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Hermetically sealed electrolytic capacitor with enhanced mechanical stability

a technology of electrolytic capacitor and mechanical stability, which is applied in the direction of hermetically sealed casings, variable capacitors, electrical apparatus casings/cabinets/drawers, etc., can solve the problems of poor stability of solid electrolytes at high temperatures, delamination of capacitor elements, and poor stability of solid electrolytes

Active Publication Date: 2012-10-11
KYOCERA AVX COMPONENTS CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about a capacitor assembly and a method of forming it. The assembly includes a capacitor element and a housing with an unoccupied interior cavity. A polymeric restraint is positioned in the interior cavity and in contact with the capacitor element and the housing. The assembly also includes an anode termination and a cathode termination. The method involves positioning the capacitor element and the polymeric restraint in the housing, and then curing a thermosetting material to form the polymeric restraint. The capacitor element and the polymeric restraint are sealed in the housing with a gaseous atmosphere containing an inert gas. The technical effects of this invention include improved stability and reliability of the capacitor assembly, as well as increased efficiency and performance of the battery.

Problems solved by technology

Unfortunately, however, the stability of such solid electrolytes is poor at high temperatures due to the tendency to transform from a doped to an un-doped state, or vice versa.
Despite the benefits achieved, however, problems nevertheless remain.
For example, the capacitor element can sometimes become mechanically instable under extreme conditions (e.g., high temperature of above about 175° C. and / or high voltage of above about 35 volts), leading to delamination of the capacitor element and poor electrical performance.
This is particularly an issue when relatively large anodes are employed, such as those used in high capacitance applications.

Method used

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  • Hermetically sealed electrolytic capacitor with enhanced mechanical stability
  • Hermetically sealed electrolytic capacitor with enhanced mechanical stability
  • Hermetically sealed electrolytic capacitor with enhanced mechanical stability

Examples

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example 1

[0083]A tantalum anode (5.20 mm×3.70 mm×0.85 mm) was anodized at 75V in a liquid electrolyte to 22 μF. A conductive polymer coating was then formed by dipping the entire anode into a poly(3,4-ethylenedioxythiophene) (“PEDT”) dispersion (Clevios™ K, solids content of 1.1%). The part was then dried at 125° C. for 20 minutes. This process was repeated 10 times. Thereafter, the part was dipped at a speed of 0.1 mm / s into a PEDT dispersion (solids content of 2.8%) so that the dispersion reached the shoulder of the part. The part was left in the dispersion for 10 seconds, dried at 125° C. for 30 minutes, and then cooled down to room temperature. This process was repeated 5 times. The part was then coated with graphite and silver. A copper-based leadframe material was used to finish the assembly process. A single cathode connective member was attached to the lower surface of the capacitor element using a silver adhesive. The tantalum wire of the capacitor element was then laser welded to a...

example 2

[0090]A tantalum anode (4.15 mm×3.45 mm×1.05 mm) was anodized at 245V in a liquid electrolyte to 3.8 μF. A conductive polymer coating was then formed by dipping the entire anode into a poly(3,4-ethylenedioxythiophene) (“PEDT”) dispersion (Clevios™ K, solids content of 1.1%). The part was then dried at 125° C. for 20 minutes. This process was repeated 10 times. Thereafter, the part was dipped at a speed of 0.1 mm / s into a PEDT dispersion (solids content of 2.1%) so that the dispersion reached the shoulder of the part. The part was left in the dispersion for 10 seconds, dried at 125° C. for 30 minutes, and then cooled down to room temperature. This process was repeated 10 times. The part was then coated with graphite and silver. One hundred (100) capacitor assemblies were then formed from the capacitor elements in the same manner described above. The parts were then tested for electrical performance (i.e., capacitance (“CAP”), and equivalent series resistance (“ESR”), before and after...

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Abstract

A capacitor assembly that is thermally and mechanically stable in high temperature environments is provided. Thermal stability is provided by enclosing and hermetically sealing the capacitor element within a housing in the presence of a gaseous atmosphere that contains an inert gas, thereby limiting the amount of oxygen and moisture supplied to the solid electrolyte of the capacitor. To provide the assembly with good mechanical stability, a polymeric restraint is also employed that is positioned adjacent to and in contact with one or more surfaces of the capacitor element. Without intending to be limited by theory, it is believed that the strength and rigidity of the polymeric restraint can help the capacitor element better withstand vibrational forces incurred during use without resulting in delamination. In this manner, the capacitor assembly is able to better function in high temperature environments.

Description

BACKGROUND OF THE INVENTION[0001]Electrolytic capacitors (e.g., tantalum capacitors) are increasingly being used in the design of circuits due to their volumetric efficiency, reliability, and process compatibility. For example, one type of capacitor that has been developed is a solid electrolytic capacitor that includes an anode (e.g., tantalum), a dielectric oxide film (e.g., tantalum pentoxide, Ta2O5) formed on the anode, a solid electrolyte layer, and a cathode. The solid electrolyte layer may be formed from a conductive polymer, such as described in U.S. Pat. No. 5,457,862 to Sakata, et al., U.S. Pat. No. 5,473,503 to Sakata, et al., U.S. Pat. No. 5,729,428 to Sakata, et al., and U.S. Pat. No. 5,812,367 to Kudoh, et al. Unfortunately, however, the stability of such solid electrolytes is poor at high temperatures due to the tendency to transform from a doped to an un-doped state, or vice versa. In response to these and other problems, capacitors have been developed that are herme...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01G9/04H01G7/00
CPCH01G9/008H01G9/08H01G9/10H01G9/15Y10T29/43H01G11/56H01G11/78H01G11/82Y02E60/13H01G11/48H01G9/012H01G9/06H01G9/025H01G9/04
Inventor ZEDNICKOVA, IVANABILER, MARTIN
Owner KYOCERA AVX COMPONENTS CORP
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