JP2013065747A - Metallized film capacitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a metallized film capacitor having excellent moisture resistance.SOLUTION: In a metallized film capacitor of the present invention, at least one of metal vapor-deposition electrodes 4a, 4b of a pair of metallized films 1, 2 includes an oxide film layer formed on a composition plane between dielectric films 3a, 3b and a magnesium-containing layer formed on the oxide film layer, and an atomic concentration ratio of magnesium is made to be maximum in the magnesium-containing layer. Accordingly, by the present invention, the magnesium-containing layer can be suppressed from being oxidized, self-healing properties can be enhanced, and a withstand voltage improving effect can be maintained.

Description

  The present invention relates to a metallized film capacitor that is used in various electronic devices, electrical devices, industrial devices, automobiles, and the like, and is particularly suitable for smoothing, filtering, and snubbing of a motor drive inverter circuit of a hybrid vehicle.

  In recent years, from the viewpoint of environmental protection, all electric devices are controlled by inverter circuits, and energy saving and high efficiency are being promoted. In particular, in the automobile industry, hybrid vehicles (hereinafter referred to as HEVs) that run on electric motors and engines have been introduced into the market, and the development of technologies relating to energy saving and high efficiency has been activated, which is friendly to the global environment.

  Since such an electric motor for HEV has a high operating voltage range of several hundred volts, a metalized film capacitor having high withstand voltage and low loss electric characteristics is attracting attention as a capacitor used in connection with this electric motor. In addition, the trend of adopting a metallized film capacitor having a very long life is conspicuous from the demand for maintenance-free in the market.

  And this metallized film capacitor | condenser is divided roughly into what uses metal foil for an electrode generally, and the thing which uses the vapor deposition metal provided on the dielectric film for an electrode. In particular, a metallized film capacitor using an evaporated metal as an electrode (hereinafter referred to as a metal evaporated electrode) has a smaller volume occupied by the electrode than a metal foil, and can be reduced in size and weight. High reliability against dielectric breakdown due to self-healing function peculiar to metal-deposited electrodes (meaning the ability of the metal-deposited electrodes around the defect to evaporate and scatter and restore the function of the capacitor, generally called self-healing) Therefore, it has been widely used conventionally. The thinner the metal-deposited electrode is, the easier it is to evaporate and scatter, and the better the self-healing property, the higher the withstand voltage.

  FIG. 6 is a cross-sectional view showing the structure of a conventional metallized film capacitor of this type, and FIGS. 7A and 7B are plan views showing a pair of metallized films used in the metallized film capacitor. is there. As shown in FIGS. 6 and 7, the metal vapor deposition electrode 101a and the metal vapor deposition electrode 101b are formed by vapor-depositing aluminum on one surface of dielectric films 102a and 102b such as a polypropylene film except for the insulation margins 103a and 103b at one end. Is formed. The metal vapor-deposited electrodes 101a and 101b are connected to metallicons 104a and 104b formed by spraying zinc at the opposite ends of the insulation margins 103a and 103b of the dielectric films 102a and 102b. The electrode is pulled out to the outside.

  Further, the metal vapor-deposited electrodes 101a and 101b are non-vapor-deposited having no metal vapor-deposited electrode formed by oil transfer on the side from the substantially central part of the width W of the effective electrode part forming the capacitance toward the insulation margins 103a and 103b. Are divided into a plurality of divided electrodes 106a and 106b by the slits 105a and 105b, and are positioned on the side opposite to the insulation margins 103a and 103b from the substantially central part of the width W of the effective electrode part and closer to the metallicons 104a and 104b. The dielectric films 102a and 102b are connected in parallel to the metal vapor-deposited electrodes 101a and 101b deposited on one surface of the dielectric films 102a and 102b by fuses 107a and 107b.

  The conventional metallized film capacitor configured as described above has a self-healing property and can realize a metallized film capacitor with less heat generation by the fuses 107a and 107b. In other words, the current passed through the metal vapor-deposited electrodes 101a and 101b increases as it approaches the metallicons 104a and 104b and decreases as it moves away. Therefore, since the fuses 107a and 107b and the divided electrodes 106a and 106b are provided on the side closer to the insulation margins 103a and 103b where the flowing current decreases, the heat generated in the fuses 107a and 107b due to the flowing current can be reduced, and the temperature rises. It was to be able to suppress.

  As prior art document information related to the invention of this application, for example, Patent Document 1 is known.

JP 2004-134561 A

  Metallized film capacitors are becoming thinner with the miniaturization. Since the thinning of the film leads to the breakdown voltage deterioration, measures for improving the breakdown voltage are necessary.

  Then, this invention aims at improving the withstand voltage of a metallized film capacitor.

  In order to solve this problem, the present invention provides an oxide film layer formed on a joint surface with a dielectric film, wherein at least one of a pair of metallized electrodes of a metallized film contains aluminum as a main component, and the oxidized film layer. A magnesium-containing layer formed on the film layer, and the atomic concentration ratio of magnesium is maximized in the magnesium-containing layer.

  The metallized film capacitor according to the present invention can exhibit excellent voltage resistance.

  The reason is that the magnesium-containing layer produced on the lower surface side of the metal vapor deposition electrode has higher self-healing property than the layer made of aluminum alone. Further, since the magnesium-containing layer is protected by the oxide film layer, the influence of oxidation can be reduced.

  As described above, the present invention can increase the withstand voltage.

Sectional drawing which showed the structure of the metallized film capacitor in the Example of this invention (A), (b) The top view which showed the structure of the metallized film used for the metallized film capacitor in the Example of this invention (A) The figure which shows the composition of the metal vapor deposition electrode in the Example of this invention, (b) The principal part enlarged view of Fig.3 (a). The figure which shows the leakage continuous flow of the metallized film capacitor in the Example of this invention The figure which shows the withstand voltage of the metallized film capacitor in the Example of this invention Sectional view showing the structure of a conventional metallized film capacitor (A), (b) The top view which showed the structure of the metallized film used for the conventional metallized film capacitor

  Hereafter, the structure of the metallized film capacitor in the Example of this invention is demonstrated using FIGS. 1-2.

  FIG. 1 is a cross-sectional view showing the configuration of the metallized film capacitor of this example. FIGS. 2 (a) and 2 (b) are plan views of a pair of metallized films used in the metallized film capacitor of the present invention. FIG.

  In FIG. 1, the 1st metallized film 1 is a metallized film for P poles, and the 2nd metallized film 2 is a metallized film for N poles. Then, the first metallized film 1 and the second metallized film 2 are overlapped as a pair, and a metallized film capacitor is formed by using a plurality of turns wound as an element.

  As shown in FIG. 1, the first metallized film 1 has a metal vapor-deposited electrode 4a formed on one surface of a dielectric film 3a made of polypropylene as a dielectric. An insulating margin 5a is provided at the end portion to insulate the second metallized film 2.

  This metal vapor deposition electrode 4a is connected to the metallicon 6a to draw out the electrode. The metallicon 6a can be formed by, for example, zinc spraying, and is formed on the end face of the metal deposition electrode 4a.

  As shown in FIG. 2A, the metal vapor-deposited electrode 4a has a vertical margin 7a and a horizontal margin 8a formed on the side from the approximate center in the width W direction of the effective electrode portion forming the capacitance toward the insulating margin 5a. Yes. The vertical margin 7a and the horizontal margin 8a are formed by oil transfer, and the metal deposition electrode 4a is not deposited. As a result, the metal deposition electrode 4a becomes the large electrode portion 9a on the metallicon 6a side, and becomes the divided small electrode portion 10a divided into a plurality of portions by the vertical margin 7a and the horizontal margin 8a on the insulating margin 5a side.

  As shown in FIG. 2A, the divided small electrode portion 10a is electrically connected in parallel by a large electrode portion 9a and a fuse 11a, and adjacent divided small electrode portions 10a are also connected to the fuse 12a. Are electrically connected in parallel.

  Here, as shown in FIG. 2A, the large electrode portion 9a is formed on one surface of the dielectric film 3a from the substantially central portion of the width W of the effective electrode portion to the metallicon 6a. The width of each divided small electrode portion 10a is about ¼ of the width W of the effective electrode portion, and is formed on one surface of the dielectric film 3a from the substantially central portion of the width W of the effective electrode portion to the insulation margin 5a. The two divided small electrode portions 10a are provided from the substantially central portion of the effective electrode portion (width W) to the insulation margin 5a. However, the present invention is not limited to this, and a configuration in which three or more are provided may be employed.

  In the actual use, when a short circuit occurs in the defective part of the insulation, the metal vapor deposition electrode 4a around the defective part is evaporated and scattered by the short circuit energy, and the insulation is restored. With this self-healing function, the function of the metallized film capacitor is recovered even if a part between the first metallized film 1 and the second metallized film 2 is short-circuited. In addition, when a large amount of current flows through the divided small electrode portion 10a due to a defect in the divided small electrode portion 10a, the fuse 11a or the fuse 12a is scattered and the portion of the divided small electrode portion 10a in which the defect is caused is scattered. The electrical connection is broken and the metalized film capacitor current returns to normal.

  Like the first metallized film 1, the second metallized film 2 is made of metal except for an insulating margin 5b at one end on one side of a dielectric film 3b made of polypropylene as a dielectric, as shown in FIG. A vapor deposition electrode 4b is formed. However, the direction in which the second metallized film 2 and the first metallized film 1 are connected to the metallicon is different, and the second metallized film 2 is a metallicon 6a to which the first metallized film 1 is connected. Are connected to a metallicon 6b arranged opposite to the above. Further, the metal vapor deposition electrode 4b has a large electrode by a non-vapor deposition vertical margin 7b and a horizontal margin 8b which do not have a metal vapor deposition electrode on the side from the substantially central portion in the width W of the effective electrode portion forming the capacitance toward the insulation margin 5b. It is divided into a portion 9b and a plurality of divided small electrode portions 10b.

  As shown in FIG. 2B, the divided small electrode portion 10b has the same configuration as the divided small electrode portion 10a of the first metallized film 1, and is arranged in parallel by the large electrode portion 9b and the fuse 11b. In addition, the divided small electrode portions 10b are connected in parallel by the fuse 12b. The effect obtained by providing the divided small electrode portion 10b and the fuses 11b and 12b is the same as that of the first metallized film 1.

  In this embodiment, the metal vapor-deposited electrodes 4a and 4b are divided into large electrode portions 9a and 9b and divided small electrode portions 10a and 10b, but they function as capacitors even when they are not divided.

  In this embodiment, polypropylene films are used as the dielectric films 3a and 3b. However, polyethylene terephthalate, polyethylene naphthalate, polyphenyl sulfide, polystyrene, and the like may be used.

  In the metallized film capacitor of this example, at least one of the metal vapor deposited electrodes 4a and 4b of the first metallized film 1 or the second metallized film 2 is mainly composed of aluminum, and the dielectric film 3a (3b). And an oxide film layer formed on the bonding surface, and a magnesium-containing layer formed on the oxide film layer. The magnesium-containing layer is a layer containing magnesium as a metal, not as an oxide. An aluminum layer is formed on the magnesium-containing layer. In this metal vapor deposition electrode 4a (4b), the atomic concentration distribution of magnesium becomes the maximum value in the magnesium-containing layer. The magnesium content in the metal vapor deposition electrodes 4a and 4b per unit area was set to 2.0 wt% to 40 wt%. By containing magnesium at a certain level or more, the magnesium-containing layer existing as the above-described metal can be left even if natural oxidation proceeds. Moreover, since resistance will become large when there is too much magnesium, it is suitable for the said range.

Example 1
The metalized film capacitor of Example 1 is configured as shown in FIG. 1 above, and aluminum and magnesium are used as electrode materials used for the metal deposition electrode 4a as the P pole and the metal deposition electrode 4b as the N pole. This alloy was used. In addition, the 1st metallized film 1 and the 2nd metallized film 2 of the present Example 1 are formed from the same manufacturing method using the same electrode material and dielectric material (polypropylene dielectric film). Therefore, the characteristics of the metallized film of Example 1 described below are common to the first metallized film 1 and the second metallized film 2.

  The metal vapor deposition electrode of Example 1 has a magnesium content (wt%) in the metal vapor deposition electrode per unit area of 4.9 wt%, and a magnesium-containing layer is formed under the aluminum layer. The oxide layer was formed under the layer.

  FIG. 3 shows the relationship between the depth (distance) converted value (nm) from the surface of the metal vapor deposition electrode and the atomic concentration (atom%) obtained from the X-ray photoelectron spectroscopy (XPS) analysis result. The depth conversion value from the surface of the metal vapor deposition electrode was converted from the comparison of the sputtering rate of the silicon dioxide film and the sputtering rate of aluminum under the same conditions. From this result, it can be seen that in Example 1, the magnesium concentration distribution becomes the maximum value at a position deeper than the position where the aluminum concentration distribution becomes the maximum value. That is, it can be seen that magnesium is present under the aluminum layer. Further, the oxygen concentration distribution takes a peak value at a position deeper than the position where the magnesium concentration distribution becomes the maximum value.

  Furthermore, FIG. 4 shows the relationship between applied voltage (V) and leakage current (mA) at high temperature (100 ° C.). As Conventional Example 1, a metallized film on which a conventional metal vapor deposition electrode composed only of an aluminum layer was formed was used. As Comparative Example 1, a metallized film of a metal-deposited electrode in which an oxide layer made of magnesium oxide was formed under an aluminum layer without including a magnesium-containing layer was used. The magnesium content (wt%) in the metal vapor deposition electrode per unit area of Comparative Example 1 was less than 2.0%.

  As a result, it can be seen that the leakage current decreases in the order of Conventional Example 1, Comparative Example 1, and Example 1. This is considered to be because a part of the magnesium layer formed under the aluminum layer is bonded to the moisture in the film and the moisture in the film is lowered. And under the aluminum layer, it is considered that the leakage current decreased as the magnesium content increased.

  From these results, it can be inferred that a magnesium oxide film layer exists on the joint surface of the metal vapor-deposited electrode with the dielectric film. In addition, although a magnesium oxide film is simply adopted this time, it is considered that the oxidation of the magnesium layer can be similarly suppressed even if an oxide film made of a metal other than magnesium is formed. For example, aluminum oxide, titanium oxide, silicon oxide, manganese oxide, or the like can be used.

  Further, a short-time withstand voltage test was performed using the metallized film capacitor of Example 1 and the above-described Conventional Example 1 and Comparative Example 1. The result is shown in FIG.

In the short-time withstand voltage test, the metallized film of this example and the metallized films of Conventional Example 1 and Comparative Example 1 were boosted by a constant voltage every predetermined time in an atmosphere of 100 ° C., and the capacitance change rate of the capacitor Is a voltage (withstand voltage) at which −5% is obtained, and the withstand voltage is obtained from the voltage. The rate of change of withstand voltage indicates (withstand voltage V _{t of} Example 1 or Comparative Example 1−withstand voltage V ₀ of Conventional Example 1) / V ₀ in percentage (%).

  Table 1 shows the withstand voltage change rate (%) of Example 1 and Comparative Example 1 in the short-time withstand voltage test.

  As can be seen from Table 1, in Example 1 in which the withstand voltage was 1426V, the withstand voltage increased by 4.9% compared to Conventional Example 1 in which the withstand voltage was 1359V. In addition, the withstand voltage is improved in this example compared to Comparative Example 1.

  The reason will be described below. That is, magnesium has a lower clearing energy when scattered than aluminum, and has higher self-healing properties. Therefore, self-healing is more likely to occur on the metal deposition electrode and dielectric film bonding surface side, and the withstand voltage is improved. Therefore, the withstand voltage is improved. Here, since magnesium reacts with water faster than aluminum, it is naturally oxidized by moisture in the air. Therefore, the oxidation of the magnesium-containing layer is suppressed by forming the oxide film layer under the magnesium-containing layer. This oxide film layer is very thin with a thickness of 0.1 nm or more and 15 nm or less, and since it is an insulator, it does not affect the self-healing property.

  The magnesium-containing layer and the oxide film layer may be provided on either of the metal vapor-deposited electrodes 4a and 4b, or may be provided on both.

  In this example, the thickness of the magnesium-containing layer was set to 1/2 or less of the thickness of the metal vapor deposition electrode. Since the specific resistance of aluminum is smaller than that of magnesium, the resistance can be lowered even if the thickness of the metal vapor-deposited electrode is reduced by making the aluminum layer thicker (as a guide, thicker than half the thickness of the metal vapor-deposited electrode). Can do.

  The metallized film capacitor according to the present invention has excellent moisture resistance, and can be suitably used as a capacitor used in various electronic equipment, electrical equipment, industrial equipment, automobiles, etc., and particularly has high moisture resistance and high withstand voltage characteristics. This is useful in the field of automobiles that are required.

DESCRIPTION OF SYMBOLS 1 1st metallized film 2 2nd metallized film 3a, 3b Dielectric film 4a, 4b Metal vapor deposition electrode 5a, 5b Insulation margin 6a, 6b Metallicon 7a, 7b Vertical margin 8a, 8b Horizontal margin 9a, 9b Large electrode Part 10a, 10b Divided small electrode part 11a, 11b Fuse 12a, 12b Fuse

Claims (3)

A pair of metallized films on which a metal vapor-deposited electrode is formed on a dielectric film, and the metal vapor-deposited electrodes formed on the pair of metallized films are overlapped so as to face each other through the dielectric film, or wound or Stacked elements,
It consists of a pair of metallicon electrodes formed on both end faces of this element,
At least one of the metal-deposited electrodes of the pair of metallized films contains aluminum as a main component, an oxide film layer formed on a bonding surface with the dielectric film, and a magnesium containing film formed on the oxide film layer A metallized film capacitor having a magnesium atomic concentration ratio that is maximized in the magnesium-containing layer. The metalized film capacitor according to claim 1, wherein the oxide film layer has a thickness of 0.1 nm to 15 nm. The thickness of the said magnesium content layer is a metallized film capacitor of Claim 1 which is 1/2 or less of the thickness of the said metal vapor deposition electrode.

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