A one-shot silicon nitride substrate process

Abstract

The present application relates to the technical field of ceramic materials, in particular to a sintering type silicon nitride substrate process, the sintering type silicon nitride substrate is prepared by mixing, ball milling, casting, degassing and sintering of alpha-Si3N4 silicon nitride powder and other additives in a specific ratio, wherein the degassing includes air degassing and nitrogen degassing, which can better remove the organic matter in the silicon nitride substrate and achieve better degassing effect; in high-temperature sintering, the silicon nitride substrate after degassing is provided with two layers of backing plates, namely boron nitride backing plate and silicon nitride plate, which can avoid damage and comprehensive performance decline caused by adhesion during high-temperature sintering, has good heat conduction capacity, effectively prevents the indentation problem caused by the boron nitride backing plate, reduces the dark cracks of the silicon nitride substrate, reduces the breakage rate and comprehensive performance, and has a wide application prospect compared with the prior art.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, and in particular to a process for instant-fired silicon nitride substrates. Background Technology

[0002] The balance between energy and the environment is a critical challenge that humanity must confront in its development. Replacing traditional fossil fuels with electricity can solve both the fossil fuel shortage and the problem of air pollution. The energy trend is shifting from fossil fuels to electricity, making the development of power electronics technology particularly important. Currently, power electronics technology is widely used in high-speed trains, new energy vehicles, and wind power generation. In pursuit of more efficient power control and conversion technologies, electronic devices are moving towards higher voltage, higher current, and higher power density.

[0003] In recent years, power devices have been widely used in electric vehicles and hybrid electric vehicles (EV / HEV), advanced electric trains, and portable electronic products. This trend will accelerate as wide-bandgap semiconductors replace silicon. However, high-power devices generate significant thermal stress, posing a major challenge to the assembly and packaging materials, especially the brittle ceramic substrates that provide electrical insulation and heat dissipation. Therefore, ceramic substrates used in high-power electronic devices require both good mechanical reliability and high thermal conductivity.

[0004] Silicon nitride ceramic materials occupy an important position in the field of high-power semiconductor device substrates due to their superior performance characteristics. Their main performance advantages are manifested in several aspects: excellent thermal conductivity (high thermal conductivity provides higher heat dissipation efficiency, ensuring stable operation of power devices in high-temperature environments and extending device lifespan); stable and excellent mechanical properties (ensuring the reliability of power device operation); good insulation and electrical breakdown capability (ensuring the safety of power devices in high-voltage, high-current operating environments); thermal expansion coefficient close to that of SiC substrates (a large difference in thermal expansion coefficients during operation can easily lead to stress accumulation); good high-frequency characteristics; and high surface flatness and smoothness, facilitating the printing of circuits on the substrate surface and increasing the accuracy of circuit printing and operational reliability.

[0005] In existing technologies, the preparation process of silicon nitride substrates generally involves ball milling of raw materials, slurry preparation, tape casting, debinding, and sintering. For example, patent document CN106631039A discloses a method for preparing silicon nitride ceramic substrates, which includes the following steps: mixing silicon powder, silicon nitride powder, sintering aid, and dispersant, adding solvent, performing a first ball milling, adding binder and plasticizer, performing a second ball milling, and obtaining a slurry after vacuum degassing; casting the slurry, drying it, obtaining a green blank, obtaining a green blank after vacuum debinding; and sintering the green blank to obtain a silicon nitride ceramic substrate. This invention obtains a low-cost silicon nitride ceramic substrate by using silicon nitride powder and inexpensive silicon powder as the main raw materials and employing a tape casting process. The silicon nitride substrate prepared by this method still needs to be polished and ground, but the secondary grinding process is prone to causing dark cracks, affecting the final comprehensive performance of the product, leading to substrate breakage and serious material loss.

[0006] Therefore, based on the relevant technologies mentioned above, there is an urgent need to develop a process for instant-burning silicon nitride substrates. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a burn-in silicon nitride substrate process to solve the problem that polished substrates are easily broken in the prior art.

[0008] To achieve the above objectives, the present invention provides a process for instant-burning silicon nitride substrates.

[0009] A process for producing silicon nitride substrates that can be fired immediately includes the following steps:

[0010] Step A1. Add α-Si3N4 silicon nitride powder, sintering aid, dispersant, defoamer and organic solvent to a drum mill jar 1 and mill for 18-20 hours to obtain mixture A. Then add organic solvent, binder and plasticizer to a drum mill jar 2 and mill for 10-12 hours to obtain mixture B. Pour mixture B into mixture A and continue to mix and mill for 40-42 hours to obtain mixture C.

[0011] Step A2. Pour mixture C into a vertical mixer for stirring, filter, pour into a degassing tank for degassing treatment, and obtain silicon nitride slurry;

[0012] Step A3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride billet;

[0013] Step A4. First, place the silicon nitride blank in an air environment for air debonding, and then perform nitrogen debonding in a nitrogen atmosphere to obtain the debonded silicon nitride substrate.

[0014] Step A5. Using boron nitride with a thickness of 3.5-4mm as the first layer, place a silicon nitride board with a thickness of 0.5-0.6mm on the boron nitride pad as the second layer. Then place the silicon nitride substrate after debinding on the second layer and sinter at high temperature. Then, reduce the temperature to 1600℃ at a cooling rate of 1℃ / min. After cooling, the sinterable silicon nitride substrate is obtained.

[0015] Preferably, the sintering aid mentioned in step A1 is a mixture of yttrium oxide and magnesium oxide in a mass ratio of 1:3;

[0016] The organic solvent is obtained by mixing ethanol and toluene in a mass ratio of 4-6:1.

[0017] Preferably, the defoamer in step A1 is any one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polydimethylsiloxane;

[0018] The dispersant is polyvinylpyrrolidone;

[0019] The adhesive is at least one of polyethylene glycol, polyvinyl butyral, and methyl acrylate.

[0020] The plasticizer is any one of phthalate, polyethylene glycol, and glycerin.

[0021] Preferably, the particle size of the α-Si3N4 silicon nitride powder in step A1 is 0.5-1 μm;

[0022] The mass ratio of the α-Si3N4 silicon nitride powder, sintering aid, dispersant, defoamer, and organic solvent is 100-130:6-12:2.5-4:1-2:40-55.

[0023] Preferably, the mass ratio of the organic solvent, binder, and plasticizer in step A1 is 10-15:5-8:3-7;

[0024] The mass ratio of mixture A to mixture B is 100:180-210.

[0025] Preferably, the stirring rate in step A2 is 400-600 r / min, and the stirring time is 2-3 h;

[0026] The vacuum degree during the degassing process is 0.1-0.5 Pa, the temperature is 45-55℃, the stirring rate is 600-800 r / min, and the degassing time is 100-120 min.

[0027] Preferably, the thickness of the silicon nitride blank in step A3 is 0.26-0.32 mm.

[0028] Preferably, the temperature of the air-discharge adhesive in step A4 is 500-600℃, and the heat preservation time is 12-14h.

[0029] Preferably, the nitrogen gas discharge temperature in step A4 is 820-1050℃, and the heat preservation time is 10-12h.

[0030] Preferably, the high-temperature sintering in step A5 includes a first high-temperature sintering and a second high-temperature sintering;

[0031] The first high-temperature sintering is carried out under vacuum at a temperature of 1250-1380℃ for 2.5-3.5 hours.

[0032] The second high-temperature sintering is carried out under nitrogen pressure of 0.5-3 MPa, and the temperature is further increased to 1770-1920℃ and held for 2-2.5 hours.

[0033] The beneficial effects of this invention are:

[0034] This invention provides a process for preparing an instant-fired silicon nitride substrate. The process involves mixing α-Si3N4 silicon nitride powder with other additives in a specific ratio, ball milling, casting, debinding, and sintering to obtain an instant-fired silicon nitride substrate. The debinding process includes air debinding and nitrogen debinding, which, under specific temperature and atmosphere conditions, allows for better removal of organic matter from the silicon nitride substrate, achieving a better debinding effect. During high-temperature sintering, two pads are placed under the debinded silicon nitride substrate: a boron nitride pad and a silicon nitride plate. The boron nitride pad effectively isolates the individual silicon nitride substrates, preventing damage and performance degradation due to adhesion during high-temperature sintering, and also possesses good thermal conductivity. The silicon nitride plate effectively isolates the indentation caused by the boron nitride pad, thereby reducing the formation of dark cracks in the silicon nitride substrate, lowering the breakage rate, and improving overall performance. Compared with existing technologies, this process has broad application prospects. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0036] The sources and properties of some of the raw materials used in this invention are as follows:

[0037] Polyvinylpyrrolidone was purchased from Dongguan Menghao New Material Technology Co., Ltd.; yttrium oxide was purchased from Hubei Qibajiu Chemical Co., Ltd.; magnesium oxide was purchased from Shandong Jiuzhong Chemical Co., Ltd.; polydimethylsiloxane was purchased from Zhejiang Rongli High-Tech Materials Co., Ltd.; polyvinyl butyral was purchased from Hebi Yimin Plastics Technology Co., Ltd.; phthalates were purchased from Sinopharm Chemical Reagent Beijing Co., Ltd.; and toluene was purchased from China Petrochemical Chemical Sales Co., Ltd. Central China Branch.

[0038] Example 1: A process for instant-fire silicon nitride substrates, comprising the following steps:

[0039] S1. Add 100g of α-Si3N4 silicon nitride powder, 6g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 2.5g of polyvinylpyrrolidone, 1g of defoamer and 40g of organic solvent to a drum ball mill jar 1. The mass ratio of ethanol to toluene in the organic solvent is 4:1. Ball mill for 18h to obtain mixture A. Then add 10g of organic solvent, 5g of polyvinyl butyral and 3g of phthalate to a ball mill jar 2. Ball mill for 10h to obtain mixture B. Then pour 180g of mixture B into 100g of mixture A and continue to mix and ball mill for 40h to obtain mixture C.

[0040] S2. Pour the mixture C into a vertical mixer and stir at a stirring rate of 400 r / min for 2 h. After filtration, pour it into a degassing tank for degassing treatment at a vacuum of 0.1 Pa, a temperature of 45 °C, a stirring rate of 600 r / min, and a degassing time of 100 min to obtain silicon nitride slurry.

[0041] S3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride blank with a thickness of 0.26 mm;

[0042] S4. First, place the silicon nitride blank in an air environment for air debonding at a temperature of 500℃ for 12 hours, and then perform nitrogen debonding in a nitrogen atmosphere at a temperature of 820℃ for 10 hours to obtain the debonded silicon nitride substrate.

[0043] S5. Using a 3.5mm thick boron nitride substrate as the first layer, a 0.5mm thick silicon nitride substrate is placed on the boron nitride substrate as the second layer. The silicon nitride substrate after debinding is then placed on the second layer. The substrate is subjected to a first high-temperature sintering under vacuum at 1250℃ for 2.5 hours. Then, a second high-temperature sintering is performed under a nitrogen pressure of 0.5MPa, with the temperature increased to 1770℃ and held for 2 hours. The temperature is then reduced to 1600℃ at a cooling rate of 1℃ / min. After cooling, the in-sintering silicon nitride substrate is obtained.

[0044] Example 2: A process for instant-fire silicon nitride substrates, comprising the following steps:

[0045] S1. Add 110g of α-Si3N4 silicon nitride powder, 8g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 3g of polyvinylpyrrolidone, 1.5g of defoamer and 45g of organic solvent to a drum mill jar 1. The mass ratio of ethanol to toluene in the organic solvent is 5:1. Mill for 19h to obtain mixture A. Then add 12g of organic solvent, 6g of polyvinyl butyral and 4g of phthalate to a drum mill jar 2. Mill for 11h to obtain mixture B. Then pour 190g of mixture B into 100g of mixture A and continue to mix and mill for 41h to obtain mixture C.

[0046] S2. Pour the mixture C into a vertical mixer and stir at a stirring rate of 500 r / min for 2.5 h. After filtration, pour it into a degassing tank for degassing treatment at a vacuum of 0.2 Pa, a temperature of 50 °C, a stirring rate of 700 r / min, and a degassing time of 110 min to obtain silicon nitride slurry.

[0047] S3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride blank with a thickness of 0.28 mm;

[0048] S4. First, place the silicon nitride blank in an air environment for air debonding at a temperature of 540℃ for 13 hours, and then perform nitrogen debonding in a nitrogen atmosphere at a temperature of 900℃ for 11 hours to obtain the debonded silicon nitride substrate.

[0049] S5. Using a 3.5mm thick boron nitride substrate as the first layer, place a 0.53mm thick silicon nitride substrate on the boron nitride substrate as the second layer. Then place the debonded silicon nitride substrate on the second layer and perform the first high-temperature sintering under vacuum at 1300℃ for 3 hours. Then perform the second high-temperature sintering under 1MPa nitrogen pressure, continue to raise the temperature to 1820℃ and hold for 2 hours. Then lower the temperature to 1600℃ at a cooling rate of 1℃ / min. After cooling, the in-sintering silicon nitride substrate is obtained.

[0050] Example 3: A process for instant-fire silicon nitride substrates, comprising the following steps:

[0051] S1. Add 120g of α-Si3N4 silicon nitride powder, 10g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 3.5g of polyvinylpyrrolidone, 1.5g of defoamer and 50g of organic solvent to a drum ball mill jar 1. The mass ratio of ethanol to toluene in the organic solvent is 5:1. Ball mill for 19.5h to obtain mixture A. Then add 14g of organic solvent, 7g of polyvinyl butyral and 5g of phthalate to a ball mill jar 2. Ball mill for 11.5h to obtain mixture B. Then pour 200g of mixture B into 100g of mixture A and continue mixing and ball milling for 41.5h to obtain mixture C.

[0052] S2. Pour the mixture C into a vertical mixer and stir at a stirring rate of 550 r / min for 2.5 h. After filtration, pour it into a degassing tank for degassing treatment at a vacuum of 0.4 Pa, a temperature of 52 °C, a stirring rate of 750 r / min, and a degassing time of 115 min to obtain silicon nitride slurry.

[0053] S3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride blank with a thickness of 0.30 mm;

[0054] S4. First, place the silicon nitride blank in an air environment for air debonding at a temperature of 580℃ for 13.5h. Then, perform nitrogen debonding in a nitrogen atmosphere at a temperature of 980℃ for 11.5h to obtain the debonded silicon nitride substrate.

[0055] S5. Using a 4mm thick boron nitride substrate as the first layer, a 0.57mm thick silicon nitride substrate is placed on the boron nitride substrate as the second layer. The silicon nitride substrate after debinding is then placed on the second layer. The substrate is subjected to a first high-temperature sintering under vacuum at 1320℃ for 3 hours. Then, a second high-temperature sintering is performed under a nitrogen pressure of 2MPa, with the temperature increased to 1870℃ and held for 2.5 hours. The temperature is then reduced to 1600℃ at a cooling rate of 1℃ / min. After cooling, the in-sintering silicon nitride substrate is obtained.

[0056] Example 4: A process for instant-fire silicon nitride substrates, comprising the following steps:

[0057] S1. Add 130g of α-Si3N4 silicon nitride powder, 12g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 4g of polyvinylpyrrolidone, 2g of defoamer and 55g of organic solvent to a drum ball mill jar 1. The mass ratio of ethanol to toluene in the organic solvent is 6:1. Ball mill for 20h to obtain mixture A. Then add 15g of organic solvent, 8g of polyvinyl butyral and 7g of phthalate to a ball mill jar 2. Ball mill for 12h to obtain mixture B. Then pour 210g of mixture B into 100g of mixture A and continue to mix and ball mill for 42h to obtain mixture C.

[0058] S2. Pour mixture C into a vertical mixer and stir at a stirring rate of 600 r / min for 3 h. After filtration, pour it into a degassing tank for degassing treatment at a vacuum of 0.5 Pa, a temperature of 55 °C, a stirring rate of 800 r / min, and a degassing time of 120 min to obtain silicon nitride slurry.

[0059] S3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride blank with a thickness of 0.32 mm;

[0060] S4. First, place the silicon nitride blank in an air environment for air debonding at a temperature of 600℃ for 14 hours, and then perform nitrogen debonding in a nitrogen atmosphere at a temperature of 1050℃ for 12 hours to obtain the debonded silicon nitride substrate.

[0061] S5. Using a 4mm thick boron nitride substrate as the first layer, a 0.6mm thick silicon nitride substrate is placed on the boron nitride substrate as the second layer. The silicon nitride substrate after debinding is then placed on the second layer. The substrate is subjected to a first high-temperature sintering under vacuum at 1380℃ for 3.5 hours. Then, a second high-temperature sintering is performed under a nitrogen pressure of 3MPa, with the temperature increased to 1920℃ and held for 2.5 hours. The temperature is then reduced to 1600℃ at a cooling rate of 1℃ / min. After cooling, the in-sintering silicon nitride substrate is obtained.

[0062] Comparative Example 1:

[0063] Compared with Example 1, this comparative example did not add a second silicon nitride plate with a thickness of 0.5 mm during the high-temperature sintering process. All other steps and parameters were the same, and will not be repeated in this comparative example. Finally, a ready-to-sinter silicon nitride substrate was obtained.

[0064] Comparative Example 2:

[0065] Compared with Example 1, this comparative example only replaces the "second silicon nitride plate with a thickness of 0.5 mm" with the "second silicon nitride plate with a thickness of 0.1 mm". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a burnable silicon nitride substrate is obtained.

[0066] Comparative Example 3:

[0067] Compared with Example 1, this comparative example only replaces the "second silicon nitride plate with a thickness of 0.5 mm" with the "second silicon nitride plate with a thickness of 2 mm". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, a burnable silicon nitride substrate is obtained.

[0068] Comparative Example 4:

[0069] S1. Add 100g of α-Si3N4 silicon nitride powder, 6g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 2.5g of polyvinylpyrrolidone, 1g of defoamer and 40g of organic solvent to a drum ball mill jar 1. The mass ratio of ethanol to toluene in the organic solvent is 4:1. Ball mill for 18h to obtain mixture A. Then add 10g of organic solvent, 5g of polyvinyl butyral and 3g of phthalate to a ball mill jar 2. Ball mill for 10h to obtain mixture B. Then pour 180g of mixture B into 100g of mixture A and continue to mix and ball mill for 40h to obtain mixture C.

[0070] S2. Pour the mixture C into a vertical mixer and stir at a stirring rate of 400 r / min for 2 h. After filtration, pour it into a degassing tank for degassing treatment at a vacuum of 0.1 Pa, a temperature of 45 °C, a stirring rate of 600 r / min, and a degassing time of 100 min to obtain silicon nitride slurry.

[0071] S3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride blank with a thickness of 0.26 mm;

[0072] S4. The silicon nitride blank is subjected to air debonding at a temperature of 800℃ for 12 hours to obtain the debonded silicon nitride substrate.

[0073] S5. Using boron nitride as the first layer, a silicon nitride board with a thickness of 0.5 mm is placed on the boron nitride pad as the second layer. The silicon nitride substrate after debinding is then placed on the second layer. The first high-temperature sintering is performed under vacuum at a temperature of 1250℃ for 2.5 hours. The second high-temperature sintering is then performed under a nitrogen pressure of 0.5 MPa, with the temperature further increased to 1770℃ and held for 2 hours. The temperature is then reduced to 1600℃ at a cooling rate of 1℃ / min. After cooling, the in-sintering silicon nitride substrate is obtained.

[0074] Comparative Example 5:

[0075] S1. Add 100g of α-Si3N4 silicon nitride powder, 6g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 2.5g of polyvinylpyrrolidone, 1g of defoamer and 40g of organic solvent to a drum ball mill jar 1. The mass ratio of ethanol to toluene in the organic solvent is 4:1. Ball mill for 18h to obtain mixture A. Then add 10g of organic solvent, 5g of polyvinyl butyral and 3g of phthalate to a ball mill jar 2. Ball mill for 10h to obtain mixture B. Then pour 180g of mixture B into 100g of mixture A and continue to mix and ball mill for 40h to obtain mixture C.

[0076] S2. Pour the mixture C into a vertical mixer and stir at a stirring rate of 400 r / min for 2 h. After filtration, pour it into a degassing tank for degassing treatment at a vacuum of 0.1 Pa, a temperature of 45 °C, a stirring rate of 600 r / min, and a degassing time of 100 min to obtain silicon nitride slurry.

[0077] S3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride blank with a thickness of 0.26 mm;

[0078] S4. The silicon nitride blank is subjected to nitrogen debinding at a temperature of 820℃ for 10 hours to obtain the debinded silicon nitride substrate.

[0079] S5. Using boron nitride as the first layer, a silicon nitride board with a thickness of 0.5 mm is placed on the boron nitride pad as the second layer. The silicon nitride substrate after debinding is then placed on the second layer. The first high-temperature sintering is performed under vacuum at a temperature of 1250℃ for 2.5 hours. The second high-temperature sintering is then performed under a nitrogen pressure of 0.5 MPa, with the temperature further increased to 1770℃ and held for 2 hours. The temperature is then reduced to 1600℃ at a cooling rate of 1℃ / min. After cooling, the in-sintering silicon nitride substrate is obtained.

[0080] Performance testing:

[0081] Silicon nitride substrates were mass-produced according to the methods in Examples 1-4 and Comparative Examples 1-5, and their cracking rate was calculated.

[0082] Bending strength test:

[0083] The fracture toughness of the silicon nitride substrates prepared in Examples 1-4 and Comparative Examples 1-5 was tested using the three-point bending method. The equipment used was a Shimadzu AGS-X series testing machine. The sample dimensions were 3mm × 4mm × 36mm, the span was 30mm, and the indenter loading rate was 0.5mm / min. The bending strength of the samples was calculated using a formula.

[0084]

[0085] Where: R is the bending strength in MPa; F is the experimental load in N; L is the span between supports in mm; b is the width of the specimen in mm; and d is the specimen thickness parallel to the loading direction in mm.

[0086] Thermal conductivity test:

[0087] The thermal conductivity of the silicon nitride substrates prepared in Examples 1-4 and Comparative Examples 1-5 was tested using the transient planar heat source method. The equipment used was a Hot Disk TPS-2500-Si3N4 thermal conductivity meter.

[0088] Table 1

[0089]

[0090]

[0091] Data Analysis:

[0092] As shown in Table 1, the ready-to-sinter silicon nitride substrate prepared by this invention exhibits a lower cracking rate, higher thermal conductivity, and higher flexural strength. This is likely due to the segmented use of air and nitrogen debinding at specific temperatures, which allows for better removal of organic matter from the silicon nitride substrate, thereby enhancing its electrical conductivity and flexural strength. Furthermore, during high-temperature sintering, the first layer, a boron nitride pad, effectively isolates the individual silicon nitride substrates, preventing damage and overall performance degradation caused by adhesion during the high-temperature sintering process. With excellent thermal conductivity, the second layer is a silicon nitride plate, which can effectively isolate the indentation problem caused by the boron nitride pad, thereby reducing the formation of dark cracks in the silicon nitride substrate, lowering the breakage rate and overall performance. However, if the silicon nitride plate is too thin, it cannot effectively isolate the indentation caused by the boron nitride pad, and the cracking rate is not significantly improved. On the other hand, if the silicon nitride plate is too thick, its thermal conductivity is low, which will cause the temperature of the instant-burning silicon nitride substrate to rise in a stepwise manner, thereby affecting the density, thermal conductivity, compressive strength and other overall performance of the silicon nitride substrate, resulting in a higher cracking rate.

[0093] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0094] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A process for instant-fired silicon nitride substrates, characterized in that, Includes the following steps: Step A1. Add α-Si3N4 silicon nitride powder, sintering aid, dispersant, defoamer and organic solvent to a drum mill jar 1 and mill for 18-20 hours to obtain mixture A. Then add organic solvent, binder and plasticizer to a drum mill jar 2 and mill for 10-12 hours to obtain mixture B. Pour mixture B into mixture A and continue to mix and mill for 40-42 hours to obtain mixture C. Step A2. Pour mixture C into a vertical mixer for stirring, filter, pour into a degassing tank for degassing treatment, and obtain silicon nitride slurry; Step A3. The silicon nitride slurry is fed into a casting machine for casting to obtain a silicon nitride billet; Step A4. First, place the silicon nitride blank in an air environment for air debonding, and then perform nitrogen debonding in a nitrogen atmosphere to obtain the debonded silicon nitride substrate. Step A5. Using boron nitride with a thickness of 3.5-4mm as the first layer, place a silicon nitride board with a thickness of 0.5-0.6mm on the boron nitride pad as the second layer. Then place the silicon nitride substrate after debinding on the second layer and sinter at high temperature. Then, reduce the temperature to 1600℃ at a cooling rate of 1℃ / min. After cooling, the sinterable silicon nitride substrate is obtained.

2. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The sintering aid mentioned in step A1 is a mixture of yttrium oxide and magnesium oxide in a mass ratio of 1:3; The organic solvent is obtained by mixing ethanol and toluene in a mass ratio of 4-6:

1.

3. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The defoamer mentioned in step A1 is any one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and polydimethylsiloxane; The dispersant is polyvinylpyrrolidone; The adhesive is at least one of polyethylene glycol, polyvinyl butyral, and methyl acrylate. The plasticizer is any one of phthalate, polyethylene glycol, and glycerin.

4. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The particle size of the α-Si3N4 silicon nitride powder mentioned in step A1 is 0.5-1 μm; The mass ratio of the α-Si3N4 silicon nitride powder, sintering aid, dispersant, defoamer, and organic solvent is 100-130:6-12:2.5-4:1-2:40-55.

5. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The mass ratio of the organic solvent, binder, and plasticizer mentioned in step A1 is 10-15:5-8:3-7; The mass ratio of mixture A to mixture B is 100:180-210.

6. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The stirring rate in step A2 is 400-600 r / min, and the stirring time is 2-3 h; The vacuum degree during the degassing process is 0.1-0.5 Pa, the temperature is 45-55℃, the stirring rate is 600-800 r / min, and the degassing time is 100-120 min.

7. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The thickness of the silicon nitride blank in step A3 is 0.26-0.32 mm.

8. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The temperature for air removal of adhesive in step A4 is 500-600℃, and the heat preservation time is 12-14h.

9. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The nitrogen gas discharge temperature in step A4 is 820-1050℃, and the heat preservation time is 10-12h.

10. The instant-fire silicon nitride substrate process according to claim 1, characterized in that, The high-temperature sintering mentioned in step A5 includes a first high-temperature sintering and a second high-temperature sintering; The first high-temperature sintering is carried out under vacuum at a temperature of 1250-1380℃ for 2.5-3.5 hours. The second high-temperature sintering is carried out under nitrogen pressure of 0.5-3 MPa, and the temperature is further increased to 1770-1920℃ and held for 2-2.5 hours.

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