Secondary-welded shaped metal ceramic heating element, preparation method and application thereof

Abstract

This invention relates to the field of electronic ceramic manufacturing, specifically to a secondary welded metal-ceramic heating component, its preparation method, and its application. The secondary welded metal-ceramic heating component includes a metal-ceramic heating element, a welding section, and two heat-dissipating aluminum fins. The welding section includes a titanium-based welding section and an aluminum-based welding section integrally connected to the titanium-based welding section. The titanium-based welding section is welded using titanium-based solder, and the aluminum-based welding section is welded using aluminum-based solder sheets. The titanium-based solder includes Ti, Al, Si, Mg, and silane coupling agent-modified graphene. Further, the aluminum-based solder sheets include Al, Si, Mg, and active metals. This component, through a secondary welding structure of titanium-based and aluminum-based solder, achieves a high-strength, high-thermal-conductivity, and low-thermal-resistance integrated connection between the ceramic heating element and the heat-dissipating aluminum fins, significantly improving the component's thermal shock resistance and long-term reliability.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramics manufacturing, specifically to a secondary welding-formed metal-ceramic heating component, its preparation method, and its application. Background Technology

[0002] Currently, existing technologies include a patent document with application number 200920054729.1 that discloses an electric heater based on a ceramic heating element. The mainstream assembly structure of this type of conventional ceramic heating electric heater is as follows: heat sinks are respectively attached and fixed to the upper and lower surfaces of the alumina ceramic heating element, and the two are completely bonded and insulated by insulating adhesive. Although this assembly method is simple, the insulating adhesive is both a thermal conductivity limitation point and a temperature limitation point: on the one hand, the thermal conductivity of the insulating adhesive is much lower than that of metals and ceramics, which greatly increases the interfacial thermal resistance, resulting in low heat transfer efficiency, slow heating speed, and poor overall energy efficiency of the heating element; on the other hand, the insulating adhesive has limited high-temperature resistance, and is prone to aging, carbonization, and bonding failure under long-term high-temperature conditions, which in turn leads to safety hazards such as separation of the ceramic sheet and the heat sink, local overheating, and decreased insulation performance.

[0003] Furthermore, existing technologies often rely on a single brazing system to connect the ceramic heating substrate and the metal heat sink, making it difficult to simultaneously address the interfacial bonding, heat transfer, and thermal stress adaptation between the ceramic and metal. For example, direct brazing with aluminum-based solder results in poor wettability to the ceramic and low interfacial bonding strength, making it prone to cracking and detachment under high-power thermal cycling. While high-temperature titanium-based solder can strengthen the ceramic interface, its welding temperature far exceeds the tolerance range of the aluminum heat sink, easily causing the aluminum to melt, deform, and oxidize, thus failing to achieve a reliable connection. Simultaneously, the significant difference in thermal expansion coefficients between ceramic and metal heat sinks makes it difficult for a single solder to achieve a gradient transition in thermal expansion, easily leading to concentrated thermal stress at the interface, further exacerbating the risk of cracking and detachment, and severely impacting the component's thermal shock resistance, long-term reliability, and service life.

[0004] Therefore, there is an urgent need to develop a metal-ceramic heating component with high welding strength, excellent thermal conductivity, and good thermal shock resistance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by providing a secondary welding-formed metal-ceramic heating component, its preparation method, and its application. This component achieves a high-strength, high-thermal-conductivity, and low-thermal-resistance integrated connection between the ceramic heating element and the heat dissipation aluminum fin through a secondary welding structure of titanium-based solder and aluminum-based solder, significantly improving the component's thermal shock resistance and long-term reliability.

[0006] The objective of this invention is achieved through the following technical solution: a secondary welded metal-ceramic heating component, comprising a metal-ceramic heating element, a welding part, and two heat-dissipating aluminum fins. The upper and lower surfaces of the metal-ceramic heating element are integrally connected to the two heat-dissipating aluminum fins via the welding part. The welding part includes a titanium-based welding part and an aluminum-based welding part integrally connected to the titanium-based welding part. The two titanium-based welding parts are respectively disposed on the upper and lower surfaces of the metal-ceramic heating element, and the two aluminum-based welding parts are integrally connected to the upper or lower end faces of the two heat-dissipating aluminum fins. The titanium-based welding part is formed by welding with titanium-based solder, and the aluminum-based welding part is formed by welding with aluminum-based solder sheets.

[0007] Furthermore, the titanium-based solder comprises the following components by mass fraction: Ti 40-50%, Al 0.5-5%, Si 1-5%, Mg 0-0.25%, and silane coupling agent modified graphene 40-50%.

[0008] Furthermore, the aluminum-based solder sheet comprises the following components by mass fraction: Al 88.5-93.25%, Si 6.5-11%, Mg 0.25-0.5%, and active metal 0-0.8%.

[0009] Furthermore, the active metal comprises the following components in mass fractions: Ti 0-0.2% and Zr 0-0.6%.

[0010] Furthermore, the silane coupling agent includes at least one of KH550 or KH570.

[0011] This invention effectively improves the wettability of the solder on the ceramic surface by introducing active metals into the aluminum-based solder sheet, resulting in a more uniform flow and distribution of the solder on the ceramic surface. Simultaneously, it promotes the diffusion and densification of the bonding layer during high-temperature brazing, forming a stronger interfacial bond. From a thermal conductivity perspective, the uniform distribution of the solder helps reduce interfacial thermal resistance, thereby improving the thermal conductivity of the welded area. Furthermore, this invention employs a two-stage welding structure design: first, a titanium-based solder is welded to the metal-ceramic heating element to form a high-strength ceramic-titanium composite interface; then, an aluminum-based solder is welded to the heat sink aluminum sheet, achieving a gradient transition in the coefficient of thermal expansion. This effectively alleviates the interfacial cracking problem caused by thermal stress concentration, significantly improving the long-term reliability of the component under high-temperature cycling conditions.

[0012] Furthermore, the preparation method of the silane coupling agent modified graphene includes the following steps: A1. Add the silane coupling agent to the ethanol-water mixture, then add glacial acetic acid to adjust the pH to 4-5, stir at room temperature for 10-15 minutes to obtain the hydrolysate; A2. Add graphene to the hydrolysate, disperse ultrasonically for 20-30 minutes, and stir in a water bath at 50-60℃ for 6-12 hours. A3. After the reaction is complete, the solid product is separated by filtration and washed 2-3 times with anhydrous ethanol. It is then dried under vacuum at 55-65℃ for 10-14 hours to obtain silane coupling agent modified graphene.

[0013] Furthermore, in step A1, the ethanol-water mixture is ethanol and water in a volume ratio of 8-10:1.

[0014] Furthermore, the mass ratio of the graphene to the silane coupling agent is 1:1-2.

[0015] Furthermore, the metal-ceramic heating element comprises an upper alumina ceramic sheet, a heating circuit, and a lower alumina ceramic sheet arranged sequentially from top to bottom, wherein both the upper and lower alumina ceramic sheets are alumina ceramic sheets with a purity of not less than 96% prepared by the casting method.

[0016] This invention also provides a method for preparing a metal-ceramic heating element through secondary welding, comprising the following steps: S1. Material preparation: Add anhydrous ethanol and binder to titanium-based solder, wet mix with roller ball mill for 1-3 hours, and degas using a vacuum centrifugal degassing machine at 250-350 rpm to obtain a paste-like titanium-based solder. S2, First welding: The paste-like solder obtained in step S1 is coated on the surface of the metal-ceramic heating element, placed in a vacuum sintering furnace, heated to 1000-1400℃, held for 25-35 minutes for sintering, and cooled to room temperature with the furnace after sintering, and then taken out to obtain the ceramic preform. S3. Secondary welding: Place the aluminum-based solder sheet between the heat dissipation aluminum sheet and the ceramic preform obtained in step S2, fix it with a clamp, place it in a vacuum brazing furnace, heat it to 580-600℃, hold it at the temperature for 10-30 minutes for brazing, and cool it with the furnace to obtain the secondary welded metal-ceramic heating component.

[0017] The preparation method of this invention is simple to operate, easy to control, and suitable for industrial production. In the first welding, graphene reacts with Ti to form titanium carbide reinforcement, which has high thermal conductivity, high strength, and thermal shock resistance. At the same time, unreacted graphene further improves thermal conductivity. In the second welding, the brazing temperature is 580-600℃ to avoid deformation of the aluminum sheet; the holding time is 10-30 minutes to prevent insufficient bonding or solder leakage. The aluminum-based solder has a similar coefficient of thermal expansion to the heat sink aluminum sheet, which can avoid high-temperature cracking. This method achieves a high-quality connection between ceramic and aluminum sheet through secondary welding, taking into account both welding strength and process stability, and is suitable for mass production. Furthermore, in step S1, the amount of anhydrous ethanol added is 30-40% of the total mass of the titanium-based solder.

[0018] Furthermore, in step S1, the binder includes at least one of cellulose or polyvinyl alcohol, and the amount of binder added is 5-10% of the total mass of the titanium-based solder.

[0019] Furthermore, the mass ratio of the titanium-based solder to the aluminum-based solder sheet is 1:0.8-1.2.

[0020] The present invention also provides the application of the above-mentioned secondary welded metal-ceramic heating element in electric heaters.

[0021] When the secondary welded metal-ceramic heating element of the present invention is used in electric heaters, it can achieve rapid heating, uniform heat dissipation, and long-term high-temperature operation without desoldering or cracking, significantly improving the heating efficiency and service life of the electric heater.

[0022] The beneficial effects of this invention are as follows: 1. This invention employs a primary welding process with a titanium-based solder and a metal-ceramic heating element to form a high-strength ceramic-titanium composite interface. The graphene in the titanium-based solder reacts with titanium to generate a titanium carbide reinforcing phase, significantly improving the thermal conductivity and mechanical properties of the weld layer. A secondary welding process is then performed with an aluminum-based solder and a heat-dissipating aluminum sheet. The matching thermal expansion coefficients of the aluminum-based solder and the aluminum sheet prevent thermal stress cracking under high-temperature cycling.

[0023] 2. By adding active metals Ti and Zr to aluminum-based solder, the wettability of the solder to the ceramic surface is improved, the solder distribution is more uniform, the bonding of the welding interface is denser, and the interface thermal resistance is significantly reduced.

[0024] 3. The secondary welding and forming method provided by the present invention is simple to operate, has a wide process window, and is suitable for industrial production. The resulting metal-ceramic heating components have the characteristics of high thermal conductivity, high shear strength, and excellent high-temperature cycle stability.

[0025] 4. This component is particularly suitable for heating equipment with high temperature, long life and high reliability, such as electric heaters, and has broad market application prospects. Detailed Implementation

[0026] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0027] Example 1 This embodiment provides a secondary welded metal-ceramic heating component, including a metal-ceramic heating element, a welding part, and two heat dissipation aluminum fins. The upper and lower surfaces of the metal-ceramic heating element are integrally connected to the two heat dissipation aluminum fins via the welding part. The welding part includes a titanium-based welding part and an aluminum-based welding part integrally connected to the titanium-based welding part. The two titanium-based welding parts are respectively disposed on the upper and lower surfaces of the metal-ceramic heating element, and the two aluminum-based welding parts are integrally connected to the upper or lower end faces of the two heat dissipation aluminum fins, respectively. The titanium-based welding part is welded using titanium-based solder, and the aluminum-based welding part is welded using aluminum-based solder sheets.

[0028] Furthermore, the titanium-based solder comprises the following components by mass fraction: Al 5%, Si 3%, Mg 0.25%, silane coupling agent modified graphene 45%, and Ti balance.

[0029] Furthermore, the aluminum-based solder sheet comprises the following components by mass fraction: Si 9%, Mg 0.35%, active metal 0.4%, and Al balance.

[0030] Furthermore, the active metal comprises the following components by mass fraction: Ti 0.2% and Zr 0.6%.

[0031] Furthermore, the silane coupling agent includes KH550.

[0032] Furthermore, the preparation method of the silane coupling agent modified graphene includes the following steps: A1. Add the silane coupling agent to the ethanol-water mixture, then add glacial acetic acid to adjust the pH to 4-5, stir at room temperature for 12 minutes to obtain the hydrolysate; A2. Add graphene to the hydrolysate, disperse it ultrasonically for 25 minutes, and stir the reaction in a water bath at 55°C for 9 hours. A3. After the reaction is complete, the solid product is separated by filtration and washed 2-3 times with anhydrous ethanol. It is then dried under vacuum at 60°C for 12 hours to obtain silane coupling agent modified graphene.

[0033] Furthermore, in step A1, the ethanol-water mixture is composed of ethanol and water in a volume ratio of 9:1.

[0034] Furthermore, the mass ratio of the graphene to the silane coupling agent is 1:1.5.

[0035] Furthermore, the metal-ceramic heating element comprises an upper alumina ceramic sheet, a heating circuit, and a lower alumina ceramic sheet arranged sequentially from top to bottom, wherein both the upper and lower alumina ceramic sheets are alumina ceramic sheets with a purity of not less than 96% prepared by the casting method.

[0036] This embodiment also provides a method for preparing a metal-ceramic heating component by secondary welding, comprising the following steps: S1. Material preparation: Add anhydrous ethanol and binder to titanium-based solder, wet mix with roller ball mill for 2 hours, and degas using a vacuum centrifugal degassing machine at 300 rpm to obtain a paste-like titanium-based solder. S2, One-time welding: The paste-like solder obtained in step S1 is coated on the surface of the metal-ceramic heating element, placed in a vacuum sintering furnace, heated to 1200℃, held for 30 minutes for sintering, and cooled to room temperature with the furnace after sintering, and then taken out to obtain the ceramic preform. S3. Secondary welding: Place the aluminum-based solder sheet between the heat dissipation aluminum sheet and the ceramic preform obtained in step S2, fix it with a clamp, place it in a vacuum brazing furnace, heat it to 590℃, hold it at that temperature for 20 minutes for brazing, and cool it with the furnace to obtain a secondary welded metal-ceramic heating component.

[0037] Furthermore, in step S1, the amount of anhydrous ethanol added is 35% of the total mass of the titanium-based solder.

[0038] Furthermore, in step S1, the binder includes at least one of cellulose or polyvinyl alcohol, and the amount of binder added is 8% of the total mass of the titanium-based solder.

[0039] Furthermore, the mass ratio of the titanium-based solder to the aluminum-based solder sheet is 1:1.

[0040] This embodiment also provides the application of the above-mentioned secondary welded metal-ceramic heating element in an electric heater.

[0041] Comparative Example 1 Unlike Example 1, this comparative example provides a secondary welded metal-ceramic heating component, including a metal-ceramic heating element, an aluminum-based welding part, and two heat-dissipating aluminum sheets. The upper and lower surfaces of the metal-ceramic heating element are integrally connected to the two heat-dissipating aluminum sheets through the aluminum-based welding part, and the aluminum-based welding part is welded by aluminum-based solder sheet.

[0042] Furthermore, the aluminum-based solder sheet comprises the following components by mass fraction: Si 9%, Mg 0.35%, active metal 0.4%, and Al balance.

[0043] Furthermore, the active metal comprises the following components by mass fraction: Ti 0.2% and Zr 0.6%.

[0044] This embodiment also provides a method for preparing a secondary welded metal-ceramic heating element, including the following steps: placing an aluminum-based solder sheet between a heat-dissipating aluminum sheet and a metal-ceramic heating sheet, fixing it with a clamp, placing it in a vacuum brazing furnace, heating it to 590°C, holding it at that temperature for 20 minutes for brazing, and cooling it with the furnace to obtain the metal-ceramic heating element.

[0045] Comparative Example 2 Unlike Example 1, this comparative example provides a method for preparing a secondary welded metal-ceramic heating element, comprising the following steps: S1. Material preparation: Add anhydrous ethanol and binder to titanium-based solder, wet mix with roller ball mill for 2 hours, and degas using a vacuum centrifugal degassing machine at 300 rpm to obtain a paste-like titanium-based solder. S2, One-time welding: The paste-like solder obtained in step S1 is coated on the surface of the metal-ceramic heating element, placed in a vacuum sintering furnace, heated to 800°C, held for 30 minutes for sintering, and cooled to room temperature with the furnace after sintering, and then taken out to obtain the ceramic preform. S3. Secondary welding: Place the aluminum-based solder sheet between the heat dissipation aluminum sheet and the ceramic preform obtained in step S2, fix it with a clamp, place it in a vacuum brazing furnace, heat it to 590℃, hold it at that temperature for 20 minutes for brazing, and cool it with the furnace to obtain a secondary welded metal-ceramic heating component.

[0046] Comparative Example 3 Unlike Example 1, the aluminum-based solder sheet in this comparative example comprises the following components by mass fraction: Si 9%, Mg 0.35%, and Al balance.

[0047] Comparative Example 4 Unlike Example 1, the active metal in this comparative example includes Ti, that is, Ti replaces Zr in an equal amount.

[0048] Comparative Example 5 Unlike Example 1, the active metal in this comparative example includes Zr, that is, Zr replaces Ti in an equal amount.

[0049] Comparative Example 6 Unlike Example 1, the titanium-based solder in this comparative example comprises the following components by mass fraction: Al 5%, Si 3%, Mg 0.25%, a mixture of graphene and carbon powder 45%, and Ti balance.

[0050] Furthermore, the graphene and carbon powder mixture is composed of graphene and carbon powder in a mass ratio of 1:0.3.

[0051] Performance testing The performance of the metal-ceramic heating elements prepared in Example 1 and Comparative Examples 1-6 was tested. The thermal conductivity, shear strength, number of high-temperature cycling cycles without cracking, and wetting angle of the metal-ceramic heating elements were measured. The results are shown in the table below:

[0052] Shear strength was tested according to GB / T 6569-2006 Test Method for Interfacial Shear Strength of Ceramic Materials; The number of high-temperature cycles without cracking (400℃) is determined by the electric heating hot-cold cycle method: heating to 400℃, holding for 10 minutes, cutting off the power, and forced air cooling to room temperature, which is recorded as one cycle; the maximum number of cycles without cracks or detachment observed at the weld interface under an optical microscope is expressed as the maximum number of cycles; the judgment criterion is to terminate when visible cracks or detachment appear.

[0053] The wetting angle is tested according to GB / T 11364-2008 "Test Method for Wetting Properties of Solder", using a high-temperature wetting angle measuring instrument to determine the spreading angle of the solder on the ceramic or aluminum surface at the corresponding soldering temperature.

[0054] The test data above show that the secondary welded metal-ceramic heating element prepared in Example 1 is significantly superior to the comparative examples in terms of thermal conductivity, shear strength, number of high-temperature cycles without cracking, and solder wettability. Comparative Example 1 omitted the titanium-based welding layer and used only aluminum-based solder to directly connect the ceramic heating element and the aluminum heat sink, resulting in low interfacial bonding strength between the ceramic and solder, mismatched thermal expansion, and a significant decrease in thermal conductivity and shear strength, reducing the number of high-temperature cycles without cracking to 4000. Comparative Example 2 had a sintering temperature of only 800℃ in a single weld, far lower than the 1200℃ of Example 1, failing to allow the Ti in the titanium-based solder to react with graphene to form a titanium carbide (TiC) reinforcing phase, weakening the interfacial bonding strength and thermal conductivity, and reducing the number of high-temperature cycles without cracking to 3000. Example 1, by simultaneously adding 0.2% Ti and 0.6% Zr, significantly reduced the wetting angle to 62°, far superior to Comparative Examples 3-5. This indicates a significant synergistic effect between Ti and Zr: Ti preferentially reacts with the oxide film on the aluminum sheet surface, disrupting the dense oxide layer and promoting contact between the solder and the fresh aluminum substrate; Zr further reduces the surface tension of the solder, enhances its fluidity, and enables the solder to form a uniform and dense spread layer on the aluminum sheet surface. The combined use of the two significantly improves wettability compared to adding either alone, thereby substantially improving the thermal conductivity and mechanical strength of the weld interface. Comparative Example 6 used an unmodified graphene and carbon powder mixture instead of silane coupling agent-modified graphene. The graphene exhibited poor dispersion and weak interfacial bonding with the titanium matrix, failing to effectively generate a uniformly distributed titanium carbide reinforcing phase. The thermal conductivity and shear strength were lower than in Example 1, and the number of high-temperature cycling cycles without cracking was only 4000.

[0055] The above results fully demonstrate that the secondary welding structure, the specific composition of titanium-based solder and aluminum-based solder, and the active metal system of Ti and Zr compounded in the aluminum-based solder have synergistic advantages, which can significantly improve the overall performance of metal-ceramic heating components.

[0056] The specific embodiments described above are further illustrations of the technical solution and beneficial effects of the present invention, and are not intended to limit the implementation methods. For those skilled in the art, any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A metal-ceramic heating element formed by secondary welding, characterized in that: The device includes a metal-ceramic heating element, a welding section, and two heat-dissipating aluminum fins. The upper and lower surfaces of the metal-ceramic heating element are integrally connected to the two heat-dissipating aluminum fins via the welding section. The welding section includes a titanium-based welding section and an aluminum-based welding section integrally connected to the titanium-based welding section. The two titanium-based welding sections are respectively disposed on the upper and lower surfaces of the metal-ceramic heating element, and the two aluminum-based welding sections are integrally connected to the upper or lower end faces of the two heat-dissipating aluminum fins, respectively. The titanium-based welding section is formed by welding with titanium-based solder, and the aluminum-based welding section is formed by welding with aluminum-based solder sheets.

2. The metal-ceramic heating component formed by secondary welding according to claim 1, characterized in that: The titanium-based solder comprises the following components by mass fraction: Ti 40-50%, Al 0.5-5%, Si 1-5%, Mg 0-0.25%, and 40-50% silane coupling agent modified graphene.

3. The metal-ceramic heating element formed by secondary welding according to claim 1, characterized in that: The aluminum-based solder sheet comprises the following components by mass fraction: Al 88.5-93.25%, Si 6.5-11%, Mg 0.25-0.5%, and active metal 0-0.8%.

4. The secondary welded metal-ceramic heating component according to claim 3, characterized in that: The active metal comprises the following components in mass fractions: Ti 0-0.2% and Zr 0-0.6%.

5. The secondary welded metal-ceramic heating component according to claim 2, characterized in that: The silane coupling agent includes at least one of KH550 or KH570.

6. A method for preparing a secondary welded metal-ceramic heating component according to any one of claims 1-5, characterized in that: Includes the following steps: S1. Material preparation: Add anhydrous ethanol and binder to titanium-based solder, wet mix with roller ball mill for 1-3 hours, and degas using a vacuum centrifugal degassing machine at 250-350 rpm to obtain a paste-like titanium-based solder. S2, First welding: The paste-like solder obtained in step S1 is coated on the surface of the metal-ceramic heating element, placed in a vacuum sintering furnace, heated to 1000-1400℃, held for 25-35 minutes for sintering, and cooled to room temperature with the furnace after sintering, and then taken out to obtain the ceramic preform. S3. Secondary welding: Place the aluminum-based solder sheet between the heat dissipation aluminum sheet and the ceramic preform obtained in step S2, fix it with a clamp, place it in a vacuum brazing furnace, heat it to 580-600℃, hold it at the temperature for 10-30 minutes for brazing, and cool it with the furnace to obtain the secondary welded metal-ceramic heating component.

7. The method for preparing a secondary welded metal-ceramic heating component according to claim 6, characterized in that: In step S1, the amount of anhydrous ethanol added is 30-40% of the total mass of the titanium-based solder.

8. The method for preparing a secondary welded metal-ceramic heating component according to claim 6, characterized in that: In step S1, the binder includes at least one of cellulose or polyvinyl alcohol, and the amount of binder added is 5-10% of the total mass of the titanium-based solder.

9. The method for preparing a secondary welded metal-ceramic heating component according to claim 6, characterized in that: The mass ratio of the titanium-based solder to the aluminum-based solder sheet is 1:0.8-1.

2.

10. The application of a secondary welded metal-ceramic heating element according to any one of claims 1-5 in an electric heater.

Images