A high-temperature-resistant flexible film capacitor and a preparation method thereof

Abstract

The application discloses a kind of high-temperature-resistant flexible film capacitors and preparation method thereof, multilayer film capacitor prepared by the application has good high-temperature stability, in the temperature range of 25-200 DEG C, the current density and power density change rate is only ±5.4%;The capacitor has fast charge and discharge capacity (t 0.9 =0.0554 μs), high energy storage density (W d =0.51 J / cm 3 ), high current density (C D =72.19 A / cm 2 ), high power density (P D =43.31 MW / cm 3 ). In addition, the capacitance is high, and the capacitance of PI composite film capacitor is 16.33 nF, which is increased by 26.4% compared with PI film capacitor. This PI high-temperature-resistant film capacitor is expected to improve the performance and reliability of electronic equipment in extreme high-temperature environment, and further promote the development of high-temperature electronic technology.

Description

Technical Field

[0001] This invention belongs to the field of electronic power film capacitors and their manufacturing, specifically providing a high-temperature resistant flexible film capacitor and its preparation method. Background Technology

[0002] Film capacitors are capacitors that use a plastic film as the dielectric. Their technology originated from paper capacitors invented in the latter half of the 19th century and was developed in the 1930s. In 2000, the film capacitor market was mainly concentrated in the home appliance sector, but with the rise of other emerging application areas and the decline of the real estate market, the market share of home appliances gradually shrank. After 2017, the industrial control sector (new energy vehicles, photovoltaics, wind power, 5G, etc.) became the main market for film capacitors, and new infrastructure construction became the main driving force for the development of film capacitors.

[0003] The current new energy industry is placing newer and higher demands on film capacitors: 1. Higher operating voltage: To further improve driving range and user experience, new energy vehicles must increase the operating voltage of their existing electrical architecture from 400V to 800V. On the one hand, as the battery capacity of a single vehicle increases, the power of the vehicle's battery also increases. If the voltage specification remains at 400V, the increased current under high power will bring a series of power losses and thermal management problems. On the other hand, to achieve faster charging of new energy vehicles with lower power losses, the bus voltage also needs to be further increased. Therefore, related electrical components also need to be able to operate stably at higher voltages. 2. Smaller size: As automobiles continue to become electrified, digitalized, and intelligent, the related electrical systems will become more complex, thus requiring more compact designs and implementations. In recent years, the size of Panasonic's film capacitor products has shown a clear trend towards miniaturization. 3. Higher reliability: During operation, especially in urban conditions, new energy vehicles frequently require acceleration and braking. The capacitors in their electric drive systems need to withstand frequent surges in instantaneous current switching on and off, further increasing the reliability requirements for capacitors and other related passive components. 4. Superior temperature stability: While the operating temperature range of film capacitors in new energy vehicles can vary, high temperature stability is typically required. A typical operating temperature range is -40 °C to +125 °C. This is because the operating conditions of new energy vehicles are relatively harsh, requiring capacitors to be able to start at low temperatures and operate stably for extended periods in high-temperature environments. Due to limitations in the properties of their base materials, the normal operating temperature of polypropylene and polyester film capacitors is between -20 °C and +85 °C. Currently, film capacitors have become a bottleneck in the temperature resistance of controllers.

[0004] Compared to commercially available polypropylene and polyester film materials and their capacitors, PI (polyimide) electronic-grade films and PI film capacitors offer the following advantages: 1. High-temperature performance: PI films and capacitors exhibit excellent high-temperature performance, maintaining stable electrical properties even under high-temperature environments. 2. Mechanical strength: PI films possess outstanding mechanical strength and abrasion resistance, capable of withstanding high-voltage, high-tension, and other stress environments, while polypropylene and polyester film materials are relatively fragile. 3. Chemical stability: PI films demonstrate good stability against chemically corrosive solvents, resisting acid and alkali corrosion and some organic solvents, whereas polypropylene and polyester film materials exhibit poor chemical stability. 4. Low dissipation factor: PI films possess a low dissipation factor, meaning they exhibit lower signal attenuation and energy loss in high-frequency applications, thus improving capacitor performance. 5. Dimensional stability: PI films demonstrate good dimensional stability under high-temperature and high-humidity conditions, maintaining stable dimensions even under extreme conditions, while polypropylene and polyester film materials are susceptible to dimensional changes due to environmental variations. Summary of the Invention

[0005] To address the aforementioned problems or shortcomings, this invention provides a high-temperature resistant flexible film capacitor and its preparation method to meet the current demand of the electronics industry for high-temperature film capacitors.

[0006] Specifically, this invention provides a high-temperature resistant flexible film capacitor, using a PI / CSO high-temperature resistant composite electronic film as the film material. The flexible film capacitor possesses rapid charge and discharge capabilities. t 0.9 = 0.0554 ms), high energy storage density ( W d = 0.51 J / cm 3 ), high current density C D = 72.19 A / cm 2 ) and high power density ( P D = 43.31 MW / cm 3 Furthermore, it exhibits excellent high-temperature stability, with current density and power density changing by only ±5.4% within a temperature range of 25-200 °C.

[0007] This invention also provides a method for preparing a high-temperature resistant flexible thin-film capacitor, the experimental procedure of which is as follows: Figure 1 As shown, it includes the following steps: (1) Raw material mixing: First, calcium silicate nanoparticles are prepared by sol-gel method. After reaction, centrifugation and washing with ethanol, the product is obtained. Then, 4,4'-diaminodiphenyl ether (ODA) is dissolved in N,N-dimethylacetamide (DMAc), and pyromellitic dianhydride (PMDA) is added at a certain molar ratio for polymerization reaction. Then, 1 wt.% calcium silicate nanoparticles are added and mixed thoroughly. After stirring, the mixture is sealed and allowed to stand to obtain a calcium silicate / polyamic acid composite system. (2) Casting: The mixed solution is then cast onto a carrier or substrate, and a thin and uniform film is formed using a scraping technique. (3) Baking: After casting, the film is heated in a controlled environment to initiate the chemical reaction that converts polyimide acid into polyimide. (4) Cutting: The film and conductive aluminum film are cut into the required size and shape using die cutting. (5) Stacking: Individual PI films are stacked to the required thickness. (6) Electrode embedding: Electrodes are embedded into the film during the stacking process. (7) Hot pressing: The stacked films are subjected to heat and pressure to bond the layers together and ensure good electrical contact between the electrodes. (8) Baking: A second baking is performed to further cure the assembly and ensure that the adhesives used in the stacking and embedding process have cured. (9) Trimming: Excess material is trimmed to achieve the precise dimensions required for the final product. (10) Testing: Finally, the electrical and thermal properties of the capacitor are evaluated to ensure that it meets the specifications required for the intended application.

[0008] Compared with the prior art, the technical effects of the present invention are reflected in: (1) Possesses fast charging and discharging capability ( t 0.9 = 0.0554 ms), high energy storage density ( W d = 0.51 J / cm 3 ), high current density ( C D = 72.19 A / cm 2 High power density P D = 43.31 MW / cm 3 ); (2) It has good high-temperature stability. In the temperature range of 25-200 °C, the change rate of current density and power density is only ±5.4%; (3) High capacitance value. Compared with PI film capacitor, the capacitance of PI composite film capacitor is 16.33 nF, which is 26.4% higher.

[0009] Some of the additional advantages, objectives and features of the present invention will be described in detail below, which will enable those skilled in the art to clearly understand the essence of the invention and guide related research or practice.

[0010] Please note that the scope of application of this invention is not limited to the specific description above, and the various objectives and advantages that this invention can achieve can be more fully understood based on the detailed description below, including but not limited to the above content. Attached Figure Description

[0011] Figure 1 This describes the fabrication process of PI film capacitors.

[0012] Figure 2 This describes the microstructure and electrical properties of PI film capacitors. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. By reading this specification, those skilled in the art will easily understand other advantages and functions of the present invention. It is worth noting that the present invention can be implemented or applied through a variety of different specific embodiments. Furthermore, the details in this specification can be appropriately adjusted or modified according to different viewpoints and applications without departing from the core concept of the present invention.

[0014] It should be noted that the process equipment or apparatus not specifically mentioned in the following embodiments are all conventional equipment or apparatus in the art.

[0015] Furthermore, it should be understood that the one or more method steps mentioned in this invention do not exclude the existence of other method steps. Other method steps may be inserted before or after the combined steps, or between the explicitly mentioned steps, unless otherwise stated. Moreover, without substantially altering the technical content, their relative relationships can be adjusted or changed, which still falls within the scope of this invention.

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0017] First, prepare a calcium chloride ethanol solution. Weigh 0.221 g of calcium chloride dihydrate and 60 mL of anhydrous ethanol, mix thoroughly, then add 4.2 mL of triethylamine and continue mixing. This is solution A. Weigh 0.312 g of tetraethyl orthosilicate and 40 mL of anhydrous ethanol, mix thoroughly, and this is solution B. Measure 4 mL of deionized water and 2 mL of hydrochloric acid, mix thoroughly, and this is solution C. Add 3 mL of solution C to solution B and continue mixing. After mixing, pour solution B directly into solution A and stir to react for 3 hours. Centrifuge the reacted solution and wash the precipitate three times with anhydrous ethanol, adding anhydrous ethanol each time, shaking thoroughly, and then centrifuging again.

[0018] A certain mass of 4,4'-diaminodiphenyl ether (ODA) was weighed and added to a three-necked flask. The solvent was N,N-dimethylacetamide (DMAc). The ODA was stirred in DMAc for 30 min until completely dissolved. Then, a corresponding mass of pyromellitic dianhydride (PMDA) was weighed, with a molar ratio of ODA to PMDA of 1:1.05. PMDA was added to the mixture in three portions, followed by rapid and thorough stirring for 8 h. Subsequently, 1% (w / w) of calcium silicate nanoparticles were added, and the mixture was stirred for 3 h to ensure uniform mixing. After sealing and standing for 8 h, the coating film was coated using a doctor blade casting method with a coating height of 100 mm. After a period of time, the wet film was kept in a 60 °C oven for 1 h. The dry film was then subjected to thermal imidization reaction at 100 °C, 200 °C, and 300 °C for 1 h. The thickness of the film after thermal imidization was 10 ± 1 mm.

[0019] After dust removal, the PI composite film and conductive aluminum film are cut into 3 cm * 3 cm squares and 2.4 cm * 3.5 cm rectangles, respectively. The PI composite film and conductive aluminum film are then arranged according to... Figure 2 The materials are overlapped in a cross pattern, a small amount of PVA is added as an adhesive, and the mixture is hot-pressed at 80 °C for 10 min, and then kept at 80 °C for 3 h.

[0020] Next, the PI film capacitors undergo a visual inspection to ensure there are no air bubbles, misalignments, or impurities. Any excess material is trimmed off to achieve the precise dimensions required for the final product. Finally, the PI composite film capacitors will undergo a series of tests to evaluate their electrical, mechanical, and thermal properties to ensure they meet the specifications required for their intended applications.

[0021] The electrical performance of the embodiment is as follows: Example 0.0554 0.51 72.19 43.31 16.33

[0022] Regarding the structure of PI composite film capacitors Figure 2 (a) and (b) show schematic diagrams of the structure of the thin film capacitor of the present invention, which is a multilayer structure. Figure 2 (c) and (d) present physical images of the film capacitor, demonstrating its good flexibility. Figure 2 (e)-(j) present scanning electron microscope images and EDS elemental distribution maps of the PI composite film capacitor, indicating that the internal structure of this capacitor is a stacked structure of Al electrode + PI composite film. Figure 2 (k) presents a comparison of the capacitance properties of PI / CSO composite film capacitors and PI film capacitors. The relatively higher capacitance of PI / CSO composite film capacitors is due to the increase in dielectric constant. Figure 2(l) shows the overdamped charge-discharge curves of PI film capacitors in the temperature range of 25-200 °C. Figure 2 (m) gives the high-temperature pulse discharge energy storage density of the PI film capacitor.

[0023] The test results, after calculation, are summarized in the table above. The PI film capacitor prepared in this embodiment of the invention has fast charge and discharge capability. t 0.9 = 0.0554 ms), high energy storage density ( W d = 0.51 J / cm 3 ), high current density ( C D = 72.19 A / cm 2 High power density P D = 43.31 MW / cm 3 Moreover, it exhibits good high-temperature stability, with current density and power density changing by only ±5.4% within a temperature range of 25-200 °C. Furthermore, it boasts high capacitance, with the PI composite film capacitor exhibiting a capacitance of 16.33 nF, representing a 26.4% improvement compared to the PI film capacitor.

[0024] While specific embodiments have been described, it should be understood that the present invention is more flexible and adaptable. Any modifications, equivalent changes, or improvements made based on the core technology of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-temperature resistant flexible film capacitor, comprising the following steps: (1) Raw material mixing: First, calcium silicate nanoparticles were prepared by sol-gel method, and the product was obtained after reaction, centrifugation and washing with ethanol; Subsequently, 4,4'-diaminodiphenyl ether (ODA) was dissolved in N,N-dimethylacetamide (DMAc), and pyromellitic dianhydride (PMDA) was added at a certain molar ratio for polymerization. Then, calcium silicate nanoparticles were added and thoroughly mixed. After stirring, the mixture was sealed and allowed to stand to obtain a calcium silicate / polyamic acid composite system; (2) Casting: The mixed solution was then cast onto a substrate, and a thin and uniform film was formed using a scraping technique; (3) Baking: After casting, the film was heated in a controlled environment to initiate a chemical reaction that converts polyamic acid into polyimide; (4) Cutting: The film and conductive aluminum film were cut into the required size and shape using die cutting; (5) Lamination: Individual films were stacked to the required thickness; (6) Electrode embedding: Electrodes were embedded into the film during the stacking process; (7) Hot pressing: The films were stacked, and heat and pressure were applied to bond the layers together and ensure good electrical contact of the electrodes; (8) Baking: A second baking is performed to further cure the components and ensure that the adhesives used in the stacking and embedding process have cured; (9) Trimming: Any excess material is trimmed off to achieve the precise dimensions required for the final product; (10) Testing: Finally, the electrical and thermal properties of the capacitor are evaluated to ensure that it meets the specifications required for the intended application.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride is 1:1.

05.

3. The preparation method according to claim 1, characterized in that, In step (2), the height of the coating applicator is controlled to be 100 μm, and the coating is applied using a doctor blade casting method.

4. The preparation method according to claim 1, characterized in that, In step (3), the heating conditions are 100°C, 200°C, and 300°C for 1 hour each.

5. The preparation method according to claim 1, characterized in that, In step (4), after dust removal, the film and the conductive aluminum film are cut into sizes of 3 cm x 3 cm and 2.4 cm x 3.5 cm, respectively.

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