JP6235291B2 - Laminate and film capacitor - Google Patents

Description

  The present invention relates to a laminate and a film capacitor.

  The film capacitor has, for example, a metal film formed by vapor deposition on the surface of a dielectric film obtained by filming a polypropylene resin as an electrode. With such a configuration, even when a short-circuit occurs in an insulation defect portion of the dielectric film, the metal film around the defect portion is evaporated and scattered by the short-circuit energy to insulate and prevent dielectric breakdown of the film capacitor. It has an advantage (see, for example, Patent Document 1).

  For this reason, film capacitors are attracting attention because they can prevent ignition and electric shock when electrical circuits are short-circuited, and in recent years, they have been applied to power supply circuits such as LED (Light Emitting Diode) lighting, and their use has expanded. (For example, see Patent Document 2).

  In addition, as with other electronic components, there is an increasing demand for miniaturization of film capacitors, and attempts have been made to make dielectric films thinner. However, when the dielectric film is made thinner, the surface roughness of the dielectric film becomes smaller and smoother. For example, workability when forming a conductor layer on the surface of the dielectric film, There is a case where the winding property or the like in the case of producing an element becomes a problem, and there is a problem that a defect occurs in the dielectric film or the electrode, or the adhesion of the dielectric film becomes non-uniform.

JP 9-129475 A JP 2010-178571 A

  The present invention has been made in view of the above-described problems, and uses a dielectric film having excellent slidability and excellent handling properties in a winding process and the like, and a laminate and a film with less defects and more uniform adhesion of the dielectric film The object is to provide a capacitor.

The laminate of the present invention is a laminate in which a plurality of dielectric films containing a metal oxide and a resin are laminated via an electrode layer, wherein the first main surface of the dielectric film is made of a resin. 1 and a ceramic particle assembly including the ceramic particles and protruding from the first resin surface, and the shape of the ceramic particle assembly when viewed in plan on the first main surface Is one of an arc shape, a linear shape, a Y shape, a cross shape, a star shape, and a dendritic shape, and the ceramic particle assembly portion is disposed so as to partition the first resin surface into a plurality of regions. The electrode layer is provided on the second main surface of the dielectric film, and the first electrode surface of the electrode layer facing the first main surface is in contact with the ceramic particle assembly, The first electrode surface and the first resin surface; And having an air gap between.

  The film capacitor of the present invention includes the above-described laminate.

  According to the present invention, it is possible to obtain a laminate and a film capacitor in which there are few defects and the adhesion of the dielectric film is more uniform.

(A) is the perspective view which showed typically a part of laminated body which is one Embodiment of this invention, (b) is XX sectional drawing in (a). It is an external appearance perspective view of a film capacitor.

  The laminated body and film capacitor of this invention are demonstrated based on FIG. 1 and 2. FIG. As shown in FIG. 1, the dielectric film 1 constituting the laminate according to one embodiment of the present invention includes ceramic particles 2 a and a resin 3, and the first main surface 1 </ b> A is made of the resin 3. The configuration includes a first resin surface 3A and a ceramic particle assembly 2 that includes the ceramic particles 2a and protrudes from the first resin surface 3A. In FIG. 1, the stacking direction of the dielectric film 1 is exaggerated for easy understanding, and does not reflect the actual dimensional relationship.

  On the other hand, the electrode layer 4 is formed on the second main surface 1B of the dielectric film 1, and the first electrode surface 4A of the electrode layer 4 and the first main surface 1A of the other dielectric film 1 are formed. A laminated body is formed by overlapping the dielectric films 1 so as to face each other. The laminated body here is one in which the dielectric films 1 and the electrode layers 4 are alternately overlapped. For example, the so-called rectangular dielectric films 1 and the electrode layers 4 are alternately laminated. In addition to the laminate, a structure in which the long dielectric film 1 and the electrode layer 4 are wound is included.

  In the present embodiment, the first electrode surface 4A and the first main surface 1A of the dielectric film 1 are in contact with each other at the ceramic particle assembly 2, and the first electrode surface 4A and the first resin surface 3A are in contact with each other. It is important to have a gap 5 between them.

  The first electrode surface 4A and the first main surface 1A of the dielectric film 1 are in contact with each other at the ceramic particle assembly portion 2, and a gap 5 is formed between the first electrode surface 4A and the first resin surface 3A. By having the contact area between the first electrode surface 4A and the first main surface 1A of the dielectric film 1, the contact area between the first electrode surface 4A and the first main surface 1A of the dielectric film 1 decreases. Improved slipperiness. As a result, even when the dielectric film 1 is wound in multiple layers, it is possible to reduce the stress generated by the restraint caused by the contact between the electrode layer 4 and the dielectric film 1, and the adhesion of the dielectric film 1 is further improved. In addition to uniforming, it is possible to suppress the occurrence of defects such as cracks caused by expansion of the dielectric film 1 when a voltage is applied by forming a film capacitor or the like.

  In addition, when it has the space | gap 5 between the 1st resin surface 3A and the 1st electrode surface 4A in this way, with the gas which exists in the space | gap 5, the 1st resin surface 3A, the 1st electrode surface 4A, A gas layer is formed between them, and the effect of improving the dielectric breakdown voltage (BDV) when a film capacitor or the like is formed is also obtained. As can be seen from Paschen's law, for example, when the gas layer is made of air at 1 atm, the thickness of the gap (the distance between the first resin surface 3A and the first electrode surface 4A), that is, In particular, when the thickness of the gas layer is 1000 nm or less, the BDV of the gas layer is about 300 V or more.

Although the ceramic particles 2a may be exposed on the surface of the ceramic particle assembly portion 2, it is preferably covered with a thin layer of the resin 3. This is because the ceramic particles 2a have higher adhesiveness with the metal constituting the electrode layer 4, and the resin 3 has higher slipperiness with the first electrode surface 4A (lower coefficient of friction). Even when the ceramic particles 2a are exposed, it is preferable that only a part of the exposed part is embedded and the other most part is buried in the resin 3. Since most of the ceramic particles 2 a are embedded in the resin 3, it is possible to prevent the ceramic particle aggregate portion 2 from falling off the dielectric film 1. The ceramic particles 2a may have a surface coated with a surface modifier or the like.

  Here, the ceramic particle aggregate part 2 is arranged so as to partition the first resin surface 3A into a plurality of regions, that is, the ceramic particle aggregate part 2 includes the first resin surface 3A and the first electrode surface 4A. , The wall 5 partitioning the gap 5 into a plurality of regions makes it possible to form a stable gap 5 even if the area ratio of the first resin surface 3A in the first main surface 1A is increased. be able to.

  The size of each region of the first resin surface 3A divided into a plurality of regions by the ceramic particle assembly portion 2 may be, for example, 500 μm or less. If it is such a magnitude | size, the space | gap 5 can be formed, without 3 A of 1st resin surfaces and 4 A of 1st electrode surfaces contacting.

  The first resin surface 3A may be partitioned into individual regions that are completely independent by the continuous ceramic particle assembly 2, but the regions of the first resin surface 3A communicate with each other. That is, it is preferable that the plurality of ceramic particle aggregate portions 2 are scattered in terms of improving the slipperiness of the dielectric film 1. Further, when the ceramic particle aggregate portion 2 has a continuous network structure or spreads in a planar shape, the resin 3 is constrained by the ceramic particle aggregate portion 2 and the dielectric film 1 itself is not easily deformed. There are concerns.

  In addition, when a plurality of ceramic particle aggregate parts 2 are scattered, the closest distance between adjacent ceramic particle aggregate parts 2 is 50 μm or more, so that the deformability of the dielectric film 1 is within a practical range. Can do.

  The shape of the ceramic particle assembly portion 2 in plan view on the first main surface 1A may be any shape such as an arc shape, a linear shape, a Y shape, a cross shape, a star shape, and a dendritic shape.

  The size (average particle size) of the ceramic particles 2a forming the ceramic particle assembly portion 2 is 10 to 200 nm because it is easy to deform when the ceramic particles 2a agglomerate and the ceramic particles 2a come into contact with each other. It is desirable that

  Further, the ratio of the ceramic particles 2a in the dielectric film 1 is preferably 1 to 10% by volume, particularly 2 to 7% by volume.

  As the dielectric film 1 having the above-described configuration, a thin film having an average thickness of 3 μm, particularly 2 μm can be suitably used. Also, the arithmetic average roughness (Sa) of the main surfaces 1A and 1B is suitable to have a smooth surface of 50 nm or less, particularly 10 nm or less.

  The second main surface 1B of the dielectric film 1 may include a ceramic particle aggregate portion 2 '. In the second main surface 1B, it is preferable that the ceramic particles 2a are exposed on the surface of the ceramic particle assembly portion 2 '. This is because the ceramic particles 2a have high adhesiveness to the metal constituting the electrode layer 4, and can firmly adhere the second main surface 1B and the electrode layer 4. The ceramic particle aggregate portion 2 ′ may protrude from the second resin surface 3B on the second main surface 1B, but is embedded in the second resin surface 3B and part of the ceramic particles 2a is the second main surface 1B. It is preferable to be exposed on the surface 1B. When the ceramic particle aggregate portion 2 ′ protrudes from the second main surface 1B, the ceramic particles 2a exposed on the surface drop off from the dielectric film 1, or from the stepped portion between the exposed ceramic particles 2a and the resin surface 3B. There is a concern that the electrode layer 4 may be peeled off. Note that a gap may be interposed between the second resin surface 3B and the second electrode surface 4B, but the second resin surface 3B and It is preferable that the second electrode surface 4B is in close contact.

  The ceramic particle aggregate portion 2 ′ on the second main surface 1 </ b> B may be connected to the ceramic particle aggregate portion 2 on the first main surface 1 </ b> A inside the dielectric film 1.

  Regarding the state of the ceramic particle assembly portion 2 of the dielectric film 1 and the presence or absence of the void 5, for example, the surface obtained by removing the electrode layer 4 from the dielectric film 1 of a laminate such as a film capacitor by a chemical method or a physical method In addition, the cross-section perpendicular to the stacking direction or the winding axis of a laminate such as a film capacitor can be confirmed by observing using a analyzer such as a scanning electron microscope (SEM).

  Such a laminate can be suitably used for a functional substrate such as a multilayer wiring board as well as a film capacitor. It can also be applied to various electronic parts such as actuators used in mobile camera drive units, artificial muscles, medical pumps, various sensors for detecting vibration, sound, acceleration, pressure, temperature, etc., and power generation elements. is there.

  FIG. 2 is an external perspective view of the film capacitor. The film capacitor of the present embodiment may be a laminated film capacitor using a so-called laminated body in which rectangular dielectric films 1 and electrode layers 4 are alternately laminated, or a long dielectric body. A winding type film capacitor using a laminate having a structure in which the film 1 and the electrode layer 4 are wound may be used. Even in the case of a multilayer film capacitor, the dielectric film 1 may be wound in the process, and defects generated in the process can be reduced by improving the slipperiness. In addition, the presence of the gap 5 provides the effect of improving the dielectric breakdown voltage (BDV) as described above regardless of the stacked type or the wound type.

  These film capacitors may further have a lead wire 15 as a terminal on the external electrode 14, but a structure without the lead wire 15 is desirable in terms of miniaturization of the film capacitor. Further, a part of the capacitor body 13, the external electrode 14, and the lead wire 15 may be covered with the exterior member 16 in terms of insulation and environment resistance.

  The laminated body of this embodiment can be obtained by the manufacturing method as shown below, for example. First, a resin 3 serving as a base material for the dielectric film 1 is prepared. As the resin 3, polyethylene terephthalate (PET), polypropylene (PP), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), cycloolefin polymer (COP), and the like are suitable.

  The relative dielectric constant (ε) of these resins 3 at room temperature (about 25 ° C.) is, for example, 3.3 for polyethylene terephthalate (PET), 2.3 for polypropylene (PP), and 3.0 for polyphenylene sulfide (PPS). The cycloolefin polymer (COP) is 2.2 to 3.0.

  The dielectric breakdown electric field (BDE) of these resins 3 at room temperature (about 25 ° C.) is, for example, 310 (V / μm) for polyethylene terephthalate (PET), 380 (V / μm) for polypropylene (PP), polyphenylene The sulfide (PPS) is 210 (V / μm), and the cycloolefin polymer (COP) is 370 to 510 (V / μm).

  As the ceramic particles 2a, a composite oxide having a perovskite structure in addition to alumina, titanium oxide, silicon oxide, and the like can be applied. In order to increase the compatibility between the ceramic particles 2a and the resin 3, the ceramic particles 2a may be subjected to a surface treatment such as a silane coupling treatment or a titanate coupling treatment.

  The dielectric film 1 can be obtained, for example, by applying a PET film as a base material and forming a resin sheet containing the ceramic particles 2a on the surface. In this case, the dielectric film 1 of the present embodiment can be obtained by adjusting the viscosity of the slurry containing the ceramic particles 2a and the resin 3 and the film thickness at the time of film formation to generate Marangoni convection. In this case, by setting the Marangoni number to 80 or more, convection occurs when the dielectric film 1 is formed, and the ceramic particles 2a gather around the cell mainly composed of the resin 3, so that the first of the dielectric film 1 is formed. In the first surface 1A, the ceramic particle aggregate portion 2 protruding from the first resin surface 3A may be arranged so as to partition the first resin surface 3A into a plurality of regions.

The film forming method may be appropriately selected from known film forming methods such as a doctor blade method, a die coater method, and a knife coater method. The Marangoni number is a value defined by the following equation.
M = t / (μk) * (| dσ / dT |) * ΔT,
M: Marangoni number,
t: film thickness (m),
μ: viscosity (N · s / m ² ),
k: thermal conductivity (W / m · K),
(| Dσ / dT |): temperature gradient of surface tension (N / m · K),
ΔT: Temperature difference between the front and back surfaces of the coating film (K)
Here, for the sake of convenience, the thermal conductivity of the organic resin (0.1 to 0.5 W / m · K) is applied to the thermal conductivity k, and in addition, the temperature gradient of the surface tension (| dσ / dT |), The temperature difference ΔT between the front surface and the back surface of the coating film is appropriately defined.

  Examples of the solvent used for film formation include methanol, isopropanol, n-butanol, ethylene glycol, ethylene glycol monopropyl ether, methyl ethyl ketone, methyl isobutyl ketone, xylene, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, dimethylacetamide, It is preferable to use an organic solvent containing cyclohexane or a mixture of two or more selected from these.

  Next, the dielectric film 1 is peeled from the base material, and a metal component such as Al (aluminum) is vapor-deposited on the second main surface 1B which is the base material side surface of the dielectric film 1 to thereby form the electrode layer 4. Then, the dielectric film 1 on which the electrode layer 4 is formed is wound to obtain a laminate.

  Next, the obtained laminated body is used as the main body 13 of the film capacitor, and the external electrode 14 is formed on the end face where the electrode layer 4 is exposed. For forming the external electrode 14, for example, metal spraying, sputtering, plating, or the like is suitable. Here, the lead wire 15 may be formed on the external electrode 14. Next, the film capacitor of the present embodiment can be obtained by forming the exterior resin 16 on the surface of the main body 13 on which the external electrodes 14 (including the lead wires 15) are formed.

  A specific material was selected to produce a dielectric film, and the following evaluation was performed.

  First, alumina particles (relative dielectric constant: 9) having an average particle diameter of 100 nm as ceramic particles and polycycloolefin polymer (molecular weight: Mw = 20000, relative dielectric constant 2.2) as resin were prepared. The alumina particles were subjected to silane coupling treatment in order to improve the compatibility with the resin.

Next, a slurry was prepared by dispersing the alumina particles in a cycloolefin polymer. At this time, cyclohexane was added as a diluent.

  Thereafter, the slurry was applied onto a polyethylene terephthalate (PET) film using a coater and formed into a sheet shape to produce a dielectric film.

  The produced dielectric film was peeled off from the substrate after removing the solvent at 180 ° C., and an Al electrode layer having an average thickness of 75 nm was formed by vacuum deposition using the surface on the substrate side as the second main surface. . The obtained dielectric film with an electrode layer was wound to form a laminate, external electrodes were formed by a metallicon treatment, and lead wires were connected to the surface of the metallicon layer to produce a film capacitor.

  The average thickness (film thickness) of the dielectric film was determined from an average value obtained by measuring a region obtained by cutting a part of the dielectric film after solvent removal and dividing it into 10 equal parts. The viscosity of the slurry was measured at room temperature (25 ° C.) using a rotating disk viscometer. The Marangoni number was calculated from the above equation using the measured slurry viscosity and film thickness. At this time, basic physical property values were used for the thermal conductivity, the temperature gradient of the surface tension, and the temperature difference between the front surface and the back surface of the coating film. Table 1 shows the volume ratio of alumina particles to the resin, slurry viscosity, Marangoni number M, and average thickness of the dielectric film.

  The state of the ceramic particle assembly on the first main surface of the dielectric film was confirmed by observation with energy dispersive X-ray spectroscopy (EDS) and scanning electron microscope (SEM). The voids in the laminate were confirmed by processing the produced film capacitor with a cross section polisher (CP) and observing the obtained cross section with a scanning electron microscope (SEM).

  The slipperiness of the dielectric film was confirmed by measuring the static friction coefficient of the dielectric film. When the static friction coefficient of the dielectric film was less than 0.6, the slipperiness was good, and when it was 0.6 or more, the slipperiness was judged as poor. These results are shown in Table 2.

From the results of Tables 1 and 2, the sample No. 1 was adjusted so that the Marangoni number was 80 or more by adjusting the slurry viscosity and the film thickness. 1 and 2, in the first main surface of the dielectric film, the ceramic particle assembly portion is arranged so as to partition the first resin surface into a plurality of regions, and the first resin surface of the laminate There was a gap between the surface of the first electrode and the dielectric film had good sliding properties.

  On the other hand, in the sample not containing ceramic particles (sample No. 3) and the sample having a Marangoni number of 80 or less (sample No. 4), the ceramic particle aggregate portion is not formed, and the first resin surface of the laminate is There was no gap between the first electrode surface and the dielectric film was inferior in slipperiness.

  Moreover, when the dielectric breakdown electric field (BDE) was measured about each sample, sample No. without a space | gap was measured. 3 and 4 were 300 V / μm or less. 1 and 2 had voids with an average thickness of less than 1000 nm, and BDE was as high as 400 V / μm.

1: Dielectric film 1A: First main surface 1B of dielectric film: Second main surface 2 of dielectric film: Ceramic particle assembly 2a: Ceramic particle 3: Resin 3A: First resin surface 3B: First 2 resin surface 4: electrode layer 4A: first electrode surface 4B: second electrode surface 5: gap 13: body 14: external electrode 15: lead 16: exterior member

Claims (6)

A dielectric film including ceramic particles and a resin is a laminate in which a plurality of dielectric films are laminated via an electrode layer,
The first main surface of the dielectric film has a first resin surface made of resin, and a ceramic particle assembly including the ceramic particles and projecting from the first resin surface,
A shape of the ceramic particle assembly portion in plan view on the first main surface is any one of an arc shape, a linear shape, a Y shape, a cross shape, a star shape, and a dendritic shape, and the ceramic particle assembly A portion is arranged so as to partition the first resin surface into a plurality of regions;
The electrode layer is provided on the second main surface of the dielectric film, and the first electrode surface of the electrode layer facing the first main surface is in contact with the ceramic particle aggregate portion, and A laminate having a gap between a first electrode surface and the first resin surface.   The laminate according to claim 1, further comprising a coating of the resin on a surface of the ceramic particle assembly portion.   3. The laminate according to claim 1, wherein a size of the region of the first resin surface partitioned by the ceramic aggregate portion is 500 μm or less.   A plurality of the ceramic particle aggregate portions are scattered on the first main surface, and the plurality of regions of the first resin surface communicate with each other on the first main surface. The laminate according to any one of claims 1 to 3.   The laminate according to claim 4, wherein the closest distance between adjacent ceramic particle aggregate portions is 50 μm or less.   A film capacitor comprising the laminate according to claim 1.