A spherical aluminum nitride powder and its preparation method

Abstract

This invention relates to a spherical aluminum nitride powder and its preparation method. Commercially available aluminum nitride powder, citric acid, and anhydrous ethanol are loaded into a nylon ball mill jar. Alumina grinding balls are added, and the mixture is ball-milled to form a wetting slurry. The slurry is dried to obtain aluminum nitride powder with a nano-carbon layer on its surface. This slurry is then calcined in a high-temperature furnace, followed by ball milling with a spheroidizing agent, carbon black, and anhydrous ethanol in the same nylon ball mill jar. After calcination, the mixed powder is removed and dried in a drying oven. The dried powder is then sieved. The powder is then calcined in a microwave furnace to form spheroidized aluminum nitride powder. This spheroidized powder is then placed in a muffle furnace for calcination to remove carbon. After calcination, the powder is cooled with the furnace and sieved to obtain the spherical aluminum nitride powder. The spherical aluminum nitride powder prepared by this invention has a sphericity ≥86%, an average particle size of 2-8 μm, and a specific surface area of ​​0.53-0.76 m². 2 / g.

Description

Technical Field

[0001] This invention relates to the field of aluminum nitride material technology, specifically to a spherical aluminum nitride powder and its preparation method. Background Technology

[0002] With the development of semiconductor devices (high-power LEDs, integrated circuits, and chips) and 5G technology, the requirements for heat dissipation management are becoming increasingly stringent. Thermally conductive fillers are crucial and a prerequisite for achieving efficient heat dissipation. Currently, most heat dissipation fillers use alumina (Al2O3) and silicon dioxide (SiO2), but both have insufficient thermal conductivity, failing to meet the requirements of existing heat dissipation management technologies and hindering the development of high-power semiconductor devices to some extent.

[0003] Aluminum nitride (AlN) possesses excellent properties such as high thermal conductivity, electrical insulation, a coefficient of thermal expansion similar to that of semiconductor silicon, high mechanical strength, good chemical stability, and non-toxicity, making it a high-performance novel thermally conductive filler. However, existing aluminum nitride thermally conductive fillers suffer from problems such as low sphericity, numerous impurities, and wide particle size distribution, which affect their filling and thermal conductivity properties, preventing the full realization of the performance advantages of AlN thermally conductive fillers. Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of low sphericity and large average particle size of existing spherical aluminum nitride powders, and to provide a spherical aluminum nitride powder and its preparation method.

[0005] The specific plan is as follows:

[0006] A method for preparing spherical aluminum nitride powder includes the following steps:

[0007] Step 1: Put commercially available aluminum nitride powder, citric acid and anhydrous ethanol into a nylon ball mill jar, add alumina grinding balls and ball mill to form a wetting slurry;

[0008] Step 2: Place the impregnated slurry in a drying oven to dry, and after drying, remove it and pass it through a sieve to obtain dried powder;

[0009] Step 3: The dried powder is placed in a high-temperature furnace for calcination, and after completion, it is removed and sieved.

[0010] Step 4: Take the calcined powder from Step 3, along with the spheroidizing agent, carbon black, and anhydrous ethanol, and put them into a nylon ball mill jar for ball milling. After the process is complete, take out the mixed powder. The spheroidizing agent is a mixture of CaF2 and O7Tb4.

[0011] Step 5: Place the mixed powder in a drying oven to dry, and then remove it and sieve it after drying.

[0012] Step Six: Place the powder that has been sieved in Step Five into a microwave calcination furnace for calcination and spheroidization to form spheroidized aluminum nitride powder;

[0013] Step 7: Place the spheroidized aluminum nitride powder into a muffle furnace and calcine to remove carbon; after the furnace is cooled down, remove the powder and pass it through a sieve to obtain spherical aluminum nitride powder.

[0014] Furthermore, the mass ratio of citric acid to commercially available aluminum nitride powder is 0.05-0.1:1, and the mass ratio of anhydrous ethanol to commercially available aluminum nitride powder is 1.2:1.

[0015] Furthermore, the drying parameters in step two are: drying temperature of 80-95℃ and drying time of 10-12h.

[0016] Furthermore, the calcination parameters described in step three are as follows: the entire process is carried out under a nitrogen atmosphere, at a temperature of 600-800℃, and for a calcination time of 1-3 hours.

[0017] Furthermore, the mass of CaF2 is 80-90% of the total mass of the spheroidizing aid, and the mass of O7Tb4 is 10-20% of the total mass of the spheroidizing aid.

[0018] Furthermore, the calcination and spheroidization parameters are as follows: the entire process is carried out under a nitrogen atmosphere, the calcination temperature is 1700-1900℃, and the calcination time is 3-5h.

[0019] Furthermore, the calcination decarbonization parameters are as follows: the entire process is carried out in an atmospheric environment, the calcination temperature is 500-600℃, and the calcination time is 1-3 hours.

[0020] The spherical aluminum nitride powder prepared by the aforementioned method.

[0021] Furthermore, the aluminum nitride powder has a sphericity ≥86%, an average particle size of 2-8 μm, and a specific surface area of ​​0.53-0.76 m². 2 / g.

[0022] Beneficial effects:

[0023] 1. This invention uses commercial aluminum nitride powder as raw material and prepares a nano-carbon layer on the surface of aluminum nitride particles. This effectively isolates the contact between powder particles and avoids sintering and bonding between particles during the subsequent high-temperature spheroidization process, thus solving the technical problem of low spheroidization rate caused by powder melting and bonding.

[0024] 2. This invention uses a mixture of CaF2 and O7Tb4 as a spheroidizing aid. During the high-temperature spheroidizing process, this spheroidizing aid can form a liquid-phase low-melting-point compound, which effectively wets the surface of aluminum nitride particles, greatly promoting surface melting and spheroidization of the aluminum nitride powder. Furthermore, it can decompose and volatilize at high temperatures, ensuring the removal of the spheroidizing aid.

[0025] 3. The spherical aluminum nitride powder prepared by this invention has a sphericity ≥0.86%, an average particle size of 2-8 μm, and a specific surface area of ​​0.53-0.76 m². 2 / g can significantly improve the overall thermal conductivity of thermally conductive materials and can be used as a thermally conductive filler for high-end chip packaging. Attached Figure Description

[0026] To more clearly illustrate the technical solution of the present invention, the accompanying drawings will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0027] Figure 1 This is a SEM microscopic image of the nano-carbon layer prepared on the surface of aluminum nitride powder provided in Example 1 of this invention;

[0028] Figure 2 These are SEM microscopic images of the spherical aluminum nitride powder provided in Embodiment 1 of the present invention;

[0029] Figure 3 These are SEM microscopic images of aluminum nitride powder provided in Comparative Example 1 of this invention;

[0030] Figure 4 This is a SEM microscopic image of the aluminum nitride powder provided in Comparative Example 2 of this invention. Detailed Implementation

[0031] Preferred embodiments of the present invention will now be described in more detail. While preferred embodiments of the present invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products. In the following embodiments, unless otherwise specified, "%" refers to weight percentage.

[0032] This embodiment provides a method for preparing spherical aluminum nitride powder, including the following steps:

[0033] Step 1: Put commercially available aluminum nitride powder, citric acid and anhydrous ethanol into a nylon ball mill jar, add alumina grinding balls and ball mill to form a wetting slurry;

[0034] Step 2: Place the impregnated slurry in a drying oven to dry. After drying, remove it and pass it through a sieve to obtain dried powder. The nano-carbon layer formed on the surface of the dried powder effectively isolates the contact between powder particles, avoiding sintering and bonding between particles during the subsequent high-temperature spheroidization process.

[0035] Step 3: The dried powder is placed in a high-temperature furnace for calcination, and after completion, it is removed and sieved.

[0036] Step 4: Take the calcined powder from Step 3, along with the spheroidizing aid, carbon black, and anhydrous ethanol, and place them into a nylon ball mill jar for ball milling. After the process is complete, remove the mixed powder. The spheroidizing aid is a mixture of CaF2 and O7Tb4. During the high-temperature spheroidizing process, the spheroidizing aid can form a liquid-phase low-melting-point compound. On the one hand, it can effectively wet the surface of aluminum nitride particles, greatly promoting the surface melting and spheroidization of aluminum nitride powder. On the other hand, it can decompose and volatilize at high temperatures, ensuring the removal of the spheroidizing aid.

[0037] Step 5: Place the mixed powder in a drying oven to dry, and then remove it and sieve it after drying.

[0038] Step Six: Place the powder that has been sieved in Step Five into a microwave calcination furnace for calcination and spheroidization to form spheroidized aluminum nitride powder;

[0039] Step 7: Place the spheroidized aluminum nitride powder into a muffle furnace and calcine to remove carbon; after the furnace is cooled down, remove the powder and pass it through a sieve to obtain spherical aluminum nitride powder.

[0040] In this embodiment, the mass ratio of citric acid to commercially available aluminum nitride powder is 0.05-0.1:1, and the mass ratio of anhydrous ethanol to commercially available aluminum nitride powder is 1.2:1.

[0041] In this embodiment, the drying parameters in step two are: drying temperature of 80-95℃ and drying time of 10-12h.

[0042] In this embodiment, the calcination parameters in step three are as follows: the entire process is carried out under a nitrogen atmosphere, the temperature is 600-800℃, and the calcination time is 1-3 hours.

[0043] In this embodiment, the mass of CaF2 is 80-90% of the total mass of the spheroidizing agent, and the mass of O7Tb4 is 10-20% of the total mass of the spheroidizing agent.

[0044] In this embodiment, the calcination spheroidization parameters are as follows: the entire process is carried out under a nitrogen atmosphere, the calcination temperature is 1700-1900℃, and the calcination time is 3-5h.

[0045] In this embodiment, the calcination decarbonization parameters are as follows: the entire process is carried out in an atmospheric environment, the calcination temperature is 500-600℃, and the calcination time is 1-3h.

[0046] This embodiment provides a method for preparing spherical aluminum nitride powder, resulting in spherical aluminum nitride powder.

[0047] In this embodiment, the aluminum nitride powder has a sphericity ≥86%, an average particle size of 2-8 μm, and a specific surface area of ​​0.53-0.76 m². 2 / g.

[0048] Example 1

[0049] 1000g of commercially available aluminum nitride powder with a particle size of 0.5-1.2μm, 80g of citric acid, and 1000g of anhydrous ethanol were placed in a nylon ball mill jar. Alumina grinding balls were added, and the mixture was ball-milled for 3 hours to form a wetted slurry. The slurry was then removed and dried in an 80℃ drying oven for 10 hours. After drying, the powder was passed through a 200-mesh sieve to obtain aluminum nitride powder with a nano-carbon layer on the surface. The powder was then placed in a high-temperature furnace and calcined at 700℃ for 2 hours under a nitrogen atmosphere. After calcination, the powder was passed through a 200-mesh sieve. 1000g of the calcined aluminum nitride powder, 120g of CaF2, 30g of O7Tb4, 50g of carbon black, and 1200g of anhydrous ethanol were weighed and placed in a nylon ball mill jar for ball milling for 3 hours. After calcination, the mixed powder was removed and dried in an 80℃ drying oven for 12 hours. After drying, the powder was passed through a 200-mesh sieve. The above-mentioned mixed powder was placed in a microwave calcination furnace and calcined at 1800℃ for 5 hours under a nitrogen atmosphere to form spheroidized aluminum nitride powder. After the calcination was completed, the powder was removed. The spheroidized powder was then placed in a muffle furnace and calcined at 550℃ for 3 hours under atmospheric conditions to remove carbon. After the calcination was completed, the powder was removed and passed through a 200-mesh sieve to obtain spherical aluminum nitride powder.

[0050] The spherical aluminum nitride powder prepared in this embodiment has a sphericity of 89%, an average particle size of 4.6 μm, and a specific surface area of ​​0.73 m². 2 / g. From Figure 1 It can be seen that the nano-carbon layer particles prepared in this embodiment are uniformly distributed on the surface of the aluminum nitride powder, by Figure 2 It can be seen that the spherical aluminum nitride powder has aluminum nitride particles with a spherical shape, uniform particle size distribution, and high sphericity.

[0051] Example 2

[0052] 1000g of commercially available aluminum nitride powder, 60g of citric acid, and 1000g of anhydrous ethanol were placed in a nylon ball mill jar, and alumina grinding balls were added. The mixture was ball-milled for 3 hours to form a slurry. This slurry was then removed and dried in an 80°C drying oven for 10 hours. After drying, the powder was passed through a 200-mesh sieve. The powder was then placed in a high-temperature furnace and calcined at 650°C for 3 hours under a nitrogen atmosphere. After calcination, the powder was passed through a 200-mesh sieve. 1000g of the above powder, 130g of CaF2, 20g of O7Tb4, 50g of carbon black, and 1200g of anhydrous ethanol were weighed and placed in a nylon ball mill jar. The mixture was ball-milled for 3 hours. After calcination, the powder was removed and dried in an 80°C drying oven for 12 hours. After drying, the powder was passed through a 200-mesh sieve. The powder was then placed in a microwave calcination furnace and calcined at 1700°C for 6 hours under a nitrogen atmosphere to form spheroidized aluminum nitride powder. The powder was then removed. The spherical powder was placed in a muffle furnace and calcined at 550°C for 3 hours under atmospheric conditions to remove carbon. After calcination, the powder was removed and passed through a 200-mesh sieve to obtain spherical aluminum nitride powder. The spherical aluminum nitride powder prepared in this embodiment has a sphericity of 87%, an average particle size of 4.2 μm, and a specific surface area of ​​0.63 m². 2 / g.

[0053] Example 3

[0054] 1000g of commercially available aluminum nitride powder, 50g of citric acid, and 1000g of anhydrous ethanol were placed in a nylon ball mill jar, and alumina grinding balls were added. The mixture was ball-milled for 3 hours to form a slurry. The slurry was then removed and placed in a drying oven at 80℃ for 10 hours. After drying, the powder was passed through a 200-mesh sieve to obtain aluminum nitride powder with a nano-carbon layer on the surface. The powder was then placed in a high-temperature furnace and calcined at 750℃ for 2 hours under a nitrogen atmosphere. After calcination, the powder was passed through a 200-mesh sieve. 1000g of the above powder, 140g of CaF2, 10g of O7Tb4, 50g of carbon black, and 1200g of anhydrous ethanol were weighed and placed in a nylon ball mill jar for ball milling for 3 hours. After calcination, the mixed powder was removed and placed in a drying oven at 80℃ for 12 hours. After drying, the powder was passed through a 200-mesh sieve. The above-mentioned mixed powder was placed in a microwave calcination furnace and calcined at 1650°C for 8 hours under a nitrogen atmosphere to form spheroidized aluminum nitride powder. The powder was then removed. The spheroidized powder was placed in a muffle furnace and calcined at 550°C for 3 hours under atmospheric conditions to remove carbon. The powder was then passed through a 200-mesh sieve to obtain spherical aluminum nitride powder. The spherical aluminum nitride powder prepared in this embodiment has a sphericity of 86%, an average particle size of 3.8 μm, and a specific surface area of ​​0.58 m². 2 / g.

[0055] Comparative Example 1

[0056] 1000g of commercially available aluminum nitride powder, 120g of CaF2, 30g of O7Tb4, 50g of carbon black, and 1000g of anhydrous ethanol were placed together in a nylon ball mill jar and ball-milled for 3 hours. After milling, the mixed powder was removed and dried in an 80℃ drying oven for 12 hours. After drying, it was passed through a 200-mesh sieve. The mixed powder was then placed in a microwave calcination furnace and calcined at 1800℃ for 5 hours under a nitrogen atmosphere to form aluminum nitride powder. The powder was then removed. The spheroidized powder was placed in a muffle furnace and calcined at 550℃ for 3 hours under atmospheric conditions to remove carbon. After calcination, the powder was passed through a 200-mesh sieve to obtain spherical aluminum nitride powder.

[0057] In this comparative example, no nano-carbon layer was prepared on the surface of the aluminum nitride powder particles, and the spheroidization and decarburization processes were consistent with those in Example 1. Figure 3 It can be seen that aluminum nitride particles are bonded together into coarse and irregular particles due to surface melting, and the particle size distribution is uneven, so the spheroidization effect cannot be achieved.

[0058] Comparative Example 2

[0059] 1000g of commercially available aluminum nitride powder, 80g of citric acid, and 1000g of anhydrous ethanol were placed in a nylon ball mill jar. Alumina grinding balls were added, and the mixture was ball-milled for 3 hours to form an impregnated slurry. The slurry was then removed and placed in a drying oven at 80°C for 10 hours. After drying, the powder was passed through a 200-mesh sieve. The powder was then placed in a high-temperature furnace and calcined at 700°C for 2 hours under a nitrogen atmosphere. After calcination, the powder was passed through a 200-mesh sieve. 1000g of the above powder, 150g of CaF2, 50g of carbon black, and an appropriate amount of anhydrous ethanol were weighed and placed in a nylon ball mill jar. The mixture was ball-milled for 3 hours. After calcination, the powder was removed and placed in a drying oven at 80°C for 12 hours. After drying, the powder was passed through a 200-mesh sieve. The powder was then placed in a microwave calcination furnace and calcined at 1800°C under a nitrogen atmosphere for 5 hours to form spheroidized aluminum nitride powder. The powder was then removed. The spheroidized powder was placed in a muffle furnace and calcined at 550°C for 3 hours in an atmospheric environment to remove carbon. After the calcination, the powder was removed and passed through a 200-mesh sieve to obtain spherical aluminum nitride powder.

[0060] In this comparative example, CaF2 spheroidizing agent was used instead of the composite spheroidizing agent of CaF2 120 g + O7Tb4 30 g; other processes were the same as in Example 1. Figure 4 It can be seen that the aluminum nitride particles are spherical in shape, but the sphericity is not high, indicating that the sphericity effect of this comparative proportion is not obvious.

[0061] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0062] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0063] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing spherical aluminum nitride powder, characterized by: It comprises the following steps: Step one: put commercially available aluminum nitride powder, citric acid and anhydrous ethanol into a nylon ball mill jar, add aluminum oxide balls for ball milling to form an infiltration slurry; Step two: put the infiltration slurry into a drying oven for drying, and after the end, take out the screen to obtain dry powder; Step three: put the dry powder into a high-temperature furnace for calcination, and after the end, take out the screen; Step four: take the calcined powder in step three and balling aid, carbon black and anhydrous ethanol into a nylon ball mill jar for ball milling, and after the end, take out the mixed powder, wherein the balling aid is a mixture of CaF2 and Tb4O7; Step five: put the mixed powder into a drying oven for drying, and after the end, take out the screen; Step six: put the screened powder in step five into a microwave calcination furnace for calcination and spheroidization to form spheroidized aluminum nitride powder; Step seven: put the spheroidized aluminum nitride powder into a muffle furnace for calcination to remove carbon; after the end, take out the screen, and the spherical aluminum nitride powder is obtained.

2. The method of claim 1, wherein the aluminum nitride powder is spherical. The mass ratio of citric acid to commercially available aluminum nitride powder is 0.05-0.1:1, and the mass ratio of anhydrous ethanol to the commercially available aluminum nitride powder is 1.2:

1.

3. The method of claim 1, wherein the aluminum nitride powder is spherical. The drying parameters in step two are: drying temperature is 80-95℃, and drying time is 10-12h.

4. The method of claim 1, wherein the aluminum nitride powder is spherical. The calcination parameters in step three are: the whole process is carried out under nitrogen atmosphere, temperature is 600-800℃, and calcination time is 1-3h.

5. The method of claim 1, wherein the spherical aluminum nitride powder is prepared by the steps of: The mass of CaF2 is 80-90% of the total mass of the spheroidization aid, and the mass of Tb4O7 is 10-20% of the total mass of the spheroidization aid. ​ 6. The method of claim 1, wherein the spherical aluminum nitride powder is prepared by the steps of: The calcination and spheroidization parameters are: the whole process is carried out under nitrogen atmosphere, calcination temperature is 1700-1900℃, and calcination time is 3-5h. ​ 7. The method of claim 1, wherein the spherical aluminum nitride powder has a particle size of 0.1 to 10 μm. The calcination and carbon removal parameters are: the whole process is carried out in an atmospheric environment, calcination temperature is 500-600℃, and calcination time is 1-3h.

8. A spherical aluminum nitride powder prepared by the method of any one of claims 1-7.

9. The spherical aluminum nitride powder of claim 8, wherein: The sphericity of the aluminum nitride powder is greater than or equal to 86%, the average particle size is 2-8 μm, and the specific surface area is 0.53-0.76 m 2 / g.

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