RU60271U1 - THERMOELECTRIC MODULE - Google Patents

Abstract

The thermoelectric module belongs to the field of refrigeration technology and can be used in the design of cooling systems, in particular, for elements of electronic computer technology, semiconductor devices, including semiconductor lasers. The objective of the utility model is the creation of such a thermoelectric module, which would, through a new implementation of the bearing plates, provide an increase in cooling capacity and an expansion of possible structural solutions, including increasing the size (length and width) of the carrier plates without increasing the temperature gradient along the plates when placing the cooled electronic element in the center of the surface of the cold plate. The problem is solved due to the fact that in the thermoelectric module containing thermocouples placed between the supporting cold and hot plates, at least one of the supporting plates is made in the form of a heat pipe. 3 ill., 1 ave.

Description

The thermoelectric module belongs to the field of refrigeration technology and can be used in the design of air conditioning systems, cooling systems for electronic components, semiconductor devices, in particular semiconductor lasers, etc.

A known design of a thermoelectric cooler, consisting of three cascades of thermocouples, an insulating heat-absorbing plate with dimensions of 3.5 × 3.5 mm, on which a photosensitive element is mounted, and a hot plate in contact with the device case (see the article by T. Aliev, authors , Akhundova D.Sh., Abdinov D.Sh. “Thermoelectric cooler at a temperature level of ~ 200 K for infrared photodetectors” in the journal “Instruments and experimental equipment”, 1999, p. 164-165). Such a cooler provides a cooling capacity of 100 mW, a heat-absorbing surface temperature of 200–205 K at an ambient temperature of ~ 295 K, a supply current of 2 A, and a power consumption of 4.5 W. The number of thermocouples is 29. The cooler can be used to cool other radio elements with a thermal load of up to 100 mW.

The disadvantage of this device is the complexity of its design, which increases the cost of its manufacture and reduces the reliability of the operation.

A typical design of a simpler (single-stage) thermoelectric module is known, containing thermoelements interconnected by copper contact plates into a series thermoelectric circuit, which are placed between two supporting insulating ceramic plates (cold and hot) made of heat-conducting beryllium ceramic (see book authors Weiner AL, Moiseev VF Combined devices of cryothermoelectric electronics. - Odessa: Negotsiant Studio, 2000. - 100 p., Fig.6.P on p. 92). The surfaces of the plates are metallized, which allows fixing devices to the module by soldering. The dimensions of a thermoelectric module, for example, type M6-127, are 40 × 40 × 3.8 mm (see Table 1, p. 86 of this book). The maximum supply current is 8 A, the maximum supply voltage is 15.4 V. The indicated thermoelectric module provides a maximum temperature difference between cold and hot ceramic plates of 68 ° C and a maximum cooling capacity of 68 W. The number of thermocouples in the module is 127.

A disadvantage of the known device is that when installing a miniature electronic element, for example, a laser semiconductor crystal, the temperature of which must be maintained at a given temperature, in the center of the cold ceramic plate, the heat generated by the laser crystal is transferred by the thermal conductivity of the cold plate along its surface to all 127 branches of thermoelements. Due to the thermal resistance of the ceramic, a temperature gradient is established over the surface of the cold ceramic plate, which increases the power consumption of the module and reduces its cooling capacity.

The second disadvantage of the known device is the significant thermal resistance in the path of the passage of high-density heat flux from a semiconductor crystal with insignificant geometric dimensions, for example 0.5 × 0.3 × 0.2 mm, through ceramics with limited thermal conductivity, in the region adjacent to the crystal. This leads to the need to provide an increased temperature difference between the cold and hot plates to ensure a given crystal temperature and to a corresponding increase in energy consumption.

The closest to the proposed combination of features and technical result is a prototype device, known from the article "Thermoelectric modules on a metal base and devices based on them", published in the journal "Devices", 2002, No. 11, p.16-17 . The thermoelectric prototype module contains thermoelements interconnected by means of contact plates in a thermoelectric circuit, which are placed between two supporting metal plates, which allowed to increase the cooling capacity and operational reliability of the thermoelectric module, significantly expand the possibility of structural solutions and speed up the output time by 2-4 times on mode. The use of heat-conducting metal plates instead of ceramic made it possible to increase the maximum geometric dimensions of the thermoelectric module. For example, a thermoelectric module of the type MD1-125-2.0 / 1.5 with metal plates has dimensions 48 × 60 × 3.5 mm and provides a maximum cooling capacity of 116.8 W, and a maximum temperature difference between cold and hot plates 71 ° C. The maximum supply current is 12.9 A, the maximum supply voltage is 15.6 V.

The disadvantage of the thermoelectric prototype module is the limited cooling capacity and maximum geometric dimensions of the supporting metal plates, which is due to an increase in the temperature gradient along the plates with an increase in their length and width (due to the existing thermal resistance of thin metal plates) when placing a miniature cooled electronic element in the center of the cold plate.

The basis of the proposed technical solution is the task of creating such a thermoelectric module, which would, by means of a new version of the bearing plates, provide an increase in cooling capacity and an expansion of possible design solutions, including increasing the size (length and width) of the carrier plates without increasing the temperature gradient along them when placing the cooled electronic element in the center of the surface of the cold plate.

This goal is achieved due to the fact that in the thermoelectric module containing thermocouples placed between the supporting cold and hot plates, at least one of the supporting plates is made in the form of a heat pipe.

The essence and principle of operation of the proposed thermoelectric module is illustrated by drawings.

Figure 1 shows a General view of a thermoelectric module. Figure 2 shows a vertical section along the line AA of a thermoelectric module with a cold plate made in the form of a heat pipe. Figure 3 shows a vertical section of a thermoelectric module, in which both the cold and hot plates are made in the form of a heat pipe.

The thermoelectric module (see Fig. 1) contains thermoelements 1 interconnected by electrically conductive contact plates 2 in a thermoelectric circuit, which are located between the cold carrier plate 3 and the hot carrier plate 4. An electronic element 5 is connected to the cold carrier plate 3 to provide thermal contact , for example, a laser diode, the temperature of which must be maintained in a predetermined temperature range, and attached to the supporting hot plate 4 to ensure thermal contact, for example, soldered, radiator 6 for dissipating heat into the environment. To ensure reliable attachment of the electronic element to the radiator to the outer surface of the carrier plates, a metallized film and a solder layer can be applied to their surface. For connecting to a current source, the thermoelectric module contains current terminals 7.

At least one carrier plate, for example a cold plate 3, is made in the form of a heat pipe (see figure 2). At the same time, it can be made, for example, of heat-conducting (beryllium) ceramics, of aluminum alloy, copper, etc. The heat pipe consists of a hollow sealed pre-evacuated body, on the inner surface of which a layer 8 of capillary material is made, for example, in the form of sintered powders or fibers, grooves, roughnesses, grids, etc. A layer of capillary material can also be formed on the inner surfaces of ceramic plates by the action of laser radiation.

The grooves or pores of the layer 8 of the capillary material are impregnated with a liquid coolant, for example, ethyl alcohol, ammonia, acetone, etc.

When making the carrier hot plate in the form of a heat pipe (see Fig. 3), its dimensions (length and / or width) can be made significantly larger than the contact zone of thermoelements 1 with the carrier hot plate 4. This makes it possible to significantly develop the heat-dissipating surface of the radiator 6. In this case, the current leads 9 have a curved shape.

In other embodiments, several electronic elements can be installed on the cold plate 3, the temperature of which must be maintained at a given level.

Electrically conductive contact plates 2 for the electrical connection of thermocouples into a thermoelectric circuit are deposited directly on the surfaces of the ceramic cold carrier plate 3 and the hot carrier plate 4. When cold and hot carrier plates are made of electrically conductive material (aluminum alloy, copper, etc.), the conductive contact plates 2 are applied on carrier plates through a layer of electrical insulating material.

Thermoelectric module operates as follows. Under the influence of the heat released in the electronic element 5, the liquid coolant in the grooves or pores of the layer 8 of capillary material on the inner surface of the carrier cold plate 3 see figure 2, figure 3) begins to evaporate (or boil). The temperature of saturated steam in the heating zone rises and exceeds the temperature of the opposite wall of the carrier cold plate, which is in thermal contact with the cold junctions of thermocouples 1 and is cooled from them.

Saturated steam condenses on the inner cold surface of the carrier plate 3 and gives it the latent heat of vaporization. Condensate under the action of capillary forces through the layer 8 of capillary material returns to the heating zone, where a cooled electronic element is installed. The heat transfer cycle by evaporation-condensation of the coolant is repeated.

The saturated steam pressure, and accordingly the temperature, are the same at all points of the vapor space inside the carrier plate 3, so that its temperature has the same value regardless of the distance between the cooled electronic element and any module thermocouple.

The heat released in this case on the surface of the carrier cold plate 3 in contact with the thermocouples 1 is transferred from the cold junctions of the thermocouples to the hot junctions, and from the latter to the contact surface of the carrier hot plate 4. Then the thermal conductivity (when making a hot plate of solid material, cm Fig. 2) or by means of an evaporation-condensation cycle inside the hot carrier plate 4 (when it is made in the form of a heat pipe, see Fig. 3), heat is transferred to the outer surface

the carrier hot plate and the radiator 6 in contact with it. Radiator 6 dissipates heat by convection and partly by radiation into the environment, for example, into the air.

Due to the fact that heat transfer in the most heat-loaded area (from the electronic element 5 to the cold plate 3) is carried out by means of a highly efficient closed evaporation-condensation cycle, a reduction in thermal resistance and temperature difference in the heating zone is achieved. Due to this, a lower temperature difference between the cold and hot plates is required, which allows to increase the cooling capacity of the thermoelectric module. The high heat transfer coefficient during steam condensation on the inner surface of the supporting hot plate 4 in contact with the hot junctions of the thermocouples 1 also helps to increase the cold-productivity of the thermoelectric module.

Maintaining the temperature of the electronic element at a predetermined level when changing the parameters of the ambient air is ensured through feedback by known methods. For example, to maintain the given temperature of the laser diode and stabilize it within the specified limits, feedback is used with the control unit and the power of the thermoelectric module through the feedback photodiode.

Due to the low inertia of the heat transfer processes by means of the evaporation-condensation cycle, the time for the device to reach the operating mode is reduced, which extends the functionality of the device.

Heat removal by means of an evaporation-condensation cycle with a low thermal resistance in the most heat-loaded section reduces the temperature of the electronic element and increases its reliability.

Thus, the proposed thermoelectric module provides increased cooling capacity and the expansion of possible design solutions, including increasing the size (length and width) of the bearing plates without increasing the temperature gradient along them with increasing size of the plates. The claimed design allows you to place one or more cooled electronic elements both in the center of the surface of the cold plate, and in any other place on its surface, as well as perform the hot plate and the radiator on it much larger than in the prototype, which expands the structural possibilities of using the claimed thermoelectric module.

The proposed thermoelectric module is new, industrially suitable and has an inventive step.

Claims (1)

Thermoelectric module containing thermocouples placed between the supporting cold and hot plates, characterized in that at least one of the supporting plates is made in the form of a heat pipe.