JP2006216777A - Method for manufacturing circuit board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a circuit board which can form a conductive pattern having a film thickness suitable for causing a large current to flow in a short time with a low cost. <P>SOLUTION: In a resist layer forming step, a first resist layer 6 is formed with a conductive layer 3 for formation of a conductive pattern 5 exposed. In a next resist layer expanding step, the first resist layer 6 is expanded by heating the first resist film 6 to thereby form a second resist film 7 having a film thickness thicker than the first resist film. In a plating step, a conductive plated layer 4 is formed on part of the conductive layer 3 exposed from the second resist layer 7. In an etching step, the second resist layer 7 is removed to expose part of the conductive layer 3 other than the formation part of the plated layer 4, the exposed part of the conductive layer 3 is removed to thereby form the conductive pattern 5 on an insulating substrate 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a circuit board manufacturing method, and more particularly to a circuit board manufacturing method capable of forming a conductive pattern having a large film thickness and a small electrical resistance that allows a large current to flow.

A conventional circuit board manufacturing method will be described with reference to FIGS. 6 to 9. In the conventional circuit board 30, a film-like flexible insulating base material 31 is disposed at the lowermost part. A thin copper foil 32 having a thickness of 0.5 to 2 μm is formed on the entire surface.
Then, in the laminating step, the alkali-soluble layer 33 is formed by laminating a thin film of the alkali-soluble resin as a dry film on the thin copper foil 32.
Next, in the printing step, a patterned heat-soluble ink layer 34 is printed on the alkali-soluble layer 33 (FIG. 6).

The heat-soluble ink layer 34 formed in the pattern is formed by thermally transferring a heat-soluble ink film of an ink ribbon mounted on a thermal transfer printer (not shown) onto the alkali-soluble layer 33, thereby forming a conductive pattern 32 'described later. It is formed in the same shape.
Next, in an etching process, the insulating base material 31 in which the heat-soluble ink layer 34 is formed on the alkali-soluble layer 33 is immersed in an alkaline etching solution.
Then, the alkali-soluble layer 33 other than the portion facing the heat-soluble ink layer 34 is removed using the heat-soluble ink layer 34 as a mask.

As a result, a patterned alkali-soluble layer 33 having the same shape as the hot-melt ink layer 34 is formed below the hot-melt ink layer 34 (FIG. 7).
Next, when the insulating substrate 31 is immersed in an acidic etching solution, the hot-soluble ink layer 34 and the alkali-soluble layer 33 serve as a mask, and the copper foil 32 other than the portion facing the alkali-soluble layer 33 is dissolved. The
Then, a conductive pattern 32 ′ is formed below the patterned alkali-soluble layer 33 (FIG. 8).
Further, in the etching step, the two layers of the heat-soluble ink layer 34 and the alkali-soluble layer 33 are simultaneously melted and removed using a solvent capable of dissolving both the heat-soluble ink layer 34 and the alkali-soluble layer 33, thereby removing the copper foil 32. A conductive pattern 32 ′ having a desired pattern is exposed and formed (FIG. 9).
As a result, a circuit board 30 on which a desired conductive pattern 32 ′ is formed is formed.
JP 2002-16344 A

However, the conductive pattern 32 ′ formed by the conventional circuit board manufacturing method has the same film thickness as the copper foil 32, which is as thin as 0.5 to 2 μm. It was unsuitable for use in the circuit part of the system.
Also, in order to reduce the electrical resistance by increasing the thickness of the conductive pattern 32 'in order to withstand a large current, the entire surface of the copper foil 32 must be thickened, which increases the cost and increases the thickness and area of the copper. There has been a problem that the etching process for removing the foil 32 takes time.
As a countermeasure against this, as shown in FIG. 10, there is a method of laminating and forming a plating layer 35 made of metal plating on a thin conductive pattern 32 ′ to make the conductive pattern 32 ′ thick. The plated layer 35 formed thereon is wider than the conductive pattern 32 ′.
Therefore, when the conductive patterns 32 ′ are formed close to each other, there is a problem that the adjacent conductive patterns 32 ′ are short-circuited and short-circuited.
Accordingly, the present invention provides a circuit board manufacturing method capable of solving the above-described problems and forming a thick conductive pattern suitable for flowing a large current at a low cost in a short time. Objective.

As a first means for solving the above-described problem, the circuit board manufacturing method of the present invention includes etching a conductive layer formed on the surface of the insulating base material to form a desired material on the insulating base material. A circuit board manufacturing method for forming a conductive pattern having a shape,
On the surface of the conductive layer, a portion of the conductive layer where the conductive pattern is to be formed is exposed to form a first resist layer made of a thermally expandable ink in a resist layer forming step, and the next resist layer expansion process is performed. Then, by heating the first resist film to a predetermined temperature, the first resist layer expands to form a second resist film that is thicker than the first resist layer,
A conductive plating layer having the same film thickness as the second resist layer is formed on the conductive layer exposed from the second resist layer by a plating process, and the second resist layer is formed by a subsequent etching process. The conductive pattern is formed on the insulating substrate by exposing the conductive layer other than the portion where the plated layer is removed and removing the conductive layer in the exposed portion. It is characterized by that.
Further, as a second solving means for solving the above-described problem, the thermally expandable ink binder is mixed with thermally expandable microcapsules containing foaming gas, and the first resist is expanded in the resist layer expanding step. The first resist layer is expanded by a foaming gas encapsulated by the thermally expandable microcapsules being destroyed by heat applied to the layer.

Further, as a third means for solving the above problems, the foaming gas is composed of at least methyl chloride.
Further, as a fourth means for solving the above-mentioned problem, the thermally expandable microcapsule is characterized in that the particle diameter is formed to be 0 to 1 to 5 μm.

5. The circuit board manufacturing method according to claim 2, wherein the wall material of the thermally expandable microcapsule is made of at least vinylidene chloride as a fifth means for solving the above problems.
As a sixth means for solving the above-mentioned problem, the film thickness of the first resist layer is 1 to 5 μm, and the film thickness of the second resist layer expanded in the resist layer expansion step is , 5 to 20 μm.

Further, as a seventh solving means for solving the above-mentioned problem, the thermally expandable ink contains 30 to 150 parts by weight of the thermally expandable microcapsule with respect to 100 parts by weight of the binder. Features.
Further, as an eighth solving means for solving the above-mentioned problem, the binder is made of at least an epoxy resin.

Further, as a ninth solving means for solving the above-mentioned problems, the binder contains a curing accelerator.
Further, as a tenth means for solving the above-mentioned problem, the curing accelerator is composed of at least an imidazole compound, and the curing accelerator is contained in an amount of 1 to 5 parts by weight with respect to 100 parts by weight of the epoxy resin. It is characterized by being.

As eleventh means for solving the above-mentioned problems, the heating temperature of the first resist layer in the resist layer expansion step is in the range of 100 to 200 ° C.
As a twelfth solving means for solving the above problem, a release layer formed of waxes having a melting point of 60 to 90 ° C. is interposed between the conductive layer and the second resist layer. It was made to be characterized.

In the present invention, on the surface of the conductive layer, a portion of the conductive layer where the conductive pattern is to be formed is exposed to form a first resist layer made of a thermally expandable ink in a resist layer forming step, and the next resist layer expansion is performed. By heating the first resist film to a predetermined temperature in the process, the first resist layer expands to form a second resist film that is thicker than the first resist layer, and the conductivity of the portion exposed from the second resist layer A conductive plating layer having the same film thickness as the second resist layer is formed on the layer by a plating step, and the conductive layer other than the portion where the plating layer is formed by removing the second resist layer in the next etching step Since the conductive pattern is formed on the insulating substrate by removing the exposed conductive layer, it is possible to form a thick conductive pattern and suitable for flowing a large current. Has a conductive pattern It can provide a method of manufacturing a circuit board.
In the etching process, the second resist layer made of a resin material and the thin conductive layer can be removed by etching, so that the etching time can be shortened and a circuit board having a thick conductive pattern can be reduced. Can be provided at a cost.
Further, the thermally expandable ink binder is mixed with thermally expandable microcapsules encapsulating foaming gas, and the thermally expandable microcapsules are destroyed and encapsulated by the heat applied to the first resist layer in the resist layer expansion step. Since the first resist layer is expanded by the foaming gas, the first resist layer can be reliably expanded in the resist layer expansion step.

Moreover, since the foaming gas is composed of at least methyl chloride, the first resist layer can be expanded more reliably.
Moreover, since the heat-expandable microcapsules are formed to have a particle size of 0 to 1 to 5 μm, the heat-expandable microcapsules can be reliably destroyed in the resist layer expansion step.

Further, since the wall material of the thermally expandable microcapsule is made of at least vinylidene chloride, the thermally expandable microcapsule can be more reliably destroyed in the resist layer expanding step.
Moreover, since the film thickness of the 1st resist layer is formed in 1-5 micrometers, and the film thickness of the 2nd resist layer expanded by heating at the resist layer expansion process is formed in 5-20 micrometers, it is 2nd A plated layer having the same thickness as the second resist layer can be formed on the conductive layer exposed from the resist layer.

Further, since the heat-expandable ink contains 30 to 150 parts by weight of the heat-expandable microcapsule with respect to 100 parts by weight of the binder, the second resist layer is surely expanded in the resist layer expansion step. A resist layer can be formed.
In addition, since the binder is made of at least an epoxy resin, the second resist film expanded by breaking the thermally expandable microcapsules in the resist layer expansion process is thermally cured, and the chemical resistance measures of the plating solution used in the plating process can do.

Moreover, since the binder contains a curing accelerator, the second resist layer can be surely thermally cured.
Moreover, since a hardening accelerator consists of an imidazole compound at least and contains 1-5 weight part of hardening accelerators with respect to 100 weight part of epoxy resins, it can heat-harden a 2nd resist layer still more reliably. .

Moreover, since the heating temperature of the 1st resist layer in a resist layer expansion | swelling process is the range of 100-200 degreeC, a 1st resist layer can be expanded before an insulating base material thermally deforms, and high quality is carried out. A circuit board can be provided.
Further, since a release layer formed of wax having a melting point of 60 to 90 ° C. is interposed between the conductive layer and the second resist layer, the second resist layer is surely removed in the etching process. Thus, the conductive layer can be exposed.

A method for manufacturing a circuit board according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a circuit board manufactured by the manufacturing method of the present invention, FIGS. 2 to 4 are cross-sectional views of a main part for explaining a method of manufacturing a circuit board according to the present invention, and FIG. FIG.
First, the circuit board 1 formed by the manufacturing method of the present invention will be described with reference to FIG. 1. The lowermost part is made of, for example, a polyimide resin having excellent heat resistance, and has a thickness of 2 to 25 μm, preferably 3 to 9 μm. The flexible insulating base material 2 is disposed.

On the surface of the insulating base material 2, a patterned conductive layer 3 ′ having a film thickness of 0.5 to 2 μm is formed.
On the patterned conductive layer 3 ′, a plating layer 4 having a film thickness larger than that of the conductive layer 3 ′ is laminated and formed in the same pattern as the conductive layer 3 ′. A conductive pattern 5 is formed of the plated layer 4 formed in a laminated manner and the conductive layer 3 ′.
The conductive pattern 5 has a thickness of 5 to 20 μm, and the conductive layer 3 ′ has a thickness of 0.5 to 2 μm. Is formed.

Next, the manufacturing method of the circuit board 1 of the present invention will be described based on the process diagrams shown in FIGS. 1 to 4 and FIG. 5. First, the circuit board 1 according to the present invention is as shown in FIG. A conductive layer 3 made of copper foil or the like and having a thickness of 0.5 to 2 μm is formed on the entire surface of one surface of the insulating substrate 2.
In the insulating substrate 2 having such a thin conductive layer 3, a first resist layer 6 is formed on the surface of the conductive layer 3 by a resist layer forming step. The first resist layer 6 is made of a heat-expandable ink, and is manufactured by mixing a heat-expandable microcapsule containing a foaming gas and a binder, and is coated with a gravure coat or the like to form the first resist layer 6. ing.

In the first resist layer 6, a conductive layer exposed portion 6 a that exposes the conductive layer 3 in the same shape as the conductive pattern 5 is formed in a portion where the conductive pattern 5 is formed.
That is, on the surface of the conductive layer 3, a first resist layer 6 made of a heat-expandable ink is formed in a resist layer forming process by exposing a portion of the conductive layer 3 where the conductive pattern 5 is to be formed.
In the thermally expandable microcapsule, the wall material containing the foaming gas is formed of at least vinylidene chloride. Examples of the wall material of the thermally expandable microcapsule include vinyl chloride, acrylonitrile, styrene, vinyl acetate, or a copolymer or blend of these resins, in addition to vinylidene chloride.

Further, the thermally expandable microcapsule is formed to have a particle size of 0.1 to 5 μm, and the encapsulated foaming gas is composed of at least methylene chloride.
Examples of the foaming gas include methylene bromide, trichloroethane, dichloroethane and the like in addition to methylene chloride.
The thermally expandable microcapsules are commercially available products such as “Matsumoto Microsphere” series F-20, F-30, F-30VS, F-40F-50, F-80S manufactured by Matsumoto Yushi Seiyaku Co., Ltd. There are F-82, F-85, F-80VS, F-100, etc., or “Expancel” series manufactured by Nippon Ferrite Co., Ltd.

Further, at least a thermosetting epoxy resin is used for the binder of the heat-expandable ink as a chemical resistance countermeasure (plating solution countermeasure). At least an imidazole compound is mixed as an epoxy resin curing accelerator.
In addition to the epoxy resin, the binder of the thermally expandable ink is a phenoxy resin, a vinyl resin such as polyvinyl acetate or polyacrylic ester, a polyester resin such as polyethylene terephthalate or polybutylene terephthalate, a polystyrene resin, a polyamide resin, Polyurethane resin, acrylic resin, etc. may be used.

Moreover, as a hardening accelerator, a urea compound, a hydrazide compound, etc. may be sufficient besides an imidazole compound.
And it is preferable that 1-5 weight part of hardening accelerators are mixed with respect to 100 weight part of epoxy resins.
Further, a release layer (not shown) formed of wax having a melting point of 60 to 90 ° C. may be interposed between the conductive layer 3 and the first resist layer 6 as necessary. .
Examples of the waxes include natural wax carnauba wax, paraffin wax, and beeswax.

Then, after the first resist layer 6 is formed in the resist layer forming step, the thermally expandable microcapsules are thermally destroyed by heating the first resist layer 6 at a temperature of 100 to 200 ° C. in the next resist layer expansion step. Then, the first resist layer 6 is expanded by the encapsulated foaming gas, and a thick second resist layer 7 is formed as shown in FIG.
The second resist layer 7 is formed to have a thickness of 5 to 20 μm, and a conductive layer exposed portion that exposes the conductive layer 3 in the same shape as the conductive pattern 5 at a portion where the conductive pattern 5 is formed. 7a is formed.

In the plating step subsequent to the resist layer expansion step, a conductive metal made of, for example, copper is plated on the portion of the conductive layer 3 exposed from the conductive layer exposed portion 7a of the second resist layer 7, A thick plating layer 4 having the same thickness as the second resist layer 7 is formed.
The thick plating layer 4 formed in the plating process is guarded by the second resist layer 7 in the width dimension, so that it does not become wide as described with reference to FIG.

Next, in the etching process, the insulating substrate 2 formed with the plating layer 4 shown in FIG. 4 is immersed in an alkaline processing solution to remove the second resist layer 7, so that the portion other than the portion where the plating layer 4 is formed. The thin conductive layer 3 is exposed.
Then, by etching the portion of the conductive layer 3 exposed from the plating layer 4 with an acidic treatment liquid, the conductive layer 3 'and the plating layer 4 as shown in FIG. A conductive pattern 5 is formed.
Since the portion of the conductive layer 3 exposed from the plating layer 4 to be etched in the etching step is thin, the etching time is short and the manufacturing time of the circuit board 1 can be shortened.

In the circuit board 1 manufactured by the manufacturing method of the present invention, since the conductive pattern 5 has a thickness of 5.5 to 22 μm and is thicker than the conductive layer 3, for example, a large current of 1 A or more is generated. It is suitable for use in a flowing power system circuit portion.
In the embodiment of the present invention, the insulating base material 2 is described as a flexible film, but the insulating base material 2 may be a hard substrate such as a phenol resin.

It is principal part sectional drawing of the circuit board manufactured with the manufacturing method of this invention. It is principal part sectional drawing explaining the manufacturing method of the circuit board of this invention. It is principal part sectional drawing explaining the manufacturing method of the circuit board of this invention. It is principal part sectional drawing explaining the manufacturing method of the circuit board of this invention. It is process drawing of the manufacturing method of the circuit board of this invention. It is principal part sectional drawing explaining the manufacturing method of the conventional circuit board. It is principal part sectional drawing explaining the manufacturing method of the conventional circuit board. It is principal part sectional drawing explaining the manufacturing method of the conventional circuit board. It is principal part sectional drawing explaining the manufacturing method of the conventional circuit board. It is a Western dance sectional drawing explaining the subject of the conventional circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Circuit board 2 Insulating base material 3 Conductive layer 4 Plating layer 5 Conductive pattern 6 1st resist layer 6a Conductive layer exposed part 7 2nd resist layer 7a Conductive layer exposed part

Claims (12)

A method of manufacturing a circuit board by etching a conductive layer formed on a surface of an insulating base material to form a conductive pattern of a desired shape on the insulating base material,
On the surface of the conductive layer, a first resist layer made of a heat-expandable ink is formed in a resist layer forming step by exposing the conductive layer in a portion where the conductive pattern is to be formed, and the next resist layer expanding step Then, by heating the first resist film to a predetermined temperature, the first resist layer expands to form a second resist film that is thicker than the first resist layer,
A conductive plating layer having the same film thickness as the second resist layer is formed on the conductive layer exposed from the second resist layer by a plating process, and the second resist layer is formed by a subsequent etching process. The conductive pattern is formed on the insulating substrate by exposing the conductive layer other than the portion where the plated layer is removed and removing the conductive layer in the exposed portion. A method of manufacturing a circuit board.   The thermally expandable ink binder is mixed with thermally expandable microcapsules enclosing a foaming gas, and the thermally expandable microcapsules are destroyed by heat applied to the first resist layer in the resist layer expanding step. 2. The method of manufacturing a circuit board according to claim 1, wherein the first resist layer is expanded by the encapsulated foaming gas.   3. The circuit board manufacturing method according to claim 2, wherein the foaming gas is made of at least methyl chloride.   4. The method of manufacturing a circuit board according to claim 2, wherein the thermally expandable microcapsule has a particle diameter of 0.1 to 5 [mu] m.   5. The circuit board manufacturing method according to claim 2, wherein the wall material of the thermally expandable microcapsule is made of at least vinylidene chloride.   The film thickness of the first resist layer is 1 to 5 μm, and the film thickness of the second resist layer expanded in the resist layer expansion step is 5 to 20 μm. A method for manufacturing a circuit board according to any one of 1 to 5.   The circuit board according to claim 2, wherein the thermally expandable ink contains 30 to 150 parts by weight of the thermally expandable microcapsule with respect to 100 parts by weight of the binder. Manufacturing method.   The method for manufacturing a circuit board according to claim 2, wherein the binder is made of at least an epoxy resin.   The method for manufacturing a circuit board according to claim 2, wherein the binder contains a curing accelerator.   10. The method of manufacturing a circuit board according to claim 9, wherein the curing accelerator is made of at least an imidazole compound, and 1 to 5 parts by weight of the curing accelerator is contained with respect to 100 parts by weight of the epoxy resin. .   The method for manufacturing a circuit board according to claim 1, wherein a heating temperature of the first resist layer in the resist layer expansion step is in a range of 100 to 200 ° C. 11. 12. The release layer formed of wax having a melting point of 60 to 90 ° C. is interposed between the conductive layer and the second resist layer. 12. The manufacturing method of the circuit board of description.

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