Capacitor

Abstract

Provided is a capacitor in which performance degradation due to moisture is mitigated. This capacitor comprises a capacitor element, an outer electrode disposed on an end face of the capacitor element, and a lead terminal electrically connected to the outer electrode, wherein the outer electrode has a moisture permeation of 18 g / (24 hours∙m2) or more and 70 g / (24 hours∙m2) or less.

Description

[Technical field]

[0001] The present invention relates to a capacitor. [Background technology]

[0002] When moisture penetrates into a capacitor, it causes a decrease in capacitance and insulation resistance. Therefore, Patent Document 1 proposes forming the external electrodes from metal particles with different average particle sizes. According to Patent Document 1, this prevents residual moisture in the sealing resin from penetrating into the capacitor element, reducing the deterioration of the insulation resistance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-214607 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is difficult to sufficiently suppress the deterioration of performance due to moisture using the method of Patent Document 1. An object of the present invention is to provide a capacitor in which the deterioration of performance due to moisture is suppressed. [Means for solving the problem]

[0005] The present invention relates to a capacitor comprising a capacitor element, an external electrode disposed on an end surface of the capacitor element, and a lead terminal electrically connected to the external electrode, the moisture permeability of the external electrode being 18 g / (24 hr m 2 ) or more 70g / (24 hours m 2 This suppresses the decrease in insulation resistance, the increase in equivalent series resistance (ESR), and the swelling of the capacitor, all of which are caused by moisture, and maintains the performance of the capacitor for a long period of time.

[0006] The maximum height Rz of the external electrodes is preferably 120 μm or more, which allows moisture in the capacitor element to be easily released to the outside through the external electrodes.

[0007] The external electrodes are, for example, metallikon electrodes, whose moisture permeability is easy to control.

[0008] The outer electrodes may include an alloy of zinc and aluminum.

[0009] The capacitor element includes an internal electrode, and the internal electrode is, for example, formed of a metallized film. The metallized film includes, for example, a resin film and a metal layer formed on at least one main surface of the resin film. That is, the capacitor of the present invention may be a film capacitor. Effect of the Invention

[0010] According to the present invention, a capacitor is provided in which deterioration of performance due to moisture is suppressed. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a schematic diagram of a capacitor according to an embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] If it is made difficult for moisture to penetrate into the inside of the capacitor element from the external electrodes as in Patent Document 1, moisture inside the capacitor element is also difficult to be released to the outside from the external electrodes. In other words, it is difficult to remove moisture that exists in the capacitor element after the external electrodes are formed. However, moisture may penetrate into the capacitor element during the process of forming the external electrodes. This is because the external electrodes of a capacitor are usually formed by metal spraying in the atmosphere.

[0013] In this disclosure, the moisture permeability of the external electrode is 18 g / (24 h m 2As a result, after the external electrodes are formed, the moisture present in the capacitor element can be removed by heat treatment.

[0014] On the other hand, the moisture permeability of the external electrode is 70g / (24h m 2 ) or less. This prevents moisture from suddenly penetrating the capacitor element from the outside during the period from the heat treatment until the sealing step, and allows the moisture content within the capacitor element to be kept low. In addition, the sealing resin is prevented from penetrating into the gaps in the external electrodes during the sealing step.

[0015] In other words, the moisture permeability of the external electrode is set to 18 g / (24 h m 2 ) or more 70g / (24 hours m 2 ) or less, moisture-induced problems such as a decrease in insulation resistance, an increase in equivalent series resistance (ESR), and capacitor swelling are suppressed, thereby maintaining the performance of the capacitor over the long term.

[0016] The moisture permeability of the external electrodes is calculated as follows. A sample is prepared that includes a capacitor element and external electrodes disposed on both end faces of the capacitor element. This sample is left to stand in an environment of 40°C and 80% RH for 24 hours to absorb moisture. The mass of the sample before and after moisture absorption is measured, and the difference is the amount of moisture permeation. The amount of moisture permeation is calculated by multiplying the cross-sectional area (m 2 ) was divided by the total moisture permeability [g / (24 h m 2 It is advisable to thoroughly dry the sample before absorbing moisture.

[0017] The cross-sectional area of ​​the external electrode is the area of ​​a cross section obtained by cutting the external electrode parallel to the end faces of the capacitor element. Alternatively, the cross-sectional area of ​​the external electrode is the area of ​​a plan view obtained by projecting the sample in the direction of a straight line connecting the centers of the two external electrodes. The area of ​​the cross section or plan view may be obtained by image processing or calculation.

[0018] [Capacitor] The capacitor according to the present disclosure comprises a capacitor element, an external electrode disposed on an end face of the capacitor element, and a lead terminal electrically connected to the external electrode. The moisture permeability of the external electrode is 18 g / (24 hr m 2 ) or more 70g / (24 hours m 2 ) or less.

[0019] The capacitor according to the present disclosure can be applied to various applications. In particular, the capacitor according to the present disclosure is suitable for use in environments with large temperature changes. Furthermore, since high connection reliability can be expected over the long term, the capacitor is suitable for use in electronic devices mounted on automobiles and industrial equipment, particularly electric compressors, pumps, and power devices. Examples of power devices include chargers, DC-DC converters, and drive inverters.

[0020] The size and shape of the capacitor are not particularly limited, and may be appropriately set according to the capacity, application, etc. The type of the capacitor is also not particularly limited. The capacitor according to the present disclosure is typically a film capacitor. Hereinafter, the capacitor according to the present disclosure will be described in detail using a film capacitor as an example. The capacitor according to the present disclosure is not limited thereto.

[0021] (Capacitor element) A capacitor element usually has two types of internal electrodes (hereinafter referred to as a first internal electrode and a second internal electrode) with different polarities. The capacitor element may be a laminated type or a wound type. In a laminated type capacitor element, the first internal electrode and the second internal electrode are cut to a predetermined size and are alternately laminated in a plurality of layers. In a wound type capacitor element, the first internal electrode and the second internal electrode are long bodies that are laminated, wound, and pressed as necessary. In this case, the cross section of the capacitor element may be elliptical (shaped like a track in an athletics stadium). The configurations of the first internal electrode and the second internal electrode may be the same or different.

[0022] Each of the internal electrodes is formed of, for example, a metallized film, which includes a resin film and a metal layer formed on at least one of the main surfaces of the resin film.

[0023] The material of the resin film is not particularly limited, and may be a thermosetting resin or a thermoplastic resin. Examples of the thermosetting resin include phenolic resin, epoxy resin, melamine resin, urea resin, unsaturated polyester resin, silicone resin, urethane resin, and thermosetting polyimide. Examples of the thermoplastic resin include polypropylene, polyethersulfone, polyetherimide, and polyaryl arylate. These may be used alone or in combination of two or more. The resin film may further contain an additive such as a leveling agent.

[0024] The thickness of the resin film may be 5 μm or less, 3.5 μm or less, or 3.4 μm or less. The thickness of the resin film may be 0.5 μm or more. In one embodiment, the thickness of the resin film is 0.5 μm or more and 5 μm or less. The thickness of the resin film can be measured using an optical film thickness meter.

[0025] The metal layer is formed on at least one of the principal surfaces of the resin film by, for example, a vapor deposition method. Examples of the metal contained in the metal layer include aluminum, zinc, titanium, magnesium, copper, and nickel.

[0026] The thickness of the metal layer is not particularly limited. From the viewpoint of damage suppression, the thickness of the metal layer is preferably 5 nm or more. The thickness of the metal layer is preferably 40 nm or less. The thickness of the metal layer can be determined by observing a cross section of the metallized film cut in the thickness direction using an electron microscope such as a field emission scanning electron microscope (FE-SEM).

[0027] (external electrode) The external electrodes are disposed on end faces of the capacitor element. The external electrodes are usually disposed on both opposing end faces of the capacitor element. For example, in the case of a wound type capacitor element, the external electrodes are disposed on both end faces of the capacitor element in the winding axis direction. The external electrodes may cover the end faces of the capacitor element.

[0028] The external electrodes are electrically connected to the internal electrodes and serve to draw the internal electrodes out. One of the external electrodes (first external electrode) is electrically connected to the first internal electrode. The other external electrode (second external electrode) is electrically connected to the second internal electrode.

[0029] The moisture permeability of the external electrode is 18g / (24h m 2 ) or more 70g / (24 hours m 2 ) or less. The moisture permeability of one or more external electrodes satisfies the above range. It is preferable that the moisture permeability of all external electrodes satisfies the above range. The moisture permeability of the external electrodes is 20 g / (24 hr m 2 ) or more is preferable, and 22g / (24 hours m 2 ) or more is preferable. The moisture permeability of the external electrode is 65g / (24 hours m 2 ) or less is preferable, and 60g / (24 hours m 2 ) or less is more preferable.

[0030] The maximum height Rz of the external electrode is, for example, 120 μm or more. When the maximum surface height Rz is within the above range, sufficient voids are often formed inside the external electrode, and the recesses on the surface of the external electrode and the voids inside the external electrode are easily connected. Therefore, moisture inside the capacitor element is easily discharged to the outside through the external electrode. The maximum height Rz of the external electrode may be 125 μm or more. In order to easily prevent external moisture from penetrating into the capacitor element through the external electrode, the maximum height Rz of the external electrode is preferably 200 μm or less. The maximum height Rz is determined in accordance with JIS B 0601-2001.

[0031] The external electrodes are typically made of a metal. Examples of metal species include zinc, aluminum, tin, and zinc-aluminum alloys. In the zinc-aluminum alloys, the aluminum content is, for example, 20% or less, 18% or less, or 15% or less. In the zinc-aluminum alloys, the aluminum content is, for example, 0.1% or more, 0.5% or more, or 1% or more.

[0032] The thickness of the external electrode is not particularly limited. The thickness of the external electrode is, for example, 0.5 mm or more and 3 mm or less. The thickness of the external electrode is the length of the external electrode in the normal direction of the end face of the capacitor element. The thickness of the external electrode is the average value of any multiple locations (preferably three or more locations).

[0033] The external electrodes are formed, for example, by spraying metal onto each end face of the capacitor element. Such external electrodes are usually called metallikon electrodes. Metallikon electrodes are preferable because their moisture permeability is easy to control. The moisture permeability of metallikon electrodes can be controlled by adjusting the air spray pressure, the amount of metal sprayed per hour, the shape of the spray nozzle, the distance from the tip of the spray nozzle to the target object, and the like. For example, by adjusting the spray air pressure to more than 0.15 MPa and less than 0.7 MPa, the moisture permeability of metallikon electrodes can be controlled to 18 g / (24 hr·m 2 ) or more 70g / (24 hours m 2 By adjusting the hourly rate of metal spraying to more than 20 g / min and less than 140 g / min, the moisture permeability of the Metallikon electrode can be controlled to 18 g / (24 h m 2 ) or more 70g / (24 hours m 2 ) can be controlled as follows:

[0034] (Lead terminal) A part of the lead terminal is usually joined to an external electrode and electrically connected thereto. Usually, one or more lead terminals are joined to one external electrode. The lead terminals are joined to the external electrodes by, for example, welding.

[0035] The position where the lead terminal and the external electrode are joined is not particularly limited. When the capacitor element and the external electrode are sealed with resin as described later, the lead terminal is joined to the external electrode so that a part of the lead terminal is exposed to the outside from the sealing resin. The lead terminal is joined to the external electrode by, for example, welding.

[0036] The material of the lead terminal is not particularly limited as long as it exhibits electrical conductivity. The lead terminal may be, for example, a steel wire or a copper wire, and these wires may be tin-plated, zinc-plated, copper-plated, nickel-plated, or the like. The cross-sectional shape of the lead terminal is also not particularly limited, and may be circular, elliptical, or rectangular.

[0037] (Sealing material) The capacitor element and the external electrodes may be sealed with a sealing material. This makes it easier to prevent moisture from penetrating into the interior. In addition, it makes it easier to improve water resistance and vibration resistance. A representative example of the sealing material is a cured product of a thermosetting resin. Examples of the thermosetting resin include epoxy resin and urethane resin. In this case, the capacitor element and the external electrodes are sealed with the cured thermosetting resin. The sealing material may further contain an inorganic filler.

[0038] (Capacitor case) The capacitor element may be housed in a case. In this case, a sealant is filled in the gap between the capacitor element and the case. This capacitor is manufactured, for example, as follows. First, a capacitor element having external electrodes is disposed, and the lead terminals are drawn out to the outside of the case. Then, a thermosetting resin is filled between the case and the capacitor element, and is cured.

[0039] 1 is a perspective view showing a schematic diagram of a capacitor according to the present disclosure. Capacitor 10 includes a capacitor element 1, two external electrodes (a first external electrode 2A and a second external electrode 2B), and two lead terminals (a first lead terminal 3A and a second lead terminal 3B). The end face shape of capacitor element 1 is elliptical. The first external electrode 2A is disposed on one end face of capacitor element 1, and the second external electrode 2B is disposed on the other end face of capacitor element 1. The first lead terminal 3A is joined to the first external electrode 2A, and the second lead terminal 3B is joined to the second external electrode 2B.

[0040] (Capacitor manufacturing method) The capacitor according to the present disclosure is manufactured by a method including, for example, a step of forming an external electrode on an end face of a capacitor element, a step of joining a lead terminal to the external electrode to electrically connect the two, and a step of heat-treating the capacitor element after the step of forming the external electrode.

[0041] The moisture permeability of the formed external electrode is 18g / (24h m 2 ) or more 70g / (24 hours m 2 ) or less. The external electrode is 18g / (24h m 2 ), the moisture remaining in the capacitor element is removed by the heat treatment process. On the other hand, the moisture permeability of the external electrodes is 70g / (24 hours m 2 ) or less, the infiltration of moisture through the external electrodes is suppressed after the heat treatment process.

[0042] The heat treatment is carried out, for example, at 125° C. or higher and 150° C. or lower for 4 to 24 hours.

[0043] After the step of joining the lead terminals and the step of heat treatment, a step of sealing the capacitor element and the external electrodes with a sealing material may be performed. As described above, the moisture permeability of the external electrodes is 70 g / (24 hours m 2 ) or less, the intrusion of the sealing material into the gaps in the external electrodes is also suppressed. EXAMPLES

[0044] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0045] [Example 1] Aluminum was vapor-deposited to a thickness of 20 nm on a urethane resin film (thickness 3 μm) to produce a metallized film. Two of these metallized films were stacked and wound to produce a capacitor element. A zinc-aluminum alloy (aluminum content 6%) was sprayed onto both end faces in the winding axis direction of the obtained capacitor element to form two external electrodes (thickness 1 mm). Then, lead terminals (tin-plated copper wire, diameter 1.2 mm) were resistance-welded to each of the two external electrodes. This produced a film capacitor.

[0046] The moisture permeability of this film capacitor was calculated as above and was found to be 18.5g / (24 hours m 2 ) The cross-sectional area of ​​the external electrodes was determined by calculation. The average value of the maximum height Rz of the two external electrodes was 125 μm. The maximum height Rz was measured using a laser microscope (Keyence Corporation, VK-8700).

[0047] [Examples 2-5, Comparative Examples 1-5] A film capacitor was produced in the same manner as in Example 1, except that the moisture permeability of the external electrodes was adjusted to the value shown in Table 1 by changing the air spray pressure and the shape of the spray nozzle when forming the external electrodes.

[0048] [evaluation] The prepared film capacitor was subjected to moisture absorption treatment and heat treatment, and then sealed with a thermosetting resin. The sealed film capacitor was evaluated as follows. The results are shown in Table 1.

[0049] (Moisture absorption treatment) The obtained film capacitor was dried at 125°C for 48 hours to make the capacitor element in an absolute dry state. 3 The film capacitor was left to stand in an environment of 40°C and 80% RH until 6.5 mg of moisture was adsorbed per unit area. (Heat treatment) The film capacitor that had absorbed moisture was heated at 125°C for 4 hours. (Sealing) The dried film capacitor was placed in a case and sealed with epoxy resin.

[0050] (1) ESR change rate The ESR of the film capacitor in an absolute dry state was set as the initial value R0. The difference (R-R0) between the ESR (R) of the sealed film capacitor and the initial value R0 was divided by the initial value R0 and multiplied by 100. In this way, the ESR change rate (△ESR) was calculated. △ESR(%)=100×(R-R0) / R0 The ESR was measured using an LCR meter (NF Corporation, ZM2371, measurement frequency 10 kHz).

[0051] (2) Capacity change rate -1 The capacitance of the film capacitor in an absolute dry state was taken as the initial value C0. The difference (C-C0) between the capacitance C of the sealed film capacitor and the initial value C0 was divided by the initial value C0 and multiplied by 100. In this way, the capacitance change rate (△C) was calculated. △C(%)=100×(C-C0) / C0 The capacitance was measured using an LCR meter (NF Corporation, ZM2371, measurement frequency 1 kHz).

[0052] (3) Capacity change rate-2 (after high temperature and high pressure load test) A voltage of 500V was applied to the sealed film capacitor in an atmosphere at 125°C for 2,000 hours. The difference (C1-C) between the capacitance C1 of the film capacitor after this test and the capacitance C of the film capacitor before the test was divided by the capacitance C and multiplied by 100. In this way, the rate of change in capacitance (△C1) before and after the load test was calculated. If △C1 is within 5%, it can be determined that the capacitor has a long life. △C1(%)=100×(C1-C) / C The capacitance was measured using an LCR meter (NF Corporation, ZM2371, measuring frequency 1 kHz) as described above.

[0053] [Table 1]

[0054] As shown in Table 1, the moisture permeability of the external electrode was 18 g / (24 h m 2 ) or more 70g / (24 hours m 2 The film capacitors of Examples 1-5 below had small ESR change rates (ΔESR), capacitance change rates (ΔC) and capacitance change rates after a load test (ΔC1).

[0055] On the other hand, the moisture permeability of the external electrode is 18g / (24 h m 2 The film capacitor of Comparative Example 1-3, which is smaller than the ESR change rate (ΔESR), capacitance change rate (ΔC), and capacitance change rate after the load test (ΔC1) are all large. In particular, the capacitance change rate after the load test (ΔC1) is large, and a long life cannot be expected. This is thought to be because moisture was not sufficiently removed in the heat treatment after the moisture absorption treatment.

[0056] The moisture permeability of the external electrode is 70g / (24 hours m 2The film capacitor of Comparative Example 4-5, which exceeds the ESR change rate (△ESR), capacitance change rate (△C), and capacitance change rate after the load test (△C1) are all large. The ESR change rate (△ESR) is particularly large. This is thought to be because moisture penetrated into the capacitor all at once after the heat treatment and before it was sealed, or because the sealing resin penetrated into the gaps in the external electrodes. [Industrial Applicability]

[0057] The capacitor of the present invention is capable of suppressing performance degradation due to moisture and is therefore applicable to various electronic devices.

[0058] This application claims priority to Patent Application No. 2021-156871, filed in Japan on September 27, 2021, the entire contents of which are incorporated herein by reference. <1> A capacitor element; an external electrode disposed on an end surface of the capacitor element; a lead terminal electrically connected to the external electrode, The moisture permeability of the external electrode is 18g / (24 h m 2 ) or more 70g / (24 hours m 2 ) or less, a capacitor. <2> The maximum height Rz of the external electrodes is 120 μm or more. <1> of capacitor. <3> The external electrode is a metallikon electrode. <1> or <2> of capacitor. <4> The external electrodes include an alloy of zinc and aluminum. <1> ~ <3> Either of the capacitors. <5> The capacitor element includes an internal electrode. The internal electrodes are made of metallized films, The metallized film comprises a resin film and a metal layer formed on at least one main surface of the resin film. <1> ~ <4> Either of the capacitors. [Explanation of symbols]

[0059] 10 Capacitor 1 Capacitor element 2A 1st external electrode 2B 2nd external electrode 3A First lead terminal 3B Second lead terminal

Claims

1. A capacitor element; an external electrode disposed on an end surface of the capacitor element; a lead terminal electrically connected to the external electrode, The moisture permeability of the external electrode is 18 g / (24 hours m ２ ) or more 70g / (24 hours / m ２ ) or less, a capacitor.

2. The capacitor according to claim 1 , wherein the maximum height Rz of the external electrodes is 120 μm or more.

3. The capacitor according to claim 1 or 2, wherein the external electrodes are metallikon electrodes.

4. 3. The capacitor of claim 1, wherein the external electrodes include an alloy of zinc and aluminum.

5. The capacitor element includes an internal electrode, The internal electrodes are made of metallized films, The capacitor according to claim 1 , wherein the metallized film comprises a resin film and a metal layer formed on at least one main surface of the resin film.

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