JP2017188519A - Metal base circuit board and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable metal base circuit board which is excellent in thermal conductivity and electric insulation and is useful as a printed wiring board for electronic circuits handling large electric power or a mounting board for heat generating electronic elements.SOLUTION: In a metal base circuit board composed of an insulating layer sandwiched between a circuit foil and a metal base, by containing organic short fibers having thermal conductivity in a longitudinal direction of the insulating layer of 50 W/mK or more, and a fiber diameter of 3 μm or more and 50 μm or less in a state oriented in an upright direction with respect to the metal base surface, a metal base circuit board that is compatible with electrical insulation and high heat dissipation is obtained.SELECTED DRAWING: None

Description

The present invention relates to a metal base substrate used for a printed wiring board and a manufacturing method thereof.

  In recent years, examples of high-density power transistors and hybrid ICs (Integrated Circuits) that are driven at high voltages have increased, and the problem of heat dissipation design has become important, so a metal base substrate with excellent heat dissipation has been used. It has come to be. In addition, the number of cases used outdoors is increasing, and not only the insulating layer but also the improvement in reliability such as moisture resistance and insulation of the resin (solder resist) to be coated on the surface is required. Resin is disclosed (refer patent document 1).

  However, according to the examination results of the present inventors, it has been confirmed that even if a coating resin (solder resist) that is considered to have good moisture resistance is applied, the electrical properties during the moisture resistance test are not at a satisfactory level. .

  In addition, it has been confirmed that such a coating resin has poor thermal conductivity and insulates the heat generated from the mounted components, thereby adversely affecting the coating resin.

  In addition, such a coating resin is generally produced by applying UV (ultraviolet rays) after coating and removing unnecessary portions with a developer, and the resin composition also uses an epoxy resin and an acrylic resin together. Since it is a system, it has been confirmed that the insulation reliability such as heat resistance and moisture resistance is inferior.

On the other hand, Patent Document 2 discloses a metal base circuit board that achieves high heat dissipation and can withstand high humidity by highly filling an inorganic filler having a plurality of particle sizes.

  However, according to the examination results of the present inventors, the insulating layer according to the invention of Patent Document 2 has high heat dissipation due to high filling of the inorganic filler, but has poor heat transfer efficiency and high filling of the filler. Hard and brittle material, resulting in poor impact resistance.

JP 2007-224169 A JP 2009-164540 A

  SUMMARY OF THE INVENTION An object of the present invention is to provide a metal base circuit board having excellent heat conductivity in the heat transfer direction and excellent heat conductivity in the heat transfer direction.

As a result of intensive studies, the present inventors have found that the above problems can be solved by the following means, and have reached the present invention.
That is, this invention consists of the following structures.
[1] In a metal base circuit board comprising an insulating layer sandwiched between a circuit foil and a metal base, the insulating layer has a thermal conductivity in the length direction of 50 W / mK or more and a fiber diameter of 3 μm or more and 50 μm or less. An organic short fiber is contained in a state of being oriented in an upright direction with respect to a metal base surface.
“2” The number of organic short fibers contained in the insulating layer having an inclination angle in the range of 60 ° to 120 ° with respect to the metal base surface is 50% or more of the total number. The metal base circuit board according to [1].
[3] The metal base circuit board “4” according to [1] or [2], wherein the area of the metal base circuit board is 500 square centimeters or more. The method of manufacturing the metal base circuit board in any one of [1] to [3] including the process of making the said organic short fiber stand upright by electric flocking.
[5] The method for producing a metal base circuit board according to [4], wherein at least a metal base previously coated with an adhesive or a circuit foil previously coated with an adhesive is used.
[6] A circuit foil and an insulating layer containing organic short fibers having a thermal conductivity in the length direction of 50 W / mK or more and a fiber diameter of 3 μm or more and 50 μm or less oriented in the thickness direction The method for producing a metal base circuit board according to any one of [1] to [3], wherein the metal base is bonded.

The metal base circuit board of the present invention contains a specific organic short fiber in the insulating layer portion in a direction oriented in the thickness direction, thereby maintaining the heat dissipation performance of the insulating layer and further improving the reliability. A base circuit board can be provided.
A technique for combining fibers with an insulating layer is widely used in printed wiring boards. However, the glass fiber used for a general printed wiring board has a low thermal conductivity, and an effect cannot be obtained in enhancing the heat dissipation characteristics of the insulating layer.
In this invention, the effect of implement | achieving high heat dissipation is acquired by containing the specific organic short fiber oriented in the thickness direction of an insulating layer. Further surprisingly, in manufacturing such a metal base circuit board, the circuit foil and the metal base can be smoothly joined despite the fact that the fibers are oriented in the thickness direction.
In the present invention, the metal base circuit board is obtained by arranging the short fibers in the vertical direction using electrostatic flocking on the metal surface, filling and fixing with a matrix resin to form an insulating layer, and sandwiching between the opposing metal surfaces. When short fibers are oriented in the vertical direction on the substrate surface by electrostatic flocking, not all short fibers are necessarily oriented and arranged in contact with the substrate. It will be arranged away from. Accordingly, the surface on which the short fibers are arranged is in a state in which the fibers are scattered apart. In such a state, when the short fibers are filled with the matrix resin and fixed with being sandwiched between the opposing surfaces, the protruding fibers become an obstacle to bonding. In addition, defects such as voids remain due to the residual gas between the jumped fibers.
However, since the organic short fiber of the present invention has a smaller elastic modulus in the compression direction than that in the tensile direction, it is easily deformed by compression in the thickness direction and maintains a sufficient degree of orientation in the thickness direction. Since the space between the metal substrates can be filled as an insulating layer, a highly reliable metal base circuit board free from voids can be obtained.

  The binder resin used in the insulating layer of the present invention is preferably excellent in heat resistance and thermal stability, and these physical properties can be adjusted to a desired range by appropriately selecting the resin used. In view of adhesion, it is preferable to select a resin having excellent flexibility or a resin having adhesiveness. For example, examples of materials having excellent flexibility include silicone resins, acrylic resins, urethane resins, EPDM, and polycarbonate resins, and examples of materials having adhesive properties include semi-curing of thermoplastic resins and thermosetting resins. The thing of a state is mentioned. As a material excellent in flexibility, a silicone resin that is less susceptible to deterioration due to a change in physical properties due to heat cycle is particularly preferable. The material having adhesiveness is preferably a urethane-based resin having good shock absorption from the viewpoint of thermal shock resistance at the bonding interface with the heating element. It is also possible to impart flame retardancy by selecting a flame retardant material.

In order to improve thermal conductivity, an inorganic filler may be added to the insulating layer and used in combination with the organic short fibers.
As an inorganic filler for improving thermal conductivity, aluminum oxide, silicon nitride, magnesium oxide, aluminum nitride, silicon nitride, boron nitride, etc., as long as they are electrically insulating and have better thermal conductivity than resin, Can be used. In addition, the inorganic filler may be spherical, crushed, rod-shaped, or fibrous.
The average particle size of the inorganic filler of the present invention is preferably from 0.3 μm to 20 μm, more preferably from 0.5 μm to 12 μm, and preferably from 0.9 μm to 6 μm. Here, the average particle diameter is D50 determined by the light scattering method. The average particle diameter of the organic filler of the present invention is preferably in the range of the same size as the fiber diameter of the organic short fiber to 1/10 of the fiber diameter. Heat transfer is particularly preferably performed when the ratio of the sizes falls within this range.

In a system containing such an inorganic filler, it is preferable to add a coupling agent such as a silane coupling agent to the resin. Since ionic impurities that deteriorate the electrical characteristics during moisture absorption are introduced in a large amount into the insulating layer by the inorganic filler, a significant improvement in characteristics can be achieved by using in combination with an ion-adsorbing inorganic substance. In addition, the deterioration of electrical characteristics during moisture absorption is greatly influenced by the interfacial adhesion between the inorganic filler and the resin, and the addition of a coupling agent that contributes to the interfacial adhesion is essential. Although the inorganic filler in an insulating layer is based on the objective to add, addition of 10 mass parts or more and 80 mass parts or less is preferable with respect to 100 mass parts of resin, and also addition of 20 mass parts or more and 50 mass parts is preferable.
The coupling agent is calculated from the coating area per unit weight of the coupling agent and the surface area of the inorganic filler as an addition amount to be covered with the monomolecular layer even if the surface area of the inorganic filler particles is small.

In the present invention, the number of organic short fibers having an inclination in the range of 60 ° to 120 ° with respect to the sheet surface is 50% or more in a cross section cut perpendicularly to the surface direction at an arbitrary position of the insulating layer. It is preferable.
The number of organic short fibers having an inclination in the range of 60 ° to 120 ° with respect to the sheet surface is 50% or more, preferably 60% or more, more preferably 75% or more, and still more preferably 85% or more. If the number of organic short fibers having an inclination in the range of 60 ° to 120 ° with respect to the sheet surface is less than the predetermined range, the degree of orientation of the organic short fibers in the thickness direction is low, and the thermal conductivity in the thickness direction is low. descend.

The orientation angle and the ratio of the organic short fibers in the present invention can be evaluated by the methods of Examples described later.

The metal base circuit board of the present invention comprises:
-It can manufacture by the method including the process of making the said organic short fiber stand upright by electrostatic flocking to either a metal base or circuit foil.
Also,
It is preferable to use at least a metal base coated with an adhesive in advance, or a circuit foil coated with an adhesive beforehand.

The metal base circuit board of the present invention is preferably manufactured by a method including at least the following steps (3) to (8), preferably further including the step (2), and including the step (1). Is more preferable.
(1) A step of coating the organic short fibers with a resin different from the binder resin or irradiating with an electron beam.
(2) A step of cutting the organic short fibers into an arbitrary length.
(3) A process in which either a metal base coated with an adhesive or a circuit foil is used as a base material, and organic short fibers are erected on the base material by electrostatic flocking.
(4) A step of bonding and fixing upright organic short fibers by heating.
(5) A step of impregnating a binder resin into organic short fibers fixed upright on a substrate to cure the binder resin.
(6) A step of forming the surface by polishing and adjusting the thickness of the substrate as it is.
(7) The process of arrange | positioning the resin layer which disperse | distributed the heat conductive filler to uncured thermosetting resin on the molded object surface which prepared thickness.
(8) A step of bonding a metal base or circuit foil on an uncured resin layer by pressing or laminating.

The metal base preferably used in the present invention is not particularly limited as long as it is a metal plate material, but aluminum, aluminum alloy, copper, and copper alloy can be preferably used.
As the circuit foil in the present invention, copper foil, copper alloy stay, nickel foil, aluminum foil, silver foil, silver alloy foil can be preferably used.

The organic short fiber used in the present invention has a fiber diameter of 3 μm or more and 50 μm or less. The fiber diameter of the organic short fiber of the present invention is preferably 5 μm or more and 30 μm, and preferably 7 μm or more and 30 μm or less. The fiber diameter may be measured on a scale by obtaining an enlarged image of the fiber with an electron microscope or the like.
The fiber diameter of the organic short fiber is important for obtaining an interaction with the heat conductive filler that is separately blended. When the fiber diameter exceeds the predetermined range, heat is transferred to and from the heat conductive filler quickly. I will not be broken. When the fiber diameter is below the specified range, the heat transfer effect is essentially increased, but the specific surface area of the fiber increases, so the amount of binder resin absorbed increases and the insulation layer is formed. Becomes difficult.

The thermal conductivity of the organic short fiber of the present invention is essential to be 25 W / mK or more, more preferably 35 W / m, and still more preferably 50 W / m.
The fiber type is not particularly limited as long as it is electrically insulating and has a predetermined high thermal conductivity and fiber diameter, and examples thereof include high-strength polyethylene fiber, polybenzazole fiber, and aromatic polyamide fiber. Among them, polybenzazole fibers that have heat resistance and are easily available are particularly preferable. Polybenzoxazole fiber, polybenzothiazole fiber, and polybenzimidazole fiber can be used as the polybenzazole fiber. Among these, Zylon manufactured by Toyobo Co., Ltd., which is a kind of polybenzazole fiber, can be preferably used. The cross-sectional shape of the organic short fiber of the present invention is preferably circular.

  The length of the organic short fiber used in the present invention is preferably 30 μm or more and 500 μm or less, more preferably 40 μm or more and 250 μm or less, and further preferably 50 μm or more and 150 μm or less.

Electrostatic flocking is a method in which a base material is placed on one side of two electrodes, and short fibers are placed on the other side. By applying a high voltage, the short fibers are charged and cast on the base material side and fixed by an adhesive. .

The electrostatic flocking in the present invention is preferably performed by an electrostatic flocking method capable of obtaining a high flocking density, and an up method is preferred. In the down method, short fibers that naturally fall by gravity are planted in addition to the short fibers that are attracted to the counter electrode along the lines of electric force by electrostatic attraction, so that the uprightness of the fibers is poor. As a result, infiltration of another fiber is prevented by the fibers that are planted at an inclination, so that it is difficult to plant at a high density. On the other hand, the up method has good uprightness because only short fibers attracted by electrostatic attraction are implanted, and can be implanted at high density.

The electric field strength E, which is the product of the inter-electrode distance r (cm) of the electrostatic flocking and the applied voltage V (kV) in the present invention, is preferably within the range of Formula 1, and the fiber length ( The quotient a of mm) and the fineness (D) is preferably within the range of Formula 2. If E is equal to or less than the range of Formula 1, the electric field strength is insufficient and high density hair transplantation cannot be performed. When E is 8 or more, dielectric breakdown occurs and electrostatic flocking cannot be performed normally. When a is 1.5 or less, the aspect ratio of the fiber becomes large, and it becomes difficult to maintain uprightness by its own weight. When a is 10.2 or more, the aspect ratio becomes small, and the polarizability in the fiber axis direction in the fiber becomes small.
0.25a + 3.37 ≦ E ≦ 8 Equation 1
(R: distance between electrodes (cm), V: applied voltage (kV), E = V / r)
2 ≦ a ≦ 10 Formula 2
(A: Fineness (D) / Fiber length (mm))
By performing electrostatic flocking within the above-mentioned range, it is possible to achieve a high density of organic short fiber penetration density.

The flocking density, that is, the fiber penetration density, can be controlled by adjusting E according to the applied voltage and the interelectrode distance. It can be adjusted by preparing a calibration curve of penetration density of E and fiber in advance and electrostatic flocking with E suitable for the desired penetration density.

  In the present invention, electrostatic flocking is preferably performed on a circuit foil or metal base coated with an adhesive. Although the material of the adhesive agent used here is not specifically limited, the direction which has electroconductivity in a non-hardened state is preferable at the point which can carry out electrostatic flocking at high density. In the present invention, it is preferable to use a water-dispersible adhesive, for example, an aqueous adhesive using an ethylene vinyl acetate copolymer, a water-dispersible ionomer, a water-dispersible acrylic resin, a water-dispersible epoxy resin, or the like. Can do. In the present invention, when a sufficient electrostatic flocking density is obtained, a solvent-based or hot-melt adhesive can also be used. In order to obtain a high flocking density in electrostatic flocking, it is preferable that the coating thickness of the adhesive is small in order to increase electrostatic attraction, but it is necessary to be large enough to fix the fibers cast on the adhesive layer. Therefore, it is preferably 10 μm or more and 50 μm or less, more preferably 10 μm or more and 30 μm or less.

In the production process of the present invention, the step of impregnating the organic short fibers fixed upright on the base material with the binder resin and curing the binder resin can be performed by any of the following methods. (i) a method in which a binder resin is dissolved in some solvent or impregnated in an emulsion state, and the solvent is evaporated and solidified by heating; (ii) a method in which the binder resin is melted by heating and is cured by cooling; and (iii) A method of impregnation in the state of monomer and heating or curing with energy rays such as ultraviolet rays, infrared rays or electron beams.

In this invention, you may include the process which planarizes the insulating resin layer which consists of binder resin and an organic short fiber. Here, as the polishing means, slicing, embossing, and polishing can be performed.
For the polishing in the present invention, a grinding machine, a polishing machine, a lapping machine, a polishing machine, a honing machine, a buffing machine, a CMP apparatus, or the like can be used.

  In the present invention, the circuit foil can be patterned by appropriately selecting a known processing method such as general etching processing or cutting processing with a high-power laser.

In the present invention,
Prepare in advance an insulating layer containing organic short fibers having a thermal conductivity in the length direction of 50 W / mK or more and a fiber diameter of 3 μm to 50 μm oriented in the thickness direction, It is also possible to manufacture a metal base circuit board by adhering a circuit foil and a metal base to the insulating layer.
In this case, the organic short fibers are similarly oriented, fixed, and impregnated with a binder resin on the temporary substrate. After surface polishing as necessary, the circuit foil and the metal base are sandwiched by pressing, laminating, etc. What is necessary is just to laminate. In this case, an adhesive layer may be separately provided on the surface of the insulating layer. Further, the adhesive layer may contain a heat conductive filler.

  The area of the metal base circuit board of the present invention is 500 square cm or more, preferably 900 square cm or more, and more preferably 1600 square cm or more. The upper limit of the area of the metal base circuit board is preferably about 14400 square cm.

EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited by a following example. In addition, the evaluation method of the physical property in the following examples is as follows.
1. The inclination of the high thermal conductivity fiber and the ratio thereof The inclination and the ratio of the high thermal conductivity fiber were evaluated by the following methods.
(1) A flocked sheet is embedded with an epoxy resin and polished to obtain a cross section in the thickness direction of the sheet.
(2) Photograph the cross section in the thickness direction of the sheet with a 20-magnification lens of an epi-illumination optical microscope.
(3) Select 100 fibers at random and measure the angle in the fiber length direction with respect to the smooth surface.
(4) From the obtained angle data, the average value of the angles, the number of fibers having an orientation angle of 60 ° or more and 120 ° C. or less, and the number of fibers of 80 ° or more and 100 ° or less are counted. Asked.
2. A TO-220 type transistor was soldered on the heat resistance copper foil of the metal base circuit board, and fixed on the water-cooled heat radiation fin via heat radiation grease. Energize the transistor, heat the transistor, measure the temperature difference between the transistor surface and the back of the metal base, measure the thermal resistance value, and correct the thermal resistance value of the heat dissipation grease to measure the thermal resistance value of the test piece did.
3. As a sample for measuring the withstand voltage of the metal base circuit board, the original plate of the metal base circuit board that was produced was etched, and the desired circuit was produced as a sample.
・ Initial ・ After migration test: after exposure under conditions of 85 ° C., humidity 85% RH, DC 1000V, 1000 hours (migration test) ・ After PCT test: conditions of 121 ° C., humidity 100% RH, 2 atm, 96 hours ( After exposure under PCT treatment)
In accordance with JIS C 2110, the dielectric breakdown voltage was measured when a parallel plate and DC were applied, and the dielectric breakdown strength was determined by dividing the dielectric breakdown voltage by the thickness of the insulating layer. As a measuring instrument, TOS-8700 manufactured by Kikusui Electronics Co., Ltd. was used.

〔Example〕
Specific examples will be described below.
Example 1
As the organic short fiber, Zylon HM (manufactured by Toyobo; fiber diameter: 12 μm, thermal conductivity in the fiber axis direction: 60 W / mK, organic short fiber A) cut to a length of 120 μm was used. As binder resin solution, Toyobo saturated copolymer polyester urethane solution UR3600 / 80.9 parts by weight, Toyobo saturated copolymer polyester urethane solution BX-10SS / 12.0 parts by weight, Toyobo epoxy resin AH-120 / 7.1 A solution in which 100 parts by weight of methyl ethyl ketone and 100 parts by weight of methyl ethyl ketone were mixed was used. As an adhesive, an aqueous solution containing 10% by mass of a water-based epoxy resin and 1% by mass of a curing agent (water-soluble polyamine) was used. As the metal base, an aluminum plate having a width of 520 mm, a length of 620 mm, and a thickness of 1.5 mm was used. The substrate was placed on the positive electrode plate, and the adhesive was applied to a thickness of 25 μm. Here, electrostatic flocking was performed for 5 minutes at a distance between electrodes of 10 mm and an applied voltage of 6 kV, and a metal base plate in which xylon was flocked was produced.
The implanted metal base plate was impregnated with a binder resin solution, vacuum degassed, and then heated at 100 ° C. for 6 hours to obtain a dry / semi-cured state. A copper foil having a thickness of 70 μm was overlaid thereon and heated by a vacuum press at 140 ° C. for 2 hours to complete the curing, thereby producing a base plate of a metal base circuit board.

  A metal base circuit board having a circuit pattern for mounting a power transistor and an electrode pattern for dielectric breakdown voltage evaluation by a conventional method using a dry film resist and cupric chloride etching solution on a copper foil of a metal base circuit board original plate Obtained.

  Each characteristic of the obtained metal base circuit board was examined as described above, and the results are shown in Table 1.

(Example 2)
Dyneema SK71 (manufactured by Toyobo; fiber diameter 11 μm, fiber axis thermal conductivity 50 W / mK, organic short fiber B) with organic short fibers cut to a length of 200 μm, drying temperature at 60 ° C. with vacuum press A metal base circuit board original plate was produced in the same manner as in Example 1 except that the temperature at the time of pressure overheating was 80 ° C. and the heating time was 4 hours.
Hereinafter, patterns were similarly formed and evaluated. (Example 3)
Except for changing to Kevlar (manufactured by Toray DuPont, aramid fiber, fiber diameter 11 μm, thermal conductivity in the fiber axis direction is 60 W / mK, organic short fiber C) obtained by cutting organic short fibers into a length of 80 μm. 1 to obtain a metal base circuit board. The results evaluated in the same manner are shown in Table 1.

Example 4
Resin solution (resin solution) mixed with liquid silicone rubber base TSE3431-A / 100 parts by mass of Momentive Performance Materials, and liquid silicone rubber curing agent TSE3431-C / 30 parts by mass of Momentive Performance Materials A metal base circuit board was obtained in the same manner as in Example 1 except for changing to Y). The results evaluated in the same manner are shown in Table 1. Shown in

(Example 5)
A metal base circuit board was obtained in the same manner as in Example 1 except that silicon dioxide (inorganic filler α) average particle size of 0.15 μm was added as an inorganic filler to the binder resin solution. The results evaluated in the same manner are shown in Table 1. Shown in

(Example 6)
As the organic short fiber, Zylon HM (manufactured by Toyobo; fiber diameter: 12 μm, thermal conductivity in the fiber axis direction: 60 W / mK, organic short fiber A) cut to a length of 360 μm was used. As binder resin solution, Toyobo saturated copolymer polyester urethane solution UR3600 / 80.9 parts by weight, Toyobo saturated copolymer polyester urethane solution BX-10SS / 12.0 parts by weight, Toyobo epoxy resin AH-120 / 7.1 A solution in which 100 parts by weight of methyl ethyl ketone and 100 parts by weight of methyl ethyl ketone were mixed was used. As an adhesive, a 10 wt% aqueous solution of polyvinyl alcohol AH-26 (manufactured by Nippon Synthetic Chemical Co., Ltd.) was used. As a temporary substrate, a stainless steel plate with a surface hard chrome processed having a thickness of 5 mm was used. The substrate was placed on the positive electrode plate, and the adhesive was applied to a thickness of 25 μm. Here, electrostatic flocking was performed at a distance of 30 mm between electrodes and a voltage of 18 kV for 5 minutes to prepare a metal base plate in which xylon was implanted.
The binder resin solution is mixed with a MEK dispersion having an average particle size of 3.6 μm aluminum oxide (inorganic filler β), impregnated with the mixed binder resin solution on a metal base plate that has been planted, and vacuum degassed. , Heated for 6 hours to a dry / semi-cured state.
Next, the surface is polished with a buff until the insulating layer thickness becomes 150 μm, then submerged in a water tank, and swelled and dissolved in polyvinyl alcohol, peeled off from the temporary support base, dried at 80 ° C. for 120 minutes, and organic short fibers Thus, an insulating resin layer oriented in the thickness direction was obtained.
Using a 5 mm thick aluminum plate as the metal base and a 70 μm thick copper foil as the circuit foil, the mixture of the binder resin solution and the MEK dispersion of the inorganic filler is applied to each surface. It was applied to 20 parts by mass with respect to 100 parts by mass of the resin and a dry thickness of 8 μm, and was heated to 100 ° C. for 1 hour to be dried and semi-cured.
Overlay the insulating layer on the metal-based resin-coated surface, and then stack the circuit foil so that the resin-coated surface is on the insulating layer side, press with a vacuum press and heat at 140 ° C. for 2 hours to complete the curing. An original substrate was produced. The results evaluated in the same manner are shown in Table 1. Shown in

(Comparative Example 1)
The metal base circuit was made in the same manner as in Example 1 except that the organic short fiber A was mixed with the binder resin without using the electrostatic flocking, and the insulating layer was formed on the metal base by coating using this binder resin solution. A substrate was obtained. The results evaluated in the same manner are shown in Table 1. Shown in

(Comparative Example 2)
A metal base circuit board was obtained in the same manner as in Comparative Example 1 except that the organic short fibers were not used and instead the inorganic filler α was used. The results evaluated in the same manner are shown in Table 1. Shown in

The metal base circuit board according to the present invention has a high thermal conductivity in the heat transfer direction by laminating an insulating layer in which organic short fibers are oriented in the thickness direction between the metal base and the circuit foil. The characteristic deterioration after the acceleration test is small and has excellent characteristics, and can exhibit excellent characteristics as a printed wiring board for electronic circuits that handle high power or a mounting substrate for heat-generating electronic elements.

Claims (6)

A metal base circuit board comprising an insulating layer sandwiched between a circuit foil and a metal base, wherein the insulating layer has a thermal conductivity in the length direction of 50 W / mK or more and a fiber diameter of 3 μm or more and 50 μm or less. Is contained in a state of being oriented in an upright direction with respect to the metal base surface.   The number of organic short fibers contained in the insulating layer having an inclination angle in the range of 60 ° to 120 ° with respect to the metal base surface is 50% or more of the total number. A metal-based circuit board according to claim 1.   3. The metal base circuit board according to claim 1, wherein an area of the metal base circuit board is 500 square cm or more.   The method for producing a metal base circuit board according to any one of claims 1 to 3, comprising a step of erecting the organic short fibers on either the metal base or the circuit foil by electrostatic flocking.   The manufacturing method of the metal base circuit board of Claim 4 using the metal base which apply | coated the adhesive previously, or the circuit foil which apply | coated the adhesive previously. A circuit foil and a metal base are formed on an insulating layer containing organic short fibers having a thermal conductivity in the length direction of 50 W / mK or more and a fiber diameter of 3 μm to 50 μm oriented in the thickness direction. A method for producing a metal base circuit board according to claim 1 by bonding.