High-thermal-conductivity spherical low-radioactivity α-al 2o 3 powder, preparation method therefor and use thereof

Abstract

The present disclosure relates to the field of materials, and provides high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder, a preparation method therefor and a use thereof. The method comprises: using a flame fusion method or a combustion synthesis method to spheroidize an alumina raw material, so as to obtain spherical alumina having a particle size D50 of 0.5-70 μm; then uniformly mixing the spherical alumina with a composite mineralizer, and then adding a dispersant solution and uniformly mixing same, so as to obtain a premix; and finally, sequentially calcining, grinding and purifying the premix to obtain a target product.

Description

High-thermal-conductivity spherical low-radioactivity alpha-Al2O3 powder, preparation method and application thereof

[0001] Cross-reference to related applications

[0002] The present disclosure claims priority to the application No. 2024113320124, filed on September 24, 2024, with the China Patent Office, and entitled "High-thermal-conductivity spherical low-radioactivity alpha-Al2O3 powder, preparation method and application thereof", the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the field of materials, in particular to a high-thermal-conductivity spherical low-radioactivity alpha-Al2O3 powder, a preparation method and application thereof. BACKGROUND

[0004] With the rapid development of AI servers, automotive driving, 5G, Internet of Things, etc., the demand for high-bandwidth memory (HBM) as a new type of GPU / CPU memory chip is gradually increasing and has become a recent industry hotspot. HBM uses 2.5D chip packaging technology and uses MUF and POP packaging processes in the production process. It is to stack many DDR memory chips together and package them with GPUs to achieve a large-capacity, high-bit-width DDR combined array. However, more memory units mean a significant increase in GPU energy consumption, which faces the urgent need to solve the heat dissipation problem, while the stability and accuracy of signal transmission need to be ensured. As an important component of the chip, epoxy molding compound (EMC) not only plays a protective role for the chip, but also bears part of the chip's heat dissipation function, while it needs to have low radioactivity and cannot emit alpha particles to cause "soft errors" and thus affect the accuracy of the signal. The inorganic filler in EMC accounts for 80-90% of the proportion, and plays a crucial role in achieving high thermal conductivity and low radioactivity of EMC.

[0005] The commonly used spherical silicon powder has a theoretical thermal conductivity of only 1 W / m.k, which cannot meet the requirements of chip heat dissipation. The conventional spherical alumina has a theoretical thermal conductivity of up to 30 W / m.k and stable chemical properties, but the content of radioactive elements such as uranium (U) and thorium (Th) reaches several hundred or even thousands of ppb, and due to the low content of alpha phase, the thermal conductivity is far from the theoretical value. Therefore, a low-radioactivity spherical alumina product with high alpha phase content can be used as a higher thermal conductivity type inorganic filler for memory chip packaging.

[0006] The preferred Bayer method for preparing aluminum hydroxide in patent CN102249276A: adding aluminum hydroxide as seed to the sodium aluminate solution produced by the Bayer method, stirring and precipitating at a temperature of 30-90℃ to obtain a boehmite crystal form, the raw material can be surface treated using a silane coupling agent, a titanate coupling agent, a fatty acid (stearic acid) ≤0.5%, and then spraying the aluminum hydroxide powder into a flame to collect the powder to obtain a low-radioactivity spherical aluminum oxide product with a uranium (U) content ≤10 ppb, preferably ≤8 ppb. The product prepared by this method can only achieve a uranium (U) content of ≤8 ppb, while the current memory chip requires a uranium (U) content of at least ≤5 ppb.

[0007] Patent CN101528604B obtains a spherical aluminum oxide with a sphericity of 0.93 or more and an α phase content of 95% or more by selecting aluminum or aluminum oxide powder, then using the powder to pass through temperature ranges of 550-900℃ and 950-1500℃ to increase the α phase content and collect the target product after cooling. In examples 1-5 of the patent, the residence time of the material at 550-900℃ is less than its residence time at 950-1500℃, which causes the material to accumulate at 950-1500℃ during processing, resulting in agglomeration or uneven heating.

[0008] Therefore, there is an urgent need to provide high-thermal-conductivity, low-radioactivity, high-flowability α-Al2O3 powder. SUMMARY

[0009] The purpose of the present disclosure is to design a high-thermal-conductivity, low-radioactivity α-Al2O3 powder and a preparation method thereof, using hydrated industrial alumina or angular α-Al2O3 as raw material, through a spheroidization process, dispersant pretreatment, phase transition process, purification, depolymerization, etc., to obtain α-Al2O3 powder with adjustable particle size (0.5-70 μm), uranium (U) content ≤5 ppb, high sphericity ≥0.95, high α phase content ≥95%, low viscosity, high flowability, and high thermal conductivity, which can meet the heat dissipation and signal transmission requirements of memory chips. At the same time, it has the characteristics of simple process and environmental friendliness, and is easy to industrialize.

[0010] The purpose of the present disclosure can be achieved by the following technical solutions:

[0011] In a first aspect, the present disclosure provides a preparation method of a high-thermal-conductivity, low-radioactivity α-Al2O3 powder, which comprises the following steps:

[0012] (1) Spheroidization: spheroidize the alumina raw material by a flame fusion method or a combustion synthesis method to obtain spherical alumina with a particle size D50 of 0.5-70 μm (e.g., 0.5 μm, 1.0 μm, 5.0 μm, 10.0 μm, 20.0 μm, 30.0 μm, 40.0 μm, 50.0 μm, 60.0 μm, 70.0 μm, etc.);

[0013] (2) Pretreatment: mix the spherical alumina with a composite mineralizer, and then mix with a dispersant solution to obtain a premix;

[0014] The composite mineralizer is at least two of an acidic reagent, ammonium fluoride, ammonium chloride, aluminum fluoride, and magnesium oxide; and the dispersant is a silane coupling agent and / or a siloxane;

[0015] (3) The premix is sequentially subjected to calcination, grinding, and purification to obtain the target product.

[0016] A method for preparing a high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder, the method comprising the following steps:

[0017] (1) providing spherical alumina with a particle size D50 of 0.5-70 μm;

[0018] (2) Pretreatment: mix the spherical alumina with a composite mineralizer, and then mix with a dispersant solution to obtain a premix; the composite mineralizer is at least two of an acidic reagent, ammonium fluoride, ammonium chloride, aluminum fluoride, and magnesium oxide; and the dispersant is a silane coupling agent and / or a siloxane;

[0019] (3) The premix is sequentially subjected to calcination, grinding, and purification to obtain the target product.

[0020] The present disclosure uses spherical alumina with a particle size D50 of 0.5-70 μm as a raw material, and the raw material is pretreated with a composite mineralizer and a dispersant. The composite mineralizer can control the morphology and size of the particles, and the dispersant can improve the uniformity of particle dispersion. Then, the particles are converted to the α phase by calcination. The alumina particles with a particle size meeting the requirements are obtained by grinding, and the surface residual impurities are removed by purification to improve the content of the α phase.

[0021] In an optional embodiment of the present disclosure, in step (1), the preparation process of the spherical alumina comprises: spheroidizing the alumina raw material by a flame fusion method or a combustion synthesis method to obtain spherical alumina with a particle size D50 of 0.5-70 μm. The spherical alumina can also be a commercially available material, and the spheroidization method is not limited to the above method.

[0022] In the optional embodiment of the present disclosure, in step (1), the alumina raw material is alumina, boehmite, or angular α-Al2O3, and the alumina raw material can be any of the above.

[0023] In an alternative embodiment of the present disclosure, the particle size D50 of the alumina raw material in step (1) is between 0.5 and 80 μm, and the particle size is preferably in this range to improve the uniformity of the particle size of the final product.

[0024] In an alternative embodiment of the present disclosure, the U content of the alumina raw material in step (1) is ≤5 ppb, and the U content is preferably not too high to produce a product with low radioactivity.

[0025] In an alternative embodiment of the present disclosure, the composite mineralizer in step (2) of the present disclosure comprises an acidic agent, ammonium fluoride and magnesium oxide, and the mass ratio of the acidic agent, ammonium fluoride and magnesium oxide is 1:(0.01-8):(0.01-3), such as 1:0.01:0.01, 1:0.05:0.02, 1:0.10:0.05, 1:1.00:0.10, 1:1.50:0.30, 1:2.00:1.00, 1:3.00:1.50, 1:4.00:1.80, 1:4.50:1.90, 1:5.00:2.00, 1:6.00:2.30, 1:7.00:2.50, 1:8.00:3.00, etc. The use of a specific ratio of acidic agent, ammonium fluoride and magnesium oxide as a composite mineralizer can control the growth of the crystal form in the direction of a spherical shape.

[0026] In a preferred embodiment, the mass ratio of the acidic agent, ammonium fluoride and magnesium oxide is 1:(0.05-4.5):(0.02-0.3). The mass ratio of the acidic agent, ammonium fluoride and magnesium oxide is preferably in the above range to further improve the effect of the pretreatment and improve the thermal conductivity of the product.

[0027] In an alternative embodiment of the present disclosure, the acidic agent in step (2) of the present disclosure is boric acid, but is not limited thereto.

[0028] In an alternative embodiment of the present disclosure, the mass ratio between the spherical alumina and the composite mineralizer in step (2) of the present disclosure is 1:(0.001-0.01), such as 1:0.001, 1:0.003, 1:0.005, 1:0.008, 1:0.010, etc. The amount of the composite mineralizer is preferably controlled in the above range to further improve the effect of the pretreatment.

[0029] In an alternative embodiment of the present disclosure, the dispersant in step (2) of the present disclosure is at least one of methyltrimethoxysilane and hexamethyldisiloxane, and the dispersant can be any one or several thereof.

[0030] In an alternative embodiment of the present disclosure, the mass ratio between the spherical alumina and the dispersant in step (2) of the present disclosure is 1:(0.001-0.01), such as 1:0.001, 1:0.003, 1:0.005, 1:0.008, 1:0.010, etc. The amount of dispersant is preferably controlled within the above range, which is beneficial to improving the fluidity of the product. If the amount of dispersant is too large, the thermal conductivity of the product will be reduced to some extent.

[0031] In a preferred embodiment of the present disclosure, the mass ratio between the spherical alumina and the dispersant in step (2) is 1:0.001-0.005, and the amount of dispersant is within the above range, which is beneficial to further improving the fluidity and thermal conductivity of the product.

[0032] In an alternative embodiment of the present disclosure, the calcination temperature in step (3) is 1200-1300℃, such as 1200℃, 1230℃, 1250℃, 1280℃, 1300℃, etc. The calcination temperature within the above range is beneficial to making the reaction proceed fully and improving the thermal conductivity of the product.

[0033] In an alternative embodiment of the present disclosure, the heating rate of calcination is 5-10℃ / min, such as 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, etc.; and the holding time is 6-8h, such as 6h, 7h, 8h, etc. In a second aspect, the present disclosure also provides a high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder, which is prepared by the above method and has the characteristics of high thermal conductivity, low radioactivity, high fluidity, etc.

[0034] In an alternative embodiment of the present disclosure, the high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder has a U content of ≤5ppb, a D50 of 0.6-70μm, and a thermal conductivity of 1.53-1.94W / m·K.

[0035] In a third aspect, the present disclosure also provides the high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder prepared by the preparation method in any of the above embodiments, and the application of the present disclosure in memory chip packaging.

[0036] In the technical scheme of the present disclosure, after the spherical alumina is obtained by spheroidization, the high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder is obtained under high temperature by the combined action of the mineralizer and the dispersant, which not only solves the problem of low α-phase content of the spherical alumina, but also avoids the occurrence of product adhesion in the phase transition process, thereby causing the decline of the product fluidity and other properties.

[0037] Thermal conductivity detection method:

[0038] Weighing: 70g of compounded spherical alumina powder, 10g of vinyl silicone oil, 0.25g of hydrogen-containing silicone oil, 0.02g of inhibitor, and 0.15g of platinum catalyst were weighed respectively. The weighed silicone oil, inhibitor, and catalyst were added to the spherical alumina powder, stirred uniformly, and solidified into a sample piece of about 3mm. A DRL-3 type thermal conductivity tester was used to test the thermal conductivity, with a pressure of 50N and a temperature difference of 40℃.

[0039] Advantages of the present disclosure:

[0040] The product of the present disclosure has the characteristics of high thermal conductivity, low radioactivity, and high flowability, can effectively reduce "soft errors" while improving the heat dissipation capacity of the device, and can be widely used in storage-related packaging materials and substrates. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is the XRD diffraction pattern of the product of Example 1.

[0042] Figure 2 is the XRD diffraction pattern of the product of Comparative Example 1. DETAILED DESCRIPTION

[0043] The present disclosure will be further described below in conjunction with examples, but the scope of protection of the present disclosure is not limited thereto:

[0044] Spheroidization was performed using a flame melting method, and the spherical alumina semi-finished product had a sphericity of ≥0.95.

[0045] Example 1

[0046] Alumina (raw material D50 between 0.5-80μm, U content of 4.8ppb) was spheroidized at a feeding rate of 100kg / h at a temperature of 2100℃ using a flame melting method, and spherical alumina (sphericity ≥0.95) with D50=0.5μm and U content of 4.8ppb was selected.

[0047] The composite mineralizer was boron acid, ammonium fluoride, and magnesium oxide with a mass ratio of 1:0.16:0.02. The composite mineralizer was pretreated in a ball mill for 1h, then the spherical alumina was added and mixed uniformly with the composite mineralizer. The addition amount of the mineralizer was 0.3%wt of the spherical alumina. Finally, methyltrimethoxysilane (methyltrimethoxysilane was added in the form of a hydrolysis solution, and the composition of the hydrolysis solution was water and methyltrimethoxysilane with a mass ratio of 2:1) was added, and the addition amount was 0.3%wt of the spherical alumina. Continue to disperse for 10 minutes to obtain the premix M1.

[0048] Put the premix M1 into the crucible and calcine, the highest temperature of calcination is 1250℃, the heating rate is 7℃ / min, and the holding time is 8h. Put the product A obtained after cooling into the ball mill and grind for 6h, purify with deionized water and dry to obtain the product. The XRD spectrum shows that the diffraction peaks of the sample corresponding to 2θ = 25.56°, 35.13°, 37.75°, 43.33° are relatively sharp, which is consistent with the characteristic peaks of α-Al2O3(PDF #74-0323) and has no impurity peaks, indicating that the product has good α-phase crystallinity.

[0049] The product is not obviously agglomerated by screening detection, and the content of the oversize is 0. The product U has a content of 1.5ppb, a particle size D50 of 0.8μm, and a thermal conductivity of 1.68W / m·K.

[0050] Example 2

[0051] Put the alumina (the raw material D50 is between 0.5-80μm, and the U content is 4.8ppb) into the ball mill and spheroidize at a feeding amount of 100kg / h at a temperature of 2100℃ by using the flame melting method, and select the spherical alumina (sphericity≥0.95) with D50=0.5μm and a U content of 4.8ppb.

[0052] The composite mineralizer is mass ratio of 1:4.5:0.3 of boric acid, ammonium fluoride, and magnesium oxide. Put the composite mineralizer into the ball mill and pretreat for 1h, then add the spherical alumina and mix the composite mineralizer uniformly, and the addition amount of the mineralizer is 0.1%wt of the spherical alumina; finally, add methyltrimethoxysilane (methyltrimethoxysilane is added in the form of hydrolyzate, and the composition of the hydrolyzate is water and methyltrimethoxysilane in a mass ratio of 2:1), and the addition amount is 0.5%wt of the spherical alumina; continue to disperse for 10 minutes to obtain the premix M1.

[0053] Put the premix M1 into the crucible and calcine, the highest temperature of calcination is 1250℃, the heating rate is 7℃ / min, and the holding time is 8h. Put the product A obtained after cooling into the ball mill and grind for 6h, purify with deionized water and dry to obtain the product. The XRD spectrum shows that the diffraction peaks of the sample corresponding to 2θ = 25.56°, 35.13°, 37.75°, 43.33° are relatively sharp, which is consistent with the characteristic peaks of α-Al2O3(PDF #74-0323) and has no impurity peaks, indicating that the product has good α-phase crystallinity; the product is not obviously agglomerated by screening detection, and the content of the oversize is less than 100ppm. The product U has a content of 2.3ppb, a particle size D50 of 0.7μm, and a thermal conductivity of 1.53W / m·K.

[0054] Example 3

[0055] Alumina (raw material D50 between 0.5-80 pm, U content of 3.2 ppb) is spheroidized by using flame melting method at a temperature of 2100°C with a feeding rate of 100 kg / h, and spherical alumina (sphericity ≥ 0.95) with D50 = 40 pm and U content of 3.2 ppb is selected.

[0056] The composite mineralizer is boron acid, ammonium fluoride and magnesium oxide with a mass ratio of 1:0.16:0.02. The composite mineralizer is put into a ball mill for pretreatment for 1 h, and then spherical alumina is added and mixed with the composite mineralizer. The addition amount of the mineralizer is 0.5% wt of the spherical alumina. Finally, methyltrimethoxysilane (methyltrimethoxysilane is added in the form of a hydrolyzate, and the composition of the hydrolyzate is water and methyltrimethoxysilane with a mass ratio of 2:1) is added, and the addition amount is 0.2% wt of the spherical alumina. Continue to disperse for 10 minutes to obtain a premix M1.

[0057] The premix M1 is put into a sagger for calcination, and the maximum calcination temperature is 1250°C, the heating rate is 7°C / min, and the holding time is 8 h. The product A obtained after cooling is ground in a ball mill for 6 h, purified with deionized water and dried to obtain a product. The XRD spectrum shows that the diffraction peaks of the sample corresponding to 2θ = 25.56°, 35.13°, 37.75°, 43.33° are relatively sharp, which is consistent with the characteristic peaks of α-Al2O3 (PDF #74-0323) and no impurity peaks, indicating that the product has good α-phase crystallinity; The sieving detection product has no obvious agglomeration, and the content of the sieve is less than 100 ppm. The product has a U content of 3.0 ppb, a particle size D50 of 42 pm, and a thermal conductivity of 1.82 W / m·K.

[0058] Example 4

[0059] Alumina (raw material D50 between 0.5-80 pm, U content of 3.2 ppb) is spheroidized by using flame melting method at a temperature of 2100°C with a feeding rate of 100 kg / h, and spherical alumina (sphericity ≥ 0.95) with D50 = 40 pm and U content of 3.2 ppb is selected.

[0060] The composite mineralizer is boron acid, ammonium fluoride and magnesium oxide with a mass ratio of 1:0.16:0.02. The composite mineralizer is put into a ball mill for pretreatment for 1 h, and then spherical alumina is added and mixed with the composite mineralizer. The addition amount of the mineralizer is 0.5% wt of the spherical alumina. Finally, methyltrimethoxysilane (methyltrimethoxysilane is added in the form of a hydrolyzate, and the composition of the hydrolyzate is water and methyltrimethoxysilane with a mass ratio of 2:1) is added, and the addition amount is 0.2% wt of the spherical alumina. Continue to disperse for 10 minutes to obtain a premix M1.

[0061] The premix M1 was put into the crucible for calcination, the maximum temperature of calcination was 1250℃, the heating rate was 7℃ / min, and the holding time was 8h. The product A obtained after cooling was put into a ball mill for grinding for 6h, purified with deionized water and dried to obtain the product. The XRD spectrum showed that the sample had sharp diffraction peaks at 2θ = 25.56°, 35.13°, 37.75°, and 43.33°, which were consistent with the characteristic peaks of α-Al2O3(PDF #74-0323) and had no impurity peaks, indicating that the product had good α-phase crystallinity; the product had no obvious agglomeration, and the content of the sieve residue was less than 100ppm. The product U had a content of 2.6ppb, a particle size D50 of 72μm, and a thermal conductivity of 1.94W / m·K.

[0062] Example 5

[0063] The difference from Example 1 is that the composite mineralizer is boric acid and ammonium fluoride with a mass ratio of 1:0.16.

[0064] The results show that the product has no obvious agglomeration after sieving. The product U has a content of 1.6ppb, a particle size larger than that of Example 1, a D50 of 1.0μm, and a thermal conductivity of 1.79W / m·K.

[0065] Example 6

[0066] The difference from Example 1 is that the composite mineralizer is boric acid and magnesium oxide with a mass ratio of 1:0.02.

[0067] The results show that a small amount of agglomeration appears in the product after sieving, and the content of the sieve residue is about 500ppm. The product U has a content of 1.7ppb, and no particle size and thermal conductivity detection is performed due to the presence of agglomeration.

[0068] Example 7

[0069] The difference from Example 1 is that the addition amount of the mineralizer is 0.1%wt of the spherical alumina.

[0070] The results show that:

[0071] The product has no obvious agglomeration after sieving, and the sieve residue is 0. The product U has a content of 1.4ppb, a particle size D50 of 0.74μm, and a thermal conductivity of 1.64W / m·K.

[0072] Example 8

[0073] The difference from Example 1 is that the addition amount of the mineralizer is 1%wt of the spherical alumina.

[0074] The results show that: sieve detection product obvious agglomeration, sieve content more than 1000 ppm. The product U content of 1.7 ppb, because of the agglomeration without particle size and thermal conductivity detection.

[0075] Example 9

[0076] The difference with example 1 is only that the dispersant is replaced with an equal amount of hexamethyl disiloxane.

[0077] The results show that: sieve detection product obvious agglomeration, sieve content more than 1000 ppm. The product U content of 1.7 ppb, because of the agglomeration without particle size and thermal conductivity detection.

[0078] Comparative Example 1

[0079] The alumina (raw material D50 between 0.5-80 μm, U content of 4.8 ppb) is spheroidized at a temperature of 2100°C using the flame melting method at a feed rate of 100 kg / h, and a spherical alumina with D50 = 0.5 μm and U content of 4.8 ppb is selected.

[0080] The product is obtained after purification with deionized water and drying. The sample with D50 = 0.5 μm is selected, and it can be seen from the XRD spectrum that the diffraction peaks of the sample are less sharp compared to example 1, and there are impurity peaks, indicating that the product has a relatively low α phase content and contains other crystal phases; sieve detection material has no obvious agglomeration, and the sieve content is almost 0.

[0081] Comparative Example 2

[0082] The alumina (raw material D50 between 0.5-80 μm, U content of 4.8 ppb) is spheroidized at a temperature of 2100°C using the flame melting method at a feed rate of 100 kg / h, and a spherical alumina with D50 = 0.5 μm and U content of 4.8 ppb (sphericity ≥ 0.95) is selected.

[0083] The sample with D50 = 0.5 μm is selected and placed in a sagger for calcination, with a maximum calcination temperature of 1250°C and a heating rate of 7°C / min, and a holding time of 8h. The product A obtained after cooling is ground in a ball mill for 6h, and the product is obtained after purification with deionized water and drying. The XRD spectrum shows that the diffraction peaks corresponding to 2θ = 25.56°, 35.13°, 37.75°, 43.33° of the sample are relatively sharp, consistent with the characteristic peaks of α-Al2O3 (PDF # 74-0323) and no impurity peaks, indicating that the product has good α phase crystallinity; however, sieve detection material has obvious agglomeration, and the sieve content is more than 1000 ppm.

[0084] Comparative Example 3

[0085] Alumina (D50 of raw material between 0.5-80 μm, U content of 4.8 ppb) is spheroidized by a flame melting method at a temperature of 2100°C at a feeding rate of 100 kg / h, and spherical alumina (sphericity ≥ 0.95) with D50 = 0.5 μm and U content of 4.8 ppb is selected.

[0086] The sample with D50 = 0.5 μm is selected, ammonium fluoride, magnesium oxide are used as a composite mineralizer, the mass ratio of ammonium fluoride and magnesium oxide is 8:1, the sample is pretreated in a ball mill for 1 h, spherical alumina is added, the ratio of spherical alumina and mineralizer is 0.1% wt, and a premix M1 is obtained.

[0087] The premix M1 is placed in a sagger for calcination, the maximum calcination temperature is 1250°C, the heating rate is 7°C / min, and the holding time is 8 h. The product A obtained after cooling is ground in a ball mill for 6 h, purified with deionized water and dried to obtain a product. The XRD spectrum shows that the diffraction peaks of the sample corresponding to 2θ = 25.56°, 35.13°, 37.75° and 43.33° are relatively sharp, which are consistent with the characteristic peaks of α-Al2O3 (PDF #74-0323) and no impurity peaks, indicating that the product has good α-phase crystallinity; the product is severely caked and needs to be treated by an additional dispersion process before use. Industrial applicability

[0088] The present disclosure provides a high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder and a preparation method thereof. The α-Al2O3 powder has adjustable particle size (0.5-70 μm), uranium (U) content ≤ 5 ppb, high sphericity ≥ 0.95, high α-phase content ≥ 95%, low viscosity, high flowability and high thermal conductivity, and can meet the heat dissipation and signal transmission requirements of internal memory chips. The process is simple and environmentally friendly, and has good industrial application prospects.

Claims

1. A method for preparing highly thermally conductive spherical low-radioactivity α-Al₂O₃ powder, characterized in that: The preparation method comprises the following steps: (1) Spheroidization: spheroidizing the alumina raw material by using a flame melting method or a combustion synthesis method to obtain spherical alumina with a particle size D50 of 0.5-70 μm; (2) Pretreatment: uniformly mixing the spherical alumina with a composite mineralizer, and then uniformly mixing the mixture with a dispersant solution to obtain a premix; The composite mineralizer is at least two of an acidic reagent, ammonium fluoride, ammonium chloride, aluminum fluoride and magnesium oxide; and the dispersant is a silane coupling agent and / or a siloxane; (3) The premix is sequentially calcined, ground and purified to obtain the target product.

2. A method for preparing a high thermal conductivity spherical low radioactivity α-Al2O3 powder, characterized in that: The preparation method comprises the following steps: (1) Providing spherical alumina with a particle size D50 of 0.5-70 μm; (2) Pretreatment: uniformly mixing the spherical alumina with a composite mineralizer, and then uniformly mixing the mixture with a dispersant solution to obtain a premix; the composite mineralizer is at least two of an acidic reagent, ammonium fluoride, ammonium chloride, aluminum fluoride and magnesium oxide; and the dispersant is a silane coupling agent and / or a siloxane; (3) The premix is sequentially calcined, ground and purified to obtain the target product.

3. The method of claim 2, wherein: In step (1), the preparation process of the spherical alumina comprises: spheroidizing the alumina raw material by using a flame melting method or a combustion synthesis method to obtain spherical alumina with a particle size D50 of 0.5-70 μm.

4. The production method according to claim 1 or 3, characterized by: In step (1), the alumina raw material is industrial alumina, boehmite or angular α-Al2O3.

5. The method of claim 1, 3 or 4, wherein: In step (1), the particle size D50 of the alumina raw material is between 0.5-80 μm.

6. The method of any one of claims 1, 3-5, wherein: In step (1), the U content of the alumina raw material is ≤5 ppb.

7. The method of any one of claims 1-6, wherein: In step (2), the composite mineralizer comprises an acidic reagent, ammonium fluoride and magnesium oxide, and the mass ratio of the acidic reagent, ammonium fluoride and magnesium oxide is 1:(0.01-8):(0.01-3).

8. The method of claim 7, wherein: The mass ratio of the acidic reagent, ammonium fluoride and magnesium oxide is 1:(0.05-4.5):(0.02-0.3).

9. The method of any one of claims 1-8, wherein: In step (2), the acidic reagent is boric acid.

10. The method of any one of claims 1-9, wherein: In step (2), the mass ratio between the spherical alumina and the composite mineralizer is 1:(0.001-0.01).

11. The method of any one of claims 1-10, wherein: In step (2), the dispersant is at least one of methyltrimethoxysilane and hexamethyldisiloxane.

12. The method of any one of claims 1-11, wherein: In step (2), the mass ratio between the spherical alumina and the dispersant is 1:(0.001-0.01).

13. The method of claim 12, wherein: In step (2), the mass ratio between the spherical alumina and the dispersant is 1:(0.001-0.005).

14. The method of any one of claims 1-13, wherein: In step (3), the calcination temperature is 1200-1300℃; And / or, the heating rate of calcination is 5-10℃ / min; And / or, the holding time of calcination is 6-8h.

15. A high thermal conductive spherically shaped low radioactivity α- Al2O3 powder, characterized by: Prepared by using the preparation method in any one of claims 1-14.

16. The high thermal conductivity, low radioactivity, spherical α-ΑΙ203 powder of any one of claim 15, wherein, The high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder satisfies: U content ≤5 ppb; And / or, D50 is 0.6-70 μm; And / or, the thermal conductivity is 1.53-1.94 W / m·K.

17. Application of the high-thermal-conductivity spherical low-radioactivity α-Al2O3 powder prepared by the preparation method in any one of claims 1-14 in an embedded memory chip package.

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