CN109400175B - Preparation method of high-thermal-conductivity silicon nitride ceramic substrate material - Google Patents

Abstract

The invention relates to a preparation method of a high-thermal-conductivity silicon nitride ceramic substrate material, which comprises the following steps: mixing silicon nitride powder or/and silicon powder serving as raw material powder with a sintering aid to obtain mixed powder; mixing the mixed powder and a binder, granulating, and performing compression molding to obtain a biscuit; and after the obtained biscuit is subjected to de-bonding and sintering, cutting into a specified thickness to obtain the silicon nitride ceramic substrate material.

Description

A kind of preparation method of high thermal conductivity silicon nitride ceramic substrate material

technical field

The invention relates to a preparation method of a silicon nitride ceramic substrate material, belonging to the preparation technology and application field of ceramics.

Background technique

High thermal conductivity silicon nitride ceramic substrate is a key thermal management material to ensure the safe operation of high-power power electronic devices. Power electronic device is the core unit of electric energy conversion and control in power equipment, and its application fields cover various fields such as energy, transportation, and basic industry. Commonly used power electronic devices include IGBTs, inverters, and the like. my country has become the world's largest demand market for power electronic devices, with a total market value of nearly 200 billion yuan in 2013, and is expected to reach 500 billion yuan in 2020, with an annual growth rate of nearly 20%. Correspondingly, the demand for ceramic substrates is also huge. It is estimated that for electric vehicles alone, the demand for ceramic substrates will reach 6 billion yuan.

High power, high frequency and integration are the development directions of power electronic devices. Its power can reach KW level or even dozens of GW. Due to the high energy density and serious heat generation, the operating temperature continues to rise, which seriously affects the working stability and life of the device. The problem of heat dissipation has become the key to be solved urgently. At present, alumina and aluminum nitride substrate materials are commonly used. Due to low thermal conductivity, aluminum oxide cannot effectively dissipate heat; while aluminum nitride ceramics have high thermal conductivity, but due to poor mechanical properties, they are easily damaged by heat during use. Cracks caused by impact. Silicon nitride ceramics have the advantages of high thermal conductivity and high reliability, and are currently the only candidate materials.

Silicon nitride ceramic is a traditional structural ceramic material. It has the advantages of high strength, high toughness and excellent high temperature performance. It has been widely used in industrial and civil fields. In recent years, the high thermal conductivity and good microwave transmission performance of silicon nitride ceramics have also attracted attention at home and abroad. Combined with its good mechanical properties and high temperature properties, it is an ideal ceramic substrate material for high-power power electronics. However, in order to effectively transfer heat, the thickness of the silicon nitride ceramic substrate is usually only 0.32mm, so the commonly used method is tape casting combined with air pressure sintering.

However, tape casting adds a lot of raw materials, the process is complicated, the cycle is long, and the cost is high. Moreover, the substrates prepared by the tape casting process often require high-temperature flattening treatment. Due to the limited number of stacked layers of substrate materials, the silicon nitride substrates loaded each time are also very limited, which ultimately leads to increased manufacturing costs.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the preparation of silicon nitride ceramic substrate materials by the traditional tape casting process, a new scheme of using block cutting is proposed. There are mainly two ways: one is to first prepare the bulk silicon nitride ceramic green body, and then sinter it. Before cutting, and then sintering; the other is cutting after sintering to prepare silicon nitride ceramic substrates.

In one aspect, the present invention also provides a method for preparing a high thermal conductivity silicon nitride ceramic substrate material, comprising:

Using silicon nitride powder or/and silicon powder as raw material powder, after mixing with sintering aid, a mixed powder is obtained;

The mixed powder and the binder are mixed and then granulated, and then pressed and formed to obtain a green body;

When the raw material powder is only silicon nitride powder, the obtained green body is subjected to debonding and bisque firing treatment, and then cut into a predetermined thickness, and then sintered to obtain the silicon nitride ceramic substrate material. The temperature of the treatment is 1200～1600℃, and the time is 1～12 hours;

Or when the raw material powder contains silicon powder, the obtained green body is subjected to debonding and nitriding treatment, then cut into a predetermined thickness, and then sintered to obtain the silicon nitride ceramic substrate material, and the nitriding treatment atmosphere It is nitrogen, the temperature is 1380～1500℃, and the time is 2～48 hours;

Alternatively, the obtained green body is debonded and sintered, and then cut into a predetermined thickness to obtain the silicon nitride ceramic substrate material.

Preferably, the sintering aid is at least two kinds of magnesium oxide, titanium oxide, Y ₂ O ₃ and lanthanide rare earth oxides; the mass ratio of the raw material powder to the sintering aid is (80-97) : (20-3), when the raw material powder contains silicon powder (silicon powder), the mass of the silicon powder is calculated according to the mass converted into silicon nitride powder.

Also, preferably, when the sintering aids include titanium oxide, Y ₂ O ₃ , at least one of lanthanide rare earth oxides, and magnesium oxide; the titanium oxide, Y ₂ O ₃ , lanthanide rare earth oxides The ratio of the molar content of at least one of these to the molar content of magnesium oxide is (2-5):5.

Also, preferably, when the sintering aid includes at least two kinds of Y ₂ O ₃ , lanthanide rare earth oxides, and magnesium oxide; and at least two kinds of Y ₂ O ₃ and lanthanide rare earth oxides The ratio of the molar content of magnesium oxide to the molar content of magnesium oxide is (2-5):5.

Preferably, the sintering aid includes at least two of Y ₂ O ₃ and lanthanide rare earth oxides.

Preferably, the particle size of the silicon nitride powder is in the range of 0.5-5 μm, and the particle size of the silicon powder is in the range of 1-20 μm.

Preferably, the cutting process is a multi-piece cutting process or a multi-wire cutting process, preferably a multi-wire cutting process; more preferably, the multi-wire cutting process includes: using a diamond wire with a diameter of 0.4 to 0.6 mm as the cutting process The wire is cut by using the swing feeding method; the running speed of the cutting wire is set to be ≤10m/s, and the feed speed is set to be 0.005-0.05mm/min. In the present disclosure, the multi-piece cutting process includes: using a plurality of blades, controlling the distance between the blades, and cutting at the same time; the multi-line cutting process includes: using a plurality of cutting lines, controlling the distance between the cutting lines (which is different from the obtained blank base) The thickness of the sheet or ceramic substrate is basically the same), and cut at the same time. Commonly used is multi-line cutting.

Preferably, the binder is polyvinyl butyral or/and polymethyl methacrylate, and the added amount is 0.5-10 wt% of the total mass of the mixed powder; The organic solvent, the dispersant and the binder are mixed, dried and granulated, and then pressed and formed to obtain a china; more preferably, the organic solvent is ethanol, methyl ethyl ketone, toluene, n-hexane, methanol, xylene, At least one of n-propanol and n-butanol, the amount added is 14 to 50% by weight of the total mass of the mixed powder; the dispersant is triolein, phosphate, castor oil, herring oil, ascorbic acid and pine oil At least one of the alcohols is added in an amount of 0.5-4 wt% of the total mass of the silicon nitride powder and the sintering aid system.

Preferably, the debonding temperature is 600-900° C., and the time is 2-48 hours.

Preferably, the sintering method is pressureless sintering, gas pressure sintering, hot pressing or isostatic pressing; , the time is 1 to 24 hours; more preferably, the heating rate of the sintering is 1 to 5 ℃ minutes.

Preferably, the molding method of the green body is dry pressing, cold isostatic pressing, dry pressing-cold isostatic pressing, gel injection molding, grouting, pressure grouting, extrusion molding. At least one of the above; preferably, the pressure of the dry pressing is 10-60 MPa, and the pressure of the cold isostatic pressing is 150-200 MPa.

Preferably, the prescribed thickness is 0.32 mm to 2 mm, preferably 0.4 to 2 mm.

On the other hand, the present invention also provides a silicon nitride ceramic substrate material with high thermal conductivity prepared according to the above-mentioned preparation method, the thickness of which is generally 0.32 mm to 2 mm. The method for preparing a silicon nitride ceramic substrate proposed by the present invention has the following characteristics. First, a variety of preparation techniques can be used to obtain silicon nitride green bodies, including dry pressing, cold isostatic pressing, dry pressing-cold isostatic pressing, gel injection molding, grouting, pressure grouting, extrusion molding and other methods. Therefore, common ceramic preparation techniques can be applied to the preparation of high thermal conductivity silicon nitride ceramic substrates. At the same time, a variety of sintering techniques can also be used, such as pressureless sintering, gas pressure sintering, hot pressing sintering and hot isostatic pressing sintering. Cutting can be carried out after bisque burning or nitriding, or after sintering, the process is more diverse, and the time is short and the cost is low, which is convenient for large-scale product preparation.

Compared with the conventional tape casting preparation scheme, the preparation scheme of the silicon nitride ceramic substrate material proposed by the present invention has the advantages of simple process, short cycle and low cost. In the present invention, the basic properties of the prepared silicon nitride ceramic substrate material are as follows: density of 3.2-3.5 g/cm ³ , toughness of 6-9 MPa·m ^1/2 and above, flexural strength of 600-900 MPa, thermal conductivity of 90 ~100W/m·K. The size of the prepared silicon nitride ceramic substrate material is 114mm*114mm*0.32mm. Surface roughness: Ra≤0.3μm; surface warpage: <0.1%.

Detailed ways

The present invention is further described below through the following embodiments, and it should be understood that the following embodiments are only used to illustrate the present invention, but not to limit the present invention.

The preparation technology of the silicon nitride ceramic substrate material proposed by the present invention is different from the common technology for preparing the ceramic substrate by tape casting, and can use a variety of traditional ceramic preparation technologies to prepare the green body, the process is simple, the cycle is short, and the operation is convenient ,low cost. It can be combined with the traditional ceramic preparation process, and it is a feasible solution for the preparation of silicon nitride ceramic substrates. Especially for thicker ceramic substrates, as well as other types of ceramic substrates, it can also be used as a reference.

The invention adopts the cutting technology, which can cut the bisque-fired or nitrided green body, and then sinter at high temperature, or cut the silicon nitride ceramic after high-temperature sintering. The process is more diverse and the time is short. , low cost, convenient for large-scale product preparation. Finally, through double-sided grinding, a silicon nitride ceramic substrate material with suitable thickness, surface roughness and surface warpage is obtained. In addition, compared with cutting silicon nitride ceramics after high temperature sintering, it is easier and cheaper to cut the bisque-fired or nitrided green body. The following will illustrate the preparation method of the high thermal conductivity silicon nitride ceramic substrate material provided by the present invention through examples.

A ceramic green body (green body) is prepared. The silicon nitride powder and sintering aid are mixed and dispersed in an organic solvent. Specifically, the silicon nitride powder and the above-mentioned sintering aid system are dispersed in an organic solvent, and then a dispersant and a binder are added to uniformly mix, and after drying, press molding to obtain a green body. Wherein, the binder is polyvinyl butyral or/and polymethyl methacrylate, and the added amount is 0.5-10 wt % of the total mass of the mixed powder. The organic solvent can be at least one of ethanol, butanone, toluene, n-hexane, methanol, xylene, n-propanol and n-butanol, and the added amount is 14-50 wt % of the total mass of the mixed powder. The dispersant is at least one of triolein, phosphate, castor oil, herring oil, ascorbic acid and terpineol, and the added amount is 0.5-4wt% of the total mass of the silicon nitride powder and the sintering aid system. A plasticizer may also be included in the green body. Wherein, the sintering aid system may be magnesium oxide and rare earth oxide, or may be magnesium oxide and double rare earth compound, or single rare earth compound (rare earth oxide), or at least two or more rare earth compounds. Then it is formed by dry pressing, isostatic pressing, dry pressing-isostatic pressing, grouting, pressure grouting, gel injection molding, etc. The mass ratio of the silicon nitride powder to the sintering aid system is (80 ~97): (20~3). Among them, the particle size of the silicon nitride powder is between 0.5 and 5 μm. The particle size of the silicon powder is between 1 and 20 μm. It can also be prepared with silicon powder or a mixed powder of silicon powder and silicon nitride powder, and the process is similar. When calculating the raw material powder, the silicon powder is converted into the mass of the silicon nitride powder for calculation. The second step is debonding and biscuit treatment, and the debonding temperature is usually 900°C. After the debonding is completed, if the bisque is to be cut, continue to heat up to within 1600°C for bisque firing before cutting. The purpose of bisque firing is to improve the strength of the ceramic green body. The green body must have a certain strength when cutting, so that it will not break (or crack) when it is cut to a specified thickness, and its strength is much lower than that of the sintered silicon nitride ceramic. , making it easier to cut. Of course, it cannot be cut before bisque firing. At this time, the ceramic bisque has a porous structure and usually has a low strength. It is easy to break when cutting, and it is not easy to operate. If you don't cut it, you don't need bisque. For silicon powder and green body prepared by mixing silicon powder and silicon nitride powder, silicon powder nitriding treatment is performed after debonding. The debonding temperature is similar to that of silicon nitride powder. The debonding temperature is 600-900°C and the time is 2-48 hours. Among them, the temperature of the nitriding treatment is usually between 1380 and 1500°C. If cut, it can be cut after nitriding. The nitriding treatment is to improve the strength of the ceramic green body. The green body must have a certain strength when cutting, so that it will not break (or crack) when it is cut to a specified thickness, and its strength is much lower than that of the sintered silicon nitride. ceramic for easier cutting. Of course, it cannot be cut before the nitriding treatment. At this time, the ceramic green body has a porous structure, and the strength is usually relatively low. It is easy to be broken during cutting and difficult to operate.

sintering. Adopt pressureless sintering, air pressure sintering, hot pressing sintering and high temperature isostatic pressing sintering process. Wherein, the sintering temperature of the silicon nitride ceramic substrate material is 1600-1950° C., the gas pressure is 0.1-10 MPa, the sintering time is 1-24 h, and the atmosphere is a nitrogen atmosphere.

In the present disclosure, the cutting process is divided into two types. Green cutting and ceramic cutting. If bisque cutting is used, there are two cases: one is that for samples using silicon nitride powder as the starting material, cutting is performed after bisque firing (bisque firing). The green body prepared from silicon powder and silicon powder and silicon nitride mixed powder is diced after nitriding treatment (nitriding). After cutting, the temperature is raised and sintered, and then the sample is polished on both sides to prepare the required ceramic substrate. The second is cutting after sintering. After cutting, double-sided grinding is performed to obtain the required substrate material, which is similar to the previous case.

In the present disclosure, the cutting may adopt a multi-piece cutting method or a multi-wire cutting method. After cutting, the substrate is polished on both sides to meet the requirements of surface roughness and surface warpage. Among them, the multi-piece cutting process includes: grinding the four sides of the sample flat, installing it on a multi-piece cutting machine, and simultaneously cutting out multiple pieces of samples by adjusting the spacing of the cutting blades. The multi-wire cutting process includes: smoothing the four sides of the sample, and simultaneously cutting multiple pieces of samples by adjusting the wire spacing on a fixed multi-wire cutting device. The main one is multi-wire cutting. Due to the high hardness and toughness of silicon nitride ceramics, multi-wire cutting equipment is easy to break, and surface knife marks will also appear. Therefore, the process parameters need to be carefully adjusted. The present invention creatively uses diamond wire with a medium diameter for cutting (the diameter can be 0.4-0.6 mm), and adopts the oscillating wire supply method to effectively improve the cutting efficiency, and at the same time, the chips are easily discharged. Set the speed of the cutting line to be less than or equal to 10m/s and the feed speed to be 0.005 to 0.05mm/min to avoid wire breakage as much as possible. If there is a broken wire, use a diamond wire with a thinner diameter (0.25-0.3mm) to introduce the thick diamond wire (0.4-0.6mm in diameter), and then continue to cut. The distance between the diamond wires is generally 0.32 mm to 2 mm (preferably 0.4 to 2 mm), which is the thickness of the obtained silicon nitride ceramic substrate after cutting. It should be noted that the above-mentioned cutting multi-wire cutting process parameters are also applicable to the green body after biscuit treatment or nitriding treatment.

The invention proposes to use the cutting method to prepare the silicon nitride ceramic substrate material, which not only has the same performance as the tape casting process. Moreover, it has the advantages of fast preparation speed and low cost, and is a new preparation scheme of ceramic substrate materials.

The invention adopts the Archimedes drainage method to measure the relative density of the silicon nitride ceramic substrate material to be 98-99.5%. The thermal conductivity of the silicon nitride ceramic substrate material was measured to be 90-100 W/m·K by means of a laser thermal conductivity meter. The toughness of the silicon nitride ceramic substrate material is measured to be 6-9 MPa·m ^1/2 and above by the single-side notch beam method. The bending strength of the silicon nitride ceramic substrate material measured by the three-point bending method is 600-900 MPa. The surface roughness of the silicon nitride ceramic substrate material is measured by a surface roughness measuring instrument: Ra≤0.3 μm. The surface warpage of the silicon nitride ceramic substrate material is measured by a warpage tester: <0.1%.

The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention, and should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present invention belong to the present invention. scope of protection. The specific process parameters and the like in the following examples are only an example of a suitable range, that is, those skilled in the art can make selections within the suitable range through the description herein, and are not intended to be limited to the specific numerical values exemplified below. Unless otherwise specified, the particle sizes of silicon nitride powder and silicon powder in the following examples are generally 0.2-2 μm. The particle size distribution of the sintering aid system is 0.5-10 μm.

Example 1

97g silicon nitride powder and 3g sintering aid (magnesium oxide-yttrium oxide) were added to 50g ethanol/butanone solvent system (the mass ratio of ethanol and butanone was 34:66), and the molar ratio of magnesium oxide and yttrium oxide was 5:2. 1 g of triolein was used as a dispersant, and 0.5 g of PVB was used as a binder. After ball milling, it was placed in an oven at 60 °C for drying for 24 h. Then take it out and pass it through a 100-mesh sieve. The sieved powder is put into a mold for dry pressing. Then use cold isostatic pressing for 200MPa-1min. After treatment, it was placed in a carbon tube furnace, heated to 900°C at a rate of 1°C/min under vacuum for 1 hour to complete debonding, and continued to heat up to 1500°C for 2 hours to complete biscuit sintering. The samples after the bisque firing were cut by multi-wire cutting equipment (CX8080 diamond wire cutting machine, slice thickness 0.40mm), with a thickness of 0.45mm. Using 0.6mm diamond wire, the wire feeding method is oscillating, the cutting wire speed is set to 10m/s, and the feed speed is set to 0.005mm/min. After cutting, the green body was sintered in a carbon tube furnace, with a heating rate of 5°C/min to 1900°C, and 0.9MPa for 2h to achieve sintering. Then, a dense and complete silicon nitride ceramic substrate is prepared after double-sided grinding.

Example 2

Add 95g silicon nitride powder and 5g sintering aid (magnesium oxide-ytterbium oxide) to 50g ethanol/butanone solvent system (the mass ratio of ethanol and butanone is 34:66), the molar ratio of magnesium oxide and ytterbium oxide 5:2. 2 g of glycerol trioleate was used as dispersant, and 1 g of PVB was used as binder. After ball milling, it was placed in an oven at 60 °C for drying for 24 h. Then take it out and pass it through a 100-mesh sieve. The sieved powder is put into a mold for dry pressing. Then use cold isostatic pressing for 200MPa-1min. After treatment, it was placed in a carbon tube furnace, and the temperature was raised to 900 °C at a rate of 1 °C/min under vacuum for 1 h to complete debonding. The debonded green body was sintered in a carbon tube furnace at a heating rate of 5°C/min to 1950°C and held at 2MPa for 2h to achieve sintering. Multi-wire cutting equipment (CX8080 diamond wire cutting machine, slice thickness 0.40mm) was used to cut the sintered ceramics with a thickness of 0.38mm. Using 0.6mm diamond wire, the wire feeding method is oscillating, the cutting wire speed is set to 9m/s, and the feed speed is set to 0.008mm/min. Dense and complete silicon nitride ceramic substrates are prepared after double-sided grinding.

Example 3

90g silicon nitride powder and 10g sintering aid (magnesium oxide-lutetium oxide) were added to 50g ethanol/butanone solvent system (the mass ratio of ethanol and butanone was 34:66), the molar ratio of magnesium oxide and lutetium oxide 5:2. 3 g of glycerol trioleate was used as a dispersant, and 2 g of PVB was used as a binder. After ball milling, it was placed in an oven at 60 °C for drying for 24 h. Then take it out and pass it through a 100-mesh sieve. The sieved powder is put into a mold for dry pressing. Then use cold isostatic pressing for 200MPa-1min. After treatment, it was placed in a carbon tube furnace, and the temperature was raised to 900 °C at a rate of 1 °C/min under vacuum for 1 h to complete debonding. The debonded green body was sintered in a carbon tube furnace, with a heating rate of 4°C/min to 1900°C, and 0.6MPa for 4h to achieve sintering. Multi-wire cutting equipment (CX8080 diamond wire cutting machine, slice thickness 0.40mm) is used to cut the sintered ceramics with a thickness of 0.38mm. 0.4mm diamond wire is used, and the wire is oscillated, and the cutting wire speed is set to 8m /s, the feed rate is set to 0.01mm/min. Then, a dense and complete silicon nitride ceramic substrate is prepared after double-sided grinding.

Example 4

Add 80g silicon nitride powder and 20g sintering aid (magnesium oxide-titanium oxide) to 50g ethanol/butanone solvent system (the mass ratio of ethanol and butanone is 34:66), the molar ratio of magnesium oxide and titanium oxide 5:2. 3 g of glycerol trioleate was used as a dispersant, and 2 g of PVB was used as a binder. After ball milling, it was placed in an oven at 60 °C for drying for 24 h. Then take it out and pass it through a 100-mesh sieve. The sieved powder is put into a mold for dry pressing. Then use cold isostatic pressing for 200MPa-1min. After treatment, it was placed in a carbon tube furnace, and the temperature was raised to 900 °C at a rate of 1 °C/min under vacuum for 1 h to complete debonding. The debonded green body was sintered in a carbon tube furnace at a heating rate of 3°C/min to 1800°C, and the sintering was achieved by holding for 6h in a nitrogen atmosphere. Use multi-wire cutting equipment (CX8080 diamond wire cutting machine, slice thickness 0.40mm) to cut the sintered ceramics with a thickness of 0.38mm. Use 0.6mm diamond wire to supply the wire by swinging, and the cutting wire speed is set to 10m /s, the feed speed is set to 0.05mm/min. Then, a dense and complete silicon nitride ceramic substrate is prepared after double-sided grinding.

Example 5

54g of silicon powder (equivalent to 90g of silicon nitride powder) and 10g of sintering aid (magnesium oxide-dysprosium oxide) were added to 50g of ethanol/butanone solvent system (the mass ratio of ethanol and butanone was 34:66), oxidized The molar ratio of magnesium to dysprosium oxide was 5:2. 3 g of glycerol trioleate was used as a dispersant, and 2 g of PVB was used as a binder. After ball milling, it was placed in an oven at 60 °C for drying for 24 h. Then take it out and pass it through a 100-mesh sieve. The sieved powder is put into a mold for dry pressing. Then use cold isostatic pressing for 200MPa-1min. After treatment, put it in a carbon tube furnace, heat up to 900°C at a rate of 1°C/min under vacuum for 1 hour to complete debonding, continue to heat up to 1400°C at a rate of 2°C/min, and keep it in a nitrogen atmosphere for 8h to complete nitriding . The green body after nitriding treatment is cut by multi-wire cutting equipment (CX8080 diamond wire cutting machine, slice thickness 0.40mm), and the thickness is 0.45mm. Using 0.6mm diamond wire, the wire feeding method is oscillating, the cutting wire speed is set to 5m/s, and the feed speed is set to 0.05mm/min. The cut green body was sintered in a carbon tube furnace, and the heating rate was 2°C/min to 1900°C, and the temperature was kept at 0.9MPa for 6h to achieve sintering. Dense and complete silicon nitride ceramic substrates are prepared after double-sided grinding.

Example 6

Add 45g silicon nitride powder, 27g silicon powder (equivalent to 45g silicon nitride powder) and 10g sintering aid (magnesium oxide-erbium oxide) in 50g ethanol/butanone solvent system (the mass ratio of ethanol and butanone is 34:66), the molar ratio of magnesium oxide and erbium oxide is 5:2. 3 g of glycerol trioleate was used as a dispersant, and 2 g of PVB was used as a binder. After ball milling, it was placed in an oven at 60 °C for drying for 24 h. Then take it out and pass it through a 100-mesh sieve. The sieved powder is put into a mold for dry pressing. Then use cold isostatic pressing for 200MPa-1min. After treatment, it was put into a carbon tube furnace, heated to 900°C at a rate of 1°C/min for 1 hour under vacuum to complete debonding, continued to heat up to 1400°C at a rate of 2°C/min, and held in a nitrogen atmosphere for 8 hours to complete nitriding . The nitrided green body was sintered in a carbon tube furnace, with a heating rate of 1°C/min to 1900°C, and 1MPa for 12h to achieve sintering. Then, multi-wire cutting equipment (CX8080 diamond wire cutting machine, slice thickness 0.40mm) was used to cut the sintered ceramics with a thickness of 0.38mm. Using 0.45mm diamond wire, the wire feeding method is oscillating, the cutting wire speed is set to 8m/s, and the feed speed is set to 0.02mm/min. After cutting and grinding, a dense and complete silicon nitride ceramic substrate is prepared.

Table 1 shows the performance parameters of the high thermal conductivity silicon nitride ceramic substrate materials prepared in Examples 1-6 of the present invention:

Claims (12)

1. a preparation method of a high-thermal-conductivity silicon nitride ceramic substrate material is characterized by comprising the following steps:

mixing silicon nitride powder or/and silicon powder serving as raw material powder with a sintering aid to obtain mixed powder;

mixing the mixed powder and a binder, granulating, and performing compression molding to obtain a biscuit;

when the raw material powder is only silicon nitride powder, the obtained biscuit is subjected to de-bonding and biscuit firing treatment, then is cut into a given thickness, and is sintered to obtain the silicon nitride ceramic substrate material, wherein the biscuit firing treatment temperature is 1200-1600 ℃ and the biscuit firing treatment time is 1-12 hours;

or when the raw material powder contains silicon powder, cutting the biscuit into a specified thickness after de-bonding and nitriding treatment, and sintering to obtain the silicon nitride ceramic substrate material, wherein the nitriding treatment is performed in nitrogen atmosphere at 1380-1500 ℃ for 2-48 hours;

the cutting process is a multi-sheet cutting process or a multi-line cutting process; the predetermined thickness is 0.32mm to 2 mm.

2. The method according to claim 1, wherein the sintering aid is magnesium oxide, titanium oxide, Y₂O₃At least two of lanthanide rare earth oxides; the mass ratio of the raw material powder to the sintering aid is (80-97): (20-3) when the raw material powder contains silicon powder, the mass of the silicon powder is calculated by the mass converted into silicon nitride powder.

3. The method according to claim 2, wherein when the sintering aid comprises titanium oxide, Y₂O₃At least one of lanthanide rare earth oxides, and magnesium oxide; the titanium oxide and Y₂O₃The ratio of the molar content of at least one of the lanthanide rare earth oxides to the molar content of the magnesium oxide is (2-5): 5.

4. the method according to claim 3, wherein when the sintering aid comprises Y₂O₃At least two of lanthanide rare earth oxides, and magnesium oxide; said Y is₂O₃The ratio of the molar contents of at least two of the lanthanide rare earth oxides to the molar content of magnesium oxide is (2-5): 5.

5. the method of claim 2, wherein the sintering aid comprises Y₂O₃And at least two of lanthanide rare earth oxides.

6. The preparation method according to claim 1, wherein the particle size of the silicon nitride powder is in a range of 0.5 to 5 μm, and the particle size of the silicon powder is in a range of 1 to 20 μm.

7. The method of manufacturing of claim 1, wherein the dicing process is a multi-wire dicing process; the multi-line cutting process comprises the following steps: cutting by using a diamond wire with the diameter of 0.4-0.6 mm as a cutting line and adopting a swinging wire supply mode; the running speed of the cutting line is set to be less than or equal to 10m/s, and the feeding speed is set to be 0.005-0.05 mm/min.

8. The preparation method according to claim 1, wherein the binder is polyvinyl butyral or/and polymethyl methacrylate, and the addition amount is 0.5-10 wt% of the total mass of the mixed powder; mixing the mixed powder, an organic solvent, a dispersant and a binder, drying and granulating, and then performing compression molding to obtain a biscuit; the organic solvent is at least one of ethanol, butanone, toluene, n-hexane, methanol, xylene, n-propanol and n-butanol, and the addition amount of the organic solvent is 14-50 wt% of the total mass of the mixed powder; the dispersing agent is at least one of triolein, phosphate ester, castor oil herring oil, ascorbic acid and terpineol, and the adding amount of the dispersing agent is 0.5-4 wt% of the total mass of the silicon nitride powder and the sintering aid system.

9. The method according to claim 1, wherein the temperature of the de-binding is 600 to 900 ℃ and the time is 2 to 48 hours.

10. The production method according to claim 1, wherein the sintering is performed by pressureless sintering, gas pressure sintering, hot press sintering, or isostatic pressing sintering; the sintering atmosphere is nitrogen atmosphere, the temperature is 1600-1950 ℃, the air pressure is 0.1-10 MPa, and the time is 1-24 hours; the temperature rise rate of the sintering is 1-5 ℃/min.

11. The method according to any one of claims 1 to 10, wherein the predetermined thickness is 0.4 to 2 mm.

12. A high thermal conductive silicon nitride ceramic substrate material prepared according to the preparation method described in any one of claims 1 to 11.