JP2002344114A - Wiring board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wiring board in which unreinforced portions and troubles caused by partial strength drops hardly occur at the time of forming recessed sections in a wiring pattern, and to provide a method of manufacturing the board. SOLUTION: In the method of manufacturing the wiring board, the recessed sections 15 are formed in the wiring pattern by arranging a top force C and a bottom force D in which different wiring patterns are respectively formed in protruding states on both surfaces of a resin board 11 having through holes 12 filled up with conductive paste 13 and maintained in a prepreg-state and curing the board 11 by pressing the forces C and D against the board 11 while the forces C and D are heated. Thereafter, wiring pattern conductors 16 composed of conducive paste, etc., are packed in the recessed sections 15 and the surfaces of the board 14 and conductors 16 are flattened. In this method, a porous film of a heat-resistant resin is used as the reinforcing material of the board 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring board having a plurality of wirings on both sides or an inner layer and a method for manufacturing the wiring board.

[0002]

2. Description of the Related Art In recent years, with the advance of miniaturization and high functionality of electronic devices, various technologies have been developed which enable high-density mounting of wiring boards on which electronic components are mounted. In particular, recently, it has been strongly demanded that a wiring board having a multilayer wiring structure be supplied at a low cost, and in particular, high electrical connection reliability and excellent high-frequency characteristics between a plurality of wiring patterns formed at a fine wiring pitch are required. It is important to be prepared.

As a multilayer wiring board meeting such a demand, for example, an inner via hole can be filled with a conductor to improve connection reliability, and an inner via hole can be formed directly below a component land or between arbitrary layers. A resin multilayer substrate having an all-layer IVH structure (Japanese Patent Application Laid-Open No. 6-268345), which can realize a reduction in the size of the substrate and high-density mounting, is known.

[0004] A method for manufacturing the resin multilayer substrate having the all-layer IVH structure will be described with reference to FIG. FIG.
(F) is a process drawing showing the production method.

First, a via hole 2 is formed by punching a support 1 made of a prepreg such as aramid epoxy resin coated on both sides with release films A and B at a required position using a laser processing machine. The via holes 2 are filled with a conductive paste 3. Next, by arranging the copper foil 4 on both sides of the support 1 and applying heat and pressure, the support 1 and the conductive paste 3 in the prepreg state are hardened, and the copper foil 4 on both sides is supported. Body 1
And the conductive paste 3 at the same time, and are electrically connected through via holes. Next, the copper foil 4 on both sides is etched by a conventional photolithography method to form wiring patterns 5a and 5b, thereby obtaining a double-sided wiring board 6.

Further, a prepreg support 1 having via holes 2a, 2b filled with conductive pastes 3a, 3b on both surfaces thereof with the double-sided wiring board 6 as a core.
a or another prepreg support 1b is arranged at a predetermined position, and further, copper foils 7a and 7b are arranged outside the prepreg support 1b and heated and pressed again to form a multilayer, and then the outermost copper foil is formed by photolithography. By etching the layers 7a and 7b, a four-layer wiring board 9 including the outer layer wiring patterns 8a and 8b is obtained.

A substrate generally used as a circuit-forming substrate for forming a resin multilayer substrate having an all-layer IVH structure is a substrate in which a base material such as aramid nonwoven fabric is impregnated with an epoxy resin as an insulating material. is there. Resin multilayer substrates formed using these circuit-forming substrates have been used in many electronic devices that require small size and light weight, taking advantage of their low expansion coefficient, low dielectric constant, and light weight. ing.
However, in the above-mentioned resin multilayer substrate, when the aramid epoxy prepreg is thermocompression-bonded, the shape of the aramid nonwoven fabric is formed on the substrate surface as it is, and irregularities are formed on the substrate surface, and a gap is generated between the copper foil and the etching resist. This makes it difficult to form a pattern as designed due to the penetration of the etching solution into the gaps, which limits the miniaturization of wiring patterns.

[0008] For this reason, Japanese Patent Application Laid-Open No. 11-186698 discloses a method for manufacturing a wiring board suitable for high-density mounting by flattening the surface of the board and the surface of the wiring pattern conductor by a simple method. As shown, a resin substrate 11F in a prepreg state in which conductive paste 13 is filled in through-holes 12
An upper mold C and a lower mold D each having a different wiring pattern formed in a convex shape on both surfaces of the resin substrate 11F are heated and pressed from both sides to cure the resin substrate 11F and simultaneously cure both surfaces of the resin substrate 14. A method is proposed in which after forming a concave portion 15 having a wiring pattern shape on the substrate, the concave portion 15 is filled with a wiring pattern conductor 16 such as a conductive paste to flatten the surface of the resin substrate 14 and the surface of the wiring pattern conductor 16. Have been.

[0009]

However, this technique also requires the use of a prepreg using a non-woven fabric as a reinforcing material. Therefore, when the convex portion of the mold is embedded in the prepreg while heating and pressurizing, the epoxy resin is used. Bleed around the concave portion, and a portion not reinforced with the nonwoven fabric was likely to occur (see FIG. 1). Since the strength of such a non-reinforced resin portion is relatively low, there is a concern that the resin may be deficient in a later step of filling the conductive paste with a squeegee or the like. Further, such a non-reinforced resin portion is likely to cause a conduction failure of the multilayer wiring board.

Accordingly, an object of the present invention is to provide a wiring board and a method of manufacturing the same, in which a non-reinforced resin portion is less likely to be formed when a concave portion having a wiring pattern shape is formed, and a problem due to a partial decrease in strength is less likely to occur. It is in.

[0011]

The above object can be achieved by the present invention as described below. That is, a method of manufacturing a wiring board according to the present invention includes a mold in which a wiring pattern mold is formed in a convex shape on at least one surface of a semi-cured resin substrate having a through hole and a conductor filled in the through hole. A pressure forming and heating step to cure the resin substrate by pressing and heating, thereby forming a wiring pattern shape on the surface of the resin substrate, and after the pattern forming step, forming the wiring pattern shape. In a method for manufacturing a wiring board, comprising a step of filling an electric conductor in a concave portion, a porous film of a heat-resistant resin is used as a reinforcing material for the resin substrate.

In the above, prior to the pattern forming step, an opening step of providing a through-hole in a semi-cured resin substrate having a release film adhered on both surfaces thereof, and forming a conductive hole in the through-hole. A resin filling step of filling the body, and a film peeling step of peeling the release film after the conductor filling step, and by the film peeling step being completed, the resin substrate in the semi-cured state Is preferably obtained.

Further, another semi-cured state in which a conductive paste is filled in a through hole provided at a position corresponding to the wiring pattern shape between a plurality of wiring boards manufactured by any of the above manufacturing methods. It is preferable that the method further includes a step of curing the another resin substrate by pressurizing and heating with the resin substrate interposed therebetween.

On the other hand, a wiring board according to the present invention is characterized by being manufactured by any one of the above-described methods for manufacturing a wiring board.

[Effects] According to the production method of the present invention,
Since a porous film is used as a reinforcing material for the resin substrate, compared to the case of using a nonwoven fabric of the same material, a non-reinforced resin portion is less likely to be generated when forming a concave portion of a wiring pattern shape as follows, and a partial Problems due to excessive strength reduction are unlikely to occur. That is, as shown in FIGS. 1A and 1B, when the reinforcing material of the resin substrate 11 is a nonwoven fabric, the nonwoven fabric fiber F is used when the convex portion of the mold C is embedded in the prepreg while heating and pressing. Since the deformation of the non-woven fabric is restricted by the two-dimensional continuity of the non-woven fabric, the epoxy resin or the like in a fluid state bleeds around the concave portion 15 and is not reinforced by the non-woven fabric.
Tends to occur. This phenomenon becomes more remarkable as the wiring pattern becomes finer.

On the other hand, as shown in FIGS. 1 (2a) and 1 (2b), when the reinforcing material of the resin substrate 11 is a porous film, the convex portion of the mold C is embedded in the prepreg while heating and pressing. At this time, the porous membrane has a three-dimensionally continuous fine structure, so that the porous membrane easily deforms, and the epoxy resin or the like in a fluid state hardly bleeds around the concave portion 15, and the portion 11a not reinforced by the nonwoven fabric is used. Is less likely to occur. For this reason, a problem due to a partial decrease in strength, such as the occurrence of resin loss, is less likely to occur in the subsequent step of filling the conductive paste with a squeegee or the like.

On the other hand, according to the wiring substrate of the present invention, since the porous film is used as a reinforcing material for the resin substrate, the non-reinforced resin portion is formed by forming the concave portion of the wiring pattern shape by the above-described effect. It is unlikely to cause a problem such as resin loss due to a partial decrease in strength. As a result, the wiring board has high reliability of the conductivity of the wiring pattern and is unlikely to cause a short circuit between the patterns.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will now be described with reference to the drawings.
The description will be made in the order of the resin substrate in the present invention. In addition, FIG.
FIG. 7 is a process chart corresponding to each embodiment.

(First Embodiment) First, as shown in FIG. 2 (a), a prepreg using a heat-resistant resin porous film as a reinforcing material, coated on both sides with release films A and B, A resin substrate 11 is prepared. The resin substrate 11 will be described later. Via holes 12 are provided in the resin substrate 11 by punching the required portions using a laser processing machine. Next, as shown in FIG. 2B, the via holes 12 are filled with a conductor 13 made of a conductive paste or the like. Next, after the release films A and B on both sides of the resin substrate 11 were peeled off, the upper mold C and the lower mold D each having a different wiring pattern formed on one surface in a convex shape are shown in FIG. (C), the resin substrate 11 from which the release films A and B have been peeled is inserted, and the resin substrate 11 and the conductive paste which are in a prepreg state by being heated and pressurized are inserted between them. 13 is cured. FIG. 2D shows that after the resin substrate 11 in the semi-cured state is sufficiently heated and compressed in the above process, the upper mold C and the lower mold D
As shown in the figure, both surfaces of a completely cured resin substrate 14 include a compression-cured conductor 13 and electrode terminals on the upper and lower surfaces of the resin substrate 14 as shown in FIG. 15 are formed.

Next, as shown in FIG. 2E, the concave portion 15 is filled with a conductive paste as an electric conductor using, for example, a squeegee, heated and cured, and then the surface of the resin substrate 14 is polished. Then, the surfaces of the resin substrate 14 and the wiring pattern conductor 16 are flattened. At this time, the conductive paste adhered to the convex surface 17 of the resin substrate 14 by the squeegee can be removed at the same time. Alternatively, the concave portion may be filled with a conductive paste by using a screen printing process.

As described above, the wiring board according to the present embodiment is obtained.

In the present embodiment, the method for manufacturing a wiring board according to the present invention has been described as including the opening step, the conductor filling step, and the film peeling step according to the present invention. For example, FIG. 2 (c) manufactured separately
May be prepared and subjected to the pattern forming step of the present invention.

(Second Embodiment) The present embodiment is different from the above-described first embodiment in the point of the electric conductor filling step of the present invention. Therefore, in the present embodiment, the same reference numerals are given to the same components as in the first embodiment, and the description will be omitted. Unless otherwise described, it is the same as in the first embodiment.

FIG. 3 is a process sectional view illustrating a method for manufacturing a wiring board according to a second embodiment of the present invention. Hereinafter, a method of manufacturing a wiring board according to the present embodiment will be described with reference to FIG. However, the steps from FIG. 2A to FIG. 2C in the first embodiment are the same as in the present embodiment, and therefore the description is omitted, and the subsequent steps will be described.

FIG. 3A shows the molds C and D shown in FIG.
This shows a state where the resin substrate 14 having the concave wiring pattern shape 15 formed on the surface after being completely cured after the heating and pressurization by the mold is taken out of the mold. In the present embodiment, first, this resin After a plating resist 18 is applied on the convex surface 17 of the substrate 14, the surface of the concave portion of the wiring pattern 15 is activated with Pd-Sn or the like using a chemical treatment solution, and the resin substrate 14 is further immersed in an electroless copper plating solution. The wiring board is provided with wiring pattern conductors by immersing in Pd-Sn and depositing metallic copper using the Pd-Sn as a nucleus to form electric conductors 19a.

In the case of the present embodiment, if the electric conductor 19a formed by electroless copper plating has the required electric conductivity and mechanical strength, the plating resist 18 is removed in the state shown in FIG. Although it can be used as a wiring board, when it is necessary to flatten the convex surface 17 of the resin substrate 14 and the surface of the electric conductor 19a, rapid electroplating is used instead of electroless plating during the formation of the electric conductor 19a. As shown in FIG. 3C, an electroplated copper 19b can be further formed on the electric conductor 19a made of electroless copper. Further, on the electric conductor 19a or 19b thus formed, Sn
Of course, other metals such as Cr, Au, and solder plating can be formed.

(Third Embodiment) The present embodiment is different from the first embodiment in that the present embodiment has a metal foil attaching step and a metal foil removing step. Therefore, in the present embodiment, components that are not particularly described are the same as those in the first embodiment, and components having the same names as those in the first embodiment are described unless otherwise specified.
It has the same function as that of the first embodiment.

FIG. 4 is a process sectional view illustrating a method of manufacturing a wiring board according to a third embodiment of the present invention. Hereinafter, a method of manufacturing a wiring board according to the present embodiment will be described with reference to FIG.

First, as shown in FIG. 4 (a), a resin substrate 21 made of a prepreg coated on both sides with release films A and B is pierced at a required portion using a laser processing machine. A via hole 22 is provided. Next, FIG.
As shown in (b), the via hole 22 is filled with a conductor 23 made of a conductive paste or the like. Next, after the release films A and B on both sides of the resin substrate 21 are peeled off, the conductive paste 23 filled in the via holes 22 rises above the substrate surface.
FIG. 4 shows a metal foil 24 made of copper foil, etc.
As shown in (c), an upper mold C and a lower mold D each having a different wiring pattern shape formed on one surface in a convex shape.
During this time, the resin substrate 21 is inserted and heated and pressed to cure the resin substrate 21 and the conductive paste 23 in the prepreg state, and at the same time, bond the copper foil 24 to the entire surface of the resin substrate 21. FIG. 4 (d) shows a state where the semi-cured resin substrate 21 is sufficiently heated and compressed in the above process, and then the upper mold C and the lower mold D are removed, as shown in the figure. Wiring pattern conductors 26 are formed on both surfaces of the completely cured resin substrate 25 by pressing the copper foil 24 onto the surface of the resin substrate 25 by the convex portions of both the dies C and D formed in the wiring pattern shape. . Further, as shown in FIG. 4D, the copper foil 27 also remains on the convex portion on the surface of the resin substrate 25 corresponding to the concave portion of the mold, but this unnecessary copper foil 27 is etched or polished. By removing, as shown in FIG. 4E, it is possible to obtain a wiring board in which the surface of the wiring pattern conductor 26 and the surface of the convex portion of the resin substrate 25 are flattened.

(Fourth Embodiment) This embodiment is different from the above-described third embodiment in that it has an electric conductor filling step of the present invention. Therefore, in the present embodiment, the same reference numerals are given to the same components as those in the third embodiment, and the description will be omitted. Unless otherwise described, it is the same as the third embodiment.

FIG. 5 is a process sectional view illustrating a method of manufacturing a wiring board according to the present embodiment. The first half of the manufacturing process in the present embodiment is the same as in the third embodiment. The difference between the manufacturing process in the present embodiment and the manufacturing process in the third embodiment is assumed in the thickness of the copper foil 28 assumed in the manufacturing process in the present embodiment and the manufacturing process in the third embodiment. The difference lies in the thickness of the copper foil 24. That is, the copper foil 24 assumed in the manufacturing process of the third embodiment has a thickness that can be used as a wiring conductor as it is when completed as a wiring board, and passes through a relatively simple second half process. In this embodiment, it is assumed that a copper foil having a thickness of 35 to 25 μm, which is usually used for a printed wiring board, is used. When a wiring pattern shape is formed by a mold on the surface of a resin substrate to which a copper foil is adhered, there is a limit in forming a wiring width and a wiring pitch with high density. Therefore, the method for manufacturing a wiring board according to the third embodiment of the present invention is directed to a method of manufacturing a wiring board according to the present invention.
This is a manufacturing method suitable for inexpensively manufacturing a resin multilayer substrate having a VH structure.

This embodiment is a development of the wiring board in the third embodiment for the purpose of forming a high-density wiring width and wiring pitch. The steps up to FIGS. As in the third embodiment, in the method of manufacturing a wiring board according to the present embodiment, the release films A and B on both surfaces of the resin substrate 21 are peeled off to form the via holes 22.
A metal foil 28 (preferably 5 to 10 μm thick) made of copper foil or the like having an extremely thin thickness is attached to both surfaces of the resin substrate 21 in a state where the conductive paste 23 filled therein rises from the substrate surface. Then, as in the case of the third embodiment, as shown in FIG. 5C, between the upper mold C and the lower mold D each having a different wiring pattern formed on one surface in a convex shape. By inserting the resin substrate 21 and applying heat and pressure, the resin substrate 21 was in a prepreg state.
And the conductive paste 23 is hardened and the copper foil 2
8 is adhered to the entire surface of the resin substrate 21. The characteristic feature of the manufacturing method according to the present embodiment is that, when the upper mold C and the lower mold D are removed as shown in FIG.
8 is press-fitted into the recess of the wiring pattern of the completely cured resin substrate 25, but since the copper foil 28 having a small thickness is used, the wiring pattern conductor 29 is
Is formed at a position lower than the surface of the convex portion. However, in the present embodiment, the extremely thin copper foil 2
By using No. 8, even if the convex wiring pattern formed on the surface of the upper mold C and the lower mold D is formed into an extremely fine pattern, the shape is sufficiently formed together with the copper foil 28 on the surface of the resin substrate 25. be able to. Therefore, in order to make the wiring pattern conductor 29 having this extremely small thickness a state similar to that of a commonly used wiring conductor, that is, a state in which the surface of the electric conductor is substantially flush with the surface of the resin substrate 25, FIG. As shown in e), the auxiliary conductor 3 is formed on the upper surface of the wiring pattern conductor 29 by a conductive paste or a plating method.
By stacking 0, a required electric conductivity and mechanical strength can be provided, and a wiring substrate having a surface smoothness on which a fine wiring pattern is formed can be obtained.

The copper foil 28 adhered to the convex portion of the resin substrate 25 is removed by etching or polishing in either the step shown in FIG. 5D or the step shown in FIG. It is.

(Fifth Embodiment) The present embodiment is different from the first embodiment in the point of the resin substrate of the present invention. Therefore, in the present embodiment, components that are not particularly described are the same as those in the first embodiment, and components having the same names as those in the first embodiment are the same as those in the first embodiment unless otherwise described. It has a function.

FIG. 6 is a process sectional view illustrating a method of manufacturing a wiring board according to the present embodiment. The configuration of the wiring board according to the present embodiment can be applied to the method of manufacturing the wiring board according to each of the above embodiments, and the wiring board according to the present embodiment is different from the wiring boards according to the first to fourth embodiments. The difference lies in the structure of the resin substrate. As shown in FIGS. 6A to 6C, the surface of the resin substrate 31 used in the first half of the manufacturing method according to each embodiment of the present invention is Resin layer 3 such as resin
2 has been provided.

That is, the resin substrate 31 made of prepreg
After applying and forming a resin layer 32 on both sides of the substrate, the upper surfaces thereof are coated with release films A and B, and a via hole 33 is formed at a predetermined location using a laser processing machine (FIG. 6).
(A)). Next, as shown in FIG. 6B, the via hole 33 is filled with a conductor 34 made of a conductive paste or the like. Next, the step of heating and pressurizing the resin substrate 31 using the upper mold and the lower mold to form a wiring pattern shape on the surface of the resin substrate 31 is the manufacturing process in the first to fourth embodiments described above. Although the description is omitted, the obtained wiring board is obtained by forming a wiring pattern conductor 36 on the surface of a completely cured resin substrate 35 via a resin layer 32 as shown in FIG. I have.

As described above, in this embodiment, since the resin layer 32 is formed on the surface of the resin substrate 31 in the prepreg state, the roughness caused by the fiber base material in the resin substrate 31 appears on the surface of the resin substrate 35. Therefore, the wiring pattern conductor 36 formed on the upper surface by the smooth surface of the resin layer 32 can be a wiring substrate having extremely excellent flatness and a smooth wiring end surface, and can form a fine wiring pattern. can do.

In the method of manufacturing a wiring board in the first to fifth embodiments described above, the upper mold C and the lower mold D are formed with different wiring pattern-shaped projections on the surface. Although the so-called double-sided wiring board in which the wiring pattern is formed on both sides of the resin substrate has been described, a wiring board in which the wiring pattern is formed on only one side of the resin substrate by making the surface of one of the two molds flat is described. It is possible to use the manufacturing method according to the invention.

(Sixth Embodiment) The present embodiment is different from the first embodiment in that the wiring board to be manufactured
This is a point relating to a multilayer wiring board having a circuit pattern layer having at least two layers. Therefore, in the present embodiment, components that are not particularly described are the same as those in the first embodiment, and components having the same names as those in the first embodiment are the same as those in the first embodiment unless otherwise described. It has a function.

FIG. 7 is a process sectional view illustrating a method of manufacturing a wiring board according to a sixth embodiment of the present invention. Hereinafter, a method for manufacturing a wiring board according to the present embodiment will be described with reference to FIG.

In the present embodiment, a wiring board in which a multi-layered internal wiring pattern is formed by using a plurality of wiring boards formed by any one of the manufacturing methods according to the first to fifth embodiments of the present invention. FIG. 7
As shown in (a), a first wiring substrate 42 having wiring patterns 41a and 41b obtained by the manufacturing method according to the first embodiment of the present invention and wiring patterns 43a and 43
3b, and a conductive paste 45 is inserted into a through hole formed at a predetermined location between the second wiring board 44
7 is inserted by inserting a semi-cured intermediate connection resin substrate 46 in which the resin is filled, is accurately aligned, and is laminated. As shown in b), it is possible to obtain a wiring board having a wiring pattern of a four-layer structure interconnected between layers by the conductors 45 in the through holes of the completely cured intermediate connection resin substrate 47.

The wiring board having a multilayer wiring structure according to the present embodiment is not limited to the above-described wiring board having a four-layer structure, and the manufacturing method according to the present embodiment is applied using a plurality of resin substrates 46 for intermediate connection. It is also possible to form a wiring board having a multilayer wiring structure of four or more layers by forming a multilayer structure.

(Seventh Embodiment) A seventh embodiment of the present invention relates to a wiring board having a structure unique to the present invention manufactured by the above-described first to sixth manufacturing methods of the present invention. And a resin substrate 14 as shown in FIG.
The conductor 13 filled in the through hole, the concave portion of the wiring pattern formed on the surface of the resin substrate 14, and the concave portion was filled and flattened on the same surface as the surface of the resin substrate 14. And a wiring pattern conductor 16.

(Resin Substrate of the Present Invention) The resin substrate of the present invention uses a porous film of a heat-resistant resin as a reinforcing material. Here, the heat-resistant resin refers to a resin having a melting point of 250 ° C. or more in consideration of the heat curing temperature of the thermosetting resin.

As the material of the porous membrane, a resin having good heat resistance and mechanical strength is preferable, and various materials such as polyimide, polyester, polyamide, especially aromatic polyamide, polyamideimide, polyetherimide, polyethersulfone and the like can be used. Resin can be employed. Among these resins, polyimide resins are preferable because they have good insulation and heat resistance and good adhesion to the metal layer. In addition, aromatic polyamide also has good insulation and heat resistance,
It is preferable because of its low coefficient of linear thermal expansion.

The formation of the porous film includes various film forming methods such as a wet coagulation method, a dry coagulation method, and a stretching method, and the wet coagulation method is preferable for obtaining a sponge structure. In the wet coagulation method, in general, a film-forming stock solution (dope) in which a resin and additives are dissolved in a solvent is prepared, and the solution is applied (cast) to a film-forming base material and immersed in the coagulation solution to form a solvent. By the substitution, the resin is solidified (gelled), and thereafter, the coagulation liquid or the like is dried and removed to obtain a porous film.

As the polyimide resin, any resin containing other copolymerization components or blend components may be used as long as it is mainly composed of a repeating unit in which an acid residue and an amine residue are imide-bonded. Preferably, it is a polyimide having an aromatic group in the main chain from the viewpoint of heat resistance, hygroscopicity, and mechanical strength, and examples thereof include a polyimide comprising a polymer of a tetracarboxylic acid component and an aromatic diamine component. In particular,
A polymer having an intrinsic viscosity (measured at 30 ° C.) of 0.55 to 3.00, preferably 0.60 to 0.85 is desirable. Those having an intrinsic viscosity in the above range,
When a porous film is formed by a wet coagulation method, a self-supporting porous film having good solubility in a solvent, high mechanical strength, and a high degree of mechanical strength is obtained.

As the polyimide resin, the polymer or its precursor (polyamic acid) can be used for film formation. However, since polyamic acid has higher solubility than polyimide, there is a restriction on the molecular structure. It has the advantage of being small.
The polymer is preferably completely imidized, but may be one having an imidation ratio of 70% or more. When a material having a relatively high imidation ratio is used for dope, it is preferable to use a polymer containing a highly flexible component such as butanetetracarboxylic dianhydride in a repeating unit.

The solvent for dissolving the polyimide resin or its precursor is not particularly limited as long as it can dissolve them, but N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide An aprotic polar solvent such as dimethyl sulfoxide can be preferably used in terms of solubility and the speed of solvent replacement with a coagulating solvent when a porous film is formed by a wet coagulation method. Preferred examples include N-methyl-2-pyrrolidone. Further, a solvent such as diethylene glycol dimethyl ether or diethylene glycol diethyl ether may be mixed to adjust the solvent replacement rate in the wet coagulation method.

On the other hand, as the aromatic polyamide, in addition to so-called para-type aramid and meta-type aramid, a part of the skeleton is diphenylether, diphenylpropane, diphenylmethane, diphenylketone, diphenylsulfoxide,
Examples include those substituted with biphenyl and the like, and those in which the hydrogen group of an aromatic ring is substituted with a methyl group, a halogen atom, and the like.

Examples of the para-type aramid include poly-p-phenylene terephthalamide and the like. Aramid composed only of rigid components such as this polymer needs to be dissolved with a special agent. Therefore, as the aromatic polyamide used for the porous membrane, it is preferable to use at least a part of an aramid or a meta-aramid whose skeleton is partially substituted with a component imparting flexibility. Examples of the component that imparts flexibility include m-phenylene, 2,7-naphthalene, diphenyl ether, 2,2-diphenylpropane, and diphenylmethane. Such a component is used as a dicarboxylic acid monomer or a diamine monomer in the copolymerization and is introduced into the skeleton. Generally, the higher the copolymerization ratio of the component, the higher the solubility in a solvent.

From the viewpoint of solubility, for example, tetramethylurea, hexamethylphosphoramide, N, N-dimethylacetamide, N
-Methyl-2-pyrrolidone, N-methylpiperidone-
2, N, N-dimethylethylene urea, N, N, N ',
N′-tetramethylalonamide, N-methylcaprolactam, N-acetylpyrrolidine, N, N-diethylacetamide, N-ethylpyrrolidone-2, N, N-dimethylpropionamide, N, N-dimethylisobutylamide, Examples include N-methylformamide, N, N-dimethylpropylene urea, and mixtures thereof. Further, aprotic polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide and N, N-dimethylformamide can be preferably used from the viewpoint of solubility and the speed of solvent replacement with a coagulating solvent. . A particularly preferred example is N-methyl-2-pyrrolidone.

A solvent such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, or the like may be mixed to adjust the rate of solvent replacement.

The dope in the wet coagulation method is preferably applied in a temperature range of -20 to 40 ° C. Further, as the coagulation liquid, without dissolving the resin to be used, as long as it has compatibility with the above-mentioned solvent, water, methanol, ethanol, alcohols such as isopropyl alcohol and a mixture thereof are used. In particular, water is preferably used. The temperature of the coagulating liquid at the time of immersion is not particularly limited, but is preferably a temperature of 0 to 90 ° C.

The polymer concentration of the stock solution is preferably in the range of 5% by weight to 25% by weight, more preferably 7% by weight to 20% by weight.
Is more preferred. If the concentration is too high, the viscosity becomes too high and handling becomes difficult. If the concentration is too low, a porous film tends to be difficult to form.

An inorganic substance such as lithium nitrate or an organic substance such as polyvinylpyrrolidone can be added for controlling the pore shape and pore diameter. The concentration of the additive is preferably from 1% by weight to 10% by weight in the solution. When lithium nitrate is added, the replacement speed between the solvent and the coagulating liquid is high, and a finger void structure (a structure having finger-like voids) is formed in the sponge structure. By adding an additive such as polyvinylpyrrolidone that slows down the coagulation speed, a porous membrane having a sponge structure uniformly spread can be obtained.

The dope is applied to a certain thickness and immersed in a coagulating liquid such as water to coagulate, or left in a steam atmosphere to coagulate and then immersed in water to remove the solvent. It becomes a porous membrane. After the formation of the porous membrane, it is taken out of the coagulation liquid and dried. The drying temperature is not particularly limited.
Drying at 0 ° C. or less is desirable.

When the precursor (polyamic acid) is used to form the porous film of the polyimide resin, the precursor (polyamic acid) is finally heat-treated at 200 to 500 ° C., and the precursor (polyamic acid) is closed by heating. To polyimide.

For impregnating the raw material composition of the thermosetting resin, the porous film in the present invention preferably has an average pore diameter of 0.05 μm or more, more preferably 0.1 μm or more, on the back or front surface of the porous film. ５5 μm. The porosity of the porous film is preferably from 30 to 98%, more preferably from 40 to 70%, in order to suitably exhibit the function as a prepreg.

The thickness of the porous film is not particularly limited. However, if the thickness is too large, it tends to take a long time to remove the solvent. In recent multilayer wiring boards, a thin, light, and one having high mechanical strength is desired. Therefore, the thickness is preferably 90 μm to 5 μm.

The prepreg of the present invention can be obtained by impregnating the raw material composition of the thermosetting resin into the pores of the porous film. At this time, the impregnation amount may be adjusted so that the porosity of the unimpregnated portion in the prepreg state is 32 to 63%.

As a method for impregnating the raw material composition, a method in which a raw material liquid of a thermosetting resin is directly applied to the surface of a porous film by various coaters or the like may be used. A method is preferred in which the coated and dried solid coating is laminated on the surface of the porous film and impregnated by heating and pressing. According to this method, the solvent contained in the raw material liquid of the curable resin can suppress the deformation of the porous film due to swelling of the aromatic polyamide or the like.

Examples of the thermosetting resin include an epoxy resin, a phenol resin, a polyimide resin, a polyamic acid, and the like, and an epoxy resin or a mixture of an epoxy resin and another resin is preferred from the viewpoint of cost and ease of handling. The raw material liquid of the thermosetting resin may contain a catalyst, a curing agent, a flame retardant, a filler, a plasticizer, an accelerator and the like in addition to the solvent. The solvent contained in the thermosetting resin raw material liquid includes ketones, acetates, ethers, aromatic hydrocarbons, alcohols, etc., depending on the type of thermosetting resin.

As the base sheet, any of resin, metal and the like can be used, but a resin film is preferable. Examples of the coating method include a coating method using a blade coater, a comma coater, a roll coater, a calendar coater, or a bar coater in any case of direct coating or indirect impregnation. The more uniform the coating thickness, the more uniform the thickness of the solid coating film, and the more uniform the impregnation amount.

In the drying of the solvent, it is not necessary to completely remove the solvent, and the solvent may be non-fluidized. As a drying method, heat drying or hot air drying is preferable in terms of efficiency. As the heating temperature, a temperature at which the curing reaction of the thermosetting resin does not proceed excessively is selected.

As a method for performing heating and pressurization, there are methods using various heat press devices, heat laminators, and devices to which a vacuum exhaust device is added. In the present invention, it is preferable to use a thermal laminator. This heating
By applying pressure, a prepreg in which a semi-cured thermosetting resin is impregnated in a porous film can be produced.

[Brief description of the drawings]

FIG. 1 is an operation explanatory view for explaining the operation and effect of the present invention.

FIG. 2 is a process cross-sectional view illustrating a method for manufacturing a wiring board according to the first embodiment of the present invention.

FIG. 3 is a process cross-sectional view illustrating a method for manufacturing a wiring board according to a second embodiment of the present invention.

FIG. 4 is a process cross-sectional view illustrating a method for manufacturing a wiring board according to a third embodiment of the present invention.

FIG. 5 is a process cross-sectional view illustrating a method for manufacturing a wiring board according to a fourth embodiment of the present invention.

FIG. 6 is a process cross-sectional view illustrating a method for manufacturing a wiring board according to a fifth embodiment of the present invention.

FIG. 7 is a process cross-sectional view illustrating a method for manufacturing a wiring board according to a sixth embodiment of the present invention.

FIG. 8 is a process sectional view showing a conventional method for manufacturing a resin multilayer substrate having an all-layer IVH structure.

FIG. 9 is a process sectional view showing another method of manufacturing a conventional resin multilayer substrate having an all-layer IVH structure.

[Explanation of symbols]

 Reference Signs List 11 resin substrate in semi-cured state 12 through-hole 13 conductive paste (conductor) 14 resin substrate completely cured 15 wiring pattern shape 16 wiring pattern conductor (electric conductor) A release film B release film C upper mold D Lower mold

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kenichi Ikeda 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 5E317 AA24 BB03 BB12 CC22 CC25 CD32 GG05 5E343 AA02 AA13 AA18 BB02 BB24 BB67 BB72 CC03 CC73 DD02 DD33 DD55 ER12 ER35 GG20 5E346 AA12 AA43 CC02 CC10 CC32 CC55 DD02 DD12 DD13 DD23 DD32 DD33 EE04 EE09 FF01 FF18 GG15 GG17 GG19 GG22 GG28 HH11

Claims (4)

[Claims] A semi-cured resin substrate having a through-hole and a conductor filled in the through-hole is pressed against at least one surface of a semi-cured resin substrate with a metal mold having a wiring pattern mold formed in a convex shape. A pattern forming step of forming a wiring pattern shape on the surface of the resin substrate by curing the resin substrate by applying pressure and heating, and after the pattern forming step, an electric conductor is filled in the concave portion of the wiring pattern shape. A method for manufacturing a wiring board, comprising: an electric conductor filling step, wherein a porous film of a heat-resistant resin is used as a reinforcing material for the resin substrate. 2. A step of forming a through hole in a semi-cured resin substrate having a release film adhered on both surfaces thereof before the pattern forming step, and a step of forming a conductor in the through hole. After the conductor filling step, after the conductor filling step, including a film peeling step of peeling the release film, by the end of the film peeling step, the resin substrate in the semi-cured state The method for manufacturing a wiring board according to claim 1, which is obtained. 3. A through hole provided at a position corresponding to the wiring pattern shape between a plurality of wiring boards manufactured by the method of manufacturing a wiring board according to claim 1 or 2 is filled with a conductive paste. A method for manufacturing a wiring board, comprising: a step of pressurizing and heating another resin substrate in a semi-cured state to cure the another resin substrate. 4. A wiring board manufactured by the method for manufacturing a wiring board according to claim 1.