JP2003209209A - Highly thermal conductive material, substrate for wiring board using it, and thermoelectric element module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable and highly thermal conductive material at a lower cost while sustaining a sufficiently high thermal conductivity, a novel substrate for wiring board utilizing that material, and a thermoelectric module. <P>SOLUTION: A mixture of carbon powder and phenol resin is compacted while applying a vibration and hot pressed to have a specified shape thus producing a highly thermal conductive material. The mixture may be admixed with a thermally conductive filler. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wiring board substrate,
It belongs to the technical field of high thermal conductivity materials suitable as substrates for power generation element modules utilizing the Seebeck effect, cooling / heating element modules utilizing the Peltier effect, and the like.

[0002]

2. Description of the Related Art Conventionally, a wiring board substrate in which a metal foil such as a copper foil is laminated on a substrate has been widely used. This wiring board substrate is made into a printed wiring board by a photolithography technique in which a wiring pattern is drawn on a metal foil portion and etching is performed along the wiring pattern, and is used in various electric and electronic devices.

The printed wiring board generally generates heat from the circuit as it is used. In this case, if heat accumulates in the vicinity of the circuit and the temperature rises, an unexpected failure such as thermal runaway may occur, so it is necessary to quickly dissipate the generated heat. However, the conventional printed wiring board substrate (that is, the wiring board substrate)
Is composed of a synthetic resin such as epoxy resin or polyimide resin, or a laminate of multiple sheets of paper impregnated with phenolic resin.Since such a synthetic resin is inferior in its thermal conductivity, it is generated. There was a problem that the heat was not sufficiently dissipated.

On the other hand, the inventor of the present invention has invented a wiring board substrate which is superior in thermal conductivity as compared with the conventional one and can dissipate generated heat quickly, and has already applied for a patent (patent application). Two
000-214963). This invention is one in which a metal foil or a lead frame is laminated on a carbonaceous substrate such as a carbon fiber reinforced composite material with an insulating adhesive layer interposed between them. It has very good heat dissipation. However, the above-mentioned carbonaceous substrate is slightly expensive, and further reduction of manufacturing cost has been desired from a commercial standpoint.

On the other hand, conventionally, thermoelectric element modules utilizing the Seebeck effect and the Peltier effect have been known. The thermoelectric element module is basically arranged by arranging a plurality of substrates facing each other, and joining metal electrodes to the facing surfaces of the respective substrates,
It has a structure in which a plurality of n-type and p-type semiconductors are alternately connected via the metal electrode. Then, this thermoelectric element module is used as a power generation element module by utilizing the Seebeck effect in which an electromotive force is generated when one substrate side is heated to a high temperature and the other substrate side is cooled to form a temperature difference. Or, when a current is passed from an n-type semiconductor to a p-type semiconductor (or vice versa), heat is absorbed on one substrate side, and heat is generated on the other substrate side. It is used as a cooling / heating element module.

As a substrate of the thermoelectric element module,
Conventionally, a ceramic plate has been mainly used. However, since the ceramic plate is inferior in thermal conductivity, there is a problem that thermal efficiency is poor. In addition, as a means for improving the thermal efficiency, one using a metal plate such as aluminum for the substrate is known. However, although the metal plate has good thermal conductivity, the coefficient of thermal expansion is much larger than that of a semiconductor or a ceramic plate, so that a large thermal stress is generated between the metal plate of the substrate and the semiconductor, resulting in a bond. There is a risk of peeling of parts, damage of the semiconductor, etc., and there was a problem in terms of reliability.

Therefore, the inventor of the present invention invented a thermoelectric element module using a carbonaceous substrate such as a carbon fiber reinforced composite material as the substrate, and has already filed a patent application (Japanese Patent Laid-Open No. 2-216058)
001-135867). This thermoelectric element module has the features that it can greatly improve the overall thermal efficiency and has high reliability because of the carbonaceous substrate having high thermal conductivity. However, as in the case of the wiring board substrate described above, since the carbonaceous substrate is slightly expensive, it has been required to further reduce the manufacturing cost.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned conventional circumstances, the present invention aims to provide a highly heat-conductive material having a low cost and a high reliability while maintaining a sufficiently high heat conductivity. And Another object of the present invention is to provide a novel wiring board substrate and a thermoelectric element module using the material.

[0009]

In order to solve the above-mentioned problems, the high thermal conductivity material of the present invention is, as claimed in claim 1, a mixture of carbon powder and phenol resin, which is heated and pressed into a predetermined shape. It is characterized by being cured.

According to the above means, the carbon powder is well dispersed in the phenol resin, and the material as a whole has excellent thermal conductivity and strength. Here, the carbon powder refers to a powder containing carbon as a main component, and may be crystalline or amorphous. Specifically, it includes graphite powder, carbon black, charcoal powder and the like.

The high thermal conductive material according to claim 2 is
It is characterized in that a mixture of carbon powder and a phenol resin is stiffened while being vibrated and heated and pressed and cured to have a predetermined shape.

According to the above means, by applying vibration, the carbon powder is cured in a state where the carbon powders are evenly arranged, so that the overall thermal conductivity is improved.

A third aspect of the present invention is the high thermal conductive material according to the first or second aspect, wherein the phenol resin is mixed in an amount of 5 to 40% by weight with respect to the mixture of carbon powder and the phenol resin. .

According to the above means, the mixing ratio of the phenol resin and the carbon powder is optimized in order to secure sufficient strength as a whole while maintaining high thermal conductivity.

A fourth aspect of the present invention is characterized in that, in the high thermal conductive material according to any one of the first to third aspects, the mixture is further mixed with a powdery thermal conductive filler.

According to the above means, a specific filler is used in combination in order to further enhance the overall thermal conductivity.

A fifth aspect of the present invention is characterized in that, in the high thermal conductivity material according to any one of the first to fourth aspects, the predetermined shape is a plate shape.

According to the above means, the shape of the high thermal conductive material is specified according to the application.

Further, a sixth aspect of the present invention is a wiring board substrate comprising a metal layer on at least one surface of the high thermal conductive material according to the fifth aspect with an insulating layer interposed therebetween.

According to the above means, there is provided a wiring board substrate which can quickly dissipate heat generated in a circuit or the like.

Further, in a seventh aspect of the present invention, a plurality of the high thermal conductive materials according to the fifth aspect are arranged so as to face each other, and a metal electrode is bonded to the facing surface of each high thermal conductive material via an insulating layer. , A thermoelectric element module in which a plurality of n-type and p-type semiconductors are alternately connected via the metal electrodes.

According to the above means, the heat conductivity of the substrate is high, so that the heat-electricity conversion efficiency by the Seebeck effect and the Peltier effect is improved. In addition, thermal stress is suppressed and reliability is improved.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The high thermal conductive material of the present invention is roughly constituted by heating a mixture of carbon powder and a phenol resin into a plate shape and pressurizing and curing the mixture.

The carbon powder may be crystalline or amorphous as long as it contains carbon as a main component.
Specific examples include carbon black, graphite, charcoal powder and the like. Carbon black is a black powder containing carbon as a main component and containing oxygen, hydrogen, and nitrogen, and can be obtained by incomplete combustion or thermal decomposition of natural gas, petroleum, animals or plants. Depending on its raw material and manufacturing method, thermal black, acetylene black, channel black, furnace black,
Lamp black, bone black, etc. are known, but any of the present invention is applicable. Further, graphite is usually a hexagonal plate-shaped flat plate having a hexagonal plate shape, and has high thermal conductivity, so that it is particularly preferably used as the carbon powder in the present invention. Graphite can be generally obtained by kneading tar pitch, petroleum coke, etc. and heating at a high temperature of 2500 ° C. or higher in an electric resistance heating furnace. Alternatively, it may be obtained by thermally decomposing carbon carbide on a high-temperature substrate, or by thermally decomposing and accumulating a polymer thin film mainly composed of carbon.

The shape of the carbon powder is not particularly limited, and a spherical shape, a fibrous shape or the like can be appropriately selected. Among them, spherical carbon powder is preferable because it is easy to uniformly disperse in the phenol resin, the orientation is random, and there is no unevenness in thermal conductivity depending on the direction, so that reliability is high when an element is formed. When fibrous carbon powder is used, the aspect ratio is set to ensure uniform dispersion.

If the particle size of the carbon powder is too large, the dispersibility in the phenol resin will deteriorate and the thermal conductivity will decrease.
The strength of the entire material tends to decrease. On the other hand, if it is too small, it is difficult to handle.

Next, as the phenol resin, novolac type and resol type are known depending on the synthesis conditions, but the present invention is applicable. Also in powder form,
Either of the melted liquids may be used, but powdery ones are more preferable in consideration of the mixing property with the carbon powder. Further, the raw material monomer is not limited to phenol, and any resin composed of a phenol derivative such as cresol, xylenol, p-ter-butylphenol, p-phenylphenol, resorcinol can be applied. Since the molecular weight of the phenol resin is generally low, it has a high affinity for the carbon powder, and therefore, even if the carbon powder is about 9 times the amount of the phenol resin, a good dispersion state can be maintained.

When a powdery phenol resin is used, its particle size is not particularly limited, but it is preferable that the particle size is about the same as that of carbon powder because it can be uniformly dispersed and the thermal conductivity becomes high.

Regarding the mixing ratio of the carbon powder and the phenol resin, when the relative amount of the phenol resin is small (the carbon powder is large), the moldability due to pressurization becomes poor and the strength of the obtained material also becomes weak. On the contrary, when the carbon powder is small (the phenol resin is large), the thermal conductivity is lowered. Therefore,
Considering these balances, the ratio of phenol resin is
5-40 for a mixture of carbon powder and phenolic resin
It is preferable to set it as a weight%, especially 5 to 20 weight%. Within this range, the carbon powders dispersed in the material are in contact with each other to maintain high thermal conductivity, and the phenol resin is evenly distributed and cured in the material,
Sufficient strength is secured.

In addition to the above carbon powder and phenol resin, various heat conductive fillers can be blended. The heat conductive filler is appropriately selected in consideration of dispersibility in the phenol resin. Specifically, Cu-Zn
Examples thereof include soft magnetic ferrites based on Ni, Zn, Mn, Mg, etc., aluminum nitride, boron nitride, aluminum powder, carbon nanotubes, carbon microcoils, and the like. The particle size of the thermally conductive filler is preferably about the same as the carbon powder from the viewpoint of uniformly mixing the raw materials.

The amount of the above-mentioned thermally conductive filler compounded is not particularly limited, but if it is too large, the moldability and strength of the material tend to decrease. Therefore, specifically, it is preferably 20% by weight or less based on the total amount of the carbon powder and the phenol resin.

In addition, a curing agent, a catalyst, a plasticizer, an antioxidant and the like can be appropriately added to the high thermal conductive material of the present invention.

The means for mixing the above-mentioned carbon powder, phenol resin and other raw materials is not particularly limited, and various mixers and the like can be appropriately selected and uniformly mixed.

Then, a mixture obtained by uniformly mixing the respective raw materials is
It is possible to complete the polymerization of the phenol resin by press-molding into a plate-like shape with various presses and heating to obtain the desired high thermal conductivity material. The heating may be performed prior to the pressure molding, or the heating may be performed simultaneously with the pressing. Alternatively, the mixture can be first kept under pressure and then heated to polymerize. If the density of the material after curing is too small, the strength of the obtained material may be weakened and the thermal conductivity may be lowered. On the other hand, if the density is too high, especially when graphite is used, the crystal itself is cleaved and destroyed, resulting in a rather low thermal conductivity, or carbon powder is oriented in one direction in the material and the thermal conductivity is reduced. The rate may be anisotropic or uneven. In addition, since the material itself may be destroyed, these are taken into consideration and set appropriately.

The pressure for pressurizing, the pressurizing time, and the temperature for heating are not particularly limited and can be set appropriately. Specifically, it varies depending on the types of carbon powder and phenolic resin, the mixing ratio, etc., and cannot be generally stated, but for example, a mixture of powdered novolac type phenolic resin and graphite powder (the ratio of phenolic resin is 10% by weight) is heated and pressure-cured,
It is appropriate that the pressure is about 200 to 3000 kgf / cm ² , the pressing time is about 5 to 30 minutes, and the heating temperature is 180 to 220 ° C.

Further, in the present invention, the thermal conductivity can be further enhanced by stiffening a mixture of carbon powder, phenol resin and other raw materials while applying vibration.
This step is usually performed before the heating / pressurizing step described above, but in some cases, it may be performed on the plate-shaped material after curing. Specifically, for example, the apparatus shown in FIG. 3 can be preferably used. In Figure 3,
The molds 31 and 31 'are set on the shaker 30, and the mixture 32 to be stiffened is sandwiched between them. And
While the high frequency vibration is applied by the vibration exciter 30, the weight 33 attached to the mold 31 ′ is moved up and down to apply impact vibration, so that the mixture 32 is solidified. As a result, the carbon powder, the phenol resin powder, and the like are evenly arranged so as to fill the gaps between them, and are quickly and strongly solidified, so that the transfer of heat becomes smoother and the overall thermal conductivity is improved. In addition, in the example of FIG. 3, a case where high frequency vibration is applied from one side and a shock due to vertical movement of the weight is applied from the other side is shown. The mixture may be compacted by subjecting both molds to high frequency vibration separately. Alternatively, one of the molds may be fixed and the other may be vibrated for hardening.

When vibration is applied using a vibration exciter or the like as described above, various conditions such as frequency, amplitude, acceleration and vibration time differ depending on the amount of the mixture and the heating / pressurizing conditions. I can't say for sure. Generally, frequencies 20-1
000 Hz, amplitude 0.01-5 mm, acceleration 0.2-1.
0 G and a vibration time of about 1 to 10 minutes are suitable, but the invention is not limited thereto.

The plate thickness of the high thermal conductive material is appropriately set in consideration of the application etc., but if it is too thin, the strength will be insufficient, and if it is too thick, carbon powder will be unevenly distributed in the center of the material during polymerization. Since the overall thermal conductivity is reduced, it is preferable to set the thickness to about 0.1 to 5 mm in consideration of the balance between them. However, it is not limited to this.

In the above, the case of manufacturing a plate-shaped high heat conductive material has been described, but the present invention is not limited to this, and it can be molded into a predetermined shape according to the final application.
Moreover, you may use what was shape | molded by block shape etc. suitably cut | disconnected to the shape according to a use. Such a highly heat-conductive material having a predetermined shape can be used as an IC for a lid, a heat spreader, etc., as well as a wiring board substrate and a thermoelectric element module described later.
It can be used for a variety of parts such as electrothermal parts for packages and parts for semiconductor lasers, optical devices, microwave devices such as carriers, submounts and stems.

Next, a wiring board substrate using a plate-shaped high thermal conductive material as a substrate will be described. FIG. 1 is a sectional view of an embodiment of a wiring board substrate. The wiring board substrate 1 of FIG. 1 is roughly configured by providing a metal layer 12 on one surface of a high thermal conductive material 10 with an insulating layer 11 interposed therebetween.

As the metal layer 12, usually, a metal foil made of various metals such as copper, nickel and aluminum is preferably used. The thickness of the metal foil is not particularly limited, but it is preferably relatively thin. In addition, the metal layer 12
Can also be formed by metal plating. The metal plating can be performed by appropriately adopting the conventionally known electroless plating method or vacuum deposition method. Then, a circuit pattern is formed on the metal layer 12 formed by the above metal foil or metal plating by means such as photolithography to obtain a printed wiring board. Further, as the metal layer 12, a so-called lead frame, which is produced by punching out a circuit pattern in advance, can be used in addition to the above metal foil and the like.

The insulating layer 11 serves to insulate and adhere between the substrate of the high thermal conductive material 10 and the metal layer 12,
Generally, it can be formed by appropriately selecting from various conventionally known adhesives under the condition that they do not melt or deteriorate at the temperature at which heat is generated from the circuit. Specific examples include rubber-based, acrylic resin-based, polyamide-based, polyimide-based, epoxy-based, ethylene-vinyl acetate copolymer, and silicone resin-based adhesives.

When the wiring board substrate 1 is manufactured, the surface of the high thermal conductive material 10 is coated with the above-mentioned adhesive by a known means such as a spraying method, a calendering method, a wire bar coating method or a dipping method. Alternatively, it can be manufactured by applying it on the surface of the metal layer 12 such as a metal foil or a lead frame, and adhering the high thermal conductive material 10 and the metal layer 12 to each other. At that time, the high thermal conductive material 10 and the metal layer 12 are laminated, and the adhesive can be cured while being pressed as necessary with various pressing machines such as a roll or a flat plate press, while being heated if necessary. The pressure at which the pressure is applied varies depending on the type of adhesive and the thickness of the substrate and is not particularly limited, but care should be taken not to increase the density of the high thermal conductive material 10 too much and reduce the thermal conductivity. . By pressurizing, the high thermal conductive material 10 and the metal layer 12 are cured while being strongly adhered to each other, so that defects between layers that cause peeling or voids later are eliminated, and high thermal conductivity is maintained. When the metal layer 12 is formed by metal plating,
Unlike the above, first, the adhesive is applied to the surface of the high thermal conductive material 10 and cured, and then the surface of the cured adhesive (the surface of the insulating layer 11) is metal-plated to obtain the target wiring board substrate 1. To manufacture.

The high thermal conductivity material 10 and the metal layer 12 are also included.
To improve the adhesiveness of the surface of the
It is also possible to apply a primer in advance. Examples of this primer include primer C (trade name: manufactured by Shin-Etsu Silicone Co., Ltd.), primer X (trade name: manufactured by Toray Dow Corning Silicone Co., Ltd.), primer Y (product name: manufactured by Toray Dow Corning Silicone Co., Ltd.), ME151 (trade name: manufactured by Toshiba Silicone Co., Ltd.) and the like can be mentioned.

In the example of FIG. 1, the case where the metal layer 12 is formed on one side of the high thermal conductive material 10 has been described, but in addition to this, the metal layer 12 may be formed on both sides of the high thermal conductive material 10. it can.

The above wiring board substrate is used as a printed wiring board by forming a circuit in accordance with a conventionally known photolithography technique, especially when a lead frame is used as a metal layer. Since this printed wiring board has excellent thermal conductivity of the substrate, it is possible to quickly dissipate heat generated from the circuit. Further, as compared with the case where a carbon fiber reinforced composite material is used as the substrate, it becomes possible to manufacture at a very low cost (1/3 to 1/5).

Next, using the above-mentioned high thermal conductive material,
The thermoelectric element module will be described. FIG. 2 is a cross-sectional view of one embodiment of the thermoelectric element module. Figure 2
The thermoelectric element module 2 of FIG.
Two 0's are arranged facing each other, and each high thermal conductive material 2
Insulating layers 21, 2 on the facing surfaces 201, 201 'of 0, 20'
The metal electrodes 22 and 22 ′ are joined via 1 ′, and a plurality of n-type semiconductors 23 and p-type semiconductors 24 are alternately connected via the metal electrodes 22 and 22 ′, thereby forming a schematic configuration.

When the thermoelectric element module 2 is used as a power generating element utilizing the Seebeck effect, for example, a cooling means such as a radiation fin is joined to the outer surface 202 of the high thermal conductive material 20, while the high thermal conductive material is used. A heating means such as a heat receiving fin is joined to the outer surface 202 ′ of the conductive material 20 ′,
An electromotive force can be obtained by forming a temperature difference between both substrates. The high thermal conductive material itself may be processed into a fin shape by forming slits in the high thermal conductive material 20, 20 'with a disc cutter, a saw blade, or the like.

When the thermoelectric element module 2 is used as a cooling / heating element utilizing the Peltier effect,
For example, when an electric current is passed from the p-type semiconductor 24 to the n-type semiconductor 23, one outer surface 202 becomes a heat absorbing side and the other outer surface 202 ′ becomes a heat generating side. Therefore, an object to be cooled is joined to the heat absorbing side to generate heat. A cooling means such as a radiation fin may be joined to the side.

The insulating layer 21 and the metal electrode 22 shown in FIG.
For the insulating layer 1 in the wiring board substrate described above,
1 and the metal layer 12 can be configured according to each. As the n-type semiconductor 23 and the p-type semiconductor 24, various conventionally known semiconductors can be appropriately selected and used. Specific examples include p-type and n-type semiconductors such as Bi-Te-based and Si-Ge-based semiconductors. In joining the n-type semiconductor 23 and the p-type semiconductor 24 to the metal electrodes 22 and 22 ', various conventionally known joining means such as soldering or brazing can be adopted.

In the thermoelectric element module 2 of FIG. 2, the case where the high thermal conductive material of the present invention is used for both of the substrates arranged to face each other has been described. However, in addition to this, one of a plurality of substrates arranged to face each other. A structure using a high thermal conductivity material may be used for the part. For example, there is a case where a high thermal conductive material is used only for the heat receiving side substrate and a conventional ceramic substrate is used for the heat radiating side substrate.

Further, the thermoelectric element module 2 shown in FIG.
Is a one-stage module in which two substrates are opposed to each other and semiconductors are arranged between them, but the invention is not limited to this, and three or more substrates are arranged and semiconductors are respectively arranged between the substrates. It is also possible to make a multi-stage thermoelectric element module.

In the above thermoelectric element module, since the substrate has excellent thermal conductivity, the efficiency of heat-electric conversion by the Seebeck effect and Peltier effect is improved. Further, since the high thermal conductivity material has a low coefficient of thermal expansion, thermal stress is not generated in the joint portion, and defects such as peeling are unlikely to occur, so that the reliability of the element is high.

[0054]

The present invention will be described in more detail with reference to Examples and Comparative Examples, but the invention is not limited thereto. (Examples 1 to 4) First, carbon powder (average particle diameter 10 μm
m) and the phenol resin powder (average particle diameter 15 μm) were uniformly mixed. The mixing ratio at that time was 5 wt% to 10 wt% of the phenol resin with respect to the total amount.
The phenol resin used was Bellpearl (registered trademark) S-899 manufactured by Kanebo Co., Ltd. This phenol resin is fine particles having a weight average molecular weight of 3000 or more, and each contains a reactive methylol group in the molecule and has heat melting / self-curing properties. Next, the above mixture is put into a molding die, and the molding pressure is 1000 kgf / cm.
² to 2000 kgf / cm ² , and mold temperature 180 ° C.
By heating and pressurizing for 10 minutes, the target high thermal conductive material was obtained.
The thermal conductivity and bending strength (according to JIS C6481) of the obtained high thermal conductive material were measured. The results are shown in Table 1. The thermal conductivity was measured using a laser flash method thermal constant measuring device TC-7000 (manufactured by ULVAC-RIKO, Inc., JIS R1611 compliant).
As shown in Table 1, the thermal conductivity of each is 8.0 W / mK.
The above is the very high thermal conductivity. The bending strength was also sufficient.

[0055]

[Table 1]

Example 5 A mixture having the same mixing ratio as in Example 1 was put into the molding apparatus shown in FIG. 3 and was solidified while being vibrated by a vibrator. The conditions of the vibrator were a frequency of 50 Hz, an acceleration of 0.5 G, and a vibration time of 10 minutes. Then, the stiffened mixture was set in a molding die similar to that in Example 1 above, and the molding pressure was 1000 kgf / c.
Heating and pressurization was performed at m ² and 180 ° C. for 10 minutes to obtain a target high thermal conductivity material. The thermal conductivity and bending strength of the high thermal conductive material thus obtained were measured. The results are shown in Table 1. From the comparison between Example 1 and Example 5 in Table 1, it is clear that the thermal conductivity is further improved (improved from 8.5 W / mK to 9.8 W / mK) by passing through the vibration / squeeze hardening process. became. Further, from the comparison between Example 2 and Example 5, it was found that the heat conductivity equal to or higher than the above can be obtained even if the molding pressure in the subsequent steps is halved by passing through the vibration / squeeze hardening step.

Example 6 To the mixture of carbon powder and phenol resin powder in Example 1 above, aluminum powder was further mixed as a heat conductive filler. The blending amount of aluminum powder was set to 10% by weight based on the total amount. Subsequently, this mixture was molded by the same method as in Example 2 above to obtain the desired high thermal conductivity material. The thermal conductivity of the high thermal conductive material thus obtained was measured. The results are shown in Table 1. As shown in Table 1, it has been clarified that the thermal conductivity is significantly increased by adding the aluminum powder.

(Comparative Example 1) As a comparative example, a printed circuit board No. 1 manufactured by Sanhayato. The thermal conductivity of the glass-epoxy substrate from which the surface copper foil was removed by etching from 31 was measured. A thermal conductivity meter QTM-500 (manufactured by Kyoto Electronics Co., Ltd.) was used for the measurement. The glass-epoxy substrate was placed on an aluminum plate (thickness: 25 mm) for the measurement. The reason why the aluminum plate is used is that a certain thickness is required to measure the thermal conductivity. Then, as a result of the measurement, a value of 0.552 (W / mK) was obtained. Although the method of measuring the thermal conductivity is different between Examples 1 to 6 and Comparative Example 1, it cannot be generally stated, but it is suggested that the thermal conductivity of the present invention is higher than that of Comparative Example 1 by one digit or more. .

Example 7 Polyimide electrodeposition coating was applied on one surface of the high thermal conductive material obtained in Example 1 above at 30V for 2.5 minutes at room temperature and at 80 ° C. for 10 minutes. It was dried and further baked at 250 ° C. for 30 minutes to form a polyimide electrodeposition coating film. Then, a 70 μm thick copper foil coated with silicone adhesive KE1800T (trade name: manufactured by Shin-Etsu Silicone Co., Ltd.) is applied to the polyimide electrodeposition coating film, and the adhesive coating surface is in contact with the polyimide electrodeposition coating film. It was laminated so that. For lamination, primer A (trade name: manufactured by Toray Dow Corning Silicone Co., Ltd.) is applied to the polyimide electrodeposition coating film and the copper foil before the adhesive is applied by brushing in advance. Have been given. Next, the air and excess adhesive are removed by applying a pressure of 294 N / cm ^{2 with} a heat press at 120 ° C. for 3 minutes, then released from the pressed state and heat-treated at 120 ° C. for 60 minutes to remove the adhesive. A target wiring board substrate was prepared by curing. Further, when the obtained wiring board substrate was subjected to etching with an appropriate circuit pattern, the circuit pattern could be sufficiently reproduced and formed. This printed wiring board had excellent heat dissipation.

Example 8 The metal surface of the wiring board substrate obtained in Example 7 was coated with a dry film type negative photoresist, and a predetermined copper electrode pattern was exposed and etched to form 127. Copper electrodes were formed. Two of these substrates are used, and a Si-based n-type semiconductor element and a Ge-based p-type semiconductor element with dimensions of 1.5 mm × 1.5 mm × 1.5 mm are connected in series via copper electrodes formed on them. 127 pieces were alternately soldered so as to obtain the desired thermoelectric element module. Aluminum radiating fins were bonded to one surface of the obtained thermoelectric element module using the silicone adhesive. Then, the other surface was heated with a flame of a gas lighter for 60 seconds, and the electromotive force due to the Seebeck effect was measured. As a result, a more rapid voltage increase was observed as compared with the conventional case. It is considered that this is because the temperature difference was efficiently generated because the substrate had high thermal conductivity.

[0061]

As described above, since the high thermal conductive material of the present invention is composed of carbon powder and phenol resin, it has sufficiently high thermal conductivity and can be manufactured at low cost.
Very useful in industry. In particular, the mixture of carbon powder and phenol resin is stiffened while being vibrated to uniformly arrange the particles, and the overall thermal conductivity can be further improved. In addition, the wiring board substrate and the thermoelectric element module using the high thermal conductive material as a substrate have high heat dissipation of generated heat and high thermo-electric conversion efficiency. In addition, the substrate is less likely to thermally expand, so that thermal stress can be suppressed. As a result, peeling of the interface does not occur and reliability is improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an embodiment of a wiring board substrate of the present invention.

FIG. 2 is a sectional view of an embodiment of the thermoelectric element module of the present invention.

FIG. 3 is a diagram illustrating a method for producing a high thermal conductive material according to the present invention.

[Explanation of symbols]

1 Wiring board substrate 10 High thermal conductivity material 11 insulating layer 12 metal layers 2 Thermoelectric element module 20 High thermal conductivity material 201 Opposing surface 201 'facing surface 202 exterior 202 'exterior 21 insulating layer 22 Metal electrode 23 n-type semiconductor 24 p-type semiconductor 30 shaker 31 mold 31 'mold 32 mixture 33 weight

Claims (7)

[Claims] 1. A highly heat-conductive material obtained by heating a mixture of carbon powder and a phenol resin into a predetermined shape and pressure-curing the mixture. 2. A high thermal conductive material obtained by stiffening a mixture of carbon powder and a phenol resin while applying vibration, and heating and pressing so as to obtain a predetermined shape. 3. The high thermal conductivity material according to claim 1, wherein the phenol resin is mixed in an amount of 5 to 40% by weight with respect to the mixture of carbon powder and phenol resin. 4. The high heat conductive material according to claim 1, wherein the mixture is further mixed with a powdery heat conductive filler. 5. The high thermal conductivity material according to claim 1, wherein the predetermined shape is a plate shape. 6. A wiring board substrate comprising a metal layer on at least one side of the high thermal conductivity material according to claim 5 with an insulating layer interposed therebetween. 7. A plurality of the high thermal conductive materials according to claim 5 are arranged facing each other, a metal electrode is bonded to an opposing surface of each high thermal conductive material via an insulating layer, and a plurality of metal electrodes are bonded via the metal electrodes. A thermoelectric element module in which n-type and p-type semiconductors are alternately connected.