A method of encapsulating a ceramic capacitor

Abstract

The application provides a kind of encapsulation method of ceramic capacitor. The method first respectively prepares bisphenol-A (di) glycidyl ether and methyl tetrahydrophthalic anhydride mixture and polyvinyl pyrrolidone, ceramic powder and N, N-dimethylformamide slurry as the inner layer and outer layer spinning solution of spinning, then ceramic composite spinning film is prepared by electrospinning and is wound on the surface of capacitor. Finally, the uniformly mixed bisphenol-A (di) glycidyl ether, methyl tetrahydrophthalic anhydride and 2,4,6-tris (dimethylaminomethyl) phenol are extracted into the mold placed with ceramic capacitor under vacuum condition to solidify and form. The method provided by the application is simple, and the process operability and repeatability are good. The requirement for equipment is low. While effectively improving the thermal conductivity of the encapsulation layer, it can ensure good encapsulation effect and insulation strength, and has good application potential in the field of pulse power capacitor.

Description

Technical Field

[0001] This invention relates to a method for encapsulating ceramic capacitors, belonging to the field of capacitor encapsulation. Background Technology

[0002] Ceramic capacitors are a crucial component of high-power pulsed power systems. To improve their surface flashover characteristics and environmental adaptability, encapsulation is generally required. Epoxy resin, with its high insulation strength and good bonding properties, is currently the most commonly used encapsulation material for pulsed power capacitors. In high-power pulsed power systems, ceramic capacitors generate significant heat during rapid discharge under ultra-high voltage and ultra-high current. Due to the low thermal conductivity of epoxy resin, heat accumulation during discharge is very pronounced in high-power pulsed capacitors, often leading to a rapid and significant increase in their operating temperature. In recent years, with the development of pulsed systems towards higher power, compactness, and higher repetition rates, the heat accumulation effect caused by epoxy resin encapsulation has increasingly become a significant factor restricting the operational stability and lifespan of pulsed power systems.

[0003] To improve the heat dissipation performance of capacitors and ensure sufficient insulation, patent CN 206179682U proposes using alumina ceramic for the capacitor terminals and encapsulating the entire capacitor with epoxy resin. However, the thermal conductivity of the metal electrodes at the capacitor terminals is far superior to that of alumina ceramic, thus limiting the effectiveness of the method proposed in this patent in improving the heat accumulation problem of capacitors. Another possible method to improve the heat dissipation of the encapsulation layer is to utilize a so-called filled epoxy resin material, combining high thermal conductivity ceramic powder with epoxy resin to increase the thermal conductivity of the encapsulation material. However, this method has limited effect on improving the thermal conductivity of the encapsulation material, making it difficult to meet the requirements of high heat dissipation capacity. At the same time, the viscosity of epoxy resin increases sharply and its fluidity deteriorates after adding a large amount of ceramic powder, making the encapsulation process difficult to implement and easily causing encapsulation defects, thereby affecting the surface insulation strength of the capacitor. In addition, some literature (such as the patent application number 201910213599.X) reports obtaining ceramic composite fiber membranes with good thermal conductivity through electrospinning and other methods, but these materials are not suitable for use as encapsulation materials for pulse power ceramic capacitors.

[0004] To address the aforementioned problems, this invention proposes a method for preparing encapsulation materials for high-power pulse ceramic capacitors. Compared to existing technologies, this method not only ensures good adhesion and high surface insulation strength of the encapsulation material, but also effectively improves the heat dissipation capability of pulse power ceramic capacitors. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for encapsulating ceramic capacitors. Compared to existing technologies, this method can effectively improve the heat dissipation capacity of the capacitor and ensure surface insulation performance.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A method for encapsulating a ceramic capacitor includes the following steps:

[0008] (1) Bisphenol-A (di) glycidyl ether and methyltetrahydrophthalic anhydride are mixed evenly to obtain a resin solution;

[0009] (2) Polyvinylpyrrolidone was dissolved in N,N-dimethylformamide to obtain a polyvinylpyrrolidone solution, and then boron nitride powder was dispersed in the polyvinylpyrrolidone solution to obtain a ceramic spinning slurry;

[0010] (3) Prepare composite spinning membrane using coaxial electrospinning device: After stirring the resin solution described in step (1) at 30-50°C for 24-48 hours, inject it into the core tube. Add the ceramic spinning slurry described in step (2) into the shell tube for coaxial spinning. Wrap the resulting spinning membrane around the surface of the ceramic capacitor and place it in a mold.

[0011] (4) Weigh out bisphenol-A (di)glycidyl ether, methyltetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl)phenol and mix them evenly to obtain a solution. Then, under vacuum, the solution is drawn into a mold and solidified to obtain a fully encapsulated ceramic capacitor.

[0012] Preferably, the mass ratio of bisphenol-A (bis) glycidyl ether and methyltetrahydrophthalic anhydride in step (1) is 100:80-60.

[0013] Preferably, the method for achieving uniform mixing in step (1) is to stir at 30–50°C for 24–48 hours.

[0014] Preferably, in the ceramic spinning slurry of step (2), the mass percentages of polyvinylpyrrolidone, boron nitride, and N,N-dimethylformamide are 5-15%, 5-25%, and 60-90%, respectively.

[0015] Preferably, the K value of the polyvinylpyrrolidone is 88 to 98.

[0016] Preferably, the parameters for coaxial electrospinning are as follows: roller speed of 25 r / min to 40 r / min, spinning voltage of 16 to 18 kV, receiving distance of 18 cm to 20 cm, spinning temperature of 25℃ to 30℃, humidity of 40% to 60%, spinning solution propulsion speed of the shell tube of 0.27 mL / h to 0.48 mL / h, and spinning solution propulsion speed of the core tube of 0.16 mL / h to 0.27 mL / h.

[0017] Preferably, the winding speed in step (3) is 1-10 r / min.

[0018] Preferably, the mass ratio of bisphenol-A (di)glycidyl ether, methyltetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl)phenol in step (4) is 100:80:1 to 3.

[0019] Preferably, the vacuum parameters in step (4) are 0.07 MPa to 0.09 MPa.

[0020] Preferably, the curing temperature in step (4) is 120-160°C, and the curing time is controlled between 1 and 3 hours.

[0021] Compared with the prior art, the beneficial effects of the present invention include:

[0022] This method can form a boron nitride / epoxy resin composite material (bisphenol-A(di)glycidyl ether as the epoxy resin, reacting with methyltetrahydrophthalic anhydride, and 2,4,6-tris(dimethylaminomethyl)phenol as the curing accelerator) and encapsulate it on the surface of a pulse power ceramic capacitor. This ensures both good encapsulation effect and insulation strength, while also improving the capacitor's heat dissipation capacity. Coaxial spinning allows the thermally conductive boron nitride powder to form a highly ordered structure, resulting in high thermal conductivity. Simultaneously, it maintains the good flowability and filling properties of the epoxy resin itself, effectively reducing encapsulation defects and ensuring the required good encapsulation and insulation effects under high-current pulse environments. This invention is simple, has good process operability and repeatability, and requires minimal equipment. It effectively improves the thermal conductivity of the encapsulation layer while ensuring good encapsulation effect and insulation strength, showing great application potential in the field of pulse power capacitors. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope image of the spun membrane prepared in Example 3. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] Example 1

[0026] A method for encapsulating a ceramic capacitor, comprising the following steps:

[0027] Bisphenol-A (di)glycidyl ether and methyltetrahydrophthalic anhydride were weighed at a mass ratio of 100:80, mixed evenly, and stirred at 30°C for 24 hours to obtain a resin solution. Polyvinylpyrrolidone (K value 88), boron nitride powder, and N,N-dimethylformamide were weighed at a mass ratio of 5:5:90. Polyvinylpyrrolidone was first fully dissolved in N,N-dimethylformamide to obtain a polyvinylpyrrolidone solution. Then, boron nitride powder was dispersed in the polyvinylpyrrolidone solution to obtain a ceramic spinning slurry. The above resin solution and ceramic spinning slurry were injected into the core tube and shell tube of the electrospinning device, respectively, for electrospinning. The parameters for coaxial electrospinning were set as follows: roller speed 25 r / min, spinning voltage 16 kV, receiving distance 18 cm, spinning temperature 25°C, humidity 40%, spinning solution feed rate of shell tube 0.27 mL / h, and spinning solution feed rate of core tube 0.16 mL / h. The obtained spun film is wound onto the surface of the ceramic capacitor at a speed of 1 r / min and then placed into a mold. Bisphenol-A (di)glycidyl ether, methyltetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl)phenol are weighed in a mass ratio of 100:80:1 and mixed evenly. The solution is then drawn into the mold under a vacuum of 0.07 MPa and kept at 120°C for 3 hours to solidify and encapsulate the ceramic capacitor.

[0028] Example 2

[0029] A method for encapsulating a ceramic capacitor, comprising the following steps:

[0030] Bisphenol-A (di)glycidyl ether and methyltetrahydrophthalic anhydride were weighed at a mass ratio of 100:60, mixed evenly, and stirred at 50°C for 48 hours to obtain a resin solution. Polyvinylpyrrolidone (K value 98), boron nitride powder, and N,N-dimethylformamide were weighed at a mass ratio of 10:15:75. Polyvinylpyrrolidone was first fully dissolved in N,N-dimethylformamide to obtain a polyvinylpyrrolidone solution. Then, boron nitride powder was dispersed in the polyvinylpyrrolidone solution to obtain a ceramic spinning slurry. The above resin solution and ceramic spinning slurry were injected into the core tube and shell tube of the electrospinning device, respectively, for electrospinning. The parameters for coaxial electrospinning were set as follows: roller speed 40 r / min, spinning voltage 18 kV, receiving distance 20 cm, spinning temperature 30°C, humidity 60%, spinning solution propulsion speed of the shell tube 0.48 mL / h, and spinning solution propulsion speed of the core tube 0.27 mL / h. The obtained spun film was wound onto the surface of the ceramic capacitor at a speed of 10 r / min and then placed into a mold. Bisphenol-A (di)glycidyl ether, methyltetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl)phenol were weighed in a mass ratio of 100:80:2 and mixed evenly. The solution was then drawn into the mold under a vacuum of 0.09 MPa and kept at 140°C for 2 hours to solidify and encapsulate the ceramic capacitor.

[0031] Example 3

[0032] A method for encapsulating a ceramic capacitor, comprising the following steps:

[0033] Bisphenol-A (di)glycidyl ether and methyltetrahydrophthalic anhydride were weighed at a mass ratio of 100:80, mixed evenly, and stirred at 40°C for 36 hours to obtain a resin solution. Polyvinylpyrrolidone (K value 98), boron nitride powder, and N,N-dimethylformamide were weighed at a mass ratio of 15:25:60. Polyvinylpyrrolidone was first fully dissolved in N,N-dimethylformamide to obtain a polyvinylpyrrolidone solution. Then, boron nitride powder was dispersed in the polyvinylpyrrolidone solution to obtain a ceramic spinning slurry. The above resin solution and ceramic spinning slurry were injected into the core tube and shell tube of the electrospinning device, respectively, for electrospinning. The parameters for coaxial electrospinning were set as follows: roller speed of 30 r / min, spinning voltage of 18 kV, receiving distance of 20 cm, spinning temperature of 30°C, humidity of 50%, spinning solution propulsion speed of shell tube of 0.35 mL / h, and spinning solution propulsion speed of core tube of 0.20 mL / h. The obtained spun film was wound onto the surface of the ceramic capacitor at a speed of 5 r / min and then placed into a mold. Bisphenol-A (di)glycidyl ether, methyltetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl)phenol were weighed in a mass ratio of 100:80:3 and mixed evenly. The solution was then drawn into the mold under a vacuum of 0.08 MPa and kept at 160°C for 1 hour to solidify and encapsulate the ceramic capacitor.

[0034] Figure 1 This is a scanning electron microscope image of the spun membrane prepared in Example 3. Figure 1 It can be seen that boron nitride particles can form a highly ordered arrangement through coaxial spinning. The scanning electron microscope images of the spun films prepared in Examples 1 and 2 are similar to those in Example 3, also showing a highly ordered arrangement.

[0035] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method of encapsulating a ceramic capacitor, characterized by, It comprises the following steps: (1) uniformly mixing bisphenol-A (di) glycidyl ether and methyl tetrahydrophthalic anhydride to obtain a resin glue solution; (2) dissolving polyvinylpyrrolidone in N,N-dimethylformamide to obtain a polyvinylpyrrolidone solution, and then dispersing boron nitride powder in the polyvinylpyrrolidone solution to obtain a ceramic spinning slurry; (3) preparing a composite spinning film by using a coaxial electrospinning device: injecting the resin glue solution of step (1) into a core layer tube after continuously stirring at 30-50°C for 24-48h, and adding the ceramic spinning slurry of step (2) into a shell layer tube for coaxial spinning; winding the obtained spinning film on the surface of a ceramic capacitor and then placing it in a mold; (4) weighing bisphenol-A (di) glycidyl ether, methyl tetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl) phenol, and uniformly mixing them to obtain a solution, and then pumping the solution into the mold under vacuum to solidify and form, thereby obtaining a ceramic capacitor with complete encapsulation.

2. The method of encapsulating a ceramic capacitor of claim 1 wherein, The mass ratio of bisphenol-A (di) glycidyl ether to methyl tetrahydrophthalic anhydride in step (1) is 100:80-60.

3. The method of claim 1, wherein the ceramic capacitor is a multilayer ceramic capacitor. The mass ratio of bisphenol-A (di) glycidyl ether, methyl tetrahydrophthalic anhydride and 2,4,6-tris(dimethylaminomethyl) phenol in step (4) is 100:80:1-3.

4. The method of claim 1, 2 or 3, wherein In the ceramic spinning slurry of step (2), the mass percentages of polyvinylpyrrolidone, boron nitride and N,N-dimethylformamide are 5-15%, 5-25% and 60-90%, respectively.

5. The method of encapsulating a ceramic capacitor of claim 4 wherein, The parameters of coaxial electrospinning are as follows: the rotating speed of the drum is 25r / min-40r / min, the spinning voltage is 16-18kv, the receiving distance is 18cm-20cm, the spinning temperature is 25°C-30°C, the humidity is 40%-60%, the pushing speed of the spinning solution of the shell layer tube is 0.27mL / h-0.48mL / h, and the pushing speed of the spinning solution of the core layer tube is 0.16mL / h-0.27mL / h.

6. The method of claim 1-3, wherein The K value of the polyvinylpyrrolidone is 88-98.

7. The method of encapsulating a ceramic capacitor of claim 6 wherein, The winding speed in step (3) is 1-10r / min.

8. The method of encapsulating a ceramic capacitor of claim 7 wherein, The vacuum parameter in step (4) is 0.07MPa-0.09Mpa.

9. The method of claim 1-2, wherein The solidification and forming temperature in step (4) is 120-160°C, and the solidification time is controlled at 1-3h.

10. The method of encapsulating a ceramic capacitor of claim 9, wherein, The uniform mixing method in step (1) is stirring at 30-50°C for 24-48h.

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