Bonding layer, heat transfer device, and produciton method for bonding layer

Abstract

A bonding layer 40 disposed on the surface of a heat transfer body 20 comprises inorganic porous bodies 36 (including fibrous structures 30) and a bonding material 31. In a plurality of cross-sections C1-C5 that extend in parallel with the surface of the heat transfer body 20 and are evenly spaced, the inorganic porous bodies 36 are unevenly distributed such that there is a cross-section where the inorganic porous bodies 36 are not present, or such that the bonding layer 40 includes a first layer in which the proportion of the inorganic porous bodies 36 in the bonding layer 40 is a first proportion, and a second layer in which said proportion is a second proportion different from the first proportion.

Description

Bonding layer, heat transfer device, and method for manufacturing the bonding layer

[0001] The present disclosure relates to a bonding layer, a heat transfer device, and a method for manufacturing a bonding layer.

[0002] Various types of heat transfer devices that dissipate heat from a heat-generating body using a cooling member have been known. In such heat transfer devices, the heat-generating body is joined to the cooling member by a bonding layer. Japanese Patent Publication No. 2022-024016 (JP2022-024016A) discloses such a heat transfer device that can efficiently dissipate heat generated by a power semiconductor chip and prevent cracks from occurring in the solder, thereby preventing an increase in thermal resistance.

[0003] In conventional heat transfer devices, the positional relationship between the inorganic porous material such as inorganic fiber and the joining member such as solder in the joining layer is not specified.

[0004] The present disclosure has been made in consideration of these points, and aims to provide a new bonding layer, a heat transfer device, and a method for manufacturing a bonding layer that specifies the positional relationship between the inorganic porous body and the bonding member.

[0005] The bonding layer of the present disclosure comprises an inorganic porous body and a bonding material, and is disposed on the surface of a heat transfer body, and is characterized in that the inorganic porous body is unevenly distributed so that, in a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body, there are cross sections in which the inorganic porous body is not present, or the bonding layer includes a first layer in which the inorganic porous body occupies a first proportion in the bonding layer and a second layer in which the proportion is a second proportion different from the first proportion.

[0006] In the bonding layer of the present disclosure, the ratio of the inorganic porous material in the bonding layer in the cross section with the smallest ratio to the average ratio of the inorganic porous material in the cross sections may be within a range of 0 to 0.5.

[0007] The thickness of the bonding layer in a direction perpendicular to the surface of the heat transfer body may be 10 μm to 200 μm.

[0008] Furthermore, the ratio of the size of the proportion in the cross section where the inorganic porous body contacts the heat transfer body to the size of the proportion in the cross section at a thickness of 5 μm from the surface of the heat transfer body may be within a range of 0 to 0.8.

[0009] The inorganic porous body may have a space factor of 25% to 95%.

[0010] The ratio of the area of ​​the inorganic porous body in contact with the heat transfer body to the area of ​​the bonding material in contact with the heat transfer body may be 0.1 to 1.5.

[0011] Furthermore, a heat transfer target body may be placed on a surface of the bonding layer opposite to a surface on which the heat transfer body is placed, and a ratio of an area of ​​the inorganic porous body in contact with the heat transfer target body to an area of ​​the inorganic porous body in contact with the heat transfer body may be 0.4 to 2.5.

[0012] The thermal expansion coefficient at 100°C to 200°C may be 5 ppm / °C to 25 ppm / °C.

[0013] The difference in linear expansion coefficient between the inorganic porous body and the bonding material at 100°C to 200°C may be 0.1 ppm / °C to 15 ppm / °C.

[0014] The bonding material may be disposed between the inorganic porous bodies.

[0015] Furthermore, the bonding material may be disposed between the inorganic porous bodies in some or all of the cross sections where the inorganic porous bodies are present among the plurality of cross sections.

[0016] Furthermore, the ratio of the volume of the bonding material disposed between the inorganic porous bodies to the volume of the bonding material in the bonding layer may be 0% to 80%.

[0017] The bonding material disposed between the inorganic porous bodies may be sintered to the inorganic porous bodies.

[0018] The inorganic porous body may also contain inorganic fibers.

[0019] The inorganic fibers may also contain copper fibers.

[0020] The heat transfer device of the present disclosure comprises a heat transfer body and a bonding layer disposed on the surface of the heat transfer body, wherein the bonding layer has an inorganic porous body and a bonding material, and is characterized in that the inorganic porous body is unevenly distributed so that, in a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body, there are cross sections in which the inorganic porous body is not present, or the bonding layer includes a first layer in which the inorganic porous body occupies a first proportion in the bonding layer and a second layer in which the proportion is a second proportion different from the first proportion.

[0021] The method for manufacturing a bonding layer according to the present disclosure is a method for manufacturing a bonding layer to be placed on the surface of a heat transfer body, and is characterized by comprising the steps of: placing an inorganic porous body on the surface of the heat transfer body; melting a bonding material and supplying the molten bonding material to the surface of the inorganic porous body; and cooling the bonding material.

[0022] In addition, in the step of melting the bonding material and supplying the molten bonding material to the surface of the inorganic porous body, the molten bonding material may be applied to the surface of the inorganic porous body.

[0023] In addition, in the step of melting the bonding material and supplying the molten bonding material to the surface of the inorganic porous body, the molten bonding material may be impregnated into the inorganic porous body.

[0024] After the step of cooling the bonding material, another bonding material may be placed on the surface of the cooled bonding material.

[0025] The manufacturing method of a bonding layer according to the present disclosure is a manufacturing method of a bonding layer to be placed on a surface of a heat transfer body, and is characterized by comprising the steps of: placing a bonding material on the bonding layer; placing an inorganic porous body on the surface of the bonding material; melting a bonding material other than the bonding material and supplying the molten other bonding material to the surface of the inorganic porous body; and cooling the other bonding material.

[0026] 1 is a longitudinal cross-sectional view schematically illustrating a configuration of a heat transfer device according to an embodiment of the present disclosure; ６ 1 is a diagram for explaining a heat transfer device according to an embodiment of the present disclosure. FIG. 2 is a longitudinal cross-sectional view schematically showing another configuration of a heat transfer device according to an embodiment of the present disclosure. FIG. 3 is a longitudinal cross-sectional view schematically showing another configuration of a heat transfer device according to an embodiment of the present disclosure. FIG. 4 is a longitudinal cross-sectional view schematically showing another configuration of a heat transfer device according to an embodiment of the present disclosure. FIG. 5 is a longitudinal cross-sectional view schematically showing another configuration of a heat transfer device according to an embodiment of the present disclosure. FIG. 6 is a longitudinal cross-sectional view schematically showing another configuration of a heat transfer device according to an embodiment of the present disclosure.

[0027] Embodiments of the present disclosure will now be described with reference to the drawings. FIGS. 1A, 1B, and 2 to 9 are longitudinal cross-sectional views schematically illustrating various configurations of heat transfer devices according to the present embodiments. The heat transfer device according to the present embodiments is characterized in that a bonding layer for bonding a heat transfer body to a heat transfer target body includes an inorganic porous body and a bonding material, and the inorganic porous body is unevenly distributed in the width direction of the bonding layer. Note that uneven distribution of the inorganic porous body in the width direction of the bonding layer refers to non-uniform distribution of the inorganic porous body in the width direction of the bonding layer, specifically, the following: The inorganic porous body is locally distributed along the width direction of the bonding layer; The inorganic porous body is unevenly arranged across the width of the bonding layer; The inorganic porous body is unevenly distributed in the width direction of the bonding layer; The inorganic porous body is unevenly positioned in the width direction of the bonding layer; or The inorganic porous body is concentrated in a specific region along the width of the bonding layer. Furthermore, the heat transfer device according to the present embodiments is not limited in its field of application, and can be used to bond materials with different linear expansion coefficients. Examples include power semiconductor elements, LED elements, laser diodes and their mounting substrates, semiconductor devices, LED modules, semiconductor lasers, semiconductor manufacturing equipment, electrostatic chucks, heat exchangers, heaters, and the like.

[0028] 1A includes a heat transfer body 20 and a bonding layer 40 for bonding a heat transfer recipient 10 to the heat transfer body 20. The heat transfer recipient 10, such as a semiconductor, is bonded to the heat transfer body 20 by the bonding layer 40. When placed on the upper surface of the bonding layer 40, the heat transfer recipient 10 is cooled or heated by the heat transfer body 20 via the bonding layer 40. In this embodiment, a heat sink (cooling member) is used as the heat transfer body 20, and the heat transfer recipient 10 is cooled by the heat sink via the bonding layer 40. However, in another embodiment, a heating member may be used as the heat transfer body 20, and the heat transfer recipient 10 may be heated by the heating member via the bonding layer 40.

[0029] The heat transfer body 20 has a base 22 and rod- or plate-shaped protruding members 24 that protrude from the surface of the base 22 in a direction perpendicular to the surface, and a fluid made of liquid or gas such as a refrigerant flows between the protruding members 24. This cools the heat transfer body 20, and heat is transferred from the heat-transferred body 10 placed on the upper surface of the bonding layer 40 to the heat transfer body 20 via the bonding layer 40.

[0030] The bonding layer 40 includes a fiber structure 30 as an inorganic porous body and a bonding material 31. In the heat transfer device 1 shown in FIG. 1A , the fiber structure 30 is included in the inorganic porous body. That is, since many pores exist between the inorganic fibers in the fiber structure 30, the fiber structure 30 can also be considered an inorganic porous body. In the heat transfer device 1 shown in FIG. 1A , an inorganic porous body other than the fiber structure 30 (for example, a densely packed metal particle body or a metal bulk body containing voids) may be used as the inorganic porous body included in the bonding layer 40.

[0031] Examples of the bonding material 31 include a metal material such as solder or brazing filler, a metal paste, and a thermally conductive resin sheet. When the bonding material 31 is made of a metal material such as solder, the melting point of the bonding material 31 is, for example, approximately 300° C. When the bonding material 31 is made of a metal paste or a thermally conductive resin sheet, the manufacturing process may include a step of vaporizing the organic matter (such as a solvent) contained therein to obtain a bonding layer.

[0032] The fibrous structure 30 includes inorganic fibers such as copper fibers, and a bonding material 31 is disposed between the fibrous structures 30 (specifically, in the gaps between the inorganic fibers). When the fibrous structure 30 is composed of, for example, copper fibers, the melting point of the fibrous structure 30 is, for example, approximately 1,100°C, which is higher than the melting point of the bonding material 31. Furthermore, inorganic fibers other than metal fibers such as copper fibers may be used as the inorganic fibers. When copper fibers are used as the inorganic fibers, the thermal conductivity of the fibrous structure 30 can be improved. In such a fibrous structure 30, the inorganic fibers such as copper fibers may be directly fixed to each other, or the inorganic fibers may be fixed to each other by a second inorganic component having a component different from the component of the inorganic fibers. Furthermore, the bonding material 31 disposed between the fibrous structures 30 may be connected to the inorganic fibers of the fibrous structure 30 by sintering or the like. Furthermore, the ratio of the volume of the bonding material 31 disposed between the fibrous structures 30 to the volume of the bonding material 31 in the bonding layer 40 is 0% to 80%. 1 , the inorganic fibers constituting the fiber structure 30 are not in contact with the heat transfer target 10 or the heat transfer target 20. The ratio of the volume of the bonding material 31 disposed between the fiber structures 30 to the volume of the bonding material 31 in the bonding layer 40 is calculated from the true specific gravities of the bonding material 31 and the fiber structure 30. The true specific gravities of the bonding material 31 and the fiber structure 30 refer to the specific gravities of the bonding material 31 and the fiber structure 30 themselves, respectively, excluding voids.

[0033] The average fiber diameter of the inorganic fibers can be set arbitrarily as long as it does not interfere with the formation of the nonwoven fabric, but is preferably 1 μm to 100 μm, 2 μm to 100 μm, 5 μm to 100 μm, more preferably 10 μm to 100 μm, and even more preferably 10 μm to 80 μm. When the average fiber diameter of the inorganic fibers is within the above range, the bonding layer can achieve both thermal stress relaxation and thermal conductivity. Inorganic fibers having two different average fiber diameters may also be combined. The average fiber diameter of one inorganic fiber may be 1 μm to 40 μm, 5 μm to 30 μm, 10 μm to 25 μm, or 10 μm to 20 μm, while the average fiber diameter of the other inorganic fiber may be 10 μm to 100 μm, 20 μm to 100 μm, or 40 μm to 100 μm. These inorganic fibers may be used in combination or separately. When the average fiber diameter of the inorganic fibers is within the above range, the inorganic fibers are less likely to form clumps when formed into a nonwoven fabric, thereby imparting shape conformability to the fiber structure 30. The ratio of the thickness of the bonding layer 31 to the average fiber diameter of the inorganic fibers may be 1 to 200, 1 to 100, 1 to 50, 1 to 20, 1 to 10, or 1 to 5. When the ratio of the thickness of the bonding layer 31 to the average fiber diameter of the inorganic fibers is within the above range, the thermal conductivity of the bonding layer 31 in the thickness direction is improved. Furthermore, the cross-sectional shape of the inorganic fibers may be circular, elliptical, approximately rectangular, irregular, etc., but preferably contains inorganic fibers with at least a circular cross section. Inorganic fibers with a circular cross section are more likely to bend (curved) under stress than fibers with a prismatic cross section, for example, and the degree of bending of the inorganic fibers is less likely to vary depending on the location of stress, so the degree of bending also tends to be more uniform. Appropriate entanglement of inorganic fibers with curved portions tends to facilitate improved shape conformability and cushioning. Here, the circular cross section does not need to be a perfect circle, but may be a circular cross section that is easy to form a moderate curve under the stress experienced in the normal production of the fiber structure 30. In addition, the "average fiber diameter" in this specification refers to the average area diameter (for example, the average value of 20 fibers) obtained by calculating the cross-sectional area of ​​the inorganic fibers based on a vertical cross section at an arbitrary location of the fiber structure 30 photographed with a microscope (for example, using known software) and calculating the diameter of a circle having the same area as the cross-sectional area.

[0034] The fiber length of the inorganic fibers is preferably in the range of 0.01 mm to 20.0 mm, more preferably 0.01 mm to 10.0 mm, and even more preferably 0.1 mm to 5.0 mm. When the average fiber length is within the above range, for example, both thermal stress relaxation properties and uniform thermal conductivity can be achieved. Furthermore, when the fiber structure 30 of the present embodiment is produced by papermaking, the formation of so-called inorganic fiber clumps is expected to be reduced, making it easier to appropriately adjust the dispersion, and the sheet strength improvement effect due to the entanglement of the inorganic fibers is also easily achieved. The fiber structure 30 is not particularly limited, but examples include nonwoven fabrics, woven fabrics, and meshes. From the viewpoint of stress relaxation, nonwoven fabrics are preferred. Nonwoven fabrics may be produced by wet papermaking, dry papermaking, or spunbonding. In this specification, the "average fiber length" refers to the average value obtained by measuring, for example, 20 fibers under a microscope. Furthermore, "papermaking" refers to the production of paper or the like by milling raw materials.

[0035] The thermal conductivity of the bonding layer 40 can be measured using a laser flash method, a thermal wave analysis method, or the like. For example, the bonding layer 40 can be cut to a predetermined size and measured using a thermal diffusivity / thermal conductivity measuring device (ai-Phase Mobile M3, manufactured by ai-Phase Corporation). Alternatively, the value obtained by this measurement method may be compared and converted from values ​​obtained by measuring standard samples of copper material C1020, aluminum material A1050, and stainless steel material SUS304, which have known thermal conductivities.

[0036] As shown in Fig. 1A, the fiber structure 30 is present non-uniformly in the width direction of the bonding layer 40. Specifically, the fiber structure 30 is present in a lower region of the bonding layer 40 but not in an upper region. That is, among a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body 20 on which the bonding layer 40 is arranged, there are cross sections where the fiber structure 30 is not present. In Fig. 1A, five cross sections C are shown as a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body 20 on which the bonding layer 40 is arranged. １ ~C ５ Here, each cross section C １ ~C ５ Distance between cross sections C ５and the distance between the heat transfer body 20 and the cross section C １ The distance between the cross section C and the heat transfer object 10 is the same. ３ ~C ５ The fiber structure 30 exists in the cross section C １ , C ２ The fiber structure 30 is not present in the cross section C. ３ ~C ５ In some or all of the above, a bonding material 31 is disposed between the fiber structures 30 .

[0037] In addition, in such a bonding layer 40, a plurality of equally spaced cross sections C extending parallel to the surface of the heat transfer body 20 are formed. １ ~C ５ , the cross section (for example, cross section C ) where this ratio is the smallest with respect to the average value of the ratio of the fiber structure 30 in the bonding layer 40 . １ , C ２ ) is in the range of 0 to 0.5 (0 in the embodiment shown in FIG. 1 ). As a result, the fiber structure 30 is present non-uniformly in the width direction of the bonding layer 40.

[0038] The number of the multiple equally spaced cross sections extending parallel to the surface of the heat transfer body 20 on which the bonding layer 40 is arranged is not limited to 5. The number of cross sections can be any number, such as 3, 4, 8, 10, 20, etc., up to a predetermined threshold value.

[0039] 1B, a cross section C at a position 5 μm thick (the size indicated by reference symbol a in FIG. 1B) from the surface of the heat transfer body 20 ６ 1B , the ratio of the proportion of the fiber structure 30 in the bonding layer 40 that is in contact with the surface of the heat transfer body 20 to the proportion of the fiber structure 30 in the bonding layer 40 is within a range of 0 to 0.8. As such, in the bonding layer 40 shown in FIG. 1B , the fiber structure 30 is not dense near the surface of the heat transfer body 20.

[0040] The thickness of the bonding layer 40 in a direction perpendicular to the surface of the heat transfer body 20 on which the bonding layer 40 is disposed is 10 μm to 200 μm. The space factor of the fiber structure 30 in the bonding layer 40 is 25% to 95%, more preferably 25% to 90%, and even more preferably 35% to 80%. When the space factor of the fiber structure 30 in the bonding layer 40 is within the above range, both stress relaxation and good thermal conductivity can be achieved. Furthermore, a sufficient amount of inorganic fibers is ensured, thereby maintaining thermal conductivity and providing shape conformability. The space factor in this specification refers to the proportion of the inorganic fibers present in the volume of the bonding layer 40, and is also the proportion of the inorganic fibers to the total volume occupied by the inorganic fibers and voids in the fiber structure 30. The space factor is defined as the ratio of the area occupied by the inorganic fibers to the area inside the outer edge of the bonding layer 40 at the cut surface when the bonding layer 40 is cut. The bonding layer 40 has a thermal expansion coefficient of 5 ppm / °C to 25 ppm / °C at 100°C to 200°C. The difference in linear expansion coefficient between the fiber structure 30 and the bonding material 31 at 100°C to 200°C is 0.1 ppm / °C to 15 ppm / °C.

[0041] Next, a method for manufacturing such a heat transfer device 1 will be described. First, the bonding material 31 is melted and applied to the surface of the heat transfer body 20. Next, the bonding material 31 is cooled and solidified. In this manner, a thin layer or film of the bonding material 31 is formed on the surface of the heat transfer body 20. Then, the fiber structure 30 is disposed on the surface of the solidified thin layer or film of the bonding material 31. Here, the fiber structure 30 disposed on the surface of the bonding material 31 is formed by connecting inorganic fibers such as copper fibers to each other by sintering or the like. Next, new bonding material 31 is melted and the molten bonding material 31 is supplied to the surface of the fiber structure 30. As a result, some of the molten bonding material 31 penetrates into gaps between the inorganic fibers in the fiber structure 30, and the bonding material 31 that has penetrated into the gaps is connected to the inorganic fibers of the fiber structure 30. Next, the bonding material 31 is cooled and solidified. In this manner, a layer composed of the fiber structure 30 and the bonding material 31 is formed. Here, when a metal paste is used as the joining material 31, the metal paste is liquid and therefore does not require a manufacturing process for melting it. Instead, the joining layer 40 can be formed by adding a manufacturing process for vaporizing the organic matter contained therein and sintering the metal powder particles together. More specifically, because the metal paste contains organic matter and the metal powder particles are separated, the processes of vaporizing the organic matter and sintering the metal powder particles together are necessary. Furthermore, new joining material 31 is melted and supplied to the surface of the layer consisting of the fiber structure 30 and the joining material 31. Next, the joining material 31 is cooled and solidified. Finally, the heat transfer target 10 is placed on the joining layer 40. In this manner, the heat transfer device 1 shown in FIG. 1 is obtained.

[0042] 1A and 1B , the fiber structure 30 is unevenly distributed near the heat transfer body 20. Therefore, compared to a case where the fiber structure is uniformly distributed throughout the entire bonding layer, it is possible to improve the thermal conductivity and the stress relaxation property.

[0043] The heat transfer device according to this embodiment is not limited to the one shown in Figures 1A and 1B. The one shown in Figure 2 may also be used as the heat transfer device. The heat transfer device 2 shown in Figure 2 differs from the heat transfer device 1 shown in Figure 1 in that a portion of the inorganic fibers constituting the fiber structure 30 of the bonding layer 40 is in contact with the heat transfer body 20, but the other configuration is substantially the same as the heat transfer device 1 shown in Figure 1. In describing the configuration of the heat transfer device 2 shown in Figure 2, a description of the configuration that is substantially the same as the heat transfer device 1 shown in Figure 1 will be omitted.

[0044] In the heat transfer device 2 shown in Fig. 2 , the fiber structure 30 is also present non-uniformly in the width direction of the bonding layer 40. Specifically, the fiber structure 30 is present in a lower region of the bonding layer 40 but not in an upper region. That is, among a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body 20 on which the bonding layer 40 is arranged, there are cross sections where the fiber structure 30 is not present. In Fig. 2 , five cross sections C are shown as a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body 20 on which the bonding layer 40 is arranged. １ ~C ５ Here, each cross section C １ ~C ５ Distance between cross sections C ５ and the distance between the heat transfer body 20 and the cross section C １ The distance between the cross section C and the heat transfer object 10 is the same. ３ ~C ５ The fiber structure 30 exists in the cross section C １ , C ２ The fiber structure 30 is not present in the cross section C. ３ ~C ５ In some or all of the above, a bonding material 31 is disposed between the fiber structures 30 .

[0045] As shown in Fig. 2, a portion of the inorganic fibers constituting the fiber structure 30 contacts the heat conductor 20 at the location indicated by reference numeral 32. This allows for improved thermal conductivity in the bonding layer 40 compared to the heat transfer device 1 shown in Fig. 1. Furthermore, a portion of the inorganic fibers constituting the fiber structure 30 is not sintered to the heat conductor 20 at the location indicated by reference numeral 32, so that the location at which a portion of the inorganic fibers constituting the fiber structure 30 contacts the heat conductor 20 changes when the heat conductor 20 or the bonding layer 40 expands or contracts. This prevents the fiber structure 30 from following the heat conductor 20 when the heat conductor 20 thermally expands or contracts, thereby preventing problems such as cracking from occurring between the heat conductor 20 and the bonding layer 40.

[0046] 2 , the ratio of the area of ​​the fiber structure 30 in contact with the heat transfer body 20 to the area of ​​the bonding material 31 in contact with the heat transfer body 20 is 0.1 to 1.5. By setting the ratio of the area of ​​the fiber structure 30 in contact with the heat transfer body 20 to the area of ​​the bonding material 31 in contact with the heat transfer body 20 to 0.1 to 1.5, it is possible to prevent the fiber structure 30 from becoming dense on the surface of the heat transfer body 20 while ensuring sufficient thermal conductivity between the heat transfer body 20 and the bonding layer 40, and therefore the heat transfer body 20 and the heat-transferred body 10 can be sufficiently bonded by the bonding layer 40.

[0047] Next, a method for manufacturing such a heat transfer device 2 will be described. First, a fibrous structure 30 is placed on the surface of a heat transfer body 20. Here, the fibrous structure 30 placed on the surface of the heat transfer body 20 is composed of inorganic fibers, such as copper fibers, sintered together. Next, a bonding material 31 is melted and supplied to the surface of the fibrous structure 30. As a result, a portion of the molten bonding material 31 penetrates into gaps between the inorganic fibers in the fibrous structure 30, and the bonding material 31 that has penetrated into the gaps connects to the inorganic fibers of the fibrous structure 30. Next, the bonding material 31 is cooled and solidified. In this manner, a layer consisting of the fibrous structure 30 and the bonding material 31 is formed. Further, new bonding material 31 is melted and supplied to the surface of the layer consisting of the fibrous structure 30 and the bonding material 31. Next, the bonding material 31 is cooled and solidified. Finally, a heat transfer target 10 is placed on the bonding layer 40. In this manner, the heat transfer device 2 shown in FIG. 2 is obtained.

[0048] In the bonding layer 40 and the heat transfer device 2 shown in Fig. 2, the fiber structure 30 is unevenly distributed near the heat transfer body 20 and is in contact with the heat transfer body 20. Therefore, compared to a bonding layer in which the fiber structure is uniformly distributed throughout the entire bonding layer, it is possible to improve thermal conductivity and stress relaxation. Furthermore, compared to the bonding layer 40 and the heat transfer device 1 shown in Fig. 1, it is possible to further improve thermal conductivity.

[0049] Alternatively, the heat transfer device shown in Fig. 3 may be used. The heat transfer device 3 shown in Fig. 3 differs from the heat transfer device 2 shown in Fig. 2 in that a portion of the inorganic fibers constituting the fiber structure 30 of the bonding layer 40 is in contact with the heat transfer target 10, but other configurations are substantially the same as those of the heat transfer device 2 shown in Fig. 2. In describing the configuration of the heat transfer device 3 shown in Fig. 3, a description of the configuration that is substantially the same as that of the heat transfer device 2 shown in Fig. 2 will be omitted.

[0050] As shown in Figure 3, a portion of the inorganic fibers constituting the fiber structure 30 contacts the heat-transfer target 10 at the location indicated by reference numeral 34. This allows for further improvement in thermal conductivity in the bonding layer 40 compared to the heat transfer device 2 shown in Figure 2. Furthermore, when the heat-transfer target 10 or the bonding layer 40 expands or contracts, the location at which a portion of the inorganic fibers constituting the fiber structure 30 contacts the heat-transfer target 10 changes. This allows for the heat-transfer target 10 not to follow the fiber structure 30 when the bonding layer 40 thermally expands or contracts, thereby preventing problems such as cracking from occurring between the heat-transfer target 10 and the bonding layer 40.

[0051] 3 , the ratio of the area of ​​the fiber structure 30 in contact with the heat-transferred body 10 to the area of ​​the fiber structure 30 in contact with the heat transfer body 20 is 0.4 to 2.5. In this case, the bonding layer 40 can exhibit sufficient thermal conductivity, and problems such as cracking can be prevented from occurring between the heat transfer body 20 and the bonding layer 40 or between the heat-transferred body 10 and the bonding layer 40.

[0052] Next, a method for manufacturing such a heat transfer device 3 will be described. First, a fibrous structure 30 is placed on the surface of a heat transfer body 20. Here, the fibrous structure 30 placed on the surface of the heat transfer body 20 is composed of inorganic fibers, such as copper fibers, sintered together. Next, a bonding material 31 is melted and supplied to the surface of the fibrous structure 30. As a result, a portion of the molten bonding material 31 penetrates into gaps between the inorganic fibers in the fibrous structure 30, and the bonding material 31 that has penetrated into the gaps connects to the inorganic fibers of the fibrous structure 30. Note that when the molten bonding material 31 is supplied to the surface of the fibrous structure 30, a portion of the fibrous structure 30 is exposed to the outside from the upper surface of the bonding material 31. Next, the bonding material 31 is cooled and solidified. In this way, a layer consisting of the fibrous structure 30 and the bonding material 31 is formed. Finally, a heat transfer target 10 is placed on the bonding layer 40. At this time, the heat transfer target 10 is brought into contact with the fibrous structure 30. In this way, the heat transfer device 3 shown in FIG. 3 is obtained.

[0053] 3, the fiber structure 30 is in contact with the heat transfer body 20 and the heat transfer target body 10. Therefore, compared to a bonding layer in which the fiber structure is not in contact with the heat transfer body or the heat transfer target body, the thermal conductivity can be improved.

[0054] Alternatively, the heat transfer device shown in Fig. 4 may be used. The heat transfer device 4 shown in Fig. 4 differs from the heat transfer device 2 shown in Fig. 2 in that the bonding layer 40 is composed of a fiber structure 30 and a bonding material 31, but the bonding material 31 does not penetrate between the inorganic fibers that make up the fiber structure 30. The rest of the configuration is substantially the same as that of the heat transfer device 2 shown in Fig. 2. In describing the configuration of the heat transfer device 4 shown in Fig. 4, a description of the configuration that is substantially the same as that of the heat transfer device 2 shown in Fig. 2 will be omitted.

[0055] In the heat transfer device 4 shown in Fig. 4, the bonding layer 40 is configured with two layers: a layer of a fiber structure 30 arranged closer to the heat transfer body 20, and a layer of a bonding material 31 arranged closer to the heat transfer body 10. The inorganic fibers that make up the fiber structure 30 are in contact with the heat transfer body 20. The inorganic fibers that make up the fiber structure 30 are also connected to the bonding material 31. In this case, when the heat transfer body 20 undergoes thermal expansion or thermal contraction, the fiber structure 30, whose inorganic fibers are in contact with the heat transfer body 20, also expands or contracts in accordance with the heat transfer body 20. This makes it possible to prevent problems such as cracking from occurring between the heat transfer body 20 and the bonding layer 40 when the heat transfer body 20 undergoes thermal expansion or thermal contraction.

[0056] In the heat transfer device 4 shown in Fig. 4, the bonding material 31 does not penetrate into the gaps between the inorganic fibers of the fiber structure 30. Furthermore, the bonding material 31 may be, for example, a metal material such as solder or brazing material, a metal paste, or a thermally conductive resin sheet. In this case, the melting point of the bonding material 31 is, for example, approximately 300°C. Furthermore, the metal material constituting the bonding material 31 may be the same type of metal (e.g., copper) as the material of the inorganic fibers of the fiber structure 30.

[0057] Next, a method for manufacturing such a heat transfer device 4 will be described. First, a fiber structure 30 is placed on the surface of a heat transfer body 20. Here, the fiber structure 30 placed on the surface of the heat transfer body 20 is made of inorganic fibers such as copper fibers sintered together. Next, a bonding material 31 is melted and applied to the surface of the fiber structure 30. The applied bonding material 31 is then cooled. At this time, some of the inorganic fibers constituting the fiber structure 30 are connected to the bonding material 31. Finally, a heat transfer target body 10 is placed on the bonding layer 40. In this manner, the heat transfer device 4 shown in FIG. 4 is obtained.

[0058] 4, the bonding layer 40 and the heat transfer device 4 are configured of two layers, namely, the fiber structure 30 and the bonding material 31, and the fiber structure 30 is disposed near the heat transfer body 20. Therefore, compared to a case where the fiber structure is uniformly present throughout the entire bonding layer, it is possible to improve thermal conductivity and stress relaxation.

[0059] Alternatively, the heat transfer device shown in Fig. 5 may be used. The heat transfer device 5 shown in Fig. 5 differs from the heat transfer device 4 shown in Fig. 4 in that a bonding material 31 is embedded in a partial region of the fiber structure 30, but other configurations are substantially the same as those of the heat transfer device 4 shown in Fig. 4. In describing the configuration of the heat transfer device 5 shown in Fig. 5, a description of the configuration that is substantially the same as that of the heat transfer device 4 shown in Fig. 4 will be omitted.

[0060] 5 , the bonding layer 40 is configured with two layers: a layer of the fiber structure 30 disposed closer to the heat transfer body 20, and a layer of the bonding material 31 disposed closer to the heat transfer body 10. However, in some regions of the fiber structure 30 (specifically, the region farther from the heat transfer body 20), some of the bonding material 31 penetrates into gaps between the inorganic fibers. The inorganic fibers that make up the fiber structure 30 are connected to the bonding material 31 that penetrates into the gaps between the fiber structures 30.

[0061] Next, a method for manufacturing such a heat transfer device 5 will be described. First, a fiber structure 30 is placed on the surface of a heat transfer body 20. Here, the fiber structure 30 placed on the surface of a bonding material 31 is made of inorganic fibers such as copper fibers sintered to each other. Next, the bonding material 31 is melted and applied to the surface of the fiber structure 30. At this time, a portion of the melted bonding material 31 penetrates into the gaps between the inorganic fibers in the fiber structure 30. Then, the applied bonding material 31 is cooled. At this time, a portion of the inorganic fibers constituting the fiber structure 30 are connected to the bonding material 31. Finally, a heat transfer target body 10 is placed on the bonding layer 40. In this manner, the heat transfer device 5 shown in FIG. 5 is obtained.

[0062] 5 , the bonding layer 40 and the heat transfer device 5 are configured such that the bonding layer 40 is composed of two layers, the fiber structure 30 and the bonding material 31, and the fiber structure 30 is disposed near the heat transfer body 20. Therefore, compared to a bonding layer in which the fiber structure is uniformly present throughout the entire bonding layer, it is possible to improve thermal conductivity and stress relaxation.

[0063] Alternatively, the heat transfer device shown in Fig. 6 may be used. The heat transfer device 6 shown in Fig. 6 differs from the heat transfer device 5 shown in Fig. 5 in that the bonding material 31 fills the entire region of the fiber structure 30, but other configurations are substantially the same as those of the heat transfer device 5 shown in Fig. 5. In describing the configuration of the heat transfer device 6 shown in Fig. 6, a description of the configuration that is substantially the same as that of the heat transfer device 5 shown in Fig. 5 will be omitted.

[0064] 6 , a portion of the bonding material 31 fills the gaps between the inorganic fibers throughout the entire region of the fiber structure 30. The inorganic fibers that make up the fiber structure 30 are connected to the bonding material 31 that fills the gaps between the inorganic fibers.

[0065] Next, a method for manufacturing such a heat transfer device 6 will be described. First, a fiber structure 30 is placed on the surface of a heat transfer body 20. Here, the fiber structure 30 placed on the surface of the heat transfer body 20 is made of inorganic fibers, such as copper fibers, sintered together. Next, a bonding material 31 is melted and applied to the surface of the fiber structure 30. At this time, a portion of the molten bonding material 31 penetrates into the gaps between the inorganic fibers in the fiber structure 30. The molten bonding material 31 is also pressed from above so that the bonding material 31 penetrates into the entire area of ​​the fiber structure 30. Then, the applied bonding material 31 is cooled. At this time, a portion of the inorganic fibers constituting the fiber structure 30 are connected to the bonding material 31. Finally, a heat transfer target 10 is placed on the bonding layer 40. In this manner, the heat transfer device 6 shown in FIG. 6 is obtained.

[0066] 6 , the bonding layer 40 and the heat transfer device 6 are configured such that the bonding layer 40 is composed of two layers, the fiber structure 30 and the bonding material 31, and the fiber structure 30 is disposed near the heat transfer body 20. Therefore, compared to a case where the fiber structure is uniformly present throughout the entire bonding layer, it is possible to improve thermal conductivity and stress relaxation.

[0067] Alternatively, the heat transfer device shown in Fig. 7 may be used. The heat transfer device 7 shown in Fig. 7 differs from the heat transfer device 1 shown in Fig. 1 in that, instead of using a bonding layer 40 containing a fiber structure 30 and a bonding material 31, an inorganic porous body 36 such as a metal porous body and a bonding material 31 are used, but the other configurations are substantially the same as those of the heat transfer device 1 shown in Fig. 1. In describing the configuration of the heat transfer device 7 shown in Fig. 7, a description of the configuration that is substantially the same as that of the heat transfer device 1 shown in Fig. 1 will be omitted.

[0068] In the heat transfer device 7 shown in Figure 7, an inorganic porous body 36 such as a metal porous body is used, which has a structure in which fine inorganic fiber particles such as fine metal fiber particles are densely packed. Here, the inorganic porous body 36 is composed of a first layer 36a and a second layer 36b, with the first layer 36a being disposed on the heat transfer target body 10 side and the second layer 36b being disposed on the heat transfer body 20 side. Furthermore, a bonding material 31 is disposed between the inorganic fibers in the first layer 36a and the second layer 36b of the fiber structure 30. Note that, in another embodiment, the bonding material 31 does not need to be disposed between the inorganic fibers in the first layer 36a and the second layer 36b of the inorganic porous body 36.

[0069] Here, the first layer 36a has a structure in which inorganic fiber particles such as fine metal fiber particles (e.g., copper fiber particles) are densely packed. For example, copper fiber particles with a diameter of 10 μm and a length of 100 μm are used as such inorganic fiber particles. This first layer 36a is characterized by excellent thermal conductivity but poor stress relaxation. The second layer 36b has a structure in which inorganic fiber particles such as metal fiber particles (e.g., copper fiber particles) are deposited in a range of sparse to dense states. For example, copper fiber particles with a diameter of 18.5 μm and a length of 3,000 μm are used as such inorganic fiber particles. This first layer 36a is characterized by poor thermal conductivity but excellent stress relaxation.

[0070] In the heat transfer device 7 shown in FIG. 7, a plurality of equally spaced cross sections C extending parallel to the surface of the heat transfer body 20 are １ ~C ５ In this case, the inorganic porous material 36 is unevenly distributed so that the bonding layer 40 includes a first layer 36a in which the inorganic porous material 36 occupies a first proportion in the bonding layer 40 and a second layer 36b in which the inorganic porous material 36 occupies a second proportion different from the first proportion. In this case, the inorganic porous material 36 is composed of two layers 36a and 36b having different space factors relative to the bonding layer 40, and since the advantages of both layers are incorporated, the inorganic porous material 36 can have excellent thermal conductivity and stress relaxation properties.

[0071] In addition, multiple cross sections C １ ~C ５Regarding the average value of the proportion of the inorganic porous body 36 in the bonding layer 40, the cross section C ４ , C ５ The magnitude of this ratio is in the range of 0 to 0.45. In this case, the inorganic porous body 36 can be more reliably distributed unevenly in the bonding layer 40.

[0072] Next, a method for manufacturing such a heat transfer device 7 will be described. First, a second layer 36b of inorganic porous body 36 is disposed on the surface of heat transfer body 20. This second layer 36b has a relatively small space factor of inorganic fiber particles. For example, copper fiber particles with a diameter of 18.5 μm and a length of 3,000 μm are used as such inorganic fiber particles. Next, bonding material 31 is melted and applied to the surface of second layer 36b of inorganic porous body 36. This allows the molten bonding material 31 to penetrate into the gaps between the inorganic fiber particles in inorganic porous body 36, and the bonding material 31 that has penetrated into the gaps connects to the inorganic fiber particles of second layer 36b of inorganic porous body 36. Next, bonding material 31 is cooled and solidified. Then, a first layer 36a of inorganic porous body 36 is disposed on the surface of the solidified bonding material 31. This first layer 36a has a relatively large space factor of inorganic fiber particles. For example, copper fiber particles having a diameter of 10 μm and a length of 100 μm are used as such inorganic fiber particles. Furthermore, when the first layer 36a of the inorganic porous body 36 is placed on the surface of the solidified bonding material 31, heating is performed to sinter some of the inorganic fiber particles constituting the first layer 36a into the second layer 36b. Next, the bonding material 31 is melted and applied to the surface of the first layer 36a of the inorganic porous body 36. This allows the molten bonding material 31 to penetrate into the gaps between the inorganic fiber particles in the inorganic porous body 36, and the bonding material 31 that has penetrated into the gaps connects to the inorganic fiber particles of the first layer 36a of the inorganic porous body 36. Next, the bonding material 31 is cooled and solidified. Finally, the heat transfer target 10 is placed on the bonding layer 40. In this manner, the heat transfer device 7 shown in FIG. 7 is obtained.

[0073] 7 , the inorganic porous body 36 is unevenly distributed in the bonding layer 40. Specifically, the inorganic porous body 36 is composed of two layers 36 a and 36 b that have different space factors relative to the bonding layer 40, thereby incorporating the advantages of both. This allows the bonding layer 40 to have excellent thermal conductivity and stress relaxation properties.

[0074] Alternatively, the heat transfer device shown in Fig. 8 may be used. The heat transfer device 8 shown in Fig. 8 differs from the heat transfer device 7 shown in Fig. 7 in that the inorganic porous body 36 constituting the bonding layer 40 is configured from three layers, including two first layers 36a having a relatively large space factor of inorganic fiber particles and a second layer 36b disposed between the two first layers 36a and having a smaller space factor of inorganic fiber particles than the first layers 36a. The remaining configuration is substantially the same as that of the heat transfer device 7 shown in Fig. 7. In describing the configuration of the heat transfer device 8 shown in Fig. 8, a description of the configuration that is substantially the same as that of the heat transfer device 7 shown in Fig. 7 will be omitted.

[0075] 8 , the inorganic porous body 36 is composed of two first layers 36a and a second layer 36b disposed between each of the first layers 36a, with one first layer 36a disposed on the heat transfer body 10 side and the other first layer 36a disposed on the heat transfer body 20 side. A bonding material 31 is disposed between the inorganic fiber particles in each of the first layers 36a of the inorganic porous body 36 and between the inorganic fiber particles in the second layer 36b. In another embodiment, the bonding material 31 does not need to be disposed between the inorganic fibers in the first layer 36a of the inorganic porous body 36 and between the inorganic fibers in the second layer 36b.

[0076] In the heat transfer device 8 shown in FIG. 8, a plurality of equally spaced cross sections C extending parallel to the surface of the heat transfer body 20 are １ ~C ５In this case, the inorganic porous material 36 is unevenly distributed so that the bonding layer 40 includes a first layer 36a in which the inorganic porous material 36 occupies a first proportion in the bonding layer 40 and a second layer 36b in which the inorganic porous material 36 occupies a second proportion different from the first proportion. In this case, the inorganic porous material 36 is composed of three layers 36a, 36b, 36a that have different space factors relative to the bonding layer 40, and since the advantages of both layers are incorporated, the inorganic porous material 36 can have excellent thermal conductivity and stress relaxation properties.

[0077] In addition, multiple cross sections C １ ~C ５ Regarding the average value of the proportion of the inorganic porous body 36 in the bonding layer 40, the cross section C ３ The magnitude of this ratio is in the range of 0 to 0.5. In this case, the inorganic porous body 36 can be more reliably distributed unevenly in the bonding layer 40.

[0078] The method for manufacturing such a heat transfer device 8 is similar to the method for manufacturing the heat transfer device 7 shown in FIG. 7, and therefore a description thereof will be omitted.

[0079] 8, the inorganic porous body 36 is unevenly distributed in the bonding layer 40. Specifically, the inorganic porous body 36 is composed of three layers 36a, 36b, and 36a, each of which has a different space factor relative to the bonding layer 40, thereby incorporating the advantages of both. This allows the bonding layer 40 to have excellent thermal conductivity and stress relaxation properties.

[0080] Alternatively, the heat transfer device shown in Fig. 9 may be used. The heat transfer device 9 shown in Fig. 9 differs from the heat transfer device 7 shown in Fig. 7 in that the inorganic porous body 36 constituting the bonding layer 40 is configured from three layers, including two second layers 36b having a relatively small space factor of inorganic fiber particles and a first layer 36a disposed between the two second layers 36b and having a larger space factor of inorganic fibers than the second layers 36b. The other configuration is substantially the same as that of the heat transfer device 7 shown in Fig. 7. In describing the configuration of the heat transfer device 9 shown in Fig. 9, a description of the configuration that is substantially the same as that of the heat transfer device 7 shown in Fig. 7 will be omitted.

[0081] 9 , the inorganic porous body 36 is composed of two second layers 36b and a first layer 36a disposed between each of the second layers 36b, with one second layer 36b disposed on the heat transfer body 10 side and the other second layer 36b disposed on the heat transfer body 20 side. Furthermore, a bonding material 31 is disposed between the inorganic fiber particles in each of the second layers 36b of the inorganic porous body 36 and between the inorganic fiber particles in the first layer 36a. Alternatively, the bonding material 31 may not be disposed between the inorganic fibers in the first layer 36a of the inorganic porous body 36 and between the inorganic fibers in the second layer 36b.

[0082] In the heat transfer device 9 shown in FIG. 9, a plurality of equally spaced cross sections C extending parallel to the surface of the heat transfer body 20 are １ ~C ５ In this case, the inorganic porous material 36 is unevenly distributed so that the bonding layer 40 includes a first layer 36a in which the inorganic porous material 36 occupies a first proportion in the bonding layer 40 and a second layer 36b in which the inorganic porous material 36 occupies a second proportion different from the first proportion. In this case, the inorganic porous material 36 is composed of three layers 36b, 36a, 36b that have different space factors relative to the bonding layer 40, and since the advantages of both layers are incorporated, the inorganic porous material 36 can have excellent thermal conductivity and stress relaxation properties.

[0083] In addition, multiple cross sections C １ ~C ５ Regarding the average value of the proportion of the inorganic porous body 36 in the bonding layer 40, the cross section C １ , C ５ The magnitude of this ratio is in the range of 0 to 0.5. In this case, the inorganic porous body 36 can be more reliably distributed unevenly in the bonding layer 40.

[0084] The method for manufacturing such a heat transfer device 9 is similar to the method for manufacturing the heat transfer device 7 shown in FIG. 7, and therefore a description thereof will be omitted.

[0085] 9, the inorganic porous body 36 is unevenly distributed in the bonding layer 40. Specifically, the inorganic porous body 36 is composed of three layers 36b, 36a, and 36b, each of which has a different space factor relative to the bonding layer 40, thereby incorporating the advantages of both. This allows the bonding layer 40 to have excellent thermal conductivity and stress relaxation properties.

[0086] According to the bonding layer 40 and heat transfer devices 1 to 9 of the present embodiment configured as described above, the bonding layer 40 disposed on the surface of the heat transfer body 20 includes the fiber structure 30, the inorganic porous body 36, and the bonding material 31. The fiber structure 30 and the inorganic porous body 36 are unevenly distributed so that, among a plurality of (e.g., five) equally spaced cross sections extending parallel to the surface of the heat transfer body 20, there are cross sections in which the fiber structure 30 is absent, or the fiber structure 30 and the inorganic porous body 36 are unevenly distributed so that the bonding layer 40 includes a first layer 36a in which the inorganic porous body 36 occupies a first proportion and a second layer 36b in which the inorganic porous body 36 occupies a second proportion different from the first proportion. In this case, sufficient thermal conductivity is maintained between the heat transfer body 20 and the heat-transferred body 10, and problems such as cracking between the heat transfer body 20 and the bonding layer 40 and deterioration of the stress relaxation property of the bonding layer 40 can be prevented when the heat transfer body 20 thermally expands or contracts.

[0087] 1A, 1B, 2, and 4 to 6, the fiber structure 30 is unevenly distributed so that, in a plurality of (e.g., five) equally spaced cross sections extending parallel to the surface of the heat transfer body 20, there are cross sections in which the fiber structure 30 is absent. In this case, sufficient thermal conductivity is maintained between the heat transfer body 20 and the heat-transferred body 10, and problems such as cracking between the heat transfer body 20 and the bonding layer 40 when the heat transfer body 20 thermally expands or contracts can be prevented. Furthermore, in the bonding layer 40 of the heat transfer devices 7 to 9 shown in FIGS. 7 to 9, the inorganic porous material 36 is unevenly distributed so that the bonding layer 40 includes a first layer 36a in which the inorganic porous material 36 occupies a first proportion in the bonding layer 40 and a second layer 36b in which the inorganic porous material 36 occupies a second proportion different from the first proportion. In this case, it is possible to prevent the stress relaxation property of the bonding layer 40 from being deteriorated while maintaining sufficient thermal conductivity between the heat transfer body 20 and the heat transfer target body 10 .

[0088] 1A, 1B, 2, and 4 to 9, the ratio of the cross section with the smallest ratio of the fiber structure 30 or the inorganic porous material 36 to the average ratio of the fiber structure 30 or the inorganic porous material 36 in the bonding layer 40 is within the range of 0 to 0.45 for a plurality of cross sections. In this case, the fiber structure 30 is sufficiently unevenly distributed in the bonding layer 40, and therefore, sufficient thermal conductivity is maintained between the heat transfer body 20 and the heat-transferred body 10, and problems such as cracking between the heat transfer body 20 and the bonding layer 40 when the heat transfer body 20 thermally expands or contracts can be prevented, and the stress relaxation property of the bonding layer 40 can be prevented from deteriorating.

[0089] 1A, 1B, and 2 to 9, the thickness of the bonding layer 40 in the direction perpendicular to the surface of the heat transfer body 20 is 10 μm to 200 μm. This makes it possible to maintain sufficient strength of the bonding layer 40 while maintaining sufficient thermal conductivity between the heat transfer body 20 and the heat-transferred body 10.

[0090] In addition, in the bonding layer 40 of the heat transfer device 1 shown in FIG. 1B, a cross section C ６The ratio of the proportion of the fiber structure 30 in contact with the surface of the heat transfer body 20 to the proportion of the fiber structure 30 in the entire surface is within a range of 0 to 0.8. In this case, the fiber structure 30 can be prevented from becoming dense near the surface of the heat transfer body 20, and therefore problems such as cracking can be prevented from occurring between the heat transfer body 20 and the bonding layer 40 when the heat transfer body 20 undergoes thermal expansion or thermal contraction.

[0091] 1A, 1B, and 2 to 9, the space factor of the fiber structure 30 and the inorganic porous material 36 is 25% to 95%. This prevents the shape conformability and cushioning properties of the bonding layer 40 from decreasing.

[0092] 2 , the ratio of the area of ​​the fiber structure 30 in contact with the heat transfer body 20 to the area of ​​the bonding material 31 in contact with the heat transfer body 20 is 0.1 to 1.5. In this case, sufficient thermal conductivity is ensured between the heat transfer body 20 and the bonding layer 40, and the fiber structure 30 can be prevented from becoming dense on the surface of the heat transfer body 20, so that the bonding layer 40 can sufficiently bond the heat transfer body 20 and the heat-transferred body 10.

[0093] 3 , the heat transfer target 10 is placed on the surface of the bonding layer 40 opposite to the surface on which the heat transfer target 20 is placed, and the ratio of the area of ​​the fiber structure 30 in contact with the heat transfer target 10 to the area of ​​the fiber structure 30 in contact with the heat transfer target 20 is 0.4 to 2.5. In this case, the bonding layer 40 can exhibit sufficient thermal conductivity, and can prevent problems such as cracking from occurring between the heat transfer target 10 and the bonding layer 40 or between the heat transfer target 20 and the bonding layer 40.

[0094] The bonding layer 40 has a thermal expansion coefficient of 5 ppm / °C to 25 ppm / °C at 100°C to 200°C.

[0095] Moreover, the difference in linear expansion coefficient between the fiber structure 30 or inorganic porous body 36 and the bonding material 31 at 100°C to 200°C is 0.1 ppm / °C to 15 ppm / °C.

[0096] In addition, in the bonding layer 40 of the heat transfer devices 1 to 9 shown in FIGS. 1A, 1B and 2 to 9, a bonding material 31 may be disposed between the fiber structure 30 and the inorganic porous body 36.

[0097] In addition, in the bonding layer 40 of the heat transfer devices 1 to 9 shown in FIGS. 1A, 1B, and 2 to 9, a plurality of cross sections C １ ~C ５ In a part or the whole of the cross section where the fiber structure 30 or the inorganic porous material 36 exists, the bonding material 31 is disposed between the fiber structure 30 or the inorganic porous material 36 .

[0098] In addition, in the bonding layer 40 of the heat transfer devices 1 to 9 shown in FIGS. 1A, 1B, and 2 to 9, the ratio of the volume of the bonding material 31 disposed between the fiber structure 30 and the inorganic porous body 36 to the volume of the bonding material 31 in the bonding layer 40 is 0% to 80%.

[0099] Furthermore, the bonding material 31 disposed between the fiber structure 30 and the inorganic porous body 36 is heat-fused to the fiber structure 30 and the inorganic porous body 36. In this case, the connection between the bonding material 31 and the fiber structure 30 and the inorganic porous body 36 can be made stronger.

[0100] Furthermore, the fiber structure 30 or the inorganic porous material 36 may or may not be bonded to the heat conductor 20 as long as they are thermally or electrically connected. Here, the connection between the fiber structure 30 or the inorganic porous material 36 and the heat conductor 20 may be direct or indirect. Direct connection includes, for example, bonding by sintering, including bonding between the inorganic porous material 36 and the heat conductor 20 via an alloy or material. Indirect connection includes, for example, bonding using a resin material or a metal paste. Bonding between the fiber structure 30 or the inorganic porous material 36 and the heat conductor 20 can further strengthen the connection between the fiber structure 30 or the inorganic porous material 36 and the heat conductor 20. On the other hand, not bonding between the fiber structure 30 or the inorganic porous material 36 and the heat conductor 20 can prevent problems such as cracking between the heat conductor 20 and the bonding layer 40 when the heat conductor 20 undergoes thermal expansion or contraction, and can prevent deterioration of the stress relaxation property of the bonding layer 40.

[0101] The inorganic porous body contains inorganic fibers, that is, a fibrous structure 30 as shown in Figures 1A, 1B, and 2 to 6 may be used as the inorganic porous body.

[0102] The inorganic fibers may also contain copper fibers, which can improve the thermal conductivity of the inorganic porous body.

[0103] The bonding layer, the heat transfer device, and the method for manufacturing the bonding layer according to the present invention are not limited to the above-described embodiments, and various modifications can be made.

[0104] For example, the surface of the heat transfer body 20 is not limited to being flat. In another embodiment, the surface of the heat transfer body 20 may be curved. In this case, the bonding layer 40 is disposed on the curved surface of the heat transfer body 20. In this case, a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body 20 also have curved surfaces.

[0105] Furthermore, the inorganic porous body included in the bonding layer is not limited to a fibrous structure or a structure in which fine inorganic fiber particles such as fine metal fiber particles are densely packed, and any other structure may be used as the inorganic porous body as long as it has many pores.

[0106] The present disclosure will be described in more detail below using examples and comparative examples.

[0107] (Bonding Materials) The following bonding materials 1 to 5 were prepared as bonding materials. Bonding material 1: Sn-1Ag-0.5Cu (melting point 227°C, linear expansion coefficient 20.9 ppm / °C) Bonding material 2: Sn-5Sb (melting point 243°C, linear expansion coefficient 22.8 ppm / °C) Bonding material 3: Ag (melting point 962°C, linear expansion coefficient 19.2 ppm / °C) Bonding material 4: Cu (melting point 1083°C, linear expansion coefficient 18.2 ppm / °C) Bonding material 5: Nano Ag paste (conductive adhesive TK paste, manufactured by Kaken Tech Co., Ltd.)

[0108] (Evaluation Sample) For Example 1, an evaluation sample was prepared using the configuration shown in Table 1. That is, bonding material 1 was melted on the surface of a C1100 copper plate (50 mm wide x 50 mm long x 2 mm thick) on a hot plate set at 250 ° C., a copper fiber structure was placed on the bonding material 1, and the molten bonding material 1 was applied from above the copper fiber structure, impregnating the bonding material between the copper fibers and cooling and solidifying. Thereafter, an aluminum oxide plate (50 mm wide x 50 mm long x 2 mm thick) was placed on the bonding material 1, and the bonding material 1 was remelted on a hot plate set at 250 ° C., cooled, and solidified to obtain a test piece. Furthermore, the test piece was cut to a width of 30 mm x a length of 30 mm to obtain an evaluation sample.

[0109] For Examples 2, 5 to 18, and 24 to 29, evaluation samples were prepared in the same manner as in Example 1 using the configurations shown in Tables 1 to 4 and 6.

[0110] For Examples 3 and 4, evaluation samples were prepared in the same manner as in Example 1 using the configuration shown in Table 1, except that the temperature at which the joining material was melted was 1100° C. (electric furnace).

[0111] For Comparative Example 1, an evaluation sample was prepared using the configuration shown in Table 4. Specifically, copper powder (low-temperature sinterable copper powder CH-0200L1, manufactured by Mitsui Mining & Smelting Co., Ltd.) was dispersed in heated and melted bonding material 1 to obtain bonding material 7. Bonding material 7 was melted on the surface of a C1100 copper plate (50 mm wide x 50 mm long x 2 mm thick) on a hot plate set at 250°C, and then an aluminum oxide plate (50 mm wide x 50 mm long x 2 mm thick) was placed on bonding material 7, followed by cooling and solidification to obtain a test piece. The test piece was then cut to a size of 30 mm wide x 30 mm long to obtain an evaluation sample.

[0112] For Example 19, an evaluation sample was prepared using the configuration shown in Table 5. That is, a copper fiber structure was placed on the surface of a copper plate C1100 (50 mm wide x 50 mm long x 1 mm thick), and then bonding material 5 was applied from above the copper fiber structure, impregnating the spaces between the copper fibers with the bonding material. An aluminum oxide plate (50 mm wide x 50 mm long x 1 mm thick) was then placed on the bonding material 5. Next, the copper plate and the copper fiber structure were sintered in an electric furnace set at 1100°C, and the organic components of the bonding material 5 were simultaneously vaporized to obtain each test piece. The test piece was cut to a width of 30 mm x a length of 30 mm to obtain an evaluation sample.

[0113] For Examples 20 to 23 and 30 to 35, evaluation samples were prepared in the same manner as in Example 19 using the configurations shown in Tables 5 and 7.

[0114]

[0115]

[0116]

[0117]

[0118]

[0119]

[0120]

[0121] <Evaluation> (Evaluation of Thermal Cycle Test) For Examples 1 to 35 and Comparative Example 1, each evaluation sample was placed in a thermostatic chamber set at -55°C and allowed to stand for 30 minutes. After that, the temperature was increased to 150°C at a temperature increase rate of 10°C / min and allowed to stand for 30 minutes. The temperature was then decreased to -55°C at a temperature decrease rate of 10°C / min and allowed to stand for 30 minutes. After that, the temperature was increased and decreased repeatedly under the same conditions as above, and a thermal cycle test was performed. The evaluation was performed according to the following criteria. A+: No cracking or peeling was observed after 500 cycles. A: Cracking or peeling was observed at 400 cycles or more but less than 500 cycles. B: Cracking or peeling was observed at 300 cycles or more but less than 400 cycles. C: Cracking or peeling was observed at 200 cycles or more but less than 300 cycles. D: Cracking or peeling was observed at less than 200 cycles.

[0122] (Evaluation of Heat Conductivity) For Examples 1 to 35 and Comparative Example 1, measurements were made using a temperature wave analysis method. That is, only the bonding layer of each evaluation sample was cut into a disk shape with a diameter of 10 mm, and the thermal conductivity was measured using a thermal diffusivity / thermal conductivity measuring device (ai-Phase Mobile M3, manufactured by Ai-Phase Corporation). The evaluation was made according to the following criteria. A: The thermal conductivity was 200 W / m·K or more. B: The thermal conductivity was 100 W / m·K or more and less than 200 W / m·K. C: The thermal conductivity was 50 W / m·K or more and less than 100 W / m·K. D: The thermal conductivity was less than 50 W / m·K.

[0123] (Overall Evaluation) Each evaluation result was converted into a numerical value in accordance with the following criteria, and the total value of each numerical value in (Evaluation of Thermal Cycle Test) and (Evaluation of Heat Transfer) was used as the overall evaluation. Here, a larger total value indicates a better evaluation result, and a smaller total value indicates a worse evaluation result. As shown in Tables 1 to 5 above, Examples 1 to 35 received an overall evaluation of 4 to 9, and good evaluations were obtained for the thermal cycle test and heat transfer. On the other hand, Comparative Example 1 received an overall evaluation of 1, and did not receive a good evaluation, particularly in the thermal cycle test, as cracking and peeling were observed less than 200 cycles. Thus, it was found that the use of copper fibers instead of copper powder as the fiber structure can prevent problems such as cracking between the heat transfer body and the bonding layer. A+: +5 A: +4 B: +2 C: +1 D: -1

Claims

1. A bonding layer comprising an inorganic porous body and a bonding material, the bonding layer being placed on the surface of a heat transfer body, wherein the inorganic porous body is unevenly distributed such that, in a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body, there are cross sections in which the inorganic porous body is not present, or the bonding layer includes a first layer in which the inorganic porous body occupies a first ratio and a second layer in which the inorganic porous body occupies a second ratio different from the first ratio.

2. The bonding layer according to claim 1, wherein the ratio of the inorganic porous material in the bonding layer in the cross section having the smallest ratio to the average ratio for a plurality of cross sections is within the range of 0 to 0.

5.

3. The bonding layer according to claim 1, wherein the thickness of the bonding layer in a direction perpendicular to the surface of the heat transfer body is 10 μm to 200 μm.

4. A bonding layer according to any one of claims 1 to 3, wherein the ratio of the magnitude of the proportion in the cross section where the inorganic porous body contacts the heat transfer body to the magnitude of the proportion in the cross section at a thickness of 5 μm from the surface of the heat transfer body is within the range of 0 to 0.

8.

5. The bonding layer according to claim 1, wherein the inorganic porous body has a volume fraction of 25% to 95%.

6. The bonding layer according to claim 1, wherein the ratio of an area of ​​said inorganic porous body in contact with said heat transfer body to an area of ​​said bonding material in contact with said heat transfer body is 0.1 to 1.

5.

7. The bonding layer according to claim 1, wherein a heat transfer target is placed on the surface of the bonding layer opposite to the surface on which the heat transfer body is placed, and the ratio of the area of ​​the inorganic porous body in contact with the heat transfer body to the area of ​​the inorganic porous body in contact with the heat transfer body is 0.4 to 2.

5.

8. The bonding layer according to claim 1, having a thermal expansion coefficient of 5 ppm / °C to 25 ppm / °C at 100°C to 200°C.

9. The bonding layer according to claim 1, wherein the difference in linear expansion coefficient between said inorganic porous body and said bonding material at 100° C. to 200° C. is 0.1 ppm / ° C. to 15 ppm / ° C.

10. The bonding layer according to claim 1, wherein the bonding material is disposed between the inorganic porous bodies.

11. The bonding layer according to claim 1, wherein the bonding material is disposed between the inorganic porous bodies in some or all of the cross sections where the inorganic porous bodies are present among the plurality of cross sections.

12. The bonding layer according to claim 11, wherein a ratio of a volume of the bonding material disposed between the inorganic porous bodies to a volume of the bonding material in the bonding layer is 0% to 80%.

13. The bonding layer according to claim 11, wherein the bonding material disposed between the inorganic porous bodies is sintered to the inorganic porous bodies.

14. The bonding layer according to claim 1, wherein the inorganic porous body comprises inorganic fibers.

15. The bonding layer of claim 14, wherein the inorganic fibers comprise copper fibers.

16. A heat transfer device comprising: a heat transfer body; and a bonding layer disposed on a surface of the heat transfer body, wherein the bonding layer has an inorganic porous body and a bonding material, and the inorganic porous body is unevenly distributed such that, in a plurality of equally spaced cross sections extending parallel to the surface of the heat transfer body, there are cross sections in which the inorganic porous body is not present, or the bonding layer includes a first layer in which the inorganic porous body occupies a first ratio and a second layer in which the ratio is a second ratio different from the first ratio.

17. A method for manufacturing a bonding layer to be placed on a surface of a heat transfer body, comprising the steps of: placing an inorganic porous body on the surface of the heat transfer body; melting a bonding material and supplying the molten bonding material to the surface of the inorganic porous body; and cooling the bonding material.

18. The method for manufacturing a bonding layer according to claim 17, wherein in the step of melting the bonding material and supplying the molten bonding material to the surface of the inorganic porous body, the molten bonding material is applied to the surface of the inorganic porous body.

19. The method for manufacturing a bonding layer according to claim 17, wherein in the step of melting the bonding material and supplying the molten bonding material to the surface of the inorganic porous body, the molten bonding material is impregnated into the interior of the inorganic porous body.

20. The method for manufacturing a bonding layer according to claim 17, further comprising the step of: after the step of cooling the bonding material, placing a bonding material different from the bonding material on a surface of the cooled bonding material.

21. A method for manufacturing a bonding layer to be placed on a surface of a heat transfer body, comprising the steps of: placing a bonding material on the bonding layer; placing an inorganic porous body on the surface of the bonding material; melting a bonding material other than the bonding material and supplying the molten bonding material to the surface of the inorganic porous body; and cooling the bonding material.

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