Preparation method of high-performance silicon nitride ceramic substrate

Abstract

The application provides a preparation method of a high-performance silicon nitride ceramic substrate and relates to the field of production and preparation of silicon nitride ceramic substrates, and comprises the following raw materials in parts by weight: 40-130 parts of silicon nitride powder, 20-110 parts of an organic solvent, 3-15 parts of a sintering aid, 5-15 parts of a binder, 2-6 parts of a plasticizer and 1-6 parts of a dispersing agent. The application adopts a flow casting method, and prepares the silicon nitride ceramic substrate through glue removal and pressure sintering. In the application, the silane coupling agent, the silicon powder, the beta-phase silicon nitride powder and the silicon carbide whisker and the like can significantly improve the strength and the thermal conductivity of the silicon nitride ceramic substrate.

Description

Technical Field

[0001] This invention relates to the field of silicon nitride ceramic substrate production, and more particularly to a method for preparing a high-performance silicon nitride ceramic substrate. Background Technology

[0002] Silicon nitride, as a novel ceramic material, possesses high thermal conductivity, high strength, high temperature resistance, and a low coefficient of thermal expansion. These properties offer broad application prospects in high-end, high-power electrical and electronic devices, particularly in fields such as new energy vehicles, high-speed rail, aerospace, wind power generation, and LED lighting. Thermal conduction in silicon nitride ceramic substrates is achieved through the transfer of heat via phonons oscillating between silicon nitride grains. Factors affecting thermal conduction include lattice oxygen, grain size, and defects, with lattice oxygen content being the primary factor; higher oxygen content results in poorer thermal conductivity. Furthermore, silicon nitride ceramic substrates play a crucial role in the load-bearing and connecting functions of electronic components, requiring high strength and toughness. However, currently produced silicon nitride ceramic substrates exhibit relatively low thermal conductivity and strength, failing to meet the demands of the high-power power electronics market. Therefore, improving the thermal conductivity and strength of silicon nitride substrates is a pressing issue that needs to be addressed in their fabrication. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a high-performance silicon nitride ceramic substrate, so as to solve the current technical problems of poor thermal conductivity and strength of silicon nitride ceramic substrates.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A high-performance silicon nitride ceramic substrate, comprising the following raw materials in parts by weight:

[0006] 40-130 parts silicon nitride powder, 20-110 parts organic solvent, 3-15 parts sintering aid, 5-15 parts binder, 2-6 parts plasticizer, and 1-6 parts dispersant.

[0007] Preferably, the organic solvent is one or more of ethanol, propyl acetate, cyclohexanone, and silane coupling agents.

[0008] Preferably, the sintering aid is one or more of yttrium oxide powder, magnesium silicon nitride powder, silicon powder, β-phase silicon nitride seed crystals, and silicon carbide whiskers.

[0009] Preferably, the binder is polyvinyl butyral, the plasticizer is polyethylene glycol, and the dispersant is polyisobutylene succinimide.

[0010] A method for preparing a high-performance silicon nitride ceramic substrate includes the following preparation steps:

[0011] 1) Adhesive preparation: Take 5-15 parts of adhesive, 20-60 parts of organic solvent, and 2-6 parts of plasticizer, mix them in a container and stir evenly;

[0012] 2) Slurry preparation: Take 10-50 parts of organic solvent, 3-15 parts of sintering aid, and 1-6 parts of dispersant, and add them to a ball mill jar for ball milling at 90 r / min for 0.5-1 h. Then take 40-130 parts of silicon nitride powder and add them to the ball mill jar for ball milling for 3-5 h. Then add the adhesive from step 1) to the ball mill jar and ball mill for 12-20 h. Degas the ball-milled slurry under a vacuum of -0.1 MPa, a rotation speed of 1500 r / min, and a temperature of 60-80℃ to obtain a silicon nitride casting slurry with a viscosity of approximately 10000 pcs.

[0013] 3) Blank making: Pour the prepared slurry into the casting machine box for casting and forming, where the flow rate is 0.25m / min, the temperature range of the five drying zones is between 35℃ and 70℃, and after drying, cut the green blanks to the required size.

[0014] 4) Degreasing: The cut green pieces are coated with powder and stacked, and placed on a firing plate for degreasing at a temperature of 550℃-600℃ for 20-25 hours.

[0015] 5) Sintering: The degreased silicon nitride wafer is placed in a sintering furnace and heated to 1400℃ at a heating rate of 10℃ / min, then heated to 1850℃-1900℃ at a heating rate of 5℃ / min and held for 3-6 hours. Then it is cooled to 1400℃ at a cooling rate of 1℃ / min and then cooled to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

[0016] The beneficial effects of this invention are:

[0017] 1. This invention uses a silane coupling agent to improve the toughness of silicon nitride ceramic substrates. The molecular structure of the silane coupling agent contains organic functional groups and silane oxygen groups. The silane oxygen groups in the molecule react with the hydroxyl groups on the surface of inorganic materials to form chemical bonds. At the same time, its organic functional groups can be compatible with materials such as organic resins, thereby forming a bridge between two materials with different properties and enhancing their bonding strength. The introduction of the silane coupling agent improves the toughness of the green body, improves the problem of uneven surface of the green body, solves the phenomenon of cracking of the green body during glue removal, and thus also improves the strength and toughness of the silicon nitride ceramic substrate after sintering.

[0018] 2. This invention uses silicon powder to improve the thermal conductivity and strength of silicon nitride ceramic substrates. The silicon powder can undergo a silicothermic reduction reaction with the silicon dioxide on the surface of the silicon nitride powder, removing oxygen in the form of silicon monoxide gas. This effectively reduces the oxygen content in the liquid phase, forming an "oxygen-deficient-nitrogen-rich" liquid phase, which helps to hinder the formation of lattice oxygen, thereby improving the thermal conductivity of the silicon nitride ceramic substrate. In addition, the high liquid phase viscosity caused by the "oxygen-deficient-nitrogen-rich" state has a greater restriction on densification, making the phase transformation rate faster than the densification rate. β-phase silicon nitride grains preferentially nucleate and develop in the low-density green body, and the steric hindrance encountered during grain growth is low. Ultimately, a bimodal morphology is formed in which coarse β-phase silicon nitride grains are distributed in the β-phase silicon nitride small grain matrix, further improving the strength and toughness of the silicon nitride ceramic substrate.

[0019] 3. This invention utilizes β-phase silicon nitride powder to enhance the thermal conductivity and toughness of silicon nitride ceramic substrates. The β-phase silicon nitride powder has a specific aspect ratio, altering the ratio of α and β-phase silicon nitride in the original material. During sintering, the pre-existing β-phase silicon nitride develops faster than the β-phase silicon nitride generated by phase transformation, ultimately forming abnormally large, high aspect ratio β-phase silicon nitride grains, thereby improving the thermal conductivity of the silicon nitride ceramic substrate. Furthermore, the grown, high aspect ratio β-phase silicon nitride grains also exhibit a self-toughening effect through crack deflection and bridging mechanisms, improving the fracture toughness of the silicon nitride ceramic substrate.

[0020] 4. This invention utilizes silicon carbide whiskers to enhance the toughness of silicon nitride ceramic substrates. Silicon carbide whiskers are high-strength, high-modulus single-crystal fibers with excellent high-temperature resistance, corrosion resistance, and electrical insulation properties. During crystallization, the atomic structure of silicon nitride whiskers is highly ordered, with almost no defects that could weaken the crystal. Through the combined effects of pull-out bridging and crack redirection mechanisms, the silicon nitride ceramic substrate can better resist external stress, thereby improving its toughness. Detailed Implementation

[0021] To facilitate understanding of the present invention, a more complete description is provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0023] Example 1

[0024] This embodiment proposes a method for preparing a high-performance silicon nitride ceramic substrate, the steps of which are as follows:

[0025] Step 1: Take 13 parts of polyvinyl butyral, 24 parts of ethanol, 24 parts of propyl acetate, 4 parts of cyclohexanone, 2 parts of silane coupling agent, and 2 parts of polyethylene glycol according to a certain ratio, mix them in a container and stir for 6 hours to obtain the desired organic adhesive.

[0026] Step 2: Take 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of magnesium silicon nitride powder, 0.5 parts of silicon powder, 0.5 parts of silicon carbide whiskers, 1 part of β-phase silicon nitride seed crystals, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone according to a certain ratio and add them to a ball mill jar for ball milling for 0.5-1 hours. Then take 91 parts of silicon nitride and add them to the ball mill jar for ball milling for 3-5 hours. Then add the organic adhesive prepared in Step 1 to the ball mill jar and ball mill for 12-20 hours. Degas the ball-milled slurry under a vacuum of -0.1 MPa, a rotation speed of 1500 r / min, and a temperature of 80℃ to obtain a silicon nitride casting slurry with a viscosity of about 10000 pcs.

[0027] Step 3: Pour the prepared slurry into the casting machine box for casting and molding. The flow rate is 0.25 m / min. The temperatures of the five drying zones are set to 38℃, 43℃, 48℃, 55℃ and 65℃ respectively. After drying, cut the green body to the required size.

[0028] Step 4: Apply powder and stack the cut green pieces, place them on a firing plate, and degrease them at 580℃ for 20-25 hours;

[0029] Step 5: Place the degreased silicon nitride wafer into a sintering furnace and heat it to 1400℃ at a heating rate of 10℃ / min. Then heat it to 1870℃ at a heating rate of 5℃ / min and hold it for 3-6 hours. Then cool it down to 1400℃ at a cooling rate of 1℃ / min and then cool it to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

[0030] Example 2

[0031] This embodiment proposes a method for preparing a high-performance silicon nitride ceramic substrate, the steps of which are as follows:

[0032] Step 1: Take 13 parts of polyvinyl butyral, 24 parts of ethanol, 24 parts of propyl acetate, 4 parts of cyclohexanone, 2 parts of silane coupling agent, and 2 parts of polyethylene glycol according to a certain ratio, mix them in a container and stir for 6 hours to obtain the desired organic adhesive.

[0033] Step 2: Take 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of magnesium silicon nitride powder, 0.5 parts of silicon powder, 0.5 parts of silicon carbide whiskers, 1.5 parts of β-phase silicon nitride seed crystals, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone according to a certain ratio and add them to a ball mill jar for ball milling for 0.5-1 hours. Then take 90 parts of silicon nitride and add them to the ball mill jar for ball milling for 3-5 hours. Then add the organic adhesive prepared in Step 1 to the ball mill jar and ball mill for 12-20 hours. Degas the ball-milled slurry under a vacuum of -0.1 MPa, a rotation speed of 1500 r / min, and a temperature of 80℃ to obtain a silicon nitride casting slurry with a viscosity of approximately 10000 pcs.

[0034] Step 3: Pour the prepared slurry into the casting machine box for casting and molding. The flow rate is 0.25 m / min. The temperatures of the five drying zones are set to 38℃, 43℃, 48℃, 55℃ and 65℃ respectively. After drying, cut the green body to the required size.

[0035] Step 4: Apply powder and stack the cut green pieces, place them on a firing plate, and degrease them at 580℃ for 20-25 hours;

[0036] Step 5: Place the degreased silicon nitride wafer into a sintering furnace and heat it to 1400℃ at a heating rate of 10℃ / min. Then heat it to 1860℃ at a heating rate of 5℃ / min and hold it for 3-6 hours. Then cool it down to 1400℃ at a cooling rate of 1℃ / min and then cool it to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

[0037] Example 3

[0038] This embodiment proposes a method for preparing a high-performance silicon nitride ceramic substrate, the steps of which are as follows:

[0039] Step 1: Take 13 parts of polyvinyl butyral, 24 parts of ethanol, 24 parts of propyl acetate, 4 parts of cyclohexanone, 2 parts of silane coupling agent, and 2 parts of polyethylene glycol according to a certain ratio, mix them in a container and stir for 6 hours to obtain the desired organic adhesive.

[0040] Step 2: Take 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of magnesium silicon nitride powder, 0.5 parts of silicon powder, 1 part of silicon carbide whiskers, 1.5 parts of β-phase silicon nitride seed crystals, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone according to a certain ratio and add them to a ball mill jar for ball milling for 0.5-1 hours. Then take 89 parts of silicon nitride and add them to the ball mill jar for ball milling for 3-5 hours. Then add the organic adhesive prepared in Step 1 to the ball mill jar and ball mill for 12-20 hours. Degas the ball-milled slurry under a vacuum of -0.1 MPa, a rotation speed of 1500 r / min, and a temperature of 80℃ to obtain a silicon nitride casting slurry with a viscosity of about 10000 pcs.

[0041] Step 3: Pour the prepared slurry into the casting machine box for casting and molding. The flow rate is 0.25 m / min. The temperatures of the five drying zones are set to 38℃, 43℃, 48℃, 55℃ and 65℃ respectively. After drying, cut the green body to the required size.

[0042] Step 4: Apply powder and stack the cut green pieces, place them on a firing plate, and degrease them at 580℃ for 20-25 hours;

[0043] Step 5: Place the degreased silicon nitride wafer into a sintering furnace and heat it to 1400℃ at a heating rate of 10℃ / min. Then heat it to 1850℃ at a heating rate of 5℃ / min and hold it for 3-6 hours. Then cool it down to 1400℃ at a cooling rate of 1℃ / min and then cool it to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

[0044] Example 4

[0045] This embodiment presents a method for preparing a high-performance silicon nitride ceramic substrate. This embodiment is the first comparative example of Example 1, and its preparation steps are as follows:

[0046] Step 1: Take 13 parts of polyvinyl butyral, 24 parts of ethanol, 24 parts of propyl acetate, 4 parts of cyclohexanone, 2 parts of silane coupling agent, and 2 parts of polyethylene glycol according to a certain ratio, mix them in a container and stir for 6 hours to obtain the desired organic adhesive.

[0047] Step 2: Take 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of magnesium silicon nitride powder, 0.5 parts of silicon powder, 0.5 parts of silicon carbide whiskers, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone according to a certain ratio and add them to a ball mill jar for ball milling for 0.5-1 hours. Then take 91 parts of silicon nitride and add them to the ball mill jar for ball milling for 3-5 hours. Then add the organic adhesive prepared in Step 1 to the ball mill jar and ball mill for 12-20 hours. Degas the ball-milled slurry under a vacuum of -0.1 MPa, a rotation speed of 1500 r / min, and a temperature of 80℃ to obtain a silicon nitride casting slurry with a viscosity of approximately 10000 pcs.

[0048] Step 3: Pour the prepared slurry into the casting machine box for casting and molding. The flow rate is 0.25 m / min. The temperatures of the five drying zones are set to 38℃, 43℃, 48℃, 55℃ and 65℃ respectively. After drying, cut the green body to the required size.

[0049] Step 4: Apply powder and stack the cut green pieces, place them on a firing plate, and degrease them at 580℃ for 20-25 hours;

[0050] Step 5: Place the degreased silicon nitride wafer into a sintering furnace and heat it to 1400℃ at a heating rate of 10℃ / min. Then heat it to 1870℃ at a heating rate of 5℃ / min and hold it for 3-6 hours. Then cool it down to 1400℃ at a cooling rate of 1℃ / min and then cool it to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

[0051] Example 5

[0052] This embodiment presents a method for preparing a high-performance silicon nitride ceramic substrate. This embodiment is the second comparative example of Example 1, and the steps are as follows:

[0053] Step 1: Take 13 parts of polyvinyl butyral, 24 parts of ethanol, 24 parts of propyl acetate, 4 parts of cyclohexanone, 2 parts of silane coupling agent, and 2 parts of polyethylene glycol according to a certain ratio, mix them in a container and stir for 6 hours to obtain the desired organic adhesive.

[0054] Step 2: Take 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of magnesium silicon nitride powder, 0.5 parts of silicon carbide whiskers, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone according to a certain ratio and add them to a ball mill jar for ball milling for 0.5-1 hours. Then take 92 parts of silicon nitride and add them to the ball mill jar for ball milling for 3-5 hours. Then add the organic adhesive prepared in Step 1 to the ball mill jar and ball mill for 12-20 hours. Degas the ball-milled slurry under a vacuum of -0.1 MPa, a rotation speed of 1500 r / min, and a temperature of 80℃ to obtain a silicon nitride casting slurry with a viscosity of approximately 10000 pcs.

[0055] Step 3: Pour the prepared slurry into the casting machine box for casting and molding. The flow rate is 0.25 m / min. The temperatures of the five drying zones are set to 38℃, 43℃, 48℃, 55℃ and 65℃ respectively. After drying, cut the green body to the required size.

[0056] Step 4: Apply powder and stack the cut green pieces, place them on a firing plate, and degrease them at 580℃ for 20-25 hours;

[0057] Step 5: Place the degreased silicon nitride wafer into a sintering furnace and heat it to 1400℃ at a heating rate of 10℃ / min. Then heat it to 1870℃ at a heating rate of 5℃ / min and hold it for 3-6 hours. Then cool it down to 1400℃ at a cooling rate of 1℃ / min and then cool it to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

[0058] The properties of the silicon nitride ceramic substrates prepared in Examples 1 to 5 are shown in Table 1. High-performance silicon nitride substrates require a thermal conductivity ≥90 W / m·K and a fracture toughness ≥7.0 MPa·m. 1 / 2 Flexural strength ≥ 800 MPa.

[0059]

[0060] Table 1

[0061] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a high-performance silicon nitride ceramic substrate, characterized in that, The preparation steps include the following: 1) Adhesive preparation: Take 13 parts polyvinyl butyral, 24 parts ethanol, 24 parts propyl acetate, 4 parts cyclohexanone, 2 parts silane coupling agent, and 2 parts polyethylene glycol according to the mass ratio and stir in a container for 6 hours to obtain the desired organic adhesive. 2) Slurry preparation: Take 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of magnesium silicon nitride powder, 0.5 parts of silicon powder, 0.5 parts of silicon carbide whiskers, 1 part of β-phase silicon nitride seed crystals, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone and add them to a ball mill jar and ball mill for 0.5-1 h. Then take 91 parts of silicon nitride and add them to the ball mill jar and ball mill for 3-5 h. Then add the organic adhesive prepared in step 1) to the ball mill jar and ball mill for 12-20 h. Degas the ball-milled slurry under a vacuum of -0.1 MPa, a rotation speed of 1500 r / min, and a temperature of 80℃ to obtain a silicon nitride casting slurry with a viscosity of 10000 cps. 3) Blank making: Pour the prepared slurry into the casting machine box for casting and forming, where the flow rate is 0.25m / min, and the temperatures of the five drying zones are set at 38℃, 43℃, 48℃, 55℃ and 65℃ respectively. After drying, cut the green blanks to the required size. 4) Degreasing: The cut green pieces are coated with powder and stacked, and then placed on a firing plate for degreasing at 580℃ for 20-25 hours; 5) Sintering: The degreased silicon nitride wafer is placed in a sintering furnace and heated to 1400°C at a heating rate of 10°C / min. Then it is heated to 1870°C at a heating rate of 5°C / min and held for 3-6 hours. Then it is cooled to 1400°C at a cooling rate of 1°C / min and then cooled to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

2. A high-performance silicon nitride ceramic substrate prepared by the preparation method described in claim 1.

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