Low-inductance electrolytic capacitor

Abstract

To provide a capacitor that is capable of exhibiting good electrical properties under various conditions.SOLUTION: An electrolytic capacitor 200 contains: a capacitor element 208 that includes a sintered porous anode body, a dielectric that overlies the anode body, and a solid electrolyte that overlies the dielectric and includes a conductive polymer; multiple exposed anode lead portions 218, 220 that are electrically connected to respective anode terminations 201, 203 and a planar cathode termination 206 that is electrically connected to the solid electrolyte.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 082,055, having a filing date of September 23, 2020, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Decoupling capacitors are often used to manage noise problems in circuit applications. They provide a stable local charge source required for switching and refreshing logic gates used in various digital circuits. However, decoupling capacitors must now be able to operate at lower voltages and higher currents, requiring performance characteristics such as lower equivalent series resistance (ESR), higher capacitance, and lower inductance (or equivalent series inductance (ESL)) within these capacitors to function at the levels required for a variety of applications in today's environment. Particularly as switching speeds in electronic circuit applications increase, the need for lower inductance to improve system performance is becoming a serious limitation. Solid electrolytic capacitors (e.g., tantalum capacitors) are typically fabricated by pressing metal powder (e.g., tantalum) around metal lead wires, sintering the compacted part, anodizing the sintered anode, and then applying a solid electrolyte. Conductive polymers are often used as solid electrolytes due to their advantageous low equivalent series resistance and "non-burn / non-ignition" failure mode. However, while solid electrolytic capacitors offer clear advantages in terms of ESR, they have not previously been able to withstand high frequency applications or exhibit the low inductance required for decoupling and fast switching. Therefore, solid electrolytic capacitors with improved performance are currently needed. Summary of the Invention [Means for solving the problem]

[0003] According to one embodiment of the present invention, there is disclosed a solid electrolytic capacitor comprising: a capacitor element including a sintered anode body, a dielectric covering the anode body, and a solid electrolyte covering the dielectric, wherein the solid electrolyte comprises a conductive polymer, and the capacitor element defines opposing first and second ends and opposing upper and lower surfaces; a first exposed anode lead portion extending from the first end of the capacitor element; a first anode terminal electrically connected to the first exposed anode lead portion; a second exposed anode lead portion extending from the second end of the capacitor element; a second anode terminal spaced from the first anode terminal and electrically connected to the second exposed anode lead portion; and a planar cathode terminal positioned adjacent to the lower surface of the capacitor element and electrically connected to the solid electrolyte.

[0004] Other features and aspects of the present invention are described in greater detail below.

[0005] A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the accompanying drawings. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1A is a side view of one embodiment of an anode body according to the present invention.

[0007] FIG. 1B is a side view of one embodiment of an anode body according to the present invention.

[0008] FIG. 1C is a side view of one embodiment of an anode body according to the present invention. [Figure 2]FIG. 1 is a side view of one embodiment of a capacitor according to the present invention. [Figure 3] FIG. 3 is a top view of the capacitor of FIG. 2. [Figure 4] FIG. 2 is a diagram showing an exemplary equivalent circuit used in Example 1. [Figure 5] 1 is a graph showing impedance versus frequency for Example 1 compared to a standard capacitor. [Figure 6] 1 is a graph showing modeled and measured S21 parameters over a wide range of frequencies for Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] It should be understood by those skilled in the art that this description is merely a description of exemplary embodiments and is not intended as a limitation of the broader aspects of the invention, which are illustratively embodied therein.

[0010] Generally speaking, the present invention is directed to a capacitor capable of exhibiting good electrical properties under a variety of conditions. The capacitor includes a capacitor element including a sintered porous anode body, a dielectric covering the anode body, and a solid electrolyte covering the dielectric and including a conductive polymer. The capacitor element has opposing first and second ends and opposing upper and lower surfaces. The capacitor also includes a plurality of anode lead portions electrically connected to respective anode terminations, and a planar cathode termination positioned adjacent the lower surface of the capacitor element and electrically connected to the solid electrolyte.

[0011] Through selective control over the specific configuration of the capacitor elements and terminals, the resulting capacitors can exhibit low ESL values, such as about 1 nanohenry or less, in some embodiments about 750 picohenry or less, in some embodiments about 350 picohenry or less, in some embodiments about 1 femtohenry to about 100 picohenry, and in some embodiments about 50 femtohenry to about 10 picohenry. Low ESL values can also be characterized by low impedance values, which reflect parasitic inductance. Impedance can be, for example, about 1 ohm or less, in some embodiments about 0.8 ohms or less, in some embodiments about 0.6 ohms or less, and in some embodiments about 1 megaohm to about 0.3 ohms. Such low ESL (e.g., impedance) can also be exhibited over a wide range of frequencies, such as from 1 kHz to about 100 MHz, in some embodiments about 100 kHz to about 100 MHz, and even in some embodiments about 1 MHz to about 100 MHz. Minimizing parasitic inductance over a wide range of frequencies can contribute to good performance, especially good decoupling performance, especially under fast transient conditions. In addition to exhibiting low ESL values, the capacitors can also exhibit low ESR values, such as about 800 megaohms or less, in some embodiments about 600 megaohms or less, in some embodiments about 500 megaohms or less, in some embodiments about 350 megaohms or less, in some embodiments about 0.01 to about 250 megaohms, and in some embodiments about 0.1 to about 150 megaohms, when measured at an operating frequency of 100 kHz and a temperature of 23° C.

[0012] Notably, the low ESR and ESL values may remain stable even at high temperatures and / or high humidity levels. For example, the capacitors may be maintained at temperatures above about 80°C, in some embodiments from about 85°C to about 180°C, and in some embodiments from about 850°C to about 150°C (e.g., about 85°C, 105°C, 125°C, or 150°C), and / or at temperatures above about 40%, in some embodiments from about 45%, in some embodiments from about 50%, and in some embodiments from about 70% or more (e.g., about 85% to 100%) for significant periods of time. % relative humidity levels. The relative humidity may be determined, for example, according to ASTM E337-02, Method A (2007). The period of exposure to high temperature and / or humidity levels may be about 100 hours or more, in some embodiments, from about 150 hours to about 3,000 hours, and in some embodiments, from about 200 hours to about 2,500 hours (e.g., 250, 500, 750, or 1,000 hours). For example, the ESR of a capacitor after 500 hours of exposure to high temperatures (e.g., about 85° C.) and / or high humidity levels (e.g., about 85%) can be about 1,500 megaohms or less, in some embodiments about 1,000 megaohms or less, in some embodiments about 800 megaohms or less, in some embodiments about 600 megaohms or less, in some embodiments about 0.01 to about 500 megaohms, and in some embodiments about 0.1 to about 200 megaohms, when measured at an operating frequency of 100 kHz and a temperature of 23° C. Similarly, the ratio of the ESR of a capacitor after 500 hours of exposure to high temperatures (e.g., about 85° C.) and / or high humidity levels (e.g., about 85%) to the capacitor's initial DCL (e.g., about 23° C.) can be about 10 or less, in some embodiments about 5 or less, in some embodiments about 3 or less, in some embodiments about 2 or less, and in some embodiments about 0.9 to about 1.5.

[0013] The resulting capacitor's ability to achieve a combination of low ESL and ESR values makes it uniquely positioned to provide robust broadband decoupling and fast switching. For example, a single capacitor according to the present invention may be used to replace multiple low capacitance or limited frequency decoupling capacitors, thereby allowing the capacitor to utilize less space, such as having a smaller height, further improving miniaturization.

[0014] Capacitors can exhibit excellent DC power filtering, as exemplified by excellent attenuation over a wide range of frequencies. As is known in the art, insertion loss is a measure of power transfer between two terminals, where an increase in power indicates gain and a decrease in power between two terminals indicates attenuation. Thus, the present capacitors exhibit high attenuation over a wide frequency range, allowing for good filtering of a wide range of frequencies. For example, the present capacitors exhibit approximately 15 dB or greater attenuation, in some embodiments, about 25 dB or greater, in some embodiments, about 30 dB or greater, in some embodiments, about 35 dB to about 70 dB, and in some embodiments, about 50 dB to about 70 dB. 21 Such attenuation may be exhibited over a wide frequency range. For example, at low frequencies ranging from about 0.1 MHz to about 500 MHz, and in some cases from about 1 MHz to about 100 MHz, the capacitors may exhibit attenuation (S) of about 40 dB or greater, in some embodiments about 50 dB or greater, in some embodiments about 55 dB or greater, and in some embodiments about 60 dB to about 70 dB. 21 Similarly, at high frequencies ranging from about 500 MHz to about 10 GHz, and in some cases from about 1 GHz to about 5 GHz, the present capacitors can exhibit attenuation (S) of about 20 dB or greater, in some embodiments about 25 dB or greater, in some embodiments about 30 dB or greater, and in some embodiments about 30 dB to about 60 dB. 21parameter). Among other things, such attenuation facilitates the use of the capacitor in DC power filtering applications. Furthermore, the capacitor can perform consistently over a wide temperature range. For example, in one embodiment, the capacitor can vary by about 5 dB or less over a large temperature range, such as a temperature change of about 25° C. or more, in some embodiments, about 50° C. or more, and in some embodiments, about 70° C. or more.

[0015] The capacitors may also exhibit other beneficial electrical properties. For example, the capacitors may exhibit low leakage current ("DCL") over a variety of conditions. Furthermore, the capacitors may exhibit low leakage current ("DCL") over a specified period of time (e.g., from about 30 minutes to about 20 hours, in some embodiments). may exhibit a DCL of about 10 microamperes ("μA") or less, in some embodiments, about 5 μA or less, in some embodiments, about 1 μA or less, and in some embodiments, about 0.01 to about 5 μA, after being subjected to an applied voltage (e.g., 16 volts) at a temperature of about 23° C. for about 1 hour to about 18 hours, and in some embodiments, about 4 hours to about 16 hours. In one embodiment, after exposure to high temperatures (e.g., about 85° C.) and / or high humidity levels (e.g., about 85%) for 500 hours, the DCL of the capacitor may be about 10 μA or less, in some embodiments, about 8 μA or less, in some embodiments, about 6 μA or less, and in some embodiments, about 0.1 to about 5 μA. Similarly, the ratio of the DCL of the capacitor after 500 hours of exposure to high temperatures (e.g., about 85°C) and / or high humidity levels (e.g., about 85%) to the initial DCL (e.g., about 23°C) of the capacitor can be about 20 or less, in some embodiments about 15 or less, in some embodiments about 10 or less, in some embodiments about 5 or less, and in some embodiments about 0.9 to about 4. The capacitor also has a DCL of about 30 nanofarads per square centimeter ("nF / cm") when measured at a frequency of 120 Hz and a temperature of 23°C. 2 ") or greater, in some embodiments, about 100 nF / cm 2 In some embodiments, the2 and in some embodiments, from about 400 to about 2,000 nF / cm 2 The capacitor may exhibit a dry capacitance of about 10 μF to about 1,000 μF, in some embodiments, about 50 μF to about 500 μF, and in some embodiments, about 60 μF to about 250 μF. Similar to the DCL and ESR values, the capacitance may also remain stable at the above-mentioned high temperature and / or high humidity level ranges. In one embodiment, for example, the ratio of the capacitance value of the capacitor after 500 hours of exposure to a high temperature (e.g., about 85°C) and / or a high humidity level (e.g., about 85%) to the capacitor's initial capacitance value (e.g., about 23°C) may be about 3.0 or less, in some embodiments, about 2.0 or less, in some embodiments, about 1.8 or less, in some embodiments, about 1.6 or less, and in some embodiments, about 0.9 to about 1.3.

[0016] It is also believed that the dissipation factor of the present capacitors can be maintained at a relatively low level. The dissipation factor generally refers to the loss that occurs in a capacitor and is usually expressed as a percentage of ideal capacitor performance. For example, the dissipation factor of the present capacitors, when measured at a frequency of 120 Hz, is typically about 250% or less, in some embodiments about 200% or less, and in some embodiments, from about 1% to about 180%.

[0017] Various embodiments of the invention will now be described in greater detail.

[0018] I. Capacitor element A. Anode body The anode body is formed from a powder containing a valve metal (i.e., a metal capable of being oxidized) or a compound based on a valve metal, such as tantalum, niobium, aluminum, hafnium, titanium, alloys thereof, oxides thereof, or nitrides thereof. The specific charge of this powder is typically from about 5,000 to about 800,000 microfarads per gram, depending on the desired application. * Volts (µF *For example, in certain embodiments, the capacitance varies from about 100,000 to about 600,000 μF. * V / g, in some embodiments, from about 120,000 to about 500,000 μF * V / g, and in some embodiments, from about 150,000 to about 400,000 μF * Highly charged powders may be used, having a specific charge of about 5,000 to about 100,000 μF / g. * V / g, in some embodiments, from about 8,000 to about 90,000 μF * V / g, and in some embodiments, from about 10,000 to about 80,000 μF * Low charge powders may be used having a specific charge of 0.05 V / g. As is known in the art, the specific charge can be determined by multiplying the capacitance by the anodization voltage used and then dividing this product by the weight of the anodized electrode body.

[0019] In one embodiment, for example, a powder is formed from tantalum. If desired, a reduction process can be used in which a tantalum salt (e.g., potassium fluorotantalate (KTaF), sodium fluorotantalate (NaTaF), tantalum pentachloride (TaCl), etc.) is reacted with a reducing agent. The reducing agent may 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. In one embodiment, for example, a tantalum salt (e.g., TaCl) 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 that can be reduced in the presence of a gaseous reducing agent (e.g., hydrogen). Further details of such reduction reactions may be found in WO 2014 / 199480 to Maeshima et al. After reduction, the product can be cooled, crushed, and washed to form a powder.

[0020] The powder may be a free-flowing, finely divided powder containing primary particles. The primary particles of the powder generally have a median size (D50) of about 5 to about 250 nanometers, in some embodiments, about 10 to about 200 nanometers, and in some embodiments, about 20 to about 150 nanometers, as determined using a laser particle size distribution analyzer from BECKMAN COULTER Corporation (e.g., LS-230), optionally after subjecting the particles to 70 seconds of ultrasonic vibration. The primary particles typically have a three-dimensional granular shape (e.g., nodular or angular). Such particles typically have a relatively low "aspect ratio," defined as 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, in some embodiments about 3 or less, and in some embodiments, about 1 to about 2. In addition to primary particles, the powder may also contain other types of particles, such as secondary particles formed by aggregation (or agglomeration) of primary particles. Such secondary particles may have a median size (D50) of from about 1 to about 500 micrometers, and in some embodiments, from about 10 to about 250 micrometers.

[0021] Agglomeration of the particles may be achieved by heating the particles and / or by using a binder. For example, agglomeration may be achieved at a temperature of from about 0°C to about 40°C, in some embodiments from about 5°C to about 35°C, and in some embodiments from about 15°C to about 30°C. Similarly, suitable binders can include, for example, poly(vinyl butyral); poly(vinyl acetate); poly(vinyl alcohol); poly(vinylpyrrolidone); cellulose polymers such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and methylhydroxyethyl cellulose; 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 fluoro-olefin copolymers; acrylic polymers such as sodium polyacrylate, poly(lower alkyl acrylates), poly(lower alkyl methacrylates), and copolymers of lower alkyl acrylates and methacrylates; and fatty acids and waxes such as stearic acid and other soapy fatty acids, vegetable waxes, microcrystalline waxes (refined paraffins), and the like. If desired, the powder may also be doped with a sinter retardant in the presence of a dopant such as acidic water (e.g., phosphoric acid). The amount of dopant added depends in part on the surface area of the powder, but is typically present in an amount of about 200 parts per million ("ppm") or less. The dopant may be added before, during, and / or after agglomeration. The powder may also contain one or more deoxidizers. A treatment may be performed. For example, the powder may be exposed to a getter material (e.g., magnesium), such as those described in U.S. Pat. No. 4,960,471. The temperature at which the powder is deoxidized can vary, but typically ranges from about 700°C to about 1,600°C, in some embodiments from about 750°C to about 1,200°C, and in some embodiments from about 800°C to about 1,000°C. The total time for the deoxidation treatment can range from about 20 minutes to about 3 hours.

[0022] The resulting powder has certain characteristics that enhance its ability to form capacitor nodes. For example, the powder may have a density of about 0.5 to about 10.0 m. 2 / g, in some embodiments, from about 0.7 to about 5.0 m 2 / g, and in some embodiments, from about 2.0 to about 4.0 m 2 Similarly, the bulk density of the powder is about 0.1 to about 0.8 grams per cubic centimeter (g / cm 3 ), in some embodiments, from about 0.2 to about 0.6 g / cm 3 and in some embodiments, from about 0.4 to about 0.6 g / cm 3 It could be.

[0023] Once formed, the powder is then typically compressed or pressed to form pellets using any conventional powder pressing device. For example, a press mold may be used, which is a single-station compression press including a die and one or more punches. Alternatively, anvil-type compression press molds may be used, which use only a die and a single lower punch. Single-station compression press molds are available in several basic types, such as single-action, double-action, floating die, moving platen, opposed ram, axial, impact, hot press, stamping, or sizing, with various capabilities, such as cam, toggle / knuckle, and eccentric / crank presses. Powders are typically compressed at a density of about 0.5 to about 20 g / cm. 3 In some embodiments, from about 1 to about 15 g / cm 3and in some embodiments, from about 2 to about 10 g / cm 3 It is pressed to a density of

[0024] The binder may be removed after pressing by heating the pellet under vacuum at a certain temperature (e.g., about 150°C to about 500°C) for several minutes. Alternatively, the binder may also be removed by contacting the pellet with an aqueous solution, such as that described in U.S. Pat. No. 6,197,252 to Bishop et al. After binder removal, the anode body may be subjected to an optional deoxidation process. In one embodiment, for example, the deoxidation process includes exposing the anode body to a getter material (e.g., magnesium, titanium, etc.) capable of removing oxygen from the anode body by chemical reaction, adsorption, etc. More specifically, the anode body is first inserted into a closure (e.g., a tantalum box) that also contains the getter material. The atmosphere within this closure is typically an inert atmosphere (e.g., argon gas). To initiate deoxidation, the atmosphere within the closure is heated to a temperature sufficient to melt and / or vaporize the getter material and deoxidize the anode body. The temperature may vary depending on the specific charge of the anode powder, but typically ranges from about 700°C to about 1,200°C, in some embodiments from about 750°C to about 1,100°C, and in some embodiments from about 800°C to about 1,000°C. The total deoxidation time may range from about 20 minutes to about 3 hours. This may be done in one or more steps. Once deoxidation is complete, the getter material typically vaporizes and forms a deposit on the walls of the closure. To ensure removal of the getter material, the anode body may also be subjected to one or more acid leaching steps, such as with solutions of nitric acid, hydrofluoric acid, hydrogen peroxide, sulfuric acid, water, or the like, or combinations thereof.

[0025] The resulting anode body has a relatively low oxygen content. For example, the anode body may have about 5,500 ppm or less of oxygen, in some embodiments about 5,000 ppm or less of oxygen, and in some embodiments, about 500 to about 4,500 ppm of oxygen. The oxygen content can be measured with a LECO oxygen analyzer and is based on the natural oxygen content of the tantalum surface. This includes oxygen in the oxide and bulk oxygen in the tantalum particles. The bulk oxygen content is controlled by the periodicity of the tantalum crystal lattice, which increases linearly with increasing oxygen content in tantalum until the solubility limit is reached. This method is described by Pozdeev-Freeman et al., "Critical Oxygen Content in Porous Anodes of Solid Tantalum Capacitors," Journal of Materials Science: Materials in Electronics, Vol. 9 (1998), pp. 309-311, where X-ray diffraction analysis (XRDA) was used to measure the periodicity of the tantalum crystal lattice. The oxygen in sintered tantalum anodes may be limited to a thin native surface oxide, while the bulk of the tantalum is substantially oxygen-free.

[0026] After optional deoxidation, the anode body can be sintered to form a porous, monolithic mass. The anode body is typically sintered at temperatures between about 700°C and about 1,600°C, in some embodiments, between about 800°C and about 1,500°C, and in some embodiments, between about 900°C and about 1,200°C, for a period of about 5 minutes to about 100 minutes, and in some embodiments, between about 8 minutes and about 15 minutes. This may be done in one or more steps. If desired, sintering may be carried out in an atmosphere that limits the transfer of oxygen atoms to the anode. For example, sintering may be carried out in a vacuum, an inert gas, or a reducing atmosphere such as hydrogen. The reducing atmosphere may have a pressure of about 10 Torr to about 2,000 Torr, in some embodiments, between about 100 Torr and about 1,000 Torr, and in some embodiments, between about 100 Torr and about 930 Torr. Mixtures of hydrogen and other gases (e.g., argon or nitrogen) may also be used. As noted above, sintering of the anode body generally occurs after any optional deoxidation. However, it should be understood that the anode body may also be subjected to one or more pre-sintering steps prior to oxidation to help achieve the desired degree of green strength for the deoxidation step. Such pre-sintering steps may be performed under the same or different conditions as the sintering step performed after deoxidation. For example, pre-sintering may be performed in one or more steps at temperatures of about 700°C to about 1,600°C, in some embodiments about 800°C to about 1,500°C, and in some embodiments about 900°C to about 1,200°C, for about 5 minutes to about 100 minutes, and in some embodiments about 8 minutes to about 15 minutes. Pre-sintering may also be performed in a reducing atmosphere, such as a vacuum, an inert gas, or hydrogen, as described above.

[0027] As noted above, the capacitor also contains multiple anode lead portions electrically connected to individual anode terminals. The anode lead portions may be formed as portions of a single anode lead (e.g., opposing ends) or as separate anode lead portions. The anode leads may have any desired shape and size and may be in the form of a wire, sheet, or the like. Typically, the anode leads extend longitudinally from the anode body and are formed from any conductive material, such as tantalum, niobium, aluminum, hafnium, titanium, and their conductive oxides and / or nitrides. Connection of the leads to the anode body can be accomplished using any known technique, such as by welding one or more leads to the body or by embedding one or more anode leads within the anode body during formation (e.g., before compaction and / or sintering).

[0028] 1A, one embodiment of an anode body 10 is shown having a first anode lead 12 with a recessed portion 24 positioned within the anode body, and an exposed first anode lead portion 26 extending from a first end 16 of the anode body 10. Similarly, a second exposed anode lead portion 14 is connected (e.g., by a bond 20) to a second end 18 of the anode body 10. As shown in FIG. 1A, the second exposed anode lead portion 14 is formed as part of a separate second anode lead extending from the second end 18 of the anode body. Of course, as shown in FIG. 1C, the first exposed anode lead portion 26 may be formed as part of a separate second anode lead. The first exposed anode lead portion 26 and the second exposed anode lead portion 14 may also be defined by opposing portions of a single continuous anode lead 22 extending from both ends 16 and 18 of the anode body 10. Regardless, it is usually desirable for the exposed anode lead portions to extend from opposing ends of the anode body generally in the same plane. Referring again to FIG. 1A, a gap may optionally exist between the inset end of the first anode lead and the end of the anode body, such that an electrical connection between the first and second anode leads is provided through the sintered anode body. In FIG. 1A, for example, this gap can be defined as the distance "t" between end 18 of the anode body and inset end 28 of the anode lead, which distance typically ranges from about 0.2 to about 5 millimeters, in some embodiments from about 0.4 to about 4 millimeters, and in some embodiments from about 0.5 to about 2 millimeters. The length "l" of the anode can likewise range from about 1.5 to about 6 millimeters, and in some embodiments, from about 2 to about 5 millimeters. In such embodiments, the ratio of distance "t" to length "l" can also range from about 0.1 to about 0.8, in some embodiments, from about 0.2 to about 0.7, and in some embodiments, from about 0.3 to about 0.6.

[0029] 1B, in which an anode body 10 has a first anode lead 12 with an inset portion 24 positioned within the anode body and an exposed first anode lead portion 26 extending from a first end 16 of the anode body 10. A second anode lead 14 with an inset portion 32 positioned within the anode body and an exposed second anode lead portion 34 extending from a second end 18 of the anode body 10. Thus, in this embodiment, the need for a welded portion of the second anode lead is not required. As with the above embodiment, a gap "t" may optionally exist between the inset ends of the first anode lead and the inset ends of the second anode lead, which can be within the ranges described above.

[0030] B. Dielectric The anode body is coated with a dielectric. The dielectric can be formed by anodizing the sintered anode body ("anodization"), resulting in a dielectric layer formed on and / or within the anode body. For example, a tantalum (Ta) anode can be anodized to tantalum pentoxide (TaO). Typically, anodization is performed by first applying a solution to the anode, such as by immersing the anode in the electrolyte. A solvent such as water (e.g., deionized water) is commonly used. To improve ionic conductivity, compounds capable of dissociating in the solvent to form ions can be used. Examples of such compounds include, for example, acids, such as those described below with respect to the electrolyte. For example, an acid (e.g., phosphoric acid) can comprise about 0.01% to about 5% by weight of the anodization solution, in some embodiments, about 0.05% to about 0.8% by weight, and in some embodiments, about 0.1% to about 0.5% by weight. Blends of acids can also be used if desired.

[0031] A current may be applied to the anodization solution to form the dielectric layer. The thickness of the dielectric layer is controlled by the value of the formation voltage. For example, the power supply may initially be set in constant current mode until the required voltage is reached. After this, the power supply may be switched to a low voltage mode to ensure the desired dielectric thickness is formed over the entire surface of the anode. Of course, other known methods, such as pulse or stepwise constant voltage methods, may also be used. The formation voltage used during anodization is generally about 20 volts or greater, in some embodiments about 30 volts or greater, in some embodiments about 35 volts or greater, and in some embodiments about 35 to about 70 volts, at a temperature of about 10°C or greater, in some embodiments about 20°C to about 200°C, and in some embodiments about 30°C to about 100°C. The resulting dielectric layer is formed on the surface of the anode and within the pores of the anode. It is possible.

[0032] By selectively controlling the particular method by which the anode body is formed, the resulting capacitor can exhibit high dielectric strength, which can improve capacitance stability. "Dielectric strength" generally refers to the ratio of the capacitor's "breakdown voltage" (the voltage at which the capacitor breaks down, measured in volts "V") to the dielectric thickness (measured in nanometers "nm"). Capacitors typically exhibit a dielectric strength of about 0.4 V / nm or greater, in some embodiments about 0.45 V / nm or greater, in some embodiments about 0.5 V / nm or greater, in some embodiments about 0.55 to about 1 V / nm, and in some embodiments about 0.6 to about 0.9 V / nm. The capacitor may exhibit a relatively high breakdown voltage, such as about 30 volts or more, in some embodiments, about 35 volts or more, in some embodiments, about 50 volts or more, in some embodiments, about 65 volts or more, in some embodiments, about 85 volts or more, in some embodiments, about 90 volts or more, in some embodiments, about 95 volts or more, and in some embodiments, about 100 volts to about 300 volts, as determined by increasing the applied voltage in 3 volt increments until the leakage current reaches 1 mA. The thickness of the dielectric may generally vary depending on the specific location of the anode body, but the "dielectric thickness" for purposes of determining dielectric strength is generally considered to be the maximum thickness of the dielectric, which typically ranges from about 50 to about 500 nm, in some embodiments, from about 80 to about 350 nm, and in some embodiments, from about 100 to about 300 nm. Dielectric thickness can be measured using a Zeiss Sigma FESEM at 20,000x to 50,000x magnification, where the sample is prepared by cutting the finished section in a plane perpendicular to the longest dimension of the finished section, and the thickness is measured where the cut is perpendicular from the dielectric layer.

[0033] C. Precoat layer Although by no means necessary, a precoat layer can optionally overly the dielectric comprising an organometallic compound. The organometallic compound can have the general formula:

[0034] [ka]

[0035] wherein M is an organometallic atom such as silicon or titanium; R1, R2, and R3 are independently alkyl (e.g., methyl, ethyl, propyl, etc.) or hydroxyalkyl (e.g., hydroxymethyl, hydroxyethyl, hydroxypropyl, etc.), wherein at least one of R1, R2, and R3 is hydroxyalkyl; n is an integer from 0 to 8, in some embodiments, from 1 to 6, and in some embodiments, from 2 to 4 (e.g., 3); and X is an organic or inorganic functional group such as glycidyl, glycidyloxy, mercapto, amino, vinyl, etc.

[0036] In certain embodiments, R1, R2, and R3 may be hydroxyalkyl (e.g., OCH3), however, in other embodiments, R1 may be alkyl (e.g., CH3) and R2 and R3 may be hydroxyalkyl (e.g., OCH3).

[0037] Additionally, in certain embodiments, M can be silicon, such that 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, Glycidoxymethyl-tripropoxysilane, Glycidoxymethyltributoxysilane, β-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, β-glycidoxyethyl-tripropoxysilane, β-glycidoxyethyl-tributoxysilane, β-glycidoxyethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, α-glycidoxyethyltripropoxysilane, α-glycidoxyethyltributoxysilane , γ-glycidoxypropyl-trimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyl-tripropoxysilane, γ-glycidoxypropyltributoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyl-triethoxysilane, β-glycidoxypropyltripropoxysilane, α-glycidoxypropyltributoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, α-glycidoxypropyltriethoxysilane glycidoxypropyl-tripropoxysilane, α-glycidoxypropyltributoxysilane, γ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltrippropoxysilane, δ-glycidoxybutyl-tributoxysilane, δ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, γ-glycidoxybutyltrippropoxysilane, γ-propoxybutyltributoxysilane, δ-glycidoxybutyl-trimethoxysilane,δ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltripropoxysilane, α-glycidoxybutyltrimethoxysilane, α-glycidoxybutyltriethoxysilane, α-glycidoxybutyltripropoxysilane, α-glycidoxybutyltributoxysilane, (3,4-epoxycyclohexyl)methyltrimethoxysilane, (3,4-epoxycyclohexyl)methyltriethoxysilane, (3,4-epoxycyclohexyl)methyltripropoxysilane, (3,4-epoxycyclohexyl)methyltributoxysilane, (3,4-epoxycyclohexyl)ethyltrimethoxysilane, (3,4-epoxycyclohexyl)ethyltriethoxysilane, Examples of the epoxy cyclohexyl include (3,4-epoxycyclohexyl)ethyl tripropoxysilane, (3,4-epoxycyclohexyl)ethyl tributoxysilane, (3,4-epoxycyclohexyl)propyl trimethoxysilane, (3,4-epoxycyclohexyl)propyl triethoxysilane, (3,4-epoxycyclohexyl)propyl tripropoxysilane, (3,4-epoxycyclohexyl)propyl tributoxysilane, (3,4-epoxycyclohexyl)butyl trimethoxysilane, (3,4-epoxycyclohexyl)butyl triethoxysilane, (3,4-epoxycyclohexyl)butyl tripropoxysilane, and (3,4-epoxycyclohexyl)butyl tributoxysilane.

[0038] The particular method by which the precoat layer is applied to the capacitor body can vary as desired. In one particular embodiment, the compound is dissolved in an organic solvent and applied to the part as a solution by screen printing, dipping, electrophoretic coating, spraying, or the like. The organic solvent can vary, but is typically an alcohol, such as methanol or ethanol. The organometallic compound can comprise from about 0.1% to about 10% by weight of the solution, in some embodiments, from about 0.2% to about 8% by weight, and in some embodiments, from about 0.5% to about 5% by weight. The solvent can comprise from about 90% to about 99.9% by weight of the solution, in some embodiments, from about 9 It can similarly comprise from 2% to about 99.8% by weight, and in some embodiments, from about 95% to about 99.5% by weight. Once applied, the part can then be dried to remove the solvent therefrom and form a precoat layer containing the organometallic compound.

[0039] D. Solid electrolyte The solid electrolyte covers the dielectric and optional precoat. The total thickness of the solid electrolyte is typically about 1 to about 50 μm, and in some embodiments, about 5 to about 20 μm. The solid electrolyte typically includes one or more layers of a conductive polymer (e.g., polyheterocycles such as polypyrroles and polythiophenes, polyanilines, polyacetylenes, poly-p-phenylenes, polyphenolates, etc.). Thiophene polymers are particularly suitable for use in the solid electrolyte. In certain embodiments, for example, thiophene polymers having repeating units of the following formula (I) can be used:

[0040] [ka]

[0041] In the formula, R7 is a linear or branched C1-C 18 Alkyl radicals (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 radicals (e.g., cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, etc.); C6-C 14 Aryl radicals (e.g., phenyl, naphthyl, etc.); C7-C 18aralkyl radicals (e.g., benzyl, o-, m-, p-tolyl, 2,3-, 2,4-, 2,5-, 2-6, 3-4-, 3,5-xylyl, mesityl, etc.), and q is an integer from 0 to 8, in some embodiments, from 0 to 2, and in one embodiment, is 0.

[0042] Particularly suitable thiophene polymers are those in which "D" is an optionally substituted C2-C3 alkylene radical. For example, the polymer can include optionally substituted poly(3,4-ethylenedioxythiophene) or a derivative thereof having repeating units of the following general formula (II):

[0043] [ka]

[0044] In one particular embodiment, "q" is 0. One commercially suitable example of 3,4-ethylenedioxythiophene is available from Heraeus under the name Clevios™ M. Other suitable monomers are also described in U.S. Pat. Nos. 5,111,327 to Blohm et al. and 6,635,729 to Groenendaal et al. Derivatives of these monomers, e.g., dimers or trimers of the above monomers, may also be used. Higher molecular derivatives, i.e., tetramers, pentamers, etc., of the monomers are suitable for use in the present invention. Derivatives may be composed of the same or different monomer units and may be used in pure form or in mixtures with each other and / or with the monomers. Oxidized or reduced forms of these precursors may also be used.

[0045] To form a polymer, the precursor monomers may be polymerized (e.g., chemically polymerized) in the presence of an oxidation catalyst. The oxidation catalyst typically contains a transition metal cation, such as iron(III), copper(II), chromium(VI), cerium(IV), manganese(IV), manganese(VII), or ruthenium(III) cation. A dopant may also be used to provide an excess charge to the conductive polymer and stabilize the polymer's conductivity. The dopant typically contains an inorganic or organic anion, such as a sulfonic acid ion (e.g., p-toluenesulfonate ion). In certain embodiments, the oxidation catalyst has both catalytic and doping functions, in that it contains a cation (e.g., a transition metal) and an anion (e.g., a sulfonic acid). For example, the oxidation catalyst can be a transition metal salt containing an iron(III) cation, such as an iron(III) halide (e.g., FeCl) or an iron(III) salt of another inorganic acid (e.g., Fe(ClO) or Fe(SO)), as well as organic acids and iron(III) salts of inorganic acids containing organic radicals. Examples of iron(III) salts of inorganic acids with organic radicals include, for example, C1-C 20 Iron(III) salts of sulfate monoesters of alkanols (e.g., iron(III) salt of lauryl sulfate) are also included. Similarly, examples of iron(III) salts of organic acids include, for example, C1-C 20 Iron(III) salts of alkanesulfonic acids (e.g., methane, ethane, propane, butane, or dodecanesulfonic acid); Iron(III) salts of aliphatic perfluorosulfonic acids (e.g., trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid); Aliphatic C1-C 20 Iron(III) salts of carboxylic acids (e.g., 2-ethylhexylcarboxylic acid); Iron(III) salts of aliphatic perfluorocarboxylic acids (e.g., trifluoroacetic acid or perfluorooctanoic acid); C1-C 20Iron(III) salts of aromatic sulfonic acids (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid) optionally substituted with alkyl groups; iron(III) salts of cycloalkanesulfonic acids (e.g., camphorsulfonic acid); etc. Mixtures of these above iron(III) salts may also be used. Iron(III)-p-toluenesulfonate, iron(III)-o-toluenesulfonate, and mixtures thereof are particularly preferred. One commercially available suitable example of iron(III)-p-toluenesulfonate is available from Heraeus under the name Clevios™ C.

[0046] The oxidation catalyst and precursor monomer may be applied sequentially or together to initiate the polymerization reaction. For example, the monomer may be first mixed with the oxidation catalyst to form a precursor solution. In certain embodiments, a less-than-stoichiometric amount of oxidation catalyst may be used to help slow the polymerization of the monomer, producing shorter oligomers than would be produced if fully polymerized into a polymer, allowing for better penetration into high-specific-charge powders. For example, when the monomer comprises a thiophene monomer (e.g., 3,4-ethylenedioxythiophene), the typically required molar ratio used to polymerize the monomer is about 1 mole of monomer to 18 moles of oxidation catalyst. However, there may be less than 18 moles of oxidation polymerization catalyst in the polymerization solution per mole of monomer (e.g., 3,4-ethylenedioxythiophene), e.g., about 15 moles or less, in some embodiments, about 4 to about 12 moles, and in some embodiments, about 5 to about 10 moles.

[0047] In addition to the monomer, oxidation catalyst, and optional dopant, the polymerization solution may also contain other components, such as one or more solvents. In particular, suitable solvents can include, for example, water, alcohols (e.g., methanol, ethanol, n-propanol, iso-propanol, and butanol); 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); triglycerides; ketones; esters (e.g., ethyl acetate, butyl acetate, diethylene glycol ether acetate, and methoxypropyl acetate); amides (e.g., dimethylformamide, dimethylacetamide, dimethylcapryl / capric fatty acid amide, and N-alkylpyrrolidone); nitriles (e.g., acetonitrile, propionitrile, butyronitrile, and benzonitrile); sulfoxides or sulfones (e.g., dimethyl sulfoxide (DMSO) and sulfolane), and the like, and mixtures of any of the above (e.g., water and alcohol).

[0048] The polymerization solution is typically maintained at a relatively low temperature, such as about −20° C. to about 50° C., in some embodiments, about −15° C. to about 30° C., and in some embodiments, about −10° C. to about 10° C., during the reaction. The solution can be applied to the anode body using any suitable application technique known in the art, such as screen printing, dipping, electrophoretic coating, and spraying. Regardless of the application technique used, the monomers present on the anode body generally begin to react once to form a polymer layer. The period during which the monomers are allowed to react on the anode body is typically long enough to allow good impregnation of the polymer into the small pores of the high specific charge powder. In most embodiments, for example, this period (the “impregnation time”) is about 1 minute or longer, in some embodiments, about 1.5 minutes or longer, and in some embodiments, about 2 to about 5 minutes. After the reaction, the resulting conductive polymer layer can be contacted with a washing solution to remove various by-products, excess catalyst, and the like. The period of time during which the washing solution is allowed to contact the conductive polymer layer ("washing time") is typically long enough to ensure that by-products, excess catalyst, etc., can be adequately removed from the small pores of the high specific charge powder. The washing period can be, for example, about 25 minutes or more, in some embodiments, about 30 minutes or more, and in some embodiments, about 45 minutes to about 90 minutes. During this period, washing can be performed in a single step or multiple steps, with the total time for each step being within the ranges described above. The washing solution can vary as desired, but typically can be one or more solvents (e.g., water, alcohol, etc.) and, optionally, a dopant, such as those described above.

[0049] Once washed, the conductive polymer layer may be dried, typically at a temperature of about 15°C or higher, in some embodiments, about 20°C or higher, and in some embodiments, from about 20°C to about 80°C. The polymer layer may also be repaired after formation. Repair may occur after each application of a conductive polymer layer, or after the entire application of the conductive polymer coating. In some embodiments, the conductive polymer may be repaired by immersing the anode body in an electrolyte solution and then applying a constant voltage to the solution until the current drops to a preselected level. If desired, such repair may be performed in multiple steps. For example, the electrolyte solution may be a dilute solution of monomer, catalyst, and dopant in an alcohol solvent (e.g., ethanol).

[0050] In the above process, the conductive polymer is generally formed "in situ" on the anode body. Of course, this is by no means necessary. In other embodiments, for example, the conductive polymer may be prepolymerized. In one embodiment, for example, a prepolymerized polymer is an inherently conductive polymer having a positive charge located on the backbone that is at least partially offset by anions covalently attached to the polymer. Such polymers can have, for example, a relatively high specific conductivity in the dry state of about 1 Siemens per centimeter ("S / cm") or greater, in some embodiments about 10 S / cm or greater, in some embodiments about 25 S / cm or greater, in some embodiments about 40 S / cm or greater, and in some embodiments about 50 to about 500 S / cm. One example of a suitable inherently conductive thiophene polymer can have a repeating unit of formula (III):

[0051] [ka]

[0052] In the formula, R is (CH2) a -O-(CH2) b -L, where L is a bond or HC([CH] cH), a is 0 to 10, in some embodiments, 0 to 6, and in some embodiments, 1 to 4 (e.g., 1), b is 1 to 18, in some embodiments, 1 to 10, and in some embodiments, 2 to 6 (e.g., 2, 3, 4, or 5), c is 0 to 10, in some embodiments, 0 to 6, and in some embodiments, 1 to 4 (e.g., 1), and Z is SO3 - , C(O)O - , BF4 - , CF3SO3 - , SbF6 - , N(SO2CF3)2 - , C4H3O4 - , ClO4 - and X is a cation such as hydrogen, an alkali metal (e.g., lithium, sodium, rubidium, cesium, or potassium), ammonium, or the like.

[0053] In one particular embodiment, Z in formula (III) is a sulfonate ion, and the inherently conductive polymer thus contains repeat units of formula (IV):

[0054] [ka]

[0055] wherein R and X are as defined above. In formula (III) or (IV), a is preferably 1 and b is preferably 3 or 4. Similarly, X is preferably sodium or potassium.

[0056] If desired, the polymer can be a copolymer containing other types of repeat units. In such embodiments, the repeat units of formula (III) typically constitute about 50 mol.% or more, in some embodiments, about 75 mol.% to about 99 mol.%, and in some embodiments, about 85 mol.% to about 95 mol.% of the total amount of repeat units in the copolymer. Of course, the polymer can also be a homopolymer, containing up to 100 mol.% of repeat units of formula (III). Specific examples of such homopolymers include poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxin-2-ylmethoxy)-1-butane-sulfonic acid, salt) and poly(4-(2,3-dihydrothieno-[3,4-b][1,4]dioxin-2-ylmethoxy)-1-propanesulfonic acid, salt).

[0057] In another embodiment, the inherently conductive polymer has repeating thiophene units of the following general formula (V):

[0058] [ka]

[0059] wherein a and b are as defined above, R5 is an optionally substituted C1-C6 linear or branched alkyl group (e.g., methyl) or a halogen atom (e.g., fluorine), and X is a hydrogen atom, an alkali metal (e.g., Li, Na, or K), NH(R 1 )3 or HNC5H5(R 1 are each independently a hydrogen atom or an optionally substituted C1-C6 alkyl group).

[0060] Specific examples of thiophene compounds that can be used to form such repeats are described in U.S. Pat. No. 9,718,905, such as 3-[(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl)methoxy]-1-methyl-1-propane. Sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-ethyl-1-propanesulfonate, Sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-propyl-1-propanesulfonate, Sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-butyl-1-propanesulfonate, Sodium 3-[(2,3-dihydrothieno[3, 4-b]-[1,4]dioxin-2-yl)methoxy]-1-pentyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-hexyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopropyl-1-propanesulfonate, sodium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopropyl-1-propanesulfonate -1-Isobutyl-1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-isopentyl-1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-fluoro-1-propanesulfonic acid sodium salt, 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid potassium salt, 3-[ (2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonic acid, ammonium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate, triethylammonium 3-[(2,3-dihydrothieno[3,4-b]-[1,4]dioxin-2-yl)methoxy]-1-methyl-1-propanesulfonate, and the like, and combinations thereof, and derivatives thereof.Each of the thiophene monomers exemplified above can be prepared from thieno[3,4-b]-1,4-dioxin-2-methanol and a branched sultone compound according to known methods (e.g., Journal of Electroanalytical Chemistry, Vol. 443, pp. 217-226 (1998)).

[0061] "External" conductive polymers may also be used, which generally require the presence of a separate counterion that is not covalently bonded to the polymer. One example of such an external conductive polymer is poly(3,4-ethylenedioxythiophene). The counterion may be an anionic monomer or polymer that counteracts the charge of the conductive polymer. Anionic polymers can be, for example, anions derived from polymeric carboxylic acids (e.g., poly(meth)acrylic acids, such as poly-2-sulfoethyl(meth)acrylate or poly-3-propylsulfo(meth)acrylate; polymaleic acids, etc.); polymeric sulfonic acids (e.g., polystyrene sulfonic acid ("PSS"), polyvinyl sulfonic acid, etc.), and the like, as well as their salts, such as alkali metal, alkaline earth metal, transition metal, or ammonium salts. Similarly, suitable anionic monomers include C1-C 20 Alkanesulfonic acids (e.g., dodecanesulfonic acid); aliphatic fluorosulfonic acids (e.g., trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, perfluorooctane sulfonic acid, trifluoromethanesulfonimide, etc.); aliphatic C1-C 20 Carboxylic acids (e.g., 2-ethylhexylcarboxylic acid); aliphatic fluorocarboxylic acids (e.g., trifluoroacetic acid or perfluorooctanoic acid); C1-C 20The counter anions may be derived from aromatic sulfonic acids, optionally substituted by alkyl groups (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid); cycloalkanesulfonic acids (e.g., camphorsulfonic acid); boron compounds (e.g., tetrafluoroboric acid); phosphoric acid compounds (e.g., hexafluorophosphoric acid); and the like, as well as their salts, such as their alkali metal, alkaline earth metal, transition metal, or ammonium salts. Particularly suitable counter anions are polymeric carboxylic or sulfonic acids. (e.g., anionic polymers such as those derived from polystyrene sulfonic acid ("PSS"). The molecular weight of such compounds typically ranges from about 1,000 to about 2,000,000, and in some embodiments, from about 2,000 to about 500,000.

[0062] The pre-polymerized polymer layer, whether intrinsically or extrinsically conductive, may be applied to the anode body in various forms, such as a solution, a dispersion, etc. Intrinsically conductive polymers, for example, are preferably applied in the form of a solution, while extrinsically conductive polymers are preferably applied in the form of a dispersion.

[0063] When a solution is used, the concentration of the polymer can vary depending on the desired viscosity of the layer to be applied to the anode and the particular method. Typically, however, the polymer comprises about 0.1 to about 10 wt. % of the solution, in some embodiments, about 0.4 to about 5 wt. %, and in some embodiments, about 0.5 to about 4 wt. %. The solvent can similarly comprise about 90 wt. % to about 99.9 wt. % of the solution, in some embodiments, about 95 wt. % to about 99.6 wt. %, and in some embodiments, about 96 wt. % to about 99.5 wt. While other solvents may certainly be used, water is generally desirable as the primary solvent, making the solution an "aqueous" solution. In most embodiments, for example, water comprises at least about 50 wt. % of the solvent used, in some embodiments, at least about 75 wt. %, and in some embodiments, about 90 wt. % to 100 wt. %. The solution, if used, may be applied to the anode using any known technique, such as dipping, casting (e.g., curtain coating, spin coating, etc.), printing (e.g., gravure printing, offset printing, screen printing, etc.), etc. The resulting conductive polymer layer may be dried and / or washed after application to the anode.

[0064] When a dispersion is used, the conductive polymer is generally in the form of prepolymerized conductive particles. Such particles typically have an average size (e.g., diameter) of about 1 to about 100 nanometers, in some embodiments, about 2 to about 80 nanometers, and in some embodiments, about 4 to about 50 nanometers. Particle diameter can be determined using known techniques, such as ultracentrifugation, laser diffraction, and the like. The shape of the particles can likewise vary. In one particular embodiment, for example, the particles are spherical in shape. However, it should be understood that other shapes, such as platelets, rods, discs, rods, tubes, irregular shapes, and the like, are also contemplated by the present invention. The concentration of particles in the dispersion can vary depending on the desired viscosity of the dispersion and the particular method by which the dispersion will be applied to the capacitor element. However, typically, the particles comprise about 0.1 to about 10 weight percent of the dispersion, in some embodiments, about 0.4 to about 5 weight percent, and in some embodiments, about 0.5 to about 4 weight percent.

[0065] The dispersion may also contain one or more binders to further enhance the adhesive properties of the polymer layer and improve the stability of the particles in the dispersion. The binder may be organic, such as polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate, polyacrylic esters, polyacrylic amides, polymethacrylic esters, polymethacrylic amides, polyacrylonitrile, styrene / acrylic esters, vinyl acetate / acrylic esters and ethylene / vinyl acetate copolymers, polybutadiene, polyisoprene, polystyrene, polyethers, polyesters, polycarbonates, polyurethanes, polyamides, polyimides, polysulfones, melamine formaldehyde resins, epoxide resins, silicone resins, or cellulose. A crosslinking agent may also be used to enhance the adhesive properties of the binder. Such crosslinkers can include, for example, melamine compounds, masked isocyanates or functional silanes (such as 3-glycidoxypropyltrialkoxysilane, tetraethoxysilane and tetraethoxysilane hydrolysates), or crosslinkable polymers (such as polyurethanes, polyacrylates or polyolefins) and subsequent crosslinking.

[0066] Dispersants may also be used to promote the application of the layer to the anode. Suitable dispersants include 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 araliphatic ethers (e.g., diethyl ether and anisole), water, and mixtures of any of the above-mentioned solvents. A particularly suitable dispersant is water.

[0067] In addition to the above, other components may also be used in the dispersion. For example, conventional fillers having a size of about 10 nanometers to about 100 micrometers, in some embodiments about 50 nanometers to about 50 micrometers, and in some embodiments about 100 nanometers to about 30 micrometers may be used. Examples of such fillers include calcium carbonate, silicates, silica, calcium or barium sulfate, aluminum hydroxide, glass fibers or bulbs, wood flour, cellulose powder, carbon black, conductive polymers, and the like. The filler may be introduced into the dispersion in powder form, but may also be present in another form, such as fiber.

[0068] Surface-active substances, such as ionic or nonionic surfactants, may also be used in the dispersion. Additionally, adhesives such as organofunctional silanes or their hydrolyzates, such as 3-glycidoxypropyltrialkoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, or octyltriethoxysilane, may also be used. Dispersions may also be used with 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 sulfonic acid derivatives. The electrolyte may contain additives to improve conductivity, such as sulfoxides (e.g., sulfolane (tetramethylene sulfone) or dimethyl sulfoxide (DMSO)), sugars or sugar derivatives (e.g., sucrose, glucose, fructose, or lactose), sugar alcohols (e.g., sorbitol or mannitol), furan derivatives (e.g., 2-furancarboxylic acid or 3-furancarboxylic acid), alcohols (e.g., ethylene glycol, glycerol, diethylene glycol, or triethylene glycol).

[0069] The dispersion can be applied using a variety of known techniques, such as by spin coating, impregnation, pouring, drop coating, injection, spraying, doctor blading, brushing, printing (e.g., ink-jet, screening, or pad printing), or immersion. The viscosity of the dispersion is typically from about 0.1 to about 100,000 mPas (100 s -1 in some embodiments, from about 1 to about 10,000 mPas, in some embodiments, from about 10 to about 1,500 mPas, and in some embodiments, from about 100 to about 1000 mPas.

[0070] The solid electrolyte may be formed from multiple layers, such as an inner layer and / or an outer layer. The term "inner" in this context refers to one or more layers that cover the dielectric, whether directly or through another layer (e.g., a precoat layer). An inner layer may be, for example, an inner layer. Typically, the solid electrolyte contains an in-situ polymerized polymer and / or an intrinsically conductive polymer, such as those described above. One or more inner layers may be used. For example, a solid electrolyte typically contains 2 to 30, in some embodiments, 4 to 20, and in some embodiments, about 5 to 15 inner layers (e.g., 10 layers). A solid electrolyte contains only "inner layers," and thus, the solid electrolyte is substantially formed from the same material, i.e., the intrinsically conductive polymer and / or in-situ polymerized layer. Nevertheless, in other embodiments, the solid electrolyte may also contain one or more optional "outer" conductive polymer layers formed from a different material than the inner layer and covering the inner layer. For example, the outer layer may be formed from a dispersion of an outer conductive polymer. In one particular embodiment, the outer layer is formed primarily from such outer conductive polymer, in that it constitutes about 50% by weight or more, in some embodiments, about 70% by weight or more, and in some embodiments, about 90% by weight or more (e.g., 100% by weight) of the individual outer layer. One or more outer layers may be used. For example, the solid electrolyte can include 2 to 30, in some embodiments, 4 to 20, and in some embodiments, about 5 to 15 outer layers.

[0071] E. Exterior Polymer Coating An external polymer coating covering the solid electrolyte may also be optionally used. When used, the external polymer coating typically comprises one or more layers formed from prepolymerized conductive polymer particles (e.g., a dispersion of external conductive polymer particles) as described above. The external coating can further penetrate the edge regions of the capacitor body to increase adhesion to the dielectric, resulting in a more mechanically robust portion, which can reduce equivalent series resistance and leakage current. Because the external coating is generally intended to improve edge coverage rather than impregnate the interior of the anode body, the particles used in the external coating can have a larger size than those used in the outer layer of the solid electrolyte. For example, the ratio of the average particle 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 typically about 1.5 to about 30, in some embodiments about 2 to about 20, and in some embodiments about 5 to about 15. For example, the particles used in the dispersion of the outer coating can have an average size of from about 80 to about 500 nanometers, in some embodiments from about 90 to about 250 nanometers, and in some embodiments, from about 100 to about 200 nanometers.

[0072] If desired, a crosslinking agent may also be used in the outer polymer coating to enhance adhesion to the solid electrolyte. Typically, the crosslinking agent is applied before the application of the dispersion used in the outer coating. Suitable crosslinking agents are described, for example, in U.S. Patent Publication No. 2007 / 0064376 to Merker et al., and include, for example, amines (e.g., diamines, triamines, oligomeric amines, polyamines, etc.); polyvalent metal cations such as salts or compounds of Mg, Al, Ca, Fe, Cr, Mn, Ba, Ti, Co, Ni, Cu, Ru, Ce, or Zn; phosphonium compounds; sulfonium compounds; and the like. Particularly suitable examples include, for example, 1,4-diaminocyclohexane, 1,4-bis(amino-methyl)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 the like, and mixtures thereof.

[0073] The crosslinker is typically applied from a solution or dispersion, the pH of which, measured at 25°C, is 1 to 10, in some embodiments 2 to 7, and in some embodiments 3 to 6. Acidic compounds can be used to help achieve the desired pH level. Examples of solvents or dispersants for the crosslinker are water or organic solvents such as alcohols, ketones, carboxylic acid esters, etc. The crosslinker may be applied to the capacitor body by any known process, such as spin coating, impregnation, casting, drop coating, spray coating, vapor deposition, sputtering, sublimation, knife-coating, painting, or printing, e.g., inkjet printing, screen printing, or pad printing. Once applied, the crosslinker may be allowed to dry before application of the polymer dispersion. This process may then be repeated until the desired thickness is reached. For example, the total thickness of the entire outer polymer coating, including the crosslinker and dispersion layers, may range from about 1 to about 50 μm, in some embodiments from about 2 to about 40 μm, and in some embodiments, from about 5 to about 20 μm.

[0074] F. Moisture Barrier Layer If desired, a moisture barrier layer may be used to cover the solid electrolyte and / or optional outer polymer coating. The moisture barrier layer may be formed from a variety of different materials, such as hydrophobic elastomers, e.g., silicones, fluoropolymers, etc. Silicone polymers are particularly suitable for use in the moisture barrier layer of the present invention. Such elastomers are typically derived from polyorganosiloxanes of the general formula:

[0075] [ka]

[0076] wherein x is an integer greater than 1, and R1, R2, R3, R4, R5, R6, R7, and R8 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.). Examples of such polyorganosiloxanes can include, for example, 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, etc. To form elastomers, the polyorganosiloxanes can be crosslinked using any of a variety of known techniques, such as by catalytic cure (e.g., platinum catalyst), room temperature vulcanization, moisture cure, etc. Crosslinkers such as alkoxysilanes having the formula Si-OR, where R is H, alkyl (eg, methyl), alkenyl, carboxyalkyl (eg, acetyl), and the like, may be used.

[0077] In addition to being hydrophobic, it is generally desirable for the material used to form the moisture barrier layer to have a relatively low modulus and some flexibility, which can help absorb some of the thermal stresses caused by casing expansion and also allow it to withstand compressive forces. The flexibility of the material can be characterized by a corresponding low modulus of elasticity ("Young's modulus"), such as about 5,000 kilopascals ("kPa") or less, in some embodiments, about 1 to about 2,000 kPa, and in some embodiments, about 2 to about 500 kPa, when measured at a temperature of about 25°C. The material also typically has some strength that enables it to retain its shape even when subjected to compressive forces. For example, the material can have a tensile strength, measured at a temperature of about 25°C, of about 1 to about 5,000 kPa, in some embodiments, about 10 to about 2,000 kPa, and in some embodiments, about 50 to about 1,000 kPa. The above conditions allow the hydrophobic elastomer to further enhance the capacitor's ability to function under harsh conditions.

[0078] Non-conductive fillers may be used in the moisture barrier layer to help achieve desired flexibility and strength properties. When used, such additives typically comprise from about 0.5% to about 30% by weight of the moisture barrier layer, in some embodiments from about 1% to about 25% by weight, and in some embodiments, from about 2% to about 20% by weight. Silicone elastomers may comprise from about 70% to about 99.5% by weight of the moisture barrier layer, in some embodiments, from about 75% to about 99% by weight, and in some embodiments, from about 80% to about 98% by weight. A specific example of such a filler includes, for example, silica. While most forms of silica contain relatively hydrophilic surfaces due to the presence of silanol groups (Si—OH), silica may also be used in applications where its surface is hydrophilic, such as (CH3) nThe moisture barrier layer may optionally be surface-treated to contain -Si- groups (where n is an integer from 1 to 3), which further enhances the hydrophobicity of the moisture barrier layer. The surface treatment agent may be, for example, an organosilicon compound monomer having a hydrolyzable group or a partial hydrolyzate thereof. Examples of such compounds may include organosilazanes, silane coupling agents such as those described above, and the like.

[0079] The moisture barrier layer may be applied to any surface of the capacitor to achieve desired properties. For example, the moisture barrier layer may be located on the top, bottom, and / or sides of the capacitor. The moisture barrier layer may also be disposed on the front and / or back surfaces of the capacitor. The moisture barrier layer may cover the entire area of the surface to which it is applied or only a portion of the surface. In one embodiment, for example, the moisture barrier layer covers at least about 30%, in some embodiments at least about 40%, and in some embodiments at least about 50% of the surface of the capacitor to which it is applied.

[0080] G. Other Optional Components If desired, the capacitor element may also contain other layers, as known in the art. For example, an adhesion layer may optionally be formed between the dielectric and the solid electrolyte. An adhesion layer may be present, for example, between the dielectric and the precoat layer and / or between the precoat layer and the solid electrolyte. Regardless, the adhesion layer is typically formed from a relatively insulating resinous material (natural or synthetic). Such materials have a resistivity greater than about 10 Ω·cm, in some embodiments greater than about 100, in some embodiments greater than about 1,000 Ω·cm, and in some embodiments, greater than about 1×10 5 Ω·cm, and in some embodiments, about 1x10 10Resistivities of greater than Ω·cm can be achieved. Some resinous materials that can be utilized in the present invention include, but are not limited to, polyurethanes, polystyrenes, esters of unsaturated or saturated fatty acids (e.g., glycerides), and the like. For example, suitable esters of fatty acids include, but are not limited to, esters of lauric acid, myristic acid, palmitic acid, stearic acid, eleostearic acid, oleic acid, linoleic acid, linolenic acid, arachidonic acid, cheloric acid, and the like. These esters of fatty acids have been found to be particularly useful for forming "drying oils" when used in relatively complex combinations; This allows the resulting coating to rapidly polymerize into a stable layer. Such drying oils can include monoglycerides, diglycerides, and / or triglycerides, which have a glycerol backbone with one, two, and three fatty acyl residues esterified, respectively. For example, some suitable drying oils that can be used include, but are not limited to, olive oil, linseed oil, castor oil, tung oil, soybean oil, and shellac. These and other adhesive layer materials are described in more detail in U.S. Patent No. 6,674,635 to Fife et al.

[0081] If desired, a carbon layer (e.g., graphite) and a silver layer may be applied to this portion, respectively. The silver coating can serve, for example, as a solderable conductor, contact layer, and / or charge collector for a capacitor, while the carbon coating can limit the silver coating's contact with the solid electrolyte. Such coatings may cover part or all of the solid electrolyte. Various techniques, such as dipping, brushing, spraying, printing, etc., may be used to apply such layers.

[0082] II. Terminals Once formed, the capacitor elements may be provided with terminations. As noted above, the capacitors generally include at least two separate, spaced apart anode terminations to which the respective exposed anode lead portions are electrically connected. The capacitors also include cathode terminations to which the solid electrolyte of the capacitor elements is electrically connected.

[0083] Any conductive material may be used to form the terminals, 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 suitable 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 terminals is generally selected to minimize the thickness of the capacitor. For example, the thickness of the terminals may range from about 0.05 to about 1 millimeter, and in some embodiments, from about 0.05 to about 0.5 millimeters, and from about 0.07 to about 0.2 millimeters. One exemplary conductive material is copper-iron alloy metal sheet available from Wieland (Germany). If desired, the surface of the terminals may be electroplated with nickel, silver, gold, tin, or the like, as known in the art, to ensure that the final part can be securely attached to a circuit board. In one particular embodiment, both surfaces of the terminals are plated with nickel and silver flash, respectively, while the mounting surface is also plated with a tin solder layer. The terminals may be connected to the capacitor element using any technique known in the art, such as resistance welding, laser welding, conductive adhesives, etc.

[0084] 2-3 , a particular embodiment of a capacitor 200 is shown, including a cathode termination 206 electrically connected to a solid electrolyte (not shown) of a capacitor element 208. The capacitor element 208 can include opposing first and second ends 205 and 207, as well as opposing lower and upper surfaces 210 and 220. The cathode termination 206 is generally planar, in the sense that it is formed primarily, if not entirely, from components extending in the same or substantially the same plane. The cathode termination 206 is positioned adjacent to the lower surface 210 of the capacitor element 208 and is generally parallel to this surface. In this particular embodiment, a conductive adhesive 212 connects the cathode termination 206 to the capacitor element 208. The conductive adhesive 212 can include, for example, conductive metal particles contained in a resin composition. The metal particles can be silver, copper, gold, platinum, nickel, zinc, bismuth, or the like. The resin composition may include a thermosetting resin (e.g., an epoxy resin), a curing agent (e.g., an acid anhydride), and a coupling agent (e.g., a silane coupling agent). Conductive adhesives may be described in U.S. Patent Publication No. 2006 / 0038304 to Osako et al. Any of a variety of techniques may be used to apply the conductive adhesive to the cathode termination 206. Printing techniques may be used, for example, for their practical and cost-saving benefits. The conductive adhesive 212 may be cured. For example, a heat press may be used to apply heat and pressure to ensure that the capacitor element 208 is properly bonded to the cathode termination 206 by the adhesive.

[0085] The capacitor 200 also includes a first exposed anode lead portion 218 extending from a first end 205 of the capacitor element 208 and a second exposed anode lead portion 220 extending from a second, opposite end 207 of the capacitor element 208. The exposed anode lead portion 218 is electrically connected to the first anode termination 201, and the exposed anode lead portion 220 is electrically connected to the second anode termination 203. The first anode termination 201 may include a planar portion 202 that is generally parallel to a lower surface 210 of the capacitor element 208 and / or the cathode termination 206. The first anode termination 201 may also contain an upstanding portion 214 that connects the planar portion 202 to the exposed first anode lead portion 218. Similarly, the second anode termination 203 may include a planar portion 204 that is generally parallel to the lower surface 210 of the capacitor element 208 and / or the cathode termination 206. The second anode termination 203 may also contain an upstanding portion 216 that connects the planar portion 204 to the exposed second anode lead portion 220. As noted, the planar portions 202, 204 of the respective anode terminations are planar and generally parallel to the lower surface 210 of the capacitor element 208, and thus may be located below the respective exposed anode lead portions 218, 220. However, in one embodiment, the first upstanding portion 214 and the second upstanding portion 216 may be thickened or extended portions of the first planar portion 202 and / or second planar portion 204 of the respective anode terminations 201, 203. For example, in one embodiment, first and / or second anode terminations 201, 203 have a height selected based on the distance "d" from bottom surfaces 222, 224 of exposed anode lead portions 218, 220 to lower surface 210 of the capacitor element, where distance "d" typically ranges from about 0.1 to about 1 millimeter, in some embodiments from about 0.2 to about 0.8 millimeters, and in some embodiments from about 0.3 to about 0.6 millimeters. Of course, planar portions 202, 204 may also have a height equal to distance "d," and thus, an upstanding portion is not required.Although not shown in FIGS. 2-3, the upstanding portions 214, 216 may have a "U-shape" to further increase surface contact and mechanical stability of the exposed anode lead portions 218, 220.

[0086] The first exposed anode lead portion 218 and the second exposed anode lead portion 220 may be electrically connected to the respective anode terminals 201, 203 (either directly to the planar portions 202, 204 or via the upstanding portions 214, 216, as discussed above) using any technique known in the art, such as resistance welding, laser welding, conductive adhesives, etc. Lasers generally include a resonator containing a laser medium capable of emitting photons by stimulated emission and an energy source that excites elements in the laser medium. One suitable type of laser is one in which the laser medium is made of aluminum and yttrium garnet (YAG) doped with neodymium (Nd). The excited particles are neodymium ions, Nd 3+ The energy source can provide continuous energy to a laser medium that emits a pulsed laser beam or an energy discharge. The same or different techniques may be used for each exposed anode lead portion.

[0087] In some cases, capacitor element 208 may have a relatively small thickness or height "h" ranging from about 0.4 to about 1.5 millimeters, in some embodiments from about 0.5 to about 1.2 millimeters, and in some embodiments, from about 0.6 to about 1 millimeter. In particular, in one embodiment, such a small height "h" may further reduce distance "d" to provide a capacitor element with a relatively small thickness or height "h" ranging from about 0.4 to about 1.5 millimeters, in some embodiments, from about 0.5 to about 1.2 millimeters, and in some embodiments, from about 0.6 to about 1 millimeter. The distance "d" can improve the capacitor's stability and further contribute to a lower ESL of the capacitor. For example, in one embodiment, the distance "d" can have a value based on the height "h." In such an embodiment, the distance "d" can have a distance that is about 0.1 times the height "h," such as about 0.2 times, such as about 0.3 times, such as about 0.4 times, or about 0.5 times the height "h," to shorten the length of the leads and terminals. The capacitor element 208 can also have a high aspect ratio (the ratio of the width "w" to the height "h" of the capacitor element), due at least in part to the small thickness discussed above. Such a high aspect ratio can be about 2 or greater, such as about 3 or greater, such as about 4 or greater, such as about 5 or greater, or about 6 or greater. In particular, as discussed above, the inventors have discovered that a capacitor having such a shape and arrangement can further contribute to the capacitor's low ESL characteristics and the formation of a small, low-profile capacitor.

[0088] III. Housing The capacitor element is generally encapsulated within a housing, such that at least a portion of the planar portion of the first anode terminal, the planar portion of the second anode terminal, and the cathode terminal are exposed for mounting on a circuit board. Referring again to Figures 2-3, for example, capacitor element 208 may be encapsulated within housing 226, such that at least the lower surface of planar portion 202 of anode terminal 201, planar portion 204 of anode terminal 203, and / or planar cathode terminal 206 are exposed. In some cases, only these surfaces are exposed. The housing is typically formed from a thermosetting resin. Examples of such resins include epoxy resins, polyimide resins, melamine resins, urea-formaldehyde resins, polyurethane resins, phenolic resins, polyester resins, and the like. Epoxy resins are also particularly suitable. Additional additives, such as photoinitiators, viscosity modifiers, suspending aids, pigments, stress reducers, non-conductive fillers, and stabilizers, may also be used. For example, non-conductive fillers can include inorganic oxide particles and composites (e.g., alumina coated silica particles), such as silica, alumina, zirconia, magnesium oxide, iron oxide, copper oxide, zeolites, silicates, clays (e.g., smectite clays), and mixtures thereof.

[0089] The present invention may be better understood by reference to the following examples.

[0090] Test Procedure S-parameters S 21 The parameters were measured using a vector network analyzer over a range of frequencies. The parameters were also modeled using the equivalent circuit shown in Figure 4. Impedance Impedance was measured over a range of frequencies using a vector network analyzer.

[0091] Equivalent series resistance (ESR) Equivalent series resistance can be measured using an HP4284A LCR meter with Kelvin leads, with a DC bias of 0 volts and a 10 mVAC signal. The operating frequency was 100 kHz and the temperature was 23°C + 2°C. ESR can be measured from the cathode terminal and one or more of the anode terminals. When multiple anode terminals are used, the average ESR may be reported.

[0092] Dielectric tangent The dissipation factor can be measured using an LCZHP4284A LCR meter with Kelvin leads, with a DC bias of 0 volts and a 10 mVAC signal. The operating frequency can be 120 Hz and the temperature can be 23°C + 2°C.

[0093] capacitance Capacitance was measured using a Keithley 3330 Precision LCZ meter with Kelvin leads at a DC bias of 2.2 volts and 0.5 volts peak to peak sinusoidal signal. The operating frequency was 120 Hz and the temperature was 23°C + 2°C.

[0094] Leakage Current The leakage current can be measured using a leakage test meter (YHP4140B) at rated voltage (e.g., 2.5V) and at a temperature of 23°C + 2°C after a minimum of 5 minutes using a 1k ohm resistor to limit the charging current.

[0095] Example 1 Anode samples were fabricated using 70,000 μFV / g tantalum powder. Each anode sample was fitted with a tantalum wire and had a density of 6.0 g / cm. 3The pellet was pressed to a density of 1000 kJ / cm². The resulting pellet measured 5.08 x 3.52 x 0.52 mm. The pellet was sintered at 1,275 °C, and then a second tantalum wire was attached to the opposite end of the pellet (Figure 1A) by welding. During lead welding, the pellet was deoxidized at 860 °C and sintered again at 1,300 °C. The pellet was anodized to 9.3 volts in a water / phosphoric acid electrolyte at 80 °C to form a dielectric layer. Next, a conductive polymer coating was formed by immersing the anode in a butanol solution of iron(III) toluenesulfonate (Clevios™ C, Heraeus) and subsequently 3,4-ethylenedioxythiophene (Clevios™ M, Heraeus) and polymerizing it. 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 a 2% aqueous solution of p-toluenesulfonic acid, followed by butanol to remove reaction by-products, anodized in liquid electrolyte, and washed again in deionized water. This process was repeated six times. The part was then immersed in a dispersion of poly(3,4-ethylenedioxythiophene) (Clevios™ K, Heraeus) with a 2.0% solids content and a viscosity of 20 mPa.s. Upon coating, the part was dried at 125°C for 20 minutes. This process was repeated three times. The part was then immersed in a dispersion of poly(3,4-ethylenedioxythiophene) (Clevios™ K, Heraeus) with a 2.0% solids content and a viscosity of 160 mPa.s. Upon coating, the part was dried at 125°C for 20 minutes. This process was repeated 14 times. The part was then coated with a graphite dispersion and dried. The part was then coated with a silver dispersion and dried. Finally, the part was mounted on a substrate having terminals as described herein and shown in Figure 1A.

[0096] Several components (12) consisting of 220 μF / 2.5 V capacitors were thus produced and encapsulated in standard silica epoxy resin. The resulting components were then tested for various electrical properties. The results are presented in the table below.

[0097] [Table 1]

[0098] The impedance of the capacitor of Example 1 was also tested at various frequencies. Figure 5 presents a graphical representation of the absolute value of the impedance (|Z|) versus frequency for Example 1 compared to a standard capacitor ("Comparative"). As shown, the impedance enhancement due to the parasitic inductance associated with the capacitor decreased substantially at higher frequencies compared to the standard capacitor. For example, at 100 MHz, there was about a 66% decrease in impedance (parasitic inductance), thus the impedance was below 0.7 ohms. Figure 6 also shows the modeled and measured insertion loss scattering parameters (S 21 ) As shown, the capacitor exhibited high attenuation over a wide frequency range, such as greater than about 50 dB over the frequency range of about 0.1 MHz to about 500 MHz. Furthermore, even in the high frequency range of 500 MHz to 10 GHz, the capacitor still maintained an attenuation of greater than about 30 dB, which allows the capacitor to be readily used in DC power filtering applications.

[0099] These and other modifications and variations of the present invention can be practiced by those skilled in the art without departing from the spirit and scope of the present invention. Moreover, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Moreover, those skilled in the art will appreciate that the foregoing description is by way of example only and is not intended to limit the invention, which is therefore further set forth in such appended claims.

Claims

1. A solid electrolytic capacitor, a capacitor element comprising a sintered anode body, a dielectric covering the anode body, and a solid electrolyte covering the dielectric, the capacitor element defining opposing first and second ends and opposing upper and lower surfaces; a first exposed anode lead portion extending from the first end of the capacitor element; a first anode terminal electrically connected to the first exposed anode lead portion; a second exposed anode lead portion extending from the second end of the capacitor element; a second anode terminal spaced apart from the first anode terminal and electrically connected to the second exposed anode lead portion; a planar cathode termination positioned adjacent the lower surface of the capacitor element and electrically connected to the solid electrolyte; Equipped with a continuous anode lead extending from the first end and the second end of the capacitor element to define the first exposed anode lead portion and the second exposed anode lead portion; a distance between the first exposed anode lead portion and the second exposed anode lead portion and the lower surface of the capacitor element is about 0.1 millimeter to about 1 millimeter.

2. 2. The solid electrolytic capacitor of claim 1, wherein the first anode terminal, the second anode terminal, or both include a planar portion that is generally parallel to a lower surface of the capacitor element.

3. 2. The solid electrolytic capacitor of claim 1, wherein the first anode terminal, the second anode terminal, or both include a planar portion that lies in substantially the same plane as the cathode terminal.

4. 2. The solid electrolytic capacitor of claim 1, wherein the cathode termination is generally parallel to a lower surface of the capacitor element.

5. 10. The solid electrolytic capacitor of claim 1, wherein the anode body comprises tantalum and the dielectric comprises tantalum pentoxide.

6. 10. The solid electrolytic capacitor of claim 1, wherein the solid electrolyte comprises at least one layer formed from a dispersion of conductive polymer particles.

7. 7. The solid electrolytic capacitor of claim 6, wherein the conductive polymer comprises poly(3,4-ethylenedioxythiophene) or a derivative thereof.

8. 10. The solid electrolytic capacitor of claim 1, wherein the anode body is formed from a valve metal powder having a specific charge of about 5,000 to about 100,000 μF*V / g.

9. 10. The solid electrolytic capacitor of claim 1, wherein the anode body is formed from a valve metal powder having a specific charge of about 100,000 to about 600,000 μF*V / g.

10. 10. The solid electrolytic capacitor of claim 1, further comprising a housing enclosing the capacitor element and leaving at least a lower surface of the cathode termination exposed.

11. 11. The solid electrolytic capacitor of claim 10, further comprising the housing enclosing the capacitor element and leaving at least an underside surface of the first anode terminal, the second anode terminal, or both exposed.

12. 12. The solid electrolytic capacitor of claim 11, wherein the exposed lower surface of the cathode termination is generally flush with the exposed lower surface of the first anode termination, the second anode termination, or both.

13. 10. The solid electrolytic capacitor of claim 1, exhibiting an impedance of about 1 ohm or less over a frequency range of about 1 kHz to about 100 MHz.

14. 10. The solid electrolytic capacitor of claim 1, which exhibits an attenuation (S21 parameter) of about 40 dB or greater over a frequency range of about 0.1 MHz to about 500 MHz.

15. 10. The solid electrolytic capacitor of claim 1, which exhibits an attenuation (S21 parameter) of about 20 dB or greater over a frequency range of about 500 MHz to about 10 GHz.

16. 10. The solid electrolytic capacitor of claim 1, exhibiting an ESR of about 800 milliohms or less when measured at an operating frequency of 100 kHz and a temperature of 23[deg.]C.

17. 2. The solid electrolytic capacitor of claim 1, wherein the capacitor element has a height, and the distance between the first exposed anode lead portion and the second exposed anode lead portion and the lower surface of the capacitor element is about 0.1 to about 0.5 times the height.

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