Instant sintering type silicon nitride substrate process

Abstract

The invention relates to the technical field of ceramic materials, in particular to an instant-firing type silicon nitride substrate process, an instant-firing type silicon nitride substrate is prepared by mixing alpha-Si3N4 silicon nitride powder and other auxiliaries according to a specific proportion, ball-milling, tape casting, glue discharging and sintering, glue discharging comprises air glue discharging and nitrogen glue discharging, and the sintering temperature is controlled to be 30-50 DEG C; organic matters in the silicon nitride substrate can be better removed, and a better glue discharging effect is achieved; in the high-temperature sintering process, two layers of base plates, namely the boron nitride base plate and the silicon nitride plate, are arranged below the silicon nitride base plate subjected to glue removal, so that on one hand, damage and comprehensive performance reduction caused by adhesion in the high-temperature sintering process can be avoided, good heat conduction capability is achieved, and on the other hand, the indentation problem generated by the boron nitride base plate can be effectively isolated; compared with the prior art, the method has the advantages that the method is wide in application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic materials, and in particular to a ready-to-fire silicon nitride substrate process. Background Art

[0002] The balance between energy and environment is a difficult problem that human development must face. Using electricity instead of traditional fossil fuels can solve the problem of fossil fuel shortage and the problem of polluting gases. Energy tends to shift from fossil fuels to electricity, so the development of power electronics technology is particularly important. Nowadays, power electronics technology has been widely used in high-speed trains, new energy vehicles, wind power generation and other fields. In order to seek more efficient power control and conversion technology, electronic devices are moving towards high voltage, high current and high 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 large thermal stresses, which poses great challenges to the assembly and packaging materials of the devices, especially the brittle ceramic substrates that provide electrical insulation and heat dissipation. Therefore, ceramic substrates used for 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 excellent performance characteristics. Their main performance advantages are reflected in many aspects: excellent thermal conductivity. High thermal conductivity can provide higher heat dissipation efficiency, ensure the stable operation of power devices in high temperature environments, and increase the service life of devices; stable and excellent mechanical properties. Ensure the reliability of power device operation; good insulation and electrical breakdown capabilities, which ensure the safety of power devices in high-voltage and high-current working environments; expansion coefficient close to the thermal expansion coefficient of the SiC substrate. During work, the large difference in expansion coefficients is prone to stress accumulation; good high-frequency characteristics; high surface flatness and smoothness, which facilitates the printing of circuits on the substrate surface, increasing the accuracy of circuit printing and operational reliability.

[0005] In the prior art, the preparation process of silicon nitride substrates is generally ball milling, slurrying, tape casting, debinding and sintering of raw materials. For example, patent technical document CN106631039A discloses a method for preparing a silicon nitride ceramic substrate, comprising the following steps: mixing silicon powder, silicon nitride powder, sintering aid and dispersant, adding solvent, performing the first ball milling, adding adhesive and plasticizer, performing the second ball milling, and obtaining slurry after vacuum degassing; tape casting the slurry, drying it to obtain a blank, and obtaining a green blank after vacuum debinding; sintering the green blank to obtain a silicon nitride ceramic substrate; the invention uses silicon nitride powder and low-cost silicon powder as the main raw materials and adopts tape casting process to obtain a low-cost silicon nitride ceramic substrate. The silicon nitride substrate prepared by this method still needs to be polished and ground, but dark cracks are easily generated during the second grinding process, which affects the final comprehensive performance of the product, resulting in substrate breakage and serious raw material loss.

[0006] Therefore, according to the above-mentioned related technologies, it is urgent to develop a ready-to-fire silicon nitride substrate process. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a sintered silicon nitride substrate process to solve the problem of easy breakage of the polished substrate in the prior art.

[0008] Based on the above purpose, the present invention provides a ready-to-fire silicon nitride substrate process.

[0009] A ready-to-fire silicon nitride substrate process comprises the following steps:

[0010] Step A1. Add α-Si3N4 silicon nitride powder, sintering aid, dispersant, defoamer and organic solvent to roller ball mill 1, ball mill for 18-20 hours to obtain mixture A, then add organic solvent, binder and plasticizer to ball mill 2, ball mill for 10-12 hours to obtain mixture B, then pour mixture B into mixture A, continue mixing and ball milling for 40-42 hours to obtain mixture C;

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

[0012] Step A3. introducing the silicon nitride slurry into a tape casting machine for tape casting to obtain a silicon nitride blank;

[0013] Step A4. placing the silicon nitride blank in an air environment for air debinding, and then performing nitrogen debinding in a nitrogen atmosphere to obtain a debinded silicon nitride substrate;

[0014] Step A5. Use a boron nitride plate with a thickness of 3.5-4 mm as the first layer of pad, place a silicon nitride plate with a thickness of 0.5-0.6 mm on the boron nitride pad as the second layer of pad, and then place the silicon nitride substrate after debinding on the second layer of pad, sinter at high temperature, and then reduce the temperature to 1600°C at a cooling rate of 1°C / min. After cooling, a ready-to-fire silicon nitride substrate is obtained.

[0015] Preferably, the sintering aid 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 defoaming agent in step A1 is any one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and polydimethylsiloxane;

[0018] The dispersant is polyvinyl pyrrolidone;

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

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

[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, the binder, and the plasticizer in step A1 is 10-15:5-8:3-7;

[0024] The mass ratio of the mixture A to the 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 treatment is 0.1-0.5 Pa, the temperature is 45-55° C., 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 air debinding temperature in step A4 is 500-600° C., and the insulation time is 12-14 hours.

[0029] Preferably, the temperature of the nitrogen debinding in step A4 is 820-1050° C., and the holding time is 10-12 h.

[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° C. for 2.5-3.5 hours;

[0032] The second high-temperature sintering is carried out under a nitrogen pressure of 0.5-3 MPa, and the temperature is continued to rise to 1770-1920° C. and kept at this temperature for 2-2.5 hours.

[0033] Beneficial effects of the present invention:

[0034] The invention provides a process for a ready-to-fire silicon nitride substrate. The invention prepares a ready-to-fire silicon nitride substrate by mixing α-Si3N4 silicon nitride powder and other additives in a specific proportion, ball milling, casting, debinding and sintering. Debinding includes air debinding and nitrogen debinding, so that organic matter in the silicon nitride substrate can be better removed under a certain temperature and a certain atmosphere, thereby achieving a better debinding effect. During high-temperature sintering, there are two layers of pads under the silicon nitride substrate after debinding, namely a boron nitride pad and a silicon nitride plate. The boron nitride pad can effectively isolate each silicon nitride substrate, thereby avoiding damage and degradation of comprehensive performance due to adhesion during high-temperature sintering, and has good thermal conductivity, while the silicon nitride plate can effectively isolate the indentation problem caused by the boron nitride pad, thereby reducing the generation of dark cracks in the silicon nitride substrate, reducing the rupture rate and comprehensive performance. Compared with the prior art, it has broad application prospects. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

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

[0037] Polyvinyl pyrrolidone 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 Plastic Technology Co., Ltd.; phthalates were purchased from Sinopharm Chemical Reagent Beijing Co., Ltd.; and toluene was purchased from Sinopec Chemical Sales Co., Ltd. Central China Branch.

[0038] Embodiment 1: A process for preparing a ready-to-fire silicon nitride substrate, comprising the following steps:

[0039] S1. 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 polyvinyl pyrrolidone, 1g of a defoamer and 40g of an organic solvent were added to a roller ball mill jar 1, where the mass ratio of ethanol to toluene in the organic solvent was 4:1, and ball milled for 18h to obtain a mixture A, and then 10g of an organic solvent, 5g of polyvinyl butyral and 3g of phthalate were added to a ball mill jar 2, and ball milled for 10h to obtain a mixture B, and then 180g of the mixture B was poured into 100g of the mixture A, and the mixing and ball milling was continued for 40h to obtain a mixture C;

[0040] S2. The mixture C was poured into a vertical mixer and stirred at a stirring rate of 400 r / min for 2 h. After filtering, it was poured into a degassing tank for degassing at a vacuum degree 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 a silicon nitride slurry;

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

[0042] S4. The silicon nitride blank is first placed in an air environment for air debinding at a temperature of 500°C for a holding time of 12 hours, and then nitrogen debinding is performed in a nitrogen atmosphere at a temperature of 820°C for a holding time of 10 hours to obtain a silicon nitride substrate after debinding;

[0043] S5. Use a 3.5mm thick boron nitride pad as the first pad, place a 0.5mm thick silicon nitride plate on the boron nitride pad as the second pad, and then place the debinded silicon nitride substrate on the second pad. Perform the first high-temperature sintering under vacuum at a temperature of 1250°C for 2.5 hours, and then perform the second high-temperature sintering under a nitrogen pressure of 0.5MPa. Continue to raise the temperature to 1770°C and keep it for 2 hours. Then, reduce the temperature to 1600°C at a cooling rate of 1°C / min. After cooling, the ready-to-fire silicon nitride substrate is obtained.

[0044] Embodiment 2: A process for preparing a ready-to-fire silicon nitride substrate, comprising the following steps:

[0045] S1. 110 g of α-Si3N4 silicon nitride powder, 8 g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 3 g of polyvinyl pyrrolidone, 1.5 g of a defoamer and 45 g of an organic solvent were added to a roller ball mill jar 1, where the mass ratio of ethanol to toluene in the organic solvent was 5:1, and the mixture was ball milled for 19 h to obtain a mixture A. 12 g of an organic solvent, 6 g of polyvinyl butyral and 4 g of phthalate were added to a ball mill jar 2, and the mixture was ball milled for 11 h to obtain a mixture B. 190 g of the mixture B was poured into 100 g of the mixture A, and the mixture was mixed and ball milled for 41 h to obtain a mixture C.

[0046] S2. The mixture C was poured into a vertical mixer and stirred at a stirring rate of 500 r / min for 2.5 h. After filtering, it was poured into a degassing tank for degassing at a vacuum degree 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 a silicon nitride slurry;

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

[0048] S4. The silicon nitride blank was first placed in an air environment for air debinding at a temperature of 540°C for a holding time of 13 hours, and then nitrogen debinding was performed in a nitrogen atmosphere at a temperature of 900°C for a holding time of 11 hours to obtain a silicon nitride substrate after debinding;

[0049] S5. Use a 3.5mm thick boron nitride pad as the first pad, place a 0.53mm thick silicon nitride plate on the boron nitride pad as the second pad, and then place the debinded silicon nitride substrate on the second pad. Perform the first high-temperature sintering under vacuum at a temperature of 1300°C for 3 hours, and then perform the second high-temperature sintering under a nitrogen pressure of 1MPa. Continue to raise the temperature to 1820°C and keep it for 2 hours. Then, reduce the temperature to 1600°C at a cooling rate of 1°C / min. After cooling, the ready-to-fire silicon nitride substrate is obtained.

[0050] Embodiment 3: A process for preparing a ready-to-fire silicon nitride substrate, comprising the following steps:

[0051] S1. 120 g of α-Si3N4 silicon nitride powder, 10 g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 3.5 g of polyvinyl pyrrolidone, 1.5 g of a defoaming agent and 50 g of an organic solvent were added to a roller ball mill jar 1, where the mass ratio of ethanol to toluene in the organic solvent was 5:1, and the mixture was ball milled for 19.5 h to obtain a mixture A. 14 g of an organic solvent, 7 g of polyvinyl butyral and 5 g of phthalate were added to a ball mill jar 2, and the mixture was ball milled for 11.5 h to obtain a mixture B. 200 g of the mixture B was poured into 100 g of the mixture A, and the mixture was mixed and ball milled for 41.5 h to obtain a mixture C.

[0052] S2. The mixture C was poured into a vertical mixer and stirred at a stirring rate of 550 r / min for 2.5 h. After filtering, it was poured into a degassing tank for degassing at a vacuum degree 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 a silicon nitride slurry;

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

[0054] S4. The silicon nitride blank is first placed in an air environment for air debinding at a temperature of 580°C for a holding time of 13.5 hours, and then nitrogen debinding is performed in a nitrogen atmosphere at a temperature of 980°C for a holding time of 11.5 hours to obtain a silicon nitride substrate after debinding;

[0055] S5. Use a 4mm thick boron nitride pad as the first pad, place a 0.57mm thick silicon nitride plate on the boron nitride pad as the second pad, and then place the debinded silicon nitride substrate on the second pad. Perform the first high-temperature sintering under vacuum at a temperature of 1320°C for 3 hours, and then perform the second high-temperature sintering under a nitrogen pressure of 2MPa. Continue to raise the temperature to 1870°C and keep it for 2.5 hours. Then, reduce the temperature to 1600°C at a cooling rate of 1°C / min. After cooling, the ready-to-fire silicon nitride substrate is obtained.

[0056] Embodiment 4: A process for preparing a ready-to-fire silicon nitride substrate, comprising the following steps:

[0057] S1. 130 g of α-Si3N4 silicon nitride powder, 12 g of yttrium oxide and magnesium oxide mixed in a mass ratio of 1:3 to obtain a sintering aid, 4 g of polyvinyl pyrrolidone, 2 g of a defoamer and 55 g of an organic solvent were added to a roller ball mill jar 1, where the mass ratio of ethanol to toluene in the organic solvent was 6:1, and the mixture was ball milled for 20 h to obtain a mixture A. Then 15 g of an organic solvent, 8 g of polyvinyl butyral and 7 g of phthalate were added to a ball mill jar 2, and the mixture was ball milled for 12 h to obtain a mixture B. Then 210 g of the mixture B was poured into 100 g of the mixture A, and the mixing and ball milling was continued for 42 h to obtain a mixture C.

[0058] S2. The mixture C was poured into a vertical mixer and stirred at a stirring rate of 600 r / min for 3 h. After filtering, it was poured into a degassing tank for degassing at a vacuum degree 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 a silicon nitride slurry;

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

[0060] S4. The silicon nitride blank is first placed in an air environment for air debinding at a temperature of 600°C for a holding time of 14 hours, and then nitrogen debinding is performed in a nitrogen atmosphere at a temperature of 1050°C for a holding time of 12 hours to obtain a silicon nitride substrate after debinding;

[0061] S5. Use a 4mm thick boron nitride pad as the first pad, place a 0.6mm thick silicon nitride board on the boron nitride pad as the second pad, and then place the debinded silicon nitride substrate on the second pad. Perform the first high-temperature sintering under vacuum at a temperature of 1380°C for 3.5 hours, and then perform the second high-temperature sintering under a nitrogen pressure of 3MPa. Continue to raise the temperature to 1920°C and keep it for 2.5 hours. Then, reduce the temperature to 1600°C at a cooling rate of 1°C / min. After cooling, the ready-to-fire silicon nitride substrate is obtained.

[0062] Comparative Example 1:

[0063] Compared with Example 1, this comparative example did not add a second layer of silicon nitride plate with a thickness of 0.5 mm during the high-temperature sintering process. The remaining steps and parameters were the same and will not be repeated in this comparative example. Finally, a ready-to-fire 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", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a ready-to-fire 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", and the remaining steps and parameters are the same, which will not be repeated in this comparative example, and finally a ready-to-fire silicon nitride substrate is obtained.

[0068] Comparative Example 4:

[0069] S1. 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 polyvinyl pyrrolidone, 1g of a defoamer and 40g of an organic solvent were added to a roller ball mill jar 1, where the mass ratio of ethanol to toluene in the organic solvent was 4:1, and ball milled for 18h to obtain a mixture A, and then 10g of an organic solvent, 5g of polyvinyl butyral and 3g of phthalate were added to a ball mill jar 2, and ball milled for 10h to obtain a mixture B, and then 180g of the mixture B was poured into 100g of the mixture A, and the mixing and ball milling was continued for 40h to obtain a mixture C;

[0070] S2. The mixture C was poured into a vertical mixer and stirred at a stirring rate of 400 r / min for 2 h. After filtering, it was poured into a degassing tank for degassing at a vacuum degree 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 a silicon nitride slurry;

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

[0072] S4. Debinding the silicon nitride blank in air at a temperature of 800° C. for a holding time of 12 h to obtain a debinding silicon nitride substrate;

[0073] S5. Boron nitride is used as the first layer of pad, and a silicon nitride plate with a thickness of 0.5 mm is placed on the boron nitride pad as the second layer of pad, and then the silicon nitride substrate after debinding is placed on the second layer of pad. The first high-temperature sintering is carried out under vacuum at a temperature of 1250°C, and the temperature is kept for 2.5 hours. Then, the second high-temperature sintering is carried out under a nitrogen pressure of 0.5 MPa, and the temperature is continued to be raised to 1770°C, and the temperature is kept for 2 hours. Then, the temperature is reduced to 1600°C at a cooling rate of 1°C / min. After cooling, the ready-to-fire silicon nitride substrate is obtained.

[0074] Comparative Example 5:

[0075] S1. 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 polyvinyl pyrrolidone, 1g of a defoamer and 40g of an organic solvent were added to a roller ball mill jar 1, where the mass ratio of ethanol to toluene in the organic solvent was 4:1, and ball milled for 18h to obtain a mixture A, and then 10g of an organic solvent, 5g of polyvinyl butyral and 3g of phthalate were added to a ball mill jar 2, and ball milled for 10h to obtain a mixture B, and then 180g of the mixture B was poured into 100g of the mixture A, and the mixing and ball milling was continued for 40h to obtain a mixture C;

[0076] S2. The mixture C was poured into a vertical mixer and stirred at a stirring rate of 400 r / min for 2 h. After filtering, it was poured into a degassing tank for degassing at a vacuum degree 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 a silicon nitride slurry;

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

[0078] S4. Debinding the silicon nitride blank with nitrogen at a temperature of 820° C. for a holding time of 10 h to obtain a debinding silicon nitride substrate;

[0079] S5. Boron nitride is used as the first layer of pad, and a silicon nitride plate with a thickness of 0.5 mm is placed on the boron nitride pad as the second layer of pad, and then the silicon nitride substrate after debinding is placed on the second layer of pad. The first high-temperature sintering is carried out under vacuum at a temperature of 1250°C, and the temperature is kept for 2.5 hours. Then, the second high-temperature sintering is carried out under a nitrogen pressure of 0.5 MPa, and the temperature is continued to be raised to 1770°C, and the temperature is kept for 2 hours. Then, the temperature is reduced to 1600°C at a cooling rate of 1°C / min. After cooling, the ready-to-fire silicon nitride substrate is obtained.

[0080] Performance Testing:

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

[0082] Bending strength test:

[0083] The fracture toughness tests of the silicon nitride substrates prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were all tested using the three-point bending method, using a Shimadzu AGS-X series testing machine, with sample specifications of 3mm×4mm×36mm, a span of 30mm, and a pressure head loading rate of 0.5mm / min. The flexural strength of the sample was calculated using the formula;

[0084]

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

[0086] Thermal conductivity test:

[0087] The thermal conductivity tests of the silicon nitride substrates prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were all conducted using a transient plane heat source method, and the equipment used was a TPS-2500-Si3N4 thermal conductivity meter from Hot Disk.

[0088] Table 1

[0089]

[0090]

[0091] Data Analysis:

[0092] It can be seen from Table 1 that the ready-to-fire silicon nitride substrate prepared by the present invention has a lower cracking rate, higher thermal conductivity and bending strength. This may be due to the use of air debinding and nitrogen debinding in stages at a specific temperature, which can better remove organic matter in the silicon nitride substrate, thereby enhancing the conductivity and bending strength of silicon nitride. In addition, during high-temperature sintering, the first layer of boron nitride pad can effectively isolate each silicon nitride substrate, thereby avoiding damage and degradation of comprehensive performance due to adhesion during high-temperature sintering. Good 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 dark cracks in the silicon nitride substrate, reducing the rupture rate and comprehensive performance. A silicon nitride plate that is too thin cannot effectively isolate the indentation caused by the boron nitride pad, and the crack rate is not greatly improved. A silicon nitride plate that is too thick has low thermal conductivity, which will cause the ready-to-fire silicon nitride substrate to rise in a step-by-step manner when heated, thereby affecting the density of the silicon nitride substrate and the decline in comprehensive performance such as thermal conductivity and compressive strength, and the crack rate is also high.

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

[0094] The present 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 the present invention should be included in the scope of protection of the present invention.

Claims

1. A ready-to-fire silicon nitride substrate process, characterized in that: The following steps are involved: Step A1. Add α-Si3N4 silicon nitride powder, sintering aid, dispersant, defoamer and organic solvent to roller ball mill 1, ball mill for 18-20 hours to obtain mixture A, then add organic solvent, binder and plasticizer to ball mill 2, ball mill for 10-12 hours to obtain mixture B, then pour mixture B into mixture A, continue mixing and ball milling for 40-42 hours to obtain mixture C; Step A2. Pour the mixture C into a vertical mixer for stirring, filter, and then pour into a degassing tank for degassing to obtain silicon nitride slurry; Step A3. introducing the silicon nitride slurry into a tape casting machine for tape casting to obtain a silicon nitride blank; Step A4. placing the silicon nitride blank in an air environment for air debinding, and then performing nitrogen debinding in a nitrogen atmosphere to obtain a debinded silicon nitride substrate; Step A5. Use a boron nitride plate with a thickness of 3.5-4 mm as the first layer of pad, place a silicon nitride plate with a thickness of 0.5-0.6 mm on the boron nitride pad as the second layer of pad, and then place the silicon nitride substrate after debinding on the second layer of pad, sinter at high temperature, and then reduce the temperature to 1600°C at a cooling rate of 1°C / min. After cooling, a ready-to-fire silicon nitride substrate is obtained.

2. The ready-to-fire silicon nitride substrate process according to claim 1, characterized in that: The sintering aid 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 ready-to-fire silicon nitride substrate process according to claim 1, characterized in that: The defoaming agent in step A1 is any one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether and polydimethylsiloxane; The dispersant is polyvinyl pyrrolidone; The binder is at least one of polyethylene glycol, polyvinyl butyral, and methyl acrylate; The plasticizer is any one of phthalate, polyethylene glycol and glycerol.

4. The ready-to-fire silicon nitride substrate process according to claim 1, characterized in that: The particle size of the α-Si3N4 silicon nitride powder 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 process for preparing a ready-to-fire silicon nitride substrate according to claim 1, characterized in that: The mass ratio of the organic solvent, the binder and the plasticizer in step A1 is 10-15:5-8:3-7; The mass ratio of the mixture A to the mixture B is 100:180-210.

6. The ready-to-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 treatment is 0.1-0.5 Pa, the temperature is 45-55° C., the stirring rate is 600-800 r / min, and the degassing time is 100-120 min.

7. The ready-to-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 ready-to-fire silicon nitride substrate process according to claim 1, characterized in that: The air debinding temperature in step A4 is 500-600° C., and the holding time is 12-14 hours.

9. The process for preparing a ready-to-fire silicon nitride substrate according to claim 1, characterized in that: The temperature of nitrogen debinding in step A4 is 820-1050° C., and the holding time is 10-12 hours.

10. The ready-to-fire silicon nitride substrate process according to claim 1, characterized in that: The high temperature sintering 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° C. for 2.5-3.5 hours; The second high-temperature sintering is carried out under a nitrogen pressure of 0.5-3 MPa, and the temperature is continued to rise to 1770-1920° C. and kept at this temperature for 2-2.5 hours.

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