Hermetically sealed capacitor assembly
A capacitor assembly that includes a conductive polymer electrolytic capacitor that is enclosed and hermetically sealed within a ceramic housing in the presence of an inert gas is provided. Without intending to be limited by theory, the present inventors believe that the ceramic housing is capable of limiting the amount of oxygen and moisture supplied to the conductive polymer of the capacitor. In this manner, the conductive polymer is less likely to oxidize in high temperature environments, thus increasing the thermal stability of the capacitor assembly.
1. A capacitor assembly comprising:
an electrolytic capacitor comprising an anode containing a porous sintered pellet that includes tantalum or niobium oxide, an anode lead wire extending from the anode, a dielectric layer formed over and within the pellet by anodic oxidation, and a cathode overlying the dielectric layer, the cathode including a conductive polymer;
a ceramic housing within which the electrolytic capacitor is enclosed, the ceramic housing being hermetically sealed to a lid, the ceramic housing defining an interior cavity having a gaseous atmosphere, the gaseous atmosphere containing an inert gas, the lid not contacting any surface of the capacitor such that the interior cavity includes a space between the lid and the capacitor, an interior surface of the ceramic housing including a first conductive trace and a second conductive trace, the first conductive trace including a surface that faces the interior cavity of the ceramic housing, wherein the anode lead wire is in direct electrical contact with the first conductive trace and the cathode is in electrical contact with the second conductive trace, a first conductive adhesive electrically connecting the first conductive trace to the anode lead wire, the only physical connection at the surface of the first conductive trace being provided by the first conductive adhesive, and a second conductive adhesive electrically connecting the second conductive trace to the cathode;
a cathode termination that is in electrical connection with the second conductive trace and located external to the ceramic housing; and
an anode termination that is in electrical connection with the first conductive trace and located external to the ceramic housing.
2. The capacitor assembly of claim 1 , wherein the pellet includes tantalum.
3. The capacitor assembly of claim 1 , wherein the pellet includes niobium oxide.
4. The capacitor assembly of claim 1 , wherein the conductive polymer includes poly(3,4-ethylenedioxythiophene) or a derivative thereof.
5. The capacitor assembly of claim 1 , wherein the inert gas includes nitrogen, helium, argon, xenon, neon, krypton, radon, or combinations thereof.
6. The capacitor assembly of claim 1 , wherein inert gases constitute from about 50 wt. % to 100 wt. % of the gaseous atmosphere.
7. The capacitor assembly of claim 1 , wherein inert gases constitute from about 75 wt. % to 100 wt. % of the gaseous atmosphere.
8. The capacitor assembly of claim 1 , wherein oxygen constitutes less than about 1 wt. % of the gaseous atmosphere.
9. The capacitor assembly of claim 1 , wherein an antireflection material is applied to one or more walls of the ceramic housing.
10. The capacitor assembly of claim 1 , wherein the assembly exhibits an equivalent series resistance after aging at 150° C. for 1000 hours of about 50 ohms or less, measured at an operating frequency of 120 Hz.
11. The capacitor assembly of claim 1 , wherein the assembly exhibits an equivalent series resistance after aging at 150° C. for 1000 hours of from about 0.01 to about 10 ohms, measured at an operating frequency of 120 Hz.
12. The capacitor assembly of claim 1 , wherein the assembly exhibits an equivalent series resistance after aging at 175° C. for 700 hours of about 50 ohms or less, measured at an operating frequency of 120 Hz.
13. The capacitor assembly of claim 1 , wherein the assembly exhibits a normalized leakage current after aging at 150° C. for 1000 hours of about 0.1 μA/μF*V or less.
14. The capacitor assembly of claim 1 , wherein the assembly exhibits an normalized leakage current after aging at 175° C. for 700 hours of about 0.1 μA/μF*V or less.
15. The capacitor assembly of claim 1 , wherein the electrolytic capacitor has a lower surface that defines a plane that crosses the interior cavity of the ceramic housing, the first conductive trace being located beneath this plane.