JPH09217179A - Method for regenerating electroless plating bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for regenerating an electroless plating bath capable of regenerating and recycling an aged electroless plating bath in which a large amt. of phosphorous and ions are accumulated by easily, surely and inexpensively removing the phosphorous acid ions from the electroless plating bath without introducing impurities therein. SOLUTION: The hardly soluble phosphite is formed and settled and the precipitate is removed by executing treatments of one or >=2 of the following (1), (2) and (3):(1) If the metals are the same as the constituting metals of the electroless plating film precipitated from the electroless plating bath or if the constituting metals are >=2 kinds, the sulfate, chloride, carbooxide, hydroxide of the same metals as the metals of at least one kind thereof or the double salts thereof are added to the plating bath at such ratios at which the concn. higher than the conon. of the metal ions in the plating work of the plating bath is attained. (2). The electroless plating bath is raised to a temp. higher than the temp. of the plating work temp. (3) The pH of the electroless plating bath is raised to the pH higher than the plating work.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a large amount of phosphite accumulated in an electroless plating bath such as electroless nickel or nickel alloy plating bath using hypophosphorous acid or hypophosphite as a reducing agent. The present invention relates to a method for regenerating an electroless plating bath, by which the electroless plating bath can be reused simply and surely.

[0002]

2. Description of the Related Art Conventionally, various electroless platings using hypophosphorous acid or hypophosphite as a reducing agent, particularly electroless nickel plating (electroless Ni-P plating), are available. Widely used in the field. In this type of electroless plating, plating is performed by reducing metal ions by the reducing action of hypophosphite ions and precipitating them on an object to be plated.

Accordingly, as the plating proceeds, the metal ions and hypophosphite ions in the plating bath decrease, and the deposition rate decreases and the composition of the precipitate (for example, Ni and P in a Ni-P plating bath). Alloy composition) changes. For this reason,
Insufficient metal ions and hypophosphite ions are appropriately replenished, the concentration of these ions is returned to the initial level, and plating is continued.

However, as described above, hypophosphite ion
When reducing metal ions by reduction,
Ions are oxidized and phosphite ions (HPO _Three ^2-)But
It forms and accumulates gradually in the plating bath.

This phosphite ion (HPO _Three ^2-)
A small amount has almost no effect on plating, but a large amount
Accumulate, for example, 50-100g / L or more, especially 150g
/ L or more may affect the plating.
For example, it gave a problem to the adhesion between the object to be plated and the plating film.
Deposits in the plating film and adversely affects its uniformity and corrosion resistance.
To dissolve the plating bath,
There is a match.

Therefore, when performing Ni-P plating, 3 to 10 turns (1 turn is the amount of nickel ions contained in the first Ni-P bath consumed or deposited, for example, the first 6 in the Ni-P bath of nickel
If g / L is present, one turn is made when 6 g / L of nickel ions are consumed or deposited. Therefore, in this case, nickel ions are 18 to 6 for 3 to 10 turns.
It means 0 g / L consumption or precipitation. ) The fact is that the Ni-P bath was discarded after use.

Therefore, the life of the Ni-P bath is relatively short,
Further, since waste liquid treatment associated with the disposal of Ni-P baths has become an industrial problem, various methods for regenerating Ni-P baths have been proposed as countermeasures, but the conventional regeneration methods are It is not widely used because it is complicated, impurities ions harmful to plating are mixed in the regenerated plating bath, and the cost of the apparatus is high.

[0008] The present invention has been made in view of the above circumstances,
A method of regenerating an electroless plating bath that can be simply and reliably regenerated and can be reused without inconvenience of mixing harmful impurity ions with the use of hypophosphorous acid or a salt thereof as a reducing agent. The purpose is to provide.

[0009]

Means for Solving the Problems and Embodiments of the Invention
The inventor achieved the above-mentioned object and performed plating for a long time.
Electroless nickel with phosphate accumulated over 100g / L or
Efficient from electroless plating bath such as nickel alloy plating bath
In addition, do not bring plating impurities into the plating bath.
As a result of earnestly studying how to remove easily and easily,
Any one or two of the following (i), (ii), (iii)
The above treatment, that is, (i) deposition from the electroless plating bath
The same as or the same as the constituent metal of the electroless plating film
If there are two or more metals, at least one of them
Metal sulfates, chlorides, carbonates, hydroxides or these
Double salt of metal ions in the plating work of the above plating bath
Add so that the concentration is higher than the concentration
The addition treatment of genus sulfate or chloride is (ii) and / or
(With the treatment of (iii)), (ii) the above electroless plating
Elevate the bath above its plating temperature, (ii
i) pH of the electroless plating bath in the plating operation
Insoluble due to the treatment of raising the pH to higher
Phosphite is surely formed and precipitates, so this precipitate
By removing the impurities in the electroless plating bath.
Phosphate (HPO _Three ^2-Ion) is reduced,
When plating is performed using a bath, the appearance of the plating film is also
Good, deposition rate returns to initial plating bath level
Based on the above findings, the present invention has been completed.

Therefore, the present invention provides a method for regenerating an electroless plating bath in which phosphite is accumulated by using hypophosphorous acid or a salt thereof as a reducing agent, wherein the above (i), (ii), (i)
There is provided a method for regenerating an electroless plating bath, which comprises performing any one or more treatments of ii) to produce and precipitate a sparingly soluble phosphite, and then removing the precipitate.

The present invention will be described in more detail below. The electroless plating bath to be regenerated according to the present invention uses hypophosphite or hypophosphite such as sodium hypophosphite as a reducing agent. Any one may be used as long as it is a single plating bath of electroless nickel, cobalt, copper or the like, or an electroless nickel-cobalt, nickel-copper, nickel-tungsten, cobalt-tungsten or other alloy plating bath. Particularly, electroless nickel and nickel alloy plating baths are preferably applied. These electroless plating baths may be any of an acidic type, a neutral type, and an alkaline type, and may have a known composition.
Particularly, it is preferably applied to an acidic bath having a pH of 4 to 6.

The regenerating method of the present invention uses the plating as described above.
By using the bath, hypophosphite HPO _Two ^2-Consumption of
(Oxidation) with phosphite (phosphite ion HPO _Three ^2-)
Plating bath (in this case, the regeneration time should be selected appropriately)
It is usually, but not limited to, 50 g / L or more.
Yes, preferably 100 g / L or more, especially 150 g / L
Above, depending on the case, the plating accumulated more than 200g / L
Bath), the method is as follows (i), (i
Any one or more of i) and (iii) is applied.
To produce and precipitate a sparingly soluble phosphite,
This precipitate is removed. (I) Electroless plating deposited from the electroless plating bath
Same as the constituent metal of the film or two or more kinds of this constituent metal
If at least one of them is the same metal sulfate, chloride
The above substances, carbonates, hydroxides or their double salts
Higher concentration than metal ion concentration in bath plating
Add so that it becomes.

For this treatment, for example, in the case of an electroless nickel plating bath, nickel sulfate, nickel chloride, nickel carbonate, nickel hydroxide, basic nickel carbonate [NiCO ₃
Ni (OH) ₂ .nH ₂ O] or the like. For example, in the case of an electroless nickel-copper alloy plating bath, copper sulfate, chloride, carbonate, water Oxides and double salts thereof are added.

In this case, the amount added in this treatment may be higher than the metal ion concentration (normal plating control metal ion concentration) in the normal plating operation of the plating bath, but the plating control metal ion is preferable. From the viewpoint of production and precipitation of the sparingly soluble phosphite, it is preferable to add it in an amount of more than 1 and 10 times by weight or less, preferably 1.2 to 10 times by weight, and particularly 1.5 to 6 times by weight. It is suitable.

The above-mentioned treatment for adding a metal sulfate or chloride causes one of the treatments (ii) and (iii) described later, because it forms and precipitates a sparingly soluble phosphite rapidly. It must be done with both treatments.

The addition of the above hydroxides and carbonates is
Usually, the following (iii) pH increase is accompanied. (Ii) Raise the electroless plating bath to a temperature higher than the plating operation temperature (normal plating control temperature).

In this case, the normal plating control temperature is 5 ° C.
It is preferable that it is above. For example, a typical acidic type electroless nickel plating bath is often plated at 90 ° C., and for such a plating bath, the boiling point is raised to 95 ° C. or higher, particularly 97 ° C. or higher, depending on the case. (Iii) The electroless plating bath is raised to a pH higher than the pH in the plating operation (ordinary plating control pH).

In this case, the normal plating control pH is less than 0.
It is preferable to increase the pH by 1 or more, particularly by 1 or more. For example, in the case of an acidic type electroless plating bath having a pH of 4 to 6, p
H 4.5-12, preferably pH 4.5-7, especially pH
In the range of 5 to 7, it is preferable to set the high pH as described above.

As a method of increasing the pH of the plating bath, there is a method of adding an alkali hydroxide such as sodium hydroxide, and a method of adding the metal hydroxide or carbonate described in (i). Is mentioned. In the latter case, in the treatment of (iii), the addition raises the pH, so that the amount of metal ion added may be smaller than that of the treatment of (i).

When the method (iii) is carried out, the plating bath may be at room temperature, but 40 to 90 ° C., especially 50 to 7
It is preferable to raise the temperature to 0 ° C. and let it stand.

The above (i), (ii), (iii)
If necessary, the treatment (1) is left under agitation to form and precipitate the sparingly soluble phosphite. In this case, it is preferable that the time is left for 30 minutes to 24 hours, particularly 1 to 5 hours.

Separation and removal of the formed precipitate can be carried out by a conventional method such as filtration. In this case, it is preferable to perform filtration at a high temperature, and a separate tank and a plurality of filtration devices are installed near the plating tank, and precipitation can be performed and filtration can be performed while one of the tanks is stopped. Alternatively, filtration may be performed in a separate tank.

This regenerated electroless plating bath can be used again for plating in the same manner after the metal ion concentration, hypophosphite ion concentration, pH, etc. have been adjusted. When acid ions are accumulated, they can be repeatedly used by performing the regeneration treatment as described above, and thus the life of the electroless plating bath can be extended.

[0024]

According to the present invention, phosphite ions can be easily, reliably and inexpensively removed and regenerated from an aged electroless plating bath in which a large amount of phosphite ions have accumulated, without introducing impurities, and regeneration, Can be reused.

[0025]

The present invention will be described below in more detail with reference to Examples, but the present invention is not limited to the following Examples. In the following examples, the specific gravity is the value at 20 ° C.

[Example 1] An electroless nickel plating bath having the following composition was constructed. Nickel sulfate 5.0 g / L (Ni ²⁺
As) NaH ₂ PO ₂ · H ₂ O 25.0 g / L sodium acetate 18.0 g / L malic acid 40.0 g / L Pb ²⁺ 0.3 mg / L (NaH ₂ PO ₃ 0 g / L) pH 4.5 Specific gravity 1.045 Using the above electroless nickel plating bath, nickel sulfate, N
aH ₂ PO ₂ · H ₂ O and NaOH (or H ₂ SO ₄ ) as a pH adjusting agent at the above-mentioned predetermined Ni ²⁺ concentration and NaH ₂ P
Replenishing was performed so that the concentration of O ₂ · H ₂ O and pH was 4.5, and if necessary, sodium acetate, malic acid, and Pb ²⁺ were appropriately replenished, and plating was performed for 8 turns (8 turns). The solution used is a bath supplemented with 5.0 g / L × 8 = 40 g / L Ni ²⁺ ). The plating temperature is 90
° C. The results of the analysis of the plating bath after using this for 8 turns are as follows. Ni ²⁺ 5.0 g / L NaH ₂ PO ₂ · H ₂ O 13.9 g / L NaH ₂ PO ₃ 205 g / L Specific gravity 1.249 Then, nickel sulfate was used as Ni in the plating bath used for 8 turns. 95% after adding ²⁺ to 30 g / L
Hold at ℃ for 1 hour. The results of the analysis of the plating bath after removing the generated precipitate are shown below. Ni ²⁺ 9.4 g / L NaH ₂ PO ₂ · H ₂ O 5.5 g / L NaH ₂ PO ₃ 119 g / L Specific gravity 1.166 The plating bath after this treatment has a Ni ²⁺ concentration of 5.0 g. / L, and further adjust NaH ₂ PO ₂ · H ₂ O, sodium acetate, malic acid, and Pb ²⁺ to the same concentration as at the time of the construction bath, and further adjust the pH to 4.5. Adjust to 90
The plating was performed at 30 ° C. for 30 minutes. In this case, the plating bath is 1L
Then, a 1 dm ² mild steel sheet pretreated by a conventional method was dipped in this, and the plating rate was determined from the weight before and after plating.
Table 1 shows the results.

Example 2 When 18 g / L of Ni (OH) ₂ was added to the plating bath used for the above 8 turns, a Ni (OH) ₂ suspension having a pH of 4.7 was obtained. 60 ℃
After keeping at room temperature for 1 hour, the formed precipitate was removed. Table 1 shows the analysis result of the plating bath after this treatment. In addition, the plating bath after this treatment was adjusted to the same concentration as the plating bath at the time of construction in the same manner as in Example 1, and plating was performed at pH 4.5 and 90 ° C. for 30 minutes. Table 1 shows the results.

Example 3 NaOH was added to the plating bath used for the above 8 turns to adjust the pH to 12.0, and this was kept at 55 ° C. for 2 hours. Table 1 shows the results of analyzing the composition of the plating bath after removing the generated precipitate. Also, adjust this plating bath to the same concentration as the plating bath at the time of construction and p
The plating was performed at H4.5 and 90 ° C. for 30 minutes. Table 1 shows the results.

Example 4 Basic nickel carbonate NiCO ₃ .Ni (OH) ₂ .n was added to the plating bath used for 8 turns.
When H ₂ O was added at 45 g / L, a nickel carbonate suspension having a pH of 4.6 was obtained. This was kept at 60 ° C for 1 hour to remove the generated precipitate. Table 1 shows the analysis result of the plating bath after this treatment. In addition, adjust this so that it has the same concentration as the bath composition at the time of the first bath, and adjust the pH to 4.5 at 90 ° C for 30
The plating was performed. Table 1 shows the results.

[0030]

[Table 1]

Table 2 shows the fluctuation of the deposition rate from the time of the above-mentioned bathing to the use after 8 turns.

[0032]

[Table 2]

From the above results, it was confirmed that the electroless nickel plating bath can be reliably regenerated and reused by the regenerating method according to the present invention.

Claims (2)

[Claims] 1. A method for regenerating an electroless plating bath in which phosphite is accumulated, using hypophosphorous acid or a salt thereof as a reducing agent, wherein any one of the following (i), (ii) and (iii) is used. Generates sparingly soluble phosphite by one or more treatments,
A method for regenerating an electroless plating bath, which comprises depositing and then removing the deposit. (I) Sulfate, chloride, carbonate of the same metal as the constituent metal of the electroless plating film deposited from the electroless plating bath, or at least one metal when the constituent metals are two or more kinds, A hydroxide or a double salt thereof is added so as to have a higher concentration than the metal ion concentration in the plating operation of the plating bath (however, the treatment of adding the metal sulfate or chloride is (ii) and / or (Iii) with treatment). (Ii) Raise the electroless plating bath to a temperature higher than the plating operation temperature. (Iii) The electroless plating bath is raised to a pH higher than that in the plating operation. 2. The regeneration method according to claim 1, wherein the electroless plating bath is an electroless nickel or nickel alloy plating bath.