JPH0681190A - Method for plating insulator - Google Patents

Abstract

PURPOSE:To attain electroplating with considerably enhanced reliability even in the case of through hole plating requiring high precision and reliability. CONSTITUTION:A coating film of an electric conductive high molecular compd. is formed on the part of an insulator to be plated and electroplating is carried out on the coating film. In this plating method, a dopant having two or more anionic groups per one molecule is incorporated into the coating film. Plating can be satisfactorily carried out on the surface of the insulator and the inner wall of a through hole.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plating method improved from a direct electroplating method using a conductive polymer compound such as polyaniline or polypyrrole as a plating base material, and a printed wiring board obtained by this plating method.

[0002]

2. Description of the Related Art In recent years,
The demand for printed wiring boards is increasing with the development of electronic devices, and in particular, the degree of integration of electronic components has recently been increasing, and the number of cases in which multiple laminated boards are used is also increasing. Along with this, demands for high reliability for printed wiring boards and environmental safety when manufacturing printed wiring boards are rapidly increasing.

When manufacturing a printed wiring board, it is necessary to form a through hole in the insulating substrate and metal-plat the inner wall of the through hole in order to enable conduction between the inner and outer layer circuits. In this case, conventionally, the electroless copper plating method using formaldehyde or the like as a reducing agent was adopted, but formaldehyde is a compound of which carcinogenicity is a concern. Therefore, instead of this electroless copper plating method, Various highly safe direct plating (direct electroplating) methods have been proposed. For example,
A method using a conductive polymer compound such as polyaniline or polypyrrole as a base material for plating (European Patent No. 41310).
9A2, European Patent 417750A2, WO89 / 083
75, see British Patent 2243838A).

However, when a conductive polymer compound such as polyaniline or polypyrrole is used as a base material for plating,
Although it is preferable in terms of cost because it is possible to perform through-hole plating relatively inexpensively, there remains a problem in the reliability of plating and it has not yet reached a practical level.

The present invention has been made in view of the above circumstances.
Electroplating method for insulators with significantly improved reliability even for through-hole plating that requires high accuracy and reliability when a conductive polymer compound such as polyaniline or polypyrrole is used as the plating base material. The purpose is to provide.

[0006]

Means and Actions for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventor has formed a film of a conductive polymer compound on a plated portion of an insulator, and formed a film on the film. In the method for plating an insulator to be electroplated, when the conductive compound film contains a dopant having two or more anion groups per molecule, the reliability of the plating is greatly improved and a simple plating process is performed. It has been found that an insulator can be electroplated by means of.

That is, since the conductive polymer compound such as polyaniline or polypyrrole is a p-type semiconductor, the present inventor normally charges positively in the doped state, and electroplating is performed by using these as a plating base material. When performed, electrostatic repulsive force acts between the metal ions and the conductive polymer compound in the plating bath, which hinders the progress of plating, which in turn lowers the reliability of plating. I suspected there might be. Therefore, the present inventor tried to use a dopant having two or more anion groups per molecule as a dopant in order to impart anionic property to the conductive polymer compound that is originally positively charged, and High precision and reliability such as through-hole plating when electroplating is performed by coating the plated part of the insulator plating object with a conductive polymer compound containing a dopant having two or more anion groups per molecule. We have found that plating reliability is greatly improved even for plating that requires
The present invention has been completed.

Therefore, according to the present invention, in the method of plating an insulator, the conductive polymer compound film is formed on the plated portion of the insulator, and electroplating is performed on the film. Provided is a method for plating an insulator, which contains a dopant having two or more anion groups per molecule.

The present invention will be described in more detail below. In the plating method of the present invention, a conductive polymer compound containing a dopant having two or more anion groups per molecule is used when an insulator is electroplated. The coating is formed on the plated portion as a base material for electroplating.

Here, the material and shape of the insulator to which the plating method of the present invention can be applied is not particularly limited, but a usual printed wiring board made of glass fiber and epoxy resin, a multi-layered board, a phenol resin, etc. Insulating materials such as polyamide resin, polyimide resin, ABS resin, acrylic resin, polycarbonate resin, polypropylene resin, polyethylene resin, polyurethane resin, glass and ceramics.

The kind of the conductive polymer compound is not particularly limited, either, but the polymer of aniline or its derivative, the polymer of pyrrole or its derivative, the polymer of thiophene or its derivative, the polymer of acetylene or its derivative, the polymer of pyridine or its derivative. Polymer of benzene or its derivative, polymer of furan or its derivative, and the like. Specifically, polyaniline, poly (N-alkylaniline), poly (o-phenylenediamine), polypyrrole, poly (N-alkylpyrrole), poly (3-alkylpyrrole), polythiophene, poly (3-alkylthiophene). , Polyfuran, and copolymers composed of two or more kinds of monomers of these polymers, and of these, polyaniline and polypyrrole are particularly preferable.

The dopant for doping the conductive polymer compound may be any substance having two or more anion groups per molecule, and is not particularly limited, but polyvinyl sulfonic acid and its salt, polystyrene. Sulfonic acid and its salts, poly (2-acrylamide-
2-methyl-1-propanesulfonic acid) and salts thereof,
Polymers having anionic groups such as sulphonic acid groups and carboxylic acid groups such as Nafion (registered trademark of DuPont), aromatic compounds such as benzene and naphthalene, and two anionic groups such as sulphone groups, hydroxy groups and carboxylic acid groups Examples include the derivatives introduced above. Specific examples of these derivatives include m-benzenedisulphonic acid, o-benzenedisulphonic acid, p-benzenedisulphonic acid,
1,2-Dihydroxy-3,5-benzenedisulphonic acid, 2,7-naphthalenedisulfonic acid, 1,6-naphthalenedisulfonic acid, 1,5-naphthalenedisulfonic acid, 2-naphthol-3,6- Derivatives obtained by introducing two or more anionic groups such as sulfonic acid groups, hydroxy groups and carboxylic acids into aromatic compounds such as benzene and naphthalene such as disulphonic acid, naphthalene-1,3,6-trisulfonic acid and salts thereof. And so on.

Among the above dopants, polyvinyl sulfonic acid and its salt, polystyrene sulfonic acid and its salt, poly (2-acrylamido-2-methyl-1-propane sulfonic acid) and its salt, Nafion, m-benzenedisulfone. Acids and salts thereof, 1,5-naphthalenedisulfonic acid and salts thereof, naphthalene-1,3,6-
Trisulphonic acid and its salts, 1,2-dihydroxy-
Particularly preferred is 3,5-benzenedisulphonic acid and salts thereof. More preferred are polyvinyl sulfonic acid and its salts, polystyrene sulfonic acid and its salts, poly (2-acrylamido-2-methyl-1-propane sulfonic acid) and its salts. The preferable molecular weight range of the polymer dopant is 1,000 to 1,000,000.
Is.

The following three methods can be mentioned as a method of doping the above-mentioned conductive polymer compound with these dopants and forming a coating film of the conductive polymer compound on a plated portion of an insulator such as a substrate. . The first method is to use a solution containing a monomer that becomes a conductive polymer compound when polymerized and the above dopant as a material for forming a coating film of a conductive polymer. A film of a conductive polymer compound containing the above dopant is formed on the insulator. In this case, a method of immersing in a solution containing a monomer and then immersing it in a solution containing a dopant can be adopted.

As the solvent for dissolving the above-mentioned monomer and dopant, one or more of water, acetonitrile, ethanol, methanol, propanol and the like can be used. In this case, the concentration of the monomer solution is 0.1
5 mol / l, the concentration of the dopant is 0.01 to 5 mol
/ L is preferable.

The second method is a coating of a conductive polymer compound on a portion to be plated using a solution in which the conductive polymer compound containing the above dopant is dissolved or a suspension or emulsion liquid in which fine particles thereof are dispersed. Is a method of forming.
In this case, the same solvent as above can be used. Further, the concentration of the conductive compound is preferably 1 to 50% by weight.

In the third method, the conductive polymer compound is doped with a dopant in a later step. The conductive compound solution is used to coat the portion to be plated, and this is dried to form the conductive polymer film. It is a method of forming and immersing in a solution containing a dopant. In this method, a conductive polymer compound such as polyaniline which is soluble in the undoped state and which can be easily doped, for example, polyaniline (emeraldine base) which is undoped by an alkali treatment and is soluble in N-methylpyrrolidone or the like. Can be applied to.

The plating process to which the plating method of the present invention can be applied is such that a film of a conductive polymer compound containing the above dopant is formed on a plated portion of an insulator, and then an electroplating method is performed on the conductive polymer film. Although it is not particularly limited as long as it is a process of plating a metal with, the following three are particularly preferable plating processes.

The first plating process is a method of through-hole plating a printed wiring board having through-holes, and the first method is applied in the following step (4). (1) Etching of substrate (2) Conditioning of substrate (3) Oxidation treatment of plated portion (4) Immersion treatment in solution containing monomer and dopant (5) Degreasing treatment, (6) Etching (7) Composition of plating bath Immersion in pretreatment liquid for maintenance (8) Electroplating (9) Drying In the steps (1) to (7), washing with water is usually performed between the steps. However, the process (3),
During the period (4), it is preferable to wash with water to such an extent that the oxidant remains on the substrate surface.

Here, in step (4), the monomer is polymerized, and at the same time as the polymerization, the target substrate surface is coated with a conductive polymer compound containing a dopant.

In the step (2), the substrate is pretreated to smoothly carry out the step (3), and a method used in a usual plating process can be applied.

The step (3) is a step called a desmearing process in a normal plating process and is performed for the purpose of cleaning the surface of the substrate. In this process, in addition to the purpose, the following step is performed. It also serves the purpose of giving the substrate surface the oxidizing power required in (4). As the oxidizing agent used in this step (3), a usual oxidizing agent such as ammonium persulfate, hydrogen peroxide, ferric chloride can be used, but potassium permanganate is particularly preferably used. In this case, the oxidizing agent is preferably used as an aqueous solution of 0.5 to 50% by weight.

The metal used for the electroplating in the step (8) is not particularly limited, but in the case of through hole plating, copper is preferably used. In this case, the plating bath is a copper sulfate plating bath or a copper pyrophosphate plating bath. Is preferably used.

Other steps (1), (5), (6),
(7) and (9) can also be performed in accordance with a normal plating process.

The second plating process includes the following step (4)
In the above, the second method is applied. (1) Etching of substrate (2) Conditioning of substrate (3) Oxidation treatment of plated portion (4) Coating conductive polymer compound containing dopant in plated portion (5) Degreasing treatment (6) Etching (7) Plating Pretreatment liquid immersion to maintain bath composition (8) Electroplating (9) Drying Here, the substrate is dried after washing with water in the step (3), and the steps other than the step (4) are the same as the first plating process. It is the same.

In the third plating process, the third method is applied in the following steps (4) and (5). (1) Etching of the substrate (2) Conditioning of the substrate (3) Oxidation treatment of the plated portion (4) Coating of the conductive polymer compound on the plated portion (5) Doping of dopant (6) Degreasing treatment (7) Etching (8) ) Pretreatment liquid immersion for maintaining plating bath composition (9) Electroplating (10) Drying Here, except for washing the substrate after washing with water in step (3) and steps (4) and (5), It is similar to the first plating process.

The above-mentioned three plating processes can be applied to all the substrates made of the above-mentioned insulating material, but the plating of the printed wiring board made of the glass fiber and the epoxy resin, especially the copper plating of the inner wall of the through hole. Can be suitably used.

[0028]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] A plating test was performed using an aniline monomer according to the first plating process described above.

First, a substrate made of glass fiber reinforced epoxy resin and having both sides coated with copper and having through holes formed by a conventional method was used at 80 ° C. for 5 minutes with an aqueous solution containing about 60% by weight of potassium permanganate. Desmear treatment (oxidation treatment),
After washing with water, aniline 0.4 mol / l, sulfuric acid 0.5 m
It was dipped in an aniline monomer treatment liquid containing 1.0 mol / l of polyvinyl sulfonic acid having an ol / l and a number average molecular weight of 70,000 for 10 minutes to form a polyaniline film on the surface of the substrate to be plated.

Next, when a copper sulfate plating bath was used as a plating bath, and a plating treatment was performed at a current of ² A / dm ² , it was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole. .

[Example 2] A plating test was conducted in exactly the same manner as in Example 1 except that polystyrene sulfonic acid 0.1 mol / l was used as the dopant in place of polyvinyl sulfonic acid 1.0 mol / l. It was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole.

Example 3 As a dopant, poly-2- (sulfonic acid) was used instead of 1.0 mol / l.
A plating test was conducted in exactly the same manner as in Example 1 except that 0.5 mol / l of acrylamido-2-methyl-1-propanesulfonic acid was used. As a result, copper was deposited on the substrate surface and the inner walls of the through holes. Was confirmed.

[Example 4] A plating test was conducted in exactly the same manner as in Example 1 except that 0.5 mol / l of m-benzenesulfonic acid was used as the dopant instead of 1.0 mol / l of polyvinyl sulfonic acid. However, it was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole.

[Example 5] A plating test was conducted in exactly the same manner as in Example 1 except that 0.5 mol / l of 1,5-naphthalenedisulfonic acid was used as the dopant in place of 1.0 mol / l of polyvinyl sulfonic acid. As a result, it was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole.

[Example 6] The same as Example 1 except that naphthalene-1,3,6-trisulfonic acid 0.5 mol / l was used as the dopant instead of polyvinyl sulfonic acid 1.0 mol / l. As a result of a plating test, it was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole.

Example 7 As a dopant, 0.5 mol of 1,2-hydroxybenzene-3,5-disulphonic acid was used instead of 1.0 mol / l of polyvinyl sulfonic acid.
A plating test was conducted in the same manner as in Example 1 except that 1 / l was used, and it was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole.

[Example 8] A plating test was conducted in the same manner as in Example 1 except that a pyrrole monomer was used in place of the aniline monomer, and copper was found to be deposited on the substrate surface and the inner wall of the through hole. confirmed.

[Comparative Example 1] A plating test was conducted in the same manner as in Example 1 except that polyvinyl sulfonic acid was not added. As a result, almost no copper deposition was observed on the substrate surface or the inner wall of the through hole.

Example 9 A plating test was conducted according to the second plating process described above. First, aniline 0.4
Ammonium persulfate was added to an aqueous solution containing mol / l, sulfuric acid 1.0 mol / l and polyvinyl sulfonic acid 1.0 mol / l so as to be 0.5 mol / l, and polyaniline having polyvinyl sulfonic acid as a dopant was polymerized. The obtained polyalin powder was washed with water and suspended in water to prepare a suspension. This suspension was applied to a substrate made of glass fiber reinforced epoxy resin and dried to form a polyaniline film having polyvinyl sulfonic acid as a dopant on the substrate surface.

Then, a copper sulfate plating bath was used as a plating bath, and a plating treatment was performed at a current value of ² A / dm ² , and it was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole. It was

Comparative Example 2 A plating test was conducted in the same manner as in Example 9 except that polyvinyl sulfonic acid was not added during the polymerization of polyaniline.
Almost no copper deposition was observed on the inner wall of the through hole.

[Example 10] A plating test was conducted in accordance with the third plating process described above. Aniline 0.4mo
Ammonium persulfate was added to an aqueous solution containing 1 / l and sulfuric acid 1.0 mol / l so as to be 0.5 mol / l,
Polyaniline was polymerized. The obtained polyaline powder was treated with a 1.0 mol / l ammonia aqueous solution to prepare dedoped polyaniline (emeraldine base). This polyaniline powder was dissolved in N-methylpyrrolidone to prepare a 5% by weight solution. This solution was applied onto a substrate made of glass fiber reinforced epoxy resin and dried to form a polyaniline film on the substrate surface. Next, this substrate was immersed in an aqueous solution containing 1.0 mol / l of sulfuric acid and 1.0 mol / l of polyvinyl sulfonic acid for 10 minutes to dope the polyaniline film with polyvinyl sulfonic acid.

Next, when a copper sulfate plating bath was used as a plating bath, and a plating treatment was performed at a current value of ² A / dm ² , it was confirmed that copper was deposited on the substrate surface and the inner wall of the through hole. It was

Comparative Example 3 A plating test was conducted in the same manner as in Example 10 except that polyvinyl sulfonic acid was not added at the time of doping the polyaniline film. I couldn't see it.

[0046]

According to the present invention, it is possible to realize electroplating with greatly improved reliability even for through-hole plating which requires high precision and reliability.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Hideyuki Hayashi, 4-2-1 Kasuga, Suita City, Osaka Prefecture (72) Daisaku Akiyama 1-1-10 Takasu-cho, Nishinomiya-shi, Hyogo Prefecture (72) Inventor Shuichi Ueda Hyogo 5-12-24 Tsukaguchi-cho, Amagasaki-shi, Japan (72) Inventor Naomi Kose 2-11-9 Higashi-ochiai, Suma-ku, Kobe-shi, Hyogo

Claims (2)

[Claims] 1. A method for plating an insulator in which a film of a conductive polymer compound is formed on a portion to be plated of an insulator and electroplating is performed on the film, and two films of the conductive compound are provided per molecule. A method for plating an insulator, which comprises the above-mentioned dopant having an anion group. 2. The plating method according to claim 1, wherein the insulator is a printed wiring board having through holes.