Solder for welding ceramic and kovar alloy, welding structure and preparation method of welding structure

Abstract

The invention discloses a welding flux for welding ceramic and kovar alloy, a welding structure and a preparation method of the welding flux. The welding flux is prepared from, by mass, 20%-50% of silver, 20%-45% of copper, 20%-45% of titanium, 5%-20% of yttrium oxide and 5%-20% of aluminum oxide. The components of the solder are optimized, so that the solder is suitable for connection of the ceramic and the kovar alloy, the welding strength and the thermal shock and impact resistance of connection of the ceramic and the kovar alloy can be improved, and the preparation method is simple in process, easy to operate and control and beneficial to industrial production.

Description

Technical Field

[0001] This invention relates to welding technology, and in particular to a solder, welding structure and preparation method for welding ceramics and Kovar alloys. Background Technology

[0002] Currently, the mainstream welding methods for achieving reliable bonding between ceramics and metals include laser welding, brazing, and diffusion bonding. However, their technical characteristics and application limitations differ significantly: 1. Brazing: This method achieves bonding by melting a low-melting-point filler metal and wetting the ceramic and metal surfaces. The process is relatively simple and low-cost, making it the most widely used method in industrial applications. However, it is limited by two core issues: First, the thermal expansion coefficients of ceramics and metals differ significantly, and internal stress is easily left at the joint after welding and cooling, leading to increased brittleness and insufficient ductility at the joint. Second, ceramics have low surface energy, resulting in poor spreadability of the filler metal on their surface. Metallization pretreatment (such as titanium plating or copper plating) is required on the ceramic surface, which not only increases process costs but may also introduce new interface defects due to poor bonding between the pretreatment layer and the substrate. 2. Diffusion bonding: Under certain temperature and pressure, a metallurgical bond is formed through atomic diffusion at the ceramic-metal interface. Because it avoids the melting of the substrate, it can retain the insulation and high-temperature resistance properties of the ceramic and the original mechanical properties of the metal to the greatest extent, resulting in outstanding overall stability. However, it has a high technical threshold: it requires high-precision control of process parameters (temperature deviation ≤ ±5℃, pressure fluctuation ≤ ±0.1MPa). Excessive temperature can easily lead to ceramic oxidation or coarse metal grains, while insufficient atomic diffusion will result in insufficient temperature. At the same time, this process requires long-term heat preservation (usually several hours), resulting in low production efficiency, high equipment energy consumption, and strict requirements on the assembly gap of the workpiece (≤ 0.05mm), making it difficult to adapt to the connection requirements of irregularly shaped components.

[0003] In summary, although the two existing welding methods each have their own technical focus, they both suffer from problems such as limited improvement in ductility, high process complexity, or low production efficiency. Low metal ductility can easily affect the welding quality at the welding position and even lead to welding failure, failing to fully meet the comprehensive requirements of "high reliability, high ductility, low cost, and easy scalability".

[0004] Therefore, it is necessary to design a new technical solution to solve the above problems. Summary of the Invention

[0005] In view of this, the present invention addresses the deficiencies of the existing technology, and its main objective is to provide a solder, welding structure, and preparation method for welding ceramics and Kovar alloys. By optimizing the composition of the solder, the present invention innovates the welding connection structure, making it suitable for joining ceramics and Kovar alloys. By adding a metal sheet during welding, the ductility of the metal is utilized to improve the ductility of the solder layer, reduce the risk of failure at the welding position, and improve the welding strength and thermal shock resistance of the ceramics-Kovar alloy connection.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A solder for welding ceramics to Kovar alloy is prepared from the following raw materials in the indicated mass percentages: 20%-50% silver, 20%-45% copper, 20-45% titanium, 5-20% yttrium oxide, and 5-20% aluminum oxide. As a preferred embodiment, it is prepared from the following raw materials by mass percentage: 40% silver, 15% copper, 25% titanium, 9.6% yttrium oxide, and 10.4% aluminum oxide.

[0007] As a preferred embodiment, it is prepared from the following raw materials by mass percentage: 30% silver, 20% copper, 30% titanium, 10% yttrium oxide, and 5% aluminum oxide.

[0008] As a preferred embodiment, it is prepared from the following raw materials by mass percentage: 33% silver, 20% copper, 23% titanium, 10.5% yttrium oxide, and 13.5% aluminum oxide.

[0009] A method for preparing a solder for welding ceramics and Kovar alloys includes the following steps: Step S1, Mixing: Take the metal raw material powder of the solder for welding ceramics and Kovar alloy, the particle size of each metal raw material powder is 1-4μm, and mix them according to the ratio to obtain mixed metal powder; Step S2, ball milling: After adding solvent to the mixed metal powder, put it into the ball mill jar of the ball mill. Based on the mass of the mixed metal powder, the ball mill jar contains 200-300 parts by weight of alumina balls with a particle size of 5-15mm. The ball mill jar is processed at a speed of 120-150r / min for 12-24 hours to obtain a uniformly mixed solder.

[0010] As a preferred embodiment, the solvent is one or more selected from terpineol, diethylene glycol monobutyl ether, n-butanol, and ethanol.

[0011] As a preferred embodiment, the solvents added are 10 parts by weight of terpineol, 20 parts by weight of diethylene glycol monobutyl ether, and 5 parts by weight of n-butanol.

[0012] A welded structure of ceramic and Kovar alloy includes ceramic, Kovar alloy and solder for welding the ceramic and Kovar alloy, wherein the ceramic and Kovar alloy are connected by solder.

[0013] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution: The main innovation lies in optimizing the composition of the solder and creating a new welding connection structure suitable for joining ceramics and Kovar alloys. By adding metal sheets during welding, the ductility of the metal is utilized to improve the ductility of the solder layer, reducing the risk of failure at the welding position. This enhances the welding strength and thermal shock resistance of the ceramic-Kovar alloy joint. Furthermore, the solder is simple to manufacture by mixing metal raw material powders with a solvent and then ball milling them. The preparation method is easy to control and conducive to industrial production.

[0014] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the manufacturing process of a preferred embodiment of the present invention; Figure 2 This is a schematic diagram illustrating the application of a preferred embodiment of the present invention.

[0016] Explanation of reference numerals in the attached diagram: 10. Kovar flange; 20. Ceramic disc; 30. Solder layer; 31. First solder; 32. Metal sheet; 33. Second solder. Detailed Implementation

[0017] First, it should be noted that in the description of this invention, the terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0018] Please refer to Figures 1 to 2 As shown, it illustrates a preferred embodiment of the preparation method of the present invention, comprising the following steps: Step S1, Mixing: Take the metal raw material powder of the solder used for welding ceramics and Kovar alloy. The particle size of each metal raw material powder is 1-4μm. Mix them according to the ratio to obtain mixed metal powder. The solder used for welding ceramics and Kovar alloys is prepared from the following raw materials by mass percentage: silver 20%-50%, copper 20%-45%, titanium 20-45%, yttrium oxide 5-20%, and aluminum oxide 5-20%. Specifically, Formula 1: silver 33%, copper 20%, titanium 23%, yttrium oxide 10.5%, and aluminum oxide 13.5%; Formula 2: silver 30%, copper 20.5%, titanium 30%, yttrium oxide 10%, and aluminum oxide 5%; Formula 3: silver 40%, copper 15%, titanium 25%, yttrium oxide 9.6%, and aluminum oxide 10.4%. In this embodiment, the particle size of each metal raw material powder is 1 μm.

[0019] Step S2, ball milling: After adding solvent to the mixed metal powder, put it into the ball mill jar of the ball mill. Based on the mass of the mixed metal powder, the ball mill jar is filled with 200-300 parts by weight of alumina balls with a particle size of 5-15mm. The ball mill jar is processed at a speed of 120-150r / min for 12-24 hours to obtain a uniformly mixed solder. The solvent is one or more of terpineol, diethylene glycol monobutyl ether, n-butanol, and ethanol; specifically, the added solvent is 10 parts by weight of terpineol, 20 parts by weight of diethylene glycol monobutyl ether, and 5 parts by weight of n-butanol. In this embodiment, the alumina balls are 250 parts by weight and have a particle size of 10 mm, the rotation speed is 120 r / min, and the processing time is 12 hours.

[0020] See Figure 2 As shown, the welding process for ceramics and Kovar alloys includes the following steps: The first step is to apply the blue film to the ceramic surface that needs to be welded, and then cut the blue film into the appropriate shape according to the weld groove of the ceramic. The second step is to evenly coat a layer of solder on the solder bath, then place a metal sheet in it, coat another layer of solder on the metal sheet, and then peel off the blue film; wherein, the metal sheet can be a gold sheet, a silver sheet, or a copper sheet. The third step is to use positioning blocks to confirm the position of the welding groove; The fourth step is to assemble the Kovar alloy into a whole according to the corresponding weld groove position determined by the positioning block, place it in the graphite pressure welding fixture for fixation, and transfer it into the vacuum pressureless furnace. The fifth step is to set the sintering regime program, holding at 850-1000℃ for 1 hour at a rate of 2-5℃ / min, and then start automatic sintering; specifically, holding at 850℃ for 1 hour at a rate of 3℃ / min. Step 6: After the sintering process is complete, open the furnace door and remove the welded product.

[0021] The welded product is a welded structure of ceramic and Kovar alloy; specifically, the welded product can be a fixed connection end structure of an aluminum nitride heater, which includes a Kovar flange 10 and a ceramic disc 20 fixedly connected to the top surface of the Kovar flange 10. The Kovar flange 10 and the ceramic disc 20 are fixedly connected by a solder layer 30. The solder layer 30 includes a first solder 31, a metal sheet 32, and a second solder 33 arranged sequentially from top to bottom. Both the first solder 31 and the second solder 33 are solders used for welding ceramic and Kovar alloy. Specifically, the bottom surface of the ceramic disc 20 is recessed upward to form a welding groove 21, the solder layer 30 is placed in the welding groove 21, the first solder 31 is connected to the top wall of the welding groove 21, the second solder 33 is connected to the Kovar flange 10, the outer peripheral side of the solder layer 30 is attached to the side wall of the welding groove 21, the thickness of the solder layer 30 is equal to the groove depth of the welding groove 21, and the outer peripheral sides of the first solder 31, the metal sheet 32, and the second solder 33 are flush. The axis of the ceramic disc 20 is aligned with the axis of the Kovar flange 10, the outer periphery of the Kovar flange 10 extends outward beyond the outer periphery of the ceramic disc 20, and the thickness of the Kovar flange 10 is greater than the thickness of the ceramic disc 20.

[0022] The welding strength test results for different solder formulations are as follows:

[0023] Based on the welding strength test results of different solder formulations, when the same metal sheet is added, the welding effect of formulation 3 is better than that of formulation 1 and formulation 2. When different metal sheets are added to the same formulation, the welding effect of adding gold sheet is better than that of adding silver sheet and copper sheet.

[0024] The key design focus of this invention is: The main innovation lies in optimizing the composition of the solder and creating a new welding connection structure suitable for joining ceramics and Kovar alloys. By adding metal sheets during welding, the ductility of the metal is utilized to improve the ductility of the solder layer, reducing the risk of failure at the welding position. This enhances the welding strength and thermal shock resistance of the ceramic-Kovar alloy joint. Furthermore, the solder is simple to manufacture by mixing metal raw material powders with a solvent and then ball milling them. The preparation method is easy to control and conducive to industrial production.

[0025] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A solder for welding ceramics to Kovar alloy, characterized in that: It is made from the following raw materials by weight percentage: silver 20%-50%, copper 20%-45%, titanium 20-45%, yttrium oxide 5-20%, and aluminum oxide 5-20%.

2. The solder for welding ceramics and Kovar alloys according to claim 1, characterized in that: It is made from the following raw materials by weight percentage: silver 40%, copper 15%, titanium 25%, yttrium oxide 9.6%, and aluminum oxide 10.4%.

3. The solder for welding ceramics and Kovar alloys according to claim 1, characterized in that: It is made from the following raw materials by weight percentage: silver 30%, copper 205%, titanium 30%, yttrium oxide 10%, and aluminum oxide 5%.

4. The solder for welding ceramics and Kovar alloys according to claim 1, characterized in that: It is made from the following raw materials by weight percentage: silver 33%, copper 20%, titanium 23%, yttrium oxide 10.5%, and aluminum oxide 13.5%.

5. A method for preparing a solder for welding ceramics and Kovar alloys, characterized in that: Includes the following steps: Step S1, Mixing: Take the metal raw material powder of the solder for welding ceramics and Kovar alloy as described in any one of claims 1 to 4, wherein the particle size of each metal raw material powder is 1-4 μm, and mix them in proportion to obtain mixed metal powder; Step S2, ball milling: After adding solvent to the mixed metal powder, put it into the ball mill jar of the ball mill. Based on the mass of the mixed metal powder, the ball mill jar contains 200-300 parts by weight of alumina balls with a particle size of 5-15mm. The ball mill jar is processed at a speed of 120-150r / min for 12-24 hours to obtain a uniformly mixed solder.

6. The method for preparing the solder for welding ceramics and Kovar alloy according to claim 5, characterized in that: The solvent is one or more of terpineol, diethylene glycol monobutyl ether, n-butanol, and ethanol.

7. The method for preparing the solder for welding ceramics and Kovar alloy according to claim 6, characterized in that: The added solvents are 10 parts by weight of terpineol, 20 parts by weight of diethylene glycol monobutyl ether, and 5 parts by weight of n-butanol.

8. A welded structure of ceramic and Kovar alloy, characterized in that: It includes ceramics, Kovar alloys, and solder for welding ceramics and Kovar alloys as described in any one of claims 1 to 4, wherein the ceramics and Kovar alloys are connected by solder.

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