High-reliability mica capacitor with end head in complete monolithic structure and preparation method of high-reliability mica capacitor

Abstract

The invention belongs to the field of capacitors, and particularly relates to a high-reliability mica capacitor with an end in a complete monolithic structure and a preparation method of the high-reliability mica capacitor. The preparation method comprises the following steps: S1, carrying out pretreatment and intercalation treatment on mica powder to obtain two-dimensional nano mica, carrying out surface modification by using aminated boron nitride, and carrying out pressing, drying and cutting to obtain a surface-modified mica sheet; s2, silver electrode layers are symmetrically printed on the two faces of the surface modified mica sheet through silk-screen printing, then the mica sheet is placed on a heating flat plate to be dried, then the mica sheet is transferred into a tunnel sintering furnace to be calcined, and a mica silver sheet is obtained; s3, carrying out laminated assembly on the mica silver sheets, and then putting the mica silver sheets into a high-temperature box-type furnace for sintering to obtain a sintered core group; and S4, silver paste is used to coat the end of the sintered core group with silver, and the sintered core group is air-dried to obtain the high-reliability mica capacitor with the end in a complete monolithic structure. The capacitor provided by the invention has good flame retardance and can resist high temperature.

Description

Technical Field

[0001] This invention belongs to the field of capacitors, specifically relating to a high-reliability mica capacitor with a completely monolithic terminal structure and its preparation method. Background Technology

[0002] With the development of electronic information technology, electronic components are gradually moving towards miniaturization, lightweighting, integration, and high performance. Capacitors, as one of the fundamental and important components in electronic devices, account for a large proportion of passive components, and almost all electronic devices require large-scale deployment of capacitors. Capacitors store and release electrical energy through electrostatic discharge, with a dielectric separating the two conductive electrodes and storing the energy within it. Their main functions include charge storage, AC filtering or bypassing, cutting off or blocking DC, and providing tuning and oscillation. Based on the type of dielectric, capacitors mainly include mica capacitors, ceramic capacitors, glass enamel capacitors, electrolytic capacitors, paper capacitors, and film capacitors.

[0003] Mica capacitors are capacitors that use mica as the intermediate dielectric. They are typically cubic in shape, possess excellent voltage withstand capability and performance, and operate on the principle of charge storage and release. When the capacitor is charging, ions in the electrolyte are adsorbed onto the electrodes under the influence of an electric field, forming positive and negative charges. When the capacitor is discharging, the stored charge is released and flows back into the electrolyte. Mica capacitors exhibit excellent electrical performance and stable physical characteristics, with low dielectric loss, high voltage withstand capability, good capacitance temperature and time stability, excellent high-frequency characteristics, high precision, and good heat resistance. They are widely used in various high-precision equipment and instruments in fields such as communications, electronics, power, aerospace, aviation, marine, and satellite electronics.

[0004] Chinese patent (publication number CN115483025B) discloses a manufacturing process for mica sheet capacitors. The specific operation method includes the following steps: mica sheet selection and peeling: thick mica sheets are selected and trimmed, then peeled using a peeling knife, and the peeled mica sheets are sorted according to thickness; mica sheet thickness classification: the thin mica sheets from the above steps are classified by thickness using a dial indicator. This invention uses green and pollution-free raw materials in the silver paste preparation, resulting in low production costs. After coating the silver paste onto the mica sheets and performing silver printing and burning, the produced products undergo withstand voltage testing, insulation resistance testing, loss tangent measurement, capacitor temperature coefficient, and capacitance stability testing, which can effectively avoid product defect rates. However, this technology lacks research on the thermal stability and flame retardancy of mica capacitors, and cannot guarantee that the reliability of the capacitors meets the requirements.

[0005] Therefore, there is an urgent need for a mica capacitor with a completely monolithic end structure. By designing the mica and silver paste materials, the thermal stability of the capacitor can be improved while ensuring good flame retardant properties, thereby achieving high reliability. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a high-reliability mica capacitor with a completely monolithic end structure and its preparation method. The present invention utilizes a liquid-phase assisted ultrasonic exfoliation method to process mica powder through multiple steps to obtain two-dimensional nano-mica, and then combines it with surface modification with aminated boron nitride to process it into surface-modified mica sheets. Based on the surface-modified mica sheets, a high-reliability mica capacitor with a completely monolithic end structure is obtained through multiple processing steps, which not only ensures good thermal stability but also improves flame retardant performance.

[0007] In a first aspect, the present invention provides a method for preparing a high-reliability mica capacitor with a completely monolithic end structure, comprising the following steps: S1. First, pre-treat the mica powder to obtain pre-treated mica powder; then, intercalate the pre-treated mica powder to obtain two-dimensional nano-mica; use aminated boron nitride to modify the surface of the two-dimensional nano-mica to obtain a mixture; then, press, dry, and cut the mixture to obtain surface-modified mica sheets. S2. A silver electrode layer is symmetrically printed on both sides of the mica sheet on the surface by screen printing, then placed on a heating plate for drying, and then transferred to a tunnel sintering furnace for calcination to obtain a mica silver sheet. S3. The mica silver sheets are stacked and assembled, and then placed in a high-temperature box furnace for sintering to obtain a sintered core assembly. S4. Apply silver paste to the ends of the sintered core assembly, let it dry, and obtain a high-reliability mica capacitor with a completely monolithic end structure.

[0008] As a preferred embodiment of the present invention, the pretreatment step is as follows: by weight, 10-20 parts of mica powder are kept at 750-800℃ for 60-80 minutes, then transferred to 400-600 parts of 5mol / L nitric acid solution, stirred at 85-95℃ for 5-7 hours, washed with water until neutral, and dried to obtain acid-treated mica powder; 10-20 parts of the acid-treated mica powder are added to 400-600 parts of 1mol / L sodium chloride solution, stirred at 80-90℃ for 4-6 hours, washed with water, and dried to obtain pretreated mica powder.

[0009] As a preferred technical solution of the present invention, the intercalation treatment step is as follows: by weight, 40-50 parts of hexadecyltrimethylammonium bromide are dissolved in 900-1000 parts of deionized water, and then 15-25 parts of the pretreated mica powder are added. The mixture is heated to 80-90°C and stirred for 20-24 hours. After centrifugation, the solid is washed with water, dried, and then dispersed in 400-500 parts of anhydrous ethanol. The mixture is ultrasonically broken up for 30-40 minutes, centrifuged to obtain a supernatant containing two-dimensional nano-mica, and vacuum dried to obtain two-dimensional nano-mica.

[0010] As a preferred technical solution of the present invention, the preparation steps of the aminated boron nitride are as follows: by weight, 6-8 parts of boron nitride, 180-200 parts of urea and 10-20 parts of deionized water are mixed and ground at a speed of 20-30 r / min for 12-16 h, then transferred to 400-500 parts of deionized water and stirred for 20-30 min, filtered, and the filter residue is dried to obtain aminated boron nitride.

[0011] The aminated boron nitride of the present invention uses boron nitride and urea as raw materials. During the grinding process, a transverse shear force is generated, which causes the boron nitride sheets to be continuously peeled and thinned with the assistance of urea. The urea wrapped on the boron nitride surface reacts with the BN bond to form a new chemical bond, thereby achieving surface modification at the same time as peeling, and thus preparing aminated boron nitride.

[0012] As a preferred technical solution of the present invention, the surface modification step is as follows: by weight, 4-6 parts of two-dimensional nano mica are dispersed in 400-600 parts of deionized water, then 0.4-0.6 parts of aminated boron nitride and 0.3-0.5 parts of sodium chloride are added, stirred at 60-70°C for 1-2 hours, and vacuum dried to obtain a mixture.

[0013] As a preferred embodiment of the present invention, the preparation steps of the surface-modified mica sheets are as follows: pressing the mixture, drying it at 85°C, and cutting it into sheets with an area of ​​1×1m². 2 Surface-modified mica sheet with a thickness of 500 μm.

[0014] This invention utilizes a liquid-phase assisted ultrasonic exfoliation method to perform multi-step pretreatment on mica powder, including thermal activation, acid treatment, and salt washing. Then, cationic surfactants are used for intercalation and ultrasonic exfoliation to finally prepare two-dimensional nano-mica. Subsequently, the surface of the two-dimensional nano-mica is modified with aminated boron nitride. The amino groups of boron nitride are tightly connected to the two-dimensional nano-mica through hydrogen bonds and electrostatic interactions. Finally, it is processed and shaped to obtain surface-modified mica sheets.

[0015] As a preferred technical solution of the present invention, the silver paste is prepared by adding 80-90 parts of silver powder and 4-8 parts of glass powder to 20-30 parts of solvent by weight, mixing and dispersing at high speed, and then transferring to a three-roll mill for grinding to obtain silver paste.

[0016] As a preferred embodiment of the present invention, the silver powder is composed of nano-silver powder and hybrid silver particles; the mass ratio of the nano-silver powder to the hybrid silver particles is (2~3):1.

[0017] This invention selects nano-silver powder and hybrid silver particles as the compounded silver powder material, and controls the mass ratio of the two to avoid both insufficient conductivity of silver paste due to insufficient nano-silver powder, which would affect the forming of capacitors, and insufficient hybrid silver particles, which would lead to a decline in capacitor performance.

[0018] As a preferred technical solution of the present invention, the method for preparing the hybrid silver particles is as follows: an intermediate product is prepared using 4-aminobenzonitrile, terephthalaldehyde and DOPO as raw materials, and the intermediate product and silver nitrate are hybridized to obtain hybrid silver particles.

[0019] As a preferred embodiment of the present invention, the preparation steps of the intermediate product are as follows: by weight, 15-25 parts of trifluoromethanesulfonic acid and 7-9 parts of 4-aminobenzonitrile are mixed and stirred for 30-40 min under ice bath conditions, then heated to 20-30℃ and stirred for 12-14 h, the pH is adjusted to neutral and centrifuged to obtain a yellow precipitate; 2-4 parts of the yellow precipitate and 3-5 parts of DOPO are added to 200-300 parts of anhydrous ethanol, then 1-3 parts of terephthalaldehyde are added and stirred for 24-30 h, centrifuged, the precipitate is washed with anhydrous ethanol and dried under vacuum to obtain the intermediate product.

[0020] As a preferred embodiment of the present invention, the hybridization process is as follows: by weight, 2-4 parts of intermediate product and 0.1-0.3 parts of polyvinylpyrrolidone are added to 500-600 parts of anhydrous ethanol and ultrasonically dispersed for 2-4 hours. Then, 24-30 parts of silver nitrate solution with a molar concentration of 0.02 mol / L are added and stirred in the dark for 4-6 hours. Then, 0.2-0.4 parts of sodium borohydride are added and stirred for 2-4 hours. The mixture is centrifuged, the precipitate is washed with anhydrous ethanol, and vacuum dried to obtain hybrid silver particles.

[0021] As a preferred embodiment of the present invention, the solvent is selected from one or more of cyclohexanone, n-butyl ether, and ethylene glycol ethyl ether.

[0022] This invention uses 4-aminobenzonitrile, terephthalaldehyde and DOPO as monomer raw materials to form polymer microspheres as intermediate products through reaction; then, using the intermediate polymer microspheres as carriers and silver nitrate as a metal source, silver nanoparticles are synthesized on the surface of the microspheres by adsorption coordination of Schiff bases and hydrogen bonding, thereby preparing hybrid silver particles.

[0023] As a preferred technical solution of the present invention, the drying conditions in step S2 are: temperature of 180~220℃ and time of 3~5min.

[0024] As a preferred technical solution of the present invention, the calcination conditions in step S2 are: calcination at a temperature of 400~600℃ for 20~30 minutes.

[0025] As a preferred technical solution of the present invention, the sintering conditions in step S3 are: temperature of 520~540℃ and time of 60~70min.

[0026] A second aspect of the present invention provides a high-reliability mica capacitor with a completely monolithic end structure prepared by the preparation method described in the first aspect.

[0027] Compared with the prior art, the present invention has the following beneficial effects: (1) In the surface-modified mica sheet of the present invention, the mica itself has an excellent layered silicate structure and is stable at high temperature. Boron nitride forms a continuous or semi-continuous thermal conduction path in the composite system. The two work together to avoid the accumulation of local hot spots and ensure the good thermal stability of the capacitor. When the material is exposed to flame, the two-dimensional nano-mica and boron nitride migrate to the surface. The two-dimensional nano-mica provides the structural framework, and the boron nitride fills the micropores and improves the thermal stability of the carbon layer. The two work together to form a dense, continuous and strong ceramic-like protective layer, which improves the flame retardant performance.

[0028] (2) The hybrid silver particles in the silver paste of the present invention have a triazine ring structure and DOPO. The rigid planar structure and strong intermolecular forces of the triazine ring make it stable at high temperature. The high thermal conductivity of the silver particles helps to dissipate heat evenly and avoid local overheating, thereby improving the high temperature resistance of the material. When heated, DOPO decomposes to generate phosphorus oxygen free radicals, which capture active free radicals in the combustion chain reaction. The triazine ring decomposes when heated to release nitrogen gas, which dilutes oxygen and combustible gas, and works synergistically with DOPO to promote the formation of a dense carbon layer, which isolates heat and oxygen, and significantly improves the flame retardant performance of the material. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The image shows the XRD patterns of mica powder and two-dimensional nano-mica in Example 1 of this invention.

[0031] Figure 2 The images show the FTIR spectra of boron nitride and aminated boron nitride in Example 1 of this invention. Detailed Implementation

[0032] 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.

[0033] Example 1 This embodiment provides a method for preparing a high-reliability mica capacitor with a completely monolithic end structure, including the following steps: S1. By weight, 20 parts of mica powder were kept at 800℃ for 60 min, then transferred to 600 parts of 5 mol / L nitric acid solution, stirred at 95℃ for 5 h, washed with water until neutral, and dried to obtain acid-treated mica powder; 20 parts of the acid-treated mica powder were added to 600 parts of 1 mol / L sodium chloride solution, stirred at 90℃ for 4 h, washed with water, and dried to obtain pretreated mica powder; 50 parts of hexadecyltrimethylammonium bromide were dissolved in 1000 parts of deionized water, and then 25 parts of the... The pretreated mica powder was heated to 90℃ and stirred for 20 hours, centrifuged, the solid was washed with water, dried, and then dispersed in 500 parts of anhydrous ethanol. The mixture was ultrasonically broken up for 40 minutes, centrifuged to obtain a supernatant containing two-dimensional mica nanoparticles, and vacuum dried to obtain two-dimensional mica nanoparticles. Six parts of the two-dimensional mica nanoparticles were dispersed in 600 parts of deionized water, and then 0.6 parts of amino-boron nitride and 0.5 parts of sodium chloride were added. The mixture was stirred at 70℃ for 1 hour and vacuum dried to obtain a mixture. The mixture was pressed, dried at 85℃, and cut into pieces with an area of ​​1×1m². 2 Surface-modified mica sheets with a thickness of 500 μm; S2. A silver electrode layer is symmetrically printed on both sides of the mica sheet on the surface by screen printing. Then, it is placed on a heated plate for drying (temperature 220℃, time 3min). Then, it is transferred to a tunnel sintering furnace for calcination at 600℃ for 20min to obtain the mica silver sheet. S3. The mica silver sheets are stacked and assembled, and then placed in a high-temperature box furnace for sintering (temperature 540℃, time 60min) to obtain a sintered core assembly. S4. Apply silver paste to the ends of the sintered core assembly, let it dry, and obtain a high-reliability mica capacitor with a completely monolithic end structure.

[0034] Preparation of the aminated boron nitride: By weight, 8 parts boron nitride, 200 parts urea and 20 parts deionized water are mixed and ground at 30 r / min for 16 h, then transferred to 500 parts deionized water and stirred for 30 min, filtered, and the filter residue is dried to obtain aminated boron nitride.

[0035] Preparation of the silver paste: By weight, 90 parts of silver powder (60 parts of nano silver powder and 30 parts of hybrid silver particles) and 8 parts of glass powder are added to 30 parts of solvent cyclohexanone, mixed and dispersed at high speed, and then transferred to a three-roll mill for grinding to obtain silver paste.

[0036] Preparation of hybrid silver particles: By weight, 25 parts of trifluoromethanesulfonic acid and 9 parts of 4-aminobenzonitrile were mixed and stirred for 40 min under ice bath conditions, then heated to 30℃ and stirred for 12 h. After adjusting the pH to neutral, the mixture was centrifuged to obtain a yellow precipitate. 4 parts of the yellow precipitate and 5 parts of DOPO were added to 300 parts of anhydrous ethanol, followed by the addition of 3 parts of terephthalaldehyde and stirring for 30 h. The mixture was centrifuged, the precipitate was washed with anhydrous ethanol, and vacuum dried to obtain an intermediate product. 4 parts of the intermediate product and 0.3 parts of polyvinylpyrrolidone were added to 600 parts of anhydrous ethanol and ultrasonically dispersed for 4 h. Then, 30 parts of silver nitrate solution with a molar concentration of 0.02 mol / L were added and stirred in the dark for 4 h. 0.4 parts of sodium borohydride were added and stirred for 4 h. The mixture was centrifuged, the precipitate was washed with anhydrous ethanol, and vacuum dried to obtain hybrid silver particles.

[0037] Example 2 This embodiment provides a method for preparing a high-reliability mica capacitor with a completely monolithic end structure, including the following steps: S1. By weight, 10 parts of mica powder were kept at 750℃ for 60 min, then transferred to 400 parts of 5 mol / L nitric acid solution, stirred at 85℃ for 7 h, washed with water until neutral, and dried to obtain acid-treated mica powder; 10 parts of the acid-treated mica powder were added to 400 parts of 1 mol / L sodium chloride solution, stirred at 80℃ for 6 h, washed with water, and dried to obtain pretreated mica powder; 40 parts of hexadecyltrimethylammonium bromide were dissolved in 900 parts of deionized water, and then 15 parts of the aforementioned... Pretreated mica powder was heated to 80℃ and stirred for 24 hours, centrifuged, the solid was washed with water, dried, and then dispersed in 400 parts of anhydrous ethanol. The mixture was ultrasonically broken up for 30 minutes, centrifuged to obtain a supernatant containing two-dimensional mica nanoparticles, and vacuum dried to obtain two-dimensional mica nanoparticles. Four parts of the two-dimensional mica nanoparticles were dispersed in 400 parts of deionized water, and then 0.4 parts of amino-boron nitride and 0.3 parts of sodium chloride were added. The mixture was stirred at 60℃ for 2 hours and vacuum dried to obtain a mixture. The mixture was pressed, dried at 85℃, and cut into pieces with an area of ​​1×1m². 2 Surface-modified mica sheets with a thickness of 500 μm; S2. A silver electrode layer is symmetrically printed on both sides of the mica sheet on the surface by screen printing. Then, it is placed on a heated plate for drying (temperature 180℃, time 5min). Then, it is transferred to a tunnel sintering furnace for calcination at 400℃ for 30min to obtain the mica silver sheet. S3. The mica silver sheets are stacked and assembled, and then placed in a high-temperature box furnace for sintering (temperature 520℃, time 70min) to obtain a sintered core assembly. S4. Apply silver paste to the ends of the sintered core assembly, let it dry, and obtain a high-reliability mica capacitor with a completely monolithic end structure.

[0038] Preparation of the aminated boron nitride: By weight, 6 parts boron nitride, 180 parts urea and 10 parts deionized water are mixed and ground at 20 r / min for 12 h. Then, the mixture is transferred to 400 parts deionized water and stirred for 20 min. After filtration, the filter residue is dried to obtain aminated boron nitride.

[0039] Preparation of the silver paste: By weight, 80 parts of silver powder (60 parts of nano silver powder and 20 parts of hybrid silver particles) and 4 parts of glass powder are added to 20 parts of solvent n-butyl ether, mixed and dispersed at high speed, and then transferred to a three-roll mill for grinding to obtain silver paste.

[0040] Preparation of hybrid silver particles: By weight, 15 parts of trifluoromethanesulfonic acid and 7 parts of 4-aminobenzonitrile were mixed and stirred for 30 min under ice bath conditions, then heated to 20℃ and stirred for 14 h. After adjusting the pH to neutral, the mixture was centrifuged to obtain a yellow precipitate. 2 parts of the yellow precipitate and 3 parts of DOPO were added to 200 parts of anhydrous ethanol, then 1 part of terephthalaldehyde was added and stirred for 24 h. After centrifugation, the precipitate was washed with anhydrous ethanol and dried under vacuum to obtain an intermediate product. 2 parts of the intermediate product and 0.1 parts of polyvinylpyrrolidone were added to 500 parts of anhydrous ethanol and ultrasonically dispersed for 2 h. Then, 24 parts of silver nitrate solution with a molar concentration of 0.02 mol / L were added and stirred in the dark for 4 h. Then, 0.2 parts of sodium borohydride were added and stirred for 2 h. After centrifugation, the precipitate was washed with anhydrous ethanol and dried under vacuum to obtain hybrid silver particles.

[0041] Example 3 This embodiment provides a method for preparing a high-reliability mica capacitor with a completely monolithic end structure, including the following steps: S1. By weight, 15 parts of mica powder were kept at 780℃ for 70 min, then transferred to 500 parts of 5 mol / L nitric acid solution, stirred at 90℃ for 6 h, washed with water until neutral, and dried to obtain acid-treated mica powder; 15 parts of the acid-treated mica powder were added to 500 parts of 1 mol / L sodium chloride solution, stirred at 85℃ for 5 h, washed with water, and dried to obtain pretreated mica powder; 45 parts of hexadecyltrimethylammonium bromide were dissolved in 950 parts of deionized water, and then 20 parts of the pretreated mica powder were added. The processed mica powder was heated to 85℃ and stirred for 22 hours, centrifuged, the solid was washed with water, dried, and then dispersed in 450 parts of anhydrous ethanol. The mixture was ultrasonically broken up for 35 minutes, centrifuged again to obtain a supernatant containing two-dimensional mica nanoparticles, and vacuum dried to obtain two-dimensional mica nanoparticles. Five parts of the two-dimensional mica nanoparticles were dispersed in 500 parts of deionized water, and then 0.5 parts of aminated boron nitride and 0.4 parts of sodium chloride were added. The mixture was stirred at 65℃ for 1.5 hours and vacuum dried to obtain a mixture. The mixture was pressed, dried at 85℃, and cut into pieces with an area of ​​1×1m². 2 Surface-modified mica sheets with a thickness of 500 μm; S2. A silver electrode layer is symmetrically printed on both sides of the mica sheet on the surface by screen printing. Then, it is placed on a heated plate for drying (temperature 200℃, time 4min). Then, it is transferred to a tunnel sintering furnace for calcination at 500℃ for 25min to obtain the mica silver sheet. S3. The mica silver sheets are stacked and assembled, and then placed in a high-temperature box furnace for sintering (temperature 530℃, time 65min) to obtain a sintered core assembly. S4. Apply silver paste to the ends of the sintered core assembly, let it dry, and obtain a high-reliability mica capacitor with a completely monolithic end structure.

[0042] Preparation of the aminated boron nitride: By weight, 7 parts boron nitride, 190 parts urea and 15 parts deionized water are mixed and ground at 25 r / min for 14 h, then transferred to 450 parts deionized water and stirred for 25 min, filtered, and the filter residue is dried to obtain aminated boron nitride.

[0043] Preparation of the silver paste: By weight, 85 parts of silver powder (60 parts of nano silver powder and 25 parts of hybrid silver particles) and 6 parts of glass powder are added to 25 parts of solvent ethylene glycol ethyl ether, mixed and dispersed at high speed, and then transferred to a three-roll mill for grinding to obtain silver paste.

[0044] Preparation of hybrid silver particles: By weight, 20 parts of trifluoromethanesulfonic acid and 8 parts of 4-aminobenzonitrile were mixed and stirred for 35 min under ice bath conditions, then heated to 25℃ and stirred for 13 h. After adjusting the pH to neutral, the mixture was centrifuged to obtain a yellow precipitate. 3 parts of the yellow precipitate and 4 parts of DOPO were added to 250 parts of anhydrous ethanol, followed by the addition of 2 parts of terephthalaldehyde and stirring for 27 h. The mixture was centrifuged, the precipitate was washed with anhydrous ethanol, and dried under vacuum to obtain an intermediate product. 3 parts of the intermediate product and 0.2 parts of polyvinylpyrrolidone were added to 550 parts of anhydrous ethanol and ultrasonically dispersed for 3 h. Then, 26 parts of silver nitrate solution with a molar concentration of 0.02 mol / L were added and stirred in the dark for 5 h. 0.3 parts of sodium borohydride were added and stirred for 3 h. The mixture was centrifuged, the precipitate was washed with anhydrous ethanol, and dried under vacuum to obtain hybrid silver particles.

[0045] Comparative Example 1 The difference between this comparative example and Example 1 is that commercially available mica powder was used instead of the mixture in the preparation of the mica sheets.

[0046] Comparative Example 2 The difference between this comparative example and Example 1 is that all the silver powder used is nano silver powder.

[0047] Comparative Example 3 The difference between this comparative example and Example 1 is that all the silver powder used is hybrid silver particles.

[0048] The performance of the capacitors provided in the above embodiments and comparative examples was tested. Capacitor thermal stability: The capacitor is placed in a temperature chamber, which is heated to 130℃±2℃ at a rate of 5℃ / min and held at that temperature for 30min. The capacitance retention rate is measured after the test. Flame retardancy test: The relevant requirements in the standard GB / T 6346.1-2024 Fixed capacitors for electronic equipment are referred to.

[0049] The performance test data above are shown in Table 1.

[0050]

[0051] As can be seen from the above, the present invention utilizes a liquid-phase assisted ultrasonic exfoliation method to process mica powder in multiple steps to obtain two-dimensional nano-mica, and then combines it with surface modification with aminated boron nitride to process it into surface-modified mica sheets. Based on the surface-modified mica sheets, a high-reliability mica capacitor with a completely monolithic structure at the end is obtained through multiple processing steps (Examples 1 to 3), which has the best overall performance.

[0052] Compared to Example 1, the use of commercially available mica powder instead of the mixed material in the preparation of mica sheets resulted in a lack of the effect of aminated boron nitride, leading to a decrease in the thermal stability and flame retardancy of the capacitor (Comparative Example 1); compared to Example 1, the use of nano-silver powder instead of hybrid silver particles resulted in a lack of the effect of hybrid silver particles, leading to a decrease in the thermal stability and flame retardancy of the capacitor (Comparative Example 2); compared to Example 1, the use of hybrid silver particles instead of nano-silver powder resulted in insufficient conductivity of the silver paste, causing the capacitor to fail the conductivity test (Comparative Example 3).

Claims

1. A method for preparing a high-reliability mica capacitor with a completely monolithic end structure, characterized in that, Includes the following steps: S1. First, pre-treat the mica powder to obtain pre-treated mica powder; then, intercalate the pre-treated mica powder to obtain two-dimensional nano-mica; use aminated boron nitride to modify the surface of the two-dimensional nano-mica to obtain a mixture; then, press, dry, and cut the mixture to obtain surface-modified mica sheets. S2. A silver electrode layer is symmetrically printed on both sides of the mica sheet on the surface by screen printing, then placed on a heating plate for drying, and then transferred to a tunnel sintering furnace for calcination to obtain a mica silver sheet. S3. The mica silver sheets are stacked and assembled, and then placed in a high-temperature box furnace for sintering to obtain a sintered core assembly. S4. Apply silver paste to the ends of the sintered core assembly, let it dry, and obtain a high-reliability mica capacitor with a completely monolithic end structure.

2. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 1, characterized in that, The pretreatment steps are as follows: by weight, 10-20 parts of mica powder are kept at 750-800℃ for 60-80 minutes, then transferred to 400-600 parts of 5mol / L nitric acid solution, stirred at 85-95℃ for 5-7 hours, washed with water until neutral, and dried to obtain acid-treated mica powder; 10-20 parts of the acid-treated mica powder are added to 400-600 parts of 1mol / L sodium chloride solution, stirred at 80-90℃ for 4-6 hours, washed with water, and dried to obtain pretreated mica powder.

3. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 1, characterized in that, The intercalation treatment steps are as follows: by weight, 40-50 parts of hexadecyltrimethylammonium bromide are dissolved in 900-1000 parts of deionized water, and then 15-25 parts of the pretreated mica powder are added. The mixture is heated to 80-90℃ and stirred for 20-24 hours. After centrifugation, the solid is washed with water, dried, and then dispersed in 400-500 parts of anhydrous ethanol. The mixture is ultrasonically broken up for 30-40 minutes, centrifuged to obtain a supernatant containing two-dimensional nano-mica, and vacuum dried to obtain two-dimensional nano-mica.

4. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 1, characterized in that, The preparation steps of the aminated boron nitride are as follows: by weight, 6-8 parts of boron nitride, 180-200 parts of urea and 10-20 parts of deionized water are mixed and ground at a speed of 20-30 r / min for 12-16 h, then transferred to 400-500 parts of deionized water and stirred for 20-30 min, filtered, and the filter residue is dried to obtain aminated boron nitride.

5. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 1, characterized in that, The surface modification steps are as follows: by weight, 4-6 parts of two-dimensional nano mica are dispersed in 400-600 parts of deionized water, then 0.4-0.6 parts of aminated boron nitride and 0.3-0.5 parts of sodium chloride are added, and the mixture is stirred at 60-70°C for 1-2 hours and then vacuum dried to obtain the mixture.

6. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 1, characterized in that, The silver paste is prepared by adding 80-90 parts by weight of silver powder and 4-8 parts by weight of glass powder to 20-30 parts by weight of solvent, mixing and dispersing at high speed, and then transferring to a three-roll mill for grinding to obtain silver paste.

7. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 6, characterized in that, The silver powder is composed of nano-silver powder and hybrid silver particles; the mass ratio of the nano-silver powder to the hybrid silver particles is (2~3):

1.

8. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 7, characterized in that, The method for preparing the hybrid silver particles is as follows: an intermediate product is prepared using 4-aminobenzonitrile, terephthalaldehyde and DOPO as raw materials, and the intermediate product is hybridized with silver nitrate to obtain hybrid silver particles.

9. The method for preparing a high-reliability mica capacitor with a completely monolithic end structure according to claim 8, characterized in that, The preparation steps of the intermediate product are as follows: by weight, 15-25 parts of trifluoromethanesulfonic acid and 7-9 parts of 4-aminobenzonitrile are mixed and stirred for 30-40 min under ice bath conditions, then heated to 20-30℃ and stirred for 12-14 h, the pH is adjusted to neutral and centrifuged to obtain a yellow precipitate; 2-4 parts of the yellow precipitate and 3-5 parts of DOPO are added to 200-300 parts of anhydrous ethanol, then 1-3 parts of terephthalaldehyde are added and stirred for 24-30 h, centrifuged, the precipitate is washed with anhydrous ethanol and dried under vacuum to obtain the intermediate product; The hybridization process is as follows: by weight, 2-4 parts of intermediate product and 0.1-0.3 parts of polyvinylpyrrolidone are added to 500-600 parts of anhydrous ethanol and ultrasonically dispersed for 2-4 hours. Then, 24-30 parts of silver nitrate solution with a molar concentration of 0.02 mol / L are added and stirred in the dark for 4-6 hours. Then, 0.2-0.4 parts of sodium borohydride are added and stirred for 2-4 hours. After centrifugation, the precipitate is washed with anhydrous ethanol and vacuum dried to obtain hybrid silver particles.

10. A high-reliability mica capacitor with a completely monolithic end structure, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 9.

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