Thermal interface structure, thermal interface structure body, method for manufacturing thermal interface structure body, and method for forming thermal interface structure

Abstract

[Problem] To provide a thermal interface structure which, even if there are fine irregularities on opposing surfaces of two components such as a heating element and a heat sink, is tightly attached to the opposing surfaces to obtain high heat transfer efficiency, is easy to mount, can maintain assembly accuracy, and can maintain stable quality even after assembly. [Solution] A thermal interface structure is provided with: a porous substrate (2) having excellent thermal conductivity, the porous substrate (2) having front and back plate surfaces facing each of two members (91, 92), the porous substrate (2) having a plurality of through-holes (20) extending in the thickness direction and opening in the front and back plate surfaces; and a heat-conducting material (3) which maintains fluidity at least in a use temperature environment in which the heat conduction is performed, which fills the through-holes (20) of the porous substrate (2), and which is in close contact with the opposing surfaces of the two members.

Description

Technical Field

[0001] The present invention relates to a thermal interface structure arranged between two components to promote heat conduction between the two components. Background Art

[0002] As such a thermal interface structure, a thermal interface material such as a thermally conductive silicone sheet, thermally conductive tape, or thermally conductive paste has been conventionally used between a heat generating element such as a semiconductor chip and a heat sink serving as a cooler (see, for example, Patent Document 1).

[0003] Thermally conductive silicone sheets and thermally conductive tapes are inherently conformable and easy to handle. However, if there are tiny bumps on the opposing surfaces of the heating element or radiator, an air layer will be formed, resulting in an increase in thermal resistance and deviation, which will reduce the heat transfer efficiency. On the other hand, thermal conductive paste has fluidity and can adhere tightly to the opposing surfaces with the above-mentioned bumps, but if the coating thickness is uneven, for example, an air layer will also be easily generated, and the assembly accuracy will also be reduced. In addition, such a paste alone will have a film thickness of at least 50μm to 100μm, and the generation of large interfacial thermal resistance is unavoidable. Moreover, there is a concern that the paste may fall off after assembly, which makes it difficult to handle, unstable, and prone to quality deviations.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 11-58591. Summary of the Invention

[0007] Problems to be solved by the invention

[0008] Therefore, in view of the above situation, the problem to be solved by the present invention is to provide a thermal interface structure that can adhere tightly to the opposing surfaces even if there are fine bumps and depressions on the opposing surfaces of two components such as a heating element and a heat sink, thereby obtaining high heat transfer efficiency, being easy to handle and maintaining assembly accuracy, and maintaining stable quality after assembly.

[0009] Technical means to solve the problem

[0010] The present invention includes the following aspects.

[0011] (1) A thermal interface structure, which is arranged between two components and is used to promote heat conduction, characterized in that it includes: a porous substrate with good thermal conductivity, which has front and back plate surfaces facing the two components respectively, and has a plurality of through holes extending in the thickness direction and opening on the front and back plate surfaces; and a thermally conductive material, which has fluidity at least under the operating temperature environment for the heat conduction, is filled in the through holes of the porous substrate, and is in close contact with the opposing surfaces of the two components.

[0012] (2) The thermal interface structure according to (1), wherein the thermally conductive material is in the form of a liquid, a semisolid, an aggregate of fine particles, or a combination thereof having good thermal conductivity under the operating temperature environment.

[0013] (3) The thermal interface structure according to (1) or (2), wherein the thermally conductive material is in a solid state with good thermal conductivity at normal temperature (room temperature).

[0014] (4) A thermal interface structure, which is arranged between two components and is used to promote heat conduction, comprising: a porous substrate with good thermal conductivity, which has front and back plate surfaces facing the two components respectively, and has a plurality of through holes extending in the thickness direction and opening on the front and back plate surfaces; and a thermal conductive material, which is composed of a fusible alloy with a melting point below 150°C, filled in the through holes of the porous substrate, and tightly adhered to the opposite surfaces of the two components, and the thermal interface structure is used in an environment with a temperature lower than the melting point of the thermal conductive material.

[0015] (5) The thermal interface structure according to (1) or (4), wherein the thermally conductive material is further interposed between the plate surface around the opening of the porous substrate and the component.

[0016] (6) The thermal interface structure according to (1) or (4), wherein the thermal interface structure includes a clamping unit that elastically clamps the porous substrate between the two members.

[0017] (7) A thermal interface structure used in any one of the thermal interface structures described in (1) to (3), comprising: the porous substrate; and a thermally conductive material filled in the through holes of the porous substrate and also present on the front and back surfaces of the plate, which is in a solid state with good thermal conductivity at normal temperature (room temperature) and has fluidity under the operating temperature environment for the heat conduction.

[0018] (8) A thermal interface structure used in the thermal interface structure described in (4), comprising: the porous substrate; and a thermally conductive material composed of a fusible alloy having a melting point below 150°C, filled in the through holes of the porous substrate and also present on the front and back surfaces of the plate, in a solid state with good thermal conductivity at normal temperature (room temperature), and the thermal interface structure is used in an environment with a temperature lower than the melting point of the thermally conductive material.

[0019] (9) A method for manufacturing a thermal interface structure, which is the method for manufacturing a thermal interface structure described in (7) or (8), wherein the thermal conductive material is fluidized by heating, and after the thermal conductive material is filled in the through holes of the porous substrate, the thermal conductive material is cured by returning to normal temperature (room temperature).

[0020] (10) A method for forming a thermal interface structure, which uses the thermal interface structure described in (7) or (8), wherein the thermal interface structure is set between two components, at least one component is heated to fluidize the thermal conductive material of the thermal interface structure and tightly adhere to the opposing surfaces of the two components, and then the temperature is restored to normal temperature (room temperature) to solidify the thermal conductive material.

[0021] Effects of the Invention

[0022] According to the thermal interface structure of the present invention, even if there are fine bumps on the opposing surfaces of two components such as a heating element or a heat sink, the thermally conductive material is in close contact with the opposing surfaces, and the thermally conductive material transfers heat, and the heat is also transferred to the porous substrate filled with the thermally conductive material. Heat can be efficiently transferred through the porous substrate with good thermal conductivity, and a high heat transfer efficiency can be obtained overall.

[0023] Furthermore, because the porous substrate functions as a conformable core material, handling is easy and excellent assembly precision can be achieved. Furthermore, because the thermally conductive material is filled into the through-holes of the porous substrate, even if the assembled thermally conductive material is fluid, it is prevented from flowing down, maintaining stable quality and, in other words, excellent heat transfer efficiency over the long term. Furthermore, because the thermally conductive material enters the through-holes, an excessive thickness of thermally conductive material is avoided between the porous substrate and the component, preventing an increase in contact thermal resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a conceptual diagram showing the thermal interface structure of the present invention.

[0025] Figure 2 1 and 2 are explanatory diagrams showing the steps of constructing the thermal interface structure.

[0026] Figure 3 1 and 2 are explanatory diagrams showing other steps of constructing the thermal interface structure.

[0027] Figure 4 FIG. 1 is an explanatory diagram showing another step of constructing the thermal interface structure.

[0028] Figure 5 FIG. 1 is an explanatory diagram showing another step of constructing the thermal interface structure.

[0029] Figure 6 This figure illustrates thermal resistance measurement experiments conducted on various samples of thermal interface structures.

[0030] Figure 7 FIG. 1 is an explanatory diagram showing another step of constructing the thermal interface structure. DETAILED DESCRIPTION

[0031] Next, embodiments of the present invention will be described in detail with reference to the drawings.

[0032] like Figure 1 As shown, the thermal interface structure S of the present invention is arranged between two components, such as a heat-generating element 91 such as a semiconductor chip and a heat sink 92 serving as a cooler, to promote heat conduction between the two components. Specifically, it is formed by a thermal interface structure 1, which includes: a porous substrate 2 with good thermal conductivity, which has front and back plate surfaces 21 and 22 facing the two components (91, 92) respectively, and has a plurality of through-holes 20 extending in the thickness direction and opening on the front and back plate surfaces; and a thermal conductive material 3, which is filled in the through-holes 20 of the porous substrate 2 and is in close contact with the facing surfaces 91a and 92a of the two components (91, 92). The thermal conductive material 3 in this example maintains fluidity at least under the operating temperature environment for the above-mentioned heat conduction.

[0033] In the thermal interface structure S of the present invention, even if there are minute irregularities on the opposing surfaces of the two components (91, 92), the thermally conductive material 3 remains in close contact with the opposing surfaces 91a, 92a, and the thermally conductive material 3 transfers heat. Furthermore, heat is also transferred to the porous substrate 2 filled with the thermally conductive material 3, enabling efficient heat transfer through the porous substrate 2. In this example, the two components 91, 92 are connected by a mounting member 8, sandwiching the thermal interface structure S in between and maintaining a state of surface pressure. The mounting member 8 shown in the figure is an example and preferably comprises a leaf spring, a wire spring, or the like, serving as a clamping means for elastically clamping the thermal interface structure 1 composed of the porous substrate 2 and the thermally conductive material 9 between the two components 91 and 92. A structure connected using such a mounting member 8 can be easily disassembled. Of course, instead of such a detachable mounting structure, fixation by brazing or welding can also be performed.

[0034] Porous substrate 2 can widely use the metal material and alloy thereof of excellent thermal conductivity such as aluminium, iron, copper.In the case of copper etc., preferably use the lotus-shaped porous metal formed body with a plurality of pores extending in one direction formed by metal solidification method, the porous plate formed by cutting in the direction perpendicular to the extending direction of the pore.But porous substrate of the present invention certainly also comprises the structure that utilizes drill bit or laser etc. to set through hole.

[0035] The lotus-shaped porous metal formed body can be formed by a known method such as a Pressurized Gas Method (for example, a method disclosed in Japanese Patent Gazette No. 4235813), a Thermal Decomposition Method, etc. The through-holes of the porous plate cut out from the lotus-shaped porous metal formed body are the pores divided by the cutting. In addition to the through-holes, there are also bottomed holes that are not penetrated (the holes that are cut off at the position where the pores are interrupted), and such bottomed holes also have the effect of increasing the contact area with the heat-conducting material 3. By using the porous plate cut out from the lotus-shaped porous metal formed body, the porous substrate 2 can be obtained easily and at low cost.

[0036] Such a porous substrate 2 functions as a conformable core material, is easy to handle, and achieves excellent assembly precision. Furthermore, since the thermally conductive material 3 is filled in the through-holes 20 of the porous substrate 2, it remains within the through-holes 20 even after assembly, preventing it from flowing outward, thereby maintaining excellent heat transfer efficiency over a long period of time.

[0037] The thermally conductive material 3 may include, for example, a liquid such as a liquid metal with good thermal conductivity that maintains fluidity from room temperature to the operating temperature; a gel- or sol-like semi-solid such as a thermally conductive gel sheet or thermally conductive grease (including those containing thermally conductive fillers); an aggregate of fine particles such as fine metal powder; or a combination thereof. Fillers widely include known fillers such as graphite, metal powder (including columnar structures), and ceramic powder. In other words, "fluidity" in the present invention encompasses deformable materials such as semi-solids and aggregates of fine particles.

[0038] The heat conducting material 3 is preferably solid at room temperature. Figure 7 As shown in (a), a thermal interface structure 1 can be constructed from a porous substrate 2 and a thermally conductive material 3 that is solid at room temperature, significantly improving handleability. For example, a fusible alloy having a melting point of 150°C or less is preferred, and can be used even in environments with temperatures lower than the melting point of the thermally conductive material. Specifically, such a fusible alloy is preferably an alloy containing one or more low-melting-point metals selected from Bi (bismuth), Pb (lead), Cd (cadmium), Sn (tin), In (indium), and Ga (gallium).

[0039] like Figure 1 As shown in the partially enlarged view, such a thermally conductive material 3 is preferably structured as follows: it is also located between the plate surface 22 (21) around the opening of the through hole 20 of the porous substrate 2 and the relative surfaces 92a (91a) of the relative components to prevent the formation of an air layer caused by tiny bumps between the two surfaces.

[0040] Then, based on Figure 2 The steps of forming the thermal interface structure S are described as follows. Figure 2 As shown in (a), a porous substrate 2 is placed on a component 91, and a heat conductive material 3 having fluidity at room temperature is flowed into and filled into the through-holes 20 from the through-hole openings on the upper surface. At this time, the heat conductive material 3 is supplied to such an extent that it leaks from the openings.

[0041] Then, if Figure 2 As shown in (b), another component 92 is placed on the upper surface of the porous substrate 2. As a result, the portion of the thermal conductive material 3 located above the opening is in close contact with the lower surface of the component 92. Figure 2 As shown in (c), the two components 91 and 92 are connected using the mounting member 8, sandwiching the thermal interface structure S and maintaining it under surface pressure. This stabilizes the thermal interface structure S. Even if the thermal conductive material 3 is in a form other than a liquid, such as a melt or a powder aggregate, it can be similarly formed by flowing from the upper surface of the porous substrate 2.

[0042] In addition, as another method, Figure 3 As shown in (a), before placing a porous substrate 2 on a component 91, a thermally conductive material 3 in liquid, sol-like or powder aggregate is laid on the component 91 in an area corresponding to the lower surface of the porous substrate 2, and the porous substrate 2 is placed thereon, thereby filling the thermally conductive material 3 into the through hole 20 of the porous substrate 2 from the opening on the lower surface side of the through hole. Figure 3 Steps (b) and (c) are the same as above Figure 2 The steps are the same as

[0043] In addition, especially when the heat conductive material 3 is a gel having a certain degree of viscosity, such as Figure 4 、 Figure 5 As shown, a heat conductive material 3 may be prepared and made into a plate shape, and arranged on one side or both sides of the porous substrate 2 placed on a component 91 ( Figure 4 Configured on both sides, Figure 5Only arranged on the upper surface side), press the other component 92 downward from it, so that the thermal conductive material 3 is filled into the interior from the opening of the porous substrate 2. The steps after filling are the same as above Figure 2 same.

[0044] In addition, as other methods, such as Figure 7 As shown in (a), a thermal interface structure 1 consisting of a porous substrate 2 and a thermally conductive material 3 that is solid at room temperature is prepared. Figure 7 In the state where the heat conducting material 3 is sandwiched between the components 91 and 21 as shown in (b) and (c), the heat conducting material 3 is heated to fluidize. Figure 7 As shown in (d), the heat conductive material 3 and the components 91 and 92 are in close contact. Then, after returning to normal temperature (room temperature) and solidifying, Figure 7 As shown in (e), the two components 91 and 92 are connected using a mounting component 8, and the thermal interface structure S is sandwiched in the middle to maintain a state in which surface pressure is applied. Specifically, for example, consider making the thermal conductive material 3 a low-melting-point metal with a melting point of 80°C, and setting the thermal interface structure 1 between the two components, the CPU and the cooling component (such as a fin). After heating to the upper limit operating temperature of the CPU (such as 80°C), the low-melting-point metal is made to adhere and flow, and then the CPU temperature is managed to be lower than the melting point temperature. Since the low-melting-point metal maintains a solid state, it is possible to suppress the material 3 from leaking between the components. It is also possible to use the mounting component 8 to apply surface pressure before returning to room temperature.

[0045] Here, the thermal interface structure 1 is formed by heating a thermally conductive material 3, such as a low-melting-point metal having a melting point of 80°C, to fluidize it, filling it into the through-holes of the porous substrate 2, and then returning it to normal temperature (room temperature) to solidify it. This allows such a thermal interface structure 1 to be prepared in advance and installed between the two components 91 and 92, improving management, construction efficiency, and safety.

[0046] While the embodiments of the present invention have been described above, the present invention is not limited to these embodiments and can, of course, be implemented in various forms within the scope not departing from the gist of the present invention.

[0047] Example

[0048] The following describes the results of thermal resistance measurement experiments conducted on various samples of thermal interface structures.

[0049] (sample)

[0050] Regarding thermal interface structures, such as Figure 6As shown, Example 1 in which a thermal interface structure composed of a porous substrate and a heat-conductive material of the present invention is set between two components (between a heater and a copper block), Comparative Example 1 in which only silicone oil is set between the components, Comparative Example 2 in which only liquid metal is set between the components, and Comparative Example 3 in which only the above-mentioned porous substrate is set between the components are prepared.

[0051] A 0.2 mm thick porous plate cut from a lotus-shaped porous copper molded body was used as the porous substrate in Example 1 and Comparative Example 3. Thermalright Silverking liquid metal compound (thermal conductivity 79 W / mK) was used as the liquid metal in Example 1 and Comparative Example 2.

[0052] (Thermal resistance measurement method)

[0053] like Figure 6 As shown in the figure, the structure of the sample (Example 1 / Comparative Example 1 / Comparative Example 2 / Comparative Example 3) with a thermal interface structure between the heater and the copper block was formed. When a predetermined load was applied, the thermal resistance value (R t ). The thermal resistance is calculated using the following formula.

[0054] R t =(T1-T2) / (QQ Leak )

[0055] R t :Thermal resistance (K / W)

[0056] T1: Heater temperature (K)

[0057] T2: Cooling fin temperature (K)

[0058] Q: Power consumption (W)

[0059] Q Leak : Leakage power (w)

[0060] The specifications of each component are as follows.

[0061] Axial-flow fan: NMB 06025SA-12T-AA, 60mm in height, 25mm in thickness, DC12V.

[0062] Radiator: External dimensions: 60mm x 60mm x 2mm; central heating surface: 30mm x 30mm x 2mm.

[0063] Heater: Sheath heater: 100V-150W 3 pieces Leakage heat coefficient: 0.07771.

[0064] Temperature sensor: Heater: Armored thermocouple, T-type, Class 2 φ0.5; Copper block: Armored thermocouple, T-type, Class 2 φ1.0; Cooling fin inlet (air temperature): Glass-covered thermocouple, T-type, Class 2 φ0.5.

[0065] Axial-flow fan: DC power supply PW24-1.5AQ manufactured by TEXIO.

[0066] Heater power supply: DC power supply PSW-720M160 manufactured by TEXIO.

[0067] Data logger: Graphtec GL840 manufactured by Graphtec Corporation.

[0068] The results are shown in Table 1 below. The structure of Example 1 achieved the lowest thermal resistance, confirming the effectiveness of the present invention. Comparative Example 1, using only silicone oil, and Comparative Example 2, using only liquid metal, are believed to have higher thermal resistance than the porous substrate and, inevitably, a certain degree of film thickness, resulting in an increase in thermal resistance compared to Example 1. Comparative Example 3, using only the porous substrate, is believed to have a small gap, or air layer, between the two components (the heater and the copper block), resulting in an increase in thermal resistance compared to the other examples.

[0069] [Table 1]

[0070]

[0071] Description of Reference Numerals

[0072] 1 Thermal interface structure

[0073] 2 porous substrates

[0074] 3. Thermally conductive materials

[0075] 8. Installing components

[0076] 20 through holes

[0077] 21, 22 board

[0078] 91, 92 parts

[0079] 91a, 92a opposite surfaces

[0080] S thermal interface structure.

Claims

1. A thermal interface structure, which is arranged between two components to promote heat conduction, characterized in that: include: A porous substrate with good thermal conductivity, having front and back plate surfaces facing the two components respectively, and having a plurality of through holes extending in the thickness direction and opening on the front and back plate surfaces; and A heat conductive material has fluidity at least in a use temperature environment where the heat conduction is performed, is filled in the through-holes of the porous substrate, and is in close contact with the facing surfaces of the two members.

2. The thermal interface structure according to claim 1, wherein: The thermally conductive material is in the form of a liquid, a semisolid, an aggregate of fine particles, or a combination thereof having good thermal conductivity under the operating temperature environment.

3. The thermal interface structure according to claim 1 or 2, wherein: The thermally conductive material is in a solid state with good thermal conductivity at normal temperature (room temperature).

4. A thermal interface structure disposed between two components for promoting heat conduction, comprising: A porous substrate with good thermal conductivity, having front and back plate surfaces facing the two components respectively, and having a plurality of through holes extending in the thickness direction and opening on the front and back plate surfaces; and A heat conductive material, which is composed of a fusible alloy having a melting point of 150° C. or less, is filled in the through-holes of the porous substrate and is in close contact with the facing surfaces of the two components. The thermal interface structure is used in an environment with a temperature lower than the melting point of the thermal conductive material.

5. The thermal interface structure according to claim 1 or 4, wherein: The thermally conductive material is further interposed between the plate surface around the opening of the porous substrate and the component.

6. The thermal interface structure according to claim 1 or 4, wherein: The thermal interface structure includes a clamping unit that elastically clamps the porous substrate between the two components.

7. A thermal interface structure, used in the thermal interface structure according to any one of claims 1 to 3, comprising: the porous substrate; and The thermally conductive material is filled in the through holes of the porous substrate and also exists on the front and back surfaces. It is in a solid state with good thermal conductivity at normal temperature (room temperature) and has fluidity under the operating temperature environment for the thermal conduction.

8. A thermal interface structure, used in the thermal interface structure according to claim 4, comprising: the porous substrate; and The thermally conductive material is composed of a fusible alloy having a melting point of 150° C. or less, is filled in the through-holes of the porous substrate, and is also present on the front and back surfaces of the substrate, and is in a solid state with good thermal conductivity at normal temperature (room temperature). The thermal interface structure is used in an environment with a temperature lower than the melting point of the thermally conductive material.

9. A method for manufacturing a thermal interface structure, which is the method for manufacturing a thermal interface structure according to claim 7 or 8, wherein: The thermally conductive material is heated to fluidize and filled into the through-holes of the porous substrate, and then returned to normal temperature (room temperature) to solidify the thermally conductive material.

10. A method for forming a thermal interface structure, using the thermal interface structure according to claim 7 or 8, wherein: The thermal interface structure is arranged between two components, At least one of the components is heated to fluidize the thermally conductive material of the thermal interface structure and bring it into close contact with the facing surfaces of the two components, and then the temperature is returned to normal (room temperature) to solidify the thermally conductive material.

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