JP2009021491A - Aluminum electrolytic capacitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the following problems: the voidage of electrolytic paper decreases, a density increases as a whole, thereby the ESR of a capacitor tends to increase and the liquid retentivity of electrolyte tends to decline since an impregnated substance is deposited to the fiber surface of the electrolytic paper in a method of impregnating the entire surface of the electrolytic paper with the substance in order to improve electrode short-circuit defects while aluminum foil is used as an anode and a cathode, is wound around through a separator to be a capacitor element and is housed in a case with a sealing plate together with the electrolyte for an aluminum electrolytic capacitor conventionally, and to reduce short-circuit defects by the disconnection burrs of a foil end face occupying a large part of the short-circuit defects while keeping the excellent liquid retentivity of the electrolyte while suppressing the increase of the ESR of the capacitor. <P>SOLUTION: The aluminum electrolytic capacitor is characterized in that a separator is the electrolytic paper whose density is larger at both end parts of the width near both width end parts of anode foil than at the center part of the width. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an aluminum electrolytic capacitor. In particular, the present invention relates to an aluminum electrolytic capacitor characterized by a separator.

Conventionally, an aluminum electrolytic capacitor has an aluminum foil as an anode and a cathode, wound around a separator, and stored as a capacitor element in a case with a sealing plate together with an electrolytic solution. In order to extract the electrode from the capacitor element, one end of a lead lead tab made of aluminum foil was connected to the anode and the cathode, and the other end of the lead lead tab was connected to an external terminal provided on the sealing plate.
Aluminum electrolytic capacitors generally use electrolytic paper as a separator. However, since electrolytic paper is impregnated with electrolytic solution, ESR (equivalent special resistance) tends to increase as a capacitor. For this reason, it is conceivable to reduce the density of the separator. Patent Document 1 describes a method for improving the tensile strength of electrolytic paper by impregnating the entire surface of electrolytic paper with starch, vegetable gum, semi-synthetic polymer, or the like in order to improve this short circuit defect.
JP-A-8-273984

The problem to be solved is that in the method of impregnating the entire surface of the electrolytic paper with the substance to improve the short-circuit defect, the impregnated substance is deposited on the fiber surface of the electrolytic paper, so the porosity of the electrolytic paper is reduced. In addition, since the overall density increases, the ESR of the capacitor tends to increase, the liquid retention of the electrolytic solution tends to decrease, and the impregnation of the wound capacitor element with the electrolytic solution tends to be difficult.
For this reason, it is an object to reduce short-circuit defects due to cutting burrs on the foil end surface, which occupies most of the short-circuit defects, while suppressing an increase in ESR of the capacitor and maintaining good liquid retentivity.
In addition, the impregnation property of the wound capacitor element with the electrolytic solution is also improved.

The present invention relates to an aluminum electrolytic capacitor in which an anode foil and a cathode foil are wound via a separator. The separator has both widths at both end portions of the width and the vicinity of the width end portion of the anode foil. The aluminum electrolytic capacitor is characterized in that it is an electrolytic paper having a portion having a density higher than that of the central portion.
Further, in the aluminum electrolytic capacitor in which the anode foil and the cathode foil are wound through the separator, the separator is at the center of the width at both end portions of the width and the portion near the width end portion of the anode foil. It is an electrolytic paper having an impregnated portion having a density higher than that of the portion.
Further, by providing an aluminum electrolytic capacitor characterized in that the separator is a stack of electrolytic paper having a density difference in the width direction and electrolytic paper having a uniform density equal to or lower than that of the electrolytic paper. is there.
It is another object of the present invention to provide the aluminum electrolytic capacitor, wherein the electrolytic paper having a density difference in the width direction is a multilayer paper having a dense fiber layer and a coarse fiber layer.

Since the density of the separator of the present invention is larger in the portion where the anode foil overlaps with the vicinity of both width ends of the anode foil than the central portion of the width, the short-circuit defect due to the cutting burr on the foil end surface that occupies most of the short-circuit defects is reduced. can do. Moreover, since the density of the center part of the width of the separator can be kept low, the liquid retainability of the electrolyte can be kept good while suppressing the increase in ESR of the capacitor. Ensuring liquid retention can suppress a decrease in capacity due to dry-up.
In addition, since a thick part is not partially formed, the separator can be thinned or reduced in density as a whole. When the separator is thinned, the capacity of the capacitor is increased or the size is reduced. When the density is lowered, ESR can be reduced and a ripple current can be increased.
In addition, by making the separator of the electrolytic paper of the present invention and the lower density electrolytic paper into a separator, it is easy to impregnate the electrolytic solution through the low density electrolytic paper from the end face of the wound capacitor element. Become.
Further, when the electrolytic paper of the present invention is a double-layer paper having a dense fiber layer having a relatively high density and a coarse fiber layer having a relatively low density, both width portions of the separator may be impregnated with an organic substance. Since the portion of the multilayer paper with the coarse fiber layer is not easily clogged, the electrolytic solution is more easily impregnated through the rough fiber portion than the end face of the wound capacitor element.

  The anode foil described in the present invention is a general anode foil used for an aluminum electrolytic capacitor. The surface of an aluminum foil having a thickness of about 50 μm to 150 μm is etched in an acid aqueous solution to have a diameter of 0.1 μm. Then, an etching pit of about 2 μm is provided and then formed by applying a voltage of about 1.5 times the rated voltage in an aqueous solution of ammonium borate or the like to form a pressure-resistant anodic oxide film as a capacitor. After the formation, a lead lead tab is attached to form an anode foil.

  The cathode foil described in the present invention is a general cathode foil used for an aluminum electrolytic capacitor. An aluminum foil having a thickness of about 20 μm to 100 μm is immersed in an acid aqueous solution as it is, and its surface is etched and drawn. A lead tab is attached to form a cathode foil.

  The separator described in the present invention is a porous sheet that physically separates the anode foil and the cathode foil and holds the electrolytic solution. The separator is an electrolytic paper that has been conventionally used such as manila paper and kraft paper. The main material. The size is selected depending on the size of the capacitor, but the width is wider than the positive electrode foil width, about 1 cm to 30 cm, the length is about several cm to several m, and the thickness is several μm to several tens μm. It is about. The separator may be rolled up by one or more sheets, and one sheet is a multi-layer paper with a high density layer with relatively dense fibers and a low density layer with relatively coarse fibers. It does not matter.

  The electrolytic paper described in the present invention has a density that changes in the width direction, and is roughly divided into a high density, a low density, and a high density, and the density is small at the center. In particular, after winding, a portion overlapping with both width end portions of the anode foil is made dense. The present technology can be applied to all types of electrolytic paper fibers and width dimensions, and the density difference and density boundary region between the width end side and the center side vary depending on the rated voltage and the product size. For example, the density is increased in a region of 5% to 20% from both ends of the width, and a layer having a density value of 0.6 to 0.95 is a high density layer, and a layer having a density value less than 0.6 is a low density layer.

As a method for increasing the density, a method in which an organic or inorganic substance dissolved or dispersed in a solvent is impregnated in a required place is used.
It is used as an organic substance to be impregnated, or it is used alone or in combination. Seaweed polymers such as gelatin, casein, albumin, collagen and other animal polymers, xanthene gum, dextran and other microbial polymers,
Semi-synthetic systems include methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, carboxyalkyl hydroxyalkyl cellulose, hydroxyalkyl cellulose, hydroxyalkyl methyl cellulose, and partial cellulose esters such as cellulose starch glycolate, starch Starch polymers such as sodium phosphate ester, seaweed polymers such as sodium alginate, propylene glycol alginate,
In the pure synthetic system, polyvinyl polymers such as polyvinyl alcohol and copolymers thereof, polyvinyl pyrrolidone and copolymers thereof, polyvinyl pyridium halide, polyvinyl methyl ether,
Acrylic polymer such as acrylic acid, methacrylic acid, C1-C6 lower alkyl acrylate ester, C1-C6 lower alkyl methacrylate ester, styrene, dialkylamino acrylate, and dialkylamino methacrylate, or acrylic such as methacrylic poly, styrene acrylic resin Resin, styrene maleic acid resin, vinyl naphthalene acrylic resin, vinyl naphthalene maleic acid resin, polymer compound having a salt of a cationic functional group such as quaternary ammonium or amino group in its side chain, natural polymer compound such as shellac, etc. Is mentioned.
As an inorganic substance, a dispersion liquid such as colloidal silica, colloidal calcium carbonate, colloidal alumina is impregnated.

  If inorganic substances are used as filler components in organic substances, general inorganic pigments such as silica, various silicates, zeolites, calcined kaolin, diatomaceous earth, barium sulfur, aluminum hydroxide, calcium carbonate and the like are mixed.

  As a solvent, water or a water-soluble organic solvent may be used in combination for easy dispersion. Examples of water-soluble organic solvents include lower alcohols such as ethanol, methanol, normal propanol, and isopropanol; ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, glycerin, low molecular weight polyethylene Polyhydric alcohols such as glycol and hexylene glycol; ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, triethylene glycol monoethyl ether, Tetraethylene glycol Polymethyl alcohol alkyl ethers such as nomethyl ether and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; N-methyl-2-pyrrolidone, 1,3- Nitrogen-containing heterocyclic compounds such as dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; amides such as formamide, N-methylformamide, N, N-dimethylformamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine Further, amines such as diethylamine and triethylamine, sulfur-containing compounds such as dimethyl sulfoxide and sulfolane, propylene carbonate, ethylene carbonate and the like can be used.

For impregnation, roll coater printing is used in the case of the raw material before cutting for each capacitor, and in the case of electrolytic paper after cutting for each capacitor, the ink jet is used to discharge the solution from the head to the electrolytic paper. Printing is preferred. The excess impregnating solution on the surface of the electrolytic paper or inside is preferably removed with an air knife if it is on the surface, or with a blower if it is inside. Impregnation may be carried out from one side or from both sides.
In addition, after the printing, if the electrolytic paper is not sufficiently impregnated and remains on the surface of the electrolytic paper, it may be pushed into the electrolytic paper while being heated as necessary with a pair of fluorine-based surface-coated rollers. It doesn't matter.

  The aluminum electrolytic capacitor described in the present invention is similar to a normal aluminum electrolytic capacitor. After the negative anode foil is cut to an appropriate width, a lead lead tab is connected, and a capacitor element wound together with a separator such as paper is placed on the upper surface. Is made of a metal material such as aluminum having an opening, and is housed in a case formed in a cylindrical shape or an elliptical cylindrical shape and sealed with a sealing plate. The other end of the lead lead tab is connected to an external terminal provided on the sealing plate. The case may be covered with an insulating tube.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
FIG. 1 shows a configuration of a capacitor element of an aluminum electrolytic capacitor according to the present invention, and schematically shows a state during winding.
The capacitor element is wound together with a separator 4 having a width wider than that of the anode foil 1 and the cathode foil 2 after cutting the anode foil 1 and the cathode foil 2 to an appropriate width, connecting the lead lead tab 3. The high-density impregnated portion 5 is a portion indicated by dots and does not necessarily have to reach the end portion of the width of the separator 4, but at least the peripheral portion that overlaps the both width end portions of the anode foil after winding. Make it dense. When the separator 4 is not at the end of the width of the separator 4 to improve the density by mixing solids, the solids do not contaminate the cutting machine or the like when the separator 4 is cut with a necessary width.

FIG. 2 schematically shows an end view of the laminated portion of the anode foil, the separator, and the cathode foil wound around the capacitor element of the aluminum electrolytic capacitor according to the present invention. The impregnated portion 5 is a portion indicated by dots in the same manner as in FIG. 1, so that at least the peripheral portion that overlaps both width end portions of the anode foil 1 after winding is high density at the end portion of the width of the separator 4. To.
FIG. 2A shows the case where the number of separators 1 is one.
FIG. 2B is a set of two separators, one sheet of electrolytic paper 6 having a density difference in the same width direction as in FIG. 2A, and the other sheet having the same or lower density in the width direction. It is shown that the electrolytic paper 7 having no density difference is used in an overlapping manner.
FIG. 2C shows a multi-layer paper having a single separator, a dense fiber layer 8 and a coarse fiber layer 9. Even if the impregnated portion 5 is impregnated at the same time, in the portion of the layer 8 where the fibers are dense, the impregnated material is more easily deposited than in the portion of the layer 9 where the fibers are coarser, and the density is easily increased accordingly. On the contrary, in the portion of the layer 9 where the fibers are rough, the impregnated material is less likely to adhere than the portion of the layer 8 where the fibers are dense, so that the density is hardly increased. As a result, in the wound capacitor element, the electrolyte can easily enter from the end face of the layer 9 where the fibers are rough.
In FIG. 2, the anode foil 1 is on the right side and the cathode foil 2 is on the left side, but there is no particular limitation, and the reverse is also possible.

Hereinafter, the present invention will be described based on examples. In addition, an Example demonstrates the case where an electrolytic capacitor of rating 400V and 5600 micro F is manufactured. First, the anode foil is manufactured by processing an aluminum foil having a thickness of 100 μm. That is, this aluminum foil is roughened by a direct current etching method so as to be 0.7 μF / cm ² . After roughening, boil in pure water. After boiling, in a boric acid chemical liquid, a chemical film is formed by applying a chemical voltage of 600 V to form a chemical film. After the chemical conversion treatment, phosphoric acid treatment is performed for stabilization, followed by baking at a temperature of 550 ° C. After the baking treatment, it is cut into a size having a width of 120 mm and a length of 8000 mm to obtain an anode foil.
Further, an aluminum foil having a thickness of 150 μm, a width of 10 mm, and a length of 160 mm that is not subjected to chemical conversion treatment is used for the anode lead tab. Then, four 100 mm long portions of the anode lead tab are connected to the anode foil every 2000 mm by a cold well.
As the cathode foil, an aluminum foil having a thickness of 60 μm is immersed in an aqueous solution made of a mixed acid of hydrochloric acid and sulfuric acid, and the surface thereof is subjected to electrolytic etching treatment, thereby providing etching pits having an average diameter of 0.8 μm, and becomes 200 μF / cm ² . Then, the surface is roughened, followed by phosphoric acid treatment. After the phosphoric acid treatment, it is cut into a size of 120 mm wide and 8300 mm long.
The cathode lead tab is manufactured by rolling an aluminum foil to a length of 150 μm and a width of 1000 mm, followed by annealing, cutting to a width of 500 mm, and further cutting to a size of 10 mm. Four cathode lead tabs are connected to the cathode foil at intervals of 2000 mm by a cold well.
As electrolytic paper, kraft paper having a thickness of 60 μm and a width of 130 mm is used.
The method for increasing the density of both width end portions was performed by ink jet printing in which the size was set near both ends of the electrolytic paper and ejected by a multi-nozzle having a size of 15 mm × 15 mm. The printing place was 10 mm width of both width margins of 1 mm of the electrolytic paper, and an impregnating solution having a concentration of 20% in which polyvinyl alcohol was dissolved in a 20% aqueous ethanol solution was applied from both sides at the portion where the electrolytic paper was vertically set.
And after ventilation drying, the anode foil and the cathode foil were laminated | stacked and wound through this electrolytic paper, and the capacitor | condenser element was formed. Thereafter, an organic acid electrolyte was impregnated.
After impregnating the electrolytic solution, the anode lead tab and the cathode lead tab drawn out from the capacitor element were respectively connected to the anode terminal and the cathode terminal provided through the sealing plate. After the connection, the capacitor element was housed in a case filled with a fixing agent before curing in advance. After storage, the fixing agent was cured and a sealing plate was attached to the end of the case to seal the case. An explosion-proof valve is attached to the sealing plate. After the case was sealed, it was left in an atmosphere at a temperature of 85 ° C. and a voltage of 425 V was applied for aging treatment. After the aging treatment, the case was covered with an insulating tube.

The density of the electrolytic paper at this time was 0.75 at both width end portions, and the density of the other region at the center portion was 0.5. Measurement was performed by the following method together with a capacitor manufactured in the same manner except that electrolytic paper having a density of 0.75 and 0.5 in the entire area was used, and the results are shown in Table 1.
〔Measuring method〕
The defect rate during aging is gradually increased to about 120% of the rated voltage for each capacitor sample, and aging is performed. At this time, the number of capacitors including appearance abnormalities such as aging short, explosion-proof valve operation, liquid leakage, and swelling of the sealing portion was divided by 50 to obtain a short-circuit defect rate. The ESR (equivalent series resistance) of the electrolytic capacitor was measured with an LCR meter at a temperature of 20 ° C. and a frequency of 120 Hz. The capacitance of the electrolytic capacitor was measured with an LCR meter at 20 ° C. and a frequency of 120 Hz. As for the leakage current of the capacitor, the rated DC voltage of the capacitor was loaded and the current value was measured after 5 minutes.

実施例１と比較して、比較例１は、含浸速度が遅く、ＥＳＲが下がらなかった。比較例２は、エージング時のショート不良が多発した。

Compared with Example 1, Comparative Example 1 had a lower impregnation rate and the ESR did not decrease. In Comparative Example 2, short defects occurred frequently during aging.

  In addition to an aluminum electrolytic capacitor in which an anode foil and a cathode foil are wound through a separator, the present invention can be applied to an electric double layer capacitor having a similar structure. Further, the present invention can also be applied to an aluminum electrolytic capacitor or an electric double layer capacitor in which an anode foil and a cathode foil are laminated via a separator. In this case, it can be applied to the four sides of the anode foil.

The structure of the capacitor | condenser element of the aluminum electrolytic capacitor which concerns on this invention is shown, and the state in the middle of winding is shown typically. 1 schematically shows an end view of a laminated portion of an anode foil, a separator, and a cathode foil wound around a capacitor element of an aluminum electrolytic capacitor according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Anode foil, 2 ... Cathode foil, 3 ... Lead lead tab, 4 ... Separator, 5 ... Impregnation part (dot display part), 6 ... Electrolytic paper with a density difference in the width direction, 7 ... No density difference in the width direction Electrolytic paper, 8... Fiber dense layer, 9... Fiber coarse layer 9.

Claims (4)

  In an aluminum electrolytic capacitor in which an anode foil and a cathode foil are wound with a separator interposed therebetween, the separator is located at both ends of the width of the aluminum electrolytic capacitor, both in the vicinity of the width end of the anode foil and from the center of the width. An aluminum electrolytic capacitor characterized by being an electrolytic paper having a portion having a high density.   In an aluminum electrolytic capacitor in which an anode foil and a cathode foil are wound with a separator interposed therebetween, the separator is located at both ends of the width of the aluminum electrolytic capacitor, both in the vicinity of the width end of the anode foil and from the center of the width. An aluminum electrolytic capacitor characterized by being an electrolytic paper having an impregnated portion having a high density. An aluminum electrolytic capacitor, wherein the separator is a laminate of the electrolytic paper according to claim 1 and the electrolytic paper having a uniform density equal to or lower than the electrolytic paper. The aluminum electrolytic capacitor according to claim 1 or 2, wherein the separator is a multilayer paper having a dense fiber layer and a coarse fiber layer.

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