JP5638049B2 - Loop type heat pipe - Google Patents

Description

  The present invention is a loop configured so that a counter flow between a working fluid that is vaporized in an evaporation section and flows toward a condensing section and a working fluid that is condensed in the condensing section and flows toward an evaporation section does not occur. More particularly, the present invention relates to a loop heat pipe in which the thermal resistance between the evaporation section and the working fluid is reduced.

  An example of a loop heat pipe is described in Patent Document 1. The loop-type heat pipe described in Patent Document 1 includes an evaporation unit that receives heat from a heating element and evaporates a liquid-phase working fluid, and a plurality of vapor-type working fluids that release heat to the outside and condense it. A condensing unit and a plurality of circulation paths for circulating the working fluid that changes phase as described above are provided. Each circulation path is provided with a valve, and the opening and closing of each valve is controlled by a valve control unit. In the loop heat pipe described in Patent Document 1, the opening and closing of each valve is controlled according to the amount of heat generated by the heating element that is in contact with the evaporation section so as to be able to transfer heat. It is comprised so that the transport destination of the heat conveyed in the form of may be changed. Specifically, when the heat generation amount of the heating element is small, a condensing unit having a small heat dissipation amount communicates with the evaporation unit, and when the heat generation amount is large, a condensing unit having a large heat dissipation amount communicates with the evaporation unit. It is configured to be.

JP 2010-2084 A

  In the configuration described in Patent Document 1 described above, the working fluid condensed in the condensing unit is injected into the evaporating unit by gravity, that is, in particular, the working fluid is not injected into the evaporating unit by applying pressure. There is a possibility that the heat transfer efficiency from the surface to the working fluid is low, and the thermal resistance during the evaporation process is high. Further, when the liquid-phase working fluid is supplied to the evaporation unit as it is, the droplets of the working fluid increase, and the area for transferring heat from the surface of the evaporation unit to the liquid-phase working fluid decreases. Furthermore, because of the surface tension of the working fluid, it is difficult for it to become small droplets during the evaporation process, so that the above-mentioned area remains small and the thermal resistance may increase. When the temperature of the evaporating part is sufficiently higher than the boiling point of the working fluid, a layer of the working fluid vaporized between the surface of the evaporating part and the liquid-phase working fluid is generated due to the Leidenfrost phenomenon. Is formed, and the liquid-phase working fluid is unlikely to come into contact with the evaporating portion, and the thermal resistance may increase.

  The present invention has been made paying attention to the above-described problems, and provides a loop heat pipe in which the contact area between the surface of the evaporation section and the liquid-phase working fluid is increased to reduce the thermal resistance therebetween. It is intended to do.

In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that the evaporating part for removing heat from the heating element and the condensing part for releasing heat to the outside communicate with each other so as to form a circulation path by the steam pipe and the liquid return pipe. And in a loop heat pipe in which a condensable fluid is sealed as a working fluid in a state where the inside of the circulation path is evacuated, the condensing part radiates heat to a position higher than the evaporation part. are arranged to, e Bei the liquid pouring means for supplying the working fluid at high pressure using merge into fine droplets to the vaporization section, the liquid pouring means, the working fluid is sealed inside the circulation path A reservoir connected to the liquid return pipe for flowing the working fluid liquefied by radiating heat in the condensing unit toward the evaporation unit, a pressurizing unit for pressurizing the reservoir, and the pressurizing unit Pressurized by pressure means A nozzle that makes the working fluid discharged from the reservoir into fine droplets, the nozzle being at least one of a single-stage nozzle and a two-stage nozzle, and the pressurizing means is , Having at least a pressurizing tank, and configured to pressurize the reservoir by supplying the pressure in the pressurizing tank to the reservoir .

According to a second aspect of the present invention, in the first aspect of the present invention, on-off valves for opening and closing the liquid return pipe are respectively provided on the upstream side and the downstream side of the liquid return pipe where the reservoir communicates. And when the upstream side open / close valve is opened and the downstream side open / close valve is closed, the working fluid is stored in the reservoir, the upstream side open / close valve is closed, and the downstream side open / close valve is opened. When the valve is opened and the reservoir is further pressurized by the pressurizing means, the working fluid is supplied from the reservoir to the evaporation section through the nozzle. It is a loop heat pipe.

According to this invention, since the working fluid made into fine droplets by the liquid injection means is supplied to the evaporation unit at a high pressure, the area for transferring heat from the surface of the evaporation unit to the working fluid can be increased. it can. Therefore, the thermal resistance between the evaporation unit and the working fluid can be reduced. Further, the occurrence of the Leidenfrost phenomenon can be prevented or suppressed. Eventually, according to the present invention, it is possible to reduce the thermal resistance in the evaporation section and thus improve the heat transport capability of the loop heat pipe.

Further, according to the present invention, the working fluid of the pressurized liquid phase by pressurizing means is in fine droplets are passed through a nozzle. Therefore, the size of the droplet can be made finer.

Further, according to the present invention, when the on-off valve on the upstream side of the portion where the reservoir in the liquid return pipe is communicated is opened and the on-off valve on the downstream side is closed, the working fluid is not supplied to the evaporation section. Even if heat is transferred from the body to the evaporation unit, the working fluid does not evaporate in the evaporation unit, and the heating element is not actively cooled. On the other hand, when the upstream open / close valve is closed and the downstream open / close valve is opened and the reservoir is pressurized by the pressurizing means, the pressurized liquid-phase working fluid is discharged from the reservoir toward the nozzle. The The high-pressure liquid-phase working fluid is made into fine droplets by the nozzle and supplied to the evaporation section, so the heat transfer area between the evaporation section and the working fluid is expanded to reduce the thermal resistance between them. can do.

It is a figure which shows typically the loop type heat pipe which concerns on this invention. It is sectional drawing which shows typically the dormant state of the loop type heat pipe which concerns on this invention. It is sectional drawing which shows typically the standby state of the loop type heat pipe which concerns on this invention. It is sectional drawing which shows typically the operation state of the loop type heat pipe which concerns on this invention. It is a figure which shows typically the part of the bonder head and stage in a semiconductor chip bonder, (A) shows the state before joining, (B) shows the state at the time of joining.

  Next, the present invention will be specifically described. The loop heat pipe according to the present invention can be used as a cooling device for a semiconductor chip bonder. First, the configuration of the semiconductor chip bonder will be briefly described. FIGS. 5A and 5B are schematic partial views showing the bonder head 1 and the stage 2. The stage 2 has the substrate 3 horizontally on the upper surface thereof. It is configured to be placed and positioned. The bonder head 1 is configured to be moved above the stage 2 in the three axial directions of the X-axis direction, the Y-axis direction, and the Z-axis direction, that is, the horizontal direction and the vertical direction. The bonder head 1 includes a metal block 4 corresponding to a base portion, and a cooling unit 5, a suction head 6, and a suction unit 7 are provided on the lower surface side of the metal block 4.

  The metal block 4 is a rectangular parallelepiped or columnar member formed of stainless steel, for example. The cooling unit 5 is attached to the lower end surface of the metal block 4, that is, the surface facing the stage 2, and the suction unit provided integrally with the lower surface of the cooling unit 5 via the suction head 6. 7 is configured to hold the semiconductor chip 8 by vacuum suction. A solder bump (hereinafter simply referred to as a bump) 9 is disposed on the substrate 3 placed and positioned on the upper surface of the stage 2, and the bonder head 1 holding the semiconductor chip 8 is moved upward. After that, as shown in FIG. 5B, the semiconductor chip 8 is lowered toward the substrate 3 and the semiconductor chip 8 is pressed against the substrate 3 so as to sandwich the bumps 9. In this state, the bump 9 is heated and melted, and then the bump 9 is cooled and solidified, whereby the semiconductor chip 8 is bonded to the substrate 3. The bump 9 is heated by energizing a ceramic heater (not shown) provided in the bonder head 1 and raising the temperature from 100 ° C. to 400 ° C. for 5 to 6 seconds. Therefore, in the example shown here, the bump 9 heated by a ceramic heater or a ceramic heater (not shown) corresponds to the heating element in the present invention. These cooling operations are performed by operating the cooling unit 5.

  FIG. 1 is a diagram schematically showing a loop heat pipe 10 according to the present invention. The loop heat pipe 10 is configured such that an evaporation unit 11 and a condensing unit 12 communicate with each other by a steam pipe 13 and a liquid return pipe 14 so as to form a circulation path as a whole. A predetermined amount of a condensable fluid such as water is sealed inside the circulation path as a working fluid in a state where non-condensable gas such as air is deaerated. The principle configuration of the loop heat pipe 10 is the same as that of a conventionally known loop heat pipe. The heat is input to the evaporation unit 11 to increase its temperature, and the heat is released from the condensation unit 12. When the temperature decreases, the working fluid evaporates in the evaporating unit 11, the vapor flows to the condensing unit 12 and dissipates heat in the condensing unit 12, and as a result, the working fluid condenses from the evaporating unit 11 in the form of its latent heat. Heat is transferred to section 12.

  The evaporation unit 11 is arranged in the cooling unit 5, and the evaporation unit 11 is configured to take heat from the bonder head 1. That is, the evaporation part 11 is a hollow flat plate-like part, and its upper surface is brought into close contact with the lower surface of the metal block 4 so as to be able to transfer heat, and the aforementioned adsorption part 7 is attached to the lower surface of the evaporation part 11. ing.

  The condensing part 12 is arrange | positioned in the position higher than the evaporation part 11, and is comprised so that it may thermally radiate outside. The heat radiation may be either air heat radiation or underwater heat radiation. FIG. 1 shows an example in which air heat radiation is performed. In other words, a steam side header pipe 12A communicated with the upper end of the steam pipe 13 is provided, and a plurality of branch pipes 12B extend from the steam side header pipe 12A. A liquid side header pipe 12C is arranged in parallel below the vapor side header pipe 12A, and an upper end portion of the liquid return pipe 14 is communicated with the liquid side header pipe 12C. The same number of branch pipes 12D as the branch pipes 12B extend from the liquid side header pipe 12C so as to be parallel to the branch pipes 12B. A plurality of finned condensing pipes 12E are arranged between the branch pipes 12B and 12D that are parallel to each other in the vertical direction so as to communicate with the branch pipes 12B and 12D. Therefore, the working fluid vapor is supplied from the steam side header pipe 12A to the condensing pipes 12E with fins through the branch pipes 12B, and the working fluid is condensed by generating heat radiation in the air through the condensing pipes 12E with fins. The liquid is configured to flow from the branch pipe 12D and the liquid side header pipe 12C to the liquid return pipe 14.

  A reservoir 15 is in communication with a liquid return pipe 14 that recirculates the liquid-phase working fluid from the condenser 12 to the evaporator 11. The reservoir 15 is for storing a liquid-phase working fluid, and the volume thereof is set to a capacity capable of storing the entire amount of the working fluid sealed in the loop heat pipe 10. A first opening / closing valve 16 that opens and closes the liquid return pipe 14 is provided in a portion of the liquid return pipe 14 that is above the location where the reservoir 15 is connected, and a portion that is below the location where the reservoir 15 is connected. In addition, a second on-off valve 17 is provided. These on-off valves 16 and 17 can be constituted by, for example, electrically controlled electromagnetic valves, and a valve body housed in an airtight state inside the liquid return pipe 14 is provided outside the liquid return pipe 14. The liquid return pipe 14 is opened and closed by being moved by the magnetic force of the electromagnetic coil. A nozzle to be described later is provided in a portion of the liquid return pipe 14 below the portion where the second on-off valve 17 is provided.

  The reservoir 15 is in communication with a pressurized tank 19 through a pressure pipe 18. The pressurized tank 19 is filled with a non-condensable inert gas such as nitrogen gas or argon gas at a high pressure. The pressure pipe 18 is provided with a pressure supply opening / closing valve 20 that supplies compressed gas filled in the pressurized tank 19 to the reservoir 15 and stops the supply thereof. This on-off valve 20 can be constituted by an electromagnetic valve that is electrically controlled as an example, and when the pressure release electromagnetic valve described later is closed, by opening the pressure supply electromagnetic valve 20, The compressed gas in the pressurized tank 19 is configured to be supplied to the reservoir 15. When the compressed gas is supplied to the reservoir 15 in this way, the internal pressure of the reservoir 15 is increased, and the working fluid stored in the reservoir 15 is supplied to the liquid return pipe 14 by the internal pressure. Yes.

  A pressure reducing pipe 21 is communicated with a portion of the pressure pipe 18 closer to the reservoir 15 than a portion where the pressure supplying electromagnetic valve 20 is provided. The end of the decompression tube 21 is in communication with the atmosphere. The pressure reducing pipe 21 is provided with a pressure release opening / closing valve 22 for releasing the pressure in the reservoir 15 into the atmosphere. The on-off valve 22 can be constituted by, for example, an electrically controlled electromagnetic on-off valve. When the pressure supplying electromagnetic valve 20 is closed, the pressure release electromagnetic valve 22 is opened. Thus, the inside of the reservoir 15 is communicated with the atmosphere, and the pressure inside the reservoir 15 is released into the atmosphere.

  FIG. 2 is a cross-sectional view of the loop heat pipe 10 according to the present invention. The reservoir 15 includes a casing 23 in which a bellows-shaped expansion / contraction container 24 is accommodated. A liquid-phase working fluid is stored inside the expandable container 24. A space formed by the expandable container 24 and the inner wall surface of the casing 23 is a pressure chamber 25, and the pressurized tank 19 is communicated with the pressure chamber 25 through the pressure pipe 18. That is, the pressure chamber 25 is a space that is completely separated from the circulation path of the loop heat pipe 10 by the extendable container 24. When the compressed gas from the pressurized tank 19 is supplied to the pressure chamber 25 and the pressure increases, the expansion / contraction container 24 is contracted and its volume decreases. The liquid-phase working fluid stored in the expansion container 24 is discharged from the reservoir 15. The stretchable container 24 is preferably made of an elastic material such as rubber or synthetic resin. In addition, a piston may be arrange | positioned inside the casing 23, and the part which stores a working fluid of a liquid phase may be separated from the pressure chamber by the piston. That is, the casing 23 may be used as a cylinder, and the above-described piston may be moved by the compressed gas in the pressurized tank 19 to discharge the liquid-phase working fluid from the reservoir 15.

  A nozzle 26 is provided in a portion of the liquid return pipe 14 below the portion where the second on-off valve 17 is provided. The nozzle 26 is used to make the liquid-phase working fluid discharged from the reservoir 15 into fine droplets. Therefore, as this nozzle 26, for example, a conventionally known single-stage type configured such that a fluid under pressure is ejected from a small-diameter orifice to disperse liquid fine particles downstream thereof. A nozzle can be used. A two-stage nozzle called a Laval nozzle configured to eject fine droplets at a higher speed than a single-stage nozzle can also be used. In the present invention, any nozzle can be used, but if a two-stage nozzle is used, finer droplets of working fluid can be sprayed onto the surface of the evaporation section 11. As will be described later, the heat transfer area and the heat transfer efficiency between the surface of the evaporation section 11 and the working fluid can be improved, and the thermal resistance between them can be reduced. The reservoir 15, the pressurizing tank 19, the electromagnetic valves 16, 17, 18, 22 and the nozzle 26 correspond to the liquid injection means in the present invention, and the pressurizing tank 19 and the electromagnetic valves 16, 17, 20, Reference numeral 22 corresponds to the pressurizing means in the present invention.

  Next, the operation of the loop heat pipe 10 according to the present invention functioning as the above-described semiconductor chip bonder cooling device will be described. The bonder head 1 adsorbs and holds the semiconductor chip 8 as shown in FIG. 5, and the substrate 9 with the bumps 9 sandwiched between the semiconductor chip 8 and the substrate 3 as shown in FIG. Press against 3 Thus, before energizing a ceramic heater (not shown) and heating the bump 9, the first on-off valve 16 is opened and the second on-off valve 17 is closed. The pressure supply solenoid valve 20 is closed, and the pressure release solenoid valve 22 is opened. This state is the state shown in FIG. 2 and is referred to as a resting state. In the resting state, the pressure in the pressure chamber 25 of the reservoir 15 is the same as the atmospheric pressure. The bellows-shaped expandable container 24 is in an expanded state, and the inside thereof is filled with a liquid-phase working fluid. That is, since the working fluid is not supplied to the evaporation unit 11, the evaporation unit 11 is in a dry-out state.

  Next, the bumps 9 are heated and melted by energizing a ceramic heater (not shown). In the process of heating the bump 9, the electromagnetic valves 16, 17, 20, and 22 are all closed, and the state where the pressure chamber 25 of the reservoir 15 communicates with the atmosphere is blocked. This state is the state shown in FIG. 3, and this is called a standby state. In the standby state shown in FIG. 3, since all the solenoid valves 16, 17, 20, and 22 are closed, the working fluid is still stored in the reservoir 15, and the evaporation unit 11 is in a dry-out state. Therefore, even if heat for heating the bumps 9 is transmitted to the evaporation unit 11 constituting the cooling unit 5, the working fluid does not evaporate in the evaporation unit 11, so that the bonder head 1 or the bumps 9 are cooled. There is no.

  The bump 9 is heated, for example, at 100 to 400 ° C. for about 5 to 6 seconds, and the bump 9 is melted. When energization of the ceramic heater is stopped and heating is stopped, the electromagnetic valve 20 for pressure supply and the second on-off valve 17 are opened almost simultaneously, and the liquid-phase working fluid is supplied to the evaporation unit 11. This state is the state shown in FIG. 4 and is referred to as an operation state. This operation state will be described more specifically. When the pressure supply solenoid valve 20 is opened, the compressed gas in the pressurized tank 19 is supplied to the pressure chamber 25 of the reservoir 15 to increase its pressure, and the expandable container 24 is contracted by the increased pressure. The working fluid stored in the expansion container 24 is discharged as the expansion container 24 contracts. The working fluid pressurized and discharged from the reservoir 15 in this way is supplied to the liquid return pipe 14, and the pressure of the working fluid in the pipe is increased. Since the first on-off valve 16 is closed, the high-pressure working fluid is supplied to the nozzle 26 via the second on-off valve 17 and sprayed from the nozzle 26. That is, the working fluid is made into fine droplets by the nozzle 26 and supplied to the evaporation unit 11. When the time required for cooling the bumps 9 is short and the amount of working fluid required is small, instead of continuing to open the electromagnetic valve 17 described above, a liquid-phase working fluid is injected (splash). Thus, the electromagnetic valve 17 may be opened for a short time.

  The liquid-phase working fluid is heated by the evaporating section 11 and first takes heat in the form of sensible heat to cool the bonder head 1 or the bumps 9. Further, the working fluid is further heated and evaporated, and heat is taken away in the form of latent heat to cool the bonder head 1 or the bumps 9. More specifically, in the present invention, as described above, since the liquid-phase working fluid is made into fine droplets by the nozzle 26 and supplied to the evaporation unit 11, the liquid-phase working fluid and the evaporation unit 11 are used. The contact area with the surface is enlarged. That is, the heat transfer area between them is expanded. In addition, since the working fluid made into fine droplets is injected into the evaporation unit 11 at a high pressure, the heat transfer rate from the surface of the evaporation unit 11 to the liquid-phase working fluid is not injected at a high pressure as described above. Compared to In addition, since the working fluid made into fine droplets is injected into the evaporation unit 11 at a high pressure, the Leidenfrost phenomenon that frequently occurs when the temperature difference between the evaporation unit 11 and the working fluid is large and the pressure is low. It can be prevented or suppressed. For this reason, in the present invention, it is possible to obtain a high heat transfer efficiency by reducing the thermal resistance between the evaporation section 11 and the liquid-phase working fluid as compared with the conventional one.

  And the vapor | steam of the working fluid produced | generated as mentioned above flows inside the vapor | steam pipe | tube 13 toward the condensation part 12 which is thermally radiated outside and temperature and pressure are low. Then, the condenser 12 dissipates heat and condenses, and the liquid-phase working fluid flows down to the liquid return pipe 14. That is, the working fluid transports heat from the evaporation section 11 to the condensation section 12 in the form of its latent heat, and as a result, the bonder head 1 or the bump 9 is deprived of its heat and cooled. In that case, since the latent heat per unit amount of the working fluid is larger than the sensible heat, and much more than the sensible heat per unit amount of air, the bonder head 1 or the bump 9 can be rapidly cooled.

  When the bump 9 is cooled and solidified as described above, the loop heat pipe 10 is brought into a resting state shown in FIG. That is, the heat transport operation of the loop heat pipe 10 is stopped, and the cooling of the bonder head 1 or the bumps 9 is stopped. At substantially the same time, the suction of the semiconductor chip 8 by the suction part 7 is released, and the bonder head 1 moves away from the semiconductor chip 8. Thus, the time required for a series of steps for bonding the semiconductor chip 8 to the substrate 3 can be shortened because the time required for cooling and solidifying the melted bump 9 is shortened. Productivity of an electronic product incorporating the chip 8 can be improved. Further, by heating and melting the bumps 9, the temperature of the air in the vicinity thereof becomes high, or even if some gas is generated, such high temperature air or gas can be diffused to the surrounding work environment. Therefore, it is possible to prevent the working environment from deteriorating.

  DESCRIPTION OF SYMBOLS 10 ... Loop type heat pipe, 11 ... Evaporating part, 12 ... Condensing part, 13 ... Steam pipe, 14 ... Liquid return pipe, 15 ... Reservoir, 19 ... Pressure tank.

Claims (2)

The evaporator section that takes heat away from the heating element and the condenser section that radiates heat to the outside communicate with each other so as to form a circulation path by the steam pipe and the liquid return pipe, and condense in a state where the inside of the circulation path is evacuated. In a loop heat pipe in which a sexual fluid is sealed as a working fluid,
The condensing part is disposed at a position higher than the evaporation part and dissipates heat to the outside,
E Bei the liquid pouring means for supplying the working fluid at high pressure using merge into fine droplets to the vaporization section,
The liquid injection means is provided in the liquid return pipe that can store the entire amount of the working fluid enclosed in the circulation path and causes the working fluid radiated and liquefied by the condensing unit to flow toward the evaporation unit. A reservoir that is communicated, a pressurizing unit that pressurizes the reservoir, and a nozzle that makes the working fluid discharged from the reservoir into fine droplets by being pressurized by the pressurizing unit,
The nozzle is at least one of a single-stage nozzle and a two-stage nozzle,
The loop heat pipe according to claim 1, wherein the pressurizing means has at least a pressurization tank, and is configured to pressurize the reservoir by supplying the pressure in the pressurization tank to the reservoir . On-off valves for opening and closing the liquid return pipe are respectively provided on the upstream side and the downstream side of the portion where the reservoir in the liquid return pipe is communicated,
When the upstream open / close valve is opened and the downstream open / close valve is closed, the working fluid is stored in the reservoir, the upstream open / close valve is closed, and the downstream open / close valve is opened. 2. The apparatus according to claim 1 , wherein when the reservoir is pressurized by the pressurizing means, the working fluid is supplied from the reservoir to the evaporation section through the nozzle. loop heat pipe as claimed in.

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