Ground electrical path from an MLCC filter capacitor on an AIMD circuit board to the ferrule of a hermetic feedthrough
An EMI/energy dissipating filter for an active implantable medical device (AIMD) comprises a first gold braze sealing an insulator to the ferrule of a glass-to-metal seal (GTMS) and a lead wire that is sealed in a passageway through the insulator by a second gold braze. A circuit board is disposed adjacent to the insulator. A two-terminal chip capacitor disposed adjacent to the circuit board has an active end metallization connected to its active electrode plates and a ground end metallization connected to its ground electrode plates. A ground electrical path extends from the ground end metallization of the chip capacitor, through a circuit board ground plate disposed on or within the circuit board, and to the ferrule. An active electrical path extends from the active end metallization of the chip capacitor to the lead wire of the GTMS.
1. A ground path for an EMI/energy dissipating filter assembly for an active implantable medical device (AIMD), the ground path comprising:
a) an electrically conductive ferrule comprising a ferrule opening, wherein at least one conductive ground pin is electrically and mechanically connected to the ferrule, and wherein the ferrule is configured to be attachable to an opening in a housing for the AIMD;
b) an insulator hermetically sealed to the ferrule in the ferrule opening, and wherein at least one insulator passageway extends through the insulator;
c) a conductive active lead wire hermetically sealed in the at least one insulator passageway;
d) a circuit board residing adjacent to the insulator, wherein at least one circuit board ground plate is disposed on or within the circuit board;
e) a filter capacitor disposed on or adjacent to the circuit board, the filter capacitor comprising a filter capacitor dielectric supporting at least one active electrode plate interleaved in a capacitive relationship with at least one ground electrode plate, wherein an active metallization is electrically connected to the at least one active electrode plate, and a ground metallization is electrically connected to the at least one ground electrode plate;
f) a ground electrical path extending from the ground metallization electrically connected to the at least one ground electrode plate of the filter capacitor, through the at least one circuit board ground plate, and to the at least one ground pin connected to the ferrule; and
g) an active electrical path extending from the active lead wire to the active metallization electrically connected to the at least one active electrode plate of the filter capacitor.
2. The ground path of claim 1 , wherein the at least one conductive ground pin is electrically and mechanically connected to the ferrule by one of a first gold braze or a laser weld.
3. The ground path of claim 2 , wherein the first gold braze and the at least one conductive ground pin at least partially reside in at least one of a ferrule countersink or a ferrule counterbore.
4. The ground path of claim 1 , wherein the filter capacitor is a two-terminal or a three-terminal capacitor.
5. The ground path of claim 4 , wherein the three-terminal capacitor comprises a flat-through capacitor or a feedthrough capacitor.
6. The ground path of claim 4 , wherein the two-terminal or three-terminal capacitor comprises at least one of a monolithic ceramic capacitor, a stacked film capacitor, a tantalum capacitor, an electrolytic capacitor, and an aluminum electrolytic capacitor.