JP3014365B2 - Wiring board, intermediate connector, method of manufacturing wiring board, and method of manufacturing intermediate connector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wiring board having a through hole and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as electronic equipment has become smaller, thinner, lighter, and more sophisticated, various electronic parts constituting the electronic equipment have become smaller and thinner, and these electronic parts have been mounted. Various technical developments have also been actively conducted for wiring boards that can be mounted at high density. In particular, recently, with the rapid development of mounting technology, there is a strong demand for inexpensively supplying a multilayer printed wiring board that can mount a semiconductor chip such as an LSI at a high density and can also handle a high-speed circuit.

As a technique that can meet such demands, a circuit for electrically connecting wiring patterns laminated on both sides of an insulating substrate with a conductive material filled in through holes or via holes is known. A forming substrate (JP-A-6-268345) is disclosed. FIG.
(A) to (f) schematically show steps of a method for manufacturing such a circuit-forming substrate. Note that FIG. 9 shows a cross section perpendicular to the main surface of the substrate (the other drawings show cross sections in the same direction). This circuit-forming substrate is manufactured as follows:

First, as shown in FIG. 9A, a non-adhesive release film (also called a release film) 1
Insulating substrate 1 made of resin-impregnated fiber sheet 1 as a prepreg such as aramid fiber / epoxy resin composite coated on both sides with 7 is pierced at a predetermined location by laser processing to provide through hole 2. Next, the through-hole 2 is filled with the conductive paste 3 by, for example, printing, and then, the peelable film 17 is removed to obtain a state as shown in FIG. 9B. The conductive paste including the conductive granular substance (for example, metal fine powder) and the thermosetting resin component as a binder slightly protrudes from the insulating substrate 1 in accordance with the thickness of the peelable film 17. Note that FIG.
In (b), the protruding state is exaggerated for easy understanding (the same applies to other drawings).

[0005] Next, the copper foil 4 is disposed on both sides of the resin-impregnated fiber sheet 1 and heated and pressed to compress the resin-impregnated fiber sheet 1 and the conductive paste 3 which have been in the prepreg state, and include them therein. The resin to be cured is cured, and the copper foil 4 is adhered to the resin-impregnated fiber sheet 1 so that
The state is as shown in FIG. Resin impregnated fiber sheet 1
Contains at least some voids, so that the resin-impregnated fiber sheet 1 is compressed by heating and pressing. At the same time, in the conductive paste, the resin component in the paste is transferred into the resin-impregnated fiber sheet 1 by heating and pressing,
As a result, the concentration of the conductive fine powder is increased (that is, the conductive fine powder is densified, and therefore, the electrical resistance of the conductive fine powder in the through hole is reduced, and the reliability of the electrical connection is increased). . Therefore, the copper foils 4 are adhered to both sides of the resin-impregnated fiber sheet 1 at the same time as the conductive paste 3
Are electrically connected through the through-hole filled with.

Next, the copper foils 4 on both sides of the resin-impregnated fiber sheet 1 are etched using a general photolithographic method, and as shown in FIG.
Thus, a double-sided wiring board 6 having a wiring pattern on both sides can be obtained. Further, the obtained double-sided wiring board 6
As shown in FIG. 9E, the through-holes 2a and 2a are formed at predetermined positions by the steps shown in FIGS. 9A and 9B.
b has conductive materials 3a and 3b and is disposed between another insulating substrates 1a and 1b functioning as an intermediate connector, and thereafter outside the insulating substrates 1a and 1b (on the side remote from the insulating substrate 1) Are placed with copper foils 7a and 7b.

Thereafter, the double-sided wiring board 6, the insulating substrates 1a and 1b, and the copper foils 7a and 7b are heated and pressed to obtain a multilayered monolith, and then the outermost copper foils 7a and 7b are formed by photolithography. 7b is etched and electrically connected to wiring patterns 5a and 5b on resin impregnated fiber sheet 1 by conductive pastes 3a and 3b filled in through holes 2a and 2b, as shown in FIG. 9 (f). Wiring patterns 8a and 8
It is also possible to obtain a multilayer wiring board 9 having four wiring layers provided with b.

[0008]

In a resin-impregnated fiber sheet such as an aramid fiber / epoxy resin prepreg in which an aramid fiber nonwoven fabric is impregnated with an epoxy resin, the aramid fibers contained in the sheet have irregularities on the surface of the resin-impregnated fiber sheet. For example, unevenness corresponding to the shape of the aramid fiber is formed on the surface of the resin-impregnated fiber sheet 1 as it is. When the wiring patterns 5a and 5b are formed by etching the copper foil 4 thermocompression-bonded on such a resin-impregnated fiber sheet 1 by photolithography, the copper foil 4 Since the surface of the substrate 4 also has irregularities, a gap is easily generated between the copper foil 4 and an etching resist (not shown).
At the time of etching, the etchant penetrates into this gap,
As a result, it becomes difficult to form the wiring patterns 5a and 5b as designed. In particular, there is a problem that it is difficult to form a fine wiring pattern corresponding to high-density mounting of ultra-small electronic components such as semiconductor bare chips.

[0009] Further, since the resin-impregnated fiber sheet is in a state in which a resin material is impregnated in a base material made of fiber, the structure of the resin-impregnated fiber sheet is hardly uniform as a whole. For example, in a resin-impregnated fiber sheet such as an aramid fiber / epoxy resin prepreg in which an aramid fiber nonwoven fabric is impregnated with an epoxy resin, the aramid fiber is discontinuously present in the surface layer portion of the sheet or partially exposed to the surface. Is prone to the following two problems:

When a resin-impregnated fiber sheet and a copper foil are thermocompression-bonded thereto, the impregnated resin contributes to adhesion. In the portion where the aramid fiber exists or is exposed in the surface layer of the insulating substrate, the amount of the impregnated resin existing under the copper foil is reduced. As a result, the adhesion between the copper foil and the resin-impregnated fiber sheet becomes insufficient, and a sufficient adhesive force between the resin-impregnated sheet and the copper foil cannot be obtained. Therefore, it is difficult to obtain high mounting strength when mounting electronic components and the like on the wiring pattern formed on such a wiring board;

In the manufacturing process of the wiring board shown in FIGS. 9A to 9F, if the surface of the resin-impregnated fiber sheet has irregularities, the release film 17 and the resin-impregnated fiber sheet 1
When the conductive paste 3 is filled in the through-holes due to insufficient adhesion to the resin paste, the releasable film 17 and the resin-impregnated fiber sheet 1
Between the conductive paste 3 and the conductive paste 3. as a result,
The conductive paste 3 extends beyond the diameter of the through hole 2 and spreads on the insulating substrate 1. Thus, when the distance between the through hole and the wiring pattern or another through hole formed on the substrate is small, these electrical short circuits are likely to occur. Therefore, there has been a limit in increasing the density of the wiring pattern.

On the other hand, as a method of forming a fine wiring pattern, a wiring pattern is previously formed on the surface of a peelable support plate, and such a wiring pattern is transferred to the surface of an insulating substrate to form a fine wiring pattern. Pattern formation method (Naoki Fukutomi et al., "Development of fine wiring technology by wiring transfer method", IEICE Transactions on Electronics, Vol.J72-C No.4, PP24
3-253, 1989). However, even when such a method is used, it is difficult to accurately transfer a fine wiring pattern onto the insulating substrate because the surface of the resin-impregnated fiber sheet that is the insulating substrate has irregularities. .

As a method for improving the adhesion strength between the insulating substrate and a metal foil such as a copper foil, a method of improving the surface of an insulating substrate made of a resin-impregnated fiber sheet impregnated with an epoxy resin or the like with an insulating adhesive resin is used. Covering method (JP-A-8-316598)
No., Japanese Patent Application Laid-Open Publication No. H11-209,036). In this method, the impregnated resin of the resin-impregnated fiber sheet and the adhesive resin compatible with the impregnated resin are both contacted in an uncured state, and then heated and pressed, compressed and cured to bond. Therefore, it was difficult to sufficiently avoid the influence of the unevenness of the surface of the nonwoven fabric.

Further, as a wiring board technology enabling high-density mounting, a technology is disclosed in which a thermosetting resin layer is present on both surfaces of an insulating substrate of a resin-impregnated fiber sheet (Japanese Patent Laid-Open No. Hei 7-263828). And JP-A-8-7880
No. 3). Here, an uncured thermosetting resin layer is formed on a cured insulating resin, then a through hole is formed, and then a conductive paste is filled and heated and pressed. ing. Thus, the insulating substrate itself is already cured, and the insulating substrate is not substantially compressed. Therefore, the conductive paste filled in the through-hole is not compressed, and as a result, the conductive paste in the through-hole does not progress in densification. Therefore, the electrical connection reliability of the wiring due to the conductive paste in the through hole (lower resistance of the paste, resistance stability, adhesion between the paste and the insulating substrate and between the paste and the wiring conductor) Securing) was inadequate.

An object of the present invention is to solve the above-mentioned problems. That is, while maintaining the advantage of the circuit forming substrate that electrically connects the wiring patterns disposed on both sides of the insulating substrate with the conductive material in the through hole, the above-described problem is solved. It is an object of the present invention to provide a printed wiring board which is capable of further increasing the density of component mounting and which is more reliable, and a method of manufacturing the same.

[0016]

Means for Solving the Problems As a result of intensive studies, the inventors have found that at least one main surface of a resin-impregnated fiber sheet as a prepreg having compressibility is substantially compatible with the resin-impregnated fiber sheet. By using a flat heat-resistant film, preferably a composite on which a heat-resistant resin film is arranged, as an insulating substrate and forming a wiring pattern thereon, the surface of the resin-impregnated fiber sheet is not substantially flat (ie, ), The surface of the insulating substrate on which the wiring pattern is formed is substantially flat, and as a result, a fine wiring pattern can be formed. The present inventors have found that it is easy to ensure the reliability of the electrical connection of the wiring, and have completed the present invention. That is, the present invention provides a resin-impregnated fiber sheet and a conductive material filled in a through-hole provided through at least one side of the insulating substrate, which is preferably formed of a heat-resistant film disposed on both sides. Thereby, a predetermined wiring pattern formed on both sides of the insulating substrate, particularly a fine wiring pattern, is electrically connected to provide a double-sided wiring board.

In this specification, "double-sided wiring board"
A wiring board having a wiring pattern layer on each side of an insulating base material (usually in a sheet-like form) means a “multi-layer wiring board” described later having at least three wiring pattern layers. A wiring board, these wiring patterns
Wirings separated from each other by an insulating base material located between two adjacent wiring patterns and connected to each other by a conductive material filled in through holes formed in the insulating base material. It means a plate (accordingly, it has a structure in which insulating base materials and wiring layers are arranged alternately).

The above-mentioned double-sided wiring board comprises: (1) a heat-resistant film disposed on at least one side of a resin-impregnated fiber sheet;
A composite insulating substrate is obtained, (2) a release film is disposed on the exposed surface of the heat-resistant film to form a wiring board preliminary body, and (3) at least one penetration penetrating the insulation substrate and the release film. Forming a hole, (4) filling the through hole with a conductive material, and (5) removing both peelable films from the wiring board preliminary body to obtain an insulating substrate having a heat-resistant film exposed on at least one side. 6) A wiring material (for example, a metal foil such as a copper foil) is arranged on both sides of the insulating substrate, and the insulating substrate and the wiring material are heated and pressed together to bond the insulating substrate and the wiring material together. Thereafter, the wiring material is formed by the method for manufacturing a double-sided wiring board of the present invention including forming a wiring material into a predetermined wiring pattern.

The formation of the wiring material into a predetermined wiring pattern, that is, patterning, may be performed by etching the wiring material using a generally performed photolithographic method. In the method of the present invention, since the surface of the insulating substrate on which the wiring material is arranged is flat, the adhesiveness between the photomask and the wiring material is improved in the wiring material etching process using a photolithographic method. Thus, a fine wiring pattern can be manufactured with high accuracy. As the wiring material, instead of the metal foil, a conductive paste, a conductive ink, or the like may be used.
The placement of the conductive material can also be performed after, rather than before, the heat and pressure treatment. Alternatively, when a predetermined wiring pattern is formed by a direct printing method, the patterning can be omitted.

According to the method of the present invention, a fine wiring pattern having higher reliability than a conventional printed wiring board having a via hole structure and capable of mounting ultra-miniaturized electronic components and the like at high density. A new printed wiring board capable of forming the same can be manufactured at low cost. In the manufacturing method of the present invention described above, instead of the step (6), (7)
A wiring pattern support plate in which a predetermined wiring pattern is formed in advance on a peelable support plate is positioned on the exposed heat-resistant film while being aligned with the through holes, and the plate and the insulating substrate are heated together. And pressurize,
Thereafter, the step of removing the releasable support plate, that is, the step of transferring the wiring pattern on the plate to the insulating substrate, can be replaced. Generally, the peelable support plate may be a sheet of a conductive material (for example, stainless steel), and after plating a wiring material (for example, copper) thereon, etching to leave a predetermined copper wiring pattern. By doing so, a wiring pattern support plate can be obtained. For details, reference can be made to the previously cited document “Development of fine wiring technology by wiring transfer method”, and the contents of this document constitute a part of this specification by this citation.

In the method of the present invention, since the exposed surface of the insulating substrate is substantially flat, a finer wiring pattern can be formed with high precision by combining with the transfer method. The formation of a through hole in the method of the present invention is also known from the three patent publications cited above, and the through hole can be formed by, for example, laser processing. For details of the formation of the through holes, reference can be made to such patent publications, and the technical matters disclosed in these publications by this citation constitute a part of the present specification. By forming the through-holes in this manner, fine through-holes corresponding to the miniaturization of the wiring pattern can be easily formed on the insulating substrate having the peelable film at a high speed.

The conductive material to be filled in the through-hole can be filled in the through-hole so long as it can electrically connect wiring patterns arranged on both sides of the insulating substrate later.
There is no particular limitation. Specifically, a conductive paste or metal (for example, solder) fine powder having excellent fluidity can be used. When such a conductive material is used, a sufficient filling property and a highly reliable connection can be ensured even if the diameter of the through hole is reduced due to the miniaturization of the wiring pattern. The filling of the conductive material into the through holes may be performed by any appropriate method. For example, the conductive paste can be filled in substantially all of the through holes by a printing method.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, an insulating substrate is composed of a resin-impregnated fiber sheet and a heat-resistant film. In the present invention, the resin-impregnated fiber sheet has been conventionally used for a wiring board, and is a so-called prepreg containing a thermosetting resin in a semi-cured state before being formed on a wiring board. Usually, such a resin-impregnated fiber sheet is obtained by impregnating a fiber product as a base material, for example, a nonwoven fabric, a woven fabric, paper or the like with a thermosetting resin, for example, a phenol resin or an epoxy resin, and semi-curing the resin. May be. The fiber product may be made of inorganic fibers (glass fibers, alumina fibers, etc.), organic fibers (polyamide fibers such as aramid, aromatic polyester-based liquid crystal polymer fibers, etc.) or a combination thereof. More specifically, the resin-impregnated fiber sheet includes a non-woven fabric of aramid fibers impregnated with a thermosetting epoxy resin. Other resin-impregnated fiber sheets that can be used in the present invention, for example,
Glass fiber / epoxy resin composite, glass fiber
Bismaleimide triazine (BT) resin composite and aramid fiber / bismaleimide triazine (BT) resin composite are included. After being formed on the wiring body, the resin-impregnated fiber sheet contains a cured resin.

Such a resin-impregnated fiber sheet is electrically substantially electrically insulating and generally compressible, that is, when heated to a predetermined curing temperature, in a direction perpendicular to the sheet surface. It is compressed and hardened by the compressive force. Typically, the sheet will include at least some voids therein, and thus the voids will be reduced or substantially eliminated by the action of pressure and heat, reducing the thickness of the sheet. However, in the present invention, even if the sheet does not substantially contain voids,
Alternatively, even when the gap portion is present but does not substantially decrease, when the compressive force is applied in a direction perpendicular to the sheet surface, even when the rolled portion becomes thinner, it is compressible. include. Of course, the case where the thickness of the sheet is reduced due to the combination of the reduction of the void portion and the effect of the rolling is also included in the aspect of the compressibility. In fact, in many cases, the thickness is reduced by about 20 to 30% by heating and pressing.

Such a resin-impregnated fiber sheet has an appropriate compressibility, and enables a conductive material (for example, a conductive paste) in the through-hole to be subjected to a compressive action when the insulating substrate is heated and compressed. As a result, as the density of the conductive material increases, the electrical connection reliability between the wiring patterns to be connected with the conductive material (reduction of the resistance of the conductive material itself,
Resistance stability, adhesion between a conductive material and a substrate material and a wiring pattern, etc.) can be easily obtained, and a wiring board excellent in heat resistance and mechanical strength can be obtained.

In the present invention, the heat-resistant film means a film that does not melt when the insulating base material is heated and pressed to cure the thermosetting resin contained therein. In the board, at least the surface of the heat-resistant film on the side away from the resin-impregnated fiber sheet is substantially flat. The heat-resistant film has insulating properties and does not have compatibility with the resin-impregnated fiber sheet. Specifically, the heat-resistant film is made of an inorganic substance (for example, a metal oxide,
In particular, it may be made of mica) or may be made of an organic substance (for example, various heat-resistant resins such as aromatic polyamide and polyimide). Such a film, under the heating and pressing conditions encountered by insulating substrates,
Most preferably, it does not melt and does not substantially deform. However, unless the surface of the heat-resistant film on the side away from the resin-impregnated fiber sheet cannot maintain its flatness due to the influence of the unevenness of the surface of the resin-impregnated fiber sheet, it will be deformed under heating and pressing conditions. Such a film can be used.

In the present invention, the heat-resistant film comprises 10
It is particularly preferred to have a breaking strength of kg / mm ² or more. Thereby, the adhesive strength of the wiring pattern on the heat resistant film is increased, and a highly reliable wiring board can be obtained. Particularly preferred heat-resistant films are heat-resistant resin films, for example, aromatic polyamides (particularly wholly aromatic polyamides), polyimides, aromatic polyesters (particularly wholly aromatic polyesters), polycarbonates, polysulfones, polytetrafluoroethylenes, polyhexas. Examples include films of resins such as fluoropropylene, polyether ketone, and polyphenylene ether.

The temperature encountered by the heat-resistant film is the highest at the temperature at which the impregnated resin of the resin-impregnated fiber sheet is cured, and varies depending on the resin-impregnated fiber sheet used. Generally, resin-impregnated fiber sheets are roughly classified into two groups according to the curing temperature of the impregnated resin (low-temperature curable resin sheet (curing temperature 1).
20-180 ° C) and a high-temperature curable resin sheet (curing temperature 180-250 ° C). A film of an aromatic polyamide (particularly wholly aromatic polyamide), polyimide or aromatic polyester can be used in the case of a fiber sheet impregnated with a high-temperature curable resin. For a fiber sheet impregnated with a low-temperature curable resin, films of polycarbonate, polysulfone, polytetrafluoroethylene, polyhexafluoropropylene, polyether ketone, and polyphenylene ether can also be used in addition to these.

The thickness of the heat-resistant film is not particularly limited as long as the irregularities on the surface of the resin-impregnated fiber sheet do not affect the insulating base material. It is not preferable that the thickness is so large as to hinder the heating. In addition, when the thickness of the heat-resistant film increases, the compressibility of the entire insulating substrate decreases, which is not preferable for densification of the conductive material. The thickness of the heat-resistant film is usually about 10 to 4 times the thickness of the resin-impregnated fiber sheet.
The thickness may be about 0%, specifically, at least several μm, preferably at least 10 μm, for example, 10 to 30 μm.

The heat-resistant film can be arranged on the resin-impregnated fiber sheet by thermocompression bonding. Thermocompression bonding is to place the heat-resistant film on a resin-impregnated sheet and apply pressure while heating these to a temperature at which the impregnated resin does not cure, thereby imparting tackiness to the impregnated resin, This is performed by bonding the heat-resistant film to the resin-impregnated fiber sheet (accordingly, thermocompression bonding). The pressure to be applied does not need to be so large, and heating and pressurization need only be performed for a short time. For example, when the impregnated resin is an epoxy resin, 0.3 to 3 kg / c
m ² pressure, several seconds to several tens of seconds, 80 to 140
The thermocompression bonding may be performed under a temperature condition of about ° C.

Further, if necessary, an adhesive layer may be interposed between the heat-resistant film and the resin-impregnated fiber sheet, and the adhesive may be activated by thermocompression bonding to adhere them.
Therefore, the heat-resistant film may have an adhesive layer on the surface facing the resin-impregnated fiber sheet. Such an adhesive layer is formed of a heat-resistant adhesive capable of maintaining an adhesive function even under the curing conditions of the impregnated resin, and such an adhesive is, for example, an epoxy resin-based or polyimide resin-based adhesive. Agent (which exhibits adhesive activity at a temperature lower than the curing temperature of the impregnated resin). From the viewpoint of ensuring the formation of a uniform coating film on the heat-resistant film, a rubber-modified epoxy resin can be used in the former example, and a polyimidesiloxane resin can be used in the latter example. When the heat-resistant film is arranged on the resin-impregnated fiber sheet as described above, the influence of the unevenness on the surface of the resin-impregnated fiber sheet is caused by the surface of the heat-resistant film remote from the resin-impregnated fiber sheet (therefore, the exposed surface of the insulating substrate). Without affecting
As a result, the flatness of the exposed surface of the insulating substrate is substantially ensured.

Next, a peelable film is disposed on the insulating substrate obtained as described above. This releasable film is a flat film that functions as a mask when filling the through hole with a conductive material, is temporarily disposed on an insulating substrate, and then can be easily peeled. There is no particular limitation. Generally, a polyester film such as a polyethylene terephthalate (PET) film is used as a release film, and in some cases, a release agent is added to the release film in order to further facilitate the release of the film from the insulating substrate. May be applied.

The disposition of the peelable film on the insulating substrate may be performed by placing the peelable film on the insulating substrate and thermocompression bonding. If sufficient adhesion cannot be obtained between the peelable film and the insulating substrate by thermocompression bonding, an adhesive layer may be interposed between them. Generally, it is preferable to interpose an adhesive layer between the insulating substrate and the releasable film, and they can be bonded together by thermocompression bonding via the adhesive layer. This adhesive layer may be the same as the adhesive layer interposed between the heat-resistant film and the resin-impregnated fiber sheet described above.
Therefore, the heat resistant film may have an adhesive layer on one or both sides. The arrangement of the peelable film on the insulating substrate may be performed by thermocompression bonding under the same conditions as the arrangement of the heat-resistant film on the resin-impregnated fiber sheet.

Therefore, when the heat-resistant film is disposed on the resin-impregnated fiber sheet and the releasable film is disposed thereon, that is, when the steps (1) and (2) are successively carried out, The steps (1) and (2) are simultaneously performed by placing a heat-resistant film on the impregnated fiber sheet, placing a peelable film on the heat-resistant film, and heating and pressing them together while aligning them. It is also possible to obtain a reserve. In this case, an adhesive layer is preferably present between the heat-resistant film and the peelable film, more preferably between the heat-resistant film and the resin-impregnated fiber sheet.

Therefore, when a through hole is formed in the wiring board preform formed as described above and a conductive material such as a conductive paste is filled therein, the peelable film and the heat resistant film are Sufficient adhesion at the flat interface prevents conductive material from penetrating such an interface. Therefore, when subsequently forming the wiring pattern by removing the peelable film, the distance between the wiring pattern and the through-hole and / or the distance between the through-hole and another through-hole is made shorter than before. However, a short circuit hardly occurs between them.

The exposed surface of the insulating substrate obtained by removing the peelable film (therefore, the exposed surface of the heat-resistant film) is substantially flat. Therefore, when the wiring pattern is provided thereon, even when the surface of the resin-impregnated fiber sheet has an uneven shape, the wiring pattern formed on the insulating base material can be substantially flattened. As a result, a fine wiring pattern can be formed on the insulating base material with high accuracy.

In the wiring board of the present invention, the insulating substrate is
Including a compressible resin-impregnated fiber sheet, the conductive paste or fine metal powder embedded in the through-holes provided in the insulating substrate receives a compressive force simultaneously when heating and compressing the insulating substrate, and the conductive paste As the contained resin component migrates to the insulating base material, the conductive material such as metal fine particles in the conductive paste becomes a densified conductive material, or the metal fine powder is densified with the conductive material. Because
The electrical connection reliability as described above (such as lowering the resistance value of the conductive material and securing the resistance stability, securing the adhesion between the conductive material and the insulating substrate and the wiring pattern, etc.) can also be easily obtained. .

The bonding between the flat heat-resistant film forming the exposed surface of the insulating substrate and the conductive material for wiring pattern (eg, metal foil such as copper foil) formed thereon is described above. By forming the adhesive layer on the heat-resistant film in advance, sufficient and temporary adhesive strength with the peelable film can be secured. After the removal of the peelable film, the adhesive layer remains, so the insulating substrate surface (that is,
In addition to the substantially flat surface of the heat-resistant film, the presence of the adhesive layer ensures a sufficient bonding state between the conductive material for wiring patterns (for example, metal foil) and the insulating substrate. Therefore, when the conductive material is patterned by etching, the etching liquid does not enter between the conductive material and the insulating substrate, so that accurate patterning can be performed. Furthermore, as the heat-resistant resin film, a film having high electric insulation and good tracking resistance (for example, a polyimide film) can be used, so that a wiring board having higher reliability can be obtained. .

The through-hole may be called a via hole, an inner via hole, or a through hole.
Generally, a conductive material such as a conductive paste or metal fine powder is filled therein, and the conductive material electrically connects predetermined wiring patterns arranged on both sides of the insulating substrate in a predetermined manner. . The conductive paste may be generally used for manufacturing a wiring board having via holes, and is usually a fine conductive material such as a metal (silver,
It is composed of fine particles (eg, copper) and a thermosetting resin (eg, epoxy resin), and can be filled in the through holes by screen printing or the like. The conductive paste filled in the through-holes, when subjected to heat and pressure treatment, due to the compressibility of the resin-impregnated fiber sheet, at least a portion of the resin component migrates from the through-hole into the resin-impregnated fiber sheet, and as a result, It becomes a conductive material in which the density of the constituents of the conductive material such as metal fine powder is increased (that is, the constituents of the conductive material are densely filled), and connects the wiring patterns on both sides of the insulating substrate.

As described above, the wiring board of the present invention has no hollow through-hole, and can mount electronic components through the wiring pattern (or the conductor land) on the through-hole in which the conductive material is embedded. This makes it possible to further enhance the high wiring accommodating property and the high-density mounting property unique to this type of wiring board, and to improve the reliability of the entire wiring board.

After disposing the conductive material in the through holes, the peelable film is removed, and the wiring material is disposed on both sides of the insulating substrate where the heat-resistant film is exposed on at least one side.
When the wiring material is a metal foil such as a copper foil, the arrangement is such that, after the wiring material is disposed, the wiring material is heated and pressed together with the insulating base material (that is, thermocompression-bonded) to the insulating substrate. The semi-cured thermosetting resin contained is cured, and the wiring material and the insulating substrate are integrally bonded.

In the thermocompression bonding, unlike the above-mentioned heat-resistant film and peelable film, the thermosetting resin is heated to a curing temperature or higher, and usually, a longer time (for example, several tens to two minutes) is used. Time), greater pressure (e.g. 20-
100 kg / cm ² ) in that the heated and pressurized state is maintained. Generally, in any thermocompression bonding, after predetermined heat and pressure treatments are completed, cooling is actively performed as necessary. Such thermocompression bonding may be performed with any suitable known equipment, method, and conditions. For example, in the thermocompression bonding of a heat-resistant film and a peelable film, a device such as a roll laminator having a heating roll is used, and a pressure of 0.3 to 3 kg / cm ² , a time of several seconds to several tens seconds, 80 to Conditions such as temperatures of around 140 ° C. can be used. In addition, for example, in the thermocompression bonding for carrying out the curing of the thermosetting resin, a device such as a heat press having a heating plate is used for 20 to 100 kg.
/ Cm ² , several tens of minutes to about two hours, 120
Conditions such as temperatures on the order of ２５０250 ° C. can be used. still,
The formation of the wiring pattern, instead of thermocompression bonding of the metal foil as described above, by previously forming a wiring pattern on another peelable support plate, by arranging it on an insulating substrate and thermocompression bonding, A method of transferring the wiring pattern to the insulating substrate and curing the thermosetting resin can also be used.

As is apparent from the above description, the present invention provides a method for forming a wiring pattern on a resin-impregnated fiber sheet by interposing a heat-resistant film between the wiring patterns. An object of the present invention is to solve a problem caused by unevenness. Therefore, the present invention can be applied not only to the above-described double-sided wiring board but also to a multilayer wiring board. That is, the multilayer wiring board of the present invention comprises at least three wiring pattern layers and a resin-impregnated fiber sheet located therebetween, and a heat-resistant film between at least one wiring pattern and the resin-impregnated sheet. Are arranged, and the wiring patterns are electrically connected by a conductive material filled in at least one through hole formed in each resin-impregnated fiber sheet.

The description of the multilayer wiring board of the present invention will be made as long as no inconvenience occurs, except that the number of wiring layers is different.
The above description of the double-sided wiring board can be substantially applied. For example, the description of a resin-impregnated fiber sheet, a heat-resistant film, a peelable film, and the like applies. In a particularly preferred embodiment, a heat-resistant film is disposed between the outermost wiring pattern of the multilayer wiring board and the resin-impregnated fiber sheet. that is,
This is because the outermost wiring pattern of such a multilayer wiring board can be made fine, and electronic components can be mounted on the multilayer wiring board with high density. Of course, as for the internal wiring pattern, a structure in which a heat-resistant film is disposed between the wiring pattern and the resin-impregnated fiber sheet can be employed, if necessary.

Such a multilayer wiring board is manufactured when the total number of layers of the wiring pattern is large (for example, about 4 to 10 layers).
In this case, a structure is formed in which at least one double-sided wiring board formed in advance as described above and at least one resin-impregnated fiber sheet in which a conductive material is disposed in a predetermined through hole are alternately stacked, or If necessary, a conductive material (for example, a metal foil) for forming an outermost wiring pattern is further arranged as an outermost portion to form a structure, and the structure is heated and pressed to cure the uncured resin. This can be implemented by integrating the structures. In this case, it is also possible to use an already formed multilayer wiring board instead of the double-sided wiring board.

In one preferred embodiment of the present invention,
Predetermined wiring patterns are arranged on both sides of the resin-impregnated fiber sheet, and these wirings are arranged in at least one double-sided wiring board electrically connected by a conductive material filled in the through holes, and in the through holes. When a multilayer wiring board in which at least one intermediate connector composed of a resin-impregnated fiber sheet having a conductive material is alternately arranged, and the intermediate connector constitutes the outermost part of the multilayer wiring board, The intermediate connector has a predetermined wiring pattern on the outermost surface, and the wiring patterns located on both sides of each intermediate connector are connected by a conductive material in a through hole of the intermediate connector, and at least one double-sided wiring The board has a heat-resistant film between at least one of the wiring patterns and the resin-impregnated fiber sheet, and the through-hole penetrates the resin-impregnated fiber sheet and the heat-resistant film. Multilayer wiring board is provided, wherein.

In one embodiment of such a multilayer wiring board,
The number of double-sided wiring boards is larger than the number of intermediate connectors by one, so that the double-sided wiring boards constitute both outermost parts of the multilayer wiring board, and at least one of the double-sided wiring boards constituting the outermost parts of the wiring board A heat-resistant film may be provided between at least the outermost wiring pattern and the resin-impregnated fiber sheet. For example, the double-sided wiring board of the present invention described above is disposed on both sides of an intermediate connector having a through hole at a predetermined position of a resin-impregnated fiber sheet as an insulating substrate, and the through hole is filled with a conductive material. The wiring patterns of both double-sided wiring boards are adhered, and are electrically connected by the conductive material filled in the through holes of the intermediate connector. In this example, the wiring board has four wiring patterns in which an intermediate connector exists between the double-sided wiring boards.

In another embodiment of such a multilayer wiring board, the number of double-sided wiring boards is one less than the number of intermediate connectors, so that the intermediate connectors constitute both outermost of the multilayer wiring boards, At least one of the double-sided wiring boards adjacent to the intermediate connector constituting the outermost surface of the multilayer wiring board may have a heat-resistant film between at least one of the wiring patterns and the resin-impregnated fiber sheet. For example, a resin-impregnated fiber sheet has a through hole at a predetermined position, and an intermediate connector filled with a conductive material in the through hole is a multilayer wiring board arranged on both sides of the double-sided wiring board of the present invention described above. Each intermediate connector has a predetermined wiring pattern on the surface remote from the double-sided wiring board, and the predetermined wiring pattern on the surface of each intermediate connector remote from the double-sided wiring board is adjacent to the intermediate connector. A multilayer wiring board is provided which is electrically connected to the wiring pattern of the double-sided connection board and the conductive material in the through hole of the intermediate connection body. Also in this example, the wiring board has four wiring patterns in which a double-sided wiring board exists between the intermediate connectors.

In such a multilayer wiring board, an extremely fine wiring pattern can be formed on a heat-resistant film included in the multilayer wiring board, and there is no hollow through-hole and a through-hole filled with a conductive material. A wiring board on which electronic components can be mounted via wiring patterns (conductor lands) on the holes is electrically connected by an intermediate connector, so that a multilayer wiring board having high wiring accommodation and high-density mounting is provided. can get.

Hereinafter, more specific embodiments of various wiring boards of the present invention will be described with reference to the drawings. Specific Embodiment 1 FIG. 1 is a schematic cross-sectional view (in a direction perpendicular to the main surface of the wiring board) of the double-sided wiring board of the present invention according to specific embodiment 1, and FIG. FIG. 3 is an enlarged schematic sectional view. In FIG. 1, for example, a heat-resistant film substantially incompatible with the resin-impregnated fiber sheet 11 is provided on both sides of a resin-impregnated fiber sheet 11 in which a thermosetting resin (already cured) is impregnated into a nonwoven fabric of organic fibers. For example, a heat-resistant resin film 15 is disposed, and these constitute a composite as the insulating substrate 10. At least one through-hole 12 is provided at a predetermined position of the insulating substrate 10, and the inside thereof is filled with a conductive material (for example, a conductive paste) 13. Predetermined wiring patterns 14 a and 14 b are formed on the heat-resistant film 15 constituting both sides of the insulating substrate 10, and these are electrically connected by the conductive material 13.
The number and positions of the through holes 12 are determined as predetermined by the wiring patterns 14a and 14b arranged on both sides of the insulating substrate 10.

As shown in FIG. 2, the heat-resistant film 15
May have an adhesive layer 16 made of, for example, a polyimide resin or an epoxy resin on one or both surfaces thereof in order to reinforce the adhesiveness with the resin-impregnated fiber sheet 11 and / or the wiring pattern 14 depending on the material. preferable. The resin impregnated in the resin-impregnated fiber sheet 11 exhibits tackiness even by thermocompression bonding of the heat-resistant sheet, and can be brought into a molten state by heating when forming the wiring board. Even if it does not exist between the heat-resistant film 15 and the resin-impregnated fiber sheet 11, sufficient adhesion to the heat-resistant film 15 can often be ensured. Since the heat-resistant film 15 does not reach a molten state in a heating / pressing step for curing and compressing the impregnated resin when finally forming the wiring board, the heat-resistant film 15 is not formed between the wiring pattern 14 and the heat-resistant film 15. The adhesiveness may not always be sufficient. In such a case, the adhesive layer 16 is provided between the wiring pattern 14 and the heat-resistant film 15 (see FIG. 2), so that the wiring pattern 14 and the heat-resistant film It is preferable to ensure sufficient adhesiveness between them.

FIG. 3 schematically shows steps of a method for manufacturing a double-sided wiring board according to the first embodiment of the present invention.
It is sectional drawing similar to. As shown in FIG. 3A, as the resin-impregnated fiber sheet 11, for example, an aromatic polyamide (for example, aramid) fiber (for example, “Kevlar” manufactured by DuPont, fineness: 1.5 denier, fiber length: 7)
A 150 μm-thick porous prepreg (the epoxy resin is in a semi-cured state) prepared by impregnating a thermosetting epoxy resin (for example, “EPON1151B60” manufactured by Shell) into a non-woven fabric having a thickness of 70 g / m ² ). A heat-resistant resin film 15 is adhered to both surfaces by thermocompression bonding, and the outer surface thereof has a thickness of, for example, polyethylene terephthalate having a thickness of 1 mm.
A 2 μm release film 17 is provided by thermocompression bonding to obtain a wiring board preform. As the heat-resistant resin film 15, for example, an adhesive 1 made of a rubber-modified epoxy resin or polyimide siloxane having a thickness of 10 μm on both sides of a wholly aromatic polyamide film (Aramika, manufactured by Asahi Kasei Corporation) having a thickness of 19 μm.
6 (not shown in FIG. 3) can be used (see FIG. 2).

Next, as shown in FIG. 3 (b), a predetermined portion of the insulating substrate 10 having the peelable film 17 is subjected to laser processing using, for example, a carbon dioxide gas laser or the like to form a hole diameter of 20 mm.
A through hole 12 of 0 μm is formed. Next, after filling the through holes 12 with a conductive material 13 such as a conductive paste or metal powder, the release film 17 is peeled off as shown in FIG. When using a conductive paste as the conductive material 13, for example, copper powder having an average particle size of 2 μm,
A conductive paste formed by blending with a binder resin made of a solventless epoxy resin at a content of 85% by weight and uniformly mixing the blend with a three-roll kneader can be used. The conductive paste 13 is filled into the through holes 12 by a printing method, and the conductive paste is printed and filled from above the peelable film 17 by a squeegee method or a roll transfer method. At this time, the release film 17 functions as a print mask. Since the surface of the heat-resistant film 15 facing the release film 17 is substantially flat, sufficient adhesion between both films is ensured, and as a result, the heat-resistant film 15 The conductive paste does not protrude from the through-hole along.

Next, as shown in FIG. 3D, the exposed adhesive layer 16 (not shown in FIG.
A 5 μm copper foil 18 is placed on each. Then, FIG.
In the state of the above, heating and pressurizing, thermocompression bonding, that is,
Insulating substrate 11 and conductive paste 1 in prepreg state
3 is compressed, the impregnating resin and the resin of the conductive paste are cured, and the copper foils 18 on both sides are simultaneously adhered to the heat resistant film 15 to be integrated. For example, 6
While applying a pressure of 0 kg / cm ² , the temperature is raised from room temperature to 200 ° C. in 30 minutes, held at 200 ° C. for 60 minutes, and then lowered to room temperature in 30 minutes to perform a thermocompression bonding step. . As a result, a double-sided copper foil-bonded circuit board in which the copper foil is electrically connected via the conductive material 13 in the through hole 12 as shown in FIG. 3E is obtained.
Finally, as shown in FIG. 3 (f), by patterning the copper foil 18 by a photolithographic method, wiring patterns 14a and 14b are formed, and a wiring board 19 having wiring patterns on both surfaces is obtained.

In the manufacturing method with reference to FIG. 3 described above, the heat-resistant resin film 15 in which the adhesive layer 16 for enhancing the adhesive strength is formed on both sides is used. The adhesive layer 16 on the side of the fiber sheet 11 may be omitted. Further, when a heat-fusible polyimide resin film is used as a heat-resistant film, a necessary adhesive strength to the resin-impregnated fiber sheet 11 and the copper foil 18 may be obtained only by applying heat and pressure. Alternatively, the application of the adhesive layers 16 on both sides of the heat-resistant film 15 can be omitted.

FIG. 4 shows a four-layer wiring layer obtained by laminating double-sided wiring boards 19 and 19 ′ (FIG. 1) according to the above-described specific embodiment 1 so as to sandwich an intermediate connector 20 described below. FIG. 4 is a cross-sectional view schematically showing a manufacturing process of a multilayer wiring board having the following. First, as shown in FIG. 4A, a non-woven fabric of, for example, an aromatic polyamide (aramid) fiber is impregnated with a thermosetting epoxy resin to be in a semi-cured state.
m impregnated fiber sheet 11 made of porous prepreg
On both sides of “a”, a 12 μm-thick releasable film 17 made of polyethylene terephthalate or the like is provided by, for example, thermocompression bonding to obtain a preliminary body 30 of an intermediate connector. Next, FIG.
As shown in (b), a through hole 12 having a hole diameter of 200 μm is formed in a predetermined portion of the preliminary body 30 of the intermediate connector by laser processing using a carbon dioxide gas laser or the like, and a conductive material such as a conductive paste or metal powder is formed. Fill with 13. Thereafter, as shown in FIG. 4C, the peelable film 17 is peeled off to obtain the intermediate connector 20. Next, as shown in FIG. 4D, each has a predetermined wiring pattern on both sides.
The intermediate connector 20 is disposed between the two double-sided wiring boards 19 and 19 ′ according to the specific embodiment 1 described above, and these are heated and pressed together from the outside to form a resin in the prepreg state of the intermediate connector 20. Impregnated fiber sheet 11a and conductive material 1
3 is compressed and cured to form an intermediate connector 20 and a double-sided wiring board 19.
And 19 ′ are bonded such that the wiring patterns 14b and 14c are electrically connected by the conductive material 13 of the intermediate connector 20. As a result, as shown in FIG. 5, a four-layer wiring pattern having four layers of outermost wiring patterns 14a and 14d and inner-layer wiring patterns 14b and 14c is provided.
A multilayer wiring board having a layered wiring pattern can be manufactured.

FIG. 6 is an enlarged schematic view of a part of a multilayer wiring board similar to the multilayer wiring board having the four wiring layers shown in FIG. 5, in which the outer wiring boards 19 and 19 'are shown. An adhesive layer 16 is provided on both sides of the heat resistant film 15. In the embodiment shown in FIG. 6, the heat-resistant resin film 15 is not provided on the surface of the intermediate connector 20, but the wiring board 19 and / or 19 ′ and the intermediate connector 20 are not provided.
Between the wiring patterns 14b and 14c,
When sufficient electric insulation is required, FIG.
3C, the heat-resistant films 1 are provided on both sides of the resin-impregnated fiber sheet 11 as shown in FIG.
5 can be used.

That is, the resin-impregnated fiber sheet and the conductive material filled in the through-hole formed in the insulating base material having a heat-resistant film on at least one side, preferably both sides, are used to form a wiring pattern arranged on both sides. An intermediate connector that can be electrically connected can be used. Such an intermediate connector can be formed by the procedure shown in FIGS. Therefore, the unevenness of the surface of the resin-impregnated fiber sheet does not affect the exposed surface of the heat-resistant film, and the surface of the heat-resistant film is substantially flat. As a result, at the time of manufacturing the connection intermediate, a sufficient adhesion state between the heat-resistant film and the peelable film is ensured. Thereby, when filling the conductive material after forming the through-hole, sufficient adhesion between the peelable film and the heat-resistant film is ensured, so that the conductive material is removed from the through-hole on the heat-resistant film. Does not protrude. Therefore, the distance between the through hole and the other through hole in the intermediate connector can be made smaller than before, and when connecting a double-sided wiring board using such a connector, a fine wiring pattern is required. It can be manufactured with high accuracy.

Accordingly, the present invention provides an intermediate connector for connecting wiring boards arranged on both sides, which is constituted by a resin-impregnated fiber sheet and a heat-resistant film arranged on at least one side thereof. To provide an intermediate connector in which a conductive material is disposed in the through hole to connect a wiring board. The thermosetting resin contained in the resin-impregnated fiber sheet of the intermediate connector is in a prepreg state, that is, a semi-cured state.

FIG. 7 is a schematic cross-sectional view (in a direction perpendicular to the main surface of the substrate) of a step of manufacturing the double-sided wiring board according to the second embodiment of the present invention. First, as shown in FIG. 7A, an insulating substrate 1 having a resin-impregnated fiber sheet 11a in a prepreg state and heat-resistant films 15 on both sides thereof.
0 is formed, and the peelable films 17 are arranged on both sides. In the illustrated embodiment, the heat-resistant film 17 has the adhesive layer 16 between the heat-resistant film 17 and the peelable film 17. Next, as shown in FIG. 7B, the through holes 12 are formed.
Thereafter, the conductive material 13 is filled into the through-holes 12, the peelable film 17 is removed as shown in FIG. 7C, and the adhesive layer 16 is exposed. FIG. 7A to FIG.
The step (c) is substantially the same as the steps shown in FIGS. Following such a process, FIG.
As shown in (d), the insulating substrate 11a in a prepreg state
A heat-resistant resin film 1 made of, for example, an aromatic polyimide film (UPILEX manufactured by Ube Industries) on both sides of
5 (having an adhesive layer 16 on the exposed surface) is provided,
On both sides of the insulating substrate 10 formed by filling the conductive paste 13 in the through-holes 12, the releasable wiring pattern supporting plates 22a and the wiring patterns 21a and 21b are separately prepared and formed on one surface. 22b
Are arranged so that the wiring patterns 21a and 21b face the insulating substrate 10, and then heated and pressed together in a thermocompression bonding process, so that the resin-impregnated fiber sheet 11a in the prepreg state and the conductive paste 13 are formed.
Compress and cure. Thereby, the heat resistant film 15
Bonding the wiring patterns 21a and 21b to both sides of the insulating substrate 10 via an adhesive 16 applied to the surface of
Wiring patterns 21a and 21b are electrically connected by conductive paste 13.

After the above-mentioned thermocompression bonding process is completed, the peelable plates 22a and 22b are peeled off to obtain FIG.
As shown in (e), a double-sided wiring board having a wiring pattern on both surfaces with a smoothed surface is obtained. As described above, the wiring patterns 21a and 21b formed in advance on the peelable wiring support plates 22a and 22b are transferred onto the heat-resistant resin film having excellent flatness by the transfer method via the adhesive layer 16, whereby more A fine wiring pattern can be formed with high accuracy.

FIG. 8 shows double-sided wiring boards 24 and 25 (similar to FIG. 7 (e)) according to the second embodiment.
It is a typical sectional view showing a manufacturing process of a multilayer wiring board which has four wiring layers obtained by laminating so that intermediate connector 23 explained below may be inserted. This intermediate connector 23 has substantially the same structure as the insulating substrate shown in FIG. First, as shown in FIG.
For example, adhesives may be applied to both surfaces of a porous prepreg 11a in which a thermosetting epoxy resin is impregnated into a non-woven fabric of aramid fibers, and to both surfaces of a heat-resistant resin film 15 made of a wholly aromatic polyester film (Kuraray, Vectran). 16 (manufactured by ThreeBond, TB-1650, for simplicity,
An adhesive layer between the resin-impregnated fiber sheet 11a and the heat-resistant film 15 (not shown) was used. The intermediate connector 23 is shown in FIGS.
It was produced in the same manner as in the step shown in (c). Different wiring patterns 21a, 21b and 21c, 21d are arranged between the two double-sided wiring boards 24 and 25 respectively formed thereon, and these are heated and pressed together from both sides thereof, whereby the resin of the intermediate connector 23 is formed. By compressing the impregnated fiber sheet 11a and the conductive paste 13 and curing the resin contained therein, a multilayer wiring board having four wiring patterns 21a, 21b, 21c, and 21d as shown in FIG. Can be obtained. In this specific embodiment, the intermediate connector 23 having the heat-resistant film 15 provided on the surface is used, but an intermediate connector without the heat-resistant film 15 may be used. In addition, although a sheet using an aramid fiber / epoxy resin composite as the resin impregnated fiber sheet has been described, instead of the aramid fiber / epoxy resin composite, a glass fiber / epoxy resin composite, a glass fiber / BT resin composite or an aramid fiber / Similar effects can be obtained by using a BT resin composite, and two or more materials can be used.

[0063]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A multilayer wiring board according to the present invention having four wiring layers by implementing the above-described specific embodiments 1 and 2 (FIGS. 5 and 8)
(B)) was manufactured. For comparison, a conventional wiring board shown in FIG. 9F was also manufactured. The electrical characteristics of the manufactured wiring board were measured, and the results are shown in Table 1.

[0064]

[Table 1] Dielectric breakdown voltage Fineness of wiring of dielectric constant Voltage (V) Change rate (%) (Good line rate (%)) 30 μm 50 μm 75 μm Aspect 1 No. 1 1600 3.4 10 37 100 100 No. 2 1500 1.8 12 40 100 No. 3 1800 1.5 10 35 100 Aspect 2 1600 1.4 100 100 100 Conventional example 500 3.6 5 21 100

Incidentally, in the case of No. 1 of the embodiment 1, In No. 1, a wholly aromatic polyamide (Aramica manufactured by Asahi Kasei) was used as a heat-resistant resin film material. As a heat-resistant resin film material of No. 2, an aromatic polyimide (UPIREX manufactured by Ube Industries)
o. As the heat-resistant resin film material of No. 3, a wholly aromatic polyester (Vectran manufactured by Kuraray) was used. In addition, an aramid fiber / epoxy resin composite was used for each of the resin-impregnated fiber sheets.

The measurement of the electrical characteristics was performed at the following three points: (1) Each wiring board had a diameter of 0.5 m covering each through hole.
The distance between the lands is 1.0 mm, and a 0.2 mm wide and 15 mm long wiring is connected to each land, and a DC voltage is applied to the wiring to cause dielectric breakdown between the lands. The voltage at which this occurs was measured. (2) The dielectric constant of the wiring board was measured at room temperature and normal humidity by the perturbation method using a cavity resonator, left in a constant temperature and humidity chamber at 60 ° C. and 95% RH for 250 hours, and taken out again. Was measured, and the change in the dielectric constant was determined. (3) The line width is 30 μm on the outermost layer surface of each wiring board.
The number of defects that occurred when 100 wiring patterns each having a length of 10 mm was formed by examining each of m, 50 μm, and 75 μm, and the yield rate was determined.

As is clear from Table 1, the dielectric breakdown voltage of the wiring boards of the specific embodiments 1 and 2 is about three times larger than that of the conventional wiring board. In addition, the rate of change of the dielectric constant is the same as that of No. 1 of the first embodiment. In the case of No. 1 of the first aspect, while the same degree as that of the wiring board having the conventional structure, 2 or No. 3 and embodiment 2
(Using the same heat-resistant resin film material as No. 3)
The water absorption of the heat-resistant resin film material used was No. 1. Since it is smaller than the wholly aromatic polyamide of No. 1, the rate of change of the dielectric constant is
It is considered to be less than half of the conventional structure.

Thus, it can be seen that the wiring board according to the present invention having a wiring layer on both sides or the wiring board having a multilayer wiring layer has improved electrical characteristics as compared with the conventional structure. The non-defective rate when a fine wiring pattern having a line width of 50 μm or less is formed is also superior to the conventional structure. In particular, the line non-defective rate of the aspect 2 in which the wiring pattern is formed by the transfer method is 30 μm, which is the smallest line width. It was found that a good result of no defect (non-defective rate 100%) could be obtained.

[0069]

As is apparent from the above description, in the present invention, an insulating substrate in which a heat-resistant film having a flat surface is laminated on at least one surface of a resin-impregnated fiber sheet is used and is provided so as to penetrate therethrough. By electrically connecting the fine wiring patterns formed on both surfaces of the insulating substrate by the via holes filled with the conductive material, even when the surface of the resin-impregnated fiber sheet has an uneven shape, it is flat. A flat wiring pattern can be formed on the surface of the heat-resistant film, and a wiring board in which a fine wiring pattern is manufactured with high precision can be obtained.

Further, the conductive material embedded in the through holes provided in the insulating substrate is densified when the insulating substrate is compressed due to the compressibility of the resin-impregnated fiber sheet which is a component of the insulating substrate. (E.g., lowering the resistance and stabilizing the resistance of the conductive material, ensuring the adhesion between the conductive material and the insulating substrate and the wiring pattern) can be easily obtained.

The bonding between the heat-resistant resin film having a flat surface and the metal foil such as a copper foil for a wiring pattern formed thereon is performed by forming an adhesive layer in advance on the heat-resistant film. By doing so, sufficient strength can be secured. In addition, the surface flatness of the heat-resistant film smoothes the surface of the insulating substrate on which the wiring pattern is to be formed, and even if the conductive material embedded in the through-hole is a conductive paste, the conductive paste on the insulating substrate is formed. Since the exudation of the conductive paste can be prevented, it is possible to prevent a short circuit between the wiring patterns due to this. Furthermore, since a heat-resistant resin film having high electric insulation and good tracking resistance can be obtained relatively inexpensively, a highly reliable wiring board can be manufactured at low cost. .

Further, since the wiring board of the present invention has no hollow through-holes and can mount electronic components through the wiring patterns (conductor lands) on the through-holes in which the conductive material is embedded, the wiring board has a fine structure. In addition to the effect of enabling formation of a wiring pattern, it is possible to provide a wiring board having high wiring accommodation and high-density mounting.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a double-sided wiring board according to a specific embodiment 1 of the present invention.

FIG. 2 is an enlarged cross-sectional view of a double-sided wiring board according to a specific embodiment 1 of the present invention.

FIG. 3 is a cross-sectional view illustrating a manufacturing process of the double-sided wiring board according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a manufacturing process of the multilayer wiring board according to Embodiment 1 of the present invention.

FIG. 5 is a cross-sectional view of a multilayer wiring board according to a specific embodiment 1 of the present invention.

FIG. 6 is an enlarged cross-sectional view of a part of the multilayer wiring board according to a specific embodiment 1 of the present invention.

FIG. 7 is a cross-sectional view illustrating a manufacturing process of the double-sided wiring board according to the second embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a manufacturing process of the multilayer wiring board according to Embodiment 2 of the present invention.

FIG. 9 is a cross-sectional view illustrating a manufacturing process of a wiring board having a conventional structure.

[Explanation of symbols]

 Reference Signs List 10 Insulating substrate 11 Resin impregnated fiber sheet 12 Through hole 13 Conductive material (conductive paste) 14a, 14b Wiring pattern 15 Heat resistant resin film 16 Release film 18 Copper foil 19 Double-sided wiring board 20 Intermediate connector 21a, 21b, 21c, 21d Wiring pattern 23 Intermediate connector 24, 25 Double-sided wiring board 30 Preliminary intermediate connector

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Masao Hasegawa 1006 Kazuma, Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-8-78803 (JP, A) JP-A-4 -189131 (JP, A) JP-A-8-316598 (JP, A) Patent 2587596 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05K 1/11 H05K 3/40 H05K 3/46

Claims (17)

(57) [Claims] An insulating substrate having a substantially flat surface by providing a heat-resistant film on at least one side of the resin-impregnated fiber sheet; a wiring pattern provided on both sides of the insulating substrate; A predetermined wiring formed on both sides of the insulating substrate by a conductive material having an adhesive layer between the conductive film and the wiring pattern and filling a through hole provided through the insulating substrate; A double-sided wiring board, wherein the patterns are electrically connected. 2. The double-sided wiring board according to claim 1, wherein the double-sided wiring board according to claim 1 has a through hole at a predetermined position, and is provided on both sides of an intermediate connector composed of a resin-impregnated fiber sheet filled with a conductive material in the through hole. When the wiring board according to claim 1 has a heat-resistant film on only one side, the heat-resistant film is located on a side distant from the intermediate connector, A multilayer wiring board, wherein wiring patterns of both adjacent double-sided wiring boards are electrically connected by a conductive material filled in a through hole of an intermediate connector. 3. An intermediate connector comprising a resin impregnated fiber sheet having a through hole at a predetermined position and a conductive material filled in the through hole is disposed on both sides of the double-sided wiring board according to claim 1. Wherein each intermediate connector has a predetermined wiring pattern on a surface remote from the double-sided wiring board, and a predetermined wiring pattern on a surface of each intermediate connector remote from the double-sided wiring board is: A multilayer wiring board electrically connected to a wiring pattern of a double-sided connection board adjacent to the intermediate connector by a conductive material in a through hole of the intermediate connector. 4. At least one double-sided wiring board in which predetermined wiring patterns are arranged on both sides of the resin-impregnated fiber sheet, and these wirings are electrically connected by a conductive material filled in the through-holes. A multilayer wiring board in which at least one intermediate connector composed of a resin-impregnated fiber sheet having a conductive material disposed in a hole is alternately arranged, and the intermediate connector constitutes the outermost part of the multilayer wiring board. The intermediate connector has a predetermined wiring pattern on the outermost surface, and the wiring patterns located on both sides of each intermediate connector are connected by a conductive material in a through hole of the intermediate connector, At least one double-sided wiring board has a heat-resistant film between the wiring pattern on at least one side and the resin-impregnated fiber sheet, and the through hole has a resin-impregnated fiber sheet and a heat-resistant film. Penetrates, heat-resistant film has an adhesive layer on the side at least the wiring pattern is formed, a multilayer wiring board is heat resistant film and the wiring pattern through which is characterized by being bonded. 5. The number of double-sided wiring boards is one more than the number of intermediate connectors.
As a result, the double-sided wiring board constitutes both outermost parts of the multilayer wiring board, and at least one of the double-sided wiring boards constituting the outermost part of the wiring board has at least one of the outermost wiring pattern and the resin-impregnated fiber sheet. The multilayer wiring board according to claim 4, further comprising a heat-resistant film therebetween. 6. The number of double-sided wiring boards is one more than the number of intermediate connectors.
As a result, the intermediate connector constitutes both outermost portions of the multilayer wiring board, and at least one of the double-sided wiring boards adjacent to the intermediate connector constituting the outermost portion of the multilayer wiring board has at least one wiring pattern. The multilayer wiring board according to claim 4, further comprising a heat-resistant film between the resin and the resin-impregnated fiber sheet. 7. The intermediate connector or at least one intermediate connector has a heat-resistant film on at least one side of the resin-impregnated fiber sheet, and the through hole is formed through the resin-impregnated fiber sheet and the heat-resistant film. Claim 2
7. The multilayer wiring board according to any one of items 1 to 6. 8. An insulating substrate having a heat-resistant film on at least one side of the resin-impregnated fiber sheet, a wiring pattern provided on both sides of the insulating substrate, and a through hole provided through the insulating substrate. A method for manufacturing a double-sided wiring board, wherein predetermined wiring patterns formed on both sides of the insulating substrate are electrically connected to each other by a conductive material filled in the resin, wherein (1) a resin having an uneven surface A step of providing a heat-resistant film on at least one side of the impregnated fiber sheet to substantially flatten the surface to obtain a composite insulating substrate; (2) disposing release films on both sides of the composite insulating substrate (3) forming a predetermined through-hole penetrating the composite insulating substrate and the releasable film; (4) filling a conductive material into the through-hole. (5) removing the releasable film from the insulating substrate in which the through holes are filled with a conductive material; (6) disposing wiring metal foils on both sides of the insulating substrate, and applying heat and pressure. Curing the resin impregnated in the resin-impregnated fiber sheet to integrate the insulating substrate and the wiring metal foil, and then forming the wiring metal foil into a predetermined wiring pattern. 9. In place of the step (6), (7) a wiring pattern support plate having a predetermined wiring pattern formed in advance on a peelable support plate is positioned on both sides of the insulating substrate while being aligned with the through holes. Placed, heated and pressed together with the insulating substrate sandwiched between these plates to cure the resin impregnated in the resin-impregnated fiber sheet, and then remove only the peelable support plate to insulate the wiring pattern. 9. The method of claim 8, comprising transferring to a substrate. 10. A step of disposing releasable films on both sides of a resin-impregnated fiber sheet having an uneven surface to form a preliminary body of an intermediate connector, and forming a predetermined through hole in the preliminary body of the intermediate connector. A step of filling the conductive material therein; a step of removing the peelable film from the preliminary body of the intermediate connector filled with the conductive material in the through-hole to obtain an intermediate connector; A step of disposing a double-sided wiring board obtained by the method according to claim 8 or 9 between intermediate connectors, a step of disposing a metal foil on a side of the intermediate connector remote from the double-sided wiring board, The metal By heating and pressing together the foil, the intermediate connector, the double-sided wiring board, the intermediate connector and the structure arranged in order with the metal foil, the impregnated resin of the resin impregnated fiber sheet of the intermediate connector is cured and Work to bond together ,
And thereafter, a metal foil constituting an outermost layer of the integrally bonded structure is formed in a predetermined wiring pattern, and the wiring pattern is electrically connected to the conductive material of the through hole of the intermediate connector and the double-sided wiring board. A method for manufacturing a multilayer wiring board including a step of connecting the wiring boards. 11. A resin-impregnated fiber sheet for forming at least one intermediate connector has a heat-resistant film on at least one side, and the through-hole of the intermediate connector is formed of a resin-impregnated fiber sheet and a heat-resistant film. The structure according to claim 10, wherein the structure is formed so as to penetrate the film, and when the intermediate connector has a heat-resistant film on only one side, the heat-resistant film is located on a side away from the double-sided wiring board. Method. 12. At least one double-sided wiring board obtained by the method according to claim 8 or 9.
Or by alternately arranging at least one intermediate connector according to 11 and heating and pressing them,
A method for producing a multilayer wiring board, comprising curing an impregnated resin of a resin-impregnated fiber sheet of an intermediate connector and bonding them together, wherein the intermediate connector constitutes the outermost part of the multilayer wiring board. ,
On the side of the intermediate connector that defines the outermost surface of the multilayer wiring board, metal foil is pre-arranged before pressing and heating, a double-sided wiring board,
A method in which the intermediate connector and the metal foil are heated and pressed together. 13. In a single step, instead of bonding the double-sided wiring board, the intermediate connector and the metal foil together, at least one double-sided wiring board and at least one
13. The method according to claim 12, wherein the two intermediate connectors have already been heated and pressed together in a separate step and bonded together. 14. The heat-resistant film has an adhesive layer on at least a side on which the wiring pattern is disposed.
14. The method according to any of claims 13 to 13. 15. A heat-resistant film comprising at least three wiring pattern layers and a resin-impregnated fiber sheet interposed therebetween, wherein a heat-resistant film is provided between at least one wiring pattern and the resin-impregnated fiber sheet. The surface is substantially flat, and an adhesive layer is provided between the heat-resistant film and the wiring pattern, and each of the wiring patterns is filled in a through hole formed in each of the resin-impregnated fiber sheets. A multilayer wiring board electrically connected by a conductive material. 16. An intermediate connector comprising: a resin-impregnated fiber sheet; a through hole provided at a predetermined position of the resin-impregnated fiber sheet; and a conductive material disposed in the through hole. The body is for connecting wiring boards arranged on both sides, and a heat-resistant film is provided on at least one side of the resin-impregnated fiber sheet to substantially flatten the surface, and the surface is formed on the heat-resistant film. Is an intermediate connector having an adhesive layer. 17. A resin-impregnated fiber sheet and a heat-resistant film on at least one side of the resin-impregnated fiber sheet, a through hole at a predetermined position, and a conductive material disposed in the through hole. A method of manufacturing an intermediate connector for connecting wiring boards disposed on both sides, wherein a heat-resistant film is disposed on at least one side of a resin-impregnated fiber sheet having an uneven surface to substantially reduce the surface. Step of forming a preliminary body of the intermediate connector by disposing releasable films on both sides of the resin-impregnated fiber sheet having the heat-resistant film, forming a predetermined through-hole in the preliminary body of the intermediate connector. Filling a conductive material therein; and removing the peelable film from a preliminary intermediate connector body filled with the conductive material.