JP6842634B2 - Thermally conductive laminate and heat dissipation structure using it - Google Patents

Description

The present invention relates to a heat conductive laminate and a heat radiating structure using the same, and is suitable as a structure that absorbs local heat generation such as an electronic component.

Conventionally, the amount of heat generated from electronic components has been increasing along with the improvement of processing speed and operating speed of electronic components and the increase in output. An allowable temperature range is set for electronic components, and if the temperature exceeds the heat resistant temperature, the operation becomes unstable and the expected processing cannot be performed.

For this reason, for electronic components that generate a large amount of heat, there is a method of forcibly absorbing heat from the heating element and quickly diffusing it to a part far from the heat generating part. For example, a fan blows hot air. There are methods such as exhausting, contacting a heat sink, a heat pipe, a heat radiating sheet, etc. with a heating element to transfer heat to a portion distant from the heating element and dissipate it.

Further, in order to reduce the contact thermal resistance between the heat generating electronic component and the heat radiating body, there is a structure in which a heat conductive laminate using thermal grease, heat radiating rubber, a graphite sheet or the like is interposed between them. For example, Patent Document 1 It is disclosed in.

Japanese Unexamined Patent Publication No. 2006-303240

In the heat conductive laminate shown in Patent Document 1, a graphite sheet and an adhesive layer are alternately laminated, and heat transfer can be measured mainly by transferring heat to the graphite sheet.

When this heat conductive laminate is provided between the heat generating electronic component and the heat sink, it is necessary to make surface contact with the heat generating electronic component or the heat sink while compressing the heat conductive laminate so as not to create a gap as much as possible. Sometimes.

However, when the heat conductive laminate is compressed, the deflection of the graphite sheet acts in the direction of peeling from the adhesive, so that the graphite sheet and the adhesive layer are separated and the heat conductive laminate is torn. There was a fear. If it is torn, the heat transfer effect of the heat conductive laminate will be reduced.

Therefore, an object of the present invention is to focus on the above-mentioned problems and to provide a heat conductive laminate having a laminated structure in which peeling due to a compression load is unlikely to occur, and a heat radiating structure using the same.

In order to achieve the above object, the heat conductive laminate of the present invention is used.
A heat conductive laminate having a predetermined heat transfer surface and having a plurality of graphite sheets laminated in parallel via an adhesive.
The graphite sheet is provided so as to be inclined with respect to the heat transfer surface.
As the pressure-sensitive adhesive, a synthetic resin material having higher flexibility than the graphite sheet is applied, and the pressure-sensitive adhesive is laminated thicker than the graphite sheet.
It is characterized by providing a reinforcing portion that further surrounds the laminate made of the graphite sheet and the pressure-sensitive adhesive so as to be bundled with the graphite sheet.

Further, the heat dissipation structure using the heat conductive laminate of the present invention is
Heat-generating components mounted on the circuit board and
A heat sink provided on the opposite surface side of the heat generating component mounting surface of the circuit board,
The heat conductive laminate according to claim 1, which comes into contact with the heat generating component and the heat sink through a through hole provided on the mounting surface of the circuit board.

Further, the heat conductive laminate is characterized in that it is held in a compressed and deformed state between the heat generating component and the heat sink.

According to the present invention, there is a heat conductive laminate having a laminated structure in which peeling due to a compression load is unlikely to occur, and a heat radiating structure using the same.

The general view which shows the embodiment of this invention. The cross-sectional view of the display device of the same embodiment. The cross-sectional view of the first unit of the same embodiment. The cross-sectional view of the light source part of the same embodiment. The cross-sectional view of the display of the same embodiment. The figure which shows the heat conduction member of the said embodiment. The figure which shows the manufacturing process of the heat conduction member of FIG. The figure after cutting the heat conductive member of FIG. FIG. 5 is a cross-sectional view of the display before mounting the heat sink in FIG. (A), (b), (c) The figure which shows another example of the heat conduction member of the same embodiment, respectively. (A), (b) The figure which shows another example of the heat conduction member of the same embodiment, respectively.

Hereinafter, an embodiment of a heat conductive laminate according to the present invention and a heat radiating structure using the same, which are mounted on a head-up display device, will be described with reference to the accompanying drawings.

The head-up display device displays a virtual image V by reflecting the display light L projected by the display device 2 provided on the dashboard 1 of the vehicle toward the vehicle driver 4 by the windshield 3. The vehicle driver 4 can visually recognize the virtual image V superimposed on the landscape. The display device 2 includes a first unit A1 and a second unit B1.

The first unit A1 is composed of a projector 10, a plane mirror 21, a transmissive screen 26, a heat sink 31, a housing 41, and the like. The second unit B1 is composed of reflectors 50, 60, a housing 71, and the like.

The projector 10 displays an image on the transmissive screen 26 by a field sequential method. The projector 10 has a light source unit 11, a mirror unit 12, a prism 13, a display 14, and a projection lens member 15, and is fixed to a heat sink 31.

The light source unit 11 of the projector 10 includes a blue light emitting diode 11a, a red light emitting diode 11b, a green light emitting diode 11c, a lens member 11d, 11e, 11f, a reflection mirror 11g, a dichroic mirror 11h, 11i, and a circuit board 11k. The lens members 11d, 11e, 11f, the reflection mirror 11g, and the dichroic mirrors 11h, 11i are held by the holding portion 11v of the frame member 11m.

The blue light emitting diode 11a, the red light emitting diode 11b, and the green light emitting diode 11c are composed of a top-view type LED, and emit blue light B, red light R, and green light G, respectively. The blue light emitting diode 11a, the red light emitting diode 11b, and the green light emitting diode 11c are mounted on the circuit board 11k. The circuit board 11k on which the blue light emitting diode 11a, the red light emitting diode 11b, and the green light emitting diode 11c are mounted is fixed to the heat sink 31 by bolts (not shown). The circuit board 11k is in contact with the heat sink 31, and the heat generated by the blue light emitting diode 11a, the red light emitting diode 11b, and the green light emitting diode 11c is dissipated by the heat sink 31 via the circuit board 11k.

The lens members 11d, 11e, and 11f collect the blue light B, the red light R, and the green light G emitted by the blue light emitting diode 11a, the red light emitting diode 11b, and the green light emitting diode 11c, respectively. The reflection mirror 11g reflects the blue light B emitted by the blue light emitting diode 11a and condensed by the lens member 11d. The dichroic mirror 11h reflects the red light R emitted by the red light emitting diode 11b and condensed by the lens member 11e, and transmits the blue light B reflected by the reflection mirror 11g. The dichroic mirror 11i reflects the green light G emitted by the green light emitting diode 11c and condensed by the lens member 11f, and also transmits the blue light B and the red light R transmitted or reflected by the reflection mirror 11g and the dichroic mirror 11h. Let me.

The display unit 19 houses the mirror unit 12, the prism 13, the display 14, and the projection lens member 15 in the case body 18. The display unit 19 is not in direct contact with the light source unit 11. The prism 13 transmits the light from the mirror unit 12 and irradiates the display 14 with the light. The display light L generated by the display 14 is reflected toward the projection lens member 15 by the inclined surface 13a of the prism 13. The projection lens member 15 magnifies the display light L and projects it onto the plane mirror 21. The projection lens member 15 may be composed of one lens member or a plurality of lens members.

The plane mirror 21 is held by the holding member 23, and reflects the display light L from the projector 10 on the transmissive screen 26. The transmissive screen 26 is held by the holding member 24, and the display light L from the projector 10 is imaged on the transmissive screen 26. The heat sink 31 is made of a metal such as aluminum and has a plurality of heat radiation fins 31a. The plane mirror 21 and the transmissive screen 26 are fixed to the heat sink 31 via the holding members 23 and 24. The housing 41 is made of a combination of an opaque resin (for example, polycarbonate) or a metal, and houses a projector 10, a plane mirror 21, a transmissive screen 26, and the like. The housing 41 is formed with a window portion 41a from which the display light L is emitted.

The reflector 50 has a plane mirror 51 and a support member 52. The plane mirror 51 reflects the display light L from the first unit A1 on the concave mirror 61. The support member 52 is fixed to the housing 71 and holds the plane mirror 35. The reflector 60 includes a concave mirror 61, a mirror holder 62, a stepping motor 63, and a support member 64. The concave mirror 61 is formed by depositing a metal (for example, aluminum) on a resin (for example, polycarbonate) to form a reflective surface 61a. The reflecting surface 61a is concave, and the display light L reflected by the plane mirror 51 is magnified to display the virtual image V. The concave mirror 61 is adhered to the mirror holder 62 with double-sided adhesive tape. The mirror holder 62 is made of resin (for example, ABS), and the gear portion 65 and the shaft portion 66 are integrally formed.

A gear 67 is attached to the rotating shaft of the stepping motor 63, and the gear 67 is meshed with the gear portion 65 of the mirror holder 62. The concave mirror 61 is supported in a rotatable state together with the mirror holder 62, and the concave mirror 61 can be rotated by the stepping motor 63 to adjust the projection direction of the display light L. The vehicle driver 4 operates a push button switch (not shown) to adjust the angle of the concave mirror 61 so that the display light L is reflected at the eye position (that is, the virtual image V can be visually recognized).

The housing 71 is made of an opaque resin (eg polypropylene) and houses the reflectors 50 and 60. The housing 71 is provided with a light-shielding wall 71a to prevent a phenomenon (washout) in which external light such as sunlight is incident on the transmissive screen 26 and the virtual image V becomes difficult to see. The light-shielding wall 71a has a flat plate shape, and is formed so as to hang diagonally from the upper part of the housing 71. An opening 71b from which the display light L is emitted is formed on the upper surface of the housing 71, and a translucent cover 72 is attached to the opening 71b. The translucent cover 72 is made of a transparent resin such as polycarbonate and has a curved shape.

Next, the display 14 will be described in detail with reference to FIG.

The display 14 includes a reflective display element 141, a circuit board 142, a heat sink 143, a heat conductive laminate 144, and a spacer 145.

The reflective display element 141 includes a DMD (Digital Micromirror Device) 141a and a socket 141b, and is mounted on a circuit board 142. The DMD 141a is a plane in which a large number of minute mirror surfaces are arranged, and is held in the socket 141b.

The DMD 141a includes a plurality of movable mirror elements, and by driving the electrodes provided under the mirror elements in a very short time, the mirror surface of each mirror element is tilted with the hinge as a fulcrum. For example, when the mirror element is on, it is tilted by +12 degrees with the hinge as a fulcrum, reflects the display light L emitted from the display unit 19, and delivers it to the screen 26 via a prism 13 or the like. When it is off, it is tilted by -12 degrees with the hinge as the fulcrum, and the display light L is not reflected in the direction of the prism 13. In this way, by individually driving each mirror element based on the display image data representing the display image, the display light L is selectively projected onto the screen 26 to obtain a display image having a desired brightness and a desired color. It is generated on the screen 26 described later. Further, in order to switch the mirror element at high speed by using electric power, it becomes a heat generating electronic component (heat generating component).

A hard wiring board can be applied to the circuit board 142, and a wiring pattern for supplying a drive signal to the DMD 141a via the socket 141b is formed. The circuit board 142 has a through hole 142a that opens so that a part of the mounting surface side of the DMD 141a faces from the heat sink 143 side.

The heat sink 143 is preferably made of a metal material such as aluminum. In this case, the heat sink 143 has a smooth surface facing the heat conductive laminate 144, and a fin shape for measuring heat dissipation into the air is formed on the opposite side of this surface with a large surface area. The heat sink 143 can be provided integrally with the housing 41, and by forming the fin shape on the outside of the housing 41, efficient heat dissipation can be expected.

As shown in FIG. 6, the heat conductive laminate 144 is formed by laminating a plurality of graphite sheets 144a in parallel via an adhesive 144b. Further, the heat conductive laminate 144 has a pair of heat transfer surfaces 144c that come into contact with other members, and is used so that one is in contact with a heat generating component and the other is in contact with a heat radiating component.

The graphite sheet 144a is laminated so that the heat conductive laminate 144 connects between the DMD 141a and the heat transfer surface 144c in contact with the heat sink 143. Further, in the graphite sheet 144a, the ab plane direction AB of the graphite crystal is formed along the plane of the graphite sheet 144a, and the heat conduction in this plane direction is particularly good. As the graphite sheet 144a, an artificial graphite sheet having a thickness of 0.1 mm or less and stable graphite particles is suitable.

The pressure-sensitive adhesive 144b is preferably a curable synthetic resin material having a relatively high thermal conductivity. In this case, a mixture of silicone rubber and a filler material that enhances thermal conductivity is applied to the surface of the graphite sheet 144a to form a layer. ing. The pressure-sensitive adhesive 144b is selected from a material having higher flexibility than the graphite sheet 144a even after being cured, and is laminated so as to be thicker than the graphite sheet 144a. The flexibility of the heat conductive laminate 144 can be controlled by setting the thickness of the pressure-sensitive adhesive 144b.

The thickness ratio of the graphite sheet 144a and the pressure-sensitive adhesive 144b is set so that the thermal resistance R1 between the heat transfer surfaces 144c and 144c becomes a predetermined value, but the heat transfer direction of the heat transfer laminate 144. When the cross-sectional area perpendicular to X is S, the thickness is T, and the equivalent thermal conductivity λ in the heat transfer direction is λ, it is represented by “R1 = T / λS”.

The equivalent thermal conductivity λ is determined by the thickness of the graphite sheet 144a, the thermal conductivity of the crystal in the ab plane direction AB, the thermal conductivity of the c-axis, the thickness of the adhesive 144b, etc. It can also be empirically requested.

In the heat conductive laminate 144, the liquid pressure-sensitive adhesive 144b was flattened using a squeegee, the graphite sheet 144a was laminated, and the process of further stacking and stretching the pressure-sensitive adhesive 144b was repeated a predetermined number of times to cure the pressure-sensitive adhesive 144b. , As shown in FIG. 7, a laminated base material 144d in which graphite sheets 144a are provided in parallel is produced. In FIGS. 6 to 8, H indicates the height, and L and W indicate the width and depth of the heat transfer surface 144c.

Next, as shown by the alternate long and short dash line in FIG. 7, the laminated base material 144d is cut by a wire saw on a surface slightly inclined from the vertical of the laminated surface, and the laminated body 144e having a cross section shown in FIG. 8 is formed. can get. By further cutting the laminated body 144e along the height H direction (dashed line), the sheet surface of the graphite sheet 144a, that is, the graphite crystal, is formed in the height (thickness) H direction which is the heat transfer direction X. A heat transfer laminate 144 in which the ab planes are laminated in an inclined state is obtained.

The spacer 145 sets the distance between the circuit board 142 and the heat sink 143, and a member having a small amount of thermal deformation and high thermal conductivity is suitable, and for example, synthetic resin or metal can be applied. As shown in FIG. 9, the spacer 145 has a dimension D including the tolerances of the socket 141b, the circuit board 142, and the spacer 145 from the mounting surface of the DMD 141a, which is slightly smaller than the height dimension H of the heat conductive laminate 144. The distance is set as such.

That is, by assembling the heat sink 143, the heat sink 143 and the DMD 141a can compress and sandwich the heat conductive laminate 144 by the difference between the dimension D and the height dimension H. Further, since the heat transfer surface 144c that is vertically compressed and the graphite sheet 144a surface are not vertical, the heat conduction laminate 144 is easily deformed by the compression. Further, at this time, since the graphite sheet 144a is arranged so as to be inclined in the same direction with respect to the compression direction, the bending direction is also constant. For this reason. Since the distance between the graphite sheets 144a is less likely to change, peeling from the adhesive 144b is less likely to occur.

Such a heat conductive laminate 144 has a predetermined heat transfer surface 144c, a plurality of graphite sheets 144a are laminated in parallel via an adhesive 144b, and the graphite sheet 144a is inclined with respect to the heat transfer surface 144c. Is provided. Therefore, the heat conductive laminated body has a laminated structure in which peeling due to a compression load is unlikely to occur.

Further, the pressure-sensitive adhesive 144b can be deformed by a compression load by applying a synthetic resin material having higher flexibility than the graphite sheet 144a and laminating it thicker than the graphite sheet 144a. Therefore, even if the dimensional tolerance of related parts changes due to aging or deformation due to heat, the elastic deformation of the heat conductive laminate 144 absorbs the tolerance and dimensional change, and the heat sink 143 and heat generating parts (reflective type) A good contact state with the display element 141) can be maintained.

Further, the heat generating component (reflective display element 141) mounted on the circuit board 142, the heat sink 143 provided on the opposite surface side of the heat generating component mounting surface of the circuit board 142, and the mounting surface of the circuit board 142 are provided. The heat generating component and the heat sink 143 come into contact with each other through the through hole 142a. Further, the heat conductive laminate 144 is held in a state of being compressed and deformed between the heat generating component and the heat sink 143. As a result, the heat conductive laminate 144 can be deformed while maintaining a contact state for heat transfer. Further, the heat dissipation structure uses a heat conductive laminated body having a laminated structure in which peeling due to a compression load is unlikely to occur.

Although the present invention has been described by way of examples in the configuration of the above-described embodiment, the present invention is not limited to this, and other configurations may vary as long as the gist of the present invention is not deviated. Of course, it is possible to improve and change the display. For example, in the above-described embodiment, the graphite sheets 144a are laminated in a flat plate shape, but as described above, they have a partially inclined shape with respect to the compression direction (heat transfer direction X). For example, as shown in FIGS. 10A, 10B, and 10C, a graphite sheet 1441a having a curved or bent shape in advance is laminated with an adhesive layer 1441b interposed therebetween. It may be formed by. When these heat conductive laminates 1441 to 1443 are subjected to a compressive load, the same operation as that of the above-described embodiment can be obtained.

Further, as shown in FIG. 11, the heat conductive laminate is provided with reinforcing portions 144f, 144 g covered with a graphite sheet or a synthetic resin material having high thermal conductivity on the surface thereof to form the heat conductive laminates 1444, 1445. It can also be applied, and the graphite sheet 144a and the pressure-sensitive adhesive 144b, which are surrounded by the reinforcing portions 144f and 144g and are contained as if they are bundled, have a structure that is more difficult to peel off.

Further, although the embodiment in which the DMD 141a is applied as the heat generating component has been described, the above-mentioned heat conduction is performed in order to apply the light source unit 11 and other electronic components as the heat generating component and transfer the heat of the heat generating component to a distant position. The laminated body 144 can be used, and the same effect as that of the above-described embodiment can be obtained.

The present invention relates to a heat conductive laminate and a heat dissipation structure using the heat conductive laminate, and is mounted on, for example, an automobile, a motorcycle, or a moving body equipped with an agricultural machine or a construction machine, and exhibits vehicle information, turn-by-turn display, etc. It is suitable as an in-vehicle head-up display that projects and displays road information and the like.

11 Light source unit 21 Plane mirror 141 Reflective display element 141a DMD (heat generating component)
142 Circuit board 143 Heat sink 144 Heat transfer laminate 144a Graphite sheet 144b Adhesive 144c Heat transfer surface L Display light X Heat transfer direction (compression direction)

Claims (3)

A heat conductive laminate having a predetermined heat transfer surface and having a plurality of graphite sheets laminated in parallel via an adhesive.
The graphite sheet is provided so as to be inclined with respect to the heat transfer surface.
As the pressure-sensitive adhesive, a synthetic resin material having higher flexibility than the graphite sheet is applied, and the pressure-sensitive adhesive is laminated thicker than the graphite sheet.
A heat conductive laminate comprising a reinforcing portion that further surrounds the laminate made of the graphite sheet and the pressure-sensitive adhesive so as to be bundled with the graphite sheet. Heat-generating components mounted on the circuit board and
A heat sink provided on the opposite surface side of the heat generating component mounting surface of the circuit board,
The heat conductive laminate according to claim 1, wherein the heat conductive component and the heat sink come into contact with each other through a through hole provided on the mounting surface of the circuit board. The heat dissipation structure used. The heat-dissipating structure using the heat-conducting laminate according to claim 2, wherein the heat-conducting laminate is held in a compression-deformed state between the heat-generating component and the heat sink.

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