing hypophosphite nickel as a main supply agent ^- process; (C) desalting step; (D) plating solution after component adjustment, the electroless nickel plating treatment step (A)
And a recycling system for recycling the electroless nickel plating solution.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to the above (A), (B),
This is an electroless nickel plating solution circulation system that sequentially goes through each of the steps (C) and (D), and is described below for each step.

In the step (A) of the present invention, the plating metal ions N
This is an electroless nickel plating step using a plating solution containing i ²⁺ and nickel hypophosphite as a main supply agent of hypophosphite ion H ₂ PO ₂ ⁻ as a reducing agent. Plating metal ions Ni ²⁺ mixed with the above electroless nickel plating solution, hypophosphite ions H ₂ P as a reducing agent
O ₂ ^- The nickel hypophosphite hydrate major supply drug, hydrate crystals such as pentahydrate and hexahydrate of nickel hypophosphite can be mentioned. Of these, Ni (H ₂ PO ₂ )
Hypophosphite nickel hexahydrate salt represented by ₂ · 6H ₂ O are preferable. A liquid substance of nickel hypophosphite is disadvantageous for storing and transporting in a liquid such as an aqueous solution because the solubility of nickel hypophosphite is small, and an anhydrous powder is not preferable because it is easily decomposed.

The method for producing the nickel hypophosphite hydrate may be in accordance with a known method. The nickel source and the hypophosphorous acid source are reacted in an aqueous system, and the resulting hydrous crystals are separated by crystallization. May be dried. Specifically, a hydrous salt crystal of nickel hypophosphite hexahydrate can be obtained by a metathesis reaction between nickel chloride and sodium hypophosphite.

In the present invention, the above Ni ²⁺ source and H ₂ P
The main supply chemicals of O ₂ ⁻ include a Ni ²⁺ source and an H ₂ PO ₂ ⁻ source used for adjusting a plating bath, and a Ni ²⁺ source and an H ₂ PO _{2 which} are auxiliary supplied to a plating bath when plating is continuously performed. ^-
Means both supply agents at the source. In addition, when replenishing nickel hypophosphite hydrate of the supply agent with a building bath or a chemical solution,
It is preferable to use it after diluting and dissolving it to a desired concentration.

[0012] The electroless nickel plating solution, Ni ²⁺ is from 0.017 to 0.34 mol / l, H ₂ PO ₂ ^- is in the range of 0.017 to 1.0 mol / liter, more H ₂ It is preferable that the molar ratio of PO ₂ ⁻ / Ni ^{2+ be} in the range of 1.0 to 4 from the viewpoint of suppressing the formation and accumulation of sulfate groups. In the case of a high-temperature bath in which plating is performed at 80 ° C. or higher, Ni ²⁺ is 0.017 to 0.15 mol / liter, and H ²⁺
₂ PO ₂ ^- is 0.017 to 0.330 mol / l,
In the case of a low-temperature bath in which plating is performed at room temperature to about 60 ° C., Ni ²⁺ contains 0.095 to 0.34 mol / liter,
H ₂ PO ₂ ^- in the range of from 0.095 to 0.472 mol / l, it is preferable to bath control in each of the molar ratio internal.

The electroless nickel plating solution preferably contains at least one selected from chelating agents, buffers, pH adjusters and stabilizers in addition to the above essential components.

Examples of the chelating agent include water-soluble malic acid, lactic acid, citric acid, tartaric acid, amino acids and salts thereof. Among them, the difference in solubility of calcium salt is considered in consideration of regeneration of plating aging solution. Larger ones are preferred. These are used alone or in combination of two or more. As the buffer, for example, acetic acid, succinic acid,
Examples thereof include malonic acid and salts thereof, and these are used alone or in combination of two or more. Further, examples of the stabilizer include acetate, nitrate, and certain sulfur compounds such as lead, bismuth, and thallium, and these may be used alone or in combination of two or more.

The pH of the electroless nickel plating solution is p
It can be adjusted by an H adjuster, and is 4.0 to 5.
5. In an alkaline bath, the concentration may be adjusted to 8 to 10 with an alkaline agent such as ammonia, an amine compound and caustic.

The electroless nickel plating solution may further contain, if necessary, an auxiliary agent such as a brightener and a surfactant, which is usually used in the electroless nickel plating solution.

When the surface of a metal plate or an inorganic powder is plated using the above electroless nickel plating solution, the amount of phosphite ions by-produced by the plating reaction may be HPO.
The molar ratio of ₃ ²⁻ / Ni ²⁺ is preferably in the range of 3 to 10.

By performing the plating treatment continuously under the above conditions, the concentration of phosphite ions increases, and eventually, a plating aging solution having reduced plating function is obtained. The composition of the plating aging solution is not particularly limited, but as an example, in many cases, Ni ²⁺ is 4 to 7 g / liter and H ₂ PO ₂ ^2-
There 10～55G / l, HPO ₃ ^2-is 80 to 160
g / L, SO ₄ ^2- 30-75 g / L, chelating agent 30-55 g / L, Na ⁺ 46-1
In the range of 20 g / l, the pH is between 3.5 and 5.5.

The step (B) of the present invention is a step of subjecting the plating aging solution from the step (A) to HPO ₃ ^2- treatment.
That is, a calcium salt is added to the reaction tank under stirring as a powder or aqueous slurry in the plating aging solution,
6 to 9, preferably 6.5 to 8.8.
PO ₃ ^2-a precipitated as calcium phosphite, is carried out by separating off.

Examples of the calcium salt include calcium hydroxide and calcium carbonate, and these are used alone or in combination of two or more. The amount of the calcium salt added is preferably close to the equivalent of HPO ₃ ^2- in the treatment solution.

The reason for setting the pH value in the range of 6 to 9 is as follows.
If the pH value is less than 6, not only unreacted phosphite ions remain, but also the solubility of calcium phosphite increases when separating and removing it later.
This is because the solubility of calcium phosphite increases again during the separation and removal of the nickel ions while precipitation occurs, which is not preferable. The treatment temperature is not particularly limited as long as it is 70 ° C. or less, but if it is 10 ° C. or less, the reaction time is undesirably long. In addition, since the treatment time is determined by the reaction between the electroless nickel plating aging solution and the calcium salt, the solubility of the calcium salt becomes the reaction rate-determining, it is necessary to take a sufficient time for the generation of calcium phosphite, and 2 hours or more, preferably 20 hours As described above, the reaction is preferably performed under stirring.

After the completion of the reaction, the treated liquid is filtered at a temperature of 30 ° C. or less to separate and remove precipitated calcium phosphite. By this filtration operation, most of the phosphite and metal impurities in the electroless plating aging solution are removed. Also, the chelating agent in the plating aging solution is not uniform depending on the kind thereof, but forms a calcium salt and is partially precipitated and removed. The above-mentioned de-HPO ₃ ^2- treatment substantially removes the HPO ₃ ^2- ion, but some of the HPO ₃ ^2- ion and calcium ion are dissolved due to the solubility of calcium phosphite and the effect of the chelating agent. I do. In this case, the concentration of calcium ions dissolved in the recovered mother liquor was 0.1
Separation and removal of calcium phosphite so as to be 2 g / liter or less is preferable from the viewpoint of avoiding a risk of adversely affecting the nickel film when the recovered mother liquor is recycled and reused. Therefore, if necessary,
When the dissolved calcium phosphite is further removed, it is preferable that the recovered mother liquor obtained in the above treatment is concentrated by heating to precipitate calcium phosphite again, which is separated and removed.

Also, the separated calcium phosphite is N
Since it does not substantially contain i ²⁺ , it can be recovered as a white powder, and can be effectively used as a reducing agent, a resin additive, a pollution-free rust preventive pigment, and various functional materials.

The step (C) of the present invention is a so-called desalting step for removing salts such as Na ⁺ and NH ₄ ⁺ present in the separated mother liquor from the step (B). These Na ⁺ , NH
₄ ⁺ such cations are those upon plating of mainly (A) step, mixed with the use of an alkaline agent or the molar ratio modifier as a pH adjusting agent in the plating bath.

As the above desalting method, there is a method in which the treatment is carried out through any one of an electrodialysis tank, a cation exchange resin and a reverse osmosis membrane.

An important requirement for the electrodialysis tank is that both sides of the dilution chamber are separated by a cation exchange membrane.
Examples of the configuration include a single cation exchange membrane, a multiple cation exchange membrane, and a multiple cation exchange membrane and a cation exchange membrane.
Specifically, for example, as shown in FIG. 1, a plurality of pairs of cation exchange membranes 1 are incorporated in the electrodialysis tank 8, and the anode chamber 6, the concentration chamber 5, and the dilution chamber 4 are arranged in this order from the anode side 3. And
After that, the concentration chambers 5 and the dilution chambers 4 are alternately arranged, and the cation exchange membrane 1 is disposed between them. Finally, the concentration chamber 5 and the cathode chamber 7 are arranged. Further, the processing solution is fed, the diluent tank 10 that flows through the dilution chamber 4 and flows in, and the electrolyte is fed. The electrolyte solution tank 11 that flows through the anode chamber 6 and the cathode chamber 7 and the concentrated solution is fed. It has a concentration tank 12 which passes and flows in.

In FIG. 1, the separated mother liquor from the step (C) is placed in the dilution chamber 5 of the electrodialysis tank 10,
Supplied at 50 cm / sec. At this time, an appropriate aqueous electrolyte solution may be supplied to the anode chamber 7 and the cathode chamber 8 located at both ends of the electrodialysis tank 10. Energization is below the limit current density,
The separation is preferably performed in the range of 0.1 to 10 A / dm ² , and the cations in the separation mother liquor supplied to the dilution chamber 5 are selectively transferred to the concentration chamber 6 through a cation exchange membrane. Cations such as Na ⁺ and NH ₄ ⁺ may be removed. The cation exchange membrane is not particularly limited.
(Manufactured by Tokuyama Soda Co., Ltd.), Nafion324 (manufactured by DuPont) and the like. The anion exchange membrane is not particularly limited,
For example, Selemion AMV (manufactured by Asahi Glass Co., Ltd.), Neocebuta A
M-1 (manufactured by Tokuyama Soda Co., Ltd.) and the like.

As the cation exchange resin, a sulfone group,
There is no particular limitation as long as it has a cation exchange group such as a carboxyl group, and examples thereof include Diaion SK-1B (manufactured by Mitsubishi Kasei Corporation). The amount of the cation exchange resin is usually equal to or more than the amount of the waste liquid, preferably 2 to 5 times. The processing speed is usually 10 to 200 ml / min, preferably 5 to 200 ml / min.
0-100 ml / min.

Examples of the material of the reverse osmosis membrane include cellulose acetate-based, aromatic polyamide-based and polybenzimidazolone-based membranes.
00 angstrom or less, preferably 5 to 50 angstrom is used. The processing pressure applied to the raw water is generally 0.5 to 100 kg / m ² , preferably 10 to 100 kg / m ² .
30 kg / m ² .

The method for operating the electrodialysis, the cation exchange resin and the reverse osmosis membrane is not particularly limited, and the operation to be performed is not particularly limited, and the composition of the separated liquid from the step (B) to be applied is economical. It is sufficient to study under the conditions, and as a result, Na ⁺ ,
The pH after removing cations such as NH ₄ ⁺ becomes 5.5 or less, preferably 4.5 or less. Next, the treated liquid is transferred to the next step (D).

Step (D) of the present invention is a regeneration circulation step in which the plating solution components are adjusted and the process returns to the electroless nickel plating step (A). In other words, the electroless nickel plating aging solution treated as described above is a hypophosphorous acid solution mainly containing Ni ²⁺ and a chelating agent. After adding a chemical such as nickel hypophosphite, a chelating agent, a pH adjuster and a stabilizer to adjust the plating solution composition in the step (A), the solution may be reused as a building bath solution or as a replenisher. Good.

As described above, according to the plating solution circulation system of the present invention, the plating aging solution can be efficiently treated and reused, and a smooth and good film can be formed unlike the plating solution containing sodium sulfate. can get. In particular, there is a remarkable advantage that the service life of the bath is longer and the so-called number of turns can be increased as compared with the conventional plating bath.

[0033]

In the electroless nickel plating solution circulation system of the present invention, in the plating step (A), the main components of plating metal ions Ni ²⁺ as a plating solution and hypophosphite ions H ₂ PO ₂ ⁻ as a reducing agent are used. By using a plating solution containing nickel hypophosphite as a supply agent, the formation and accumulation of sulfate during plating can be suppressed. Further, even if the plating function of the plating solution decreases due to repeated plating, even if the plating aging solution is supplied with a calcium salt in the step (B), HPO ₃ ^2-
By the following formula: HPO ₃ ^2- + Ca ²⁺ → CaHPO ₃ ↓ Substantially only calcium phosphite can be selectively precipitated to perform a separation treatment. Further, by the step (C), low molecular weight salts such as Na ⁺ and NH ₄ ⁺ in the plating aging solution can be selectively removed. Further, in the step (D), the liquid composition is confirmed, and if necessary, chemicals such as insufficient nickel hypophosphite, a chelating agent, a pH adjuster and a stabilizer are added to adjust the liquid composition. It can be reused as a bath solution.

[0034]

Next, the present invention will be described in more detail by way of examples, which are illustrative and do not limit the present invention.

Example 1 Step (A) Electroless nickel of pH 4.5 consisting of 30.3 g / l of nickel hypophosphite hexahydrate, 25 g / l of malic acid, 10 g / l of succinic acid and 2 mg / l of lead nitrate 2 liters of the plating solution was placed in a 3 liter glass beaker. Next, after heating to 90 ° C., ten pieces of iron (5 cm × 10 cm × 0.2 mm) degreased and acid-washed were immersed at a time, and electroless nickel plating was performed for 30 minutes. Next, the same process was performed 16 times, replacing the iron pieces. During the plating operation, a chemical (mainly nickel hypophosphite) consumed by the plating reaction was supplied 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, the maximum thickness is 8.3 μm and the minimum thickness is 7.6 μ on the iron piece.
m, a nickel plating film having an average thickness of 8.0 μm was deposited, and the formed plating layers were all smooth and exhibited excellent metallic luster. Table 1 shows the composition of the plating aging solution after the completion of the plating treatment.

Step (C) 2 liters of plating aging solution (pH 3.
6, liquid temperature 70 ° C.), slaked lime was charged with stirring, the pH was adjusted to 6.1 to 8.0, and the mixture was kept at room temperature for 24 hours. After the treatment, the white precipitate generated by the metathesis reaction was filtered at a temperature of 30 ° C. or lower by a conventional method to remove calcium phosphite and separate. Table 1 shows the composition of the mother liquor after filtration.

Step (B) Next, 1 liter of the treated mother liquor was supplied to an electrodialysis tank comprising six cation exchange membranes Selemion CMW (manufactured by Asahi Glass Co., Ltd.) having an effective area of 150 cm ² . The direct current supplied to the electrodialysis tank was 5 A, and the voltage was 10 V. Table 1 shows the liquid composition after the electrodialysis treatment.

Step (D) and Again Step (A) To 1 liter of the above treated mother liquor, add 30 g of nickel hypophosphite hexahydrate, 20 g of sodium hypophosphite monohydrate, 24.8 g of malic acid and 9 parts of succinic acid. 0.5 g and 2 mg lead nitrate,
Further, a plating solution was prepared by adjusting the solution amount to 2 liters with pure water. Next, the plating solution having the above composition was adjusted to pH 4.5.
And put it in a 3 liter glass beaker,
After heating to 0 ° C., degreased and acid-washed iron pieces (5 cm × 1
(0 cm × 0.2 mm) were immersed at a time, and electroless nickel plating was performed 16 times again for 30 minutes. During the plating operation, a chemical (mainly nickel hypophosphite) consumed by the plating reaction is replenished every 30 minutes to adjust the pH of the solution to 4.5.
The sodium hydroxide aqueous solution was constantly replenished to maintain the water content, and demineralized water was added to replenish the evaporating water.
By this electroless nickel plating, the maximum thickness is 8.2 μm, the minimum thickness is 7.4 μm, and the average thickness is 7.8 μm on the iron piece.
The nickel plating film having a thickness of m was deposited, and the formed plating layers were all smooth and excellent in metallic luster, and were not different from those plated with the plating solution initially prepared.

[0039]

[Table 1]

Example 2 (A) Step The same plating solution as in Example 1 was used except that sodium hypophosphite monohydrate was newly added at 5 g / liter and lead nitrate was changed from 2 mg / liter to 1 mg / liter. The plating was performed in the same manner. By this electroless nickel plating, the maximum thickness is 10.3 μm and the minimum thickness is 9.1 μm on the iron piece.
m, a nickel plating film having an average thickness of 9.6 μm was deposited, and the formed plating layers were all smooth and exhibited excellent metallic luster. Table 2 shows the composition of the plating aging solution after the completion of the plating treatment.

Step (B) was performed in the same manner as in Example 1. Table 2 shows the composition of the mother liquor after filtration in the step (B).

Step (C) Next, 1 liter of the treated mother liquor was placed in a column (7.5 cm in diameter × 60 cm in length) packed with 2 liters of a cation exchange resin (Diaion SK-1B; manufactured by Mitsubishi Kasei Corporation) at 90 ml / min. A desalting treatment was performed by pumping at a flow rate of Then
It was transferred to the plating bath in the next step. Table 2 shows the liquid composition after the cation exchange resin treatment.

Step (D) and Step (A) Again To 1 liter of the treated mother liquor having the above composition, 60 g of nickel hypophosphite hexahydrate, 26 g of malic acid, 10 g of succinic acid and 4 mg of lead nitrate were added. To prepare a plating solution such that the solution amount became 2 liters. The plating treatment after the preparation of the plating solution was performed in the same manner as in Example 1. By this electroless nickel plating treatment, a maximum thickness of 10.0 μm was formed on the iron piece.
m, a minimum thickness of 8.8 μm, and an average thickness of 9.3 μm. A nickel plating film is deposited, and the formed plating layers are all smooth and have excellent metallic luster. Was not something different.

[0044]

[Table 2]

Example 3 Step (A) A plating treatment was carried out in the same manner as in Example 1, except that 10 g / liter of sodium hypophosphite monohydrate was newly added. By this electroless nickel plating treatment, a nickel plating film having a maximum thickness of 10.8 μm, a minimum thickness of 9.7 μm, and an average thickness of 10.3 μm was deposited on the iron piece, and all the formed plating layers exhibited smooth and excellent metallic luster. Was something. Table 3 shows the composition of the plating aging solution after the completion of the plating treatment.

Step (B) was performed in the same manner as in Example 1. Table 3 shows the composition of the mother liquor after filtration in the step (B).

Step (C) Next, 1 liter of the treated mother liquor was desalted through a reverse osmosis membrane at a pressure of 30 kg / cm ² . Then, it was transferred to the plating bath of the next step. Table 3 shows the liquid composition after passing through the reverse osmosis membrane.

Step (D) and Again Step (A) To 1 liter of the treated mother liquor having the above composition, 900 ml of pure water was added, and further, 30 g of nickel hypophosphite hexahydrate, 34 g of sodium hypophosphite monohydrate, 9.2 g of malic acid, 11.7 g of succinic acid and 2 mg of lead nitrate were added to prepare a plating solution. The plating treatment after the preparation of the plating solution was performed in the same manner as in Example 1. By this electroless nickel plating treatment, the maximum thickness was 10.5 μm and the minimum thickness was 9.5 μm on the iron piece.
m, a nickel plating film having an average thickness of 9.9 μm is deposited, and the formed plating layers are all smooth and have excellent metallic luster, and are not different from the plating products using the plating solution initially constructed. Was.

[0049]

[Table 3]

[0050]

According to the electroless nickel plating solution circulation system of the present invention, there is no formation and accumulation of sulfate in the plating solution, and the plating solution can have a long life. In addition, HPO ₃ ^2- and Na ⁺ and NH ₄ ⁺
Low molecular cations and the like can be separated and removed industrially very advantageously, and the aging solution can be recycled. Moreover, even if plating treatment is performed using a recycled aging solution, a good plating film which is not different from the initial plating film can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing the concept of an electrodialysis tank used in step (C) of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cation exchange membrane 2 Cathode 3 Anode 4 Dilution room 5 Concentration room 6 Anode room 7 Cathode room 8 Electrodialysis tank 10 Diluent tank 11 Electrode solution tank 12 Concentrate solution tank

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C02F 1/469 C02F 1/58 R 1/58 1/46 103 (72) Inventor Hidehiro Nakao 2-3-3 Yoshino-cho, Omiya-shi, Saitama No. 1 MelTex Corporation Research Department (72) Inventor Takehiko Tashiro 2-3-1 Yoshino-cho, Omiya City, Saitama Prefecture MelTex Corporation Research Department

Claims (4)

[Claims] (A) Plating treatment is performed using a plating solution containing plating metal ion Ni ²⁺ and nickel hypophosphite as a main supply agent of hypophosphite ion H ₂ PO ₂ ⁻ as a reducing agent. electroless nickel plating process; (B) wherein (a) de-HPO for processing plating aging solution from step ₃ ^{2 -} process; (C) desalting step; (D) after the plating liquid component adjustment, the electroless Nickel plating process (A)
A circulation system for the electroless nickel plating solution, which sequentially goes through the steps of: 2. The circulation system for an electroless nickel plating solution according to claim 1, wherein the plating solution in the step (A) further contains a chelating agent, a buffer, a pH adjuster or a stabilizer. 3. The step (B) comprises adjusting the pH of the plating aging solution after the step (A) to 6 to 9 with a calcium salt to form a precipitate of calcium phosphite, and separating and removing the precipitate. A circulation system for the electroless nickel plating solution according to claim 1. 4. The method according to claim 1, wherein the step (C) comprises treating the separated mother liquor obtained in the step (B) through an electrodialysis tank, a cation exchange resin or a reverse osmosis membrane. A circulation system for the electroless nickel plating solution according to any one of the preceding claims.