Glue discharging process of high-thermal-conductivity silicon nitride ceramic green body

Abstract

The invention provides a glue discharging process of a high-thermal-conductivity silicon nitride ceramic green body, which comprises the following steps: carrying out tape casting on silicon nitride raw powder to prepare a silicon nitride ceramic green body, stacking the silicon nitride ceramic green body into a recrystallized silicon carbide jig, putting the silicon nitride ceramic green body into a horizontal graphite furnace, and carrying out segmented glue discharging to obtain the high-thermal-conductivity silicon nitride ceramic green body. By switching the vacuum environment and the negative pressure environment and controlling the flow rate of nitrogen gas, full release and discharge of organic gas are facilitated in the glue discharging process of the silicon nitride ceramic green body, external oxygen elements are prevented from entering the silicon nitride green body to form lattice oxygen, the oxygen content in the green body is effectively controlled to be lower than 1.5%, and the service life of the green body is prolonged. The pre-sintering process at the temperature of 1400-1500 DEG C is adopted, so that the content of residual carbon in a green body after glue removal is reduced, pores in the green body are reduced, the density of the silicon nitride green body is promoted, the strength of the ceramic green body is improved, and the silicon nitride ceramic substrate is more stable in the subsequent processing process.

Description

Technical Field

[0001] The invention relates to the technical field of silicon nitride green body debinding, in particular to a debinding process for a high thermal conductivity silicon nitride ceramic green body. Background Art

[0002] Usually, debinding of silicon nitride green body is done in air atmosphere or nitrogen atmosphere. When debinding in air atmosphere, redox reaction between oxygen and organic matter in the green body will occur during the heating process, forming lattice oxygen, which makes it difficult to improve the thermal conductivity of the silicon nitride ceramic green body. When debinding in nitrogen atmosphere, a large amount of residual carbon will be formed in the ceramic green body after the decomposition of organic matter. In the subsequent sintering process, the excessive residual carbon will participate in the reaction, causing the green body to shrink inconsistently, resulting in deformation, color difference and other problems. Summary of the invention

[0003] The technical problem to be solved by the present invention is: in order to overcome the shortcomings of the prior art that debinding of silicon nitride green bodies in air atmosphere makes it difficult to improve the thermal conductivity of the prepared silicon nitride ceramic green bodies, and debinding of silicon nitride green bodies in nitrogen atmosphere causes inconsistent shrinkage of the green bodies, resulting in deformation, color difference and other problems, the present invention provides a debinding process for high thermal conductivity silicon nitride ceramic green bodies.

[0004] The technical solution to be adopted by the present invention to solve the technical problem is: a debinding process of a high thermal conductivity silicon nitride ceramic body, placing a recrystallized silicon carbide fixture with a silicon nitride ceramic body in a horizontal graphite furnace for debinding, and the specific steps are as follows:

[0005] (a) In a high vacuum environment with a pressure of 1 to 3 Pa in a graphite furnace, the graphite furnace is heated from room temperature to 190°C at a heating rate of 0.5 to 2°C / min;

[0006] (b) Under a graphite furnace pressure of 1k-2kPa and a nitrogen flow rate of 50-100L / min, the graphite furnace is heated from 190°C to 380°C at a heating rate of 0.1-0.3°C / min and kept at this temperature for 5-6 hours;

[0007] (c) Under a graphite furnace pressure of 1 kPa to 2 kPa and in an atmosphere of nitrogen flow rate of 100 to 150 L / min, the graphite furnace is heated from 380°C to 550 to 600°C at a heating rate of 0.2 to 0.4°C / min and kept at this temperature for 4 to 6 hours;

[0008] (d) Under a graphite furnace pressure of 50k-55kPa and a nitrogen flow rate of 150-200L / min, the graphite furnace is heated from 600°C to 1400-1500°C at a heating rate of 1-3°C / min and kept at this temperature for 4-6 hours;

[0009] (e) Under a graphite furnace pressure of 50k-55kPa and a nitrogen flow rate of 150-200L / min, the temperature is lowered to 30-40°C for 18 to 20 hours.

[0010] Furthermore, the silicon nitride ceramic embryo is made by tape casting silicon nitride raw powder, and a layer of boron nitride powder is applied on the surface of the silicon nitride ceramic embryo.

[0011] Furthermore, the silicon nitride ceramic body tape casting molding includes the following steps: based on the total mass of the slurry, preparing 2-5wt% sintering aid, 35-60wt% silicon nitride, 7-15wt% binder, 0.5-4wt% dispersant, 2-7w% plasticizer, and 30-45wt% ethanol solvent raw materials, mixing them in a ball mill and defoaming them in a vacuum defoaming machine, tape casting, drying, rolling and vacuum hot pressing to obtain a silicon nitride ceramic body.

[0012] Furthermore, the sintering aid is at least one oxide, and the oxide is at least one of ZrO2, MgO, Yb2O3, Y2O3, and Gd2O3.

[0013] Furthermore, the binder is polyvinyl butyral.

[0014] Furthermore, the dispersant is pentaerythritol tetraisostearate.

[0015] Furthermore, the plasticizer is dibutyl phthalate.

[0016] The beneficial effects of the present invention are:

[0017] 1. Since the solid solution reaction of oxygen atoms in the lattice will generate silicon vacancies and cause lattice distortion, it will cause phonon scattering, thereby reducing thermal conductivity. The present invention facilitates the full release and discharge of organic gas during the debinding process of silicon nitride ceramic green body by switching between vacuum environment and negative pressure environment and controlling the nitrogen gas flow rate, and isolates external oxygen elements from entering the silicon nitride green body to form lattice oxygen. The oxygen content in the green body is effectively controlled to be less than 1.5%, so that a high thermal conductivity silicon nitride ceramic substrate can be prepared.

[0018] 2. The present invention reduces the residual carbon content in the green body after debinding and reduces the pores in the green body through a pre-sintering process at 1400°C-1500°C, thereby promoting the density of the silicon nitride green body and improving the strength of the ceramic body, making it more stable in subsequent processing.

[0019] 3. Use a recrystallized silicon carbide debinding fixture, which has both high porosity and high mechanical strength, high temperature stability, and can withstand an operating temperature of 1600°C. It can ensure the flatness and cleanliness of the green body during debinding and pre-sintering, avoid the introduction of impurities, and is conducive to large-scale mass production. DETAILED DESCRIPTION

[0021] A debinding process for a high thermal conductivity silicon nitride ceramic body of the present invention comprises placing a recrystallized silicon carbide jig with a silicon nitride ceramic body in a horizontal graphite furnace for debinding, and the specific steps are as follows:

[0022] (a) In a high vacuum environment with a pressure of 1 to 3 Pa in a graphite furnace, the graphite furnace is heated from room temperature to 190°C at a heating rate of 0.5 to 2°C / min;

[0023] (b) Under a graphite furnace pressure of 1k-2kPa and a nitrogen flow rate of 50-100L / min, the graphite furnace is heated from 190°C to 380°C at a heating rate of 0.1-0.3°C / min and kept at this temperature for 5-6 hours;

[0024] (c) Under a graphite furnace pressure of 1 kPa to 2 kPa and in an atmosphere of nitrogen flow rate of 100 to 150 L / min, the graphite furnace is heated from 380°C to 550 to 600°C at a heating rate of 0.2 to 0.4°C / min and kept at this temperature for 4 to 6 hours;

[0025] (d) Under a graphite furnace pressure of 50k-55kPa and a nitrogen flow rate of 150-200L / min, the graphite furnace is heated from 600°C to 1400-1500°C at a heating rate of 1-3°C / min and kept at this temperature for 4-6 hours;

[0026] (e) Under a graphite furnace pressure of 50k-55kPa and a nitrogen flow rate of 150-200L / min, the temperature is lowered to 30-40°C for 18 to 20 hours.

[0027] The silicon nitride ceramic embryo is made of silicon nitride raw powder through tape casting, and a layer of boron nitride powder is applied on the surface of the silicon nitride ceramic embryo.

[0028] The silicon nitride ceramic body tape casting molding includes the following steps: based on the total mass of the slurry, preparing raw materials of 3wt% Y203, 42wt% silicon nitride, 11wt% polyvinyl butyral, 2.5wt% pentaerythritol tetraisostearate, 4.5w% dibutyl phthalate, and 37wt% ethanol solvent; mixing them in a ball mill, defoaming them with a vacuum defoaming machine, tape casting them, drying, rolling them up, and vacuum hot pressing them to obtain a silicon nitride ceramic body.

[0029] Working process:

[0030] The raw materials of rare earth oxide, silicon nitride, polyvinyl butyral, pentaerythritol tetraisostearate, dibutyl phthalate and ethanol solvent are ball-milled and mixed in a nitrogen protective atmosphere according to a proportion, and then defoamed by a vacuum defoamer, cast, dried, rolled and vacuum hot-pressed to obtain a silicon nitride ceramic body, and a layer of boron nitride powder is applied on the surface of the silicon nitride ceramic body.

[0031] Place the silicon nitride ceramic body into a recrystallized silicon carbide fixture, and then place the recrystallized silicon carbide fixture into a horizontal graphite furnace. The silicon nitride ceramic body is debinded in sections in the horizontal graphite furnace. The specific steps are as follows:

[0032] (a) In a high vacuum environment with a pressure of 1 Pa in a graphite furnace, the graphite furnace is heated from room temperature to 190 °C at a heating rate of 0.5 °C / min;

[0033] (b) Under a graphite furnace pressure of 1 kPa and a nitrogen flow rate of 50 L / min, the graphite furnace is heated from 190°C to 380°C at a heating rate of 0.1°C / min and kept at this temperature for 5-6 hours;

[0034] (c) under a graphite furnace pressure of 1 kPa and an atmosphere of nitrogen flow rate of 100 L / min, the graphite furnace is heated from 380°C to 550°C at a heating rate of 0.2°C / min and kept at this temperature for 4 to 6 hours;

[0035] (d) Under a graphite furnace pressure of 50 kPa and a nitrogen flow rate of 150 L / min, the graphite furnace is heated from 600°C to 1400°C at a heating rate of 1°C / min and kept at this temperature for 4-6 hours;

[0036] (e) Under a graphite furnace pressure of 50 kPa and a nitrogen flow rate of 150 L / min, the temperature is lowered to 30-40° C. for 18 to 20 hours.

[0037] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the scope of the present invention through the above description. The technical scope of this invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A debinding process for a high thermal conductivity silicon nitride ceramic body, characterized in that: The recrystallized silicon carbide fixture with the silicon nitride ceramic body is placed in a horizontal graphite furnace for debinding. The specific steps are as follows: (a) In a high vacuum environment with a pressure of 1 to 3 Pa in a graphite furnace, the graphite furnace is heated from room temperature to 190°C at a heating rate of 0.5 to 2°C / min; (b) Under a graphite furnace pressure of 1k-2kPa and a nitrogen flow rate of 50-100L / min, the graphite furnace is heated from 190°C to 380°C at a heating rate of 0.1-0.3°C / min and kept at this temperature for 5-6 hours; (c) Under a graphite furnace pressure of 1 kPa to 2 kPa and in an atmosphere of nitrogen flow rate of 100 to 150 L / min, the graphite furnace is heated from 380°C to 550 to 600°C at a heating rate of 0.2 to 0.4°C / min and kept at this temperature for 4 to 6 hours; (d) Under a graphite furnace pressure of 50k-55kPa and a nitrogen flow rate of 150-200L / min, the graphite furnace is heated from 600°C to 1400-1500°C at a heating rate of 1-3°C / min and kept at this temperature for 4-6 hours; (e) Under a graphite furnace pressure of 50k-55kPa and a nitrogen flow rate of 150-200L / min, the temperature is lowered to 30-40°C for 18 to 20 hours.

2. A binder removal process for a high thermal conductivity silicon nitride ceramic body as claimed in claim 1, characterized in that: The silicon nitride ceramic embryo is made of silicon nitride raw powder through tape casting, and a layer of boron nitride powder is applied on the surface of the silicon nitride ceramic embryo.

3. A binder removal process for a high thermal conductivity silicon nitride ceramic body as claimed in claim 1, characterized in that: The silicon nitride ceramic blank tape casting molding comprises the following steps: based on the total mass of the slurry, preparing raw materials of 2-5wt% sintering aid, 35-60wt% silicon nitride, 7-15wt% binder, 0.5-4wt% dispersant, 2-7w% plasticizer, and 30-45wt% ethanol solvent, mixing in a ball mill, defoaming in a vacuum defoaming machine, tape casting, drying, rolling, and vacuum hot pressing to obtain a silicon nitride ceramic blank.

4. A binder removal process for a high thermal conductivity silicon nitride ceramic body as claimed in claim 3, characterized in that: The sintering aid is at least one oxide, and the oxide is at least one of ZrO2, MgO, Yb2O3, Y2O3, and Gd2O3.

5. A binder removal process for a high thermal conductivity silicon nitride ceramic body as claimed in claim 3, characterized in that: The binder is polyvinyl butyral.

6. A binder removal process for a high thermal conductivity silicon nitride ceramic body as claimed in claim 3, characterized in that: The dispersant is pentaerythritol tetraisostearate.

7. A binder removal process for a high thermal conductivity silicon nitride ceramic body as claimed in claim 3, characterized in that: The plasticizer is dibutyl phthalate.