JP2007019130A - Heat dissipator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat dissipator which is low in height and excellent in heat dissipating properties. <P>SOLUTION: A graphite sheet 2 has anisotropic thermal conductive properties. It has low thermal conductivity in a thickness direction but has thermal conductivity equal to or above that of metal in an in-plane direction. An insulating layer 4 is formed of material, such as ceramic etc, which is high in both electric insulating properties and thermal conductivity. A device serving as a heating source, such as a semiconductor chip 1 etc, is bonded on the upper surface of the insulating layer 4. The insulating layer 4 absorbs heat released from the semiconductor chip 1 and also function as a conductor of transmitting heat to the graphite sheet 2. The heat transmitted to the graphite sheet 2 from the insulating layer 4 is conducted from the center of the graphite sheet 2 to its peripheral area. The heat conducted to the peripheral area of the graphite sheet 2 is absorbed by a heat sink 3 and dissipated into the air from the surface of the heat sink 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heat dissipation device, and more particularly to a heat dissipation device that absorbs heat generated from a semiconductor chip and dissipates heat from a heat sink.

  In recent years, in consideration of environmental problems, development of automobiles using a motor as a drive source, such as hybrid cars and fuel cell cars, has been promoted. And semiconductor devices, such as a power module which controls these motors, are required to have high heat dissipation from the viewpoint of reliability and durability.

  In a conventional semiconductor device, a heat conductive insulating layer is bonded to the upper surface of the heat sink, and an element such as a semiconductor chip is bonded to the upper surface of the insulating layer, so that the heat sink, the insulating layer, and the semiconductor chip are vertically arranged in this order. Many stacked structures are used. In such a structure, heat generated from the semiconductor chip is transmitted downward in the insulating layer toward the heat sink, and is absorbed and dissipated by the heat sink. The reason why many such structures are adopted is that, considering various materials used for the insulating layer (generally materials having isotropic thermal conductivity), a heat sink is disposed immediately below the insulating layer. This is because it has been considered that it is most efficient to transmit the heat generated from the semiconductor chip downward.

  In addition, development of materials for efficiently transmitting heat generated from a semiconductor chip to a heat sink is also underway.For example, while thermal conductivity in the thickness direction is low, thermal conductivity in the in-plane direction is about the same as that of metal or There is a graphite sheet having a higher anisotropic thermal conductivity than that.

  However, in order to mount a conventional semiconductor device in which a heat sink, an insulating layer, and a semiconductor chip are stacked in a vertical direction on a car, the vertical dimension of the semiconductor device becomes large, so such a thick three-dimensional structure is mounted. There is a problem that it is necessary to secure a space for this in the automobile.

  In addition, in a conventional semiconductor device in which a heat sink, an insulating layer, and a semiconductor chip are stacked in the vertical direction, if a graphite sheet having anisotropic thermal conductivity is simply used as an insulating layer, the following problems occur: Occurs. That is, since graphite has a certain degree of electrical conductivity, a plurality of semiconductor chips to be insulated are electrically connected to each other via the graphite sheet and the heat sink, which may cause damage or malfunction of the semiconductor chips. In addition, since the graphite sheet has low thermal conductivity in the thickness direction, the efficiency of heat conduction from the semiconductor chip to the heat sink is worsened.

  The present invention has been made to solve such problems, and an object of the present invention is to obtain a heat dissipation device that is thin and has high heat dissipation efficiency.

  A heat dissipation device according to a first aspect of the present invention includes a thermally conductive sheet-like member, a bottom surface bonded onto the top surface in the central portion of the sheet-like member, and a top surface to which an element to be endothermic is bonded. It is characterized by comprising a conductive insulating layer and a heat sink that surrounds the insulating layer and is bonded onto the upper surface of the peripheral portion of the sheet-like member.

  The heat radiating device according to the second invention is characterized in that, in the heat radiating device according to the first invention, the sheet-like member is a graphite sheet having higher thermal conductivity in the in-plane direction than in the thickness direction.

  The heat radiating device according to the third invention is characterized in that, in the heat radiating device according to the first invention, in particular, the sheet-like member is a heat conductive metal foil.

  According to the heat dissipation device according to the first to third inventions, both the insulating layer and the heat sink are bonded on the upper surface of the sheet-like member. Therefore, as compared with a heat dissipation device of a type in which an insulating layer is stacked on a heat sink, the vertical dimension can be reduced, and the device can be thinned.

  In particular, according to the heat radiating device of the second invention, the graphite sheet has high thermal conductivity in the in-plane direction, so that the heat transferred from the element to the graphite sheet through the insulating layer is efficiently transferred to the heat sink. can do.

  In particular, according to the heat dissipation device according to the third aspect of the present invention, since the heat conductive metal foil has high thermal conductivity not only in the thickness direction but also in the in-plane direction, a voltage is applied from the element to the metal foil through the insulating layer. The generated heat can be efficiently transferred to the heat sink.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same code | symbol in different drawing shall show the same or corresponding element.

  FIG. 1 is a top view showing a structure of a semiconductor device provided with a heat dissipation device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a cross-sectional structure relating to the position along line II-II shown in FIG.

  With reference to FIGS. 1 and 2, the heat dissipating device according to the present embodiment includes a graphite sheet 2, an insulating layer 4 bonded on the upper surface of a central portion (including the center and substantially the center) of the graphite sheet 2, An annular heat sink 3 bonded to the upper surface of the peripheral edge (including the peripheral edge and substantially the peripheral edge) of the graphite sheet 2 is provided so as to surround the periphery of the insulating layer 4.

  The heat sink 3 is made of a metal having high thermal conductivity such as copper or aluminum (that is, a metal having good thermal conductivity). In order to increase the heat dissipation efficiency, cooling fins may be formed on the surface of the heat sink 3. Alternatively, the heat sink 3 may be cooled by a water cooling device or the like.

  Referring to FIG. 2, the graphite sheet 2 has a low thermal conductivity in the thickness direction (up and down direction of the paper), while the thermal conductivity in the in-plane direction (left and right direction of the paper surface) is equal to or higher than that of the metal. High and anisotropic thermal conductivity. For example, the thermal conductivity in the in-plane direction is about 3 times that of aluminum and about 2 times that of copper.

  The insulating layer 4 is made of a material that is electrically insulating and has high thermal conductivity, such as ceramic. On the upper surface of the insulating layer 4, elements such as the semiconductor chip 1 serving as a heat source are bonded, and the insulating layer 4 functions to electrically separate the semiconductor chip 1 and the graphite sheet 2 from each other.

  Further, as indicated by an arrow in FIG. 2, the insulating layer 4 also functions to absorb heat generated from the semiconductor chip 1 and transmit it to the graphite sheet 2. The heat transmitted from the insulating layer 4 to the graphite sheet 2 is transmitted from the central portion of the graphite sheet 2 toward the peripheral portion. Since the graphite sheet 2 has a high thermal conductivity in the in-plane direction, the heat conduction from the central part to the peripheral part of the graphite sheet 2 is efficiently performed. The heat transmitted to the peripheral edge of the graphite sheet 2 is absorbed by the heat sink 3 and radiated from the surface of the heat sink 3 to the atmosphere.

  FIG. 3 is a cross-sectional view showing another structure of the heat dissipation device according to the present embodiment, corresponding to FIG. Instead of the graphite sheet 2 shown in FIG. 2, a thermally conductive metal foil 5 such as copper or aluminum is disposed. The metal foil 5 has isotropic thermal conductivity. That is, it has high thermal conductivity not only in the thickness direction but also in the in-plane direction. Therefore, similarly to the graphite sheet 2, the heat transmitted from the insulating layer 4 to the metal foil 5 is transmitted from the central portion of the metal foil 5 toward the peripheral portion. The heat transmitted to the peripheral edge of the metal foil 5 is absorbed by the heat sink 3 and radiated from the surface of the heat sink 3 to the atmosphere.

  As described above, according to the heat dissipation device according to the present embodiment, the insulating layer 4 and the heat sink 3 are both bonded to the upper surface of the graphite sheet 2 or the metal foil 5 as shown in FIGS. . Therefore, as compared with a conventional semiconductor device in which a heat sink, an insulating layer, and a semiconductor chip are stacked in the vertical direction, the size in the vertical direction can be reduced, and the thickness of the device can be reduced.

It is a top view which shows the structure of the semiconductor device provided with the thermal radiation apparatus which concerns on embodiment of this invention. It is sectional drawing which shows the cross-section regarding the position along line II-II shown in FIG. It is sectional drawing which shows the other structure of the thermal radiation apparatus which concerns on FIG. 2 according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor chip 2 Graphite sheet 3 Heat sink 4 Insulating layer 5 Metal foil

Claims (3)

A thermally conductive sheet-like member;
A thermally conductive insulating layer having a bottom surface bonded to the top surface in the central portion of the sheet-like member, and a top surface to which an element that is an object of heat absorption is bonded;
A heat radiating device including a heat sink that surrounds the periphery of the insulating layer and is bonded onto the upper surface of the peripheral edge of the sheet-like member.   The heat dissipation device according to claim 1, wherein the sheet-like member is a graphite sheet having higher thermal conductivity in an in-plane direction than in a thickness direction.   The heat dissipation device according to claim 1, wherein the sheet-like member is a thermally conductive metal foil.

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