Electronic device and method for manufacturing electronic device

Abstract

To reduce thermal resistance between an electronic component and a cooling body by pressurization of a predetermined value or less in an electronic device in which the electronic component and the cooling body are thermally connected via a plurality of high thermal conductive materials.SOLUTION: In the electronic device, the electronic component 1, the heat dissipation sheet 2, and the cooling body 3 are stacked in this order and held under pressure. The heat dissipation sheet 2 includes a plurality of high heat conduction materials 22 extended in a predetermined direction, and a fixing layer 21 for fixing one end 221 of the high heat conduction material 22 to the side of the electronic component 1. The other ends 222 opposite to the one ends 221 of the plurality of high heat conduction materials 22 are in contact with the 3a of the facing surface of the coolant 3, and are aligned along the 3a of the facing surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electronic device in which an electronic component and a cooling body are thermally connected by a heat dissipation sheet, and a method for manufacturing the same. [Background technology]

[0002] Conventionally, electronic devices have been known in which an electronic component having a semiconductor element such as a power MOSFET is connected to a cooling body via a heat dissipation sheet, and heat from the electronic component is transferred to the cooling body to prevent the electronic component from overheating. MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor. A proposed structure for this type of electronic device uses a heat dissipation sheet containing a highly thermally conductive material such as carbon nanotubes (CNTs), and applies pressure to bring the highly thermally conductive material into direct contact with the electronic component to reduce the interfacial thermal resistance between the material and the electronic component (see, for example, Patent Document 1).

[0003] The electronic device described in Patent Document 1 uses a heat dissipation sheet with multiple CNTs arranged in it, and has a structure in which an electronic component and a cooling body are thermally connected by the CNTs, with one end of the CNT abutting the electronic component and the other end of the CNT abutting the cooling body while being fixed to the cooling body by an adhesive layer. This electronic device is manufactured by pressurizing and heating the heat dissipation sheet with multiple CNTs to fix it to the cooling body with the adhesive layer, and then pressurizing and fixing the cooling body with the heat dissipation sheet fixed to it and the electronic component mounted on a substrate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-185562 Summary of the Invention [Problem to be solved by the invention]

[0005] Electronic components such as power modules are composites of various materials with different linear expansion coefficients, which can cause warping and undulations on the surface that comes into contact with the heat dissipation sheet. Furthermore, when a heat dissipation sheet is made of multiple CNTs as high-thermal-conductivity materials, the individual high-thermal-conductivity materials vary in length within the heat dissipation sheet. Therefore, if the pressure applied to pressurize and fix the heat dissipation sheet and electronic component is below a certain level, the in-plane pressure will be uneven due to the mismatch in the surface shapes of these components, resulting in some of the multiple high-thermal-conductivity materials not coming into contact with the electronic component, increasing the thermal resistance at the interface.

[0006] Furthermore, if the pressure applied during the pressure fixation is high, for example, exceeding 3 MPa, the high thermal conductivity material and the electronic component can be securely abutted against each other, preventing an increase in interfacial thermal resistance. However, in this case, a rigid spring member or the like is required as a pressure mechanism to maintain the cooling body and the electronic component in a pressurized state at high pressure, which increases the size of the electronic device itself.

[0007] In view of the above, the present disclosure aims to provide an electronic device and a manufacturing method thereof in which an electronic component and a cooling body are thermally connected via a heat dissipation sheet having multiple high thermal conductivity materials, and in which the interfacial thermal resistance between the electronic component and the cooling body can be reduced by applying a pressure below a predetermined level. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, an electronic device includes: Electronic components (1), a cooling body (3) thermally connected to the electronic component; a heat dissipation sheet (2) that thermally connects the electronic component and the cooling body and conducts heat from the electronic component to the cooling body; The heat dissipation sheet has a plurality of highly thermally conductive materials (22) extending in a direction connecting the electronic component and the cooling body, and a fixing layer (21) arranged at a position not in contact with the cooling body and fixing one end of the highly thermally conductive material to the electronic component side; The plurality of highly thermally conductive materials have one end opposite to the other end in contact with the cooling body, and the other ends are aligned along the opposing surface (3a) of the cooling body that faces the heat dissipation sheet.

[0009] This electronic device has a structure in which the electronic component and the cooling body are thermally connected by a heat dissipation sheet containing multiple high-thermal-conductivity materials, one end of each of the multiple high-thermal-conductivity materials fixed to the electronic component by a fixing layer and the other end aligned along the surface of the cooling body facing the heat dissipation sheet. Even when the electronic component is warped, the other ends of the multiple high-thermal-conductivity materials facing the cooling body are aligned along the surface facing the cooling body. Therefore, even if the pressure applied when pressing and holding the electronic component and the cooling body is below a predetermined level, the in-plane pressure within the heat dissipation sheet is approximately uniform, maintaining stable contact between the electronic component, the heat dissipation sheet, and the cooling body, resulting in an electronic device with reduced interfacial thermal resistance between them.

[0010] According to another aspect of the present disclosure, a method for manufacturing an electronic device includes: forming an adhesive layer (21) on the prepared electronic component (1) by coating; a sheet having a plurality of highly thermally conductive materials is placed on the adhesive layer, and the sheet is pressed against the electronic component using a jig (J), and one end (221) of the plurality of highly thermally conductive materials is bonded to the adhesive layer while aligning the position of the other end (222) opposite to the one end; After placing a cooling body (3) at the other end that has been aligned, the cooling body is pressed against the electronic component, thereby thermally connecting the cooling body and the plurality of highly thermally conductive materials.

[0011] This method for manufacturing an electronic device includes applying an adhesive layer to an electronic component, adhering one end of each of the plurality of high-thermal-conductivity materials to the adhesive layer, and then aligning the other ends of the plurality of high-thermal-conductivity materials using a jig. Even if the electronic component is warped, the other ends of the plurality of high-thermal-conductivity materials are aligned. Therefore, even if the electronic component is warped, the in-plane pressure is substantially uniform, even when the pressure applied to pressurize and fix the cooling body and the electronic component is below a predetermined level, allowing the high-thermal-conductivity materials and the cooling body to be stably maintained in contact with each other. This allows the electronic component and the cooling body to be thermally connected via the heat dissipation sheet, making it possible to manufacture an electronic device in which the interfacial thermal resistance between the electronic component and the cooling body can be reduced by applying a pressure below a predetermined level.

[0012] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and the specific components described in the embodiments described below. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view showing a main part of an electronic device according to a first embodiment. [Figure 2] FIG. 2 is an explanatory diagram showing an example of a highly thermally conductive material in a heat dissipation sheet. [Figure 3] FIG. 10 is an explanatory diagram showing another example of a highly thermally conductive material in a heat dissipation sheet. [Figure 4] FIG. 2 is a cross-sectional view showing an example of a pressure mechanism in the electronic device according to the first embodiment. [Figure 5] FIG. 4 is a cross-sectional view showing another example of the pressure mechanism in the electronic device according to the first embodiment. [Figure 6A] 3A and 3B are cross-sectional views showing a first step in the manufacture of the electronic device of the first embodiment. [Figure 6B] FIG. 6B is a cross-sectional view showing a step subsequent to FIG. 6A. [Figure 6C] FIG. 6C is a cross-sectional view showing a step subsequent to FIG. 6B. [Figure 6D] FIG. 6D is a cross-sectional view showing a step subsequent to FIG. 6C. [Figure 7] 7 is a diagram showing a state in which the highly thermally conductive material is in a strip shape, as viewed from the VII direction in FIG. 6D. FIG. [Figure 8] FIG. 4 is a cross-sectional view showing a first modified example of the electronic device of the first embodiment. [Figure 9] 9 is a cross-sectional view showing a step corresponding to FIG. 6C in the manufacturing process of the electronic device of FIG. 8. FIG. [Figure 10] FIG. 8 is a diagram corresponding to FIG. 7 and showing a second modified example of the electronic device of the first embodiment. [Figure 11] FIG. 8 is a diagram corresponding to FIG. 7 and showing a third modified example of the electronic device of the first embodiment. [Figure 12] FIG. 10 is a cross-sectional view showing a fourth modified example of the electronic device of the first embodiment. [Figure 13]FIG. 13 is an enlarged cross-sectional view of a region XIII in FIG. 12. [Figure 14] FIG. 10 is a cross-sectional view showing a fifth modified example of the electronic device of the first embodiment. [Figure 15] FIG. 10 is a cross-sectional view showing a main part of an electronic device according to a second embodiment. [Figure 16A] 10A and 10B are cross-sectional views showing a first step in the manufacture of the electronic device according to the second embodiment. [Figure 16B] FIG. 16B is a cross-sectional view showing a step subsequent to FIG. 16A. [Figure 16C] FIG. 16C is a cross-sectional view showing a step subsequent to FIG. 16B. [Figure 16D] FIG. 16D is a cross-sectional view showing a step subsequent to FIG. 16C. [Figure 16E] FIG. 16B is a cross-sectional view showing a step subsequent to FIG. 16D. [Figure 17] FIG. 10 is a cross-sectional view showing another example of the pressure mechanism in the electronic device according to the second embodiment. [Figure 18] FIG. 10 is a cross-sectional view showing a first modified example of the electronic device of the second embodiment. [Figure 19] FIG. 11 is a cross-sectional view showing an example of a pressure mechanism in a first modified example of the electronic device of the second embodiment. [Figure 20] FIG. 11 is a cross-sectional view showing another example of a pressure mechanism in the first modified example of the electronic device of the second embodiment. [Figure 21] FIG. 10 is a cross-sectional view showing a second modified example of the electronic device of the second embodiment. [Figure 22] 10A and 10B are cross-sectional views showing other examples of the shapes of the plurality of highly thermally conductive materials. [Figure 23] 10A and 10B are cross-sectional views showing other examples of the shapes of the plurality of highly thermally conductive materials. [Figure 24] 10A and 10B are cross-sectional views showing other examples of the shapes of the plurality of highly thermally conductive materials. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the following embodiments, identical or equivalent parts will be denoted by the same reference numerals.

[0015] (First embodiment) An electronic device 100 according to a first embodiment will be described.

[0016] [Basic configuration] 1, electronic device 100 of this embodiment includes electronic component 1, heat dissipation sheet 2, and cooling body 3, with electronic component 1 thermally connected to cooling body 3 via heat dissipation sheet 2. In electronic device 100, a pressure mechanism holds electronic component 1 and cooling body 3 in a pressurized state at a pressure equal to or less than a predetermined pressure, aligning the other ends 222 of multiple high thermal conductive materials 22 in heat dissipation sheet 2 and reducing the interfacial thermal resistance between electronic component 1 and cooling body 3. The pressure mechanism will be described later.

[0017] The electronic component 1 is, for example, a heat generating element such as a power module. In this embodiment, as shown in Fig. 1, the electronic component 1 includes an insulating substrate 10, a semiconductor element 11, and a sealing resin 12, and the semiconductor element 11 is mounted on the insulating substrate 10 with a bonding material such as solder (not shown), and the semiconductor element 11 is sealed with the sealing resin 12. The electronic component 1 is in a warped state due to, for example, differences in the linear expansion coefficients of the constituent materials of the insulating substrate 10, the semiconductor element 11, and the sealing resin 12.

[0018] For ease of explanation, the direction connecting the electronic component 1 and the cooling body 3, i.e., the direction along the thickness of the electronic device 100, as shown in Figure 1, will be referred to as the "thickness direction D1," and the surface of the electronic component 1 to which the heat dissipation sheet 2 is adhered will be referred to as the "surface 1a."

[0019] The insulating substrate 10 includes, for example, a thermally conductive layer, an insulating layer, and a wiring layer, which are stacked in this order, with the wiring layer and the thermally conductive layer being electrically independent components due to the insulating layer. The insulating substrate 10 has, for example, a wiring layer and a thermally conductive layer made of a metal material such as Cu (copper), and the insulating layer made of an insulating material such as Al2O3 (alumina), AlN (aluminum nitride), or SiN (silicon nitride). Examples of the insulating substrate 10 include a DBC substrate and an AMB substrate. DBC stands for Direct Bonded Copper. AMB stands for Active Metal Brazing. The insulating substrate 10 has, for example, a semiconductor element 11 mounted on the wiring layer using a bonding material (not shown), such as solder or Ag (silver) sintered material, and a heat dissipation sheet 2 bonded to the thermally conductive layer exposed from the sealing resin 12.

[0020] The semiconductor element 11 is, for example, a power semiconductor element such as a power MOSFET or an IGBT, and is manufactured by a known semiconductor process. IGBT is an abbreviation for Insulated gate Bipolar Transistor.

[0021] The sealing resin 12 is made of any insulating thermosetting resin material such as epoxy resin, and is formed by a known resin molding method.

[0022] 1, the heat dissipation sheet 2 comprises a fixing layer 21 arranged away from the cooling body 3, a plurality of highly thermally conductive materials 22, and a binder resin 23, and transfers heat from the electronic component 1 to the cooling body 3 via the plurality of highly thermally conductive materials 22. In other words, the heat dissipation sheet 2 is sandwiched between the electronic component 1 and the cooling body 3 and serves as a thermal connection layer that thermally connects these components. While the heat dissipation sheet 2 is fixed on the surface 1a side of the electronic component 1 by the fixing layer 21, it is only in contact with the cooling body 3 and is not fixed thereto, which reduces stress compared to when the heat dissipation sheet 2 is fixed on both sides of the electronic component 1 and the cooling body 3.

[0023] The fixing layer 21 is an adhesive made of, for example, an epoxy-based, urethane-based, or acrylic-based thermosetting or thermoplastic resin material, and fixes the plurality of high-thermal-conductivity materials 22 to the electronic component 1. The thickness of the fixing layer 21 in the thickness direction D1 is, for example, within a range of 1 / 10 to 1 / 4 of the thickness of the heat dissipation sheet 2 so as not to inhibit deformation of the high-thermal-conductivity materials 22 due to pressure. The fixing layer 21 may contain a filler made of a material with high thermal conductivity, such as an inorganic oxide, inorganic nitride, graphite, Ag, or Cu, in the adhesive to improve thermal conductivity between the electronic component 1 and the high-thermal-conductivity materials 22. When the fixing layer 21 contains a filler, the particle size of the filler is set to, for example, 40 μm or less, preferably 20 μm or less, and more preferably 10 μm or less, to facilitate impregnation of the filler between the high-thermal-conductivity materials 22. The fixing layer 21 preferably contains a filler having a particle size equal to or less than the above-mentioned predetermined particle size, because this further reduces the thermal resistance between the electronic component 1 and the plurality of high-thermal-conductivity materials 22. The fixing layer 21 is formed, for example, by applying it to the surface 1a of the electronic component 1, adhering and adjusting the positions of a plurality of highly thermally conductive materials 22, and then curing the material.

[0024] The highly thermally conductive material 22 contacts the electronic component 1 and the cooling body 3 by a pressure mechanism (described later), thermally connecting the electronic component 1 and the cooling body 3. The highly thermally conductive material 22 is made of a material with high thermal conductivity, such as a metal or alloy material such as Cu, a carbon material such as graphite-based CNT or graphite, or a nitride ceramic such as AlN or BN (boron nitride). The thermal conductivity of the highly thermally conductive material 22 is approximately 370 W / mK for Cu, approximately 200 W / mK for AlN, approximately 45 W / mK for BN, approximately 1700 W / mK for graphite (artificial graphite), and a theoretical value of approximately 6000 W / mK for CNT. For example, a carbon material can be used as the highly thermally conductive material 22 when thermal conductivity is a priority, or a nitride ceramic can be used when insulation is required or when concerns about insulating foreign matter arising from detachment are to be minimized.

[0025] The high thermal conductivity materials 22 extend along the direction connecting the electronic component 1 and the cooling body 3, i.e., the thickness direction. They are arranged regularly or irregularly in a plane direction intersecting the thickness direction D1 and are held together by the binder resin 23. The high thermal conductivity materials 22 are, for example, cylindrically linear as shown in FIG. 2 or strip-shaped as shown in FIG. 3, with both ends in the thickness direction exposed from the binder resin 23. A strip-shaped configuration is preferable to a linear configuration, because it facilitates uniform deformation of the individual high thermal conductivity materials 22, such as tilt, bending, and curvature, and the direction of deformation, thereby facilitating uniform contact with the opposing surface 3a of the cooling body 3. Note that in FIGS. 2 and 3, to clearly show the arrangement of the high thermal conductivity materials 22, the outlines of the high thermal conductivity materials 22, including the portions hidden from the outside by the binder resin 23, are indicated by solid lines, while the portions of the outline of the binder resin 23 that are not visible from the perspective of the figures are indicated by dashed lines.

[0026] The plurality of highly thermally conductive materials 22 have one ends 221 in the thickness direction fixed to the surface 1a of the electronic component 1 by the fixing layer 21, and an end face of the other ends 222 opposite to the one ends 221 is in direct contact with the cooling body 3. For example, some of the highly thermally conductive materials 22 have one ends 221 abutting the electronic component 1 while other ends 221 do not abut the electronic component 1, but all of the one ends 221 are fixed by the fixing layer 21. The one ends 221 of the plurality of highly thermally conductive materials 22 that do not abut the electronic component 1 are impregnated into the fixing layer 21, so that they are thermally connected to the electronic component 1.

[0027] Before the multiple highly thermally conductive materials 22 are brought into pressurized contact with the cooling body 3, the positions of the other ends 222 are aligned to the surface shape of the opposing surface 3a of the cooling body 3 in a preliminary process using a jig J, which will be described later. As a result, even if the pressure during pressurized contact between the electronic component 1 to which the heat dissipation sheet 2 is attached and the cooling body 3 is below a predetermined level, the in-plane pressure becomes approximately uniform, the multiple highly thermally conductive materials 22 come into stable contact with the cooling body 3, and the interfacial thermal resistance between the heat dissipation sheet 2 and the cooling body 3 is reduced. This will be described in detail later. Some of the multiple highly thermally conductive materials 22 have one ends 221 in contact with the electronic component 1, while all or almost all of the other ends 222 are in contact with the cooling body 3, resulting in a state in which the contact area and / or contact points with the cooling body 3 are larger than those of the electronic component 1.

[0028] The binder resin 23 is made of a low-elasticity resin material and is a member that constrains the multiple highly thermally conductive materials 22 arranged in the planar direction to a degree that allows them to deform, while being deformable together with the highly thermally conductive materials 22 when pressure is applied. The binder resin 23 has an elastic modulus equal to or less than a predetermined value so that, when the electronic component 1 and the cooling body 3 are brought into contact under pressure, the surface of the binder resin 23 that contacts the cooling body 3 can deform to follow the surface irregularities of the cooling body 3, and so that the multiple highly thermally conductive materials 22 have a certain degree of freedom of deformation. The binder resin 23 may be configured to include, for example, a thermoplastic resin material, or may have voids therein.

[0029] The cooling body 3 is made of a metal material with high thermal conductivity, such as aluminum or copper, or an alloy thereof, and is a member that dissipates heat from the electronic component 1 transmitted via the heat dissipation sheet 2 to the outside. The cooling body 3 is, for example, a cooler with a flow path for a coolant such as a general antifreeze, or a heat dissipation body with heat dissipation fins. The cooling body 3 has a facing surface 3a that faces the heat dissipation sheet 2 and is in contact with multiple highly thermally conductive materials 22. The facing surface 3a can have any shape, such as a flat surface, a curved surface, or an uneven surface with projections and recesses.

[0030] The above is the basic configuration of the electronic device 100 of this embodiment, excluding the pressure mechanism.

[0031] [Pressure mechanism] Next, the pressure mechanism 4 in the electronic device 100 will be described.

[0032] 4, the pressure mechanism 4 is a mechanism that applies pressure to at least one of the electronic component 1 and the cooling body 3 toward the other in a state in which the heat dissipation sheet 2 is disposed between the electronic component 1 and the cooling body 3, thereby maintaining the pressed state of the heat dissipation sheet 2. In other words, the pressure mechanism 4 presses the heat dissipation sheet 2 and maintains the other ends 222 of the multiple high thermal conductivity materials 22 in direct contact with the opposing surface 3a of the cooling body 3, thereby reducing the interfacial thermal resistance between the heat dissipation sheet 2 and the cooling body 3.

[0033] The pressure mechanism 4 can be configured, for example, by a leaf spring 41 that contacts the electronic component 1 and a plurality of screws 42 for fixing the leaf spring 41 to the cooling body 3. The pressure mechanism 4 can be configured in any way that can maintain a low pressure of 2 MPa or less on the heat dissipation sheet 2 sandwiched between the electronic component 1 and the cooling body 3. This is because, prior to attachment of the pressure mechanism 4, in the manufacturing process of the electronic device 100 described below, the positions of the other ends 222 of the plurality of high thermal conductivity materials 22 are aligned, thereby reducing the pressure required to reliably contact the plurality of high thermal conductivity materials 22 with the cooling body 3. This will be described in more detail later.

[0034] 5, the pressure mechanism 4 may be formed by an adhesive 43 that directly bonds the electronic component 1 and the cooling body 3. In this case, the pressure mechanism 4 is formed, for example, by placing the heat dissipation sheet 2 between the electronic component 1 and the cooling body 3, applying pressure with a jig (not shown), and then curing the applied adhesive at any timing. In this way, the pressure mechanism 4 may be a mechanical fixing structure or an adhesive fixing structure using an adhesive such as an epoxy-based resin material, and may be designed as appropriate.

[0035] [Manufacturing method] Next, we will explain the manufacturing method of the electronic device 100 of this embodiment. However, since the manufacturing method of the electronic component 1 is publicly known and the pressure mechanism 4 is as described above, we will mainly explain the process of integrating the electronic component 1, heat dissipation sheet 2, and cooling body 3.

[0036] First, as shown in Fig. 6A, for example, electronic component 1 and an existing sheet 201 in which a plurality of highly thermally conductive materials 22 are integrated with binder resin 23 are prepared. Then, for example, a liquid adhesive made of an epoxy resin material or the like is applied to surface 1a of electronic component 1 by any application method such as dispenser application, to form adhesive layer 200.

[0037] 6B, for example, sheet 201 is placed on adhesive layer 200 and temporarily fixed. At this time, sheet 201 is in a state where one end 221 and the other end 222 of the plurality of high thermal conductivity materials 22 are not aligned due to variations in the lengths of the plurality of high thermal conductivity materials 22.

[0038] Next, as shown in FIG. 6C , a jig J is prepared, and the surface of the sheet 201 where the other ends 222 are exposed is pressed with the jig J. The jig J is a correction jig for aligning the positions of the other ends 222 of the multiple high thermal conductive materials 22 on the sheet 201 on the curved electronic component 1. The jig J is made of any rigid material that does not deform when the multiple high thermal conductive materials 22 are pressurized and heated. The contact surface J1 of the jig J that comes into contact with the sheet 201 has the same surface shape as the opposing surface 3a of the cooling body 3 that will ultimately contact the other ends 222 of the multiple high thermal conductive materials 22. The pressure applied in the pressing step using the jig J is, for example, approximately 0.5 to several MPa so that the multiple high thermal conductive materials 22 do not deform excessively along the surface 1a of the electronic component 1. This pressing step using the jig J aligns the positions of the other ends 222 of the multiple high thermal conductive materials 22, regardless of variations in length in the thickness direction D1 or the warpage of the electronic component 1. Then, for example, by heating at about 80°C to 180°C while maintaining the pressure applied by the jig J, the adhesive layer 200 is hardened and a fixing layer 21 is formed, thereby forming a heat dissipation sheet 2 in which the other ends 222 of the multiple high thermal conductive materials 22 are aligned. Note that the jig J may have a mounter with a suction function or a low-adhesion adhesive layer (not shown) formed on the contact surface J1 to more easily align the other ends 222 of the multiple high thermal conductive materials 22.

[0039] Next, as shown in FIG. 6D , a cooling body 3 is prepared, and the electronic component 1 to which the heat dissipation sheet 2 is attached is brought into contact with the opposing surface 3a of the cooling body 3. In this process, because the heat dissipation sheet 2 has undergone the above-described straightening process, even if the electronic component 1 is warped, the surface opposite the electronic component 1 has the same surface shape as the opposing surface 3a of the cooling body 3 to be attached in the next process. For example, if the opposing surface 3a of the cooling body 3 is flat, the other ends 222 of the multiple high thermal conductivity materials 22 of the heat dissipation sheet 2 are aligned at a predetermined position P1 in the thickness direction D1. If the high thermal conductivity materials 22 are strip-shaped, as shown in FIG. 7 , even if the lengths of the high thermal conductivity materials 22 in the depth direction D2 vary in the thickness direction D1, the position of the other ends 222 is straightened, thereby reducing the interfacial thermal resistance with the cooling body 3. The depth direction D2 is, for example, a direction perpendicular to the thickness direction D1 and the orientation direction in which the plurality of highly thermally conductive materials 22 are arranged, and is along the highly thermally conductive materials 22.

[0040] Finally, the electronic device 100 can be manufactured by fixing one or both of the electronic component 1 and the cooling body 3 in a state where they are pressurized approximately uniformly at a low pressure of 2 MPa or less using a pressure mechanism 4 (not shown).

[0041] According to this embodiment, the electronic component 1 and the cooling body 3 are thermally connected by a heat dissipation sheet 2 having a fixing layer 21 and multiple highly thermally conductive materials 22. The other ends 222 of the highly thermally conductive materials 22 facing the cooling body 3 are aligned along the opposing surface 3a of the cooling body 3, resulting in an electronic device 100. The multiple highly thermally conductive materials 22 are fixed to the electronic component 1 by the fixing layer 21, and the other ends 222 facing the cooling body 3 are aligned even when the electronic component 1 is warped and the lengths of the highly thermally conductive materials 22 vary. This ensures that the pressure at the contact surface between the heat dissipation sheet 2 and the cooling body 3 is substantially uniform when a pressure equal to or less than a predetermined level is applied to the electronic device 100, resulting in stable contact between the multiple highly thermally conductive materials 22 and the cooling body 3 and reduced thermal resistance at the interface between them. Furthermore, the electronic device 100 has a structure in which one ends 221 of the multiple highly thermally conductive materials 22 are fixed to the electronic component 1 via the fixing layer 21, thereby reducing thermal resistance between them. The electronic device 100 of this embodiment also has the following features.

[0042] (1) The contact area or number of contact points between the plurality of highly thermally conductive materials 22 and the cooling body 3 is larger than the contact area or number of contact points between the plurality of highly thermally conductive materials 22 and the electronic component 1 .

[0043] (2) The plurality of highly thermally conductive materials 22 may be graphite or carbon nanotubes. Alternatively, the plurality of highly thermally conductive materials 22 may be strip-shaped graphite. In this case, the thermal conductivity of the highly thermally conductive materials 22 is higher than when they are made of a metal material or its nitride, resulting in electronic device 100 with reduced thermal resistance between electronic component 1 and the cooling body.

[0044] (3) Fixing layer 21 is an adhesive made of an epoxy-based resin material, a urethane-based resin material, or an acrylic-based resin material. Fixing layer 21 also contains a filler made of one of inorganic oxides, nitrides, graphite, Ag, and Cu in the adhesive. This provides electronic device 100 with the advantage of further reducing the thermal resistance between electronic component 1 and the plurality of highly thermally conductive materials 22.

[0045] (4) Electronic device 100 has pressure mechanism 4 that holds the configuration in which heat dissipation sheet 2 is disposed between electronic component 1 and cooling body 3 in a pressurized state at a pressure equal to or less than a predetermined pressure.

[0046] (First Modification of the First Embodiment) In electronic device 100, facing surface 3a of cooling body 3 may have an uneven surface with unevenness, as shown in Fig. 8, for example. Electronic device 100 according to this modification is manufactured by preparing a jig J having a contact surface J1 with the same uneven surface as facing surface 3a of cooling body 3, applying pre-pressure using this jig J, and then holding the heat dissipation sheet 2 and cooling body 3 under pressure, as shown in Fig. 9, for example. In this case, in heat dissipation sheet 2, the other ends 222 of the multiple high thermal conductivity materials 22 are arranged in an uneven pattern along the facing surface 3a of cooling body 3 due to the pressure applied by jig J, and the multiple high thermal conductivity materials 22 and cooling body 3 are in stable contact with each other at low pressure.

[0047] This modification also provides an electronic device 100 that can achieve the same effects as the first embodiment. In this way, the opposing surface 3a of the cooling body 3 and the contact surface J1 of the jig J may have various shapes, such as a flat surface, a surface with irregularities, steps, or grooves, a roughened surface, or a curved surface having a curved surface in part, or the like. The jig J can be designed appropriately to match the shape of the cooling body 3.

[0048] (Second Modification of the First Embodiment) 10 , the electronic device 100 may have a configuration in which the high thermal conductivity material 22 is strip-shaped and has a slit 223 formed near the center in the depth direction D2. In this case, when the heat dissipation sheet 2 is in pressurized contact with the cooling body 3, the multiple high thermal conductivity materials 22 are likely to deform along the opposing surface 3a of the cooling body 3. Note that the slits 223 may not be formed in the sheet 201, for example, but may be formed after the multiple high thermal conductivity materials 22 are fixed to the electronic component 1 by the fixing layer 21. This improves workability in the process of forming the slits 223 in the multiple high thermal conductivity materials 22, and allows the high thermal conductivity materials 22 having the slits 223 to be formed stably.

[0049] According to this modified example, the same effects as those of the first embodiment can be obtained, and the end faces of the other ends 222 of the multiple high thermal conductivity materials 22 and the cooling body 3 are in more stable contact with each other, resulting in an electronic device 100 with an improved effect of reducing the interfacial thermal resistance.

[0050] (Third Modification of the First Embodiment) 11, the electronic device 100 may have a configuration in which the highly thermally conductive material 22 is strip-shaped and is divided into multiple pieces in the depth direction D2. In this case, when the heat dissipation sheet 2 comes into pressure contact with the cooling body 3, each of the divided pieces of highly thermally conductive material 22 along the opposing surface 3a of the cooling body 3 is likely to follow and deform.

[0051] This modification also provides the electronic device 100 with the same effects as the second modification.

[0052] (Fourth Modification of the First Embodiment) 12, the electronic device 100 may be configured such that the heat dissipation sheet 2 further includes a metal film 24 covering the other end 222 of the high thermal conductivity material 22 made of a carbon material such as CNT or graphite. The high thermal conductivity material 22 obtained by growing CNT or graphite has a structure oriented along the extension direction of the carbon material, i.e., the growth direction, and therefore has anisotropic thermal conductivity in which the thermal conductivity is very high in the extension direction but low in other directions.

[0053] Metal film 24 is an auxiliary layer provided in the vicinity of other end 222 of high thermal conductivity material 22 to improve thermal conduction in directions other than the extension direction, as indicated by the arrows in Fig. 13, for example, in order to assist heat diffusion to cooling body 3. Metal film 24 is formed, for example, by a film formation method such as sputtering after sheet 201 is fixed to electronic component 1 by fixing layer 21. Note that in Fig. 13, the extension direction of high thermal conductivity material 22 is indicated by a thick solid line to make it easier to understand.

[0054] According to this modified example, the effects of the first embodiment are obtained, and the electronic device 100 has a structure that improves thermal conductivity in a direction intersecting the extension direction when the high thermal conductivity material 22 is made of a carbon material, making it easier for the heat from the electronic component 1 to be diffused by the cooling body 3.

[0055] (Fifth Modification of the First Embodiment) 14, the electronic device 100 may have a fixing layer 21 that is a metal bonding layer made of a metal material such as solder or a sintered metal material such as sintered Ag or sintered Cu. In this case, the fixing layer 21 is formed, for example, by forming a metal thin film on the surface 1a of the electronic component 1 in advance by a film formation method such as plating or sputtering, placing a sheet 201 on the metal thin film, heating and softening it, and then applying pressure and correction to the sheet 201 with a jig J to harden it.

[0056] According to this modified example, the effects of the first embodiment are obtained, and the fixing layer 21 is a metal bonding layer having a higher thermal conductivity than the resin material, resulting in an electronic device 100 in which the thermal resistance between the electronic component 1 and the high thermal conductivity material 22 is further reduced.

[0057] (Second embodiment) An electronic device 100 according to the second embodiment will be described.

[0058] 15, the electronic device 100 of this embodiment differs from the first embodiment in that the configurations of the electronic component 1 and the heat dissipation sheet 2 are changed. This difference will be mainly described in this embodiment.

[0059] 15 , electronic component 1 in this embodiment has first heat sink 13, block body 14, and second heat sink 15 instead of insulating substrate 10, with first heat sink 13, semiconductor element 11, block body 14, and second heat sink 15 stacked in this order. In electronic component 1, the surfaces of first heat sink 13 and second heat sink 15 opposite semiconductor element 11 are exposed from sealing resin 12, resulting in a double-sided heat sink structure in which heat from semiconductor element 11 is dissipated to the outside by the two heat sinks. First heat sink 13, block body 14, and second heat sink 15 are made of, for example, a metal material or alloy material having electrical conductivity and high thermal conductivity, such as Cu, and serve as both a heat dissipation path and a current path for electronic component 1. In this embodiment, the electronic component 1 has a front surface 1a on which the first heat sink 13 is exposed and a back surface 1b on which the second heat sink 15 is exposed, and a heat dissipation sheet 2 and a cooling body 3 are connected to both surfaces of these surfaces.

[0060] In this embodiment, the heat dissipation sheet 2 further includes an insulating layer 25 disposed between the electronic component 1 and the fixing layer 21, making it possible to ensure insulation between the electronic component 1 and the cooling body 3.

[0061] The insulating layer 25 is a sheet-like insulator made of, for example, an insulating thermosetting resin material and a filler made of a nitride or oxide of a metal material with high thermal conductivity, with the filler dispersed in the layer made of the thermosetting resin material. The insulating layer 25 may contain a non-particle-sized filler to enhance thermal conductivity. The insulating layer 25 is configured, for example, to have an overall thermal conductivity of approximately 8 to 20 W / mK to suppress an increase in thermal resistance from the electronic component 1 to the cooling body 3. The insulating layer 25 only needs to have sufficient insulation to prevent breakdown due to the voltage applied when the electronic component 1 is driven and sufficient heat resistance to withstand the heat generated by the electronic component 1 and during the formation of the fixing layer 21. The constituent materials of the insulating layer 25 can be changed as appropriate. For example, the insulating layer 25 may have a glass transition temperature of 175°C or higher after the thermosetting resin material is cured, but this is not limited thereto.

[0062] Next, an example of a manufacturing process for the electronic device 100 of this embodiment will be described.

[0063] 16A, for example, electronic component 1 and insulating resin sheet 202 are prepared, and insulating resin sheet 202 is pressurized and heated by a heat press or the like to surface 1a of electronic component 1, thereby hardening the insulating resin material and bonding these components together. At this time, a film (not shown) made of a fluorine-based resin material such as PTFE is placed on the surface of insulating resin sheet 202 opposite electronic component 1 to prevent unintended attachment of other jigs or the like. Through the above process, insulating layer 25 is formed on surface 1a of electronic component 1.

[0064] 16B, for example, a liquid adhesive layer 200 is applied onto insulating layer 25 formed on electronic component 1 using a dispenser or the like, and a separately prepared sheet 201 is placed on adhesive layer 200.

[0065] 16C, similarly to the first embodiment, a jig J is prepared, and the sheet 201 is pressurized and heated by the jig J to align the other ends 222 of the multiple high thermal conductive materials 22 and harden the sheet 201 to form the fixing layer 21. By this process, the first heat dissipation sheet 2 is formed on the front surface 1a side of the electronic component 1.

[0066] 16A to 16C, as shown in Fig. 16D, insulating layer 25 is formed on rear surface 1b of electronic component 1, adhesive layer 200 is applied, sheet 201 is arranged, other ends 222 of multiple high thermal conductive materials 22 are corrected, and fixing layer 21 is formed. By this process, a second heat dissipation sheet 2 is formed on rear surface 1b side of electronic component 1.

[0067] 16E, cooling bodies 3 are brought into contact with the two heat dissipation sheets 2 formed on the front surface 1a and back surface 1b of electronic component 1, respectively, and the pressure mechanism 4 presses and holds the two cooling bodies 3 against the electronic component 1 at a pressure not greater than a predetermined value. In this embodiment, the pressure mechanism 4 is composed of, for example, a first leaf spring 41 that presses the cooling body 3 arranged on the front surface 1a side of electronic component 1, a second leaf spring 41 that presses the cooling body 3 arranged on the back surface 1b side, and multiple screws 42 that connect the two leaf springs.

[0068] 17, the pressure mechanism 4 may be formed of an adhesive 43. In this case, the pressure mechanism 4 is formed by applying and curing adhesive 43 while a jig (not shown) presses the heat dissipation sheet 2 and electronic component 1 together via the two cooling bodies 3 at a pressure equal to or less than a predetermined pressure, and then removing the jig.

[0069] Through the above steps, the electronic device 100 of this embodiment can be manufactured.

[0070] According to this embodiment, electronic device 100 is configured such that electronic component 1 has a double-sided heat dissipation structure in which first heat sink 13 and second heat sink 15 are not insulated from semiconductor element 11, and heat dissipation sheet 2 has insulating layer 25 disposed between electronic component 1 and fixing layer 21. In electronic device 100, insulating layer 25 ensures insulation between electronic component 1 and cooling body 3, while stabilizing contact between heat dissipation sheet 2 and cooling body 3 at low pressure, thereby achieving the effect of reducing the interfacial thermal resistance between heat dissipation sheet 2 and cooling body 3.

[0071] (First modified example of the second embodiment) 18, when the electronic component 1 has a one-sided heat dissipation structure without the block body 14 and the second heat sink 15, and the exposed portion of the first heat sink 13 is not insulated from the semiconductor element 11, the electronic device 100 is equipped with one heat dissipation sheet 2 and one cooling body 3. In this case, the electronic device 100 is also equipped with only one pressure mechanism 4. For example, the pressure mechanism 4 may be a mechanical structure having a leaf spring 41 and a screw 42 as shown in FIG. 19, or a non-mechanical structure made of an adhesive 43 as shown in FIG. 20.

[0072] This modification also provides the electronic device 100 with the same effects as those of the second embodiment.

[0073] (Second Modification of the Second Embodiment) 21, the electronic device 100 may have a fixing layer 21 that is a metal bonding layer made of a metal material such as solder or a sintered metal material such as sintered Ag or sintered Cu. In this case, the fixing layer 21 is formed, for example, by forming a metal thin film on an insulating layer 25 that has been formed in advance on the surface 1a of the electronic component 1 by a film formation method such as sputtering, and then performing a process similar to that of the fifth modified example of the first embodiment.

[0074] According to this modified example, the effects of the second embodiment are obtained, and the fixing layer 21 is a metal bonding layer having a higher thermal conductivity than the resin material, resulting in an electronic device 100 in which the thermal resistance between the electronic component 1 and the high thermal conductivity material 22 is further reduced.

[0075] (Other embodiments) Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and modifications within the scope of equivalents. In addition, various combinations and forms, as well as other combinations and forms including only one element, more than one, or less than one, are also within the scope and spirit of the present disclosure.

[0076] (1) In the above-described embodiments and their modified examples, the case where the plurality of high thermal conductivity materials 22 are primarily perpendicular to the opposing surface 3a of the cooling body 3 has been described as a representative example, but the present invention is not limited thereto. The portions of the plurality of high thermal conductivity materials 22 that protrude from the fixing layer 21 (hereinafter referred to as "protruding portions") may be uniformly inclined at a predetermined angle, as shown in FIG. 22, for example. Furthermore, the protruding portions of the plurality of high thermal conductivity materials 22 may be bent on the way to the other end 222, as shown in FIG. 23, for example, or may be curved on the way to the other end 222, as shown in FIG. 24, for example. As described above, the shape of the portions of the plurality of high thermal conductivity materials 22 that protrude from one end 221 to the other end 222 is arbitrary as long as the other ends 222 are aligned along the opposing surface 3a of the cooling body 3.

[0077] (2) In the electronic device 100 according to each of the above embodiments and their variations, for example, in order to reduce the thermal resistance between the electronic component 1 and the plurality of high thermal conductive materials 22, another high thermal conductive material made of a material with high thermal conductivity may be formed on the surface 1a of the electronic component 1.

[0078] (3) It goes without saying that in each of the above embodiments, the elements constituting the embodiments are not necessarily essential unless they are specifically stated as essential or are clearly considered essential in principle. Furthermore, in each of the above embodiments, when the numbers, values, amounts, ranges, etc. of the components of the embodiments are mentioned, they are not limited to the specific numbers unless they are specifically stated as essential or are clearly limited to a specific number in principle. Furthermore, in each of the above embodiments, when the shapes, positional relationships, etc. of the components are mentioned, they are not limited to the shapes, positional relationships, etc. unless they are specifically stated or are clearly limited to a specific shape, positional relationship, etc. in principle. [Explanation of symbols]

[0079] 1...electronic component, 2...heat dissipation sheet, 21...fixing layer, 22...highly thermally conductive material, 221...one end, 222...other end, 223...notch, 24...metal film, 25...insulating layer, 3...cooling body, 3a...opposing surface, 4...pressure mechanism, J...jig

Claims

1. An electronic component (1); a cooling body (3) thermally connected to the electronic component; a heat dissipation sheet (2) that thermally connects the electronic component and the cooling body and conducts heat from the electronic component to the cooling body, The heat dissipation sheet has a plurality of high thermal conductivity materials (22) extending in a direction connecting the electronic component and the cooling body, and a fixing layer (21) arranged in a position not in contact with the cooling body and fixing one end (221) of the high thermal conductivity material to the side of the electronic component, The electronic device has a plurality of high thermal conductivity materials whose other ends (222) opposite to the one end contact the cooling body, and whose other ends are aligned along an opposing surface (3a) of the cooling body that faces the heat dissipation sheet.

2. The electronic device according to claim 1 , wherein the number of contact areas or contact points between the plurality of highly thermally conductive materials and the cooling body is greater than the number of contact areas or contact points between the plurality of highly thermally conductive materials and the electronic component.

3. The heat dissipation sheet further includes an insulating layer (25) disposed on the electronic component; The electronic device according to claim 1 , wherein the fixing layer fixes the highly thermally conductive material onto the insulating layer.

4. The electronic device according to claim 1 , wherein the plurality of high thermal conductivity materials are graphite or carbon nanotubes.

5. The electronic device according to claim 4 , wherein the plurality of high thermal conductivity materials are strips of graphite.

6. 6. The electronic device according to claim 5, wherein the plurality of high thermal conductivity materials are arranged apart from each other, and notches (223) are formed in a direction (D2) perpendicular to the orientation direction in which the plurality of high thermal conductivity materials are arranged.

7. The electronic device according to claim 5 , wherein the plurality of high thermal conductivity materials are arranged apart from each other and divided in a direction (D2) perpendicular to an orientation direction in which the plurality of high thermal conductivity materials are arranged.

8. 5. The electronic device according to claim 4, wherein the other ends of the plurality of highly thermally conductive materials are covered with a metal film (24).

9. 9. The electronic device according to claim 1, wherein the fixing layer is an adhesive made of an epoxy-based resin material, a urethane-based resin material, or an acrylic-based resin material.

10. 10. The electronic device according to claim 9, wherein the adhesive contains a filler made of one of inorganic oxides, nitrides, graphite, Ag, and Cu.

11. 9. The electronic device according to claim 1, wherein the fixing layer is a solder or sintered metal material.

12. 9. The electronic device according to claim 1, further comprising a pressure mechanism (4) for applying pressure to and fixing the heat dissipation sheet via at least one of the electronic component and the cooling body.

13. Forming an adhesive layer (200) on the prepared electronic component (1) by coating; placing a sheet having a plurality of high thermal conductive materials on the adhesive layer, and pressing the sheet toward the electronic component using a jig (J), and fixing one end (221) of the plurality of high thermal conductive materials to the adhesive layer while aligning the position of the other end (222) opposite to the one end; A method for manufacturing an electronic device, comprising: placing a cooling body (3) at the aligned other end, then pressing the cooling body against the electronic component, and thermally connecting the cooling body to multiple of the high thermal conductivity materials.

14. 14. The method for manufacturing an electronic device according to claim 13, wherein forming the adhesive layer on the electronic component comprises forming an insulating layer (25) made of an insulating resin material on the surface of the electronic component, and then laminating the adhesive layer on the insulating layer.

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