Preparation method of high-performance silicon nitride ceramic substrate

Abstract

The invention 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 the high-performance silicon nitride ceramic substrate comprises the following raw materials 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 dispersant. A tape casting method is adopted, the silicon nitride ceramic substrate is prepared through glue discharging and air pressure sintering, and the silane coupling agent, the silicon powder, the beta-phase silicon nitride powder, the silicon carbide whiskers and other ingredients can remarkably improve the strength and the thermal conductivity of the silicon nitride ceramic substrate.

Description

Technical Field

[0001] The invention relates to the field of production and preparation of silicon nitride ceramic substrates, and in particular to a method for preparing a high-performance silicon nitride ceramic substrate. Background Art

[0002] As a new type of ceramic material, silicon nitride has the characteristics of high thermal conductivity, high strength, high temperature resistance and small thermal expansion coefficient. These characteristics have broad application prospects in high-end high-power power and electronic devices, especially in the fields of new energy vehicles, high-speed rail, aerospace, wind power generation, LED lighting, etc. The thermal conduction of silicon nitride ceramic substrates is completed by the transmission of thermal oscillations between silicon nitride grains through phonons, and the factors affecting its thermal conduction include lattice oxygen, grain size and defects. The main factor is the lattice oxygen in the silicon nitride ceramic substrate. The higher the oxygen content, the worse the thermal conductivity. In addition, silicon nitride ceramic substrates play a role of bearing and connection in electronic components, and there are also high requirements for their strength and toughness. However, the thermal conductivity and strength of the currently produced silicon nitride ceramic substrates are relatively low, which can no longer meet the needs of the high-power power electronics market. Therefore, how to improve the thermal conductivity and strength of silicon nitride substrates is an urgent problem to be solved in the current preparation of silicon nitride ceramic substrates. Summary of the invention

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

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

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

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

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

[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 comprises the following preparation steps:

[0011] 1) Glue 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: 10-50 parts of organic solvent, 3-15 parts of sintering aid, and 1-6 parts of dispersant are added to a ball mill in sequence, the speed of the ball mill is 90r / min, and the ball milling is performed for 0.5-1h. Then 40-130 parts of silicon nitride powder are added to the ball mill for 3-5h. Then, the glue in step 1) is added to the ball mill for 12-20h. The ball-milled slurry is degassed under a vacuum degree of -0.1MPA, a speed of 1500r / min, and a temperature of 60-80°C to obtain a silicon nitride tape casting slurry with a viscosity of about 10,000 pcs.

[0013] 3) Blank making: Pour the prepared slurry into the material box of the tape casting machine for tape casting, wherein the flow rate is 0.25m / min, the temperature range of the five drying zones is between 35°C and 70°C, and the green blanks of the required size are cut after drying;

[0014] 4) Degreasing: The cut green pieces are powdered and stacked, and then placed on a firing plate for degreasing at 550°C-600°C for 20-25 hours;

[0015] 5) Sintering: Place the degreased silicon nitride wafer into a sintering furnace, heat it to 1400°C at a heating rate of 10°C / min, heat it to 1850°C-1900°C at a heating rate of 5°C / min and keep it at that temperature for 3-6h, then cool it to 1400°C at a cooling rate of 1°C / min, and then cool it to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

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

[0017] 1. The present invention adopts a silane coupling agent to improve the toughness of the silicon nitride ceramic substrate. The molecular structure of the silane coupling agent contains an organic functional group and a silaneoxy group. The silaneoxy group in the molecule reacts with the hydroxyl group on the surface of the inorganic material to form a chemical bond. At the same time, its organic functional group can be compatible with materials such as organic resins, thereby forming a bridge between two materials of 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 green body surface, solves the phenomenon of green body cracking during debinding, and further improves the strength and toughness of the sintered silicon nitride ceramic substrate.

[0018] 2. The present invention uses silicon powder to improve the thermal conductivity and strength of the silicon nitride ceramic substrate. The silicon powder can undergo a silicon thermal reduction reaction with the silicon dioxide on the surface of the silicon nitride powder to remove oxygen in the form of silicon monoxide gas, effectively reducing the oxygen content in the liquid phase and forming an "oxygen-deficient-nitrogen-rich" liquid phase, which is beneficial 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 "oxygen-deficient-nitrogen-rich" has a greater restriction on densification, making the phase transformation rate faster than the densification rate. The β-phase silicon nitride grains preferentially nucleate and develop in the low-density green body, and the steric hindrance encountered during grain growth is relatively low, ultimately forming a bimodal morphology 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. The present invention uses β-phase silicon nitride powder to improve the thermal conductivity and toughness of silicon nitride ceramic substrates. The β-phase silicon nitride powder has a certain aspect ratio, which changes the ratio of α-phase and β-phase silicon nitride in the original material. The pre-existing β-phase silicon nitride in the sintering process develops faster than the β-phase silicon nitride produced by the phase change, and finally forms abnormally grown β-phase silicon nitride grains with a high aspect ratio, thereby improving the thermal conductivity of the silicon nitride ceramic substrate. In addition, the grown β-phase silicon nitride grains with a high aspect ratio also have a self-toughening effect through crack deflection, bridging and other mechanisms, thereby improving the fracture toughness of the silicon nitride ceramic substrate.

[0020] 4. The present invention uses silicon carbide whiskers to improve the toughness of silicon nitride ceramic substrates. Silicon carbide whiskers are a type of high-strength, high-modulus single-crystal fiber with excellent high-temperature resistance, corrosion resistance and electrical insulation properties. The atomic structure of silicon nitride whiskers is highly ordered during crystallization, and there are almost no defects that can weaken the crystal. Through the combined action of the pull-out bridging and crack deflection mechanisms, the silicon nitride ceramic substrate can better resist external stress when subjected to force, thereby improving its toughness. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention is described more fully below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0023] Example 1

[0024] In this embodiment, a method for preparing a high-performance silicon nitride ceramic substrate is proposed, and the steps are as follows:

[0025] Step 1: according to a certain ratio, 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 were mixed in a container and stirred for 6 hours to obtain the desired organic glue;

[0026] Step 2: According to a certain ratio, 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of silicon nitride magnesium powder, 0.5 parts of silicon powder, 0.5 parts of silicon carbide whisker, 1 part of β-phase silicon nitride seed, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone are added to a ball mill for ball milling for 0.5-1h, and then 91 parts of silicon nitride are added to the ball mill for ball milling for 3-5h, and then the organic glue prepared in step 1 is added to the ball mill for ball milling for 12-20h. The ball-milled slurry is degassed under a vacuum degree of -0.1MPA, a rotation speed of 1500r / min, and a temperature of 80°C to obtain a silicon nitride tape casting slurry with a viscosity of about 10000pcs;

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

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

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

[0030] Example 2

[0031] In this embodiment, a method for preparing a high-performance silicon nitride ceramic substrate is proposed, and the steps are as follows:

[0032] Step 1: according to a certain ratio, 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 were mixed in a container and stirred for 6 hours to obtain the desired organic glue;

[0033] Step 2: According to a certain ratio, 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of silicon nitride magnesium powder, 0.5 parts of silicon powder, 0.5 parts of silicon carbide whiskers, 1.5 parts of β-phase silicon nitride seeds, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone are added to a ball mill for ball milling for 0.5-1h, and then 90 parts of silicon nitride are added to the ball mill for ball milling for 3-5h, and then the organic glue prepared in step 1 is added to the ball mill for ball milling for 12-20h. The ball-milled slurry is degassed under a vacuum degree of -0.1MPA, a rotation speed of 1500r / min, and a temperature of 80°C to obtain a silicon nitride tape casting slurry with a viscosity of about 10,000pcs;

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

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

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

[0037] Example 3

[0038] In this embodiment, a method for preparing a high-performance silicon nitride ceramic substrate is proposed, and the steps are as follows:

[0039] Step 1: according to a certain ratio, 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 were mixed in a container and stirred for 6 hours to obtain the desired organic glue;

[0040] Step 2: According to a certain ratio, 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of silicon nitride magnesium powder, 0.5 parts of silicon powder, 1 part of silicon carbide whisker, 1.5 parts of β-phase silicon nitride seed, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone are added to a ball mill and ball milled for 0.5-1h, and then 89 parts of silicon nitride are added to the ball mill and ball milled for 3-5h, and then the organic glue prepared in step 1 is added to the ball mill and ball milled for 12-20h. The ball-milled slurry is degassed under a vacuum degree of -0.1MPA, a rotation speed of 1500r / min, and a temperature of 80°C to obtain a silicon nitride tape casting slurry with a viscosity of about 10000pcs;

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

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

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

[0044] Example 4

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

[0046] Step 1: according to a certain ratio, 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 were mixed in a container and stirred for 6 hours to obtain the desired organic glue;

[0047] Step 2: According to a certain ratio, 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of silicon nitride magnesium powder, 0.5 parts of silicon powder, 0.5 parts of silicon carbide whisker, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone are added to a ball mill and ball milled for 0.5-1h, and then 91 parts of silicon nitride are added to the ball mill and ball milled for 3-5h, and then the organic glue prepared in step 1 is added to the ball mill and ball milled for 12-20h. The ball-milled slurry is degassed under a vacuum degree of -0.1MPA, a rotation speed of 1500r / min, and a temperature of 80°C to obtain a silicon nitride casting slurry with a viscosity of about 10000pcs;

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

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

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

[0051] Example 5

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

[0053] Step 1: according to a certain ratio, 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 were mixed in a container and stirred for 6 hours to obtain the desired organic glue;

[0054] Step 2: According to a certain ratio, 2.5 parts of polyisobutylene succinimide, 5 parts of yttrium oxide powder, 2.5 parts of silicon nitride magnesium powder, 0.5 parts of silicon carbide whisker, 26 parts of ethanol, 26 parts of propyl acetate, and 4.5 parts of cyclohexanone are added to a ball mill and ball milled for 0.5-1h, and then 92 parts of silicon nitride are added to the ball mill and ball milled for 3-5h, and then the organic glue prepared in step 1 is added to the ball mill and ball milled for 12-20h. The ball-milled slurry is degassed under a vacuum degree of -0.1MPA, a rotation speed of 1500r / min, and a temperature of 80°C to obtain a silicon nitride casting slurry with a viscosity of about 10000pcs;

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

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

[0057] Step 5: Place the degreased silicon nitride wafer into a sintering furnace, heat it to 1400°C at a heating rate of 10°C / min, then heat it to 1870°C at a heating rate of 5°C / min and keep it warm for 3-6 hours, then cool it to 1400°C at a cooling rate of 1°C / 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 obtained in Examples 1 to 5 are shown in Table 1. The high-performance silicon nitride substrate requires a thermal conductivity of ≥90 W / m·k and a fracture toughness of ≥7.0 MPA·m 1 / 2 , flexural strength ≥800MPa.

[0059]

[0060] Table 1

[0061] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high-performance silicon nitride ceramic substrate, characterized in that: The invention comprises the following raw materials in parts by weight: 40-130 parts of silicon nitride powder, 20-110 parts of organic solvent, 3-15 parts of sintering aid, 5-15 parts of binder, 2-6 parts of plasticizer, and 1-6 parts of dispersant.

2. A high performance silicon nitride ceramic substrate according to claim 1, characterized in that: The organic solvent is one or more of ethanol, propyl acetate, cyclohexanone and a silane coupling agent.

3. A high performance silicon nitride ceramic substrate according to claim 1, characterized in that: The sintering aid is one or more of yttrium oxide powder, magnesium silicon nitride powder, silicon powder, beta-phase silicon nitride seed crystal, and silicon carbide whisker.

4. A high performance silicon nitride ceramic substrate according to claim 1, characterized in that: The binder is polyvinyl butyral, the plasticizer is polyethylene glycol, and the dispersant is polyisobutylene succinimide.

5. A method for preparing a high-performance silicon nitride ceramic substrate as claimed in claim 1, characterized in that: The method comprises the following preparation steps: 1) Glue 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; 2) Slurry preparation: 10-50 parts of organic solvent, 3-15 parts of sintering aid, and 1-6 parts of dispersant are added to a ball mill in sequence, the speed of the ball mill is 90r / min, and the ball milling is performed for 0.5-1h. Then 40-130 parts of silicon nitride powder are added to the ball mill for 3-5h. Then, the glue in step 1) is added to the ball mill for 12-20h. The ball-milled slurry is degassed under a vacuum degree of -0.1MPA, a speed of 1500r / min, and a temperature of 60-80°C to obtain a silicon nitride tape casting slurry with a viscosity of about 10,000 pcs. 3) Blank making: Pour the prepared slurry into the material box of the tape casting machine for tape casting, wherein the flow rate is 0.25m / min, the temperature range of the five drying zones is between 35°C and 70°C, and the green blanks of the required size are cut after drying; 4) Degreasing: The cut green pieces are powdered and stacked, and then placed on a firing plate for degreasing at 550°C-600°C for 20-25 hours; 5) Sintering: Place the degreased silicon nitride wafer into a sintering furnace, heat it to 1400°C at a heating rate of 10°C / min, heat it to 1850°C-1900°C at a heating rate of 5°C / min and keep it at that temperature for 3-6h, then cool it to 1400°C at a cooling rate of 1°C / min, and then cool it to room temperature with the furnace to obtain a silicon nitride ceramic substrate.

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