Solid electrolytic capacitors with stable electrical characteristics at high temperatures

Abstract

A solid electrolytic capacitor is provided that includes a casing material encapsulating a capacitor element. The casing material is formed from a curable resinous matrix having a coefficient of thermal expansion of about 42 ppm / °C or less at temperatures above the glass transition temperature of the resinous matrix. Furthermore, the capacitor exhibits an initial equivalent series resistance of about 200 milliohms or less, as determined at an operating frequency of 100 kHz and a temperature of 23°C, and the ratio of the equivalent series resistance of the capacitor after 560 hours of exposure to a temperature of 125°C to the initial equivalent series resistance of the capacitor is about 2.0 or less. [Selected Figure] Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 687,961, filed on 21 June 2018 (which is incorporated herein by reference in its entirety). [Background technology]

[0002] Electrolytic capacitors (e.g., tantalum capacitors) are increasingly used in circuit design due to their volumetric efficiency, reliability, and process compatibility. For example, one type of capacitor developed is the solid-state electrolytic capacitor, which comprises a tantalum anode, a dielectric layer, and a conductive polymer solid electrolyte. To help protect the capacitor from the external environment and provide it with good mechanical stability, the capacitor element is also enclosed in a casing material (e.g., epoxy resin) such that the anode termination and part of the cathode termination remain exposed for surface mounting. Unfortunately, the high temperatures often used during capacitor manufacturing (e.g., reflow) can cause residual moisture to vaporize as water vapor, which is expelled from the case with considerable force, potentially forming microcracks within the casing material. These microcracks can also lead to delamination of the casing material from the capacitor element and rapid degradation of electrical properties, especially when the capacitor is exposed to high temperatures. Therefore, there is a need for improved solid-state electrolytic capacitors that exhibit relatively stable electrical properties at high temperatures. [Overview of the project]

[0003] According to one embodiment of the present invention, there is provided a capacitor element including a sintered porous anode body, a dielectric disposed on the anode body, and a solid electrolyte disposed on the dielectric; an anode lead extending from the surface of the capacitor element; an anode terminal electrically connected to the anode lead; a cathode terminal electrically connected to the solid electrolyte; and a casing material encapsulating the capacitor element and the anode lead. The casing material is formed from a curable resinous matrix having a coefficient of thermal expansion of about 42 ppm / °C or less at a temperature higher than the glass transition temperature of the resinous matrix. Further, this capacitor exhibits an initial equivalent series resistance of about 200 milliohms or less when measured at an operating frequency of 100 kHz and a temperature of 23°C, and the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 560 hours to the initial equivalent series resistance of the capacitor is about 2.0 or less.

[0004] Other features and embodiments of the present invention are shown in more detail below. A complete and practicable disclosure of the present invention, including the best mode of the present invention for those skilled in the art, is shown in more detail in the remainder of this specification with reference to the accompanying drawings.

Brief Description of the Drawings

[0005] [Figure 1] FIG. 1 is a schematic view of one embodiment of a solid electrolytic capacitor that can be formed in accordance with the present invention.

Mode for Carrying Out the Invention

[0006] The repeated use of reference numerals in this specification and the drawings is intended to represent the same or similar features or components of the present invention. This discussion is only an explanation of representative embodiments and is not intended to limit the broader form of the present invention, which will be understood by those skilled in the art to be embodied in representative configurations.

[0007] Generally, the present invention relates to a solid electrolytic capacitor comprising a capacitor element including a porous anode body, a dielectric disposed on the anode body, and a solid electrolyte disposed on the dielectric. The anode lead extends from the anode body and is in electrical contact with the anode end. The cathode end is in electrical contact with the solid electrolyte. Furthermore, the casing material encloses the capacitor element and the anode lead, leaving at least a portion of the anode end and cathode end exposed for external contact. The casing material is formed from a curable resinous matrix having a relatively low coefficient of thermal expansion. For example, the resinous matrix typically has a coefficient of thermal expansion of about 42 ppm / °C or less at temperatures higher than the glass transition temperature of the resinous matrix, about 40 ppm / °C or less in some embodiments, and about 20 ppm / °C to about 38 ppm / °C in some embodiments. Furthermore, the resinous matrix also typically has a coefficient of thermal expansion of about 11 ppm / °C or less at temperatures below the glass transition temperature of the resinous matrix, about 10 ppm / °C or less in some embodiments, and about 1 to about 9 ppm / °C in some embodiments. The glass transition temperature of the resinous matrix may be in the range of, for example, about 50°C to about 180°C, about 60°C to about 160°C in some embodiments, and about 80°C to about 150°C in some embodiments. The coefficient of thermal expansion and the glass transition temperature can be determined using techniques known in the art, such as thermomechanical analysis (TMA) in accordance with ISO-11359-2:1999. Although not intended to be limited by theory, it is thought that using a resinous matrix with such a low coefficient of thermal expansion can result in a casing material that is less prone to delamination from the capacitor element when exposed to the high temperatures often experienced during capacitor manufacturing (e.g., reflow).

[0008] By selectively controlling certain properties of the casing material and the interface coating, the resulting capacitor can be resistant to delamination during manufacture and thus exhibit excellent electrical characteristics. For example, the capacitor can exhibit a relatively low equivalent series resistance (ESR) of about 200 milliohms when measured at an operating frequency of 100 kHz and a temperature of 23 °C, less than about 150 milliohms in some embodiments, about 0.1 to about 125 milliohms in some embodiments, and about 1 to about 100 milliohms in some embodiments. The capacitor can also exhibit a dry capacitance of about 30 nanofarads per square centimeter (nF / cm 2 ) or more, about 100 nF / cm or more in some embodiments, about 200 to about 3,000 nF / cm in some embodiments, and about 400 to about 2,000 nF / cm in some embodiments 2 when measured at a frequency of 120 Hz and a temperature of 23 °C. 2 2

[0009] In particular, such electrical properties (e.g., ESR and / or capacitance) can remain stable even at high temperatures. For example, the capacitor can exhibit ESR and / or capacitance values ​​within the above ranges even after exposure to temperatures of approximately 80°C or higher, approximately 100°C to approximately 150°C in some embodiments, approximately 105°C to approximately 130°C (e.g., 105°C or 125°C) for a considerable period of time, such as approximately 700 hours to approximately 2,000 hours in some embodiments, and approximately 900 hours to approximately 1,500 hours in some embodiments (e.g., 240, 420, 560, 750, 1,000, or 1,250 hours). In one embodiment, for example, the ratio of the ESR and / or capacitance value of a capacitor after exposure to a high temperature (e.g., 125°C) for 560, 750, 1,000, and / or 1,250 hours to the initial ESR and / or capacitance value of the capacitor (e.g., at 23°C) is about 2.0 or less, about 1.5 or less in some embodiments, and 1.0 to about 1.3 in some embodiments. The capacitor may also exhibit ESR and / or capacitance values ​​within the above range after exposure to a high relative humidity level at either room temperature or a high temperature (e.g., 85°C or 125°C). Such a high relative humidity level may be, for example, about 40% or more, about 45% or more in some embodiments, about 50% or more in some embodiments, and about 70% or more in some embodiments (e.g., about 85% to 100%) for the considerable time described above. The relative humidity can be determined, for example, according to ASTM-E337-02, Method A (2007). In one embodiment, for example, the ratio of the ESR and / or capacitance value of a capacitor after exposure to high humidity (e.g., 85%) for 240 hours to the initial ESR and / or capacitance value of the capacitor is about 2.0 or less, about 1.5 or less in some embodiments, and 1.0 to about 1.3 in some embodiments.

[0010] Furthermore, this capacitor can also exhibit a DCL of only about 50 microamperes (μA) or less, about 40 μA or less in some embodiments, about 20 μA or less in some embodiments, and about 0.1 to about 10 μA in some embodiments. Moreover, this capacitor can exhibit a high percentage of its wet capacitance, which allows it to have only small capacitance loss and / or variation in the presence of atmospheric humidity. This performance characteristic is expressed by the formula: Recovery rate = (Dry capacitance / Wet capacitance) × 100 It is quantified by the "capacitance recovery rate" determined by [a specific method / function].

[0011] This capacitor can exhibit a capacitance recovery rate of approximately 50% or more, approximately 60% or more in some embodiments, approximately 70% or more in some embodiments, and approximately 80% to 100% in some embodiments.

[0012] Here, various embodiments of the capacitor are described in more detail. I. Capacitor elements: A. Anode body: A capacitor element includes an anode containing a dielectric formed on a sintered porous body. The porous anode body can be formed from a powder containing valve metal (i.e., a metal that can be oxidized) or valve metal-based compounds, such as tantalum, niobium, aluminum, hafnium, titanium, their alloys, their oxides, or their nitrides. The powder is usually formed from a reduction process in which a tantalum salt (e.g., potassium fluorotantalate (K2TaF7), sodium fluorotantalate (Na2TaF7), tantalum pentachloride (TaCl5), etc.) is reacted with a reducing agent. The reducing agent can be provided in the form of a liquid, a gas (e.g., hydrogen), or a solid, such as a metal (e.g., sodium), a metal alloy, or a metal salt. For example, in one embodiment, a tantalum salt (e.g., TaCl5) can be heated to a temperature of about 900°C to about 2,000°C, in some embodiments about 1,000°C to about 1,800°C, and in some embodiments about 1,100°C to about 1,600°C to form a vapor, which can then be reduced in the presence of a gaseous reducing agent (e.g., hydrogen). Further details of such a reduction reaction are described in WO-2014 / 199480 by Maeshima et al. After reduction, the product can be cooled, pulverized, and washed to form a powder.

[0013] The specific charge of the powder typically varies from about 2,000 to about 600,000 microfarads / volt / gram (μF·V / g) depending on the desired application. For example, in some embodiments, high-charge powders with specific charges of about 100,000 to about 550,000 μF·V / g, in some embodiments, about 120,000 to about 500,000 μF·V / g, and in some embodiments, about 150,000 to about 400,000 μF·V / g can be used. In other embodiments, low-charge powders with specific charges of about 2,000 to about 100,000 μF·V / g, in some embodiments, about 5,000 to about 80,000 μF·V / g, and in some embodiments, about 10,000 to about 70,000 μF·V / g can be used. As is well known in this technology, the charge-to-capacitance ratio can be determined by multiplying the capacitance by the anodizing voltage used and then dividing this product by the weight of the anodized electrode.

[0014] The powder may be a free-flowing fine powder containing primary particles. The primary particles of the powder generally have a median diameter (D50) of about 5 to about 500 nanometers, about 10 to about 400 nanometers in some embodiments, and about 20 to about 250 nanometers in some embodiments, and are determined using, for example, a laser particle size distribution analyzer (e.g., LS-230) from Beckman Coulter Corporation, after the particles have been subjected to ultrasonic vibration for 70 seconds. The primary particles usually have a three-dimensional particle shape (e.g., spherical or angular). Such particles usually have a relatively low "aspect ratio," i.e., the average diameter or width of the particle divided by the average thickness (D / T). For example, the aspect ratio of the particles may be about 4 or less, about 3 or less in some embodiments, and about 1 to about 2 in some embodiments. In addition to the primary particles, the powder may contain other types of particles, such as secondary particles formed by the aggregation (or coagulation) of the primary particles. Such secondary particles may have a median diameter (D50) of about 1 to about 500 micrometers, and in some embodiments, about 10 to about 250 micrometers.

[0015] Particle aggregation can be achieved by heating the particles and / or by using a binder. For example, aggregation can be achieved at temperatures of about 0°C to about 40°C, about 5°C to about 35°C in some embodiments, and about 15°C to about 30°C in some embodiments. Suitable binders include, for example, poly(vinyl butyral); poly(vinyl acetate); poly(vinyl alcohol); poly(vinylpyrrolidone); cellulose polymers, such as carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, and methylhydroxyethylcellulose; atactic polypropylene, polyethylene; polyethylene glycol (e.g., Carbowax from Dow Chemical Co.); polystyrene, poly(butadiene / styrene); polyamides, polyimides, and polyacrylamides, high molecular weight polyethers; copolymers of ethylene oxide and propylene oxide; fluoropolymers, such as polytetrafluoroethylene, polyvinylidene fluoride, and fluoroolefin copolymers; acrylic polymers, such as sodium polyacrylate, poly(lower alkyl acrylate), poly(lower alkyl methacrylate), and copolymers of lower alkyl acrylate and methacrylate; and fatty acids and waxes, such as stearic acid and other soap fatty acids, vegetable waxes, microwaxes (purified paraffin), etc.

[0016] The resulting powder can be compressed to form pellets using any conventional powder press equipment. For example, a press molding machine, which is a single-station compression press including a die and one or more punches, can be used. Alternatively, an anvil-type compression press molding machine using only a die and a single downward punch can be used. Single-station compression press molding machines are available in several basic types, such as cam presses, toggle / knuckle presses, and eccentric / crank presses, with various capabilities such as single-action, double-action, floating die, movable platen, opposing ram, screw, impact, hot press, stamping, or sizing. The powder can be compressed around an anode lead, which may be in the form of a wire, sheet, etc. The lead can be extended longitudinally from the anode body and can be formed from any conductive material such as tantalum, niobium, aluminum, hafnium, titanium, etc., and their conductive oxides and / or nitrides. The connection of the lead can also be achieved using other known techniques, for example, by welding the lead to the anode body or by embedding it inside the anode body during formation (e.g., before compression and / or sintering).

[0017] The binder can be removed after pressing by heating the pellets under vacuum at a constant temperature (e.g., about 150°C to about 500°C) for several minutes. Alternatively, the binder can be removed by contacting the pellets with an aqueous solution, as described in U.S. Patent 6,197,252 by Bishop et al. The pellets are then sintered to form a porous, integral component. The pellets are sintered for about 5 to 100 minutes, and in some embodiments for about 8 to 15 minutes, at a temperature typically about 700°C to about 1800°C, about 800°C to about 1700°C in some embodiments, and about 900°C to about 1400°C in some embodiments. This can be done in one or more steps. If desired, sintering can be carried out in an atmosphere that restricts the movement of oxygen atoms to the anode. For example, sintering can be carried out in a reducing atmosphere such as under vacuum, under an inert gas, or under hydrogen. The reducing atmosphere may be at a pressure of approximately 10 Torr to approximately 2000 Torr, approximately 100 Torr to approximately 1000 Torr in some embodiments, and approximately 100 Torr to approximately 930 Torr in some embodiments. A mixture of hydrogen and other gases (e.g., argon or nitrogen) may also be used.

[0018] B. Dielectrics: The anode is also coated with a dielectric. The dielectric can be formed by anodizing the sintered anode so that a dielectric layer is formed on and / or within the anode. For example, a tantalum (Ta) anode can be anodized to tantalum pentoxide (Ta2O5). Typically, anodizing is carried out by first applying a solution to the anode, such as by immersing the anode in an electrolyte. Solvents such as water (e.g., deionized water) are commonly used. To increase ionic conductivity, compounds that can dissociate in the solvent to form ions can be used. Examples of such compounds include, for example, acids with respect to the electrolyte, as described below. For example, an acid (e.g., phosphoric acid) can constitute about 0.01% to about 5% by weight of the anodizing solution, about 0.05% to about 0.8% by weight in some embodiments, and about 0.1% to about 0.5% by weight in some embodiments. If desired, a blend of multiple acids can also be used.

[0019] A dielectric layer is formed by passing an electric current through an anodizing solution. The thickness of the dielectric layer is controlled by the value of the oxidation voltage. For example, the power supply can first be set to a constant current mode until the required voltage is reached. Then, the power supply can be switched to a constant potential mode to ensure that the desired dielectric thickness is formed over the entire surface of the anode. Of course, other known methods such as pulsed or step constant potential methods can also be used. The voltage used for anodizing is typically in the range of about 4 to about 250V, about 5 to about 200V in some embodiments, and about 10 to about 150V in some embodiments. During oxidation, the anodizing solution can be maintained at a rising temperature, for example, above about 30°C, about 40°C to about 200°C in some embodiments, and about 50°C to about 100°C in some embodiments. Anodizing can also be carried out below ambient temperature. The resulting dielectric layer can be formed on the surface of the anode and within its pores.

[0020] While not mandatory, in some embodiments, the dielectric layer may have a distinct thickness across the entire anode, having a first portion located on the outer surface of the anode and a second portion located on the inner surface of the anode. In such embodiments, the first portion is selectively formed to be thicker than the second portion. However, it should be understood that the thickness of the dielectric layer does not need to be uniform within a particular region. Some portions of the dielectric layer adjacent to the outer surface may be thinner than, for example, some portions of the layer on the inner surface, and vice versa. Nevertheless, the dielectric layer can be formed such that at least a portion of the layer on the outer surface is thicker than at least a portion on the inner surface. The actual difference in these thicknesses can vary depending on the specific application, but the ratio of the thickness of the first portion to the thickness of the second portion is typically about 1.2 to about 40, about 1.5 to about 25 in some embodiments, and about 2 to about 20 in some embodiments.

[0021] A multi-step method is commonly used to form dielectric layers with distinct thicknesses. In each step of this process, the sintered anode is anodized to form a dielectric layer (e.g., tantalum pentoxide). In the first step of anodizing, a relatively small conversion voltage, e.g., in the range of about 1 to 90 volts, about 2 to 50 volts in some embodiments, and about 5 to 20 volts in some embodiments, is usually used to ensure that the desired dielectric thickness with respect to the internal region is achieved. The sintered body can then be anodized in the second step of the process to increase the dielectric thickness to a desired level. This is generally achieved by anodizing in an electrolyte at a higher voltage than the voltage used in the first step, e.g., in the range of about 50 to 350 volts, about 60 to 300 volts in some embodiments, and about 70 to 200 volts in some embodiments. During the first and / or second stage, the electrolyte can be maintained at a temperature in the range of about 15°C to about 95°C, about 20°C to about 90°C in some embodiments, and about 25°C to about 85°C in some embodiments.

[0022] The electrolytes used in the first and second stages of the anodizing process may be the same or different. However, it is generally desirable to use different solutions to better facilitate obtaining a greater thickness in the outer portion of the dielectric layer. For example, in order to prevent a substantial amount of oxide film from forming on the inner surface of the anode, it may be desirable for the electrolyte used in the second stage to have a lower ionic conductivity than the electrolyte used in the first stage. In this regard, the electrolyte used in the first stage may contain acidic compounds such as nitric acid, sulfuric acid, phosphoric acid, polyphosphate, boric acid, boronic acid, etc. Such electrolytes may have a conductivity of about 0.1 to about 100 mS / cm, about 0.2 to about 20 mS / cm in some embodiments, and about 1 to about 10 mS / cm in some embodiments, as determined at a temperature of 25°C. The electrolyte used in the second stage usually contains a salt of a weak acid so that the hydronium ion concentration increases in the pores as a result of charge passage within the pores. Ion transport or ion diffusion occurs as needed to balance the charge, causing anions of weak acids to move into the pores. As a result, the concentration of the major conductive species (hydronium ions) decreases as equilibrium is formed between hydronium ions, acid anions, and non-dissociated acids, leading to the formation of non-conductive species. The decrease in the concentration of conductive species results in a relatively high voltage drop in the electrolyte, which hinders further anodizing inside, while a thicker oxide layer accumulates on the outside for high conversion voltages in a continuous high-conductivity region. Suitable weak salts include, for example, ammonium salts or alkali metal salts (e.g., sodium, potassium, etc.) such as boric acid, boronic acid, acetic acid, oxalic acid, lactic acid, and adipic acid. Particularly preferred salts include sodium tetraborate and ammonium pentaborate. Such electrolytes typically have a conductivity of about 0.1 to about 20 mS / cm, about 0.5 to about 10 mS / cm in some embodiments, and about 1 to about 5 mS / cm in some embodiments, measured at a temperature of 25°C.

[0023] If desired, each step of the anodizing process can be repeated once or multiple times to achieve the desired dielectric thickness. Furthermore, the anode may be rinsed or washed with another solvent (e.g., water) after the first and / or second steps to remove the electrolyte.

[0024] C. Solid electrolyte: A solid electrolyte is placed on a dielectric and generally functions as the cathode for a capacitor. Examples of solid electrolytes include conductive polymers (e.g., polypyrroles, polythiophenes, polyanilines, etc.) and materials known in the art, such as manganese dioxide. In one embodiment, for example, the solid electrolyte comprises one or more layers containing extrinsically conductive and / or intrinsically conductive polymer particles. One advantage of using such particles is that they eliminate ionic species (e.g., Fe) that can cause dielectric breakdown under high electric fields due to ion transfer, which are generated during conventional in-situ polymerization processes. 2+ or Fe 3+ The advantage is that the presence of () can be minimized. Thus, by applying the conductive polymer as pre-polymerized particles rather than by in-situ polymerization, the resulting capacitor can exhibit a relatively high "dielectric breakdown voltage". If desired, the solid electrolyte can be formed from one or more layers. When multiple layers are used, one or more layers can contain conductive polymer formed by in-situ polymerization. However, if it is desirable to achieve a very high dielectric breakdown voltage, it may be desirable to form the solid electrolyte mainly from the conductive particles described above and generally not include conductive polymer formed by in-situ polymerization. Regardless of the number of layers used, the resulting solid electrolyte typically has a total thickness of about 1 micrometer (μm) to about 200 μm, about 2 μm to about 50 μm in some embodiments, and about 5 μm to about 30 μm in some embodiments.

[0025] Thiophene polymers are particularly suitable for use in solid electrolytes. For example, in some embodiments, the following formula (I):

[0026] [Chemical Formula]

[0027] (wherein R7 is a linear or branched C1-C 18 alkyl group (e.g., methyl, ethyl, n- or isopropyl, n-, iso-, sec-, or tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-hexadecyl, n-octadecyl, etc.); C5-C 12 cycloalkyl group (e.g., cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, etc.); C6-C 14 aryl group (e.g., phenyl, naphthyl, etc.); C7-C 18 aralkyl group (e.g., benzyl, o-, m-, p-tolyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, 3,5-xylenyl, mesityl, etc.); q is an integer from 0 to 8, in some embodiments from 0 to 2, and in one embodiment 0) of the "exogenous" conductive thiophene polymer having repeating units can be used in solid electrolytes. In one particular embodiment, "q" is 0 and the polymer is poly(3,4-ethylenedioxythiophene). One commercially suitable example of a monomer suitable for forming such a polymer is 3,4-ethylenedioxythiophene available from Heraeus under the name Clevios® M.

[0028] Polymers of formula (I) are generally considered "extrinsically" conductive in that they typically require the presence of another counterion that is not covalently bonded to the polymer. The counterion may be a monomer or polymer anion that neutralizes the charge of the conductive polymer. Polymer anions may be anions such as polymer carboxylic acids (e.g., polyacrylic acid, polymethacrylic acid, polymaleic acid, etc.); polymer sulfonic acids (e.g., polystyrene sulfonic acid (PSS), polyvinyl sulfonic acid, etc.). The acids may also be copolymers such as copolymers of vinyl carboxylic acids and vinyl sulfonic acids with other polymerizable monomers such as acrylic acid esters and styrene. Furthermore, suitable monomer anions include, for example, C1-C 20 Alkanesulfonic acids (e.g., dodecanesulfonic acid); aliphatic perfluorosulfonic acids (e.g., trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid); aliphatic C1-C 20 Carboxylic acids (e.g., 2-ethylhexylcarboxylic acid); aliphatic perfluorocarboxylic acids (e.g., trifluoroacetic acid or perfluorooctanoic acid); depending on the case, C1-C 20 Examples of anions include aromatic sulfonic acids substituted with alkyl groups (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid); and cycloalkanesulfonic acids (e.g., camphorsulfonic acid, or tetrafluoroborate, hexafluorophosphate, perchlorate, hexafluoroantimonate, hexafluoroarcenate, or hexachloroantimonate). Particularly preferred counteranions are polymer anions such as polymer carboxylic acids or sulfonic acids (e.g., polystyrenesulfonic acid (PSS)). The molecular weight of such polymer anions is typically in the range of about 1,000 to about 2,000,000, and in some embodiments, about 2,000 to about 500,000.

[0029] Alternatively, a positively charged intrinsically conductive polymer can be used, which is located on the main chain and at least partially compensated for by anions covalently bonded to the polymer. For example, one example of a suitable intrinsically conductive thiophene polymer is given by equation (II):

[0030] [ka]

[0031] (In the formula, R is (CH2) a -O-(CH2) b -L(wherein L is a bond or HC([CH2] c H) is; a is 0 to 10, 0 to 6 in some embodiments, and 1 to 4 (e.g., 1) in some embodiments; b is 1 to 18, 1 to 10 in some embodiments, and 2 to 6 in some embodiments (e.g., 2, 3, 4, or 5); c is 0 to 10, 0 to 6 in some embodiments, and 1 to 4 (e.g., 1) in some embodiments; Z is SO3 - , C(O)O - BF4 - CF3SO3 - SbF6 - , N(SO2CF3)2 - C4H3O4 - ClO4 - Anions such as; X is a cation such as hydrogen, an alkali metal (e.g., lithium, sodium, rubidium, cesium, or potassium), or ammonium. It may have repeating units.

[0032] In one particular embodiment, Z in formula (II) is a sulfonate ion, and the intrinsic conductive polymer is given by the following formula (III):

[0033] [ka]

[0034] (In the formula, R and X are as defined above.) It includes repeating units. In formula (II) or (III), a is preferably 1 and b is preferably 3 or 4. Furthermore, X is preferably sodium or potassium.

[0035] If desired, the polymer may be a copolymer containing other types of repeating units. In such embodiments, the repeating units of formula (II) typically constitute about 50 mol% or more of the total amount of repeating units in the copolymer, about 75 mol% to about 99 mol% in some embodiments, and about 85 mol% to about 95 mol% in some embodiments. Of course, the polymer may also be a homopolymer in that it contains 100 mol% of the repeating units of formula (II). Specific examples of such homopolymers include poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxin-2-ylmethoxy)-1-butanesulfonic acid, salt) and poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxin-2-ylmethoxy)-1-propanesulfonic acid, salt).

[0036] Regardless of the specific properties of the polymer, the resulting conductive polymer particles typically have an average diameter (e.g., diameter) of about 1 to about 80 nanometers, about 2 to about 70 nanometers in some embodiments, and about 3 to about 60 nanometers in some embodiments. The particle diameter can be determined using known techniques such as ultracentrifugation and laser diffraction. Furthermore, the shape of the particles can be varied. For example, in one particular embodiment, the particles are spherical. However, it should be understood that other shapes such as plates, rods, disks, bars, tubes, and irregular shapes are also intended by the present invention.

[0037] While not strictly necessary, conductive polymer particles can be applied in the form of a dispersion. The concentration of the conductive polymer in the dispersion can be varied depending on the desired viscosity of the dispersion and the specific method by which the dispersion is applied to the capacitor element. However, typically the polymer constitutes about 0.1 to about 10% by weight of the dispersion, about 0.4 to 5% by weight in some embodiments, and about 0.5 to about 4% by weight in some embodiments. The dispersion may also contain one or more components to improve the overall properties of the resulting solid electrolyte. For example, a binder can be added to the dispersion to further enhance the adhesion of the polymer layer and also increase the stability of the particles within the dispersion. The binder may be organic in nature, such as polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate, polyacrylic acid ester, polyacrylamide, polymethacrylate, polymethacrylate, polyacrylonitrile, styrene / acrylic acid ester, vinyl acetate / acrylic acid ester and ethylene / vinyl acetate copolymer, polybutadiene, polyisoprene, polystyrene, polyether, polyester, polycarbonate, polyurethane, polyamide, polyimide, polysulfone, melamine formaldehyde resin, epoxide resin, silicone resin, or cellulose. Crosslinking agents may also be used to increase the adhesive ability of the binder. Examples of such crosslinking agents include melamine compounds, masked isocyanates, or crosslinkable polymers, such as polyurethane, polyacrylate, or polyolefin, and may include subsequent crosslinking. Dispersants may also be used to promote the ability of the layer to be applied to the anode.Suitable dispersants include solvents such as aliphatic alcohols (e.g., methanol, ethanol, i-propanol, and butanol), aliphatic ketones (e.g., acetone and methyl ethyl ketone), aliphatic carboxylic acid esters (e.g., ethyl acetate and butyl acetate), aromatic hydrocarbons (e.g., toluene and xylene), aliphatic hydrocarbons (e.g., hexane, heptane, and cyclohexane), chlorinated hydrocarbons (e.g., dichloromethane and dichloroethane), aliphatic nitriles (e.g., acetonitrile), aliphatic sulfoxides and sulfones (e.g., dimethyl sulfoxide and sulfolane), aliphatic carboxylic acid amides (e.g., methylacetamide, dimethylacetamide, and dimethylformamide), aliphatic and aromatic aliphatic ethers (e.g., diethyl ether and anisole), water, and mixtures of any of the above solvents. Water is a particularly suitable dispersant.

[0038] In addition to those mentioned above, other components can also be used in the dispersion. For example, conventional fillers having dimensions of about 10 nanometers to about 100 micrometers, about 50 nanometers to about 50 micrometers in some embodiments, and about 100 nanometers to about 30 micrometers in some embodiments can be used. Examples of such fillers include calcium carbonate, silicate, silica, calcium sulfate or barium, aluminum hydroxide, glass fibers or glass spheres, wood powder, cellulose powder, carbon black, conductive polymers, etc. Fillers can be introduced into the dispersion in powder form, but they can also be present in other forms, such as fibers.

[0039] Surface active substances such as ionic or nonionic surfactants can also be used in the dispersion. Furthermore, adhesives such as organic functional silanes or their hydrolysates, for example, 3-glycidoxypropyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, or octyltriethoxysilane can be used. The dispersion may also contain ether group-containing compounds (e.g., tetrahydrofuran), lactone group-containing compounds (e.g., γ-butyrolactone or γ-valerolactone), amide or lactam group-containing compounds (e.g., caprolactam, N-methylcaprolactam, N,N-dimethylacetamide, N-methylacetamide, N,N-dimethylformamide (DMF), N-methylformamide, N-methylformanilide, N-methylpyrrolidone (NMP), N-octylpyrrolidone, or pyrrolidone), sulfones, and The material may also contain additives that increase conductivity, such as sulfoxides (e.g., sulfolane (tetramethylene sulfone) or dimethyl sulfoxide (DMSO)), sugars or sugar derivatives (e.g., saccharose, glucose, fructose, or lactose), sugar alcohols (e.g., sorbitol or mannitol), furan derivatives (e.g., 2-furanic acid or 3-furanic acid), or alcohols (e.g., ethylene glycol, glycerol, di- or triethylene glycol).

[0040] The dispersion can be applied using various known techniques such as spin coating, impregnation, pouring, drop application, injection, spraying, doctor blade application, brush application, printing (e.g., inkjet, screen, or pad printing), or immersion. The viscosity of the dispersion is typically about 0.1 to about 100,000 mPas (100s). -1 (Measured by shear rate), in some embodiments it is about 1 to about 10,000 mPas, in some embodiments it is about 10 to about 1,500 mPas, and in some embodiments it is about 100 to about 1,000 mPas.

[0041] i.Inner layer: Solid electrolytes are generally formed from one or more "inner" conductive polymer layers. In this context, the term "inner" refers to one or more layers that are placed directly on the dielectric or via other layers (e.g., pre-coat layers). One or more inner layers can be used. For example, a solid electrolyte typically comprises 2 to 30 inner layers, 4 to 20 in some embodiments, and about 5 to 15 in some embodiments (e.g., 10 layers). One or more inner layers may contain, for example, intrinsically conductive and / or exogenously conductive polymer particles as described above. For example, such particles may constitute about 50% by weight or more, about 70% by weight or more in some embodiments, and about 90% by weight or more (e.g., about 100% by weight) of one or more inner layers. In another embodiment, one or more inner layers may contain in-situ polymerized conductive polymers. In such embodiments, the in-situ polymerized polymer may constitute about 50% by weight or more of one or more inner layers, about 70% by weight or more in some embodiments, and about 90% by weight or more (e.g., about 100% by weight) in some embodiments.

[0042] ii. Outer layer: The solid electrolyte may also include one or more optional "outer" conductive polymer layers, formed from different materials and positioned on top of one or more inner layers. For example, one or more outer layers may contain exogenous conductive polymer particles. In one particular embodiment, one or more outer layers are formed primarily from such exogenous conductive polymer particles, in such a way that the exogenous conductive polymer particles constitute about 50% by weight or more, about 70% by weight or more in some embodiments, and about 90% by weight or more (e.g., 100% by weight) in each outer layer. One or more outer layers may be used. For example, the solid electrolyte may contain 2 to 30, 4 to 20 in some embodiments, and about 5 to 15 outer layers, each of which may optionally be formed from a dispersion of exogenous conductive polymer particles.

[0043] D. External polymer coating: Furthermore, an external polymer coating can be placed on top of the solid electrolyte. The external polymer coating may include one or more layers formed from pre-polymerized conductive polymer particles as described above (e.g., a dispersion of exogenous conductive polymer particles). The external coating can further penetrate into the edge region of the capacitor body, increasing adhesion to the dielectric and providing a more mechanically robust component, thereby reducing the equivalent series resistance and leakage current. Generally, since the intention is to improve the coverage of the edges rather than impregnating the interior of the anode body, the particles used in the external coating are usually larger in size than those used in the solid electrolyte. For example, the ratio of the average size of the particles used in the external polymer coating to the average size of the particles used in any dispersion of the solid electrolyte is usually about 1.5 to about 30, about 2 to about 20 in some embodiments, and about 5 to about 15 in some embodiments. For example, the particles used in the dispersion of the external coating may have an average size of about 80 to about 500 nanometers, about 90 to about 250 nanometers in some embodiments, and about 100 to about 200 nanometers in some embodiments.

[0044] If desired, a crosslinking agent can be used in the external polymer coating to increase adhesion to the solid electrolyte. Typically, the crosslinking agent is applied before applying the dispersion used in the external coating. Suitable crosslinking agents are described, for example, in U.S. Patent Publication 2007 / 0064376 by Merker et al., and include, for example, amines (e.g., diamines, triamines, oligomeric amines, polyamines, etc.); salts or compounds of polyvalent metal cations, such as Mg, Al, Ca, Fe, Cr, Mn, Ba, Ti, Co, Ni, Cu, Ru, Ce, or Zn; phosphonium compounds; sulfonium compounds, etc. Particularly preferred examples include, for example, 1,4-diaminocyclohexane, 1,4-bis(aminomethyl)cyclohexane, ethylenediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine, N,N-dimethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,4-butanediamine, and mixtures thereof.

[0045] The crosslinking agent is typically applied from a solution or dispersion having a pH of 1 to 10, 2 to 7 in some embodiments, and 3 to 6 in some embodiments, at 25°C. Acidic compounds can be used to help achieve the desired pH level. Examples of solvents or dispersants for the crosslinking agent include water or organic solvents, such as alcohols, ketones, carboxylic acid esters, etc. The crosslinking agent can be applied to the capacitor body by any known process such as spin coating, impregnation, casting, dropwise application, spray application, vapor deposition, sputtering, sublimation, knife coating, painting, or printing, such as inkjet, screen, or pad printing. Once applied, the crosslinking agent can be dried before applying the polymer dispersion. This process can then be repeated until the desired thickness is achieved. For example, the total thickness of the entire outer polymer coating, including the layers of crosslinking agent and dispersion, may range from about 1 to about 50 μm, about 2 to about 40 μm in some embodiments, and about 5 to about 20 μm in some embodiments.

[0046] E. Cathode coating: If desired, the capacitor element may also use a cathode coating that is placed on top of a solid electrolyte and other optional layers (e.g., an external polymer coating). The cathode coating may include a layer of metal particles containing a number of conductive metal particles dispersed within a polymer matrix. The particles typically constitute about 50% to about 99% by weight of the layer, about 60% to about 98% by weight in some embodiments, and about 70% to about 95% by weight in some embodiments, while the polymer matrix typically constitutes about 1% to about 50% by weight of the layer, about 2% to about 40% by weight in some embodiments, and about 5% to about 30% by weight in some embodiments.

[0047] Conductive metal particles can be formed from various different metals such as copper, nickel, silver, zinc, tin, lead, aluminum, molybdenum, titanium, iron, zirconium, magnesium, and alloys thereof. Silver is a particularly suitable conductive metal for use in the layer over which it is applied. The metal particles often have relatively small dimensions, such as an average diameter of about 0.01 to about 50 micrometers, about 0.1 to about 40 micrometers in some embodiments, and about 1 to about 30 micrometers in some embodiments. It should be understood that usually only one layer of metal particles is used, but multiple layers can be used if desired. The total thickness of such one or more layers is in the range of about 1 μm to about 500 μm, about 5 μm to about 200 μm in some embodiments, and about 10 μm to about 100 μm in some embodiments.

[0048] The polymer matrix typically comprises a polymer that may be inherently thermoplastic or thermosetting. However, the polymer is usually selected to contain a relatively small amount of polar groups so as to act as a barrier against the electromigration of silver ions and to minimize the degree of water adsorption in the cathode coating. In this regard, the inventors have found that vinyl acetal polymers such as polyvinyl butyral and polyvinyl formal are particularly suitable for this purpose. For example, polyvinyl butyral can be formed by reacting polyvinyl alcohol with an aldehyde (e.g., butyraldehyde). Since this reaction is usually incomplete, polyvinyl butyral generally has a residual hydroxyl content. However, by minimizing this content, the polymer can have a lower degree of strongly polar groups (the absence of which leads to a high degree of moisture adsorption and silver ion migration). For example, the residual hydroxyl content in polyvinyl acetal can be about 35 mol% or less, about 30 mol% or less in some embodiments, and about 10 mol% to about 25 mol% in some embodiments. One commercially available example of such a polymer is available from Sekisui Chemical Co., Ltd. under the name "BH-S" (polyvinyl butyral).

[0049] To form the cathode coating, a conductive paste is typically applied to the capacitor in layers on top of the solid electrolyte. Generally, one or more organic solvents are used in the paste. In general, various different organic solvents can be used, such as glycols (e.g., propylene glycol, butylene glycol, triethylene glycol, hexylene glycol, polyethylene glycol, ethoxydiglycol, and dipropylene glycol); glycol ethers (e.g., methyl glycol ether, ethyl glycol ether, and isopropyl glycol ether); ethers (e.g., diethyl ether and tetrahydrofuran); alcohols (e.g., benzyl alcohol, methanol, ethanol, n-propanol, iso-propanol, and butanol); triglycerides; ketones (e.g., acetone, methyl ethyl ketone, and methyl isobutyl ketone); esters (e.g., ethyl acetate, butyl acetate, diethylene glycol ether acetate, and methoxypropyl acetate); amides (e.g., dimethylformamide, dimethylacetamide, dimethylcapryl / caprin fatty acid amide, and N-alkylpyrrolidone); nitriles (e.g., acetonitrile, propionnitrile, butyronitrile, and benzonitrile); sulfoxides or sulfones (e.g., dimethyl sulfoxide (DMSO) and sulfolane); etc., as well as mixtures thereof. One or more organic solvents typically constitute about 10% to 70% by weight of the paste, about 20% to 65% by weight in some embodiments, and about 30% to 60% by weight in some embodiments. Typically, metal particles constitute about 10% to 60% by weight of the paste, about 20% to 45% by weight in some embodiments, and about 25% to 40% by weight in some embodiments, and a resinous matrix constitutes about 0.1% to 20% by weight of the paste, about 0.2% to 10% by weight in some embodiments, and about 0.5% to 8% by weight in some embodiments.

[0050] The paste may have a relatively low viscosity, which makes it easy to handle and apply to the capacitor element. The viscosity may be in the range of about 50 to about 3,000 centipoise, in some embodiments 100 to about 2,000 centipoise, and in some embodiments about 200 to about 1,000 centipoise, measured using, for example, a Brookfield DV-1 viscometer (cone plate) operating at a speed of 10 rpm and a temperature of 25°C. If desired, the viscosity can be increased or decreased by using thickeners or other viscosity modifiers in the paste. Furthermore, the thickness of the applied paste may be relatively thin, and the desired properties can still be achieved. For example, the thickness of the paste may be about 0.01 to about 50 micrometers, in some embodiments about 0.5 to about 30 micrometers, and in some embodiments about 1 to about 25 micrometers. After application, the metal paste may optionally be dried to remove some components such as organic solvents. For example, drying can be carried out at temperatures of approximately 20°C to 150°C, approximately 50°C to 140°C in some embodiments, and approximately 80°C to 130°C in some embodiments.

[0051] F. Other ingredients: If desired, other layers known in the art may also be included in the capacitor. For example, in some embodiments, a carbon layer (e.g., graphite) can be placed between the solid electrolyte and the silver layer to help further limit contact between the silver layer and the solid electrolyte. Furthermore, a pre-coat layer containing an organometallic compound, which is placed on the dielectric, may also be used, as described in more detail below.

[0052] II. Termination: Once the desired layer is formed, the capacitor can be terminated as shown above. More specifically, the capacitor includes an anode termination to which the anode leads of the capacitor element are electrically connected, and a cathode termination to which the solid electrolyte of the capacitor is electrically connected. The termination can be formed using any conductive material such as conductive metals (e.g., copper, nickel, silver, nickel, zinc, tin, palladium, lead, copper, aluminum, molybdenum, titanium, iron, zirconium, magnesium, and alloys thereof). Particularly preferred conductive metals include, for example, copper, copper alloys (e.g., copper-zirconium, copper-magnesium, copper-zinc, or copper-iron), nickel, and nickel alloys (e.g., nickel-iron). The thickness of the termination is generally selected to minimize the thickness of the capacitor. For example, the thickness of the termination may range from about 0.05 to about 1 millimeter, in some embodiments from about 0.05 to about 0.5 millimeters, and from about 0.07 to about 0.2 millimeters. One typical conductive material is a copper-iron alloy metal plate available from Wieland (Germany). If desired, the terminal surfaces may be electroplated with nickel, silver, gold, tin, etc., to ensure that the final components can be mounted onto the circuit board, as is known in the art. In one particular embodiment, both surfaces of the terminal are plated with nickel and silver flash, respectively, while the mounting surface is plated with a tin solder layer.

[0053] The terminations can be connected to the capacitor element using any technique known in the art. For example, in one embodiment, a lead frame can be provided that defines the cathode and anode terminations. To attach the capacitor element to the lead frame, a conductive adhesive can first be applied to the surface of the cathode termination. The conductive adhesive can, for example, contain conductive metal particles contained in a resin composition. The metal particles may be silver, copper, gold, platinum, nickel, zinc, bismuth, etc. The resin composition can contain a thermosetting resin (e.g., epoxy resin), a curing agent (e.g., acid anhydride), and a coupling agent (e.g., silane coupling agent). A suitable conductive adhesive is described in Osako et al., U.S. Patent Application Publication No. 2006 / 0038304. The conductive adhesive can be applied to the cathode termination using any various techniques. For example, printing techniques can be used for their practical and cost-saving benefits. The anode lead can also be electrically connected to the anode termination using any technique known in the art, such as mechanical welding, laser welding, or conductive adhesive. Once the anode leads are electrically connected to the anode terminals, the conductive adhesive can then be cured to ensure that the electrolytic capacitor adheres properly to the cathode terminals.

[0054] Referring to Figure 1, for example, the electrolytic capacitor 30 is shown to include an anode terminal 62 and a cathode terminal 72 electrically connected to a capacitor element 33 having a top surface 37, a bottom surface 39, a front surface 36, a back surface 38, a first side surface 35, and an opposing side surface (not shown). The cathode terminal 72 can be provided by electrically contacting any surface of the capacitor element 33, for example, by a conductive adhesive. In the embodiment shown, for example, the cathode terminal 72 includes a first component 73 that is generally parallel to and adjacent to the top surface 37, and a second component 75 that is generally parallel to and adjacent to the bottom surface 39. The first component 73 is also electrically in contact with the top surface 37. The cathode terminal 72 may also include a third component that extends generally perpendicular to the first component 73 and the second component 75. If desired, the third component 77 may be provided by electrically contacting the back surface 38 of the capacitor element 33. Furthermore, the anode termination 62 includes a first component 63 that is generally parallel to the lower surface 39 of the capacitor element 33, and a second component 67 that is generally parallel to the anode lead 16. In addition, the anode termination 62 may include a third component 64 that is generally perpendicular to the first component 63, and a fourth component 69 that is generally perpendicular to the second component 67 and positioned adjacent to the anode lead 16. In the embodiment shown, the second component 67 and the fourth component 69 define a region 51 for connection to the anode lead 16. Although not shown in Figure 1, the region 51 may have a "U-shape" to further increase surface contact and mechanical stability of the lead 16.

[0055] The terminations can be connected to the capacitor element using any technique known in the art. For example, in one embodiment, a lead frame can be provided that defines the cathode termination 72 and the anode termination 62. To attach the capacitor element 33 to the lead frame, a conductive adhesive 49 can first be applied to the surface of the cathode termination 72. In one embodiment, the anode termination 62 and the cathode termination 72 are bent to the positions shown in Figure 1. The capacitor element 33 is then placed on the cathode termination 72 such that its lower surface 39 is in contact with the adhesive 49 and the anode lead 16 is in contact with the region 51. Next, the anode lead 16 is electrically connected to the region 51 using any technique known in the art, such as mechanical welding, laser welding, or conductive adhesive. For example, the anode lead 16 can be welded to the anode termination 62 using a laser. The laser generally includes a resonator containing a laser medium capable of emitting photons by stimulated emission, and an energy source for exciting elements in the laser medium. One suitable type of laser is one in which the laser medium consists of neodymium (Nd)-doped aluminum and yttrium garnet (YAG). The excited particles are neodymium ions Nd 3+ The energy source can provide continuous energy to the laser medium to emit a continuous laser beam, or provide an energy discharge to emit a pulsed laser beam. Once the anode lead 16 is electrically connected to the anode terminal 62, the conductive adhesive can then be cured. For example, heat and pressure can be applied using a heat press to ensure that the electrolytic capacitor element 33 is properly bonded to the cathode terminal 72 by the adhesive 49.

[0056] To further help minimize the possibility of delamination, an interfacial coating may be used that covers at least a portion of the anode and / or cathode ends and is in contact with the casing material. Unlike the metallic components commonly used in anode and cathode ends, the interfacial coating can be formed from a resinous material having a coefficient of thermal expansion substantially equivalent to that of the curable resinous matrix used in the casing material. Here again, this can further reduce the possibility of delamination from the anode leads and / or capacitor elements due to expansion of the casing material during manufacturing.

[0057] One or more coverings can be used. For example, in one embodiment, an interface covering can be used that covers at least a portion of the anode termination. In such an embodiment, the covering can also be in contact with at least a portion of the surface of the capacitor element, such as the front, bottom, and / or top surface of the capacitor element. Furthermore, the covering can also be in contact with at least a portion of the anode leads. In another embodiment, an interface covering can be used that covers at least a portion of the cathode termination. In such an embodiment, the covering can also be in contact with at least a portion of the surface of the capacitor element, such as the back, top, and / or bottom surface. Referring again to Figure 1, for example, capacitor 30 is shown having an interface covering 90 present on the anode termination 62. More specifically, in the shown embodiment, the covering 90 is in contact with the second component 67 and the fourth component 69 of the anode termination 62 so as to generally cover the region 51. The covering 90 is also in contact with at least a portion of the anode leads 16, particularly at locations around the region 51 where the leads 16 are connected to the anode termination 62. Of course, it should be understood that the coating can be provided in other configurations and can be placed on any desired surface. For example, in one embodiment, the coating can be in contact only with the second component 67 of the anode terminal 62.

[0058] Regardless of its placement, the resinous material used in the interfacial coating can be selectively controlled to impart several desired properties to the resulting capacitor. For example, in one embodiment, the interfacial coating may include hydrophobic resinous materials such as low surface energy polymers (e.g., fluoropolymers, silicones) or organometallic compounds. Fluoropolymers may include, for example, hydrocarbon backbone polymers (e.g., polyolefins) in which some or all of the hydrogen atoms are substituted with fluorine groups such as fluoroalkyl groups (e.g., trifluoromethyl, trifluoroethyl, etc.). The backbone polymer can also be formed from ethylenically unsaturated monomers (e.g., olefins, olefinic acrylates, olefinic methacrylates, etc.). Suitable monomers may have carbon chains with lengths of 3 to 20 atoms, 6 to 12 carbon atoms in some embodiments, and 8 to 10 carbon atoms in some embodiments. Particularly suitable fluoroalkyl-substituted monomers for use in the present invention are fluoroalkyl (meth)acrylates such as perfluorohexyl (meth)acrylate, perfluoroheptyl (meth)acrylate, perfluorooctyl (meth)acrylate, perfluorononylperfluorodecyl (meth)acrylate, perfluoroundecyl (meth)acrylate, or perfluorododecyl (meth)acrylate, as well as mixtures thereof. As used herein, the term "(meth)acrylic" encompasses both acrylate monomers and methacrylate monomers.

[0059] Another suitable low surface energy polymer that can be used is a silicone polymer. Such polymers typically have the following general formula (IV):

[0060] [ka]

[0061] (In the formula, y is an integer greater than 1; R8, R9, R 10 , R11 , R 12 , R 13 , R 14 , and R 15 These are, independently, monovalent groups typically containing 1 to about 20 carbon atoms, such as alkyl groups (e.g., methyl, ethyl, propyl, pentyl, octyl, undecyl, octadecyl, etc.); alkoxy groups (e.g., methoxy, ethoxy, propoxy, etc.); carboxyalkyl groups (e.g., acetyl); cycloalkyl groups (e.g., cyclohexyl); alkenyl groups (e.g., vinyl, allyl, butenyl, hexenyl, etc.); aryl groups (e.g., phenyl, tolyl, xylyl, benzyl, 2-phenylethyl, etc.); and halogenated hydrocarbon groups (e.g., 3,3,3-trifluoropropyl, 3-chloropropyl, dichlorophenyl, etc.). These polyorganosiloxanes are derived from polyorganosiloxanes that have the following properties: polydimethylsiloxane (PDMS), polymethylhydrogensiloxane, dimethyldiphenylpolysiloxane, dimethyl / methylphenylpolysiloxane, polymethylphenylsiloxane, methylphenyl / dimethylsiloxane, vinyldimethyl-terminated polydimethylsiloxane, vinylmethyl / dimethylpolysiloxane, vinyldimethyl-terminated vinylmethyl / dimethylpolysiloxane, divinylmethyl-terminated polydimethylsiloxane, vinylphenylmethyl-terminated polydimethylsiloxane, dimethylhydro-terminated polydimethylsiloxane, methylhydro / dimethylpolysiloxane, methylhydro-terminated methyloctylpolysiloxane, methylhydro / phenylmethylpolysiloxane, fluoro-modified polysiloxane, and others. To form hydrophobic materials, polyorganosiloxanes can be crosslinked using various known techniques, such as catalytic curing (e.g., platinum catalyst), room temperature vulcanization, and moisture curing. Crosslinking agents such as alkoxysilanes having the formula: Si-OR (wherein R is H, alkyl (e.g., methyl), alkenyl, or carboxyalkyl (e.g., acetyl) can be used.

[0062] Of course, other hydrophobic materials can also be used in the interfacial coating. For example, in one embodiment, the hydrophobic material may be the following general formula:

[0063] [ka]

[0064] (In the formula, M is an organometallic atom such as silicon or titanium; R 16 , R 17 , and R 18 R is independently an alkyl group (e.g., methyl, ethyl, propyl, etc.) or a hydroxyalkyl group (e.g., hydroxymethyl, hydroxyethyl, hydroxypropyl, etc.), 16 , R 17 , and R 18 At least one of them is a hydroxyalkyl group; n is an integer between 0 and 8, in some embodiments between 1 and 6, and in some embodiments between 2 and 4 (e.g., 3); and X is an organic or inorganic functional group such as glycidyl, glycidyloxy, mercapto, amino, vinyl, etc. Examples of organometallic compounds that possess the following properties can be given.

[0065] In some embodiments, R 16 , R 17 , and R 18 R may be a hydroxyalkyl group (e.g., OCH3). However, in other embodiments, R 16 R may be an alkyl group (e.g., CH3), 17 and R 18 This can be a hydroxyalkyl group (e.g., OCH3).

[0066] In some embodiments, M may be silicon, and the organometallic compound is an organosilane compound such as an alkoxysilane. Suitable alkoxysilanes include, for example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, and glycidoxymethyltrimethoxysilane. , glycidoxymethyltriethoxysilane, glycidoxymethyltripropoxysilane, glycidoxymethyltributoxysilane, β-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, β-glycidoxyethyltripropoxysilane, β-glycidoxyethyltributoxysilane, β-glycidoxyethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, α-glycidoxyethyltripropoxysilane, α-glycidoxyethyltributoxysilane, γ-glycidoxy glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyltriethoxysilane, β-glycidoxypropyltripropoxysilane, α-glycidoxypropyltributoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, α-glycidoxypropyltripropoxysilane Lan, α-glycidoxypropyltributoxysilane, γ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltripropoxysilane, δ-glycidoxybutyltributoxysilane, δ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, γ-glycidoxybutyltripropoxysilane, γ-propoxybutyltributoxysilane, δ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane,δ-Glycidoxybutyl tripropoxysilane, α-Glycidoxybutyltrimethoxysilane, α-Glycidoxybutyltriethoxysilane, α-Glycidoxybutyl tripropoxysilane, α-Glycidoxybutyl tripropoxysilane, (3,4-Epoxycyclohexyl)-methyltrimethoxysilane, (3,4-Epoxycyclohexyl)methyltriethoxysilane, (3,4-Epoxycyclohexyl)methyltripropoxysilane, (3,4-Epoxycyclohexyl)methyltributoxysilane, (3,4-Epoxycyclohexyl)ethyltrimethoxysilane, (3,4-Epoxycyclohexyl)ethyltriethoxysilane, (3,4-Epoxycyclohexyl Examples include (3,4-epoxycyclohexyl)ethyl tripropoxysilane, (3,4-epoxycyclohexyl)ethyl tripropoxysilane, (3,4-epoxycyclohexyl)propyl triproxylsilane, (3,4-epoxycyclohexyl)propyl tripropoxysilane, (3,4-epoxycyclohexyl)propyl tripropoxysilane, (3,4-epoxycyclohexyl)propyl tripropoxysilane, (3,4-epoxycyclohexyl)butyl triproxylsilane, (3,4-epoxycyclohexyl)butyl tripropoxysilane, and (3,4-epoxycyclohexyl)butyl tripropoxysilane.

[0067] To assist in its application, the interfacial coating can first be prepared in the form of a coating formulation containing a hydrophobic resinous material in combination with an organic solvent that is normally liquid at room temperature. When used, such solvent typically constitutes about 90% to about 99.9% by weight of the formulation, about 92% to about 99.8% by weight in some embodiments, and about 95% to about 99.5% by weight in some embodiments, while the hydrophobic resinous material may constitute about 0.1% to about 10% by weight of the solution, about 0.2% to about 8% by weight in some embodiments, and about 0.5% to about 5% by weight in some embodiments. The one or more solvents used are determined in part by the properties of the resinous material, but generally include organic alcohols, hydrocarbon solvents, and fluorinated hydrocarbon solvents. For example, solvents particularly suitable for use with fluoropolymers include fluorinated hydrocarbon solvents, such as hydrofluoroethers, fluorinated ketones, and fluorinated olefins. For example, in one particular embodiment, the coating formulation may have the following general structure (VI): (R 1 -O) x -R 2 (VI) (In the formula, x is either 1 or 2; R 1 and R 2 (One is a perfluoroaliphatic or perfluorocyclic group, and the other is an aliphatic or cyclic hydrocarbon group.) It can contain a hydrofluoroether having R. For example, R 1 and / or R 2 Examples include substituted and unsubstituted alkyl, aryl, and alkylaryl groups, as well as their derivatives. A representative example of a suitable hydrofluoroether is the following compound: C5F 11Examples include OC2H5, C3F7OCH3, C4F9OCH3, C4F9OC2H5, C3F7OCF(CF3)CF2OCH3, C4F9OC2F4OC2F4OC2H5, C4F9O(CF2)3OCH3, C3F7CF(OC2H5)CF(CF3)2, C2F5CF(OCH3)CF(CF3)2, and C4F9OC2H4OC4F9. Ethyl nonafluoroisobutyl ether and ethyl nonafluorobutyl ether (both represented by the structure: C4F9OC2H5) are particularly preferred.

[0068] III. Casing materials: As shown, the capacitor element and anode lead are generally enclosed in casing material such that at least a portion of the anode and cathode ends are exposed for mounting onto a circuit board. Referring again to Figure 1, for example, the capacitor element 33 and anode lead 16 can be enclosed in casing material 28 such that a portion of the anode end 62 and a portion of the cathode end 72 are exposed. As described above, the resinous matrix used to form the casing material has a relatively low coefficient of thermal expansion, which helps reduce the possibility of it delaminating from the capacitor element when exposed to high temperatures. The resinous matrix is ​​also generally substantially hydrophobic.

[0069] For example, in some embodiments, the resinous matrix may comprise a polycyanate containing at least two cyanate ester groups. For example, upon curing, the polycyanate can form a polycyanurate having a triazine ring. Due to the high degree of symmetry in the triazine ring where the dipoles involved in the carbon-nitrogen and carbon-oxygen bonds are balanced, the resulting polycyanurate can exhibit a relatively low degree of thermal expansion. Suitable polycyanates include, for example, bisphenol A dicyanate; 4,4'-dihydroxydiphenyl, 4,4'-dihydroxydiphenyl oxide, resorcinyl, hydroquinone, 4,4'-thiodiphenol, 4,4'-sulfonyldiphenyl, 3,3',5,5'-tetrabromobisphenol A, 2,2',6,6'-tetrabromobisphenol A, 2,2'-dihydroxydiphenyl, 3,3'-dihydroxybisphenol A, and 4,4'-dihydroxydiphenyl carbonate. Examples include dicyanates such as dicyclopentadiene diphenol, 4,4'-dihydroxybenzophenone, 4,4'-dihydroxydiphenylmethane, and tricyclopentadiene diphenol; tricyanates of tris(hydroxyphenyl)methane, tetracyanates of 2,2',4,4'-tetrahydroxydiphenylmethane, polycyanates of phenol-formaldehyde condensation products (novolac); and polycyanates of condensation products of dicyclopentadiene and phenol. If desired, polycyanates also include C7-C, such as cyclopentadiene, norbornane, bornane, norbornadiene, tetrahydroindene, methyltetrahydroindene, dicyclopentadiene, bicyclo-(2,2,1)-hepta-2,5-diene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 5-propenyl-2-norbornene, 5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene, and others. 20The polycyanate may contain one or more polycyclic aliphatic groups, such as polycyclic aliphatic groups, each containing two or more cyclic rings. For example, in one particular embodiment, the polycyanate may be a dicyclopentadiene bisphenol cyanate ester. While not intended to be theoretically limited, such polycyclic groups can act as nonpolar bridging groups for the polycyanate, which is thought to help improve its resistance to thermal expansion.

[0070] The resinous matrix may also contain epoxy resin, either alone or in combination with polycyanate. When used in combination, the epoxy resin may react with the polycyanate upon curing to form copolymers and / or crosslinks with the polycyanate resin. Examples of suitable epoxy resins include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, orthocresol novolac type epoxy resins, brominated epoxy resins and biphenyl type epoxy resins, cyclic aliphatic epoxy resins, glycidyl ester type epoxy resins, glycidylamine type epoxy resins, cresol novolac type epoxy resins, naphthalene type epoxy resins, phenol aralkyl type epoxy resins, cyclopentadiene type epoxy resins, and heterocyclic epoxy resins. However, to help provide a desired degree of resistance to thermal expansion, it is particularly desirable to use epoxyphenol novolac (EPN) resin, which is a glycidyl ether of phenol novolac resin. These resins can be produced, for example, by reacting phenols with excess formaldehyde in the presence of an acidic catalyst to produce phenol novolac resins. Next, novolac epoxy resins are produced by reacting the phenol novolac resin with epichlorohydrin in the presence of sodium hydroxide. Specific examples of novolac-type epoxy resins include phenol-novolac epoxy resins, cresol-novolac epoxy resins, naphthol-novolac epoxy resins, naphthol-phenol co-condensed novolac epoxy resins, naphthol-cresol co-condensed novolac epoxy resins, and brominated phenol-novolac epoxy resins. Regardless of the type of resin selected, the resulting phenol novolac epoxy resins usually have more than two oxirane groups, and these can be used to produce cured coating compositions with high crosslinking density, which may be particularly suitable for increasing resistance to thermal expansion. One such phenol novolac epoxy resin is poly[(phenylglycidyl ether)-co-formaldehyde].Other suitable resins are commercially available from Huntsman under the trade name ARALDITE (e.g., GY289, EPN1183, EP1179, EPN1139, and EPN1138).

[0071] By crosslinking polycyanate and / or epoxy resin with a co-reacting substance (curing agent), the mechanical properties of the composition can be further improved, and its resistance to thermal expansion can also be increased as described above. Examples of such co-reacting substances include, for example, polyamides, amideamines (e.g., aromatic amideamines such as aminobenzamide, aminobenzanilide, and aminobenzenesulfonamide), aromatic diamines (e.g., diaminodiphenylmethane, diaminodiphenylsulfone, etc.), aminobenzoates (e.g., trimethylene glycol di-p-aminobenzoate and neopentyl glycol di-p-aminobenzoate), aliphatic amines (e.g., triethylenetetramine, isophorone diamine), alicyclic amines (e.g., isophorone diamine), imidazole derivatives, guanidines (e.g., tetramethylguanidine), carboxylic acid anhydrides (e.g., methylhexahydrophthalic anhydride), carboxylic acid hydrazides (e.g., adipic acid hydrazide), phenol-novolac resins (e.g., phenol novolac, cresol novolac, etc.), carboxylic acid amides, and combinations thereof. Phenol-novolac resins may be particularly suitable for use in the present invention.

[0072] Furthermore, the casing material may also contain inorganic oxide fillers. Such fillers are typically maintained at a high level in the casing material, usually about 75% to 99.5% by weight, about 76% to 99% by weight in some embodiments, and about 77% to 90% by weight in some embodiments, while the resinous matrix typically constitutes about 0.5% to 25% by weight, about 1% to 24% by weight in some embodiments, and about 10% to 23% by weight in some embodiments. The properties of the inorganic oxide fillers may vary, such as silica, alumina, zirconia, magnesium oxide, iron oxide (e.g., yellow iron oxyhydroxide), titanium oxide (e.g., titanium dioxide), zinc oxide (e.g., boron zinc hydroxide oxide), copper oxide, zeolite, silicate, clay (e.g., smectite clay), and composites (e.g., alumina-coated silica particles), as well as mixtures thereof. However, regardless of the specific filler used, a substantial, if not all, portion of the inorganic oxide filler is usually in the form of silica glass, which is thought to further improve the moisture resistance of the casing material due to its high purity and relatively simple chemical form. Silica glass may constitute, for example, about 30% by weight or more of the total weight of the fillers used in the composition, about 35% to about 90% by weight in some embodiments, about 40% to about 80% by weight in some embodiments, and about 20% to about 70% by weight of the whole composition, about 25% to about 65% by weight in some embodiments, and about 30% to about 60% by weight in some embodiments. Of course, other forms of silica, such as quartz, fumed silica, and cristobalite, can also be used in combination with silica glass.

[0073] It should be understood that, in addition to the components mentioned above, other additives such as photoinitiators, viscosity modifiers, suspension aids, pigments, stress reducers, coupling agents (e.g., silane coupling agents), and stabilizers may also be used in the casing material. When used, such additives typically constitute about 0.1 to about 20% by weight of the total composition.

[0074] The specific method for applying the casing material to the capacitor element can be varied as desired. In one particular embodiment, the capacitor element is placed in a mold, and the casing material is applied to the capacitor element so that it occupies a space defined by the mold, exposing at least a portion of the anode and cathode ends. The casing material can initially be prepared in the form of one or more compositions. For example, the first composition may contain a resinous matrix and fillers, and the second composition may contain a co-reacting substance. Nevertheless, after application, the casing material can be heated or left at ambient temperature to allow the resinous matrix to crosslink with the co-reacting substance, thereby curing the casing material and solidifying it into the desired shape of the case. For example, the casing material can be heated to a temperature of about 15°C to about 150°C, about 20°C to about 120°C in some embodiments, and about 25°C to about 100°C in some embodiments.

[0075] Although not strictly necessary, a moisture barrier layer can be used to cover all or part of the casing material. The moisture barrier layer is generally formed from hydrophobic materials such as silicone, fluoropolymers, or organometallic compounds, as described above. [Examples]

[0076] The present invention can be better understood by referring to the following examples. Test procedure: capacitance: Capacitance can be measured using a Keithley 3330 precision LCZ meter with Kelvin leads, using a 2.2-volt DC bias and a 0.5-volt peak-to-peak sinusoidal signal. The operating frequency may be 120 Hz and the temperature may be 23°C ± 2°C. In some cases, "wet-to-dry" capacitance can be determined. "Dry capacitance" refers to the capacitance of the component before the application of solid electrolytes, graphite, and silver layers, while "wet capacitance" refers to the capacitance of the component after dielectric formation, measured in 14% nitric acid, using a 1 mF tantalum cathode as a reference, with a 10-volt DC bias and a 0.5-volt peak-to-peak sinusoidal signal, after 30 seconds of electrolyte immersion.

[0077] Equivalent series resistance (ESR): The equivalent series resistance can be measured using a Keithley 3330 precision LCZ meter with Kelvin leads, with a 2.2-volt DC bias and a 0.5-volt peak-to-peak sinusoidal signal. The operating frequency may be 100 kHz, and the temperature may be 23°C ± 2°C.

[0078] Loss factor: The loss factor can be measured using a Keithley 3330 precision LCZ meter with Kelvin leads, using a 2.2-volt DC bias and a 0.5-volt peak-to-peak sinusoidal signal. The operating frequency may be 120 kHz, and the temperature may be 23°C ± 2°C.

[0079] Leakage current: Leakage current can be measured using a leakage test meter at a temperature of 23°C ± 2°C and rated voltage, after a minimum of 60 seconds.

[0080] High-temperature storage test: The high-temperature storage test is based on IEC-60068-2-2:2007 (condition Bb, temperature 125°C). All ESR measurements are performed at a temperature of 23°C + 2°C after 1-2 hours of recovery from the test conditions. The samples are not mounted on a substrate. For various samples (e.g., 25 samples), the ratio of the actual average ESR of all tested units to the initial average ESR is determined.

[0081] Example 1: Anode samples were formed using tantalum powder with a density of 50,000 μFV / g. Tantalum wires were embedded in each anode sample, sintered at 1350°C, and pressed to obtain a density of 5.8 g / cm². 3 The density was adjusted to . The resulting pellets had dimensions of 1.7 × 2.4 × 1.0 mm. The pellets were anodized to 23.5 volts in a water / phosphoric acid electrolyte with a conductivity of 8.6 mS / cm at a temperature of 85°C to form a dielectric layer. These pellets were then anodized again to 80 volts for 25 seconds in a water / boric acid / disodium tetraborate solution with a conductivity of 2.0 mS / cm at a temperature of 30°C to form a thicker oxide layer deposited on the outside.

[0082] Next, a conductive polymer coating was formed by polymerizing the anode by immersion in a butanol solution of iron(III) toluenesulfonate (Clevios® C, HC Starck), followed by 3,4-ethylenedioxythiophene (Clevios® M, HC Starck). After 45 minutes of polymerization, a thin layer of poly(3,4-ethylenedioxythiophene) was formed on the surface of the dielectric. The anode was washed in methanol to remove reaction byproducts, anodized in a liquid electrolyte, and washed again in methanol. This process was repeated six times. Subsequently, the component was immersed in dispersed poly(3,4-ethylenedioxythiophene) (Clevios® K, Heraeus) with a solid content of 2.0% and a viscosity of 20 mPa·s. After coating, the component was dried at 125°C for 20 minutes. This process was repeated three times. Subsequently, the components were immersed in a dispersed poly(3,4-ethylenedioxythiophene) (Clevios® K, Heraeus) with a solid content of 2.0% and a viscosity of 160 mPa·s. After coating, the components were dried at 125°C for 20 minutes. This process was repeated 12 times. Next, the components were immersed in a graphite dispersion and dried. Finally, the components were immersed in a silver dispersion and dried. In this way, a large number of 47μF / 10V capacitor components (2,000) were fabricated and encapsulated in silica-filled resin having a temperature coefficient of 13 ppm / °C below the glass transition temperature and 51 ppm / °C above the glass transition temperature.

[0083] Example 2: Capacitors were formed in the same manner as described in Example 1, except that the obtained components were encapsulated in the resinous matrix described herein. After forming 25 components of a 47μF / 10V capacitor, they were subjected to the high-temperature storage test described above. The results are shown in Table 1 below.

[0084] [Table 1]

[0085] These and other modifications and changes to the present invention can be implemented by those skilled in the art without departing from the spirit and scope of the invention. Furthermore, it should be understood that multiple forms of various embodiments can be interchanged, either whole or in part. Moreover, those skilled in the art will recognize that the above description is merely an example and is not intended to limit the invention further described in the appended claims. The present invention includes the following embodiments. [1] A solid electrolytic capacitor, A capacitor element comprising a sintered porous anode, a dielectric disposed on the anode, and a solid electrolyte disposed on the dielectric; Anode leads extending from the surface of the capacitor element; Anode terminal electrically connected to the anode lead, and cathode terminal electrically connected to the solid electrolyte; and A casing material enclosing the capacitor element and the anode lead, wherein the casing material is formed from a curable resinous matrix having a thermal expansion coefficient of about 42 ppm / °C or less at a temperature higher than the glass transition temperature of the resinous matrix; Includes; The capacitor exhibits an initial equivalent series resistance of approximately 200 milliohms or less at an operating frequency of 100 kHz and a temperature of 23°C, and the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 560 hours to the initial equivalent series resistance of the capacitor is approximately 2.0 or less. [2] The solid electrolytic capacitor according to [1], wherein the resinous matrix has a thermal expansion coefficient of about 11 ppm / °C or less at a temperature lower than the glass transition temperature of the resinous matrix. [3] The solid electrolytic capacitor according to [1], wherein the resinous matrix has a glass transition temperature of about 50°C to about 180°C. [4] The solid electrolytic capacitor according to [1], wherein the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 750 hours to the initial equivalent series resistance of the capacitor is approximately 2.0 or less. [5] The solid electrolytic capacitor according to [1], wherein the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 1,000 hours to the initial equivalent series resistance of the capacitor is approximately 2.0 or less. [6] The solid electrolytic capacitor according to [1], wherein the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 1,250 hours to the initial equivalent series resistance of the capacitor is approximately 2.0 or less. [7] The solid electrolytic capacitor according to [1], wherein the interfacial coating covers at least a portion of the anode terminal. [8] The solid electrolytic capacitor according to [7], wherein the interface coating also covers at least a portion of the anode lead. [9] The solid electrolytic capacitor according to [7], wherein the interfacial coating comprises a fluoropolymer, a silicone polymer, an organometallic compound, or a combination thereof.

[10] The solid electrolytic capacitor according to [1], wherein the resinous matrix comprises a polycyanate containing at least two cyanate ester groups.

[11] The solid electrolytic capacitor according to

[10] , wherein the polycyanate comprises a polycyclic aliphatic group including two or more cyclic rings.

[12] The solid electrolytic capacitor according to

[11] , wherein the polycyclic aliphatic group comprises cyclopentadiene, norbornane, bornane, norbornadiene, tetrahydroindene, methyltetrahydroindene, dicyclopentadiene, bicyclo-(2,2,1)-hepta-2,5-diene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 5-propenyl-2-norbornene, 5-(4-cyclopentenyl)-2-norbornene, 5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene, or a combination thereof.

[13] The solid electrolytic capacitor according to

[12] , wherein the polycyanate is dicyclopentadiene bisphenol cyanate ester.

[14] The solid electrolytic capacitor according to [1], wherein the resinous matrix comprises an epoxy resin.

[15] The solid electrolytic capacitor according to

[14] , wherein the epoxy resin is a phenol novolac epoxy resin.

[16] The solid electrolytic capacitor according to

[15] , wherein the phenol novolac epoxy resin is a phenol-novolac epoxy resin, a cresol-novolac epoxy resin, a naphthol-novolac epoxy resin, a naphthol-phenol cocondensed novolac epoxy resin, a naphthol-cresol cocondensed novolac epoxy resin, a brominated phenol-novolac epoxy resin, or a combination thereof.

[17] The solid electrolytic capacitor according to [1], wherein the resinous matrix further comprises an inorganic oxide filler in an amount of about 75% to about 99.5% by weight of the matrix.

[18] The solid electrolytic capacitor according to

[17] , wherein the inorganic oxide filler comprises silica.

[19] The solid electrolytic capacitor according to [1], further comprising a cathode film including a metal particle layer disposed on the solid electrolyte, wherein the capacitor element comprises a plurality of conductive metal particles.

[20] The solid electrolytic capacitor according to

[19] , wherein the metal particles contain silver.

[21] The solid electrolytic capacitor according to [1], wherein the anode body comprises tantalum.

[22] The solid electrolytic capacitor according to [1], wherein the solid electrolyte comprises a conductive polymer.

[23] The conductive polymer is given by the following formula: [ka] (In the formula, R 7 C is linear or branched. 1 ~C 18 Alkyl alkyl group, C 5 ~C 12 Cycloalkyl groups, C 6 ~C 14 Aryl group, C 7 ~C 18 It is an aralkyl group, or a combination thereof; (q is an integer between 0 and 8) A solid electrolytic capacitor according to

[22] , having a repeating unit.

[24] The solid electrolytic capacitor according to

[23] , wherein the exogenous conductive polymer is poly(3,4-ethylenedioxythiophene) or a derivative thereof.

[25] The solid electrolytic capacitor according to

[22] , wherein the solid electrolyte also comprises polymer counterions.

[26] The solid electrolytic capacitor according to [1], further comprising an external polymer coating disposed on the solid electrolyte and containing prepolymerized conductive polymer particles and a crosslinking agent.

Claims

1. It is a solid electrolytic capacitor, A capacitor element comprising a sintered porous anode, a dielectric disposed on the anode, and a solid electrolyte disposed on the dielectric; Anode lead extending from the front of the capacitor element; Anode terminal electrically connected to the anode lead, and cathode terminal electrically connected to the solid electrolyte; and A casing material that contacts the front surface of the capacitor element and the anode lead, and encloses the capacitor element and the anode lead, wherein the casing material is formed from a curable resinous matrix having a thermal expansion coefficient of about 20 ppm / °C to about 42 ppm / °C at temperatures higher than the glass transition temperature of the resinous matrix, and about 11 ppm / °C or less at temperatures lower than the glass transition temperature of the resinous matrix; Including; The capacitor exhibits an initial equivalent series resistance of approximately 200 milliohms or less at an operating frequency of 100 kHz and a temperature of 23°C, the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 560 hours to the initial equivalent series resistance of the capacitor is approximately 1.3 or less, and the resinous matrix contains epoxy resin alone as the resin, and the epoxy resin contains cresol-novolac epoxy resin, wherein the solid electrolytic capacitor.

2. The solid electrolytic capacitor according to claim 1, wherein the resinous matrix has a glass transition temperature of about 50°C to about 180°C.

3. The solid electrolytic capacitor according to claim 1, wherein the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 750 hours to the initial equivalent series resistance of the capacitor is approximately 2.0 or less.

4. The solid electrolytic capacitor according to claim 1, wherein the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 1,000 hours to the initial equivalent series resistance of the capacitor is approximately 2.0 or less.

5. The solid electrolytic capacitor according to claim 1, wherein the ratio of the equivalent series resistance of the capacitor after exposure to a temperature of 125°C for 1,250 hours to the initial equivalent series resistance of the capacitor is approximately 2.0 or less.

6. The solid electrolytic capacitor according to claim 1, wherein the interface coating covers at least a portion of the anode terminal.

7. The solid electrolytic capacitor according to claim 6, wherein the interface coating also covers at least a portion of the anode lead.

8. The solid electrolytic capacitor according to claim 6, wherein the interface coating comprises a fluoropolymer, a silicone polymer, an organometallic compound, or a combination thereof.

9. The solid electrolytic capacitor according to claim 1, wherein the resinous matrix further comprises an inorganic oxide filler in an amount of about 75% to about 99.5% by weight of the matrix.

10. The solid electrolytic capacitor according to claim 9, wherein the inorganic oxide filler contains silica.

11. The solid electrolytic capacitor according to claim 1, further comprising a cathode coating including a metal particle layer disposed on the solid electrolyte, wherein the metal particle layer includes a plurality of conductive metal particles.

12. The solid electrolytic capacitor according to claim 11, wherein the metal particles contain silver.

13. The solid electrolytic capacitor according to claim 1, wherein the anode body includes tantalum.

14. The solid electrolytic capacitor according to claim 1, wherein the solid electrolyte includes a conductive polymer.

15. The conductive polymer is given by the following formula: 【Chemistry 1】 (In the formula, R ７ is a linear or branched C １ -C １８ alkyl group, C ５ -C １２ cycloalkyl group, C ６ -C １４ aryl group, C ７ -C １８ aralkyl group, or a combination thereof; (q is an integer between 0 and 8) A solid electrolytic capacitor according to claim 14, having a repeating unit.

16. The solid electrolytic capacitor according to claim 15, wherein the exogenous conductive polymer is poly(3,4-ethylenedioxythiophene) or a derivative thereof.

17. The solid electrolytic capacitor according to claim 14, wherein the solid electrolyte also includes polymer pairions.

18. The solid electrolytic capacitor according to claim 1, further comprising an external polymer coating disposed on the solid electrolyte and containing pre-polymerized conductive polymer particles and a crosslinking agent.

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