CN110862572B - Application of heat-conducting ceramic powder low-melting-point alloy composite powder - Google Patents
Application of heat-conducting ceramic powder low-melting-point alloy composite powder Download PDFInfo
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- 239000000843 powder Substances 0.000 title claims abstract description 100
- 239000000956 alloy Substances 0.000 title claims abstract description 72
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 72
- 239000000919 ceramic Substances 0.000 title claims abstract description 46
- 239000002131 composite material Substances 0.000 title claims abstract description 39
- 238000003756 stirring Methods 0.000 claims abstract description 43
- 238000002844 melting Methods 0.000 claims abstract description 39
- 230000008018 melting Effects 0.000 claims abstract description 39
- 239000004519 grease Substances 0.000 claims abstract description 33
- 229920001296 polysiloxane Polymers 0.000 claims abstract description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000000463 material Substances 0.000 claims abstract description 26
- 238000002360 preparation method Methods 0.000 claims abstract description 24
- 238000002604 ultrasonography Methods 0.000 claims abstract description 18
- 238000002156 mixing Methods 0.000 claims abstract description 17
- 238000010438 heat treatment Methods 0.000 claims abstract description 16
- 238000001816 cooling Methods 0.000 claims abstract description 13
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- 239000000126 substance Substances 0.000 claims abstract description 8
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- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical group N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 claims description 55
- 229910052582 BN Inorganic materials 0.000 claims description 53
- 239000004205 dimethyl polysiloxane Substances 0.000 claims description 29
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 claims description 29
- -1 polydimethylsiloxane Polymers 0.000 claims description 25
- 239000000203 mixture Substances 0.000 claims description 8
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- 229910021641 deionized water Inorganic materials 0.000 claims description 7
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- C09K5/14—Solid materials, e.g. powdery or granular
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- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K3/00—Use of inorganic substances as compounding ingredients
- C08K3/38—Boron-containing compounds
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Abstract
The invention relates to the technical field of thermal interface materials, in particular to a preparation method and application of heat-conducting ceramic powder low-melting-point alloy composite powder. The preparation method of the low-melting-point alloy composite powder of the heat-conducting ceramic powder comprises the following steps: step 1): adding the low-melting-point alloy and the heat-conducting ceramic powder into a container filled with water, and uniformly mixing the low-melting-point alloy and the heat-conducting ceramic powder under the simultaneous action of stirring and ultrasound at a temperature from the melting point of the low-melting-point alloy to the boiling point of the water; step 2): turning off the ultrasound, stopping heating, and keeping stirring for naturally cooling; step 3): and after cooling, carrying out suction filtration on the substances in the container, taking filter residues, and putting the filter residues into an oven for drying to obtain powder. The composite powder prepared by the preparation method can be well and uniformly mixed, and the heat-conducting silicone grease prepared by the composite powder has high heat conductivity coefficient and low interface thermal resistance.
Description
Technical Field
The invention relates to the technical field of thermal interface materials, in particular to a preparation method and application of heat-conducting ceramic powder low-melting-point alloy composite powder.
Background
In the aspect of solving the heat dissipation problem of the electronic device, whether the material has high thermal conductivity can well wet the surface of the heating device, fill the gap, eliminate air in the gap and reduce interface thermal resistance is the key to consider whether a heat-conducting interface material is excellent or not.
In recent years, the use of Low melting-point alloys (LMPAs) as a component of the thermally conductive filler has gradually been the direction to solve this problem. Besides the characteristic of high heat conductivity coefficient, LMPAs have the advantages of being used as heat conduction materials due to the excellent thermophysical properties of wide application range, good fluidity, stable performance and the like. By using the LMPAs, the heat-conducting layer can be newly increased at the periphery of the heat-conducting network, and other non-metallic fillers can be adhered through the high-temperature melting characteristic of the LMPAs to form a more ordered and compact heat-conducting network. Meanwhile, after the temperature of the heating device reaches the melting point of LMPAs, the metal is liquefied, so that the surface of the heating device can be wetted to the maximum extent, and the interface thermal resistance is reduced.
The LMPAs and the insulating ceramic powder (such as BN, AlN and the like) are compounded and added into the polymer matrix, so that the leakage problem can be effectively solved, and high thermal conductivity, low thermal resistance and good moving safety tolerance are realized. However, if LMPAs and the heat-conducting ceramic powder are used as the heat-conducting filler for preparing the heat-conducting interface material, the LMPAs and the heat-conducting ceramic powder cannot be well mixed, so that the heat conductivity coefficient, the interface thermal resistance value and the like of the prepared heat-conducting interface material cannot meet the requirements.
Particularly, when the heat-conducting interface material is heat-conducting silicone grease and the preparation raw material contains Polydimethylsiloxane (PDMS), the density of LMPAs is far greater than that of PDMS, so that the PDMS is difficult to be uniformly mixed with the LMPAs or the LMPAs and the heat-conducting ceramic powder to be used as a heat-conducting material, the use of the material is limited, and a heat-conducting filler (composite powder) capable of being well mixed with the PDMS is urgently needed.
Disclosure of Invention
The invention aims to overcome the defects and provides a preparation method and application of heat-conducting ceramic powder low-melting-point alloy composite powder. The low melting point alloy of the present invention refers to an alloy having a melting point lower than the boiling point of water.
In order to achieve the purpose, the invention adopts the technical scheme that:
a preparation method of heat-conducting ceramic powder low-melting-point alloy composite powder comprises the following steps:
step 1): adding the low-melting-point alloy and the heat-conducting ceramic powder into a container filled with water, and uniformly mixing the low-melting-point alloy and the heat-conducting ceramic powder under the simultaneous action of stirring and ultrasound at a temperature from the melting point of the low-melting-point alloy to the boiling point of the water;
step 2): turning off the ultrasound, stopping heating, and keeping stirring for naturally cooling;
step 3): and (3) cooling to a temperature below the melting point temperature of the low-melting-point alloy, carrying out suction filtration on the substances in the container, taking filter residues, and putting the filter residues into an oven for drying to obtain powder.
As a further improvement, the heat-conducting ceramic powder is boron nitride; the water is deionized water.
As a further improvement, the mass ratio of the heat-conducting ceramic powder to the low-melting-point alloy is (0.5-8): 1; the low melting point alloy is blocky.
As a further improvement, in the step 3), when the alloy is dried in the oven, the temperature in the oven is below the melting point of the alloy.
As a further improvement, the ultrasonic power is more than 200 watts, and the ultrasonic time is more than 1 hour; the melting point of the low-melting-point alloy is 70 ℃, and in the step 3): cooling to room temperature, suction filtering the materials in the container, taking the filter residue, and drying in a 50 ℃ oven to obtain powder.
As a further improvement, the preparation method of the step 1) comprises the following steps: adding the low-melting-point alloy into a container filled with water, heating to a temperature higher than the melting point of the alloy and lower than the boiling point of the water, adding ceramic powder, and uniformly mixing the low-melting-point alloy and the ceramic powder under the action of ultrasound and stirring.
The invention also provides application of the heat-conducting ceramic powder low-melting-point alloy composite powder prepared by the method in preparation of heat-conducting interface materials. The heat-conducting interface material can be heat-conducting silicone grease, and the preparation method of the heat-conducting silicone grease comprises the following steps:
uniformly stirring and mixing polydimethylsiloxane and the composite powder, standing for more than 24 hours, putting into a vacuum stirrer, and stirring for more than 2 hours again in a vacuum state at the temperature of more than 80 ℃ to the decomposition temperature of the polydimethylsiloxane; wherein, in the vacuum stirrer, the stirring speed is 50-200rpm, and the dispersion speed is 500-2000 rpm.
In a further improvement, the mixture of polydimethylsiloxane and the composite powder is in a slurry state, and the vacuum stirrer is a planetary vacuum stirrer.
As a further improvement, the viscosity of the polydimethylsiloxane is 500-1000 mPas.
As a further improvement, the mass ratio of the composite powder to the polydimethylsiloxane is as follows: (0.75-2):1.
Compared with the prior art, the technical scheme of the invention has the following advantages:
1) the invention adopts deionized water as a solvent, the heat-conducting ceramic powder and the low-melting-point alloy can be well and uniformly mixed under the combined action of stirring and ultrasound, and the powdery composite powder which is very uniformly mixed can be obtained after drying. When the prepared heat-conducting interface material is the heat-conducting silicone grease, compared with the prior art, the powder is not prepared, and the raw materials are mixed together when the heat-conducting silicone grease is prepared. Meanwhile, compared with the prior art that stirring and ultrasound are not carried out simultaneously, various substances are difficult to mix well, and the finally prepared heat-conducting silicone grease has low heat conductivity and high interface thermal resistance, thereby having unexpected technical effects. Has remarkable progress.
2) Because the adopted water (or deionized water) does not need to use an organic solvent, the cost is saved, and various components in the composite powder can be well mixed uniformly.
3) After stirring and ultrasonic treatment are finished, suction filtration is carried out, filter residues are dried, drying is easy, no residue is left, and the heat conductivity coefficient and the interface thermal resistance of a subsequent process and a heat-conducting interface material obtained by taking composite powder as a filler are not influenced. Compared with the prior art that the organic solvent is easy to remain, the heat conductivity coefficient and the interface thermal resistance of the heat-conducting interface material are influenced, and the method has remarkable progress.
4) The invention adopts the low-melting-point alloy composite powder of the heat-conducting ceramic powder prepared firstly and then prepares the heat-conducting silicone grease with the polydimethylsiloxane, so that the preparation method is simple, the energy and the cost are saved, no residue exists, the prepared heat-conducting silicone grease has high heat conductivity and low interface thermal resistance (when the temperature is 80 ℃, the heat conductivity of the prepared heat-conducting silicone grease can be increased to 1.8W/K.m, the interface thermal resistance can be reduced to 0.09 ℃/W, and the interface thermal resistance which is low cannot be seen in the performance of the heat-conducting silicone grease at present) can be well used in electronic products.
Drawings
FIG. 1 is a macro-topography of BN and BN-LMPAs;
FIG. 2 shows BN 1 -LMPAs 2 Surface topography and elemental analysis of (a); wherein:
FIG. (a) shows BN 1 -LMPAs 2 Scanning electron microscope macroscopic view;
FIG. (b) is a partially enlarged view of FIG. (a);
FIG. (c) is BN 1 -LMPAs 2 Surface topography of the middle Bi element;
FIG. d is BN 1 -LMPAs 2 Surface topography of In element;
FIG. (e) is BN 1 -LMPAs 2 Surface topography of medium Pb element;
FIG. f is BN 1 -LMPAs 2 Surface topography of the medium Sn element;
FIG. 3 is a DSC plot of BN, LMPAs and BN-LMPAs;
wherein 1 is BN 1 -LMPAs 1 (ii) a 2 is BN 2 -LMPAs 1 (ii) a 3 is BN 4 -LMPAs 1 (ii) a 4 is BN 8 -LMPAs 1 (ii) a 5 is BN; 6 is BN 1 -LMPAs 2 (ii) a 7 are LMPAs;
FIG. 4 shows BN 1 -LMPAs 2 A morphological change of phase change melting; wherein (a) is 0s, (b) is 150s, (c) is 300s, and (d) is 450 s.
Detailed Description
A preparation method of heat-conducting ceramic powder low-melting-point alloy composite powder comprises the following steps:
step 1): adding the low-melting-point alloy and the heat-conducting ceramic powder into a container filled with water, and uniformly mixing the low-melting-point alloy and the heat-conducting ceramic powder under the action of stirring and ultrasound at a temperature (such as 75-85 ℃) between the melting point of the low-melting-point alloy and the boiling point of the water;
step 2): turning off the ultrasound, stopping heating, and keeping stirring for naturally cooling;
step 3): cooling to a temperature below the melting point of the low-melting-point alloy (such as room temperature of 25 ℃), performing suction filtration on the substances in the container, taking filter residues, and putting the filter residues into an oven for drying to obtain powder. The melting point of the low melting point alloy may be 70 ℃.
Preferably, the heat-conducting ceramic powder is boron nitride; the water is deionized water.
As a heat conducting filler, boron nitride has higher heat conductivity (about 300W/(m.K)), lower thermal expansion coefficient and electrical resistivity, good chemical stability and thermal stability (can bear high temperature of 2000 ℃), and activated BN with increased hydroxyl groups can be obtained after surface treatment, thus providing better precondition for subsequent surface treatment.
Preferably, the mass ratio of the heat-conducting ceramic powder to the low-melting-point alloy is (0.5-8): 1 (or (8-0.5): 1), so that the application requirements can be better met after uniform mixing; the low melting point alloy is in a block shape (for example, the size of a biscuit or an iron block is large, and the length, width and height can be more than 20mm, 20mm and 20 mm), the block shape is generally not mixed with BN, and the block shape low melting point alloy can be uniformly mixed with heat-conducting ceramic powder by adopting the method of the invention.
Preferably, in the step 3), the temperature in the oven is below the melting point of the alloy during oven drying, so that a more uniformly mixed powdery substance can be obtained.
Preferably, the ultrasonic power is more than 200 watts, and the ultrasonic time is more than 1 hour; the melting point of the low-melting-point alloy is 70 ℃, and in the step 3): cooling to room temperature (25 deg.C), vacuum filtering, collecting the residue, and oven drying at 50 deg.C to obtain powder.
Preferably, the preparation method of step 1) is as follows: adding the low-melting-point alloy into a container filled with water, heating to a temperature higher than the melting point of the alloy and lower than the boiling point of the water, adding ceramic powder, and uniformly mixing the low-melting-point alloy and the ceramic powder under the action of ultrasound and stirring.
The invention also provides application of the heat-conducting ceramic powder low-melting-point alloy composite powder prepared by the method in preparation of heat-conducting interface materials. The thermally conductive interface material may be a thermally conductive silicone grease.
The preparation method of the heat-conducting silicone grease comprises the following steps:
uniformly stirring and mixing polydimethylsiloxane and the composite powder, standing for more than 24 hours, putting into a vacuum stirrer, and stirring for more than 2 hours again in a vacuum state at the temperature of more than 80 ℃ to the decomposition temperature of the polydimethylsiloxane; wherein, in the vacuum stirrer, the stirring speed is 50-200rpm, and the dispersion speed is 500-2000 rpm.
As a further improvement, the mixture obtained by uniformly stirring and mixing the polydimethylsiloxane and the composite powder is slurry or wet powder, and the vacuum stirrer is a planetary vacuum stirrer.
As a further improvement, the viscosity of the polydimethylsiloxane is 500-1000 mPas.
As a further improvement, the mass ratio of the composite powder to the polydimethylsiloxane is as follows: (0.75-2):1.
Example 1:
in this example, the names, specifications and manufacturer parts of the main experimental raw materials are shown in Table 1
TABLE 1
| Name of raw materials | Specification of | Manufacturer of the product |
| 70℃LMPAs | - | DONGGUAN WOCHANG METAL PRODUCTS Co.,Ltd. |
| BN | 1μm | ZIBO JONYE CERAMICS TECHNOLOGY Co.,Ltd. |
| 500 mPas polydimethylsiloxane | Analytical purity | Guangzhou ear Xin chemical Co Ltd |
Note that: (ii) a 500 mPas in the polydimethylsiloxane 500 mPas means that the viscosity of the polydimethylsiloxane at 25 ℃ is 500 mPas.
In this example, the main experimental apparatus and equipment are shown in Table 2.
TABLE 2
| Name of instrument | Model number | Manufacturer of the product |
| Electronic analysisBalance with a movable handle | FA1204 | Shanghai Jingke industries Ltd |
| Planetary vacuum stirrer | MT-0.75L | GUANGZHOU PRECISEMIX MACHINERY EQUIPMENT Co.,Ltd. |
| Differential scanning calorimeter | Q2000 | Mettler-toledo USA |
| Scanning electron microscope | ATC-SCUT | German Karl Chuiss |
| Optical microscope | MP41 | GUANGZHOU MICRO-SHOT TECHNOLOGY Co.,Ltd. |
| Heat conductivity meter | TC-3000 | XI'AN XIATECH ELECTRONICS Co.,Ltd. |
| Thermal resistance tester | LW-9389 | Raila science and technology Ltd |
A preparation method of heat-conducting ceramic powder low-melting-point alloy composite powder comprises the following steps:
step 1): adding low-melting-point alloy (LMPAs) and Boron Nitride (BN) into a container filled with deionized water (the amount of water is just enough to submerge the solid), and uniformly mixing the low-melting-point alloy and the BN under the simultaneous action of stirring and ultrasound (the ultrasonic power is 200 watts, and the ultrasonic time is 1 hour) at the temperature from the melting point of the low-melting-point alloy to the boiling point of the water. Can be as follows: adding the low-melting-point alloy into a container filled with deionized water, heating to 80 ℃ to completely melt the low-melting-point alloy, adding BN, and uniformly mixing the low-melting-point alloy and the BN under the action of ultrasound and stirring (more than 200 rpm).
Step 2): turning off the ultrasound, stopping heating, and keeping stirring for naturally cooling;
step 3): cooling to room temperature, vacuum filtering the material in the container, collecting the filter residue, oven drying to obtain powder, wherein the heat-conducting ceramic powder is low-melting-point alloy composite powder (BN-LMPAs powder in this embodiment, wherein, if numbers are provided at the bottom right corner of BN and LMPAs, the numbers represent the mass ratio of BN and LMPAs used in the preparation of BN-LMPAs powder, such as BN 1 -LMPAs 2 Meaning that the mass ratio of BN to LMPAs is 1: 2. When the mixture is dried in an oven, the temperature in the oven is 50 ℃. The mass ratio of BN to low-melting-point alloy can be selected to be (0.5-8): 1.
performance testing
1) Scanning electron microscope testing
And spraying gold on the sample, adhering the sample to the conductive adhesive of the objective table, and observing the sample at an accelerating voltage of 15.0 kV.
2) Optical microscope testing
BN 1 -LMPAs 2 The powder was placed on a glass slide, covered with a coverslip and the slide and coverslip clamped with a clamp. The slide was placed on a hot stage, warmed to 80 ℃, observed with transmitted light and photographed with a self-contained camera at 5s intervals.
3) Differential scanning calorimeter measurement
Under the nitrogen atmosphere, the heating rate is 10 ℃/min, and the temperature range is from room temperature to 400 ℃.
4) Thermal conductivity test
The sheet for the heat conduction test was room-temperature-pressed with the aid of a custom-made square hollow mold using a tablet press (i.e., the sheet for the heat conduction test was room-temperature-pressed with the tablet press with the heat conductive silicone grease poured into the hollow mold so that the sheet thickness was 2 mm). Test of thermal conductivity the experiment employed a transient hot wire method, test voltage: 2.5V, acquisition time: 5s, acquisition mode: normal, time interval: 3min, repetition number: 3 times.
5) Thermal resistance test
And coating the heat-conducting silicone grease on the surface of the test platform, and covering the plastic frame with the hollow bottom to enable the plastic frame to be tightly attached to the heat-conducting silicone grease film (so that the thickness of the heat-conducting silicone grease film is 0.4mm), thereby ensuring that the thickness is the same in each measurement. The platform temperature is set to be 80 ℃, the testing pressure is set to be 60Psi, and the testing time is 30 min.
This frame is configured for the test equipment in order to hold the thermally conductive silicone grease in place in a certain area and to ensure consistent thickness for each test.
And (3) testing results:
1) influence of the content of the low-melting-point alloy on the appearance of the low-melting-point alloy composite powder (BN-LMPAs powder for short in this embodiment) of the heat-conducting ceramic powder
The BN powder was pure white. When the proportion of LMPAs in the composite powder is increased, the integral color of the BN-LMPAs powder is deepened along with the increase of the proportion of LMPAs, and the color is uniform, which shows that by adopting the preparation method, BN and LMPAs can be mixed uniformly in a macroscopic view, and a guarantee is provided for the subsequent preparation of a heat-conducting interface material, particularly heat-conducting silicone grease, and the specific result is shown in figure 1.
2) SEM and elemental distribution
As can be seen from fig. 2(a) and (b), BN is adhered by LMPAs. BN agglomerated under the action of LMPAs, and LMPAs cannot be directly observed. And (3) carrying out element distribution analysis on the BN-LMPAs by using a scanning electron microscope element distribution (mapping) function. As can be seen from FIGS. 2(c) - (f), the elements Bi, In, Pb, Sn, etc. In LMPAs are uniformly distributed In the whole space. Therefore, the LMPAs and the BN are microscopically uniformly compounded.
3) Differential thermal analysis
The latent heat of phase change and the phase change temperature are one of the most important thermophysical energy parameters of the phase change material, and determine the applicability of the material. TIM prepared from phase change materialThe heat conducting interface material can play a role in quickly absorbing heat and reducing temperature when the electronic device generates heat. It is necessary to perform DSC (modern thermal analysis) test on BN, LMPAs and BN-LMPAs to examine the influence of BN on the change rule of the melting point of the LMPAs. As can be seen from FIG. 3, BN does not have an absorption peak between room temperature and 150 ℃. The phase transition temperature of the LMPAs is 45-73 ℃, the LMPAs are in the heating temperature range of a common electronic device, the LMPAs reach the maximum absorption peak at 63 ℃, and the phase transition latent heat value is 23.8W/g. When BN is compounded with LMPAs, the phase-change starting temperature of BN-LMPAs rises, the melting range becomes narrow, and the phase-change latent heat value rises along with the increase of the proportion of the LMPAs. The reason is BN (K) BN 300W/(m.K)) has higher heat transfer capacity (K) Pb ＝34.8W/(m·K)，K Sn ＝67.0W/(m·K)，K Bi ＝7.9W/(m·K)，K In 82.0W/(m · K)), which when mixed homogeneously with LMPAs on a microscopic level, enables heat to diffuse more rapidly and act on all LMPAs, and thus LMPAs become more responsive to temperature and the phase transition temperature range narrows. Meanwhile, the LMPAs are proved to be mixed with BN uniformly on a microscopic level. Since LMPAs are phase change components in the composite, the energy absorbed by melting is directly proportional to the amount of LMPAs in the composite. That is, as LMPAs increases, the latent heat of the composite powder increases. This result demonstrates that HCSG prepared using BN-LMPAs can rapidly change phase to absorb heat before the temperature of the electronic device reaches a limit, and function.
4) Surface conformability analysis
FIG. 4 shows BN observed by transmitted light of an optical microscope during a temperature rise from room temperature (25 ℃) to 80 ℃ at a rate of 5 s/DEG C (after melting, the temperature rise rate becomes slow) 1 -LMPAs 2 Spreading (interfacial bonding) process under a certain pressure. Under the irradiation of transmitted light, due to BN 1 -LMPAs 2 Light is blocked, and BN exists in the image 1 -LMPAs 2 The part(s) of (1) shows black, and the other part(s) shows white light. In the temperature rise process, the image of the hot stage temperature is basically not changed in about 150s, which shows that BN 1 -LMPAs 2 No melting has occurred or melting is insignificant. When the temperature of the hot stage exceeds 70 ℃, the area of the black part in the image begins to be gradually enlarged, which shows thatBN 1 -LMPAs 2 Melting occurred and spread out under the pressure applied from the outside (in fig. 4, spreading was evident at 300s, and temperature rise was not evident due to melting). BN when the heating time is 450s (80 ℃ C., the temperature is again 80 ℃ C. at 450s, since the temperature does not rise significantly any more in the case of the same heat quantity obtained per unit time due to the melting process) 1 -LMPAs 2 Further enlarging the area of the slide, wetting almost the entire slide surface. Observation through an optical microscope shows that the BN-LMPAs have good fluidity after reaching the melting point, and can well fill tiny gaps on the surface of the heating device. Also stated therein, BN 1 -LMPAs 2 The mixing of the medium BN and the LMPAs is very uniform.
The invention also provides application of the heat-conducting ceramic powder low-melting-point alloy composite powder prepared by the method in preparation of heat-conducting interface materials. The heat-conducting interface material can be heat-conducting silicone grease, and the preparation method of the heat-conducting silicone grease comprises the following steps:
uniformly stirring and mixing polydimethylsiloxane and BN-LMPAs prepared in example 1, standing for 24 hours (stirring and standing are generally carried out at room temperature), putting the mixture into a vacuum stirrer, and stirring for more than 2 hours (generally stirring for 2-4 hours) again at 80 ℃ in a vacuum state (the vacuum degree is-0.1 MPa); wherein, in the vacuum stirrer, the stirring speed is 50-200rpm, and the dispersion speed is 500-2000 rpm.
The method specifically comprises the following steps: adding polydimethylsiloxane with a certain mass into the weighed BN-LMPAs powder, and primarily stirring, wherein the composite powder occupies a sample with a lower mass fraction and can be stirred into a slurry shape; stirring a sample with high mass fraction of the composite powder into wet powder, and standing for 24 hours to obtain a mixture; the mixture was again stirred in a planetary vacuum stirrer. The stirring speed is 50-200rpm, the dispersion speed is 500-2000rpm, and the stirring time is 2-4 h. The vacuum degree in the stirring pot is kept at-0.1 MPa and the temperature is 80 ℃ in the whole process.
When the mixture is put into a planetary vacuum stirrer to be stirred again, the stirring can be carried out in four stages, namely: stirring speed 100rpm, dispersing speed 500rpm, 10 min; and a second stage: stirring speed 150rpm, dispersing speed 1000rpm, 20 min; and a third stage: stirring speed 200rpm, dispersing speed 2000rpm, 90 min; a fourth stage: stirring speed 100rpm, dispersing speed 500rpm, 60 min. Stirring in four stages is performed to achieve better mixing uniformity.
The thermal conductivity and interface thermal resistance data of the heat-conducting silicone grease are obtained as follows:
when the heat-conducting silicone grease is prepared, the BN is 40 parts by mass, the LMPAs are 0 part by mass (namely, no LMPAs are added, a blank comparison experiment is carried out), and when the polydimethylsiloxane is 60 parts by mass, the heat-conducting coefficient of the heat-conducting silicone grease is 0.46W/K.m at the temperature of 80 ℃, and the interface thermal resistance value is 1.6 ℃/W; the thermal conductivity coefficient is increased and the interface thermal resistance value is reduced along with the increase of the content of LMPAs, when the thermal conductive silicone grease is prepared, when the BN is 40 parts by mass, the LMPAs is 80 parts by mass and the polydimethylsiloxane is 60 parts by mass, the thermal conductivity coefficient of the thermal conductive silicone grease is increased to 1.8W/K.m and the interface thermal resistance value is reduced to 0.09 ℃/W, so that the low interface thermal resistance is not seen in the performance of the thermal conductive silicone grease at present, and unexpected technical effects are generated.
Table 3 shows the case of interfacial thermal resistance of the thermal grease and the thermal conductivity of the thermal grease at 80 ℃ when BN, LMPAs, and polydimethylsiloxane are different in parts by mass when the thermal grease is prepared.
TABLE 3
The heat conductivity coefficient of the heat-conducting silicone grease prepared by the composite powder is obviously increased, and the interface thermal resistance is obviously reduced.
It should be noted that the parts may be replaced by mass units such as "kg" or "g" or other mass units.
However, the above description is only a preferred embodiment of the present invention, and should not be taken as limiting the scope of the invention, which is intended to cover all the modifications and equivalents of the claims and the specification. In addition, the abstract and the title are provided to assist the patent document searching and are not intended to limit the scope of the invention.
Claims (7)
1. The application of the heat-conducting ceramic powder low-melting-point alloy composite powder in preparing a heat-conducting interface material is characterized in that the heat-conducting interface material is heat-conducting silicone grease, and the preparation method of the heat-conducting silicone grease comprises the following steps: uniformly stirring and mixing polydimethylsiloxane and low-melting-point alloy composite powder of heat-conducting ceramic powder, standing for more than 24 hours, putting into a vacuum stirrer, and stirring for more than 2 hours again in a vacuum state at a temperature of more than 80 ℃ to below the decomposition temperature of the polydimethylsiloxane;
the preparation method of the heat-conducting ceramic powder low-melting-point alloy composite powder comprises the following steps:
step 1): adding the low-melting-point alloy and the heat-conducting ceramic powder into a container filled with water, and uniformly mixing the low-melting-point alloy and the heat-conducting ceramic powder under the simultaneous action of stirring and ultrasound at a temperature from the melting point of the low-melting-point alloy to the boiling point of the water;
step 2): turning off the ultrasound, stopping heating, and keeping stirring for naturally cooling;
step 3): cooling to a temperature below the melting point of the low-melting-point alloy, carrying out suction filtration on substances in the container, taking filter residues, and putting the filter residues into an oven for drying to obtain powder; the mass ratio of the heat-conducting ceramic powder to the low-melting-point alloy is (0.5-8): 1; the low-melting-point alloy is blocky; in the step 3), when the drying oven is used for drying, the temperature in the drying oven is below the melting point temperature of the alloy; the heat-conducting ceramic powder is boron nitride; the low melting point alloy has a melting point lower than the boiling point of water.
2. The use of claim 1, wherein the water is deionized water; the low melting point alloy is blocky.
3. The use according to claim 1, wherein the ultrasound power is 200 watts or more and the ultrasound time is 1 hour or more; the melting point of the low-melting-point alloy is 70 ℃, and in the step 3): cooling to room temperature, suction filtering the materials in the container, taking the filter residue, and drying in a 50 ℃ oven to obtain powder.
4. The use according to claim 1, wherein the preparation method of step 1) is: adding the low-melting-point alloy into a container filled with water, heating to a temperature higher than the melting point of the alloy and lower than the boiling point of the water, adding ceramic powder, and uniformly mixing the low-melting-point alloy and the ceramic powder under the action of ultrasound and stirring.
5. The use as claimed in claim 1, wherein the stirring speed is 50-200rpm and the dispersion speed is 500-2000rpm in the vacuum stirrer.
6. The use according to claim 1, wherein the mixture of polydimethylsiloxane and the heat-conducting ceramic powder low-melting-point alloy composite powder is in a slurry state, and the vacuum stirrer is a planetary vacuum stirrer.
7. The use according to claim 1 or 5, wherein the polydimethylsiloxane has a viscosity of 500-1000 mPas; the mass ratio of the composite powder to the polydimethylsiloxane is as follows: (0.75-2):1.
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