Instant-fired silicon nitride ceramic substrate and preparation method thereof

Abstract

The invention discloses an instant-fired silicon nitride ceramic substrate and a preparation method thereof, a roll-to-roll tape casting technology is adopted, boron nitride, silicon nitride and boron nitride are subjected to tape casting in sequence to obtain a thick film green tape with a boron nitride / silicon nitride / boron nitride three-layer structure, and finally, the instant-fired silicon nitride ceramic substrate with good flatness and high strength is prepared through glue discharging and sintering.

Description

Technical Field

[0001] The present application relates to the technical field of semiconductor ceramic substrates, and in particular to a ready-to-fire silicon nitride ceramic substrate and a preparation method thereof. Background Art

[0002] Silicon nitride ceramic substrates have excellent thermal conductivity, mechanical properties, low thermal expansion coefficient and high thermal shock resistance, and are one of the key alternative materials for high-power third-generation semiconductors. For ceramic substrates with large area and thin thickness, warping and edge bending are prone to occur after sintering, which may lead to problems such as uneven thickness or shape of the metallization layer or heating element, affecting its direct use. At present, production mainly uses secondary correction and grinding to ensure the flatness of ceramic substrates to meet the use requirements. The correction process is used to ensure the flatness of the substrate, that is, secondary sintering. The disadvantage is that it will cause secondary growth of grains, resulting in grain growth and reduced product flexural strength. Secondly, secondary sintering will lead to a decrease in production efficiency and an increase in labor and energy costs, which is not conducive to mass production and marketization of products. Most companies use grinding technology to ensure the flatness of the substrate, which requires sufficient grinding allowance to be reserved for the sintered product, thereby increasing the production and material costs of the product. When the ceramic substrate is large in size or thin in thickness, defects such as cracking and defects are prone to occur during the grinding process.

[0003] In view of this, this application is filed. Summary of the invention

[0004] The object of the present invention is to provide a ready-to-fire silicon nitride ceramic substrate and a preparation method thereof, which adopts roll-to-roll tape casting technology to sequentially tape boron nitride, silicon nitride, and boron nitride to obtain a thick film green ceramic tape with a three-layer structure of boron nitride / silicon nitride / boron nitride, and finally prepares a ready-to-fire silicon nitride ceramic substrate with good flatness and high strength through debinding and sintering.

[0005] In order to solve the above technical problems, the present invention adopts the following solutions:

[0006] A method for preparing a ready-to-fire silicon nitride ceramic substrate comprises the following steps:

[0007] Step 1: After preparing boron nitride slurry and silicon nitride slurry, respectively perform defoaming treatment to obtain boron nitride tape casting slurry and silicon nitride tape casting slurry;

[0008] Step 2: Roll-to-roll casting of boron nitride casting slurry, silicon nitride casting slurry, and boron nitride casting slurry to obtain a green porcelain tape;

[0009] Step 3: Post-processing: Debinding and sintering the green ceramic tape to obtain a ready-to-fire silicon nitride ceramic substrate.

[0010] Furthermore, when preparing the boron nitride slurry, by mass percentage, 60-65% of boron nitride powder, 5-10% of binder I, 1-5% of dispersant I, 1-5% of defoaming agent, and 25-35% of anhydrous ethanol are mixed and ball-milled for 10-20 hours.

[0011] Furthermore, the purity of the boron nitride powder is greater than 99.8%, and the average particle size D 50 The surface area is 15-25 μm and the specific surface area is 5-10 m 2 / g;

[0012] The binder I is one of polyvinyl butyral, methyl cellulose, ethyl cellulose and polyacrylic acid;

[0013] The dispersant I is one of polyacrylic acid salt, polyacrylamide, polyelectrolyte ammonium, and triolein;

[0014] The defoaming agent is one of polypropylene glycol, polysiloxane, isooctyl alcohol and diethylhexanol.

[0015] Furthermore, when preparing silicon nitride slurry, 55-60% silicon nitride powder, 5-10% sintering aid, 0.5-1.5% dispersant II, and 15-20% organic solvent are placed in a ball mill by weight percentage, and a dispersed slurry is obtained after one ball milling; 5-10% binder II and 1-5% plasticizer are placed in the dispersed ball material, and silicon nitride slurry is obtained after a second ball milling.

[0016] Furthermore, the purity of the silicon nitride powder is greater than 99.8%, and the average particle size D 50 The surface area is 0.4-0.8 μm and the specific surface area is 10-15 m 2 / g;

[0017] The sintering aid is a mixture of magnesium oxide and yttrium oxide, with an average particle size D 50 0.1~0.5μm, 1.0~1.5μm respectively;

[0018] The dispersant II is one of herring oil, castor oil and triethanolamine;

[0019] The binder II is one of polyvinyl butyral and methyl ethyl ketone;

[0020] The plasticizer is at least one of dibutyl phthalate and polyethylene glycol;

[0021] The organic solvent is at least two of toluene, isopropanol, anhydrous ethanol and xylene.

[0022] Furthermore, silicon nitride magnetic balls are added into the ball mill, the volume of the silicon nitride magnetic balls is 1 / 3 of the volume inside the ball mill, the rotation speed is 100-200 r / min, the first ball milling time is 10-20 h, and the second ball milling time is 20-30 h.

[0023] Furthermore, the viscosity of the boron nitride tape casting slurry is 1000-2000 cps, and the viscosity of the silicon nitride tape casting slurry is 5000-10000 cps.

[0024] Furthermore, the casting speed of the boron nitride casting slurry is 0.5-2 m / min, and the casting speed of the silicon nitride casting slurry is 0.1-2 m / min; the green porcelain tape is a three-layer structure of boron nitride / silicon nitride / boron nitride, with a total thickness of 0.4-1.0 mm, a thickness of boron nitride of 0.02-0.1 mm, and a thickness of silicon nitride of 0.4-1.0 mm.

[0025] Furthermore, during the debinding process, the temperature is 450-600°C, the heating rate is 0.5-2°C / min, and the holding time is 5-10h;

[0026] During sintering, the sintering temperature is 1700-1900°C, the heating rate is 1-5°C / min, and the holding time is 1-5h.

[0027] A ready-to-fire silicon nitride ceramic substrate is prepared by the above-mentioned preparation method of a ready-to-fire silicon nitride ceramic substrate. The silicon nitride ceramic substrate has a warpage of less than 3 / 1000, a flexural strength of more than 800 MPa, and a thermal conductivity of more than 80 W / mK.

[0028] The beneficial effects of the present invention are as follows: the present invention adopts roll-to-roll casting technology to replace the current traditional powder coating process, and casts a layer of boron nitride film on both sides of the silicon nitride thick film to obtain a thick film green porcelain tape with a three-layer structure of boron nitride / silicon nitride / boron nitride. The transformation process of the boron nitride slurry from a rheological body to a viscoelastic body improves the dispersion uniformity and stability of the boron nitride powder. At the same time, the reduction of the powder coating process not only reduces the harm of dust to the human body and reduces the process cost, but also reduces the introduction of residual stress and pollutants in the green body; the boron nitride film forms a layer of stable BN skeleton on both surfaces of the silicon nitride thick film, reduces the thermal stress of debinding sintering, and improves the warping defect; finally, a ready-to-fire silicon nitride substrate is prepared through debinding and sintering, and the warping degree is less than 3 / 1000, the flexural strength is greater than 800Mpa, and the thermal conductivity is greater than 80W / mK. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a physical picture of the silicon nitride ceramic substrate in Example 2;

[0030] Figure 2 This is a microscopic cross-sectional view of the silicon nitride ceramic substrate in Example 2. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Additionally, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness.One of ordinary skill in the art will recognize that various changes and modifications may be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0033] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0034] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0035] Preparation of boron nitride slurry: by mass percentage, 65% boron nitride powder, 5% polyvinyl butyral, 1.5% triolein, 2.5% polypropylene glycol, and 26% anhydrous ethanol were mixed, and the mixture was ball-milled at a speed of 50 r / min for 5 h to obtain boron nitride slurry.

[0036] Preparation of silicon nitride slurry: by mass percentage, 60% silicon nitride powder, 6% mixture of magnesium oxide and yttrium oxide (the mass ratio of magnesium oxide to yttrium oxide is 1:1), 1.5% castor oil, 19.5% toluene and anhydrous ethanol (the mass ratio of toluene to anhydrous ethanol is 1:2) are mixed and placed in a ball mill, 1 / 3 of the internal volume of the ball mill is added with silicon nitride ceramic balls, and silicon nitride dispersion slurry is obtained after a first ball milling at a speed of 200 r / min for 10 hours; then 10% polyvinyl butyral and 3% dibutyl phthalate are placed in the silicon nitride dispersion slurry, and silicon nitride slurry is obtained after a second ball milling at a speed of 100 r / min for 20 hours.

[0037] Degassing treatment: Place the silicon nitride slurry in degassing tank II, start the thermal cycle, control the temperature to 35°C, and evacuate to a vacuum degree of -98Kpa, start low-speed stirring at 20r / min for 4h until the slurry viscosity reaches 7000-8000cps, and finally age for 5h to obtain silicon nitride tape casting slurry; use this silicon nitride tape casting slurry to prepare the ready-to-fire silicon nitride ceramic substrate in Examples 1-4.

[0038] Example 1

[0039] A method for preparing a ready-to-fire silicon nitride ceramic substrate comprises the following steps:

[0040] (1) placing the boron nitride slurry in a degassing tank I, starting a thermal cycle, controlling the temperature to 20°C, evacuating to a vacuum degree of -98Kpa, stirring at a speed of 20r / min for 1h until the slurry viscosity reaches 1000cps, and finally aging for 2h to obtain a boron nitride tape casting slurry;

[0041] (2) Roll-to-roll casting was performed in sequence, and a 100-mesh screen was installed at the outlet of degassing tanks I and II, and the blade heads I and II of the casting machine were connected with plastic hoses respectively; first, the degassing tank I and the blade head I were connected for casting, and the scraper height was adjusted to 0.1-0.2 mm, the casting speed was 2 m / min, and the oven of the casting machine was divided into 5 temperature zones, and the gradient temperatures were set to 25, 45, 65, 85, and 100 °C, respectively. After drying, a boron nitride film with a thickness of 20 μm was finally obtained;

[0042] (3) Then switch to degassing tank II and blade II casting, adjust the scraper height to 0.5-1.0 mm, the casting speed to 0.5 m / min, and the oven temperature of the casting machine to 25, 45, 65, 85, and 100 ° C, respectively. After drying, a layer of silicon nitride thick film with a thickness of 0.4 mm is obtained on the surface of the boron nitride film;

[0043] (4) Then switch back to the degassing tank I and the cutter head I to cast another layer of boron nitride film with the same thickness as step (2), and finally obtain a green body of a boron nitride / silicon nitride / boron nitride structure with a thickness of 0.44 mm;

[0044] (5) The green body was cut into a size of 200*250 mm, and then debinding was performed, and the debinding temperature was set to 600°C, the heating rate was 0.5°C / min, and the holding time was 2h; finally, it was sintered at 1900°C under gas pressure, the heating rate was 5°C / min, and the holding time was 2h, and the ready-to-fire silicon nitride ceramic substrate was obtained.

[0045] The boron nitride film thickness of Example 1 was 20 μm, and the prepared ready-to-fire ceramic substrate showed adhesion, and separation resulted in substrate cracking, wherein the warpage was 5 / 1000, the flexural strength was 790 MPa, and the thermal conductivity was 80 W / mK.

[0046] Example 2

[0047] A method for preparing a ready-to-fire silicon nitride ceramic substrate comprises the following steps:

[0048] (1) placing the boron nitride slurry in a degassing tank I, starting a thermal cycle, controlling the temperature to 25°C, evacuating to a vacuum degree of -98 KPa, stirring at a speed of 20 r / min for 1 h until the slurry viscosity reaches 1200 cps, and finally aging for 2 h to obtain a boron nitride tape casting slurry;

[0049] (2) Roll-to-roll casting was performed in sequence, firstly connecting the degassing tank I and the blade head I for casting, adjusting the scraper height to 0.1-0.2 mm, the casting speed to 1.5 m / min, and setting the oven gradient temperature to 25, 45, 65, 85, and 100 °C, respectively, and finally obtaining a boron nitride film with a thickness of 40 μm after drying;

[0050] (3) Then switch to degassing tank II and blade II casting, adjust the scraper height to 0.5-1.0 mm, the casting speed to 0.5 m / min, and the oven temperature of the casting machine to 25, 45, 65, 85, and 100 ° C, respectively. After drying, a layer of silicon nitride thick film with a thickness of 0.4 mm is obtained on the surface of the boron nitride film;

[0051] (4) Then switch back to the degassing tank I and the cutter head I to cast another layer of boron nitride film with the same thickness as step (2), and finally obtain a green body of a boron nitride / silicon nitride / boron nitride structure with a thickness of 0.48 mm;

[0052] (5) The green body was cut into a size of 200*250 mm, and then debinding was performed, and the debinding temperature was set to 600°C, the heating rate was 0.5°C / min, and the holding time was 2h; finally, it was sintered at 1900°C under gas pressure, the heating rate was 5°C / min, and the holding time was 2h, and the ready-to-fire silicon nitride ceramic substrate was obtained.

[0053] The boron nitride film of Example 2 has a thickness of 40 μm, and the prepared ready-to-fire ceramic substrate has good flatness and no adhesion or cracking, wherein the warpage is 2 / 1000, the flexural strength is 820 MPa, and the thermal conductivity is 82 W / mK.

[0054] Example 3

[0055] A method for preparing a ready-to-fire silicon nitride ceramic substrate comprises the following steps:

[0056] (1) placing the boron nitride slurry in a degassing tank I, starting a thermal cycle, controlling the temperature to 30°C, evacuating to a vacuum degree of -98Kpa, stirring at a speed of 20r / min for 1h until the slurry viscosity reaches 1400cps, and finally aging for 2h to obtain a boron nitride tape casting slurry;

[0057] (2) Roll-to-roll casting was performed in sequence, firstly connecting the degassing tank I and the blade head I for casting, adjusting the scraper height to 0.1-0.2 mm, the casting speed to 1.0 m / min, and setting the oven gradient temperature to 25, 45, 65, 85, and 100 °C, respectively, and finally obtaining a boron nitride film with a thickness of 60 μm after drying;

[0058] (3) Then switch to degassing tank II and blade II casting, adjust the scraper height to 0.5-1.0 mm, the casting speed to 0.5 m / min, and the oven temperature of the casting machine to 25, 45, 65, 85, and 100 ° C, respectively. After drying, a layer of silicon nitride thick film with a thickness of 0.4 mm is obtained on the surface of the boron nitride film;

[0059] (4) Then switch back to the degassing tank I and the cutter head I to cast another layer of boron nitride film with the same thickness as step (2), and finally obtain a green body of a boron nitride / silicon nitride / boron nitride structure with a thickness of 0.52 mm;

[0060] (5) The green body was cut into a size of 200*250 mm, and then debinding was performed, and the debinding temperature was set to 600°C, the heating rate was 0.5°C / min, and the holding time was 2h; finally, it was sintered at 1900°C under gas pressure, the heating rate was 5°C / min, and the holding time was 2h, and the ready-to-fire silicon nitride ceramic substrate was obtained.

[0061] The boron nitride film of Example 3 has a thickness of 60 μm, and the prepared ready-to-fire ceramic substrate exhibits cracking and slight warping, wherein the warping degree is 8 / 1000, the flexural strength is 770 MPa, and the thermal conductivity is 81 W / mK.

[0062] Example 4

[0063] A method for preparing a ready-to-fire silicon nitride ceramic substrate comprises the following steps:

[0064] (1) placing the boron nitride slurry in a degassing tank I, starting a thermal cycle, controlling the temperature to 30°C, evacuating to a vacuum degree of -98Kpa, stirring at a speed of 20r / min for 1.5h until the slurry viscosity reaches 1600cps, and finally aging for 2h to obtain a boron nitride tape casting slurry;

[0065] (2) Roll-to-roll casting was performed in sequence, firstly connecting the degassing tank I and the blade head I for casting, adjusting the scraper height to 0.1-0.2 mm, the casting speed to 0.5 m / min, and setting the oven gradient temperature to 25, 45, 65, 85, and 100 °C, respectively, and finally obtaining a boron nitride film with a thickness of 80 μm after drying;

[0066] (3) Then switch to degassing tank II and blade II casting, adjust the scraper height to 0.5-1.0 mm, the casting speed to 0.5 m / min, and the oven temperature of the casting machine to 25, 45, 65, 85, and 100 ° C, respectively. After drying, a layer of silicon nitride thick film with a thickness of 0.4 mm is obtained on the surface of the boron nitride film;

[0067] (4) Then switch back to the degassing tank I and the cutter head I to cast another layer of boron nitride film with the same thickness as step (2), and finally obtain a green body of a boron nitride / silicon nitride / boron nitride structure with a thickness of 0.56 mm;

[0068] (5) The green body was cut into a size of 200*250 mm, and then debinding was performed, and the debinding temperature was set to 600°C, the heating rate was 0.5°C / min, and the holding time was 2h; finally, it was sintered at 1900°C under gas pressure, the heating rate was 5°C / min, and the holding time was 2h, and the ready-to-fire silicon nitride ceramic substrate was obtained.

[0069] The boron nitride film thickness of Example 4 is 80 μm, and the prepared ready-to-fire ceramic substrate has a large number of bulges, cracks and severe warping, wherein the warping degree is 15 / 1000, the flexural strength is 670 MPa, and the thermal conductivity is 78 W / mK.

[0070] Comparative Example 1

[0071] A method for preparing a silicon nitride ceramic substrate by a conventional powder coating process comprises the following steps:

[0072] (1) According to the mass percentage, 1% carboxymethyl cellulose, polyvinyl alcohol and 76% deionized water were mixed in a stirring box and stirred at a speed of 50 r / min for 1 hour to obtain a glue solution, and then 20% boron nitride powder and 3% herring oil were added to the glue solution and stirred for 2 hours to obtain a boron nitride powder slurry, and the speed was controlled to be 80 r / min.

[0073] (2) Turn on the powder coating machine, and convey the silicon nitride green body with a thickness of 0.4 mm to the inside of the atomizer through the powder coating machine conveyor belt. The boron nitride powder coating slurry is evenly atomized onto the surface of the green body through the atomizer, and then passed through a 60°C heating section to dry the boron nitride powder coating slurry and firmly adhere to the surface of the green body to obtain a single-sided powder coating layer with a thickness of 20 μm. The green body with one side coated is then turned over and coated on the other side to obtain a double-sided powder coating structure green body with a thickness of 0.44 mm.

[0074] (3) The powder coated green sheet is debinded at a debinding temperature of 600°C, a heating rate of 0.5°C / min, and a holding time of 2h; finally, it is subjected to gas pressure sintering at 1900°C, a heating rate of 5°C / min, and a holding time of 2h to obtain a silicon nitride ceramic substrate.

[0075] The boron nitride powder coating layer of Comparative Example 1 has a thickness of 20 μm, and the prepared silicon nitride ceramic substrate has partial pits and severe adhesion, with a warpage of 7 / 1000, a flexural strength of 720 MPa, and a thermal conductivity of 76 W / mK.

[0076] Comparative Example 2

[0077] A method for preparing a silicon nitride ceramic substrate by a conventional powder coating process comprises the following steps:

[0078] (1) According to the mass percentage, 2% carboxymethyl cellulose, polyvinyl alcohol and 75% deionized water were mixed in a stirring box and stirred at a speed of 50 r / min for 1 hour to obtain a glue solution, and then 20% boron nitride powder and 3% herring oil were added to the glue solution and stirred for 2 hours to obtain a boron nitride powder slurry, and the speed was controlled to be 80 r / min.

[0079] (2) Turn on the powder coating machine, and convey the silicon nitride green body with a thickness of 0.4 mm to the inside of the atomizer through the powder coating machine conveyor belt. The boron nitride powder coating slurry is evenly atomized onto the surface of the green body through the atomizer, and then passed through a 60°C heating section to dry the boron nitride powder and firmly adhere to the surface of the green body to obtain a single-sided powder coating layer with a thickness of 40 μm. The green body with one side coated is then turned over and coated on the other side to obtain a double-sided powder coating structure green body with a thickness of 0.48 mm.

[0080] (3) The powder coated green sheet is debinded at a debinding temperature of 600°C, a heating rate of 0.5°C / min, and a holding time of 2h; finally, it is subjected to gas pressure sintering at 1900°C, a heating rate of 5°C / min, and a holding time of 2h to obtain a silicon nitride ceramic substrate.

[0081] The boron nitride powder coating layer of Comparative Example 2 has a thickness of 40 μm, and the prepared silicon nitride ceramic substrate has partial pits, a small amount of adhesion and cracking, with a warpage of 4 / 1000, a flexural strength of 750 MPa, and a thermal conductivity of 77 W / mK.

[0082] Comparative Example 3

[0083] A method for preparing a silicon nitride ceramic substrate by a conventional powder coating process comprises the following steps:

[0084] (1) According to the mass percentage, 3% carboxymethyl cellulose, polyvinyl alcohol and 74% deionized water are mixed in a stirring box and stirred at a speed of 50 r / min for 1 hour to obtain a glue solution, and then 20% boron nitride powder and 3% herring oil are added to the glue solution and stirred for 2 hours to obtain a boron nitride powder slurry, and the speed is controlled to be 80 r / min.

[0085] (2) Turn on the powder coating machine, and convey the silicon nitride green body with a thickness of 0.4 mm to the inside of the atomizer through the powder coating machine conveyor belt. The boron nitride powder coating slurry is evenly atomized onto the surface of the green body through the atomizer, and then passed through a 60°C heating section to dry the boron nitride powder and firmly adhere to the surface of the green body to obtain a single-sided powder coating layer with a thickness of 60 μm. The green body with one side coated is then turned over and coated on the other side to obtain a double-sided powder coating structure green body with a thickness of 0.52 mm.

[0086] (3) The powder coated green sheet is debinded at a debinding temperature of 600°C, a heating rate of 0.5°C / min, and a holding time of 2h; finally, it is subjected to gas pressure sintering at 1900°C, a heating rate of 5°C / min, and a holding time of 2h to obtain a silicon nitride ceramic substrate.

[0087] The boron nitride powder coating layer of Comparative Example 3 has a thickness of 60 μm, and the prepared silicon nitride ceramic substrate has a large number of pits, dislocations and the like, wherein the warpage is 9 / 1000, the flexural strength is 710 MPa, and the thermal conductivity is 78 W / mK.

[0088] Comparative Example 4

[0089] A method for preparing a silicon nitride ceramic substrate by a conventional powder coating process comprises the following steps:

[0090] (1) According to the mass percentage, 4% carboxymethyl cellulose, polyvinyl alcohol and 73% deionized water were mixed in a stirring box and stirred at a speed of 50 r / min for 1 hour to obtain a glue solution, and then 20% boron nitride powder and 3% herring oil were added to the glue solution and stirred for 2 hours to obtain a boron nitride powder slurry, and the speed was controlled to be 80 r / min.

[0091] (2) Turn on the powder coating machine, and convey the silicon nitride green body with a thickness of 0.4 mm to the inside of the atomizer through the powder coating machine conveyor belt. The boron nitride powder coating slurry is evenly atomized onto the surface of the green body through the atomizer, and then passed through a 60°C heating section to dry the boron nitride powder and firmly adhere to the surface of the green body to obtain a single-sided powder coating layer with a thickness of 80 μm. The green body with one side coated is then turned over and coated on the other side to obtain a double-sided powder coating structure green body with a thickness of 0.56 mm.

[0092] (3) The powder coated green sheet is debinded at a debinding temperature of 600°C, a heating rate of 0.5°C / min, and a holding time of 2h; finally, it is subjected to gas pressure sintering at 1900°C, a heating rate of 5°C / min, and a holding time of 2h to obtain a silicon nitride ceramic substrate.

[0093] The boron nitride powder coating layer of Comparative Example 4 has a thickness of 80 μm, and the prepared silicon nitride ceramic substrate exhibits severe warping, wherein the warping degree is 20 / 1000, the flexural strength is 650 MPa, and the thermal conductivity is 74 W / mK.

[0094] The performance comparison of the silicon nitride ceramic substrates prepared in the examples and comparative examples of the present application is shown in Table 1:

[0095] Table 1 Performance comparison table of embodiments and comparative examples

[0096]

[0097] Referring to Table 1, compared with the double-sided dressing of the silicon nitride green embryo in the conventional dressing method in Comparative Examples 1-4, the silicon nitride ceramic substrate prepared in Example 2 has the smallest warpage, high flexural strength and thermal conductivity, and no adhesion or cracking. Figure 1 and Figure 2 .

[0098] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a ready-to-fire silicon nitride ceramic substrate, characterized in that: The following steps are involved: Step 1: After preparing boron nitride slurry and silicon nitride slurry, respectively perform defoaming treatment to obtain boron nitride tape casting slurry and silicon nitride tape casting slurry; Step 2: Roll-to-roll casting of boron nitride casting slurry, silicon nitride casting slurry, and boron nitride casting slurry to obtain a green porcelain tape; Step 3: Post-processing: Debinding and sintering the green ceramic tape to obtain a ready-to-fire silicon nitride ceramic substrate.

2. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 1, characterized in that: When preparing the boron nitride slurry, according to mass percentage, 60-65% of boron nitride powder, 5-10% of binder I, 1-5% of dispersant I, 1-5% of defoaming agent, and 25-35% of anhydrous ethanol are mixed and ball-milled for 10-20 hours.

3. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 2, characterized in that: The purity of the boron nitride powder is greater than 99.8%, and the average particle size D 50 The surface area is 15-25 μm and the specific surface area is 5-10 m 2 / g; The binder I is one of polyvinyl butyral, methyl cellulose, ethyl cellulose and polyacrylic acid; The dispersant I is one of polyacrylate, polyacrylamide, polyelectrolyte ammonium, and triolein; The defoaming agent is one of polypropylene glycol, polysiloxane, isooctyl alcohol and diethylhexanol.

4. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 2, characterized in that: When preparing silicon nitride slurry, 55-60% silicon nitride powder, 5-10% sintering aid, 0.5-1.5% dispersant II, and 15-20% organic solvent are placed in a ball mill by weight percentage, and a dispersed slurry is obtained after one ball milling; 5-10% binder II and 1-5% plasticizer are placed in the dispersed ball material, and silicon nitride slurry is obtained after a second ball milling.

5. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 4, characterized in that: The purity of the silicon nitride powder is greater than 99.8%, and the average particle size D 50 The surface area is 0.4-0.8 μm and the specific surface area is 10-15 m 2 / g; The sintering aid is a mixture of magnesium oxide and yttrium oxide, with an average particle size D 50 0.1~0.5μm, 1.0~1.5μm respectively; The dispersant II is one of herring oil, castor oil and triethanolamine; The binder II is one of polyvinyl butyral and methyl ethyl ketone; The plasticizer is at least one of dibutyl phthalate and polyethylene glycol; The organic solvent is at least two of toluene, isopropanol, anhydrous ethanol and xylene.

6. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 4, characterized in that: Add silicon nitride magnetic balls into the ball mill, the volume of the silicon nitride magnetic balls is 1 / 3 of the inside of the ball mill, the rotation speed is 100-200r / min, the first ball milling time is 10-20h, and the second ball milling time is 20-30h.

7. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 4, characterized in that: The viscosity of the boron nitride tape-casting slurry is 1000-2000 cps, and the viscosity of the silicon nitride tape-casting slurry is 5000-10000 cps.

8. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 4, characterized in that: The casting speed of the boron nitride casting slurry is 0.5-2 m / min, and the casting speed of the silicon nitride casting slurry is 0.1-2 m / min; the green porcelain tape is a three-layer structure of boron nitride / silicon nitride / boron nitride, with a total thickness of 0.4-1.0 mm, a thickness of boron nitride of 0.02-0.1 mm, and a thickness of silicon nitride of 0.4-1.0 mm.

9. The method for preparing a ready-to-fire silicon nitride ceramic substrate according to claim 4, characterized in that: During debinding, the temperature is 450-600℃, the heating rate is 0.5-2℃ / min, and the holding time is 5-10h; During sintering, the sintering temperature is 1700-1900°C, the heating rate is 1-5°C / min, and the holding time is 1-5h.

10. A ready-to-fire silicon nitride ceramic substrate, characterized in that: The silicon nitride ceramic substrate is made by the preparation method of any one of claims 1 to 9, wherein the warpage of the silicon nitride ceramic substrate is less than 3 / 1000, the flexural strength is greater than 800Mpa, and the thermal conductivity is greater than 80W / mK.

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