High-thermal-conductivity boron nitride/epoxy resin composite material and preparation method and application thereof
Technical Field
The invention relates to the technical field of electronic packaging materials, in particular to a high-thermal-conductivity boron nitride/epoxy resin composite material and a preparation method and application thereof.
Background
Due to the miniaturization and high performance requirements of electronic devices, the performance and lifetime of electronic devices are severely affected by the heat accumulation caused by high integration density and high power density. The thermal interface material is used as a heat conduction path for leading heat from a heat source to a heat sink, and the heat conduction performance and the mechanical performance of the thermal interface material play a key role in the thermal management capacity of the electronic device. The high molecular polymer based composite material becomes the microelectronic packaging material which is most widely applied at present due to the easy processing property and low cost. Generally, high molecular polymers have low thermal conductivity (about 0.2W/mK), so high thermal conductive fillers (graphene, carbon nanotubes, aluminum nitride, boron nitride, etc.) are required to be added to improve the thermal conductivity of the high molecular polymer composite material. The hexagonal boron nitride is similar to a hexagonal crystal structure of graphite, has very high thermal conductivity, electrical insulation performance, thermal stability, chemical stability and corrosion resistance, and is widely applied to preparation of high-thermal-conductivity and electrical-insulation high-molecular polymer-based composite materials as a thermal-conductive filler. However, the thermal conductivity of the composite material prepared by simply mixing the thermally conductive filler into the high molecular polymer matrix is still not high due to the low thermal conductivity enhancement efficiency, and the mechanical properties and processability of the composite material are reduced by adding a large amount of filler to enhance the thermal conductivity of the composite material. Therefore, the research on the heat-conducting composite material with high heat conductivity and good mechanical property is very important for improving the heat management capability and reliability of the power device.
Chinese patent CN105985566A discloses a high-thermal-conductivity insulating polymer-based composite material and a preparation method thereof, and the method specifically comprises the steps of firstly grinding boron nitride, polypropylene, polytetrafluoroethylene, ultra-high molecular weight polyethylene, graphite and zinc oxide into powder, then heating and stirring uniformly, finally adding a silane coupling agent, and cooling and forming. The composite material prepared by simply heating and mixing boron nitride and polypropylene and the like by the method has low resistivity. Chinese patent CN103172924A discloses a high-thermal-conductivity polymer composite material and a preparation method thereof, the method comprises the steps of modifying hexagonal boron nitride, then modifying carbon fiber, and finally blending the polymer, the modified hexagonal boron nitride and the modified carbon fiber to obtain the composite material, wherein the modification of the hexagonal boron nitride is specifically that the hexagonal boron nitride is added into a solvent, then stirred in an oil bath pot, and then subjected to suction filtration and vacuum drying until the weight is constant. The mechanical property of the composite material can be improved to a certain extent by adopting the method of blending the polymer, the modified hexagonal boron nitride and the modified carbon fiber, and the thermal conductivity of the composite material is about 2.663W/mK and needs to be further improved.
Therefore, it is necessary to provide a functional boron nitride nanosheet filled epoxy resin composite material which has high thermal conductivity and thermal stability and good mechanical properties, and the composite material is used as a thermal interface material to solve the problem of efficient heat dissipation and transmission heat management of a three-dimensional integrated power device and greatly improve the use reliability of the power device.
Disclosure of Invention
The invention provides a high-thermal-conductivity boron nitride/epoxy resin composite material and a preparation method and application thereof, and aims to connect a boron nitride nanosheet with high thermal conductivity with epoxy resin into a whole through silane coupling agent molecules, improve the matching property between a filler-matrix interface to reduce the interface thermal resistance, simultaneously enhance the dispersity of the boron nitride nanosheet in the epoxy resin by utilizing the functionalized boron nitride nanosheet of the silane coupling agent, facilitate the formation of a thermal conductive network, realize the high-efficient thermal conduction in the arrangement direction by fully exerting the characteristic of high thermal conductivity in the in-plane direction of the boron nitride nanosheet in an oriented arrangement manner, and efficiently release the heat energy generated by a three-dimensional integrated power device by taking the boron nitride/epoxy resin composite material with high thermal conductivity as a thermal interface material, thereby greatly improving the performance and prolonging the service life of high-end electronic components.
In order to achieve the above object, the embodiments of the present invention provide the following technical solutions:
a preparation method of a high-thermal-conductivity boron nitride/epoxy resin composite material comprises the following steps:
(1) carrying out ultrasonic stripping on boron nitride powder in a mixed solution of isopropanol and deionized water; centrifuging the ultrasonically stripped upper-layer dispersion liquid, and performing vacuum filtration and drying on the obtained centrifugal liquid to obtain a boron nitride nanosheet;
(2) magnetically stirring the boron nitride nanosheets obtained in the step (1) in a silane coupling agent solution to obtain a dispersion liquid; filtering, cleaning and drying the obtained dispersion liquid to obtain silane functionalized boron nitride nanosheets; wherein the mass of the silane coupling agent accounts for 0.05-10% of that of the boron nitride nanosheet;
(3) dispersing the silane functionalized boron nitride nanosheets obtained in the step (2), and mixing with an epoxy resin solution to obtain a mixed solution; heating and stirring the mixed solution, and then cooling to obtain a mixture of silane functionalized boron nitride nanosheets and epoxy resin; wherein the silane functionalized boron nitride nanosheet accounts for 5-40% of the total mass of the silane functionalized boron nitride nanosheet and the epoxy resin;
(4) and (4) spin-coating the mixture obtained in the step (3) on a glass sheet or a silicon sheet, and then performing pre-curing, hot-pressing and curing to obtain the high-thermal-conductivity boron nitride/epoxy resin composite material.
Preferably, the silane coupling agent solution in the step (2) is obtained by hydrolyzing a silane coupling agent in an aqueous ethanol solution.
Preferably, the magnetic stirring in the step (2) is carried out at 70-90 ℃ for 5-10 h.
Preferably, the washing in the step (2) is specifically washing with absolute ethyl alcohol and deionized water for more than two times.
Preferably, the silane-functionalized nanosheets in step (3) are dispersed by adding the silane-functionalized nanosheets into an isopropanol solution for ultrasonic dispersion.
Preferably, step (4) further comprises the steps of adding a curing agent and ultrasound, stirring and repeatedly vacuumizing before spin-coating the mixture of silane-functionalized boron nitride nanosheets and epoxy resin.
Preferably, the hot pressing in the step (4) is specifically hot pressing for 20-60 min under the conditions of 4-10 MPa and 70-100 ℃.
The pre-curing in the step (4) is performed by standing for 3-5 hours at room temperature; the curing is performed by standing for 4-6 hours at the temperature of 55-65 ℃.
The invention also provides a high-thermal-conductivity boron nitride/epoxy resin composite material, which is prepared by the method.
The invention also provides an application of the composite material in a power device.
The factors influencing the thermal conductivity of the composite material mainly include: intrinsic thermal conductivity of the filler, dispersibility of the filler in the matrix, compatibility between the filler and the matrix interface, orientation of the filler in the matrix, and the like. First, compared to the original boron nitride powder (400W/mK), boron nitride nanoplates have higher thermal conductivity (600W/mK) because phonon-phonon scattering is reduced as the number of layers is reduced, while interlayer interactions and couplings in multilayer boron nitride break the two-dimensional selection rule. Meanwhile, the boron nitride nanosheet is more beneficial to forming a heat conducting network in a high molecular polymer matrix due to the thinner thickness. Secondly, effective dispersion of boron nitride nanoplates is a fundamental requirement for increasing the thermal conductivity of polymer-based composites, requiring an interconnected network of contacts between the boron nitride nanoplate particles, thereby creating an optimal heat transfer path through the matrix through particle-particle connectivity. The two-dimensional plate-like fillers exist in different dispersed states in the polymer matrix depending on the technique used to prepare the composite and the affinity between the matrix and the filler. Furthermore, due to the presence of a large number of interfaces between the filler and the matrix or between the filler and the matrix in the composite material, phonon scattering at the interfaces generates interface thermal resistance, which is decisive for the performance of the composite material. Therefore, the compatibility between interfaces is improved, and the interface thermal resistance generated by phonon scattering is reduced, so that the thermal conductivity of the composite material is improved. In order to improve the properties of the composite, it is necessary to fix the polymer on the surface of the nanoparticles so that a continuous phase is created between the filler and the matrix. Filler surface functionalization is a process used to improve the interfacial compatibility of fillers with the matrix to achieve high levels of dispersion. At present, the modification of boron nitride mainly comprises covalent modification and non-covalent modification, wherein the covalent modification can connect the boron nitride with a polymer matrix through a covalent bond, and the non-covalent modification bonds the boron nitride with the polymer matrix through pi-pi action. Finally, the orientation of the filler in the polymer matrix also determines the thermal conductivity of the composite due to the anisotropy of the two-dimensional material. The fillers are arranged along the same direction under the action of an external field, so that the thermal conductivity of the composite material can be effectively improved. Therefore, to achieve high thermal conductivity of the composite material, factors such as intrinsic thermal conductivity of the filler, dispersibility of the filler, matching between the filler and the matrix interface, and arrangement of the filler in the polymer matrix need to be considered.
Under the background, boron nitride nanosheets are obtained by carrying out ultrasonic stripping on original boron nitride powder, the boron nitride nanosheets are modified by utilizing a silane coupling agent through a sol-gel method so as to enhance the dispersibility of the boron nitride nanosheets in epoxy resin and the matching property between interfaces, and finally, the ordered arrangement of the functionalized boron nitride nanosheets in an epoxy resin matrix is realized by adopting a method combining spin coating and hot pressing. The functional boron nitride nanosheet filled epoxy resin composite material with high thermal conductivity, high thermal stability and good mechanical property can be used as a thermal interface material to solve the problem of efficient heat dissipation and transmission heat management of a three-dimensional integrated power device, and the use reliability of the power device is greatly improved.
The scheme of the invention has the following beneficial effects:
(1) according to the preparation method of the high-thermal-conductivity boron nitride/epoxy resin composite material, the boron nitride powder is ultrasonically stripped to obtain the boron nitride nanosheets, and the boron nitride nanosheets are thinner, so that interlayer phonon scattering is reduced, a thermal conductive network is easily formed in the epoxy resin, and the thermal conductivity of the composite material is improved.
(2) According to the preparation method provided by the invention, the boron nitride nanosheets are subjected to functionalization treatment to obtain silane functionalized boron nitride nanosheets, and the boron nitride nanosheets are covalently connected with the epoxy resin through the silane coupling agent, so that the interface matching property and the bonding strength between the boron nitride and the epoxy resin are improved, the interface thermal resistance is reduced, the thermal conductivity of the composite material is improved, and meanwhile, the silane coupling agent can enhance the dispersibility of the boron nitride in the epoxy resin.
(3) According to the preparation method provided by the invention, spin coating and hot pressing are combined, so that the functionalized boron nitride nanosheets are directionally arranged along the plane of the film in the epoxy resin under the action of an external field, the characteristic of high thermal conductivity in the plane of the two-dimensional structure of the boron nitride is fully utilized, and the in-plane thermal conductivity of the composite material film is greatly improved.
(4) The high-thermal-conductivity boron nitride/epoxy resin composite material provided by the invention has improved dynamic thermodynamic properties, glass transition temperature and other properties. Wherein the thermal conductivity is about 5.86W/mK.
(5) The high-thermal-conductivity boron nitride/epoxy resin composite material provided by the invention is applied to a high-power device as a thermal interface material, so that the heat dissipation performance of the power device can be effectively improved, and the overall reliability of the device is greatly improved.
Drawings
FIG. 1 is a flow chart of a production process of the present invention;
fig. 2 is a schematic diagram of the application of the high thermal conductivity boron nitride/epoxy resin composite material in a high power device.
Description of the drawings: 1. a substrate; 2. micro-bumps; 3. a chip; 4. a heat sink; 5. a heat sink; 6. an underfill material; 7. a thermal interface material I; 8. and a thermal interface material II.
Detailed Description
In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following detailed description is given with reference to specific embodiments.
The preparation method of the high-thermal-conductivity boron nitride/epoxy resin composite material comprises the step of carrying out ultrasonic stripping on original boron nitride powder in a mixed solution of isopropanol and deionized water by using an ultrasonic-assisted liquid phase stripping method, wherein in the ultrasonic stripping process, hydroxyl is generated on the surface and the edge of boron nitride due to hydrolysis reaction, so that the stripped boron nitride nanosheet can be directly functionalized by a silane coupling agent in the next step without additional hydroxylation treatment, and stripping and hydroxylation can be synchronously realized due to ultrasonic treatment of boron nitride in the mixed solution of isopropanol and deionized water. And functionalizing the stripped boron nitride nanosheet with hydroxyl in an ethanol aqueous solution of a silane coupling agent by adopting a sol-gel method, wherein the using amount of the silane coupling agent needs to be controlled to be between 0.05 and 10 mass percent of the boron nitride, and the boron nitride nanosheet is insufficiently modified when the using amount is less than 0.05 percent, while the intrinsic thermal conductivity of the boron nitride nanosheet is reduced when the using amount is more than 10 percent. The method comprises the steps of uniformly dispersing functional boron nitride nanosheets in an epoxy resin matrix under the action of magnetic stirring by a solution mixing method, spin-coating a mixture of the functional boron nitride nanosheets and epoxy resin on a glass sheet or a silicon sheet, and then carrying out hot pressing on a pre-cured composite material to obtain the high-thermal-conductivity boron nitride/epoxy resin composite material.
Example 1
The method comprises the following steps: weighing 3g of original boron nitride powder, adding the powder into 600mL of mixed solution of isopropanol and deionized water (volume ratio is 1:1), and carrying out ultrasonic treatment in a water bath for 12h for stripping;
step two: centrifuging the ultrasonically treated upper-layer dispersion liquid at the rotating speed of 2000rpm for 20min to remove residual non-stripped boron nitride, then carrying out vacuum filtration on the upper-layer dispersion liquid, and drying at 100 ℃ for 10h to obtain boron nitride nanosheets;
step three: adding a silane coupling agent with the mass of 9 percent (0.18g) of boron nitride nanosheets into 300mL of ethanol aqueous solution, and magnetically stirring the mixed solution at 60 ℃ for 30min to hydrolyze the silane coupling agent;
step four: adding 2g of boron nitride nanosheet powder into the solution obtained in the third step, and magnetically stirring for 10 hours at the temperature of 70 ℃ again to functionalize the boron nitride nanosheets;
step five: filtering the dispersion liquid obtained in the fourth step, repeatedly cleaning the dispersion liquid with absolute ethyl alcohol and deionized water for three times, and drying the dispersion liquid at 100 ℃ for 12 hours to obtain silane functionalized boron nitride nanosheets;
step six: weighing 1g of silane functionalized boron nitride nanosheet, adding the silane functionalized boron nitride nanosheet into 20ml of isopropanol solution, and dispersing for 1h under the action of ultrasound;
step seven: weighing 3.2g of epoxy resin, adding the epoxy resin into 15ml of isopropanol solution, and dispersing for 30min at 50 ℃ under the action of ultrasound;
step eight: mixing the silane functionalized boron nitride nanosheet dispersion liquid with an epoxy resin solution under the action of continuous ultrasound, stirring the mixed solution at 60 ℃ for 4 hours, and cooling to obtain a mixture of the silane functionalized boron nitride nanosheet and the epoxy resin;
step nine: adding 0.8g of curing agent into the mixture, carrying out ultrasonic treatment and stirring for 5min to uniformly disperse the curing agent, and then repeatedly vacuumizing the generated mixture for three times for 10 min;
step ten: coating the mixture obtained in the ninth step on a glass sheet for 1min at 2000rpm by using a spin coater, standing for 3h at room temperature to volatilize the solvent and perform pre-curing;
step eleven: and (3) carrying out hot pressing on the pre-cured silane functionalized boron nitride nanosheet and the epoxy resin composite material for 60min under the conditions of 10MPa and 100 ℃, and then completely curing for 4h at 65 ℃ to obtain the final high-thermal-conductivity boron nitride/epoxy resin composite film material.
Example 2
The method comprises the following steps: weighing 3g of original boron nitride powder, adding the powder into 600ml of mixed solution of isopropanol and deionized water (the volume ratio is 1:1), and carrying out water bath ultrasonic treatment for 12h for stripping; the particle size of the original boron nitride powder is 1-2 μm; the ultrasonic power is 180W, and the ultrasonic time is 12 h;
step two: centrifuging the ultrasonically treated upper-layer dispersion liquid at the rotating speed of 2000rpm for 20min to remove residual non-stripped boron nitride, then carrying out vacuum filtration on the upper-layer dispersion liquid, and drying at 100 ℃ for 10h to obtain boron nitride nanosheets; the plane size of the obtained boron nitride nanosheet is 50-500 nm, wherein the statistical average size of 100 samples is about 301 nm; the thickness is 2-3 nm;
step three: adding a silane coupling agent with the mass of 3 percent (0.06g) of boron nitride nanosheets into 100ml of ethanol aqueous solution, and magnetically stirring the mixed solution at 60 ℃ for 30min to hydrolyze the silane coupling agent;
step four: adding 2g of boron nitride nanosheet powder into the solution obtained in the third step, and magnetically stirring the solution at the temperature of 80 ℃ for 6 hours again to functionalize the boron nitride nanosheets;
step five: filtering the dispersion liquid obtained in the fourth step, repeatedly cleaning the dispersion liquid with absolute ethyl alcohol and deionized water for three times, and drying the dispersion liquid at 100 ℃ for 12 hours to obtain silane functionalized boron nitride nanosheets;
step six: weighing 1g of silane functionalized boron nitride nanosheet, adding the silane functionalized boron nitride nanosheet into 20ml of isopropanol solution, and dispersing for 1h under the action of ultrasound;
step seven: weighing 1.2g of epoxy resin, adding the epoxy resin into 5ml of isopropanol solution, and dispersing for 30min at 50 ℃ under the action of ultrasound;
step eight: mixing the silane functionalized boron nitride nanosheet dispersion liquid with an epoxy resin solution under the action of continuous ultrasound, stirring the mixed solution at 60 ℃ for 4 hours, and cooling to obtain a mixture of the silane functionalized boron nitride nanosheet and the epoxy resin;
step nine: adding 0.3g of curing agent into the mixture, carrying out ultrasonic treatment and stirring for 5min to uniformly disperse the curing agent, and then repeatedly vacuumizing the generated mixture for three times for 10 min;
step ten: coating the mixture obtained in the ninth step on a glass sheet for 1min at 2000rpm by using a spin coater, standing for 4h at room temperature to volatilize the solvent and perform pre-curing;
step eleven: and (3) carrying out hot pressing on the pre-cured silane functionalized boron nitride nanosheet and the epoxy resin composite material for 30min under the conditions of 5MPa and 80 ℃, and then completely curing for 5h at 60 ℃ to obtain the final high-thermal-conductivity boron nitride/epoxy resin composite film material.
The thermal conductivity of the pure epoxy resin is 0.21W/mK, the thermal conductivity of the boron nitride is 3.03W/mK, and the thermal conductivity of the composite film material containing 40% of silane functionalized boron nitride nanosheets is improved to about 5.86W/mK.
The infrared characterization test of the composite material film heated at the central hot spot at 65 ℃ shows that: the surface temperature of the 40% functionalized boron nitride nanosheet filled epoxy resin composite film reaches a stable state after being heated for two minutes, the surface temperature of the pure epoxy resin film and the 40% original boron nitride filled epoxy resin composite film reaches the stable state after being heated for four minutes, meanwhile, the surface temperature of the 40% functionalized boron nitride nanosheet filled epoxy resin composite film is more uniformly distributed, the temperature of a hot spot is reduced to 49 ℃, the lowest temperature of the edge is 33 ℃, the highest temperatures of the hot spot of the pure epoxy resin film and the 40% original boron nitride filled epoxy resin composite film are respectively 59 ℃ and 53 ℃, and the lowest temperatures of the edge are respectively 28 ℃ and 31 ℃, which shows that the 40% functionalized boron nitride nanosheet filled epoxy resin composite film has more excellent heat management capability.
The obtained high-thermal-conductivity boron nitride/epoxy resin composite film material is applied to high-power devices and is used as a thermal interface material. As shown in fig. 2, the substrate 1 and the chip 3 are I/O interconnected through the micro bumps 2, the thermal stress caused by the mismatch of thermal expansion coefficients is relieved by adding the underfill 6 in the gap, the heat generated by the power chip 3 is transferred to the heat sink 4 through the thermal interface material I7, and then is transferred to the heat sink 5 through the thermal interface material ii 8, and finally is exhausted. The high-thermal-conductivity boron nitride/epoxy resin composite material is used as a thermal interface material, so that heat energy generated by the service of a three-dimensional integrated power device can be efficiently released, and the performance and the service life of high-end electronic components are greatly improved.
Example 3
The method comprises the following steps: weighing 3g of original boron nitride powder, adding the powder into 600ml of mixed solution of isopropanol and deionized water (the volume ratio is 1:1), and carrying out water bath ultrasonic treatment for 12h for stripping;
step two: centrifuging the ultrasonically treated upper-layer dispersion liquid at the rotating speed of 2000rpm for 20min to remove residual non-stripped boron nitride, then carrying out vacuum filtration on the upper-layer dispersion liquid, and drying at 100 ℃ for 10h to obtain boron nitride nanosheets;
step three: adding a silane coupling agent with the mass of 0.05 percent (0.001g) of boron nitride nanosheets into 20ml of ethanol aqueous solution, and magnetically stirring the mixed solution at 60 ℃ for 30min to hydrolyze the silane coupling agent;
step four: adding 2g of boron nitride nanosheet powder into the solution obtained in the third step, and magnetically stirring for 5 hours at 90 ℃ to functionalize the boron nitride nanosheets;
step five: filtering the dispersion liquid obtained in the fourth step, repeatedly cleaning the dispersion liquid with absolute ethyl alcohol and deionized water for four times, and drying the dispersion liquid at 100 ℃ for 12 hours to obtain silane functionalized boron nitride nanosheets;
step six: weighing 1g of silane functionalized boron nitride nanosheet, adding the silane functionalized boron nitride nanosheet into 20ml of isopropanol solution, and dispersing for 1h under the action of ultrasound;
step seven: weighing 15.2g of epoxy resin, adding the epoxy resin into 60ml of isopropanol solution, and dispersing for 30min at 50 ℃ under the action of ultrasound;
step eight: mixing the silane functionalized boron nitride nanosheet dispersion liquid with an epoxy resin solution under the action of continuous ultrasound, stirring the mixed solution at 60 ℃ for 4 hours, and cooling to obtain a mixture of the silane functionalized boron nitride nanosheet and the epoxy resin;
step nine: adding 3.8g of curing agent into the mixture, carrying out ultrasonic treatment and stirring for 5min to uniformly disperse the curing agent, and then repeatedly vacuumizing the generated mixture for three times for 10 min;
step ten: coating the mixture obtained in the ninth step on a glass sheet for 1min at 2000rpm by using a spin coater, standing for 5h at room temperature to volatilize the solvent and perform pre-curing;
step eleven: and (3) carrying out hot pressing on the pre-cured silane functionalized boron nitride nanosheet and the epoxy resin composite material for 20min under the conditions of 4MPa and 70 ℃, and then completely curing for 6h at 55 ℃ to obtain the final high-thermal-conductivity boron nitride/epoxy resin composite film material.
Embodiments 1 to 3 uniformly disperse functionalized boron nitride nanosheets in epoxy resin by using a solution mixing method, the functionalized boron nitride nanosheets account for 5% to 40% of the total mass of the silane functionalized boron nitride nanosheets and the epoxy resin, amino groups of silane molecules on the boron nitride nanosheets react with epoxy groups of the epoxy resin to covalently connect the boron nitride nanosheets and the epoxy resin into a whole, and the directionally arranged functionalized boron nitride nanosheets filled epoxy resin composite material film is prepared by combining spin coating and hot pressing.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.