U.S. patent application number 14/465879 was filed with the patent office on 2014-12-11 for feedthrough assembly including a capacitive filter array.
The applicant listed for this patent is Medtronic, Inc.. Invention is credited to Simon E. Goldman, Rajesh V. Iyer, Thomas P. Miltich.
Application Number | 20140360748 14/465879 |
Document ID | / |
Family ID | 46755159 |
Filed Date | 2014-12-11 |
United States Patent
Application |
20140360748 |
Kind Code |
A1 |
Iyer; Rajesh V. ; et
al. |
December 11, 2014 |
FEEDTHROUGH ASSEMBLY INCLUDING A CAPACITIVE FILTER ARRAY
Abstract
A feedthrough assembly may include a ferrule defining a ferrule
opening, a feedthrough at least partially disposed within the
ferrule opening, and a capacitive filter array at least partially
disposed within the ferrule opening. The feedthrough may include at
least one feedthrough conductive pathway and the capacitive filter
array may include at least one filter array conductive pathway. In
some examples, the feedthrough assembly includes a thick film
conductive paste electrically connecting the at least one
feedthrough conductive pathway and the at least one filter array
conductive pathway. In some examples, the capacitive feedthrough
array includes a perimeter conductive contact and a capacitive
filter electrically coupling the at least one filter array
conductive pathway and the perimeter conductive contact. In some of
these examples, the feedthrough assembly includes a thick film
conductive paste electrically connecting the perimeter conductive
contact and the ferrule.
Inventors: |
Iyer; Rajesh V.; (Eden
Prairie, MN) ; Goldman; Simon E.; (St. Louis Park,
MN) ; Miltich; Thomas P.; (Otsego, MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medtronic, Inc. |
Minneapolis |
MN |
US |
|
|
Family ID: |
46755159 |
Appl. No.: |
14/465879 |
Filed: |
August 22, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13308136 |
Nov 30, 2011 |
8844103 |
|
|
14465879 |
|
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61530249 |
Sep 1, 2011 |
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Current U.S.
Class: |
174/50.53 |
Current CPC
Class: |
A61N 1/3754 20130101;
A61N 1/3968 20130101; Y10T 29/49208 20150115; H03H 7/0138 20130101;
H05K 13/00 20130101; Y10T 29/49171 20150115; Y10T 29/49002
20150115; Y10T 29/43 20150115; Y10T 29/435 20150115; Y10T 29/49165
20150115; H03H 2001/0042 20130101 |
Class at
Publication: |
174/50.53 |
International
Class: |
A61N 1/375 20060101
A61N001/375; A61N 1/39 20060101 A61N001/39 |
Claims
1. A feedthrough assembly comprising: a ferrule defining a ferrule
opening; a feedthrough at least partially disposed within the
ferrule opening and having a perimeter wall attached to an interior
wall of the ferrule to form a hermetic seal between the feedthrough
and the ferrule, wherein the feedthrough includes at least one
feedthrough conductive pathway; a capacitive filter array at least
partially disposed within the ferrule opening and having a
perimeter wall attached to an interior wall of the ferrule, the
capacitive filter array defining at least one passageway extending
between an internally-facing capacitor filter array side and
externally-facing capacitor filter array side, wherein the
capacitive filter array includes at least one capacitor filter
array conductive pathway; and a thick film conductive paste within
the at least one passageway electrically connecting the at least
one feedthrough conductive pathway and the at least one capacitor
filter array conductive pathway.
2. The feedthrough assembly of claim 1, wherein the thick film
conductive paste comprises a silver and palladium mixture or
alloy.
3. The feedthrough assembly of claim 2, wherein the thick film
conductive paste further comprises glass frit.
4. The feedthrough assembly of claim 1, wherein the capacitive
filter further comprises a perimeter conductive contact and a
capacitive filter electrically coupling the at least one filter
array conductive pathway and the perimeter conductive contact,
wherein the thick film conductive paste comprises a first thick
film conductive paste, and wherein the feedthrough assembly further
comprises a second thick film conductive paste electrically
connecting the perimeter conductive contact and the ferrule.
5. The feedthrough assembly of claim 1, wherein the at least one
feedthrough conductive pathway comprises an externally-facing
feedthrough conductive pad positioned on or near an
externally-facing side of the feedthrough, an internally-facing
feedthrough conductive pad positioned on or near an
internally-facing side of the feedthrough, and a feedthrough
conductive via extending between the externally-facing feedthrough
conductive pad and the internally-facing feedthrough conductive
pad.
6. The feedthrough assembly of claim 5, wherein the at least one
filter array conductive pathway comprises an externally-facing
filter conductive pad positioned on or near an externally-facing
side of the capacitive filter array, an internally-facing filter
conductive pad positioned on or near an internally-facing side of
the capacitive filter array, and a filter conductive via extending
between the externally-facing filter conductive pad and the
internally-facing filter conductive pad.
7. The feedthrough assembly of claim 6, wherein the thick film
conductive paste electrically connects the externally-facing filter
conductive pad and the internally-facing feedthrough conductive
pad.
8. The feedthrough assembly of claim 1, wherein the at least one
feedthrough conductive pathway comprises an externally-facing
feedthrough conductive pad positioned on or near an
externally-facing side of the feedthrough, an internally-facing
feedthrough conductive pad positioned on or near an
internally-facing side of the feedthrough, and a feedthrough
conductive via extending between the externally-facing feedthrough
conductive pad and the internally-facing feedthrough conductive
pad, and wherein the externally-facing end of the thick film
conductive paste contacts the internally-facing feedthrough
conductive pad.
9. The feedthrough assembly of claim 1, further comprising an
electrically insulating material disposed between an
internally-facing feedthrough side and an externally-facing filter
array side.
10. The feedthrough assembly of claim 9, wherein the electrically
insulating material comprises at least one of a non-conductive
polyimide, an epoxy, a glass, or a high temperature cofired
ceramic.
11. The feedthrough assembly of claim 1, wherein at least one of
the feedthrough, the ferrule, or the capacitive filter array
defines an underfill access channel.
12. A feedthrough assembly comprising: a ferrule defining a ferrule
opening; a feedthrough at least partially disposed within the
ferrule opening, wherein the feedthrough includes at least one
feedthrough conductive pathway; a capacitive filter array at least
partially disposed within the ferrule opening, wherein the
capacitive filter array includes at least one filter array
conductive pathway, a perimeter conductive contact, and a
capacitive filter electrically coupling the at least one filter
array conductive pathway and the perimeter conductive contact; and
a thick film conductive paste electrically connecting the perimeter
conductive contact and the ferrule.
13. The feedthrough assembly of claim 12, wherein the thick film
conductive paste comprises a silver and palladium mixture or
alloy.
14. The feedthrough assembly of claim 13, wherein the thick film
conductive paste further comprises glass frit.
15. The feedthrough assembly of claim 12, wherein the thick film
conductive paste comprises a first thick film conductive paste,
wherein the at least one feedthrough conductive pathway comprises:
an externally-facing feedthrough conductive pad positioned on or
near an externally-facing side of the feedthrough, an
internally-facing feedthrough conductive pad positioned on or near
an internally-facing side of the feedthrough, and a feedthrough
conductive via extending between the externally-facing feedthrough
conductive pad and the internally-facing feedthrough conductive
pad, wherein the at least one filter array conductive pathway
comprises: an externally-facing filter conductive pad positioned on
or near an externally-facing side of the capacitive filter array,
an internally-facing filter conductive pad positioned on or near an
internally-facing side of the capacitive filter array, and a filter
conductive via extending between the externally-facing filter
conductive pad and the internally-facing filter conductive pad, and
wherein the feedthrough assembly further comprises a second thick
film conductive paste electrically connecting the externally-facing
filter conductive pad and the internally-facing feedthrough
conductive pad.
16. The feedthrough assembly of claim 12, wherein the at least one
filter array conductive pathway comprises the thick film conductive
paste, and wherein the thick film conductive paste extends from an
externally-facing side of the capacitive filter array to an
internally-facing side of the capacitive filter array.
17. The feedthrough assembly of claim 16, wherein an
externally-facing end of the thick film conductive paste contacts
the at least one feedthrough conductive pathway.
18. The feedthrough assembly of claim 12, further comprising an
electrically insulating material disposed between an
internally-facing feedthrough side and an externally-facing filter
array side.
19. The feedthrough assembly of claim 18, wherein the electrically
insulating material comprises at least one of a non-conductive
polyimide, an epoxy, a glass, or a high temperature cofired
ceramic.
20. The feedthrough assembly of claim 12, wherein at least one of
the feedthrough, the ferrule, or the capacitive filter array
defines an underfill access channel.
Description
[0001] This application is a divisional of U.S. application Ser.
No. 13/308,136, now allowed, which claims the benefit of U.S.
Provisional No. 61/530,249 to Iyer et al., entitled, "CAPACITIVE
FILTERED FEEDTHROUGH ARRAY FOR IMPLANTABLE MEDICAL DEVICE," and
filed on Sep. 1, 2011, which is incorporated herein by reference in
its entirety.
TECHNICAL FIELD
[0002] The disclosure relates to electrical feedthroughs for
implantable medical devices.
BACKGROUND
[0003] Electrical feedthroughs may provide an electrical pathway
between an interior of a hermetically-sealed housing of an
electronics device to a point outside the housing. For example,
implantable medical devices (IMDs), such as implantable stimulation
devices, implantable sensing devices, cardiac pacemakers,
implantable cardioverter/defibrillators (ICDs) and neuromodulators,
may use one or more electrical feedthroughs to make electrical
connections between electrical circuitry within the implantable
medical device and leads, electrodes, or sensors external to the
device within a patient.
SUMMARY
[0004] In general, the disclosure is directed to feedthrough
assemblies and techniques for forming feedthrough assemblies. In
some examples, the feedthrough assemblies may be used to provide
electrical connections between an exterior of a housing of an IMD
and an interior of the housing of the IMD. The feedthrough
assemblies may be filtered feedthrough assemblies, and may include
at least one capacitive filter and/or a capacitive filter
array.
[0005] In some examples, the disclosure describes feedthrough
assemblies that include a thick film conductive paste for making
electrical connection between a conductive pathway of a feedthrough
and a conductive pathway of a capacitive filter array. Additionally
or alternatively, feedthrough assemblies may include a thick film
conductive paste used for making electrical connection between a
perimeter conductive contact of the capacitive filter array and a
ferrule of the feedthrough assembly. In some implementations, the
thick film conductive paste may include a silver-palladium (Ag--Pd)
alloy or mixture and, optionally, glass frit.
[0006] In one aspect, the disclosure is directed to a feedthrough
assembly that includes a ferrule defining a ferrule opening, a
feedthrough at least partially disposed within the ferrule opening,
a capacitive filter array at least partially disposed within the
ferrule opening. In some examples, the feedthrough includes at
least one feedthrough conductive pathway and the capacitive filter
array includes at least one filter array conductive pathway. The
feedthrough assembly also may include a thick film conductive paste
electrically connecting the at least one feedthrough conductive
pathway and the at least one filter array conductive pathway.
[0007] In another aspect, the disclosure is directed to a
feedthrough assembly that includes a ferrule defining a ferrule
opening, a feedthrough at least partially disposed within the
ferrule opening, and a capacitive filter array at least partially
disposed within the ferrule opening. In some examples, the
feedthrough includes at least one feedthrough conductive pathway
and the capacitive filter array includes at least one filter array
conductive pathway, a perimeter conductive contact, and a
capacitive filter electrically coupling the at least one filter
array conductive pathway and the perimeter conductive contact. The
feedthrough assembly may further include a thick film conductive
paste electrically connecting the perimeter conductive contact and
the ferrule.
[0008] In another aspect, the disclosure is directed to method that
includes applying a thick film conductive paste to at least one of
an internally-facing feedthrough conductive pad disposed on an
internally-facing feedthrough side of a feedthrough, an interior
wall of a ferrule, an externally-facing filter conductive pad
disposed on an externally-facing filter array side of a capacitive
filter array, or a perimeter conductive contact disposed on a
perimeter wall of the capacitive filter array. The method may
further include positioning the capacitive filter array in a
desired position relative to the ferrule and the feedthrough.
Additionally, the method may include heating the capacitive filter
array, the ferrule, the feedthrough, and the thick film conductive
paste to convert the thick film conductive paste from a paste to a
relatively solid material.
[0009] In an additional aspect, the disclosure is directed to a
method that includes attaching a perimeter wall of a capacitive
filter array to an interior wall of a ferrule, where the capacitive
filter array defines at least one passageway extending between an
internally-facing filter array side and an externally-facing filter
array side. The method may also include depositing a thick film
conductive paste within the at least one passageway to form a
filter array conductive pathway. Further, the method may include
heating the ferrule, the capacitive filter array, and the thick
film conductive paste to convert the thick film conductive paste
from a paste to a relatively solid material.
[0010] The details of one or more examples are set forth in the
accompanying drawings and the description below. Other features,
objects, and advantages of the disclosure will be apparent from the
description and drawings, and from the claims.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a side view that illustrates an example
feedthrough assembly.
[0012] FIG. 2 is a top view that illustrates an example feedthrough
assembly.
[0013] FIG. 3 is a bottom view that illustrates an example
feedthrough assembly.
[0014] FIGS. 4A and 4B are a cross-sectional views taken along
section lines A-A and B-B of FIG. 3 that illustrate an example
configuration of a feedthrough assembly.
[0015] FIG. 5 is a cross-sectional view taken along section line
A-A of FIG. 3 that illustrates another example configuration of a
feedthrough assembly.
[0016] FIG. 6 is a flow diagram that illustrates an example
technique for forming a feedthrough assembly that includes a thick
film conductive paste.
[0017] FIG. 7 is a flow diagram that illustrates another example
technique for forming a feedthrough assembly that includes a thick
film conductive paste.
[0018] FIG. 8 is a cross-sectional view taken along section line
A-A of FIG. 3 that illustrates an example configuration of a
feedthrough assembly.
[0019] FIG. 9 is a flow diagram that illustrates another example
technique for forming a feedthrough assembly that includes a lead
frame assembly.
[0020] FIG. 10 is a cross-sectional view taken along section line
A-A of FIG. 3 that illustrates another example configuration of a
feedthrough assembly.
[0021] FIG. 11 is a cross-sectional view taken along section line
A-A of FIG. 3 that illustrates a further example configuration of a
feedthrough assembly.
[0022] FIG. 12 is a cross-sectional view taken along section line
A-A of FIG. 3 that illustrates an additional example configuration
of a feedthrough assembly.
[0023] FIG. 13 is a flow diagram that illustrates an example
technique for forming a feedthrough assembly.
[0024] FIG. 14 is a conceptual diagram that illustrates an example
feedthrough assembly attached to a housing of an IMD.
DETAILED DESCRIPTION
[0025] In some cases, an IMD is implanted at a location within the
patient that is different than the target tissue that is being
stimulated and/or diagnosed. The IMD may be electrically coupled to
a lead that includes electrical conductors that extend from the IMD
to the electrodes or sensors located at the target tissue. At the
IMD, the electrical conductors may be electrically coupled to a
conductive pathway through a feedthrough to allow a lead conductor
to be electrically coupled to circuitry contained within the
hermetically sealed housing of the IMD. In some examples, the lead
conductors may act as antennae that are affected electromagnetic
signals, including electromagnetic interference (EMI). The
electromagnetic signals may be transmitted along the lead
conductor, through the feedthrough, and to circuitry within the
IMD. In some cases, the electromagnetic signals may interfere with
normal operation of circuitry within the IMD.
[0026] EMI due to stray electromagnetic signals conducted by the
lead conductors may be addressed by utilizing a capacitor with the
feedthrough to form a filtered feedthrough assembly. The capacitor
may act as a low-pass filter, transmitting relatively high
frequency electromagnetic signals to ground (e.g., the housing of
the IMD) and passing relatively low frequency signals to circuitry
within the IMD. In some examples, the feedthrough assembly may
include a multi-conductor feedthrough and a capacitor or capacitor
array that accommodates multiple lead conductors. The capacitor or
capacitor array may be attached to the multi-conductor feedthrough
so that each of the conductive pathways through the multi-conductor
feedthrough is electrically coupled to a corresponding conductive
path in the capacitor or capacitor array while providing for a
hermetic seal around each conductive pathway and between the
multi-conductor feedthrough and the ferrule.
[0027] In other examples, an IMD may include one or more electrodes
formed on a housing of the IMD (e.g., a leadless IMD). In some
implementations, a leadless IMD may include a feedthrough assembly
through which a conductor that connects the electrodes formed on
the housing of the IMD to circuitry within the leadless IMD passes.
The feedthrough assemblies described herein may also be utilized in
leadless IMDs.
[0028] This disclosure describes various feedthrough assemblies and
techniques for forming feedthrough assemblies. The feedthrough
assemblies generally may include a feedthrough, a capacitive filter
array, and a ferrule. In some examples, the disclosure describes
feedthrough assemblies that include a thick film conductive paste
for making electrical connection between a conductive pathway of
the feedthrough and a conductive pathway of the capacitive filter
array. Additionally or alternatively, feedthrough assemblies may
include a thick film conductive paste used for making electrical
connection between a perimeter conductive contact of the capacitive
filter array and the ferrule. In some implementations, the thick
film conductive paste may include a silver-palladium (Ag--Pd) alloy
or mixture and, optionally, glass frit.
[0029] In some examples, the disclosure described a feedthrough
assembly that includes a lead frame assembly for making electrical
connection between a conductive pathway of the feedthrough and a
conductive pathway of the capacitive filter array. Additionally or
alternatively, feedthrough assemblies may include a lead frame
assembly used for making electrical connection between a perimeter
conductive contact of the capacitive filter array and the ferrule.
In some implementations, the lead frame assembly may be configured
to maintain physical separation between opposing surfaces of the
feedthrough and the capacitive filter array.
[0030] In some examples, the disclosure described a feedthrough
assembly that includes an electrically insulating material disposed
between an externally-facing side of a capacitive filter array and
an internally-facing side of a feedthrough. In some examples, the
electrically insulating material extends substantially continuously
between the externally-facing side of the capacitive filter array
and the internally-facing side of the feedthrough. In some
implementations, the electrically insulating material may be
introduced into a gap between the externally-facing side of the
capacitive filter array and the internally-facing side of the
feedthrough through an underfill access channel. The underfill
access channel may be defined in the feedthrough, the capacitive
filter array, or a ferrule of the feedthrough assembly. In some
examples, the electrically insulating material may be introduced
through the underfill access channel into the gap between the
externally-facing side of the capacitive filter array and the
internally-facing side of the feedthrough after the feedthrough,
the ferrule, and the capacitive filter array have been attached to
each other.
[0031] FIG. 1 is a side view of an example feedthrough assembly 10.
Feedthrough assembly 10 includes an internally-facing side 12 and
an externally-facing side 14. FIG. 2 shows a top view of
feedthrough assembly 10 showing the externally-facing side 14 of
feedthrough assembly 10. FIG. 3 shows a bottom view of feedthrough
assembly 10 showing internally-facing side 12 of feedthrough
assembly 10. The terms "internally-facing," "inwardly," and the
like, when used herein in regards to feedthrough assembly 10, may
generally refer to a direction toward the interior of an
electronics device (e.g., an IMD) when assembly 10 is incorporated
in the electronics device. Conversely, the terms
"externally-facing," "outwardly," and the like, when used herein in
regards to feedthrough assembly 10 generally refer to a direction
toward the exterior of the electronics device when assembly 10 is
incorporated in the electronics device.
[0032] As shown in FIGS. 1-3, feedthrough assembly 10 comprises a
ferrule 16, a feedthrough 18, and a capacitive filter array 20.
Feedthrough 12 may be coupled to capacitive filter array 20 by a
plurality of electrically conductive members. The electrically
conductive members may take a variety of forms, and will be
described in detail below.
[0033] Ferrule 16 comprises an internally-facing ferrule side 22
and an externally facing ferrule side 24. Ferrule 16 also defines a
ferrule opening 30 that extends between internally-facing side 22
and externally-facing side 24. Feedthrough 12 and capacitive filter
array 20 are at least partially disposed in ferrule opening 30.
Ferrule 16 may be configured to be mounted to or within the housing
of the electronics device, such as an IMD. In some examples,
ferrule 16 may include a flange or other mechanical feature that
facilitates mounting of ferrule 16 to or within the housing of the
electronics device. Ferrule 16 may be mounted to the IMD housing,
for example, by welding or brazing.
[0034] In one example, ferrule 16 comprises a material that
facilitates mounting of ferrule 16 to the housing of an IMD. For
example, the IMD housing may comprise titanium or a titanium alloy,
and ferrule 16 may comprise titanium or a titanium alloy that can
be welded to the IMD housing. Examples of materials from which
ferrule 18 may be formed include niobium; titanium; titanium alloys
such as titanium-6Al-4V or titanium-vanadium; platinum; molybdenum;
zirconium; tantalum; vanadium; tungsten; iridium; rhodium; rhenium;
osmium; ruthenium; palladium; silver; and alloys, mixtures, and
combinations thereof. In one example, the material from which
ferrule 16 is formed is selected so that ferrule 16 has a
coefficient of thermal expansion (CTE) that is compatible with the
CTE of feedthrough 18. In this manner, damage resulting from the
heating of ferrule 16 and feedthrough 18, such as during the
formation of a diffusion bonded, glassed, or brazed joint between
ferrule 16 and feedthrough 18, may be reduced or substantially
prevented.
[0035] Feedthrough 18 may be mounted to ferrule 16 within ferrule
opening 30 using a hermetic seal 26 formed between feedthrough 18
and ferrule 16. Hermetic seal 26 may prevent bodily fluids of the
patient from passing into the interior of IMD housing between
ferrule 16 and feedthrough 18, which could lead to damage to the
internal electronics of the IMD. In one example, hermetic seal 26
comprises a braze joint between feedthrough 18 and ferrule 16
(e.g., formed using laser brazing). In other examples, hermetic
seal 26 may be formed using diffusion bonding. Examples of
materials that may be used to form a hermetic seal 26 include any
biocompatible, biostable material capable for forming a hermetic
seal 26, such as, gold, a nickel-gold alloy, platinum, and
platinum-iridium. Laser sintering of glass may also be used to bond
feedthrough 18 to ferrule 16.
[0036] FIGS. 4A and 4B are cross-sectional views of an example
feedthrough assembly 10a taken along section lines A-A and B-B
shown in FIG. 3, respectively. As shown in FIGS. 4A and 4B,
feedthrough 18 includes a feedthrough substrate 34. Feedthrough
substrate 34 defines an externally-facing feedthrough side 36 and
an internally-facing feedthrough side 38. Externally-facing
feedthrough side 36 is oriented generally opposite to
internally-facing feedthrough side 38. Feedthtrough substrate 34
also defines a feedthrough substrate perimeter wall 40, which is
oriented facing a first interior wall 42 of ferrule 16. Feedthrough
18 also includes a plurality of feedthrough conductive vias 44,
which each extend between externally-facing feedthrough side 36 and
internally-facing feedthrough side 38. Each of conductive vias 44
is electrically and physically coupled to a respective one of
externally-facing feedthrough conductive pads 28 and a respective
one of internally-facing feedthrough conductive pads 46.
Externally-facing feedthrough conductive pads 28 may be disposed on
or near externally-facing feedthrough side 36. Internally-facing
feedthrough conductive pads 46 may be disposed on or near
internally-facing feedthrough side 38. Each of feedthrough
conductive vias 44 may be substantially electrically isolated from
the other feedthrough conductive vias 44. Although FIG. 4A shows an
example in which feedthrough 18 includes three externally-facing
feedthrough conductive pads 28, three feedthrough conductive vias
44, and three internally-facing feedthrough conductive pads 46, in
other examples, feedthrough 18 may include fewer or more
externally-facing feedthrough conductive pads 28, feedthrough
conductive vias 44, and internally-facing feedthrough conductive
pads 46 (e.g., one, two, or at least four).
[0037] In some examples, feedthrough substrate 34 comprises a
ceramic material formed from a single layer. In other examples,
feedthrough substrate 34 includes multi-layer ceramic formed from a
plurality of generally planar ceramic layers (not shown in FIGS. 4A
and 4B). In examples in which feedthrough substrate 34 is formed
from multiple ceramic layers, each ceramic layer may be shaped in a
green state to have a layer thickness and a plurality of via holes
extending there through between an internally facing layer surface
and an externally facing layer surface. The ceramic layers then may
be coupled together, such as by laminating the layers together, and
may be cofired together so that the layers form a substantially
monolithic feedthrough substrate 34. In some examples, the via
holes of each ceramic layer may be substantially aligned to form
generally cylindrical passages that are filled with an electrically
conductive material to form conductive vias 44.
[0038] In some examples, feedthrough 34 may comprise a
high-temperature cofired ceramic (HTCC) material, e.g., a ceramic
that is sintered at a temperature of at least about 1300.degree.
C., for example a material that is sintered at a temperature of at
least about 1600.degree. C. In some embodiments, HTCC uses 1) an
electrical insulator that includes alumina and may include oxides
of Si (silica), Ca (calcium), Mg (magnesia), Zr (zirconia), and the
like, and 2) an electrical conductor, such as platinum or Pt--Ir.
The assembly of the electrical insulator and electrical conductor
can be fired (sintered) above 1000.degree. C., such as about
1600.degree. C. In this sintering process, polymeric binders may be
driven off and the particles forming the ceramic and metal coalesce
and fuse. Grains may diffuse together forming larger grains at the
expense of smaller grains.
[0039] In one example, feedthrough substrate 34 comprises an HTCC
liquid-phase, sintered alumina with platinum metallization. In one
example, feedthrough substrate 34 may comprise at least about 70%
alumina, for example at least about 90% alumina having a sintering
temperature of between about 1550.degree. C. and about 1600.degree.
C. In some examples, feedthrough substrate 34 consists essentially
of a HTCC, and in some examples, feedthrough substrate 34 consists
of a HTCC.
[0040] Examples of materials and methods for making a cofired
ceramic substrate are described in the commonly assigned U.S.
Provisional Patent Application having the Ser. No. 61/530,249,
filed on Sep. 1, 2011; the commonly assigned U.S. Provisional
Patent Application having the Ser. No. 61/238,515, filed on Aug.
31, 2009; the commonly assigned U.S. patent application having the
Ser. No. 12/693,772, filed on Jan. 26, 2010, the commonly assigned
U.S. Pat. No. 6,414,835, issued on Jul. 2, 2002, the
commonly-assigned U.S. Pat. No. 6,660,116, issued on Dec. 9, 2003,
U.S. patent application having the Ser. No. 13/196,661, filed on
Aug. 2, 2011, U.S. patent application having the Ser. No.
13/196,683, filed on Aug. 2, 2011, and U.S. patent application
having the Ser. No. 13/196,695, filed on Aug. 2, 2011, the entire
disclosures of which are incorporated herein by reference.
[0041] Conduction of electrical signals between externally-facing
feedthrough side 36 and internally-facing feedthrough side 38 may
be accomplished using externally-facing feedthrough conductive pads
28, electrically conductive vias 44 and internally-facing
feedthrough conductive pads 46. Together, a respective one of
externally-facing feedthrough conductive pads 28, a respective one
of electrically conductive vias 44, and a respective one of
internally-facing feedthrough conductive pads 46 form a feedthrough
conductive pathway between externally-facing feedthrough side 36
and internally-facing feedthrough side 38. The electrically
conductive pathways provide for an electrical pathway for
electrical signals to be transmitted across feedthrough substrate
34, such as stimulation signals transmitted from electronics within
an IMD housing for stimulation of a target tissue, or bioelectric
signals sensed proximate a target tissue that are transmitted into
the IMD housing for analysis by IMD electronics.
[0042] Electrically conductive vias 44 may comprise a conductive
material, such as a metal or alloy, that substantially fills a
passageway that extends through feedthrough substrate 34. In one
example, a hermetic seal is formed at the interface between each of
electrically conductive vias 44 and feedthrough substrate 34. The
hermetic seal may be formed by many methods, such as by forming a
braze joint between the material that forms via 44 and the material
that forms feedthrough substrate 34. In one example, described in
more detail below, the hermetic seal is formed by cofiring the
materials that form feedthrough substrate 34 and electrically
conductive vias 44 so that the material that forms vias 44 bonds
with the material that forms feedthrough substrate 34.
[0043] Each electrically conductive pathway also may include an
internally-facing feedthrough conductive pad 46 at
internally-facing side 38. Each conductive pad 46 may provide a
contact area to provide for electrical and/or mechanical coupling
between the respective electrically conductive pathway and a
respective one of the electrically conductive pathways in
capacitive filter array 20. In some examples, each
internally-facing feedthrough conductive pad 46 is electrically and
mechanically coupled to a corresponding one of electrically
conductive vias 44.
[0044] Each electrically conductive pathway may also include an
externally-facing feedthrough conductive pad 28 at
externally-facing side 36. Each conductive pad 28 may provide
contact area to provide for electrical and/or mechanical coupling
of a conductor, such as a lead conductor for an IMD, to the
respective electrically conductive pathway (e.g., the conductive
pad 28). In some examples, each externally-facing feedthrough
conductive pad 28 is electrically and mechanically coupled to a
corresponding one of vias 44.
[0045] In some examples, vias 44 and conductive pads 28, 46 each
include an electrically conductive material, such as an
electrically conductive metal or alloy. Examples of electrically
conductive materials that may be used for vias 44 and/or conductive
pads 28, 46 include, but are not limited to, transition metals
(e.g., noble metals), rare earth metals (e.g., actinide metals and
lanthanide metals), alkali metals, alkaline-earth metals, and rare
metals. Examples of materials that may be used to form vias 44
and/or conductive pads 28, 46 include, but are not limited to,
copper (Cu), silver (Ag), gold (Au), platinum (Pt), palladium (Pd),
niobium (Nb), iridium (Ir), titanium (Ti), tungsten (W), molybdenum
(Mb), zirconium (Zr), osmium (Os), tantalum (Ta), vanadium (V),
rhodium (Rh), rhenium (Re), and ruthenium (Ru), platinum-gold
alloys, platinum-iridium alloys, platinum-palladium alloys,
gold-palladium alloys, titanium alloys, such as Ti-6Al-4V, Ti-45Nb,
Ti-15Mo or titanium-vanadium, tungsten-molybdenum alloys, and
alloys, mixtures, and combinations thereof.
[0046] With respect to internally-facing feedthrough conductive
pads 46, in some examples, the material and structure of conductive
pads 46 may be selected to support bonding of a corresponding
electrical connection (such as one of thick film conductive paste
48) to provide electrical and mechanical coupling between
respective ones of internally-facing feedthrough conductive pad 46
and respective ones of externally-facing filter conductive pads
60.
[0047] With respect to externally-facing feedthrough conductive
pads 28, the material and structure of conductive pads 28 may be
selected to support welding of a conductor, such as a wire or
conductor used in a lead for an IMD, to external surfaces of
respective ones of conductive pads 28. Examples of materials that
may be used in an IMD lead conductor that may be welded to
conductive pads 28 include, but are not limited to, niobium (Nb), a
MP35N or MP35NLT nickel-based alloy, silver core Co--Cr--Ni alloy,
tantalum, silver core Ta, Ti, Ti-45Nb, Ti--Mo alloys, and alloys
meeting ASTM standard F562. Examples of processes that may be used
to attach the lead conductor to conductive pads 28 include, but are
not limited to, laser welding, parallel gap welding, thermosonic
bonding, diffusion bonding, ultrasonic welding, opposed gap
welding, laser brazing, step gap resistance welding, brazed
interposer, percussion arc welding, or soldering (conventional or
laser).
[0048] In some examples in which feedthrough substrate 34 comprises
a HTCC material, conductive vias 44 and/or externally-facing
feedthrough conductive pads 28 and/or internally-facing feedthrough
conductive pads 46 may include a conductive paste that is used to
fill passageways extending from externally-facing feedthrough side
36 and internally-facing feedthrough side 38 to form vias 44. The
conductive paste may comprise, for example, a metallic paste that
is applied to the passageways, for example a platinum-containing
paste, a tungsten-containing paste, Nb-containing paste,
Ta-containing paste, Au-containing paste, or a
molymanganese-containing paste. Such materials may be biocompatible
and biostable materials. In one example, the metallic paste
primarily comprises a metallic powder, such as platinum powder, and
an additive to promote bonding with the material of feedthrough
substrate 34. The additive may additionally or alternatively
provide for thermal expansion compatibility between the conductive
paste used to form vias 44 (and/or pads 28, 46) and the HTCC
material of feedthrough substrate 34. In one example, the additive
comprises alumina, so that the metallic paste may comprise, for
example, a majority of metallic powder, such as platinum powder,
and a minority of alumina powder or particles mixed therein.
[0049] In some examples, conductive vias 44 and/or pads 28, 46
formed from a conductive paste, such as a platinum and alumina
containing paste, and a feedthrough substrate 34 comprising an HTCC
material, such as a sintered alumina, are cofired together, e.g.,
at a temperature of around 1600.degree. C., so that the conductive
paste and HTCC material bond together and form hermetic seal.
[0050] Referring still to FIGS. 4A and 4B, feedthrough assembly
includes capacitive filter array 20. Capactive filter array 20 may
include a capacitive filter substrate 50 that defines an
internally-facing filter array side 52 and an externally-facing
filter array side 54. Capacitive filter substrate 50 also defines a
capacitive filter perimeter 56, which generally faces a second
interior wall 58 of ferrule 16. Disposed along a perimeter of
capacitive filter substrate is a perimeter conductive contact 72.
Capacitive filter array 20 further includes a plurality of filter
array conductive pathways. In the example illustrated in FIGS. 4A
and 4B, each of the filter array conductive pathways includes a
respective one of externally-facing filter conductive pads 60, a
respective one of filter conductive vias 62, and a respective one
of internally-facing filter conductive pads 32. Respective filter
array conductive pathways may be substantially electrically
isolated from the other filter array conductive pathways. Although
FIG. 4A illustrates an example capacitive filter array 20 that
includes three filter array conductive pathways, in other examples,
capacitive filter array 20 may include fewer or more than three
filter array conductive pathways (e.g., one, two, or at least
four).
[0051] Capacitive filter array 20 further includes a plurality of
capacitive filters 64 defined within capacitive filter substrate
50, respective ones of which are electrically connected to
respective ones of the filter array conductive pathways. Each of
the plurality of conductive pathways provide an electrical pathway
for electrical signals to be transmitted through capacitive filter
array 20, such as stimulation signals transmitted from electronics
within an IMD housing for stimulation of a target tissue or
bioelectric signals sensed proximate a target tissue that are
transmitted into the IMD housing for analysis by IMD electronics.
Capacitive filter array 20 filters the electrical signals
transmitted through capacitive filter array 20 using capacitive
filters 64.
[0052] Capacitive filter substrate 50 may be formed of a ceramic
material, such as barium titanate (BaTiO.sub.3) or alumina. In some
examples, capacitive filter substrate 50 may be formed from a
single layer. In other examples, capacitive filter substrate 50
includes a multi-layer ceramic formed from a plurality of generally
planar ceramic layers (not shown in FIGS. 4A and 4B). In examples
in which capacitive filter substrate 50 is formed from multiple
ceramic layers, each ceramic layer may be shaped in a green state
to have a layer thickness and a plurality of via holes extending
there through between an internally facing layer surface and an
externally facing layer surface. The ceramic layers then may be
coupled together, such as by laminating the layers together, and
may be cofired together so that the layers form a substantially
monolithic capacitive filter substrate 50. In some examples, the
passageways of each ceramic layer may be substantially aligned to
form generally cylindrical passages that are filled with an
electrically conductive material to form conductive vias 62.
[0053] In some examples, capacitive filter substrate 50 may
comprise a high-temperature cofired ceramic (HTCC) material, e.g.,
a ceramic that is sintered at a temperature of at least about
1300.degree. C., for example a material that is sintered at a
temperature of at least about 1600.degree. C. In some embodiments,
HTCC uses 1) an electrical insulator that includes barium titanate
(BaTiO.sub.3) or alumina and may include oxides of Si (silica), Ca
(calcium), Mg (magnesia), Zr (zirconia), and the like and 2) an
electrical conductor, such as platinum or Pt--Ir. The assembly of
the electrical insulator and electrical conductor can be fired
(sintered) above 1000.degree. C., such as about 1600 C. In this
sintering process, polymeric binders may be driven off and the
particles forming the ceramic and metal coalesce and fuse. Grains
may diffuse together forming larger grains at the expense of
smaller grains.
[0054] Capacitive filter array 20 also includes a plurality of
filter array conductive pathways. As described above, each filter
array conductive pathway includes a respective one of
externally-facing filter conductive pads 60, a respective one of
filter conductive vias 62, and a respective one of
internally-facing filter conductive pads 32. Filter conductive vias
62 and conductive pads 32, 60 each may include an electrically
conductive material, such as an electrically conductive metal or
alloy. Examples of electrically conductive materials that may be
used for vias 62 and/or conductive pads 32, 60 include, but are not
limited to, transition metals (e.g., noble metals), rare earth
metals (e.g., actinide metals and lanthanide metals), alkali
metals, alkaline-earth metals, and rare metals. Examples of
materials that may be used to form vias 62 and/or conductive pads
32, 60 include, but are not limited to, copper (Cu), silver (Ag),
gold (Au), platinum (Pt), palladium (Pd), niobium (Nb), iridium
(Ir), titanium (Ti), tungsten (W), molybdenum (Mb), zirconium (Zr),
osmium (Os), tantalum (Ta), vanadium (V), rhodium (Rh), rhenium
(Re), and ruthenium (Ru), platinum-gold alloys, platinum-iridium
alloys, platinum-palladium alloys, gold-palladium alloys, titanium
alloys, such as Ti-6Al-4V, Ti-45Nb, Ti-15Mo or titanium-vanadium,
tungsten-molybdenum alloys, and alloys, mixtures, and combinations
thereof.
[0055] With respect to externally-facing filter conductive pads 60,
in some examples, the material and structure of conductive pads 60
may be selected to support bonding of a corresponding electrical
connection (such as one of thick film conductive paste 48) to
provide electrical and mechanical coupling between respective ones
of internally-facing feedthrough conductive pads 46 and respective
ones of externally-facing filter conductive pads 60.
[0056] With respect to internally-facing filter conductive pads 32,
in some examples, the material and structure of conductive pads 32
may be selected to support an electrical connection to a
corresponding electrical conductor that extends between
internally-facing filter conductive pads 32 and circuitry of the
IMD (e.g., sensing circuitry, therapy delivery circuitry, or the
like).
[0057] In some examples, an electrical insulation layer 70 may be
placed between feedthrough 18 and filter array 20 in order to
reduce or prevent high-voltage arcing between feedthrough 18 and
filter array 20. Electrical insulation layer 70 may also be
provided to prevent arcing between the conductive path (which may
be continuous between the externally-facing feedthrough conductive
pads 28 and filter array 20) and ferrule 16, between the conductive
path and perimeter conductive contact 72, or between adjacent
conductive paths, as any direct line of sight between the
conductive two electrically conductive materials may cause surface
arcing. In this sense, electrical insulation layer 70 may reduce or
substantially prevent surface arcing.
[0058] Electrical insulation layer 70 may include an electrically
insulating material, such as an electrically insulating polymer
formed on externally-facing filter array side 54. In one example,
electrical insulation layer 70 comprises a polyimide polymer with a
glass transition temperature of greater than about 400.degree. C.
In some examples, electrically insulating layer 70 may comprise a
low temperature cofired ceramic material or a HTCC material.
[0059] Although not shown in FIGS. 4A and 4B, in some examples,
electrically insulating layer 70 may additionally or alternatively
be formed on internally-facing feedthrough side 38 (e.g., as
embodied by feedthrough electrically insulating layer 112 of FIG.
8), internally-facing filter array side 52, and/or
externally-facing feedthrough side 36. In some examples, as
described below with respect to FIGS. 10-12, an electrically
insulating layer may extend substantially continuously in the space
between externally-facing filter array side 54 and
internally-facing feedthrough side 38.
[0060] At least a portion of each of filter conductive vias 62 is
electrically connected to a corresponding capacitive filter 64 that
provides for filtering of electrical signals that are conducted
through the corresponding via 62. For example, each capacitive
filter 64 may provide for filtering of current induced in an IMD
lead by external electromagnetic fields so that the induced current
is not inadvertently interpreted by the IMD circuitry as a signal,
such as a telemetry signal. In one example, best seen in FIG. 4B,
each capacitive filter 64 comprises a plurality of layers (not
shown) of ceramic, such as barium titanate, with conductive active
electrodes 66 and ground electrodes 68 formed on the layers, such
as by printing the material of electrodes 66, 68, for example
silver, silver-palladium, or silver-platinum, onto the layers
before stacking and laminating the layers. In one example, active
electrodes 66 substantially radially surround a corresponding one
of filter conductive vias 62. Respective active electrodes 66 are
electrically coupled to respective filter conductive vias 62.
Ground electrodes 68 are electrically connected to a common
ground.
[0061] Ground electrodes 68 may be electrically coupled to a
perimeter conductive contact 72. Perimeter conductive contact 72
may extend substantially along the entire length of capacitive
filter perimeter 56, as shown in FIGS. 4A and 4B, so that each
ground electrode 68 is electrically coupled to perimeter conductive
contact 72. In other examples, perimeter conductive contact 72 may
be discontinuous about capacitive filter perimeter 56. For example,
a respective perimeter conductive contact 72 may be electrically
coupled to a respective one of ground electrodes 68 (or a
respective set (two or more) of ground electrodes 68), and
capacitive filter array 20 may include a plurality of perimeter
conductive contacts 72.
[0062] Perimeter conductive contact 72 is electrically coupled to a
common ground so that the EMI signals being filtered by capacitive
filter array 20 are grounded. In some examples, shown in FIGS. 4A
and 4B, perimeter conductive contact 72 is grounded by being
electrically coupled to ferrule 16, which in turn is electrically
coupled to the IMD housing.
[0063] In accordance with some aspects of the disclosure, perimeter
conductive contact 72 may be electrically and mechanically
connected to ferrule 16 using a thick film conductive paste 48e,
48f. Additionally or alternatively, interior-facing feedthrough
conductive pads 46 maybe electrically and mechanically connected to
exterior-facing filter conductive pads 60 using thick film
conductive paste 48a, 48b, 48c. Hence, in some examples, perimeter
conductive contact 72 may be electrically and mechanically
connected to ferrule 16 using thick film conductive paste 48e, 48f,
and interior-facing feedthrough conductive pads 46 maybe
electrically and mechanically connected to exterior-facing filter
conductive pads 60 using thick film conductive paste 48a, 48b, 48c.
In other examples, perimeter conductive contact 72 may be
electrically and mechanically connected to ferrule 16 using thick
film conductive paste 48e, 48f, and interior-facing feedthrough
conductive pads 46 maybe electrically and mechanically connected to
exterior-facing filter conductive pads 60 using another
electrically conductive connection, such as a solder connection. In
other examples, perimeter conductive contact 72 may be electrically
and mechanically connected to ferrule 16 using an electrically
conductive connection, such as solder or brazing, and
interior-facing feedthrough conductive pads 46 maybe electrically
and mechanically connected to exterior-facing filter conductive
pads 60 using thick film conductive paste 48a, 48b, 48c.
[0064] In some examples, thick film conductive paste 48a, 48b, 48c,
48d, 48e (collectively, "thick film conductive paste 48") may
include a silver-palladium (Ag--Pd) mixture or alloy. In some
implementations, the Ag--Pd mixture or alloy may include about 70
weight percent (wt. %) Ag and about 30 wt. % Pd. In some examples,
the Ag--Pd mixture or alloy may also include glass frit (e.g.,
glass particles mixed in the Ag--Pd mixture or alloy). In some
examples, the glass frit includes a zinc borosilicate glass
particles, and may be dispersed in an organic binder.
[0065] Thick film conductive paste 48 may be applied to any desired
thickness. In some examples, the thickness of at least one of thick
film conductive paste 48a, 48b, 48c, 48d, 48e is about 0.00254
millimeters (mm; (about 0.0001 inch).
[0066] In some examples, thick film conductive paste 48 may form
the only mechanical connections between feedthrough 18 and
capacitive filter array 20 and/or between capacitive filter array
20 and ferrule 16. Thick film conductive paste 48 may possess
sufficient mechanical strength to function as the only mechanical
connection between feedthrough 18 and capacitive filter array 20
and between capacitive filter array 20 and ferrule 16 (e.g., after
firing to convert thick film conductive paste 48 from a paste to a
relatively solid material). In some examples, the mechanical
connection formed via thick film conductive paste may be
supplemented by using another types of mechanical connection, e.g.,
solder, in combination with thick film conductive paste 48.
[0067] In some examples, as shown in FIGS. 4A and 4B, thick film
conductive paste 48a, 48b, 48c may be disposed between
interior-facing feedthrough conductive pads 46 and exterior-facing
filter conductive pads 60. Thick film conductive paste 48a, 48b,
48c may take the place of, or be used in combination with a solder
or other mechanical and electrical connection between
interior-facing feedthrough conductive pads 46 and exterior-facing
filter conductive pads 60.
[0068] In some examples, capacitive filter array 20 may not include
externally-facing filter conductive pads 60, filter conductive vias
62, and internally-facing filter conductive pads 32 (as does the
example of filter array 20 shown in FIGS. 4A and 4B). Feedthrough
assembly 10b shown in FIG. 5 is similar to feedthrough assembly 10a
shown in FIGS. 4A and 4B. Some reference numerals have been omitted
in FIG. 5 for sake of clarity; nevertheless, in some examples,
feedthrough assembly 10b may be substantially similar to
feedthrough assembly 10a, aside from the differences described
herein. Compared to feedthrough assembly 10a shown in FIGS. 4A and
4B, feedthrough assembly 10b shown in FIG. 5 includes an example
capacitive filter array 20 that includes filter array conductive
pathways 82 formed of a thick film conductive paste, such as
Ag--Pd, instead of externally-facing filter conductive pads 60,
filter conductive vias 62, and internally-facing filter conductive
pads 32.
[0069] As shown in FIG. 5, capacitive filter substrate 50 defines a
plurality of passageways between internally facing side 52 and
externally facing side 54. The thick film conductive paste is
disposed in the plurality of passageways and forms filter array
conductive pathways 82. Externally-facing ends 84 of filter array
conductive pathways 82 may extend to or beyond externally facing
side 54 of capacitive filter substrate 50. In this way,
externally-facing ends 84 may electrically and mechanically connect
to respective ones of internally-facing feedthrough conductive pads
46 (of feedthrough 18). Externally-facing ends 84 thus may
mechanically connect capacitive filter array 20 to feedthrough
18.
[0070] Internally-facing ends 86 of filter array conductive
pathways 82 may extend to or beyond internally facing side 52 of
capacitive filter substrate 50. In this way, internally-facing ends
86 may be functionally similar to internally-facing filter
conductive pads 32. For example, internally-facing ends 86 of
filter array conductive pathways 82 may provide a location for
electrically connecting respective electrical conductors that
extend to circuitry within the IMD, such as sensing circuitry,
therapy delivery circuitry, or the like.
[0071] FIG. 6 is a flow diagram that illustrates an example
technique for forming a feedthrough assembly 10 that includes a
thick film conductive paste. The technique illustrated in FIG. 6
will be described with concurrent reference to feedthrough assembly
10a shown in FIGS. 4A and 4B for clarity. However, it will be
appreciated by those of skill in the art that the technique shown
in FIG. 6 may be used to construct other feedthroughs.
[0072] The technique shown in FIG. 6 may include attaching
feedthrough 18 to ferrule 16 (92). Feedthrough 18 may be connected
to ferrule 16 using any technique that forms hermetic seal 26
between feedthrough 18 and ferrule 16. For example, ferrule 16 and
feedthrough 18 may be connected using brazing, diffusion bonding,
laser sintering of glass, or the like. Hermetic seal 26 may be
formed using a biocompatible, biostable material. Examples of
materials that may be used to form a hermetic seal 26 include gold,
a nickel-gold alloy, platinum, platinum-iridium, or a biocompatible
glass.
[0073] The technique also may include applying thick film
conductive paste 48 to desired locations of feedthrough 18, ferrule
16, and/or capacitive filter array 20 (94). In some examples, the
technique may include applying thick film conductive paste 48 to
internally-facing feedthrough conductive pads 46. In other
examples, the method may include applying thick film conductive
paste 48 to externally-facing filter conductive pads 60. In other
examples, the technique may include applying thick film conductive
paste 48 to second interior wall 58 of ferrule 16. In other
examples, the method may include applying thick film conductive
paste 48 to perimeter conductive contact 72. In other examples, the
technique may include applying thick film conductive paste 48 to
internally-facing feedthrough conductive pads 46 and second
interior wall 58. In other examples, the technique may include
applying thick film conductive paste 48 to internally-facing
feedthrough conductive pads 46 and perimeter conductive contact 72.
In other examples, the technique may include applying thick film
conductive paste 48 to externally-facing filter conductive pads 60
and second interior wall 58. In other examples, the technique may
include applying thick film conductive paste 48 to
externally-facing filter conductive pads 60 and perimeter
conductive contact 72.
[0074] Thick film conductive paste 48 may be applied to the desired
locations of feedthrough 18, ferrule 16, and/or capacitive filter
array 20 (94) using any one or combination of a variety of
techniques, including, for example, screen printing, brushing,
using a dispenser, or the like. Thick film conductive paste 48 may
initially be in paste form (e.g., a suspension of a powder mixture
of Ag, Pd, and, optionally, glass frit in a liquid carrier). In
some examples, the amount of liquid carrier may be selected such
that thick film conductive paste 48 is relatively viscous and does
not flow readily from the locations at which it is applied (after
application). For example, thick film conductive paste may have a
viscosity of between about 100 kilocentipoise (kcps; about 1,000
poise) and about 250 (kcps; about 2,500 poise).
[0075] Once the thick film conductive paste 48 has been applied to
the desired locations of feedthrough 18, ferrule 16, and/or
capacitive filter array 20 (94), capacitive filter array 20 may be
positioned in a desired orientation relative to ferrule 16 and
feedthrough 18 (96). For example, this may include positioning
capacitive filter array 20 such that externally-facing filter array
side 54 is proximate (near) to internally-facing feedthrough side
38 (e.g., so that, in examples in which thick film conductive paste
48 is used to electrically connect internally-facing feedthrough
conductive pads 46 and externally-facing filter array conductive
pads 60, thick film conductive paste 48a, 48b, 48c is contacting
both internally-facing feedthrough conductive pads 46 and
externally-facing filter array conductive pads 60). This may also
include positioning capacitive filter array 20 such that capacitive
filter perimeter 56 is proximate (near) to second interior wall 58
of ferrule 16 (e.g., so that, in examples in which thick film
conductive paste 48 is used to electrically connect perimeter
conductive contact 72 and second interior wall 56, thick film
conductive paste 48d and 48e are contacting both perimeter
conductive contact 72 and second interior wall 56).
[0076] After capacitive filter array 20 has been positioned in the
desired orientation relative to ferrule 16 and feedthrough 18 (96),
feedthrough assembly 10a may be heated to convert thick film
conductive paste 48 from a paste to a relatively solid (e.g., an
Ag--Pd alloy with glass frit) material (98). For example,
feedthrough assembly 10a may be heated at a temperature between
about 700.degree. C. and about 850.degree. C. for between about 30
minutes and about 60 minutes, with about 10 minutes of
substantially constant temperature at the peak temperature. By
heating feedthrough assembly 10a and converting thick film
conductive paste 48 to a relatively solid material, mechanical and
electrical connection may be made between respective ones of
internally-facing feedthrough conductive pads 46 and respective
ones of externally-facing filter array conductive pads 60, which
may result in mechanical connection between feedthrough 18 and
capacitive filter array 20. Similarly, heating feedthrough assembly
10a and converting thick film conductive paste 48 to a relatively
solid material may make mechanical and electrical connection
between perimeter conductive contact 72 and second interior wall
58, which may result in mechanical connection between ferrule 16
and capacitive filter array 20.
[0077] FIG. 7 is a flow diagram that illustrates another example
technique for forming a feedthrough assembly in accordance with
aspects of this disclosure. The example technique shown in FIG. 7
will be described with concurrent reference to feedthrough assembly
10b shown in FIG. 5. The technique shown in FIG. 7 may include
attaching feedthrough 18 to ferrule 16 (92). Feedthrough 18 may be
connected to ferrule 16 using any technique that forms hermetic
seal 26 between feedthrough 18 and ferrule 16. For example, ferrule
16 and feedthrough 18 may be connected using brazing, diffusion
bonding, laser sintering of glass, or the like. Hermetic seal 26
may be formed using a biocompatible, biostable material. Examples
of materials that may be used to form a hermetic seal 26 include
gold, a nickel-gold alloy, platinum, platinum-iridium, or a
biocompatible glass.
[0078] The technique shown in FIG. 7 also includes applying thick
film conductive paste 48d, 48e to second interior wall 58 of
ferrule 16 (102). Alternatively, thick film conductive paste 48d,
48e may be applied to perimeter conductive contact 72 of capacitive
filter array 20 (102). Thick film conductive paste 48d, 48e may be
applied to second interior wall 58 and/or perimeter conductive
contact 72 (102) using any one or combination of a variety of
techniques, including, for example, screen printing, brushing,
using a dispenser, or the like. Thick film conductive paste 48d,
48e may initially be in paste form (e.g., a suspension of a powder
mixture of Ag, Pd, and, optionally, glass frit in a liquid
carrier). In some examples, the amount of liquid carrier may be
selected such that thick film conductive paste 48d, 48e is
relatively viscous and does not flow readily from the locations at
which it is applied (after application). For example, thick film
conductive paste may have a viscosity of between about 100
kilocentipoise (kcps; about 1,000 poise) and about 250 (kcps; about
2,500 poise).
[0079] Once thick film conductive paste 48d, 48e has been applied
to second interior wall 58 and/or perimeter conductive contact 72
(102), capacitive filter array 20 may be positioned in a desired
orientation relative to ferrule 16 and feedthrough 18 (104). For
example, this may include positioning capacitive filter array 20
such that externally-facing filter array side 54 is proximate
(near) to internally-facing feedthrough side 38. In some examples,
externally-facing filter array side 54 may be positioned near to
internally-facing feedthrough side 38 with a space or gap between
externally-facing filter array side 54 and internally-facing
feedthrough side 38. In other examples, externally-facing filter
array side 54 may be positioned near to internally-facing
feedthrough side 38 with substantially no space or gap between
externally-facing filter array side 54 and internally-facing
feedthrough side 38 (e.g., electrical insulation layer 70 may
contact internally-facing feedthrough side 38, internally-facing
feedthrough conductive pads 46, or an electrically insulating
material disposed on internally-facing feedthrough side 38).
Positioning capacitive filter array 20 in a desired orientation
relative to ferrule 16 and feedthrough 18 (104) may also include
positioning capacitive filter array 20 such that capacitive filter
perimeter 56 is proximate (near) to second interior wall 58 of
ferrule 16 (e.g., so that thick film conductive paste 48d and 48e
are contacting both perimeter conductive contact 72 and second
interior wall 56).
[0080] In some examples, the technique may optionally include
heating ferrule 16, feedthrough 18, capacitive filter array 20, and
thick film conductive paste 48d and 48e to convert thick film
conductive paste 48d and 48e from a paste to a relatively solid
material and mechanically and electrically connect capacitive
filter array 20 to ferrule 16 using thick film conductive paste 48d
and 48e (106). In other examples, the technique may not include
step (106). For example, feedthrough assembly 10b may be heated at
a temperature between about 700.degree. C. and about 850.degree. C.
for between about 30 minutes and about 60 minutes, with about 10
minutes of substantially constant temperature at the peak
temperature.
[0081] Regardless of whether the technique includes step (106), the
technique proceeds with depositing thick film conductive paste
within passageways through capacitive filter substrate 50 to form
filter array conductive pathways 82 (108). As described above,
thick film conductive paste may be deposited using any one or
combination of a variety of techniques, including, for example,
screen printing, brushing, using a dispenser, or the like. The
thick film conductive paste may initially be in paste form (e.g., a
suspension of a powder mixture of Ag, Pd, and, optionally, glass
frit in a liquid carrier). In some examples, the amount of liquid
carrier may be selected such that the thick film conductive paste
is relatively viscous and does not flow readily from the locations
at which it is applied (after application). For example, thick film
conductive paste may have a viscosity of between about 100
kilocentipoise (kcps; about 1,000 poise) and about 250 (kcps; about
2,500 poise).
[0082] Sufficient thick film conductive paste may be applied within
the passageways through capacitive filter substrate 50 to result in
externally-facing ends 84 contacting internally-facing feedthrough
conductive pads 46. In some examples, this may result in
externally-facing ends 84 extending beyond externally-facing filter
array side 54 (and/or electrically insulating layer 70). In other
examples, such as when there is substantially no space or gap
between electrically insulating layer 70 and internally-facing
feedthrough side 38, externally-facing ends 84 may not extend
beyond externally-facing filter array side 54 (and/or electrically
insulating layer 70). Additionally or alternatively, sufficient
thick film conductive paste may be applied within the passageways
through capacitive filter substrate 50 to result in
internally-facing ends 86 extending to or beyond internally-facing
filter array side 52.
[0083] The example technique of FIG. 7 also includes heating
ferrule 16, feedthrough 18, capacitive filter array 20, filter
array conductive pathways 82, and thick film conductive paste 48d
and 48e to convert thick film conductive paste 48d and 48e and
filter array conductive pathways 82 from a paste to a relatively
solid material (110). In some examples in which the technique
includes step (106), the heating step (110) may not convert thick
film conductive paste 48d and 48e from a paste to a relatively
solid material, as thick film conductive paste 48d and 48e may
already be a relatively solid material.
[0084] In some examples, feedthrough assembly 10b may be heated at
a temperature between about 700.degree. C. and about 850.degree. C.
for between about 30 minutes and about 60 minutes, with about 10
minutes of substantially constant temperature at the peak
temperature. By heating feedthrough assembly 10b and converting
filter array conductive pathways 82 to a relatively solid material,
mechanical and electrical connection may be made between respective
ones of internally-facing feedthrough conductive pads 46 and filter
array conductive pathways 82, which may result in mechanical
connection between feedthrough 18 and capacitive filter array
20.
[0085] Thick film conductive paste is one example of a material
that may be used to mechanically and electrically connect
feedthrough 18 and capacitive filter array 20, and capacitive
filter array 20 and ferrule 16. However, in other example, other
structures may be used to electrically and mechanically connect the
respective structures. For example, in accordance with some aspects
of the disclosure, a lead frame assembly may be used to make
mechanical and electrical connection between feedthrough 18 and
capacitive filter array 20 and/or between capacitive filter array
20 and ferrule 16.
[0086] FIG. 8 illustrates an example feedthrough assembly 10c in
which a lead frame assembly 116 mechanically and electrically
connects feedthrough 18 and capacitive filter array 20 and
capacitive filter array 20 and ferrule 16. In FIG. 8, lead frame
assembly 116 is formed by a combination of electrically conductive
leads 114a, 114b, 114c, and 114d (collectively, "electrically
conductive leads 114").
[0087] In some examples, feedthrough assembly 10c is substantially
similar to feedthrough assemblies 10a and 10b described with
reference to FIGS. 4A, 4B, and 5, except for the differences noted
herein. Similar to FIG. 5, certain reference numerals shown in
FIGS. 4A and 4B are omitted from FIG. 8 for the sake of
clarity.
[0088] As shown in FIG. 8, lead frame assembly 116 mechanically and
electrically connects feedthrough 18 and capacitive filter array
20. Lead frame assembly 116 may include a first electrically
conductive lead 114a, a second electrically conductive lead 114b,
and a third electrically conductive lead 114c, which electrically
connect respective ones of filter conductive vias 62 with
respective ones of internally-facing feedthrough conductive pads
46. Lead frame assembly 116 also may include fourth electrically
conductive lead 114d, which electrically connects perimeter
conductive contact 72 with ferrule 16.
[0089] Each of electrically conductive leads 114 may be formed of
an electrical conductive metal, such as niobium; titanium; titanium
alloys such as titanium-6Al-4V or titanium-vanadium; platinum;
molybdenum; zirconium; tantalum; vanadium; tungsten; iridium;
rhodium; rhenium; osmium; ruthenium; palladium; silver; and alloys,
mixtures, and combinations thereof. In some examples, at least some
of electrically conductive leads 114 possess sufficient mechanical
strength to allow first electrically conductive lead 114a, second
electrically conductive lead 114b, and/or third electrically
conductive lead 114c to maintain a gap between electrically
insulating layer 70 formed on externally-facing filter array side
54 and feedthrough electrically insulating layer 112 formed on
internally-facing feedthrough side 38. In some examples,
electrically conductive leads 114 may include bare metal (e.g.,
with no electrical insulation formed on a surface of electrically
conductive leads 114). In other examples, at least one of
electrically conductive leads 114 may include electrical insulation
formed on a surface of the at least one of electrically conductive
leads 114, such as an electrically insulating polymer.
[0090] FIG. 8 illustrates three filter conductive vias 62 and
corresponding first electrically conductive lead 114a, second
electrically conductive lead 114b, and third electrically
conductive lead 114c. However, in other examples, as described
above, capacitive filter array may include fewer than three filter
conductive vias 62 or more than three filter conductive vias 62. In
some such examples, feedthrough assembly 10c may include a
corresponding number of electrically conductive leads 114 (e.g.,
one electrically conductive lead 114 for each filter conductive
vias 62).
[0091] Additionally or alternatively, as described above,
capacitive filter array 20 may include a single perimeter
conductive contact 72, which may extend at least partially (or
substantially fully) around capacitive filter perimeter 56, or
capacitive filter array 20 may include a plurality of discrete
perimeter conductive contacts 72 (e.g., one perimeter conductive
contact 72 for each one of filter conductive vias 62). In either
example, although FIG. 8 illustrates one electrically conductive
lead (fourth electrically conductive lead 114d) connecting
perimeter conductive contact 72 to ferrule 16, in other
implementations, feedthrough assembly 10c may include more than one
electrically conductive lead connecting perimeter conductive
contact 72 to ferrule 16. For example, feedthrough assembly 10c may
include a plurality of electrically conductive leads 114 that
connect a single perimeter conductive contact 72 to ferrule 16. As
another example, feedthrough assembly 10c may include a plurality
of electrically conductive leads 114 that connect a plurality of
discrete perimeter conductive contacts 72 to ferrule 16 (e.g., one
electrically conductive lead 114 for each discrete perimeter
conductive contact 72 or more than one electrically conductive lead
114 for each discrete perimeter conductive contact 72).
[0092] FIG. 9 is a flow diagram that illustrates an example
technique for forming feedthrough assembly 10c. Although the
technique of FIG. 9 will be described with reference to feedthrough
assembly 10c shown in FIG. 8, one of ordinary skill will appreciate
that the technique of FIG. 9 may be used to construct other
feedthrough assemblies.
[0093] The technique of FIG. 9 includes attaching feedthrough 18 to
ferrule 16 (92). As described above, feedthrough 18 may be
connected to ferrule 16 using any technique that forms hermetic
seal 26 between feedthrough 18 and ferrule 16. For example, ferrule
16 and feedthrough 18 may be connected using brazing, diffusion
bonding, laser sintering of glass, or the like. Hermetic seal 26
may be formed using a biocompatible, biostable material. Examples
of materials that may be used to form a hermetic seal 26 include
gold, a nickel-gold alloy, platinum, platinum-iridium, or a
biocompatible glass.
[0094] The technique shown in FIG. 9 also includes attaching lead
frame assembly 116 to capacitive filter array 20 (122). In some
examples, attaching lead frame assembly 116 includes attaching
first electrically conductive lead 114a directly to a first one of
filter conductive vias 62, attaching second electrically conductive
lead 114b directly to a second one of filter conductive vias 62,
attaching third electrically conductive lead 114c directly to a
third one of filter conductive vias 62, and attaching fourth
electrically conductive lead 114d to perimeter conductive contact
72. In other examples, capacitive filter array 20 may include a
plurality of externally-facing filter conductive pads 60 (see FIGS.
4A and 4B), and first electrically conductive lead 114a, second
electrically conductive lead 114b, and third electrically
conductive lead 114c may be attached to respective ones of
externally-facing filter conductive pads 60.
[0095] Electrically conductive leads 114 may be attached to
capacitive filter array 20 using a variety of techniques. For
example, electrically conductive leads 114 may be attached to
capacitive filter array 20 using laser welding, parallel gap
welding, thermosonic bonding, diffusion bonding, ultrasonic
welding, opposed gap welding, laser brazing, step gap resistance
welding, percussion arc welding, or soldering (conventional or
laser).
[0096] In other examples, electrically conductive leads 114 may be
attached to capacitive filter array 20 using a firing process. In a
firing process, capacitive filter array 20 and metals leads 114 may
be heated to a temperature between about 700.degree. C. and about
850.degree. C. for between about 30 minutes and about 60 minutes,
with about 10 minutes of substantially constant temperature at the
peak temperature. The heating process may result in a mechanical
connection between electrically conductive leads 114 and filter
conductive vias 62 and perimeter conductive contact 72.
[0097] Once lead frame assembly 116 has been attached to capacitive
filter array 20 (122), capacitive filter array 20 (including lead
frame assembly 116) may be positioned in a desired position
relative to ferrule 16 and feedthrough 18 (124). The desired
position may include a position in which respective ones of
electrically conductive leads 114 contact respective ones of
internally-facing feedthrough conductive pads 46 and ferrule 16, as
shown in FIG. 8. In some examples, as shown in FIG. 10, feedthrough
18 may not include internally-facing feedthrough conductive pads
46, and capacitive filter array 20 may be positioned so that
respective ones electrically conductive leads 114 contact
respective ones of feedthrough conductive vias 44.
[0098] In some examples, described above, metals leads 114a, 114b,
and/or 114c may possess sufficient mechanical strength to maintain
separation between capacitive filter array 20 and feedthrough 18
when capacitive filter array 20 is positioned in the desired
position relative to ferrule 16 and feedthrough 18 (124). For
example, as shown in FIG. 8, electrically conductive leads 114a,
114b, and/or 114c may be sufficiently long to result in formation
of a gap 118 between electrically insulating layer 70 and
feedthrough electrically insulating layer 112. In other examples,
electrically conductive leads 114a, 114b, 114c may be shorter, such
that electrically insulating layer 70 and feedthrough electrically
insulating layer 112 contact each other when capacitive filter
array 20 is positioned in the desired position relative to ferrule
16 and feedthrough 18 (124).
[0099] The desired position of capacitive filter array 20 relative
to ferrule 16 may include positioning fourth electrically
conductive lead 114d contacting ferrule 16. As described above,
ferrule 16 may form a portion of an electrically conductive path
between capacitive filter array 20 (e.g., plurality of capacitive
filters 64) and the housing of the IMD in which feedthrough
assembly 10c is used. In some examples, as shown in FIG. 8, fourth
electrically conductive lead 114d may contact ferrule 16 at
internally-facing ferrule side 22. In other examples, fourth
electrically conductive lead 114d may contact ferrule 16 at a
different position, such as, for example, second interior wall
58.
[0100] In some examples, ferrule 16 may include or consist
essentially of an electrically conducting material, and fourth
electrically conductive lead 114d may contact ferrule 16 at
substantially any position of ferrule 16 (e.g., any position of
ferrule 16 that will be positioned within a housing of an IMD once
ferrule 16 is attached to the IMD). In other examples, some
portions of ferrule 16 may include an electrically insulating
material and other portions of ferrule 16 may include an
electrically conducting material. In these examples, fourth
electrically conductive lead 114d may contact ferrule 16 at a
portion of ferrule that includes an electrically conducting
material.
[0101] Once capacitive filter array 20 has been positioned in the
desired position relative to ferrule 16 and feedthrough 18,
electrically conductive leads 114 may be attached to respective
portions of feedthrough 18 and ferrule 16 (126). For example, first
electrically conductive lead 114a, second electrically conductive
lead 114b, and third electrically conductive lead 114c may be
attached to respective ones of internally-facing feedthrough
conductive pads 46 (or respective ones of feedthrough conductive
vias 44, as shown in FIG. 10) using laser welding, parallel gap
welding, thermosonic bonding, diffusion bonding, ultrasonic
welding, opposed gap welding, laser brazing, step gap resistance
welding, brazed interposer, percussion arc welding, or soldering
(conventional or laser). Fourth electrically conductive lead 114d
may be attached to ferrule 16 using a similar process.
[0102] In accordance with some aspects of the disclosure, an
electrically insulating material may be introduced between
capacitive filter array 20 and feedthrough 18 after feedthrough 18,
capacitive filter array 20 and ferrule 16 have been assembled
(e.g., using a backfill or underfill process). FIGS. 10-12
illustrate examples of feedthrough assemblies that include
electrically insulating material introduced, e.g., using a backfill
or underfill process.
[0103] In some examples, feedthrough assembly 10d may be similar to
or substantially the same as feedthrough assembly 10c shown in FIG.
8, aside from the differences noted herein. Feedthrough assembly
10d includes first electrically conductive lead 114a, second
electrically conductive lead 114b, and third electrically
conductive lead 114c, which electrically and mechanically collect
respective ones of filter conductive vias 62 with respective ones
of feedthrough conductive vias 44. As described above with respect
to FIG. 8, in some examples, feedthrough 18 may include
internally-facing feedthrough conductive pads 46 and/or capacitive
filter array 20 may include externally-facing filter conductive
pads 60.
[0104] Feedthrough assembly 10d also includes an electrically
insulating material 132 disposed between feedthrough 18 and
capacitive filter array 20. Electrically insulating material 132
may extend substantially continuously between externally-facing
filter array side 54 and internally-facing feedthrough side 38.
Electrically insulating material 132 thus may electrically insulate
metals leads 114 from one another, may electrically insulate
electrically conductive leads 114 from perimeter conductive contact
72, and/or may electrically insulate electrically conductive leads
114a, 114b, and 114c from ferrule 16. In some examples,
electrically insulating material 132 also may be disposed in the
space between perimeter conductive contact 72 and ferrule 16, and
may electrically insulate perimeter conductive contact 72 from
ferrule 16.
[0105] In some examples, electrically insulating material 132 may
contribute to mechanical connection between ferrule 16 and
feedthrough 18, between feedthrough 18 and capacitive filter array
20, and/or between ferrule 16 and capacitive filter array 20.
[0106] Electrically insulating material 132 may include any
suitable electrically insulating material. For example,
electrically insulating material 132 may include an electrically
non-conducting (i.e., electrically insulating) polyimide, epoxy,
glass, or other electrically insulating polymer. Electrically
insulating material 132 may be a material that can be introduced
into the gap between internally-facing feedthrough side 38 and
externally-facing feedthrough side 54 in a flowable state (e.g., a
liquid or polymer melt), and then be converted into a substantially
solid state (e.g., by cooling the material or removing a
liquid/solvent from the material).
[0107] In some examples, electrically insulating material 132 may
be introduced into the gap (e.g., gap 118 shown in FIG. 8) between
internally-facing feedthrough side 38 and externally-facing
feedthrough side 54 after capacitive filter array 20 has been
attached to feedthrough 18 using electrically conductive leads
114a, 114b, and 114c. As shown in FIG. 10, ferrule 16 may define an
underfill access channel 134. Underfill access channel 134 may be
sized and positioned to allow introduction of electrically
insulating material 132 into the gap between internally-facing
feedthrough side 38 and externally-facing feedthrough side 54. For
example, underfill access channel 134 may extend between an
exterior wall 136 of ferrule 16 and first interior wall 42 of
ferrule 16. In other examples, underfill access channel 134 may
extend between exterior wall 136 and second interior wall 58.
[0108] In some examples, as shown in FIG. 10, underfill access
channel 134 may be located at a position of ferrule 16 that will be
on an interior of a housing of an IMD in which feedthrough assembly
10d is used. This may promote a hermetic seal between the housing
of the IMD and feedthrough assembly 10d, and prevent movement of
fluids (e.g., bodily fluids) between an interior and an exterior of
the IMD. Further details regarding attachment of an example
feedthrough assembly to an IMD housing are shown in FIG. 14 and
described below.
[0109] FIG. 11 is a cross-sectional diagram that illustrates
another example feedthrough assembly 10e. Feedthrough assembly 10e
may be similar to feedthrough assembly 10a illustrated in FIGS. 4A
and 4B, aside from the differences noted herein. Feedthrough
assembly 10e also includes an electrically insulating material 132
disposed between feedthrough 18 and capacitive filter array 20.
Electrically insulating material 132 may extend substantially
continuously between externally-facing filter array side 54 and
internally-facing feedthrough side 38. Electrically insulating
material 132 thus may electrically insulate the conductive pathways
(e.g., including internally facing feedthrough conductive pads 46,
thick film conductive paste 48, and externally-facing filter
conductive pads 60) from one another, may electrically insulate the
conductive pathways from perimeter conductive contact 72, and/or
may electrically the conductive pathways from ferrule 16. In some
examples, electrically insulating material 132 also may be disposed
in the space between perimeter conductive contact 72 and ferrule
16, and may electrically insulate perimeter conductive contact 72
from ferrule 16.
[0110] As described above, electrically insulating material 132 may
include any suitable electrically insulating material, such as an
electrically non-conducting (i.e., electrically insulating)
polyimide, epoxy, glass, or other electrically insulating
polymer.
[0111] In some examples, electrically insulating material 132 may
be introduced into the gap (e.g., gap 118 shown in FIG. 8) between
internally-facing feedthrough side 38 and externally-facing
feedthrough side 54 after capacitive filter array 20 has been
attached to feedthrough 18 and ferrule 16 using thick film
conductive paste 48. As shown in FIG. 11, feedthrough 18 may define
an underfill access channel 144. Underfill access channel 144 may
be sized and positioned to allow introduction of electrically
insulating material 132 into the gap between internally-facing
feedthrough side 38 and externally-facing feedthrough side 54. For
example, underfill access channel 144 may extend between
externally-facing feedthrough side 36 and internally-facing
feedthrough side 38.
[0112] In some examples, as shown in FIG. 11, electrically
insulating material 132 may form a hermetic seal with feedthrough
18, e.g., in underfill access channel 144. In other examples,
feedthrough assembly 10e may include another material that forms a
hermetic seal within underfill access channel 144, such as gold, a
nickel-gold alloy, platinum, and platinum-iridium. This may promote
a hermetic seal between the housing of the IMD and feedthrough
assembly 10e, and prevent movement of fluids (e.g., bodily fluids)
between an interior and an exterior of the IMD. Further details
regarding attachment of an example feedthrough assembly to an IMD
housing are shown in FIG. 14 and described below.
[0113] FIG. 12 is a cross-sectional diagram that illustrates
another example feedthrough assembly 10f Feedthrough assembly 10e
may be similar to feedthrough assembly 10a illustrated in FIGS. 4A
and 4B, aside from the differences noted herein. Feedthrough
assembly 10e also includes an electrically insulating material 132
disposed between feedthrough 18 and capacitive filter array 20.
Electrically insulating material 132 may extend substantially
continuously between externally-facing filter array side 54 and
internally-facing feedthrough side 38. Electrically insulating
material 132 thus may electrically insulate the conductive pathways
(e.g., including internally facing feedthrough conductive pads 46,
thick film conductive paste 48, and externally-facing filter
conductive pads 60) from one another, may electrically insulate the
conductive pathways from perimeter conductive contact 72, and/or
may electrically the conductive pathways from ferrule 16. In some
examples, electrically insulating material 132 also may be disposed
in the space between perimeter conductive contact 72 and ferrule
16, and may electrically insulate perimeter conductive contact 72
from ferrule 16.
[0114] In some examples, electrically insulating material 132 may
be introduced into the gap (e.g., gap 118 shown in FIG. 8) between
internally-facing feedthrough side 38 and externally-facing
feedthrough side 54 after capacitive filter array 20 has been
attached to feedthrough 18 and ferrule 16 using thick film
conductive paste 48. As shown in FIG. 12, capacitive filter array
20 may define an underfill access channel 154. Underfill access
channel 154 may be sized and positioned to allow introduction of
electrically insulating material 132 into the gap between
internally-facing feedthrough side 38 and externally-facing filter
array side 54. For example, underfill access channel 154 may extend
between internally-facing filter array side 52 and
externally-facing filter array side 54. In some examples,
positioning underfill access channel 154 in capacitive filter array
20 may promote a hermetic seal between the housing of the IMD and
feedthrough assembly 10f, and prevent movement of fluids (e.g.,
bodily fluids) between an interior and an exterior of the IMD.
Further details regarding attachment of an example feedthrough
assembly to an IMD housing are shown in FIG. 14 and described
below.
[0115] FIG. 13 is a flow diagram that illustrates an example
technique for forming a feedthrough assembly that includes an
electrically insulating material between feedthrough 18 and
capacitive filter array 20. The technique illustrated in FIG. 13
includes attaching feedthrough 18 to ferrule 16 (92). As described
above, feedthrough 18 may be connected to ferrule 16 using any
technique that forms hermetic seal 26 between feedthrough 18 and
ferrule 16. For example, ferrule 16 and feedthrough 18 may be
connected using brazing, diffusion bonding, laser sintering of
glass, or the like. Hermetic seal 26 may be formed using a
biocompatible, biostable material. Examples of materials that may
be used to form a hermetic seal 26 include gold, a nickel-gold
alloy, platinum, platinum-iridium, or a biocompatible glass.
[0116] The technique illustrated in FIG. 13 also includes attaching
capacitive filter array 20 to feedthrough 18 and ferrule 16 (156).
In some examples, as described above with respect to FIG. 6,
attaching capacitive filter array to feedthrough 18 and ferrule 16
(156) may include applying thick film conductive paste 48 to
desired locations of feedthrough 18, ferrule 16, and/or capacitive
filter array 20 (94), positioning capacitive filter array 20 in a
desired orientation relative to ferrule 16 and feedthrough 18 (96),
and heating the feedthrough assembly (e.g., feedthrough assembly
10a, 10e, or 10f) to convert thick film conductive paste 48 from a
paste to a relatively solid material (98). In other examples, as
described above with respect to FIG. 7, attaching capacitive filter
array to feedthrough 18 and ferrule 16 (156) may include applying
thick film conductive paste 48d, 48e to second interior wall 58 of
ferrule 16 or perimeter conductive contact 72 (102), positioning
capacitive filter array 20 in a desired orientation relative to
ferrule 16 and feedthrough 18 (104), heating thick film conductive
paste 48d and 48e to convert thick film conductive paste 48d and
48e from a paste to a relatively solid material (106), depositing
thick film conductive paste within passageways through capacitive
filter substrate 50 to form filter array conductive pathways 82
(108), and heating ferrule 16, feedthrough 18, capacitive filter
array 20, filter array conductive pathways 82, and thick film
conductive paste 48d and 48e to convert thick film conductive paste
48d and 48e and filter array conductive pathways 82 from a paste to
a relatively solid material (110). In other examples, as described
above with respect to FIG. 9, attaching capacitive filter array to
feedthrough 18 and ferrule 16 (156) may include attaching lead
frame assembly 116 to capacitive filter array 20 (122), positioning
capacitive filter array 20 (including lead frame assembly 116) in a
desired position relative to ferrule 16 and feedthrough 18 (124),
and attaching electrically conductive leads 114 to respective
portions of feedthrough 18 and ferrule 16 (126).
[0117] Once capacitive filter array 20 has been attached to ferrule
16 and feedthrough 18, the gap (e.g., gap 118 shown in FIG. 8)
between internally-facing feedthrough side 38 and externally-facing
filter array side 54 may be underfilled with electrically
insulating material 132 (158). As described above, electrically
insulating material 132 may include a material that can be present
in a flowable form, such as a liquid, suspension or polymer melt.
Electrically insulating material 132 may be introduced into the gap
between internally-facing feedthrough side 38 and externally-facing
filter array side 54 through an underfill access channel, such as
underfill access channel 134 defined by ferrule 16, underfill
access channel 144 defined by feedthrough 20, or underfill access
channel 154 defined by capacitive filter array 20. Once the
flowable electrically insulating material 132 has been introduced
into the gap between internally-facing feedthrough side 38 and
externally-facing filter array side 54, electrically insulating
material 132 may be converted to a substantially solid material,
such as by cooling electrically insulating material 132 or removing
a liquid carrier or solvent from electrically insulating material
132.
[0118] Any of the feedthrough assemblies 10 illustrated and
described above may be utilized as a feedthrough assembly for an
IMD. FIG. 14 is a conceptual diagram that illustrates an example
feedthrough assembly attached to a housing of an IMD and
electrically coupled to a plurality of leads and a plurality of
electrical connections to circuitry. Although feedthrough assembly
10f is depicted in FIG. 14, any of the other feedthrough assemblies
described herein may be utilized in an IMD in a similar manner.
[0119] IMD 160 includes a housing 162 and defines an opening in
which feedthrough assembly 10f is disposed. Feedthrough assembly
10f is mechanically attached to a housing 162 of IMD 160 by a
hermetic seal 164. For example, hermetic seal 164 may be formed
between an exterior wall 136 of ferrule 16 and housing 162.
Hermetic seal 164 may prevent bodily fluids of the patient from
passing into the interior of IMD housing between ferrule 16 and
housing 162, which could lead to damage to the internal electronics
of the IMD 160. In one example, hermetic seal 164 comprises a braze
joint between ferrule 16 and housing 162 (e.g., formed using laser
brazing). In other examples, hermetic seal 164 may be formed using
diffusion bonding. Examples of materials that may be used to form a
hermetic seal 164 include any biocompatible, biostable material
capable for forming a hermetic seal 164, such as, gold, a
nickel-gold alloy, platinum, and platinum-iridium. Laser sintering
of glass may also be used to bond ferrule 16 and housing 162.
[0120] In other examples, hermetic seal 164 may include a weld
formed between housing 162 and ferrule 16. The weld may be formed
of a material that is compatible with the material of housing 162
and the material of ferrule 16. As described above, in some
examples, ferrule 16 may include titanium or a titanium alloy, and
housing 162 also may include a titanium or titanium alloy. In some
examples, the weld is formed using a laser welding process, e.g.,
to form a Ti--Ti weld.
[0121] In some examples, hermetic seal 164 may provide an
electrical connection between housing 162 and ferrule 16 and may
form a portion of the electrically conductive path between ground
electrodes 68 of capacitive filter arrays 64 (see FIG. 4B) and
housing 162. In some of these examples, housing 162 may act as an
electrical ground for the signals filtered by capacitive filter
arrays 64.
[0122] In some examples, IMD 160 may be device that is configured
to deliver a therapy and/or monitor a physiologic condition of a
patient. For example, IMD 160 may be a cardiac pacemaker, an
implantable cardioverter/defibrillator, or an implantable
neurostimulator, and may deliver therapy to or monitor physiologic
signals from a patient's heart, muscle, nerve, brain, stomach, or
another organ.
[0123] IMD 160 encloses circuitry, such as therapy delivery
circuitry or sensing circuitry. Therapy delivery circuitry and/or
sensing circuitry are represented in FIG. 14 as a printed board
(PB) 172. Although not shown in FIG. 14, PB 172 may include
electrical components, such as resistors, capacitor, inductors,
batteries, integrated circuits, hybrid circuits, analog circuits,
or the like mounted to or incorporated into PB 172. PB 172 also
includes a plurality of contact pads 170, to which wires 168 are
electrically connected.
[0124] Wires 168 electrically connect circuitry in or on PB 172 to
internally-facing filter array conductive pads 32. Respective wires
168 may be electrically connected to respective contact pads 170
and respective internally-facing filter array conductive pads 32.
Electrical connection between wires 168 and contact pads 170 and
respective internally-facing filter array conductive pads 32 may be
made by, for example, welding or soldering.
[0125] IMD 160 is also electrically connected to a plurality of
lead conductors 166 via feedthrough assembly 10f. For example,
respective ones of lead conductors 166 may be electrically
connected to respective ones of externally-facing feedthrough
conductive pads 28. Lead conductors 166 may be carried by at least
one lead body, which may also carry electrodes, to which lead
conductors 166 are electrically connected. Lead conductors 166
provide an electrical path through which IMD 160 may deliver
electrical stimulation of a target tissue and/or sense physiologic
signals from a target tissue.
[0126] Various examples have been described. These and other
examples are within the scope of the following claims.
* * * * *