JP5252059B2 - Cooling system - Google Patents

Description

  The present invention relates to a cooling device used for cooling a heat-generating semiconductor such as a microprocessing unit (hereinafter abbreviated as MPU) used in a personal computer or the like, or an electronic component having another heat-generating portion.

  In recent years, in electronic devices, the contact temperature of each electronic component has been reduced for the normal operation of the electronic component against the increase in heat generation due to higher integration of electronic components such as semiconductors and higher operating clock frequencies. How to keep within the operating temperature range has become a major issue. In particular, high integration and high frequency of the MPU are remarkable, and heat radiation countermeasures are important problems from the viewpoints of operational stability and ensuring the operational life.

  However, the conventional air-cooling method combining a heat sink and a fan is increasingly lacking in capacity for electronic components with high heat generation. In view of this, for example, a highly efficient cooling device with higher capacity that circulates a working fluid as shown in (Patent Document 1) has been proposed.

  In general, in order to cool a heating element having a high calorific value such as an MPU, a method of radiating heat absorbed by the heat receiving portion from a heat radiating portion having a large area to the air is employed. Here, a conventional technique disclosed in (Patent Document 1) will be described with reference to FIG.

  FIG. 14 is a block diagram of a conventional cooling device and a heat receiving part structure diagram. Normally, such a cooling device includes a heat receiving unit 1 that removes heat from the heating element 2, a pipe 20 that transports the working fluid that has received heat by the heat receiving unit 1, and the working fluid as shown in FIG. It comprises a pump 13 that moves and a heat radiating section 11 that radiates heat from the working fluid. The main cooling principle is that the temperature of the working fluid rises as the heat generated in the heating element 2 is transferred to the inside of the heat receiving unit 1 and exchanged with the working fluid circulating inside as shown in FIG. Next, the working fluid is transported by the pump 13 through the pipe line 20 to the heat radiating portion 11, and the temperature of the heat radiating portion 11 is increased. Next, a method is adopted in which air is sent from the fan 10 mounted on the heat radiating unit to the surface of the heat radiating unit 11 that has reached a high temperature and is heat-exchanged to be diffused into the air.

  In recent years, along with the miniaturization of electronic components (thinning of manufacturing processes), the size of the heating element itself tends to decrease, and the heat density per unit area is steadily increasing. For this reason, the cooling performance of the cooling device is determined by the performance of both the heat receiving unit and the heat radiating unit, and in particular, high performance of the heat receiving unit is a major issue. This is because, for example, even in a cooling device that has been able to cool a heating element with an area of 100 square mm that generates heat of 100 W, the heat density is reduced when the heating area is reduced to 50 square mm by thinning the electronic component manufacturing process. Is doubled, the endothermic performance is insufficient, and the same cooling device cannot be cooled.

  Moreover, in the heat receiving part of the system in which the working fluid circulates as shown in FIG. 14A, a structure as shown in FIG. 14B is adopted, and a metal having a high thermal conductivity (for example, copper, It has been devised to improve the performance by providing a conduit for the working fluid to circulate in the aluminum). However, even in this case, the efficiency with which heat is exchanged from the metal to the working fluid inside the heat receiving part greatly depends on the area of the inner wall of the pipe, so simply by arranging the pipe inside the heat receiving part, In many cases, the heat receiving area is small and sufficient performance cannot be obtained. And it is thought that performance shortage will become more remarkable by future reduction of the heating element size.

  Therefore, as a method for further improving the heat absorption performance of the heat receiving part, another conventional technique devised is to seal the both ends of a cylindrical tube as shown in FIG. 15 and to install a heat pipe with a desired working fluid inside. The cooling device used. A cooling device using a heat pipe includes a heat receiving portion in contact with a heating element and a heat radiating portion having heat radiating fins. The heat from the heating element is transferred to the cylindrical wall, and the working fluid undergoes a phase change (evaporation) on the inner wall to take away latent heat of vaporization. Next, the steam moves at high speed in the cylinder and condenses on the inner wall of the heat radiating portion, so that the heat of condensation is transmitted to the fins via the inner wall and finally radiated to the air. Next, the condensed working fluid is transferred to the original heat receiving part by a wick that generates capillary action provided on the tube wall. Cooling is continued by repeating this series of cycles. Since heat transfer in this case involves a phase change, the heat transfer performance is higher than that of the simple refrigerant circulation system shown in FIG.

Japanese Patent Laid-Open No. 10-213370

  However, as described above, electronic components such as semiconductors tend to generate more heat or increase in heat density due to further progress in performance. Even in the case of another conventional cooling device using the heat pipe shown in FIG. 14, since the internal volume is small, the working fluid that can be sealed is small, and as a result, the heat transport capability of the heat pipe alone is several tens of watts for electronic devices. Many things are often used, and in order to increase the total heat transport amount, it is common to use a plurality of them arranged in parallel. In addition, the total heat transport capacity can be accommodated to some extent by increasing the number, but as mentioned above, there is still a problem with increasing the heat density, and as a countermeasure, a heat pipe is attached to the heat receiving plate with high thermal conductivity. A method has been selected that uses heat spread as much as possible in parallel. However, even in this case, the number of heat pipes that actually function is limited in terms of arrangement, and it remains difficult to achieve both sufficient heat transport capability and high heat density. Furthermore, when using a relatively thick heat receiving plate to spread heat to a plurality of heat pipes, the distance from the center of the heating element to the vaporization surface where the working fluid actually undergoes phase change (evaporation) is naturally long. Therefore, the thermal resistance during that time increases, and as a result, a sudden temperature rise occurs between the start of heating and the actual start of phase change (evaporation), resulting in a large problem that the temperature exceeds the guaranteed operating temperature of the electronic component. was there.

  Therefore, the present invention has been made in view of the above problems, and provides a cooling device with excellent cooling performance that suppresses a rapid temperature rise and dryout at the initial stage of heating while maintaining high heat receiving performance and has high operational stability. For the purpose.

In order to achieve the above object, the present invention is a cooling device that circulates a working fluid and cools it by a phase change between a liquid phase and a gas phase, wherein a heating element is disposed on one surface of the outer wall, and corresponds to one surface of the outer wall. A box-shaped heat receiving part for transferring heat to the inner wall, an introduction pipe for injecting the working fluid into the heat receiving part, and a lead-out pipe for discharging the steam by converting the working fluid injected into the heat receiving part into steam by heat. An operation that is provided above the heat receiving portion and that releases the heat of the steam via the outlet tube, and a check valve provided on the opening side of the introduction tube, and is liquefied by the radiator The fluid is returned to the heat receiving portion via the check valve, and the circulation direction of the working fluid is determined by an increase in pressure on the outlet side after the check valve, and on the outer periphery of the inlet pipe opening on the inner wall. Slip from the inside to the outside of the enclosed surface Is provided, that the pressure of the introduction pipe portion is raised, characterized in that the air bubbles and unevaporated working fluid is discharged to the outlet pipe side become multiphase flow.

As described above, the cooling device of the present invention is a cooling device that circulates a working fluid and cools it by a phase change between a liquid phase and a gas phase, and a heating element is disposed on one surface of the outer wall, and corresponds to one surface of the outer wall. A box-shaped heat receiving part for transferring heat to the inner wall, an introduction pipe for injecting the working fluid into the heat receiving part, and a lead-out pipe for discharging the steam by converting the working fluid injected into the heat receiving part into steam by heat. An operation that is provided above the heat receiving portion and that releases the heat of the steam via the outlet tube, and a check valve provided on the opening side of the introduction tube, and is liquefied by the radiator The fluid is returned to the heat receiving portion via the check valve, and the circulation direction of the working fluid is determined by an increase in pressure on the outlet side after the check valve, and on the outer periphery of the inlet pipe opening on the inner wall. Slit from inside to outside of enclosed surface Use a pump because the pressure inside the introduction pipe is increased and bubbles and un-evaporated working fluid are mixed-phased and discharged to the outlet pipe side. Therefore, the cooling device has a sufficient vaporization area and excellent heat absorption performance.

  Moreover, since the surface area of the inner wall surface is increased by providing the slit, the heat transfer performance of the inner wall can be improved.

  Furthermore, by providing a slit on the inner wall from the inside to the outside of the surface surrounded by the outer periphery of the opening of the introduction tube, the bubbles generated in the slit are moved along the slit due to an increase in pressure accompanying the evaporation of the working fluid in the slit. Since it is discharged from the inside to the outside of the surface surrounded by the outer periphery of the opening, the evaporation of the working fluid is not hindered by the retention of bubbles, and the heat absorption characteristics of the heat receiving part are enhanced, improving the performance of the entire cooling device Can be made.

With the above-described configuration, it is possible to provide a cooling device that maintains high heat receiving performance and suppresses rapid temperature rise and dry-out in the initial stage of heating and has high operational stability and excellent cooling performance.

(A) The perspective view at the time of arrange | positioning the cooling device in Example 1 of this invention in PC housing | casing, (b) Structural drawing of a cooling device (A) The central vertical sectional view of the heat receiving unit according to the first embodiment of the present invention, (b) the cross sectional perspective view of the heat receiving unit of FIG. 2 (a), (c) the horizontal cross sectional view of the heat receiving unit of FIG. (D) A cross-sectional detail view of part A shown in FIG. (A) Central vertical sectional view of the heat receiving unit in Example 1 of the present invention, (b) Central vertical sectional view in the direction of 90 degrees, (c) Detailed cross-sectional view of the A part of the slit portion of the heat receiving unit A graph showing changes in normalized thermal resistance when the heat generation size is changed The schematic diagram showing the relationship between the heating element temperature and the vaporization temperature by slit formation from the temperature distribution in the thickness direction of the heat receiving plate in Example 1 of the present invention. The graph which showed the temperature change of the heating initial stage using the heat receiving part in Example 1 of this invention. The graph which showed the relationship between the ratio of the heat receiving plate thickness in the Example 1 of this invention, the slit part bottom thickness, and the temperature ratio of an initial stage of a heating. (A) Central vertical sectional view of another heat receiving unit in Embodiment 2 of the present invention, (b) Cross sectional perspective view of the heat receiving unit, (c) Horizontal sectional view of the heat receiving unit, (d) Detail of section A of slit part Figure (A) The central vertical sectional view of the heat receiving unit in Embodiment 3 of the present invention, (b) The cross sectional perspective view of the heat receiving unit, (c) The horizontal cross sectional view of the heat receiving unit, (d) The cross sectional detail view of the A section of the slit portion (A) The central vertical sectional view of the heat receiving unit in Embodiment 3 of the present invention, (b) The cross sectional perspective view of the heat receiving unit, (c) The horizontal cross sectional view of the heat receiving unit, (d) The cross sectional detail view of the A section of the slit portion (A) The central vertical sectional view of the heat receiving unit in Embodiment 4 of the present invention, (b) The cross sectional perspective view of the heat receiving unit, (c) The horizontal cross sectional view of the heat receiving unit, (d) The cross sectional detail view of the A section of the slit portion (A) Central vertical sectional view of another heat receiving unit in Embodiment 4 of the present invention, (b) Cross sectional perspective view of the heat receiving unit, (c) Horizontal sectional view of the heat receiving unit, (d) Detail of section A of slit part Figure (A) Central vertical sectional view of another heat receiving unit in Example 5 of the present invention, (b) A sectional perspective view of the heat receiving unit, (c) A horizontal sectional view of the heat receiving unit, (d) A section detail of the slit part A Figure (A) The block diagram of the conventional cooling device, (b) The figure which shows the heat-receiving part structure of the conventional cooling device Configuration diagram of another conventional cooling device using a heat pipe

According to invention of Claim 1, it is a cooling device which circulates a working fluid and cools by the phase change of a liquid phase and a gaseous phase, Comprising: A heat generating body is arrange | positioned on one surface of an outer wall, and it respond | corresponds to one surface of the said outer wall. A box-shaped heat receiving part for transferring heat to the inner wall, an introduction pipe for injecting the working fluid into the heat receiving part, and a lead-out pipe for discharging the steam by converting the working fluid injected into the heat receiving part into steam by heat. An operation that is provided above the heat receiving portion and that releases the heat of the steam via the outlet tube, and a check valve provided on the opening side of the introduction tube, and is liquefied by the radiator The fluid is returned to the heat receiving portion via the check valve, and the circulation direction of the working fluid is determined by an increase in pressure on the outlet side after the check valve, and on the outer periphery of the inlet pipe opening on the inner wall. A slit from the inside to the outside of the enclosed surface Vignetting, by pressure of the introduction pipe portion is raised, characterized in that the air bubbles and unevaporated working fluid is discharged to the outlet pipe side become multiphase flow.

  Thus, by providing a slit from the inside to the outside of the surface surrounded by the outer periphery of the opening of the introduction pipe on the inner wall, the thermal resistance is reduced by reducing the thickness of the inner wall at the bottom of the slit, and the phase change of the working fluid The temperature difference between the temperature and the heating element can be reduced. As a result, it is possible to suppress the temperature rise of the heating element in the initial heating state.

  Moreover, since the surface area of the inner wall surface is increased by providing the slit on the inner wall, the heat transfer performance of the inner wall can be improved.

  Furthermore, by providing a slit on the inner wall from the inside to the outside of the surface surrounded by the outer periphery of the opening of the introduction tube, the bubbles generated in the slit are moved along the slit due to an increase in pressure accompanying the evaporation of the working fluid in the slit. Since it is discharged from the inside to the outside of the surface surrounded by the outer periphery of the opening, the evaporation of the working fluid is not hindered by the retention of bubbles, and the heat absorption characteristics of the heat receiving part are enhanced, improving the performance of the entire cooling device Can be made.

  According to invention of Claim 2, it is a cooling device of Claim 1, Comprising: By the heat source of a heat generating body being arrange | positioned inside the outer periphery of an inlet pipe opening part in the outer wall in which a heat generating body is arrange | positioned, The heat from the heating element can be efficiently transmitted to the place where the working fluid is introduced, and the temperature rise of the heating element can be suppressed in the initial heat state, and stable operation can be realized.

  According to a third aspect of the present invention, in the cooling device according to the first aspect, since the introduction pipe opening is in contact with the inner wall, an increase in pressure that contributes to bubble elimination during evaporation at the introduction pipe opening. Can be further generated.

  According to a fourth aspect of the present invention, in the cooling device according to the first aspect, by forming a plurality of slits in parallel, the surface area of the inner wall surface becomes larger, so the heat transfer characteristics of the inner wall are further improved. Can be made.

  According to the fifth aspect of the present invention, in the cooling device according to the first aspect, since the slits are formed radially from the center of the introduction pipe, the surface area of the inner wall surface becomes larger, so The heat transfer characteristics can be further improved.

  According to invention of Claim 6, it is a cooling device of Claim 1, Comprising: By providing the slit in the center part of the inner wall enclosed by the outer periphery of an opening part, the thermal resistance by the thickness of an inner wall is provided. Is reduced and the evaporation of the working fluid is promoted, so that the heat transfer characteristics of the inner wall can be further improved.

  According to a seventh aspect of the present invention, in the cooling device according to the first aspect, by increasing the width of the slit as the distance from the center of the introduction pipe increases, the pressure when the working fluid is vaporized is reduced to the center of the introduction pipe. Since it acts as a force in the direction away from the air, it promotes the discharge of bubbles generated in the slit, prevents bubbles from staying in the way that hinders evaporation of the working fluid, improves the heat absorption characteristics of the heat receiving part, and further improves the performance of the cooling device be able to.

  According to invention of Claim 8, it is a cooling device of Claim 1, Comprising: Thickness h from the bottom part of a slit to one surface of an outer wall with respect to thickness H from the inner wall which does not provide a slit to one surface of an outer wall When the ratio (h / H) is 0.1 to 0.3, the thermal resistance of the inner wall is reduced, so that the heat absorption characteristics of the heat receiving portion can be improved while maintaining the mechanical strength of the heat receiving portion. it can.

  According to invention of Claim 9, it is a cooling device of Claim 1, Comprising: By making the clearance gap between an inlet-tube opening part and an inner wall into 0.2 mm or less, a bubble is made into a working fluid with the flow of a working fluid. Since it is discharged, the evaporation of the working fluid on the inner wall surface is not hindered by the retention of bubbles, the heat absorption characteristics of the heat receiving part can be improved, and the performance of the cooling device can be improved.

  According to a tenth aspect of the invention, in the cooling device according to the first aspect, the working fluid that flows through other than the slit by providing a groove that intersects the slit and inserting the inlet pipe opening into the groove. Since the amount of the working fluid supplied to the inner wall can be ensured regardless of the direction of gravity, the heating element can be disposed beside the heat receiving portion.

According to invention of Claim 11, it is a cooling device which circulates a working fluid and cools by the phase change of a liquid phase and a gaseous phase, Comprising: A heat generating body is arrange | positioned on one surface of an outer wall, and the inner wall corresponding to one surface of an outer wall is provided. A box-shaped heat receiving part that transfers heat, an introduction pipe that injects working fluid into the heat receiving part, a lead-out pipe that discharges steam by the working fluid injected by the heat of the inner wall, and a derivation that is provided above the heat receiving part includes a radiator for releasing heat of the steam passing through the tube, the heating element is placed inside the outer periphery of the inlet tube opening in arranged outer wall, that the pressure of the inlet tube portion is raised, non-a bubble The evaporating working fluid is mixed and discharged to the outlet pipe side, and the thickness of the inner wall corresponding to the portion where the heating element is disposed is made thinner than the thickness of the surrounding inner wall. .

  As a result, the heat source of the heating element is arranged inside the outer periphery of the introduction tube opening in the outer wall where the heating element is arranged, and the thickness of the inner wall corresponding to the portion where the heating element is arranged is determined from the thickness of the surrounding inner walls. By reducing the thickness, the thermal resistance of the inner wall corresponding to the portion where the heating element is disposed is reduced, and the temperature difference between the temperature of the heating element and the temperature of the inner wall corresponding to the portion where the heating element is disposed is reduced. As a result, it is possible to suppress the temperature rise of the heating element in the initial heating state. As a result, since the heat of the heating element is removed by evaporation of the working fluid from a state where the temperature of the heating element is relatively low, an increase in temperature when the heating element starts to generate heat can be suppressed.

  According to invention of Claim 12, it is a cooling device of Claim 11, Comprising: By providing the slit in the inner wall and making the thickness of the inner wall thin, the surrounding part thicker than the slit provided the slit in the inner wall Since the thin portion is reinforced, it is possible to suppress an increase in temperature when the heating element starts to generate heat while maintaining the strength of the inner wall.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 is a perspective view of the cooling device according to the first embodiment of the present invention arranged in a personal computer (hereinafter referred to as PC) housing and a structural diagram of the cooling device of the present invention. In FIG. 1A, reference numeral 16 denotes a PC housing, in which a cooling device of the present invention is arranged together with PC components such as a power supply unit 15 and a mother board 18. The cooling device includes a box-type heat receiving unit 1 connected to the heating element socket 17, a heat radiating unit 11, and a fan 10 that cools the heat radiating unit 11.

  The cooling device of the present invention will be further described. As shown in FIG. 1B, a box-type heat receiving unit 1 including a heat receiving plate 3, a heat radiating unit 11, and a check valve 7 that determines the circulation direction of the working fluid. An introduction pipe 5 for connecting the three main components, the check valve 7 and the heat receiving unit 1, a lead-out pipe 6 for discharging the working fluid from the heat-receiving unit 1, a pipe line 8 for connecting the lead-out pipe 6 and the heat radiating portion 11, and It is comprised from the circulation system of the pipe line 9 which connects the check valve 7 and the heat radiating part 11.

  Next, the detailed structure of the heat receiving unit 1 will be described with reference to FIG. 2A is a central vertical sectional view of the heat receiving unit according to the first embodiment of the present invention, FIG. 2B is a cross-sectional perspective view of the heat receiving unit of FIG. 2A, and FIG. 2A is a horizontal cross-sectional view of the heat receiving unit, and FIG. 2D is a detailed cross-sectional view of a portion A shown in FIG. In FIG. 2A, 1 represents the whole heat receiving unit. Reference numeral 2 denotes a heating element, and 3 denotes a heat receiving plate that contacts the heating element 2 and absorbs heat. For example, a material having a low thermal resistance, such as copper or aluminum, is used. As shown in FIG. 2A, a slit 4 is formed substantially in parallel inside the heat receiving plate 3 of the heat receiving unit 1 in the vicinity immediately above the heating element, and the introduction pipe 5 contacts the heat receiving plate 3 so as to cover it. Or it is arranged with a slight gap. That is, from FIG. 2C, the length W1 of the slit 4 is larger than the tube diameter D1 of the introduction tube 5, and the introduction tube 5 covers the central portion of the slit 4 near the heating element.

  Hereinafter, the operation of the cooling device of the present invention configured as described above will be described. When the heating element 2 generates heat, the working fluid 14 in the heat receiving unit 1 undergoes a phase change (evaporation) on the surface of the heat receiving plate 3 (hereinafter referred to as a vaporization surface) inside the heat receiving unit 1 due to heat transferred from the heating element 2 to the heat receiving plate 3. The steam receives heat as the latent heat of vaporization and cools the heating element 2. The evaporated steam flows from the outlet pipe 6 in the direction of the arrow through the pipe line 8 to the heat radiating section 11, and the steam cooled in the heat radiating section 11 is condensed and liquefied. At this time, the heat of condensation due to liquefaction is released to raise the temperature of the heat radiating section. Then, the air from the fan 10 mounted on the heat radiating unit is sent to the surface of the heat radiating unit 11 at a high temperature and heat exchange is performed, so that heat is finally dissipated into the air. The liquefied working fluid 14 returns to the heat receiving unit 1 again from the introduction pipe 5 through the conduit 9 and the check valve 7 immediately before the heat receiving unit 1. Cooling is continued by repeating this series of cycles.

  Here, the operation in the vicinity of the heat receiving plate 3 will be further described with reference to FIG. 3A is a central vertical sectional view of the same heat receiving unit as FIG. 2A, and FIG. 3B is a central vertical sectional view in which the cutting direction is further changed by 90 degrees, and FIG. FIG. 2 is a detailed cross-sectional view of an A part of a slit part. As shown in FIG. 3 (c), the working fluid 14 that has flowed into the slit 4 from the introduction pipe 5 comes into contact with the heat receiving surface closest to the heating element when passing through the slit 4, and operates according to the amount of heat generated. The fluid undergoes a phase change (evaporation). At this time, the latent heat of vaporization is deprived on the heat receiving surface, and at the same time, bubbles grow due to volume expansion accompanying the phase change, and the pressure inside the introduction pipe 5 increases, so that the bubbles and the non-evaporated working fluid 14 become a multiphase flow. And discharged to the outlet pipe 6 side. A check valve 7 is mounted on the introduction pipe 5, and the pressure rise here occurs on the outlet side after the check valve 7, and determines the circulation direction of the working fluid 14. Further, the bottom thickness h of the slit portion is considerably thinner than the heat receiving plate thickness H.

  By reducing the slit bottom thickness h in this way, the thermal resistance due to the thickness can be reduced, and even at the same calorific value, the evaporation temperature is reached in a relatively short time, and vaporization starts. Can be suppressed. Moreover, by forming the slit 4, a sufficient vaporization area can be secured at the same time, and the heat absorption performance can be improved.

  In order to discharge the bubbles in the slit 4 together with the non-evaporated working fluid 14 due to the pressure increase, the flow path resistance of the gap between the heat receiving plate 3 and the introduction pipe 5 needs to be larger than the flow path resistance of the slit 4. There is.

  In other words, when the gap between the heat receiving plate 3 and the introduction pipe 5 where the slit 4 is not provided is zero, the working fluid 14 is discharged from the gap between the heat receiving plate 3 and the introduction pipe 5 where the slit 4 is not provided. Instead, the working fluid is discharged only from the slit 4, and bubbles generated in the slit 4 by the flow of the working fluid 14 can be effectively discharged.

  Further, even when there is a gap between the heat receiving plate 3 and the introduction pipe 5, the depth and width of the slit 4 so that the flow resistance of the slit 4 is smaller than the flow resistance of the gap where the slit 4 is not provided. Is selected, the working fluid 14 can easily flow in the slit 4.

  Here, in general, in the cooling of electronic components, as described above, heat is absorbed by the heat receiving unit 1 in contact with the heat generating element 2 from the contact surface (hereinafter referred to as the heat receiving surface) between the heat generating element 2 and the heat receiving plate 3 and becomes fins. The heat generating body 2 is cooled by heat being transferred through heat exchange with the working fluid flowing between the fins. However, the size of the heating element 2 is steadily decreasing with the recent reduction in size and cost, and even if the calorific value itself hardly changes, the heat density from the heating element 2 (per unit area) The calorific value) increases rapidly, contrary to the size. As described above, this point means that the same cooling device leads to a significant decrease in endothermic performance, and the reason is shown in FIG. This graph is a grab obtained by experimentally determining the change in thermal resistance when the same cooling device is used and the heat generation size is changed while the heat generation amount is fixed. The horizontal axis represents the size (area S: mm2) of the heating element 2, and the vertical axis represents the ratio between the thermal resistance R0 of the cooling device when the heating element size is 100 mm2 and the thermal resistance R1 when the size is reduced. The normalized thermal resistance ratio (R1 / R0) is shown. The upper horizontal axis also shows an example of generation of the minimum line width of the semiconductor process necessary for realizing each size in the future. From the graph, it can be seen that as the heat generation size decreases, the thermal resistance also deteriorates rapidly. This is due to the increase in the heat density accompanying the reduction in the heat generation size as described above, which means a substantial decrease in the heat absorption performance of the cooling device. Furthermore, the generation change of the minimum line width shown here is usually performed in 2 to 3 years, and even if the increase in the number of semiconductor elements in the meantime is taken into account, the size is reduced to about 70% in one generation. It is said. The fact that it is becoming difficult to actually secure endothermic performance sufficient to cope with the increase in heat density due to this generational change has become increasingly apparent.

  Accordingly, it goes without saying that there is an urgent need to improve the performance of the heat receiving part with respect to this problem, but for this purpose, it is effective to use the latent heat of vaporization due to the phase change such as evaporation described above to improve the heat absorption performance. However, a vaporization area is required to perform evaporation to some extent even in actual phase change. In particular, as the element size of the heating element becomes smaller, it becomes more difficult to secure the vaporization area of the working fluid that becomes the heat exchange area immediately above the element. Therefore, there are two methods for expanding the vaporization area. The first method is a method of arranging fins as densely as possible directly above the heating element, and the second method is to increase the thickness of the heat receiving plate 3 and increase the distance from the heating element 2, thereby This is a method of expanding the diffusion range and securing a vaporization area. A method of densely arranging the first fins has been conventionally performed, and a microchannel or the like can be said to be a representative example. However, this method can increase the vaporization area as the fin density increases, but there is a drawback that the more difficult the method, including the cost, becomes larger as the fin density increases.

  Further, the conventional microchannel type fins are closely arranged on the order of microns, but in this structure, a pump is required for flowing a working fluid between the fins.

  The method of increasing the thickness of the second heat receiving plate is easy in terms of cost and construction method. However, even with this method, a considerable thickness is required to secure a sufficient vaporization area, and problems such as an increase in thermal resistance and an increase in weight due to the thickness arise. In particular, an increase in thermal resistance is likely to cause a rapid temperature increase at the beginning of heating when phase change begins, and it can be said that a structure that can appropriately cope with these problems is required.

  Therefore, the present invention employs a structure in which a plurality of slits are formed on the heat receiving plate close to the introduction pipe on the order of millimeters, thereby ensuring a sufficient vaporization area and increasing the temperature at the initial stage of heating without using a pump. A cooling device with excellent heat absorption performance is realized.

  The effect of suppressing the temperature rise at the initial heating stage of the heating element 2 will be described with reference to FIGS. 5 and 6. FIG. 5 is a schematic diagram showing the temperature distribution F in a state where the slit 4 is formed in the heat receiving plate 3. The temperature distribution F on the heat receiving surface is such that the temperature of the heating element 2 is Tc, the temperature difference ΔTh at the bottom (plate thickness h) of the slit 4 and the temperature difference ΔTH (> ΔTh) of the heat receiving plate 3 (plate thickness H). Yes. Thus, it can be seen that the temperature difference increases as the plate thickness increases. That is, when the temperature of the heating element 2 is Tc, the temperature of the bottom of the slit 4 is Tc−ΔTh, and the temperature of the surface of the heat receiving plate 3 is Tc−ΔTH. Therefore, the shorter the distance from the heating element 2, that is, the thinner the heat receiving plate, the smaller the temperature difference from the heating element 2, and the heating element 2 is required when vaporizing with the heat receiving plate 3 without the slit 4 provided. The temperature of the heating element 2 when vaporizing at the slit 4 can be lowered from a certain temperature.

  FIG. 6 is a graph showing time and temperature change of the heat receiving surface when the slit 4 is formed on the heat receiving plate 3 and when the slit 4 is not formed. The horizontal axis represents the time from the start of heating (min), and the vertical axis represents the temperature Tc of the heat receiving surface, which is the contact surface between the heat generating element 2 and the heat receiving plate 3, until the initial temperature change due to the presence or absence of slits and the stable state. This represents the transition of From the graph, when there is no conventional slit, a rapid temperature rise appears immediately after the start of heating, and the maximum temperature Tc-p exceeds the stable operating temperature of the electronic component (around 75 ° C. in the case of CPU). Then, there is a high possibility of thermal runaway at the beginning of power-on. On the other hand, the one having the slit according to the present invention shows a slight increase immediately after the start of heating, but immediately shifts to a stable state and can suppress the maximum temperature Tc-p to be equal to or lower than the stable operating temperature. Further, since the evaporation area is increased by forming the slit, the temperature Tc-st in the stable state is also lowered, and the heat absorption performance can be improved.

  The bottom thickness of the slit 4 will be described with reference to FIG. FIG. 7 shows an example in which the thickness H of the heat receiving plate 3 is 4 mm. The horizontal axis represents the thickness ratio (h / H) of the heat receiving plate thickness H and the slit bottom thickness h, and the vertical axis represents heating. It is the graph which showed the relationship of the temperature ratio (Tc-p / Tc-st) of the maximum temperature Tc-p of an initial heat receiving surface, and the stable state temperature Tc-st. From the graph, it can be seen that if the thickness ratio is 0.3 or less, the temperature ratio is about 1.3 or less, which is suppressed to a temperature increase level of about 30% from the steady state temperature Tc-st.

  However, the actual heat receiving plate 3 does not mean that the thinner the slit bottom thickness h, the better. If the slit bottom thickness h becomes thinner than a certain level, the temperature ratio will not decrease, and if it is made extremely thin, the mechanical strength will also decrease. It is necessary to consider the width, number, arrangement interval, etc.

  As a result, the cooling device of the present invention can reduce the thermal resistance due to the thin slit bottom thickness by providing a slit on the inner wall of the heat receiving part, and can reach the evaporation temperature in a relatively short time even with the same calorific value. Therefore, the temperature rise of the heat receiving surface at the initial stage of heating can be suppressed.

  Moreover, since the surface area of the inner wall surface is increased by providing the slit on the inner wall, the heat transfer performance of the inner wall can be improved.

  Furthermore, by providing a slit on the inner wall from the inside to the outside of the surface surrounded by the outer periphery of the opening of the introduction pipe, bubbles generated in the slit are caused in the slit due to an increase in pressure caused by evaporation of the working fluid. Along the surface surrounded by the outer periphery of the opening, it is discharged from the inside to the outside, so that the evaporation of the working fluid due to bubble retention is not hindered, the heat absorption characteristics of the heat receiving part are improved, and the performance of the cooling device is improved. Can do.

  In addition, by setting the gap between the heat receiving plate 3 and the introduction pipe 5 to be 0.2 mm or less, bubbles generated in the slit 4 can be separated by the flow of the working fluid 14, and bubbles remaining in the slit 4 can be reduced. . As a result, the phase change, that is, evaporation of the working fluid 14 on the surface of the heat receiving plate 3 provided with the slits 4 can be promoted, and the overall heat absorption performance of the heat receiving unit 1 can be improved.

  Further, by forming the slit 4 with an inclination or a curvature, the generated bubbles can be easily discharged into the upper space by the flow of the working fluid 14, and as a result, it is possible to reduce the retention of the bubbles in the slit 4. it can.

(Example 2)
In Example 2, the slits of Example 1 are arranged radially. In addition, the same code | symbol is attached | subjected about the same component as Example 1, and the thing of Example 1 is used for the specific description.

  A cooling device in Embodiment 2 of the present invention will be described with reference to FIG. 8A is a central vertical sectional view of another heat receiving unit according to the second embodiment of the present invention, FIG. 8B is a cross-sectional perspective view of the heat receiving unit of FIG. 8A, and FIG. FIG. 8A is a horizontal sectional view of the heat receiving unit, and FIG. 8D is a detailed cross-sectional view of a portion A shown in FIG. 8A. As shown in FIG. 8A, the shape of the slit 4 formed in the heat receiving plate 3 of the heat receiving unit 1 directly above the heat generating element is formed radially from the central axis of the heat generating element. By adopting this slit structure, the thickness of the heat receiving plate immediately above the heating element is a slit bottom thickness h that can be operated as a vaporized surface with low thermal resistance if the slit width is the same, and this thin bottom The range of the thickness h is a structure that can be secured relatively wide compared to the type of FIG. Therefore, by adopting this structure, high endothermic performance can be realized as in the case of FIG.

(Example 3)
In the third embodiment, no slit is provided at the center of the heat receiving plate 3 with which the heating element 2 is in contact. In addition, about the same component as Example 1, 2, the same code | symbol is attached | subjected for convenience, and the thing of Example 1, 2 is used for the specific description.

  First, the case where the slits 4 are arranged in parallel will be described with reference to FIG. 9A is a central vertical sectional view of the heat receiving unit 1 according to the third embodiment of the present invention, FIG. 9B is a cross-sectional perspective view of FIG. 9A, and FIG. 9C is a diagram. 9A is a horizontal cross-sectional view of the heat receiving unit, and FIG. 9D is a detailed cross-sectional view of the A portion shown in FIG. 9A. As shown in FIG. 9A, the arrangement of the substantially parallel slits 4 formed in the heat receiving plate 3 of the heat receiving unit 1 immediately above the heat generator is arranged avoiding a part directly above the heat generator 2. . In other words, a portion with the original thickness H of the heat receiving plate remains immediately above the heat generating member 2, which is an area directly connected to the portion with the heat receiving plate thickness H around the heat generating member. In the case of Example 2 in FIG. 2 or FIG. 8, it is considered that the mechanical strength is insufficient as described above depending on the density of the slits. Therefore, in this example, by adopting the structure as shown in FIG. The required mechanical strength is maintained. Then, by selecting an appropriate slit density, it is possible to realize a cooling device excellent in endothermic performance that secures a sufficient vaporization area and suppresses a temperature increase in the initial stage of heating.

  Next, the case where the slits 4 are arranged radially will be described with reference to FIG. 10A is a central vertical sectional view of the heat receiving unit 1 according to the third embodiment of the present invention, FIG. 10B is a cross-sectional perspective view of FIG. 10A, and FIG. 10C is a diagram. 10 (a) is a horizontal cross-sectional view of the heat receiving unit, and FIG. 10 (d) is a detailed cross-sectional view of the A portion of the slit portion shown in FIG. 10 (a). As shown in FIG. 10A, the basic configuration is the same as in FIG. 8, and the slits 4 formed in the heat receiving plate 3 are also formed radially from the center of the heating element. However, the arrangement of the slits 4 formed in the heat receiving plate 3 of the heat receiving unit 1 immediately above the heat generating element is arranged radially avoiding a part directly above the heat generating element 2 as in the case of FIG. That is, in this case as well, a portion with the original thickness H of the heat receiving plate remains immediately above the heat generating member 2 and is an area directly connected to the portion with the heat receiving plate thickness H around the heat generating member. Therefore, as in the case of FIG. 9, the necessary mechanical strength is maintained by adopting this structure, and by selecting an appropriate slit density, a sufficient vaporization area and endothermic performance with suppressed temperature rise at the beginning of heating are achieved. An excellent cooling device can be realized.

Example 4
In Example 4, the width of the slit 4 is gradually increased as the distance from the heating element 2 increases in order to further improve the heat absorption performance. In addition, the same code | symbol is attached | subjected about the same component as Examples 1-3, and the thing of Examples 1-3 is used for the specific description.

  First, the case where the slits 4 are arranged in parallel will be described with reference to FIG. 11A is a central vertical sectional view of the heat receiving unit 1 according to the fourth embodiment of the present invention, FIG. 11B is a cross-sectional perspective view of the heat receiving unit of FIG. 11A, and FIG. 11A is a horizontal cross-sectional view of the heat receiving unit, and FIG. 11D is a detailed cross-sectional view of the A portion of the slit portion shown in FIG. As shown in FIG. 11 (a), the arrangement of the slits 4 formed in the heat receiving plate 3 of the heat receiving unit 1 immediately above the heat generating element avoids a part directly above the heat generating element 2 as in the case of FIG. In addition, the width of the slit 4 into which the working fluid 14 directly under the introduction pipe 5 flows is gradually increased as the distance from the center of the heating element 2 increases. By adopting this structure, it becomes possible to promote the stable circulation of the working fluid by increasing the bubble detachability of the vapor which is vaporized in the slit 4 and becomes a bubble and is discharged from the other end of the slit 4. Particularly when a working fluid having a high surface tension is used, the bubbles generated in the slit 4 are easily held (trapped), and the circulation of the working fluid is hindered, resulting in a rapid decrease in heat absorption performance. There is a fear. Therefore, this bubble detachability is an important parameter for ensuring stable operation in an apparatus using phase change. In Example 4, as well as in the case of FIG. 9, while maintaining the necessary mechanical strength, by selecting an appropriate slit density, the heat absorption performance that secures a sufficient vaporization area and suppresses the temperature rise in the initial stage of heating. It is the same that an excellent cooling device can be realized.

  Next, the case where the slits 4 are arranged radially will be described with reference to FIG. 12 (a) is a central vertical sectional view of another heat receiving unit 1 according to the fourth embodiment of the present invention, FIG. 12 (b) is a sectional perspective view of the heat receiving unit of FIG. 12 (a), and FIG. 12 (c). FIG. 12A is a horizontal sectional view of the heat receiving unit in FIG. 12A, and FIG. 12D is a detailed sectional view of the A portion of the slit portion shown in FIG. As shown in FIG. 12A, the arrangement of the slits 4 formed in the heat receiving plate 3 of the heat receiving unit 1 directly above the heat generating element 2 avoids a part directly above the heat generating element 2 as in the case of FIG. In the same manner as in the case of FIG. 11, the width of the slit 4 into which the working fluid 14 directly under the introduction pipe 5 flows is gradually increased as the distance from the center of the heating element increases. In addition, as in the case of FIG. 11, the effect of adopting this structure is not only the improvement of the bubble detachability described above, but also the sufficient slit strength can be selected while maintaining the necessary mechanical strength. Therefore, it is possible to realize a cooling device excellent in endothermic performance with suppressed vaporization area and temperature increase in the initial stage of heating.

  Moreover, when it arrange | positions radially compared with the case where the slit 4 is arrange | positioned in parallel, more slits can be provided, a heat receiving area can be increased, and the performance of a cooling device can be improved further.

  In this embodiment, the slit 4 is not provided at the center of the heat receiving plate 3 with which the heating element 2 is in contact, but the slit 4 may be provided.

(Example 5)
In Example 5, when the heat receiving plate 3 is used upright, a groove having the same size as the outer periphery of the opening of the introduction pipe 5 is provided in the heat receiving plate 3 so as to intersect the slit 4, and the opening of the introduction port 5 is provided. It is inserted into the heat receiving plate 3. In addition, about the same component as Examples 1-4, the same code | symbol is attached | subjected for convenience, The thing of Examples 1-4 is used for the specific description.

  FIG. 13 (a) is a central vertical sectional view of a heat receiving unit according to the fifth embodiment of the present invention, FIG. 13 (b) is a sectional perspective view of FIG. 13 (a) the heat receiving unit, and FIG. 13 (a) is a horizontal sectional view of the heat receiving unit, and FIG. 13 (d) is a detailed sectional view of the A portion of the slit portion shown in FIG. 13 (a). In FIG. 13A, 1 represents the whole heat receiving unit.

  Here, as shown in FIG. 13 (d), the leading end of the introduction pipe 5 is in a state of slightly entering the inside of the heat receiving plate 3. By adopting such a structure, even when the actual heat receiving unit 1 is arranged as shown in the sectional perspective view of FIG. 13A, the working fluid supplied from the introduction pipe 5 leaks in the direction of gravity. Can be reliably introduced into the slit 4. Thereby, the freedom degree of the arrangement | positioning direction of the heat receiving unit 1 spreads from horizontal to vertical, and the cooling device of the electronic component which raised the possibility of expansion | deployment to various uses is realizable.

  In the first to fourth embodiments, the heat receiving unit 1 operates by being arranged vertically. However, when the heat receiving unit 1 is arranged vertically, the introduction pipe 5 is inserted into the heat receiving plate 3 as described above. It is desirable to form.

  According to the cooling device of the present invention, since it has high endothermic characteristics, it is particularly suitable for cooling electronic parts having a high calorific value due to high integration and high frequency such as MPU.

DESCRIPTION OF SYMBOLS 1 Heat receiving unit 2 Heat generating body 3 Heat receiving plate 4 Slit 5 Introducing pipe 6 Outlet pipe 7 Check valve 8, 9 Pipe line 10 Fan 11 Radiating part 12 Wick 13 Pump 14 Working fluid 15 Power supply unit 16 PC housing 17 Heating element socket 18 Motherboard

Claims (12)

A cooling device that circulates a working fluid and cools it by a phase change between a liquid phase and a gas phase, wherein a heating element is disposed on one surface of the outer wall, and a box-shaped heat receiving unit that transfers heat to the inner wall corresponding to the one surface of the outer wall; , An introduction pipe for injecting the working fluid into the heat receiving part, a working pipe injected into the heat receiving part into steam by heat, a lead-out pipe for discharging the steam, and a lead-out pipe provided above the heat receiving part. A radiator for releasing the heat of the steam via a pipe, and a check valve provided on the opening side of the introduction pipe, and the working fluid liquefied by the radiator is received through the check valve for the heat reception The circulation direction of the working fluid is determined by the pressure increase on the outlet side after the check valve, and a slit is provided from the inner side to the outer side of the inner wall surrounded by the outer periphery of the inlet pipe opening. It is the pressure of the introduction pipe portion By increasing the cooling apparatus characterized by bubbles and unevaporated working fluid is discharged to the outlet pipe side become multiphase flow. 2. The outer wall on which the heating element is arranged, wherein the heat source center of the heating element is arranged inside the outer periphery of the inlet pipe opening located symmetrically across the wall. Cooling system. The cooling apparatus according to claim 1, wherein the introduction pipe opening is in contact with the inner wall. The cooling device according to claim 1, wherein a plurality of the slits are formed in parallel. The cooling device according to claim 1, wherein the slits are formed radially from the center of the inlet tube opening. The cooling device according to claim 1, wherein the slit is provided in a central portion of the inner wall surrounded by an outer periphery of the introduction pipe opening. The cooling device according to claim 1, wherein the width of the slit increases as the distance from the center of the inlet tube opening increases. The ratio (h / H) of the thickness h of one surface from the bottom of the slit to the outer wall to the thickness H from the inner wall to the outer surface where the slit is not provided is 0.1 to 0.3. The cooling device according to claim 1, wherein the cooling device is provided. The cooling device according to claim 1, wherein a gap between the introduction pipe opening and the inner wall is 0.2 mm or less. The cooling apparatus according to claim 1, wherein a groove that intersects the slit is provided, and the introduction pipe opening is inserted into the groove. A cooling device that circulates a working fluid and cools it by a phase change between a liquid phase and a gas phase, wherein a heating element is disposed on one surface of the outer wall, and a box-shaped heat receiving unit that transfers heat to the inner wall corresponding to one surface of the outer wall; An introduction pipe for injecting the working fluid into the heat receiving part, a deriving pipe from which the working fluid injected by the heat of the inner wall becomes steam to discharge the steam, and an outlet pipe provided above the heat receiving part. A heat radiator that releases the heat of the vapor that has passed therethrough, disposed inside the outer periphery of the inlet pipe opening on the outer wall on which the heating element is arranged, and the pressure inside the inlet pipe rises, The structure is such that the non-evaporated working fluid is discharged into the outlet pipe side as a multiphase flow, and the thickness of the inner wall corresponding to the portion where the heating element is disposed is made thinner than the thickness of the surrounding inner wall. A cooling device characterized. The cooling device according to claim 11, wherein a slit is provided in the inner wall to reduce the thickness of the inner wall.

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