JP2019201026A - Heat receiving jacket, liquid cooling system, and manufacturing method for heat receiving jacket - Google Patents

Abstract

To provide a heat receiving jacket that can improve a liquid cooling effect and be made to be compact.SOLUTION: A heat receiving jacket 10 of the present invention is a heat receiving jacket for a liquid cooling system, the heat receiving jacket housing porous metal 22 inside to receive heat of an exothermic body 400 (cooling target). The heat receiving jacket 10 comprises a heat receiving plate 30 that receives heat from the exothermic body 400 and made from solid metal. The heat receiving plate 30 and the porous metal 22 are joined using solder material. A boundary surface between the porous metal 22 and the heat receiving plate 30 is configured by fusion material of the solder material and porous metal. The height of the porous metal 22 after the joining is smaller than a pore size, a pitch of the porous metal 22.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a liquid cooling system that targets water or the like as a cooling medium and transfers heat from a high temperature fluid to a high temperature fluid, and a heat receiving jacket capable of improving heat transfer performance and a liquid cooling system equipped with the heat receiving jacket And a manufacturing method thereof.

  In recent years, liquid cooling systems and other heat transport systems have become more sophisticated and smaller in size, and with this, heat sinks mounted on the heat receiving jacket of the liquid cooling system have to be improved in performance, size and weight. . In general, a liquid cooling system mounted on a power module, a server, or the like not only fails to maintain the functions of the power module, the server, and the like when heat transfer performance decreases, but may be damaged in some cases. For this reason, as a requirement for the liquid cooling system, a technology for efficiently exchanging heat has become stronger as performance of a power module, a server, or the like is improved.

  As a method for efficiently transporting heat of a semiconductor element mounted on a power module, a server, or the like, it is common to circulate a refrigerant liquid by a pump and dissipate heat to the outside air. Generally, the heat receiving jacket connected to the semiconductor element of this liquid cooling system efficiently transfers the heat of the semiconductor element to the refrigerant liquid.

  As a prior art, in Patent Document 1, a brazing material (Al—Si alloy; BA4343) containing Si is disposed between a solid metal plate and a porous metal, and brazing is performed by heating to 590 to 610 ° C. There is a description to do. However, FIG. 6 shows a structure in which the height of the porous metal after brazing is larger than the pore size of the porous metal.

  Patent Document 2 describes a water-cooled heat sink in which a porous metal member is brazed to a copper plate, and a method for manufacturing the water-cooled heat sink. An oxygen-free copper base material at a temperature of 800 ° C. using a brazing material having a melting temperature of about 800 ° C., in which a brazing material not containing Si and a porous metal are arranged on the heat receiving plate in the order of brazing material and porous metal. And a laminating process for brazing copper and porous copper with a brazing material containing no Si.

  Patent Document 3 describes a composite plate obtained by laminating a copper plate, a copper porous foam metal, and a brazing material (JISZ3264 BCUP-4) not containing Si and brazing at a temperature of 720 ° C.

JP 63-077658 JP 2006-179491 A JP 2006-344500 A

  In the above-described prior art, Patent Documents 1 to 3 all relate to a method for joining a porous metal and a metal plate, but the single-layer refrigerant liquid circulation in which only a single layer (liquid) of the refrigerant liquid is circulated. There is no description regarding high performance and compactness when a porous metal is used for the heat receiving part of the cooling module. Therefore, the patent document has a high heat transfer coefficient in a liquid cooling system or the like, does not have a porous metal structure considering fin efficiency, and cannot improve the performance of a heat receiving jacket for a liquid cooling system. That is, the structure of the porous metal after brazing is further reduced to a structure in which the height of the porous metal is smaller than the pore size of the porous metal while maintaining the shape and porosity of the porous metal before brazing. There is no description of a manufacturing method that can achieve the above, and no consideration is given to high performance and compactness of a liquid cooling system equipped with a porous metal.

  This invention is invention for solving the said subject, Comprising: It aims at providing the manufacturing method of a heat receiving jacket, a liquid cooling system, and a heat receiving jacket which can heighten and make liquid cooling effect compact.

  In order to achieve the above object, a heat receiving jacket according to the present invention is a heat receiving jacket for a liquid cooling system in which a porous metal is housed and receives heat from the heating element, and the heat receiving jacket is a heat receiving jacket from the heating element. The heat receiving plate is made of a solid metal, and the heat receiving plate and the porous metal are joined with a brazing material, and the interface between the porous metal and the heat receiving plate is composed of a molten material of the brazing material and the porous metal, The height of the porous metal after joining is characterized by being lower than the pore size, which is the pitch of the porous metal. Other aspects of the present invention will be described in the embodiments described later.

  According to the present invention, the liquid cooling effect can be enhanced and the size can be reduced.

It is a perspective view of the liquid cooling system which connected the heat receiving jacket to the heat generating body which is one Embodiment of this invention. FIG. 2 is a perspective view around a heat receiving jacket of FIG. 1. It is AA sectional drawing of the heat receiving jacket of FIG. It is a heat resistance ratio of the heat receiving jacket with respect to a change in the height of the porous metal, modeling the porous metal as an embodiment of the present invention as a fin. It is a change figure of the ratio of Si with respect to the aluminum alloy which is one Embodiment of this invention, and melting | fusing point of an aluminum alloy. It is a series figure of the manufacturing method at the time of using the heat receiving board which comprises the heat receiving jacket which is one Embodiment of this invention, and the atmospheric furnace at the time of brazing a porous metal. It is a series figure of the manufacturing method at the time of using the heat receiving board which comprises the heat receiving jacket which is embodiment of this invention, and the vacuum furnace at the time of brazing a porous metal. It is an example of the water cooling jacket which is embodiment of this invention, (a) is a side view around the heat-receiving board which mounted the porous metal after brazing, (b) is the enlarged view. As a typical example of a power module according to another embodiment of the present invention, a heat receiving jacket sectional view of a liquid cooling system for transferring heat of a semiconductor element to a heat receiving jacket, where the heat receiving jacket is sealed by an O-ring. It is. It is a perspective view which shows the state which removed the cover body as an example of an internal structure about the electronic device to which the liquid cooling system using the porous metal of this invention is applied. It is a top view for demonstrating the arrangement | positioning state of the liquid cooling system in the server housing | casing of FIG. It is sectional drawing of a heat receiving jacket in case there are two or more heat receiving plates. It is explanatory drawing which shows the example which applied the heat receiving jacket of this embodiment to the semiconductor module for 3 phases.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a perspective view of a liquid cooling system 1 in which a heat receiving jacket 10 is connected to a heating element 400 (an object to be cooled) according to an embodiment of the present invention. The liquid cooling system 1 includes a heat receiving jacket 10, a radiator 160, a pump 200 and a pipe 300. The heat receiving jacket 10 is provided with a refrigerant liquid inlet 23 through which the refrigerant liquid 100 flows from the pump 200, and a refrigerant liquid outlet 24 through which the refrigerant liquid 100 flows out to the radiator 160. The heating element 400 is thermally connected to the outer wall 26 of the heat receiving jacket 10 through the heat conductive grease 500. As will be described later, a porous metal 22 (see FIG. 3) is mounted inside the heat receiving jacket 10, and the heat of the heating element 400 is transferred to the porous metal 22 and transferred to the refrigerant liquid 100. The material of the heat receiving jacket 10 is a solid metal. The refrigerant liquid 100 is water or the like.

  The refrigerant liquid 100 that has flowed out of the heat receiving jacket 10 flows through the pipe 300 and is transported by heat to the radiator 160. The radiator 160 has headers 162 on both sides, a large number of flat tubes 161 in the middle, and heat radiation fins 163 such as corrugated fins in a region sandwiched by the flat tubes 161. The refrigerant liquid 100 that has flowed into the radiator 160 flows into the header 162, branches by the flat tube 161, joins at the header 162, and flows to the pump 200 via the pipe 300. Air 110 is supplied to the radiation fins 163 of the radiator 160 by the cooling fan 710. The cooling fan 710 drives the air 110 by rotating a blade by a motor. The refrigerant liquid 100 that has exchanged heat with the heat receiving jacket 10 and has reached a high temperature is transferred to the air 110 having a low temperature by the radiator 160, and the refrigerant liquid 100 has a low temperature. The refrigerant liquid 100 flows into the pump 200 at a low temperature and flows from the refrigerant liquid inlet 23 of the heat receiving jacket 10 to the heat receiving jacket 10. In the radiator 160, the air 110 that has passed through the radiation fins 163 is heat-exchanged and diffused to the atmosphere at a high temperature. As described above, the heat of the heating element 400 is transmitted to the air 110 via the heat receiving jacket 10, the refrigerant liquid 100, and the radiator 160, and heat transport is performed. Thus, the heating element 400 can be cooled without exceeding the allowable temperature. When the heating element 400 is a semiconductor element, the operation of the semiconductor element can be ensured, and the reliability of the apparatus can be improved.

  FIG. 2 is a perspective view around the heat receiving jacket 10 of FIG. The inside of the heat receiving jacket 10 is indicated by a broken line, and a porous metal 22 is mounted inside the heat receiving jacket 10. The inner area of the heat receiving jacket 10 and the porous metal 22 have substantially the same shape, and the inner surface of the outer wall 26 of the heat receiving jacket 10 and the porous metal 22 are in physical contact. The material of the heat receiving jacket 10 is a solid metal. A heating element 400 is attached to one surface of the outer wall 26 of the heat receiving jacket 10 via a heat conductive grease 500. The inner surface of the heat receiving plate 30, which is the outer wall 26 of the heat receiving jacket 10 to which the heat generating body 400 is attached, and the porous metal 22 are bonded together by metal bonding 25 such as brazing. Thereby, the heat of the heat generating body 400 can be favorably transmitted from the outer wall 26 of the heat receiving jacket 10 to the porous metal 22. The heat receiving jacket 10 is provided with a refrigerant liquid inlet 23 and a refrigerant liquid outlet 24. The refrigerant liquid 100 flows into the heat receiving jacket 10 from the refrigerant liquid inlet 23, passes through the porous metal 22, and passes through the refrigerant liquid. It flows out from the outlet 24.

  FIG. 3 is a cross-sectional view taken along the line AA of the heat receiving jacket 10 of FIG. A heat receiving plate 30 is provided as one surface of the outer wall 26 of the heat receiving jacket 10. A heating element 400 is attached to the heat receiving plate 30 via a heat conductive grease 500. A porous metal 22 is metallicly bonded 25 (for example, brazing material) to the heat receiving jacket 10. The material of the heat receiving jacket 10 is a solid metal. Thereby, the heat of the heat generating body 400 can be favorably transmitted from the outer wall 26 of the heat receiving jacket 10 to the porous metal 22.

  The porous metal 22 includes an infinite number of fine wires 20 and a cavity 21. The fine wire 20 is made of a metal material such as aluminum or copper. A refrigerant liquid inlet 23 and a refrigerant liquid outlet 24 provided on the outer wall 26 of the heat receiving jacket 10 are provided. The refrigerant liquid flows into the heat receiving jacket 10 from the refrigerant liquid inlet 23, and the cavity 21 of the porous metal 22. And flows out from the refrigerant liquid outlet 24. The porous metal 22 has almost no directivity of the flow of the refrigerant liquid 100, and the refrigerant liquid 100 flows through the entire area of the porous metal 22. For this reason, heat can be transferred to the refrigerant liquid 100 over the entire large surface area of the porous metal 22, and the refrigerant liquid 100 is not wasted.

  This is compared with a pin fin conventionally used as a heat transfer surface of the heat receiving jacket 10. For the same volume, the heat transfer area of the porous metal 22 can be several times to several tens of times larger than the heat transfer area of the pin fin. Even if the difference in fin efficiency between the pin fin and the porous metal 22 is taken into consideration, the volume having the same thermal resistance defined by the value obtained by dividing the temperature difference between the heat transfer surface temperature and the refrigerant liquid inlet temperature by the calorific value is porous. In the case of the high quality metal 22, the heat receiving jacket 10 can be reduced in height (thinner thickness can be reduced), and the heat receiving jacket 10 can be reduced in size. As a result, the heating element 400 can be cooled without exceeding the allowable temperature with the compact heat receiving jacket 10, and when the heating element 400 is a semiconductor element, the operation of the semiconductor element can be ensured and the reliability of the apparatus is improved. it can.

  Moreover, the following three types can be considered as a method of making the porous metal 22 thin. (1) Milling a thick porous metal with a mill, (2) Forming a thin porous metal using a 3D printer, (3) Melting the porous metal using erosion during brazing. Of these, (3) does not use cutting or cutting, so there are no problems such as unsuitable for mass production, such as the cut surface of the porous metal is scraped, and the scrap after cutting enters the space of the porous metal ( The production method 3) is more preferable.

  Here, the bonding interface between the porous metal 22 that is the metallic bond 25 and the heat receiving plate 30 is composed of a brazing material for bonding and a molten material of the porous metal 22. In particular, when the porous metal 22 is aluminum, the component of the brazing material portion of the metallic joint 25 is rich in Si—Al alloy. The height of the porous metal 22 is smaller than the pore size (= number of porous metal cells / 25 (unit mm)) which is the pitch of the porous metal.

  FIG. 4 shows the heat resistance ratio of the heat receiving jacket with respect to a change in the height of the porous metal 22 modeled as the fins of the porous metal 22 according to one embodiment of the present invention. The horizontal axis of FIG. 4 is the height of the porous metal 22, and the vertical axis is the thermal resistance ratio of the heat receiving jacket 10. This is an example in which the porous metal 22 is considered as a pin fin, and the porous metal 22 is a hollow fin having a wire diameter of 100 μm and a wall thickness of 10 μm. The heat resistance ratio of the heat receiving jacket 10 is represented by a heat resistance ratio of the porous metal 22 with a height of 2 mm. From FIG. 4, the height of the porous metal 22 is 1.2 mm and the thermal resistance ratio takes the minimum value. When the height of the porous metal 22 is higher than 1.2 mm, the thermal resistance ratio slightly increases. When the ratio is lower than 1.2 mm, the thermal resistance ratio increases rapidly. This is because the heat dissipation area is reduced due to the lower fins.

  From the above, by setting the height 44 of the porous metal 22 to about 1.2 mm, the heat receiving jacket 10 can have high performance and can be made compact. When the optimum value of the height of the porous metal 22 is 1.2 mm, when the number of porous metal cells is 20 ppi (pores per inch) (the number of cells per inch (25.4 mm)), the aforementioned pore size is 1. 25 mm. That is, the optimum value of the height of the porous metal 22 is smaller than the pore size of the porous metal 22. In this case, when forming the porous metal 22, it does not form, and it turns out that the heat receiving jacket 10 cannot be manufactured as it is. The manufacturing method according to this embodiment will be described later with reference to FIG.

  FIG. 5 is a change diagram of the ratio of Si to the aluminum alloy and the melting point of the aluminum alloy according to an embodiment of the present invention. The horizontal axis in FIG. 5 is the ratio of Si in the aluminum alloy, and the vertical axis is the melting point of the aluminum alloy. When the proportion of Si contained in the aluminum alloy is about 12% and the melting point of the aluminum alloy is a minimum value of 580 ° C., when the proportion of Si contained in the aluminum alloy is less than 12%, the melting point of the aluminum alloy gradually increases, and aluminum The melting point is 660 ° C. with pure aluminum having an Si content of 8% and a melting point of 600 ° C., and an Si content of 0%. Further, when the proportion of Si contained in the aluminum alloy is greater than 12%, the melting point of the aluminum alloy increases as in the case where the proportion of Si contained in the aluminum alloy is less than 12%. However, when the proportion of Si contained in the aluminum alloy is greater than 12% than when the proportion of Si contained in the aluminum alloy is less than 12%, the rate of increase in the melting point of the aluminum alloy (the slope of the graph) is steep. is there. Therefore, the melting point of the aluminum alloy can be stably set by controlling the Si content contained in the aluminum alloy at a side smaller than 12%.

  In the case of brazing with pure aluminum, pure aluminum melts into the brazing material during brazing. Although the amount of Si contained in the brazing material does not change, in particular, the porous metal contacts the innumerable aluminum skeleton at the point of the brazing material, unlike the case of the heat receiving plate that contacts the entire surface. For this reason, Si concentrates on the aluminum skeleton of the porous metal, and the porous metal is actively melted. From the above, considering that the furnace temperature during brazing is relatively low, such as 580 ° C. to 600 ° C., the ratio of Si to the aluminum alloy that is the brazing material before brazing is about 8 to 12% ( The range of 38) is a reasonable value.

FIG. 6 is a series diagram of a manufacturing method using an atmosphere furnace when brazing the heat receiving plate 30 and the porous metal 22 constituting the heat receiving jacket 10 according to the embodiment of the present invention.
(1) A member is prepared (see FIG. 6A). The member includes porous metal 22 (for example, 5 mm height (h) or thickness, A1000 range (A1050, melting point 657 ° C.)), brazing material 29 (for example, 50 μm thickness, A4000 range (A4045, melting point 575 ° C., Si ratio is about 10%)), heat receiving plate 30 (for example, flat plate A3000 series (A3003, melting point 654 ° C.)), nocoloc flux (aqueous solution) in order to remove the oxide film formed on the aluminum member surface at high temperature in the atmosphere furnace ).
(2) In preparation before brazing, the sawlock flux 31 is applied to one side of the brazing material 29 and one side of the heat receiving plate 30 (see FIG. 6B).
(3) In fixing before brazing, the heat receiving plate 30 coated with the nocolok flux 31 of the above (2), the brazing material 29 coated with the nocolok flux 31 and the porous metal 22 are stacked in this order (FIG. 6C). )reference).
(4) In brazing, the heat receiving plate 30, the brazing material 29, and the heat receiving jacket 10 made of the porous metal 22 installed in (3) above are installed on the belt 33. When the belt 33 moves 34, the belt 33 passes through the atmosphere furnace 32 whose temperature in the furnace becomes about 600 ° C. (see FIG. 6D).

  When passing through the atmosphere furnace 32, the heat receiving plate 30, the brazing material 29, and the heat receiving jacket 10 of the porous metal 22 become the same temperature as the temperature in the furnace, and the brazing material 29 having a low melting point can be unwound. Because of the atmospheric furnace 32, an oxide film is generated on the aluminum surface from the air in the furnace. Since this oxide film inhibits brazing, the oxide film is removed with the nocolok flux 31. For example, the brazing material 29 is A4000 series and contains 10% of Si. As the brazing material 29 melts, Si precipitates and diffuses into the A1000 series porous metal 22 and the A3000 series heat receiving plate 30. In particular, since the porous metal 22 has a porosity of about 90% to 97% and a heat capacity smaller than that of the heat receiving plate 30 that is a metal solid, the diffusion of Si increases toward the porous metal 22 side. As a result, the porous metal 22 is eutectic with Si, and erosion that melts at a temperature lower than the melting point of the A1000 series, which is the material of the porous metal 22, substantially at the same temperature as the brazing material 29 occurs. Thereby, the porous metal 22 melts at the interface of the brazing material 29, and the height of the porous metal 22 gradually decreases.

  On the other hand, the porous metal 22 is A1000 series aluminum, and since the molten aluminum of the porous metal 22 enters the brazing material 29, the proportion of Si in the brazing material 29 is reduced, and as described with reference to FIG. When the ratio of Si to the alloy decreases, the melting point of the aluminum alloy increases, and the erosion stops at the ratio of Si having the melting point of the aluminum alloy that becomes the furnace temperature. For example, the ratio of Si in the thickness of 50 μm is 10% for the brazing material 29 of A4045. If the furnace temperature is 600 ° C., the proportion of Si in the aluminum alloy is 8%. As described above, at the interface between the porous metal 22 and the brazing material 29, the aluminum skeleton of numerous porous metals contacts the brazing material. For this reason, Si concentrates on the aluminum skeleton of the porous metal, and the porous metal 22 is actively melted. If the porosity of the porous metal 22 is 95% (the aluminum filling rate is 5%), the aluminum of the porous metal 22 eutectizes with Si in the brazing material, and the interface between the porous metal 22 and the brazing material 29 Lower the melting point at. Thereby, the porous metal 22 is melted at a temperature of 660 ° C. or lower of pure aluminum. In the brazing portion in which the porous metal 22 is dissolved, the component of the brazing material 29 is in a rich state of the Si—Al alloy, and the thickness of the brazing material 29 includes aluminum in which the porous metal 22 is melted. Therefore, it is thicker than the initial brazing material 29.

Moreover, the thickness of the porous metal 22 after brazing becomes a value smaller than the pore size of the porous metal 22, and the height of the porous metal 22 can be lowered (thinner thickness is reduced). In addition, when reducing the thickness of the porous metal, a load is applied to the porous metal and the porous metal is not crushed in the thickness direction. And the porosity does not change. That is, by crushing the porous metal, the skeleton shape of the porous metal becomes dense and the porosity decreases, so that a large increase in pressure loss can be considered when flowing the refrigerant liquid through the heat receiving jacket. There is a concern that the operating flow rate at the pump of the system decreases and the cooling performance of the liquid cooling system decreases. On the other hand, when the porous metal is melted as in this embodiment, there is no increase in pressure loss when the refrigerant liquid is passed through the heat receiving jacket, and the operating flow rate of the pump of the liquid cooling system 1 can be predicted as designed. There is no decrease in the cooling performance of the liquid cooling system 1.
(5) After brazing, the heat receiving jacket 10 is sufficiently cooled to complete the heat receiving jacket 10 (see FIG. 6E).

  In the case of the present embodiment, when the pore size of the porous metal 22 is Dpore, the height h of the porous metal 22 was initially greater than, for example, Dpore × 3 times (see FIG. 6A). The characteristic is that the height h of the porous metal 22 is less than Dpore after brazing (see FIG. 6E).

Next, an example of a method for producing a porous metal will be described.
[Substrate]
The substrate uses a three-dimensional network structure having a skeleton that is three-dimensionally connected and pores that are three-dimensionally connected by the skeleton. This substrate is supported by adhering aluminum powder and / or aluminum alloy powder to the surface of the skeleton, and is composed of a resin because it should be decomposed and disappeared by heating. Specifically, polyurethane foam is most commonly used as the substrate, but silicone resin, polyester resin foam, and the like can also be used.

[Aluminum powder or aluminum alloy powder]
As the powder to be adhered to the resin skeleton of the substrate, aluminum powder is used in view of the balance of thermal conductivity and specific gravity, but aluminum alloy powder in which a component that strengthens aluminum is previously alloyed may be used instead of aluminum powder. For example, when aluminum alloy powder in which alloying elements such as Cu, Mn, Mg, and Si are prealloyed is used for Al, the skeleton of the aluminum-based porous body is formed of the aluminum alloy, and the aluminum-based porous body Strength can be improved. By adding alloying elements such as Cu, Mn, Mg, and Si to Al, the thermal conductivity is lower than that of Al alone, but the base metal is Al, so it maintains a sufficiently high thermal conductivity. can do. As the aluminum powder or aluminum alloy powder, a general one, that is, a powder having an oxide film (alumina: Al2O3) of about 10 mm on the surface is used.

  The aluminum powder and / or aluminum alloy powder to be adhered to the resin skeleton of the substrate is preferably a fine one because it can adhere closely to the surface of the resin skeleton of the thin substrate. As the powder becomes larger, it becomes difficult to adhere closely to the resin skeleton surface of the substrate, and due to the increase in the mass of the powder, it becomes difficult to adhere to the resin skeleton surface of the substrate and easily falls off. From this viewpoint, it is preferable to use an aluminum powder and / or an aluminum alloy powder having an average particle size of 50 μm or less. Furthermore, it is preferable that the average particle size is 50 μm or less and does not contain powder having a particle size exceeding 100 μm. However, since Al is an active metal, it is difficult to handle an excessively fine powder. From this viewpoint, it is preferable to use an aluminum powder and / or an aluminum alloy powder having an average particle size of 1 μm or more.

[Adhesion process]
Various conventional methods can be applied to adhere the aluminum powder and / or aluminum alloy powder to the resin skeleton of the substrate. The following describes typical methods. (1) Wet method A dispersion is prepared by dispersing aluminum powder and / or aluminum alloy powder in a dispersion medium, and the substrate is immersed in this dispersion, and then the substrate is dried. It is a method to make it. As the dispersion medium, a liquid having a volatile property such as alcohol or water as a solvent and a binder dissolved therein can be used. In this case, a dispersant may be added to the dispersion medium so that the powder does not settle. Moreover, as a dispersion medium, you may use the solution of high molecular organic substances, such as a phenol resin.
(2) Dry method Acrylic or rubber adhesive solution or adhesive resin solution such as phenol resin, epoxy resin, furan resin, etc. is applied to the surface of the substrate to provide adhesiveness. In this method, the powder is deposited on the surface of the skeleton by rocking or spraying the powder on the substrate.

[Heating process]
The substrate on which the aluminum powder or the aluminum alloy powder is adhered to the surface of the skeleton is heated to a temperature higher than the melting point of the aluminum powder and / or the aluminum alloy powder in a non-oxidizing atmosphere. In the process of raising the temperature to the melting point, the resin substrate is decomposed and removed to disappear.

  When the heating temperature exceeds the melting point of aluminum (melting point: 660.4 ° C.) or aluminum alloy, the aluminum powder or aluminum alloy powder melts inside. That is, the surface of the aluminum powder or aluminum alloy powder is covered with an oxide film (alumina: Al 2 O 3), and the melting point of alumina is as high as 2072 ° C., so the oxide film on the surface of the aluminum powder or aluminum alloy powder does not melt. The inside of the powder melts. The aluminum or aluminum alloy thus melted inside breaks the oxide film on the surface of the powder and wets and covers the powder surface, and the molten aluminum or molten aluminum alloy generated from each powder is mixed and bonded. At this time, the oxide film formed on the powder surface becomes a substitute skeleton, maintains the shape of the skeleton, and the surface tension of the molten aluminum or molten aluminum alloy bonded to each other makes the skeleton surface relatively smooth and the neck portion disappears. It becomes a continuous metal surface.

  On the other hand, when the heating temperature is lower than the melting point of aluminum or aluminum alloy, a strong oxide film formed on the surface of aluminum powder or aluminum alloy powder becomes a barrier, and diffusion between aluminum powders or aluminum alloy powders Sintering does not proceed due to hindering the joining.

When the atmosphere in the heating process is an oxidizing atmosphere such as air, the molten aluminum or molten aluminum alloy exposed by breaking the oxide film on the powder surface is immediately oxidized and wetted to cover the powder surface, and the melting generated from each powder Mixing of aluminum or molten aluminum alloy is prevented, and bonding between the powders is hindered. For this reason, it is desirable that the atmosphere in the heating step be a non-oxidizing atmosphere such as nitrogen gas or inert gas. The above heating step is not intended to remove the oxide film on the surface of the aluminum powder or aluminum alloy powder, so it is not necessary to be in a reducing atmosphere such as hydrogen gas or a hydrogen mixed gas. Since this atmosphere is a non-oxidizing atmosphere, it may be a reducing atmosphere. Moreover, it is good also as a pressure reduction atmosphere (vacuum atmosphere) whose pressure is 10 < ^-3 > Pa or less.

  The heating temperature can be melted as long as the temperature exceeds the melting point of the aluminum powder or aluminum alloy powder adhered to the substrate. However, heating at a temperature greatly exceeding the melting point requires extra energy and melting. The heating temperature is preferably up to the melting point + 100 ° C., because the viscosity of the aluminum or aluminum alloy is lowered and the mold is likely to lose its shape.

  The three-dimensional network structure of the aluminum-based porous body manufactured by the above manufacturing method is the one in which the three-dimensional network structure of the resin base is maintained as it is. Therefore, by changing the three-dimensional network structure of the resin substrate, the three-dimensional network structure of the aluminum porous body can be changed, and the porosity and pore size of the entire aluminum porous body can be changed. It is possible to adjust to the desired one. Specifically, the porosity can be 85 to 95%, the pore size can be 30 to 4000 μm, and the porosity is 6 to 80 ppi (cell number / 25.4 mm). The body can be manufactured easily.

  In the case of forming an aluminum-based porous body with an aluminum alloy, a component (Cu, Mg, etc.) that generates a eutectic liquid phase with Al as a raw material powder was added to the aluminum powder as a simple powder or an aluminum alloy powder. A method of using an aluminum-based mixed powder, attaching the aluminum-based mixed powder to the surface of a resin substrate having a three-dimensional network structure, and sintering at a temperature at which a eutectic liquid phase is generated can be considered. Then, the distribution of the component elements in the aluminum-based porous body is not uniform, and the aluminum oxide is not dispersed inside the skeleton, so that it is difficult to obtain a desired strength.

  On the other hand, the distribution of the component elements in the aluminum-based porous body becomes uniform by using the aluminum prealloy powder in which the component elements are previously alloyed in Al as described above. In addition, aluminum oxide resulting from the manufacturing method is dispersed inside the skeleton. For this reason, high intensity | strength can be acquired compared with the method of sintering by a eutectic liquid phase using aluminum type mixed powder.

  Also, during the heating step, a relatively high-speed gas is blown onto the porous metal, or the metal-shaped front part is changed to a curved surface and the rear part is changed to a long and thin shape by centrifugal force or the weight of the porous metal itself. Can do.

  It should be noted that porous metal made of a metal and a space can also be produced by a method for producing a mold other than the above-mentioned production methods.

FIG. 7 is a series diagram of a manufacturing method using a vacuum furnace when brazing the heat receiving plate 30 and the porous metal 22 constituting the heat receiving jacket 10 according to the embodiment of the present invention. Only differences from the embodiment of FIG. 6 will be described.
(1) Since a vacuum furnace is used in the preparation of the member, no coloc flux (aqueous solution) is required to remove the oxide film formed on the surface of the aluminum member at a high temperature. Is not required to be applied to one side of the brazing material 29 and one side of the heat receiving plate 30 (see FIG. 7A).
(2) In fixing before brazing, the heat receiving plate 30, the brazing material 29, and the porous metal 22 are stacked in this order (see FIG. 7B).
(3) In brazing, the heat receiving plate 30, the brazing material 29, and the heat receiving jacket 10 of the porous metal 22 stacked in (2) are installed in the vacuum furnace 35 (see FIG. 7C). The furnace temperature in the vacuum furnace 35 is about 600 ° C., and the heat receiving plate 30, the brazing material 29, and the heat receiving jacket of the porous metal 22 have the same temperature. The brazing material 29 having a low melting point can be dissolved. Since there is no air in the vacuum furnace 35, no oxide film is generated.
(4) After brazing, the heat receiving jacket 10 is sufficiently cooled to complete the heat receiving jacket 10 (see FIG. 7D).

  FIG. 8 is an example of a water-cooling jacket according to an embodiment of the present invention, in which (a) is a side view around the heat receiving plate 30 on which the porous metal 22 after brazing is mounted, and (b) is an enlarged view thereof. It is. The heat receiving jacket 10 is manufactured by the manufacturing method described in FIGS. 6 and 7, and the porous metal 22 is metal-bonded (brazed) 25 to the heat receiving plate 30. In order to observe the detail 39 of the brazing material part of this heat receiving jacket 10, an enlarged view is shown in FIG.8 (b).

  In the detail 39 of the brazing material portion, the thickness 40 (height h) of the porous metal 22 after brazing is a value smaller than the pore size 42 of the porous metal 22. As described above, the thickness 41 of the brazing material after brazing is larger than the thickness of the brazing material before brazing. This is because the porous metal 22 is eutectic with Si contained in the brazing material, melts at a lower melting point than aluminum, which is the material of the porous metal 22, and melts into the brazing material. Further, the Si—Al alloy becomes rich 43 near the brazing material in contact with the skeleton of the porous metal 22. Furthermore, the shape of the skeleton of the porous metal 22 after brazing is the same as the shape of the skeleton of the porous metal 22 before brazing, and a load is applied in the thickness direction of the porous metal 22 to apply the porous metal 22. It can be seen that the structure is not reduced by reducing the height of the porous metal. Thereby, the skeleton shape of the porous metal 22 becomes dense, the porosity does not decrease, the pressure loss does not increase when the refrigerant liquid flows through the heat receiving jacket 10, and the pump 200 of the liquid cooling system 1 The operation flow rate can also be predicted as designed, and there is no decrease in the cooling performance of the liquid cooling system 1.

  FIG. 9 is a cross-sectional view of a heat receiving jacket of a liquid cooling system that transfers heat of a semiconductor element to the heat receiving jacket 10 as a representative example of a power module that is another embodiment of the present invention. The heat receiving jacket 10 is an O-ring. 27 is sealed. The power module is obtained by joining a power device 402 such as an IGBT (Insulated Gate Bipolar Transistor) to an insulating substrate 1001 with solder or the like, and is used for running control of an automobile, a railway vehicle, or the like. When the heat of the power device 402 is transported, the liquid cooling system 1 is used. The heat receiving jacket 10 in the liquid cooling system 1 is connected to the power module via the heat conductive grease 500. The porous metal 22 is mounted inside the heat receiving jacket 10, and the outer wall 26 is integrated as the heat receiving jacket 10 with an O-ring 27 and a fixing screw 28. Although the refrigerant liquid inlet and the refrigerant liquid outlet are not shown, the refrigerant liquid flows into the heat receiving jacket 10 from the refrigerant liquid inlet and flows out of the refrigerant liquid outlet. From the above, the heat of the power device 402 is transmitted to the porous metal 22 of the small heat receiving jacket 10 and can be transported by the refrigerant liquid. Thereby, it can cool, without exceeding the allowable temperature of the power device 402, operation | movement of the power device 402 can be ensured, and the reliability of an apparatus can be improved.

  FIG. 10 is a perspective view showing an electronic device to which the liquid cooling system 1 using the porous metal 22 of the present invention is applied, with its lid removed as an example of the internal structure. FIG. 11 is a top view for explaining an arrangement state of the liquid cooling system 1 in the server housing of FIG.

  In general, considering the maintainability, for example, a plurality of (three in this example) hard disk drives 51, which are large-capacity recording devices, are provided on one side (in this example, the front side shown on the right side of the figure). A plurality of (four in this example) cooling fans 710 for air-cooling these hard disk drives, which also serve as heat generation sources in the housing, are attached to the rear side. A block 54 is provided between the other surface of the server housing 5 (that is, in the rear space, together with a cooling fan 711, housing a power source, a LAN as an interface for communication means, and the like. In the remaining space, a circuit board 1000 having a plurality of heat generating semiconductor elements mounted thereon is arranged on the surface of the liquid cooling system 1. The liquid cooling system 1 includes the small heat receiving jacket 10, the radiator 160, the pump, as described above. 200 and a pipe 300 that connects them, a semiconductor element as a plurality of heat generation sources is attached to a small heat receiving jacket 10 via a heat conductive grease 500. The heat of the semiconductor element is reduced to a small heat receiving jacket 10. From the radiator 160 to the radiator 160, and from the radiator 160 to the air by the cooling fan 710, To release to the atmosphere from.

  The two semiconductor elements 403 are provided with two sets of the liquid cooling system 1 of the present invention described above. That is, the surfaces of the two sets of semiconductor elements 403 are connected to the bottom and side surfaces of the heat receiving jacket 10 through the thermally conductive grease 500 applied between them to ensure good thermal bonding. Further, a radiator 160 constituting the liquid cooling system 1 is disposed behind four cooling fans 710 for air-cooling the hard disk drive 51. That is, the radiator 160 which comprises the liquid cooling system 1 is arrange | positioned along with the path | route of the air (cooling air) supplied from the exterior by the cooling fan 710. FIG. That is, the radiator 320 is attached in parallel with the row of cooling fans 710.

  As described above, in the structure of the electronic device described above, the cooling fan 710 which is a cooling unit of another device incorporated in the server housing 5 is used as a cooling unit (for the radiator 160 constituting the liquid cooling system 1 of the present invention). It is used (or shared) as a cooling fan. According to this, it is possible to cool the semiconductor element 403, which is a heat source in the housing, without having a dedicated cooling fan, in other words, relatively easily and inexpensively, and efficiently and reliably. It becomes possible. Moreover, according to the liquid cooling system 1 of the present invention, heat exchange efficiency is relatively high, and the electronic device such as a server that requires high-density mounting due to its relatively simple structure, Arrangement with a high degree of freedom is possible.

  Further, the radiator 160 constituting the liquid cooling system 1 is disposed so as to cover the exhaust surfaces of the plurality of cooling fans 710. According to such a configuration, even if any one of the cooling fans 710 is stopped due to a failure, the cooling of the radiator 160 is continued by the cooling air generated by the remaining cooling fans 710, that is, redundancy can be ensured. Therefore, it is suitable as a structure of a cooling system for an electronic device. If the area facing the radiator 160 is closer to the cooling fan 710 side, the redundancy can be further improved against a stop due to a failure of one of the cooling fans 710. As described above, a highly reliable electronic device system can be provided.

  In the present embodiment, for example, with the configuration of FIG. 3, the heat receiving plate 30 that is the outer wall 26 that is in thermal contact with the heating element 400 via the thermally conductive grease 500 or the like and the porous metal 22 are metallicly bonded. 25 (for example, brazing), and the interface between the porous metal 22 and the solid metal that is the heat receiving plate 30 is a molten material of the brazing material and the porous metal 22, so that the heat transfer between the heat receiving plate 30 and the porous metal 22 is performed. Can be good. Further, the shape and porosity of the porous metal 22 after brazing are the same as the porous metal 22 before brazing, and the height of the porous metal 22 is larger than the pore size which is the pitch of the porous metal 22. By making the height low, the heat receiving jacket 10 can be made small, and the liquid cooling system can be made compact.

  In FIG. 3, the case where there is one heat receiving plate 30 has been described, but the present invention is not limited to this. For example, the case where there are a plurality of heat receiving plates 30 will be described with reference to FIGS.

  FIG. 12 is a cross-sectional view of the heat receiving jacket 10A when there are a plurality of heat receiving plates. About the same function as FIG. 3, the same code | symbol is attached | subjected and description is abbreviate | omitted. The heat receiving jacket 10 </ b> A has two heat receiving plates 30 at the top and bottom of the drawing, and each heat receiving plate 30 is metal-bonded 25 (for example, brazed) to the porous metal 22, and the porous metal 22 and the heat receiving plate 30. When the solid metal interface is a molten material of brazing material and porous metal, heat transfer between the heat receiving plate 30 and the porous metal 22 can be improved.

  FIG. 13 is an explanatory diagram showing an example in which the heat receiving jackets 10 and 10A of the present embodiment are applied to a three-phase semiconductor module. The heating elements 400a, 400b, 400c of the semiconductor module shown in FIG. 13 have cooling surfaces on both sides facing each other. In order to efficiently cool the three-phase semiconductor modules, the heat receiving jacket 10 of FIG. 3 is arranged at the left and right ends of the figure, and the heat receiving jacket 10A of FIG. 13 is arranged at the center. Thereby, the heat generating body 400a can be cooled by the heat receiving jackets 10 and 10A. The heating element 400b can be cooled by the heat receiving jackets 10A and 10A. The heating element 400c can be cooled by the heat receiving jackets 10A and 10. According to the embodiment of FIG. 13, the semiconductor modules for three phases can be efficiently cooled.

DESCRIPTION OF SYMBOLS 1 Liquid cooling system 5 Server housing | casing 10 Heat receiving jacket 20 Fine wire material 21 Cavity part 22 Porous metal 23 Refrigerant liquid inflow port 24 Refrigerant liquid outflow port 25 Metallic joining (brazing)
26 Outer wall 27 O-ring 28 Fixing screw 29 Brazing material 30 Heat receiving plate 31 Noclock flux 32 Atmospheric furnace 33 Belt 34 Movement 35 Vacuum furnace 38 Ratio of Si to aluminum alloy as brazing material before brazing 39 Details of brazing material part 40 Thickness of porous metal after brazing 41 Thickness of brazing material after brazing 42 Vacuum furnace 43 Rich Si-Al alloy 51 Hard disk drive 54 Block housing LAN 100 Refrigerant liquid 110 Air 160 Radiator 161 Flat tube 162 Header 163 Radiating fin 200 Pump 300 Piping 400 Heating element (object to be cooled)
402 Power Device 403 Semiconductor Element 500 Thermal Conductive Grease 710, 711 Cooling Fan 1000 Circuit Board 1001 Insulating Board

Claims (5)

A heat receiving jacket for a liquid cooling system that contains porous metal inside and receives heat from a heating element,
The heat receiving jacket includes a heat receiving plate that receives heat from the heating element and is made of a solid metal,
The heat receiving plate and the porous metal are joined with a brazing material,
The interface between the porous metal and the heat receiving plate is composed of the brazing material and the molten material of the porous metal,
The heat-receiving jacket, wherein the height of the porous metal after joining is lower than a pore size that is a pitch of the porous metal. The heat receiving jacket according to claim 1, wherein the heat receiving plate and the outer wall covering the porous metal are fixed through brazing or an O-ring sealing material. The heat receiving jacket according to claim 1, wherein at least a plurality of the heat receiving plates are provided. The heat receiving jacket according to any one of claims 1 to 3, a refrigerant supply pump that supplies a refrigerant to the heat receiving jacket, heat of the refrigerant from the heat receiving jacket, and after the heat dissipation A liquid cooling system comprising: a heat dissipation radiator that supplies the refrigerant to the refrigerant supply pump. A method for producing a heat receiving jacket of a liquid cooling system comprising a heat receiving plate made of a solid metal and a porous metal,
A lamination step of laminating a brazing material containing Si and a porous metal having a thickness larger than the pore size on the heat receiving plate;
By maintaining the laminated body obtained by the laminating step at a temperature not lower than the melting point of the brazing material and not higher than the melting points of the porous metal and the heat receiving plate, the thickness is smaller than the pore size of the porous metal. And a brazing step of obtaining a heat receiving plate on which a thin porous metal is brazed.

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