JP2008277408A - Heat dissipation sheet - Google Patents

Abstract

An object of the present invention is to provide a heat-dissipating sheet that can obtain a high cooling effect by simply sticking heat generated from an electronic component or a circuit board on which the electronic component is mounted directly to the component or circuit board.
A flexible substrate is provided with a heat-dissipating layer made of a heat-dissipating material on one surface and a bonding layer made of an adhesive material on the other surface, and the surface of the bonding layer is connected to the flexible substrate. By configuring the heat dissipating sheet provided with the heat transfer section communicating with the heat generating member, the heat generating member can be efficiently cooled.
[Selection] Figure 1

Description

  The present invention relates to a heat-dissipating sheet that absorbs and dissipates heat generated from circuit boards and mounted electronic components of electric / electronic products.

  In recent years, with the digitization of home portable photographing devices (digital video cameras and the like), many LSIs that perform high-speed processing are used, and the amount of heat generated by these internal elements is increasing. With the miniaturization of equipment, heat release processing by such a heating element in the housing has become a big problem. For heat dissipation of heat-generating parts, heat sinks such as heat sinks that are fixed to heat-generating parts and heat-dissipating sheets that are used without being fixedly connected are known. And heat dissipation sheets are frequently used.

  The conventional heat dissipation sheet is made of a metal or insulating flexible substrate with an adhesive surface on one side and an infrared radiation film made of ceramics on the opposite surface, and the adhesive surface is in close contact with the heat dissipation member. It can be installed without restriction and is devised to dissipate heat (see, for example, Patent Document 1). Therefore, an organic adhesive or an organic adhesive tape is used for the adhesive surface.

In addition, in heat transfer sheets that connect the heat-dissipating member and the heat sink in contact, a metal protrusion such as solder is formed on the heat transfer sheet or metal plate that is contact-connected via a thermally conductive silicon gel, etc., and the periphery is bonded. A heat transfer sheet made of an agent has also been developed (see, for example, Patent Document 2).
JP 2004-200199 A JP 2005-93842 A

  However, in the conventional configuration related to the heat dissipation sheet, since the surface in contact with the heat dissipation member is formed of an organic resin material, there is a problem that the thermal conductivity is not sufficient and the cooling effect is poor.

  The present invention solves the above-described conventional problems. Heat generated from an electronic component or a circuit board on which the electronic component is mounted is directly affixed to the component or the circuit board, thereby efficiently absorbing and radiating the heat. An object of the present invention is to provide a heat dissipating sheet that can obtain a high cooling effect.

  In order to solve the conventional problem, the heat dissipation sheet of the present invention is provided with a heat dissipation layer made of a heat dissipation material on one surface of a flexible substrate and a bonding layer made of an adhesive material on the other surface, A heat transfer portion that communicates so as to connect the surface of the bonding layer and the flexible substrate is provided.

  In the heat dissipation sheet of the present invention, a bonding layer made of an adhesive material is provided on one side of a heat dissipation substrate having flexibility, and the surface of the bonding layer is connected to the heat dissipation substrate having flexibility. It is characterized by providing a heat transfer section communicating with the.

  According to the heat-dissipating sheet of the present invention, the metal heat-transfer material on the bonded joint surface can be obtained by simply affixing the heat-dissipating sheet to any circuit board or mounting component without electrically shorting the terminals of the electronic component to be dissipated. Can efficiently absorb and dissipate heat generated from an electronic component or a circuit board on which the electronic component is mounted in contact with the heat radiating member, thereby exhibiting a high cooling effect.

  Below, embodiment of the thermal radiation sheet of this invention is described in detail with drawing.

(Embodiment 1)
FIG. 1 is a diagram showing an example of a heat dissipation sheet in the first embodiment of the present invention. In FIG. 1, a flexible substrate 1 is provided with a heat radiating surface m made of a heat radiating material 2 on one side and a joint surface n made of a heat transfer portion 3 and an adhesive material 4 on the opposite surface opposite to the heat radiating surface m. ing. In the configuration example of FIG. 1A, the heat transfer section 3 has a configuration that communicates with the flexible substrate 1 from the surface of the joint surface n. The heat transfer section 3 on the joint surface n in contact with the heat radiating member is composed of a plurality of independent regions, and the regions are the gaps between the conductor terminals of the mounted parts exposed on the joint surface of the heat radiated member and the conductors of the circuit board. It has a structure smaller than the gap between them. For example, as shown in FIG. 1B, when the heat transfer section 3 is a quadrangle, if the horizontal dimension of the heat transfer section is x and the vertical dimension is y, the gap c between the conductor terminals of the mounted component shown in FIG. 3 has a relationship of (x <c, y <c) or (x <d, y <d) with the gap d between the conductors of the circuit board shown in FIG. In addition, when the heat transfer section 3 is circular as shown in FIG. 1C, if the diameter of the heat transfer section is z, the gap c between the conductor terminals 21 of the mounting component 20 shown in FIG. There is a relationship of (z <c) or (z <d) with the gap d between the conductors 32 of the circuit board 30 shown. In the above example, the case where the shape of the heat transfer portion on the joint surface n is a quadrangle and a circle has been described. Is not to be done. Moreover, although the structure which arrange | positioned the several heat-transfer part equally was shown, random arrangement | positioning may be sufficient and it does not specifically limit.

  The heat dissipating sheet configured as described above is bonded to a heat radiating member such as an electronic component or a circuit board on which the electronic component is mounted, so that a plurality of adjacent heat transfer portions 3 on the joint surface n are electrically connected to each other. Without conducting, it is in direct contact with a heat-dissipating member such as the conductor terminal 21 of the mounted component or the conductor 32 of the circuit board and is fixed by the adhesive material 4. As a result, the heat of the heat radiating member is efficiently transferred to the flexible substrate 1 through the heat transfer section 3 having high thermal conductivity without causing an electrical short circuit between the component terminals or between the circuit board conductors, and is flexible. The heat radiation material 2 provided on the conductive substrate 1 is diffused as radiated light such as air convection and infrared rays.

  The material of the heat transfer section may be a material having a high thermal conductivity, for example, a metal material such as gold, silver, copper, aluminum, tungsten, gallium, nickel, solder, or an alloy thereof, or the metal material. Disperse and mix in organic materials such as epoxy resin, acrylic resin, polyimide resin, olefin resin, silicon resin, acrylic rubber, butadiene rubber and silicon gel after processing into suitable shapes such as particles, fibers, flakes, etc. Composite materials. Further, for example, a carbon material such as graphite, carbon fiber, silicon carbide, silicon nitride, or a composite material thereof other than the metal material may be used.

  The material of the heat dissipation material may be an electrically insulating material with high heat dissipation and heat radiation. For example, ceramic materials or ceramic materials with high infrared radiation receiving ability such as alumina, silicon dioxide, glass, etc. may be made of silicon resin or epoxy. A composite material mixed with an organic resin such as a resin is desirable.

  The constituent material of the flexible substrate may be any material that has strength, insulation and flexibility enough to mount a heat-dissipating material. For example, polyimide resin, polyethylene resin, polyethylene terephthalate resin, cellulose resin, polytetrafluoroethylene resin Examples thereof include plastic films made of polypropylene resin, organic materials such as silicon rubber, acrylic rubber and butadiene rubber, and inorganic materials such as glass cloth.

  The adhesive material only needs to have sufficient adhesive strength to make the heat transfer part contact the heat radiating member. Polyester resin, epoxy resin, silicon resin, thermoplastic polyimide resin, polycarbodiimide resin, vinyl acetate resin, acrylic resin Etc.

  Next, the heat dissipation effect of the invention in the first embodiment will be described in detail below. A heat radiating sheet having a structure shown in FIG. 1A having a heat radiating material on one side of a flexible substrate and an adhesive material and a heat transfer part on the other side was prepared, and performance was evaluated.

  For the flexible substrate, polyimide film (Toray DuPont) thickness of 300μm, 50mm × 50mm, silicon resin (made by Shin-Etsu Silicone) dispersed with solder balls of about φ200μm on one side, 40mm × 40mm, thickness Apply a thickness of about 0.3mm, and press and apply a Teflon (registered trademark) jig on top of it to stand and cure at room temperature to form a joint surface with the exposed heat transfer section and adhesive material. did. Next, powdered alumina, powdered silicon dioxide (manufactured by Wako Pure Chemical Industries) 50:50 is mixed with an appropriate amount of varnish on the opposite surface facing the bonding surface, and the dispersed paste is 40 × 40 mm so as to face the bonding surface, A heat-dissipating surface made of a heat-dissipating material having infrared radiation-receiving ability was formed by applying a thickness of about 0.4 mm, leaving it at room temperature, drying and solidifying. Then, the surrounding polyimide film was cut and deleted, and a heat radiation sheet having a size of about 40 mm × 40 mm and a thickness of about 1 mm was produced.

Next, a test board on which a power transistor is mounted on a printed circuit board made of glass epoxy of 75 mm × 75 mm is driven, and a junction surface of a heat radiation sheet is attached so as to cover the printed circuit where the transistor terminal portion and the conductor are exposed. Combined and left for about 30 minutes. Thereafter, the surface temperature near the center of the heat-dissipating sheet was measured using a thermocouple and found to be 52.9 ° C. still,
Next, as a comparative example, a heat radiating sheet that does not form a heat transfer portion, which is a conventional technique, is produced (a heat radiating sheet is produced in the same manner as in Example 1 except that a heat transfer portion using solder balls is not formed) The surface temperature of the heat dissipation sheet was measured by the same method as in the first embodiment. The surface temperature at this time is 56.9 degreeC, and it turns out that the heat dissipation effect is weak compared with 52.9 degreeC of this invention. In addition, since the surface temperature of the transistor before bonding the heat dissipation sheet was 65.2 ° C., it was found that the heat dissipation effect of the heat dissipation sheet was excellent.

(Embodiment 2)
FIG. 4 is a diagram showing an example of a heat dissipation sheet in the second embodiment of the present invention. In FIG. 4, the heat dissipation substrate 5 having flexibility is provided with a joint surface n composed of the heat transfer section 3 and the adhesive material 4 on one surface. In the configuration example of FIG. 4A, the heat transfer section 3 has a configuration that communicates with the flexible substrate 1 from the surface of the bonding surface n. The heat transfer section 3 on the joint surface n in contact with the heat radiating member is composed of a plurality of independent regions, and the regions are the gaps between the conductor terminals of the mounted parts exposed on the joint surface of the heat radiated member and the conductors of the circuit board. It has a structure smaller than the gap between them. For example, as shown in FIG. 4B, when the heat transfer section 3 is a quadrangle, when the horizontal dimension of the heat transfer section is x and the vertical dimension is y, the gap c between the conductor terminals of the mounted component shown in FIG. 3 has a relationship of (x <c, y <c) or (x <d, y <d) with the gap d between the conductors of the circuit board shown in FIG. Further, when the heat transfer section 3 is circular as shown in FIG. 4C, if the diameter of the heat transfer section is z, the gap c between the conductor terminals 21 of the mounting component 20 shown in FIG. There is a relationship of (z <c) or (z <d) with the gap d between the conductors 32 of the circuit board 30 shown. In the above example, the case where the shape of the heat transfer portion on the joint surface n is a quadrangle and a circle has been described. Is not to be done. Moreover, although the structure which arrange | positioned the several heat-transfer part equally was shown, random arrangement | positioning may be sufficient and it does not specifically limit.

  The heat dissipating sheet configured as described above is bonded to a heat radiating member such as an electronic component or a circuit board on which the electronic component is mounted, so that a plurality of adjacent heat transfer portions 3 on the joint surface n are electrically connected to each other. Without conducting, it is in direct contact with a heat-dissipating member such as the conductor terminal 21 of the mounted component or the conductor 32 of the circuit board and is fixed by the adhesive material 4. As a result, the heat of the heat radiating member is efficiently transferred to the heat radiating board 5 through the heat transfer portion 3 having high thermal conductivity without causing an electrical short circuit between the component terminals or between the circuit board conductors, and the heat radiating surface m. Is emitted as radiant light such as air convection and infrared rays.

  The constituent material of the heat transfer section may be a material having high thermal conductivity as in the first embodiment. For example, a metal material such as gold, silver, copper, aluminum, tungsten, gallium, nickel, solder, or the like Alloys or metal materials are processed into suitable shapes such as particles, fibers, flakes, etc., such as epoxy resin, acrylic resin, polyimide resin, olefin resin, silicon resin, acrylic rubber, butadiene rubber, silicon gel, etc. Examples include composite materials dispersed and mixed in organic materials. Further, for example, a carbon material such as graphite, carbon fiber, silicon carbide, silicon nitride, or a composite material thereof other than the metal material may be used.

  The material of the heat dissipation substrate may be an electrically insulating material having flexibility, heat dissipation, and high heat radiation. For example, a ceramic material having high infrared radiation receiving ability, such as alumina, silicon dioxide, and glass, is made of silicon. Examples thereof include a composite material mixed with an organic resin such as resin or epoxy resin and impregnated in glass cloth or plastic fiber. The plastic fiber may be any material that has both strength, insulation and flexibility enough to hold a ceramic material. For example, polyimide fiber, polyethylene resin, polyethylene terephthalate resin, cellulose resin, polytetrafluoroethylene resin, polypropylene resin, etc. Examples thereof include plastic film, silicon rubber, acrylic rubber, and butadiene rubber.

  The adhesive material only needs to have sufficient adhesive strength to make the heat transfer part contact the heat radiating member. Polyester resin, epoxy resin, silicon resin, thermoplastic polyimide resin, polycarbodiimide resin, vinyl acetate resin, acrylic resin Etc.

  Next, the heat dissipation effect of the invention in the second embodiment will be described in detail below. In this example, a heat radiating sheet having a structure shown in FIG. 4A and having a pressure-sensitive adhesive material and a heat transfer portion on one side of a heat radiating substrate was produced, and performance was evaluated.

  For the heat-radiating substrate having flexibility, glass cloth (manufactured by Sumitomo Electric), 300 μm thick, 40 mm × 40 mm, powdered alumina, powdered silicon dioxide (manufactured by Wako Pure Chemical Industries) 50:50 is used as an appropriate amount of varnish. A mixed and dispersed paste was applied and impregnated, left at room temperature, dried, and solidified to form a heat-radiating substrate having infrared radiation receiving ability. Next, a silicon resin (made of Shin-Etsu Silicone) in which solder balls with a diameter of about 200 μm are dispersed is applied on one side of the heat-dissipating board, and a Teflon (registered trademark) jig is pressed on top. A heat radiating sheet in which a joining surface having the exposed heat transfer portion and an adhesive material was formed by leaving and curing at room temperature while applying pressure was produced. Next, when the surface temperature of the heat-radiation sheet was measured by the same method as in Example 1, it was 50.5 ° C.

  Next, as a comparative example, a heat-dissipating sheet that does not form a heat transfer part, which is a conventional technique, was produced (the same as in the first embodiment), and the surface temperature of the heat-dissipating sheet was measured by the same method as in the first embodiment. The surface temperature at this time is 56.9 degreeC, and it turns out that the heat dissipation effect is weak compared with 50.5 degreeC of this invention. In addition, since the surface temperature of the transistor before bonding the heat dissipation sheet was 65.2 ° C., it was found that the heat dissipation effect of the heat dissipation sheet was excellent.

  Efficiently absorbs and dissipates heat generated from electronic components and circuit boards on which electronic components are mounted, thereby producing a high cooling effect, and simple general-purpose cooling that alleviates and reduces internal heat generation of electrical and electronic products It is effective as a means. In particular, since it is not necessary to bring the heat radiation surface into contact with a cooler such as a heat sink, it is effective for a motor drive unit of a device having a small installation space such as a portable device or a device that requires cooling around the power source or self-temperature control.

Configuration diagram of heat dissipation sheet in Embodiment 1 of the present invention Application diagram of heat dissipation sheet to electronic component in Embodiment 1 of the present invention Application diagram to circuit board of heat dissipation sheet in Embodiment 1 of the present invention Configuration diagram of heat dissipation sheet in Embodiment 2 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Flexible substrate 2 Heat dissipation material 3 Heat-transfer part 4 Adhesive material

Claims (8)

A heat dissipation layer made of a heat dissipation material is provided on one surface of the flexible substrate and a bonding layer made of an adhesive material is provided on the other surface, and communicated so as to connect the surface of the bonding layer and the flexible substrate. A heat dissipating sheet provided with a heat transfer section. The heat-radiating sheet according to claim 1, wherein the heat transfer portion includes a plurality of independent small regions, and a maximum value of the small regions is smaller than a pitch of connection terminals of electronic components connected to the bonding layer. The heat-radiating sheet according to claim 1, wherein the heat transfer portion is made of a metal or a composite material in which a resin and a metal are mixed. The heat dissipating sheet according to claim 1, wherein the heat dissipating material is an infrared radiation light receiving material. A bonding layer made of an adhesive material is provided on one side of a heat-radiating substrate having flexibility, and a heat transfer portion is provided to communicate with the surface of the bonding layer and the heat-radiating substrate having flexibility. Heat dissipation sheet. The heat-radiating sheet according to claim 5, wherein the heat transfer portion includes a plurality of independent small regions, and a maximum value of the small regions is smaller than a pitch of connection terminals of electronic components connected to the bonding layer. The heat-radiating sheet according to claim 5, wherein the heat transfer portion is made of a metal or a composite material in which a resin and a metal are mixed. The heat dissipating sheet according to claim 5, wherein the heat dissipating material is an infrared radiation light receiving material.

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