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Medical Patent Abstract
A connector assembly for coupling to an implantable medical device
includes a core element formed of a first thermoplastic material
shaped to receive a connector member for receiving a lead. The connector
assembly further includes a circuit member positioned adjacent to
the core element. The circuit member includes a portion extending
along the core element to the connector member and an antenna structure
extending over a portion of the core element outer surface.
Medical Patent Claims
The invention claimed is:
1. A connector assembly to be coupled to an implantable medical
device, comprising: a core element formed of a first thermoplastic
material shaped to receive a connector member for receiving a lead,
the core element having an outer surface; a circuit member positioned
adjacent to the core element, the circuit member including a portion
extending along the core element to the connector member and including
an antenna structure extending over a portion of the core element
outer surface; and an overmold portion formed of a second thermoplastic
material to extend over and adhere to the core element.
2. The connector assembly of claim 1 wherein the antenna structure
includes a curve portion corresponding to the portion of the core
element outer surface.
3. The connector assembly of claim 1 wherein the core element outer
surface comprises a first major side, a second major side and a
curvilinear minor side separating the first major side and the second
major side and wherein the antenna structure extends along the curvilinear
minor side.
4. The connector assembly of claim 1 wherein the core element outer
surface comprises a first flange and a second flange and wherein
the antenna structure extends between the first and second flanges.
5. The connector assembly of claim 1 wherein the antenna structure
is a wire member antenna.
6. The connector assembly of claim 5 wherein the antenna structure
is formed having a free end, a fixed end, a first turn, a first
segment extending between the free end and the first turn, a final
turn, and a final segment extending from the final turn substantially
parallel to the first segment.
7. The connector assembly of claim 6 wherein the antenna structure
includes a penultimate turn and a penultimate segment extending
from the first turn to the penultimate turn substantially parallel
to the first and second segments.
8. The connector assembly of claim 6 wherein the first turn having
a first turn width and the final turn having a second turn width
substantially equal to the first turn width.
9. The connector assembly of claim 6 wherein the first turn having
a first turn width and the final turn having a second turn width
greater than the first turn width.
10. The connector assembly of claim 7 wherein the antenna structure
is formed in a flat coil structure corresponding to the first segment
being positioned between the penultimate and final segments.
11. The connector assembly of claim 7 wherein the antenna structure
is formed in an elongated serpentine structure corresponding to
the penultimate segment being positioned between the first and final
segments.
12. The connector assembly of claim 1 wherein the core element
outer surface comprises a first major side, a second major side
and a curvilinear minor side separating the first major side and
the second major side and wherein the antenna structure extends
along one of the first major side and the second major side.
Medical Patent Description
TECHNICAL FIELD
This invention relates to a process for molding a circuit component;
and more particularly, to a two-shot thermoplastic molding process
for manufacturing an electrical connector.
BACKGROUND
Electrical connectors and other similar electrical components often
include electrical conductors embedded within an insulating housing
to isolate the conductor from the surrounding environment. Embedding
the conductor within a housing protects the conductor from damage,
and also prevents the delivery of an electrical shock. Electrical
isolation is particularly important when the connector is to be
coupled to an implantable medical device such as a pacemaker or
defibrillation system.
One way to form an electrical connector having conductors embedded
therein is to mold a solid set-screw block using injection molding
techniques. After the molding is completed, the surface of the set-screw
block is formed to include channels. Wires or other types of connectors
are pressed into the channels. Generally, each end of each wire
is welded to some type of electrical contact. An insulating adhesive
is then applied over the wires and channels. If the connector is
to be used with an implantable medical device, a medical adhesive
is often employed for this purpose. The adhesive is cured to form
a protective, insulating layer that isolates the wires from external
elements.
Although the afore-mentioned method is relatively straight-forward,
it requires manual application of the adhesive. This introduces
variables into the manufacturing process. If the adhesive is not
properly dispensed, some portions of the conductor may become exposed.
As a result, shorts may develop between adjacent conductors. Additionally,
a conductor may come in contact with external elements, causing
degradation and loss of conductive capabilities. Moreover, because
a manual process is employed, the manufacturing mechanism is relatively
time-consuming and expensive.
An alternative approach to the use of adhesives involves the positioning
of one or more conductors within a mold in some predetermined orientation.
An insulating plastic is then introduced into the mold to encapsulate
the conductors. The plastic hardens to provide the necessary insulating
layer around the conductors. While this process eliminates the variables
associated with a manual step, it is nevertheless difficult to implement
with other than a simple design. This is because the introduction
of the plastic into the mold at high pressures generally causes
the position of the conductors to shift. This may result in shorts
between multiple conductors, or conversely, may result in loss of
a desired electrical connection. While plastic injection systems
of this nature generally include mechanisms to hold the conductors
in place during the injection process, the process is more prone
to failure than other methods because shifting of components may
occur regardless of the efforts to prevent it. Additionally, a more
complex tooling system is required to implement the process. Finally,
the difficulty associated with maintaining isolation between multiple
conductors places limits on the assembly dimensions. That is, an
assembly cannot be made too small because shorts will occur between
closely spaced conductors that shift during the mold injection process.
Yet another approach used to create connector assembly includes
use of a two-step thermoset casting process. A first mold is used
to receive a thermoset plastic material such as an epoxy. As is
known in the art, a thermoset plastic hardens because of a chemical
reaction occurring between the various components of the plastic
material. After the curing process is complete, the first molded
connector element is removed from the mold. Conductors are selectively
positioned on the exterior of this first element. The first element
is then positioned within a second mold and a thermoset material
is selectively applied to the first element to encapsulate the conductors.
The two-step thermoset process provides a mechanism for embedding
conductors within a connector in a more precise manner. This is
because the first element holds the conductors in position while
the second molding step is performed. However, because thermoset
material requires a relatively long time to cure, the process is
slow. The manufacture time is increased since two serial curing
steps are required. Moreover, because the final products may not
be removed from the molds until the curing is completed, many molds
must be employed to increase output.
What is needed, therefore, is an improved mechanism for creating
more complex connector structures using a faster production cycle.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front perspective view of a connector core element
of one embodiment of the current invention.
FIG. 2 is a front perspective view of a core member loaded with
respective set-screw blocks and connector members.
FIG. 3 is a back perspective view of an alternative embodiment
of the core member.
FIG. 4 is a bottom perspective view of core member.
FIG. 5 is side perspective view of an alternative embodiment of
the circuit member.
FIG. 6 is side perspective view of an alternative embodiment of
the core element adapted to engage the circuit member of FIG. 5.
FIG. 7 is a side perspective view of circuit member positioned
on the surface of core element.
FIG. 8 is a front perspective view of a lead core assembly.
FIG. 9 is a perspective view of a core element being prepared for
the overmolding process.
FIG. 10 is a side perspective view of an alternative embodiment
of a core element which is designed to minimize core element mass.
FIG. 11 is a perspective side view of a connector assembly formed
after injection of the second-shot material.
FIG. 12 is an alternative embodiment of the second-shot mold assembly
of FIG. 9.
FIG. 13 is a flowchart of an assembly process.
FIG. 14 is a side perspective view of a completed connector assembly
coupled to an implantable medical device (IMD).
FIG. 15 is side perspective view of an alternative embodiment of
the circuit member.
FIG. 16 is a side perspective view of a core element adapted to
engage the circuit member of FIG. 15.
FIG. 17 is a side perspective view of the circuit member of FIG.
15 positioned on the surface of the core element of FIG. 16.
FIG. 18 is a side perspective view of an alternative embodiment
of the circuit member including a serpentine antenna structure.
FIG. 19 is a perspective view of an alternative embodiment of the
circuit member including a coiled antenna structure.
FIG. 20 is a top perspective view of a core element adapted to
engage the circuit member of FIG. 19.
FIG. 21 is perspective view of a circuit member positioned on the
surface of core element the core element of FIG. 20.
FIG. 22 is a perspective view of an alternative embodiment of a
circuit member including an elongated serpentine telemetry antenna.
FIG. 23 is a top perspective view of the circuit member of FIG.
22 positioned on the surface of a core element.
FIG. 24 is a side perspective view of an alternative embodiment
of the circuit member including a telemetry antenna adapted to extend
along a major side of a core element.
FIG. 25 is a perspective view of the circuit member shown in FIG.
24 assembled with a core element adapted to engage the circuit member
to form an assembly.
FIG. 26 is a side perspective view of an alternative embodiment
of the circuit member including an elongated serpentine telemetry
antenna adapted to extend along a major side of the core element.
FIG. 27 is a perspective view of the circuit member shown in FIG.
26 assembled with a core element adapted to engage the circuit member
to form an assembly.
DETAILED DESCRIPTION
FIG. 1 is a front perspective view of a connector core element
2 of one embodiment of the current invention. Core element is integrally
formed of a biocompatible thermoplastic material, which may be a
polyurethane such as pellathane commercially available from The
Polymer Technology Group (PTG) Incorporated, or Tecothane.RTM. commercially
available from Thermedics Incorporated. Other polyurethane materials
are suitable for use in the current inventive process, as are other
thermoplastic materials such as polysulfone. In one embodiment,
a suitable biocompatible polyurethane may have a hardness of between
50 D and 90 D (Shore), and is preferably about 75 D.
The core element 2 is formed by heating the thermoplastic material
to a temperature that is at, or slightly above, the melt point.
The material is then injected into a primary mold formed into the
desired shape of the core element and allowed to cool. Cooling is
generally completed in between twenty to seventy seconds. This is
much shorter than the curing period for thermoset materials, which
may be as much as one hour. After cooling, core element 2 is removed
from the mold. The removal process involves opening the mold, which
includes an ejection mechanism that automatically releases the core
element.
Core element 2 may take many different shapes. In one embodiment,
core element includes a structure that supports various metal piece
parts in a stable manner that can be maintained during a second-shot
molding process to be discussed below. In the embodiment of FIG.
1, core element 2 includes receptacles 4, 6, and 8. Each of the
receptacles is adapted to receive a respective set-screw block,
such as set-screw block 10 to be inserted within receptacle 6, and
set screw block 12 to be inserted within receptacle 8. Receptacle
4 is adapted to receive a similar set-screw block not shown in FIG.
1 for purposes of simplification. Set-screw blocks may be formed
entirely, or partially, from a conductive material such as MP35N,
stainless steel or titanium.
The set-screw blocks are loosely maintained within a respective
receptacle by the shape of core element 2 until the second-shot
over-molding process is completed. Each of these set-screw blocks
includes an opening such as opening 16 to receive a set screw, and
a second opening such as opening 17 to receive the pin or ring connector
provided at the proximal end of a medical lead. A set screw inserted
within opening 16 is used to mechanically couple to a lead connector
pin or ring to hold the lead in place, as will be described further
below.
In an alternative embodiment, the various receptacles need not
be included and the set-screw blocks may be integrally formed within
the core element by positioning the set-screw blocks with the primary
mold prior to injecting the thermoplastic material to form core
element 2. In this instance, sealing means must be provided to prevent
the thermoplastic from being injected into the openings of the set-screw
blocks. For example, the primary mold could include peg members
adapted to be loaded into the openings of set-screw blocks so that
a tight seal is formed prior to injecting the thermoplastic into
the mold. The pegs would also retain the set-screw blocks in position
during the high-pressure injection process.
Returning to FIG. 1, core element 2 also includes additional circular
receptacles 24 and 26. Each circular receptacle includes an aperture
25 and 27, respectively, to receive the connector pin of a medical
electrical lead. For example, during use, a lead connector pin may
be inserted within aperture 25 and further through opening 17. The
lead is held in place by a fastening member inserted within opening
16 of set-screw block 10 and tightened on the lead pin or ring as
is known in the art.
In the embodiment shown, each circular receptacle 24 and 26 is
adapted to receive a respective connector member such as connector
member 30. This type of connector member may be formed entirely
or partially of a conductive material such as stainless steel or
titanium. Connector member 30 is shown to include a multi-beam connector
(MBC) 32 adapted to couple electrically and mechanically to a ring
connector of a bipolar medical electrical lead. This type of connector
member would support a lead having a connector conforming to the
IS-1 standard, for example. Other types of connector members may
be utilized to form an electrical and/or mechanical connection,
as is known in the art.
In an alternative embodiment, the connector members may be eliminated
by integrally forming the connectors such as connector member 30
within core element 2. This may be accomplished by loading the primary
mold with the connectors prior to injecting the thermoplastic. As
discussed above with respect to the set-screw blocks, some mechanism
must be provided to prevent the thermoplastic from flowing over
the conductive surface of the connectors. Additionally, the connector
members must be retained in position during the high-pressure injection
process.
Core element 2 further includes additional lead bores 28 and 29
to receive the connector pins of additional leads. These lead bores
may be adapted to couple to the pin of a lead conforming to the
DF-1 standard for medical electrical leads, for example. Additional
apertures such as apertures 20 may be provided to couple to additional
circuit components in a manner to be discussed below. Core element
may further have one or more guide members shown as guide members
21 and 23 integrally formed on the surface of core element 2. These
guide members serve as support and positioning mechanisms for the
additional circuit components, and also improves the overmolding
process, as is described below.
FIG. 1 further illustrates a circuit member 40 which is formed
of a conductive material such as stainless steel, titanium, niobium,
tantalum, or any other conductive biocompatible conductive material.
Circuit member 40 includes multiple conductive traces or finger
elements 42 through 52, each extending to a respective connector
pads 53 through 57. When the circuit member 40 is initially coupled
to core member 2, connector pads may be electrically and mechanically
joined to make the assembly process more efficient. Circuit member
40 may be soldered or welded to the various metal piece parts associated
with core element 2, including set-screw blocks 10 and 12, and the
various connector members 30 in a manner to be discussed below.
As noted above, using a single circuit member 40 having conductive
finger elements that are mechanically and electrically joined makes
the initial assembly process easier since multiple elements need
not be loaded onto the core element 2. However, in this embodiment,
an additional step is required later in the assembly process to
electrically isolate these components, as will be discussed below.
In another embodiment, each of the multiple conductive finger elements
42 through 52 may be an individual circuit element that is not mechanically
or electrically coupled to the other finger elements. In this embodiment,
the multiple finger elements must be individually loaded onto the
core element. However, the additional step of electrically isolating
these components later is not required. In yet another embodiment,
the conductive finger elements may be joined in a single circuit
member via insolated material. In this embodiment, the circuit member
is a unified structure that couples the conductive finger elements
mechanically, but provides electrical isolation. In this embodiment,
the additional step of electrically isolating these components later
is not required.
In yet another embodiment, the circuit member 40 could be integrally
formed to include the various connector members and set-screw blocks
so that the soldering or welding process may be eliminated. Using
this embodiment, attaching the circuit member 40 to the core element
involves loading the receptacles and apertures of the core element
with the set-screw blocks and connector members, respectively.
FIG. 2 is a front perspective view of core member 2 with respective
set-screw blocks inserted into receptacles 4,6 and 8, and with connector
members 58 and 30 inserted into circular receptacles 24 and 26.
This view further illustrates circuit member 40 coupled to core
member 2. In this embodiment, finger elements 48 and 50 of circuit
member may extend through apertures provided within core element
2. For example, finger element 50 is inserted through aperture 20,
which is a channel that extends through the core member. Similarly,
finger element 48 extends through an additional aperture (not shown
in FIG. 2) to position circuit member in a precise location with
respect to core element 2. In one manner of use, finger elements
48 and 50 are formed of a material that is deformable, and which
may be temporarily straightened to be threaded through a respective
aperture such as aperture 20. In another embodiment, finger elements
48 and 50 are initially straight, and may be manually or automatically
bent in the manner shown in FIG. 2 after being inserted within a
respective aperture.
After circuit member 40 is coupled to core member 2, it may be
soldered or welded to form predetermined electrical and mechanical
connections between connector members and set-screw blocks and respective
ones of the conductive finger elements. For example, finger element
46 may be coupled to set-screw block 10, whereas finger element
48 is electrically coupled to set-screw block 60.
Additional circuit elements may further be coupled to the core
element using soldering, welding, or any other appropriate process.
For example, jumper 62 may be soldered or welded to both finger
element 46 and connector member 58 to form an electrical connection
between the two components. Jumper 66 may be positioned on the surface
of core member 2 using guide members 21 and 23 to align the circuit
member in a desired location so that an electrical connection may
be formed between set-screw block 12 and a predetermined respective
one of the finger elements.
FIG. 3 is a back perspective view of an alternative embodiment
of the core member designated core member 2a. Although similar in
almost every respect to the core members of FIGS. 1 and 2 discussed
above, this core member includes a support structure 70 that is
integrally molded into core element 2, and which is provided to
receive and support connector members such as connector members
30 and 58. This support structure has a cutaway portion 72 to allow
circuit element 62 to be welded or soldered to connector member
58. Although this support structure helps maintain the connector
members in position during the second-shot overmolding process,
it may make insertion of the connector members more cumbersome,
and adds additional mass to the core element 2, which may be undesirable
for reasons to be discussed further below.
FIG. 3 further illustrates the manner in which finger elements
48 and 50 of circuit member 40 are threaded through apertures of
core member 2. Further illustrated is circuit element 66, which
is maintained in position on the surface of core element by guide
members 21 and 23 to form an electrical connection between set-screw
block 12 and finger element 42.
FIG. 4 is a bottom perspective view of core member 2. This view
illustrates the manner in which finger elements 48 and 50 extend
through apertures 20 and 64, respectively. This view also shows
the manner in which the various finger elements may be electrically
coupled to connector members and set-screw blocks. For example,
finger element 44 is jumpered via circuit element 70 to set-screw
block 72; finger element 46 is electrically coupled to set-screw
block 10, and so on.
As shown in FIG. 4, one manner of retaining circuit member 40 in
position in proximity to core element 2 is through the use of apertures
that extend through the core member and are adapted to receive respective
finger elements of the circuit member 40. While this helps to prevent
shifting of the circuit member 40 during the second-shot molding
process, the process of threading the finger members through the
various apertures is cumbersome and time-consuming.
FIG. 5 is side perspective view of an alternative embodiment of
the circuit member. In this view, like features of circuit member
40b as compared to circuit member 40 of FIGS. 1 through 4 are designated
with like numeric identifiers including an additional suffix. This
embodiment includes finger elements 44b through 46b that are not
adapted to engage apertures in a core element. Instead, these elements
are adapted to be placed externally on the surface of the core element
to reduce assembly time prior to the second-shot overmolding step.
One or more of the finger elements such as finger element 42b may
have a longer, flexible conductive end. This end is adapted to be
manually shaped to conform to a surface of the core member, as described
below. FIG. 5 also illustrates the use of alignment apertures 90
and 92, which are provided to position the core element at a predetermined
location within the second-shot mold to be discussed below.
FIG. 6 is side perspective view of an alternative embodiment of
the core element adapted to engage the circuit member 40b of FIG.
5. As in FIG. 5, like features of core element 2b as compared to
core element 2 of FIGS. 1 through 4 are designated with like numeric
identifiers including an additional suffix. Core element 2b includes
channel guides such as channel guides 100 through 110 that are provided
to guide the finger elements of circuit member 40b into the desired
position on the surface of core element 2b. During the second-shot
overmolding process, these channel guides retain the finger elements
in position, and prevent shifting that may results in shorts between
adjacent finger elements. These channel guides also promote integration
of the material of the core element with the additional thermoplastic
material provided during the overmolding process, as will be discussed
further below.
FIG. 7 is a side perspective view of circuit member 40b positioned
on the surface of core element 2b. This figure illustrates the manner
in which finger elements are positioned using the guide members.
For example, finger element 52b is positioned between guide members
104 and 106, and finger element 42b is positioned between guide
members 108 and 110 provided on the bottom surface of core member
2b. The finger elements may be soldered or welded to the conductive
components such as the set-screw blocks that are inserted in core
member 2b in the manner discussed above. Other circuit elements
may also be used to form electrical connections between circuit
member 40b and a predetermined conductive component. Alternatively,
the longer finger elements such a finger element 42b having a flexible
elongated end 42c (FIG. 5) may be manually shaped into position
and welded to form the desired connection as shown in FIG. 7. In
this example, the end 42c of finger element 42b is shaped along
the top surface of core member 2c to electrically couple to set-screw
block 12c. This use of longer conductive finger elements makes the
assembly process more efficient by eliminating the need for additional
circuit components, and by minimizing the number of locations that
must be welded or soldered.
After all conductive components have been inserted into the core
element and the circuit member 40b has been welded, soldered, or
otherwise fixed into place, the resulting core element assembly
may be prepared to undergo the second-shot overmolding process.
This preparation may involve inserting pin members into the connector
members and the apertures of the set-screw blocks so that thermoplastic
material does not fill these structures during the overmolding process.
FIG. 7 illustrates pin members 120 and 122 being inserted into connector
members 58b and 30b, respectively. Pin members 124 and 126 are similarly
inserted into lead bores 29b and 28b, respectively. Additional pin
members or bushings (not shown in FIG. 7 for clarity) may be inserted
into the apertures of each of the set-screw blocks of core element
2b. These pin members are made of a material that will withstand
the temperature and pressure conditions associated with the injection
molding process. For example, the pin members may be made of a tool
steel or another type of stainless steel. In one embodiment, multiple
ones of the pin members may be incorporated into a core assembly
structure to make insertion into the core element easier.
FIG. 8 illustrates an lead core assembly 130, which is assembly
that provides the pin members 120 through 126 shown in FIG. 7. The
lead core assembly aligns the pin members, and allows them to be
inserted in one step.
In an alternative embodiment, ones of the pin members such as those
inserted into the set-screw blocks may be eliminated by using protrusions
in the second-shot mold assembly. These protrusions are inserted
into the set-screw blocks as the core element is placed within the
mold and the mold is closed, thereby eliminating the step of manually
inserting the pin members into the core element. This is discussed
further below.
FIG. 9 is a perspective view of a core element being prepared for
the overmolding process. This view, which is similar to that shown
in FIG. 3, illustrates core member 2a and the associated metal piece
parts that have been loaded into the core member. Lead core assembly
130 is utilized to insert pin members 120, 122, 124, and 126 into
the respective structures of the core element as discussed in reference
to FIG. 8. Similar bushings 140, 142, 144 and 146 may be inserted
into the apertures of the set-screw blocks. As noted above, bushings
144 and 146 may be eliminated by instead providing protrusions within
cavity 148 of the bottom portion 150 that are aligned with the set-screw
blocks. Similar protrusions may be provided in the top portion 172
of the mold to replace bushings 140 and 142. Providing such structures
in the mold itself eliminates the requirement of manually loading
the bushings into the core element.
After the core element is prepared for the overmolding process,
the entire assembly may then be loaded into cavity 148 of a bottom
portion 150 of a second-shot mold fixture. The lead core assembly
is positioned within the mold as shown by dashed lines 152 and 154.
In this position, the lead core assembly suspends the core element
within the cavity of the mold so that the surface of the core element
is not in contact with the interior surface of the mold. The positioning
of the core assembly may further be aided by fitting predetermined
ones of the apertures included in the circuit member 40 with the
alignment pins 160 and 162 of the mold as illustrated by dashed
lines 164 and 166. For example, the apertures in connector pads
54 and 56 of circuit member 40 (FIGS. 2 and 3) or the alignment
apertures 90 and 92 (FIG. 5) could be used for this purpose. The
circuit member 40 may further be supported by a shoulder member
170.
After the assembly has been properly aligned within the bottom
portion 150, the top portion 172 of the second-shot mold fixture
is aligned with the bottom portion. This may be accomplished by
inserting pegs 174 and 176 into channel members 178 and 180. Both
top and bottom mold portions may include additional channels such
as channels 182 and 184 to accommodate set-screws 140 and 142, respectively.
Similar channels may be provided in the bottom portion 150 of the
mold fixture.
When the bottom and top portions of the mold fixture have been
aligned, a press may be utilized to maintain the alignment during
the high-pressure injection procedure. A thermoplastic material
is heated to at least the melting temperature, or preferably, slightly
above the melting temperature, of the material, and is injected
into cavity 148 via injection port 190. The same, or a different,
thermoplastic material may be used in the second-shot injection
process as compared to that used in the core element. Moreover,
the second-shot material may entirely encapsulate the core element,
or alternatively, need only cover a portion of the core element.
For example, it may be desirable to leave exposed a portion of the
thermoplastic material included in the core element in the region
of the circuit member connector pads.
During the second-shot injection process, it is important to ensure
that bonding occurs between the core element and the second shot
material. If bonding does not occur, very small amounts of ionic
liquid pool between the core element 2 and the overmold material
after the connector has been implanted within a living body for
an extended period of time. This may result in what is an unacceptably
large leakage current between adjacent finger elements of the circuit
element. One way to ensure that adequate bonding is achieved is
to heat the second-shot plastic as hot as the material characteristics
will allow, and to inject the material as quickly as possible. This
allows the core element to be heated by, and thereafter bonded to,
the second-shot material.
Another method used to enhance the bonding process is to ensure
that the mass of the core element is as small as possible. This
allows the core element to be heated sufficiently during the overmold
process. In one embodiment, the mass of the thermoplastic material
incorporated into the core element is less than half of the mass
of the material utilized during the overmold process, and is preferably
less than thirty percent of that of the overmold structure.
Another mechanism for enhancing the bonding of the core element
to the overmold material involves heating the core element prior
to injecting the second shot of thermoplastic material. If this
method is utilized, the mass of the core element may be greater
while still achieving adequate bonding. This is because the second
shot of thermoplastic material is not providing all of the heat
needed to warm the core element, with at least some of the heat
being provided during the heating step that precedes the injection
step. In one embodiment, the mass of the core element is greater
than fifty percent of the thermoplastic material used during the
overmold process while still retaining adequate bonding.
Integration of the core element with the overmold material may
be further enhanced by providing relatively thin protruding structures
to the core member surface. Because these relatively thin structures
are readily melted and integrated with the second-shot material,
integration of the core element with the overmold structure is enhanced.
For example, guide members 100 through 110 (FIG. 6) serve not only
to guide circuit elements on the surface of the core member, but
also facilitate this type of bonding between the core element 2
and the overmold material. In one embodiment, additional thin fin-like
structures may be provided in arbitrary shapes along various surfaces
of the core member to facilitate additional integration. Such structures
may be included in the first-shot mold assembly. Although such structures
do enhance integration, the addition of such structures makes the
molding of the core element more complex.
Following the injection of the overmold material, the entire assembly
is allowed to cool for twenty to seventy seconds, depending on the
type of thermoplastic material utilized as determined by the manufacturer
specifications. The top portion of the mold is removed from the
bottom portion, causing the finished connector assembly to be released.
After removal from the mold, the connector pads of the circuit member
40 may be separated, if necessary, to achieve electrical isolation,
as may be performed by cutting away the intervening conductive traces.
The pads may then be soldered or welded to respective connectors
of an implantable medical device such as a pacemaker or cardioverter/defibrillator,
and overlaid with a medical adhesive to maintain electrical isolation
in the connection area. It may be noted that if individual circuit
elements are utilized in place of circuit member 40 or 40b, the
step of removing the intervening conductive traces between finger
elements may be eliminated.
As discussed in the foregoing paragraphs, one way to promote the
formation of an adequate bond between the core member and the overmold
material is to utilize a core element that is as small as possible.
An alternative embodiment of a core element directed to minimizing
core element mass is shown in FIG. 10. It may be noted that in this
embodiment, the walls defining receptacles 4c, 6c, and 8c are relatively
thin structures as compared to similar structures shown in FIGS.
1 and 6. Other structure adjacent to receptacle 8c has also been
eliminated.
FIG. 11 is a perspective side view of an connector assembly formed
after injection of the second-shot material. The side view of FIG.
11 corresponds to the view of core element 2b in FIG. 6. Circuit
member 40 has been trimmed in the manner discussed above to achieve
the necessary isolation between pads. This view further illustrates
an additional bore 190, which may be integrally formed by a protrusion
provided within the cavity of the bottom portion 150 or top portion
172 of the mold. This type of bore is provided to allow for tightening
of the set-screws after a lead is insert into a respective lead
receptacle such as receptacle 200 in this instance. This bore will
be fitted with a stop member such as a grommet and/or a washer to
form a fluid-tight opening that is adapted to receive a tool used
during the tightening of the set-screw to the lead pin or ring connector.
In one embodiment, other apertures 202a and 202b are provided to
allow the connector to be sutured to tissue within the implant cavity.
This type of aperture may be formed by a pin that extends between
the bottom portion 150 and top portion 172 of the mold assembly.
FIG. 12 is an alternative embodiment of the second-shot mold assembly
of FIG. 9. This view illustrates core element 2a, the associated
metal piece parts that have been loaded into the core member, and
circuit member 40. This loaded core element assembly is then positioned
in the bottom portion 150a of the second-shot mold fixture. In a
manner similar to that discussed above with respect to FIG. 9, apertures
provided within the circuit element may be positioned over pins
203 and 204 of shoulder member 205 to properly align and suspend
core member over cavity 206 of the mold. Two slidable members 207
and 208 are provided to move into position around the core element
assembly, as shown by arrows 209 and 210, respectively. These slidable
members may be adapted to slide within tracks of the bottom portion
150a. Each of the slidable members includes one or more pegs such
as pegs 211 and 212 of slidable member 207 to engage the set-screw
block apertures so that additional bushings 140 through 146 (FIG.
9) are not needed. The slidable members provide additional stability
during the second-shot injection mold process, and make removal
of the connector assembly following the second-shot injection process
less difficult.
Also shown in FIG. 12 is lead core assembly 130, which may be slidably
positioned within the bottom portion 150a of the mold as illustrated
by arrow 211 to engage the connector members of the core element
2a in the manner discussed above. Once the lead core assembly 130
and slidable members 207 and 208 are in position, a top portion
of the mold which is similar to top portion 172 (FIG. 9) may be
positioned over the bottom portion 150a. This top portion is held
in position by a press or other mechanism during the second-shot
injection process, as discussed above.
FIG. 13 is a flowchart indicating the steps utilized to make a
connector assembly. Although for discussion purposes the associated
description involves the core element of FIG. 1, it will be understood
the described process is equally applicable to the production of
any connector type, or an entirely different type of thermoplastic
component. In step 220, core member 2 is created. This may be accomplished
by injecting a thermoplastic material into a primary mold assembly,
or by fabricating a core member such as by a machining process.
In step 222, the core member is loaded with the various conductive
components such as the set-screw blocks and connector members to
form the core member assembly. This step includes welding or solder
the circuit member 40 to the various other conductive components.
Processing continues with step 224, wherein the core member assembly
is loaded onto the lead core assembly. Additional bushings may be
inserted into set-screw blocks in 226 to ensure these structures
remain open during the overmolding process, although this step is
unnecessary if protrusions adapted to be inserted in the set-screw
blocks are included in the second-shot mold assembly.
Next, in step 228, the core member assembly is loaded into the
bottom portion 150 of the second-shot mold assembly. If desired,
apertures in the circuit member 40 may be used to align the core
member assembly within the mold cavity in a manner discussed above.
The top portion 172 of the mold assembly is positioned over the
bottom portion 150 as indicated by step 230, and the two portions
are held together using a press, for example. Processing continues
with step 232, wherein the thermoplastic material is injected to
create the overmold. To bond the core member 2 with the overmold
material, it is critical to heat the core member adequately. This
may be accomplished by ensuring the mass of the core member is as
small as possible as compared to the mass of the overmold material.
In one embodiment, the mass of the core element is less than fifty
percent of the mass of the overmolding material, and is preferably
less than thirty percent of the overmold mass, as is discussed above.
The bonding process may further be enhanced by pre-heating the core
element prior to the overmold process, or by utilizing a thermoplastic
material that can be heated to a relatively high temperature without
altering the material characteristics. In either of these instances,
the core element may have a mass that is greater than fifty percent
of the overmold process while still achieving adequate bonding.
The connector assembly is cooled in step 234, and then removed
from the mold assembly in step 236. The lead core assembly and optional
bushings may be removed in step 238, and the various connector pads
of the circuit member may be electrically isolated, as by removing
interconnecting ones of the conductive traces. This is illustrated
in step 240. As noted above, if individual circuit elements are
used, this step is not needed.
FIG. 14 is a side perspective view of a completed connector assembly
248 which is similar to that shown in FIG. 11. Connector assembly
248 is coupled to an implantable medical device (IMD) 250, which
may be a pacemaker, cardio/defibrillator, neurological pain stimulator,
or any other type of implantable medical device utilizing medical
electrical leads. In one embodiment, the connector pads such as
pads 252 through 258 of the connector assembly 248 are welded or
soldered to a feedthrough pattern of the IMD. This provides the
desired electrical connections between the connector assembly and
the IMD.
FIG. 15 is side perspective view of an alternative embodiment of
the circuit member. In this view, like features of circuit member
40c as compared to circuit member 40 of FIGS. 1 through 4 are designated
with like numeric identifiers including an additional suffix. Circuit
member 40c includes a telemetry antenna 300 adapted to be positioned,
for example, externally on the surface of the core element prior
to the second-shot overmolding step. Telemetry antenna 300 includes
a wire member curved to have a substantially 90 degree bend 306
into orthogonally extending first and second telemetry antenna segments
302 and 304. The second telemetry antenna segment 304 extends from
the substantially 90 degree bend 306 to a wire member free end 305.
The first telemetry antenna segment 302 extends from the substantially
90 degree bend 306 to a lateral wire member bend 308 over to a finger
element 310, which extends to a fixed end 312, joining antenna 300
to the remainder of circuit member 40c.
When the circuit member 40c is assembled with a core member, the
finger elements 310 and 42c through 52c are electrically and mechanically
joined to make the assembly process more efficient. Circuit member
40c is soldered or welded to the various metal piece parts associated
with a core element, such as set screw block and connector members
as described previously in conjunction with FIGS. 1-4. By including
antenna 300 in a single circuit member 40c with other conductive
finger elements 42c-52c, the initial assembly process of the overall
connector assembly is made easier since multiple elements need not
be loaded onto the core element.
FIG. 16 is a side perspective view of a core element 2c adapted
to engage the circuit member 40c of FIG. 15. As in FIG. 15, like
features of core element 2c as compared to core element 2 of FIGS.
1 through 4 are designated with like numeric identifiers including
an additional suffix. Core element 2c includes channel guides such
as channel guides 100c through 110c that are provided to guide the
finger elements of circuit member 40c into the desired position
on the surface of core element 2c. Core element 2c further includes
a channel guide 320 for guiding the lateral bend portion 308 (FIG.
15) of the telemetry antenna 300 (FIG. 15). The outer surfaces of
core element 2c include a first and second major sides 340 and 342
separated by a curvilinear minor side 344. Curvilinear minor side
344 is provided with flanges 324 and 326 forming an outer channel
322 therebetween. Outer channel 322 is adapted to receive telemetry
antenna 300 shown in FIG. 15. During the second-shot overmolding
process, channel guide 320 and outer channel 322 retain the telemetry
antenna in position and prevent shorts between the antenna and other
finger elements of the circuit member.
FIG. 17 is a side perspective view of circuit member 40c positioned
on the surface of core element 2c. This figure illustrates the manner
in which the telemetry antenna 300 is positioned over the core member
2c. Lateral wire member bend 308 is positioned along channel guide
320 and antenna elements 302, 304 and 306 (indicated by dashed line
in the view of FIG. 17) are positioned along outer channel 322.
Telemetry antenna free end 305 is supported in outer channel 322.
After all conductive components have been inserted into the core
element 2c and the circuit member 40c has been welded, soldered,
or otherwise fixed into place, the resulting core element assembly
42c may be prepared to undergo the second-shot overmolding process
as discussed above.
Following the injection of the overmold material, the individual
finger elements or connector pads of the circuit member 40c maybe
separated by cutting or trimming intervening conductive traces.
The finger individually isolated elements/connector pads may then
be electrically coupled to respective circuits included in an implantable
medical device. For example, the finger elements/connector pads
included in circuit member 40c are welded or soldered to a feedthrough
pattern of the IMD. This provides the desired electrical connections
between the connector assembly 42c and the IMD. In particular, antenna
finger element 310 becomes electrically coupled to telemetry circuitry
contained within IMD.
FIG. 18 is a side perspective view of an alternative embodiment
of the circuit member. In this view, like features of circuit member
40d as compared to circuit member 40c of FIG. 15 are designated
with like numeric identifiers including an additional suffix. This
embodiment includes a serpentine telemetry antenna 300b having first
and second elements 302b and 306b and bend 308b fabricated as a
continuous wire member having a width 330 formed into a serpentine
configuration having a pitch 332. Pitch 332 is defined as the distance
between two subsequent similar points along the serpentine windings,
e.g., peak to peak as illustrated. The width 330 and pitch 332 are
selected to achieve the desired length of telemetry antenna 300b.
Telemetry antenna 300b is provided with a total length corresponding
to the wavelength of a driving signal for distance telemetry. Generally,
an antenna length of at least one-fourth to one-half the wavelength
of the driving frequency is desired and the length is generally
an integral multiple of the half wavelength of the driving frequency.
The serpentine configuration of telemetry antenna 300b allows antenna
300b to be provided with a longer overall length than the generally
straight wire member elements shown in FIG. 15. The width of the
outer channel of a corresponding core element is provided to appropriately
accommodate the serpentine telemetry antenna 300b. Serpentine telemetry
antenna configurations are generally disclosed in U.S. Patent Publication
No. 2005/0203584, incorporated herein by reference in its entirety.
The serpentine telemetry antenna 300b may be positioned along the
outer channel 322 of core element 2c (shown in FIG. 16) in a similar
manner to the positioning of the wire member antenna 300 as discussed
above and shown in FIG. 17.
FIG. 19 is a perspective view of an alternative embodiment of the
circuit member. In this view, like features of circuit member 40e
as compared to circuit member 40 of FIG. 1 are designated with like
numeric identifiers including an additional suffix. Circuit member
40e includes a telemetry antenna 350 configured in an elongated
or generally flat coil. Telemetry antenna 350 is formed as a wire
member including substantially parallel segments 352, 356, and 360
with intervening turns 354 and 358. Antenna 350 and other antenna
configurations described herein may be formed by die cutting or
punching the wire member in the configuration desired. In other
embodiments, folded or bent antenna structures may be included in
the circuit member.
Telemetry antenna 350 includes a curve 351 corresponding to a curvilinear
side of a core element adapted to engage circuit member 40e as will
be described below. In the configuration shown in FIG. 19, telemetry
antenna 350 includes a first parallel segment 352, a penultimate
turn 354 forming a substantially 180-degree turn, a penultimate
parallel segment 356, a final turn 358 forming a substantially 180-degree
turn, and a final parallel segment 360.
First parallel segment 352 extends between penultimate turn 354
and a free end 362 and is positioned between penultimate parallel
segment 356 and final parallel segment 360. Final turn 358 is provided
having a greater turn width 393 than the turn width 397 of penultimate
turn 354. Telemetry antenna 350 further includes lateral bend 370
extending from final parallel segment 360 to a finger element 372
extending to fixed end 374.
Antenna 350 is shown having two turns 354 and 358 thereby creating
three parallel segments 352, 356, and 360. It is recognized that
telemetry antenna 350 could include additional turns and parallel
segments, such as having three turns thereby forming four parallel
segments and so on. The parallel segments are separated by sequentially
increasing turn widths, to form the generally flat or elongated
coil antenna configuration shown. The parallel segments 352, 356,
and 360 are substantially straight between the turns 354 and 358
but may be formed with parallel curves, e.g. curve 351 between the
turns 354 and 358 for shaping the antenna to conform to a core element
outer surface. It is also recognized that a telemetry antenna including
two parallel segments could be substituted for the antenna shown
in FIG. 19.
FIG. 20 is a top perspective view of a core element 400 adapted
to engage circuit member 40e. Core element 400 includes first and
second major sides 406 and 408 separated by a curvilinear minor
side 404. Major sides 406 and 408 include various receptacles and
apertures for receiving connector members, set screw blocks, circuit
member finger elements, etc., which are not shown in full detail
in FIG. 20 for the sake of simplicity, but may generally correspond,
for example, to those included in core element 2 shown in FIG. 2.
Curvilinear minor side 404 is formed having a first flange 392 and
a second flange 398 forming an outer channel 402 therebetween for
receiving the telemetry antenna. Outer channel 402 includes first
and second antenna guides 380 and 382 extending along at least a
portion of curvilinear minor side 404 between, and substantially
parallel to, flanges 392 and 398. First antenna guide 380 extends
between a first end 395 and a second end 397, and second antenna
guide 382 extends between a first end 390 and a second end 391.
Outer channel 402 and antenna guides 380 and 382 form three grooves
384, 386, and 388 therebetween for receiving telemetry antenna 350.
A guide 410 is provided for guiding a lateral bend of the telemetry
antenna.
FIG. 21 is perspective view of circuit member 40e positioned on
the surface of core element 400. In particular, telemetry antenna
350 is shown positioned along the outer channel 402 of core element
400. The free end 362 and first parallel segment 352 of telemetry
antenna 350 are positioned between antenna guides 380 and 382 in
the middle groove 386. Penultimate turn 354 wraps around the first
end 390 of antenna guide 382. Penultimate parallel segment 356 is
positioned between antenna guide 382 and outer channel flange 392,
in groove 384. Final turn 358 wraps around second end 391 of antenna
guide 382 and second end 397 of antenna guide 380. The final parallel
segment 360 of telemetry antenna 350 is positioned between antenna
guide 380 and outer channel flange 398 in groove 388. Parallel segments
352, 356, and 360 of antenna 350 are thus positioned to extend longitudinally
along curvilinear side 404 of core element 400. The width W of the
wire member material used to form telemetry antenna 350 and the
widths 393 and 397 (shown in FIG. 19) of penultimate and final turns
354 and 358 are selected to fit within the limitations of the width
of outer channel 402 of curvilinear side 404.
The remaining finger elements 42e through 52e may extend over the
outer surface along major side 406 or into core element 400 through
individual apertures to enable connection of finger elements 42e
through 52e to the various set screw blocks, connector members,
etc. assembled in core element 400. Positioning of finger elements
42e through 52 may generally correspond to the configurations described
above, e.g. as in FIGS. 1-4.
FIG. 22 is a perspective view of an alternative embodiment of a
circuit member including an elongated serpentine telemetry antenna.
In this view, like features of circuit member 40f as compared to
circuit member 40 of FIG. 1 are designated with like numeric identifiers
including an additional suffix. Circuit member 40f includes a telemetry
antenna 450 formed from a continuous wire member. Antenna 450 is
formed by cutting or punching the wire member in an elongated serpentine
pattern as compared to the flat coil configuration of antenna 350
of FIG. 19. First parallel segment 452 extends from free end 462
to penultimate turn 454 and is positioned adjacent penultimate parallel
segment 456. Penultimate parallel segment 456 extends between penultimate
turn 454 and final turn 458, and is positioned adjacent final parallel
segment 460. Penultimate turn 454 and final turn 458 are provided
with substantially equal turn widths to form the elongated serpentine
pattern. Parallel segments 452, 456 and 460 are substantially straight
between turns 454 and 458 but do include parallel curves to form
bend or curve 480 for conforming to the curvilinear minor side of
the core element. Telemetry antenna 450 further includes lateral
bend 470 extending from final parallel segment 460 to a finger element
472 extending to fixed end 474.
FIG. 23 is a top perspective view of circuit member 40f positioned
on the surface of core element 400 shown in FIG. 20. The first parallel
segment 452 of telemetry antenna 450 is positioned between antenna
guide 382 and outer channel flange 392 in groove 384. Penultimate
turn 454 wraps around a first end 390 of antenna guide 382. Penultimate
parallel segment 456 is positioned between antenna guide 382 and
antenna guide 380 in grove 386. Final turn 458 wraps around second
end 397 of antenna guide 380. Final turn 458 is provided having
a turn width substantially equal to the turn width of penultimate
turn 454. The final parallel segment 360 is positioned between antenna
guide 380 and outer channel side 398. Parallel segments 352, 356,
and 360 are thus positioned to extend longitudinally along a majority
of the length of curvilinear minor side 404 of core element 400.
The width W of the wire member material used to form telemetry antenna
450 and the widths of penultimate and final turns 454 and 458 are
selected to fit within the limitations of the width of curvilinear
side 404 formed with outer channel 402.
The width W of the wire member used to from the antenna, the number
and width of the turns and the number of parallel segments will
be determined according to a particular application. Telemetry antennas
350 and 450 shown in FIGS. 19 and 22, respectively, are provided
with a total length corresponding to the wavelength of a driving
signal for distance telemetry. As described above, an antenna length
is generally at least one-fourth to one-half the wavelength of the
driving frequency and generally an integral multiple of the half
wavelength of the driving frequency. The configurations of telemetry
antennas 350 and 450 allow the antenna to be provided with a longer
overall length than a generally straight wire member antenna as
shown in FIG. 15.
While antennas 350 and 450 are shown extending over the curvilinear
minor side of the core element 400, it is recognized that an antenna
structure included in a circuit member assembled with a core element
may be adapted to conform to any outer non-conductive surface of
the core element, for example along either of major sides 406 or
408 of core element 400 shown in FIG. 20.
FIG. 24 is a side perspective view of an alternative embodiment
of the circuit member including a telemetry antenna adapted to extend
along a major side of a core element. In this view, like features
of circuit member 40g as compared to circuit member 40 of FIGS.
1 through 4 are designated with like numeric identifiers including
an additional suffix. Circuit member 40g includes a telemetry antenna
500 adapted to be positioned externally on a major side outer surface
of the core element prior to the second-shot overmolding step. Telemetry
antenna 500 includes a wire member bent at a substantially 90 degree
bend 504 for conforming to an outer surface of the core element
and to direct an antenna segment 502 along the surface of a major
side of the core element. Antenna segment 502 is shown in a serpentine
configuration extending from bend 504 to free end 514. Antenna 500
further includes a lateral segment 506 extending from a finger element
510 to bend 504. Finger element 510 terminates at fixed end 512
where antenna 500 is joined to the remainder of circuit member 40g.
FIG. 25 is a perspective view of the circuit member 40g assembled
with a core element 602 adapted to engage circuit member 40g to
form assembly 600. Core element 602 includes various receptacles
and apertures for receiving connector members, set screw blocks,
circuit member finger elements, etc., which are not shown in full
detail in FIG. 25 for the sake of simplicity, but may generally
correspond, for example, to those included in core element 2 shown
in FIG. 2. Core element 602 includes first and second major sides
604 and 606 separated by a minor side 608. An outer channel 614
is formed between first and second flanges 610 and 612 extending
from major side 604.
Circuit member 40g is positioned along core element 602. Antenna
lateral segment 506 extends along core element 602 and bend 504
conforms to the outer surface of core element 602 to position antenna
segment 502 along major side 604. Serpentine antenna segment 502
extends from bend 504 within outer channel 614 to antenna free end
514.
FIG. 26 is a side perspective view of an alternative embodiment
of the circuit member including a telemetry antenna adapted to extend
along a major side of the core element. In this view, like features
of circuit member 40h as compared to circuit member 40 of FIGS.
1 through 4 are designated with like numeric identifiers including
an additional suffix. Circuit member 40h includes a telemetry antenna
550 adapted to be placed externally on a major side outer surface
of the core element prior to the second-shot overmolding step. Telemetry
antenna 550 includes a wire member bent at a substantially 90 degree
bend 554 for conforming to an outer surface of the core element
and to direct antenna segment 552 along the outer surface of a major
side of the core element. Antenna segment 552 is shown in an elongated
serpentine configuration. In an alternative embodiment, antenna
segment 552 may be formed in a flat coil pattern as described previously
in conjunction with FIG. 19. Antenna 550 further includes a lateral
segment 556 extending from a finger element 560 to bend 554. Finger
element 560 terminates at fixed end 562 where antenna 550 is joined
to the remainder of circuit member 40h.
FIG. 27 is a perspective view of the circuit member 40h assembled
with a core element 652 adapted to engage circuit member 40h to
form assembly 650. Core element 652 includes various receptacles
and apertures for receiving connector members, set screw blocks,
circuit member finger elements, etc., which are not shown in full
detail in FIG. 27 for the sake of simplicity, but may generally
correspond, for example, to those included in core element 2 shown
in FIG. 2. Core element 652 includes first and second major sides
654 and 656 separated by a minor side 658. Core element 652 further
includes first and second flanges 660 and 662 forming an outer channel
668 for positioning antenna segment 552. Antenna guides 664 and
666 extend between and substantially parallel to flanges 660 and
662.
Circuit member 40h is positioned along core element 652. Antenna
lateral segment 556 extends along core element 652 and bend 554
conforms to the outer surface of core element 652. Antenna segment
552 extends from bend 554 along major side 654 within outer channel
666 to antenna free end 564. Antenna guides 664 and 666 extend substantially
parallel to flanges 660 and 662 to support and maintain the position
of antenna segment 552 during the overmolding process and prevent
shorts between parallel segments of antenna 550.
Although the above description discusses a particular type of connector
assembly adapted to couple to four leads having particular types
of connectors, it may be noted that the inventive process may be
adapted to manufacture any type of connector assembly having any
number of shapes and sizes, and that is adapted to couple to any
type of lead connector. Alternatively, the process could be utilized
to manufacture any other type of thermoplastic component that is
adapted to include conductive piece parts. Thus, the description
of the specific connector assembly set forth above should be considered
merely illustrative in nature.
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