Preparation method of zirconium oxide-doped aluminum nitride ceramic substrate

Abstract

According to the preparation method of the zirconium oxide-doped aluminum nitride ceramic substrate provided by the invention, the zirconium oxide powder is added into the aluminum nitride ceramic powder, and the high-toughness aluminum nitride ceramic is prepared through a series of working procedures of premixing, ball milling, defoaming and the like, so that the bending strength of the aluminum nitride ceramic substrate can be obviously improved; the generation of cracks of the aluminum nitride substrate in actual use is reduced, and the use reliability of the product is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of DCB substrate manufacturing, and in particular relates to a method for preparing a zirconium oxide-doped aluminum nitride ceramic substrate. Background Art

[0002] Aluminum nitride ceramic substrates have become ideal heat dissipation and packaging materials for the new generation of large-scale integrated circuits and semiconductor power devices due to their high thermal conductivity (6 to 8 times that of aluminum oxide substrates), high electrical insulation, and low thermal expansion. However, since the bending strength of aluminum nitride substrates is lower than that of aluminum oxide substrates, cracks are prone to occur in actual use, causing product scrapping, which has a certain impact on the widespread use of aluminum nitride substrates.

[0003] Zirconia, with the chemical formula ZrO2, is the main oxide of zirconium. It is usually white, odorless and tasteless crystals, and is difficult to dissolve in water, hydrochloric acid and dilute sulfuric acid. It is chemically inactive and has the properties of high melting point, high resistivity, high refractive index and low thermal expansion coefficient, making it an important high temperature resistant material, ceramic insulation material and ceramic sunscreen, and also the main raw material for artificial diamonds.

[0004] The present invention utilizes the unique toughness of zirconium oxide to develop a technology for doping aluminum nitride ceramics with zirconium oxide materials. Zirconium oxide powder is added to aluminum nitride ceramic powder, and a series of processes such as premixing, ball milling, and degassing are performed to produce high-toughness aluminum nitride ceramics, thereby significantly improving the bending strength of the aluminum nitride substrate, reducing the generation of cracks in the aluminum nitride substrate in actual use, and improving the reliability of product use. No related attempts have been seen in the prior art. Summary of the invention

[0005] The present invention is based on the above problem and provides a method for preparing an aluminum nitride ceramic substrate doped with zirconium oxide. The reliability of the aluminum nitride substrate can be significantly improved by adding 2% zirconium oxide, such as DCB bending strength greater than 900Mpa, furnace pass 325℃ can be increased 5 times, TC cycle can be increased 50 times.

[0006] The specific technical solutions of the present invention are as follows:

[0007] In a first aspect, the present invention provides a method for preparing a zirconium oxide-doped aluminum nitride ceramic substrate, comprising the following steps:

[0008] A. Raw material preparation and processing

[0009] Adding zirconium oxide powder to aluminum nitride ceramic powder at a mass ratio of 2%, then adding chemical additives to premix into slurry, and removing bubbles in the slurry after ball milling;

[0010] B. Sheet preparation

[0011] The slurry is cast into a strip green body under the conditions of 20-30°C, humidity ≤70%RH, and line speed 255-265mm / min, and the strip green body is punched into a single piece of a certain size, and then two single pieces are hot pressed into one piece;

[0012] C. Sintering

[0013] After applying powder on the surface of the sheet (to prevent poor adhesion during sintering), the chemical additives are discharged, and the green sheet is sintered into a mature sheet at 1650-1750℃ in an inert gas atmosphere for 10-12h;

[0014] D. Grinding and cleaning

[0015] The ceramic sheet is ground to a specified thickness and then ultrasonically cleaned with pure water.

[0016] The preferred process conditions for the above steps are as follows:

[0017] In step A, the particle size of the zirconium oxide powder is about 2 μm, and the purity is 99.99%; the particle size of the aluminum nitride ceramic powder is about 1.3 μm, and the purity is 99.99%;

[0018] The chemical additive is selected from any one of anhydrous hexanol and a plasticizer, and the additive addition ratio is 4.5%;

[0019] The premixing process parameters are as follows: speed 450-550 r / min, time 4.5-5.5 h;

[0020] The ball milling process parameters are as follows: rotation speed 30-40 r / min, ball milling time 17.5-18.5 h;

[0021] The process parameters for slurry degassing are as follows: degassing time 1.5-2.5h, water bath temperature: 40-45°C, vacuum degree ≤-0.085MP.

[0022] In step B, when punching, the air pressure is 0.4-0.6 MPa;

[0023] The hot pressing process parameters are as follows: pressure 50-80T, temperature: upper mold 90-110°C, lower mold 70-100°C; holding time: 20-50s.

[0024] In step C, the powder coating process conditions are as follows: conveying speed: 950-1050 mm / min; temperature: 40-50° C.;

[0025] Pressure: 0.2MPa;

[0026] The chemical additive discharge conditions are as follows: temperature 450-550℃; debonding time: 18-22h;

[0027] During sintering, the inert gas is nitrogen and the nitrogen pressure is 0.4MPa.

[0028] In step D, the grinding process conditions are as follows: pressure 0.4 MPa, rotation speed: 18-22 r / min.

[0029] In a second aspect, the present invention provides a zirconium oxide-doped aluminum nitride ceramic substrate prepared by any of the methods described above.

[0030] Functions and Effects of the Invention

[0031] The present invention adds zirconium oxide powder to aluminum nitride ceramic powder, and through a series of processes such as premixing, ball milling, and degassing, a high-toughness aluminum nitride ceramic is prepared, thereby significantly improving the reliability of the aluminum nitride substrate. Compared with the zirconium-free aluminum nitride substrate, the bending strength of the ceramic sheet of the present invention is increased from 450Mpa to more than 550Mpa, the bending strength of the DCB substrate is increased from 750Mpa to more than 900Mpa, the failure rate at 325°C is increased from 2 failures to 5 failures, and the TC life is increased from 25 failures to 50 failures. DETAILED DESCRIPTION

[0032] The present invention is described in detail below in conjunction with the examples. However, the following examples should not be considered as limiting the scope of the present invention.

[0033] 1. Ingredients

[0034] Aluminum nitride ceramic powder is mixed with 2% zirconium oxide powder; wherein the zirconium oxide powder has a particle size of about 2 μm and a purity of 99.99%;

[0035] Aluminum nitride ceramic powder: particle size about 1.3μm; purity 99.99%.

[0036] 2. Premix

[0037] 1) The ingredients are premixed after adding chemical additives, and the additive addition ratio is 4.5%;

[0038] 2) Premixing process parameters

[0039] Premixing speed: 450~550r / min; time: 4.5~5.5h.

[0040] 3. Ball milling

[0041] 1) The ingredients are pre-mixed into a slurry and then ball-milled to make the particles uniform;

[0042] 2) Process parameters

[0043] Ball mill speed: 30~40r / min; ball mill time: 17.5~18.5h.

[0044] 4. Slurry degassing

[0045] 1) Remove bubbles from the slurry;

[0046] 2) Process parameters

[0047] Degassing time: 1.5~2.5h; water bath temperature: 40~45℃; vacuum degree ≤-0.085MPa.

[0048] 5. Casting

[0049] 1) The slurry is tape-casted into a strip-shaped green body;

[0050] 2) Process parameters

[0051] Temperature: 20~30℃; Humidity: ≤70%RH; Line speed: 255~265mm / min;

[0052] Blade height: Adjust according to the thickness of the ceramic sheet.

[0053] 6. Film processing

[0054] 1) Punching the strip green body into a single piece of a certain size;

[0055] 2) Process parameters: air pressure: 0.4~0.6MPa.

[0056] 7. Hot pressing

[0057] 1) Stack two sheets into one sheet;

[0058] 2) Process parameters

[0059] Pressure: 50~80T; Temperature: upper mold 90~110℃, lower mold 70~100℃; Holding time: 20~50s.

[0060] 8. Apply powder

[0061] 1) Powder is applied to the surface of the single piece to prevent poor adhesion during sintering

[0062] 2) Process parameters

[0063] Conveying speed: 950~1050mm / min; temperature: 40~50℃; pressure: 0.2MPa.

[0064] 9. Glue removal

[0065] 1) Expel chemical additives

[0066] 2) Process parameters

[0067] Temperature: 450~550℃; Debinding time: 18~22h.

[0068] 10. Sintering

[0069] 1) Sintering the green body into a mature body (ceramic sheet);

[0070] 2) Process parameters

[0071] Temperature: 1650~1750℃; Holding time: 10~12h; Nitrogen pressure: 0.4MPa

[0072] 11. Grinding

[0073] 1) Grind the ceramic sheet to the specified thickness;

[0074] 2) Process parameters

[0075] Pressure: 0.4MPa; speed: 18~22r / min.

[0076] 12. Cleaning

[0077] The ceramic sheet was ultrasonically cleaned with pure water.

[0078] Through the above steps, aluminum nitride ceramics containing zirconium oxide material can be manufactured.

[0079] Comparative Example 1

[0080] Ingredients: aluminum nitride ceramic powder not doped with zirconium oxide. The remaining steps are the same as those in Example 1.

[0081] The aluminum nitride ceramic sheets prepared in Example 1 and Comparative Example 1 and the DCB boards prepared therefrom were tested under the same conditions, as shown in Table 1 below:

[0082] Table 1 Performance comparison of zirconium-containing ceramic substrates and non-zirconium-containing ceramic substrates

[0083] project Zirconium-containing materials Zirconium-free materials Ceramic sheet bending strength 550Mpa and above 450Mpa Bending strength of DCB substrate 900MPA 750MPA DCB substrate TC life 50 failures 25 failures 325℃ furnace test 5 failures 2 failures

[0084] The results show that by implementing the above invention, the technology of adding zirconium oxide materials to aluminum nitride ceramics can be realized, the bending strength of the aluminum nitride substrate can be improved, the generation of cracks in actual use can be reduced, and the reliability of product use can be improved.

[0085] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. The present invention may be subject to various changes and improvements without departing from the spirit and scope of the present invention. These changes and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a zirconium oxide-doped aluminum nitride ceramic substrate, characterized in that: The steps include: A. Raw material preparation and processing Adding zirconium oxide powder to aluminum nitride ceramic powder at a mass ratio of 2%, then adding chemical additives to premix into slurry, and removing bubbles in the slurry after ball milling; B. Sheet preparation The slurry is cast into a strip green body under the conditions of 20-30°C, humidity ≤70%RH, and line speed 255-265mm / min, and the strip green body is punched into a single piece of a certain size, and then two single pieces are hot pressed into one piece; C. Sintering After the sheet surface is powdered, the chemical additives are discharged, and the green sheet is sintered into a mature sheet at 1650-1750℃ in an inert gas atmosphere for 10-12h; D. Grinding and cleaning The ceramic sheet is ground to a specified thickness and then ultrasonically cleaned with pure water.

2. The method for preparing the zirconium oxide-doped aluminum nitride ceramic substrate according to claim 1, characterized in that: in, In step A, the particle size of the zirconium oxide powder is about 2 μm, and the purity is 99.99%; the particle size of the aluminum nitride ceramic powder is about 1.3 μm, and the purity is 99.99%.

3. The method for preparing the zirconium oxide-doped aluminum nitride ceramic substrate according to claim 1, characterized in that: in, In step A, the chemical auxiliary agent is selected from any one of anhydrous hexanol and a plasticizer, and the auxiliary agent is added in an amount of 4.5%; The premixing process parameters are as follows: speed 450-550 r / min, time 4.5-5.5 h; The ball milling process parameters are as follows: rotation speed 30-40 r / min, ball milling time 17.5-18.5 h.

4. The method for preparing the zirconium oxide-doped aluminum nitride ceramic substrate according to claim 1, characterized in that: in, In step A, the process parameters for degassing the slurry are as follows: degassing time 1.5 to 2.5 h, water bath temperature: 40 to 45° C., vacuum degree ≤-0.085 MPa.

5. The method for preparing the zirconium oxide-doped aluminum nitride ceramic substrate according to claim 1, characterized in that: in, In step B, when punching, the air pressure is 0.4-0.6 MPa; The hot pressing process parameters are as follows: pressure 50-80T, temperature: upper mold 90-110°C, lower mold 70-100°C; holding time: 20-50s.

6. The method for preparing the zirconium oxide-doped aluminum nitride ceramic substrate according to claim 1, characterized in that: in, In step C, the powder coating process conditions are as follows: conveying speed: 950-1050 mm / min; temperature: 40-50° C.; pressure: 0.2 MPa; The chemical additive discharge conditions are as follows: temperature 450-550℃; debonding time: 18-22h; During sintering, the inert gas is nitrogen and the nitrogen pressure is 0.4MPa.

7. The method for preparing the zirconium oxide-doped aluminum nitride ceramic substrate according to claim 1, characterized in that: in, In step D, the grinding process conditions are as follows: pressure 0.4 MPa, rotation speed: 18-22 r / min.

8. A zirconium oxide-doped aluminum nitride ceramic substrate, characterized in that: The method is prepared by any one of claims 1 to 7.