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

Abstract

The application belongs to the field of electronic components, and particularly relates to a MCM-1A type high-frequency metal packaging mica capacitor. The capacitor is composed of a metal packaging shell, a core group in the shell is fixed by a silver-plated metal gasket, and the core group is composed of multiple pieces of white mica sheets printed with electrodes and silver-plated metal lead-out sheets alternately stacked. A dielectric topological insulator heterojunction composite nanomaterial is introduced into the silver-plated metal gasket. The material takes a bismuth diselenide nanosheet as a core, coats a barium strontium titanate shell through an atomic layer deposition process, and is modified through surface polymer coating. The composite nanomaterial effectively optimizes the interface characteristics and high-frequency conductivity of the electrode. The capacitor has a simple preparation process, is compatible with the existing production line, has lower loss and higher temperature stability at high frequency, and is suitable for high-frequency circuits.

Description

Technical Field

[0001] This invention belongs to the field of electronic components technology, specifically relating to an MCM-1A type high-frequency metal-encapsulated mica capacitor. Background Technology

[0002] Mica capacitors, as a classic type of inorganic dielectric capacitor, have long held an irreplaceable and crucial position in circuits for high-frequency oscillation, resonance, coupling, and bypassing due to their inherent advantages such as high dielectric strength, low loss tangent, stable temperature and frequency characteristics, and excellent reliability. Their typical structure typically uses natural or synthetic mica sheets as the dielectric, with a silver layer deposited on their surface to form electrodes. Multiple such silver-coated mica sheets are alternately stacked with metal leads, and then sealed in a metal casing using mechanical compression or welding to achieve a robust and durable fully sealed structure. This structure, especially the metal-encapsulated models, effectively resists the effects of external humidity, dust, and mechanical stress, ensuring long-lasting and stable electrical performance. Therefore, they are widely used in communication equipment, precision testing instruments, and various high-requirement 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 for power handling capabilities and adaptability to extreme environments, traditional mica capacitors are gradually revealing some limitations in performance. When the frequency enters the very high frequency (VHF) and even microwave bands, the skin effect in the conductor causes current to concentrate on the conductor surface, reducing the effective conductive area of ​​the electrodes and significantly increasing the equivalent series resistance. This leads to a decrease in the overall quality factor of the capacitor and increased heat generation. Simultaneously, the difference in thermal expansion coefficients between the electrode metal materials and the mica dielectric can accumulate thermomechanical stress at the interface under severe temperature cycling or high-temperature operating conditions. Long-term effects may lead to microcracks at the interface, increased contact resistance, and even failure, manifesting as capacitance drift and reduced long-term reliability. Furthermore, the electron scattering characteristics of traditional silver electrode materials themselves limit further improvements in their high-frequency conductivity. These factors collectively restrict the application expansion of mica capacitors in cutting-edge high-performance fields.

[0004] To address these challenges, industry and academia have explored various approaches. Common improvement strategies include doping or surface modification of the mica dielectric material itself to optimize its dielectric constant and losses, or experimenting with different metals or alloys as electrodes to improve conductivity and adhesion strength. However, these methods often only provide limited improvements in one aspect of performance and fail to systematically solve the intertwined problems of high-frequency losses, interface stability, and thermal matching. Especially in the core region of the electrode-dielectric interface, which determines the final performance of the capacitor, proactive microstructural design and control using the latest advancements in materials science remains a promising but underdeveloped area. Therefore, there is an urgent need for an innovative technological solution that can fundamentally optimize the overall performance of the electrode system, particularly high-frequency characteristics and environmental stability, without altering the mature and reliable overall packaging process of mica capacitors, thereby meeting the stringent requirements of next-generation high-end electronic devices for key basic components. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide an MCM-1A type high-frequency metal-encapsulated mica capacitor.

[0006] In a first aspect, the present invention provides an MCM-1A type high-frequency metal-encapsulated mica capacitor, which is formed by pressing a metal encapsulation shell containing a core assembly using a molding machine.

[0007] The metal encapsulation shell is a silver-plated metal encapsulation shell. Inside the metal encapsulation shell, from bottom to top, there are silver-plated metal "T"-shaped gaskets, one or more parallel core groups, and silver-plated metal "T"-shaped gaskets. 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.

[0008] The silver-plated metal "T"-shaped gasket contains dielectric-topological insulator heterojunction composite nanomaterials.

[0009] In this invention, dielectric-topological insulator heterojunction composite nanomaterials are applied to the fabrication of MCM-1A type high-frequency metal-encapsulated mica capacitors. The overall mechanism lies in "interface empowerment" and "performance upgrade" of traditional devices through material innovation, without altering their mature and reliable macroscopic packaging process. The core mechanism begins with the doping and application of this material in silver-plated metal components. When the material is incorporated into or combined with the plating of a "T"-shaped gasket, under the influence of the internal electric field of the capacitor, the surface states of the topological insulator core can provide an additional, efficient path for charge transport. This effect is particularly significant at high frequencies, helping to counteract the skin effect and reduce the equivalent series resistance of the entire electrode system. Meanwhile, the barium strontium titanate dielectric shell encapsulating the capacitor plays multiple roles: First, its high dielectric constant optimizes the electric field distribution at the electrode edges, mitigating local field strength and contributing to improved reliability; second, this shell acts as a robust barrier, protecting the internal topological insulator material from environmental influences and ensuring long-term performance stability; third, the ceramic shell's coefficient of thermal expansion falls between that of the metal electrode and the mica dielectric, acting as a stress buffer during temperature changes, reducing interfacial microcracks caused by thermal mismatch, and thus significantly enhancing the device's temperature cycle life. From a device integration perspective, the entire capacitor fabrication mechanism follows the principle of "complex materials, simple processes." The complex heterojunction material is prepared in the early stages as standardized additives, and in the subsequent capacitor assembly process, whether it's the stacking of the core assembly, the assembly of the encapsulation shell, or the final pressing molding, the mature process flow of traditional metal-encapsulated mica capacitors, which has been proven in the industry, is fully utilized. This design allows the advantages of cutting-edge nanomaterials to be seamlessly integrated into classic device architectures, ultimately achieving a comprehensive performance improvement in capacitors with lower losses at high frequencies, better temperature stability, and higher long-term reliability, while ensuring the feasibility and economy of production.

[0010] According to a preferred embodiment of the present invention, when multiple core groups are connected in parallel, silver foil is also provided between the core groups.

[0011] According to a preferred embodiment of the present invention, the metal encapsulation shell is a copper shell with an inner silver-plated layer, and the silver-plated mica sheet is a white mica sheet with electrodes printed on it.

[0012] According to a preferred embodiment of the present invention, the silver-plated metal "T"-shaped gasket is a silver-plated copper sheet, which is tightly fitted to the inner wall of the metal encapsulation shell.

[0013] According to a preferred embodiment of the present invention, the metal lead-out sheet is a silver-plated thin copper sheet, and the shape of the silver-plated thin copper sheet is zigzag.

[0014] According to a preferred embodiment of the present invention, the method for preparing the dielectric-topological insulator heterojunction composite nanomaterial includes:

[0015] 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.

[0016] 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.

[0017] A3. Disperse core-shell nanoparticles in N,N-dimethylformamide, sonicate, then add polyvinylpyrrolidone, stir and reflux at 78-82℃ to obtain a mixture;

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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).

[0023] According to a preferred embodiment of the present invention, in step A4, the washing with ether is performed 3-5 times.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (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.

[0026] (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.

[0027] (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

[0028] 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.

[0029] Example 1

[0030] 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:

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] Fabrication of MCM-1A type high-frequency metal-encapsulated mica capacitor:

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] Example 2

[0041] The difference between this embodiment and Embodiment 1 is that,

[0042] Preparation of dielectric-topological insulator heterojunction composite nanomaterials:

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] Fabrication of MCM-1A type high-frequency metal-encapsulated mica capacitor:

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] Example 3

[0053] The difference between this embodiment and Embodiment 1 lies in the preparation of the dielectric-topological insulator heterojunction composite nanomaterial:

[0054] 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.

[0055] 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 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.

[0056] 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.

[0057] 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.

[0058] Fabrication of MCM-1A type high-frequency metal-encapsulated mica capacitor:

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] Comparative Example 1

[0064] 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.

[0065] 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.

[0066] Comparative Example 2

[0067] 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.

[0068] 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.

[0069] Comparative Example 3

[0070] 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.

[0071] 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.

[0072] 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:

[0073] 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.

[0074] 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.

[0075] The performance test data above are shown in Table 1.

[0076] Table 1 Performance Test Results

[0077]

[0078] 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.

[0079] 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.

[0080] 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).

[0081] 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. A high frequency metal encapsulated mica capacitor of MCM-1A type, characterized in that, The metal packaging shell encapsulating the core group is pressed by a molding machine; The metal packaging shell is a silver-plated inner layer metal packaging shell, and the silver-plated metal "T" gaskets are sequentially placed in the metal packaging shell from bottom to top; the core group comprises 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. The preparation method of the dielectric-topological insulator heterojunction composite nanomaterial comprises: A1, a bismuth nitrate pentahydrate solution dissolved in ethylenediamine and selenium powder pre-reduced by hydrazine hydrate are mixed to obtain a precursor solution; the precursor solution is transferred to a high-pressure reaction kettle and reacted at 175-185℃; after natural cooling, the precipitate is collected, washed with anhydrous ethanol and deionized water, and finally dried in a vacuum drying oven at 55-65℃ to obtain bismuth selenide nanosheets; A2, the bismuth selenide nanosheets are placed in an atomic layer deposition reaction chamber, the reaction temperature is set to 245-255℃, argon is used as the carrier gas, and a super cycle process is used to deposit a barium strontium titanate shell; each super cycle is composed of a strontium deposition sub-cycle, a barium deposition sub-cycle and a titanium deposition sub-cycle; the strontium deposition sub-cycle is: double (triisopropylcyclopentadienyl) strontium and deionized water are introduced in sequence, and argon is introduced after each pulse; the barium deposition sub-cycle is: double (pentamethylcyclopentadiene) barium and deionized water are introduced in sequence, and argon is introduced after each pulse; the titanium deposition sub-cycle is: titanium acid tetraisopropyl ester and deionized water are introduced in sequence, and argon is introduced after each pulse; the super cycle is repeated to obtain core-shell nanoparticles; A3, the core-shell nanoparticles are dispersed in N,N-dimethylformamide, ultrasonic treatment is performed, then polyvinylpyrrolidone is added, and stirring reflux is performed at 78-82℃ to obtain a mixed solution; A4, the mixed solution is poured into ether to precipitate, and the solid product is obtained by centrifugal separation, and the solid product is washed with ether, and the washed solid product is dispersed in terpineol again.

2. The MCM-1A high frequency metal encapsulated mica capacitor of claim 1, wherein, When multiple core groups are connected in parallel, silver foil is arranged between the core groups.

3. The MCM-1A high frequency metal encapsulated mica capacitor of claim 1, wherein, The metal packaging shell is a silver-plated inner layer copper shell, and the silver mica sheet is an electrode printed on a white mica sheet.

4. The MCM-1A high frequency metal encapsulated mica capacitor of claim 1, wherein, The silver-plated metal "T" gasket is a silver-plated copper sheet, which is tightly attached to the inner wall of the metal packaging shell.

5. The MCM-1A high frequency metal encapsulated mica capacitor of claim 1, wherein, The silver-plated thin copper sheet is in the shape of a "Z" character.

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

7. The MCM-1A high frequency metal encapsulated mica capacitor of claim 1, wherein, In step A2, the number of repetitions of the supercycle is 500-600; 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.

8. The MCM-1A high frequency metal encapsulated mica capacitor of claim 1, wherein, In step A3, the mass ratio of the core-shell nanoparticles to polyvinylpyrrolidone is 1:(0.5-2).

9. The MCM-1A high frequency metal encapsulated mica capacitor of claim 1, wherein, In step A4, the number of times of washing with diethyl ether is 3-5.

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