Thin film capacitor

Abstract

A film capacitor (1) is provided with: a capacitor element (10) including an element main body (11) and an external electrode (12) provided on an end surface of the element main body (11); and a lead-out terminal (20) electrically connected to the external electrode (12). The element main body (11) is a laminate including a metallized film (e.g., a first metallized film (51)) in which a metal layer (e.g., a first metal layer (55)) is provided on at least one main surface of a dielectric film (e.g., a first dielectric film (53)). The external electrode (12) is connected to a metal layer (for example, a first metal layer (55)). The leading-out terminal (20) is welded to the external electrode (12). The surface roughness Ra of the external electrode (12) is 20 [mu] m or more and 45 [mu] m or less, and the recessed depth (D) of the lead-out terminal (20) from the surface of the external electrode (12) is 0.5 mm or more.

Description

Technical Field

[0001] The present invention relates to film capacitors. Background Art

[0002] As one type of capacitor, a film capacitor having the following structure is known: a flexible resin film is used as a dielectric film, and metal layers are arranged opposite to each other via the dielectric film. The capacitor element constituting the film capacitor is manufactured, for example, by preparing a laminated body in which a metalized film having a metal layer provided on the surface of the dielectric film is wound or laminated, and then external electrodes (also called metal sprayed electrodes) are formed on both end surfaces of the laminated body.

[0003] Lead terminals such as lead wires and bus bars are connected to the external electrodes of the capacitor element. Examples of methods for connecting the lead terminals include methods of joining the lead terminals to the external electrodes of the capacitor element by soldering or resistance welding.

[0004] Patent document 1 discloses a metallized film capacitor having a capacitor element having a metallized film wound or laminated and having a metal-sprayed electrode, and a metal strip connected to the metal-sprayed electrode by soldering, wherein the metal strip is provided with a convex portion for soldering. According to patent document 1, by providing a lead electrode connected to the capacitor element with a metal strip having a cross-sectional area required in a circuit, a structure capable of flowing a large current is formed, and by providing a convex portion for soldering on the metal strip, only the soldering connection range is heated during soldering, thereby reducing the heat effect on the capacitor element and ensuring the reliability of the connection of the lead electrode and the capacitor characteristics.

[0005] Patent document 2 discloses a film capacitor, which includes a capacitor element, a metal sprayed electrode formed by spraying molten metal such as lead or tin on both ends of the capacitor element, and one lead and another lead connected / fixed to the metal sprayed electrode by an electric welder, etc. The film capacitor described in patent document 2 is characterized in that any surface of the metal sprayed joint surface of the lead is continuously formed in a substantially mountain shape or a substantially sawtooth shape in a vertical direction.

[0006] Prior Art Literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2004-349447

[0009] Patent Document 2: Japanese Patent Application Publication No. 2008-166457 Summary of the invention

[0010] Problems to be solved by the invention

[0011] As described in Patent Document 1, in a method of joining a lead terminal such as a lead wire to an external electrode of a capacitor element by soldering, a high-temperature soldering iron is brought into contact with the joining portion, so that the heat of the soldering iron is transferred to the inside of the capacitor element via the external electrode. As a result, the capacitor element is damaged by heat, which may cause a decrease in the performance of the film capacitor.

[0012] On the other hand, as described in Patent Document 2, in a method of joining a lead terminal such as a lead wire to an external electrode of a capacitor element by resistance welding, a large current flows from the welding electrode while the external electrode and the lead terminal are pressed by the welding electrode, thereby welding the lead terminal to the external electrode.

[0013] Although resistance welding uses a large current, the time for which the large current flows is very short, so compared with soldering, the damage to the capacitor element caused by heat is reduced. However, from the perspective of increasing the bonding strength between the external electrodes of the capacitor element and the lead terminals, it can be said that there is room for improvement.

[0014] An object of the present invention is to provide a film capacitor having a high bonding strength between an external electrode of a capacitor element and a lead terminal.

[0015] Means for solving problems

[0016] The film capacitor of the present invention comprises: a capacitor element, which includes an element body and an external electrode provided on an end surface of the element body; and a lead terminal, which is electrically connected to the external electrode. The element body is a laminate, which includes a metalized film having a metal layer provided on at least one main surface of a dielectric film. The external electrode is connected to the metal layer. The lead terminal is welded to the external electrode. The surface roughness Ra of the external electrode is greater than 20 μm and less than 45 μm, and the lead terminal is sunk to a depth of greater than 0.5 mm from the surface of the external electrode.

[0017] Effects of the Invention

[0018] According to the present invention, it is possible to provide a film capacitor having a high bonding strength between an external electrode of a capacitor element and a lead terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a perspective view schematically showing a thin film capacitor according to one embodiment of the present invention.

[0020] Figure 2 yes Figure 1 Front view of a film capacitor shown.

[0021] Figure 3 A is a side view schematically showing an example of an external electrode and a lead terminal before welding, Figure 3 B is a side view schematically showing an example of the external electrodes and lead terminals after welding.

[0022] Figure 4 A is a front view schematically showing an example of an external electrode and a lead terminal before welding. Figure 4 B is a front view schematically showing an example of the external electrodes and lead terminals after welding.

[0023] Figure 5 This is a front view schematically showing an example of a lead terminal sunken into an external electrode.

[0024] Figure 6 This is a front view schematically showing another example of the lead terminal sunken into the external electrode.

[0025] Figure 7 It is a perspective view schematically showing an example of a capacitor element constituting the film capacitor of the present invention.

[0026] Figure 8 yes Figure 7 A cross-sectional view of the capacitor element taken along line bb is shown.

[0027] Fig. 9 It is a schematic diagram showing the composition Figure 7 and Figure 8 A perspective view of an example of an element body of a capacitor element shown.

[0028] Fig.10 It is a schematic diagram showing the composition Figure 7 and Figure 8 A perspective view of another example of the element body of the capacitor element shown.

[0029] Fig.11 A and Fig.11 B is a schematic diagram showing Figure 1 A perspective view showing an example of how to use the film capacitor shown.

[0030] Fig.12 is a schematic diagram for explaining a tensile test. DETAILED DESCRIPTION

[0031] The film capacitor of the present invention is described below. In addition, the present invention is not limited to the following structure, and can also be appropriately changed within the scope of the present invention. In addition, the structure obtained by combining multiple preferred structures described below also belongs to the present invention.

[0032] In this specification, terms that indicate the relationship between elements (for example, "vertical", "parallel", "orthogonal", etc.) and terms that indicate the shape of an element do not express only the strict meaning, but also include expressions that also include substantially equivalent ranges, such as differences of several percent.

[0033] The following drawings are schematic diagrams and their dimensions, aspect ratios, etc. may differ from those of actual products.

[0034] Figure 1 It is a perspective view schematically showing a thin film capacitor according to one embodiment of the present invention. Figure 2 yes Figure 1 Front view of a film capacitor shown.

[0035] Figure 1 and Figure 2 The film capacitor 1 shown includes a capacitor element 10 and lead terminals 20 .

[0036] Capacitor element 10 includes element body 11 and external electrodes 12 provided on end surfaces of element body 11. Specifically, a pair of external electrodes 12 are provided on both end surfaces of element body 11. The structure of capacitor element 10 will be described below.

[0037] The lead terminals 20 are electrically connected to the external electrodes 12. Specifically, the pair of lead terminals 20 are electrically connected to the pair of external electrodes 12, respectively.

[0038] like Figure 1 and Figure 2 As shown, the pair of lead terminals 20 may extend from the external electrode 12 so that the distance between them becomes larger. Alternatively, the pair of lead terminals 20 may extend from the external electrode 12 so that the distance between them becomes constant.

[0039] The lead terminal 20 is welded to the external electrode 12. Specifically, the lead terminal 20 is resistance-welded to the external electrode 12.

[0040] like Figure 1 and Figure 2 As shown, the welding portion of the lead terminal 20 may also be in the shape of a flat plate.

[0041] As an example, the lead terminal 20 is a lead wire. In this case, the lead wire may have a plated layer on the surface or may not have a plated layer on the surface. The welding portion of the lead wire may be processed into a flat plate shape.

[0042] As another example, the lead terminal 20 is a bus bar. The bus bar is in a flat plate shape as a whole including a welding portion.

[0043] Figure 3 A is a side view schematically showing an example of an external electrode and a lead terminal before welding, Figure 3 B is a side view schematically showing an example of the external electrodes and lead terminals after welding. Figure 4 A is a front view schematically showing an example of an external electrode and a lead terminal before welding. Figure 4 B is a front view schematically showing an example of the external electrodes and lead terminals after welding.

[0044] like Figure 3 A and Figure 4 As shown in A of FIG. 1 , in resistance welding, a large current flows from the welding electrode 80 while the welding electrode 80 is pressing the external electrode 12 and the lead terminal 20. The large current generates heat at the interface between the external electrode 12 and the lead terminal 20, thereby softening the external electrode 12. As a result, Figure 3 B and Figure 4 As shown in B, the lead terminal 20 is sunken into the external electrode 12 .

[0045] Figure 5 This is a front view schematically showing an example of a lead terminal sunken into an external electrode.

[0046] The lead terminal 20 sunk into the external electrode 12 is Figure 5 It is difficult to separate from the external electrode 12 due to the force shown by the arrow in FIG.

[0047] Figure 6 This is a front view schematically showing another example of the lead terminal sunken into the external electrode.

[0048] like Figure 6 As shown, the entire lead terminal 20 may be sunken into the external electrode 12 .

[0049] The deeper the lead terminal 20 sinks into the external electrode 12, the larger the contact area between the external electrode 12 and the lead terminal 20. Therefore, by increasing the depth of the lead terminal 20 sinking from the surface of the external electrode 12, the bonding strength between the external electrode 12 and the lead terminal 20 can be increased.

[0050] The film capacitor of the present invention is characterized in that the lead terminal is sunken to a depth (in Figure 3 B and Figure 4 The length shown in B and D) is 0.5 mm or more.

[0051] As will be described in the examples described later, if the lead terminal is sunken to a depth of 0.5 mm or more from the surface of the external electrode, sufficient bonding strength can be ensured.

[0052] Furthermore, the sinking depth of the lead terminal can be easily controlled by the displacement amount of the welding machine, so that a film capacitor with stable quality can be manufactured.

[0053] Thus, in the film capacitor of the present invention, the bonding strength between the external electrode and the lead terminal can be controlled by the sinking depth of the lead terminal. Therefore, even if the lead terminal (e.g., the plating layer provided on the surface of the lead) and the external electrode are not alloyed by welding, sufficient bonding strength can be ensured. In addition, in the film capacitor of the present invention, the lead terminal and the external electrode may be alloyed or may not be alloyed.

[0054] For example, by measuring the welded portion using 3D measurement using a digital microscope on a sample after the weld strength measurement, the depth of the lead terminal's penetration from the surface of the external electrode can be measured.

[0055] From the viewpoint of improving the bonding strength between the external electrode and the lead terminal, the lead terminal is preferably sunken to a depth of 0.7 mm or more from the surface of the external electrode.

[0056] The upper limit of the depth of the lead terminal is that the lead terminal can be sunk to the thickness of the external electrode at most. Therefore, the depth of the lead terminal from the surface of the external electrode is less than or equal to the thickness of the external electrode.

[0057] On the other hand, the lead terminal can only be sunken into the external electrode by the thickness of the welding portion. Therefore, the depth of the lead terminal sunk from the surface of the external electrode is preferably less than the thickness of the welding portion of the lead terminal.

[0058] Since the lead terminal is sunk to a depth of 0.5 mm or more from the surface of the external electrode, the thickness of the welded portion of the lead terminal is preferably 0.5 mm or more. In addition, since the lead terminal is sunk to a depth of 0.7 mm or more from the surface of the external electrode, the thickness of the welded portion of the lead terminal is more preferably 0.7 mm or more. In addition, there is no particular upper limit on the thickness of the welded portion of the lead terminal.

[0059] In the film capacitor of the present invention, the surface roughness Ra of the external electrode is 20 μm or more and 45 μm or less.

[0060] As described in the examples below, if the surface roughness Ra of the external electrode is 20 μm to 45 μm, soldering can be performed at a temperature of 300° C. or less. Therefore, the lead terminal can be sunk into the external electrode in a short time without damaging the capacitor element.

[0061] On the other hand, when the surface roughness Ra of the external electrode exceeds 45 μm, problems such as a decrease in strength of the external electrode and a decrease in moisture resistance are likely to occur.

[0062] The surface roughness Ra of the external electrode can be measured by, for example, using a laser microscope (VK-8700 manufactured by KEYENCE Corporation) at two locations at both ends and three locations in the center of the external electrode, and the average value thereof is defined as the value of the surface roughness Ra.

[0063] In the film capacitor of the present invention, the element body constituting the capacitor element is a laminate including a metallized film having a metal layer provided on at least one main surface of a dielectric film, and the external electrode constituting the capacitor element is connected to the metal layer.

[0064] The stacked body is, for example, in the shape of a column having an oblong cross section, and external electrodes formed by, for example, metal spraying (metal spraying) are provided on both end surfaces in the central axis direction thereof.

[0065] The laminated body may be a rolled body formed by rolling up the metallized films in a laminated state.

[0066] Hereinafter, as an example of a film capacitor, a wound film capacitor in which metallized films are wound in a stacked state will be described, but a stacked film capacitor in which metallized films are stacked may also be used.

[0067] Figure 7 It is a perspective view schematically showing an example of a capacitor element constituting the film capacitor of the present invention. Figure 8 yes Figure 7 A cross-sectional view of the capacitor element taken along line bb is shown.

[0068] exist Figure 7 and Figure 8 In the capacitor element 10 shown, the element body 11 is a laminated body including the first metallized film 51 and the second metallized film 52. For example, the element body 11 is a wound body formed by winding the first metallized film 51 and the second metallized film 52 in a laminated state. A pair of external electrodes 12 are electrically connected to both end surfaces of the element body 11.

[0069] like Figure 8 As shown, the first metallized film 51 includes a first dielectric film 53 and a first metal layer 55 provided on the surface of the first dielectric film 53 , and the second metallized film 52 includes a second dielectric film 54 and a second metal layer 56 provided on the surface of the second dielectric film 54 .

[0070] like Figure 8 As shown, the first metal layer 55 and the second metal layer 56 face each other via the first dielectric film 53 or the second dielectric film 54. The first metal layer 55 is electrically connected to one external electrode 12, and the second metal layer 56 is electrically connected to the other external electrode 12.

[0071] The first dielectric film 53 and the second dielectric film 54 may have different structures, but preferably have the same structure.

[0072] The first metal layer 55 is formed so as to reach one side edge but not the other side edge on one surface of the first dielectric film 53. On the other hand, the second metal layer 56 is formed so as to reach the other side edge but not the one side edge on one surface of the second dielectric film 54. The first metal layer 55 and the second metal layer 56 are composed of, for example, aluminum layers or the like.

[0073] Fig. 9 It is a schematic diagram showing the composition Figure 7 and Figure 8 A perspective view of an example of an element body of a capacitor element shown.

[0074] like Figure 8 and Fig. 9 As shown, the first dielectric film 53 and the second dielectric film 54 are mutually spaced in the width direction ( Figure 8 The first metal layer 55 and the second metal layer 56 are stacked in a staggered manner in the left-right direction (in the left-right direction) so that the end of the first metal layer 55 that reaches the side edge of the first dielectric film 53 and the end of the second metal layer 56 that reaches the side edge of the second dielectric film 54 are both exposed from the stacked films. Fig. 9 As shown, the element body 11 is formed by winding the first dielectric film 53 and the second dielectric film 54 in a stacked state to form a metallized film roll, and the first metal layer 55 and the second metal layer 56 are stacked with their ends exposed.

[0075] exist Figure 8 and Fig. 9 In the embodiment, the second dielectric film 54 is wound so as to be located outside the first dielectric film 53, and the first metal layer 55 and the second metal layer 56 of each of the first dielectric film 53 and the second dielectric film 54 are respectively directed inward.

[0076] Fig.10 It is a schematic diagram showing the composition Figure 7 and Figure 8 A perspective view of another example of the element body of the capacitor element shown.

[0077] When the element body 11 of the capacitor element is composed of a wound body of a metallized film, as shown in FIG. Fig.10 As shown, it is preferable to press the film into a flat shape such as an ellipse or an oval in cross section, which is more compact than a shape having a perfect circle in cross section. In this case, the film capacitor can be made smaller as a whole.

[0078] The wound body of the metallized film may also include a cylindrical winding shaft. The winding shaft is disposed on the central axis of the wound metallized film and serves as a winding shaft when the metallized film is wound.

[0079] The external electrodes 12 are formed by, for example, spraying zinc on each end surface of the element body 11 obtained as described above. One external electrode 12 contacts the exposed end of the first metal layer 55, thereby being electrically connected to the first metal layer 55. The other external electrode 12 contacts the exposed end of the second metal layer 56, thereby being electrically connected to the second metal layer 56.

[0080] In the film capacitor of the present invention, the dielectric film constituting the element body of the capacitor element may contain a curable resin as a main component or a thermoplastic resin as a main component. From the viewpoint of improving the heat resistance of the film capacitor, the dielectric film preferably contains a curable resin as a main component.

[0081] In this specification, the "main component of the dielectric film" refers to the component with the largest weight percentage, preferably, the component with a weight percentage exceeding 50% by weight. Therefore, the dielectric film may also contain additives such as silicone resin, and uncured parts of initial materials such as the first organic material and the second organic material described later as components other than the main component.

[0082] The curable resin may be a thermosetting resin or a photocurable resin.

[0083] In this specification, thermosetting resin refers to a resin that can be cured by heat, and the curing method is not limited. Therefore, as long as it is a resin that can be cured by heat, resins that are cured by methods other than heat (for example, light, electron beam, etc.) are also included in thermosetting resins. In addition, depending on the material, sometimes the reaction starts due to the reactivity of the material itself, and resins that are not necessarily cured by applying heat or light from the outside are also thermosetting resins. The same is true for photocurable resins, and the curing method is not limited.

[0084] The curable resin may have at least one of a carbamate bond and a urea bond, or may not have at least one of the carbamate bond and the urea bond. As such a resin, for example, a carbamate resin having a carbamate bond, a urea resin having a urea bond, etc. are cited. In addition, a resin having both a carbamate bond and a urea bond may also be used.

[0085] Furthermore, the presence of the urethane bond and / or the urea bond can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR).

[0086] The curable resin preferably includes a cured product of the first organic material and the second organic material, for example, a cured product obtained by reaction of a hydroxyl group (OH group) of the first organic material and an isocyanate group (NCO group) of the second organic material.

[0087] When a cured product is obtained by the above reaction, an uncured portion of the initial material may remain in the film. For example, the dielectric film may contain at least one of an isocyanate group and a hydroxyl group. In this case, the dielectric film may contain either an isocyanate group or a hydroxyl group, or both.

[0088] Furthermore, the presence of the isocyanate group and / or the hydroxyl group can be confirmed using a Fourier transform infrared spectrophotometer (FT-IR).

[0089] The first organic material is preferably a polyol having a plurality of hydroxyl groups in the molecule. Examples of the polyol include polyether polyol, polyester polyol, and polyvinyl acetal. As the first organic material, two or more organic materials may be used simultaneously.

[0090] The second organic material is preferably an isocyanate compound, epoxy resin or melamine resin having multiple functional groups in the molecule. As the second organic material, two or more organic materials may be used simultaneously. Among the second organic materials, an isocyanate compound is desirable.

[0091] Examples of the isocyanate compound include aromatic polyisocyanates such as diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI), and aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI). Modified products of these polyisocyanates may include those having carbodiimide or urethane.

[0092] The epoxy resin is not particularly limited as long as it is a resin having an epoxy ring, and examples thereof include bisphenol A type epoxy resin, biphenyl skeleton epoxy resin, cyclopentadiene skeleton epoxy resin, naphthalene skeleton epoxy resin, and the like.

[0093] The melamine resin is not particularly limited as long as it is an organic nitrogen compound having a triazine ring at the center of the structure and three amino groups around it, and examples thereof include alkylated melamine resins, etc. In addition, a modified form of melamine may be used.

[0094] In the film capacitor of the present invention, the dielectric film constituting the element body of the capacitor element is preferably obtained by forming a resin solution containing the first organic material and the second organic material into a film shape and then curing it by heat treatment.

[0095] In the film capacitor of the present invention, the dielectric film constituting the element body of the capacitor element may also include a vapor-deposited polymer film as a main component. The vapor-deposited polymer film may have at least one of a urethane bond and a urea bond, or may not have at least one of the urethane bond and the urea bond.

[0096] In addition, the vapor-deposited polymer film refers to a film formed by a vapor-deposition polymerization method, and is basically contained in a curable resin.

[0097] In the film capacitor of the present invention, the dielectric film constituting the element body of the capacitor element may contain a thermoplastic resin as a main component. Examples of the thermoplastic resin include polypropylene, polyethersulfone, polyetherimide, and polyarylate.

[0098] In the film capacitor of the present invention, the dielectric film constituting the element body of the capacitor element may also contain additives for adding other functions. For example, smoothness can be imparted by adding a leveling agent. The additive is more preferably a material having a functional group that reacts with a hydroxyl group and / or an isocyanate group and forming a part of the cross-linked structure of the cured product. As such a material, for example, a resin having at least one functional group selected from the group consisting of an epoxy group, a silanol group, and a carboxyl group is cited.

[0099] In the film capacitor of the present invention, the thickness of the dielectric film constituting the element body of the capacitor element is not particularly limited, but may be appropriately set in accordance with the required electrostatic capacitance and required element volume of the capacitor to be produced.

[0100] In addition, the thickness of the dielectric thin film can be measured using an optical film thickness meter.

[0101] In the thin film capacitor of the present invention, the type of metal contained in the metal layer constituting the element body of the capacitor element is not particularly limited, but the metal layer preferably includes any one selected from the group consisting of aluminum (Al), titanium (Ti), zinc (Zn), magnesium (Mg), tin (Sn) and nickel (Ni).

[0102] In the film capacitor of the present invention, the thickness of the metal layer constituting the element body of the capacitor element is not particularly limited, but from the viewpoint of suppressing damage to the metal layer, the thickness of the metal layer is preferably 5 nm to 40 nm.

[0103] The thickness of the metal layer can be determined by observing a cross section of the metallized thin film cut in the thickness direction using an electron microscope such as a field emission scanning electron microscope (FE-SEM).

[0104] Fig.11 A and Fig.11 B is a schematic diagram showing Figure 1A perspective view showing an example of how to use the film capacitor shown.

[0105] like Fig.11 As shown in FIG. 1A , first, the film capacitor 1 is housed in the outer case 30 .

[0106] The outer casing 30 may be a resin casing or a metal casing.

[0107] exist Fig.11 In the example shown in A of FIG. 1 , a rectangular parallelepiped space is formed inside the outer casing 30. Fig.11 Although not shown in FIG. 1A , capacitor element 10 is preferably separated from the inner surface of outer case 30 and arranged at the center of the interior of outer case 30 .

[0108] The outer case 30 is, for example, a bottomed cylinder having an opening 31 at one end. In this case, the outer case 30 includes a bottom wall 32 facing the opening 31 and sealing the other end, and a side wall 33 protruding from the bottom wall 32 toward the opening 31 .

[0109] exist Fig.11 In the example shown in A of FIG. 1 , the outer casing 30 is in the shape of a square tube with a bottom, which has a substantially rectangular opening 31 at one end, and includes a bottom wall 32 that is opposite to the opening 31 and seals the other end, and a square tube-shaped side wall 33 that protrudes from the bottom wall 32 toward the opening 31. In addition, the outer casing 30 may also have a bottomed tube shape including a cylindrical side wall 33 instead of the square tube-shaped side wall 33.

[0110] like Fig.11 As shown in A, it is preferred that a recess 33a is provided on the side of the side wall 33 of the outer casing 30 on the side of the opening 31. By providing the recess 33a on the opening surface of the outer casing 30, when the film capacitor is mounted on the substrate, it is possible to prevent the film capacitor and the substrate from being sealed and causing the internal pressure to rise. In addition, the recess 33a may not be provided on the outer casing 30.

[0111] Although in Fig.11 Although not shown in FIG. 1A , a guide groove for limiting the position of the lead terminal 20 may be provided on the inner surface of the outer casing 30 .

[0112] Then, if Fig.11 As shown in FIG. 1B , by filling the filling resin 40 into the interior of the outer casing 30 , the periphery of the film capacitor 1 is covered with the filling resin 40 , and the opening 31 of the outer casing 30 is sealed. The lead terminal 20 protrudes from the interior of the outer casing 30 toward the outside. Fig.11 As shown in B, the distance between a pair of lead terminals 20 is fixed.

[0113] As the filling resin 40, a resin corresponding to the required function can be appropriately selected. As the filling resin 40, for example, epoxy resin, silicone resin, urethane resin, etc. can be cited. As a curing agent for epoxy resin, amine curing agent, imidazole curing agent, etc. can also be used. In addition, as the filling resin 40, only resin can be used, but in order to improve the strength, a reinforcing agent can also be added. As the reinforcing agent, for example, inorganic filling materials such as silica and alumina, organic filling materials such as polyethylene fiber and polyamide fiber, and organic-inorganic composite filling materials in which the surface of inorganic powder is coated with an organic material such as a silane coupling agent can be used.

[0114] The height of the filling resin 40 is related to the height of the outer case 30 in such a way that the resin in the opening 31 of the outer case 30 is as thick as possible and can reach the inner side of the outer case 30, can be completely full, and can slightly overflow due to surface tension.

[0115] The film capacitor of the present invention is not limited to the above-mentioned embodiment as long as the lead terminal is welded to the external electrode, the surface roughness Ra of the external electrode is greater than 20 μm and less than 45 μm, and the lead terminal is sunken from the surface of the external electrode to a depth of greater than 0.5 mm. Therefore, various applications and modifications can be made to the structure and manufacturing conditions of the film capacitor within the scope of the present invention.

[0116] In the thin film capacitor of the present invention, when a pair of external electrodes are provided on both end surfaces of the element body and a pair of lead terminals are electrically connected to the pair of external electrodes, at least one external electrode and the lead terminal electrically connected to the external electrode only need to satisfy the relationship described in the above embodiment.

[0117] exist Fig.11 A and Fig.11 Although B shows an example in which a single capacitor element is housed inside a single outer casing, a plurality of capacitor elements may be housed inside a single outer casing as described in Japanese Patent Application Laid-Open No. 2012-69840, for example.

[0118] In the film capacitor of the present invention, the portion where the lead terminal such as the lead wire is electrically connected to the external electrode of the capacitor element is arranged in a small area of ​​the external electrode. Therefore, when a load is applied to the lead terminal, the lead terminal may be separated from the external electrode. Therefore, inside the outer casing, the filling resin is preferably located outside the external electrode of the capacitor element and the lead terminal to fix the two tightly. Thus, even if a load is applied to the protruding portion of the lead terminal, the connection between the lead terminal and the external electrode can be strengthened by the filling resin, and the separation of the two can be suppressed.

[0119] The connection position between the external electrode and the lead terminal is not particularly limited, for example, Figure 1 As shown in FIG. 1 , the central portion of the external electrode may be provided, or as in Japanese Patent No. 4733566. Figure 1 As described, it is the case opening side, but it may also be the case bottom side.

[0120] The following contents are disclosed in this specification.

[0121] <1>

[0122] A film capacitor having:

[0123] A capacitor element comprising an element body and external electrodes provided on end surfaces of the element body; and

[0124] A lead terminal electrically connected to the external electrode,

[0125] The element body is a laminated body including a metalized film having a metal layer provided on at least one main surface of a dielectric film.

[0126] The external electrode is connected to the metal layer.

[0127] The lead terminal is welded to the external electrode.

[0128] The surface roughness Ra of the external electrode is not less than 20 μm and not more than 45 μm.

[0129] The lead terminal is sunken to a depth of 0.5 mm or more from the surface of the external electrode.

[0130] <2>

[0131] In the film capacitor described in <1>,

[0132] The lead terminal is sunken to a depth of 0.7 mm or more from the surface of the external electrode.

[0133] <3>

[0134] In the film capacitor described in <1> or <2>,

[0135] The lead terminal is sunken into the surface of the external electrode to a depth that is equal to or less than the thickness of the welding portion of the lead terminal.

[0136] <4>

[0137] In the film capacitor described in any one of <1> to <3>,

[0138] The thickness of the welding portion of the lead terminal is greater than 0.5 mm.

[0139] <5>

[0140] In the film capacitor described in any one of <1> to <4>,

[0141] The welding portion of the lead terminal is in the shape of a flat plate.

[0142] <6>

[0143] In the film capacitor described in any one of <1> to <5>,

[0144] The lead terminals are lead wires.

[0145] <7>

[0146] In the film capacitor described in any one of <1> to <6>,

[0147] The laminated body is a rolled body obtained by rolling up the metallized films in a laminated state.

[0148] Example

[0149] Hereinafter, examples of the film capacitor of the present invention will be described in more detail. However, the present invention is not limited to these examples.

[0150] Prepared with Figure 1 Film capacitors of the same structure.

[0151] A lead wire with an outer diameter of 1.2 mm was used as the lead terminal, and the welded portion of the lead wire was processed into a flat plate shape with a thickness of 0.75 mm.

[0152] By changing the thermal spraying conditions (for example, the spraying pressure) when forming the external electrodes, the surface roughness Ra of the external electrodes was adjusted to fall within the range of 20 μm to 45 μm.

[0153] By changing the displacement of the welding machine, the sinking depth of the lead wire as the lead terminal was changed within the range of 0.2 mm to 0.75 mm.

[0154] Regarding the film capacitor, the bonding strength between the external electrodes and the lead terminals was evaluated by the following tensile test.

[0155] Fig.12 is a schematic diagram for explaining a tensile test.

[0156] like Fig.12 As shown, the capacitor element 10 connected with the lead terminal 20 is fixed and the lead terminal 20 is oriented in the winding axis direction ( Fig.12 The tensile strength in the coaxial direction was measured when the sample was bent (in the direction indicated by the arrow in FIG).

[0157] One lead terminal was pulled outward along the winding axis direction, and the tensile strength of the lead terminal when it was peeled off from the external electrode was measured using a digital dynamometer (ZTA-50N manufactured by IMONDA). The tensile strength was taken as the bonding strength between the external electrode and the lead terminal. The results are shown in Table 1.

[0158] When the bonding strength is 7N or more and preferably 8N or more, it is evaluated as having sufficient bonding strength. In Table 1, the case where the minimum bonding strength is less than 7N is indicated as × (poor), the case where the minimum bonding strength is 7N or more and less than 8N is indicated as ○ (good), and the case where the minimum bonding strength is 8N or more is indicated as ◎ (excellent).

[0159] [Table 1]

[0160]

[0161] As can be seen from Table 1, there is a correlation between the lead wire penetration depth and the bonding strength, and when the lead wire penetration depth is 0.5 mm or more, sufficient bonding strength is ensured.

[0162] In addition, when the surface roughness Ra of the external electrode is 20 μm or more and 45 μm or less, the temperature at which the dimensional change rate measured by thermomechanical analysis (TMA) reaches 5% is 300°C or less. In contrast, for example, when the surface roughness Ra of the external electrode is 12 μm, the temperature at which the dimensional change rate measured by TMA reaches 5% is 383°C. Based on these results, it is believed that if the surface roughness Ra of the external electrode is 20 μm or more and 45 μm or less, welding can be performed at a temperature of 300°C or less, so that the lead terminal can be sunk into the external electrode in a short time without damaging the capacitor element.

[0163] In addition, the dimensional change rate of the external electrode was calculated as follows.

[0164] <TMA measurement mode>

[0165] Needle insertion mode

[0166] <TMA measurement method: Calculation of dimensional change rate>

[0167] Cut the external electrode into a given size as a sample. The size of the sample can be about 5mm×5mm. Place an indenter in the center of the surface of the sample, apply a load of 100gf to the indenter, and heat the sample to 450°C at a heating rate of 10°C / minute. Measure the penetration depth of the indenter from the start of the measurement until it is heated to 450°C. Divide the penetration depth by the thickness of the sample and multiply by 100. This operation is also performed on the four samples obtained by cutting other parts of the external electrode. The average of the five values ​​obtained is taken as the dimensional change rate of the external electrode.

[0168] That is, this means that when the surface roughness Ra of the external electrode is 20 μm to 45 μm, when heated to 450°C and measured, the temperature at which the dimensional change rate of the external electrode reaches 5% (the temperature at which the indenter penetrates 5%) is always 300°C or less.

[0169] Description of Reference Numerals

[0170] 1 film capacitor;

[0171] 10 Capacitor elements;

[0172] 11 Component body;

[0173] 12 external electrodes;

[0174] 20 lead terminals;

[0175] 30 outer casing;

[0176] 31 opening;

[0177] 32 bottom wall;

[0178] 33 sidewall;

[0179] 33a recess;

[0180] 40 filling resin;

[0181] 51 first metallized film;

[0182] 52 second metallized film;

[0183] 53 a first dielectric film;

[0184] 54 a second dielectric film;

[0185] 55 first metal layer;

[0186] 56 second metal layer;

[0187] 80 welding electrodes;

[0188] D is the depth of the lead terminal from the surface of the external electrode.

Claims

1. A film capacitor comprising: A capacitor element comprising an element body and external electrodes provided on end surfaces of the element body; and A lead terminal electrically connected to the external electrode, The element body is a laminated body including a metalized film having a metal layer provided on at least one main surface of a dielectric film. The external electrode is connected to the metal layer, The lead terminal is welded to the external electrode, The surface roughness Ra of the external electrode is greater than or equal to 20 μm and less than or equal to 45 μm. The lead terminal is sunken to a depth of 0.5 mm or more from the surface of the external electrode.

2. The film capacitor according to claim 1, wherein: The lead terminal is sunken to a depth of 0.7 mm or more from the surface of the external electrode.

3. The film capacitor according to claim 1 or 2, wherein: The lead terminal is sunken into the surface of the external electrode to a depth that is less than or equal to a thickness of a welding portion of the lead terminal.

4. The film capacitor according to any one of claims 1 to 3, wherein: The thickness of the welding portion of the lead terminal is greater than 0.5 mm.

5. The film capacitor according to any one of claims 1 to 4, wherein: The welding portion of the lead terminal is in a flat plate shape.

6. The film capacitor according to any one of claims 1 to 5, wherein: The lead terminals are leads.

7. The film capacitor according to any one of claims 1 to 6, wherein: The laminated body is a rolled body formed by rolling up the metallized films in a laminated state.

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