JP2012227242A - Heat radiation structure and electronic apparatus included in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit unnecessary electromagnetic waves from being radiated from a heat sink due to an electromagnetic wave caused in an electromagnetic field generation source other than an element with which the heat sink is thermally connected.SOLUTION: A heat radiation structure 150 includes a heat sink 30 and a magnetic sheet 40. The heat sink 30 thermally connects with a large scale integration (LSI) 51 and has multiple columns 32. The magnetic sheet 40 is formed by dispersing a magnetic material in a resin layer and are fixed to the multiple columns 32. Providing the magnetic sheet 40 causes the loss in an electromagnetic field occurring in an electromagnetic field generation source in the surrounding area, thereby effectively inhibiting unnecessary electromagnetic waves from being radiated from the multiple columns 32 of the heat sink 30.

Description

  The present invention relates to a heat dissipation structure and an electronic device included therein.

  Since circuit elements exemplified by LSI (Large Scale Integration) generate heat during operation, there are cases in which measures against exhaust heat are taken such that a heat sink is thermally connected to the circuit elements. The heat sink generally has a structure in which columnar portions are arranged in a matrix, thereby increasing the contact area with air and improving the heat exhaust efficiency. The thermal connection between the circuit element and the heat sink is preferably ensured through a lubricant such as silicon grease.

  The heat sink is usually made of a metal having good thermal conductivity (for example, a body (Cu), aluminum (Al), etc.). Therefore, if an electromagnetic field leaks from a circuit element that exists directly under the heat sink, the heat sink and the circuit element may be electromagnetically coupled. When electromagnetic coupling from the circuit element to the heat sink occurs, the columnar portion of the heat sink functions as an antenna, and unnecessary electromagnetic waves may be radiated. Such unnecessary emission of electromagnetic waves causes EMI (Electro Magnetic Interference).

  In Patent Document 1, an electromagnetic noise absorbing sheet is disposed between an electronic component and a heat sink. It is disclosed that an opening is provided in an electromagnetic noise absorbing sheet, and the deterioration of thermal connection is suppressed by filling the opening with a material having high thermal conductivity.

  Patent Document 2 discloses that the cooling unit is covered with a shield, and discloses that a large number of holes are provided in the shield. As disclosed in paragraph 0029 of the same document, it is disclosed that the shield is made of a steel plate having a good magnetic permeability, such as a soft magnetic steel plate, more preferably a highly magnetic permalloy. It is also disclosed that Ni plating is applied.

JP 2004-22738 A JP-A-8-125363

  Usually, circuit elements such as LSI are mounted on boards such as a mother board. A large number of circuit elements are generally mounted on a mother board or the like, and wiring is often laid on the mother board or the like at a high density. Therefore, when a heat sink is mounted on an LSI mounted on a mother board, a plurality of electromagnetic field generation sources exist around the heat sink. In this case, unnecessary electromagnetic waves may be radiated from the heat sink due to circuit elements to which the heat sink is thermally connected, and unnecessary from the heat sink due to electromagnetic field generation sources existing around the heat sink. There is a risk of radiation of electromagnetic waves.

  As is clear from the above description, the present inventors have proposed a novel method of suppressing unnecessary electromagnetic waves from being radiated from the heat sink due to electromagnetic field generation sources other than the elements to which the heat sink is thermally connected. I found a problem.

  The heat dissipating structure according to the present invention is configured to be thermally connected to an exhaust heat target, and to be configured with a plurality of columnar portions provided with a heat dissipating member and a magnetic material scattered with respect to the base layer. A sheet-like member fixed to the plurality of columnar portions.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that unnecessary electromagnetic waves are radiated | emitted from a heat sink resulting from electromagnetic field generation sources other than the element to which a heat sink is thermally connected.

1 is a schematic diagram showing a schematic configuration of a computer according to a first embodiment and a mother board incorporated therein; FIG. 1 is a schematic perspective view of a heat dissipation structure according to a first embodiment. 1 is a schematic perspective view of a heat dissipation structure according to a first embodiment. 1 is a schematic diagram illustrating a configuration of a magnetic sheet according to a first embodiment. FIG. 5 is a schematic diagram illustrating a configuration of a magnetic sheet according to a second embodiment. FIG. 6 is a schematic perspective view of a heat dissipation structure according to a second embodiment. FIG. 6 is a schematic perspective view of a heat dissipation structure according to a second embodiment. FIG. 6 is a schematic perspective view of a heat dissipation structure according to a second embodiment. FIG. 6 is a schematic perspective view of a heat dissipation structure according to a second embodiment. FIG. 6 is a schematic perspective view of a heat dissipation structure according to a second embodiment. It is a schematic diagram which shows the variation of a structure of a magnetic sheet. It is a figure which shows a test result.

  The embodiments described below are not individually independent but can be combined with each other, and a synergistic effect based on the combination can also be claimed. In principle, duplicate descriptions between the embodiments are eliminated. The same reference numerals are given to the same elements in the embodiments, and redundant description is omitted. The drawings are created for the purpose of explaining the invention, and it is not allowed to limit the technical scope of the present invention based on this disclosure.

Embodiment 1
An embodiment of the present invention will be described with reference to FIGS. As will be apparent from the description below, the heat dissipation structure 150 according to the present embodiment includes the heat sink 30 and the magnetic sheet 40 (see FIGS. 2 and 3). The heat sink 30 is thermally connected to an LSI (exhaust heat target) 51 (see FIG. 1). The magnetic sheet 40 is configured by interposing a magnetic body 42 with respect to a resin layer (base layer) 41 (see FIG. 4). The magnetic sheet 40 is fixed to the plurality of columnar portions 32 of the heat sink 30 (see FIGS. 2 and 3). By providing the magnetic sheet 40, a magnetic loss occurs in the electromagnetic field generated in the surrounding electromagnetic field generation source. That is, the electromagnetic field is absorbed by the magnetic sheet 40. Thereby, it can suppress effectively that unnecessary electromagnetic waves are radiated | emitted from the columnar part 32 of the heat sink 30. FIG. In this way, generation of EMI (Electro Magnetic Interference) can be effectively suppressed.

  FIG. 1 is a schematic diagram showing a schematic configuration of a computer and a mother board incorporated therein. 2 and 3 are schematic perspective views of the heat dissipation structure 150. FIG. 4 is a schematic diagram showing the configuration of the magnetic sheet.

  As shown in FIG. 1, the computer 100 is a general computer including a housing 10 and a display device 20 connected to a connector provided in the housing 10. A motherboard 50 is stored in the housing 10. An LSI 51 is mounted on the motherboard 50. A heat sink 30 is mounted on the LSI 51 via a lubricant such as silicon grease. A magnetic sheet 40 is attached to the heat sink 30. Note that the heat sink 30 may be mounted on the LSI 51 via the electromagnetic noise absorbing sheet disclosed in Patent Document 1.

  For example, the magnetic sheet 40 is attached to the heat sink 30 as shown in FIG. 2 or FIG. As described above, the magnetic sheet 40 has a property of giving a magnetic loss to the electromagnetic field generated in the surrounding electromagnetic field generation source, and the electromagnetic field is absorbed by the magnetic sheet 40. Thereby, it is possible to effectively suppress unnecessary electromagnetic waves from being radiated from the heat sink 30 due to the electromagnetic field generation sources existing around the LSI 51.

  The magnetic sheet 40 according to the present embodiment is formed through a semiconductor process or a process similar thereto. Each magnetic sheet 40 is manufactured by dividing a mother sheet manufactured through the process into innumerable pieces by a cutting machine. By adopting a sheet-like member as means for causing magnetic loss, the magnetic sheet 40 can be attached to the heat sink 30 in an arbitrary manner as illustrated in FIGS. 2 and 3. . Thereby, the position of the magnetic sheet 40 can be easily and flexibly adjusted in consideration of the presence of surrounding electromagnetic field generation sources and the like. In other words, the heat dissipating structure 150 is simply manufactured simply by sticking the magnetic sheet 40 to the heat sink 30.

  As is clear from FIGS. 2 and 3, the heat sink 30 includes a flat plate portion 31 and a plurality of columnar portions 32. The heat sink 30 is made of a metal such as a trunk (Cu) or aluminum (Al) and has conductivity. Since the heat sink 30 is made of a metal material, it has high thermal conductivity. The plurality of columnar portions 32 are arranged in a matrix on the upper surface of the flat plate portion 31. The arrangement state, the number, and the like of the columnar portions 32 can be changed as appropriate.

  In the case illustrated in FIG. 2, the magnetic sheet 40 is placed on the outer surface of the columnar portion 32 disposed on the outermost side. Here, two magnetic sheets 40 are prepared, and these are arranged so as to face each other. The method for fixing the magnetic sheet 40 to the heat sink 30 is arbitrary. For example, the magnetic sheet 40 may be bonded and fixed to the heat sink 30 via an adhesive or the like. A structure for receiving and holding the magnetic sheet 40 with respect to the heat sink 30 may be provided.

  As shown in FIG. 2, by arranging the two magnetic sheets 40 to face each other, a gas flow path (for example, air) as schematically shown by an arrow in FIG. 2 can be secured. Thereby, by fixing the magnetic sheet 40 with respect to the heat sink 30, it can suppress that the heat dissipation of the heat sink 30 falls.

  In the case shown in FIG. 3, the magnetic sheet 40 is placed on the columnar portion group. In other words, the magnetic sheet 40 is in surface contact with the top surfaces of the individual columnar portions 32 constituting the columnar portion group. Even in this case, a sufficient gas flow path can be secured as in the case of FIG. That is, in this case as well, by fixing the magnetic sheet 40 to the heat sink 30, it is possible to prevent the heat dissipation of the heat sink 30 from being deteriorated.

  FIG. 4 shows a schematic sectional view of the magnetic sheet 40. As shown in FIG. 4, the magnetic sheet 40 is configured, for example, by dispersing magnetic bodies 42 with respect to the resin layer 41. The kind of the magnetic material scattered in the resin layer 41 is, for example, ferrite, nickel iron alloy, magnetic metal, or the like. The constituent material of the resin layer 41 is, for example, a polymer resin, an epoxy resin, or the like. The volume content of the magnetic body 42 with respect to the resin layer 41 is preferably 20 to 80%, but this value should be adjusted through field verification or the like. The thickness of the magnetic sheet 40 is about 1 mm and has sufficient flexibility. By providing the magnetic sheet 40 with flexibility, the ease of handling thereof is improved. The thickness of the magnetic sheet 40 can be adjusted as appropriate, and may be about 0.5 mm, for example. The magnetic bodies 42 scattered in the resin layer 41 have an average particle diameter of about 50 μm, for example. The volume content of the magnetic body 42 with respect to the resin layer 41 is, for example, 50%.

  As is clear from the above description, in the present embodiment, the magnetic sheet 40 having the property of imparting magnetic loss to the electromagnetic field is fixed to the columnar portion 32 of the heat sink 30. As a result, the electromagnetic field generated in the surrounding electromagnetic field generation source is absorbed by the magnetic sheet 40 and is prevented from reaching the columnar portion 32 of the heat sink 30. Thereby, it is possible to effectively suppress unnecessary electromagnetic waves from being radiated from the heat sink 30 due to the electromagnetic field generated in the external electromagnetic field generation source. Note that Patent Document 2 only discloses a structure unrelated to the idea of giving a loss to an electromagnetic field. This point is clear from the shielding material disclosed in this document.

Embodiment 2
The second embodiment will be described with reference to FIGS. In this embodiment, unlike Embodiment 1, the ventilation holes 43 are provided in a matrix on the magnetic sheet 40 (see FIG. 5). As a result, the effects described in the first embodiment can be obtained, and when the magnetic sheet 40 is provided on the columnar portion 32 of the heat sink 30, it is possible to effectively suppress the loss of ventilation. . The size of the ventilation hole is desirably 1/10 or less of the wavelength of the target electromagnetic wave so that the electromagnetic wave does not leak through the ventilation hole.

  FIG. 5 is a schematic diagram showing the configuration of the magnetic sheet. 6 to 10 are schematic perspective views of the heat dissipation structure 150. FIG. 11 is a schematic diagram showing a variation of the configuration of the magnetic sheet.

  As shown in FIG. 5, the magnetic sheet 40 is provided with ventilation holes 43 arranged in a matrix. The magnetic sheet 40 shown in FIG. 5 is fixed to the columnar portion 32 of the heat sink 30, for example, as shown in FIGS. 6 to 10. Even in such a case, the same effect as in the first embodiment can be obtained. Further, by providing a large number of ventilation holes 43 in the magnetic sheet 40, the ventilation property is ensured as described above, and the heat exhaust efficiency of the heat sink 30 is effectively suppressed from being deteriorated due to the arrangement of the magnetic sheet 40. can do.

  As shown in FIG. 6, similarly to the case of FIG. 2, the magnetic sheet 40 may be placed on the outer surface of the columnar part 32 located on the outermost side. As shown in FIG. 7, the magnetic sheet 40 may be placed on the inner surface of the columnar part 32 located on the outermost side. In the case shown in FIGS. 6 and 7, the air permeability in the z-axis direction can be ensured as compared with the case shown in FIG. 2.

  As shown in FIG. 8, the four magnetic sheets 40 may be arranged in such a manner as to surround the columnar portion group of the heat sink 30 from the lateral direction. By arranging the magnetic sheet 40 in this way, the amount of electromagnetic field leaking from an external electromagnetic field generation source can be increased, and the heat sink 30 can be more effectively suppressed from functioning as an antenna. it can. Even in this case, since the plurality of ventilation holes 43 are provided in the magnetic sheet 40 as described above, the heat dissipation efficiency of the heat sink 30 can be within an allowable range.

  As shown in FIG. 9, the object surrounded by the magnetic sheet 40 may be limited to a columnar portion group existing inside the annularly arranged columnar portion group located on the outermost side. Even in this case, the same effect as in the case of FIG. 8 can be obtained.

  As shown in FIG. 10, as compared with the case of FIG. 8, a magnetic sheet 40 may be further placed above the columnar portion group. As a result, compared to the case of FIG. 8, it becomes possible to more sufficiently absorb the electromagnetic field generated by the external electromagnetic field generation source, and the columnar portion 32 of the heat sink 30 functions as an antenna, and unnecessary electromagnetic waves are generated. It is possible to more effectively / fully suppress the release. Since each magnetic sheet 40 is provided with the ventilation holes 43, the exhaust heat efficiency of the heat sink 30 can be kept within an allowable range.

  The specific shape of the ventilation hole 43 is arbitrary, and is not limited to the circular shape shown in FIG. 5, but may be a rectangular shape as shown in FIG. 11. In other words, as shown in FIG. 11, the magnetic sheet 40 may be configured in a lattice shape. In this case, the size of the opening formed in the lattice-shaped magnetic sheet 40 is desirably 1/10 or less of the wavelength of the target electromagnetic wave so that the electromagnetic wave does not leak from the heat sink 30.

Example An example will be described with reference to FIG. The heat dissipation structure according to the example has the configuration shown in FIG. As the magnetic sheet 40, a 1 mm thick magnetic sheet in which ferrite powder is dispersed in an epoxy resin is used. Four rectangular sheets were cut out from a magnetic sheet of about 5 cm square, and ventilation holes having a diameter of 2 mm were formed in a matrix at intervals of 2 mm using a drill for each sheet. Thereafter, the four rectangular sheets were fixed to the heat sink 30 with an adhesive as shown in FIG.

  12A shows the magnetic field strength distribution above the heat sink 30 when the magnetic sheet 40 is not present, and FIG. 12B shows the magnetic field strength distribution above the heat sink 30 when the magnetic sheet 40 is present. Show. The magnetic field was measured by operating a loop type magnetic field probe on the heat sink 30 two-dimensionally. The measurement frequency is 2.4 GHz, and the diameter of the ventilation hole provided in the magnetic sheet 40 is smaller than 1/10 of the wavelength converted from this frequency. As is clear from a comparison between FIG. 12A and FIG. 12B, when the magnetic sheet 40 is present, the magnetic field strength is weak in the entire measurement area, and the strength is reduced by 10 dB or more depending on the location. . As a result, it was confirmed that the strength of the electromagnetic field leaking from the heat sink 30 was reduced by arranging the magnetic sheet 40, and the effectiveness of the above-described embodiment was confirmed.

  In FIGS. 12A and 12B, a range of 118 dBm or more is indicated by a dotted line, and a range of 108 dBm or less is indicated by a one-dot chain line. In FIG. 12A, a range of 118 dBm or more exists relatively large in the center of the area. On the other hand, in FIG. 12B, it is only small on the left side of the area. In FIG. 12B, the right side of the alternate long and short dash line is in a range of approximately 108 dBM or less, and it can be understood that the magnetic field strength is reduced in a wide range.

  Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, the specific shape of the heat sink is arbitrary. The specific shape of the magnetic sheet is arbitrary. The specific shape, number, etc., of the columnar portions of the heat sink are arbitrary. The heat dissipating structure is not limited to electronic components / electronic devices, and is mounted on various other heat-generating objects (exhaust heat target). A material other than resin may be employed as the base layer.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Appendix 1)
It is thermally connected to the exhaust heat target object, and a plurality of columnar portions are provided, and a heat radiator and a magnetic body are scattered with respect to the base layer. A heat dissipating structure comprising the sheet-like member.

(Appendix 2)
The heat dissipation structure according to supplementary note 1, wherein the sheet-like member is fixed to the plurality of columnar portions in a manner facing the side surfaces of the plurality of columnar portions.

(Appendix 3)
The heat dissipation structure according to appendix 1 or 2, wherein the sheet-like member is provided with a plurality of ventilation holes.

(Appendix 4)
The plurality of columnar portions provided on the heat radiator are arranged in a matrix, and the sheet-like member is opposed to each side surface of the plurality of columnar portions. The heat dissipation structure as described in any one of thru | or 3.

(Appendix 5)
The heat dissipation structure according to any one of supplementary notes 1 to 4, wherein the sheet-like member is provided as a first sheet-like member, wherein the magnetic material is dispersed in the base layer, and at least a plurality A second sheet-like member fixed to the columnar part.

(Appendix 6)
The heat dissipation structure according to appendix 5, wherein the first sheet-like member and the second sheet-like member are disposed to face each other.

(Appendix 7)
Item 7. The supplementary note 5 or 6, further comprising: third and fourth sheet-like members fixed to at least a plurality of the columnar portions while being configured to be scattered with respect to the base layer. Heat dissipation structure.

(Appendix 8)
The heat dissipation structure according to appendix 7, wherein the first to fourth sheet-like members are arranged so as to surround at least a part of the plurality of columnar parts arranged in a matrix.

(Appendix 9)
An electronic apparatus comprising: the heat dissipation structure according to any one of appendices 1 to 8; and an electronic component thermally connected to the heat dissipation body.

100 computers

DESCRIPTION OF SYMBOLS 10 Case 20 Display apparatus 30 Heat sink 31 Flat plate part 32 Columnar part 40 Magnetic sheet 41 Resin layer 42 Magnetic body 43 Ventilation hole 50 Mother board

Claims (9)

While being thermally connected to the exhaust heat object, a plurality of columnar portions are provided, and a heat radiator,
A magnetic material is interspersed with respect to the base layer, and a sheet-like member fixed to at least the plurality of columnar parts;
A heat dissipation structure comprising:   2. The heat dissipation structure according to claim 1, wherein the sheet-like member is fixed to the plurality of columnar portions in a manner facing the side surfaces of the plurality of columnar portions.   The heat dissipation structure according to claim 1 or 2, wherein the sheet-like member is provided with a plurality of ventilation holes. The plurality of columnar portions provided on the heat radiator are arranged in a matrix,
The heat dissipation structure according to any one of claims 1 to 3, wherein the sheet-like member is opposed to each side surface of the plurality of columnar portions. The heat dissipation structure according to any one of claims 1 to 4, comprising the sheet-like member as a first sheet-like member,
A magnetic material is interspersed with the base layer, and a second sheet-like member fixed to at least the plurality of columnar portions is further provided.   The heat dissipation structure according to claim 5, wherein the first sheet-like member and the second sheet-like member are disposed so as to face each other.   The structure according to claim 5 or 6, further comprising: third and fourth sheet-like members fixed to at least a plurality of the columnar portions while being configured to be scattered with respect to the base layer. The heat dissipation structure described.   The heat dissipation structure according to claim 7, wherein the first to fourth sheet-like members are arranged so as to surround at least a part of the plurality of columnar parts arranged in a matrix. A heat dissipation structure according to any one of claims 1 to 8,
An electronic component thermally connected to the radiator;
Electronic equipment comprising.