High-humidity-resistant and large-current-resistant thin film capacitor

Abstract

The invention relates to a high-humidity-resistant and large-current-resistant thin-film capacitor which comprises a capacitor shell, a thin-film capacitor core, a capacitor end cover and pins, a resin injection hole is formed in the center of the capacitor end cover, and the capacitor shell is filled with a compact epoxy resin layer which completely wraps the thin-film capacitor core. An epoxy resin layer is further filled between the capacitor end cover and the compact epoxy resin layer, and megasonic vibration is applied to a liquid epoxy resin adhesive and negative pressure air exhaust is carried out in the process that the liquid epoxy resin adhesive is cured into a solid epoxy resin adhesive by the compact epoxy resin layer. The high-humidity-resistant and high-current-resistant thin film capacitor still has excellent high-current resistance even in a high-humidity environment, and the compact epoxy resin layer for packaging is compact in structure, low in internal bubble content, good in insulativity and high in compression strength.

Description

Technical Field

[0001] The invention relates to a high-humidity and high-current 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 housing, a film capacitor core located inside the capacitor housing, a capacitor end cover used to encapsulate the capacitor housing, and pins installed on the capacitor end cover. One end of the capacitor housing is open and the other end is closed. The pins are electrically connected to the film capacitor core. A resin injection hole is provided in the center of the capacitor end cover. Liquid epoxy resin adhesive that completely wraps the film capacitor core is filled into the capacitor housing through the resin injection hole. After the liquid epoxy resin adhesive is cured, an insulating packaging layer that completely wraps the film capacitor core is formed.

[0004] However, as the capacity requirements of film capacitors for energy storage become larger and larger, especially in the field of new energy vehicles, film capacitors that are resistant to high humidity and high current are needed; and the curing of epoxy resin adhesives used in existing capacitors is room temperature curing. After curing, epoxy resin is not absolutely waterproof and has certain water absorption and permeability; in addition, the liquid epoxy resin adhesive that completely wraps the film capacitor core will inevitably produce bubbles. Even if it is left to stand for 1-2 days, the bubbles cannot be emptied at all due to the certain viscosity of the epoxy resin. These all lead to the limited resistance of the cured insulating layer to high humidity and high current, which significantly affects the service life of the film capacitor.

[0005] Based on this, the present invention is proposed. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a high-humidity and high-current resistant film capacitor, and the specific technical solution is as follows:

[0007] A high-humidity and high-current resistant film capacitor, comprising a capacitor housing, a film capacitor core located inside the capacitor housing, a capacitor end cap used to encapsulate the capacitor housing, and pins installed on the capacitor end caps, wherein one end of the capacitor housing is open and the other end is closed, the pins are electrically connected to the film capacitor core, a resin injection hole is provided at the center of the capacitor end cap, the capacitor housing is filled with a dense epoxy resin layer that completely wraps the film capacitor core, an epoxy resin layer is also filled between the capacitor end cap and the dense epoxy resin layer, and the dense epoxy resin layer and the epoxy resin layer are both made of cured epoxy resin adhesive;

[0008] During the process of curing the liquid epoxy resin adhesive into a solid epoxy resin adhesive, the dense epoxy resin layer applies megasonic vibration to the liquid epoxy resin adhesive and performs negative pressure exhaust.

[0009] As a further improvement, a first threaded column is fixedly connected to the outside of the bottom of the capacitor housing.

[0010] A further improvement is that a megasonic vibration table is used to apply megasonic vibration to the liquid epoxy resin adhesive. The megasonic vibration table includes a metal table top, the surface of the metal table top is provided with a plurality of mounting holes adapted to the first threaded column, the capacitor housing is located above the metal table top, and a locking nut matching the first threaded column is provided below the metal table top; a plurality of megasonic vibrators distributed in an array are fixedly mounted on the lower surface of the metal table top.

[0011] As a further improvement, a hot melt adhesive layer is provided between the film capacitor core and the bottom of the capacitor shell, and the hot melt adhesive layer is made of hot melt adhesive.

[0012] A further improvement is that a negative pressure exhaust sleeve is used to negatively exhaust the liquid epoxy resin adhesive. The negative pressure exhaust sleeve includes a sleeve that is sleeved on the outside of the open end of the capacitor housing, one end of the sleeve is open and the other end is closed, the open end of the sleeve is sealed to the open end of the capacitor housing, and a one-way valve connected to the inner cavity of the sleeve is embedded in the center of the closed end of the sleeve.

[0013] As a further improvement, the initial air pressure in the sleeve is 70,000 to 80,000 Pa.

[0014] As a further improvement, the megasonic vibrator vibrates intermittently, with a vibration time of 5 to 10 minutes per hour; and the megasonic frequency of the megasonic vibrator is 0.87 MHz.

[0015] As a further improvement, the power of the megasonic vibrator varies every minute and changes in a sharp pulse shape within a range of 20 to 50W.

[0016] As a further improvement, table legs are respectively installed on both sides of the metal table top.

[0017] As a further improvement, a plurality of reinforcing ribs are arranged on the outer side of the capacitor end cover, and the intersection of the reinforcing ribs is located at the resin injection hole.

[0018] Beneficial effects of the present invention:

[0019] The high-humidity and high-current resistant film capacitor of the present invention still has excellent high-current resistance performance even in a high-humidity environment. The dense epoxy resin layer used for packaging has a dense structure, less internal air bubbles, good insulation and high compressive strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the high-humidity and high-current resistant film capacitor of the present invention;

[0021] Figure 2 A schematic top view of the capacitor end cover of the present invention;

[0022] Figure 3 is a schematic diagram of the interior of the capacitor housing of the present invention;

[0023] Figure 4 It is a schematic diagram of the connection between the megasonic vibration table, the capacitor housing and the negative pressure exhaust sleeve of the present invention;

[0024] Figure 5 This is a photo of the actual packaging of the high-humidity and high-current resistant film capacitor of the present invention;

[0025] Figure 6 This is a real photo of the high-humidity and high-current resistant film capacitor described in the present invention. DETAILED DESCRIPTION

[0026] 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.

[0027] Example 1

[0028] like Figures 1 to 3 As shown, the high-humidity and high-current resistant film capacitor includes a capacitor housing 10, a film capacitor core 30 located inside the capacitor housing 10, a capacitor end cover 20 used to encapsulate the capacitor housing 10, and a pin 40 installed on the capacitor end cover 20. One end of the capacitor housing 10 is open and the other end is closed. The pin 40 is electrically connected to the film capacitor core 30. A resin injection hole 21 is provided in the center of the capacitor end cover 20. A first threaded column 11 is fixedly connected to the outside of the shell bottom of the capacitor housing 10.

[0029] The capacitor housing 10 is filled with a dense epoxy resin layer 50 that completely wraps the film capacitor core 30 , and an epoxy resin layer 51 is also filled between the capacitor end cover 20 and the dense epoxy resin layer 50 . Both the dense epoxy resin layer 50 and the epoxy resin layer 51 are made of cured epoxy resin adhesive.

[0030] During the process of curing the liquid epoxy resin adhesive into a solid epoxy resin adhesive, the dense epoxy resin layer 50 applies megasonic vibration to the liquid epoxy resin adhesive and performs negative pressure exhaust.

[0031] That is to say, the capacitor housing 10 is first injected with an existing common liquid epoxy resin adhesive, and then megasonic vibration is applied to the liquid epoxy resin adhesive and negative pressure is evacuated, and finally the dense epoxy resin layer 50 is obtained after curing; finally, the capacitor end cover 20 is installed, and then the existing common liquid epoxy resin adhesive is injected through the resin injection hole 21. At this time, it is no longer necessary to apply megasonic vibration to the liquid epoxy resin adhesive and negative pressure evacuate, and it can be left to stand for 1 day in the existing manner. After curing, the existing conventional epoxy resin layer 51 is obtained.

[0032] The final product can be seen in the photo Figure 5 , 6 .

[0033] Example 2

[0034] like Figure 4 As shown, a megasonic vibration table is used to apply megasonic vibration to the liquid epoxy resin adhesive. The megasonic vibration table includes a metal table plate 70. The surface of the metal table plate 70 is provided with a plurality of mounting holes adapted to the first threaded column 11. The capacitor housing 10 is located above the metal table plate 70. A locking nut 12 matching the first threaded column 11 is provided below the metal table plate 70. A plurality of megasonic vibrators 72 distributed in an array are fixedly mounted on the lower surface of the metal table plate 70.

[0035] The megasonic vibrator 72 vibrates intermittently, with a vibration time of 5 to 10 minutes per hour; the megasonic frequency of the megasonic vibrator 72 is 0.87 MHz. The power of the megasonic vibrator 72 varies every minute, and changes in a sharp pulse shape within the range of 20 to 50 W. For example, the vibration time is 5 minutes per hour. In one cycle, in the first minute, the power of the megasonic vibrator 72 is 20 W, in the second minute, it is 50 W, in the third minute, it is 35 W, in the fourth minute, it is 27 W, and in the fifth minute, it is 20 W.

[0036] A negative pressure exhaust sleeve is used to negatively exhaust the liquid epoxy resin adhesive. The negative pressure exhaust sleeve includes a sleeve 20 that is sleeved on the outside of the open end of the capacitor housing 10. One end of the sleeve 20 is open and the other end is closed. The open end of the sleeve 20 is sealed to the open end of the capacitor housing 10, such as by using hot melt adhesive for sealing. After the sealing is completed, it is cut open with a knife; a one-way valve 60 connected to the inner cavity of the sleeve 20 is embedded in the center of the closed end of the sleeve 20.

[0037] The initial air pressure in the sleeve 20 is 70000-80000 Pa. The atmospheric pressure is 101325 Pa, and the sleeve 20 is under negative pressure. A vacuum pump is used to evacuate the inner cavity of the sleeve 20 through the one-way valve 60. After the evacuation is completed, the inner cavity of the sleeve 20 maintains a negative pressure due to the one-way valve 60.

[0038] In this embodiment, due to megasonic vibration + negative pressure adsorption, the bubbles in the liquid epoxy resin adhesive can be directed into the sleeve 20; in addition, the megasonic vibration can also improve the curing effect of the liquid epoxy resin adhesive, and the structure after curing is denser and the compressive strength is further improved.

[0039] Comparative Example 1

[0040] In this example, during the process of curing the dense epoxy resin layer 50 from liquid epoxy resin adhesive to solid epoxy resin adhesive, only megasonic vibration is applied to the liquid epoxy resin adhesive without negative pressure exhaust; the rest is the same as in Example 2.

[0041] Comparative Example 2

[0042] In this example, during the process of curing the dense epoxy resin layer 50 from liquid epoxy resin adhesive to solid epoxy resin adhesive, megasonic vibration is not applied to the liquid epoxy resin adhesive, and only negative pressure exhaust is performed; the rest is the same as in Example 2.

[0043] Comparative Example 3

[0044] In this example, the megasonic vibrator 72 is replaced by an ultrasonic vibrator, and the ultrasonic frequency is 20 kHz; the rest is the same as in Example 2.

[0045] Comparative Example 4

[0046] In this example, the megasonic frequency is 0.85 MHz, and the rest is the same as in Example 2.

[0047] Comparative Example 5

[0048] In this example, the megasonic frequency is 0.9 MHz, and the rest is the same as in Example 2.

[0049] Comparative Example 6

[0050] In this example, the megasonic frequency is 1 MHz, and the rest is the same as in Example 2.

[0051] Comparative Example 7

[0052] In this example, the power of the megasonic vibrator 72 varies every minute, and changes in a triangular wave shape within the range of 20 to 50 W; the rest is the same as in the second embodiment.

[0053] Comparative Example 8

[0054] In this example, the power of the megasonic vibrator 72 varies every minute, and changes in a sawtooth wave shape within the range of 20 to 50 W; the rest is the same as in the second embodiment.

[0055] Reference ratio

[0056] The film capacitor in this example is an existing film capacitor, which does not have a dense epoxy resin layer 50 , but only a conventional epoxy resin layer 51 completely wrapping the film capacitor core 30 .

[0057] 《Film capacitor high humidity and high current resistance test》

[0058] 1. Put the film capacitor into a water tank, pour distilled water into the water tank to completely submerge the film capacitor, cover the tank cover and seal it, and inject compressed air into the water tank until the air pressure in the water tank is 0.2Mpa; let it stand for 1 day, open the tank cover, take out the film capacitor, and put it into an oven to dry at 60°C for 30 minutes (at this time, if it is in a high-pressure water environment, water will enter the capacitor housing 10 through the epoxy resin layer 51 at the resin injection hole 21 in the film capacitor. If the density of the dense epoxy resin layer 50 is not enough, the dense epoxy resin layer 50 will also absorb a small amount of moisture, resulting in a decrease in the insulation of the device. At this time, it is impossible to dry the moisture in the dense epoxy resin layer 50 by relying solely on low-temperature baking at 60°C. It must be baked for at least more than 12 hours to be effective); then, take it out and test whether it breaks down at different current values.

[0059] 2. After the test is completed, the capacitor housing 10 is peeled off, the dense epoxy resin layer 50 is taken out, and its compressive strength is measured.

[0060] The test results of Example 2, Comparative Examples 1-8 and Reference Examples are shown in Table 1:

[0061] Table 1

[0062]

[0063]

[0064] In Comparative Examples 7 and 8, the different degrees of power change mainly affect the duration of megasonic vibration. In Comparative Examples 7 and 8, the vibration duration per hour needs to reach more than 20 minutes to increase the breakdown current value to nearly 610 mA; while in Comparative Examples 3 to 6, even if the vibration duration per hour reaches 60 minutes, the breakdown current value will not increase.

[0065] In addition, the breakdown current value of the film capacitor in Example 1 in the initial state (not immersed in a water tank) is 650 mA, while the breakdown current value of the film capacitor in the reference example in the initial state (not immersed in a water tank) is 600 mA.

[0066] Example 3

[0067] In Example 2, in order to ensure that the film capacitor core 30 always maintains a central position during vibration, a hot melt adhesive layer 31 is provided between the film capacitor core 30 and the bottom of the capacitor housing 10, and the hot melt adhesive layer 31 is made of hot melt adhesive.

[0068] The hot melt adhesive layer 31 is first used for fixing and positioning, and then the liquid epoxy resin adhesive is filled.

[0069] Example 4

[0070] For easy installation, table legs 71 are respectively installed on both sides of the metal table top 70.

[0071] Example 5

[0072] To improve the strength of the capacitor end cover 20 itself, in some embodiments, to ensure the connection strength between the epoxy resin layer 51 and the capacitor end cover 20 , a plurality of reinforcing ribs 22 are provided on the outer side of the capacitor end cover 20 , and the intersection of the reinforcing ribs 22 is located at the resin injection hole 21 .

[0073] 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-humidity and high-current resistant film capacitor, comprising a capacitor housing (10), a film capacitor core (30) located inside the capacitor housing (10), a capacitor end cover (20) used to encapsulate the capacitor housing (10), and a pin (40) mounted on the capacitor end cover (20), wherein one end of the capacitor housing (10) is open and the other end is closed, the pin (40) is electrically connected to the film capacitor core (30), and a resin injection hole (21) is provided in the center of the capacitor end cover (20), characterized in that: The capacitor housing (10) is filled with a dense epoxy resin layer (50) that completely wraps the film capacitor core (30), and an epoxy resin layer (51) is also filled between the capacitor end cover (20) and the dense epoxy resin layer (50), and both the dense epoxy resin layer (50) and the epoxy resin layer (51) are made of epoxy resin adhesive after curing; During the process of curing the liquid epoxy resin adhesive into a solid epoxy resin adhesive, the dense epoxy resin layer (50) applies megasonic vibration to the liquid epoxy resin adhesive and performs negative pressure exhaust.

2. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A first threaded column (11) is fixedly connected to the outside of the bottom of the capacitor housing (10).

3. The high-humidity and high-current resistant film capacitor according to claim 2, characterized in that: A megasonic vibration table is used to apply megasonic vibration to liquid epoxy resin adhesive, the megasonic vibration table comprising a metal table top (70), the plate surface of the metal table top (70) being provided with a plurality of mounting holes matched with the first threaded column (11), the capacitor housing (10) being located above the metal table top (70), and a locking nut (12) matching with the first threaded column (11) being provided below the metal table top (70); a plurality of megasonic vibrators (72) distributed in an array are fixedly mounted on the lower surface of the metal table top (70).

4. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A hot melt adhesive layer (31) is provided between the film capacitor core (30) and the shell bottom of the capacitor shell (10), and the hot melt adhesive layer (31) is made of hot melt adhesive.

5. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A negative pressure exhaust sleeve is used to exhaust liquid epoxy resin adhesive under negative pressure. The negative pressure exhaust sleeve comprises a sleeve (20) which is sleeved on the outside of an open end of a capacitor housing (10). One end of the sleeve (20) is open and the other end is closed. The open end of the sleeve (20) is sealed to the open end of the capacitor housing (10). A one-way valve (60) which is in communication with the inner cavity of the sleeve (20) is embedded in the center of the closed end of the sleeve (20).

6. The high-humidity and high-current resistant film capacitor according to claim 5, characterized in that: The initial air pressure in the sleeve (20) is 70,000-80,000 Pa.

7. The high-humidity and high-current resistant film capacitor according to claim 3, characterized in that: The megasonic vibrator (72) vibrates intermittently, with a vibration time of 5 to 10 minutes per hour; the megasonic frequency of the megasonic vibrator (72) is 0.87 MHz.

8. The high-humidity and high-current resistant film capacitor according to claim 7, characterized in that: The power of the megasonic vibrator (72) varies every minute and changes in a sharp pulse shape within a range of 20 to 50 W.

9. The high-humidity and high-current resistant film capacitor according to claim 3, characterized in that: Table legs (71) are respectively installed on both sides of the metal table top (70).

10. The high-humidity and high-current resistant film capacitor according to claim 1, characterized in that: A plurality of reinforcing ribs (22) are arranged on the outer side of the capacitor end cover (20), and the intersection of the reinforcing ribs (22) is located at the resin injection hole (21).

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