Heat absorber / dissipator and casting method for heat absorber / dissipator

Abstract

To provide a heat absorber / dissipator excellent in heat absorption and dissipation performance and having a surface layer with strong adhesive strength, and a casting method for such a heat absorber / dissipator.SOLUTION: According to the present invention, there is provided a heat absorber / dissipator having a die-cast portion and a porous portion formed from a metal material, in which at least some of the pores of the porous portion located within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface between the porous portion and the die-cast portion are filled with the die-cast material that forms the die-cast portion.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat absorber / dissipator manufactured by die casting and a casting method for a heat absorber / dissipator. [Background technology]

[0002] Die casting is a casting method for manufacturing metal parts, and can produce castings with precise shapes and good casting surfaces. In particular, when metals such as Al and Cu are used as materials, they have good thermal conductivity and heat dissipation properties, making them suitable for making parts that may be exposed to high temperatures, such as electronic device casings and engine parts that require high heat dissipation.

[0003] In order to further improve the heat dissipation of die-cast parts manufactured by die casting, a method of coating the surface of the die-cast parts with resin has been conventionally used. For example, a technique is known in which a base body of a heat dissipation base is molded by die casting, and a resin coating layer is applied to the heat dissipation surface of the base body by resin injection molding using a mold. Patent Document 1 discloses a technique for applying a resin coating layer by putting resin into a mold and performing resin injection molding while the base body is in a high temperature state immediately after being molded by die casting.

[0004] Patent Document 2 proposes a technology for increasing the heat dissipation area by sintering a porous layer made of metal powder on the surface of a metal base material. This technology is suitable for dissipating heat in small, narrow spaces where it is difficult to mount a fin-shaped heat dissipation component.

[0005] However, when covering the casting surface of a die-cast part with a resin coating, the resin is applied using an injection molding machine, which not only complicates the manufacturing process but also requires large-scale facilities. In addition, it is difficult to adjust the resin thickness, and since resin is used in the first place, the resin layer may deteriorate before the base material depending on the usage environment. In addition, it is difficult to secure a contact area between the base material and the porous metal layer created by sintering a porous metal layer on the surface of the base material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 57-202683 [Patent Document 2] Japanese Patent Application Publication No. 57-153458 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a heat absorber / dissipator which is excellent in heat absorption and dissipation performance and has an interface with strong adhesive strength, and a casting method for such a heat absorber / dissipator. [Means for solving the problem]

[0008] Therefore, in order to achieve the above-mentioned object, according to a first aspect of the present invention, there is provided a heat absorber having a die-cast portion and a porous portion formed from a metal material, in which at least a portion of the pores of the porous portion located within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface between the porous portion and the die-cast portion are filled with the die-cast material forming the die-cast portion. Such a heat sink has a small occupying volume and high heat dissipation performance, and can be used as a heat sink for electronic components, for example. The die-cast material constituting the base material of the heat absorber is preferably a metal such as Al, Cu, Zn, Mg, etc., or an alloy thereof. The material forming the porous portion is preferably a metal such as Al, Cu, Zn, Mg, etc., or an alloy thereof, and may be the same as the base material or a different material.

[0009] In one embodiment of the present invention, the bonding length ratio of the bonding surface where the porous portion and the die-cast portion are bonded can be 40% or more within a range of up to 100 μm in a direction perpendicular to the bonding surface.

[0010] In another embodiment of the present invention, the porosity of the porous portion can be 30% or more and 70% or less.

[0011] In still another embodiment of the present invention, the porous portion may have an average neck diameter of 10 μm or more and 80 μm or less when pore distribution is calculated by a bubble point method.

[0012] In still another embodiment of the present invention, the ratio of the volume of the pores that are not connected to the outside to the entire volume of the porous portion may be 20% or less.

[0013] Furthermore, according to a second aspect of the present invention, there is provided a method for casting a heat absorber or dissipator, comprising: a holding step of holding a first surface of a porous body in contact with an inner surface of a mold; and a pressing step of pressing a molten metal of a die-casting metal material toward a second surface of the porous body opposite the first surface.

[0014] In yet another embodiment of the present invention, the pressing step can include a filling step of filling pores in the porous portion located within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface between the porous body and the die-cast portion with a die-casting material that forms the die-cast portion. Effect of the Invention

[0015] According to the present invention, it is possible to provide a heat absorber that is excellent in heat absorption and heat dissipation performance and has an interface with strong adhesive strength. [Brief description of the drawings]

[0016] [Figure 1] 3 is a cross-sectional photograph of the heat absorber / dissipator according to the first embodiment. [Diagram 2] 5 is a schematic diagram illustrating the bonding length between the die-cast portion and the porous portion. FIG. [Diagram 3] 1 is a graph comparing the integral emissivity of each surface layer. [Figure 4]FIG. 11A is a diagram showing a preparation step in the casting method for a heat absorber / dissipator according to the second embodiment, FIG. 11B is a diagram showing a step of pouring molten metal by applying pressure to the molten metal with a plunger, FIG. 11C is a diagram showing a step of pouring the die-casting material toward a second surface of the porous body, and FIG. 11D is a diagram showing a step of filling the pores of the porous body with the die-casting material. [Diagram 5] 1 is a flowchart of a heat sink casting method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, detailed description may be omitted. For example, detailed description of already well-known matters or duplicate description of substantially the same configuration may be omitted. Note that the accompanying drawings and the following description are provided to enable a person skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0018] (First embodiment) The first embodiment will be described below with reference to FIGS. 1 to 3. FIG. [1-1. Configuration] FIG. 1 is a cross-sectional photograph of a heat absorber 10 according to the first embodiment, taken along a cross section perpendicular to the XY plane, where the bonding surface 25 between the die-cast portion 30 and the porous portion 20 cast by the die-casting method is the XY plane. Here, in the cross section, the straight line connecting two points in contact with the die-cast portion 30 at the outer edge portion of the porous portion 20 that is convex in the thickness direction of the porous portion 20, i.e., in the negative direction of the Z axis direction in FIG. 1, is defined as the bonding surface 25. The porous portion 20 is the same as the porous body 60 that is prepared in advance and placed inside the mold 50 in the casting method for the heat absorber described later. Inside the porous portion 20, there are pores 40. The average circle-equivalent diameter of the pores 40 is less than 1 mm. Preferably, the average circle-equivalent diameter of the pores 40 is less than 500 μm.

[0019] Here, the average circle equivalent diameter of the pores 40 refers to the average value of the diameters of perfect circles equivalent to the area of ​​the cross section of the pores 40. For example, the average value is calculated for the cross sections of all the pores 40 within the field of view of the microscope.

[0020] FIG. 2 is a schematic diagram for explaining the bonding length ratio between the die-casting portion 30 and the porous portion 20. Here, in a cross section perpendicular to the XY plane in the heat absorber 10, the length of the boundary generated when the die-casting material constituting the die-casting portion 30 is melted and filled inside the pores 40 (see FIG. 1) of the porous portion 20 is defined as the bonding length 45 with the base material. Also, the ratio of the bonding length 45 with the base material to the outer edge 47 of the porous portion 20 is defined as the bonding length ratio. In this case, for the heat absorber 10 according to this embodiment, the bonding length ratio is 40% or more in a range of 2000 μm in the Y-axis direction in FIG. 2 and 100 μm from the bonding surface 25 in the direction perpendicular to the bonding surface 25 (Z-axis direction in the figure). It is desirable that the bonding length ratio is 50% or more.

[0021] The heat absorber 10 has a die-casting part 30 manufactured by a die-casting method and a porous part 20 formed of a metal material on the surface of the die-casting part 30, and at least a part of the pores 40 of the porous part 20 within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface 25 between the porous part 20 and the die-casting part 30 is filled with the die-casting material forming the die-casting part 30. As the die-casting material constituting the base material of the heat absorber 10, metals such as Al, Cu, Zn, Mg, etc. and alloys thereof are preferable. As the material forming the porous part 20, metals such as Al, Cu, Zn, Mg, etc. and alloys thereof are preferable, and the same as the base material or a different material can be selected.

[0022] The thickness of the porous portion 20 constituting the heat absorber 10 in the direction perpendicular to the adhesive surface 25 (Z-axis direction in FIG. 2) is 0.5 mm or more to maintain strength. The thickness of the porous portion 20 is 4 mm or less to prevent defects in the heat absorber 10, and preferably 0.5 mm or more and 2 mm or less.

[0023] The porosity of the porous portion 20 in the heat absorber 10 is 30% or more and 70% or less, and preferably 40% or more and 60% or less.

[0024] Moreover, the porous portion 20 has an average neck diameter of 10 μm or more and 80 μm or less when the distribution of the pores 40 is calculated by the bubble point method.

[0025] The measurement of the pores 40 by the bubble point method is performed, for example, using a Perm Porometer POROLUX Revo manufactured by PMI, Inc. The term "neck" refers to the narrowest part of the pores that connect the multiple linked pores 40, and the width of the neck is defined as the neck diameter.

[0026] The ratio of the volume of the pores 40 that are not connected to the outside to the entire volume of the porous portion 20 is 20% or less.

[0027] FIG. 3 is a graph comparing the integral emissivity of each surface layer. Specifically, in FIG. 3, from the left, the integral emissivity 100 from the bulk aluminum surface, the integral emissivity 110 from the surface of the aluminum base material on which a porous layer is formed by sintering metal powder, and the integral emissivity 120 from the surface of the heat absorber 10 according to this embodiment are shown. All of the samples to be measured were 30 mm square plates with a thickness of 3 mm. The conditions for the integral emissivity measurement were a heating temperature of 200° C. for each sample and a measurement wavelength range of 4.5 μm to 15.4 μm. The measured integral emissivity was 3% for the integral emissivity 100 from the bulk aluminum surface, 32% for the integral emissivity 110 from the surface of the aluminum base material on which a porous layer is formed by sintering metal powder, and 35% for the integral emissivity 120 from the surface of the heat absorber 10 according to this embodiment. A high integral emissivity means that it is easy to absorb or radiate thermal energy. Therefore, it is understood that the heat absorber 10 according to this embodiment has superior heat dissipation performance compared to the other two comparative cases.

[0028] The reason why the heat dissipation performance of the heat absorber 10 according to this embodiment, in which a porous layer is formed by sintering metal powder on the surface of an aluminum base material, is superior to that of bulk aluminum is believed to be because the surface is porous, thereby increasing the surface area of ​​the heat dissipation surface.

[0029] Moreover, the reason why the heat absorber 10 according to this embodiment has superior heat dissipation performance compared to a porous layer formed by sintering metal powder on the surface of an aluminum base material is believed to be because the bond between the die-cast portion 30, which is the base material, and the porous portion 20 is strong, resulting in superior heat transfer coefficient. This is also clear from the following consideration.

[0030] In other words, the heat flux q, which is the amount of heat transferred per unit area, is calculated by multiplying the thickness of the base material constituting the sample by A , the thickness of the surface material is X B , the thermal conductivity of the base material is k A , the thermal conductivity of the surface material is k B , the contact heat transfer coefficient between the base material and the surface material is h C If the temperature of the base material is T1 and the temperature of the surface material is T3, then from Fourier's law, q = (T1-T3) / {(X A / k A )+(1 / h C )+(X B / k B Here, if the adhesion between the porous portion 20, which is the surface member constituting the surface, and the die-cast portion 30, which is the base material, is strong, the contact heat transfer coefficient h C becomes larger, and the amount of heat transferred from the die-cast portion 30 to the porous portion 20 increases. Therefore, T3, which is the temperature of the porous portion 20, becomes larger, and as a result, the heat dissipation property becomes higher.

[0031] [1-2. Effects, etc.] (Configuration 1) The heat absorber 10 of the first embodiment is a heat absorber 10 having a die-cast portion 30 and a porous portion 20 formed from a metal material, and at least a portion of the pores 40 of the porous portion 20 located within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface 25 between the porous portion 20 and the die-cast portion 30 is filled with the die-cast material that forms the die-cast portion 30. According to the heat absorber of the present disclosure, the base material cast by the die casting method and the metal porous material are anchored and firmly bonded by the die casting material that is filled three-dimensionally into the pores of the porous portion, thereby providing a heat absorber with strong adhesive strength and excellent heat dissipation properties.

[0032] (Configuration 2) The heat absorber 10 of the first embodiment provides the heat absorber 10 described in configuration 1, in which the bonding length ratio of the bonding surface 25 where the porous portion 20 and the die-cast portion 30 are bonded is 40% or more within a range of up to 100 μm in the direction perpendicular to the bonding surface 25. According to the heat absorber of the present disclosure, the base material cast by a die casting method and the surface layer composed of a porous metal are firmly bonded together by the anchor effect of the die casting material filled in the pores, thereby providing the excellent effect of providing a heat absorber with strong adhesive strength between the base material and the surface layer and excellent heat dissipation properties.

[0033] (Configuration 3) The heat absorber 10 according to the first embodiment provides the heat absorber 10 according to configuration 1 or 2, in which the porosity of the porous portion 20 is 30% or more and 70% or less. If the porosity of the porous portion is too high, the strength of the entire heat absorber / dissipator may be weakened. The heat absorber / dissipator according to the present disclosure has an excellent effect of being able to provide a heat absorber / dissipator having high overall strength.

[0034] (Configuration 4) The heat absorber 10 of the first embodiment provides a heat absorber according to any one of configurations 1 to 3, in which the porous portion 20 has an average neck diameter of 10 μm or more and 80 μm or less when the distribution of pores 40 is calculated by the bubble point method. If the average neck diameter is too small, the molten metal will not easily penetrate into the pores, making it difficult to obtain the effect of increasing the adhesive strength. Conversely, if the average neck diameter is too large, the molten metal will penetrate too far into the pores, and in some cases, the first surface that contacts the inner wall of the mold will be filled with molten metal, and the unevenness of the surface of the porous body will disappear. Also, when the heat absorber is used for liquid cooling, if the molten metal penetrates into the pores, the internal surface area available for heat exchange will be reduced. The heat absorber and dissipator according to the present disclosure has the excellent effect of providing a heat absorber and dissipator having a strong adhesive strength between the base material and the porous body, and a large internal surface area effect, thereby achieving a large heat dissipation effect.

[0035] (Configuration 5) The heat absorber 10 of the first embodiment provides a heat absorber according to any one of configurations 1 to 4, in which the volume of the pores 40 that are not connected to the outside world accounts for 20% or less of the total volume of the porous portion 20. High adhesion can be achieved by the die-casting material penetrating into the three-dimensional network of holes that exists inside the porous portion. However, the effect is reduced if there are many closed holes. When using liquid cooling as a heat sink, the heat exchange efficiency is reduced if there are many closed holes. The heat absorber and dissipator according to the present disclosure has the excellent effect of providing a heat absorber and dissipator having a strong adhesive strength between the base material and the porous body, and a large internal surface area effect, thereby achieving a large heat dissipation effect.

[0036] Second embodiment The second embodiment will be described below with reference to FIGS.

[0037] [2-1. Casting method] FIGS. 4(a), 4(b), 4(c), and 4(d) are diagrams illustrating a casting method for a heat absorber / dissipator 10 according to a second embodiment of the present invention.

[0038] FIG. 4(a) is a diagram showing a preparation step in a casting method for the heat absorber / dissipator 10 according to the second embodiment. In this specification, the casting method is assumed to be a die-casting method, but other general casting methods may be used as long as the press-in process described later is possible. An operator prepares a die 50 that defines the overall shape of the heat absorber / dissipator 10, and places a porous body 60 that will ultimately constitute the porous portion 20 of the heat absorber / dissipator 10 inside the die. At this time, it is necessary to make the first surface 63 of the porous body 60 adhere to the inner wall of the die 50 so that the molten metal of the die-casting material does not fill the pores 40 that open to the first surface 63. The porous body 60 may be manufactured by sintering metal powder or by other methods.

[0039] Fig. 4(b) is a diagram showing a stage in which the molten metal is poured into the inside of the die 50 by applying pressure to the molten metal with a plunger 80. Fig. 4(c) is a diagram showing a stage in which the die-casting material is poured toward the second surface 65 of the porous body 60.

[0040] Fig. 4(d) is a diagram showing a stage in which the die-casting material is filled into the holes 40 opening on the second surface 65 of the porous body 60. At this time, it is desirable that a larger pressure is applied to the molten metal by the plunger 80 than in Fig. 4(c).

[0041] It is preferable that the pouring speed of the molten metal from FIG. 4(a) to FIG. 4(b) is slower than the pouring speed of the molten metal from FIG. 4(b) to FIG. 4(c).

[0042] FIG. 5 is a flowchart of the heat absorber casting method according to this embodiment.

[0043] First, the porous body 60 constituting the porous portion 20 is held inside the mold 50 (step S1: holding step). Next, the plunger 80 applies pressure to the molten metal to press the die-casting material in (step S2: pressing step). The plunger 80 applies even greater pressure to the molten metal to fill the voids 40 opening in the second surface 65 of the porous body 60 with the molten die-casting material (step S3: filling step). At this time, it is desirable to apply a greater pressure to the molten metal by the plunger 80 than in the pressing step of step S2. Next, the product is cooled (step S4). Then, the mold 50 is opened, and the heat absorber / dissipator 10, which is the product, is taken out (step S5).

[0044] [2-2. Effects, etc.] (Configuration 6) The casting method for a heat absorber / dissipator according to the second embodiment provides a casting method for a heat absorber / dissipator, which includes a holding step of holding a first surface 63 of a porous body 60 in intimate contact with the inner surface of a mold 50, and a pressing step of pressing a molten metal of a die-casting metal material toward a second surface 65 of the porous body 60 opposite the first surface 63. According to the casting method for a heat absorber / dissipator of the present disclosure, the base material cast by the die casting method and the surface layer composed of a porous metal are firmly bonded to each other, thereby achieving the excellent effect of providing a heat absorber / dissipator having strong adhesive strength, heat absorption, and excellent heat dissipation properties.

[0045] (Configuration 7) The second embodiment of the casting method for a heat absorber / dissipator according to the present invention provides a casting method for a heat absorber / dissipator as described in configuration 6, in which the pressing step includes a filling step of filling at least a portion of the pores 40 of the porous body 60 located within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface 25 between the porous body 60 and the die-cast portion 30 with a die-casting material that forms the die-cast portion 30. According to the casting method for a heat absorber / dissipator of the present disclosure, the base material cast by the die casting method and the surface layer composed of a porous metal are firmly bonded to each other, thereby achieving the excellent effect of providing a heat absorber / dissipator having strong adhesive strength, heat absorption, and excellent heat dissipation properties.

[0046] The step units shown in Fig. 5 are divided according to the main process contents in order to facilitate understanding of the casting method, and the casting method is not limited by the manner in which the process units are divided or the names thereof. The casting method may be divided into more step units according to the process contents. Furthermore, one step unit may be divided to include more processes. Furthermore, the order of the steps may be changed as appropriate within the scope of the present disclosure.

[0047] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, and the like can be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0048] The present disclosure is applicable to a heat absorber having a surface layer with excellent heat absorption and heat dissipation performance and strong adhesive strength. Specifically, the present disclosure is applicable to a heat sink used for dissipating heat from electronic components, and a casting method for the heat sink. [Explanation of symbols]

[0049] 10 Heat sink / radiator 20 Porous part 25 Adhesive surface 30 Die Casting Department 40 Vacancies 50 Mold 60 Porous bodies 63 First Side 65 Second Side 80 Plunger

Claims

1. A heat absorber having a die-cast portion and a porous portion formed from a metal material, wherein at least some of the pores of the porous portion located within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface between the porous portion and the die-cast portion are filled with the die-cast material that forms the die-cast portion.

2. 2. The heat absorber according to claim 1, wherein the bonding length ratio of the bonding surface where the porous portion and the die-cast portion are bonded to each other is 40% or more within a range of 100 μm in a direction perpendicular to the bonding surface.

3. 3. The heat absorber according to claim 1, wherein the porosity of the porous portion is 30% or more and 70% or less.

4. 3. The heat absorber according to claim 1, wherein the porous portion has an average neck diameter of 10 [mu]m or more and 80 [mu]m or less when the pore distribution is calculated by a bubble point method.

5. 3. The heat absorber according to claim 1, wherein a ratio of a volume of said pores not connected to the outside to a total volume of said porous portion is 20% or less.

6. A casting method for a heat sink or radiator, comprising the steps of: a holding step of holding the first surface of the porous body in a state of intimate contact with the inner surface of the mold; a pressurizing step of pressurizing a molten metal of a die-casting metal material toward a second surface of the porous body opposite to the first surface; The casting method for a heat sink / dissipator comprises the steps of:

7. 7. The method for casting a heat absorber or dissipator according to claim 6, wherein the pressing step includes a filling step of filling at least a portion of the pores of the porous body located within a range of 50 μm or more and 500 μm or less (excluding 500 μm) from the bonding surface between the porous body and the die-cast portion with a die-cast material that forms the die-cast portion.

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