JP2007165357A - Wiring board - Google Patents

Abstract

A wiring board having a substrate made of a fiber reinforced composite material containing fibers and a matrix material, and having high thermal conductivity not only in an in-plane direction but also in a surface thickness direction, isotropic That is, the present invention provides a wiring board having a fiber-reinforced composite material substrate having no thermal conductivity anisotropy.
In a wiring board having a substrate made of a fiber-reinforced composite material containing fibers and a matrix material, the fibers are fibers having a crystallinity of 50% or more, and the thermal conductivity in the thickness direction of the substrate and A wiring board having a thermal conductivity in the plate surface direction of 0.5 W / m · k or more.
[Selection] Figure 1

Description

  The present invention relates to a wiring board having a substrate made of a fiber-reinforced composite material containing fibers and a matrix material, and not only in a plate surface direction (hereinafter referred to as “in-plane direction”) but also in a thickness direction (hereinafter referred to as “in-plane direction”). It also relates to a wiring board having a fiber-reinforced composite material substrate that has high thermal conductivity and isotropic, that is, has no thermal conductivity anisotropy.

  A wiring board used for LED mounting is required to have low thermal expansion, high strength, high elasticity, light weight, high thermal conductivity, and the like. In addition, transparency may be required for trimming the built-in passive element. Among these required characteristics, in recent years, the demand for high thermal conductivity is increasing. That is, with the recent increase in performance, functionality and compactness in the field of electronics equipment, the heat generated inside various equipment continues to increase, and in order to dissipate the heat efficiently, the wiring board Therefore, it is desired to have excellent heat conductivity and high heat dissipation. In this case, in order to dissipate heat efficiently, the thermal conductivity of the wiring board is excellent not only in the in-plane direction but also in the thickness direction, that is, has isotropic thermal conductivity. desired.

  In addition, the present applicant previously contains a fiber having an average fiber diameter of 4 to 200 nm and a matrix material as a wiring board having excellent transparency, low thermal expansion, high strength, and light weight, and a wavelength in terms of 50 μm thickness. A wiring board including a transparent substrate made of a fiber-reinforced composite material having a light transmittance of 400 to 700 nm of 60% or more has been proposed (Japanese Patent Laid-Open No. 2005-60680).

However, in the wiring board disclosed in Japanese Patent Laid-Open No. 2005-60680, the thermal conductivity in the in-plane direction (plate surface direction) shows a high thermal conductivity of, for example, 1 W / m · K. Thermal conductivity is not clarified.
JP 2005-60680 A

  The present invention is a wiring board having a substrate made of a fiber-reinforced composite material containing fibers and a matrix material, and has high thermal conductivity not only in the in-plane direction but also in the thickness direction, and isotropic In other words, an object of the present invention is to provide a wiring board having a fiber-reinforced composite material substrate having no thermal conductivity anisotropy.

  The wiring board of the present invention (Claim 1) is a wiring board having a substrate made of a fiber-reinforced composite material containing fibers and a matrix material, and the fibers are fibers having a crystallinity of 50% or more. The thermal conductivity in the thickness direction and the thermal conductivity in the plate surface direction are both 0.5 W / m · k or more.

  A wiring board according to a second aspect is characterized in that, in the first aspect, the fiber is a fiber having an average fiber diameter of 4 to 200 nm.

  A wiring board according to a third aspect is characterized in that, in the first or second aspect, the fiber is a cellulose fiber.

  According to a fourth aspect of the present invention, in the wiring board according to the third aspect, the cellulose fiber is bacterial cellulose.

  A wiring board according to a fifth aspect is the wiring board according to the third aspect, wherein the cellulose fiber is separated from the plant fiber.

  The wiring board according to a sixth aspect is characterized in that the cellulose fiber is obtained by further grinding the microfibrillated cellulose fiber in the fifth aspect.

  According to a seventh aspect of the present invention, in the wiring board according to any one of the first to sixth aspects, the fibers are randomly oriented in the substrate.

  A wiring board according to an eighth aspect is characterized in that, in any one of the first to seventh aspects, the content of the fiber in the fiber-reinforced composite material is 10% by weight or more.

  A wiring board according to a ninth aspect is characterized in that, in any one of the first to eighth aspects, the total light transmittance at a wavelength of 400 to 700 nm in terms of 50 μm thickness of the board is 80% or more.

  A wiring board according to a tenth aspect is characterized in that, in the ninth aspect, the parallel light transmittance in terms of a thickness of 50 μm of the board is 60% or more.

  The wiring board according to claim 11 is the wiring substrate according to any one of claims 1 to 10, wherein the matrix material is an organic polymer, an inorganic polymer, or a hybrid polymer of an organic polymer and an inorganic polymer. Features.

  A wiring board according to a twelfth aspect is characterized in that, in the eleventh aspect, the matrix material is a synthetic polymer.

  The wiring board according to claim 13 is the wiring board according to claim 12, wherein the matrix material is acrylic resin, methacrylic resin, epoxy resin, urethane resin, phenol resin, melamine resin, novolac resin, urea resin, guanamine resin, alkyd resin, unsaturated resin. One or more selected from the group consisting of polyester resins, vinyl ester resins, diallyl phthalate resins, silicone resins, furan resins, ketone resins, xylene resins, thermosetting polyimide resins, styrylpyridine resins, and triazine resins It is characterized by being.

  A wiring board according to a fourteenth aspect is characterized in that in any one of the first to thirteenth aspects, the wiring board includes a wiring circuit formed on the board.

A wiring board according to a fifteenth aspect is the one according to the fourteenth aspect, wherein the board contains a passive element.
A wiring board according to a sixteenth aspect is the one according to the fourteenth aspect, wherein a semiconductor chip is mounted on the substrate.

  Since the substrate of the wiring board of the present invention contains highly crystalline fibers having a crystallinity of 50% or more, it exhibits high thermal conductivity. That is, the thermal conductivity of the fiber-reinforced composite material is affected by the crystallinity of the contained fiber, and a high thermal conductivity can be obtained if the fiber has a high crystallinity. Thus, if the substrate has a high thermal conductivity of 0.5 W / m · k or more in both the in-plane direction and the surface thickness direction, the wiring substrate is excellent in heat dissipation due to its isotropic thermal conductivity. Can be provided. Such isotropic high thermal conductivity can be easily realized by randomly orienting the fibers in the substrate.

  In particular, in the present invention, by using a fiber having an average fiber diameter of 4 to 200 nm and an average fiber diameter smaller than the visible light wavelength (380 to 800 nm), visible light is hardly refracted at the interface between the matrix material and the fiber. Therefore, in the entire visible light region, regardless of the refractive index of the matrix material, the visible light scattering loss hardly occurs at the interface between the fiber and the matrix material. A substrate having the same can be provided.

  Moreover, since the board | substrate which concerns on this invention can be made into a thing with a small coefficient of linear thermal expansion by the mixing | blending of a fiber, distortion, a deformation | transformation, and a shape precision fall do not become a problem easily by atmospheric temperature. Further, by selecting a fiber material, it can be made light and inexpensive.

  In the present invention, in particular, the industrial utility of a wiring board having high transparency and isotropic high thermal conductivity using fibers having an average fiber diameter of 4 to 200 nm is very large. That is, for example, inorganic glass known as a material having high thermal conductivity exhibits high thermal conductivity of about 1 W / m · K in both the in-plane direction and the surface thickness direction as in Comparative Example 2 described later. There are problems in terms of lightness and price. In addition, as a highly transparent resin, a general-purpose epoxy resin exhibits only a thermal conductivity of about 0.2 W / m · K in both the in-plane direction and the surface thickness direction, as shown in Comparative Example 1 described later. When this epoxy resin is blended with a ceramic filler having high thermal conductivity, the thermal conductivity is improved, but the transparency is greatly impaired.

  On the other hand, according to the present invention, by selecting a fiber, it is possible to provide a wiring board that is highly transparent and that exhibits isotropic high thermal conductivity and that is inexpensive and lightweight.

  In the present invention, by using a biodegradable cellulose fiber as the fiber, when it is discarded, it can be processed only in accordance with the processing method of the matrix material, which is advantageous for disposal or recycling.

  Hereinafter, embodiments of the wiring board of the present invention will be described in detail.

[Fiber-reinforced composite materials]
First, the fiber reinforced composite material which comprises the board | substrate of the wiring board of this invention is demonstrated.
The fiber reinforced composite material according to the present invention includes fibers having a crystallinity of 50% or more and a matrix material.

<Fiber>
In the present invention, the degree of crystallinity of the fiber can be measured, for example, by XRD (X-ray diffraction method) as follows.

(Measurement method of crystallinity)
The crystallinity was defined as the ratio of the crystal scattering peak area on the X-ray diffraction diagram obtained by X-ray diffraction measurement. The manufactured fiber assembly was mounted on a sample holder, and the diffraction angle of X-ray diffraction was manipulated from 10 ° to 32 ° for measurement. After removing background scattering from the obtained X-ray diffraction pattern, the area connecting 10 °, 18.5 °, and 32 ° with a straight line on the X-ray diffraction curve becomes an amorphous part, and the other part is a crystal part. Become. The cellulose crystallinity was calculated by the following formula as a ratio of the crystal part to the area of the entire diffraction pattern.
Crystallinity = (Area of crystal part) / (Area of entire X-ray diffraction diagram) × 100 (%)

  If the crystallinity of the fiber used in the present invention is less than 50%, sufficient high thermal conductivity cannot be obtained. The crystallinity of the fiber is particularly preferably 60% or more, particularly 65% or more.

  The method for obtaining such a highly crystalline fiber is not particularly limited. For example, in the case of a cellulose fiber described later, it is hydrolyzed in a 3% sulfuric acid aqueous solution at about 100 ° C. for about 1 hour, and then sufficiently The method of raising the crystallinity degree by washing with water is mentioned.

<Preferred fiber>
In the present invention, as described above, since a highly transparent substrate can be obtained, it is preferable to use fibers having an average fiber diameter of 4 to 200 nm as the fibers.

  The fibers having an average fiber diameter of 4 to 200 nm used in the present invention may be composed of single fibers that are sufficiently separated so that the liquid for impregnation described later enters between them without being aligned. Good. In this case, the average fiber diameter is the average diameter of single fibers. Further, the fiber according to the present invention may be one in which a plurality of (may be many) single fibers are gathered into a bundle to form one yarn. The fiber diameter is defined as the average value of the diameter of one yarn. Bacterial cellulose to be described later is composed of the latter yarn.

  In the present invention, when the average fiber diameter of the fibers used exceeds 200 nm, the wavelength of visible light approaches, the refraction of visible light tends to occur at the interface with the matrix material, and the transparency is lowered. The upper limit of the average fiber diameter of the fibers used in is preferably 200 nm. A fiber having an average fiber diameter of less than 4 nm is difficult to produce. For example, since a single fiber diameter of bacterial cellulose described below suitable as a fiber is about 4 nm, the lower limit of the average fiber diameter of the fiber used in the present invention is preferably 4 nm. And The average fiber diameter of the fiber used in the present invention is more preferably 4 to 100 nm, still more preferably 4 to 60 nm.

  The fibers used in the present invention may contain fibers having a fiber diameter outside the range of 4 to 200 nm as long as the average fiber diameter is preferably in the range of 4 to 200 nm. Is preferably 30% by weight or less, and desirably, the fiber diameter of all the fibers is 200 nm or less, particularly 100 nm or less, particularly 60 nm or less.

  The length of the fiber is not particularly limited, but the average length is preferably 100 nm or more. If the average length of the fibers is shorter than 100 nm, the reinforcing effect is low, and the strength of the obtained substrate may be insufficient. The fibers may contain fibers having a fiber length of less than 100 nm, but the ratio is preferably 30% by weight or less.

  In the present invention, it is preferable to use a cellulose fiber as the fiber because a lightweight, inexpensive and environmentally friendly wiring board can be provided.

  Cellulose fibers refer to cellulose microfibrils constituting the basic skeleton of plant cell walls or the like, or constituent fibers thereof, and are usually aggregates of unit fibers having a fiber diameter of about 4 nm.

  In the present invention, the cellulose fiber to be used may be one separated from a plant, or bacterial cellulose produced by bacteria. As bacterial cellulose, it is preferable to use a product obtained by dissolving a bacterial product by alkali treatment of a product from the bacteria without disaggregation.

  Hereinafter, cellulose fibers separated from bacterial cellulose and plant fibers will be described. In the present invention, one of the following fibers may be used alone, or two or more of them may be used in combination.

<Bacterial cellulose (hereinafter sometimes abbreviated as “BC”)>
The organisms that can produce cellulose on the earth are not limited to the plant kingdom, but the ascidians in the animal kingdom, various algae, oomycetes, slime molds, etc. in the protozoan kingdom. It is distributed in a part of bacteria. At present, the ability to produce cellulose has not been confirmed in the fungal kingdom (fungi). Among these, examples of the acetic acid bacterium include the genus Acetobacter, and more specifically, Acetobacter aceti, Acetobacter subsp., Acetobacter subsp. xylinum) and the like, but is not limited thereto.

  By culturing such bacteria, cellulose is produced from the bacteria. Since the obtained product contains bacteria and cellulose fibers (bacterial cellulose) produced from the bacteria and connected to the bacteria, the product is removed from the medium, washed with water, or treated with alkali. By removing the bacteria, water-containing bacterial cellulose that does not contain bacteria can be obtained. Bacterial cellulose can be obtained by removing water from the water-containing bacterial cellulose.

  Examples of the medium include agar-like solid medium and liquid medium (culture solution). Examples of the culture solution include 7% by weight of coconut milk (total nitrogen content 0.7% by weight, lipid 28% by weight), sucrose. A culture solution containing 8% by weight and adjusted to pH 3.0 with acetic acid, glucose 2% by weight, bacto yeast extract 0.5% by weight, bacto peptone 0.5% by weight, disodium hydrogen phosphate 0 And an aqueous solution (SH medium) adjusted to pH 5.0 with hydrochloric acid at 27 wt%, citric acid 0.115 wt%, magnesium sulfate heptahydrate 0.1 wt%, and the like.

  Examples of the culture method include the following methods. Acetic acid bacteria such as Acetobacter xylinum FF-88 are inoculated into a coconut milk culture solution. For example, in the case of FF-88, static culture is performed at 30 ° C. for 5 days to obtain a primary culture solution. obtain. After removing the gel content of the obtained primary culture solution, the liquid part is added to the same culture solution at a rate of 5% by weight, and static culture is performed at 30 ° C. for 10 days to obtain a secondary culture solution. . This secondary culture solution contains about 1% by weight of cellulose fibers.

  As another culture method, as a culture solution, glucose 2% by weight, bacto yeast extract 0.5% by weight, bacto peptone 0.5% by weight, disodium hydrogen phosphate 0.27% by weight, citric acid 0. An example is a method using an aqueous solution (SH culture solution) adjusted to pH 5.0 with hydrochloric acid at 115% by weight and magnesium sulfate heptahydrate 0.1% by weight. In this case, the SH culture solution is added to the strain of acetic acid bacteria in a freeze-dried storage state, followed by static culture for 1 week (25-30 ° C.). Bacterial cellulose is produced on the surface of the culture solution. Among these, a relatively thick one is selected, and a small amount of the culture solution of the strain is taken and added to a new culture solution. And this culture solution is put into a large incubator, and a static culture is performed at 25-30 degreeC for 7-30 days. Bacterial cellulose is thus obtained by repeating the process of “adding a part of an existing culture solution to a new culture solution and performing static culture for about 7 to 30 days”.

  The following procedure is performed when a problem such as difficulty in producing the cellulose by the bacteria occurs. That is, a small amount of a culture solution in the culture of bacteria is spread on an agar medium prepared by adding agar to the culture solution, and allowed to stand for about one week to produce colonies. Each colony is observed, and a colony that makes cellulose relatively well is taken out from the agar medium, put into a new culture solution, and cultured.

  The bacterial cellulose thus produced is taken out from the culture solution, and the bacteria remaining in the bacterial cellulose are removed. Examples of the method include washing with water or alkali treatment. Examples of the alkali treatment for dissolving and removing the bacteria include a method of pouring bacterial cellulose taken out from the culture solution into an alkaline aqueous solution of about 0.01 to 10% by weight for 1 hour or more. Then, when the alkali treatment is performed, the bacterial cellulose is taken out from the alkali treatment solution, sufficiently washed with water, and the alkali treatment solution is removed.

  The water-containing bacterial cellulose (usually bacterial cellulose having a water content of 95 to 99% by weight) thus obtained is then subjected to a water removal treatment.

This water removal method is not particularly limited, but first, water is drained to some extent by standing or cold press, and then left as it is, or the remaining water is completely removed by hot press or the like. Thereafter, a method of removing water by applying a dryer or drying naturally is exemplified.
The leaving as a method for removing water to some extent is a method of gradually evaporating water over time.

  The cold press is a method of extracting water by applying pressure without applying heat, and a certain amount of water can be squeezed out. The pressure in this cold press is preferably 0.01 to 10 MPa, and more preferably 0.1 to 3 MPa. If the pressure is less than 0.01 MPa, the remaining amount of water tends to increase. If the pressure is more than 10 MPa, the resulting bacterial cellulose may be destroyed. Moreover, although temperature is not specifically limited, Room temperature is preferable for the convenience of operation.

  The standing as a method for completely removing the remaining water is a method of drying bacterial cellulose over time.

  The hot press is a method of extracting water by applying pressure while applying heat, and the remaining water can be completely removed. The pressure in this hot press is preferably 0.01 to 10 MPa, and more preferably 0.2 to 3 MPa. If the pressure is less than 0.01 MPa, water cannot be removed. If the pressure is greater than 10 MPa, the resulting bacterial cellulose may be destroyed. Moreover, 100-300 degreeC is preferable and 110-200 degreeC is more preferable. When the temperature is lower than 100 ° C., it takes time to remove water. On the other hand, when the temperature is higher than 300 ° C., decomposition of bacterial cellulose may occur.

  Moreover, 100-300 degreeC is preferable also about the drying temperature by the said dryer, and 110-200 degreeC is more preferable. If the drying temperature is lower than 100 ° C., water may not be removed. On the other hand, if the drying temperature is higher than 300 ° C., the cellulose fibers may be decomposed.

The bacterial cellulose thus obtained varies depending on the culture conditions, the subsequent pressurization and water heating conditions, etc., but usually has a bulk density of about 1.1 to 1.3 kg / m ³ and a thickness of 40. It has a sheet shape of about ˜60 μm (hereinafter sometimes referred to as “BC sheet”).

<Cellulose fibers separated from plant fibers>
In the present invention, as the fiber, in addition to bacterial cellulose as described above, seaweed and sea squirt sac, plant cell wall, etc., treatment such as beating and crushing, high-temperature and high-pressure steam treatment, treatment using phosphate, etc. You may use the cellulose fiber which gave.

  In this case, the above beating and pulverization is performed by directly applying force to the plant cell wall from which the lignin and the like have been removed, the seaweed and squirt sac, and performing the beating and pulverization to separate the fibers to obtain cellulose fibers. Is the law.

More specifically, as shown in the examples described later, microfibrillated cellulose fibers (hereinafter referred to as “MFC”) obtained by treating pulp and the like with a high-pressure homogenizer and microfibrillating to an average fiber diameter of about 0.1 to 10 μm. (Abbreviated) is made into a water suspension of about 0.1 to 3% by weight and further subjected to repeated grinding or crushing treatment with a grinder or the like, and nano-order MFC (hereinafter, “Nano”) having an average fiber diameter of about 10 to 100 nm. Abbreviated as “MFC”). The Nano MFC is made into an aqueous suspension of about 0.01 to 1% by weight, and this is filtered to form a sheet.
The grinding or crushing treatment can be performed using, for example, a grinder “Pure Fine Mill” manufactured by Kurita Machine Seisakusho.

  This grinder is a stone mill that pulverizes raw materials into ultrafine particles by impact, centrifugal force, and shearing force generated when the raw material passes through the gap between the upper and lower two grinders. Shearing, grinding, atomization , Dispersion, emulsification, and fibrillation can be performed simultaneously. In addition, the grinding or fusing treatment can be performed using an ultrafine grinding machine “Super Mass Collider” manufactured by Masuko Sangyo Co., Ltd. The Super Mass Collider is a grinder that enables ultra-fine atomization that feels like melting beyond the mere grinding area. A super mass collider is a stone mill type ultrafine grinding machine composed of two top and bottom non-porous grindstones whose spacing can be freely adjusted. The upper grindstone is fixed and the lower grindstone rotates at high speed. The raw material thrown into the hopper is fed into the gap between the upper and lower grindstones by centrifugal force, and the raw material is gradually crushed and micronized by the strong compression, shearing, rolling frictional force and the like generated there.

  The high-temperature and high-pressure steam treatment is a treatment method for obtaining cellulose fibers by dissociating fibers by exposing a plant cell wall from which lignin or the like has been removed, or a capsule of seaweed or sea squirt to high-temperature and high-pressure steam.

  In addition, treatment with phosphate, etc. means that the surface of seaweed, sea squirt sac, plant cell wall, etc. is phosphorylated to weaken the binding force between cellulose fibers, and then perform refiner treatment. Thus, the fiber is separated to obtain a cellulose fiber. For example, plant cell walls from which lignin and the like have been removed, seaweed and sea squirt capsules are immersed in a solution containing 50 wt% urea and 32 wt% phosphoric acid, and the solution is sufficiently soaked between cellulose fibers at 60 ° C. After that, the phosphorylation proceeds by heating at 180 ° C. This is washed with water, hydrolyzed in a 3% by weight aqueous hydrochloric acid solution at 60 ° C. for 2 hours, and washed again with water. Thereafter, phosphorylation is completed by treatment in a 3 wt% aqueous sodium carbonate solution at room temperature for about 20 minutes. And a cellulose fiber is obtained by defibrating this processed material with a refiner.

  In addition, you may use these cellulose fibers in mixture of 2 or more types obtained from a different plant etc., or the thing which performed the different process.

  The water-containing Nano MFC thus obtained usually has a single-fiber subnetwork structure with an average fiber diameter of about 100 nm (although it does not have a complete (clean) network structure such as the above-mentioned bacterial cellulose, but locally. (A structure forming a network) is impregnated with water.

  In addition, as a raw material for producing Nano MFC, in addition to pulp, cotton (for example, absorbent cotton or cotton linter) or a product obtained by purifying pulp by various methods, for example, “Tencel” (registered trademark) manufactured by Lenzing, “Theolas” (registered trademark) manufactured by Asahi Kasei Chemicals Corporation, “Avicel” (registered trademark) manufactured by Asahi Kasei Chemicals Corporation, or purified cotton, for example, copper ammonia method regenerated cellulose (cupra) can be used.

<Modification of fiber>
The fibers used in the present invention may be those obtained by chemically and / or physically modifying the cellulose fibers as described above to enhance functionality. Here, as chemical modification, functional groups are added by acetylation, cyanoethylation, acetalization, etherification, isocyanateation, etc., and inorganic substances such as silicates and titanates are combined or coated by chemical reaction or sol-gel method. For example. The chemical modification method includes, for example, a method in which a BC sheet or a Nano MFC sheet is immersed in acetic anhydride and heated, and the acetylation reduces the water absorption and heat resistance without reducing the light transmittance. Can be improved. Physical modifications include physical vapor deposition (PVD method) such as vacuum vapor deposition, ion plating, sputtering, chemical vapor deposition (CVD method), plating methods such as electroless plating and electrolytic plating, etc. And surface coating.

<Fiber content in fiber reinforced composite material>
In the present invention, the fiber content in the fiber-reinforced composite material constituting the substrate is preferably 10% by weight or more, particularly 30% by weight or more, particularly preferably 50% by weight or more, and 99% by weight or less, particularly 95% by weight. % Or less is preferable. If the fiber content in the fiber reinforced composite material is too small, the effects of improving the thermal conductivity, bending strength, bending elastic modulus, and linear thermal expansion coefficient of the substrate due to fibers such as cellulose fibers tend to be insufficient. If the amount is too large, adhesion between fibers by the matrix material or filling of the space between the fibers becomes insufficient, and the strength, transparency, and flatness of the surface when cured may be reduced.

<Matrix material>
The matrix material of the fiber reinforced composite material according to the present invention is a material that becomes a base material of the fiber reinforced composite material according to the present invention, and can obtain a high thermal conductivity substrate intended in the present invention. There is no particular limitation as long as it can produce a substrate satisfying suitable physical properties, and one kind of organic polymer, inorganic polymer, hybrid polymer of organic polymer and inorganic polymer, or the like alone or Two or more kinds can be mixed and used.

  Although the matrix material suitable for this invention is illustrated below, the matrix material used by this invention is not limited to the following thing at all.

  Examples of the inorganic polymer of the matrix material include ceramics such as glass, silicate material, and titanate material, and these can be formed by, for example, dehydration condensation reaction of alcoholate. Examples of organic polymers include natural polymers and synthetic polymers.

  Examples of natural polymers include regenerated cellulose polymers such as cellophane and triacetyl cellulose.

  Examples of the synthetic polymer include vinyl resins, polycondensation resins, polyaddition resins, addition condensation resins, and ring-opening polymerization resins.

  Examples of the vinyl resins include general-purpose resins such as polyolefins, vinyl chloride resins, vinyl acetate resins, fluororesins, (meth) acrylic resins, engineering plastics obtained by vinyl polymerization, super engineering plastics, and the like. These may be a homopolymer or a copolymer of each monomer constituted in each resin.

  Examples of the polyolefin include homopolymers or copolymers such as ethylene, propylene, styrene, butadiene, butene, isoprene, chloroprene, isobutylene and isoprene, or cyclic polyolefins having a norbornene skeleton.

  Examples of the vinyl chloride resin include homopolymers or copolymers such as vinyl chloride and vinylidene chloride.

  The vinyl acetate resin is polyvinyl acetate which is a homopolymer of vinyl acetate, polyvinyl alcohol which is a hydrolyzate of polyvinyl acetate, polyvinyl acetal obtained by reacting vinyl acetate with formaldehyde or n-butyraldehyde, polyvinyl Examples thereof include polyvinyl butyral obtained by reacting alcohol or butyraldehyde.

  Examples of the fluororesin include homopolymers or copolymers such as tetrachloroethylene, hexpropylene, chlorotrifluoroethylene, vinylidene fluoride, vinyl fluoride, and perfluoroalkyl vinyl ether.

  As said (meth) acrylic-type resin, homopolymers or copolymers, such as (meth) acrylic acid, (meth) acrylonitrile, (meth) acrylic acid ester, (meth) acrylamides, are mentioned. In this specification, “(meth) acryl” means “acryl and / or methacryl”. Here, examples of (meth) acrylic acid include acrylic acid and methacrylic acid. Examples of (meth) acrylonitrile include acrylonitrile and methacrylonitrile. Examples of (meth) acrylic acid esters include (meth) acrylic acid alkyl esters, (meth) acrylic acid monomers having a cycloalkyl group, and (meth) acrylic acid alkoxyalkyl esters. Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) Examples include benzyl acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, hydroxyethyl (meth) acrylate, and the like. Examples of the (meth) acrylic acid monomer having a cycloalkyl group include cyclohexyl (meth) acrylate and isobornyl (meth) acrylate. Examples of (meth) acrylic acid alkoxyalkyl esters include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, and the like. (Meth) acrylamides include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N -N-substituted (meth) acrylamides such as isopropyl (meth) acrylamide, Nt-octyl (meth) acrylamide and the like.

  Examples of the polycondensation resin include amide resins and polycarbonate.

  Examples of the amide resins include aliphatic amide resins such as 6,6-nylon, 6-nylon, 11-nylon, 12-nylon, 4,6-nylon, 6,10-nylon, and 6,12-nylon. And aromatic polyamides composed of aromatic diamines such as phenylenediamine and aromatic dicarboxylic acids such as terephthaloyl chloride and isophthaloyl chloride or derivatives thereof.

  The polycarbonate refers to a reaction product of bisphenol A or a bisphenol that is a derivative thereof and phosgene or phenyl dicarbonate.

  Examples of the polyaddition resins include ester resins, U polymers, liquid crystal polymers, polyether ketones, polyether ether ketones, unsaturated polyesters, alkyd resins, polyimide resins, polysulfones, polyphenylene sulfide, and polyether sulfones. It is done.

  Examples of the ester resin include aromatic polyester, aliphatic polyester, and unsaturated polyester. As said aromatic polyester, the copolymer of diols mentioned later, such as ethylene glycol, propylene glycol, 1, 4- butanediol, and aromatic dicarboxylic acids, such as a terephthalic acid, is mentioned. Examples of the aliphatic polyester include copolymers of diols described later and aliphatic dicarboxylic acids such as succinic acid and valeric acid, and homopolymers or copolymers of hydroxycarboxylic acids such as glycolic acid and lactic acid, as described above. Examples thereof include diols, copolymers of the above aliphatic dicarboxylic acids and the above hydroxycarboxylic acids. Examples of the unsaturated polyester include diols described later, unsaturated dicarboxylic acids such as maleic anhydride, and copolymers with vinyl monomers such as styrene as necessary.

  As said U polymer, the copolymer which consists of bisphenol A and its derivative bisphenol, a terephthalic acid, an isophthalic acid, etc. is mentioned.

  The liquid crystal polymer refers to a copolymer of p-hydroxybenzoic acid and terephthalic acid, p, p'-dioxydiphenol, p-hydroxy-6-naphthoic acid, polyterephthalic acid ethylene, or the like.

  Examples of the polyether ketone include homopolymers and copolymers such as 4,4'-difluorobenzophenone and 4,4'-dihydrobenzophenone.

  Examples of the polyether ether ketone include copolymers of 4,4'-difluorobenzophenone and hydroquinone.

  Examples of the alkyd resin include copolymers composed of higher fatty acids such as stearic acid and palmitic acid, dibasic acids such as phthalic anhydride, and polyols such as glycerin.

  Examples of the polysulfone include copolymers such as 4,4'-dichlorodiphenylsulfone and bisphenol A.

  Examples of the polyphenylene sulfide include copolymers such as p-dichlorobenzene and sodium sulfide.

  Examples of the polyethersulfone include a polymer of 4-chloro-4'-hydroxydiphenylsulfone.

  Examples of the polyimide resin include pyromellitic acid type polyimides such as polymellitic anhydride and 4,4′-diaminodiphenyl ether, aromatic diamines such as anhydrous chlorotrimetic acid and p-phenylenediamine, and diisocyanate compounds described later. Copolymers such as trimellitic acid type polyimide, biphenyltetracarboxylic acid, 4,4'-diaminodiphenyl ether, p-phenylenediamine, etc., benzophenone tetracarboxylic acid, 4,4'-diaminodiphenyl ether, etc. Benzophenone type polyimides made of, bismaleimide, bismaleimide type polyimides made of 4,4′-diaminodiphenylmethane and the like.

  Examples of the polyaddition resins include urethane resins.

  The urethane resin is a copolymer of diisocyanates and diols. Examples of the diisocyanates include dicyclohexylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, 2,4-tolylene diisocyanate, 2,6 -Tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate and the like. Examples of the diols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5- Relatively low molecular weight diols such as pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, trimethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexanedimethanol, and polyester Examples include diol, polyether diol, and polycarbonate diol.

  Examples of the addition condensation resin include phenol resin, urea resin, and melamine resin.

  Examples of the phenol resin include homopolymers or copolymers of phenol, cresol, resorcinol, phenylphenol, bisphenol A, bisphenol F, and the like.

  The urea resin and melamine resin are copolymers of formaldehyde, urea, melamine and the like.

  Examples of the ring-opening polymerization resin include polyalkylene oxide, polyacetal, and epoxy resin. Examples of the polyalkylene oxide include homopolymers or copolymers such as ethylene oxide and propylene oxide. Examples of the polyacetal include copolymers of trioxane, formaldehyde, ethylene oxide, and the like. Examples of the epoxy resin include an aliphatic epoxy resin composed of a polyhydric alcohol such as ethylene glycol and epichlorohydrin, and an aliphatic epoxy resin composed of bisphenol A and epichlorohydrin.

  In the present invention, among such matrix materials, a synthetic polymer having an amorphous and high glass transition temperature (Tg) is preferable for obtaining a highly durable fiber-reinforced composite material having excellent transparency. Among them, the degree of amorphousness is preferably 10% or less, particularly 5% or less in terms of crystallinity, and Tg is preferably 110 ° C. or higher, particularly 120 ° C. or higher, particularly 130 ° C. or higher. When the Tg is less than 110 ° C., there is a problem in durability in applications such as transparent parts and optical parts, such as deformation when contacted with boiling water. Tg is obtained by measurement by the DSC method, and the crystallinity is obtained by a density method for calculating the crystallinity from the densities of the amorphous part and the crystalline part.

  In the present invention, preferred transparent matrix resins include acrylic resins, methacrylic resins, epoxy resins, urethane resins, phenol resins, melamine resins, novolac resins, urea resins, guanamine resins, alkyd resins, unsaturated polyester resins, vinyl ester resins, Examples include thermosetting resins such as diallyl phthalate resin, silicone resin, furan resin, ketone resin, xylene resin, thermosetting polyimide resin, styrylpyridine resin, and triazine resin. Among these, acrylic resin having particularly high transparency, Methacrylic resin is preferred.

  These matrix materials may be used individually by 1 type, and 2 or more types may be mixed and used for them.

  When cellulose fibers are used as the fibers, the entire substrate according to the present invention can be made biodegradable by using a biodegradable polylactic acid resin as a matrix material, facilitating disposal. Can do.

[Substrate manufacturing method]
Next, a method for manufacturing a substrate according to the present invention will be described.

<Impregnation method>
In order to produce the substrate according to the present invention, the fiber assembly is impregnated with an impregnating liquid which can form a matrix material as described above.

  Here, the liquid material for impregnation includes a fluid matrix material, a fluid matrix material raw material, a fluidized material obtained by fluidizing the matrix material, a fluidized material obtained by fluidizing the matrix material raw material, and a matrix material solution. , And one or more selected from a raw material solution of the matrix material can be used.

  Examples of the fluid matrix material include those in which the matrix material itself is fluid. Moreover, as a raw material of the said fluid matrix material, polymerization intermediates, such as a prepolymer and an oligomer, etc. are mentioned, for example.

  Furthermore, examples of the fluidized material obtained by fluidizing the matrix material include a material in which a thermoplastic matrix material is heated and melted.

  Furthermore, examples of the fluidized material obtained by fluidizing the raw material of the matrix material include, for example, a polymer intermediate such as a prepolymer or an oligomer in a state in which these are heated and melted.

  Examples of the matrix material solution and the matrix material raw material solution include solutions in which the matrix material and the matrix material raw material are dissolved in a solvent or the like. This solvent is appropriately determined according to the matrix material to be dissolved and the raw material of the matrix material. However, when removing it in a later step, the above matrix material or the raw material of the matrix material is not decomposed. Solvents having boiling points below about a temperature are preferred.

  Such a liquid for impregnation is impregnated into a fiber assembly, preferably a single layer of the aforementioned BC sheet or Nano MFC sheet, or a laminate obtained by laminating one or more of these, The liquid for impregnation is sufficiently infiltrated between the fibers. This impregnation step is preferably carried out partly or entirely with the pressure changed. As a method of changing the pressure, there is a reduced pressure or an increased pressure. When the pressure is reduced or increased, it is easy to replace the air existing between the fibers with the liquid for impregnation, and bubbles can be prevented from remaining.

  As said pressure reduction conditions, 0.133 kPa (1 mmHg)-93.3 kPa (700 mmHg) are preferable. If the depressurization condition is larger than 93.3 kPa (700 mmHg), air may not be sufficiently removed, and air may remain between the fibers. On the other hand, the decompression condition may be lower than 0.133 kPa (1 mmHg), but the decompression equipment tends to be excessive.

  The treatment temperature in the impregnation step under reduced pressure is preferably 0 ° C. or higher, and more preferably 10 ° C. or higher. When this temperature is lower than 0 ° C., air may not be sufficiently removed, and air may remain between the fibers. For example, when a solvent is used for the impregnating liquid, the upper limit of the temperature is preferably the boiling point of the solvent (the boiling point under the reduced pressure condition). If the temperature is higher than this temperature, the volatilization of the solvent becomes intense, and on the contrary, there is a tendency that bubbles tend to remain.

  As said pressurization conditions, 1.1-10 MPa is preferable. If the pressure condition is lower than 1.1 MPa, air may not be sufficiently removed, and air may remain between the fibers. On the other hand, the pressurization condition may be higher than 10 MPa, but the pressurization equipment tends to be excessive.

  0-300 degreeC is preferable and the processing temperature of the impregnation process on pressurization conditions has more preferable 10-100 degreeC. When this temperature is lower than 0 ° C., air may not be sufficiently removed, and air may remain between the fibers. On the other hand, when the temperature is higher than 300 ° C., the matrix material may be denatured.

<Impregnation method using mediator solution>
As described above, the cellulose fiber aggregate obtained by removing moisture from the hydrous BC or hydrous Nano MFC fiber aggregate by cold pressing, hot pressing, drying by a dryer or the like is due to the three-dimensional cross structure of the fibers. In some cases, the impregnation liquid described above has poor permeability and cannot be efficiently impregnated.

Therefore, in the present invention, an impregnation treatment using a medium solution may be performed as follows.
That is, first, in the manufacturing process of the cellulose fiber assembly described above, the water-containing fiber assembly such as water-containing BC or water-containing Nano MFC containing water before the water removal treatment is performed, if necessary, only by cold pressing, Only a part of the water is removed to obtain a state containing some water, and the water in the water-containing fiber assembly is replaced with a mediating solution that is compatible with water and / or the liquid for impregnation described above. Thus, a fiber-reinforced composite material precursor is obtained (first step), and then the intermediate liquid in the fiber-reinforced composite material precursor is replaced with a liquid for impregnation to obtain a fiber-reinforced composite material (second step). .

  In the present invention, “compatible” means that two liquids are not separated into two layers when left in an arbitrary ratio after being mixed.

  As the mediating liquid, the water contained in the water-containing fiber assembly is replaced with the mediating liquid in the first step, and the mediating liquid contained in the fiber assembly and the impregnating liquid in the second step described later are used. In order to smoothly perform the substitution, in addition to exhibiting compatibility with each other, the medium liquid preferably has a lower boiling point than water and the liquid for impregnation, and in particular, alcohols such as methanol, ethanol, propanol, and isopropanol; Ketones such as acetone; ethers such as tetrahydrofuran and 1,4-dioxane; amides such as N, N-dimethylacetamide and N, N-dimethylformamide; carboxylic acids such as acetic acid; nitriles such as acetonitrile; and other pyridines Water-soluble organic solvents such as aromatic heterocyclic compounds are preferred. Emissions, and the like are preferable. These water-soluble organic solvents may be used alone or in combination of two or more.

  As the mediator solution, the mediator solution is compatible with both water and the liquid for impregnation, or is compatible with one of the liquids for impregnation, and further compatible with the liquid for impregnation. Depending on the type of the impregnating liquid, it may be appropriately selected and used. However, depending on the case, water, a mixture of the water-soluble solvent and water, an aqueous solution in which an inorganic compound is dissolved, or the like may be used. it can.

  There is no particular restriction on the method of replacing the water in the water-containing fiber assembly with the medium solution, but the water in the water-containing fiber assembly is mediated by immersing the water-containing fiber assembly in the medium solution and leaving it for a predetermined time. There is a method in which the water in the fiber assembly is replaced with the medium liquid by leaching to the liquid side and appropriately replacing the medium liquid containing the leached water. The temperature condition for the immersion substitution is preferably about 0 to 60 ° C. in order to prevent volatilization of the medium, and is usually performed at room temperature.

  The replacement ratio of water to the medium is most preferably 100%, but at least 10% or more of the water in the water-containing fiber assembly is preferably replaced with the medium.

  Prior to replacing the water in the water-containing fiber assembly with the medium, the water-containing fiber assembly may be cold pressed to remove a part of the water contained in the fiber assembly. It is preferable for efficient replacement with.

  The degree of this press is designed so that a fiber-reinforced composite material having the desired fiber content can be obtained with a press prior to replacement of the liquid medium for impregnation of the medium liquid in the fiber-reinforced composite material precursor described later. However, in general, it is preferable that the thickness of the hydrous fiber aggregate is approximately ½ to 1/20 of the thickness before pressing by pressing. The pressure and holding time during the cold pressing is 0.01 to 100 MPa (however, when pressing at 10 MPa or more, the fiber assembly may be broken, so pressing is performed by slowing the pressing speed or the like. ), Suitably determined in accordance with the degree of pressing in the range of 0.1 to 30 minutes, but the pressing temperature is about 0 to 60 ° C. for the same reason as the temperature condition at the time of the replacement of the water and the medium. However, it is usually carried out at room temperature. The water-containing fiber aggregate whose thickness has been reduced by this press treatment is substantially maintained even when the water and the medium are replaced. However, this press is not necessarily required, and the water-containing fiber assembly obtained in the first step may be immersed in the medium as it is to replace the water with the medium.

  In this way, a fiber reinforced composite material precursor in which the fiber assembly is impregnated with the medium solution is obtained by replacing the water in the water-containing fiber assembly with the medium solution. The fiber content of the fiber reinforced composite material precursor is 0.1% by weight or more, preferably 10 to 70% by weight, more preferably 20 to 20% by weight, although it depends on the degree of press prior to the replacement of water with the medium. About 70% by weight.

In the first step, replacement of the water-containing fiber assembly with the water medium may be performed in two or more stages. That is, in the compatibility between water and the liquid for impregnation, the compatibility with water is first medium liquid> second medium liquid, and the compatibility with liquid for impregnation is first medium liquid <first medium liquid. Two kinds of mediating liquids, ie, a first mediating liquid (for example, ethanol) and a second mediating liquid (for example, acetone) that are compatible with each other and are prepared, The water inside is replaced with the first media solution to obtain a fiber assembly in which the fiber assembly is impregnated with the first media solution, and then the fiber assembly in the fiber assembly impregnated with the first media solution is obtained. It is also possible to obtain a fiber assembly in which the first media solution is replaced with the second media solution and the fiber assembly is impregnated with the second media solution as a fiber reinforced composite material precursor. Furthermore, substitution can be performed in three or more stages using three or more kinds of mediating solutions.

The fiber reinforced composite material precursor then replaces the medium contained therein with the impregnating liquid. Here, the mediating liquid impregnated in the fiber-reinforced composite material precursor is compatible with at least the liquid for impregnation.
In this replacement, the fiber reinforced composite material precursor may be cold-pressed to remove a part of the medium in the fiber reinforced composite material precursor.

  The degree of cold pressing is appropriately determined according to the fiber content of the target fiber-reinforced composite material, but in general, the thickness of the fiber-reinforced composite material precursor is reduced by pressing to the thickness before pressing. It is preferable to be about 1/2 to 1/20. The pressure and holding time during the cold pressing is 0.01 to 100 MPa (however, when pressing at 10 MPa or more, the fiber assembly may be destroyed, so pressing is performed by slowing the pressing speed or the like. ), Is appropriately determined depending on the degree of pressing in the range of 0.1 to 30 minutes, but the pressing temperature is preferably about 0 to 60 ° C., usually room temperature. However, this press treatment is performed to adjust the fiber content of the finally obtained fiber-reinforced composite material. Therefore, when the fiber content is sufficiently adjusted by the press in the first step, This press is not necessarily required, and the fiber-reinforced composite material precursor obtained in the first step may be used as it is for the replacement of the medium solution and the liquid for impregnation.

  There is no particular limitation on the method for replacing the liquid medium in the fiber reinforced composite material precursor with the liquid for impregnation, but the method in which the fiber reinforced composite material precursor is immersed in the liquid for impregnation and maintained under reduced pressure. Is preferred. As a result, the intermediate liquid in the fiber reinforced composite material precursor is volatilized and, instead, the impregnating liquid enters the fiber assembly, so that the intermediate liquid in the fiber reinforced composite precursor is changed to the impregnating liquid. Replaced.

  Although there is no restriction | limiting in particular about this pressure reduction condition, 0.133 kPa (1 mmHg)-93.3 kPa (700 mmHg) are preferable. If the depressurization condition is larger than 93.3 kPa (700 mmHg), the removal of the medium solution may be insufficient, and the medium solution may remain between the fibers of the fiber assembly. On the other hand, the decompression condition may be lower than 0.133 kPa (1 mmHg), but the decompression equipment tends to be excessive.

  The treatment temperature in the substitution step under reduced pressure is preferably 0 ° C. or higher, more preferably 10 ° C. or higher. When this temperature is lower than 0 ° C., the removal of the medium is insufficient, and the medium may remain between the fibers. The upper limit of the temperature is preferably the boiling point of the solvent (boiling point under reduced pressure) when a solvent is used for the impregnating liquid. If the temperature is higher than this temperature, the volatilization of the solvent becomes intense, and on the contrary, there is a tendency that bubbles tend to remain.

  Further, the liquid medium for impregnation can be smoothly impregnated with the liquid medium in the fiber reinforced composite material precursor by alternately repeating the pressure reduction and the pressurization while the fiber reinforced composite material precursor is immersed in the liquid for impregnation. Can be replaced.

  The decompression condition in this case is the same as the above condition, but the pressurization condition is preferably 1.1 to 10 MPa. If the pressurization condition is lower than 1.1 MPa, the removal of the medium solution may be insufficient, and the medium solution may remain between the fibers. On the other hand, the pressurization condition may be higher than 10 MPa, but the pressurization equipment tends to be excessive.

  0-300 degreeC is preferable and the processing temperature of the impregnation process on pressurization conditions has more preferable 10-100 degreeC. When this temperature is lower than 0 ° C., the removal of the medium is insufficient, and the medium may remain between the fibers. On the other hand, when it is higher than 300 ° C., the matrix resin may be denatured.

  Most preferably, the replacement ratio of the medium in the fiber reinforced composite material precursor to the liquid for impregnation is 100%, but at least 0.2% or more of the medium in the fiber reinforced composite material precursor is impregnated. It is preferable to replace the liquid for use.

<Curing method>
In this way, after impregnating the fiber assembly with the liquid for impregnation, it is molded and cured into a predetermined shape to obtain the substrate according to the present invention. This curing method may be performed according to the curing method of the impregnating liquid used. For example, when the impregnating liquid is a fluid matrix material, a crosslinking reaction, a chain extension reaction, and the like can be given. In the case where the liquid for impregnation is a raw material for the fluid matrix material, a polymerization reaction, a crosslinking reaction, a chain extension reaction, and the like can be given.

  In addition, when the liquid for impregnation is a fluidized product obtained by fluidizing the matrix material, cooling or the like can be given. Further, when the liquid for impregnation is a fluidized product obtained by fluidizing the raw material of the matrix material, a combination of cooling and the like, a polymerization reaction, a crosslinking reaction, a chain extension reaction, and the like can be given.

  Moreover, when the liquid for impregnation is a solution of a matrix material, removal of the solvent in the solution by evaporation, air drying or the like can be mentioned. Furthermore, when the liquid for impregnation is a raw material solution of the matrix material, a combination of removal of the solvent in the solution and the like, polymerization reaction, crosslinking reaction, chain extension reaction, and the like can be mentioned. Note that the above evaporation removal includes not only evaporation removal under normal pressure but also evaporation removal under reduced pressure.

  The substrate according to the present invention is obtained by impregnating a fiber assembly with a liquid material for impregnation into a semi-cured state (hereinafter sometimes referred to as “prepreg”) as necessary. It can be easily manufactured by laminating, forming into a predetermined shape, and further curing.

  The semi-cured state of the prepreg is preferably a state in which the degree of cure (reactivity) is about 45 to 70% with respect to the completely cured state.

[Thermal conductivity of the substrate]
The substrate according to the present invention has a thermal conductivity in the thickness direction (surface thickness direction) and a thermal conductivity in the plate surface direction (in-plane direction) of 0.5 W / m · K or more, preferably 1 W / m · K or more.
As described above, an isotropic high thermal conductivity having high thermal conductivity in both the surface thickness direction and the in-plane direction can provide a wiring board excellent in heat dissipation.

  In the present invention, the thermal conductivity in the surface thickness direction and the in-plane direction of the substrate is a value measured as follows.

<Measurement method of thermal conductivity>
For the substrate according to the present invention, the thermal conductivity in the in-plane direction is measured by an optical alternating current method, and the thermal conductivity in the thickness direction is measured by a temperature wave thermal analysis method. A more specific measuring method is as described in Examples described later.

[Ingenuity to obtain isotropic high thermal conductivity]
In order for the substrate according to the present invention to obtain isotropic high thermal conductivity having high thermal conductivity in both the surface thickness direction and the in-plane direction as described above, the substrate of the present invention is manufactured by the above-described method. In this case, it is preferable to orient the above-mentioned fibers having a crystallinity of 50% or more in a random direction in the substrate by making the following measures. That is, as described above, NBC or Nano MFC obtained by repeatedly grinding or crushing bacterial cellulose or plant fiber with a grinder or the like is oriented in a random direction in the composition. It is preferable to use MFC.

[Light transmittance of substrate]
The substrate according to the present invention has a total light transmittance at a wavelength of 400 to 700 nm in terms of 50 μm thickness of 80% or more, particularly 85% or more, and the parallel light transmittance of 60% or more, particularly 65% or more, particularly 70% or more, Further, it is preferably a highly transparent substrate of 80% or more, particularly 90% or more.

  In the present invention, the total light transmittance at a wavelength of 400 to 700 nm in terms of 50 μm thickness of the substrate (hereinafter sometimes referred to as “50 μm thickness total visible light transmittance”) and parallel light transmittance (hereinafter referred to as “50 μm thickness parallel”). May be referred to as “visible light transmittance”.) Is a value measured as follows.

<Measurement method of 50 μm thickness total visible light transmittance and 50 μm thickness parallel visible light transmittance>
The average value of the total light transmittance and the parallel light transmittance (linear light transmittance) in the whole wavelength range when the substrate according to the present invention is irradiated with light having a wavelength of 400 to 700 nm in the thickness direction is 50 μm thick. Are converted to 50 μm thickness total visible light transmittance and 50 μm thickness parallel visible light transmittance, respectively.
Note that the light transmittance is determined by placing the light source and the detector through the substrate to be measured (sample substrate) and perpendicular to the substrate with air as a reference, total transmitted light, linearly transmitted light (parallel light) ) Can be obtained by measuring, and specifically, it can be measured by the measuring method described in the examples described later.

[Other physical properties of the substrate]
More preferably, the substrate according to the present invention has the following physical properties.

The linear thermal expansion coefficient is preferably 0.05 × 10 ^{−5 to} 5 × 10 ⁻⁵ K ⁻¹ , more preferably 0.2 × 10 ⁻⁵ to 2 × 10 ⁻⁵ K ⁻¹ . Particularly preferably, it is 0.3 × 10 ⁻⁵ to 1 × 10 ⁻⁵ K ⁻¹ . Although a linear thermal expansion coefficient may be smaller than 0.05 * 10 <^-5> K < ^{-1 >} , when linear thermal expansion coefficient, such as a cellulose fiber, is considered, realization may be difficult. On the other hand, when the linear thermal expansion coefficient is larger than 5 × 10 ⁻⁵ K ⁻¹ , the fiber reinforcement effect is not expressed, and due to the difference from the linear thermal expansion coefficient with glass or metal material, the deflection or In some cases, distortion may occur, and problems such as imaging performance and refractive index deviation may occur in optical components.

  The bending strength is preferably 30 MPa or more, and more preferably 100 MPa or more. If the bending strength is less than 30 MPa, sufficient strength cannot be obtained, which may affect the use in applications where force is applied. The upper limit of the bending strength is usually about 600 MPa, but it is also expected to realize a high bending strength of about 1 GPa and further about 1.5 GPa by an improved method such as adjusting the fiber orientation.

  About a bending elastic modulus, Preferably it is 0.1-100 GPa, More preferably, it is 1-40 GPa. If the flexural modulus is less than 0.1 GPa, sufficient strength cannot be obtained, which may affect use in applications where force is applied. On the other hand, a thing larger than 100 GPa is difficult to realize.

  About specific gravity, it is preferable that it is 1.0-2.5. More specifically, when the porous material is used as a matrix material, such as a silicate compound such as glass, an organic polymer other than an inorganic polymer such as a titanate compound or alumina, or a porous material even if it is an inorganic polymer, it is included in the present invention. The specific gravity of the substrate is preferably 1.0 to 1.8, more preferably 1.2 to 1.5, and still more preferably 1.3 to 1.4. The specific gravity of the matrix material other than glass is generally less than 1.6, and the specific gravity of the cellulose fibers is around 1.5. Therefore, when the specific gravity is attempted to be smaller than 1.0, the content of cellulose fibers and the like Decreases, and the strength improvement by the cellulose fiber or the like tends to be insufficient. On the other hand, if the specific gravity is larger than 1.8, the weight of the obtained wiring board is increased, and it is disadvantageous to use it for the purpose of reducing the weight as compared with the glass fiber reinforced material.

  Further, when a silicate compound such as glass, an inorganic polymer such as titanate compound or alumina (excluding a porous material) is used as a matrix material, the specific gravity of the substrate according to the present invention is 1.5 to 2.5. Preferably, 1.8 to 2.2 is more preferable. The specific gravity of the glass is generally 2.5 or more, and the specific gravity of the cellulose fiber is around 1.5. Therefore, when the specific gravity is attempted to be larger than 2.5, the content ratio of the cellulose fiber and the like is reduced. There exists a tendency for the strength improvement by a cellulose fiber etc. to become inadequate. On the other hand, if the specific gravity is less than 1.5, the filling of the gaps between the fibers may be insufficient.

[Configuration and features of wiring board]
Next, the wiring board of the present invention in which a wiring circuit is formed on the above-described board will be described.

  The wiring board of the present invention is manufactured by forming a wiring circuit on the above-described board according to a conventional method.

  For example, the wiring circuit may be formed by pressing a foil of a metal such as copper, silver, gold, aluminum, magnesium, tantalum or the like or an alloy thereof on the substrate, or forming such a metal or alloy film by vapor deposition, sputtering, or the like. This can be formed by etching into a predetermined circuit shape according to a conventional method.

  The wiring board of the present invention can be a multilayer wiring board in which a plurality of boards on which wiring circuits are formed are laminated, and a through hole can be formed in the board for conduction between the front and back surfaces of the board. .

  The substrate of the wiring board of the present invention has isotropic high thermal conductivity, and further has characteristics such as high transparency, low thermal expansion, high strength, and high elasticity. Has an effect.

(1) Since it has isotropic high thermal conductivity and is excellent in heat dissipation, it exhibits excellent heat dissipation as a wiring board for large currents used in power systems such as automotive integrated LED lighting systems. Incidentally, the thermal conductivity of the substrate according to the present invention is much higher than that of the conventional wiring board resin (generally 0.17 to 0.22 W / m · k), and is a resin with high silica filler filling. It is equivalent to a substrate.

(2) Since it is transparent, the built-in passive element can be trimmed.
Conventional substrates are opaque, and it is impossible to finely adjust (trim) the capacitance of a substrate incorporating a passive element from the outside. For this reason, it was necessary to sort non-defective / defective products once they were created. In contrast, since the substrate according to the present invention can be transparent, the position of the built-in passive element can be confirmed from the outside, and further, trimming can be performed from the outside using a laser or the like. Therefore, after the creation, fine adjustment can be made according to the characteristics, and the yield can be increased.

(3) Low thermal expansion (for example, 7 × 10 ⁻⁶ K ⁻¹ ) and suitable for a package substrate on which a chip is directly mounted.
A conventional general substrate is a combination of resin and glass cloth, and the coefficient of linear thermal expansion is about 15 × 10 ^{−6 to} 20 × 10 ⁻⁶ K ⁻¹ . On the other hand, the semiconductor chip (silicon) is 3 × 10 ⁻⁶ to 4 × 10 ⁻⁶ K ⁻¹ , and when the chip is directly mounted, an underfill agent is filled to alleviate the thermal stress due to the difference in thermal expansion coefficient. ing. On the other hand, the substrate according to the present invention has a low thermal expansion property similar to that of glass, and can have characteristics close to the thermal expansion coefficient of the chip, so there is no problem of thermal stress due to the difference in thermal expansion from the chip.

(4) High strength (for example, bending strength of about 460 MPa) and high elastic modulus (for example, bending elastic modulus of about 30 Gpa and about twice that of glass) are suitable for thin package substrates.
If the conventional substrate is thin, the rigidity is not sufficient, and the single-side molded package has a large warp, and there is a problem in reliability, etc., but the elastic modulus of the substrate according to the present invention can be very high compared to glass. Therefore, even a thin substrate has very high rigidity, and even when applied to a single-sided molded package, warpage can be very small.

[Application of wiring board]
The wiring board of the present invention is expected to be applied to the field of semiconductor mounting wiring boards, particularly flip chip type packages that will be required in the future, and passive element built-in technology fields. Useful for.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the following, methods for measuring various physical properties are as follows.

[Fiber crystallinity]
The crystallinity was defined as the ratio of the crystal scattering peak area on the X-ray diffraction diagram obtained by X-ray diffraction measurement. The manufactured fiber assembly was mounted on a sample holder, and the diffraction angle of X-ray diffraction was manipulated from 10 ° to 32 ° for measurement. After removing background scattering from the obtained X-ray diffraction pattern, the area connecting 10 °, 18.5 °, and 32 ° with a straight line on the X-ray diffraction curve becomes an amorphous part, and the other part is a crystal part. Become. The cellulose crystallinity was calculated by the following formula as a ratio of the crystal part to the area of the entire diffraction pattern.
Crystallinity = (Area of crystal part) / (Area of entire X-ray diffraction diagram) × 100 (%)

[50 μm thick total visible light transmittance]
The average value of the total light transmittance and parallel light transmittance (linear light transmittance) in the entire wavelength range when the cured product is irradiated with light having a wavelength of 400 to 700 nm in the thickness direction is converted into a thickness of 50 μm. The total visible light transmittance is 50 μm and the parallel visible light transmittance is 50 μm.
Note that the light transmittance is determined by placing the light source and the detector through the substrate to be measured (sample substrate) and perpendicular to the substrate with air as a reference, total transmitted light, linearly transmitted light (parallel light) ) Can be obtained by measuring.

[50 μm thickness parallel visible light transmittance]
<Measurement device>
Uses "UV-4100 spectrophotometer" (solid sample measurement system) manufactured by Hitachi High-Technologies Corporation.

<Measurement conditions>
-Use of a light source mask of 6 mm x 6 mm-Measured the measurement sample at a position 22 cm away from the integrating sphere opening. By placing the sample at this position, the diffuse transmitted light is removed, and only the linear transmitted light reaches the light receiving portion inside the integrating sphere.
・ No reference sample. Since there is no reference (reflection caused by the difference in refractive index between the sample and air. When Fresnel reflection occurs, the linear transmittance cannot be 100%), there is a loss of transmittance due to Fresnel reflection.
・ Scanning speed: 300nm / min
・ Light source: tungsten lamp, deuterium lamp ・ Light source switching: 340 nm

[Thermal conductivity (surface thickness direction)]
For measuring the thermal conductivity in the surface thickness direction, a probe method was adopted and a QTM-D3 rapid thermal conductivity meter manufactured by Kyoto Electronics Industry Co., Ltd. was used. Three types of standard plates: 150 mm long x 60 mm wide x 20 mm thick silicon rubber (thermal conductivity 0.239 W / mK), quartz glass (1.416 W / mK) and zirconia (3.35 W / mK) Using. The sample size was 100 mm in length, 60 mm in width, and 0.5, 1, and 1.5 mm in thickness (3 types). A sample (laminated plate or Macor) was placed in close contact with a standard plate, and a probe was placed on the sample to measure the thermal conductivity. Plot the thermal conductivity of the standard plate on the horizontal axis and the deviation (= {(measured value)-(thermal conductivity of the standard plate)} / (thermal conductivity of the standard plate)) on the vertical axis. The thermal conductivity when the deviation in the approximate curve becomes 0 was obtained by interpolation, and was defined as the thermal conductivity in the surface thickness direction of the laminate.

[Thermal conductivity (in-plane direction)]
For measuring the thermal conductivity in the in-plane direction, the Xe flash method was adopted, and a Nanoflash LFA447 flash method thermal diffusivity measuring device manufactured by Bruker-axs (manufacturer NETZSCH) was used. Note that this method can measure not only in-plane but also thermal conductivity in the thickness direction depending on the sample placement method. Both sides of a sample with a thickness of 1 to 3 mm cut into 10 mm squares were blackened with graphite spray, fixed to a standard holder, and the thermal diffusivity in the thickness direction was measured. The sample thickness was 0.8 to 1 mm for the laminate, 1 to 3 mm for Macor, and 1 mm for the resin / ceramic molding. The in-plane direction of the laminate was evaluated using a layered sample holder (lamella holder). Samples having a width of 13 mm were cut into strips having a constant width (about 1.2 mm), and aligned and fixed on the holder while being rotated by 90 °. Pulse light irradiation was performed under the conditions of a pulse width of 0.2 ms and an applied voltage of 202V. All measurements were performed at a set ambient temperature of 25 ° C. The thermal conductivity was calculated from the obtained thermal diffusivity, specific heat, and density.

[Fiber content]
It calculated | required from the weight of the manufactured fiber reinforced composite resin board | substrate, and the weight of the fiber assembly used for manufacture of this fiber reinforced composite resin board | substrate.

Example 1: Substrate made of BC-containing fiber-reinforced composite resin First, a culture solution was added to a strain (FF-88) of acetic acid bacteria in a freeze-dried storage state, followed by static culture for one week (25-30 ° C). Among the bacterial celluloses produced on the surface of the culture solution, those having a relatively large thickness were selected, and a small amount of the culture solution of the strain was taken and added to a new culture solution. And this culture solution was put into the large incubator, and the static culture was performed at 25-30 degreeC for 7-30 days. The culture broth contained 2% glucose, 0.5% by weight Bacto yeast extract, 0.5% by weight Bacto peptone, 0.27% by weight disodium hydrogen phosphate, 0.115% by weight citric acid, 7 mg magnesium sulfate An aqueous solution (SH medium) having a hydrate content of 0.1% by weight and adjusted to pH 5.0 with hydrochloric acid was used.

  The bacterial cellulose thus produced is taken out from the culture solution and boiled in a 2% by weight alkaline aqueous solution for 2 hours, and then the bacterial cellulose is taken out from the alkaline treatment solution, sufficiently washed with water, and the alkaline treatment solution is removed. Bacteria in bacterial cellulose were dissolved and removed. Subsequently, the obtained water-containing bacterial cellulose (bacterial cellulose having a water content of 95 to 99% by weight) was hot-pressed at 120 ° C. and 2 MPa for 3 minutes to obtain a BC sheet (water content 0% by weight) having a thickness of about 50 μm. It was. The physical properties and the like of this BC sheet are as shown in Table 1 below. The crystallinity was as shown in Table 2.

  This BC sheet is immersed in a transparent epoxy resin (“Celloside 2021” manufactured by Daicel Chemical Industries, Ltd.) under reduced pressure (0.08 MPa) for 12 hours to produce a fiber-reinforced composite material in which BC is randomly oriented in the composition. did. The fiber content of this fiber reinforced composite material was as shown in Table 2.

  Further, this fiber reinforced composite resin material was cured in accordance with a curing method of a liquid precursor of a matrix resin to prepare a sample having a diameter of 50 mm and a thickness of 10 mm, and then cut into a plate shape for measurement. Thick total visible light transmittance, 50 μm thick parallel visible light transmittance, and thermal conductivity were measured, and the results are shown in Table 2.

Example 2: Substrate made of pulp-derived Nano MFC-containing fiber reinforced composite resin Microfibrillated cellulose: MFC (microfibrillated softwood kraft pulp (NBKP) by high-pressure homogenizer treatment, average fiber diameter of 1 μm) sufficiently in water Stir to prepare 7 kg of a 1% by weight aqueous suspension and use a grinder (“Pure Fine Mill KMG1-10” manufactured by Kurita Kikai Co., Ltd.) at 1200 rpm in a state where the aqueous suspension is almost in contact. The operation of passing between the rotating discs from the center toward the outside was performed 30 times (30 passes).

  Nano MFC (average fiber diameter 60 nm) obtained by the grinder treatment was prepared in a 0.2 wt% water suspension, and then filtered through a glass filter to form a film. This was dried at 55 ° C. to obtain a Nano MFC sheet having a fiber content of about 70% and a thickness of 43 μm. The crystallinity of the Nano MFC was as shown in Table 2.

  This Nano MFC sheet was impregnated with an epoxy resin in the same manner as in Example 1 to produce a fiber reinforced composite material in which NaNO MFC was randomly oriented in the composition. In the same manner as in Example 1, this fiber reinforced composite material was produced. Was cured to produce a substrate. The fiber reinforced composite material and the substrate were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Example 3: Cotton-derived Nano MFC-containing fiber reinforced composite material A Nano MFC sheet was produced in the same manner as in Example 2 except that cotton (absorbent cotton) was used instead of pulp. The crystallinity of the Nano MFC was as shown in Table 2. This Nano MFC sheet was impregnated with an epoxy resin in the same manner as in Example 1 to produce a fiber reinforced composite material in which NaNO MFC was randomly oriented in the composition. The material was cured to produce a substrate. The fiber reinforced composite material and the substrate were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 1
The cured epoxy resin was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 2
The inorganic glass was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

Comparative Example 3
A BC sheet was produced in which bacterial cellulose was not oriented randomly but oriented in the plane direction. The crystallinity of this BC was as shown in Table 2. This BC was impregnated with an epoxy resin in the same manner as in Example 1 to produce a fiber-reinforced composite material in which NaNO MFC was randomly oriented in the composition, and the fiber-reinforced composite material was cured in the same manner as in Example 1. The substrate was manufactured. The fiber reinforced composite material and the substrate were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

  From Table 2, it can be seen that according to the present invention, a wiring board having isotropic high thermal conductivity and excellent heat dissipation is provided.

Example 4: Multilayer wiring board In this example, a multilayer wiring board was prepared. Hereinafter, a description will be given with reference to FIG.
-Preparation of microfibrillated cellulose (FMC) prepreg Dispersed chops (average fiber length 2 mm) of microfibrillated cellulose (average fiber diameter 20 nm) treated with a grinder and randomly deflated in water at a rate of 5% by weight, The dispersion was suction filtered, ethanol was poured into the dispersion, and the process of re-stirring with a mixer was repeated three times. Fibers that have been defibrated by re-stirring with a mixer are maintained in the dispersion medium in a random state, and become a non-oriented, random nonwoven fabric. Subsequently, the step of injecting an epoxy resin varnish in place of ethanol was repeated three times in the same manner, and finally, press-compressed to a thickness of 200 μm with a press to obtain a prepreg.

  The epoxy resin varnish is 11.4 parts by weight of metaphenylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.) as a curing agent with respect to 100 parts by weight of a bisphenol A type epoxy resin (“Epicoat 828” manufactured by Yuka Shell), a curing accelerator. It was obtained by dissolving 0.2 parts by weight of 1-cyanoethyl-2-ethyl-4-methylimidazole (“2E4MZ · CN” manufactured by Shikoku Kasei Co., Ltd.) in methyl ethyl ketone. The solid content concentration of the varnish was 50% by weight.

  A sample in which the nonwoven fabric was impregnated with an epoxy resin varnish was dried at 110 ° C. for 5 minutes and then at 120 ° C. for 5 minutes to remove the solvent and obtain the final prepreg 1. The resin content impregnated was 56% by weight of the whole prepreg.

-Production of copper-clad laminate By installing copper foil 2 (manufactured by Nippon Electrolytic Co., Ltd., 18 μm thickness) on both sides of the prepreg 1 obtained above and thermocompression bonding with a press, as shown in FIG. A copper-clad laminate 3 shown in FIG. The pressing conditions were a pressure of 30 kgf / cm ² , a temperature was raised from room temperature to 170 ° C. at 10 ° C./min, and pressure bonding was further performed at 170 ° C. for 60 minutes.

-Production of inner layer wiring board In order to establish electrical continuity between the upper and lower sides of the board, as shown in FIG. 1 (c), a hole 3A is formed in a predetermined portion of the copper clad laminate 3 obtained as described above. As shown in (d), the inner wall portion of the hole 3A was plated to form a through hole 3B. Furthermore, a predetermined wiring circuit was formed on the conductor portions on both sides by resist exposure development and etching processes to obtain an inner layer double-sided wiring board 4 shown in FIG.

Production of multilayer wiring board As shown in FIGS. 1 (f) and (g), a plurality of inner wiring boards 4 produced in the above (three in this case) and two outermost copper foils 2 are used. The multilayer board 5 was formed by thermocompression using a press using the prepreg 1 as an adhesive layer. The pressing conditions were a pressure of 15 kgf / cm ² , a temperature was raised from room temperature to 170 ° C. at 10 ° C./min, and pressure bonding was further performed at 170 ° C. for 60 minutes. In order to establish electrical connection between the respective layers of the obtained multilayer board 5, as shown in FIGS. 1 (h) and (i), a through hole 5A is formed in a predetermined portion, and the inner wall portion of the hole 5A is further plated. Hole 5B was formed. Further, a predetermined wiring circuit was formed on the conductor portion of the outermost layer by a resist exposure development and etching process, and finally a multilayer wiring board 6 shown in FIG. 1 (j) was obtained.

The obtained multilayer wiring board 6 was transparent at all portions of the insulating layer, and all the wiring circuits formed from the internal copper conductor could be confirmed from the appearance.
The characteristics of the multilayer wiring board of this example were room temperature strength 500 MPa, room temperature elasticity 30 GPa, and coefficient of thermal expansion 8 ppm / K.

Example 5: Multi-layer wiring board with built-in capacitor In this example, a multi-layer wiring board with a built-in capacitor was manufactured. Hereinafter, a description will be given with reference to FIG.
Production of the microfibrillated cellulose prepreg 1, the copper clad laminate 3, and the double-sided wiring board 4 for the inner layer was carried out in the same manner as in Example 4.

-Production of inner layer substrate for built-in capacitor In order to form a built-in capacitor, an inner layer wiring substrate using a high dielectric constant resin for the insulating layer was produced separately from the above substrate.
The high dielectric constant resin varnish is 60 parts by weight of barium titanate (manufactured by Toho Titanium Co., Ltd., average particle size 0.2 μm) and bisphenol A type epoxy resin used in Example 4 (“Epicoat 828” manufactured by Yuka Shell Co., Ltd.). ) 40 parts by weight, 4.6 parts by weight of metaphenylenediamine (manufactured by Wako Pure Chemical Industries, Ltd.) as a curing agent, and 1-cyanoethyl-2-ethyl-4-methylimidazole (“2E4MZ · CN”, manufactured by Shikoku Kasei Co., Ltd.) as a curing accelerator ) It was obtained by dissolving 0.08 parts by weight in methyl ethyl ketone. The varnish concentration was 80% by weight of solid content.

  As shown in FIGS. 2 (a) and 2 (b), the obtained varnish 7 was coated on one side of a copper foil 2 (manufactured by Nippon Electrolytic Co., Ltd., 18 μm thick) with an average thickness of 28 μm, and then at 80 ° C. for 10 minutes. The solvent was removed by hot air drying. As shown in FIGS. 2 (c) and 2 (d), another copper foil (manufactured by Nihon Electrolytic Co., Ltd., 18 μm thickness) is further stacked on the varnish coated surface, and heat-pressed with a press in the same manner as a normal copper-clad laminate. Thus, a double-sided copper-clad substrate 9 in which the copper foil 2 was formed on both sides of the dielectric 8 was obtained. Pressing was performed by controlling the thickness and pressing, the temperature was raised from room temperature to 170 ° C. at 10 ° C./min, and further pressure-bonded at 170 ° C. for 60 minutes. The thickness was 20 μm. The capacity of the built-in capacitor is determined by the area of the electrode formed by the double-sided copper foil. A wiring circuit pattern was formed by a resist exposure development and etching process, and an internal capacitor internal layer substrate 10 shown in FIG.

Production of multilayer wiring board As shown in FIGS. 2 (f) and 2 (g), two inner wiring boards 4, two inner capacitor inner boards 10 and two outermost copper foils 2 are used. Then, a multilayer board was formed by thermocompression using a press using the prepreg 1 as an adhesive layer. The pressing conditions were a pressure of 15 kgf / cm ² , a temperature was raised from room temperature to 170 ° C. at 10 ° C./min, and pressure bonding was further performed at 170 ° C. for 60 minutes. As shown in FIGS. 2 (h) and 2 (i), in order to establish electrical connection between the respective layers of the obtained multilayer board 11, a through hole 11A is formed in a predetermined portion, and the inner wall portion of the hole 11A is plated to make a through-hole. Hole 11B was formed. Further, a predetermined wiring circuit was formed on the conductor portion of the outermost layer by resist exposure development and etching processes, and finally a multilayer wiring board 12 incorporating a capacitor shown in FIG.

In the multilayer wiring board 12 with a built-in capacitor according to the present embodiment, the capacitor formed inside can also be confirmed from the appearance. Therefore, as shown in FIG. 2 (k), after mounting the component 13 on the multilayer wiring board 12 with a built-in capacitor, the internal capacitor can be easily trimmed with a laser or the like by checking the characteristics. Further, since the shape and position of the inductor as well as the capacitor can be confirmed from the outside, trimming can be easily performed with a laser or the like.
The characteristics of the multilayer wiring board with a built-in capacitor of this example were room temperature strength of 400 MPa, room temperature elasticity of 25 GPc, and a thermal expansion coefficient of 9 ppm / K.

  The multilayer wiring boards produced in Examples 4 and 5 have excellent thermal conductivity not only in the in-plane direction but also in the surface pressure direction because the substrate material in which the fibers are randomly oriented in the matrix material is used. Excellent heat dissipation. Moreover, it turns out that the obtained board | substrate is high intensity | strength and a high elasticity modulus, and is excellent in a mechanical characteristic. When the elastic modulus of the substrate is low, if the substrate is made thin, deflection is likely to occur during the package manufacturing process or component mounting, and workability and reliability are significantly reduced. On the other hand, when the elastic modulus is high as in the present embodiment, the amount of flexure is small even if it is thin, contributing to high-density mounting and cost reduction. Further, not only double-sided mounting but also single-sided mounting, in the case of high elastic modulus, it is possible to take various mounting forms with less warping. In addition, a substrate having high strength characteristics can be equipped with a large number of components, and further, it is possible to prevent the occurrence of defects such as cracks in various reliability tests such as temperature cycling, thermal shock, and high temperature storage. As described above, the substrate obtained in this example is suitable for a thin package substrate, and high-density mounting is possible.

A conventional general substrate is a combination of resin and glass cloth, and has a thermal expansion coefficient of about 15 to 20 ppm / K. On the other hand, the semiconductor chip (silicon) is 3 to 4 ppm / K, and when the chip is directly mounted, an underfill agent is generally filled in order to relieve the thermal stress due to the mismatch of the thermal expansion coefficient.
Since the thermal expansion coefficient of the substrate obtained in this example is 10 ppm / K or less as described above, the thermal expansion coefficient of the substrate is closer to that of the chip, and thermal stress can be reduced. High reliability can be realized. In some cases, the underfill agent can be removed, and the cost can be further reduced.

FIG. 10 is a process diagram showing a manufacturing procedure of the multilayer wiring board in Example 4; FIG. 11 is a process diagram showing a manufacturing procedure of the capacitor built-in multilayer wiring board in Example 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Prepreb 2 Copper foil 3 Copper clad laminated board 4 Double-sided wiring board for inner layers 5 Multilayer board 6 Multilayer wiring board 7 Varnish 8 Dielectric 9 Double-sided copper-clad board 10 Inner layer board for built-in capacitor 11 Multilayer board 12 Multilayer wiring board 13 Parts

Claims (16)

In a wiring board having a substrate made of a fiber-reinforced composite material containing fibers and a matrix material,
The fibers are fibers having a crystallinity of 50% or more;
A wiring board characterized in that the thermal conductivity in the thickness direction and the thermal conductivity in the plate surface direction of the board are both 0.5 W / m · k or more.   2. The wiring board according to claim 1, wherein the fiber is a fiber having an average fiber diameter of 4 to 200 nm.   3. The wiring board according to claim 1, wherein the fiber is a cellulose fiber.   4. The wiring board according to claim 3, wherein the cellulose fiber is bacterial cellulose.   4. The wiring board according to claim 3, wherein the cellulose fibers are separated from plant fibers.   6. The wiring board according to claim 5, wherein the cellulose fiber is obtained by further grinding a microfibrillated cellulose fiber.   The wiring board according to any one of claims 1 to 6, wherein the fibers are randomly oriented in the substrate.   8. The wiring board according to claim 1, wherein the fiber content in the fiber-reinforced composite material is 10% by weight or more.   9. The wiring board according to claim 1, wherein the total light transmittance at a wavelength of 400 to 700 nm in terms of a thickness of 50 μm of the substrate is 80% or more.   The wiring board according to claim 9, wherein the parallel light transmittance of the board in terms of a thickness of 50 μm is 60% or more.   11. The wiring board according to claim 1, wherein the matrix material is an organic polymer, an inorganic polymer, or a hybrid polymer of an organic polymer and an inorganic polymer.   The wiring board according to claim 11, wherein the matrix material is a synthetic polymer.   The matrix material according to claim 12, wherein the matrix material is acrylic resin, methacrylic resin, epoxy resin, urethane resin, phenol resin, melamine resin, novolac resin, urea resin, guanamine resin, alkyd resin, unsaturated polyester resin, vinyl ester resin, diallyl. Wiring characterized by being one or more selected from the group consisting of phthalate resin, silicone resin, furan resin, ketone resin, xylene resin, thermosetting polyimide resin, styrylpyridine resin, and triazine resin substrate.   14. The wiring board according to claim 1, comprising the board and a wiring circuit formed on the board.   The wiring board according to claim 14, wherein the board contains a passive element.   15. The wiring board according to claim 14, wherein a semiconductor chip is mounted on the substrate.

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