Preparation method of high-transmittance aluminum nitride ceramic substrate

Abstract

This invention relates to the field of aluminum nitride ceramic substrate preparation technology, and provides a method for preparing a high-transmittance aluminum nitride ceramic substrate, solving the defects of low transmittance and low thermal conductivity of aluminum nitride in the prior art. The preparation steps include: (1) deoxygenation treatment of aluminum nitride powder raw material; (2) placing the aluminum nitride powder treated in step (1) into a graphite mold, and then sending it into a spark plasma sintering furnace for pre-sintering to obtain an aluminum nitride pre-sintered body; the pre-sintering temperature is controlled at 1500-1650℃, the holding time is 5-10 min, and the pressure in the spark plasma sintering furnace is controlled at 8-15 MPa; (3) microwave sintering; (4) slicing, grinding, and polishing treatment.

Description

Technical Field

[0001] This invention relates to the field of aluminum nitride ceramic substrate preparation technology, and more particularly to a method for preparing a high-transmittance aluminum nitride ceramic substrate. Background Technology

[0002] Aluminum nitride ceramics, due to their high thermal conductivity, low dielectric constant, high electrical resistance, and non-toxicity, have become ideal electronic packaging materials, attracting widespread attention and research. High-transmittance aluminum nitride not only possesses the advantages of aluminum nitride ceramics but also exhibits high transmittance, making it promising for applications in infrared hoods and window materials. However, because aluminum nitride is a strongly covalent compound with low sintering activity, pure aluminum nitride does not produce a liquid phase even at high temperatures, making dense sintering difficult. To obtain dense aluminum nitride ceramics, sintering aids are added or the sintering time is extended. However, even with the addition of sintering aids, the light transmittance of the resulting ceramic remains relatively poor.

[0003] Chinese Patent Application No. 02115663.8 discloses a method for preparing transparent aluminum nitride ceramics using spark plasma sintering. The method involves placing high-purity aluminum nitride powder directly into a graphite mold, which is then placed in a spark plasma sintering furnace. An axial pressure of 20-30 MPa is applied, and sintering is carried out under vacuum conditions better than 6 Pa or in an N2 atmosphere at a sintering temperature of 1700-2000 °C. The temperature is increased at a rate of 100-800 °C / min, held for 4-20 min, and then cooled to room temperature in the furnace to produce transparent aluminum nitride ceramics. The aluminum nitride powder contains 1.0-1.1 wt% oxygen, 33-33.5 wt% nitrogen, and other impurities below 50 ppm. This method can shorten the sintering time, consume less energy, and obtain aluminum nitride ceramics with high transparency. The maximum transmittance of the sample in the mid-infrared band (2.5-25μm) is greater than 70%. However, the process has a high sintering temperature and fast speed, which will leave defects such as pores, dislocations, stacking faults, and second-phase inclusions in the sintered body. These defects will not only affect the transmittance but also reduce the thermal conductivity of aluminum nitride. Summary of the Invention

[0004] Therefore, in view of the above problems, the present invention provides a method for preparing a high-transmittance aluminum nitride ceramic substrate, which solves the defects of low light transmittance and low thermal conductivity of aluminum nitride in the prior art.

[0005] To achieve the above objectives, the present invention employs the following technical solution: a method for preparing a high-transmittance aluminum nitride ceramic substrate, comprising the following preparation steps:

[0006] (1) Deoxidation treatment of aluminum nitride powder raw material: aluminum nitride powder with a particle size of 0.1-2μm is fed into a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1wt%.

[0007] (2) The aluminum nitride powder treated in step (1) is placed into a graphite mold and then sent into a spark plasma sintering furnace for pre-sintering to obtain an aluminum nitride pre-sintered body; the pre-sintering temperature is controlled at 1500-1650℃, the holding time is 5-10min, and the pressure inside the spark plasma sintering furnace is controlled at 8-15MPa.

[0008] (3) Microwave sintering: The aluminum nitride pre-sintered body is sent into a microwave oven for sintering. The microwave source power is controlled at 2-8kW, the sintering temperature is controlled at 1500-1680℃, the holding time is 1-2h, the heating rate is 10-15℃min, and sintering is carried out in a nitrogen atmosphere.

[0009] (4) Slicing, grinding and polishing.

[0010] Further, the specific steps of the deoxidation treatment in step (1) are as follows: aluminum nitride powder is placed into a vacuum heat treatment container and sealed, then vacuum treatment is performed, then heated to 900-1200℃, held for 30-60 minutes, and then cooled to room temperature.

[0011] Furthermore: During cooling, the cooling rate is controlled at 10-20℃ / min.

[0012] Further: Step (4) grinding includes coarse grinding and fine grinding.

[0013] Furthermore: the abrasive used in the coarse grinding is diamond abrasive.

[0014] Furthermore: the abrasive used in the fine grinding is silicon nitride micro powder abrasive.

[0015] By adopting the aforementioned technical solution, the beneficial effects of the present invention are as follows:

[0016] 1. This invention combines spark plasma sintering and microwave sintering, which shortens the preparation time compared to traditional high-temperature sintering, saving time and costs and resulting in higher economic benefits.

[0017] 2. The aluminum nitride powder used in this invention has undergone deoxygenation treatment to reduce the oxygen content of the aluminum nitride powder to less than 0.1 wt%. The oxygen content in aluminum nitride powder will significantly affect its light transmittance. Deoxygenation treatment can make the final product have a higher light transmittance.

[0018] 3. The deoxygenated aluminum nitride powder is placed in a graphite mold and then fed into a spark plasma sintering furnace for pre-sintering. Pre-sintering allows the powder particles to initially bond together, forming a pre-sintered body with a certain strength. The pre-sintering temperature is controlled at 1500-1650℃, a temperature range that helps the aluminum nitride powder sinter without causing excessive grain growth. The holding time is controlled at 5-10 minutes to ensure sufficient bonding of the powder particles. Simultaneously, the pressure inside the spark plasma sintering furnace is controlled at 8-15 MPa, which helps to densify the powder particles during the sintering process.

[0019] 4. The pre-sintered body undergoes microwave sintering. Microwave sintering offers advantages such as rapid heating, uniform temperature, and short sintering time, which helps obtain aluminum nitride ceramic substrates with high light transmittance. The microwave source power is controlled between 2-8 kW to ensure sufficient energy during sintering; the sintering temperature is controlled between 1500-1680℃ to promote densification and grain growth of the aluminum nitride ceramic. The heating rate is controlled at 10-15℃ / min to avoid thermal stress problems caused by excessively rapid heating. The entire sintering process is carried out under a nitrogen atmosphere to prevent oxidation of the ceramic substrate at high temperatures.

[0020] 5. After sintering, the aluminum nitride ceramic substrate is sliced, ground, and polished. Slicing allows for the production of ceramic substrates with the specific shape and size required by the customer; grinding removes burrs and uneven surfaces generated during slicing; polishing further improves the surface smoothness and flatness of the ceramic substrate. These processing steps help to obtain aluminum nitride ceramic substrates with high light transmittance and good appearance quality. Detailed Implementation

[0021] Example 1

[0022] A method for preparing a high-transmittance aluminum nitride ceramic substrate includes the following preparation steps:

[0023] (1) Deoxidation treatment of aluminum nitride powder raw material: aluminum nitride powder with a particle size of 0.1μm is fed into a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1wt%.

[0024] The specific steps of the deoxidation treatment are as follows: aluminum nitride powder is placed in a vacuum heat treatment container and sealed, then vacuum treatment is performed, then heated to 900℃ and held for 30 minutes, and then cooled to room temperature; during cooling, the cooling rate is controlled at 10℃ / min.

[0025] (2) The aluminum nitride powder treated in step (1) is placed into a graphite mold and then sent into a spark plasma sintering furnace for pre-sintering to obtain an aluminum nitride pre-sintered body; the pre-sintering temperature is controlled at 1500℃, the holding time is 5min, and the pressure inside the spark plasma sintering furnace is controlled at 8MPa.

[0026] (3) Microwave sintering: The aluminum nitride pre-sintered body is sent into a microwave oven for sintering. The microwave source power is controlled at 2kW, the sintering temperature is controlled at 1500℃, the holding time is 1h, the heating rate is 10℃min, and sintering is carried out in a nitrogen atmosphere.

[0027] (4) Slicing, grinding and polishing; grinding includes coarse grinding and fine grinding, wherein the abrasive used in coarse grinding is diamond abrasive and the abrasive used in fine grinding is silicon nitride micro powder abrasive.

[0028] Example 2

[0029] A method for preparing a high-transmittance aluminum nitride ceramic substrate includes the following preparation steps:

[0030] (1) Deoxidation treatment of aluminum nitride powder raw material: Aluminum nitride powder with a particle size of 1μm is fed into a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1wt%; the specific process of deoxidation treatment is as follows: aluminum nitride powder is loaded into a vacuum heat treatment container and sealed, then vacuum treatment is performed, then heated to 1100℃ and held for 45min, and then cooled to room temperature, with the cooling descent rate controlled at 15℃ / min.

[0031] (2) The aluminum nitride powder treated in step (1) is placed into a graphite mold and then sent into a spark plasma sintering furnace for pre-sintering to obtain an aluminum nitride pre-sintered body; the pre-sintering temperature is controlled at 1600℃, the holding time is 7min, and the pressure inside the spark plasma sintering furnace is controlled at 12MPa.

[0032] (3) Microwave sintering: The aluminum nitride pre-sintered body is sent into a microwave oven for sintering. The microwave source power is controlled at 5kW, the sintering temperature is controlled at 1600℃, the holding time is 1.5h, the heating rate is 12℃min, and sintering is carried out in a nitrogen atmosphere.

[0033] (4) Slicing, grinding and polishing treatment, including coarse grinding and fine grinding. The abrasive used for coarse grinding is diamond abrasive, and the abrasive used for fine grinding is silicon nitride micro powder abrasive.

[0034] Example 3

[0035] A method for preparing a high-transmittance aluminum nitride ceramic substrate includes the following preparation steps:

[0036] (1) Deoxidation treatment of aluminum nitride powder raw material: Aluminum nitride powder with a particle size of 2μm is fed into a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1wt%; The specific steps of the deoxidation treatment are as follows: aluminum nitride powder is loaded into a vacuum heat treatment container and sealed, then vacuum treatment is performed, then heated to 1200℃ and held for 60min, and then cooled to room temperature; During cooling, the cooling descent rate is controlled at 20℃ / min;

[0037] (2) The aluminum nitride powder treated in step (1) is placed into a graphite mold and then sent into a spark plasma sintering furnace for pre-sintering to obtain an aluminum nitride pre-sintered body; the pre-sintering temperature is controlled at 1650℃, the holding time is 10min, and the pressure inside the spark plasma sintering furnace is controlled at 15MPa.

[0038] (3) Microwave sintering: The aluminum nitride pre-sintered body is sent into a microwave oven for sintering. The microwave source power is controlled at 8kW, the sintering temperature is controlled at 1680℃, the holding time is 2h, the heating rate is 15℃min, and sintering is carried out in a nitrogen atmosphere.

[0039] (4) Slicing, grinding and polishing; grinding includes coarse grinding and fine grinding, wherein the abrasive used for coarse grinding is diamond abrasive and the abrasive used for fine grinding is silicon nitride micro powder abrasive.

[0040] Comparative Example 1

[0041] Referring to Example 1, the preparation method of the aluminum nitride ceramic substrate in this comparative example does not perform deoxygenation treatment on the raw material aluminum nitride powder, and directly performs step (2) discharge plasma sintering on the aluminum nitride raw material. Other technical solutions are the same as in Example 1.

[0042] Comparative Example 2

[0043] Referring to Example 1, the preparation method of the aluminum nitride ceramic substrate in this comparative example does not involve microwave sintering, but extends the discharge plasma sintering time to 1.5 hours. Other technical solutions are the same as in Example 1.

[0044] The substrate performance of Embodiments 1 to 3 of the present invention, as well as Comparative Examples 1 and 2, was tested, and the results are shown in the table below:

[0045] Testing items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 transparency% 75 83 81 43 38 Thermal conductivity (W / (m˙K)) 220 217 213 175 130

[0046] Transparency refers to the light transmittance of a substrate in the 2.5-25μm wavelength range.

[0047] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A method for preparing a high-transmittance aluminum nitride ceramic substrate, characterized in that, The preparation steps include the following: (1) Deoxidation treatment of aluminum nitride powder raw material: aluminum nitride powder with a particle size of 0.1-2μm is fed into a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1wt%; (2) The aluminum nitride powder treated in step (1) is placed into a graphite mold and then sent into a spark plasma sintering furnace for pre-sintering to obtain an aluminum nitride pre-sintered body; the pre-sintering temperature is controlled at 1500-1650℃, the holding time is 5-10min, and the pressure inside the spark plasma sintering furnace is controlled at 8-15MPa. (3) Microwave sintering: The aluminum nitride pre-sintered body is sent into a microwave oven for sintering. The microwave source power is controlled at 2-8kW, the sintering temperature is controlled at 1500-1680℃, the holding time is 1-2h, the heating rate is 10-15℃ / min, and sintering is carried out in a nitrogen atmosphere. (4) Slicing, grinding, and polishing; The specific steps of deoxidation treatment in step (1) are as follows: aluminum nitride powder is placed into a vacuum heat treatment container and sealed, then vacuum treatment is performed, then heated to 900-1200℃, held for 30-60 minutes, and then cooled to room temperature.

2. The method for preparing a high-transmittance aluminum nitride ceramic substrate according to claim 1, characterized in that: During cooling, the cooling rate is controlled at 10-20℃ / min.

3. The method for preparing a high-transmittance aluminum nitride ceramic substrate according to claim 1, characterized in that: The grinding in step (4) includes coarse grinding and fine grinding.

4. The method for preparing a high-transmittance aluminum nitride ceramic substrate according to claim 3, characterized in that: The abrasive used in the coarse grinding is diamond abrasive.

5. The method for preparing a high-transmittance aluminum nitride ceramic substrate according to claim 3, characterized in that: The abrasive used in the fine grinding is silicon nitride micro powder abrasive.