JPH1022612A - Manufacture of printed wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To omit the etching process of a conductive coating film, by eliminating the conductive coating film by eliminating the surface of a substratum under the conductive coating film except an electroplated part. SOLUTION: A conductive coating film 3 composed of a palladium sulfide coating film is formed on the surface of a substratum composed of insulator. Plating resist 4 is formed in a part except a desired conductive pattern. By electroplating, a conductor layer 5 is formed in a region except the part coated with the plating resist 4. The plating resist 4 is peeled off. The conductive coating film 3 in the part except the region where the conductor layer 5 is formed is eliminated. Since the conductive coating film 3 is thin and does not completely cover the surface of the substratum 1, the surface can be dissolved. By dissolving and eliminating the surface of the substratum 1, the conductive coating film 3 can be eliminated. Thereby the etching process of a conductive coating film which has been necessary in the conventional technique can be omitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a printed wiring board, and more particularly to a method for manufacturing a printed wiring board in which a conductive layer is formed on a surface of a substrate made of an insulator by plating.

[0001]

2. Description of the Related Art There are various methods for forming a conductor layer on a surface of a base material made of an insulator by plating. In general, a conductive layer is formed by forming a thin conductive film made of a metal on the surface of a base material by electroless plating, and then performing electroplating with a desired thickness. Also, a method of forming a conductor layer without using electroless plating has been reported. Hereinafter, a "method of forming a conductive pattern" reported in JP-A-57-49295 will be described as a conventional technique with reference to FIG.

FIG. 3 shows a surface of a base material 13 made of an insulator.
As shown in (b), the adhesive 14 is applied. Then, FIG.
As shown in (c), molten copper particles are sprayed onto the adhesive 14 in a vacuum or an inert gas atmosphere to form a conductive film 15 made of copper. Next, as shown in FIG. 3 (d), a plating resist 16 is formed on portions excluding necessary circuit portions, and as shown in FIG. 3 (e), the conductor layer 17 is formed by electroplating.
Get. Next, as shown in FIG. 3 (f), the plating resist 16 is peeled off, and the conductive film 15 is removed by etching to obtain a desired conductive pattern.

[0003]

The above-mentioned prior art has the following problems.

In order to remove the conductive film 15, an etching process must be performed. For the etching treatment, an aqueous solution of cupric chloride, ferric chloride, persulfates, hydrogen peroxide and sulfuric acid, ammonia and hydrochloric acid, etc. is used. High costs are also incurred when treating without affecting the environment. This is a problem that cannot be ignored in providing an inexpensive printed wiring board. Similarly, when a conductive film made of metal is formed by electroless plating, etching is necessary,
This is a problem in providing an inexpensive printed wiring board.

In the prior art, since the adhesive 14 always exists under the conductor layer 17, it cannot be connected to another conductor layer at the through hole wall or the bottom of the via hole. Therefore, it can be applied to a single-sided or double-sided printed wiring board, but cannot be applied to a multilayer printed wiring board.

[0006] The present invention provides a method for manufacturing a printed wiring board which overcomes the disadvantages of the prior art.

[0007]

SUMMARY OF THE INVENTION The present invention comprises a step of forming a conductive film on the surface of a base material made of an insulator, a step of forming a resist for plating on portions except for necessary circuit portions, and Forming a circuit by electroplating only on the circuit portion, stripping the resist for plating, and removing the surface layer of the base material under the conductive film other than the portion subjected to electroplating to form the conductive film. And a method for manufacturing a printed wiring board, the method including:

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment will be described with reference to FIG. A circuit having a desired pattern is obtained on the surface of the printed wiring board, and a plating film is formed on the through holes.

(1) First, as shown in FIG. 1A, a through hole 2 is formed in a base material 1 made of an insulator such as epoxy or imide by using a known method such as a drill or a laser. If there is an inner layer connection on the hole wall of through hole 2,
A permanganate treatment is performed to remove smears generated by the drill and residues generated by the laser.
(2) Next, as shown in FIG. 1B, a conductive film 3 is formed on the surface of the substrate 1. This time, as the conductive film 3, "Crimson Process" provided by Shipley (Japanese Patent Laid-Open No.
-65292, JP-A-1-268896). Table 1 shows the processing conditions of the process. First, a sensitizer process is performed. The sensitizer treatment solution contains an alkaline surfactant and amines, and cleans the substrate surface,
Improve the turn of the tin-palladium colloid in the post-activator treatment.

Next, a pre-activator process is performed. The pre-activator treatment solution is composed of the same medium as the activator treatment solution and does not contain a tin-palladium colloid. It contains sodium chloride as a main component and prevents the pH and chloride concentration of the activator treatment in the next step from being changed by the washing water.

Next, an activator process is performed. The activator treatment solution contains a tin-palladium colloid, and the substrate 1
A tin-palladium colloid is adsorbed on the surface of.

Next, converter processing is performed. The converter treatment liquid contains borohydrofluoric acid and removes a part of tin from the tin-palladium colloid adsorbed on the surface of the substrate 1 to form a film mainly composed of palladium.

Next, an enhancer process is performed. The enhancer treatment solution contains an alkali metal sulfide, and turns the palladium film adsorbed on the surface of the substrate 1 into a palladium sulfide film.

Next, a stabilizer process is performed. The stabilizer treatment liquid contains sodium hydroxide and stabilizes the palladium sulfide film adsorbed on the surface of the substrate 1.

Next, a micro etching process is performed. The microetching solution contains sulfuric acid and hydrogen peroxide,
The palladium sulfide film formed on the exposed copper surface is removed. The micro-etching process is necessary when the conductor layer 5 formed in the subsequent step (4) is connected to another layer at the bottom of a through hole wall or a via hole. If there is no connection, there is no need to do this.

By the above processing, the substrate 1 made of an insulator
A conductive film 3 made of a palladium sulfide film is formed on the surface of the substrate with a thickness of several hundred angstroms. In recent years, many processes for forming such a conductive film have been devised and provided. In addition to the Crimson Process, Atotech's Neopact Process, which forms a palladium film, Conducton DP Process, which is formed by Lilonal, MacDamid's Black Hole Process, which forms a carbon film, and Ebara Densan Co., Ltd. Processes such as a "shadow process" and a "DMS-2 process" of LPW which forms a polypyrrole film can be applied.

(3) Next, as shown in FIG. 1C, a plating resist 4 is formed on portions other than the desired conductor pattern. Usually, the plating resist 4 is formed through the steps of pretreatment, lamination of a dry film, exposure and development. In the pre-treatment, a solution of 40 g / L of hydrogen peroxide and 200 g / L of sulfuric acid was used for soft etching for 30 seconds. The development was performed using a 10 g / L sodium carbonate solution for 3 minutes.

(4) Next, as shown in FIG. 1D, a conductor layer 5 having a desired thickness is formed by electroplating on a portion other than the portion covered with the plating resist 4. The thickness of the conductor layer 5 greatly affects the reliability of the printed wiring board. Usually 20 μm to 3
It often has a thickness of 0 μm. As pretreatment, degreasing,
Soft etching was performed. 40g soft etching
/ L hydrogen peroxide and 200 g / L sulfuric acid solution for 30 seconds. A copper sulfate plating solution was used as the plating solution. 80 g / L copper sulfate, 200 g / L sulfuric acid, 50 p
The conductor layer 5 was immersed in a plating solution in which a slight amount of brightener was added to pm hydrochloric acid for 45 minutes, and electrolyzed at a current density of 2.5 A / dm2 to obtain a conductor layer 5 having an average of 25 μm.

(5) Next, as shown in FIG. 1E, the plating resist 4 is peeled off. The peeling was performed using a 30 g / L sodium hydroxide solution for 3 minutes.

(6) Next, as shown in FIG. 1F, the conductive coating 3 other than the portion where the conductor layer 5 is formed is removed. The conductive film 3 is firmly adhered to the surface of the substrate 1 by chemical adsorption, is chemically stable, and it is difficult to dissolve or decompose the conductive film 3 itself and remove it. However, since the conductive film 3 is thin and does not completely cover the surface of the substrate 1, the surface of the substrate 1 can be dissolved. Therefore, by dissolving and removing the surface of the substrate 1, the conductive coating 3
Can be removed. For dissolving and removing the substrate 1, a permanganate treatment was used. Application of concentrated sulfuric acid treatment or the like is also possible. In this embodiment, as in the step (1), the permanganate treatment is widely applied to the removal of smear in the production of a printed wiring board. Table 2 shows the processing conditions of the permanganate treatment. When the conductive film 3 is removed, the amount of the base material 1 dissolved is improved by immersion for about twice as long as when smear is removed after drilling as performed in the step (1). The conductive film 3 can be completely removed by dissolving the surface of the base material 1 on average by about 3 μm. By removing the conductive film 3 in this manner, the etching process of the conductive film 15 required in the related art can be omitted.

Through the above steps, the conductor layer 5 having a desired pattern is formed on the surface of the substrate 1 and the inner wall of the through hole 8.

A second embodiment will be described with reference to FIG. In a build-up method in which a conductor layer and an insulating layer are sequentially formed and a desired number of layers are stacked, a circuit having a desired pattern is formed on the surface of the insulating layer, and a plating film is formed in a via hole.

(1) First, as shown in FIG. 2A, a via hole 8 is formed in an insulating layer 6 of epoxy, imide or the like by using a laser or the like. There is also a method of forming a via hole 8 by photolithography using a photosensitive resin for the insulating layer 6.

(2) Next, as shown in FIG. 2B, a conductive film 9 is formed on the surface of the insulating layer 6. As the conductive film 9, a palladium sulfide film having a thickness of about several hundred angstroms is formed by using, for example, “Crimson process” provided by Shipley. Table 1 shows the processing conditions of the process.

[0025]

[Table 1]

(3) Next, as shown in FIG. 2C, a plating resist 10 is formed on portions other than the desired conductor pattern. Usually, the plating resist 10 is formed through steps of pretreatment, lamination of a dry film, exposure, and development. In the pre-treatment, a solution of 40 g / L of hydrogen peroxide and 200 g / L of sulfuric acid was used for soft etching for 30 seconds. The development was performed using a 10 g / L sodium carbonate solution for 3 minutes. (4) Next, as shown in FIG. 2D, a conductor layer 11 having a desired thickness is formed by electroplating on a portion other than the portion covered with the plating resist 10. The thickness of the conductor layer 11 greatly affects the reliability of the printed wiring board. Usually, it often has a thickness of 20 μm to 30 μm. As pretreatment, degreasing and soft etching were performed. Soft etching was performed for 30 seconds using a solution of 40 g / L hydrogen peroxide and 200 g / L sulfuric acid. A copper sulfate plating solution was used as the plating solution. 80 g / L copper sulfate, 200 g / L
The conductive layer 11 was immersed in a plating solution obtained by adding a slight amount of brightener to sulfuric acid of 50 L and 50 ppm of hydrochloric acid for 45 minutes, and electrolyzed at a current density of 2.5 A / dm 2, thereby obtaining a conductor layer 11 having an average of 25 μm.

(5) Next, as shown in FIG. 2E, the plating resist 10 is peeled off. The peeling was performed using a 30 g / L sodium hydroxide solution for 3 minutes.

(6) Next, as shown in FIG. 2F, the conductive coating 9 other than the portion where the conductor layer 11 is formed is removed.
Since the conductive film 9 is thin and does not completely cover the surface of the insulating layer 6, the conductive film 9 formed on the insulating layer 6 can be removed by dissolving the surface of the insulating layer 6. Permanganate treatment was used for removal. Table 2 shows the processing conditions of the permanganate treatment.

[0029]

[Table 2]

By removing the conductive film 9 in this manner, the etching of the conductive film 15 required in the prior art can be omitted.

Through the above steps, the conductor layer 11 having a desired pattern is formed on the surface of the insulating layer 6 and the inner wall of the via hole 8, and the conductor layer 11 and the conductor layer 7 are connected.

[0032]

As described above, the present invention provides a manufacturing method for obtaining an inexpensive printed wiring board by omitting the etching treatment of the conductive film 15 which is required in the conventional manufacturing method.

Further, the present invention provides a method for manufacturing a printed wiring board which can be applied not only to a single-sided or double-sided printed wiring board but also to a multilayer printed wiring board.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a method of the present invention.

FIG. 2 is a cross-sectional view showing the method of the present invention.

FIG. 3 is a sectional view showing a conventional method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Through hole 3 Conductive film 4 Plating resist 5 Conductive layer 6 Insulating layer 7 Conductive layer 8 Via hole 9 Conductive film 10 Plating resist 11 Conductive layer 12 Base material 13 Through hole 14 Adhesive 15 Conductive film 16 Plating resist 17 Conductive layer

Claims (7)

[Claims] 1. A step of forming a conductive film on a surface of a base material made of an insulator, a step of forming a plating resist on portions excluding required circuit portions, and electroplating only required circuit portions. Forming a circuit, removing the resist for plating, and removing the conductive film by removing the surface of the substrate under the conductive film other than the electroplated portion. A method for manufacturing a printed wiring board, which is characterized by the following. 2. The method for manufacturing a printed wiring board according to claim 1, wherein a palladium sulfide film is formed on the surface of the substrate as the conductive film. 3. The method for manufacturing a printed wiring board according to claim 1, wherein a palladium film is formed on the surface of the substrate as the conductive film. 4. The method according to claim 1, wherein a carbon film is formed on the surface of the substrate as the conductive film. 5. The method for producing a printed wiring board according to claim 1, wherein a polypyrrole film is formed on the surface of the substrate as the conductive film. 6. The method according to claim 1, wherein the step of removing the conductive film by removing a surface layer of the base material under the conductive film other than the electroplated portion is permanganate treatment. The method for producing a printed wiring board according to the above. 7. The method according to claim 1, wherein the step of removing the conductive film by removing a surface layer of the base material under the conductive film other than the electroplated portion is a concentrated sulfuric acid treatment. Manufacturing method of printed wiring board.