CN1851908A - Power semi-conductor device evaporation cooling apparatus - Google Patents

Abstract

An evaporative cooling device for power semiconductor devices. Hollow pipes are arranged in the evaporative cooling radiator [1]. The upper and lower ends of the radiator are provided with liquid inlet pipes [15] and steam outlet pipes [9]. The pipes are filled with evaporative cooling medium [10]. The high-power semiconductor device [2] is installed on the surface of the outer plate of the evaporative cooling radiator [1]. The heat generated by the power semiconductor device [2] is transferred to the evaporative cooling radiator [1] in contact with the device. Mechanism, the evaporative cooling medium [10] absorbs heat, and evaporates at the boiling point to produce a phase change. Due to the flow pressure head generated by the density and pressure difference under the action of gravity acceleration, it overcomes the resistance pressure drop to form a certain flow cycle, so that the cooling medium evaporates at the boiling point It rises to the upper part of the condenser [3] in a vapor state, and exchanges heat with the cooling circulating water in it to condense into a liquid, and then flows back to the evaporative cooling radiator [1]. The invention has small volume and high cooling efficiency.

Description

An evaporative cooling device for power semiconductor devices

technical field

The invention relates to a cooling device for power semiconductor devices, in particular to an evaporation cooling device for power semiconductor devices.

Background technique

With the increasingly widespread application of high-voltage AC transmission technology and AC frequency conversion speed regulation technology, the compactness and reliability of power electronic devices have attracted more and more attention from the majority of electric power technicians. Among the various factors that affect the reliability of power electronic devices, heat dissipation is a crucial one. The heat generated by high-power semiconductor devices (also known as power electronic devices) will increase the temperature of the chip. If there are no proper heat dissipation measures, the temperature of the chip may exceed the maximum allowable junction temperature, which will cause device performance. deterioration to damage. Therefore, in the circuit design, choosing an appropriate heat dissipation method and carrying out a reasonable design is one of the indispensable important links to make the potential of the device fully utilized and improve the reliability of the circuit.

Modern power electronic devices are generally air-cooled or water-cooled. It should be said that from the perspective of heat dissipation, water cooling is ideal. However, the water circulation system has high technological requirements, complicated installation, heavy maintenance workload, and once water leaks, it will bring safety hazards. Therefore, if you can use air cooling to solve the problem, don't use water cooling. The use of water cooling must solve the two major problems of the purity of the cooling water and the reliability and corrosion of the system during long-term operation. In short, the development and selection of new high-efficiency heat dissipation technology to cool power electronic devices is an important measure to ensure the reliability of the device and reduce the size of the device.

Chinese patent 200320129492.1 discloses an evaporative cooling device for high-power power electronic devices, including an evaporative cooling box 8 and a condenser 9, the condenser 9 is placed above the evaporative cooling box 8, and the condenser 9 has a condenser tube 3 and a water inlet 1 and water outlet 2; the evaporative cooling box 8 is connected to the condenser 9 as a whole or separated from the condenser 9, and the two are connected through the connecting pipe 7; the wall surface in contact with the device in the evaporative cooling box 8 is a plane, and the inside is filled with The liquid 5 and the power module 4 are fixed on the surface of the outer plate of the evaporative cooling box 8 . This evaporative cooling box adopts a volumetric structure, with a large internal volume and a large amount of liquid. The joints on the wall of the box are welded, and there is a steam outlet on the upper part to conduct heat transfer with the device. After several prototype tests, it was found that its structure has the following disadvantages, such as: large volume, many welding surfaces and sealing surfaces, which makes processing, installation and maintenance inconvenient; the cost of cooling medium is high and specific, and the amount of filling liquid is large, and the cost is also low. High, heavy, and the design margin is too large.

Contents of the invention

In order to overcome the shortcomings of the prior art, the present invention optimizes the design of the prior art and provides an improved non-immersion evaporative cooling device. The invention has simpler processing, good sealing performance, small volume and can reduce cost. Can work under certain special conditions.

The invention consists of an evaporative cooling radiator and a condenser for installing devices. The condenser is placed above the evaporative cooling radiator and communicated with a connecting pipe. It is fixed on the wall of the evaporative cooling radiator. There is a condensing pipe in the condenser. There are water inlets and outlets on the outside of the condenser to facilitate the connection of user water pipes. The secondary cooling water is passed through the condensing pipe. The evaporative cooling radiator is filled with an evaporative cooling medium, and the cooling medium adopts an evaporative cooling medium with a moderate boiling point and meets environmental protection requirements.

The power semiconductor device, that is, the base of the power electronic device for dissipating heat, is installed on the surface of the outer plate of the evaporative cooling radiator. The evaporative cooling radiator is filled with a cooling medium, and the heat generated by the power semiconductor device is transmitted to the contact with the device through the heating surface of the device. The evaporative cooling radiator, according to the boiling heat transfer mechanism, the cooling medium in the evaporative cooling radiator absorbs heat, and evaporates at the boiling point to produce a phase change. Due to the flow pressure head generated by the density pressure difference under the action of gravity acceleration, it overcomes the resistance pressure drop to form The circulation of a certain flow makes the cooling medium evaporate into a vapor state at the boiling point and rise to the upper part of the condenser, and exchange heat with the cooling circulating water in it to condense into a liquid, and then flow back to the evaporative cooling radiator. Such an evaporative cooling method can effectively cool high-power power electronic devices due to the large heat absorption of the phase change. The structure of the power device is easy to assemble and install, and the chip of the power device can also be directly packaged with the evaporative cooling radiator. The radiator is made of conductive metal material, and at the same time it is used as the electrode lead. The structure of the entire electrical system is simple and flexible. The power devices of the box structure are concentrated on the four walls of the box, which is inconvenient for device installation and electrical connection.

The evaporative cooling radiator of the present invention has a pipeline structure, and the interior of the radiator is a hollow pipeline, which can be a threaded tube, a micro-rib tube, a shrink tube, or a porous surface tube, and is made of profile or casting to reduce the welding surface. The upper and lower ends of the radiator are provided with a liquid inlet and a steam outlet. The cooling medium flows in the pipe and conducts heat transfer with the device. Due to the adoption of the pipeline structure, the present invention has smaller structure volume, less filling liquid volume and less structural sealing surface than the structure of Chinese patent 200320129492.1.

The invention is based on the principle of fluid boiling heat exchange in tubes. Flow boiling refers to the boiling phenomenon that occurs when the liquid flows through the heating surface at a certain flow rate under the action of pressure difference. The volumetric structure of the evaporative cooling box in the prior art adopts the principle of large-volume boiling heat transfer. The so-called large-volume saturated boiling refers to the boiling phenomenon that occurs when the heating surface is immersed in a liquid without forced convection. Because the bubble growth at the heating surface is affected by the additional effect of the fluid flow direction, the local gasification process changes, such as changing the initial boiling conditions, reducing the bubble escape diameter, increasing the bubble escape frequency, and affecting the bubble polymerization process. Therefore, the mechanism of boiling in tubes is more complicated than that of large volume boiling. There are many factors that affect the boiling in the tube, the first is the influence of the flow velocity of the liquid in the tube, according to the convective heat release equation of forced flow

$\mathrm{<span\; class="notranslate">\; N</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.021</span>}{\mathrm{<span\; class="notranslate">\; Re</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 0.8</span>}}<span\; class="notranslate">\; .</span>\mathrm{<span\; class="notranslate">\; P</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}^{\mathrm{<span\; class="notranslate">\; 0.43</span>}}<span\; class="notranslate">\; .</span>{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; PR</span>}}_{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; /</span>{\mathrm{<span\; class="notranslate">\; PR</span>}}_{\mathrm{<span\; class="notranslate">\; w</span>}}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 0.25</span>}}$

When the heat load is very low, that is, the boiling is very weak, the heat release coefficient α is basically consistent with the convective heat release when there is no boiling. Only when the flow velocity w is very small, the enhancement effect of boiling on heat release is shown. When q increases continuously, the value of α also increases continuously, and the influence of flow velocity gradually weakens; only when the flow velocity is very high, does it show an effect on α has an effect.

The arrival of the critical state when boiling in the tube depends to a large extent on the conditions under which the formed bubbles break away from the heating surface. Therefore, when the flow velocity increases, the bubbles are easily washed away from the heating surface by the liquid flow, making the critical point come later, thereby increasing the value of q _KP (critical heat load).

The amount of steam content in the tube also has a great influence on the heat release of boiling. The above-mentioned relational expression about the heat release coefficient of liquid flowing and boiling in the tube refers to the situation that the steam content in the liquid is not large when boiling. When the steam content in the unit volume is very large When the value of α is large, α increases rapidly. This is because the steam that accounts for most of the volume flows in the center of the tube, while the liquid is squeezed to the wall to form a thin film. This thin film is flowing at a high speed, thus forming a favorable environment for heat dissipation. Conditions to improve the heat transfer efficiency of the liquid.

When boiling in large volume, natural convection caused by temperature difference, flow boiling is a boiling phenomenon that flows through the heating surface at a certain flow rate and in the same direction as the bubbles, which has a strengthening effect on the heat transfer of nucleate boiling, and the smaller the pipe diameter, the strengthening effect The more obvious, h natural convection < h flow convection.

Due to the use of the pipe structure, the forced convection heat transfer coefficient can be improved by changing the surface shape of the flow channel. The pipe can adopt various forms of inner finned pipes, inner spiral pipes, zoom pipes, horizontal grained pipes, etc., such as vertical ascending thread The heat transfer coefficient of the tube is 1.6-2 times that of the light tube. Or use the internal micro-finned tube, the heat transfer coefficient of the micro-finned tube is 1.2-1.5 times that of the light tube. Changing the shape of the flow channel can enhance the boiling, because The fluid particle velocity changes or the violent vortex generated continuously scours the flow boundary layer, so that the flow boundary layer and heat transfer boundary layer are correspondingly thinned, thereby improving the heat transfer efficiency. The porous surface tube is also a heat transfer formed by covering a porous layer on a smooth surface, which can also significantly enhance the boiling heat transfer. According to different processing techniques, it is divided into four types: sintering type, machining type, spraying type and electrochemical corrosion type. Its heat transfer coefficient can reach about 5 times that of a smooth surface. The reason why the porous surface can achieve a better enhanced heat transfer effect is that it has a large number of gasification cores and a higher frequency of bubble detachment, the two-phase flow rate increases, and the heat transfer coefficient increases. At the same time, its structural characteristics make the porous layer A stable gas-liquid two-phase flow and heat and mass transfer cycle can be established.

The box structure of Chinese patent 200320129492.1 belongs to natural convection heat transfer. The present invention adopts a pipeline structure and various measures to enhance heat transfer to improve convective heat transfer efficiency. Therefore, from the principle analysis, the heat transfer effect of the present invention is better. The internal pipe structure of the evaporative cooling radiator can be determined according to the heat load capacity, medium flow rate and other parameters and the interactive calculation of the critical heat flux density.

Because the failure rate of power devices increases exponentially with the increase of junction temperature, it is necessary to ensure that the internal junction temperature of the device is always kept within the allowable junction temperature when the device is running. In order to reduce the junction temperature of the device, it is necessary to design a heat flow path with the lowest possible thermal resistance so that the heat of the device can be dissipated as soon as possible through it. According to the basic principle of heat transfer, it is necessary to improve the convective heat transfer coefficient and reduce the surface contact thermal resistance . It can be known from the above that the heat transfer coefficient of the pipeline structure of the present invention is higher than that of the box structure of Chinese patent 200320129492.1. In order to reduce the surface contact thermal resistance, that is to say, the wall thickness of the heat sink in contact with the heating surface of the component can be reduced. Metals with good thermal conductivity (such as copper) can be used, and silicone grease with good thermal conductivity can be added between the contact surfaces to reduce the heat dissipation. The gap between the contact surfaces, these measures can reduce the thermal resistance.

The invention has high cooling efficiency, relatively simple structure, and convenient device installation and maintenance. At the same time, because the cooling medium itself has insulation, the reliability of the device is improved. The future failure and the investment in water treatment equipment are economical.

Description of drawings

Figure 1a is one of the embodiments of the present invention: a schematic diagram of the split structure of an air condenser type evaporative cooling radiator, and Figure 1b is an internal side view of the radiator;

Figure 2a is the second embodiment of the present invention: a schematic diagram of the parallel structure of multiple evaporative cooling radiators of the water condenser type, and Figure 2b is a side view internal cross-sectional view of the radiator;

Fig. 3a is a schematic diagram of the third embodiment of the present invention: an integrated structure of an external air-cooled evaporative cooling radiator, and Fig. 3b is a front view internal cross-sectional view of the radiator.

In the figure: 1 evaporative cooling radiator, 2 power semiconductor devices, 3 water condenser or air cooler, 4 cooling water or air inlet, 5 cooling water or air outlet, 6 liquid collection pipe, 7 liquid return pipe, 8 pressure equalization Pipe, 9 steam outlet pipe, 10 evaporative cooling medium, 11 fixing bolt, 12 electrical connector, 13 heat sink, 14 radiator shell, 15 liquid inlet pipe.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

One embodiment of the present invention is shown in Fig. 1a, an air condenser type evaporative cooling radiator split structure. The condenser is an air cooler 3, the evaporative cooling radiator 1 and the air cooler 3 are separated, the air cooler 3 is placed above the evaporative cooling radiator 1, and the two are connected through the steam outlet pipe 9, and the fan is blown in from the inlet 4 Cold wind blows out from outlet 5. External dimensions of the evaporative cooling radiator 1: width×thickness×height are 100mm×30mm×630mm. As shown in Figure 1b, the evaporative cooling radiator 1 is 100 mm wide x 30 mm thick x 590 high, and the inside is a square pipe with a width of 90 mm x 15 mm thick x 590 high. Frequency, strengthen the heat transfer effect. The interior of the radiator 1 is filled with an evaporative cooling medium 10 . The surface of the outer plate of the evaporative cooling radiator 1 is processed into a smooth plane, and a power semiconductor device 2 is mounted thereon. The heat of the power semiconductor device 2 is transferred to the evaporative cooling medium 10 inside through the outer plate of the evaporative cooling radiator 1, and the cooling medium 10 evaporates at the boiling point, resulting in phase change and endothermic heat, due to the flow generated by the density pressure difference under the action of gravitational acceleration The pressure head overcomes the resistance pressure drop to form a certain flow cycle, so that the cooling medium 10 evaporates at the boiling point into a vapor state and rises to the upper part of the air cooler 3, and exchanges heat with the cold air inside, condenses into a liquid, and then flows back to evaporate cooling radiator 1. The placement of the air cooler or water condenser in this way is more flexible, the structure is simple, and the maintenance is convenient. Multiple power devices are installed on the same surface. Since copper and other conductive materials are used as heat sinks, it is no longer necessary to lead out electrical connecting wires on the device plate. The heat sink can also be used as lead wires of the electrode plate and connected to the external power line through the electrical connector 12. . Figure 1b is a cross-sectional view of the internal structure.

Experiments show that: in this embodiment, when the working current is 2520A and the pressure is 0.008MPa, the average wall temperature of the power semiconductor device 2 is 63°C, and the shell temperature is 76°C; The temperature is 64°C, and the case temperature can be controlled within 78°C; when the working current is 2520A, the pressure is 0.0225MPa, the voltage is 3.79v, and the power is 3528w, the average wall temperature of power semiconductor device 2 is 65°C, and the case temperature can be controlled within 78°C ; As the vapor pressure of the cooling medium in the evaporative cooling radiator 1 increases, the shell temperature will increase slightly, this is because the boiling point of the cooling medium 10 increases with the pressure, causing the wall temperature to rise, if it is negative pressure, the wall temperature will decrease, and the shell temperature will decrease accordingly.

Using non-immersion evaporative cooling to cool high-power devices can achieve ideal cooling effects. Moreover, one heat sink can cool multiple power devices, and the structure is simple and the cooling efficiency is high.

In another embodiment of the present invention, multiple evaporative cooling radiators are connected in parallel and separated from the water condenser as shown in Figure 2a. Six evaporative cooling radiators 1 communicate with each other through the steam outlet pipe 15 and the pressure equalizing pipe 8. The water condenser 3 communicates, and the condenser is equipped with a condensation pipe. The power semiconductor device 2 is sandwiched between the outer plate surfaces of the evaporative cooling radiator 1 and fixed with fixing bolts 11 . In order to improve the thermal conductivity, the evaporative cooling radiator 1 is a hollow shell, and the outer surface is processed smooth and flat. The internal structure of the radiator 1 is shown in Figure 2b. In the interior of the radiator 1, 9 inner spiral circular tubes with a diameter of 10 mm are uniformly arranged side by side in the width direction as the center. Liquid inlet pipe 15 and steam outlet pipe 9. Apply thermal grease between the power semiconductor device 2 and the contact wall to reduce thermal resistance, the hollow shell in the evaporative cooling radiator 1 is filled with evaporative cooling medium 10, and the water condenser 3 includes a water inlet 4, a water outlet 5, six The upper part of the evaporative cooling radiator 1 communicates with the pressure equalizing pipe 8 through the end steam outlet pipe 9, the lower part communicates with the liquid collecting pipe 6 through the end liquid inlet pipe 15, and the liquid collecting pipe 6 communicates with the top condenser 3 through the liquid return pipe 7 . The heat generated by the power semiconductor device 2 is transmitted to the cooling medium 10 through the outer plate of the evaporative cooling radiator 1 through the outer plate of the evaporative cooling radiator 1. The cooling medium 10 in the evaporative cooling radiator 1 absorbs heat and evaporates at the boiling point to produce a phase change. The flow pressure head generated under the action of gravity acceleration overcomes the resistance pressure drop to form a certain flow cycle, so that the cooling medium evaporates into a vapor state at the boiling point and rises to the upper part of the condenser 3, and performs heat exchange and condensation with the cooling circulating water in it. After becoming liquid, it flows back to the evaporative cooling radiator 1 through the condenser 3, the liquid return pipe 7, the liquid collecting pipe 6 and the liquid inlet pipe 15. Due to the use of internal pipes, the nucleate boiling is strengthened and the heat exchange efficiency is improved.

Embodiment 3 of the present invention: The integrated structure of the external air-cooled evaporative cooling radiator is shown in Figure 3a. The horizontally arranged evaporative cooling radiator 1 is integrated with the vertically arranged air cooling fins 13 . The air cooling fins 13 are provided with circulation passages for the cooling medium 10, and these passages communicate with the pipes of the horizontal evaporative cooling radiator 1, the internal structure of which is shown in Figure 3b. Evaporative cooling radiator 1 bottom plate width × thickness × length is 100mm × 30mm × 200mm, the inner width × thickness × height is a hollow cuboid of 80mm × 24mm × 180mm, and the upper part is a hollow cylindrical heat sink to increase the heat exchange area and improve The cooling effect is similar to that of heat pipe fins. The radiator 1 is filled with an evaporative cooling medium 10 . The power semiconductor device 2 is installed on the surface of the outer plate of the evaporative cooling radiator 1, the heat of the power semiconductor device 2 is transmitted to the cooling medium 10 in the radiator 1 through the outer plate of the evaporative cooling radiator 1, and the cooling medium 10 evaporates at the boiling point, generating a phase It becomes endothermic, because the density pressure difference generates a flow pressure head under the action of gravity acceleration, and overcomes the resistance pressure drop to form a certain flow cycle, so that the cooling medium 10 evaporates into a vapor state at the boiling point and rises to the air cooling fin 13, and dissipates heat through the air The sheet 13 exchanges heat with the external cold air, and after being condensed into a liquid, it flows down through the inner surface of the air cooling sheet 13 and returns to the evaporative cooling radiator 1 . The air radiator in this way is small in size and can be used in special environments where water is scarce. Multiple power devices are installed on the same surface. Since conductive materials such as copper are used as heat sinks, it is not necessary to lead out electrical connecting wires on the device plate. The heat sink can also be used as lead wires of the electrode plate and connected to the external power line through the connector 12. Simple structure, convenient installation and maintenance. As shown in Figure 3b.

The advantage of these three structures is that the power semiconductor device 2 is fixed on the outer surface of the evaporative cooling radiator 1 by fixing bolts and thermally conductive glue (grease), which is convenient for installation and maintenance, and does not need to open the evaporative cooling radiator when replacing the device. Due to the low boiling point of the cooling medium 10, the maximum temperature of the power semiconductor device 2 is controlled within the allowable range of the junction temperature of the device.

Claims (7)

1. An evaporative cooling device for power semiconductor devices, including an evaporative cooling radiator [1] and a condenser [3], the condenser [3] is placed above the evaporative cooling radiator [1], and the condenser [3] has Condenser pipe, cooling water or cold air inlet [4] and cooling water or hot air outlet [5]; it is characterized in that the evaporative cooling radiator [1] is equipped with a pipe made of profile or casting inside the radiator, and the pipe can be a threaded pipe , micro-finned tube, shrink tube, or porous surface tube, its shape is rectangular, circular or polygonal, the upper and lower ends of the radiator [1] are provided with a liquid inlet pipe [15] and a steam outlet pipe [9], and the pipe is filled with into the evaporative cooling medium [10]; in the evaporative cooling radiator [1], the surface of the outer plate in contact with the device is a smooth plane, and the power semiconductor device [2] is fixed on the surface of the outer plate; when the high-power semiconductor device [2] works The heat is transmitted to the evaporative cooling radiator [1] in contact with the device through the heating surface of the device, and the evaporative cooling medium [10] in the pipeline of the evaporative cooling radiator [1] evaporates at the boiling point to produce a phase change. The flow pressure head generated under the action overcomes the resistance pressure drop to form a certain flow cycle, so that the cooling medium evaporates into a vapor state at the boiling point and rises to the upper part of the condenser [3], and exchanges heat with the cooling circulating water or cold air in it. After condensing into a liquid, it flows back into the evaporative cooling radiator [1]. 2. The evaporative cooling device for power semiconductor devices according to claim 1, characterized in that the condenser [3] is an air cooling tube type [3] or an air cooling fin type [13]; the evaporative cooling radiator [1] and When the air cooling tubular cooler [3] is separated, the two are connected through the steam outlet pipe [9]; when the air cooling fin [13] is used as a condenser, the evaporative cooling radiator [1] is arranged horizontally, which is different from the vertical arrangement The air cooling fins [13] are connected as a whole, and the air cooling fins [13] are provided with the circulation channel of the cooling medium [10], and the circulation channel communicates with the pipeline of the horizontal evaporative cooling radiator [1]. 3. The evaporative cooling device for power semiconductor devices according to claim 1, characterized in that one or more power semiconductor devices [2] can be sandwiched between two evaporative cooling radiators [1], or multiple evaporative cooling devices A plurality of power semiconductor devices [2] are sandwiched between the cooling radiator [1]. 4. The evaporative cooling device for power semiconductor devices according to claim 1, characterized in that when a plurality of evaporative cooling radiators [1] are connected, the upper part of the evaporative cooling radiator [1] passes through the end steam outlet pipe [9] and The pressure equalizing pipe [8] is connected, the lower part is connected with the liquid collection pipe [6] through the liquid inlet pipe [15], and the liquid collection pipe [6] is connected with the liquid return pipe [7] to the upper condenser [3] or cooler [ 3]. 5. The evaporative cooling device for power semiconductor devices according to claim 1, characterized in that the evaporative cooling medium circulation can be powered by a pump or self-circulation without a pump. 6. The evaporative cooling device for power semiconductor devices according to claim 1, wherein the boiling point of the evaporative cooling medium does not exceed 70°C. 7. The evaporative cooling device for power semiconductor devices according to claim 1, characterized in that thermal grease (glue) can be applied between the power semiconductor device [2] and the evaporative cooling radiator [1].

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