CN1971195A - Flat heat pipe for thermal diffusion - Google Patents

Abstract

A flat heat pipe for thermal diffusion, comprising a metal fin or fin radiator and a metal cover that seals its surroundings, the top of the metal fin or fin is connected to the inner wall of the metal cover, and the fin or fin The cavity formed by the radiator and the metal cover is provided with a liquid working medium, and the surface of the fin or fin column, the base of the fin or fin column, and the inner wall of the metal cover are provided with capillary cores for the return flow of the liquid working medium . The metal fins or fin columns can enhance the mechanical strength of the heat pipe, and the capillary wicks provided on the surface for liquid backflow can shorten the path of liquid backflow and improve the heat transfer effect. When in use, the heat generated by the power device evaporates the liquid on the heating wall, and the steam reaches the heat dissipation wall through the interconnected channels between the fins or fin columns, condenses on the heat dissipation wall to release heat, and the condensed liquid returns to the heating wall through the capillary core.

Description

A flat heat pipe for thermal diffusion

technical field

The invention relates to the encapsulation and heat dissipation technology of a power module, in particular to a flat heat pipe for heat diffusion with high heat density.

Background technique

With the advancement of modern power electronics technology, the number of components integrated in the limited space of power electronic devices is increasing, and the functions of the devices are becoming more and more powerful. Then, the high heat flux generated inside the device has become a major obstacle that affects the performance and reliability of the device and restricts the development of the device in the direction of miniaturization and miniaturization. The key to overcoming this obstacle lies in the use of efficient cooling devices to dissipate the heat generated by high heat density heat sources.

To solve the heat dissipation problem of high heat density heat sources, the concentrated heat source must first be diffused to a large area. Only by spreading the concentrated heat source first can the full utilization of the radiator (air-cooled, water-cooled, etc.) be guaranteed. The effect of thermal diffusion greatly affects the performance of the radiator. cooling efficiency. Even high-cost gold foil and diamond film are used for thermal diffusion in microelectronic circuits. The high-power devices in the power module, such as IGBT, have a heat flux density of up to 400W/cm ² . At present, the thermal diffusion devices used in power modules are mainly metal substrates with high thermal conductivity, such as copper plates and aluminum plates. Although the thermal conductivity of the metal substrate is high, there is still a temperature difference on the bottom surface of the substrate, and the efficiency of the heat sink is low. In addition, due to the limitation of the thermal diffusion capacity of the metal substrate, the distance between high-power devices should not be too close to avoid heat concentration. However, in terms of reducing parasitic parameters, it is hoped that the distance between power devices should be as close as possible. Therefore, it is very beneficial to improve the power and electrical performance of the module to adopt a thermal diffusion device with stronger thermal diffusion ability than the metal substrate and a lower cost.

Heat pipes are also commonly used in power electronic devices to spread and transport heat. The shape of the flat heat pipe is very conducive to the diffusion of the concentrated heat source. The structure of the flat heat pipe is that the central part of the metal substrate is made into a cavity, the inner wall of the cavity is provided with a capillary structure, the cavity is evacuated, and a working medium of a certain capacity is injected. The heat generated by the heat source vaporizes the liquid working medium near the heating wall and takes away the heat. The steam condenses into liquid on the cooling wall and releases heat. The liquid working medium returns to the heating wall by the action of capillary force. The heat generated by the heat source. Since the equivalent thermal conductivity of the heat pipe is much higher than that of metal, the thermal diffusion capacity of the flat heat pipe is also much higher than that of the solid metal substrate. When the heat flux density of the heat source is high, the temperature difference on the cooling surface of the flat heat pipe is only about 1°C (Hong Yuping, Li Qiang, Xuan Yimin, Experimental Research on Heat Transfer of Small Flat Heat Pipe, Journal of Nanjing University of Science and Technology, 2001, 25(1): 32- 35). Various flat plate heat pipes have been proposed in some patent literature, as follows:

Delta Electronics Co., Ltd. Zhuang Mingde et al. applied for the invention patent "Platform Heat Pipe and Its Supporting Structure" (Application No.: 200410089845.9), which proposes a flat heat pipe. The support structure is widely distributed in the steam chamber of the heat pipe to avoid Capillary stripping. The support structure is a multi-layer or single-layer porous material. The support structure can not only support the capillary tissue, reduce the thermal resistance between the capillary tissue and the inner wall of the heat pipe, but also provide a space for steam to flow, and further provide capillary force to make the working fluid flow back. However, since the support structure is a porous material, it is inferior to metal materials in terms of heat conduction and mechanical strength.

The invention patent "Heat Transfer Enhancement Structure of Flat Heat Pipe" (Application No.: 200310121710.1) applied by Xu Jincheng and others from the Industrial Technology Research Institute of the Foundation has several abutting joints on the upper and lower parts of the heat pipe cavity at higher temperatures. The heat conduction column on the wall serves as a strengthening structure for heat conduction and reduces the thermal resistance on the heat conduction path. The design of this structure focuses on strengthening the heat conduction of the upper and lower walls of the heat pipe cavity, so the heat conduction column is only set at a higher temperature in the heat pipe cavity, and this structure does not consider shortening the steam return path and strengthening the mechanical strength of the heat pipe. .

Contents of the invention

The object of the present invention is to provide a flat heat pipe for thermal diffusion that can not only fully ensure the mechanical strength of the heat pipe, but also greatly reduce the return path of the working fluid, thereby improving the heat transfer performance of the heat pipe.

In order to achieve the above object, the technical scheme adopted by the present invention is: comprise fin or fin radiator and a metal cover plate that seals its surroundings, it is characterized in that, the fin of said fin or fin radiator or The top of the finned column is connected to the inner wall of the metal cover plate, and a liquid working medium is arranged in the cavity formed by the finned or finned column radiator and the metal cover plate, and the The base of the column and the inner wall of the metal cover are provided with capillary cores for the backflow of liquid working fluid.

The fins or fins of the present invention have cylindrical fins, square column fins or rectangular fins; the capillary core is a sintered metal powder, wire mesh, heat-conducting fiber, nanofiber or fine groove structure; the fin or The finned column radiator is made of metal with high thermal conductivity; the channels between the metal fins or the finned columns are connected to each other; the liquid working medium is deionized water, ethanol or acetone.

Since the surface of the fin or fin column of the present invention is provided with a capillary core for liquid backflow, it can not only shorten the path of liquid backflow, improve the heat transfer effect, but also enhance the mechanical strength of the heat pipe. When in use, the heat generated by the power device evaporates the liquid on the heating wall surface. The steam reaches the heat dissipation wall surface through the interconnected channels between the fins or fin columns, and condenses on the heat dissipation wall surface to release heat. The condensed liquid passes through the inner wall surface of the metal cover plate, the fin Capillary structures on the surface of the fin or fin and on the base of the fin or fin return to the heated wall. Using the flat heat pipe instead of the metal base plate can not only improve the thermal diffusion capacity of the base plate, increase the power density of the power module, but also reduce the weight of the power module.

Description of drawings

Fig. 1 is the overall structure schematic diagram of the present invention;

Fig. 2 is the structural representation of fin or fin radiator of the present invention, wherein Fig. 2 a is a cylindrical fin radiator, Fig. 2 b is a square column fin radiator, and Fig. 2 c is a rectangular fin radiator;

FIG. 3 is a schematic diagram of a power module of the present invention.

Detailed ways

The structural principle and working principle of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Referring to Fig. 1, the present invention comprises the fin or fin radiator 8 that is made of the metal of high thermal conductivity and a metal cover plate 9 that fin or fin radiator 8 are sealed all around, heat dissipation in fin or fin radiator There are several sets of metal fins or fin columns 802 connected to the fin or fin column radiator base 801 and the inner wall surface of the metal cover plate 9 respectively in the device 8, and the passages between the metal fins or fin columns 802 communicate with each other, and in The cavity formed by the fin or fin radiator 8 and the metal cover plate 9 is provided with deionized water, ethanol or acetone liquid working fluid 10, on the surface of the fin or fin 802 and with the fin or fin base 801 1. On the inner wall surface 901 of the metal cover plate, there are capillary cores 11 for the reflux of the liquid working medium 10, and the capillary cores 11 are sintered metal powder, wire mesh, heat-conducting fibers, nanofibers or fine groove structures.

Referring to FIG. 2, the fins or fins 802 of the present invention are cylindrical fins, square column fins or rectangular fins.

Referring to Fig. 3, the flat heat pipe proposed by the present invention can be used as a thermal diffusion substrate for high-power devices. The high-power device 12 is welded on one side of the fin or fin base of the flat heat pipe 13 , and the radiator 14 is mounted on the other side opposite to it. The flat heat pipe 13 is connected with the radiator 14 by screws 15 . The heat generated by the power device 12 evaporates the liquid on the heating wall surface, and the steam reaches the heat dissipation wall surface through the interconnected channels between the fins or fin columns 802, and condenses on the heat dissipation wall surface to release heat, and the condensed liquid passes through the inner wall surface of the metal cover plate and the fins. The capillary core 11 on the sheet or fin surface returns to the heated wall.

The metal fins or fin columns 802 can enhance the mechanical strength of the flat heat pipe, and the capillary wick 11 on it can shorten the return flow path of the liquid. Since the thermal diffusion capacity of the flat heat pipe is much higher than that of the solid metal substrate, the heat pipe substrate can efficiently diffuse the concentrated heat generated by the power device, which better solves the heat concentration problem of the high heat density power module. In addition, the use of flat heat pipes instead of solid metal substrates also greatly reduces the weight of the module.

Claims (6)

1, a kind of thermal diffusion flat-plate heat pipe, comprise fin or wing post radiator (8) and a metal cover board (9) with sealing around it, it is characterized in that: the fin of said fin or wing post radiator (8) or the top of wing post (802) are connected with metal cover board (9) internal face, and in the cavity that fin or wing post radiator (8) and metal cover board (9) constitute, be provided with liquid working substance (10), on the surface of fin or wing post (802) and with (801) at the bottom of fin or the wing base for post, be equipped with the capillary wick (11) of working medium (10) backflow for liquid on the metal cover board internal face (901).

2, a kind of thermal diffusion flat-plate heat pipe according to claim 1 is characterized in that: said fin or wing post (802) are for having cylindrical wing post, square column type wing post or rectangular fin.

3, a kind of thermal diffusion flat-plate heat pipe according to claim 1 is characterized in that: said capillary wick (11) is sintering metal powder, woven wire, heat conducting fiber, nanofiber or thin groove structure.

4, a kind of thermal diffusion flat-plate heat pipe according to claim 1 is characterized in that: said fin or wing post radiator (8) are made by the metal of high thermal conductivity.

5, a kind of thermal diffusion flat-plate heat pipe according to claim 1 is characterized in that: the passage between said metal fin or wing post (802) is interconnected.

6, a kind of thermal diffusion flat-plate heat pipe according to claim 1 is characterized in that: said liquid working substance (10) is deionized water, ethanol or acetone.