A method for sealing AlN ceramics with glass-ceramic

Abstract

A method for sealing AlN ceramics with glass-ceramics, and relates to a method for sealing AlN ceramics. The present invention is to solve the technical problems of low room temperature strength and non-insulation of AlN ceramic joints currently connected by metal brazing. The glass-ceramic solder provided by the present invention is used for sealing AlN ceramics. The solder has strong adaptability, has no requirements on the surface roughness of the ceramic base material, and directly seals AlN ceramics under an Ar gas or N2 gas atmosphere. After the glass-ceramics are melted, they interact at the AlN interface to form an element interdiffusion layer at the interface, so that the interface bonding is reliable, and a ceramic phase is generated in the weld by a crystallization reaction. The final weld is composed of a ceramic phase and a small amount of residual glass phase, and the maximum room temperature shear strength of the joint obtained by keeping warm at 1380°C for 10 minutes reaches 57MPa. The glass-ceramic solder of the present invention is used for the AlN ceramic sealing method, providing technology for the application of AlN in semiconductor heat-bearing components.

Description

Technical Field

[0001] The invention relates to a method for sealing AlN ceramics. Background Art

[0002] Aluminum nitride (AlN) ceramics have been widely used in many fields such as heat exchangers, electronic packaging base plates, and semiconductor heating components due to their high thermal conductivity, low dielectric constant, high temperature dissipation, and corrosion resistance. AlN ceramics have excellent properties such as non-toxicity and high thermal conductivity. The theoretical thermal conductivity (320W / m·K) is close to the high thermal conductivity BeO (370W / m·K), which is 7 to 8 times the thermal conductivity of Al2O3 ceramics; its mechanical strength and dielectric properties are better than Al2O3, and its dielectric properties are similar to those of Al2O3 ceramics. However, the practical application of ceramics is often limited by connection technology. The requirements for aluminum nitride joints include sufficient mechanical strength and high temperature and corrosion resistance, and non-conductivity when used for insulation.

[0003] Brazing is a common method for joining ceramics to ceramics or ceramics to metals, due to its simple process, low cost and potential for mass production. The main limitation of brazing is to find appropriate brazing compositions with ideal properties. So far, most studies have focused on brazing AlN to AlN or to metals using AgCu-based alloys. Diffusion bonding has also developed methods for AlN connection, but this method has limitations on the shape and size of the parts to be connected and does not meet the requirements for precision connection of complex parts. B. Chen et al. developed Au–Pd–Co–Ni–V high-temperature active brazing material for AlN ceramic connection, and the joints were reliably bonded by the reaction of V elements with AlN (Journal of Materials Science & Technology 31 (2015) 1034-1038). Although active metal brazing technology has achieved certain results in joining AlN ceramics, in terms of the application environment, if AlN ceramics are used in high-temperature acidic or alkaline environments, the corrosion resistance of the metal brazing joints is poor and it is difficult to meet the application requirements. Therefore, it is urgent to develop a new connection technology. Glass and glass-ceramic sealing are widely considered to be an efficient connection technology due to the high tolerance of glass connection materials to the surface roughness of ceramic substrates, low cost, and high chemical stability. Yanru Ji et al. selected ZnO–B2O3–SiO2 (ZBS) glass with a gradient thermal expansion coefficient (TEC) to connect Al2O3 and AlN dissimilar ceramics. This glass solder is composed of two glasses with different TEC. After being kept in a muffle furnace at 850°C for 1h, Al2O3 and AlN ceramics were successfully combined with glass. The connection interface of the Al2O3 / AlN ceramic joint connected by the glass was crack-free and the strength reached 40MPa (Ceramics International 46 (2020) 12806–12811). Summary of the invention

[0004] The present invention aims to solve the technical problems of low room temperature strength and non-insulation of AlN ceramic joints connected by metal brazing, and provides a method for sealing AlN ceramics with glass-ceramic.

[0005] The method for sealing AlN ceramic with glass-ceramic of the present invention is carried out according to the following steps:

[0006] Step 1: Put the four oxide raw materials together and mix them by low-speed ball milling to obtain uniformly mixed oxide powders, then melt the uniformly mixed oxide powders at 1550° C. to 1600° C. for 2 h to 2.5 h to form liquid glass, and the liquid glass is sequentially rapidly cooled, crushed, ground and sieved to obtain glass powder, and a dispersant and a binder are added to the glass powder, and the glass solder paste is obtained by ball milling again;

[0007] The four oxide raw materials are Li2O, MgO, Al2O3 and SiO2 or Li2O, CaO, Al2O3 and SiO2;

[0008] The molar fraction of Li2O in the uniformly mixed oxide powder is 9% to 10%, the molar fraction of MgO or CaO is 20% to 30%, the molar fraction of Al2O3 is 10% to 15%, and the balance is SiO2;

[0009] Step 2: Treatment of AlN ceramic matrix: After cutting, the surface of the AlN ceramic matrix is ​​cleaned with an organic cleaning solution to remove oil stains on the surface;

[0010] Step 3, weldment assembly: use a scraper or screen printing method to apply the glass solder paste prepared in step 1 to the surface to be welded of one AlN ceramic base material, and align the surface to be welded of another AlN ceramic base material onto the solder layer to form a sandwich structure;

[0011] Step 4, sealing process: from room temperature to debinding temperature, the heating rate is 2℃ / min~5℃ / min, the debinding temperature is 400℃~500℃, the time is 2h~2.5h, and the air environment; then evacuate, introduce inert gas to make the cavity under inert gas protection conditions, continue to heat up to the connection temperature at a heating rate of 5℃ / min~10℃ / min and keep warm for 5min~30min, then cool down to 300℃~310℃ at a cooling rate of 5℃ / min~10℃ / min, and naturally cool to room temperature with the furnace to complete the sealing of AlN ceramics.

[0012] The present invention provides a glass-ceramic solder and realizes the sealing of AlN ceramic itself under the protection of inert gas, and has the following beneficial effects:

[0013] The glass-ceramic solder provided by the present invention is used for sealing AlN ceramics. The solder has strong adaptability and no requirements on the surface roughness of the ceramic base material. The AlN ceramics are directly sealed in an Ar gas or N2 gas atmosphere. After the glass-ceramic is melted, it interacts at the AlN interface to form an element interdiffusion layer at the interface, so that the interface bonding is reliable. A ceramic phase is generated in the weld by a crystallization reaction. The final weld is composed of a ceramic phase and a small amount of residual glass phase. The maximum shear strength of the joint obtained by keeping warm at 1380°C for 10 minutes reaches 57MPa at room temperature. The glass-ceramic solder of the present invention is used for the AlN ceramic sealing method, providing technology for the application of AlN in semiconductor insulation heat-bearing components. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The weld structure of Example 4;

[0015] Figure 2 This is the microstructure diagram of the joint interface in Example 4;

[0016] Figure 3 for Figure 2 Element line scan analysis diagram in;

[0017] Figure 4 This is the microstructure diagram of the joint interface of Example 4;

[0018] Figure 5 for Figure 4 Energy spectrum point analysis diagram of point 1 in the middle;

[0019] Figure 6 for Figure 4 Energy spectrum point analysis diagram of the two points in the middle. DETAILED DESCRIPTION

[0020] Specific implementation method 1: This implementation method is a method for sealing AlN ceramics with glass-ceramic, which is specifically carried out in the following steps:

[0021] Step 1: Put the four oxide raw materials together and mix them by low-speed ball milling to obtain uniformly mixed oxide powders, then melt the uniformly mixed oxide powders at 1550° C. to 1600° C. for 2 h to 2.5 h to form liquid glass, and the liquid glass is sequentially rapidly cooled, crushed, ground and sieved to obtain glass powder, and a dispersant and a binder are added to the glass powder, and the glass solder paste is obtained by ball milling again;

[0022] The four oxide raw materials are Li2O, MgO, Al2O3 and SiO2 or Li2O, CaO, Al2O3 and SiO2;

[0023] The molar fraction of Li2O in the uniformly mixed oxide powder is 9% to 10%, the molar fraction of MgO or CaO is 20% to 30%, the molar fraction of Al2O3 is 10% to 15%, and the balance is SiO2;

[0024] Step 2: Treatment of AlN ceramic matrix: After cutting, the surface of the AlN ceramic matrix is ​​cleaned with an organic cleaning solution to remove oil stains on the surface;

[0025] Step 3, weldment assembly: use a scraper or screen printing method to apply the glass solder paste prepared in step 1 to the surface to be welded of one AlN ceramic base material, and align the surface to be welded of another AlN ceramic base material onto the solder layer to form a sandwich structure;

[0026] Step 4, sealing process: from room temperature to debinding temperature, the heating rate is 2℃ / min~5℃ / min, the debinding temperature is 400℃~500℃, the time is 2h~2.5h, and the air environment; then evacuate, introduce inert gas to make the cavity under inert gas protection conditions, continue to heat up to the connection temperature at a heating rate of 5℃ / min~10℃ / min and keep warm for 5min~30min, then cool down to 300℃~310℃ at a cooling rate of 5℃ / min~10℃ / min, and naturally cool to room temperature with the furnace to complete the sealing of AlN ceramics. The connection temperature is 1250℃~1380℃.

[0027] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the rapid cooling described in step 1 is water cooling. The rest is the same as the specific implementation method 1.

[0028] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the crushing described in step 1 is smashing. The rest is the same as specific implementation method 1 or 2.

[0029] Specific implementation method 4: This implementation method is different from the specific implementation methods 1 to 3 in that the binder in step 1 is terpineol. The rest is the same as the specific implementation methods 1 to 3.

[0030] Specific embodiment 5: This embodiment is different from specific embodiment 4 in that the dispersant in step 1 is ethyl cellulose. The rest is the same as specific embodiment 4.

[0031] Specific embodiment 6: This embodiment is different from specific embodiment 5 in that the mass ratio of terpineol to ethyl cellulose in step 1 is 9:1. The rest is the same as specific embodiment 5.

[0032] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that: in step 1, terpineol and ethyl cellulose are mixed to obtain an organic solvent, and the mass ratio of glass powder to organic solvent is 8:2. Other aspects are the same as specific embodiment 6.

[0033] Specific embodiment eight: This embodiment differs from specific embodiment seven in that the organic cleaning liquid in step two is alcohol or acetone. The rest is the same as specific embodiment seven.

[0034] Specific embodiment 9: This embodiment is different from specific embodiment 8 in that the thickness of the glass solder layer in the sandwich structure described in step 3 is 50 μm to 150 μm. Other aspects are the same as specific embodiment 8.

[0035] Specific embodiment 10: This embodiment differs from specific embodiment 9 in that the inert gas in step 4 is argon or nitrogen. The rest is the same as specific embodiment 9.

[0036] The present invention is verified by the following examples:

[0037] A method for sealing AlN ceramic with glass-ceramic is specifically carried out according to the following steps:

[0038] Step 1: Put the four oxide raw materials together and mix them by ball milling at a low speed to obtain a uniformly mixed oxide powder, then keep the uniformly mixed oxide powder at a melting temperature (temperature and time are shown in Table 1), melt at high temperature to form liquid glass, and the liquid glass is successively water-cooled, crushed, ground and sieved to obtain glass powder, add a dispersant and a binder to the glass powder, and ball mill again to obtain a glass solder paste;

[0039] The specific compositions of the four oxide raw materials are shown in Table 1;

[0040] The binder described in step 1 is terpineol, the dispersant is ethyl cellulose, and the mass ratio of terpineol to ethyl cellulose is 9:1; terpineol and ethyl cellulose are mixed to obtain an organic solvent, and the mass ratio of glass powder to the organic solvent is 8:2;

[0041] Step 2: Treatment of AlN ceramic matrix: After cutting, the surface of AlN ceramic matrix can be cleaned with alcohol to remove oil stains on the surface;

[0042] Step 3, weldment assembly: use a scraper or screen printing method to apply the glass solder paste prepared in step 1 to the surface to be welded of one AlN ceramic base material, align the surface to be welded of another AlN ceramic base material on the solder layer to form a sandwich structure, wherein the thickness of the glass solder layer is 50 μm to 150 μm;

[0043] Step 4, sealing process: from room temperature to debinding temperature, the heating rate is 2℃ / min, the debinding temperature is 400℃, the time is 2h, and the air environment; then evacuate, introduce inert gas to make the cavity under inert gas protection conditions, continue to heat up to the connection temperature at a heating rate of 5℃ / min and keep warm for 20min, then cool down to 300℃ at a cooling rate of 5℃ / min, and naturally cool to room temperature with the furnace to complete the sealing of AlN ceramics. The connection temperature and time are shown in Table 1.

[0044] Table 1

[0045]

[0046] Figure 1 This is the weld structure of Example 4. 1 and 3 are both AlN ceramic base materials, and 2 is the weld. It can be seen that there are a small amount of porosity defects in the weld, and a glass-ceramic weld is formed in the weld.

[0047] Figure 2 is the microstructure diagram of the joint interface in Example 4, Figure 3 for Figure 2 From the element line scanning analysis diagram, it can be seen that there is a diffusion transition layer at the interface through the distribution of Si and Al elements.

[0048] Figure 4 This is the microstructure diagram of the joint interface of Example 4, Figure 5 for Figure 4 Energy spectrum analysis diagram of point 1 in the middle, Figure 6 for Figure 4 Energy spectrum point analysis diagram of the two points in the middle.

[0049] Table 2 Figure 4 The element composition table of the corresponding points in the figure shows that spodumene phase (LiAlSi2O6) is precipitated in the weld (corresponding to point 1), and there is a small amount of residual glass phase at the interface (corresponding to point 2).

[0050] Table 2

[0051] 1 point 2 o'clock element At% At% O 57.58 28.72 Mg 3.51 08.91 Al 12.01 14.49 Si 26.91 47.88 phase of matter <![CDATA[Li2AlSi2O6]]> Glass Phase

Claims

1. A method for sealing AlN ceramics with glass-ceramic, characterized in that The method of glass-ceramic sealing AlN ceramic is carried out in the following steps: Step 1: Put the four oxide raw materials together and mix them by ball milling at a low speed to obtain uniformly mixed oxide powders, then melt the uniformly mixed oxide powders at 1550° C. for 2 hours to form liquid glass, and sequentially water-cool the liquid glass, crush, grind and sieve to obtain glass powder, add a dispersant and a binder to the glass powder, and ball mill again to obtain a glass solder paste; The four oxide raw materials are Li2O, MgO, Al2O3 and SiO2; The molar fraction of Li2O in the uniformly mixed oxide powder is 9%, the molar fraction of MgO is 20%, the molar fraction of Al2O3 is 10%, and the balance is SiO2; The binder is pineol, the dispersant is ethyl cellulose, and the mass ratio of pineol to ethyl cellulose is 9:1; pineol and ethyl cellulose are mixed to obtain an organic solvent, and the mass ratio of glass powder to the organic solvent is 8:2; Step 2: Treatment of AlN ceramic matrix: After cutting, the surface of AlN ceramic matrix can be cleaned with alcohol to remove oil stains on the surface; Step 3, welding assembly: using a scraper or screen printing method, apply the glass solder paste prepared in step 1 to the surface to be welded of one AlN ceramic base material, and align the surface to be welded of another AlN ceramic base material onto the solder layer to form a sandwich structure; the thickness of the glass solder layer in the sandwich structure is 50 μm to 150 μm; Step 4, sealing process: from room temperature to debinding temperature, the heating rate is 2℃ / min, the debinding temperature is 400℃, the time is 2h, and the air environment; then evacuate, introduce inert gas to make the cavity under inert gas protection conditions, continue to heat to the connection temperature at a heating rate of 5℃ / min and keep warm for 20min, then cool to 300℃ at a cooling rate of 5℃ / min, and naturally cool to room temperature with the furnace to complete the sealing of AlN ceramics. The connection temperature is 1380℃; the room temperature shear strength of the obtained joint is 57MPa.

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