HK1111802B - Solid electrolytic capacitor assembly - Google Patents

Description

Solid electrolytic capacitor assembly

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application serial No.60/795,970, filed on 2006, month 4 and 28, which is incorporated herein by reference in its entirety.

Background

A wide variety of modern technology applications create a need for efficient electronic devices and integrated circuits for use in these applications. Capacitors are fundamental devices used for filtering, decoupling, bypassing, and other aspects of these modern applications, which may include wireless communications, high speed processing, networking, circuit switching, and many other applications. Dramatic increases in the speed and packing density of integrated circuits require advances in decoupling capacitor element technology. Performance characteristics become increasingly important as large capacitive decoupling capacitors are subjected to the high frequencies of many current applications. Since capacitors are essential for these large range applications, the accuracy and efficiency of the capacitors is essential. Thus, many well-defined aspects of capacitor design have been the focus of improving the performance characteristics of capacitors. Solid electrolytic capacitors, such as tantalum capacitors, have long played a major role in the miniaturization of electronic circuits and enabling these circuits to be used in extreme environments. For example, tantalum capacitors are typically manufactured by pressing tantalum powder into pellets, sintering the pellets to form a porous body, and anodizing the porous body to form a continuous dielectric oxide film on the sintered body. The capacitance of a tantalum anode is a direct function of the specific surface area of the sintered powder. Therefore, in order to increase the capacitance, a larger specific surface area can be achieved by the use of finer tantalum particles. Unfortunately, during sintering, a "bottleneck" tends to form between the fine particles. During use, these bottlenecks tend to overheat when current passes through the anode, resulting in damage to the capacitor.

There is therefore a need for a capacitor which meets the requirements of the industry in terms of size and performance, and which also avoids overheating during use due to insufficient power dissipation.

Disclosure of Invention

According to one embodiment of the present invention, a capacitor assembly is disclosed that includes a first solid electrolytic capacitor element and a second solid electrolytic capacitor element positioned adjacent to the first solid electrolytic capacitor element. Each of the first and second solid electrolytic capacitor elements includes an anode formed of a valve metal composition (e.g., tantalum oxide or niobium oxide) having a charge-to-mass ratio of about 70,000 μ F V/g or greater. A thermally conductive material (e.g., a metal) is positioned between the first and second solid electrolytic capacitor elements, wherein the thermally conductive material has a thermal conductivity of about 100W/m-K or greater at a temperature of 20 ℃. The case encloses the first and second solid electrolytic capacitor elements.

In accordance with another embodiment of the present invention, a capacitor assembly is disclosed that includes a first solid electrolytic capacitor element and a second solid electrolytic capacitor element positioned adjacent to the first solid electrolytic capacitor element. Each of the first and second solid electrolytic capacitor elements includes an anode formed of an electron tube metal composition. Such anodes have a thickness of from about 0.1 to about 4 millimeters. The first solid electrolytic capacitor element has a first anode lead and the second solid electrolytic capacitor element has a second anode lead, wherein the first anode lead is substantially parallel to and substantially horizontally aligned with the second anode lead. The assembly also includes an anode terminal including a portion having an upper region electrically connected to the first anode lead and a lower region electrically connected to the second anode lead. A cathode terminal is located between and electrically connected to the first and second solid electrolytic capacitor elements, wherein the cathode terminal comprises a thermally conductive material. A casing encloses the first and second solid electrolytic capacitor elements, wherein the casing leaves exposed portions of the anode and cathode terminals.

In accordance with yet another embodiment of the present invention, a method of forming a capacitive assembly is disclosed. The method includes providing a first solid electrolytic capacitor element and a second solid electrolytic capacitor element, the first and second solid electrolytic capacitor elements including first and second anode leads, respectively, extending from an anode, wherein the anode is formed from an electron tube metal composition. A lead frame is also provided, the lead frame having a first surface and an opposing second surface, wherein the lead frame defines a cathode terminal and an anode terminal, and the lead frame comprises a thermally conductive material. . The first solid electrolytic capacitor element is electrically connected to the first surface of the cathode terminal, and the first anode lead is welded to the anode terminal. A second solid electrolytic capacitor element is electrically connected to the second surface of the cathode terminal and a second anode lead is welded to the anode terminal.

Other features and aspects of the present invention are set forth in detail below.

Drawings

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended figures in which:

FIG. 1 is a perspective view of one embodiment of a capacitor assembly of the present invention;

FIG. 2 is a cross-sectional top view of one embodiment of a leadframe used in the present invention;

FIG. 3 is a perspective view of one embodiment of a portion of a lead frame for use in the present invention;

fig. 4 is a perspective view of one embodiment of mounting a first solid electrolytic capacitor to the lead frame shown in fig. 3;

FIG. 5 is a perspective view of one embodiment of a laser welding the first solid electrolytic capacitor shown in FIG. 4 to a lead frame;

fig. 6 is a perspective view of one embodiment of mounting a second solid electrolytic capacitor to the lead frame shown in fig. 3;

FIG. 7 is a perspective view of one embodiment of a laser soldering the second solid electrolytic capacitor shown in FIG. 6 to a lead frame;

fig. 8 is a perspective view of the capacitor assembly shown in fig. 1, the capacitor assembly shown having an encapsulating housing.

Repeat use of reference characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.

Detailed Description

It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary constructions.

In general, the present invention relates to an integrated capacitor assembly that provides improved performance characteristics in a convenient and space-saving package. The capacitor assembly includes at least two solid electrolytic capacitor elements adjacent to one another (e.g., stacked). Each capacitive element includes an anode formed from an electron tube metal composition. The valve metal component may have a high charge-to-mass ratio, such as about 70,000 microfarad volts per gram ("μ F V/g") or greater, in certain embodiments about 80,000 μ F V/g or greater, in certain embodiments about 100,000 μ F V/g or greater, and in certain embodiments about 120,000 μ F V/g or greater. Valve metal components include valve metals (i.e., metals capable of oxidation) or valve metal-based compounds such as tantalum, niobium, aluminum, hafnium, titanium, alloys thereof, oxides thereof, nitrides thereof, and the like. For example, the anode may be formed from a valve metal oxide having an atomic ratio of metal to oxygen of 1: less than 25, in certain embodiments 1: less than 2.0, in certain embodiments 1: less than 1.5, and in certain embodiments 1: 1. Examples of such valve metal oxides may include niobium oxides (e.g., NbO) and tantalum oxides, and the like, and are described in detail in U.S. patent No.6,322,912 to Fife, which is incorporated by reference herein in its entirety for all purposes.

A variety of conventional fabrication procedures may be generally used to form such anodes. In one embodiment, a tantalum or niobium oxide powder having a certain particle size is first selected. The particle size may be varied depending on the desired voltage of the resulting capacitive element. For example, powders having a relatively large particle size (e.g., about 10 microns) are typically used to make high voltage capacitive elements, while powders having a relatively small particle size (e.g., about 0.5 microns) are typically used to make low voltage capacitive elements. The particles are then optionally mixed with a binder and/or lubricant to ensure that the particles are sufficiently bonded to each other when the particles are pressed to form the anode. Suitable binders may include camphor, stearin and other fatty acids in soap form, polyethylene glycol (Union Carbide), calanthan resin (General Electric), polyvinyl alcohol, naphthalene, vegetable waxes and microcrystalline waxes (purified paraffin wax). The binder may be dissolved and dispersed in a solvent. Exemplary solvents may include water, acetone, methyl isobutyl alcohol, trichloroiodomethane, fluorinated hydrocarbons (freon) (DuPont), alcohols, and chlorinated hydrocarbons (carbon tetrachloride). When used, the percentage of binder and/or lubricant by weight of the entire weight may range from about 0.1% to about 8%. However, it is to be understood that binders and lubricants are not required in the present invention. Once the powder is formed, the powder is compacted using any conventional powder press mold. For example, the press mold may be a single station compression press using a die and one or more dies. Alternatively, an anvil type press may be used, which uses only a die and a single lower die. Several basic types of single station compression presses are available, such as cams, toggle/toggle and eccentric/crank presses, which have varying capacities, such as single action, double action, spring die, movable platen, opposed ram, screws, impact, hot press, coining or coining. The powder may be pressed tightly around the anode lead (e.g., tantalum wire). It is also understood that the anode lead may also be attached (e.g., welded) to the anode after pressing and/or sintering of the anode.

After compression, the binder/lubricant may be removed by heating the pellets in a vacuum at a temperature (e.g., from about 150 ℃ to about 500 ℃) for a few minutes. Alternatively, the binder/lubricant may be removed by contacting the pellets with an aqueous solution, as described in U.S. patent No.6,197,252 to Bishop et al, which is incorporated by reference herein in its entirety for all purposes. Thereafter, the pellets are sintered to form a porous monolithic block. For example, in one embodiment, the pellets may be sintered at a temperature of from about 1200 ℃ to about 2000 ℃, and in certain embodiments, the pellets may be sintered in a vacuum at a temperature of from about 1500 ℃ to about 1800 ℃. Upon sintering, the pellets shrink due to the increased bonding between the particles. In addition to the techniques described above, any other technique for forming an anode may be used in accordance with the present invention, such as those described in U.S. patent No.4,085,435 to Galvagni, U.S. patent No.4,945,452 to Sturmer et al, U.S. patent No.5,198,968 to Galvagni, U.S. patent No.5,357,399 to Salisbury, U.S. patent No.5,394,295 to Galvagni et al, U.S. patent No.5,495,386 to Kulkarni, and U.S. patent No.6,322,912 to Fife, which are incorporated by reference in their entirety for all purposes.

Regardless of the manner in which the particles are formed, the thickness of the anode is selected in accordance with the present invention to enhance the electrical performance of the capacitor assembly. For example, the thickness (in the-z direction in fig. 1) of the anode of each individual capacitive element generally ranges from about 0.1 to about 4 millimeters, in certain embodiments, from about 0.2 to about 3 millimeters, and in certain embodiments, from about 0.4 to about 1 millimeter. This relatively small anode thickness (i.e., "low profile") facilitates the dissipation of heat generated by the high charge-to-mass ratio powder and also provides a shorter transport path to reduce ESR and inductance. Moreover, while the combined anode thickness of the capacitive elements may be comparable to that of a conventional single capacitor, the small anode thickness for each individual capacitive element allows for improved impregnation of the dielectric and solid electrolyte, resulting in improved electrical performance.

The shape of the anode may also be selected to enhance the electrical performance of the composite capacitive element. For example, the anode may have a curved, sinusoidal, rectangular, U-shaped, V-shaped, or the like shape. The anode may also have a concave shape in that the anode has one or more grooves, depressions, or notches to increase the surface to volume ratio to reduce ESR and extend the frequency response of the capacitor. Such "concave" shaped anodes are described, for example, in U.S. patent No.6,191,936 to Webber et al, U.S. patent No.5,949,639 to Maeda et al, and U.S. patent No.3,345,545 to Bourgault et al, and U.S. patent application No.2005/0270725 to Hahn et al, which are incorporated by reference herein in their entirety for all purposes.

The anode may be anodized toA dielectric film is formed over and within the porous anode. Anodization is an electrochemical process by which an anodic metal is oxidized to form a material with a relatively high dielectric constant. For example, a tantalum anode may be anodized to form tantalum pentoxide (Ta)₂O₅) This tantalum pentoxide has a dielectric constant "k" of about 27. The anode may be immersed in a weak acid solution (e.g., phosphoric acid) at an elevated temperature (e.g., about 85 c) that is provided with a controlled amount of voltage and current to form a tantalum pentoxide coating having a certain thickness. The supply of powder is initially maintained at a constant current until the desired formation voltage is reached. The powder is then held at a constant voltage to ensure the desired amount of dielectric is formed on the surface of the tantalum pellet. The anodization voltage typically varies from about 5 to about 200 volts, and in some embodiments from about 20 to about 100 volts. In addition to being formed on the surface of the anode, a portion of the dielectric oxide film is also typically formed on the surface of the pores. It should be understood that the dielectric film may also be formed with other types of materials and using different techniques.

Once the dielectric film is formed, it may optionally be coated with a protective coating, such as one made of a relatively insulating (natural or synthetic) resin material. These materials may have a resistivity greater than about 0.05ohm-cm, in certain embodiments greater than about 5ohm-cm, in certain embodiments greater than about 1,000ohm-cm, in certain embodiments greater than 1 x 10⁵ohm-cm, in certain embodiments greater than 1 x 10¹⁰ohm-cm. Some resinous materials that may be used 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, laurates, myristates, palmitates, stearates, eleostearates, oleates, linoleates, linolenates, laccainates, and the like. These fatty acid esters have been found to be particularly useful when used in relatively complex compositions to form "drying oils" which allow synthetic films to be rapidly polymerized into stable layers. The drying oil may comprise a monoglycerideDiglycerides and/or triglycerides, each of which has a glyceride main component having one, two and three esterified fatty acyl residues, respectively. For example, 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 detail in U.S. patent No.6,674,635 to Fife et al, which is incorporated by reference herein in its entirety for all purposes.

Thereafter, the anodized portion is subjected to a step of forming a cathode according to a conventional technique. For example, a solid electrolytic cathode can be formed on a dielectric film. Can be prepared by manganese nitrate (Mn (NO)₃)₂) To form a cathode to form manganese dioxide (MnO)₂) And a cathode. This technique is described, for example, in U.S. patent No.4,945,452 to Sturmer et al, which is incorporated by reference herein in its entirety for all purposes. Alternatively, a conductive polymer coating may be used to form the cathode of the solid electrolytic capacitor element. Such conductive polymer coatings may include one or more conductive polymers such as polypyrrole, polythiophene, polyaniline, polyacetylene, polyphenylene oxide and their derivatives, polythiophene such as poly 3, 4-ethylenedioxythiophene (PEDT). Also, if desired, multiple conductive polymer layers may be used to form the conductive polymer coating. For example, in one embodiment, the conductive polymer coating comprises one layer formed with PEDT and another layer formed with polypyrrole. Different methods can be used to apply the conductive polymer coating to the anode portion. For example, conventional techniques such as electropolymerization, screen printing, dip coating, electrophoretic coating, and spray coating may be used to form the conductive polymer coating. For example, in one embodiment, the monomers used to form the conductive polymer (e.g., 3, 4-ethylenedioxythiophene) may be initially mixed with a polymerization catalyst to form a dispersion. For example, one suitable polymerization catalyst is BAYTRON C, which is a mixture of iron tosylate and n-butanol, sold by Bayer Corporation. BAYTRON C is a commercial candidate for BAYTRON MThe catalyst, BAYTRON M, is poly 3, 4-ethylenedioxythiophene, poly 3, 4-ethylenedioxythiophene is PEDT monomer also sold by Bayer. In most embodiments, once applied, the conductive polymer is cured. Curing may occur after each application of the resulting polymer, or may occur after application of the entire polymer. Although various methods are described in the foregoing, it should be understood that any other method for coating a cathode layer may be used in the present invention.

Once the solid electrolyte layer is formed, the part is coated with a carbon coating (e.g., graphite) and a silver coating, respectively. The silver coating can act as a solderable conductor and/or charge collector for the capacitive element, and the carbon coating limits the contact of the silver coating with the solid electrolyte. Lead electrodes may then be provided, as is well known in the art. The total thickness of each individual capacitive element ranges from about 0.1 to about 4 millimeters, in some embodiments, from about 0.2 to about 3 millimeters, and in some embodiments, from about 0.4 to about 1 millimeter.

Any number of solid electrolytic capacitor elements may be used in the present invention, such as from 2 to 8 capacitor elements (e.g., 2, 3, or 4), and in one particular embodiment, 2 capacitor elements are used. Regardless of the number of capacitive elements used, a thermally conductive material is disposed between at least two capacitive elements to further dissipate heat generated by the large charge-to-mass ratio anode. This allows the capacitive assembly to handle larger currents, which typically result in overheating. In general, the thermally conductive material has a thermal conductivity of about 100 Watts per meter-Kelvin (W/m-K) or greater, in some embodiments, from about 150 to about 500W/m-K, and in some embodiments, from about 200 to about 400W/m-K, when measured at a temperature of 20 ℃. Any thermally conductive material may be used, such as a conductive metal (e.g., copper, nickel, silver, zinc, tin, palladium, lead, copper, aluminum, molybdenum, titanium, iron, zirconium, magnesium, and alloys thereof). Particularly suitable conductive materials include, for example, copper alloys (e.g., copper-zirconium alloys, copper-magnesium alloys, copper-zinc alloys, or copper-iron alloys), nickel, and nickel alloys (e.g., nickel-iron alloys). The thickness of the thermally conductive material is typically selected to optimize thermal dissipation and volumetric efficiency. For example, the thickness of the thermally conductive material ranges from about 0.01 to about 1 millimeter, in some embodiments from about 0.05 to about 0.5 millimeters, and in some embodiments, from about 0.1 to about 0.2 millimeters. An exemplary thermally conductive material is a copper-iron alloy metal plate available from Batten & Allen corporation (uk).

The properties of the solid electrolytic capacitor element can be controlled to optimize the performance of the resulting capacitor assembly. For example, solid electrolytic capacitor elements can exhibit a low Equivalent Series Resistance (ESR), which refers to the range of capacitance elements having a resistance in series with the capacitor that delays charging and discharging and causes losses in the electronic circuit. For example, the electrolytic capacitor element may have an ESR of less than about 1 ohm, in certain embodiments less than about 300 milliohms, in certain embodiments less than about 200 milliohms, and in certain embodiments less than about 100 milliohms, as measured with a bias of 2 volts and a 1 volt signal at a frequency of 100 kHz. Likewise, the equivalent series inductance ("ESL") value may also be less than about 10 nanohenries ("nH"), and in certain embodiments, less than about 1.5nH, when measured with a bias voltage of 2 volts and a 1 volt signal at a frequency of 100 kHz. The capacitance of the solid electrolytic capacitor element can also range from about 1 to about 5,000 microfarads, in certain embodiments from about 250 to about 2,500 microfarads, and in certain embodiments, from about 400 to about 1,000 microfarads, when measured at a frequency of 120 Hz.

In addition to the solid electrolytic capacitor element itself, the capacitor assembly also includes an anode terminal to which the anode lead of the capacitor element is electrically connected. The anode leads are generally substantially parallel to each other and face the same side. Thus, the anode leads are placed in close abutting relationship, which improves efficiency, and the leads can be connected to the anode terminals by this relationship. The anode leads may also be placed in substantial horizontal alignment (i.e., in the x-direction), which improves the dimensional stability of the capacitor assembly. This may be accomplished, for example, by connecting one anode lead to an upper region of the anode terminal and another anode lead to a lower region of the anode terminal. The capacitor assembly also includes a cathode terminal to which the cathode of the solid electrolytic capacitor element is electrically connected. For example, in one embodiment, the cathode termination is located between the capacitive elements such that the cathode termination acts as a thermally conductive material at the same time. The capacitor assembly also includes a housing that encloses the individual components, but leaves respective portions of the terminals exposed to form a mounting surface for circuit applications.

Referring to fig. 1, one particular embodiment of the capacitor assembly 64 of the present invention is shown and will now be described in detail. Capacitor assembly 64 includes a first solid electrolytic capacitor element 22, first solid electrolytic capacitor element 22 in electrical communication with a second solid electrolytic capacitor element 24. In this embodiment, the solid electrolytic capacitor elements have a generally right-angled prismatic shape and are stacked so that the surfaces having the largest area abut one another to optimize the volumetric efficiency of the assembly 64. More specifically, the surface 90 of the solid electrolytic capacitor element 22 defined by the width (-x direction) and the length (-y direction) of the solid electrolytic capacitor element 22 is placed adjacent to the surface 80 of the corresponding solid electrolytic capacitor element 24. The solid electrolytic capacitor elements 22 and 24 may be stacked in a vertical configuration, wherein the surface 90 is disposed in a plane substantially perpendicular to the-x direction and/or the-y direction and is in a horizontal configuration, and the surface 90 is disposed in a plane substantially perpendicular to the-z direction. For example, in the depicted embodiment, capacitive elements 22 and 24 are horizontally stacked in a plane perpendicular to the-z direction. It should be understood that capacitive elements 22 and 24 need not extend in the same direction. For example, surface 90 of capacitive element 22 may be disposed in a plane substantially perpendicular to the-x direction, while surface 80 of capacitive element 24 may be disposed in a plane substantially perpendicular to the-y direction. However, it is desirable that the capacitive elements 22 and 24 extend in substantially the same direction.

Solid electrolytic capacitor elements 22 and 24 are connected in parallel to a common electrical terminal to form capacitor assembly 64. For example, the capacitor assembly 64 includes a cathode terminal 72, the cathode terminal 72 being electrically connected to the cathodes of the solid electrolytic capacitor elements 22 and 24. In this particular embodiment, the cathode terminal 72 is located between the solid electrolytic capacitor elements 22 and 24 and is initially disposed in a plane substantially parallel to the bottom surface 77 of the capacitor assembly 64. However, as described in detail below, the cathode terminal 72 includes an exposed portion 42, and the exposed portion 42 may be subsequently bent to form a mounting terminal. Thus, although the portion of cathode terminal 72 located between capacitive elements 22 and 24 will generally remain parallel to bottom surface 77, depending on the manner in which exposed portion 42 is bent, exposed portion 42 can be placed in the final capacitive assembly 64 at any of a variety of angles (e.g., perpendicular) relative to surface 77.

When formed of a thermally conductive material, the cathode terminal 72 may also serve as the previously described thermally conductive material for dissipating heat generated during use. For example, the cathode terminal 72 may be formed from thermally conductive copper or copper alloy. If desired, the surface of the cathode terminal 72 may be plated with nickel, silver, gold, tin, or the like as is known in the art to ensure that the final part can be mounted to a circuit board. In one particular embodiment, both surfaces of the cathode terminal 72 are plated with nickel and silver, respectively, and the mounting surface is plated with a layer of tin solder. It should be understood, however, that the cathode termination need not be a thermally conductive material, and that these components may be discrete. For example, the thermally conductive material may be electrically connected to the cathode termination (e.g., laser welding, conductive adhesive, etc.) directly or through an additional electrically conductive element (e.g., metal).

The capacitor assembly 64 also includes an anode terminal 62, the anode terminal 62 being formed from a first portion 65 and a second portion 67. As shown in fig. 1, the first portion 65 is integral with the second portion 67. However, it should be understood that these portions 65 and 67 may also be discrete pieces connected together, either directly or through additional conductive elements (e.g., metal). In the illustrated embodiment, first portion 65 is initially disposed in a plane that is substantially parallel to a bottom surface 77 of capacitive assembly 64. However, as described in detail below, the first portion 65 may be substantially bent to form the mounting terminal. Accordingly, depending on the manner in which first portion 65 is bent, first portion 65 may be placed in final capacitive assembly 64 at any of a variety of angles (e.g., perpendicular) relative to surface 77.

The second portion 67 of the anode terminal 62 is disposed in a plane generally perpendicular to the bottom surface 77 of the capacitor assembly 64. The second portion 67 has an upper region 51 and a lower region 53, the upper region 51 being electrically connected to the anode lead 6a, and the lower region 53 being electrically connected to the anode lead 6 b. As shown, the second portion 67 maintains the anode leads 6a and 6b in a substantially horizontal alignment (i.e., in the-x direction) to further improve the dimensional stability of the capacitor assembly 64. The regions 51 and 53 may also have a "U-shape" to improve surface contact and mechanical stability of the leads 6a and 6 b. The second portion 67 further includes an upper arcuate surface 55 and a lower arcuate surface 57, the upper arcuate surface 55 and the lower arcuate surface 57 being located adjacent the upper and lower regions 51 and 53, respectively. An opening 75 is defined between surfaces 55 and 57, opening 75 facilitating operation of anode terminal 62 when connecting anode terminal 62 to capacitive elements 22 and 24. Although not required, the second portion 67 further includes two additional opposing arcuate surfaces 58 and 59, and these arcuate surfaces 58 and 59 may further enhance the strength of the second portion 67. When constructed in the manner described above, the anode terminal 62 can be readily connected to the solid electrolytic capacitor elements 22 and 24 in an efficient and practical manner.

One embodiment of a technique for forming capacitive assembly 64 shown in fig. 2-7 will now be described in detail. In this regard, fig. 2 shows a lead frame 87, the lead frame 87 being useful in forming a plurality of capacitor assemblies according to the present invention. When multiple capacitive element assemblies are manufactured in batches, the lead frame 87 may be cut into individual assemblies (as shown in fig. 3) after the capacitive elements are attached to the frame 87. For simplicity, an exemplary manner of attaching these capacitive elements to lead frame 87 will be described with reference to a single capacitive assembly.

A conductive adhesive 89 is initially applied to the surface 33 of the cathode terminal 72. The conductive adhesive 89 may include, for example, conductive metal particles contained in a resin mixture. The metal particles may be silver, copper, gold, platinum, nickel, zinc, bismuth, and the like. The resin mixture may include a thermosetting resin (e.g., an epoxy resin), a curing agent (e.g., an acid anhydride), and a coupling agent (e.g., a silane coupling agent). One particularly useful adhesive is a silver-containing epoxy resin available from Emerson and Carming as "Amicon CE 3513". Other suitable conductive adhesives are described in U.S. patent application No.2006/0038304 to Osako et al, which is incorporated herein by reference in its entirety for all purposes. The conductive adhesive 89 can be applied to the cathode terminal 72 using any of a variety of techniques. For example, printing techniques may be employed because of their practical and cost-effective advantages.

As indicated by the directional arrows shown in fig. 4, the second portion 67 of the anode terminal 62 is bent upward such that the portion 67 is positioned substantially perpendicular to the surface 90 of the capacitive element 22. Thereafter, the capacitive element 22 is placed on the surface 33 of the cathode terminal 72 such that the bottom surface 90 of the capacitive element 22 contacts the adhesive 89 and the anode lead 6a is received by the upper U-shaped area 51. The anode lead 6a is then electrically connected to the upper region 50 using any technique known in the art, such as mechanical welding, laser welding, conductive adhesive, and the like. For example, as shown in fig. 5, the anode lead 6a may be welded to the upper region 51 using a laser 97. Lasers typically have resonant cavities that include a lasing medium capable of releasing photons by stimulated emission and an energy source that excites an element of the lasing medium. One type of suitable laser is one in which the lasing medium comprises neodymium (Nd) doped aluminum yttrium garnet (YAG). The excited particles being neodymium ions Nd³⁺. The energy source may provide continuous energy to the lasing medium to emit a pulsed laser beam. The conductive adhesive 89 may be cured while the anode lead 6a is electrically connected to the anode terminal 62. For example, heat and pressure may be applied using a hot press to ensure that capacitive element 22 is sufficiently bonded to cathode terminal 72 by adhesive 89. The heating temperature and time are generally based on the curing temperature of the adhesive (e.g., about 195 ℃ for Amicon CE 3513, for a time of10 seconds) was used.

Referring to fig. 6, a conductive adhesive 89 is then applied to the surface 35 of the opposing cathode terminal 72. The second capacitive element 24 is then placed adjacent the surface 35 of the cathode terminal 72 such that the top surface 80 of the second capacitive element 24 contacts the adhesive 99 and the anode lead 6b is received by the lower U-shaped region 53. The anode lead 6b is then electrically connected to the lower region 53 by a laser welder 97 as shown in fig. 7. If desired, a laser welder 97 can also be placed on the other side of the capacitive assembly 64 during welding to reduce the degree of interference with other components of the assembly. As previously described, heat and pressure may be applied using a heat press to ensure that capacitive element 24 is sufficiently bonded to cathode terminal 72 by adhesive 99. It should be understood, however, that the adhesives 89 and 99 may be cured simultaneously, thus not requiring a separate hot pressing step.

Once these capacitive elements are attached, the lead frame is encapsulated within a resin housing, such as a "V housing," "D" housing, or "Y" housing (AVX corporation), which may then be filled with silicon dioxide or any other known encapsulation material. One embodiment of such a package housing is shown in fig. 8 as element 58. The package housing 58 provides additional structural and thermal protection to the capacitor assembly 64. After encapsulation, the exposed portions 65 and 42 of the anode and cathode terminals 62 and 72, respectively, are trimmed and bent along the outside of the housing 58 (e.g., at an angle of about 90). Thus, portions 65 and 42 form a J-lead for the finished capacitor assembly 64, although any other known configuration may be formed in accordance with the present invention. The resulting capacitive assembly 64 includes a surface 77 that can be mounted to a desired surface.

As a result of the present invention, a capacitive component can be formed that exhibits good electrical performance. For example, relatively high peak inrush and ripple currents may be achieved due to the heat dissipation capabilities of the present termination capacitor assembly. For example, the peak rush current may be about 12.0 amps or greater, in certain embodiments about 13.0 amps or greater, and in certain embodiments, from about 14.0 to about 30.0 amps. Likewise, the maximum ripple current (i.e., the current required to raise the temperature of the capacitive component to 10 ℃ at a frequency of 100 kHz) may also be about 2.5 amps or greater, in some embodiments about 3.0 amps or greater, and in some embodiments, about 3.5 amps or greater. The equivalent series resistance of the capacitive component may also be less than about 60 milliohms, in some embodiments less than about 50 milliohms, and in some embodiments, less than about 35 milliohms, as measured with a 2 volt bias and a 1 volt signal at a frequency of 100 kHz. It is also believed that the Dissipation Factor (DF) of the capacitive assembly can also be kept at a relatively low level. Dissipation Factor (DF) generally refers to the loss that occurs in a capacitive component and is usually expressed as a percentage of ideal performance. For example, the capacitive components of the present invention typically have a dissipation factor of less than about 15%, and in certain embodiments, less than about 5%, when measured at a frequency of 120 Hz. Likewise, the capacitance of the component may range from about 100 to 5,000 μ F, in certain embodiments from about 150 to 1,500 μ F, and in certain embodiments, from about 200 to 800 μ F, when measured at a frequency of 120 Hz.

The invention may be further understood by reference to the following examples.

Test program

Equivalent Series Resistance (ESR), capacitance, and dissipation factor:

the equivalent series resistance was measured using an angiont 4284A Precision inductance capacitance resistance meter with an angiont 16089B kelvin lead having a bias of 2 volts and a signal of 1 volt. The operating frequency was 100 kHz. The percentage of wet to dry capacitance is also determined. The "dry capacitance" is the capacitance after coating of the graphite and silver layers, while the "wet capacitance" is the capacitance after formation of the dielectric layer, measured in a liquid electrolyte. The percentage of wet to dry capacitance is determined by dividing the wet capacitance by the dry capacitance, then subtracting "1" and then multiplying by "100".

Leakage current:

leakage current ("DCL") was measured using an MC 190 leakage test device manufactured by mantracour Electronics ltd. The MC 190 test measures the leakage current at a temperature of 25 c and after 10 seconds at a certain rated voltage.

Breakdown voltage:

the value of the breakdown voltage of the capacitor is determined by increasing the applied voltage in increments of 0.5 volts at a constant current. The voltage at which the capacitor failed was recorded as the breakdown voltage.

Peak impact current:

to determine the peak inrush current, the measured capacitor was pre-charged at the nominal voltage for 45 seconds through a 5 kilo ohm resistor and then discharged. The electrolytic capacitor, pre-charged to 1.1 x nominal voltage, was then discharged through a 0.33 ohm resistor to the measured capacitor. After only a few microseconds, the current in the circuit reaches its peak or maximum value and then decreases, with the RC constant of the circuit. The maximum current was monitored using a "PLUT" test device (Placepower UK.K.).

Ripple current:

the ripple current is the current required to raise the temperature of the capacitive component to 10 ℃ at a frequency of 100 kHz. Using Fluke99B (Fluke Corp.) and then using Infratrics Thermacam^TMThe PM250 (fluid systems, boston, ma) measures the temperature of the capacitor.

Example 1

Two tantalum capacitive elements are used to form a capacitive assembly as described above and shown in figures 1 to 8. The tantalum powder used to form each capacitive element had a charge to mass ratio (available from h.c. starck) of 150,000 μ F V/g. The tantalum powder was compacted using known techniques such that the resultant pellets had a length of about 5.35 mm, a width of 3.7 mm and a thickness of 0.75 mm. The pellets were sintered at 1245 ℃ for 10 minutes. The pellets were anodized at a voltage of 15 volts, impregnated with manganese dioxide, and then coated with graphite and silver layers in the manner previously described. Each individual tantalum segment has a capacitance of about 500 muf. These sections are then connected in parallel with common anode and cathode terminals as previously described so that the resulting capacitance of the assembly is approximately 1000 muf and rated at 4 volts. The capacitor assemblies are enclosed in a housing having a length of about 7.5mm, a width of about 4.5mm, and a height of about 3.1mm ("D" housing, AVX corporation).

Comparative example 1

Tantalum powder (available from h.c. starck) having a charge to mass ratio of 150,000 μ F V/g was used to form a mono-tantalum capacitor. The tantalum powder was compacted using known techniques such that the resultant pellets had a length of about 5.00 mm, a width of 3.7 mm and a thickness of 1.95 mm. The pellets were sintered at 1245 ℃ for 10 minutes. The pellets were anodized at a voltage of 15 volts, impregnated with manganese dioxide, and then coated with graphite and silver layers in the manner previously described. The synthesized tantalum part has a capacitance of about 1000 muf. The capacitors are terminated and enclosed in a housing having a length of about 7.5mm, a width of about 4.5mm and a height of about 3.1mm using conventional techniques ("D" housing, AVX corporation). Various electrical properties were tested on 10 to 50 samples of example 1 and comparative example 1. The test results are listed in table 1 below.

Table 1: comparison of Electrical Properties

(average of measured values)

Parameter(s)	Comparative example 1	Example 1
			Capacitor (mu F)	893.00	1070.00
Wet to dry capacitance (%)	42.70	10.30
			Dissipation factor (%)	54.60	19.30
ESR(mΩ)	78.00	32.00
			DCL(μA)	11.38	7.45
Breakdown voltage (V)	11.80	14.10
			Impact failure probability (%)	0.70	0.05
Peak impact Current (A)	11.60	14.00
			Maximum ripple current (A)	2.00	3.50

As shown in the table, the capacitor assembly of the present invention exhibited superior electrical performance to the comparative sample.

Example 2

Two niobium oxide ("NbO") capacitive elements are used to form a capacitive assembly as described above and shown in fig. 1-8. The niobium oxide powder used to form these capacitive elements had a charge to mass ratio (available from h.c. starck) of 80,000 μ F V/g. The niobium oxide powder was compacted using known techniques such that the resultant pellets had a length of about 5.35 mm, a width of 3.7 mm and a thickness of 0.75 mm. The pellets were sintered at 1380 ℃ for 10 minutes. The pellets were anodized at a voltage of 27 volts, impregnated with manganese dioxide, and then coated with graphite and silver layers in the manner previously described. Each individual niobium oxide portion has a capacitance of about 110 muf. These sections are then connected in parallel with common anode and cathode terminals as previously described so that the resulting capacitance of the assembly is about 220 muf and rated at 4 volts. The capacitor assemblies are enclosed in a housing having a length of about 7.5mm, a width of about 4.5mm, and a height of about 3.1mm ("D" housing, AVX corporation).

Example 3

A capacitor was constructed as described in example 2, except that the anode was slotted and a forming voltage of 21 volts was used. The slotted anode has two parallel grooves running along the entire length of the anode on each side (-x direction). Each groove has a width of 0.4 mm and a thickness of 0.25 mm. The slotted anode had a length of 5.35 mm, a width of 3.7 mm and a thickness of 0.76 mm.

Comparative example 2

Niobium monoxide capacitors were constructed from niobium oxide powders having a charge to mass ratio of 80,000 μ F V/g (available from h.c. starck). The niobium oxide powder was compacted using known techniques such that the resultant pellets had a length of about 4.10 mm, a width of 3.7 mm and a thickness of 1.95 mm. The pellets were sintered at 1380 ℃ for 10 minutes. The pellets were anodized at a voltage of 27 volts, impregnated with manganese dioxide, and then coated with graphite and silver layers in the manner previously described. The resulting part has a capacitance of about 220 muf. The capacitors are terminated and enclosed in a housing having a length of about 7.5mm, a width of about 4.5mm and a height of about 3.1mm using conventional techniques ("D" housing, AVX corporation).

Comparative example 3

A niobium monoxide capacitor was constructed as described in comparative example 2, except that the anode was grooved and anodized at a voltage of 27 volts. The slotted anode has two parallel grooves running along the entire length of the anode on each side (-x direction). The corners of the anode are rounded. Each groove has a width of 0.4 mm and a thickness of 0.25 mm. The slotted anode had a length of 4.90 mm, a width of 3.6 mm and a thickness of 1.95 mm. Various electrical properties were tested on 10 to 50 samples of examples 2 and comparative examples 2 and 3. The test results are listed in table 2 below.

Table 2: comparison of Electrical Properties

(average of measured values)

Parameter(s)	Comparative example 2	Comparative example 3	Example 2	Example 3
					Capacitor (mu F)	211.00	219.00	229.00	225.00
Wet to dry capacitance (%)	-14.00	-12.40	-9.80	-8.00
					Dissipation factor (%)	3.50	2.30	1.60	1.70
ESR(mΩ)	82.00	48.00	31.00	29.00
					DCL(μA)	0.87	0.67	0.84	1.36
Breakdown voltage (V)	12.10	12.80	13.70	13.90
					Impact failure probability (%)	0.70	0.40	0.03	0.02
Peak impact Current (A)	12.00	14.00	14.50	14.80
					Maximum ripple current (A)	1.50	2.80	3.40	3.60

As shown in the table, the capacitor assembly of the present invention exhibited superior electrical performance to the comparative sample.

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. Moreover, it should be understood that aspects of the various embodiments may be interchanged both 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 defined by the appended claims.

Claims (44)

1. A capacitive assembly comprising:

a first solid electrolytic capacitor element;

a second solid electrolytic capacitor element, wherein the first and second solid electrolytic capacitor elements each comprise an anode formed from an electron tube metal composition having a 70,000 μ F^*A charge to mass ratio of V/g or greater, the anode having a thickness of from 0.1 to 4 millimeters;

a thermally conductive material positioned between and electrically connected to the first and second solid electrolytic capacitor elements, wherein the thermally conductive material has a thermal conductivity of 100W/m-K or greater at a temperature of 20 ℃; and

a case enclosing the first and second solid electrolytic capacitor elements.

2. The capacitive assembly of claim 1, wherein: the valve metal component has a thickness of 80,000 μ F^*V/g or greater.

3. The capacitive assembly of claim 1, wherein: the valve metal component has a thickness of 120,000 μ F^*V/g or greater.

4. The capacitive assembly of claim 1, wherein: the valve metal component comprises tantalum.

5. The capacitive assembly of claim 1, wherein: the valve metal component comprises niobium oxide.

6. The capacitive assembly of claim 1, wherein: the first and second solid electrolytic capacitor elements include a dielectric film covering the anode and a solid electrolyte covering the dielectric film.

7. The capacitive assembly of claim 1, wherein: the anode has a thickness of from 0.2 to 3 millimeters.

8. The capacitive assembly of claim 1, wherein: the anode has a thickness of from 0.4 to 1 millimeter.

9. The capacitive assembly of claim 1, wherein: the thermally conductive material has a thermal conductivity of from 200 to 400W/m-K at a temperature of 20 ℃.

10. The capacitive assembly of claim 1, wherein: the thermally conductive material is formed with a metal selected from the group consisting of copper, nickel, silver, nickel, zinc, tin, palladium, lead, copper, aluminum, molybdenum, titanium, iron, zirconium, magnesium, and alloys thereof.

11. The capacitive assembly of claim 10 wherein: the metal is copper or a copper alloy.

12. The capacitive assembly of claim 1, wherein: the thermally conductive material has a thickness of from 0.01 to 1 millimeter.

13. The capacitive assembly of claim 1, wherein: the thermally conductive material has a thickness of from 0.1 to 0.2 millimeters.

14. The capacitive assembly of claim 1, wherein: the first and second solid electrolytic capacitor elements are stacked in a horizontal configuration.

15. The capacitive assembly of claim 1, wherein: the thermally conductive material is electrically connected to the first and second solid electrolytic capacitor elements by a conductive adhesive.

16. The capacitive assembly of claim 1, wherein: further comprising:

an anode terminal to which first and second anode leads of the first and second solid electrolytic capacitor elements are electrically connected, respectively; and

a cathode terminal to which cathodes of the first and second solid electrolytic capacitor elements are electrically connected, respectively, wherein the case leaves exposed portions of the anode and cathode terminals.

17. The capacitive assembly of claim 16 wherein: the thermally conductive material is formed from the cathode termination.

18. The capacitive assembly of claim 16 wherein: the anode terminal includes a portion having an upper region and a lower region, the upper region being electrically connected to the first anode lead and the lower region being electrically connected to the second anode lead.

19. The capacitive assembly of claim 18 wherein: the upper region, the lower region, or both have a U-shape.

20. The capacitive assembly of claim 18 wherein: the first anode lead is parallel to and horizontally aligned with the second anode lead.

21. The capacitive assembly of claim 18 wherein: the portion of the anode terminal includes two or more arcuate surfaces with an opening defined between the arcuate surfaces.

22. The capacitive assembly of claim 18 wherein: the portion of the anode terminal is located perpendicular to a bottom surface of the capacitive element.

23. The capacitive assembly of claim 1, wherein: further solid electrolytic capacitor elements are included.

24. The capacitive assembly of claim 1, wherein: the assembly has a peak inrush current of 12.0 amps or greater.

25. The capacitive assembly of claim 1, wherein: the assembly has a peak inrush current of from 14.0 to 30.0 amps.

26. The capacitive assembly of claim 1, wherein: the assembly has a maximum ripple current of 2.5 amps or greater.

27. The capacitive assembly of claim 1, wherein: the assembly has a maximum ripple current of 3.5 amps or greater.

28. A capacitive assembly comprising:

a first solid electrolytic capacitor element;

a second solid electrolytic capacitor element, wherein each of the first and second solid electrolytic capacitor elements comprises an anode formed from an electronic tube metal composition, the anode having a thickness of from 0.1 to 4 millimeters, the first solid electrolytic capacitor element having a first anode lead and the second solid electrolytic capacitor element having a second anode lead, wherein the first anode lead is parallel to and horizontally aligned with the second anode lead;

an anode terminal including a portion having an upper region and a lower region, the upper region being electrically connected to the first anode lead and the lower region being electrically connected to the second anode lead; and

a cathode terminal located between and electrically connected to the first and second solid electrolytic capacitor elements, wherein the cathode terminal comprises a thermally conductive material; and

a case enclosing the first and second solid electrolytic capacitor elements, wherein the case leaves exposed portions of the anode and cathode terminals.

29. The capacitive assembly of claim 28 wherein: the valve metal component has a particle size of 70,000 μ F^*V/g or greater.

30. The capacitive assembly of claim 28 wherein: the valve metal component has a thickness of 120,000 μ F^*V/g or greater.

31. The capacitive assembly of claim 28 wherein: the valve metal component comprises tantalum or niobium oxide.

32. The capacitive assembly of claim 28 wherein: the anode has a thickness of from 0.4 to 1 millimeter.

33. The capacitive assembly of claim 28 wherein: the thermally conductive material has a thermal conductivity of 100W/m-K or greater at a temperature of 20 ℃.

34. The capacitive assembly of claim 28 wherein: the heat conductive material is copper or a copper alloy.

35. The capacitive assembly of claim 28 wherein: the first and second solid electrolytic capacitor elements are stacked in a horizontal configuration.

36. The capacitive assembly of claim 28 wherein: the upper region, the lower region, or both have a U-shape.

37. The capacitive assembly of claim 28 wherein: the portion of the anode terminal includes two or more arcuate surfaces with an opening defined between the arcuate surfaces.

38. The capacitive assembly of claim 28 wherein: the portion of the anode terminal is located perpendicular to a bottom surface of the capacitive element.

39. A method of forming the capacitive assembly of any one of claims 1-38, the method comprising:

providing a first solid electrolytic capacitor element and a second solid electrolytic capacitor element, said first and second solid electrolytic capacitor elements comprising first and second anode leads extending from an anode, respectively;

providing a lead frame having a first surface and an opposing second surface, wherein the lead frame defines a cathode terminal and an anode terminal, and the lead frame comprises a thermally conductive material;

electrically connecting the first solid electrolytic capacitor element to the first surface of the cathode terminal;

welding the first anode lead to the anode terminal;

electrically connecting the second solid electrolytic capacitor element to the second surface of the cathode terminal;

welding the second anode lead to the anode terminal.

40. The method of claim 39, wherein: the anode terminal includes a portion having an upper region and a lower region.

41. The method of claim 40, wherein: further comprising bending a portion of the anode terminal and then soldering the upper region to the first anode lead and the lower region to the second anode lead.

42. The method of claim 39, wherein: laser welding the first and second anode leads to the anode terminal.

43. The method of claim 39, wherein: further comprising enclosing the capacitive element in a housing.

44. The method of claim 39, wherein: further comprising bending portions of the lead frame along a periphery of the housing to form first and second surface mount terminals.