CN1842615A - Electroless plating method and electrically nonconductive plating object with plating film formed thereon - Google Patents

Abstract

The invention relates to a plating film without catalyst process to form high adhesive without electric plating on the non-conductive object, wherein it adds the conductive medium (2) with catalytic to the oxidization of reducer (R) into the plating bath (1) of the reducer (R) that outputting metallic ion and the metallic ion (M+) for forming plating film (5); the metallic ion receives the electron generated by the oxidization of reducer to be reduced and output at the surface medium (2); and the output metal is adhered on the surface of medium 92); via impacting object (4) with medium (2), the metal (3) is compressed on the surface of object (4), and using said metal (3) as core, to form plating film (5).

Description

Electroless plating method and non-conductive object to be plated to form plated film

technical field

The present invention relates to an electroless plating method for a non-conductive to-be-plated object and a non-conductive to-be-plated object with a plated film formed by the electroless plating method.

Background technique

Formation of metal films is required in various fields such as decorative plating and electrode formation of electronic components. Plating is often used in the formation of metal films. When the object to be plated is non-conductive, in order to form a metal film, usually electroless plating cannot be applied instead of electroplating. Typically, in electroless plating, a reducing agent is added to a plating bath, and metal is deposited on the surface of an object to be plated using electrons generated by the oxidation reaction of the reducing agent. This plating method is called autocatalytic electroless plating.

In self-catalytic electroless plating, it is necessary to make the surface of the object to be plated catalytically active for the oxidation reaction of the reducing agent. Therefore, in the past, as described in Japanese Patent Application Laid-Open No. 2002-314309 (Patent Document 1), for example, the surface of the object to be plated is made catalytically active by immersing the object to be plated in a catalyst solution containing Pd (palladium) in advance. change.

The catalyst mainly composed of Pd has the strongest catalytic effect in the self-catalyzed electroless plating, and also has the advantage of many types of applicable reducing agents, and is most widely used in industry.

However, when an object to be plated is immersed in a catalyst solution containing Pd, there is a problem that a degreasing process, an etching process, and the like are required as a pretreatment for imparting a Pd catalyst, which complicates the production process. In addition, there is a problem that Pd is expensive. In addition, there is a problem in that an intermediate layer composed of Pd remaining as a catalyst between the object to be plated and the plated film weakens the adhesion of the plated film to the object to be plated.

In Japanese Patent Laid-Open No. 2003-183843 (Patent Document 2), the following plating method is disclosed: adding metal ions forming a plating film to the conductive electrode portion formed on the surface of the object to be plated and separating the metal ions A method of electroless plating in a plating bath of a reducing agent, characterized in that a conductive medium exhibiting catalytic activity for the oxidation reaction of the reducing agent is thrown into the plating bath together with the object to be plated.

In the plating method described in Patent Document 2, it is possible to form an electroless plating film on the electrode portion without applying the above-mentioned Pd catalyst to the electrode portion. However, Patent Document 2 does not disclose the formation of a plated film of an object to be plated made of a nonconductive body.

Patent Document 1: Japanese Patent Laid-Open No. 2002-314309

Patent Document 2: Japanese Patent Laid-Open No. 2003-183843

disclosure of invention

The problem to be solved by the invention

An object of the present invention is to provide an electroless plating method capable of forming a plating film on a non-conductive object to be plated without a prior catalyst application step.

Another object of the present invention is to provide a non-conductive object to be plated in which a plated film with high adhesion is formed.

Solution to the problem

The present invention is firstly a plating method for electroless plating of a non-conductive object to be plated using a plating bath that has added metal ions forming a plated film and a reducing agent that precipitates the metal ions. It is characterized in that the oxidation reaction to the reducing agent is A conductive medium exhibiting catalytic activity is in contact with the object to be plated.

In the electroless plating method of the present invention, in order to make the conductive medium contact the object to be plated more effectively, it is preferable to prepare a container that allows the plating solution to pass through, and put the non-conductive object to be plated and the conductive medium into the container. , Rotate, shake or vibrate the container filled with the non-conductive object to be plated and the conductive medium in the plating bath.

In the electroless plating method according to the present invention, it is preferable to deposit the above-mentioned metal ions on the conductive medium, to attach the deposited metal to the conductive medium, and to contact the conductive medium with the non-conductive object to be plated. Transfer the precipitated metal attached to the conductive medium to the non-conductive object to be plated, thereby forming a plated film on the non-conductive object to be plated.

In the preferred first embodiment of the electroless plating method described in the present invention, the main component of the plating film is made of Ni, Co, Au or Pt or their alloys, the reducing agent contains phosphoric acid compounds, and the conductive medium contains Ni, Co At least one of , Au and Pt.

In the preferred second embodiment of the electroless plating method described in the present invention, the main component of the coating film is made of Ni, Co, Au or Pt or their alloys, the reducing agent contains boron compounds, and the conductive medium contains Ni, Co, etc. at least on the surface. At least one of , Au and Pt.

In a preferred third embodiment of the electroless plating method of the present invention, the main component of the plating film is composed of Ni, Co or Pt or their alloys, the reducing agent contains nitrogen compounds, and the conductive medium contains Ni, Co and Pt at least on the surface At least 1 of them.

In a preferred fourth embodiment of the electroless plating method according to the present invention, the main component of the plated film is composed of Cu, Ag or Au or their alloys, the reducing agent contains aldehyde compounds, and the conductive medium contains Cu, Ag and Au at least on the surface At least 1 of them.

The present invention is also a non-conductive object to be plated that forms a plated film mainly composed of at least one metal selected from Ni, Co, Cu, Ag, Au, and Pt, or an alloy thereof. It is characterized in that the coating film is formed by the above-mentioned electroless plating method of the present invention, and it is also characterized in that the coating film is not directly connected to the non-conductive layer through a layer composed of a substance that exhibits catalytic activity for the reduction of the reducing agent. The state of being bonded to the plated object.

The effect of the invention

According to the electroless plating method of the present invention, since it is not necessary to provide a catalyst such as Pd to the non-conductive object to be plated in advance, it is possible to form a plated film at low cost without complicated steps.

In addition, with the electroless plating method of the present invention, since the plated film is directly bonded to the non-conductive object to be plated without passing through an intermediate layer composed of a Pd catalyst or the like, it is possible to obtain a material having high adhesion to the object to be plated. coating.

A brief description of the drawings

[ Fig. 1] Fig. 1 is a diagrammatic explanatory view of a plated film formation process using the electroless plating method according to the present invention.

Explanation of symbols

1 electroless plating bath

2 conductive medium

3 Precipitation of metal

4 Non-conductive objects to be plated

5 coating

The best way to practice the invention

First, the electroless plating method according to the present invention will be described.

In short, the electroless plating method of the present invention is a plating method in which a non-conductive object to be plated is electrolessly plated using a plating bath that adds metal ions forming a plated film and a reducing agent that precipitates the metal ions, and is characterized in that The method is to bring a conductive medium, which exhibits catalytic activity to the oxidation reaction of the reducing agent, into contact with the object to be plated.

Referring to Figure 1, it will be described in more detail. As shown in Figure 1(a), the metal ions (M ⁺ ) contained in the electroless plating bath 1 undergo the oxidation reaction ( ) generated electrons (e ⁻ ) are reduced and easily deposited and attached to the surface of the conductive medium 2 . As a result, first, the precipitated metal 3 derived from the metal ion (M ⁺ ) adheres to the surface of the conductive medium 2 .

Next, as shown in FIG. 1( b), the precipitated metal 3 attached to the conductive medium 2 is attached to the object to be plated 4 by pressing or rubbing when the conductive medium 2 hits the nonconductive object to be plated as shown by the arrow. The surface, as shown in Figure 1(c), is transferred to the surface of the object to be plated 4. As a result, the deposited metal 3 transferred to the surface of the object to be plated 4 adheres to the object to be plated 4 by the fixation effect.

Next, with the precipitated metal 3 adhered to the object 4 as the nucleus, as shown by the dotted line in FIG. Especially when the precipitated metal 3 has catalytic activity with respect to the reducing agent, the formation of the plated film 5 is accelerated as the formed plated film 5 expands after the nuclei of the precipitated metal 3 are formed.

The above-mentioned plated film 5 is in a state of being directly bonded to the non-conductive object to be plated 4 without a layer composed of a substance exhibiting catalytic activity for the reducing action of the reducing agent.

As a specific embodiment, it is preferable to apply the following method: prepare a container that allows the plating solution to pass through, put the non-conductive object to be plated and the conductive medium in the container, and put the non-conductive object to be plated and the conductive medium into the container. The container of the medium is rotated, shaken or vibrated in the plating bath, so that the non-conductive object to be plated is in effective contact with the conductive medium. In this case, a barrel such as that used in the usual electroplating method can be preferably used as the above-mentioned container. In addition, the cylinder may be rotated, shaken or vibrated in a tilted state.

Comparing the plating method described in the present invention with the plating method described in Patent Document 2, it is superior in terms of not needing to provide a catalyst such as Pd in advance and to make a conductive medium exhibiting catalytic activity to a reducing agent contact the object to be plated. Common. However, in the plating method described in Patent Document 2, there is a big difference in that the object to be plated has a conductor portion such as an electrode, and that the plated film is formed only on the conductor portion.

That is, in the plating method described in Patent Document 2, when the conductive medium having catalytic activity contacts the surface of the conductive part of the object to be plated, an oxidation reaction of the reducing agent occurs in the vicinity of the contact point. The electrons generated by the reaction flow to the conductor of the object to be plated. Metal ions near the conductor in the plating bath receive electrons on the conductor, and the metal is deposited on the conductor. By repeating this reaction, a plating film is formed only on the conductor.

On the other hand, since there is no flow of electrons generated by the oxidation reaction of the reducing agent on the non-conductor portion of the object to be plated except for the conductor portion, no plating film is formed according to the mechanism described in Patent Document 2. However, in the non-conductor part, if according to the above-mentioned mechanism of the present invention, that is, the mechanism in which the precipitated metal precipitated and attached on the conductive medium is transferred to the plated object and adhered to the plated object when the conductive medium hits the plated object, it is speculated that There should also be a coating formed. However, with the mechanism described in Patent Document 2, since metal ions in the plating bath are preferentially deposited on the conductor portion, almost no plated film is formed on the non-conductor portion.

In summary, even if the same metal ion and the same conductive medium having catalytic activity to the reducing agent are used, the mechanism of plating film formation will be completely different depending on whether the object to be plated contains a conductive part or not. That is, since the plating method according to the present invention is aimed at forming a plated film on a nonconductive body, the object to be plated which is the object of the present invention does not actually contain a conductive part.

Because the plating method described in the present invention is based on the above-mentioned mechanism, so compared with the situation of the plating method described in the above-mentioned patent document 1, or the surface to form the plated film as described in the patent document 2 is Compared with the case of a conductor, the film formation rate is slow. However, as mentioned above, if it is taken into consideration that the film formation rate becomes faster by forming an autocatalytic metal-precipitating nucleus, this will not be a practical problem.

As mentioned above, using the plating method of the present invention, the metal ions in the plating bath are mainly precipitated on the conductive medium with catalytic activity, and then contact the plated object through the conductive medium, and the precipitated metal is transferred to the plated object. object and glue. Using the bonded precipitated metal as a nucleus, a plated film is formed by the autocatalytic property of the precipitated metal. Thereby, even if the object to be plated is non-conductive, an electroless plated film can be formed without going through a previous catalyst application step.

At least the surface of the conductive medium must be catalytically active towards the reducing agent in the plating bath. The types of reducing agents that can be used and the metal elements constituting the conductive medium corresponding thereto will be described below.

As the reducing agent, phosphoric acid-based compounds, boron-based compounds, nitrogen-based compounds, aldehyde-based compounds and the like are generally and widely used. Studies have been reported on metals that are catalytically active against these reducing agents.

For example, Au, Ni, Co, and Pt have been reported to be catalytically active for the oxidation reaction of sodium hypophosphite (NaH ₂ PO ₂ ) as a phosphoric acid-based reducing agent (Ohno, Wakabayashi, and Haruyama Shiro, "Electroless Plating for Secondary Catalytic activity of metals by anodic oxidation of sodium phosphate (catalytic activity of electroless めつきにおける おぺてきにおける おぺけるりりるウムのアノイドルトスるるののcatalytic activity) for metals)", Metal Surface Technology, Vol. 34, No. 12, 1983 , pp.594-599).

Therefore, in the case of using a phosphate-based reducing agent, at least one of Au, Ni, Co, and Pt is used as the metal constituting the surface of the conductive medium, so that it can be plated on a non-conductive substrate without a prior catalyst imparting process. The coating of Ni, Co, Au, Pt, etc. is formed on the surface of the object.

In addition, it has been reported that when boron compounds such as sodium borohydride (NaBH ₄ ) and DMAB ((CH ₃ ) ₂ NHBH ₃ ) are used as reducing agents, Ni, Co, Pt, and Au can catalyze the oxidation of these boron compounds. Activity (Ohno, Wakabayashi, Haruyama Shiro, "Catalytic activity of metals for the anodic oxidation of sodium borohydride and dimethylamine borane in electroless plating (electroless めつきにおけるホウ hydrohydration ナトリウム りよびジメチルアミンボランのアノ一ぉ酸化に或するmetalのcatalyst activity)", Electrochemistry, Vol. 53, No. 3, 1985, pp.196-201).

Therefore, when a boron compound is used as a reducing agent, at least one of Au, Ni, Co, and Pt is used as the metal constituting at least the surface of the conductive medium, and the non-conductive medium can be formed without a prior catalyst imparting process. Plating films of Ni, Co, Au, Pt, etc. are formed on the surface of the object to be plated.

In addition, it has been reported that when hydrazine (N ₂ H ₄ ), which is a nitrogen compound, is used as a reducing agent, Ni, Co, and Pt have catalytic activity for the oxidation reaction of N ₂ H ₄ (by Ohno Haru, Wakabayashi Ri, and Haruyama Shiro, pp. "Catalytic activity of metals for anodic oxidation of formaldehyde and hydrazine in electroless plating (electroless めつきにぉける holmu アルデヒド およびびヒヒドラジンのアノ一ドアノイドイニトトルタルのcatalytic activity)", Electrochemistry, Vol. 53, No. No. 3, 1985, pp.190-195).

Therefore, in the case of using a nitrogen compound as a reducing agent, at least one of Ni, Co, and Pt is used as the metal constituting the surface of the conductive medium, and the non-conductive substrate can be plated without a prior catalyst imparting process. Ni, Co, Pt and other coatings are formed on the surface of the object.

In addition, it has been reported that when formaldehyde (HCHO) is used as a reducing agent, Cu, Au, and Ag have catalytic activity for the oxidation reaction of HCHO (Ohno, Wakabayashi, Haruyama Shiro, "Anodic oxidation of formaldehyde and hydrazine in electroless plating Catalytic Activity of Metals", Electrochemistry, Vol. 53, No. 3, 1985, pp.190-195).

Therefore, in the case of using an aldehyde compound as a reducing agent, at least one of Cu, Au and Ag is used as the metal constituting the surface of the conductive medium, and the non-conductive substrate can be plated without a prior catalyst imparting process. Coated films of Cu, Au, Ag, etc. are formed on the surface of the object.

The relationship between the plating bath and the conductive medium preferable for the plating method according to the present invention has been described above. In the above description, the reducing agents are divided into four types: phosphoric acid compounds, boron compounds, nitrogen compounds and aldehyde compounds, but the plating method of the present invention is not limited to the above four types. As long as the metal component in the plating bath and the metal component on the surface of the conductive medium exhibit catalytic activity with respect to the reducing agent used, other combinations are of course also conceivable.

In addition, as for the conductive medium, it is sufficient that at least the surface thereof is conductive and has catalytic activity with respect to the reducing agent, and the internal conductivity and catalytic activity are not related.

The size of the conductive medium can be appropriately selected according to the size of the object to be plated. If the sizes of the conductive medium and the object to be plated are expressed in volume, the volume of the conductive medium is preferably about 1/1000 to 1/1 of the volume of the object to be plated. If the conductive medium is too small, the formation of the film will be slow due to the weak force of pressing and depositing metal when it collides with the object to be plated. On the other hand, if the conductive medium is too large, the formation of the film will be slow due to the low probability of collision with the object to be plated.

The various conditions of the plating bath, such as the concentration of metal ions, the concentration of reducing agents, pH, temperature, and the types and amounts of various additives such as stabilizers and surfactants, etc., need to be selected according to the plating method to be implemented. The type of reducing agent and metal ion can be adjusted appropriately.

Next, a non-conductive object to be plated on which an electroless plated film is formed using the plating method according to the present invention will be described.

As mentioned above, the non-conductive object to be plated in the present invention is a non-conductive material formed with a coating film mainly composed of at least one metal selected from Ni, Co, Cu, Ag, Au, and Pt, or an alloy thereof. The conductive object to be plated is characterized in that the plated film is in a state of being directly bonded to the object to be plated without passing through a layer composed of a metal or a compound mainly composed of, for example, Pd.

Therefore, according to the present invention, no intermediate layer exists between the object to be plated and the plated film because there is no need for a prior step of adding a catalyst such as Pd. Therefore, the adhesion of the plating film is improved.

The premise of a non-conductive object to be plated is that at least the surface portion forming the plated film is non-conductive. Non-conductivity inside the object to be plated where no plated film is formed is not a problem. If there are conductor parts on the surface, the non-conductor part will not form a plated film for the above-mentioned reason, so it is outside the scope of the present invention.

In addition, since the object to be plated is non-conductive, the coating film of the present invention adheres directly to the object to be plated through the fixing effect. Therefore, the greater the surface roughness of the surface of the object to be plated, the greater the adhesion of the plated film. The surface roughness Ra of the object to be plated is preferably at least 0.1 μm, more preferably at least 1 μm.

After forming, for example, a Ni plating film using the plating method of the present invention, a commonly used replacement Au plating layer can be formed on its surface. In addition, there is no problem in forming a Sn plating layer.

Hereinafter, the electroless plating method and the non-conductive object to be plated according to the present invention will be described based on more specific examples.

Example 1

As a non-conductive object to be plated, 100 cube-shaped dielectric ceramic cells having a length of 3 mm, a width of 3 mm, and a height of 7 mm were prepared.

On the other hand, a plating bath having the following composition and conditions was prepared.

Metal salt: copper sulfate 0.04 mol/L

Reducing agent: formaldehyde 0.70 mol/liter

Complexing agent: EDTA 0.08 mol/L

pH: 12.0

Bath temperature: 45°C

Next, put 100 of the dielectric ceramic units and 8.6 g (approximately 1,500 pieces) of Cu balls with a diameter of about 0.7 mm into a shaker with an inner volume of 1.90×10 ⁴ m ³ , and dip the shaker into the above-mentioned plating bath. , while performing air stirring, the shaker was shaken at a speed of 8 to 16 reciprocations/minute for 60 minutes to form a Cu plating film on the surface of the dielectric ceramic unit.

By performing electroless plating as described above, it is possible to form a Cu plated film having a film thickness of about 2.0 μm without the problems of adhesive strength and deposition unevenness without going through a previous catalyst treatment step. The film thickness of the coating film was measured with a fluorescent X-ray film thickness meter (SEA5120 manufactured by Seiko Instruments Co., Ltd.). The above-mentioned plated dielectric ceramic unit is suitably used as a dielectric resonator.

Example 2

As non-conductive objects to be plated, 100 plastic frames with a length of 5 mm, a width of 5 mm, and a height of 1.5 mm were prepared.

On the other hand, "Ebasild TN" manufactured by Ebara Yujilite, which is a commercially available Ni-P alloy bath, was prepared as a plating bath, and the bath temperature was set at 63°C.

Next, the above-mentioned 100 plastic frames and 7.9 g (about 1500 pieces) of Ni balls with a diameter of about 0.7 mm were put into a shaking cylinder with an inner volume of 1.90×10 ⁴ m ³ , and the shaking cylinder was immersed in the above-mentioned plating bath. In this process, the shaker was shaken at a speed of 8 to 16 reciprocations/minute for 60 minutes while air stirring, and a Ni—P film was formed on the surface of the plastic frame.

By performing electroless plating as described above, it is possible to form a Ni-P plating film having a film thickness of about 6.0 μm without the problems of adhesive strength and deposition unevenness without a prior catalyst treatment step. The plastic frame on which the coating is formed is suitably used as an electromagnetic wave shielding material.

Example 3

As a non-conductive object to be plated, 100 Al ₂ O ₃ spheres with a diameter of about 3.0 mm were prepared.

On the other hand, as a plating bath, "Top Chemi Aroi B-1" manufactured by Okuno Pharmaceutical Co., Ltd., which is a Ni-B alloy bath sold on the market, was prepared, and the pH was set to 6.7, and the bath temperature was set to 60°C.

Next, put the above-mentioned 100 Al ₂ O ₃ spheres into a rotating drum with an inner volume of 1.90×10 ⁴ m ³ , and simultaneously put 7.9 g (about 1,500 pieces) of Ni balls with a diameter of about 0.7 mm, and dip the rotating drum into the above-mentioned plated In the bath, the rotating cylinder was rotated at a rotation speed of 0.05 s ^-1 (= 3 rpm) for 40 minutes while stirring with air to form a Ni-B coating on the surface of the Al ₂ O ₃ spheres.

By performing electroless plating as described above, it is possible to form a Ni-B plating film having a film thickness of about 1.5 μm without the problems of adhesive strength and deposition unevenness without a prior catalyst treatment step. The above-mentioned Al ₂ O ₃ spheres formed with a coating film are suitable for use as a low-temperature heating element.

Claims (8)

1. An electroless plating method for forming a plating film on a non-conductive plating object by electroless plating using a plating bath to which metal ions for forming a plating film and a reducing agent for precipitating the metal ions are added,

a step for preparing a conductive medium that exhibits catalytic activity for the oxidation reaction of the reducing agent;

and a step of bringing the conductive medium into contact with the non-conductive object to be plated in order to form the plating film on the non-conductive object to be plated.

2. The electroless plating method according to claim 1, further comprising a step of preparing a container that allows a plating solution constituting the plating bath to pass therethrough, and a step of charging the non-conductive plating object and the conductive medium into the container, wherein the step of bringing the conductive medium into contact with the non-conductive plating object comprises a step of bringing the non-conductive plating object and the conductive medium into contact while rotating, shaking, or vibrating the container charged with the non-conductive plating object and the conductive medium in the plating bath.

3. The electroless plating method according to claim 1, wherein the step of bringing the conductive medium into contact with the non-conductive plating object comprises the steps of: depositing the metal ions on the conductive medium to attach a deposited metal to the conductive medium; and transferring the precipitated metal attached to the conductive medium to the non-conductive object to be plated by bringing the conductive medium into contact with the non-conductive object to be plated.

4. The electroless plating method according to claim 1, wherein the plating film is composed mainly of Ni, Co, Au, or Pt or an alloy thereof, the reducing agent contains a phosphoric acid-based compound, and the conductive medium contains at least 1 of Ni, Co, Au, and Pt on at least a surface thereof.

5. The electroless plating method according to claim 1, wherein the plating film is composed mainly of Ni, Co, Au, or Pt or an alloy thereof, the reducing agent contains a boron-based compound, and the conductive medium contains at least 1 of Ni, Co, Au, and Pt on at least a surface thereof.

6. The electroless plating method according to claim 1, further characterized in that the plating film is composed mainly of Ni, Co, or Pt, or an alloy thereof, the reducing agent contains a nitrogen-based compound, and the conductive medium contains at least 1 of Ni, Co, and Pt on at least a surface thereof.

7. The electroless plating method according to claim 1, wherein a main component of the plating film is Cu, Ag, or Au or an alloy thereof, the reducing agent contains an aldehyde compound, and at least the surface of the conductive medium contains at least 1 of Cu, Ag, and Au.

8. A non-conductive plating object having a plating film formed mainly of at least 1 metal selected from the group consisting of Ni, Co, Cu, Ag, Au and Pt, or an alloy thereof,

the plating film is formed by the electroless plating method according to any one of claims 1 to 7, and the plating film is in a state of being directly bonded to the non-conductive plating object without passing through a layer composed of a substance exhibiting a catalytic activity for a reducing action of the reducing agent.