Patent Description:
Feedthroughs typically include an insulator (e.g., a ceramic material) and electrical conductors or feedthrough pins which extend through the insulator to provide electrical pathways between the exterior and the hermetically sealed interior. A frame-like metal ferrule is disposed about a perimeter surface of the insulator, with the ferrule and insulator being joined to one another, such as by a brazing or soldering process. The ferrule, in-turn, is arranged to fit within a corresponding opening in the metal housing, and is mechanically and hermetically attached to the housing, typically via welding (e.g., laser welding), with the insulator electrically insulating the feedthrough pins from one another and from the metal ferrule and housing. For example, <CIT> refers to an apparatus for providing electrical communication through a housing that is metallic and hermetically sealed. <CIT>describes a feedthrough of an implantable medical electronic device.

However, mechanical strains resulting from the welding of the ferrule to the housing can potentially damage the insulator and the interface between the insulator and the ferrule, and thereby compromise the hermetic seal between the feedthrough and the housing. For these and other reasons there is a need for the example ferrules described by the disclosure.

The accompanying drawings are included to provide a further understanding of embodiments and are incorporated in and constitute a part of this specification.

In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as "top," "bottom," "front," "back," "leading," "trailing," etc., is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the invention is defined by the appended claims.

It is to be understood that the features of the various exemplary embodiments described herein may be combined with each other, unless specifically noted otherwise.

<FIG> is a block and schematic diagram generally illustrating an example of an implantable medical device <NUM> (e.g., a cardiac pacemaker) in which a feedthrough device including a ferrule in accordance with the disclosure may be employed. Implantable medical device <NUM> includes a hermetically sealed metal case or housing <NUM>, typically formed of titanium, which defines a hermetically sealed interior space <NUM> in which device electronics <NUM> are disposed and protected from fluids of the body fluid side <NUM> external to housing <NUM>. A header <NUM> attaches to housing <NUM> and includes a connector block <NUM> which typically includes one or more sockets for connecting to one or more sensing and/or stimulating leads <NUM> that extend between implantable medical device <NUM> and desired regions of the body (e.g., the human heart and brain). A feedthrough device <NUM> establishes electrical pathways or connections through housing <NUM> that maintain the integrity of hermetically sealed interior space <NUM> and provide electrical connection of leads <NUM> to internal device electronics <NUM>.

<FIG> is a cross-sectional view generally illustrating an example of a known, prior art feedthrough device <NUM>, such as for use with medical device <NUM> of <FIG>, including an insulator assembly <NUM> having an insulator body <NUM> through which pass a number of feedthrough pins or conducting elements <NUM>, and an example of a known ferrule <NUM> for connecting to insulator body <NUM> and for connecting feedthrough device <NUM> to housing <NUM> of medical device <NUM>.

According to one example, as illustrated, ferrule <NUM> includes a metal frame body <NUM> to which insulator <NUM> is attached, and which is to attach to metal housing <NUM> (e.g., see <FIG> below). Although not explicitly illustrated in the cross-sectional view of <FIG>, frame body <NUM> is a frame-like or ring-like body having an interior perimeter surface <NUM> which defines an opening <NUM> to receive insulator body <NUM> and to which insulator body <NUM> is attached. Frame-like metal body <NUM> may be of any suitable geometric shape (e.g., circular, oval, rectangular, etc.). In examples, such as illustrated by <FIG>, ferrule <NUM> may include one or more flanges extending from frame body <NUM>, such as insulator flange <NUM> for assisting in connection to insulator body <NUM>, and housing flange <NUM> for assisting in connection to housing <NUM> of medical device <NUM>. Ferrule <NUM> comprises a bio-compatible material (e.g., titanium) which is to be mechanically and hermetically attached to housing <NUM>, such as by laser welding, or similar techniques (see <FIG>).

In one example, insulator body <NUM> includes a number of openings or vias <NUM> through which conducting elements <NUM> pass, where conducting elements <NUM> are formed of an electrically conductive material to provide electrically conductive pathways from the external body fluid side <NUM> of housing <NUM> to hermetically sealed interior space <NUM>. Insulator body <NUM> is formed of a non-electrically conductive material, such as a ceramic material (e.g., aluminum oxide (Al<NUM>O<NUM>)), for example, and electrically isolates conducting elements <NUM> from one another and from ferrule <NUM> (and housing <NUM>).

In one example, a perimeter surface of insulator body <NUM> is metalized (through a sputter coating process, for example) to provide a thin metal coating <NUM> thereon. In one example, ferrule <NUM> is joined to insulator <NUM> via metal coating <NUM> using a braze <NUM>, such as of gold, for example, to form a biocompatible and hermetic seal. In one example, the interior surfaces of vias <NUM> are similarly coated with thin metal coating <NUM> and a braze <NUM> (e.g. gold) is used to couple conducting elements <NUM> to insulator <NUM> to form a biocompatible and hermetic seal.

With reference to <FIG>, known, prior art feedthrough <NUM> is attached to housing <NUM> by welding ferrule <NUM> to housing <NUM>, such as by laser welding (as indicated by lasers <NUM>), where the welded connection forms a hermetic seal between feedthrough <NUM> and housing <NUM>. In one example, both ferrule <NUM> and housing <NUM> may be made of titanium. In other examples, other suitable biocompatible and weld-compatible materials may be employed.

While welding is effective at forming a hermetic seal between ferrule <NUM> and housing <NUM>, the molten metal at weld joint <NUM> contracts as it cools. With housing <NUM> being generally stationary relative to ferrule <NUM>, the contraction of weld joint <NUM> results in horizontal and/or vertical forces, illustrated as Fh and Fv, being applied to ferrule <NUM>, with Fh pulling ferrule <NUM> toward housing <NUM>, and Fv pulling ferrule <NUM> toward interior space <NUM> of housing <NUM>. If contraction forces Fh and Fv are great enough, ferrule <NUM> may pull away and separate from insulator body <NUM>, and may even fracture insulator body <NUM>, thereby compromising the hermitic seal between feedthrough <NUM> and housing <NUM> and rendering medical device <NUM> unusable.

<FIG> is a cross-sectional view illustrating a portion of a ferrule <NUM> employing a strain relief spacer for use with an implantable medical device, in accordance with one example of the disclosure. In one example, ferrule <NUM> includes a first frame body <NUM> having a first perimeter surface, such as perimeter surface <NUM>, to make a brazed connection to a first medical device component <NUM>, and a second frame body <NUM> having a first perimeter surface, such as perimeter surface <NUM>, to make a welded connection to a second medical device component <NUM>. A spacer flange <NUM> extends between and connects a second perimeter surface of first frame body <NUM>, such as perimeter surface <NUM>, with second perimeter surface of second frame body <NUM>, such as perimeter surface <NUM>, so as to space and cantilever second frame body <NUM> from first frame body <NUM>. In one example, first frame body <NUM>, second frame body <NUM>, and extension flange <NUM> are formed of a single, monolithic piece of material (e.g., titanium). Although not explicitly illustrated in the cross-sectional view of <FIG>, ferrule <NUM> is a frame-like or ring-like body (e.g., see <FIG> and <FIG>).

In one example, , spacer flange <NUM> has a thickness, Th1, between a top surface 100a and a bottom surface 100b, first frame body <NUM> has a thickness, Th2, between a bottom surface <NUM> and a top surface <NUM>, and second frame body <NUM> has a thickness, Th3, between a top surface 95a and a top surface 95b. In one example, thickness Th1 of spacer flange <NUM> is less than thickness Th2 of first frame body <NUM>, and less than thickness Th3 of second frame body <NUM>, such that a gap, g, is formed between first frame body <NUM> and second frame body <NUM>. As will be described in greater detail below, by making spacer flange <NUM> thinner and, thus, less mechanically rigid than first frame body <NUM>, spacer flange <NUM> deflects relative to first frame body <NUM> in response to forces being applied to second frame body <NUM> to reduce transmission of forces from second frame <NUM> to first frame <NUM>, such as weld strain from the second frame body <NUM> to the first frame body <NUM>, for example, and thereby reduce potential strain on a braze connection, for example.

As will be described in great detail below, first medical device component <NUM> may be any number of components, such as a medical device housing and a feedthrough assembly, for example, and second medical device component <NUM> may be any number of components, such as a medical device housing or another metallic component, such as a ferrule of another component, for example.

<FIG> generally illustrate one example of a ferrule <NUM>, in accordance with the application, which, as will be described in greater detail below, reduces or inhibits transmission of mechanical strain to insulator body <NUM> and to the braze joint between ferrule <NUM> and insulator body <NUM> created by the welding of ferrule <NUM> to housing <NUM>.

<FIG> is a cross-sectional view of ferrule <NUM>, where ferrule <NUM> includes a first frame body <NUM> having a perimeter surface <NUM> for attachment to insulator assembly <NUM>, and a second frame body <NUM> having a perimeter surface <NUM> for attachment to a housing <NUM>. In one example, as illustrated, perimeter surface <NUM> of first frame body <NUM> is continuous interior surface defining an interior opening <NUM> to receive insulator assembly <NUM>, and perimeter surface <NUM> of second frame body <NUM> is a continuous exterior surface for connecting to housing <NUM> (e.g., via welding). A spacer flange <NUM> extends between and connects first frame body <NUM> with second frame body <NUM> so as to space second frame body <NUM> from first frame body <NUM>. In one example, first frame body <NUM>, second frame body <NUM>, and extension flange <NUM> are of a single, monolithic piece of material (e.g., titanium).

<FIG> is an enlarged cross-sectional view of a portion of ferrule <NUM>. In one example, as illustrated, spacer flange <NUM> extends between an exterior perimeter surface <NUM> of first frame body <NUM>, which is opposite perimeter surface <NUM>, to a perimeter surface <NUM> of second frame body <NUM>, which is opposite perimeter surface <NUM>, where perimeter surface <NUM> represents an exterior perimeter surface of second frame body <NUM> and perimeter surface <NUM> represents an interior perimeter surface of second frame body <NUM>. While extension flange <NUM> is illustrated in <FIG> as extending from exterior perimeter surface <NUM> in a fashion flush with a bottom surface <NUM> of first frame body <NUM>, in other examples, extension flange <NUM> may extend from exterior perimeter surface <NUM> at any position between bottom surface <NUM> and top surface <NUM>. Additionally, in other examples, extension flange <NUM> may extend from a perimeter surface of first frame body <NUM> other than a perimeter surface which is opposite the perimeter surface <NUM> to which housing <NUM> is to be attached (e.g., see <FIG>).

Continuing with <FIG>, first frame body <NUM> has depth, D1, between perimeter surfaces <NUM> and <NUM>, and second frame body <NUM> has a depth, D2, between perimeter surfaces <NUM> and <NUM>. In one example, as illustrated, D2 < D1. Additionally, as described above, spacer flange <NUM> has a thickness, Th1, between top and bottom surfaces 100a and 100b, while first and second frame bodies <NUM> and <NUM>, respectively, have thicknesses Th2 and Th3. In one example, as illustrated, spacer flange <NUM> extends perpendicularly to perimeter surfaces <NUM> and <NUM>. In one example, Th1 < Th3 < Th2, such that first and second frame bodies <NUM> and <NUM> and spacer flange <NUM> together form a channel <NUM> that spaces second frame body <NUM> from first frame body <NUM> body a gap distance, g, of channel <NUM>.

As will be described in greater detail below (e.g., <FIG>), by spacing second frame body <NUM> from first frame body <NUM> via spacer flange <NUM>, and by making second frame body <NUM> and spacer flange <NUM> less mechanically rigid relative to first frame body <NUM> (e.g., D2<D1; Th1<Th3<Th2), ferrule <NUM>, according to the application, reduces the transfer of mechanical strain to first frame body <NUM> and the braze joint with insulator body <NUM> caused by weld forces Fh and Fv introduced by welding of second frame body <NUM> to housing <NUM>.

<FIG> is top view of ferrule <NUM> of <FIG> illustrating interior opening <NUM> defined by interior perimeter surface <NUM> of first frame body <NUM>, and second frame body <NUM> spaced from first frame body <NUM> by gap, g, by spacer flange <NUM>. In the example implementation of <FIG>, first and second frame bodies <NUM> and <NUM> are concentric relative to one another, with first frame body <NUM> representing a first or inner ferrule for connection to insulator body <NUM>, and second frame body <NUM> representing a second or outer ferrule for connection to housing <NUM>. In other implementations, such as illustrated by <FIG> below, first and second frame bodies <NUM> and <NUM> may be parallel with one another rather than concentric. Also, while illustrated as being generally rectangular in shape in <FIG>, first and second frame bodies <NUM> and <NUM>, and s spacer flange <NUM> may have any suitable geometric shape (e.g., oval, circular). By employing a first ferrule (e.g., first frame body <NUM>) for connection to the insulator body, and a second ferrule (e.g., second frame body <NUM>) for connection to the housing, and by cantilevering the second ferrule from the first ferrule (via spacer flange <NUM>) and making the cantilever and second ferrule less mechanically rigid than the first ferrule, ferrule <NUM>, as disclosed herein, reduces mechanical strain on the connection between the first ferrule and the insulator body generated by welding of the second ferrule to the housing.

<FIG> is a cross-sectional view illustrating another example of ferrule <NUM>, in accordance with the disclosure. The implementation of <FIG> is similar to the example of <FIG>, except that first frame body <NUM> includes an insulator flange <NUM> extending from interior perimeter surface <NUM> to provide assistance in attachment of insulator body <NUM> to first frame body <NUM>, and second frame body <NUM> includes a housing flange <NUM> to provide assistance in attachment of housing <NUM> to second frame body <NUM>. Additionally, spacer flange <NUM> is not disposed flush with bottom surface <NUM> of first frame body <NUM>, but is positioned along exterior perimeter surface <NUM> between bottom and top surfaces <NUM> and <NUM> such that housing <NUM> is generally flush with insulator body <NUM>.

<FIG> are cross-sectional views generally illustrating the welding of feedthrough device <NUM> employing ferrule <NUM> of <FIG>, in accordance with the disclosure, to housing <NUM>, such as via laser welding (as indicated by lasers <NUM>). <FIG> is an enlarged view illustrating portions of feedthrough device <NUM> of <FIG>. In one example, if horizontal weld force, Fh, generated by cooling and contraction of weld joint <NUM> is great enough, horizontal force Fv results in enough torque being applied to second frame body <NUM> to deflect frame body <NUM> about its base <NUM> where it joins extension flange <NUM>, as indicated by deflection angle θ1. In one example, the magnitude of horizontal force, Fh, needed to generate enough torque to deflect second frame body <NUM> about base <NUM> is less than an amount of horizontal force, Fh, needed to apply enough torque to first frame body <NUM> (via spacer flange <NUM>) to damage braze joint <NUM> between first frame body <NUM> and insulator body <NUM> and/or to fracture insulator body <NUM>.

With reference to <FIG>, if vertical weld force, Fv, generated by cooling and contraction of weld joint <NUM> is great enough, vertical force Fv results in enough torque being applied to second frame body <NUM> to deflect spacer flange <NUM> about its base <NUM> where it joins first frame body <NUM>, as indicated by deflection angle θ2. In one example, the magnitude of vertical force, Fv, needed to generate enough torque to deflect spacer flange <NUM> about base <NUM> is less than an amount of vertical force, Fv, needed to apply enough torque to first frame body <NUM> to damage braze joint <NUM> between first frame body <NUM> and insulator body <NUM> and/or to fracture insulator body <NUM>.

By employing second frame body <NUM> for connecting to housing <NUM>, and by spacing second frame body <NUM> from first frame body <NUM> and making second frame body <NUM> and spacer flange <NUM> less mechanically rigid relative to first frame body <NUM> and braze joint <NUM>, ferrule <NUM>, in accordance with the application, reduces transmission of mechanical strain to first frame body <NUM>, braze joint <NUM>, and insulator body <NUM>. Instead, such mechanical strain is relieved via deflection of second frame body <NUM> and spacer flange <NUM> by horizontal and vertical weld forces Fh and Fv, with weld joint <NUM> continuing to provide a hermetic seal between housing <NUM> and second frame body <NUM>.

<FIG> is a cross-sectional view generally illustrating another example of ferrule <NUM>, in accordance with the example. In the example implementation of <FIG>, second frame body <NUM> extends to a height, H1, above housing flange <NUM> which is greater than a thickness, Th4, of housing <NUM> to better enable successful welds to be made between second frame body <NUM> and housing <NUM> when housing <NUM> is non-planar, as illustrated by the gap, g2, between housing flange <NUM> and housing <NUM> on the right-hand side of <FIG>. In one example, when an offset distance, Do, between housing <NUM> and top surface <NUM> of second frame body <NUM> does not exceed <NUM>% of the thickness, Th4, of housing <NUM>, a successful weld is possible between housing <NUM> and second frame body <NUM>.

<FIG> respectively illustrate cross-sectional and top views generally illustrating another example of ferrule <NUM>, in accordance with the disclosure. In the example implementation of <FIG>, rather than being concentrically positioned relative to one another, such as illustrated by <FIG>, first and second frame bodies <NUM> and <NUM> are positioned parallel with one another. Rather than extending from a perimeter surface of first frame body <NUM> which is opposite interior perimeter surface <NUM> to which insulator body <NUM> is to be connected, spacer flange <NUM> extends from bottom surface <NUM>. Deflection of second frame body <NUM> and spacer flange <NUM> in response to weld forces resulting from welding of housing <NUM> to exterior perimeter surface <NUM> of frame body <NUM> is similar to that described above by <FIG>.

Claim 1:
A ferrule (<NUM>, <NUM>) for an implantable medical device (<NUM>), the ferrule (<NUM>, <NUM>) comprising a first frame body (<NUM>) to attach to an insulator assembly (<NUM>) of the implantable medical device (<NUM>) and characterized by:
a second frame body (<NUM>) to attach to a housing of the implantable medical device (<NUM>); and
a spacer flange (<NUM>) that connects between and cantilevers the second frame body (<NUM>) from the first frame body (<NUM>), the spacer flange (<NUM>) to deflect relative to the first frame body (<NUM>) in response to forces applied to the second frame body (<NUM>) to limit transfer of forces from the second frame body (<NUM>) to the first frame body (<NUM>).