JPWO2001019145A1 - PCB for wiring board - Google Patents

Abstract

(57) [Abstract] The present invention provides a metal-clad laminate that provides a printed wiring board having excellent thermal conductivity and the ability to rapidly dissipate generated heat, and a wiring board substrate having the same properties, in which a lead frame is laminated on the substrate. To achieve this, a wiring board substrate is constructed by laminating a metal foil (3) or a lead frame via an insulating adhesive layer (2) on a carbonaceous substrate (1) made of a carbonaceous material. When the metal foil (3) is laminated, the wiring board substrate takes the form of a metal-clad laminate, and when the lead frame is laminated, the wiring board substrate takes the form of a wiring board substrate in which the lead frame is laminated on the substrate.

Description

Detailed Description of the Invention

TECHNICAL FIELD The present invention relates to a substrate for a wiring board. More specifically, the present invention relates to a metal-clad laminate plate on which a metal foil is laminated to be used as a substrate for a printed wiring board, or a substrate for a wiring board in which a lead frame is laminated on a substrate, and even more specifically, to the above-mentioned substrates which are made of a plate made of a carbonaceous material and have excellent thermal conductivity. BACKGROUND ART Conventionally, a so-called metal-clad laminate plate in which a metal foil such as copper foil is laminated on a substrate has generally been used,
A wiring pattern is then drawn on the metal-clad laminate using a photoresist, and etching or the like is performed in accordance with the wiring pattern. This photolithography technique produces printed wiring boards with printed wiring formed thereon, which are used as wiring boards for various electrical and electronic devices. The formation of printed wiring using this metal-clad laminate is suitable for microfabrication, making it possible to easily form extremely fine wiring patterns, thereby producing printed wiring boards with extremely fine wiring patterns. Conventional metal-clad laminates generally use substrates made of synthetic resins, such as phenolic resins, as substrates. Conventionally, wiring board substrates in which a so-called lead frame, produced by punching a wiring pattern from a metal plate such as a copper plate, is laminated on a substrate have generally been used as wiring boards for various electrical and electronic devices. A wiring board substrate (hereinafter referred to as a "leadframe laminate substrate") laminated with such a lead frame is inferior in the fine patterning capability compared to a printed wiring board manufactured from the metal-clad laminate. However, the manufacturing process is simple, allowing the wiring board substrate to be manufactured at low cost. Furthermore, by using a lead frame with an appropriate thickness, it can handle large currents and easily manufacture a wiring board substrate with reduced resistance loss. The leadframe laminate substrate and the printed wiring board made from the metal-clad laminate are used in accordance with their respective advantages and disadvantages, the various requirements for the intended wiring board substrate, and the various requirements for the electrical and electronic devices to which they are applied. Conventional leadframe laminate substrates generally use substrates made of synthetic resins, such as phenolic resins. Generally, circuits using printed wiring boards or leadframe laminate substrates may generate heat, depending on the type of circuit-forming elements mounted thereon.
If heat accumulates and the temperature of the circuit rises, unexpected failures may occur, so it is necessary to quickly dissipate the generated heat. However, both printed wiring boards manufactured from metal-clad laminates using conventional synthetic resin substrates and lead frame laminates using conventional synthetic resin substrates have the problem that the thermal conductivity of the synthetic resin substrates is poor, making it difficult to meet the need for rapid dissipation of the generated heat. In view of the above-mentioned conventional situation, it is an object of the present invention to provide a metal-clad laminate that provides a printed wiring board with excellent thermal conductivity and capable of quickly dissipating generated heat, and a lead frame laminate that similarly has excellent thermal conductivity and can quickly dissipate generated heat. Disclosure of the Invention As a result of intensive research to achieve the above-mentioned object of the present invention, the present inventors have found that, when constructing a metal-clad laminate that provides a printed wiring board or a lead frame laminate, a carbonaceous substrate made of a carbonaceous material with excellent thermal conductivity is used as the substrate,
The present inventors have also found that the above-mentioned object of the present invention can be achieved by using an adhesive layer that can firmly adhere to the carbonaceous substrate and has insulating properties for bonding to the metal foil or lead frame to be laminated thereon, and have completed the present invention. That is, in order to achieve the above-mentioned object of the present invention, the present invention provides a wiring board substrate characterized in that a metal foil or lead frame is laminated to a carbonaceous substrate made of a carbonaceous material via an insulating adhesive layer. Best Mode for Carrying Out the Invention The wiring board substrate of the present invention takes the form of a metal-clad laminate when a metal foil is laminated thereon, and takes the form of a leadframe laminated substrate when a leadframe is laminated thereon. The carbonaceous substrate used in the wiring board substrate of the present invention in the form of a metal-clad laminate or leadframe laminated substrate is generally a plate-like object made of a carbonaceous material, such as a carbon fiber-reinforced carbon composite material having carbon fiber as a reinforcing material and carbon as a matrix, or an isotropic high-density carbon material. The thickness of this carbonaceous substrate is set appropriately taking into consideration the fact that a too thin substrate results in a decrease in the strength of the substrate, while a too thick substrate leads to an increase in weight and cost. Generally, a thickness of 0.3 to 5 mm is appropriate. As the carbon fiber reinforced carbon composite material used for the carbonaceous substrate, various conventionally known carbon fiber reinforced carbon composite materials can be appropriately selected and used. Carbon fiber reinforced carbon composite materials generally have various carbon fiber arrangements, such as primary orientation in which carbon fibers are aligned in one direction and bundled together, plain weave, twill weave, and so on.
Examples of carbon fiber reinforced carbon composites include those with secondary orientations such as woven fabrics (e.g., satin weave), those with tertiary orientations (e.g., three-dimensional weaving), and those using carbon fibers in the form of felt or short fibers. In the present invention, various carbon fiber arrangements can be appropriately selected and used. Carbon fiber reinforced carbon composite materials are generally produced by impregnating carbon fiber aggregates with the above-described various orientations with a matrix material, such as a thermosetting synthetic resin (e.g., phenolic resin) or a pitch (e.g., petroleum pitch), to prepare a prepreg. Multiple such prepregs are then laminated as needed, heated under pressure to cure the matrix material, and then fired at high temperatures in an inert atmosphere to carbonize the matrix material. When the carbon fibers are short fibers, the carbon fiber reinforced carbon composite material is generally produced by mixing short carbon fibers with the matrix material, molding the mixture into a predetermined shape, heating the molded product under pressure to cure the matrix material, and then firing at high temperatures in an inert atmosphere to carbonize the matrix material.
The carbon fiber reinforced carbon composite material used for the carbonaceous substrate may be manufactured in the shape of a plate having a predetermined thickness as a carbonaceous substrate, or may be cut out from a block of carbon fiber reinforced carbon composite material by cutting it into a plate having a predetermined thickness as a carbonaceous substrate. The carbon fibers and carbon matrix constituting the various carbon fiber reinforced carbon composite materials may be graphitized. Among the various carbon fiber reinforced carbon composite materials, a plate-like product in which carbon fibers are aligned in the thickness direction in a carbon matrix, such as a block of carbon fiber reinforced carbon composite material with a primary orientation in which the carbon fibers are aligned in one direction, is cut into a plate having a predetermined thickness in a direction perpendicular to the alignment direction of the carbon fibers.
Since it has excellent thermal conductivity, particularly in the thickness direction, it is preferably used as a carbonaceous substrate. Cutting out a plate-shaped object from the block of the carbon fiber reinforced carbon composite material can be performed by a known cutting means such as a wire saw or a rotary diamond saw. A cross section of an example of a metal-clad laminate, which is one form of the wiring board substrate of the present invention, is shown in FIG. 1 when the plate-shaped carbon fiber reinforced carbon composite material having carbon fibers arranged in the thickness direction is used as the carbonaceous substrate. In the example of the metal-clad laminate form of FIG. 1, an insulating adhesive layer 2 and a metal foil layer 3 are sequentially provided on each side of a carbonaceous substrate 1 having carbon fibers 1b arranged in the thickness direction in a carbon matrix 1a. In the wiring board substrate of the present invention in the form of a metal-clad laminate,
The metal foil can be provided on both sides of the carbonaceous substrate as in the example of Figure 1, or on only one side. Figures 2 to 4 show schematic cross sections of an example of a leadframe laminate substrate, which is another form of the wiring board substrate of the present invention when a plate-like material such as the one described above is used as the carbonaceous substrate. In the example of the leadframe laminate substrate form of Figures 2 to 4, an insulating adhesive layer 2 and a leadframe layer 4 are sequentially provided on one side of a carbonaceous substrate 1 formed by arranging carbon fibers 1b in the thickness direction in a carbon matrix 1a. In the wiring board substrate of the present invention in the form of a leadframe laminate substrate, the leadframe layer 4 can be provided on only one side of the carbonaceous substrate 1 as in the examples of Figures 2 to 4, or on both sides. The insulating adhesive layer 2 may be provided only between the lead frame layer 4 and the carbonaceous substrate 1 as shown in FIG. 2, or may be provided so as to cover the surface of the carbonaceous substrate 1 as shown in FIG. 3, or may be provided so as to sink the lead frame layer 4 into the insulating adhesive layer 2 so that the surfaces of the lead frame layer 4 and the insulating adhesive layer 2 are in contact with each other as shown in FIG.
The lead frame layer 4 may be provided so as to be flat in the gaps between the wiring patterns. When an isotropic high-density carbon material is used as the carbonaceous substrate, various conventionally known isotropic high-density carbon materials may be appropriately selected and used. Isotropic high-density carbon materials are generally produced by pressing fine particles of sinterable graphite precursor such as raw coke or mesocarbon microbeads while firing them at high temperatures.
Alternatively, they are produced by mixing graphite particles or carbon whisker powder with a binder made of a carbon precursor such as pitch or synthetic resin, followed by pressure molding and sintering. The isotropic high-density carbon material used for the carbonaceous substrate may be manufactured into a plate shape of a predetermined thickness for the carbonaceous substrate, or may be cut from a block of isotropic high-density carbon material manufactured into a plate shape of a predetermined thickness for the carbonaceous substrate. The various isotropic high-density carbon materials may also be graphitized. The carbon fiber-reinforced carbon composite materials and isotropic high-density carbon materials generally have micropores derived from their manufacturing process and are porous. Impregnating the micropores of these materials with an inorganic coating agent or metal to render them non-porous further improves the thermal conductivity of the material. Therefore, in the present invention, the micropores of the above carbonaceous materials can be impregnated with an inorganic coating agent or metal and used as a carbonaceous substrate, as needed. This is preferable from the viewpoint of further improving the thermal conductivity of the substrate. The inorganic coating agent to be impregnated into each of the carbonaceous materials can be appropriately selected from various inorganic coating agents that are liquid and can be impregnated into the micropores of the carbonaceous material and harden to form an inorganic cured product that makes the carbonaceous material non-porous after impregnation. Examples include inorganic silicon-containing polymers that undergo a crosslinking reaction at room temperature or under heat to form a ceramic-like cured product, cements such as alumina cement, and inorganic binders containing water glass. These inorganic coating agents can be diluted with an organic solvent to enhance their impregnation properties. Further, more specific examples of the inorganic coating agent include the HEATLESSGLASS GA series (product name: manufactured by Homer Technology) that forms a silicon-containing polymer, Tonen Polysilazane (product name: manufactured by Tonen Corporation) which is a polysilazanes, and the Redproof MR-100 series (product name: manufactured by Nekken Co., Ltd.) which is an inorganic binder. Methods for impregnating the inorganic coating agent into the micropores of a carbonaceous material include a method of applying the inorganic coating agent to the carbonaceous material with a brush or the like, a method of immersing the carbonaceous material in the inorganic coating agent, a method of forcing the inorganic coating agent into the carbonaceous material at high pressure, and a method of sucking the inorganic coating agent into the carbonaceous material at high vacuum. The inorganic coating agent impregnated into the carbonaceous material is cured. At this time, the curing conditions for the inorganic coating agent can be appropriately set depending on the type of inorganic coating agent used. For example, when the inorganic coating agent is HEATLESS GL
In the case of ASS, it is generally appropriate to heat at about 130°C for 60 minutes. The metals to be impregnated into the above carbonaceous materials are generally aluminum, copper,
As a method for impregnating the micropores of the carbonaceous material with a metal, a method of impregnating a metal such as molten aluminum or copper under high temperature and pressure can be used. As an example of the carbonaceous material impregnated with aluminum, CC-
Examples of suitable carbonaceous materials include MA (trade name: C/C composite base with linearly aligned carbon fibers, manufactured by Advanced Materials Co., Ltd.) and C-MA (trade name: isotropic high-density carbon material base, manufactured by Advanced Materials Co., Ltd.), and examples of carbonaceous materials impregnated with copper include MB-18 (trade name: C/C composite base with linearly aligned carbon fibers, manufactured by Mobius A.T. Co., Ltd.) When the wiring board substrate of the present invention is in the form of a metal-clad laminate, the metal foil used can be appropriately selected from various metal foils conventionally known for use in producing metal-clad laminates, and generally, copper or nickel foil is preferably used.
The metal foil can be provided on both sides of the carbonaceous substrate as described above, or on only one side, as required. Furthermore, as the lead frame used when the wiring board substrate of the present invention is in the form of a lead frame laminated substrate, various lead frames conventionally known for use in wiring board manufacture, which are prepared by punching a desired wiring pattern from a metal plate, can be appropriately selected and used, and generally, copper or nickel lead frames are preferably used. The lead frame is:
[0023] As described above, the insulating adhesive layer may be provided on both sides of the carbonaceous substrate, or on only one side, as required. Next, the insulating adhesive layer will be described. In the wiring board substrate of the present invention, the insulating adhesive layer that bonds the carbonaceous substrate made of the carbonaceous material to the metal foil or lead frame can be formed using an appropriate selection of various adhesives, etc., as long as it is thin but has sufficient insulation properties and can sufficiently firmly bond the carbonaceous substrate made of the carbonaceous material to the metal foil or lead frame. However, carbonaceous materials generally have relatively poor compatibility with many adhesives and have very poor adhesion.
Therefore, by adopting as the insulating adhesive layer (i) a layer composed of a polyimide coating film provided on a carbonaceous substrate and an adhesive layer provided on the polyimide coating film, or (ii) a layer composed of a polyimide vapor deposition polymerization layer provided on a carbonaceous substrate and an adhesive layer provided on the polyimide vapor deposition polymerization layer, or (iii) a layer composed of a polyimide layer having adhesive properties provided on a carbonaceous substrate, or (iv) a layer composed of a metal plating layer provided on a carbonaceous substrate and an adhesive layer provided on the metal plating layer, or (e) a layer composed of a primer layer provided on a carbonaceous substrate and an elastomer-based adhesive layer provided on the primer layer, it is possible to obtain a wiring board substrate that is practical in terms of insulation and adhesion between the carbonaceous substrate and the metal foil or lead frame. That is, only when a base such as a polyimide coating film, polyimide vapor-deposition polymerization layer, metal plating layer, or primer layer is pre-formed, or when a polyimide layer having adhesive properties is selected as the insulating adhesive layer, can a carbonaceous material be bonded to a metal foil or lead frame with sufficient strength for practical use. Furthermore, the insulating adhesive layer is generally preferably thin so as not to impair thermal conductivity in the thickness direction of the intended wiring board substrate. First, the above-mentioned form (a) will be explained. When forming the insulating adhesive layer of the above-mentioned form (a), the polyimide coating film can be formed by applying various conventional polyimide coating materials to the carbonaceous substrate. While both polyimide acid dissolved in a solvent and polyimide resin dissolved in a solvent are applicable as polyimide coating materials, the latter are preferred because they do not require a dehydration imidization process by heating and can produce a coating film with excellent insulating properties at relatively low temperatures. Examples of such coating materials include Rikacoat (trade name: manufactured by New Japan Chemical Co., Ltd.) and Upilex S (trade name: manufactured by Ube Industries, Ltd.). In addition, various additives can be added to the polyimide coating to improve the insulation properties and coating film stability. Then, a metal foil or lead frame is laminated onto the polyimide coating film provided on the carbonaceous substrate via an adhesive layer, and then the polyimide coating film is pressure-bonded under heat or at room temperature, thereby sufficiently firmly bonding the metal foil or lead frame to the carbonaceous substrate to form the desired wiring board substrate. The bonding process conditions can be appropriately set depending on the type of polyimide coating film used, etc. FIG. 5 shows a schematic cross-section of an example of a wiring board substrate of the present invention in the form of a metal-clad laminate employing the insulating adhesive layer (a). In the example of the metal-clad laminate shown in FIG. 5, an insulating adhesive layer 22 consisting of a polyimide coating film 22a and an adhesive layer 22b, and a metal foil layer 23 are sequentially provided on both sides of a carbonaceous substrate 21, respectively, to form a wiring board substrate in the form of a metal-clad laminate. A particularly preferred form of the polyimide coating film in the insulating adhesive layer (a) above is a polyimide electrodeposition coating film. Polyimide electrodeposition coatings can be formed from various polyimide electrodeposition paints, each containing a polyimide resin and a cationic solution as the medium. Various additives can be added to the polyimide electrodeposition paint to improve the insulating properties and coating film stability. Polyimide electrodeposition coatings can be obtained by electrodeposition coating the polyimide electrodeposition paint onto a carbonaceous substrate. The electrodeposition coating method can be appropriately selected and adopted from conventionally known methods. A metal foil or lead frame is further laminated onto the polyimide electrodeposition coating formed by electrodeposition coating via an adhesive layer, and then the laminate is pressure-bonded under heat or at room temperature, thereby sufficiently firmly bonding the metal foil or lead frame to the carbonaceous substrate to form the desired wiring board substrate. The bonding conditions can be appropriately set depending on the type of polyimide electrodeposition paint used. Figure 6 shows a schematic cross-section of an example of a wiring board substrate of the present invention in the form of a metal-clad laminate, in which a polyimide electrodeposition coating is used as the polyimide coating in the insulating adhesive layer (a). In the example of the metal-clad laminate shown in FIG. 6, an insulating adhesive layer 32 made of a polyimide electrodeposition coating film 32a and an adhesive layer 32b is formed on each side of a carbonaceous substrate 31.
2 and a metal foil layer 33 are sequentially provided to form a wiring board substrate in the form of a metal-clad laminate. Next, the above-mentioned (ii) embodiment will be described. The polyimide vapor deposition polymerization layer in the insulating adhesive layer of the above-mentioned (ii) embodiment can be formed by appropriately selecting and employing various vapor deposition polymerization methods. That is, it can be formed by co-depositing an acid anhydride such as pyromellitic dianhydride, biphenyltetracarboxylic dianhydride, or benzophenonetetracarboxylic dianhydride with an aromatic diamine such as oxydianiline, paraphenylenediamine, or benzophenonediamine on a carbonaceous substrate and then imidizing the layer by heating or other methods. A metal foil or lead frame is further laminated on the polyimide vapor deposition polymerization layer via an adhesive layer, and then pressure-bonded under heat or at room temperature, thereby adhering the metal foil or lead frame to the carbonaceous substrate to form the desired wiring board substrate. The polyimide vapor deposition polymerization layer is easy to control in thickness and has excellent film uniformity, allowing it to securely and firmly adhere to the carbonaceous substrate while reliably insulating the metal foil or lead frame. A cross section of an example of a wiring board substrate of the present invention in the form of a metal-clad laminate employing the insulating adhesive layer (B) is shown in FIG. 7. In the example of the metal-clad laminate shown in FIG. 7, an insulating adhesive layer 35 consisting of a polyimide vapor-deposited polymerization layer 35a and an adhesive layer 35b, and a metal foil layer 36 are sequentially provided on both sides of a carbonaceous substrate 34, thereby forming a wiring board substrate in the form of a metal-clad laminate. Next, the above-mentioned form (C) will be described. As described above, in the above-mentioned forms (A) and (B), the insulating adhesive layer is formed from multiple layers consisting of a polyimide coating film or a polyimide vapor-deposited polymerization layer and an adhesive layer, and although the number of steps is increased, a particularly strong adhesive strength is desired. In contrast, the above-mentioned form (C) is a case in which the polyimide layer also functions as the "adhesive layer" in the above-mentioned forms (A) and (B), thereby reducing the number of steps. Examples of such polyimide layers having adhesive properties include layers made of polyimide adhesives such as Iupitite (trade name: manufactured by Ube Industries, Ltd.) and Kapton (trade name: manufactured by DuPont-Toray Co., Ltd.).
When preparing a wiring board substrate via the adhesive polyimide layer, the metal foil or lead frame and the carbonaceous substrate can be bonded together using a method appropriate for the type of polyimide adhesive used (thermosetting, thermoplastic, film-type, solvent-type, etc.). For example, when using a film-type thermoplastic polyimide adhesive, the film-type polyimide adhesive can be sandwiched between the metal foil or lead frame and the carbonaceous substrate, followed by hot pressing to firmly bond them together to obtain a wiring board substrate. A cross-section of an example of a wiring board substrate of the present invention in the form of a metal-clad laminate employing the insulating adhesive layer (C) is shown in FIG. 8. In the example of the metal-clad laminate shown in FIG. 8, an insulating adhesive layer consisting of an adhesive polyimide layer 38 and a metal foil layer 39 are sequentially formed on both sides of a carbonaceous substrate 37, thereby forming a wiring board substrate in the form of a metal-clad laminate. The polyimide adhesive in (C) can also be used as an adhesive layer formed on the polyimide coating film (A) or the polyimide vapor-deposition polymerization layer (B). That is, a polyimide coating film (including a polyimide electrodeposition coating film) or a polyimide vapor-deposition polymerized layer is formed on a carbonaceous substrate, and a metal foil or lead frame is adhered to the polyimide coating film or polyimide vapor-deposition polymerized layer via an adhesive layer made of the polyimide adhesive described above in (c) to obtain the desired wiring board substrate. For example, if a polyimide coating film is formed on a carbonaceous substrate and a thermoplastic film-type polyimide adhesive is used as the adhesive layer thereon, when a metal foil or lead frame is laminated and pressure-bonded, the coating material forming the polyimide coating film flows into the voids in the holes on the carbonaceous substrate surface to fill them, resulting in close contact and improved thermal conductivity of the entire wiring board substrate. Furthermore, since the film-type polyimide adhesive is interposed between the carbonaceous substrate and the metal foil or lead frame, insulation is ensured by reliably separating them. Next, the above-mentioned embodiment (d) will be described. When forming the insulating adhesive layer described above in (d), the metal plating layer can be formed by appropriately selecting and employing a conventionally known electroless plating method or electrolytic plating method. Examples of metals to be plated include:
Examples of suitable materials include copper and nickel. A metal foil or lead frame is laminated on the metal plating layer via an adhesive layer, and then the metal foil or lead frame is pressure-bonded to the carbonaceous substrate under heat or at room temperature, thereby firmly adhering the metal foil or lead frame to the carbonaceous substrate to form the desired wiring board substrate. The adhesive layer provided on the metal plating layer must be insulating. In this case (d), the metal plating layer functions as a primer, with the highest priority placed on adhesion to the carbonaceous substrate. A cross-section of an example of a wiring board substrate of the present invention in the form of a metal-clad laminate employing the insulating adhesive layer (d) is shown in FIG. 9 . In the example of the metal-clad laminate shown in FIG. 9 , an insulating adhesive layer 42 consisting of a metal plating layer 42a and an adhesive layer 42b, and a metal foil layer 43 are sequentially provided on both sides of a carbonaceous substrate 41, respectively, to form a wiring board substrate in the form of a metal-clad laminate. In the insulating adhesive layers (a), (b), and (d), examples of adhesives used in the adhesive layers include the polyimide adhesives described above, as well as epoxy resin adhesives, silicone adhesives, etc. For example, silicone adhesives include KE180
0T (trade name: manufactured by Shin-Etsu Silicone Co., Ltd.), TES-3260 (trade name: manufactured by Toshiba Silicone Co., Ltd.), etc. are preferably used. It should be noted that inorganic coating agents such as heatless glass, which are listed as materials to be impregnated into carbonaceous materials, can also be used as the adhesive. These adhesives are applied to the polyimide coating film, polyimide vapor deposition polymerization layer, or metal plating layer (hereinafter referred to as the "base" in this paragraph) to form an adhesive layer, and this method can be appropriately selected and adopted from various conventionally known application methods. When applying the adhesive, (a) the adhesive can be first applied to the base provided on the carbonaceous substrate, and then a metal foil or a lead frame can be laminated on the coating film, or (b) the adhesive can be first applied to one side of the metal foil or lead frame, and then the metal foil or lead frame can be laminated so that the adhesive coating surface comes into contact with the base provided on the carbonaceous substrate, or (c)
(d) The adhesive may be applied to both the substrate provided on the carbonaceous substrate and one side of the metal foil or lead frame, and the layers may be stacked so that the coating surfaces of the adhesives are in contact with each other, or (d) the adhesive formed into a semi-cured film and the metal foil or lead frame may be stacked in this order on the substrate provided on the carbonaceous substrate. When stacking the metal foil or lead frame, it is advisable to apply pressure with a roll or flat press to remove any remaining air and ensure close contact. Furthermore, before bonding, the substrate and the metal foil or lead frame may be primed in advance by brushing on various primers as described below. The conditions for drying or heat-curing the adhesive may be set as appropriate depending on the type of adhesive used. For example, the adhesive may be TES-3260 (
When using a primer (trade name: manufactured by Toshiba Silicone Co., Ltd.), it is advisable to heat and press at 150°C for 60 minutes to form the layer. Next, the above-mentioned form (e) will be explained. When forming the insulating adhesive layer of the above-mentioned (e), examples of the primer to be used in the primer layer include Primer A (trade name), a mixture of Primer X (trade name) and Primer Y (trade name) manufactured by Toray Dow Corning Silicone Co., Ltd. Furthermore, the elastomer-based adhesive layer provided on the primer layer must have insulating properties, and specific examples include:
An elastomer adhesive such as SOTEFA-70 (trade name: silicone elastomer adhesive) manufactured by Toray Dow Corning Silicone Co., Ltd. is preferably used. This elastomer adhesive can also be used as the adhesive for the insulating adhesive layers (a), (b), and (d) above. If necessary, a suitable amount of fine particulate thermally conductive filler such as SiN, SiC, _{or Al2O3} can be added to this elastomer adhesive. The thermally conductive filler can be
It can also be added to various adhesive layers in the insulating adhesive layers of (A), (B) and (D) above, or to the polyimide layer having adhesive properties in (C) above. The elastomeric adhesive layer provided on the primer layer is then dried or heat-cured, thereby sufficiently firmly adhering the metal foil or lead frame to the carbonaceous substrate to form the desired wiring board substrate. The processing conditions for drying or heat-curing the elastomeric adhesive layer can be appropriately set depending on the type of elastomeric adhesive used, etc. Figure 10 shows a schematic cross section of an example of a wiring board substrate of the present invention in the form of a metal-clad laminate that employs the insulating adhesive layer of (E). In the example of the metal-clad laminate form of Figure 10, an insulating adhesive layer 52 consisting of a primer layer 52a and an elastomeric adhesive layer 52b, and a metal foil layer 53 are sequentially provided on both sides of a carbonaceous substrate 51, to form a wiring board substrate in the form of a metal-clad laminate. Furthermore, when forming the insulating adhesive layers of (A) to (E) above,
A suitable amount of fine particle filler having spacer function can be added to each adhesive layer in (a), (b), (d) and (e), or to the polyimide layer having adhesive function in (c). Examples of fillers having spacer function include silica, spherical alumina, hollow balloons, etc. Furthermore, when forming the insulating adhesive layers in (a) to (e), as needed, (
An insulating woven or nonwoven fabric can be embedded in each of the adhesive layers in (a), (b), (d), and (e), or in the polyimide layer having adhesive properties in (c). An example of this is shown in Fig. 11. Fig. 11 shows an adhesive layer 62 in which a base 62a such as a polyimide coating film and a nonwoven fabric 62c are embedded on both sides of a carbonaceous substrate 61.
2b, and a metal foil layer 63. By embedding the woven or nonwoven fabric in this way, the woven or nonwoven fabric functions as a spacer, reliably separating the carbonaceous substrate from the metal foil or lead frame by at least the thickness of the woven or nonwoven fabric, thereby improving the dielectric breakdown strength of the wiring board substrate. The woven or nonwoven fabric may be, provided that it has insulating and heat-resistant properties,
A suitable material can be selected from woven and nonwoven fabrics of various synthetic fibers, natural fibers, glass fibers, etc. Specifically, a suitable example is a nonwoven fabric made of aramid fibers such as Meta-Aramid Paper (trade name: manufactured by DuPont Teijin Advanced Papers). The thickness of the woven or nonwoven fabric is set appropriately taking into consideration that if it is too thick, the thermal conductivity of the entire wiring board substrate decreases, and conversely, if it is too thin, the insulation between the metal foil or lead frame and the carbonaceous substrate cannot be ensured. Specifically, a thickness of about 30 to 150 μm is suitable, but is not limited to this. When producing a wiring board substrate using the above woven or nonwoven fabric, if the insulating adhesive layer consists of a base such as a polyimide coating film and an adhesive layer, for example, the following procedure is performed. That is, (a) a base such as a polyimide coating film is formed on a carbonaceous substrate, and (b) a base such as a polyimide coating film is formed on the carbonaceous substrate, and
(b) A woven or nonwoven fabric impregnated with adhesive by coating, dipping, or the like is laminated on the base, and (c) a metal foil or lead frame is further laminated on top of that to produce a wiring board substrate. In another example, in (b) above, adhesive may be applied to the base, a woven or nonwoven fabric is placed on top of that, and further adhesive may be applied to form an adhesive layer in which the woven or nonwoven fabric is embedded. In this case, taking into consideration the possibility of volumetric sinking due to adhesive hardening, it is necessary to apply a sufficient amount of adhesive so that the woven or nonwoven fabric hardens in a state where it is embedded in the adhesive layer (not exposed on the surface of the adhesive layer). Also, when the insulating adhesive layer in the wiring board substrate is made of a polyimide layer having adhesive properties, it can be produced in accordance with the above (a) to (c), except that no base is formed on the carbonaceous substrate. When using a thermoplastic film-type polyimide adhesive, the substrate can be prepared by, for example, sandwiching a woven or nonwoven fabric between two sheets of film-type adhesive, laminating a metal foil or lead frame, and then melting and curing the adhesive. In this case, the woven or nonwoven fabric must, of course, have a heat resistance higher than the melting temperature of the film-type adhesive. When laminating the metal foil or lead frame, it is preferable to apply pressure using a roll or flat press to eliminate air residue and ensure adhesion. When the wiring board substrate of the present invention is in the form of a metal-clad laminate, the metal-clad laminate can be suitably formed into a printed wiring board by conventional photolithography techniques, and the resulting printed wiring board can be suitably used as a wiring board for various electrical and electronic devices. When the wiring board substrate is in the form of a lead frame laminate, the lead frame laminate can be suitably used as a wiring board for various electrical and electronic devices. The wiring board substrate of the present invention has excellent thermal conductivity and heat dissipation properties, and a printed wiring board derived from the wiring board substrate of the present invention in the form of a metal-clad laminate, or a wiring board substrate of the present invention in the form of a lead frame laminate, can be suitably used in circuits of various electric and electronic devices, which generate heat. The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. (Example 1) A 3 mm thick wiring board having carbon fibers arranged in the thickness direction in a carbon matrix was prepared.
A carbon fiber reinforced carbon composite material (hereinafter referred to as "C/C composite") in the form of a plate, CC (trade name: manufactured by Advanced Materials Co., Ltd.), was used as the carbonaceous substrate.
A polyimide electrodeposition paint was electrodeposited on one side of the composite at 30 V for 2.5 minutes at room temperature, dried at 80°C for 10 minutes, and baked at 250°C for 30 minutes to form a polyimide electrodeposition coating. A 70 μm thick copper foil coated with a silicone adhesive KE1800T (product name: Shin-Etsu Silicone Co., Ltd.) was then laminated onto the polyimide electrodeposition coating so that the adhesive-coated surface was in contact with the polyimide electrodeposition coating. Prior to lamination, the polyimide electrodeposition coating and the copper foil prior to adhesive application were primed by brushing Primer A (product name: Dow Corning Toray Silicone Co., Ltd.). The laminate was then heat-pressed at 120°C for 3 minutes under a pressure of 294 N/ ^cm² to remove air and excess adhesive. The pressure was then released and the adhesive was cured by heat treatment at 120°C for 60 minutes to produce a copper-clad laminate. The thickness of the polyimide electrodeposition coating film on this copper-clad laminate was 20 μm. The thickness of the adhesive layer was 100 μm, resulting in a total thickness of 3.19 mm. (Example 2) Rikacoat PN-20 (trade name: manufactured by New Japan Chemical Co., Ltd.), a polyimide coating, was brushed onto one side of a 3 mm-thick C/C composite plate similar to that used in Example 1, and baked at 200° C. for 30 minutes to form a polyimide coating film. A silicone adhesive KE1800T (trade name: manufactured by Shin-Etsu Silicone Co., Ltd.) was applied to the polyimide coating film.
A 70 μm thick copper foil coated with Primer A (trade name: manufactured by Dow Corning Toray Silicone Co., Ltd.) was laminated on the polyimide coating so that the adhesive-coated surface was in contact with the polyimide coating. Before lamination, the polyimide coating and the copper foil before adhesive coating had been primed by brushing Primer A on them.
The laminate was then heat-pressed at 120°C for 3 minutes under a pressure of 294 N/ ^cm² to remove air and excess adhesive, and then heated at 120°C for 60 minutes to heat-cure the adhesive, producing a copper-clad laminate. The polyimide coating on this copper-clad laminate had a thickness of 20 μm, and the adhesive layer had a thickness of 100 μm.
Example 3 Both sides of a 3 mm thick C/C composite plate similar to that used in Example 1 were plated with nickel by electroless plating, and a silicone adhesive KE1800T (product name: manufactured by Shin-Etsu Silicone Co., Ltd.) was applied to both nickel-plated layers to form a 7 mm thick sheet.
A 120 μm copper foil was laminated on the nickel plated layer so that the adhesive-coated surface was in contact with the nickel plated layer. Before lamination, the nickel plated layer and the copper foil before the adhesive were coated were primed by brushing Primer A (trade name: manufactured by Dow Corning Toray Silicone Co., Ltd.).
The copper-clad laminate was fabricated by applying a pressure of 294 N/ ^cm² to a heat press at 0°C for 3 minutes to remove air and excess adhesive, and then heating at 120°C for 60 minutes to heat-cure the adhesive. The nickel-plated layer on the resulting copper-clad laminate was 50 μm thick, and the adhesive layer was 100 μm thick.
Example 4 Primer X (product name: manufactured by Toray Dow Corning Silicone Co., Ltd.) was applied by brushing to one side of a 3 mm thick C/C composite plate similar to that used in Example 1.
A primer layer was formed by drying at room temperature for 30 minutes. A film-shaped silicone elastomer adhesive SOTEFA-70 (trade name: manufactured by Toray Dow Corning Silicone Co., Ltd.) and a copper foil having a thickness of 70 μm were laminated on the primer layer in this order, and the resulting laminate was then dried for 130 minutes.
The adhesive was heat cured at 0°C for 30 minutes under a pressure of 98 N/ ^cm2 to prepare a copper-clad laminate. The thickness of the primer layer on the obtained copper-clad laminate was 1 µm.
The thickness of the elastomer adhesive layer was 100 μm. (Example 5) A 3 mm thick C/C composite plate similar to that used in Example 1 was dipped in Heatless Glass GA-4(N) (trade name: room temperature curing silica solution manufactured by Homer Technology) under a reduced pressure of 70 mmHg, impregnating the micropores of the C/C composite plate with the heatless glass. The plate was then left at room temperature for 50 minutes and then heated at 120°C for 60 minutes to harden the heatless glass, yielding a C/C composite plate impregnated with the heatless glass. A copper-clad laminate was produced in the same manner as in Example 1, except that this C/C composite plate impregnated with the heatless glass was used as the carbonaceous substrate. (Example 6) A 3 mm thick MB-18 (trade name: Mobius A with linearly aligned carbon fibers) impregnated with copper under high temperature and high pressure was used instead of the C/C composite plate used in Example 1.
- Except for using a C/C composite base made by T Company as the carbonaceous substrate,
A copper-clad laminate was prepared in the same manner as in Example 1. The thickness of the polyimide electrodeposition coating film on this copper-clad laminate was 20 μm. The thickness of the adhesive layer was 100 μm.
The thickness of the copper-clad laminate obtained in Example 6 was 3.12 mm, and the copper foil on the surface was removed by etching. The resulting laminate (3.12 mm thick) was then placed on an aluminum plate (25 mm thick), and its thermal conductivity was measured using a thermal conductivity meter QTM-500 (Kyoto Electronics Co., Ltd.). The aluminum plate was used because a certain thickness is required to measure thermal conductivity. The measurement resulted in a value of 22.64 (W/m·K). (Comparative Example 1) As a comparative example, Sanhayato Co., Ltd.'s printed circuit board No. 31 (1.6 mm thick) was used. This printed circuit board was a glass-epoxy board with copper foil attached to both sides. The surface copper foil was removed from the printed circuit board by etching to obtain a glass-epoxy board. The resulting glass-epoxy board was then placed on an aluminum plate (25 mm thick).
The aluminum plate was placed on a 1000-m thick plate and the thermal conductivity was measured using a thermal conductivity meter QTM-500 (Kyoto Electronics Co., Ltd.). The reason for using an aluminum plate here is the same as in Example 6, because a certain thickness is required to measure the thermal conductivity.
The thermal conductivity was measured using two laminated boards of Comparative Example 1 at a thickness of 3.2 mm to achieve approximately the same thickness for Example 6 and Comparative Example 1. To ensure the surface of the object being measured was insulated, the surface of the laminated board from Example 6, from which the copper foil had been removed, was covered with plastic wrap (10 μm thick) for the measurement. Although the glass-epoxy board of Comparative Example 1 is insulating and therefore does not need to be covered with plastic wrap for thermal conductivity measurement, it was measured using plastic wrap to achieve the same conditions as Example 6. From the above measurement results, the thermal conductivity of Comparative Example 1 was 0.552 (W/m·K), while that of Example 6 was 22.64 (W/m·K), demonstrating a significant improvement in thermal conductivity. Furthermore, the metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention, has strong adhesion between the carbonaceous substrate and the metal foil, and its properties such as volume resistivity, surface resistivity, relative dielectric constant, and dielectric loss tangent fully satisfy the standard values of conventional metal-clad laminates, and can be used suitably. The equipment used for the above measurements is shown in Table 1, and the measurement results are summarized in Table 2. (Example 7) A leadframe laminated substrate was produced in the same manner as in Example 1, except that a leadframe produced by punching a predetermined wiring pattern from a 500 μm thick copper plate was used instead of the copper foil in Example 1. The leadframe substituting for the copper foil was removed by etching from the obtained leadframe laminated substrate in the same manner as in Example 6, and the thermal conductivity of the resulting substrate was measured. As in Example 6, a thermal conductivity significantly higher than that of Comparative Example 1 was obtained. (Example 8) Upilex S (polyimide varnish, product name: manufactured by Ube Industries, Ltd.) was brushed onto one side of a 3 mm thick plate-shaped C/C composite similar to that used in Example 1, and then a 20 μm thick film of Iupitite (model number UP) was applied as a film-type polyimide adhesive.
A 70 μm thick copper foil was then laminated on the laminate, and the laminate was heated at 170° C. for 30 minutes under a pressure of 294 N/cm ^{2, and then heated at 250° C. for 30 minutes under a pressure of 294 N/cm 2} .
The copper-clad laminate was prepared by bonding the copper-clad laminate by pressing at 20 N/ ^cm2 for 2 minutes at 20 °C. The thermal conductivity of the copper-clad laminate was measured in the same manner as in Example 6, and a high thermal conductivity was obtained, similar to that of the above-mentioned examples.
The peel strength measured according to IS C6481 was 1.2 kgf/cm
A sufficiently high value of 20 μm was obtained. (Example 9) A 20 μm thick Iupitite (model number UPA-N) film-type polyimide adhesive was applied to one side of a 3 mm thick C/C composite plate similar to that used in Example 1.
111, product name: manufactured by Ube Industries, Ltd.) and a copper foil with a thickness of 70 μm was laminated thereon.
The copper-clad laminate was prepared by bonding the copper-clad laminate at 0°C for 3 minutes under a pressure of 50 N/ ^cm² . The thermal conductivity of the copper-clad laminate was measured in the same manner as in Example 6, and a high thermal conductivity was obtained, similar to that of the previous examples.
The peel strength measured according to JIS C6481 was 1.1 kgf/cm
Example 10 A copper-clad laminate was produced in the same manner as in Example 1, except that a polyimide vapor deposition polymerization layer was formed in a vacuum instead of the polyimide electrodeposition coating film. The thickness of the polyimide vapor deposition polymerization layer in this copper-clad laminate was 20 μm.
The thermal conductivity of the copper-clad laminate obtained was measured in the same manner as in Example 6, with the copper foil removed. As in Example 6, a significantly higher thermal conductivity than that of Comparative Example 1 was obtained. (Example 11) One side of a 3 mm thick C/C composite plate similar to that used in Example 1 was brushed with Rikacoat PN-20 (trade name: manufactured by New Japan Chemical Co., Ltd.), a polyimide coating, and baked at 200°C for 30 minutes to form a 20 μm thick polyimide coating film. Next, a 120 μm thick meta-aramid paper (trade name: manufactured by DuPont Teijin Advanced Paper Co., Ltd.), an aramid nonwoven fabric impregnated with a silicone adhesive KE1800T (trade name: manufactured by Shin-Etsu Silicone Co., Ltd.), was laminated on the polyimide coating film, and a 70 μm thick copper foil was further laminated on it. Note that, during lamination, Primer A (trade name: manufactured by DuPont Teijin Advanced Paper Co., Ltd.) was pre-applied to the polyimide coating film and the copper foil before the adhesive was applied.
The plate was then primed by brushing on a primer (manufactured by Toray Dow Corning Silicone Co., Ltd.). The plate was then heat pressed at 120°C for 3 minutes at a pressure of 294 N/cm.
The copper-clad laminate was then pressed to a pressure of ² to remove air and excess adhesive, and then released from the pressure and heated at 120°C for 60 minutes to harden the adhesive, producing a copper-clad laminate. The copper foil was removed from the resulting copper-clad laminate in the same manner as in Example 6, and the thermal conductivity was measured. As in Example 6, a significantly higher thermal conductivity than that of Comparative Example 1 was obtained. Furthermore, when the dielectric breakdown strength was measured according to JIS K6911, a sufficiently high value of 10.8 kV was obtained. INDUSTRIAL APPLICABILITY According to the present invention, wiring board substrates having excellent thermal conductivity and capable of rapidly dissipating generated heat are provided in the form of metal-clad laminates and lead frame laminate substrates. Also provided is a wiring board substrate in which a carbonaceous substrate is firmly bonded to a metal foil or a lead frame. The wiring board substrate of the present invention can be produced at low cost because the carbonaceous material used as the substrate is inexpensive. In addition, the wiring board substrate of the present invention is lightweight because the carbonaceous material used as the substrate is lightweight, and electrical and electronic equipment using the lightweight wiring board substrate can be easily manufactured.
The weight of the electronic equipment is reduced.

[Brief explanation of the drawings]

FIG. 1 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 2 is a schematic cross-sectional view of an example of a leadframe laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 3 is a schematic cross-sectional view of an example of a leadframe laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 4 is a schematic cross-sectional view of an example of a leadframe laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 5 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 6 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 7 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 8 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 9 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 10 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention. FIG. 11 is a schematic cross-sectional view of an example of a metal-clad laminate, which is one embodiment of the wiring board substrate of the present invention.

[Procedure Amendment] Submission of a copy of amendments under Article 19 of the Patent Cooperation Treaty (Official)

[Submission date] January 19, 2001 (2001.1.19)

[Procedural Correction 1]

[Name of document to be corrected] Statement

[Item to be amended] Claims

[Correction method] Change

[Contents of the amendment]

[Claims]

⁷仕様番号 FI H05K 3/38 H01L 23/14 M (81) Designated States EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE), CN, JP, KR, US (Note) This publication is based on the gazette published internationally by the International Bureau (WIPO). The effect of the international publication of the Japanese language patent application (Japanese language utility model registration application) related to this publication arises pursuant to Article 184-10, Paragraph 1 of the Patent Act (Article 48-13, Paragraph 2 of the Utility Model Act) and is unrelated to this publication.

Claims (28)

[Claims] 1. A substrate for wiring boards, comprising a carbonaceous substrate made of a carbonaceous material and a metal foil or a lead frame laminated thereon via an insulating adhesive layer. 2. The wiring board substrate according to claim 1, wherein a metal foil is laminated on the carbonaceous substrate via an insulating adhesive layer, and the substrate is in the form of a metal-clad laminate. [Claim 3] A wiring board substrate as described in claim 1, wherein a lead frame is laminated on the carbonaceous substrate via an insulating adhesive layer, and the wiring board substrate is in the form of a lead frame laminated on a substrate. 4. The insulating adhesive layer comprises a polyimide coating film provided on a carbonaceous substrate;
and an adhesive layer provided on the polyimide coating film.
10. The wiring board substrate according to claim 9, wherein the wiring board substrate is a substrate for a wiring board. 5. The wiring board substrate according to claim 4, wherein the polyimide coating film is a polyimide electrodeposition coating film. [Claim 6] A substrate for wiring boards described in any one of claims 1 to 3, wherein the insulating adhesive layer is composed of a polyimide vapor deposition polymerization layer provided on a carbonaceous substrate and an adhesive layer provided on the polyimide vapor deposition polymerization layer. 7. The wiring board substrate according to claim 1, wherein the insulating adhesive layer is formed of a polyimide layer having adhesive properties and provided on a carbonaceous substrate. [Claim 8] A substrate for wiring boards described in any one of claims 1 to 3, wherein the insulating adhesive layer is composed of a metal plating layer provided on a carbonaceous substrate and an adhesive layer provided on the metal plating layer. [Claim 9] A wiring board substrate described in any one of claims 1 to 3, wherein the insulating adhesive layer is composed of a primer layer provided on a carbonaceous substrate and an elastomer-based adhesive layer provided on the primer layer. 10. The wiring board substrate according to claim 4, wherein an insulating woven or nonwoven fabric is embedded in the adhesive layer. 11. The wiring board substrate according to claim 5, wherein an insulating woven or nonwoven fabric is embedded in the adhesive layer. 12. The wiring board substrate according to claim 6, wherein an insulating woven or nonwoven fabric is embedded in the adhesive layer. 13. The wiring board substrate according to claim 7, wherein an insulating woven or nonwoven fabric is embedded in the polyimide layer having an adhesive function. 14. The wiring board substrate according to claim 8, wherein an insulating woven or nonwoven fabric is embedded in the adhesive layer. 15. The wiring board substrate according to claim 9, wherein an insulating woven or nonwoven fabric is embedded in the adhesive layer. 16. The wiring board substrate according to claim 4, wherein the adhesive layer contains a filler having a spacer function. 17. The wiring board substrate according to claim 5, wherein the adhesive layer contains a filler having a spacer function. 18. The wiring board substrate according to claim 6, wherein the adhesive layer contains a filler having a spacer function. 19. The wiring board substrate according to claim 7, wherein the polyimide layer having an adhesive function contains a filler having a spacer function. 20. The wiring board substrate according to claim 8, wherein the adhesive layer contains a filler having a spacer function. 21. The wiring board substrate according to claim 9, wherein the adhesive layer contains a filler having a spacer function. 22. The wiring board substrate according to claim 1, wherein the fine pores of the carbonaceous material of the carbonaceous substrate are impregnated with an inorganic coating agent or a metal. 23. The wiring board substrate according to claim 4, wherein the fine pores of the carbonaceous material of said carbonaceous substrate are impregnated with an inorganic coating agent or a metal. 24. The wiring board substrate according to claim 5, wherein the fine pores of the carbonaceous material of said carbonaceous substrate are impregnated with an inorganic coating agent or a metal. 25. The wiring board substrate according to claim 6, wherein the fine pores of the carbonaceous material of said carbonaceous substrate are impregnated with an inorganic coating agent or a metal. 26. The wiring board substrate according to claim 7, wherein the fine pores of the carbonaceous material of said carbonaceous substrate are impregnated with an inorganic coating agent or a metal. 27. The wiring board substrate according to claim 8, wherein the fine pores of the carbonaceous material of said carbonaceous substrate are impregnated with an inorganic coating agent or a metal. 28. The wiring board substrate according to claim 9, wherein the fine pores of the carbonaceous material of said carbonaceous substrate are impregnated with an inorganic coating agent or a metal.