Method of manufacturing an improved coupling of acoustic window and lens for medical ultrasound transducers

#This invention relates to transducers and more particularly to broadband phased array transducers for use in the medical diagnostic field.

#Ultrasound machines are often used for observing organs in the human body. Typically, these machines incorporate transducer arrays for converting electrical signals into pressure waves and vice versa. Generally, the transducer array is in the form of a hand-held probe which may be adjusted in position while contacting the body to direct the ultrasound beam to the region of interest. Transducer arrays may have, for example, 128 phased transducer elements for generating an ultrasound beam.

#An electrode is placed at the front and rear portion of the transducer elements for individually exciting each element. The pressure waves generated by the transducer elements are directed toward the object to be observed, such as the heart of a patient being examined. Each time the pressure wave confronts tissue having different acoustic characteristics, a portion of the ultrasound wave is reflected backward. The array of transducers may then convert the reflected pressure waves into corresponding electrical signals. An example of a phased array acoustic imaging system is described in U.S. Pat. No. 4,550,607 granted Nov. 5, 1985 to Maslak et al. and is incorporated herein by reference. That patent illustrates circuitry for focusing the incoming signals received by the transducer array in order to produce an image on the display screen.

#FIG. 1 illustrates a prior art transducer array 10 for generating an ultrasound beam.

#FIG. 2 illustrates a cross-sectional view of a transducer array according to a first preferred embodiment of the present invention.

#FIG. 3 illustrates a portion of the RFI shield shown in FIG. 2 taken along the elevation direction.

#FIG. 1 illustrates generally a transducer array 10 for generating an ultrasound beam. Typically, such an array may have 128 transducer elements 12 in the azimuthal direction. Adapted from radar terminology, the x, y, and z directions are referred to as the azimuthal, elevation, and range directions, respectively.

#Each transducer element 12, typically rectangular in cross-section, may comprise a first electrode 14, a second electrode 16 and a piezoelectric layer 18. In addition, one or more acoustic matching layers 20 may be disposed over the piezoelectric layer 18 to increase the efficiency of the sound energy transfer to the external medium. The electrode 14 for a given transducer element 12 may be part of a flexible circuit 15 for providing the hot wire or excitation signal to the piezoelectric layer 18. Electrode 16 for a given transducer element may be connected to a ground shield return 17. To further increase performance, the piezoelectric layer 18 may be plated or metalized on its top and bottom surfaces and the matching layer 20 may also be plated or metalized on all surfaces so that electrode 16 which is in physical contact with the matching layer 20 is electrically coupled to a surface of the piezoelectric layer 18 by the plating.

#The transducer elements 12 are disposed on a support or backing block 24. The backing block 24 may be highly attenuative such that ultrasound energy radiated in its direction (i.e., away from an object 32 of interest) is substantially absorbed. In addition, a mechanical lens 26 may be placed on the matching layer 20 to help confine the generated beam in the elevationrange plane and focus the ultrasound energy to a clinically useful depth in the body. Alternately the piezoelectric layer 18 may have a curved surface facing the object to be imaged and a low loss acoustic window may be disposed over the piezoelectric layer such as the transducer array described in U.S. Pat. No. 5,415,175 granted May 16, 1995 to Hanafy et al. which is specifically incorporated herein by reference.