Transducers, devices and systems containing the transducers, and methods of manufacture

A catheter assembly for an intravascular ultrasound system includes a catheter and an imaging core. The catheter includes a lumen extending along the longitudinal length of the catheter from the proximal end to the distal end and the imaging core is configured and arranged for inserting into the lumen. The imaging core includes a rotatable driveshaft, at least one transducer mounted to the distal end of the rotatable driveshaft, and a twisted wire cable coupled to the at least one transducer. In addition, a number of different transducer arrangements and methods of making transducers are presented.

TECHNICAL FIELD

The present invention is directed to the area of transducers for ultrasound imaging systems, devices and systems containing the transducers, and methods of making and using the transducers. The present invention is also directed to transducers for an intravascular ultrasound imaging system.

BACKGROUND

Intravascular ultrasound (“IVUS”) imaging systems have proven diagnostic capabilities for a variety of diseases and disorders. For example, IVUS imaging systems have been used as an imaging modality for diagnosing blocked blood vessels and providing information to aid medical practitioners in selecting and placing stents and other devices to restore or increase blood flow. IVUS imaging systems have been used to diagnose atheromatous plaque build-up at particular locations within blood vessels. IVUS imaging systems can be used to determine the existence of an intravascular obstruction or stenosis, as well as the nature and degree of the obstruction or stenosis. IVUS imaging systems can be used to visualize segments of a vascular system that may be difficult to visualize using other intravascular imaging techniques, such as angiography, due to, for example, movement (e.g., a beating heart) or obstruction by one or more structures (e.g., one or more blood vessels not desired to be imaged). IVUS imaging systems can be used to monitor or assess ongoing intravascular treatments, such as angiography and stent placement in real (or almost real) time. Moreover, IVUS imaging systems can be used to monitor one or more heart chambers.

IVUS imaging systems have been developed to provide a diagnostic tool for visualizing a variety is diseases or disorders. An IVUS imaging system can include a control module (with a pulse generator, an image processor, and a monitor), a catheter, and one or more transducers disposed in the catheter. The transducer-containing catheter can be positioned in a lumen or cavity within, or in proximity to, a region to be imaged, such as a blood vessel wall or patient tissue in proximity to a blood vessel wall. The pulse generator in the control module generates electrical pulses that are delivered to the one or more transducers and transformed to acoustic pulses that are transmitted through patient tissue. Reflected pulses of the transmitted acoustic pulses are absorbed by the one or more transducers and transformed to electric pulses. The transformed electric pulses are delivered to the image processor and converted to an image displayable on the monitor.

BRIEF SUMMARY

One embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy. The transducer element further comprises a first non-transducing pad defined in the transducer element. The ultrasound transducer also includes a first metal layer substantially disposed over a first surface of the transducer element and over the first non-transducing pad; and a second metal layer substantially disposed over a second surface of the transducer element.

Another embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy; a first metal layer substantially disposed over a first surface of the transducer element; a second metal layer substantially disposed over a second surface of the transducer element (the second surface opposing the first surface); a backing layer disposed over the second metal layer; and a third metal layer disposed over the backing layer. The third metal layer defines a first contact and a second contact that are separated from each other. The first contact is coupled to the first metal layer by a first contact via and the second contact is coupled to the second metal layer by a second contact via.

Yet another embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy. The ultrasound transducer further includes a first thin film circuit comprising a first substrate with metal traces disposed on opposing sides of the first substrate and electrically coupled together. The metal traces are configured and arranged to provide a contact pad on one side of the first substrate and an electrode for providing electrical signals to the transducer element on another side of the first substrate. The ultrasound transducer also includes a second thin film circuit comprising a second substrate with metal traces disposed on opposing sides of the second substrate and electrically coupled together. The metal traces are configured and arranged to provide a contact pad on one side of the second substrate and an electrode for providing electrical signals to the transducer element on another side of the second substrate. The transducer element is disposed between the first and second thin film circuits.

A further embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy; a carrier substrate comprising a first surface and a second surface opposing the first surface; a first metal layer disposed on the first surface of the carrier substrate and defining a first contact and a second contact that are separate from each other; a second metal layer disposed on the second surface of the carrier substrate and in electrical communication with the second contact on the first surface of the carrier substrate; a third metal layer; and a conducting structure electrically coupling the first contact with the third metal layer. The transducer element is disposed between the second metal layer and the first metal layer. The conducting structure itself is electrically insulated from the transducer element.

Another embodiment is an ultrasound transducer that includes a transducer element comprising a material configured and arranged to convert electrical energy to ultrasound energy. The transducer element has a first surface, a second surface opposing the first surface, and an edge surface between the first and second surfaces. The ultrasound transducer further includes a first metal layer disposed over the first surface of the transducer element; a second metal layer disposed over the second surface of the transducer element; a first contact extending from the first metal layer along a first portion of the edge surface of the transducer element; and a second contact extending from the first metal layer along a second portion of the edge surface of the transducer element.

Yet another embodiment is a method of making an ultrasound transducer including forming at least one first vertical slot extending from a first surface partway through a transducer element. Metal is disposed within the first vertical slot(s) to at least coat exposed surfaces of the transducer element within the first vertical slot(s). A first metal layer is disposed over the first surface of the transducer element and in contact with the metal disposed within the first vertical slot(s). At least one second vertical slot is formed extending from a second surface partway through the transducer element. The second surface of the transducer element opposes the first surface of the transducer element. Metal is disposed within the second vertical slot(s) to at least coat exposed surfaces of the transducer element within the second vertical slot(s). A second metal layer is disposed over the second surface of the transducer element and in contact with the metal disposed within the second vertical slot(s). The transducer element is cut through the first and second vertical slots to form an ultrasound transducer with first and second contacts formed from the metal disposed in the first and second vertical slots, respectively.

A further embodiment is a catheter assembly for an intravascular ultrasound system that includes a catheter and an imaging core. The catheter has a longitudinal length, a distal end, and a proximal end. The catheter also includes a lumen extending along the longitudinal length of the catheter from the proximal end to the distal end. The imaging core is configured and arranged for inserting into the lumen. The imaging core includes a rotatable driveshaft having a distal end and a longitudinal length, at least one transducer mounted to the distal end of the rotatable driveshaft, and a twisted wire cable. The at least one transducer is configured and arranged for transforming applied electrical pulses to acoustic pulses and also for transforming received echo pulses to electrical pulses. The twisted wire cable includes i) two wires running along the cable and electrically coupled to respective contacts of the at least one transducer, and ii) a shield extending along the cable and within which a portion of the two wires are disposed.

DETAILED DESCRIPTION

The present invention is directed to the area of transducers for ultrasound imaging systems, devices and systems containing the transducers, and methods of making and using the transducers. The present invention is also directed to transducers for an intravascular ultrasound imaging system.

Suitable intravascular ultrasound (“IVUS”) imaging systems include, but are not limited to, one or more transducers disposed on a distal end of a catheter configured and arranged for percutaneous insertion into a patient. Examples of IVUS imaging systems with catheters are found in, for example, U.S. Pat. Nos. 7,246,959; 7,306,561; and 6,945,938; as well as U.S. Patent Application Publication Nos. 20060253028; 20070016054; 20060106320; 20070038111; 20060173350; and 20060100522, all of which are incorporated by reference.

FIG. 1illustrates schematically one embodiment of an IVUS imaging system100. The IVUS imaging system100includes a catheter102that is coupleable to a control module104. The control module104may include, for example, a processor106, a pulse generator108, a motor110, and one or more displays112. In at least some embodiments, the pulse generator108forms electric pulses that may be input to one or more transducers (312inFIG. 3) disposed in the catheter102. In at least some embodiments, mechanical energy from the motor110may be used to drive an imaging core (306inFIG. 3) disposed in the catheter102. In at least some embodiments, electric pulses transmitted from the one or more transducers (312inFIG. 3) may be input to the processor106for processing. In at least some embodiments, the processed electric pulses from the one or more transducers (312inFIG. 3) may be displayed as one or more images on the one or more displays112. In at least some embodiments, the processor106may also be used to control the functioning of one or more of the other components of the control module104. For example, the processor106may be used to control at least one of the frequency or duration of the electrical pulses transmitted from the pulse generator108, the rotation rate of the imaging core (306inFIG. 3) by the motor110, the velocity or length of the pullback of the imaging core (306inFIG. 3) by the motor110, or one or more properties of one or more images formed on the one or more displays112. In some embodiments, the parts of the control module104(i.e., the processor106, the pulse generator108, the motor110, and the one or more displays112) may be in one unit. In other embodiments, the parts of the control module104are in two or more units.

FIG. 2is a schematic side view of one embodiment of the catheter102of the IVUS imaging system (100inFIG. 1). The catheter102includes an elongated member202and a hub204. The elongated member202includes a proximal end206and a distal end208. InFIG. 2, the proximal end206of the elongated member202is coupled to the catheter hub204and the distal end208of the elongated member is configured and arranged for percutaneous insertion into a patient. In at least some embodiments, the catheter102defines at least one flush port, such as flush port210. In at least some embodiments, the flush port210is defined in the hub204. In at least some embodiments, the hub204is configured and arranged to couple to the control module (104inFIG. 1). In some embodiments, the elongated member202and the hub204are formed as a unitary body. In other embodiments, the elongated member202and the catheter hub204are formed separately and subsequently assembled together.

FIG. 3is a schematic perspective view of one embodiment of the distal end208of the elongated member202of the catheter102. The elongated member202includes a sheath302and a lumen304. An imaging core306is disposed in the lumen304. The imaging core306includes an imaging device308coupled to a distal end of a rotatable driveshaft310.

The sheath302may be formed from any flexible, biocompatible material suitable for insertion into a patient. Examples of suitable materials include, for example, polyethylene, polyurethane, polytetrafluoroethylene (PTFE), other plastics, and the like or combinations thereof.

One or more transducers312may be mounted to the imaging device308and employed to transmit and receive acoustic pulses. In a preferred embodiment (as shown inFIG. 3), an array of transducers312are mounted to the imaging device308. In other embodiments, a single transducer may be employed. In yet other embodiments, multiple transducers in an irregular-array may be employed. Any number of transducers312can be used. For example, there can be two, three, four, five, six, seven, eight, nine, ten, twelve, fifteen, sixteen, twenty, twenty-five, fifty, one hundred, five hundred, one thousand, or more transducers. As will be recognized, other numbers of transducers may also be used.

The one or more transducers312may be formed from one or more known materials capable of transforming applied electrical pulses to pressure distortions on the surface of the one or more transducers312, and vice versa. Examples of suitable materials include piezoelectric ceramic materials, piezocomposite materials, piezoelectric plastics, barium titanates, lead zirconate titanates, lead metaniobates, polyvinylidenefluorides, lead magnesium niobate-lead titanates, and the like. These materials will be collectively referred to as “piezoelectric materials”. Additionally, capacitive micromachined ultrasound transducers (CMUTs) or the like may be used.

Pressure distortions on the surface of the one or more transducers312can be generated in order to form acoustic pulses of a frequency based on the resonant frequencies of the one or more transducers312. The resonant frequencies of the one or more transducers312may be affected by the size, shape, and material used to form the one or more transducers312. The one or more transducers312may be formed in any shape suitable for positioning within the catheter102and for propagating acoustic pulses of a desired frequency or frequencies in one or more selected directions. For example, transducers may be disc-shaped, block-shaped, ring-shaped, layered, and the like. The one or more transducers may be formed in the desired shape by any process including, for example, dicing, machining, dice and fill, chemical etching, plasma etching, reactive ion etching, microfabrication, and the like.

In at least some embodiments, the one or more transducers312can be used to form a radial cross-sectional image of a surrounding space. Thus, for example, when the one or more transducers312are disposed in the catheter102and inserted into a blood vessel of a patient, the one more transducers312may be used to form an image of the walls of the blood vessel and tissue surrounding the blood vessel.

In at least some embodiments, the imaging core306may be rotated about a longitudinal axis of the catheter102. As the imaging core306rotates, the one or more transducers312emit acoustic pulses in different radial directions. When an emitted acoustic pulse with sufficient energy encounters one or more medium boundaries, such as one or more tissue boundaries, a portion of the emitted acoustic pulse is reflected back to the emitting transducer as an echo pulse. Each echo pulse that reaches a transducer with sufficient energy to be detected is transformed to an electrical signal in the receiving transducer. The one or more transformed electrical signals are transmitted to the control module (104inFIG. 1) where the processor106processes the electrical-signal characteristics to form a displayable image of the imaged region based, at least in part, on a collection of information from each of the acoustic pulses transmitted and the echo pulses received. In at least some embodiments, the rotation of the imaging core306is driven by the motor110disposed in the control module (104inFIG. 1).

As the one or more transducers312rotate about the longitudinal axis of the catheter102emitting acoustic pulses, a plurality of images are formed that collectively generate a radial cross-sectional image of a portion of the region surrounding the one or more transducers312, such as the walls of a blood vessel of interest and the tissue surrounding the blood vessel. In at least some embodiments, the radial cross-sectional image can be displayed on one or more displays112.

In at least some embodiments, the imaging core306may also move longitudinally along the blood vessel within which the catheter102is inserted so that a plurality of cross-sectional images may be formed along a longitudinal length of the blood vessel. In at least some embodiments, during an imaging procedure the one or more transducers312may be retracted (i.e., pulled back) along the longitudinal length of the catheter102. In at least some embodiments, the motor110drives the pullback of the imaging core306within the catheter102. In at least some embodiments, the motor110pullback distance of the imaging core is at least 5 cm. In at least some embodiments, the motor110pullback distance of the imaging core is at least 10 cm. In at least some embodiments, the motor110pullback distance of the imaging core is at least 15 cm. In at least some embodiments, the motor110pullback distance of the imaging core is at least 20 cm. In at least some embodiments, the motor110pullback distance of the imaging core is at least 25 cm.

The quality of an image produced at different depths from the one or more transducers312may be affected by one or more factors including, for example, bandwidth, transducer focus, beam pattern, as well as the frequency of the acoustic pulse. The frequency of the acoustic pulse output from the one or more transducers312may also affect the penetration depth of the acoustic pulse output from the one or more transducers312. In general, as the frequency of an acoustic pulse is lowered, the depth of the penetration of the acoustic pulse within patient tissue increases. In at least some embodiments, the IVUS imaging system100operates within a frequency range of 1 MHz to 60 MHz.

In at least some embodiments, one or more conductors314electrically couple the transducers312to the control module104(SeeFIG. 1). In at least some embodiments, the one or more conductors314extend along a longitudinal length of the rotatable driveshaft310.

In at least some embodiments, the catheter102with one or more transducers312mounted to the distal end208of the imaging core308may be inserted percutaneously into a patient via an accessible blood vessel, such as the femoral artery, at a site remote from the selected portion of the selected region, such as a blood vessel, to be imaged. The catheter102may then be advanced through the blood vessels of the patient to the selected imaging site, such as a portion of a selected blood vessel.

In many conventional transducer arrangements, the transducer is coupled to the remainder of the system using a coaxial cable. One contact of the transducer is coupled to the conductor that runs through the center of the coaxial cable and the other contact of the transducer is coupled to the cylindrical shield of the coaxial cable. Such an arrangement can lead to an unbalanced electrical connection between the transducer and the other electronic components of the ultrasound system.

Moreover, the connections to the transducer are often made using conductive adhesive to avoid other wire attachment techniques, such as welding and soldering, that would raise the temperature of the heat-sensitive piezoelectric material of the transducer. Conductive adhesives, however, can be unreliable. For example, the adhesives may lose their ability to reliably attach the wires to the transducer when exposed to chemical sterilizing agents, such as ethylene oxide, which are often used to sterilize the ultrasound catheter between uses.

FIG. 4illustrates an alternative arrangement in which the transducer412, disposed in the catheter402, is coupled to the remainder of the electronics of the imaging system using a shielded twisted pair cable420. The shielded twisted pair cable420includes two insulated wires422,424, that are twisted together along the cable, as well as a metal shield426that can be electrically grounded. One of the wires422can be coupled to a first contact of the transducer412and the other wire424can be coupled to a second contact of the transducer. This arrangement provides for a balanced electrical connection with the transducer. The transducer412can be any transducer including currently available transducers. The wires420,422can be attached to the transducer using any suitable method including conductive adhesives. As described in more detail below, the transducer can be arranged to allow the wires to be attached using heat-generating techniques, such as welding, soldering, thermal compression bonding, and the like.

FIG. 5illustrates another arrangement in which a transducer512, disposed in a catheter502, is coupled to a shielded twisted pair cable520(with two wires522,524and a conductive shield526) using a modular fitting530. In at least some embodiments of this arrangement, the transducer512includes contacts (not shown) that couple (e.g., using a conductive adhesive or simply by contact) to corresponding contacts (not shown) on the modular fitting530. The contacts on the modular fitting530are electrically coupled to pads (not shown) to which the wires522,524can be attached. The wires522,524can be attached to the pads of the modular fitting using any suitable technique. In particular, heat-generating techniques can be used for attachment of the wires522,524because the piezoelectric material of the transducer is sufficiently distant that the heat will not damage it. In at least some instances, the wires may be attached to the modular fitting before the transducer is attached to the modular fitting. A modular arrangement, such as that illustrated inFIG. 5, may also allow the transducer512to be removed or replaced without detaching the wires of the twisted pair cable520from the transducer.

There are a variety of arrangements and methods for forming a transducer. Typically, transducers have a number of different components including a transducer element, made of piezoelectric material or the like, that is disposed between at least two metal layers (or contact layers) through which electrical signals are provided to cause the transducer to emit ultrasound energy. The metal layers also receive electrical signals from the transducer element when the element receives ultrasound signals. The transducer may also optionally include at least one backing layer, and optionally, at least one matching layer.

Any suitable transducer element can be used in the transducers disclosed herein. In general, the transducer element is made of a material, such as a piezoelectric material or the like, that converts electrical signals into ultrasound signals and vice versa. The transducer element, unless otherwise indicated, can be a single crystal transducer element or the transducer element can have one or more individual transducing members optionally separated by non-transducing material (see e.g.,FIG. 6) or any other suitable arrangement of transducing members.

The metal layers and contact layers can be formed using any suitable conductive material including metals, alloys, and multi-layer conductive arrangements (e.g., multiple layers of different metals or alloys). Any metal or alloy can be used. For biological applications (e.g., intravascular ultrasound (IVUS) imaging), preferably any exposed portion of the metal or contact layers is made of a material (such as gold, platinum, platinum/iridium alloy, or silver-filled epoxy) that does not corrode when exposed to biological fluids under typical operating conductions. These materials may be plated over other metals, such as copper, Ni/Cr, Ni/Zn, and the like that may otherwise corrode. For example, copper or Ni/Cr can be covered by gold.

The optional matching layer is made of a material that acoustically matches the transducer element to the biological environment. For example, the matching layer may facilitate matching the high acoustic impedance of the transducer element with the lower acoustic impedance of the surroundings, such as tissue and fluids within which the catheter is disposed. Any suitable material may be used including, but not limited to, parylene, epoxy, polyimide, other polymers, and the like.

In some embodiments, the matching layer is non-conductive. In other embodiments, particularly when the matching layer is disposed between the transducer element and a metal layer, the matching layer is conductive. The matching layer can be made conductive by using, for example, a conductive polymer or by including conductive particles (e.g., metal, graphite, or alloy particles) within the polymeric material of the matching layer.

The optional backing layer can be provided for a variety of purposes including, but not limited to, device stability, protection, acoustic matching, or acoustic absorption. The backing layer can be made using any suitable material including, but not limited to, parylene, epoxy, filled epoxies, other polymers, and the like. In some embodiments, the backing layer is non-conductive. In other embodiments, particularly when the backing layer is disposed between the transducer element and a metal layer, the backing layer is conductive. The backing layer can be made conductive by using, for example, a conductive polymer or by including conductive particles (e.g., metal, graphite, or alloy particles) within the polymeric material of the backing layer. Optionally, the backing layer may also function as a matching layer and be formed using a material that acoustically matches the transducer element.

The backing and matching layers may be disposed on other layers of the transducer using any suitable method. Examples of methods for forming the backing and matching layers include, but are not limited to, spin coating, dip coating, spraying, vacuum deposition, chemical deposition, sputtering, casting, and the like or even adhering a pre-made backing or matching layer to another layer using an adhesive.

FIG. 6illustrates one embodiment of a transducer element602that, when coupled to metal layers as described below, can be used to form a transducer. The transducer element602includes piezoelectric material604that forms multiple piezoelectric transducing members606. Each of the transducing members is separated from the others by non-transducing material610, such as epoxy, polyimide, silicon, alumina, and the like. In at least one embodiment, the transducer element is formed from a slab of piezoelectric material (typically disposed on a carrier) that is etched, scored, sliced, cut, diced, or otherwise separated into the individual transducing members. The non-transducing material may then be disposed between the transducing members using a suitable technique, such as coating methods.

The transducer element602also includes at least two non-conductive pads608. Preferably, these pads are made of a heat-resistant material and, more preferably, are made of a material that does not readily conduct heat. For example, the pads can be made of epoxy, filled epoxy, and the like. For example, a low viscosity epoxy such as Epotek™ 301-2 (Epoxy Technology, Bilerica, Mass.) may be used. The pads608may be made of he same material as the non-transducing material610and may be formed using the same techniques as are used to dispose the non-transducing material between the transducing members.

These non-conductive pads608will be disposed below, or above, metal contact sites, as described in more detail below, so that the wires (see, e.g., wires422,424ofFIG. 4) that couple the transducer to the remainder of the imaging system electronics can be attached using, for example, heat-based bonding techniques, such as, for example, laser welding, hot bar solder reflow, thermal compression bonding, gold ball bonding, other soldering or welding techniques, or other techniques that include the application of heat to attach the wires. The non-conductive pads608provide protection from heat to the piezoelectric material of the transducing members so that these wire attachment techniques can be used.

FIG. 7illustrates one embodiment of a transducer700that uses the transducer element602ofFIG. 6. The transducer element602includes the piezoelectric material604(formed as individual transducing members as illustrated inFIG. 6, although this detail is not shown inFIG. 7for purposes of clarity) and the non-conductive pads608. The transducer700includes a top metal layer710and a bottom metal layer712. A metal pad716is disposed on the top of the transducer element602, but is electrically isolated from the top metal layer710by a separation720(e.g., by the removal of conductive material between the metal pad and the top metal layer.). The metal pad716is electrically coupled to the bottom metal layer712through a conductive via718that is formed by making a hole through at least the pad608and plating or filling the hole with metal or another suitable electrically conducting material. The portion714of the top metal layer710and the metal pad716are each disposed over one of the non-conductive pads608of the transducer element602and provide attachment sites for a wire (seeFIG. 4).

The metal layers710,712can be disposed on the transducer element602using any suitable method including, but not limited to, electroless plating, electroplating, evaporation, sputtering, chemical or physical vapor deposition, and the like. The separation720between the top metal conductive layer710and the metal pad716can be formed using an suitable technique including patterning a metal layer disposed on the top of the transducer element602using a positive or negative photoresist and etching away, or otherwise removing, a portion of that metal layer to form the top metal layer710and the metal pad716with separation720. Alternatively, the transducer element602may be masked prior to the deposition of the metal so that the separation720is formed with the deposition of the metal layer710and metal pad716.

The via718can be formed by any suitable method including, but not limited to, drilling, plasma etching, chemical etching, laser ablating, sputter etching, or otherwise making a hole through at least the non-conductive pad608of the transducer element. In one embodiment, this hole is formed prior to disposing the top metal layer710or bottom metal layer712(or both) on the transducer element602so that the hole can be coated or filled with metal as the top or bottom metal layer is formed. It will be understood, however, that the hole can be opened and the via718coated or filled with metal after the top and bottom metal layers710,712are formed.

FIG. 8illustrates one arrangement in which four transducers700a,700b,700c,and700dcan be formed together and then separated along lines780,782. Such an arrangement permits the simultaneous patterning of a metal layer to form the top metal layer710, metal pad716, and separation720for all four transducers. It will be recognized that this arrangement can be repeated as a larger arrangement to prepare more than four transducers together.

FIG. 9illustrates an alternate arrangement for forming four transducers700a′,700b′,700c′ and700d′. In this arrangement, instead of four vias, a single via718′ is provided. In addition, the separation720′ between the metal layer710and metal pad716′ may be circular, rather than square or rectangular, although it will be understood that in any of the embodiments inFIGS. 7-10, the separation can have any shape as long as the top metal layer710and metal pad716,716′ are not in electrical contact.FIG. 10illustrates one of the transducers700′ ofFIG. 9with the same elements as the transducer700ofFIG. 7except that a portion718′ of the side surface of non-conductive pad608is coated with metal to electrically couple the metal pad716to the bottom metal conductive layer712.

Any of the embodiments inFIGS. 7-10can be bonded to a backing layer (preferably, attached to the bottom metal layer). This backing layer may also be an acoustic matching layer. In addition, an acoustic matching layer may be disposed over at least a portion of the top metal layer.

FIGS. 11A-11Eillustrate yet another embodiment of a transducer750.FIGS. 11A and 11Bare side views from opposing sides of the transducer. The transducer750includes a transducing element752, a first patterned metal layer754(FIG. 11C), a second patterned metal layer756(FIG. 11D), a third patterned metal layer758(FIG. 11E), and a backing layer760.FIGS. 11C-11Ecorrespond to the first, second, and third patterned metal layers, respectively, and are illustrated in an arrangement for generating multiple transducers (similar to the arrangements inFIGS. 8 and 9). Each transducer corresponds to one of the rectangular regions bounded by the dotted lines (e.g., lines762,764). Any transducer element can be used including, for example, the transducer element602ofFIG. 6(although, for this embodiment, the pads608are unnecessary and may be omitted or replaced with additional transducing elements.)

In forming this transducer, vias766,768are formed through all of the layers of the transducer and either coated or filled with metal or alloy. When the transducers are separated from each other, each via766,768will be exposed similar to the via718′ inFIG. 10. In addition, a separation770is formed around via766in the first metal layer754and a separation is formed772around via768in the second metal layer756. In the third metal layer758, a separation774divides the layer758into a first contact776and a second contact778. The respective separations in each metal layer can be formed as each of the metal layers is deposited or the respective separations can be formed by patterning and etching (or otherwise removing a portion of the metal) a previously formed metal layer.

The vias are generally made and coated/filled after forming each of the layers of the transducer. The via766couples the majority of second metal layer756to the second contact778. The via768couples the majority of the first metal layer754to the first contact776. The wires from the remainder of the electronics of the ultrasound system can be connected to the first and second contacts776,778(see, e.g.,FIG. 4). The presence of the backing layer760may permit the use of heat-based attachment methods for attaching the wires to the first and second contact776,778by protecting the transducer element750from the heat generated by attachment. This embodiment also lends itself to electrical connection via preformed pads in the modular fitting530shown inFIG. 5.

FIG. 12illustrates another arrangement of a transducer800with a transducer element802comprising piezoelectric regions804separated by non-piezoelectric regions806. The transducer800also includes two metal layers808and810; a matching layer812, and a backing layer814. The transducer800is coupled to the remainder of the device electronics via contact wires816and818that are disposed next to, or over, a non-piezoelectric region806′.

FIGS. 13A-13Gillustrate one embodiment of a method of making the transducer800. It will be understood that a variety of other methods can be used to form the transducer800. A piezoelectric material804′ is removably attached to a carrier820using any suitable technique including adhesives, waxes, and the like, as illustrated inFIG. 13A. Cuts are formed in the piezoelectric material804′ to form piezoelectric regions804, as illustrated inFIG. 13B. The cuts can be formed using any suitable technique including coating the piezoelectric material804′ with a positive or negative photoresist; patterning and developing the photoresist to expose the portions of the piezoelectric material804′ to be removed; and etching the exposed piezoelectric material to form the cuts. Other methods for forming the cuts include, for example, wet chemical etching, reactive ion etching, plasma etching, microdicing, and the like. After the cuts are formed, the cuts can be filled with a suitable non-piezoelectric material, such as, for example, epoxy, filled adhesive, or the like, to form the non-piezoelectric regions806, as illustrated inFIG. 13B. Any suitable method for filling the cuts can be used including, for example, spin coating, dip coating, silkscreening, and the like. At least one of the non-piezoelectric regions806′ is formed for later use in coupling a wire816to the metal layer808over that region (seeFIG. 12) and may be larger than other non-piezoelectric regions.

The exposed surface of the piezoelectric regions804and non-piezoelectric regions806is metallized to generate metal layer810, as illustrated inFIG. 13C. The metallization can be performed using any suitable technique including, but not limited to, electroplating, electroless plating, sputtering, chemical or physical vapor deposition, and the like.

A backing layer814is formed over the metal layer810, as illustrated inFIG. 13D. The backing layer can be formed using any suitable technique including casting, chemical or physical vapor deposition, coating (e.g., spin coating, dip coating, sputtering), and the like. The backing layer is typically formed using a non-conductive material and preferably is used to acoustically match the piezoelectric material.

The carrier layer820is removed, as illustrated inFIG. 13E. A second metal layer808is formed over the exposed at least a portion of the exposed surface of the piezoelectric regions804and non-piezoelectric regions806, as illustrated inFIG. 13F. The metallization can be performed using any suitable technique including, but not limited to, electroplating, electroless plating, sputtering, chemical or physical vapor deposition, and the like. A portion822of the exposed surface of the piezoelectric regions804may be left exposed by masking the portion of the surface prior to form the metal layer808. Alternatively or additionally, the portion822of the exposed surface of the piezoelectric regions804may be exposed after forming the metal layer808by patterning and etching the metal layer using, for example, a positive or negative photoresist.

The exposed portion822of the piezoelectric region804can be removed using an suitable technique, for example, selective etching the of the piezoelectric material804, to expose a portion of the underlying metal layer810, as illustrated inFIG. 13G. A matching layer812is disposed over the metal layer808and, optionally, over the exposed portion of the metal layer810, as also illustrated inFIG. 13G. The matching layer can be formed by any suitable technique including, but not limited to, casting, chemical or physical vapor deposition, coating (e.g., spin coating, dip coating, sputtering), and the like. The matching layer is typically formed using a non-conductive material and is used to acoustically match the piezoelectric material.

A portion of the matching layer812is removed to exposed portions of the metal layer808and810to allow for attachment of wires816and818, as illustrated inFIG. 12. It should be noted that the wires816and818are not attached to portions of the metal layers808and810that are directly over or under a piezoelectric region804. Accordingly, in at least some embodiments, heat-based attachment methods can be used to attach the wires816and818to the metal layers808and810.

FIGS. 14A-14Cillustrate another transducer900with top and bottom flexible circuit layers902,904; a transducer element906; a matching layer908; and a backing layer910(which may also function as a matching layer).FIG. 14Ais a partially exploded view of one embodiment that includes multiple transducers that can be separated along the dotted lines.FIGS. 14B and 14Cillustrate side views (taken along two orthogonal sides) of a single transducer.

The transducer element906may be a single crystal of piezoelectric material or any other suitable arrangement of piezoelectric material that can form a transducer element (see e.g., the transducer element ofFIG. 6with or without the non-transducing pads). The matching layer908and can be formed using any suitable conductive material that is acoustically matched to the piezoelectric material. The backing layer910can be formed using any suitable conductive material and may, in at least some embodiments, be acoustically matched to the piezoelectric material of layer906.

The flexible circuit layers902,904are each formed from a non-conductive carrier substrate920,930, respectively, such as polyimide or any other suitable polymeric material, with metal traces922,924,932,934formed on the top and bottom of the non-conductive carrier substrate and electrically coupled by at least one metallic via926,936extending through the non-conductive base920,930. The metal traces can be made using a single metal or alloy or can be made using layers of metals or alloys. The metal traces can be patterned or may cover an entire surface of the carrier substrate. In one embodiment, the conductive metal traces and vias are formed using copper and the exposed traces are then covered with Ni/Cr and then gold or another metal that is inert under physiological conditions. It will be understood that the via can be positioned anywhere within the flexible circuit layer (e.g., in the middle or along the edge of the flexible circuit layer).

Wires can then be coupled to the flexible circuit layers902,904to electrically connect the transducer to the remaining electronics of the ultrasound system. The flexible circuit, matching layer, and backing layer separate the wires from the transducer element to reduce heating of the transducer element if a heat-based bonding method is used to attach the wires to the transducer.

FIGS. 15A and 15Billustrate another embodiment of a transducer1000. This transducer1000includes a transducer element1002; a first metal layer forming separated contacts1008,1010; second and third metal layers1004,1006; backing layer1012; matching layer1014; carrier layer1016; via1018; non-conductive wall1020; and vertical conductor1022. Any suitable transducer element1002can be used including single crystal elements or transducer elements with multiple transducing members (as illustrated, for example, inFIG. 6with or without the non-transducing pads.)

The backing layer1012and matching layer1014can be made of the same or different materials. The backing layer1012in the illustrated embodiment is conductive. In an alternative embodiment, the matching layer can be disposed between the transducer element1002and the third metal layer1004. In this alternative embodiment, the matching layer1014is also conductive.

In at least some embodiments, the carrier layer1016, metal layer1006, and contacts1008,1010can be any thin film or thick film circuit material. The carrier layer1016can be any suitable non-conductive substrate material including, but not limited to, polymeric materials and ceramic materials. The first metal layer is patterned to form the contacts1008,1010. This thick or thin film circuit can be bonded to the backing layer1012using any technique including, but not limited to, using conductive adhesive, conductive epoxy, and the like. In one embodiment, the carrier layer1016, metal layer1006, and contacts1008,1010are a ceramic thick film circuit.

The contact1008is electrically coupled to the metal layer1006through the conductive via1018. The contact1010is coupled to the metal layer1004through the vertical conductor1022. The non-conductive wall1020insulates the transducer element1002from the vertical conductor1022. The non-conductive wall1020and vertical conductor1022can be attached to the other components using any suitable technique including, but not limited to, using conductive adhesive, conductive epoxy, and the like. In at least some embodiments, the vertical sidewall of the carrier layer1016adjacent to the vertical conductor1022is coated with metal to facilitate coupling the vertical conductor1022to the contact1010. Wires to the remainder of the system electronics can be attached to the contact layers1008,1010. This embodiment also lends itself to electrical connection via preformed pads in the modular fitting530shown inFIG. 5.

FIG. 16illustrates another embodiment of a transducer1100. The transducer1100includes a transducer element1102; metal layers1104,1106with corresponding vertical contact pads1108,1110for attachment of wires1112,1114; a backing layer1116; and a matching layer1118.

FIGS. 17A-17Fillustrate one embodiment of a method of making the transducer1100. Transducer material1102′ is removably disposed on a carrier1120, as illustrated inFIG. 17A. A portion of the transducer material1102′ is then removed to form one or more vertical slots1122, as illustrated inFIG. 17B. Preferably, the vertical slots are between ½ to ¾ the thickness of the transducer material1102′. For example, the transducer material1102′ can be patterned and etched using a positive or negative photoresist material or the transducer material1102′ can be cut or otherwise diced. A metal layer1104is formed over the transducer material1102′ and within the vertical slot(s)1122, as illustrated inFIG. 17C. The metal layer1104can be formed using any suitable method including, but not limited to, electroplating, electroless plating, sputtering, chemical or physical vapor deposition, and the like. Any suitable metal, alloy, or combinations thereof may be used. For example, the metal layer may be formed by plating the surface with Ni/Cr and then with gold. A backing layer1116is disposed over the metal layer1104and the carrier layer1120is removed, as illustrated inFIG. 17D.

One or more vertical slots1124are then formed in the opposite side of the transducer material1102′ and then filled with metal, along with the formation of metal layer1106, as illustrated inFIG. 17E. Preferably, the vertical slots are between ½ to ¾ the thickness of the transducer material1102′. As an example, the metal layer may be formed by plating the surface with Ni/Cr and then with gold. A matching layer1118is disposed over the metal layer1106and the construct is then diced apart along lines1126,1128to expose contact layers1108,1110, as illustrated inFIGS. 17F and 16. This embodiment also lends itself to electrical connection via preformed pads in the modular fitting530shown inFIG. 5.