USRE46699E1 - Low impedance oxide resistant grounded capacitor for an AIMD - Google Patents

Abstract

A hermetically sealed filtered feedthrough assembly for an AIMD includes an insulator hermetically sealed to a conductive ferrule or housing. A conductor is hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule or housing between a body fluid side and a device side. A feedthrough capacitor is disposed on the device side. A first low impedance electrical connection is between a first end metallization of the capacitor and the conductor. A second low impedance electrical connection is between a second end metallization of the capacitor and the ferrule or housing. The second low impedance electrical connection includes an oxide-resistant metal addition attached directly to the ferrule or housing and an electrical connection coupling the second end metallization electrically and physically directly to the oxide-resistant metal addition.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional application Ser. No. 61/841,419, filed on Jun. 30, 2013. The present application also claims priority to and is a continuation-in-part application of U.S. application Ser. No. 13/873,832, filed on Apr. 30, 2013, the contents of which are incorporated herein by reference. The present application also claims priority to and is a continuation-in-part application of U.S. patent application Ser. No. 13/743,276, filed on Jan. 16, 2013, the contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to feedthrough capacitors. More particularly, the present invention relates to a feedthrough capacitor located on the device side with a low impedance and oxide-resistance electrical connection.

BACKGROUND OF THE INVENTION

Feedthrough capacitors and MLCC chip capacitors are well known in the prior art for active implantable medical devices (AIMDs). One is directed to U.S. Pat. Nos. 5,333,095; 5,905,627; 6,275,369; 6,529,103; and 6,765,780 all of which are incorporated herein by reference. The hermetic seal feedthrough terminal assemblies generally consist of a titanium ferrule into which an alumina hermetic seal is gold brazed. One or more lead wires penetrate through the alumina in non-conductive relationship with the ferrule. Gold brazes are also used to form a hermetic terminal between the one or more leadwires and the alumina ceramic.

First, some general information concerning good engineering design practice for electromagnetic interference (EMI) filters. It is very important to intercept the EMI at the point of lead conductor ingress and egress to the AIMD. It would be an inferior practice to put filtering elements down in the circuit board as this would draw EMI energy inside of the AIMD housing where it could re-radiate or cross-couple to sensitive AIMD circuits. A superior approach is to mount one or more feedthrough or MLCC-type capacitors right at the point of leadwire entrance so that it can be coupled to high frequency EMI signals from the lead conductors directly to the AIMD housing, which acts as an energy dissipating surface.

There are some interesting design challenges however. The titanium ferrule, which is laser welded into the overall AIMD housing, is at ground potential. Titanium tends to form oxides which act as either insulators or semi-conductors. Accordingly, grounding the feedthrough capacitor electrode plates directly to the titanium ferrule is contra-indicated. Reference is made to U.S. Pat. No. 6,465,779 (which is incorporated with this reference) which describes gold bond pad areas where the feedthrough capacitor external metallization can be directly connected to gold. The gold to which the feedthrough capacitor is directly connected is the braze material used to form the hermetic seal between the alumina and the titanium ferrule. As noted above, the hermetic seal is formed via a brazing process. By attaching the capacitor's ground plates to the gold, one can be assured that there will be no oxide that will increase the capacitor's equivalent series resistance (ESR) which can seriously degrade the capacitor's performance at high frequency. An undesirable aspect of using the gold braze for attachment is that gold is very expensive. Accordingly, there is a need for methods that provide a reliable low impedance ground path which are oxide resistant for grounding of AIMD filter capacitors. The present invention fulfills these needs and provides other related advantages.

SUMMARY OF THE INVENTION

An exemplary embodiment of a hermetically sealed filtered feedthrough assembly for an implantable medical device includes an insulator hermetically sealed to a conductive ferrule or housing. A conductor is hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule or housing between a body fluid side and a device side. A feedthrough capacitor is disposed on the device side. The feedthrough capacitor includes a first and a second end metallization, wherein the first end metallization is connected to at least one active electrode plate and wherein the second end metallization is connected to at least one ground electrode plate. The at least one active electrode plate is interleaved and disposed parallel to the at least one ground electrode plate, wherein the at least one active and at least one ground electrode plates are disposed within a capacitor dielectric. A first low impedance electrical connection is between the first end metallization and the conductor. A second low impedance electrical connection is between the second end metallization and the ferrule or housing. The second low impedance electrical connection includes an oxide-resistant metal addition attached directly to the ferrule or housing and an electrical connection coupling the second end metallization electrically and physically directly to the oxide-resistant metal addition.

In other exemplary embodiments the oxide-resistant metal addition may include a different material as compared to the ferrule or housing. The oxide-resistant metal addition may include a noble metal such as gold, platinum, palladium, silver and combinations thereof. The oxide-resistant metal addition may be laser welded to the ferrule or housing. The oxide-resistant metal addition may include a brazed metal such as gold. Possible braze materials include gold, gold-based metal, platinum, platinum based metal, palladium, palladium based metal, silver and silver based metal. Non-limiting noble metal based braze examples are gold-palladium, gold-boron, and palladium-silver. It is anticipated that proprietary brazes such as but not limited to the Pallabraze product family (palladium-containing) and Orobraze product family (gold-containing) offered by Johnson Matthey may be used. The braze material may be a rod, a ribbon, a powder, a paste, a cream, a wire and a preform such as but not limited to stamped washers.

A grounding loop may be defined on the device side having the first low impedance electrical connection and the second low impedance connection from the conductor through the feedthrough capacitor to the ferrule or housing. The total resistance of the grounding loop may be less than 1 milliohm. The total inductance of the grounding loop may be less than 10 nanohenries or less than 1 nanohenry.

The conductor may include a leadwire having platinum, palladium, silver or gold.

The insulator may be flush with the ferrule or housing on the device side. The insulator may include an alumina substrate comprised of at least 96% alumina and the conductor having a substantially closed pore and substantially pure platinum fill disposed within a via hole and extending between the body fluid side and the device side of the alumina substrate.

A hermetic seal may be between the platinum fill and the alumina substrate, wherein the platinum fill forms a tortuous and mutually conformal knitline or interface between the alumina substrate and the platinum fill, wherein the hermetic seal has a leak rate that is no greater than 1×10⁻⁷std cc He/sec.

An inherent shrink rate during a heat treatment of the alumina dielectric substrate in a green state may be greater than that of the platinum fill in the green state.

The oxide-resistant metal addition may include a wire, a pad, an L-shaped pad or an L-shaped pad with cutouts or combinations thereof.

A ground wire may be disposed through both the insulator and the feedthrough capacitor, where the ground wire is not electrically coupled to the at least one active and one ground electrode plate.

The ferrule or housing may include an integrally formed conductive peninsula, where the ground wire is electrically coupled to the peninsula.

The feedthrough capacitor may have a resonant frequency above 400 MHz. The feedthrough capacitor may have a capacitance of between 300 picofarads and 10,000 picofarads.

Other features and advantages of the present invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 illustrates a wire-formed diagram of a generic human body showing various types of active implantable and external medical devices currently in use;

FIG. 2 is an isometric cut-away view of a unipolar feedthrough capacitor;

FIG. 3 is a cross-sectional view of the unipolar capacitor ofFIG. 2 shown connected to the hermetic terminal of an AIMD;

FIG. 4 is a schematic diagram of the unipolar feedthrough capacitor shown inFIGS. 2 and 3;

FIG. 5 is an exploded view of the cover sheets and internal electrodes of the unipolar capacitor previously described inFIGS. 2 and 3;

FIG. 6 is a diagrammatic exploded view of a typical AIMD;

FIG. 7 is an isometric view of the quad polar feedthrough capacitor previously described in the prior art pacemaker ofFIG. 6;

FIG. 8 is a sectional view taken from section8-8 ofFIG. 7 and illustrates the quad polar feedthrough capacitor interior electrode plates;

FIG. 9 is an exploded view of the quad polar feedthrough capacitor ofFIG. 7;

FIG. 10 is the schematic diagram of the quad polar feedthrough capacitor ofFIG. 7;

FIG. 11 illustrates a prior art quad polar feedthrough capacitor that is rectangular instead of round;

FIG. 12 is an isometric view of the feedthrough assembly before the feedthrough capacitor is placed;

FIG. 13 is taken from section13-13 fromFIG. 11 showing the four active electrode plates;

FIG. 14 is taken from section14-14 fromFIG. 11 and illustrates the ground electrode plate;

FIG. 15 is an assembly view taken fromFIGS. 11-14 showing the quad polar rectangular feedthrough capacitor mounted onto the hermetic seal housing and the ferrule;

FIG. 16 is a sectional view taken from section16-16 fromFIG. 15;

FIG. 17 is the schematic diagram of the quad polar feedthrough capacitors previously illustrated inFIGS. 14 and 15;

FIG. 18 is a perspective view showing gold bond pads used to eliminate the problem of attachment to oxides of titanium between the feedthrough capacitor outside diameter and its ground electrode plate sets;

FIG. 19 shows that the electrical connections between the capacitor's ground metallization is now directly connected to this oxide resistant noble pad;

FIG. 20 is a sectional view of the structure ofFIG. 19 taken through lines20-20;

FIG. 21 is very similar toFIG. 19, except that the quad polar capacitor is round which is consistent with the feedthrough capacitor previously illustrated in the cardiac pacemaker ofFIG. 6;

FIG. 22 is generally taken from section22-22 fromFIG. 21 and illustrates the capacitor's internal structure including its ground and active electrode plates;

FIG. 23 illustrates the schematic diagram of the improved rectangular quad polar feedthrough capacitor ofFIG. 19 and the round quad polar capacitor ofFIG. 21;

FIG. 24 illustrates attenuation versus frequency comparing the ideal feedthrough capacitor to one that has undesirable ground electrode plate connection to an oxidized surface;

FIG. 25 is a perspective view of an exemplary feedthrough capacitor embodying the present invention;

FIG. 26 is a sectional view taken along line26-26 of the structure ofFIG. 25;

FIG. 27 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 27A is an exploded view of the structure ofFIG. 27 showing the peninsula portion of the ferrule;

FIG. 28 is a sectional view taken along line28-28 of the structure ofFIG. 27;

FIG. 28A is an enlarged view of a novel embodiment of a similar structure ofFIG. 28 taken alonglines28A-28A;

FIG. 28B is another embodiment of the structure ofFIG. 28A now showing a rectangular shaped structure attached to the ferrule;

FIG. 28C is a view similar to27A except now showing a recess on the ferrule for the wire to fit within;

FIG. 29 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 30 is a sectional view taken along line30-30 of the structure ofFIG. 29;

FIG. 31 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 32 is a sectional view taken along line32-32 of the structure ofFIG. 31;

FIG. 33 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 34 is a sectional view taken along line34-34 of the structure ofFIG. 33;

FIG. 35 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 36 is an exploded view of the structure ofFIG. 35 showing the peninsula portion of the ferrule;

FIG. 37 is a sectional view taken along line37-37 of the structure ofFIG. 35;

FIG. 38 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 39 is a sectional view taken along line39-39 of the structure ofFIG. 38 now showing a ground electrode plate;

FIG. 40 is an sectional view taken along line40-40 of the structure ofFIG. 38 now showing an active electrode plate;

FIG. 41 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 42 is an sectional view taken along line42-42 of the structure ofFIG. 41 now showing a ground electrode plate;

FIG. 43 is an sectional view taken along line43-43 of the structure ofFIG. 41 now showing an active electrode plate;

FIG. 44 is a sectional view taken along lines44-44 of the structures of bothFIGS. 38 and 41;

FIGS. 45A, 45B and 45C are perspective views of various embodiments of the novel ground attachments shown inFIGS. 38, 41 and 44;

FIG. 46 is a perspective view of another exemplary feedthrough capacitor embodying the present invention;

FIG. 47 is an exploded view of the structure ofFIG. 46 showing the novel ground attachment below the capacitor;

FIG. 48 is a perspective view of another exemplary feedthrough embodying the present invention now showing novel rectangular ground attachments in the ferrule;

FIG. 49 is a perspective view of another exemplary feedthrough embodying the present invention now showing novel circular ground attachments in the ferrule;

FIG. 50 is similar to eitherFIG. 48 or 49 now showing the capacitor grounded to the ferrule;

FIG. 51 is a sectional view taken along line51-51 of the structure ofFIG. 50 now showing a ground electrode plate;

FIG. 52 is a sectional view taken along line52-52 of the structure ofFIG. 50 now showing an active electrode plate;

FIG. 53 is a perspective view of another exemplary feedthrough embodying the present invention now showing novel ground attachments around the continuous perimeter of the ferrule;

FIG. 54 is an exploded view of another exemplary feedthrough capacitor embodying the present invention now showing novel ground attachment plate; and

FIG. 55 is the perspective assembled view of the structure ofFIG. 54 showing the capacitor metallization grounded to the novel plate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a wire-formed diagram of a generic human body showing various types of active implantable and externalmedical devices100 that are currently in use.100A is a family of external and implantable hearing devices which can include the group of hearing aids, cochlear implants, piezoelectric sound bridge transducers and the like.100B includes an entire variety of neurostimulators and brain stimulators. Neurostimulators are used to stimulate the Vagus nerve, for example, to treat epilepsy, obesity and depression. Brain stimulators are similar to a pacemaker-like device and include electrodes implanted deep into the brain for example but not limited to sensing the onset of the seizure and also providing electrical stimulation to brain tissue to prevent the seizure from actually happening, or for treating memory loss, Alzheimer's and the like. The lead wires that come from a deep brain stimulator are often placed using real time imaging. Most commonly such lead wires are placed during real time MRI.100C shows a cardiac pacemaker which is well-known in the art.100D includes the family of left ventricular assist devices (LVAD's), and artificial hearts, including the recently introduced artificial heart known as the ABIOCOR.100E includes an entire family of drug pumps which can be used for dispensing of insulin, chemotherapy drugs, pain medications and the like. Insulin pumps are evolving from passive devices to ones that have sensors and closed loop systems. That is, real time monitoring of blood sugar levels will occur. These devices tend to be more sensitive to EMI than passive pumps that have no sense circuitry or externally implanted lead wires.100F includes a variety of external or implantable bone growth stimulators for rapid healing of fractures.100G includes urinary incontinence devices.100H includes the family of pain relief spinal cord stimulators and anti-tremor stimulators.100H also includes an entire family of other types of neurostimulators used to block pain.100I includes a family of implantable cardioverter defibrillators (ICD) devices and also includes the family of congestive heart failure devices (CHF). This is also known in the art as cardio resynchronization therapy devices, otherwise known as CRT devices.100J illustrates an externally worn pack. This pack could be an external insulin pump, an external drug pump, an external neurostimulator, a Holter monitor with skin electrodes or even a ventricular assist device power pack.

FIG. 2 is an isometric cut-away view of aunipolar feedthrough capacitor132. It has anoutside diameter metallization142 and aninside diameter metallization144.Active electrode plates148 andground electrode plates146 are interleaved in the dielectric body. The active electrode plate set148 is connected to theinside diameter metallization144. The ground electrode plate set146 is connected to theoutside diameter metallization142. Metallization surfaces142 and144 can be glass fritted platinum silver or various types of plating. The metallization surfaces142 and144 are very important as it is easy to make electrical connection to these surfaces to other circuit elements.

FIG. 3 is a cross-sectional view of the unipolar capacitor ofFIG. 2 shown connected to the hermetic terminal of an active implantable medical device, such as a cardiac pacemaker. Shown is a hermetic seal formed from aninsulator160, such as an alumina ceramic, glass or the like. Agold braze162 forms a hermetic seal between theinsulator160 and leadwire114,111. The leadwire labeled114 on the body fluid side is generally directed to an implantable lead that has an electrode contactable to biological cells (not shown). And there is asecond gold braze150 which hermetically connects the outside diameter of theinsulator material160 to aferrule112. In the prior art, the ferrule is generally of titanium. TheAIMD housing116 is also generally of titanium. Alaser weld154 is formed which connects theferrule112 to theAIMD housing116 electrically and mechanically. Thelaser weld154 also forms a hermetic seal. Theunipolar feedthrough capacitor132 ofFIG. 2 is shown mounted directly to the hermetic seal insulator. Anelectrical connection156 connects the capacitor insidediameter metallization144 toleadwire111. There is also anelectrical connection material152 connected directly to theferrule112 as shown. Thiselectrical connection152 is substantially inferior to the present invention and thus undesirable. As shown, an electrical connection is being made directly to thetitanium surface112. It is well known that titanium, particularly when brought to elevated temperatures, forms oxides. Oxides of titanium, for example, titanium dioxide is so stable, it's used as a paint pigment. It is also highly resistive and also has semi-conductive properties. For this reason, this inserts an undesirable series resistance R_OXIDEbetween the feedthrough capacitor and theferrule112 and/orAIMD housing116.

FIG. 4 is a schematic diagram of unipolar feedthrough capacitor shown inFIGS. 2 and 3. Shown is an ideal feedthrough capacitor C. In general, feedthrough capacitors are three-terminal devices in that there is an input side114 (terminal one), an output side111 (terminal two) and a ground116 (terminal three). It is well known that an implanted lead can undesirably act as an antenna and couple to high frequency electromagnetic interference (EMI) energy. This EMI energy may be undesirably coupled along the implanted leadwire conductors to lead111, which is directed to sensitive AIMD electronics. It is well known that EMI can disrupt the proper operation of AIMD electronic circuitry. For example, there have been a number of case reports of complete inhibition of cardiac pacemakers when EMI was falsely detected as a normal cardiac rhythm and the pacemaker inhibited. This is immediately life-threatening as its leaves a pacemaker dependent patient without a heart beat during the entire time of the EMI exposure. The feature in the feedthrough capacitor as illustrated inFIGS. 2 and 3 is to divert incoming EMI energy in the implanted lead and dissipate it to the electromagnetically shieldedhousing116 of the AIMD which said EMI energy may be dissipated as a harmless amount of thermal or RF energy. In other words, it is the job of feedthrough capacitors to protect the sensitive AIMD electronics while at the same time freely allowing pacing or therapeutic pulses to pass and also to allow the AIMD to sense biological signals that are generally in the frequency range from zero to 2000 Hz without interruption. The capacitor is also known as a frequency variable impedance element. The capacitive reactance X_cin ohms:
X_c=1/[2πfc]
This inverse relationship with frequency means that, at very low frequencies, the capacitor looks like an open circuit (as if it were not there at all), and at very high frequencies, the capacitor acts as a short circuit where it diverts undesirable RF energy such as emissions from cellular telephones, microwave ovens or the like.

Referring once again toFIG. 4, one can see R_OXIDE. This resistive element is highly undesirable because it degrades the performance of the feedthrough capacitor all across its frequency range. There is also a great deal of variability in this oxide. During the gold brazing operation or during the formation of the hermetic seal, oxide poisoning may reach any corner or part of the brazing oven. The inventors have experienced some of the parts to be relatively oxide free where others in the lot may have a very thick or heavy oxide build-up.

FIG. 5 is an exploded view of thecover sheets147 and internal electrodes of theunipolar capacitor132 previously described inFIGS. 2 and 3. One can see that there areactive electrode plates148 screened ontodielectric layers149 and interleaved withground electrode plates146. A number ofblank cover sheets147 are placed on top and bottom for insulative and mechanical strength purposes.

FIG. 6 is a diagrammatic explosion of a typical AIMD, such as acardiac pacemaker100C. It has an overall electromagnetic shieldedtitanium housing116 along with a polymer header block (connector block)101. Shown, are two implantable leads107 and107′, which in this case are directed to chambers of theheart124. There are additional electrodes located at point109 in the right ventricle and distal electrodes109′ located in the right atrium. In the art, this is known as a simple dual chamber bipolar pacemaker. As shown, EMI can be undesirably coupled to leads107 and107′ where it can be conductive to theleadwires114 of thehermetic seal assembly120. Thefeedthrough capacitor element132 diverts the EMI conducted onleads114 into theconductive AIMD housing116 where it is dissipated as eddy currents or RF energy (EMI′) as simply coupled to surrounding body tissues. In any event, the EMI is prevented from reaching the delicateAIMD circuit boards122.

FIG. 7 is an isometric view of the quadpolar feedthrough capacitor132 previously described in the prior art pacemaker ofFIG. 6. The quad polar feedthrough capacitor has anoutside diameter metallization142 and four feedthrough holes all of which have insidediameter metallization144.

FIG. 8 is a sectional view taken from section8-8 ofFIG. 7 and illustrates the quad polar feedthrough capacitor interior electrode plates. There is a ground electrode plate set146 which is coupled to theoutside diameter metallization142. There are four different sets ofactive electrode plates148 which are each coupled to their own individual feedthrough hole134.

FIG. 9 is an exploded view of the quad polar feedthrough capacitor ofFIG. 7. Shown, are the four activeelectrode plate areas148 and theground electrode plates146. As previously described, these active and ground electrode plates are in interleaved relationship. There are also a number of blankceramic cover sheets147 added on top and bottom for mechanical strength and electrical insulation. Those skilled in the capacitor art will understand that a higher voltage capacitor could be built by interleaving additional blank electrodes between the active and ground electrode plates thereby building up the dielectric thickness. Typically, the dielectric material could be of barium titanate ceramic and could vary in dielectric constant k anywhere from 50 all the way up to several thousand.

FIG. 10 is the schematic diagram of the quad polar feedthrough capacitor ofFIG. 7. Again, as previously described for the unipolar capacitor ofFIG. 2 andFIG. 4, there is an undesirable resistance R_OXIDEas shown. Ideally, feedthrough capacitors are three-terminal devices that have no series inductance or series resistance. This is why they make such effective broadband electromagnetic interference filters. In general, a feedthrough capacitor can provide attenuation over a very broad frequency range extending even to 18 to 20 GHz. However, this oxide is highly undesirable as it can seriously degrade filter performance. In general, filter performance is described by the terms insertion loss or by attenuation. Both of these are generally measured in a balanced 50 ohm system with the measurement units in decibels.

FIG. 11 illustrates a prior art quad polar feedthrough capacitor that, in this case, is rectangular instead of round. It still has anoutside metallization142, but in this embodiment, instead of being all around a perimeter or outside diameter, it is shown only over a portion of the rectangular edge of the capacitor. This can actually be done in many ways. One way would be to extend themetallization142 around the entire perimeter of the capacitor.Feedthrough metallization144 is provided for each of the four feedthrough holes.FIG. 11 in combination withFIG. 12 illustrates an exploded assembly view wherein the capacitor ofFIG. 11 is designed to be mounted atop a prior art quad polar hermetic terminal ofFIG. 12. The hermetic terminal ofFIG. 12 has fourleadwires111,114, ahermetic insulator124 and a ferrule, generally oftitanium112. There is agold braze150 which forms a hermetic joint between theferrule112 and the generally aluminaceramic insulator124. There are four more gold brazes162 which join leadwire111 to the inside diameter holes of thehermetic insulator124.

FIG. 13 is taken from section13-13 fromFIG. 11. Shown are the fouractive electrode plates148 of the feedthrough capacitor.

FIG. 14 is taken from section14-14 fromFIG. 11 and illustrates theground electrode plate146 of the feedthrough capacitor.

FIG. 15 is an assembly view taken fromFIGS. 11 and 12 showing the quad polar rectangular feedthrough capacitor mounted onto the hermetic seal housing and theferrule112. Anelectrical connection152 is generally made with a thermal-setting conductive adhesive between thecapacitor metallization142 directly to theferrule112.

FIG. 16 is a sectional view taken from section16-16 fromFIG. 15. This sectional view goes through one of theleadwires111 and shows the interior ground electrode plate set146 and the active electrode plate set148. Theground electrode plates146 make electrical and mechanical contact to thecapacitor ground metallization142. There is anelectrical connection152 shown directly to the top surface of thetitanium ferrule112. There is across-hatched area164 which shows the formation of a very undesirable layer of titanium oxides. For simplicity, this layer is shown only on the top surface, but in reality, it would coat all of the surfaces of the titanium cross-section. As previously mentioned, the formation of this oxide can happen during initial gold brazing, during subsequent storage and handling of the overall filter feedthrough subassembly, or during laser welding of theferrule112 into theAIMD housing116. One particular problem is that the thermal-settingconductive adhesive152 always contains a certain amount of available oxygen. When a laser weld is formed to the AIMD housing, which is positioned to be placed inslot163, this significantly raises the temperature of thermal-settingconductive adhesive152. This is why a thermal-setting conductive polyimide is the connection material of choice, as a conductive polyimide is stable at temperatures well above 300 degrees C. This is in comparison to most epoxies which are only rated to about 230 degrees C. When this assembly is raised through laser welding to high temperature, oxygen can be released from a thermal-settingconductive material152 and then be formed as a titanium dioxide ortrioxide164 on theferrule112 of the hermetic seal.

FIG. 17 is the schematic diagram of the quad polar feedthrough capacitors previously illustrated inFIGS. 11, 15 and 16. Shown, is the undesirable R_OXIDEwhich is shown in series between the ideal feedthrough capacitor and ground, which is the same electrical potential as theAIMD housing116. As will be shown, the presence of this resistive oxide seriously degrades the filter performance.

FIG. 18 is taken from FIG. 20 of U.S. Pat. No. 6,765,779 which describes gold bond pads to eliminate the problem of attachment to oxides of titanium between the feedthrough capacitor outside diameter and its ground electrode plate sets. Referring toFIG. 18, one can see that there are novelgold braze pads165 that have been added. Referring toFIG. 12, one can see that thesegold braze pads165 are not present.

FIG. 19 shows that theelectrical connections152 between the capacitor'sground metallization142 is now directly made to this non-oxidizable noble pad. U.S. Pat. No. 6,765,779 is incorporated herein by reference. As is shown in this '779 patent, a preferred material for the oxideresistant pad165 is gold. In a particularly preferred embodiment, thisgold pad165 is continuous and is co-formed at the same time the hermetic seal (gold braze) is made to thealumina ceramic insulator160. In fact, this is a limitation of U.S. Pat. No. 6,765,779 in that thegold bond pad165 is always formed as part of the co-braze to thealumina ceramic insulator160.

FIG. 20 is generally taken from section20-20 fromFIG. 19. It is very similar toFIG. 16 except that thegold braze area165 has been enlarged to include the goldbond pad area165. Pure gold has a high melting point (1064° C.) which is above the allotropic transformation temperature of titanium (883° C.). Titanium is soluble in gold, particularly more so at elevated temperature. Elevated temperature maximizes titanium dissolution into gold. As previously noted, titanium is highly reactive to air readily forming surface oxides. Brazing to titanium, therefore, is generally performed at high vacuum. At high vacuum brazing temperatures, when a gold brazed joint164 165 is formed between, for example, a gold braze preform and a titanium ferrule, the titanium reacts with the gold to form a direct metallurgical bond to thetitanium ferrule112. As this direct metallurgical bond is gold-rich, it essentially retains the high conductivity of the gold and its oxide resistant properties. In this regard, the enlarged gold braze area surface, that is, the bonding pad that is formed is part of the oxide-resistant metallurgical bond. This enlarged gold braze area serves as the, electrical connection material that is connectable to thecapacitor ground metallization142. To summarize, a continuous electrical connection that is consistent in its conductivity over the service life of the device is made. The electrical connection is between thetitanium ferrule112 and the filtercapacitor ground metallization142 via theelectrical connection material152 directly to the non-oxidizablegold bond pad165.

FIG. 21 is very similar toFIG. 19, except in this case, the quad polar capacitor is round which is consistent with thefeedthrough capacitor132 previously illustrated in the cardiac pacemaker ofFIG. 6.

FIG. 22 is generally taken from section22-22 fromFIG. 21 and illustrates the capacitor's internal structure including its ground and active electrode plates. Importantly, outside diameterelectrical connection material152, which connects theoutside diameter metallization142 to theferrule112, is directly attached to thegold braze material165. The fact that some of this overlaps onto the titanium surface is not important. What is critical is that a suitable amount of theelectrical connection material152 is directly attached to an oxide resistant noble surface, such that an undesirable resistance can never develop.

FIG. 23 illustrates the schematic diagram of the improved rectangular quad polar feedthrough capacitor ofFIG. 19 and the round quad polar capacitor ofFIG. 21. One can see that we now have insignificant resistance in the connection from the feedthrough capacitor toground116, which is the overall shielded equipotential surface of the electromagnetically shieldedhousing116.

FIG. 24 is attenuation versus frequency curves which compares the ideal feedthrough capacitor to one that has undesirable ground electrode plate connection to an oxidized surface. One can see that the feedthrough capacitor with the resistive oxide R_OXIDEhas greatly reduced attenuation all across the frequency band as compared to the ideal feedthrough capacitor.

FIG. 25 illustrates a filtered feedthrough assembly of thepresent invention210. Illustrated is aferrule216 of the hermetic seal. The ferrule is generally of titanium. In this case, it has acontinuous slot217, which can receive the can halves of an active implantable medical device, such as a cardiac pacemaker. These titanium can halves are then laser welded to thetitanium ferrule216. In general, afeedthrough capacitor212 would be oriented towards the inside of the can to protect it from body fluids. In this case, there are novel roundplatinum iridium wires218, which have been laser welded220 directly to theferrule216.Laser weld220 could also be replaced by a resistance weld or a secondary braze operation at a lower temperature using for example, but not limited to, copper based brazing materials such as Cu—SiI or Ti—Cu—SiI, silver based brazing materials such as SiIvaloy (Ag—Cu—Zn) or Gapasil (Ag—Pd—Ga), gold based brazing materials such as Au—Cu, Au—Cu—Ag, or Au—Cu—Ni, or palladium based braze materials such as Pd—Ni—Si. Acapacitor ground metallization223 is attached using solder or thermal-settingconductive adhesives222 to theplatinum iridium wire218. The platinum iridium wire can actually be of any noble material including platinum, gold and its alloys, palladium and its alloys, silver and its alloys and combinations thereof.Leadwires214 through214′″ pass through the feedthrough capacitor and through the hermetic seal. This is best understood by referring toFIG. 26, which is taken from section26-26 from the structure ofFIG. 25.

FIG. 26 illustrates thelaser weld220, thenoble wire218 and the solder or thermal-settingconductive adhesive222. InFIG. 26, one can see the capacitor interior electrode plate stacks. A groundelectrode plate stack230 and an active electrode plate stack are designated by232′ and232′″ which are connected respectively toterminal pins214′ and214′″. (The preformed capacitor feedthrough hole, inside diameter metallization of the capacitor feedthrough hole and electrical connection material has been omitted for clarity. It is understood by one skilled in the art that various structures and techniques are used to connect the active electrode plates to the lead wires. In this case, theactive electrodes232 are shown directly contacting thelead214′. It will be appreciated that these other features which have been omitted incorporate part of the invention.) On the body fluid side of the capacitor, one can seegold brazes226 and228.Gold braze226 connects theferrule216 to thealumina insulator224 providing a robust mechanical and hermetically sealed joint.Gold braze228 forms a robust mechanical and hermetic seal between thealumina ceramic224 and theleads214.

Referring once again toFIGS. 25 and 26, one can see that theleadwire218 provides a very novel feature, that is,electrical connection material222 does not directly attach to theferrule216. The reason for this is that the ferrule is typically of titanium, which commonly forms titanium oxides. Titanium oxides are very resistive and can also act as semiconductors. This means that a direct connection to titanium would degrade the effectiveness of the capacitor ground electrode plate stack. Thenoble wire218 acts as an intermediate surface. By laser welding it to thetitanium ferrule216, one forms a very strong oxide resistant metallurgical bond. Now, the surface onwire218 is relatively oxide free. For example, it could be gold, platinum or the like which are oxide resistant at room temperatures. In fact, it would be preferable if thewire218 be pure platinum and not platinum iridium. The reason for this is that the iridium can form oxides.

Referring once again toFIG. 26, shown is that the gold brazes forming thehermetic seals226 and228 are on the body fluid side. There are a number AIMD manufacturers that prefer having the gold braze on the body fluid side. By having the gold braze in this location, however, making a connection to the capacitor's outside perimeter ordiameter metallization223 to the same gold braze surface becomes impossible. In other words, as previously described inFIG. 18, there is no possibility to provide thegold bond pad165, which is a contiguous part of thehermetic seal braze226. This is major driving feature of the present invention in that a methodology is provided so that the feedthrough capacitor can be properly grounded to an oxide resistant surface even when the gold brazes are disposed on the opposite side (the body fluid side).

FIGS. 27-28 are similar toFIGS. 25-26 but now show apeninsula structure244 formed as part of theferrule216. Aground wire242 is attached to thepeninsula244. As can be seen best in the cross-section ofFIG. 28, theground wire242 is not connected to theground electrode plates230. The ground electrode plates are still electrically coupled to themetallization223 which is then electrically coupled to theferrule216 through theweld220, thewire218 and the thermosetting conductive adhesive222 or solder.

Referring once again toFIG. 27A, one can see that the groundedpeninsula244, which is a continuous part of the machinedferrule216, is electrically attached viamaterial219 to the groundedpin242. The ground material could be a laser weld, a gold braze, a solder, a thermal-setting conductive adhesive or the like. In general,pin242 is provided as a convenience to the AIMD manufacturer to either ground the internal circuit board, or to provide an addition pacing vector to a conductor of an implanted lead (not shown) or both. The electrical ground attachment from thepeninsula244 to lead242 is very low in resistivity, meaning that it would also be applicable for high voltage implantable cardioverter defibrillator applications. In such an application, a very light shock current would flow through this ground joint to an external electrode (not shown).

FIG. 28A is an enlarged view of a new embodiment of the structure fromFIG. 28 taken fromlines28A-28A now showing thewire218 recessed into theferrule216. In this way thewire218 may be positioned and affixed in a more efficient manner.

FIG. 28B is an enlarged view of another embodiment of the structure fromFIG. 28 taken fromlines28B-28B now showing therectangular wire218 recessed into theferrule216. In this way therectangular wire218 may be positioned and affixed in a more efficient manner.

FIG. 28C shows a perspective view similar toFIG. 27A now with therecess231 and inserts233 clearly shown. Theinserts233 are placed in therecess231 before thewire218 is placed and may be gold metal, gold brazed or any of the material variations and connection methods already described herein.

FIG. 29 is similar toFIG. 25 and illustrates that the twowires218 could be replaced by a number ofpads234 as shown. In general, the pads could be formed as a continuous part (not shown) of the machining of theferrule216 or they could be added as a subsequent assembly by gold brazing or laser welding220 as shown. Thepads234 would be of the same noble materials previously described as for thewire218. This means that a convenient oxide resistantelectrical connection222 could be made using solder or thermal-setting conductive adhesives.

Throughout the invention, the intermediate biostable and oxide resistant intermediate structure, such aslead218 shown inFIG. 27 withpad234 as illustrated inFIG. 29, must have the following properties: 1) they must be weldable or brazable to thetitanium ferrule216; 2) this weld or braze joint must break through any oxides of titanium and form a metallurgical bond between thestructure218 or220 and theferrule216; and 3) the intermediate biostable wire ofpad234 must be connectable to the capacitor'sexternal metallization223. The number of connection methods to the capacitor's external metallization is limited. This includes solders, solder paste and all types of thermal-setting inductive adhesives. In general, although possible, it is not reliably possible to braze or weld directly to the capacitor'sexternal metallization223, hence this option is not a preferred embodiment. In summary, thebiostable wire218 or pad234 need not be platinum, but it can consist of a long list of metals that would meet the above criteria. Obvious choices would be gold, palladium, tantalum, and niobium. Additional non-limiting considerations include: tungsten, iridium, ruthenium, rhodium, silver, osmium, or combinations thereof. Other nonlimiting examples include platinum based materials such as platinum-rhodium, platinum-iridium, platinum-palladium, or platinum-gold, and naturally occurring alloys like platiniridium (platinum-iridium), iridiosmium and osmiridium (iridium-osmium).

FIG. 30 is a sectional view taken from section30-30 fromFIG. 29 illustrating that thepads234 and234′ are disposed on both sides of the capacitor. It will be obvious to those skilled in the art that they could also be disposed at the ends of the capacitor (not shown). It will be appreciated to one skilled in the art that the pads could be connected. For example, referring once again toFIG. 27,pads234 and234a could be filled in between so that there was one large continuous pad. These pads could also have holes in them to further facilitate the electrical attachment between the pad and the capacitorexternal ground metallization223.

FIG. 31 is a perspective view of another embodiment similar toFIGS. 25-30 now showing a different configuration ofpad234. Here,pad234 is shown in an L-shape. There is a hole in the bottom of the pad facilitating the laser weld or braze220 to theferrule216.FIG. 32 is a sectional view taken along line32-32 from the structure ofFIG. 31.

FIG. 33 is a perspective view of yet another embodiment of afeedthrough capacitor assembly210 similar toFIGS. 25-32. Here thepad234 is a long pad that spans the length of the long side of thecapacitor212. Thepad234 has a large hole to facilitate the placement and bonding of theconductive adhesive222.FIG. 34 is a sectional view taken from lines34-34 from the structure ofFIG. 33.

FIG. 34 is a sectional view taken from section34-34 fromFIG. 33. It shows thelong bracket234 cross-section along withlaser weld222.

FIG. 35 is similar toFIG. 25 except in this case there are moreterminal pins214. Accordingly, it is necessary that the oxide-free biostable wire220 be longer and have more laser welds222. This is because it would be undesirable to have a long distance between a filtered terminal pin and its associated ground. This is because inductance and resistance can build up across an internal ground plane, thereby degrading the RF filtered performance of a distal filtered pin.FIG. 36 is an exploded view of the structure ofFIG. 35. InFIG. 36, theground pin242 is shown laser welded or gold brazed into theferrule216 in thepeninsula area244. In this case, the capacitor is a conventional capacitor wherein the ground electrode plates are terminated223 with metallization disposed along the two long outside ends of thecapacitor212. In this case, there is no connection betweenterminal pin242 and the capacitor's groundelectrode plate stack230. In a different embodiment (not shown), a capacitor's ground electrode plates could be connected to this grounded pin as completely described in U.S. Pat. No. 6,765,779, the contents of which are incorporated herein by reference. Referring once again toFIGS. 35-37, an alternative is given wherein a direct connection toterminal pin242 and the grounding of the capacitor's electrode stacks230 is nonexistent. That is, the electrical connection is between thecapacitor metallization223 and thenoble wires218.

FIG. 37 is a sectional view taken from section37-37 fromFIG. 35 illustrating that any one of theactive pins214 passes through feedthrough holes near the center of thecapacitor212 in a staggered pattern where thepin214 makes contact with its own individual set of active electrode plates (not shown) or many active electrode plates. The ground electrode plates contact the capacitor's long-side perimeter metallization223 and then electrical attachment material, which can be solder or thermal-setting conductive adhesive, attaches thecapacitor ground metallization223 to thenoble wire218.

FIG. 38 is similar toFIG. 35, which illustrates an alternative method of grounding the capacitor'sground electrode stack230. Referring back toFIG. 36, one can see thenovel ferrule pedestal244 to whichground pin242 is electrically and mechanically attached. InFIG. 28,ground pin242 is electrically attached to theferrule216 and is thereby grounded in a similar manner as shown inFIG. 36. A novel L-shapedclip246′ is electrically attached toground pin242 and engages a portion of the capacitor'sexternal ground metallization223. This is best illustrated inFIG. 28, where theground clip246′ being electrically connected222 to the capacitor'sground metallization223 is shown.

Referring back toFIG. 38, illustrated isclip246′ disposed on the top surface of thecapacitor212. There is an insulatingstructure252 that is disposed on top ofcapacitor212. This can be a conformal coating of insulation, an insulation sheet with adhesive layer, or even an alumina ceramic thin sheet of insulation. For the case where thisinsulation sheet252 is alumina ceramic, it may have a cut-out pocket so that theclip246′ drops down into it and fits flush with the top of the insulatinglayer252. This would help to hold theclip246′ in place and to index it.

FIG. 39 shows theground electrode plate230 which does not make contact with theleadwires214 or the groundedwire242. Theground electrode plate230 makes contact withmetallization223 which is then in electrical contact withnovel pad246′.

FIG. 40 shows a multitude ofactive electrode plates232 electrically coupled to theleadwires214. Note that the groundedpin242 lacks anactive electrode plate232.

FIGS. 41-43 are very similar toFIGS. 28-30.FIGS. 41-43 show a different embodiment of thenovel pad246a.Pad246a is longer along the length of increasedmetallization223. This design would increase filter performance due to the shortened electrical pathways. In this way, the inductance across the ground planes of the capacitor is greatly reduced. This means thatouter pins214 will have improved attenuation and greater insertion loss than the structure previously illustrated inFIG. 38.

FIG. 44 is a sectional view for bothFIGS. 38 and 41. One can see better the peninsula or extension that attaches to theground wire242. It will be understood thatnovel pad246 could also extend over the opposite side metallization and also make electrical contact. This would further improve filter performance by lowering electrical pathway lengths.

FIGS. 45A, 45B and 45C illustrate various types of L-shapedclips246. InFIG. 45C, one can see the advantage of having a clip with anelliptical hole247 because this allowselectrical connection material222, which can be a solder or a thermal-setting conductive adhesive, to be placed on the outside of the clip and also inside the elliptical hole. This increases the electrical contact area and thereby reduces the resistance as well as improves mechanical strength.

FIGS. 46 and 47 are an alternative embodiment ofclip246b previously illustrated inFIGS. 38 and 41. Thenovel clip246b is under thecapacitor212 sandwiched between theferrule216 and thecapacitor212. A hole is also in theclip246b to facilitate placement ofconductive adhesive222.FIG. 47 is an exploded view that best shows the shape ofnovel clip246b.

In the alternative embodiment shown inFIG. 46, theclip246 is disposed underneath thecapacitor212 and electrically and mechanically attached directly to the peninsula structure. Having theclip246′ disposed underneath thecapacitor212, and then coming up on the side as is illustrated, would improve the RF performance of the capacitor. Effectively, this would shorten theground pin242 to almost zero thereby reducing the impedance and inductance of theground clip246′. A notch (not shown) could be put in theferrule216 of the hermetic terminal to facilitate the clip coming out through the bottom so that thecapacitor212 still would sit flush on top of theferrule structure216.

FIGS. 48-53 are similar toFIGS. 25-34 except that in this case pockets248 and noble metal inserts250 have been formed so that an oxide resistantelectrical attachment222 can be made between thecapacitor ground metallization223 and theferrule216. Analternative embodiment250′ is shown where first, a brazing perform, such as agold braze perform250a, is placed and then aplatinum cap250b is placed over it. Alternative metals may be used as noted earlier. In addition, instead of a braze250a, one could use a resistance weld or lower temperature brazes such as those listed previously with the Cu—SiI or Ti—Cu—SiI examples.Platinum pad250b would be slightly longer in the length direction and slightly longer in the width direction than the underlying pre-form150A. This overlaying would prevent it from reflowing and leaking out during a gold braze operation. In addition, thepad250b would protrude above the surface of the ferrule. This turns out to be very convenient during electrical attachment of the feedthrough capacitor (not shown) outsideperimeter metallization223. In other words, the protrudingpad250b would provide a convenient stop for a solder paste, a solder pre-form or a thermal-setting conductive adhesive (dispensed by robot). This is best understood by referring toFIGS. 48 and 49, which shows that apocket248 and248a are first formed at the time of manufacturing theferrule216 of thehermetic seal subassembly210. These pockets can be rectangular (as shown), can be rectangular with rounded ends or it can be round holes as illustrated as248a or even a continuous groove or slot as illustrated inFIG. 53 as248c. Into these pockets orgrooves248 can be placed anoble wire218 as previously described inFIG. 25, or amaterial250, such as CuSiI or TiCuSiI, gold or any other material as disclosed earlier that can form a metallurgically sound bond to titanium while at the same time, providing an oxide resistant surface to whichelectrical attachment222 can form a solid bond.

Referring once again toFIG. 49, one can see that there is an alternative arrangement similar to that previously described inFIG. 48. In this case, a circular gold braze pre-form250Ab could first be placed into thecounter-bore hole248a and then a platinum or equivalent cap250Aa could be placed over it. These could all be reflowed into place leaving a convenient area to make electrical attachment between the capacitorexternal ground metallization223, through the oxide resistant pad250Aa, through the braze material250Ab and, in turn, to theferrule216.

FIG. 50 is an isometric view of the quadpolar feedthrough capacitor212 shown mounted to the hermetically sealed ferrule assembly previously illustrated inFIG. 48. Shown is anelectrical attachment material222 between thecapacitor ground metallization223 that connects to the oxideresistant connection pads250,250′. Referring once again toFIG. 50, one can see that there ismetallization223 on both short ends of thecapacitor212. Thismetallization223 could extend along the long sides or, alternatively, along all perimeter sides of the capacitor. In the case where the length of theperimeter metallization223 is made longer, then additional pockets and oxideresistant pads250 would be required.

FIGS. 51 and 52 illustrate the ground and active electrode plate sets of thecapacitor212 previously illustrated inFIG. 50. InFIG. 51, shown is that theground electrode plate230 does not make contact with any of the terminal pins214. Themetallization223 contacts the ground electrode plate set230 on its left and right ends.FIG. 52 illustrates theactive electrode plates232. In this case, theactive electrode plates232 are connected to each one of the feedthrough terminal pins214.

FIG. 53 is the same ferrule as previously described inFIGS. 49 and 50 except that instead of a discrete number of machinedpads248, there is acontinuous groove248c formed around the entire perimeter of the capacitor. This would be filled with a gold braze, Cu—SiI or Ti—Cu—SiI or other material previously listed to form an oxide resistant connection area for the feedthrough capacitor (not shown). Afeedthrough capacitor212, in this case, would haveperimeter metallization223 along all four of its perimeter sides and either a continuous or a multiplicity of shortelectrical connections222 would be made between thecapacitor metallization223 and the gold braze or equivalent material that has been flowed in thetrough248c (not shown).

FIGS. 54 and 55 are yet another embodiment of the present invention. As shown inFIG. 54,gold films250b may be placed on top of theferrule216. Then aconductive sheet254 is laid overtop thegold films250b. In a brazing procedure the gold films or plates bond between theconductive sheet254 and theferrule216. Thecapacitor212 can be placed overtop theconductive sheet254 and then an electrical connection usingconductive adhesives222 can be made between theexternal metallization223 and theconductive sheet254. As shown inFIGS. 54 and 55, the metallization is around the entirety of thecapacitor212. This design would also reduce both the inductance and equivalent series resistance of thecapacitor212.

Although several embodiments have been described in detail for purposes of illustration, various modifications may be made to each without departing from the scope and spirit of the invention. Various features of one embodiment may be incorporated into another embodiment, as each embodiment is not exclusive of the other features taught and shown herein. Accordingly, the invention is not to be limited, except as by the appended claims.

Claims (33)

What is claimed is:

1. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:

a) an insulator of electrically non-conductive material, the insulator comprising an outer insulator outer surface extending longitudinally from a first an insulator first end to a second an insulator second end, wherein the insulator has at least one conductor bore extending there through to the first and second insulator first and second ends;

b) a ferrule of an electrically conductive material, the ferrule comprising a ferrule sidewall defining a ferrule opening, wherein the insulator is hermetically sealed to the conductive ferrule sidewall in the ferrule opening;

c) a conductor comprising an electrically conductive material extending from a first conductor first end to a second conductor second end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule;

d) a filter capacitor, comprising:

i) a dielectric comprising an outer a dielectric outer surface extending longitudinally from a first dielectric first end to a second dielectric second end;

ii) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and

iii) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends,

iv) wherein the second dielectric second end is disposed adjacent to the first insulator first end;

e) a first metallization electrically contacted to the at least one active electrode plate in the terminal in pin bore;

f) a first electrical connection electrically coupling the first metallization to the conductor extending through the terminal pin bore in the dielectric;

g) a second metallization electrically contacted to the at least one ground electrode plate at at least a portion of the outer dielectric outer surface; and

h) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:

i) at least one oxide-resistant metal noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the noble-metal metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof;

ii) a first conductive material electrically and physically coupling a first portion of the oxide-resistant metal at least one noble-metal addition directly to the ferrule; and

iii) a second conductive material electrically and physically coupling a second portion of the oxide-resistant metal at least one noble-metal addition to the second metallization at the outer dielectric outer surface of the filter capacitor,

iv) wherein the first and second conductive materials are different.

2. The assembly ofclaim 1, wherein the oxide-resistant metal at least one noble-metal addition comprises a different material as compared to the ferrule.

3. The assembly ofclaim 1, wherein the oxide-resistant metal addition comprises a noble metal.

4. The assembly ofclaim 1, wherein the oxide-resistant metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof.

5. The assembly ofclaim 1, wherein the first conductive material is a weld portion of the oxide-resistant metal at least one noble-metal addition electrically and physically coupling to the ferrule.

6. The assembly ofclaim 1, wherein the first conductive material comprises a brazed metal electrically and physically coupling the oxide-resistant metal the at least one noble-metal addition to the ferrule.

7. The assembly ofclaim 6, wherein the brazed metal comprising the oxide-resistant metal addition is selected from the group consisting of gold, gold-based metal, platinum, platinum based metal, palladium, palladium based metal, silver, silver based metal, gold-palladium, gold-boron, and palladium silver.

8. The assembly ofclaim 1, wherein the conductor comprises a leadwire.

9. The assembly ofclaim 8, wherein the leadwire is selected from the group consisting of platinum, palladium, silver, and gold.

10. The assembly ofclaim 1, wherein the first side of the insulator is flush with the ferrule adjacent to the second dielectric second end of the filter capacitor.

11. The assembly ofclaim 1, wherein the insulator comprises an alumina substrate comprised of at least 96% alumina and the conductor comprises a substantially closed pore and substantially pure platinum fill disposed within the conductor bore and extending from the first insulator first end to the second insulator second end of the alumina substrate.

12. The assembly ofclaim 11, wherein the platinum fill forms a tortuous and mutually conformal knitline or interface at the hermetic seal to the alumina substrate comprising the insulator, and wherein the hermetic seal has a leak rate that is no greater than 1×10⁻⁷std cc He/sec.

13. The assembly ofclaim 12, wherein the alumina dielectric substrate and the platinum fill are characterized as the alumina dielectric substrate being in a green state having a first inherent shrink rate during a heat treatment that is greater than a second inherent shrink rate of the platinum fill in the green state during the heat treatment.

14. The assembly ofclaim 1, wherein the oxide-resistant metal the at least one noble-metal addition is selected from the group consisting of a wire, a pad, an L-shaped pad, and an L-shaped pad with cutouts.

15. The assembly ofclaim 1, including a ground wire disposed through both the insulator and the dielectric of the filter capacitor, where the ground wire is not electrically coupled to the at least one active and ground electrode plates, but is electrically coupled to the ferrule.

16. The assembly ofclaim 15, wherein the ferrule comprises an integrally formed conductive peninsula, and wherein the ground wire is electrically coupled to the peninsula.

17. The assembly ofclaim 1, wherein the feedthrough capacitor has a resonant frequency above 400 MHz.

18. The assembly ofclaim 1, wherein the feedthrough capacitor has a capacitance of from 300 picofarads to 10,000 picofarads.

19. The assembly ofclaim 1, wherein the second conductive material is selected from a solder and a thermal-setting conductive adhesive.

20. The assembly ofclaim 1, wherein the first and second conductor first and second ends are spaced from the respective first and second insulator first and second ends.

21. The assembly ofclaim 1, wherein the at least one oxide-resistant metal noble-metal addition is received in a pocket in the ferrule.

22. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:

a) a ferrule comprising a conductive peninsula or extension;

b) an insulator hermetically sealed to the conductive ferrule;

c) a conductor hermetically sealed and disposed through the insulator in non-conductive relation to the conductive ferrule between a body fluid side and a device side;

d) a feedthrough capacitor located on the device side, the feedthrough capacitor comprising a first and a second end metallization, wherein the first end metallization is connected to at least one active electrode plate and wherein the second end metallization is connected to at least one ground electrode plate, wherein the at least one active electrode plate is interleaved and disposed parallel to the at least one ground electrode plate, wherein the at least one active and ground electrode plates are disposed within a capacitor dielectric;

e) a first low impedance electrical connection between the first end metallization and the conductor;

f) a ground conductor disposed through the feedthrough capacitor in non-conductive relation with the at least one ground and active electrode plates, where the ground conductor is electrically coupled to the conductive peninsular peninsula or extension; and

g) an oxide-resistant metal addition attached directly at one end to the ground conductor and connected at the other end to the second end metallization of the feedthrough capacitor.

23. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:

a) an insulator of electrically non-conductive material, the insulator comprising an outer insulator surface extending longitudinally from a first an insulator first end to a second an insulator second end, wherein the insulator has at least one conductor bore extending there through to the first and second insulator first and second ends;

b) a ferrule of an electrically conductive material, the ferrule comprising' a ferrule sidewall including a peninsula and defining a ferrule opening, wherein the insulator is hermetically sealed to the conductive ferrule in the ferrule opening;

c) a conductor comprising an electrically conductive material extending from a first conductor first end to a second conductor second end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule;

d) a filter capacitor located adjacent to the first insulator first end, the filter capacitor comprising:

i) a dielectric comprising an outer a dielectric outer surface extending longitudinally from a first dielectric first end to a second dielectric second end;

ii) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and

iii) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends,

iv) wherein the second dielectric second end is disposed adjacent to the first insulator first side;

e) a first metallization electrically contacted to the at least one active electrode plate in the terminal pin bore;

f) a first electrical connection electrically coupling the first metallization to the conductor extending through the terminal pin bore in the dielectric;

g) a second metallization electrically contacted to the at least one ground electrode plate at the outer dielectric outer surface;

h) a ground conductor disposed through the filter capacitor in non-conductive relation with the at least one ground and active electrode plates, wherein the ground conductor is electrically coupled to the conductive peninsula; and

i) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:

i) at least one noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the noble-metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof;

ii) a first conductive material electrically and physically coupling a first portion of the oxide-resistant metal noble-metal addition to the ferrule; and

iii) a second conductive material electrically and physically coupling a second portion of the noble metal noble-metal addition to the second metallization at the outer dielectric surface of the filter capacitor,

iv) wherein the first and second conductive materials are different.

24. The assembly ofclaim 23, wherein the first conductive material is a weld portion of the oxide-resistant metal noble-metal addition electrically and physically coupling to the ferrule.

25. The assembly ofclaim 23, wherein the first conductive material comprises a brazed metal electrically and physically coupling the oxide-resistant metal noble-metal addition to the ferrule.

26. The assembly ofclaim 23, wherein the second conductive material is selected from a solder and a thermal-setting conductive adhesive.

27. The assembly ofclaim 23, wherein the second conductive material does not contact the conductive material.

28. An implantable medical device, comprising:

a) a thermally or electrically conductive AIMD housing containing at least one of tissue-stimulating and biological-sensing circuits for the AIMD, wherein the housing has an opening providing passage from a body fluid side outside the housing to a device side inside the housing; and

b) a filtered feedthrough assembly hermetically sealed in the housing opening, the filtered feedthrough assembly comprising:

i) an insulator of electrically non-conductive material, the insulator comprising an outer insulator outer surface extending from a body fluid side an insulator body fluid side end to a device side an insulator device side end, wherein the insulator has at least one conductor bore extending there through to the body fluid and device side insulator body fluid and device side ends;

ii) a ferrule of an electrically conductive material electrically and physically connected to the housing in the housing opening, the ferrule comprising a ferrule sidewall having an inner a ferrule inner sidewall surface defining a ferrule opening and an outer a ferrule outer sidewall surface hermetically sealed to the device housing, wherein the insulator is received in the ferrule opening and hermetically sealed to the ferrule at the inner ferrule inner surface;

iii) a conductor comprising an electrically conductive material extending from a body fluid side conductor body fluid side end to a device side conductor device side end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule;

iv) a filter capacitor, comprising:

A) a dielectric comprising an outer a dielectric outer surface extending from a first dielectric first end to a second dielectric second end;

B) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and

C) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends,

D) wherein the second end of the capacitor dielectric is located adjacent to the device side of the insulator;

v) a first metallization electrically contacted to the at least one active electrode plate in the terminal pin bore;

vi) a first electrical connection electrically coupling the first metallization to the conductor in the terminal pin bore extending through the dielectric;

vii) a second metallization electrically contacted to the at least one ground electrode plate at the outer dielectric outer surface; and

viii) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:

A) at least one oxide-resistant metal noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the at least one noble-metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof;

B) a first conductive material electrically and physically coupling a first portion of the oxide-resistant metal at least one noble-metal addition directly to the ferrule hermetically sealed to the device housing; and

C) a second conductive material electrically and physically coupling a second portion of the oxide-resistant metal at least one noble-metal addition to the second metallization at the outer dielectric outer surface of the filter capacitor,

D) wherein the first and second conductive materials are different.

29. The implantable medical device ofclaim 28, wherein the first conductive material is a weld portion of the oxide-resistant metal at least one noble-metal addition electrically and physically coupling to the ferrule.

30. The implantable medical device ofclaim 28, wherein the first conductive material comprises a brazed metal electrically and physically coupling the oxide-resistant metal at least one noble-metal addition to the ferrule.

31. The implantable medical device ofclaim 28, wherein the second conductive material is selected from a solder and a thermal-setting conductive adhesive.

32. The implantable medical device ofclaim 28, wherein the second conductive material, does not contact the ferrule.

33. A hermetically sealed filtered feedthrough assembly for an implantable medical device, the filtered feedthrough assembly comprising:

a) an insulator of electrically non-conductive material, the insulator comprising an outer insulator outer surface extending from a first an insulator first end to a second an insulator second end, wherein the insulator has at least one conductor bore extending there through to the first and second insulator first and second ends;

b) a ferrule of an electrically conductive material, the ferrule comprising a ferrule sidewall defining a ferrule opening, wherein the insulator is hermetically sealed to the conductive ferrule sidewall in the ferrule opening;

c) a conductor comprising an electrically conductive material extending from a first conductor first end to a second conductor second end, wherein the conductor is hermetically sealed and disposed through the at least one conductor bore in the insulator and in a non-conductive relation with the conductive ferrule;

d) a filter capacitor, comprising:

i) a dielectric comprising an outer a dielectric outer surface extending from a first dielectric first end to a second dielectric second end;

ii) at least one active electrode plate supported by the dielectric in an interleaved, partially overlapping relationship with at least one ground electrode plate; and

iii) at least one terminal pin bore extending through the dielectric to the first and second dielectric first and second ends,

iv) wherein the second dielectric second end is disposed adjacent to the first insulator first end;

e) a first metallization electrically contacted to the at least one active electrode plate in the terminal pin bore;

f) a first electrical connection electrically coupling the first metallization to the conductor extending through the terminal pin bore in the dielectric;

g) a second metallization electrically contacted to the at least one ground electrode plate at the outer dielectric outer surface; and

h) a second electrical connection electrically coupling the second metallization to the ferrule, wherein the second electrical connection comprises:

i) at least one noble-metal addition supported by the ferrule adjacent to the second metallization, wherein the at least one noble-metal addition is selected from the group consisting of gold, platinum, palladium, silver, and combinations thereof;

ii) a weld portion of the oxide-resistant metal at least one noble-metal addition electrically and physically coupling to the ferrule; and

iii) a solder or thermal-setting material electrically and physically coupling a second portion of the oxide-resistant metal at least one noble-metal addition to the second metallization at the outer dielectric outer surface of the filter capacitor.

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