JP3001485B2 - Manufacturing method of multilayer printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer printed wiring board, and more particularly to a method for manufacturing a multilayer printed wiring board using a metal foil-clad inner layer material having conductor layers of different thicknesses and types. It is.

[0002]

2. Description of the Related Art As electronic devices have become more sophisticated, printed wiring boards used in these electronic devices have also been required to have higher densities and more complicated patterns. Different printed wiring boards are being manufactured.

Conventionally, a technique for manufacturing a printed wiring board using a double-sided copper-clad board having different thicknesses of copper foils on both sides is disclosed in Japanese Patent Application Laid-Open No. 60-218486. According to this technique, as shown in FIG. 4, two substrates 1 each having a pattern of an etching resist 8 formed on both surfaces of a copper-clad substrate 1 having copper foils 3 and 4 having different thicknesses are connected to copper foils having the same thickness. Lay 4 on the outside. The superposed substrates are etched to etch the non-coated portions of the copper foil 4 with the etching resist, and then the two substrates are separated. Next, the two substrates 1 are stacked with the copper foil 4 inside, and after etching similarly, the two original substrates are returned to obtain the irregular double-sided board. As a method of superposing the substrates in the above technique, pinning using a guide hole or the like for positioning or tape fixing is used. Further, in the case of an ultra-thin copper foil in which the penetration of the etching solution cannot be ignored, the periphery of the stacked substrates is all sealed with a tape or the like so as to prevent the penetration of the etching solution.

In the above technique, as a method of superposing two substrates, a method of pinning using a guide hole or a method of tapering the periphery of the superposed substrate is used. No. 247,596 discloses a method of bonding the peripheral ends of two substrates with a double-sided tape.

[0005] This technique will be described with reference to FIG. FIG. 5A is a configuration perspective view of a substrate in a case where the peripheral ends of two substrates are bonded to each other with a double-sided tape, and FIG.
FIG. 2 is an enlarged cross-sectional view of a substrate after two substrates are bonded together. First, two copper-clad substrates 1 are made to face each other with copper foils 4 of the same thickness facing each other (FIG. 5 (a)), and then bonded together with a double-sided tape 12, and as shown in FIG. Adhesive and integrated with tape 12. Then, after performing processing such as surface preparation, lamination, exposure, development, and etching on the three surfaces of the copper foil,
The double-sided tape 12 is dissolved with an organic solvent or the like, and the two substrates are separated. Generally, in the method using this double-sided tape,
The surface of the copper foil 4 is a surface on which circuit formation, oxidation treatment (laminating pretreatment), and the like are not performed.

[0006]

In the above-mentioned prior art, since the plate edge of the substrate is sealed with a tape or the like, a peeling operation is performed to make the two original substrates, so that the work technique is increased. And inefficient. Moreover, as the thickness of the printed wiring board becomes thinner, it is more difficult to peel off the tape at the board edge of the board, and at the time of peeling, problems such as cracking of the board tend to occur.

In the method of bonding two substrates with the above-mentioned double-sided tape, the processing liquid infiltrates the interface between the double-sided tape and the substrate, causing a problem that the surface of the substrate is oxidized. Since a solvent is required, there are problems in terms of working environment and manufacturing cost.

An object of the present invention is to provide a method for manufacturing a multilayer printed wiring board which solves the above-mentioned conventional problems.

[0009]

According to the present invention, there is provided a method for manufacturing a multilayer printed wiring board, comprising:
A step of chemically depositing an adhesive organic film on one side of a copper foil having the same thickness on one side of a double-sided copper-clad substrate, and pressing the two copper-clad substrates through the adhesive organic film; A step of forming an etching resist with an alkali developing type photosensitive resist on the surface and side surfaces of the substrate and etching to form circuits on both surfaces of the pressed substrate, and immersing the pressed substrate in an alkaline stripping solution. A step of removing the etching resist, a step of immersing the press-bonded substrate in an aqueous acid solution and separating, and a step of laminating the two separated substrates on the circuit surface inside through a prepreg. And

In the present invention, the adhesive organic coating layer is preferably composed of 2
Not only can one substrate be pressed and fixed, and the subsequent steps can be performed as if one substrate were processed, but foreign substances can be prevented from entering between the pressed substrates. Even if the alkali developing solution enters between the press-bonded substrates during the development of the resist, it has an effect of protecting the surface of the copper foil.

[0011]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part of a substrate for explaining a process sequence of a method for manufacturing a multilayer printed wiring board according to a first embodiment of the present invention.

First, an adhesive organic film 20 is chemically deposited on the copper foil 4 of the double-sided copper-clad substrate 1 and the substrate 2 having copper foils 3 and 4 having different thicknesses on both surfaces (FIG. 1 (a)). . The copper foil 3 of the substrates 1 and 2 may be a 35 μm or 70 μm thick copper foil, and the copper foil 4 may be an 18 μm thick copper foil.

Next, the copper foils 4 of the substrates 1 and 2 are pressure-bonded to each other via a 20-layer adhesive organic film, and as shown in FIG.
The masking tape 5 is attached so as to cover the side surfaces of the substrates 1 and 2 from 3 to 10 mm from the ends of the substrates 1 and 2. The above-mentioned adhesive organic film 20 is chemically deposited by bringing the copper foil surface into contact with an aqueous solution containing an imidazole compound, and the preferred film thickness is 1 to 5 μm. This sticky organic coating layer 2
It is not necessary to use an organic solvent for peeling 0, and it can be easily peeled off with an acid aqueous solution or the like, and can be easily separated mechanically from the interface between the adhesive organic coatings 20 on the substrates 1 and 2. .

As the masking tape 5, a strong alkali-soluble photosensitive resin tape having a thickness of 20 to 50 μm, such as an acrylic resin, an aldehyde resin, a phenol resin, or a carboxylic acid resin, can be used. This masking tape 5 is resistant to a developing solution of an aqueous solution such as sodium carbonate or sodium metasilicate having a concentration of about 2% by weight, and can be peeled off with a strong alkaline stripping solution such as sodium hydroxide of 2 to 5% by weight. . The masking tape 5 is thermocompression-bonded to the substrate by a heat roll at 100 to 130 ° C. Next, 10-20
After the surfaces of the copper foils 3 of the substrates 1 and 2 have been subjected to a surface treatment with a soft etching solution containing 2% by weight of sulfuric acid and 0.2 to 1% by weight of hydrogen peroxide, the photosensitive layer 5 is photosensitive so as not to overlap the masking tape 5. Laminated dry film 6 (FIG. 1)
(C)).

Further, as shown in FIG. 1 (d), a mask film 7 having an inner layer pattern capable of exposing the masking tape 5 is aligned on both sides of the substrates 1 and 2, and after irradiating the dry film 6 with ultraviolet rays, the exposure is reduced to 0.8 to An unexposed portion of the dry film 6 is removed with a developing solution such as a 1.2% by weight aqueous sodium carbonate solution to obtain an etching resist 8 (FIG. 1E).

Then, the exposed copper foil 3 as shown in FIG.
5 to 15% by weight hydrochloric acid at a temperature of 40 to 60 ° C, 2 to 10%
After removal by etching with an etching solution of an aqueous cupric chloride solution or an aqueous solution of ferric chloride containing 2 wt% of hydrogen peroxide, the etching resist 8 is removed with an alkaline stripping solution such as a 2 to 5 wt% aqueous sodium hydroxide solution. The masking tape 5 is removed at the same time, and then the four surfaces of the copper foil 4 are separated from each other to obtain a substrate 1a and a substrate 2a each having a circuit 9 and a circuit 10 formed on one surface, respectively (FIG. 1 (g). A method of dissolving the above-mentioned adhesive organic coating layer 20 with a hydrochloric acid or sulfuric acid solution having a concentration of 5 to 10% by weight, or mechanically separating the interface between the adhesive organic coating layers 20 on the copper foils of the substrates 1 and 2. Can be done by any method.

These substrates 1a and 2a are connected to circuits 9, 1
Laminating through a prepreg with 0 inside, drilling, plating, printing and etching using conventional techniques to produce a multilayer printed wiring board.

Next, a second embodiment of the present invention will be described. FIG. 2 is a cross-sectional view of a main part of a substrate for explaining a process sequence of a method for manufacturing a multilayer printed wiring board according to a second embodiment of the present invention. In the present embodiment, a dry film is used instead of the masking tape in the first embodiment, and the surface and side surfaces of the substrate are masked with the dry film.

First, as in the first embodiment, the copper foil 4 of the double-sided copper-clad substrate 1 and the substrate 2 having the copper foils 3 and 4 having different thicknesses on both surfaces has adhesiveness. The adhesive organic coating layer 20 is chemically deposited (FIG. 2A). Next, the copper foil 4 surfaces of the substrates 1 and 2 are adhered to each other by the adhesive organic coating 2 on the copper foil 4.
Then, the dry film 6 is laminated on the copper foil 3 of the substrates 1 and 2 so as to protrude from the edge of the substrate by about 2 mm to 10 mm as shown in FIG. 2B. The dry film is protected on the non-laminated side with a heat-resistant resin such as Mylar. Next, as shown in FIG. 2C, the dry films protruding from the plate ends of the substrates 1 and 2 are combined with each other at a temperature of 100-1.
Thermocompression bonding at 30 ° C.

In the subsequent steps, exposure (FIG. 2D) and development (FIG. 2D) are performed in the same manner as in the first embodiment.
(E)), etching (FIG. 2F), etching resist peeling and substrate separation (formation of substrate 1a and substrate 2a) (FIG. 2)
(G)). Next, the separated substrate 1a and substrate 2a are laminated via a prepreg, and a multilayer printed wiring board is manufactured using ordinary drilling, plating, printing and etching techniques.

In the method for manufacturing a multilayer printed wiring board according to the second embodiment, the side surfaces of the press-bonded substrates 1 and 2 are also covered with the dry film 6. The manufacturing process can be simplified as compared with the manufacturing method.

Next, a third embodiment of the present invention will be described. FIG. 3 is a cross-sectional view of a main part of a substrate for explaining a process sequence of a method for manufacturing a multilayer printed wiring board according to a second embodiment of the present invention. In the present embodiment, the substrate surface and side surfaces are masked with a photosensitive liquid resist instead of the dry film in the second embodiment.

First, as in the first and second embodiments, two double-sided copper-clad substrates 1 and 2 each having copper foils 3 and 4 each having a different thickness are provided. An adhesive organic coating layer 20 having an adhesive surface is formed (FIG. 3A). Next, the copper foils 4 of the substrates 1 and 2 are pressure-bonded to each other via the adhesive organic coating 20 layer on the copper foil 4, and the photosensitive foil 3 is applied to the copper foils 3 of the substrates 1 and 2 as shown in FIG. Of the liquid resist 11 is applied. A dipping method is suitable as a coating method. In addition, as a component of the liquid resist, an acrylic resin, an aldehyde resin, a phenol resin, a carboxylic acid resin, or the like can be used, and its coating thickness is suitably from 10 to 20 μm. After applying the liquid resist 11, it is dried with hot air at a temperature of 80 to 100 ° C. for about 30 minutes. Thereafter, a multilayer printed wiring board is manufactured by the same steps as those in the first and second embodiments.

[0024]

According to the present invention, two double-sided copper-clad substrates having copper foils having different thicknesses on both sides are bonded together via a chemically deposited adhesive organic film on the copper foil surfaces of the same thickness. rear,
The following effects can be obtained by forming a photosensitive dry film or the like on the surface and side surfaces of the substrate and performing pattern formation processing. (1) Since there is no need to remove the tape attached to the peripheral portion of the substrate as in the conventional example, the working efficiency of pattern formation is reduced to 1
It can be improved by 0 to 30%. (2) Since it is not necessary to use an organic solvent for peeling off the tape as in the related art, the manufacturing cost can be reduced. (3) The quality of the multilayer printed wiring board can be improved because the bonded substrates can be easily separated and the occurrence of cracks in the substrate can be prevented. (4) The quality of the outer layer circuit pattern of the multilayer printed wiring board can be improved because the surface of the laminated copper foil is protected by the adhesive organic film during the pattern formation, and the oxidation and discoloration of the copper foil surface can be prevented. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of a substrate for explaining a process sequence of a method for manufacturing a multilayer printed wiring board according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a main part of a substrate for describing a process order of a method for manufacturing a multilayer printed wiring board according to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of a main part of a substrate for describing a process order of a method for manufacturing a multilayer printed wiring board according to a third embodiment of the present invention.

FIG. 4 is a cross-sectional view of a main part of a substrate showing an example of manufacturing a conventional printed wiring board.

FIG. 5 is a cross-sectional view of a main part of a substrate showing an example of manufacturing a conventional printed wiring board.

[Explanation of symbols]

 1,2,1a, 2a Substrate 3,4 Copper foil 5 Masking tape 6 Dry film 7 Mask film 8 Etching resist 9,10 Circuit 11 Liquid resist 12 Double-sided tape 20 Adhesive organic coating layer

Claims (5)

(57) [Claims] 1. An adhesive organic film is chemically deposited on one side of a copper foil of the same thickness on one side of two double-sided copper-clad boards having copper foils having different thicknesses on both sides, and the two copper-clad boards are provided. Pressure-bonding via the adhesive organic film, and forming an etching resist on the surface and side surfaces of the pressure-bonded substrate with an alkali-developable photosensitive resist to form circuits on both surfaces of the pressure-bonded substrate Removing the etching resist by immersing the press-bonded substrate in an alkaline stripper, and immersing the press-bonded substrate in an acidic aqueous solution to separate the two substrates. A method for manufacturing a multilayer printed wiring board, comprising a step of laminating a circuit surface inside through a prepreg. 2. The method for producing a multilayer printed wiring board according to claim 1, wherein the adhesive organic film is chemically deposited to a thickness of 1 to 5 μm by bringing the copper-clad substrate into contact with an aqueous solution containing an imidazole compound. 3. The method for producing a multilayer printed wiring board according to claim 1, wherein an alkali-developing dry film is used as said photosensitive resist. 4. An alkali-developing masking tape and an alkali-developing dry film are used as the photosensitive resist, and the masking tape is formed on the side and peripheral portions of the press-bonded substrate. 3. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein a film is formed on the surface of the press-bonded substrate. 5. The method for manufacturing a multilayer printed wiring board according to claim 1, wherein a liquid resist of an alkali development type is used as said photosensitive resist.