Ultrasonic probe

[0002] 1. Field of the Invention

[0003] The present invention relates to an ultrasonic probe, and more particularly to a variable type ultrasonic probe capable of changing over the focus from one to the other in a depth direction by separate arrangement of piezoelectric elements in a widthwise direction.

[0004] 2. Description of the Related Art

[0005] An ultrasonic probe is used in, for example, ultrasonic diagnostic equipment for medical care purpose, as an ultrasonic transducer, which transmits and receives an ultrasonic wave, for acquiring information of a living organism from the disease portions. There are various kinds of ultrasonic probes depending on functions and shapes of the probes, and as one of them, there is an ultrasonic probe capable of changing over the focus thereof in a depth direction from the surface of a living body, i.e., a tested body. This type of an ultrasonic probe is called a variable type probe.

[0006] FIG. 1 illustrates the constitution of a conventional variable type probe in which a plurality of piezoelectric units 1 is arrayed in a line on backing member 2. Each piezoelectric unit 1 is provided with a piezoelectric member, and excitation electrodes provided on the upper and lower faces of the piezoelectric member, respectively. Further, piezoelectric unit 1 is separated into three pieces, namely, piezoelectric elements 1a, 1band 1c, in the widthwise direction.

[0007] The variable type probe is manufactured by the method described hereinbelow:

[0008] For example, flexible printed boards 3a, 3b, and 3c, which are used for externally conducting the excitation electrodes, are attached to the center and opposite sides of the bottom face of a plate-like member of piezoelectric body, and then inpouring or filling of resin is performed so as to form backing member 2. Subsequently, cuttings reaching from the piezoelectric plate-like member to backing member 2 are applied so as to sever the piezoelectric plate member in a lengthwise direction to thereby obtain a plurality of separate piezoelectric units 1. Then, the piezoelectric plate-like member is severed in a widthwise direction, so that each piezoelectric unit 1 is separate into three piezoelectric elements 1a, 1band 1c, i.e., one central and two side-arranged elements. The lower face electrodes of piezoelectric elements 1a, 1band 1care led by flexible printed board 3a, 3band 3c, respectively. Although upper face electrodes of piezoelectric elements 1a, 1band 1care not shown in FIG. 1, these upper face electrodes of piezoelectric elements 1a, 1band 1care electrically connected to and grounded by common electrode (not shown) which is arranged to cover the plurality of piezoelectric units 1.

[0009] In the described variable type ultrasonic probe, either three piezoelectric elements 1a, 1band 1cseparated widthwise are commonly driven or only the central piezoelectric element 1bis driven to thereby change over the focus from the surface of a living body from one to the other focal point. When the three piezoelectric elements 1a, 1band 1care simultaneously driven, the focal distance becomes long. On the other hand, when only the central piezoelectric element 1bis driven, the focal distance becomes short.

[0010] At this stage, in the ultrasonic probe, there are different types such as, for example, a convex type probe and a linear type probe, depending on how a plurality of piezoelectric elements are arranged in respective probes. In the convex type probe, as shown in FIG. 2, a plurality of piezoelectric elements 1 are arrayed to be directed outward along an arcuate line, and is therefore suitable for arcuately emitting ultrasonic wave so as to detect ultrasonic echo within a predetermined angular range. On the other hand, in the linear type probe, a plurality of piezoelectric elements 1 is arrayed in a straight line to be oriented in the same direction. The linear type probe is used for emitting ultrasonic wave in only a specified direction.

[0011] Backing member 2 of the variable probe shown in FIG. 1 has an approximately planar face without any curve, and piezoelectric units 1 are arrayed on such backing member 2. Thus, the variable type probe of FIG. 1 can be classified in the linear type probe.

[0012] In the variable type probe of FIG. 1, flexible printed board 3bis connected to central piezoelectric element 1b, which is one of three piezoelectric elements 1a, 1b, and 1cconstituting piezoelectric element 1, so as to depend vertically as shown in FIG. 1 to thereby permit the lower face electrode to be led. Therefore, when the surface of backing member 2 is arcuately curved as shown in FIG. 2 while permitting a plurality of piezoelectric units 1 are arrayed thereon, flexible printed board 3bdepending from the central piezoelectric elements 1bof respective piezoelectric units 1 might mutually interfere. Accordingly, in the variable type probe as shown in FIG. 1, it is difficult to constitute a convex type probe by arraying piezoelectric units 1 on a surface arcuately curved in a lengthwise direction, i.e., in a direction of array.

[0013] Therefore, an object of the present invention is to provide a variable type probe, which is easy to curvedly arrange a plurality of piezoelectric units on a curved face.

[0014] The above object of the present invention can be achieved by an ultrasonic probe including a backing member, a piezoelectric unit which is arranged on the backing member and constituted by at least three piezoelectric elements separated into one end portion, a central portion, and the other end portion, each of the piezoelectric elements having a lower face electrode thereof led out, wherein the ultrasonic probe comprises a leading-out wiring board having, on both major faces thereof, electrically conducting paths, and wherein the lower face electrode of the piezoelectric element of the one end portion being electrically led out by an upper one of the major faces of the leading-out wiring board, and the lower face electrode of the piezoelectric element of the central portion being electrically led out by a lower one of the major faces of the leading-out wiring board.

[0015] In the present invention, the leading-out wiring board having electrically conductive paths on both major faces is used, so that a lower face electrode of the piezoelectric element of the one end portion is electrically led by the upper face electric conductive path of the leading-out wiring board, and so that a lower face electrode of the piezoelectric element of the central portion is electrically led by the lower face electric conductive path of the leading-out wiring board. Therefore, the lower face electrode of the piezoelectric element of the central portion can be electrically led in a horizontal direction. Thus, according to adoption of this arrangement of the present invention, even when the surface of the backing member is arcuately curved, mutual interference among the leading-out wiring boards would not occur, so that, for example, a variable type probe formed in the convex type can be easily provided.

[0016] FIG. 1 is a perspective view illustrating the conventional variable type ultrasonic probe;

[0017] FIG. 2 is a front view illustrating the conventional convex type ultrasonic probe; and

[0018] FIG. 3 is a side view illustrating a variable type ultrasonic probe according to an embodiment of the present invention.

[0019] In FIG. 3 illustrating a variable type probe according to an embodiment of the present invention, constituents of the unit designated by reference numerals the same as those of FIG. 1 are the same or like constituents, and accordingly description thereof in detail will not be repeated hereinbelow.

[0020] The variable type ultrasonic probe shown in FIG. 3 has, as described before, such a constitution that a plurality of piezoelectric units 1, each being constituted by piezoelectric elements 1a, 1b, and 1c, are arranged on backing member 2. The plurality of piezoelectric units 1 is arrayed in a direction vertical to the surface of the drawing sheet of FIG. 3. Further, lower face electrodes 1dof respective piezoelectric elements 1a, 1b, and 1care electrically led out by two pieces of flexible printed boards 4aand 4b. One of flexible printed boards 4aand 4b, i.e., the flexible printed board 4ais formed in a multi-layer construction to have electric conductive paths 5aand 5bor patterns on both major faces thereof. Electric conductive path 5bon the rear face of multi-layer flexible printed board 4ais extended toward the front face side via through-hole 5cat the tip end of flexible printed board 4a. The other flexible printed board 4bis formed in a single-layer construction similar to the prior art construction and has electric conductive path 5 on only the upper face of flexible printed board 4b.

[0021] Now, a description of the manufacturing method of this variable type probe will be provided hereinbelow.

[0022] First, a multi-layer flexible printed board 4ais connected, by conductive adhesive or by soldering, to one side of a lower face of a piezoelectric plate provided with lower face electrode id and upper face electrode le formed on the respective major faces thereof, and a single-layer flexible printed board 4bis also connected, by conductive adhesive or by soldering, to the other side of the piezoelectric plate. At this stage, compared with the manufacturing of the conventional variable type probe, the multiple-layer flexible printed board 4ais attached to the piezoelectric plate in a manner such that it comes close to the central portion of the latter piezoelectric plate. Specifically, flexible printed board 4ais extended to a position confronting the central piezoelectric element 1b, and at that position, flexible printed board 4ais also connected to lower face electrode 1dof the piezoelectric plate.

[0023] Subsequently, the piezoelectric plate to which flexible printed boards 4aand 4bare connected in the described manner is fixedly secured onto backing member 2 in a manner similar to the prior art. Then, cuttings reaching from the surface of the piezoelectric plate to backing member 2 are provide for severing the piezoelectric plate in a lengthwise direction, in order to separate it into a plurality of separate piezoelectric units 1. Thereafter, each piezoelectric unit 1 is separated into three pieces by the application of cuttings in a widthwise direction from the upper face of the piezoelectric plate to thereby produce three piezoelectric elements 1a, 1band 1c. At this stage, on one side of respective piezoelectric units 1, cuttings are carried out so as to sever respective piezoelectric unit 1 until apertures reaching multi-layer flexible printed board 4aare provided. During this cutting operation, electric conductive path 5aon the front side of flexible printed board 4amay be cut, but electric conductive path 5bon the rear side should be prevented from being cut. On the other side of respective piezoelectric units 1, cutting are carried out until cutting apertures reach backing member 2, to thereby sever respective piezoelectric units 1. Then, a common electrode to which each upper face electrode le is connected in common is provided by a method well known in the art.

[0024] According to the described constitution, lower face electrode id of piezoelectric elements 1aand 1bof one side portion and the central portion of respective piezoelectric units 1 are electrically led outside by electric conductive paths 5aand 5bon upper and lower faces of multi-layer flexible printed board 4a. Further, flexible printed boards 4aand 4bare led out of respective piezoelectric units 1 in horizontal directions, respectively. Therefore, even if each of piezoelectric units 1 are curvedly arranged in a direction of array, any mutual interference among the flexible printed boards which lead out of a plurality of piezoelectric units 1 would not occur, and accordingly it is possible to easily acquire a convex type ultrasonic probe.

[0025] In the embodiment of the foregoing description, although multi-layer flexible printed boards 4aare arranged on only one side of piezoelectric units 1, and although each of piezoelectric units 1 is cut and separated into three pieces, multi-layer flexible printed boards 4amay be arranged on, for example, both sides of the piezoelectric units and the each piezoelectric unit may be separated into four pieces. Also, the number of layers of flexible printed board 4amight be increased from two to three or more layers, so as to comply with a case where the respective piezoelectric units are separated into five or more pieces. Further, although the wiring board for the leading of the electrode is constituted by a flexible printed board, for example, a mere printed circuit board formed by providing electric conductive paths on a resin-made board may be used for constituting the wiring board for leading of the electrode.