CN107426946B - Direct contact heat dissipation method for vibrating device based on microarray structure - Google Patents

Abstract

The invention discloses a direct contact heat dissipation method and application of a vibration device based on a microarray structure. For a high-frequency vibration device similar to a piezoelectric transformer, direct contact heat dissipation usually has large contact thermal resistance, severe device wear, and affects vibration performance. To solve such problems, an elastic microarray contact heat dissipation structure with low thermal resistance and high thermal conductivity is provided. Through the large-scale growth of a microarray structure with a high aspect ratio and an appropriate array density on the heat sink substrate, based on its good longitudinal thermal conductivity and van der Waals force, as well as good lateral flexibility, it can be used for vibration devices that are not suitable for direct contact heat dissipation occasion. This kind of vibration device thermal management scheme, because there is no relative sliding, no contact wear, high flexibility perpendicular to the heat transfer direction, small damping, low impact on device vibration, and no additional force for fixing in the heat transfer direction, the structure It is simple and can meet the thermal management requirements of vibration devices to a certain extent.

Description

A Direct Contact Heat Dissipation Method for Vibrating Devices Based on Microarray Structure

technical field

The invention relates to the thermal management field of microarray structures and vibration devices, in particular to the application of a carbon nanotube array structure in heat dissipation of piezoelectric transformers, that is, a direct contact heat dissipation method and application of a vibration device based on a microarray structure.

Background technique

As people's requirements for product portability are getting higher and higher, miniaturization, light weight, and low cost have become an inevitable development trend. However, people's diversified requirements for functions make the power requirements of products higher and higher, so their power density is also higher and higher, and the thermal management of devices is becoming more and more important. For some vibration devices, it is usually not suitable for direct contact heat dissipation, and water cooling or oil cooling is generally used. However, if the vibration device is still charged, these methods may affect the vibration performance and cannot be used, so it is necessary to consider a suitable heat treatment scheme.

Taking the piezoelectric transformer in the vibration device as an example, it is an energy transmission device that uses the piezoelectric effect and inverse piezoelectric effect of materials to realize the conversion from electrical energy to mechanical energy and then to electrical energy. It is small in size, light in weight, simple in structure, and Has a high energy density. However, various losses generated during the working process of the piezoelectric transformer will cause temperature rise. When the operating temperature of the piezoelectric device reaches the Curie temperature, its piezoelectric performance begins to decay; at the same time, the loss of the piezoelectric transformer increases with the temperature rise. The increase will also increase rapidly, forming an uncontrollable positive feedback effect, resulting in a rapid decline in the performance of piezoelectric devices. At present, contact heat dissipation schemes for piezoelectric transformers have been proposed at home and abroad. By directly contacting the piezoelectric transformer with a metal heat sink (such as a copper sheet), the problem of insufficient heat dissipation of the piezoelectric transformer itself can be improved.

For high-frequency vibration devices such as piezoelectric transformers, there are some problems in the direct contact heat dissipation method. The contact between the piezoelectric transformer and the metal heat sink belongs to the direct contact of two rigid interfaces. Due to the influence of surface defects and roughness, it is impossible to completely fit the contact surfaces. There is an air gap and large thermal resistance, which affects the heat dissipation effect. At the same time, the piezoelectric transformer is in a state of high-frequency vibration during work, and there is relative sliding between it and the heat sink, which will affect the performance of the piezoelectric transformer; in addition, this high-frequency relative sliding will cause contact fretting wear on the electrode surface of the piezoelectric transformer , greatly reducing the service life and performance of the transformer. Therefore, suitable thermal interface materials are the key to contact heat dissipation for vibration devices.

Contents of the invention

The technical problem of the present invention is to overcome the deficiencies of the prior art, provide a direct contact heat dissipation method and application of vibration devices based on microarray structure, and provide high-frequency vibration devices (up to hundreds of kilohertz, even megahertz level) An elastic microarray contact heat dissipation structure with low thermal resistance and high thermal conductivity (thermal resistance <0.1cm ² ·K/W, thermal conductivity >10W/m·K).

The purpose of the present invention is achieved through the following technical solutions:

The heat dissipation method for a vibration device based on a microarray structure of the present invention uses methods such as laser etching, photolithography, or chemical vapor deposition to prepare any of the following microarray structures:

The substrate is in the shape of rectangle, disk, ring, triangle and trapezoid, on which a vertically arranged microarray structure is processed, the unit size can be micron or nanoscale, and the material can be carbon nanotubes, or Copper, but not limited to copper is a metal material that conducts heat well.

The above-mentioned microarray structure of the present invention can be used for contact heat dissipation in the operation of vibration devices such as piezoelectric transformers.

It can be seen from the above-mentioned technical solutions provided by the present invention that the contact heat dissipation method and application of the piezoelectric transformer based on the microarray structure provided by the present invention have the following advantages:

(1) The longitudinally aligned carbon nanotubes grown on a large scale first have excellent thermal conductivity and ultra-high mechanical strength in the longitudinal direction when the array density is appropriate.

(2) A carbon nanotube microarray is processed on a copper substrate. A single carbon nanotube has a diameter of 100 nanometers and a height of about 100 micrometers. Such a high aspect ratio makes it highly mechanically flexible when used as a thermal interface material. When the high-frequency vibration piezoelectric transformer is bonded to the microarray structure, since the vibration displacement is generally at the micron level, the highly flexible carbon tube will produce follow-up movement, so that there will be no relative sliding between the two, eliminating or greatly reducing the The fretting wear of the electrode surface of the piezoelectric device improves the service life. At the same time, the follow-up in this highly flexible state will not produce large damping, so that the microarray heat dissipation structure has little influence on the vibration of the transformer, ensuring the working performance.

(3) The micro-nano-scale carbon nanotube array can easily fill the gaps or defects on the contact surface of the piezoelectric transformer, and the surface roughness of the transformer is not high, which fully guarantees the direct contact between the microarray structure and the transformer The area can reduce thermal resistance and improve heat dissipation performance.

(4) Millions of carbon tubes grown on the substrate, when in contact with the surface of the piezoelectric transformer, the van der Waals force generated by it can ensure the stable and close contact between the carbon tube array and the surface of the transformer, during the working process of the transformer There is no need to apply additional force to make the two stick together, the heat dissipation structure will be simpler, and at the same time, the impact of additional force on the performance of the transformer is reduced.

In summary, on the heat sink substrate, such as copper or silicon wafers, microarray structures with high aspect ratio and suitable array density are grown on a large scale, not limited to array structures such as carbon nanotubes or copper nanowires. Good thermal conductivity and van der Waals force, as well as good lateral flexibility, can be used in the occasions where traditional vibration devices, especially high-frequency vibration devices, are not suitable for contact heat dissipation. This vibration device thermal management solution based on the microarray structure has good thermal conductivity, low interface thermal resistance, no relative sliding, no contact wear, high flexibility perpendicular to the heat transfer direction and small damping, low impact on device vibration, and transmission No additional force is required for fixing in the thermal direction, and the structure is simple, which can meet the thermal management requirements of vibration devices to a certain extent.

Description of drawings

Fig. 1a and Fig. 1b are schematic diagrams of microarray heat dissipation structures in which the substrate provided by the embodiment of the present invention is a rectangle, and the microarray unit is a cylinder or a cuboid;

Fig. 2 is a schematic diagram of the planar expansion mode shape of a rectangular piezoelectric transformer in an embodiment of the present invention;

Fig. 3 is the heat dissipation experiment of the carbon nanotube or copper nanowire microarray structure used in the working mode of piezoelectric transformer plane expansion in the embodiment of the present invention;

Figure 4a shows the heat dissipation experiments of piezoelectric transformers under three different thermal interface conditions;

Figure 4b shows the experimental results of the temperature rise of the piezoelectric transformer at the same working power under these three different thermal interface conditions;

5 is a schematic diagram of the torsional vibration mode of the piezoelectric ceramic tube in an embodiment of the present invention; a shows a schematic diagram of the torsional vibration mode of the piezoelectric ceramic tube; schematic diagram;

Fig. 6 is the heat dissipation application of the microarray structure in other vibration devices in the embodiment of the present invention, taking the heat dissipation structure of the piezoelectric ceramic tube in the torsional vibration as an example, where a is the compression force of the torsional vibration by using the ring-shaped distributed microarray thermal interface material The overall structure diagram of the electroceramic tube for contact heat dissipation, b is the top view of the structure in a.

Detailed ways

For high-frequency vibration devices, as long as there is loss, there will be a certain temperature rise. When the temperature rise reaches a certain level, it will affect the performance and life of the vibration device. For some occasions where it is not suitable to use grease for heat dissipation, the present invention proposes a method of using a microarray structure with high flexibility, low thermal resistance, and high thermal conductivity to conduct contact heat dissipation on the vibration device.

The purpose of the present invention is achieved through the following technical solutions:

First, a microarray structure with a certain distribution density is prepared on a metal or silicon substrate. The array is arranged vertically to the substrate. The unit size can be micron or nanoscale. The material can be carbon nanotubes or copper nanowires, and not only Other metal materials that conduct heat well are limited to these two materials.

The base of the microarray structure can be planar or thin circular, and the microarray structure perpendicular to the surface is grown inside the circular ring.

The above-mentioned microarray structure of the present invention can be directly used as a thermal interface material in the contact heat dissipation of vibration devices such as piezoelectric transformers. The microarray structure is directly attached to the vibrating device, and due to the superposition of large-scale van der Waals forces, the structure will be directly adsorbed on the device without additional pre-tightening force. The size of the micro-array unit is at the micro-nano level, which can well fill the holes or defects on the surface of the device and reduce the contact thermal resistance; at the same time, the high flexibility of the micro-array structure will not affect the vibration performance of the device, and there is no relative sliding between the device and the device. No contact wear occurs. As long as the array density is appropriate, its good thermal conductivity can meet the thermal management requirements of vibration devices to a certain extent.

For the aforementioned vibrating device of the present invention, due to the anisotropy of the microarray structure, the vibration direction of the device during operation may be perpendicular to the array unit.

Example 1:

The following takes carbon nanotube microarray as an example of thermal interface material to explain its application in heat dissipation of piezoelectric transformer in detail:

Figure 1a shows the microarray structure of carbon nanotubes grown on a rectangular silicon wafer substrate. The carbon nanotubes are vertically arranged and distributed on the substrate. About 1%, its thermal conductivity measured by laser interferometry is 10-20W/m·K.

FIG. 2 shows a schematic view of the rectangular piezoelectric transformer and its planar expansion mode shape to be subjected to heat dissipation treatment in this embodiment. The piezoelectric transformer is in a state of high-frequency vibration in the lateral direction. If a rigid radiator is directly used for contact heat dissipation, there will be relative sliding between the stationary radiator and the transformer, which will affect the vibration performance of the transformer; at the same time, contact wear will occur. The electrodes on the contact surface between the long transformer and the heat dissipation structure are severely worn, which greatly reduces the service life of the transformer.

Fig. 3 is a schematic diagram of the structure of the carbon nanotube or copper nanowire microarray used for contact heat dissipation of the piezoelectric transformer. Taking the carbon nanotube microarray as an example, the piezoelectric transformer is directly in contact with the vertically arranged carbon nanotube array on the substrate. The size of the end of the array unit is at the nanometer level, so it can well fill the tiny defects or voids on the contact surface of the piezoelectric transformer and reduce the thermal resistance of the contact surface. When the millions of carbon tubes grown on the substrate are in contact with the surface of the piezoelectric transformer, the van der Waals force generated by it can ensure the stable and close contact between the carbon tube array and the surface of the transformer. Additional force is applied to make the two stick together, and the heat dissipation structure will be simpler. In addition, carbon nanotubes with a high aspect ratio have strong mechanical flexibility in the lateral direction. When a high-frequency vibration piezoelectric transformer is attached to a microarray structure, since the vibration displacement is generally at the micron level, the highly flexible carbon nanotubes will Follow-up is generated, so that there will be no relative sliding between the two, eliminating or greatly reducing the fretting wear on the electrode surface of the piezoelectric device, and improving the service life. At the same time, the follow-up in this highly flexible state will not produce large damping, so that the microarray heat dissipation structure has little influence on the vibration of the transformer, ensuring the working performance.

Fig. 4a is a schematic diagram of heat dissipation experiments of piezoelectric transformers under three different thermal interface conditions. (1) in Fig. 4a sticks polypropylene film PP on the silicon wafer as a thermal interface material to contact the piezoelectric transformer, and then places it on a copper heat sink for heat dissipation; (2) in Fig. 4a grows carbon on the silicon wafer The nanotube array is in contact with the piezoelectric transformer as a thermal interface material, and then placed on a copper heat sink for heat dissipation; (3) in Figure 4a directly uses the polypropylene film PP as a thermal interface material in contact with the piezoelectric transformer, and then placed on a copper radiator Heat dissipation on the radiator.

Figure 4b shows the temperature rise of the piezoelectric transformer after it has been working stably for a period of time under the same driving power under the three different thermal interface conditions shown in Figure 4a and without any heat dissipation measures. It can be seen that when no heat dissipation measures are added, the temperature rise of the piezoelectric transformer reaches 23°C; when the polypropylene film + silicon chip + copper sheet is used as a contact heat dissipation measure, the temperature rise of the piezoelectric transformer is 13°C; When direct polypropylene film + copper sheet is used for contact heat dissipation without silicon chip, the temperature rise of piezoelectric transformer is 10°C; when carbon nanotube array + silicon chip + copper sheet are used as contact heat dissipation measures, the temperature rise of piezoelectric transformer Only 8°C.

Example 2:

Carbon nanotube microarray structure heat dissipation application technical scheme in columnar vibration devices:

Diagram a in Fig. 5 shows a schematic diagram of the torsional vibration mode of the piezoelectric ceramic tube. For this kind of circular vibration device, because it is not in a normal plane motion state, it is usually inconvenient to manage its heat dissipation.

Graph b in FIG. 5 is a schematic diagram of a microarray structure of carbon nanotubes grown radially on the inner wall of a ring-shaped substrate. Based on the high thermal conductivity and high flexibility of the above-mentioned carbon nanotube array, it can reduce the thermal resistance of the contact surface in the application of contact heat dissipation, and there is no relative sliding and no contact wear, so it can be used for thermal management applications of circular vibration devices.

FIG. 6 is a schematic diagram of applying the above-mentioned radially grown carbon nanotube microarray structure to a torsional vibration piezoelectric ceramic tube for contact heat dissipation. A ring-shaped heat dissipation base with a certain density of carbon nanotube arrays growing radially on the inner wall is placed on the outside of the piezoelectric ceramic tube, and the carbon nanotube array is in close contact with the ceramic tube. The van der Waals force generated by the millions of carbon tubes grown on the substrate can ensure the stable and close contact between the carbon tube array and the surface of the ceramic tube, providing good contact and heat dissipation conditions, and at the same time, there is no need for Apply additional force for fixation. Carbon nanotubes with high aspect ratio have strong mechanical compliance along the circumferential direction, while the displacement of high-frequency piezoelectric ceramic tubes is generally on the order of microns, so there will be no relative sliding between the two, which will not affect the vibration of the device performance while eliminating or greatly reducing fretting wear on the electrode surfaces of piezoelectric devices.

Example 3:

The following takes copper nanowire microarray as an example of thermal interface material to explain its application in heat dissipation of piezoelectric transformer in detail:

Figure 1b shows a copper nanowire microarray structure processed by laser etching or photolithography on a rectangular copper substrate. The copper nanowires are arranged vertically on the substrate, and its units are cuboids with a cross-sectional size of hundreds of nanometers. The height is on the order of microns, and the array density is around 1%.

For the embodiment in which the piezoelectric transformer uses a copper nanowire microarray structure for contact heat dissipation in the planar expansion working mode, a schematic diagram of the heat dissipation structure of this solution can also be shown in FIG. 3 . The piezoelectric transformer is directly in contact with the copper nanowire arrays vertically arranged and distributed on the substrate. The size of the end of the array unit is at the nanometer level, so it can well fill the tiny defects or voids on the contact surface of the piezoelectric transformer and reduce the thermal resistance of the contact surface. Based on the same high mechanical compliance in the horizontal direction and high thermal conductivity in the vertical direction of the copper nanowire array, it has the advantage of contact heat dissipation similar to that of the carbon nanotube array, which does not affect the vibration performance of the transformer itself, and can transfer heat loss well. .

In a word, the present invention grows a microarray structure with high aspect ratio and suitable array density on a large scale on the heat sink substrate, based on its good thermal conductivity and van der Waals force effect in the longitudinal direction, and good flexibility in the lateral direction, it can be used for vibration devices that are not suitable for Where there is direct contact with heat dissipation. This kind of vibration device thermal management scheme, because there is no relative sliding, no contact wear, high flexibility perpendicular to the heat transfer direction, small damping, low impact on device vibration, and no additional force for fixing in the heat transfer direction, the structure It is simple and can meet the thermal management requirements of vibration devices to a certain extent.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (8)

1. a kind of vibration device based on micro array structure is in direct contact heat dissipating method, it is characterised in that：Using raw in substrate Micro array structure that is long or processing certain density is as thermal interfacial material, the directly vibration device to needing progress thermal losses transfer Contact heat dissipation；

Array element of the direction of vibration of the vibration device in micro array structure；

If substrate is planar, the direction of vibration of vibration device is parallel to base plane, and vertical with array element；

If substrate is cylindric or circular, the direction of vibration and substrate circumferencial direction of vibration device are tangent, and and array Unit is vertical.

2. the vibration device according to claim 1 based on micro array structure is in direct contact heat dissipating method, it is characterised in that： Elastic micro array structure as thermal interfacial material has high-termal conductivity, i.e. thermal conductivity factor is higher than 10W/mK, the microarray Array element in structure is the nonmetallic of carbon nanotube, the metal nanometer line either good silicon of other thermal conductivity or silica Micro-nano structure.

3. the vibration device according to claim 2 based on micro array structure is in direct contact heat dissipating method, it is characterised in that： The size of array element in the micro array structure is micro/nano-scale, and the shape of array element is cylinder or cuboid.

4. the vibration device according to claim 1 based on micro array structure is in direct contact heat dissipating method, it is characterised in that： The substrate is that can carry out the heat safe Heat Conduction Material of micro array structure growth and processing, including silicon, silica or copper etc. Metal material.

5. the vibration device based on micro array structure according to claim 1 or 4 is in direct contact heat dissipating method, feature exists In：The shapes of substrates is planar or cylinder, annular shape, described planar including following any shape：Rectangle, disk Shape, circular ring shape, triangle or trapezoidal.

6. the vibration device according to claim 1 based on micro array structure is in direct contact heat dissipating method, it is characterised in that： Carbon nanotube microarray is grown on silicon chip or copper sheet substrate, and the contact under piezoelectric transformer plane vibration mode dissipates Heat；The piezoelectric transformer plane vibration mode include it is following any one or more：Strip vibration mode, radial vibration mould Formula, thickness vibration mode, radiation vibration mode.

7. the vibration device according to claim 1 based on micro array structure is in direct contact heat dissipating method, it is characterised in that： Laser ablation or lithography process copper nano-wire microarray in copper sheet substrate, and under piezoelectric transformer plane vibration mode Contact heat dissipation；The piezoelectric transformer plane vibration mode include it is following any one or more：Strip vibration mode, radial direction Vibration mode, thickness vibration mode, radiation vibration mode.

8. the vibration device according to claim 1 based on micro array structure is in direct contact heat dissipating method, it is characterised in that： In annulus or cylindric substrate inner wall growth carbon nanotube microarray, and for the contact under piezoelectric ceramic tube torsion modes Heat dissipation.