Medical device containing a solid electrolytic capacitor
A capacitor bank for use in a medical device is provided. Through selective control over the individual capacitors employed in the bank, a low ESR can be achieved without adversely impacting other properties of the resulting medical device. More particularly, at least one capacitor in the bank may contain a solid electrolytic capacitor element that includes an anode and a solid electrolyte overlying the anode. The anode includes an anodically oxidized, sintered porous pellet and the solid electrolyte includes a plurality of conductive polymer particles.
1. A capacitor bank for a medical device, the bank comprising two or more individual capacitors that are connected in series, wherein at least one of the capacitors in the bank comprises:
a capacitor element having a front surface and a lower surface, that contains an anode and a solid electrolyte, wherein the anode contains a sintered porous pellet and a dielectric layer formed thereon, and further wherein the solid electrolyte overlies the dielectric layer and contains a plurality of pre-polymerized conductive polymer particles;
an anode lead, wherein the anode lead extends from the front surface of the capacitor element;
an anode termination that is in electrical connection with the anode;
a cathode termination that is in electrical connection with the solid electrolyte; and
a casing that encapsulates the capacitor element and leaves exposed at least a portion of the anode termination and the cathode termination;
wherein the capacitor bank exhibits an equivalent series resistance (ESR) of about 3 ohms or less measured at an operating frequency of 100 Hz; and
wherein the capacitor bank provides a therapeutic high voltage of between about 500 volts to about 950 volts.
2. The capacitor bank of claim 1 , wherein the dielectric layer includes tantalum pentoxide and the pellet includes tantalum.
3. The capacitor bank of claim 1 , wherein the anode has a D-shape.
4. The capacitor bank of claim 1 , wherein the pre-polymerized conductive polymer particles include a substituted polythiophene having the following general structure:
wherein,
R 7 is a linear or branched, optionally substituted C 1 to C 18 alkyl radical; optionally substituted C 6 to C 14 aryl radical; optionally substituted C 1 to C 4 hydroxyalkyl radical, or hydroxyl radical;
q is an integer from 0 to 8; and
n is from 2 to 5,000.
5. The capacitor bank of claim 1 , wherein the pre-polymerized conductive polymer particles include poly(3,4-ethylenedioxythiophene) or a derivative thereof.
6. The capacitor bank of claim 1 , wherein the pre-polymerized conductive polymer particles have an average diameter of from about 1 to about 200 nanometers.
7. The capacitor bank of claim 1 , wherein the solid electrolyte also includes a hydroxyl-functional nonionic polymer.
8. The capacitor bank of claim 1 , wherein the solid electrolyte is generally free of conductive polymers formed by in situ polymerization.
9. The capacitor bank of claim 1 , wherein the solid electrolyte includes one or more layers, wherein the pre-polymerized conductive polymer particles are in a layer in direct contact with the dielectric layer.
10. The capacitor bank of claim 1 , wherein the casing includes a resinous material.
11. The capacitor bank of claim 1 , wherein the bank contains at least three capacitors.
12. The capacitor bank of claim 1 , wherein multiple capacitors in the bank comprise:
a capacitor element having a front surface and a lower surface, that contains an anode and a solid electrolyte, wherein the anode contains a sintered porous pellet and a dielectric layer formed thereon, and further wherein the solid electrolyte overlies the dielectric layer and contains a plurality of pre-polymerized conductive polymer particles;
an anode lead, wherein the anode lead extends from the front surface of the capacitor element;
an anode termination that is in electrical connection with the anode;
a cathode termination that is in electrical connection with the solid electrolyte; and
a casing that encapsulates the capacitor element and leaves exposed at least a portion of the anode termination and the cathode termination.
13. A medical device that comprises a capacitor bank provided within a housing, wherein the bank comprises two or more individual capacitors that are connected in series, wherein at least one of the capacitors in the bank comprises:
a capacitor element having a front surface and a lower surface, that contains an anode and a solid electrolyte, wherein the anode contains a sintered porous pellet and a dielectric layer formed thereon, and further wherein the solid electrolyte overlies the dielectric layer and contains a plurality of pre-polymerized conductive polymer particles;
an anode lead, wherein the anode lead extends from the front surface of the capacitor element;
an anode termination that is in electrical connection with the anode;
a cathode termination that is in electrical connection with the solid electrolyte; and
a casing that encapsulates the capacitor element and leaves exposed at least a portion of the anode termination and the cathode termination;
wherein the capacitor bank exhibits an equivalent series resistance (ESR) of about 3 ohms or less measured at an operating frequency of 100 Hz; and
wherein the capacitor bank provides a therapeutic high voltage of between about 500 volts to about 950 volts.
14. The medical device of claim 13 , wherein the device is an implantable defibrillator.
15. The medical device of claim 14 , further comprising one or more leads that are capable of being electrically coupled between the device and a patient's heart.
16. The medical device of claim 13 , wherein the capacitor bank is coupled to a battery.