Flexible circuit with redundant connection points for ultrasound array

Flex circuits and methods for ultrasound transducers are provided herein. In at least one embodiment, an ultrasound device includes a plurality of transducer elements and a flex circuit. The flex circuit includes an insulating layer having a first surface and a second surface opposite the first surface. A plurality of first conductive pads is included on the first surface of the insulating layer, and each of the first conductive pads is electrically coupled to a respective transducer element. A plurality of second conductive pads are included on the second surface of the insulating layer, and each of the second conductive pads is electrically coupled to a respective first conductive pad and the respective transducer element.

BACKGROUND

Technical Field

The present application pertains to ultrasound systems, and more particularly to ultrasound systems including a flex circuit for attachment to ultrasound transducer elements in an acoustic stack.

Description of the Related Art

Ultrasonic transducers generally include piezoelectric transducer elements, which are electrically connected to circuitry such as driving or receiving circuitry for driving the transmission of an ultrasound signal (e.g., an ultrasound pulse) and/or for receiving a reflected ultrasound signal (e.g., an echo signal). The transducer elements are coupled to a flex circuit, which provides signal lines for transmitting signals between the transducer elements and the driving circuitry, receiving circuitry, processing circuitry or the like. Such circuitry is typically included in electronic equipment that is positioned external to the ultrasound probe, such as an equipment cart or a handheld computing device. The flex circuit thus couples the transducer elements to the processing, driving and/or receiving circuitry.

During operation, an electrical pulse is applied to electrodes of the transducer elements, which causes a mechanical change in dimension of the transducer elements and generates an acoustic wave that is transmitted toward a target structure of interest, e.g., an organ or other physiological feature within a patient's body. The transmitted acoustic wave is then reflected from the target structure of interest and is received at the surface of the transducer elements, which in response generate a voltage that is detectable as a receive signal by the associated processing and/or receiving circuitry.

Ultrasonic transducers may include transducer elements that are arranged as phased arrays having one or more rows of transducer elements that are electrically and acoustically isolated from one another. Such arrays may include 64 or more individual transducer elements. An acoustic stack may be formed, including such transducer elements, as a layered structure including a backing layer, a flex circuit, the transducer elements (e.g., piezoelectric ceramic elements), and an acoustic matching layer. The flex circuit typically includes conductive traces formed on one side of an insulating layer. The conductive traces are then coupled to respective transducer elements.

An important feature of an ultrasound array, and of the design of such an array, is the reliability of the signal pulse path to and from the transducer elements in the array. If there is a short circuit, open circuit, high resistance, or any defect in the signal path, the signals provided to and from the connected transducer elements may not produce reliable information from which an ultrasound image can accurately be formed.

The point at which the conductive traces of the flex circuit are coupled to respective transducer elements is thus a critical coupling point, as all driving signals to be provided from the driving circuitry to the transducer elements are provided through the individual conductive traces. Similarly, received echo signals may be provided from the transducer elements to the receiving and/or processing circuitry through the individual conductive traces coupled to the transducer elements.

BRIEF SUMMARY

The present disclosure, in part, addresses a desire for better signal path continuity through a flex circuit in an ultrasound transducer. Improving signal path continuity through the flex circuit results in more reliable signal communication between the processing, driving and/or receiving circuitry and the transducer elements.

Embodiments provided by the present disclosure improve signal communication through a flex circuit by providing redundant connection points for transmitting a signal to each transducer element in the ultrasound transducer, e.g., in the acoustic stack of the ultrasound transducer. Redundant connection points may be provided by including conductive pads on both sides of an insulating layer of the flex circuit. The conductive pads on one side of the insulating layer are coupled to respective conductive traces formed on the same side of the insulating layer. Further, conductive pads are formed on an opposite side of the insulating layer, and corresponding conductive pads on opposite sides of the insulating layer are aligned with one another and coupled to one another by conductive vias formed through the insulating layer. Accordingly, even if a defect exists in the attachment point of one of the conductive pads to a transducer element (which defect may cause, for example, an open circuit, high resistance, or the like), signals may still be reliably provided to and from the transducer element through a second electrical connection point provided by the conductive pad formed on the opposite side of the insulating layer.

In at least one embodiment, an ultrasound transducer is provided that includes a plurality of transducer elements and a flex circuit. The flex circuit includes an insulating layer having a first surface and a second surface opposite the first surface. A plurality of first conductive pads is formed on the first surface of the insulating layer, and each first conductive pad is electrically coupled to a respective transducer element. A plurality of second conductive pads is formed on the second surface of the insulating layer, and each of the second conductive pads is electrically coupled to a respective first conductive pad and the respective transducer element.

In another embodiment, an ultrasound transducer is provided that includes a flex circuit. The flex circuit includes an insulating layer having a first surface and a second surface opposite the first surface, a plurality of conductive traces on the first surface of the insulating layer that are each electrically coupled to respective first conductive pads on the first surface of the insulating layer, and a plurality of second conductive pads on the second surface of the insulating layer. The flex circuit further includes a plurality of conductive vias, each of which extend through a respective first conductive pad, the insulating layer, and a respective second conductive pad. Each of the conductive vias electrically couple respective first and second conductive pads to each another. The ultrasound transducer may further include a plurality of transducer elements, with each of the transducer elements being electrically coupled to a respective first conductive pad and a respective second conductive pad.

In yet another embodiment, a method is provided that includes forming a plurality of conductive traces on a first surface of an insulating layer; forming a plurality of first conductive pads on the first surface of the insulating layer, each of the first conductive traces being electrically coupled to a respective first conductive pad; forming a plurality of second conductive pads on a second surface of the insulating layer, the second surface being opposite the first surface; and electrically coupling each of the first conductive pads to a respective second conductive pad.

DETAILED DESCRIPTION

In various embodiments described herein, a flex circuit for an ultrasound transducer may include conductive pads formed on each of two opposite sides of an insulating layer of the flex circuit. The conductive pads on a first side of the insulating layer are respectively electrically coupled to corresponding conductive pads on a second side of the insulating layer by a conductive via formed through the corresponding conductive pads and the insulating layer. The conductive pads on one of the first side or the second side of the insulating layer are electrically coupled to respective conductive traces on the flex circuit. The flex circuit may be coupled to an acoustic stack such that each transducer element in the acoustic stack is electrically coupled to at least two conductive pads, i.e., conductive pads on opposite sides of the insulating layer that are electrically coupled to each other by a conductive via. The flex circuit thus provides at least two points of contact, provided by each of the conductive pads coupled to one another through the conductive via, through which a signal transmitted along a conductive trace (e.g., a driving signal for driving a connected transducer element to transmit an ultrasound pulse or an echo signal received by a connected transducer element) may be provided to or received from a transducer element.

FIG. 1is a perspective view of at least one embodiment of a flex circuit10for an acoustic stack in an ultrasound transducer. The flex circuit10includes an insulating layer12, conductive traces14, and conductive pads16.

The insulating layer12is made of any suitable flexible insulating material, such as polyimide. Conductive traces14are formed on a first surface11(e.g., a front surface) of the insulating layer12. The conductive traces14may be made of any conductive material and may be formed using any suitable process, such as by deposition of the conductive material on the insulating layer12using one or more masks or deposition patterns. In one or more embodiments, the conductive traces14include copper.

Each of the conductive traces14formed on the first surface11of the insulating layer12is coupled to a respective conductive pad16aon the first surface11. The conductive pads16amay be formed in a same process, and of a same material, as the conductive traces14.

In the embodiment shown inFIG. 1, each of the conductive pads16aon the first surface11of the insulating layer12is aligned with, and electrically coupled to, a respective conductive pad16bthat is formed on a second surface13(e.g., a back surface) of the insulating layer12. The conductive pads16a,16bare electrically coupled to one another by a conductive through-hole or via18.

The via18is formed through the aligned, corresponding conductive pads16aon the first surface11and conductive pads16bon the second surface13. A through-hole may be formed, for example, by drilling, punching or the like through the aligned conductive pads16a,16bon the first and second surfaces11,13of the insulating layer12, and the through-hole may then be plated with a conductive material, such as copper. As such, the vias18electrically couple respective conductive pads16a,16bthrough the insulating layer12. Accordingly, a signal provided through a trace14on the first surface11of the insulating layer12is provided to a conductive pad16aon the first surface11, as well as to a corresponding conductive pad16bon the second surface13, through the via18.

The flex circuit10thus provides redundant points of electrical contact when attached to an acoustic stack. That is, the flex circuit10may be attached to the acoustic stack such that corresponding conductive pads16a,16bformed on each side of the insulating layer12are each in contact with a respective transducer element in the acoustic stack. Additionally, since the corresponding conductive pads16a,16bare electrically coupled to one another by the conductive via18, a signal provided through a trace14on the first surface11of the insulating layer12will be transmitted to the respective transducer element by the corresponding conductive pads on both surfaces11,13of the insulating layer12. Accordingly, transmission of a signal (e.g., a driving signal) to a transducer element in an acoustic stack may be facilitated even in the event, for example, that one of the corresponding conductive pads16a,16bhas a faulty connection with the transducer element or is in any way deteriorated in its ability to carry an electrical signal.

The flex circuit10may be diced into individual conductive paths using, for example, a dicing saw. The flex circuit10may be diced so that each of the conductive paths includes a respective conductive trace14and corresponding conductive pads16a,16bformed on respective surfaces of the insulating layer12. The flex circuit10may be cut, for example, along dicing lines22,24, as shown inFIG. 1.

FIG. 2is a perspective view of a flex circuit100in accordance with one or more alternative embodiments of the present disclosure. The flex circuit100ofFIG. 2is similar in structure and in function to the flex circuit10ofFIG. 1, except for the differences that will be discussed below. The features shared by the flex circuits10and100will not be described here again in the interest of brevity.

The main difference between the flex circuits10and100is that, in the flex circuit100ofFIG. 2, conductive pads on the second surface13of the insulating layer12are formed from a single conductive bus116. The conductive bus116may be formed, for example, of copper using a deposition technique. Alternatively, the conductive bus116may be a prefabricated piece of conductive material that is bonded to the second surface13of the insulating layer12using, for example, an adhesive. In one or more embodiments, the conductive bus116has a height (h) of about 5 millimeters. The conductive bus116is formed on or bonded to an opposite surface of the insulating layer12(e.g., the second surface13, as shown) as the conductive pads16a. As in the flex circuit10ofFIG. 1, conductive vias18are formed through the conductive pads16aon the first surface11of the insulating layer12, thereby electrically coupling the conductive pads16ato corresponding regions of the conductive bus116on the second surface13of the insulating layer12.

The flex circuit100may then be diced into individual conductive paths using a dicing saw and cutting, for example, along dicing lines122,124. After dicing through the conductive bus116and the insulating layer12, as shown at dicing lines122,124, the flex circuit100includes individual conductive paths made up of the traces14formed on the first surface11of the insulating layer, as well as conductive pads16aon the first surface11and corresponding conductive regions of the conductive bus116on the second surface13(i.e., portions of the conductive bus116after dicing) that are coupled to respective conductive pads16athrough the conductive vias18.

FIG. 3Ais a front view illustrating an ultrasound transducer acoustic stack200including a flex circuit in accordance with one or more embodiments of the present disclosure, andFIG. 3Bis a side view of the acoustic stack200shown inFIG. 3A.

The acoustic stack200includes a plurality of transducer elements32, an acoustic matching layer34, and a flex circuit10. The flex circuit10is attached to a lower surface of the transducer elements32, and the acoustic matching layer34is attached to an upper surface of the transducer elements32.

The flex circuit10, transducer elements32, and acoustic matching layer34may be attached to one another to form the acoustic stack200using an adhesive material, such as an epoxy. In one or more embodiments, the transducer elements32are made of a piezoelectric material, such as a piezoelectric ceramic material. The transducer elements32may include electrodes (e.g., signal electrodes and/or ground electrodes) which are electrically coupled to the conductive pads16a,16bformed on the first and second surfaces11,13, respectively, of the insulating layer12. Alternatively, the transducer elements32may be electrically coupled to respective conductive pads16a,16bby attaching the transducer elements32to the flex circuit10with a conductive epoxy, solder, solder paste, or the like. The flex circuit10is attached to the transducer elements32in such a way that each transducer element32is electrically coupled to two conductive pads16a,16b, one on each surface11,13of the insulating layer12, thereby establishing redundant points of contact for transmitting a signal from the associated conductive trace14to the transducer element32.

The acoustic block200shown inFIGS. 3A and 3Bmay be formed by a variety of fabrication processes. In one embodiment, the transducer elements32may be provided initially as a single block of piezoelectric material. Similarly, the conductive pads16aon the first surface11of the insulating layer12and/or the conductive pads16bon the second surface13of the insulating layer13may initially be provided as a block of conductive material (e.g., the conductive bus116shown inFIG. 2) electrically coupled to the respective traces14on the insulating layer12.

Through-holes may be formed e.g., by drilling, punching or the like, through the conductive bus116on the second surface13at locations that will be included in the conductive pads16b, once formed. The through-holes are formed to extend through the conductive bus116, the insulating layer12, and the conductive pads16aon the first surface11of the insulating layer12. The through-holes may then be plated or otherwise coated with a conductive material, such as copper, to form the conductive vias18which electrically couple the conductive pads16ato associated regions of the conductive bus116that, after dicing, will become conductive pads16bon the second surface13of the insulating layer12.

The piezoelectric block may be attached to the flex circuit10such that the conductive pads16aon the first surface11and the conductive bus116on the second surface13are in contact with the piezoelectric block. The piezoelectric block and the flex circuit10may then be diced into individual transducer elements32and corresponding conductive pads16a,16busing a dicing saw. As such, a plurality of individual transducer elements32may be formed, with each transducer element32being electrically coupled to a pair of associated conductive pads16a,16bof the flex circuit10. Each of the conductive pads16ais electrically coupled to a corresponding trace14formed on the first surface11of the insulating layer12, and each conductive pad16ais further coupled by a conductive via18to a respective conductive pad16bon the second surface13of the insulating layer12. Accordingly, a redundant electrical connection is formed between the flex circuit10and the transducer elements32, as each trace14of the flex circuit10is coupled to a conductive pad16aon the first surface11of the insulating layer12, as well as to a conductive pad16bon the second surface13of the insulating layer12.

After the piezoelectric block has been diced into individual transducer elements32, as described above, gaps formed between transducer elements32and/or between adjacent conductive pads16a,16bof the flex circuit10may be filled with an adhesive material, such as an epoxy filling40.

The acoustic matching layer34may then be attached to an upper surface of the transducer elements32and/or epoxy filling40using any suitable adhesive, such as an epoxy.

The conductive pads16aon the first surface11of the insulating layer12do not necessarily have the same dimensions as the corresponding conductive pads16bon the second surface13of the insulating layer12. For example, as shown inFIG. 2, the conductive pads16bmay be formed by dicing through the conductive bus116, while the conductive pads16amay be already formed of suitable dimensions, along with the traces14. In such a case, the conductive pads16bformed after dicing the flex circuit10may have a larger area dimension than the pre-formed conductive pads16a.

In another embodiment, the transducer elements32may be initially provided as a single block of piezoelectric material, while the flex circuit10may have been previously cut into a plurality of traces14and associated conductive pads16a,16bwith conductive vias18formed through corresponding conductive pads16a,16b. The pre-cut flex circuit10may be attached to the piezoelectric block such that each associated pair of conductive pads16a,16bcontacts the piezoelectric block at regions that will later be cut into individual transducer elements32. The piezoelectric block is then diced into individual transducer elements32, for example, using a dicing saw.

In yet another embodiment, the acoustic stack10may be formed from transducer elements32that have already been diced, and from the flex circuit10that has also already been diced to form a plurality of traces14and associated conductive pads16a,16bwith conductive vias18formed through corresponding conductive pads16a,16b. In such a case, the transducer elements32may be directly attached or otherwise electrically coupled to respective conductive pads16a,16bon the first and second surfaces11,13, respectively, of the insulating layer12. The epoxy filling40may be applied, and the acoustic matching layer34may be attached to the transducer elements32as described herein.