JP2019140311A - High heat dissipation lightweight heat sink - Google Patents

Abstract

Provided is a heat sink with high heat dissipation and light weight while ensuring strength. A heat sink is a heat sink using a graphite plate obtained by graphitizing a polymer film in which a plurality of laminated polymer films are laminated by applying pressure and baking. And a base portion in which the second graphite plate is incorporated, and the first graphite plate and the second graphite plate are in contact with each other. [Selection] Figure 2

Description

  The present invention relates to a heat sink capable of managing heat emitted from a heat source such as an electronic device.

  Electronic devices, microprocessors and electronic and electrical components are capable of operating at high processing speeds and high frequencies, are small and have more complex power requirements. Also, the development of electronic devices, including other technologically advanced devices such as integrated circuits of devices, and other devices such as high power optical devices, is becoming increasingly sophisticated. In these devices, extremely high temperatures may occur.

  However, microprocessors, integrated circuits, and other high-performance electronic components typically operate efficiently only under a specific range of threshold temperatures. Excessive heat generated during operation of electronic components is not only detrimental to its inherent performance, but it can also impair the performance and reliability of the entire system and cause system failure. The increasing range of environmental conditions, including extreme temperatures expected by the operation of electronic systems, also contributes to the negative effects of excessive heat.

  As the need for heat dissipation from small electronic devices increases, management becomes an increasingly important factor in the design of electronic products. Both the performance reliability and expected lifetime of the electronic device are inversely proportional to the component temperature of the device. For example, by reducing the operating temperature of a device such as a typical silicon semiconductor, the device processing speed, reliability, and expected lifetime can be increased. Therefore, the most important thing to obtain maximum component life and reliability is to control the device operating temperature within the limits set by the designer.

  A carbon material represented by graphite is attracting attention as a material excellent in such heat management. Graphite has the same thermal conductivity as aluminum and copper, which are common high thermal conductivity materials, and also has better heat transport properties than copper, so heat spreaders for LSI chips, heat sinks for semiconductor power modules, etc. Has attracted attention as a material for radiating fins.

  In a heat sink using a conventional carbon material, for example, as shown in Patent Document 1, brittle carbon particles are compressed and solidified, and then coated with a metal film to prevent peeling of graphite and to increase mechanical strength. An improved heat sink has been proposed. Moreover, as shown in Patent Document 2, a heat sink that has both weight reduction and thermal conductivity has been proposed by kneading scaly graphite having a high aspect ratio with a resin.

Special table 2009-505850 WO2006-063540

  However, since the heat sink of Patent Document 1 is produced from the compression of carbon particles, a dense graphite structure is not formed in the plane direction, and thus the heat transport performance is low. Moreover, since the coating agent and the base material are metal, the entire heat sink becomes heavy. On the other hand, the heat sink shown in Patent Document 2 can be reduced in weight by kneading with a resin, but scaly graphite can only deal with heat generation of about several tens of watts, which is an LED level.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and an object thereof is to provide a heat radiating and lightweight heat sink that can cope with heat generation of several hundreds of watts.

In order to achieve the above object, a heat sink according to the present invention is a heat sink using a graphite plate graphitized by applying pressure and baking a plurality of laminated polymer films,
A fin portion composed of a first graphite plate;
A base part in which a second graphite plate is built into the resin;
With
The first graphite plate and the second graphite plate are in contact with each other.

  With the heat sink according to the present invention, it is possible to provide a heat sink with high heat dissipation and light weight that can cope with heat generation of several hundreds of watts.

1 is a schematic view showing a configuration of a high heat dissipation light weight heat sink according to Embodiment 1. FIG. It is AB sectional drawing of the high heat dissipation lightweight heat sink in FIG. It is a schematic perspective view which shows the basal surface and non-basal surface of a graphite plate. FIG. 2 is a schematic perspective view showing respective processing states of a first graphite plate 102 and a second graphite plate 104 in FIG. 1. FIG. 2 is a schematic view showing a joining state of a first graphite plate 102 and a second graphite plate 104 in FIG. 1. It is a TEG schematic diagram of a thermal conductivity evaluation test in an embodiment and a comparative example.

The heat sink according to the first aspect is a heat sink using a graphite plate graphitized by applying pressure and baking a plurality of polymer films laminated,
A fin portion composed of a first graphite plate;
A base part in which a second graphite plate is built into the resin;
With
The first graphite plate and the second graphite plate are in contact with each other.

  With the above configuration, it is possible to provide a heat sink with high heat dissipation and light weight that can cope with heat generation of several hundred W level.

  In the heat sink according to the second aspect, in the first aspect, at least one of the contact surfaces of the first graphite plate and the second graphite plate may be a non-basal surface.

  In the heat sink according to the third aspect, in the first or second aspect, the resin constituting the base portion may be kneaded with a heat conductive filler.

  Hereinafter, heat sinks according to embodiments will be described with reference to the accompanying drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

(Embodiment 1)
FIG. 1 is a schematic diagram showing a configuration of a resin-based graphite heat sink 101 according to the first embodiment. 2 is a cross-sectional view of the resin-based graphite heat sink 101 taken along the line AB in FIG. For convenience, the surface of the resin 103 in which the second graphite plate 104 is built is defined as the xy plane, and the direction in which each first graphite plate 102 extends is defined as the z direction. The arrangement direction of the plurality of first graphite plates 102 is the x direction. That is, FIG. 2 is a zx sectional view as seen from the y direction.
A heat sink 101 according to Embodiment 1 is a heat sink using graphite plates 102 and 104 obtained by graphitizing a plurality of laminated polymer films by applying pressure and baking. The heat sink 101 includes a fin portion composed of a first graphite plate 102 and a base portion in which a second graphite plate 104 is built in a resin 103. Further, the first graphite plate 102 and the second graphite plate 104 are in contact with each other.
According to the heat sink 101, since the first graphite plate 102 and the second graphite plate 104 are in contact with each other, it is possible to provide a highly heat-dissipating and lightweight heat sink that can cope with heat generation of several hundreds of watts. That is, as shown in FIG. 2, heat from the heat generating portion 105 provided on the back surface of the base portion can be quickly radiated from the second graphite plate 104 to the first graphite plate 102.

  The members constituting the heat sink 101 will be described below.

<Polymer film>
Examples of the polymer film include polyoxadiazole, polybenzothiazole, polybenzobisthiazole, polybenzoxazole, polybenzobisoxazole, polypyromellitimide, aromatic polyamide, polyphenylene benzimitazole, polyphenylene benzobis At least one polymer film of the group consisting of mitazole, polythiazole, and polyparaphenylene vinylene can be used. The first graphite plate 102 and the second graphite plate 104 are formed by stacking a plurality of the one or more polymer films and firing while controlling the applied pressure to form a graphitized graphite plate. .

<Graphite plate>
FIG. 3 is a schematic perspective view showing the basal surface 106 and the non-basal surface 107 of the graphite plate. The first graphite plate 102 constitutes a graphite fin. The second graphite plate 104 is built in the resin 103 and forms a base portion. As shown in FIG. 3, the first graphite plate 102 and the second graphite plate 104 each have a basal surface 106 having a low heat conduction in a direction perpendicular to the surface and a heat conduction in a direction perpendicular to the surface. And a high non-basal surface 107.

FIG. 4 is a schematic perspective view showing an example of a processed state of the first graphite plate 102 and the second graphite plate 104 in FIG. In order to carry the heat of the heat generating portion 105 to the tip of the graphite fin 102 at the shortest distance, it is preferable that at least one of the first graphite plate 102 and the second graphite plate 104 is in contact with the non-basal surface. Most preferably, it is most preferable that the non-basal surfaces 107 of the first graphite plate 102 and the second graphite plate 104 on the side close to the heat generating portion 105 are processed so as to expose each other and the non-basal surfaces are brought into contact with each other. In FIG. 4, the first graphite plate 102 is provided with an inclined surface of the non-basal surface 107 so as to intersect the z direction and the x direction. Of the plurality of first graphite plates 102, the angle of the inclined surface on the origin side of the x axis with respect to the z axis is −45 °. In addition, the second graphite plate 104 is provided with an inclined surface of the non-basal surface 107 so as to intersect the z direction and the x direction. The angle of the inclined surface on the origin side of the x axis of the second graphite plate 104 with respect to the x axis is + 45 °. In addition, in FIG. 4, the inclined surfaces of the non-basal surface 107 provided on the surface of the second graphite plate 104 have four inclined surfaces in the -x direction and four inclined surfaces in the + x direction along the x direction. Provided. In addition, it is preferable to provide each inclined surface so that it may mutually contact. In this way, by making the orientations of the plurality of inclined surfaces different from each other, the direction of the stress generated on the contact surface between the first graphite plate 102 and the second graphite plate 104 can be dispersed.
The second graphite plate 104 is processed into a shape that follows the processing of the first graphite plate 102 and fixed in contact (FIG. 5). Finally, resin molding is performed to reinforce the joint portion and the base portion of the first graphite plate 102 and the second graphite plate 104, and a resin base graphite heat sink 101 as shown in FIGS. 1 and 2 is obtained.

<Reinforced resin material>
The reinforcing resin material preferably has a thermal conductivity of 10 W / m · K or more, and most preferably 12 W / m · K or more. Reinforcing resins with a thermal conductivity of 10 W / m · K or less cannot respond to heat generation of several hundreds of watts because heat transport is slow.

  The resin thickness of the contact surface with the heat generating part 105 is preferably 0 to 1 mm. 0.5-1 mm is particularly preferable. When the resin thickness is 1 mm or more, heat transport through the resin is slow, so that it cannot cope with heat generation of several hundred W level.

  On the other hand, the resin thickness on the surface opposite to the heat generating portion 105 is preferably 1/12 to 1/10 of the length of the first graphite plate 102. When the resin thickness exceeds 1/10, heat exchange at the fin portion is insufficient, and it becomes impossible to cope with heat generation of several hundred W level.

The reinforcing resin material is obtained by kneading a high thermal conductivity filler in a base resin.
Base resins include epoxy resin, polyolefin resin, bismaleimide resin, polyimide resin, polyether resin, phenol resin, silicone resin, polycarbonate resin, polyamide resin, polyester resin, fluorine resin, acrylic resin, melamine resin, urea resin, urethane Resins can be used.
As the high thermal conductive filler, for example, alumina (Al ₂ O ₃ ), boron nitride (BN), a metal filler such as Cu and Al, a carbon filler, or the like can be used.
According to this configuration, it is possible to provide a heat sink that is lighter and lighter than the metal base alone, and that can cope with heat generation of several hundreds of watts.

Example 1
A heat sink according to Example 1 was produced as follows.
The first graphite plate 102 was a pressure-laminated product of highly oriented graphite having a length of 50 mm, a width of 50 mm, and a thickness of 1 mm. The second graphite plate 104 was a pressure-laminated product of highly oriented graphite having a length of 50 mm, a width of 50 mm, and a thickness of 1 mm. As starting materials for the first graphite plate 102 and the second graphite plate 104, a film made of polyoxadiazole as a raw material was used as a polymer film. A plurality of the polymer films were laminated and baked while controlling the applied pressure to obtain a graphitized graphite plate. Using this graphite plate, a heat sink was constructed with 8 fins and a pitch of 4 mm. In this heat sink, the joint surfaces of the first graphite plate 102 and the second graphite plate 104 are fixed in contact with each other by exposing the non-basal surface 107 at an angle of 45 °. As the reinforcing resin, a resin using a polycarbonate resin as a base resin and a BN filler as a filler was used. A heat sink was manufactured with a thickness of 0.8 mm on the heat generating portion side and a thickness of 3 mm on the opposite side. The fabricated heat sink was evaluated for performance by a drop test and a thermal conductivity test before and after the vibration test.

(Example 2)
In contrast to the first embodiment, the difference is that the joining surfaces of the first graphite plate 102 and the second graphite plate 104 are fixed in a structure in which the non-basal surface 107 and the basal surface 106 are alternately fitted. A heat sink was produced in the same manner as in Example 1 except for the above.

(Example 3)
Compared with Example 1, the difference was that the thickness of the reinforcing resin on the heat generating portion side was 1 mm. Otherwise, a heat sink was produced in the same manner as in Example 1.

Example 4
Compared with Example 1, the difference was that the thickness on the side opposite to the heat generating part was 5 mm. Otherwise, a heat sink was produced in the same manner as in Example 1.

(Example 5)
In contrast to Example 1, a graphite heat sink was manufactured in the same manner as in Example 1 except that a 5 μm thick polyimide coating was applied to the entire surface of the first graphite plate 102.

(Comparative Example 1)
As Comparative Example 1, a heat-sink was produced using a pressure laminate produced using a polyester film as the polymer film, and the other conditions were the same as in Example 1.

(Comparative Example 2)
As Comparative Example 2, the first graphite plate 102 and the second graphite plate 104 in Example 1 were fixed via a reinforcing resin without being directly joined, and other conditions were the same as in Example 1 to produce a heat sink. did.

(Comparative Example 3)
As a comparative example 3, a heat sink was manufactured under the same conditions as in the example 1 except that the thickness of the reinforcing resin on the heat generating portion side was 1.5 mm.

(Comparative Example 4)
As Comparative Example 4, a heat sink was manufactured in the same manner as in Example 1 except that the thickness of the reinforcing resin on the side opposite to the heat generating portion side was 10 mm.

<Evaluation method>
(Thermal conductivity evaluation test)
The samples produced in the examples and comparative examples were subjected to a thermal conductivity evaluation test before and after the drop test and the vibration test. FIG. 6 is a schematic perspective view showing a thermal conductivity evaluation TEG. In the evaluation by the forced cooling environment, the temperature measuring unit 109 (□ 10 mm, t5 mm, made of copper) and the heater 111 (□ 10 mm, t1 mm, made of ceramic) are grease 108 just below the center of the graphite heat sink described in the above-mentioned examples and comparative examples. 0.3mm is applied and bonded, and □ 50mm size fan 110 (model number UDQF56C11CET (Panasonic)) is installed directly above, and the boundary between the heater and heat sink when the heater 111 and fan 110 are operated at input 11V The temperature of was measured and evaluated. The whole was supported by a support plate 112.

(Drop test / Vibration test)
Each sample was tested under the conditions shown below.

<Discussion>
Table 1 shows the thermal conductivity evaluation results of Examples 1 to 5 and Comparative Examples 1 to 4.

The thermal conductivity evaluation is judged by comparison with the evaluation result of the conventional aluminum heat sink. The structure of the aluminum heat sink was evaluated using a sample in which the base portion and the fin portion were integrated. As for the size, a base portion having a diameter of 50 mm, a thickness of 5 mm, and a fin portion having a height of 48 mm, a thickness of 0.5 mm, a number of 8 pieces, and a pitch of 4 mm were used.
The evaluation criteria are as follows.

Regarding the weight, compared to a conventional aluminum heat sink, the weight ratio is 0.8 when the weight ratio is 0.8 or more, ◯ when it is less than 0.8, and ◎ when it is less than 0.7.
The thermal conductivity evaluation before and after the drop and vibration test is based on the following criteria.
(1) Before the drop / vibration test, the thermal conductivity evaluation result is less than 51.5 ° C, and the difference between before and after the drop / vibration test is less than 0.5 ° C.
(2) Before the drop / vibration test, the thermal conductivity evaluation result is 51.5 ° C. or higher, or the difference between before and after the drop / vibration test is 0.5 ° C. or higher.

In addition, the evaluation criteria for strength evaluation are: ○, if cracks are not generated due to breakage of the graphite layer due to impact and vibration after cross-sectional observation after conducting thermal conductivity evaluation after drop and vibration tests If it did, it was set as x.
Finally, as a comprehensive evaluation, only when both the thermal conductivity evaluation and the strength evaluation are ◎ or ◯ is ○, and when either one or both are ×, it is ×.

  As shown in Examples 1 and 2, since the joint surfaces of the first graphite plate 102 and the resin built-in graphite plate 104 are fixed in contact with each other, heat transport by graphite is ensured, and high heat dissipation performance is exhibited. . Moreover, as shown in Examples 3 and 4, it is possible to achieve both strength, heat dissipation performance, and light weight by setting the reinforcing resin to an appropriate thickness.

  On the other hand, as shown in Comparative Example 1, when a polymer film other than the material shown in Example 1 is used, graphitization is insufficient and thermal conductivity cannot be ensured. In addition, due to the lack of strength, measurement cannot be performed after the drop / vibration test, and the heat sink does not function. Further, as shown in Comparative Example 2, when the first graphite plate 102 and the second graphite plate 104 are fixed without being in contact with each other, heat transport is hindered by the resin portion, and thermal conductivity cannot be ensured. Further, as shown in Comparative Example 3, even when the resin on the surface in contact with the heat generating portion is thick, heat transport is blocked by the resin portion, and thermal conductivity cannot be ensured. Furthermore, as shown in Comparative Example 4, when the thickness of the reinforcing resin on the side opposite to the heat generating portion is thick, heat exchange at the fin portion is insufficient, and heat conductivity cannot be ensured.

  It should be noted that the present disclosure includes appropriately combining any of the various embodiments and / or examples described above, and each of the embodiments and / or examples. The effect which an Example has can be show | played.

  The heat sink according to the present invention is capable of high heat dissipation capable of dealing with heat generation of several hundred W level and is lightweight. Therefore, this heat sink can be applied to heat radiation of a heat generating part in industrial equipment and in-vehicle fields.

101 Resin-based graphite heat sink 102 First graphite plate 103 Resin base 104 Second graphite plate 105 Heat generating portion 106 Basal surface (surface with low thermal conductivity in a direction perpendicular to the surface)
107 Non-basal surface (surface with high thermal conductivity in the direction perpendicular to the surface)
108 Grease 109 Temperature sensor (thermocouple)
110 Fan 111 Heater 112 Support plate

Claims (3)

A heat sink using a graphite plate graphitized by applying pressure and firing a polymer film laminated in a plurality of layers,
A fin portion composed of a first graphite plate;
A base part in which a second graphite plate is built into the resin;
With
The heat sink, wherein the first graphite plate and the second graphite plate are in contact with each other.   2. The heat sink according to claim 1, wherein at least one of the contact surfaces of the first graphite plate and the second graphite plate is a non-basal surface.   The heat sink according to claim 1 or 2, wherein the resin constituting the base portion is kneaded with a heat conductive filler.

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