JP2010114173A - Separator and solid electrolytic capacitor using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable capacitor by improving the heat resistance (dimension stability by heating for instance) of a separator and the hygroscopicity of the separator. <P>SOLUTION: The particles of an inorganic substance such as anhydrous aluminum silicate, silicon nitride, zirconia or titanium oxide are mixed only in the sheath portion of core-in-sheath structure fibers such as synthetic fibers or cellulose having a core-in-sheath structure configuring the separator at least for 1.5 wt.% or more to the weight of the separator, and at least one of the mixed core-in-sheath fibers is mixed so as to be at least 30 wt.% to the weight of the separator. For the inorganic substance particles mixed in the sheath part, it is desirable that the average particle size is 0.01-1.0 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a separator that is interposed between an anode foil and a cathode foil of a solid electrolytic capacitor and can hold, for example, a conductive polymer as an electrolyte, and a solid electrolytic capacitor using the separator.

  A typical wound aluminum electrolytic capacitor is formed by winding a separator between an anode aluminum foil and a cathode aluminum foil to form a capacitor element, and the capacitor element is immersed in a liquid electrolyte. It was manufactured by impregnating the electrolyte and sealing it.

  As an electrolytic solution, a solution in which solutes such as boric acid, ammonium adipate, and ammonium hydrogen maleate are dissolved in ethylene glycol (EG), dimethylformamide (DMF), or γ-butyrolactone (GBL) as a solvent is usually used. It is manufactured by infiltrating from both ends of the capacitor element.

  In recent years, digitalized commercial and consumer electronic devices have dramatically increased the operating frequency, and there is a strong demand for power saving as a whole electronic device. Therefore, electrolytic capacitors that are components constituting these electronic devices are also required to have low impedance characteristics, particularly equivalent series resistance (hereinafter referred to as “ESR”), in order to increase the operating frequency and save power. It has been.

  Specifically, with the increase in the speed of computers (CPUs) built in electronic devices, reduction of ESR in a high frequency range is required. For example, in an electrolytic capacitor having a rated voltage of 4 V and a rated capacitance of 100 μF, There is a demand for an ESR of 100 kHz to be 20 mΩ or less.

  On the other hand, lead-free solder has been introduced in recent years because lead in solder has an adverse effect on the environment. As a result, in surface mount electronic components, the solder reflow temperature has risen from the conventional 180 ° C. to about 270 ° C., and inevitably the heat resistance of various electronic components used in electronic devices is higher than ever. To do so is an inevitable requirement.

  However, it has been difficult to sufficiently reduce ESR in a high frequency range in an electrolytic capacitor using the above-described electrolytic solution as an electrolyte. This is because the specific resistance of the electrolytic solution itself cannot be lowered. For this reason, solid electrolytic capacitors using manganese dioxide and TCNQ complexes have been developed as electrolytes with lower specific resistance.

  Furthermore, recently, electrolytic capacitors using a conductive polymer such as polypyrrole or polythiophene as an electrolyte have been developed. The specific resistance of these conductive polymers is much smaller than the specific resistance of manganese dioxide and TCNQ complexes, and it is possible to produce a solid electrolytic capacitor having a good ESR, which has been attracting attention and used. .

  However, in a solid electrolytic capacitor using a conductive polymer as an electrolyte, particularly a wound aluminum solid electrolytic capacitor for surface mounting, a separator having higher heat resistance is required due to an increase in solder reflow temperature. In particular, as for heat resistance, heat resistance of 280 ° C., more preferably 290 ° C. is required.

  In addition, there is a problem that the conductive polymer reacts with water to lower the conductivity, resulting in a decrease in capacitance and an increase in ESR. This is because when moisture is present in the capacitor element, hydrogen gas is generated at the cathode by voltage application, and affects the conductive polymer in contact with the cathode. This is a cause of a decrease in capacity and an increase in ESR.

  Furthermore, when an electrolytic capacitor using a conductive polymer as an electrolyte, particularly a winding type conductive polymer aluminum electrolytic capacitor is to be manufactured, a separator made from cellulose used in conventional aluminum electrolytic capacitors is used. There was a problem that it could not be used as it is. This is because the cellulose in the separator inhibits impregnation of the polymerization solution of the conductive polymer or polymerization of the conductive polymer.

  In order to suppress such an influence, when using a cellulose fiber separator, it has been attempted to heat the wound capacitor element and carbonize the separator. However, since the separator in the capacitor element is carbonized, the process becomes complicated, heat resistant and oxidation resistant materials must be used for the members used, the element shape collapses due to carbonization, and heating There is a problem that the LC (leakage current) of the capacitor increases due to the stress caused by the above, so that when the heating temperature exceeds 260 ° C., the practicality is lacking.

  Further, Patent Document 1 discloses a solid electrolytic capacitor using vinylon fibers as a separator. However, vinylon fibers have a problem of low heat resistance at a decomposition temperature of 240 ° C., and solder when used in a surface mount type. There was a problem that the product expanded at the reflow temperature.

  Patent Document 2 discloses a solid capacitor using a polyethylene terephthalate (hereinafter referred to as “PET”) fiber with a separator at 20 ° C. and a relative humidity of 65% and an equilibrium moisture content of 0.4%. The melting point of the fiber is 260 ° C., which is lower than the solder reflow temperature, and there is a problem in terms of heat resistance.

  Patent Document 3 discloses a solid capacitor using a polyethylene naphthalate (hereinafter referred to as “PEN”) fiber having a equilibrium moisture content of 0.6% at 20 ° C. and a relative humidity of 65% as a separator. PEN fiber has a melting point of 272 ° C., which is close to the solder reflow temperature and is not sufficiently heat resistant.

  Patent Document 4 discloses a separator for a solid electrolytic capacitor using a polyketone fiber having an equilibrium moisture content of 0.5 to 0.6% at 20 ° C. and a relative humidity of 65%, but the melting point of the polyketone fiber is 271. It is close to the solder reflow temperature of ˜273 ° C. and is not sufficiently heat resistant.

  Patent Document 5 discloses a solid electrolytic capacitor using a semi-aromatic polyamide fiber having an equilibrium moisture content of 1.8% at 20 ° C. and a relative humidity of 65%. The melting point of the semi-aromatic polyamide fiber is 265. There is a problem in terms of heat resistance, which is lower than ℃ and solder reflow temperature.

  Patent Document 6 discloses a solid electrolytic capacitor using an acrylic fiber having an equilibrium moisture content of 2.0% at 20 ° C. and a relative humidity of 65%. Acrylic fibers are highly heat-resistant fibers having a decomposition temperature of 300 ° C., but there is a problem that the dimensions of the fibers change due to heating. This is because the fiber produced by heating and drawing by fiber spinning tends to return to its original form by heating. For this reason, there is a problem that the dimensions of the separator change at the time of heating, and there is a problem in productivity such as a characteristic that changes due to this.

  Patent Document 7 discloses a separator for a solid electrolytic capacitor using an aramid fiber or an aramid fibrid having an equilibrium moisture content of 5.0 to 6.5% at 20 ° C. and a relative humidity of 65%. Aramid is a high heat-resistant fiber having a decomposition temperature of 290 ° C. or higher, but has a high hygroscopic property and has a problem in reliability of capacitor characteristics due to moisture.

Table 1 shows vinylon fibers (patent document 1) and PET fibers (patent document 2), PEN fibers (patent document 3), polyketone fibers (patent document 4), semi-aromatic polyamide fibers (patent document 5), acrylic fibers (patents) 6 is a table summarizing the equilibrium moisture content, decomposition temperature, and melting point of Polyamideimide and Para-Aramid (Patent Document 7) at 20 ° C. in a 65% relative humidity atmosphere of rayon, acetate, and hemp.

  As shown in Table 1, the melting point and decomposition temperature of each fiber excluding acrylic fiber, polyamideimide, and para-aramid were 290 ° C. or less, and there was a problem with heat resistance.

  In addition, the decomposition temperature of polyamideimide and para-aramid has a temperature of 290 ° C. or higher, but the equilibrium moisture content at 20 ° C. and relative humidity of 65% is 4% or higher, which causes a problem in hygroscopicity.

  Furthermore, acrylic has a good equilibrium moisture content at a decomposition temperature of 20 ° C. and a relative humidity of 65%, but has a problem that the dimensional change of the fiber due to heating is large. Rayon and acetate had problems with heat resistance and moisture absorption.

Japanese Patent No. 3319501 Japanese Patent No. 3606137 JP 2005-197310 A JP 2006-351733 A JP 2004-111582 A JP 2004-146707 A JP 2007-59789 A

  The present invention has been made for the purpose of solving the above-described problems, improving the heat resistance (for example, dimensional stability by heating) of the separator and the hygroscopicity of the separator, and providing a highly reliable capacitor. As a means for achieving the object, for example, the following configuration is provided.

  That is, the separator is a separator capable of holding an electrolyte by interposing between an anode foil and a cathode foil of a solid electrolytic capacitor, and including a fiber mixed with at least inorganic particles.

  For example, the fiber is a synthetic resin fiber. Alternatively, the synthetic resin fiber is a separator characterized by being one or more synthetic fibers of acrylic, polyethylene terephthalate, polyethylene naphthalate, semi-aromatic polyamide, para-aramid, polyamide-imide, and polyketone.

  Further, for example, the fibers are cellulose derivative fibers such as cellulose fibers such as rayon fibers. For example, the rayon fiber includes at least one of solvent-spun rayon, viscose rayon, and cupra rayon.

  Further, for example, the separator is a cellulose derivative fiber such as a semi-synthetic fiber. Alternatively, the separator is characterized in that the semi-synthetic fibers are acetate fibers.

  For example, the fiber is a core-sheath structure fiber, and the separator contains at least 30% by weight or more of the separator weight of the fiber containing the inorganic particles in the sheath part.

  Alternatively, the separator is a separator capable of holding an electrolyte by interposing an anode foil and a cathode foil of a solid electrolytic capacitor, and including a fibrid mixed with at least inorganic particles.

  For example, the fibrid is para-aramid having a binder effect. Or it is set as the separator characterized by containing an inorganic particle in the range of 10 to 60 weight% with respect to the fibrid weight.

Further, for example, the separator is characterized in that the average particle diameter of the inorganic particles is 1 μm or less. Or it is set as the separator characterized by containing 1.5 weight% or more of inorganic substance particles with respect to the separator weight.
Or it is set as the electrolytic capacitor characterized by using any of the above separators.

  Further, for example, an electrolytic capacitor using any one of the above separators and further using at least one of polypyrrole, polythiophene, polyaniline, or a derivative thereof as the conductive polymer is provided.

  According to the present invention, the heat resistance of the separator used in the solid electrolytic capacitor and the hygroscopicity of the separator can be improved, and the solid with high reliability that reduces the influence of heat and moisture in the solid electrolytic capacitor using the separator. An electrolytic capacitor can be provided.

  Hereinafter, an embodiment of an invention according to the present invention will be described in detail. Influence of heat and moisture by using any of the separators described below, or by using an electrolytic capacitor that uses at least one of polypyrrole, polythiophene, polyaniline, or derivatives thereof as a conductive polymer. It is possible to provide a highly reliable solid electrolytic capacitor with reduced noise.

  The separator according to the present embodiment has a core-sheath structure in order to improve the heat resistance of the separator (particularly dimensional stability by heating) and the hygroscopicity of the separator, which have been problems to be solved by conventional separators. 30% by weight or more of the fiber to be mixed with inorganic particles is blended, and 5% by weight or more of the inorganic particles are mixed with respect to the weight of the fiber (at least 1.5% by weight with respect to the separator weight). By blending the types, it is possible to reduce the influence of heat and moisture of the solid electrolytic capacitor, improve the ESR and capacity, and suppress the change in characteristics due to the moisture.

  Specifically, a synthetic fiber having a core-sheath structure, or a core-sheath fiber such as cellulose, an inorganic substance such as anhydrous aluminum silicate, silicon nitride, zirconia, titanium oxide, carbon black, boron nitride (hereinafter “ The particles of “mixture”) are mixed at least 1.5% by weight or more with respect to the separator weight, and at least one of the mixed core-sheath fibers is mixed so as to be 30% by weight or more with respect to the weight of the palator. The average particle diameter of the inorganic particles mixed in the sheath is 2 μm or less, and preferably the average particle diameter is 0.01 to 1.0 μm.

  Thereby, the heat resistance can be improved as will be described in detail later. Furthermore, even in an atmosphere of 20 ° C. and a relative humidity of 65%, the equilibrium moisture content can be suppressed to 4% or less, and the hygroscopicity of the entire capacitor element using the separator can be improved.

  Even in the solid electrolytic capacitor having the separator configured as described above, the influence of heat resistance and moisture on the characteristics is reduced, and a highly reliable solid electrolytic capacitor is realized.

  Hereinafter, the configuration of the separator according to the embodiment of the present invention will be described in detail.

  The separator of the present embodiment holds a conductive polymer as an electrolyte and is interposed between the anode foil and the cathode foil of the electrolytic capacitor.

  As the synthetic fiber of the core-sheath structure fiber constituting the separator of this embodiment, a fiber made of a resin such as PET, PEN, polyketone, semi-aromatic polyamide, acrylic, polyamideimide, para-aramid, or the like can be used.

  Further, as the fibrid having a binder effect, it is desirable to use para-aramid fibrid produced by the para-aramid jet span method. The mixing amount of para-aramid fibrid is in the range of 10 to 60% by weight with respect to the fiber.

  It is desirable to use rayon fiber or semi-synthetic fiber as the fiber made of cellulose of core-sheath structure fiber and its derivatives constituting the separator of this embodiment.

  The rayon fibers are preferably solvent-spun rayon, viscose rayon, and cupra rayon. The semi-synthetic fiber is preferably an acetate fiber.

  The inorganic particles constituting the above mixture are blended to improve heat resistance and hygroscopicity, and specific inorganic materials include, for example, silicon nitride, silicon carbide, zirconia, alumina, silica, aluminum nitride, silicic anhydride Aluminum, titanium oxide, or the like can be used, but is not limited to the above examples, and any one can be used as long as the same effect can be obtained.

  As an average particle diameter of the mixture particles (inorganic material) used for the fibers constituting the separator of the present embodiment, those having a particle size of 2 μm or less can be used. This is because if the average fiber diameter exceeds 2 μm, the fibers cannot be produced successfully due to nozzle clogging or thread breakage. The average particle diameter of the mixture is preferably 1 μm or less, more preferably 0.3 μm or less. Incidentally, particles having a particle diameter of less than 0.01 μm are difficult to disperse in the resin and are not practical.

  In the sheath portion of the core-sheath structure fiber according to the present embodiment (fibers having a core-sheath structure in which the core portion and the sheath portion of the fiber are made of the same kind of synthetic resin or cellulose), at least one kind of the above mixed particles is used with respect to the separator weight Mix at least 1.5% by weight. If it is 1.5% by weight or less, the effects expected of the heat resistance and hygroscopicity of the separator cannot be obtained. Further, in the case of general spinning, when the mixing amount is increased to 30% by weight or more with respect to the weight of the fiber, the fiber strength is decreased, yarn breakage occurs frequently, and spinning is difficult.

  In this embodiment, for example, by using para-aramid fibrids by a jet span method, the binder effect can be mixed from 10 to 60% by weight without losing the binder effect. This is because if the mixing amount is 10% by weight or less, a sufficient moisture-proof effect cannot be obtained, and if it exceeds 60% by weight, a sufficient binder effect cannot be obtained.

  About the core-sheath structure fiber used for the separator of this Embodiment, it describes in the patent document 8 shown below, for example.

Next, a specific configuration example will be described.

  For example, 30% by weight (1.5% by weight with respect to the separator weight) of the fiber (A) shown in Table 2 in which 5% by weight of the anhydrous aluminum silicate as an inorganic substance is mixed in the sheath part of the core-sheath structure with respect to the fiber weight Each sheet is made by using 40% of synthetic fiber (B) not mixed with inorganic material and 30% by weight of polyvinyl alcohol binder fiber (C) not mixed with inorganic material as a binder, using a circular net paper machine. As for the heat resistance, the thickness retention ratio and the area dimension retention ratio were evaluated by heating at 290 ° C. for 10 minutes.

  Here, PET, acrylic fiber, and viscose rayon are used as fiber types, and (A) is mixed with 5B by weight of anhydrous aluminum silicate as an inorganic substance in the same fiber type as (B) with respect to the fiber weight. Fibers were used.

Table 2 Separator composition (3 types of fiber: PET, acrylic fiber and viscose rayon)

Table 3 Separator sample numbers corresponding to the above composition

[Thickness dimensional retention formula]
The thickness dimension retention rate is calculated from the following formula.

Thickness dimension retention rate (%) =
Difference in thickness before and after heat treatment / Thickness before heat treatment × 100
Specifically, ten test pieces of 250 mm × 15 mm are stacked, the test piece is stopped with a staple, and the thickness is defined in JIS B7502. The outer micrometer (spindle diameter 6.35 mm, measurement length 25 mm or less) And the thickness per sheet was obtained from the sample before and after the treatment.
[Area dimensional retention formula]
The area dimension retention is calculated from the following formula.

Dimension retention of area (%) =
Difference in area before and after heat treatment / area before heat treatment × 100
Specifically, the vertical and horizontal dimensions are measured with a caliper on a 100 mm × 100 mm test piece, and the area before processing is calculated. Similarly, the vertical and horizontal dimensions of the test piece after heat treatment are measured with a caliper, and the area after treatment is calculated. And the area of each sample was computed from said formula.

  The evaluation results using the above samples are shown in Tables 4-1 to 4-4. Table 4-1 is a table that specifically shows the mixing ratio and thickness dimension retention of anhydrous aluminum silicate for each fiber, and Table 4-2 is the mixing ratio and thickness dimension retention of anhydrous aluminum silicate for each fiber. It is a table | surface which shows the example which displayed the rate measurement result on the graph.

  Table 4-3 is a table that specifically shows the mixing ratio of aluminum silicate anhydrous and area dimension retention (290 degrees C-10 minutes) for each fiber, and Table 4-4 is the anhydrous aluminum silicate for each fiber. It is a table | surface which shows the example which displayed the measurement result of the mixing rate and the area dimension retention (290 degree C-10 minutes) in the graph.

Each dimensional retention rate indicates that the closer the value is to 100, the higher the retention rate and the better the heat resistance. As a synthetic fiber having a melting point of 290 ° C. or less, PET softens and dissolves when the amount of inorganic particles mixed is small and the area retention is high, but the form as a separator is lost and its function cannot be exhibited.
In addition, the thickness tends to decrease when the mixing amount of the inorganic particles is small and the fibers soften and dissolve to reduce the dimensional retention. In the thickness dimension retention rate, an error of about 7% to 11% occurs when the mixing rate is 4%, an error rate of 3% or less occurs when the mixing rate is 5%, and an error occurs when the mixing rate is 10% or more. Absent. From this, it became clear that 5% should be mixed with inorganic particles.

  The function of the separator is to keep the conductive polymer, which is an electrolyte, uniform and to keep the clearance between the electrodes uniform and prevent short circuit.

  Next, when acrylic fibers are employed, if the amount of inorganic particles is not in the range of 5% by weight or more, the thickness dimension retention rate becomes larger than 100% due to the dimensional change of the acrylic fibers due to heating. The area shrinks and the area dimension retention becomes smaller than 100%.

  In addition, when viscose rayon is used as the rayon fiber, if the amount of the inorganic particles is not in the range of 5% by weight or more, the thickness dimension retention rate becomes larger than 100% as in the case of acrylic fiber, and the area shrinks. It was found that the area dimension retention rate was smaller than 100%.

  In addition, even if 30% by weight of mixed fibers containing 5% by weight or less of inorganic particles or the like are blended (less than 1.5% by weight with respect to the separator weight), the effect of heat is great, and a separator with sufficient dimensional retention Turned out not to be able to get.

  When the capacitor element is actually created, if the area retention rate decreases, it causes a short circuit or an increase in leakage current (LC). Due to the increase in thickness dimension retention rate, there is a problem that the element stop tape is cut and the element can be flipped. Conversely, when the thickness dimension retention ratio decreases, the distance between the electrodes increases and the ESR and capacitance are deteriorated.

  In order to solve this problem, the thickness dimension retention is preferably as close to 100 as possible. Therefore, from these results, it is necessary to blend at least 30% by weight of a fiber obtained by mixing 5% by weight or more of inorganic particles in the sheath of the core-sheath structure with respect to the fiber weight.

Next, the result of inspecting the relationship between the thickness dimension retention ratio, the capacitance, and the ESR, which have a great influence on the capacitor characteristics, is shown. Table 5 shows the composition of the separator sample used. Table 5 is a table showing the thickness retention (290 ° C.-10 minutes), ESR, capacitance, and composition of the separator used for evaluation (A40% + B30% + C30%).

  The relationship between the thickness dimension retention ratio and the capacitance, which has a great influence on the characteristics, is shown in the graph of Table 6. Similarly, the relationship between the thickness dimension retention ratio and the ESR is shown as a graph in Table 7.

  The element was heat-treated under the same conditions as each dimension retention rate, and then polythiophene polymerized to produce a 4 WV, 100 μF solid electrolytic capacitor. Thereafter, the reflow test was performed twice under the condition of being exposed to a maximum temperature of 270 ° C. The maximum temperature of the solder reflow is several seconds, and if the separator has a heat resistance of 290 ° C. for 10 minutes, sufficient characteristics can be obtained.

  As a result of evaluation with a capacitor, as described above, 30% or more of mixed fibers in which the amount of inorganic particles mixed in the sheath of the core-sheath structure is 5% by weight or more with respect to the fibers (1.5% by weight with respect to the separator weight) As described above, it has been found that, by mixing, the conventional problems of the separator can be solved and a solid electrolytic capacitor having the desired characteristics can be obtained. It has been found that the mixing amount is more preferably good when 10 to 60% by weight of mixed fiber is mixed with at least 30% to 80% by weight of the fiber.

Next, test results on the effects of moisture and capacitor characteristics were performed.
A separator comprising 100% by weight of sisal pulp (hereinafter also referred to as “natural cellulose separator (S1)”) and a para-aramid fiber and 30% by weight of polyvinyl alcohol binder fiber (hereinafter referred to as “PVA”) as a binder ( (Hereinafter also referred to as “aramid separator (S2)”), a separator in which para-aramid fibers are changed to amidoimide (hereinafter also referred to as “amideimide separator (S3)”), and a separator in which viscose rayon is changed as rayon fibers (hereinafter referred to as “rayon”). A separator (hereinafter also referred to as “para-aramid fibrid separator (S5)”) in which the para-aramid fibers were changed to para-aramid fibrids was produced with a circular net paper machine. The natural cellulose separator (S1) and the rayon separator (S4) were heated at 270 ° C. for 1 hour to carbonize the separator.

The equilibrium water content of the sample was determined from the following method.
4 separators of 250 mm x 250 mm were dried with a dryer, and the weight immediately after drying was measured. Then, the separator was left in a constant temperature and humidity room and the moisture content was (20 ° C-relative humidity 65% RH). The amount was determined from the following formula.

Moisture content (%) =
(Measurement weight-weight immediately after drying) / weight immediately after drying × 100
Tables 8 and 9 show the moisture absorption test results of the uncarbonized cellulose separator or carbonized cellulose separator (S1), para-aramid separator (S2), polyamideimide separator (S3), rayon separator or carbonized rayon separator (S4). .

Table 8 is a table showing the moisture absorption test results of each separator in numerical values, and Table 9 is a table showing the moisture absorption test results of each separator in a graph.
Note that the moisture content of the separator of the present embodiment refers to the moisture content measured and calculated under the above conditions.

  Next, the influence of the water content of the separator on the capacitance and ESR, which are basic characteristics of the solid electrolytic capacitor, was verified. The separator shown in the following example used for verification is manufactured by a conventional method using a circular net paper machine. As shown in Examples and Comparative Examples described later, the moisture content of the separators of various compositions measured in a constant temperature and humidity laboratory controlled at (20 ° C.-relative humidity 45% RH) depends on the fiber composition constituting the separator. Depending on it, it varied from 0.5% to 6%.

  Using these separators of various compositions, solid electrolytic capacitors were prepared in a constant temperature and humidity laboratory controlled at (20 ° C.—relative humidity 45% RH).

A solid electrolytic capacitor was prepared using this separator, and the solder reflow test was performed twice under the condition of being exposed to a maximum temperature of 270 ° C. In the reliability test, the solid electrolytic capacitor subjected to the solder reflow test was used as a test sample, stored for 3000 hours under an environmental condition of (temperature 105 ° C.-relative humidity 65% RH), and the characteristics and reliability test 3000 after the solder reflow test The characteristics after time were compared.
And the change rate by the reliability test of an electrostatic capacitance and ESR was evaluated as a basic characteristic of these solid electrolytic capacitors. Tables 10 to 12 show evaluation results of the separator moisture content, the capacitance change rate, and the ESR change rate extracted from the above-described examples, conventional examples, and comparative examples.

  The capacitance change rate is a numerical value obtained by dividing the difference between the values before and after the reliability test shown in the following formula by the value before the reliability test and multiplying it by a factor of 100. The value before the reliability test is the value after the solder reflow test. The larger this value, the greater the change in capacitance.

Capacitance change rate =
(Before Reliability Test-After Reliability Test) / Before Reliability Test x 100
The test results are shown in Table 10 and Table 11. Table 10 is a table showing the change rate of capacitance and the change rate of ESR with respect to the moisture content of the separator, extracted from the examples, conventional examples, and comparative examples. Table 11 is the moisture content of the separator in each example in Table 10. It is the table | surface which displayed the change rate of the electrostatic capacitance in the graph.

  As shown in Table 10 and Table 11, when the water content was 4% or less, a satisfactory result was shown in which the rate of change in capacitance was 10% or less. Further, it has been found that the rate of change in capacitance is more preferably 1.6% or less, and even more preferably 0.9% or less.

  The ESR change rate is a value obtained by dividing the difference between the values after the reliability test and before the reliability test by the value before the reliability test and multiplied by a factor of 100.

ESR change rate =
(After reliability test-before reliability test) / Before reliability test x 100
The value before the reliability test is the value after the solder flow test. It shows that the change of ESR is so large that this figure is large.

  Table 12 shows the inspection results. Table 12 is a table in which the rate of change of ESR with respect to the moisture content of the separator in each example shown in Table 10 is displayed in a graph.

  As shown in Table 12, when the water content was 4% or less, the ESR change rate was a good result of 10.2% or less. Further, it has been found from the rate of change of ESR that it is more preferably 2.2% or less, and even more preferably 0.9% or less.

  Next, the evaluation result about the moisture content of the separator is shown. Fiber mixed with para-aramid fiber or solvent-spun rayon fiber and inorganic aluminum silicate as an inorganic substance in the sheath portion of the core-sheath structure, 5% by weight with respect to the fiber weight, or 10% with respect to the weight of the fibril produced by the jet span method Tables 13 to 16 show the moisture content of the separator with respect to the blending amount of the mixed para-aramid fiber and untreated para-aramid fiber, acrylic fiber, semi-aromatic polyamide fiber, PVA, solvent-spun rayon, and sisal hemp pulp. When viscose rayon fiber or sisal hemp pulp is blended as the cellulose fiber, it is the amount of water when the separator is heated and carbonized at 270 ° C. for 60 minutes.

  Table 13 shows a mixture of inorganic aluminum silicate as an inorganic substance in a sheath portion of a core-sheath structure in an amount of 5% by weight with respect to the fiber weight, and 10% by weight with respect to the weight of the fibrid produced by the jet span method. Table 14 shows as a specific numerical table the relationship between each inorganic raw material blended in the blending amount shown in the table and the moisture content of the separator with respect to the inorganic mixed fiber made of para-aramid fibrid, Table 14 is Table 13 It is the table | surface which displayed in graph the relationship between each raw material with which the inorganic substance mix | blended with the ratio of this, and the equilibrium moisture content of a separator.

  Table 15 shows the amount of inorganic aluminum silicate as an inorganic substance mixed in the sheath part of the core-sheath structure in an amount of 5% by weight based on the fiber weight with respect to the inorganic mixed solvent spun rayon fiber (viscose rayon). Table showing as a specific numerical table the relationship between each inorganic raw material to be blended and the moisture content of the separator, Table 16 shows the balance between each inorganic raw material blended in the ratio of Table 15 and the equilibrium moisture content of the separator It is the table | surface which displayed the relationship graphically.

  From the inspection results, it was found that the water content of the separator can be reduced to 4% by blending inorganic particles. In addition, even if natural cellulose was carbonized at 270 ° C. for 1 hour, the moisture content of the separator could not be reduced to 4% or less. In addition, it was found that para-aramid, para-aramid fibrid, and viscose rayon fiber also had a result that the water content of the separator could not be reduced to 4% or less when the content was 30% by weight or less.

  Since the para-aramid fibrid is manufactured by the jet span method, it is not a core-sheath structure, so it was confirmed that it was necessary to mix twice as much inorganic substance to obtain the same effect as the aramid fiber.

  The conductive polymer refers to a polymer that has conductivity and can be used as an electrolyte of a solid electrolytic capacitor, and other polymers than those described above may be used as long as the polymer has such properties. It can be used. For example, as specific examples, at least one of polypyrrole, polythiophene, polyaniline, or derivatives thereof can be used.

  The conductive polymer polymerization solution is prepared by mixing a thiophene or polypyrrole monomer solution and an oxidizing agent solution. Specific product names include Clevios M (3,4 ethylenedioxythiophene) and Clevios C (butanol solution of iron paratoluenesulfonate) from H.C. As widely used. As the solvent, i-propanol, methanol, ethanol, butanol, and acetone can be used.

  In the present embodiment, as described above, the synthetic fiber mixed with the sheath portion of the core-sheath structure fiber so that the mixture particles such as inorganic substances are at least 1.5% by weight or more with respect to the separator weight as described above. The heat resistance of the separator can be improved by mixing at least one fiber made of cellulose with at least 30% by weight of the separator weight. In addition, by adjusting the equilibrium moisture content to 4% or less in an atmosphere of 20 ° C and relative humidity of 65%, and improving the hygroscopicity of the entire device, the influence on the heat resistance and moisture characteristics of the solid capacitor is solved. It becomes possible to achieve high reliability.

  As described above, according to the present embodiment, a synthetic fiber or a fiber made of cellulose in which a mixture particle of an inorganic compound or the like is mixed with a sheath part of a core-sheath structure at least 1.5% by weight with respect to the separator weight. By blending at least one kind and 30% by weight or more, the heat resistance of the separator is increased, and the equilibrium moisture content of the separator is reduced to 4% or less in an atmosphere of 20 ° C. and a relative humidity of 65%. Reduce the moisture absorption of the element, provide a solid electrolytic capacitor that solves the influence of moisture, improve the water absorption of the element, reduce the influence of the solid capacitor on heat resistance and moisture, and reduce the ESR and capacitance It is possible to realize a highly reliable capacitor that can be improved and the change in characteristics due to moisture can be suppressed.

〔Example〕
A specific embodiment according to the present invention will be described below together with a conventional example and a comparative example.
First, in each of the following examples, an anode aluminum foil and a cathode aluminum foil were formed in a slit shape having desired dimensions, and then a lead rod was attached to each of the anode aluminum foil and the cathode aluminum foil. Example 1 shown in Table 6 ˜24, Conventional Examples 1 to 8 and Comparative Examples 1 to 11 were wound to form capacitor elements. Note that solid electrolytic capacitors using cellulose fibers are carbonized by heat treatment.

  In the separator of Example 1, 30% by weight of PET fiber was used as the mixture fiber, and 70% by weight of unstretched PET binder fiber was used as the binder.

  In the sheath part of the PET fiber, anhydrous aluminum silicate particles as inorganic mixture particles were mixed so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the PET fiber.

  In the separator of Example 2, 30% by weight of PET fiber was used as the mixture fiber, and 70% by weight of unstretched PET binder fiber was used as the binder.

  Anhydrous aluminum silicate particles as inorganic mixture particles were mixed in the sheath portion of the PET fiber so that the weight of the mixture in the separator was 3% by weight and 10% by weight of the PET fiber.

  In the separator of Example 3, 30% by weight of PET fiber was used as the mixture fiber, and 70% by weight of unstretched PET binder fiber was used as the binder.

  The sheath of PET fiber was mixed with anhydrous aluminum silicate as inorganic mixture particles so that the weight of the mixture in the separator was 9% by weight and 30% by weight of PET fiber.

  In the separator of Example 4, 30% by weight of PET fiber was used as a mixture fiber, 40% by weight of unstretched PET binder fiber as a binder, and 30% by weight of Poval (PVA) which is a wet heat fusion resin.

  Anodized aluminum silicate as inorganic mixture particles was mixed in the sheath portion of the PET fiber so that the weight of the mixture in the separator was 0.3% by weight and 1% by weight of the PET fiber. In addition, silicon nitride as inorganic mixture particles was mixed in the sheath portion of the unstretched PET binder fiber so that the weight of the mixture in the separator was 1.2% by weight and 3% by weight of the PET binder fiber.

  In the separator of Example 5, 30% by weight of PEN fiber was used as a mixture fiber, 40% by weight of unstretched PET binder fiber as a binder, and 30% by weight of Poval (PVA) which is a wet heat fusion resin.

  The sheath of PEN fiber is made of anhydrous aluminum silicate as inorganic mixture particles. The weight of the mixture in the separator is 0.3% by weight, 1% by weight of PEN fiber, and the sheath of unstretched PET binder fiber is made of silicon nitride. The mixture was mixed so that the weight of the mixture was 1.2% by weight and 3% by weight of the PET binder fiber.

  In the separator of Example 6, 30% by weight of PEN fiber was used as a mixture fiber, and 70% by weight of PEN binder fiber was used as a binder.

  Anhydrous aluminum silicate as inorganic mixture particles was mixed in the sheath portion of the PEN fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the PEN fiber.

  In the separator of Example 7, 30% by weight of semi-aromatic polyamide fiber was used as a mixture fiber, 40% by weight of para-aramid fibrid as a binder, and 30% by weight of poval (PVA) which is a wet heat fusion resin.

  Anhydrous aluminum silicate as inorganic mixture particles was mixed in the sheath of the semi-aromatic polyamide fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the semi-aromatic polyamide fiber.

  In the separator of Example 8, 50% by weight of semi-aromatic polyamide fiber was used as a mixture fiber, 20% by weight of para-aramid fibrid was used as a binder, and 30% by weight of unstretched PET binder fiber was used.

  Silicon carbide particles as an inorganic mixture were mixed in the sheath portion of the unstretched PET binder fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the PET binder fiber.

  In the separator of Example 9, 30% by weight of polyketone fiber which is a synthetic fiber as a mixture fiber, 40% by weight of sisal pulp which is a natural cellulose fiber, and 30% of poval (PVA) which is a wet heat fusion resin as a binder. %Using.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath of the polyketone fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the polyketone fiber.

  In the separator of Example 10, 30% by weight of polyketone fiber was used as a mixture fiber, 40% by weight of para-aramid fibrid was used as a binder, and 30% by weight of poval (PVA) which is a wet heat fusion resin.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath of the polyketone fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the polyketone fiber.

  In the separator of Example 11, 30% by weight of acrylic fiber, which is a synthetic fiber, 40% by weight of sisal pulp, which is a natural cellulose fiber, and 30% of poval (PVA), which is a wet heat fusion resin, as a binder. %Using.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath of the acrylic fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the acrylic fiber.

  In the separator of Example 12, 30% by weight of acrylic fiber was used as the mixture fiber, 50% by weight of fibrillated acrylic fiber was used as the binder, and 20% by weight of Poval (PVA), which is a wet heat fusion resin.

  In the sheath part of the acrylic fiber, zirconia particles as an inorganic mixture were mixed so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the mixed fiber.

  In the separator of Example 13, 30% by weight of para-aramid fiber was used as a mixture fiber, 40% by weight of para-aramid fiber as a binder, and 30% by weight of poval (PVA) which is a wet heat fusion resin.

  Anhydrous silicon silicate particles as an inorganic mixture were mixed in the sheath of the para-aramid fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the para-aramid fiber.

  In the separator of Example 14, 35% by weight of semi-aromatic polyamide fiber was used as the mixture fiber, 35% by weight of unstretched PET binder fiber and 30% by weight of para-aramid fibrid were used as the binder.

  In the sheath portion of the semi-aromatic polyamide fiber, titanium oxide as an inorganic mixture particle is mixed so that the weight of the mixture in the separator is 1.75% by weight and 5% by weight of the semi-aromatic polyamide fiber. Anhydrous silicon silicate particles as inorganic mixture particles were mixed in the sheath of the brid so that the weight of the mixture in the separator was 3% by weight and 10% by weight of para-aramid fibrids.

  In the separator of Example 15, 30% by weight of polyamideimide fiber, which is a synthetic fiber, 40% by weight of sisal pulp, which is a natural cellulose fiber, and 30% of poval (PVA), which is a wet heat fusion resin, as a binder. % By weight was used.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath portion of the polyamideimide fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the polyamideimide fiber.

  In the separator of Example 16, 30% by weight of viscose rayon fiber, which is a cellulose fiber, 60% by weight of sisal pulp, which is a natural cellulose fiber, and 10% by weight of polyacrylamide as a binder were used as a mixture fiber.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath of the viscose rayon fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the viscose rayon fiber.

  In the separator of Example 17, 30% by weight of viscose rayon fiber which is a cellulose fiber as a mixture fiber, 35% by weight of Manila hemp pulp which is a natural cellulose fiber, 15% by weight of esparto pulp, and poval (PVA) as a binder. 30% by weight was used.

  Alumina particles as an inorganic mixture were mixed in the sheath of the viscose rayon fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the viscose rayon fiber.

  In the separator of Example 18, 40% by weight of viscose rayon fiber, which is cellulose fiber, 30% by weight of solvent-spun rayon fiber, and 30% by weight of Poval (PVA) as a binder were used as the mixture fiber.

  In the sheath part of the viscose rayon fiber, aluminum nitride particles as an inorganic mixture are mixed so that the weight of the mixture in the separator is 1% by weight and 2.5% by weight of the viscose rayon fiber, and the sheath of the solvent-spun rayon fiber In the part, titanium oxide particles as an inorganic mixture were mixed so that the weight of the mixture in the separator was 0.5% by weight and 1.6% by weight of the solvent-spun rayon fiber.

  In the separator of Example 19, 30% by weight of solvent-spun rayon fiber, which is cellulose fiber, 60% by weight of sisal pulp, which is natural cellulose fiber, and 10% by weight of polyacrylamide as a binder were used as the mixture fiber.

  Boron nitride particles as an inorganic mixture were mixed in the sheath of the solvent-spun rayon fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the solvent-spun rayon fiber.

  The separator of Example 20 is composed of 20% by weight of semi-aromatic polyamide fiber as a mixture fiber, 60% by weight of sisal pulp as a natural cellulose fiber, 10% by weight of para-aramid fibrid as a binder, and wet heat fusion resin. 10% by weight of some poval (PVA) was used.

  Anhydrous aluminum silicate as inorganic mixture particles is mixed in the sheath of the semi-aromatic polyamide fiber so that the weight of the mixture in the separator is 1.5% by weight and 7.5% by weight of the semi-aromatic polyamide fiber, The para-aramid fibrid was mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator was 1.5% by weight and 10% by weight of the para-aramid fibrid.

  In the separator of Example 21, 20% by weight of polyketone fiber as a mixture fiber, 45% by weight of sisal pulp as natural cellulose fiber, 15% by weight of para-aramid fibrid as a binder, Poval (wet heat fusion resin) 20% by weight of PVA) was used.

  The sheath of the polyketone fiber is mixed with anhydrous aluminum silicate as inorganic mixture particles so that the weight of the mixture in the separator is 2% by weight and 10% by weight of the polyketone fiber, and the para-aramid fibrid is coated with anhydrous aluminum silicate. The mixture was mixed so that the weight of the mixture was 1.5% by weight and 10% by weight of para-aramid fibrids.

  For the separator of Example 22, 30% by weight of acetate fiber as a mixed cellulose fiber, 50% by weight of sisal pulp as natural cellulose fiber, and 20% by weight of poval (PVA) which is a wet heat fusion resin as a binder It was.

  Carbon black particles were mixed in the sheath portion of the acetate fiber so that the weight of the mixture in the separator was 1.5% by weight and 5% by weight of the acetate fiber.

  In the separator of Example 23, 70% by weight of para-aramid fiber was used as the mixture fiber, and 30% by weight of para-aramid fibrid was used as the binder.

  Para-aramid fibrid was mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator was 3% by weight and 10% by weight of para-aramid fibrid.

  In the separator of Example 24, 70% by weight of para-aramid fiber was used as the mixture fiber, and 30% by weight of para-aramid fibrid was used as the binder.

  The para-aramid fibrid was mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator was 18% by weight and 60% by weight of the para-aramid fibrid.

  Next, the following eight types of separators not mixed with inorganic particles were prepared as conventional examples.

Conventional Example 1

  As the separator of Conventional Example 1, sisal pulp was used as natural cellulose fiber.

Conventional example 2

  As the separator of Conventional Example 2, 70% by weight of vinylon fiber and 30% by weight of Poval (PVA) which is a wet heat fusion resin as a binder were used.

Conventional example 3

  As the separator of Conventional Example 3, 40% by weight of PET fiber as synthetic fiber and 60% by weight of unstretched PET binder fiber as binder were used.

Conventional example 4

  As the separator of Conventional Example 4, 40% by weight of PEN fiber and 60% by weight of unstretched PEN binder fiber as a binder were used.

Conventional Example 5

  As the separator of Conventional Example 5, 70% by weight of polyketone fibers and 30% by weight of unstretched PEN binder fibers were used as binders.

Conventional Example 6

  As separator of Conventional Example 6, 40% by weight of semi-aromatic polyamide fiber as synthetic fiber, 30% by weight of PET fiber, 5% by weight of sisal hemp as natural cellulose fiber, and 25% by weight of unstretched PEN binder fiber as binder Using.

Conventional Example 7

  As a separator of Conventional Example 7, 30% by weight of acrylic fiber as synthetic fiber, 40% by weight of sisal pulp as natural cellulose fiber, and 30% by weight of Poval (PVA) which is a wet heat fusion resin as a binder were used.

Conventional Example 8

  As the separator of Conventional Example 8, 70% by weight of para-aramid fiber was used as a synthetic fiber, and 30% by weight of para-aramid fibrid was used as a binder.

  Next, the following 11 separators were prepared as comparative examples.

Comparative Example 1

  In the separator of Comparative Example 1, 25% by weight of PET fiber was used as a synthetic fiber. As the binder, 75% by weight of unstretched PET binder fiber was used.

  To the PET fiber, anhydrous aluminum silicate was mixed so that the weight of the mixture in the separator was 1.2% by weight and 4.8% by weight of the PET fiber.

Comparative Example 2

  In the separator of Comparative Example 2, 40% by weight of PET fiber was used as a synthetic fiber. As the binder, 60% by weight of unstretched PET binder fiber was used.

  The PET binder fiber was mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator was 1.4% by weight and 2.4% by weight of the PET binder fiber.

Comparative Example 3

  In the separator of Comparative Example 3, 50% by weight of PET fiber was used as a synthetic fiber. As the binder, 50% by weight of unstretched PET binder fiber was used.

  The PET fiber was mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator was 1.3% by weight and 2.5% by weight of the PET fiber.

Comparative Example 4

  In the separator of Comparative Example 4, 20% by weight of PET fiber was used as a synthetic fiber. As the binder, 50% by weight of unstretched PET binder fiber and 30% by weight of poval (PVA) which is a wet heat fusion resin were used.

  The PET fiber is mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator is 0.4% by weight and 1.8% by weight of the PET fiber. The PET binder fiber is silicon nitride with the weight of the mixture in the separator being 0%. It mixed so that it might become 1.8 weight% of PET binder fiber in 9 weight%.

Comparative Example 5

  In the separator of Comparative Example 5, as in Example 7, 30% by weight of semi-aromatic polyamide fiber as a mixture fiber, 40% by weight of para-aramid fibrid as a binder, and poval (PVA) which is a wet heat fusion resin. 30% by weight was used.

  Anhydrous aluminum silicate as inorganic mixture particles was mixed in the sheath portion of the semi-aromatic polyamide fiber so that the weight of the mixture in the separator was 1.4% by weight and 4.5% by weight of the semi-aromatic polyamide fiber.

Comparative Example 6

  As in Example 9, the separator of Comparative Example 6 is 30% by weight of polyketone fiber, which is a synthetic fiber, 40% by weight of sisal pulp, which is a natural cellulose fiber, and a wet heat fusion resin as a binder. 30% by weight of poval (PVA) was used.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath of the polyketone fiber so that the weight of the mixture in the separator was 1.4% by weight and 4.5% by weight of the polyketone fiber.

Comparative Example 7

  As in Example 11, the separator of Comparative Example 7 is 30% by weight of acrylic fiber, which is a synthetic fiber, 40% by weight of sisal pulp, which is a natural cellulose fiber, and a wet heat fusion resin as a binder. 30% by weight of poval (PVA) was used.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath of the acrylic fiber so that the weight of the mixture in the separator was 1.4% by weight and 4.5% by weight of the acrylic fiber.

Comparative Example 8

  In the separator of Comparative Example 8, as in Example 16, 30% by weight of viscose rayon fiber, which is cellulose fiber, 60% by weight of sisal pulp, which is natural cellulose fiber, and 10% of polyacrylamide as binder. % By weight was used.

  Anhydrous aluminum silicate particles as an inorganic mixture were mixed in the sheath of the viscose rayon fiber so that the weight of the mixture in the separator was 1.4% by weight and 4.5% by weight of the viscose rayon fiber.

Comparative Example 9

  For the separator of Comparative Example 9, 30% by weight of acetate fiber as a mixed cellulose fiber, 40% by weight of sisal pulp as natural cellulose fiber, and 30% by weight of poval (PVA) which is a wet heat fusion resin as a binder It was.

  Carbon black particles were mixed in the sheath portion of the acetate fiber so that the weight of the mixture in the separator was 1.4% by weight and 4.5% by weight of the acetate fiber.

Comparative Example 10

  In the separator of Comparative Example 10, as in Example 23, 70% by weight of para-aramid fiber was used as a mixture fiber and 30% by weight of para-aramid fibrid was used as a binder.

  Para-aramid fibrid was mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator was 2.7% by weight and 9% by weight of para-aramid fibrid.

Comparative Example 11

  As in Example 24, the separator of Comparative Example 11 used 70% by weight of para-aramid fiber as the mixture fiber and 30% by weight of para-aramid fibrid as the binder.

  The para-aramid fibrid was mixed with anhydrous aluminum silicate so that the weight of the mixture in the separator was 16.3% by weight and 61% by weight of the para-aramid fibrid.

  In addition, the solid electrolytic capacitor using the cellulose fiber of each of the above examples is carbonized by heat treatment.

  Each separator was made into a sheet by a circular paper machine, and the mixed fibers used for the sheet were made by mixing inorganic particles with the following fibers. The polyketone fiber used was Cyvalon fiber manufactured by Asahi Kasei Fibers, the semi-aromatic polyamide used was Kuraray Co., Ltd. sold under the trade name “A590”, and the acrylic fiber used was a general-purpose homoacrylic fiber or fibrillated acrylic fiber.

  PET fiber, PET binder fiber, PEN fiber, and PEN binder fiber were fibers manufactured by Teijin Fibers Limited. The polyamideimide fiber used was a fiber manufactured by Kelmer.

  Semi-finished products were used for vinylon fiber and PVA. Paraaramid fibers and paraaramid fibrites used were Twaron made by Teijin Techno Products Co., Ltd. In particular, fibrites used para-aramid fibrites by the jet span method.

  The separator evaluation method is as follows.

  First, the thickness, density, and tensile strength of the separator were measured by the methods specified in JIS C2301 (1990 edition, electrolytic capacitor paper).

  The liquid absorption was measured by replacing water with i-propanol according to the water absorption test method defined in JIS C2301 (1990 edition, electrolytic capacitor paper). The elongation was measured by a method specified in JIS C2111 (1990 edition, electrical insulating paper test method).

Table 17 shows the configuration and evaluation results of each example. A part of this list is extracted in the description of the embodiment.

  Table 17 shows the content (% by mass), the thickness (μm), the density (g / cm 3), the tensile strength (N / 15 mm) of the fiber element in each sample for the surface mount type solid electrolytic capacitor separator. Elongation (%), liquid absorbency (i-propanol, mm / 10 min), short-circuit failure rate after element heating (only when heating and carbonizing separator substrate), after conducting polymer polymerization as solid electrolytic capacitor 2 shows the short-circuit defect rate and initial characteristics (capacitance, ESR), ESR after the reflow test, appearance abnormality, and characteristics after the reliability test (capacitance, ESR). The reflow test was performed twice under the condition of being exposed to a maximum temperature of 270 ° C.

  Since no oxide film was formed on the end surface of the aluminum foil of the obtained capacitor element, chemical conversion treatment was performed in a 1.0 mass% ammonium adipate aqueous solution at a temperature of 60 ° C. In Examples 10 to 15, Conventional Example 1, and Comparative Examples 6 to 10 after the chemical conversion treatment, the element was heated at 260 ° C. for 1 hour to carbonize the separator.

  Next, after immersing 3,4 ethylenedioxythiophene and iron (III) p-toluenesulfonate in a polymerization solution (monomer: oxidant = 1: 1.5, molar ratio) dissolved in i-propanol, A solid electrolyte layer of polyethylene dioxythiophene (PEDT) was formed by chemical polymerization by holding at 100 ° C. for 60 minutes.

  A capacitor element having a solid electrolyte layer obtained by repeating this solid electrolyte layer forming method twice is dried and heated, and then placed in a case. The opening is sealed with a sealing agent, and the surface is mounted on the sealing agent side. A seat plate was attached, and 1000 surface mount solid electrolytic capacitors each having a rated voltage of 4 V and a rated capacitance of 100 μF were produced.

[Capacitor evaluation]
Each sample capacitor was evaluated by a short circuit test.
First, regarding the short-circuit defect rate after heating the element, the element was heated at 270 ° C. for 60 minutes to carbonize the separator, and then the continuity due to a short between both electrodes was confirmed by a tester. The short defect rate was inspected for 1000 elements, and the ratio of the short elements to the total number of elements was defined as the short defect rate.

  Next, the short-circuit defect rate of the element after impregnation with the conductive polymer was confirmed by a tester for continuity due to a short between both electrodes after a solid electrolyte was formed on the capacitor element. The short defect rate was inspected for 1000 elements, and the ratio of the short elements to the total number of elements was defined as the short defect rate.

  The ESR of the capacitor was measured before and after the reflow test with an LCR meter under the conditions of a temperature of 20 ° C. and a frequency of 100 kHz. The capacitance was measured with an LCR meter at 20 ° C. and a frequency of 120 Hz.

  In the reliability test, characteristics after 3000 hours were measured for capacitance and ESR under the conditions of a temperature of 105 ° C. and a relative humidity of 65%.

  As described above, in each of the above Examples (for example, Examples 1 to 7, 9 to 21), as a result of mixing the mixture particles in the sheath part of any core-sheath structure fiber by 1.5% by weight or more based on the separator weight, Although both the change in the area and thickness of the separator are within the range where the error is small, in Comparative Examples 1 to 9 which is 1.4% by weight or less, a change of about 5% or more occurs. If it is less than 5% by weight, the expected effect is not obtained. In the conventional example, the change is further remarkable.

  The fiber containing 1.5% by weight or more of the inorganic particles in the sheath part is better than the comparative example and the conventional separator by blending at least 30% by weight of the separator weight. The characteristics after the reflow test can be achieved, and the low ESR characteristics are also achieved.

  Further, as a binder, for example, para-aramid fibrids obtained by a jet span method can be mixed without losing the binder effect from 10 to 60% by weight. This is because if the mixing amount is 10% by weight or less, a sufficient moisture-proof effect cannot be obtained, and if it exceeds 60% by weight, a sufficient binder effect cannot be obtained.

  In addition to mixing inorganic particles into the fibers constituting the separator, even if inorganic particles (for example, anhydrous aluminum silicate) are contained in the range of 10% by weight to 60% by weight with respect to the weight of the fibrid, the comparative example and the conventional ones are similarly used. Compared with the example separator, good post-reflow characteristics can be achieved and low ESR characteristics are also achieved.

  As described above in detail, the separator used in the electrolytic capacitor according to the embodiment and the example of the present invention has excellent reflow resistance, excellent ESR characteristics, long life, and high reliability. It can be used as an electrolytic capacitor.

Claims (15)

A separator capable of holding an electrolyte by interposing an anode foil and a cathode foil of a solid electrolytic capacitor,
A separator comprising at least fibers mixed with inorganic particles. The separator according to claim 1, wherein the fiber is a synthetic resin fiber. The separator according to claim 2, wherein the synthetic resin fiber is one or more synthetic fibers of acrylic, polyethylene terephthalate, polyethylene naphthalate, semi-aromatic polyamide, para-aramid, polyamide-imide, and polyketone. The separator according to any one of claims 1 to 3, wherein the fibers are cellulose fibers such as rayon fibers. The separator according to claim 4, wherein the rayon fiber contains at least one of solvent-spun rayon, viscose rayon, and cupra rayon. The separator according to any one of claims 1 to 3, wherein the fibers are cellulose derivative fibers such as semi-synthetic fibers. The separator according to claim 6, wherein the semi-synthetic fiber is an acetate fiber. The separator according to any one of claims 1 to 7, wherein the fiber is a core-sheath structure fiber, and at least 30% by weight or more of the separator weight is mixed with the fiber containing the inorganic particles in the sheath part. . A separator capable of holding an electrolyte by interposing an anode foil and a cathode foil of a solid electrolytic capacitor,
A separator comprising a fibrid mixed with at least inorganic particles. The separator according to claim 9, wherein the fibrid is para-aramid having a binder effect. The separator according to claim 9 or 10, wherein the inorganic particles are contained in a range of 10 wt% to 60 wt% with respect to the fibrid weight. The separator according to any one of claims 1 to 11, wherein the average particle size of the inorganic particles is 2 µm or less. The separator according to any one of claims 1 to 12, wherein the inorganic particles are contained in an amount of 1.5% by weight or more based on the weight of the separator. An electrolytic capacitor using the separator according to any one of claims 1 to 13. While using the separator according to any one of claims 1 to 13,
Furthermore, the electrolytic capacitor characterized by having at least one of polypyrrole, polythiophene, polyaniline or derivatives thereof as a conductive polymer.