US20170176117A1

US20170176117A1 - Heat dissipation module

Info

Publication number: US20170176117A1
Application number: US14/981,970
Authority: US
Inventors: Jin-Bao Wu; Wei-Chien Tsai; Hao-Wen Cheng; Ming-Sheng Leu; Jia-Jen Chang; Hsien-Lin Hu
Original assignee: Industrial Technology Research Institute ITRI
Current assignee: Industrial Technology Research Institute ITRI
Priority date: 2015-12-22
Filing date: 2015-12-29
Publication date: 2017-06-22
Also published as: TW201724403A; TWI579987B

Abstract

A heat dissipation module adapted to perform heat dissipation on a heat generating component is provided. The heat dissipation module includes a graphite sheet and an insulating and heat conducting layer. The graphite sheet includes a plurality of through holes, an attaching surface and a heat dissipating surface opposite to the attaching surface, wherein the attaching surface is configured to be attached to the heat generating component. Each of the through holes penetrates the graphite sheet, so the attaching surface and the heat dissipating surface are connected via the through holes. The insulating and heat conducting layer covers the graphite sheet. The insulating and heat conducting layer least covers the attaching surface, the heat dissipating surface and inner walls of the through holes.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 104143069, filed on Dec. 22, 2015. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The present disclosure relates to a heat dissipation module.

Related Art

In recent years, electronic technology, particularly the processing technology in an integrated circuit (IC), has developed very quickly, and thus functions of electronic components are greatly improved. Along with improvements of a processing speed and efficiency of an electronic component, heat generated by the electronic components in operating is also increased. If waste heat cannot be taken away effectively, the electronic components may fail or be unable to reach optimal efficiency. In an electronic device such as a smart phone, a tablet PC or a laptop, etc., the main heat generating components are CPU, chipset on a circuit board and graphics processing unit (GPU), etc. Generally, heat dissipation components such as heat sinks, heat pipes, heat dissipation fins and fans, etc., are usually disposed on the heat source to lower the temperature of the heat source.
Currently, electronic devices develop towards the trend of lightness and thinness. The known heat dissipation components such as heat sinks, heat pipes, heat dissipation fins and fans usually take up significant weight and volume, so it is hard for the electronic devices having the same to meet the requirement of lightness and thinness. Accordingly, it is an important goal for the industry to provide a light heat dissipation component without sacrificing the heat dissipation performance.

SUMMARY

In one of exemplary embodiments, a heat dissipation module configured to perform heat dissipation on a heat generating component is provided. The heat dissipation module includes a graphite sheet and an insulating and heat conducting layer. The graphite sheet includes a plurality of through holes, an attaching surface and a heat dissipating surface, wherein the attaching surface is configured to be attached to the heat generating component. The heat dissipating surface is opposite to the attaching surface, and the through holes penetrate the graphite sheet, so the attaching surface and the heat dissipating surface are connected to each other via the through holes. The insulating and heat conducting layer covers the graphite sheet, wherein the insulating and heat conducting layer at least covers the attaching surface, the heat dissipating surface and inner walls of the through holes.
Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure.

FIG. 1 is a cross-sectional view of a heat dissipation module according to an exemplary embodiment.

FIG. 2 is a schematic view of a heat dissipation module according to an exemplary embodiment.

FIG. 3 is a partial cross-sectional view of a heat dissipation module according to an exemplary embodiment.

FIG. 4 is an X-ray diffraction diagram of an insulating and heat conducting layer according to an exemplary embodiment.

FIG. 5 is a wide spectrum diagram of a surface of an insulating and heat conducting layer according to an exemplary embodiment.

FIG. 6 is a binding energy diagram of a surface of an insulating and heat conducting layer according to an exemplary embodiment.

FIG. 7 is a time temperature transfoimation diagram of an attaching surface and a heat dissipating surface of a known heat dissipation module.

FIG. 8 is a time temperature transformation diagram of an attaching surface and a heat dissipating surface of a heat dissipation module according to an exemplary embodiment.

DESCRIPTION OF THE EMBODIMENTS

The present disclosure will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown.
The terms used herein such as “top,” “bottom,” “front,” “back,” “left,” and “right” are for the purpose of describing directions in the figures only and are not intended to be limiting of the disclosure. Moreover, in the following embodiments, the same or similar reference numbers denote the same or like components.
The disclosure is directed to a heat dissipation module with great heat dissipation efficiency along a vertical axis, and an overall thickness thereof is rather thin.
FIG. 1 is a cross-sectional view of a heat dissipation module according to an exemplary embodiment. FIG. 2 is a schematic view of a heat dissipation module according to an exemplary embodiment. FIG. 3 is a partial cross-sectional view of a heat dissipation module according to an exemplary embodiment. Referring to FIG. 1, FIG. 2 and FIG. 3, a heat dissipation module 100 is configured to perform heat dissipation on a heat generating component 200. In the present embodiment, the heat dissipation module 100 includes a graphite sheet 110 and an insulating and heat conducting layer 120. The graphite sheet 110 includes an attaching surface 112, a heat dissipating surface 114 and a plurality of through holes 116, wherein the attaching surface 112 is configured to be attached to the heat generating component 200. The heat dissipating surface 114 is opposite to the attaching surface 112, and the through holes 116 penetrate the graphite sheet 110, so the attaching surface 112 and the heat dissipating surface 114 are connected to each other via the through holes 116. In one embodiment, the graphite sheet 110 may be a pyrolytic graphite sheet (PGS). The insulating and heat conducting layer 120 covers the graphite sheet 110. In detail, the insulating and heat conducting layer 120 at least covers the attaching surface 112, the heat dissipating surface 114 and inner walls of the through holes 116. In the present embodiment, the thickness of the graphite sheet 110 may substantially range from 50 μm to 1 mm. To be more specific, the thickness of the graphite sheet 110 may substantially range from 50 μm to 55 μm. Certainly, it will be apparent to those skilled in the art that the numbers shown in the present embodiment are merely for illustrations, and the disclosure is not limited thereto.
In the present embodiment, the heat dissipation module 100 may further include an adhesive layer 130 shown in FIG. 1, which is disposed on the attaching surface 112 of the graphite sheet 110, such that the heat dissipation module 100 may be attached to the heat generating component 200 with its own attaching surface 112 through the adhesive layer 130. Moreover, the heat dissipation module 100 may further includes a release tape, which is detachably disposed on a surface of the adhesive layer 130 attaching to the heat generating component 200, so as to temporarily protect the attaching surface of the adhesive layer 130.
Under such arrangement, after the release tape is removed, the heat dissipation module 100 may be attached to the heat generating component 200 with its attaching surface 112 through the adhesive layer 130. For instance, the heat generating component 200 may be a central processing unit (CPU), a chipset or single chip on a circuit board, etc. In the present embodiment, the adhesive layer 130 may be, for example, a pressure sensitive adhesive (PSA). In general, the PSA is an adhesive which forms a bond when pressure is applied to many the adhesive with an object.
The main composition may include rubber, acrylic, silica gel, Polyurethane (PU), etc. Certainly, the present embodiment is merely for illustration, and the disclosure does not limit the types or formations of the heat generating component 200 and the adhesive layers 130.
In detail, the material of the insulating and heat conducting layer 120 includes insulation carbide. Specifically, the insulation carbide includes silicon carbide, which can be formed on the surface of the graphite sheet 110 by chemical vapor deposition (CVD) process under low pressure and high temperature. The molecular formula of the silicon carbide in the insulating and heat conducting layer 120 formed by the process described above is SiCx, and x may substantially range from 0.5 to 1. To be more specific, x may substantially range from 0.55 to 1. It is noted that the range set for the value of x is regarding manufacturing capability. In ideal circumstances, x may be 1. Moreover, composition of the insulating and heat conducting layer 120 may include cubic crystal structure of 3C—SiC. Certainly, the present embodiment is merely for illustration, the disclosure does not limit composition and forming method of the insulating and heat conducting layer 120 as long as it can provide insulation and has high thermal conductivity.
As such, the heat dissipation efficiency of the insulating and heat conducting layer 120 is outstanding, wherein a thermal conductivity of the insulating and heat conducting layer 120 along a vertical axis is substantially greater than or equal to 100 W/m·K, and the vertical axis is parallel to a longitudinal direction of each of the through holes 116. Moreover, the insulating and heat conducting layer 120 comprehensively covers the inner walls of the through holes 116 to connect and cover the attaching surface 112 and heat dissipating surface 114 opposite to each other. Accordingly, the heat dissipation module 100 of the present embodiment may vertically conduct the thermal energy from the attaching surface 112 to the heat dissipating surface 114 through the insulating and heat conducting layer 120. Therefore, the heat dissipation module 100 of the present embodiment not only have great heat dissipation efficiency in horizontal direction (parallel to the direction of the attaching surface 112) owing to the graphite sheet 110, but also enhances the heat dissipation efficiency in vertical direction (longitudinal direction of each through hole 116) by the insulating and heat conducting layer 120 covering the through holes 116.
Furthermore, a resistivity of the insulating and heat conducting layer 120 is substantially greater than or equal to 10⁵Ω·cm, so it has great insulation property. Therefore, owing to the insulating and heat conducting layer 120 covering the graphite sheet 110, the heat dissipation module 100 of the present embodiment not only enhances the thermal conductivity thereof along the vertical direction (the longitudinal direction of the through holes 116), but also can provide insulation effect, such that there is no need to additionally attach an insulation tape such as polyethylene terephthalate (PET) on the heat dissipation module 100, so as to reduce the production cost and the overall thickness of the heat dissipation module 100.
In addition, in the present embodiment, a diameter of each of the through holes 116 may substantially range from 1 μm to 1000 μm, and a thickness of the insulating and heat conducting layer 120 may be substantially greater than or equal to 1 μm, and substantially equal to or smaller than half of the diameter of each of the through holes 116. Namely, the insulating and heat conducting layer 120 at most can completely fill up each of the through holes 116 of the graphite sheet 110. Moreover, a cross section of each of the through holes 116 may be in circular, triangular or rectangular shape. The disclosure does not limit the shapes of the cross sections of the through holes 116 as long as the through holes 116 penetrate the graphite sheet 110 to connect the attaching surface 112 and the heat dissipating surface 114 opposite to each other.
In detail, to faun the insulating and heat conducting layer 120 described above, an apparatus capable of controlling temperature for chemical vapor deposition (CVD) process may be adopted, and halogen containing silane may be adopted as volatile precursor. By applying hydrogen, argon and methane at around 1300° C., the halogen containing silane as precursor is brought into the reaction chamber of the apparatus by argon, so as to diffuse to the surface of the graphite sheet 110. At the time, the graphite sheet 110 is heated to the specific temperature for the process, so the precursor is decomposed into atoms or small molecules such as silicon, carbon, hydrogen, and halogen, etc., by pyrolysis under high temperature to be adsorbed to the surface of the graphite sheet 110, and then is nucleated on the surface of the graphite sheet 110 to form the insulating and heat conducting layer 120 at least covering the attaching surface 112, the heat dissipating surface 114 and the inner walls of the through holes 116 of the graphite sheet 110. In the present embodiment, the diameter of each of the through holes 116 may substantially range from 260 μm to 265 μm, and the thickness of the insulating and heat conducting layer 120 may range from 40 μm to 45 μm. Certainly, the numbers shown in the present embodiment are merely for illustration, the present disclosure does not limit the diameters of the through holes 116 and the thickness of the insulating and heat conducting layer 120. In terms of manufacturing capability, the thickness of the insulating and heat conducting layer 120 formed by CVD process can reach 1000 μm. Namely, the thickness of the insulating and heat conducting layer 120 may range from 1 μm to 1000 μm.
In one embodiment, the insulating and heat conducting layer 120 is formed by CVD process under low pressure and high temperature, so the insulating and heat conducting layer 120 composed of silicon carbide is formed on the graphite sheet 110. To be more specific, in the present embodiment, the insulating and heat conducting layer 120 composed of silicon carbide is formed on the graphite sheet 110 by halogen containing silane, methane, hydrogen, and argon, and the temperature for the CVD process may range from 1000° C. to 1400° C., and the pressure for the CVD process may substantially range from 10 pa to 50000 pa to deposit the insulating and heat conducting layer 120 composed of silicon carbide. The insulating and heat conducting layer 120 formed under such conditions have great insulation property and also have great adhesion and step coverage to the graphite sheet 110. Therefore, the insulating and heat conducting layer 120 can completely cover the surface of the graphite sheet 110, which includes the attaching surface 112, the heat dissipating surface 114 and the inner walls of the through holes 116.
FIG. 4 is an X-ray diffraction diagram of an insulating and heat conducting layer according to an exemplary embodiment. To understand the film structure and the crystal phase of the insulating and heat conducting layer 120 composed of silicon carbide, the present embodiment adopts the analysis of X-ray diffraction (XRD) to obtain the X-ray diffraction diagram shown in FIG. 4. The X-ray diffraction is a technique for non-destructive analysis, which is for detecting properties of crystalline materials, so as to provide analyses of structure, phase, primary crystal orientation and other structural parameters such as an average of granularity, crystallinity, strain and crystal defect, etc. The diffraction peak of X-ray is generated by constructive interference of monochromatic light diffracted at a specific angle through a lattice plane of a film under test, and the intensity of the peak value is determined by the distribution of the atoms in the lattice. It is shown in FIG. 4 that there are 3 diffraction peaks in the spectrum, and the intensity of the diffraction peaks are (111), (220) and (311), respectively. To further compared with Joint. Committee on Powder Diffraction Standards (JCPDS), it is shown that the micro structures of the insulating and heat conducting layer 120 composed of silicon carbide are all crystal structures of 3C—SiC, which are the cubic crystal structures of silicon carbide with 3-layered stacking period (stacking sequence is ABC).
FIG. 5 is a wide spectrum diagram of a surface of an insulating and heat conducting layer according to an exemplary embodiment. FIG. 6 is a binding energy diagram of a surface of an insulating and heat conducting layer according to an exemplary embodiment. To understand the binding type of the insulating and heat conducting layer 120 composed of silicon carbide, in the present embodiment, after cleaning process is performed on the surface of the graphite sheet 100 by Ar⁺, the analysis of X-ray photoelectron spectroscopy (XPS) is applied to obtain the wide spectrum diagram shown in FIG. 5. It is shown in FIG. 5 that the energy spectrum of the insulating and heat conducting layer 120 includes the compositions of carbon and silicon. To be more specific, it is shown in the energy spectrum of XPS in FIG. 6, apart from having the composition of carbon and silicon. Moreover, from composition identification, the insulating and heat conducting layer 120 is composed of SiC_0.55. Certainly, the numbers shown in the present embodiment are merely for illustration. In ideal circumstances, the insulating and heat conducting layer 120 is composed of SiC.
Table 1 shown below illustrates the data of several properties of the insulating and heat conducting layer 120 obtained by analyses in the present embodiment. In detail, ρ represents film density of the insulating and heat conducting layer 120; C_prepresents heat capacity at constant pressure, which means the heat energy absorbed or released by unit mass of the insulating and heat conducting layer 120 as its temperature increases 1° C. or 1K at constant pressure; a represents thermal diffusivity, which means the thermal conductivity divided by volumetric heat capacity; and K represents thermal conductivity, the quantity of heat that passes in unit time through a unit area and length of the insulating and heat conducting layer 120 when its opposite faces differ in unit temperature. It should be noted that the value of K shown herein is the thermal conductivity of the insulating and heat conducting layer 120 along the vertical axis (parallel to the longitudinal direction of the through holes 116). The table shown below clearly indicates that the insulating and heat conducting layer 120 has great property and performance in thermal conductivity.

TABLE 1

Material	ρ (g/cm³)	C_p(J/gK)	α (mm²/s)	K (W/m · K)

SiC	3.17	0.707	57.805	129.571

It is noted that the present embodiment takes the pyrolytic graphite sheet 110 for example, whose thermal conductivity along the horizontal axis (parallel to the attaching surface 112 or heat dissipating surface 114) can reach about 1500 W/m·K. Therefore, with the coverage of the insulating and heat conducting layer 120, the heat dissipation module 100 of the present embodiment enhances its own heat dissipation performance along the vertical axis.
FIG. 7 is a time temperature transformation diagram of an attaching surface and a heat dissipating surface of a known heat dissipation module. FIG. 8 is a time temperature transformation diagram of an attaching surface and a heat dissipating surface of a heat dissipation module according to an exemplary embodiment. It is noted that, in order to proof the thermal conductivity of the heat dissipation module 100 of the disclosure is greater than that of a known heat dissipation module, i.e. the structure of a known graphite sheet attached with an insulation tape, the heat dissipation module 100 shown in FIG. 2 is disposed in a thermal resistance measuring apparatus, and a heating process with 80 W of heating power is performed on the attaching surface 112 to simulate a heating scenario for the attaching surface 112 of the heat dissipation module 100 attached to the heat generating component 200. Then, the temperatures of the attaching surface 112 and the heat dissipating surface 114 of the heat dissipation module 100 are measured. Similarly, the same experiment is also performed to the known heat dissipation module, and the experiment results of the known heat dissipation module and the heat dissipation module 100 in the present embodiment are respectively illustrated in FIG. 7 and FIG. 8, wherein T1 represents the temperature of the attaching surface of the heat dissipation module, and T2 represents the temperature of the heat dissipating surface of the heat dissipation module.
Referring to both FIG. 7 and FIG. 8, it is shown in FIG. 7 that the temperature difference between the temperature T1 of the attaching surface and the temperature T2 of the heat dissipating surface of the known heat dissipation module is about 30.4° C. Accordingly, the thermal resistance of the known heat dissipation module can be calculated by formula of thermal resistance (R=(T1−T2)/Q_out), and is about 0.38° C./W. On the contrary, it is shown in FIG. 8 that the temperature difference between the temperature T1 of the attaching surface 112 and the temperature T2 of the heat dissipating surface 114 of the heat dissipation module 100 is about 8.1° C. Accordingly, the thermal resistance of the heat dissipation module 100 can be calculated by thermal resistance formula (R=(T1−T2)/Q_out), and is about 0.1° C./W. Therefore, the heat dissipation module 100 in the present embodiment can effectively decrease the thermal resistance along the vertical axis, and further improves the thermal conductivity of the heat dissipation module 100 along the vertical axis.
In sum, in the heat dissipation module of the present disclosure, the graphite sheet includes a plurality of through holes, and the insulating and heat conducting layer covers the inner walls of the through holes to connect and cover the attaching surface and the heat dissipating surface of the graphite sheet. Under such disposition, the heat dissipation module of the present disclosure can vertically conduct the heat generated by the heat generating components from the attaching surface to the heat dissipating surface through the insulating and heat conducting layer, so as to solve the issue of poor thermal conductivity of a known graphite sheet along the vertical axis. Therefore, the heat dissipation module of the present disclosure not only has great thermal conductivity along the horizontal axis (parallel to the attaching surface), but also enhances the thermal conductivity of the heat dissipation module along the vertical axis (the longitudinal direction of the through holes) through the insulating and heat conducting layer covering the through holes.
In addition, the insulating and heat conducting layer of the present disclosure also has great insulation effect. Therefore, owing to the insulating and heat conducting layer covering the surface of the graphite sheet, the heat dissipation module of the present disclosure not only enhances the thermal conductivity thereof along the vertical direction, but also can provide insulation effect, such that there is no need to additionally attach an insulation tape such as polyethylene terephthalate (PET) on the heat dissipation module. Accordingly, the present disclosure indeed reduces the production cost of the heat dissipation module and reduces the overall thickness of the heat dissipation module. It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.

Claims

What is claimed is:

1. A heat dissipation module, configured to perform heat dissipation on a heat generating component, the heat dissipation module comprising:

a graphite sheet including a plurality of through holes, an attaching surface and a heat dissipating surface, wherein the attaching surface is configured to be attached to the heat generating component, the heat dissipating surface is opposite to the attaching surface, and the through holes penetrate the graphite sheet, so the attaching surface and the heat dissipating surface are connected to each other via the through holes; and

an insulating and heat conducting layer covering the graphite sheet, wherein the insulating and heat conducting layer at least covers the attaching surface, the heat dissipating surface and inner walls of the through holes.

2. The heat dissipation module as claimed in claim 1, further comprising an adhesive layer disposed on the attaching surface, such that the heat dissipation module is attached to the heat generating component through the adhesive layer.

3. The heat dissipation module as claimed in claim 2, wherein the adhesive layer comprises a pressure sensitive adhesive (PSA).

4. The heat dissipation module as claimed in claim 2, further comprising a release film disposed on a surface of the adhesive layer attaching to the heat generating component.

5. The heat dissipation module as claimed in claim 1, wherein a thermal conductivity of the insulating and heat conducting layer along a vertical axis is substantially greater than or equal to 100 W/m·K.

6. The heat dissipation module as claimed in claim 1, wherein a resistivity of the insulating and heat conducting layer is substantially greater than or equal to 10⁵Ω·cm.

7. The heat dissipation module as claimed in claim 1, wherein material of the insulating and heat conducting layer comprises insulation carbide.

8. The heat dissipation module as claimed in claim 1, wherein composition of the insulating and heat conducting layer comprises SiCx, and x substantially ranges from 0.5 to 1.

9. The heat dissipation module as claimed in claim 1, wherein composition of the insulating and heat conducting layer comprises crystal structure of 3C—SiC.

10. The heat dissipation module as claimed in claim 1, wherein a diameter of each of the through holes substantially ranges from 1 μm to 1000 μm.

11. The heat dissipation module as claimed in claim 1, wherein a diameter of each of the through holes substantially ranges from 260 μm to 265 μm.

12. The heat dissipation module as claimed in claim 1, wherein a thickness of the insulating and heat conducting layer is substantially greater than or equal to 1 μm, and substantially equal to or smaller than half of a diameter of each of the through holes.

13. The heat dissipation module as claimed in claim 1, wherein a thickness of the insulating and heat conducting layer substantially ranges from 40 μm to 45 μm.

14. The heat dissipation module as claimed in claim 1, wherein a thickness of the graphite sheet substantially ranges from 50 μm to 1 mm.

15. The heat dissipation module as claimed in claim 1, wherein a thickness of the graphite sheet substantially ranges from 50 μm to 55 μm.

16. The heat dissipation module as claimed in claim 1, wherein a cross section of each of the through holes is in circular, triangular or rectangular shape.

17. The heat dissipation module as claimed in claim 1, wherein the insulating and heat conducting layer is formed by chemical vapor deposition (CVD) process.

18. The heat dissipation module as claimed in claim 17, wherein temperature for the CVD process substantially ranges from 1000° C. to 1400° C.

19. The heat dissipation module as claimed in claim 17, wherein pressure for the CVD process substantially ranges from 10 pa to 50000 pa.

20. The heat dissipation module as claimed in claim 17, wherein the graphite sheet comprises pyrolytic graphite sheet (PGS).