JP2011044459A - Resin composition for electronic substrate, and electronic substrate using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin composition for an insulating layer that enables a through hole etc., of the electronic substrate, especially, a small-diameter through hole to be bored with good operability, and can suppress cracking in a heat cycle. <P>SOLUTION: This invention relates to the resin composition for an insulating layer of the electronic substrate such that a thermosetting resin includes alumina and aluminum hydroxide at the same time, and the electronic substrate having the insulating layer laminated. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a resin composition for an insulating layer of an electronic substrate incorporated in an electronic device such as a communication device or a measuring device, and a multilayer wiring substrate using the same.

Epoxy resin plates are often used as a substrate material for printed wiring boards incorporated in electronic devices such as communication devices and measuring devices. The epoxy resin plate is usually configured by using glass fiber or the like as a reinforcing material (base material) and a cured product of an epoxy resin composition including an epoxy resin, an epoxy resin curing agent, a flame retardant, and the like as a matrix.
Epoxy resin has little shrinkage during curing, no generation of gas or water during curing, the resin after curing has excellent electrical insulation performance, excellent resistance to chemicals, etc. It is used as a matrix material for printed wiring boards.

  An epoxy resin plate using a glass woven fabric as a reinforcing material is manufactured, for example, by the following method. A glass woven fabric is impregnated with a varnish containing an epoxy resin composition, the reaction of the resin proceeds while drying and removing the solvent, and a so-called prepreg that is semi-cured before full curing is obtained. Then, depending on the thickness of the laminated plate, the prepreg is singly or a predetermined number of layers are laminated. Further, a metal foil such as a copper foil is disposed on one or both surfaces of the prepreg, and sandwiched between stainless steel plates or the like, and heated and pressed to form a metal foil An epoxy resin plate is obtained. Next, a printed wiring board is obtained by forming a circuit by removing unnecessary portions of the metal foil of the metal foil-clad epoxy resin laminate by means of etching or the like.

  As the epoxy resin, bisphenol A type epoxy resin is commonly used, but as a substrate material for printed wiring boards incorporated in electronic devices that require high reliability such as communication equipment and measuring equipment, glass transition of the matrix High temperature (Tg) is required, and an epoxy resin composition in which a bisphenol A type epoxy resin is blended with a polyfunctional epoxy resin, for example, an o-cresol novolac type epoxy resin, is used.

  On the other hand, in order to improve the heat dissipation of the wiring board, a method of filling a resin with a filler having high thermal conductivity is used for manufacturing a metal board. Metal nitrides such as silicon nitride and boron nitride are excellent as insulating fillers with high thermal conductivity. However, the amount that can be filled is limited due to the relationship between the particle size and form, and the characteristics cannot be exhibited, so it is very expensive. Therefore, it is not used much. In contrast, alumina (aluminum oxide) has a thermal conductivity several tens of times that of silica (silicon oxide), and products for filling purposes that are spherical and have a particle size designed like silica are being prepared. Since the price is about the same as the high grade grade of silica, it is blended into an adhesive with high thermal conductivity. However, when alumina is blended in the resin sheet, the resin layer cured with the alumina blend is very hard and brittle, and requires machining such as machining of the outer periphery of the substrate and formation of a drill through hole. A problem occurs. An increase in the number of replacements due to damage to special molds or drill bits is a problem from a cost standpoint.

  Moreover, in order to improve heat dissipation, Patent Document 1 discloses that by improving the layer structure of the metal core printed wiring board, heat dissipation, processing accuracy, and workability can be improved, and formation of small-diameter through holes is facilitated. Although an epoxy resin is blended in the insulating layer, the specific composition of the epoxy resin is not described.

  Further, in permanent hole filling of a printed wiring board, voids are inevitably generated due to air entrainment or the like when filling the hole portion such as a through hole or a via hole with an epoxy resin composition. Such voids are difficult to remove completely even if pre-curing or main curing is performed, and cannot be eliminated. Such a phenomenon becomes more prominent as the depth of the hole is deeper (in the case of a through hole, the thicker the core substrate), and the higher the viscosity of the epoxy resin composition. Further, in the permanent hole filling process of the printed wiring board, there is a problem that cracks occur during preliminary curing. Furthermore, there is a problem that the shrinkage at the time of heat curing is large, and a gap is generated between the through hole wall after the main curing.

JP 2007-242740 A

Conventionally, a resin that forms an insulating layer in an electronic substrate has a large coefficient of thermal expansion, and is likely to crack. As a solution, a method of adding a filler to a resin is known, and alumina is a typical example. However, alumina is a material with high hardness, and it may cause wear and breakage of the bit by applying a load to the drill or router in the drilling process of the through hole. Therefore, there is a problem that blending alumina into the resin deteriorates the workability of the substrate.
Therefore, the problem of the present invention is that it is possible to drill through holes and the like of a printed wiring board with good workability, crack generation during heat cycle, deterioration of insulation reliability, and the top of the cured product filled in the hole. Provided is a highly reliable thermosetting resin composition for an electronic substrate that is excellent in insulation reliability, heat resistance, moisture resistance, PCT resistance, etc. There is.
Further, another object of the present invention is to suppress a problem that a drill breaks during processing in order to realize a high density of an electronic substrate, and to enable drilling of a small diameter through hole.

The object of the present invention has been achieved by the following means (1) to (6).
(1) A resin composition for an insulating layer of an electronic substrate containing at least a thermosetting resin and alumina and aluminum hydroxide as fillers.
(2) The resin composition for an insulating layer of an electronic substrate according to the above (1), wherein the thermosetting resin is an epoxy resin.
(3) The resin composition for an insulating layer of an electronic substrate according to the above (1) or (2), which contains about 30 to about 42% by mass of alumina and about 20 to about 33% by mass of aluminum hydroxide as fillers.
(4) The blending ratio of alumina and aluminum hydroxide is any one of the above (1) to (3), wherein the aluminum hydroxide ratio is about 1: 1 to about 2.1: 1 with respect to alumina. Resin composition for insulating layer of electronic substrate.
(5) The resin composition for an insulating layer of an electronic substrate according to any one of (2) to (4), wherein the epoxy resin is a bisphenol A type epoxy resin.
(6) An electronic substrate having a metal core layer, at least one insulating layer stacked thereon, and a conductive layer stacked on the insulating layer, and having a through hole penetrating the metal core layer An electronic substrate in which an epoxy resin and a resin composition containing at least alumina and aluminum hydroxide as fillers are laminated as an insulating layer.

  In the resin composition of the present invention, aluminum hydroxide is inferior in thermal conductivity to alumina, but the flame retardancy of the electronic substrate is improved and the hardness is softer than that of alumina. Therefore, alumina and aluminum hydroxide are blended at the same time. As a result, it was possible to prepare an insulating layer having a higher thermal conductivity than that of a general resin, high flame retardancy, and improved workability.

  In general, electronic boards include printed wiring boards and module boards, and in many cases, multilayer boards are used. In the multilayer wiring board, a first wiring pattern is formed on the surface of the substrate, an insulating layer of a resin composition is formed so as to cover the first wiring pattern, and further, a second wiring pattern is formed on the surface of the insulating layer. Formed and sequentially multilayered.

In many cases, a copper-clad laminate is mainly used as a printed wiring board substrate. Since the resin is an insulator, it is electrically suitable as a raw material. However, since the coefficient of thermal expansion is high and the strength is not sufficient, it is reinforced by impregnating the resin into fibers, glass cloth, or the like.
Then, a circuit pattern is exposed and developed on a copper clad laminate with a copper film, and a circuit is formed by removing unnecessary parts. In the case of a double-sided board, etc., a hole is made to connect the circuits on both sides. Apply copper plating. After that, a protective film called solder resist is applied to prevent wiring shorts, symbol marks are printed, and the terminals that connect the printed wiring board and the power source are plated with gold to complete the printed wiring board. After that, parts are mounted.

  As the resin, many types of thermosetting resins can be used, but thermosetting resins mainly composed of epoxy resin and phenol resin as curing agent are excellent in adhesion and heat resistance. Therefore, when the resin layer is provided on the resin insulation layer lamination side of the base material by baking and curing, the base material on both sides and the prepreg (adhesive) are firmly adhered, and even if heated by soldering, the adhesiveness Does not drop. Examples of the thermosetting resin layer include polyester resins, acrylic resins, polyurethane resins, and melamine resins. When the curing agent is isocyanate or melamine, the adhesiveness and heat resistance are more excellent.

  Metal core boards such as metal core printed wiring boards, metal core type printed boards, and metal core printed circuit boards, which use metal as a substrate, are suitable for radiating and leveling heat generated by electrical components mounted on the mounting surface. An electric circuit board in which a metal plate having good thermal conductivity such as aluminum and copper is used as a metal core (that is, a metal base), and a conductor layer is provided on the metal core via an insulating layer mainly composed of resin. is there.

  In order to form the insulating layer, a prepreg (that is, a glass fiber fabric formed by knitting glass fibers into a sheet shape) is usually used as an insulating resin impregnated with an epoxy resin. In a metal core substrate in which a through hole for a through hole is provided in a metal core, the through hole of the metal core is filled with an insulating resin in order to insulate the conductor layer from the metal core. The hole filling is generally performed by a method in which an insulating resin that flows out from the prepreg is poured into the through-hole when the prepreg laminated on the metal core is integrated by heating and pressing.

  For example, the metal core substrate having a through hole is manufactured as follows more specifically. First, a plate-shaped metal core in which through holes for through holes are formed in the plate thickness direction by drilling such as drilling, X-ray drilling (that is, laser drilling) and punching is prepared.

  Next, as a plurality of prepregs and conductive metal foils, for example, copper foils are sequentially laminated on both main surface sides of the metal core, and in this state, heating and pressing are performed. Then, a copper foil-clad laminate is obtained. That is, in the state where a plurality of prepregs and copper foil are laminated on the metal core, the through hole of the metal core forms a void, but by the heat and pressure forming, the above-mentioned by the flow, filling and curing of the insulating resin from the prepreg Thus, a copper foil-clad laminate in which the through holes are integrally filled is obtained.

  In the copper foil-clad laminate thus obtained, a through-hole that is coaxial with the through-hole of the metal core and smaller in diameter than the through-hole is formed by drilling such as drilling and X-ray drilling (ie, laser drilling). To do. After that, the entire surface of the copper foil-clad laminate including the inner wall surface defining the through hole is plated, thereby forming a through hole made of conductive metal, and then a required circuit pattern forming process by etching or the like. And a metal core board | substrate is obtained by performing a resist formation process etc.

  In producing the resin composition necessary for producing the prepreg of the present invention, (A) resin, (B) filler, (C) curing agent and other additives are blended using a mixer or the like. As other additives, for example, conventionally known additives such as curing accelerators, inorganic fillers, lubricants, dispersants, plasticizers, flame retardants, pigments, silane coupling agents, modifiers and discoloration inhibitors are necessary. Depending on the case, it can be blended appropriately.

(A) Resin As resin used for the resin composition of this invention, a thermoplastic resin and a thermosetting resin can be used, for example. Examples of the thermosetting resin include an epoxy resin, a phenol resin, an unsaturated polyester resin, a silicone resin, a polyimide resin, and a vinyl ester resin. Examples of the thermoplastic resin include polyolefin resins such as polypropylene and polyvinyl chloride resins, EEA resins, EVA resins, polyester resins, polyether imides, polyether sulfones, and polyether ether ketones. Among these, a thermosetting resin is preferable, and an epoxy resin is particularly preferable.

  As the epoxy resin, a conventionally known epoxy resin having at least one epoxy group in one molecule can be used. Examples of such epoxy resins include bisphenol A type epoxy resins, tetrabromobisphenol A type epoxy resins, phenol F type epoxy resins, alicyclic epoxy resins, phenol novolac type epoxy resins, brominated phenol novolak type epoxy resins, Cresol novolak type epoxy resin, heterocyclic epoxy resin, hydrogenated bisphenol A type epoxy resin, glycidyl ester type epoxy resin of aromatic / aliphatic or alicyclic carboxylic acid, spiro ring containing epoxy resin, dicyclopentadiene skeleton containing epoxy Resin. These can be used alone or in combination of two or more. Among them, bisphenol A type epoxy resin, tetrabromobisphenol A type epoxy resin, phenol novolac type epoxy resin and brominated phenol novolac type epoxy resin are preferable, and bisphenol A type epoxy resin and phenol novolac type epoxy resin are particularly preferable. is there.

(B) Filler
Examples of the filler used in the resin composition of the present invention include extender pigments such as silica, alumina, aluminum hydroxide, precipitated barium sulfate, talc, calcium carbonate, silicon nitride and aluminum nitride, and copper, tin, zinc and nickel. , Metal powders such as silver, palladium, aluminum, iron, cobalt, gold and platinum. Such fillers are classified into spherical fillers and pulverized fillers other than spherical shapes depending on their shapes.

  The resin composition of the present invention is preferably blended with alumina and aluminum hydroxide as fillers. The blending ratio of both is about 30 to about 42% by weight of alumina, about 20 to about 33% by weight of aluminum hydroxide, and the alumina / aluminum hydroxide ratio is about 1: 1 to about 2.1: 1. That's fine.

  Moreover, it is preferable that the average particle diameter of the alumina and aluminum hydroxide in the resin composition of this invention is 0.5-5 micrometers. When the average particle diameter is in such a range, the smoothness of the surface is excellent when the resin composition containing aluminum hydroxide is used as a substrate material for a printed wiring board. Moreover, since it is excellent also in the dispersibility in a resin composition, the mechanical strength of a resin composition also becomes favorable. If the average particle size is less than 0.5 μm, the aluminum hydroxide particles are small and difficult to handle, the cohesive force between the particles increases, and the dispersibility in the resin composition may decrease. . On the other hand, when the thickness exceeds 5 μm, the smoothness of the substrate surface decreases when the resin composition containing aluminum hydroxide is used as a substrate material for a printed wiring board.

  Although the preparation of aluminum hydroxide to be blended in the resin composition of the present invention is not limited, it can be produced by performing a heating step of heat-treating aluminum hydroxide having three water molecules and dehydrating the bound water. By the heating step, the gibbsite-type aluminum hydroxide having a bound water number of 3 is partially transferred to a boehmite type having a bound water number of 1, so that the bound water number is in the range of 1.8 to 2.7. Some aluminum hydroxide can be obtained. There is no restriction | limiting in the method of heat processing, It heats on the conditions according to heating methods, such as a stationary heating method of heating in the state which left aluminum hydroxide still, using a dryer, an electric furnace, etc. Therefore, the heating conditions can be set at the discretion of those skilled in the art in consideration of required properties and productivity.

Commercially available aluminum hydroxide may be used. Examples of the product include H42I (average particle size: 1.1 μm, Na ₂ O amount: 0.29%, Showa Denko KK), HS330 ( Average particle size: 7 μm, Na ₂ O amount: 0.04%, manufactured by Showa Denko KK) and CL303 (center particle size: 2.5 μm, Na ₂ O amount: 0.21%, Sumitomo Chemical Co., Ltd.) Etc.).

Moreover, you may perform the silane coupling process process which processes the particle | grain surface of aluminum hydroxide with a silane coupling agent. Silane coupling treatment improves adhesion between aluminum hydroxide and the resin, can impart not only flame retardancy but also strength to the resin composition, and improves dispersibility in the resin composition. .
As the coupling, for example, vinyltrimethoxysilane, vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane and γ-glycidoxypropyltrimethoxysilane Etc.

(C) Curing agent
Examples of the curing agent used in the resin composition of the present invention include amine compounds (alicyclic polyamines, polyamide polyamines and aromatic polyamines), guanidine compounds represented by dicyandiamide (DICY), acid anhydride compounds, phenols, and the like. Examples thereof include resin compounds and polymercaptans. Although these hardening | curing agents can be added in the range of 0.5-60 mass parts per 100 mass parts of resin, the usage-amount is suitably selected with the kind of hardening | curing agent and the kind and quantity of each resin.
Moreover, a conventionally well-known compound can be used as a hardening accelerator, for example, imidazole compounds, such as 2-ethyl-4-methylimidazole and 1-benzyl-2-methylimidazole, are used individually or in combination of 2 or more types. be able to. Particularly preferred is 2-ethyl-4-methylimidazole. It is preferable to mix | blend a hardening accelerator in the ratio of about 0.01-0.5 mass part with respect to 100 mass parts of said resins.

  And by kneading these, the resin composition of the present invention is obtained. Usually, each material of the resin composition is kneaded while dissolving in an organic solvent to prepare a varnish. As the organic solvent, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, or the like can be used. Among them, preferred are methyl ethyl ketone, methyl isobutyl ketone, xylene and ethylene glycol monomethyl ether, and particularly preferred are methyl ethyl ketone, xylene and ethylene glycol monomethyl ether.

  The varnish is preferably prepared so that the nonvolatile content is about 10 to 80% by mass. More preferably, it is about 30-70 mass%, More preferably, it is about 40-60 mass%. Next, the obtained varnish is impregnated into the base material, and the reaction of the resin proceeds while drying and removing the solvent, thereby obtaining a semi-cured prepreg.

  Dry removal of the solvent is about 80 to 200 ° C., more preferably about 120 to 180 ° C., even more preferably about 140 to 160 ° C., about 2 to 10 minutes, more preferably about 3 to 8 minutes, More preferably, it can be performed for about 4 to 6 minutes.

  In this way, a resin prepreg is obtained. The obtained resin prepreg is not sticky and easy to handle. The resin prepreg is a 3 mm thick resin plate obtained by stacking a predetermined number of sheets and heating and pressing in the thickness direction by the method described later, under the conditions of a frequency of 1 MHz and a temperature of 23 ° C. according to the bridge method specified in JIS K6911. The dielectric constant is preferably about 2.7 to 3.5. More preferably, it is about 2.8 to 3.4, and still more preferably about 2.8 to 3.3.

When manufacturing a resin copper clad board, the said resin prepreg is piled up 1 sheet or 2 sheets or more first, and copper foil is arrange | positioned on the single side | surface or both surfaces. The copper foil having a thickness of about 5 to 70 μm can be used. Subsequently, it heats and pressurizes in the thickness direction using the hot press normally used for manufacture of a copper clad board. The hot press conditions can be a molding temperature of about 160 to 220 ° C., a molding pressure of about 10 to 120 kg / cm ² , and a molding time of about 30 to 300 minutes.

  Further, when preparing a resin circuit board, an unnecessary copper foil portion of the resin copper clad plate may be selectively removed by etching using a ferric chloride solution, an alkaline etching solution, or the like. Furthermore, in the case of a double-sided circuit board, the back and front circuits may be connected by through-hole plating, conductive resin, jumper wires, eyelet pins, or the like.

  In addition, a resin circuit board can be produced by a conventionally known method using the resin prepreg. For example, in a state where one or two or more of the resin prepregs are stacked, a resin plate is manufactured by heating and pressing with the above-described hot press, and a conductive circuit is formed by electroless copper plating or the like on one or both sides of the resin plate. In the case of a double-sided circuit board, the resin circuit board can also be obtained by connecting the front and back circuits by through-hole plating or the like.

  In any case, when the connection between the front and back circuits is made by through-hole plating, the through-hole can be easily formed using a laser. This is because an aramid base material is used as the base material of the prepreg in the resin circuit board, and the aramid base material is made of an organic material unlike a glass base material, and therefore ablation is caused by laser.

Conventionally known lasers can be used, for example, He-Ne laser, Ar laser, Kr laser, CO ₂ laser, N ₂ laser, excimer laser, metal vapor laser, He-Cd laser, ruby laser, YAG. A laser, a glass laser, a semiconductor laser, etc. are mentioned. Among these, a CO ₂ laser, an excimer laser, and a YAG laser are preferable, and a CO ₂ laser and an excimer laser are particularly preferable.

  In manufacturing the resin multilayer circuit board, usually, one or two to five prepregs and one or two to 12 resin circuit boards are appropriately arranged between a pair of copper foils, What is necessary is just to connect between each layer circuit by heat-pressing by pressure press and through-hole plating etc. FIG. The hot-pressing conditions can be the same as in the production of the resin circuit board. The copper foil having a thickness of about 5 to 35 μm can be used.

  Further, the outer layer circuit may be formed by selectively removing unnecessary portions of the outermost copper foil by etching using a ferric chloride solution, an alkaline etching solution, or the like.

  EXAMPLES Hereinafter, although an Example and a test example are shown and this invention is demonstrated in detail, this invention is not restrict | limited to these Examples.

<Preparation of epoxy resin plate>
Brominated bisphenol A type epoxy resin with epoxy equivalent of 500 (Asahi Kasei Epoxy, # 8049 (trade name)) 10.22 parts by mass, brominated novolak type epoxy resin with epoxy equivalent of 316 (NRA-75, NRA-75) (Product name)) 15.32 parts by mass, dicyandiamide (DICY) (described as product name, company name, etc.) parts by mass as a curing agent, 0.02 parts by mass of 2-ethyl-4-methylimidazole as a curing accelerator, first Alumina and aluminum hydroxide described in the table were added and kneaded in a mixed solvent of methyl ethyl ketone and ethylene glycol monomethyl ether at 80 ° C. for about 1 hour to prepare an insulating layer varnish having a nonvolatile content of about 50 mass%.

The prepared varnish was impregnated into a 0.1 mm thick aramid paper substrate (manufactured by Teijin Limited, Technora (trade name)) and dried at 140 ° C. for 5 minutes to prepare a prepreg. 30 sheets of the prepreg were stacked and pressed at a temperature of 190 ° C. and a pressure of 100 kg / cm ² for 100 minutes to prepare a double-sided epoxy resin plate having a thickness of 3 mm. The prepared resin plate was tested with the following evaluation items. The results are shown in Table 2.

<Evaluation of machinability>
The surface of the cured resin was drawn with a commercially available cutter knife and tested to what extent the resin could be cut with a blade. That is, a 10 mm long line is drawn with a commercially available cutter knife on the surface of the cured resin, and the state of the line every 10 times and the state of wear of the cutter knife are observed, and the number of times the line cannot be drawn by scraping the resin surface. Asked. The results are shown in Table 2.

<Measurement of thermal conductivity>
Table 2 shows the results of measuring the thermal conductivity of the resin composition and setting it as “◯” with a maintenance of about 20 w / mk or more.

<Measurement of electrical insulation>
Laminate the resin board before heat curing on the laminated board designed with a comb circuit (line / space = 0.2 mm / 0.2 mm) (conditions: lamination temperature 120 ° C., vacuum degree 40 torr, speed 2 m / min) And cured at 170 ° C. for 1 hour. Then, after applying to the environmental test (85 degreeC / 85% RH, applied electrode 50V (DC)) for 500 hours, the insulation resistance value between lines after applying the voltage of 500V for 60 second was measured. As a result, “×” was maintained with a maintenance of 1 × 10 ¹¹ [Ω] or more. The results are shown in Table 2.

  As a result of testing a resin plate for an insulating layer for the above evaluation items, when alumina and aluminum hydroxide were blended in the resin composition at the same time, the thermal conductivity was the same as when only alumina was blended, and the hardness of the resin plate surface As a result, the peripheral processing of the substrate and the drilling performance were improved and the manufacturability of the electronic substrate was improved.

  As a result of the combined use of alumina and aluminum hydroxide in the thermosetting resin composition of the present invention, the elastic modulus of the insulating resin layer is reduced, and through holes such as through holes in electronic substrates can be made with good workability. It was possible to drill through holes. In addition, there is no generation of cracks, deterioration of insulation reliability, insulation resin layer formed on the cured material filled in the hole or delamination of the lid plating, etc., greatly increasing the productivity of the electronic substrate manufacturing process Improved.

Claims (6)

  A resin composition for an insulating layer of an electronic substrate containing at least a thermosetting resin and alumina and aluminum hydroxide as fillers.   The resin composition for an insulating layer of an electronic substrate according to claim 1, wherein the thermosetting resin is an epoxy resin.   The resin composition for an insulating layer of an electronic substrate according to claim 1 or 2, wherein the filler contains about 30 to about 42% by mass of alumina and about 20 to about 33% by mass of aluminum hydroxide.   4. The insulating layer for an electronic substrate according to claim 1, wherein the mixing ratio of alumina and aluminum hydroxide is about 1: 1 to about 2.1: 1 with respect to alumina. 5. Resin composition.   The resin composition for an insulating layer of an electronic substrate according to any one of claims 2 to 4, wherein the epoxy resin is a bisphenol A type epoxy resin.   In an electronic substrate having a metal core layer, at least one insulating layer laminated thereon, and a conductive layer laminated on the insulating layer, and having a through-hole penetrating the metal core layer, An electronic substrate in which an epoxy resin and a resin composition containing alumina and aluminum hydroxide as fillers are laminated as an insulating layer.