MCM-1A type high-frequency metal packaging mica capacitor

Abstract

The invention belongs to the field of electronic components, and particularly relates to an MCM-1A type high-frequency metal packaging mica capacitor, which is formed by packaging core groups by pressing a metal packaging shell, and is characterized in that the core groups connected in parallel are fixed in the shell through silver-plated metal gaskets; and the core group is formed by alternately overlapping a plurality of muscovite sheets printed with electrodes and silver-plated metal lead-out sheets. A dielectric topological insulator heterojunction composite nano material doped in a silver-plated metal gasket is introduced, a bismuth triselenide nanosheet is used as a core of the material, a barium strontium titanate shell layer is coated outside the bismuth triselenide nanosheet through an atomic layer deposition process, and the bismuth triselenide nanosheet is coated and modified through a surface polymer. The composite nano material effectively optimizes the interface characteristics and high-frequency conductivity of the electrode. The capacitor is simple in preparation process and compatible with an existing production line, and the obtained product has lower loss and higher temperature stability under high frequency and is suitable for a high-frequency circuit.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electronic components, and particularly relates to a MCM-1A type high-frequency metal packaging mica capacitor. BACKGROUND

[0002] As a classic inorganic dielectric capacitor, mica capacitor has long occupied an irreplaceable key position in high-frequency oscillation, resonance, coupling and bypass circuits due to its inherent advantages of high dielectric strength, low loss tangent, stable temperature-frequency characteristics and excellent reliability. The typical structure of the mica capacitor usually adopts natural or synthetic mica sheets as the dielectric, and silver layers are coated on the surfaces of the mica sheets to form electrodes. After a plurality of silver-coated mica sheets and metal lead sheets are alternately stacked, the stacked structure is placed in a metal shell and sealed by mechanical pressing or welding to obtain a durable and reliable fully-sealed structure. This structure, especially the metal packaging type, can effectively resist the influence of external humidity, dust and mechanical stress, and ensure long-term stable electrical performance. Therefore, the mica capacitor is widely used in communication equipment, precision test instruments and various high-demand military electronic equipment.

[0003] However, with the rapid development of modern wireless communication technology towards higher frequency bands, wider bandwidths and denser integration, and the increasingly stringent requirements of electronic systems on power handling capability and extreme environment adaptability, the traditional structure of the mica capacitor has gradually exposed some limitations in performance. When the frequency enters the very high frequency or even the microwave frequency band, the skin effect in the conductor causes the current to concentrate on the surface layer of the conductor, which reduces the effective conductive area of the electrode and significantly increases the equivalent series resistance, thereby causing the quality factor of the entire capacitor to decrease and the heat generation to increase. At the same time, the difference in the coefficient of thermal expansion between the electrode metal material and the mica dielectric will accumulate thermal mechanical stress at the interface between the two under severe temperature cycling or high-temperature working conditions. Long-term effects may cause interface micro-cracks, increased contact resistance, or even failure, which is manifested as a drift in capacitance and a decrease in long-term reliability. In addition, the electronic scattering characteristics of the traditional silver electrode material also limit the further improvement of its high-frequency conductive performance. These factors jointly restrict the application expansion of the mica capacitor in the more advanced performance fields.

[0004] To address the above challenges, the industry and academia have explored from multiple angles. Common improvement ideas include doping or surface modification of mica medium materials themselves to optimize their dielectric constant and loss, or trying to use different metals or alloys as electrodes to improve electrical conductivity and adhesion strength. However, these methods can only improve certain aspects of performance to a limited extent, and it is difficult to systematically solve the intertwined problems of high-frequency loss, interface stability and thermal matching. In particular, at the electrode-medium interface, which is the core area that determines the final performance of the capacitor, through the latest achievements of material science to actively design and control the microstructure, it is still a potential but not fully developed field. Therefore, there is an urgent need for an innovative technical solution that can fundamentally optimize the comprehensive performance of the electrode system of the mica capacitor without changing the mature and reliable overall packaging process, especially the high-frequency characteristics and environmental stability, to meet the stringent requirements of the next generation of high-end electronic devices for key basic components. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a MCM-1A type high-frequency metal packaging mica capacitor.

[0006] In a first aspect of the present application, a MCM-1A type high-frequency metal packaging mica capacitor is provided, which is formed by pressing the metal packaging shell containing the core group by a forming machine. The metal packaging shell is a silver-plated metal packaging shell, and the metal packaging shell contains, from bottom to top, a silver-plated metal "T" gasket, one or more parallel core groups, and a silver-plated metal "T" gasket. The core group includes a plurality of silver mica sheets and silver-plated metal lead-out sheets arranged between the silver mica sheets, and one end of the metal lead-out sheet extends out of the metal packaging shell. The silver-plated metal "T" gasket contains a dielectric-topological insulator heterojunction composite nanomaterial.

[0007] In the present application, the dielectric-topological insulator heterojunction composite nanomaterial is applied to the preparation of MCM-1A type high-frequency metal packaging mica capacitor, and the overall mechanism is embodied in the "interface empowerment" and "performance upgrade" of the traditional device through material innovation without changing its mature and reliable macroscopic packaging process. The core mechanism starts from the doping and application of the material in the silver-plated metal component. When the material is doped or combined with the plating layer of the "T" type gasket, under the action of the electric field in the capacitor, the surface state of the topological insulator core can provide an additional and efficient path for charge transport, which is particularly significant at high frequencies, which helps to resist the skin effect and reduce the equivalent series resistance of the entire electrode system. At the same time, the barium strontium titanate dielectric shell wrapped outside plays multiple roles: first, its high dielectric constant characteristics can optimize the electric field distribution of the electrode edge, alleviate the local field strength, and help to improve the reliability; second, the shell serves as a strong barrier to protect the internal topological insulator material from the environment, ensuring long-term stability of performance; third, the ceramic shell is between the metal electrode and the mica medium in terms of thermal expansion coefficient, which can act as a stress buffer when the temperature changes, reducing the interface micro-cracks caused by thermal mismatch, thereby significantly enhancing the temperature cycle life of the device. From the perspective of device integration, the preparation mechanism of the entire capacitor follows the principle of "complex material and simple process". The complex heterojunction material is prepared in the form of standard additives in the early stage, and in the subsequent assembly process of the capacitor, whether it is the lamination of the core group, the assembly of the packaging shell, or the final press forming, it completely follows the mature process flow of the traditional metal packaging mica capacitor which has been verified by the industry. This design enables the advantages of cutting-edge nanomaterials to be seamlessly integrated into classic device architectures, ultimately achieving a comprehensive performance improvement in capacitor loss at high frequencies, temperature stability, and long-term reliability, while ensuring the feasibility and economy of production.

[0008] According to the preferred embodiment of the present application, when a plurality of core groups are connected in parallel, silver foils are also arranged between the core groups.

[0009] According to the preferred embodiment of the present application, the metal packaging shell is a silver-plated copper shell, and the silver mica sheet is a white mica sheet with printed electrodes.

[0010] According to the preferred embodiment of the present application, the silver-plated metal "T" type gasket is a silver-plated copper sheet, which is tightly attached to the inner wall of the metal packaging shell.

[0011] According to the preferred embodiment of the present application, the metal lead sheet is a silver-plated thin copper sheet, and the shape of the silver-plated thin copper sheet is a "Z" shape.

[0012] According to the preferred embodiment of the present application, the preparation method of the dielectric-topological insulator heterojunction composite nanomaterial comprises: A1. A solution of bismuth nitrate pentahydrate dissolved in ethylenediamine was mixed with selenium powder pre-reduced by hydrazine hydrate to obtain a precursor solution. The precursor solution was transferred to a high-pressure reactor and reacted at 175-185℃. After natural cooling, the precipitate was collected, washed with anhydrous ethanol and deionized water, and finally dried in a vacuum drying oven at 55-65℃ to obtain bismuth triselide nanosheets. A2. Bismuth triselenide nanosheets were placed in an atomic layer deposition (ALD) chamber. The reaction temperature was set to 245-255℃. Argon was used as the carrier gas, and a barium strontium titanate shell was deposited using a supercycle process. Each supercycle consisted of a strontium deposition subcycle, a barium deposition subcycle, and a titanium deposition subcycle. The strontium deposition subcycle consisted of sequentially pulsed introduction of bis(triisopropylcyclopentadienyl)strontium and deionized water, followed by argon purging after each pulse. The barium deposition subcycle consisted of sequentially pulsed introduction of bis(pentamethylcyclopentadienyl)barium and deionized water, followed by argon purging after each pulse. The titanium deposition subcycle consisted of sequentially pulsed introduction of tetraisopropyl titanate and deionized water, followed by argon purging after each pulse. The supercycle was repeated to obtain core-shell nanoparticles. A3. Disperse core-shell nanoparticles in N,N-dimethylformamide, sonicate, then add polyvinylpyrrolidone, stir and reflux at 78-82℃ to obtain a mixture; A4. Pour the mixture into diethyl ether to precipitate, and obtain a solid product by centrifugation. Wash the solid product with diethyl ether, and redisperse the washed solid product in terpineol.

[0013] In this invention, the preparation of dielectric-topological insulator heterojunction composite nanomaterials integrates a series of precise chemical reactions and interface engineering processes. Its core mechanism lies in the step-by-step construction and synergistic utilization of the unique physical properties of different material systems. First, a topological insulator nanosheet substrate is synthesized via a solvothermal method. In this process, selenium powder pretreated with a strong reducing agent provides a highly active selenium source, which reacts with bismuth ions in an ethylenediamine solvent under high temperature and pressure. Essentially, selenium ions combine with bismuth ions and preferentially grow along specific crystal planes, ultimately forming layered bismuth selenide nanosheets. The material is an insulator internally, but its surface is protected by topological properties, exhibiting highly mobile metallic electronic states. Subsequently, an atomic layer deposition supercycle process is used to construct a dielectric shell on its surface. The mechanism of this process involves cyclical, self-limiting surface chemical reactions: different metal-organic precursors (strontium, barium, and titanium sources) are sequentially chemically adsorbed on the nanosheet surface and react with water. By precisely controlling the repetition ratio of each sub-cycle, the ordered deposition and interweaving of barium, strontium, and titanium oxide units are achieved at the atomic scale, thereby growing a stoichiometric barium strontium titanate film in situ. An atomically smooth, tightly bonded heterogeneous interface is formed between this dielectric shell and the topological insulator core. Finally, functionalization is achieved through surface polymer coating. Polymer molecules are anchored to the core-shell particle surface through physical adsorption or weak chemical action. The mechanism involves reducing the surface energy of the nanoparticles and preventing their aggregation in organic solvents through steric hindrance, thus obtaining a stable dispersion suitable for subsequent electrode slurry preparation. The resulting composite material, with its core-shell structure, microscopically integrates the excellent conductive channels of the topological insulator surface with the polarization characteristics of a high-dielectric-constant material, laying the material foundation for achieving novel electrical properties in macroscopic electronic devices.

[0014] According to a preferred embodiment of the present invention, in step A1, the ratio of bismuth nitrate pentahydrate, selenium powder pre-reduced by hydrazine hydrate, ethylenediamine and hydrazine hydrate is (3.5-4.5) g: 1.0 g: (18.0-22.0) mL: (9.0-11.0) mL.

[0015] According to a preferred embodiment of the present invention, in step A2, the supercycle is repeated 500-600 times; the ratio of the number of repetitions of the barium deposition subcycle to the number of repetitions of the strontium deposition subcycle is (0.6-0.8):(0.2-0.4), and the ratio of the number of repetitions of the titanium deposition subcycle to the sum of the number of repetitions of the strontium deposition subcycle and the number of repetitions of the barium deposition subcycle is (0.9-1.1):1.

[0016] According to a preferred embodiment of the present invention, in step A3, the mass ratio of core-shell nanoparticles to polyvinylpyrrolidone is 1:(0.5-2).

[0017] According to a preferred embodiment of the present invention, in step A4, the washing with ether is performed 3-5 times.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention modifies the traditional structure by introducing a carefully designed composite nanomaterial, achieving significant technical advantages over existing products in several aspects. First, the most prominent improvement is reflected in the high-frequency performance of the capacitor. The dielectric topological insulator heterojunction nanomaterial incorporated into key components has unique surface conductivity in its core topological insulator component, providing carrier channels with extremely high mobility. This characteristic is crucial under high-frequency conditions, effectively overcoming the problem of uneven current distribution caused by the skin effect in traditional metal conductors, and significantly reducing the equivalent series resistance of the electrodes under high-frequency AC signals. At the same time, the dense dielectric shell encasing the electrodes has a high dielectric constant, which helps to optimize the electric field distribution at the electrode edges and reduce the additional losses caused by edge effects. The synergistic effect of these two factors results in a capacitor with lower loss tangent and higher quality factor in the very high frequency to microwave frequency bands, significantly improving power transmission efficiency and signal fidelity.

[0019] (2) The technical solution of this invention greatly enhances the long-term stability and operational reliability of capacitors under harsh environments. In traditional structures, the interfacial stress generated by the difference in thermal expansion coefficients between the metal electrode and the mica dielectric during temperature changes is the main cause of performance drift and even failure. The core-shell structured nanomaterial used in this invention has a dielectric shell with a thermal expansion coefficient between that of the electrode metal and the mica dielectric, playing an excellent role as a mechanical buffer layer. It can effectively absorb and dissipate the thermal stress generated by temperature cycling, thereby protecting the integrity of the interface between the electrode and the dielectric. In addition, the shell constructed by atomic layer deposition technology is extremely uniform and dense, providing excellent physical protection for the internal core material and preventing it from oxidizing or degrading during subsequent processing or use. Therefore, the capacitor prepared using this invention exhibits a very small capacitance change rate after undergoing a wide range of temperature cycling shocks, demonstrating excellent temperature stability, while also having a longer service life and higher environmental tolerance.

[0020] (3) While achieving the aforementioned superior performance improvement, this invention cleverly maintains the simplicity and efficiency of the product manufacturing process, possessing excellent potential for industrialization. The core innovation of the entire technical solution lies in the upstream modified material preparation stage, which is designed as a stable and dispersible slurry additive. In the specific capacitor production process, this additive can be integrated into the existing mature electrode slurry formula or used as a plating modifier to exert its effect without requiring any complex modifications to the existing large-scale production processes such as silvering, stacking, and encapsulation. This design concept of "complex and precise modified materials, simple and universal capacitor manufacturing" enables the production of high-performance products to seamlessly connect with existing production lines and technologies without the need for expensive equipment modification costs, greatly reducing the threshold and risk of technology upgrades, and facilitating the rapid realization of stable production and large-scale application of high-performance MCM series mica capacitors. Detailed Implementation

[0021] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0022] Example 1 This embodiment provides a method for fabricating an MCM-1A type high-frequency metal-encapsulated mica capacitor: Preparation of dielectric-topological insulator heterojunction composite nanomaterials: A1. Preparation of bismuth triselenide nanosheets. 4.0 g of bismuth nitrate pentahydrate and 1.0 g of selenium powder were accurately weighed. The bismuth nitrate pentahydrate was added to 20 mL of ethylenediamine and magnetically stirred in a 50 °C water bath for 30 minutes until completely dissolved, yielding a clear solution A. The selenium powder was added to 10 mL of hydrazine hydrate and ultrasonically dispersed at room temperature for 15 minutes, yielding suspension B. While continuously stirring, suspension B was slowly added dropwise to solution A, maintaining the solution temperature below 35 °C during the mixing process. After the addition was complete, stirring was continued for 1 hour to obtain a uniform black precursor solution. This precursor solution was transferred entirely to a 50 mL polytetrafluoroethylene-lined high-pressure reactor, ensuring a filling degree of approximately 60%. The reactor was sealed and placed in a forced-air drying oven, where the temperature was increased to 180 °C at a rate of 3 °C / min and maintained at this temperature for 48 hours for a solvothermal reaction. After the reaction, the reactor was allowed to cool naturally to room temperature in an oven. Open the reaction vessel and transfer all the material inside to a 100mL centrifuge tube. Centrifuge at 8000rpm for 5 minutes, discard the supernatant, and collect the precipitate. Add 50mL of anhydrous ethanol to the precipitate and vortex vigorously for 1 minute to redisperse the precipitate. Centrifuge again at 8000rpm for 5 minutes. Repeat this washing process three times. Then, wash the precipitate three times with 50mL of deionized water in the same manner. Transfer the final wet precipitate to a watch glass and dry it in a vacuum drying oven at 60℃ for 12 hours to obtain a dry black powder, which is bismuth triselenide nanosheets. Remove it and store it in a desiccator for later use.

[0023] A2. A barium strontium titanate shell was prepared via atomic layer deposition (ALD). 0.5 g of the prepared bismuth triselenide nanosheets were removed from the desiccator and evenly spread on a 100 mm diameter silicon wafer carrier. Both nanosheets were then placed into the sample tray of the ALD reaction chamber. After sealing the reaction chamber, the vacuum system was activated, and the base pressure inside the chamber was evacuated to 1.0 × 10⁻⁶. -2Below Pa. High-purity argon was introduced as both carrier gas and purge gas, with a flow rate set to 200 sccm. The sample stage temperature was set to 250℃ and stabilized for 30 minutes. The deposition process employed a supercycle technique, with each supercycle consisting of three subcycles in sequence. The specific parameters were as follows: First, the strontium deposition subcycle involved pulsed introduction of bis(triisopropylcyclopentadienyl)strontium precursor into the chamber for 0.5 seconds, followed by purging with argon for 15 seconds; then pulsed introduction of deionized water for 0.1 seconds, followed by purging with argon for 15 seconds. Next, the barium deposition subcycle involved pulsed introduction of bis(pentamethylcyclopentadienyl)barium precursor for 0.6 seconds, followed by purging for 15 seconds; then pulsed introduction of deionized water for 0.1 seconds, followed by purging for 15 seconds. Finally, the titanium deposition subcycle involved pulsed introduction of tetraisopropyl titanate precursor for 0.4 seconds, followed by purging for 15 seconds; then pulsed introduction of deionized water for 0.1 seconds, followed by purging for 15 seconds. In each supercycle, the barium deposition subcycle is executed 7 times, the strontium deposition subcycle is executed 3 times, and the titanium deposition subcycle is executed 10 times to ensure a stoichiometric ratio of approximately Ba is achieved. 0.7 Sr 0.3 TiO3 shell. This supercycle was repeated 550 times. After deposition, the sample was cooled to below 80°C under an argon atmosphere and then removed, yielding core-shell nanoparticles with a uniformly coated barium strontium titanate shell.

[0024] A3. Surface Functionalization and Dispersion of Core-Shell Nanoparticles. Weigh 0.5 g of the above core-shell nanoparticles and add them to a 250 mL three-necked round-bottom flask containing 50 mL of N,N-dimethylformamide. Place the flask in an ultrasonic cleaner and sonicate at 40 kHz for 2 hours to obtain a preliminarily dispersed suspension. Add 0.5 g of polyvinylpyrrolidone to the suspension, install a reflux condenser, and heat the oil bath to 80 °C with magnetic stirring. Stir and reflux at this temperature for 12 hours. After the reaction is complete, stop heating and cool the mixture to room temperature.

[0025] A4. The cooled mixture was added dropwise to 200 mL of rapidly stirred diethyl ether, immediately producing a large amount of precipitate. After standing for 5 minutes, all liquid and precipitate were transferred to a centrifuge tube and centrifuged at 7500 rpm for 8 minutes, discarding the supernatant. 50 mL of fresh diethyl ether was added to the precipitate, vortexed, and centrifuged again. This washing process was repeated 3 times. The final solid product was placed in a fume hood and allowed to stand for 30 minutes to allow residual diethyl ether to evaporate. Then, 10 g of terpineol was added, and the mixture was dispersed at 10000 rpm for 15 minutes using a high-speed shear emulsifier to obtain a uniform and stable dispersion slurry, which is the dielectric-topological insulator heterojunction composite nanomaterial, labeled as slurry M1.

[0026] Fabrication of MCM-1A type high-frequency metal-encapsulated mica capacitor: S1, Preparation of modified silver paste. Accurately weigh 100.0 g of ultrafine silver powder with an average particle size of 1.0 μm, 6.0 g of terpineol, 2.5 g of ethyl cellulose, and 1.5 g of the previously prepared paste M1. Add all raw materials together to a 500 mL zirconia ball mill jar, and add 300 g of zirconia grinding balls with a diameter of 5 mm. Fix the ball mill jar on a planetary ball mill, set the revolution speed to 300 rpm and the rotation speed to 600 rpm, and continuously ball mill for 8 hours. After ball milling, filter out the grinding balls through a 200-mesh nylon sieve to obtain a modified silver paste with uniform texture and suitable viscosity.

[0027] S2, Printing Electrodes and Assembling the Core Assembly. High-quality mica sheets with a thickness of 0.03 mm and a dielectric strength greater than 150 V / μm were selected and cut into 10 mm × 10 mm squares. Using a 200-mesh stainless steel wire mesh and a 100 μm thick latex squeegee, modified silver paste was printed onto designated circular areas on both sides of the mica sheets, with an electrode diameter of 8 mm. The printed mica sheets were placed on a conveyor belt in a drying oven and dried at 125°C for 20 minutes to completely remove organic solvents. Twenty dried silver-plated mica sheets and 19 pre-stamped zigzag-shaped, 0.05 mm thick silver-plated copper lead sheets were taken and alternately stacked in the order of "mica sheet - lead sheet - mica sheet," ensuring good contact between both sides of each lead sheet and the silver electrode of the adjacent mica sheet. The stacked components are placed in a special fixture and held under a pressure of 5 MPa for 30 seconds. After being pressed, they are removed to form a complete core assembly.

[0028] S3, Parallel Connection and Packaging Preparation. Take two identical core assemblies described above, and place a 0.05mm thick, size-matched pure silver foil between the two core assemblies. Place this parallel structure as a whole into a copper housing with silver-plated inner walls. A stamped, silver-plated copper "T"-shaped gasket has been pre-placed at the bottom of the housing. Place the parallel core assemblies on the gasket, ensuring that the ends of all the zigzag leads of both core assemblies protrude parallel to each other from the same row of pre-drilled holes on the side of the housing. Finally, cover the top of the core assemblies with another identical silver-plated copper "T"-shaped gasket.

[0029] S4, Sealing and Molding. The assembled housing assembly is transferred to the worktable of a precision pneumatic encapsulation machine using a specially designed round-mouth mold. The machine is started, and initial edge curling is performed, rolling the edges of the housing opening inwards to pre-secure the internal components. Then, a pressure of 25 MPa is applied for final pressure sealing, with a holding time of 3 seconds. After encapsulation, the leads extending from the housing are shaped to conform to standard pin profiles. The final capacitor product is marked C1.

[0030] Example 2 The difference between this embodiment and Embodiment 1 is that, Preparation of dielectric-topological insulator heterojunction composite nanomaterials: A1. Preparation of bismuth triselenide nanosheets. Accurately weigh 3.8 g of bismuth nitrate pentahydrate and 1.0 g of selenium powder. Add bismuth nitrate pentahydrate to 18 mL of ethylenediamine and magnetically stir in a 48 °C water bath for 35 minutes until completely dissolved, obtaining solution A. Add selenium powder to 9 mL of hydrazine hydrate and ultrasonically disperse at room temperature for 18 minutes to obtain suspension B. Add solution B dropwise to solution A with stirring, controlling the temperature below 35 °C. After the addition is complete, stir for 1.5 hours to obtain the precursor solution. Transfer the solution to a 50 mL reaction vessel liner, with a filling degree of approximately 54%. Seal the reaction vessel and place it in a forced-air drying oven, heating to 178 °C at 2.5 °C / min and maintaining the temperature for 50 hours. After natural cooling, collect the precipitate by centrifugation. Wash three times with 50 mL of anhydrous ethanol, and then three times with 50 mL of deionized water. Place the wet precipitate in a 58 °C vacuum drying oven and dry for 14 hours to obtain bismuth triselenide nanosheet powder.

[0031] A2, atomic layer deposition of barium strontium titanate shell. Weigh 0.5 g of bismuth triselenide nanosheets and evenly spread them on a silicon wafer, then place them in the reaction chamber. Evacuate to a base pressure below 1.0 × 10⁻⁶. -2 Pa. The argon flow rate was set to 200 sccm, and the stage temperature was raised to 248℃ and stabilized for 30 minutes. The parameters for each supercycle were as follows: Strontium cycle: pulsed bis(triisopropylcyclopentadienyl)strontium 0.5 s, purge 15 s; pulsed water 0.1 s, purge 15 s. Barium cycle: pulsed bis(pentamethylcyclopentadienyl)barium 0.6 s, purge 15 s; pulsed water 0.1 s, purge 15 s. Titanium cycle: pulsed tetraisopropyl titanate 0.4 s, purge 15 s; pulsed water 0.1 s, purge 15 s. Each supercycle consisted of 6 barium cycles, 3 strontium cycles, and 9 titanium cycles. This supercycle was repeated 500 times. After deposition, the particles were cooled to below 80℃ under argon atmosphere and removed to obtain core-shell nanoparticles.

[0032] A3, Surface Functionalized Dispersion. Weigh 0.5 g of core-shell nanoparticles and add them to a 250 mL three-necked flask containing 50 mL of N,N-dimethylformamide. Sonicate for 2.5 hours. Add 0.8 g of polyvinylpyrrolidone, install a condenser, and heat the oil bath to 78 °C with magnetic stirring. Reflux for 14 hours.

[0033] A4, after cooling, the mixture was added dropwise to 200 mL of rapidly stirred diethyl ether to precipitate. The precipitate was collected by centrifugation at 7500 rpm for 8 minutes and washed three times with 50 mL of diethyl ether. After evaporating the residual diethyl ether, 10 g of terpineol was added, and the mixture was dispersed at 10000 rpm for 15 minutes using a high-speed shear emulsifier to obtain slurry M2.

[0034] Fabrication of MCM-1A type high-frequency metal-encapsulated mica capacitor: S1, Preparation of modified silver paste. Weigh 100.0g of ultrafine silver powder, 5.8g of terpineol, 2.2g of ethyl cellulose and 1.2g of paste M2, add them to a 500mL ball mill jar, and add 300g of zirconia grinding balls. Ball mill on a planetary ball mill at 300rpm revolution and 600rpm rotation for 7.5 hours, and obtain the modified silver paste after passing through a 200-mesh sieve.

[0035] S2, Printing Electrodes and Assembling Cores. Modified silver paste is printed on both sides of a 10mm × 10mm mica sheet (electrode diameter 8mm), and dried in an oven at 122℃ for 22 minutes. Fifteen silver-plated mica sheets and fourteen zigzag silver-plated thin copper lead sheets are alternately stacked and pressed under 5MPa for 30 seconds using a clamp to form a core assembly.

[0036] S3, Packaging Preparation. Place the individual chip assembly into the silver-plated copper housing, with a silver-plated copper "T" shaped gasket already placed at the bottom. Make the lead-out end protrude from the side hole of the housing, and cover the top with another "T" shaped gasket.

[0037] S4, Sealing and Molding. The edges are rolled and pressure-sealed using a mold on a precision pneumatic packaging machine at a pressure of 24 MPa for 3 seconds. After packaging, the leads are shaped to obtain the finished capacitor C2.

[0038] Example 3 The difference between this embodiment and Embodiment 1 lies in the preparation of the dielectric-topological insulator heterojunction composite nanomaterial: A1. Preparation of bismuth triselenoside nanosheets. 4.2 g of bismuth nitrate pentahydrate and 1.0 g of selenium powder were accurately weighed. Bismuth nitrate pentahydrate was added to 22 mL of ethylenediamine and dissolved by magnetic stirring in a 52 °C water bath for 25 minutes to obtain solution A. Selenium powder was added to 11 mL of hydrazine hydrate and ultrasonically dispersed for 12 minutes to obtain suspension B. Solution B was added dropwise to solution A with stirring, maintaining the temperature below 35 °C. After the addition was complete, the mixture was stirred for 50 minutes to obtain the precursor solution. The solution was transferred to a 50 mL reactor liner, with a filling degree of approximately 66%. The reactor was sealed and placed in a forced-air drying oven, where the temperature was increased to 182 °C at a rate of 3.5 °C / min and maintained for 45 hours. After natural cooling, the precipitate was collected by centrifugation. The precipitate was washed three times with 50 mL of anhydrous ethanol and then three times with 50 mL of deionized water. The wet precipitate was dried in a 62 °C vacuum drying oven for 10 hours to obtain bismuth triselenoside nanosheet powder.

[0039] A2, atomic layer deposition of barium strontium titanate shell. Weigh 0.5 g of bismuth triselenide nanosheets and evenly spread them on a silicon wafer, then place them in the reaction chamber. Evacuate to a base pressure below 1.0 × 10⁻⁶. -2Pa. The argon flow rate was set to 200 sccm, and the stage temperature was raised to 252℃ and stabilized for 30 minutes. The parameters for each supercycle were as follows: Strontium cycle: pulsed bis(triisopropylcyclopentadienyl)strontium 0.5 s, purge 15 s; pulsed water 0.1 s, purge 15 s. Barium cycle: pulsed bis(pentamethylcyclopentadienyl)barium 0.6 s, purge 15 s; pulsed water 0.1 s, purge 15 s. Titanium cycle: pulsed tetraisopropyl titanate 0.4 s, purge 15 s; pulsed water 0.1 s, purge 15 s. Each supercycle consisted of 7 barium cycles, 2 strontium cycles, and 8 titanium cycles. This supercycle was repeated 600 times. After deposition, the samples were cooled to below 80℃ under argon atmosphere and removed to obtain core-shell nanoparticles.

[0040] A3, Surface Functionalized Dispersion. Weigh 0.5 g of core-shell nanoparticles and add them to a 250 mL three-necked flask containing 50 mL of N,N-dimethylformamide. Sonicate for 1.5 hours. Add 0.3 g of polyvinylpyrrolidone, install a condenser, and heat the oil bath to 82 °C with magnetic stirring. Reflux for 10 hours.

[0041] A4, after cooling, the mixture was added dropwise to 200 mL of rapidly stirred diethyl ether to precipitate. The precipitate was collected by centrifugation at 7500 rpm for 8 minutes and washed three times with 50 mL of diethyl ether. After evaporating the residual diethyl ether, 10 g of terpineol was added, and the mixture was dispersed at 10000 rpm for 15 minutes using a high-speed shear emulsifier to obtain slurry M3.

[0042] Fabrication of MCM-1A type high-frequency metal-encapsulated mica capacitor: S1, Preparation of modified silver paste. Weigh 100.0g of ultrafine silver powder, 6.2g of terpineol, 2.8g of ethyl cellulose, and 1.8g of paste M3, add them to a 500mL ball mill jar, and add 300g of zirconia grinding balls. Mill the paste in a planetary ball mill at 300rpm revolution and 600rpm rotation for 8.5 hours, and pass it through a 200-mesh sieve to obtain the modified silver paste.

[0043] S2, Printing Electrodes and Assembling Cores. Modified silver paste was printed onto both sides of 10mm × 10mm mica sheets (electrode diameter 8mm), and dried in a 128℃ oven for 18 minutes. 25 silver-coated mica sheets and 24 zigzag silver-plated thin copper lead sheets were alternately stacked and pressed under 5MPa for 30 seconds using a clamp to form a core assembly. Three identical core assemblies were prepared in total.

[0044] S3, Parallel Connection and Packaging Preparation. Arrange the three core groups in parallel, with a 0.05mm thick pure silver foil between every two core groups. Place this parallel assembly into a silver-plated copper casing, with a silver-plated copper "T" shaped gasket already placed at the bottom. Ensure that all lead-out ends protrude from the side holes of the casing, and cover the top with another "T" shaped gasket.

[0045] S4, Sealing and Molding. The edges are rolled and pressure-sealed using a mold on a precision pneumatic packaging machine at a pressure of 26 MPa for 3 seconds. After packaging, the leads are shaped to obtain the finished capacitor C3.

[0046] Comparative Example 1 The difference between this comparative example and Example 1 is that barium strontium titanate nanoparticles (purchased from Shandong Sitaili Metal Materials Co., Ltd.) were directly used as the starting material. These were added to a 250 mL three-necked flask containing 50 mL of N,N-dimethylformamide and sonicated for 2 hours. 0.5 g of polyvinylpyrrolidone was added, a condenser was installed, and the mixture was stirred and refluxed in an 80°C oil bath for 12 hours. After cooling, the mixture was added dropwise to 200 mL of rapidly stirred diethyl ether to precipitate. The precipitate was collected by centrifugation at 7500 rpm for 8 minutes and washed three times with 50 mL of diethyl ether. After evaporating the residual diethyl ether, 10 g of terpineol was added, and the mixture was dispersed at 10000 rpm for 15 minutes using a high-speed shear emulsifier to obtain the comparative slurry D1.

[0047] When preparing the capacitor, except that paste D1 is used instead of paste M1 in Example 1, the silver paste formula, core structure, parallel connection method and all packaging process parameters are exactly the same as in Example 1, and the comparative capacitor CD1 is obtained.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is that the first step of Example 1 is exactly the same. 4.0 g of bismuth nitrate pentahydrate and 1.0 g of selenium powder were weighed, reacted, washed, and dried to prepare pure bismuth triselide nanosheets. 0.5 g of these nanosheets were weighed and, without atomic layer deposition, directly underwent surface treatment: they were added to a 250 mL three-necked flask containing 50 mL of N,N-dimethylformamide and sonicated for 2 hours. 0.5 g of polyvinylpyrrolidone was added, a condenser was installed, and the mixture was stirred and refluxed in an 80°C oil bath for 12 hours. After cooling, the mixture was dropwise added to 200 mL of rapidly stirred diethyl ether to precipitate. The precipitate was collected by centrifugation at 7500 rpm for 8 minutes and washed three times with 50 mL of diethyl ether. After evaporating the residual diethyl ether, 10 g of terpineol was added, and the mixture was dispersed at 10000 rpm for 15 minutes using a high-speed shear emulsifier to obtain comparative slurry D2.

[0049] When preparing the capacitor, except that paste D2 is used instead of paste M1 in Example 1, the silver paste formula, core structure, parallel connection method and all packaging process parameters are exactly the same as in Example 1, resulting in the comparative capacitor CD2.

[0050] Comparative Example 3 The difference between this comparative example and Example 1 is that a conventional silver paste was prepared, with the following formula: 100.0g ultrafine silver powder, 6.5g terpineol, and 3.0g ethyl cellulose. All raw materials were added to a 500mL ball mill jar, along with 300g of zirconia grinding balls. The mixture was ball-milled for 8 hours in a planetary ball mill at 300rpm revolution and 600rpm rotation, and then passed through a 200-mesh sieve to obtain the conventional silver paste.

[0051] When fabricating the capacitor, the conventional silver paste was used to print the electrodes and assemble the core assembly (the same structure as in Example 1, with 20 mica sheets and 19 lead sheets, and two core assemblies connected in parallel). All subsequent packaging process parameters were exactly the same as in Example 1, resulting in the conventional comparison capacitor CD3.

[0052] The performance of the MCM-1A high-frequency metal-encapsulated mica capacitors provided in the above embodiments and comparative examples was tested using the following methods: All core electrical performance tests of the capacitors were conducted under strictly controlled conditions, primarily evaluating their high-frequency loss characteristics and temperature stability. High-frequency loss characteristic testing was performed using a precision impedance analyzer equipped with a four-terminal test fixture. Before formal testing, the impedance analyzer was preheated for at least 30 minutes, followed by open-circuit, short-circuit, and 50Ω load calibration procedures to eliminate systematic errors. The capacitor sample under test was soldered to the center of a dedicated high-frequency test fixture, ensuring that its two leads were straight and symmetrical in length, each not exceeding 2mm, to minimize measurement deviations caused by lead inductance. The test fixture was connected to the impedance analyzer's test port via a phase-stable coaxial cable with a characteristic impedance of 50Ω and a length not exceeding 1m. In the instrument's operating software, the test frequency was set to 100MHz, the test signal level to 100mVRMS, and a parallel equivalent circuit model was selected for measurement. The entire high-frequency testing process was conducted in a constant temperature and humidity laboratory at 23±1℃ and 50±5% relative humidity. After each capacitor sample is fixed in the test fixture, it is left to stand for 2 minutes to reach thermal equilibrium. Then, 5 measurements are taken consecutively, and the average value of the loss tangent among these 5 readings is taken as the final result of the sample.

[0053] Temperature stability testing was performed using a high and low temperature humidity test chamber coupled with a high-precision automatic balancing bridge system. First, the bridge's test leads were connected to dedicated vacuum-sealed terminals on the outer wall of the test chamber. Inside the chamber, high-temperature resistant PTFE insulated wires were used to connect the terminals to the capacitor under test, which was fixed to a ceramic sample holder. The bridge's test program was set to a measurement frequency of 1 kHz, a test voltage of 1 V, and a series equivalent capacitance measurement mode. At the start of the test, the chamber temperature was stabilized at 25°C and maintained for 30 minutes; the capacitance value measured under these conditions was used as the baseline value C0. Then, a preset temperature cycle was executed: the chamber temperature was lowered to -55°C at a rate of 5°C / min, and then held at this temperature for 30 minutes. The capacitance value C was immediately measured and recorded. low Next, the temperature was increased to +125℃ at a rate of 5℃ / min, and held at this temperature for 30 minutes. The capacitance value C was then measured and recorded. high Calculate the rate of change of capacitance at low and high temperatures respectively: ((C low -C0) / C0)×100% and ((C high -C0) / C0)×100%. Take the larger absolute value of these two percentage values ​​as the final capacitance change rate of the capacitor sample. Each sample undergoes the entire above test procedure independently and completely to ensure the accuracy and comparability of the data.

[0054] The performance test data above are shown in Table 1.

[0055] Table 1 Performance Test Results

[0056] As can be seen from the above, Examples 1-3, compared with Comparative Examples 1-3, systematically solve the two major core technical problems faced by traditional metal-encapsulated mica capacitors in high-frequency application scenarios.

[0057] First, regarding high-frequency loss, Comparative Example 3, as a conventional structure without any added modification materials, exhibits the highest loss tangent (0.0020), quantitatively confirming that the skin effect of conventional silver electrodes at high frequencies, leading to a significant increase in equivalent series resistance, is an inherent defect. While Comparative Examples 1 (dielectric material only) and 2 (topological insulator only) show reduced loss values ​​(0.0015 and 0.0012, respectively), the effect is limited, demonstrating that single-component modification cannot fundamentally optimize the high-frequency conductivity mechanism. Examples 1 to 3, employing a complete core-shell heterojunction structure, provide a topologically protected high-mobility conductive channel on the surface. Working synergistically with the shell, this significantly reduces high-frequency loss to below 0.0009 (0.0008 in Example 1), decreasing it to approximately 40% of the level of conventional products, effectively suppressing the skin effect.

[0058] Secondly, regarding temperature stability, Comparative Example 3 exhibited the largest capacitance change rate (±3.0%), revealing the key issue of capacitance drift caused by interfacial stress due to thermal expansion mismatch. Comparative Example 2 (±2.5%) showed only slight performance improvement due to the lack of buffer protection from the dielectric shell; Comparative Example 1 (±1.8%), while providing some buffering effect, lacked the stable support of the internal conductive network. The core-shell structure of Examples 1-3 played a crucial synergistic role: the outer dielectric shell served as an effective thermal stress buffer layer, protecting the interface integrity; simultaneously, its dense structure ensured the stability of the internal topological insulator core within the temperature range of -55℃ to +125℃, thereby controlling the capacitance change rate within ±0.7% (±0.5% for Example 1).

[0059] Therefore, this invention, through the precise composite of dielectric materials and topological insulators at the nanoscale, simultaneously overcomes the challenges of high-frequency loss and temperature stability from a physical mechanism perspective, achieving a significant improvement in the overall performance of capacitors.

Claims

1. An MCM-1A type high-frequency metal-encapsulated mica capacitor, characterized in that, The metal encapsulation shell containing the core assembly is formed by pressing with a molding machine; The metal encapsulation shell is a silver-plated metal encapsulation shell. Inside the metal encapsulation shell, from bottom to top, are placed a silver-plated metal "T"-shaped gasket, one or more parallel core groups, and a silver-plated metal "T"-shaped gasket. The core group includes multiple silver-plated mica sheets and silver-plated metal lead-out sheets disposed between the silver-plated mica sheets. One end of the metal lead-out sheet extends out of the metal encapsulation shell. The silver-plated metal "T"-shaped gasket contains dielectric-topological insulator heterojunction composite nanomaterials.

2. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 1, characterized in that, When multiple cores are connected in parallel, silver foil is also placed between the cores.

3. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 1, characterized in that, The metal encapsulation shell is a copper shell with an inner silver-plated layer, and the silver-plated mica sheet has electrodes printed on it.

4. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 1, characterized in that, The silver-plated metal "T"-shaped gasket is a silver-plated copper sheet, which is tightly fitted to the inner wall of the metal packaging shell.

5. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 1, characterized in that, The metal lead-out sheet is a silver-plated thin copper sheet, and the shape of the silver-plated thin copper sheet is "Z".

6. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 1, characterized in that, The preparation method of the dielectric-topological insulator heterojunction composite nanomaterial includes: A1. A solution of bismuth nitrate pentahydrate dissolved in ethylenediamine was mixed with selenium powder pre-reduced by hydrazine hydrate to obtain a precursor solution. The precursor solution was transferred to a high-pressure reactor and reacted at 175-185℃. After natural cooling, the precipitate was collected, washed with anhydrous ethanol and deionized water, and finally dried in a vacuum drying oven at 55-65℃ to obtain bismuth triselide nanosheets. A2. Bismuth triselenide nanosheets were placed in an atomic layer deposition (ALD) chamber. The reaction temperature was set to 245-255℃. Argon was used as the carrier gas, and a barium strontium titanate shell was deposited using a supercycle process. Each supercycle consisted of a strontium deposition subcycle, a barium deposition subcycle, and a titanium deposition subcycle. The strontium deposition subcycle consisted of sequentially pulsed introduction of bis(triisopropylcyclopentadienyl)strontium and deionized water, followed by argon purging after each pulse. The barium deposition subcycle consisted of sequentially pulsed introduction of bis(pentamethylcyclopentadienyl)barium and deionized water, followed by argon purging after each pulse. The titanium deposition subcycle consisted of sequentially pulsed introduction of tetraisopropyl titanate and deionized water, followed by argon purging after each pulse. The supercycle was repeated to obtain core-shell nanoparticles. A3. Disperse core-shell nanoparticles in N,N-dimethylformamide, sonicate, then add polyvinylpyrrolidone, stir and reflux at 78-82℃ to obtain a mixture; A4. Pour the mixture into diethyl ether to precipitate, and obtain a solid product by centrifugation. Wash the solid product with diethyl ether, and redisperse the washed solid product in terpineol.

7. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 6, characterized in that, In step A1, the ratio of bismuth nitrate pentahydrate, selenium powder pre-reduced by hydrazine hydrate, ethylenediamine and hydrazine hydrate is (3.5-4.5) g: 1.0 g: (18.0-22.0) mL: (9.0-11.0) mL.

8. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 6, characterized in that, In step A2, the supercycle is repeated 500-600 times; the ratio of the number of repetitions of the barium deposition subcycle to the number of repetitions of the strontium deposition subcycle is (0.6-0.8):(0.2-0.4), and the ratio of the number of repetitions of the titanium deposition subcycle to the sum of the number of repetitions of the strontium deposition subcycle and the number of repetitions of the barium deposition subcycle is (0.9-1.1):

1.

9. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 6, characterized in that, In step A3, the mass ratio of core-shell nanoparticles to polyvinylpyrrolidone is 1:(0.5-2).

10. The MCM-1A type high-frequency metal-encapsulated mica capacitor according to claim 6, characterized in that, In step A4, the ether washing is performed 3-5 times.

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