JP2553574B2 - Silver stripper - Google Patents

Description

TECHNICAL FIELD The present invention relates to a silver stripping solution.

More specifically, the present invention selectively peels a silver adherent fixed on the surface of a metal base by means such as plating without damaging the metal base, and also provides a thin silver adherent in an unnecessary portion. Silver stripping solution that can remove the thin silver-specific material in unnecessary parts of the product that is not recognized as a product, without damaging the appearance of thick silver adherents in other necessary parts and without damaging the metal substrate. Regarding

(Prior Art) Conventionally, various methods for peeling silver from a plated product or the like plated with silver have been reported.

The conventional method of dissolving silver including nitric acid or aqua regia in a metallic base material cannot naturally reuse the metallic base material. Also, the influence of the use of acid on the working environment, wastewater treatment, etc. There's a problem.

In the complexation method of forming a silver complex salt with ethylenediaminetetraacetic acid or its alkali salt and hydrogen peroxide (Japanese Patent Laid-Open No. 52-78632), the dissolved silver is a chemically stable chelate compound. Although it is described that it does not precipitate, the amount of silver dissolved is 0.1 to 0.2 g /
Substitutional precipitation of silver was observed to some extent, and the amount of silver solution processed was insufficient.

In addition, ammonium salts and hydrogen peroxide (JP-A-55-1640)
In the complexation method of forming a complex salt of silver according to 75), it is difficult to completely dissolve silver, and even if the silver is completely dissolved, substitutional deposition of silver on the metal substrate occurs, or the metal substrate is re-formed. In many cases, it corrodes to the extent that it cannot be used, and when the unnecessary thin portion of the silver fixing material is peeled off, the appearance of the other necessary portion of the thick silver fixing material is impaired.

Furthermore, also in the electrolysis method, the metal substrate is also corroded to the extent that it cannot be reused, and the peeling of the thin silver adherents in unnecessary portions impairs the appearance of thick silver adherents in other necessary portions. Get lost.

The same applies to the method using a cyanide compound and an organic oxidant or thiourea.

(Object of the invention) The object of the present invention is to enable dissolution treatment of a large amount of silver, and to effectively dissolve and peel off silver adhered matter fixed to the surface of the metal substrate without damaging the metal substrate to re-deposit the metal substrate. It is recognized as a product because of the silver stripping solution used for the purpose of reusing the metal substrate (hereinafter referred to as "the purpose of reusing the metal substrate") and the presence of thin silver adherents in unnecessary parts. When you peel off the unnecessary silver thin adhered material on the unnecessary part,
Another object of the present invention is to provide a silver stripping solution which is used for the purpose of commercializing the product without impairing the appearance of a thick silver-fixed product in other necessary portions as in the case of a metal substrate (hereinafter referred to as "product modification purpose").

(Means for Solving Problems) As a means for solving the above problems, the present invention comprises 0.01 to 50 g / of at least one selected from chlorinated organic compounds capable of producing free chlorine ions in a solution.
And at least one compound selected from ammonium salts, compounds containing an amino group and / or an imino group, in an amount of 0.01 to 70 g /
The present invention provides a silver stripping solution containing hydrogen peroxide in an amount of 1 to 250 g / hydrogen.

Chlorinated organic compounds capable of producing free chlorine ions in the solution contained in the silver stripper of the present invention (hereinafter,
The "chlorinated organic compound") has a function of preventing damage to the metal substrate and removing the dissolved silver ions as silver chloride out of the system to prevent substitution precipitation. Such a chlorinated organic compound may be one that can generate free chlorine ions in an acidic solution, but as particularly preferable, chloroanisic acid, chlorobenzoic acid, chlorocinnamic acid, chloroacetic acid, chlorosalicylic acid, Chlorinated organic acids such as chlorosulfonic acid, chloronicotinic acid, chlorophenylacetic acid, chlorophenoxyacetic acid, chlorophthalic acid, chloropropionic acid, chlorobenzenesulfonic acid, chloromaleic acid, chloromandelic acid, and chlorobutyric acid, and salts and derivatives thereof, acetyl. Acyl halides and derivatives thereof such as chloride, oxalyl chloride, phthaloyl chloride, propionyl chloride, benzoyl chloride and malonyl chloride, and halides such as chloroaniline and chlorobenzylpyridine and derivatives thereof, etc. It can be.

Usually, one or more of these chlorinated organic compounds are contained in a concentration of 0.01 to 50 g /, preferably 0.1 to 20 g /. It is preferable that the metal substrate is contained in a concentration of 5 to 20 g / for the purpose of reuse, and a concentration of 0.1 to 5 g / for the purpose of correcting the product. If it is less than 0.01 g / g, substitutional precipitation of the metal substrate and silver will occur, and the effect of protecting the metal substrate will be insufficient, resulting in corrosion of the metal substrate, which is not practical. When the concentration of the chlorinated organic compound exceeds 50 g /, the peeling speed of the silver-fixed matter decreases and the dissolution becomes difficult or impossible.

A compound containing an ammonium salt, an amino group and / or an imino group (hereinafter referred to as “ammonia compound”) is
By complexing the dissolved silver ion, it has the effect of promoting the dissolution. As such an ammonia compound, for example, ammonium benzoate, ammonium citrate, ammonium succinate, ammonium acetate, ammonium nitrate, ammonium carbonate, ammonium phthalate, ammonium salts such as ammonium nitrate, aminopyridine, ethanolamine, ethylamine, ethylenediamine, Examples thereof include amine compounds such as quinolylamine, diethylamine, trimethylamine, propanediamine and methylamine and their derivatives, and imine compounds such as propaneimine and their derivatives.

One or more of these ammonia compounds
It is contained at a concentration of 0.01 to 70 g /, preferably 0.1 to 50 g /. It is preferable that the metal substrate is contained in a concentration of 5 to 50 g / for reuse and 0.1 to 5 g / for modification of the product. If it is less than 0.01g /, the dissolution rate of silver adherent will decrease,
Not practical. If it exceeds 70 g /, the effect of protecting the metal substrate is insufficient, corrosion of the metal substrate may occur, and it may be difficult to reuse the metal substrate.

Hydrogen peroxide has a function of rapidly dissolving a silver-fixed substance as an oxidizing agent, and is usually used as hydrogen peroxide solution. Hydrogen peroxide is 1-250 g /, preferably 3
Include at a concentration of ~ 200g /. It is preferable that the metal substrate is contained in a concentration of 60 to 200 g / for the purpose of reuse, and the concentration of 3 to 60 g / for the purpose of correcting the product. If it is 1 g / g or less, the dissolution rate of silver-adhered substances decreases, which is not practical. Also, 250g /
If it exceeds, the protective effect of the metal substrate is insufficient, corrosion of the metal substrate may occur, and it may be difficult to reuse the metal substrate.

The conditions for using the silver stripping solution of the present invention are not particularly limited to pH, but the lower the pH, the higher the stripping speed of the silver-fixed material, and it is usually preferred to use the pH of about 3 to 7. The temperature is also not particularly limited, but the higher the temperature, the higher the peeling speed of the silver adhered matter,
It is preferably used at about 20 to 60 ° C. Further, although the peeling of the silver stripping solution proceeds without stirring, it is naturally preferable to stir the silver stripping solution to promote the peeling of the silver-fixed material.

Examples of the form of the silver adherent to which the silver stripping solution of the present invention is applied include electroplating, electroless plating, chemical vapor deposition (CVD), physical vapor deposition (PVD), paste baking, and the like. Examples thereof include a silver film formed on the entire surface or a part of the surface, but the present invention is not limited to this, and can be used for peeling a silver adhered material in any form.

The type of metal of the metal substrate to which the silver adherent is fixed is not particularly limited, but the silver stripping solution of the present invention has a substrate of copper, copper alloy, zinc, nickel, iron, chromium, titanium, niobium, molybdenum. Alternatively, it is effective in the case of alloys based on these metals, and the silver adhered substance can be peeled off without damaging the metal substrate. Further, the shape and form of the metal substrate is not limited at all, and includes a metal coating layer formed on metal, ceramics, plastic, rubber or the like.

The method of applying the silver stripping solution of the present invention to a silver-fixed material is not particularly limited, but generally a method of immersing the whole substrate in the silver stripping solution is common. When the target silver film is dissolved by immersing it in the silver stripping solution for an appropriate time, the metal substrate is lifted from the solution, washed with water to wash off the silver stripping solution, and then pickled to remove the inertness formed on the surface of the metal substrate. The layer dissolves and can be easily removed, and its surface remains so smooth that it can be immediately recoated with silver.

The silver stripping solution used was repeatedly stripped, and when the active ingredient in the solution fell below a certain level, silver had already partially precipitated as silver chloride. Precipitate as silver. By this method, silver can be efficiently recovered.

(Examples) Hereinafter, the present invention will be described in detail according to Examples and Comparative Examples, but is not particularly limited thereto.

Example 1 Chlorobenzoic acid 5 g /, ammonium benzoate 20 g /
A silver stripping solution consisting of an aqueous solution containing 200 g / hydrogen peroxide was prepared, and the pH of the silver stripping solution was adjusted to 5.0 and the temperature was adjusted to 30 ° C. using benzoic acid or 28% aqueous ammonia as a pH adjusting reagent. Next, in this silver stripper, 25 × 40 mm, thickness 1 mm
5μ thickness on the strike plate of copper on the copper plate
What was subjected to m spot silver plating was immersed as a test piece.

After 7 minutes the silver had completely dissolved. After the copper plate after the silver peeling was washed with water, pickled and dried, the obtained copper plate was uniform on the entire surface and no trace of silver spots was observed. This copper plate was again subjected to silver spot plating of 5 μm, but no difference was observed with the appearance of the test piece used, and there was no corrosion of the substrate (copper plate), and reuse was possible.

Also, after adding and dissolving 1.5 g of silver powder to this silver stripping solution and treating the test piece in the same manner, the silver was completely dissolved after 10 minutes and no substitution precipitation of silver was observed. Similar results were obtained as before.

Example 2 It was immersed in a silver stripping solution for 8 hours in the same manner as in Example 1 except that the silver spot plating was not performed. After the copper plate after the immersion was washed with water, pickled and dried, the obtained copper plate was uniform on the entire surface, and no difference from the appearance of the test piece before the immersion was observed. Also, the weight of the copper plate before and after immersion is the same within the measurement error range,
There was no difference in surface roughness, and no corrosion of the substrate (copper plate) was observed.

When 1.5 g / g of silver powder was added to this silver stripping solution and dissolved, and then a test piece was treated in the same manner, substitution precipitation of silver was not observed, and the same results as before addition and dissolution of silver powder were obtained.

Example 3 In Example 1, the test piece was 25 × 40 mm, and the thickness was 0.
It was immersed in a silver stripping solution for 8 hours in the same manner as in Example 1 except that a 25 mm iron-nickel alloy plate (42 alloy plate) was used (without copper strike plating and silver spot plating). The 42 alloy plate after immersion was washed with water, pickled and dried, and then obtained
The 42 alloy plate was uniform on the entire surface, and no difference was observed from the appearance of the test piece before immersion. Further, the weight of the 42 alloy plate before and after the immersion was the same in the measurement error range, there was no difference in surface roughness, and no corrosion of the substrate (42 alloy plate) was observed.

When 1.5 g / g of silver powder was added to this silver stripping solution and dissolved, and then a test piece was treated in the same manner, substitution precipitation of silver was not observed, and the same results as before addition and dissolution of silver powder were obtained.

Example 4 A silver stripping solution comprising an aqueous solution containing 0.1 g of chloroacetic acid / 0.1 g of ammonium acetate / 33 g / of hydrogen peroxide was prepared and the silver stripping solution was prepared by using acetic acid or 28% ammonia water as a pH adjusting reagent. The pH was adjusted to 4.0 and the temperature was adjusted to 40 ° C. Next, this silver stripper is applied to a lead bronze bronze with a thickness of 0.25 mm, which is strike-plated with copper.
Those subjected to silver spot plating of m (spot A) and 0.1 μm (spot B) were immersed as test pieces.

After 30 seconds, the silver in spot B was completely dissolved. After the lead frame after silver peeling was washed with water, pickled and dried, the silver film thickness of spot A was 4.9 μm and the appearance was good.
The appearance and surface roughness of the copper part were the same before and after peeling, and no corrosion was observed.

Also, this silver stripping solution should be replenished with chloroacetic acid, ammonium acetate and hydrogen peroxide at the same ratios as above, while adding silver powder
When 1.7 g / was added and dissolved, and the test piece was treated in the same manner, substitution precipitation of silver was not observed, and the same results as before addition and dissolution of silver powder were obtained.

Example 5 Chlorosulfonic acid 20 g /, ammonium sulfate 50 g /,
A silver stripping solution consisting of an aqueous solution containing 133 g / of hydrogen peroxide was prepared, and the pH of the silver stripping solution was adjusted to 5.0 and the temperature was adjusted to 50 ° C. using sulfuric acid or 28% ammonia water as a pH adjusting reagent.
Next, this silver stripper was strike-plated with copper on a copper alloy plate containing iron with a thickness of 25 × 40 mm and a thickness of 1 mm, and a thickness of 5 μ
What was subjected to m spot silver plating was immersed as a test piece.

After 5 minutes the silver had completely dissolved. After the copper plate after the silver peeling was washed with water, pickled and dried, the obtained copper alloy plate was uniform on the entire surface and no trace of silver spots was observed. This copper alloy plate was again subjected to 5 μm gold spot plating, but no difference was observed from the appearance of the test piece used, and there was no corrosion of the substrate, and reuse was possible.

In addition, after adding and dissolving 1.5 g of silver powder to this silver stripping solution and treating the test piece in the same manner, the silver was completely dissolved after 7 minutes and no substitution precipitation of silver was observed. Similar results were obtained as before.

Example 6 Chloropropionic acid 1 g /, trimethylamine 2 g /,
A silver stripping solution consisting of an aqueous solution containing 3 g of hydrogen peroxide was prepared, and the pH of the silver stripping solution was adjusted to 3.5 and the temperature was adjusted to 40 ° C. using propionic acid or 28% ammonia water as a pH adjusting reagent. Next, this silver stripping solution is applied to a lead frame made of copper alloy containing tin and having a thickness of 5 μm (spot A) and 0.05 μm (spot B) on a lead alloy of copper alloy containing tin.
What was subjected to silver spot plating was immersed as a test piece.

After 20 seconds, the silver in spot B was completely dissolved. After the lead frame after the silver peeling was washed with water, pickled and dried, the silver film thickness of the spot A was 4.9 μm, and the appearance was good except that the gloss was slightly lost. The appearance and surface roughness of the copper portion were the same before and after peeling, and no corrosion was observed.

Further, while adding chloropropionic acid, trimethylamine, and hydrogen peroxide in the same ratio as above to this silver stripping solution at a suitable time, 1.0 g / g of silver powder was added and dissolved, and then the test piece was treated in the same manner. The same results as before the addition and dissolution of silver powder were obtained.

Example 7 A silver stripper was prepared from an aqueous solution containing chloroacetic acid 5 g /, ammonium carbonate 10 g /, and hydrogen peroxide 200 g /, and the pH of the silver stripper was adjusted using acetic acid or 28% ammonia water as a pH adjusting reagent. Was adjusted to 3.5 and the temperature was adjusted to 60 ° C. Next, a 25 × 40 mm, 1 mm thick chromium-containing copper alloy plate, which was strike-plated with copper, was plated with silver spot plating with a thickness of 5 μm, and immersed in this silver stripping solution as a test piece.

After 4 minutes the silver had completely dissolved. After the copper plate after the silver peeling was washed with water, pickled and dried, the obtained copper alloy plate was uniform on the entire surface and no trace of silver spots was observed. This copper alloy plate was again subjected to silver spot plating of 5 μm, but no difference was observed with the appearance of the test piece used, and there was no corrosion of the substrate, and reuse was possible.

In addition, 1.2g / of silver powder was added to this silver stripping solution, and after dissolution,
When the test piece was treated in the same manner, the silver was completely dissolved after 6 minutes, no substitution precipitation of silver was observed, and the same results as before the addition and dissolution of the silver powder were obtained.

Comparative Example 1 Chlorobenzoic acid 0.001 g /, ammonium benzoate 100
A stripping solution consisting of an aqueous solution containing g /, hydrogen peroxide 200 g / was prepared, and the pH of the stripping solution was adjusted to 5.0 and the temperature was adjusted to 30 ° C. using benzoic acid or 28% ammonia water as a pH adjusting reagent. Then, a strip of 25 × 40 mm and a thickness of 1 mm, which was strike-plated with copper, and spot-plated with silver having a thickness of 5 μm, was immersed in this stripping solution as a test piece.

After 15 minutes the silver had almost dissolved. Rinse the copper plate after removing the silver,
After pickling and drying, the obtained copper plate had silver replaced and deposited, and the entire surface was white.

Comparative Example 2 A stripping solution consisting of an aqueous solution containing 5 g / chloroacetic acid and 200 g / hydrogen peroxide was prepared, and the pH of the stripping solution was 5.0 and the temperature was 3 using acetic acid or sodium hydroxide as a pH adjusting reagent.
The temperature was adjusted to 0 ° C. Next, in this stripper, a thickness of 25 × 40 mm,
A 1 mm-thick copper plate, which was strike-plated with copper, was plated with 5 μm-thick silver spots, and was immersed as a test piece.

After 15 minutes, wash the test piece with water, pickle it and dry it,
In the obtained test piece, no silver dissolution was observed,
The surface of the substrate was corroded and blackening was observed.

Comparative Example 3 Chloropropionic acid 1 g /, ammonium acetate 80 g /
A stripping solution consisting of an aqueous solution containing 3 g / of hydrogen peroxide was prepared, and the pH of the stripping solution was adjusted to 3.5 and the temperature was adjusted to 40 ° C. using propionic acid or 28% ammonia water as a pH adjusting reagent. Next, the stripping solution was plated with copper on a lead frame made of a tin-containing copper alloy having a thickness of 0.25 mm and was subjected to silver spot plating having a thickness of 5 μm (spot A) and 0.05 μm (spot B). The thing was immersed as a test piece.

After 20 seconds, the silver in spot B was completely dissolved. After the lead frame after the peeling of silver was washed with water, pickled and dried, the silver film thickness of spot A was 4.9 μm, and the appearance was good, except that the gloss was slightly lost. However, the copper part was corroded, and unevenness and discoloration were observed.

Comparative Example 4 A stripping solution comprising an aqueous solution containing 50 g / nitrobenzenesulfonic acid and 40 g / potassium cyanide was prepared, and the pH of the stripping solution was adjusted by using potassium hydroxide as a pH adjusting reagent.
11, the temperature was adjusted to 55 ℃. Next, add 25x to this stripper
A 40 mm, 1 mm thick copper plate, which was strike-plated with copper, was plated with 5 μm thick silver spots, and was immersed as a test piece.

After 7 minutes the silver had completely dissolved. After the copper plate after the silver peeling was washed with water, pickled and dried, the obtained copper plate was also corroded on the surface of the substrate and turned black.

Comparative Example 5 A stripping solution composed of an aqueous solution containing 10 g / of disodium ethylenediaminetetraacetic acid and 17 g / of hydrogen peroxide was prepared,
The temperature of the stripping solution was adjusted to 30 ° C. Next, a test piece was dipped in this stripping solution as a test piece having a thickness of 25 × 40 mm and a thickness of 1 mm, which was strike-plated with copper and then silver-plated with a thickness of 5 μm.

After 8 minutes the silver had almost dissolved. Rinse the copper plate after removing the silver,
After pickling and drying, the obtained copper alloy plate was almost uniform on the entire surface, and traces of silver spots were hardly observed.

Further, when 0.1 g / g of silver powder was added to this stripping solution and dissolved, and then the test piece was treated in the same manner, dissolution of silver was not observed and substitutional precipitation was observed on the surface of the substrate.

Comparative Example 6 A stripping solution composed of an aqueous solution containing 50 g of disodium ethylenediaminetetraacetic acid and 200 g of hydrogen peroxide was prepared, and the temperature of the stripping solution was adjusted to 30 ° C. Then, a strip of 25 × 40 mm and a thickness of 1 mm, which was strike-plated with copper, and spot-plated with silver having a thickness of 5 μm, was immersed in this stripping solution as a test piece.

After 5 minutes the silver had almost dissolved. Rinse the copper plate after removing the silver,
After pickling and drying, the obtained copper alloy plate was slightly corroded, and traces of silver spots were hardly recognized.

Further, when 0.1 g / g of silver powder was added to this stripping solution and dissolved, and then the test piece was treated in the same manner, dissolution of silver was not observed and substitutional precipitation was observed on the surface of the substrate.

Comparative Example 7 A stripping solution composed of an aqueous solution containing 63 g / ammonia and 17 g / hydrogen peroxide was prepared, and the temperature of the stripping solution was adjusted to 30 ° C. Then, a strip of 25 × 40 mm and a thickness of 1 mm, which was strike-plated with copper, and spot-plated with silver having a thickness of 5 μm, was immersed in the stripping solution as a test piece.

After 15 minutes the silver had almost dissolved. Rinse the copper plate after removing the silver,
After pickling and drying, in the obtained copper plate, substitutional deposition of silver was found on a part of the surface of the substrate, and the substrate was corroded and turned black throughout.

(Effects of the Invention) As described in detail above, by using the silver stripping solution of the present invention, it is possible to dissolve a large amount of silver, which has been difficult with the conventional silver stripping solution. Without damage, the metal substrate can be reused, and what is not recognized as a product due to the thin silver film on unnecessary parts can be used without damaging the thick silver film on necessary parts. The product can be modified into a product by peeling off the thin silver film on unnecessary portions.

Claims (1)

(57) [Claims] 1. At least one kind selected from chlorinated organic compounds capable of generating free chlorine ions in a solution, 0.01 to 50 g /, and an ammonium salt, an amino group and / or
Or 0.01 to 70 g / containing at least one selected from imino group-containing compounds, and 1 to 1 hydrogen peroxide.
A silver stripping solution characterized by containing 250 g /.