HK1165084B - Solid electrolytic capacitor assembly with multiple cathode terminations - Google Patents

Description

Solid electrolytic capacitor assembly with multiple cathode terminals

Technical Field

The present invention relates to a capacitor device, in particular a solid electrolytic capacitor assembly with a plurality of cathode terminals.

Background

Solid electrolytic capacitors (e.g., tantalum capacitors) have made a major contribution to the miniaturization of electronic circuits, which makes such electronic circuits applicable in extreme environments. Many conventional solid electrolytic capacitors are constructed of terminals that are surface mounted to a printed circuit board. For example, metal lead frames are typically provided with an anode terminal and a cathode terminal. The anode terminal may include a portion bent upward toward the capacitor and welded to the anode lead-out wire. The cathode terminal is flat and receives the bottom surface of the capacitor. However, one problem with such conventional solid electrolytic capacitors is that the ripple frequency generates damaging heat within the capacitor due to the current flowing through the resistance welding defect (resistive electroplating), resulting in a relatively high Equivalent Series Resistance (ESR). Accordingly, there is a need for an improved solid electrolytic capacitor assembly.

Disclosure of Invention

In one embodiment of the invention, a solid electrolytic capacitor is disclosed that includes a capacitor element including an anode, a dielectric layer overlying the anode, and a cathode including a solid electrolyte overlying the dielectric layer. An anode lead is led out from the capacitor element in one direction and electrically connected to the anode. The first anode terminal is electrically connected to the anode lead. The assembly further includes a first cathode termination comprising a first member substantially parallel to and in electrical contact with the lower surface of the capacitor element and a second cathode termination comprising a second member substantially parallel to and in electrical contact with the upper surface of the capacitor element.

In another embodiment of the present invention, a method of manufacturing a capacitor assembly is disclosed. The method includes providing a solid electrolytic capacitor element, and leading out an anode lead from the solid electrolytic capacitor element in one direction; securing a capacitor element to a first lead frame comprising a first anode terminal and a first cathode terminal, wherein the first cathode terminal comprises a first member substantially parallel to and in electrical contact with a lower surface of the capacitor element, the first anode terminal comprising a recess for receiving a first anode lead; the anode lead is electrically connected with the first anode terminal; securing a second lead frame over the capacitor element including a second cathode termination, wherein the second cathode termination includes a second portion substantially parallel to and in electrical contact with the upper surface of the capacitor element; the first and second cathode terminals are electrically connected to the capacitor element.

Other features of the present invention will be described in more detail below.

Drawings

A full and enabling description of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures. In the description and drawings of the present invention, the same reference numerals are used for the same or similar parts. Wherein:

FIG. 1 is a perspective view of one embodiment of mounting a capacitor element to a first anode terminal and a first cathode terminal;

FIG. 2 is a perspective view of an assembly including the capacitor element of FIG. 1 with first anode and cathode terminations installed;

FIG. 3 is a perspective view of one embodiment of the capacitor assembly of FIG. 2 mounted to a second anode terminal and a second cathode terminal;

FIG. 4 is a perspective view of an assembly including the capacitor element of FIG. 1 with first and second anode terminals and first and second cathode terminals mounted thereto;

fig. 5 is a side view of the capacitor assembly shown in fig. 4.

Detailed Description

For those skilled in the art, the following description is only illustrative of exemplary embodiments of the present invention and does not limit the scope of the present invention.

Generally, the present invention relates to a capacitor assembly including a solid electrolytic capacitor element, an anode lead extending from the capacitor element, first and second cathode terminals, and an anode terminal. The first cathode termination includes a first portion that is substantially parallel to and in electrical contact with the lower surface of the capacitor element and the second cathode termination includes a second portion that is substantially parallel to and in electrical contact with the upper surface of the capacitor element. By the "sandwich" structure, the degree of surface contact between the cathode terminal and the capacitor element is increased, which aids in heat dissipation, enabling it to operate at higher currents that would normally lead to overheating. The terminals may also add mechanical support.

Referring to fig. 4 and 5, in one embodiment, capacitor assembly 30 includes a first cathode terminal 72 and a second cathode terminal 172 that are electrically connected to capacitor element 33. Specifically, the first cathode terminal 72 includes a first portion 73 that is generally parallel to and in electrical contact with the lower surface 39 of the capacitor element 33. The first cathode terminal 72 may also include a feature 74. Although illustrated as a "flat" configuration, member 74 may also be angled (e.g., substantially perpendicular) to first member 73 and may optionally be in electrical contact with rear surface 38 of capacitor element 33. Thus, the member 74 may define an aperture 76 to facilitate bending. Although described as a unitary body, it should be understood that the components may be discrete components, connected together either directly or through other conductive elements (e.g., metal).

Similarly, second cathode terminal 172 includes a second portion 173 that is generally parallel to and in electrical contact with upper surface 37 of capacitor element 33. As described above, the second cathode terminal 172 can also include a feature 174 that can be "flat" or angled (e.g., substantially perpendicular) to the second feature 173 and can optionally be in electrical contact with the back surface 38 of the capacitor element 33.

As shown, the capacitor assembly also includes a first anode terminal 62 in electrical contact with anode lead 16 of capacitor element 33. Anode lead 16 (e.g., a wire, a foil, etc.) leads from any surface of capacitor element 33, such as front surface 36, back surface 38, upper surface 37, and/or lower surface 39. For example, in the illustrated embodiment, the lead wires 16 are led out in the longitudinal "a" direction from the front surface 36 of the capacitor element 33 in the form of embedded wires. The anode lead 16 is composed of a conductive material such as tantalum, niobium, nickel, aluminum, hafnium, titanium, etc., and oxides and/or nitrides thereof. The lead 16 is electrically connected to the anode of the capacitor element 33 and may be connected using a variety of known connection means, such as by resistance or laser welding, with the lead 16 embedded in the anode during the molding process (e.g., prior to sintering).

In the illustrated embodiment, the first anode terminal 62 includes a third portion 64 that is angled with respect to the direction of exit of the lead 16. For example, third component 64 is generally perpendicular (e.g., 90 ° ± 5 °) to the longitudinal "a" direction. The upper surface 53 of the third member 64 has a recess 51 (see fig. 1) for receiving the anode lead 16. If desired, third member 64 may also be provided with an opening 69 to facilitate operation when anode terminal 62 is connected to capacitor element 33. The opening 69 may be provided between opposing arcuate surfaces for added strength (see fig. 3). First anode terminal 62 may also include an optional fourth feature 63 that is substantially parallel to lower surface 39 of capacitor element 33 and substantially perpendicular to third feature 64. The fourth part 63 may remain in a "flat" configuration in the resulting capacitor assembly, or may be bent into an angled configuration as desired. Although described above as a unitary body, it should be understood that the components may be discrete components, connected together either directly or through conductive elements (e.g., metal).

A second anode terminal 162 may also optionally be employed. In the illustrated embodiment, the second anode terminal 162 includes a fifth portion 164 that is angled with respect to the direction of exit of the lead 16 (e.g., the fifth portion 164 is substantially perpendicular to the longitudinal "a" direction). The lower surface 153 of the fifth member 164 is provided with a groove 151 (see fig. 3) for receiving the anode lead 16. The fifth member 164 may also be provided with an opening 169 to facilitate the connection operation of the anode terminal 162 (refer to fig. 3). As noted above, second anode terminal 162 may also include an optional sixth feature 163, with sixth feature 163 being substantially parallel to lower surface 39 of capacitor element 33 and substantially perpendicular to fifth feature 164. Sixth member 163 may be held in a "flat" configuration in the resulting capacitor assembly, or may be bent into an angled configuration as desired.

The grooves 51 and 151 on the anode terminal in this patent are located on specific surfaces. However, it should be understood that the grooves may be provided on other surfaces of the respective anode terminals. Further, more than one groove may be provided on each anode terminal, particularly in those embodiments employing multiple anode leads. Further, more terminals may be employed, with or without such grooves. In any case, the grooves 51 and 151 of the first and second anode terminals may be fitted together so that the anode lead 16 passes therethrough. More specifically, the lower portion 16a of the anode lead 16 may be located near the groove 51, and the upper portion 16b of the anode lead 16 may be located near the groove 151. The shape and size of the grooves 51 and 151 may be changed as needed to accommodate the corresponding portions of the anode lead 16. For example, in the illustrated embodiment, the grooves 51 and 151 are curved to form, when mated, an oval or circular slot that engages each other to receive the cylindrical anode lead 16. Of course, other shapes or sizes may be used. Typical shapes of the slots formed by the mating grooves may include, for example, circular, elliptical, oval, rectangular, diamond, square, and the like. Likewise, typical shapes of the grooves themselves may include, for example, curved shapes (e.g., U-shaped, semi-circular, etc.), V-shaped, etc.

Any of the conductive materials may be used to form the previously described terminals, such as conductive metals (e.g., copper, nickel, silver, zinc, tin, palladium, lead, copper, aluminum, molybdenum, titanium, iron, zirconium, magnesium, and alloys thereof). Preferred conductive metals include, for example, copper alloys (e.g., copper-zirconium, copper-magnesium, copper-zinc, or copper-iron alloys), nickel, and nickel alloys (e.g., nickel-iron alloys). The thickness of the terminals is typically selected to minimize the thickness of the capacitor. For example, the thickness of the terminals may vary from about 0.05 mm to about 1mm, and in some embodiments from about 0.05 mm to about 0.5mm, or from about 0.07 mm to about 0.2 mm. An example of a conductive material is a copper-iron alloy sheet available from Wieland, germany. As will be appreciated by those skilled in the art, the surfaces of the terminals may also be plated with nickel, silver, gold, tin, etc., if desired, to ensure that the finished product can be mounted on a circuit board. In one embodiment, the surfaces of both terminals are flash plated with nickel and silver layers, respectively, and the mounting surface is also plated with a tin solder layer.

The manner in which the capacitor elements are connected to the terminals is described in detail below in connection with fig. 1-3. For the sake of brevity, only the formation of a single capacitor component is described. However, it should be understood that the lead frame may include a plurality of terminals that are inserted into each capacitor assembly. As described above, fig. 1 shows a portion of a first lead frame, including the first anode terminal 62 and the first cathode terminal 72. It should be understood that only a portion of the lead frame is shown, and that the lead frame will typically include other components not explicitly shown. For example, the terminals may first be connected by a foil that is subsequently removed during the capacitor manufacturing process.

The first lead frame shown in fig. 1 adopts the following structure: wherein the first part 64 is bent upwardly from part 63, the cathode terminal 72 is of a "flat" construction. As indicated by the directional arrow in fig. 1, capacitor element 33 is positioned in this direction with its lower surface 39 in contact with member 73 of first cathode terminal 72 and anode lead 16 received by recess 51. If desired, a conductive adhesive (not shown) may be applied between first cathode terminal 72 and capacitor element 33 to enhance the degree of connection. The conductive adhesive may include, for example, conductive metal particles including a resin composition. The metal particles may be silver, copper, gold, platinum, nickel, zinc, bismuth, and the like. The resin composition includes 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). One particularly suitable adhesive is "Amicon CE 3513" silver loaded epoxy from Emerson and Cuming corporation. Other suitable conductive adhesives are described in U.S. patent application publication No. 2006/0038304 to Osako et al, which is incorporated by reference in its entirety for all purposes.

Anode lead 16 is electrically connected to first terminal 62 at groove 51 using any technique known in the art, such as mechanical welding, laser welding, and conductive adhesive. In one embodiment, for example, anode lead 16 is welded (e.g., laser welded) at groove 51.

Once the "pre-assembled assembly" shown in fig. 2 is formed, a second lead frame may be attached thereto. More specifically, the second lead frame shown in fig. 3 has a structure in which the second part 164 is bent upward from the part 163, and the second cathode terminal 172 has a "flat" structure. As shown by the directional arrow in fig. 3, the capacitor element 33 is placed in this direction with its upper surface 37 in contact with the part 173 of the second cathode terminal 172, and the anode lead 16 is received by the groove 151. If necessary, a conductive adhesive (not shown) is applied between the capacitor element 33 and the second cathode terminal 172 to improve the degree of connection. Anode lead 16 is electrically connected to second terminal 162 at groove 151 using any means known in the art, such as mechanical welding, laser welding, conductive adhesive, and the like. In one embodiment, for example, the anode lead 16 is attached at the groove 151 using a conductive adhesive. Any conductive adhesive used may be cured by known techniques, for example, heat and pressure may be applied using a hot press to ensure proper connection of capacitor element 33 to first cathode terminal 72, second cathode terminal 172, and second anode terminal 162. The final capacitor assembly 30 is shown in fig. 4.

Once the capacitor elements are connected, the lead frame is encapsulated in a resin casing 58 (see fig. 5) filled with silicon dioxide or any other known encapsulation material. The length and width of the housing may vary depending on the requirements of a given application. Suitable housings include, for example, "a", "B", "F", "G", "H", "J", "K", "L", "M", "N", "P", "R", "S", "T", "W", "Y", or "X" types (AVX corporation). After encapsulation, the exposed portions 262 and 272 corresponding to the first anode terminal 62 and the first cathode terminal 72 may be trimmed and/or bent (e.g., at an approximately 90 ° angle) along the exterior of the housing 58. Likewise, the exposed portions 362 and 372 corresponding to the second anode and cathode terminals 162 and 172 may be trimmed and/or bent (e.g., at an approximately 90 ° angle) along the exterior of the housing 58. The exposed portion of the capacitor assembly 30 completed in the above manner may be formed into a J-shaped pin, but any other known shape may be formed according to the present invention.

The capacitor elements employed in the capacitor assemblies described above and set forth in this patent generally include an anode, dielectric, and solid electrolyte. The anode is comprised of a valve metal composition having a high specific load, for example, about 5,000 muF V/g or more, in some embodiments about 25,000 muF V/g or more, in some embodiments about 40,000 muF V/g or more, in some embodiments about 70,000 muF V/g-200, 000 muF V/g or more. The valve metal composition comprises a valve metal (i.e., a metal capable of oxidation) or a compound based on a valve metal, for example, tantalum, niobium, aluminum, hafnium, titanium and alloys thereof, oxides thereof, nitrides thereof, and the like. For example, the valve metal composition may include an electrically conductive oxide of niobium, e.g., niobium oxide having a niobium to oxygen atomic ratio of 1:1.0 + -1.0, in some embodiments 1:1.0 + -0.3, in some embodiments 1:1.0 + -0.1, and in some embodiments, 1:1.0 + -0.05. For example, the niobium oxide may be NbO_0.7、NbO_1.0、NbO_1.1And NbO₂. In a preferred embodiment, the composition comprises NbO_1.0It is a conductive niobium oxide that remains chemically stable even after high temperature sintering. Examples of such valve metal oxides are found in Fife patent No. 6,322,912, Fife et al patent No. 6,391,275, Fife et al patent No. 6,416,730, Fife patent No. 6,527,937, Kimmel et al patent No. 6,576,099, Fife et al patent No. 6,592,740, Kimmel et al patent No. 6,639,787, Kimmel et al patent No. 7,220,397, Schnitter application publication No. 2005/0019581, Schnitter et al application publication No. 2005/0103638, and Thomas et al application publication No. 2005/0013765, all of which are incorporated herein by reference in their entirety for all purposes.

The anode is typically formed using conventional fabrication procedures. In one embodiment, a tantalum or niobium oxide powder having a particular particle size is first selected. For example, the particles may be in the form of platelets, horns, nodules, and mixtures or variations thereof. The particles have a sieve size distribution of at least about 60 mesh, in some embodiments about 60 mesh to about 325 mesh, and in some embodiments about 100 mesh to about 200 mesh. Further, the specific surface area is about 0.1 to 10.0m²A/g, in some embodiments about 0.5 to about 5.0m²A/g, in some embodiments about 1.0 to about 2.0m²(ii) in terms of/g. The "specific surface area" is a surface area measured by a physical gas adsorption (B.E.T.) method published by Brunauer, Emmet and Teller in J.Am.Chem.Soc.1938, page 309, and the adsorbed gas is nitrogen. Also, the bulk (or Scott) density is typically about 0.1-5.0g/cm³And in some embodiments, about 0.2 to about 4.0g/cm³And in some embodiments about 0.5 to about 3.0 g/cm³。

To facilitate the fabrication of the anode, other components may also be added to the conductive particles. For example, the conductive particles may optionally be mixed with a binder and/or lubricant to ensure that the particles properly adhere to each other when pressed into an anode body. Suitable binders include camphor, stearic acid and other soap fatty acids, polyethylene glycol (Carbowax) (united states carbide), glyphosate (glyphosate) (united states general electric), polyvinyl alcohol, naphthalene, vegetable waxes, and microcrystalline waxes (refined paraffin waxes). The binder is soluble and dispersible in the solvent. Examples of the solvent include water, alcohol and the like. The percentage of binder and/or lubricant is about 0.1% to about 8% by weight of the total mass. However, it should be understood that the present invention does not necessarily require the use of binders and lubricants.

The resulting powder may be compacted using any conventional powder molding press. For example, the molding press may be a single station molding press that employs a mold and one or more punches. Alternatively, an anvil-type molding press using only a single die and a single lower punch may also be employed. There are several basic types of single station presses, such as cam presses, toggle presses/toggle plate presses and eccentric presses/crank presses with different production capacities, which may be, for example, single-action, double-action, floating-bed presses, movable-plate presses, opposed-plunger presses, screw presses, impact presses, hot-pressing presses, impression presses or finishing presses. The powder may be compacted around an anode lead (e.g., a tantalum lead). Furthermore, it should be further appreciated that the anode lead may be connected (e.g., welded) to the anode body after pressing and/or sintering of the anode body. After compaction, the granules may be heated at a temperature (e.g., about 150 ℃ to 500 ℃) under vacuum for several minutes to remove any binder/lubricant. Alternatively, binder/lubricant removal by contacting the particles with an aqueous solution may be used, as described in U.S. patent No. 6,197,252 to Bishop et al, which is incorporated by reference in its entirety for all purposes. The particles are then sintered to form porous monolithic particles. For example, in one embodiment, the particles may be sintered at a temperature between about 1200 ℃ and 2000 ℃, and in some embodiments, the particles are sintered at a temperature between about 1500 ℃ and 1800 ℃ in a vacuum or inert atmosphere. During sintering, the particles shrink due to the growth of the bonds between the particles. In addition to the above techniques, anodes according to the present invention may be made by any other means, such as those described in U.S. Pat. No. 4,085,435 to Galvagni, patent No. 4,945,452 to Sturmer et al, patent No. 5,198,968 to Galvagni, patent No. 5,357,399 to Salisbury, patent No. 5,394,295 to Galvagni et al, patent No. 5,495,386 to Kulkarni, and patent No. 6,322,912 to Fife, which are incorporated by reference in their entirety for all purposes.

Although not required, the electrical performance of the capacitor can be improved by selecting the thickness of the anode. For example, the thickness of the anode is less than or equal to about 4 mm, in some embodiments, the anode is about 0.05 mm to about 2mm, and in some embodiments, the anode is about 0.1 mm to about 1 mm. The shape of the anode may also be selected to improve the electrical performance of the capacitor. For example, the anode may be curved, sinusoidal, rectangular, U-shaped, V-shaped, and the like. The anode may also be "slot" shaped, including one or more grooves, depressions, or indentations within the slot to increase the surface area to volume ratio, minimize ESR, and extend the frequency response of the capacitor. The "slots" are described in U.S. patent 6,191,936 to Webber et al, U.S. patent 5,949,639 to Maeda et al, U.S. patent 3,345,545 to Bourgault et al, and U.S. patent 2005/0270725 to Hahn et al, which are incorporated by reference in their entirety for all purposes.

Once fabricated, the anode may be anodized to form a dielectric layer over and/or within the anode. Anodization is an electrochemical process by which the anode is oxidized to form a material with a relatively high dielectric constant. For example, a niobium oxide (NbO) anode may be anodized to niobium pentoxide (Nb)₂O₅). Generally, anodization begins with the application of an electrolyte to the anode, such as by dipping the anode into the electrolyte. The electrolyte is typically in the form of a liquid, such as a solution (e.g., aqueous or non-aqueous), dispersion, melt, or the like. Solvents such as water (e.g., deionized water) are typically employed in the electrolyte; ethers (e.g., diethyl ether and tetrahydrofuran); alcohols (e.g., methanol, ethanol, n-propanol, isopropanol, and butanol); a triglyceride; ketones (e.g., acetone, methyl ethyl ketone, and methyl isobutyl ketone); esters (e.g., ethyl acetate, butyl acetate, diethylene glycol ethyl ether acetate, and propylene glycol methyl ether acetate); amides (e.g., dimethylformamide, dimethylacetamide, dimethyloctyl/decyl 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. The solvent is present in the electrolyte in an amount of about 50wt% to about 99.9wt%, in some embodiments about 75wt% to about 99wt%, and in some embodiments about 80wt% to about 95 wt%. Although not required, an aqueous solvent (e.g., water) is often employed in order to obtain the desired oxide. In fact, water may be present in the electrolyte in a mass percentage of the solvent usedAbout 50wt% or more, in some embodiments about 70wt% or more, and in some embodiments, about 90wt% to 100 wt%.

The electrolyte has an ionic conductivity of about 1 milliSiemens per centimeter (mS/cm) or greater, in some embodiments about 30 mS/cm or greater, and in some embodiments, from about 40 mS/cm to about 100 mS/cm, as measured at a temperature of 25 ℃. In order to enhance the ionic conductivity of the electrolyte, a compound capable of dissociating in a solvent to form ions may be used. Suitable ionic compounds for this purpose include, for example, acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, boric acid, organic boric acid (boronic acid), and the like; organic acids including carboxylic acids such as acrylic acid, methacrylic acid, malonic acid, succinic acid, salicylic acid, sulfosalicylic acid, adipic acid, maleic acid, malic acid, oleic acid, gallic acid, tartaric acid, citric acid, formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, phthalic acid, isophthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, itaconic acid, trifluoroacetic acid, barbituric acid, cinnamic acid, benzoic acid, 4-hydroxybenzoic acid, aminobenzoic acid, and the like; sulfonic acids such as methanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, trifluoromethanesulfonic acid, styrenesulfonic acid, naphthalenedisulfonic acid, hydroxybenzenesulfonic acid, dodecylsulfonic acid, dodecylbenzenesulfonic acid and the like; polymeric acids, such as poly (acrylic acid) or poly (methacrylic acid) and copolymers thereof (e.g., maleic acid-acrylic acid copolymers, sulfonic acid-acrylic acid copolymers, styrene-acrylic acid copolymers), carrageenan, carboxymethyl cellulose, alginic acid, and the like. The concentration of the ionic compound is selected to obtain the desired ionic conductivity. For example, the acid (e.g., phosphoric acid) may be present in an amount of about 0.01 wt% to about 5wt%, in some embodiments about 0.05 wt% to about 0.8 wt%, and in some embodiments, about 0.1 wt% to about 0.5 wt% of the electrolyte. If desired, mixtures of ionic compounds can also be used in the electrolyte.

And passing current through the electrolyte to form a dielectric layer. The voltage value determines the thickness of the dielectric layer. For example, the power supply may initially be set in constant current mode until the desired voltage value is reached. The power supply can then be switched to a constant potential mode to ensure that the desired thickness of the dielectric layer is formed on the anode surface. Of course, other known methods, such as potentiostatic pulse method or potentiostatic step method, may also be employed. The voltage is typically about 4-200V, and in some embodiments, about 9-100V. During anodization, the electrolyte is maintained at an elevated temperature, for example, about 30 ℃ or above, in some embodiments, about 40 ℃ to about 200 ℃, and in some embodiments, about 50 ℃ to about 100 ℃. The anodization may also be performed at room temperature or lower. The resulting dielectric layer may be formed on the surface of the anode or within the anode hole.

Once the dielectric layer is formed, a protective coating may optionally be applied, for example, using a relatively insulating resinous material (natural or synthetic) as the protective layer, such material having a specific resistance greater than about 10W/cm, in some embodiments greater than about 100W/cm, in some embodiments greater than about 1,000W/cm, and in some embodiments greater than about 1 × 10⁵W/cm, and in some embodiments greater than about 1 × 10¹⁰W/cm. Certain resinous materials useful in the present invention include, but are not limited to, polyurethanes, polystyrenes, unsaturated or saturated fatty acid esters (e.g., glycerol esters), and the like. For example, suitable fatty acid esters include, but are not limited to, laurate, myristate, palmitate, stearate, eleostearate, oleate, linoleate, linolenate, elaeostearate, laccaite, and the like. These fatty acid esters have been found to be particularly useful when used in relatively complex combinations to form "drying oils" which enable the resulting films to rapidly polymerize to form stable layers. The drying oil may comprise mono-, di-and/or triglycerides having a glycerol backbone with one, two and three esterified fatty acyl residues, respectively. For example, certain suitable drying oils that may be used include, but are not limited to, olive oil, linseed oil, castor oil, tung oil, soybean oil, and shellac. These protective coating materials and other protective coating materials are described in more detail in U.S. Pat. No. 6,674,635 to Fife et al, which is incorporated by reference in its entirety for all purposes。

The anodized oxide is then subjected to a step to form a cathode comprising a solid electrolyte such as manganese dioxide, a conductive polymer, or the like. For example, manganese dioxide solid electrolyte can be prepared by manganese nitrate (Mn (NO)₃)₂) Is formed by pyrolysis. Such techniques are described in U.S. patent No. 4,945,452 to Sturmer et al, which is incorporated by reference in its entirety for all purposes. Alternatively, polymers comprising one or more poly-heterocycles (e.g., polypyrrole; polythiophene, poly (3, 4-vinyldioxythiophene) (PEDT); polyaniline); polyacetylene; poly-p-phenylene; a polyphenolate; and their respective derivatives. Further, the conductive polymer coating layer may also be a multi-layer conductive polymer layer, if necessary. For example, in one embodiment, the conductive polymer cathode may comprise one layer formed from PEDT and another layer formed from polypyrrole. A conductive polymer coating can be applied over the anode by various methods. For example, a conductive polymer coating can be formed using conventional methods, such as electrochemical polymerization, screen printing, dipping, electrophoretic coating, spray coating, and the like. For example, in one embodiment, the monomer used to form the conductive polymer (e.g., 3, 4-ethylenedioxythiophene) may be first mixed with a polymerization catalyst to form a solution. For example, one suitable polymerization catalyst is CLEVIOS C, which is iron (III) toluene-sulfonate sold by the company h.c. Starck. CLEVOS C is a commercial catalyst for CLEVOS M. CLEVIOS M is 3, 4-ethylenedioxythiophene, which is also a PEDT monomer sold by h.c. Starck. Once the catalyst dispersion is formed, the anode part may then be immersed in the dispersion so that polymer forms on the surface of the anode part. Alternatively, the catalyst and monomer may be applied separately to the anode member. In one embodiment, for example, the catalyst may be dissolved in a solvent (e.g., butanol) and then applied to the anode member in the form of an impregnation solution. The anode part is then dried to remove the solvent thereon. The anode part is then dipped into a solution containing a suitable monomer. Once the monomer is in contact with the surface of the catalyst-containing anode part, it is allowed to rise thereonAnd (4) carrying out biochemical polymerization. In addition, the catalyst (e.g., CLEVOS C) may also be mixed with the material (e.g., resinous material) used to form the optional protective coating. In this case, the anode part is immersed in a solution containing a monomer (CLEVIOS M). As a result, the monomer may come into contact with the catalyst inside and/or on the surface of the protective coating and react therewith to form a conductive polymer coating. Although various methods are described above, it should be understood that any other method of applying a conductive coating to an anode may be used in the present invention. For example, other methods of applying such conductive polymer coatings are described in U.S. Pat. Nos. 5,457,862, 5,473,503, 5,729,428 to Sakata et al and 5,812,367 to Kudoh et al, which are incorporated by reference in their entirety for all purposes.

In most embodiments, the solid electrolyte is healed once applied (heal). Healing may be performed after each application of the solid electrolyte layer or after the application of the entire coating. In some embodiments, for example, the solid electrolyte healing process is by immersing the particles in an electrolyte solution, e.g., a phosphoric acid solution and/or a sulfuric acid solution, and then applying a constant voltage to the solution until the current is reduced to a preselected level. This healing can be accomplished in multiple steps, if desired. For example, in one embodiment, the particles with the conductive polymer coating are first dipped into a phosphoric acid solution and a voltage of about 20V is applied, then dipped into a sulfuric acid solution and a voltage of 2V is applied. In this embodiment, the use of a second low voltage sulfuric acid solution or toluenesulfonic acid solution helps to increase the capacitance and reduce the loss factor (DF) of the resulting capacitor. After coating some or all of the above layers, the particles may be cleaned, if necessary, to remove various by-products, excess catalyst, etc. In addition, in some cases, drying may be performed after some or all of the above-described impregnation operations. For example, after application of the catalyst and/or washing, the particles may need to be dried to open the pores of the particles so that it can receive liquid in a later impregnation step.

The component may optionally be coated with an outer coating, if desired. The outer coating may comprise at least one carbonaceous layer and at least one metallic layer overlying the carbonaceous layer. The metal layer may act as a solderable conductor, contact layer and/or charge collector for the capacitor. The metal layer may be formed of a conductive metal such as copper, nickel, silver, zinc, tin, palladium, lead, aluminum, molybdenum, titanium, iron, zirconium, magnesium, and alloys thereof. Silver is a particularly suitable conductive metal for this metal layer. The carbon layer may limit contact between the metal layer and the solid electrolyte. Such contact increases the resistance of the capacitor. The carbonaceous layer may be formed using various known carbonaceous materials, such as graphite, activated carbon, carbon black, and the like. The thickness of the carbonaceous layer is generally about 1 μm to 50 μm, in some embodiments about 2 μm to 30 μm, and in some embodiments about 5 μm to 10 μm. Likewise, the thickness of the metal layer is generally about 1 μm to 100 μm, in some embodiments about 5 μm to 50 μm, and in some embodiments about 10 μm to 25 μm.

The invention will be better understood from the following examples.

Examples of the invention 1

Initially, tantalum powder (specific charge 59,750 CV/g) was pressed into pellet samples having a length of 5.1 mm, a width of 3.7 mm and a thickness of 0.9 mm. During the pressing step, a tantalum wire (0.24 mm diameter) was inserted into the anode pellet. And sintering the pellets in vacuum at 1320 ℃, and carrying out anodic oxidation in 12V and 0.1% phosphoric acid electrolyte to obtain a capacitor of 330 mu F at 120 Hz. The method comprises the steps of sequentially applying CLEVIOS-C (iron (III) tosylate and CLEVIOS-M (3, 4-ethylenedioxythiophene) in a butanol solvent to form a cathode of a conductive polymer, more specifically, dissolving CLEVIOS-C in a butanol solvent and applying the solution to pellets in the form of a dipping solution, drying the pellets to remove the solvent from the pellets, dipping the pellets in a solution containing CLEVIOS-M, anodizing the pellets again in a 0.1% phosphoric acid solution, and drying at room temperature for 2 hours, continuously repeating the dipping 6 times to accumulate a uniform outer layer of polymer, forming an outer carbon coating and a silver coating, and completing the manufacturing process of an anode.

Once formed, the capacitor element is connected to a single copper-based lead frame having a flat cathode terminal (pad) and a U-shaped groove (anode terminal) for connecting an anode lead. More specifically, the cathode terminal is connected to the lower surface of the capacitor element using a silver adhesive. The anode lead is adjusted to properly "set" (seat) the lead on the U-shaped groove, and then laser welding is used to weld the lead on the groove. Once the capacitor elements are connected, the lead frame is encapsulated in epoxy, with the exposed terminals bent along the exterior of the housing. The capacitance (at 120 Hz) and ESR (at 100 kHz) of each fraction were measured at room temperature using an HP4192A impedance analyzer. Each part was subjected to a standard lead-free reflow temperature profile (peak temperature of 255 ℃) and then the capacitance was re-measured using the same equipment. Table 1 below summarizes the median output of the three test samples (90 portions of each sample).

As shown in the table above, the ESR value increased significantly after reflow soldering. It is believed that the increase in ESR is due in part to the significant difference in the coefficient of thermal expansion of the capacitor, resulting in significant thermo-mechanical stress.

Example 2

A capacitor was formed as described in example 1, with the addition of a second lead frame. The second lead frame and the first lead frame are the same in the following respects: it also has a flat cathode terminal (pad) and a U-shaped groove for connecting a lead (anode terminal). The cathode terminal of the second leadframe is connected to the upper surface of the capacitor element using a silver adhesive (as shown and described herein). The U-shaped groove of the second lead frame is adjusted to receive the anode lead, which is then laser welded into the groove. Once the capacitor elements are connected in such a "sandwich" configuration, the lead frame is encapsulated in epoxy, with the exposed terminals bent along the exterior of the housing. The capacitance (at 120 Hz) and ESR (at 100 kHz) of each fraction were measured at room temperature using an HP4192A impedance analyzer. Each part was subjected to a standard lead-free reflow temperature profile (peak temperature of 255 ℃) and then the capacitance was re-measured using the same equipment. Table 2 below summarizes the median output of the three test samples (90 portions of each sample).

As shown in the table above, the increase in ESR for these samples was much less than the increase observed for the single leadframe capacitor in example 1.

These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention. Additionally, it should be understood that aspects of the various embodiments may be substituted in whole or in part. Furthermore, 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 so further described in such appended claims.

Claims (14)

1. A capacitor assembly, comprising:

a capacitor element comprising an anode, a dielectric layer overlying the anode, and a cathode comprising a solid electrolyte overlying the dielectric layer, wherein the capacitor element has an upper surface and an opposite lower surface;

an anode lead wire led out from the capacitor element in one direction and electrically connected to the anode;

a first anode terminal electrically connected to the anode lead, said first anode terminal comprising a third member angled with respect to the direction of the anode lead, the third member having an upwardly facing recess for receiving the lower portion of the anode lead;

a second anode terminal comprising a fourth member angled with respect to the anode lead direction, the fourth member having a downwardly facing recess for receiving the upper portion of the anode lead;

a first cathode termination including a first member substantially parallel to and in electrical contact with the lower surface of the capacitor element;

a second cathode termination comprising a second member substantially parallel to and in electrical contact with the upper surface of the capacitor element; and a case enclosing the capacitor element, at least a portion of the first cathode terminal, the second cathode terminal, the first anode terminal, and the second anode terminal being exposed outside the case.

2. The capacitor assembly of claim 1 wherein the anode lead is positioned between and in electrical contact with the upwardly facing recess and the downwardly facing recess.

3. The capacitor assembly of claim 2 wherein the grooves fit together with each other.

4. The capacitor assembly of claim 2 wherein the upward facing groove, the downward facing groove, or both grooves are U-shaped.

5. The capacitor assembly of claim 1, wherein the anode comprises tantalum, niobium, or a conductive oxide thereof.

6. The capacitor assembly of claim 1, wherein the solid electrolyte comprises manganese dioxide, a conductive polymer, or a combination thereof.

7. A method of forming a capacitor assembly, the method comprising:

providing a solid electrolytic capacitor element, and leading out an anode from the capacitor element in one direction;

securing the capacitor element to a first lead frame comprising a first anode terminal and a first cathode terminal, wherein the first cathode terminal comprises a first member substantially parallel to and in electrical contact with the lower surface of the capacitor element, the first anode terminal comprising a recess for receiving an anode lead;

electrically connecting an anode lead to a first anode terminal, the first anode terminal comprising a third member oriented at an angle to the direction of the anode lead, the third member having an upwardly facing recess for receiving the lower portion of the anode lead;

securing a second lead frame to a capacitor element including a second cathode termination, wherein the second cathode termination includes a second portion substantially parallel to and in electrical contact with the upper surface of the capacitor element, wherein the second lead frame further includes a second anode termination including a fourth portion angled with respect to the direction of the anode lead, the fourth portion having a downwardly facing recess for receiving the upper portion of the anode lead; and

and electrically connecting the capacitor element with the first cathode terminal and the second cathode terminal, wherein a case encloses the capacitor element and exposes at least a portion of the first cathode terminal, the second cathode terminal, the first anode terminal, and the second anode terminal to the outside.

8. The method of claim 7 wherein a conductive adhesive is applied between the first part of the first cathode termination and the lower surface of the capacitor element.

9. The method of claim 7 wherein a conductive adhesive is applied between the second part of the second cathode termination and the upper surface of the capacitor element.

10. The method of claim 7, wherein the anode lead is laser welded to the first anode terminal at the groove.

11. The method of claim 7, wherein an anode lead is positioned between and in electrical contact with the upwardly facing groove and the downwardly facing groove.

12. The method of claim 11, wherein the grooves fit together with each other.

13. The method of claim 7, wherein the groove is U-shaped.

14. The method of claim 7 wherein the capacitor element comprises an anode, a dielectric layer overlying the anode, and a cathode comprising a solid electrolyte overlying the dielectric layer.