Silicon nitride tape-casting blank waste recycling method, tape-casting blank and application

Abstract

The invention belongs to the technical field of silicon nitride tape-casting blank waste recycling, and particularly relates to a silicon nitride tape-casting blank waste recycling method, a tape-casting blank and application, the silicon nitride tape-casting blank waste and a liquid medium are mixed according to the mass ratio of 10: (3-4), wet ball milling is conducted for 5-36 h, and slurry is obtained; wherein the particle size of a ball milling medium for wet ball milling is 8-12mm; the slurry is filtered and then subjected to tape casting, and a tape casting blank is obtained; according to the method, recycling of the waste materials can be achieved only by adopting a wet ball milling method, the cost is effectively reduced, the waste material recovery rate can reach 90% or above, the silicon nitride ceramic substrate prepared from the casting blank can meet the use requirement, the utilization efficiency of the silicon nitride casting blank waste materials is effectively improved, and the silicon nitride ceramic substrate has the advantages of being environmentally friendly and free of pollution. And the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of recycling and reusing waste silicon nitride tape-casting embryos, and in particular relates to a method for recycling waste silicon nitride tape-casting embryos, a tape-casting embryo and an application thereof. Background Art

[0002] In recent years, with the rapid development of integrated circuits, 5G communications, aerospace and other fields, power electronic equipment is gradually moving towards high power, high frequency and integration, which has led to the rapid development of silicon nitride ceramic substrates. However, in the silicon nitride molding process, mixing, casting, shaping, cold / warm isostatic pressing, waste will be generated, which not only wastes raw materials and increases raw material costs, but also the treatment of waste also puts great pressure on the environment.

[0003] At present, the treatment and utilization of waste materials are relatively low, and some treatment methods are cumbersome to operate, which greatly increases the cost of products and affects the industry application and sustainable development of silicon nitride substrates. In the operation of the manufacturing industry, higher requirements are also placed on environmental protection. While vigorously developing heat dissipation materials such as silicon nitride substrates, the comprehensive recycling and utilization of waste materials and cost reduction have become the main development direction. Patent No. CN202311030581.9 discloses a method for recycling ceramic cast film waste to prepare high-performance ceramics. This solution requires the waste to be subjected to liquid nitrogen brittle fracture treatment or hardening treatment, and then cast molding is performed to obtain a cast embryo. The entire treatment process is relatively cumbersome, and during the brittle fracture treatment or hardening treatment, there will be problems such as uneven mixing, agglomeration, and a long treatment time of more than 2 days. The prior art also has a method of preparing a recycled ceramic tape-cast embryo body waste into a slurry, and obtaining a tape-cast embryo body by tape-casting the slurry. For example, Patent No. CN202411295097.3 discloses a method for preparing a recycled slurry prepared from magnesium oxide ceramic green body waste, wherein the magnesium oxide ceramic green body waste scraped off by a scraper during the tape-casting process is crushed and mixed with magnesium oxide powder, and then a supplementary solvent, a binder, and a dispersant are added to obtain a slurry, and the slurry is tape-cast to obtain a tape-cast embryo body; Patent No. CN202410988919.X discloses a method for recycling silicon nitride substrate tape-cast green bodies, wherein the recycled green bodies are vacuum pretreated and crushed, and solvents, plasticizers, dispersants and defoaming agents are added to obtain slurry, and the slurry is mixed with normal newly prepared slurry in proportion; and then filtered, degassed, and aged to obtain a silicon nitride tape. It can be seen that the above method for recycling ceramic tape-cast embryo waste is not only complicated, but also requires the addition of multiple reagents during the recycling process, which greatly increases the recycling cost. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for recycling silicon nitride tape-cast embryo waste, a tape-cast embryo and its application. The tape-cast embryo obtained by wet ball milling can be used to prepare a silicon nitride ceramic substrate. The whole process is simple to operate, the mixing is uniform, and no agglomeration will occur.

[0005] In order to achieve the above-mentioned purpose, the technical solution of the present invention is specifically as follows.

[0006] A method for recycling silicon nitride tape-casting embryo waste comprises the following steps:

[0007] The silicon nitride tape casting embryo waste is mixed with the liquid medium in a mass ratio of 10:3-4, and wet ball milled for 5h-36h with a ball milling medium with a particle size of 8mm-12mm to ensure that the internal structure of the silicon nitride tape casting embryo waste is not damaged and is evenly dispersed in the liquid medium, and a slurry is obtained after wet ball milling;

[0008] The slurry is filtered and then tape-cast to obtain a tape-cast embryo body.

[0009] The present invention uses wet ball milling to mix silicon nitride tape casting embryo waste with liquid medium in a mass ratio of 10:3-4, wet ball milling for 5h-36h, and ball milling with 8mm-12mm ball milling medium, so that the obtained slurry does not contain solid particles, and the silicon nitride tape casting embryo waste is evenly dispersed in the solvent, so that the final slurry does not have problems such as uneven mixing and agglomeration. Only liquid medium is used in the entire treatment process, and no other additional reagents need to be added, which greatly reduces the recycling cost, and the recycling treatment time is short, and the treatment can be completed in as fast as 5h, which effectively shortens the treatment time and improves production efficiency.

[0010] More importantly, the present invention uses ball milling media with a particle size of 8 mm to 12 mm, which can ensure that the internal structure of the silicon nitride tape-cast embryo waste will not be damaged during the ball milling process, thereby ensuring that the tape-cast embryo obtained after the silicon nitride tape-cast embryo waste is recycled can be normally used to prepare silicon nitride ceramic substrates without affecting the performance of the silicon nitride ceramic substrates. If ball milling media with other particle sizes are used, the above effect cannot be achieved.

[0011] In another preferred embodiment, the rotation speed of the wet ball mill is 80 rpm to 150 rpm.

[0012] In another preferred embodiment, the viscosity of the slurry is 1500Mpa.s to 4000Mpa.s, which is more conducive to tape casting.

[0013] In another preferred embodiment, the ball milling media for wet ball milling are silicon nitride balls.

[0014] In another preferred embodiment, the liquid medium is water or anhydrous ethanol.

[0015] In another preferred embodiment, the filtration is performed using a 120-180 mesh sieve.

[0016] In another preferred embodiment, the silicon nitride tape-cast embryo body is cut to a length less than 20 mm before being wet-ball-milled.

[0017] In another preferred embodiment, the silicon nitride tape casting embryo waste refers to the waste in the process of preparing silicon nitride ceramic substrates, specifically including the washed material in the tape casting filtration process, defective waste in the tape casting process, cutting waste after lamination and waste in the isostatic pressing process.

[0018] The second aspect of the present invention provides the cast embryo body.

[0019] The third aspect of the present invention provides the use of the tape-cast embryo body in preparing a silicon nitride ceramic substrate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The recycling and reuse method of silicon nitride tape-cast embryo waste in the present invention is economical and simple, and only one process of wet ball milling is used, and no reagents need to be added during the treatment process, which effectively reduces the recycling cost. By selecting a ball milling medium with a particle size of 8mm to 12mm for wet ball milling, it can not only ensure that the silicon nitride tape-cast embryo waste is evenly dispersed in the liquid medium, but also avoid the problem of poor dispersion effect due to excessively large ball milling medium particle size, and damage to the structure of the silicon nitride tape-cast embryo waste due to excessively small ball milling medium particle size, thereby affecting the performance of subsequent products. And by controlling the wet ball milling time, the uniformity is further improved, the agglomeration problem is effectively solved, and more than 90% of the silicon nitride tape-cast embryo waste is utilized. The slurry obtained after ball milling is easy to tape-cast, and the entire treatment process is short. It takes only 5 hours to complete the recycling at the fastest, which effectively shortens the treatment time and reduces the cost.

[0022] (2) The thermal conductivity of the silicon nitride ceramic substrate prepared by the tape-cast embryo body of the present invention can reach 100 W / m·K, and the flexural strength can reach 700 MPa. The waste silicon nitride tape-cast embryo body is treated by the wet ball milling method of the present invention without damaging its performance, and the obtained silicon nitride ceramic substrate can continue to be used. In addition, no additional cost is added during the treatment process, which effectively improves the utilization efficiency of the waste silicon nitride tape-cast embryo body and reduces the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1It is a scanning electron microscope image of the slurry in Example 1 of the present invention, and Spectrum 1 is a spectrum signal.

[0024] Figure 2 This is a photo of the material to be processed in Example 1 of the present invention.

[0025] Figure 3 This is a photo of the slurry in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with specific examples, but they should not be construed as limiting the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified, and the materials, reagents, etc. used in the following examples are commercially available unless otherwise specified.

[0027] Waste will appear in the process of forming, laminating, shaping, and cold / warm pressure reduction of silicon nitride cast embryos, and the proportion is as high as 10% to 30%. The existing technology usually volatilizes the residual solvent in the ceramic cast film waste until the weight no longer changes to obtain the material to be treated; the material to be treated is first subjected to liquid nitrogen brittle fracture treatment or hardening treatment, and then crushed to obtain a granular raw material; the obtained granular raw material and the solvent are mixed to obtain a mixed slurry; the obtained mixed slurry is subjected to cast molding to obtain a ceramic cast film; the obtained ceramic cast film is subjected to at least one of the processes of trimming, laminating, and metallization, and then debonded and sintered to obtain high-performance ceramics. The above-mentioned processing process is complicated, and the brittle fracture treatment or hardening treatment, and the treated material needs to be ground before it can be mixed, otherwise there will be problems such as uneven mixing, agglomeration, and long mixing time.

[0028] The embodiments of the present invention provide a method for recycling silicon nitride tape-cast embryo waste, a tape-cast embryo and an application thereof. Only wet ball milling is used. By mixing a solvent with the silicon nitride tape-cast embryo waste and ball milling, the waste can be reused. This not only solves the problem of waste recycling and reuse, but also effectively reduces costs.

[0029] The following is a detailed description of a method for recycling silicon nitride tape-cast embryo waste, the tape-cast embryo and its application. The silicon nitride ceramic tape-cast embryo waste involved in the following embodiments includes washed material in the filtration process, defective waste in the tape-casting process, cutting waste after lamination, and unqualified waste in the cooling / warming process.

[0030] Example 1

[0031] A method for recycling silicon nitride tape-casting embryo waste comprises the following steps:

[0032] S1. Cut the silicon nitride tape-cast embryo waste into small pieces with a length not greater than 20 mm to obtain the material to be processed, such as Figure 2shown.

[0033] S2. Select the liquid medium according to the residual solvent in the material to be treated; the residual solvent in the material to be treated is water, so deionized water is selected as the liquid medium for ball milling; the material to be treated and deionized water are mixed in a mass ratio of 10:6 and then placed in a mixer for ball milling for 5 hours, the ball milling medium is 8mm silicon nitride balls, the rotation speed is 160 rpm, and a slurry is obtained, such as Figure 3 shown.

[0034] S3. Use a viscometer to test the viscosity of the slurry. The viscosity is controlled at 1800Mpa.s. If the viscosity is too high, add deionized water; if it is too low, add the material to be treated and re-mill until the viscosity meets the requirement of 1800Mpa.s.

[0035] S4, filtering the slurry with a 120-mesh sieve and then performing tape casting to obtain a tape-cast embryo body.

[0036] The recovery rate of silicon nitride tape-casting embryo waste is above 95%.

[0037] Example 2

[0038] A method for recycling silicon nitride tape-casting embryo waste comprises the following steps:

[0039] S1. Cut the silicon nitride cast embryo into small pieces with a length not exceeding 20 mm to obtain a material to be processed.

[0040] S2. Select the liquid medium according to the residual solvent in the material to be treated; the residual solvent in the material to be treated is water, so deionized water is selected as the liquid medium for ball milling; the material to be treated and deionized water are mixed in a mass ratio of 10:5.5 and then placed in a mixer for ball milling for 5 hours. The ball milling medium is 10mm silicon nitride balls, and the mixer speed is 180 rpm to obtain a slurry.

[0041] S3. Use a viscometer to test the viscosity of the slurry. The viscosity is controlled at 1700Mpa.s. If the viscosity is too high, add deionized water; if it is too low, add the material to be treated and re-mill until the viscosity meets the requirement of 1700Mpa.s.

[0042] S4, filtering the slurry with a 150-mesh sieve and then performing tape casting to obtain a tape-cast embryo body.

[0043] The recovery rate of silicon nitride tape-casting embryo waste is above 95%.

[0044] Example 3

[0045] A method for recycling silicon nitride tape-casting embryo waste comprises the following steps:

[0046] S1. Cut the silicon nitride cast embryo into small pieces with a length not exceeding 20 mm to obtain a material to be processed.

[0047] S2. Select the liquid medium according to the residual solvent in the material to be treated; the residual solvent in the material to be treated is anhydrous ethanol, so anhydrous ethanol is selected as the liquid medium for ball milling; the material to be treated and deionized water are mixed in a mass ratio of 10:5 and placed in a mixer for ball milling for 5 hours. The ball milling medium is 12 mm silicon nitride balls, and the mixer speed is 170 rpm to obtain a slurry.

[0048] S3. Use a viscometer to test the viscosity of the slurry. The viscosity is controlled at 1600Mpa.s. If the viscosity is too high, add deionized water; if it is too low, add the material to be treated and re-mill until the viscosity meets the requirement of 1600Mpa.s.

[0049] S4, filtering the obtained slurry with a 180-mesh sieve and then performing tape casting to obtain a tape-cast embryo body.

[0050] The recovery rate of silicon nitride tape-casting embryo waste is above 95%.

[0051] The tape-cast embryos prepared in Examples 1 to 3 were respectively used to prepare silicon nitride ceramic substrates according to conventional processes, and their performance and appearance were statistically analyzed, and the results are shown in Table 1. The length×width×height of the silicon nitride ceramic substrate is 139 mm×190 mm×0.32 mm.

[0052] Table 1 Performance indicators of silicon nitride ceramic substrate

[0053]

[0054] It can be seen from the results in Table 1 that the appearance, thermal conductivity and flexural strength of the silicon nitride ceramic substrate obtained by the tape-cast embryo body prepared by the method of the present invention all meet the use requirements of the product. It shows that the treatment of silicon nitride tape-cast embryo body waste by the wet ball milling method of the present invention does not damage its performance, and the obtained silicon nitride ceramic substrate can continue to be used, and no additional cost is added during the treatment process, which effectively improves the utilization efficiency of silicon nitride tape-cast embryo body waste and reduces production costs.

[0055] The slurry in Example 1 was subjected to scanning electron microscopy analysis, and the results were as follows: Figure 1 As shown. Figure 1It can be seen that after the silicon nitride tape-cast embryo waste is treated by wet ball milling, there is no agglomeration and uniform mixing inside the waste, and this effect can be achieved after only 5 hours of ball milling, which shows that the method of the present invention can effectively simplify the process of recycling silicon nitride tape-cast embryo waste. By controlling the mass ratio of the material to be treated and the liquid medium, and ball milling for 5 hours under a ball milling medium with a particle size of 8mm to 12mm, the silicon nitride tape-cast embryo waste can be recycled, and the obtained slurry viscosity is 1500Mpa.s to 4000Mpa.s, which is more conducive to tape-casting. The performance of the silicon nitride ceramic substrate prepared from the obtained tape-cast embryo meets the use requirements.

[0056] It can be seen from the above experiments that the present invention wet-ball-mills the silicon nitride cast embryo waste and the liquid medium at a mass ratio of 10:3-4 for 5h-36h, and uses 8mm-12mm ball milling media for ball milling. This can ensure that the obtained slurry does not contain particulate matter, and can make the silicon nitride cast embryo waste evenly dispersed in the solvent. The final slurry will not have problems such as uneven mixing and agglomeration. The entire treatment process is short. Compared with the prior art which requires a treatment time of about 2 days, the present invention only needs about 1 day to complete the treatment, effectively shortening the treatment time.

[0057] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for recycling silicon nitride tape casting embryo waste, characterized in that: The following steps are involved: The silicon nitride tape casting embryo waste is mixed with the liquid medium in a mass ratio of 10:3-4, and wet ball milled for 5h-36h with a ball milling medium with a particle size of 8mm-12mm to ensure that the internal structure of the silicon nitride tape casting embryo waste is not damaged and is evenly dispersed in the liquid medium, and a slurry is obtained after wet ball milling; The slurry is filtered and then tape-cast to obtain a tape-cast embryo body.

2. The method for recycling silicon nitride tape casting embryo waste according to claim 1, characterized in that: The rotation speed of the wet ball mill is 80 rpm to 150 rpm.

3. The method for recycling silicon nitride tape casting embryo waste according to claim 1, characterized in that: The viscosity of the slurry is 1500Mpa.s to 4000Mpa.s.

4. The method for recycling silicon nitride tape casting embryo waste according to claim 1, characterized in that: The ball milling medium of the wet ball milling is silicon nitride ball.

5. The method for recycling silicon nitride tape casting embryo waste according to claim 1, characterized in that: The liquid medium is water or anhydrous ethanol.

6. The method for recycling silicon nitride tape casting embryo waste according to claim 1, characterized in that: The filtration is performed using a 120-180 mesh sieve.

7. The method for recycling silicon nitride tape-casting embryo waste according to claim 1, characterized in that: Before the silicon nitride tape-cast embryo waste is subjected to wet ball milling, the method further includes cutting the silicon nitride tape-cast embryo waste to a length less than 20 mm.

8. The method for recycling silicon nitride tape casting embryo waste according to claim 1, characterized in that: The silicon nitride tape casting embryo waste refers to the waste in the process of preparing silicon nitride ceramic substrates, specifically including the washed material in the tape casting filtration process, the defective waste in the tape casting process, the cutting waste after lamination and the waste in the cold / warm isostatic pressing process.

9. A tape-cast embryo body obtained by the method according to any one of claims 1 to 8.

10. Use of the tape-cast embryo body according to claim 9 in preparing a silicon nitride ceramic substrate.

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