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, for example. The ferrule, in-turn, is arranged to fit within a corresponding opening in the metal housing and is attached thereto, typically via welding (e.g., laser welding), to form a hermetic seal, where the insulator serves to electrically insulate the feedthrough pins from one another and from the metal ferrule and housing. For example, feedthroughs are known from <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

However, non-planarity of the housing surface about the opening in which the feedthrough device is mounted may result in a weld failure between the ferrule and housing such that a hermetic seal is not achieved. For these and other reasons there is a need for a ferrule in accordance with the teachings of 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) suitable for employing a feedthrough device including a ferrule in accordance with examples of the disclosure. 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>. Feedthrough device <NUM> includes an insulator assembly <NUM> having an insulator body <NUM> through which a number of feedthrough pins or conducting elements <NUM> pass, 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>. Ferrule <NUM> comprises a bio-compatible material, such as titanium, which is to be mechanically and hermetically attached to housing <NUM>, such as by laser welding, or similar techniques (see <FIG>, for example).

According to one example, ferrule <NUM> includes a metal frame body <NUM> having an interior perimeter wall or surface <NUM>, an exterior perimeter wall or surface <NUM>, an upper perimeter surface <NUM> (to face body fluid side <NUM>, see <FIG>), and a lower perimeter surface <NUM> (to face interior space <NUM>). Although not illustrated by the cross-sectional view of <FIG>, metal frame body <NUM> is a continuous ring-like or frame-like structure having any suitable geometric shape (e.g., circular, oval, rectangular, etc.), with interior perimeter surface <NUM> defining an interior opening <NUM> which is configured to receive insulator assembly <NUM>. Ferrule <NUM> includes a housing flange <NUM> which extends outwardly from exterior perimeter surface <NUM> (away from interior opening <NUM>), where housing flange <NUM> is to be welded (such as via laser welding) to housing <NUM> of implantable medical device <NUM> (see <FIG>). Ferrule <NUM> further includes an insulator flange <NUM> extending perpendicularly inwardly from interior perimeter surface <NUM> (toward interior opening <NUM>) to assist in the connection of insulator assembly <NUM> to ferrule <NUM>.

As described above, conducting elements, or vias, <NUM> pass through insulator body <NUM> in a hermetically sealed fashion to transmit electrical signals between 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 serves to electrically isolate 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 there between.

<FIG> is a cross-sectional view illustrating an example of the known, prior art attachment of feedthrough device <NUM> to housing <NUM> via laser welding housing, as indicated by lasers <NUM>. According to one example, as illustrated, feedthrough device <NUM> is first positioned within an opening <NUM> in housing <NUM> such that a lower surface <NUM> of flange <NUM> faces exterior surface <NUM> of housing <NUM>. Laser <NUM> then melts portions of housing flange <NUM> and housing <NUM> such that, upon cooling, the molten portions join together and solidify to form a weld <NUM> that creates a hermetic seal between ferrule <NUM> and housing <NUM> about the exterior perimeter of ferrule <NUM>. Such a weld <NUM> between overlapping portions of housing <NUM> and flange <NUM> is sometimes referred to as a "lap-weld". In one example, both ferrule <NUM> and housing <NUM> may be made of titanium. However, other suitable biocompatible and weld-compatible materials may be employed.

While lap-welding is effective to hermetically join housing <NUM> to flange <NUM> when the surface <NUM> of housing <NUM> about opening <NUM> is substantially planar, such as illustrated by <FIG>, portions of lap-weld <NUM> about a perimeter of ferrule <NUM> may fail if the non-planarity of housing surface <NUM> about opening <NUM> exceeds a tolerance level.

<FIG> is a cross-sectional view of feedthrough device <NUM> employing known, prior art ferrule <NUM> and generally illustrating a scenario where exterior surface <NUM> of housing <NUM> is non-planar about opening <NUM>. When surface <NUM> is non-planar, while some portions of flange <NUM> may be suitably positioned relative to surface <NUM> to form a successful lap-weld <NUM> therewith, such as illustrated on the left side of ferrule <NUM> in <FIG>, gaps may exist between other portions of flange <NUM> and housing <NUM>, such as illustrated on the right-hand side of ferrule <NUM> by a gap having a gap distance, g1, between lower surface <NUM> of flange <NUM> and surface <NUM> of housing <NUM>. It is noted that the gap distance, g1, represents the non-planarity of surface <NUM> of housing <NUM>. If the non-planarity or gap distance, g1, is too large, a weld between flange <NUM> of ferrule <NUM> and housing <NUM> is likely not possible to be made or likely to fail. It has been found that a suitable weld is not likely to be made when the gap distance, g1, between lower surface <NUM> of flange <NUM> and exterior surface <NUM> of housing <NUM> is approximately <NUM>% or more of the thickness, Th1, of flange <NUM>.

Commonly employed thicknesses, Th1, for flange <NUM> are in the range of <NUM> - <NUM> inches (<NUM>-<NUM>), and in the range of <NUM> - <NUM> inches (<NUM>-<NUM>) for a thickness, Th2, of housing <NUM>, with a <NUM>-inch (<NUM>) flange being employed with <NUM> inch (<NUM>) thick housing, and a <NUM> inch (<NUM>) flange being employed with a <NUM> inch (<NUM>) thick housing. Using these thicknesses as an example, welds are likely to be unsuccessful when gap distance, g1, is at or exceeds approximately <NUM> inches (<NUM>) in the case of a <NUM> inch (<NUM>) ferrule (<NUM> * <NUM>) being used with a <NUM> inch (<NUM>) thick housing, and <NUM> inches (<NUM>) in the case of a <NUM> inch (<NUM>) ferrule (<NUM> * <NUM>) being used with a <NUM> inch (<NUM>) thick housing. In other words, to better ensure a successful lap-weld, ferrule <NUM> tolerates a non-planarity of up to <NUM> inches (<NUM>) in surface <NUM> of a <NUM> inch (<NUM>) thick housing <NUM>, and up to <NUM> inches (<NUM>) in a <NUM> inch (<NUM>) thick housing <NUM>.

While increasing the thickness, Th1, of flange <NUM> may potentially increase an amount of non-planarity in housing <NUM> which may be tolerated by ferrule <NUM> while still achieving a successful weld, an amount of energy needed to form the weld when employing a thicker flange is also increased, where such increase in weld energy may, in some cases, adversely affect the braze connection <NUM> between ferrule <NUM> and insulator <NUM>.

<FIG> is a cross-sectional view illustrating an example of a ferrule <NUM>, in accordance with the disclosure. As will be described in greater detail below, ferrule <NUM> increases an amount of non-planarity able to be tolerated in surface <NUM> of housing <NUM> when welding ferrule <NUM> to housing <NUM> by maintaining a relationship between thicknesses and relative positions of ferrule <NUM> and housing <NUM> and employing a butt-weld (in lieu of a lap-weld) there between.

According to one example, ferrule <NUM> includes a frame body <NUM> having an interior perimeter surface or wall <NUM>, an exterior perimeter surface or wall <NUM>, an upper perimeter surface <NUM> (to face body fluid side <NUM>, <FIG>), and a lower perimeter surface <NUM> (to face interior space <NUM>, <FIG>). Though not illustrated in the cross-sectional view of <FIG>, in one example, frame body <NUM> is a continuous ring-like or frame-like structure having any suitable geometry (e.g., circular, oval, rectangular, etc.), with interior perimeter surface <NUM> defining an interior opening <NUM> to receive insulator assembly <NUM>. In examples, ferrule <NUM> may be formed using any suitable bio-compatible material, such as titanium, for example, which is able to be mechanically attached to insulator assembly <NUM> (e.g., via brazing) and to housing <NUM> (e.g., via welding).

In accordance with the disclosure, ferrule <NUM> includes a housing flange <NUM> which extends outwardly from exterior perimeter wall <NUM> (away from interior opening <NUM>) between upper and lower surfaces <NUM> and <NUM> of frame body <NUM> and serves as a stop for positioning housing <NUM> at a desired position along exterior perimeter wall <NUM>. In one example, housing flange <NUM> extends perpendicularly from exterior perimeter wall <NUM>. In one example, flange <NUM> is disposed along exterior surface <NUM> such that an upper surface <NUM> of flange <NUM> limits an upper surface <NUM> of housing to not more than a selected maximum offset distance, D1, below an upper surface <NUM> of frame body <NUM>. In one example, the selected maximum offset distance, D1, is proportional to a thickness, Th2, of housing <NUM>. In accordance with the disclosure, it has been found that a successful butt-weld can be made between housing <NUM> and exterior perimeter wall <NUM> when a maximum offset distance between upper surface <NUM> of frame body <NUM> and upper surface <NUM> of housing <NUM> does not exceed one-half the thickness, Th2, of housing <NUM>. Accordingly, in one example, offset distance, D1, is approximately equal to one-half a thickness, Th2, of housing <NUM> (D1 = <NUM>*Th2), such that a thickness, Th3, of frame body <NUM> along exterior perimeter surface <NUM> between upper surface <NUM> of frame body <NUM> and an upper surface <NUM> of housing flange <NUM> is approximately equal to one-and-a-half times the thickness, Th2, of housing <NUM> (Th3 = Th2 + <NUM>*Th2 = <NUM>*Th2).

In examples, as will be described in greater detail below, such as with reference to <FIG>/B and 5A/5B, for instance, by limiting a relative position (e.g., a vertical position) between upper surface <NUM> of housing <NUM> and upper surface <NUM> of frame body <NUM> along exterior perimeter surface at not more than selected maximum offset distance D1 (i.e., upper surface <NUM> above or below upper surface <NUM> by selected distance D1), a successful butt-welds is able to be made between housing <NUM> and exterior perimeter surface <NUM> of frame body <NUM> with a greater degree of non-planarity in surface <NUM> of housing <NUM> as compared to a known lap-type weld, such as illustrated by <FIG>.

<FIG> are cross-sectional views illustrating the welding of a feedthrough assembly <NUM>' employing ferrule <NUM>, in accordance with one example of the disclosure, to housing <NUM> such as by laser welding (as indicated by lasers <NUM>). In the example of <FIG>, housing <NUM> is substantially planar, such that there negligible or no offset in the exterior surface <NUM> of housing <NUM> about opening <NUM> relative to flange <NUM> of ferrule <NUM>. In the example of <FIG>, it is noted that ferrule <NUM> further includes a feedthrough flange <NUM> extending from interior perimeter surface <NUM> toward opening <NUM> to assist with connection of insulator assembly <NUM> to ferrule <NUM>.

According to one example, feedthrough device <NUM>' is positioned within opening <NUM> in housing <NUM> such that upper surface <NUM> of housing flange <NUM> faces a lower or interior surface <NUM> of housing <NUM>. In one example, housing flange <NUM> is disposed at a position along exterior perimeter surface <NUM> of frame body <NUM> between upper and lower surfaces <NUM> and <NUM> such that upper surface <NUM> of housing flange <NUM> engages lower surface <NUM> of housing <NUM> to limit a position of upper surface <NUM> of housing <NUM> to not than more than selected maximum offset distance, D1, below upper surface <NUM> of frame body <NUM>. In one example, the selected maximum offset distance D1 is approximately equal to one-half the thickness, Th2, of housing <NUM> (<NUM> * Th2), such that the distance or thickness, Th3, of frame body <NUM> from upper surface <NUM> of housing flange <NUM> and upper surface <NUM> of frame body <NUM> is equal to a sum of the housing thickness, Th2, and the selected maximum offset distance D1 (e.g., Th3 = Th2 + D1 = Th2 + <NUM> * Th2 = <NUM>*D1).

With reference to <FIG>, by positioning housing <NUM> relative to ferrule <NUM> such that the maximum offset distance, D1, between exterior surface <NUM> of housing <NUM> does not exceed more than one-half the thickness, Th2, of housing <NUM> below the upper surface <NUM> of frame body <NUM>, a successful butt-weld <NUM> can be achieved between ferrule <NUM> and housing <NUM> using a laser <NUM> having an energy level low enough so as to not damage braze joint <NUM> between insulator body <NUM> and interior perimeter surface <NUM> of frame body <NUM>. If the maximum offset distance, D1, exceeds one-half the thickness, Th2, of housing <NUM>, an energy of laser <NUM> needed to melt portions of frame body <NUM> and housing <NUM> to form a weld there between may result in damage to braze joint <NUM> and/or to housing <NUM>.

Commonly employed thicknesses, Th2, for housing <NUM> are in a range from <NUM> inches to <NUM> inches (<NUM>-<NUM>). With such a range, maximum offset distance, D1, of the example illustrated by <FIG> is in a range from <NUM>-<NUM> inches (<NUM>-<NUM>).

<FIG> are cross-sectional views illustrating the attachment of feedthrough assembly <NUM>', according to one example, where housing <NUM> is non-planar about opening <NUM>. According to one example, feedthrough device <NUM>' is positioned within opening <NUM> of housing <NUM> such that upper face <NUM> of housing flange <NUM> engages portions of housing <NUM> such that upper surfaces <NUM> of such portions of housing <NUM> are offset from upper surface <NUM> of body <NUM> by maximum offset distance, D1, such as illustrated by the portion of housing <NUM> shown on the left-hand side of <FIG>.

Due to the non-planarity of housing <NUM>, while some portions of housing <NUM> will be engaged by flange <NUM>, remaining portions of housing <NUM> will be spaced from upper surface <NUM> flange <NUM> by a gap having a gap distance indicated as gap distance, g2, with gap distance g2 representing the non-planarity of housing <NUM>. If gap distance, g2, exceeds one-half the thickness, Th2, of housing <NUM>, upper surface <NUM> of housing <NUM> will extend above upper surface <NUM> of frame body <NUM> by an offset distance, D2, as illustrated in <FIG>.

With reference to <FIG>, with flange <NUM> positioning upper surface <NUM> of the portion of housing <NUM> on the left-hand side of ferrule <NUM> at maximum offset distance, D1, from upper surface <NUM> of frame body <NUM>, a successful butt-weld will be achieved between housing <NUM> and frame body <NUM>, as indicated by weld <NUM>. Additionally, as long as offset distance, D2, does not exceed maximum offset distance, D1, a successful butt-weld will be achievable between frame body <NUM> and housing <NUM> on the left side of ferrule <NUM>, as indicated by weld <NUM>. In a case where offset distance, D2, is equal to maximum offset distance, D1, the gap distance, g2, between upper surface <NUM> of flange <NUM> and lower surface <NUM> of housing <NUM> is equal to the thickness, Th2, of housing <NUM>, as illustrated by <FIG>. If offset distance, D2, exceeds maximum offset distance, D1, meaning that gap distance, g2, is greater than thickness, Th2, of housing <NUM>, a successful butt-weld between frame body <NUM> and housing <NUM> is not likely to be achievable. In other words, as long as the non-planarity in housing <NUM> does not exceed the thickness, Th2, of housing <NUM>, meaning that the gap distance, g2, does not exceed the thickness, Th2, of housing <NUM>, ferrule <NUM> enables a butt-weld to be successfully made between housing <NUM> and frame body <NUM>.

Thus, when welding feedthrough device <NUM>' to housing <NUM>, ferrule <NUM>, in accordance with the disclosure, ferrule <NUM> tolerates a non-planarity in surface <NUM> of housing <NUM> which is equal to the thickness, Th2, of housing <NUM>. As described above, commonly employed thicknesses, Th2, for housing <NUM> are in a range from <NUM> inches to <NUM> inches (<NUM>-<NUM>). Thus, relative to ferrule <NUM> (see <FIG>), ferrule <NUM>, in accordance with the disclosure, tolerates a non-planarity of <NUM> inches (<NUM>) for a <NUM> inch (<NUM>) thick housing, and a non-planarity of <NUM> inches (<NUM>) for a <NUM> inch (<NUM>) thick housing. This represents an improvement in tolerance in non-planarity of surface <NUM> of housing <NUM> of approximately <NUM>% for a <NUM> inch (<NUM>) thick housing, and approximately <NUM>% for a <NUM> inch (<NUM>) thick housing relative to ferrule <NUM>.

<FIG> and <FIG> generally illustrate cross-sectional views of ferrule <NUM>, according to examples of the disclosure, where frame body <NUM> is stepped to lessen potential adverse impact of welding housing <NUM> to frame body <NUM> on braze joint <NUM> between interior perimeter surface <NUM> and insulator body <NUM>.

<FIG> generally illustrate an example where frame body <NUM> is stepped such that exterior perimeter surface <NUM> has a first portion 86a and a second portion 86b, such that upper surface <NUM> includes first upper surface 88a extending between first and second portions 86a and 86b of exterior perimeter wall <NUM>, and a second upper surface 88b extending between second portion 86b of exterior perimeter wall <NUM> and interior perimeter wall <NUM>. According to the example of <FIG>, first upper surface 88a is disposed closer to upper surface <NUM> of housing flange <NUM> than second upper surface 88b, such that second upper surface 88b is vertically higher than first upper surface 88a relative to upper surface <NUM> of housing flange <NUM>. In one example, first portion 86a of exterior perimeter wall extends vertically from upper surface <NUM> of flange <NUM> by a distance equal to the sum of the thickness, Th1, of housing <NUM> and the selected maximum offset distance, D1, similar to that illustrated by the <FIG>. In one example, first upper surface 88a has a width, W1, not more than approximately the thickness, Th1, of housing <NUM>.

<FIG> and <FIG> respectively illustrate welding of housing <NUM> to frame body <NUM> when lower/interior surface <NUM> of housing <NUM> engages upper surface <NUM> of flange <NUM>, and when upper surface <NUM> of housing <NUM> is disposed above first upper surface 88a by not more than the selected maximum offset distance, D1.

<FIG> generally illustrate an example where frame body <NUM> is stepped such that upper surface <NUM> has a first upper surface 88a disposed adjacent to exterior perimeter surface <NUM>, and a second upper surface 88b disposed adjacent to interior perimeter surface <NUM>, where first upper surface 88a is disposed further away from upper surface <NUM> of housing flange <NUM> than second upper surface 88b such that exterior perimeter wall <NUM> extends above second upper surface 88b relative to upper surface <NUM> of housing flange <NUM>.

In one example, as illustrated, exterior perimeter wall <NUM> extends vertically from upper surface <NUM> of flange <NUM> by a distance equal to the sum of the thickness, Th1, of housing <NUM> and the selected maximum offset distance, D1, similar to that illustrated by the <FIG>. In one example, first upper surface 88a has a width, W1, not more than approximately the thickness, Th1, of housing <NUM>.

Claim 1:
A feedthrough assembly for an implantable medical device (<NUM>), having an insulator body and a ferrule (<NUM>), the ferrule (<NUM>) having a frame body (<NUM>) including an upper surface (<NUM>) and an opposing lower surface (<NUM>), an interior perimeter surface (<NUM>) extending between the upper and lower surfaces (<NUM>,<NUM>) and defining an interior opening in which the insulator body is disposed, and an exterior perimeter surface (<NUM>) extending between the upper and lower surfaces (<NUM>,<NUM>) for attachment to a housing (<NUM>), and characterized by:
a single flange (<NUM>) extending from the exterior perimeter surface (<NUM>) and having an upper surface (<NUM>) facing the upper surface (<NUM>) of the frame body (<NUM>), the upper surface (<NUM>) of the single flange (<NUM>) to serve as a stop against an interior surface (<NUM>) of a housing (<NUM>) of the implantable medical device (<NUM>) to limit a distance of an exterior surface of the housing (<NUM>) from the upper surface (<NUM>) of the frame body (<NUM>) along the exterior perimeter surface (<NUM>) in a direction toward the bottom surface of the frame body (<NUM>), wherein a distance from the top surface of the single flange (<NUM>) to the top surface of the frame body (<NUM>) is not greater than <NUM> times a thickness of the housing (<NUM>) to enable a butt weld to be made between exterior perimeter surface (<NUM>) and housing (<NUM>).