Thin film capacitor

Abstract

A thin film capacitor (1) has a capacitor element (10). A first metal layer (41) is connected to a first external electrode (51). A second metal layer (42) is connected to a second external electrode (52). A first dielectric thin film (31) projects toward the first external electrode (51) side with respect to a second dielectric thin film (32), and a first projection width becomes larger toward an outermost periphery of the laminate (20) in a thickness direction (T) at an outer periphery portion of the laminate (20). The second dielectric thin film (32) projects toward the second external electrode (52) side with respect to the first dielectric thin film (31), and a second projection width becomes larger toward the outermost periphery of the laminate (20) in the thickness direction (T) at the outer periphery portion of the laminate (20).

Description

Technical Field

[0001] This invention relates to thin-film capacitors. Background Technology

[0002] As a type of capacitor, a film capacitor is known to have the following structure: a flexible film is used as the dielectric film, and a first metal layer and a second metal layer are disposed between the film and opposite each other. The capacitor element constituting the film capacitor is manufactured, for example, by winding or stacking the film having the first metal layer and the film having the second metal layer to form a laminate, and then forming external electrodes at both end faces of the laminate.

[0003] Such film capacitors are used, for example, with the outer periphery of the capacitor element covered by an outer casing. As the outer casing of the film capacitor, the capacitor element is typically coated with a thermosetting resin such as epoxy resin, and the capacitor element is coated with a shell filled with a thermosetting resin such as epoxy resin. As the material for the shell, resins such as polyphenylene sulfide can be used.

[0004] Patent Document 1 discloses a thin-film capacitor comprising a metallized thin film formed by overlapping a first thin-film member and a second thin-film member having a metal film formed on at least one side of their surfaces, and forming a metallized thin film by winding the metallized thin film. Electrode members are connected to both ends of the wound metallized thin film in the width direction. The first thin-film member is configured to protrude in the width direction relative to the second thin-film member, thereby being configured such that a first protruding end and a first recessed end are repeatedly stacked in the layering direction in the wound metallized thin film. The metal film is configured such that a portion of the first protruding end protruding in the width direction from the first recessed end is exposed.

[0005] Prior art literature

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-4916 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] In the thin-film capacitor described in Patent Document 1, the first protruding end and the first recessed end are repeatedly configured, which makes it easier to connect the electrode component to the metal film. Therefore, it is possible to improve the mechanical strength of the contact portion between the metallized film and the electrode component without processing the first thin-film component.

[0010] However, for film capacitors like those described in Patent Document 1, repeated use at low and high temperatures is not envisioned. If such repeated use occurs, the capacitor will repeatedly contract and expand. In this case, due to the difference in thermal shrinkage rates between the film, external electrodes, and outer casing within the laminate, thermal stress will concentrate at locations close to these three points. Therefore, it can be said that there is room for improvement in terms of reliability relative to stress load.

[0011] The present invention was made to solve the above-mentioned problems, and its purpose is to provide a thin-film capacitor that can alleviate thermal stress in areas of thermal stress concentration even when used repeatedly at low and high temperatures.

[0012] Technical solutions for solving the problem

[0013] The thin-film capacitor of the present invention includes a capacitor element. The capacitor element includes: a laminate having a first end face and a second end face opposed in the width direction; a first external electrode connected to the first end face of the laminate; and a second external electrode connected to the second end face of the laminate. The laminate includes a first dielectric film, a second dielectric film, a first metal layer, and a second metal layer. The first dielectric film has a first main face and a second main face opposed in the thickness direction orthogonal to the width direction. The second dielectric film has a third main face and a fourth main face opposed in the thickness direction. In the laminate, the second main face of the first dielectric film and the third main face of the second dielectric film are opposed in the thickness direction. The first metal layer is connected to the first external electrode. The second metal layer is connected to the second external electrode. In the first and second dielectric films adjacent in the thickness direction, the first dielectric film protrudes towards the first external electrode relative to the second dielectric film. When the length of the protrusion of the first dielectric film relative to the second dielectric film in the width direction is defined as the first protrusion width, the first protrusion width is larger than the central portion of the laminate in the thickness direction at its outer periphery, and increases towards the outermost periphery of the laminate in the thickness direction. Similarly, in the second and third dielectric films adjacent in the thickness direction, the second dielectric film protrudes towards the second external electrode relative to the first dielectric film. When the length of the protrusion of the second dielectric film relative to the first dielectric film in the width direction is defined as the second protrusion width, the second protrusion width is larger than the central portion of the laminate in the thickness direction at its outer periphery, and increases towards the outermost periphery of the laminate in the thickness direction.

[0014] Invention Effects

[0015] According to the present invention, a thin-film capacitor can be provided that can alleviate thermal stress in areas of thermal stress concentration even when used repeatedly at low and high temperatures. Attached Figure Description

[0016] Figure 1 This is a cross-sectional schematic diagram illustrating an example of a thin-film capacitor according to the present invention.

[0017] Figure 2 This is a cross-sectional schematic diagram illustrating another example of the thin-film capacitor of the present invention.

[0018] Figure 3 This is a cross-sectional schematic diagram showing an example of a capacitor element constituting the thin-film capacitor of the present invention.

[0019] Figure 4 This is a perspective view showing a step in the fabrication of a first metallized thin film, which is an example of a method for manufacturing a thin-film capacitor according to the present invention.

[0020] Figure 5 This is a perspective view showing a step in the fabrication of a second metallized thin film, which is an example of a method for manufacturing a thin-film capacitor according to the present invention.

[0021] Figure 6 This is a cross-sectional schematic diagram showing the fabrication process of a laminate, which is an example of a method for manufacturing a thin-film capacitor according to the present invention.

[0022] Figure 7 It shows the difference from Figure 6 A top-down view of the first metallized film being unwound from the first film reel.

[0023] Figure 8 This is a cross-sectional schematic diagram showing the capacitor element constituting the thin-film capacitor according to Embodiment 1.

[0024] Figure 9 This is a cross-sectional schematic diagram showing the capacitor element constituting the thin-film capacitor involved in Reference Example 1.

[0025] Figure 10 This is a schematic cross-sectional view showing the capacitor element constituting the thin-film capacitor involved in Comparative Example 1.

[0026] Figure 11 This is a cross-sectional schematic diagram showing the capacitor element constituting the thin-film capacitor involved in Comparative Example 2.

[0027] Figure 12 This is a cross-sectional schematic diagram showing an example of a thin-film capacitor model that is modeled according to Example 1 and used as the object of analysis.

[0028] Figure 13 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Embodiment 1.

[0029] Figure 14 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Reference Example 1.

[0030] Figure 15 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Comparative Example 1.

[0031] Figure 16 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Comparative Example 2.

[0032] Figure 17This is a cross-sectional schematic diagram showing a first variation of the thin-film capacitor model that is modeled according to Example 1 and used as the object of analysis.

[0033] Figure 18 This is a cross-sectional schematic diagram showing a second variation of the thin-film capacitor model that is modeled according to Example 1 and used as the object of analysis. Detailed Implementation

[0034] The thin-film capacitor of the present invention will now be described. Furthermore, the present invention is not limited to the following structures, and appropriate modifications can be made without changing the spirit of the invention. Moreover, structures combining multiple preferred structures described below are also part of the present invention.

[0035] Hereinafter, as an example of the film capacitor of the present invention, a so-called wound film capacitor, which is formed by winding films including metallized films in a stacked state, will be described, wherein a metal layer is provided on the main surface of the dielectric film of the metallized film. The film capacitor of the present invention may also be a so-called stacked film capacitor, which is formed by stacking films including metallized films, wherein a metal layer is provided on the main surface of the dielectric film of the metallized film.

[0036] Figure 1 This is a cross-sectional schematic diagram illustrating an example of a thin-film capacitor according to the present invention.

[0037] Figure 1 The thin-film capacitor 1 shown includes a capacitor element 10. The capacitor element 10 includes a laminate 20, a first external electrode 51, and a second external electrode 52. Figure 1 In the first external electrode 51, a first lead 61 is electrically connected, and a second lead 62 is electrically connected to the second external electrode 52.

[0038] Figure 1 The film capacitor 1 shown also includes an outer casing resin 70, which is one example of an outer casing. The outer casing resin 70 covers the outer periphery of the capacitor element 10.

[0039] Figure 2 This is a cross-sectional schematic diagram illustrating another example of the thin-film capacitor of the present invention.

[0040] Figure 2 The thin-film capacitor 2 shown includes a capacitor element 10. The capacitor element 10 includes a laminate 20, a first external electrode 51, and a second external electrode 52. Figure 2 In the first external electrode 51, a first lead 61 is electrically connected, and a second lead 62 is electrically connected to the second external electrode 52.

[0041] Figure 2The film capacitor 2 shown also includes a filling resin 71 and an outer casing 72, which are examples of outer casings. The outer casing 72, which is filled with the filling resin 71 between itself and the capacitor element 10, covers the outer periphery of the capacitor element 10.

[0042] For example, thermosetting resins such as epoxy resin, silicone resin, and urethane resin can be used as the material for the outer resin 70 or the filler resin 71. Amine curing agents and imidazole curing agents can also be used for epoxy resins. Furthermore, while resin alone can be used for the outer resin 70 or the filler resin 71, reinforcing agents can be added to improve strength. Reinforcing agents such as silica and alumina can be used.

[0043] For example, resins such as polyphenylene sulfide (PPS) and liquid crystal polymer (LCP) can be used as materials for the outer casing 72.

[0044] When LCP is used as the material for the outer casing 72, for example, LCP having p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid groups on the skeleton can be used. In addition to p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid groups, LCPs that have formed condensation polymers using various components such as phenol, phthalic acid, and polyethylene terephthalate can also be used.

[0045] The outer casing 72 preferably contains inorganic filler material in addition to resin. In this case, the inorganic filler material contained in the outer casing 72 is preferably a material with a melting point higher than LCP, and more preferably a material with a melting point of 680°C or higher.

[0046] There are no particular limitations on the form of inorganic fillers; for example, fibrous or plate-like forms with a long dimension can be listed. Two or more of these inorganic fillers can also be used in combination.

[0047] In this specification, "fibrous" means a state in which the length of the filler material along its longitudinal direction and the diameter of the cross-section perpendicular to the longitudinal direction are such that the length along the longitudinal direction ÷ the diameter of the cross-section is ≥ 5 (i.e., the aspect ratio is 5:1 or greater). Here, the cross-section diameter is defined as the distance between two points on the outer perimeter of the cross-section that is the longest. When the cross-section diameter differs along the longitudinal direction, the measurement is performed at the location where the cross-section diameter becomes the largest. Furthermore, "plate-like" means a state in which the diameter of the cross-section of the surface with the largest projected area and the maximum height in the direction perpendicular to that cross-section are such that the diameter of the cross-section ÷ the height is ≥ 3.

[0048] The inorganic filler material is preferably an inorganic filler material having a diameter of at least 5 μm and a length of at least 50 μm.

[0049] Specifically, inorganic fillers such as fibrous glass fillers, plate-like talc, or mica can be used. In particular, inorganic fillers preferably contain glass fillers as the main component.

[0050] The resin-containing outer casing 72 can be manufactured, for example, by injection molding or other methods.

[0051] The surface free energy of the outer surface of the outer housing 72 is preferably 34 mN / m or more and 40 mN / m or less. In this case, additional components can be firmly fixed to the outer surface of the outer housing 72 with an adhesive force of 400 N or more using adhesives, adhesive tapes, etc. Furthermore, the model number, characteristics, etc., can be printed on the outer surface of the outer housing 72 using ink with high surface tension.

[0052] The surface free energy of the outer surface of the outer housing 72 can be changed by the composition of the outer housing 72 (resin type, filler content) or the injection molding method of the outer housing 72. These are just examples; other methods can also be used to control the surface free energy of the outer surface of the outer housing 72.

[0053] It is possible to measure the wetting tension when a liquid is applied to the outer casing 72, and use it as the surface free energy of the outer surface of the outer casing 72.

[0054] The wetting tension of the outer surface of the outer casing 72 can be measured, for example, using a Tension Checker TC-B-30~56 (film wetting tension test pen) manufactured by Pacific Chemical Co., Ltd. Specifically, a line is drawn on the outer surface of the outer casing 72 using a pen with a certain value. If the ink line does not form a droplet and remains unchanged for two seconds, the wetting tension of the outer casing 72 is determined to be the same as or higher than the value of that pen. On the other hand, if the liquid film breaks down or the entire structure contracts within approximately two seconds, the same determination is repeated using a test pen with a lower value, thereby determining the wetting tension of the outer casing 72.

[0055] Furthermore, the adhesive strength of the adhesive to the outer surface of the outer housing 72 can be measured, for example, by the following method: 0.1g of Momentive's silicone-based adhesive TSE322 is applied to the outer surface of the outer housing 72, and then the adhesive-coated side of the outer housing 72 is pressed onto a glass epoxy board R-1705 (1.6mm thick) manufactured by Panasonic Electric Works Co., Ltd. After heat curing at 80°C for two hours, the strength at which the outer housing 72 is peeled off by pressing is measured using a digital force gauge manufactured by Imada Co., Ltd., thereby determining the adhesive strength to the outer surface of the outer housing 72.

[0056] Figure 3 This is a cross-sectional schematic diagram showing an example of a capacitor element constituting the thin-film capacitor of the present invention.

[0057] In this instruction manual, such as Figure 3 As shown, the thickness direction and width direction of the capacitor element are defined by T and W, respectively. Here, the thickness direction T and the width direction W are orthogonal to each other.

[0058] Figure 3 The capacitor element 10 shown includes a laminate 20, a first external electrode 51, and a second external electrode 52.

[0059] The laminate 20 has a first end face 20a and a second end face 20b that are opposed in the width direction W.

[0060] The laminate 20 is a wound body formed by winding the first metallized film 21 and the second metallized film 22 in a stacked state in the thickness direction T.

[0061] In capacitor element 10, from a low-profile viewpoint, preferably, in the direction of observation relative to the roll axis of laminate 20 (in... Figure 3 When the cross-section is perpendicular to the width direction (W), the cross-sectional shape of the laminate 20 is flat. More specifically, it is preferable that the cross-sectional shape of the laminate 20 is pressed into a flat shape like an ellipse or an oblong, so as to make a shape with a thickness smaller than when the cross-sectional shape of the laminate 20 is a perfect circle.

[0062] Whether the cross-sectional shape of the laminate is flattened can be confirmed, for example, by the presence of pressing marks in the laminate.

[0063] The capacitor element 10 may also have a cylindrical winding shaft. The winding shaft is disposed on the central axis of the first metallized film 21 and the second metallized film 22 in the winding state, and becomes the winding shaft when the first metallized film 21 and the second metallized film 22 are wound.

[0064] The first metallization film 21 includes a first dielectric film 31 and a first metal layer 41.

[0065] The first dielectric thin film 31 has a first main surface 31a and a second main surface 31b opposite each other in the thickness direction T.

[0066] The first metal layer 41 is disposed on the first main surface 31a of the first dielectric film 31. More specifically, the first metal layer 41 on the first main surface 31a of the first dielectric film 31 is configured to reach one side edge of the first dielectric film 31 in the width direction W, but not reach the other side edge of the first dielectric film 31.

[0067] The second metallization film 22 includes a second dielectric film 32 and a second metal layer 42.

[0068] The second dielectric thin film 32 has a third main surface 32a and a fourth main surface 32b opposite each other in the thickness direction T.

[0069] The second metal layer 42 is disposed on the third main surface 32a of the second dielectric film 32. More specifically, the second metal layer 42 on the third main surface 32a of the second dielectric film 32 is configured such that, in the width direction W, it does not reach one side edge of the second dielectric film 32, but reaches the other side edge of the second dielectric film 32.

[0070] In the laminate 20, the first metallized film 21 and the second metallized film 22 adjacent in the thickness direction T are staggered in the width direction W, such that the end of the first metal layer 41 reaching the side edge of the first dielectric film 31 is exposed on the first end face 20a of the laminate 20, and the end of the second metal layer 42 reaching the side edge of the second dielectric film 32 is exposed on the second end face 20b of the laminate 20. That is, among the first metallized film 21 and the second metallized film 22 adjacent in the thickness direction T, the first metallized film 21 protrudes toward the first external electrode 51 relative to the second metallized film 22. Furthermore, among the first metallized film 21 and the second metallized film 22 adjacent in the thickness direction T, the second metallized film 22 protrudes toward the second external electrode 52 relative to the first metallized film 21. In this state, the first metal layer 41 is connected to the first external electrode 51, and the second metal layer 42 is connected to the second external electrode 52. Furthermore, the first metal layer 41 is not connected to the second external electrode 52, and the second metal layer 42 is not connected to the first external electrode 51.

[0071] In the laminate 20, the first metallized film 21 and the second metallized film 22 adjacent in the thickness direction T are offset in the width direction W as described above. Therefore, among the first dielectric film 31 and the second dielectric film 32 adjacent in the thickness direction T, the first dielectric film 31 protrudes towards the first external electrode 51 relative to the second dielectric film 32. Furthermore, among the first dielectric film 31 and the second dielectric film 32 adjacent in the thickness direction T, the second dielectric film 32 protrudes towards the second external electrode 52 relative to the first dielectric film 31.

[0072] The laminate 20 is formed by winding the first metallized film 21 and the second metallized film 22 in a stacked state in the thickness direction T. Therefore, it can be said that it sequentially includes the first dielectric film 31, the first metal layer 41, the second dielectric film 32, and the second metal layer 42 in the thickness direction T. Furthermore, it can also be said that the laminate 20 is a wound body formed by winding the first dielectric film 31, the first metal layer 41, the second dielectric film 32, and the second metal layer 42 in a stacked state in the thickness direction T.

[0073] In the laminate 20, the second main surface 31b of the first dielectric film 31 and the third main surface 32a of the second dielectric film 32 are opposite each other in the thickness direction T. Furthermore, the first main surface 31a of the first dielectric film 31 and the fourth main surface 32b of the second dielectric film 32 are opposite each other in the thickness direction T. Thus, in the laminate 20, the first metallization film 21 and the second metallization film 22 are wound in a stacked state in the thickness direction T. In other words, in the laminate 20, the first metallization film 21 and the second metallization film 22 are wound in a stacked state in the thickness direction T, such that the first metallization film 21 is the inner side of the second metallization film 22; more specifically, the first metal layer 41 is the inner side of the first dielectric film 31, and the second metal layer 42 is the inner side of the second dielectric film 32. In other words, in the laminate 20, the first metal layer 41 and the second metal layer 42 sandwich the first dielectric film 31 or the second dielectric film 32 and are opposite to each other.

[0074] When the length of the first dielectric film 31 protruding relative to the second dielectric film 32 in the width direction W is defined as the first protrusion width, such as Figure 3 As shown, the first protrusion width of the outer periphery of the laminate 20 in the thickness direction T is larger than that of the central portion of the laminate 20 in the thickness direction T, and increases toward the outermost periphery of the laminate 20 in the thickness direction T.

[0075] Furthermore, when the length of the second dielectric film 32 protruding in the width direction W relative to the first dielectric film 31 is defined as the second protrusion width, such as Figure 3 As shown, the second protrusion has a wider width than the central portion of the laminate 20 in the thickness direction T on the outer periphery, and it increases toward the outermost periphery of the laminate 20 in the thickness direction T.

[0076] As described above, when film capacitors are used repeatedly at both low and high temperatures, thermal stress concentrates at locations close to the film, external electrode, and outer casing due to differences in thermal shrinkage rates among the film, external electrode, and outer casing of the laminate. In the film capacitor of the present invention, the bonding shape between the film and the external electrode is improved by designing the film's protruding width at the outer periphery of the laminate to be larger than that at the center of the laminate and increasing towards the outermost periphery. This alleviates thermal stress at locations where thermal stress concentration occurs.

[0077] At the center of the laminate 20 in the thickness direction T, the first protruding width is preferably as follows: Figure 3 The height difference shown is fixed, but it can also be less than 50 μm. Similarly, at the center of the laminate 20 in the thickness direction T, the second protrusion width is preferably as shown. Figure 3 The height difference shown is fixed, but it can also have a height difference of less than 50μm.

[0078] When observing the cross-section along the thickness direction T and the width direction W, the end of the first dielectric film 31 that is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest first protrusion width is designated as point X1, and the end of the first dielectric film 31 that is closest to point X1 and has the smallest first protrusion width is designated as point Y1. The angle formed by the straight line passing through points X1 and Y1 and the straight line passing through the end of the first dielectric film 31 with the smallest first protrusion width (in...) Figure 3 In this case, the angle shown as θ1 (also called the first pitch angle θ1) is preferably 50° or more and 80° or less. Under these conditions, the thermal stress at point X1 is effectively relieved.

[0079] When observing the cross-section along the thickness direction T and the width direction W, the end of the first dielectric film 31 that is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest first protrusion width is designated as point X1, and the end of the first dielectric film 31 that is closest to point X1 and has the smallest first protrusion width is designated as point Y1. At this time, the length in the width direction W between points X1 and Y1 (in...) Figure 3 In the diagram, H1 represents the length, also known as the first pitch height H1. Preferably, it represents the length in the width direction W between the outer end of the first external electrode 51 and point X1. Figure 3 In this case, the length shown by T1 (also known as the first electrode thickness TI) is more than 5% and less than 50%. This provides a good effect in relieving thermal stress at point X1.

[0080] The second main surface 31b of the first dielectric film 31, which is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest first protrusion width, can be as follows: Figure 3The capacitor element 10 may be covered by the first external electrode 51, or it may not be covered by the first external electrode 51. In other words, when the outer periphery of the capacitor element 10 is covered by the outer casing, the end of the first dielectric film 31, which is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest first protrusion width, may or may not be in contact with the outer casing.

[0081] When observing the cross-section along the thickness direction T and the width direction W, the end of the second dielectric film 32 that is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest second protrusion width is designated as point X2, and the end of the second dielectric film 32 that is closest to point X2 and has the smallest second protrusion width is designated as point Y2. The angle formed by the straight line passing through points X2 and Y2 and the straight line passing through the end of the second dielectric film 32 with the smallest second protrusion width (in...) Figure 3 In the above case, the angle shown as θ2 (also called the second pitch angle θ2) is preferably 50° or more and 80° or less. In this case, the effect of relieving thermal stress at point X2 is good.

[0082] When observing the cross-section along the thickness direction T and the width direction W, the end of the second dielectric film 32 that is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest second protrusion width is designated as point X2, and the end of the second dielectric film 32 that is closest to point X2 and has the smallest second protrusion width is designated as point Y2. At this time, the length in the width direction W between points X2 and Y2 (in...) Figure 3 In the middle, the length shown by H2, also called the second pitch height H2), is preferably the length in the width direction W between the outer end of the second external electrode 52 and point X2 (in Figure 3 In this case, the length shown by T2 (also known as the thickness of the second electrode T2) is more than 5% and less than 50%. This provides a good effect in relieving thermal stress at point X2.

[0083] The fourth main surface 32b of the second dielectric film 32, which is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest second protrusion width, can be as follows: Figure 3 The capacitor element 10 may be covered by the second external electrode 52, or it may not be covered by the second external electrode 52. In other words, when the outer periphery of the capacitor element 10 is covered by the outer casing, the end of the second dielectric film 32, which is closest to the outermost periphery of the laminate 20 in the thickness direction T and has the largest second protrusion width, may or may not be in contact with the outer casing.

[0084] The ends of the first dielectric film 31, the second dielectric film 32, the outer ends of the first external electrode 51, and the outer ends of the second external electrode 52 are preferably flat, but they may also have a height difference of less than 50 μm.

[0085] Regarding the lengths of the first pitch height H1, the second pitch height H2, the first electrode thickness T1, and the second electrode thickness T2, for example, they can be manufactured using a rotary grinding machine, etc. Figure 3 The cross-section shown was measured using a microscope with length measuring capabilities.

[0086] The first dielectric film 31 may also contain a curable resin as the main component.

[0087] In this specification, the principal component means the component with the highest weight percentage, preferably, it means the component with a weight percentage greater than 50% by weight.

[0088] The curing resin can be either a thermosetting resin or a photocuring resin.

[0089] In this specification, thermosetting resin means a resin that can be cured by heat, but does not limit the curing method. Therefore, any resin that can be cured by heat, including resins that can be cured by methods other than heat (e.g., light, electron beam, etc.), is also included in thermosetting resin. Furthermore, depending on the material, there are cases where a reaction begins due to the reactivity of the material itself; resins that cure even without external heat are also called thermosetting resins. The same applies to light-curing resin; any resin that can be cured by light also includes resins that can be cured by methods other than light (e.g., heat, etc.).

[0090] The curable resin preferably comprises a cured product containing a first organic material having hydroxyl (OH) groups and a second organic material having isocyanate (NCO) groups. In this case, the curable resin comprises a cured product containing urethane bonds obtained by reacting the hydroxyl groups of the first organic material and the isocyanate groups of the second organic material.

[0091] The presence of urethane bonds in the first dielectric film 31 can be confirmed by analysis using a Fourier transform infrared spectrophotometer (FT-IR).

[0092] When a curable resin is obtained through the above reaction, sometimes an uncured portion of the starting material may remain in the first dielectric film 31. For example, the first dielectric film 31 may also contain at least one of hydroxyl and isocyanate groups. In this case, the first dielectric film 31 may contain one of hydroxyl and isocyanate groups, or it may contain both hydroxyl and isocyanate groups.

[0093] The presence of hydroxyl groups and / or isocyanate groups in the first dielectric film 31 can be confirmed by FT-IR analysis.

[0094] Examples of first organic materials include phenoxy resins, polyvinyl acetal resins, and polyvinyl butyral resins.

[0095] As the primary organic material, it can be used in conjunction with a variety of other organic materials.

[0096] Examples of second organic materials include, for example, aromatic polyisocyanates such as diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI), and aliphatic polyisocyanates such as hexamethylene diisocyanate (HDI). Modified forms of at least one of these polyisocyanates, or mixtures of at least one of these polyisocyanates and their modifiers, can be used as the second organic material.

[0097] As a second organic material, it can also be used in conjunction with multiple organic materials.

[0098] The first dielectric film 31 may also contain thermoplastic resin as the main component.

[0099] Examples of thermoplastic resins include, for example, polypropylene, polyethersulfone, polyetherimide, and polyarylate.

[0100] The first dielectric film 31 may also contain additives for adding various functions.

[0101] As an additive, for example, leveling agents used to impart smoothness can be listed.

[0102] The additive preferably has functional groups that react with hydroxyl and / or isocyanate groups to form part of the cross-linked structure of the cured product. Examples of such additives include resins having at least one functional group selected from the group consisting of hydroxyl, epoxy, silanol, and carboxyl groups.

[0103] Like the first dielectric film 31, the second dielectric film 32 may contain either a curable resin or a thermoplastic resin as its main component. Furthermore, like the first dielectric film 31, the second dielectric film 32 may also contain additives.

[0104] The compositions of the first dielectric film 31 and the second dielectric film 32 may be different from each other, but are preferably the same.

[0105] The thickness of the first dielectric film 31 and the second dielectric film 32 is preferably 1 μm or more and 10 μm or less, more preferably 3 μm or more and 5 μm or less.

[0106] The thicknesses of the first dielectric film 31 and the second dielectric film 32 may be different from each other, but are preferably the same.

[0107] The thicknesses of the first dielectric film 31 and the second dielectric film 32 can be measured using an optical thickness gauge.

[0108] The first dielectric film 31 and the second dielectric film 32 are preferably manufactured by molding a resin solution containing the resin material described above into a film and then curing it by heat treatment.

[0109] Materials that form the first metal layer 41 and the second metal layer 42 include, for example, metals such as aluminum, zinc, titanium, magnesium, tin, and nickel.

[0110] The compositions of the first metal layer 41 and the second metal layer 42 may be different from each other, but are preferably the same.

[0111] The thickness of the first metal layer 41 and the second metal layer 42 is preferably 5 nm or more and 40 nm or less.

[0112] The thicknesses of the first metal layer 41 and the second metal layer 42 may be different from each other, but are preferably the same.

[0113] The thickness of the first metal layer 41 can be determined by observing a cross-section of the first metallized thin film 21 in the thickness direction using a transmission electron microscope (TEM). The thickness of the second metal layer 42 can also be determined in the same way as the thickness of the first metal layer 41.

[0114] The first metal layer 41 and the second metal layer 42 are preferably formed by vapor deposition of the metals described above on the main surfaces of the first dielectric film 31 and the second dielectric film 32, respectively.

[0115] A fuse section may also be provided in the first metal layer 41. The fuse section in the first metal layer 41 is the portion that connects the segmented electrode section and the electrode section within the first metal layer 41. The segmented electrode section is formed by dividing the portion opposite to the second metal layer 42 into multiple parts, while the electrode section is the portion not opposite to the second metal layer 42. Examples of electrode patterns for the first metal layer 41 where the fuse section is provided include those disclosed in Japanese Patent Application Publication No. 2004-363431 and Japanese Patent Application Publication No. Hei 5-251266.

[0116] Similar to the first metal layer 41, a fuse section may also be provided in the second metal layer 42.

[0117] The first external electrode 51 is connected to the first end face 20a of the laminate 20. More specifically, the first external electrode 51 is connected to the first metal layer 41 by contacting the end of the first metal layer 41 exposed on the first end face 20a of the laminate 20. On the other hand, the first external electrode 51 is not connected to the second metal layer 42.

[0118] The second external electrode 52 is connected to the second end face 20b of the laminate 20. More specifically, the second external electrode 52 is connected to the second metal layer 42 by contacting the end of the second metal layer 42 exposed on the second end face 20b of the laminate 20. On the other hand, the second external electrode 52 is not connected to the first metal layer 41.

[0119] Materials used to form the first external electrode 51 and the second external electrode 52 include, for example, metals such as zinc, aluminum, tin, and zinc-aluminum alloys.

[0120] The compositions of the first external electrode 51 and the second external electrode 52 may be different from each other, but are preferably the same.

[0121] The first external electrode 51 and the second external electrode 52 are preferably formed by sputtering the metal described above onto the first end face 20a and the second end face 20b of the laminate 20, respectively.

[0122] Capacitor element 10 can be manufactured, for example, by the following methods.

[0123] <Fabrication process of metallized thin films>

[0124] Figure 4 This is a perspective view showing a step in the fabrication of a first metallized thin film, which is an example of a method for manufacturing a thin-film capacitor according to the present invention. Figure 5 This is a perspective view showing a step in the fabrication of a second metallized thin film, which is an example of a method for manufacturing a thin-film capacitor according to the present invention.

[0125] First, for example, the first organic material, the second organic material, additives, etc., described above are mixed to prepare a resin solution. Then, the obtained resin solution is molded into a thin film, and then cured by heat treatment to produce a product such as... Figure 4 as well as Figure 5 The first dielectric film 31 and the second dielectric film 32 are shown.

[0126] Next, as Figure 4As shown, a first metal layer 41 is formed on the first main surface 31a of the first dielectric film 31 by vapor deposition of metals such as aluminum, zinc, titanium, magnesium, tin, and nickel, thereby fabricating a first metallized film 21. At this time, the first metal layer 41 is formed such that, in the width direction, it reaches one side edge of the first dielectric film 31 but does not reach the other side edge of the first dielectric film 31.

[0127] In addition, such as Figure 5 As shown, a second metal layer 42 is formed on the third main surface 32a of the second dielectric film 32 by vapor deposition of metals such as aluminum, zinc, titanium, magnesium, tin, and nickel, thereby fabricating the second metallized film 22. At this time, the second metal layer 42 is formed such that, in the width direction, it does not reach one side edge of the second dielectric film 32, but reaches the other side edge of the second dielectric film 32.

[0128] <Fabrication process of laminated bodies>

[0129] Figure 6 This is a cross-sectional schematic diagram showing the fabrication process of a laminate, which is an example of a method for manufacturing a thin-film capacitor according to the present invention.

[0130] First, such as Figure 6 As shown, a first film reel 101 with a first metallized film 21 wound on a first reel shaft 111 and a second film reel 102 with a second metallized film 22 wound on a second reel shaft 112 are prepared.

[0131] Next, the first metallized film 21 is unwound from the first film reel 101, and the second metallized film 22 is unwound from the second film reel 102. At this time, the first metallized film 21 and the second metallized film 22 are unwound such that the second main surface 31b of the first dielectric film 31 and the third main surface 32a of the second dielectric film 32 are facing each other.

[0132] Then, the unwound first metallized film 21 and second metallized film 22 are wound onto the winding shaft 200 in a staggered and overlapping state in the width direction.

[0133] Figure 7 It shows the difference from Figure 6 A top-down view of the first metallized film being unwound from the first film reel.

[0134] like Figure 7 As shown, when the first metallized film 21 is unwound, the first reel shaft 111 can swing in the width direction (in the direction indicated by the double arrows) orthogonal to the unwinding direction. By swinging the first reel shaft 111 in the width direction, the first metallized film 21 is unwound while moving in the same width direction.

[0135] Similarly, when unwinding the second metallized film 22, the second reel shaft 112 can oscillate in a width direction orthogonal to the unwinding direction. Thus, the second metallized film 22 is unwound while moving in the same width direction.

[0136] Therefore, by oscillating the first reel shaft 111 and the second reel shaft 112, adjusting the oscillation timing, oscillation distance, and other oscillation conditions, the aforementioned first protrusion width and second protrusion width can be adjusted. As a result, it is possible to manufacture a device with the aforementioned characteristics while wound around the winding shaft 200. Figure 3 The layered structure shown is 20.

[0137] Furthermore, the winding speed of the winding shaft 200 can be adjusted by combining it with the swaying conditions of the first winding shaft 111 and the second winding shaft 112, thereby adjusting the first protrusion width and the second protrusion width.

[0138] Furthermore, even if instead of oscillating the first reel shaft 111 and the second reel shaft 112 in the width direction, the winding shaft 200 is oscillated in the width direction, or the moving roller is oscillated in the width direction, it is still possible to manufacture a device having such a state of being wound around the winding shaft 200. Figure 3 The laminate 20 shown has a structure in which a moving roller moves the first metallized film 21 and the second metallized film 22.

[0139] Then, if necessary, the resulting laminate 20 can be clamped from a direction orthogonal to the width direction and pressed into an elliptical cylindrical shape.

[0140] <External Electrode Formation Process>

[0141] At the first end face 20a of the laminate 20, a metal such as zinc, aluminum, tin, or zinc-aluminum alloy is sputtered, thereby forming Figure 3 The first external electrode 51 shown is connected to the first metal layer 41.

[0142] Furthermore, on the second end face 20b of the laminate 20, a metal such as zinc, aluminum, tin, or zinc-aluminum alloy is sputtered, thereby forming... Figure 3 The second external electrode 52 shown is connected to the second metal layer 42.

[0143] Through the above, it is possible to manufacture Figure 3 The capacitor element 10 shown.

[0144] Then, if necessary, conductor terminals such as leads can be connected to the obtained first external electrode 51 and second external electrode 52 respectively, and then the outer periphery of the capacitor element 10 can be covered with an outer casing.

[0145] Through the above, it is possible to manufacture Figure 1The thin film capacitor 1 shown is or Figure 2 The thin-film capacitor 2 shown.

[0146] Example

[0147] The following describes embodiments of the thin-film capacitor of the present invention in more detail. However, the present invention is not limited to these embodiments.

[0148] Figure 8 This is a cross-sectional schematic diagram showing the capacitor element constituting the thin-film capacitor according to Embodiment 1. Figure 9 This is a cross-sectional schematic diagram showing the capacitor element constituting the thin-film capacitor involved in Reference Example 1. Figure 10 This is a schematic cross-sectional view showing the capacitor element constituting the thin-film capacitor involved in Comparative Example 1. Figure 11 This is a cross-sectional schematic diagram showing the capacitor element constituting the thin-film capacitor involved in Comparative Example 2.

[0149] In Example 1, Reference Example 1, Comparative Example 1 and Comparative Example 2, a model of a thin-film capacitor was used as the analysis object for stress analysis based on FEM (finite element method).

[0150] Figure 12 This is a cross-sectional schematic diagram showing an example of a thin-film capacitor model that is modeled according to Example 1 and used as the object of analysis. Figure 13 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Embodiment 1.

[0151] like Figure 12 As shown, the structure is configured such that the width of the thin film portion A and the outer electrode portion C is 30 mm, the thickness is 5 mm, and the entire structure is covered by an outer casing portion B with a thickness of 1 mm. The contact point between the thin film portion A, the outer casing portion B, and the outer electrode portion C is designated as point X1, and the point closest to point X1 and the lowest point of the thin film portion A is designated as point Y1.

[0152] exist Figure 12 In this case, the first pitch angle θ1 is set to 71°, and the first pitch height H1 is set to 1.5mm (the ratio of the first pitch height H1 to the first electrode thickness T1 is set to 30%).

[0153] Figure 14 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Reference Example 1. Figure 15 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Comparative Example 1. Figure 16 This is a cross-sectional schematic diagram showing the thin-film capacitor model of Comparative Example 2.

[0154] In the film capacitor models of Example 1, Reference Example 1, Comparative Example 1, and Comparative Example 2, the film portion A is made of a thermosetting resin film (coefficient of linear expansion: 60 × 10⁻⁶). -6 The outer part B is composed of epoxy resin (coefficient of linear expansion: 27×10⁻⁶℃). -6 The external electrode section C is composed of Al-Zn electrodes (linear expansion coefficient: 30.2 × 10⁻⁶ °C). -6 The composition is shown in Table 1. The properties of the thermosetting resin film, epoxy resin, and Al-Zn electrode are presented.

[0155] [Table 1]

[0156]

[0157] For the thin-film capacitor models of Example 1, Reference Example 1, Comparative Example 1, and Comparative Example 2, the maximum thermal stress applied at point X1 when the ambient temperature was changed from 25°C to 125°C was confirmed. Furthermore, the maximum thermal stress applied at point X2, which is opposite to point X1, was confirmed. The results are shown in Table 2.

[0158] [Table 2]

[0159] Example 1 6MPa 6MPa Reference Example 1 14MPa 20MPa Comparative Example 1 47MPa 47MPa Comparative Example 2 20MPa 14MPa

[0160] According to Table 2, in Example 1, the thermal stress at points X1 and X2 was alleviated compared with Reference Example 1, Comparative Example 1 and Comparative Example 2.

[0161] For the thin-film capacitor model of Example 1, the first pitch angle θ1 and the first pitch height H1 were changed to the values ​​shown in Table 3, and the maximum thermal stress applied to points X1 and X2 was confirmed using the same method as described above. Based on Reference Example 1 in Table 2, if the maximum thermal stress applied to points X1 and X2 is less than 20 MPa, it is rated as "○"; if it is 20 MPa or more but less than 25 MPa, it is rated as "Δ". The results are shown in Table 3.

[0162] [Table 3]

[0163]

[0164] According to Table 3, within a given range of the ratio of the first pitch angle θ1 and the first pitch height H1 to the first electrode thickness T1, the thermal stress applied to points X1 and X2 is alleviated compared to Reference Example 1 in Table 2.

[0165] For the film capacitor model of Example 1, instead of a thermosetting resin film, a polypropylene film (coefficient of linear expansion: 100 × 10⁻⁶) was used as the thermoplastic resin film. -6The film capacitor model ( / ℃) is constructed with the same shape as in Table 3. The properties of the polypropylene film are shown in Table 4.

[0166] [Table 4]

[0167]

[0168] The maximum thermal stresses applied at points X1 and X2 were confirmed using the same method described above. The results are shown in Table 5.

[0169] [Table 5]

[0170]

[0171] According to Table 5, in all ranges of the first pitch angle θ and the ratio of the first pitch height H1 to the first electrode thickness T1 shown in Table 5, the thermal stress at points X1 and X2 was relieved compared to Reference Example 1 in Table 2.

[0172] Figure 17 This is a cross-sectional schematic diagram showing a first variation of the thin-film capacitor model that is modeled according to Example 1 and used as the object of analysis.

[0173] exist Figure 17 In this design, the thickness of the external electrode C is 5 mm, the first pitch angle θ1 is set to 71°, and the first pitch height H1 is set to 2.5 mm (the ratio of the first pitch height H1 to the first electrode thickness T1 is set to 50%). In this case, the thermal stress at point X1 is 5.7 MPa. The thermal stress at point X2, on the opposite side of point X1, is also 5.7 MPa.

[0174] Figure 18 This is a cross-sectional schematic diagram showing a second variation of the thin-film capacitor model that is modeled according to Example 1 and used as the object of analysis.

[0175] exist Figure 18 In this design, the thickness of the external electrode C is 1 mm, the first pitch angle θ1 is set to 71°, and the first pitch height H1 is set to 0.5 mm (the ratio of the first pitch height H1 to the first electrode thickness T1 is set to 50%). In this case, the thermal stress at point X1 is 5.7 MPa. The thermal stress at point X2, on the opposite side of point X1, is also 5.7 MPa.

[0176] Based on the above, it can be assumed that the thermal stress applied to points X1 and X2 depends on the ratio of the first pitch angle θ1 and the first pitch height H1 to the thickness T1 of the first electrode.

[0177] Explanation of reference numerals in the attached figures

[0178] 1, 2: Film capacitors;

[0179] 10: Capacitor components;

[0180] 20: Layered body;

[0181] 20a: The first end face of the laminate;

[0182] 20b: The second end face of the laminate;

[0183] 21: The first metallized film;

[0184] 22: The second metallized film;

[0185] 31: First dielectric thin film;

[0186] 31a: The first principal surface of the first dielectric thin film;

[0187] 31b: The second principal surface of the first dielectric thin film;

[0188] 32: Second dielectric thin film;

[0189] 32a: The third principal surface of the second dielectric thin film;

[0190] 32b: The fourth principal surface of the second dielectric thin film;

[0191] 41: First metal layer;

[0192] 42: Second metal layer;

[0193] 51: First external electrode;

[0194] 52: Second external electrode;

[0195] 61: First lead;

[0196] 62: Second lead;

[0197] 70: Outer resin (outer body);

[0198] 71: Filler resin (outer body);

[0199] 72: External casing (outer body);

[0200] 101: No. 1 film reel;

[0201] 102: The second film reel;

[0202] 111: First reel shaft;

[0203] 112: Second reel shaft;

[0204] 200: winding shaft;

[0205] H1: First pitch height;

[0206] H2: Second pitch height;

[0207] T1: Thickness of the first electrode;

[0208] T2: Thickness of the second electrode;

[0209] θ1: First pitch angle;

[0210] θ2: Second pitch angle.

Claims

1. A thin-film capacitor comprising a capacitor element, wherein, The capacitor element comprises: a laminate having a first end face and a second end face opposed in the width direction; a first external electrode connected to the first end face of the laminate; and a second external electrode connected to the second end face of the laminate. The laminate includes a first dielectric film, a second dielectric film, a first metal layer, and a second metal layer. The first dielectric film has a first main surface and a second main surface facing each other in a thickness direction orthogonal to the width direction. The second dielectric film has a third main surface and a fourth main surface opposite each other in the thickness direction. In the laminate, the second principal surface of the first dielectric film and the third principal surface of the second dielectric film are opposite each other in the thickness direction. The first metal layer is connected to the first external electrode. The second metal layer is connected to the second external electrode. In the adjacent first and second dielectric films along the thickness direction, the first dielectric film protrudes towards the first external electrode side relative to the second dielectric film. When the length of the first dielectric film protruding relative to the second dielectric film in the width direction is defined as the first protrusion width, the first protrusion width is larger than the central portion of the laminate in the thickness direction at the outer periphery of the laminate, and increases towards the outermost periphery of the laminate in the thickness direction. In the adjacent first and second dielectric films along the thickness direction, the second dielectric film protrudes relative to the first dielectric film toward the second external electrode side. When the length of the second dielectric film protruding relative to the first dielectric film in the width direction is defined as the second protrusion width, the second protrusion width is larger than the central portion of the laminate in the thickness direction at the outer periphery of the laminate, and increases toward the outermost periphery of the laminate in the thickness direction.

2. The thin-film capacitor according to claim 1, wherein, When observing the cross-section along the thickness direction and the width direction, the end of the first dielectric film that is closest to the outermost periphery of the laminate in the thickness direction and has the largest first protrusion width is designated as point X1, and the end of the first dielectric film that is closest to point X1 and has the smallest first protrusion width is designated as point Y1. At this time, the angle between the straight line passing through point X1 and point Y1 and the straight line passing through the end of the first dielectric film with the smallest first protrusion width is 50° or more and 80° or less.

3. The film capacitor according to claim 1 or 2, wherein, When observing the cross-section along the thickness direction and the width direction, the end of the first dielectric film that is closest to the outermost periphery of the stack in the thickness direction and has the largest first protrusion width is designated as point X1, and the end of the first dielectric film that is closest to point X1 and has the smallest first protrusion width is designated as point Y1. At this time, the length in the width direction between point X1 and point Y1 is more than 5% and less than 50% of the length in the width direction between the outer end of the first external electrode and point X1.

4. The film capacitor according to any one of claims 1 to 3, wherein, When observing the cross-section along the thickness direction and the width direction, the end of the second dielectric film that is closest to the outermost periphery of the laminate in the thickness direction and has the largest second protrusion width is designated as point X2, and the end of the second dielectric film that is closest to point X2 and has the smallest second protrusion width is designated as point Y2. At this time, the angle between the straight line passing through point X2 and point Y2 and the straight line passing through the end of the second dielectric film with the smallest second protrusion width is more than 50° and less than 80°.

5. The film capacitor according to any one of claims 1 to 4, wherein, When observing the cross-section along the thickness direction and the width direction, the end of the second dielectric film that is closest to the outermost periphery of the laminate in the thickness direction and has the largest second protrusion width is designated as point X2, and the end of the second dielectric film that is closest to point X2 and has the smallest second protrusion width is designated as point Y2. At this time, the length in the width direction between point X2 and point Y2 is more than 5% and less than 50% of the length in the width direction between the outer end of the second external electrode and point X2.

6. The film capacitor according to any one of claims 1 to 5, wherein, The first metal layer is not connected to the second external electrode. The second metal layer is not connected to the first external electrode.

7. The film capacitor according to any one of claims 1 to 6, wherein, The first metal layer is disposed on the first main surface of the first dielectric thin film. The second metal layer is disposed on the third main surface of the second dielectric film.

8. The film capacitor according to any one of claims 1 to 7, wherein, The first dielectric film and the second dielectric film contain a curable resin as the main component.

9. The film capacitor according to any one of claims 1 to 7, wherein, The first dielectric film and the second dielectric film contain thermoplastic resin as the main component.

10. The thin-film capacitor according to any one of claims 1 to 9, wherein, It also includes: an outer casing that covers the outer periphery of the capacitor element.

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