JP2001323383A - Method for imparting catalyst for electroless plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for imparting a catalyst for electroless plating by using a catalyst imparting solution containing a palladium compound and a stannous compound, in which a good electroless plating film having less defects nonplated can be formed, and to provide a treating solution usable therefor. SOLUTION: In this method for imparting a catalyst for electroless plating, the object to be plated is brought into contact with a catalyst imparting solution composed of a solution containing a palladium compound, a stannous compound and acid and water as a medium, is thereafter, if required, brought into contact with an acidic aqueous solution of pH <=2 or an alkaline aqueous solution of pH >=13 and is then brought into contact with an aqueous solution of pH 3 to 11 containing an oxidizer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for applying a catalyst for electroless plating.

[0002]

2. Description of the Related Art A method of forming a metal film on a nonconductive material by performing electroless plating on a nonconductive material, particularly plastics, and subsequently performing electroplating, has been widely used. Plastics coated with metal in this way are lightweight and have a metallic appearance, so that they are widely used as automobile parts and electric appliance parts.

As a method for coating plastics with a metal, an etching treatment with a chromic acid-sulfuric acid aqueous solution for the purpose of hydrophilizing and roughening (roughening) the plastic surface is performed, and then a noble metal compound, particularly a palladium compound is contained. A method of applying a catalyst for inducing electroless plating using an aqueous solution, performing electroless plating, and subsequently performing electroplating has been widely adopted.

In such a metal coating method, as a method for applying a catalyst, at first, a surface treatment with a stannous chloride aqueous solution of hydrochloric acid (sensitizer treatment) and a surface treatment with palladium chloride aqueous solution of hydrochloric acid (activator treatment) ) Two-stage processing was performed. However, in this method of applying a catalyst, fine projections are often formed on the surface of the formed electroless plating film, and the plating appearance is impaired. Therefore, a brushing treatment is often performed on the electroless plating film with a sponge or the like. After that, it was necessary to shift to the next electroplating, and the processing steps were complicated.

[0005] As an alternative method of providing a catalyst, a palladium colloid solution called a catalyst solution prepared by heating and stirring an aqueous solution of stannous chloride in hydrochloric acid and adding an aqueous solution of palladium chloride thereto is used. The plastics to be plated is brought into contact with this catalyst solution, and then brought into contact with a strong acid aqueous solution or a strong alkaline aqueous solution called an accelerating solution (accelerator solution) to perform an accelerating process (accelerator process). A method has been proposed and is now widely adopted. This method is an economical method in which the amount of consumed palladium is small and the electroless plating film to be formed is smooth and has relatively few pinholes.

However, when a catalyst is applied by this method, a black portion is often formed on a film in an actual working process. Such a portion is a non-plated portion when viewed microscopically, and causes pits in the subsequent electroplating process, and significantly reduces the yield of products.

[0007]

SUMMARY OF THE INVENTION The main object of the present invention is to:
In a method of applying a catalyst for electroless plating using a catalyst applying solution containing a palladium compound and a stannous compound, a catalyst applying method capable of forming a good electroless plating film having almost no non-plated portion, And to provide a processing solution that can be used therefor.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of the above problems, and as a result, have found that after applying a catalyst using a catalyst application liquid containing a palladium compound, a stannous compound and an acid. By using an aqueous solution having a pH of 3 to 11 containing an oxidizing agent instead of the conventionally used accelerating solution as the accelerating solution and bringing the object to be plated into contact therewith,
It has been found that a high catalytic activity can be imparted to the object to be plated, and a good electroless plating film can be formed with almost no non-plated portions, and the present invention has been completed.

That is, the present invention provides the following method for applying a catalyst for electroless plating, a method for electroless plating, and an accelerating solution. 1. After the object to be plated is brought into contact with a plating solution comprising a solution containing water as a medium containing a palladium compound, a stannous compound and an acid, it is brought into contact with an aqueous solution having a pH of 3 to 11 containing an oxidizing agent. A method for applying a catalyst for electroless plating. 2. After the object to be plated is brought into contact with a catalyst-imparting solution comprising a solution containing water containing a palladium compound, a stannous compound and an acid, the object is brought into contact with an acidic aqueous solution of pH 2 or lower or an alkaline aqueous solution of pH 13 or higher, and A method for applying a catalyst for electroless plating, which comprises contacting an aqueous solution having a pH of 3 to 11 containing an agent. 3. Item 3. The method for applying a catalyst for electroless plating according to Item 1 or 2, wherein the oxidizing agent is at least one selected from hydrogen peroxide, sodium percarbonate, sodium perborate, sodium persulfate, and ammonium persulfate. 4. 4. An electroless plating method, comprising: applying an electroless plating catalyst to an object to be plated by the method according to any one of the above items 1 to 3; 5. Consisting of an aqueous solution of pH 3 to 11 containing an oxidizing agent,
Item 5. An accelerating solution used in the method for applying a catalyst for electroless plating according to any one of Items 1 to 3 above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for applying a catalyst according to the present invention, an object for plating is brought into contact with an aqueous solution containing an oxidizing agent after the object to be plated is brought into contact with a catalyst applying solution. Can be granted.

As the catalyst-providing liquid, a solution containing water as a medium containing a palladium compound, a stannous compound and an acid, which is generally called a catalyst liquid, is used. In the catalyst application liquid, the palladium compound and the stannous compound are considered to exist as colloid particles or a water-soluble complex in water. As such a catalyst-providing liquid, a commonly used well-known catalyst liquid can be used.

The palladium compound which can be used in the catalyst-providing liquid is preferably a compound which can easily dissociate in water to release palladium ions, and palladium chloride (PdCl 2)
₂ ) and palladium sulfate (PdSO ₄ ). As the stannous compound, those capable of easily dissociating in water to release stannous ions are preferable, and examples thereof include stannous chloride and stannous sulfate. As the acid, for example, hydrochloric acid, sulfuric acid and the like can be used.

In the catalyst-providing liquid, the concentration of the palladium compound is preferably about 0.01 to 10 mmol / L, more preferably about 0.1 to 8 mmol / L. The concentration of the stannous compound is
The concentration is preferably about 0.5 to 500 mmol / L, more preferably about 1 to 300 mmol / L. The ratio of the palladium compound and the stannous compound is preferably set to about palladium compound / stannic compound (molar ratio) = 1/1 to 1/100,
More preferably, it is set to be about 1/20 to 1/100.

Regarding the acid concentration in the catalyst-providing liquid,
Although not particularly limited, usually, it may be about 0.5 to 3 mol / liter.

Further, sodium chloride, potassium chloride, sodium sulfate, potassium sulfate and the like can be added to the catalyst-providing liquid for the purpose of stabilizing the liquid. The amount of these compounds to be added is not particularly limited, and may be appropriately determined from the concentration range in which the compounds can be dissolved.
The amount may be about mmol / liter or more.

As an example of a method for preparing the catalyst-providing liquid, a method in which a concentrated aqueous hydrochloric acid solution in which stannous chloride is dissolved is heated to about 100 ° C. and an aqueous palladium chloride solution is added with stirring can be mentioned. It is not limited to such a preparation method. The catalyst-providing liquid is usually commercially available as a concentrated solution in which stannous chloride and palladium chloride are dissolved, and may be used after being diluted to an appropriate concentration when used.

The method for applying the catalyst may be such that the object to be plated is brought into contact with the solution for applying the catalyst. Usually, the object to be plated is placed in the solution for applying the catalyst at a temperature of about 20 to 40 ° C. for about 1 to 5 minutes. What is necessary is just to soak.

In the method of the present invention, after the object to be plated is brought into contact with the catalyst-providing liquid by the above-mentioned method, it is brought into contact with an aqueous solution containing an oxidizing agent.

As the oxidizing agent, nitrates such as potassium nitrate, sodium nitrate and ammonium nitrate; peroxides and salts thereof such as hydrogen peroxide, sodium peroxide, sodium percarbonate and sodium perborate; sodium persulfate and potassium persulfate; Examples thereof include peroxo acids such as ammonium persulfate and salts thereof; oxygen acids such as potassium chlorate, potassium perchlorate, potassium iodate and potassium periodate, and salts thereof. These oxidizing agents can be used alone or in combination of two or more. Among these, a compound having good solubility in water, an aqueous solution being nearly neutral and generating no gas such as a halogen gas is preferable, and hydrogen peroxide, sodium percarbonate, sodium perborate, sodium persulfate,
Ammonium persulfate and the like are particularly preferred.

The concentration of the oxidizing agent in the aqueous solution varies depending on the oxidizing power of the oxidizing agent, the amount of the catalyst adsorbed, the state of the catalyst adsorbed, and the like.
About 100 g / l is more preferable. If the concentration of the oxidizing agent is too low, the catalytic activity becomes insufficient, and it becomes difficult to form good electroless plating. On the other hand, increasing the concentration of the oxidizing agent more than necessary is uneconomical because the effect is not improved.

The aqueous solution containing the oxidizing agent has a pH of 3 to 11.
Degree, preferably in the range of about 5 to 11. When the pH is within the above range, the catalytic effect on electroless plating can be greatly improved.

As a treatment method using an aqueous solution containing an oxidizing agent, the object to be plated may be brought into contact with the aqueous solution. Usually, the object to be plated is placed in an aqueous solution having a liquid temperature of about 10 to 50 ° C. It may be immersed for about a minute. If the liquid temperature is too low, the catalytic effect is not sufficiently exerted, which is not preferable. On the other hand, if the liquid temperature is too high, a catalytic effect can be exerted, but the oxidizing agent self-decomposes and the liquid life is shortened, which is not preferable.

By contacting an object to be plated with an aqueous solution containing an oxidizing agent in such a manner, a high catalytic activity for electroless plating can be imparted.

The reason why such a high catalytic activity can be imparted by the method of the present invention is not necessarily clear, but a palladium compound which is considered to be adsorbed on the object to be plated as colloidal particles is divalent or tetravalent. It is oxidized to a valence state, and the palladium compound in this state is considered to exhibit high catalytic activity for the deposition of electroless plating.

In the catalyst application method of the present invention, after the object to be plated is brought into contact with the catalyst application solution by the above-mentioned method, and before contact with an aqueous solution containing an oxidizing agent, if necessary, pH 2
It can be brought into contact with the following acidic aqueous solution or an alkaline aqueous solution having a pH of 13 or more. By performing this treatment, the catalytic activity for electroless plating can be further improved. According to this treatment, tin, which is an amphoteric metal, is dissolved and removed from the catalyst component containing the tin compound and the palladium compound attached to the object to be plated,
As a result, it is considered that the catalyst activity is further improved by increasing the ratio of Pd as a catalyst component. As the acidic aqueous solution used in this treatment, for example, an aqueous solution containing an acidic compound such as sulfuric acid or hydrochloric acid can be used. The concentration of the acidic compound in these aqueous solutions is not particularly limited, and may be any concentration as long as the pH becomes 2 or less. Usually, the concentration of the acidic compound is preferably about 10 to 200 g / l, and 50 to 150 g. / L is more preferable. If the concentration of the acidic compound is too low, the effect of improving the catalytic activity cannot be sufficiently obtained, while if the concentration of the acidic compound is too high, the catalyst component P
d seems to dissolve, and the catalytic activity tends to decrease. Further, as the alkaline aqueous solution, an aqueous solution containing an alkaline compound such as sodium hydroxide, potassium hydroxide, and ammonia can be used. The concentration of the alkaline compound in the aqueous solution is not particularly limited, and may be a concentration at which the pH becomes 13 or more. Usually, the concentration of the alkaline compound is preferably about 2 to 100 g / l, and 5 to 50 g / l. More preferably, it is about l. If the concentration of the alkaline compound is too low, the effect of improving the catalytic activity cannot be sufficiently obtained, while if the concentration is too high, the catalytic activity tends to decrease.

As a treatment method using an acidic aqueous solution having a pH of 2 or less or an alkaline aqueous solution having a pH of 13 or more, an object to be plated may be brought into contact with the aqueous solution.
What is necessary is just to immerse the object to be plated in an aqueous solution at a liquid temperature of about ° C for about 1 to 30 minutes.

According to the method of the present invention, a good electroless plating film can be formed with almost no non-plated portions by performing electroless plating according to a conventional method after applying a catalyst. As the electroless plating solution, any autocatalytic electroless plating solution containing a reducing agent can be used without particular limitation. Specific examples of such an electroless plating solution include an acidic electroless nickel plating solution using sodium hypophosphite as a reducing agent, an ammonia alkaline electroless nickel plating solution using sodium hypophosphite as a reducing agent, and dimethylamine. Examples thereof include an acidic or alkaline electroless nickel plating solution using a boron compound such as borane as a reducing agent, an alkaline copper plating solution using formalin as a reducing agent, and an acidic electroless copper plating solution using sodium hypophosphite as a reducing agent. The electroless plating method may be a conventional method, and may be appropriately determined depending on the type of the plating solution to be used.

The catalyst application method of the present invention can be applied to any material which does not have catalytic activity for the deposition reaction of electroless plating as it is. Examples of the object to be plated to which the catalyst applying method of the present invention can be applied include plastics,
In addition to non-conductive materials such as ceramics and glasses, metals such as copper and brass that do not exhibit catalytic activity can also be mentioned. In particular, the method for applying a catalyst of the present invention is a method capable of forming a plating film having a good appearance.
Usefulness as a catalyst application method in a decorative plating method using plastics such as polycarbonate (PC) resin, PC / ABS alloy resin, PC / acrylic rubber (ASA) alloy resin, nylon resin, polyolefin resin, and noryl resin as objects to be plated. Is a high method.

When applying a catalyst according to the method of the present invention, prior to the catalyst applying step, pretreatment may be performed according to a conventional method according to the type of the object to be plated.

For example, when plastics are to be plated, the adhesion of the electroless plating film can be improved by performing an etching treatment using a mixed aqueous solution of chromic acid and sulfuric acid. For example, when an ABS resin is used as an object to be plated, an etching solution (350 to 450 g of chromic acid) composed of a mixed aqueous solution of chromic acid and sulfuric acid is used.
/ L and about 380 to 420 g / l of sulfuric acid, preferably 380 to 420 g / l of chromic acid and 380 to 400 g of sulfuric acid
Immersing the object to be plated in a mixed aqueous solution of about 420 g / l at about 60 to 70 ° C. for about 5 to 15 minutes to oxidize and roughen the surface of the object to be plated, and then applying the catalyst application method of the present invention. Thereby, the adhesion of the formed electroless plating film can be improved.

According to the catalyst applying method of the present invention, a higher catalytic activity can be imparted as compared with the conventional catalyst applying method, so that the deposition reaction of the electroless plating proceeds reliably and quickly,
The occurrence of microscopically non-plated portions is prevented over the entire surface of the object to be plated, and a good electroless plating film having almost no such defective portions can be formed.

After performing the electroless plating by the method described above,
Various types of electroplating can be performed according to a conventional method. In this case, the formed electroplating film hardly has a defective portion such as a pinhole, and a plating film having an excellent appearance is formed.

[0033]

According to the method for applying a catalyst of the present invention, excellent catalytic activity can be imparted to an object to be plated, and a good electroless plating film containing almost no unplated portion can be formed.

In addition, since the electroless plating reaction can be induced more sensitively than the conventional method of applying a catalyst, the electroless plating solution to be used can be more stabilized, and the life of the electroless plating solution can be extended. Can be extended.

[0035]

The present invention will be described in more detail with reference to the following examples.

Example 1 An ABS resin plate (120 × 120) manufactured by Mitsubishi Rayon Co., Ltd.
× 3 mm) as a material to be plated, and after applying a catalyst in the following steps A to C, an accelerating treatment is performed under the conditions shown in Table 1 or Table 2, and then sodium hypophosphite is reduced with a reducing agent. An electroless nickel plating film was formed by immersion in a 35 ° C. ammonia alkaline electroless nickel plating solution (TMP Chemical Nickel A 160 ml / l, B 160 ml / l, manufactured by Okuno Pharmaceutical Co., Ltd.).
Water washing was performed between each treatment. In all the treatment methods shown in Tables 1 and 2, the electroless nickel plating time was set to the same time of 2 minutes to clarify the effect of the accelerating treatment. Degreasing treatment Immersion in an alkaline degreasing agent (Ascreen A-220 50 g / l manufactured by Okuno Pharmaceutical Co., Ltd.) at 50 ° C. for 5 minutes. Etching Immersion at 70 ° C. for 10 minutes in an aqueous solution containing 400 g / l of chromic anhydride and 400 g / l of 98% sulfuric acid. Catalyst application treatment (Catalyst treatment) Catalyst solution composed of a protective colloidal solution of palladium with stannous chloride (Catalyst C 40 ml manufactured by Okuno Pharmaceutical Co., Ltd.)
/ L and an aqueous solution containing 180 ml / l of 35% hydrochloric acid) at 30 ° C for 30 minutes. Before the treatment, the palladium chloride concentration was 0.1 g / l and the stannous chloride concentration was 8 g / l. With respect to the electroless nickel plating film formed by the above-described method, the ratio of the plating deposition portion was determined, taking the case where the nickel plating solution was deposited on the entire surface of the ABS resin plate as 100%. The results are shown in Table 1 below.

[0037]

[Table 1]

[0038]

[Table 2]

As is clear from the above results, it is understood that the catalyst application method of the present invention can provide excellent catalytic activity.

Claims (5)

[Claims] An object to be plated is brought into contact with a catalyst-imparting solution comprising a solution containing water as a medium containing a palladium compound, a stannous compound and an acid, and then brought into contact with an aqueous solution containing an oxidizing agent and having a pH of 3 to 11. A method for applying a catalyst for electroless plating, comprising: 2. An object to be plated is brought into contact with a plating solution comprising a solution containing water containing a palladium compound, a stannous compound and an acid as a medium, and then an acidic aqueous solution having a pH of 2 or less or a pH of 2 or less.
A method for applying a catalyst for electroless plating, comprising contacting with an aqueous alkaline solution of at least 13 and then contacting with an aqueous solution containing an oxidizing agent and having a pH of 3 to 11. 3. The method according to claim 1, wherein the oxidizing agent is at least one selected from hydrogen peroxide, sodium percarbonate, sodium perborate, sodium persulfate and ammonium persulfate.
3. The method for applying a catalyst for electroless plating according to item 2. 4. An electroless plating method, comprising: applying an electroless plating catalyst to an object to be plated by the method according to claim 1; 5. The accelerating solution used in the method for applying a catalyst for electroless plating according to claim 1, comprising an aqueous solution containing an oxidizing agent and having a pH of 3 to 11.