Cooling system

Abstract

By increasing the range of coolant options, this system provides a cooling system that can reduce maintenance and material costs. [Solution] This cooling system 100 comprises a substrate portion 20 having a heat-generating portion 40 during operation, a cooling liquid 30 that removes heat generated in the substrate portion 20, and a cooling tank 10 that houses the substrate portion 20 and the cooling liquid 30 and is configured to allow the substrate portion 20 to be immersed in the cooling liquid 30. The cooling system 100 also includes a covering portion 15. The covering portion 15 is composed of silicon-containing fine particles and covers at least the region of the substrate portion 20 that includes the heat-generating portion 40.

Description

Technical Field

[0001] The present invention relates to a cooling system used for, for example, servers, storage devices and the like in data centers.

Background Art

[0002] In general, data centers use ICT (Information and Communication Technology) equipment such as servers and storage devices. The ICT equipment is equipped with semiconductors such as processors. In recent years, high integration of semiconductors and high density of ICT equipment itself are often required. In this case, the heat generation amount of ICT equipment tends to increase significantly.

[0003] Therefore, a technology for sufficiently cooling ICT equipment is required. To meet this requirement, for example, cooling systems disclosed in the following Patent Documents 1 and 2 have been proposed. This cooling system cools electronic components with a cooling liquid. The electronic components are configured to be immersed in the cooling liquid. For this reason, heat generated from the electronic components is directly removed by the cooling liquid. Accordingly, it can be expected that sufficient cooling can be achieved even when the heat generation amount is large.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

[0005] Conventional technologies of this type require ensuring the electrical insulation properties of the coolant. Often, fluorine-based liquids are used as the coolant for their superior electrical insulation capabilities. Furthermore, since immersion alone in a fluorine-based liquid results in low cooling capacity, techniques exist to improve cooling performance by actively evaporating the fluorine-based liquid. However, such techniques require replenishment of the fluorine-based liquid each time it is cooled, leading to problems with high maintenance and material costs.

[0006] The objective of the present invention is to provide a cooling system that can reduce maintenance costs and material costs by increasing the range of coolant options available.

[0007] The cooling system of the present invention comprises a substrate portion having a part that generates heat during operation, a cooling liquid that removes the heat generated in the substrate portion, and a cooling tank that houses the substrate portion and the cooling liquid and is configured to allow the substrate portion to be immersed in the cooling liquid.

[0008] A key feature of the cooling system of the present invention is that it includes a covering portion that covers at least the region of the substrate portion that includes the heat-generating part.

[0009] According to the present invention, the coating portion can improve the electrical insulation of the substrate portion. Therefore, the requirement to ensure electrical insulation on the coolant side can be reduced. In other words, the restrictions on the electrical insulation of the coolant can be relaxed. That is, the range of coolants that can be selected, rather than being limited to fluorine-based liquids, can be increased. Therefore, by selecting the coolant, the need to actively evaporate the coolant can also be reduced. Consequently, the need to replenish the coolant is also reduced, and maintenance costs and material costs can be suppressed.

[0010] In the cooling system according to the present invention, the coolant is preferably a mixture of one or two selected from water and alcohol.

[0011] In the cooling system according to the present invention, it is preferable that the cooling system includes a first cooling circuit in which a cooling tank is interposed, and the cooling liquid is circulated to allow flow to the cooling tank.

[0012] In the cooling system according to the present invention, it is preferable that the cooling system includes an ion removal unit interposed in the first cooling circuit to remove ions present in the cooling liquid.

[0013] In the cooling system according to the present invention, it is preferable that the cooling system comprises a cooling tank and a first cooling circuit installed indoors, a heat exchange unit interposed in the first cooling circuit to remove heat from the cooling liquid, and a second cooling circuit separate from the first cooling circuit, interposed in the heat exchange unit to guide heat from the heat exchange unit to the outside.

[0014] In the cooling system according to the present invention, the cooling tank includes at least a first cooling tank and a second cooling tank, the first cooling tank having a first inlet for the coolant and a first outlet for the coolant, and the second cooling tank having a second inlet for the coolant and a second outlet for the coolant, and when the first cooling tank and the second cooling tank are installed, it is preferable that the distance from the first inlet to the second inlet is greater than the distance from the first outlet to the second inlet. [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic diagram showing a cooling system according to one embodiment of the present invention. [Figure 2] This is a perspective view of the first and second cooling tanks in the cooling system shown in Figure 1. [Figure 3] This is a front view of the cooling tank to explain the positional relationship of the coolant inlet and outlet in the cooling system shown in Figure 1. [Figure 4] Figure 1 shows a perspective view and a close-up view of the main components of the substrate and coating parts of the cooling system. [Figure 5] It is a vertical cross-sectional view of the substrate portion and the covering portion in Figure 4. [Figure 6] It is an enlarged partial view further enlarging the substrate portion and the covering portion in Figure 5. [Figure 7] It is a cross-sectional view showing the state of the surface of the covering portion when the substrate portion and the covering portion in Figure 4 are exposed to water. [Figure 8] It is a diagram for explaining a method for covering the covering portion on the substrate portion included in the cooling system of Figure 1. [Mode for Carrying Out the Invention]

[0016] Hereinafter, one embodiment of the cooling system according to the present invention will be described with reference to the drawings. In each of the drawings, the left-right direction, up-down direction, and front-back direction correspond to the L(Left)-R(Right) direction, U(Up)-D(Down) direction, and F(Front)-B(Back) direction of the arrows in the drawings, respectively.

[0017] <Cooling System> Figure 1 is a schematic diagram showing the schematic configuration of the cooling system according to the present embodiment. The cooling system 100 shown in Figure 1 includes a cooling tank 10, a first cooling circuit 50, and a second cooling circuit 70. This cooling system 100 further includes a substrate portion 20, a cooling liquid 30, a covering portion 15, a heat exchange portion 60, and a chiller 73.

[0018] The cooling system 100 is used for, for example, data centers, servers, and the like. The data center, server, or the like may include the substrate portion 20. The cooling system 100 is configured to be able to cool the substrate portion 20 (the heat generating portion 40 which is the heat generating site thereof). Cooling of the substrate portion 20 is achieved by immersion in the cooling liquid 30. In immersion cooling, the covering portion 15 is provided to improve the electrical insulation of the substrate portion 20 with respect to the cooling liquid 30. The covering portion 15 covers the region including the heat generating portion 40 in the substrate portion 20. The aspect of covering in the covering portion 15 will be described in detail later.

[0019] The substrate portion 20 and the cooling liquid 30 are accommodated in the cooling tank 10. In the cooling tank 10, the substrate portion 20 is immersed in the cooling liquid 30. Through the immersion, the heat generated in the substrate portion 20 is directly transferred to the cooling liquid 30. As a result, the temperature rise in the heat generating portion 40 of the substrate portion 20 is suppressed. On the other hand, the temperature of the cooling liquid 30 in the cooling tank 10 rises.

[0020] The cooling liquid 30 with increased temperature flows out from the cooling tank 10 to the first cooling circuit 50, and reaches the heat exchange portion 60. In the heat exchange portion 60, heat exchange is performed between the cooling liquid 30 of the first cooling circuit 50 and the medium of the second cooling circuit 70. That is, the heat retained by the cooling liquid 30 is indirectly transferred to the medium of the second cooling circuit 70 via the heat exchange portion 60. As a result, the temperature of the cooling liquid 30 that has undergone heat exchange decreases. The cooling liquid 30 with decreased temperature flows from the first cooling circuit 50 into the cooling tank 10, and is used again for immersing the substrate portion 20. On the other hand, the temperature of the medium of the second cooling circuit 70 that has undergone heat exchange rises.

[0021] The medium of the second cooling circuit 70 with increased temperature reaches the chiller 73. In the chiller 73, heat exchange is performed between the medium of the second cooling circuit 70 and the outside air. That is, the heat retained by the medium of the second cooling circuit 70 is indirectly transferred to the outside air via the chiller 73. As a result, the temperature of the medium of the second cooling circuit 70 that has undergone heat exchange decreases. The medium of the second cooling circuit 70 with decreased temperature is reused for heat exchange in the heat exchange portion 60.

[0022] As described above, in the cooling system 100, the heat generated in the substrate portion 20 is released to the outside air through the cooling liquid 30 of the first cooling circuit 50, the heat exchange portion 60, the medium of the second cooling circuit 70, and the chiller 73 in this order. Here, the cooling liquid 30 of the first cooling circuit 50 and the medium of the second cooling circuit 70 each circulate. As long as this circulation continues, the heat generated in the substrate portion 20 is continuously released to the outside air through the above-described path. As described above, in the cooling system 100, the substrate portion 20 (the heat generating portion 40 which is the portion that generates heat) is continuously cooled.

[0023] <Cooling tank> As shown in Figures 2 and 3, the cooling tank 10 is a bottomed container that houses the substrate portion 20 and the cooling liquid 30, and is configured to allow the substrate portion 20 to be immersed in the cooling liquid 30. The cooling tank 10 includes at least a first cooling tank 11 and a second cooling tank 12. Figures 1 and 3 show, as an example, a case in which the cooling tank 10 has two first cooling tanks 11 and two second cooling tanks 12.

[0024] Figure 2 is a perspective view showing a specific example of the inside of a cooling tank. In Figure 2, as an example, a case is shown in which multiple substrate parts 20 are housed in the cooling tank 10 together with a cooling liquid 30. Each substrate part 20 is arranged with its longitudinal direction oriented in the vertical direction (U-D direction) and with a predetermined spacing in the front-to-back direction (F-B direction). Note that the arrangement of the substrate parts 20 is not limited to this. Each substrate part 20 is equipped with a covering part 15. Details of the covering part 15 will be described later.

[0025] As shown in Figure 2(a), the first cooling tank 11 is a rectangular parallelepiped-shaped container with an openable / closable lid and has an internal space. The rectangular surface on the U-direction side of the first cooling tank 11 may be configured as a lid. For example, in the first cooling tank 11, when the lid is opened, multiple substrate parts 20 may be aligned and fixed in the internal space without any coolant 30 present. After that, the lid may be closed so that the multiple substrate parts 20 are housed in the internal space of the first cooling tank 11. After the substrate parts 20 are housed, the coolant 30 may be injected into the internal space separately from the first inlet 11a, which will be described later. In this way, the substrate parts 20 and the coolant 30 are housed inside the first cooling tank 11.

[0026] As shown in Figure 2(b), in this embodiment, the second cooling tank 12 has the same dimensions and mechanism as the first cooling tank 11 so that it is housed in the same manner. That is, the first cooling tank 11 and the second cooling tank 12 may have the same dimensions and be rectangular parallelepiped shape with a lid. In this embodiment, the first cooling tank 11 and the second cooling tank 12 differ only in the position of the inlet and outlet for their respective coolant 30.

[0027] The first cooling tank 11 has a first inlet 11a and a first outlet 11b. The second cooling tank 12 has a second inlet 12a and a second outlet 12b. On the front wall 11f of the first cooling tank 11, the first inlet 11a for the coolant 30 is provided in the lower left corner, and the first outlet 11b for the coolant 30 is provided in the upper right corner. On the front wall 12f of the second cooling tank 12, the second inlet 12a for the coolant 30 is provided in the lower right corner, and the second outlet 12b for the coolant 30 is provided in the upper left corner.

[0028] As shown in Figure 3, in this example, the cooling tank 10 is divided into four sections in a front view: upper left, lower left, upper right, and lower right. One first cooling tank 11 is installed in the upper left and lower right sections. One second cooling tank 12 is installed in the upper right and lower left sections. In the cooling tank 10, the first cooling tank 11L, second cooling tank 12L, second cooling tank 12R, and first cooling tank 11R are defined to correspond to the upper left, lower left, upper right, and lower right positions.

[0029] The first cooling tank 11R and the second cooling tank 12L are installed adjacent to each other in the left-right direction (L-R direction). That is, the sides of the first cooling tank 11R and the second cooling tank 12L are in contact with each other. The first cooling tank 11R and the second cooling tank 12R are installed adjacent to each other in the up-down direction (U-D direction). That is, the top surface of the first cooling tank 11R and the bottom surface of the second cooling tank 12R are in contact with each other.

[0030] The first cooling tank 11L and the second cooling tank 12R are installed adjacent to each other in the left-right direction (L-R direction). That is, the sides of the first cooling tank 11L and the second cooling tank 12R are in contact with each other. The first cooling tank 11L and the second cooling tank 12R are installed adjacent to each other in the up-down direction (U-D direction). That is, the bottom surface of the first cooling tank 11L and the top surface of the second cooling tank 12L are in contact with each other.

[0031] In other words, in this embodiment, the second cooling tank 12R is mounted above the first cooling tank 11R, and the first cooling tank 11L is mounted above the second cooling tank 12L. That is, the arrangement of the first cooling tank 11 and the second cooling tank 12 is in a 2x2 configuration. Note that the number and arrangement of the first cooling tank 11 and the second cooling tank 12 are not limited to this. For example, instead of the arrangement in this embodiment, an mxn configuration (where m and n are any number other than "2") may be adopted.

[0032] Furthermore, the cooling tank 10 has two first inlets 11a, two first outlets 11b, two second inlets 12a, and two second outlets 12b. The first cooling tank 11R has a first inlet 11aR and a first outlet 11bR. The first cooling tank 11L has a first inlet 11aL and a first outlet 11bL. The second cooling tank 12R has a second inlet 12aR and a second outlet 12bR. The second cooling tank 11L has a second inlet 12aL and a second outlet 12bL.

[0033] The positional relationship of the inlets and outlets in the first cooling tank 11R and the second cooling tank 12R will now be explained. In the first cooling tank 11R, the first inlet 11aR is located in the lower left, and the first outlet 11bR is located in the upper right (see Figure 2(a)). In the second cooling tank 12R, the second inlet 12aR is located in the lower right, and the second outlet 12bR is located in the upper left (see Figure 2(b)). Therefore, when the second cooling tank 12R is installed above the first cooling tank 11R, the distance from the first inlet 11aR to the second inlet 12aR is greater than the distance from the first outlet 11bR to the second inlet 12aR.

[0034] The positional relationship of the inlets and outlets in the first cooling tank 11L and the second cooling tank 12L will now be explained. In the first cooling tank 11L, the first inlet 11aL is located in the lower left, and the first outlet 11bL is located in the upper right (see Figure 2(a)). In the second cooling tank 12L, the second inlet 12aL is located in the lower right, and the second outlet 12bL is located in the upper left (see Figure 2(b)). Therefore, when the second cooling tank 12L is installed below the first cooling tank 11L, the distance from the second inlet 12aL to the first inlet 11aL is greater than the distance from the second outlet 12bL to the first inlet 11aL.

[0035] The first inlet 11aR and the second inlet 12aL are connected to the branch side of the bifurcated branch pipe 52a, respectively. The consolidating side of the branch pipe 52a is connected to the piping 52 of the first cooling circuit 50. The first outlet 11bR and the second inlet 12aR are connected via a connecting pipe 55. The second outlet 12bL and the first inlet 11aL are connected via a connecting pipe 56. The first outlet 11bL and the second outlet 12bR are connected to the branch side of the bifurcated branch pipe 51a, respectively. The consolidating side of the branch pipe 51a is connected to the piping 51 of the first cooling circuit 50.

[0036] The coolant 30 flows through the piping 52 from right to left. In the branch pipe 52a, the flowing coolant 30 is evenly divided into two. One of the divided coolant 30 flows into the first cooling tank 11R from the first inlet 11aR. The flowing coolant 30 flows out of the first cooling tank 11R from the first outlet 11bR. The flowing coolant 30 flows into the second cooling tank 12R from the second inlet 12aR via the connecting pipe 55. The flowing coolant 30 flows out of the second cooling tank 12R from the second outlet 12bR.

[0037] Therefore, within the first cooling tank 11R, the coolant 30 flows diagonally upward to the right along direction F1. Within the connecting pipe 55, the coolant 30 flows upward along direction F2. Within the second cooling tank 12R, the coolant 30 flows diagonally upward to the left along direction F3.

[0038] Of the distributed coolant 30, the other flows into the second cooling tank 12L from the second inlet 12aL. The flowing coolant 30 flows out of the second cooling tank 12L from the second outlet 12bL. The outflowing coolant 30 flows into the first cooling tank 11L from the first inlet 11aL via the connecting pipe 56. The flowing coolant 30 flows out of the first cooling tank 11L from the first outlet 11bL.

[0039] Therefore, within the second cooling tank 12L, the coolant 30 flows diagonally upward to the left along direction F4. Within the connecting pipe 56, the coolant 30 flows upward along direction F5. Within the first cooling tank 11L, the coolant 30 flows diagonally upward to the right along direction F6.

[0040] The coolant 30 flowing out from the first outlet 11bL and the second outlet 12bR is collected in the branch pipe 51a. The collected coolant 30 flows from left to right through the pipe 51. In this way, the flow of coolant 30 along directions F1, F3, F4, and F6 generates convection in all four compartments of the cooling tank 10. This makes it possible to increase the cooling capacity through convection.

[0041] <1st cooling circuit> As shown in Figure 1, the first cooling circuit 50 includes a cooling tank 10, a heat exchange unit 60, and an ion removal unit 53. The first cooling circuit 50 is configured to allow the cooling liquid 30 to circulate and flow to the cooling tank 10. The first cooling circuit 50 includes piping 51, piping 52, and a pump 54. The first cooling circuit 50, together with the cooling tank 10, is installed inside (indoors) of the data center 80. One end of piping 51 is connected to the first outlet 11bL and the second outlet 12bR (see Figure 3) via branch pipe 51a. One end of piping 52 is connected to the first inlet 11aR and the second inlet 12aL (see Figure 3) via branch pipe 52a.

[0042] The heat exchange unit 60 is interposed in the first cooling circuit 50 to remove heat from the coolant 30. As will be described later, the heat exchange unit 60 is also interposed in the second cooling circuit 70. Therefore, the heat exchange unit 60 exchanges heat between the first cooling circuit 50 and the second cooling circuit 70. The heat exchange unit 60 has a primary flow path 61 and a secondary flow path 62. The inlet of the primary flow path 61 is connected to the other end of the pipe 51. The outlet of the primary flow path 61 is connected to the other end of the pipe 52. As a result, the coolant 30 flows from the pipe 51 into the primary flow path 61 and flows out from the primary flow path 61 into the pipe 52. The connection of the second cooling circuit 70 in the secondary flow path 62 will be described in detail later.

[0043] The coolant 30 is a fluid substance used to remove heat generated in the substrate 20 (heat-generating part 40). The coolant 30 is housed in the cooling tank 10 together with the substrate 20. The substrate 20 is immersed in the coolant 30. The water level of the coolant 30 in the cooling tank 10 is adjusted to a height that completely submerges the substrate 20. A sufficient amount of coolant 30 to maintain this water level is sealed in the cooling tank 10 and the cooling circuit 50.

[0044] The coolant 30 is, for example, a mixture of one or two selected from water and alcohol. Examples of alcohols include methanol, ethanol, ethylene glycol, and propylene glycol. Water and alcohol, as liquids, have relatively high thermal conductivity and heat capacity. Therefore, even when the amount of heat generated from the heat-generating part 40 becomes very large, the heat can be reliably removed.

[0045] The coolant 30 may be, for example, a mixture of water and alcohol. In this case, the freezing point of the coolant 30 can be lowered. Specifically, the freezing point of the mixture is significantly lower than the freezing point of water (0°C). Therefore, even if, for example, the second cooling circuit 70 is a refrigeration cycle and the refrigerant vaporizes in the secondary flow path 62, the freezing of the coolant 30 is suppressed. Consequently, the temperature difference in the heat exchange section 60 can be increased while ensuring fluidity in the first cooling circuit 50. As a result, heat exchange in the heat exchange section 60 can be achieved more efficiently.

[0046] The ion removal unit 53 removes ions present in the coolant 30. The ion removal unit 53 is interposed in the piping 51. The ion removal unit 53 may be, for example, a packed bed of ion exchange resin. That is, an ion exchange resin may be packed as a packed bed in a container having an inlet and outlet. As the coolant 30 passes through this packed bed, ions are adsorbed onto the resin. Specific examples of ion exchange resins include the UltraClean® series manufactured by Purolite Corporation.

[0047] A pump 54 is installed in the piping 52. This pump 54 circulates the coolant 30 through the first cooling circuit 50. The circulation of the coolant 30 transfers heat from the substrate 20 from the cooling tank 10 to the primary flow path 61 of the heat exchange unit 60. In addition, the circulation of the coolant 30 removes ions present in the coolant 30 in the ion removal unit 53.

[0048] <Second cooling circuit> As shown in Figure 1, the second cooling circuit 70 includes a heat exchange unit 60 and a chiller 73. The second cooling circuit 70 guides heat from the heat exchange unit 60 to the outside (outside the data center 80). The second cooling circuit 70 is configured to have a separate path from the first cooling circuit 50. The medium of the second cooling circuit 70 can be any fluid. This medium may be, for example, industrial water, and may contain impurities.

[0049] The second cooling circuit 70 includes a pipe 71, a pipe 72, and a pump 74. One end of pipe 71 is connected to the outlet of the secondary flow path 62 of the heat exchange unit 60. The other end of pipe 71 is connected to the inlet of chiller 73. One end of pipe 72 is connected to the inlet of the secondary flow path 62 of the heat exchange unit 60. The other end of pipe 72 is connected to the outlet of chiller 73. Any type of chiller 73 can be used as long as it can release the heat of the medium to the outside air. For example, chiller 73 may be air-cooled, water-cooled, or have an added heat pump.

[0050] A pump 74 is installed in the piping 71. This pump 54 circulates the medium through the second cooling circuit 70. Through the circulation of the medium, heat is transferred from the secondary flow path 62 of the heat exchange section 60 to the chiller 73. Finally, the following temperature conditions must be met for the chiller 73 to release the heat from the medium into the outside air.

[0051] Temperature of heat-generating part 40 > Temperature of coolant 30 > Temperature of medium > Ambient air temperature

[0052] The greater the temperature difference, the more efficiently heat is transferred. In other words, the smaller the temperature difference, the more difficult heat transfer becomes. For this reason, for example, when the temperature of the coolant 30 is low or the ambient temperature is high, it is preferable to actively increase the temperature difference with the medium. From this viewpoint, the second cooling circuit 70 may constitute a refrigeration cycle.

[0053] In this case, a refrigerant for a heat pump is used as the medium for the second cooling circuit 70. In the second cooling circuit 70, an expansion valve, a compressor, and a condenser may be provided instead of the chiller 73 and pump 74. The secondary flow path 62 of the heat exchange section 60 may function as an evaporator.

[0054] The vaporization of the refrigerant in the secondary flow path 62 (i.e., the evaporator) can significantly lower the temperature of the medium in the secondary flow path 62. Therefore, even when the temperature of the coolant 30 is low, the temperature difference with the medium can be actively increased. Furthermore, the condensation of the refrigerant in the condenser can significantly raise the temperature of the medium in the condenser. Therefore, even when the ambient temperature is high, the temperature difference with the medium can be actively increased. In this way, heat can be efficiently transferred by the refrigeration cycle.

[0055] <Circuit board section> As shown in Figure 4, the substrate portion 20 may be, for example, a substrate portion that constitutes a server. The substrate portion 20 includes a heat-generating portion 40 and a wiring portion 21. The heat-generating portion 40 is a part that generates heat during operation, and is, for example, an integrated circuit, a GPU (Graphics Processing Unit), a CPU (Central Processing Unit), etc. The heat-generating portion 40 is arranged on one surface of the substrate portion 20 so as to be connected to the wiring portion 21. The wiring portion 21 extends in three directions from the heat-generating portion 40 on one surface of the substrate portion 20. The first wiring portion 21 extends in the U direction from the heat-generating portion 40. The second wiring portion 21 extends in the D direction from the heat-generating portion 40. The third wiring portion 21 extends in the R direction from the heat-generating portion 40.

[0056] The heating element 40 comprises a molded section 41 and a terminal section 42. A chip is embedded within the molded section 41. The molded section 41 is a flat plate with a roughly rectangular shape when viewed from above. The molded section 41 is made of metal or the like. The long and short sides of the molded section 41 correspond to the L-R direction and the D-U direction, respectively.

[0057] The terminal sections 42 are located on two long sides and one short side of the molded section 41. The terminal sections 42 are electrically connected to the chip embedded in the molded section 41. The terminal sections 42 are arranged at equal intervals along the two long sides and one short side of the molded section 41. The number and position of the terminal sections 42 correspond to the number and position of the wiring sections 21. The terminal sections 42 are connected to the wiring sections 21, for example, by soldering.

[0058] <Covered part> Figure 5 is a longitudinal cross-sectional view of the substrate portion shown in Figure 4. As shown in Figure 5, the covering portion 15 of the cooling system 100 covers at least the area of ​​the substrate portion 20 that includes the heat-generating portion (heat-generating portion 40). In this embodiment, the covering portion 15 continuously covers the entire outer surface of the mold portion 41, the entire surface of the terminal portion 42, and a part of the wiring portion 21. The A1-A1 cutting line in Figure 4 is parallel to the L-R direction. This cutting line defines the longitudinal cross-section near the terminal portion 42. The A2-A2 cutting line is parallel to the D-U direction. This cutting line defines the longitudinal cross-section over the entire heat-generating portion 40. Figure 5(a) is a longitudinal cross-sectional view of A1-A1. Figure 5(b) is a longitudinal cross-sectional view of A2-A2.

[0059] As shown in Figure 5(a), the covering portion 15 is in close contact with both sides in the L and R directions and the top surface in the F direction of each terminal portion 42, including the wiring portion 21. As shown in Figure 5(b), the covering portion 15 is in close contact with both sides in the D and U directions and the top surface in the F direction of the molded portion 41, and with the entire surface of the terminal portion 42 protruding from the molded portion 41 in the B direction, including the wiring portion 21. Note that the thickness of the covering portion 15 shown in Figure 5 is drawn relatively large for the sake of explanation. The actual ratio of the thickness of the covering portion 15 to the size of other components may differ from that shown in Figure 5.

[0060] Figure 6 is an enlarged view of the main part near the terminal portion shown in Figure 5. This enlarged view is a cross-sectional view of the covering portion 15, the terminal portion 42, and the wiring portion 21. The covering portion 15 covers the terminal portion 42 and the wiring portion 21 by adhering closely to the surface of the covering region. The covering portion 15 is not limited to inorganic or organic materials, and various coating materials can be used. For example, silicon-containing fine particles P may be used. In addition, silicon dioxide, alumina, silicon carbide, epoxy, silicone, etc. may be used. As the coating material, it is preferable to select a material with a sufficiently small dielectric constant Dk and dielectric loss Df. In this embodiment, an example described below will be explained. The covering portion 15 is composed of silicon-containing fine particles P. Silicon-containing fine particles P adhere very strongly to the surface of an electrically conductive material (e.g., metal). This is because the silicon-containing fine particles P are sufficiently smaller than the fine irregularities on the surface of the covering region. The scale of these irregularities is often around 20 μm to 250 μm. The silicon-containing microparticles P are embedded in the irregularities, stacking up in multiple layers to cover the entire surface.

[0061] The silicon-containing fine particles P may exhibit various embodiments. The particle size (average diameter) of the silicon-containing fine particles P is preferably, for example, less than 10 nm, less than 7 nm, or less than 2 nm. In particular, it is even more preferable if the particle size is in the range of 1.5 nm or more and less than 2.0 nm.

[0062] The silicon-containing nanoparticles P may be, for example, nanoparticles made of a compound with a silicon atom as its backbone, which contains one, two, or all of the following atoms: oxygen, carbon, and hydrogen. Alternatively, the silicon-containing nanoparticles P may be nanoparticles of a mixture of several of the above compounds. Alternatively, the silicon-containing nanoparticles P may be nanoparticles made of only silicon atoms. Alternatively, the silicon-containing nanoparticles P may be nanoparticles of a mixture of the above compounds and nanoparticles made of only silicon atoms. Examples of compounds with a silicon atom as its backbone include, but are not limited to, silicon dioxide, silanol, silicon ether, and siloxane.

[0063] Figure 7 is a cross-sectional view showing the state of the surface of the coating when the coating is exposed to water. Figure 7(a) shows, as an example, a state in which liquid water W is sprinkled on the coating 15. The water W adheres to the surface of the coating 15. Subsequently, as shown in Figure 7(b), the water W becomes droplets DR on the surface of the coating 15. The water W does not penetrate into the interior of the coating 15. The water W does not reach either the terminal portion 42 or the wiring portion 21. It is preferable that the coating 15 has water-repellent properties. The droplets DR on the surface of the coating 15 have a contact angle CA with respect to the surface. The degree of water repellency can be indicated, for example, by the contact angle CA. In this embodiment, it is preferable that the coating 15 is configured such that the contact angle CA is greater than 90 degrees or greater than 100 degrees. As described above, the terminal portion 42 and the wiring portion 21 are protected by the coating 15.

[0064] Figure 8 is a diagram illustrating a method for covering the substrate portion 20 with the covering portion 15. The method for covering the covering portion 15 in this embodiment involves, for example, the steps shown in Figure 8(a). First, in preparation step 501, the substrate portion 20 equipped with the heating portion 40 is prepared.

[0065] Next, in coating step 502, the dispersion liquid DP is applied to the substrate portion 20. Specifically, the dispersion liquid DP is stored in a container beforehand, and the substrate portion 20 is dipped into the dispersion liquid DP. At least the area of ​​the substrate portion 20 including the heat-generating portion 40 is thoroughly immersed in the dispersion liquid DP. For example, the entire substrate portion 20 may be immersed in the dispersion liquid DP. The immersion time may be, for example, a few seconds to a few minutes. After immersion, the substrate portion 20 is removed from the dispersion liquid DP. This coats the heat-generating portion 40 with the dispersion liquid DP.

[0066] The dispersion DP is a liquid obtained by dispersing the silicon-containing fine particles described above in a solvent. The concentration of silicon-containing fine particles in the dispersion DP is arbitrary. The solvent is not limited as long as it is a liquid that can disperse silicon-containing fine particles. The solvent is preferably, for example, oil. This is based on the viewpoint of good dispersion of silicon-containing fine particles and easy removal of the solvent in a later step. When using oil or the like as a solvent, it is especially preferable to use one with low viscosity. This is based on the viewpoint of easily penetrating narrow gaps with the dispersion DP and applying a thin layer of the dispersion DP.

[0067] Next, in coating step 503, the coating portion 15 described above is formed on the substrate portion 20 removed from the dispersion DP. The solvent is removed from the dispersion DP, leaving only silicon-containing fine particles in the coating region. The solvent is preferably removed by vaporizing the solvent, for example. Heating increases the vapor pressure of the solvent, which allows for solvent removal in a shorter time. As a result, the coating portion 15 is formed as shown in Figure 5.

[0068] The coating method for the coating portion 15 follows, for example, the steps shown in Figure 8(b). This process differs from the process shown in Figure 8(a) only in the coating step 504. In the coating step 504 following the preparation step 501, the dispersion liquid DP is sprayed onto the substrate portion 20. Specifically, the dispersion liquid DP is stored in a container beforehand, and the stored dispersion liquid DP is sprayed through a nozzle. The dispersion liquid DP is sprayed sufficiently onto at least the area of ​​the substrate portion 20 that includes the heat-generating portion 40. For example, the dispersion liquid DP may be sprayed over the entire substrate portion 20. This coats the coating area with the dispersion liquid DP. After that, the coating step 503 is performed. This also forms the coating portion 15 as shown in Figure 5. Note that means other than dipping or spraying may be used. In addition, other means such as ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), and underfill filling may be used. Examples of underfill materials include low-viscosity epoxy (non-chloride type) and silicone.

[0069] <Effects of the Embodiment> As described above, according to the cooling system 100 of one embodiment of the present invention, the covering portion 15 can improve the electrical insulation of the substrate portion 20. Therefore, the requirement to ensure electrical insulation on the coolant 30 side can be reduced. In other words, the restrictions on the electrical insulation of the coolant 30 can be relaxed. That is, the coolant 30 is not limited to fluorine-based liquids, and the range of coolant selections can be increased. Therefore, by selecting the coolant 30, the need to actively evaporate the coolant 30 can also be reduced. Consequently, the need to replenish the coolant 30 is also reduced, and maintenance costs and material costs can be suppressed.

[0070] Furthermore, in this embodiment, the coolant 30 is preferably a mixture of one or two selected from water and alcohol. From the viewpoint of electrical insulation, water and alcohol are compatible with silicon. Therefore, the silicon of the coating portion 15 can effectively provide electrical insulation to the coolant 30. This is based on the property that silicon easily repels OH groups, which are common to the molecular structures of water and alcohol. In addition, water and alcohol have exceptionally high thermal conductivity and heat capacity among liquids. Therefore, when cooling, reliable cooling can be achieved simply by immersing the substrate portion 20 in the coolant 30, without even needing to evaporate the coolant 30. This further reduces maintenance costs and material costs.

[0071] Furthermore, in this embodiment, a first cooling circuit 50 is used. With this, convection can be generated in the cooling tank 10 by circulating the coolant 30 through the first cooling circuit 50. This makes it possible to increase the cooling capacity through convection. As a result, the space required to house the coolant 30 in the cooling tank 10 for cooling can be reduced. In other words, it is no longer necessary to keep a large amount of coolant 30 in the cooling tank 10. Also, since the coolant 30 is circulated in the first cooling circuit 50, it can be reused immediately after cooling. Therefore, since the required amount of liquid can be suppressed, maintenance costs and material costs can be suppressed more reliably.

[0072] Furthermore, in this embodiment, an ion removal unit 53 is used. With this, ions present in the coolant 30 can be removed by the ion removal unit 53, thus maintaining a high level of electrical insulation on the coolant 30 side. Generally, when the coolant 30 is circulated, ions tend to dissolve into the coolant 30 from the metal materials of the components that make up the substrate 20. Also, if the coolant 30 contains alcohol, acid is formed due to aging degradation, making it easier for ions to be present in the coolant 30. By using the ion removal unit 53, there is more room to reduce the degree of electrical insulation on the substrate 20 side, making it possible to design the coating 15 to be thinner or to reduce the area of ​​the coating 15. From this viewpoint as well, maintenance costs and material costs can be more reliably suppressed.

[0073] Furthermore, in this embodiment, it is preferable that the cooling tank 10 and the first cooling circuit 50 are installed indoors, and that the cooling system 100 includes a heat exchange unit 60 that removes heat from the coolant 30 and a second cooling circuit 70 that guides the heat from the heat exchange unit 60 to the outside. For example, there are cases where the cooling tank 10 and the first cooling circuit 50 are installed indoors, such as when a server is installed indoors. In this case, it becomes unnecessary to extend the first cooling circuit 50 (piping 51 and piping 52) to the outside, and an increase in the circulation amount of the coolant 30 can be suppressed. That is, by deliberately separating the first cooling circuit 50 and the second cooling circuit 70 and moving the second cooling circuit 70 to the outside, the total amount of coolant 30 that needs to be sealed in the first cooling circuit 50 can be reduced. From this viewpoint as well, maintenance costs and material costs can be suppressed more reliably.

[0074] Furthermore, in this embodiment, when the first cooling tank 11 and the second cooling tank 12 are installed, it is preferable that the distance from the first inlet 11aR to the second inlet 12aR is greater than the distance from the first outlet 11bR to the second inlet 12aR (see Figure 3). This makes it easier to route the coolant piping and connectors when the first cooling tank 11 and the second cooling tank 12 are installed adjacent to each other in a predetermined direction such as horizontal or vertical. In particular, when the first cooling tank 11 and the second cooling tank 12 are arranged in series in this order, the length of the piping (connecting pipes 55, 56) connecting the first cooling tank 11 and the second cooling tank 12 can be minimized. Therefore, even when multiple cooling tanks 10 are installed, the increase in coolant 30 due to the piping connecting them can be suppressed. From this viewpoint as well, maintenance costs and material costs can be more reliably suppressed.

[0075] The cooling system according to the above-described embodiment can be modified in various ways within the scope of each claim. In the above-described embodiment, an example was given in which the cooling system 100 has a cooling tank 10, a first cooling circuit 50, and a second cooling circuit 70, but it is not limited to this. The cooling system 100 may have only a cooling tank 10 without the first cooling circuit 50 and the second cooling circuit 70, or it may have only a cooling tank 10 and the first cooling circuit 50 without the second cooling circuit 70.

[0076] In the embodiments described above, an example was given in which the ion removal unit 53 is interposed in the piping 51, but the invention is not limited to this. The ion removal unit 53 does not need to be interposed in the piping 51. [Explanation of symbols]

[0077] 10...Cooling tank, 11...First cooling tank, 11a...First inlet, 11b...First outlet, 12...Second cooling tank, 12a...Second inlet, 12b...Second outlet, 15...Coating part, 20...Substrate part, 30...Cooling liquid, 40...Heat generating part, 50...First cooling circuit, 53...Ion removal part, 60...Heat exchange part, 70...Second cooling circuit, 100...Cooling system

Claims

1. A circuit board having a part that generates heat during operation, A cooling liquid to remove the heat generated in the substrate portion, A cooling tank comprising the substrate portion and the cooling liquid, configured to allow immersion of the substrate portion in the cooling liquid, In a cooling system equipped with, At least a covering portion that covers the region of the substrate portion including the heat-generating part. A cooling system characterized by having the following features.

2. In the cooling system according to claim 1, The aforementioned coolant is It is a mixture of one or two substances selected from water and alcohol. Cooling system.

3. In the cooling system according to claim 2, A first cooling circuit is configured such that the cooling tank is interposed and the cooling liquid circulates to the cooling tank. A cooling system equipped with a cooling system.

4. In the cooling system according to claim 3, An ion removal unit interposed in the first cooling circuit removes ions present in the cooling liquid. A cooling system equipped with a cooling system.

5. In the cooling system according to claim 4, The cooling tank and the first cooling circuit are, Installed indoors, Interposed in the first cooling circuit is a heat exchange unit that removes heat from the coolant, A second cooling circuit, separate from the first cooling circuit, is provided with the heat exchanger section and guides the heat from the heat exchanger section to the outside. A cooling system equipped with a cooling system.

6. In the cooling system according to any one of claims 3 to 5, The cooling tank is It includes at least a first cooling tank and a second cooling tank, The first cooling tank is, The system comprises a first inlet for the coolant and a first outlet for the coolant. The second cooling tank is The system comprises a second inlet for the coolant and a second outlet for the coolant. When the first cooling tank and the second cooling tank are installed, the distance from the first inlet to the second inlet is greater than the distance from the first outlet to the second inlet. Cooling system.

Images