A low shrinkage ceramic composite material and a method for preparing the same

Abstract

The application provides a low-shrinkage ceramic composite material and a preparation method thereof. The low-shrinkage ceramic composite material is prepared by using bismuth trioxide, boron nitride and aluminum oxide as raw materials, mixing and ball milling, pre-sintering, adding a binder to the pre-sintered material, granulating, pressing and sintering, and adopting a solid phase sintering method, so that the shrinkage rate, mechanical property and thermal conductivity can be well balanced; or the low-shrinkage ceramic composite material is prepared by adding a solvent, a dispersing agent, a binder and a plasticizer to the pre-sintered material, ball milling to obtain a uniform slurry, casting the mixed slurry into a green ceramic sheet, and performing glue removal and sintering after cutting the green ceramic sheet, so that the shrinkage rate of a single-layer sintered sheet is less than 5%, and the shrinkage rate of a five-layer laminated sintered sheet is less than 1%. The preparation process is simple and easy to implement, and the application prospect is wide in the fields of electronic packaging, precision part manufacturing and dentistry.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic materials, in particular to a low-shrinkage ceramic composite material and a preparation method thereof. BACKGROUND

[0002] With the rapid development of information communication industry, the characteristics of electronic communication products are turning into miniaturization, integration and portability. The development of miniaturization and integration inevitably requires electronic ceramic substrates to have higher sintering precision, heat dissipation performance and mechanical strength to ensure the normal performance after sintering.

[0003] LTCC material is an important electronic ceramic material, mainly used in the packaging field, and the most widely used system is the glass-ceramic composite system. The low melting point of glass leads to sintering even at no more than 1000 DEG C, but it will have a large sintering shrinkage, which seriously affects the accuracy of electronic circuit positioning. Commercially, self-constraint method is always used to control the shrinkage of LTCC, but this method not only increases the cost of equipment and time, but also increases the complex process of peeling off the sacrificial layer. If the ceramic material, especially the ceramic tape casting sheet added with a lot of adhesive, has a low or even near-zero shrinkage, it can greatly save energy, as well as financial and human cost, and also can provide a good material selection in dental and other precision manufacturing.

[0004] Most of the low-shrinkage ceramic materials currently studied have low sintering shrinkage, but have high porosity, which leads to poor thermal and mechanical properties. Therefore, it is a difficult challenge to develop a ceramic material with low shrinkage and good thermal conductivity and mechanical properties. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of low-shrinkage low-temperature co-fired ceramic material, which has high thermal conductivity and high bending strength.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: a preparation method of low-shrinkage low-temperature co-fired ceramic material, comprising the following steps:

[0007] S1, alumina, bismuth trioxide and boron nitride with a mass ratio of 1:(0.5-0.9):(0-0.9) are weighed, mixed and ball milled after adding a medium, and dried to obtain a mixture;

[0008] S2, the mixture is pre-fired at 400-800 DEG C for 0.5-3h, mixed and ball milled after adding a medium, and dried to obtain a pre-fired material;

[0009] S3, granulating the pre-sintered material by adding a binder, sieving, and then compression molding; placing the compression molded material in a sintering furnace at 700-900 DEG C for 1-3 hours, and cooling to room temperature to obtain the low-shrinkage ceramic composite material;

[0010] Alternatively, adding a solvent, a dispersant, a binder, and a plasticizer to the pre-sintered material, and ball-milling to obtain a uniform slurry; casting the uniform slurry on a polyimide film, drying at room temperature to form a green ceramic sheet, cutting the green ceramic sheet to obtain a single-layer green ceramic sheet, or cutting the green ceramic sheet and stacking multiple layers to obtain a multi-layer green ceramic sheet, then placing the single-layer green ceramic sheet or the multi-layer green ceramic sheet in a sintering furnace at 400-800 DEG C for 0.5-3 hours for degassing, and then sintering at 700-900 DEG C for 1-3 hours, and cooling to room temperature to obtain the low-shrinkage ceramic composite material.

[0011] Further improvement of the preparation method of the low-shrinkage low-temperature co-fired ceramic material is provided.

[0012] Preferably, the boron nitride is hexagonal boron nitride.

[0013] Preferably, the ball-mixing time in step S1 is 1-8 hours, and the medium is anhydrous ethanol or water.

[0014] Preferably, the drying temperature in step S1 is 50-100 DEG C, and the drying time is 2-8 hours.

[0015] Preferably, the pre-sintering temperature increasing rate in step S2 is 2-5 DEG C / min, and the sintering temperature increasing rate in step S3 is 2-5 DEG C / min.

[0016] Preferably, the sieve mesh in step S3 is 50-200 mesh, and the compression molding pressure is 10-100 MPa; the temperature for stacking and compression molding of the multi-layer green ceramic sheet is 65-80 DEG C, and the pressure is 9-12 MPa.

[0017] Preferably, the mass ratio of the pre-sintered material, the solvent, the dispersant, the binder, and the plasticizer in step S3 is 1:(0.5-2):(0.01-0.05):(0.05-0.20):(0.05-0.20).

[0018] Preferably, the solvent in step S3 is ethanol or cyclohexanone, and the dispersant is triacetamide.

[0019] Preferably, the binder in step S3 is polyvinyl butylal, and the plasticizer is butyl benzyl phthalate or polyethylene glycol.

[0020] The second object of the present application is to provide a low-shrinkage low-temperature co-fired ceramic material prepared by the preparation method of the low-shrinkage low-temperature co-fired ceramic material.

[0021] The beneficial effects of the present application compared with the prior art are:

[0022] 1) The present application provides a method for preparing a low-shrinkage ceramic composite material, using bismuth trioxide, boron nitride and / or aluminum oxide as raw materials, and preparing by solid phase sintering method or tape casting method. The raw materials used in the present application are inexpensive and common, and the process adopted is simple and easy to operate, and is suitable for factory production. When bismuth trioxide, boron nitride and aluminum oxide are used as raw materials, bismuth trioxide reacts with boron nitride at high temperature to generate boron oxide, and the boron oxide reacts with aluminum oxide to generate aluminum borate. This reaction is a restructured phase change reaction, and volume expansion occurs during the reaction process, thereby making up for the volume shrinkage during sintering, so that the volume remains unchanged before and after sintering. At the same time, bismuth trioxide and boron oxide can generate amorphous glass, which wets the generated aluminum borate whiskers, so that they become an integral whole, improving the mechanical properties and thermal conductivity.

[0023] 2) The aluminum borate ceramic prepared in the present application has a low sintering shrinkage due to its high aspect ratio, and the aluminum borate ceramic itself has good mechanical properties, thermal conductivity and oxidation resistance, so that a low-shrinkage ceramic composite material with high thermal conductivity and bending strength can be obtained. In the field of electronic packaging, precision electronic devices, and dental field, there is a great application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The scanning picture of the sintered sheet prepared by the solid phase sintering method of Example 3;

[0025] Figure 2 The scanning picture of the sintered sheet prepared by the tape casting method of Example 4. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the following combines examples to further explain the present application. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] Example 1

[0028] The present embodiment provides a method for preparing a low-shrinkage ceramic composite material by solid phase sintering method, which specifically comprises the following steps:

[0029] (1) Take aluminum oxide and bismuth trioxide with a mass ratio of 1:0.8, and mix them uniformly in a ball mill with anhydrous ethanol as medium for 4h, and the ball mill speed is 350r / min. The milled powder is dried in an oven at 60℃, and a mixture is obtained;

[0030] (2) The mixture was pre-calcined at 600℃ for 1 hour at a heating rate of 5℃ / min. After adding deionized water, it was ball-milled for 4 hours at a speed of 350r / min. Then it was dried in an oven at 60℃ to obtain the pre-calcined material.

[0031] (3) Add polyvinyl butyral binder to the pre-fired material, granulate, pass through a 100-mesh sieve, press the material at a pressure of 25 MPa, sinter the pressed material at 900℃ for 2 hours, with a heating rate of 4℃ / min, and cool to room temperature to obtain the low-shrinkage ceramic composite material 1.

[0032] Example 2

[0033] This embodiment provides a method for preparing low-shrinkage ceramic composite materials by solid-state sintering, specifically including the following steps:

[0034] (1) Weigh alumina, bismuth trioxide and hexagonal boron nitride in a mass ratio of 1:0.8:0.3, and mix them evenly in a ball mill for 4 hours with anhydrous ethanol as the medium. The ball mill speed is 350 r / min. The powder after ball milling is placed in an oven and dried at 60°C to obtain the mixture.

[0035] (2) The mixture was pre-calcined at 600℃ for 1 hour at a heating rate of 5℃ / min. After adding deionized water, it was ball-milled for 4 hours at a speed of 350r / min. Then it was dried in an oven at 60℃ to obtain the pre-calcined material.

[0036] (3) Add polyvinyl butyral binder to the pre-fired material, granulate, pass through a 100-mesh sieve, press the material at a pressure of 25 MPa, sinter the pressed material at 900℃ for 2 hours, with a heating rate of 4℃ / min, and cool to room temperature to obtain the low-shrinkage ceramic composite material 2.

[0037] Example 3

[0038] This embodiment provides a method for preparing low-shrinkage ceramic composite materials by solid-state sintering, specifically including the following steps:

[0039] (1) Weigh alumina, bismuth trioxide and hexagonal boron nitride in a mass ratio of 1:0.8:0.5, and ball mill them in an anhydrous ethanol medium for 4 hours to mix them evenly. The ball mill speed is 350 r / min. The powder after ball milling is placed in an oven and dried at 60°C to obtain the mixture.

[0040] (2) The mixture was pre-calcined at 600℃ for 1 hour at a heating rate of 5℃ / min. After adding deionized water, it was ball-milled for 4 hours at a speed of 350r / min. Then it was dried in an oven at 60℃ to obtain the pre-calcined material.

[0041] (3) Add polyvinyl butyral binder to the pre-fired material, granulate, pass through a 100-mesh sieve, press the material at a pressure of 25 MPa, sinter the pressed material at 900℃ for 2 hours, with a heating rate of 4℃ / min, and cool to room temperature to obtain the low-shrinkage ceramic composite material 3.

[0042] Figure 1 This is a scanned image of the sintered sheet prepared by solid-state sintering in Example 3; by Figure 1 It is known that when the raw materials contain both bismuth trioxide and boron nitride, the system generates aluminum borate whiskers, and the bismuth oxide glass effectively encapsulates and wets the whiskers, resulting in a dense structure that is beneficial for improving its mechanical strength and thermal conductivity.

[0043] Examples Linear shrinkage (%) Thermal conductivity (W / mK) Bending strength (MPa) 1 5.56％ 6.373 55.05 2 2.57％ 2.476 87.87 3 0.031％ 2.883 125.10

[0044] Tests showed that the low-shrinkage ceramic composite materials prepared by solid-state sintering in Examples 1-3 had a linear shrinkage rate of 0.031%-5.56%, a thermal conductivity of 2.476-6.373 W / mK, and a flexural strength of 55.05-125.10 MPa. Example 3 exhibited the lowest linear shrinkage rate (0.031%) and the highest flexural strength (125 MPa). This demonstrates that, with a suitable ratio of alumina, bismuth trioxide, and boron nitride, the sintered sheets produced by this invention can effectively balance shrinkage rate, mechanical properties, and thermal conductivity, thus solving the problem of the inability to simultaneously achieve both shrinkage rate and mechanical properties in existing technologies.

[0045] Example 4

[0046] This embodiment provides a method for preparing low-shrinkage ceramic composite materials by casting, specifically including the following steps:

[0047] (1) Weigh aluminum oxide, bismuth trioxide and hexagonal boron nitride in a mass ratio of 1:0.8:0.7, and ball mill them in an anhydrous ethanol medium for 4 hours to mix them evenly. The ball mill speed is 350 r / min. The powder after ball milling is placed in an oven and dried at 60°C to obtain the mixture.

[0048] (2) The mixture was pre-calcined at 600℃ for 1 hour at a heating rate of 5℃ / min. After adding deionized water, it was ball-milled for 4 hours at a speed of 350r / min. Then it was dried in an oven at 60℃ to obtain the pre-calcined material.

[0049] (3) Take 12g of pre-fired material, add 7g of ethanol, 7g of cyclohexanone, 0.396g of dispersant triethanolamine, 1.02g of binder polyvinyl butyral and 1.2g of plasticizer polyethylene glycol. The mass ratio of pre-fired material, solvent, dispersant, binder and plasticizer is 1:1.17:0.03:0.085:0.1. Ball mill to obtain a uniform slurry. Cast the uniform slurry on a polyimide film and dry it at room temperature to form a single-layer green ceramic sheet. Then heat it to 600℃ and keep it at 600℃ for 2h to remove the glue. The heating rate during glue removal is 2℃ / min. Continue to heat it to 900℃ and sinter for 2h at a heating rate of 4℃ / min. Cool it to room temperature to obtain a single-layer low-shrinkage ceramic composite material.

[0050] Alternatively, the single-layer green ceramic sheet obtained in step (3) of Example 4 can be cut into the same size, stacked together, and pressed at 70°C and 10MPa pressure. Then, the temperature is raised to 600°C and held for 2 hours to remove the glue. The heating rate during glue removal is 2°C / min. The temperature is then raised to 900°C and sintered for 2 hours at a heating rate of 4°C / min. After cooling to room temperature, a 5-layer laminated low-shrinkage ceramic composite material is obtained.

[0051] Figure 2 These are scanned images of the single-layer low-shrinkage ceramic composite material prepared by the above casting method, from... Figure 2 It is known that aluminum borate crystals are generated during the sintering process, with a length of about 3μm and a diameter of 300-500nm. The aluminum borate whiskers are wetted by bismuth oxide glass. However, due to the presence of a large amount of organic matter in the system, its density is lower than that of the sintered sheet obtained by the pressing method.

[0052] Tests have shown that the low-shrinkage ceramic composite material prepared by pressureless sintering using the tape casting method in this embodiment has a shrinkage rate of less than 5% for a single-layer sintered sheet and less than 1% for a 5-layer stack, which is far lower than the 15-20% shrinkage rate of general glass ceramic sintering. Moreover, the raw materials are readily available and the process is simple. This invention opens up a new method for the preparation of low-shrinkage low-temperature co-fired ceramic substrates.

[0053] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments. It should be noted that many modifications and improvements can be made by those skilled in the art, and all modifications or improvements not exceeding the scope of the claims should be considered within the protection scope of the present invention.

Claims

1. A method for preparing a low-shrinkage ceramic composite material, characterized in that, Includes the following steps: S1. Weigh aluminum oxide, bismuth trioxide and boron nitride in a mass ratio of 1:0.8:(0.3-0.7), add media, ball mill and mix, and dry to obtain a mixture. S2. Place the mixture at 400-800℃ for 0.5-3 hours, add the medium, ball mill and mix, and dry to obtain the pre-calcined material; S3. Add a binder to the pre-fired material, granulate, sieve, and then press into shape; sinter the pressed material at 700-900℃ for 1-3 hours, and cool to room temperature to obtain a low-shrinkage ceramic composite material. Alternatively, solvent, dispersant, binder and plasticizer are added to the pre-fired material, and ball milling is performed to obtain a uniform slurry; the uniform slurry is cast onto a polyimide film and dried at room temperature to form a green ceramic sheet; the green ceramic sheet is cut to obtain a single-layer green ceramic sheet, or the green ceramic sheet is cut and then multi-layered and pressed to obtain a multi-layered green ceramic sheet; then the single-layered or multi-layered green ceramic sheet is placed at 400-800℃ for heat preservation and glue removal, and then sintered at 700-900℃ for 1-3 hours, and cooled to room temperature to obtain a low-shrinkage ceramic composite material.

2. The method for preparing the low-shrinkage ceramic composite material according to claim 1, characterized in that, The boron nitride is hexagonal boron nitride.

3. The method for preparing the low-shrinkage ceramic composite material according to claim 1, characterized in that, The ball milling mixing time in step S1 is 1-8 hours, and the medium is anhydrous ethanol or water.

4. The method for preparing the low-shrinkage ceramic composite material according to claim 1, characterized in that, The drying temperature in step S1 is 50-100℃ and the time is 2-8 hours.

5. The method for preparing the low-shrinkage ceramic composite material according to claim 1, characterized in that, The heating rate for pre-firing in step S2 is 2-5℃ / min, and the heating rate for sintering in step S3 is 2-5℃ / min.

6. The method for preparing the low-shrinkage ceramic composite material according to claim 1, characterized in that, In step S3, the sieve used for sieving is 50-200 mesh, and the pressing pressure is 10-100 MPa; the temperature for pressing multiple layers of green ceramic sheets is 65-80℃, and the pressure is 9-12 MPa.

7. The method for preparing the low-shrinkage ceramic composite material according to claim 1, characterized in that, The mass ratio of the pre-calcined material, solvent, dispersant, binder and plasticizer mentioned in step S3 is 1:(0.5-2):(0.01-0.05):(0.05-0.20):(0.05-0.20).

8. The method for preparing the low-shrinkage ceramic composite material according to claim 1 or 7, characterized in that, The solvent in step S3 is ethanol and / or cyclohexanone, and the dispersant is triacetamide.

9. The method for preparing the low-shrinkage ceramic composite material according to claim 1 or 7, characterized in that, The adhesive mentioned in step S3 is polyvinyl butyral, and the plasticizer is butyl benzyl phthalate or polyethylene glycol.

10. A low-shrinkage ceramic composite material prepared by the method of any one of claims 1-9.

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