CN112126928B

CN112126928B - Method for preparing heat pipe by vapor deposition

Info

Publication number: CN112126928B
Application number: CN202010948931.XA
Authority: CN
Inventors: 朱艳杰; 朱胜利; 王宏华
Original assignee: Anhui Dequan New Material Technology Co ltd
Current assignee: Anhui Dequan New Material Technology Co ltd
Priority date: 2020-09-10
Filing date: 2020-09-10
Publication date: 2023-06-02
Anticipated expiration: 2040-09-10
Also published as: CN112126928A

Abstract

The invention relates to the field of heat pipes, in particular to a method for preparing a heat pipe by vapor deposition. The method comprises the following steps: preparing a mixed metal deposition layer on the inner surface of the heat pipe by vapor deposition; performing heat treatment on the heat pipe, and sintering the mixed metal deposition layer on the inner wall of the heat pipe to form a mixed metal layer; depositing graphene on the surface of the mixed metal layer by adopting a vapor deposition mode again to form a graphene layer; and pre-oxidizing the graphene layer to obtain the heat pipe. The invention can effectively improve the limit heat transfer power of the heat pipe to 535W/cm ² The above; when heat transfer and heat dissipation are carried out at the same environmental temperature, the superheat degree of the heat pipe can be obviously reduced; the heat pipe has good heat transfer efficiency.

Description

Method for preparing heat pipe by vapor deposition

Technical Field

The invention relates to the field of heat pipes, in particular to a method for preparing a heat pipe by vapor deposition.

Background

In recent years, with the development of intellectualization and miniaturization of electronic devices, the integration of electronic components in a small smiling space causes serious high heat flux problem to the electronic devices, namely, extremely large heat dissipation problem is generated, and more than 50% of electronic device failures are caused by high temperature problem according to statistics, so that the working performance and stability of the electronic devices are affected, and the electronic devices become updated elbows, so that the development of the electronic devices is restricted.

Naturally convection cooling is obviously not suitable for heat dissipation of electronic packaging products, and limit dissipation of air forced convectionThe heat flux density is about 100W/cm ² The heat flux density of the existing electronic equipment is generally 60-100W/cm ² About, even part of the water can reach 500W/cm ² Therefore, the air forced convection cannot meet the heat dissipation requirement of the existing electronic equipment. The heat pipe is used as a heat transfer element for gas-liquid phase change, has the advantages of high heat conductivity, good temperature uniformity, high reliability, no need of extra energy driving and the like, is a choice with very outstanding effect in the heat dissipation technical scheme, and can form a large-scale standardized heat design scheme. Heat pipes are typically composed of three parts: the device comprises a tube shell, an internal flowing working medium and a capillary wick structure.

However, the existing heat pipe is also provided with an ultrathin micro heat pipe with the thickness of generally less than or equal to 2mm, the main difference between the ultrathin micro heat pipe and the conventional heat pipe is that the heat transfer performance of the micro heat pipe is obviously reduced under the condition of small thickness, and the influence of the process parameters on the performance of the heat pipe is very great, including parameters such as the type of the liquid suction core, the arrangement of the liquid suction core, the space distribution of the liquid suction core and a steam cavity, the liquid filling amount and the like. Meanwhile, the heat transfer mechanism of the ultrathin heat pipe is better and more complex, and the heat transfer limit is not necessarily limited to the common capillary limit.

Currently, many researchers have attempted to improve the heat transfer performance of ultra-thin micro heat pipes. Such as Weibel J A, kousalya A S, fisher T S, et al Charabacteria and nanostructured enhancement of boiling incipience in capillary-fed, ultra-thin sintered powder wicks [ C]//IEEE Intersociety Conference on Thermal&Thermomechanical Phenomena in Electronic systems IEEE 2012, 2012 discloses a solution showing that sintered copper powder wicks can withstand up to 437W/cm at 23 ℃ superheat ² Meanwhile, the heat flux density of the carbon nano tube coating can effectively reduce the superheat degree and increase the heat transfer capacity. However, the ultimate heat transfer power thereof remains to be improved.

Disclosure of Invention

The invention provides a method for preparing a heat pipe by vapor deposition, which aims to solve the problems that the limit heat transfer power of the existing ultrathin micro heat pipe is generally low, the existing large amount of liquid suction cores are poor in improvement scheme or improvement effect, the cost is too high, or the ultrathin micro heat pipe is inapplicable.

The invention aims at:

1. the limit heat transfer power of the heat pipe is improved;

2. the superheat degree of the heat pipe can be effectively reduced;

3. and the heat transfer efficiency of the heat pipe is improved.

In order to achieve the above purpose, the present invention adopts the following technical scheme.

A method for preparing a heat pipe by vapor deposition,

the method comprises the following steps:

1) Preparing a mixed metal deposition layer on the inner surface of the heat pipe by vapor deposition;

2) Performing heat treatment on the heat pipe, and sintering the mixed metal deposition layer on the inner wall of the heat pipe to form a mixed metal layer;

3) Depositing graphene on the surface of the mixed metal layer by adopting a vapor deposition mode again to form a graphene layer;

4) And pre-oxidizing the graphene layer to obtain the heat pipe.

According to the technical scheme, the mixed metal deposition layer is firstly deposited and prepared on the inner wall of the heat pipe, the mixed metal layer is formed after heat treatment, the mixed metal layer plays a role in promoting and guiding the deposition of graphene so as to realize the preparation of multi-layer graphene, and finally, the graphene layer is subjected to pre-oxidation treatment, so that the hydrophilicity and specific surface area of the graphene are improved, the ultimate heat transfer power of the whole heat pipe is improved, and the superheat degree is reduced.

As a preferred alternative to this,

step 1), the mixed metal deposition layer contains copper and nickel;

the content of nickel in the mixed metal deposition layer is 58-66.5 wt%, and the balance is copper and unavoidable impurities.

Copper and nickel can cooperate with each other, wherein copper can effectively promote the formation and growth of single-layer graphene, and nickel can promote the growth of multi-layer graphene. The growth mechanism of the graphene mainly comprises surface adsorption, copper is usually used as a main dominant element, carbon is difficult to weld in a large amount in nickel, the growth of the graphene is closely related to the mass fraction of copper elements in the alloy substrate, and the proper increase of the mass fraction of copper elements is beneficial to accelerating the growth of the graphene.

As a preferred alternative to this,

the vapor deposition in step 1) is vacuum sputtering.

The vacuum sputtering is a common physical vapor deposition method, and the technical scheme of the invention adopts a vacuum sputtering mode to prepare the mixed metal deposition layer so as to realize the preparation of the multi-metal composite plating layer.

As a preferred alternative to this,

the vacuum sputtering parameters are as follows:

setting the magnetic control target power at 40-120W and background vacuum degree at 3.0X10 ^-4 ～5.0×10 ^-4 Pa, argon flow is 15-20 mL/min, and pressure is 1.0-1.5 Pa.

The mixed metal deposition layer prepared under the parameter condition has good structural stability, is not easy to fall off and other problems, has higher uniformity and has good promotion effect on the subsequent graphene deposition preparation.

As a preferred alternative to this,

the vacuum sputtering includes three stages of copper sputtering, copper nickel sputtering and nickel sputtering;

the copper sputtering process adopts copper metal as a target material for sputtering, and the power of the copper target is 40-45W;

sputtering copper nickel by adopting copper nickel alloy as a target material, wherein the target power is 80-85W;

the nickel sputtering process adopts nickel metal as a target material for sputtering, and the power of the nickel target is 115-120W.

Under the condition, the prepared mixed metal deposition layer can form a three-layer composite structure of copper/copper nickel/nickel under the condition of preliminary deposition formation, a double-distribution gradient of copper elements and nickel elements is formed, the copper element concentration of the inner layer is higher, the innermost layer is basically pure copper, the concentration of the nickel element is higher towards the outer layer, and the concentration of the copper element is reduced. According to the research, in the composite structure, graphene can be used for rapidly and effectively forming single-layer graphene, and further growing to form ordered multi-layer graphene, so that the specific surface area of the wick on the inner wall of the heat pipe is increased. In the preparation process, the thickness of the magnetron sputtering layer is controlled to be less than or equal to 0.2mm. Meanwhile, the nickel content in the copper-nickel alloy is 68-72 wt%.

As a preferred alternative to this,

and 2) performing the heat treatment in a non-oxidizing atmosphere, setting the heat treatment temperature to be 600 ℃ or above, preserving the heat for 30-40 min, then cooling to 320-335 ℃, and preserving the heat for 1-2 h.

The non-oxidizing atmosphere includes, but is not limited to, nitrogen, argon, etc., and nitrogen atmosphere is generally used in the present invention. After heat treatment is carried out under the heat treatment condition, a Ni-Cu tissue structure rich in Ni can be formed on the surface of the mixed metal layer, and a good promoting effect can be generated on ordered growth of graphene.

As a preferred alternative to this,

the vapor deposition in step 3) is chemical vapor deposition.

The chemical vapor deposition mode can be used for preparing the graphene layer structure with low cost and rapidness.

As a preferred alternative to this,

the chemical vapor deposition is as follows:

setting background vacuum degree to 0.8-1.0X10 ^-4 And after the Pa is heated to 940-960 ℃, introducing carbon source gas, controlling the pressure to be stable at 10-12 Pa, and keeping the pressure for 11-13 s.

The carbon source gas is preferably acetylene. And chemical vapor deposition can be carried out for a plurality of times, and after each deposition is finished, vacuum is pumped again to 0.8 to 1.0x10 ^-4 Pa, and then introducing carbon source gas with the pressure of 10-12 Pa, wherein the temperature is kept at 940-960 ℃.

As a preferred alternative to this,

step 4) the pre-oxidation is:

placing the mixture in an atmosphere containing oxygen, and preserving the temperature for 160-180 min at 60-70 ℃.

The preoxidation can greatly improve the hydrophilicity of the graphene so as to obviously reduce the superheat degree of the heat pipe and improve the performance of the heat pipe. The effect of the pre-oxidation under the above conditions is excellent.

As a preferred alternative to this,

the heat pipe is a flattened ultrathin copper pipe;

the thickness of the flattened ultrathin copper pipe is less than or equal to 2mm.

The flattened ultrathin copper pipe is a pipe shell part of a conventional ultrathin micro-heat pipe and is made of pure copper or common copper alloy. If no special description exists, the technical proposal of the invention is that the flattening type ultrathin copper pipe is made of pure copper. The technical scheme of the invention also has the uniqueness of being capable of being well suitable for preparing the flattened ultrathin micro-heat pipe.

The beneficial effects of the invention are as follows:

1) Can effectively improve the limit heat transfer power of the heat pipe to 535W/cm ² The above;

2) When heat transfer and heat dissipation are carried out at the same environmental temperature, the superheat degree of the heat pipe can be obviously reduced;

3) The heat pipe has good heat transfer efficiency.

Drawings

FIG. 1 is a graph comparing the results of the ultimate heat transfer power test in test I;

FIG. 2 is a graph comparing the results of the superheat test in test I;

FIG. 3 is a graph comparing the results of the ultimate heat transfer power test in test II;

FIG. 4 is a graph comparing the results of the superheat test in test II.

Detailed Description

The invention is described in further detail below with reference to specific examples and figures of the specification. Those of ordinary skill in the art will be able to implement the invention based on these descriptions. In addition, the embodiments of the present invention referred to in the following description are typically only some, but not all, embodiments of the present invention. Therefore, all other embodiments, which can be made by one of ordinary skill in the art without undue burden, are intended to be within the scope of the present invention, based on the embodiments of the present invention.

The raw materials used in the examples of the present invention are all commercially available or available to those skilled in the art unless specifically stated otherwise; the methods used in the examples of the present invention are those known to those skilled in the art unless specifically stated otherwise.

The superheat measured in the examples of the present invention refers to the lowest temperature difference from the evaporating state to the boiling state, and the ultimate heat transfer power measurement in this application refers to the ultimate heat transfer power at 120 ℃.

Example 1

A method of vapor deposition for making a heat pipe, the method comprising:

1) Preparing a Ni-Cu mixed metal deposition layer by depositing on the inner surface of a flattened ultrathin copper pipe with the thickness of 1.8mm and the pipe wall thickness of 0.3mm in a vacuum sputtering mode, wherein the background vacuum degree of vacuum sputtering is 5.0x10 ^-4 Pa, argon flow is 20mL/min, and pressure is 1.0Pa;

3) Depositing graphene on the surface of the mixed metal layer by using acetylene as a carbon source gas and adopting a CVD method, wherein the background vacuum degree of the CVD method is 1.0x10 ^-4 Pa, the temperature is 950 ℃, and a graphene layer is formed;

4) And pre-oxidizing the graphene layer to obtain the heat pipe.

The specific preparation parameters of this example are shown in table 1 below.

Table 1: specific parameters

Example 2

The specific operation was the same as in example 1 except that:

the specific preparation parameters of this example are shown in table 2 below.

Table 2: specific parameters

Example 3

The specific operation was the same as in example 1 except that:

the specific preparation parameters of this example are shown in table 3 below.

Table 3: specific parameters

Example 4

The specific operation was the same as in example 1 except that:

the specific preparation parameters of this example are shown in table 4 below.

Table 4: specific parameters

Example 5

The specific operation was the same as in example 1 except that:

the specific preparation parameters of this example are shown in table 5 below.

Table 5: specific parameters

Example 6

The specific operation was the same as in example 1 except that:

preparing a Ni-Cu mixed metal deposition layer by depositing on the inner surface of a flattened ultrathin copper pipe with the thickness of 1.8mm and the pipe wall thickness of 0.3mm in a vacuum sputtering mode, wherein the background vacuum degree of vacuum sputtering is 3.0x10 ^-4 Pa, argon flow is 15mL/min, and pressure is 1.5Pa.

Example 7

The specific operation was the same as in example 1 except that:

background vacuum of CVD method of 0.8X10 ^-4 Pa, the temperature is 960 ℃.

Example 8

The specific operation was the same as in example 1 except that:

background vacuum of 1.0X10 by CVD method ^-4 Pa, the temperature is 940 ℃.

Comparative example 1

The thickness of the flattened ultrathin copper pipe with the specification thickness of 1.8mm and the pipe wall thickness of 0.3mm is sold in the market, the liquid suction core is sintered copper powder, and the thickness of the liquid suction core is 0.18mm.

Comparative example 2

The specific operation was the same as in example 1 except that:

the mixed metal deposition layer adopts copper-nickel alloy with the nickel content of 62.5 weight percent, the target power is set to be 85W, and vacuum sputtering is carried out under the same condition to obtain the mixed metal deposition layer, and the thickness of the mixed metal deposition layer is 0.18mm.

Comparative example 3

The specific operation was the same as in example 1 except that:

the copper-nickel sputtering process adopts nickel-copper alloy with the nickel content of 65 weight percent as a target material.

Comparative example 4

The specific operation was the same as in example 1 except that:

the heat treatment stage is only carried out at 650 ℃ for 35min.

Comparative example 5

The specific operation was the same as in example 1 except that:

the heat treatment stage was carried out for only 1.5 hours at 330 ℃.

Comparative example 6

The specific operation was the same as in example 1 except that:

and the heat treatment stage is carried out for 35min at 650 ℃, and then the temperature is reduced to 360 ℃ for heat treatment for 1.5h.

Test I

The ultra-thin micro heat pipes prepared in examples 1 to 8 and comparative examples 1 to 6 were subjected to the measurement of the heat transfer power at the limit and the degree of superheat under isothermal conditions.

The test results of the ultimate heat transfer power (Limit heat transfer power) are shown in FIG. 1, in which X-axis coordinate system numbers 1 to 8 correspond to examples 1 to 8, respectively, and numbers 9 to 14 correspond to examples 1 to 6, respectively. Each test object is subjected to five effective tests, the single test result is displayed in a histogram, and the test mean value is shown in a dotted line graph. As apparent from the test results of FIG. 1, the ultra-thin micro-heat pipe prepared by the embodiment of the invention has stable performance and the ultimate heat transfer power can basically reach 535W/cm ² As described above, the commercial ultra-thin micro heat pipe of comparative example 1 is remarkably poor in performance, and the ultimate heat transfer efficiency is only 370W/cm ² The method is characterized in that the method comprises the steps of preparing a completely uniform nickel-copper alloy in a deposition mode, wherein the nickel-copper component in the obtained mixed metal deposition layer is high in uniformity and does not form gradient distribution, and the test result shows that the limit heat transfer power of the comparative example 2 is obviously reduced, because the uniform nickel-copper in the ratio has no good promotion effect on the formation and growth of graphene during the deposition of graphene, the chemical deposition of graphene is incomplete and full, the performance is reduced, the nickel-copper ratio of a sputtering layer in the middle layer is adjusted in the comparative example 3, the limit heat transfer power of the obtained ultrathin micro heat pipe is influenced to a certain extent mainly because the compactness of the outer layer of the mixed metal layer is reduced after the adjustment, the concentration gradient of the nickel-copper is changed to a certain extent, the influence is small, the limit heat transfer power of the ultrathin micro heat pipe is basically negligible under the treatment condition, and the limit heat transfer power of the ultrathin micro heat pipe is influenced to a poor effect on the sintering of the mixed metal deposition layer of the ultrathin micro heat pipe under the condition that the high temperature is not treated.

And (5) measuring the superheat degree under isothermal conditions. On the other hand, the degree of primary superheat of each test obtained was examined. As shown in FIG. 2, the results of the test of the degree of Superheat (super) are shown in the figure, wherein X-axis coordinate system numbers 1 to 8 correspond to examples 1 to 8, respectively, and numbers 9 to 14 correspond to examples 1 to 6, respectively. As is apparent from the figure, the superheat degree of the ultra-thin micro heat pipe prepared in the invention is about 20 ℃, the superheat degree is only about 5 ℃, the ultra-thin micro heat pipe can be basically kept below 5.5 ℃, the ultra-thin micro heat pipe shows excellent technical effects, the influence on the superheat degree is small under the condition of changing the intermediate layer component of the mixed metal layer, the superheat performance of the ultra-thin micro heat pipe is obviously adversely affected by directly performing vacuum sputtering on an alloy target material in comparative example 3, the influence on the superheat performance of the ultra-thin micro heat pipe is obviously increased in the condition that the low temperature heat treatment is not performed in comparative example 4 and comparative example 6, and the superheat degree of the ultra-thin micro heat pipe prepared in the condition that the low temperature heat treatment is only performed in comparative example 5 is obviously better than that in comparative example 4 and comparative example 6. Researchers draw a substantially similar conclusion through similar temperature orthogonal tests, and low-temperature heat treatment can produce significant optimization on the overheat performance of the ultrathin micro heat pipe, so that the heat pipe can respond and dissipate heat more timely.

Example 9

The specific operation was the same as in example 1, except that:

depositing graphene by CVD method for three times, and vacuumizing again to 1.0X10 from the second deposition ^-4 Pa, and then introducing carbon source gas with the value pressure of 10Pa, wherein the temperature is kept at 950 ℃.

Example 10

The specific operation was the same as in example 9, except that:

graphene deposition was performed five times in total.

Example 11

The specific operation was the same as in example 9, except that:

graphene deposition was performed seven times in total.

Comparative example 7

The specific procedure was as in comparative example 2, except that:

Comparative example 8

The specific procedure was as in comparative example 4, except that:

Comparative example 9

The specific procedure was as in comparative example 6, except that:

Test II

The same tests as those of test I were conducted for examples 9 to 11 and comparative examples 7 to 9.

The limit heat transfer power test is only carried out in examples 9-11 and comparative examples 8-9, and the test results show that after the graphene is deposited by multiple CVD, the limit heat transfer power of the ultrathin micro heat pipe of the invention is obviously improved, but when the deposition time reaches 7 times, obvious performance fallback is generated, and the invention researchers' orthogonal test shows that the limit heat transfer power can reach 600W/cm when the deposition time is within 3-6 times ² Above, and after reaching 7 times above, the performance was inferior to that of the single deposition, whereas the performance of comparative example 8 and comparative example 9 was substantially unchanged after the three depositions, indicating that the effect of the multi-layer deposition was poor. The superheat test was carried out at the same temperature as test I, and the test was carried out only for examples 9 to 11 and comparative example 7.

The overheat test also shows that the overheat degree is kept low when the deposition times are less than or equal to 6 times, and the overheat degree is obviously increased once reaching 7 times, and the overheat degree is obviously increased after the deposition for a plurality of times in comparative example 7, and the performance is obviously reduced.

From the test, it is obvious that the ultrathin micro heat pipe prepared by the technical scheme of the invention has excellent performance, and the performance peak value can be reached after carrying out CVD chemical deposition on graphene for 3-6 times. The whole is extremely excellent in both the ultimate heat transfer power and the superheat degree.

Claims

1. A method of vapor deposition for making a heat pipe, the method comprising:

4) Pre-oxidizing the graphene layer to obtain a heat pipe;

step 1), the mixed metal deposition layer contains copper and nickel; the content of nickel in the mixed metal deposition layer is 58-66.5 wt%, and the balance is copper and unavoidable impurities;

step 2) the heat treatment is carried out in a non-oxidizing atmosphere, the heat treatment temperature is set to be 600 ℃ or above, the temperature is kept for 30-40 min, then the temperature is reduced to 320-335 ℃, and the temperature is kept for 1-2 h;

step 4) the pre-oxidation is: placing the mixture in an atmosphere containing oxygen, and preserving the temperature for 160-180 min at 60-70 ℃.

2. A method for preparing a heat pipe by vapor deposition according to claim 1,

the vapor deposition in step 1) is vacuum sputtering.

3. A method for preparing a heat pipe by vapor deposition according to claim 2,

the vacuum sputtering parameters are as follows: setting magnetic control targetThe power is 40-120W, the background vacuum degree is 3.0X10 ^-4 ～5.0×10 ^-4 Pa, argon flow is 15-20 mL/min, and pressure is 1.0-1.5 Pa.

4. A method of preparing a heat pipe by vapor deposition according to claim 3,

5. A method for preparing a heat pipe by vapor deposition according to claim 1,

the vapor deposition in step 3) is chemical vapor deposition.

6. A method for preparing a heat pipe by vapor deposition according to claim 5,

the chemical vapor deposition is as follows: setting background vacuum degree to 0.8-1.0X10 ^-4 And after the Pa is heated to 940-960 ℃, introducing carbon source gas, controlling the pressure to be stable at 10-12 Pa, and keeping the pressure for 11-13 s.

7. A method for preparing a heat pipe by vapor deposition according to claim 1,

the heat pipe is a flattened ultrathin copper pipe; the thickness of the flattened ultrathin copper pipe is less than or equal to 2mm.