JPS60145378A - Method for regenerating exhausted electroless plating solution - Google Patents

Abstract

PURPOSE:To regenerate easily an exhausted electroless plating soln. contg. sodium hypophosphite by adding calcium sulfate to the soln. in the presence of an ethyleneamine compound to precipitate phosphite ions. CONSTITUTION:When an electroless plating soln. contg. sodium hypophosphite as a reducing agent is exhausted, the exhausted soln. is regenerated by adding calcium sulfate in the presence of an ethyleneamine compound such as ethylenediamine. The calcium sulfate is preferably added in the form of a slurry, and it is added by an amount (mole) 1-1.2 times the amount of phosphite in the exhausted soln. The pH of the soln. is about 6-7, the reaction temp. is about 50- 60 deg.C, and the reaction time is about 30min-2hr. After finishing the reaction, produced calcium phosphite and unreached calcium sulfate are settled and removed. Sodium sulfate in the soln. may be crystallized by concn. or cooling and removed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for regenerating an aged electroless plating solution.

In general, in an electroless plating bath using sodium hypophosphite as a reducing agent, following the use of the plating process, (1) Sodium hypophosphite is oxidized and the concentration of sodium phosphite increases. , along with this increase in sodium phosphite,
Not only deterioration of the plating film, such as a decrease in plating speed and deterioration of the mechanical properties of the deposited metal, but also self-decomposition of the plating bath itself.

This causes the so-called aging of the plating bath, which eventually becomes unusable as a plating solution.

However, this plating solution is expensive, and
Due to its high COD, it is discarded after being used a few times.
It is clear that converting to a new plating solution is a big loss for the industry. Therefore, in this type of technical field, there is a strong demand for the development of a technology that allows plating solutions to be used repeatedly many times, rather than being discarded after a few uses.

Conventionally, there is no excellent method for regenerating aged liquid and it has not been implemented industrially, but for example, Japanese Patent Publication No. 36-3557 describes
A method for separating phosphite using (OH)2 or a combination of this and Ca5O+ has been described (2). However, this method not only has a poor removal rate of sulfite, but also a large amount of calcium salts are eluted into the solution, so it takes extra effort to add fluoride and remove the calcium salts by precipitation.

Furthermore, when the plating solution is reused, a considerable amount of sulfuric acid is required to adjust the pH. Therefore, the increase in salt concentration in the plating solution is accelerated, leading to an increase in the frequency of regeneration treatment, which is advantageous.

Furthermore, JP-A-5FI-142866 provides a method of oxidizing phosphite with hydrogen peroxide in a phosphate solution, but this method does not oxidize even hypophosphite in the liquid. There is no mention of the separation and removal of phosphates that not only oxidize, but also oxidize. Therefore, this method cannot be said to be complete.

As a result of intensive research in response to the above-mentioned demands, the present inventors added calcium sulfate in the presence of an ethyleneamine compound to an aging solution for electroless plating that uses at least sodium hypophosphite as a reducing agent. When processed,
Oxidation Production (3) The present invention was completed based on the discovery that the main phosphite ion easily produces insoluble calcium salts, and the removal rate of phosphite ions increases significantly.1. Ta.

That is, in the present invention, when regenerating an aging solution for electroless plating using at least sodium hypophosphite as a reducing agent, calcium sulfate is added in the presence of an ethyleneamine compound to reduce the amount of calcium sulfate present in the aging solution. The present invention relates to a method for regenerating an aged electroless plating solution, which is characterized in that phosphite ions are generated as calcium phosphite, and this is separated and removed.

The aging solution for electroless plating according to the present invention uses sodium hypophosphite as a reducing agent (hereinafter simply referred to as aging solution).
The target is

Normally, when calcium sulfate is added to an aging solution to precipitate phosphite ions caused by the acid of sodium hypophosphite as calcium phosphite, the solubility of calcium phosphite increases due to the influence of the by-produced sodium sulfate due to the reaction. However, the regeneration effect cannot be expected. Therefore, by simultaneously using a (4) Ca''1 supplying material such as slaked lime, this drawback is compensated for.

However, when the above reaction is carried out in the presence of an ethyleneamine compound, there is virtually no effect of sodium sulfate, and the addition of calcium sulfate alone is sufficient to insolubilize the phosphite ions in the aging solution. Can be separated and removed.

Therefore, according to the present invention, the ethyleneamine compound is
In the conventional plating bath composition, it is sometimes used as a complexing agent, so in the case of such an aging solution, there is no need to add the compound again, and the compound can be applied as is. If calcium sulfate is not present, other aging fluids can also be applied by dissolving calcium sulfate in the aging fluid in an amount equal to or larger than that normally used as a complexing agent. Since it has a strong complexing power for calcium, the amount of calcium sulfate added is different from that of (5), diethylenetriamine, triethylenetetramine,
triaminoethylamine, etc., and they may be used alone or in combination of two or more. Ethylenediamine is particularly preferred.

On the other hand, the calcium sulfate used in the present invention may be any of its anhydrides, hemihydrates, dihydrates, etc.
Its manufacturing history does not matter.

As described above, the method for regenerating aging plating solution according to the present invention is as follows:
Since the purpose is to regenerate an aged solution when sodium hypophosphite is used as a reducing agent, other liquid compositions may be used without limitation, and nickel or nickel-cobalt may be used as the plating metal. , nickel-copper, nickel-zinc alloys, etc., and can be applied to these aging solutions.

The method for regenerating the aged liquid is as follows.

(6) Calcium sulfate may be added to the electroless agate aging solution either in the form of a powder (15) or in the form of a slurry. I like things.

The amount to be added is 1.2 times the molar equivalent to the phosphite in the aged solution, but the removal rate of phosphite is better if the molar amount is higher than the molar equivalent. The pH of the liquid should be 5 or more, and 6 to 7 is preferable. Reaction temperature is 40-80°
C is good and the removal rate is better at higher temperatures, but when considering the decomposition of the liquid, it is 5.
A temperature of 0 to 60°C is preferable. The reaction time varies depending on the temperature, but 30 minutes to 2 hours is sufficient.

In addition, in order to accelerate the reaction, if a small amount of calcium phosphite is added as a seed 7 and the reaction is carried out, the reaction time can be shortened and the removal rate of phosphite can also be increased.

After the reaction is completed, the produced calcium phosphite and unreacted calcium sulfate are removed by precipitation, and if necessary, the sodium sulfate in the liquid is crystallized and removed by concentrating or cooling.

The method for regenerating an aged electroless plating solution of the present invention has the following advantages: (7) (1) Since there is no need to remove dissolved calcium, the process is simplified.

(2) Since the removal rate of phosphite is high, the frequency of regeneration treatment is reduced, making it economical.

(3) Since the plating solution is treated with neutral or weak acidity, oxidative decomposition of sodium hypophosphite in the plating solution is suppressed, and the amount of chemicals required for pH adjustment during reuse can be greatly reduced. This leads to the removal of phosphites and is economical.

There are advantages such as

This will be specifically explained below by giving examples.

(8) (Example 1) Nickel sulfate 0.114 mol/L % Sodium hypophosphite O 1283 mob/l, Sodium phosphite 0°8m
ot/l, sodium sulfate 0.35 mob/l, sodium acetate 0.14.7 mol/l and ethylenedia,
O08mob/l was added to the electroless nickel plating aging solution containing 55mot7t and pH 6.5.
Add calcium sulfate dihydrate (sodium phosphite and Naokoi) in powder form, stir and react for 1 hour at a liquid temperature of 50°C, then sieve and remove the hypophosphorous in the P solution. Sodium acid and sodium phosphite were prepared by the oxidation-reduction method, and calcium was prepared using El)
Each was quantified by the TA method.

(Example 2) Addition amount of calcium sulfate dihydrate was 0.96 mol/l
The same operation as in Example 1 was carried out except that the amount was changed to 1.2 times the equivalent of sodium phosphite.

(Example 3) Addition amount of calcium sulfate dihydrate was 0.96 mot/l
(1.2 times equivalent of sodium phosphite) and the liquid temperature to 60
The same operation (9) as in Example 1 was performed except that the temperature was changed to °C. (Example 4) Add 0.7 O of sodium sulfate as an electroless nickel plating aging solution.
rnol/l and the amount of calcium sulfate dihydrate added to O096 mol/l (1.2 times the amount of sodium phosphite)
The same operation as in Example 1 was performed except for the following.

(Example 5) Instead of calcium sulfate dihydrate powder, 0.96
mol/l (1.2 times equivalent of sodium phosphite) calcium sulfate/anhydride slurry (slurry concentration 2
The same operation as in Example 1 was performed except that the setting was 0).

(Example 6) During the reaction, a small amount of calcium phosphite powder 0.5 g/l
Example 1 except that was added to the solution and the reaction time was 40 minutes.
The same operation was performed.

(10) (Comparative Example 1) 0.15% sodium citrate instead of ethylenediamine
The same operations as in Example (1) were performed except that mot/ was added.

(Comparative Example 2) Sodium malate was used instead of ethylenediamine at 0, 20
All operations were performed in the same manner as in Example (1) except that t/l was added.

(Comparative Example 3) Sodium tartrate was used instead of ethylenediamine at 0.25 m
All operations were performed in the same manner as in Example (1) except that 0 l/l was added. (Comparative Example 4) 0.60 mot of sodium lactate was added in place of ethylenediamine.
The same operations as in Example (1) were performed except that 1/l was added.

(Comparative Example 5) 0.6mat/lactic acid soda was used instead of ethylenediamine.
The same operations as in Example (1) were carried out except that the pH of the liquid was adjusted to 9.0.

(11,) (Comparative Example 6) Omo the sodium sulfate! All comparative examples except for /2 (
The same operation as in 1) was performed.

The analysis results of Examples 1 to 6 and Comparative Examples 1 to 1 are shown in Table 1.

Table 1 (]2) As shown in the results in Table 1, in each example, the removal rate of sodium phosphite was 88% or more, meaning that phosphite ions were substantially removed and the plating solution was regenerated. For each comparative example in which the reaction was carried out but not in the presence of ethylenediamine, it was almost impossible to reproduce, and a clear difference was observed.

Patent applicant Nihon Kagaku Kogyo Co., Ltd. (13)

Claims (2)

[Claims] (1) When regenerating an electroless plating aging solution using sodium hypophosphite as a reducing agent, calcium sulfate is added in the presence of an ethyleneamine compound to form phosphite ions present in the aging solution. A method for regenerating an aged electroless plating solution, which comprises precipitating calcium arsenite as calcium arsenite and separating and removing this. (2) Method 0 for regenerating an aged electroless plating solution according to claim 1, wherein the ethyleneamine compound is ethylenediamine.