Preparation method of high-light-transmittance aluminum nitride ceramic substrate

Abstract

The invention relates to the technical field of preparation of aluminum nitride ceramic substrates, provides a preparation method of a high-light-transmittance aluminum nitride ceramic substrate, and solves the defects of low light transmittance and low heat conductivity of aluminum nitride in the prior art. Comprising the following steps: (1) deoxidizing an aluminum nitride powder raw material; (2) putting the aluminum nitride powder treated in the step (1) into a graphite mold, and then feeding the graphite mold into a spark plasma sintering furnace for pre-sintering to obtain an aluminum nitride pre-sintered body; the pre-sintering temperature is controlled to be 1500-1650 DEG C, the heat preservation time is 5-10 min, and the pressure in the discharge plasma sintering furnace is controlled to be 8-15 MPa; (3) microwave sintering; and (4) slicing, grinding and polishing.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of aluminum nitride ceramic substrates, and in particular to a preparation method of an aluminum nitride ceramic substrate with high light transmittance. Background Art

[0002] Aluminum nitride ceramics have become ideal electronic packaging materials due to their high thermal conductivity, low dielectric constant, high resistance and non-toxicity, and have received widespread attention and research. High-transmittance aluminum nitride not only has the advantages of aluminum nitride ceramics, but also has high transmittance, and has broad application prospects in the fields of infrared deflectors and window materials. However, since aluminum nitride is a strong covalent bond compound with low sintering activity, pure aluminum nitride does not produce a liquid phase even at high temperatures, so it is difficult to achieve dense sintering. In order to obtain dense aluminum nitride ceramics, some sintering aids are added or the sintering time is extended. However, even with the addition of sintering aids, the light transmittance of the obtained ceramics is still poor.

[0003] Chinese patent application No. 02115663.8 discloses a spark plasma sintering method for preparing transparent aluminum nitride ceramics. The spark plasma sintering method is used to prepare aluminum nitride ceramics. High-purity aluminum nitride powder is directly placed in a graphite mold, and the mold is placed in a spark plasma sintering furnace. An axial pressure of 20-30MPa is applied. A vacuum condition with a vacuum degree better than 6Pa or an N2 atmosphere is used. The sintering is performed at a sintering temperature of 1700-2000°C, and the temperature is increased at a heating rate of 100-800°C / min. After keeping the temperature for 4-20 minutes, the aluminum nitride ceramics are cooled to room temperature with the furnace to prepare transparent aluminum nitride ceramics. The oxygen content in the aluminum nitride powder is 1.0-1.1wt%, the nitrogen content is 33-33.5wt%, and the contents of other impurities are all less than 50ppm. This scheme can shorten the sintering time and consume less energy. The obtained aluminum nitride ceramics have high transparency. The maximum transmittance of the sample in the mid-infrared band (2.5-25μm) is greater than 70%. However, the sintering temperature of this process is high and the sintering speed is fast. Defects such as pores, dislocations, stacking faults, and second phase inclusions will be left in the sintered body, which 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 to solve the defects of low transmittance and low thermal conductivity of aluminum nitride in the prior art.

[0005] To achieve the above object, the present invention adopts 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 0.1-2 μm is sent to a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1 wt%;

[0007] (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° C., the holding time is 5-10 min, and the pressure in the spark plasma sintering furnace is controlled at 8-15 MPa;

[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 2-8 kW, the sintering temperature is controlled at 1500-1680° C., the holding time is 1-2 h, the heating rate is 10-15° C. min, and the sintering is performed in a nitrogen atmosphere;

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

[0010] Furthermore, the specific steps of the deoxidation treatment in step (1) are: the aluminum nitride powder is placed in a vacuum heat treatment container for sealing, followed by vacuum treatment, and then heated to 900-1200° C., maintained for 30-60 minutes, and then cooled to room temperature.

[0011] Furthermore: during cooling, the cooling rate is controlled at 10-20°C / min.

[0012] Furthermore: the grinding in step (4) includes coarse grinding and fine grinding.

[0013] Further: the abrasive used for the rough grinding is diamond abrasive.

[0014] Further: the abrasive used for the fine grinding is silicon nitride micro-powder abrasive.

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

[0016] 1. The present invention combines spark plasma sintering with microwave sintering, and the time required for the preparation process is shorter than that of the traditional high-temperature sintering stage, which saves time costs and has higher economic benefits.

[0017] 2. The raw material aluminum nitride powder used in the present invention has been subjected to a deoxygenation treatment, so that the oxygen content of the aluminum nitride powder raw material is less than 0.1wt%. The oxygen content in the aluminum nitride powder will significantly affect its light transmittance. The deoxygenation treatment can make the final finished product have a higher light transmittance.

[0018] 3. The aluminum nitride powder after deoxidation treatment is placed in a graphite mold and then sent to a spark plasma sintering furnace for pre-sintering. The pre-sintering allows the powder particles to initially combine to form a pre-sintered body with a certain strength. The pre-sintering temperature is controlled at 1500-1650°C. This temperature range is conducive to the sintering of aluminum nitride powder without causing excessive grain growth. The holding time is controlled at 5-10 minutes to allow the powder particles to fully combine. At the same time, the pressure in the spark plasma sintering furnace is controlled at 8-15MPa, which is conducive to the densification of the powder particles during the sintering process.

[0019] 4. The pre-sintered body is subjected to microwave sintering. Microwave sintering has the advantages of fast heating speed, uniform temperature, and short sintering time, which is helpful to obtain aluminum nitride ceramic substrates with high light transmittance. The microwave source power is controlled at 2-8kW to ensure sufficient energy during the sintering process; the sintering temperature is controlled at 1500-1680℃, which is conducive to the densification and grain growth of aluminum nitride ceramics. The heating rate is controlled at 10-15℃ / min to avoid thermal stress problems caused by too fast heating. The entire sintering process is carried out in a nitrogen atmosphere to prevent the ceramic substrate from oxidizing at high temperatures.

[0020] 5. After sintering, the aluminum nitride ceramic substrate is sliced, ground and polished. Slicing can obtain a ceramic substrate of a specific shape and size required by the customer; grinding can remove burrs and uneven surfaces generated during the slicing process; polishing can further improve the surface finish and flatness of the ceramic substrate. These processing steps help to obtain an aluminum nitride ceramic substrate with high light transmittance and good appearance quality. DETAILED DESCRIPTION

[0021] Embodiment 1

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

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

[0024] The specific steps of the deoxidation treatment are: the aluminum nitride powder is placed in a vacuum heat treatment container for sealing, then vacuumized, heated to 900°C, maintained for 30 minutes, and then cooled to room temperature; during cooling, the cooling rate is controlled at 10°C / min;

[0025] (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° C., the holding time is 5 min, and the pressure in the spark plasma sintering furnace is controlled at 8 MPa;

[0026] (3) Microwave sintering: the aluminum nitride pre-sintered body is placed in a microwave oven for sintering, the microwave source power is controlled at 2 kW, the sintering temperature is controlled at 1500° C., the holding time is 1 h, the heating rate is 10° C. min, and the sintering is performed in a nitrogen atmosphere;

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

[0028] Embodiment 2

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

[0030] (1) Deoxidation treatment of aluminum nitride powder raw material: aluminum nitride powder with a particle size of 1 μm is sent to a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1 wt%. The specific process of the deoxidation treatment is as follows: the aluminum nitride powder is placed in a vacuum heat treatment container for sealing treatment, followed by vacuum treatment, and then heated to 1100°C, maintained for 45 minutes, and then cooled to room temperature, with the cooling rate controlled at 15°C / min.

[0031] (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 1600° C., the holding time is 7 min, and the pressure in the spark plasma sintering furnace is controlled at 12 MPa;

[0032] (3) Microwave sintering: the aluminum nitride pre-sintered body is placed in a microwave oven for sintering, the microwave source power is controlled at 5 kW, the sintering temperature is controlled at 1600° C., the holding time is 1.5 h, the heating rate is 12° C. min, and the sintering is performed in a nitrogen atmosphere;

[0033] (4) Slicing, grinding and polishing. The grinding includes 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] Embodiment 3

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

[0036] (1) Deoxidation treatment of aluminum nitride powder raw material: aluminum nitride powder with a particle size of 2 μm is sent to a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1 wt%; the specific steps of the deoxidation treatment are: the aluminum nitride powder is placed in a vacuum heat treatment container for sealing treatment, followed by vacuum treatment, and then heated to 1200°C, maintained for 60 minutes, and then cooled to room temperature; during cooling, the cooling descent rate is controlled at 20°C / min;

[0037] (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 1650° C., the holding time is 10 min, and the pressure in the spark plasma sintering furnace is controlled at 15 MPa;

[0038] (3) Microwave sintering: the aluminum nitride pre-sintered body is placed in a microwave oven for sintering, the microwave source power is controlled at 8 kW, the sintering temperature is controlled at 1680° C., the holding time is 2 h, the heating rate is 15° C. min, and the sintering is performed in a nitrogen atmosphere;

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

[0040] Comparative Example 1

[0041] Referring to Example 1, in the preparation method of the aluminum nitride ceramic substrate of this comparative example, the raw aluminum nitride powder is not subjected to deoxidation treatment, and the aluminum nitride raw material is directly subjected to step (2) spark plasma sintering. Other technical solutions are the same as those of Example 1.

[0042] Comparative Example 2

[0043] With reference to Example 1, the preparation method of the aluminum nitride ceramic substrate of this comparative example does not perform microwave sintering, and at the same time prolongs the spark plasma sintering time to 1.5 hours. Other technical solutions are the same as those of Example 1.

[0044] The performance of the substrates of Examples 1 to 3 and Comparative Examples 1 and 2 of the present invention was tested, and the results are shown in the following table:

[0045] Test items Embodiment 1 Embodiment 2 Embodiment 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 the substrate in the 2.5-25μm band.

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

Claims

1. A method for preparing a high-transmittance aluminum nitride ceramic substrate, characterized in that: The method comprises the following preparation steps: (1) Deoxidation treatment of aluminum nitride powder raw material: aluminum nitride powder with a particle size of 0.1-2 μm is sent to a vacuum heat treatment device for deoxidation treatment to obtain aluminum nitride powder with an oxygen content of less than 0.1 wt%; (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° C., 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: the aluminum nitride pre-sintered body is sent into a microwave oven for sintering, the microwave source power is controlled at 2-8 kW, the sintering temperature is controlled at 1500-1680° C., the holding time is 1-2 h, the heating rate is 10-15° C. min, and the sintering is performed in a nitrogen atmosphere; (4) Slicing, grinding and polishing.

2. The method for preparing a high-transmittance aluminum nitride ceramic substrate according to claim 1, characterized in that: The specific steps of the deoxidation treatment in step (1) are as follows: the aluminum nitride powder is placed in a vacuum heat treatment container for sealing, followed by vacuum treatment, and then heated to 900-1200° C., maintained for 30-60 minutes, and then cooled to room temperature.

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

4. 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.

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

6. The method for preparing a high-transmittance aluminum nitride ceramic substrate according to claim 4, characterized in that: The abrasive used for the fine grinding is silicon nitride micro-powder abrasive.