High-temperature-resistant and high-voltage-resistant thin film capacitor

Abstract

The invention relates to a high-temperature-resistant and high-voltage-resistant film capacitor which comprises a capacitor shell, a capacitor core located in the capacitor shell and an epoxy resin packaging layer used for completely wrapping the capacitor core, the epoxy resin packaging layer is doped with insulating heat-conducting filler, and the insulating heat-conducting filler is an AlN (at) g-C3N4 composite material. According to the high-temperature-resistant and high-voltage-resistant thin film capacitor disclosed by the invention, the epoxy resin glue in the existing thin film capacitor is optimally designed, and the AlN-coated g-C3N4 composite material is doped into the epoxy resin glue, so that the heat conductivity coefficient of the epoxy resin packaging layer is remarkably improved, and the high-temperature-resistant and high-voltage-resistant thin film capacitor is high-temperature-resistant and high-voltage-resistant; alN and g-C3N4 react under a liquid-electric effect to generate a composite material, so that the defects that the existing AlN is easy to agglomerate and non-uniformly distributed and the heat-conducting property is reduced after the AlN absorbs moisture in epoxy resin are overcome.

Description

Technical Field

[0001] The invention relates to a high temperature and high voltage resistant film capacitor, belonging to the technical field of capacitors. Background Art

[0002] Film capacitors are also called plastic film capacitors, which use plastic film as dielectric.

[0003] The structure of an existing film capacitor generally includes a capacitor case, a film capacitor core located inside the capacitor case, a capacitor end cover used to encapsulate the capacitor case, and pins installed on the capacitor end cover. One end of the capacitor case is open and the other end is closed. The pins are electrically connected to the film capacitor core. The inside of the capacitor case is filled with liquid epoxy resin glue that completely wraps the film capacitor core. After the liquid epoxy resin glue is cured, an insulating packaging layer that completely wraps the film capacitor core is formed.

[0004] In order to improve the heat dissipation of the capacitor itself and enable it to operate at high temperatures for a long time, it is usually necessary to improve the thermal conductivity of the epoxy resin glue. Otherwise, it is easy to cause large-scale breakdown due to excessive temperature inside the capacitor due to poor heat dissipation.

[0005] At present, the technology commonly used to improve the thermal conductivity of epoxy resin glue is to add thermal conductive fillers, such as alumina, aluminum nitride and other high thermal conductivity fillers, into the epoxy resin glue. Among them, the thermal conductivity of aluminum nitride AlN is very high, but it has disadvantages. After aluminum nitride absorbs moisture, it will react with water and hydrolyze. The Al(OH)3 produced by hydrolysis will interrupt the thermal conductivity path, thereby affecting the transmission of phonons, and ultimately leading to low local thermal conductivity. Because the insulating packaging layer in the capacitor cannot exhaust all the bubbles when the epoxy resin glue is poured, and the small molecules produced after the resin is cured, the epoxy resin itself eventually has a certain moisture absorption (the water absorption rate is usually 0.5% to 1.5%); therefore, once the capacitor absorbs moisture due to aging and other reasons, it will cause the insulating packaging layer doped with aluminum nitride to have a large area of ​​reduced thermal conductivity, thereby affecting its use. In addition, even if aluminum nitride is surface treated with silane coupling agent, it cannot be guaranteed that the aluminum nitride is 100% covered. In addition, due to the self-adsorption of aluminum nitride particles, if the amount added is too large, although a higher thermal conductivity can be achieved, not only will the viscosity of the epoxy resin glue increase, it will be more difficult to discharge bubbles, and the aluminum nitride particles are very easy to agglomerate, and it is easy to cause the local thermal conductivity to be too low due to uneven distribution.

[0006] Based on this, the present invention is proposed. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention provides a high temperature and high voltage resistant film capacitor, and the specific technical solution is as follows:

[0008] A high temperature and high voltage resistant film capacitor comprises a capacitor shell, a capacitor core located inside the capacitor shell, and an epoxy resin packaging layer used to completely wrap the capacitor core, wherein the epoxy resin packaging layer is doped with an insulating thermally conductive filler, and the insulating thermally conductive filler is an AlN@g-C3N4 composite material.

[0009] As a further improvement, the epoxy resin encapsulation layer is made by curing epoxy resin glue doped with AlN@g-C3N4 composite material, and the mass fraction of AlN@g-C3N4 composite material in the epoxy resin glue doped with AlN@g-C3N4 composite material is 10-20%.

[0010] As a further improvement, the preparation method of the AlN@g-C3N4 composite material comprises the following steps:

[0011] After AlN powder, g-C3N4 powder and acetone are stirred and mixed evenly, electrodes are inserted and high-voltage pulse electricity is applied. AlN powder and g-C3N4 powder react for 2 to 3 minutes under the liquid-electric effect. After the reaction is completed, the powder is dried and ground to obtain the AlN@g-C3N4 composite material.

[0012] As a further improvement, the voltage of the high-voltage pulse electricity is 20-25 kV, the maximum energy of a single pulse is 7.5 kJ, and the frequency is 0.3-0.5 Hz.

[0013] As a further improvement, the mass ratio of the AlN powder, g-C3N4 powder and acetone is 10:2.3:(100-200).

[0014] As a further improvement, the particle size D50 of the AlN powder is 3-20 μm.

[0015] As a further improvement, AlN powder and g-C3N4 powder react for 2 to 3 minutes under the electrohydraulic effect, and after the reaction, they are dried at a temperature of 60 to 65°C.

[0016] Beneficial effects of the present invention:

[0017] The high temperature and high voltage resistant film capacitor of the present invention optimizes the design of the epoxy resin glue in the existing film capacitor and dopes the epoxy resin glue with AlN@g-C3N4 composite material, which not only significantly improves the thermal conductivity of the epoxy resin packaging layer and makes it resistant to high temperature and high voltage; AlN and g-C3N4 react under the liquid-electric effect to form a composite material, which solves the defects of the existing AlN that is easy to agglomerate and unevenly distributed, and the thermal conductivity decreases after absorbing moisture in the epoxy resin. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a real photo of the high temperature and high voltage resistant film capacitor of the present invention;

[0019] Figure 2 It is a curve chart of the change of y value and the variance value of the corresponding insulation board. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] Example 1

[0022] A high temperature and high voltage resistant film capacitor, such as Figure 1 As shown, it includes a capacitor housing, a capacitor core located inside the capacitor housing, and an epoxy resin packaging layer for completely wrapping the capacitor core, wherein the epoxy resin packaging layer is doped with an insulating thermally conductive filler, and the insulating thermally conductive filler is an AlN@g-C3N4 composite material.

[0023] The epoxy resin encapsulation layer is made by curing epoxy resin glue doped with AlN@g-C3N4 composite material, and the mass fraction of AlN@g-C3N4 composite material in the epoxy resin glue doped with AlN@g-C3N4 composite material is 17%.

[0024] The preparation method of the AlN@g-C3N4 composite material comprises the following steps:

[0025] After AlN powder, g-C3N4 powder and acetone are stirred and mixed in a mass ratio of 10:2.3:150, electrodes are inserted and high-voltage pulse electricity is applied. AlN powder and g-C3N4 powder react for 3 minutes under the liquid-electric effect. After the reaction is completed, they are dried at 65°C and ground to obtain the AlN@g-C3N4 composite material. The particle size D50 of the AlN powder is 3 to 20 μm; the voltage of the high-voltage pulse electricity is 25 kV, the maximum energy of a single pulse is 7.5 kJ, and the frequency is 0.5 Hz.

[0026] The high temperature and high voltage resistant film capacitor can work continuously for 36 hours at a high temperature of 70°C without breakdown; at room temperature, the breakdown voltage is 2200V (breakdown occurs only when the voltage reaches 2200V).

[0027] Example 2

[0028] A high temperature and high voltage resistant film capacitor comprises a capacitor shell, a capacitor core located inside the capacitor shell, and an epoxy resin packaging layer used to completely wrap the capacitor core, wherein the epoxy resin packaging layer is doped with an insulating thermally conductive filler, and the insulating thermally conductive filler is an AlN@g-C3N4 composite material.

[0029] The epoxy resin encapsulation layer is made by curing epoxy resin glue doped with AlN@g-C3N4 composite material, and the mass fraction of AlN@g-C3N4 composite material in the epoxy resin glue doped with AlN@g-C3N4 composite material is 10%.

[0030] The preparation method of the AlN@g-C3N4 composite material comprises the following steps:

[0031] After AlN powder, g-C3N4 powder and acetone are stirred and mixed in a mass ratio of 10:2.3:100, electrodes are inserted and high-voltage pulse electricity is applied. AlN powder and g-C3N4 powder react for 2 minutes under the liquid-electric effect. After the reaction is completed, they are dried at 60°C and ground to obtain the AlN@g-C3N4 composite material. The particle size D50 of the AlN powder is 3 to 20 μm; the voltage of the high-voltage pulse electricity is 20 kV, the maximum energy of a single pulse is 7.5 kJ, and the frequency is 0.3 Hz.

[0032] The high temperature and high voltage resistant film capacitor can work continuously for 36 hours at a high temperature of 70°C without breakdown; at room temperature, the breakdown voltage is 2200V.

[0033] Example 3

[0034] A high temperature and high voltage resistant film capacitor comprises a capacitor shell, a capacitor core located inside the capacitor shell, and an epoxy resin packaging layer used to completely wrap the capacitor core, wherein the epoxy resin packaging layer is doped with an insulating thermally conductive filler, and the insulating thermally conductive filler is an AlN@g-C3N4 composite material.

[0035] The epoxy resin encapsulation layer is made by curing epoxy resin glue doped with AlN@g-C3N4 composite material, and the mass fraction of AlN@g-C3N4 composite material in the epoxy resin glue doped with AlN@g-C3N4 composite material is 20%.

[0036] The preparation method of the AlN@g-C3N4 composite material comprises the following steps:

[0037] After AlN powder, g-C3N4 powder and acetone are stirred and mixed in a mass ratio of 10:2.3:200, electrodes are inserted and high-voltage pulse electricity is applied. AlN powder and g-C3N4 powder react for 3 minutes under the liquid-electric effect. After the reaction is completed, they are dried at 65°C and ground to obtain the AlN@g-C3N4 composite material. The particle size D50 of the AlN powder is 3 to 20 μm; the voltage of the high-voltage pulse electricity is 25 kV, the maximum energy of a single pulse is 7.5 kJ, and the frequency is 0.5 Hz.

[0038] The high temperature and high voltage resistant film capacitor can work continuously for 36 hours at a high temperature of 70°C without breakdown; at room temperature, the breakdown voltage is 2200V.

[0039] Comparative Example 1

[0040] The difference between this example and Example 1 is that in this example, the insulating thermal conductive filler is AlN, and the rest remains unchanged.

[0041] Comparative Example 2

[0042] The difference between this example and Example 1 is that in this example, the insulating thermal conductive filler is a mixture of AlN and g-C3N4, and the rest remain unchanged. The mixture of AlN and g-C3N4 refers to the mixture of AlN powder and g-C3N4 powder in a mass ratio of 10:2.3 after being stirred and evenly mixed.

[0043] Comparative Example 3

[0044] The difference between this example and Example 1 is that in this example, the insulating thermal conductive filler is AlN and g-C3N4 ultrasonic dispersion material, and the rest remains unchanged. AlN powder, g-C3N4 powder and acetone are stirred and mixed in a mass ratio of 10:2.3:150, and then ultrasonically treated at an ultrasonic frequency of 20 kHz for 10 minutes. After the dispersion is completed, the mixture is dried at 60°C and ground to obtain AlN and g-C3N4 ultrasonic dispersion material.

[0045] 《Thermal conductivity characterization test》

[0046] 1. Test the thermal conductivity of the epoxy resin encapsulation layer according to ASTM D7984 standard; measure 5 times and take the average value to obtain the thermal conductivity X1 of the encapsulation layer.

[0047] 2. Make an insulating board (1m×0.6m×3mm) with epoxy resin glue or epoxy resin glue doped with insulating thermal conductive fillers, randomly sample 20 locations, test the thermal conductivity according to ASTM D7984 standard, and calculate the mean X2 and variance value.

[0048] 3. Soak the above insulation board in distilled water for 2 hours, take it out, dry it, randomly sample 20 places, test the thermal conductivity according to ASTMD7984 standard, and take the average value X3.

[0049] The test results of Example 1 and Comparative Examples 1 to 3 are shown in Table 1:

[0050] Table 1

[0051]

[0052] From the above, it can be seen that, compared with conventional stirring mixing and ultrasonic dispersion mixing, the reaction based on the hydroelectric effect enables AlN powder and g-C3N4 powder to be fully combined to finally form a coating material; the AlN@g-C3N4 composite material is not easy to form agglomeration, is evenly dispersed in the epoxy resin glue, has a small variance value of the thermal conductivity, and the thermal conductivity decrease rate after moisture absorption does not exceed 5%; the present invention solves the defect that the thermal conductivity of the existing AlN decreases after moisture absorption in the epoxy resin by compounding the AlN powder and the g-C3N4 powder under the hydroelectric effect.

[0053] Comparative Example 4

[0054] In Example 1, the mass ratio of the AlN powder to the g-C3N4 powder is 10:y, and y varies in the range of 2 to 3. The variance change curve of the corresponding insulating board is shown in FIG. Figure 2 .

[0055] As y increases, the variance of the thermal conductivity first decreases and then increases. The reason is that when there is too much g-C3N4 powder, some local thermal conduction pathways will be interrupted, which will affect the transmission of phonons and ultimately lead to low local thermal conductivity.

[0056] Finally, y is preferably 2.3.

[0057] In the above embodiment, the epoxy resin glue is Nan Ya epoxy resin NPEL-128. g-C3N4 is a graphite-like carbon nitride, which is a polymer semiconductor.

[0058] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high temperature and high voltage resistant film capacitor, comprising a capacitor housing, a capacitor core located inside the capacitor housing, and an epoxy resin encapsulation layer for completely encapsulating the capacitor core, characterized in that: The epoxy resin packaging layer is doped with an insulating thermally conductive filler, and the insulating thermally conductive filler is an AlN@g-C3N4 composite material.

2. The high temperature and high voltage resistant film capacitor according to claim 1, characterized in that: The epoxy resin encapsulation layer is made by curing epoxy resin glue doped with AlN@g-C3N4 composite material, and the mass fraction of AlN@g-C3N4 composite material in the epoxy resin glue doped with AlN@g-C3N4 composite material is 10-20%.

3. The high temperature and high voltage resistant film capacitor according to claim 1, characterized in that: The preparation method of the AlN@g-C3N4 composite material comprises the following steps: After AlN powder, g-C3N4 powder and acetone are stirred and mixed evenly, electrodes are inserted and high-voltage pulse electricity is applied. AlN powder and g-C3N4 powder react for 2 to 3 minutes under the liquid-electric effect. After the reaction is completed, the powder is dried and ground to obtain the AlN@g-C3N4 composite material.

4. The high temperature and high voltage resistant film capacitor according to claim 3, characterized in that: The voltage of the high-voltage pulse electricity is 20-25 kV, the maximum energy of a single pulse is 7.5 kJ, and the frequency is 0.3-0.5 Hz.

5. The high temperature and high voltage resistant film capacitor according to claim 3, characterized in that: The mass ratio of the AlN powder, g-C3N4 powder and acetone is 10:2.3:(100-200).

6. The high temperature and high voltage resistant film capacitor according to claim 3, characterized in that: The particle size D50 of the AlN powder is 3 to 20 μm.

7. The high temperature and high voltage resistant film capacitor according to claim 3, characterized in that: The AlN powder and g-C3N4 powder react for 2 to 3 minutes under the hydroelectric effect. After the reaction, they are dried at 60 to 65°C.

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