Solid electrolytic capacitor assembly

Abstract

To provide a capacitor assembly functioning well under conditions of high humidity (e.g., 60% relative humidity).SOLUTION: A capacitor assembly 30 comprises a solid electrolytic capacitor element 33 that contains a sintered porous anode body, a dielectric that overlies the anode body, and a solid electrolyte that overlies the dielectric. An anode termination 62 is in electrical connection with the anode body and a cathode termination 72 is in electrical connection with the solid electrolyte. A first coating is disposed on at least a portion of the anode termination 62 and contains an organometallic compound, and a second coating is disposed on at least a portion of the cathode termination 72 and contains an organometallic compound. Further, a casing material 28 accommodates the capacitor element 33 and leaves a mounting surface of the anode termination 62 and the cathode termination 72 exposed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 467,276, having a filing date of March 6, 2017, which is incorporated herein by reference in its entirety. [Background technology]

[0002] Electrolytic capacitors (e.g., tantalum capacitors) are increasingly being used in circuit design due to their volumetric efficiency, reliability, and process compatibility. For example, one type of capacitor that has been developed is a solid electrolytic capacitor element that includes a tantalum anode, a dielectric, and a conductive polymer solid electrolyte. To surface mount the capacitor element, the anode is connected to an anode termination and the solid electrolyte is connected to a cathode termination. Furthermore, To help protect the capacitor from the external environment and provide it with good mechanical stability, the capacitor element is also encapsulated with a resinous casing material (e.g., epoxy resin) such that a portion of the anode and cathode terminations are exposed for surface mounting. Unfortunately, the high temperatures often used during capacitor fabrication (e.g., reflow) can cause microcracks to form in the anode and / or cathode terminations. When exposed to high humidity levels, these microcracks can absorb moisture, which can lead to oxidation of the conductive polymer solid electrolyte and cause rapid degradation of electrical properties.

[0003] Therefore, a need exists for improved solid electrolytic capacitors for use at high humidity levels. Summary of the Invention

[0004] According to one aspect of the invention, a capacitor assembly is disclosed that includes a solid electrolytic capacitor element including a sintered porous anode body, a dielectric disposed on the anode body, and a solid electrolyte disposed on the dielectric. An anode termination is electrically connected to the anode body, and a cathode termination is electrically connected to the solid electrolyte. A first coating including an organometallic compound is disposed on at least a portion of the anode termination, and a second coating including an organometallic compound is disposed on at least a portion of the cathode termination. Additionally, a casing material encases the capacitor element and leaves mounting surfaces of the anode termination and the cathode termination exposed.

[0005] Other features and aspects of the present invention are set forth in more detail below. 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 appended drawings, in which: [Brief description of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram of one embodiment of a capacitor that can be formed in accordance with the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or components of the invention. It will be appreciated by those skilled in the art that this discussion is a description of exemplary embodiments only and is not intended to limit the broader aspects of the invention, which may be embodied in the exemplary configurations.

[0008] Generally speaking, the present invention comprises a sintered porous anode body, a dielectric disposed over the anode body, and The present invention relates to a capacitor assembly including a capacitor element including a solid electrolyte disposed on a dielectric. The anode body is electrically connected to the anode termination, and the solid electrolyte is electrically connected to the cathode termination. The capacitor element is further encapsulated with a casing material such that at least one surface of the anode termination and the cathode termination is exposed for mounting to an electronic component (e.g., a printed circuit board). In particular, a first coating is disposed on at least a portion of the anode termination, and a second coating is disposed on at least a portion of the cathode termination. The first and second coatings include an organometallic compound that can improve adhesion of the casing material to the termination and reduce the number of microcracks that would otherwise form after exposure to high temperatures (e.g., during reflow), such as peak reflow temperatures of about 150° C. to about 350° C., and in some embodiments, 200° C. to about 300° C. (e.g., 250° C.).

[0009] Due to its unique structure, the resulting capacitor assembly is not sensitive to moisture and therefore can exhibit excellent electrical properties even when exposed to high humidity levels, such as when placed in contact with an atmosphere having a relative humidity of about 40% or more, in some embodiments about 45% or more, in some embodiments about 50% or more, and in some embodiments about 60% or more (e.g., about 60% to about 85%). The relative humidity can be determined, for example, according to ASTM-E337-02, Method A (2007). The high humidity atmosphere can be part of the internal atmosphere of the capacitor assembly itself, or it can be an external atmosphere to which the capacitor assembly is exposed during storage and / or use. The capacitors can exhibit, for example, a relatively low equivalent series resistance (ESR) when exposed to a high humidity atmosphere (e.g., 60% relative humidity), such as about 200 milliohms, in some embodiments less than about 150 milliohms, in some embodiments about 0.01 to about 125 milliohms, and in some embodiments about 0.1 to about 100 milliohms, measured at an operating frequency of 100 kHz. The capacitor assemblies may exhibit a DCL of only about 50 microamps (μA) or less, in some embodiments about 40 μA or less, in some embodiments about 20 μA or less, and in some embodiments, about 0.1 to about 10 μA. The capacitor assemblies may also exhibit a high percentage of their wet capacitance, enabling them to have only a small capacitance loss and / or variation in the presence of atmospheric moisture. This performance characteristic can be expressed by the equation: Wet to dry capacitance = (dry capacitance / wet capacitance) x 100 The wet-to-dry capacitance is quantified by the "wet-to-dry capacitance percentage" as determined by:

[0010] The capacitor assemblies may exhibit a wet to dry capacitance percentage of about 50% or greater, in some embodiments about 60% or greater, in some embodiments about 70% or greater, and in some embodiments, about 80% to 100%. The dry capacitance is about 30 nanofarads per square centimeter (nF / cm) measured at a frequency of 120 Hz. 2 ) or more, in some embodiments, about 100 nF / cm 2 In some embodiments, the range is about 200 to about 3,000 nF / cm 2 In some embodiments, the range is from about 400 to about 2,000 nF / cm 2 It may be.

[0011] In particular, the ESR, DCL, and capacitance values ​​may also be maintained for significant periods of time at high humidity levels, for example, for at least about 10 hours, in some embodiments, from about 20 hours to about 30 hours, and in some embodiments, from about 40 hours to about 80 hours (e.g., 24 hours, 48 ​​hours, or 72 hours) when tested at temperatures of from about 20° C. to about 50° C., and in some embodiments, from about 25° C. to about 40° C. (e.g., 30° C.).

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

[0013] The specific charge of the powder typically varies from about 2,000 to about 800,000 microfarad·volts per gram (μF·V / g) depending on the desired application. For example, in some embodiments, high charge powders can be used having a specific charge of about 100,000 to about 800,000 μF·V / g, in some embodiments, about 120,000 to about 700,000 μF·V / g, and in some embodiments, about 150,000 to about 600,000 μF·V / g. In other embodiments, low charge powders can be used having a specific charge of about 2,000 to about 100,000 μF·V / g, in some embodiments, about 5,000 to about 80,000 μF·V / g, and in some embodiments, about 10,000 to about 70,000 μF·V / g. 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.

[0014] The powder may be a free-flowing fine powder comprising primary particles. The primary particles of the powder generally have a size of about 5 to 100 nm, as determined, for example, using a laser particle size distribution analyzer (e.g., LS-230) from BECKMAN COULTER Corporation, optionally after subjecting the particles to ultrasonic vibration for 70 seconds. The primary particles typically have a three-dimensional particle shape (e.g., spherical or angular). Such particles typically have a relatively low "aspect ratio," i.e., the average diameter or width of the particle divided by the average thickness (D / T). For example, the aspect ratio of the particles may be about 4 or less, in some embodiments about 3 or less, and in some embodiments about 1 to about 2. In addition to the primary particles, the powders may contain other types of particles, such as secondary particles formed by aggregation (or agglomeration) of the primary particles. Such secondary particles may have a median diameter (D50) of about 1 to about 500 micrometers, in some embodiments about 10 to about 250 micrometers. stomach.

[0015] The particles can be aggregated by heating the particles and / or by using a binder. For example, the aggregation can be carried out at a temperature of about 0° C. to about 40° C., in some embodiments, about 5° C. to about 35° C., and in some embodiments, about 15° C. to about 30° C. Suitable binders include, for example, poly(vinyl butyral); poly(vinyl acetate); poly(vinyl alcohol); poly(vinyl pyrrolidone); cellulose polymers such as carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, and methylhydroxyethyl cellulose; atactic polypropylene, polyethylene; polyethylene glycols (e.g., Carbowax, manufactured by Dow Chemical Co.); poly styrene, poly(butadiene / styrene); polyamides, polyimides, and polyacrylamides, high molecular weight polyethers; copolymers of ethylene oxide and propylene oxide; fluoropolymers such as polytetrafluoroethylene, polyvinylidene fluoride, and fluoroolefin copolymers; acrylic polymers such as sodium polyacrylate, poly(lower alkyl acrylates), poly(lower alkyl methacrylates), and copolymers of lower alkyl acrylates and methacrylates; and fatty acids and waxes such as stearic acid and other soap fatty acids, vegetable waxes, microcrystalline waxes (refined paraffins), and the like.

[0016] The resulting powder can be compressed to form pellets using any conventional powder pressing equipment. For example, a press can be used that is a single station compression press that includes a die and one or more punches. Alternatively, an anvil type compression press can be used that uses only a die and a single lower punch. Single station compression presses are available in several basic types such as cam presses, toggle / knuckle presses, and eccentric / crank presses with various capabilities such as single action, double action, floating die, moving platen, opposed ram, screw, impact, hot pressing, coining, or sizing. The powder can be compressed around the anode lead, which can be in the form of a wire, sheet, etc. The lead can extend longitudinally from the anode body and can be formed from any conductive material such as tantalum, niobium, aluminum, hafnium, titanium, etc., and conductive oxides and / or nitrides thereof. Connection of the lead can also be accomplished using other known techniques, for example, by welding the lead to the anode body or embedding it within the anode body during formation (e.g., prior to compression and / or sintering).

[0017] The binder can be removed by heating the pellets after pressing under vacuum at a certain temperature (e.g., about 150°C to about 500°C) for several minutes. Alternatively, the binder can be removed by contacting the pellets with an aqueous solution such as that described in U.S. Patent 6,197,252 to Bishop et al. The pellets are then sintered to form a porous integral member. The pellets are typically sintered at a temperature of about 700°C to about 1600°C, in some embodiments about 800°C to about 1500°C, in some embodiments about 900°C to about 1200°C, for about 5 minutes to about 100 minutes, in some embodiments about 8 minutes to about 15 minutes. This can be done in one or more steps. If desired, sintering can be done in an atmosphere that limits the migration of oxygen atoms to the anode. For example, sintering can be done in a reducing atmosphere such as under vacuum, inert gas, or hydrogen. The reducing atmosphere may be at a pressure from about 10 Torr to about 2000 Torr, in some embodiments from about 100 Torr to about 1000 Torr, and in some embodiments from about 100 Torr to about 930 Torr. Mixtures of hydrogen and other gases, such as argon or nitrogen, can also be used.

[0018] B. Dielectric: The anode is also coated with a dielectric. The dielectric can be formed by anodizing a sintered anode such that a dielectric layer is formed on and / or in the anode. For example, a tantalum (Ta) anode can be anodized to tantalum pentoxide (Ta2O5). 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 increase ionic conductivity, compounds that can dissociate in the solvent to form ions can be used. Examples of such compounds include acids, such as those described below with respect to the electrolyte. For example, an acid (e.g., phosphoric acid) can comprise from about 0.01% to about 5% by weight, in some embodiments from about 0.05% to about 0.8% by weight, and in some embodiments from about 0.1% to about 0.5% by weight of the anodization solution. Blends of acids can also be used if desired.

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

[0020] Although not required, in some embodiments, the dielectric layer can have a differentiated thickness throughout the anode in that it has a first portion disposed on the outer surface of the anode and a second portion disposed on the inner surface of the anode. In such embodiments, the first portion is selectively formed such that its thickness is greater than the thickness of the second portion. However, it should be understood that the thickness of the dielectric layer need not be uniform within a particular region. Some portions of the dielectric layer adjacent to the outer surface, for example, may actually be thinner than some portions of the layer at the inner surface, and vice versa. Nevertheless, the dielectric layer can be formed such that at least a portion of the layer at the outer surface has a greater thickness than at least a portion at the inner surface. While the actual difference in these thicknesses can vary depending on the particular application, the ratio of the thickness of the first portion to the thickness of the second portion is typically from about 1.2 to about 40, in some embodiments from about 1.5 to about 25, and in some embodiments from about 2 to about 20.

[0021] A multi-step process is generally used to form dielectric layers having differentiated thicknesses. In each step of the process, a sintered anode is anodized to form a dielectric layer (e.g., tantalum pentoxide). During the first step of anodization, a relatively low formation voltage is typically used to ensure that the desired dielectric thickness is achieved for the interior region, for example, a formation voltage in the range of about 1 to about 90 volts, in some embodiments about 2 to about 50 volts, and in some embodiments about 5 to about 20 volts. The sintered body can then be anodized in a second step of the process to increase the dielectric thickness to the desired level. This is generally accomplished by anodizing in an electrolyte at a formation voltage higher than that used during the first step, for example, a formation voltage in the range of about 50 to about 350 volts, in some embodiments about 60 to about 300 volts, and in some embodiments about 70 to about 200 volts. During the first and / or second stages, the electrolyte can be maintained at a temperature within the range of from about 15°C to about 95°C, in some embodiments, from about 20°C to about 90°C, and in some embodiments, from about 25°C to about 85°C.

[0022] The electrolytes used during the first and second stages of the anodization process may be the same or different. However, it is usually desirable to use different solutions to help better facilitate obtaining a greater thickness on the outer portion of the dielectric layer. For example, it may be desirable for the electrolyte used in the second stage to have a lower ionic conductivity than the electrolyte used in the first stage, so that a significant amount of oxide film is not formed on the inner surface of the anode. In this regard, the electrolyte used during the first stage may include an acidic compound, such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, boric acid, boronic acid, and the like. Such electrolytes may have a conductivity of about 0.1 to about 100 mS / cm, in some embodiments about 0.2 to about 20 mS / cm, and in some embodiments about 1 to about 10 mS / cm, measured at a temperature of 25° C. The electrolyte used during the second stage usually includes a salt of a weak acid to ensure that the hydronium ion concentration is sufficient to reduce the charge in the pores. The concentration of the weak acid increases in the pores as a result of the passage of the weak acid. Ion transport or diffusion occurs such that anions of the weak acid migrate into the pores as necessary to balance the charge. As a result, the concentration of the main conductive species (hydronium ions) decreases as an equilibrium is formed between the hydronium ions, the acid anions, and the undissociated acid, forming poorly conductive species. The decrease in the concentration of the conductive species results in a relatively high voltage drop in the electrolyte, which prevents further anodization in the interior, while a thicker oxide layer accumulates on the exterior for high formation voltages in the continuously high conductivity regions. Suitable weak acid salts can include, for example, ammonium or alkali metal salts (e.g., sodium, potassium, etc.) of boric acid, boronic acid, acetic acid, oxalic acid, lactic acid, adipic acid, and the like. Particularly suitable salts include sodium tetraborate and ammonium pentaborate. Such an electrolyte solution usually has a conductivity measured at a temperature of 25° C. of about 0.1 to about 20 mS / cm, in some embodiments, about 0.5 to about 10 mS / cm, and in some embodiments, about 1 to about 5 mS / cm.

[0023] If desired, each step of anodization can be repeated one or more times to achieve the desired dielectric thickness. Additionally, the anode can be rinsed or washed with other solvents (e.g., water) after the first and / or second steps to remove the electrolyte.

[0024] C. Solid electrolyte: As indicated above, a solid electrolyte is disposed over the dielectric and typically functions as the cathode for the capacitor assembly. The solid electrolyte can include materials known in the art such as conductive polymers (e.g., polypyrroles, polythiophenes, polyanilines, etc.), manganese dioxide, and the like. Typically, however, the solid electrolyte includes one or more layers that include extrinsically conductive and / or intrinsically conductive polymer particles. One benefit of using such particles is that they prevent dielectric breakdown under high electric fields due to ion migration that occurs during conventional in-situ polymerization processes. Ion species that can cause 2+ or Fe 3+ ) can be minimized. Thus, the conductive polymer can be prepared in advance rather than by in-situ polymerization. By applying the particles as pre-polymerized particles, the resulting capacitors are comparatively If desired, the solid electrolyte may be formed from one or more layers. When multiple layers are used, one or more layers may be coated with a dielectric constant material by in-situ polymerization. However, the inventors have found that when it is desired to achieve very high breakdown voltages, the solid electrolyte is formed primarily from the conductive particles described above, typically a conductive polymer formed by in situ polymerization. Regardless of the number of layers used, the resulting solid electrolyte typically has a total thickness of from about 1 micrometer (μm) to about 200 μm, in some embodiments from about 2 μm to about 50 μm, and in some embodiments, from about 5 μm to about 30 μm.

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

[0026] [ka]

[0027] (In the formula, R7 is a linear or branched C1-C 18Alkyl groups (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 to C 12 Cycloalkyl groups (e.g., cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, etc.); C6-C 14 Aryl groups (e.g., phenyl, naphthyl, etc.); C7-C 18 aralkyl groups (e.g., benzyl, o-, m-, p-tolyl, 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, 3,5-xylyl, mesityl, etc.); q is an integer of 0 to 8, in some embodiments 0 to 2, and in one embodiment 0. An "extrinsic" conductive thiophene polymer having a repeat unit of the formula: can be used in the solid electrolyte. In one particular embodiment, "q" is 0 and the polymer is poly(3,4-ethylenedioxythiophene). One commercially suitable example of a monomer suitable for forming such a polymer is available from Heraeus under the name Clevios® M. The compound is 3,4-ethylenedioxythiophene.

[0028] The polymers of formula (III) are generally considered to be "extrinsically" conductive in that they usually require the presence of another counterion that is not covalently bonded to the polymer. The counterion may be a monomeric or polymeric anion that neutralizes the charge of the conductive polymer. The polymeric anion may be, for example, a polymeric carboxylic acid (e.g., polyacrylic acid, polymethacrylic acid, polymaleic acid, etc.); a polymeric sulfonic acid (e.g., polystyrene sulfonic acid (PSS), polyvinyl sulfonic acid, etc.); and the like. The acid may also be a copolymer, such as a copolymer of vinyl carboxylic acid and vinyl sulfonic acid with other polymerizable monomers, such as acrylate esters and styrene. Additionally, suitable monomeric anions include, for example, C1-C 20 Alkanesulfonic acids (e.g., dodecanesulfonic acid); aliphatic perfluorosulfonic acids (e.g., trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid); aliphatic C1-C 20 Carboxylic acids (e.g. 2-ethylhexyl carboxylic acid); aliphatic perfluorocarboxylic acids (e.g. trifluoroacetic acid or perfluorooctanoic acid); optionally C1-C 20 Examples of the counter anion include aromatic sulfonic acids substituted with alkyl groups (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid); cycloalkanesulfonic acids (e.g., camphorsulfonic acid, or tetrafluoroborate, hexafluorophosphate, perchlorate, hexafluoroantimonate, hexafluoroarsenate, or hexachloroantimonate); and the like. Particularly suitable counter anions are polymeric anions such as polymeric carboxylic or sulfonic acids (e.g., polystyrene sulfonic acid (PSS)). The molecular weight of such polymeric anions is usually in the range of about 1,000 to about 2,000,000, and in some embodiments, about 2,000 to about 500,000.

[0029] Also, inherently conductive polymers can be used that have positive charges disposed on the backbone that are at least partially compensated by anions covalently attached to the polymer. For example, one example of a suitable inherently conductive thiophene polymer has the following formula (IV):

[0030] [ka]

[0031] (In the formula, R is (CH2) a -O-(CH2) b and; 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); Z is SO3 - , C(O)O - , BF4 - , CF3SO3 - , SbF6 - , N(SO2CF3)2 - , C4H3O4 - , ClO4 - etc., anions such as; X is a cation such as hydrogen, an alkali metal (e.g., lithium, sodium, rubidium, cesium, or potassium), ammonium, etc. It may have the repeat unit:

[0032] In one particular embodiment, Z in formula (IV) is a sulfonate ion and the intrinsically conductive polymer has the following formula (V):

[0033] [ka]

[0034] (wherein R and X are as defined above). In formula (IV) or (V), a is preferably 1, and b is preferably 3 or 4. Furthermore, X is preferably sodium or potassium.

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

[0036] Regardless of the particular nature of the polymer, the resulting conductive polymer particles will generally have a size of from about 1 to about 80 nanometers, and in some embodiments, from about 2 to about 70 nanometers. In some cases, the particles have an average size (e.g., diameter) of about 3 to about 60 nanometers. The diameter of the particles can be determined using known techniques such as ultracentrifugation, laser diffraction, and the like. Additionally, the shape of the particles can vary. For example, in one particular embodiment, the particles are spherical in shape. However, it should be understood that other shapes, such as plates, rods, disks, bars, tubes, irregular shapes, and the like, are also contemplated by the present invention.

[0037] Although not required, the conductive polymer particles can be applied in the form of a dispersion. The concentration of the conductive polymer in the dispersion can vary depending on the desired viscosity of the dispersion and the particular method of applying the dispersion to the capacitor element. Typically, however, the polymer comprises from about 0.1 to about 10 weight percent of the dispersion, in some embodiments from about 0.4 to about 5 weight percent, and in some embodiments, from about 0.5 to about 4 weight percent. The dispersion can also include one or more components to improve the overall properties of the resulting solid electrolyte. For example, the dispersion can include a binder to further enhance the adhesion of the polymer layer and also to increase the stability of the particles within the dispersion. The binder may be of organic nature, 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. Crosslinking agents may also be used to increase the adhesive capacity of the binder. Such crosslinking agents may include, for example, melamine compounds, masked isocyanates or crosslinkable polymers such as polyurethanes, polyacrylates or polyolefins, which may include subsequent crosslinking. Dispersing agents may also be used to facilitate the ability to apply the layer to the anode.Suitable dispersants include solvents such as aliphatic alcohols (e.g., methanol, ethanol, i-propanol, and butanol), aliphatic ketones (e.g., acetone and methyl ethyl ketone), aliphatic carboxylic acid esters (e.g., ethyl acetate and butyl acetate), aromatic hydrocarbons (e.g., toluene and xylene), aliphatic hydrocarbons (e.g., hexane, heptane, and cyclohexane), chlorinated hydrocarbons (e.g., dichloromethane and dichloroethane), aliphatic nitriles (e.g., acetonitrile), aliphatic sulfoxides and sulfones (e.g., dimethyl sulfoxide and sulfolane), aliphatic carboxylic acid amides (e.g., methylacetamide, dimethylacetamide, and dimethylformamide), aliphatic and aromatic aliphatic ethers (e.g., diethyl ether and anisole), water, and any mixture of the above solvents.A particularly suitable dispersant is water.

[0038] In addition to those mentioned above, other components may also be used in the dispersion. For example, conventional fillers having dimensions of about 10 nanometers to about 100 micrometers, in some embodiments about 50 nanometers to about 50 micrometers, 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 glass spheres, wood flour, cellulose powder, carbon black, conductive polymers, and the like. The fillers may be introduced into the dispersion in powder form, but may also be present in other forms, such as fibers.

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

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

[0041] i.Inner layer: A solid electrolyte is generally formed from one or more "inner" conductive polymer layers. The term "inner" in this context refers to one or more layers disposed on the dielectric, either directly or via another layer (e.g., a precoat layer). One or more inner layers can be used. For example, a solid electrolyte typically includes 2-30, in some embodiments 4-20, and in some embodiments about 5-15 inner layers (e.g., 10 layers). The inner layer or layers can include, for example, intrinsically conductive and / or extrinsically conductive polymer particles as described above. For example, such particles can comprise about 50% or more by weight, in some embodiments about 70% or more by weight, and in some embodiments about 90% or more by weight (e.g., about 100% by weight) of the inner layer or layers. In another embodiment, the inner layer or layers can include an in-situ polymerized conductive polymer. In such embodiments, In some cases, the in-situ polymerized polymer may comprise at least about 50% by weight of one or more of the inner layers. In some embodiments, it may comprise about 70% by weight or more, and in some embodiments, about 90% by weight or more (eg, about 100% by weight).

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

[0043] D. Outer polymer coating: An outer polymer coating can also be disposed over the solid electrolyte. The outer polymer coating is generally comprised of prepolymerized conductive polymer particles (e.g., extrinsic conductive polymer particles) as described above. The outer coating may further penetrate into the edge regions of the capacitor body to increase adhesion to the dielectric, providing a more mechanically robust part, which may reduce equivalent series resistance and leakage current. Generally, the particles used in the outer coating will have a larger size than those used in the solid electrolyte, since the intention is to improve edge coverage, rather than impregnate the interior of the anode body. For example, the ratio of the average size of the particles used in the outer polymer coating to the average size of the particles used in any dispersion of the solid electrolyte is typically from about 1.5 to about 30, in some embodiments from about 2 to about 20, and in some embodiments from about 5 to about 15. For example, the particles used in the outer coating dispersion may 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.

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

[0045] The crosslinker is typically applied from a solution or dispersion, the pH of which is 1-10, in some embodiments 2-7, and in some embodiments 3-6, determined at 25° C. An acidic compound may be used to assist in achieving the desired pH level. Examples of solvents or dispersants for the crosslinker include water, or organic solvents, such as alcohols, ketones, carboxylic acid esters, and the like. The crosslinker may be applied to the capacitor body by any known process, such as spin coating, impregnation, casting, drop application, spray application, vapor deposition, sputtering, sublimation, knife coating, painting, or printing, such as inkjet, screen, or pad printing. Once applied, the crosslinker may be dried before applying the polymer dispersion. This process may then be repeated until the desired thickness is achieved. For example, the total thickness of the entire outer polymer coating, including the layers of crosslinker and dispersion, 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.

[0046] E. Cathode Coating: If desired, the capacitor element may also employ a cathode coating disposed over the solid electrolyte and other optional layers (e.g., an outer polymer coating). The cathode coating may include a metal particle layer including a plurality of conductive metal particles dispersed within a resinous polymer matrix. The particles typically comprise from about 50% to about 99% by weight of the layer, in some embodiments from about 60% to about 98% by weight, and in some embodiments from about 70% to about 95% by weight, while the resinous polymer matrix typically comprises from about 1% to about 50% by weight, in some embodiments from about 2% to about 40% by weight, and in some embodiments from about 5% to about 30% by weight of the layer.

[0047] The conductive metal particles may be a variety of different metals such as copper, nickel, silver, nickel, zinc, tin, lead, copper, aluminum, molybdenum, titanium, iron, zirconium, magnesium, etc. The conductive metal may be formed from a metal particle layer, such as a conductor layer, a conductor layer, or a conductor layer of a conductive material. ...

[0048] The resinous polymer matrix typically includes a polymer that may be thermoplastic or thermosetting in nature. However, typically the polymer is selected to contain a relatively small amount of polar groups that can act as a barrier to electromigration of silver ions and also to minimize the degree of water adsorption in the cathode coating. In this regard, the inventors have found that vinyl acetal polymers such as polyvinyl butyral, polyvinyl formal, and the like, are particularly suitable for this purpose. For example, polyvinyl butyral can be formed by reacting polyvinyl alcohol with an aldehyde (e.g., butyraldehyde). Because this reaction is usually not complete, polyvinyl butyral generally has a residual hydroxyl content. However, by minimizing this content, the polymer can have a lower degree of strongly polar groups that would otherwise cause a high degree of moisture adsorption and migration of silver ions. For example, the residual hydroxyl content in polyvinyl acetal can be about 35 mol % or less, in some embodiments about 30 mol % or less, and in some embodiments, from about 10 mol % to about 25 mol %. One commercially available example of such a polymer is available from Sekisui Chemical Co., Ltd. under the designation "BH-S" (polyvinyl butyral).

[0049] To form the cathode coating, a conductive paste is typically applied to the capacitor over the solid electrolyte, typically using one or more organic solvents in the paste. In general, a variety of different organic solvents can be used, such as glycols (e.g., propylene glycol, butylene glycol, triethylene glycol, hexylene glycol, polyethylene glycol, ethoxydiglycol, and dipropylene glycol); glycol ethers (e.g., methyl glycol ether, ethyl glycol ether, and isopropyl glycol ether); ethers (e.g., diethyl ether and tetrahydrofuran); alcohols (e.g., benzyl alcohol, methanol, ethanol, n-propanol, iso-propanol, and butanol); triglycerides; ketones (e.g., acetone, methyl ethyl ketone, and methyl isobutyl ketone); esters (e.g., ethyl acetate, butyl acetate, diethylene glycol ether acetate, and methoxypropyl acetate); amides (e.g., dimethylformamide, dimethylacetamide, dimethylcapryl / capric fatty acid amide, and N-alkylpyrrolidones); nitriles (e.g., acetonitrile, propiononitrile, butyronitrile, and benzonitrile); sulfoxides or sulfones (e.g., dimethylsulfoxide (DMSO) and sulfolane); and the like, as well as mixtures thereof. The organic solvent(s) typically comprise from about 10% to about 70% by weight of the paste, in some embodiments from about 20% to about 65% by weight, and in some embodiments from about 30% to about 60% by weight. The metal particles typically comprise from about 10% to about 60% by weight of the paste, in some embodiments from about 20% to about 45% by weight, and in some embodiments from about 25% to about 40% by weight, and the resinous polymer matrix typically comprises from about 0.1% to about 20% by weight of the paste, in some embodiments from about 0.2% to about 10% by weight, and in some embodiments from about 0.5% to about 8% by weight.

[0050] The paste may have a relatively low viscosity, which allows it to be easily handled and applied to the capacitor element. Viscosity may be measured, for example, using a Brookfield DV-1 viscometer (cone The viscosity may range from about 50 to about 3,000 centipoise, in some embodiments from 100 to about 2,000 centipoise, and in some embodiments from about 200 to about 1,000 centipoise, as measured using a gypsum plate or the like operating at a speed of 10 rpm and a temperature of 25° C. If desired, thickeners or other viscosity modifiers can be used in the paste to increase or decrease the viscosity. Additionally, the paste may be applied at a relatively thin thickness and still achieve the desired properties. For example, the paste may be applied at a thickness of about 0.01 to about 50 micrometers, in some embodiments from about 0.5 to about 30 micrometers, and in some embodiments from about 1 to about 25 micrometers. Once applied, the metal paste may optionally be dried to remove some components, such as organic solvents. For example, drying may be performed at a temperature of about 20° C. to about 150° C., in some embodiments from about 50° C. to about 140° C., and in some embodiments from about 80° C. to about 130° C.

[0051] F. Other Ingredients: If desired, other layers known in the art may also be included in the capacitor. For example, in some embodiments, a carbon layer (e.g., graphite) may be disposed between the solid electrolyte and the silver layer to help further limit contact between the silver layer and the solid electrolyte. Additionally, in some embodiments, a precoat layer may be used that is disposed over the dielectric and includes an organometallic compound, as described in more detail below.

[0052] II. Termination: Once the capacitor elements are formed, the capacitor assembly can be provided with terminations. For example, the capacitor assembly can include an anode termination to which the anode lead of the capacitor element is electrically connected, and a cathode termination to which the cathode of the capacitor element is electrically connected. Any conductive material can be used to form the terminations, 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 terminations is generally selected to minimize the thickness of the capacitor. For example, the thickness of the terminations can range from about 0.05 to about 1 millimeter, in some embodiments, from about 0.05 to about 0.5 millimeters, and from about 0.07 to about 0.2 millimeters. One exemplary conductive material is a copper-iron alloy available from Wieland (Germany). The terminations are metal plates of 1000 Ω or more. If desired, the surfaces of the terminations can be electroplated with nickel, silver, gold, tin, etc., as known in the art, to ensure that the final component can be mounted to a circuit board. In one particular embodiment, both surfaces of the terminations are plated with nickel and silver flash, respectively, while the mounting surface is also plated with a tin solder layer.

[0053] Regardless of the particular material used to form the terminations, at least a portion of the anode termination includes a first coating and at least a portion of the cathode termination includes a second coating. The first coating can be formed from the same or different materials. Regardless, both the first and second coatings include an organometallic compound having the following general formula:

[0054] [ka]

[0055] (In the formula, M is an organometallic atom such as silicon, titanium, etc.; R1, R2, and R3 are independently alkyl (e.g., methyl, ethyl, propyl, etc.) or hydroxyalkyl (e.g., hydroxymethyl, hydroxyethyl, hydroxypropyl, etc.), and 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. may have the following structure:

[0056] In some embodiments, R1, R2, and R3 can be hydroxyalkyl (e.g., OCH3), however, in other embodiments, R1 can be alkyl (e.g., CH3) and R2 and R3 can be hydroxyalkyl (e.g., OCH3).

[0057] Additionally, in some embodiments, M may be silicon and the organometallic compound is an organosilane compound such as an alkoxysilane. Suitable alkoxysilanes include, for example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, and glycidoxymethyltrimethoxysilane. , Glycidoxymethyltriethoxysilane, Glycidoxymethyltripropoxysilane, Glycidoxymethyltributoxysilane, β-Glycidoxyethyltrimethoxysilane, β-Glycidoxyethyltriethoxysilane, β-Glycidoxyethyltripropoxysilane, β-Glycidoxyethyltributoxysilane, β-Glycidoxyethyltrimethoxysilane, α-Glycidoxyethyltriethoxysilane, α-Glycidoxyethyltripropoxysilane, α-Glycidoxyethyltributoxysilane, γ-Glycidoxy glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyltriethoxysilane, β-glycidoxypropyltripropoxysilane, α-glycidoxypropyltributoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, α-glycidoxypropyltrippropoxysilane Lan, α-glycidoxypropyl tributoxysilane, γ-glycidoxybutyl trimethoxysilane, δ-glycidoxybutyl triethoxysilane, δ-glycidoxybutyl tripropoxysilane, δ-glycidoxybutyl tributoxysilane, δ-glycidoxybutyl trimethoxysilane, γ-glycidoxybutyl triethoxysilane, γ-glycidoxybutyl tripropoxysilane, γ-propoxybutyl tributoxysilane, δ-glycidoxybutyl trimethoxysilane, δ-glycidoxybutyl triethoxysilane,δ-glycidoxybutyl tripropoxysilane, α-glycidoxybutyl trimethoxysilane, α-glycidoxybutyl triethoxysilane, α-glycidoxybutyl tripropoxysilane, α-glycidoxybutyl tributoxysilane, (3,4-epoxycyclohexyl)-methyl trimethoxysilane, (3,4-epoxycyclohexyl) methyl triethoxysilane, (3,4-epoxycyclohexyl) methyl tripropoxysilane, (3,4-epoxycyclohexyl) methyl tributoxysilane, (3,4-epoxycyclohexyl) ethyl trimethoxysilane, (3,4-epoxycyclohexyl) ethyl triethoxysilane, (3,4-epoxycyclohexyl) ethyl tripropoxysilane, Examples of the epoxy silane include (3,4-epoxycyclohexyl)ethyl tributoxy silane, (3,4-epoxycyclohexyl)propyl trimethoxy silane, (3,4-epoxycyclohexyl)propyl triethoxy silane, (3,4-epoxycyclohexyl)propyl tripropoxy silane, (3,4-epoxycyclohexyl)propyl tributoxy silane, (3,4-epoxycyclohexyl)butyl trimethoxy silane, (3,4-epoxycyclohexyl)butyl triethoxy silane, (3,4-epoxycyclohexyl)butyl tripropoxy silane, and (3,4-epoxycyclohexyl)butyl tributoxy silane.

[0058] The particular method of applying the first and second coatings to their respective terminations can be varied as desired. In one particular embodiment, the organometallic compound can be dissolved in an organic solvent to form a solution which is then coated onto the terminations. Suitable coating techniques can include, for example, screen printing, dipping, electrophoretic coating, spraying, and the like. The organic solvent can vary, but is typically an alcohol such as methanol, ethanol, and the like. 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 also comprise from about 90% to about 99.9% by weight, in some embodiments from about 92% to about 99.8% by weight, and in some embodiments from about 95% to about 99.5% by weight of the solution. The particular location of the coating on a given termination can also be varied as desired. Typically, it is desirable to include a coating on at least one surface of the termination (e.g., the anode termination and / or the cathode termination) that contacts the casing material. For example, the top, bottom, and / or edges of the terminations may include a coating. The coating may cover the entire surface of the termination, or it may be applied in a pattern. In certain embodiments of the invention, each surface of the anodic termination includes a first coating and each surface of the cathodic termination includes a second coating. Once applied, the coating may then be cured to ensure a desired degree of adhesion to the termination. Curing may occur before, after, and / or during the process of applying the casing material. Typically, the curing process is performed at a relatively high temperature, such as a temperature of about 50° C. to about 250° C., in some embodiments, about 80° C. to about 200° C., and in some embodiments, about 100° C. to about 150° C.

[0059] 1, one embodiment of a capacitor assembly 30 is shown as including an anode termination 62 and a cathode termination 72 in electrical communication with the capacitor element 33. Although the cathode termination 72 may be in electrical contact with either surface of the capacitor element 33, in the embodiment shown the cathode termination 72 is in electrical communication with the bottom surface 39 via a conductive adhesive. More specifically, the cathode termination 72 includes a first part 73 in electrical contact with and generally parallel to the bottom surface 39 of the capacitor element 33. The cathode termination 72 may also include a second part 74 that is substantially perpendicular to the first part 73 and in electrical contact with the back surface 38 of the capacitor element 33. The anode termination 62 also includes a first part 63 that is disposed substantially perpendicular to a second part 64. The first part 63 is in electrical contact with and generally parallel to the bottom surface 39 of the capacitor element 33. The second part 64 includes a region 51 that supports the anode lead 16. As discussed above, at least a portion of the anode termination 62 (e.g., first part 63 and / or second part 64) includes a first coating (not shown), and at least a portion of the cathode termination 72 (e.g., first part 73 and / or second part 73) includes a second coating (not shown).

[0060] In general, a variety of methods can be used to attach the terminations. For example, in one embodiment, second part 64 of anode termination 62 is first bent upwardly to the position shown in FIG. 1. Capacitor element 33 is then placed over cathode termination 72 such that bottom surface 39 of capacitor element 33 contacts the adhesive and anode lead 16 is received by area 51. If desired, an insulating material (not shown), such as a plastic pad or tape, can be applied to the capacitor. Anode lead 16 may be placed between bottom surface 39 of pacitor element 33 and first part 63 of anode termination 62 to electrically isolate the anode and cathode terminations. Anode lead 16 is then electrically connected to region 51 using any technique known in the art, such as mechanical welding, laser welding, conductive adhesives, etc. For example, a laser may be used to weld anode lead 16 to anode termination 62. Lasers generally include a resonator that contains a laser medium capable of emitting photons by stimulated emission, and an energy source that excites the elements of the laser medium. One type of suitable laser is one in which the laser medium is composed of aluminum yttrium garnet (YAG) doped with neodymium (Nd). The excited particles are neodymium ions: Nd 3+ The laser medium may be continuously energized by an energy source to emit a continuous laser beam or may be radiated with energy to emit a pulsed laser beam. Once the anode lead 16 is electrically connected to the anode termination 62, the conductive adhesive may then be cured. For example, a heat press may be used to apply heat and pressure to ensure that the adhesive properly bonds the electrolytic capacitor element 33 to the cathode termination 72.

[0061] III. Casing material: The capacitor element is typically encapsulated in a casing material such that at least a portion of the anode and cathode terminations are exposed for mounting on a circuit board. For example, as shown in FIG. 1, capacitor element 33 may be encapsulated in casing material 28 such that a portion of anode termination 62 and a portion of cathode termination 72 are exposed.

[0062] In some embodiments, the casing material may include an epoxy composition comprising a resinous material including one or more epoxy resins crosslinked with one or more inorganic oxide fillers and, optionally, a co-reactant (hardener). To help improve the overall moisture resistance of the casing material, the inorganic oxide filler content is maintained at a high level, such as at least about 75% by weight of the composition, at least about 76% by weight, and in some embodiments, from about 77% to about 90% by weight. The nature of the inorganic oxide filler may include, but is not limited to, silica, alumina, zirconia, magnesium oxide, iron oxide (e.g., iron hydroxide oxide yellow), titanium oxide (e.g., titanium dioxide), zinc oxide (e.g., arsenic oxide), and the like. For example, the filler may vary from boron zinc hydroxide oxide, copper oxide, zeolites, silicates, clays (e.g., smectite clays), and the like, and composites (e.g., alumina-coated silica particles), and mixtures thereof. Regardless of the particular filler used, however, a significant portion, if not all, of the inorganic oxide filler is usually in the form of silica glass, which is believed to further enhance the moisture resistance of the casing material due to its high purity and relatively simple chemical form. The silica glass may, for example, comprise greater than about 30% by weight, in some embodiments from about 35% to about 90% by weight, in some embodiments from about 40% to about 80% by weight, and in some embodiments from about 20% to about 70% by weight, in some embodiments from about 25% to about 65% by weight, and in some embodiments from about 30% to about 60% by weight of the total composition, of the total weight of the filler used in the composition. Of course, other forms of silica, such as quartz, fumed silica, cristobalite, and the like, may also be used in combination with the silica glass.

[0063] The resin material typically comprises from about 0.5% to about 25% by weight of the composition, in some embodiments from about 1% to about 24% by weight, and in some embodiments from about 10% to about 23% by weight. Generally speaking, any of a variety of different types of epoxy resins can be used in the present invention. Examples of suitable epoxy resins include, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, ortho-cresol novolac type epoxy resins, brominated epoxy resins and biphenyl type epoxy resins, cycloaliphatic epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, cresol novolac type epoxy resins, and the like. Examples of epoxy resins include epoxy resins of the phenolic novolac type, naphthalene type epoxy resins, phenol aralkyl type epoxy resins, cyclopentadiene type epoxy resins, heterocyclic epoxy resins, etc. However, in order to facilitate imparting the desired degree of moisture resistance, it is particularly desirable to use epoxy phenol novolac (EPN) resins, which are glycidyl ethers of phenol novolac resins. These resins can be prepared, for example, by reacting phenols with excess formaldehyde in the presence of an acid catalyst to produce phenol novolac resins. The phenol novolac resins are then reacted with epichlorohydrin in the presence of sodium hydroxide to produce novolac epoxy resins. Specific examples of novolac type epoxy resins include phenol-novolac epoxy resins, cresol-novolac epoxy resins, naphthol-novolac epoxy resins, naphthol-phenol co-condensed novolac epoxy resins, naphthol-cresol co-condensed novolac epoxy resins, brominated phenol-novolac epoxy resins, etc. Regardless of the type of resin selected, the resulting phenolic novolac epoxy resins usually have more than two oxirane groups and can be used to produce cured coating compositions with high crosslink density, which may be particularly suitable for increasing moisture resistance. One such phenolic novolac epoxy resin is poly[(phenyl glycidyl ether)-co-formaldehyde]. Other suitable resins are commercially available from Huntsman under the ARALDITE trade name (e.g., GY289, EPN1183, EP1179, EPN1139, and EPN1138).

[0064] As indicated, the epoxy resin can optionally be crosslinked with a co-reactant (hardener) to further improve the mechanical properties of the composition and also increase its overall moisture resistance as discussed above. Examples of such coreactants may include, for example, polyamides, amidoamines (e.g., aromatic amidoamines such as aminobenzamide, aminobenzanilide, and aminobenzenesulfonamide), aromatic diamines (e.g., diaminodiphenylmethane, diaminodiphenylsulfone, and the like), aminobenzoates (e.g., trimethylene glycol di-p-aminobenzoate, and neopentyl glycol di-p-aminobenzoate, and the like), aliphatic amines (e.g., triethylenetetramine, isophoronediamine), cycloaliphatic amines (e.g., isophoronediamine), imidazole derivatives, guanidines (e.g., tetramethylguanidine), carboxylic anhydrides (e.g., methylhexahydrophthalic anhydride), carboxylic hydrazides (e.g., adipic hydrazide), phenol-novolac resins (e.g., phenol novolac, cresol novolac, and the like), carboxylic amides, and the like, as well as combinations thereof. Phenol-novolac resins may be particularly suitable for use in the present invention.

[0065] It should be understood that, aside from the components listed above, still other additives may also be used in the epoxy compositions used to form the casing, such as photoinitiators, viscosity modifiers, suspending aids, pigments, stress reducers, coupling agents (e.g., silane coupling agents), stabilizers, etc. If used, such additives will typically comprise from about 0.1 to about 20 weight percent of the total composition.

[0066] The particular manner in which the casing material is applied to the capacitor body can vary as desired. In one particular embodiment, the capacitor element is placed in a mold and the casing material is applied to the capacitor element such that it occupies the space defined by the mold and exposes at least a portion of the anode and cathode terminations. The casing material can be initially provided in the form of a single or multiple compositions. For example, a first composition can include an epoxy resin and a second composition can include a co-reactant. Regardless, once applied, the casing material can be heated or allowed to stand at ambient temperature to allow the epoxy resin to crosslink with the co-reactant, thereby curing and solidifying the epoxy composition into the desired shape of the case. For example, the composition can be heated to between about 15° C. and about 150° C. for several hours. In some embodiments, the mixture may be heated to a temperature of from about 20°C to about 120°C, and in some embodiments, from about 25°C to about 100°C.

[0067] Although by no means required, a moisture barrier layer can also be used which covers all or a portion of the casing material. Moisture barrier layers are generally formed from hydrophobic elastomers such as silicones, fluoropolymers, and the like. Silicone elastomers are particularly suitable for use in the moisture barrier layer of the present invention. Such elastomers usually have the following general formula:

[0068] [ka]

[0069] (In the formula, x is an integer greater than 1; R1, R2, R3, R4, R5, R6, R7, and R8 are independently monovalent groups typically containing from 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.). The polyorganosiloxanes are derived from polyorganosiloxanes such as those having the formula: ##STR1## Examples of such polyorganosiloxanes 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 polysiloxanes, and the like. The polyorganosiloxanes can be crosslinked to form elastomers using any of a variety of known techniques, such as by catalytic cure (e.g., platinum catalysis), room temperature vulcanization, moisture cure, and the like. Crosslinkers such as alkoxysilanes having the formula: Si-OR, where R is H, alkyl (eg, methyl), alkenyl, carboxyalkyl (eg, acetyl), can be used.

[0070] 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 of elasticity and some flexibility, which may help absorb some of the thermal stresses caused by the expansion of the casing, and may also allow it to be subjected to compressive forces. The flexibility of the material may be characterized by a correspondingly low modulus of elasticity (Young's modulus), such as less than about 5,000 kilopascals (kPa), in some embodiments from about 1 to about 2,000 kPa, and in some embodiments, from about 2 to about 500 kPa, measured at a temperature of about 25° C. The material also typically has some strength that allows it to retain its shape even when subjected to compressive forces. For example, the material may be The hydrophobic elastomer may have a tensile strength of from about 1 to about 5,000 kPa, in some embodiments from about 10 to about 2,000 kPa, and in some embodiments, from about 50 to about 1,000 kPa, measured at a temperature of about 25° C. Using the above conditions, the hydrophobic elastomer can further enhance the ability of the capacitor to function under extreme conditions.

[0071] Non-conductive fillers may be used in the moisture barrier layer to help achieve the desired flexibility and strength properties. If used, such additives typically comprise from about 0.5% to about 30%, in some embodiments from about 1% to about 25%, and in some embodiments from about 2% to about 20% by weight of the moisture barrier layer. Silicone elastomers may comprise from about 70% to about 99.5%, in some embodiments from about 75% to about 99%, and in some embodiments from about 80% to about 98% by weight of the moisture barrier layer. One particular example of such a filler is, for example, silica. Most forms of silica contain a relatively hydrophilic surface due to the presence of silanol groups (Si-OH), but in some cases, silica may be surface treated to make the surface more hydrophilic (CH3) nThe surface treatment agent may contain -Si- groups (wherein n is an integer of 1 to 3), which further increases 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 include organosilazanes and the silane coupling agents described above.

[0072] Due to its unique structure, the resulting capacitor assembly can exhibit various beneficial properties. For example, the dissipation factor of the capacitor assembly can be maintained at a relatively low level. Dissipation factor generally refers to the losses that occur in a capacitor and is usually expressed as a percentage of ideal capacitor performance. For example, the dissipation factor of the capacitor of the present invention is typically about 1% to about 25%, in some embodiments about 3% to about 10%, and in some embodiments about 5% to about 15%, measured at a frequency of 120 Hz. The capacitor assembly can also be used in high voltage applications, such as rated voltages of about 35 volts or more, in some embodiments about 50 volts or more, and in some embodiments about 60 volts to about 200 volts. For example, the capacitor assembly can exhibit a relatively high "breakdown voltage" (the voltage at which the capacitor fails to operate), such as about 2 volts or more, in some embodiments about 5 volts or more, in some embodiments about 10 volts or more, and in some embodiments about 10 to about 100 volts. Additionally, the capacitor assembly can also be capable of withstanding relatively high surge currents, which are also typical in high voltage applications. The peak surge current may be, for example, greater than or equal to about 100 amps, in some embodiments greater than or equal to about 200 amps, and in some embodiments, from about 300 amps to about 800 amps. EXAMPLES

[0073] The invention may be better understood with reference to the following examples. Test procedure: Equivalent series resistance (ESR): The equivalent series resistance was measured using a Keithley 3330 precision LCZ meter with Kelvin leads at 2 The measurements may be taken with a DC bias of 0.2 volts and a sine wave signal of 0.5 volts peak-to-peak. The operating frequency may be 100kHz and the temperature may be 23°C ±2°C.

[0074] Loss factor: Loss factor was measured using a Keithley 3330 precision LCZ meter with Kelvin leads at 2.2. The measurements may be taken with a DC bias of 1.5 V and a sine wave signal of 0.5 V peak-to-peak. The operating frequency may be 120 kHz and the temperature may be 23 °C ± 2 °C.

[0075] capacitance: Capacitance was measured using a Keithley 3330 precision LCZ meter with Kelvin leads. Measurements may be taken with a DC bias of 2.2 volts and a sine wave signal of 0.5 volts peak-to-peak. The operating frequency may be 120 Hz and the temperature may be 23°C ± 2°C.

[0076] Leakage Current: The leakage current may be measured using a leakage test meter at a temperature of 23° C.±2° C. and at rated voltage (eg, 16 volts) after a minimum of 60 seconds (eg, 180 seconds, 300 seconds).

[0077] Moisture sensitivity: Moisture sensitivity level testing (J-STD-020E) can be performed (50 parts) after exposure to a temperature of 30°C and a relative humidity of 60% for 24 and 48 hours. After reflow on the collected samples, electrical parameters and external cracks can be recorded by using an optical microscope and then compared.

[0078] Example 1: Anode samples were prepared using 70,000 μFV / g tantalum powder. Each anode sample was embedded with a tantalum wire, sintered at 1410 °C, and pressed to a mass of 5.1 g / cm 3 The resulting pellet had dimensions of 5.60 x 3.65 x 0.90 mm. The pellet was anodized to 71.0 volts in a water / phosphoric acid electrolyte having a conductivity of 8.6 mS at a temperature of 85°C to form a dielectric layer. The pellet was anodized again to 150 volts for 25 seconds in a water / boric acid / disodium tetraborate electrolyte having a conductivity of 2.0 mS at a temperature of 30°C to form a thicker oxide layer deposited on the outside.

[0079] A conductive polymer coating was formed by immersing the anode directly, without a precoat layer, in a dispersed poly(3,4-ethylenedioxythiophene) (Clevios® K, Heraeous) with a solids content of 1.1% and a viscosity of 20 mPa·s. Once coated, the part was dried at 125° C. for 20 minutes. This process was repeated 10 times. The part was then immersed in a dispersed poly(3,4-ethylenedioxythiophene) (Clevios® K, Heraeus) with a solids content of 2.0% and a viscosity of 20 mPa·s. Once coated, The parts were dried at 125° C. for 20 minutes. This process was repeated three times. The parts were then immersed in a dispersion of poly(3,4-ethylenedioxythiophene) (Clevios® K, Heraeus) with a solids content of 2% and a viscosity of 160 mPa·s. Once coated, the parts were The parts were then dried at 125°C for 20 minutes. This process was repeated 8 times. The parts were then dipped in a graphite dispersion and dried. Finally, the parts were dipped in a silver dispersion and dried. In this way, a large number of parts (3000) of 47μF / 35V capacitors were produced and encapsulated in silica resin.

[0080] Example 2: Capacitors were fabricated as described in Example 1, except that three layers of the organometallic solution were applied to the anode and cathode portions of the leadframe before encapsulation with silica resin. More specifically, the solution contained (3-glycidyloxypropyl)trimethoxysilane in ethanol (1.0%). A number of parts (3000) of 47 μF / 35V capacitors were fabricated. The median results of electrical parameters in the moisture sensitivity level test are shown in Table 1 below. External cracks from the top and bottom sides of the capacitors in the moisture sensitivity level test are shown in Table 2 below.

[0081] [Table 1]

[0082] [Table 2]

[0083] These and other modifications and variations of the present invention may be implemented 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 aspects may be interchanged both in whole or in part. Moreover, those skilled in the art will recognize that the above description is by way of example only and is not intended to limit the invention as further described in the appended claims.

Claims

1. A method for manufacturing a capacitor assembly, wherein the capacitor assembly comprises a sintered porous anode body, a dielectric disposed on the anode body, and a solid electrolyte capacitor element disposed on the dielectric, wherein the solid electrolyte comprises a plurality of conductive polymer particles, and the conductive polymer particles have the following formula (III): 【Chemical 1】 (wherein, R ７ is a linear or branched, C １ -C １８ alkyl group, C ５ -C １２ cycloalkyl group, C ６ -C １４ aryl group, C ７ -C １８ aralkyl group, or a combination thereof; q is an integer from 0 to 8) and contain an exogenous conductive polymer having a repeating unit of; an anode terminal electrically connected to the anode body, wherein at least a part of the anode terminal has a first coating containing an organometallic compound disposed thereon; a cathode terminal electrically connected to the solid electrolyte, wherein at least a part of the cathode terminal has a second coating containing an organometallic compound disposed thereon; and a casing material that houses the capacitor element and exposes the mounting surfaces of the anode terminal and the cathode terminal, wherein the casing material comprises an epoxy composition containing a silica filler of 75% by weight or more and a resinous material containing an epoxy resin that may be crosslinked with a co-reactant; comprising the organometallic compound of the first coating, the organometallic compound of the second coating, or both have the following general formula: 【Chemical Formula 2】 (wherein, M is an organometallic atom; R １ 、 R ２ 、 and R ３ are, independently, alkyl or hydroxyalkyl, and at least one of R １ 、 R ２ 、 and R ３ is hydroxyalkyl; n is an integer from 0 to 8; X is an organic or inorganic functional group) and the first coating disposed on at least a part of the anode terminal exists between the anode terminal and the casing material, and the second coating disposed on at least a part of the cathode terminal exists between the cathode terminal and the casing material, the method comprising coating a solution containing 0.5 to 1.0% by weight of the organometallic compound and an organic solvent on one or both of the anode terminal and the cathode terminal to form one or both of the first coating and the second coating, and housing the capacitor element in the casing material The method as described above.

2. The organometallic compound of the first coating, the organometallic compound of the second coating, or both have the following general formula: 【Chemical Formula 1】 (wherein, M is an organometallic atom; R1, R2, and R3 are independently alkyl or hydroxyalkyl, and at least one of R1, R2, and R3 is hydroxyalkyl; n is an integer from 0 to 8; X is an organic or inorganic functional group) The method according to claim 1, which has

3. The method according to claim 2, wherein M is silicon.

4. The method according to claim 3, wherein the hydroxyalkyl is OCH3.

5. The method according to claim 2, wherein R1, R2, and R3 are hydroxyalkyl.

6. The organometallic compound is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropylmethyldiethoxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, glycidoxymethyltripropoxysilane, glycidoxymethyltributoxysilane, β-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, β-glycidoxyethyltripropoxysilane, β-glycidoxyethyltributoxysilane, β-glycidoxyethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, α-glycidoxyethyltripropoxysilane, α-glycidoxyethyltributoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, β-glycidoxypropyltri The method according to claim 1, which is toxysilane, β-glycidoxypropyltriethoxysilane, β-glycidoxypropyltripropoxysilane, α-glycidoxypropyltributoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, α-glycidoxypropyltripropoxysilane, α-glycidoxypropyltributoxysilane, γ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltripropoxysilane, δ-glycidoxybutyltributoxysilane, δ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, γ-glycidoxybutyltripropoxysilane, γ-propoxybutyltributoxysilane, δ-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltripropoxysilane, α-glycidoxybutyltrimethoxysilane, α-glycidoxybutyltriethoxysilane, α-glycidoxybutyltripropoxysilane, α-glycidoxybutyltributoxysilane, or a combination thereof.

7. The method according to claim 1, wherein each surface of the anode terminal includes a first coating.

8. The method according to claim 1, wherein each surface of the cathode terminal includes a second coating.

9. The capacitor element further includes a cathode coating including a metal particle layer disposed on the solid electrolyte, and the metal particle layer includes a plurality of conductive metal particles dispersed in a resinous polymer matrix. The method according to claim 1.

10. The method according to claim 1, wherein the anode body includes tantalum and the dielectric includes tantalum pentoxide.

11. The method according to claim 1, wherein the solid electrolyte further includes a plurality of conductive polymer particles.

12. The conductive polymer particles have the following formula (IV): [Chemical Formula 3] (wherein, R is (CH2)a - O - (CH2)b; a is from 0 to 10; b is from 1 to 18; Z is an anion; X is a cation) The method according to claim 11, which includes a conductive polymer having a repeating unit of.

13. The method according to claim 1, wherein the capacitor assembly is disposed on the solid electrolyte and further includes an outer polymer coating containing pre-polymerized conductive polymer particles and a cross-linking agent.

14. The method according to claim 1, wherein the capacitor is in contact with an atmosphere having a relative humidity of about 40% or more.

15. The method according to claim 1, wherein the capacitor assembly further includes a moisture barrier layer that covers at least a part of the casing material.

16. The method according to claim 15, wherein the moisture barrier layer includes a silicone elastomer.

Images