Low thermal expansion coefficient glass solder for joining ceramics, method of manufacture and method of joining

Abstract

The application relates to a low-thermal-expansion coefficient glass solder for connecting ceramics, a preparation method and a connecting method. The chemical composition of the low-thermal-expansion coefficient glass solder comprises 1-8 wt.% of Na2O, 30-55 wt.% of B2O3, 1-4 wt.% of Al2O3 and 40-60 wt.% of SiO2, and the sum of the mass percentages of the components is 100 wt.%. The application effectively improves the connecting quality of the ceramics by regulating the components of the glass solder to obtain a thermal expansion coefficient that is very matched with structural ceramics.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of ceramic material welding, and particularly relates to a low-thermal-expansion-coefficient glass solder for connecting ceramics, a preparation method and a connecting method. BACKGROUND

[0002] Structural ceramics develop rapidly in the field of materials due to their stable chemical properties, high thermal conductivity, small thermal expansion coefficient, small density, good wear resistance, large hardness, high mechanical strength, and chemical corrosion resistance, and are widely used in the fields of ceramic ball bearings, valves, semiconductor materials, gyroscopes, measuring instruments, aerospace, etc. However, due to the inherent brittleness of ceramic materials and the limitations of existing preparation technologies, it is difficult to directly process them into applicable complex components, which to some extent limits their application. Welding technology is an effective technical route to solve the engineering manufacturing problems of complex ceramic parts and large-size ceramic parts.

[0003] The existing ceramic connecting technologies include active metal connection, glass connection and diffusion connection. The glass solder connection process is a simple and feasible connection method with low cost, but the current research range is focused on high-temperature system glass, the strength of the glass solder is generally not high, all connections need to be carried out in an oxidizing atmosphere, and it is difficult to be applied to the precision semiconductor industry. Therefore, a low-thermal-expansion-coefficient glass solder needs to be designed to improve the poor matching of the thermal expansion coefficient between the glass solder and the ceramic matrix, so as to improve the strength and connection quality of the joint. SUMMARY

[0004] In view of the defects of the prior art, the present application aims to provide a low-thermal-expansion-coefficient glass solder for connecting ceramics, a preparation method and a connecting method. By adjusting the components of the glass solder, a thermal expansion coefficient that is very matched with the structural ceramic can be obtained. In addition, the connecting technology can obtain a structural ceramic joint with excellent room temperature strength and high temperature strength, and the process is simple, the engineering application is high, and has a good application prospect.

[0005] In the first aspect, the present application provides a low-thermal-expansion-coefficient glass solder for connecting ceramics, and the chemical composition of the low-thermal-expansion-coefficient glass solder comprises: 1-8 wt.% Na2O, 30-55 wt.% B2O3, 1-4 wt.% Al2O3 and 40-60 wt.% SiO2, and the sum of the mass percentages of the components is 100 wt.%. Preferably, it comprises: 3-5 wt.% Na2O, 40-55 wt.% B2O3, 3-4 wt.% Al2O3 and 40-50 wt.% SiO2.

[0006] Preferably, the ceramic comprises silicon carbide, aluminum nitride or silicon nitride.

[0007] Preferably, the glass solder is in powder form, with a particle size of 1-44 μm.

[0008] Preferably, the glass solder has a glass transition temperature of 430-470 °C and a softening point of 580-620 °C.

[0009] Preferably, the glass solder has a thermal expansion coefficient of (4.0-4.4) x 10 -6 K -1 .

[0010] In a second aspect, the present application also provides a method for preparing the low-thermal-expansion-coefficient glass solder as described above, comprising:

[0011] (1) weighing and mixing Na2CO3 powder, H3BO3 powder, SiO2 powder and Al2O3 powder according to a certain proportion, and obtaining a mixture after ball milling, drying, grinding and sieving;

[0012] (2) melting the mixture to obtain a molten sample;

[0013] (3) quenching the molten sample in deionized water to obtain a blocky glass sample, and obtaining the glass solder after crushing, drying and sieving.

[0014] Preferably, in step (1), the purity of the Na2CO3 powder, SiO2 powder and Al2O3 powder is all ≥ 99.0%; the purity of the H3BO3 powder is ≥ 99.5%; and the average particle size of the Na2CO3 powder, H3BO3 powder, SiO2 powder and Al2O3 powder is 5-10 μm.

[0015] The ball milling is wet ball milling, and the parameters of the wet ball milling include: the mixing medium is anhydrous ethanol, the amount of anhydrous ethanol added is 20-40% of the mixture, the grinding balls are zirconia ceramic balls, and the ratio of raw material to grinding ball is (1-2):(2-3); the rotation speed is 300-600 rpm, and the time is 10-14 hours.

[0016] The drying temperature is 50-80 °C, and the drying time is 2-4 h.

[0017] The sieving mesh size is 80-100 mesh.

[0018] Preferably, in step (2), the melting parameters include: the melting temperature is 1400-1500 °C, the melting time is 1-3 hours, the heating rate is 5-10 °C / min, and preferably 10 °C / min.

[0019] Preferably, in step (3), the drying temperature is 60-100 °C, and the time is 3-5 hours.

[0020] The mesh size of the sieving is 325-1250 mesh.

[0021] In a third aspect, the present application provides a method for connecting ceramics by using the low thermal expansion coefficient glass solder, comprising:

[0022] (1) mixing the glass solder and the organic carrier to obtain a glass paste;

[0023] (2) uniformly coating the obtained glass paste on the surface of the pretreated ceramic by using a screen printing method to obtain a glass paste layer, and drying to obtain a ceramic coated with a glass solder layer;

[0024] (3) fixing the ceramic coated with the glass solder layer and the ceramic without coating in a sandwich structure, and after welding treatment, naturally cooling to room temperature in the furnace, thereby completing the connection of the ceramics.

[0025] Preferably, in step (1), the organic carrier comprises a binder and a solvent; wherein the mass ratio of the binder to the solvent is (5-10):(90-95);

[0026] The binder is at least one of methyl cellulose, ethyl cellulose, polyvinyl alcohol and phenolic resin;

[0027] The solvent is at least one of terpineol, triterpene alcohol, ethyl acetate and butyl acetate;

[0028] The preparation method of the organic carrier comprises: mixing the binder and the solvent according to the mass ratio, and stirring at 20-100°C for 4-8h to obtain the organic carrier;

[0029] The amount of the organic carrier is 25-40wt.% of the mass of the glass solder.

[0030] Preferably, in step (2), the parameters of the screen printing method include: the distance between the screen and the ceramic is 100-200μm, and the inclination angle of the rubber brush is 40-50°;

[0031] The pretreatment is: ultrasonic cleaning of the ceramic surface with anhydrous ethanol; preferably, the ceramic is silicon carbide ceramic, and the ceramic surface needs to be pre-oxidized in air before ultrasonic cleaning.

[0032] Preferably, in step (2), the drying temperature is 60-100°C, and the drying time is 2-4h; preferably, the drying temperature is 60°C, and the drying time is 4h;

[0033] The thickness of the glass paste layer is 100-200μm.

[0034] Preferably, in step (3), the parameters of the welding process include: at least one of air, vacuum, argon as the atmosphere; increasing the temperature from room temperature to 240-260 DEG C at a rate of 4-5 DEG C / min, then increasing the temperature to 440-460 DEG C at a rate of 1-3 DEG C / min, maintaining the temperature for 20-30 min, then increasing the temperature to 1000-1200 DEG C at a rate of 2 DEG C / min, maintaining the temperature for 30-60 min.

[0035] In a fourth aspect, the present application provides a ceramic joint prepared by the method described above, which includes a silicon carbide joint, an aluminum nitride joint or a silicon nitride joint; wherein the silicon carbide ceramic joint has a room temperature three-point bending strength of ≥180 MPa and a 450 DEG C high-temperature three-point bending strength of ≥150 MPa; the aluminum nitride ceramic joint has a room temperature three-point bending strength of ≥160 MPa and a 450 DEG C high-temperature three-point bending strength of ≥140 MPa; and the silicon nitride ceramic joint has a room temperature three-point bending strength of ≥150 MPa and a 450 DEG C high-temperature three-point bending strength of ≥100 MPa.

[0036] Compared with the traditional Na2O-B2O3-SiO2 glass solder, the added Al2O3 can more finely adjust the thermal expansion coefficient, and the transformation point and crystallization temperature of the glass can also be improved or reduced without changing the connecting performance by changing the content of Al2O3. In addition, the addition of Al2O3 can reduce the excessively high glass melting temperature due to the high content of SiO2, and simplify the operation difficulty of the process flow.

[0037] The Na2O-B2O3-Al2O3-SiO2 glass solder of the present application has the particularity of its components. Sodium oxide and silicon oxide will generate molten sodium silicate at a certain temperature, and this silicate structure not only promotes the reaction, but also has a good connecting effect on inorganic ceramic materials due to its high adhesion. At the same time, since silicon and carbon elements will diffuse in the silicon-oxygen tetrahedron and boron-oxygen tetrahedron, the glass solder has a good connecting effect on silicon carbide and silicon nitride ceramics. In addition, when Al 3+ In the [AlO4], the grid is composed of silicon-oxygen tetrahedrons, and a small amount of Al2O3 is introduced. 3+ The non-bridge oxygen can be captured to form aluminum-oxygen tetrahedrons in the silicon-oxygen grid, the broken grid in the glass grid is reconnected, and the glass structure tends to be compact. Therefore, due to the presence of a small amount of Al2O3, a series of properties of the glass are improved. At the same time, since the grid has a certain binding force on aluminum nitride, the glass solder of the present application can also be applied to the connection of aluminum nitride.

[0038] Advantages:

[0039] (1) The Na2O-B2O3-Al2O3-SiO2 glass solder adopted in the present application has good chemical compatibility with ceramic substrates such as silicon carbide, aluminum nitride and silicon nitride, and has a thermal expansion coefficient of (4.0-4.4) x 10 -6 K -1 , which is compatible with the thermal expansion coefficients of the connected ceramic substrates such as silicon carbide, aluminum nitride and silicon nitride, effectively improving the connection quality of the aforementioned ceramics.

[0040] (2) The Na2O-B2O3-Al2O3-SiO2 glass solder adopted in the present application can realize the connection of ceramics such as silicon carbide, aluminum nitride and silicon nitride at 1000-1200℃, reducing the process difficulty of the aforementioned ceramic connection. The room temperature three-point bending strength of the silicon carbide ceramic joint connected by the glass solder is above 180MPa, and the high temperature three-point bending strength at 450℃ is above 150MPa; the room temperature three-point bending strength of the aluminum nitride ceramic joint is above 160MPa, and the high temperature three-point bending strength at 450℃ is above 140MPa; the room temperature three-point bending strength of the silicon nitride ceramic joint is above 150MPa, and the high temperature three-point bending strength at 450℃ is above 100MPa.

[0041] (3) The glass soldering process adopted in the present application is stable and reliable, easy to operate, and has important application value. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The glass powder prepared for Example 1 is shown in the figure;

[0043] Figure 2 The micro-morphology diagram of the silicon carbide ceramic joint prepared for Example 1 is shown in the figure;

[0044] Figure 3 The glass powder prepared for Comparative Example 1 is shown in the figure. DETAILED DESCRIPTION

[0045] To further illustrate the invention content, features and actual effects of the present application, the present application will be described in detail below in conjunction with examples. It should be pointed out that the modification method of the present application is not limited to these specific embodiments. On the premise of not deviating from the spirit and connotation of the present application design, equivalent replacement and modification made by those skilled in the art on the basis of the content of the present application is also within the scope of the present application.

[0046] In the present application, the chemical composition of the glass solder includes: 1-8wt.% Na2O, 30-45wt.% B2O3, 1-3wt.% Al2O3 and 40-60wt.% SiO2. The thermal expansion coefficient of the glass solder is (4.0-4.4) x 10 -6 K-1 The thermal expansion coefficient is very matched with ceramics such as silicon carbide, aluminum nitride, silicon nitride, and the like, and good chemical compatibility is provided between the foregoing ceramics. In the present application, the role of Al2O3 is to regulate the thermal expansion coefficient, reduce the glass melting temperature, and improve the mechanical properties of the glass. If the content of Al2O3 is too low, the thermal expansion coefficient of the glass solder obtained will increase significantly, resulting in a mismatch in the thermal expansion coefficient with the foregoing ceramics, which will reduce the joint strength. If the content of Al2O3 is too high, it will affect the electrical properties of the glass powder, resulting in an increase in electrical conductivity, which will affect the insulation performance of the ceramic device, so the content of Al2O3 needs to be strictly controlled. If the content of Na2O, SiO2, and B2O3 is too high or too low, the softening point of the glass solder will change, which will change the welding process, and at the same time, it will cause the thermal expansion coefficient of the glass solder and the ceramic substrate to be mismatched, resulting in stress concentration at the joint, which will significantly reduce the strength of the ceramic joint.

[0047] In the present application, the glass solder process is simple and suitable for industrial production. The preparation method of the low thermal expansion coefficient glass solder provided by the present application is described below.

[0048] Preparation of the mixture: Na2CO3 powder, H3BO3 powder, Al2O3 powder, and SiO2 powder are weighed and mixed according to the mass ratio, and the mixture is obtained after ball milling, drying, grinding, and sieving.

[0049] In an optional embodiment, the purity of the Na2CO3 powder, SiO2 powder, and Al2O3 powder is all ≥ 99.0%; the purity of the H3BO3 is ≥ 99.5%; and the average particle size of the Na2CO3 powder, H3BO3 powder, SiO2 powder, and Al2O3 powder is 5-10 μm.

[0050] The ball milling is wet ball milling; the parameters of the wet ball milling include: the mixing medium is anhydrous ethanol, the addition amount of anhydrous ethanol is 20-40% of the mixture, the grinding ball is a zirconia ceramic ball, the ratio of raw material to grinding ball is (1-2):(2-3), the rotation speed can be 300-600 rpm, and the time can be 10-14 hours.

[0051] The drying temperature can be 50-80℃, and the drying time can be 2-4h; the mesh number of the sieving can be 80-100 mesh, preferably, the drying temperature is 60℃, the time is 2h, and the mesh number of the sieving is 80 mesh.

[0052] Preparation of the glass sample: the mixture is placed in a crucible and melted in a muffle furnace, and then the molten sample is directly poured into deionized water at a holding temperature to obtain a blocky glass sample.

[0053] In an optional embodiment, the melting parameters include: the melting temperature can be 1400-1500℃, the heating rate can be 5-10℃ / min, preferably 10℃ / min. Too high melting temperature can cause crystallization in the glass, and too low melting temperature can cause uneven melting. The melting time can be 1-3 hours, too short melting time can cause uneven melting, and too long melting time can cause loss of glass powder quality.

[0054] Preparation of glass solder: After crushing the bulk glass sample into powder using a multifunctional crusher, continue to grind in a mortar, dry, sieve to obtain Na2O-B2O3-Al2O3-SiO2 glass solder powder.

[0055] In an optional embodiment, the drying temperature can be 60-100℃, and the time can be 3-5 hours. The mesh size of the sieving can be 325-1250 mesh. Preferably, the drying temperature is 80℃, the time is 4h, and the mesh size of the sieving is 325 mesh.

[0056] The following exemplary describes the method of connecting ceramics using the above low thermal expansion coefficient glass solder.

[0057] Mixing the glass solder and the organic carrier to obtain a glass paste.

[0058] In an optional embodiment, the organic solution includes a binder and a solvent; wherein the mass ratio of the binder to the solvent can be (5-10):(90-95). The binder is at least one of methyl cellulose, ethyl cellulose, polyvinyl alcohol, and phenolic resin. The solvent is at least one of terpineol, triterpene alcohol, ethyl acetate, and butyl acetate. Preferably, the organic carrier is a solution of ethyl cellulose in terpineol, and the mass ratio of ethyl cellulose to terpineol is 5:95.

[0059] The preparation method of the organic carrier includes: mixing the binder and the solvent according to the mass ratio, and stirring at 20-100℃ for 4-8h to obtain the organic carrier. The role of the organic carrier is to make the glass powder into a glass paste with certain viscosity, and to fix the glass powder into a shape after drying, thereby reducing the possibility of connection failure due to loss of solder.

[0060] The amount of the organic carrier is 25-40wt.% of the mass of the glass solder.

[0061] The obtained glass paste is uniformly coated on the surface of the pretreated ceramic using a screen printing method to obtain a glass paste layer, and dried to obtain a ceramic with a glass solder layer coated on the surface.

[0062] In an optional embodiment, the parameters of the screen printing method include: a screen-ceramic spacing of 100-200 μm, and a rubber brush inclination angle of 40-50°; the screen printing method is used to uniformly apply the glass solder on the ceramic surface, and has the advantage of being capable of controlling the thickness of the glass solder.

[0063] The pretreatment is: ultrasonic cleaning of the ceramic surface with anhydrous ethanol; preferably, the ceramic is silicon carbide ceramic, and the ceramic surface is pre-oxidized in air before the ultrasonic cleaning.

[0064] The drying temperature is 60-100 °C, and the time is 2-4 hours; preferably, the drying temperature is 60 °C, and the time is 4 hours.

[0065] The thickness of the glass paste layer is 100-200 μm; a thickness that is too small may cause the glass solder to gather during the connection process, resulting in the presence of pores, and a thickness that is too large may reduce the mechanical properties of the ceramic joint.

[0066] The ceramic coated with the glass solder layer and the uncoated ceramic are fixed by a clamp (for example, an alumina clamp), a certain counterweight pressure is applied, and the ceramics are placed in a muffle furnace for welding treatment; after the heat preservation is completed, the furnace is naturally cooled to complete the connection of the ceramics.

[0067] In an optional embodiment, the parameters of the welding treatment include: an atmosphere environment of at least one of air, vacuum, and argon; a rate of 4-5 °C / min from room temperature to 240-260 °C, a rate of 1-3 °C / min for continued heating to 440-460 °C, heat preservation for 20-30 min, and a rate of 2 °C / min for continued heating to 1000-1200 °C, heat preservation for 30-60 min; a welding temperature that is too low may result in a failed connection, a welding temperature that is too high may cause crystallization in the glass phase, a welding time that is too short may result in poor interface bonding, and a welding time that is too long may cause the glass solder to gather during the connection process, resulting in the presence of pores; the purpose of the segmented heating is: rapid heating in the first heating system to reduce the reaction time, volatilization of the organic carrier in the second heating system to reduce impurities, and completion of the uniform transformation of the glass in the third heating system to achieve the connection; compared to one-step heating, the segmented heating effectively reduces the reaction time, ensures the purity of the weld, improves the connection performance, and is more conducive to industrialized production in various fields.

[0068] The glass solder prepared in the application is compatible with the thermal expansion coefficient of ceramic matrix such as silicon carbide, aluminum nitride and silicon nitride, and has good chemical compatibility, so that the connection of the aforementioned ceramics is realized, and the connection strength and quality of the ceramics are effectively improved, and the process is stable and reliable.

[0069] In the application, the room temperature three-point bending strength of the silicon carbide ceramic joint connected by the glass solder is above 180 MPa, and the 450°C high temperature three-point bending strength is above 150 MPa; the room temperature three-point bending strength of the aluminum nitride ceramic joint connected by the glass solder is above 160 MPa, and the 450°C high temperature three-point bending strength is above 140 MPa; and the room temperature three-point bending strength of the silicon nitride ceramic joint connected by the glass solder is above 150 MPa, and the 450°C high temperature three-point bending strength is above 100 MPa.

[0070] The following further examples are further illustrated in detail. It should also be understood that the following examples are only used to further illustrate the application, and cannot be understood as limiting the protection scope of the application, and some non-essential improvements and adjustments made by the person skilled in the art according to the above content of the application all belong to the protection scope of the application. The specific process parameters and the like in the following examples are only one example in the appropriate range, that is, the person skilled in the art can select within the appropriate range through the description herein, and not limited to the specific values of the following examples.

[0071] Example 1

[0072] (I) Preparation of glass powder

[0073] (1) The raw materials such as Na2CO3, H3BO3, SiO2 and Al2O3 were weighed and mixed according to the mass ratio shown in the formula. The formula and ratio of the glass solder are shown in Table 1. The raw materials were mixed by wet ball milling method. The solvent used for mixing was anhydrous ethanol with a purity of 99.5%, and the amount of addition was 40% of the mixed powder. The ball milling medium was zirconia ball, and the ratio of raw material to grinding ball was 1:2. The above-mentioned raw materials were sequentially added to the ball mill pot and ball-milled at 300 r / min for 10 h to obtain the mixed powder.

[0074] Table 1 shows the raw materials and ratio of the glass solder:

[0075]

[0076] (2) The mixed powder was dried in a 60°C oven for 2h, ground and sieved through an 80 mesh sieve. A certain amount of glass raw material was placed in an alumina crucible and high-temperature melted in a high-temperature lifting furnace at a heating rate of 10°C / min to 1400°C, and kept for 2h. Then the molten sample was directly poured into deionized water for rapid cooling to obtain a blocky glass sample.

[0077] (3) The bulk glass sample was broken by a multifunctional crusher and then ground by hand in a mortar. The glass powder was dried in an oven at 80 °C for 4 h and then sieved through a 325 mesh screen to obtain Na2O-B2O3-Al2O3-SiO2 glass powder.

[0078] Figure 1 The glass powder prepared in Example 1 was observed by eye. As shown in the figure, the glass powder was white, the powder particles were distinct, and there was no agglomeration.

[0079] (II) Bonding of silicon carbide ceramics

[0080] (1) Ethyl cellulose and terpineol were weighed according to a mass ratio of 5:95, poured into a sealed beaker, and stirred in a thermostatic magnetic stirrer at 90 °C for 4 h until the ethyl cellulose was completely dissolved. The organic carrier was then cooled to room temperature. A certain amount of glass powder obtained in step (I) was mixed with the organic carrier to obtain a glass paste, and the amount of the organic carrier was 30 wt.% of the glass powder.

[0081] (2) The surface of the silicon carbide ceramic to be welded was polished by using 500#, 800#, 1200# and 1600# water sandpaper, and was pre-oxidized in air. Then, the surface was cleaned by ultrasonic cleaning with anhydrous ethanol.

[0082] (3) The glass paste was uniformly coated on the polished surface of the silicon carbide ceramic by screen printing, and the coating thickness was 200 μm. Then, the coated silicon carbide ceramic was placed in a 60 °C oven for drying for 4 h.

[0083] (4) The coated silicon carbide ceramic and the uncoated silicon carbide ceramic were fixed by using an alumina clamp and were vertically applied with a pressure of 5 kPa. The silicon carbide ceramics were placed in a muffle furnace for welding. The temperature was raised from room temperature to 250 °C at a rate of 5 °C / min, and then the temperature was continuously raised to 450 °C at a rate of 2 °C / min, and was kept for 30 min. Then, the temperature was continuously raised to 1050 °C at a rate of 2 °C / min, and was kept for 30 min. After the furnace was naturally cooled, the bonding of the silicon carbide ceramics was completed.

[0084] The glass solder obtained in Example 1 had a glass transition temperature of 440 °C, a softening point of 590 °C, and a thermal expansion coefficient of 4.27 x 10 -6 K -1 which was close to the thermal expansion coefficient of the silicon carbide ceramic. The interface bonding effect after the bonding by the glass solder was good, and the room temperature three-point bending strength of the obtained silicon carbide ceramic joint reached 209 MPa, and the high temperature three-point bending strength at 450 °C reached 161 MPa.

[0085] Figure 2The micro-morphology of the silicon carbide ceramic joint prepared in Example 1 is shown in the figure. It can be seen from the figure that the weld is full and uniform, the glass is free of crystal precipitation, and the interface is firmly bonded.

[0086] Example 2

[0087] The preparation method of the low-thermal expansion coefficient glass solder and the joining process of the silicon carbide ceramic in this example 2 refer to Example 1, and the only difference is that the component proportions of the glass solder are different, as shown in Table 2.

[0088] Table 2 shows the raw materials and proportions of the glass solder:

[0089]

[0090] The glass transition temperature of the glass solder obtained in this example 2 is 466℃, the softening point is 611℃, and the thermal expansion coefficient between 20-400℃ is 4.36x10 -6 K -1 , which is close to the thermal expansion coefficient of the silicon carbide ceramic. After joining through the glass solder, the interface bonding effect is good, and the room temperature three-point bending strength of the obtained silicon carbide ceramic joint reaches 192MPa, and the high temperature three-point bending strength at 450℃ reaches 151MPa.

[0091] Example 3

[0092] The preparation method of the low-thermal expansion coefficient glass solder and the joining process of the silicon carbide ceramic in this example 3 refer to Example 1, and the only difference is that (1) the preparation of the glass powder: in step (2), the melting treatment process is: increasing the temperature from room temperature to 1500℃ at a rate of 10℃ / min, and keeping the temperature for 2h.

[0093] The glass transition temperature of the glass solder obtained in this example 3 is 443℃, the softening point is 592℃, and the thermal expansion coefficient between 20-400℃ is 4.13x10 -6 K -1 , which is close to the thermal expansion coefficient of the silicon carbide ceramic. After joining through the glass solder, the interface bonding effect is good, and the room temperature three-point bending strength of the obtained silicon carbide ceramic joint reaches 185MPa, and the high temperature three-point bending strength at 450℃ reaches 152MPa.

[0094] Example 4

[0095] The preparation method of the low-thermal expansion coefficient glass solder and the joining process of the silicon carbide ceramic in this example 4 refer to Example 1, and the only difference is that (1) the preparation of the glass powder: in step (2), the melting treatment process is: increasing the temperature from room temperature to 1400℃ at a rate of 10℃ / min, and keeping the temperature for 1h.

[0096] The glass solder obtained in this embodiment 4 has a glass transition temperature of 440℃, a softening point of 588℃, and a thermal expansion coefficient of 4.06x10 -6 K -1 The thermal expansion coefficient of the glass solder is close to that of the silicon carbide ceramic, and the interface bonding effect after connection is good. The room temperature three-point bending strength of the obtained silicon carbide ceramic joint is 184 MPa, and the 450℃ high temperature three-point bending strength is 150 MPa.

[0097] Embodiment 5

[0098] The preparation method of the low thermal expansion coefficient glass solder and the connection process of the silicon carbide ceramic in this embodiment 5 refer to embodiment 1, and the only difference is that (ii) connection of the silicon carbide ceramic: in step (3), the thickness of the screen printing glass paste is 100 μm.

[0099] The interface bonding effect after connection is good in this embodiment 5, and the room temperature three-point bending strength of the obtained silicon carbide ceramic joint is 185 MPa, and the 450℃ high temperature three-point bending strength is 153 MPa.

[0100] Embodiment 6

[0101] The preparation method of the low thermal expansion coefficient glass solder and the connection process of the silicon carbide ceramic in this embodiment 6 refer to embodiment 1, and the only difference is that (ii) connection of the silicon carbide ceramic: in step (4), the welding process is: from room temperature to 250℃ at a rate of 5℃ / min, then continue to heat to 450℃ at a rate of 2℃ / min, keep for 30 min, then continue to heat to 1150℃ at a rate of 2℃ / min, keep for 30 min.

[0102] The interface bonding effect after connection is good in this embodiment 6, and the room temperature three-point bending strength of the obtained silicon carbide ceramic joint is 183 MPa, and the 450℃ high temperature three-point bending strength is 178 MPa.

[0103] Embodiment 7

[0104] The preparation method of the low thermal expansion coefficient glass solder and the connection process of the silicon carbide ceramic in this embodiment 7 refer to embodiment 1, and the only difference is that (ii) connection of the silicon carbide ceramic: in step (4), the welding process is: from room temperature to 250℃ at a rate of 5℃ / min, then continue to heat to 450℃ at a rate of 2℃ / min, keep for 30 min, then continue to heat to 1050℃ at a rate of 2℃ / min, keep for 60 min.

[0105] The interface bonding effect after connection by the glass solder in this embodiment 7 is good, and the room temperature three-point bending strength of the obtained silicon carbide ceramic joint reaches 185 MPa, and the 450℃ high temperature three-point bending strength reaches 160 MPa.

[0106] Embodiment 8

[0107] The preparation method of the low thermal expansion coefficient glass solder and the connection process of the silicon carbide ceramic in this embodiment 8 refer to embodiment 1, and the only difference is that (ii) connection of the silicon carbide ceramic: in step (4), the welding process is as follows: the welding environment atmosphere is vacuum, the temperature is increased from room temperature to 250℃ at a rate of 5℃ / min, then the temperature is continuously increased to 450℃ at a rate of 2℃ / min, and the temperature is kept for 30 min, then the temperature is continuously increased to 1150℃ at a rate of 2℃ / min, and the temperature is kept for 30 min.

[0108] The interface bonding effect after connection by the glass solder in this embodiment 8 is good, and the room temperature three-point bending strength of the obtained silicon carbide ceramic joint reaches 256 MPa, and the 450℃ high temperature three-point bending strength reaches 241 MPa.

[0109] Embodiment 9

[0110] The preparation method of the low thermal expansion coefficient glass solder and the connection process of the silicon carbide ceramic in this embodiment 9 refer to embodiment 1, and the only difference is that (ii) connection of the silicon carbide ceramic: in step (2), the ceramic is aluminum nitride ceramic, and the surface of the ceramic is not subjected to pre-oxidation treatment.

[0111] The interface bonding effect after connection by the glass solder in this embodiment 9 is good, and the room temperature three-point bending strength of the obtained aluminum nitride ceramic joint reaches 186 MPa, and the 450℃ high temperature three-point bending strength reaches 154 MPa.

[0112] Embodiment 10

[0113] The preparation method of the low thermal expansion coefficient glass solder and the connection process of the silicon carbide ceramic in this embodiment 10 refer to embodiment 1, and the only difference is that (ii) connection of the silicon carbide ceramic: in step (2), the ceramic is silicon nitride ceramic, and the surface of the ceramic is not subjected to pre-oxidation treatment.

[0114] The interface bonding effect after connection by the glass solder in this embodiment 10 is good, and the room temperature three-point bending strength of the obtained silicon nitride ceramic joint reaches 166 MPa, and the 450℃ high temperature three-point bending strength reaches 106 MPa.

[0115] Comparative Example 1

[0116] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in Comparative Example 1 refer to Example 1, the only difference is that: (1) the preparation of the glass powder: in step (1), Na2CO3, H3BO3, SiO2, Al2O3 raw materials are weighed and mixed according to the mass ratio in Table 4.

[0117] Figure 3 The glass powder prepared for Comparative Example 1 is light gray in color due to the low Al2O3 content.

[0118] Comparative Example 2

[0119] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in Comparative Example 2 refer to Example 1, the only difference is that: (1) the preparation of the glass powder: in step (1), Na2CO3, H3BO3, SiO2, Al2O3 raw materials are weighed and mixed according to the mass ratio in Table 4.

[0120] Comparative Example 3

[0121] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in Comparative Example 3 refer to Example 1, the only difference is that: (1) the preparation of the glass powder: in step (1), Na2CO3, H3BO3, SiO2, Al2O3 raw materials are weighed and mixed according to the mass ratio in Table 4.

[0122] Comparative Example 4

[0123] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in Comparative Example 4 refer to Example 1, the only difference is that: (2) the connecting of the silicon carbide ceramic: in step (1), Na2CO3, H3BO3, SiO2, Al2O3 raw materials are weighed and mixed according to the mass ratio in Table 4.

[0124] Comparative Example 5

[0125] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in Comparative Example 5 refer to Example 1, the only difference is that: (2) the connecting of the silicon carbide ceramic: in step (3), the coating thickness of the glass paste is 50 μm.

[0126] Comparative Example 6

[0127] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in Comparative Example 6 refer to Example 1, the only difference is that: (2) the connecting of the silicon carbide ceramic: in step (4), the welding process: from room temperature to 250℃ at a rate of 5℃ / min, then continue to heat to 450℃ at a rate of 2℃ / min, keep for 30 min, then continue to heat to 950℃ at a rate of 2℃ / min, keep for 30 min.

[0128] Comparative Example 7

[0129] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in this comparative example 7 refer to Example 1, the only difference being that (ii) connecting of the silicon carbide ceramic: in step (4), the welding process is to increase the temperature from room temperature to 250°C at a rate of 5°C / min, then continue to increase the temperature to 450°C at a rate of 2°C / min, keep for 30 min, then continue to increase the temperature to 1250°C at a rate of 2°C / min, keep for 30 min.

[0130] Comparative Example 8

[0131] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in this comparative example 8 refer to Example 1, the only difference being that (ii) connecting of the silicon carbide ceramic: in step (3), the coating thickness of the glass paste is 300 μm.

[0132] Comparative Example 9

[0133] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in this comparative example 9 refer to Example 1, the only difference being that (ii) connecting of the silicon carbide ceramic: in step (4), the welding process is to increase the temperature from room temperature to 250°C at a rate of 5°C / min, then continue to increase the temperature to 450°C at a rate of 2°C / min, keep for 30 min, then continue to increase the temperature to 1050°C at a rate of 2°C / min, keep for 90 min.

[0134] Comparative Example 10

[0135] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in this comparative example 10 refer to Example 1, the only difference being that (ii) connecting of the silicon carbide ceramic: in step (4), the welding process is to increase the temperature from room temperature to 250°C at a rate of 5°C / min, then continue to increase the temperature to 450°C at a rate of 2°C / min, keep for 30 min, then continue to increase the temperature to 1050°C at a rate of 2°C / min, keep for 10 min.

[0136] Comparative Example 11

[0137] The preparation method of the low thermal expansion coefficient glass solder and the connecting process of the silicon carbide ceramic in this comparative example 11 refer to Example 1, the only difference being that (i) preparation of the glass powder: in step (2), the melting treatment process is to increase the temperature to 1400°C at a rate of 10°C / min, keep for 30 min.

[0138] Comparative Example 12

[0139] The preparation method of the low thermal expansion coefficient glass solder and the joining process of the silicon carbide ceramic in Comparative Example 12 refer to Example 1, except that (1) the preparation of the glass powder: in step (2), the melting treatment process is as follows: heating to 1400°C at a heating rate of 10°C / min, and holding for 5h.

[0140] Table 4 is the composition, preparation parameters and properties of the obtained glass solder:

[0141]

[0142] Table 5 is the welding parameters and properties of the obtained silicon carbide ceramic joint:

[0143]

[0144]

[0145] From the tables, it can be seen that (1) the thermal expansion coefficient of the glass increases greatly and the mechanical properties decrease greatly after the content of the Al2O3 component in the glass composition is reduced, which indicates that the Al2O3 component has a great influence on the thermal expansion coefficient of the glass system; (2) too short melting time of the glass solder will lead to uneven melting of the raw materials, resulting in a decrease in the uniformity of the powder and affecting the subsequent joining performance; although the bending strength of the silicon carbide ceramic joint in Comparative Example 12 reaches the range protected by the present application, the glass quality is lost due to too long melting time, and the mass of the prepared glass powder is reduced by at least 60% compared with the raw material, so we also do not use the process parameters in Comparative Example 12 for ceramic joining in practice; (3) too high welding temperature will cause crystallization in the glass, and too low welding temperature will lead to incomplete glass transition, both of which will reduce the mechanical properties of the joint; too long welding time will lead to an increase in the pores of the weld, and too short welding time will lead to uneven distribution of the weld, which also has a serious impact on the mechanical properties of the ceramic joint.

Claims

1. A low thermal expansion coefficient glass solder for joining ceramics, characterized by, The chemical composition of the low-thermal expansion coefficient glass solder includes 4.81-6.23 wt.% Na2O, 36.33-50.25 wt.% B2O3, 2.23-3.68 wt.% Al2O3 and 41.26-55.21 wt.% SiO2, and the sum of the mass percentages of the components is 100 wt.%; the ceramic is silicon carbide, aluminum nitride or silicon nitride ceramic; The low thermal expansion coefficient glass solder has a thermal expansion coefficient of (4.0~4.4)×10 -6 K -1 ; The low-thermal expansion coefficient glass solder has a glass transition temperature of 430-470℃ and a softening point of 580-620℃, and the ceramic is connected at 1000-1200℃.

2. The low coefficient of thermal expansion glass solder of claim 1, wherein, The low-thermal expansion coefficient glass solder is in powder form and has a particle size of 1-44 μm.

3. A method of producing a low thermal expansion coefficient glass solder as claimed in claim 1 or 2, characterized by, The method comprises the following steps: (1) proportionally weighing and mixing Na2CO3 powder, H3BO3 powder, SiO2 powder and Al2O3 powder, and obtaining a mixture after ball milling, drying, grinding and sieving; (2) melting the mixture to obtain a molten sample; (3) quenching the molten sample in deionized water to obtain a blocky glass sample, and obtaining the glass solder after crushing, drying and sieving.

4. The production method according to claim 3, characterized by, In step (1), the purity of the Na2CO3 powder, SiO2 powder and Al2O3 powder is all ≥99.0%; the purity of the H3BO3 is ≥99.5%; and the average particle size of the Na2CO3 powder, H3BO3 powder, SiO2 powder and Al2O3 powder is all 5-10 μm; The rotation speed of the ball milling is 300-600 rpm, and the time is 10-14 hours; The drying temperature is 50-80℃, and the drying time is 2-4 h; and the mesh number of the sieving is 80-100.

5. The preparation method according to claim 3, characterized in that, In step (2), the melting parameters include a melting temperature of 1400-1500℃, a melting time of 1-3 hours and a temperature rising rate of 5-10℃ / min.

6. The preparation method according to claim 5, characterized in that, The temperature rising rate is 10℃ / min.

7. The preparation method according to claim 3, characterized in that, In step (3), the drying temperature is 60-100℃, and the time is 3-5 hours; The mesh number of the sieving is 325-1250.

8. A method of joining ceramics with low thermal expansion coefficient glass solder according to any one of claims 1 to 2, characterized by, The method comprises the following steps: (1) mixing the glass solder and an organic carrier to obtain a glass paste; (2) uniformly coating the glass paste on the surface of the pretreated ceramic by using a silk screen printing method to obtain a glass paste layer, and obtaining a ceramic coated with a glass solder layer after drying; (3) fixing the ceramic coated with the glass solder layer and the ceramic without coating in a sandwich structure, naturally cooling to room temperature after welding treatment, and thus completing the connection of the ceramic.

9. The method of claim 8, wherein, In step (1), the organic carrier comprises a binder and a solvent; wherein the mass ratio of the binder to the solvent is (5-10):(90-95); The binder is at least one of methyl cellulose, ethyl cellulose, polyvinyl alcohol and phenolic resin; The solvent is at least one of terpineol, triterpene alcohol, ethyl acetate and butyl acetate; The preparation method of the organic carrier comprises mixing the binder and the solvent according to the mass ratio, and stirring at 20-100℃ for 4-8 h to obtain the organic carrier; The amount of the organic carrier is 25-40 wt.% of the mass of the glass solder.

10. The method of claim 8, wherein, In step (2), the pretreatment is ultrasonic cleaning of the ceramic surface with anhydrous ethanol; The drying temperature is 60-100 DEG C, and the time is 2-4 hours; The thickness of the glass paste layer is 100-200 mu m.

11. The method of claim 10, wherein, The ceramic is silicon carbide ceramic, and the ceramic surface needs to be pre-oxidized in air before ultrasonic cleaning.

12. The method of claim 8, wherein, In step (3), the parameters of the welding treatment include: at least one of air, vacuum and argon as the atmosphere; from room temperature to 240-260 DEG C at a rate of 4-5 DEG C / min, then continue to heat to 440-460 DEG C at a rate of 1-3 DEG C / min, and keep for 20-30 min, then continue to heat to 1000-1200 DEG C at a rate of 2 DEG C / min, and keep for 30-60 min.

13. A ceramic joint obtained by the method of any one of claims 8-10, characterized in that, The ceramic joint includes a silicon carbide joint, an aluminum nitride joint or a silicon nitride joint; wherein the room temperature three-point bending strength of the silicon carbide ceramic joint is greater than or equal to 180 MPa, and the 450 DEG C high-temperature three-point bending strength is greater than or equal to 150 MPa; the room temperature three-point bending strength of the aluminum nitride ceramic joint is greater than or equal to 160 MPa, and the 450 DEG C high-temperature three-point bending strength is greater than or equal to 140 MPa; the room temperature three-point bending strength of the silicon nitride ceramic joint is greater than or equal to 150 MPa, and the 450 DEG C high-temperature three-point bending strength is greater than or equal to 100 MPa.

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