Low inductance and low resistance hermetically sealed filtered feedthrough for an AIMD
A hermetically sealed filtered feedthrough includes a chip capacitor disposed on a circuit board on a device side. A first low impedance electrical connection is between a capacitor first end metallization and a conductor which is disposed through an insulator. A second low impedance electrical connection is between the capacitor second end metallization and a ferrule or housing. The second low impedance electrical connection may include an oxide-resistant electrical connection forming the hermetic seal between the insulator and the ferrule or housing and an electrical connection between and to the second end metallization and directly to the oxide-resistant electrical connection. Alternatively, the second low impedance electrical connection may include an oxide-resistant metal addition attached directly to the ferrule or housing and an electrical connection between and to the second end metallization and directly to the oxide-resistant metal addition.
1. A hermetically sealed feedthrough filter assembly for an implantable medical device, the feedthrough filter assembly comprising:
a) a ferrule comprising an electrically conductive material 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 at least partially residing in the ferrule opening where a first hermetic seal connects the insulator to the ferrule, wherein the insulator extends to spaced apart insulator first and second sides with an insulator via hole extending through the insulator to the insulator first and second sides;
c) an electronic circuit board comprising an active circuit trace and a ground circuit trace, wherein the active circuit trace extends from an active circuit trace first portion to an active circuit trace second portion, and the ground circuit trace extends from a ground circuit trace first portion to a ground circuit trace second portion, and wherein the circuit board has at least one circuit board active via hole extending therethrough;
d) a conductor extending to a conductor first portion and a conductor second portion, wherein the conductor is disposed through the insulator via hole where a second hermetic seal connects the conductor to the insulator so that the conductor is in a non-electrically conductive relation with the ferrule, and wherein the conductor first portion resides in the circuit board active via hole and the conductor second portion is electrically connectable to an implantable lead having an electrode configured for contact with body tissue;
e) a two-terminal chip capacitor comprising at least one active electrode plate interleaved within a capacitor dielectric 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 of the two-terminal chip capacitor;
f) a first electrical connection electrically connecting the active metallization of the two-terminal chip capacitor to both:
A) the active circuit trace first portion; and
B) the conductor first portion residing in or adjacent to the circuit board active via hole,
C) wherein the active circuit trace second portion is electrically connectable to electronic circuits for an implantable medical device; and
g) a second electrical connection electrically connecting the ground metallization of the two-terminal chip capacitor to both:
A) the ground circuit trace first portion; and
B) the ground circuit trace second portion to the first hermetic seal contacting the ferrule.
2. The feedthrough filter assembly of claim 1 , wherein at least one of the first and second electrical connections comprise a noble metal structure.
3. The feedthrough filter assembly of claim 1 , wherein at least one of the first and second electrical connections comprise a gold braze.
4. The feedthrough filter assembly of claim 1 , wherein the conductor first portion extends into, but not completely through the circuit board active via hole.
5. The feedthrough filter assembly of claim 1 , wherein the second electrical connection comprises a solder contacting the first hermetic seal and an electrical connection material connecting the solder to the ground metallization of the two-terminal chip capacitor.
6. The feedthrough filter assembly of claim 1 , wherein a ground impedance loop extends from the conductor through the first electrical connection to the two-terminal chip capacitor and then from the two-terminal chip capacitor to the second electrical connection to the first hermetic seal contacting the ferrule.
7. The feedthrough filter assembly of claim 6 , wherein a total resistance of the ground impedance loop is greater than zero, but less than 0.5 ohms.
8. The feedthrough filter assembly of claim 6 , wherein a total inductance of the ground impedance loop is greater than zero, but less than 10 nanohenries.
9. The feedthrough filter assembly of claim 1 , wherein the two-terminal chip capacitor is selected from the group consisting of a monolithic ceramic chip capacitor (MLCC), a stacked film capacitor, a tantalum chip capacitor, an electrolytic chip capacitor, and a reverse geometry two-terminal chip capacitor.
10. The feedthrough filter assembly of claim 1 , wherein the circuit board is at least partially supported by the insulator.
11. The feedthrough filter assembly of claim 1 , wherein the conductor comprises a leadwire.
12. The feedthrough filter assembly of claim 11 , wherein the leadwire comprises platinum or gold.
13. The feedthrough filter assembly of claim 1 , wherein at least one of the insulator first and second sides is flush with a corresponding first and second side of the ferrule.
14. The feedthrough filter assembly of claim 1 , including at least one nonconductive adhesive washer or epoxy that is disposed between one of:
i) the circuit board and the ferrule;
ii) the circuit board and the insulator; and
ii) the circuit board and both the ferrule and the insulator.
15. The feedthrough filter assembly of claim 1 , wherein the insulator comprises an alumina substrate comprised of at least 96% alumina.
16. The feedthrough filter assembly of claim 1 , wherein the conductor first portion extends through the circuit board active via hole and the first electrical connection electrically couples to the conductor first portion extending outwardly from the circuit board active via hole.
17. The feedthrough filter assembly of claim 1 , wherein the second electrical connection material electrically connects the ground circuit trace second portion to the first hermetic seal contacting the ferrule.
18. The feedthrough filter assembly of claim 1 , wherein the circuit board comprises a flexible portion.
19. The feedthrough filter assembly of claim 1 , wherein at least one of the first and second electrical connections comprises a ball grid array.
20. The feedthrough filter assembly of claim 1 , wherein the two-terminal chip capacitor has a resonant frequency above 400 MHz.
21. The feedthrough filter assembly of claim 1 , wherein the two-terminal chip capacitor has a capacitance in a range from 300 picofarads to 10,000 picofarads.
22. A hermetically sealed feedthrough filter assembly for an active implantable medical device, the feedthrough filter assembly comprising:
a) a ferrule comprising an electrically conductive material 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) a noble metal structure welded to the ferrule spaced from the ferrule opening;
c) an insulator at least partially residing in the ferrule opening where a first hermetic seal connects the insulator to the ferrule, wherein the insulator extends to spaced apart insulator first and second sides with an insulator via hole extending through the insulator to the insulator first and second sides;
d) an electronic circuit board comprising a circuit board first side and a circuit board second side, wherein the circuit board second side is located adjacent to the insulator first side, and wherein the circuit board comprises an active circuit trace and a ground circuit trace, the active circuit trace extending from an active circuit trace first portion to an active circuit trace second portion, and the ground circuit trace extending from a ground circuit trace first portion to a ground circuit trace second portion, and wherein the circuit board has at least one circuit board active via hole extending therethrough;
e) a conductor extending to a conductor first portion and a conductor second portion, wherein the conductor is disposed through the insulator via hole where a second hermetic seal connects the conductor to the insulator so that the conductor is in a non-electrically conductive relation with the ferrule, and wherein the conductor first portion resides in the circuit board active via hole and the conductor second portion is electrically connectable to an implantable lead having an electrode configured for contact with body tissue;
f) a two-terminal chip capacitor supported on the circuit board first side, the two-terminal chip capacitor comprising at least one active electrode plate interleaved within a capacitor dielectric with at least one ground electrode plate, wherein an active metallization is connected to the at least one active electrode plate and a ground metallization is connected to the at least one ground electrode plate of the two-terminal chip capacitor;
g) a first electrical connection electrically and physically extending from the active metallization of the two-terminal chip capacitor to both:
A) the active circuit trace first portion; and
B) the conductor first portion residing in or adjacent to the circuit board active via hole,
C) wherein the active circuit trace second portion is electrically connectable to electronic circuits for an implantable medical device; and
h) a second electrical connection electrically and physically extending from the ground metallization of the two-terminal chip capacitor to both:
A) the ground circuit trace first portion; and
B) the ground circuit trace second portion to the noble metal structure welded to the ferrule spaced from the ferrule opening.
23. The feedthrough filter assembly of claim 22 , wherein the conductor first portion extends into, but not completely through the circuit board active via hole.
24. The feedthrough filter assembly of claim 22 , wherein the two-terminal chip capacitor has a resonant frequency above 400 MHz and a capacitance in a range from 300 picofarads to 10,000 picofarads.
25. The feedthrough filter assembly of claim 22 , wherein the second electrical connection comprises a conductive material selected from a solder and a thermal-setting conductive adhesive.
26. The feedthrough filter assembly of claim 22 , wherein a ground impedance loop having a total resistance that is greater than zero, but less than 0.5 ohm and a total inductance that is greater than zero, but less than 10 nanohenries extends from the conductor through the first electrical connection to the two-terminal chip capacitor and then from the two-terminal chip capacitor to the second electrical connection to the noble metal structure welded to the ferrule.
27. An implantable medical device, comprising:
a) a hermetically sealed device housing containing device electronic circuits;
b) a feedthrough filter assembly, comprising:
i) a ferrule comprising an electrically conductive material defining a ferrule opening, wherein the ferrule is hermetically mounted in an opening in the device housing to thereby provide a ferrule device side inside the device housing and a ferrule body fluid side outside the device housing;
ii) an insulator at least partially residing in the ferrule opening where a first hermetic seal connects the insulator to the ferrule, wherein the insulator has an insulator device side adjacent to the ferrule device side and an insulator body fluid side adjacent to the ferrule body fluid side, and wherein an insulator via hole extends through the insulator to the insulator device side and the insulator body fluid side;
iii) an electronic circuit board located inside the device housing and comprising a circuit board first side and a circuit board second side, wherein the circuit board second side is adjacent to the insulator first device side, and wherein the circuit board comprises an active circuit trace and a ground circuit trace, the active circuit trace extending from an active circuit trace first portion to an active circuit trace second portion, and the ground circuit trace extending from a ground circuit trace first portion to a ground circuit trace second portion, and wherein the circuit board has at least one circuit board active via hole extending therethrough;
iv) a conductor extending to a conductor first portion and a conductor second portion, wherein the conductor is disposed through the insulator via hole where a second hermetic seal connects the conductor to the insulator so that the conductor is in a non-electrically conductive relation with the ferrule and the device housing, and wherein the conductor first portion resides in the circuit board active via hole and the conductor second portion is electrically connectable to an implantable lead having an electrode configured for contact with body tissue;
v) a two-terminal chip capacitor located inside the device housing, wherein the two-terminal chip capacitor comprises at least one active electrode plate interleaved within a capacitor dielectric with at least one ground electrode plate, and 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 of the two-terminal chip capacitor;
vi) a first electrical connection electrically connecting the active metallization of the two-terminal chip capacitor to both:
A) the active circuit trace first portion; and
B) the conductor first portion residing in or adjacent to the circuit board active via hole,
C) wherein the active circuit trace second portion is electrically connected to the device electronic circuits; and
vii) a second electrical connection electrically connecting the ground metallization of the two-terminal chip capacitor to both:
A) the ground circuit trace first portion; and
B) either the ground circuit trace second portion and the first hermetic seal between the insulator and the ferrule or, the ground circuit trace second portion and to the ferrule hermetically mounted in the opening in the device housing,
viii) wherein, with the active circuit trace being electrically connected to the device electronic circuits and the conductor second portion being electrically connected to a lead having an electrode that is in contact with body tissue, and
A) under a low frequency EMI condition with the two-terminal chip capacitor resonating at greater than zero, but less than 400 MHz, the two-terminal chip capacitor permits passage of biological signals having frequencies that are greater than zero up to 1 kHz to pass from the conductor to the active circuit trace of the circuit board and then to the device electronic circuits, and
B) under a high frequency EMI condition with the two-terminal chip capacitor resonating at at least 400 MHz, the two-terminal chip capacitor acts as an open circuit that does not permit biological signals having frequencies greater than zero up to 1 kHz to pass from the conductor to the active circuit trace of the circuit board and then to the device electronic circuits.
28. The implantable medical device of claim 27 , wherein a ground impedance loop having a total resistance that is greater than zero, but less than 0.5 ohm and a total inductance that is greater than zero, but less than 10 nanohenries extends from the conductor through the first electrical connection to the two-terminal chip capacitor and then from the two-terminal chip capacitor to the second electrical connection and the ground circuit trace and to the first hermetic seal contacting the ferrule.
29. The implantable medical device of claim 27 , wherein, under the high frequency EMI condition, the two-terminal chip capacitor resonates at over 800 MHz.
30. The implantable medical device of claim 27 , wherein the circuit board resides adjacent to the insulator device side with the conductor first portion extending into, but not completely through the circuit board active via hole.
31. The feedthrough filter assembly of claim 27 , wherein, under the high frequency EMI condition, the two-terminal chip capacitor resonates at over 800 MHz.
32. The feedthrough filter assembly of claim 27 , wherein the two-terminal chip capacitor has a resonant frequency above 400 MHz.
33. The feedthrough filter assembly of claim 27 , wherein the two-terminal chip capacitor has a capacitance in a range from 300 picofarads to 10,000 picofarads.
34. An implantable medical device, comprising:
a) a hermetically sealed device housing containing device electronic circuits;
b) a feedthrough filter assembly, comprising:
i) a ferrule comprising an electrically conductive material defining a ferrule opening, wherein the ferrule is hermetically mounted in an opening in the device housing to thereby provide a ferrule device side inside the device housing and a ferrule body fluid side outside the device housing;
ii) an insulator at least partially residing in the ferrule opening where a first hermetic seal connects the insulator to the ferrule, wherein the insulator has an insulator device side adjacent to the ferrule device side and an insulator body fluid side adjacent to the ferrule body fluid side, and wherein an insulator via hole extends through the insulator to the insulator device side and the insulator body fluid side, and wherein at least one of the insulator device and body fluid sides is flush with the adjacent ferrule device and body fluid side;
iii) an electronic circuit board located inside the device housing and comprising a circuit board first side and a circuit board second side, and wherein the circuit board comprises an active circuit trace and a ground circuit trace, the active circuit trace extending from an active circuit trace first portion to an active circuit trace second portion, and the ground circuit trace extending from a ground circuit trace first portion to a ground circuit trace second portion, and wherein the circuit board has at least one circuit board active via hole extending therethrough;
iv) a conductor extending to a conductor inside device portion and a conductor body fluid portion, wherein the conductor is disposed through the insulator via hole where a second hermetic seal connects the conductor to the insulator so that the conductor is in a non-electrically conductive relation with the ferrule and the device housing, and wherein the conductor inside device portion resides in the circuit board active via hole and the conductor body fluid portion is electrically connectable to an implantable lead having an electrode configured for contact with body tissue;
v) a two-terminal chip capacitor located inside the device housing and supported on the circuit board first side, wherein the two-terminal chip capacitor comprises at least one active electrode plate interleaved within a capacitor dielectric with at least one ground electrode plate, and 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 of the two-terminal chip capacitor;
vi) a first electrical connection electrically connecting the active metallization of the two-terminal chip capacitor to both:
A) the active circuit trace first portion; and
B) the conductor inside device portion residing in or adjacent to the circuit board active via hole,
C) wherein the active circuit trace second portion is electrically connected to the device electronic circuits; and
vii) a second electrical connection electrically connecting the ground metallization of the two-terminal chip capacitor to both:
A) the ground circuit trace first portion; and
B) either the ground circuit trace second portion and the first hermetic seal between the insulator and the ferrule or, the ground circuit trace second portion and directly to the ferrule hermetically mounted in the opening in the device housing,
viii) wherein, with the active circuit trace being electrically connected to the device electronic circuits and the conductor body fluid portion being electrically connected to a lead having an electrode that is in contact with body tissue, and
A) under a low frequency EMI condition with the two-terminal chip capacitor resonating at greater than zero, but less than 400 MHz, the two-terminal chip capacitor permits passage of biological signals having frequencies that are greater than zero up to 1 kHz to pass from the conductor to the active circuit trace of the circuit board and then to the device electronic circuits, and
B) under a high frequency EMI condition with the two-terminal chip capacitor resonating at at least 400 MHz, the two-terminal chip capacitor acts as an open circuit that does not permit biological signals having frequencies greater than zero up to 1 kHz to pass from the conductor to the active circuit trace of the circuit board and then to the device electronic circuits.
35. The implantable medical device of claim 34 , wherein the circuit board resides adjacent to the insulator device side with the conductor inside device portion extending into, but not completely through the circuit board active via hole.
36. The implantable medical device of claim 34 , wherein the two-terminal chip capacitor has a resonant frequency above 400 MHz and a capacitance in a range from 300 picofarads to 10,000 picofarads.
37. The feedthrough filter assembly of claim 34 , wherein a ground impedance loop having a total resistance that is greater than zero, but less than 0.5 ohm and a total inductance that is greater than zero, but less than 10 nanohenries extends from the conductor through the first electrical connection to the two-terminal chip capacitor and then from the two-terminal chip capacitor to the second electrical connection and the ground trace and to the first hermetic seal contacting the ferrule.
38. A hermetically sealed feedthrough filter assembly for an implantable medical device, the feedthrough filter assembly comprising:
a) a ferrule comprising an electrically conductive material 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 at least partially residing in the ferrule opening where a first hermetic seal connects the insulator to the ferrule, wherein the insulator extends to spaced apart insulator first and second sides with an insulator via hole extending through the insulator to the insulator first and second sides;
c) an electronic circuit board comprising an active circuit trace and a ground circuit trace, wherein the active circuit trace extends from an active circuit trace first portion to an active circuit trace second portion, and the ground circuit trace extends from a ground circuit trace first portion to a ground circuit trace second portion, and wherein the circuit board has at least one circuit board active via hole extending therethrough;
d) a conductor extending to a conductor first portion and a conductor second portion, wherein the conductor is disposed through the insulator via hole where a second hermetic seal connects the conductor to the insulator so that the conductor is in a non-electrically conductive relation with the ferrule, and wherein the conductor first portion resides in the circuit board active via hole and the conductor second portion is electrically connectable to an implantable lead having an electrode configured for contact with body tissue;
e) a two-terminal chip capacitor comprising at least one active electrode plate interleaved within a capacitor dielectric 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 of the two-terminal chip capacitor;
f) a first electrical connection electrically connecting the active metallization of the two-terminal chip capacitor to both:
A) the active circuit trace first portion; and
B) the conductor first portion residing in or adjacent to the circuit board active via hole,
C) wherein the active circuit trace second portion is electrically connectable to electronic circuits for an implantable medical device; and
g) a second electrical connection electrically connecting the ground metallization of the two-terminal chip capacitor to the ground circuit trace first portion; and
h) a third electrical connection electrically connecting the ground circuit trace second portion to the first hermetic seal between the insulator and the ferrule or directly to the ferrule.
39. The feedthrough filter assembly of claim 38 , wherein the conductor first portion extends into, but not completely through the circuit board active via hole.
40. The feedthrough filter assembly of claim 38 , wherein the two-terminal chip capacitor has a resonant frequency above 400 MHz and a capacitance in a range from 300 picofarads to 10,000 picofarads.
41. The feedthrough filter assembly of claim 38 , wherein the second electrical connection comprises a conductive material selected from a solder and a thermal-setting conductive adhesive.
42. The feedthrough filter assembly of claim 38 , wherein a ground impedance loop having a total resistance that is greater than zero, but less than 0.5 ohm and a total inductance that is greater than zero, but less than 10 nanohenries extends from the conductor through the first electrical connection to the two-terminal chip capacitor and then from the two-terminal chip capacitor to the second electrical connection to the ground circuit trace first portion and the third electrical connection from the ground circuit trace second portion to the first hermetic seal contacting the ferrule.