CN110572993A

CN110572993A - Heat dissipation piece for electronic equipment, preparation method and electronic equipment

Info

Publication number: CN110572993A
Application number: CN201910995546.8A
Authority: CN
Inventors: 李明峰
Original assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Current assignee: Guangdong Oppo Mobile Telecommunications Corp Ltd
Priority date: 2019-10-18
Filing date: 2019-10-18
Publication date: 2019-12-13

Abstract

The application discloses a heat dissipation piece for an electronic device, a preparation method and the electronic device. This heat dissipation member includes: a graphite layer; and the metal layer is positioned on the graphite layer, the surface of the metal layer, which is far away from one side of the graphite layer, is provided with a microstructure, and the emissivity of infrared heat radiation of the heat dissipation piece under the wavelength of 8 microns is higher than 0.6. Therefore, the heat radiating piece can radiate heat outwards while ensuring that the heat is rapidly conducted outwards from the heat source, and the main energy of the heat radiation is not absorbed by the shell, so that the heat radiated by the heat radiating piece can be prevented from being concentrated at the shell, and the problem of local overheating of the shell is relieved.

Description

Heat dissipation piece for electronic equipment, preparation method and electronic equipment

Technical Field

The present application relates to the field of electronics, and in particular, to a heat sink for an electronic device, a method of making, and an electronic device.

Background

Along with the improvement of the performance requirements of users on the electronic equipment, the power consumption of the electronic equipment is gradually increased, and the heat dissipation performance also becomes an important parameter influencing the comprehensive performance of the electronic equipment. The heat dissipation mainly comprises three modes of conduction, convection and heat radiation. Naturally radiating electronic devices mainly use conduction and radiation to solve the overheating problem. Specifically, the main heat generating devices in the electronic devices are generally soaked with a thermal diffusion material (such as copper foil, graphite, graphene, etc.) to lower the temperature of the surface of the heat generating devices, and at the same time, the heat is transferred to one side of the housing in a thermal radiation manner and is transferred to the environment through the housing.

however, heat dissipation members, manufacturing methods, and electronic devices for electronic devices are still in need of improvement.

disclosure of Invention

The present application aims to mitigate or solve at least to some extent at least one of the above mentioned problems.

In one aspect of the present application, a heat sink for an electronic device is presented. This heat dissipation member includes: a graphite layer; and the metal layer is positioned on the graphite layer, the surface of the metal layer, which is far away from one side of the graphite layer, is provided with a microstructure, and the emissivity of infrared heat radiation of the heat dissipation piece under the wavelength of 8 microns is higher than 0.6. Therefore, the heat radiating piece can radiate heat from the heat source to the outside while ensuring that the heat is rapidly conducted to the outside, and the main energy of the heat radiation is not absorbed by the shell, so that the heat radiated by the heat radiating piece can be prevented from being concentrated at the shell, the problem of local overheating of the shell can be solved, and the heat radiating performance of the electronic equipment utilizing the heat radiating piece is improved.

in another aspect of the present application, a method of preparing a heat sink for an electronic device is presented, the method comprising: providing a graphite layer; forming a metal layer on the graphite layer, the metal layer having a microstructure on a surface on a side remote from the graphite layer, the method comprising controlling a shape of the microstructure so that an emissivity of infrared heat radiation of the heat sink at a wavelength of 8 μm or less is higher than 0.6. Therefore, the heat dissipation piece can be obtained simply and conveniently, the heat dissipation piece can radiate heat outwards while ensuring that the heat is rapidly conducted outwards from the heat source, and the main energy of the heat radiation is not absorbed by the shell, so that the heat radiated out by the heat dissipation piece can be prevented from being concentrated at the shell, the problem of local overheating of the shell can be relieved, and the heat dissipation performance of the electronic equipment utilizing the heat dissipation piece is improved.

In yet another aspect of the present invention, the present invention provides an electronic device including: a housing defining an accommodating space; the heat dissipation piece is located in the accommodating space, and one side of the graphite layer of the heat dissipation piece is close to the heat source in the electronic equipment. Therefore, the electronic equipment has better heat dissipation performance, and can relieve or even solve the phenomenon that the shell is locally overheated in the use process.

Drawings

The above and/or additional aspects and advantages of the present application will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

fig. 1 shows a schematic view of a heat sink according to an example of the present application;

FIG. 2 shows an enlarged schematic view of a portion of the area of FIG. 1;

Fig. 3 shows a schematic partial structure of a heat sink according to an example of the present application;

Fig. 4 shows a partial structural schematic view of a heat sink according to another example of the present application;

Fig. 5 shows a schematic flow diagram of a method of making a heat sink according to an example of the present application;

FIG. 6 shows a schematic structural diagram of an electronic device according to an example of the present application;

FIG. 7 shows a schematic diagram of a partial structure of an electronic device according to an example of the present application;

FIG. 8 shows test results for infrared reflectivity of an enclosure according to an example of the present application;

Fig. 9 shows radiation patterns of an example and a comparative example according to the present application.

Description of reference numerals:

1000: a heat sink; 100: a graphite layer; 200: a metal layer; 21: a microcavity; 210: a copper sub-layer; 300: a photosensitive resin; 310: a microcavity mask; 320: exposing a mask; 2000: a housing; 3000: a heat source.

Detailed Description

reference will now be made in detail to embodiments of the present application, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are exemplary only for the purpose of explaining the present application and are not to be construed as limiting the present application.

in one aspect of the present application, a heat sink for an electronic device is presented. Referring to fig. 1, the heat sink 1000 includes: graphite layer 100 and metal layer 200. The metal layer 200 is located on the graphite layer 100 and has a microstructure on the surface on the side remote from the graphite layer 100. The emissivity of the infrared heat radiation of heat sink 1000 is higher than 0.6 at wavelengths below 8 microns. Therefore, the heat radiating piece can radiate heat from the heat source to the outside while ensuring that the heat is rapidly conducted to the outside, and the main energy of the heat radiation is not absorbed by the shell, so that the heat radiated by the heat radiating piece can be prevented from being concentrated at the shell, the problem of local overheating of the shell can be solved, and the heat radiating performance of the electronic equipment utilizing the heat radiating piece is improved.

For ease of understanding, the following first briefly explains the principle by which the heat sink according to the present application can achieve the above-described advantageous effects:

At present, in electronic equipment, particularly electronic equipment taking materials such as glass, composite plates and the like as shells, a phenomenon that local areas of shells are easily overheated in the using process generally exists. The inventors have found that this is mainly due to the inadequacy of the material and structure of the heat sink. Specifically, the method comprises the following steps: the thermal infrared radiation is electromagnetic waves with the wavelength range of 3-15 mu m, and the frequency bands and the intensities of the electromagnetic waves absorbed by different shell materials are different. As mentioned above, the heat dissipation of the electronic device is realized by transferring heat to one side of the housing in a thermal radiation manner and finally transferring the heat to the environment, so that when the housing is formed by a glass or polymer plate with a relatively low thermal conductivity (lower than the heat dissipation member), the heat transferred to the housing by the thermal radiation cannot be rapidly transferred to the environment, which causes a local overheating phenomenon of the housing portion, and further affects the user experience, and reduces the service life of the housing. However, the absorption wavelength of the main heat radiation of the case made of materials such as glass and polymer is about 8 μm, so if most of the heat radiated by the heat sink is absorbed by the materials such as glass, which have poor heat dissipation performance, the case is easily overheated locally (near the heat source or the heat sink).

The inventor finds that, if a good heat dissipation effect is to be obtained, the heat dissipation member needs to have a high thermal conductivity first, so that the hot spot can be eliminated quickly. Secondly, it is necessary to adjust the thermal emissivity (or so-called emissivity) of the heat dissipation element to ensure that the heat mainly in the thermal radiation emitted by the heat dissipation element is not absorbed by the housing, in particular by the housing formed of a material having a slightly lower thermal dissipation property, but can be transmitted through the housing to the environment. Therefore, the graphite layer 100 with high heat conductivity coefficient is adopted, and hot spots are eliminated quickly. Meanwhile, the microstructure of the metal layer 200 far away from the graphite layer 100 is utilized to realize the selective adjustment of the thermal radiation wavelength, so that the thermal radiation wavelength of the heat radiating element is low corresponding to the thermal radiation rate of the shell, the heat is radiated to the outside while the rapid heat conduction is realized, and a good cooling effect is obtained on the surface of the heat source and the shell.

according to some examples of the present application, the material of the graphite layer 100 is not particularly limited. As long as the heat of the heat source can be conducted quickly. For example, the thermal conductivity of the graphite layer 100 may be selected to be greater than 1000W/k.m. Therefore, the cooling effect of the heat dissipation part can be improved. The graphite layer 100 may be formed by using synthetic graphite, and the thickness of the graphite layer 100 may be 15 to 150 micrometers, specifically 17 micrometers, 25 micrometers, 32 micrometers, 40 micrometers, 70 micrometers, or 70 to 140 micrometers, for example, 75 to 120 micrometers, 80 to 100 micrometers, and the like, and the thickness of the graphite layer 100 may fall within a range formed by any two endpoints of the above values.

According to some examples of the present application, the specific structure of the microstructure is not particularly limited as long as it is periodically arranged with a function of adjusting the selectivity of the heat radiation wavelength of the heat radiating member. Namely: the center wavelength of the heat radiation of heat sink 1000 (the wavelength range in which the peak of higher energy in the heat radiation is located) can be adjusted to be outside the wavelength range that the housing can absorb. Specifically, the major infrared radiation absorption wavelengths of most glass and composite sheets (e.g., based on PMMA, PA, PC, etc.) are centered around 8 microns. So long as the microstructures can adjust the center wavelength of the heat radiation of the heat sink 1000 to 8 μm or less. Specifically, the emissivity of infrared heat radiation of heat sink 1000 at a wavelength of 8 μm or less may be adjusted to be higher than 0.6. Therefore, the main infrared heat radiation of the heat sink 1000 can be concentrated below 8 microns, and further not absorbed by the housing with poor heat dissipation performance, but can be directly radiated to the environment through the housing to realize heat dissipation.

It should be particularly noted that the heat sink 1000 according to the present invention is not only suitable for electronic devices using glass, composite board, etc. as the housing, but also can be used to improve heat dissipation performance when using metal material as the housing: due to the good heat conduction performance of the heat dissipation member, heat at a hot spot can be rapidly transferred outwards. Materials such as metal have better heat dissipation performance than glass or polymer materials, so that when the heat sink 1000 radiates the hot spot capability outwards, the heat is prevented from being absorbed by the material with poorer heat dissipation performance.

According to some specific examples of the present application, the microstructure may be a plurality of micro-cavities 21 arranged periodically, i.e., a plurality of regularly arranged pits extending from one side of the metal layer to one side of the graphite layer. The depth of the microcavities 21 is less than the thickness of the metal layer 200, i.e.: the microcavity 21 does not extend through the metal layer 200. By designing the size and arrangement of the micro-cavities 21, the heat radiation wavelength of the heat sink 1000 can be adjusted. Specifically, referring to fig. 2 (an enlarged view of a dotted line region in fig. 1), the opening ratio of the microstructure may be 0.4 to 0.7, that is, the microcavity period Δ and the microcavity width a satisfy a/Δ (0.4 to 0.7), and the aspect ratio of the microcavity may be 2 to 4, that is, the microcavity width a and the microcavity depth d satisfy d/a (2 to 4). The microcavity period Δ is the sum of the width a of the microcavity and the distance between two adjacent microcavities 21. The inventor finds that the size of the opening ratio influences the radiation wavelength of the heat dissipation element, and the opening ratio is controlled to be 0.4-0.7, so that the central wavelength of the heat radiation of the heat dissipation element can be ensured to be less than 8 microns, such as less than 6 microns. The aspect ratio of the microcavity affects the intensity of the radiation, and too small an aspect ratio makes it difficult to maintain a large intensity of the radiation at the center wavelength, and thus heat cannot be efficiently transferred out by means of thermal radiation. If the aspect ratio is too large, it is difficult to realize the aspect ratio in terms of process, and the cost for manufacturing the heat sink 1000 is greatly increased. When the opening ratio and the aspect ratio are within the above ranges, the microstructure can adjust the strong radiation wavelength of the heat sink 1000 to 8 micrometers or less, even to 6 micrometers or less, and maintain the radiation intensity of the partial heat radiation to be greater than 0.6. According to some examples of the present application, the microstructures may simultaneously modulate the infrared thermal radiation of the heat spreading member to an emissivity below 0.45 at wavelengths above 8 microns. That is, the microstructure can make the infrared radiation of the heat sink have a high emissivity under a wavelength of 8 microns, that is, the main energy of the thermal radiation is concentrated under a wavelength of 8 microns, and at the same time, the emissivity is low in a waveband (8 microns and above) which is easily absorbed by materials such as glass and polymers, that is, the thermal radiation energy in the waveband which can be absorbed by the glass and polymers is low. Thereby, the heat dissipation performance of the heat sink 1000 can be further improved.

Specifically, the depth d of the microcavity may be 5 to 15 micrometers, the microcavity 21 does not penetrate through the metal layer 200, and the distance from the surface of the metal layer 200 on the side close to the graphite layer 100 to the bottom of the microcavity 21 may be 1 to 5 micrometers. The plurality of micro-cavities 21 may be of uniform size, i.e., the depth d and width a of the plurality of micro-cavities 21 are all equal. The micro-cavity 21 may extend in a direction perpendicular to the plane of the graphite layer 100, and the cross-section of the micro-cavity 21 along the plane of the graphite layer 100 is rectangular, oval or circular. For example, referring to fig. 3 and 4, the micro-cavities 21 of the metal layer 200 may be all rectangular or all circular.

According to an example of the present application, the metal layer 200 may be formed of a metal having superior heat dissipation performance. Specifically, the material forming the metal layer 200 may include copper. More specifically, the metal layer 200 may be formed of copper. In order to further improve the heat dissipation performance of the heat sink 1000 and enhance the bonding between the metal layer 200 and the graphite layer 100, a transition metal layer may be further included between the graphite layer 100 and the metal layer 200. The transition metal layer may include at least one of Ti and Cr, and the transition metal layer may have a thickness of less than 100 nm. Therefore, the graphite layer 100 and the metal layer 200 can be bonded more firmly, and the service life of the heat sink 1000 can be prolonged.

In another aspect of the present application, a method of making a heat sink for an electronic device is presented. The heat sink prepared by this method may have all of the features of the heat sink described previously. According to some examples of the present application, the method may include the steps of providing a graphite layer and forming a metal layer on the graphite layer. Wherein the metal layer has a microstructure on a surface thereof remote from the graphite layer, the method comprising controlling the shape of the microstructure so that the emissivity of infrared thermal radiation of the heat sink at wavelengths below 8 microns is higher than 0.6. Therefore, the heat dissipation piece can be obtained simply and conveniently, the heat dissipation piece can radiate heat outwards while ensuring that the heat is rapidly conducted outwards from the heat source, and the main energy of the heat radiation is not absorbed by the shell, so that the heat radiated out by the heat dissipation piece can be prevented from being concentrated at the shell, the problem of local overheating of the shell can be relieved, and the heat dissipation performance of the electronic equipment utilizing the heat dissipation piece is improved.

According to some examples of the present application, the graphite layer may be formed of synthetic graphite, and those skilled in the art may select an appropriate synthetic graphite to form the graphite layer. In particular, the thermal conductivity of the graphite layer may be greater than 1000W/k.m. The graphite layer may have a thickness of 15-150 microns. The thickness of the graphite layer has been described in detail above and will not be described in detail. Therefore, the heat dissipation piece prepared by the method can be provided with good heat conductivity, so that the hot spot can be eliminated quickly.

according to some examples of the application, forming the metal layer may specifically comprise the steps of sputtering a metal material, and forming a microstructure on a side of the metal material remote from the graphite layer. Specifically, referring to (a) and (b) in fig. 5, a copper sub-layer 210 may be first formed on the graphite layer 100 by vacuum sputtering a metallic material, for example, sputtering Cu. The thickness of the copper sub-layer 210 may be 1 to 5 μm.

Subsequently, referring to (c) and (d) in fig. 5, a photosensitive resin 300 may be coated on the side of the copper sub-layer 210 away from the graphite layer 100. In this step, the thickness of the photosensitive resin can be made to coincide with the depth d of the microcavity to be formed. In other words, the photosensitive resin 300 coated in this step may serve as a template when the micro-cavities are subsequently formed, and thus the thickness of the micro-cavities finally formed may be controlled by controlling the thickness of the photosensitive resin 300. Subsequently, a predetermined region of the photosensitive resin 300 may be subjected to light irradiation treatment, and the photosensitive resin 300 at the predetermined region is removed to form the microcavity mask 310. Specifically, the light-irradiated region may be controlled by the exposure mask 320, so that a specific region of the photosensitive resin 300 is irradiated with light and removed. In fig. 5, only one mode of exposure of the photosensitive resin 300 is shown, and when a different type of photosensitive resin is used, the photosensitive resin in the irradiated portion may be left and the portion not irradiated may be removed. In general, in this step, a microcavity mask 310 is formed by exposing a photosensitive resin to light, leaving the photosensitive resin 300 with a certain thickness at the locations where microcavities are to be formed, exposing the copper sub-layer 210 at the locations where microcavities are not to be formed.

subsequently, referring to (e) and (f) of fig. 5, an electroplating process may be performed on the side of the copper sub-layer having the microcavity mask to deposit metallic copper at locations in the copper sub-layer not covered by the microcavity mask to fill the gap between the copper sub-layer and the microcavity mask with the electroplated metallic copper. After the microcavity mask is removed, a recess extending toward one side of the graphite layer 100 can be formed at the position of the microcavity mask, and then a plurality of periodically arranged microcavities 21 can be formed, thereby forming the microstructure. The detailed description of the specific structure of the microstructure is not repeated herein. For example, the opening ratio of the microstructure may be 0.4 to 0.7, that is, the microcavity period Δ and the microcavity width a satisfy a/Δ ═ 0.4 to 0.7, and the aspect ratio of the microcavity may be 2 to 4, that is, the microcavity width a and the microcavity depth d satisfy d/a ═ 2 to 4. Similarly, the emissivity of the infrared heat radiation of the heat sink at a wavelength of 8 μm or more can be adjusted to be lower than 0.45 by controlling the opening ratio and aspect ratio of the microstructure.

The microstructure formed by the method can more accurately control the specific appearance of the microstructure. Specifically, the microcavity obtained by the above method is formed after removing the microcavity mask 310, and thus, the etching precision can be higher compared to the cavity formed by etching with the etching liquid or the etching gas. In addition, the method can also avoid that the thickness of the copper layer at different positions cannot be controlled more accurately due to the fact that the copper layer is deposited too thick at one time.

According to some examples of the present application, in order to improve the bonding force between the graphite layer and the metal layer, the method further includes a step of performing a plasma activation treatment on the graphite layer in advance before forming the metal layer. It will be understood by those skilled in the art that the graphite layer is composed of six-membered carbon rings having a conjugated structure, and thus has good electron transporting ability and thermal conductivity. However, the structure is not beneficial to improving the bonding between the metal and the carbon material, so that before the metal layer is formed, the surface of the graphite layer on the side where the metal layer is required to be formed can be activated by using plasma, and on the premise of not influencing the whole heat-conducting property of the graphite layer, the surface of the graphite layer is activated, so that the bonding force between the metal and the carbon is improved.

according to other examples of the present application, a transition metal layer may be formed on the graphite layer surface in advance between the formation of the metal layers. Specifically, the transition metal layer may include at least one of Ti and Cr, and the transition metal layer may have a thickness of less than 100 nm. For example, a transition metal layer of Ti or Cr may be formed by vacuum sputtering. According to some specific examples of the present application, the transition metal layer may also be formed after the plasma activation treatment.

In yet another aspect of the present invention, an electronic device is presented. Referring to fig. 6, the electronic apparatus includes a housing 2000, and the housing 2000 defines an accommodating space. The heat sink (not shown) is located inside the accommodating space, and the graphite layer side of the heat sink is disposed close to the heat source inside the electronic device. Therefore, the electronic equipment has better heat dissipation performance, and can relieve or even solve the phenomenon that the shell is locally overheated in the use process.

specifically, referring to fig. 7, the case 2000 may be formed of at least one of glass and a polymer material. For example, the heat source 3000 is located in the receiving space defined by the case 2000, and the side of the heat sink 1000 having the graphite layer may be in contact with the heat source 3000. Thus, the heat of the heat source 3000 is quickly transferred and radiated outward (toward the housing 2000 side) by heat radiation. As described above, since the metal layer side of the heat sink 1000 has the microstructure, the central wavelength of the radiation can be controlled to be a wavelength at which the housing absorbs weakly, so that it can be ensured that the main heat is not absorbed by the housing 2000, but is transmitted to the environment through the housing 2000. Thus, rapid heat dissipation of the electronic device can be achieved, while alleviating or even avoiding the problem of local overheating of the housing 2000 at the heat source 3000.

The specific type of the electronic device described in the present application is not particularly limited, and may be, for example, a mobile phone, a smart watch, a palm computer, or a notebook computer. The electronic device may be any of various types of computer system devices that are mobile or portable and perform wireless communication. In particular, the electronic device may be a mobile or smart phone (e.g., an iPhone (TM) based phone), a Portable gaming device (e.g., Nintendo DS (TM), PlayStation Portable (TM), Gameboy Advance (TM), iPhone (TM)), a laptop, a PDA, a Portable internet device, a music player, and a data storage device, other handheld devices, and a head-mounted device such as a watch, an in-ear headphone, a pendant, a headset, etc., and other wearable devices (e.g., a head-mounted device (HMD) such as an electronic necklace, an electronic garment, an electronic bracelet, an electronic tattoo, or a smart watch).

The electronic device may also be any of a number of electronic devices including, but not limited to, cellular phones, smart phones, other wireless communication devices, personal digital assistants, audio players, other media players, music recorders, video recorders, cameras, other media recorders, radios, medical devices, vehicle transportation equipment, calculators, programmable remote controllers, pagers, laptop computers, desktop computers, printers, netbook computers, Personal Digital Assistants (PDAs), Portable Multimedia Players (PMPs), moving picture experts group (MPEG-1 or MPEG-2) audio layer 3(MP3) players, portable medical devices, and digital cameras and combinations thereof.

In some cases, the electronic device may perform a variety of functions (e.g., playing music, displaying videos, storing pictures, and receiving and sending telephone calls). If desired, the electronic device may be a portable device such as a cellular telephone, media player, other handheld device, wristwatch device, pendant device, earpiece device, or other compact portable device.

The present application is described below by way of specific examples, and those skilled in the art will appreciate that the following specific examples are for illustrative purposes only and do not limit the scope of the present application in any way. In addition, in the following examples, materials and equipment used are commercially available unless otherwise specified. If in the examples that follow, specific processing conditions and processing methods are not explicitly described, processing may be performed using conditions and methods known in the art. The thermal conductivity was tested using german wok-resistant (LFA 467).

Example 1

The thickness of the graphite layer is 40 microns, and the thermal conductivity is 1100W/k. The metal layer is Cu, the depth of the microcavity is 10 microns, the opening ratio a/delta of the microcavity is 0.6, and the aspect ratio d/a of the microcavity is 3.3.

Example 2

the thickness of the graphite is 40 microns, and the thermal conductivity is 1100W/k. The metal layer is Cu, the depth of the micro-cavity is 15 microns, the opening ratio a/delta of the micro-cavity is 0.8, and the aspect ratio d/a of the micro-cavity is 2.5.

example 3

The thickness of the graphite is 40 microns, and the thermal conductivity is 1100W/k. The metal layer is Cu, the depth of the micro-cavity is 7 microns, the opening ratio a/delta of the micro-cavity is 0.3, and the aspect ratio d/a of the micro-cavity is 1.8.

Comparative example

the thickness of the graphite sheet is 60 microns, and the heat conductivity coefficient is 1100W/k.

To illustrate the heat dissipation performance of the heat sink obtained in the above example, first, the infrared reflectance of the case made of glass or the like is tested. The shell comprises glass and high polymer materials such as acrylic ink, epoxy ink, PE foam and the like adhered on the surface of the glass. The ir reflectance of the inside and outside of the housing (measured using fourier transform infrared spectroscopy (FTIR)) was measured and the results are shown in fig. 8, where the ir reflectance of the inside and outside of the housing is substantially uniform, with the major peaks centered around 8.5 microns, i.e. the ir reflectance around 8.5 microns is low, where the housing absorbs high ir radiation. The heat sink obtained in example 1 and the comparative example were tested for emissivity using a hemispherical spectral emissivity tester, and the emissivity of the heat sink of example 1 was very low (<0.1) above 8 microns as viewed from the emissivity map (see fig. 9), i.e., the heat sink of example 1 was able to effectively isolate the heat from transferring outward, thereby reducing the temperature of the housing. The average emissivity value below 8 microns is higher than 0.6, namely, the heat source radiates heat through the wavelength region, so that the temperature of the heat source is reduced. Meanwhile, the material of the shell with the wave band below 6 microns has low absorptivity (high reflectivity), namely, the temperature of the shell is favorably reduced. By comparison, the radiation pattern of the heat sink of the comparative example is significantly higher than that of example 1 at 6-8 microns. The heat dissipation effects of the heat sinks of examples 1-3 and comparative example were tested using a heat source test of the same power (1W). The heat dissipation piece is fixed on the heat source, the outer side of the heat dissipation piece is provided with a shell, and the temperature of the heat source and the temperature of the shell are respectively tested after the temperature reaches a stable state. The heat dissipation effect test results are shown in table 1 below:

TABLE 1

as can be seen from table 1 above, the heat source temperature was reduced by 0.7 and the jacket temperature was reduced by 1.3 in example 1, compared with the graphite sheet having a slightly larger thickness. Compared with the comparative example, in the example 2 with smaller cavity height, the temperature of the heat source is reduced by 0.6 degrees, and the temperature of the shell is reduced by 1.0 degree. Compared with the comparative example, in the example 3 with a larger cavity height, the temperature of the heat source is reduced by 1.0 degree, and the temperature of the shell is reduced by 0.7 degree.

In the description of the present application, the terms "upper", "lower", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present application but do not require that the present application must be constructed and operated in a specific orientation, and thus, cannot be construed as limiting the present application.

In the description herein, references to the description of "one embodiment," "another embodiment," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Although embodiments of the present application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present application, and that variations, modifications, substitutions and alterations may be made to the above embodiments by those of ordinary skill in the art within the scope of the present application.

Claims

1. A heat sink for an electronic device, comprising:

A graphite layer; and

A metal layer which is located on the graphite layer and has a microstructure on a surface of a side remote from the graphite layer,

The emissivity of the infrared heat radiation of the heat sink is higher than 0.6 at wavelengths below 8 microns.

2. the heat sink of claim 1, wherein the heat sink has an emissivity of infrared thermal radiation below 0.45 at wavelengths above 8 microns.

3. the heat sink of claim 1, wherein the graphite layers have a thermal conductivity greater than 1000W/k.m.

4. The heat sink of claim 3, wherein the graphite layers have a thickness of 15-150 microns.

5. the heat sink of claim 1, wherein the microstructure is a plurality of microcavities arranged periodically.

6. The heat sink of claim 5, wherein the micro-structures have a microcavity period Δ and a microcavity width a satisfying: a/delta is (0.4 to 0.7),

The width a and the depth d of the microcavity satisfy the following conditions: d/a is (2-4).

7. the heat sink of claim 6, wherein the depth d of the microcavity is 5-15 microns, the microcavity does not extend through the metal layer, and the metal layer is spaced from the surface on the side adjacent to the graphite layer to the bottom of the microcavity by a distance of 1-5 microns.

8. The heat sink of claim 5, wherein the metal layer comprises copper,

optionally, the microcavity has a rectangular, elliptical or circular cross-section along the plane of the graphite layer.

9. the heat sink of claim 8, further comprising a transition metal layer between said graphite layer and said metal layer, said transition metal layer comprising at least one of Ti and Cr,

Optionally, the transition metal layer has a thickness of less than 100 nanometers.

10. a method of making a heat sink for an electronic device, comprising:

Providing a graphite layer;

Forming a metal layer on the graphite layer, the metal layer having a microstructure on a surface on a side remote from the graphite layer,

the method comprises controlling the shape of the microstructures such that the emissivity of the infrared thermal radiation of the heat sink is higher than 0.6 at wavelengths below 8 microns.

11. The method of claim 10, wherein the graphite layers are formed from synthetic graphite, the graphite layers having a thermal conductivity greater than 1000W/k.m;

Optionally, the graphite layer has a thickness of 15 to 150 microns;

Optionally, the heat sink has an emissivity of infrared thermal radiation below 0.45 at wavelengths above 8 microns.

12. the method of claim 10, wherein forming the metal layer comprises:

Forming a plurality of micro-cavities which are periodically arranged on the surface of the metal material far away from the graphite layer by sputtering the metal material on the graphite layer in a vacuum manner to form the micro-structure,

And the microcavity period delta and the microcavity width a of the microstructure satisfy the following conditions: a/delta is (0.4 to 0.7),

13. the method of claim 12, wherein forming the metal layer comprises:

forming a copper sub-layer on the graphite layer through vacuum sputtering, wherein the thickness of the copper sub-layer is 1-5 microns;

coating photosensitive resin on one side of the copper sub-layer, which is far away from the graphite layer, and enabling the thickness of the photosensitive resin to be consistent with the depth d of the micro-cavity to be formed;

performing light irradiation treatment on a preset area of the photosensitive resin, and removing the photosensitive resin at the preset area to form a microcavity mask;

Performing an electroplating process on the side of the copper sub-layer having the microcavity mask to deposit metallic copper in the copper sub-layer at locations not covered by the microcavity mask;

And removing the microcavity mask to form the microstructure.

14. The method of claim 10, further comprising at least one of:

performing plasma activation treatment on the graphite layer in advance between the formation of the metal layers; and

And forming a transition metal layer on the surface of the graphite layer between the metal layers, wherein the transition metal layer comprises at least one of Ti and Cr, and the thickness of the transition metal layer is less than 100 nanometers.

15. An electronic device, comprising:

a housing defining an accommodating space;

the heat sink of any of claims 1-9, the heat sink being located inside the accommodation space with the graphite layer side of the heat sink being disposed proximate to a heat source inside the electronic device.

16. The electronic device of claim 15, wherein the housing is formed from at least one of glass and a polymer material.