JPH09162062A - Metallized film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallized film capacitor which can effectively suppress the heat deterioration of a dielectric film caused by corona discharge between an external metallicon electrode and a vapor-deposited metal. SOLUTION: A metallized film capacitor is manufactured by forming a capacitor element 16 by winding a pair of metallized films 14 formed on the surface of a dielectric film 12 except a margin section 24 by vapor deposition around the dielectric film 12 and external electrodes 18 by melt-spraying a metallic material upon both end faces of the element 16. Each metallized film 14 is provided with a thin film section 26 which is grown by using metallic particles as nuclei and an ungrown thin film section 28 to which metallic particles are attracted by an electrostatic interaction, such as the van del Waals force, etc., and the section 28 is formed so that one end 28a side of the section 28 can be brought into contact with the margin section 24 and the other end 28b side with the section 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallized film capacitor, and more particularly, to a corona discharge generated between a metallized film vapor-deposited metal and a metallikon external electrode.
The present invention relates to a metallized film capacitor in which measures are taken to suppress thermal deterioration of a dielectric film.

[0002]

2. Description of the Related Art A conventional metallized film capacitor is a metallized film in which an electrode film made of aluminum, zinc, or the like is applied to the surface of a dielectric film made of polypropylene, polyethylene, or the like to a thickness of 10 nm to 80 nm. After stacking, wind with a winder to fix the end part,
This is subjected to heat and pressure treatment to form a capacitor element, and a metal material is sprayed on both end surfaces of the capacitor element to form external electrodes (metallikon electrodes) for connecting lead terminals. On the surface of the dielectric film, a margin portion (that is, a portion not covered with the electrode film) is secured with a predetermined width along one side. Further, a similar margin portion is secured on the surface of the other dielectric film along the side opposite to the above.

FIG. 15 is a cross-sectional view showing the internal structure of the metallized film capacitor 70 obtained as described above, in which the electrode films 72 are opposed to each other with the dielectric film 12 interposed therebetween. It is drawn that it is. Further, one end portions 72a of the laminated electrode films 72 are alternately connected to the left and right external electrodes 18, respectively. Further, the other end portion 72b of each electrode film 72 (the margin portion of the dielectric film 12 is
A space 32 is formed between the end portion (on the side in contact with 24) and either the left or right external electrode 18.

[0004]

By the way, each electrode film 72
The gap 32 formed between the end 72b of the
Originally, a sufficient width corresponding to the margin portion 24 should be ensured, but actually, when the external electrode 18 is formed, the molten metallikon enters the void 32,
The width will be considerably narrowed. Moreover, the surface of the metallikon that has entered has a non-uniform shape and a sharp portion is generated, so that the electric field is concentrated there, and a creeping corona discharge is generated between the external electrode 18 and the end 72b of the electrode film 72 at a relatively low voltage. Is generated. This creeping corona discharge eventually shifts to a space discharge in the air gap 32, and the heat energy of the corona discharge heats the electrode film 72, and the dielectric film 12 is thermally deteriorated, which causes dielectric breakdown in extreme cases. The electrode films 72 disposed above and below the dielectric film 12,
72 will be short-circuited.

Originally, a metallized film capacitor has a self-healing property that immediately recovers the insulating property even if a short circuit occurs between electrode films due to partial dielectric breakdown in the dielectric film. In a situation where corona discharge frequently occurs, the number of occurrences of partial dielectric breakdown also increases, the capacitance of the dielectric film fluctuates, and the final thermal breakdown occurs. Particularly, in the case of a capacitor for preventing electromagnetic interference of a power source, AC1000 is required when the rated voltage is 250 [V].
A withstand voltage of [V] or higher is required, but if such a high voltage is continuously applied, corona discharge occurs at a very high frequency, so it is essential to take some measure against heat. . Also, even if the capacitor is not a capacitor for preventing electromagnetic interference of the power supply, the film capacitor generally has various safety standards set in consideration of product safety. For example, in a withstand voltage test of a certain safety standard, a test voltage of 1500 Vrms is used. Dielectric breakdown does not occur even if applied for 60 seconds,
Since it is required that the insulation resistance, capacitance, or dielectric loss tangent be kept within the standard tolerance, it is necessary to minimize the thermal deterioration of the dielectric film due to corona discharge.

Therefore, the dielectric film is made thick to improve the heat resistance, the margin width is set to be large to suppress the occurrence of corona discharge, the metallized film is wound tightly to prevent the infiltration of the metallikon, the silicon-based material. The above-mentioned measures have been taken such as vacuum impregnation of the oil from both end surfaces of the capacitor element to remove the above-mentioned void as a discharge space.

[0007] However, there is a drawback in that the above-mentioned and (2) lead to an increase in size and cost of the element, or inferior in effectiveness. In this case, the performance can be almost satisfactory, but the impregnation process itself requires a lot of work and the wiping process after impregnation is indispensable. I had a problem with. There was also a risk that the impregnating agent would leak out during use.

The present invention has been devised in order to solve the above-mentioned problems of the conventional example, and it is possible to provide an external electrode made of metallikon without enlarging the element, increasing the cost, and complicating the process. It is possible to effectively suppress the thermal deterioration of the dielectric film due to corona discharge between the vapor-deposited metal,
The objective is to realize a metallized film capacitor with long life and high reliability.

[0009]

To achieve the above object, in a metallized film capacitor according to the present invention, a margin portion is formed on each surface of a pair of dielectric films along one side. As described above, a metal material is vapor-deposited to form a metallized film, both metallized films are laminated so that their respective margins are arranged on opposite sides, and this is wound to form a capacitor element, and the capacitor is formed. In a metallized film capacitor formed by spraying a metal material on both end surfaces of an element to form an external electrode, the metallized film includes a thin film growth portion in which metal particles are thinned by nuclear growth and metal particles are electrostatically charged. A thin film ungrown portion adsorbed by dynamic interaction, one end side of the thin film ungrown portion contacts the margin portion, and the other end side contacts the thin film grown portion. The features. It is desirable that an insulating oxide film be formed on the surface of the thin film ungrown portion.

Since the thin film ungrown portion is interposed between the thin film grown portion corresponding to the original electrode film and the margin portion, the dielectric film is formed by corona discharge between the external electrode and the vapor-deposited metal. Can be effectively prevented from being thermally deteriorated. That is, the conventional metallized film has an electrode film that is sufficiently thin-film-grown (nucleus-grown) up to the boundary with the margin part by the vacuum deposition method, and the metal particles are substantially uniformly aligned on the end surface. It had a relatively smooth surface. Therefore, when corona discharge is generated between the external electrode and the end portion of the electrode film, a portion of the end surface where electric field is relatively likely to be concentrated (such as a scratch portion accidentally generated during the film formation process or As a result of concentrated discharge being generated at locations where metal particles are non-uniformly arranged, thermal shock due to corona discharge is also concentrated at limited locations on the dielectric film, and the extent of damage is correspondingly increased. It was Further, in the metal film, since the metal particles are extremely densely and firmly bonded to each other, when the electrons or ions accelerated by the discharge collide with the metal particles, the impact is not widely dispersed, There was a tendency to concentrate in a relatively narrow range. Further, the corona discharge tends to be repeatedly generated at the location where the corona discharge has once been generated, and the dielectric film near the location is additionally damaged.
Moreover, since a hollow is formed at the discharge location due to the impact of the discharge, the hollow cathode effect is generated, the duration of the discharge is extended, and the damage given to the dielectric film is further promoted.

On the other hand, in the present invention, in the above-mentioned thin film growth portion, like the conventional electrode film, the metal particles are arranged relatively uniformly and regularly, and the original function of the capacitor electrode is sufficiently exhibited. What is obtained is that the metal particles are arranged in a concave-convex manner on the tip portion and the surface of the ungrown portion of the thin film. Therefore, corona discharge is also generated in a distributed manner at the same time in a large number of locations in the thin film ungrown portion and the external electrodes, and large discharge energy is not locally applied.
As a result, thermal shock due to corona discharge is also dispersed in a relatively wide area of the dielectric film, and it is possible to effectively avoid a large damage to a specific area.

Moreover, the metal particles in the ungrown portion of the thin film have a van der Waals force (van der force), which is an extremely weak interparticle bonding force as compared with the bonding force between the film-grown metal particles.
Since they are bound by electrostatic interaction such as Waals force), when the electrons or ions accelerated by the corona discharge force collide with a metal particle, the metal particle causes elastic or inelastic scattering. And scattered,
The metal particles collide with other metal particles in a chain manner, and the impact of the collision is spread over a relatively wide range within a short time. As a result, even if the total amount of heat energy due to the discharge does not change, it is possible to avoid intensively adding heat to a narrow portion of the dielectric film.

Further, once a corona discharge is generated at a portion of the thin film ungrown portion, the heat energy of the discharge causes the metal particles to be fused to each other, and the portion becomes relatively rounded and uneven. Since the electric field is less likely to be concentrated than other portions, the probability that the next corona discharge will be generated at that location is low. As a result, it is possible to prevent electric discharge from being repeatedly generated in a limited narrow place and to locally damage the dielectric film.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIGS. 1 and 2, a metallized film capacitor 10 according to the present invention has a dielectric film 12 made of polypropylene, polyethylene or the like on the surface of which a metal material such as aluminum or zinc is used. After laminating a pair of metallized films 14 formed by vapor-depositing (FIG. 1), they were wound by a winder (not shown) to fix the terminal end, and subjected to heat and pressure treatment to be flattened. The capacitor element 16 is formed, and a metallikon for spraying a metallic material such as copper or solder is applied to both end surfaces of the capacitor element 16 to form the external electrodes 18 (FIG. 2). Each external electrode 18
A lead terminal 22 is connected to each of them via a solder 20. Although not shown in the drawings, it is desirable that the surface of the metallized film capacitor 10 be provided with a suitable insulating exterior such as a resin mold.

As shown in FIG. 1, on the surface of the metallized film 14, there is provided a margin portion 24 having a predetermined width (for example, 2 m) along which the metal material is not deposited along the opposite sides.
m). Further, as shown in FIG. 3, the portion where the metal material is vapor-deposited is formed by the thin film growth portion 26 in which the metal particles are thinned by the nucleus growth and the metal particles by electrostatic interaction such as van der Waals force. It is composed of a thin film ungrown portion 28 that has just been adsorbed and has not grown. One end 28a of the thin film ungrown portion 28 is in contact with the margin portion 24, and the other end 28b is in contact with the end portion of the thin film grown portion 26. The thin film ungrown portion 28 is formed with a predetermined width (for example, 0.3 mm to 0.1 mm) along the margin portion 24. Further, the thin film ungrown portion 28 does not have a uniform thickness over the entire area, and as shown in FIG.
The thickness is gradually increased from the boundary with 24 to the boundary with the thin film growth portion 26.

The thin film growth portion 26 is formed as follows, for example. First, a vacuum chamber (not shown) (degree of vacuum:
The dielectric film 12 is placed in about 10 ⁻⁴ Torr), and the molten metal tank containing the molten metal material is placed below the dielectric film 12. When the metal particles leaving the molten metal tank reach the surface of the dielectric film 12, they are trapped in a more easily trapped location on the surface (trap center, that is, an atomic size dent, a corner, a step, etc.) to form a nucleus. Form. These nuclei grow by being combined with the next arriving metal particles and some or all of the adjacent nuclei, and become stable at a certain critical value or higher (this is called a “stable nucleus”). Then, a large number of stable nuclei are formed on the surface of the dielectric film 12, contact with each other, and coalesce into an island structure (island stage), the islands are connected to leave a strait (channel stage), and the strait is shrunk into a hole. After going through a hole stage, it finally becomes a uniform continuous body and constitutes the thin film growth portion 26.

On the other hand, if the deposition of the metal particles is stopped before the thin film is formed, the thin film ungrown portion 28
Can be formed. For example, as shown in FIGS. 5 to 8, after covering the right end of the surface (lower surface) of the dielectric film 12 with the mask tape 30, the metal vapor α is guided to the surface of the dielectric film 12 from below in the figure, If the mask tape 30 is shifted to the right with the lapse of time, the portion not covered with the mask tape 30 from the beginning will be exposed to the metal vapor for a sufficiently long time, and the thin film growth portion 26 will be formed. (FIG. 8). Further, no metal particles can reach the portion covered with the mask tape 30 until the end, and this will form the margin portion 24 (FIG. 8). Further, in the newly exposed portion due to the movement of the mask tape 30, metal particles in an amount corresponding to the exposure time will be attached, but compared with the portion not covered by the mask tape 30 from the beginning Since the amount of adhered particles is small, a thin film cannot be formed, and this constitutes the thin film ungrown portion 28 (FIG. 8). Even in the same thin film ungrown portion 28, the stage of nucleus growth differs depending on the exposure time, and the portion that has been exposed the longest (that is, the portion that is in contact with the thin film grown portion 26) has relatively thick metal particles. Is attached, and it is in a state just before the thin film formation. On the other hand, the shortest exposed portion (that is, the portion in contact with the margin portion 24) is in the very early stage of nucleus growth, and the metal particles are bonded to each other by a very weak adsorption force. When the metallized film 14 thus obtained is taken out of the vacuum chamber and exposed to air, an oxide film is formed on the surface of the thin film ungrown portion 28, and particularly the surface of the portion in contact with the margin portion 24 is almost completely insulated. Turn into a thing.

FIG. 9 is a sectional view showing the internal structure of the metallized film capacitor 10 in which the thin film growth portions 26 are opposed to each other with the dielectric film 12 interposed therebetween. One ends 26a of the thin film growth portions 26 are alternately and closely connected to the left and right external electrodes 18, respectively. On the other end 26b side of the thin film growth portion 26, a gap 32 corresponding to the margin portion 24 is formed with a predetermined width.
Furthermore, the other end 26b of the thin film growth portion 26 and the margin portion 24
A thin film ungrown portion 28 is arranged at the boundary portion between the and.

As described above, since the thin film ungrown portion 28 is interposed between the thin film grown portion 26 corresponding to the original electrode film (capacitor electrode) and the margin portion 24, the dielectric is generated by the corona discharge in the gap 32. The thermal deterioration of the body film 12 can be effectively avoided, and the reason for this will be described in comparison with the conventional example. That is, as shown in FIG. 10, the conventional metallized film is formed by sufficiently growing a thin film up to the boundary with the margin portion 24 to form an electrode film 72 in which metal particles are substantially uniformly aligned. As shown in FIG. 7, the end surface 72a was also aligned substantially perpendicular to the surface of the dielectric film 12, and was a relatively smooth surface. As a result, when corona discharge X is generated between the external electrode 18 and the end surface 72a of the electrode film 72, a portion of the end surface 72a where electric field is relatively likely to be concentrated (for example, when the electrode film 72 is formed). Discharge was generated intensively in the (wound portion that was accidentally generated), and a large discharge energy tended to be locally applied. For this reason, the thermal shock due to the corona discharge X is also concentrated on the limited portion of the dielectric film 12, and the degree of damage is increased accordingly. In addition, as shown in FIG.
When 34 collide with metal particles 34 having electrons or ions 36 accelerated by electric discharge, the impacts do not spread widely, There was a tendency that a large amount of heat energy was concentrated in a relatively narrow range. Further, at the location where the corona discharge is once generated, there is a tendency that the corona discharge is repeatedly generated many times thereafter, and the dielectric film 12 in the vicinity of the location is additionally damaged. Moreover, FIG.
As shown in FIG. 3, since a hollow is generated at the discharge location due to the impact of the discharge, the hollow cathode effect is generated and the duration of the discharge is extended, and the damage given to the dielectric film 12 is further promoted.

On the other hand, according to the present invention, since the tip portion (the side in contact with the margin portion 24) and the surface of the thin film ungrown portion 28 are in a state in which the metal particles are arranged in an uneven shape, the corona The discharge X is also generated in a distributed manner at the same time in a large number of places of the thin film ungrown portion 28 and the external electrode 18 (FIG. 3), and large discharge energy is not locally applied.
As a result, the thermal shock due to corona discharge is also applied to the dielectric film 12.
Therefore, it is possible to effectively avoid a large damage to a specific place.

Moreover, since the metal particles are bonded by electrostatic interaction such as van der Waals force, which is extremely weak compared with the bonding force between the metal particles grown in the thin film, as shown in FIG. When the electrons or ions 36 accelerated by the corona discharge force collide with the metal particle 34, the metal particle 34 causes elastic scattering or inelastic scattering and scatters, and is chained to a plurality of other metal particles 34. The impact of the collision spreads in a relatively wide range within a short time. As a result, even if the total amount of heat energy due to discharge does not change, it is possible to prevent heat from being intensively applied to a narrow portion of the dielectric film 12.

Furthermore, once a corona discharge is generated at a certain location, the heat energy generated by the discharge causes the metal particles in the vicinity of the discharge location to be fused to each other, resulting in a relatively rounded state. The electric field is less likely to be concentrated than in the area. As a result, the probability that the next corona discharge will be generated at the location is reduced, and discharge is repeatedly generated in a limited narrow location, preventing the dielectric film 12 from being locally damaged. You can

As described above, when the thickness of the thin film ungrown portion 28 is configured to gradually increase from the one end 28a side in contact with the margin portion 24 to the other end 28b side in contact with the thin film growth portion 26, the thin film Compared with the case where the entire ungrown portion 28 is formed from the margin portion 24 to the thin film grown portion 26 with the minimum necessary thickness, the volume of the void 32 formed between the outer electrode 18 and the outer electrode 18 is reduced (FIG. 9), Since the amount of electrons and ions contained in the void 32 is reduced, there is an advantage that the corona discharge is difficult to sustain.
In addition, since an insulating oxide film is formed on the surface of the thin film ungrown portion 28 as described above, an effect that it becomes difficult to generate corona discharge can be expected.

[0024]

In the metallized film capacitor according to the present invention, a thin film film in which metal particles are adsorbed by a comparatively weak force is provided between the thin film growth part that originally functions as an electrode film and the margin part. Since the growth portion is interposed, the thermal shock due to the corona discharge is dispersed in a relatively wide area of the dielectric film, and it is possible to effectively prevent the specific area from being greatly damaged. Therefore, a metallized film capacitor having a long life and high reliability can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which a metallized film according to the present invention is stacked and wound.

FIG. 2 is a perspective view showing a metallized film capacitor according to the present invention.

FIG. 3 is a partial plan view showing a metallized film according to the present invention.

FIG. 4 is a schematic side view showing a metallized film according to the present invention.

FIG. 5 is a schematic side view showing a manufacturing process of the metallized film according to the present invention.

FIG. 6 is a schematic side view showing a manufacturing process of the metallized film according to the present invention.

FIG. 7 is a schematic side view showing a manufacturing process of the metallized film according to the present invention.

FIG. 8 is a schematic side view showing a manufacturing process of the metallized film according to the present invention.

FIG. 9 is a partial cross-sectional view showing the internal structure of the metallized film capacitor according to the present invention.

FIG. 10 is a partial plan view showing a conventional metallized film.

FIG. 11 is a schematic side view showing a conventional metallized film.

FIG. 12 is a schematic view showing an arrangement of metal particles in a conventional metallized film.

FIG. 13 is a schematic view showing an arrangement of metal particles in a conventional metallized film.

FIG. 14 is a schematic view showing an arrangement of metal particles in the metallized film of the present invention.

FIG. 15 is a partial cross-sectional view showing the internal structure of a conventional metallized film capacitor.

[Explanation of symbols]

 10 Metallized film capacitor 12 Dielectric film 14 Metallized film 16 Capacitor element 18 External electrode 24 Margin part 26 Thin film growth part 28 Thin film ungrown part 28a One end of thin film ungrown part 28 Other end of thin film ungrown part 34 Metal particles

Claims (2)

[Claims] 1. A metallized film is formed by vapor-depositing a metal material on a surface of a pair of dielectric films so that a margin portion is formed along each side, and both metallized films are provided with respective margins. Laminated so that the parts are arranged on the opposite side, and winding this to form a capacitor element,
In a metallized film capacitor formed by spraying a metal material on both end faces of the capacitor element to form external electrodes,
The metallized film comprises a thin film growth portion in which metal particles are thinned by nuclear growth, and a thin film ungrown portion in which metal particles are adsorbed by electrostatic interaction, and one end side of the thin film ungrown portion is A metallized film capacitor, characterized in that it is in contact with the margin part and the other end is in contact with the thin film growth part. 2. The metallized film capacitor according to claim 1, wherein an insulating oxide film is formed on the surface of the thin film ungrown portion.