CN111777840A - A kind of epoxy resin micro-nano blended composite material for encapsulating power electronic high-power device and preparation method thereof - Google Patents

Abstract

The invention discloses an epoxy resin micro-nano blended composite material for encapsulating power electronic high-power devices and a preparation method, and belongs to the cross field of high voltage and insulation technology and composite materials. In the process of preparing the composite material, the nano-aluminum nitride surface modified by silane coupling agent is first prepared as a thermally conductive filler, which is uniformly dispersed in the epoxy resin by ultrasonic waves, and the micro-nano composite material is prepared by vacuum degassing, infusion molding and other processes. mixed composite materials. The micro-nano blended composite material has excellent thermal conductivity and electrical insulation properties, and can be used as a packaging material for power electronic high-power devices. The preparation method of the micro-nano blended composite material is simple, easy to operate, and low in cost, and is suitable for industrial production.

Description

A kind of epoxy resin micro-nano blended composite material for encapsulation of power electronic high-power devices materials and preparation method

technical field

The invention belongs to the intersecting fields of high voltage and insulation technology and composite materials, in particular to an epoxy resin micro-nano blended composite material for encapsulating power electronic high-power devices and a preparation method.

Background technique

With the development of new energy in the 21st century, the demand for global energy interconnection and the introduction of the ubiquitous power Internet of Things, power electronics have gradually developed from the first generation of controllable rectifiers (SCR) to the second generation of bipolar junction transistors (BJTs). ), turn-off transistor (GTO), semiconductor field effect transistor (MOSFET), third-generation insulated gate bipolar transistor (IGBT) to fourth-generation intelligent integrated circuits and intelligent power module power electronic devices. In just 50 years, power electronics technology has undergone rapid development, and the performance of power electronic devices based on silicon (Si) has restricted the development of power electronic devices towards high voltage, high temperature and high frequency. Therefore, power devices such as silicon carbide (SiC) and gallium nitride (GaN) based on wide bandgap (WBG) materials have begun to attract the attention of power electronics engineers. Compared with traditional silicon power devices, SiC power devices have lower intrinsic carrier concentration (10-35 orders of magnitude), higher breakdown electric field (4-20 times), higher thermal conductivity (3- 13 times) and larger saturation electron drift velocity (2-2.5 times). At the same time, SiC power devices can withstand higher breakdown voltages, higher currents, higher operating temperatures (200-300°C), higher switching speeds and lower switching losses. When SiC power devices are subjected to high temperature and high pressure, higher requirements are placed on the heat resistance and electrical resistance of the external package, and according to the IEC JEDEC standard, there are test items about the maximum energy/current of the case in the device test items, so SiC The packaging materials of power devices seriously restrict the development of power devices.

Therefore, the rise of a new generation of power electronic devices has put forward higher requirements for packaging insulating materials. The thermal conductivity and electrical properties of insulating materials are critical to the safe operation of power electronic devices and the stability of electrical equipment. Epoxy resin is one of the main packaging materials at present. However, its thermal conductivity and thermal stability have always restricted the development of the device. The heat generated during the operation of the device cannot be dissipated in time, resulting in a decrease in the dielectric strength and insulation life of the epoxy resin. Therefore, it is very important to study the thermal and electrical properties of epoxy resins for improving the reliability of devices.

Since the concept of "nanodielectric" was formally proposed in 1994, many researchers at home and abroad have devoted themselves to improving the thermal conductivity and electrical properties of polymer insulating materials by adding nanoparticles. Particles can effectively improve the breakdown characteristics, electrical conductivity and space charge characteristics of polymer insulating materials. The thermal conductivity and electrical properties of epoxy resins are the key factors limiting the performance and reliability of SiC power devices. Therefore, it is very necessary to use nanotechnology to improve the thermal conductivity and electrical properties of epoxy resins. There are relatively many studies on improving the thermal conductivity of epoxy resins, and there are many different nanoparticles that can be added to epoxy resins to improve their thermal conductivity. Due to the low thermal conductivity of epoxy resins (~0.2W/mK), for aluminum nitride (AIN), aluminum oxide (Al ₂ O ₃ ), silicon carbide (SiC), silicon nitride (Si ₃ N ₄ ) , boron nitride (BN), and graphene (GO) particles with high thermal conductivity are incorporated into epoxy resin matrix, which can significantly improve the thermal conductivity of composites. The mechanism of action of thermal conductivity originates from the transport of phonons inside the material. The addition of fillers promotes the formation of a thermally conductive network, which can reduce the scattering of phonons to a certain extent and improve thermal conductivity. The formation of the thermal network is closely related to the thermal conductivity, size and content of the filler. However, the improvement of nanoparticles on epoxy resin composites is very limited. Compared with nanometer particles, it is easier to establish a stable thermal conduction network, but it will lead to a large number of defects and voids between the filler and the matrix, resulting in increased dielectric loss, decreased dielectric strength and other insulation problems. Appropriate nanoparticle loading can improve the dielectric properties of materials by suppressing charge injection and trapping mobile charges through deep traps. However, the addition of nanoparticles increases the interface between the filler and the matrix, limiting the conductive properties of the composites. Gradually, mixed fillers combining the advantages of microparticles and nanoparticles are applied in epoxy composites to develop composites with high electrical conductivity and excellent dielectric breakdown strength. AIN is also a commonly used inorganic filler because of its high thermal conductivity (150-300W/(mk)) and excellent insulating properties. High particle loading can improve the thermal conductivity of epoxy resins. Furthermore, surface modification of the filler is essential to reduce the thermal resistance between the filler and the matrix. Silane coupling agents are widely used in the modification of surface fillers due to their low price, simple operation, and industrialized processing.

To sum up, the micro-nano blended composite materials after adding micro-nano materials to epoxy resins at home and abroad are in the laboratory research stage, and certain progress has been made in recent years. Using nanomaterials with high thermal conductivity and high electrical properties to improve the thermal conductivity and electrical properties of epoxy resins has become one of the key technologies to break through the bottleneck of a new generation of power electronic devices. There are few studies on the application of composite materials in the encapsulation of power electronic devices, so epoxy resin micro-nano blended composite materials with high thermal conductivity and high electrical performance have broad research prospects and engineering significance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a surface modification process of aluminum nitride suitable for encapsulation of power electronic high-power devices.

Another object of the present invention is to provide an aluminum nitride reinforced high thermal conductivity epoxy resin composite material for encapsulating power electronic high-power devices and a preparation process thereof. The micro-nano blended composite material prepared according to the process has high thermal conductivity. , The characteristics of excellent electrical performance.

The technical problem to be solved by this invention adopts the following technical scheme to realize:

The invention firstly discloses a preparation method of epoxy resin micro-nano blended composite material for encapsulating power electronic high-power devices, which comprises the following steps:

Step 1: Mix micron aluminum nitride and nano aluminum nitride by 20 parts by mass: 2 to 4 parts by mass to obtain micro and nano aluminum nitride particles, and dry the micro and nano aluminum nitride particles; ~20 parts by mass: 3-4 parts by mass are mixed, and then the dried micro-nano aluminum nitride particles are added to an aqueous ethanol solution to undergo a hydration reaction at 40-50 °C;

Step 2: Add a silane coupling agent to the solution after the reaction in step 1, and oscillate ultrasonically, then centrifuge the micro-nano aluminum nitride and the solution, and the separated micro-nano aluminum nitride is dried and ground to obtain modification After the micro-nano aluminum nitride particles;

Step 3: adding the modified micro-nano aluminum nitride particles into the epoxy resin for ultrasonic dispersion, and leaving the mixed solution after the ultrasonic dispersion completed to stand at room temperature to fully mix to obtain a mixed solution;

Step 4: Add the curing agent to the mixed solution and stir it evenly, then add the accelerator and stir it evenly, and then carry out vacuum degassing;

Step 5: The mold is sprayed with a release agent in advance, and after drying, it is cooled to room temperature, and the solution after vacuum degassing in step 4 is poured into the mold, pre-cured at 70-90 ℃, and then cured at 130-150 ℃; finally The mold is removed to stand at room temperature, and the micro-nano blended composite material is obtained after demoulding.

As a preferred solution of the present invention, the mass ratio of the micron aluminum nitride and the nanometer aluminum nitride is preferably 20:3.

In one embodiment, the particle size of the micron aluminum nitride is 10 μm; the particle size of the nano aluminum nitride is 50 nm.

In one embodiment, the drying described in steps 1 and 2 is vacuum drying at 130° C., and the drying time is 1-3 h.

In one embodiment, the silane coupling agent is KH560, and the amount thereof is 1.3-1.5 parts by mass.

In one embodiment, the epoxy resin is bisphenol A epoxy resin, and the amount thereof is 42-44 parts by mass.

In one embodiment, the curing agent is methyl hexahydrophthalic anhydride, and the amount thereof is 33-35 parts by mass.

In one embodiment, the accelerator is tris(dimethylaminomethyl)phenol, and the amount thereof is 0.8-1 part by mass.

In one embodiment, the pre-curing time is 3-5 hours, and the curing time is 3-5 hours.

Another aspect of the present invention discloses an epoxy resin micro-nano blended composite material for encapsulation of power electronic high-power devices prepared by the method.

The mixing process in the preparation method of the present invention can adopt mechanical stirring, and the dispersing process can adopt ultrasonic vibration dispersion; in general, the mechanical stirring and ultrasonic vibration dispersion can be used in combination to achieve the purpose of uniform mixing of materials, and the rotational speed of the mechanical stirring And the power of ultrasonic oscillation can be selected according to actual needs.

The mold is dried in vacuum at 130° C., and the drying time is 1-3 hours; the mold filling is preferably carried out in a vacuum, and the vacuum filling can avoid air in the epoxy resin, and the prepared material has better effect.

In one embodiment, the temperature of the vacuum degassing is 40-50° C., the time is 30-60 min, and the vacuum degree can be selected to be less than 0.1 kPa. The temperature selection of 40-50 °C can remove the air and impurities in the epoxy resin during vacuum degassing, and increase the fluidity during the pouring process, but the temperature is too high and it is not suitable for operation.

The beneficial effects of the present invention are as follows:

The present invention uses filler micro-aluminum nitride and nano-aluminum nitride as the functional phase. Since the nitride is not as rich in hydroxyl groups as the oxide surface, the surface of the aluminum nitride particle is treated with hydroxyl groups through a hydration reaction between a reasonable configuration of water-containing ethanol and the particle. Then, through the silane reaction, the aluminum nitride particles and the epoxy resin have a synergistic effect to promote the dispersibility of the aluminum nitride particles in the epoxy resin. The high specific surface of the aluminum nitride after silanization can also promote the epoxy resin dispersion in. After chemical blending, the micro-nano aluminum nitride has strong compatibility, the distribution is very uniform, and there is no obvious agglomeration and precipitation. The addition of micron aluminum nitride promotes the formation of a thermally conductive network, which can reduce the scattering of phonons to a certain extent and improve thermal conductivity. Micro-particles can more easily establish a stable thermal conduction network, but will lead to a large number of defects and voids between the filler and the matrix, leading to insulation problems such as increased dielectric loss and reduced dielectric strength. Appropriate nanoparticle content can fill the defects and voids existing between fillers and epoxy resins, and can improve the electrical properties of composites by suppressing charge injection and generating deep traps to capture mobile charges to enhance their electrical resistance. Therefore, by configuring a suitable proportion of micro-nano filled epoxy resin, it is helpful to obtain a micro-nano blended composite material with high electrical conductivity and excellent dielectric properties. Regardless of the particle modification process or the material preparation process, the operation process is simple, the cost is low, and the industrial production is easy. The invention belongs to the technical field of high voltage and insulation, and is mainly used for the insulation of high-power equipment and devices such as power electronics, high-voltage electrical, aerospace, etc., especially the packaging that requires high thermal performance and electrical resistance performance.

Description of drawings

1 is a schematic diagram of the preparation process of the micro-nano blended composite material of the present invention.

Fig. 2 is the infrared spectrogram of the nano-aluminum nitride before and after the surface treatment of the present invention.

3 is a differential scanning calorimetry analysis diagram of four cases of the present invention.

FIG. 4 is a thermal conductivity diagram of four cases of the present invention.

FIG. 5 is a diagram of the DC breakdown field strength of the four cases of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the examples, which are only preferred embodiments of the present invention and are not intended to limit the present invention.

Example 1:

An epoxy resin micro-nano blended composite material for encapsulating power electronic high-power devices, according to the mass fraction, the preparation method is as follows:

1 Put 45.5 parts of micron aluminum nitride into a 130 ℃ vacuum drying oven to dry, and put anhydrous ethanol and distilled water into a beaker according to 34.2 parts: 11.4 parts, and mechanically stir for 1 minute, then the dried micro-nano aluminum nitride The hydration reaction occurs at 40 °C in the ethanol aqueous solution of the particle road;

2 Add 3 parts of silane coupling agent KH560 to the solution, ultrasonically vibrate for 30 minutes, then use a centrifuge to separate the micro-nano aluminum nitride from the solution, put it into a 130 ℃ vacuum drying box to dry for 2 hours, grind and dry to obtain the modified Micro-nano aluminum nitride particles;

3 Put the micro-nano aluminum nitride into 100 parts of epoxy resin, ultrasonically disperse the mixture at 40°C for 1 hour, and leave the mixture after ultrasonic dispersion for 2-4 hours at room temperature to fully mix it. liquid;

4 Add 80 parts of curing agent to the mixture, stir mechanically for 30 minutes at 40 °C, add 2 parts of accelerator, stir mechanically for 30 minutes, and then degas under vacuum for 60 minutes at 40 °C;

5. The mold was sprayed with release agent in advance, placed at 130 °C for 2 hours, and then cooled to room temperature. The vacuum-pumped solution was poured into the mold, pre-cured at 80 °C for 3 hours, and cured at 130 °C for 3 hours; finally, remove the mold to room temperature for static Set, after demolding, a micron composite material with a mass fraction of micron aluminum nitride of 20% (referred to as M20N0) is obtained.

Example 2:

An epoxy resin micro-nano blended composite material for encapsulating power electronic high-power devices, according to the mass fraction, the preparation method is as follows:

1 Put the micron aluminum nitride and nano aluminum nitride particles in 46 parts: 2.3 parts in a vacuum drying oven at 130 °C to dry, and put anhydrous ethanol and distilled water in a beaker according to 36.3 parts: 12.1 parts, and mechanically stir for 1 minute. Then the dried micro-nano aluminum nitride particles are hydrated in an aqueous ethanol solution at 40°C;

2 Add 3.1 parts of silane coupling agent KH560 to the solution, oscillate ultrasonically for 30 minutes, then use a centrifuge to separate the micro-nano aluminum nitride from the solution, put it into a 130 ℃ vacuum drying box to dry for 2 hours, grind and dry to obtain a modified Micro-nano aluminum nitride particles;

3 Put the micro-nano aluminum nitride into 100 parts of epoxy resin, ultrasonically disperse the mixture at 40°C for 1 hour, and leave the mixture after ultrasonic dispersion for 2-4 hours at room temperature to fully mix it. liquid;

4 Add 80 parts of curing agent to the mixture, stir mechanically for 30 minutes at 40 °C, add 2 parts of accelerator, stir mechanically for 30 minutes, and then degas under vacuum for 60 minutes at 40 °C;

5. The mold was sprayed with release agent in advance, placed at 130 °C for 2 hours, and then cooled to room temperature. The vacuum-pumped solution was poured into the mold, pre-cured at 80 °C for 3 hours, and cured at 130 °C for 3 hours; finally, remove the mold to room temperature for static The micro-nano blended composite material (referred to as M20N1) with a mass fraction of micron aluminum nitride of 20% and a mass fraction of nano-aluminum nitride of 1% was obtained after demolding.

Example 3:

An epoxy resin micro-nano blended composite material for encapsulating power electronic high-power devices, according to the mass fraction, the preparation method is as follows:

1 Put micron aluminum nitride and nano aluminum nitride particles in 47.5 parts: 7.1 parts into a vacuum drying oven at 130 ° C to dry, and put anhydrous ethanol and distilled water in a beaker in 42 parts: 13 parts, and mechanically stir for 1 minute. Then the dried micro-nano aluminum nitride particles are hydrated in an aqueous ethanol solution at 40°C;

2 Add 3.5 parts of silane coupling agent KH560 to the solution, oscillate ultrasonically for 30 minutes, then use a centrifuge to separate the micro-nano aluminum nitride from the solution, put it in a vacuum drying box at 130 ° C for drying for 2 hours, grind and dry to obtain a modified Micro-nano aluminum nitride particles;

3 Put the micro-nano aluminum nitride into 100 parts of epoxy resin, ultrasonically disperse the mixture at 40°C for 1 hour, and leave the mixture after ultrasonic dispersion for 2-4 hours at room temperature to fully mix it. liquid;

4 Add 80 parts of curing agent to the mixture, stir mechanically for 30 minutes at 40 °C, add 2 parts of accelerator, stir mechanically for 30 minutes, and then degas under vacuum for 60 minutes at 40 °C;

5. The mold was sprayed with release agent in advance, placed at 130 °C for 2 hours, and then cooled to room temperature. The vacuum-pumped solution was poured into the mold, pre-cured at 80 °C for 3 hours, and cured at 130 °C for 3 hours; finally, remove the mold to room temperature for static Set, after demolding, a micro-nano blended composite material (referred to as M20N3) with a mass fraction of micron aluminum nitride of 20% and a mass fraction of nano-aluminum nitride of 3% is obtained.

Example 4:

An epoxy resin micro-nano blended composite material for encapsulating power electronic high-power devices, according to the mass fraction, the preparation method is as follows:

1 Put the micron aluminum nitride and nano aluminum nitride particles in 48.4 parts: 12.1 parts into a vacuum drying oven at 130 °C to dry, and put anhydrous ethanol and distilled water in a beaker according to 45.6 parts: 15.2 parts. Mechanical stirring for 1 minute, Then the dried micro-nano aluminum nitride particles are hydrated in an aqueous ethanol solution at 40°C;

2 Add 3.5 parts of silane coupling agent KH560 to the solution, oscillate ultrasonically for 30 minutes, then use a centrifuge to separate the micro-nano aluminum nitride from the solution, put it in a vacuum drying box at 130 ° C for drying for 2 hours, grind and dry to obtain a modified Micro-nano aluminum nitride particles;

3 Put the micro-nano aluminum nitride into 100 parts of epoxy resin, ultrasonically disperse the mixture at 40°C for 1 hour, and leave the mixture after ultrasonic dispersion for 2-4 hours at room temperature to fully mix it. liquid;

4 Add 80 parts of curing agent to the mixture, stir mechanically for 30 minutes at 40 °C, add 2 parts of accelerator, stir mechanically for 30 minutes, and then degas under vacuum for 60 minutes at 40 °C;

5. The mold was sprayed with release agent in advance, placed at 130 °C for 2 hours, and then cooled to room temperature. The vacuum-pumped solution was poured into the mold, pre-cured at 80 °C for 3 hours, and cured at 130 °C for 3 hours; finally, remove the mold to room temperature for static The micro-nano blended composite material (referred to as M20N5) with a mass fraction of micron aluminum nitride of 20% and a mass fraction of nano-aluminum nitride of 5% was obtained after demolding.

The sample preparation process corresponding to each embodiment is shown in FIG. 1 . Figure 2 shows the infrared spectrum of the micro-nano aluminum nitride surface before and after the steps 1 and 2 in the embodiment. It can be seen that the transmission peaks of Si-O and N-H are obvious, indicating that the silane treatment is effective. Figure 3 is the differential scanning thermal analysis diagram obtained from the four case samples. It can be seen from the figure that the four case samples obtained are: 119.6, 121.1, 132.1, and 126.2. Among them, the glass transition temperature of the M20N3 sample was significantly increased, which contributed to the thermal stability of the material. Figure 4 shows the thermal conductivity of the four case samples. It can be seen from the figure that the thermal conductivity distributions of the four case samples are 0.671, 0725, 0.745, 0737W/mk. If the thermal conductivity of commercially available pure epoxy is 0.2W/mk as a benchmark, their respective improvement rates are: 198%, 222%, 231%, 227%. The Weibull distribution of the breakdown field strength obtained by the four case samples is shown in Figure 5. The breakdown field strength obtained by the four case samples with the national standard 63.2% breakdown probability are: 91.2, 113.02, 171.58, 155.53MV/ m.

It can be seen from Figure 3, Figure 4 and Figure 5 that in Example 3, the thermal conductivity of the micro-nano blended composite material (ie M20N3) medium with a mass fraction of micron aluminum nitride of 20% and a mass fraction of nano-aluminum nitride of 3% Performance (thermal conductivity and thermal stability) and electrical properties are significantly better.

The above-mentioned embodiment only expresses the embodiment of the present invention, and the relevant description is more specific and detailed, but it should not be construed as a limitation of the patent scope of the present invention. Any technical solutions obtained in the form of equivalent replacement or equivalent transformation, All should fall within the protection scope of the present invention.

Claims (10)

1. a preparation method of epoxy resin micro-nano blended composite material for power electronic high-power device encapsulation, is characterized in that comprising the steps: Step 1: Mix micron aluminum nitride and nano aluminum nitride by 20 parts by mass: 2 to 4 parts by mass to obtain micro and nano aluminum nitride particles, and dry the micro and nano aluminum nitride particles; ~20 parts by mass: 3-4 parts by mass are mixed, and then the dried micro-nano aluminum nitride particles are added to an aqueous ethanol solution to undergo a hydration reaction at 40-50 °C; Step 2: Add a silane coupling agent to the solution after the reaction in step 1, and oscillate ultrasonically, then centrifuge the micro-nano aluminum nitride and the solution, and the separated micro-nano aluminum nitride is dried and ground to obtain modification After the micro-nano aluminum nitride particles; Step 3: adding the modified micro-nano aluminum nitride particles into the epoxy resin for ultrasonic dispersion, and leaving the mixed solution after the ultrasonic dispersion completed to stand at room temperature to fully mix to obtain a mixed solution; Step 4: Add the curing agent to the mixed solution and stir it evenly, then add the accelerator and stir it evenly, and then carry out vacuum degassing; Step 5: The mold is sprayed with a release agent in advance, and after drying, it is cooled to room temperature, and the solution after vacuum degassing in step 4 is poured into the mold, pre-cured at 70-90 ℃, and then cured at 130-150 ℃; finally The mold is removed to stand at room temperature, and the micro-nano blended composite material is obtained after demoulding. 2 . The preparation method according to claim 1 , wherein the particle size of the micron aluminum nitride is 10 μm; the particle size of the nano aluminum nitride is 50 nm. 3 . 3 . The preparation method according to claim 1 , wherein the drying in steps 1 and 2 is vacuum drying at 130° C., and the drying time is 1-3 h. 4 . 4 . The preparation method according to claim 1 , wherein the silane coupling agent is KH560, and the amount thereof is 1.3-1.5 parts by mass. 5 . 5 . The preparation method according to claim 1 , wherein the epoxy resin is bisphenol A epoxy resin, and the amount thereof is 42-44 parts by mass. 6 . 6 . The preparation method according to claim 1 , wherein the curing agent is methyl hexahydrophthalic anhydride, and the amount thereof is 33 to 35 parts by mass. 7 . 7 . The preparation method according to claim 1 , wherein the accelerator is tris(dimethylaminomethyl)phenol, and the amount thereof is 0.8 to 1 part by mass. 8 . 8 . The preparation method according to claim 1 , wherein the temperature of the vacuum degassing is 40-50° C., and the time is 30-60 min. 9 . 9 . The preparation method according to claim 1 , wherein the pre-curing time is 3-5 h, and the curing time is 3-5 h. 10 . 10. An epoxy resin micro-nano blended composite material for encapsulation of power electronic high-power devices prepared by the method of claim 1.

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