WO2023047944A1

WO2023047944A1 - Capacitor

Info

Publication number: WO2023047944A1
Application number: PCT/JP2022/033433
Authority: WO
Inventors: 大矢西島; 智生稲倉; 淳史川畑
Original assignee: 株式会社村田製作所; 株式会社指月電機製作所
Priority date: 2021-09-27
Filing date: 2022-09-06
Publication date: 2023-03-30
Also published as: CN117981024A

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

capacitor

The present invention relates to capacitors.

When moisture enters the capacitor, the capacitance and insulation resistance value decrease. Therefore, Patent Literature 1 proposes forming external electrodes from metal particles having different average particle sizes. According to Patent Document 1, this suppresses the infiltration of residual moisture in the sealing resin into the capacitor element, thereby reducing the deterioration of the insulation resistance.

JP 2013-214607 A

However, with the method of Patent Document 1, it is difficult to sufficiently suppress performance deterioration due to moisture. SUMMARY OF THE INVENTION An object of the present invention is to provide a capacitor in which deterioration of performance due to moisture is suppressed.

The present invention comprises a capacitor element, an external electrode arranged on an end surface of the capacitor element, and a lead terminal electrically connected to the external electrode, and the external electrode has a water permeability of 18 g/(24 hours·m ² ) or more and 70 g/(24 hours·m ² ) or less. As a result, a decrease in insulation resistance, an increase in equivalent series resistance (ESR), swelling of the capacitor, and the like caused by moisture are suppressed, and the performance of the capacitor is maintained for a long period of time.

The maximum height Rz of the external electrodes is preferably 120 μm or more. This facilitates the release of moisture in the capacitor element to the outside through the external electrodes.

The external electrode is, for example, a metallikon electrode. The moisture permeability of metallikon electrodes is easy to control.

The external electrode may contain an alloy of zinc and aluminum.

The capacitor element has an internal electrode, and the internal electrode is made of, for example, 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.

According to the present invention, a capacitor is provided in which deterioration of performance due to moisture is suppressed.

1 is a perspective view schematically showing a capacitor according to an embodiment of the invention; FIG.

As in Patent Document 1, when it is difficult for water to enter the inside of the capacitor element from the external electrodes, the water inside the capacitor element is also difficult to be released to the outside from the external electrodes. That is, it is difficult to remove the moisture present in the capacitor element after the external electrodes are formed. However, water may enter the capacitor element in the process of forming the external electrodes. This is because the external electrodes of the capacitor are usually formed by metal spraying in the atmosphere.

In the present disclosure, the moisture permeability of the external electrode is 18 g/(24 hours·m ² ) or more. As a result, the moisture present in the capacitor element can be removed by heat treatment after forming the external electrodes.

On the other hand, the moisture permeability of the external electrodes is 70 g/(24 hours·m ² ) or less. As a result, the infiltration of moisture into the capacitor element from the outside at once after the heat treatment and before the sealing process can be suppressed, and the moisture content in the capacitor element can be kept low. In addition, intrusion of the sealing resin into the gaps of the external electrodes is suppressed during the sealing process.

That is, by setting the moisture permeability of the external electrodes to 18 g/(24 hours·m ² ) or more and 70 g/(24 hours·m ² ) or less, the decrease in insulation resistance value and equivalent series resistance value ( ESR) increase, swelling of the capacitor, etc. are suppressed, and the performance of the capacitor is maintained for a long period of time.

The moisture permeability of the external electrodes is calculated as follows.
A sample is prepared that includes a capacitor element and external electrodes arranged on both end surfaces of the capacitor element. This sample is allowed 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 taken as the moisture permeation amount. A value obtained by dividing the amount of water permeation by the sum of the cross-sectional areas (m ² ) of the two external electrodes is defined as the water permeability [g/(24 hours·m ² )]. It is desirable to thoroughly dry the sample prior to moisture absorption.

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

[Capacitor]
A capacitor according to the present disclosure includes a capacitor element, external electrodes arranged on end faces of the capacitor element, and lead terminals electrically connected to the external electrodes. The water permeability of the external electrode is 18 g/(24 hours·m ² ) or more and 70 g/(24 hours·m ² ) or less.

The capacitor according to the present disclosure can be applied to various uses. The capacitor according to the present disclosure is particularly suitable for use in environments with large temperature changes. Furthermore, since high connection reliability can be expected over the long term, it is suitably used for 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.

The size and shape of the capacitor are not particularly limited, and can be set appropriately according to the capacity, application, etc. The type of capacitor is also not particularly limited. Capacitors according to the present disclosure are typically film capacitors. Hereinafter, the capacitor according to the present disclosure will be described in detail by taking a film capacitor as an example. A capacitor according to the present disclosure is not limited to this.

(capacitor element)
A capacitor element generally includes two types of internal electrodes having different polarities (hereinafter referred to as a first internal electrode and a second internal electrode). The capacitor element may be of the laminated type or of the wound type. In the multilayer capacitor element, the first internal electrodes and the second internal electrodes are cut to a predetermined size and laminated alternately. In the wound-type capacitor element, the first internal electrode and the second internal electrode are long bodies, which are laminated, then wound, and pressed if necessary. In this case, the cross-section of the capacitor element can be elliptical (the track shape of an athletics stadium). The configurations of the first internal electrode and the second internal electrode may be the same or different.

Each internal electrode is composed of, for example, a metallized film. A metallized film includes a resin film and a metal layer formed on at least one main surface of the resin film.

The material of the resin film is not particularly limited, and may be a thermosetting resin or a thermoplastic resin. Thermosetting resins include, for example, phenol resins, epoxy resins, melamine resins, urea resins, unsaturated polyester resins, silicone resins, urethane resins, and thermosetting polyimides. Examples of thermoplastic resins include polypropylene, polyethersulfone, polyetherimide, and polyallyl arylate. These are used singly or in combination of two or more. The resin film may further contain an additive such as a leveling agent.

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 aspect, 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 thickness gauge.

The metal layer is formed on part of at least one main surface of the resin film, for example, by vapor deposition. Metal species contained in the metal layer include, for example, aluminum, zinc, titanium, magnesium, copper, and nickel.

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 specified by observing a cross section obtained by cutting the metallized film in the thickness direction using an electron microscope such as a field emission scanning electron microscope (FE-SEM).

(external electrode)
The external electrodes are arranged on the end faces of the capacitor element. The external electrodes are generally arranged on opposite end faces of the capacitor element, respectively. For example, in the case of a wound-type capacitor element, the external electrodes are arranged on both respective end faces in the direction of the winding axis of the capacitor element. The external electrode may cover the end surface of the capacitor element.

The external electrodes are electrically connected to the internal electrodes and play a role in drawing out the internal electrodes to the outside. One of the external electrodes (first external electrode) is electrically connected to the first internal electrode. Another external electrode (second external electrode) is electrically connected to the second internal electrode.

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

The maximum height Rz of the external electrodes 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 electrodes, and the recesses on the surface of the external electrodes and the voids inside the external electrodes are easily communicated with each other. . Therefore, the moisture in the capacitor element is easily released to the outside through the external electrodes. The maximum height Rz of the external electrodes may be 125 μm or more. The maximum height Rz of the external electrodes is preferably 200 μm or less in that it is easy to prevent external moisture from entering the capacitor element through the external electrodes. Maximum height Rz is obtained according to JIS B 0601-2001.

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

The thickness of the external electrodes 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 direction normal to the end face of the capacitor element. The thickness of the external electrode is the average value of arbitrary multiple locations (preferably three or more locations).

The external electrodes are formed, for example, by spraying a metal onto each end face of the capacitor element. Such external electrodes are commonly referred to as metallikon electrodes. A metallikon electrode is preferable in that the moisture permeability can be easily controlled. The moisture permeability of the metallikon electrode 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 object, and the like. For example, by adjusting the blowing air pressure to more than 0.15 MPa and less than 0.7 MPa, the moisture permeability of the metallikon electrode can be controlled to 18 g/(24 hours·m ² ) or more and 70 g/(24 hours·m ² ) or less. . The water permeability of the metallikon electrode is controlled to 18 g/(24 hours/m ² ) or more and 70 g/(24 hours/m ² ) or less by adjusting the thermal spraying of the metal per hour to more than 20 g/minute and less than 140 g/minute. can.

(Lead terminal)
A part of the lead terminal is usually joined to the external electrode for electrical connection. One or more lead terminals are usually joined to one external electrode. The lead terminals are joined to the external electrodes by welding, for example.

The joint position between the lead terminal and the external electrode is not particularly limited. As will be described later, when the capacitor element and the external electrodes are resin-sealed, the lead terminals are joined to the external electrodes so that a portion of the lead terminals are exposed outside from the sealing resin. The lead terminals are joined to the external electrodes by welding, for example.

The material of the lead terminal is not particularly limited as long as it exhibits 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.

(sealant)
The capacitor element and the external electrodes may be sealed with a sealing material. This makes it easier to suppress penetration of water into the interior. In addition, water resistance, vibration resistance, etc. are likely to be improved. A typical example of the sealing material is a cured product of a thermosetting resin. Examples of thermosetting resins include epoxy resins and urethane resins. In this case, the capacitor element and the external electrodes are sealed with a hardened thermosetting resin. The sealing material may further contain an inorganic filler.

(capacitor case)
The capacitor element may be housed in a case. In this case, the gap between the capacitor element and the case is filled with a sealing material. This capacitor is manufactured, for example, as follows. First, a capacitor element having an external electrode is arranged, and lead terminals are led out of the case. Thereafter, a thermosetting resin is filled between the case and the capacitor element and cured.

FIG. 1 is a perspective view schematically showing a capacitor according to the present disclosure. The capacitor 10 includes a capacitor element 1, two external electrodes (first external electrode 2A, second external electrode 2B), and two lead terminals (first lead terminal 3A, second lead terminal 3B). The end face shape of capacitor element 1 is elliptical. First external electrode 2A is arranged on one end surface of capacitor element 1 , and second external electrode 2B is arranged on the other end surface 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.

(Manufacturing method of capacitor)
The capacitor according to the present disclosure includes, for example, a step of forming an external electrode on an end surface of a capacitor element, a step of joining lead terminals to the external electrode to electrically connect them, and a step of forming the external electrode. and heat-treating the capacitor element.

The moisture permeability of the formed external electrodes is 18 g/(24 hours·m ² ) or more and 70 g/(24 hours·m ² ) or less. Since the external electrodes have a high moisture permeability of 18 g/(24 hours·m ² ) or more, the heat treatment process removes moisture remaining in the capacitor element. On the other hand, since the water permeability of the external electrodes is suppressed to 70 g/(24 hours·m ² ) or less, the infiltration of water through the external electrodes is suppressed after the heat treatment process.

The heat treatment is performed, for example, at 125°C or higher and 150°C or lower for 4 to 24 hours.

After the step of joining the lead terminals and the heat treatment step, a step of sealing the capacitor element and the external electrodes with a sealing material may be performed. As described above, since the water permeability of the external electrodes is suppressed to 70 g/(24 hours·m ² ) or less, the encapsulant is also suppressed from entering the gaps of the external electrodes.

The present invention will be described more specifically with the following examples, but the present invention is not limited to these. In the examples, "parts" and "%" are based on mass unless otherwise specified.

[Example 1]
Aluminum was vapor-deposited on a urethane resin film (thickness: 3 μm) to a thickness of 20 nm to prepare a metallized film. A capacitor element was produced by laminating two sheets of this metallized film and winding them. A zinc-aluminum alloy (6% aluminum content) was thermally sprayed on both end surfaces of the obtained capacitor element in the direction of the winding axis to form two external electrodes (thickness: 1 mm). After that, lead terminals (tinned copper wire, diameter 1.2 mm) were resistance-welded to each of the two external electrodes. A film capacitor was thus obtained.

When the water permeability of this film capacitor was calculated as described above, it was 18.5 g/(24 hours·m ² ). The cross-sectional area of the external electrode was obtained by calculation. The average value of the maximum heights Rz of the two external electrodes was 125 μm. The maximum height Rz was measured using a laser microscope (Keyence VK-8700).

[Example 2-5, Comparative Example 1-5]
A film capacitor was formed in the same manner as in Example 1, except that the air spray pressure and the shape of the spray nozzle when forming the external electrodes were changed to adjust the moisture permeability of the external electrodes to the values shown in Table 1. was made.

[evaluation]
The produced film capacitor was subjected to moisture absorption treatment and heat treatment, and then sealed with a thermosetting resin. The sealed film capacitors were evaluated as follows. Table 1 shows the results.

(moisture absorption treatment)
The resulting film capacitor was dried at 125° C. for 48 hours to make the capacitor element absolutely dry. After that, the film capacitor was allowed to stand in an environment of 40° C. and 80% RH until 6.5 mg of water per unit volume (1 cm ³ ) of the capacitor element was adsorbed.
(Heat treatment)
The moisture-adsorbed film capacitor was heated at 125° C. for 4 hours.
(sealing)
The dried film capacitor was placed in a case and sealed with epoxy resin.

(1) ESR change rate The ESR of the absolutely dry film capacitor was taken as the initial value _R0 . The difference (RR ₀ ) between the ESR (R) of the sealed film capacitor and the initial value R ₀ was divided by the initial value R ₀ and multiplied by 100. Thus, the ESR change rate (ΔESR) was calculated.
ΔESR (%) = 100 × (RR ₀ )/R ₀
The ESR was measured using an LCR meter (ZM2371 manufactured by NF Circuit Design Block, measurement frequency 10 kHz).

(2) Capacity change rate -1
The initial value _C0 was taken as the capacity of the film capacitor in an absolutely dry state. The difference (CC ₀ ) between the capacitance C of the sealed film capacitor and the initial value C ₀ was divided by the initial value C ₀ and multiplied by 100. Thus, the capacity change rate (ΔC) was calculated.
ΔC (%) = 100 × (C−C ₀ )/C ₀
The capacity was measured using an LCR meter (ZM2371 manufactured by NF Circuit Design Block, measurement frequency 1 kHz).

(3) Capacity change rate -2 (after high temperature and high pressure load test)
A voltage of 500 V was applied to the sealed film capacitor in an atmosphere of 125° C. for 2,000 hours. The difference (C ₁ −C) between the capacitance C ₁ of the film capacitor after the test and the capacitance C of the film capacitor before the test was divided by the capacitance C and multiplied by 100. Thus, the rate of change in capacity (ΔC ₁ ) before and after the load test was calculated. If _ΔC1 is within 5%, it can be determined that the life is long.
ΔC ₁ (%) = 100 × (C ₁ -C)/C
The capacitance was measured using an LCR meter (ZM2371 manufactured by NF Circuit Design Block, measurement frequency 1 kHz) in the same manner as described above.

As shown ⁱⁿ Table 1 ^, the ESR change rate ( ΔESR), the rate of change in capacity (ΔC), and the rate of change in capacity after the load test (ΔC ₁ ) are all small.

On the other hand, the ESR change rate (ΔESR), capacity change rate (ΔC), and after load test of the film capacitor of Comparative Example 1-3, in which the water permeability of the external electrode is less than 18 g/(24 hours·m ² ) The rate of change in capacity (ΔC ₁ ) is large in both cases. In particular, the capacity change rate (ΔC ₁ ) after the load test is large, and a long life cannot be expected. This is probably because moisture was not sufficiently removed in the heat treatment after the moisture absorption treatment.

ESR rate of change (ΔESR), capacity rate of change (ΔC), and capacity change after load test of the film capacitor of Comparative Example 4-5 in which the water permeability of the external electrode exceeds 70 g/(24 hours·m ² ) Both ratios (ΔC ₁ ) are large. In particular, the ESR change rate (ΔESR) is large. It is considered that this is because moisture suddenly entered the inside of the capacitor after the heat treatment and before the capacitor was sealed, or the sealing resin entered the gaps of the external electrodes.

The capacitor of the present invention can be applied to various electronic devices because it suppresses deterioration in performance due to moisture.

This application claims priority based on Japanese Patent Application No. 2021-156871 filed in Japan on September 27, 2021, the entire contents of which are incorporated herein by reference.

10 Capacitor 1 Capacitor Element 2A First External Electrode 2B Second External Electrode 3A First Lead Terminal 3B Second Lead Terminal

Claims

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 capacitor, wherein the moisture permeability of the external electrode is 18 g/(24 hours·m 2 ) or more and 70 g/(24 hours·m 2 ) or less.
The capacitor according to claim 1, wherein the maximum height Rz of the external electrodes is 120 µm or more.
The capacitor according to claim 1 or 2, wherein the external electrodes are metallikon electrodes.
The capacitor according to any one of claims 1 to 3, wherein the external electrodes contain an alloy of zinc and aluminum.
The capacitor element includes an internal electrode,
The internal electrode is composed of a metallized film,
5. The capacitor according to claim 1, wherein said metallized film comprises a resin film and a metal layer formed on at least one main surface of said resin film.