JP2007211330A - Electroplating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroplating method having reduced environmental influence for forming an electrically conductive metal layer on the surface of a planar or cubic insulator such as glass and ceramics. <P>SOLUTION: The method for electroplating an electrically conductive metal layer on the surface of a planar or cubic insulator comprises: a step (a) where the surface of the insulator is coated with a graphite-dispersed liquid which comprises graphite particles with an average particle diameter of 0.05-20 μm in an amount of 1 to 20 mass%, a natural or synthetic organic matter or surfactant for dispersing the graphite particles into a water medium in an amount of 0.1 to 30 mass% to the graphite particles, and the water medium, and whose pH lies in the range of 5 to 12; a step (b) where the coated material on the insulator is dried to form a film mainly made up of the graphite particles; and a step (c) where, as an electrically conductive layer, a metal or an alloy is electroplated on the film. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for electroplating a conductive metal layer on a planar or three-dimensional surface of an insulator, in particular an insulator made of glass, plastic or ceramics.

  As a method of forming a metal layer on the surface of an insulator such as glass or ceramic, a method of applying a metal-containing paint to the insulator by screen printing or a doctor blade method and curing it to form a film, vapor deposition or sputtering And a method of forming a film on an insulator and a method of forming a film by plating.

Among these, the plating method is known as a method for forming a conductive or decorative film in industrial mass production. After contacting a metal complex with an insulator, the metal complex is thermally decomposed. There has been reported a plating method in which a metal oxide is formed, and then palladium is applied on the metal oxide film in an alkaline catalyst solution, and further a metal film is formed in an electroless plating solution (for example, Patent Documents). 1).
JP-A-8-144061

  However, the plating method as described above uses various chemicals and materials, and the process is complicated. In addition, chemical solutions must be managed because harmful substances that have environmental impacts are used.

  Therefore, an object of the present invention is to provide an electroplating method with little environmental influence in order to form a conductive metal layer on a planar or three-dimensional insulator surface such as glass or ceramics.

  The electroplating method of the present invention is for solving the above-described problems, and is a method of electroplating a conductive metal layer on the surface of a flat or three-dimensional insulator, and (a) an average particle diameter of 0.05 1 to 20% by mass of graphite particles of ˜20 μm, 0.1 to 30% by mass with respect to the graphite particles, natural or synthetic organic substances or surfactants for dispersing the graphite particles in an aqueous medium, A step of applying a graphite dispersion composed of water and having a pH in the range of 5 to 12 to the surface of the insulator; and (b) drying the coating on the insulator to mainly produce graphite particles. And (c) a step of electroplating a metal or alloy as a conductive layer on the coating.

  According to the present invention, since the conductive metal layer is formed on the surface of an insulator such as glass or ceramics, it is possible to form the electroplating layer with little environmental influence.

  In the electroplating method of the present invention, as shown in FIG. 1, masking 2 is applied to an unnecessary portion of the surface of a planar or three-dimensional insulator 1, and a repellency suppressing agent 3 is applied if necessary, A specific graphite dispersion is applied to form a graphite film 4, and a metal or alloy as a conductive layer is electroplated thereon, masking 2 is removed, and the surface of a flat or three-dimensional insulator is electrically conductive. In this method, the metal layer 5 is electroplated. Hereinafter, materials and processes used in the electroplating method of the present invention will be described.

  In the present invention, the graphite dispersion is obtained by dispersing 1 to 20% by mass of graphite particles having an average particle diameter of 0.05 to 20 μm and 0.1 to 30% by mass of the graphite particles in an aqueous medium with respect to the graphite particles It is a graphite dispersion having a pH in the range of 5 to 12, which basically comprises a natural or synthetic organic substance or surfactant to be produced and water as a medium.

  The average particle diameter of the graphite particles is 0.05 to 20 μm, preferably 0.05 to 10 μm, and particularly preferably 0.1 μm. When the average particle diameter of the graphite particles exceeds 20 μm, the graphite particles are coarse, and irregularities are generated on the surface of the coating, resulting in non-uniform electroplating on the coating. On the other hand, if the average particle diameter is less than 0.05 μm, that is, the graphite particles have a fine average particle diameter, the graphite particles tend to aggregate in the dispersion, and a coating with a uniform thickness cannot be obtained.

 It is essential that the content of graphite particles having such a particle diameter in the graphite dispersion is 1 to 20% by mass. If the content is less than 1% by mass, the resulting coating is too thin and not sufficient, that is, the graphite particle content is too small. On the other hand, when the graphite particle content exceeds 20% by mass, a large amount of dispersant component for dispersing the graphite particles (content exceeding 30% by mass with respect to graphite) is required. However, even if the dispersant component remains in the coating, it does not contribute to conductivity, and thus is unnecessary after the coating. Therefore, when the dispersant component is an organic substance, it is not present (desorbed) in the film by volatilization or baking during the film formation process. This desorption reduces the resistance value of the film and makes it possible to form an electroplated film. However, when a large amount of organic matter is contained, the organic matter is desorbed, causing the film to become porous or cause cracks. As a result, the conductivity of the coating is lowered.

  On the other hand, if the dispersant component is less than 1% by mass with respect to the graphite particles, the graphite particles cannot be dispersed in the medium. From these viewpoints, the content of the dispersant component is 1 to 30% by mass with respect to the graphite particles.

  Moreover, cellulose or acrylic can be used as a natural or synthetic organic substance of the dispersant component, and an anionic or nonionic surfactant can be used.

  Furthermore, the graphite dispersion in the present invention has a basic structure in which graphite particles are dispersed in an aqueous medium containing a dispersant component, and the pH is in the range of 5 to 12, that is, the hydrogen ion concentration in the fairly weak acidic to alkaline region. And When the pH is less than 5, that is, from a weakly acidic to a strongly acidic region, graphite particles aggregate in the dispersion, which is not preferable. In addition, as preferable pH of a graphite dispersion liquid, it is the range of 8-11.

  A further feature of the present invention is that additional inorganic or organic compounds are added to the graphite dispersion. Such an organic compound is any one or more of an acrylic resin, an epoxy resin, a phenol resin, and a silane compound, or an anionic or nonionic material. Moreover, as an inorganic compound, either or both of water glass and colloidal silica can be employed. The amount of the organic or inorganic compound added is preferably about 1 to 40% by mass with respect to the solid in the graphite dispersion, and by adding an appropriate amount to the paint, the graphite dispersion state in the paint can be reduced. In addition, the wettability and affinity with insulators such as glass, plastic, and ceramics can be improved, so that the film formability and adhesion of the graphite film to be formed can be improved.

  In the present invention, an electroplating layer is formed on an insulator, and this insulator is made of glass, plastic or ceramics. As a product made of glass, it can be used without any particular limitation, such as a panel of a flat display device, a glass ornament, a glass plate for building materials, a glass for automobile windshield. In addition, as a plastic product, there is basically no limitation on the material such as an acrylic plate or an ABS plate. The printed circuit board is usually made of phenol or glass epoxy, and the printed circuit board can be said to be made of plastic. Furthermore, as ceramics, structural ceramics such as silicon nitride and zirconia, and electronic device ceramics such as alumina, titanium nitride, barium titanate, and mullite can be used. Can be used.

  The above graphite dispersion is applied to a desired place on the surface of such a planar or three-dimensional insulator, and the coated material is dried or further subjected to a baking treatment of less than about 400 ° C. to mainly produce graphite particles. To form a coating. As a method of applying the graphite dispersion to the insulator, a generally well-known coating method such as a spray method, a droplet coating method, a spin coating method, a screen printing method or a doctor blade method can be employed. In addition, in order to suppress the repelling of the graphite dispersion on the insulator (improve the wet state), a cationic surfactant is applied before the graphite dispersion is applied, and the charge on the insulator surface is positively charged. When the graphite dispersion is applied after the charge is adjusted, the wet state of the graphite dispersion on the insulator surface can be improved. This is because the surface of the graphite particles in the dispersion has a negative charge.

  In order to form a coating on a coating, heat drying is generally used, but methods such as air drying and vacuum drying can also be employed.

  The film mainly composed of graphite particles has electrical conductivity due to the conductivity of graphite. By utilizing this conductivity, an electroplating layer can be formed on the surface of the insulator by an electroplating process in a subsequent process.

  In this invention, the processing time of the plating layer by electroplating can be shortened, so that the electrical resistance value of this film is low. From this viewpoint, the sheet resistance value of the film mainly composed of graphite is less than 1000 Ω / □, more preferably less than 100 Ω / □ in terms of film thickness of 1 μm.

  As described above, the graphite film is prepared by drying the coating film. However, when the dried graphite film is further baked at about 180 to 350 ° C., the dispersant and organic additive components remaining in the coating film can be burned out. Thereby, the resistance value of a graphite film can be reduced and it contributes to shortening of plating film formation. The sheet resistance value indicates the conductivity (ease of electricity flow) of the formed film, and it can be said that the smaller the resistance value, the easier the electricity flows.

  In the present invention, the electroplating layer described above is used as a first plating layer, and a plating layer made of another metal or alloy that is the same as or different from the metal of the first plating layer is further formed on the first plating layer. It is also possible to form the above. If a further plating layer is formed of the same metal or alloy as the first plating layer and the thickness of the plating layer is increased, a large current can be passed in the case of an electronic device application. In the case of forming a metal or alloy different from the first plating layer, for example, a second (upper layer) plating layer is formed, and the hardness of the upper plating layer surface is improved, so that the reliability is excellent. An electroplated layer can be formed on the insulator.

Hereinafter, the effectiveness of the present invention will be clarified by giving examples, but the present invention is not limited to the following examples.
(1) Preparation of Graphite Dispersion 14 g of carboxymethylcellulose (manufactured by Daicel Chemical) as a dispersant component was added to 700 ml of distilled water and dissolved by stirring, and then 300 g of graphite particles (manufactured by Hitachi Powdered Metals) were added and stirred. A mixed solution was prepared. Next, this mixed liquid was subjected to a dispersion treatment while pulverizing the graphite particles with a ball mill until the average particle diameter became 0.1 μm to prepare a graphite dispersion. To this graphite dispersion, an organic or inorganic compound having the composition shown in Table 1 was prepared and mixed again using a stirrer to prepare various graphite dispersions (17 types of paints A to Q). Here, the blending ratio is the ratio of the solid content of the graphite dispersion, that is, the total of the graphite mass and the dispersant component mass.

  The average particle size of the graphite particles was measured using a centrifugal sedimentation type particle size distribution measuring device manufactured by Shimadzu Corporation, and the average particle size (D50) was determined. Moreover, the pH (hydrogen ion concentration) of the graphite dispersion was adjusted to 10.0 while measuring using a pH meter manufactured by Toa DKK Corporation.

(2) Formation of graphite film Next, as an insulator, a vertical 178 mm × width 127 mm × thickness 3 mm glass plate for flat panel display (trade name: PD200, manufactured by Asahi Glass), and length 178 mm × width 127 mm × thickness A 1 mm thick ABS plate (made of plastic in the cylinder) was prepared. For the glass plate, masking other than the film forming portion, by spray coating method, and for the ABS plate, by applying the above-mentioned graphite dispersion liquid to each of these insulators by the doctor blade method, The graphite film was formed by holding in a hot air dryer at 70 ° C. for 10 minutes. In addition, for the purpose of facilitating adhesion of the graphite dispersion to the insulator, before applying the graphite dispersion, the insulator is subjected to a repellency suppression treatment with a cationic surfactant (trade name: Cotamine 24P, manufactured by Kao). A graphite coating was also produced.

  The resistance value of the graphite film produced as described above was measured using a four-terminal four-probe measuring instrument manufactured by Mitsubishi Chemical Corporation, and the results are shown in Tables 2 and 3. Moreover, about the formation state of this graphite film, what was favorable was evaluated as (circle), and what was unsatisfactory was evaluated as x, and the result was also shown in Table 2 and 3. In Table 2, a sample using a glass substrate as an insulator is shown, and in Table 3, a sample using an ABS substrate as an insulator is shown.

(3) Production of electroplating layer Using a solution in which 200 g of copper sulfate and 50 g of sulfuric acid are dissolved in 750 ml of pure water, a current density of 3 A / dm ^{2 is applied} for 10 minutes to form on each of the above insulators. A copper plating layer was formed on the graphite film by electroplating. Regarding the formation state of the copper plating layer thus produced, the copper plating layer thickness was 1 to 5 μm, ○, 0.5 to 1 μm was Δ, and the copper plating layer could not be formed. Those were evaluated as x, and the results are shown in Tables 2 and 3.

(4) Evaluation As is apparent from Tables 2 and 3, it was shown that a graphite film and a copper plating layer can be satisfactorily formed by using the electroplating method of the present invention. In addition, about the sample using the coating material A which does not contain the organic or inorganic compound in a graphite dispersion liquid, by performing a squeeze suppression process, the coating materials E, G, which do not contain an organic compound in a graphite dispersion liquid, For samples using H, J, M, N, and Q, it is clear that a graphite film and a copper plating layer can be satisfactorily formed by applying a haze suppression treatment when the insulator is an ABS resin. did. Furthermore, for the samples using the paints O, P and Q having a sheet resistance value of 1000 Ω / □ or more for the graphite film, it has been clarified that the copper plating layer becomes slightly thin.

  Using the three types of graphite dispersions of paints E, M, and Q in Example 1, a glass plate for a flat panel display device having a length of 178 mm, a width of 127 mm, and a thickness of 3 mm, which is an insulator (trade name: PD200, manufactured by Asahi Glass) ), Except for the coating forming part, and the above-mentioned graphite dispersion liquid is applied by a spray coating method, kept in a hot air dryer at 70 ° C. for 10 minutes, and further in air at 300 ° C. A heat treatment for a time was performed to form a graphite film containing no organic matter. In addition, for the purpose of facilitating adhesion of the graphite dispersion to the insulator, before applying the graphite dispersion, the insulator is subjected to a repellency suppression treatment with a cationic surfactant (trade name: Cotamine 24P, manufactured by Kao). A graphite coating was also produced.

  The resistance value of the graphite film produced as described above was measured using a four-terminal four-probe measuring instrument manufactured by Mitsubishi Chemical Corporation, and the results are shown in Table 4. Moreover, about the formation state of this graphite film, what was favorable was evaluated as (circle), and what was unsatisfactory was evaluated as x, and the result was also shown in Table 4.

Next, using a solution in which 200 g of copper sulfate and 50 g of sulfuric acid were dissolved in 750 ml of pure water, the current density was 3 A / dm ² , and the current was applied for 5 minutes. On the graphite film formed on each of the above insulators, A copper plating layer was formed by electroplating. With respect to the state of formation of the copper plating layer thus produced, the copper plating layer thickness of 1 to 5 μm was evaluated as ○, and the thickness of less than 1 μm was evaluated as ×, and the results are shown in Table 4. .

  As is apparent from Table 4, by firing the graphite film at 300 ° C., the dispersant component remaining in the film disappeared in the drying process, so that the sheet resistance value of the film can be lowered. Thus, it was confirmed that a coating of copper plating can be formed even with the paint Q in which copper plating was not formed when dried at 70 ° C. (Example 1).

A glass plate is used as an insulator, and the copper plating layer of the sample using the paint J of Example 1 is used as a first layer. On this copper plating layer, a copper plating layer as a second layer is further formed by electroplating. Formed. As the copper plating conditions, a solution in which 200 g of copper sulfate and 50 g of sulfuric acid were dissolved in 750 ml of pure water was used, and the current density was 3 A / dm ² and the current was applied for 10 minutes.

  As a result, the thickness of the copper plating layer could be 50 μm. As a result, it has been clarified that a large current can flow through the copper plating film, and that it can be used for applications such as a heating element.

Using an ABS plate that has not been subjected to squeeze suppression treatment as an insulator, a copper plating layer of a sample using the paint C of Example 1 is used as a first layer, and nickel as a second layer is further formed on this copper plating layer A plating layer was formed by electroplating. The nickel plating conditions were such that a solution obtained by dissolving 330 g of nickel sulfate, 45 g of nickel chloride, and 35 g of boric acid in 590 ml of pure water was used for 10 minutes with a current density of 3 A / dm ² .

  As a result, by coating the copper plating layer with a nickel plating layer, the corrosion resistance of the plated portion can be improved, thereby enabling outdoor use such as satellite broadcasting antennas and solar cell panel electrode portions. It was clarified that it can be used for installed purposes.

It is the conceptual diagram which showed the process of the electroplating method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulator, 2 ... Masking, 3 ... Hajike suppression processing agent, 4 ... Graphite film,
5: Conductive metal layer.

Claims (9)

A method of electroplating a conductive metal layer on the surface of a planar or three-dimensional insulator,
(A) 1-20% by mass of graphite particles having an average particle size of 0.05-20 μm;
0.1 to 30% by mass with respect to the graphite particles, natural or synthetic organic substances or surfactants for dispersing the graphite particles in an aqueous medium;
Applying a graphite dispersion having a pH of 5 to 12 to the surface of the insulator, the medium comprising water,
(B) drying the coating on the insulator to form a film mainly composed of graphite particles;
And (c) a step of electroplating a metal or alloy as a conductive layer on the coating.   The electroplating method according to claim 1, wherein the insulator is made of glass, plastic, or ceramics.   The electroplating method according to claim 1 or 2, wherein an inorganic or organic compound is further added to the graphite dispersion in an amount of 1 to 40% by mass with respect to a solid content in the graphite dispersion.   The electroplating method according to claim 3, wherein the organic compound is one or more of an acrylic resin, an epoxy resin, a phenol resin, and a silane compound.   The electroplating method according to claim 3, wherein the organic compound is either an anionic or nonionic material.   The electroplating method according to claim 3, wherein the inorganic compound is one or both of water glass and colloidal silica.   The electroplating method according to claim 1, wherein a sheet resistance value of the coating is less than 1000 Ω / □ in terms of a film thickness of 1 μm.   The electroplating method according to claim 1, wherein a sheet resistance value of the coating is less than 100 Ω / □ in terms of a film thickness of 1 μm.   The electroplating method according to claim 1, wherein the electroplating layer is a first plating layer, and at least one plating layer made of the same or other metal or alloy is further formed on the first plating layer. .

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