Aluminum nitride ceramic large-area pressure diffusion sealing method based on glass solder and application of aluminum nitride ceramic large-area pressure diffusion sealing method

Abstract

The invention discloses an aluminum nitride ceramic large-area pressure diffusion sealing method based on glass solder and application thereof, and belongs to the technical field of ceramic materials. According to the method, glass powder with specific components is adopted as interlayer welding flux, aluminum nitride ceramic and the welding flux are assembled into a sandwich structure, and then the sandwich structure is heated to a certain temperature. Glass solder softened at a high temperature is densified through a pressure diffusion sealing technology, chemical elements in ceramic and glass are mutually diffused to achieve metallurgical bonding, large-area sealing connection is achieved, and the strength of a connector is good. Large-area sealing connection of the aluminum nitride ceramic not smaller than 50 * 50 mm < 2 > can be achieved, the internal welding rate of a connector exceeds 99.0%, and the bending strength reaches 260 MPa or above. The large-area pressure diffusion sealing method for the aluminum nitride ceramic is applied to the field of sealing of internal large-size complex structural members such as aluminum nitride ceramic heaters and liquid cooling plates.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials technology, specifically to a method for large-area pressure diffusion sealing of aluminum nitride ceramics based on glass solder and its application. Background Technology

[0002] Aluminum nitride ceramics, as a high-performance structural-functional integrated material, are widely used in cutting-edge fields such as microelectronic packaging, thermal management of high-power semiconductor devices, and high-temperature industrial applications due to their unique physicochemical properties, including high thermal conductivity, low coefficient of thermal expansion, and high resistivity. In these applications, large and complex internal structural components such as aluminum nitride ceramic heaters and liquid cooling plates require assembly using sealing technology.

[0003] Currently, the sealing technology for aluminum nitride ceramics mainly employs brazing, using active metal filler metals as the sealing material. While this method can achieve effective sealing of aluminum nitride ceramics, the mismatch between the thermal expansion coefficient of the metal filler metal and the aluminum nitride ceramic leads to significant residual stress within the joint and poor surface oxidation resistance. Furthermore, the electrical conductivity of the metal filler metal limits its widespread application in insulation-sensitive applications. In contrast, glass filler metals are considered a suitable material for sealing aluminum nitride ceramics due to their good chemical compatibility with ceramic materials, flexible controllable thermal expansion coefficients, and excellent insulation properties. However, due to insufficient wettability of glass filler metals on non-oxide ceramic surfaces, voids often appear within the weld, making it difficult to fabricate large-area, defect-free aluminum nitride ceramic joints using brazing. Current literature reports that the sealing area of ​​aluminum nitride ceramics does not exceed 20 × 20 mm². Therefore, there is an urgent need to develop a joint fabrication method that can achieve large-area sealing of aluminum nitride ceramics and possesses excellent mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a large-area pressure diffusion sealing method for aluminum nitride ceramics based on glass solder and its application. This method uses glass powder of a specific composition as the intermediate layer solder. The aluminum nitride ceramic joint is heated to above the glass softening temperature. Pressure diffusion sealing technology densifies the high-temperature softened glass solder, and metallurgical bonding is achieved through the mutual diffusion of chemical elements within the ceramic and glass. This results in a tight seal with a sealing area of ​​not less than 50×50 mm², while ensuring good joint strength. This sealing method has a wide range of applications, including but not limited to sealing large-size complex internal structural components such as aluminum nitride ceramic heaters and liquid cooling plates.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for large-area pressure diffusion sealing of aluminum nitride ceramics based on glass solder is disclosed, which involves using glass solder to perform large-area pressure diffusion sealing of aluminum nitride ceramic substrate. The glass solder has the following composition by weight percentage: RE2O3: 15-35%, Al2O3: 10-30%, SiO2: 5-25%, B2O3: 10-30%, CaO: 5-10%, ZnO: 5-10%, P2O5: 5-10%.

[0006] Furthermore, the preferred weight percentage composition of the glass solder is: RE2O3: 20-32%, Al2O3: 15-25%, SiO2: 8-22%, B2O3: 12-28%, CaO: 5-10%, ZnO: 5-10%, P2O5: 5-10%.

[0007] Furthermore, the RE2O3 is one of Yb2O3, Gd2O3, Y2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3, and Lu2O3.

[0008] Furthermore, the aluminum nitride ceramic is a commercially available aluminum nitride ceramic with an aluminum nitride content of 85-99.9 wt.% and a coefficient of thermal expansion of 4-5.5 × 10⁻⁶. -6 / ℃; Large-area sealing refers to a sealing surface of a single aluminum nitride ceramic substrate with an area of ​​50×50mm. 2 above.

[0009] The sealing method specifically includes the following steps: (1) Pretreatment of the base material: Aluminum nitride ceramics are ultrasonically cleaned with acetone as the medium to remove oil stains. The ultrasonic time is 10-20 minutes. Then, they are dried with a hair dryer for later use. (2) Preparation of glass solder: Weigh the corresponding raw materials according to the composition of glass solder, mix them evenly, and then prepare glass solder by melt water quenching method; (3) Slurry preparation: The glass solder and the binder are mixed in proportion and stirred to obtain a uniformly mixed glass slurry; (4) Slurry coating: Apply glass slurry evenly to the surfaces of the two aluminum nitride ceramics to be sealed; (5) Debonding treatment: Place two aluminum nitride ceramics with glass solder coating on their surfaces in a muffle furnace and heat them to the debonding temperature at a certain heating rate and keep them at that temperature for a period of time to ensure that the adhesive inside the dissolved glass solder evaporates and cools down to room temperature with the furnace. (6) Joint assembly: Assemble the two pieces of aluminum nitride ceramic to be welded to form a "sandwich" assembly structure of "ceramic / glass solder / ceramic"; (7) Joint sealing: The joint assembled in step (6) is placed in a heating furnace with air atmosphere, vacuum atmosphere or inert gas atmosphere, and heated to the sealing temperature at a certain heating rate under a certain pressure. After holding at the temperature for a certain time, the furnace is then slowly cooled to room temperature.

[0010] Further, in step (2), in the composition of the glass solder, B2O3 is introduced from H3BO3 raw material, CaO is introduced from CaCO3 raw material, P2O5 is introduced from H3PO4 raw material, and other components are introduced from corresponding oxide raw materials, and the purity of each raw material is higher than 99.9%; the preparation process of the glass solder is as follows: the weighed raw material powders of each component are placed in a ball mill jar for ball milling, with alcohol or deionized water as the medium, a rotation speed of 500-800 rpm, and a time of 4-5 h. After ball milling, the mixed powder is dried and poured into a platinum or corundum crucible, placed in an air atmosphere muffle furnace and heated to 1500-1600℃, kept at the temperature for 1-3 h, and the glass melt is quickly poured into deionized water to obtain glass fragments. Subsequently, the glass fragments are ground and passed through a 100 to 300 mesh sieve to finally obtain glass solder powder with a particle size not exceeding 30 μm.

[0011] In step (3), the adhesive added to the glass slurry is composed of terpineol, anhydrous ethanol and polyvinyl alcohol; in the slurry, the weight ratio of terpineol is 10-35%, the weight ratio of anhydrous ethanol is 2-10%, and the weight ratio of polyvinyl alcohol is 2-10%.

[0012] In step (4), the coating method can be screen printing, manual coating or spraying, or a combination of multiple methods can be used for coating. When screen printing is used, the mesh count of the screen is between 80 and 200, and the thickness of the glass solder coating on the surface of the aluminum nitride ceramic to be welded is 50-100 μm.

[0013] In step (5), the heating rate is 5-20℃ / min, the glue discharge temperature is 200-500℃, and the heat preservation time is 1-5h.

[0014] In step (7), the heating rate of the joint sealing process is 5-20℃ / min, the sealing temperature is 900-1200℃, and the holding time is 0.5-3h; during the cooling process, the cooling rate is less than 10℃ / min between the sealing temperature and 750℃, and there is no requirement for the cooling rate after the temperature drops below 450℃. During this period, the applied pressure is maintained at 0.3-5 MPa, and the inert gas atmosphere includes but is not limited to N2, Ar, He, etc.

[0015] The aforementioned large-area pressure diffusion sealing method for aluminum nitride ceramics is applied to the sealing of large-sized complex internal structural components such as aluminum nitride ceramic heaters and liquid cooling plates.

[0016] The design mechanism and beneficial effects of this invention are as follows: (1) This invention uses commercial aluminum nitride ceramic as the base material and densifies the high-temperature softened glass solder through pressure diffusion sealing technology, promoting the mutual diffusion of chemical elements between the ceramic and the glass to achieve metallurgical bonding, thereby achieving a sealing area of ​​aluminum nitride ceramic of not less than 50×50 mm. 2 The joint is tightly sealed, with an internal welding rate exceeding 99.0%.

[0017] (2) The thermal expansion coefficient of the glass interlayer prepared by the present invention matches that of the aluminum nitride ceramic matrix, and has excellent mechanical properties. The bending strength of the joint reaches more than 260 MPa.

[0018] (3) The pressure diffusion sealing method described in this invention is simple and convenient, and can realize the preparation of large-size complex aluminum nitride ceramic components with low cost and high performance. The application fields of this sealing method include, but are not limited to, sealing of large-size complex internal components such as aluminum nitride ceramic heaters and liquid cooling plates. Attached Figure Description

[0019] Figure 1 The thermal expansion curves are those of the glass and aluminum nitride ceramics prepared in Example 1.

[0020] Figure 2 This is a macroscopic photograph of the aluminum nitride connector obtained in Example 1.

[0021] Figure 3 This is an optical microscope image of the aluminum nitride connector obtained in Example 1.

[0022] Figure 4 This is a scanning electron microscope image of the aluminum nitride connector obtained in Example 1.

[0023] Figure 5 This is a scanning electron microscope image of the glass / ceramic interface of the aluminum nitride connector obtained in Example 1. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0025] In the following examples and comparative examples, the composition of the glass solder is as follows: B2O3 is introduced from H3BO3 raw material, CaO is introduced from CaCO3 raw material, P2O5 is introduced from H3PO4 raw material, and other components are introduced from corresponding oxide raw materials, and the purity of each raw material is higher than 99.0%. Example 1:

[0026] In this embodiment, the glass material is coated onto the surface of aluminum nitride ceramic and then assembled and pressure-diffused sealed, including the following steps: Material preparation: The aluminum nitride ceramic used is a commercially available aluminum nitride ceramic with an aluminum nitride content of 99% and dimensions of 50×50×2 mm. 3 The aluminum nitride ceramic to be strengthened was ultrasonically cleaned with acetone as the medium to remove oil stains. The ultrasonic cleaning time was 20 minutes, and then it was dried for later use.

[0027] (2) Preparation of glass solder: The composition of glass solder is (wt.%): Y2O3: 30%, Al2O3: 20%, SiO2: 10%, B2O3: 25%, CaO: 5%, ZnO: 5%, P2O5: 5%.

[0028] Weigh the raw materials according to the above glass welding composition. Place the weighed oxide raw material powder into a ball mill jar and mill at 500 rpm for 4 hours using alcohol or deionized water as the medium. After ball milling, dry the mixed powder and pour it into a platinum or corundum crucible. Heat the crucible to 1500 °C in an air atmosphere muffle furnace and hold for 1 hour. Quickly pour the glass melt into deionized water to obtain glass fragments. Then, grind the glass fragments. Next, use an automatic sieving device to sieve the ground glass through a 300-mesh sieve to obtain glass powder with a particle size of approximately 30 μm.

[0029] (3) Slurry preparation: Add a binder composed of terpineol, anhydrous ethanol and polyvinyl alcohol to the glass solder. Use a glass rod to quickly stir the glass solder and binder until they are completely mixed and a stable slurry is formed. The slurry contains 30 wt.% terpineol, 5 wt.% anhydrous ethanol and 5 wt.% polyvinyl alcohol.

[0030] (4) Slurry coating: The slurry is uniformly coated on the two aluminum nitride ceramic surfaces to be sealed using a screen printing machine. The screen printing mesh is 100 mesh, and the glass solder coating thickness on the aluminum nitride ceramic surfaces to be welded is 50 μm.

[0031] (5) Debonding treatment: Place two aluminum nitride ceramic pieces coated with glass solder in a muffle furnace and heat at 5℃ / min The temperature was increased to 400℃ at a certain rate, and after holding at that temperature for 1 hour, it was cooled to room temperature with the furnace and then removed.

[0032] (6) Joint assembly: Assemble the two pieces of aluminum nitride ceramic to be welded to form a "sandwich" assembly structure of "ceramic / glass solder / ceramic"; (7) Joint sealing: The joints treated in steps (2) and (3) are placed in an air atmosphere pressure furnace and heated to 900°C at a heating rate of 8°C / min. After holding at the temperature for 30 minutes, they are cooled to room temperature at a cooling rate of 5°C / min. During this period, the applied pressure is kept constant at 2 MPa.

[0033] Figure 1 The figures show the thermal expansion curves of the glass solder and the aluminum nitride ceramic used in Example 1. The coefficients of thermal expansion (CTE) of the aluminum nitride ceramic and the glass solder in the temperature range of 20℃-900℃ are 5.22 × 10⁻⁶. -6 / ℃, 4.5×10 -6 At ℃, the coefficient of thermal expansion of glass solder is slightly lower than that of aluminum nitride ceramic, indicating that the coefficients of thermal expansion of glass solder and aluminum nitride ceramic are well matched.

[0034] Figure 2 This is a macroscopic photograph of the large-area aluminum nitride ceramic sealing joint successfully prepared in Example 1. The joint measures 50 × 50 × 2 mm. 3 . Figure 3 The image shown is an optical microscope image of the aluminum nitride connector obtained in Example 1, which shows that there are no defects inside the connector. Figure 4 This is a scanning electron microscope image of the aluminum nitride connector in Example 1. Figure 5 This is a scanning electron microscope (SEM) image of the aluminum nitride connector at the glass-ceramic interface in Example 1. Figure 4 and Figure 5 It was found that under the combined effects of high temperature and sealing pressure, the softened glass solder was effectively embedded mechanically into the pores of the aluminum nitride ceramic surface, achieving an almost completely dense state within the intermediate layer, and exhibiting excellent and defect-free bonding at the glass-ceramic interface. As shown in Table 1, the average bending strength of the aluminum nitride joint prepared in Example 1 was 277 MPa, and the weld rate was 99.8% when the joint was tested using ultrasonic flaw detection equipment. Example 2:

[0035] In step (2), the glass material composition by weight percentage is: Lu2O3: 30%, Al2O3: 20%, SiO2: 15%, B2O3: 20%, CaO: 5%, ZnO: 5%, K2O: 5%. The atmosphere inside the heating furnace is vacuum, and all other steps are the same as in Example 1. The average bending strength of the aluminum nitride joint obtained in Example 2 is 269 MPa. The joint was tested using an ultrasonic flaw detector, and the welding rate was 99.3%. Example 3:

[0036] In step (2), the glass material composition by weight percentage is: Yb₂O₃: 30%, Al₂O₃: 20%, SiO₂: 20%, B₂O₃: 15%, CaO: 5%, ZnO: 5%, P₂O₅: 5%. The furnace atmosphere is N₂, and all other steps are the same as in Example 1. The average bending strength of the aluminum nitride joint obtained in Example 3 is 263 MPa. The joint was tested using an ultrasonic flaw detector, and the welding rate was 99.1%. Example 4:

[0037] In step (2), the glass material composition by weight percentage is: Tm2O3: 25%, Al2O3: 20%, SiO2: 15%, B2O3: 25%, CaO: 5%, ZnO: 5%, P2O5: 5%. The furnace atmosphere is Ar, and all other steps are the same as in Example 1. The average bending strength of the aluminum nitride joint obtained in Example 4 is 273 MPa. The joint was tested using an ultrasonic flaw detector, and the welding rate was 99.6%. Example 5:

[0038] In step (1), the applied pressure is increased to 3 MPa, and the holding time is extended to 1 hour. The aluminum nitride to be welded has dimensions of 100×100×2 mm. 3 The other steps are the same as in Example 1. The average bending strength of the aluminum nitride / joint obtained in Example 5 is 281 MPa. The joint was tested with an ultrasonic flaw detector, and the welding rate was 99.8%. Comparative Example 1:

[0039] In step (5), the pressure is reduced to 0.05 MPa. All other steps are the same as in Example 1. The average bending strength of the aluminum nitride joint obtained in Comparative Example 1 is 90 MPa. Although glass has good plastic deformation capacity at 900°C, under limited pressure, the glass solder is not completely embedded in the pores of the ceramic surface. This results in numerous micropores at the glass / ceramic interface, preventing complete densification of the weld and thus affecting the bonding quality between the glass and ceramic, leading to poor bending strength of the joint. Comparative Example 2:

[0040] In step (3), the sealing temperature was set to 850°C. All other steps were consistent with Example 1. The flexural strength of the aluminum nitride joint obtained in Comparative Example 2 was 65 MPa. Due to the relatively low sealing temperature, the softening ability of the glass solder was weakened. Under limited pressure, the bonding force between the ceramic / glass interface and the glass powder was insufficient, resulting in incomplete densification of the joint interior and therefore, the strength was not significantly improved. Comparative Example 3:

[0041] In step (3), the sealing temperature was set to 1300°C. All other steps remained the same as in Example 1. The flexural strength of the aluminum nitride joint obtained in Comparative Example 3 was 78 MPa. Due to the relatively high sealing temperature, crystals precipitated inside the glass solder. During crystallization, a significant density difference existed between the formed crystals and the glass itself, making it prone to voids and stress concentration after crystallization. Therefore, the joint was not completely densified, and its strength was not significantly improved.

[0042] The welding joint effects of the above embodiments and comparative examples are shown in Table 1.

[0043] Table 1. Connector test data for the examples and comparative examples. sample Bending strength Welding rate Example 1 277MPa 99.8% Example 2 269MPa 99.3% Example 3 263MPa 99.1% Example 4 273MPa 99.6% Example 5 281MPa 99.8% Comparative Example 1 90MPa - Comparative Example 2 65MPa - Comparative Example 3 78MPa - The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.

Claims

1. A glass-solder based aluminum nitride ceramic large area pressure diffusion sealing method, characterized by: The sealing method is to seal the aluminum nitride ceramic base material by using glass solder with components in percentage by weight: RE2O3: 15-35%, Al2O3: 10-30%, SiO2: 5-25%, B2O3: 10-30%, CaO: 5-10%, ZnO: 5-10%, P2O5: 5-10%.

2. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method according to claim 1, characterized by: The aluminum nitride ceramic is a commercially available aluminum nitride ceramic, wherein: the aluminum nitride content is 85-99.9wt.%, the coefficient of thermal expansion is (4-5.5)×10 -6 / ℃; the large area refers to the area of the sealing surface of a single aluminum nitride ceramic base material being 50×50mm² or more.

3. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method of claim 1, wherein: In the components of the glass solder, RE2O3 is one of Yb2O3, Gd2O3, Y2O3, Tb2O3, Dy2O3, Ho2O3, Er2O3, Tm2O3 and Lu2O3.

4. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method of claim 3, wherein: The sealing method specifically comprises the following steps: (1) Base material pretreatment: ultrasonic cleaning of the aluminum nitride ceramic with acetone as the medium to remove oil stains, ultrasonic time is 10-20 min, and then blow dry with a hair dryer for standby; (2) Glass solder preparation: weigh each corresponding raw material according to the composition of the glass solder, uniformly mix, and then prepare the glass solder by using the molten water quenching method; (3) Preparation of slurry: mix the glass solder and the binder in proportion, stir to obtain uniformly mixed glass slurry; (4) Slurry coating: uniformly coat the glass slurry on the surfaces of the two aluminum nitride ceramics to be sealed; (5) Desorption treatment: place the two aluminum nitride ceramics coated with glass solder in a muffle furnace, heat at a certain heating rate to the desorption temperature and keep for a period of time to ensure that the internal binder of the glass solder is volatilized, and then cool to room temperature with the furnace; (6) Joint assembly: assemble the two aluminum nitride ceramics to be welded to form a "sandwich" assembly structure of "ceramic / glass solder / ceramic"; (7) Joint sealing: place the joint assembled in step (6) into a heating furnace in an air atmosphere, vacuum atmosphere or inert gas atmosphere, heat at a certain pressure to a sealing temperature at a certain heating rate, keep for a certain time, and then slowly cool to room temperature with the furnace.

5. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method of claim 4, wherein: In step (2), in the composition of the glass solder, B2O3 is introduced by H3BO3 raw material, CaO is introduced by CaCO3 raw material, P2O5 is introduced by H3PO4 raw material, and other components are introduced by corresponding oxide raw materials, and the purity of each raw material is higher than 99.9%; the preparation process of the glass solder is: put the weighed raw material powder into a ball mill tank for ball milling, use alcohol or deionized water as the medium, the rotation speed is 500-800 rpm, the ball milling time is 4-5 h; after ball milling, dry the mixed powder, pour it into a platinum or corundum crucible, heat it to 1500-1600℃ in an air atmosphere muffle furnace, keep for 1-3 h, quickly pour the obtained glass melt into deionized water to get glass fragments; then, grind the glass fragments through a 100-300 mesh sieve, and finally obtain glass solder powder with a particle size of not more than 30 μm.

6. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method of claim 4, wherein: In step (3), the adhesive is composed of terpineol, anhydrous ethanol and polyvinyl alcohol; in the slurry, the weight proportion of terpineol is 10-35%, the weight proportion of anhydrous ethanol is 2-10%, and the weight proportion of polyvinyl alcohol is 2-10%.

7. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method of claim 4, wherein: In step (4), the coating method is selected from one or a combination of screen printing, manual coating and spraying, wherein when screen printing is used, the mesh number is between 80-200, and the coating thickness of the glass solder on the surface of the sintered aluminum nitride ceramic is 50-100 μm.

8. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method of claim 4, wherein: In step (5), the heating rate is 5-20 ℃ / min, the degassing temperature is 200-500 ℃, and the holding time is 1-5 h.

9. The glass solder based aluminum nitride ceramic large area pressure diffusion seal method of claim 4, wherein: In step (7), the heating rate of the joint sealing process is 5-20 ℃ / min, the sealing temperature is 900-1200 ℃, and the holding time is 0.5-3 h; during the cooling process, the cooling rate between the sealing temperature and 750 ℃ is less than 10 ℃ / min, and after the temperature is reduced to below 450 ℃, there is no requirement for the cooling rate, the applied pressure is maintained at 0.3-5 MPa during this period, and the inert gas atmosphere is N2, Ar or He.

10. Use of a glass-solder based aluminium nitride ceramic large area pressure diffusion sealing method according to any one of claims 1 to 9, characterized in that: The sealing method is applied to the sealing of large-size complex internal structures of aluminum nitride ceramic heater, liquid cooling plate and the like.

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