US20180149436A1

US20180149436A1 - High efficiency thermal conductivity structure

Info

Publication number: US20180149436A1
Application number: US15/820,953
Authority: US
Inventors: Sen-Yung Lee; Cho-Yin Lee
Original assignee: National Cheng Kung University NCKU
Current assignee: National Cheng Kung University NCKU
Priority date: 2016-11-30
Filing date: 2017-11-22
Publication date: 2018-05-31
Also published as: TW201821585A; CN108124407A

Abstract

A high efficiency thermal conductivity structure includes a substrate, and plural thermally conductive wires formed on both surfaces of the substrate. The substrate is capable of forming the thermally conductive wires made of a high thermal conductivity material by a physical or chemical method. The thermally conductive wire includes a carbon nanotube or a tubular or columnar material with high thermal conductivity. The thermally conductive wire has a diameter or cross section in microscale or nanoscale size, a length in nanoscale to millimeter-scale size. During use, the thermal conductivity structure is placed between a heat source and a cooling unit. Heat from a heat source is conducted through the thermally conductive wire to the substrate. After the heat at the substrate re-adjusts its heat conduction path, the heat can be conducted from the thermally conductive wire on the other surface to the cooling unit efficiently.

Description

FIELD OF THE INVENTION

The present invention relates to a high efficiency thermal conductivity structure, and more particularly to the thermal conductivity structure having a sheet substrate, a plurality of thermally conductive wires formed on both surfaces of the substrate respectively, and the thermal conductivity structure of the invention is placed between a heat source and a cooling unit during use; and the heat of a heat source is conducted through the thermally conductive wires to the sheet substrate, and after the heat at the substrate adjusts its heat conduction path, the heat can be conducted from the thermally conductive wire on the other surface to the cooling unit more efficiently, and the thermal conductivity structure of the present invention is flexible and may be applied to a surface with different flatness and curvature.

BACKGROUND OF THE INVENTION

Cooling is one of the mainstream technologies. Various types of equipments convert energy of different forms into heat during their operation, and an increase of heat quantity and temperature may affect the performance of the operation of the equipment or even may give rise to a risk of burning or damaging the equipment, so that an electric appliance is generally equipped with a cooling device for dissipating heat and maintaining a normal operation of the electric appliance.
Among a variety of cooling technologies, one is thermal conduction, wherein a cooling unit has a structure such as a fin installed at an end of the cooling unit to increase the contact area with air and the other end contacted with the heat source directly through the cooling unit. After the heat of the heat source is conducted to the cooling unit, the fin of the cooling unit dissipates the heat to the air or any other fluid by thermal convection.
Since both contact surfaces of the cooling unit and heat source are irregular concave/convex surfaces, there are gaps between the contact surfaces of the cooling unit and heat source. These gaps have air of a very low thermal conductive coefficient (0.024W/m-k), and thus result in a poor thermal conduction effect. To improve the thermal conductivity efficiency, a thermal paste with a high thermal conductivity coefficient (10-15W/m-k) such as a silver paste is generally coated between the cooling unit and the heat source and used to replace the air of the very low thermal conductive coefficient, so that there will be no gap between the heat source and the cooling unit, and the heat can be conducted through the thermal paste to the cooling unit effectively. However, the thermal paste is usually composed of a main ingredient of a high thermal conductivity coefficient such as a mixture of metal particles, graphite, carbon tube, diamond, and linking agents, but these linking agents have a thermal conductivity coefficient much lower than that of the material of the cooling unit (such as aluminum with the thermal conductivity coefficient of 237W/m-k), and the linking agents are covered onto the main ingredient of the high thermal conductivity coefficient and thus fail to conduct the heat of the heat source through the main ingredient of the high thermal conductivity coefficient to the cooling unit directly, and the thermal conduction is interfered and affected by the linking agents of the low conductivity coefficient. As a result, the overall thermal conductivity efficiency cannot be improved effectively. Obviously, the conventional thermal conductivity structure requires improvements.
In P.R.C. Pat. No. CN100517661C, a manufacturing method of a cooling device is disclosed, carbon nanotubes with a very high thermal conductivity coefficient (20000W/m-k) are grown directly on the contact surface of the cooling unit and the heat source, and the carbon nanotubes of the cooling unit are contacted with the heat source to conduct the heat of the heat source to the cooling unit directly. To avoid growing carbon nanotubes on a non-contact surface, the manufacturing process requires coating a passivation layer (20) onto the whole cooling unit, and then removing the passivation layer (20) in contact with the heat source in order to grow the carbon nanotubes. Since the volume of the cooling unit is not too small, and the shape of the cooling unit is relatively complicated, this manufacturing method is not simple, and the transportation of the product occupies much space and requires protection.
In the prior art, a “Thermal Interface Material Manufacturing Method” as disclosed in R.O.C. Pat. No. 1331132, a “Carbon Nanotube Composite Material and Method for Manufacturing the Same” as disclosed in U.S. Pat. Publication No. 2007/0244245, a “Method for Manufacturing a Thermal Interface Material” as disclosed in U.S. Pat. No. 7,674,410 a “Thermal Interface Material and Method for Making the Same” as disclosed in U.S. Publication No. 2006/0234056, and a “Thermal Interface Material and Method for Manufacturing the Same” as disclosed in U.S. Publication No. 2008/0081176 have taught the method of forming and arranging carbon nanotubes in the same direction, and then filling a liquid linking agent, and finally positioning the carbon nanotubes after the linking agent is solidified, so as to form the thermal interface material. However, the arrangement of carbon nanotubes is not easy, and the gaps between the carbon tubes are very small, and it is very difficult, if not impossible, to fill a linking agent with high viscosity into the gaps between the carbon nanotubes. Even if the manufacture can be accomplished, the carbon nanotubes covered by the linking agent will have a cooling efficiency along the radial direction lower than that of the conventional thermal paste.
Taiwanese Patent 1458933 discloses a “Heat-Dissipation Structure And Electronic Device Using The Same”, wherein the carbon nanotubes are parallel with the surface of the heat source, and cannot be used to surfaces with protrusion-recess surface in nano-scale. When the surface of the heat source or the heat dissipation unit is a protrusion-recess surface, there are gaps formed between the carbon nanotube and the heat source or the heat dissipation unit, and the dissipation efficiency will be dramatically reduced. Furthermore, for the carbon nanotubes, the efficiency for dissipating heat in the axial direction is higher than that in the radial direction, so that the arrangement that the carbon nanotube is parallel with the surface of the heat source obviously affects the efficiency for dissipating heat.
Besides, Taiwanese Patent Publication Number 200951063 discloses “The Characterization And Fabrication Of high Efficiency Nanowires Of Thermal Interface Membrane”, wherein the baes material is AAO a module board which includes copper wires extending through the base material. However, the thermos-conductive efficient of Alumina is low and its strength is weak. Furthermore, the heat is conducted by the copper wires and not by the AAO module board so that the ability for thermos reforming is low and cannot evenly conduct the heat. Besides, the processes for manufacturing is complicated, because the copper has to be deposited in the holes of the module board, and the module board is dissolved by the solution liquid so as to expose the copper wires. This specific process restricts the length of the copper wires. The copper cannot be properly deposited if the holes is too deep. During the process of dissolving, the solution liquid cannot dissolve the module board between the copper wires because of the high density of the copper wires. Therefore, the yield rate decreases and cannot proceed large-area production.

SUMMARY OF THE INVENTION

Therefore, it is a primary objective of the present invention to overcome the aforementioned problem of the prior art by providing a high efficiency thermal conductivity structure comprising a substrate configured to be in the shape of a sheet, the thickness of the substrate is not limited and can be varied according to practical needs; a plurality of thermally conductive wires are arranged and formed at both surfaces of the substrate respectively; the substrate is capable of forming a plurality of thermally conductive wires made of a high thermal conductivity material such as copper, aluminum, silver, carbon, diamond film thereon by a physical or chemical method; the thermally conductive wires are made of a material with a high thermal conductivity such as carbon nanotube, aluminum, copper or silver and in a columnar or tubular shape; the thermally conductive wires have a diameter or cross section in a microscale or nanoscale size and a length in a nanoscale to millimeter-scale size.
During use, the thermal conductivity structure of the present invention is placed between the heat source and the cooling unit, and the heat of the heat source is conducted through the thermally conductive wires to the substrate. If the temperature of the cooling unit is non-uniform (since the position of each thermally conductive wire varies, and heat is transferred from high temperature to low temperature), the heat at the substrate will re-adjust its heat conduction path, so that the heat can be conducted by the thermally conductive wire on the other surface to the cooling unit efficiently. In addition, the thermal conductivity structure is flexible and can be applied to uneven surfaces, and its manufacture is simple and easy.
Since the thermally conductive wire are arranged independently and are not covered by any adhesive, and the contact surface between the heat source and the cooling unit is uneven, a portion of the thermally conductive wires may be bent and contacted with each other during the assembling process, and thus improving the thermal conduction path and the thermal conduction efficiently. In addition, the thermally conductive wires are flexible and can be applied to an uneven surface.
The production of the thermal conductivity structure of the present invention just requires forming the thermally conductive wires onto both surfaces of the substrate directly. Since the thermally conductive wires have been fixed and arranged on the substrate, no further rearrangement is required, or no linking agent is required to be filled between the thermally conductive wires, therefore the production of the thermal conductivity structure is feasible and low-cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the present invention;

FIG. 2 is a side view of the present invention;

FIG. 3 is a sectional view of a thermally conductive wire having an surface contacted with a heat source and the other surface contacted with a cooling unit in accordance with the present invention; and

FIG. 4 is a perspective view of a thermally conductive wire having a surface contacted with a heat source and the other surface exposed to air and arranged in a fin-shape in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The technical contents of the present invention will become apparent with the detailed description of preferred embodiments accompanied with the illustration of related drawings as follows. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive.
With reference to FIGS. 1 and 2 for a high efficiency thermal conductivity structure in accordance with a preferred embodiment of the present invention, the high efficiency thermal conductivity structure comprises the following elements:
A substrate 1 is in form of a thin sheet and capable of forming a plurality of thermally conductive wires made of a high thermal conductivity material such as copper, aluminum, silver, carbon, or diamond film thereon by a physical or chemical method. The thickness of the substrate 1 is not limited, and can be varied according to practical needs.
A plurality of thermally conductive wires 2 a, 2 b are arranged and formed on both surfaces of the substrate 1 respectively.
The thermally conductive wires 2 a, 2 b are made of a material with a high thermal conductivity such as carbon nanotube, aluminum, copper, or silver and in a tubular or columnar shape; the thermally conductive wires 2 a, 2 b have a diameter or cross-sectional length in a microscale or nanoscale and a length in a nanoscale to millimeter-scale size.
As to the formation of the thermally conductive wires 2 a, 2 b, a physical or chemical method may be used. Since such physical or chemical formation method is a prior art, and will not be described in detail here.
With reference to FIG. 3 for a thermal conductivity structure in accordance with this preferred embodiment of the present invention, the thermal conductivity structure is placed between a heat source 3 and a cooling unit 4. In other words, the substrate 1 is disposed between the heat source 3 and the cooling unit 4, and the thermally conductive wire 2 a on one of the surfaces of the substrate 1 is coupled to the heat source 3, and the thermally conductive wire 2 b on the other surface of the substrate is coupled to the cooling unit 4, and both of the heat source 3 and the cooling unit 4 have irregular concave/convex surfaces. Since the substrate 1 and the thermally conductive wires 2 a, 2 b on both surfaces of the substrate 1 are made of a flexible material with a high thermal conductivity, therefore when the cooling unit 4 and the heat source 3 are laminated, the thermal conductivity structure of the present invention is attached to the cooling unit 4 and the heat source 3 tightly and effectively, so that the heat of the heat source 3 can be conducted to the cooling unit 4 directly and effectively.
The cooling unit 4 may have different configurations or cooling conditions, so that the cooling unit 4 will have uneven temperature, and the cooling unit 4 will have a high-temperature distribution area H and a low-temperature distribution area L, and these areas will affect the cooling efficiency of the cooling unit 4. Since heat is transferred from high temperature to low temperature, therefore when the heat of the heat source 3 is conducted to the substrate 1 through the thermally conductive wire 2 b on one of the surfaces of the substrate 1, the substrate 1 adjusts its heat conduction path as indicated by the arrow direction in FIG. 3, and the heat can be conducted to the aforementioned low-temperature area L to further improve the cooling efficiency.
During assembly, if the thermally conductive wires 2 a, 2 b are bent by force due to the uneven surfaces of the heat source 3 and the cooling unit 4, then the adjacent thermally conductive wires 2 a, 2 b may be contacted with each other, and it will improve the thermal conduction path and the thermal conductivity efficiency.
If the space is too small and narrow and the cooling unit 4 cannot be installed, the configuration as shown in FIG. 4 may be used, wherein the thermally conductive wire 2 a on one of the surfaces of the substrate 1 is coupled to a surface of a heat source 3, and the other surfaces of the substrate 1 is coupled to the thermally conductive wire 2 b which is directly exposed to air, and the thermally conductive wire 2 b on the other surface may be pressed into a fin-shape to improve the contact area with the flowing air in order to dissipate heat by thermal convection more efficiently.
It is noteworthy that the thermally conductive wires 2 a, 2 b are arranged and formed on both surfaces of the substrate 1 respectively, and the thermally conductive wires 2 a, 2 b are not covered by other objects (such as a polymer material or a thermal paste as used in the prior art), so that the heat of the heat source 3 will not be blocked, but can be conducted to the cooling unit 4 directly.

Claims

What is claimed is:

1. A high efficiency thermal conductivity structure, comprising:

a substrate, having a plurality of thermally conductive wires formed on both surfaces of the substrate respectively; wherein the thermally conductive wires are configured to be in a columnar or tubular shape, and the thermally conductive wires have a cross-sectional length of a microscale or nanoscale size, and the thermally conductive wires are of a nanoscale to millimeter-scale size; and the substrate and the thermally conductive wire are made of a material of a high thermal conductivity.

2. The high efficiency thermal conductivity structure of claim 1, wherein the thermally conductive wires are formed on both surfaces of the substrate respectively by a physical method or chemical method.

3. The high efficiency thermal conductivity structure of claim 1, wherein the substrate is capable of forming the thermally conductive wires made of a high thermal conductivity material thereon by a physical method or chemical method, and the substrate is made of a material selected from the group consisting of copper, aluminum, silver, carbon, and diamond film.

4. The high efficiency thermal conductivity structure of claim 1, wherein the thermally conductive wires are made of a material of a high thermal conductivity and in a columnar or tubular shape, and the thermally conductive wires are made of a material selected from the group consisting of carbon nanotube, aluminum, copper, and silver.

5. The high efficiency thermal conductivity structure of claim 1, wherein the substrate is configured to be in the shape of a sheet or in any geometric shape.

6. The high efficiency thermal conductivity structure of claim 1, further comprising a heat source and a cooling unit, and the substrate being disposed between the heat source and the cooling unit, and the thermally conductive wire at one of the surfaces of the substrate being coupled to the heat source, the thermally conductive wire at the other surface of the substrate being coupled to the cooling unit.

7. The high efficiency thermal conductivity structure of claim 1, further comprising a heat source, the thermally conductive wire at one of the surfaces of the substrate being coupled to the heat source, and the thermally conductive wire at the other surface of the substrate being exposed to air.

8. The high efficiency thermal conductivity structure of claim 7, wherein the thermally conductive wire at the other surface of the substrate is pressed and formed into a fin-shape.