ULTRASOUND DEVICE, AND ASSOCIATED CABLE ASSEMBLY
BACKGROUND OF THE DISCLOSURE
Field of the Disclosure
Aspects of the present disclosure relate to ultrasonic transducers, and, more particularly, to
an ultrasound apparatus having a cable assembly for forming a connection with a piezoelectric
micromachined ultrasonic transducer housed in a catheter.
Description of Related Art
Some micromachined ultrasonic transducers (MUTs) may be configured, for example, as a
piezoelectric micromachined ultrasonic transducer (pMUT) as disclosed in U.S. Patent No.
7,449,821 assigned to Research Triangle Institute, also the assignee of the present disclosure, which
is also incorporated herein in its entirety by reference.
The formation of a pMUT device, such as the pMUT device defining an air-backed cavity
as disclosed in U.S. Patent No. 7,449,821, may involve the formation of an electrically-conductive
connection between the first electrode (i.e., the bottom electrode) of the transducer device, wherein
the first electrode is disposed on the front side of the substrate opposite to the air-backed cavity of
the pMUT device, and the conformal metal layer(s) applied to the air-backed cavity for providing
subsequent connectivity, for example, to an integrated circuit ("IC") or a flex cable.
In some instances, one or more pMUTs, for example, arranged in a transducer array, may be
incorporated into the end of an elongate catheter or endoscope. In those instances, for a forwardlooking
arrangement, the transducer array of pMUT devices must be arranged such that the plane of
the piezoelectric element of each pMUT device is disposed perpendicularly to the axis of the
catheter / endoscope. This configuration may thus limit the lateral space about the transducer array,
between the transducer array and the catheter wall, through which signal connections may be
established with the front side of the substrate. Further, directing such signal connections laterally
to the transducer array to the front side thereof, may undesirably and adversely affect the diameter
of the catheter (i.e., a larger diameter catheter may undesirably be required in order to
accommodate the signal connections passing about the transducer array).
Where the transducer array is a one-dimensional (ID) array, external signal connections to
the pMUT devices may be accomplished by way of a flex cable spanning the series of pMUT
devices in the transducer array so as to be in electrical engagement with (i.e., bonded to) each
pMUT device via the conformal metal layer thereof. For instance, As shown in Figure 1, in one
exemplary ID transducer array 100 (e.g., 1x64 elements), pMUT devices forming the array
elements 120 may be attached directly to a flex cable 140, with the flex cable 140 including one
electrically-conductive signal lead per pMUT device, plus a ground lead. For a forward-looking
transducer array, the flex cable 140 is bent about the opposing ends of the transducer array such
that the flex cable 140 can be routed through the lumen of the catheter/endoscope which, in one
instance, may comprise an ultrasound probe. However, for a forward-looking transducer array in a
relatively small catheter/endoscope, such an arrangement may be difficult to implement due to the
severe bend requirement for the flex cable (i.e., about 90 degrees), which may also be compounded
by the number of conductors comprising the flex cable and the engagement of the electricallyconductive
signal leads to the pMUT devices (also about a bend of about 90 degrees), in order for
the transducer array to be disposed within the lumen of the catheter/endoscope.
Further, for a forward-looking two-dimensional (2D) transducer array, signal
interconnection with the individual pMUT devices may also be difficult. That is, for an exemplary
2D transducer array (e.g. 14x14 to 40x40 elements), there may be many more required signal
interconnections with the pMUT devices, as compared to a ID transducer array. As such, more
wires and/or multilayer flex cable assemblies may be required to interconnect with all of the pMUT
devices in the transducer array. However, as the number of wires and/or flex cable assemblies
increases, the more difficult it becomes to bend the larger amount of signal interconnections about
the ends of the transducer device to achieve the 90 degree bend required to integrate the transducer
array into a catheter/endoscope. In addition, the pitch or distance between adjacent pMUT devices
may be limited due to the required number of wires/conductors. Accordingly, such limitations may
undesirably limit the minimum size (i.e., diameter) of the catheter/endoscope that can readily be
achieved.
Co-pending U.S. Patent Application No. 61/329,258 (Methods for Forming a Connection
with a Micromachined Ultrasonic Transducer, and Associated Apparatuses; filed April 29, 2010,
and assigned to Research Triangle Institute, also the assignee of the present application), discloses
improved methods of forming an electrically-conductive connection between a pMUT device and,
for example, an integrated circuit ("IC"), a flex cable, or a cable assembly, wherein individual
signal leads extend parallel to the operational direction of the transducer array or perpendicularly to
the transducer array face to engage the respective pMUT devices in the transducer array (see
generally, e.g., FIG. 2). Furthermore, the '258 application discloses that additional signal
processing integrated circuits (IC's) can be integrated between the transducer array and the
corresponding connective elements, thereby increasing the dimension of the transducer/connective
element stack in a longitudinal direction of the disposition thereof in the catheter, but not increasing
the lateral spacing around the transducer array, thus facilitating the configuration of the catheter to
achieve a minimal diameter for a forward-looking transducer array configuration.
In the case of side- or lateral-looking transducer arrays, the transducer array is arranged
such that the plane of the piezoelectric element of each transducer device is disposed in parallel to
the axis of the catheter/endoscope. In such instances, there is relatively more lateral space about
the transducer array, between the transducer array and the catheter wall, along the length of the
transducer array, which may be used to attach connective elements thereto. However, the space
between the back side of the transducer array and the catheter wall may be limited, particularly, for
example, in catheters having an inner diameter of about 3 mm or less. Further, the previouslynoted
thicker stacks placed in a transducer arrangement, as illustrated in FIG. 2 and including a
transducer array, signal processing IC's and connective elements, may not necessarily be feasible in
instances of the limited catheter inner diameter. Such a configuration may also undesirably impart
mechanical stresses to the signal lead (which must be bent about 90 degrees to be routed from the
transducer and along the catheter) and/or transducer array interface due to the thickness of the
transducer / IC stack and the limited space available across the catheter diameter. One particular
example of a prior art side-looking ultrasound catheter transducer is shown in Figure 3, wherein a
piezoelectric element 200 may be attached to a flex cable 210 using conductive epoxy 220. A top
electrode 230 and matching layer 240 may then be deposited on the piezoelectric element 200, and
the structure is then diced using a saw, wherein the cuts extend down to the flex cable 210 in order
to form the elements of the transducer array 250. An acoustic backing 260 may then be applied to
the back of the flex cable 210. However, such a configuration may be limited with respect to the
number of transducer elements that can be practically implemented due, for instance to the
resolution limit of the signal traces of the flex cable. For example, for a 3 mm catheter, only 16
traces with 100 mih pitch (plus ground strips on each side) may fit laterally within the lumen of the
catheter. As such, an appropriate flex cable, such as a Siemens AcuNav flex cable with 64
elements, may undesirably have to be folded into 4 layers of 16 traces each (plus grounds) to
connect all of the elements of a 64 element transducer array. Further, for 2D transducer arrays,
high element counts (e.g., 196 to 1,600 elements) may require multilayer flex cabling for
attachment and interconnection of all transducer elements, further increasing cost and complexity
of the flex cabling. Multilayer flex cable could require up to 16 levels to connect all transducer
elements due to limitations, for example, related to the pitch of conductor traces and interlevel vias
in the flex cable (i.e., typically having a minimum of 100 mhi pitch or more, depending on the
number of levels). Further, for 2D arrays, a flex cable containing several hundred conductors may
be too large in dimension (i.e., too wide and/or too thick) to fit within a 3 mm diameter catheter. A
multiple level flex cable may thus be undesirably expensive, difficult (or impossible) to
manufacture, and may not be robust due to a relatively high probability of short circuits in light of
the increased number of metal levels and vias. Other disadvantages of multilayer flex cabling may
include higher conductor impedance, higher insertion loss, greater cross coupling between element
traces, and higher shunt-to-ground capacitance which may reduce penetration depth compared to
coaxial cabling (though typical coaxial cabling cannot be made with sufficiently fine pitch to be
used in such catheter applications). Flex cabling may also be typically limited to segments of
approximately 1 foot in length. Thus for a catheter that is 3 feet in total length, multiple flex cable
segments must be serially connected in order to complete the electrical connection through the
entire catheter, thereby undesirably increasing complexity and cost of assembly.
Thus, there exists a need in the ultrasonic transducer art, particularly with respect to a
piezoelectric micromachined ultrasound transducer ("pMUT"), whether having an air-backed
cavity or not, for improved methods of forming an electrically-conductive connection between the
pMUT device and, for example, an integrated circuit ("IC") and/or corresponding connective
elements. More particularly, it would be desirable for such an electrically-conductive connection
with the pMUT device to be configured to avoid bending of the flex cable/wiring about the pMUT
device upon integration thereof in the tip of a probe/catheter/endoscope used, for example, in
cardiovascular devices, intravascular and intracardiac ultrasound devices, and laparoscopic surgery
devices. Furthermore, it would be desirable to provide a method for forming electrical connections
with a transducer array having a relatively higher transducer element count/density that is cost
efficient (i.e., relatively low cost) and relatively manufacturable. Such solutions should desirably
be effective for 2D transducer arrays, particularly 2D pMUT transducer arrays, but should also be
applicable to ID transducer arrays, in forward-looking and/or side looking arrangements, and
should desirably allow greater scalability in the size of the probe / catheter / endoscope having such
transducer arrays integrated therein.
BRIEF SUMMARY OF THE DISCLOSURE
The above and other needs are met by aspects of the present disclosure, wherein one such
aspect relates to an ultrasound device comprising an ultrasonic transducer device comprising a
plurality of transducer elements forming a transducer array. Each transducer element comprises a
piezoelectric material disposed between a first electrode and a second electrode. One of the first
and second electrodes comprises a ground electrode and the other of the first and second electrodes
comprises a signal electrode. The ultrasound device further includes a cable assembly comprising a
plurality of connective signal elements and a plurality of connective ground elements extending in
substantially parallel relation therealong. Each connective element is configured to form an
electrically-conductive engagement with respective ones of the signal electrodes and the ground
electrodes of the transducer elements in the transducer array. The connective ground elements are
configured to be alternatingly disposed with the connective signal elements across the cable
assembly, to provide shielding between the connective signal elements.
Yet another aspect of the present disclosure provides an ultrasound device comprising an
ultrasonic transducer device comprising a plurality of transducer elements forming a transducer
array. Each transducer element comprises a piezoelectric material disposed between a first
electrode and a second electrode. One of the first and second electrodes comprises a ground
electrode and the other of the first and second electrodes comprises a signal electrode. The
ultrasound device further comprises a catheter member having a distal end and defining a
longitudinally-extending lumen, wherein the lumen is configured to receive the ultrasonic
transducer device about the distal end. The ultrasound device further comprises a cable assembly
comprising a plurality of connective signal elements and a plurality of connective ground elements
extending in substantially parallel relation therealong. Each connective element is configured to
form an electrically-conductive engagement with respective ones of the signal electrodes and the
ground electrodes of the transducer elements in the transducer array. The connective ground
elements are configured to be alternatingly disposed with the connective signal elements across the
cable assembly such that the connective ground elements provide shielding between the connective
signal elements.
Aspects of the present disclosure thus address the identified needs and provide other
advantages as otherwise detailed herein.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)
Having thus described the disclosure in general terms, reference will now be made to the
accompanying drawings, which are not necessarily drawn to scale, and wherein:
FIGS. 1 and 2 schematically illustrate a prior art arrangements for forming a connection
with a forward-looking transducer apparatus disposed in a lumen;
FIG. 3 schematically illustrates a prior art arrangement for forming a connection with a
side-looking transducer apparatus disposed in a lumen;
FIG. 4 schematically illustrates a cross-sectional view of an exemplary piezoelectric
ultrasonic transducer device, having both ground and signal electrodes disposed about the back side
of the substrate, according to one aspect of the disclosure;
FIG. 5 is a schematic end view of a pMUT device (array) having ground electrodes
arranged about the periphery thereof, with signal electrodes within the periphery, according to one
aspect of the disclosure;
FIG. 6 is a schematic perspective view of an arrangement for assembling connective signal
elements with a connection support substrate, according to one aspect of the disclosure;
FIG. 7 is a schematic end view of the arrangement illustrated in FIG. 6;
FIG. 8 is a schematic cross-sectional view of a cable assembly configured to form a
connection, for example, with the device shown in FIG. 5, according to one aspect of the
disclosure;
FIG. 9 is a schematic end view of a pMUT device (array) having ground electrodes
interstitially disposed with respect to signal electrodes, according to one aspect of the disclosure;
FIG. 10 is a schematic perspective view of an arrangement for forming a connection with a
pMUT device, according to one aspect of the disclosure;
FIG. 11 is a schematic cross-sectional view of a cable assembly configured to form a
connection, for example, with the device shown in FIG. 9, according to one aspect of the
disclosure;
FIG. 12 schematically illustrates a top view of an interposer device arrangement for
forming a connection with a side-looking two-dimensional pMUT device, according to another
aspect of the disclosure;
FIG. 13 schematically illustrates an exemplary pMUT device having connective signal and
ground elements engaged therewith, according to one aspect of the disclosure;
FIG. 14 schematically illustrates a forward-looking ultrasound device, according to one
aspect of the present disclosure;
FIG. 15 schematically illustrates a side-looking ultrasound device, according to one aspect
of the present disclosure;
FIG. 16 is a schematic plan view of an arrangement for forming a connection with a pMUT
device, according to still another aspect of the disclosure;
FIG. 17 is a schematic partial cut away view of the arrangement illustrated in FIG. 16;
FIG. 18A is a schematic cross-sectional side view of an arrangement for forming a
connection with a forward-looking two-dimensional piezoelectric micromachined ultrasonic
transducer device, according to a further aspect of the disclosure;
FIG. 18B is a schematic cross-sectional side view of another arrangement for forming a
connection with a forward-looking two-dimensional piezoelectric micromachined ultrasonic
transducer device, according to a further aspect of the disclosure;
FIG. 19 is a schematic cross-sectional side view of an arrangement for forming a
connection with a forward-looking two-dimensional piezoelectric micromachined ultrasonic
transducer device, according to still another aspect of the disclosure;
FIG. 20 is a schematic cross-sectional side view of an arrangement for forming a
connection with a forward-looking two-dimensional piezoelectric micromachined ultrasonic
transducer device, according to still yet another aspect of the disclosure;
FIGS. 2 1 and 22 are schematic end views of pMUT devices (arrays) having ground
electrodes disposed about a periphery thereof with respect to signal electrodes, according to various
aspects of the disclosure;
FIGS. 23 and 24 are schematic cross-sectional side views of arrangements for forming a
connection with a forward-looking two-dimensional piezoelectric micromachined ultrasonic
transducer device, according to various aspects of the disclosure;
FIG. 25A schematically illustrates a forward-looking ultrasound device, according to one
aspect of the present disclosure;
FIG. 25B schematically illustrates a side-looking ultrasound device, according to one
aspect of the present disclosure;
FIG. 26 schematically illustrates an exemplary interposer device, according to one aspect of
the present disclosure;
FIG. 27 schematically illustrates an exemplary interposer device incorporated into a circuit
board assembly, according to one aspect of the present disclosure;
FIG. 28 schematically illustrates a exemplary component layout for an ultrasound device
including associated cable assembly and termination element, according to one aspect of the
present disclosure;
FIGS. 29 and 30 schematically illustrate an exemplary pMUT device (array) engaged with
a connection support substrate having associated connective signal and ground elements, according
to one aspect of the present disclosure;
FIGS. 3 1 and 32 schematically illustrate a exemplary termination element, such as a
printed circuit board, engaged with a cable assembly having associated connective signal and
ground elements, according to one aspect of the present disclosure; and
FIG. 33 schematically illustrates the distal end of an exemplary catheter assembly having a
transducer array, a connection support substrate, and connective signal and ground elements
disposed in the catheter housing, according to one aspect of the present disclosure.
DETAILED DESCRIPTION OF THE DISCLOSURE
The present disclosure now will be described more fully hereinafter with reference to the
accompanying drawings, in which some, but not all aspects of the disclosure are shown. Indeed,
the disclosure may be embodied in many different forms and should not be construed as limited to
the aspects set forth herein; rather, these aspects are provided so that this disclosure will satisfy
applicable legal requirements. Like numbers refer to like elements throughout.
Aspects of the present disclosure are generally applicable to ultrasonic transducers, though
particular aspects are particularly directed to a piezoelectric micromachined ultrasound transducer
("pMUT") having an air-backed cavity. More particularly, aspects of the present disclosure are
directed to methods of forming an electrically-conductive connection between a pMUT device and,
for example, an integrated circuit ("IC") and/or corresponding connective elements, whereby
individual signal and ground leads may extend parallel to the operational direction of the transducer
array to engage the respective pMUT devices in the transducer array (see generally, e.g., FIG. 2).
The pMUT device may be disposed within a catheter member 350 having a distal end or tip 310
(see, e.g., FIGS. 14 and 15). The catheter member 350 may further define a longitudinallyextending
lumen configured to receive the pMUT device about the distal end 310. The pMUT
device may further comprise a cable assembly 325 comprising connective elements, and having one
or more connection support substrates 155 disposed about the distal end 310 and proximal end 315
of the catheter.
In such aspects, a representative pMUT or ultrasonic transducer device 270 that may be
implemented in both ID and 2D transducer arrays, may generally comprise a plurality of transducer
elements forming a transducer array, wherein each transducer element 272 comprises a
piezoelectric material disposed between a first electrode and a second electrode, and wherein one of
the first and second electrodes comprises a ground electrode and the other of the first and second
electrodes comprising a signal electrode. More particularly, as shown, for example, in FIG. 4, a
transducer element 272 may be disposed on a dielectric layer 274 of a device substrate 276,
wherein the transducer element 272 includes a piezoelectric material 278 disposed between a first
electrode 280 and a second electrode 282. The primary substrate 284 defines a first via 286
extending to the device substrate 276, while the device substrate further defines a second via 288
extending therethrough to the first electrode 280. In some instances, the first and second via 286,
288 arrangement may extend to the first electrode 280, which is engaged with the second electrode
282 (shown generally at element 290), thereby connecting the second electrode 282 to the back side
of the substrate. Such an arrangement may be applied, for example, as a back side ground pad or
ground electrode for the pMUT device 270. In such instances, the first and second vias 286, 288
may have a conformal insulating layer 292 deposited therein, before the first and second vias 286,
288 are substantially filled with first and second conductive materials, respectively 294, 296. In
some aspects, the first and second electrode engagement 290 may be disposed, as necessary or
desired about a pMUT array. In some instances, such an arrangement 290 may be disposed about
the periphery of the pMUT array incorporating the pMUT device structure 270 (see, e.g., FIG. 5),
or in interstices between adjacent pMUT device structures 270 within a pMUT array (see, e.g., FIG.
9). Such pMUT devices 270 are disclosed, for example, in U.S. Provisional Patent Application No.
61/299,514 ("Methods for Forming a Micromachined Ultrasonic Transducer, and Associated
Apparatuses"), assigned to Research Triangle Institute, and which is incorporated herein in its
entirety by reference.
Particular materials that can be implemented for the piezoelectric material 278 include, for
example, ceramics including ZnO, A1N, LiNb0 4, lead antimony stannate, lead magnesium
tantalate, lead nickel tantalate, titanates, tungstates, zirconates, or niobates of lead, barium, bismuth,
or strontium, including lead zirconate titanate (Pb(Zr Tii -x)0 3 (PZT)), lead lanthanum zirconate
titanate (PLZT), lead niobium zirconate titanate (PNZT), BaTi0 3, SrTi0 3, lead magnesium niobate,
lead nickel niobate, lead manganese niobate, lead zinc niobate, lead titanate. Piezoelectric polymer
materials such as polyvinylidene fluoride (PVDF), polyvinylidene fluoride-trifluoroethylene
(PVDF-TrFE), or polyvinylidene fluoride-tetrafluoroethylene (PVDF-TFE) can also be used.
One method of forming an electrically-conductive connection with one configuration of a
pMUT device 270, in the form of a two-dimensional forward-looking pMUT array, is
schematically illustrated, for example, in FIGS. 6-8. In such instances, the pMUT device (array)
270 may incorporate a plurality of pMUT elements 272, with the pMUT array having ground pads
or electrodes 298 (e.g., as associated with the first and second electrode engagement 290 of the
pMUT device 270, as shown in FIG. 4) arranged about the periphery of the array such that the
signal pads or electrodes 300 (see, e.g., FIG. 5; as associated with transducer element 272 of the
pMUT device 270) are arranged within the periphery, for example, in regular rows. In such
aspects, signal leads (connective elements) and ground leads (connective elements) extending
parallel to the operational direction of the transducer array may be configured to form electrically
conductive engagements with the respective ground and signal electrodes 298, 300 of the pMUT
elements 272 within the array, wherein, in some instances, one or more of the ground electrodes
298 may be common to more than one of the pMUT elements 272 within the array 270.
According to one aspect, as shown in FIGS. 6 and 7, a 2D array of connective elements
(i.e., wires) may include connective signal elements 150 and connective ground elements 160, each
of which may or may not be coated with an insulator layer. In one instance, it may be desirable that
at least the connective signal elements 150 each be coated with an insulator layer. In order to form
the electrically-conductive engagement between the connective signal and ground elements 150,
160 and the respective signal and ground electrodes 300, 298 of the pMUT device (array) 270, the
connective signal and ground elements 150, 160 may first be arranged such that first ends thereof
are engaged with and supported by a connection support substrate 155. Such an engagement may
be accomplished, for instance, using a guide substrate 170 defining a plurality of parallel, spacedapart
channels 180 extending across the width thereof (and along the length of the guide substrate
170), wherein the lateral pitch of the channels 180 generally corresponds to the lateral pitch of the
connective elements 150, 1 0 of the pMUT device 270. Once the connective elements 150, 160 are
inserted into the respective channels 180, so as to extend longitudinally outward thereof, a retaining
member 190 may be removably applied over the channels 180 so as to retain the connective
elements 150, 160 within the channels 180. Once prepared, the guide substrate 170 may be
disposed adjacent to the intended connection support substrate 155 (i.e., using micropositioners),
and the connective elements 150, 160 directed along the channels 180 to engage the connection
support substrate 155 for securement therein. The connection support substrate 155 may be, for
example, a silicon substrate with through-holes etched using deep reactive ion etching (D IE) to
provide straight (i.e., substantially vertical or otherwise substantially perpendicular to the plane of
the substrate) sidewalls in the through-holes, which may facilitate high density arrays of holes (i.e.
without lateral angled sidewalls created by a wet etching process such as KOH etching). Once
engaged with the connection support substrate 155, the connective elements 150, 160 maybe fixed
in the through-holes of the connection support substrate 155 using an adhesive material such as, for
instance, an insulating epoxy. The free or unengaged surface of the connection support substrate
155 may then be polished or otherwise planarized to facilitate subsequent bonding to the pMUT
device 270. Such a process for engaging the connective elements 150, 160 with a connection
support substrate 155 is disclosed, for example, in U.S. Patent Application No. 61/329,258
("Methods for Forming a Connection with a Micromachined Ultrasonic Transducer, and Associated
Apparatuses"), previously been incorporated by reference, and which discloses other methods for
engaging connective elements with a connection support substrate, as well as forming an
electrically-conductive engagement between the connective elements and a pMUT device, a
transducer array, or an intermediate device such as an interposer.
In this regard, the connection support substrate 155, having the connective signal and
ground elements 1 0, 160 engaged therewith, may be configured to engage the pMUT device 270
about the signal and ground electrodes 300, 298, so as to provide, for example, an appropriate pitch
or spacing of the connective signal and ground elements 150, 160 in correspondence with the
pMUT device 270, as well as mechanical support for the direct electrically-conductive engagement
between the connective signal and ground elements 150, 160 and the respective signal and ground
electrodes 300, 298. As shown in FIG. 8, the connective elements 150, 160 may thus be assembled
with the connection support substrate 155 such that the connective ground elements 160 are
disposed about the periphery of the connection support substrate 155 so as to correspond to the
ground electrodes 298 and to facilitate the formation of the electrically-conductive connection
therewith. The conductive signal elements 150 are thus disposed within the periphery of the
connection support substrate 155 so as to correspond to the signal electrodes 300 and to facilitate
the formation of the electrically-conductive connection therewith.
Further aspects of the present disclosure may be directed to a method of forming an
electrically-conductive connection with another configuration of a pMUT device 270, in the form
of a two-dimensional forward-looking pMUT array, is schematically illustrated, for example, in
FIGS. 9-11. In such instances, the pMUT device (array) 270 may incorporate a plurality of pMUT
elements 272, with the pMUT array having the signal pads or electrodes 300 (see, e.g., FIG. 5; as
associated with transducer element 272 of the pMUT device 270) arranged, for example, in regular
rows, with the ground pads or electrodes 298 (e.g., as associated with the first and second electrode
engagement 290 of the pMUT device 270, as shown in FIG. 4) arranged in the interstices of the
signal electrodes 300 of the array (see, e.g., FIG. 9). According to such an arrangement, the ground
electrodes 298 may be considered interspersed within the regular rows of signal electrodes 300, or
the rows of ground electrodes 298 may be laterally shifted by about half of the pitch or spacing
between signal electrodes 300 such that alternating rows of signal electrodes 300 and ground
electrodes 298 are staggered with respect to each other. In such aspects, signal leads (connective
elements) and ground leads (connective elements) extending parallel to the operational direction of
the transducer array may be correspondingly configured (see, e.g., FIGS. 10 and 11) to form
electrically conductive engagements with the respective ground and signal electrodes 298, 300 of
the pMUT elements 272 within the array, wherein, in some instances, one or more of the ground
electrodes 298 may be common to more than one of the pMUT elements 272 within the array 270.
As such, one skilled in the art will appreciate that various arrangements of the connective elements
150, 160 may be required to form the electrically-conductive engagements with the various
arrangements of pMUT elements 272 within the pMUT device (array) 270.
According to some aspects, the connective elements 150, 160 may be electrically- engaged
with a side- or lateral-looking transducer array. A representative ultrasound device implementing a
side- or lateral-looking transducer array is disclosed, for example, in U.S. Provisional Patent
Application No. 61/419,534 ("Method for Forming an Ultrasound Device, and Associated
Apparatus"), filed concurrently herewith, and which is incorporated herein in its entirety by
reference. In such instances, particularly when the pMUT device (array) is disposed within a
catheter, the connective elements 150, 160 extend along the catheter, and are required to engage the
transducer array having the ground and signal electrodes 298, 300 of the pMUT elements 272
perpendicularly disposed with respect to the longitudinal axis of the catheter. In such instances, the
connection support substrate 155 may be configured to facilitate navigation of the change in
direction (i.e., having the channels extending therethrough at an angle of about 90 degrees with
respect to the longitudinal axis of the catheter). In other instances, the connective elements 150,
160 may be configured to engage an interposer device 400, as shown, for example, in FIG. 12,
configured to receive, engage and support an ultrasonic transducer apparatus (array - not shown)
such that a device plane of the ultrasonic transducer apparatus extends substantially parallel to the
interposer device 400. In some instances, the interposer device 400 also includes at least two
conductors 450 extending therealong (i.e., through the interposer device 400 or along a surface
thereof), wherein the conductors 450 each have opposed first and second ends 450A, 450B. One of
the ends 450B may be configured to engage the respective signal and ground electrodes 298, 300,
in some instances, via wirebond pads such as, for example in a wire bonding process; while the
other of the ends 450A may be configured to engage the connective signal and ground elements
150, 160, whether directly or via a connection support substrate.
As shown in FIG. 13, one end of the cable assembly 325, incorporating the connection
support substrate 155 and the connective signal and ground elements 150, 160, may be polished or
otherwise planarized (i.e., perpendicularly to the longitudinal axis) so as to provide a planar surface
for bonding, with an appropriate bonding material 167, the same to the pMUT device (array) 270.
Thus, the cable assembly 325 may be bonded or otherwise engaged with the pMUT device 270 in a
number of manners, for example, according to methods and configurations described, for example,
in U.S. Patent Application No. 61/329,258 ("Methods for Forming a Connection with a
Micromachined Ultrasonic Transducer, and Associated Apparatuses"), previously incorporated by
reference. In general, connective elements 150, 160 may be assembled into connection support
substrates and bonded to transducer arrays / pMUT devices, interposers or other termination
element, as disclosed, for example, in U.S. Patent Application No. 61/329,258 ("Methods for
Forming a Connection with a Micromachined Ultrasonic Transducer, and Associated
Apparatuses") assigned to Research Triangle Institute (also the assignee of the present disclosure),
and previously incorporated herein by reference. In some instances, as shown, for example, in
FIGS. 14 and 15, the cable assembly 325, incorporating the connection support substrate 155 and
the connective signal and ground elements 150, 160, may be terminated at both ends 310, 315
thereof with a connection support substrate, interposer, or other termination element. More
particularly, one end 310 is configured to engage the pMUT device (array) 270, whether directly
via a connection support substrate or via an interposer device, while the opposing end 315 extends
along and/or outwardly of the catheter 350, away from the tip thereof, to engage a connection
support substrate, interposer, circuit board (i.e., associated with a computer device), semiconductor
package, or other termination element (see, generally, element 375) configured to provide external
connectivity between the pMUT device (array) 270 disposed in the catheter 350 and, for example,
an external ultrasound system or other image display device. The connective elements 150, 160
may be individually assembled at both ends of the cable assembly 325 such that the connective
elements 150, 160 may be mapped or otherwise tracked with respect to connectivity to the
transducer elements 272 within the array 270, such that, for instance, the locations of the transducer
elements within the transducer array can be identified and controlled by the appropriate electronic
channels in the external ultrasound system.
In light of the aspects previously disclosed, with respect to forming electrically-conductive
engagements with the pMUT elements 272 in the pMUT array 270, some aspects of the present
disclosure are further directed to a cable assembly 325 comprising a plurality of connective signal
elements 150 and a plurality of connective ground elements 160 extending in substantially parallel
relation along the cable assembly 325, with each being configured to form an electricallyconductive
engagement with respective ones of the signal electrodes 300 and the ground electrodes
298 of the transducer elements 272 in the transducer array 270. More particularly, in some aspects,
the connective ground elements 160 are configured to be altematingly disposed (i.e., whether
constructively or actually) with the connective signal elements 150 across the cable assembly 325,
so as to provide shielding between the connective signal elements 150.
In some instances, as shown, for example, in FIGS. 16 and 17, the cable assembly 325 may
be configured to provide altematingly disposed connective ground elements 160 and connective
signal elements 150 (i.e., in actual correspondence with the configuration of the signal and ground
electrodes 300, 298 of the transducer array 270). That is, the connective ground elements 160 may
be interspersed among the connective signal elements 150, or otherwise be disposed between two
or more connective signal elements 150 (i.e., in interstices between adjacent connective signal
elements 150). The altematingly disposed connective ground elements 160 and connective signal
elements 150 (see, e.g., FIG. 11) may further be engaged at opposing ends 310, 315 with
connection support substrates 155, wherein at one such end 310, a connection support substrate 155
may be engaged with the transducer array 270, in some instances with an interposer device
disposed therebetween, while the opposing end 315 may have one or more connection support
substrates 155 engaged with an interposer, circuit board, semiconductor package, or other
termination element, as previously disclosed. By actually alternating the connective ground
elements 160 and the connective signal elements 150, the connective ground elements 160 may
function as a shield or ground between the connective signal elements 150 in order, for example, to
reduce cross-talk between the connective signal elements 150 with respect to signals from the
transducer elements 272. The connective elements 150, 160, comprised of, for example, relatively
fine gauge wire (e.g., insulated magnet wire having a diameter of between about 40 AWG and
about 50 AWG), may be individually engaged with the connection support substrates 155 between
opposing ends so as to provide a registration with respect to the connective ground and signal
elements 150, 160. In some instances, for example, a color indicia scheme may be implemented to
distinguish the connective ground and signal elements 150, 160.
In some instances, the connective elements 150, 160 of the cable assembly 325 may be
encapsulated with a dielectric material, such as, for example, a conformal dielectric coating 320, to
seal and bundle the connective elements 150, 160 to form the cable assembly 325. In other
instances, the connective elements 150, 160 may be wrapped with an outer covering, such as, for
example, a shrinkable tubing, extending therealong so as to provide a flexible but robust cable
assembly 325. In further instances, additional shielding for the connective elements 150, 160 may
be provided, for example, by a conductive film, such as, for example, a metal foil material 322
(e.g., MYLAR®), wrapped about the connective elements 150, 160. The dielectric coating 320
may be applied to cover the conductive film 322, such that the conductive film 322 is disposed
between the connective elements 150, 160 and the dielectric coating 320. In other instances (not
shown), a conductive film may be wrapped about the dielectric material 320, so as to be disposed
between the catheter member 350 and the dielectric material 320 encapsulating the connective
signal and ground elements 150, 160. In either instance, the conductive film 322 may provide
additional shielding for at least the connective signal elements 150, 160. Still in other instances,
additional shielding may be molded or otherwise incorporated into the catheter member 350 such
as, for example, a metal braid (not shown) molded into the catheter member 350.
In some aspects, the ground electrodes 298 arranged about the periphery of the transducer
array 270 may be much less than the number of transducer elements 272 (and thus the
corresponding number of signal electrodes 300) in the array 270. For example, a 20x20 transducer
array with 125 m pitch may yield a transducer array of about 2.5 mm in width. In such an
instance, a catheter size of 10 French (2.8 mm I.D.) would be needed. Thus, only one ring of
ground electrodes 298 could be disposed about the periphery of the transducer array, resulting in a
22x22 array with an overall width of about 2.75 mm. As such, the arrangement would include 400
transducer elements 272 (corresponding to 400 signal electrodes 300 disposed within the periphery)
and 84 ground electrodes 298. If corresponding connective signal and ground elements 150, 160
are incorporated into the corresponding cable assembly 325, the relatively few connective ground
elements 160 may not necessarily provide adequate shielding for the connective signal elements
150. As such, further aspects of the present disclosure are directed to other arrangements, whether
actual or constructive, wherein the connective ground elements 298 of the cable assembly 325 are
alternatingly disposed or otherwise interspersed with respect to the connective signal elements 150
along the length of the cable assembly 325. One skilled in the art will appreciate that other
arrangements may be provided in order to increase the ratio of ground to signal wires without
increasing one or both lateral dimensions of the transducer array. For example, as shown in FIG.
21, additional columns of connective ground elements 298 may be arranged only along one axis of
the transducer array 270 adjacent to the connective signal elements 300. More particularly, such an
arrangement may include, for example, a 20x26 array containing 400 connective signal elements
and 120 connective ground elements, or a 20x40 array containing 400 connective signal elements
and 400 connective ground elements. In another aspect, for instance, the corners of the array can
be implemented as connective ground elements 298 in order to maintain array size along both
cross-sectional axes. More particularly, for example, the 20x20 array shown in FIG. 22 may be
configured to include 340 connective signal elements and 60 connective ground elements.
In this regard, as shown in FIG. 18A, the connective signal elements 150 and connective
ground elements 160 may be intermingled such that the connective ground elements are
substantially or constructively alternatingly disposed or otherwise interspersed with respect to the
connective signal elements 150, regardless of the position in which the respective connective
ground element 160 interacts with the termination element (i.e., connection support substrate 155).
That is, in instances where the connective ground elements engage the termination element (i.e.,
connection support substrate 155) about the periphery thereof, the respective connective ground
elements 160 may be routed between the connective signal elements 1 0 at least partially along the
length of the cable assembly 325 (i.e., from the periphery about the first termination element, along
the cable assembly 325 at an interstitial site, and back to the periphery about the opposing second
termination element). Further, in some instances, the connective signal elements 150 and
connective ground elements 160 may be twisted (i.e., in pairs or larger number of such elements)
together, at least partially along the length of the cable assembly 325, as another manner of routing
the connective ground elements 160 between the connective signal elements 150 at least partially
along the length of the cable assembly 325. Further, as shown in FIG. 18B, additional connective
ground elements 165 may be attached or otherwise incorporated in to the cable assembly 325 using,
for example, a conductive epoxy 306 applied to the support substrate 155 and/or otherwise to the
cable assembly 325, wherein such additional connective ground elements 165 may be further
interspersed between the connective signal elements 150. Such additional connective ground
elements 165 may further be inserted into the connection support substrate 155, or may be separate
elements, externally-attached using, for example, a conductive epoxy material. The additional
connective ground elements 165 may be, for instance, individual wires, strips of metal foil, and/or
other conductive material interspersed between the connective signal elements (i.e., wires) to
provide additional shielding therefor.
In another aspect, as shown in FIG. 19, the connective signal elements 150 maybe insulated
along the length of the cable assembly 325, while the connective ground elements may be bare, or
at least partially bare, conductive material (i.e., bare or partially bare copper wire). In such
instances, a conductive epoxy material 306 may be applied to the connective elements 150, 160 so
as to extend between the collective elements 150, 160 and collectively encapsulate the connective
elements 150, 160. The conductive epoxy material 306 may extend along the cable assembly 325
between the opposed ends, as shown in FIG. 19, or only partially along the length of the cable
assembly 325, as shown in FIG. 20. The conductive epoxy material 306 may be, for example, a
silicone, a urethane-based epoxy or other flexible epoxy filled with conductive particles or
otherwise having conductive particles incorporated therein, or other suitable material, wherein such
epoxy materials may promote or facilitate flexibility of the cable assembly 325. Further, such a
conductive epoxy material 306 may form an electrically-conductive engagement with the
connective ground elements (bare or partially bare conductive material) 160 so as to essentially
form a single conductive body extending about and between all connective signal elements 150.
Such a configuration thus constructively facilitates connective ground elements 160 that are
altematingly disposed with respect to the connective signal elements 150 along the cable assembly
325.
According to another aspect, the connective signal elements 150 may be coated with a
conductive coating material applied to each such elongate insulated element extending along the
cable assembly 325. In such instances, the connective ground elements 160 may be at least
partially in electrically-conductive communication with the connective signal elements 150 via the
conductive coating material, thus also constructively facilitating connective ground elements 160
that are altematingly disposed with respect to the connective signal elements 150 along the cable
assembly 325. For example, a conformal thin film copper layer may be deposited on the insulator
material covering the connective signal elements 150 by metal organic chemical vapor deposition
(MOCVD), electroless plating, or a conductive spray process. Such a coating may form a coaxial
conductor configuration for each connective signal element 150, such that this outer coating may be
electrically-connected to the connective ground elements 160 via the conductive epoxy 306 applied
thereto, thus providing additional shielding around each connective signal element 150. Coating
the connective signal elements 150 with a conductive substance may further facilitate increased
flexibility of the cable assembly 325 by allowing the conductive epoxy material 306 to be applied
only partially along the length of the cable assembly 325, as shown in FIG. 20. In such an aspect,
the conductive epoxy material 306 may be applied to the connective elements 150, 160 proximate
to the connection support substrates 155 and not along the entire length of the cable assembly 325.
Such a configuration constructively facilitates connective ground elements 160 that are
alternatingly disposed with respect to the connective signal elements 150 about the connection
support substrates 155 by way of the conductive epoxy material 306, while such alternating
disposition of the connective ground elements 160 is otherwise facilitated by the conductive
coating material applied to the connective signal elements 150 (i.e., by way of conductive physical
contact between the conductive coating material and the bare conductive material of the conductive
ground elements 160) along the length of the cable assembly 325 free of the conductive epoxy
material 306.
The cable assemblies shown in FIGS. 16-20 are exemplary cable assemblies for forwardlooking
ID or 2D arrays as shown, for instance, in FIG. 14. In another aspect, similar cable
assemblies can be configured, for example, as shown in FIG. 23, for side-looking D and 2D
arrays, as shown in FIG. 15. In such instances, the connection support substrate 255 bonded to or
otherwise engaged with the transducer array 270 may be configured to facilitate a change in
direction of the connective signal and ground elements 150, 160 extending longitudinally along the
catheter to a mating arrangement for the transducer array 270, wherein such a mating arrangement
may be oriented perpendicularly to the longitudinal axis of the catheter. Once engaged with the
mating arrangement, the signal and ground wires (the connective signal and ground elements) can
then be bent approximately 90 degrees to extend the connective elements substantially parallel with
the longitudinal axis of the catheter. Such a configuration of the cable assembly may thus also
facilitate bending of the connective signal and ground elements, for example, in comparison to a
multiple level flex cable arrangement that may be relatively stiffer and more difficult to bend
without risk of damage to the flex cable assembly. For the assembly shown in FIG. 23, each
individual conductor wire (conductive element) may have a relatively small diameter (e.g., between
about 40 AWG and about 50 AWG), and may thus be relatively flexible and readily bent at about a
90 degree angle. The bent conductors may then be, for example, encapsulated by an epoxy material
such as, for example, a potting epoxy 400, as shown in FIG. 25B, to provide stiffness and/or strain
relief for the conductors, adjacent to the connection support substrate 255 attached to the transducer
array 270 disposed at the distal end 310 of the catheter member 350.
In some instances, the distal end 310 of the catheter member 350 may also include a fluidcontaining
or fluid-filled capsular member 410, as shown in FIGS. 25A and 25B, configured to
house at least the pMUT device 270. The fluid contained within the capsular member 410 may, for
example, facilitate acoustic transmission of the acoustic energy emitted by the pMUT device 270
through the catheter wall and into the body or fluid bed of the organ being imaged, for example, the
heart or a vessel. Some standard or existing piezoelectric ultrasound transducers may be embedded
in an epoxy material to facilitate acoustic transmission via an epoxy matching layer. However,
pMUT devices according to aspects of the present disclosure include flexible transducer
membranes (i.e., piezoelectric material 278) that are preferably configured and arranged to avoid
mechanically loading or constraint by a mechanical impediment such as an epoxy layer. Thus, the
fluid medium contained within the capsular member 410 and in contact with the pMUT transducer
array 270 may provide an advantageous configuration for improve signal transmission and imaging
capabilities. The fluid contained within the capsular member 410 may comprise, for instance,
silicone or other fluid with appropriate viscosity, for example, between about 1 cSt and about 100
cSt, and/or appropriate acoustic impedance, for example, between about 1 MRayl and about 1.5
MRayl, or less than about 5 MRayl. Once formed, the pMUT device 270 having the connection
support substrate 255 engaged therewith may be inserted into the lumen of the catheter and, in turn,
into the capsular member 410 disposed about the distal end 310 of the catheter. In other aspects,
the capsular member 410 may be engaged with the distal end 310 of the catheter, externally or
substantially externally to the lumen of the catheter. The capsular member 410 may then be filled
or substantially filled with the appropriate fluid, and the capsular member then be sealed, whether
about the cable assembly 325 or otherwise, using, for example, heat or epoxy, to form a fluid tight
seal. In some aspects the capsular member 410 may be sealed to as to contain at least the pMUT
device 270. However, in some instances, the capsular member 410 may be sealed about the
connection support substrate 255 engaged with the pMUT device 270, about the epoxy material
(i.e., potting epoxy 400), if present, applied to the connective elements of the cable assembly 325
adjacent to the connection support substrate 255, or about the cable assembly 325 itself.
At the proximal end 315 of the catheter 350, the connection support substrate 355 of the
cable assembly 325 may be engaged with or otherwise terminated by a termination element 375,
such as, for example, an interposer, circuit board or semiconductor package. In this regard, the
distal end connection support substrate 255 may have a pitch of the connective signal and ground
elements 150, 160 that is approximately the same as the transducer array 270 in order to facilitate
bonding and electrical engagement of the connective elements to the pMUT array 270. Such a
relatively fine pitch may also facilitate extension of the connective elements substantially parallel
(or first bent at about 90 degrees and then extension substantially parallel) to the longitudinal axis
of the catheter in a close-packed configuration. Such an arrangement may, for instance, allow
several hundred conductors to fit within a small, for example, 3 mm diameter, catheter 350. About
the proximal end 315 of the catheter 350, the connective signal and ground elements 150, 160
engaged with the connection support substrate 355 may be configured to electrically-engage
corresponding conductor elements associated with a termination element 375 such as, for example,
an interposer, circuit board or semiconductor package. Such conductor elements may comprise, for
example, metal conductors deposited by electroplating, RF sputtering or evaporation, and patterned
on the surface of the termination element 375. The conductor elements of the termination element
375 may, for example, facilitate an electrically-conductive engagement between the connective
signal and ground elements 150, 160 associated with the connection support substrate 355, and, for
instance, a connector cable for the ultrasound system, solder bumps attaching additional circuitry
by flip chip bumping, or other devices configured to facilitate generation of the ultrasound image
by an external device or system. In another aspect, such an arrangement may be advantageous, for
example, by providing a cable assembly 325 having a relatively lower materials cost. For example,
insulated magnet wire may cost approximately $0 004 per meter length, whereas some flex cables
containing 16 conductors may cost approximately $10 per meter length. Thus, for 256 conductors
in a 1 meter length catheter, magnet wire may cost about $ 1 per catheter, whereas flex cable could
cost about $160 per catheter. Such an example thus illustrates the magnitude of the cost savings
that may be realized according to various aspects of the present disclosure.
In some instances, the pitch of the connective signal and ground elements 150, 160 may be
increased in order to facilitate engagement with the termination element 375 and, in turn,
engagement between the termination element 375 and the external ultrasound system. For
example, routing 400 connective signal elements (20x20 array) with respect to an interposer device
having an element pitch of between about 100 microns and about 200 microns may be difficult
without requiring conductor traces on the interposer device to be extremely narrow and close
together. Such a configuration could undesirably cause cross talk between conductor traces, as well
as increased oh c resistance thereof, which could degrade the signals carried thereby. An
example of such a termination interposer device 500 is shown, for example, in FIG. 26, wherein
such an interposer device 500 includes a 20x20 array of signal pads 10 for engaging the
connective signal elements 150. Such signal pads 510 are routed through signal traces 520 to
connection pads 530, wherein the interposer device can then be electrically-connected through the
connection pads 530, via wirebonding or solder bumping, for example, to a circuit board or other
semiconductor package. In instances where the spacing between the signal pads 510 is about 75
mh , the pitch of the signal traces 520 may be as small as about 16 m h, with the width of the signal
traces 520 being as small as about 8 m , and the length of the signal traces 520 being at least
several millimeters from the signal pads 510 to the connection pads 530 disposed about the edges
of the interposer device. The 20x20 array may be about 4 mm in width, while the interposer device
may have a width of about 17 mm. Further, as many as 4 signal traces 520 may be routed between
signal pads 510. Such a relatively fine pitch and relatively narrow trace width could thus carry the
risk of causing signal degradation.
As such, according to some aspects, an arrangement for termination of the connection
support substrate 355 is shown, for example, in FIGS. 24 and 27. In such aspects, the main cable
assembly 325, containing several hundred conductors, can be divided into smaller cable
subassemblies 330 near the proximal end 315, as shown, for example, in FIG. 24. For example, a
cable assembly 325 with 600 conductors can be divided into 8 subassemblies 330 containing 75
conductors each, with each subassembly 330 toward the proximal end 315 having its own
termination connection support substrate 355. Each subassembly 330 may be bonded to an
individual interposer device 610 configured as shown, for example, in FIG. 27. As shown in FIG.
27, a termination circuit board 600 may include routing to connect termination interposer devices
610 to connectors 620 for a cable extending to the external ultrasound system. For example, for a
cable assembly 325 having 512 signal wires (connective signal elements), each termination
interposer device 610 may include, for example, 64 signal traces. One or more interposer devices
610 can be connected to connection pads 630 on the termination circuit board 600, for instance, via
wirebonding, by solder bumping, or by mounting the interposer devices 610 into semiconductor
packages (not shown) that are connected to the termination circuit board 600. The routing
associated with the termination circuit board 600 may then be implemented to electrically engage
the signal traces to the connector 620 associated with the external ultrasound system. In such
instances, signal trace routing associated with the interposer device 610 can be accomplished with
relatively shorter traces, relatively wider signal traces, and relatively larger pitch, thus reducing or
otherwise eliminating signal degradation.
An exemplary overall schematic of a component layout for a pMUT array 270 with
associated cable assembly and termination element is shown in FIG. 28. The transducer array 270
may be bonded to the distal connection support substrate 255 having the connective signal and
ground elements 150, 160 (not shown) engaged therewith using, for example, solder bumps, gold
stud bumps or an anisotropic conductive epoxy, to provide an electrically-conductive connection
between the pMUT array elements and the connective signal and ground elements (wires) 150, 160.
The connective elements extend as part of the cable assembly (not shown) to the proximal
connection support substrate(s) 355 (i.e., the termination). The connection support substrates 355
may then be bonded to the termination interposer devices 610 using, for example, solder bumps,
gold stud bumps or an anisotropic conductive epoxy, to provide an electrically-conductive
connection between the connective signal and ground elements (wires) 150, 160, and the signal
pads 510 of the respective interposer device 610. The interposer routing 520 subsequently provides
an electrically-conductive connection to the connection pads 530 of that interposer device 610,
which may then, in turn, be wirebonded or otherwise electrically connected to the connection pads
630 of a termination PC board 600 associated with the external ultrasound system. In other aspects,
the interposer devices 610 may be wirebonded into semiconductor packages 640 that may be
mounted onto termination PC boards 600 using, for example, electrically conductive pins or solder
bumps. In still other aspects, the interposer devices 610 may instead include through-silicon vias or
through-substrate vias substantially filled with a conductive material, wherein such vias, or other
conductive traces associated with the interposer device 610, may be attached to connection pads
530 on the termination PC board 600, for instance, via solder bumps, gold stud bumps, or an
anisotropic conductive epoxy. The termination PC board 600 further routes the connections with
the connective elements from the interposer device to the connector 620 associated with a cable
650 extending to the external ultrasound system. In some instances, the termination PC board 600
may also include other circuitry to facilitate forming of an ultrasound image, for example, transmit
pulsers, transmit beamformers, amplifiers, receive beamformers, transmit/receive switches, timing
circuits, and other appropriate circuitry and/or components, as will be appreciate by one skilled in
the art.
Aspects of a cable assembly 325 as disclosed herein may be implemented, in some
instances, with other types of appropriately-configured ultrasound transducers, as will be
appreciated by one skilled in the art. Such an appropriately configured ultrasound transducer may
comprise, for example, a PZT ceramic ultrasound transducer with signal and/or ground electrodes
on at least one side of the transducer array for connection to a connection support substrate of the
cable assembly 325. In another aspect, such an ultrasound transducer may comprise, for instance, a
capacitive micromachined ultrasound transducer (cMUT), that may include through-silicon or
through- substrate vias for providing electrically-conductive connections with the back side of the
substrate, may be bonded to a connection support substrate of the cable assembly 325. Thus, a
cable assembly 325 according to aspects of the present disclosure may be implemented with many
other types and configurations of ultrasound transducers to facilitate the connection of a relatively
large number of connective signal and ground elements in a relatively small diameter probe, such
as a catheter or endoprobe. In some exemplary instances, pMUT arrays or other transducer arrays
assembled with such cable assemblies may be advantageous in catheters or other probes having a
relatively small diameter and a relatively high number of transducer elements, for instance, for use
in interventional cardiology or interventional radiology applications, such as intravascular or
intracardiac surgical procedures. In other instances, such transducers and cable assemblies may be
advantageous in other types of endoprobe devices having a relatively small diameter and a
relatively high number of transducer elements, such as laparoscopic ultrasound probes used for
minimally invasive surgeries, such as prostate, liver or gall bladder procedures.
Many modifications and other aspects of the disclosures set forth herein will come to mind
to one skilled in the art to which these disclosures pertain having the benefit of the teachings
presented in the foregoing descriptions and the associated drawings. For example, one such aspect
of an ultrasound transducer with associated cable assembly may be provided in instances where the
transducer and cable assembly are configured for use in a side-looking intracardiac catheter, having
an outer diameter of about 14 French (about 4.6 mm). More particularly, a pMUT array may be
fabricated with 512 transducer (pMUT) elements 272 (i.e., a 16x32 array) and 96 ground pads or
electrodes 298, generally configured as shown, for example, in FIG. 4. As disclosed, the pMUT
array may be configured such that the structure of the pMUT elements 272 includes throughsubstrate
vias/interconnects, so as to provide electrically-conductive connections to the ground and
signal electrodes 298, 300 of the pMUT elements 272 within the array on the back side of the
substrate. The pitch of the pMUT elements in the pMUT array may be on the order of about 175
mpi for an overall array size of about 2.8 mm x 5.6 mm. The 2.8 mm array width is configured to
fit within the lumen of a 14 French catheter (inner diameter of about 3.8 mm). Such a pMUT array
is thus configured to be capable of real-time 3D ultrasound imaging. As a result of such a
configuration, one signal conductor is required per pMUT element in the pMUT array in order to
allow the pMUT elements to be individually actuated. However, this arrangement results in a
relatively higher number of required conductors in the cable assembly than conventional flex cable,
micro-coax cable or micro-ribbon cable can provide in a sufficiently small form factor for
implementation in an intracardiac catheter. Conventional 2D linear array devices used in
ultrasound catheters typically include only 64 transducer elements; therefore, conventional cabling
can be used in such instances.
Accordingly, in order to overcome the noted limitations of conventional cables, while
meeting the noted requirements, one exemplary aspect may be directed to a cable assembly, as
shown in FIG. 29, including on the order of 512 connective signal elements and 128 connective
ground elements. However, in some instances, the cable assembly may include at least 100
connective signal elements though, in other instances, the cable assembly may include at least 400
connective signal elements, consistent with the principles discussed in relation to the these and
other aspects of the disclosure. In such an aspect, the connection support substrate 155 may be
comprised, for example, of silicon or any other suitable material, in which vias may be etched
therethrough using, for instance, a DRIE process. The connective signal and ground elements may
then be directed/inserted into the etched vias in a connection support substrate in correlation with
the pattern of transducer elements and ground pads in the pMUT array. The connective signal and
ground elements may be on the order of between about 40 AWG and about 50 AWG in diameter,
wherein, in one instance, the connective signal and ground elements may be 45 AWG insulated
magnet wire. For differentiation/distinction during formation of the cable assembly, the connective
signal elements 150 may be configured to have red insulation, while the connective ground
elements 160 may be configured to have clear, white, or any other suitable color insulation
distinguishable from the insulation of the connective signal elements. In some instances, the pitch
of the vias/through-holes in the connection support substrate may be on the order of less than 200
microns though, in other instances, the pitch may be on the order of less than about 100 microns.
In one particular aspect, the pitch about 175 mh to correspond to the pitch of the connections for
the pMUT array 270 previously disclosed. The connective signal and ground elements may be
secured in the vias of the connection support substrate using, for example, a low-viscosity
insulating epoxy material or any other suitable bonding material. In any instance, the surface of the
connection support substrate configured to engage the pMUT array 270 may first be polished to
expose the ends of the connective signal and ground elements extending therethrough and to
provide a flat surface for bonding to the pMUT array. The pMUT array and connection support
substrate may be bonded together, for example, using an epoxy material, wherein the exposed ends
of the connective signal and ground elements are in electrically-conductive engagement with the
signal and ground contacts on the back side of the pMUT array. FIG. 29 shows one example of a
pMUT array 270 bonded to a connection support substrate 155 with associated connective signal
and ground elements (i.e., wires) 150, 160, as previously disclosed. The wires, proximate to the
ends thereof, may also be individually bent at an angle of about 90 degrees to provide a sidelooking
catheter configuration as shown, for example, in FIG. 23. Because the cable is made of
individual wires, there may be little or no mechanical stress on the conductors, compared to
bending a flex cable assembly (e.g., as shown in FIG. 1), wherein such bending may impart
significant stress on the collective flex cable assembly.
The connective ground elements may be connected to the ground contacts of the pMUT
array laterally outward of the connective signal elements as shown, for example, in FIG. 21.
Additional connective ground elements (wires) 165 may be provided in the cable assembly over the
number of available ground contacts in the pMUT array, for example, to provide additional
shielding of the connective signal elements, as shown, for instance, in FIG. 30 (see also, e.g., FIG.
18B), wherein in one aspect, a total of 128 ground wires may be provided in the cable assembly for
connection to the ground contacts of the pMUT array and to shield the 512 connective signal
elements in the cable assembly. In such instances, for example, every 4 connective signal elements
(wires) may be twisted together with one connective ground element (wire) in the cable assembly
to facilitate shielding of the connective signal elements by interspersing the connective ground
elements among the connective signal elements. Sheathing, such as shrink tubing 320 may be
provided and installed about the connective elements of the cable assembly so as to provide a more
robust sheathed cable assembly 325. In some aspects, the connective elements of the cable
assembly may be terminated opposite to the connection support substrate by a termination element
such as, for example, a printed circuit board (PCB) 375 as shown in FIG. 31. The PCB itself may
also include a connector 620 for forming an electrically-conductive connection with an ultrasound
system. The conductive signal and ground elements 150, 160 may b e engaged (i.e., soldered) with
conductively-plated vias 151 in the PCB 375 as shown, for example, in FIG. 32. There maybe, for
example, between one and eight PCB's engaged with the free ends of the connective signal and
ground elements of the cable assembly, opposite to the connection support substrate, as necessary
or desired, depending, for instance, on the number of connective signal and ground elements in the
cable assembly and the number of pinouts on the respective PCB, though the number of PCB's may
vary considerably.
The cable assembly 325 shown, for example, in FIG. 31, may have a length of about 50" for
implementation in a 36" length intracardiac catheter. The distal end of a 14 French catheter
assembly is shown, for example, in FIG. 33, with the transducer array 270, connection support
substrate 155 and connective signal and ground elements 150, 160 visible in the distal tip of the
catheter assembly. The catheter housing may be comprised of Pebax® with embedded metal
braiding. In some instances, the catheter housing may include a marker band for facilitating
visualization of the tip under fluoroscopy and/or a pull wire to deflect the catheter tip (i.e., catheter
control/steering). In particular aspects, the catheter assembly may be particularly configured for
real-time 3D intracardiac ultrasound imaging. For example, the catheter assembly may be placed in
the right atrium via the inferior vena cava for imaging an ablation catheter in the left atrium during
a pulmonary ablation procedure.
Other examples of transducer and cable assemblies, such as disclosed in the present aspect,
may be used for intravascular imaging. In such instances, the catheter assembly may be required to
have a relatively smaller outer diameter, for example, of no more than about 6 French (about 2
mm). In order to meet the size constraints of the catheter assembly, the transducer array may have
fewer elements and, as such, the corresponding cable assembly may have fewer signal wires that
must fit within the inner diameter of the catheter. For example, in such instances, the size
constraint may be met by a transducer array of 256 pMUT elements (16x16 transducer array), with
a pMUT element pitch of about 60 microns, and with the cable assembly including 256 connective
signal elements and 64 connective ground elements. In such a configuration, the connection
support substrate would require a via pitch of about 60 microns to correspond with the signal and
ground contact pitch of the transducer array, so as to facilitate an electrically-conductive
engagement therebetween. In some instances, the connective signal and/or ground elements (wires)
may be configured with a relatively smaller diameter, e.g., between about 45 AWG and about 50
AWG, so as to reduce, or further reduce, the lateral dimension of the cable assembly. Such an
intravascular catheter could be used, for example, for real-time 3D ultrasound imaging of a stent
placed in an artery or for imaging an occlusion in an artery. Accordingly, such a catheter assembly
may be appropriately scaled, for example, so as to be configured to fit within a 2 mm catheter (i.e.,
with >100 connective signal elements at a pitch of <100 mpi for intravascular ultrasound
applications), or to fit within a 3-4 mm catheter (i.e., with >400 connective signal elements at a
pitch of <200 mh for intracardiac echo applications).
Therefore, it is to be understood that the disclosures are not to be limited to the specific
aspects disclosed and that modifications and other aspects are intended to be included within the
scope of the appended claims. Although specific terms are employed herein, they are used in a
generic and descriptive sense only and not for purposes of limitation.
THAT WHICH IS CLAIMED:
1. An ultrasound device, comprising:
an ultrasonic transducer device comprising a plurality of transducer elements forming a
transducer array, each transducer element comprising a piezoelectric material
disposed between a first electrode and a second electrode, one of the first and second
electrodes comprising a ground electrode and the other of the first and second
electrodes comprising a signal electrode; and
a cable assembly comprising a plurality of connective signal elements and a plurality of
connective ground elements extending in substantially parallel relation therealong,
each being configured to form an electrically-conductive engagement with
respective ones of the signal electrodes and the ground electrodes of the transducer
elements in the transducer array, the connective ground elements being configured
to be alternatingly disposed with the connective signal elements across the cable
assembly, to provide shielding between the connective signal elements.
2. An ultrasound device according to Claim 1, further comprising a connection support
substrate disposed about at least one end of the cable assembly and configured to receive the
connective signal elements and the connective ground elements of the cable assembly therethrough.
3. An ultrasound device according to Claim 2, wherein a first connection support
substrate is configured to be engageable with the ultrasonic transducer device so as to form the
electrically-conductive engagement between the connective signal elements and connective ground
elements and the respective ones of the signal electrodes and the ground electrodes.
4. An ultrasound device according to Claim 3, wherein a second connection support
substrate is configured to be engageable with one of an interposer device and a termination
element.
5. An ultrasound device according to Claim 2, further comprising at least one printed
circuit board engaged with the connective signal elements and the connective ground elements
opposite the connection support substrate.
6. An ultrasound device according to Claim 2, wherein at least one end of the cable
assembly comprises one of a plurality of connection support substrates and a plurality of
termination elements engaged therewith and in communication with the connective signal elements
and the connective ground elements, each of the plurality of connection support substrates being
configured to be engageable with one of an interposer device and a termination element.
7. An ultrasound device according to Claim 4, wherein the interposer device comprises
at least two conductors, each conductor having opposed first and second ends, and configured to
form electrically-conductive engagements with the connective signal elements and the connective
ground elements, via the other of the connection support substrates.
8. An ultrasound device according to Claim 1, wherein at least one of the connective
signal elements and at least one of the connective ground elements of the cable assembly are
twisted together to provide shielding between the connective signal elements.
9. An ultrasound device, according to Claim 1, further comprising a conductive epoxy
material in electrically-conductive engagement between the connective ground elements, and
extending between the connective signal elements, so as to provide shielding between the
connective signal elements.
10. An ultrasound device according to Claim 2, wherein at least one of the ends of the
cable assembly includes an epoxy material applied about the connective signal elements and the
connective ground elements adjacent to the corresponding connection support substrate.
11. An ultrasound device according to Claim 9, wherein the conductive epoxy material
extends at least partially along the cable assembly.
12. An ultrasound device according to Claim 9, wherein the conductive epoxy material
comprises a flexible epoxy material having conductive particles incorporated therein.
13. An ultrasound device according to Claim 1, wherein the connective signal elements
comprise elongate insulated elements and the connective ground elements comprise elongate
uninsulated elements.
14. An ultrasound device according to Claim 13, further comprising a conductive
coating material applied to each elongate insulated element, the connective ground elements being
at least partially in electrically-conductive communication between the connective signal elements
via the conductive coating material.
15. An ultrasound device according to Claim 14, wherein the conductive coating
material comprises one of a conformal copper thin film coating, an electroless plating, and a
conductive spray film.
16. An ultrasound device according to Claim 1, further comprising at least one external
ground conductor arranged in an electrically-conductive engagement with the connective ground
elements and extending therefrom to a ground.
17. An ultrasound device according to Claim 16, wherein the at least one external
ground conductor comprises one of a metal wire, a metal foil, and a conductive epoxy material.
18. An ultrasound device, comprising:
an ultrasonic transducer device comprising a plurality of transducer elements forming a
transducer array, each transducer element comprising a piezoelectric material
disposed between a first electrode and a second electrode, one of the first and second
electrodes comprising a ground electrode and the other of the first and second
electrodes comprising a signal electrode;
a catheter member having a distal end and defining a longitudinally-extending lumen, the
lumen being configured to receive the ultrasonic transducer device about the distal
end; and
a cable assembly comprising a plurality of connective signal elements and a plurality of
connective ground elements extending in substantially parallel relation therealong,
each being configured to form an electrically-conductive engagement with
respective ones of the signal electrodes and the ground electrodes of the transducer
elements in the transducer array, the connective ground elements being configured
to be alternatingly disposed with the connective signal elements across the cable
assembly such that the connective ground elements provide shielding between the
connective signal elements.
19. An ultrasound device according to Claim 18, further comprising a connection
support substrate disposed about at least one end of the cable assembly and configured to receive
the connective signal elements and the connective ground elements of the cable assembly
therethrough.
20. An ultrasound device according to Claim 19, wherein a first connection support
substrate is configured to be engageable with the ultrasonic transducer device so as to form the
electrically-conductive engagement between the connective signal elements and connective ground
elements and the respective ones of the signal electrodes and the ground electrodes of the ultrasonic
transducer device about the distal end of the catheter member.
21. An ultrasound device according to Claim 20, wherein a second connection support
substrate is configured to be engageable with one of an interposer device and a termination
element away from the distal end.
22. An ultrasound device according to Claim 19, further comprising at least one printed
circuit board engaged with the connective signal elements and the connective ground elements
opposite the connection support substrate.
23. An ultrasound device according to Claim 19, wherein at least one end of the cable
assembly comprises one of a plurality of connection support substrates and a plurality of
termination elements engaged therewith and in communication with the connective signal elements
and the connective ground elements, each of the plurality of connection support substrates being
configured to be engageable with one of an interposer device and a termination element.
24. An ultrasound device according to Claim 20, wherein the interposer device
comprises at least two conductors, each conductor having opposed first and second ends, and
configured to form electrically-conductive engagements with the connective signal elements and
the connective ground elements, via the other of the connection support substrates.
25. An ultrasound device according to Claim 18, wherein at least one of the connective
signal elements and at least one of the connective ground elements of the cable assembly are
twisted together to provide shielding between the connective signal elements.
26. An ultrasound device, according to Claim 1 , further comprising a conductive epoxy
material in electrically-conductive engagement between the connective ground elements, and
extending between the connective signal elements, so as to provide shielding between the
connective signal elements.
27. An ultrasound device according to Claim 19, wherein at least one of the ends of the
cable assembly includes an epoxy material applied about the connective signal elements and the
connective ground elements adjacent to the corresponding connection support substrate.
28. An ultrasound device according to Claim 26, wherein the conductive epoxy material
extends at least partially along the cable assembly.
29. An ultrasound device according to Claim 26, wherein the conductive epoxy material
comprises a flexible epoxy material having conductive particles incorporated therein.
30. An ultrasound device according to Claim 1 , wherein the connective signal elements
comprise elongate insulated elements and the connective ground elements comprise elongate
uninsulated elements.
3 1. An ultrasound device according to Claim 30, further comprising a conductive
coating material applied to each elongate insulated element, the connective ground elements being
at least partially in electrically-conductive communication between the connective signal elements
via the conductive coating material.
32. An ultrasound device according to Claim 30, wherein the conductive coating
material comprises one of a conformal copper thin film coating, an electroless plating, and a
conductive spray film.
33. An ultrasound device according to Claim 18, further comprising at least one external
ground conductor arranged in an electrically-conductive engagement with the connective ground
elements and extending therefrom to a ground.
34. An ultrasound device according to Claim 33, wherein the at least one external
ground conductor comprises one of a metal wire, a metal foil, and a conductive epoxy material.
35. An ultrasound device according to Claim 18, further comprising a dielectric material
collectively encapsulating the connective signal elements and the connective ground elements of
the cable assembly.
36. An ultrasound device according to Claim 35, wherein the dielectric material
comprises one of a conformal dielectric coating and shrinkable tubing.
37. An ultrasound device according to Claim 35, further comprising a conductive film
collectively wrapped about the connective signal elements and the connective ground elements of
the cable assembly, between the dielectric material and the connective signal elements and the
connective ground elements, to provide shielding about the connective signal elements.
38. An ultrasound device according to Claim 35, further comprising a conductive film
wrapped about the dielectric material, between the catheter member and the dielectric material
collectively encapsulating the connective signal elements and the connective ground elements, to
provide shielding about the connective signal elements.
39. An ultrasound device according to Claim 35, further comprising a conductive
element incorporated into the catheter member so as to surround the dielectric material collectively
encapsulating the connective signal elements and the connective ground elements, and to provide
shielding about the connective signal elements.
40. An ultrasound device according to Claim 18, further comprising a fluid-containing
capsular member operably engaged with the distal end of the catheter member, the capsular
member housing at least the ultrasonic transducer device.
41. An ultrasound device according to Claim 27, further comprising a fluid-containing
capsular member operably engaged with the distal end of the catheter member, the capsular
member housing the ultrasonic transducer device, the corresponding connection support substrate
engaged therewith, and the epoxy material applied about the connective signal elements and the
connective ground elements adjacent to the connection support substrate.
42. A cable arrangement, comprising:
at least one connection support substrate; and
an elongate cable assembly having the at least one connection support substrate disposed
about at least one end thereof, the cable assembly including a plurality of connective
signal elements and a plurality of connective ground elements extending in
substantially parallel relation therealong, each being configured to extend through
the at least one connection support substrate and adapted to form an electricallyconductive
engagement with respective ones of signal electrodes and ground
electrodes of transducer elements in a transducer array, the connective ground
elements being configured to be alternatingly disposed with the connective signal
elements across the cable assembly such that the connective ground elements
provide shielding between the connective signal elements.
43. A cable arrangement according to Claim 42, wherein a first connection support
substrate is disposed about a first end of the cable assembly and a second connection support
substrate is disposed about a second end of the cable assembly.
44. A cable arrangement according to Claim 42, further comprising at least one printed
circuit board engaged with the connective signal elements and the connective ground elements
opposite the at least one connection support substrate.
45. A cable arrangement according to Claim 42, wherein the connective signal elements
and connective ground elements each have a diameter of between about 40 AWG and about 50
AWG.
46. A cable arrangement according to Claim 42, wherein the cable assembly includes at
least 100 connective signal elements.
47. A cable arrangement according to Claim 42, wherein the cable assembly includes at
least 400 connective signal elements.
48. A cable arrangement according to Claim 42, wherein the at least one connection
support substrate is comprised of silicon and defines vias etched therein, the vias being configured
to receive the connective signal elements and connective ground elements therein.
49. A cable arrangement according to Claim 48, wherein the connective signal elements
and connective ground elements are secured within the at least one connection support substrate
using an insulating epoxy material.
50. A cable arrangement according to Claim 48, wherein a pitch of the vias in the at
least one connection support substrate is less than about 100 microns.
51. A cable arrangement according to Claim 48, wherein a pitch of the vias in the at
least one connection support substrate is less than about 200 microns.