JPH1030188A - Catalyst liquid for electroless plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a catalyst liquid for electroless plating having good absorptivity to an object to be plated and excellent catalyst activity by preparing an aq. soln. contg. specific ratios of a silver salt, cationic surfactant and reducing agent. SOLUTION: The aq. soln. contg. 0.01 to 100 millimol/l silver salt (silver nitrate, silver acetate, etc.), 0.01 to 0.5wt.% anionic surfactant (sodium polyoxyethylene lauryl ether sulfate, etc.) and the reducing agent of 0.1 to 0.8 times mol the silver salt (sodium, boron hydride, etc.) and contg. 0.01 to 0.5 millimol/l palladium salt (palladium chloride, etc.) at need is prepd. As a result, the catalyst liquid for electroless plating having excellent stability is obtd. at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a catalyst solution for electroless plating and a method for electroless plating using the catalyst solution.

[0002]

2. Description of the Related Art Non-conductive substances such as plastics, ceramics, and glass have no catalytic activity for electroless plating, and an electroless plating film cannot be directly formed thereon. In the case of performing electroless plating on such a substance having no catalytic activity, a method is generally employed in which a catalytic substance such as metallic palladium is attached to an object to be plated, and then electroless plating is performed.

As such a plating method, for example, as disclosed in US Pat. No. 2,702,253, an object to be plated is immersed in a strongly acidic stannous chloride solution, washed with water, and then immersed in a strongly acidic palladium chloride solution. In this method, metal palladium is deposited on the surface of the object to be plated, and then immersed in an electroless plating solution to perform electroless plating using the metal palladium as a catalyst. No. 3
No. 011920 discloses that the object to be plated is immersed in a strongly acidic palladium-tin colloid solution to impart the colloid to the surface of the object to be plated, and then treated with an acid or alkali to exhibit catalytic activity. A method for performing electroless plating is described. All of these methods use a large amount of palladium, which is an expensive noble metal as a catalyst metal, so that the cost of the treatment solution is high, and at least two-stage treatment is required to provide the catalyst, and the process is extremely difficult. There is a disadvantage that it becomes complicated. Furthermore, both methods use a tin compound, and since tin acts as a catalyst poison for electroless plating, it is necessary to completely remove tin before electroless plating.
There is a problem that non-precipitation of the plating film and a decrease in adhesion between the portion to be plated and the plating film occur.

As a method using a metal other than palladium as a catalyst, Japanese Patent Application Laid-Open No. 1-68478 discloses a method using a silver salt as a catalyst. In this method, a large amount of a reducing agent of 2 to 4 times the amount of a silver salt is added to an aqueous solution containing a silver salt and a surfactant to form a silver hydrosol, and this is brought into contact with an object to be plated. This is a method of performing electroless plating after applying silver colloid. However, this method has disadvantages that the production cost is high due to the large amount of the reducing agent used, the stability of the formed silver hydrosol is poor, and coagulation precipitation is likely to occur. Furthermore, silver has a lower catalytic activity than palladium, and silver colloid has a low adsorptivity, so it is likely to fall off from the object to be plated in a washing step or an electroless plating step, and an uneven plating film is easily formed. In addition, there is also a problem that when the colloidal silver is brought in, the electroless plating solution is decomposed to lower the stability.

Japanese Patent Application Laid-Open No. 2-93076 discloses a method of adding a reducing agent to an aqueous solution containing metal ions such as nickel, cobalt, and copper, and further using a metal fine particle dispersion in which a dispersant, a stabilizer and the like are further blended. It describes a method of applying a catalyst for electroless plating to an object to be plated. However, these metal fine particles have poor catalytic activity compared to palladium, and are susceptible to air oxidation due to their high tendency to ionize, and it is necessary to mix a large amount of a reducing agent as a stabilizer to prevent oxidation. There is a disadvantage that the cost increases. Furthermore, the reducing agent is easily washed away by washing, and when the reducing agent flows out, the metal fine particles are instantaneously oxidized in the air and lose catalytic activity. Although it is necessary to immerse directly in the electroless plating solution, such a method has a problem that the electroless plating solution is contaminated by a large amount of metal fine particles brought in, and the plating solution is easily decomposed.

[0006]

SUMMARY OF THE INVENTION The main object of the present invention is to:
An object of the present invention is to provide a low-cost catalyst solution for electroless plating, which has good adsorbability to an object to be plated, has excellent catalytic activity, and is also excellent in stability.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have used inexpensive and hardly oxidizable silver as a catalyst metal and added an anionic ion to an aqueous solution of silver salt. According to the catalyst liquid of a specific composition in which a surfactant is blended and a small amount of a reducing agent of 0.1 to 0.8 times mol with respect to silver ions, the stability of the solution becomes extremely good, and It has been found that the adsorptivity of the catalyst component to various kinds of objects to be plated is improved, and it is possible to impart excellent catalytic activity. Further, when a very small amount of palladium ion is present in such a catalyst solution, the catalytic activity is remarkably improved, and the cost is very low as compared with the conventional palladium-containing catalyst, but the same or equivalent. The inventors have found that a catalyst solution capable of imparting further catalytic activity can be obtained, and have completed the present invention.

That is, according to the present invention, a silver salt is used in an amount of 0.01 to 100 mmol / l, an anionic surfactant is used in an amount of 0.01 to 0.5% by weight, and a silver salt is used in an amount of 0.1 to 0.8 times. A catalyst solution for electroless plating, comprising an aqueous solution containing a reducing agent, and a catalyst solution for electroless plating further comprising 0.01 to 0.5 mmol / l of a palladium salt added to the catalyst solution. Is provided.

Further, the present invention also provides an electroless plating method characterized by immersing an object to be plated in the above-mentioned catalyst solution and then immersing it in a self-catalytic electroless plating solution.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The catalyst solution of the present invention is an aqueous solution containing a silver salt, an anionic surfactant and a small amount of a reducing agent.

As the silver salt, a water-soluble silver compound can be used, for example, inorganic silver salts such as silver nitrate, silver cyanate, silver perchlorate, silver sulfite, silver acetate, silver citrate, silver salicylate, and the like. Organic silver salts such as silver tartrate can be used.

The concentration of the silver salt in the aqueous solution is from 0.01 to 10
The range is about 0 mmol / l, preferably 0.5 to
The range is about 50 mmol / l. If the concentration of the silver salt is too low, the amount of the generated silver fine particles becomes extremely small, and the catalytic activity becomes insufficient, so that a good electroless plating film cannot be obtained. On the other hand, if the concentration of the silver salt is too high, the generated silver fine particles are liable to agglomerate and the catalyst liquid becomes unstable, which is not preferable.

The catalyst liquid of the present invention needs to contain an anionic surfactant. By using such a specific surfactant and adding a small amount of a reducing agent less than equimolar to the silver salt as described later, the adsorptivity of silver as a catalytic metal to the object to be plated is improved. As a result, the object to be plated can be uniformly activated by a catalyst to form a good electroless plating film. Examples of the anionic surfactant include an alkyl sulfate such as sodium dodecyl sulfate, an alkylbenzene sulfonate such as sodium dodecyl benzene sulfonate, and a polyoxyethylene such as sodium polyoxyethylene (POE) lauryl ether sulfate. Alkyl ether sulfates, sulfosuccinates such as disodium lauryl sulfosuccinate, lauryl phosphoric acid, polyoxyethylene (POE) stearyl ether phosphoric acid, polyoxyethylene (PO.
E) Phosphate ester type such as alkyl phenyl ether phosphoric acid, taurine derivative, sarcosine derivative and the like can be used. Among these surfactants, anionic surfactants having a polyoxyethylene moiety in the molecule, such as sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene stearyl ether phosphate, polyoxyethylene alkyl phenyl ether phosphate, etc. When is used, the adsorptivity becomes particularly good, and particularly excellent catalytic activity can be imparted.

The compounding amount of the anionic surfactant is about 0.01 to 0.5% by weight in the catalyst solution, and preferably 0.1 to 0.5% by weight.
It is set to about 0.5 to 0.1% by weight. When the amount of surfactant is 0.0
When the amount is less than 1% by weight, the dispersion stability of the silver fine particles is reduced, and the silver fine particles may be aggregated and precipitated, which is not preferable. On the other hand, when the amount of the surfactant is more than 0.5% by weight, the state of the silver fine particle dispersion is not greatly affected but is uneconomical.

Examples of the reducing agent include alkali metal borohydride compounds such as sodium borohydride and potassium borohydride, boron-based reducing agents such as dimethylamine borane and diethylamine borane, and phosphorus-based reducing agents such as sodium hypophosphite. Reducing agents, aldehyde compounds such as formaldehyde and glyoxylic acid, ascorbic acid, hydrazine and the like can be used.

The amount of the reducing agent used is 0.1 to
It is necessary to be in the range of 0.8 times mol. According to the present invention, by using such a small amount of the reducing agent less than equimolar to the silver salt, the stability of the silver fine particles is improved, and the aggregation and precipitation hardly occur. Combined with the use of the activator, the silver adsorbability becomes good, and it becomes possible to impart good catalytic activity to the plating object. The amount of the reducing agent used is 0.1
It is more preferably about 0.5 times mole, and the stability of the catalyst solution, the catalyst activity and the like become more favorable.

When the amount of the reducing agent used is below the above range, the amount of silver salt reduced becomes insufficient, and the amount of silver fine particles generated in the catalyst solution becomes extremely small, whereby a good electroless plating film is obtained. Can not do. If the amount of the reducing agent is too large, the reduction of the silver salt proceeds too much, the stability of the silver fine particles is reduced, and coagulation and precipitation may occur.

The catalyst solution of the present invention is an aqueous solution containing the above-mentioned silver salt, anionic surfactant and reducing agent, and can be obtained by blending the respective components and uniformly stirring. Usually, it is preferably prepared by a method of adding a reducing agent to an aqueous solution containing a silver salt and an anionic surfactant and mixing and stirring. In the catalyst solution thus prepared, a part of the silver salt is reduced to silver fine particles, which are stably dispersed in the aqueous solution.

The catalyst liquid of the present invention may further contain a small amount of a palladium salt, if necessary. By adding a palladium salt, the catalytic activity is greatly improved, and the catalytic activity is equal to or higher than that of a conventional expensive catalyst solution containing a large amount of metallic palladium as a catalytic metal. In the catalyst solution of the present invention, the palladium salt can greatly improve the catalytic activity with a very small amount of about 0.01 mmol / l or slightly more, so that the conventional palladium-containing catalyst solution can be used. Is usually 2 mmol / mol
Compared to being about l, an extremely small blending amount is sufficient, and the increase in cost due to the use of palladium is very small. Even if the amount of the palladium salt is too large, there is no significant adverse effect on the catalytic activity, but in view of an increase in cost,
It is appropriate that the amount is 0.5 mmol / l or less. Therefore, in order to exhibit the effect of improving the catalytic activity, it is appropriate that the amount of the palladium salt is about 0.01 to 0.5 mmol / l, and 0.02 to 0.2 mmol / l.
It is preferred to be about mmol / l.

As the palladium salt, a water-soluble palladium salt can be used, for example, palladium chloride,
Examples include inorganic palladium salts such as palladium sulfate and palladium nitrate, and palladium complexes such as tetraamminepalladium chloride and diethylenediamine palladium chloride.

When the palladium salt is added to the catalyst solution, the method of addition is not particularly limited. The palladium salt is added to the aqueous solution simultaneously with the silver salt and the anionic surfactant, and then the reducing agent is added. Alternatively, a palladium salt may be added to a catalyst liquid in which silver particles, an anionic surfactant and a reducing agent are already added and silver fine particles are dispersed.

In the catalyst solution of the present invention, if necessary,
Other metal salts, as long as they do not adversely affect the properties of the catalyst solution
An organic compound or the like may be blended.

In order to carry out electroless plating using the catalyst solution for electroless plating of the present invention, pretreatment such as degreasing and surface conditioning is carried out in accordance with a conventional method, depending on the type of the object to be plated. Thereafter, a silver catalyst is applied to the object to be plated with the catalyst solution of the present invention, and then, electroless plating may be performed according to a conventional method.

As a method of applying a silver catalyst to an object to be plated, a method generally used when applying an electroless plating catalyst to an object to be plated, for example, a method of immersing the object to be plated in a catalyst solution, A method of applying the catalyst solution to the object to be plated and then drying the applied solution can be applied. In particular, a method of immersing the object in the catalyst solution is preferred. Can be adhered to. The method of immersion in the catalyst solution is not particularly limited, and usually the temperature of the catalyst solution is about 0 to 80 ° C, preferably 15 to 50 ° C.
To this extent, the object to be plated may be immersed in this. If the liquid temperature is too low, the silver fine particles are likely to aggregate, while if the liquid temperature is too high, the stability of the catalyst solution is also lowered and aggregate precipitation tends to occur, which is not preferable. Regarding the immersion time, when immersed for a long time, the adsorption amount of the silver fine particles increases and the deposition property of the electroless plating becomes good, so depending on the type of the electroless plating solution to be used, the type of the object to be plated, etc. The necessary immersion time may be appropriately determined. Usually, 30
The immersion time may be in the range of about 10 to 10 minutes. The pH of the catalyst solution is preferably about 1 to 7,
More preferably, it is about 2 to 5. If the pH is too low, the solubility of the surfactant is reduced, and the stability of the catalyst solution is reduced, and aggregation and precipitation are easily caused.On the other hand, if the pH is too high, the dispersion stability becomes extremely good, It is not preferable because the adsorption amount of the silver catalyst decreases and the deposition property of the electroless plating decreases.

According to the above-described method, a silver catalyst is applied to the object to be plated using the catalyst solution of the present invention, followed by washing with water and then electroless plating according to a conventional method.
An electroless plating film having a uniform and good appearance can be formed. According to the catalyst solution of the present invention, since the silver catalyst has a strong adsorption power and silver, which is a catalyst metal, is hard to be oxidized. Absent. Further, since there is no desorption of the catalytic metal in the electroless plating solution, the stability of the electroless plating solution is not hindered.

As the electroless plating solution, any of known electrocatalytic electroless plating solutions can be used. Metal species, reducing agent species, complexing agent species, hydrogen ion concentration, etc. contained in the plating solution can be used. Is not particularly limited. As a specific example,
Examples of electroless copper plating solution, electroless nickel-phosphorous plating solution, electroless nickel-boron plating solution, electroless palladium plating solution, electroless palladium-phosphorous plating solution, electroless silver plating solution, electroless gold plating solution, etc. it can.

The object to be plated in the present invention is:
There is no particular limitation, and various materials having no catalytic activity for the electroless plating solution can be used. For example,
A metal-non-conductive material composite material such as a printed circuit board, a non-conductive material such as plastic, ceramic, and glass, a woven material such as paper and cloth, a metal, and a metal oxide can be used.

[0028]

The catalyst solution of the present invention uses silver, which is a very inexpensive metal, as compared with palladium, which has been mainly used as a catalyst metal, and is a low-cost catalyst solution. The catalyst liquid has extremely excellent stability, and has good catalytic metal adsorption to the plating object and excellent catalytic activity. Therefore, by using the catalyst solution of the present invention, a uniform and good electroless plating film can be formed. In addition, since the catalyst metal has good adsorption properties, there is almost no desorption in the electroless plating solution, and the stability of the electroless plating solution is not impaired.

In particular, a catalyst solution containing a small amount of a palladium salt has improved catalytic activity without impairing the above-mentioned excellent properties at all, and is equivalent to a conventional expensive catalyst solution containing a large amount of metal palladium as a catalyst metal. Or it will have more catalytic activity.

[0030]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 10 mmol of silver nitrate was dissolved in 800 ml of pure water, and 100 ml of an aqueous solution containing 100 mg of sodium dodecyl sulfate was added to this solution with stirring so as to be uniform.
Next, 100 ml of an aqueous solution containing 8 mmol of sodium borohydride was added to this solution with vigorous stirring so as to be uniform. When the color of the solution suddenly changed to reddish brown, the stirring was stopped. As a result, 1000 ml of a uniform and transparent dispersion of silver fine particles was obtained. This silver fine particle dispersion is referred to as catalyst liquid 1.

As an object to be plated, an epoxy plate (5 × 5c)
m), and electroless plating was performed in the following steps using the above catalyst solution 1. The volume of each processing solution was 500 ml. Water washing was performed between each treatment.

Plating process: Degreasing: A commercially available degreasing agent (trademark: A-screen A-2)
20, Okuno Pharmaceutical Co., Ltd.) for 3 minutes in a treatment liquid at 60 ° C.

2. Surface preparation: Commercial surface conditioner (trademark:
It was immersed in a treatment solution at 60 ° C. for 3 minutes using OPC-370 Condiclean M, manufactured by Noh Pharmaceutical Co., Ltd.).

3. Catalyst application: The catalyst solution 1 was adjusted to pH 2.5 and immersed in a solution at 25 ° C. for 3 minutes.

4. Electroless plating: Three types of plated objects subjected to the above processes 1 to 3 were prepared, and the following three types of electroless plating were performed.

(A) Electroless nickel-phosphorus plating: Using a commercially available electroless nickel-phosphorus plating solution (trade name: TMP Chemical Nickel, manufactured by Okuno Pharmaceutical Co., Ltd.), the pH is adjusted to 9.
0 was immersed in a plating solution at 40 ° C. for 10 minutes.

(B) Electroless nickel-boron plating: Using a commercially available electroless nickel-boron plating solution (trade name: Top Chemalloy 66, manufactured by Okuno Pharmaceutical Co., Ltd.), p
It was immersed in a plating solution of H6.5 at 60 ° C. for 10 minutes.

(C) Electroless copper plating: Using a commercially available electroless copper plating solution (trade name: TMP Chemical Copper # 100, manufactured by Okuno Pharmaceutical Co., Ltd.), 25% in a plating solution having a pH of 13.0.
C. for 10 minutes.

With respect to each of the obtained electroless plating films, the film coverage and the appearance of the object to be plated were examined by the following methods. The results are shown in Table 1 below.

Test method: Film coverage (%): Indicates the ratio of the area where the plating film was formed on the object to be plated.

2. Appearance of plating object: The appearance of the plating film was visually inspected.

As a plating bath stability test, a metal salt of a plating bath component, a reducing agent and p
While replenishing the H adjuster, the test piece was replaced every 10 minutes and electroless plating was continuously performed, and metal other than the object to be plated was precipitated in the plating bath, and the reaction of the plating bath rapidly progressed. Then, the number of turns until the plating film was not formed at a constant appearance and deposition rate with the stability of the plating bath being impaired was examined. One turn is a period in which metal ions corresponding to the amount contained in the plating bath at the start of the electroless plating are supplied.

Example 2 10 mmol of silver sulfate was dissolved in 800 ml of pure water, and 100 ml of an aqueous solution containing 500 mg of polyoxyethylene (POE) stearyl ether phosphoric acid was stirred into this solution while stirring so as to be uniform. Was added. Subsequently, 50 ml of an aqueous solution containing 5 mmol of dimethylamine borane was added to this solution.
was added with vigorous stirring to make it uniform. When the color of the solution rapidly changed to reddish brown, 50 ml of an aqueous solution containing 0.02 mmol of palladium nitrate was added. As a result, 1000 ml of a uniform and transparent fine silver particle dispersion was obtained. This is referred to as catalyst liquid 2.

Electroless plating was performed in the same manner as in Example 1 except that the catalyst solution 2 was used instead of the catalyst solution 1, and the obtained electroless plating film was subjected to film coverage and plating. The object appearance was examined. Further, the stability of the plating bath was examined in the same manner as in Example 1. The results are shown in Table 1 below.

Example 3 10 mmol of silver perchlorate was dissolved in 800 ml of pure water, and 100 ml of an aqueous solution containing 5 g of disodium lauryl sulfosuccinate was added to this solution with vigorous stirring. 50 ml of an aqueous solution containing 10 mmol were added with vigorous stirring. When the color of the solution rapidly changed to reddish brown, 50 ml of an aqueous solution containing 0.05 mmol of tetraamminepalladium chloride was added. As a result, a uniform and transparent silver fine particle dispersion liquid 1000
m1 was obtained. This dispersion is referred to as “catalyst liquid 3”.

Electroless plating was carried out in the same manner as in Example 1 except that the catalyst solution 3 was used instead of the catalyst solution 1, and the resulting electroless plated film was subjected to film coverage and plating. The object appearance was examined. Further, the stability of the plating bath was examined in the same manner as in Example 1. The results are shown in Table 1 below.

COMPARATIVE EXAMPLE 1 While vigorously stirring a solution of 0.5 mmol of silver nitrate (I) in 940 ml of pure water, this solution contains 100 mg of polyethylene glycol-p-nonylphenyl ether which is a nonionic surfactant. 10 ml of an aqueous solution and 50 ml of an aqueous solution containing 2 mmol of sodium borohydride corresponding to 4 times the molar amount of silver nitrate were sequentially added.
As a result, the color of the solution rapidly changed to yellowish brown, and 1000 ml of a uniform transparent silver hydrosol having a pH of 9.6 was obtained. This is designated as Comparative Catalyst Liquid 1.

Instead of the catalyst liquid 1, the comparative catalyst liquid 1 was adjusted to pH
Electroless plating was carried out in the same manner as in Example 1, except that 9.6 was used as it was, and the obtained electroless plated film was examined for the film coverage and the appearance of the object to be plated. Further, the stability of the plating bath was examined in the same manner as in Example 1.
The results are shown in Table 1 below.

Comparative Example 2 150 ml of concentrated hydrochloric acid (35%) was diluted with 750 ml of pure water, and a commercially available palladium-tin colloid solution as a catalyst for electroless plating (trade name: Catalyst C, manufactured by Okuno Pharmaceutical Co., Ltd.) 60 ml was added, and pure water was added to make 1000 ml. This is designated as Comparative Catalyst Liquid 2.

A comparative catalyst solution 2 was used in place of the catalyst solution 1,
In the plating method of Example 1, after the catalyst is applied, a treatment of immersing in an aqueous solution containing 98% H ₂ SO ₄ at 150 g / l at 60 ° C. for 5 minutes as an activation treatment is performed, and then electroless plating is performed. Except for the above, electroless plating was performed in the same manner as in Example 1, and the obtained electroless plated film was examined for the film coverage and the appearance of the object to be plated. Further, the stability of the plating bath was examined in the same manner as in Example 1.
The results are shown in Table 1 below.

[0052]

[Table 1]

As is clear from the above results, the catalyst solution 1
In Examples 1 to 3 using Nos. 1 to 3, a good electroless plating film could be formed on the epoxy plate as the object to be plated. In particular, in Examples 2 and 3 using the catalyst solutions 2 and 3,
Very excellent catalytic activity could be imparted, and particularly a uniform and good electroless plating film could be formed. The catalyst liquid 1 has a slightly lower catalytic activity than the catalyst liquids 2 and 3,
Compared to the comparative catalyst liquid 1 using silver as a catalyst metal, the catalyst solution had a very excellent catalytic activity and was much superior in the film coverage. Also, the catalyst liquids 1 to 3,
The adsorptivity to the object to be plated was good, and the stability of the electroless plating solution was not hindered by the falling off of the catalytic metal in the plating solution.

In Comparative Example 2, although the film coverage by electroless plating was good, the stability of the electroless plating bath was impaired. In addition, since the number of processing steps is one more than that of other catalyst solutions, the processing is complicated.

Catalyst Solution Stability Test Stability tests were performed on the catalyst solutions 1 to 3 and the comparative catalyst solutions 1 and 2 used in Examples 1 to 3 and Comparative Examples 1 and 2 by the following method. The results are shown in Table 2 below.

1. Air blowing test: Air was introduced at a rate of 1000 ml / min into each catalyst liquid having a liquid temperature of 25 ° C. and a liquid volume of 500 ml, and the time required for coagulation and precipitation to occur in the catalyst liquid was determined.

2. Hexavalent chromium addition test: To 500 ml of each catalyst solution, 1 ml of an aqueous solution containing 2 mol / l of chromic anhydride was added, and coagulation and precipitation occurred in the catalyst solution or the catalyst solution became transparent. The amount to be added was determined.

3. Chloride ion addition test: 500 ml of each catalyst solution contained one aqueous solution containing 10 g / l of chloride ions.
ml was added, and the amount added until coagulation and precipitation occurred in the catalyst solution was determined.

[0059]

[Table 2]

As is clear from the above results, each of the catalyst solutions 1 to 3 as the catalyst solution of the present invention has much higher stability than the comparative catalyst solutions 1 and 2 as the known catalyst solutions. Good.

Claims (4)

[Claims] 1. A reducing agent comprising 0.01 to 100 mmol / l of a silver salt, 0.01 to 0.5% by weight of an anionic surfactant and 0.1 to 0.8 times mol of a silver salt. A catalyst solution for electroless plating, comprising an aqueous solution containing the catalyst. 2. The catalyst solution for electroless plating according to claim 1, which is obtained by adding and mixing a reducing agent to an aqueous solution containing a silver salt and an anionic surfactant. 3. The catalyst solution for electroless plating according to claim 1, further comprising 0.01 to 0.5 mmol / l of a palladium salt. 4. An electroless plating method comprising immersing an object to be plated in the catalyst solution according to claim 1 and then immersing the object in a self-catalytic electroless plating solution.