CN114702828A - Boron nitride filled heat conduction interface material and preparation method thereof - Google Patents
Boron nitride filled heat conduction interface material and preparation method thereof Download PDFInfo
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Abstract
The application provides a boron nitride filled thermal interface material, comprising: a filler skeleton and a silicone resin matrix; the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in the vertical direction; wherein the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged; the silicone resin matrix comprises silicone resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-sealed vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50. This application can dispel the heat more evenly effectively in the 3D space, possesses good mechanical properties and electrical insulation simultaneously, in addition, still has lower hardness and higher percentage elongation to the easy volatile oil impregnate possesses better ageing-resistant performance.
Description
Technical Field
The application relates to the technical field of heat-conducting interface materials, in particular to a boron nitride filled heat-conducting interface material and a preparation method thereof.
Background
In the field of electronic information industry, heat is inevitably generated in the operation process of electronic equipment, and the reliability is reduced by 10 percent when the temperature of an electronic component is increased by 2 ℃ every time; the lifetime at 50 ℃ was only 1/6 at 25 ℃. With the rapid development of electronic technology, technological progress and market demand promote the development of electronic components towards miniaturization, precision, high performance and intellectualization, the integration degree and power density of electronic components are continuously improved, and the dissipation power density and heat productivity of electronic components are increasingly larger. Therefore, it is becoming more and more important to solve the heat dissipation problem, and the requirements for the thermal management technology are also more stringent.
Boron Nitride (BN) comprises six crystal forms, and common BN are cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN). Cubic boron nitride is similar to diamond and is commonly used in the manufacture of cutting tools. The hexagonal boron nitride has a graphite-like layered structure and excellent mechanical properties, and the in-plane mechanical strength of the hexagonal boron nitride can reach 500N/m. The hexagonal boron nitride also has excellent high temperature resistance, and the oxidation resistance temperature in air is 900 ℃, and can reach 2000 ℃ under the vacuum condition. Meanwhile, the hexagonal boron nitride also has ultrahigh heat conductivity and excellent insulating property. The thermal conductivity of hexagonal boron nitride measured at 300k with high purity single crystal is 730W/m.k, the thermal conductivity of cubic boron nitride is more than 1000W/m.k, while the thermal conductivity of the most common sphere-like diamond filler in the market at present is only 30W/m.k. The boron nitride can effectively improve the thermal conductivity of the polymer matrix and simultaneously keep the electrical insulation of the material, so the boron nitride is the first choice for preparing the filling type high-thermal-conductivity and insulating composite material. The high-thermal-conductivity interface material prepared by filling the silicon gel substrate with the boron nitride has a very low dielectric constant, ensures that the delay time in signal transmission is short enough, but does not block the signal transmission, thereby ensuring the smooth proceeding of signal receiving and transmission, and therefore, the high-thermal-conductivity interface material is also widely applied to network communication equipment at first. The most mature low dielectric thermal conductive material is TFLEX 700HD developed by Laerd, having a dielectric constant of 5.0 and a thermal conductivity of 5W/mk.
However, boron nitride has good chemical stability, is not easy to form chemical bonds, and is easy to agglomerate, so that boron nitride has poor affinity with a matrix material, and is difficult to be uniformly mixed in a filling process. In addition to poor dispersibility, with the increase of the filling amount of boron nitride, the viscosity of the matrix material is high, so that the matrix material cannot fully wet all boron nitride powder, and powder falling and dry cracking phenomena may occur in the processing process. Moreover, during the assembly process, the chip may be crushed due to the high hardness of the thermal interface material, and the product itself may be crushed due to the low elongation. In order to improve the flexibility of products, a large amount of micromolecular silicone oil is adopted as a plasticizer in the conventional heat-conducting interface material, but the micromolecular silicone oil is very easy to volatilize and separate out at high temperature, so that the aging resistance of the products is rapidly reduced, and after long-time high-temperature work, the products are easy to crack and pulverize, so that the heat-conducting function is reduced and even loses efficacy. In addition, the existing production process is difficult to avoid wrapping air when mixing boron nitride and a matrix material, so that a large number of cavities and depressions appear in a finished product, and the yield is greatly influenced.
Disclosure of Invention
In view of the problems, the present application is proposed to provide a boron nitride filled thermal interface material and a method of making the same that overcome or at least partially solve the problems, comprising:
a boron nitride filled thermally conductive interface material comprising: a filler skeleton and a silicone resin matrix;
the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in a vertical direction; wherein the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged;
the filler framework comprises boron nitride compound powder and a forming agent; the boron nitride compound powder comprises modified boron nitride powder, first spherical diamond powder, second spherical diamond powder and third spherical diamond powder; the modified boron nitride powder comprises spherical boron nitride powder and a silicon nitride film deposited on the surface of the spherical boron nitride; the particle size of the modified boron nitride powder is 200 mu m; the particle size of the first spherical diamond powder is 20-30 μm, the particle size of the second spherical diamond powder is 1-3 μm, and the particle size of the third spherical diamond powder is 100-300 nm;
the silicon resin matrix comprises silicon resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-seal vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50; the mass ratio of the silicone resin, the chain extender, the cross-linking agent, the catalyst and the inhibitor is 100: 20-40: 30-50: 8: 1.
preferably, the forming agent is nano silicon dioxide.
Preferably, the chain extender is hydrogen-terminated silicone oil; the cross-linking agent is side chain hydrogen-containing silicone oil; the catalyst is a platinum catalyst; the inhibitor is ethynl cyclohexanol.
A method of making a thermally conductive interface material according to any of the above, comprising:
uniformly mixing modified boron nitride powder, first spherical diamond powder, second spherical diamond powder and third spherical diamond powder to obtain boron nitride compound powder;
uniformly mixing the boron nitride compound powder and the forming agent to prepare mixed slurry;
constructing the mixed slurry into the filler skeleton with the honeycomb network structure through 3D printing;
mixing the silicone resin, the chain extender, the cross-linker, the catalyst and the inhibitor in a ratio of 100: 20-40: 30-50: 8: 1, and uniformly mixing to obtain the silicon resin matrix;
and injecting the silicon resin matrix into the gap of the filler framework through vacuum impregnation to obtain the heat-conducting interface material.
Preferably, the step of uniformly mixing the modified boron nitride powder, the first spherical diamond powder, the second spherical diamond powder and the third spherical diamond powder to obtain the boron nitride compound powder further comprises the following steps:
putting the spherical boron nitride powder into a reaction furnace and heating to a first specified temperature;
sequentially inputting nitrogen-containing gas and azido trimethyl silane gas into the reaction furnace;
and continuously rotating the reaction furnace within a first specified time to fully contact the spherical boron nitride powder with the nitrogen-containing gas and the azido trimethyl silane gas to prepare the modified boron nitride powder.
Preferably, the particle size of the modified boron nitride powder is 200 μm; the particle size of the first sphere-like diamond powder is 20-30 μm, the particle size of the second sphere-like diamond powder is 1-3 μm, and the particle size of the third sphere-like diamond powder is 100-300 nm; the method for preparing the boron nitride compound powder by uniformly mixing the modified boron nitride powder, the first spherical diamond powder, the second spherical diamond powder and the third spherical diamond powder comprises the following steps:
adjusting a first mixing proportion according to a first specified gradient, measuring a first tap density of the modified boron nitride powder and the first spherical diamond powder which are uniformly mixed according to the first mixing proportion until the first tap density reaches a maximum value, and taking the first mixing proportion corresponding to the maximum first tap density as a first optimal mixing proportion;
uniformly mixing the modified boron nitride powder and the first spherical diamond powder according to the first optimal mixing ratio to prepare first-level boron nitride compound powder;
adjusting a second mixing proportion according to a second specified gradient, measuring a second tap density of the primary boron nitride compound powder and the second sphere-like diamond powder which are uniformly mixed according to the second mixing proportion until the second tap density reaches a maximum value, and taking the second mixing proportion corresponding to the maximum second tap density as a second optimal mixing proportion;
uniformly mixing the first-grade boron nitride compound powder and the second spherical-like diamond powder according to the second optimal mixing proportion to prepare second-grade boron nitride compound powder;
adjusting a third mixing proportion according to a third specified gradient, measuring a third tap density of the secondary boron nitride compound powder and the third spheroidal diamond powder which are uniformly mixed according to the third mixing proportion until the third tap density reaches a maximum value, and taking the third mixing proportion corresponding to the maximum third tap density as a third optimal mixing proportion;
and uniformly mixing the second-stage boron nitride compound powder and the third spherical diamond-like powder according to the third optimal mixing proportion to obtain the boron nitride compound powder.
Preferably, the mixing of the silicone resin, the chain extender, the cross-linker, the catalyst and the inhibitor is performed in a ratio of 100: 20-40: 30-50: 8: 1, and before the step of preparing the silicone resin matrix, the method further comprises the following steps:
removing all first siloxane and more than half second siloxane in the double-sealed vinyl silicone oil to prepare the silicone resin; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50.
The application has the following advantages:
in the examples of the present application, by a filler skeleton and a silicone matrix; the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in a vertical direction; wherein the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged; the filler framework comprises boron nitride compound powder and a forming agent; the boron nitride compound powder comprises modified boron nitride powder, first spherical diamond powder, second spherical diamond powder and third spherical diamond powder; the modified boron nitride powder comprises spherical boron nitride powder and a silicon nitride film deposited on the surface of the spherical boron nitride; the particle size of the modified boron nitride powder is 200 mu m; the particle size of the first spherical diamond powder is 20-30 μm, the particle size of the second spherical diamond powder is 1-3 μm, and the particle size of the third spherical diamond powder is 100-300 nm; the silicon resin matrix comprises silicon resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-seal vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50; the mass ratio of the silicone resin, the chain extender, the cross-linking agent, the catalyst and the inhibitor is 100: 20-40: 30-50: 8: the filler framework can establish a macroscopic and continuous heat conduction network in the silicone resin matrix, can uniformly and effectively dissipate heat in a 3D space (the heat conduction coefficient reaches more than 10W/mk), has good mechanical property and electrical insulation property, can effectively reduce interface thermal resistance, enables interface phonon scattering to be minimum, and has low hardness, high elongation, difficult volatilization and oil leakage and good aging resistance.
Drawings
In order to more clearly illustrate the technical solutions of the present application, the drawings required to be used in the description of the present application will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings may be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic illustration of a filler skeleton according to an embodiment of the present disclosure;
fig. 2 is a schematic structural diagram of a boron nitride compound powder provided in an embodiment of the present application;
fig. 3 is a flowchart illustrating steps of a method for preparing a thermal interface material according to an embodiment of the present disclosure.
The reference numbers in the drawings of the specification are as follows:
1. modifying boron nitride powder; 2. a first spherical diamond powder; 3. second sphere-like diamond powder; 4. and the third kind of spherical diamond powder.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1, in an embodiment of the present application, a boron nitride-filled thermal interface material is provided, which specifically includes:
a filler skeleton and a silicone resin matrix;
the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in the vertical direction; wherein the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged;
the silicon resin matrix comprises silicon resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-seal vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50.
It should be noted that, compared with the conventional scheme in which boron nitride powder is randomly mixed in a matrix material, the filler framework provided by the present application can establish a macroscopic and continuous heat conducting network in the silicone resin matrix, can more uniformly and effectively dissipate heat in a 3D space (the heat conductivity coefficient reaches more than 10W/mk), and has good mechanical properties and electrical insulation properties, so that the interface thermal resistance can be effectively reduced, and the interface phonon scattering is minimized.
In addition, the first siloxane is a component which is volatile at high temperature, the second siloxane is a component which is easy to exude at high temperature, the silicone resin matrix is a macromolecular reticular polymer formed by the addition reaction of the double-seal vinyl silicone oil which is obtained by removing all the first siloxane and more than half of the second siloxane, the chain extender and the cross-linking agent, and the silicone resin matrix has the characteristics of low viscosity, low hardness, high elongation (the elongation reaches more than 1000%), low volatility and low oil permeability, can fully meet the processing and assembling requirements of products, and prolongs the service life of the products.
Next, a boron nitride-filled thermal interface material in the present exemplary embodiment will be further described.
Referring to fig. 2, in the embodiment, the filler skeleton includes boron nitride compound powder and a forming agent; the boron nitride compound powder comprises modified boron nitride powder 1, first spherical diamond powder 2, second spherical diamond powder 3 and third spherical diamond powder 4; the particle size of the modified boron nitride powder 1 is 200 mu m; the grain diameter of the first spherical diamond powder 2 is 20-30 μm, the grain diameter of the second spherical diamond powder 3 is 1-3 μm, and the grain diameter of the third spherical diamond powder 4 is 100-300 nm. It should be noted that, due to the irregular shape of the powder, when the powder is randomly stacked, it cannot be stacked like a cube without a seam, and a large number of gaps are always present between the powder, the gaps need to be filled with a matrix, so that the powder filling amount of a finished product is very low, the boron nitride compound powder provided by the application is prepared by compounding the modified boron nitride powder 1 (first-stage component) with the particle size of 200 mu m, the first-class spherical diamond powder 2 (second-stage component) with the particle size of 20-30 mu m, the second-class spherical diamond powder 3 (third-stage component) with the particle size of 1-3 mu m and the third-class spherical diamond powder 4 (fourth-stage component) with the particle size of 100-300nm, the method can effectively reduce gaps among the powders, and fully exert the heat conduction effect of the boron nitride compound powder, so that the heat conduction coefficient of the product reaches more than 10W/mk.
In this embodiment, the modified boron nitride powder 1 includes spherical boron nitride powder and a silicon nitride film deposited on the surface of the spherical boron nitride.
It should be noted that the traditional boron nitride powder is a flaky crystal in appearance, the specific surface area is very large, the actual filling rate is low, and the heat conduction interface material prepared by directly using the traditional boron nitride powder has a heat conduction coefficient which cannot exceed 2W/mk. According to the preparation method, spherical boron nitride powder with a small specific surface area is selected as a base material, and a silicon nitride film (Si3N4) is deposited on the surface of the spherical boron nitride powder through a Chemical Vapor Deposition (CVD) method, so that the compatibility of the spherical boron nitride powder and the silicon resin matrix is improved, and meanwhile, the interface thermal resistance of the spherical boron nitride powder and the silicon resin matrix is reduced, and the mixed material has lower viscosity and higher thermal conductivity coefficient under the condition of the same filling rate.
In the embodiment, the forming agent is nano silicon dioxide with the mass fraction of 1-3%.
In this embodiment, the mass ratio of the silicone resin, the chain extender, the cross-linking agent, the catalyst, and the inhibitor is 100: 20-40: 30-50: 8: 1, preferably 100: 30: 40: 8: 1. the proportion is favorable for the addition reaction of the silicone resin, the chain extender and the cross-linking agent to form a macromolecular reticular polymer so as to realize the high toughness of the silicone resin matrix.
In this embodiment, the chain extender is hydrogen-terminated silicone oil; the cross-linking agent is side chain hydrogen-containing silicone oil; the catalyst is a platinum catalyst; the inhibitor is ethynl cyclohexanol. The terminal hydrogen-containing silicone oil is polysiloxane introduced with a silicon-hydrogen bond at the tail end of a terminal through a hydrosilation reaction; the side chain hydrogen-containing silicone oil is polysiloxane with a silicon-hydrogen bond introduced to the side chain end through a hydrosilation reaction; the platinum catalyst takes metal platinum as a main active component, and has the advantages of high catalytic activity, strong selectivity, convenient preparation of the catalyst, small usage amount and the like; the ethynl cyclohexanol is white crystal or colorless transparent liquid, and can be used as inhibitor for silicon-hydrogen addition reaction.
In the embodiment, the viscosity of the double-sealing vinyl silicone oil is 50-1000cps, and preferably 500 cps.
The thermal conductivity tests and results for the thermal interface material are discussed below:
[ example 1 ] A method for producing a polycarbonate
A boron nitride filled thermally conductive interface material comprising:
a filler skeleton and a silicone resin matrix;
the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in a vertical direction; wherein the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged;
the silicon resin matrix comprises silicon resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-seal vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50.
[ example 2 ]
A boron nitride filled thermally conductive interface material comprising:
a filler skeleton and a silicone resin matrix;
the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in a vertical direction; the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged;
the silicon resin matrix comprises silicon resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-seal vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50.
[ example 3 ]
A boron nitride filled thermally conductive interface material comprising:
a filler skeleton and a silicone resin matrix;
the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in a vertical direction; the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged;
the silicon resin matrix comprises silicon resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-sealed vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50.
Comparative example 1
TFLEX 700HD, developed by leyder corporation.
On the premise of excessive heat dissipation power, the temperature difference between the chip and the heat dissipation sheet on the chip in a working state is tested by replacing the heat conduction interface material (temperature difference delta T is the chip temperature T)1-temperature t of the heat sink2). Firstly, the assembly test of the comparative example 1 is used, when the temperature of the chip and the temperature of the radiating fin are basically stable after working for a certain time, the temperature of the chip and the temperature of the radiating fin are recorded, and the temperature difference delta T is calculated0. Then respectively using the installation machines of the embodiments 1 to 3 to test, recording the temperature of the chip and the temperature of the radiating fin when the temperature of the chip and the radiating fin are basically stable after working for a certain time, and respectively calculating the temperature difference delta T1、△T2、△T3. And finally calculating the heat dissipation performance improvement rate (the heat dissipation performance improvement rate is equal to (delta T)n-△T0)/△T0)，n∈{1、2、3})。
The test data for examples 1-3 and comparative example 1 are shown in table 1:
| item | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Temperature difference (. degree. C.) | 24.2 | 26.5 | 28.8 | 18.3 |
| Heat radiation performance improvement rate (%) | 32.2 | 44.8 | 57.4 | - |
As can be seen from the data in table 1, the heat-conducting interface material provided by the present application can achieve a heat dissipation performance improvement rate of over 30%.
Referring to fig. 3, in an embodiment of the present application, there is further provided a method for preparing a thermal interface material, including:
s110, uniformly mixing modified boron nitride powder 1, first spherical diamond powder 2, second spherical diamond powder 3 and third spherical diamond powder 4 to obtain boron nitride compound powder;
s120, uniformly mixing the boron nitride compound powder and the forming agent to prepare mixed slurry;
s130, constructing the mixed slurry through 3D printing to form the filler skeleton with the honeycomb network structure;
s140, mixing the silicone resin, the chain extender, the cross-linking agent, the catalyst and the inhibitor according to a ratio of 100: 20-40: 30-50: 8: 1, and uniformly mixing to obtain the silicon resin matrix;
s150, injecting the silicon resin matrix into the gap of the filler framework through vacuum impregnation to obtain the heat-conducting interface material.
It should be noted that, compared with the conventional scheme in which boron nitride powder is randomly mixed in a polymer matrix, the filler skeleton is designed into the honeycomb network structure, so that heat dissipation in a 3D space is facilitated more effectively (the thermal conductivity coefficient reaches more than 10W/mk), and the filler skeleton has good mechanical properties and electrical insulation properties. In addition, a single thermally conductive filler has a limited effect on improving the thermal conductivity of the composite material, and the conventional method of improving the thermal conductivity by adding a single boron nitride thermally conductive filler generally cannot achieve the expected effect. According to the preparation method, the traditional boron nitride powder is compounded in a multi-stage manner, so that the formed boron nitride compound powder has excellent heat conductivity (the heat conductivity coefficient reaches more than 10W/mk).
During processing, the viscosity of the silicone resin matrix is too high, so that the silicone resin matrix is difficult to be sufficiently combined with the filler framework, and a dry cracking phenomenon can occur; in the assembling process, too high hardness of the heat-conducting interface material can lead to the chip being crushed, and too low elongation can lead to the product itself being crushed, the application matches the silicone resin with the chain extender the cross-linking agent forms macromolecular reticular polymer through the addition reaction of vinyl and silicon-hydrogen, can obtain low viscosity, low hardness, high elongation (the elongation reaches more than 1000%), the silicone resin matrix can fully meet the processing and assembling requirements of the product.
In addition, air is easily wrapped in the mixing process of the filler framework and the silicon resin matrix, so that a large number of cavities and depressions are formed in a finished product, and the yield is greatly influenced. The vacuum impregnation process is adopted, bubbles can be effectively avoided, and the product yield is greatly improved.
Next, a method for preparing a thermal interface material according to the present exemplary embodiment will be further described.
And step S110, uniformly mixing the modified boron nitride powder 1, the first spherical diamond powder 2, the second spherical diamond powder 3 and the third spherical diamond powder 4 to obtain the boron nitride compound powder.
Firstly, uniformly mixing the modified boron nitride powder 1 and the first spherical diamond powder 2 according to a first optimal mixing ratio measured in advance to prepare primary boron nitride compound powder; secondly, uniformly mixing the primary boron nitride compound powder and the second spherical diamond-like powder 3 according to a second optimal mixing ratio measured in advance to prepare secondary boron nitride compound powder; finally, uniformly mixing the secondary boron nitride compound powder and the third spherical-like diamond powder 4 according to a third optimal mixing ratio measured in advance to prepare the boron nitride compound powder; wherein the particle size of the modified boron nitride powder is 200 μm; the grain diameter of the first sphere-like diamond powder 2 is 20-30 μm, the grain diameter of the second sphere-like diamond powder 3 is 1-3 μm, and the grain diameter of the third sphere-like diamond powder 4 is 100-300 nm.
And step S120, uniformly mixing the boron nitride compound powder and the forming agent to prepare mixed slurry.
And uniformly mixing the boron nitride compound powder and the forming agent under strong shearing force to prepare the mixed slurry. Specifically, the forming agent is nano silicon dioxide with the mass fraction of 1-3%. The forming agent is beneficial to sintering and forming the boron nitride compound powder.
And building the mixed slurry into the filler skeleton with the honeycomb network structure through 3D printing as described in step S130.
According to the three-dimensional model of honeycomb network structure design, to three-dimensional model handles and saves after obtaining the data message of each processing aspect STL (stereo lithography) file and guides into SLS (Selective Laser Sintering) former, sets up suitable preheating temperature, Laser power, scanning speed, scanning interval and spread shaping technological parameter such as powder thickness, right the mixed thick liquids carry out the SLS shaping, obtain the filler skeleton.
As set forth in step S140, mixing the silicone resin, the chain extender, the cross-linking agent, the catalyst, and the inhibitor in a ratio of 100: 20-40: 30-50: 8: 1, and uniformly mixing to obtain the silicon resin matrix.
Uniformly mixing 100 parts by mass of the silicone resin, 20-40 parts by mass of the chain extender, 30-50 parts by mass of the cross-linking agent, 8 parts by mass of the catalyst and 1 part by mass of the inhibitor to obtain the silicone resin matrix. Specifically, the chain extender is hydrogen-terminated silicone oil; the cross-linking agent is side chain hydrogen-containing silicone oil; the catalyst is a platinum catalyst; the inhibitor is ethynl cyclohexanol.
And as stated in step S150, injecting the silicone resin matrix into the voids of the filler skeleton by vacuum impregnation to obtain the thermal interface material.
And in a vacuum box, injecting the silicon resin matrix into an impregnation container, placing the filler framework into the impregnation container, and repeatedly pumping and deflating for 5-8 hours to fully inject the silicon resin matrix into gaps of the filler framework to obtain the heat-conducting interface material. Specifically, the vacuum impregnation negative pressure is more than or equal to 5Mpa, and the impregnation time is 4-15 h.
In this embodiment, before the step of uniformly mixing the modified boron nitride powder 1, the first spherical diamond powder 2, the second spherical diamond powder 3, and the third spherical diamond powder 4 to obtain the boron nitride compound powder, the method further includes:
putting the spherical boron nitride powder into a reaction furnace and heating to a first specified temperature; specifically, the spherical boron nitride powder can be prepared by adding a binder into a flaky traditional boron nitride powder and then performing spray sintering, wherein the particle size of the spherical boron nitride powder is 50-500 μm; the reaction furnace may be a tube furnace; the first specified temperature may be 600 ℃.
Sequentially inputting nitrogen-containing gas and azido trimethyl silane gas into the reaction furnace; specifically, the nitrogen-containing gas has a composition of nitrogen (N)2) (ii) a The azidotrimethylsilane gas consists of azidotrimethylsilane (C)3H9N3Si)。
And continuously rotating the reaction furnace within a first specified time to fully contact the spherical boron nitride powder with the nitrogen-containing gas and the azido trimethyl silane gas to prepare the modified boron nitride powder 1. Specifically, the first specified time period may be 30 min.
It is noted that the chemical vapor deposition method is referred to as chemical vapor depositionThe reaction of chemical gases or vapors on the surface of a substrate to form a coating or nanomaterial is the most widely used technique in the semiconductor industry for depositing a variety of materials, including a wide range of insulating materials, most metallic materials and metallic alloy materials. Depositing a silicon nitride film (Si) on the surface of the spherical boron nitride powder by a chemical vapor deposition method3N4) The method belongs to a boron nitride scale non-covalent bond surface treatment process, wherein under the condition of excessive nitrogen-containing gas, the azido trimethylsilane gas fully reacts to form the silicon nitride film with high heat conductivity (the heat conductivity coefficient reaches 150W/mk), the whole process does not produce wastewater or waste gas pollution, the compatibility of the spherical boron nitride powder and the silicon resin matrix can be improved, and simultaneously the interface thermal resistance between the spherical boron nitride powder and the silicon resin matrix is reduced, so that the mixed material has lower viscosity and higher heat conductivity coefficient under the condition of the same filling rate.
In this embodiment, the particle size of the modified boron nitride powder is 200 μm; the particle size of the first spherical diamond powder 2 is 20-30 μm, the particle size of the second spherical diamond powder 3 is 1-3 μm, and the particle size of the third spherical diamond powder 4 is 100-300 nm; the method for preparing the boron nitride compound powder by uniformly mixing the modified boron nitride powder 1, the first spherical diamond powder 2, the second spherical diamond powder 3 and the third spherical diamond powder 4 comprises the following steps:
adjusting a first mixing proportion according to a first specified gradient, measuring a first tap density of the modified boron nitride powder 1 and the first spherical diamond powder 2 which are uniformly mixed according to the first mixing proportion until the first tap density reaches a maximum value, and taking the first mixing proportion corresponding to the maximum first tap density as a first optimal mixing proportion;
uniformly mixing the modified boron nitride powder 1 and the first spherical diamond powder 2 according to the first optimal mixing ratio to prepare primary boron nitride compound powder;
adjusting a second mixing proportion according to a second specified gradient, measuring a second tap density of the primary boron nitride compound powder and the second sphere-like diamond powder 3 which are uniformly mixed according to the second mixing proportion until the second tap density reaches a maximum value, and taking the second mixing proportion corresponding to the maximum second tap density as a second optimal mixing proportion;
uniformly mixing the first-grade boron nitride compound powder and the second spherical diamond-like powder 3 according to the second optimal mixing proportion to prepare second-grade boron nitride compound powder;
adjusting a third mixing proportion according to a third specified gradient, measuring a third tap density of the secondary boron nitride compound powder and the third spheroidal diamond powder 4 which are uniformly mixed according to the third mixing proportion until the third tap density reaches a maximum value, and taking the third mixing proportion corresponding to the maximum third tap density as a third optimal mixing proportion;
and uniformly mixing the second-stage boron nitride compound powder and the third spherical diamond-like powder 4 according to the third optimal mixing proportion to obtain the boron nitride compound powder.
It should be noted that the calculation model of the sphere stacking theory assumes that the powder is a perfect sphere with a single particle size, however, no matter what powder, the shape of the powder is not a perfect sphere, the particle size of the powder is normally distributed, and the theoretical particle size accounts for a small amount of the powder. Therefore, the optimal particle size and the optimal proportion calculated by the sphere accumulation theory can only be used as reference. This application is through the mass ratio of constantly adjusting two kinds of powders, tests the tap density of mixed powder after the misce bene, when tap density is the biggest, records the best compound proportion, and it obtains finally to compound step by step in this way compound powder of boron nitride can effectively reduce the space between the powder, fully exerts the heat conduction effect of compound powder of boron nitride to the coefficient of heat conductivity that realizes the product reaches more than 10W mk.
In this embodiment, the ratio of the silicone resin, the chain extender, the cross-linking agent, the catalyst, and the inhibitor is in the range of 100: 20-40: 30-50: 8: 1, and before the step of preparing the silicon resin matrix, the method also comprises the following steps:
removing all first siloxane and more than half second siloxane in the double-sealed vinyl silicone oil to prepare the silicone resin; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50. Specifically, a film evaporation device and a short-range molecular distillation device are adopted to remove all the first siloxane and more than half of the second siloxane in the double-seal vinyl silicone oil.
It should be noted that the first siloxane is a component which is volatile at high temperature, the second siloxane is a component which is easy to exude at high temperature, and these small molecule silicone oils can cause accelerated drying and embrittlement of the product during use, thereby affecting the reliability of the product. This application is through taking off in the two vinyl silicone oil seal all first siloxane and most the second siloxane can obtain low volatility, the oil impregnate of hypovolysis the silicone resin base member to effectively promote the life of product.
It should be noted that, in the embodiment of the preparation method of the heat conduction interface material provided by the present application, the product form of the heat conduction interface material is a cylindrical form, in practical applications, the heat conduction interface material may be directly used as a final finished product, or a cutting device may be used to cut the heat conduction interface material into a plurality of sheets along an axial direction, so as to obtain the heat conduction gasket with a smaller thickness, so as to meet the use requirements in different scenes.
While preferred embodiments of the present application have been described, additional variations and modifications of these embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all such alterations and modifications as fall within the true scope of the embodiments of the application.
Finally, it should also be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "include", "including" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or terminal device including a series of elements includes not only those elements but also other elements not explicitly listed or inherent to such process, method, article, or terminal device. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or terminal that comprises the element.
The boron nitride filled thermal interface material and the preparation method thereof provided by the present application are introduced in detail, and the principle and the implementation manner of the present application are explained by applying specific examples, and the description of the above examples is only used to help understanding the method and the core idea of the present application; meanwhile, for a person skilled in the art, according to the idea of the present application, the specific implementation manner and the application scope may be changed, and in summary, the content of the present specification should not be construed as a limitation to the present application.
Claims (7)
1. A boron nitride filled thermally conductive interface material, comprising: a filler skeleton and a silicone resin matrix;
the filler framework is of a honeycomb network structure; the honeycomb network structure is formed by extending mesh planes in a vertical direction; wherein the reticular plane is formed by a plurality of hollow regular hexagon periodically arranged;
the filler framework comprises boron nitride compound powder and a forming agent; the boron nitride compound powder comprises modified boron nitride powder, first spherical diamond powder, second spherical diamond powder and third spherical diamond powder; the modified boron nitride powder comprises spherical boron nitride powder and a silicon nitride film deposited on the surface of the spherical boron nitride; the particle size of the modified boron nitride powder is 200 mu m; the particle size of the first spherical diamond powder is 20-30 μm, the particle size of the second spherical diamond powder is 1-3 μm, and the particle size of the third spherical diamond powder is 100-300 nm;
the silicon resin matrix comprises silicon resin, a chain extender, a cross-linking agent, a catalyst and an inhibitor; the silicone resin is double-seal vinyl silicone oil with all the first siloxane and more than half of the second siloxane removed; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50; the mass ratio of the silicone resin, the chain extender, the cross-linking agent, the catalyst and the inhibitor is 100: 20-40: 30-50: 8: 1.
2. the thermal interface material of claim 1, wherein the forming agent is nanosilica.
3. The thermal interface material of claim 1, wherein the chain extender is a hydrogen terminated silicone oil; the cross-linking agent is side chain hydrogen-containing silicone oil; the catalyst is a platinum catalyst; the inhibitor is ethynl cyclohexanol.
4. A method for preparing a thermal interface material according to any one of claims 1-3, comprising:
uniformly mixing the modified boron nitride powder, the first spherical diamond powder, the second spherical diamond powder and the third spherical diamond powder to prepare the boron nitride compound powder;
uniformly mixing the boron nitride compound powder and the forming agent to prepare mixed slurry;
constructing the mixed slurry into the filler skeleton with the honeycomb network structure through 3D printing;
mixing the silicone resin, the chain extender, the cross-linker, the catalyst and the inhibitor in a ratio of 100: 20-40: 30-50: 8: 1, and uniformly mixing to obtain the silicon resin matrix;
and injecting the silicon resin matrix into the gap of the filler framework through vacuum impregnation to obtain the heat-conducting interface material.
5. The preparation method according to claim 4, wherein before the step of uniformly mixing the modified boron nitride powder, the first spherical diamond powder, the second spherical diamond powder and the third spherical diamond powder to obtain the boron nitride compound powder, the method further comprises the following steps:
putting the spherical boron nitride powder into a reaction furnace and heating to a first specified temperature;
sequentially inputting nitrogen-containing gas and azido trimethyl silane gas into the reaction furnace;
and continuously rotating the reaction furnace within a first specified time to fully contact the spherical boron nitride powder with the nitrogen-containing gas and the azido trimethyl silane gas to prepare the modified boron nitride powder.
6. The preparation method according to claim 4, wherein the step of uniformly mixing the modified boron nitride powder, the first spherical diamond powder, the second spherical diamond powder and the third spherical diamond powder to obtain the boron nitride compound powder comprises the following steps:
adjusting a first mixing proportion according to a first designated gradient, measuring a first tap density of the modified boron nitride powder and the first spherical diamond powder which are uniformly mixed according to the first mixing proportion until the first tap density reaches a maximum value, and taking the first mixing proportion corresponding to the maximum first tap density as a first optimal mixing proportion;
uniformly mixing the modified boron nitride powder and the first spherical diamond powder according to the first optimal mixing ratio to prepare first-level boron nitride compound powder;
adjusting a second mixing proportion according to a second specified gradient, measuring a second tap density of the primary boron nitride compound powder and the second spheroidal diamond powder which are uniformly mixed according to the second mixing proportion until the second tap density reaches a maximum value, and taking the second mixing proportion corresponding to the maximum second tap density as a second optimal mixing proportion;
uniformly mixing the first-grade boron nitride compound powder and the second spherical-like diamond powder according to the second optimal mixing proportion to prepare second-grade boron nitride compound powder;
adjusting a third mixing proportion according to a third specified gradient, measuring a third tap density of the secondary boron nitride compound powder and the third spheroidal diamond powder which are uniformly mixed according to the third mixing proportion until the third tap density reaches a maximum value, and taking the third mixing proportion corresponding to the maximum third tap density as a third optimal mixing proportion;
and uniformly mixing the second-stage boron nitride compound powder and the third spherical diamond-like powder according to the third optimal mixing proportion to obtain the boron nitride compound powder.
7. The method of claim 4, wherein the silicone resin, the chain extender, the cross-linker, the catalyst, and the inhibitor are mixed in a ratio of 100: 20-40: 30-50: 8: 1, and before the step of preparing the silicone resin matrix, the method further comprises the following steps:
removing all first siloxane and more than half second siloxane in the double-sealed vinyl silicone oil to prepare the silicone resin; wherein the first siloxane comprises a siloxane having a number of silicon atoms of 3 to 20 and the second siloxane comprises a siloxane having a number of silicon atoms of 20 to 50.
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