JP2019125680A - Graphite heat sink - Google Patents

Abstract

To provide a heat sink having excellent heat dissipation and mechanical reliability.SOLUTION: The heat sink includes: a fin made of a graphite plate; and a base metal for fixing the fin made of a graphite plate at its end. The fin which consists of a graphite plate is equipped at its end with at least one or more notch processing parts. The base metal is contained in at least a part of the notch processing parts.SELECTED DRAWING: Figure 1C

Description

  The present invention relates to a high reliability, high heat dissipation composite heat sink made from a high thermal conductivity material, graphite fins and a base metal.

  In recent years, the market for power semiconductors, which is a key device that can greatly contribute to energy saving of electric devices, has been rapidly expanding toward the realization of a low carbon society. Power semiconductors are used for power control of power converters such as converters and inverters of electric vehicles. Progress in integrated circuits such as CPUs (Central Processing Units) used for power semiconductors and signal processing, GPUs (Graphics Processing Units) used for image processing, and LEDs (Light Emitting Diodes) for energy-saving lighting applications Therefore, the output of the device is significantly increased, and the amount of heat generated by the electronic device is increasing accordingly.

  On the other hand, smaller and lighter electronic devices are also required as circuit designs, and the density of generated heat is further increased. In order to quickly dissipate the heat generated in the electrical device circuit and the periphery thereof, a heat sink with high performance is required.

  In general, the heat sink uses an extrusion method in which rail-shaped aluminum heated from aluminum is extruded from a mask nozzle taken at high pressure from a mold, cooled and cured, and then cut.

  Further, as a heat sink excellent in heat dissipation, Patent Document 1 discloses a heat sink (FIG. 10) having fins brazed to the inside made of a graphite film excellent in thermal conductivity. The heat sink comprises cooling fins 1001 made of graphite film, which project from the base plate 1002 and are designed to dissipate heat therefrom. On the surface of the metal base plate 1002, notches 1003 are formed to incorporate the cooling fins 1001. The cooling fin 1001 is brazed 1004 inside the notch 1003 of the base plate 1002. Therefore, the cooling fin 1001 made of a graphite film protrudes at least toward the inside of the cut 1003 (fixed area). A metal coating is provided in the area of the surface. Thus, Patent Document 1 discloses a heat sink fixed to the inside of the notch of the base plate 1002 by brazing a fin made of a graphite film.

Special table 2009-505850

  However, in the conventional caulking method, there is a risk that the fins may come off due to vibration or a mechanical external force because of differences in materials of the base metal and the fins. In addition, since the base metal bites into the fin, the fin is cracked, which becomes a starting point of breakage in a long-term thermal and mechanical reliability test, and has a problem in securing the reliability. In addition, even when the heat dissipating fins are metal or copper, which has particularly high heat conductivity, there is a problem in that the heat dissipating fins are increased in size, for example, by increasing the length of the heat dissipating fins as an application requiring a heat sink with higher heat dissipation. have.

Further, in the joint by brazing described in Patent Document 1, since the materials of the base plate and the fin are different, it is an issue to secure thermal reliability due to repeated thermal stress due to difference in coefficient of linear expansion.
As described above, it has been difficult to ensure high heat dissipation and mechanical and thermal long-term reliability with the conventional heat sink.
In order to solve the above problems, a highly reliable high heat dissipation composite heat sink made of heat dissipating fins with high thermal conductivity and a base metal is required.

  An object of the present invention is to provide a heat sink that is excellent in heat dissipation and mechanical reliability.

The heat sink according to the present invention comprises a fin made of a graphite plate,
A base metal fixing at its end a fin made of the graphite plate;
Equipped with
The fin made of the graphite plate is provided with at least one or more notched parts at the end,
The base metal is contained in at least a part of the notched portion.

  As described above, according to the heat sink according to the present invention, the base metal enters the notched portion, so that the fin does not easily come off from the base metal at the time of a drop impact or vibration, and the mechanical reliability is excellent. Can provide a heat sink. Therefore, without increasing the size of the heat sink due to the heat dissipation due to the increase in the output of elements such as power semiconductors of energy saving devices, integrated circuits such as CPUs and GPUs, and LEDs for energy saving applications, mechanical reliability It is possible to dissipate heat without losing the quality.

It is a perspective view of the heat sink which used the graphite board concerning Embodiment 1 as a fin. It is sectional drawing seen from the AA line | wire direction of FIG. 1A. It is sectional drawing seen from the BB line | wire direction of FIG. 1A. It is the schematic which shows the shape of a graphite board. It is sectional drawing which shows the omission prevention structure which the base metal entered in a part of notch processing part by crimping process by deformation | transformation. It is sectional drawing which shows the omission prevention structure which the base metal deform | transformed by caulking to the whole notch process part, and it entered. FIG. 2 is a schematic cross-sectional view showing a configuration of a base metal used in the heat sink according to Embodiment 1. FIG. 7 is a schematic cross-sectional view showing a step of the method of manufacturing the heat sink according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a step of the method of manufacturing the heat sink according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a step of the method of manufacturing the heat sink according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a step of the method of manufacturing the heat sink according to the first embodiment. FIG. 7 is a schematic cross-sectional view showing a step of the method of manufacturing the heat sink according to the first embodiment. It is the schematic which shows the measurement system of heat dissipation evaluation. FIG. 7 is a perspective view of a heat sink according to a second embodiment. It is sectional drawing seen from the CC line | wire direction of FIG. 8A. It is sectional drawing seen from the DD line direction of FIG. 8A. FIG. 10 is a cross-sectional view of the heat sink in the second embodiment. FIG. 20 is a cross-sectional view of another example of the heat sink in the second embodiment. FIG. 14 is a cross-sectional view of still another example of the heat sink in the second embodiment. FIG. 14 is a cross-sectional view of still another example of the heat sink in the second embodiment. It is sectional drawing of the heat sink in a prior art.

The heat sink according to the first aspect is a fin made of a graphite plate;
A base metal for fixing the fin made of the graphite plate at its end;
Equipped with
The fin made of the graphite plate is provided with at least one or more notched parts at the end,
The base metal is contained in at least a part of the notched portion.

  The heat sink according to a second aspect is the heat sink according to the first aspect, wherein the total dimension of the width of the notched portion provided on the fin made of the graphite plate is the base on which the fin made of the graphite plate is fixed When the dimension of the metal is L, it may be (1-1 / 6.25) × L or less.

In the heat sink according to the third aspect, in the first aspect, the fin made of the graphite plate further includes a holed portion inside the surface,
The base metal may be contained in at least a part of the drilled portion.

  In the heat sink according to the fourth aspect, in the third aspect, the total dimension of the width of the notched portion provided on the fin made of the graphite plate and the width of the holed portion in the plane is When the dimension of the base metal for fixing the fin made of the graphite plate is L, it may be (1-1 / 6.25) × L or less.

  The heat sink according to the embodiment will be described below with reference to the attached drawings. In the drawings, substantially the same members are denoted by the same reference numerals.

Embodiment 1
A heat sink excellent in mechanical strength according to the first embodiment will be described.
FIG. 1A is a perspective view of a heat sink 100 using the graphite plate 101 of Embodiment 1 as a fin. FIG. 1B is a cross-sectional view α seen from the direction of the line AA of FIG. 1A. FIG. 1C is a cross-sectional view β viewed from the direction of the line B-B in FIG. 1A. For convenience, the direction in which the fins of the graphite plate 101 extend is the z direction, the direction of arrangement of the fins of the graphite plate 101 is the x direction, and the width direction of the fins of the graphite plate 101 is the y direction. .
The heat sink 100 is provided with one notch processed portion 102 at one or more places of the graphite plate 101, here, at both ends in the width direction (y direction). The base metal 103 is inserted into the notched portion 102 by, for example, caulking, so that the detachment prevention structure 104 is formed. In the removal prevention structure 104, the base metal 103 wraps around a part of the recess of the notch processing portion 102, and the graphite plate 101 is less likely to be removed from the base metal 103. Since the graphite plate 101 is a brittle material by the detachment prevention structure 104, it is possible to suppress the damage at the time of caulking and fix the graphite plate 101.

  FIG. 2 is a schematic view showing the shape of the graphite plate 101 used in the first embodiment. The shape of the notched portion 102 is indicated by the width 201 of the notched portion 102 in the y direction and the height 202 of the notched portion 102 in the z direction. The base metal 103 is caulked into part or the whole of the notch processing portion 102. As described later, the base metal 103 is deformed by “crimping” to fix the fins of the graphite plate 101 inserted into the cut groove 501. Furthermore, the base metal 103 intrudes into a part or the whole of the notch processing portion 102 by “squeeze processing”, and the removal prevention structure 104 is configured. The graphite plate 101 is less likely to come off the base metal 103 by the detachment prevention structure 104.

  FIG. 3 is a cross-sectional view showing that the base metal 103 enters a part of the notch processing portion 102 by caulking and is deformed to form the detachment prevention structure 104 a. In the detachment preventing structure 104 a, the base metal 103 wraps around in a part of the concave part of the notch processing part 102 on both sides from the −y direction or the + y direction, and the graphite plate 101 is difficult to be detached from the base metal 103. Further, FIG. 4 is a cross-sectional view showing that the base metal 103 enters the whole of the notch processing portion 102 by caulking and is deformed to form the detachment prevention structure 104 b. In the removal prevention structure 104 b, the base metal 103 wraps around the entire recess of the notched parts 102 on both sides from the −y direction or the + y direction, and the graphite plate 101 is difficult to remove from the base metal 103. The falling prevention structure in the first embodiment may be in any state of FIG. 3 and FIG. 4.

  The shape of the notch processing portion 102 may be any shape, for example, various shapes such as a semicircular shape, a half-round shape, a long hole shape, a square, and a rectangle. Desirably, it is a semicircular shape (R 1 mm or greater) in which no corner is formed due to the processability of the graphite plate 101 (FIG. 1C, FIG. 2). The base metal 103 enters the notch processing portion 102 to form the detachment prevention structure 104 (FIG. 3, FIG. 4).

FIG. 5 is a schematic cross-sectional view showing the configuration of the base metal 103 used in the first embodiment. Since the fins of the graphite plate 101 are inserted into the upper surface of the base metal 103, a plurality of cut grooves 501 are provided. The width 502 of the cut groove 501 is 0.02 mm or more and 1.0 mm or less with respect to the thickness of the graphite plate 101. That is, the width of the cut groove is represented by "graphite plate thickness + (0.02 to 1.5) mm". If the width 502 of the cut groove 501 is less than 0.02 mm, the insertion of the graphite plate 101 is difficult to insert due to the dispersion of the graphite thickness and the surface roughness. In addition, if the width 502 of the cut groove 501 is 1.0 mm or more, a gap is generated between the caulking base metal 103 and the graphite plate 101, the contact area is reduced, and caulking can not be performed. I can not get it.
In addition, since different materials are used for the base metal and the fin as described above, “crimming” is used as a technique for bonding the base metal 103 and the fin of the graphite plate 101. In the “crimming process”, the notch groove 501 is made in the base metal 103, the fin of the graphite plate 101 is inserted, and the portion in the vicinity of the notch groove 501 of the base metal 103 is pressed with a die 601 for caulking By deforming 103, the fins of the graphite plate 101 inserted into the cut groove 501 are fixed.

6A to 6E are schematic cross-sectional views showing the method of manufacturing the heat sink according to the first embodiment.
(A) First, a base metal 103 (FIG. 6A) having a cutting groove as shown in FIG. 5 and a graphite plate 101 having a notch 102 at least partially formed as shown in FIG. prepare.
(B) Insert the graphite plate 101 according to the cut groove 501 of the base metal 103 (FIG. 6B). At this time, the notch processed portion 102 of the graphite plate 101 is adjusted in height so that the notch processed portion 102 and the graphite plate 101 are positioned on the upper surface of the base metal 103.
(C) Next, the upper portion of the base metal 103 in the vicinity of the notched portion 102 formed in the graphite is pressed by the caulking die 601 (FIG. 6C, FIG. 6D).
(D) By the above, the base metal 103 is deformed, and the base metal 103 enters the notch 102 to fix the graphite plate 101 and the base metal 103 (FIG. 6E). At this time, the graphite plate 101 and the base metal 103 are also simultaneously crimped, and desirably brought into contact without causing mechanical cracks, resulting in a structure excellent in heat conduction.

  Table 1 shows the results of the heat dissipation and the reliability of the heat sink in vibration of the examples and comparative examples of the graphite heat sink according to the first embodiment.

As an example and a comparative example of a graphite heat sink, the base metal 103 uses aluminum A5052 material, and the width of the cut groove of the part which inserts the fin of the graphite plate 101 is 0.02 to 1.5 mm for the thickness of the graphite plate 101 It was added dimensions.
Cutting groove width = graphite plate thickness + (0.02 to 1.5) mm
Moreover, the depth of the cut groove was 3 mm. The thickness of the graphite plate 101 was 0.5 mm. Therefore, the width of the notched portion 102 is 0 to 1.0 mm, and the height of the notched portion 102 is 0 to 1.0 mm. The size and the number of fins of the graphite plate 101 were eight plates with an outer size of 50 × 50 mm and a thickness of 0.5 mm. The outer shape of the base metal 103 was aluminum and the outer diameter was 50 mm × 50 mm and the thickness was 5 mm.

  In Comparative Example 1, an integral aluminum heat sink made by extrusion molding was used. In the aluminum heat sink, the outer size of the base portion is 50 mm × 50 mm, the thickness of the base metal portion is 5 mm, and the fin portion has an outer shape of 50 mm × 50 mm and a thickness of 0.5 mm, and has eight sheets. Further, as Comparative Example 2, the groove width of the base metal 103 was 0.3 mm, the thickness 0.5 mm as the graphite plate 101, and the notch processing to the graphite plate 101 was not performed and the graphite plate 101 was fixed to the base metal with silver paste. .

(Evaluation of heat dissipation)
FIG. 7 is a schematic view showing a measurement system of heat dissipation evaluation. A ceramic heater 701 having a size of 10 × 10 mm and a thickness of 1 mm was fixed to the base metal via a grease 702 as a heat source at the center of the lower surface of the base metal of the heat sink. A thermocouple 703 was fixed to the grease 702 so that the temperature of the ceramic heater 701 could be measured. When the ceramic heater was heated using a power supply device and the aluminum heat sink of Comparative Example 1 was used, the temperature was adjusted to 45 ° C. In the heat radiation evaluation, if a temperature lower than this temperature is indicated based on the temperature of the ceramic heater of the comparative example 1, it can be said that the heat sink is excellent in heat radiation as compared to the aluminum heat sink.

(Drop impact test)
In the drop impact test, the heat sink was fixed to a drop test case, and was conducted under the conditions of applying 300 G in the X, Y, and Z directions. The falling of the fins and the deformation of the appearance were confirmed, and the judgment was carried out with no change in the temperature of the ceramic heater. In the vibration test, the box of the case used in the drop impact test is fixed to the tester, and as a sine wave vibration test, the sweep speed is 1 octave / min, displacement: 0.7 mmp-p, in a frequency range of 10 to 55 Hz. The number of sweep cycles was carried out at a frequency of 10 angular axes, the falling off of the fins and the deformation of the appearance were confirmed, and the judgment was carried out with no change in the temperature of the ceramic heater.

  In the aluminum heat sink of Comparative Example 1, the temperature of the ceramic heater exhibiting heat dissipation was 45.degree. The drop impact test and the vibration test have no particular problems because they are integrated with aluminum.

  In the heat sink using the graphite plate 101 of Comparative Example 2, the base metal 103 and the fin were fixed using a silver paste material having a thermal conductivity of 30 W / K. With regard to heat dissipation, the characteristics were improved compared to the aluminum heat sink by using the graphite plate 101 and by using a silver paste material with high thermal conductivity, but in the drop impact test and in the vibration impact test both of the fins were detached It was confirmed, and the mechanical strength was not satisfactory.

  With regard to the graphite heat sinks of Examples 1 to 4 and Comparative Example 3, aluminum A5052 is used for the base metal 103, and the width of the notches is 0.02 mm, 0.5 mm, 0 mm as compared with the thickness 0.5 mm of the graphite plate 101. A large groove of .8 mm, 1 mm, 1.5 mm was machined. The notched portion 102 of the graphite plate 101 formed a semicircular notched portion 102 of R 0.1 mm and was fixed by caulking. The groove width of 2.0 mm, which was added by 1.5 mm to the thickness of the graphite plate 101 of Comparative Example 3, could not be fixed by caulking and could not be evaluated. The heat radiation characteristics of Examples 1 to 4 were all superior to those of the aluminum heat sink of Comparative Example 1, and there were no problems with the drop impact test and the vibration test.

  The width | variety of the notch process part 102 of the graphite plate 101 was 0.3 mm, 0.5 mm, and 1 mm in Examples 5-7. The height of the notch processing part 102 was 0.2 mm. As the width of the notched portion 102 increases, the cross-sectional area through which heat is conducted from the base metal 103 to the heat dissipating fin is reduced, so that the heat dissipating characteristics are degraded. It was not. Also, there were no problems with the drop impact test and the vibration test

(About the width of notch processing part)
Here, if the width of the notched portion 102 is increased, the cross-sectional area of heat conduction from the base metal 103 to the heat dissipating fin is reduced, so that the heat dissipating property may be reduced. The graphite plate 101 has a thermal conductivity of 1500 W / m · K, aluminum has 240 W / m · K, and the graphite plate 101 is 6.25 times better in heat dissipation than aluminum. Accordingly, since the heat conduction is proportional to the cross sectional area, at least the dimension in the y direction for fixing the graphite plate 101 to the base metal 103 made of aluminum is preferably at least 1 / 6.25 as the ratio to the size of the base metal. That is, assuming that the fixed length dimension of the graphite plate 101 to the base metal is L, the dimension for fixing the graphite plate 101 to the base metal 103 needs to be 1 / 6.25 × L. In the first embodiment, since L = 50 mm, the dimension required to fix the graphite plate 101 to the base metal 103 is 1 / 6.25 × 50 mm = 8 mm. That is, the dimension for fixing the graphite plate 101 to the base metal 103 has a characteristic that the heat dissipation is excellent compared to the aluminum heat sink if the fixing dimension for fixing the graphite plate 101 to the base metal 103 is 8 mm or more. Therefore, if the width of the whole notch processing part 102 of the fin of the graphite board 101 is (1-1 / 6.25) xL or less, it has the outstanding heat dissipation characteristic compared with an aluminum heat sink. As for the height of the notched portion 102 of the graphite plate 101, the mechanical strength does not matter even if it is R 0.1 mm, and therefore, the height is 0.2 mm or more.

Second Embodiment
A heat sink 800 excellent in mechanical strength according to the second embodiment will be described.
FIG. 8A is a perspective view of a heat sink 800 using the graphite plate 101 according to the second embodiment as a fin. FIG. 8B is a cross-sectional view γ seen from the direction of the line C-C of FIG. 8A. FIG. 8C is a cross-sectional view δ seen from the direction of line D-D of FIG. 8A.
The graphite plate 101 is provided with a notched portion 102 at one or more places. Further, a hole processing portion 801 is provided at one or more places so as to be located on the upper surface of the base metal 103. In the heat sink 800, the base metal 103 is contained in the notch processed portion 102 and the hole processed portion 801 by caulking, for example. Specifically, the base metal 103 intrudes into the recess of the notch processing portion 102 from the −y direction or the + y direction to form the removal prevention structure 104. In addition, the base metal 103 wraps around the hole drilling portion 801 from the −x direction or the + x direction to form the removal prevention structure 802.

  In the first embodiment, the notched portion 102 is provided only at the end of the graphite plate 101 to form the detachment preventing structure 104. However, in the second embodiment, the holed portion 801 is provided also in the surface of the graphite plate 101. They differ in that they A graphite heat sink with higher mechanical reliability can be obtained by increasing the removal prevention structure 802 in which the base metal 103 enters the hole formation portion 801.

  As in the first embodiment, when the width of the notched portion is increased, the cross-sectional area of heat conduction from the base metal 103 to the heat dissipating fin is reduced, so that the heat dissipating property may be reduced. Therefore, according to the same concept as the first embodiment, the sum of the width of the notched portion 102 provided on the graphite plate 101 and the width of the in-plane holed portion 801 is (1-1 / 6.25) × It must be less than or equal to L.

  FIGS. 9A to 9D show some examples of the shape of the heat sink in the second embodiment. Holes to be machined in the plane of the graphite plate 101 are circular (FIG. 8C, FIG. 9A), long round hole (FIG. 9B), square (FIG. 9C), rectangular (FIG. 9D), or It may be polygonal (not shown). A circular shape and an elongated round hole shape are desirable from the workability of graphite.

  Note that the present disclosure includes appropriate combinations of any of the various embodiments and / or examples described above, and the respective embodiments and / or examples. The effects of the embodiment can be exhibited.

  According to the heat sink according to the present invention, the base metal enters the notched portion, thereby providing a heat sink having excellent mechanical reliability, with the fall preventing structure in which the fins are less likely to come off from the base metal during drop impact or vibration. be able to.

DESCRIPTION OF SYMBOLS 100 Heat sink 101 Graphite plate 102 Notched part 103 Base metal 104 Removal prevention structure 201 Width of notched part 202 Height of notched part 501 Notched groove 502 Notched groove width 601 Mold 701 for caulking 702 grease 703 thermocouple 800 heat sink 801 hole processing part 802

Claims (4)

With fins made of graphite plates,
A base metal for fixing the fin made of the graphite plate at its end;
Equipped with
The fin made of the graphite plate is provided with at least one or more notched parts at the end,
A heat sink, wherein the base metal is contained in at least a part of the notched portion.   Assuming that the total dimension of the width of the notched portion provided on the fin made of the graphite plate is L, the dimension of the base metal for fixing the fin made of the graphite plate is (1-1 / 6.25 The heat sink according to claim 1, wherein the heat sink has a size of not more than × L. The fin made of the graphite plate further comprises a holed portion inside the surface,
The heat sink according to claim 1, wherein the base metal is contained in at least a part of the hole processing portion.   The total dimension of the width of the notched portion provided on the fin made of the graphite plate and the width of the bored portion in the plane corresponds to the dimension of the base metal for fixing the fin made of the graphite plate. The heat sink according to claim 3, which is less than (1-1 / 6.25) × L.

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