Preparation method of silicon nitride ceramic substrate and silicon nitride ceramic substrate

Abstract

The invention relates to a preparation method of a silicon nitride ceramic substrate and the silicon nitride ceramic substrate. The preparation method of the silicon nitride ceramic substrate comprises the following steps: preparing slurry by using silicon-based powder, a sintering aid and a dispersion medium; wherein the sintering aid comprises magnesium oxide sol, and the sintering aid further comprises at least one of rare earth oxide sol; carrying out tape casting on the slurry to obtain a green sheet; and sintering the green blank sheet in a nitrogen atmosphere. According to the preparation method of the silicon nitride ceramic substrate, the slurry is prepared by using the sintering aid comprising the magnesium oxide sol and the rare earth oxide sol, the silicon-based powder and the dispersion medium, silicon nitride powder and sintering aid particles in the slurry are relatively uniformly dispersed and are not easy to agglomerate, and a relatively uniformly dispersed green sheet can be obtained through tape casting; therefore, the strength consistency of different areas of the prepared silicon nitride ceramic substrate is relatively good, and the discreteness is relatively small.

Description

Technical Field

[0001] The present application relates to the technical field of silicon nitride ceramics, and particularly to a preparation method of a silicon nitride ceramic substrate and a silicon nitride ceramic substrate. Background Art

[0002] Silicon nitride ceramic substrates have excellent physical and chemical properties and show broad application potential in multiple high-tech fields. In the field of new energy vehicles, silicon nitride substrates are crucial for improving battery thermal management performance. Tape casting, as a commonly used method for producing silicon nitride ceramic substrates, usually prepares a slurry with a certain viscosity and rheology from silicon raw materials and sintering aids, and obtains a silicon nitride ceramic substrate through tape casting, cutting, debinding, and sintering.

[0003] However, in traditional preparation methods, it is difficult to uniformly disperse silicon raw material powders and sintering aid particles in the slurry, and agglomeration is likely to occur, resulting in an unevenly dispersed green sheet after tape casting, and further leading to problems of poor consistency and large discreteness in the strength of different regions of the prepared silicon nitride ceramic substrate. Summary of the Invention

[0004] Based on this, it is necessary to provide a preparation method of a silicon nitride ceramic substrate and a silicon nitride ceramic substrate. In the preparation method of the silicon nitride ceramic substrate of the present application, the silicon nitride powder and sintering aid particles in the slurry are relatively uniformly dispersed, not easily agglomerated, and a relatively uniformly dispersed green sheet can be obtained by tape casting, and further, the consistency of the strength of different regions of the prepared silicon nitride ceramic substrate can be better and the discreteness can be smaller.

[0005] In a first aspect, the present application provides a preparation method of a silicon nitride ceramic substrate, including the following steps:

[0006] Preparing a slurry using a silicon-based powder, a sintering aid, and a dispersion medium; wherein, the sintering aid includes magnesium oxide sol, and the sintering aid further includes at least one of rare earth oxide sols;

[0007] Obtaining a green sheet by tape casting the slurry;

[0008] Performing a sintering treatment on the green sheet in a nitrogen atmosphere.

[0009] In some embodiments, the molar percentage of magnesium element in the magnesium oxide sol in the silicon element in the silicon-based powder is 5% - 10%.

[0010] In some embodiments, the molar percentage of rare earth element in the rare earth oxide sol in the silicon element in the silicon-based powder is 1% - 8%.

[0011] In some of these embodiments, the silicon-based powder includes at least one of silicon powder and silicon nitride powder.

[0012] In some of these embodiments, in the magnesium oxide sol, the mass percentage of magnesium oxide in the magnesium oxide sol is 8% - 20%.

[0013] In some of these embodiments, in the rare earth oxide sol, the mass percentage of rare earth oxide in the rare earth oxide sol is 10% - 15%.

[0014] In some of these embodiments, the rare earth oxide sol includes at least one of yttrium oxide sol, ytterbium oxide sol, lutetium oxide sol, lanthanum oxide sol, and cerium oxide sol.

[0015] In some of these embodiments, the particle size of magnesium oxide in the magnesium oxide sol is 3 nm - 60 nm.

[0016] In some of these embodiments, the particle size of rare earth oxide in the rare earth oxide sol is 2 nm - 10 nm.

[0017] In some of these embodiments, the total mass of the liquid in the dispersion medium and the sintering aid accounts for 20% - 50% of the mass of the silicon-based powder.

[0018] In some of these embodiments, the slurry further includes a dispersant.

[0019] In some of these embodiments, the slurry further includes a binder.

[0020] In some of these embodiments, the slurry further includes a plasticizer.

[0021] In some of these embodiments, the dispersant includes at least one of polyethylene glycol, polypropylene glycol, oleic acid, palmitic acid, citric acid, acrylic acid, polyacrylic acid, styrene maleic anhydride copolymer, and styrene maleic anhydride acrylic copolymer.

[0022] In some of these embodiments, in the slurry, the mass percentage of the dispersant in the silicon-based powder is 0.3% - 5%.

[0023] In some of these embodiments, the binder includes at least one of polyvinyl alcohol, polyvinyl butyral, polyacrylic acid resin, and polyurethane.

[0024] In some of these embodiments, in the slurry, the mass percentage of the binder in the silicon-based powder is 8% - 35%.

[0025] In some of these embodiments, the plasticizer includes at least one of glycerol, polyethylene glycol, polypropylene glycol, methyl silicone oil, and silane coupling agent.

[0026] In some of these embodiments, in the slurry, the mass percentage of the plasticizer in the silicon-based powder is 1% - 15%.

[0027] In some of these embodiments, before sintering the green sheet, the following steps are further included:

[0028] Performing debinding treatment on the green sheet;

[0029] Among them, the temperature of the debinding treatment is 450°C - 650°C, and the time of the debinding treatment is 20h - 80h.

[0030] In a second aspect, the present application provides a silicon nitride ceramic substrate prepared by the preparation method of the silicon nitride ceramic substrate described in any one of the above.

[0031] In some of these embodiments, the flexural strength of the silicon nitride ceramic substrate is 600 MPa - 950 MPa, and the Weibull distribution shape factor m of the flexural strength of the silicon nitride ceramic substrate is > 20.

[0032] In the above preparation method of the silicon nitride ceramic substrate, a sintering aid including magnesium oxide sol and rare earth oxide sol, a silicon-based powder, and a dispersion medium are used to prepare a slurry. The dispersion of silicon nitride powder and sintering aid particles in the slurry is relatively uniform and not easily agglomerated. A green sheet with relatively uniform dispersion can be obtained by tape casting, and thus the consistency of the strength of different regions of the prepared silicon nitride ceramic substrate is better and the discreteness is smaller. Description of the Drawings

[0033] Figure 1 It is a schematic diagram of the test results of the silicon nitride ceramic substrate sample in Example 1 of the present application;

[0034] Figure 2 It is a schematic diagram of the test results of the silicon nitride ceramic substrate sample in Example 2 of the present application;

[0035] Figure 3 It is a schematic diagram of the test results of the silicon nitride ceramic substrate sample in Example 3 of the present application;

[0036] Figure 4 It is a schematic diagram of the test results of the silicon nitride ceramic substrate sample in Example 4 of the present application;

[0037] Figure 5 It is a schematic diagram of the test results of the silicon nitride ceramic substrate sample in Example 5 of the present application;

[0038] Figure 6 Schematic diagram of the test results of the silicon nitride ceramic substrate sample in Comparative Example 1 of the present application;

[0039] Figure 7 Schematic diagram of the test results of the silicon nitride ceramic substrate sample in Comparative Example 2 of the present application;

[0040] Figure 8 Schematic diagram of the test results of the silicon nitride ceramic substrate sample in Comparative Example 3 of the present application. Detailed implementation manners

[0041] To make the above objects, features, and advantages of the present application more apparent and understandable, the following provides a detailed description of the specific implementation manners of the present application. Many specific details are set forth in the following description to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the related listed items.

[0043] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0044] In this application, unless otherwise clearly defined and limited, terms such as "installed", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0045] An embodiment of the present application provides a method for preparing a silicon nitride ceramic substrate, including the following steps:

[0046] Prepare a slurry using silicon-based powder, sintering aids, and a dispersion medium; wherein, the sintering aids include magnesium oxide sol, and the sintering aids further include at least one of rare earth oxide sols;

[0047] Obtain a green sheet by casting the slurry;

[0048] Sinter the green sheet under a nitrogen atmosphere.

[0049] In the traditional method for preparing a silicon nitride ceramic substrate by the tape casting method, magnesium oxide and yttrium oxide powders are used as sintering aids. When the above sintering aids are dispersed and mixed with the silicon-based powder in the dispersion medium, they are prone to agglomeration and the dispersion effect is poor. In the method for preparing a silicon nitride ceramic substrate of the present application, a sintering aid including magnesium oxide sol and rare earth oxide sol and silicon-based powder are used to prepare the slurry. It can be understood that both magnesium oxide sol and rare earth oxide sol are commercially available products. The dispersion of silicon nitride powder and sintering aid particles in the slurry is relatively uniform and not prone to agglomeration. A green sheet with relatively uniform dispersion can be obtained by tape casting, and thus the consistency of the strength of different regions of the prepared silicon nitride ceramic substrate is good and the discreteness is small.

[0050] In some embodiments, the mole percentage of magnesium element in the magnesium oxide sol to the silicon element in the silicon-based powder is 5% - 10%.

[0051] Optionally, the mole percentage of magnesium element in the magnesium oxide sol to the silicon element in the silicon-based powder is 5%, 6%, 7%, 8%, 9% or 10%, or the mole percentage of magnesium element in the magnesium oxide sol to the silicon element in the silicon-based powder can also be within the range between any two of the above percentages.

[0052] In some embodiments, the sintering aids may further include magnesium salts.

[0053] In some embodiments, the magnesium salts include at least one of magnesium oxide, magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium stearate, magnesium palmitate, magnesium citrate, magnesium silicide, magnesium nitride, and magnesium fluoride.

[0054] In some embodiments, the total mole percentage of magnesium element in the magnesium oxide sol and the magnesium salts to the silicon element in the silicon-based powder is 5% - 10%.

[0055] Optionally, the total mole percentage of magnesium element in the magnesium oxide sol and the magnesium salts to the silicon element in the silicon-based powder is 5%, 6%, 7%, 8%, 9% or 10%, or the total mole percentage of magnesium element in the magnesium oxide sol and the magnesium salts to the silicon element in the silicon-based powder can also be within the range between any two of the above percentages.

[0056] In some of these embodiments, the molar percentage of the rare earth element in the rare earth oxide sol in the silicon element in the silicon-based powder is 1% to 8%.

[0057] Optionally, the molar percentage of the rare earth element in the rare earth oxide sol in the silicon element in the silicon-based powder is 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8%, or the molar percentage of the rare earth element in the rare earth oxide sol in the silicon element in the silicon-based powder can also be within the range between any two of the above percentages.

[0058] In some of these embodiments, the sintering aid may further include a rare earth compound.

[0059] In some of these embodiments, the rare earth compound includes at least one of yttrium oxide, yttrium silicide, yttrium fluoride, yttrium chloride, yttrium nitrate, lanthanum oxide and ytterbium oxide.

[0060] In some of these embodiments, the total rare earth element in the rare earth oxide sol and the rare earth compound accounts for 1% to 8% of the silicon element in the silicon-based powder.

[0061] Optionally, the total rare earth element in the rare earth oxide sol and the rare earth compound accounts for 1%, 2%, 3%, 4%, 5%, 6%, 7% or 8% of the silicon element in the silicon-based powder, or the total rare earth element in the rare earth oxide sol and the rare earth compound accounts for the silicon element in the silicon-based powder. The molar percentage can also be within the range between any two of the above percentages.

[0062] In some of these embodiments, the silicon-based powder includes at least one of silicon powder and silicon nitride powder.

[0063] In some of these embodiments, the D50 particle size of the silicon powder is 1 μm to 5 μm.

[0064] Optionally, the D50 particle size of the silicon powder is 1 μm, 2 μm, 3 μm, 4 μm or 5 μm, or the D50 particle size of the silicon powder can also be within the range between any two of the above D50 particle sizes.

[0065] In some of these embodiments, the purity of the silicon powder is greater than or equal to 99.9%.

[0066] In some of these embodiments, the D50 particle size of the silicon nitride powder is 0.3 μm to 1 μm.

[0067] Optionally, the D50 particle size of the silicon nitride powder is 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm or 1 μm, or the D50 particle size of the silicon nitride powder can also be within the range between any two of the above D50 particle sizes.

[0068] In some of these embodiments, the purity of the silicon nitride powder is greater than or equal to 99.5%.

[0069] In some of these embodiments, the proportion of the α-phase in the silicon nitride powder is greater than or equal to 90%.

[0070] In some of these embodiments, the oxygen content in the silicon nitride powder is less than or equal to 1%.

[0071] In some of these embodiments, the rare earth oxide sol includes at least one of yttrium oxide sol, ytterbium oxide sol, lutetium oxide sol, lanthanum oxide sol, and cerium oxide sol.

[0072] In some of these embodiments, the particle size of magnesium oxide in the magnesium oxide sol is 3 nm to 60 nm.

[0073] Optionally, the particle size of magnesium oxide in the magnesium oxide sol is 3 nm, 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, 30 nm, 40 nm, 50 nm, or 60 nm, or the particle size of magnesium oxide in the magnesium oxide sol can also be within the range between any two of the above particle sizes.

[0074] In some of these embodiments, the purity of the magnesium oxide sol is greater than or equal to 99%.

[0075] In some of these embodiments, in the magnesium oxide sol, the mass percentage of magnesium oxide in the magnesium oxide sol is 8% to 16%.

[0076] Optionally, in the magnesium oxide sol, the mass percentage of magnesium oxide in the magnesium oxide sol is 8%, 10%, 12%, 14%, or 16%, or in the magnesium oxide sol, the mass percentage of magnesium oxide in the magnesium oxide sol can also be within the range between any two of the above mass percentages.

[0077] In some of these embodiments, the purity of the rare earth oxide sol is greater than or equal to 99%.

[0078] In some of these embodiments, in the rare earth oxide sol, the mass percentage of the rare earth oxide in the rare earth oxide sol is 10% to 15%.

[0079] Optionally, in the rare earth oxide sol, the mass percentage of the rare earth oxide in the rare earth oxide sol is 10%, 11%, 12%, 13%, 14%, or 15%, or in the rare earth oxide sol, the mass percentage of the rare earth oxide in the rare earth oxide sol can also be within the range between any two of the above mass percentages.

[0080] In some of these embodiments, the particle size of the rare earth oxide in the rare earth oxide sol is 2 nm to 10 nm.

[0081] Optionally, the particle size of the rare earth oxide in the rare earth oxide sol is 2 nm to 10 nm, or alternatively, the particle size of the rare earth oxide in the rare earth oxide sol can also be within the range between any two of the above particle sizes.

[0082] It can be understood that when directly using nano-sized sintering aid powders, due to their high surface energy, the nano-powders have a large amount of agglomeration, are difficult to disperse, and it is very difficult to obtain a uniformly dispersed silicon nitride - yttrium oxide - magnesium oxide slurry system. Using a magnesium oxide sol with a particle size of 3 nm to 60 nm of magnesium oxide in the sol and a rare earth oxide sol with a particle size of 2 nm to 10 nm of rare earth oxide in the sol can achieve a slurry with a better dispersion effect. At the same time, a silicon nitride ceramic substrate with higher strength can also be obtained.

[0083] In some of these embodiments, the total mass percentage of the liquid in the dispersion medium and the sintering aid in the mass of the silicon-based powder is 20% to 50%.

[0084] Optionally, the total mass percentage of the liquid in the dispersion medium and the sintering aid in the mass of the silicon-based powder is 20%, 25%, 30%, 35%, 40%, 45% or 50%, or alternatively, the total mass percentage of the liquid in the dispersion medium and the sintering aid in the mass of the silicon-based powder can also be within the range between any two of the above percentages.

[0085] In some of these embodiments, the dispersion medium includes water.

[0086] In some of these embodiments, the liquid in the sintering aid includes water.

[0087] In some of these embodiments, the mass percentage of water in the slurry in the mass of the silicon-based powder is 20% to 50%.

[0088] In some of these embodiments, before sintering the green sheet, the following steps are further included:

[0089] Performing a debinding treatment on the green sheet.

[0090] In some of these embodiments, the temperature of the debinding treatment is 450 °C to 650 °C.

[0091] Optionally, the temperature of the debinding treatment is 450 °C, 500 °C, 550 °C, 600 °C or 650 °C, or alternatively, the temperature of the debinding treatment can also be within the range between any two of the above temperatures.

[0092] In some of these embodiments, the time of the debinding treatment is 40 h to 80 h.

[0093] Optionally, the debinding treatment time is 40h, 50h, 60h, 70h or 80h, or the debinding treatment time can also be within the range between any two of the above times.

[0094] In some embodiments, the debinding treatment is carried out in a nitrogen or air atmosphere.

[0095] In some embodiments, the debinding treatment of the green compact includes the following steps:

[0096] The green compact is loaded into a boron nitride crucible after powder application and lamination, and then put into a debinding furnace for debinding.

[0097] In some embodiments, the preparation of the slurry by mixing the silicon-based powder, sintering aid, dispersant and dispersing medium includes the following steps:

[0098] The silicon-based powder, sintering aid and dispersing medium are mixed and subjected to a first ball milling treatment to obtain a first mixed raw material;

[0099] The first mixed raw material is subjected to sand milling dispersion treatment to obtain a second mixed raw material;

[0100] The second mixed raw material is mixed with a binder and a plasticizer and subjected to a second ball milling treatment to obtain a slurry.

[0101] In some embodiments, the time of the first ball milling treatment is 18h - 24h.

[0102] Optionally, the time of the first ball milling treatment is 18h, 19h, 20h, 21h, 22h, 23h or 24h, or the time of the first ball milling treatment can also be within the range between any two of the above times.

[0103] In some embodiments, the rotation speed of the first ball milling treatment is 100r / min - 300r / min.

[0104] Optionally, the rotation speed of the first ball milling treatment is 100r / min, 120r / min, 140r / min, 160r / min, 180r / min, 200r / min, 220r / min, 240r / min, 260r / min, 280r / min or 300r / min, or the rotation speed of the first ball milling treatment can also be within the range between any two of the above rotation speeds.

[0105] In some embodiments, the time of the sand milling dispersion treatment is 0.5h - 5h.

[0106] Optionally, the time of the sanding and dispersion treatment is 0.5 h, 1 h, 2 h, 3 h, 4 h or 5 h. Alternatively, the time of the sanding and dispersion treatment can also be within the range between any two of the above times.

[0107] In some of these embodiments, the rotation speed of the sanding and dispersion treatment is 500 r / min to 3000 r / min.

[0108] Optionally, the rotation speed of the sanding and dispersion treatment is 500 r / min, 1000 r / min, 1500 r / min, 2000 r / min, 2500 r / min or 3000 r / min. Alternatively, the rotation speed of the sanding and dispersion treatment can also be within the range between any two of the above rotation speeds.

[0109] In some of these embodiments, the time of the second ball milling treatment is 3 h to 15 h.

[0110] Optionally, the time of the second ball milling treatment is 3 h, 5 h, 8 h, 10 h, 12 h or 15 h. Alternatively, the time of the second ball milling treatment can also be within the range between any two of the above times.

[0111] In some of these embodiments, the rotation speed of the second ball milling treatment is 80 r / min to 250 r / min.

[0112] Optionally, the rotation speed of the second ball milling treatment is 80 r / min, 100 r / min, 120 r / min, 150 r / min, 180 r / min, 200 r / min, 220 r / min or 250 r / min. Alternatively, the rotation speed of the second ball milling treatment can also be within the range between any two of the above rotation speeds.

[0113] In some of these embodiments, the pressure of the sintering treatment is 0.5 MPa to 10 MPa.

[0114] Optionally, the pressure of the sintering treatment is 0.5 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa or 10 MPa. Alternatively, the pressure of the sintering treatment can also be within the range between any two of the above pressures.

[0115] In some of these embodiments, the holding temperature of the sintering treatment is 1800 °C to 1950 °C.

[0116] Optionally, the holding temperature of the sintering treatment is 1800 °C, 1820 °C, 1850 °C, 1880 °C, 1900 °C, 1920 °C or 1950 °C. Alternatively, the holding temperature of the sintering treatment can also be within the range between any two of the above temperatures.

[0117] In some of these embodiments, the holding time of the sintering process is 3h to 24h.

[0118] Optionally, the holding time of the sintering process is 3h, 5h, 8h, 10h, 12h, 15h, 18h, 20h, 22h or 24h. Alternatively, the holding time of the sintering process can also be within the range between any two of the above times.

[0119] In some of these embodiments, the heating rate of the sintering process is 0.3°C / min to 15°C / min.

[0120] Optionally, the heating rate of the sintering process is 0.3°C / min, 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 5°C / min, 8°C / min, 10°C / min, 12°C / min or 15°C / min. Alternatively, the heating rate of the sintering process can also be within the range between any two of the above rates.

[0121] In some of these embodiments, the sintering process is carried out in a nitrogen atmosphere.

[0122] It can be understood that when using silicon powder as the silicon-based powder, nitriding treatment of the green sheet is also included during the sintering process.

[0123] In some of these embodiments, the holding temperature of the nitriding treatment is 1300°C to 1400°C.

[0124] Optionally, the holding temperature of the nitriding treatment is 1300°C, 1320°C, 1340°C, 1360°C, 1380°C or 1400°C. Alternatively, the holding temperature of the nitriding treatment can also be within the range between any two of the above temperatures.

[0125] In some of these embodiments, the holding time of the nitriding treatment is 2h to 6h.

[0126] Optionally, the holding time of the nitriding treatment is 2h, 3h, 4h, 5h or 6h. Alternatively, the holding time of the nitriding treatment can also be within the range between any two of the above times.

[0127] In some of these embodiments, the slurry further includes a dispersant.

[0128] In some of these embodiments, the slurry further includes a binder.

[0129] In some of these embodiments, the slurry further includes a plasticizer.

[0130] In some of these embodiments, the dispersant includes at least one of polyethylene glycol, polypropylene glycol, oleic acid, palmitic acid, citric acid, acrylic acid, polyacrylic acid, styrene maleic anhydride copolymer, and styrene maleic anhydride acrylic copolymer.

[0131] In some of these embodiments, in the slurry, the mass percentage of the dispersant in the silicon-based powder is 0.3% to 5%.

[0132] Optionally, in the slurry, the mass percentage of the dispersant in the silicon-based powder is 0.3%, 0.5%, 1%, 2%, 3%, 4%, or 5%, or, in the slurry, the mass percentage of the dispersant in the silicon-based powder can also be within the range between any two of the above percentages.

[0133] In some of these embodiments, the binder includes at least one of polyvinyl alcohol, polyvinyl butyral, polyacrylic resin, and polyurethane.

[0134] In some of these embodiments, in the slurry, the mass percentage of the binder in the silicon-based powder is 8% to 35%.

[0135] Optionally, in the slurry, the mass percentage of the binder in the silicon-based powder is 8%, 10%, 15%, 20%, 25%, 30%, or 35%, or, in the slurry, the mass percentage of the binder in the silicon-based powder can also be within the range between any two of the above percentages.

[0136] In some of these embodiments, the plasticizer includes at least one of glycerol, polyethylene glycol, polypropylene glycol, methyl silicone oil, and silane coupling agent.

[0137] In some of these embodiments, in the slurry, the mass percentage of the plasticizer in the silicon-based powder is 1% to 15%.

[0138] Optionally, in the slurry, the mass percentage of the plasticizer in the silicon-based powder is 1%, 3%, 5%, 8%, 10%, 12%, or 15%, or, in the slurry, the mass percentage of the plasticizer in the silicon-based powder can also be within the range between any two of the above percentages.

[0139] Another embodiment of the present application provides a silicon nitride ceramic substrate prepared by the preparation method of the silicon nitride ceramic substrate according to any one of the above.

[0140] In some of these embodiments, the flexural strength of the silicon nitride ceramic substrate is 600 MPa to 950 MPa, and the Weibull distribution shape factor m of the flexural strength of the silicon nitride ceramic substrate is > 20.

[0141] For a traditional silicon nitride ceramic substrate prepared by the tape casting method using magnesium oxide and yttrium oxide powders as sintering aids, the Weibull distribution shape factor m of its flexural strength is usually between 10 and 20, that is, the consistency of the strength in different regions of the silicon nitride ceramic substrate is poor and the discreteness is large. The silicon nitride ceramic prepared in this application not only has a high flexural strength but also can achieve a relatively large Weibull distribution shape factor for its flexural strength.

[0142] It can be understood that in the analysis of the strength of ceramic materials, the Weibull distribution shape factor m is used to describe the dispersion and reliability of the material strength. Its meaning is as follows: The shape factor m reflects the uniformity of the material strength: when the m value is larger, the material strength distribution is concentrated and the dispersion is small, indicating that there are fewer internal defects in the material and the strength is relatively uniform; when the m value is smaller, the material strength distribution is dispersed, indicating that there are more internal defects in the material and the strength is not uniform. The shape factor m reflects the reliability of the material strength: the larger the m value, the more concentrated the material strength distribution and the higher the reliability. The smaller the m value, the more dispersed the material strength distribution and the lower the reliability. To test the flexural strength δ of the ceramic substrate, reference can be made to the standards ASTM C161 and ISO 14704.

[0143] The following are specific examples

[0144] Example 1

[0145] Preparation method of silicon nitride ceramic substrate:

[0146] (1) Sequentially add 95.2 g of magnesium oxide sol with a mass concentration of 15%, 28.6 g of magnesium nitride, 107.6 g of yttrium oxide sol with a mass concentration of 15%, 16.1 g of yttrium oxide, and 1000 g of silicon nitride powder into 277.6 g of deionized water for ball milling. The ball milling time is 5 h and the ball milling speed is 250 r / min.

[0147] (2) Transfer the ball-milled material to a sand mill for re-dispersion. The sand milling time is 1 h and the sand milling speed is 1500 r / min.

[0148] (3) Add 140 g of polyvinyl butyral as a binder and 50 g of polyethylene glycol as a plasticizer to the sand-milled material, and perform secondary ball milling. The ball milling time is 8 h and the ball milling speed is 150 r / min to prepare a slurry.

[0149] (4) Subject the prepared slurry to defoaming and tape casting processes to prepare a ceramic green sheet.

[0150] (5) Pass the prepared green sheet through processes such as cutting, powder application, lamination, and loading into a boron nitride crucible, and place it in a debinding furnace for debinding. The debinding temperature is 500 °C, the debinding atmosphere is air, and the debinding time is 55 h.

[0151] (6) Place the debinded green sheet into a gas pressure sintering furnace for sintering. The sintering atmosphere is nitrogen, the pressure is 1 MPa, the sintering temperature is 1850 °C, the heating rate is 0.5 °C / min, and the holding time is 4 h.

[0152] The silicon nitride ceramic substrate in Example 1 was tested. The flexural strength (scale) was 872 MPa, and the Weibull distribution shape factor m of 100 samples was 27.69.

[0153] Example 2

[0154] The preparation method of the silicon nitride ceramic substrate in Example 2 is only different from that in Example 1 in that in step (1), 95.2 g of magnesium oxide sol, 28.6 g of magnesium nitride, 155.2 g of lanthanum oxide sol, 23.3 g of lanthanum oxide and 1000 g of silicon nitride powder are successively added to 237.1 g of deionized water for ball milling.

[0155] The silicon nitride ceramic substrate in Example 2 was tested. The flexural strength (scale) was 886.6 MPa, and the Weibull distribution shape factor m of 100 samples was 26.63.

[0156] Example 3

[0157] The preparation method of the silicon nitride ceramic substrate in Example 3 is only different from that in Example 1 in that in step (1), 95.2 g of magnesium oxide sol, 28.6 g of magnesium nitride, 187.6 g of ytterbium oxide sol, 28.1 g of ytterbium oxide and 1000 g of silicon nitride powder are successively added to 209.6 g of deionized water for ball milling.

[0158] The silicon nitride ceramic substrate in Example 3 was tested. The flexural strength (scale) was 860.8 MPa, and the Weibull distribution shape factor m of 100 samples was 25.91.

[0159] Example 4

[0160] The preparation method of the silicon nitride ceramic substrate in Example 4 is only different from that in Example 1 in that in step (1), 57.1 g of magnesium oxide sol, 40 g of magnesium nitride, 107.6 g of yttrium oxide sol, 16.1 g of yttrium oxide and 1000 g of silicon nitride powder are successively added to 310 g of deionized water for ball milling.

[0161] The silicon nitride ceramic substrate in Example 4 was tested. The flexural strength (scale) was 862.1 MPa, and the Weibull distribution shape factor m of 100 samples was 24.5.

[0162] Example 5

[0163] The preparation method of the silicon nitride ceramic substrate in Example 5 is only different from that in Example 1 in that in step (1), 95.2 g of magnesium oxide sol, 28.6 g of magnesium silicon nitride, 75.3 g of yttrium oxide sol, 21 g of yttrium oxide and 1000 g of silicon nitride powder are successively added to 305 g of deionized water for ball milling.

[0164] The silicon nitride ceramic substrate in Example 5 was tested, and the flexural strength (scale) was 880.4 MPa, and the Weibull distribution shape factor m of 100 samples was 23.92.

[0165] Comparative Example 1

[0166] The preparation method of the silicon nitride ceramic substrate in Comparative Example 1 is only different from that in Example 1 in that in step (1), 95.2 g of magnesium oxide sol, 28.6 g of magnesium silicon nitride, 32.3 g of yttrium oxide and 1000 g of silicon nitride powder are successively added to 369 g of deionized water for ball milling.

[0167] The silicon nitride ceramic substrate in Comparative Example 1 was tested, and the flexural strength (scale) was 780.9 MPa, and the Weibull distribution shape factor m of 100 samples was 14.56.

[0168] Comparative Example 2

[0169] The preparation method of the silicon nitride ceramic substrate in Comparative Example 2 is only different from that in Example 1 in that in step (1), 57.1 g of magnesium silicon nitride, 32.3 g of yttrium oxide and 1000 g of silicon nitride powder are successively added to 450 g of deionized water for ball milling.

[0170] The silicon nitride ceramic substrate in Comparative Example 2 was tested, and the flexural strength (scale) was 739.3 MPa, and the Weibull distribution shape factor m of 100 samples was 14.58.

[0171] Comparative Example 3

[0172] The preparation method of the silicon nitride ceramic substrate in Comparative Example 3 is only different from that in Example 1 in that in step (1), 57.1 g of magnesium silicon nitride, 107.6 g of yttrium oxide sol, 16.1 g of yttrium oxide and 1000 g of silicon nitride powder are successively added to 358.5 g of deionized water for ball milling.

[0173] The silicon nitride ceramic substrate in Comparative Example 3 was tested, and the flexural strength (scale) was 745.1 MPa, and the Weibull distribution shape factor m of 100 samples was 17.04.

[0174] Refer to Figures 1 to 8As shown, and from the above test results, it can be seen that in Comparative Example 1, the sintering aid only includes magnesium oxide sol and does not include rare earth oxide sol. The flexural strength (scale) of the silicon nitride ceramic substrate prepared is 780.9 MPa, and the Weibull distribution shape factor m of 100 samples is 14.56. In Comparative Example 2, the sintering aid does not include magnesium oxide sol and rare earth oxide sol. The flexural strength (scale) of the silicon nitride ceramic substrate prepared is 739.3 MPa, and the Weibull distribution shape factor m of 100 samples is 14.58. In Comparative Example 3, the sintering aid only includes rare earth oxide sol and does not include magnesium oxide sol. The flexural strength (scale) of the silicon nitride ceramic substrate prepared is 745.1 MPa, and the Weibull distribution shape factor m of 100 samples is 17.04. In Examples 1 to 5, the sintering aid includes both magnesium oxide sol and rare earth oxide sol at the same time. The flexural strength (scale) of the silicon nitride ceramic substrate prepared and the Weibull distribution shape factor m of the samples are higher than those of all comparative examples. At the same time, by comparing the test results of Examples 1 to 3 and the test results of Examples 4 and 5, it can be seen that by controlling the molar percentage of magnesium element in magnesium oxide sol in the silicon element in the silicon-based powder within the range of 5% to 10%, and controlling the molar percentage of rare earth element in rare earth oxide sol in the silicon element in the silicon-based powder to be 1% to 8%, the flexural strength (scale) of the silicon nitride ceramic substrate prepared and the Weibull distribution shape factor m of the samples can be made higher. That is, the preparation method of the silicon nitride ceramic substrate of the present application can make the consistency of the strength of different regions of the prepared silicon nitride ceramic substrate better and the discreteness smaller.

[0175] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0176] The above embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims, and the specification can be used to explain the content of the claims.

Claims

1. A preparation method of a silicon nitride ceramic substrate, characterized in that, It includes the following steps: Prepare a slurry using silicon-based powder, a sintering aid, and a dispersion medium; wherein, the sintering aid includes magnesium oxide sol, and the sintering aid further includes at least one of rare earth oxide sols; Obtain a green sheet by casting the slurry; Perform a sintering treatment on the green sheet in a nitrogen atmosphere.

2. The preparation method of the silicon nitride ceramic substrate according to claim 1, characterized in that, The molar percentage of magnesium element in the magnesium oxide sol to the silicon element in the silicon-based powder is 5-10%; The molar percentage of rare earth element in the rare earth oxide sol to the silicon element in the silicon-based powder is 1-8%.

3. The preparation method of the silicon nitride ceramic substrate according to claim 1, characterized in that, The particle size of magnesium oxide in the magnesium oxide sol is 3nm-60nm; In the magnesium oxide sol, the mass percentage of magnesium oxide in the magnesium oxide sol is 8%-20%; The particle size of rare earth oxide in the rare earth oxide sol is 2nm-10nm; In the rare earth oxide sol, the mass percentage of rare earth oxide in the rare earth oxide sol is 10%-15%; The rare earth oxide sol includes at least one of yttrium oxide sol, ytterbium oxide sol, lutetium oxide sol, lanthanum oxide sol, and cerium oxide sol.

4. The preparation method of the silicon nitride ceramic substrate according to claim 1, characterized in that, The silicon-based powder includes at least one of silicon powder and silicon nitride powder; The D50 particle size of the silicon nitride powder is 0.3μm-1μm; The D50 particle size of the silicon powder is 1μm-5μm.

5. The preparation method of the silicon nitride ceramic substrate according to claim 1, wherein, The total mass of the dispersion medium and the liquid in the sintering aid accounts for 20%-50% of the mass of the silicon-based powder.

6. The preparation method of the silicon nitride ceramic substrate according to claim 1, characterized in that, The slurry further includes a dispersant; and / or, The slurry further includes a binder; and / or, The slurry further includes a plasticizer.

7. The preparation method of the silicon nitride ceramic substrate according to claim 6, wherein, The dispersant includes at least one of polyethylene glycol, polypropylene glycol, oleic acid, palmitic acid, citric acid, acrylic acid, polyacrylic acid, styrene maleic anhydride copolymer, and styrene maleic anhydride acrylic copolymer; and / or, In the slurry, the mass percentage of the dispersant to the silicon-based powder is 0.3%-5%; and / or, The binder includes at least one of polyvinyl alcohol, polyvinyl butyral, polyacrylic resin, and polyurethane; and / or, In the slurry, the mass percentage of the binder to the silicon-based powder is 8%-35%; and / or, The plasticizer includes at least one of glycerol, polyethylene glycol, polypropylene glycol, methyl silicone oil, and silane coupling agent; and / or, In the slurry, the mass percentage of the plasticizer to the silicon-based powder is 1%-15%.

8. The preparation method of the silicon nitride ceramic substrate according to any one of claims 1 to 7, characterized in that, Before performing the sintering treatment on the green sheet, the following steps are further included: Perform a debinding treatment on the green sheet; Perform a sintering treatment on the green sheet after the debinding treatment; Wherein, the temperature of the debinding treatment is 450°C-650°C, and the time of the debinding treatment is 20h-80h.

9. A silicon nitride ceramic substrate, characterized in that, It is prepared by the preparation method of the silicon nitride ceramic substrate according to any one of claims 1-8.

10. The silicon nitride ceramic substrate according to claim 9, characterized in that, The flexural strength of the silicon nitride ceramic substrate is 600MPa-950MPa, and the Weibull distribution shape factor m of the flexural strength of the silicon nitride ceramic substrate is >20.

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