JP2003338670A - Fluororesin printed wiring board and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluororesin printed wiring board with high relative permittivity, few partial variation of relative permittivity and dielectric loss tangent, a smooth surface with no minute irregularity, and with superior dimensional stability in X, Y and Z-directions, to provide a method for manufacturing it, and to provide a fluororesin printed wiring board with the superior adhesion force of metal foil and the small percentage of absorption in addition to the above properties, and a method for manufacturing it. <P>SOLUTION: A primary sheet, formed by wet sheet forming aqueous slurry containing at least inorganic particulates and heat-resistant insulating fiber with a fluororesin fiber as a main component, is heat-treated at a fusing point or above of the fluororesin, to form a sheet-like material. At least two sheets of the sheet-like materials are laminated by making them cross with each other at 90 degrees with a longitudinal direction or a lateral direction as a reference, to form an insulating layer. This fluororesin printed wiring board comprises the insulating layer and a conductive layer of a circuit pattern provided at least on one surface of the insulating layer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The fluororesin printed wiring board of the present invention relates to a printed wiring board having a high relative dielectric constant and a method for manufacturing the same. In particular, the present invention relates to a printed wiring board suitable for wiring of antenna parts used in a high frequency band in information communication equipment and the like, high-density wiring of semiconductors such as IC packages and precision wiring of small equipment, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In a conventional printed wiring board-related field, a printed wiring board substrate having excellent dielectric properties and a method for manufacturing the same are generally as follows, for example, as disclosed in JP-A-7-323501. Target. That is, using a glass cloth as a substrate, a sheet prepared by repeating impregnation of a polytetrafluoroethylene (hereinafter referred to as PTFE) resin dispersion and firing treatment on the substrate several times is overlaid with a copper foil, and hot pressed. And then integrated into a substrate. When a plurality of the above-mentioned sheets are laminated to form a substrate, a tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin layer or a tetrafluoroethylene / hexafluoropropylene copolymer resin layer may be interposed between the sheets as a film. Alternatively, the resin layer may be formed by coating or the like, and the above resin layer may be formed between the outermost layer and the copper foil, and the stacked sheets and the copper foil may be heat-pressed to be integrally formed. is there. By such a method, the relative dielectric constant is 2-3.
5. A printed circuit board having a dielectric loss tangent of about 0.0010 is manufactured.

In the fluororesin printed wiring board using the conventional glass cloth as described above, the longitudinal direction (longitudinal direction), the width direction (horizontal direction) and the thickness direction of the substrate are respectively X-direction, Y-direction and In the Z direction, the dimensional change rates in the X and Y directions are small due to the presence of the glass cloth, but the Z direction is large. Further, due to the difference in tension remaining between the warp yarn and the weft yarn in the glass cloth, a difference in dimensional change in the X direction and the Y direction occurs during the formation of the conductive layer of the circuit pattern, heat treatment, etc. The value of the dimensional change may increase due to the displacement or movement of the glass fibers in the stitch portion of the cloth. Also, there are fine irregularities due to the stitches on the surface of the printed wiring board. Due to these, the accuracy of pattern formation and through hole formation decreases,
Since the conductive part expands and contracts to cause damage, there is a problem that the reliability of the performance is insufficient particularly in a small wiring board.

Further, in the conventional fluororesin printed wiring board using the glass cloth, since the glass cloth has a knitted structure, the material composition is non-uniform in parts, so that the relative permittivity and the dielectric loss tangent are small. Is uneven in parts. That is, when viewed from the circuit on the wiring board, the relative permittivity and the dielectric loss tangent vary depending on whether the portion directly below is the opening portion, the glass fiber portion, or the intersection portion of the warp and the weft. For this reason, there is a problem in that the characteristics of the high frequency filter and the like provided on the wiring board are not stable. Problems due to non-uniformity due to the stitch structure,
This also occurs in the Z direction of the printed wiring board. For example, not only the plated layer of through holes is not formed uniformly,
In some cases, the plating layer may be missing in the portion where the fluororesin is large. In addition, there are also problems that fine voids remain at the interface between the glass cloth and PTFE, the etching liquid easily enters the voids, the water absorption is large, or the moisture in the air is easily taken in, and the relative dielectric constant and dielectric loss tangent become large. is there.

Further, in the conventional high-frequency printed wiring board, since the wavelength of the signal in the substrate is short, a high relative permittivity of the dielectric material is required especially for high-density wiring and miniaturization of the substrate. There is. Needless to say, a low dielectric loss tangent is required at the same time to obtain a printed wiring board compatible with high frequencies, and a printed wiring board having a high relative dielectric constant and a low dielectric loss tangent is required. Specifically, it is a field that uses a high frequency band such as mobile communication, wireless communication, and high-speed communication.

Therefore, as a method of manufacturing a printed wiring board having a high relative dielectric constant, there is, for example, the following method. In order to increase the relative permittivity, inorganic fine particles having a high relative permittivity are dispersed in the PTFE dispersion and impregnated in the glass cloth. In this case, it is difficult to uniformly impregnate the glass cloth due to the difference in specific gravity between the PTFE particles and the inorganic particles, the glass cloth stitches, and the like, and since the inorganic particles are unevenly present on the sheet surface, a fine wiring pattern cannot be formed. The problem arises. In addition, in the thickness direction, since the inorganic fine particles are exposed to the outermost layer, the adhesion of the copper foil is reduced and the water absorption is increased.

Further, Japanese Patent Laid-Open No. 3-218690 discloses a base sheet for a printed wiring board obtained by heat-sintering a sheet prepared by wet-texturing polytetrafluoroethylene fiber and inorganic fiber. ing. Since the sheet obtained by wet papermaking has a uniform fiber distribution, when it is used as a printed wiring board, there is no problem of partial variation in dielectric properties as in the case of the glass cloth type, and the dimensional change rate in the Z direction is small. However, it is larger than the glass cloth type in the X and Y directions, and
In order to reduce the difference in the dimensional change rate between the Y-direction and the Y-direction, even if paper-making conditions such that the appearance is random in terms of fiber orientation are selected, the paper-making direction (longitudinal direction) or width direction ( It is not possible to suppress the tendency of the fibers to be oriented in the (horizontal direction) unevenly, and as a result, in the case of a printed wiring board, the dimensional change rate is small in the direction in which the fibers are oriented, and conversely increases in the direction perpendicular to the direction. Therefore, there is a problem that the printed wiring board is deformed. Furthermore, in order to adjust the relative permittivity of the printed wiring board, when the inorganic particles are contained in the fluororesin fiber primary sheet, the yield in the primary sheet is low, and the printed wiring board having a desired relative permittivity is obtained. There are problems that it is difficult to obtain, that the inorganic fine particles existing on the surface of the primary sheet are easily detached from the surface, that the adhesion of the metal foil is poor and that the water absorption rate is large.

[0008]

Therefore, the problem to be solved by the present invention is to have a high relative permittivity, a small partial variation in the relative permittivity and the dielectric loss tangent, and a small amount on the surface of a printed wiring board. It is an object to provide a fluororesin printed wiring board which is smooth without unevenness and has excellent dimensional stability in the X, Y and Z directions, and a method for producing the same. Further, in addition to the above-mentioned characteristics, it is to provide a fluororesin printed wiring board having excellent adhesion to a metal foil and a small water absorption, and a method for manufacturing the same.

[0009]

Means for Solving the Problems The present inventors have found the following means as a result of various studies for solving the above problems. The present invention contains a fluororesin fiber as a main component, a primary sheet obtained by wet papermaking of an aqueous slurry containing at least inorganic fine particles and a heat-resistant insulating fiber, is heat-treated at a temperature not lower than the melting point of the fluororesin to give a paper-like material, At least 2 of the paper-like material
A fluororesin printed wiring board comprising: an insulating layer formed by stacking a plurality of the sheets so as to be orthogonal to each other at 90 ° with respect to the vertical direction or the horizontal direction, and a conductive layer having a circuit pattern provided on at least one surface of the insulating layer. There is (claim 1). Further, after the fluororesin is adhered to at least one surface portion of the primary sheet obtained by wet papermaking of an aqueous slurry containing fluororesin fibers as a main component and containing at least inorganic fine particles and heat resistant insulating fibers, An insulating layer obtained by heat-treating at a melting point or higher to form a paper-like material, and at least two paper-like materials laminated at right angles to each other at 90 ° with respect to the longitudinal direction or the transverse direction, and a circuit provided on at least one surface of the insulating layer. A fluororesin printed wiring board having a patterned conductive layer (claim 2). Further, the relative dielectric constant is 5 to 20.
The fluororesin printed wiring board according to claim 1 or 2, wherein the fluororesin fiber is a polytetrafluoroethylene fiber. 5. The fluororesin printed wiring board according to claim 3 (claim 4), wherein the inorganic fine particles are titanium-based ceramic fine particles, and the fluororesin print according to any one of claims 1 to 4. It is a wiring board (Claim 5), and the heat-resistant insulating fiber is glass fiber. The fluororesin printed wiring board according to any one of claims 1 to 5, (Claim 6), The fluororesin printed circuit board according to any one of claims 1 to 5, wherein the heat-resistant insulating fibers are glass fibers and polyparaphenylenebenzobisoxazole fibers. A wire plate (claim 7), wherein the content of the inorganic fine particles is 10 to 70% by weight based on the total amount of the fluororesin fiber, the inorganic fine particles and the heat resistant insulating fiber. The fluororesin printed wiring board according to any one of claims 1 to 7 (claim 8), wherein the blending amount of the heat resistant insulating fiber is 3 to 40 relative to the total of the fluororesin fiber, the inorganic fine particles and the heat resistant insulating fiber. The fluororesin printed wiring board according to any one of claims 1 to 8, wherein the fluororesin printed wiring board has a weight% (claim 9).

Further, the present invention comprises a step of wet-making an aqueous slurry containing fluororesin fibers as a main component and containing at least inorganic fine particles and heat-resistant insulating fibers to form a primary sheet, at a temperature not lower than the melting point of the fluororesin. A step of heat-treating to fuse the fluororesin fibers to each other to form a paper-like material, and at least two paper-like materials laminated at 90 ° orthogonal to the longitudinal direction or the transverse direction to form an insulating layer, and A step of arranging a conductive metal foil on at least one surface of the insulating layer to form a conductive layer, a step of vacuum heating and pressing at a temperature equal to or higher than the melting point of the fluororesin to prepare a fluororesin laminate for a printed wiring board, and a desired conductive layer A method for producing a fluororesin printed wiring board, which comprises the step of forming a circuit pattern according to (10).
Further, a step of wet-paper-making an aqueous slurry containing a fluororesin fiber as a main component and containing at least inorganic fine particles and a heat-resistant insulating fiber to form a primary sheet, a step of adhering a fluororesin to at least one surface portion of the primary sheet A step of heat-treating the fluororesin at a temperature equal to or higher than the melting point of the fluororesin to fuse the fluororesin fibers with each other and the fluororesin fiber and the fluororesin on the surface to form a paper-like material, and at least two sheets of the paper-like material A step of forming an insulating layer by stacking them orthogonally to each other at 90 ° with respect to the vertical direction or the horizontal direction, and disposing a conductive metal foil on at least one surface of the insulating layer to form a conductive layer, and vacuuming at a temperature equal to or higher than the melting point of the fluororesin A method for producing a fluororesin printed wiring board comprising a step of heating and pressing to produce a fluororesin laminated board for a printed wiring board, and a step of forming a conductive layer into a desired circuit pattern. Ri (Claim 11), the fluorine resin to be adhered to the surface portion of the primary sheet, according to claim 1 which comprises using a fluorine resin dispersion
The method for producing a fluororesin printed wiring board according to item 1 (claim 12).

Each material used in the present invention will be described below. The fluororesin fibers used in the present invention include, in addition to the PTFE fibers, tetrafluoroethylene / hexafluoropropylene copolymer (FEP), tetrafluoroethylene / perfluoroalkylvinylether copolymer (PFA), polychlorotrifluoro. Ethylene (PCTFE), polyvinylidene fluoride (PVD)
F), polyvinyl fluoride, ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene / hexafluoropropylene / perfluoroalkyl vinyl ether copolymer (FEPPFA) Fibers. Among them, PTFE fiber is preferable for obtaining the fluororesin printed wiring board of the present invention because it has a low relative dielectric constant and a low dielectric loss tangent and is excellent in heat resistance and chemical resistance. The fluororesin fibers used in the present invention may be used as a mixture of two or more thereof.

The diameter and the fiber length of the fluororesin fiber used in the present invention are not particularly limited as long as they can be made by the wet papermaking method of the present invention, and the shape is simple fibrous or granular ( Spherical shape, amorphous shape, etc., fibrid shape, pulp shape, and various other shapes are not particularly limited, but for example, those having a diameter of 1 μm to 50 μm and a length of 0.1 mm to 10 mm are used. . If the diameter and the length are less than the lower limits of the above ranges, the dehydration property during papermaking is poor and the productivity is lowered, and if the diameter and the length exceed the upper limits, it becomes difficult to produce a thin sheet.

Further, as the fluororesin fiber, the properties required for the fluororesin fiber paper-like material, specifically, the sheet strength, the dimensional stability, the content of the inorganic fine particles and the heat-resistant insulating fiber, etc. in the present invention, It is possible to select and use a fibrillated form of the fluororesin fiber and a non-fibrillated form thereof, and in some cases, they can be mixed and used.

The degree of fibrillation is determined in relation to the average pore diameter, maximum pore diameter, sheet strength, etc. of the fluororesin fiber paper material. For example, when stronger sheet strength is required, it is preferable to use fibers having an advanced degree of fibrillation. In addition, the adhesion between the fluororesin fiber and other materials is also improved thereby. The degree of fibrillation can be represented by the freeness described in JIS P8121: 1995. As a means for fibrillation, a general beating machine such as a ball mill, beater, lampen mill, PFI mill, SDR (single disc refiner), DDR (double desk refiner), and other refiners can be used.

As an example of the PTFE fiber which can be used in the present invention, PTFE fine particles are dispersed in a hydrophilic binder matrix such as viscose, carboxymethyl cellulose, polyvinyl alcohol, etc., and spun into the coagulation bath through the pores. The obtained stretched or unstretched fiber may be mentioned. In this case, the obtained stretched or unstretched PTFE fiber is
It is cut into a length of 15 mm and dispersed in water using a dispersant such as polyacrylamide together with inorganic fine particles, heat resistant insulating fibers and other raw materials to prepare a papermaking raw material. The papermaking raw material is paper-made by a cylinder paper machine, a fourdrinier paper machine, a short-net paper machine, a tilt paper machine or the like to prepare a primary sheet of PTFE fiber. In forming a primary sheet of PTFE fiber, the matrix substance mixed with the PTFE fiber exhibits a binding function between fibers during papermaking.

Further, in the present invention, inorganic fine particles are used for the purpose of increasing the relative dielectric constant of the printed wiring board and improving the dimensional stability. By selecting and mixing the type of inorganic fine particles, the relative dielectric constant is increased while the dielectric loss tangent of the printed wiring board is low, and the thermal expansion coefficient and dimensional change of the printed wiring board in the X, Y, and Z directions can be suppressed. Mechanical strength such as flexural strength and flexural modulus of the printed wiring board can also be improved.

In the present invention, it is preferable that the inorganic fine particles have a high relative dielectric constant. Specifically, titanium dioxide ceramics, barium titanate ceramics, lead titanate ceramics, strontium titanate ceramics,
Examples thereof include calcium titanate-based ceramics, bismuth titanate-based ceramics, magnesium titanate-based ceramics and other titanium-based ceramics, lead zirconate-based ceramics and the like, and titanium dioxide, silver oxide, zinc oxide and the like. The titanium dioxide ceramic is a system that contains only titanium dioxide in terms of composition, or a system that contains a small amount of other additives in titanium dioxide, and the crystal structure of titanium dioxide as the main component is retained. It is a thing. The same applies to ceramics of other systems. Among the above inorganic fine particles,
Titanium-based ceramic fine particles are preferable in terms of relative dielectric constant.
Further, a plurality of kinds of the above-mentioned inorganic fine particles can be mixed and used.

The shape and size of the inorganic fine particles are not particularly limited as long as the primary sheet can be formed by the wet papermaking method of the present invention, and the shape can be spherical, granular, hollow, fibrous,
There are various shapes such as irregular shapes, amorphous shapes and the like, but for example, a spherical shape is common, and the particle size is preferably about 50 μm or less, more preferably 0.1 to 50 μm. 20 μm, more preferably 0.1-15
It is in the μm range. When the particle size of the inorganic fine particles is large, it is difficult to uniformly disperse the slurry in the papermaking slurry, and it becomes easy to make an uneven distribution in the fluororesin fiber primary sheet. On the other hand, if it is too small, the handleability is poor, and the yield in the primary sheet during wet papermaking is poor, making it difficult to control the content in the primary sheet.

The blending amount of the inorganic fine particles is determined by the balance between the relative dielectric constant of the printed wiring board and the dimensional stability. In consideration of the above balance, the content of the inorganic fine particles is preferably 10 to 70% by weight based on the total amount of the fluororesin fiber, the inorganic fine particles and the heat resistant insulating fiber. 1
If it is less than 0% by weight, the effect of increasing the relative dielectric constant of the printed wiring board tends to be insufficient, and if it exceeds 70% by weight, it becomes difficult to uniformly disperse it in the papermaking slurry. There are problems such as non-uniformity, easy detachment from the primary sheet, and decrease in strength of the primary sheet, resulting in poor workability. Further, when the printed wiring board is used, the mechanical strength is lowered, which is not preferable. Since the appropriate range of the relative permittivity of the printed wiring board is subdivided for each specific use, the compounding amount of the inorganic fine particles is set to a narrower range according to the specific use.

In the present invention, for the purpose of further improving the dimensional stability of the printed wiring board, heat-resistant insulating fibers are used in the papermaking raw material. By incorporating heat-resistant insulating fibers, the thermal expansion coefficient and dimensional change rate of the printed wiring board in the X, Y and thickness directions (Z direction) can be significantly suppressed, and the bending strength and bending elasticity of the printed wiring board can be reduced. Mechanical strength such as rate can also be improved. Further, the relative permittivity of the printed wiring board can be adjusted by the kind and blending amount of the heat resistant insulating fiber.

The heat-resistant insulating fibers include inorganic fibers and organic fibers, but in order to suppress the coefficient of thermal expansion and the dimensional change rate of the printed wiring board, it is preferable that the fibers themselves have a large elastic modulus and be rigid. As the inorganic fibers, there are glass fibers, silica fibers, alumina fibers, aluminum silicate fibers and the like, but glass fibers that can sufficiently achieve the purpose and are inexpensive are preferably used. As the organic fibers, high heat resistance, high strength and high elastic modulus fibers called so-called super fibers can be used. For example, polyparaphenylene benzobisoxazole fibers (hereinafter referred to as PBO fibers),
Aromatic polyester fibers, polyphenylene sulfide fibers, wholly aromatic polyamide fibers and the like can be used, but PBO fibers having the highest elastic modulus are preferable. Further, a plurality of types of the above heat resistant insulating fibers may be mixed and used.

The shape of the heat-resistant insulating fiber is not particularly limited, but the diameter is preferably 50 μm or less,
The length is preferably 0.1 to 20 mm. Diameter is 50 μm
If it exceeds, it becomes difficult to produce a thin sheet. If the length is less than 0.1 mm, it is difficult to obtain the effect of dimensional stability.
If it exceeds 0 mm, it becomes difficult to disperse uniformly.

The blending amount of the heat resistant insulating fiber is determined by the characteristics required for the printed wiring board, that is, the dielectric characteristics and the dimensional stability. Generally, when the blending amount of the heat resistant insulating fiber is small, the dielectric property is prioritized over the dimensional stability, and conversely, when the dimensional stability is desired, the blending amount of the heat resistant insulating fiber may be increased. Generally, when the blending amount of the heat resistant insulating fiber is large, the dielectric property, especially the value of the dielectric loss tangent becomes large, and it becomes difficult to apply as a high frequency compatible printed wiring board. Therefore, the blending amount of the heat resistant insulating fiber is determined by the balance between the dielectric properties and the dimensional stability. Considering the above balance, the blending amount of the heat resistant insulating fiber is preferably 3 to 40% by weight based on the total amount of the fluororesin fiber, the inorganic fine particles and the heat resistant insulating fiber. If the content of the heat-resistant insulating fiber is less than 3% by weight, it is difficult to obtain the effect of dimensional stabilization, and if it is more than 40% by weight, the strength of the fluororesin fiber paper-like material decreases and it becomes difficult to handle in the subsequent steps. At the same time, the dielectric loss tangent of the printed wiring board tends to become too large.

When the heat-resistant insulating fiber is an organic fiber, it can be fibrillated and used, whereby the entanglement between the fibers is strengthened, and the entanglement in the three-dimensional direction is strengthened. Dimensional stability including thermal expansion in the direction is greatly improved. The degree of fibrillation is determined in relation to the sheet strength of the fluororesin fiber paper-like material and the content of inorganic fine particles. For example, when stronger sheet strength is required, or when the amount of the inorganic fine particles added is large, it is desirable to use fibers having a higher degree of fibrillation. This also improves the yield of the inorganic fine particles.

As the method for producing the primary sheet of the fluororesin fiber of the present invention, the wet papermaking method used in ordinary papermaking is used. That is, a specified amount of fluororesin fibers, inorganic fine particles, heat-resistant insulating fibers, etc. are stirred and mixed in water, and preferably a slurry whose concentration is adjusted so that the solid content concentration is 0.5% or less It is applied to wet paper machines such as long-mesh type, short-mesh type and inclined type, dehydrated in a continuous wire mesh dewatering part, and then dried with a multi-cylinder dryer or Yankee dryer to obtain a primary sheet. . A fourdrinier type in which the fiber orientation is likely to be random in terms of reducing the difference between the dimensional change rates of the printed wiring board in the X and Y directions,
The short-net type and the inclined type are preferable, and the inclined type is more preferable. Especially in the case of the tilt type, it is also possible to orient the heat-resistant insulating fibers in the thickness direction, that is, to make the fibers stand in the thickness direction in the paper-like material, which is effective for the dimensional stability in the Z direction of the printed wiring board. Exert.

The inorganic fine particles are preferably agglomerated in advance as described below in order to prevent the fine particles from being washed away during wet papermaking, to secure the yield and to contain a predetermined amount in the primary sheet. That is, a prescribed amount of inorganic fine particles is weighed and stirred in water together with an aggregating agent to aggregate the inorganic fine particles. The agglomerated particles and a prescribed amount of fluororesin fiber and heat resistant insulating fiber are stirred and mixed in water to obtain a papermaking slurry.

As the coagulant used in the present invention, a general coagulant used in ordinary papermaking, coagulation treatment of industrial wastewater and domestic wastewater, etc. can be applied. Specifically, sulfuric acid band, polyaluminum chloride, ferric chloride, polysulfuric acid second
Iron, ferrous sulfate, dimethyldiallylammonium chloride, condensate of alkylamine / epichlorohydrin, condensate of ethyleneimine / alkylenedichloride / polyalkylenepolyamine, dicyandiamide / formalin condensate, polyacrylamide system, sodium polyacrylate, poly (meta ) Acrylic acid aminoalkyl ester type, Mannich modified product of polyacrylamide, chitosan, other inorganic coagulants, organic coagulants, polymer coagulants, depending on the type of inorganic fine particles to be contained in the fluororesin fiber primary sheet, A flocculant suitable for it can be selected and used. Further, in order to increase the aggregation effect of the inorganic fine particles and improve the yield, in particular, a combined use of an inorganic coagulant and an organic coagulant or a polymer coagulant, and further, a synthetic viscous agent such as polyacrylamide-based or polyethylene oxide-based Addition is preferred. Further, the addition amount of the aggregating agent is determined according to the aggregating state of the fine particles.

Further, the fluororesin fiber primary sheet of the present invention may be blended with various paper strength enhancers, dispersants, defoamers, synthetic sticky agents, pigments and other additives used in ordinary papermaking. .

The fluororesin fiber primary sheet of the present invention thus obtained has a distribution of various raw materials in the X-direction, Y-direction and Z-direction as compared with a sheet using glass cloth as a base material and a dry process nonwoven fabric. It has the excellent characteristics that it is uniform and the texture is uniform, and as a result, it has the advantage that the dielectric characteristics of the printed wiring board also have a small partial variation.

In the fluororesin printed wiring board of the present invention, when the metal foil is required to have a particularly high adhesion, the fluororesin is adhered to at least one surface portion of the primary sheet. As an additional effect, it also has an effect of preventing the inorganic fine particles from being desorbed from the surface of the primary sheet and reducing the water absorption rate of the printed wiring board. The process may be performed before or after drying the primary sheet dehydrated in the dehydration part. Further, it is not always necessary to cover the entire surface of the primary sheet, and spots, nets, lattices, etc. that are uniformly present may be used. As a method of attaching the fluororesin to the surface portion of the primary sheet, coating by spraying a fluororesin dispersion, coating and impregnation by a coating machine,
There are printing, laminating with a fluororesin film, and other methods. For example, a fluororesin dispersion is sprayed onto a wet paper, and then dried with a dryer such as a multi-cylinder dryer, a Yankee dryer, an air dryer or an infrared dryer to obtain a primary sheet to which the fluororesin is attached.
The method of attaching the fluororesin to the surface portion is not limited to the above method, and is not limited to the use of the fluororesin dispersion or the fluororesin film.

Further, the amount of the fluororesin adhered should be close to that of the copper foil.
Ensures adhesion and detaches inorganic fine particles from the surface of the primary sheet
It should be possible to prevent it, but one side is 1g / m^Two~ 100g
/ M ^TwoIs preferred, 5 g / m^Two~ 50g / m^TwoIs better
Good 1 g / m^TwoBelow, the effect of improving adhesion with copper foil
Is difficult to obtain, and inorganic fine particles are not
We cannot control desorption. 100 g / m^TwoOver
And the ratio of fluororesin with a low dielectric constant is very large.
This makes it difficult to set the relative permittivity of the printed wiring board to the desired value.
It

Next, the obtained fluororesin fiber primary sheet is fired at a temperature not lower than the melting point of the fluororesin in an electric furnace or the like to obtain a fluororesin fiber paper-like material. Between fluororesin fibers by firing, between fluororesin fibers and inorganic fine particles, between fluororesin fibers and heat-resistant insulating fibers, and when fluororesin is attached to the surface portion of the primary sheet, between fluororesin fibers and fluororesins The organic substances are pyrolyzed and removed together with the fusion. When the above PTFE fiber is used,
The matrix resin in the PTFE fiber is thermally decomposed and removed in this step.

The basis weight of the fluororesin fiber paper material in the present invention is 10 to 1500 g / m ² , and an appropriate basis weight is determined according to the intended use.

The porous fluororesin fiber paper material thus obtained is attached to a metal foil in the following manner.

The above-mentioned paper-like material is cut into a certain size, and for example, two or more paper-like materials cut from the same direction are overlapped at 90 ° with respect to the longitudinal direction or the transverse direction.
That is, in the laminated plate, the flow direction of the papermaking (longitudinal direction) and the width direction of the papermaking (horizontal direction) are alternately overlapped with each other at 90 °. In the present invention, the number of sheets to be superposed is not particularly limited, and is determined depending on the intended thickness of the laminated plate and the thickness or basis weight of the paper-like material to be used. However,
In order to minimize the dimensional change rates of the wiring boards in the X direction and the Y direction and the difference between them, it is preferable that the number of stacked sheets is an even number. The thus-obtained material is used as an insulating layer, and metal foil as a conductor layer is laid on both upper and lower surfaces or one surface of the insulating layer, and heat-pressed at a temperature not lower than the melting point of the fluororesin. The back surface of the metal foil, that is, the surface that comes into contact with the insulating layer, is provided with a large number of minute projections, which are present between the insulating layer, that is, between the fibers of the paper-like material whose main component is fluororesin fiber. It is hot-pressed in a state of entering the void.
As a result, the metal foil closely adheres to the insulating layer and becomes a conductive layer.

An example of molding conditions in the case of using the PTFE fiber paper-like material is that a copper foil is arranged on both sides (in some cases, one surface) of the PTFE fiber paper-like material, and the temperature of the melting point of PTFE is 327 ° C. or higher, for example, 380. A double-sided copper clad board for a printed wiring board can be integrally formed by performing heat compression processing by a vacuum press for 90 minutes at a temperature of 1 ° C. and a pressure of 1 MPa.

After that, a post-process for forming a conductive layer having a circuit pattern is performed to obtain a fluororesin printed wiring board provided with a conductive path having a desired pattern. The pattern formation is performed using a peeling development type photoresist, a melt development type photoresist, or the like. For example, an alkali development type photoresist film is formed on the surface of a copper foil, and a desired pattern is exposed through a photomask. Next, the exposed portion of the copper foil is removed by etching or the like, and the exposed portion of the photoresist is dissolved and removed to obtain a fluororesin printed wiring board having a conductive layer having a desired pattern.

As the metal foil used in the conductive layer of the present invention, a single foil of copper, aluminum, brass, nickel, iron or the like, an alloy foil, a composite foil or the like can be used, but a copper foil is particularly preferable. Is preferable in terms of good electrical conductivity. In this case, neither electrolytic copper foil nor rolled copper foil is limited. Further, a metal foil in which a circuit is formed on the above metal foil including these copper foils can also be used. In addition, an adhesive layer can be provided on one surface of the metal foil if necessary.

The thickness of the metal foil is not particularly limited, but a thickness of 9 to 35 μm is preferable in terms of ensuring the processing accuracy of the high frequency printed circuit.

The relative permittivity of the fluororesin printed wiring board of the present invention produced as described above is preferably 5 to 20. The relative permittivity of the printed wiring board is often adjusted mainly by the type and blending amount of the inorganic fine particles, but it can also be adjusted by the type and blending amount of the heat resistant insulating fiber. Further, since the appropriate range of the relative permittivity of the printed wiring board differs depending on the specific application, the present invention also sets the range to be narrower in the above range according to the specific application.

[0041]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

<Example 1> Strontium titanate fine particles as inorganic fine particles in water (manufactured by Sakai Chemical Industry Co., Ltd., trade name:
ST-03, average particle size 0.3 μm) and an inorganic flocculant (manufactured by Nippon Light Metal Co., Ltd., trade name: sulfuric acid band) at 2.0% by weight based on the above fine particles, a polymer flocculant (manufactured by Kurita Water Industries Co., Ltd., product Name: High holder 109) 1.0 for the above fine particles
Weight% and synthetic sticky agent (manufactured by Diafrock, trade name: ACR
YPERSE PMP) was added to the above fine particles in an amount of 1.5% by weight and stirred to obtain a suspension in which the strontium titanate fine particles were aggregated. In the suspension, PTFE fiber (manufactured by Toray Fine Chemical Co., trade name: Toyofuron, diameter 15 μm, fiber length 3 mm) as fluororesin fiber and glass fiber (manufactured by Unitika Glass Fiber Co., Ltd., trade name: PDE1 /) as heat resistant insulating fiber. 8ZA509, diameter 6μ
m, fiber length 3 mm) in a weight ratio of PTFE fiber: strontium titanate fine particles: heat resistant insulating fiber = 45: 5
Add so that it becomes 0: 5, stir, and disperse uniformly. This raw material dispersion liquid was prepared to have a slurry concentration of 0.5%, papermaking was carried out using a slant type wet paper machine, and dehydration was carried out.
TFE resin dispersion liquid (manufactured by Mitsui Dupont Fluorochemical Co., Ltd., trade name: 30-J, concentration 30%) was sprayed on one surface so that a solid resin content of 10 g / m ² of PTFE resin was adhered to 130 ° C. A primary sheet was obtained through a drying process using a Yankee dryer that was heat-adjusted. After that, the primary sheet is heat-treated through an electric furnace whose temperature is adjusted to 350 ° C. to fuse the fibers to each other to obtain a basis weight of 2
A paper-like material containing 50 g / m ² of a fluororesin fiber as a main component was obtained. From the obtained paper-like material, two sheets each having a size of 300 × 300 mm were cut out in the longitudinal direction, and they were stacked at 90 ° with respect to the longitudinal direction. At that time, the surface to which the fluororesin was attached was used as the outermost layer, and the surfaces to which the fluororesin was not attached were opposed to each other. Further, electrolytic copper foils (manufactured by Fukuda Metal Foil Industry Co., Ltd., trade name: CF-T9, thickness 18 μm) are placed on top of each other as metal foils and placed under vacuum at a pressure of 1 MPa and heating at 380 ° C. to 90 ° C.
After pressing for minutes, a fluororesin laminate for a printed wiring board of the present invention was obtained. Subsequently, an alkali development type photoresist film is formed on the copper foil surface, the pattern is exposed through a photomask, the exposed part of the copper foil is removed by etching, the exposed part of the photoresist is dissolved and removed, and a book with a circuit pattern is formed. The fluororesin printed wiring board of the invention was obtained.

Example 2 The compounding ratio of PTFE fiber, strontium titanate fine particles and glass fiber was 50:10:
A fluororesin printed wiring board of the present invention was obtained in the same manner as in Example 1 except that the number was changed to 40.

Example 3 The compounding ratio of PTFE fiber, strontium titanate fine particles and glass fiber was 27:70:
A fluororesin printed wiring board of the present invention was obtained in the same manner as in Example 1 except that the number was changed to 3.

Example 4 PBO fiber (manufactured by Toyobo Co., Ltd., trade name: Zylon AS, diameter 12 μm, fiber length 3 mm) was fibrillated to a freeness of 500 ml as a heat resistant insulating fiber by beating. Using the prepared PBO pulp, the compounding ratio of the PTFE fiber, the strontium titanate fine particles, the glass fiber and the PBO pulp is 40: 50: 5:
A fluororesin printed wiring board of the present invention was obtained in the same manner as in Example 1 except that the number was changed to 5.

Example 5 A fluororesin printed wiring board of the present invention was obtained in the same manner as in Example 1 except that the fluororesin was not sprayed on the primary sheet.

Comparative Example 1 A fluororesin printed wiring board for comparison was obtained in the same manner as in Example 1 except that the fluororesin fiber papers were superposed in the same direction.

Comparative Example 2 A strontium titanate was not used, but the compounding ratio of PTFE fiber, strontium titanate fine particles and glass fiber was set to 60: 0: 40.
A fluororesin printed wiring board for comparison was obtained in the same manner as in Example 1.

<Comparative Example 3> PT without using glass fiber
Fluorine for comparison was used in the same manner as in Comparative Example 1 except that the compounding ratio of the FE fiber, the strontium titanate fine particles and the glass fiber was 50: 50: 0, and the PTFE resin dispersion was not sprayed on the fluororesin fiber primary sheet. A resin printed wiring board was obtained.

<Comparative Example 4> As a printed wiring board, a high relative dielectric constant type commercially available fluororesin copper clad board for printed wiring, which is made of glass cloth as a base material and impregnated with fluororesin dispersion, is AR1000. A pattern was formed on (Aaron Co.) in the same manner as in Comparative Example 1 to obtain a fluororesin printed wiring board for comparison.

The following evaluations were performed on the copper-clad substrates of Examples 1 to 5 and Comparative Examples 1 to 4 before the pattern formation of the fluororesin printed wiring boards. 1. Relative permittivity: 10MH according to JIS C6481
It was measured at z. 2. Water absorption rate: Measured according to JIS C6481. 3. Copper foil adhesion (peel strength): JIS C648
It measured according to 1. 4. Z-direction thermal expansion coefficient: Measured according to JIS C6481. A sample obtained by removing the copper foil of the obtained fluororesin printed wiring board by etching was heated at 25 ° C. to 150 ° C. at 2 ° C./min using a thermal analysis apparatus TMA, and the thickness direction (Z direction). Was measured, and the coefficient of thermal expansion was calculated. 5. Dimensional change rate: X after heat treatment (150 ° C / 30 minutes)
The dimensional change rates in the Y and Y directions were measured according to JIS C6481. Table 1 shows the evaluation results of the above items.

[0052]

[Table 1]

From Table 1, the following points were confirmed. That is, the dimensional change rate of the fluororesin copper-clad substrate produced by stacking the fluorofiber papers taken in the vertical direction at 90 ° perpendicular to each other is significantly smaller than that in the same direction, and the X direction It is clear that there is almost no difference between the Y direction and the Y direction. Moreover, compared with the glass cloth type of Comparative Example 4, the dimensional change rate is small in the X direction and the Y direction, the difference between the X direction and the Y direction is small, and the coefficient of thermal expansion in the Z direction is equal to or less than that. It became clear to get.
In addition to glass fiber as heat-resistant insulating fiber, PBO
It was revealed that the use of pulp suppresses the dimensional change of the substrate in the Z direction. It was also clarified that the coefficient of thermal expansion in the Z direction becomes large if the inorganic fine particles are not used. Further, it has been clarified that by attaching the fluororesin to the surface portion of the fluororesin fiber primary sheet, the water absorption is small and the copper foil adhesion is improved.

[0054]

The present invention is a simple method as compared with the prior art, and there is no partial variation in relative permittivity and dielectric loss tangent.
A fluororesin printed wiring board having a high relative dielectric constant, which is smooth without any fine irregularities on the surface of the printed wiring board, and has epoch-making dimensional stability in the X, Y and Z directions, and a method for producing the same. Can be provided. Further, in addition to the above-mentioned characteristics, a high relative dielectric constant fluororesin printed wiring board having a small water absorption rate and excellent metal foil adhesion, and a method for producing the same can be provided. Further, it is possible to provide a fluororesin printed wiring board having a uniform distribution of raw materials in the Z direction and capable of uniformly forming a plated layer in a through hole, and a method for manufacturing the same.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F100 AA00A AD00A AG00A AK17A                       AK17B AK18A AK80A AR00C                       BA03 BA10A BA10C BA22                       DE01A DG01A DG01B DG10A                       DG10B GB16 GB43 HB31C                       JG01C JG04A JG05 JJ03A

Claims (12)

[Claims] 1. A primary sheet obtained by wet papermaking of an aqueous slurry containing fluororesin fibers as a main component and containing at least inorganic fine particles and heat-resistant insulating fibers is heat-treated at a temperature not lower than the melting point of fluororesin to give a paper-like material. And an insulating layer in which at least two sheets of the paper-like material are laminated orthogonally to each other at 90 ° with respect to the vertical direction or the horizontal direction, and a conductive layer having a circuit pattern provided on at least one surface of the insulating layer. Fluororesin printed wiring board. 2. A fluororesin is adhered to at least one surface portion of a primary sheet obtained by wet papermaking of an aqueous slurry containing fluororesin fibers as a main component and containing at least inorganic fine particles and heat-resistant insulating fibers, A heat treatment is performed at a temperature equal to or higher than the melting point of the fluororesin to form a paper-like material, and an insulating layer in which at least two paper-like materials are laminated orthogonally to each other at 90 ° with respect to the longitudinal direction or the transverse direction, and at least one surface of the insulating layer A fluororesin printed wiring board having a conductive layer of a circuit pattern provided. 3. The fluororesin printed wiring board according to claim 1, which has a relative dielectric constant of 5 to 20. 4. The fluororesin fiber is a polytetrafluoroethylene fiber.
The fluororesin printed wiring board according to any one of 1. 5. The fluororesin printed wiring board according to any one of claims 1 to 4, wherein the inorganic fine particles are titanium-based ceramic fine particles. 6. The fluororesin printed wiring board according to claim 1, wherein the heat-resistant insulating fiber is glass fiber. 7. The fluororesin printed wiring board according to claim 1, wherein the heat resistant insulating fibers are glass fibers and polyparaphenylenebenzobisoxazole fibers. 8. The blending amount of the inorganic fine particles is 10 with respect to the total amount of the fluororesin fiber, the inorganic fine particles and the heat resistant insulating fiber.
The fluororesin printed wiring board according to any one of claims 1 to 7, wherein the fluororesin printed wiring board is from 70 to 70% by weight. 9. The blending amount of the heat resistant insulating fiber is 3 with respect to the total of the fluororesin fiber, the inorganic fine particles and the heat resistant insulating fiber.
It is 40 weight% or less, The fluororesin laminated board for printed wiring boards in any one of Claim 1 thru | or 8 characterized by the above-mentioned. 10. A step of wet-fabrication of an aqueous slurry containing fluororesin fibers as a main component and containing at least inorganic fine particles and heat-resistant insulating fibers to form a primary sheet, which is heat-treated at a temperature equal to or higher than the melting point of the fluororesin. A step of fusing resin fibers together to form a paper-like material, and at least 2
A step of laminating sheets so as to be orthogonal to each other at 90 ° with respect to the longitudinal direction or the transverse direction to form an insulating layer, and arranging a conductive metal foil on at least one surface of the insulating layer to form a conductive layer, a temperature not lower than the melting point of the fluororesin. A method for producing a fluororesin printed wiring board, comprising: a step of vacuum heating and pressing to produce a fluororesin laminate for a printed wiring board; and a step of forming a conductive layer into a desired circuit pattern. 11. A step of wet-fabrication an aqueous slurry containing a fluororesin fiber as a main component and containing at least inorganic fine particles and a heat-resistant insulating fiber to form a primary sheet, the fluororesin being provided on at least one surface portion of the primary sheet. A step of adhering, a step of heat-treating at a temperature equal to or higher than the melting point of the fluororesin to fuse the fluororesin fibers with each other and the fluororesin fibers and the fluororesin on the surface to form a paper-like material, and at least the paper-like material 90 ° with 2 pieces as vertical or horizontal direction
A step of forming an insulating layer by stacking it orthogonally to and forming a conductive metal foil on at least one surface of the insulating layer to form a conductive layer, vacuum heating pressing at a temperature equal to or higher than the melting point of the fluororesin, and laminating a fluororesin for printed wiring board A method for manufacturing a fluororesin printed wiring board, comprising the steps of producing a board and forming a conductive layer into a desired circuit pattern. 12. The method for producing a fluororesin printed wiring board according to claim 11, wherein a fluororesin dispersion is used as the fluororesin attached to the surface portion of the primary sheet.