Low equivalent series resistance RF filter for an AIMD

A low equivalent series resistance filter capacitor assembly for an active implantable medical device, the filter capacitor assembly comprising:

• a) an electrically conductive ferrule defining a ferrule opening, wherein the ferrule is configured to be attachable to an opening in a housing of an active implantable medical device;
• b) an alumina insulator at least partially residing in the ferrule opening and being hermetically sealed to the ferrule, wherein the alumina insulator extends from an insulator body fluid side to an insulator device side;
• c) a conductive pathway hermetically sealed to the alumina insulator, the conductive pathway extending from a conductive pathway body fluid side to a conductive pathway device side, wherein the conductive pathway is in a non-conductive relationship with the ferrule, and wherein the conductive pathway is selected from the group consisting of a conductive leadwire, a platinum fill, and a conductive paste, and combinations thereof, the platinum fill and conductive paste characterized as having been co-fired with the alumina insulator;
• d) a filter capacitor, comprising:
• i) a ceramic dielectric body having a dielectric constant that is greater than zero, but less than 1,000;
• ii) at least two active electrode plates interleaved with at least two ground electrode plates supported in the ceramic dielectric body;
• iii) a capacitance that ranges from 10 and 20,000 picofarads;
• and
• iv) an equivalent series resistance (ESR), which is the sum of a dielectric loss plus an ohmic loss of the ceramic dielectric body, that is greater than zero, but less than 2.0 ohms at a range of MRI RF pulsed frequencies,
• v) wherein an active metallization supported on the ceramic dielectric body is electrically connected to the at least two active electrode plates, and a ground metallization supported on the ceramic dielectric body is electrically connected to the at least two ground electrode plates of the filter capacitor, and
• vi) wherein, starting from the alumina insulator on the device side, the filter capacitor is the first capacitor that is electrically connected between the conductive pathway and the ferrule;
• and
• e) a first electrical connection material electrically connecting the conductive pathway device side to the active metallization of the filter capacitor;
• and
• f) a second electrical connection material electrically connecting the ground metallization of the filter capacitor to the ferrule.

A filter assembly for an active implantable medical device, the filter assembly comprising:

• a) an electrically conductive ferrule defining a ferrule opening, wherein the ferrule is configured to be attachable to an opening in a housing of an active implantable medical device;
• b) an insulator hermetically sealed to the ferrule, wherein the insulator extends from an insulator body fluid side to an insulator device side;
• c) a hermetically sealed conductive pathway extending through the insulator to the insulator body fluid side and to the insulator device side, the conductive pathway being in a non-conductive relationship with the ferrule;
• d) a filter capacitor, comprising:
• i) a ceramic dielectric body having a dielectric constant that is greater than zero, but less than 1,000;
• ii) at least two active electrode plates interleaved with at least two ground electrode plates supported in the ceramic dielectric body,
• iii) a capacitance that ranges from 10 and 20,000 picofarads;
• and
• iv) an equivalent series resistance (ESR), which is the sum of a dielectric loss plus an ohmic loss of the ceramic dielectric body, that is greater than zero, but less than 2.0 ohms at a range of MRI RF pulsed frequencies,
• v) wherein an active metallization supported on the ceramic dielectric body is electrically connected to the at least two active electrode plates, and a ground metallization supported on the ceramic dielectric body is electrically connected to the at least two ground electrode plates of the filter capacitor;
• e) a first electrical connection from the active metallization of the filter capacitor to the device side of the conductive pathway;
• and
• f) a second electrical connection from the ground metallization of the filter capacitor to the ferrule,
• g) wherein the filter capacitor is a first capacitor element connected to the conductive pathway.