KR20010027885A - Cooling apparatus and its cooling method for multipchip module - Google Patents

Abstract

PURPOSE: A multi chip module(MCM) cooling device and its cooling method are provided to decrease the difference temperature between the upper and the lower of MCM by increasing the heat radiating area, and to maintain the MCM surface temperature under the 55 °C by forming the fins and a fluid passage over the cooling plate. CONSTITUTION: The multi chip module(3) cooling device comprises a refrigerant fluid passage(1) formed with natural circulation loop structure, a cooling device(11) for absorbing the radiated heat from the MCM, a condensational apparatus(22) for condensing the vapor. The cooling device has a refrigerant fluid channel and a plurality of fins to increase the heat radiating area. The condensational apparatus keeps refrigerant in storage groove for a moment and a cooling water groove under the condensing surface. The method includes steps of injecting the refrigerant into the refrigerant fluid passage via condensational refrigerant fluid passage, absorbing the radiating heat by the circulating refrigerant and fins, emitting the vaporized refrigerant by heat siphon effect, keeping the circulating refrigerant vapor in the storage groove within the condensational apparatus, and emitting the condensed refrigerant vapor to the condensational refrigerant channel by using the gravity.

Description

COOLING APPARATUS AND ITS COOLING METHOD FOR MULTIPCHIP MODULE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device and a cooling method for effectively cooling high heat generated in a multichip module (MCM) that is mainly used in a high density and high density system such as a broadband integrated network system. The present invention relates to a cooling apparatus and a cooling method of a multichip module that maximizes the convection effect and introduces a condensation means suitable for the change in temperature and pressure of the system.

In general, in order to realize a high-speed broadband asynchronous transfer mode (ATM) switching system, a large number of high-speed, high-volume (VLSI) chips are required, and due to the high density and high integration of chips, they are generated inside the integrated circuit. Since the calorific value continues to increase, a cooling module is required to cool it. If the chips that generate such high heat generation are left as it is in the indoor air, it becomes a very high temperature not only causes the failure of the components, but also generates high heat inside the system equipment, delaying the signal transmission time between each component, In the morning, the system's reliability drops dramatically. Since this is a barrier to the development of a system that is becoming more dense in the future, the selection of a cooling method and the development of the cooling technology corresponding to the development of the system can be said to be essential for successful system development.

In addition, in a method of mounting a system, a narrow band integrated information network (N-ISDN) using a card on board (COB) can be seen in FIG. 1 because the heat flux of the chip module is only 0.01 ?? 0.1 W / cm 2. As described above, the system is cooled by a natural convection cooling method using air or a low velocity forced convection cooling method. However, in the case of B-ISDN, which aims to transmit images, the information processing rate should be hundreds of gigabytes (Gbps), which is 10 to 100 times larger than that of narrow-band integrated telecommunication networks. In this case, the chip module has higher circuit density than the conventional single-chip module (SCM) method, which minimizes signal propagation delay between circuit lines and reduces electromagnetic wave emission, and improves the performance of an exchange system. It is advantageous to use a multi-chip module (MCM) method that can greatly improve.

However, in the case of using the multi-chip module, a new mounting technique and a cooling method are required in consideration of the heat flux of the chip module reaching 2 W / cm 2.

Recently, many thermo-siphon cooling modules for cooling the MCM have been proposed to meet the above requirements. However, in these cooling devices, the flow path in the cooling plate is horizontal so that the refrigerant filled in the flow path is boiling. It has the disadvantages of rapid temperature rise while delayed and reaching steady state.

In addition, in the case of a horizontal flow path, forced convection does not occur using a pumping action by boiling, and thus there is a problem in that heat cannot be absorbed by forced convection. That is, in NTT, eight 8mm 4mm diameter pipes are connected to each other and arranged in a metal plate 100mm × 100mm × 10mm, and when the heat is transferred from the MCM attached to the metal plate while the refrigerant flows horizontally along the pipe, boiling occurs. The movement takes place. However, in this case, not only boiling is easy to occur, but also pumping action by boiling is difficult to expect.

On the other hand, conventionally, a method of pinning the heat generated when condensing the vapor evaporated from the cooling plate to the condenser by means of natural or forced convection of air is proposed, but all the vapor evaporated per hour in the cooling plate To condense, there is a problem that a condenser needs 10 to 20 times larger than the size of the cold plate.

In order to overcome the above problems, in the 95-55865 filed by the applicant of the present application, the evaporative cooler and the condenser have a closed heat siphon structure, and by installing a baffle in the space in the evaporative cooler to control the space between the refrigerant flow path and condenser In the present invention, there is disclosed a structure in which the refrigerant vapor is condensed in a horizontal flow passage in which a coolant flows and in a horizontal flow passage adjacent to a metal so as to generate forced convection by the pumping by boiling due to the thermosiphon effect.

However, in such a structure, the heat transfer area of the evaporative cooler is small, so that the temperature difference of the multi-chip module cannot be reduced, and the fluctuation of the vertical pressure of the evaporative cooler is large, and the refrigerant vapor flow path is formed horizontally in the condenser. As a result, there is no space in which the refrigerant vapor can stay, so that the pressure is increased, thereby adversely affecting the system.

Accordingly, the present invention has been made to solve the above problems, by forming a fin and a flow path on the upper surface of the cooling plate to increase the boiling heat transfer area with the cooling plate to reduce the vertical temperature difference of the multi-chip module, Power consumption is increased due to high integration and high speed, so the surface temperature of MCM, which is expected to generate heat per unit area, that is, heat flow rate of 2.5W / ㎠, is kept below 55 ℃, and can be reliably cooled without fluctuation of pressure and temperature of system. It is an object of the present invention to provide a cooling device and a cooling method for a multichip module.

In addition, the present invention provides a cooling apparatus and a cooling method of a multi-chip module to stably change the temperature and pressure of the system by mitigating the pressure and temperature flow of the system due to the cooling plate boiling by forming a refrigerant vapor storage chamber in the condenser. Has a different purpose.

In addition, the present invention compensates for the disadvantages of the conventionally proposed heat-siphon cooling module to reduce the temperature difference on the surface of the MCM by the absorption of heat using boiling heat transfer and forced convective heat transfer in the cooling plate flow path, and evaporated per hour in the cooling plate flow path. Another object of the present invention is to provide a cooling device and a cooling method of a multichip module designed to miniaturize a condenser capable of condensing refrigerant vapor.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a table showing possible cooling schemes in relation to heat generation rate and heat flux per unit area of a chip module in a communication system.

Figure 2 is a schematic diagram showing an embodiment configuration of a multi-chip module cooling apparatus according to the present invention.

3A to 3C are a plan view, a side view, and a front view showing a detailed configuration of a cooler which is a main part of the present invention.

4A to 4C are a plan view, a side view, and a front view showing a detailed configuration of a condenser which is the main part of the present invention.

5A and 5B are graphs showing thermal characteristics when controlling a heat flux of 1 W / cm 2 using the cooling apparatus of the present invention.

6A and 6B are graphs showing thermal characteristics when controlling a heat flux of 2.5 W / cm 2 using the cooling apparatus of the present invention.

7a and 7b are graphs showing the thermal characteristics according to the various heat flux of the cooling module according to the present invention and the amount of refrigerant injected into the cooling module.

FIG. 8 shows data experimenting with refrigerant R-11 and HCFC-123 which are alternative refrigerants of R-11 at various heat fluxes. FIG.

* Explanation of symbols for main parts of the drawings

1: condensation refrigerant channel 2: refrigerant steam channel

3: multichip module 11: cooler

12: pin 13: refrigerant path

14, 24: fixing screw 16: cooling plate cover

21: condenser 22: storage compartment

23: coolant flow path 25: condenser cover

In order to achieve the above object, the present invention, a refrigerant flow path of the refrigerant circulation path formed of a natural circulation loop structure; Cooling means mounted on the circulation path of the refrigerant flow pipe, the cooling means for absorbing the heat discharged from the multi-chip module by forming a plurality of fins formed at a predetermined interval to form a refrigerant flow path and increase the heat transfer area; And a condenser means formed on one surface of the tube to temporarily hold the refrigerant vapor of the tube, and a condensing means having a coolant flow path groove under the condensation surface to cool and condense the vapor staying inside the storage compartment. It provides a cooling device for a multichip module.

In addition, the present invention provides a cooling method applied to a cooling apparatus of a multi-chip module having the above configuration, comprising: a first step of introducing a refrigerant into a cooling means through a condensation refrigerant passage of the refrigerant passage tube; A second step of allowing the refrigerant to flow in a flow path between the plurality of fins provided in the cooling means, and absorbing heat flux generated from the surface of the multichip module through boiling of the refrigerant and the surface of the fin; A third step of forced convection of the refrigerant vapor evaporated from the cooling means by pumping by boiling of the refrigerant and discharging the refrigerant vapor to the refrigerant vapor flow path by a thermal siphon effect: staying in the storage compartment of the condensation means A fourth step to ensure that; And a fifth step of condensing the refrigerant vapor staying in the storage compartment of the condensation means with the cooling water flowing through the cooling water channel located under the condensation surface, and the condensed refrigerant is discharged to the condensation refrigerant channel side by gravity. It provides a cooling method.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings of FIG. 2.

The cooling device and the cooling method of the multi-chip module according to the present invention are implemented to reduce the vertical temperature difference of the multi-needle module and to prevent the pressure rise in the condenser, as shown in FIG. The refrigerant flowing through the cooler 11 absorbs the heat flux generated by the multi-chip module 3, and the absorbed refrigerant vapor is forced to convection in the cooler 11 by the pumping action of the refrigerant. It flows into the condenser 21 through the flow path pipe 2. The condenser 21 condenses the refrigerant vapor and flows back into the condensation refrigerant channel 1. It has a natural circulation loop structure that cools the multichip module while the refrigerant naturally circulates in a closed heat siphon effect method.

Here, the cooler 11 mounted on the circulation path of the refrigerant flow paths 1 and 2 is equipped with a multi chip module 3 on one surface thereof, as shown in FIG. The outlet 11a and the condensation refrigerant inlet 11b are formed. Here, up to two multichip modules 3 may be attached to the cooler 11. In addition, a fin 12 is provided inside the cooler 11 to protrude at predetermined intervals so as to increase the transfer area of the heat flux generated from the multichip module 3. A refrigerant passage 13 is formed in the interspace to maximize the pumping action of the refrigerant by boiling the refrigerant.

Here, the fin 12 has a heat transfer area of at least two times because the heat is transferred to the end of the fin 12 by heat conduction, and the heat transferred to the surface of the fin 12 causes boiling of the refrigerant. Since it is large enough to cause more active boiling in the refrigerant passage, it is possible to increase the pumping effect by boiling of the refrigerant, and to increase the absorption of heat by forced convective heat transfer. Accordingly, since the fin 12 increases the heat transfer area and maximizes forced convection by the pumping action of the bubbles, it is possible to absorb heat by boiling and forced convection, so that the multi-chip module 3 attached to the cooler 11 is provided. The temperature difference between the upper and lower sides can be reduced within a predetermined range. A lid 16 is attached to the upper surface of the cooler 11 by a fixing screw 14.

On the other hand, as shown in Figure 4, the condenser 21 to take the latent heat of the refrigerant vapor evaporated in the flow path of the multi-chip module 3 to condense the refrigerant vapor of the refrigerant flow pipes (1, 2) for a while A storage chamber 22 is formed on one surface to stay therein, and both sides of the condenser 21 are respectively connected to the condensation refrigerant flow channel 1 and the refrigerant vapor flow channel 2 so as to communicate with the storage chamber 22. A refrigerant vapor hole 21a and a condensation refrigerant hole 21b are formed. Here, the bottom surface of the storage chamber 22 is the condensation surface 22a.

In addition, in order to cool the vapor temporarily staying inside the storage chamber 22, a cooling water flow path 23 is formed at a predetermined interval in the lower portion thereof so that the cooling water flow path 23 passes through the condenser 21, and Both surfaces of the cooling water flow path 23 have a structure in which a U-shaped pipe (not shown) is connected. In this embodiment, the heat insulating member 26 is provided on the bottom surface of the condenser 21 so as to be used for condensing the refrigerant vapor without heat loss of the cooling water flow path 23.

The lid 25 is fixed to the upper surface of the condenser 21 by a fixing screw 24.

Here, the condenser 21 is formed of an aluminum block, the space of the storage chamber is formed of a rectangular parallelepiped, even if the pressure in the cooling module is given a heat flux of the multi-chip module is below the specified temperature, that is, the operating temperature of the multi-chip 85 ℃ It can be kept lower than 55 ℃. In addition, since the cooling water flow path 23 and the condensation surface 22a are concentrated in the aluminum block, heat resistance due to heat conduction can be minimized.

Referring to the cooling method of the present invention configured as described above are as follows.

As the refrigerant flows into the cooler 11 through the condensation refrigerant flow path 1 of the coolant flow channel, the coolant flows into the flow path 13 between the plurality of fins 12 provided in the cooler 11, At this time, the heat flux generated on the surface of the multichip module 3 is absorbed through the boiling of the refrigerant and the surface area of the fin 12.

Then, the refrigerant vapor evaporated in the cooler 11 is forced convection by pumping by boiling of the refrigerant and discharged to the refrigerant vapor flow path side by a thermal siphon effect.

Therefore, the fins 12 forming the refrigerant passage 13 of the cooler 11 effectively dissipate heat emitted from the multi-chip module MCM and increase the area where boiling occurs, thereby eliminating boiling hysteresis. By maximizing the heat-siphon effect by creating a small refrigerant passage 13, the temperature difference between the upper and lower MCMs can be minimized.

Meanwhile, the refrigerant vapor flowing through the refrigerant vapor passage 2 stays in the storage chamber 22 through the refrigerant vapor hole 21a of the condenser, and the refrigerant vapor staying in the storage chamber 22 of the condenser 21 is cooled water. The heat is transferred to the condensation surface 22a by the cooling water flowing in the flow path 23 to condense. Accordingly, the condensed refrigerant is discharged toward the condensation refrigerant flow path 1 through the condensation refrigerant hole 21b of the condenser 21. Will be. At this time, the cooling water is insulated by the heat insulating member 26 attached to the bottom surface of the condenser 21 so that the cooling water is used to condense the refrigerant vapor without heat loss.

As described above, in the present invention, when the refrigerant boils in the refrigerant passage 13 having the fin 12 and becomes steam, the condenser is connected along the refrigerant passage pipe connecting the cooler 11 and the condenser 21 by the density difference. Ascending to 21, the condenser 21 takes an ideal flow natural circulation system in which the refrigerant in the gaseous phase is condensed back into the liquid phase and the refrigerant flows to the cooler 11 by gravity.

In addition, the condenser 21 can increase the condensation heat transfer area by making the bottom surface of the storage chamber 22 a condensation surface, and can prevent excessive pressure rise because the condenser 21 has an effect of suppressing a pressure increase due to a temporary excessive increase. This will reduce the fluctuations in pressure and temperature.

According to the present invention, when the refrigerant is Freon 11 (hereinafter referred to as "R-11"), a heat flux of 2.0 W / m 2 can be stably controlled at a temperature of 44 ° C. and a pressure of 1.22 bar. When the amount is increased by about 10%, the temperature of the heat flux cooler 11 of 2.5 W / cm 2 can be stably controlled while maintaining the temperature at 55 ° C. In addition, when heat flux is applied to the MCM, the time to reach a steady state can be minimized.

FIG. 5 shows a thermal characteristic graph of the cooling module of the present invention when a refrigerant having R-11 is supplied with a heat flux of 1.0 W / cm 2. In (a), it can be seen that the time between the condenser 21 and the cooler 11 reaches an equilibrium state is about 10 minutes, and the pressure of the cooling module reaches an equilibrium state within a short time of about 15 minutes. In addition, it can be seen that both types of temperature and pressure changes to steady state without fluctuation. In (b), when the temperature of each point of the cooler 11 is viewed, the temperature difference of the cooler 11 is about 9 ° C. In the case of the channel 13 without the fin 12, the upper and lower temperature difference of the cooler 11 is 12 ° C. In view of this, it can be seen that the temperature difference between the upper and lower coolers 11 when the fin 12 is present decreases considerably.

Figure 3 shows a thermal characteristic graph of the cooling module of the present invention when the refrigerant is R-11, when supplying a heat flux of 2.0W / ㎠. In (a), the temperature of the cooler 11 and the condenser 21 reaches the equilibrium state within 10 minutes, and the pressure also reaches the equilibrium state in 20 minutes. In addition, both types of temperature and pressure changes are stable, and even in (b), the temperature of the cooler 11 is stable, and the temperature difference between the cooler 11 and the top and bottom of the cooler 11 is considerably smaller than that of 15 ° C. without the fin 12, which is 7 ° C. have.

FIG. 7 shows a thermal characteristic graph of the cooling module of the present invention when a refrigerant having R-11 is supplied with a heat flux of 2.5 W / cm 2. In (a), the temperature of the condenser 21 and the cooler 11 and the pressure of the cooling module are shown. The temperature of the condenser 21 and the cooler 11 was in a stable equilibrium within 10 minutes and the pressure reached the equilibrium after about 30 minutes. (b) shows the temperature distribution from the top to the bottom of the cooler 11, the temperature difference is about 7 ℃. It can also be seen that the type of temperature at each point of the condenser 21 is also very stable. As can be seen in Figures 2 to 4 it can be seen that the cooling module of the present invention can control the heat flux below the regulation without any change even in the change of the heat flux of the MCM.

FIG. 8 shows data of experiments of refrigerants R-11 and HCFC-123, which are alternatives to R-11, at various heat fluxes. The amount of the refrigerant was indicated by setting a state in which the cooling plate having a volume of 338 cm 3 was filled with the refrigerant at 100%. As can be seen from the figure, it can be seen that the amount of refrigerant to be inserted has a great influence on the performance of the cooling module when the heat flux is changed. In the case of R-11, even when the same heat flux of 2.5W / cm 2 is supplied to the cooler 11, when 120% of the refrigerant is injected, the temperature of the cooler 11 can be controlled to be 52 ° C. or lower, and the pressure is independent of the temperature. It appears to be proportional to the amount of. As with R-11, the same result was obtained with HCFC-123. Therefore, it can be seen that the cooling module of the present invention requires a little more amount of refrigerant to safely cool a large heat flux such as 2.5 W / cm 2.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and alterations are possible within the scope without departing from the technical spirit of the present invention. It is obvious to those who have knowledge of the world.

As described above, according to the present invention, the fins in the cooling plate flow path effectively dissipates heat from the MCM and increases the area where boiling occurs, thereby eliminating boiling hysteresis, and also creates a micro flow path to use the heat-siphon effect. Heat absorption by convection can be maximized to minimize the temperature difference generated above and below the MCM in contact with the cold plate. In addition, the condensation heat transfer area is increased by using the condenser condenser as a flat plate, and the effect of increasing the space where the refrigerant vapor stays can be prevented, so that excessive pressure rise of the refrigerant vapor can be prevented. Can be reduced.

In addition, it is possible to control the stability of the pressure and temperature changes of the system by the above effects, and also to maintain the temperature and pressure of the system properly by optimizing the size of the condenser in the closed heat-siphon cooling module. In addition, when the heat flux is applied to the MCM, it is effective to minimize the time to reach a steady state.

Claims (4)

A refrigerant flow passage in which a circulation path of the refrigerant is formed in a natural circulation loop structure; Cooling means mounted on the circulation path of the refrigerant flow pipe, the cooling means for absorbing the heat discharged from the multi-chip module by forming a plurality of fins formed at a predetermined interval to form a refrigerant flow path and increase the heat transfer area; And A condenser means having a storage compartment groove formed on one surface to temporarily hold the refrigerant vapor of the tube, and a condensing means having a cooling water flow path groove below the condensation surface for cooling and condensing the vapor staying inside the storage compartment. Cooling device of a multi-chip module comprising a. The method of claim 1, Cooling apparatus of a multi-chip module, characterized in that the storage chamber of the condensation means is formed of a rectangular parallelepiped channel. The method according to claim 1 or 2, And a plate-shaped flow path through which the coolant flow path and the coolant flow are integrated in one metal block to minimize heat resistance between the coolant and the refrigerant increase period. A first step of introducing the refrigerant into the cooling means through the condensation refrigerant passage of the refrigerant passage tube; A second step of allowing the refrigerant to flow in a flow path between the plurality of fins provided in the cooling means, and absorbing heat flux generated from the surface of the multichip module through boiling of the refrigerant and the surface of the fin; A third step of forced convection of the refrigerant vapor evaporated by the cooling means by pumping by boiling of the refrigerant and discharging the refrigerant vapor to the refrigerant vapor flow path by a thermal siphon effect: A fourth step of allowing the refrigerant vapor flowing through the refrigerant vapor passage to remain in the storage chamber of the condensation means; And A fifth step of condensing the refrigerant vapor staying in the storage chamber of the condensation means with the cooling water flowing through the cooling water channel located at the lower portion of the condensation surface, and the condensed refrigerant is discharged to the condensation refrigerant channel side by gravity; Cooling method of a multi-chip module comprising a.