Robust, simple, and efficiently manufacturable transducer array

Abstract

A transducer array for ultrasound applications includes a plurality of transducer elements that are provided with self-aligned connections to a flexible cable. The array is easy to manufacture and suited for wearable, wireless, and other small ultrasound devices. A simple and efficient method of producing a robust transducer array involves at least partially separating the transducer elements after their connection to their respective conductors.

Claims

1. A method of producing a simplified transducer array, comprising providing a plate of transducer material with first and second electrode layers on respective first and second surfaces, providing at least n conductors in a flexible cable, wherein n≥8, at one side of the plate forming, preferably by soldering, a single contact with the ends of the conductors and over a width of the plate while maintaining the temperature of the plate below 220° C., preferably at 10° C. or more below a temperature at which de-poling of the transducer material may occur, dividing the transducer material into an array of at least n transducer elements by providing at least n−1, at least partial, separations at a side of the soldering, wherein the separations fully extend through the soldering thereby dividing the single contact into n separate self-aligned contacts, each contact being in connection with an individual conductor of the flexible cable, and placing the divided and connected transducer material in a casing, and optionally fixating the transducer material in the casing, such as by gluing, by bonding, by applying a force, and combinations thereof.

2. The method according to claim 1, wherein a first surface of the transducer is protected by an optional layer over the transducer for providing mechanical stiffness, protection of the transducer in the casing, and as an acoustical backing layer, and/or wherein the single contact has a width of 0.2 mm to 2 mm, and/or wherein the single contact is applied on the ends of a flex cable, and/or wherein the transducer material is cooled during soldering.

3. The method according to claim 1, wherein the single contact is formed by soldering and the soldering is applied during less than 10 seconds.

4. The method according to claim 1, wherein after forming the single contact but before dividing the transducer material, the ends of the connecting cables are bent downwards out of the cutting path.

5. The method according to claim 1, wherein a ground contact is provided which extends from the second electrode layer at the second surface of the plate, along at least one side of the plate, to at least one electrode on the first surface of the plate, wherein the at least one electrode is in electrical contact with at least one of the conductors of the flexible cable.

6. A robust, simple, and efficiently manufacturable transducer array for ultrasound, optionally obtainable by the method of claim 1, comprising a transducer array of at least n transducer elements, wherein n≥8, wherein two adjacent transducer elements are provided with at least partial first separations there in between, a flexible cable comprising at least n conductors, preferably a flat flex cable, at least two conductors electrically connected to at least two individual transducer elements by a self-aligned electrical contact, preferably a soldered contact, optionally including at least one ground contact, an electrical power source and/or an electrical circuit, for supply of signals, such as pulses, and for driving a transducer element, in electrical connection with at least one contact, typically at an other side of a respective conductor of the flexible cable, and a casing for the transducer array, in which casing the transducer array is provided, preferably in which casing the transducer array is embedded.

7. The transducer array according to claim 6, wherein each individual transducer element comprises a piezoelectric material selected from titanates, bulk piezo material, piezocomposite material, active piezoelectric material, such as lead zirconate titanate (PZT) (Pb[Zr.sub.xTi.sub.1-x]O.sub.3 0≤x≤1), AlN, (PbMg.sub.0.33Nb.sub.0.67).sub.1-x(PbTiO.sub.3).sub.x, preferably with x=0.28-0.5 (PMNT), Cobalt MNT, ceramic and crystalline material, a Microelectromechanical system (MEMS), such as a CMUT and PMUT, and combinations thereof.

8. The transducer array according to claim 7, wherein the transducer element material has a thickness of 0.1 mm to 2 mm.

9. The transducer array according to claim 6, wherein at least one transducer element is provided with a conducting material for electrical contact, preferably a coated conducting material, preferably on a top and bottom side thereof, and/or wherein self-aligned electrical contacts to the flex cable are soldered contacts, conductive glued contacts, or capacitive coupled contacts.

10. The transducer array according to of claim 6, wherein transducer elements in the array are separated by a spacing, preferably an air-filled spacing, wherein the spacing has a width of 0.01 mm to 1 mm, and where the separations between the elements are 50% to 95% of the element thickness.

11. The transducer array according to claim 6, wherein a ground contact is provided which extends from a contact at a bottom side of the transducer material, along at least one side of the transducer material, to at least one part of the contact on the top side of the transducer material.

12. The transducer array according to claim 6, wherein the casing comprises a polymer, and wherein a thickness of the casing at a side where ultrasound is transmitted is from 0.05 mm to 2 mm, and/or where the other side of the transducer is protected by an optional layer over the transducer that gives mechanical stiffness, protects the transducer in the casing and/or serves as an acoustical backing layer.

13. The transducer array according to claim 6, wherein the casing comprises space holders for determining a thickness of a matching layer, and/or wherein the casing is part of an ultrasound path, such as an acoustical layer, an acoustical matching layer, an acoustical lens, or an acoustical prism.

14. The transducer array according to claim 6, wherein the array comprises from 10 to 1024 transducer elements, wherein at least one transducer element is at least partly provided with a secondary separation at the opposite side with respect to the first separations, perpendicular to the first separation, and with a secondary separation length of <90% of the first separation length, and/or a p.sup.th fraction of p≥3 of the electrode length is connected to a p.sup.th electrode connector, wherein p is preferably 3, 4 or 5, perpendicular to the long transducer elements, and/or wherein transducer elements have a pitch of 40-800 microns, and/or wherein transducer elements operate at a frequency of 20 kHz-50 MHz, and/or wherein at least two neighbouring transducer elements are at a mutual distance of approximately 0.5 wavelength (λ±10%).

15. Ultrasound device comprising a simplified transducer array according to claim 6, comprising transmission control electronics for beam steering of the array comprising at least one high-voltage pulse source, wherein a source are linked to a low-voltage timing circuit for timing of the at least one pulse sources, and/or receiving control electronics simplified to limit energy consumption when processing received ultrasound, wherein the receiving control electronics is preferably selected from (i) at least one and preferably all ultrasound receiving transducer element are adapted for determining ultrasound energy in connection with a rectifying amplifier and the rectifying amplifier in connection with an analogue adder for adding the outputs of the rectifying amplifiers, (ii) <50%, of the n transducer elements connected or connectable to receive electronics, and (iii) combinations thereof, and/or wherein the transducers elements are capable of operating separately, sequentially, in phase-shift mode, in parallel mode, in frequency scan mode, in spatial scan mode, in intensity mode, in pulsed mode, in harmonic mode, variations thereof, or combinations thereof.

16. Product comprising a simplified transducer array according to claim 6, comprising a positioner for maintaining the product in a position, a contacting means for contacting the product to a skin of the body, an energy scavenger, an ADC for converting analogue array signals to digitized output signals, wherein the product is wearable and is substantially flat, and/or comprising a movement sensor, such as an accelerometer, gyroscope, and a magnetic sensor.

17. (canceled)

18. The product of claim 16, wherein the product is selected from a wearable device, a portable device, a medical device, a non-destructive testing device, or combinations thereof, such as a small wireless ultrasound device for signalling a change in a body tissue, body vessel or body cavity, such as a bladder, preferably a stand-alone device.

Description

SUMMARY OF FIGURES

[0054] FIG. 1. shows a perspective view of an ultrasound array.

[0055] FIG. 2: shows an end elevation of the array of FIG. 1.

[0056] FIG. 3: shows a detail taken at III of the array of FIG. 1.

[0057] FIG. 4: shows a perspective view of an array according to a second embodiment.

[0058] Figure: shows a side elevation of the array of FIG. 4.

[0059] FIG. 6: shows a plan view of the array of FIG. 4 mounted in a casing.

[0060] FIG. 7: shows a cross-section through the device of FIG. 6 taken along line VII-VII.

[0061] FIG. 8: shows a device including an array according to a third embodiment in a similar cross-section to FIG. 7.

DETAILED DESCRIPTION OF FIGURES

[0062] FIG. 1 shows in perspective view a transducer array 10 for ultrasound application. The transducer array 10 comprises a plate 12 formed of transducer material and having opposed first and second surfaces 14A, 14B, with first and second side faces 16A, 16B, and first and second end faces 18A, 18B therebetween. The first and second surfaces 14A, 14B are provided with respective first and second electrode layers 20A, 20B.

[0063] An electrical cable 30 comprising a plurality of parallel conductors 32A-N, is connected electrically to the first electrode layer 20A by a single contact in the form of a connecting strip 34 extending transversally to the cable 30 over a width W of the plate 12.

[0064] The plate 12 is provide with grooves 22 extending along the first surface 14A from the first end face 18A to the second end face 18B, the grooves 22 extending through the first electrode layer 20A and into the transducer material to a depth sufficient to divide the plate 12 into an array of n transducer elements 24A-N, each having an individual first electrode 26 A-N and sharing as a common second electrode, the second electrode layer 20B. The grooves 22 extend through the single contact in the form of a connecting strip 34 to also separate one conductor 32A from an adjacent conductor 32B, whereby each conductor 32A-N is connected to a respective individual first electrode 26A-N.

[0065] The transducer material in the illustrated embodiment is a piezoelectric material comprising lead zirconate titanate, (Pb[Zr.sub.0.52Ti.sub.0.48]O.sub.3) although other known alternatives may also be applied. The plate 12 has a length L of 40 mm, a width W of 20 mm and a thickness t of 1 mm. The electrodes layers 20A, 20B are silver of micron thickness although they have been indicated as considerably thicker merely for illustrative purposes. The cable 30 is a 20 pin flex cable of 0.5 mm pitch with 0.25 mm copper conductors 32 stripped back to have 2 mm of bare copper for connection to the first electrode layer 20A.

[0066] Also illustrated in FIG. 1 is a ground contact 40 extending from the second electrode layer 20B to the first surface 14A of the plate across the first side face 16A and electrically connected to the individual first electrode 26A of the first transducer element 24A adjacent to the first side face 16A.

[0067] Although referred to as the first transducer element 24A, this transducer element has its respective first and second electrodes effectively shorted by the ground contact 40 and cannot thus operate as a transducer element. This first transducer element 24A is thus used as a connection to the common second electrode layer 20B and to the first conductor 32A of the cable 30.

[0068] FIG. 2, is an end elevation of the transducer array 10 of FIG. 1 viewed towards the second end face 18B. The transducer elements 24 can be seen separated by grooves 22. The grooves 22 have a width of 50 microns and a depth of 0.9 mm. They are applied at a pitch of 0.5 mm, such that the individual transducer elements 24 have a width of around 0.45 mm.

[0069] With reference to the first transducer element 24A, each transducer element has a similar construction. Starting from the first surface 14A, the transducer element 24A comprises a portion of conductor 32A extending from the cable 30. Beneath the conductor 32A is the connecting strip 34. The connecting strip 34 is formed of a 62/36/2 Sn/Pb/Ag solder having a low melt temperature of 179 C to avoid approaching the Curie temperature of the piezo material. The 2% silver avoids the possibility of the silver electrode layer 20A dissolving during processing. It will also be understood that the solder of the connecting strip 34 may no longer be identifiable as a distinct layer as it will have flowed around the conductor 32A.

[0070] Beneath the connecting strip 34 is the individual first electrode 26A above the piezoelectric material of the plate 12. At the lowermost portion of the first transducer element 24A, an intact region 13 of the plate 12 is not cut or separated and still extends across the full width W of the transducer array 10. This intact region 13 has a thickness of around 80 microns, which has been found sufficient to ensure adequate stability of the structure. Beneath the intact region 13 is the second electrode layer 20B, which serves as a common second electrode for the first transducer element 24A and all of the other transducer elements 24B to 24N.

[0071] FIG. 3 is a detail of part of the array 10 of FIG. 1 at III. In this detail, the manner in which the cable 30 is bent downwards adjacent to the first end face 18A can better be seen. This allows the grooves 22 to also partially cut into the insulation 31 surrounding the conductors 32A-N. It can also be seen how the conductors 32A-N and the connecting strip 34 only extend a short distance in the length direction of the array. Also visible is the ground contact 40, which connects the second electrode layer 20B to the individual first electrode 26A and the first conductor 32A of the cable 30.

[0072] In FIG. 4, a perspective view from the underside of an alternative implementation of an array 110 is presented, showing the first side face 116A and the second end face 118B. In this embodiment, like elements to the previous figures are referenced with similar reference numerals preceded by 100. This second embodiment has first and second ground electrodes 142A, 142B at the second surface 114B. The ground electrodes 142A, 142B may be formed by cutting or ablating through the second electrode layer 120B in a direction perpendicular to the grooves 122 at the first surface 114A. In the illustrated embodiment, the plate 112 has been cut through by a secondary separation 123 to the depth of the intact region 113 such that the grooves 122 are also visible through the secondary separation 123.

[0073] To connect each of the ground electrodes 142A, 142B at the second surface 114B to one of the individual first electrodes 126A-N at the first surface 114A, there are provided first and second ground contacts 140A, 140B. In this manner, the ground electrodes 142A, 142B can be connected with the cable 130 via the first and last individual first electrodes 126A, 126N. This is convenient as it allows all of the electrical connections to be arranged via one cable 130.

[0074] FIG. 5 shows in side elevation, the array 110 of FIG. 4, viewed towards the second side face. In this view, the second ground contact 140B is visible, extending between the second ground electrode 142B and the last individual first electrode 126N, whence it connects to the last connector 132N of the cable 130.

[0075] The second embodiment of FIGS. 4 and 5 depicts an array of ten transducer elements 124A-N, separated by nine grooves 122. In this case, although the first and last elements 124A, 124N are referred to as transducer elements, they are in fact inoperative, since their contacts are shorted by the respective first and second ground contacts 140A, 140B. The remaining eight transducer elements 124B-124N−1 are connected with respectively two ground contacts 142A, 142B at the bottom side and one first electrode 126B-126N−1 each at the top side, enabling separate activation of two sections of each transducer element 124B-124N−1.

[0076] FIG. 6 shows a plan view of the array 110 of FIGS. 4 and 5 embedded in a casing 150. The cable 130 is attached to a printed circuit board (PCB) 152 at a ZIF (zero insertion force) connector 154. The PCB 152 supports a microprocessor 155 provided with the required processing capability to drive the array 110, a memory 156 for storing data and instructions, a wireless communication module 157 for communicating data and instructions and a battery 158. In the illustrated embodiment, the casing is of polycarbonate although ABS plastic is also suitable. The casing is held together with screws 160.

[0077] FIG. 7 shows a cross-section taken through the casing 150 of FIG. 6 in the direction VII-VII. As can be seen, the casing 150 is formed in three parts, comprising a base plate 162, a ring 164 and a cover 166.

[0078] The base plate 162 includes a window region 168, of reduced thickness, against which the second surface 114B of the array 110 is located. In order to ensure good coupling, the array 110 is spaced from the window region 168 by a matching layer 170. Spacers 172 forming part of the casing 150 are provided to ensure a correct thickness of the matching layer.

It will be understood that the transducer can alternatively be mounted directly into the casing using epoxy, with only the casing material for acoustical matching.

[0079] The first surface 114A of the array 110 is covered with an acoustic backing layer 174. The backing layer 174 is a magnetic rubber tape material that is glued to the first surface of the array 110. Barium ferrite synthetic rubber tape has been found most suitable for this purpose. It not only makes an excellent acoustical backing but also serves to stabilise the free ends of the separated transducer elements.

[0080] FIG. 8 shows in a cross section similar to that of FIG. 7, a third embodiment of an array 210 in which like elements to earlier embodiments are provided with similar reference numerals preceded by 200.

[0081] The array 210 is mounted in a housing 250, similar to the previous embodiment but in this case, the array 210 is divided in the length direction into three sections 210A, 210B and 210C by secondary separations 223, which extend through the full thickness of the plate 212. The secondary separations extend to the first electrode layer 220A. In actual fact, the secondary separation can be cut to just short of this layer and then the remaining portion of piezo material can be carefully broken. This preferably takes place after application of the rubber acoustic backing layer 274, which serves to maintain the integrity of the array 210 once the three sections 210A-C have been broken apart. Each section 210A-C has its own respective ground electrode 242A-C. In this embodiment however the ground electrodes 242A-C have respective ground contacts 240A-C that can be connected by conventional solder connections to ground terminals (not shown) within the casing 250.

[0082] The secondary separations 223 allow the three sections 210A-C to be angled with respect to one another for directional transmission of the ultrasound. To this end, the window region 268 also has three regions 268A, 268B, 268C. The inner surface of the central second window region 268B is parallel to the lower surface of the base plate 262. The first window region 268A is angled by 4 degrees away from the second window region 268B, while the third window region 268C is angled by 4 degrees in the opposite direction. In this case, the second surface 214B of the array 210 is coupled directly to the base plate 262 without any matching layer or spacers.

[0083] Although in this third embodiment, the three sections 210AC of the array 210 are angled to one another, it will be understood that the advantages of three such sections that can be separately driven can also be achieved without angling the sections or without complete separation. Acoustic prisms may be implemented within the casing to achieve a similar effect.

[0084] The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying examples and figures and in particular, the following embodiments.

1. A transducer array for ultrasound application, comprising:

[0085] a plate formed of transducer material and having opposed first and second surfaces with first and second side faces and first and second end faces therebetween, the first and second surfaces being provided with respective first and second electrode layers,

[0086] an electrical cable comprising a plurality of parallel conductors, connected electrically to the first electrode layer by a single contact extending generally transversally to the cable over a width of the plate,

[0087] wherein the plate is provide with grooves extending along the first surface from the first end face to the second end face, the grooves extending through the first electrode layer and into the transducer material to a depth sufficient to divide the plate into an array of n transducer elements, each having an individual first electrode and sharing a common second electrode, the grooves extending through the single contact to also separate each conductor from an adjacent conductor, whereby each conductor is connected to a respective individual first electrode.

2. Transducer array according to embodiment 1, wherein the transducer material comprises a piezoelectric material selected from titanates, bulk piezo material, piezocomposite material, active piezoelectric material, such as lead zirconate titanate (PZT) (Pb[ZrxTi1-x]O3 0≤x≤1), AlN, (PbMg0.33Nb0.67)1-x(PbTiO3)x, preferably with x=0.28-0.5 (PMNT), Cobalt MNT, ceramic and crystalline material, a microelectromechanical system (MEMS), such as a CMUT and PMUT, and combinations thereof.
3. Transducer array according to embodiment 1 or 2, wherein the plate has a thickness of 0.1-2 mm, preferably 0.3-1.0 mm.
4. Transducer array according to any of embodiments 1 to 3, wherein the plate has a surface area of from 10 mm2 to 1000 mm2, preferably between 20 mm2 and 600 mm2, most preferably between 60 mm2 and 500 mm2.
5. Transducer array according to any of embodiments 1-4, wherein the single contact comprises solder, metal, conductive glue or a capacitive coupled contact.
6. Transducer array according to any of embodiments 1-5, wherein the grooves separating the respective transducer elements have a width of 0.01-1 mm, such as 0.05 mm.
7. Transducer array according to any of embodiments 1-6, wherein the grooves separating the respective transducer elements extend to a depth corresponding to 50-95% of the thickness of the plate.
8. Transducer array according to any of embodiments 1-7, further comprising a ground contact extending from the second electrode layer to the first surface of the plate across the first side face and electrically connected to the individual first electrode of the transducer element adjacent to the first side face.
9. Transducer array according to any of embodiments 1-8, wherein the single contact is connected to the first electrode layer adjacent to the first end face and preferably extends less than 5 mm, preferably less than 2 mm but more than 0.2 mm in the direction of the second end face.
10. Transducer array according to any of embodiments 1-9, further comprising a polymer casing, preferably of ABS or polycarbonate, and wherein a thickness of the casing at a side where ultrasound is transmitted is from 0.05-5 mm or 0.05 to 2 mm.
11. Transducer array according to any of embodiments 1-10, wherein the first surface of the plate is provided with a protective layer that gives mechanical stiffness and/or serves as an acoustical backing layer.
12. Transducer array according to any of embodiments 1-11, wherein the array comprises from 10 to 1024 transducer elements, preferably from 12 to 256 transducer elements, more preferably from 14 to 128 transducer elements, 16 to 64 transducer elements or 20 to 32 transducer elements or 24 to 32 transducer elements.
13. Transducer array according to any of embodiments 1-12, further comprising a secondary separation extending transversally with respect to the grooves across the second surface from the first side face to the second side face whereby the second electrode layer is split in two halves and preferably, half of the second electrode layer is connected to a first conductor and the other half of the second electrode layer is connected to a further conductor, to allow separate activation of the two halves.
14. Transducer array according to embodiment 13, comprising one or more secondary separations that extend from the second surface, through the transducer material to a depth sufficient to divide each transducer element into m sections, having common individual first electrodes and separate second electrodes.
15. Transducer array according to embodiment 14, wherein the secondary separations extend more than 50% or more than 90% or more than 95% through the plate.
16. Transducer array according to embodiment 15, wherein the secondary separations extend completely through the plate but not through the first electrode layer, and the sections are angled with respect to each other, preferably by between 1 degree and 15 degrees.
17. Transducer array according to any of embodiments 1-16, further comprising an electrical circuit for supply of signals for driving the transducer elements, the electrical circuit being in electrical connection with the transducer elements via the electrical cable.
18. Ultrasound device comprising a transducer array according to embodiment 17, wherein the electrical circuit comprises transmission control electronics for beam steering of the array as a phased array.
19. Ultrasound device according to embodiment 18, comprising at least one high-voltage pulse source, linked to a low-voltage timing circuit for timing of the at least one high-voltage pulse source.
20. Ultrasound device according to any of embodiments 18 or 19, comprising, receiving control electronics wherein less than 50%, preferably less than 20% of the n transducer elements are connected or connectable to the receiving control electronics.