Silicon nitride tape casting slurry and preparation method thereof, silicon nitride ceramic chip and copper-clad ceramic substrate

Abstract

The invention provides silicon nitride tape casting slurry and a preparation method thereof, a silicon nitride ceramic chip and a copper-clad ceramic substrate, and the silicon nitride tape casting slurry comprises the following raw materials in parts by mass: 40-50 parts of silicon nitride powder; 1-5 parts of a sintering aid; 5 to 15 parts of a binder; 30 to 40 parts of a solvent; 0.1 part to 0.5 part of an organic silicon wetting dispersant; 5 to 15 parts of a plasticizer; wherein the solvent comprises ethylene glycol and butyl acetate in a mass ratio of (3-5): 1. According to the silicon nitride tape-casting slurry provided by the invention, the specific solvent and the organic silicon wetting dispersant are adopted, and other components are reasonably matched, so that the dispersion uniformity and sedimentation resistance of all the components in the silicon nitride tape-casting slurry are ensured, and toxic substances cannot be volatilized in the use process.

Description

Technical Field

[0001] The invention relates to the field of inorganic non-metallic materials, and in particular to a silicon nitride casting slurry and a preparation method thereof, a silicon nitride ceramic sheet, and a copper-clad ceramic substrate. Background Art

[0002] At present, the forming methods of silicon nitride ceramics include: tape casting, hot pressing, slip casting, cold isostatic pressing, etc. Among them, tape casting is the preferred process that can simultaneously meet the requirements of miniaturization and refinement of size and realize the directional growth of silicon nitride grains, and the tape casting slurry of tape casting is the most critical factor in determining the performance of the green blank.

[0003] At present, the traditional silicon nitride tape casting slurry has the following shortcomings: (1) Commonly used organic solvents often contain components such as benzene and ketone that are toxic to the human body; (2) In order to ensure the stability of the slurry and the strength of the green body, too much organic binder and plasticizer are added, which reduces the density during sintering and makes it difficult for the strength of the silicon nitride ceramic sheet to meet the standard; (3) The slurry has poor anti-sedimentation performance and is difficult to store for a long time, resulting in waste. It is also easy to cause problems such as uneven thickness of the tape casting sheet. Summary of the invention

[0004] The invention provides a silicon nitride tape casting slurry. The silicon nitride tape casting slurry adopts a specific solvent, an organic silicon wetting dispersant and reasonably mixes other components, thereby ensuring the dispersion uniformity and good anti-sedimentation property of each component in the silicon nitride tape casting slurry, and no toxic substances are volatilized during use.

[0005] The present invention also provides a method for preparing the silicon nitride tape-casting slurry. The method can prepare the silicon nitride tape-casting slurry and has a simple process.

[0006] The present invention also provides a silicon nitride ceramic sheet. Since the silicon nitride ceramic sheet is prepared by using the silicon nitride tape casting slurry, the silicon nitride ceramic sheet has a higher density, a higher bending strength and a better thermal conductivity.

[0007] The present invention also provides a method for preparing a silicon nitride ceramic sheet. The method uses the silicon nitride tape casting slurry as a raw material to prepare a silicon nitride ceramic sheet with high density, high bending strength and high thermal conductivity, and the process is simple.

[0008] The present invention also provides a copper-clad ceramic substrate. Since it includes the silicon nitride ceramic sheet, the copper-clad ceramic substrate has the advantages of stable shape, high thermal conductivity, etc.

[0009] In a first aspect, the present invention provides a silicon nitride casting slurry, wherein the raw materials thereof include, by weight:

[0010] Silicon nitride powder: 40 to 50 parts;

[0011] Sintering aid: 1 to 5 parts;

[0012] Binder: 5 to 15 parts;

[0013] Solvent: 30 to 40 parts;

[0014] Silicone wetting and dispersing agent: 0.1 to 0.5 parts;

[0015] Plasticizer: 5 to 15 parts;

[0016] Wherein, the solvent comprises ethylene glycol and butyl acetate in a mass ratio of 3 to 5:1.

[0017] Further, the organosilicon wetting and dispersing agent includes γ-aminopropyltriethoxysilane and / or monovinyl-terminated dimethyl.

[0018] Furthermore, the sintering aid includes magnesium oxide and ytterbium oxide.

[0019] Furthermore, the mass ratio of magnesium oxide to ytterbium oxide is 1:0.5-2.

[0020] Furthermore, in the silicon nitride powder, the α phase accounts for more than 95 wt %; and / or the D50 of the silicon nitride powder is 0.5 to 0.8 μm.

[0021] Further, the binder is polyvinyl butyral;

[0022] And / or, the plasticizer is triethylene glycol diisooctanoate.

[0023] Furthermore, it also includes: defoaming agent: 0.1 part to 1 part.

[0024] In a second aspect, the present invention provides a method for preparing the above-mentioned silicon nitride casting slurry, comprising the following steps:

[0025] 1) dispersing an organosilicon wetting and dispersing agent, a sintering aid and silicon nitride powder in part of the solvent, and performing a ball milling treatment to obtain a primary ball milling slurry;

[0026] 2) a binder and a plasticizer are dispersed in the remaining solvent, mixed with the primary ball-milled slurry, and subjected to secondary ball-milling treatment to obtain secondary ball-milled slurry;

[0027] 3) The silicon nitride tape casting slurry is obtained by vacuum degassing the secondary ball milling slurry.

[0028] In a third aspect, the present invention provides a silicon nitride ceramic sheet, the raw material of which includes the silicon nitride tape casting slurry of the first aspect.

[0029] In a fourth aspect, the present invention provides a method for preparing a silicon nitride ceramic sheet, comprising the following steps:

[0030] The silicon nitride casting slurry described in the first aspect is used for casting and drying to obtain a silicon nitride casting sheet; the silicon nitride casting sheet is subjected to degreasing treatment and gas pressure sintering treatment to obtain the silicon nitride ceramic sheet.

[0031] In a fifth aspect, the present invention provides a copper-clad ceramic substrate, comprising the silicon nitride ceramic sheet of the third aspect or the silicon nitride ceramic sheet prepared in the fourth aspect.

[0032] The silicon nitride tape casting slurry provided by the present invention has the advantages of environmental protection, excellent dispersibility, good stability, etc. The main reason is that: the present invention adopts non-toxic ethylene glycol and butyl acetate as the compound solvent, which ensures the good dissolution ability of the solvent for the binder, and the solvent will not volatilize toxic substances in the later tape casting stage, which ensures the dispersibility of the slurry while improving the environmental protection; furthermore, by adding a certain amount of organic silicon wetting dispersant, the wetting ability of the slurry system on the silicon nitride powder can be improved, which can play the role of coating the silicon nitride powder, further increasing the dispersibility and stability of the powder, thereby ensuring the dispersibility and stability of the silicon nitride tape casting slurry.

[0033] The silicon nitride ceramic sheet provided by the present invention uses a silicon nitride tape-casting slurry with a specific formula as a raw material, so it has the advantages of high density, high bending strength, high thermal conductivity, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0035] Figure 1 The figures are pictures of silicon nitride tape casting slurry of Example 1 and Comparative Example 1, wherein a is a picture of silicon nitride tape casting slurry of Comparative Example 1, and b is a picture of silicon nitride tape casting slurry of Example 1;

[0036] Figure 2 These are pictures of the cast green sheets obtained by casting the silicon nitride casting slurry of Example 1 and Comparative Example 2, wherein a is a picture of the cast green sheet obtained by casting the silicon nitride casting slurry of Example 1, and b is a picture of the cast green sheet obtained by casting the silicon nitride casting slurry of Comparative Example 2. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the scheme of the present invention, the present invention is further described in detail below. The specific implementation methods listed below are only for describing the principles and features of the present invention. The examples are only used to explain the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In order to solve the problems of existing silicon nitride casting slurry, such as high toxicity, poor anti-settling performance and poor stability, the present invention adopts the following technical solutions:

[0039] In a first aspect, the present invention provides a silicon nitride casting slurry, wherein the raw materials thereof include, by weight:

[0040] Silicon nitride powder: 40 to 50 parts;

[0041] Sintering aid: 1 to 5 parts;

[0042] Binder: 5 to 15 parts;

[0043] Solvent: 30 to 40 parts;

[0044] Modified silicone wetting and dispersing agent: 0.1 to 0.5 parts;

[0045] Plasticizer: 5 to 15 parts;

[0046] Wherein, the solvent comprises ethylene glycol and butyl acetate in a mass ratio of 3 to 5:1.

[0047] In the present invention, by using ethylene glycol and butyl acetate as a compound solvent, on the one hand, the solvent has a good solubility for the binder, and the non-toxic ethylene glycol and butyl acetate will not volatilize toxic substances in the later casting stage, which meets the industrial environmental protection requirements; on the other hand, since the volatilization rate of ethylene glycol is faster than that of butyl acetate, the shrinkage yield and recovery rate of the silicon nitride green body during sintering are relatively suitable, which helps to improve the density and strength of the silicon nitride ceramic sheet; secondly, the present invention also improves the wetting ability of the slurry system on the silicon nitride powder by adding a certain amount of organic silicon wetting and dispersing agent, plays a role in coating the silicon nitride powder, further increases the dispersibility and stability of the powder, is beneficial to the uniform dispersion of the powder and organic matter in all directions during the subsequent casting, and is beneficial to the later sintering to prepare the silicon nitride ceramic sheet with high density and high strength.

[0048] In a specific embodiment, the organosilicon wetting and dispersing agent includes γ-aminopropyltriethoxysilane and / or monovinyl-terminated dimethyl. The organosilicon wetting and dispersing agent can be better coated on the surface of silicon nitride powder to increase the repulsive force between powder particles, overcome the agglomeration caused by the van der Waals attraction between particles, thereby forming a well-dispersed silicon nitride casting slurry, making the entire slurry system more uniform.

[0049] The sintering aid can be selected from conventional sintering aids in the art, for example, alkali metal compounds and rare earth compounds, wherein the alkali metal compound is at least one of magnesium oxide, magnesium fluoride, aluminum oxide and calcium oxide, and the rare earth compound is at least one of ytterbium oxide, yttrium fluoride, yttrium oxide and cerium oxide; but in order to better improve the density and mechanical strength of the silicon nitride ceramic sheet, in a specific embodiment, the sintering aid includes magnesium oxide and ytterbium oxide; further, the mass ratio of the magnesium oxide to the ytterbium oxide is 1:0.5-2.

[0050] Illustratively, the mass ratio of magnesium oxide to ytterbium oxide is any one of 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.2, 1:1.5, 1:1.7, 1:1.9, etc.

[0051] The particle size of silicon nitride powder will affect the dispersibility and stability of silicon nitride tape casting slurry. At the same time, its particle size combined with purity is also a key factor affecting the sintering performance of silicon nitride ceramics. In order to ensure the dispersibility and stability of silicon nitride tape casting slurry and the strength of subsequent silicon nitride ceramic sheets, in a specific embodiment, the α phase accounts for more than 95wt% of the silicon nitride powder; and / or the D50 of the silicon nitride powder is 0.5-0.8μm.

[0052] The D50 of the silicon nitride powder refers to the particle size value corresponding to 50% (by volume) of the cumulative amount in the particle size cumulative distribution curve, which can be regarded as the median particle size of the silicon nitride powder and is generally obtained by testing with a laser diffraction particle size distribution instrument.

[0053] In addition, in the present invention, the silicon nitride powder is preferably silicon nitride raw powder, and the oxygen content of the silicon nitride raw powder is preferably ≤1%, and the impurity content is preferably ≤0.2%.

[0054] In a specific embodiment, the binder is polyvinyl butyral. The binder has excellent solubility in the solvent of the present invention and can form a miscible system with the solvent, which is conducive to the stable and uniform dispersion of silicon nitride powder.

[0055] In a specific embodiment, the plasticizer is triethylene glycol diisooctanoate.

[0056] In a specific embodiment, it further includes: defoaming agent: 0.1 part to 1 part.

[0057] The present invention does not particularly limit the above-mentioned defoaming agent, and technicians can choose well-known commercial products, including but not limited to: mineral oils, alcohols, fatty acids and fatty acid esters, amides, phosphates, silicones, polyethers, polyether-modified polysiloxane defoaming agents, etc.

[0058] In a second aspect, the present invention provides a method for preparing the above-mentioned silicon nitride casting slurry, comprising the following steps:

[0059] 1) dispersing an organosilicon wetting and dispersing agent, a sintering aid and silicon nitride powder in part of the solvent, and performing a ball milling treatment to obtain a primary ball milling slurry;

[0060] 2) a binder and a plasticizer are dispersed in the remaining solvent, mixed with the primary ball-milled slurry, and subjected to secondary ball-milling treatment to obtain secondary ball-milled slurry;

[0061] 3) The silicon nitride tape casting slurry is obtained by vacuum degassing the secondary ball milling slurry.

[0062] The above preparation method first ball-mills the organosilicon wetting dispersant, sintering aid and silicon nitride powder, and then configures the first ball-milled slurry with a binder and a plasticizer to form a carrier for a second ball-milling, which can further improve the dispersibility of the silicon nitride casting slurry, specifically, it can reduce the original viscosity of the slurry by about 10%.

[0063] In addition, in the above preparation method, the amount distribution of part of the solvent and the remaining solvent only needs to ensure the dissolution or dispersion of the corresponding materials, but in order to further optimize the dispersibility of the final silicon nitride casting slurry, the volume ratio of part of the solvent and the remaining solvent is 1-2:1-2, more preferably 1:1.

[0064] In step 1), the organosilicon wetting and dispersing agent, the sintering aid and the silicon nitride powder are dispersed in part of the solvent, preferably under stirring. The present invention does not have any special restrictions on the stirring rate and time. The stirring rate and time familiar to those skilled in the art are adopted to ensure that the silicon nitride and the sintering aid are evenly mixed.

[0065] In order to better disperse the materials, for example, a silicone wetting dispersant can be added to the solvent and stirred with a glass rod to dissolve it in the solvent. Subsequently, a certain mass proportion of sintering aid is added. After stirring and dispersing, a certain mass of silicon nitride powder is weighed and added in batches, with each batch adding about 1 / 3 of the total amount until all the silicon nitride powder is added. Then, a certain mass ratio of grinding balls is added, and ball milling is performed for 15 hours at a rotation speed of 250r / min to obtain a primary ball milling slurry.

[0066] In step 2), the binder and the plasticizer are dispersed in the remaining solvent, preferably in an emulsifying homogenizer. The present invention does not have any special restrictions on the homogenization rate and time. The rate and time familiar to those skilled in the art are used to ensure that the binder and the plasticizer are evenly mixed.

[0067] Illustratively, in the present invention, the grinding balls used in the first ball milling treatment and the second ball milling treatment are preferably silicon nitride grinding balls; the mass ratio of the grinding balls to the mixed material is preferably 1.5 to 1.8:1, more preferably 1.6 to 1.7:1.

[0068] In step 3), the secondary ball-milling slurry also includes a vacuum degassing process; the present invention does not have any special limitation on the vacuum degassing process, and it can be carried out by a process familiar to those skilled in the art and capable of ensuring complete degassing. In a specific embodiment, the vacuum degassing is preferably carried out in a vacuum degassing machine.

[0069] In a third aspect, the present invention provides a silicon nitride ceramic sheet, the raw material of which includes the silicon nitride tape casting slurry described in the first aspect.

[0070] In a fourth aspect, the present invention provides a method for preparing a silicon nitride ceramic sheet, comprising the following steps:

[0071] The silicon nitride casting slurry described in the first aspect is used for casting and drying to obtain a silicon nitride casting sheet; the silicon nitride casting sheet is subjected to degreasing treatment and gas pressure sintering treatment to obtain the silicon nitride ceramic sheet.

[0072] In a specific embodiment, the method for preparing the above silicon nitride ceramic sheet specifically comprises the following steps:

[0073] S1: tape casting: silicon nitride tape casting slurry is tape cast to obtain silicon nitride tape casting sheet after drying, and the silicon nitride tape casting sheet is cut into silicon nitride tape casting sheets of suitable size;

[0074] S2: Degreasing treatment: The silicon nitride cast sheet is sintered in a degreasing furnace, and the temperature is increased at a heating rate of 0.2-0.3°C / min to 500-600°C, and kept at this temperature for 2-3 hours.

[0075] S3: Gas pressure sintering: The degreased silicon nitride cast sheet is heated at a heating rate of 10-12°C / min in a protective atmosphere. When the temperature reaches 1800-1900°C, a pressure of 30-35MPa is applied. The temperature and pressure are maintained for 1-2h. After the pressure maintenance, the sample is cooled with the furnace and demolded to obtain a silicon nitride ceramic sheet.

[0076] In a fifth aspect, the present invention provides a copper-clad ceramic substrate, comprising the silicon nitride ceramic sheet of the third aspect or the silicon nitride ceramic sheet prepared in the fourth aspect.

[0077] In order to further understand the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments 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.

[0078] Unless otherwise specified, the reagents involved in the embodiments of the present invention are all commercially available products and can be purchased through commercial channels.

[0079] Among them, polyvinyl butyral CAS number: 63148-65-2; monovinyl-terminated dimethyl CAS number: 68083-19-2; γ-aminopropyltriethoxysilane CAS number: 919-30-2; in the silicon nitride powder, the α phase accounts for 98wt%; and the D50 of the silicon nitride powder is 0.65μm.

[0080] Example 1

[0081] This example provides a silicon nitride tape casting slurry, and its raw materials include, by weight:

[0082] Silicon nitride powder: 45 parts;

[0083] Sintering aid: 1.5 parts;

[0084] Binder: 7 parts;

[0085] Solvent: 40 parts;

[0086] Silicone wetting and dispersing agent: 0.1 part;

[0087] Plasticizer: 5.9 parts;

[0088] Defoaming agent: 0.5 parts;

[0089] The solvent is composed of ethylene glycol and butyl acetate in a mass ratio of 4:1, the sintering aid is composed of magnesium oxide and ytterbium oxide in a mass ratio of 1:1, the plasticizer is triethylene glycol diisooctanoate, the defoamer is BYK 1790, the silicone wetting and dispersing agent is monovinyl-terminated dimethyl, and the binder is polyvinyl butyral.

[0090] The preparation method thereof comprises the following steps:

[0091] 1) Weigh a certain proportion of ethylene glycol and butyl acetate and mix them, then divide them into two parts by volume as ball mill slurry solvent, add organosilicon wetting and dispersing agent to one part of the solvent, stir with a glass rod to dissolve it, then add sintering aid, stir and disperse, then add silicon nitride powder in batches, add about 1 / 3 of the total amount each time, continue to add after it is evenly dispersed, add grinding balls after all silicon nitride powders are evenly stirred, and perform a ball milling treatment at a ball milling speed of 250r / min for 15 hours to obtain a primary ball mill slurry;

[0092] 2) The binder, the plasticizer and another portion of the solvent are placed in an emulsifying homogenizer, and emulsified and homogenized for 2 hours at a parameter of 180 r / min. The obtained mixture and the primary ball-milled slurry are mixed and placed in a ball mill, and a secondary ball-milling treatment is performed at a ball-milling speed of 250 r / min for 15 hours to obtain a secondary ball-milled slurry;

[0093] 3) The secondary ball-milled slurry is subjected to vacuum degassing at an air pressure of -0.09 MPa, with a vacuum degassing rate of more than 10 minutes / liter, and the silicon nitride tape casting slurry is obtained after vacuum degassing.

[0094] Example 2

[0095] This example provides a silicon nitride tape casting slurry, and its raw materials include, by weight:

[0096] Silicon nitride powder: 45 parts;

[0097] Sintering aid: 1 part;

[0098] Binder: 5.5 parts;

[0099] Solvent: 30 parts;

[0100] Silicone wetting and dispersing agent: 0.1 part;

[0101] Plasticizer: 5 parts;

[0102] Defoaming agent: 0.5 parts;

[0103] The solvent is composed of ethylene glycol and butyl acetate in a mass ratio of 4:1, the sintering aid is composed of magnesium oxide and ytterbium oxide in a mass ratio of 1:1, the plasticizer is triethylene glycol diisooctanoate, the defoamer is BYK 1790, the silicone wetting and dispersing agent is monovinyl-terminated dimethyl, and the binder is polyvinyl butyral.

[0104] The preparation method thereof is referred to Example 1.

[0105] Example 3

[0106] This example provides a silicon nitride tape casting slurry, and its raw materials include, by weight:

[0107] Silicon nitride powder: 45 parts;

[0108] Sintering aid: 5 parts;

[0109] Binder: 15 parts;

[0110] Solvent: 40 parts;

[0111] Silicone wetting and dispersing agent: 0.5 parts;

[0112] Plasticizer: 15 parts;

[0113] Defoaming agent: 1 part;

[0114] The solvent is composed of ethylene glycol and butyl acetate in a mass ratio of 4:1, the sintering aid is composed of magnesium oxide and ytterbium oxide in a mass ratio of 1:1, the plasticizer is triethylene glycol diisooctanoate, the defoamer is BYK 1790, the silicone wetting and dispersing agent is monovinyl-terminated dimethyl, and the binder is polyvinyl butyral.

[0115] The preparation method thereof is referred to Example 1.

[0116] Example 4

[0117] This example provides a silicon nitride casting slurry, which is different from Example 1 only in that the organosilicon wetting and dispersing agent is γ-aminopropyltriethoxysilane.

[0118] Example 5

[0119] This example provides a silicon nitride casting slurry, which is different from Example 1 only in that the solvent is composed of ethylene glycol and butyl acetate in a mass ratio of 3:1.

[0120] Example 6

[0121] This example provides a silicon nitride casting slurry, which is different from Example 1 only in that the solvent is composed of ethylene glycol and butyl acetate in a mass ratio of 5:1.

[0122] Example 7

[0123] This example provides a silicon nitride tape casting slurry, which is different from Example 1 only in that the sintering aid is composed of magnesium oxide and ytterbium oxide in a ratio of 1:0.5.

[0124] Example 8

[0125] This example provides a silicon nitride tape casting slurry, which is different from Example 1 only in that the sintering aid is composed of magnesium oxide and ytterbium oxide in a ratio of 1:2.

[0126] Example 9

[0127] This example provides a silicon nitride casting slurry, which is different from Example 1 only in that the preparation method includes the following steps:

[0128] 1) Weigh a certain proportion of ethylene glycol and butyl acetate and mix them as a solvent, add an organosilicon wetting and dispersing agent to the solvent, stir with a glass rod to dissolve it, then add a sintering aid, stir and disperse, and finally add silicon nitride powder in batches, adding about 1 / 3 of the total amount each time, and continue to add after it is evenly dispersed, and all the silicon nitride powder is evenly stirred to obtain a first mixture;

[0129] 2) adding the binder, the plasticizer and the remaining solvent to the first mixed material, placing the mixture in a ball mill, adding grinding balls, and performing ball milling at a ball milling speed of 250 r / min for 15 hours to obtain a ball milled slurry;

[0130] 3) The ball milled slurry is subjected to vacuum degassing at an air pressure of -0.09 MPa, with a vacuum degassing rate of more than 10 minutes / liter, and the silicon nitride tape casting slurry is obtained after vacuum degassing.

[0131] Comparative Example 1

[0132] This example provides a silicon nitride casting slurry, which is different from Example 1 only in that the organosilicon wetting and dispersing agent is replaced with triethyl phosphate.

[0133] Comparative Example 2

[0134] This example provides a silicon nitride casting slurry, which is different from Example 1 only in that the solvent is replaced with a single ethylene glycol.

[0135] Comparative Example 3

[0136] This example provides a silicon nitride casting slurry, which is different from Example 1 only in that the solvent is composed of ethylene glycol and butyl acetate in a mass ratio of 3:2.

[0137] Comparative Example 4

[0138] This example provides a silicon nitride casting slurry, which differs from Example 2 only in that, by weight, its raw materials include:

[0139] Silicon nitride powder: 45 parts;

[0140] Sintering aid: 1 part;

[0141] Binder: 20 parts;

[0142] Solvent: 30 parts;

[0143] Silicone wetting and dispersing agent: 0.1 part;

[0144] Plasticizer: 5 parts;

[0145] Defoaming agent: 0.5 parts.

[0146] Comparative Example 5

[0147] This example provides a silicon nitride casting slurry, which differs from Example 2 only in that, by weight, its raw materials include:

[0148] Silicon nitride powder: 45 parts;

[0149] Sintering aid: 1 part;

[0150] Binder: 5.5 parts;

[0151] Solvent: 30 parts;

[0152] Silicone wetting and dispersing agent: 1 part;

[0153] Plasticizer: 5 parts;

[0154] Defoaming agent: 0.5 parts.

[0155] Comparative Example 6

[0156] This example provides a silicon nitride casting slurry, which differs from Example 2 only in that, by weight, its raw materials include:

[0157] Silicon nitride powder: 45 parts;

[0158] Sintering aid: 5 parts;

[0159] Binder: 5.5 parts;

[0160] Solvent: 40 parts;

[0161] Silicone wetting and dispersing agent: 0.5 parts;

[0162] Plasticizer: 17 parts;

[0163] Defoaming agent: 0.5 parts.

[0164] Application Examples

[0165] Silicon nitride ceramic sheets were prepared using the silicon nitride tape casting slurries of the above embodiment and comparative example, respectively, comprising the following steps:

[0166] S1: tape casting: tape casting the silicon nitride tape casting slurry, and obtaining a silicon nitride tape casting green sheet after drying;

[0167] S2: Debinding: The silicon nitride tape-cast green sheet is sintered in a debinding furnace, and the temperature is increased at a heating rate of 0.2°C / min to 500°C, and kept at this temperature for 2h;

[0168] S3: Sintering: The degreased silicon nitride tape-cast green sheet is heated at a heating rate of 10°C / min in a protective atmosphere. When the temperature reaches 1800°C, a pressure of 30MPa is applied and the temperature and pressure are maintained for 1h. After the pressure maintenance, the sample is cooled with the furnace and demolded to obtain a silicon nitride ceramic sheet.

[0169] Comparison of some casting results: The components of the silicon nitride casting slurry of each embodiment are completely dissolved, the viscosity is moderate, and the casting can be performed normally. The casting green sheet of Example 1 is as follows: Figure 1 As shown in b; the cast green body obtained by tape casting has no cracks, no pores, uniform surface and uniform thickness, as shown in Figure 2 a; and the components of the silicon nitride casting slurry of Comparative Example 1 were not completely dissolved, such as Figure 1 As shown in a, the viscosity is too large and there is no fluidity, so the next step of casting operation cannot be performed; the casting green sheet obtained by casting in Comparative Example 2 is as follows Figure 2 As shown in b, cracks occur and the thickness is uneven. It can be seen that the single solvent ethylene glycol evaporates quickly during the casting and drying stage, resulting in peeling, which causes cracks in the cast sheet. When the silicon nitride casting slurry in Comparative Example 3 is cast and dried at the same temperature and for the same time as in Example 1, it is difficult to dry completely, and the green body is too soft, resulting in poor green body performance. If complete drying is required, the temperature must be increased. In actual mass production, the energy consumption of the casting section is greatly increased, and the increased temperature drying will cause the obtained green body to be insufficient in strength. In the process of cutting into sheets, the cut edges will crack and slag will fall off, and the obtained cast green body does not meet the requirements of subsequent sintering.

[0170] Test Case

[0171] 1. The silicon nitride tape casting slurries of the embodiment and the comparative example were sampled, and the viscosity of the slurries was tested using a Brookfield DV2T viscometer. The viscosity of the slurries was measured again after being placed for a long time (30 days). The results are shown in Table 1.

[0172] 2. The thickness of the silicon nitride tape-cast green sheets corresponding to Example 1 was measured using a micrometer. Eight points were randomly selected for measurement on each sheet. The results are shown in Table 2.

[0173] 3. The density, flexural strength and thermal conductivity of the silicon nitride ceramic sheet of Application Example 1 were tested respectively, wherein the density was measured by the Archimedes drainage method; the flexural strength was tested by the three-point bending method according to ASTM-D790, and the indenter loading speed was 0.5 mm / min; thermal conductivity: the thermal diffusion coefficient of the sample was first determined using a laser thermal conductivity meter, and then the thermal conductivity was calculated according to Formula 1; the test results are shown in Table 1.

[0174] λ=ρ·c·α Formula 1,

[0175] Where, α: thermal diffusion coefficient, unit: m 2 / s;

[0176] λ: thermal conductivity, unit: W / (m·K);

[0177] ρ: sample density, unit Kg / m3 ;

[0178] c: Specific heat capacity of the sample, unit: J / (Kg·K).

[0179] Table 1:

[0180]

[0181]

[0182] In Table 1, “ / ” indicates that there is no test result for this item.

[0183] It can be seen from Table 1 that compared with the comparative example, the viscosity of the silicon nitride casting slurry of the embodiment is 8100-11600mpas, and there is no obvious sedimentation after long-term placement (30 days). The cast sheet obtained by casting is relatively smooth and has no obvious bubbles. The silicon nitride ceramic sheet prepared using it also has the advantages of high density, high bending strength and high thermal conductivity.

[0184] Table 2:

[0185]

[0186] It can be seen from Table 2 that the thickness of the cast sheets obtained by casting the silicon nitride casting slurry of Examples 1-9 is relatively uniform.

[0187] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A silicon nitride tape casting slurry, characterized in that: The raw materials include, by mass: Silicon nitride powder: 40 to 50 parts; Sintering aid: 1 to 5 parts; Binder: 5 to 15 parts; Solvent: 30 to 40 parts; Silicone wetting and dispersing agent: 0.1 to 0.5 parts; Plasticizer: 5 to 15 parts; Wherein, the solvent comprises ethylene glycol and butyl acetate in a mass ratio of 3 to 5:

1.

2. The silicon nitride tape casting slurry according to claim 1, characterized in that: The organosilicon wetting and dispersing agent includes gamma-aminopropyltriethoxysilane and / or monovinyl terminated dimethyl.

3. The silicon nitride tape casting slurry according to claim 1 or 2, characterized in that: The sintering aid includes magnesium oxide and ytterbium oxide.

4. The silicon nitride tape casting slurry according to claim 3, characterized in that: The mass ratio of the magnesium oxide to the ytterbium oxide is 1:0.5-2.

5. The silicon nitride tape casting slurry according to any one of claims 1 to 4, characterized in that: In the silicon nitride powder, the α phase accounts for more than 95wt%; and / or the D50 of the silicon nitride powder is 0.5-0.8μm.

6. The silicon nitride tape casting slurry according to any one of claims 1 to 5, characterized in that: The binder is polyvinyl butyral; and / or the plasticizer is triethylene glycol diisooctanoate.

7. The silicon nitride tape casting slurry according to any one of claims 1 to 6, characterized in that: Also includes: Defoaming agent: 0.1 to 1 part.

8. A method for preparing the silicon nitride tape casting slurry according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) dispersing an organosilicon wetting and dispersing agent, a sintering aid and silicon nitride powder in part of the solvent, and performing a ball milling treatment to obtain a primary ball milling slurry; 2) a binder and a plasticizer are dispersed in the remaining solvent, mixed with the primary ball-milled slurry, and subjected to secondary ball-milling treatment to obtain secondary ball-milled slurry; 3) The silicon nitride tape casting slurry is obtained by vacuum degassing the secondary ball milling slurry.

9. A silicon nitride ceramic sheet, characterized in that: The raw material comprises the silicon nitride tape casting slurry as described in any one of claims 1-7.

10. A method for preparing a silicon nitride ceramic sheet, characterized in that: The following steps are involved: The silicon nitride casting slurry according to any one of claims 1 to 7 is used for casting and drying to obtain a silicon nitride casting sheet; the silicon nitride casting sheet is subjected to degreasing treatment and gas pressure sintering treatment to obtain the silicon nitride ceramic sheet.

11. A copper-clad ceramic substrate, characterized in that: The invention comprises the silicon nitride ceramic sheet as claimed in claim 9 or the silicon nitride ceramic sheet prepared by the preparation method of claim 10.

Images