HK1221817B - Carrier wire for solid electrolytic capacitors - Google Patents

Description

Carrier wire for solid electrolytic capacitors

Technical Field

The present invention relates to the field of solid electrolytic capacitors, and in particular to a carrier wire for solid electrolytic capacitors.

Background Art

Solid electrolytic capacitors (such as tantalum capacitors) have made significant contributions to the miniaturization of electronic circuits, enabling their use in extreme environments. The anode of a typical solid electrolytic capacitor consists of a porous anode body from which an anode lead extends and connects to the capacitor's anode terminal. The anode is prepared by first pressing tantalum powder into pellets and then sintering them to form a fused bond between the individual powder particles. A problem with many conventional solid electrolytic capacitors is the small particle size of the tantalum pellets, which reduces the volumetric contact between the anode body and the anode lead. In practice, it is difficult to find many contact points between the anode lead and the powder particles. As the contact area between the anode body and the anode lead decreases, the resistance at the contact point between the anode lead and the anode increases. This increase in equivalent series resistance (ESR) reduces the capacitor's electrical performance. On the other hand, as the anode lead diameter increases, the internal resistance of the anode lead itself increases. This increase in internal resistance can offset any improvement (or reduction) in ESR that results from the increased number of contact points between the anode body and the anode lead. Furthermore, an increase in the diameter of the anode lead wire results in an increase in the energy required to weld the anode lead wire to the anode termination portion of the lead frame using resistance welding or laser welding.

Therefore, there is a need for an improved solid electrolytic capacitor that has the benefit of increasing the number of contact points between the anode body and the anode lead without the undesirable effect of the lead wire's inherent resistance increasing as its diameter increases, achieving a balance between these benefits and undesirable effects, thereby significantly improving the capacitor's electrical performance by achieving ultra-low ESR levels. There is also a need for achieving this balance while minimizing the energy required to electrically connect the anode lead wire to the anode terminal.

Summary of the Invention

According to one embodiment of the present invention, a solid electrolytic capacitor including a capacitor element and an anode lead assembly is disclosed. The capacitor element includes a sintered porous anode body; a dielectric layer covering the sintered porous anode body; and a cathode covering the dielectric layer and including a solid electrolyte. The anode lead assembly includes a first anode lead having an embedded portion located within the sintered porous anode body and an outer portion extending longitudinally from the surface of the sintered porous anode body. In addition, the outer portion includes a substantially flat surface. In addition, a second anode lead is located outside the sintered porous anode body and includes a first portion and a second portion, wherein the first portion includes a substantially flat surface. In addition, the substantially flat surface of the first portion of the second anode lead is connected to the substantially flat surface of the outer portion of the first anode lead.

According to another embodiment of the present invention, a method of forming a solid electrolytic capacitor is disclosed. The method includes placing a first anode lead within a powder formed from a valve metal composition, wherein the first anode lead includes an embedded portion within a porous anode body and an outer portion extending longitudinally from a surface of the anode body, wherein the outer portion includes a substantially flat surface; compacting the powder around the embedded portion of the first anode lead; sintering the compacted powder to form a sintered porous anode body; placing a second anode lead outside the sintered porous anode body, wherein the second anode lead includes a first portion and a second portion, wherein the first portion includes a substantially flat surface; connecting the substantially flat surface of the first portion of the second anode lead to the substantially flat surface of the outer portion of the first anode lead; and connecting the second portion of the second anode lead to an anode terminal, forming an electrical connection between the second portion of the second anode lead and the anode terminal.

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

BRIEF DESCRIPTION OF THE DRAWINGS

A complete and enabling description of the present invention, including the best embodiment known to those skilled in the art, and referenced figures, are further described in detail in the remainder of this specification.

FIG1 is a perspective top view of an electrolytic capacitor according to an embodiment of the present invention;

FIG2 is a perspective side view of an embodiment of an electrolytic capacitor of the present invention;

FIG3 is a top view of the electrolytic capacitor of FIG1 and FIG2;

4 is another top view of the electrolytic capacitor of FIGS. 1 and 2 with the anode lead assembly welded to the anode terminal;

FIG5 is a bottom view of the electrolytic capacitor of FIG1 to FIG4;

FIG6 is a side view of the electrolytic capacitor of FIG1 to FIG5;

FIG7 is a side view of another electrolytic capacitor of the present invention;

FIG8 is a side view of an embodiment of an anode lead assembly of the present invention; and

FIG9 is a perspective view of another embodiment of a solid electrolytic capacitor according to the present invention, wherein the capacitor includes two capacitor elements and two anode lead assemblies.

In the present specification and drawings, repeated use of reference numerals refers to the same or similar parts or elements.

DETAILED DESCRIPTION

Those skilled in the art should understand that the discussion herein is merely an exemplary description of the present invention and is not intended to limit the broader scope of protection of the present invention.

In general, the present invention relates to a solid electrolytic capacitor comprising a capacitive element, the solid electrolytic capacitor comprising a sintered porous anode body, a dielectric layer overlying the sintered porous anode body, and a cathode overlying the dielectric layer and comprising a solid electrolyte. The capacitor further comprises an anode lead assembly comprising a first anode lead and a second anode lead. The first anode lead comprises an embedded portion positioned within the porous anode body and an outer portion extending longitudinally from a surface of the porous anode body. The outer portion of the first anode lead comprises a substantially flat surface. The substantially flat surface can be formed by flattening, pressing, or changing the geometry of all or a portion of the outer portion of the first anode lead. Thus, in some embodiments, a dimension (e.g., height/thickness) of all or a portion of the outer portion of the first anode lead is smaller than a corresponding dimension (e.g., height/thickness) of the embedded portion. In addition, the capacitor comprises a second anode lead positioned outside the porous anode body, wherein the second anode lead comprises a first portion and a second portion, wherein the first portion comprises a substantially flat surface. The substantially flat surface can be formed by flattening, pressing, or changing the geometry of the first portion of the second anode lead. Thus, in some embodiments, the dimensions (e.g., height/thickness) of the first portion of the second anode lead are smaller than the corresponding dimensions (e.g., height/thickness) of the second portion of the second anode lead. Furthermore, the substantially flat surface of the first portion of the second anode lead contacts the substantially flat surface of the outer portion of the first anode lead. By ensuring that the surfaces of the two anode leads in contact with each other are substantially flat or horizontal, such substantially flat surfaces facilitate welding the second anode lead to the first anode lead to form a proper connection. By employing a first anode lead having an outer portion with a substantially flat surface and a second anode lead having a first portion with a substantially flat surface, the inventors have discovered that the outer portion of the first anode lead and the first portion of the second anode lead can be more efficiently and simply connected together by resistance welding.

Furthermore, the first and second anode leads can be made of different materials. For example, the first anode lead can be made of tantalum, while the second anode lead can be made of a non-tantalum material (e.g., stainless steel, nickel, or a nickel-iron alloy). In this manner, since the material cost of the second anode lead, which serves as a carrier wire during production, can be lower than the material cost of the first anode lead, a more cost-effective lead frame assembly can be used. In these embodiments, using a non-tantalum second anode lead to support the anode during chemical processing (e.g., anodization and cathode formation) can reduce material costs. For example, since a portion of the second portion of the second anode lead (e.g., a carrier wire) does not need to be part of the finished capacitor and is ultimately trimmed from the capacitor, a less expensive material can be used than the first anode lead. However, it should be understood that in some embodiments, the first anode lead can be made of a non-tantalum material, and in some embodiments, the second anode lead can be made of a tantalum material. For example, the first and second anode leads may both be tantalum, the first and second anode leads may both be non-tantalum, or the first anode lead may be non-tantalum and the second anode lead may be tantalum.

Furthermore, the embedded portion of the first anode lead can have a thickness/height, where it should be understood that the terms thickness and height can also refer to diameter when the anode lead is circular. The thickness/height or diameter of the embedded portion can be greater than the thickness/height or diameter of the second portion of the second anode lead. For example, the thickness/height or diameter of the embedded portion of the first anode lead can be between approximately 100 microns and approximately 2000 microns, while the thickness/height or diameter of the second portion of the second anode lead can be between approximately 10 microns and approximately 1800 microns. Furthermore, the thickness/height or diameter of the second portion of the second anode lead can be between approximately 10% and approximately 90% of the thickness/height or diameter of the embedded portion of the first anode lead.

The present inventors have discovered that when the thickness/height or diameter of the embedded portion of the first anode lead increases, the contact area between the embedded portion of the first anode lead and the anode body increases, thereby reducing the ESR by reducing the resistance at various points of contact between the first anode lead and the anode body. However, as the thickness/height or diameter of the anode lead increases, the internal resistance of the anode lead also increases. Therefore, in order to reduce the impact of the increase in the internal resistance of the embedded portion of the first anode lead caused by the increase in the thickness/height or diameter of the first anode lead, the length of the outer portion of the first anode lead can be minimized. Therefore, as a component of the final capacitor, the total length of the outer portion of the first anode lead (i.e., the length of the first outer portion and the second outer portion) is about 1 micron to about 10 mm, while the length of the second anode lead (i.e., the length of the first portion and the second portion) can be about 1 micron to about 20 mm. The present inventors have discovered that adopting the dual two anode lead structure reduces the ESR of the resulting capacitor.

Furthermore, the overall height/thickness or diameter of the second anode lead (represented by the second portion of the second anode lead) can be smaller than the overall height/thickness or diameter of the first anode lead (represented by the embedded portion). Since anode leads with a smaller height/thickness or diameter are easier to handle than anode leads with a larger height/thickness or diameter, various processing steps can be simplified. Furthermore, since the second anode lead has a smaller height/thickness or diameter than the first anode lead, it is less likely to bend, thereby increasing the overall stability of the anode lead assembly. Furthermore, during chemical processing (such as anodization and cathode formation), using the second anode lead with a smaller height/thickness or diameter to support the anode can reduce material costs because a portion of the second anode lead (e.g., a carrier wire) will ultimately be trimmed away from the capacitor itself and does not need to be a component of the final capacitor product.

Various embodiments of the present invention will be described in more detail below.

I. Capacitor Components

The capacitor element of the present invention comprises an anode, a dielectric layer and a cathode, as well as optional other layers, which will be described in more detail below.

A. Anode

The porous anode bodies of the capacitors of the present invention are typically formed from valve metal compositions having a high specific charge, such as a specific charge of about 2,000 μF*V/g or greater, in some embodiments, about 5,000 μF*V/g or greater, and in some embodiments, about 10,000 μF*V/g or greater. For example, such powders may have a specific charge of about 10,000 to about 600,000 μF*V/g, in some embodiments, about 40,000 to about 500,000 μF*V/g, in some embodiments, about 70,000 to about 400,000 μF*V/g, in some embodiments, about 100,000 to about 350,000 μF*V/g, and in some embodiments, about 150,000 to about 300,000 μF*V/g. As is well known in the art, the specific charge can be determined by multiplying the capacitance by the applied anodization voltage and then dividing this product by the weight of the anodized electrode body.

The valve metal composition comprises a valve metal (i.e., a metal capable of oxidation) or a valve metal-based compound, such as tantalum, niobium, aluminum, hafnium, titanium, and their respective alloys, oxides, nitrides, and the like. For example, the valve metal composition may comprise a conductive niobium oxide, such as a niobium oxide having a niobium to oxygen atomic ratio of 1:1.0±1.0, in some embodiments, a niobium to oxygen atomic ratio of 1:1.0±0.3, in some embodiments, a niobium to oxygen atomic ratio of 1:1.0±0.1, and in some embodiments, a niobium to oxygen atomic ratio of 1:1.0±0.05. For example, the niobium oxide may be NbO _0.7 , NbO _1.0 , NbO _1.1 , and NbO ₂ . In a preferred embodiment, the composition comprises NbO _1.0 , a conductive niobium oxide that remains chemically stable even after high-temperature sintering. Examples of such valve metal oxides are described in U.S. Patent 6,322,912 to Fife ; U.S. Patent 6,391,275 to Fife et al .; U.S. Patent 6,416,730 to Fife et al .; U.S. Patent 6,527,937 to Fife ; U.S. Patent 6,576,099 to Kimmel et al .; U.S. Patent 6,592,740 to Fife et al.; U.S. Patent 6,639,787 to Kimmel et al.; U.S. Patent 7,220,397 to Kimmel et al., and U.S. Patent Application Publication No. 2005/0019581 to Schnitter, U.S. Patent Application Publication No. 2005/0103638 to Schnitter et al., and U.S. Patent Application Publication No. 2005/0013765 to Thomas et al ., all of which are incorporated herein by reference in their entirety.

To form the anode, a powder of a valve metal composition is typically used. The powder can comprise particles of any shape, such as nodules, horns, flakes, and mixtures of these shapes. Particularly suitable powders are tantalum powders available from Cabot Corp. (e.g., C255 flake powder, TU4D flake/nodular powder, and the like) and H.C. Starck (e.g., NH175 nodular powder). Although not required, the powder can be agglomerated by any method known in the art, such as by heat treatment. Before the powder is formed into the anode shape, the powder can also be optionally mixed with a binder and/or lubricant to ensure that the particles are properly bonded to each other when pressed into the anode body. The powder is then compacted into pellets using any conventional powder pressing equipment. For example, the press can be a single-station press comprising a die and one or more punches. Alternatively, an anvil-type press using only a single die and a single lower punch can be used. 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. For example, they can be single-action, double-action, floating die presses, movable platen presses, opposed plunger presses, screw presses, impact presses, hot presses, coining presses or finishing presses.

Regardless of the specific composition employed, referring to FIG. 1 , the powder is compacted around the embedded portion 60 of the first anode lead 59, such that a first outer portion 61 and a second outer portion 62 of the first anode lead 59 extend from the compacted porous anode body 33, as shown in FIG. 1 and discussed in greater detail below. It should be understood, however, that while FIG. 1-8 illustrates the first anode lead 59 having a first outer portion 61 and a second outer portion 62, wherein only the second outer portion 62 has a reduced height/thickness compared to the embedded portion 60 of the first anode lead 59, this is not required, and in some embodiments, the entire outer portion of the first anode lead 59 has a reduced height/thickness compared to the embedded portion 60 of the first anode lead 59. In one specific embodiment, a die having two or more sections (e.g., an upper section and a lower section) is employed. During use, the sections of the die can be positioned adjacent to one another so that the walls of the sections are substantially aligned, forming a die cavity having the desired shape of the anode. The embedded portion 60 of the first anode lead 59 can be embedded in the mold cavity before, during, and/or after a certain amount of powder is loaded into the mold cavity. The mold defines one or more slots for inserting the anode lead. After the mold is filled with powder and the first anode lead is embedded therein, the mold cavity is closed and pressure is applied using a die punch. Generally, pressure is applied in a direction generally parallel to or generally perpendicular to the length of the first anode lead extending along the longitudinal axis (i.e., the z-axis in Figures 1-8). This forces the particles into close contact with the first anode lead, forming a strong lead-powder bond.

After compaction, the pellets can be heated under vacuum at a temperature (e.g., about 150° C. to about 500° C.) for several minutes to remove any binder/lubricant. Alternatively, the pellets can be exposed to an aqueous solution to remove the binder/lubricant, as described in U.S. Patent No. 6,197,252 to Bishop et al ., which is incorporated herein by reference in its entirety for all purposes. The porous anode body is then sintered to form a porous monolith. Typically, the pellets are sintered at a temperature of about 1200° C. to about 2000° C., in some embodiments, about 1300° C. to about 1900° C., and in some embodiments, about 1500° C. to about 1800° C., for a sintering time of about 5 minutes to about 100 minutes, and in some embodiments, about 30 minutes to about 60 minutes. If desired, sintering can be carried out in an atmosphere that limits the transfer of oxygen atoms to the anode. For example, sintering can be carried out in a reducing atmosphere, such as vacuum, an inert gas, hydrogen, or the like. The pressure of the reducing atmosphere is about 10 Torr to about 2000 Torr, in some embodiments, about 100 Torr to about 1000 Torr, and in some embodiments, about 100 Torr to about 930 Torr. Mixtures of hydrogen and other gases such as argon or nitrogen may also be used.

In the specific embodiment shown in Figures 1-7, the sintered porous anode body 33 is in the shape of a rectangular pellet. However, in addition to being rectangular, the anode can also be cubic, cylindrical, circular, or any other geometric shape. The anode can also be "grooved," including one or more grooves, recesses, depressions, or indentations to increase the surface area-to-volume ratio, minimize ESR, and extend the frequency response of the capacitor. Such "grooved" anodes are described, for example, in U.S. Patent Nos. 6,191,936 to Webber et al .; 5,949,639 to Maeda et al .; and 3,345,545 to Bourgault et al. , and U.S. Patent Application Publication No. 2005/0270725 to Hahn et al. , each of which is incorporated herein by reference in its entirety for all purposes.

1-7 , the capacitors 100 and 200 disclosed herein can include a porous anode body 33 formed as described above, and an anode lead assembly 50 including a first anode lead 59 and a second anode lead 70, which are described in detail below. Generally speaking, FIG. 1 is a perspective top view of the porous anode body 33 formed around the first anode lead 59, illustrating the arrangement and dimensions of the porous anode body 33, the first anode lead 59, and the second anode lead 70. For example, the porous anode body 33 (and the capacitor element formed therefrom) has a first side surface 31, a second side surface 32, a front surface 36, a rear surface 37, an upper surface 38, and a lower surface 39. Referring to FIG. 3-7 , the porous anode body 33 also has a width W, which refers to, for example, the width of the front surface 36 along the x-axis, and a height H, which refers to, for example, the height or thickness of the front surface 36 along the y-axis. The width W of the front surface 36 of the porous anode body 33 ranges from about 200 microns to about 8,000 microns, in some embodiments, from about 400 microns to 6,000 microns, and in some embodiments, from about 600 microns to about 4,000 microns. Furthermore, the height H of the front surface 36 of the porous anode body 33 ranges from about 200 microns to about 8,000 microns, in some embodiments, from about 400 microns to about 6,000 microns, and in some embodiments, from about 600 microns to about 4,000 microns.

B. Dielectric

Although not shown, it should be understood that the porous anode body is covered or coated with a dielectric. The dielectric can be formed by anodic oxidation ("anodizing") the sintered anode body to form a dielectric layer on and/or within the anode body. For example, a tantalum (Ta) anode body can be anodized to tantalum _pentoxide ( _Ta2O5 ). Generally, anodization begins by applying a solution to the anode body, for example by immersing the anode body in an electrolyte. A solvent, such as water (e.g., deionized water), is typically used. To enhance ionic conductivity, a compound that dissociates in the solvent to form ions can be used. Examples of such compounds include, for example, acids, as described below in the electrolyte section. For example, an acid (e.g., phosphoric acid) can comprise from about 0.01 wt.% to about 5 wt.%, in some embodiments, from about 0.05 wt.% to about 0.8 wt.%, and in some embodiments, from about 0.1 wt.% to about 0.5 wt.% of the anodizing solution. A mixture of acids can also be used, if desired.

A current is passed through the anodizing solution to form a dielectric layer. The voltage at which the dielectric layer is formed determines the thickness of the dielectric layer. For example, the power supply is initially established in a constant current mode until the required voltage is reached. The power supply can then be switched to a constant potential mode to ensure that the required dielectric layer thickness is formed on the entire surface of the anode body. Of course, other methods that are familiar to people can also be used, such as pulse or step constant potential methods. The anodizing voltage typically ranges from about 4 to about 250V, in some embodiments, from about 9 to about 200V, and in some embodiments, from about 20 to about 150V. During the oxidation process, the anodizing solution can be carried out at an elevated temperature, such as at about 30°C or higher, in some embodiments, at about 40°C to about 200°C, and in some embodiments, at about 50°C to about 100°C. Anodizing can also be carried out at room temperature or lower. The final dielectric layer can be formed on the surface of the anode body or in the pores of the anode body.

C. Solid Electrolyte

The capacitive element also includes a solid electrolyte that serves as the capacitor cathode. The manganese dioxide solid electrolyte can be formed, for example, by thermal decomposition of manganese nitrate (Mn(NO ₃ ) ₂ ). Such a method is described, for example, in U.S. Pat. No. 4,945,452 to Sturmer et al ., which is incorporated herein by reference in its entirety for all purposes.

Alternatively, the solid electrolyte may be formed from one or more conductive polymer layers. The conductive polymer employed may be a π-conjugated polymer and have a conductivity after oxidation or reduction, such as a conductivity of at least about 1 μS·cm ^-1 after oxidation. Examples of the π-conjugated conductive polymer include, for example, polyheterocycles (e.g., polypyrrole, polythiophene, polyaniline, etc.), polyalkynes, poly-p-phenylene, polyphenolates, and the like. Particularly suitable conductive polymers are substituted polythiophenes having the following general structure:

in,

T is O or S;

D is an optionally substituted _C1 to C5 _alkene group (e.g., methylene, ethylene, n-propylene, n-butylene, n-pentylene, etc.);

_R7 is a linear or branched optionally substituted _C1 to _C18 alkyl group (for example, methyl, ethyl, n-propyl or isopropyl, n-butyl, isobutyl, sec-butyl 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.); an optionally substituted _C5 to _C12 cycloalkyl group (such as cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, etc.); an optionally substituted _C6 to _C14 aryl group (such as phenyl, naphthyl, etc.); an optionally substituted C7 _...7 to C12 cycloalkyl group (such as cyclopentyl, cyclo 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.); optionally substituted C ₁ to C ₄ hydroxyalkyl groups or hydroxy groups; and

q is an integer from 0 to 8, in some embodiments, an integer from 0 to 2, and in some embodiments, 0; and

n is 2 to 5000, in some embodiments, 4 to 2000, and in some embodiments, 5 to 1000. Examples of substituents for "D" or "R ₇ " include, for example, alkyl, cycloalkyl, aryl, aralkyl, alkoxy, halogen, ether, thioether, disulfide, sulfoxide, sulfone, sulfonate, amino, aldehyde, ketone, carboxylate, carboxylic acid, carbonate, carboxylate, cyano, alkylsilane and alkoxysilane groups, carboxamide, and the like.

Particularly suitable thiophene polymers are those in which "D" is an optionally substituted _C2 to _C3 olefin group. For example, the polymer may be an optionally substituted poly(3,4-ethylenedioxythiophene) having the following general structure:

Methods for forming conductive polymers such as those described above are well known in the art. For example, U.S. Patent No. 6,987,663 to Merker et al . describes various techniques for forming substituted polythiophenes from monomeric precursors. This patent is incorporated herein by reference in its entirety for all purposes. For example, a monomeric precursor has the following structure:

in,

T, D, R ₇ and q are as defined above. Particularly suitable thiophene monomers are those in which "D" is an optionally substituted C ₂ to C ₃ olefin group. For example, optionally substituted 3,4-olefinyldioxythiophene () having the following general structure can be used:

wherein R ₇ and q are as defined above. In one embodiment, "q" is 0. An example of a commercially suitable 3,4-ethylenedioxythiophene is the product designated Clevios ^™ M by Heraeus Clevios. Other suitable monomers are described in U.S. Patent No. 5,111,327 to Blohm et al. and U.S. Patent No. 6,635,729 to Groenendaal et al., which are incorporated herein by reference in their entirety for all purposes. Derivatives of these monomers may also be used, such as dimers or trimers of the above monomers. Derivatives with higher molecular weights, such as tetramers and pentamers of the monomers, are suitable for use in the present invention. The derivatives may be composed of the same or different monomer units and may be used in pure form or in a mixture with another derivative and/or the monomer. Oxidized or reduced forms of these monomer precursors may also be used.

In the presence of an oxidation catalyst, the thiophene monomer undergoes chemical polymerization. The oxidation catalyst typically includes a transition metal cation, such as iron (III), copper (II), chromium (VI), cerium (IV), manganese (IV), manganese (VII) or ruthenium (III) cations. A dopant may also be used to provide excess charge to the conductive polymer to stabilize the conductivity of the polymer. The dopant typically includes an inorganic or organic anion, such as a sulfonic acid ion. In certain embodiments, the oxidation catalyst used in the precursor solution includes a cation (such as a transition metal) and an anion (such as a sulfonic acid), thereby providing it with both catalytic and doping functions. For example, the oxidation catalyst may be a transition metal salt, including an iron (III) cation, such as an iron (III) halide (such as FeCl ₃ ) or other inorganic acid iron (III) salts, such as Fe(ClO ₄ ) ₃ or Fe ₂ (SO ₄ ) ₃ and an organic acid iron (III) salt and an inorganic acid iron (III) salt containing an organic group. Examples of the inorganic acid iron (III) salt having an organic group include, for example, sulfuric acid monoester iron (III) salts of C ₁ to C ₂₀ alkanols (such as lauryl sulfate iron (III) salt). Likewise, examples of organic acid iron (III) salts include, for example, C ₁ to C ₂₀ alkylsulfonic acid iron (III) salts (e.g., methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, or dodecylsulfonic acid); aliphatic perfluorosulfonic acid iron (III) salts (e.g., trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid); aliphatic C ₁ to C ₂₀ carboxylic acid iron (III) salts (e.g., 2-ethylhexylcarboxylic acid); aliphatic perfluorocarboxylic acid iron (III) salts (e.g., trifluoroacetic acid or perfluorooctanoic acid); aromatic sulfonic acid iron (III) salts optionally substituted with C ₁ to C ₂₀ alkyl groups (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid); cycloalkanesulfonic acid iron (III) salts (e.g., camphorsulfonic acid), etc. Mixtures of the above-mentioned iron (III) salts may also be used. Iron (III) p-toluenesulfonate and iron (III) o-toluenesulfonate, and mixtures thereof, are particularly suitable for the present invention. A commercially suitable iron (III) o-toluenesulfonate salt is the product sold under the name Clevios ^™ C by Heraeus Clevios.

Various methods can be used to form the conductive polymer layer. In one embodiment, the oxidation catalyst and the monomer are either applied sequentially or applied together so that the polymerization reaction is carried out in situ on the anode component. Suitable coating techniques for forming the conductive polymer coating include screen printing, dipping, electrophoretic coating and spraying. For example, the monomer can be initially mixed with the oxidation catalyst to form a precursor solution. Once the mixture is formed, it can be applied to the anode component and then allowed to polymerize to form a conductive coating on the surface. Alternatively, the oxidation catalyst and the monomer can be applied in sequence. For example, in one embodiment, the oxidation catalyst can be dissolved in an organic solvent (e.g., butanol) and then applied in the form of an impregnation solution. The anode component is then dried to remove the solvent from the anode component. The anode component is then immersed in a solution containing the monomer.

Depending on the oxidant used and the desired reaction time, polymerization is typically carried out at a temperature of about -10°C to about 250°C, and in some embodiments, at a temperature of about 0°C to about 200°C. Suitable polymerization methods, such as those described above, are described in more detail in Biler , U.S. Patent 7,515,396. Other methods for applying such conductive coatings are described in Sakata et al ., U.S. Patent 5,457,862; Sakata et al ., U.S. Patent 5,473,503; Sakata et al., U.S. Patent 5,729,428; and Kudoh et al ., U.S. Patent 5,812,367. Each of these patents is hereby incorporated by reference in its entirety for all purposes.

In addition to in-situ coating, the conductive polymer layer can also be applied in the form of a dispersion of conductive polymer particles. Although the particle size can vary, it is generally desired that the particles have a small particle size to increase the surface area for adhesion of the anode component. For example, the average particle size of the particles is from about 1 nanometer to about 500 nanometers, in some embodiments, from about 5 nanometers to about 400 nanometers, and in some embodiments, from about 10 nanometers to about 300 nanometers. The _D90 value of the particles (particles with a particle size less than or equal to _D90 account for 90% of the total volume of all solid particles) can be about 15 microns or less, in some embodiments, about 10 microns or less, and in some embodiments, from about 1 nanometer to about 8 microns. The diameter of the particles can be determined using well-known methods such as ultracentrifugation, laser diffraction, etc.

Independent counterions can be used to neutralize the positive charge carried by the substituted polythiophene to promote the formation of particles of the conductive polymer. In some cases, the polymer may have a positive charge and a negative charge in the structural unit, the positive charge being located on the main chain, and the negative charge being optionally located on the "R" substituent, such as a sulfonate group or a carboxylate group. The positive charge of the main chain can be partially or completely neutralized by the anionic groups optionally present on the "R" substituent. From a holistic perspective, in these cases, the polythiophene can be cationic, neutral, or even anionic. However, because the polythiophene main chain is positively charged, they are all considered to be cationic polythiophenes.

The counterion can be a monomeric anion or a polymeric anion. Polymeric anions include, for example, anions of polycarboxylic acids (e.g., polyacrylic acid, polymethacrylic acid, polymaleic acid, etc.); anions of polysulfonic acids (e.g., polystyrenesulfonic acid ("PSS"), polyvinylsulfonic acid, etc.); and the like. The acid can also be a copolymer, such as a copolymer of vinyl carboxylic acid and vinylsulfonic acid with other polymerizable monomers (e.g., acrylate and styrene). Likewise, suitable monomeric anions include, for example, anions of C ₁ -C ₂₀ alkylsulfonic acids (e.g., dodecylsulfonic acid); anions of aliphatic perfluorosulfonic acids (e.g., trifluoromethanesulfonic acid, perfluorobutanesulfonic acid, or perfluorooctanesulfonic acid); anions of aliphatic C ₁ -C ₂₀ carboxylic acids (e.g., 2-ethylhexylcarboxylic acid); anions of aliphatic perfluorocarboxylic acids (e.g., trifluoroacetic acid or perfluorooctanoic acid); anions of aromatic sulfonic acids optionally substituted with C ₁ -C ₂₀ alkyl groups (e.g., benzenesulfonic acid, o-toluenesulfonic acid, p-toluenesulfonic acid, or dodecylbenzenesulfonic acid); anions of cycloalkanesulfonic acids (e.g., camphorsulfonic acid or tetrafluoroborate, hexafluorophosphate, perchlorate, hexafluoroantimonate, hexafluoroarsenate, or hexachloroantimonate); etc. Particularly suitable counterions are polymeric anions, such as polycarboxylic acids or polysulfonic acids (e.g., polystyrenesulfonic acid ("PSS")). The molecular weight of such polymeric anions is generally from about 1,000 to about 2,000,000, and in some embodiments, from about 2,000 to about 500,000.

When counterions are employed, the weight ratio of such counterions to the substituted polythiophene in a given layer is generally from about 0.5: 1 to about 50: 1, in some embodiments from about 1: 1 to about 30: 1, and in some embodiments from about 2: 1 to about 20: 1. The weight of the substituted polythiophene mentioned in the above weight ratios refers to the weight of the monomer portion used, assuming complete conversion of the monomer during polymerization.

The dispersion also comprises one or more binding agents, further strengthens the adhesion properties of the polymer layer, and can also increase the stability of particles in the dispersion.This binding agent can be organic in nature, such as polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl chloride, polyvinyl acetate, polyvinyl butyrate, polyacrylate, polyacrylamide, polymethacrylate, polymethacrylic acid amide, polyacrylonitrile, styrene/acrylate, vinyl acetate/acrylate and ethylene/vinyl acetate copolymer, polybutadiene, polyisoprene, polystyrene, polyether, polyester, polycarbonate, polyurethane, polyamide, polyimide, polysulfone, melamine-formaldehyde resin, epoxy resin, silicone resin or cellulose.Also can adopt crosslinking agent to strengthen the adhesion ability of binding agent.This type of crosslinking agent comprises, for example, melamine compound, blocked isocyanate or functional silane, such as 3-glycidyloxypropyl trialkylsilane, tetraethoxysilane and tetraethoxysilane hydrolyzate or crosslinkable polymer, such as polyurethane, polyacrylate or polyolefin. As is well known in the art, the dispersion may also include other ingredients such as a dispersant (eg, water), a surfactant, and the like.

If necessary, one or more coating steps described above can be repeated until a coating of desired thickness is obtained. In certain embodiments, only a relatively thin coating is formed once. The total target thickness of the coating varies conventionally according to the performance required by the capacitor. Generally speaking, the thickness of the resulting conductive polymer coating is approximately 0.2 micron to approximately 50 microns, approximately 0.5 micron to approximately 20 microns in certain embodiments, and approximately 1 micron to approximately 5 microns in certain embodiments. It should be understood that the coating thickness does not need to be identical everywhere on the anode component. However, the average thickness of the coating on the substrate is typically within the above-described range.

The conductive polymer layer is optionally cured. Healing can be performed after each application of the conductive polymer layer or after the entire coating has been applied. In some embodiments, the conductive polymer can be cured by immersing the component in an electrolyte solution and then applying a constant voltage to the solution until the current drops to a preselected level. If desired, this healing can be accomplished in multiple steps. For example, the electrolyte solution can be a diluted solution of the monomer, catalyst, and dopant in an alcohol solvent (such as ethanol). If desired, the coating can also be washed to remove various by-products, excess reagents, etc.

D. Other layers

Although not required, an outer polymer coating may also be applied to the anode body, covering the solid electrolyte. The outer polymer coating typically comprises one or more layers formed from a dispersion of prepolymerized conductive particles (e.g., as described in detail above). The outer coating can further penetrate the edge regions of the capacitor body, thereby improving the adhesion of the dielectric layer and resulting in a more mechanically stable component, which can reduce equivalent series resistance and leakage current. Because the goal is generally to improve edge coverage rather than infiltrate the interior of the anode body, the particle size of the particles used in the outer coating is typically larger than the particle size of the particles used in any optional dispersion in the solid electrolyte. For example, the ratio of the average particle size of the particles used in the outer polymer coating to the average particle size of the particles used in any dispersion in the solid electrolyte is typically about 1.5 to about 30, in some embodiments, about 2 to about 20, and in some embodiments, about 5 to about 15. For example, the average particle size of the particles used in the outer coating dispersion is about 50 nanometers to about 500 nanometers, in some embodiments, about 80 nanometers to about 250 nanometers, and in some embodiments, about 100 nanometers to about 200 nanometers.

If desired, a crosslinking agent may also be used in the outer polymer coating to improve adhesion to the solid electrolyte. Generally, the crosslinking agent is applied before the dispersion used in the outer coating is applied. Suitable crosslinking agents are described, for example, in U.S. Patent Publication No. 2007/0064376 to Merker et al . and include, for example, amines (such as diamines, triamines, oligoamines, polyamines, etc.); multivalent metal cations, such as salts or compounds of Mg, Al, Ca, Fe, Cr, Mn, Ba, Ti, Co, Ni, Cu, Ru, Ce, or Zn; phosphorus compounds, sulfonium compounds, etc. Particularly suitable examples include, for example, 1,4-cyclohexanediamine, 1,4-bis(amino-methyl)cyclohexane, ethylenediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,12-dodecanediamine, N,N-dimethylethylenediamine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,4-butanediamine, and the like, and mixtures thereof.

The crosslinker is typically applied from a solution or dispersion having a pH of 1 to 10, in some embodiments, 2 to 7, and in some embodiments, 3 to 6, as measured at 25°C. Acidic compounds may be used to help achieve the desired pH level. Examples of solvents or dispersions for the crosslinker include water or organic solvents such as alcohols, ketones, carboxylates, and the like. The crosslinker may be applied to the capacitor body using any of the familiar methods, such as spin coating, dipping, casting, drop coating, spraying, vapor deposition, sputtering, sublimation, doctor blade coating, brushing, or printing (e.g., inkjet printing, screen printing, or pad printing). Once applied, the crosslinker may be dried prior to 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 crosslinker and dispersion layers, is from about 1 micron to about 50 microns, in some embodiments, from about 2 microns to about 40 microns, and in some embodiments, from about 5 microns to about 20 microns.

If desired, the capacitor may also include other layers. For example, a protective coating, such as one formed from a relatively insulating resin material (natural or synthetic), may be optionally formed between the dielectric layer and the solid electrolyte. Such materials have a specific resistivity greater than about 10 Ω·cm, in some embodiments, greater than about 100 Ω·cm, in some embodiments, greater than about 1000 Ω·cm, in some embodiments, greater than about 1×10 ⁵ Ω·cm, and in some embodiments, greater than about 1×10 ¹⁰ Ω·cm. Certain resin materials that may be used in the present invention include, but are not limited to, polyurethane, polystyrene, and unsaturated or saturated fatty acid esters (such as glycerides). For example, suitable fatty acid esters include, but are not limited to, laurate, myristate, palmitate, stearate, eleostearate, oleate, linoleate, linolenate, eleostearate, and lac esters. It has been found that these fatty acid esters are particularly useful when used in relatively complex combinations to form a "drying oil," which allows the resulting film to rapidly polymerize to form a stable layer. The drying oil may comprise monoglycerides, diglycerides, and/or triglycerides having a glycerol backbone with one, two, and three esterified fatty acyl residues, respectively. 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 and other protective coating materials are described in greater detail in U.S. Patent No. 6,674,635 to Fife et al ., which is incorporated herein by reference in its entirety for all purposes.

If desired, the component can also be coated with a carbon layer (e.g., graphite) and a silver layer. For example, the silver layer can serve as a solderable conductor, contact layer, and/or charge collector for a capacitor, while the carbon layer can limit contact between the silver layer and the solid electrolyte. Such coatings can cover part or all of the solid electrolyte.

II. Anode lead assembly

As described above, the electrolytic capacitor of the present invention includes a first anode lead and a second anode lead forming an anode lead assembly. The first anode lead has an embedded portion embedded within the porous anode body and an outer portion extending longitudinally along the surface of the anode body. Meanwhile, the second anode lead is not embedded within the porous anode body and has a first portion in contact with the outer portion of the first anode lead and a second portion in contact with the anode terminal of the lead frame. The first and second anode leads can be made of conductive materials such as tantalum, niobium, nickel, aluminum, hafnium, titanium, stainless steel, and alloys, oxides, and/or nitrides thereof. For example, in some embodiments, the first anode lead can be made of tantalum and the second anode lead can be made of stainless steel, nickel, or a nickel alloy, which helps reduce the cost of the anode lead assembly. In one specific embodiment, the second anode lead can be made of (a nickel-iron alloy). While in some embodiments, the first anode lead is made of tantalum and the second anode lead is made of a non-tantalum material, it should be understood that in other embodiments, the first and second anode leads can be made of the same material (e.g., tantalum).

Furthermore, the first and second anode leads can have any desired cross-sectional shape, such as circular, elliptical, square, rectangular, triangular, trapezoidal, perfectly oval, racetrack oval, or combinations thereof. For example, the embedded portion and first outer portion of the first anode lead and the first portion of the second anode lead can be circular, while the second outer portion of the first anode lead can be trapezoidal, and the first portion of the second anode lead can be perfectly oval or racetrack oval. For example, the difference in shape can be achieved by flattening, pressing, or compressing, or by reshaping the second outer portion of the first anode lead to provide a substantially flat surface and reshaping the first portion of the second anode lead to provide a substantially flat surface, wherein the two substantially flat surfaces are connected together, as discussed in detail below. Furthermore, it should be understood that any portion of the first and second anode leads can have any of the aforementioned shapes or any other suitable shape. For example, the entire outer portion of the first anode lead can be flattened, pressed, compressed, or otherwise modified so that the entire outer portion of the first anode lead comprises a substantially flat surface.

Furthermore, because the outer portion of the first anode lead forms a substantially flat surface, the embedded portion and, in some embodiments, the first outer portion of the first anode lead have a greater thickness, height, or diameter than the second portion of the second anode lead, thereby improving the bond between the embedded portion of the first anode lead and the anode body particles, thereby reducing ESR. The second portion of the second anode lead can have a smaller thickness, height, or diameter than the embedded portion and, in some embodiments, the first outer portion of the first anode lead, thereby reducing the internal resistance of the entire anode lead assembly, which can also reduce ESR. Therefore, the combination of a larger diameter first anode lead and a smaller diameter second anode lead can synergistically reduce the ESR of the capacitor. For example, because the embedded portion of the first anode lead has a greater thickness, height, or diameter, the number of contact points between the first anode lead and the anode body is increased, reducing the resistance at the contact points. Furthermore, in some embodiments, while the first outer portion of the first anode lead has the same greater thickness/height or diameter as the embedded portion of the first anode lead, to minimize the length of the first outer portion of the first anode lead having a larger diameter, the first outer portion extends only a shorter distance from the surface of the anode body. This, in turn, minimizes the effect of increased internal resistance of the lead due to its larger diameter. Furthermore, in some embodiments, to minimize the effect of increased internal resistance of the lead due to its larger diameter, the entire outer portion of the first anode lead has a reduced diameter compared to the embedded portion of the first anode lead. Simultaneously, the diameter of the second portion of the second anode lead (which may be used to form an electrical connection with the anode terminal) may be smaller than the diameter of the embedded portion of the first anode lead. This reduces the internal resistance of the second portion of the second anode lead, thereby minimizing the ESR of the anode lead assembly extending from/outside the porous anode body.

As described above and shown in Figures 1-8, in some embodiments, for example, when the first anode lead comprises tantalum and the second anode lead comprises a non-tantalum material, the anode lead assembly 50 includes a first anode lead 59 that generally has a thickness/height or diameter greater than the thickness/height or diameter of the second anode lead 70. For example, with reference to Figures 6-7, the embedded portion 60 and the first outer portion 61 of the first anode lead 59 have a thickness/height or diameter H1 of about 100 microns to about 2000 microns, such as about 200 microns to about 1500 microns, such as about 250 microns to about 1000 microns. However, it should be understood that while Figures 1-8 illustrate the first anode lead 59 having a first outer portion 61 and a second outer portion 62, with only the second outer portion 62 having a reduced height/thickness compared to the embedded portion 60 of the first anode lead 59, in some embodiments, the entire outer portion of the first anode lead 59 has a reduced height/thickness compared to the embedded portion 60 of the first anode lead 59.

Meanwhile, the second portion 72 of the second anode lead 70 has a height/thickness or diameter H4 of about 10 μm to about 1800 μm, such as about 50 μm to about 1200 μm, such as about 100 μm to about 750 μm. Furthermore, the second portion 72 of the second anode lead 70 has a height/thickness or diameter H4 of about 10% to about 90% of the height/thickness or diameter H1 of the embedded portion 60 of the first anode lead 59, such as about 15% to about 85% of the height/thickness or diameter H1 of the embedded portion 60 of the first anode lead 59, such as about 20% to about 80% of the height/thickness or diameter of the embedded portion 60 of the first anode lead 59, and such as about 25% to about 75% of the height/thickness or diameter of the embedded portion 60 of the first anode lead 59. The reduced height/thickness or diameter H4 of the second portion 72 of the second anode lead 70 compared to the height/thickness or diameter H1 of the embedded portion 60 of the first anode lead 59 can reduce ESR and also reduce the energy required to connect the anode lead assembly 50 to the anode terminal 35.

6-7 , in some embodiments, the second outer portion 62 of the first anode lead 59 has a thickness/height H2 that is less than the thickness/height or diameter H1 of the embedded portion 60 and the first outer portion 61 of the first anode lead 59. However, it should be understood that in alternative embodiments, the entire outer portion of the first anode lead 59 can have a thickness/height H2 that is less than the thickness/height or diameter H1 of the embedded portion 60 of the first anode lead 59. For example, the thickness/height H2 of the second outer portion 62 of the first anode lead 59 can range from about 5% to about 99.9%, such as about 10% to about 90%, or about 20% to about 80%, of the thickness/height or diameter H1 of the embedded portion 60 and the first outer portion 61 of the first anode lead 59. Meanwhile, the first portion 71 of the second anode lead 70 has a height/thickness H3 that is less than the thickness/height or diameter H4 of the second portion 72 of the second anode lead 70. For example, the height/thickness H3 of the first portion 71 of the second anode lead 70 ranges from about 5% to about 99.9%, such as from about 10% to about 90%, and such as from about 20% to about 80%, of the thickness/height or diameter H4 of the second portion 72 of the second anode lead 70. The second outer portion 62 of the first anode lead 59 has a smaller height than the first outer portion 61 of the first anode lead 59, and the first portion 71 of the second anode lead 70 has a smaller height than the second portion 72 of the second anode lead 70, due to flattening, pressing, compressing, or otherwise altering the geometry of the portions of the first and second anode leads to form substantially flat surfaces thereon. This can facilitate a more effective connection between the second outer portion 62 of the first anode lead 59 and the first portion 71 of the second anode lead 70, thereby requiring less energy, for example, during resistance welding. For example, as shown in FIG8 , the outer portion of the first anode lead 59 can include a substantially flat lower surface 65 and a substantially flat upper surface 67 formed by flattening, pressing, compressing, or otherwise changing the geometry of the first anode lead 59. In FIG8 , the substantially flat surfaces 65 and 67 are shown as being formed only on the second outer portion 62 of the first anode lead 59, but it should be understood that in other embodiments, these substantially flat surfaces can be located on the entire outer portion of the first anode lead 59. As shown in FIG8 , the first portion 71 of the second anode lead 70 can include a substantially flat upper surface 66 and a substantially flat lower surface 68 formed by flattening, pressing, compressing, or otherwise changing the geometry of the second anode lead 70. 8 , the substantially flat lower surface 65 of the second outer portion 62 of the first anode lead 59 is connected to the substantially flat upper surface 66 of the first portion 71 of the second anode lead 70 , however, it should be understood that in alternative embodiments, the substantially flat upper surface 67 of the second outer portion 62 of the first anode lead 59 may be connected to the substantially flat lower surface 68 of the first portion 71 of the second anode lead 70 .

3-4 , the embedded portion 60 and, in some embodiments, the first outer portion 61 of the first anode lead 59 may have a width W1 of about 100 μm to about 2000 μm, such as about 200 μm to about 1500 μm, or about 250 μm to about 1000 μm. Meanwhile, the second portion 72 of the second anode lead 70 may have a width W4 of about 10 μm to about 1800 μm, such as about 50 μm to about 1200 μm, or about 100 μm to about 750 μm. Furthermore, the second portion 72 of the second anode lead 70 has a width W4 that is from about 10% to about 90% of the width W1 of the embedded portion 60 of the first anode lead 59, such as from about 15% to about 85% of the width W1 of the embedded portion 60 of the first anode lead 59, such as from about 20% to about 80% of the height/thickness or diameter of the embedded portion 60 of the first anode lead 59, such as from about 25% to about 75% of the height/thickness or diameter of the embedded portion 60 of the first anode lead 59. The reduced width W4 of the second portion 72 of the second anode lead 70 compared to the width W1 of the embedded portion 60 of the first anode lead 59 reduces ESR and may also reduce the amount of energy required to connect the anode lead assembly 50 to the anode terminal 35.

3-4 and as described above, when the first anode lead 59 and the second anode lead 70 are flattened, pressed, compressed, or otherwise altered to form the aforementioned substantially flat surface thereon to improve resistance welding of the two leads, the height/thickness of the second outer portion 62 of the first anode lead 59 and the first portion 71 of the second anode lead 70 are respectively reduced compared to the embedded portion 60 and the first outer portion 61 of the first anode lead 59 and the second portion 72 of the second anode lead 70. Thus, the width W2 of the second outer portion 62 of the first anode lead 59 and the width W3 of the first portion 71 of the second anode lead 70 can be the same as the width W1 of the first outer portion 61 of the first anode lead 59 and the width W4 of the second portion 72 of the second anode lead 70, respectively, or, depending on the amount of flattening, pressing, compression, etc., W2 and W3 can be increased.

3 , the width W2 of the second outer portion 62 of the first anode lead 59 can vary along the z-direction, such that the second outer portion 62 has a trapezoidal shape. The end of the second outer portion 62 adjacent to the first outer portion 61 of the first anode lead 59 can have the same width as the first outer portion 61. Since the second outer portion 62 near the anode terminal 35 is flattened, the end of the second outer portion 62 has an increased width compared to the width of the first outer portion 61. Furthermore, the first outer portion 61 can be rounded. In some embodiments, the width W2 of the second outer portion 62 of the first anode lead 59 is approximately 100% to approximately 250%, such as approximately 110% to approximately 225%, and such as approximately 120% to approximately 200%, of the width W1 of the first outer portion 61 of the first anode lead 59. 3 and as described above, it will be appreciated that the width W2 of the second outer portion 62 can vary longitudinally along the z-axis such that, depending on where width W2 of the second outer portion 62 is measured, width W2 can be from about 100% to about 250% of the width W1 of the first outer portion 61 of the first anode lead 59. Furthermore, it will be appreciated that such varying width can occur along the entire outer portion of the first anode lead 59, rather than just the second outer portion 62, when the entire outer portion of the first anode lead 59, rather than just the second outer portion 62, is flattened, pressed, compressed, etc., to form a substantially flat surface thereon.

Meanwhile, as shown in FIG4 , the width W3 of the first portion 71 of the second anode lead 70 is generally constant along the z-direction. Due to the flattening, pressing, or compression of the first portion 71, the width W3 is greater than the width W4 of the second portion 72 of the second anode lead 70. However, it should be understood that the first portion 71 and the second portion 72 of the second anode lead 70 can have substantially the same width. In some embodiments, the width W3 of the first portion 71 of the second anode lead 70 is approximately 100% to approximately 200% of the width W4 of the second portion 72 of the second anode lead 70, such as approximately 105% to approximately 175%, or approximately 110% to approximately 150%. Furthermore, as shown in FIG4 , in some embodiments, due to the substantially flat surface formed on the first portion 71, the first portion 71 of the second anode lead 70 can have a racetrack oval or a standard oval shape, while the second portion 72 of the second anode lead 70 can have a circular shape.

6 , in some embodiments where the outer portion of the first anode lead 59 includes a first outer portion 61 and a second outer portion 62, a longitudinal or z-axial length L1 of the first outer portion 61 of the first anode lead 59 (i.e., the portion of the first anode lead extending from the surface of the porous anode body in the longitudinal or z-axial direction) is shorter than a longitudinal or z-axial length L2 of the second outer portion 62 (e.g., when flattened) of the first anode lead 59. Minimizing the length L1 of the first outer portion 61 of the first anode lead 59 reduces the ESR of the capacitor (attributable to an increase in the internal resistance of the first outer portion 61 of the first anode lead 59 due to its greater height/thickness or diameter compared to the second anode lead 70), and improves the stability of the lead assembly 50 by reducing the risk of bending due to the weight of the first anode lead 59. Thus, in some embodiments, the length L2 of the second outer portion 62 of the first anode lead 59 is about 100% to about 250%, such as about 110% to about 225%, such as about 120% to about 200%, of the length L1 of the first outer portion 61 of the first anode lead 59 .

6 , the first portion 71 of the second anode lead 70 has a length L3, and the second portion 72 of the second anode lead 70 has a length L4. Typically, before trimming the second portion 72 (discussed in detail below), the length L4 is greater than the length L3. Thus, in some embodiments, before any trimming, the length L4 of the second portion 72 of the second anode lead 70 is from about 100% to about 1000%, such as from about 125% to about 900%, such as from about 150% to about 800%, of the length L3 of the first portion 71 of the second anode lead 70. However, it should be understood that when the second portion 72 of the second anode lead 70 is welded to the anode terminal 35 and excess anode lead material is trimmed, the length L4 can be less than, the same as, or greater than L3, depending on the specific configuration of the capacitor. In any case, as shown in Figure 6, the length L3 of the first portion 71 of the second anode lead 70 can be equal to or less than the length L2 of the second outer portion 62 of the first anode lead 60, thereby facilitating welding (such as resistance welding) the first portion 71 of the second anode lead 70 to the second outer portion 62 of the first anode lead 59.

Furthermore, the total length L1+L2 of the first outer portion 61 and the second outer portion 62 of the first anode lead 59 can be from about 1 μm to about 10 mm, such as from about 5 μm to about 7.5 mm, or from about 10 μm to about 5 mm. Meanwhile, before trimming, the total length L3+L4 of the first portion 71 and the second portion 72 of the second anode lead 72 can be from about 1 μm to about 20 mm, such as from about 100 μm to about 15 mm, or from about 1000 μm to about 10 mm. Furthermore, after trimming, the total length L3+L4 can vary depending on the specific design of the capacitor and the location of the anode terminal 35, as the second portion 72 of the second anode lead 70 must extend at least to the anode terminal 35 in order to be welded thereto.

Furthermore, it should be understood that the anode lead assembly 50 can have different configurations depending on the location at which the second anode lead 70 is connected to the first anode lead 59. For example, in FIG6 , the upper surface 63 of the second outer portion 62 of the first anode lead 59 is in contact with the lower surface 74 of the first portion 71 of the second anode lead 70. On the other hand, in another embodiment, in FIG7 , the lower surface 64 of the second outer portion 62 of the first anode lead 59 is in contact with the upper surface 73 of the first portion 71 of the second anode lead 70. However, it should also be understood that in other embodiments, any surface of the second outer portion 62 of the first anode lead 59 can be connected to any surface of the first portion 71 of the second anode lead 70. Regardless, as shown in FIG1-7 , the second anode lead 70 can extend longitudinally or in the z-axis direction from the second portion 62 of the first anode lead 59. Furthermore, the first portion 71 of the second anode lead 70 can be connected to the second outer portion 62 of the first anode lead 59 using any suitable method, such as resistance welding, laser welding, or a conductive adhesive. 8 , in a particular embodiment, the leads are connected by resistance welding a substantially flat surface 66 of a first portion 71 of a second anode lead 70 to a substantially flat surface 65 of an outer portion of a first anode lead 59 , for example, wherein the substantially flat surface 65 of the outer portion of the first anode lead 59 does not extend along the entire length of the outer portion of the first anode lead 59 , although, in some embodiments, it may extend along the entire length.

In another embodiment, the capacitor of the present invention may include more than one anode body, for example, two, three, four, five, or six anode bodies. For example, as shown in FIG9 , capacitor 300 includes a first porous anode body 33 a and a second porous anode body 33 b disposed within encapsulation material 78. First porous anode body 33 a includes a first anode lead 59 a and a second anode lead 70 a, wherein first anode lead 59 a includes a first outer portion 61 a and a second outer portion 62 a, and second anode lead 70 a includes a first portion 71 a and a second portion 72 a; second porous anode body 33 b includes a first anode lead 59 b and a second anode lead 70 b, wherein first anode lead 59 b includes a first outer portion 61 b and a second outer portion 62 b; and second anode lead 70 b includes a first portion 71 b and a second portion 72 b. The second outer portions 62a and 62b of the first anode leads 59a and 59b include substantially flat side surfaces 95a and 95b, respectively, and the first portions 71a and 71b of the second anode leads 70a and 70b include substantially flat side surfaces 97a and 97b, respectively, wherein the substantially flat side surfaces 97a and 97b of the first portions 71a and 71b of the second anode leads 70a and 70b are connected to the substantially flat side surfaces 95a and 95b of the second outer portions 62a and 62b of the first anode leads 59a and 59b by, for example, side resistance welding. However, it should be understood that the second outer portions 62a and 62b of the first anode leads 59a and 59b and the first portions 71a and 71b of the second anode leads 70a and 70b can be connected at a flat surface located anywhere on each anode lead, for example, at a substantially flat upper or lower surface, as discussed above with reference to FIGs. 1-7. Furthermore, it should be understood that although in FIG9 , the substantially flat side surfaces 95a and 95b of the outer portions of the first anode leads 59a and 59b do not extend along the entire length of the outer portions of the first anode leads 59a and 59b, in some embodiments, the substantially flat side surfaces 95a and 95b of the outer portions of the first anode leads 59a and 59b may extend along the entire length of the outer portions of the first anode leads 59a and 59b.

As is well known in the art, regardless of the specific design or method of forming capacitor 100 or 200, it can be connected to the terminals. For example, the anode terminal and the cathode terminal can be electrically connected to the second anode lead and the cathode, respectively. As is well known in the art, the specific structure of the terminals can vary. Although not required, as shown in Figures 1-7, for example, the cathode terminal 44 can include a flat portion 45 and an upright portion 46, the flat portion 45 being in electrical contact with the lower surface 39 of the capacitor 100 of Figures 1-6 or the capacitor 200 of Figure 7, and the upright portion 46 being substantially perpendicular to the flat portion 45 and in electrical contact with the rear surface 37 of the capacitor 100 of Figures 1-6 or the capacitor 200 of Figure 7. In order to connect the capacitor to the cathode terminal, a conductive adhesive well known in the art can be used. The conductive adhesive can include, for example, conductive metal particles contained in a resin composition. The metal particles can be silver, copper, gold, platinum, nickel, zinc, bismuth, etc. The resin composition includes a thermosetting resin (such as an epoxy resin), a curing agent (such as an acid anhydride), and a coupling agent (such as a silane coupling agent). Suitable conductive adhesives are described in US Patent Application Publication No. 2006/0038304 to Osako et al., which is incorporated herein by reference in its entirety for all purposes.

Referring to Figures 1-7, although not required, the anode terminal 35 can also include a flat portion 41 and an upstanding portion 42. The upstanding portion 42 can include an area for connecting to the second portion 72 of the second anode lead 70 of the present invention. For example, this area includes a groove 43 for receiving the second portion 72 of the second anode lead 70. The groove can have any desired shape, such as a U-shape, a V-shape, a circle, an ellipse, an oval, a rectangle, a square, a trapezoid, etc., to further enhance surface contact and mechanical stability of the second portion 72 of the second anode lead 70 at the anode terminal 35. For example, the geometry of the groove 43 can match the geometry of the second portion 72 of the second anode lead 70. The second portion 72 of the second anode lead 70 can be electrically connected to the anode terminal 35 by any suitable method, such as laser welding, resistance welding, or the use of a conductive adhesive. As shown in Figures 2 and 4, in one embodiment, the second portion 72 of the second anode lead 70 is laser welded to the anode terminal 35 at the groove 43 using a laser beam 80. Regardless of the welding method used to connect the second portion 72 of the second anode lead 70 to the anode terminal 35, the energy required to achieve an adequate weld is reduced compared to directly connecting the first outer portion 61 of the first anode lead 59, which has a greater thickness/height or diameter, to the anode terminal 35. Therefore, by directly connecting the smaller second anode lead 70 to the anode terminal 35, the benefits of embedding the relatively thick embedded end 60 of the first anode lead 59 within the porous anode body 33 (i.e., improved contact with the porous anode body and reduced ESR) can still be achieved, while the reduced thickness/height or diameter of the second anode lead 70, particularly the second portion 72, allows for welding to be performed in a more efficient and cost-effective manner to form an electrical connection with the anode terminal 35.

In addition, once a capacitor element is formed and connected to the terminal, as described above, and once the excess length (if any) of the second portion 72 of the second anode lead 70 is trimmed off, the capacitor element and the anode lead assembly can be encapsulated in a resin shell, and then, silicon dioxide or any other packaging material familiar to people are filled therein. The width and length of the shell vary with the target application. However, the total thickness of the shell is usually less, so that the resulting assembly can be easily put into a low profile product (such as an "IC card"). For example, the thickness range of the shell is approximately 4.0 millimeters or below, and in some embodiments, is approximately 100 microns to approximately 2.5 millimeters, and in some embodiments, is approximately 150 microns to approximately 2.0 millimeters. Suitable shells include, for example, "A", "B", "H" or "T" class shells (AVX Corporation). After encapsulation, the exposed portion of each anode terminal and cathode terminal can be aged, masked and trimmed. If necessary, the exposed portion can be optionally bent twice (such as with approximate 90 ° bending) along the outside of the shell.

As the final product disclosed in the present invention, a capacitor with excellent electrical properties is formed. The electrical properties are measured according to the test procedures described below. For example, the capacitors of the present invention have an ultra-low ESR, such as an ESR of about 300 milliohms (mΩ) or less , in some embodiments, about 100 mΩ or less, in some embodiments, about 0.01 mΩ to about 50 mΩ, and in some embodiments, about 0.1 mΩ to about 20 mΩ, as measured at a frequency of 100 kHz and a temperature of 23°C + 2°C. In addition, leakage current (generally referring to the current flowing from one conductor to a nearby conductor through an insulator) can be maintained at a relatively low level. For example, the normalized leakage current of the capacitors of the present invention is, in some embodiments, about less than 0.1 μA/μF*V, in some embodiments, about less than 0.01 μA/μF*V, and in some embodiments, about less than 0.001 μA/μF*V, where μA is microamperes and μF*V is the product of capacitance and rated voltage.

Test Procedure

Equivalent Series Resistance (“ESR”)

ESR generally refers to the degree to which a capacitor acts as a resistor when charging and discharging in an electronic circuit, and is usually expressed as the resistance in series with the capacitor. ESR is typically measured using a Keithley 3330 Precision LCZ Tester with Kelvin leads, using a 2.2 volt DC bias and a 0.5 volt peak-to-peak sinusoidal signal at a frequency of 100 kHz and a temperature of 23°C + 2°C.

Capacitor (“CAP”)

Capacitance can be measured using a Keithley 3330 Precision LCZ Tester with Kelvin leads, with a DC bias of 2.2 V and a peak-to-peak sinusoidal signal of 0.5 V. The operating frequency is 120 Hz and the temperature is 23°C + 2°C.

Leakage current:

The leakage current ("DCL") is measured using a leakage tester at a temperature of 23°C + 2°C and rated voltage for at least 30 seconds. Laser welding:

Laser welding is performed using a Trumpf Nd:YaG HAAS laser (emitting near-infrared light at a wavelength of approximately 1064 nm). The welding energy required generally refers to the amount of laser energy required to bond the anode lead to the leadframe anode terminal assembly. Welding energy is expressed in joules.

Example 1

Tantalum powder with a density of 70,000 μFV/g was pressed into small agglomerates to form porous anode bodies with a length of 1.79 millimeters (mm), a width of 2.41 mm, and a thickness of 1.21 mm. The tantalum powder was loaded into the hopper of an automatic tantalum powder forming machine and automatically formed together with a first tantalum wire with a diameter of 0.50 mm (500 microns) to a density of 6.8 g/ ^cm³ , producing the porous anode body. 70% of the total length of the anode lead wire was embedded within the porous anode body. The lead wire inserted into the porous body accounted for 70% of the anode length. This formed anode body was maintained upright at 1300°C under reduced pressure to produce a sintered anode body.

The first tantalum wire was flattened and then resistance welded to a second tantalum wire having a diameter of 0.19 mm (190 microns) as shown in Figure 6. The second tantalum wire having a diameter of 0.19 mm was then welded to an auxiliary stainless steel bar.

The tantalum anode was anodized at 12.5 V in a 0.1% phosphoric acid liquid electrolyte to produce a 150 μF capacitor at 120 Hz. The anode was then immersed in a butanol solution of iron (III) toluenesulfonate (Clevios ^™ C, HC Starck) for 5 minutes and then immersed in 3,4-ethylenedioxythiophene (Clevios ^™ M, HC Starck) for 1 minute to form a conductive polymer coating. After 45 minutes of polymerization, a thin layer of poly(3,4-ethylenedioxythiophene) was formed on the dielectric layer. The anode was washed in methanol to remove reaction byproducts, anodized in a liquid electrolyte, and washed again in methanol. This process was repeated 12 times. The component was then immersed in a graphite dispersion and dried. Finally, the component was immersed in a silver dispersion and dried. The finished component was obtained using conventional assembly techniques and tested. The assembly process was completed using a copper lead frame. Once the capacitor element is connected by laser welding the anode lead to the anode terminal, the length L2 of the second anode lead 40 is trimmed to 0.80 mm. Next, the lead frame is encapsulated with an encapsulating epoxy resin. In this way, multiple (1370) 150 μF/6.3 V capacitor components are manufactured.

Example 2

The capacitors were prepared using the method described in Example 1, except that a second tantalum wire having a diameter of 0.19 mm was welded to the first tantalum wire having a diameter of 0.50 mm. A plurality of (1370) components were prepared in this manner, see FIG.

Comparative Example 3

Capacitors were prepared using the method described in Example 1, but using only one lead wire of 0.19 mm diameter. A number of (5700) parts were prepared in this manner.

Table 1 below summarizes the characteristics of each of the examples discussed above, including tantalum wire diameter, laser welding settings, median DCL, median capacitance, and median ESR of the finished capacitors. As shown in the table, the ESR of Examples 1 and 2 is lower than that of Comparative Example 3.

Table 1

Those skilled in the art may implement the present invention and other modifications and variations thereof without departing from the spirit and scope of the present invention. Furthermore, it should be understood that various aspects of the various embodiments may be interchanged in whole or in part. Furthermore, those skilled in the art should understand that the foregoing description is by way of example only and is not intended to limit the scope of the present invention as further described in the claims.

Claims (23)

1. A solid electrolytic capacitor, comprising: A capacitor element, wherein the capacitor element includes a sintered porous anode; a dielectric layer covering the sintered porous anode; and a cathode covering the dielectric layer and comprising a solid electrolyte; and An anode lead assembly, wherein the anode lead assembly includes a first anode lead and a second anode lead, the first anode lead having an embedded portion located within a sintered porous anode body and an outer portion extending longitudinally from the surface of the sintered porous anode body, wherein the outer portion of the first anode lead includes a first outer portion and a second outer portion, wherein the second outer portion includes a substantially flat surface, and wherein the width of the second outer portion is greater than the width of the first outer portion; the second anode lead is located outside the sintered porous anode body and includes a first portion and a second portion, wherein the first portion has a substantially flat surface, and wherein the substantially flat surface of the first portion of the second anode lead is connected to the substantially flat surface of the outer portion of the first anode lead. 2. The solid electrolytic capacitor according to claim 1, wherein the first anode lead and the second anode lead comprise different materials. 3. The solid electrolytic capacitor according to claim 1, wherein the first anode lead is tantalum and the second anode lead is a non-tantalum material. 4. The solid electrolytic capacitor according to claim 1, wherein the height of the second outer portion of the first anode lead is less than the corresponding height of the first outer portion of the first anode lead. 5. The solid electrolytic capacitor according to claim 1, wherein the width of the first portion of the second anode lead is greater than the width of the second portion of the second anode lead. 6. The solid electrolytic capacitor according to claim 1, wherein the height of the first portion of the second anode lead is less than the corresponding height of the second portion of the second anode lead. 7. The solid electrolytic capacitor according to claim 1, wherein the height of the second portion of the second anode lead is less than the height of the embedded portion of the first anode lead. 8. The solid electrolytic capacitor according to claim 7, wherein the height of the second portion of the second anode lead is 10% to 90% of the height of the first anode lead embedded portion. 9. The solid electrolytic capacitor of claim 1, wherein the substantially flat surface of the first portion of the second anode lead is connected to the substantially flat surface of the second outer portion of the first anode lead by resistance welding. 10. The solid electrolytic capacitor of claim 1, further comprising an anode terminal, wherein a second portion of the second anode lead is laser-welded to the anode terminal. 11. The solid electrolytic capacitor according to claim 1, further comprising a cathode terminal electrically connected to the cathode. 12. The solid electrolytic capacitor according to claim 1, wherein the anode body is formed from a powder with a specific charge of 10,000 μF*V/g to 600,000 μF*V/g, wherein the powder comprises tantalum, niobium, aluminum, hafnium, titanium and their conductive oxides, or their conductive nitrides. 13. The solid electrolytic capacitor of claim 1, further comprising a second capacitor element and a second anode lead assembly, wherein the second capacitor element comprises a sintered porous anode body; a dielectric layer covering the sintered porous anode body; and a cathode covering the second dielectric layer and comprising a solid electrolyte; wherein the second anode lead assembly comprises a third anode lead and a fourth anode lead, wherein the third anode lead has an embedded portion within the sintered porous anode body and an outer portion extending longitudinally along the surface of the sintered porous anode body, wherein the outer portion comprises a substantially flat surface; the fourth anode lead is located outside the sintered porous anode body, wherein the fourth anode lead comprises a first portion and a second portion, wherein the first portion has a substantially flat surface, and wherein the substantially flat surface of the first portion of the fourth anode lead is connected to the substantially flat surface of the outer portion of the third anode lead. 14. A method for forming a solid electrolytic capacitor, the method comprising: The first anode lead is placed within the powder formed of the valve metal composition, such that the first anode lead includes an embedded portion within the porous anode body and an outer portion extending longitudinally from the surface of the porous anode body, wherein the outer portion of the first anode lead includes a first outer portion and a second outer portion, wherein the second outer portion includes a substantially flat surface, and wherein the width of the second outer portion is greater than the width of the first outer portion. Compact the powder surrounding the first anode lead embedding portion; Sintered and compacted powder forms a sintered porous anode body; The second anode lead is placed outside the sintered porous anode body, wherein the second anode lead includes a first portion and a second portion, wherein the first portion includes a substantially flat surface; Connect the substantially flat surface of the first portion of the second anode lead to the substantially flat surface of the outer portion of the first anode lead; and The second part of the second anode lead is connected to the anode terminal, thus forming an electrical connection between the second part of the second anode lead and the anode terminal. 15. The method of claim 14, further comprising trimming excess anode lead material of the second anode lead after soldering a second portion of the second anode lead to the anode terminal. 16. The method of claim 14, wherein the substantially flat surface of the second outer portion of the first anode lead is formed by flattening or pressing the first anode lead. 17. The method of claim 14, wherein the height of the second portion of the second anode lead is less than the height of the first anode lead embedded portion. 18. The method of claim 14, wherein a first portion of the second anode lead is connected to a second outer portion of the first anode lead by resistance welding. 19. The method of claim 14, wherein a second portion of the second anode lead is connected to the anode terminal by laser welding. 20. The method of claim 14, wherein the substantially flat surface is formed by flattening, pressing, or compressing. 21. The method of claim 14, further comprising: A porous anode body formed by anodic oxidation sintering constitutes a dielectric layer; and A solid electrolyte is applied to the sintered porous anode body that has undergone anodic oxidation to form a cathode. 22. The method of claim 21, further comprising: An electrical connection is formed between the cathode and the cathode terminal; and The capacitor is encapsulated using a molded material, thereby exposing at least a portion of the anode terminal and a portion of the cathode terminal to the outside. 23. The method of claim 14, further comprising: The third anode lead is placed within the powder formed of the valve metal composition, such that the third anode lead includes an embedded portion within the second porous anode body and an outer portion extending longitudinally from the surface of the second porous anode body, wherein the outer portion includes a substantially flat surface. Compact the powder surrounding the embedded portion of the third anode lead; The sintered and compacted powder forms a second sintered porous anode body; The fourth anode lead is placed outside the second sintered porous anode body, wherein the fourth anode lead includes a first portion and a second portion, wherein the first portion includes a substantially flat surface; Connect the substantially flat surface of the first portion of the fourth anode lead to the substantially flat surface of the outer portion of the third anode lead; and The second part of the fourth anode lead is connected to the anode terminal, forming an electrical connection between the second part of the fourth anode lead and the anode terminal.