Preparation method of high-purity aluminum nitride single crystal powder

Abstract

The invention discloses a preparation method of high-purity aluminum nitride single crystal powder. The method comprises the following steps: uniformly mixing raw materials aluminum powder and aluminum nitride powder according to a ratio, putting the mixture into an air pressure sintering furnace, vacuumizing, introducing high-pressure argon, heating to a set temperature, introducing nitrogen, carrying out a fire blast reaction, cooling to room temperature, and crushing to obtain the high-purity aluminum nitride single crystal powder with D50 of 20-200 microns. According to the method, the synthesis of the coarse-particle high-purity aluminum nitride single crystal powder is realized by utilizing the rapid nitridation explosion reaction of the aluminum powder in the high-temperature and high-pressure nitrogen, the method has the characteristics of simple process and low preparation cost, and the prepared high-purity aluminum nitride single crystal powder can be used as a high-thermal-conductivity filler for electronic packaging.

Description

Technical Field

[0001] This invention belongs to the field of thermally conductive filler preparation technology, specifically relating to a method for preparing high-purity aluminum nitride single crystal powder. Background Technology

[0002] As electronic devices evolve towards higher power density and miniaturization, the heat generated per unit volume increases significantly. If this heat cannot be dissipated in time, the device temperature will rise significantly, leading to performance degradation or even failure. Polymer-based thermally conductive composite materials are made by adding thermally conductive fillers (such as alumina, boron nitride, and graphene) to a polymer matrix (e.g., epoxy resin, silicone rubber, polyimide). Polymer-based thermally conductive composite materials are becoming core materials in fields such as electronic heat dissipation and new energy, driving the development of electronic devices towards higher power density and higher reliability. Thermally conductive fillers, as the core component of polymer-based thermally conductive composite materials, construct a thermally conductive network within a polymer matrix with low intrinsic thermal conductivity, transferring heat from the chip to the heat dissipation device. They are crucial materials for ensuring the reliability of electronic devices.

[0003] Aluminum nitride has a high intrinsic thermal conductivity (~320 W / m) -1 K -1 Low coefficient of thermal expansion (4.5×10⁻⁶) -6 / K, close to silicon) and high resistivity (4.0×10 9 With its excellent properties such as Ω·m, aluminum nitride (AN) thermally conductive filler has attracted much attention. Although AN has been applied in polymer-based thermally conductive composites, its thermal conductivity still needs further improvement to meet the ever-increasing heat dissipation requirements of electronic devices. Currently, AN thermally conductive fillers are mainly divided into two categories: fine-particle (<20μm) single-crystal powder and coarse-particle (>20μm) spherical polycrystalline powder. Fine-particle single-crystal powder is mainly prepared by methods such as carbide reduction nitridation, direct nitridation, and combustion synthesis. Spherical polycrystalline powder is prepared by granulation and sintering of fine-particle AlN powder. In polymer-based thermally conductive composites, coarse-particle thermally conductive fillers play the role of overlapping thermal conductive networks, and their intrinsic thermal conductivity determines the upper limit of the composite material's thermal conductivity. It should be noted that existing methods have difficulty preparing coarse-grained single-crystal powders, while spherical polycrystalline powders, due to the formation of secondary phases from the addition of sintering aids and grain boundary scattering, have low thermal conductivity (typically between 170 and 220 W / m). -1 K -1 The actual values ​​differ significantly from the theoretical values, which greatly limits the improvement of the thermal conductivity of composite materials. In addition, the fine-particle single-crystal powders prepared by existing synthesis methods also suffer from low purity (usually ≤99.99%) due to the complexity of the process and the easy introduction of impurities. This is also one of the fundamental reasons affecting the thermal conductivity of fillers. Summary of the Invention

[0004] To address the technical problems of low intrinsic thermal conductivity, complex preparation process, and high cost of existing aluminum nitride thermally conductive fillers, this invention provides a method for preparing high-purity aluminum nitride single crystal powder. This method utilizes the rapid nitridation and combustion reaction of aluminum powder in high-temperature, high-pressure argon and nitrogen gas to synthesize high-purity aluminum nitride single crystal powder. It features a simple process and low preparation cost, and the prepared high-purity aluminum nitride single crystal powder can be used as a high thermal conductivity filler for electronic packaging.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing high-purity aluminum nitride single crystal powder includes the following steps:

[0007] After mixing the raw aluminum powder and aluminum nitride powder in a certain proportion, the mixture is placed in a gas pressure sintering furnace, vacuumed, and then heated to 1300-1500℃ by introducing 1-3MPa high-pressure argon gas. Nitrogen gas at 4-7MPa is then introduced to induce a combustion and explosion reaction. The mixture is then cooled to room temperature and crushed to obtain aluminum nitride single crystal powder with D50=20-200μm and purity ≥99.999%.

[0008] Preferably, the aluminum powder has a particle size D50 of 10-50 μm, more preferably 20-50 μm, and a purity ≥99.999%.

[0009] Preferably, the aluminum nitride powder has a particle size D50 of 5-10 μm, more preferably 7-10 μm, and a purity ≥99.999%.

[0010] Preferably, based on the total mass of raw materials (100%), the mass percentage of aluminum powder is 40%-70% and the mass percentage of aluminum nitride powder is 30%-60%. More preferably, the mass percentage of aluminum powder is 60%-70% and the mass percentage of aluminum nitride powder is 30%-40%.

[0011] Preferably, the combustion and explosion reaction time is 3 to 5 minutes.

[0012] Preferably, the temperature is raised to 1400-1500℃.

[0013] Preferably, the pressure of argon is 1~2 MPa and the pressure of nitrogen is 5~7 MPa.

[0014] This invention utilizes the rapid nitridation and combustion reaction of aluminum powder in high-temperature, high-pressure nitrogen gas to synthesize high-purity aluminum nitride single-crystal powder, featuring a simple process and low preparation cost. By using an aluminum nitride separator and high-pressure argon gas, the melting and volatilization of aluminum powder during the heating process is suppressed. High-pressure nitrogen gas is introduced at high temperature, utilizing the ultra-high temperature generated by the combustion reaction of aluminum and high-temperature, high-pressure nitrogen gas. By controlling the pressure of each gas, the mass percentage of aluminum powder and aluminum nitride powder in the raw materials, and the particle size, coarse-particle aluminum nitride single-crystal powder can be synthesized quickly and efficiently. The aluminum nitride powder prepared by this invention has high purity and large particle size, and can be used as a high thermal conductivity filler in the field of electronic packaging, solving the heat dissipation problem of electronic devices. Attached Figure Description

[0015] Figure 1 Here is a SEM image of the AlN particles synthesized in Example 1;

[0016] Figure 2 Here is a SEM image of the AlN particles synthesized in Example 2;

[0017] Figure 3 This is an optical microscope image of the AlN particles synthesized in Example 5. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0019] Unless otherwise specified, any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0020] Example 1

[0021] Aluminum powder with a particle size of 10 μm and a purity of 99.999% and aluminum nitride powder with a particle size of 10 μm and a purity of 99.999% were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 40%:60%, and then placed in a boron nitride crucible in a pressure sintering furnace. After evacuation, argon gas at a pressure of 1 MPa was introduced, and the temperature was raised to 1300℃. Then, nitrogen gas at a pressure of 4 MPa was rapidly introduced, and the temperature was held for 5 minutes before cooling with the furnace. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. A suitable sample was taken for particle size analysis, and the results showed that the product particle size D50 was 20.5 μm. The sample was characterized by SEM, as shown below. Figure 1 As shown, the AlN particles exhibit a angular single-crystal morphology with no obvious sintering or agglomeration. ICP analysis of the sample revealed impurities such as Fe, Si, and Ca, with a total content less than 10 ppm.

[0022] Example 2

[0023] Aluminum powder with a particle size of 20 μm and a purity of 99.999% and aluminum nitride powder with a particle size of 10 μm and a purity of 99.999% were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 50%:50%, and then placed in a boron nitride crucible in a pressure sintering furnace. After evacuation, argon gas at a pressure of 2 MPa was introduced, and the temperature was raised to 1400℃. Then, nitrogen gas at a pressure of 5 MPa was rapidly introduced, and the temperature was held for 5 minutes before cooling with the furnace. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. A suitable sample was taken for particle size analysis, and the results showed that the product particle size D50 was 55.2 μm. The sample was characterized by SEM, as shown below. Figure 2 As shown, the AlN particles exhibit a angular single-crystal morphology with no obvious sintering or agglomeration. ICP analysis of the sample revealed impurities such as Fe, Si, and Ca, with a total content less than 10 ppm.

[0024] Example 3

[0025] Aluminum powder with a particle size of 30 μm and a purity of 99.999% and aluminum nitride powder with a particle size of 7 μm and a purity of 99.999% were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 60%:40%, and then placed in a boron nitride crucible in a pressure sintering furnace. After evacuation, argon gas at a pressure of 2 MPa was introduced, and the temperature was raised to 1400℃. Then, nitrogen gas at a pressure of 6 MPa was rapidly introduced, and the temperature was held for 5 minutes before cooling with the furnace. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. A suitable sample was taken for particle size analysis, and the results showed that the product particle size D50 was 112.7 μm. SEM characterization of the sample showed that the AlN particles had an angular single crystal morphology and no obvious sintering agglomeration. ICP analysis of the sample showed that the total impurity content of Fe, Si, and Ca was less than 10 ppm.

[0026] Example 4

[0027] Aluminum powder with a particle size of 40 μm and a purity of 99.999% and aluminum nitride powder with a particle size of 7 μm and a purity of 99.999% were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 65%:35%, and then placed in a boron nitride crucible in a pressure sintering furnace. After evacuation, argon gas at a pressure of 2 MPa was introduced, and the temperature was raised to 1500℃. Then, nitrogen gas at a pressure of 6 MPa was rapidly introduced, and the temperature was held for 5 minutes before cooling with the furnace. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. A suitable sample was taken for particle size analysis, and the results showed that the product particle size D50 was 150.3 μm. SEM characterization of the sample showed that the AlN particles had an angular single crystal morphology and no obvious sintering agglomeration. ICP analysis of the sample showed that the total impurity content of Fe, Si, and Ca was less than 10 ppm.

[0028] Example 5

[0029] Aluminum powder with a particle size of 50 μm and a purity of 99.999% and aluminum nitride powder with a particle size of 5 μm and a purity of 99.999% were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 70%:30%, and then placed in a boron nitride crucible in a pressure sintering furnace. After evacuation, argon gas at a pressure of 3 MPa was introduced, and the temperature was raised to 1500℃. Then, nitrogen gas at a pressure of 7 MPa was rapidly introduced, and the temperature was held for 5 minutes before cooling with the furnace. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. A suitable sample was taken for particle size analysis, and the results showed that the product particle size D50 was 200.6 μm. The morphology of the sample was characterized using an optical microscope, as shown below. Figure 3 As shown, the results indicate that the AlN particles have an angular single-crystal morphology and no obvious sintering agglomeration. ICP analysis of the sample revealed that the total impurity content of Fe, Si, and Ca was less than 10 ppm.

[0030] Example 6

[0031] The method and reaction conditions in Example 6 were basically the same as in Example 1, except that the ratio of Al powder to AlN powder in the raw materials was different. The influence of the raw material ratio on the particle size and phase of the synthesized product was studied. Specifically, aluminum powder with a particle size of 10 μm and a purity of 99.999% and aluminum nitride powder with a particle size of 10 μm and a purity of 99.999% were selected as raw materials. The raw materials were weighed and mixed according to the ratio in Table 1, and then placed in a boron nitride crucible in a gas pressure sintering furnace. After evacuation, argon gas at a pressure of 1 MPa was introduced. After heating to 1300℃, nitrogen gas at a pressure of 4 MPa was rapidly introduced. After holding at this temperature for 5 min, the furnace was cooled. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. The results are shown in Table 1.

[0032] Table 1. Effects of different raw material ratios on product particle size and phase composition.

[0033]

[0034] As can be seen from Table 1, when the Al powder ratio is 35%, that is, less than 40%, the particle size of the synthesized product is <20μm, and coarse-particle aluminum nitride single crystal powder cannot be synthesized; when the Al powder ratio reaches 75%, that is, more than 70%, due to the melting and agglomeration of aluminum powder, there is unreacted residual aluminum in the product.

[0035] Example 7

[0036] The method and reaction conditions in Example 7 were basically the same as in Example 5, except for the different particle sizes of the raw materials. The influence of raw material particle size on the particle size and phase composition of the synthesized product was studied. Specifically, aluminum powder with a purity of 99.999% and aluminum nitride powder with a purity of 99.999% (as shown in Table 2) were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 70%:30%, and then placed in a boron nitride crucible in a pressure sintering furnace. After evacuation, argon gas at a pressure of 3 MPa was introduced. The temperature was raised to 1500℃, and then nitrogen gas at a pressure of 7 MPa was rapidly introduced. After holding at this temperature for 5 minutes, the furnace was cooled. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. The results are shown in Table 2.

[0037] Table 2. Effects of different raw material particle sizes on product particle size and phase composition.

[0038]

[0039] As shown in Table 2, when the Al powder particle size is 5 μm (below 10 μm), unreacted residual aluminum is present in the product due to the melting and agglomeration of the aluminum powder. When the Al powder particle size reaches 60 μm (above 50 μm), some aluminum powder contains residual aluminum due to incomplete reaction. When the AlN powder particle size is below 5 μm or above 10 μm, unreacted residual aluminum is present in the product due to the melting and agglomeration of the aluminum powder.

[0040] Example 8

[0041] The method and reaction conditions in Example 8 were basically the same as in Example 2, except for the gas pressure. The effect of gas pressure on the particle size and phase composition of the synthesized product was studied. Specifically, aluminum powder with a particle size of 20 μm and a purity of 99.999% and aluminum nitride powder with a particle size of 10 μm and a purity of 99.999% were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 50%:50%, and then placed in a boron nitride crucible in a gas pressure sintering furnace. After evacuation, high-pressure argon gas was introduced, and the temperature was raised to 1400℃. High-pressure nitrogen gas was then rapidly introduced, and the temperature was maintained for 5 minutes before cooling with the furnace. The product block was removed, crushed, and aluminum nitride single crystal powder was obtained. The pressures of argon and nitrogen gas are shown in Table 3. The results are shown in Table 3.

[0042] Table 3. Effects of different gas pressures on product particle size and phase composition.

[0043]

[0044] As shown in Table 3, when the argon pressure is 0.5 MPa (below 1 MPa), residual aluminum is present in the product due to the melting and volatilization of aluminum particles at high temperatures. The product particle size decreases slightly with increasing argon pressure. When the nitrogen pressure is 3 MPa (below 4 MPa), residual aluminum is present in the product. The product particle size increases slightly with increasing nitrogen pressure.

[0045] Example 9

[0046] The method and reaction conditions in Example 9 were basically the same as in Example 3, except for the reaction temperature. The effect of reaction temperature on the particle size and phase composition of the synthesized product was studied. Specifically, aluminum powder with a particle size of 30 μm and a purity of 99.999% and aluminum nitride powder with a purity of 7 μm were selected as raw materials. The raw materials were weighed and mixed according to a mass percentage of Al:AlN = 60%:40%, and then placed in a boron nitride crucible in a pressure sintering furnace. After evacuation, argon gas at a pressure of 2 MPa was introduced. The temperature was raised to the temperatures shown in Table 4, and then nitrogen gas at a pressure of 6 MPa was rapidly introduced. After holding at this temperature for 5 minutes, the furnace was cooled, and the product block was removed, crushed, and aluminum nitride single crystal powder was obtained. The results are shown in Table 4.

[0047] Table 4. Effects of different reaction temperatures on product particle size and phase composition.

[0048]

[0049] As shown in Table 4, when the reaction temperature is 1200℃, i.e., below 1300℃, the raw material does not undergo a rapid nitriding reaction. As the reaction temperature increases, the particle size of the product gradually increases. When the reaction temperature reaches 1600℃, i.e. above 1500℃, the raw aluminum powder melts and agglomerates severely, and residual aluminum is present in the product.

[0050] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing high-purity aluminum nitride single crystal powder, characterized by comprising the steps of: preparing a high-purity aluminum nitride single crystal powder by a method according to any one of claims 1 to 6. The method comprises the following steps: After the raw material aluminum powder and aluminum nitride powder are mixed uniformly according to the proportion, the mixture is placed in a gas pressure sintering furnace, vacuumized, and then 1-3 MPa high-pressure argon is introduced to heat the mixture to 1300-1500 DEG C, 4-7 MPa nitrogen is introduced to cause a combustion explosion reaction, and then the mixture is cooled to room temperature, and after being crushed, aluminum nitride single crystal powder with D50=20-200 mu m and purity of greater than or equal to 99.999% is obtained.

2. The production method according to claim 1, characterized by, The particle size D50 of the aluminum powder is 10-50 mu m, and the purity is greater than or equal to 99.999%.

3. The production method according to claim 1, characterized by, The particle size D50 of the aluminum powder is 20-50 mu m, and the purity is greater than or equal to 99.999%.

4. The preparation method according to claim 1, characterized in that, The particle size D50 of the aluminum nitride powder is 5-10 mu m, and the purity is greater than or equal to 99.999%.

5. The preparation method according to claim 1, characterized in that, The particle size D50 of the aluminum nitride powder is 7-10 mu m, and the purity is greater than or equal to 99.999%.

6. The method of claim 1, wherein, The mass percentage of the aluminum powder is 40%-70% and the mass percentage of the aluminum nitride powder is 30%-60% based on the total mass of the raw materials being 100%.

7. The preparation method according to claim 1, characterized in that, The mass percentage of the aluminum powder is 60%-70% and the mass percentage of the aluminum nitride powder is 30%-40% based on the total mass of the raw materials being 100%.

8. The method of claim 1, wherein, The combustion explosion reaction time is 3-5 min.

9. The method of claim 1, wherein, The temperature is raised to 1400-1500 DEG C.

10. The method of claim 1, wherein, The pressure of the argon is 1-2 MPa and the pressure of the nitrogen is 5-7 MPa.

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