Solid electrolytic capacitor and method for manufacturing the same

Abstract

When oxygen enters the case of a solid electrolytic capacitor, the solid electrolyte containing conductive polymers deteriorates, leading to a problem of increased ESR (Electrolytic Stress Rating). [Solution] The capacitor element comprises an anode, a cathode, and a solid electrolyte; a case for housing the capacitor element; and a sealing member for sealing the case, wherein the oxygen permeability coefficient of the sealing member is 3.550 × 10⁻⁶. ―10 [cc·cm / (cm 2 A solid electrolytic capacitor characterized by having a value of less than or equal to (·s·cmHg).

Description

[Technical Field]

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

[0002] Solid electrolytic capacitors use conductive polymers, such as polyethylenedioxythiophene (abbreviated as PEDOT), as the solid electrolyte. Due to their high heat resistance and conductivity, they are commonly used in consumer electronics components and laptop computers.

[0003] A capacitor comprises a capacitor element, a case that houses the capacitor element, and a sealing member that seals the opening of the case. In electrolytic capacitors that use a liquid electrolyte, the electrolyte is held in the capacitor element, which is wound with a separator between the anode and cathode. On the other hand, in solid electrolytic capacitors, the material used as the electrolyte is a solid electrolyte containing a conductive polymer. Therefore, compared to electrolytic capacitors that use a liquid electrolyte, solid electrolytic capacitors have advantages such as lower equivalent series resistance (abbreviated as ESR), longer lifespan, and good temperature characteristics. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-297574 [Overview of the project] [Problems that the invention aims to solve]

[0005] As shown in Patent Document 1, in a solid electrolytic capacitor, when oxygen enters the case through the sealing member, there is a problem that the solid electrolyte containing a conductive polymer deteriorates and the ESR increases. When the conductive polymer contained in the solid electrolyte comes into contact with oxygen, the conductive polymer is oxidized and decomposed, and long molecules are cleaved. Due to the decrease in the conjugated system caused by the reduction in molecular weight, the electron conductivity of the solid electrolyte decreases, and the ESR of the solid electrolytic capacitor increases.

[0006] The inventors of the present invention have found that by adjusting the oxygen permeability coefficient of the sealing member and the caulking state for sealing the sealing member and the case, the intrusion of oxygen into the case can be suppressed, the increase in the ESR of the solid electrolytic capacitor can be suppressed, and a long service life can be achieved.

Means for Solving the Problems

[0007] In order to solve the above problems, the solid electrolytic capacitor of the present embodiment includes a capacitor element having an anode body, a cathode body, and a solid electrolyte, a case for housing the capacitor element, and a sealing member for sealing the case, and the oxygen permeability coefficient of the sealing member is 3.550×10 ,

[0011] , [cc·cm / (cm 2 ·s·cmHg)] or less.

[0008] Furthermore, it may include a lateral caulking portion of the sealing member that integrates the side surface of the case and the sealing member housed inside, and the thickness from the minimum diameter portion of the lateral caulking portion of the sealing member to the end surface on the case opening side of the sealing member may be 47% or more with respect to the overall thickness of the sealing member.

[0009] Furthermore, the thickness from the minimum diameter portion of the lateral caulking portion of the sealing member to the end surface on the case opening side of the sealing member may be 70% or less with respect to the overall thickness of the sealing member.

[0010] Furthermore, the small diameter portion including the minimum diameter portion of the lateral caulking portion of the sealing member may be 20% or more with respect to the overall thickness of the sealing member. [[ID= Furthermore, the small-diameter portion of the sealing member, including the smallest diameter portion of the lateral crimping section, may be 70% or less of the overall thickness of the sealing member.

[0012] Furthermore, in order to solve the above problems, the method for manufacturing a solid electrolytic capacitor of this embodiment is a method for manufacturing a solid electrolytic capacitor comprising a capacitor element having an anode, a cathode, and a solid electrolyte, a case for housing the capacitor element, and a sealing member for sealing the case, the method comprising a sealing step of arranging the capacitor element inside the case and sealing the capacitor element inside the case with the sealing member, wherein the oxygen permeability coefficient of the sealing member is 3.550 × 10 ―10 [cc·cm / (cm 2 It is less than or equal to (·s·cmHg)

[0013] Furthermore, the sealing step includes a crimping step of the sealing member that integrates the side surface of the case with the sealing member housed inside, and the thickness from the minimum diameter portion of the lateral crimping portion of the sealing member to the case opening side end face of the sealing member may be adjusted to 47% or more of the overall thickness of the sealing member. [Effects of the Invention]

[0014] According to the present invention, it is possible to suppress the rise in ESR of solid electrolytic capacitors and extend their lifespan. [Brief explanation of the drawing]

[0015] [Figure 1] This is a cross-sectional view showing an example of a solid electrolytic capacitor according to an embodiment. [Figure 2] This is an enlarged cross-sectional view of the sealing member according to the embodiment. [Figure 3] This is a cross-sectional view showing the state of a solid electrolytic capacitor with a deformed sealing member. [Figure 4] This is a cross-sectional view showing the small-diameter portion of the lateral crimping section of the sealing member of a solid electrolytic capacitor. [Modes for carrying out the invention]

[0016] The following describes a solid electrolytic capacitor according to an embodiment of the present invention. However, the present invention is not limited to the embodiments described below.

[0017] Embodiments of the present invention will be described with reference to the drawings. Figure 1 is a cross-sectional view showing the internal structure of the solid electrolytic capacitor of the present invention. The solid electrolytic capacitor 1 is manufactured by inserting a capacitor element 3 into a bottomed cylindrical case 2 having an opening, with the lead terminals 5 inserted through the sealing member 4, fitting the sealing member 4 into the opening of the case 2, crimping the sealing member 4 from the side of the case 2 (lateral crimping), and crimping the sealing member 4 from the open end of the case 2 (vertical crimping). Although not shown, the capacitor element 3 is formed by winding an anode body and a cathode body made of a valve-acting metal such as aluminum, with an oxide film formed on their surfaces, via a separator, and a solid electrolyte containing a conductive polymer is formed in this capacitor element 3.

[0018] The anode body is made of a valve metal such as aluminum, and an expanding layer is formed on one or both sides thereof, with an oxide film formed on its surface. The expanding layer is an etched layer obtained by etching the foil body, a sintered layer obtained by sintering valve metal powder, or a vapor-deposited layer obtained by depositing valve metal particles. In other words, the expanding layer has a porous structure and consists of tunnel-shaped pits, sponge-like pits, or densely packed powder or voids between particles.

[0019] The sintered layer is produced by pasteuring powder of the same or different valve metal as the foil with a binder and solvent, coating and drying it, and then heating and sintering it in a vacuum or reducing atmosphere. The vapor-deposited layer is produced, for example, by resistance heating vapor deposition or electron beam heating vapor deposition. This vapor-deposited layer is formed by heating the same or different valve metal as the foil with resistance heat or electron beam energy to evaporate it, and depositing the vapor of valve metal particles onto the surface of the foil.

[0020] Tunnel-shaped etching pits are holes carved in the direction of the foil thickness. These tunnel-shaped etching pits are typically formed by passing a direct current through an acidic aqueous solution containing halogen ions, such as hydrochloric acid. The tunnel-shaped etching pits are further expanded by passing a direct current through an acidic aqueous solution containing nitric acid, for example. Sponge-like etching pits cause the expanded layer to become a sponge-like layer with a series of fine voids. These sponge-like etching pits are formed by passing an alternating current through an acidic aqueous solution containing halogen ions, such as hydrochloric acid.

[0021] The cathode body, like the anode body, is made of a valve metal such as aluminum, and may be either surface-enlarged by etching or otherwise treated, or in a plain form. If necessary, a cathode body that has undergone a chemical conversion treatment of approximately 2V, or one in which a layer of metal nitride, metal carbide, or metal carbonitride is formed by vapor deposition, may also be used. Furthermore, a cathode body coated with carbon material may also be used.

[0022] The anode and cathode are connected to lead terminals 5 for connecting their respective electrodes to the outside by known means such as stitching or ultrasonic welding. These lead terminals 5 are made of aluminum or the like and consist of a connection part to the anode and cathode and an external connection part that handles the electrical connection to the outside, and are led out from one end face of the wound capacitor element 3.

[0023] The separator can be made of, for example, a nonwoven fabric mainly composed of synthetic fibers, or glass fibers, natural fibers, or a blend thereof. Suitable synthetic fibers include polyester fibers, nylon fibers, and rayon fibers. Natural fibers such as kraft fibers, Manila fibers, and hemp fibers may also be used as separators.

[0024] The capacitor element 3 is formed by winding an anode body and a cathode body, both made of a valve-acting metal such as aluminum and having an oxide film formed on their surfaces, with a separator in between. The dimensions of the electrode bodies of both poles are arbitrary according to the specifications of the solid electrolytic capacitor 1 to be manufactured, and it is preferable to use a separator with a width slightly larger than the dimensions of the electrode bodies of both poles.

[0025] The capacitor element 3 is then impregnated with a conductive polymer precursor solution, and the conductive polymer produced by the polymerization reaction is held as a solid electrolyte in a separator. The conductive polymer precursor solution refers to a solution containing monomers, which are conductive polymer precursors. The capacitor element 3 may be impregnated with a mixture of the monomer solution and the oxidizing agent solution, or the monomer solution and the oxidizing agent solution may be impregnated separately.

[0026] Suitable monomers include thiophene, pyrrole, or their derivatives. More specifically, 3,4-ethylenedioxythiophene (abbreviated as EDOT) can be given as an example of a thiophene derivative. When EDOT is used as the monomer, it is preferable to use an EDOT solution in which EDOT is dissolved in a volatile solvent to impregnate the capacitor element 3, with a concentration of 25-32 wt%.

[0027] As an oxidizing agent, any known compound that releases a dopant may be used, such as trivalent iron salts like iron(III) p-toluenesulfonate, iron(III) naphthalenesulfonate, iron(III) anthraquinonesulfonate, or peroxodisulfates like peroxodisulfate, ammonium peroxodisulfate, or sodium peroxodisulfate. A single compound may be used, or two or more compounds may be used.

[0028] Examples of conductive polymers include poly(3,4-ethylenedioxythiophene) (PEDOT) doped with sulfonic acid dopants such as p-toluenesulfonic acid and polystyrenesulfonic acid (PSS).

[0029] While there are no strict limitations on the polymerization temperature, it is generally in the range of 10 to 200°C. The polymerization time is generally in the range of 10 minutes to 30 hours.

[0030] The formation of the solid electrolyte is not limited to the above-described method. The solid electrolyte may be formed by impregnating the capacitor element 3 in a conductive polymer solution obtained by dispersing or dissolving a conductive polymer in a solvent such as water, and then drying it. Alternatively, the solid electrolyte may be formed by electropolymerization using a conductive polymer precursor solution obtained by dissolving monomers and a supporting electrolyte.

[0031] The capacitor element 3 may, if necessary, contain an electrolyte solution in addition to the solid electrolyte.

[0032] Case 2 is not particularly limited as long as it can accommodate the capacitor element 3 and can be crimped to the sealing member 4, and is usually a bottomed cylindrical metal case. Examples of materials for the metal case include aluminum, aluminum alloys, copper, copper alloys such as brass, iron, stainless steel, etc.

[0033] The sealing member 4 is fitted into the opening of the case 2 and is a member that seals the case 2 so as to ensure airtightness of the solid electrolytic capacitor 1.

[0034] The sealing member 4 comprises, for example, a polymer component and an inorganic filler as its composition.

[0035] The polymer component is, for example, butyl rubber, which is an isobutylene-isoprene copolymer obtained by cationic polymerization of isobutylene and a small amount of isoprene. In addition to butyl rubber, the polymer component may also contain one or more other resins.

[0036] Examples of inorganic fillers include clay, talc, mica, silica, kaolin, titania, and alumina, and these may be mixed together.

[0037] The composition may further contain a crosslinking agent, and from the viewpoint of heat resistance, it is preferable to include a crosslinking agent for butyl rubber. In this invention, "crosslinking agent" is a concept that includes crosslinking accelerators.

[0038] The composition may further contain a carbon material. Examples of carbon materials include carbon black, carbon fiber, and graphite, with carbon black being preferred.

[0039] The composition may contain other additives not mentioned above, as long as they do not impair the effects of the present invention. Examples of other additives include, but are not limited to, processing aids such as stearic acid, modifiers such as coupling agents, antioxidants, and dispersing aids. Other additives may be used individually or in combination of two or more in any combination and ratio.

[0040] The oxygen permeability coefficient of the sealing member 4 can be adjusted by the amount of inorganic filler added. A smaller oxygen permeability coefficient indicates that oxygen is less likely to permeate the sealing member 4. The oxygen permeability coefficient can also be adjusted using other additives such as processing aids, coupling agents, and resins, and is not limited to these methods.

[0041] Here, the more easily oxygen permeates the sealing member 4, the more easily thermal oxidative degradation progresses inside the sealing member, and as a result, the thermal oxidative degradation of the sealing member 4 as a whole progresses more rapidly. In this invention, the oxygen permeability coefficient is set to 3.550 × 10⁻⁶. ―10 [cc·cm / (cm 2 By adjusting the pH to below (·s·cmHg), it is possible to suppress oxygen from the air outside the solid electrolytic capacitor from entering the solid electrolytic capacitor through the sealing member 4.

[0042] (Method for measuring oxygen permeability coefficient) The oxygen permeability coefficient was measured using a differential pressure gas / water vapor permeability meter (GTR-30XANC, manufactured by GTR Tech). The oxygen permeability coefficient was measured in accordance with Japanese Industrial Standards JIS K6275-1:2009 "Vulcanized rubber and thermoplastic rubber - Method for determining gas permeability - Part 1: Differential pressure method" and JIS K7126-1:2006 "Plastics - Films and sheets - Gas permeability test method - Part 1: Differential pressure method". Specifically, a sealing member 4 with a thickness of 1.5 mm was prepared, and the oxygen permeability coefficient was measured after 336 hours in a 105°C environment using air as the test gas.

[0043] The position of the lateral crimping portion 6 of the sealing member 4 will be explained using Figure 2. The lateral crimping portion 6 is formed by crimping (lateral crimping) the sealing member 4 from the side of the case 2 after the sealing member 4 has been fitted into the opening of the case 2. Lateral crimping deforms the case 2 by pressing the outer surface of the case 2 along the circumferential direction, and as the case 2 deforms, the sealing member 4 is pressed, thereby integrating the sealing member 4 and the case 2. The lateral crimped portion is formed as a recess toward the sealing member 4 compared to the side of the case 2 that has not been lateral crimped.

[0044] The thickness from the smallest diameter portion of the lateral crimping portion 6 of the sealing member 4 to the case opening side end face of the sealing member 4 is shown by a, and the total thickness of the sealing member 4 in the sealed state is shown by b. In this specification, the ratio value of the position of the lateral crimping portion 6 of the sealing member 4 is the value of a / b expressed as a percentage. The smallest diameter portion of the lateral crimping portion 6 of the sealing member 4 is the smallest diameter portion of the recess formed by the lateral crimping process. In other words, the lateral crimping portion 6 of the sealing member 4 is the position where the diameter of the sealing member 4 is smallest.

[0045] The small-diameter portion of the lateral crimping portion 6 of the sealing member 4 will be explained using Figure 4. The small-diameter portion of the lateral crimping portion 6 includes the minimum diameter portion of the lateral crimping portion 6 and includes a diameter portion up to 10% larger than the minimum diameter portion. The thickness of the small-diameter portion of the lateral crimping portion 6 of the sealing member 4 is shown by c, and the overall thickness of the sealing member 4 in the crimped state is shown by b. In this specification, the ratio value of the small-diameter portion of the lateral crimping portion 6 of the sealing member 4 is expressed as c / b as a percentage. As mentioned above, the small-diameter portion of the lateral crimping portion 6 also includes a diameter portion up to 10% larger than the minimum diameter portion of the lateral crimping portion 6. Therefore, the ratio value of the small-diameter portion of the lateral crimping portion 6 of the sealing member 4 to the overall thickness b of the sealing member 4 is the ratio value of the thickness of the portion of the sealing member 4 having a diameter of 110% or less of the minimum diameter of the lateral crimping portion 6 of the sealing member 4.

[0046] (Manufacturing method) Such a solid electrolytic capacitor 1 is manufactured through a capacitor element formation process, a solid electrolyte formation process, a case housing process, and a crimping process.

[0047] The capacitor element formation process includes an anode formation step for forming an anode, a cathode formation step for forming a cathode, and a winding step for winding the anode and cathode with a separator in between. After the winding step, a repair and chemical conversion step may be provided to repair the exposed base metal portion of the valve acting metal when the anode and cathode are cut to a desired width, and to repair defects in the anode and cathode caused by physical stress such as winding.

[0048] In the solid electrolyte formation process, the capacitor element 3 is impregnated with a conductive polymer precursor solution, and a solid electrolyte containing the conductive polymer is formed by a polymerization reaction. Alternatively, the capacitor element 3 may be impregnated with a conductive polymer solution obtained by dispersing or dissolving the conductive polymer in a solvent such as water, and the solid electrolyte may be formed by drying.

[0049] The capacitor manufacturing process includes a case housing step in which the capacitor element 3 is inserted into a bottomed cylindrical case 2 having an opening, with the lead terminals 5 inserted through the sealing member 4. Subsequently, an oxygen permeability coefficient of 3.550 × 10⁻¹⁰ is applied to the opening of the case 2. ―10 [cc·cm / (cm 2The caulking process includes fitting the sealing member 4 adjusted to below

Example

[0050] Hereinafter, the solid electrolytic capacitor will be described in more detail based on examples. Note that the present invention is not limited to the following examples.

[0051] (Manufacture of Sealing Member) The sealing member 4 was obtained by kneading and molding 100 parts by mass of butyl rubber, 50 parts by mass of carbon black, fired clay, talc, a predetermined amount of a crosslinking agent, and other additives. And the oxygen transmission coefficient of the sealing member 4 is 3.439×10 ―10 [cc·cm / (cm 2 ·s·cmHg)] to 4.003×10 ―10 [cc·cm / (cm 2 ·s·cmHg)]. The blending of fired clay and talc was adjusted between 80 and 150 parts by mass so that the oxygen transmission coefficient was 3.439×10 ―10 [cc·cm / (cm 2 ·s·cmHg)], 3.541×10 ―10 [cc·cm / (cm 2 ·s·cmHg)] and 4.003×10 ―10 [cc·cm / (cm 2 ·s·cmHg)]. Three types of sealing members 4 with different oxygen transmission coefficients were obtained. The overall thickness of the sealing member 4 is 2.4 mm.

[0052] 〔Example 1〕 Example 1 used the sealing member 4 with an oxygen transmission coefficient of 3.439×10 -10 [cc·cm / (cm 2 ·s·cmHg).

[0053] (Manufacture of Solid Electrolytic Capacitor) ​First, a capacitor element 3 is fabricated by winding an anode and a cathode, to which lead terminals 5 have been pre-connected, with a separator in between. This capacitor element 3 is then impregnated in a conductive polymer precursor solution and heated to form a solid electrolyte containing a conductive polymer. In this case, etched aluminum foil with an oxide film on its surface is used as the anode, and aluminum foil with a metal carbide vapor deposition layer (titanium carbide) is used as the cathode. The conductive polymer precursor solution is a solution containing 3,4-ethylenedioxythiophene, p-toluenesulfonic acid, and ethanol. By impregnating the capacitor element 3 in this conductive polymer precursor solution and heating it at 150°C for 60 minutes, the 3,4-ethylenedioxythiophene is polymerized, thereby fabricating a solid electrolytic capacitor 1 containing poly(3,4-ethylenedioxythiophene) doped with p-toluenesulfonic acid as the solid electrolyte.

[0054] The lead terminals 5 of the capacitor element 3, which has a solid electrolyte formed on it, are inserted into the sealing member 4, the capacitor element 3 is inserted into an aluminum case 2, and the sealing member 4 is fitted into the opening of the case 2. Then, the case 2 is sealed by vertical and horizontal crimping to obtain a solid electrolytic capacitor 1. The position ratio of the horizontal crimping portion 6 of the sealing member 4 is 47.0%. The dimensions of the solid electrolytic capacitor 1 are a diameter of 6.3 mm, a height of 7.0 mm, a rated voltage of 16 WV, and a capacitance of 100 μF.

[0055] [Examples 2-7] Example 2 has an oxygen permeability coefficient of 3.541 × 10⁻⁶ -10 [cc·cm / (cm 2 A sealing member 4 with the properties of (·s·cmHg) was used. Furthermore, the positional ratio of the lateral crimping portion 6 of the sealing member 4 was set to 47.0%. In other words, the solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except for the change in the sealing member 4.

[0056] Example 3 has an oxygen permeability coefficient of 3.439 × 10⁻⁶ ―10 [cc·cm / (cm 2A sealing member 4 with a pressure of (·s·cmHg) was used. The positional ratio of the lateral crimping portion 6 of the sealing member 4 was set to 56.0%. In other words, the solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except that the positional ratio of the lateral crimping portion 6 of the sealing member 4 was changed.

[0057] Example 4 has an oxygen permeability coefficient of 3.541 × 10⁻⁶ ―10 [cc·cm / (cm 2 A sealing member 4 with a pressure of (·s·cmHg) was used. The positional ratio of the lateral crimping portion 6 of the sealing member 4 was set to 56.0%. In other words, the solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except that the sealing member 4 and the positional ratio of the lateral crimping portion 6 of the sealing member 4 were changed.

[0058] Example 5 has an oxygen permeability coefficient of 3.439 × 10⁻⁶ ―10 [cc·cm / (cm 2 A sealing member 4 with a pressure of (·s·cmHg) was used. Furthermore, the positional ratio of the lateral crimping portion 6 of the sealing member 4 was set to 63.0%. In other words, the solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except that the positional ratio of the lateral crimping portion 6 of the sealing member 4 was changed.

[0059] Example 6 has an oxygen permeability coefficient of 3.439 × 10⁻⁶. ―10 [cc·cm / (cm 2 A sealing member 4 with a pressure of (·s·cmHg) was used. The positional ratio of the lateral crimping portion 6 of the sealing member 4 was set to 43.3%. In other words, the solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except that the positional ratio of the lateral crimping portion 6 of the sealing member 4 was changed.

[0060] Example 7 has an oxygen permeability coefficient of 3.541 × 10⁻⁶ ―10 [cc·cm / (cm 2 A sealing member 4 with a pressure of (·s·cmHg) was used. The positional ratio of the lateral crimping portion 6 of the sealing member 4 was set to 43.3%. In other words, the solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except that the sealing member 4 and the positional ratio of the lateral crimping portion 6 of the sealing member 4 were changed.

[0061] [Comparative Examples 1-2] Comparative Examples 1 and 2 had an oxygen permeability coefficient of 4.003 × 10⁻⁶. -10 [cc·cm / (cm 2 A sealing member 4 with a pressure of (·s·cmHg) was used. The positional ratios of the lateral crimping portion 6 of the sealing member 4 were set to 47.0% and 56.0%. In other words, a solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except that the positional ratios of the sealing member 4 and the lateral crimping portion 6 of the sealing member 4 were changed.

[0062] (Method for measuring ESR) After measuring the initial ESR of the fabricated solid electrolytic capacitor 1, the product was removed at arbitrary intervals under a 125°C environment with the rated voltage applied, and its ESR characteristics were measured. The intervals at which the product was removed and the ESR was measured were 8000 hours, 9000 hours, and 10000 hours. The ESR was measured using an LCR meter (Keysight Technologies, E4980AL). The ambient temperature during measurement was 20°C, the DC bias was 0V, the AC signal level was a 1.0Vrms sine wave, and the measurement frequency was 100kHz.

[0063] Table 1 shows the ESR values ​​at the initial stage, after 8,000 hours of testing, after 9,000 hours of testing, and after 10,000 hours of testing, when the oxygen permeability coefficient of the sealing member 4 is varied and the proportion of the position of the lateral crimping portion 6 is set to 47.0%. Table 2 shows the ESR values ​​at the initial stage, after 8,000 hours of testing, after 9,000 hours of testing, and after 10,000 hours of testing, when the oxygen permeability coefficient of the sealing member 4 is varied and the proportion of the position of the lateral crimping portion 6 is set to 56.0%. Note that if the ESR exceeds 50 mΩ, it is judged as an ESR failure and is indicated as "NG".

[0064] [Table 1]

[0065] [Table 2] From Tables 1 and 2, even if the ratio value of the position of the lateral crimping portion 6 is the same, the oxygen permeability coefficient of the sealing member 4 is 3.541 × 10 ―10 [cc·cm / (cm2 It was confirmed that the increase in ESR after the test was significantly suppressed by keeping the oxygen permeability coefficient of the sealing member 4 below 3.439 × 10⁻⁶. ―10 [cc·cm / (cm 2 Examples 1 and 3, which are (·s·cmHg), or 3.541 × 10 ―10 [cc·cm / (cm 2 Examples 2 and 4, which had an ESR of 4.003 × 10¹⁶ (·s·cmHg), maintained a low ESR even after 10,000 hours of testing. In contrast, the oxygen permeability coefficient of sealing member 4 was 4.003 × 10¹⁶. ―10 [cc·cm / (cm 2 Comparative Examples 1 and 2 (·s·cmHg) showed an increase in ESR to over 50 mΩ after 8000 hours.

[0066] Here, although the details of the mechanism for suppressing the rise in ESR are not clear, we estimate it as follows. First, the thermal oxidative degradation that occurs in the sealing member 4 does not occur only on the outer side of the sealing member 4 that is exposed to the air outside the solid electrolytic capacitor, but also progresses inside the sealing member 4 due to oxygen that permeates through the sealing member 4. Therefore, the easier it is for oxygen to permeate the sealing member 4, the easier it is for thermal oxidative degradation to progress inside the sealing member 4, and as a result the thermal oxidative degradation of the sealing member 4 as a whole progresses more rapidly.

[0067] Furthermore, this thermal oxidative degradation causes shrinkage of the sealing member 4, which creates a gap between the sealing member 4 and the case 2, making it easier for oxygen from the air outside the solid electrolytic capacitor to enter the solid electrolytic capacitor. Moreover, it is presumed that this thermal oxidative degradation will eventually cause the sealing member 4 to crack.

[0068] Furthermore, when oxygen from the air outside the solid electrolytic capacitor enters the capacitor, the conductive polymer is oxidized by the oxygen, and long molecules are broken down. In other words, long conductive paths are shortened by oxidative decomposition. Due to the reduction of the conjugated system caused by the reduction of molecular weight, the electronic conductivity of the solid electrolyte decreases, and the ESR of solid electrolytic capacitor 1 increases.

[0069] Therefore, the sealing member 4 has a high oxygen permeability coefficient, for example, 4.003 × 10 ―10 [cc·cm / (cm 2 In the case of (·s·cmHg), thermal oxidative degradation of the sealing member 4 makes it easier for oxygen in the air outside the solid electrolytic capacitor to penetrate into the solid electrolytic capacitor, resulting in a deterioration of the ESR of the solid electrolytic capacitor 1. In contrast, the oxygen permeability coefficient of the sealing member 4 is 3.550 × 10⁻⁶. ―10 [cc·cm / (cm 2 Examples 1-4, which used values ​​below (·s·cmHg), successfully suppressed oxygen intrusion into the solid electrolytic capacitor and inhibited the rise in ESR.

[0070] Next, Table 3 shows how the ratio value of the position of the lateral crimping portion 6 of the sealing member 4 is varied, and the oxygen permeability coefficient of the sealing member 4 is 3.439 × 10⁻⁶. ―10 [cc·cm / (cm 2 Table 4 shows the ESR at the initial stage, after 8000 hours of testing, after 9000 hours of testing, and after 10000 hours of testing, assuming the value is (·s·cmHg). Table 4 shows the oxygen permeability coefficient of the sealing member 4 when the ratio value of the position of the lateral crimping portion 6 of the sealing member 4 is changed, and the oxygen permeability coefficient of the sealing member 4 is 3.541 × 10⁻⁶. ―10 [cc·cm / (cm 2 The ESR values ​​are shown for the initial state (·s·cmHg), after 8000 hours of testing, after 9000 hours of testing, and after 10000 hours of testing. If the ESR exceeds 50mΩ, it is judged as an ESR failure and is indicated as "NG".

[0071] [Table 3]

[0072] [Table 4] Tables 3 and 4 show that when using sealing members 4 with equivalent oxygen permeability coefficients, if the proportion of the position of the lateral crimping portion 6 of the sealing member 4 is 47.0% or higher, none of the ESRs after 10,000 hours of testing exceeded 50 mΩ. In contrast, when the proportion of the position of the lateral crimping portion 6 was 43.3%, the ESR remained low after 8,000 hours, but rose to over 50 mΩ after 9,000 hours.

[0073] Based on these results, the oxygen permeability coefficient of the sealing member 4 is 3.550 × 10⁻⁶. ―10 [cc·cm / (cm 2 By keeping the oxygen permeability coefficient of the sealing member 4 below 3.550 × 10¹⁶ (3.550 × 10¹⁶), and setting the positional ratio of the lateral crimping portion 6 of the sealing member 4 to 47% or more, the intrusion of oxygen into the case is suppressed, and the ESR of the solid electrolytic capacitor 1 is kept low. Furthermore, if the positional ratio of the lateral crimping portion 6 of the sealing member 4 exceeds 70.0%, the stress on the sealing member 4 increases, and the sealing member 4 deforms so as to bulge outwards from the solid electrolytic capacitor 1 as shown in Figure 3. Along with this deformation that causes it to bulge outwards, the lead terminal 5 is pulled outwards, and a load is applied to the connection between the anode and cathode. This load increases the connection resistance, and the ESR of the solid electrolytic capacitor 1 increases. Therefore, the oxygen permeability coefficient of the sealing member 4 should be set to 3.550 × 10¹⁶. ―10 [cc·cm / (cm 2 The ESR of the solid electrolytic capacitor 1 is kept even lower by setting the position ratio of the lateral crimping portion 6 of the sealing member 4 to 47.0% or more, more preferably 47.0% or more and 70.0% or less.

[0074] Next, the ratio of the small diameter portion of the lateral crimping portion 6 of the sealing member 4 was adjusted, and its effect on the ESR of the solid electrolytic capacitor 1 was confirmed.

[0075] [Examples 8-11] In Examples 8-11, similar to Example 1, the oxygen permeability coefficient was 3.439 × 10⁻⁶. ―10 [cc·cm / (cm 2A sealing member 4 with a value of (·s·cmHg) was used, and the positional ratio of the lateral crimping portion 6 of the sealing member 4 was set to 47.0%. Compared to the 30.0% ratio of the small diameter portion of the lateral crimping portion 6 of the sealing member 4 in Example 1, the ratios of the small diameter portion of the lateral crimping portion 6 of the sealing member 4 in Examples 8-11 were 25.0%, 20.0%, 15.0%, and 10.0%, respectively. In other words, the solid electrolytic capacitor 1 was manufactured in the same manner as in Example 1, except that the ratio of the small diameter portion of the lateral crimping portion 6 of the sealing member 4 was changed. Table 5 shows the ESR of Example 1 and Examples 8-11 at the initial stage, after 8000 hours of testing, after 9000 hours of testing, and after 10000 hours of testing. Note that if the ESR exceeded 50 mΩ, it was judged as an ESR failure and indicated as "NG".

[0076] [Table 5] Table 5 shows that even when using sealing members 4 with equivalent oxygen permeability coefficients and the same ratio of the position of the lateral crimping portion 6, if the ratio of the small diameter portion of the lateral crimping portion 6 of the sealing member 4 is 20.0% or more, none of the ESRs after 10,000 hours of testing exceeded 50 mΩ. In contrast, when the ratio of the small diameter portion of the lateral crimping portion 6 of the sealing member 4 was less than 20.0%, the ESR remained low after 9,000 hours, but rose to over 50 mΩ after 10,000 hours. Furthermore, when the ratio of the small diameter portion of the lateral crimping portion 6 of the sealing member 4 exceeds 70.0%, the sealing member 4 deforms to bulge outwards from the solid electrolytic capacitor 1. This deformation increases the connection resistance between the lead terminals 5 and the anode and cathode, resulting in a higher ESR of the solid electrolytic capacitor 1. Therefore, by setting the ratio of the small-diameter portion of the lateral crimping portion 6 of the sealing member 4 to 20.0% or more and 70.0% or less, the ESR of the solid electrolytic capacitor 1 can be kept even lower. [Explanation of Symbols]

[0077] 1. Solid electrolytic capacitor 2 cases 3. Capacitor element 4...Sealing member 5... Output terminal 6. Horizontal crimping section

Claims

1. A capacitor element having an anode, a cathode, and a solid electrolyte, A case for housing the aforementioned capacitor element, A sealing member for sealing the aforementioned case, Equipped with, The oxygen permeability coefficient of the sealing member is 3.550 × 10 ―１０ [cc・cm / (cm ２ (s・cmHg) must be less than or equal to: A solid electrolytic capacitor characterized by the following features.

2. The case is equipped with a lateral crimping portion of the sealing member that integrates the side of the case with the sealing member housed inside, The thickness of the sealing member from the minimum diameter portion of the lateral crimping portion to the case opening side end face of the sealing member is 47% or more of the overall thickness of the sealing member. A solid electrolytic capacitor according to claim 1, characterized by the above.

3. The thickness of the sealing member from the minimum diameter portion of the lateral crimping portion to the case opening side end face of the sealing member is 70% or less of the total thickness of the sealing member. A solid electrolytic capacitor according to claim 2, characterized by the above.

4. The solid electrolytic capacitor according to claim 2 or claim 3, characterized in that the small diameter portion, including the minimum diameter portion of the lateral crimping portion of the sealing member, accounts for 20% or more of the overall thickness of the sealing member.

5. The solid electrolytic capacitor according to claim 4, characterized in that the small diameter portion of the sealing member, including the smallest diameter portion of the lateral crimping portion, is 70% or less of the overall thickness of the sealing member.

6. A capacitor element having an anode, a cathode, and a solid electrolyte, A case for housing the aforementioned capacitor element, A sealing member for sealing the aforementioned case, A method for manufacturing a solid electrolytic capacitor comprising: The steps include: placing the capacitor element inside the case; The oxygen permeability coefficient is 3.550 × 10⁻⁶. ―１０ [cc・cm / (cm ２ A sealing step in which the capacitor element is sealed inside the case using the sealing member adjusted to s / cmHg or less, Including, A method for manufacturing solid electrolytic capacitors characterized by the following.

7. The aforementioned sealing process is, The process includes a crimping step for the sealing member, which integrates the side surface of the case with the sealing member housed inside the case. The thickness of the sealing member, from the minimum diameter portion of the lateral crimping section to the case opening end face of the sealing member, was adjusted to be 47% or more of the overall thickness of the sealing member. A method for manufacturing a solid electrolytic capacitor according to claim 6, characterized by the above.

Images