JP2007053145A - Heat-transfer sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-transfer sheet having a good heat conductivity and a good conformability for improving a heat conductive performance as a whole, by modifying a heat-transfer sheet made of a sheetlike material having layered structures formed in the same direction as one another, while noticing that the heat conductivity is not generally good in the thickness direction but excellent in the planar direction. <P>SOLUTION: The heat-transfer sheet A1 includes the sheetlike material 2 having the layered structures 1 formed in the same direction as one another, and has distorted parts 3 formed on the sheetlike material 2 with end surfaces of the structures 1 formed to be leveled with the surface as the sheetlike material 2. The distorted parts 3 are configured by folding right and left ends of the sheetlike material 2 downward to make the end surfaces of the sheetlike material 2 leveled with the bottom of the sheetlike material 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat transfer sheet, and more specifically, for heat dissipation of electronic parts with heat generation such as a CPU, light emitting diode, transformer, power transistor, liquid crystal panel, plasma display, etc., or a heating element or cooling in an electronic device. The present invention relates to a heat transfer sheet used as an efficient heat transfer medium for the body.

  The above electronic components in electronic devices generate heat with use, and the performance may be degraded by the heat generated by them. Generally, heat is quickly dissipated using a heat sink such as a heat sink or housing. Means are taken. In this case, a heat transfer sheet is often interposed between the heat generating electronic component and the heat radiating body as a heat transfer interface.

  Conventional heat transfer sheets are known that use a silicon sheet or silicon grease (Patent Document 1 or Patent Document 2) as a sheet-like body, or a sheet using a metal plate made of aluminum alloy or copper (Patent Document 3). It has been. Also, an expanded graphite sheet obtained by laminating a metal foil and a synthetic resin sheet material, or an expanded graphite sheet having a layered structure (sheet-like body having a layered structure portion) that is formed by pressurizing and integrating graphite after being expanded. What cuts into the predetermined shape (for example, patent document 4 and patent document 5) is also known.

  A conventional heat transfer sheet made of a silicon-based material has an advantage of excellent compatibility with a heating element (heating electronic component) and a radiator, but has a disadvantage of being inferior in thermal conductivity. Although the metal-based heat transfer sheet has an advantage of high thermal conductivity, it has a disadvantage that it is inferior in compatibility with a heating element and a heat dissipation element. The laminate of the metal foil and the synthetic resin has good thermal conductivity in the plane direction (direction parallel to the plane), but is inferior in thermal conductivity in the thickness direction. In addition, the expanded graphite sheet exhibits excellent thermal conductivity in the plane direction, but has a drawback that the thermal conductivity in the thickness direction is less than 1/20 of the plane direction.

As described above, any of the types of heat transfer sheets described above has their advantages and disadvantages, and no heat transfer sheet having the ability to pull out has been obtained. The actual situation was to select and use from the three.
Japanese Patent Laid-Open No. 10-040823 JP 2002-222904 A JP 2005-101025 A JP-A-10-231111 JP-A 64-014139

  The object of the present invention is that, in a heat transfer sheet composed of sheet-like bodies having layered structures formed in the same direction, the heat conductivity is generally not good in the thickness direction, but has excellent characteristics in the surface direction. It is in the point which provides the heat-transfer sheet | seat which obtains favorable heat conductivity and favorable familiarity by paying attention to having and improving favorable heat conductivity, and improves the heat conductivity performance as a whole.

  The invention according to claim 1 is a heat transfer sheet comprising a sheet-like body 2 having a layered structure portion 1 formed in the same direction, and the end surface of the layered structure portion 1 is a surface as the sheet-like body 2 The distorted portion 3 configured to be in the same plane as that of the sheet-like body 2 is formed on the sheet-like body 2.

  According to a second aspect of the present invention, in the heat transfer sheet according to the first aspect, the warped portion 3 is such that the end surface of the sheet-like body 2 is flush with the front or back surface of the sheet-like body 2. Further, the sheet-like body 2 is formed by bending an end portion.

  The invention according to claim 3 is the heat transfer sheet according to claim 1, wherein the warped portion 3 has a surface 22A on either the front or back side of the sheet-like body 22 so that the fault of the layered structure portion 21 is exposed. By compressing the entire sheet-like body 22 in the state in which the scraping recess 24 is formed in the thickness direction, the concave surface 24a of the scraping recess 24 is flush with any one of the surfaces 22A. It is characterized by being made to adapt so.

  The invention according to claim 4 is a heat transfer sheet comprising a sheet-like body 32 having layered structures 31 formed in the same direction and at least one of the layered structures 31 adjacent in the layer direction. The short-circuit part 33 in a state where the end surface of the layered structure part 31 is in contact with the other layered structure part 31 is formed.

  The invention according to claim 5 is the heat transfer sheet according to claim 4, wherein the short-circuit portion 33 mechanically forms a hole 34 extending in the thickness direction of the sheet-like body 32, whereby the hole 34. In the portion, the end surface of at least one layered structure portion 31 of the layered structure portions adjacent to each other in the layer direction is configured to be bent and contacted with the other layered structure portion 31. It is.

  The invention according to claim 6 is the heat transfer sheet according to claim 4, wherein the short-circuit portion 33 has a thickness in a state in which the granular material 54 is interposed between the layered structure portions 51 adjacent in the layer direction. The layered structure portion 51 is partially broken by compressing in the direction, and the end face of at least one of the layered structure portions 51 adjacent to each other in the layer direction is the other in the broken portion 51b It is comprised by the means contact | abutted to the layered structure part 51 of this.

  The invention according to claim 7 is the heat transfer sheet according to any one of claims 1 to 6, wherein the layered structure parts 1, 21, 31, 51 are made of expanded graphite, metal foil, or synthetic resin. It is formed from any one material.

  The invention according to claim 8 is the heat transfer sheet according to claim 5, wherein the sheet-like body 32 is provided with a metal foil 44 between the layered structure portions 31 adjacent in the layer direction. And the hole 34 is formed so as to penetrate the metal foil 44.

  According to the invention of claim 1, since the end surface of the layered structure portion is flush with either of the front and back surfaces of the sheet-like body in the distorted portion, the excellent thermal conductivity in the surface direction is also distributed in the thickness direction. As a result, the thermal conductivity in the thickness direction can be improved. As a result, by improving the heat transfer sheet composed of a sheet-like body having a plurality of layered structures, it is possible to obtain good thermal conductivity in the thickness direction and good conformability, and improve the overall heat conduction performance Heat transfer sheet can be provided.

  Since the heat transfer sheet is interposed between the heat generating body and the heat radiating body, there is an advantage that the heat transfer efficiency between the heat generating body and the heat radiating body can be greatly improved by improving the thermal conductivity in the thickness direction. Further, the material of the layered structure portion can be selected from expanded graphite, metal foil, and synthetic resin as described in claim 7.

  In this case, as in claim 2, if the distorted portion is formed by bending the end portion of the sheet-like body, there is an advantage that the thermal conductivity in the thickness direction is clearly improved at the end portion of the sheet-like body. As in claim 3, the entire sheet-like body in a state in which the recessed portion is formed on either the front or back surface of the sheet-like body so as to expose the fault of the layered structure portion is compressed in the thickness direction. By forming a distorted part by adapting the concave surface of the scraping recess to be flush with any surface, the thermal conductivity in the thickness direction at the location where the scraping recess is set is clearly There are benefits to be improved.

  According to the invention of claim 4, since the end face of the layered structure portion abuts on the adjacent layered structure portion in the thickness direction in the short-circuit portion, excellent thermal conductivity in the surface direction is also present in the thickness direction in the short-circuit portion. It becomes an equipped state and can improve the thermal conductivity in the thickness direction. As a result, by improving the heat transfer sheet that is formed by laminating a plurality of layered structures to form a sheet-like body, good heat conductivity in the thickness direction and good familiarity are obtained, and the heat as a whole is obtained. An improved heat transfer sheet with improved conduction performance can be provided.

  In this case, the holes extending in the thickness direction are formed in the sheet-like body as in the fifth and eighth aspects, and the end surface of the layered structure portion is bent at the hole portion and comes into contact with the adjacent layered structure portion in the layer direction. If the short-circuit part to be formed is formed, the thermal conductivity in the thickness direction at the hole portion is clearly improved, and the granular material is arranged between the layered structure parts as in claim 6 in the thickness direction. If the short-circuit part is formed by compressing to a thickness, the thermal conductivity in the thickness direction does not occur only in specific parts of the sheet-like body, but can be improved evenly, improving the thermal conductivity in the thickness direction on average. Can be done. Further, in claim 8, the thermal conductivity is improved in both the surface direction and the thickness direction by embedding the metal foil in the sheet-like body.

  Embodiments of a heat transfer sheet according to the present invention will be described below with reference to the drawings. 1 to 3 show a heat transfer sheet according to Example 1, FIGS. 4 and 5 show a heat transfer sheet according to Example 2, and FIGS. 6 to 8 show a heat transfer sheet according to Examples 3 to 5, respectively. ing. Although the heat transfer sheet is very thin, for the purpose of understanding the drawings, in each drawing, the sheet-like body is intentionally made thick.

[Example 1]
A heat transfer sheet A1 according to Example 1 is shown in FIG. This heat transfer sheet A1 is composed of a sheet-like body (expanded graphite sheet) 2 having a large number of layered structure parts 1 mainly composed of expanded graphite, and the end surface of the layered structure part 1 is a surface as a sheet-like body 2. The distortion part 3 comprised in the state which becomes the same surface as (flat surface) is formed in the sheet-like body 2. FIG. The distorted portion 3 is formed by bending the left and right ends of the sheet-like body 2 downward by press molding or the like so that the left and right end faces of the sheet-like body 2 are flush with the back surface (bottom surface) 2A of the sheet-like body 2. It is configured (see FIG. 3).

  Here, expanded graphite is superior in heat resistance and heat conductivity compared to tetrafluoroethylene resin (PTFE, PFA, etc.) or rubber generally used as a constituent material for various sealing materials, It is a known material that is being used frequently in recent years. In addition, the expanded graphite sheet allows the expanded graphite particles to be brought into close contact with each other by re-adhering the expanded bellows-like layers (between the layered structure portions 1 and 1) that are expanded by press forming or roll forming. It is self-adhesive and is manufactured into a sheet shape. In other words, this means that the sheet-like body has “layered structure portions formed in the same direction as each other”, and in the claims, “formed in the same direction as each other” is omitted and “sheet having layered structure portions” The meaning in the scope of rights is the same even if it is expressed as “like body ...”. In the manufacturing means described above, it can be considered that each layered structure portion inside from the surface is formed in the same direction as the layered structure portion exposed on the surface. Even if it is expressed as “a sheet-like body having a layered structure portion formed in the direction...”, The meaning in the scope of rights is the same.

  The sheet-like body 2 is created by a method as shown in FIG. First, as shown in FIG. 3 (a), on the left and right ends of an expanded graphite sheet 2 having a density of 1.0 g / cm @ 3 and rectangular in plan view and having a predetermined thickness, a bottom surface 2A which is a horizontal plane is provided. An end face (inclined end face) 4 is formed so as to be inclined at an angle of 30 degrees. The formation method of this end surface 4 is not ask | required. Then, the left and right end portions of the sheet-like body 2 are mainly pressed downward by the pressing force of a press or the like, and as shown in FIG. In addition, the right and left distortion portions 3 and 3 are formed by forcibly bending the right end portion. As a result, the heat transfer sheet A1 shown in FIG. 1 is obtained.

  The usage example of the heat-transfer sheet | seat A1 of Example 1 is shown in FIG. In FIG. 2, reference numeral 11 denotes a heating element such as a power transistor, and 12 denotes a heat radiator such as a heat sink. A heat transfer sheet A <b> 1 is interposed between the heat generator 11 and the heat radiator 12. In the left and right distorted portions 3, 3, the end surfaces 4, 4 are in a state in which the end surfaces 4, 4 are in close contact with the upper surface 12 a of the radiator 12. Therefore, the heat transmitted from the heat generating body 11 to the heat transfer sheet A1 is transmitted to the heat radiating body 12 through the bottom surface 2A of the sheet-like body 2, and is also transmitted to the heat radiating body 12 from the left and right end surfaces 4 and 4. The

  As described above, the expanded graphite sheet has an excellent thermal conductivity in the surface direction. Therefore, in a sample piece (30 mm × 30 mm × 0.25 mm) having a predetermined shape, the conventional product (the left and right end surfaces are vertical). The heat conductivity in the thickness direction (layer direction) of the cut sheet) was 5.0 (W / mK), but the heat transfer sheet A1 according to Example 1 improved to 7.1 (W / mK). It was found from the experimental data. That is, the thermal conductivity from the heat generating element 11 to the heat radiating body 12 is clearly improved and the performance is improved in spite of the simple modification of bending the left and right end portions of the sheet-like body 2 downward.

  For example, in addition to the left and right end portions of the sheet-like body 2, the front and rear end portions are also bent downward to form the curved portions 3 and 3 to improve the thermal conductivity in the thickness direction with respect to the radiator 12, or the front and rear end portions upward. As the bent bent portions 3 and 3, the heat transfer sheet A <b> 1 that improves the thermal conductivity in the thickness direction with respect to the heating element 11 having a larger plan view shape than the sheet-like body 2 may be used. Further, the distorted portion 3 may be formed locally rather than penetrating in the front-rear direction of the sheet-like body 2.

[Example 2]
A heat transfer sheet A2 according to Example 2 is shown in FIG. Like the heat transfer sheet A1 of Example 1, this heat transfer sheet A2 is a sheet-like body (expanded graphite sheet) 22 in a state in which a large number of layered structure portions 21 made of expanded graphite as a main raw material are stacked one above the other. And a distorted portion 23 is formed on the sheet-like body 22 so that the end surface of the layered structure portion 21 is flush with the surface (flat surface) 22A as the sheet-like body 22. is there.

  The distorted portion 23 has the entire thickness of the sheet-like body 22 in a state where the recess 24 is formed on the surface of the back surface (bottom face) 22A of the sheet-like body 22 so that the fault of the layered structure portion 22 is exposed. By compressing in the direction, the concave surface 24a of the scraping concave portion 24 is deformed so as to be flush with the bottom surface 22A and is adapted. The preparation method (manufacturing method) is as follows.

  First, as shown in FIG. 5 (a), a plurality of locations (for example, two on the left and right sides) of the bottom surface 22A of the expanded graphite sheet-like body 22 having a density of 0.8 g / cm 3, a rectangular plan view, and a thickness D. In a place), a scraping recess 24 having a width of about 2 mm that is recessed upward in an arc shape is formed in a state of penetrating in the front-rear direction. Then, the entire sheet-like body 2 is strongly pressed downward by a pressing force of a press or the like, and as shown in FIG. 5B, the concave surface 24a of the scraping concave portion 24 is a predetermined plane that is flush with the bottom surface 22A. The thickness is d and compressed, and the distorted portions 23 and 23 are created at two locations on the left and right. The density of the sheet-like body 22 after compression deformation was 1.0 g / cm 3. As a result, the heat transfer sheet A2 shown in FIG. 4 is obtained.

  In each of the distorted portions 23, 23, the end surface (tomographic surface) as the thin film sheet body 1 is formed on the same surface as the bottom surface 22A. It has been found that the conductivity is remarkably improved. That is, the sample piece (30 mm × 30 mm × 0.25 mm) having a predetermined shape is greatly improved from 5.0 (W / mK) to 13.3 (W / mK) in the heat transfer sheet A2 according to Example 2. ing. That is, despite the modification to the extent that the groove-shaped scraping recess 24 is formed at the two left and right sides of the bottom surface side of the sheet-like body 2 and compressed in the thickness direction, the thermal conductivity as the heat conduction medium is dramatically increased. It is possible to provide the heat transfer sheet A2 that has been improved and can achieve outstanding performance improvement.

  As described above, in the heat transfer sheets A1 and A2 of the first and second embodiments, the heat flux transferred in the surface direction is changed in the thickness direction to change the heat transfer surface (the bottom surfaces 2A and 22A and the radiator 12). Therefore, the thermal conductivity in the thickness direction can be greatly improved. For example, when there is a portion with a large amount of heat transfer locally in the heat generating body or the heat radiating body, the design can be made such that the distorted portions 3 and 23 are matched with the portion where the heat generation or heat dissipation is large, and heat can be transmitted more efficiently. There is an advantage that can provide a heat transfer sheet that can.

  Since the thermal conductivity in the thickness direction is improved, the thickness can be increased to absorb irregularities and undulations on the surface of the heating element and the heat radiating body, and excellent conformability can be ensured. Thereby, the secondary effect which thermal conductivity further improves is also acquired. It is possible to reduce a difference in heat transfer characteristics between a good thermal conductivity in the plane direction (example: 150 W / mK) and a poor thermal conductivity in the thickness direction (example: 5 W / mK). Therefore, the thermal conductivity excellent in the surface direction of the expanded graphite can be effectively utilized as compared with the conventional case, and the heat transfer sheets A1 and A2 having excellent thermal conductivity can be provided.

  For example, before the compression molding, the scraping recesses 24 are formed in advance at a plurality of positions above and below the sheet-like body 22, and the distortion portions 23 are formed above and below the sheet-like body 22. Alternatively, the heat transfer sheet A2 having a structure in which the thermal conductivity in the thickness direction is improved may be used. Further, the distorted portion 23 formed by the scraping recess 24 may be a local portion that does not penetrate the sheet-like body 22 in the front-rear direction. Further, in the heat transfer sheet A1 shown in FIG. 2, a configuration in which a curved portion 23 caused by the scraping recess 24 is additionally formed on the upper surface of the sheet-like body 2 is also possible.

Example 3
A heat transfer sheet A3 according to Example 3 is shown in FIG. In the heat transfer sheet A3, a sheet-like body 32 having a plurality of layered structure parts 31 is configured, and the end surface 31a of at least one of the layered structure parts 31 adjacent to each other in the layer direction is the other. The short-circuit part 33 in a state of contacting the layered structure part 31 is formed. The short-circuit portion 33 is formed by mechanically forming a relatively small diameter hole 34 extending in the thickness direction in the sheet-like body 32, so that at least one of the layered structure portions 31 adjacent in the layer direction at the hole 34 portion. The end surface of the layered structure portion 31 is bent to contact the other layered structure portion 31.

  For example, as shown by phantom lines in FIG. 6, there can be considered a means for forming the hole 34 by piercing the pointed bar-shaped perforating member 35 into the sheet-like body 32 in the thickness direction. When stabbed downward from above, the end surface of the burring portion 31b that is broken and bent downward in the layered structure portion 31 comes into contact with the root portion of the burring portion 31b of the lower layered structure portion 31. is there. You may form the hole 34 by piercing from the bottom upwards. Since the thermal conductivity in the thickness direction is improved at the portion of the hole 34, heat can be more efficiently transferred if the hole 34 is set so as to be aligned with a portion where heat generation or heat dissipation is particularly desired. Further, as the number of holes 34 increases, the thermal conductivity in the thickness direction can be improved.

  As an example, a layered structure 31 made of an expanded graphite sheet with a thickness of 0.25 mm is needle processed in the thickness direction to form a large number of through holes 34, and the layers (between the layered structures) are short-circuited. did it. Note that the number, depth, perforation direction (vertical, oblique), and the like of the holes 34 can be set as appropriate according to various conditions such as the location where the heat transfer sheet A3 is used and temperature conditions.

Example 4
A heat transfer sheet A4 according to Example 4 is shown in FIG. This heat transfer sheet A4 is the same except that the metal foil 44 is embedded in the upper and lower middle of the sheet-like body 32 of Example 3, and different points will be described. That is, the sheet-like body 42 is configured such that the metal foil 44 is interposed between the layer structure portions 31 adjacent in the layer direction, and the vertically oriented holes 34 are formed so as to penetrate the metal foil 44. A thermal sheet A4 is configured. The end surface of the bent burring portion 44b in the metal foil 44 is in contact with the layered structure portions 31 adjacent to each other at the top and bottom to form a short circuit portion 33. In the metal foil 44 region, the effect of improving the thermal conductivity in the thickness direction can be obtained more clearly.

  As an example, an aluminum foil 44 having a thickness of 50 μm is disposed and laminated between two sheets of an expanded graphite sheet having a thickness of 0.125 mm to form a sheet-like body 42, which is then subjected to needle processing to form an aluminum foil as an intermediate layer. A number of torn 44 (short-circuited portions) 44 are formed to short-circuit the layered structure portions 31 and 31 (short-circuit the orientation layers of expanded graphite).

Example 5
A heat transfer sheet A5 according to Example 5 is shown in FIG. In the heat transfer sheet A5, the short circuit portion 33 is partially compressed by compressing in the thickness direction in a state in which the granular materials (eg, steel balls 54 are interposed) between the layered structure portions 51 adjacent in the layer direction. The layered structure portion 51 is broken, and at the broken portion, at least one of the layered structure portions 51 adjacent to each other in the layer direction is configured as means for abutting the other layered structure portion 51. That is, in the sheet-like body 52, the end face of the crushing part 51b formed by being broken by the granular material 54 comes into contact with the adjacent layered structure parts 51 in the upper and lower sides, and thereby, in the thickness direction. Thermal conductivity is greatly improved.

  As an example, expanded graphite and metal particles were mixed and then pressed to produce an expanded graphite sheet having a thickness of 0.25 mm. In the heat transfer sheet A5 of Example 5, the heat conductivity in the thickness direction is improved at various locations of the heat transfer sheet by mixing a large amount of metal particles (steel balls). It can be set as the heat-transfer sheet A5 in which conductivity is improved. The sheet-like body 2 may be formed by laminating a plurality of thin film sheet materials. In this case, the “layered structure portion” is read as “thin film sheet material”.

The perspective view which shows the heat-transfer sheet | seat by Example 1. The perspective view which shows the usage example of the heat-transfer sheet | seat of FIG. (A), (b) is each process drawing which shows the manufacturing method of the heat-transfer sheet | seat of FIG. The perspective view which shows the heat-transfer sheet | seat by Example 2. (A), (b) is each process drawing which shows the manufacturing method of the heat-transfer sheet | seat of FIG. Sectional drawing which shows the heat-transfer sheet | seat by Example 3 Sectional drawing which shows the heat-transfer sheet | seat by Example 4. Sectional drawing which shows the heat-transfer sheet | seat by Example 5.

Explanation of symbols

1, 21, 31, 51 Layered structure portion 2, 22, 32 Sheet-like body 3, 23 Distorted portion 22A Either front or back surface of sheet-like body 24 Scraping recess 24a Concave surface 33 Short-circuit portion 34 Hole 44 Metal foil 51b Break Part 54 granular material A1-A5 heat transfer sheet

Claims (8)

  The sheet-like body is formed of a sheet-like body having layered structure portions formed in the same direction, and the distortion portion is configured such that an end surface of the layered structure portion is flush with the surface of the sheet-like body. Heat transfer sheet formed on.   The said distortion part is comprised by bend | folding the edge part of the said sheet-like body so that the end surface of the said sheet-like body may become the same surface as the surface of either the front or back of the said sheet-like body. Heat transfer sheet.   The distortion portion compresses the entire sheet-like body in the thickness direction in a state in which a recess is formed on either the front or back surface of the sheet-like body so that a fault of the thin-film sheet material is exposed. The heat transfer sheet according to claim 1, wherein the heat transfer sheet is configured by adjusting the concave surface of the scraping recess so as to be flush with any one of the surfaces.   A state in which the end surfaces of at least one layered structure part of the layered structure parts adjacent to each other in the layer direction are in contact with the other layered structure part. The heat transfer sheet in which the short circuit part is formed.   The short-circuit portion mechanically forms a hole extending in the thickness direction in the sheet-like body, whereby at least one of the layered structure portions adjacent to each other in the layer direction in the hole portion. The heat transfer sheet according to claim 4, wherein the heat transfer sheet is configured as a means in which an end surface is bent and abuts against the other layered structure portion.   In the broken part, the short circuit part partially breaks the layered structure part by compressing in the thickness direction in a state in which the granular material is interposed between the layered structure parts adjacent in the layer direction. 5. The heat transfer sheet according to claim 4, wherein the end surface of at least one of the layered structure portions adjacent to each other in the layer direction is configured to be in contact with the other layered structure portion.   The heat transfer sheet according to any one of claims 1 to 6, wherein the layered structure portion is formed of any one material of expanded graphite, metal foil, and synthetic resin. 6. The sheet-like body according to claim 5, wherein a metal foil is interposed between the layered structures adjacent to each other in the layer direction, and the hole is formed so as to penetrate the metal foil. Heat transfer sheet.

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