Heat dissipation device

Abstract

The present invention provides a heat dissipation device that enables good heat dissipation for a heating element having a polygonal ring-shaped heating element in plan view, while reducing the waste of heat conductive sheets and improving the success rate of installation work. [Solution] A heat dissipation device comprising a heating element having a heating element and a heat-conducting member laminated on the heating element, wherein the heating element and the heat-conducting member have a substantially polygonal annular shape in plan view, and the heat-conducting member consists of a plurality of heat-conducting sheets located on the same plane.

Description

Technical Field

[0001] The present invention relates to a heat dissipation device, and more particularly to a heat dissipation device using a heat conduction sheet.

Background Art

[0002] In recent years, electronic elements included in semiconductor packages, power modules, integrated circuits (ICs, LSIs), plasma display panels (PDPs), etc. that make up electronic devices have been generating increasing amounts of heat as their performance improves. Examples of such electronic elements include semiconductor elements such as insulated gate bipolar transistors (IGBTs), field effect transistors (FETs), and diodes such as light emitting diodes (LEDs).

[0003] And in order to prevent malfunctions of electronic devices caused by temperature rises of these electronic elements, for example, it is necessary to enhance the heat dissipation performance from the electronic elements and efficiently release the heat generated from the electronic elements to the outside.

[0004] Here, as a method for enhancing the heat dissipation performance from electronic elements, generally, a method is adopted in which a heat dissipation body such as a metal heat sink is attached to a heat generating body such as an electronic element or a power module including the electronic element to promote heat dissipation. And when using a heat dissipation body, in order to efficiently transfer heat from the heat generating body to the heat dissipation body, a sheet-like member having heat conductivity (heat conduction sheet) is used, and a method is used in which the heat generating body and the heat dissipation body are brought into close contact via the heat conduction sheet to promote heat dissipation.

[0005] Therefore, for example, in Patent Document 1, a heat conduction sheet having a square shape in plan view and a thermal conductivity in the thickness direction of 15 W / m·K or more is sandwiched between a heat generating body and a heat dissipation body to achieve high heat dissipation performance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] In recent years, with the diversification of applications and structures of electronic devices, the shape of the heating element has also diversified. Specifically, while conventional heating elements with a rectangular heating element in plan view were widely used, in recent years, heating elements with a heating element that is a polygonal ring in plan view (hereinafter simply referred to as "polygonal ring"), such as a rectangular ring in plan view, are sometimes used.

[0008] However, when a heat conductive sheet with a rectangular shape in plan view is laminated to cover the entire heating element, as described above, the heat conductive sheet located on top of the non-heating area inside the annular heating element becomes wasted. On the other hand, when a heat conductive sheet is punched out to match the shape of the heating element, the remaining pieces produced when the heat conductive sheet is punched out are limited in shape and size, making them difficult to utilize effectively. Furthermore, due to the bending of the heat conductive sheet, it is difficult to position the annular heat conductive sheet in the desired location on the annular heating element.

[0009] Therefore, there was a need to develop a technology that enables good heat dissipation for heating elements having a polygonal ring-shaped heating element in plan view, while reducing the waste of thermal conductive sheets and improving the success rate of installation work. [Means for solving the problem]

[0010] The present invention aims to advantageously solve the above problems, and [1] the heat dissipation device of the present invention is a heat dissipation device comprising a heating element having a heating element and a heat conductive member laminated on the heating element, wherein the heating element and the heat conductive member have a substantially polygonal annular shape in plan view, and the heat conductive member consists of a plurality of heat conductive sheets located on the same plane. In this way, by forming a heat conductive member having a substantially polygonal annular shape in plan view with a plurality of heat conductive sheets located on the same plane, compared to the case in which a heat conductive member having a substantially polygonal annular shape in plan view is formed with a single heat conductive sheet, it is possible to reduce the generation of punched-out pieces of heat conductive sheets when manufacturing the heat conductive member and to improve the success rate of the heat conductive sheet installation work. In this invention, "approximately polygonal ring" includes not only polygonal rings but also shapes in which a part of the side of a polygonal ring is cut off, and shapes in which a part of the corner of a polygonal ring is cut off. Specifically, "approximately polygonal ring" includes polygonal rings such as the quadrilateral ring shown in Figure 1(a) and the hexagonal ring shown in Figure 1(b), shapes in which a part of the side of a polygonal ring (a quadrilateral ring in the illustrated example) is cut off, and shapes in which a part of the corner of a polygonal ring (a quadrilateral ring in the illustrated example) is cut off, as shown in Figure 1(d). In this specification, the "corner" of a polygonal ring having a predetermined width refers to the portion C enclosed by the outer perimeter and the perpendicular line (shown as a dotted line in Figures 1(a) and (b)) drawn from the vertex of the polygon formed by the inner perimeter to the outer perimeter, as shown in Figures 1(a) and (b). Furthermore, "side portion" refers to the rectangular portion S enclosed by the perpendicular line (shown as a dotted line in Figures 1(a) and (b)) located between adjacent corners, the outer perimeter, and the inner perimeter. In this specification, if the number of sides of the polygon formed by the outer perimeter constituting a polygonal ring (n-gonal ring) is different from the number of sides of the polygon formed by the inner perimeter constituting the polygonal ring, the smaller number of sides is referred to as "n". Specifically, for example, as shown in Figure 7, if the inner perimeter forms a quadrilateral and the outer perimeter forms a polygon with a number of sides greater than 4 (an octagon in Figure 7(a) and a 20-gon in Figure 7(b)), the shape is referred to as a quadrilateral ring.

[0011] Herein, [2] it is preferable that the heat dissipation device of the present invention is the heat dissipation device described in [1] above, wherein the plan view shape of the heat conductive member is an n-sided ring (where n is an integer of 3 or more), and the heat conductive member consists of n heat conductive sheets. By constructing the n-sided ring-shaped heat conductive member with n heat conductive sheets, it is possible to further improve the success rate of the heat conductive sheet installation work while suppressing an excessive increase in the work time required to install the heat conductive sheets.

[0012] Furthermore, [3] it is preferable that the heat dissipation device of the present invention is the heat dissipation device described in [2] above, wherein the plan view shapes of at least two of the heat conductive sheets are congruent to each other. If the plan view shapes of at least two of the n heat conductive sheets constituting the heat conductive member are the same in dimensions and shape, the management of the member is easier and the workability during installation is improved.

[0013] Furthermore, [4] it is preferable that the heat dissipation device of the present invention is the heat dissipation device according to any one of [1] to [3] above, wherein the heat conductive member consists of three or more heat conductive sheets. By configuring the heat conductive member with three or more heat conductive sheets, it is possible to further improve the success rate of the heat conductive sheet installation work while suppressing an excessive increase in the work time required to install the heat conductive sheet.

[0014] Furthermore, [5] it is preferable that the heat dissipation device of the present invention is the heat dissipation device described in any of [1] to [4] above, wherein the plan view shape of the heat generating part and the heat conductive member is substantially rectangular and annular.

[0015] Furthermore, [6] it is preferable that the heat dissipation device of the present invention is the heat dissipation device described in any of [1] to [5] above, wherein the plan view shape of the heat conductive sheet is substantially rectangular. If the plan view shape of the heat conductive sheet is substantially rectangular, the generation of punched-out pieces of the heat conductive sheet during the manufacture of the heat conductive member can be further reduced, and the workability during installation can be improved. In this invention, "approximately rectangular" includes not only rectangular shapes but also shapes in which a portion of the vertices of a rectangle is cut off, or shapes with holes or notches. Specifically, "approximately rectangular" includes, for example, a rectangular shape with a portion of the vertices cut off as shown in Figure 8(a), a rectangular shape with a notch on a portion of the edge as shown in Figure 8(b), and a rectangular shape with a hole as shown in Figure 8(c).

[0016] Furthermore, [7] the heat dissipation device of the present invention is preferably the heat dissipation device described in [6] above, wherein the substantially rectangular shape has a length in the longitudinal direction that is 8 times or more than the length in the short direction. A substantially rectangular heat conductive sheet with a length in the longitudinal direction that is 8 times or more than the length in the short direction is prone to a decrease in the success rate of installation work due to bending, etc., but there is a great effect in improving the success rate of installation work when the heat conductive member is formed by multiple heat conductive sheets located on the same plane.

[0017] Furthermore, [8] it is preferable that the heat dissipation device of the present invention is the heat dissipation device described in any of [1] to [7] above, wherein the self-weight deflection distance of the heat conductive sheet is 15 mm or more and 40 mm or less. If the self-weight deflection distance of the heat conductive sheet is less than or equal to the above upper limit, the success rate of the installation work of the heat conductive sheet can be further improved. Also, if the self-weight deflection distance of the heat conductive sheet is greater than or equal to the above lower limit, the effect of improving the success rate of the installation work when the heat conductive member is formed with multiple heat conductive sheets located on the same plane is significant. In this invention, the "self-weight deflection distance" can be measured using the method described in the examples.

[0018] Furthermore, [9] the heat dissipation device of the present invention is preferably the heat dissipation device described in any of [1] to [8] above, wherein the heat conductive sheet comprises a resin and a heat conductive filler. The heat conductive sheet comprising a resin and a heat conductive filler has excellent adhesion and thermal conductivity.

[0019] Furthermore,

[10] the heat dissipation device of the present invention is preferably the heat dissipation device described in [9] above, wherein the resin is (meth)acrylic resin or fluororesin. In the present invention, "(meth)acryl" means acrylic and / or methacrylic.

[0020] Further,

[11] in the heat dissipation device of the present invention, the heat conduction sheet has a structure in which strips including a resin and a heat conductive filler are joined in parallel, and the angle formed by the longitudinal direction of the heat conduction sheet and the longitudinal direction of the strips is the same among the plurality of heat conduction sheets. It is preferable that the heat dissipation device is any one of the above [1] to

[10] . In this way, when using a heat conduction sheet having a structure in which strips are joined in parallel, it is possible to suppress stress from concentrating on a portion with low strength.

[0021] And,

[12] in the heat dissipation device of the present invention, it is preferable that the longitudinal direction of the heat conduction sheet and the longitudinal direction of the strips are in the same direction, which is the heat dissipation device described in

[11] above. In this way, breakage of the heat conduction sheet is less likely to occur.

Advantages of the Invention

[0022] According to the present invention, for a heating element having a heat generating portion in a polygonal ring shape in plan view, it is possible to achieve good heat dissipation while reducing the generation of waste of the heat conduction sheet and improving the success rate of installation work.

Brief Description of the Drawings

[0023] [Figure 1] (a) to (d) are plan views for explaining the shapes included in "substantially polygonal ring shape". [Figure 2] It is a plan view showing a schematic configuration of an example of a heat dissipation device according to the present invention. [Figure 3] (a) to (g) are plan views showing examples of heat conductive members. [Figure 4] (a) to (d) are plan views showing examples of the joining portions of the heat conduction sheets constituting the heat conductive member. [Figure 5]This is a plan view showing a thermal conductive sheet having a structure in which multiple strips are joined in parallel, where (a) shows the case where the longitudinal direction of the thermal conductive sheet and the longitudinal direction of the strips are in the same direction, and (b) shows the case where the longitudinal direction of the thermal conductive sheet and the longitudinal direction of the strips are perpendicular to each other. [Figure 6] This diagram illustrates a method for measuring the self-weight deflection distance of a thermal conductive sheet. [Figure 7] (a) and (b) are plan views used to explain the definition of the term "n-gon" in the context of "n-gon rings". [Figure 8] (a) to (c) are plan views illustrating the shapes included in "roughly rectangular". [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described in detail below. Each component disclosed in this embodiment, as well as preferred embodiments, numerical ranges, and thresholds defining such numerical ranges, can be independently combined with each other in any manner.

[0025] (Heat dissipation device) Here, the heat dissipation device of the present invention comprises a heating element having a heat-generating section and a thermally conductive member laminated on the heat-generating section, and usually further comprises a heat dissipation element on the thermally conductive member. In the heat dissipation device of the present invention, the heat-generating section and the thermally conductive member have a substantially polygonal annular shape in plan view. Furthermore, the thermally conductive member is composed of multiple thermally conductive sheets located on the same plane.

[0026] Specifically, as shown in Figure 2 in a plan view of an example of the heat dissipation device of the present invention, the heat dissipation device 100 comprises a heating element 10 having a rectangular annular (square annular in the illustrated example) heat-generating section 11, and a heat-conductive member 20 laminated on the heat-generating section 11. The heat-conductive member 20 is formed by arranging four rectangular (rectangular in the illustrated example) heat-conductive sheets 21 on the same plane in a rectangular annular (square annular in the illustrated example) shape. More specifically, the heat-conductive member 20 is formed by arranging four rectangular heat-conductive sheets 21, which are identical in shape and dimensions (i.e., congruent to each other) in a rectangular shape in a plan view, on one surface of the heating element 10, opposite the heat-generating section 11, such that each heat-conductive sheet constitutes one corner of a square annular and one side adjacent to that corner. In this heat-conductive member 20, the joints of adjacent heat-conductive sheets 21 are located on the boundary line between the corner and the side, and are not located on the same straight line. In Figure 2, for ease of illustration, the dimensions of the thermal conductive member 20 are shown as being larger than those of the heat-generating part 11. However, as long as the heat from the heat-generating part can be sufficiently transferred to the heat sink, the dimensions of the thermal conductive member may be the same as or smaller than those of the heat-generating part. Furthermore, the thermal conductive member 20 may have through holes such as screw holes or notches.

[0027] Here, Figure 2 shows a case where the thermal conductive member 20 is composed of four rectangular thermal conductive sheets 21 that are congruent to each other, but the configuration of the thermal conductive member 20 is not limited to that shown in Figure 2. Specifically, the number of thermal conductive sheets that make up the thermal conductive member is not particularly limited as long as there are two or more. Also, the shape of the thermal conductive sheets that make up the thermal conductive member is not particularly limited and can be, for example, the shapes shown in Figures 3(a) to (g). Furthermore, the shape of the ends of the thermal conductive sheets, that is, the shape of the joints between adjacent thermal conductive sheets, is not particularly limited and can be, for example, the shapes shown in Figures 4(a) to (d). Although not shown, the thermal conductive sheets may have through holes such as screw holes or notches.

[0028] Specifically, in the example shown in Figure 3(a), the thermal conductive member 20 is formed by arranging four L-shaped thermal conductive sheets 21, which are identical in shape and dimensions (i.e., congruent to each other) in a plan view, so that the ends of adjacent thermal conductive sheets 21 are in contact with each other. In this thermal conductive member 20, the joints of adjacent thermal conductive sheets 21 are located on a straight line that passes through the center point of the square ring and is perpendicular to the edges of the thermal conductive member 20.

[0029] In the example shown in Figure 3(b), the thermal conductive member 20 is formed by arranging four thermal conductive sheets 21 that are identical in shape and dimensions (i.e., congruent to each other) and are roughly L-shaped in plan view, so that the ends of adjacent thermal conductive sheets 21 are in contact with each other. In this thermal conductive member 20, the joints of adjacent thermal conductive sheets 21 are located on two straight lines (crosshairs) that intersect perpendicularly at the center point of the square ring and at an angle (greater than 0° but less than 90°) to the sides of the thermal conductive member 20.

[0030] In the example shown in Figure 3(c), the thermal conductive member 20 is formed by arranging four thermal conductive sheets 21, each trapezoidal in plan view (isosceles trapezoidal in the illustrated example), so that the legs of adjacent thermal conductive sheets 21 are in contact with each other. In the illustrated example, since the thermal conductive member 20 is a square ring in plan view, the four trapezoidal thermal conductive sheets 21 are identical in shape and dimensions (i.e., congruent to each other). In this thermal conductive member 20, the joints of adjacent thermal conductive sheets 21 are located on the diagonals of the square ring.

[0031] In the example shown in Figure 3(d), the thermal conductive member 20 is formed by four thermal conductive sheets 21 that are rectangular in plan view (rectangular in the illustrated example). Two thermal conductive sheets 21 (located on opposite sides, top and bottom in the illustrated example) form two corners of a square ring and one side located between those corners, while the remaining two thermal conductive sheets 21 (located on opposite sides, left and right in the illustrated example) form one side of the square ring between the thermal conductive sheets 21 that form the two corners and one side. In the illustrated example, the two thermal conductive sheets 21 located on opposite sides, top and bottom, are identical in shape and dimensions (i.e., congruent to each other), and the two thermal conductive sheets 21 located on opposite sides, left and right, are identical in shape and dimensions (i.e., congruent to each other). Furthermore, in this heat-conducting member 20, the joints of adjacent heat-conducting sheets 21 are located on the boundary line between the corner and the edge, and two of the four joints are located on the same straight line, while the remaining two joints are located on different straight lines.

[0032] In the example shown in Figure 3(e), the thermal conductive member 20 is formed by arranging two U-shaped (or U-shaped) thermal conductive sheets 21 (located vertically in the illustrated example) and two rectangular (or rectangular) thermal conductive sheets 21 (located horizontally in the illustrated example) such that the rectangular thermal conductive sheet 21 is positioned between the ends of the two opposing U-shaped thermal conductive sheets 21. In the illustrated example, the two vertically positioned thermal conductive sheets 21 are identical in shape and dimensions (i.e., congruent to each other), and the two horizontally positioned thermal conductive sheets 21 are also identical in shape and dimensions (i.e., congruent to each other). In this thermal conductive member 20, the joints of adjacent thermal conductive sheets 21 are located on the left and right sides of a rectangular ring.

[0033] In the example shown in Figure 3(f), the thermal conductive member 20 is formed by arranging four thermal conductive sheets 21, which are roughly L-shaped in plan view, so that the ends of adjacent thermal conductive sheets 21 are in contact with each other. In this thermal conductive member 20, the joints of adjacent thermal conductive sheets 21 are located on two parallel straight lines that intersect the edges of the thermal conductive member 20 at an angle of more than 0° but less than 90°.

[0034] In the example shown in Figure 3(g), the thermal conductive member 20 is formed by arranging two thermal conductive sheets 21 that are roughly L-shaped in plan view and two thermal conductive sheets 21 that are triangular in plan view, such that the ends of the two roughly L-shaped thermal conductive sheets 21 abut against the triangular thermal conductive sheets 21 in plan view. In this thermal conductive member 20, the joints of adjacent thermal conductive sheets 21 are located on two parallel lines passing through the vertices of a rectangle formed around the inner periphery (the upper right and lower left vertices in the illustrated example).

[0035] Furthermore, in Figures 2 and 3(a) to (g) above, the joints of adjacent heat conductive sheets 21 (i.e., the edges of the heat conductive sheets 21) are shown as straight lines in plan view, for example, as enlarged in Figure 4(a), from the viewpoint of ease of processing and handling. However, the shape of the edges of the heat conductive sheets 21 is not limited to straight lines, and can be as shown in Figures 4(b) to (d), for example.

[0036] Specifically, the fitting shape can be a stepped shape in plan view as shown in Figure 4(b), a zigzag shape in plan view as shown in Figure 4(c), or a combination of a convex shape and a concave shape in plan view as shown in Figure 4(d), without any particular limitations. If the edge of the heat conductive sheet 21 that forms the joint is a zigzag shape in plan view as shown in Figure 4(c), the positional accuracy of the heat conductive sheet during installation can be improved. Furthermore, if a stepped shape in plan view as shown in Figure 4(b) or a fitting shape as shown in Figure 4(d) is used, a good balance can be achieved between ease of processing and handling and positional accuracy during installation.

[0037] <Heating element> Here, the heat-generating element of the heat dissipation device of the present invention described above is not particularly limited as long as it generates heat in various devices such as electronic equipment and has a heat-generating part with a substantially polygonal annular shape in plan view. Examples of types of heat-generating elements include semiconductor elements such as transistors, diodes, thyristors, organic ELs, and inorganic ELs; and integrated circuits (ICs, LSIs) such as memory and central processing units (CPUs) equipped with such semiconductor elements, and semiconductor-related components such as IC chips, semiconductor packages, semiconductor encapsulation cases, semiconductor die bonding, power modules, power transistors, and power transistor cases; and wiring boards such as rigid wiring boards, flexible wiring boards, ceramic wiring boards, build-up wiring boards, and multilayer substrates (wiring boards also include printed wiring boards); and so on. Examples of the transistors mentioned above include field-effect transistors (FETs), metal-oxide-semiconductor field-effect transistors (MOSFETs), and insulated-gate bipolar transistors (IGBTs). Furthermore, examples of the diodes mentioned above include light-emitting diodes (LEDs) and photodiodes.

[0038] The plan view shape of the heating element's heating portion is the same as that of the thermally conductive member described later, so the explanation is omitted here.

[0039] <Heat sink> Furthermore, the heat sinks that can be placed on the thermally conductive member in the heat dissipation device of the present invention are not particularly limited and include, for example, a heat sink having plate-shaped parts such as fins; a block connected to a heat pipe; a block having an internal structure for circulating a cooling liquid with a pump; a Peltier element; a heat sink equipped with a Peltier element; and a block equipped with a Peltier element. Here, from the viewpoint of good heat dissipation, the heat sink and block are usually made of metal such as aluminum or copper. The planar shape of the heat sink is not particularly limited as long as it can effectively dissipate the heat transferred through the heat-conducting member, and may be a polygonal ring shape similar to the heat-generating part and the heat-conducting member, or it may be any other arbitrary shape.

[0040] <Thermal conductive material> The thermal conductive member is formed by arranging multiple thermal conductive sheets on the same plane so that their planar shape is approximately a polygonal ring, at positions corresponding to the heat-generating part, such as positions facing the heat-generating part of a heating element. When a heat-generating section with a roughly polygonal annular shape in plan view is covered with a single large thermal conductive sheet, the thermal conductive sheet will also be located on the non-heat-generating section (the square portion indicated by reference numeral 12 in Figure 2) located inside the heat-generating section, resulting in waste. Therefore, from the viewpoint of avoiding the wasteful use of thermal conductive sheets, it is preferable to place the thermal conductive sheet only in the position corresponding to the heat-generating section and not on the non-heat-generating section. On the other hand, when using a thermal conductive sheet with the same roughly polygonal annular shape in plan view as the heat-generating section, both the outer and inner edges of the thermal conductive sheet must be aligned to the desired position. However, due to bending of the thermal conductive sheet, the lamination position may shift or the thermal conductive sheet may become distorted, which tends to reduce the success rate of the installation work. In addition, thermal conductive sheets with a roughly polygonal annular shape in plan view are usually manufactured by punching out a thermal conductive sheet as the base material, but the shape and dimensions of the remaining pieces depend on the shape and dimensions of the non-heat-generating section of the heating element, resulting in low flexibility for reuse. In contrast, the heat dissipation device of the present invention described above is composed of multiple heat conductive sheets, forming a thermal conductive member that is roughly polygonal and annular in plan view. Compared to the case where a single thermal conductive sheet that is roughly polygonal and annular in plan view is used, positioning is easier and bending is less likely to occur, thus improving the success rate of installation work. Furthermore, since the thermal conductive sheets can be cut from the base thermal conductive sheet while minimizing dead space, waste is reduced.

[0041] Here, the above-mentioned "approximately polygonal ring" is not particularly limited, but is preferably an approximately quadrilateral ring, an approximately pentagonal ring, or an approximately hexagonal ring, more preferably an approximately quadrilateral ring, even more preferably an approximately rectangular ring, and particularly preferably an approximately rectangular ring or an approximately square ring.

[0042] Furthermore, while the number of thermal conductive sheets constituting the thermal conductive member is not particularly limited as long as it is two or more, from the viewpoint of further improving the success rate of the installation work while suppressing an excessive increase in the work time required to install the thermal conductive sheets, it is preferable to have three or more sheets, more preferably four or more sheets, preferably eight or fewer sheets, more preferably six or fewer sheets, and particularly preferable to have four sheets.

[0043] In particular, when the above-mentioned "approximately polygonal ring" is an n-sided ring (wherein n is an integer of 3 or more, preferably 4 or more and 8 or less, more preferably 4 or more and 6 or less, and even more preferably 4), the number of thermal conductive sheets constituting the thermal conductive member is preferably n-1 or more, more preferably n or more, preferably 2n or less, more preferably n+2 or less, and most preferably n (that is, as shown in the example in Figures 2 and 3, for example, the number of sides of the polygon and the number of thermal conductive sheets are equal). If the number of thermal conductive sheets is above the lower limit, the success rate of the thermal conductive sheet installation work can be further improved. Also, if the number of thermal conductive sheets is below the upper limit, an excessive increase in the work time required for installing the thermal conductive sheets can be suppressed.

[0044] Furthermore, it is preferable that the multiple heat conductive sheets constituting the heat conductive member have congruent planar shapes of at least two sheets, as shown in Figures 2 and 3, and more preferably that all heat conductive sheets have congruent planar shapes, as shown in Figures 2 and 3(a) to (c). If the planar shapes of the heat conductive sheets constituting the heat conductive member are the same in dimensions and shape, it is easier to manage the members and improves workability during installation.

[0045] Furthermore, while the plan view shape of the thermal conductive sheet constituting the thermal conductive member is not particularly limited, from the viewpoint of further reducing the generation of punched-out fragments of the thermal conductive sheet during the manufacture of the thermal conductive member and improving workability during installation, it is preferable that it be approximately square, more preferably approximately rectangular, even more preferably rectangular, and particularly preferably rectangular. For example, with thermal conductive sheets having bent portions, such as the approximately L-shaped thermal conductive sheet in plan view shown in Figures 3(a), (b), (f), and (g), or the U-shaped thermal conductive sheet in plan view shown in Figure 3(e), alignment during installation is difficult. Moreover, when using a thermal conductive sheet with a structure in which strips are joined in parallel, as described later, stress concentration is likely to occur because the strength differs between the vertical and horizontal parts of the L-shape or U-shape. However, with a thermal conductive sheet with an approximately square shape in plan view, as shown in Figures 2 and 3(c) and (d), alignment is easier compared to a thermal conductive sheet with bent portions, and stress concentration is less likely to occur even when using a thermal conductive sheet with a structure in which strips are joined in parallel, as described later. Furthermore, if the heat conductive sheet is roughly rectangular in plan view, as shown in Figures 2 and 3(d), more specifically rectangular in plan view, it is possible to reduce the loss generated when punching out the heat conductive sheet from the base material, and to suppress damage to the heat conductive sheet during punching, compared with the trapezoidal heat conductive sheet shown in plan view, as shown in Figure 3(c).

[0046] Furthermore, when the heat conductive sheet constituting the heat conductive member has a roughly rectangular shape in plan view, such as the rectangular shape described above, it is preferable that the length in the longitudinal direction is 8 times or more the length in the short direction, more preferably 10 times or more, even more preferably 15 times or more, preferably 50 times or less, more preferably 30 times or less, and even more preferably 25 times or less. A roughly rectangular heat conductive sheet with a longitudinal length of 8 times or more the length in the short direction is prone to a decrease in the success rate of installation work due to bending, etc. However, when the heat conductive member is formed by multiple heat conductive sheets located on the same plane, as in the heat dissipation device of the present invention, the effect of improving the success rate of installation work is significant. In addition, if the ratio of the length in the longitudinal direction to the length in the short direction is less than or equal to the above upper limit, a decrease in workability during installation can be suppressed.

[0047] Furthermore, the self-weight deflection distance of the heat-conducting sheet constituting the heat-conducting member is usually 40 mm or less, preferably 15 mm to 40 mm, more preferably 15 mm to 35 mm, and even more preferably 15 mm to 30 mm. If the self-weight deflection distance of the heat-conducting sheet is below the above upper limit, the success rate of the heat-conducting sheet installation work can be further improved. Also, if the self-weight deflection distance of the heat-conducting sheet is above the above lower limit, the effect of improving the success rate of the heat-conducting sheet installation work is significant. Furthermore, the self-weight deflection distance of the thermal conductive sheet can be adjusted, for example, by changing the composition, structure, and thickness of the thermal conductive sheet.

[0048] Furthermore, the average thickness of the thermal conductive sheet is preferably 50 μm or more, more preferably 100 μm or more, preferably 600 μm or less, and more preferably 500 μm or less. If the average thickness of the thermal conductive sheet is above the lower limit, the success rate of the thermal conductive sheet installation work can be further improved. Also, if the average thickness of the thermal conductive sheet is below the upper limit, the effect of improving the success rate of the thermal conductive sheet installation work is significant. The average thickness of a thermal conductive sheet can be determined by measuring the thickness at five arbitrary points on the thermal conductive sheet using a thickness gauge (for example, if the thermal conductive sheet is rectangular in plan view, the approximate center point and the four corners (a total of five points)), and calculating the arithmetic mean.

[0049] Furthermore, the thermal conductive sheet described above is not particularly limited, and any known thermal conductive sheet can be used. In particular, from the viewpoint of excellent adhesion and thermal conductivity, it is preferable to use a thermal conductive sheet that includes a resin and a thermal conductive filler.

[0050] Here, the resin is not particularly limited, and any resin that can be used as a resin for a thermal conductive sheet can be used. Specifically, examples of resins that can be used include (meth)acrylic resin, silicone resin, fluororesin, and styrene-butadiene rubber, with (meth)acrylic resin or fluororesin being preferred. In this specification, "rubber" is included in "resin."

[0051] Furthermore, the thermally conductive filler is not particularly limited, and known thermally conductive fillers such as metal fillers and carbon fillers can be used. Among these, it is preferable to use carbon materials such as particulate carbon materials and fibrous carbon materials as the thermally conductive filler, and it is more preferable to use particulate carbon materials.

[0052] Here, the particulate carbon material is not particularly limited, and for example, graphite such as artificial graphite, flake graphite, flaked graphite, natural graphite, acid-treated graphite, expandable graphite, and expanded graphite; carbon black; etc. These may be used individually or in combination of two or more.

[0053] In particular, expanded graphite is preferred as the particulate carbon material. Expanded graphite can be obtained, for example, by chemically treating graphite such as flake graphite with sulfuric acid to obtain expandable graphite, which is then heat-treated to expand it and then refined. Examples of expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all are product names) manufactured by Ito Graphite Industries Co., Ltd.

[0054] Furthermore, the aspect ratio (major axis / minor axis) of the particulate carbon material is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less. In this invention, the "aspect ratio of particulate carbon material" can be determined by observing the cross-section of the thermal conductive sheet in the thickness direction with an SEM (scanning electron microscope), measuring the maximum diameter (major diameter) and the particle diameter in the direction perpendicular to the maximum diameter (minor diameter) for any 50 particulate carbon materials, and calculating the average value of the ratio of major diameter to minor diameter (major diameter / minor diameter).

[0055] Furthermore, the fibrous carbon material that the thermal conductive sheet may contain is not particularly limited, and examples include carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut pieces thereof. These may be used individually or in combination of two or more.

[0056] In particular, as the fibrous carbon material, it is preferable to use fibrous carbon nanostructures such as carbon nanotubes (hereinafter sometimes referred to as "CNTs"), and it is even more preferable to use fibrous carbon nanostructures containing CNTs.

[0057] The aspect ratio (major axis / minor axis) of fibrous carbon materials is typically greater than 10. In this invention, the "aspect ratio of the fibrous carbon material" can be determined by using a TEM (transmission electron microscope) to measure the maximum diameter (long diameter) and the outer diameter (short diameter) in the direction perpendicular to the maximum diameter of 100 randomly selected fibrous carbon materials, and then calculating the average value of the ratio of the long diameter to the short diameter (long diameter / short diameter).

[0058] In this regard, from the viewpoint of enabling the thermal conductive sheet to exhibit excellent thermal conductivity, it is preferable that the thermal conductive filler is oriented in the thickness direction of the thermal conductive sheet. In this specification, "oriented in the thickness direction" means that the orientation angle of the thermal conductive filler with respect to the main surface of the thermal conductive sheet is 45° or more and 90° or less. The orientation angle of the thermal conductive filler can be determined by observing a cross-section of the thermal conductive sheet cut in the thickness direction using a scanning electron microscope (SEM) at a magnification that captures the entire cross-section from top to bottom, drawing lines along the major axes of 50 thermal conductive fillers in that cross-section, and calculating the average angle of the major axes with respect to the main surface of the thermal conductive sheet. If the angle is 90° or more, a supplementary angle is used.

[0059] Furthermore, the thermal conductive sheet in which the thermal conductive filler described above is oriented in the thickness direction can be manufactured using known methods without any particular limitations. Specifically, the thermal conductive sheet can be manufactured, for example, by (1) forming a sheet from a composition containing at least a resin and a thermal conductive filler by mold molding or the like, then performing an orientation operation of the thermal conductive filler, such as an orientation operation using a magnetic field, and then optionally curing the resin; or by (2) forming a sheet from a composition containing components such as a resin and a thermal conductive filler by pressurizing it, using the resulting sheet-like molded body as a pre-thermal conductive sheet, and slicing a laminate of multiple pre-thermal conductive sheets in a substantially lamination direction.

[0060] Here, when a thermal conductive sheet is manufactured by the method described in (2) above, the thermal conductive sheet, which consists of slices of a laminate, has a structure in which strips 30 containing at least resin and thermal conductive filler are joined in parallel in the width direction of the strips 30, as shown in Figures 5(a) and (b), for example. Specifically, the thermal conductive sheet 21 has a structure in which a plurality of strips 30 containing resin and thermal conductive filler are joined in parallel in the width direction of the strips 30 such that adjacent strips 30 share sides that extend in the longitudinal direction of the strips (left-right direction in Figure 5(a), up-down direction in Figure 5(b)).

[0061] Furthermore, if the thermal conductive sheet has a structure in which strips are joined in parallel in the width direction of the strips, it is preferable that the angle between the longitudinal direction of the thermal conductive sheet and the longitudinal direction of the strips (0° in Figure 5(a), 90° in Figure 5(b)) is the same for multiple thermal conductive sheets constituting the thermal conductive member. If the angle between the longitudinal direction of the thermal conductive sheet and the longitudinal direction of the strips is the same for multiple thermal conductive sheets constituting the thermal conductive member, it is possible to suppress the concentration of stress in the parts of the thermal conductive member with low strength.

[0062] Furthermore, if the thermal conductive sheet has a structure in which strips are joined in parallel in the width direction of the strips, it is preferable that the longitudinal direction of the thermal conductive sheet and the longitudinal direction of the strips are in the same direction, as shown in Figure 5(a). When the longitudinal direction of the thermal conductive sheet and the longitudinal direction of the strips are in the same direction, the bonding area between the strips is larger compared to when the longitudinal direction of the strips is inclined or perpendicular to the longitudinal direction of the thermal conductive sheet, making it less likely for the thermal conductive sheet to break. [Examples]

[0063] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, the self-weight deflection distance was measured by the following method.

[0064] <Self-weight deflection distance> A test sample was prepared by cutting a rectangular shape measuring 10 mm wide x 50 mm long from the thermal conductive sheet used as the base material. At this time, the long direction of the test sample was cut to match the long direction of the plan view shape of the thermal conductive sheet used in the example. The obtained test sample was fixed on a stand as shown in Figure 6. Specifically, the test sample was fixed on the stand so that the distance L protruding from the stand was 40 mm. Then, the support was removed from the test sample, which was held horizontally with support, and the deflection distance D (the vertical distance from the surface of the stand to the protruding edge of the test sample) was measured after 5 seconds. This measurement was performed three times (n=3) for the same test sample, and the average value was taken as the self-weight deflection distance.

[0065] (Example 1) <Preparation of Composition> 70 parts of liquid acrylic resin (manufactured by Toagosei Co., Ltd., product name "ARUFON UH-2190"), 30 parts of solid acrylic resin (manufactured by Nippon Zeon Co., Ltd., product name "Nipol H570"), and 145 parts of expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., product name "EC-300", volume average particle size: 50 μm) as a thermally conductive filler were mixed and stirred for 5 minutes using a Hobart mixer (manufactured by Kodaira Seisakusho Co., Ltd., product name "ACM-5LVT type"). The resulting mixture was degassed under vacuum for 30 minutes and then put into a crusher to crush it and obtain the composition. <Fabrication of pre-heat conductive sheets> Next, 7 kg of the obtained composition was sandwiched between 100 μm thick PET films (protective films) that had been released from the mold, and rolled (primary pressurized) under the conditions of a roll gap of 700 μm, a roll temperature of 70°C, a roll linear pressure of 1500 N / cm, and a roll speed of 1 m / min to obtain a pre-heat-conductive sheet with a thickness of 800 μm. <Fabrication of laminates> Next, the obtained pre-heat conductive sheets were cut to 150 mm in length, 150 mm in width, and 800 μm in thickness. 200 sheets were stacked in the thickness direction of the pre-heat conductive sheets, and then pressed (secondary pressurized) in the stacking direction at a temperature of 25°C and a pressure of 1.5 MPa for 90 minutes to obtain a resin molded body with a height of approximately 160 mm. <Fabrication of thermal conductive sheets> Subsequently, while pressing the laminated sides of the secondary-pressurized laminate with a pressure of 0.3 MPa, a woodworking slicer (manufactured by Marunaka Iron Works Co., Ltd., product name "Super Finishing Planer Super Mecha S") was used to slice the laminate at a 45-degree angle to the lamination direction, thereby obtaining a heat-conducting sheet that would serve as the base material, measuring 150 mm in length, 150 mm in width, and 0.2 mm in thickness. Then, a heat-conductive sheet having the dimensions and shape shown in Table 1 and the structure shown in Figure 5(a) was cut from the base heat-conductive sheet. Furthermore, to form 28 thermal conductive sheets in total (14 sheets each of two types with the dimensions shown in Table 1) for seven thermal conductive components, the loss rate was calculated as the ratio of the amount of base material used to the amount of unusable fragments discarded (= (amount of fragments / amount of base material) × 100). The results are shown in Table 1. <Manufacturing of heat dissipation devices> To simulate a heating element, we prepared an aluminum (A5052) component processed into a square ring shape in plan view (outer dimensions: 120mm x 120mm, inner dimensions: 110mm x 110mm, thickness: 5mm) as shown in Figure 2. Next, as shown in Figure 3(d), four rectangular thermal conductive sheets were arranged in a square ring shape on the heating element, and the thermal conductive component was placed on the heating element. In this process, if the position of the edge of the thermal conductive sheet was shifted by 1 mm or more from the position of the edge of the heating element, or if the thermal conductive sheet was warped, the installation was considered a failure. If all four thermal conductive sheets were successfully placed, the installation was considered a success. Then, by repeating the above process, the success rate of installation (= (number of successful installations / 50) × 100) when thermal conductive material was placed on 50 heating elements was calculated. In addition, the average amount of work time required to install the thermal conductive material on each heating element was calculated. The results are shown in Table 1.

[0066] (Example 2) The composition, pre-heat conductive sheet, laminate, heat conductive sheet, and heat dissipation device were prepared in the same manner as in Example 1, except that the slicing conditions were changed during the preparation of the heat conductive sheet to obtain a heat conductive sheet with a thickness of 0.1 mm. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0067] (Example 3) The composition, pre-heat conductive sheet, laminate, heat conductive sheet, and heat dissipation device were fabricated in the same manner as in Example 1, except that the direction in which the heat conductive sheet was cut from the base heat conductive sheet during the fabrication of the heat conductive sheet was changed to obtain a heat conductive sheet having the dimensions and shape shown in Table 1 and the structure shown in Figure 5(b). Then, various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.

[0068] (Example 4) The composition, pre-thermal conductive sheet, laminate, thermal conductive sheet, and heat dissipation device were prepared in the same manner as in Example 1, except that 70 parts of thermoplastic fluororubber (manufactured by Daikin Industries, Ltd., product name "Daiel G-101") were used instead of 70 parts of thermoplastic acrylic resin (manufactured by Toagosei Co., Ltd., product name "UH2190") during composition preparation, and 30 parts of thermoplastic fluororubber (manufactured by 3M Japan Limited, product name "Dynion FC2211") were used instead of 30 parts of thermoplastic acrylic rubber (manufactured by Nippon Zeon Co., Ltd., product name "ZEON HyTemp H570") during composition preparation. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0069] (Comparative Examples 1 and 2) Except for cutting a square-ring-shaped heat conductive sheet (outer dimensions: 120mm x 120mm, inner dimensions: 110mm x 110mm) from the base heat conductive sheet during the fabrication of the heat conductive sheet, and replacing the four heat conductive sheets with the square-ring-shaped heat conductive sheet on the heating element during the manufacturing of the heat dissipation device, the composition, pre-heat conductive sheet, laminate, heat conductive sheet, and heat dissipation device were fabricated in the same manner as in Examples 1 and 2. Various evaluations were then performed in the same manner as in Example 1. The results are shown in Table 1.

[0070] [Table 1]

[0071] Table 1 shows that in Examples 1 to 4, the loss rate can be reduced compared to Comparative Examples 1 and 2, and the success rate of the installation work can be improved. [Industrial applicability]

[0072] According to the present invention, a heating element having a polygonal annular heating element in plan view can achieve good heat dissipation while reducing the waste of heat conductive sheets and improving the success rate of installation work. [Explanation of symbols]

[0073] 10 Heating element 11 Heat-generating part 12 Non-heating parts 20 Thermally conductive material 21 Thermal conductive sheet 30 strips 100 Heat dissipation device

Claims

1. A heat dissipation device comprising a heating element having a heat-generating portion and a heat-conducting member laminated on the heat-generating portion, The heat-generating part and the heat-conducting member have a substantially polygonal annular shape in plan view. The heat dissipation device comprises a plurality of heat conductive sheets located on the same plane.

2. The plan view shape of the aforementioned heat-conducting member is an n-sided annular shape (where n is an integer of 3 or more), The heat dissipation device according to claim 1, wherein the heat conductive member consists of n heat conductive sheets.

3. The heat dissipation device according to claim 2, wherein the planar shapes of at least two of the heat conductive sheets are congruent to each other.

4. The heat dissipation device according to claim 1, wherein the heat conductive member consists of three or more heat conductive sheets.

5. The heat dissipation device according to claim 1, wherein the plan view shape of the heat-generating part and the heat-conducting member is substantially rectangular and annular.

6. The heat dissipation device according to claim 1, wherein the plan view shape of the heat conductive sheet is substantially rectangular.

7. The heat dissipation device according to claim 6, wherein the substantially rectangular shape has a length in the longitudinal direction that is eight times or more than the length in the short direction.

8. The heat dissipation device according to claim 6, wherein the self-weight deflection distance of the heat conductive sheet is 15 mm or more and 40 mm or less.

9. The heat dissipation device according to claim 1, wherein the heat conductive sheet comprises a resin and a heat conductive filler.

10. The heat dissipation device according to claim 9, wherein the resin is a (meth)acrylic resin or a fluororesin.

11. The aforementioned heat-conducting sheet has a structure in which strips containing resin and a heat-conducting filler are joined in parallel. The heat dissipation device according to any one of claims 1 to 10, wherein the angle between the longitudinal direction of the heat conductive sheet and the longitudinal direction of the strip is the same among the plurality of heat conductive sheets.

12. The heat dissipation device according to claim 11, wherein the longitudinal direction of the heat conductive sheet and the longitudinal direction of the strip are in the same direction.

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