Abstract:
Ultrasonic transducers having a reduced size in comparison with prior art ultrasonic transducers and including a thermally-conductive body, a flexible circuit bent at least partially around the body, an acoustic assembly arranged on the flexible circuit and electronic components for controlling the acoustic assembly to transmit and receive ultrasonic waves. Signal transmission lines, such as coax wires, are coupled to the flexible circuit such that the electronic components, the acoustic assembly and the signal transmission lines are connected in a circuit defined in part by the flexible circuit. By bending the flexible circuit with the acoustic assembly, and optionally the electronic components, arranged thereon about the body, they are positioned in a vertical configuration which allows for a compact transducer which has a small, even miniature size in comparison to prior art ultrasonic transducers.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to ultrasonic transducers having a sufficiently small size to enable their use in small medical instruments, in particular, transesophageal examination devices, laproscopic examination devices and intra-cardiac examination devices, and more particularly to such ultrasonic transducers having acoustic elements mounted over an integrated circuit.  
         [0002]     The present invention also relates to methods for manufacturing ultrasonic transducers having a size small enough to enable their use in medical instruments, in particular, transesophageal examination devices, laproscopic examination devices and intra-cardiac examination devices.  
       BACKGROUND INFORMATION  
       [0003]     A typical ultrasonic transducer used in a medical instrument for imaging portions of the body to generate a three-dimensional image has a complicated interconnection of the various components of the transducer. As a result, it has proven to be costly to build such transducers. Moreover, it is a drawback of such transducers that in view of the complicated interconnection of components, they require a relatively large amount of space and therefore cannot be used in applications where a very small or miniature ultrasonic transducer is needed, such as for examining the esophagus and heart and other relatively small parts of the body.  
         [0004]     Thus, while such transducers can be used as transthorasic transducers, they cannot be used as transesophageal transducers, laproscopic transducers and intra-cardiac transducers because they are too large.  
       SUMMARY OF THE INVENTION  
       [0005]     It is an object of the present invention to provide a new and improved ultrasonic transducer which has a very small, miniature size.  
         [0006]     It is another object of the present invention to provide a new and improved ultrasonic transducer having a sufficiently small size to enable its use in small medical instruments, in particular, transesophageal examination devices, laproscopic examination devices and intra-cardiac examination devices.  
         [0007]     It is yet another object of the present invention to provide a new and improved ultrasonic transducer which includes a flexible circuit thereby enabling the size of the transducer to be reduced in comparison with prior art ultrasonic transducers.  
         [0008]     It is still another object of the present invention to provide a new and improved method for manufacturing ultrasonic transducers having a size small enough to enable their use in small medical instruments, in particular, transesophageal examination devices, laproscopic examination devices and intra-cardiac examination devices.  
         [0009]     In order to achieve these objects and others, an ultrasonic transducer in accordance with the invention comprises a thermally-conductive body, a flexible circuit bent at least partially around the body, an acoustic assembly connected to the flexible circuit and electronic components for controlling the acoustic assembly to transmit and receive ultrasonic waves. Signal transmission lines or conduits, such as coax wires, flat ribbon cables or long flexible circuits, are coupled to the flexible circuit such that the electronic components, the acoustic assembly and the signal transmission lines are connected in a circuit defined in part by the flexible circuit. The electronic components and acoustic assembly are optionally arranged on the flexible circuit. By bending the flexible circuit with the acoustic assembly and the electronic components arranged thereon about the body, they are positioned in a vertical configuration which allows for a compact transducer which has a small, even miniature size in comparison to prior art ultrasonic transducers.  
         [0010]     More particularly, the flexible circuit is bent around the body such that one part having the acoustic assembly arranged thereon is on a first side of the body and a second part having the electronic components arranged thereon is on a second, opposite side. A 180° bend around a leg portion of the body separates the two parts of the flexible circuit. Additional bends are provided to enable terminal end portions of the flexible circuit to be vertically spaced from the body arrangement, with the signal transmission lines being coupled to the terminal end portions, possibly by means of additional flexible circuits. Preferably, the electronic components are positioned in a cavity defined by the body. The part of the flexible circuit to which the electronic components are mounted may be positionable in the cavity as well.  
         [0011]     In one embodiment, the acoustic assembly includes acoustic elements and an integrated circuit electrically coupled to the acoustic elements. The integrated circuit is also electrically coupled to the flexible circuit. Specifically, the flexible circuit and the integrated circuit each have connection sites or connector pads with wire-bonds being provided to connect the connection sites of the integrated circuit and the flexible circuit.  
         [0012]     Another embodiment of an ultrasonic transducer in accordance with the invention includes a housing, acoustic elements arranged in the housing and an integrated circuit arranged in the housing adjacent the acoustic elements and connected to the acoustic elements. The integrated circuit is connected to electrical transmission lines. Connection sites for the connections to the integrated circuit are arranged on a common surface thereof. More specifically, the integrated circuit may be connected to the acoustic elements and the signal transmission lines using metal bumps, solder bumps, polymer bumps, thin-line bonding, z-axis conductive elastomeric connectors, z-axis conductive adhesive, z-axis conductive film and/or reflow solder. In addition, the integrated circuit may be coupled to an intermediate interconnection substrate, such as an at least partially flexible circuit, using wire-bonds, direct wire attachments and/or tab bonding of leads. The interconnection substrate may also be a thin film circuit or ceramic circuit and/or use laminate circuit technology. Still another embodiment of an ultrasonic transducer in accordance with the invention includes a flexible circuit having connection sites, an acoustic assembly mounted on the flexible circuit and an integrated circuit having connection sites and acoustic elements electrically coupled to the integrated circuit, and electronic components for controlling the acoustic assembly to cause the acoustic assembly to transmit and receive ultrasonic waves. Wire-bonds are formed to connect the connection sites of the integrated circuit and the connection sites of the flexible circuit. The acoustic assembly and electronic components are thus connected in a circuit defined in part by the flexible circuit. The wire-bonds may be formed along only a portion of the periphery of the integrated circuit. In one embodiment, two rows of wire-bonds are formed along each of a pair of opposed edges of the integrated circuit.  
         [0013]     In accordance with another embodiment of the invention, a method for manufacturing miniature ultrasonic transducers includes the steps of arranging an acoustic assembly on a flexible circuit, e.g., when the flexible circuit is flat, coupling electronic components for controlling the acoustic assembly to the acoustic assembly circuit, coupling signal transmission lines to the flexible circuit such that the electronic components, the acoustic assembly and the signal transmission lines are connected in a circuit defined in part by the flexible circuit and bending the flexible circuit at least partially around a thermally-conductive body to form at least one 180° bend about the body. When the electronic components are also mounted on the flexible circuit, after the bending of the flexible circuit about the body, the acoustic assembly will be vertically spaced from the electronic components. In this manner, the acoustic assembly and electronic components are in a vertical arrangement one substantially above the other so that a compact transducer is provided which has a sufficiently small size to enable its use in transesophageal examination devices, laproscopic examination devices and intra-cardiac examination devices.  
         [0014]     These and other objects, features and advantages of the present invention will be explained below with reference to the following drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a cross-sectional view of a transducer in accordance with the invention shown in the outline of a tip of a transesophageal examination probe;  
         [0016]      FIG. 2  is an illustration of an acoustic assembly in which acoustic elements are mounted over an integrated circuit;  
         [0017]      FIG. 3  is an enlarged view of a first embodiment of the section designated  3  in  FIG. 2 .  
         [0018]      FIG. 4  is an enlarged view of a second embodiment of the section designated  3  in  FIG. 2 ;  
         [0019]      FIG. 5  is a top view of the transducer in accordance with the embodiment of the invention shown in  FIG. 1 ;  
         [0020]      FIG. 6  is a cross-sectional view of another embodiment of a transducer in accordance with the invention shown in the outline of a tip of a transesophageal examination probe;  
         [0021]      FIG. 7  is a cross-sectional view of another embodiment of a transducer in accordance with the invention shown in the outline of a tip of a transesophageal examination probe;  
         [0022]      FIG. 8  is a sectional view taken along line  8 - 8  of  FIG. 7 ; and  
         [0023]      FIG. 9  is a cross-sectional view of another embodiment of a transducer in accordance with the invention shown in the outline of a tip of a transesophageal examination probe.  
     
    
     DESCRIPTION OF THE INVENTION  
       [0024]     Referring to the accompanying drawings wherein like reference numerals refer to the same or similar elements,  FIG. 1  shows a first embodiment of an ultrasonic transducer in accordance with the invention which is generally designated as  10 . The ultrasonic transducer is small enough to fit within the tip of a standard-size transesophageal examination probe, represented by the line  12 , or another similarly-sized or smaller probe housing. Previously, miniaturization of an ultrasonic transducer to fit within the tip of such a device would not be possible.  
         [0025]     To achieve this miniaturization, the transducer  10  includes a thermally-conductive body  14  and a flexible circuit  16  which is bent around the body  14 . By providing the flexible circuit  16  and coupling the components necessary for operation of the transducer  10  to the flexible circuit  16 , the flexible circuit  16  can be bent into a desired shape to enable it to fit within the tip  12  of the examination device. The flexible circuit  16  is a laminate including electrically-conductive paths and connection sites enabling electrical connection to electrical components. As described below, it serves an intermediate interconnection substrate for connecting an integrated circuit to signal transmission lines. The flexible circuit  16  is bent around the body  14  which has a substantially U-shaped cross-section at the portion around which the flexible circuit  16  is bent and thereby defines a cavity  18 . The body  14  has a central support portion  14   a  and leg portions  14   b ,  14   c , one at each end of the support portion  14   a , with the flexible circuit  16  being supported by the support portion  14   a  and bent over the leg portions  14   b ,  14   c.    
         [0026]     The flexible circuit  16  is not required to be flexible over its entire length to achieve the objects of the invention, although it is a possibility. Rather, it suffices that those portions of the flexible circuit  16  which are bent, e.g., those portions bent over the leg portions  14   b ,  14   c , are flexible. Other portions of the flexible circuit  16  which are not bent, such as those planar portions which support components of the transducer  10  described below, may be rigid. Thus, the flexible circuit  16  may be formed from a combination of one or more flexible circuit boards and one or more rigid circuit boards such as PCBs (printed circuit boards) or ceramic circuit boards.  
         [0027]     As shown in  FIG. 1 , the cavity  18  is formed on the underside of the body  14 . The flexible circuit  16  has a first planar portion  16   a  above the body  14 , a second planar portion  16   b  situated in the cavity  18 , a terminal end  16   c  separated from the first planar portion  16   a  by a one-hundred-eighty degree (180°) bend  16   d  and a second terminal end  16   e  separated from the second planar portion  16   b  by a one-hundred-eighty degree (180°) bend  16   f . In the embodiment shown in  FIG. 1 , the terminal ends  16   c  and  16   e  are substantially planar and situated at least partially opposite one another below the body  14 . The flexible circuit  16  also includes a curved portion  16   g  adjacent the portion  16   b  in the cavity  18  and a one-hundred-eighty degree (180°) bend  16   h  between the portion  16   a  above the body  14  from the curved portion  16   g.    
         [0028]     The one-hundred-eighty degree (180°) bends  16   d ,  16   f  and  16   h  may include a pair of ninety degree (90°) bends separated by a straight portion as shown in  FIG. 1  or be entirely arcuate. The form of the bends would depend on the shape of the body  14 . In general, the flexible circuit  16  is bent so as to provide one portion above the body  14  and one portion below the body  14 .  
         [0029]     An acoustic assembly  20  is mounted to an upper surface of the first planar portion  16   a  of the flexible circuit  16 . Although the acoustic assembly  20  may be any type of known acoustic assembly for transmitting and receiving ultrasonic waves, in a preferred embodiment, the acoustic assembly  20  includes a stack of acoustic elements  22  connected to connector pads or sites on the upper surface of an integrated circuit  24  using a flip-chip interconnection technique, the specific details of which will be apparent to one of ordinary skill in the art. The number of interconnections between the acoustic elements  22  and the integrated circuit  24  may vary depending on the number of acoustic elements  22  and the size and shape of the acoustic elements  22  and integrated circuit  24  and may even be as high as in the order of about 3000. The acoustic elements  22  may be arranged in a linear array, i.e., a line of acoustic elements to provide a one-dimensional transducer, or in a multi-dimensional array, e.g., a two-dimensional matrix of acoustic elements to provide a two-dimensional transducer. The acoustic assembly  20  may be planar or curved.  
         [0030]     Other methods for connecting the acoustic elements  22  to the integrated circuit  24  include the use of metal, solder or polymer bumps  26  (as shown in  FIGS. 3 and 4 ), thin-line bonding, z-axis conductive elastomeric connectors, z-axis conductive adhesive, z-axis conductive film and reflow solder. In  FIG. 3 , the bumps  26  are formed on the integrated circuit  24  whereas in  FIG. 4 , the bumps  26  are formed on the acoustic elements  22  and openings  28  are formed in the upper surface of the integrated circuit  24  to enable contact with a conductive layer in the integrated circuit  24 . Reverse flip-chip interconnection techniques can also be used.  
         [0031]     As shown in  FIG. 5 , the integrated circuit  24  is connected to the flexible circuit  16  by wire-bonding, i.e., connection sites or connector pads  30  on the flexible circuit  16  are connected to connection sites or connector pads  32  on the upper surface of the integrated circuit  24  by short wires  34  (also referred to as wire-bonds). Thus, the electrical connections, i.e., the connector pads or sites, for the acoustic elements  22  and for the flexible circuit  16  are both arranged on the upper surface of the integrated circuit  24 . Nevertheless, the connections may be arranged on different surfaces in other embodiments. The wire-bonding between the flexible circuit  16  and the integrated circuit  24  can be provided all around the periphery of the integrated circuit  24  or as shown in  FIG. 5 , only along one or more discrete portions of the periphery. More specifically, as shown in  FIG. 5 , on a pair of opposite sides of the integrated circuit  24 , there are two rows of wire-bonds (also referred to as a double-row). By having multiple rows of wire-bonds  34  on only a pair of opposite sides of an integrated circuit  24 , a more ergonomic design of the transducer  10  is provided, i.e., a narrower transducer.  
         [0032]     Instead of wire-bonds, a direct wire attachment or tab bonding of leads can be provided between the connector pads  30  and the connector pads  32 .  
         [0033]     Preferably, the integrated circuit  24  is situated as close as possible to the body  14  to provide a short heat path to the body  14 . A short heat path between the integrated circuit  24  and the body  14  enables heat generated by the integrated circuit  24  to be transferred to the body  14  and dissipated thereby. The body  14  thus serves as a heat sink and accordingly is made of materials which have good thermal conductivity such as copper, aluminum, brass, graphite and mixtures thereof, or other thermally conductive materials.  
         [0034]     In one embodiment shown in  FIG. 6 , the integrated circuit  24  is in direct contact with the body  14 , thereby providing the shortest possible heat path. This is made possible by forming the flexible circuit  16  around the integrated circuit  24 .  
         [0035]     Electronic operational components  36  required for operation and control of the transducer  10  are mounted to the second planar portion  16   b  of the flexible circuit  16  in any manner known in the art, e.g., by surface-mounting, such that the components  36  are located in the cavity  18 . Typically, there may be ten or more such components. The components  36  are thus situated in the cavity  18  and do not project beyond the lower surface of the body  14 . It should be noted that in view of the bending of the flexible circuit  16  about the body  14 , the acoustic assembly  20  and components  36  are mounted on the same side of the flexible circuit  16  during the manufacture of the transducer  10  (described below).  
         [0036]     The reduction in the vertical size of the transducer  10  is obtained when the flexible circuit  16  is bent. In one embodiment, the flexible circuit  16  may be bent until the vertical size of an assembly of the flexible circuit  16  (bent around the body  14 ), the acoustic elements  22  and the integrated circuit  24  is less than seventy-five percent, or even less than fifty percent, of the horizontal length of the integrated circuit  24 .  
         [0037]     To connect the flexible circuit  16  to a plurality of coax wires  38  leading from the examination device to associated equipment, such as a monitor and recording device, a pair of additional flexible circuits  40 , 42  is used, each having appropriate connections for coax wires  38  such as connection sites or connector pads  44 . The number of coax wires  38  may vary depending on the application of the transducer  10  but may be as high as 160 or even as high as 200. Each flexible circuit  40 , 42  is connected to a portion of the coax wires  38  by bonding exposed, conductive portions  38   a  of the coax wires  38  to the connection sites of the flexible circuits  40 , 42 , e.g., using a known bonding process. The flexible circuits  40 , 42  may be entirely flexible or have a flexible portion and a rigid portion, and might even be entirely rigid.  
         [0038]     Connection of the coax wires  38  to the flexible circuits  40 , 42  may be performed separate from the manufacture of the flexible circuit  16  with the acoustic assembly  20  and optional electronic components  36 . This provides a significant advantage in view of the number of coax wires  38  because it enables separate manufacture of the flexible circuit  16  and associated componentry and of the connection mechanism for connecting the flexible circuit  16  to the external devices (the coax wires  38  and flexible circuits  40 , 42 ).  
         [0039]     The flexible circuits  40 , 42  are connected to the flexible circuit  16  using an electrical interconnection such as z-axis conductive film or conductive adhesive  46 . In this manner, an electrical connection between the flexible circuit  16  and the coax wires  38  is provided via the flexible circuits  40 , 42  and the adhesive  46 . Instead of z-axis conductive film or adhesive, it is possible to use a z-axis conductive elastomeric connector or reflow solder.  
         [0040]     Instead of mounting the electronic components  36  to the flexible circuit  16 , electronic components or electronics for controlling the acoustic assembly  20  may be mounted on the flexible circuits  40 , 42  or at the end of the coax wires  38  distanced from the transducer  10 . The electronic components could also be integrated into the integrated circuit  24 .  
         [0041]     To manufacture the transducer  10 , the body  14  is formed and the flexible circuit  16  is formed and cut to the necessary size to enable it to be bent around the body  14 . The acoustic assembly  20  and the electronic components  36  are mounted to the same side of the flexible circuit  16  in connection with or after the formation of the flexible circuit  16 . To enable mounting of the acoustic assembly  20  to the flexible circuit  16 , adhesive is applied to the underside of the integrated circuit  24 . The mounting locations of the acoustic assembly  20  and electronic components  36  are selected to position the acoustic assembly  20  above the cavity  18  and the electronic components  36  in the cavity  18  as shown in  FIG. 1 . The connection sites  32  of the acoustic assembly  20  are then connected to the connection sites  30  of the flexible circuit  16  by wire bonds  34 . The acoustic assembly  20  may be pre-formed by mounting the stack of acoustic elements  22  on the integrated circuit  24  and connecting them using a flip-chip interconnection technique.  
         [0042]     Flexible circuits  40 , 42  are formed with the required connection sites for electrical connection with the flexible circuit  16  and the coax wires  38  and then attached to the coax wires  38 , e.g., by soldering. The flexible circuits  40 , 42  are also attached to the terminal ends  16   c ,  1   6   e  of the flexible circuit  16  using z-axis conductive film or conductive adhesive  46 . The flexible circuits  40 , 42  may be attached to the coax wires  38  first and then to the flexible circuit  16  or vice versa.  
         [0043]     Once the acoustic assembly  20 , electronic components  36  and flexible circuits  40 , 42  (preferably with the coax wires  38  attached thereto) are attached to the flexible circuit  16 , adhesive is applied to the portions of the flexible circuit  16  which will come into contact with the body  14  (and/or applied to portions of the body  14  against which the flexible circuit  16  will rest) and then the flexible circuit  16  is bent around the body  14  such that the planar portion  16   a  of the flexible circuit having the acoustic assembly  20  mounted thereon is situated on the support portion  14   a  of the body  14 , the planar portion  16   b  having the electronic components  36  mounted thereon is situated in the cavity  18  in the body  14 , and the terminal portions  16   c  and  16   e  having the flexible circuits  40 , 42  attached thereto are situated underneath the body  14 . Further, bending of the flexible circuit  16  over the body  14  is performed such that the bend  16   d  of the flexible circuit  16  is situated partially over the leg portion  14   b  of the body  14 , the bend  16   f  is situated partially inside the cavity  18  of the body  14 , the arcuate portion  16   g  is situated in the cavity  18  and the bend  16   h  is situated over the leg portion  14   c  of the body  14 . The acoustic assembly  20 , the electronic components  36  and the attachment mechanism for attaching the flexible circuit  16  to the coax wires  38  are thus all positioned in a vertical arrangement, vertically spaced from one another, thereby reducing the horizontal size of the transducer. In fact, it can be seen from  FIG. 5  that the size of the transducer  10  is not much larger than the size of the integrated circuit  24 . A compact transducer is thus provided which can fit in the tip of a transesophageal examination device (line  12  as shown in  FIG. 1 ).  
         [0044]      FIGS. 7 and 8  show another embodiment of a transducer in accordance with the invention. In this embodiment, another flexible circuit  48  is provided having appropriate connections for coax wires  38  such as connection sites or connector pads. The flexible circuit  48  is connected to a portion of the coax wires  38  by bonding exposed, conductive portions of the coax wires  38  to the connection sites of the flexible circuit  48 , e.g., using a known bonding process. The flexible circuit  48  may be entirely flexible or have a flexible portion and a rigid portion, and might even be entirely rigid. Connection of the coax wires  38  to the flexible circuit  48  may be performed separate from the manufacture of the flexible circuit  48  with the acoustic assembly  20  and optional electronic components  36 . By having three flexible circuits  40 , 42 , 48 , the number of coax wires  38  on each flexible circuit  40 , 42 , 48  is less than the number when only two flexible circuits  40 , 42  are provided (assuming the same total number of coax wires  38 ) thereby further reducing the thickness of the transducer  10 .  
         [0045]     The flexible circuit  48  is connected to the flexible circuit  16  using an electrical interconnection such as z-axis conductive film or conductive adhesive  46 . More specifically, the flexible circuit  48  is connected to a lateral flap portion  16   k  of the flexible circuit  16  which is separated from one lateral edge of the second planar portion  16   b  of the flexible circuit by a 180° bend  16   j . To further reduce the thickness of the transducer  10 , it is possible to provide another flap extending from the other lateral edge of the second planar portion  16   b  of the flexible circuit  16 . It is also conceivable that flexible circuits may be used extending only from the lateral edges of one or both of the planar portions of the flexible circuit  16 .  
         [0046]      FIG. 9  shows another embodiment of a transducer in accordance with the invention. In this embodiment, the transducer  50  includes a thermally-conductive body  52  and a flexible circuit  54  which is bent around the body  52 . By providing the flexible circuit  54  and coupling the components necessary for operation of the transducer  50  to the flexible circuit  54 , the flexible circuit  54  can be bent into a desired shape to enable it to fit within the tip  12  of the examination device.  
         [0047]     The body  52  has a central support portion  52   a  and leg portions  52   b , 52   c , one at each end of the support portion  52   a , with the flexible circuit  54  being supported by the support portion  52   a  and bent over the leg portions  52   b ,  52   c . A cavity  58  is formed in the underside of the body  52  below the support portion  52   a.    
         [0048]     The flexible circuit  54  has a first terminal planar portion  54   a  facing the cavity  58 , a second planar portion  54   b  above the support portion  52   a  of the body  52 , a terminal end  54   c  separated from the second planar portion  54   b  by a one-hundred-eighty degree (180°) bend  54   d  and a one-hundred-eighty degree (180°) bend  54   e  separating the first terminal planar portion  54   a  from the second planar portion  54   b . The terminal end  54   c  is substantially planar and situated below the body  52 . The one-hundred-eighty degree (180°) bends  54   d  and  54   e  may include a pair of ninety degree (90°) bends separated by a straight portion as shown in  FIG. 9  or be entirely arcuate. The form of the bends would depend in part on the shape of the body  52 .  
         [0049]     The flexible circuit  54  is not required to be flexible over its entire length to achieve the objects of the invention, but rather, at least those portions which are bent should be flexible. Other portions of the flexible circuit  54  which are not bent, such as those planar portions which support components of the transducer  50  described below, may be rigid. An acoustic assembly  20  is mounted to an upper surface of the second planar portion  54   b  of the flexible circuit  54  and in the preferred embodiment shown, includes an array of acoustic elements  22  and an integrated circuit  24 . The mounting of the acoustic assembly  20  to the flexible circuit  54  may be the same as the mounting of the acoustic assembly  20  to the flexible circuit  16  described above, i.e., via wire bonds  34  connecting connection sites  30  on the flexible circuit  54  to connection sites  32  on the integrated circuit  24 . The flexible circuit  54  may have an opening to enable the integrated circuit  24  to be in direct contact with the body  52 .  
         [0050]     Electronic components  36  required for operation and control of the transducer  50  are mounted to the first planar portion  54   a  such that the components  36  are located in the cavity  58 . The cavity  58  is thus formed with a shape designed to accommodate the electronic components  36 . It should be noted that in view of the bending of the flexible circuit  54  around the body  52 , the acoustic assembly  20  and components  36  are mounted on opposite sides of the flexible circuit  54  during the manufacture of the transducer  50  (described below).  
         [0051]     To connect the flexible circuit  54  to a plurality of coax wires  38  leading from the examination device to associated equipment, such as a monitor and recording device, an additional flexible circuit  60  is used and has appropriate connections for coax wires  38  such as connection sites or connector pads. The flexible circuit  60  has a U-shaped portion  60   a , with one leg opposite the terminal end  54   c  of the flexile circuit  54  and the other leg opposite the first planar portion  54   a  of the flexible circuit  54 , and a V-shaped portion  60   b  having two planar sections. The planar sections of the V-shaped portion  60  are connected to the coax wires  38  by bonding exposed, conductive portions  38   a  of the coax wires  38  to the connector sites of the flexible circuit  60  using a known bonding process. The flexible circuits  60  may be entirely flexible or have a flexible portion or portions and a rigid portion or portions.  
         [0052]     The flexible circuit  60  is connected to the flexible circuit  54  (the terminal end  54   c  of the flexible circuit  54  being connected to the opposed leg of the U-shaped portion  60   a  of the flexible circuit  60 ) using an electrical interconnection such as z-axis conductive film or conductive adhesive  62 . In this manner, an electrical connection between the flexible circuit  54  and the coax wires  38  is provided via the flexible circuit  60  and the adhesive  62 . Instead of z-axis conductive film or adhesive, it is possible to use a z-axis conductive elastomeric connector or reflow solder.  
         [0053]     Instead of mounting the electronic components  36  to the flexible circuit  54 , electronic components or electronics for controlling the acoustic assembly  20  may be mounted on the flexible circuit  60  or at the end of the coax wires  38  distanced from the transducer  10 . The electronic components could also be integrated into the integrated circuit  24 .  
         [0054]     To manufacture the transducer  50 , the body  52  is formed and the flexible circuit  54  is formed and cut to the necessary size to enable it to be bent around the body  52 . The acoustic assembly  20  and the electronic components  36  are mounted to opposite sides of the flexible circuit  54  in connection with or after the formation of the flexible circuit  54 . To enable mounting of the acoustic assembly  20  to the flexible circuit  54 , adhesive is applied to the underside of the integrated circuit  24 . The mounting locations of the acoustic assembly  20  and electronic components  36  are selected to position the acoustic assembly  20  above the cavity  58  and the electronic components  36  in the cavity  58  as shown in  FIG. 9 . The connection sites on the acoustic assembly  20  are connected to the connection sites on the flexible circuit  54  using wire bonds  34 . The acoustic assembly  20  may be pre-formed by mounting the stack of acoustic elements  22  on the integrated circuit  24  and connecting them using a flip-chip interconnection technique.  
         [0055]     Flexible circuit  60  is formed with the required connector sites for electrical connection with the flexible circuit  54  and the coax wires  38  and then attached to the coax wires  38 . The flexible circuit  60  is also attached to the terminal end  54   c  of the flexible circuit  54  using z-axis conductive film or conductive adhesive  62 . The flexible circuit  70  may be attached to the coax wires  38  first and then to the flexible circuit  54  or vice versa. Once the acoustic assembly  20 , electronic components  36  and flexible circuit  60  (preferably with the coax wires  38  attached thereto) are attached to the flexible circuit  54 , adhesive is applied to the portions of the flexible circuit  54  which will come into contact with the body  52  (and/or applied to portions of the body  52  against which the flexible circuit  54  will rest) and the flexible circuit  54  is bent around the body  52  such that the planar portion  54   b  of the flexible circuit  54  having the acoustic assembly  20  mounted thereon is situated on the support portion  52   a  of the body  52 , the planar portion  54   a  having the electronic components  36  mounted thereon is situated below the cavity  58  in the body  52  with the electronic components  36  being situated in the cavity  58 , and the terminal portion  54   c  having the flexible circuit  60  attached thereto is situated underneath the body  52 . Further, bending of the flexible circuit  54  over the body  52  is performed such that the bend  54   d  of the flexible circuit  54  is situated partially over the leg portion  52   b  of the body  52  and the bend  54   e  is situated over the leg portion  52   c  of the body  52 . The acoustic assembly  20 , the electronic components  36  and the attachment mechanism for attaching the flexible circuit  54  to the coax wires  38  are thus all positioned in a vertical arrangement thereby reducing the horizontal size of the transducer. A compact transducer is thus provided which can fit in the tip of a transesophageal examination device (line  12  as shown in  FIG. 9 ).  
         [0056]     The embodiments shown in the drawings use coax wires  38 . However, the invention also contemplates the use of other types of signal transmission lines, including but not limited to, flat ribbon cables and long flexible circuits. Signal transmission lines for use in the invention would include a electrically-conducting element which would be electrically coupled to the connector sites on the flexible circuits.  
         [0057]     Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to these precise embodiments, and that various other changes and modifications may be effected therein by one of ordinary skill in the art without departing from the scope or spirit of the invention.