Submicron and micron spherical alumina, and preparation method and application thereof

Abstract

The invention discloses submicron and micron spherical aluminum oxide as well as a preparation method and application thereof. According to the invention, a high-temperature oxidation method is adopted, elemental aluminum and a compound thereof are used as raw materials, and submicron and micron-sized spherical alumina are prepared at the same time through high-temperature oxidation. The method provided by the invention can realize synchronous preparation of spherical fillers with different sizes, the heat-conducting filler formed by compounding the prepared submicron and micron spherical alumina has the characteristics of low viscosity, high fluidity, high heat conductivity and the like in semiconductor packaging, and the performance of a packaging material can be remarkably improved; the strict requirements of high-end electronic equipment on the packaging material are met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of heat-conducting fillers, and particularly relates to sub-micron and micron spherical alumina and a preparation method and application thereof. BACKGROUND

[0002] With the strict requirements of AI devices on thermal management and the development of electronic devices in the direction of lightness, thinness and smallness, the heat-conducting properties of electronic packaging materials are increasingly required. Especially in the fields of liquid plastic packaging materials and underfill adhesives, the demand for sub-micron and micron spherical alumina is increasing. These fillers not only need to have high thermal conductivity, but also need to have good mechanical and electrical properties.

[0003] At present, the methods for preparing sub-micron and micron spherical alumina fillers mainly include liquid phase synthesis, plasma method, gasification method, flame method and high-temperature oxidation method. However, these methods each have its limitations. The liquid phase synthesis method uses organic solvents which are not environmentally friendly, has high cost, long production cycle and is difficult to obtain cost-effective products in batches; the plasma method is a physical process, but its running cost is high, the production capacity is low, and it is difficult to mass-produce; the gasification method can obtain sub-micron products, but the method is still in the development stage, and the stability of the produced products is poor (CN115448317A).

[0004] The flame method is one of the main methods for preparing spherical alumina at present. This method sends the filler into a high-temperature environment formed by combustible gas-oxygen to melt and cool at high temperature, and the spherical alumina filler is finally formed by the surface tension effect. However, the traditional flame method is difficult to realize products less than 3 μm; the high-temperature oxidation method can only obtain sub-micron fillers, and it is difficult to simultaneously prepare sub-micron and micron fillers to meet the strict requirements of high-end application fields (CN116081667A, CN115991893A).

[0005] Therefore, it is urgent to develop a new preparation method which can simultaneously obtain sub-micron and micron spherical alumina, maintain good particle morphology and thermal conductivity, and also consider low surface hydroxyl content, excellent dispersion performance and excellent rheological properties to meet the diversified needs of modern electronic packaging fields. SUMMARY

[0006] In view of the problems that the traditional flame method is difficult to prepare sub-micron and micron spherical alumina at the same time, and the particle size control is difficult and the surface morphology is not ideal during the preparation process, the present application provides a kind of sub-micron and micron spherical alumina and its preparation method and application. The present application uses high temperature oxidation method, and uses elemental aluminum and its compounds as raw materials. Sub-micron (0.1-1.0 μm) and micron (1-20 μm) spherical alumina are prepared by high temperature oxidation at the same time. The thermal conductive filler formed by compounding the spherical alumina has low viscosity, high fluidity and high thermal conductivity, and is suitable for semiconductor packaging and other fields.

[0007] The technical scheme of the present application is as follows:

[0008] A preparation method of sub-micron and micron spherical alumina, comprising the following steps:

[0009] Elemental aluminum and aluminum-containing compounds are used as raw materials. After mixing the elemental aluminum and the aluminum-containing compounds, high temperature oxidation reaction occurs in the flame formed by the fuel gas and the combustion-supporting gas. After cooling, the product is classified to obtain sub-micron spherical alumina and micron spherical alumina. The aluminum-containing compound is one or more of aluminum alcohol (Al(OC2H5)3) and aluminum hydroxide (Al(OH)3).

[0010] Further, the mass of elemental aluminum accounts for more than 50% of the total mass of the raw materials, preferably 50%-80%.

[0011] Further, the fuel gas is a common fuel gas for preparing spherical alumina by flame method in the art, such as natural gas, methane, ethane, acetylene, etc. The combustion-supporting gas is a common combustion-supporting gas for preparing spherical alumina by flame method in the art, such as air, oxygen, etc.

[0012] The present application provides sub-micron and micron spherical alumina prepared by the above preparation method.

[0013] Further, the average particle size of the sub-micron spherical alumina is 0.1-1.0 μm, and the aluminum hydroxyl number is ≤1500 μg / g; the average particle size of the micron spherical alumina is 1-20 μm, and the volume fraction of particles less than 1 μm is ≤70%, and the aluminum hydroxyl number is ≤400 μg / g. Further, the average particle size of the sub-micron spherical alumina is 0.1-0.7 μm, and the aluminum hydroxyl number is 500-1500 μg / g; the average particle size of the micron spherical alumina is 2-12 μm, and the volume fraction of particles less than 1 μm is 20-70%, and the aluminum hydroxyl number is 200-400 μg / g.

[0014] The present application also provides the application of the above-mentioned sub-micron and micron spherical alumina in preparing thermal conductive fillers.

[0015] Further, in the heat-conductive filler, the mass ratio of the sub-micron and micron spherical alumina is 100%:0%-0%:100%, preferably 30%-50%:70%-50%, based on 100% of the total mass of the sub-micron and micron spherical alumina.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] (1) The present application uses elemental aluminum and aluminum-containing compounds with low exothermic or endothermic as raw materials, and simultaneously prepares sub-micron and micron spherical alumina by high-temperature oxidation method, realizing the synchronous preparation of spherical fillers of different sizes.

[0018] (2) The present application can accurately control the average particle size and aluminum hydroxyl number of the sub-micron spherical alumina, ensuring that the average particle size is 0.1-1.0 μm and the aluminum hydroxyl number is ≤1500 μg / g, thereby significantly improving the flowability and performance stability of the product; at the same time, the average particle size and aluminum hydroxyl number of the micron spherical alumina are controlled, so that the average particle size is 1-20 μm and the aluminum hydroxyl number is ≤400 μg / g, and the volume fraction of particles less than 1 μm is controlled to ≤70%, giving the product excellent flowability.

[0019] (3) The heat-conductive filler prepared by compounding the sub-micron and micron spherical alumina prepared by the method of the present application has low viscosity, high flowability, and high thermal conductivity in semiconductor packaging, which can significantly improve the performance of the packaging material and meet the strict requirements of high-end electronic equipment on packaging materials.

[0020] (4) The process of the present application is simple, easy to operate, and easy to scale up, and has low energy consumption, controllable production cost, and good economic benefit. DETAILED DESCRIPTION

[0021] The technical solutions of the present application will be further described below in conjunction with specific examples.

[0022] Example 1

[0023] A mixture of elemental aluminum and Al(OC2H5)3 mixed in a mass ratio of 80:20 is used as raw material, and a high-temperature oxidation reaction occurs in the flame formed by the combustion gas and the combustion-supporting gas. After burning, the product is cooled and classified to obtain 0.7 μm spherical alumina product A and 10.2 μm spherical alumina product B. The aluminum hydroxyl number of the sub-micron product A is 521 μg / g, the volume fraction of particles less than 1 μm in the micron spherical product B is 23%, and the aluminum hydroxyl number is 63 μg / g.

[0024] The product B is filled with bisphenol A epoxy resin at a ratio of 88%, and after dispersion by a vacuum degassing machine, a rheometer is used for constant temperature and shear test, and the corresponding rheological curve is obtained. The viscosity of the product at 50 s-1 is 1.2 Pa·s, the viscosity at 100 s-1 is 1.5 Pa·s, the viscosity at 200 s-1 is 1.8 Pa·s, and the viscosity at 300 s-1 is 2.0 Pa·s.-1 The viscosity value at 50 s"1was 125.4 Pa.s. The flowability test was performed using a dispensing machine, and the time to extrude 10 g of the mixture was recorded as 107 s.

[0025] Product B was filled with 500 cp vinyl silicone oil at a ratio of 90%, mixed using a vacuum degassing machine, and then hydrogen-containing silicone oil, platinum catalyst, and accelerator were added and mixed uniformly. The mixture was poured into a mold to form a 4 mm thick thermal pad, which was cured by heating at 120°C. The thermal conductivity was tested using a DRL-III thermal conductivity tester, and the thermal conductivity was measured to be 1.54 W / (m.K).

[0026] Example 2

[0027] A mixture of elemental aluminum Al(OH)3in a mass ratio of 80:20 was used as a raw material, and a high-temperature oxidation reaction occurred in the flame formed by the fuel gas and the combustion-supporting gas. After burning, the product was cooled and classified to obtain 0.3 pm spherical aluminum oxide product A and 5.8 pm spherical aluminum oxide product B. The aluminum hydroxyl number of the sub-micron product A was 782 pg / g, and the volume fraction of particles less than 1 pm in the micron-sized spherical product B was 48%, with an aluminum hydroxyl number of 142 pg / g.

[0028] Product B was filled with bisphenol A epoxy resin at a ratio of 85%, and the mixture was dispersed using a vacuum degassing machine. A constant temperature and shear test was performed using a rheometer, and the corresponding rheological curve was obtained. The viscosity value at 50 s"1was 129.5 Pa.s. The flowability test was performed using a dispensing machine, and the time to extrude 10 g of the mixture was recorded as 121 s. -1

[0029] Product B was filled with 500 cp vinyl silicone oil at a ratio of 87%, mixed using a vacuum degassing machine, and then hydrogen-containing silicone oil, platinum catalyst, and accelerator were added and mixed uniformly. The mixture was poured into a mold to form a 4 mm thick thermal pad, which was cured by heating at 120°C. The thermal conductivity was tested using a DRL-III thermal conductivity tester, and the thermal conductivity was measured to be 1.32 W / (m.K).

[0030] Example 3

[0031] A mixture of elemental aluminum and Al(OC2H5)3in a mass ratio of 80:20 was used as a raw material, and a high-temperature oxidation reaction occurred in the flame formed by the fuel gas and the combustion-supporting gas. After burning, the product was cooled and classified to obtain 0.7 pm spherical aluminum oxide product A and 10.2 pm spherical aluminum oxide product B. The aluminum hydroxyl number of the sub-micron product A was 521 pg / g, and the volume fraction of particles less than 1 pm in the micron-sized spherical product B was 23%, with an aluminum hydroxyl number of 63 pg / g.

[0032] ​Sub-micron product A and micron product B are compounded according to a mass ratio of 30:70 to obtain product C.

[0033] Product C is filled with bisphenol A epoxy resin at a ratio of 85%, and after dispersion by a vacuum degassing machine, constant temperature and variable shear tests are performed by a rheometer to obtain the corresponding rheological curve. The viscosity value of product C at 50 s -1 is 116.1 Pa.s. The flowability test is performed by using a dispensing machine, and the time for extruding 10 g of the mixture is recorded as 74 s.

[0034] After product C is filled with 500 cp vinyl silicone oil at a ratio of 92%, mixing is performed by a vacuum degassing machine, and then hydrogen-containing silicone oil, platinum catalyst and accelerator are added and uniformly mixed. The mixture is poured into a mold to form a 4 mm thick thermal pad, which is heated and cured at 120°C. The thermal conductivity is tested by using a DRL-III thermal conductivity tester, and the thermal conductivity is measured as 1.66 W / (m.K).

[0035] Example 4

[0036] A mixture of elemental aluminum and Al(OC2H5)3 mixed according to a mass ratio of 95:5 is used as a raw material to undergo high-temperature oxidation reaction in a flame formed by combustion gas and combustion-supporting gas. After combustion, the product is cooled and classified to obtain 0.9 μm spherical aluminum oxide product A and 17.2 μm spherical aluminum oxide product B. The aluminum hydroxyl number of the sub-micron product A is 433 μg / g, and the volume fraction of particles less than 1 μm in the micron spherical product B is 4.1%, and the aluminum hydroxyl number is 47 μg / g.

[0037] Sub-micron product A and micron product B are compounded according to a mass ratio of 30:70 to obtain product C.

[0038] Product C is filled with bisphenol A epoxy resin at a mass ratio of 85%, and after dispersion by a vacuum degassing machine, constant temperature and variable shear tests are performed by a rheometer to obtain the corresponding rheological curve. The viscosity value of product C at 50 s -1 is 104.6 Pa.s. The flowability test is performed by using a dispensing machine, and the time for extruding 10 g of the mixture is recorded as 86 s.

[0039] After product C is filled with 500 cp vinyl silicone oil at a ratio of 90%, mixing is performed by a vacuum degassing machine, and then hydrogen-containing silicone oil, platinum catalyst and accelerator are added and uniformly mixed. The mixture is poured into a mold to form a 4 mm thick thermal pad, which is heated and cured at 120°C. The thermal conductivity is tested by using a DRL-III thermal conductivity tester, and the thermal conductivity is measured as 1.93 W / (m.K).

[0040] Example 5

[0041] The mixture of elemental aluminum and Al(OC2H5)3 mixed in a mass ratio of 50:50 is used as raw material to occur high-temperature oxidation reaction in the flame formed by combustion gas and combustion-supporting gas. After cooling and grading, 0.3 μm spherical alumina product A and 4.1 μm spherical alumina product B are obtained. The aluminum hydroxyl number of submicron product A is 782 μg / g, the volume fraction of particles less than 1 μm in micron-level spherical product B is 52%, and the aluminum hydroxyl number is 288 μg / g.

[0042] The submicron product A and micron-level product B are compounded in a mass ratio of 30:70 to obtain product C.

[0043] The product C is filled with bisphenol A epoxy resin at a ratio of 85%, and after dispersion by a vacuum degassing machine, constant temperature and shear test is performed by a rheometer to obtain the corresponding rheological curve. The viscosity value at 50 s -1 is 136.3 Pa.s. The flowability test is performed by using a dispensing machine, and the time for extruding 10 g of the mixture is recorded as 128 s.

[0044] After the product C is filled with 500 cp vinyl silicone oil at a ratio of 87%, mixing is performed by a vacuum degassing machine, and then hydrogen-containing silicone oil, platinum catalyst and accelerator are uniformly mixed and poured into a mold to press into a 4 mm thick heat-conducting gasket. After heating and curing at 120°C, the thermal conductivity is tested by using a DRL-III thermal conductivity tester, and the thermal conductivity is measured as 1.43 W / (m.K).

[0045] Example 6

[0046] The mixture of elemental aluminum and Al(OH)3 mixed in a mass ratio of 50:50 is used as raw material to occur high-temperature oxidation reaction in the flame formed by combustion gas and combustion-supporting gas. After cooling and grading, 0.1 μm spherical alumina product A and 2.7 μm spherical alumina product B are obtained. The aluminum hydroxyl number of submicron product A is 1496 μg / g, the volume fraction of particles less than 1 μm in micron-level spherical product B is 68%, and the aluminum hydroxyl number is 384 μg / g.

[0047] The product B is filled with bisphenol A epoxy resin at a ratio of 85%, and after dispersion by a vacuum degassing machine, constant temperature and shear test is performed by a rheometer to obtain the corresponding rheological curve. The viscosity value at 50 s -1 is 162.5 Pa.s. The flowability test is performed by using a dispensing machine, and the time for extruding 10 g of the mixture is recorded as 133 s.

[0048] The product B is filled with 500 cp vinyl silicone oil at a ratio of 85%, mixed by a vacuum degassing machine, and then hydrogen-containing silicone oil, platinum catalyst and accelerator are added and uniformly mixed. The mixture is poured into a mold to form a 4 mm thick thermal pad, which is cured at 120°C and then tested for thermal conductivity using a DRL-III thermal conductivity tester. The thermal conductivity is 1.26 W / (m.K).

[0049] Comparative Example 1

[0050] Al2O3 is used as raw material to undergo high-temperature reaction in a flame formed by combustion gas and combustion-supporting gas. After burning, the product is classified after cooling to obtain 3 μm spherical alumina product A and 12.5 μm spherical alumina product B. The aluminum hydroxyl number of the micron product A is 176 μg / g, and the volume fraction of particles less than 1 μm in the micron spherical product B is 18%, and the aluminum hydroxyl number is 48 μg / g.

[0051] The product B is filled with bisphenol A epoxy resin at a ratio of 85%, and then dispersed by a vacuum degassing machine. The rheometer is used for constant temperature and variable shear test to obtain the corresponding rheological curve. The viscosity value of the product at 50 s -1 is 169.5 Pa.s. The dispensing machine is used for flowability test, and the time for extruding 10 g of the mixture is recorded as 135 s.

[0052] The product B is filled with 500 cp vinyl silicone oil at a ratio of 85%, mixed by a vacuum degassing machine, and then hydrogen-containing silicone oil, platinum catalyst and accelerator are added and uniformly mixed. The mixture is poured into a mold to form a 4 mm thick thermal pad, which is cured at 120°C and then tested for thermal conductivity using a DRL-III thermal conductivity tester. The thermal conductivity is 1.42 W / (m.K).

[0053] Comparative Example 2

[0054] Al(OC2H5)3 is used as raw material to undergo high-temperature reaction in a flame formed by combustion gas and combustion-supporting gas. After burning, the product is classified after cooling to obtain 0.3 μm spherical alumina product A and 0.7 μm spherical alumina product B. The aluminum hydroxyl number of the micron product A is 852 μg / g, and the volume fraction of particles less than 1 μm in the micron spherical product B is 79%, and the aluminum hydroxyl number is 664 μg / g.

[0055] The product B is filled with bisphenol A epoxy resin at a ratio of 85%, and the filling difficulty is large, and the dispersion is not possible.

[0056] Product B was filled with 500cp vinyl silicone oil at a ratio of 70%, and then mixed using a vacuum degassing machine. Hydrogen-containing silicone oil, platinum catalyst, and accelerator were added and mixed evenly. The mixture was then poured into a mold and pressed into a 4mm thick thermally conductive pad. After curing at 120℃, the thermal conductivity was tested using a DRL-III thermal conductivity tester, and the measured thermal conductivity was 0.98W / (mK).

[0057] Comparative Example 3

[0058] Using elemental aluminum as raw material, a high-temperature oxidation reaction is carried out in a flame formed by fuel gas and oxidizing gas. After the combustion product is cooled and graded, only spherical alumina product B with a size of 16.4 μm is obtained, of which particles smaller than 1 μm account for 16% of the volume and the number of aluminum hydroxyl groups is 29 μg / g.

[0059] Product B was filled with bisphenol A epoxy resin at a ratio of 85%, dispersed using a vacuum degassing machine, and then subjected to isothermal shear testing using a rheometer to obtain the corresponding rheological curve. The rheological curve was obtained at 50 s. -1 The viscosity was 121 Pa·s. A flowability test was performed using a dispensing machine, and the time to extrude 10g of the mixture was recorded as 96s.

[0060] Product B was filled with 500cp vinyl silicone oil at a ratio of 92%, and mixed using a vacuum degassing machine. Then, hydrogen-containing silicone oil, platinum catalyst, and accelerator were added and mixed evenly. The mixture was then poured into a mold and pressed into a 4mm thick thermally conductive pad. After curing at 120℃, the thermal conductivity was tested using a DRL-III thermal conductivity tester, and the measured thermal conductivity was 1.52W / (mK).

[0061]

[0062] As can be seen from Comparative Example 3, when only elemental aluminum is used as raw material, small particles are prone to agglomerate into large-diameter spherical particles due to the high heat release during the combustion process. However, in Examples 1 to 6, aluminum-containing compounds such as aluminum alkoxide and aluminum hydroxide, which have low or endothermic heat release, are added to the raw materials, which can significantly reduce the reaction temperature in the furnace, thereby achieving the simultaneous preparation of submicron and micron-sized spherical alumina, and exhibiting low surface hydroxyl content, excellent dispersion performance and excellent rheological properties.

[0063] Comparing the particle size of product C prepared in Examples 3-4, it can be seen that, under the condition of using micron-sized product B with the same particle size, adding submicron-sized spherical alumina product A to form thermally conductive filler product C can reduce the viscosity of the product and improve its fluidity, maximum filling ratio and thermal conductivity.

Claims

1. A method for preparing submicron and micron-sized spherical alumina, characterized in that, Includes the following steps: Using elemental aluminum and aluminum-containing compounds as raw materials, the elemental aluminum and aluminum-containing compounds are mixed and subjected to a high-temperature oxidation reaction in a flame formed by fuel gas and oxidizing gas. After combustion, the products are cooled and graded to obtain submicron-sized spherical alumina and micron-sized spherical alumina. The aluminum-containing compounds are one or more of aluminum alkoxide and aluminum hydroxide.

2. The preparation method according to claim 1, characterized in that, Elemental aluminum accounts for more than 50% of the total mass of the raw materials.

3. The preparation method according to claim 1, characterized in that, Elemental aluminum accounts for 50% to 80% of the total mass of the raw materials.

4. The preparation method according to claim 1, characterized in that, The fuel gas is natural gas, methane, ethane, or acetylene, and the oxidizing agent is air or oxygen.

5. Submicron and micron-sized spherical alumina prepared by any of the preparation methods according to claims 1 to 4.

6. The submicron and micron-sized spherical alumina according to claim 5, characterized in that, The average particle size of submicron spherical alumina is 0.1~1.0μm, and the number of aluminum hydroxyl groups is ≤1500μg / g; the average particle size of micron spherical alumina is 1~20μm, the volume ratio of particles smaller than 1μm is ≤70%, and the number of aluminum hydroxyl groups is ≤400μg / g.

7. The submicron and micron-sized spherical alumina according to claim 5, characterized in that, The average particle size of submicron spherical alumina is 0.1~0.7μm, and the number of aluminum hydroxyl groups is 500~1500μg / g; the average particle size of micron spherical alumina is 2~12μm, the volume ratio of particles smaller than 1μm is 20~70%, and the number of aluminum hydroxyl groups is 200~400μg / g.

8. The application of the submicron and micron-sized spherical alumina according to claim 5 in the preparation of thermally conductive fillers.

9. The application according to claim 8, characterized in that, In the thermally conductive filler, the mass ratio of submicron and micron-sized spherical alumina is 100%:0%~0%:100%, with the total mass of submicron and micron-sized spherical alumina being 100%.

10. The application according to claim 8, characterized in that, In the thermally conductive filler, with the total mass of submicron and micron-sized spherical alumina as 100%, the mass ratio of submicron to micron-sized spherical alumina is 30%~50%:70%~50%.

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