Electrolytic capacitor and method for manufacturing the same

Abstract

This invention provides a method for manufacturing electrolytic capacitors that prevents the electrode foil from tearing and the electrolytic paper from ripping. [Solution] The manufacturing method of the electrolytic capacitor 1 comprises a winding step, a resin injection step, and a resin curing step. In the winding step, the anode foil 14a and cathode foil 15a, to which lead tabs 14 and 15 for drawing out electrodes are connected, are overlapped via a separator 16 and wound together to form a capacitor element 11. In the resin injection step, resin 30 is injected into the gap 11c between the anode foil 14a and cathode foil 15a and the separator 16. The gap 11c is formed in the capacitor element 11 by the difference in thickness between the parts of the anode foil 14a and cathode foil 15a to which the lead tabs 14 and 15 are connected and the other parts of the anode foil 14a and cathode foil 15a. In the resin curing step, the resin 30 injected into the capacitor element 11 is cured.

Description

Technical Field

[0001] The present invention relates to an electrolytic capacitor and a method for manufacturing the same.

Background Art

[0002] Conventionally, an electrolytic capacitor has a capacitor element in which an anode foil and a cathode foil, which are electrode foils, are wound through a separator. The capacitor element impregnated with an electrolytic solution and / or formed with a solid electrolyte is housed in a bottomed cylindrical exterior case, and the open end side of the exterior case is closed by a sealing body. Further, a lead tab for drawing out the electrode to the outside is connected to the electrode foil of the capacitor element. Generally, one end portion of the lead tab flattened is connected to the electrode foil, and the other end portion of the lead tab is inserted through the sealing body and drawn out to the outside. For example, in Patent Document 1, with respect to the capacitor element housed inside the electrolytic capacitor being displaced due to vibration or temperature change, such as the anode foil and the cathode foil, the anode foil and the separator, or the cathode foil and the separator constituting the capacitor element, an insulating resin layer is applied and cured on the surface connection portion of the lead tab terminal at the connection portion of the lead tab of the anode foil before winding (and the portion facing the connection portion between the anode foil and the lead tab terminal on the other surface of the anode foil on the side opposite to the one surface to which the lead tab terminal is connected).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the electrolytic capacitor described in Patent Document 1 above, an insulating resin layer is provided along the surface of the lead tab of the anode foil. However, the following problem sometimes occurred due to the condition of the electrode foil on one side to which the lead tab is connected. Specifically, the electrode foil is thicker at the connection point with the flattened lead tab by the thickness of the lead tab compared to the rest of the electrode foil. When wound, a gap is created in the overlapping portion with the separator at the connection point (the portion sandwiched between the electrode foil and the separator on both sides of the lead tab). Therefore, when stress is applied to the lead tab, the electrode foil twists within the gap, causing the lead tab to move, which could lead to the electrode foil breaking or the separator tearing.

[0005] The object of the present invention is to provide a method for manufacturing an electrolytic capacitor that prevents electrode foil breakage and separator tearing. [Means for solving the problem]

[0006] The present invention provides a method for manufacturing an electrolytic capacitor, comprising a winding step, a resin injection step, and a resin curing step. The winding step involves winding electrode foils, to which lead tabs for drawing out electrodes are connected, overlapping them via a separator to form a capacitor element. The resin injection step involves injecting resin into the gap between the electrode foil and the separator, which is formed in the capacitor element due to the difference in thickness between the portion of the electrode foil to which the lead tabs are connected and the other portions of the electrode foil. The resin curing step involves curing the resin injected into the capacitor element.

[0007] Furthermore, the electrolytic capacitor of the present invention comprises a capacitor element in which electrode foils, to which lead tabs for drawing out electrodes are connected, are wound together with a separator in between, A resin held in the gap between the electrode foil and the separator, formed in the capacitor element by the difference in thickness between the portion of the electrode foil to which the lead tab is connected and the other portion of the electrode foil, It is equipped with.

[0008] According to the above configuration, in the resin injection process, resin is injected into the gaps of the capacitor element formed in the winding process and hardened, so that the lead tab, the electrode foil connected to the lead tab, and the separator can be fixed by the resin. As a result, even if stress is generated on the lead tab, the movement of the lead tab can be restricted. Consequently, it becomes possible to prevent the electrode foil from tearing and the separator from rupturing. [Effects of the Invention]

[0009] According to the present invention, it is possible to prevent the electrode foil from tearing and the separator from breaking. [Brief explanation of the drawing]

[0010] [Figure 1] This is a cross-sectional view showing the configuration of electrolytic capacitor 1. [Figure 2] This is a perspective view showing the capacitor element 11 of the electrolytic capacitor 1. [Figure 3] This is an explanatory diagram showing the winding process of the capacitor element 11. [Figure 4] This is a cross-sectional view of the capacitor element 11. [Figure 5] This figure shows the air gap 11c between the electrode foil of the capacitor element 11 and the separator 16. [Figure 6] This figure shows the air gap 11c between the electrode foil of the capacitor element 11 and the separator 16. [Modes for carrying out the invention]

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[0012] Figure 1 shows an electrolytic capacitor 1 manufactured by a manufacturing method according to an embodiment of the present invention. The electrolytic capacitor 1 includes a capacitor element 11, an outer case 12, a sealing body 13, and lead tabs 14 and 15.

[0013] As shown in Figure 2, the capacitor element 11 consists of an anode foil (anodic aluminum foil) 14a and a cathode foil (cathode aluminum foil) 15a, which have been etched and subjected to dielectric oxide film formation treatment, wound in a cylindrical shape via a separator 16, and secured with element fixing tape 21 (see Figure 1). This capacitor element 11 is housed in an outer case 12 (see Figure 1).

[0014] The outer case 12 is a bottomed cylindrical case. A sealing body 13 is fitted to the opening of the outer case 12, and the opening has a structure that is sealed by drawing. The sealing body 13 seals the opening of the outer case 12. For example, the sealing body 13 is an elastic material. For example, the sealing body 13 is a rubber elastic material. The sealing body 13 may be natural rubber or synthetic rubber.

[0015] Lead tabs 14 and 15 are drawn out from the capacitor element 11. Lead wires 14b and 15b are welded to lead tabs 14 and 15, respectively. Lead wires 14b and 15b are formed to be thinner in diameter than lead tabs 14 and 15. Lead wires 14b and 15b are drawn out to the outside through through holes 131 and 132 of the sealing body 13, respectively. At this time, lead tabs 14 and 15 are inserted into the sealing body 13. The outer case 12 is covered by a sleeve 22 (see Figure 1).

[0016] Lead tab 14 is an anode-side lead tab connected to the anode foil 14a by methods such as crimping or welding. Lead tab 15 is a cathode-side lead tab connected to the cathode foil 15a by methods such as crimping or welding.

[0017] The anode foil 14a (see Figure 2) is a valve metal with a dielectric oxide film formed on its surface. Examples of valve metals include at least one selected from the group consisting of aluminum, tantalum, niobium, and titanium. The oxide film is formed, for example, by roughening the surface of the valve metal foil through etching, followed by a chemical conversion treatment.

[0018] The cathode foil 15a is formed using a valve action metal. As the cathode foil 15a, for example, a foil obtained by roughening the surface of a valve action metal foil by etching, or a foil subjected to chemical conversion treatment after roughening is used. As the cathode foil 15a, a plane foil not subjected to etching treatment may be used. Further, a coating foil formed with a metal thin film containing at least one metal selected from the group consisting of titanium, nickel, titanium carbide, nickel carbide, titanium nitride, nickel nitride, titanium carbonitride, and nickel carbonitride may be used on the surface of the roughened foil or the plane foil. Also, a coating foil formed with a carbon thin film on the surface of the roughened foil or the plane foil may be used.

[0019] The material of the separator 16 is not particularly limited. As the separator 16, for example, a material mainly composed of cellulose fibers may be used, or a mixed fiber in which chemical fibers are mixed may be used. Examples of chemical fibers include synthetic fibers such as polyester fibers, polyamide fibers, acrylic fibers, polyimide fibers, aramid fibers, and nylon fibers. The electrolyte is held in the separator 16. The electrolyte is not particularly limited. The electrolyte may contain a low-viscosity solvent and a hardly volatile solvent, or may contain one of the low-viscosity solvent and the hardly volatile solvent. Also, instead of the electrolyte, a solid electrolyte containing a conductive polymer such as poly-3,4-dioxythiophene, polypyrrole, or polyaniline may be formed, and the solid electrolyte may be impregnated with the electrolyte after formation.

[0020] Next, a method for manufacturing the electrolytic capacitor 1 will be described.

[0021] First, a slit process for cutting out the anode foil 14a and the cathode foil 15a (see FIG. 2) to a predetermined width is performed. At this time, the anode foil 14a to be cut out is one that has been subjected to chemical conversion treatment. Then, a winding process is performed in which the anode foil 14a and the cathode foil 15a are wound through the separator 16 to form the capacitor element 11.

[0022] Specifically, an example of the winding process is shown. As shown in Figure 3, in the winding process, anode foil 14a and cathode foil 15a are used, each with lead tabs 14 and 15 pre-attached to predetermined positions. Lead wires 14b and 15b are welded to the tips of the lead tabs 14 and 15, respectively. A laminate 11a, in which separator 16, cathode foil 15a, separator 16, and anode foil 14a are stacked in that order, is attached to the winding core 101. Next, the winding core 101 is rotated by a rotary drive device (not shown) and the laminate 11a is wound around the winding core 101. This forms a winding body 11b. Then, element fixing tape 21 (see Figure 1) is wrapped around the outer circumference of this winding body 11b, and the winding body 11b is removed from the winding core 101. This manufactures a capacitor element 11.

[0023] After the winding process is completed, a resin injection process is performed in which resin 30 (see Figure 6) is injected into the gap 11c (see Figures 5 and 6) between the electrode foils (anode foil 14a and cathode foil 15a) and the separator 16. In the capacitor element 11 manufactured in the winding process, a gap 11c is formed between the electrode foils (anode foil 14a and cathode foil 15a) and the separator 16. Next, this gap 11c will be described.

[0024] As shown in Figure 4, the anode-side lead tab 14 has a round bar portion 141 that protrudes from the end face of the capacitor element 11 (see Figure 1) on the sealing body 13 (see Figure 1) side, and a flattened portion 142 formed at one end of this round bar portion 141 to which the anode foil 14a is connected. For example, the lead tab 14 is formed by pressing one end of a round bar-shaped member made of aluminum to a predetermined length to form the flattened portion 142, and making the remaining part the round bar portion 141. The lead wire 14b is connected to the tip of the round bar portion 141 (the end opposite to the flattened portion 142). Similarly, the cathode-side lead tab 15 also has a round bar portion 151 (see Figure 5) that protrudes from the end face of the capacitor element 11, and a flattened portion 152 (see Figure 6) formed at one end of this round bar portion 151 to which the cathode foil 15a is connected. The lead wire 15b is welded to the tip of the round bar portion 151 (the end opposite to the flattened portion 152).

[0025] Here, the direction in which the anode foil 14a (cathode foil 15a) extends is defined as the left-right direction X. The direction in which the separator 16 is superimposed on the anode foil 14a (cathode foil 15a) is defined as the stacking direction Y. The direction in which the lead tab 14 (lead tab 15) is pulled out is defined as the up-down direction Z. In the up-down direction Z, the side (direction) from which the lead tab 14 is pulled out is defined as the lower side Z2, and the opposite side (direction) of the lower side Z2 is defined as the upper side Z1. The left-right direction X, the stacking direction Y, and the up-down direction Z are mutually orthogonal.

[0026] As described above, the anode foil 14a and cathode foil 15a are stacked so as to overlap in the Y direction via the separator 16. At this time, due to the difference in thickness between the portion of the anode foil 14a to which the lead tab 14 is connected and the other portion of the anode foil 14a, a gap 11c (see Figures 5 and 6) is formed between the anode foil 14a and the separator 16 in the capacitor element 11. During the winding process, for example, gaps 11c are formed on both sides in the left-right direction X of the flattened portion 142 of the lead tab 14.

[0027] Figure 6 shows a partially enlarged view of the capacitor element 11 as seen from the upper side Z1. As shown in the partially enlarged view of Figure 6, a gap 11c is formed between the cathode foil 15a and the separator 16 on the side to which the flattened portion 142 of the cathode foil 14a is connected. This gap 11c is formed during the winding process due to the difference in thickness between the portion of the cathode foil 15a to which the lead tab 14 is connected and the other portion of the cathode foil 15a. In the resin injection process after the winding process, resin 30 is injected into this gap 11c (see Figures 5 and 6). The resin 30 may be injected from the lower side Z2 (the side from which the electrodes of the capacitor element 11 are drawn out) or from the upper side Z1 (the side opposite to the side from which the electrodes of the capacitor element 11 are drawn out). Alternatively, the resin 30 may be injected into the gap between the round rod portions 141 and 151 and the wound body 11b. The method of injecting the resin 30 is not particularly limited, but for example, it may be injected manually using a syringe.

[0028] The resin 30 is an insulating resin, and any resin having insulating properties can be used, such as a thermosetting resin or an ultraviolet-curable resin. Examples of thermosetting resins include phenolic resin, acrylic resin, epoxy resin, melamine resin, silicone resin, and acrylic-modified silicone resin. Examples of ultraviolet-curable resins include epoxy acrylate resin, polyester acrylate resin, and their methacrylate-modified products. The curing method can be any of the following: thermosetting, ultraviolet curing, electron beam curing, etc., as long as it cures. The lower limit of the viscosity of the resin 30 before curing is preferably 500 mPa·s (millipascal-seconds), and more preferably 2000 mPa·s. The upper limit of the viscosity of the resin 30 before curing is preferably 20000 mPa·s, and more preferably 10000 mPa·s.

[0029] Next, a resin curing process is performed to harden the resin 30 injected into the capacitor element 11. In the resin curing process, depending on the resin 30 used for injection, a resin curing treatment such as heating in an infrared furnace or ultraviolet irradiation with an ultraviolet irradiator is performed. As the resin hardens, it is retained in the voids.

[0030] Then, after the capacitor element 11 is impregnated with electrolyte solution in the separator 16, it is housed in the outer case 12 (see Figure 1). The opening of the outer case 12 is sealed by a sealing body 13 (see Figure 1).

[0031] As described above, the manufacturing method of the electrolytic capacitor 1 of this embodiment comprises a winding step, a resin injection step, and a resin curing step. In the winding step, the anode foil 14a and cathode foil 15a, to which lead tabs 14 and 15 for drawing out electrodes are connected, are overlapped via a separator 16 and wound together to form a capacitor element 11. In the resin injection step, resin 30 is injected into the gap 11c between the anode foil 14a and cathode foil 15a and the separator 16. The gap 11c is formed in the capacitor element 11 by the difference in thickness between the portion of the anode foil 14a and cathode foil 15a to which the lead tabs 14 and 15 are connected and the other portion of the anode foil 14a and cathode foil 15a. In the resin curing step, the resin injected into the capacitor element 11 is cured.

[0032] According to the above configuration, in the resin injection process, resin 30 is injected into the gap 11c of the capacitor element 11 formed in the winding process and hardened, so that the lead tabs and the electrode foil and separator connected to the lead tabs can be fixed by the resin. As a result, even if stress is generated on the lead tabs 14 and 15, the movement of the lead tabs 14 and 15 can be restricted. Consequently, it is possible to prevent the anode foil 14a and cathode foil 15a from tearing, and the separator 16 from rupturing.

[0033] Furthermore, in the manufacturing method of the electrolytic capacitor 1 of this embodiment, during the resin injection process, resin 30 is injected into the void 11c from either the side from which the electrodes of the capacitor element 11 are drawn out, or from the side opposite to the side from which the electrodes of the capacitor element 11 are drawn out, or both.

[0034] Furthermore, in the manufacturing method of the electrolytic capacitor 1 of this embodiment, the resin 30 is a thermosetting resin or an ultraviolet curing resin.

[0035] Furthermore, in the manufacturing method of the electrolytic capacitor 1 of this embodiment, the viscosity of the resin 30 before curing is 500 to 20000 Pa·s.

[0036] Furthermore, the electrolytic capacitor 1 of the present invention comprises a capacitor element 11 and a resin 30. The capacitor element 11 is wound by overlapping electrode foils (anode foil 14a and cathode foil 15a), to which lead tabs 14 and 15 for drawing out electrodes are connected, via a separator 16. The resin 30 is held in the gap between the electrode foils and the separator 16. The gap between the electrode foils (anode foil 14a and cathode foil 15a) and the separator 16 is formed in the capacitor element 1 by the difference in thickness between the portion of the electrode foil to which the lead tabs 14 and 15 are connected and the other portion of the electrode foil.

[0037] According to the above configuration, the lead tabs 14 and 15, the electrode foils connected to the lead tabs 14 and 15, and the separator 16 are fixed by the resin 30 held in the air gap 11c of the capacitor element 11. As a result, even if stress is generated on the lead tabs 14 and 15, the movement of the lead tabs 14 and 15 can be restricted by the resin 30. Consequently, it is possible to prevent the anode foil 14a and cathode foil 15a from tearing, and the separator 16 from rupturing.

[0038] Although embodiments of the present invention have been described above, these are merely illustrative examples and do not particularly limit the present invention. Specific configurations and other aspects can be modified as appropriate. Furthermore, the actions and effects described in the embodiments of the invention are merely a list of the most preferred actions and effects resulting from the present invention, and the actions and effects according to the present invention are not limited to those described in the embodiments.

[0039] (Examples) Next, the characteristics of the electrolytic capacitors in the conventional example and the example (Examples 1, 2, and 3) were evaluated. The electrolytic capacitors used in the conventional example and the example had a rated voltage of 35V, a rated capacitance of 220μF, and a product size of φ10 × 7.7L (mm).

[0040] Conventional examples used conventional electrolytic capacitors in which resin was not injected into the gap between the electrode foil and separator formed during the winding process. Examples 1 to 3 used electrolytic capacitors in which UV-curable resin was injected into the gap between the electrode foil and separator formed during the winding process after the winding process. Example 1 used a resin with a viscosity of 2300 mPa·s before curing. The hardness A of the resin used in Example 1 after curing was 80. Example 2 used a resin with a viscosity of 8750 mPa·s before curing. The hardness A of the resin used in Example 2 after curing was 60. Example 3 used a resin with a viscosity of 7930 mPa·s before curing. The hardness D of the resin used in Example 3 after curing was 77.

[0041] A load was applied to the capacitor elements (10 each) of the conventional and the examples (Examples 1, 2, and 3) of the electrolytic capacitors. Specifically, a load (500g) was applied to the round bar portion of the cathode lead tab of the capacitor element from the side (from one side in the left-right direction X in Figure 4). The capacitor elements were then disassembled, and the results of checking for foil breakage and short circuits are shown in Table 1. Table 1 shows the number of capacitor elements out of 10 in which each event occurred. Foil breakage refers to a tear in the electrode foil. Short circuit occurs when a tear occurs in the separator, resulting in a short circuit between the anode foil and the cathode foil.

[0042] [Table 1]

[0043] As shown in Table 1, in the conventional example, foil breakage occurred in 8 out of 10 units and short circuits occurred in 3 out of 10 units, but in the example, no foil breakage or short circuits occurred in any of the units.

[0044] Thus, compared to conventional examples, Examples 1 to 3 prevent foil breakage and short circuits, demonstrating the effectiveness of injecting resin after winding the capacitor element.

[0045] In the above embodiment, it was found that when a resin with a viscosity in the range of 2300 to 8750 mPa·s before curing was used as the resin injected into the gap between the anode foil and cathode foil and the separator, foil breakage and short circuits could be prevented. If the viscosity of the resin was too low, the resin would disperse inside the capacitor element, resulting in the problem that the resin would not cure in a way that filled the gaps. Conversely, if the viscosity of the resin was too high, the problem that the resin would not penetrate into the gaps occurred. Therefore, under the above implementation conditions, if the resin had a viscosity in the range of 1000 to 10000 mPa·s before curing, the above problems could be suppressed and foil breakage and short circuits could be prevented. Furthermore, depending on the implementation conditions of the capacitor element, etc., if the resin had a viscosity in the range of 500 to 20000 mPa·s before curing, the above problems could be suppressed and foil breakage and short circuits could be prevented. [Explanation of Symbols]

[0046] 1: Electrolytic capacitor 11: Capacitor element 11a: Laminate 11b: Coiled body 11c: void 12: Outer case 13: Sealing body 14: Lead Tab 14a: Anode foil 14b: Lead wire 15: Lead Tab 15a: Cathode foil 15b: Lead wire 16: Separator 21: Element fixing tape 22: Sleeves 30: Resin 101: Core 131: Through hole 132: Through hole

Claims

1. A winding process in which electrode foils, to which lead tabs for drawing out electrodes are attached, are overlapped via a separator and wound to form a capacitor element, A resin injection step in which resin is injected into the gap between the electrode foil and the separator, which is formed in the capacitor element by the difference in thickness between the portion of the electrode foil to which the lead tab is connected and the other portion of the electrode foil, A resin curing step for curing the resin injected into the capacitor element, A method for manufacturing an electrolytic capacitor having [a certain characteristic].

2. A method for manufacturing an electrolytic capacitor according to claim 1, The aforementioned resin is a thermosetting resin or an ultraviolet curing resin. A method for manufacturing electrolytic capacitors.

3. A method for manufacturing an electrolytic capacitor according to claim 1, The viscosity of the aforementioned resin before curing is 500 to 20,000 mPa·s. A method for manufacturing electrolytic capacitors.

4. A capacitor element is formed by winding electrode foils, each with lead tabs for drawing out the electrodes connected to it, overlapping them via a separator, A resin held in the gap between the electrode foil and the separator, formed in the capacitor element by the difference in thickness between the portion of the electrode foil to which the lead tab is connected and the other portion of the electrode foil, An electrolytic capacitor characterized by having the following features.

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