JP2005295588A - Ultrasonic transducer and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic transducer in which the number of vibrators arrayed on a vibrator plate can be increased and the array pitch of the vibrators can be reduced. <P>SOLUTION: In the ultrasonic transducer, a plurality of conductor exposed parts 23 provided on a printed wiring board in a distributed manner are electrically connected with electrodes on the backs of a plurality of ultrasonic vibrators provided on a vibrator plate, and the printed wiring board is configured by arranging, on the conductor exposed parts 23, conductive layers according to a predetermined wiring pattern, electric insulating layers provided on the conductive layers and exposure holes extending from the electric insulating layers to the conductive layers. In such an ultrasonic transducer, the printed wiring board includes a plurality of conductive layers 20 and electric insulating layers 21 which overlap with each other alternately. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic transducer connected to an ultrasonic diagnostic apparatus and a method for manufacturing the same.

  Among this type of ultrasonic transducers known so far, a so-called two-dimensional array type ultrasonic transducer has a plurality of ultrasonic transducers (piezoelectric transducers) arranged in a matrix. According to such a two-dimensional array ultrasonic transducer, the drive aperture and focus distance can be adjusted freely, and a three-dimensional region can be scanned with an ultrasonic beam while the probe is fixed to the subject. The two-dimensional array ultrasonic transducer contributes to improving the image quality and is suitable for creating a three-dimensional image.

  A two-dimensional array type ultrasonic transducer electrically connects a flexible printed wiring board (FPC), on which a plurality of signal lines for extracting signals transmitted and received by individual ultrasonic transducers, and a piezoelectric plate, and then connects the piezoelectric plate. In general, it is manufactured by dividing into an array and forming a piezoelectric vibrator array. Among the two-dimensional array type ultrasonic transducers, a convex type ultrasonic transducer in which a piezoelectric vibrator array is arranged in a convex shape (convex transducer) is formed by dividing a piezoelectric plate to form a piezoelectric vibrator array. The array is bent into a curved shape along the direction to form a convex shape.

  In such a convex transducer, a slit is formed in the wiring pattern gap of the FPC, and the FPC is divided and folded for each slit. That is, such a slit is provided in order to fold the FPC with good storage properties even when the transducer array is bent into a curved surface.

  9 to 11 are views showing a structure and a manufacturing method of an ultrasonic transducer according to a conventional example. First, as shown in FIGS. 9A and 9B, the FPC 3 in which the slits 5 are previously formed in the gaps between the individual wiring patterns 2 and the piezoelectric plate 1 are joined. The slit 5 is formed to reach the vicinity of the piezoelectric plate 1. In the FPC 3 shown in FIG. 9, the individual wiring patterns 2 are parallel to each other. However, in other FPCs, the circuit gap is gradually widened so that the signal extraction from the piezoelectric plate is easy, and the wiring pattern is changed. Generally it is radial.

  Next, as shown in FIGS. 10A and 10B, a part of the piezoelectric plate 1 and the FPC 3 is divided to form an arrayed ultrasonic transducer. At the position of the slit 5 of the FPC 3, the FPC 3 is completely divided in the gap of the wiring pattern 2 in which the slit 5 is formed simultaneously with the division of the piezoelectric plate 1. Before and after this step, backing material connection, acoustic matching layer formation, and ground electrode extraction are appropriately performed.

  Then, as shown in FIG. 11, in order to make the ultrasonic transducer array into a convex shape, the array transducer formed in a planar shape is bent along the array arrangement direction and separated by slits and piezoelectric plate division. FPC is folded for each separation block. This makes it possible to process the FPC with good storage properties even in a convex transducer.

  However, such a convex-type ultrasonic transducer has the following problems. When the arrangement pitch of the piezoelectric vibrators constituting the array is reduced and the circuit wiring pitch of the FPC is reduced accordingly, there is a possibility that slits cannot be formed in the gaps of the wiring pattern due to manufacturing limitations. 12 shows the case where the slit 5 can be formed up to the vicinity of the piezoelectric plate 1, and FIG. 13 shows the case where the slit 5 cannot be formed up to the vicinity of the piezoelectric plate 1.

  Therefore, the FPC cannot be folded by deforming the transducer array into a curved surface, or cannot be folded at a position adjacent to the piezoelectric transducer. Therefore, there is a problem that the storage property of the ultrasonic transducer is deteriorated.

  By the way, a printed wiring board is arranged on the back surface of the piezoelectric vibrator, and an electric terminal is electrically connected to a conductor exposed portion (conductor pad) provided at a predetermined position of the printed wiring board and a driving electrode on the back face of the piezoelectric vibrator. 2. Description of the Related Art Two-dimensional array ultrasonic transducers characterized by extraction are known. Such a two-dimensional array ultrasonic transducer generally employs a bump (protrusion) structure as a conductor exposed portion.

  14 and 15 are diagrams showing a wiring pattern and a structure of a printed wiring board disposed on the back surface of the vibrator plate, and a second example of the printed wiring board used in the two-dimensional array transducer in which eight elements are arranged in the column direction. The wiring pattern of the conductor exposed part connected to an m-row transducer is shown. FIG. 14 shows a wiring pattern for independently pulling out drive electrodes of 8 elements in the column direction. FIG. 15 shows a wiring pattern for connecting and extracting the drive electrodes in the fourth and fifth rows in the central portion and the third and sixth rows in common.

  FIG. 16 is a view showing a cross section of a conductor exposed portion of a printed wiring board. An exposed hole is formed in the electrical insulating layer (polyimide) on the wiring pattern to form a conductor exposed portion. The exposed hole is filled with a conductive member, and the bump 200 is formed so as to protrude from the surface of the electrical insulating layer. In FIG. 16, 201 is a cover lay (polyimide), 202 is an adhesive, 203 is a conductor layer, and 204 is a base.

  Such a conventional printed wiring board has the following problems. The arrangement pitch and the number of arrangement of the conductor exposed portions are limited by the manufacturing limit of the circuit wiring of the printed wiring board, and this restricts the method of forming the wiring pattern. That is, the number of patterns that can be wired is limited according to the distance (repeated pitch) between adjacent conductor exposed portions in order to form the wiring pattern while avoiding the conductor exposed portions. For this reason, the number of wiring circuits cannot be increased so as to satisfy the required number of exposed conductors. In addition, there are restrictions on complicated wiring such as common connection of exposed conductors. There is also a limitation in narrowing the distance (repeated pitch) between adjacent conductor exposed portions.

  Therefore, there is a problem that the number of piezoelectric vibrators connected to the conductor exposed portion or the arrangement pitch of the piezoelectric vibrators is limited. In the printed wiring board shown in FIG. 14, the repetition pitch in the row direction cannot be reduced due to the limit of the wiring pattern formation. Even if the repetition pitch is the same, the number of exposed conductors in the column direction that leads to an increase in the number of wiring patterns cannot be increased. Therefore, there is a problem that the transducer arrangement pitch in the row direction cannot be reduced. Also, the number of transducer arrays in the column direction cannot be increased.

  In the printed wiring board shown in FIG. 15, the conductor exposed portions of the first column and the eighth column, and the second column and the seventh column are shared without increasing the repeat pitch in the row direction (that is, the transducer pitch in the row direction). There is a problem in that the conductor exposed portions that are connected and at symmetrical positions in the column direction cannot be completely commonly connected on the printed wiring board.

  An object of the present invention is to provide an ultrasonic transducer capable of increasing the number of vibrators arranged on a vibrator plate and reducing the arrangement pitch of the vibrators.

  In the ultrasonic transducer of the present invention, a plurality of exposed conductor portions provided dispersedly on a printed wiring board are electrically connected to electrodes on the back surfaces of the plurality of ultrasonic transducers provided on the vibrator plate. The printed wiring board has a conductive layer according to a predetermined wiring pattern, an electric insulating layer provided on the conductive layer, and an exposed hole reaching the conductive layer from the electric insulating layer on the conductor exposed portion. In the ultrasonic transducer, the printed wiring board has a plurality of conductive layers and electrical insulating layers that are alternately stacked.

  According to the present invention, it is possible to provide an ultrasonic transducer capable of increasing the number of vibrators arranged on the vibrator plate and reducing the arrangement pitch of the vibrators.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1A and 1B are diagrams showing a configuration of a two-dimensional array ultrasonic transducer according to a first embodiment of the present invention, where FIG. 1A is a plan view and FIG. 1B is a cross-sectional view. The same component parts as those in the conventional example shown in FIGS. 9 to 13 are denoted by the same reference numerals, and detailed description thereof is omitted.

  First, as shown in FIG. 1A, the ultrasonic transducer of this embodiment is connected to a transducer plate 1 in which a plurality of ultrasonic transducers are two-dimensionally arranged, and these ultrasonic transducers. It has an FPC (flexible printed circuit board) 3 on which a signal line 2 is wired, and a through hole 4 reaching from the front surface to the back surface is formed at a predetermined position of the FPC 3. The through hole 4 can be formed by removing the resin portion of the FPC by laser etching or chemical etching after forming the FPC. The through hole 4 has a width larger than the shortest length of the wiring interval of the signal lines 2 on the FPC 3. The through hole 4 is formed not only in a single wiring pattern gap but also in a plurality of adjacent wiring pattern gaps. According to the forming method, the through hole 4 is formed only in a single wiring pattern gap. You may comprise as follows.

  As shown in FIG. 1B, the signal line 2 wired at the position overlapping the through hole 4 is exposed on both the front side and the back side of the FPC 3, and the exposed portion of the signal line 2 is defined as a specific covering member. For example, you may coat | cover with the member (resin) different from the other part of FPC.

  Hereinafter, a method for manufacturing a two-dimensional array ultrasonic transducer will be specifically described with reference to FIGS. First, as shown in FIGS. 2A to 2C, the FPC 91 is mounted on the back surface of the vibrator plate 90 on which the divided electrodes are formed, and then acoustic leakage is prevented on the back surface of the FPC 91. A backing material 92 for mounting is attached. The FPC 91 has a plurality of through holes as described above (not shown). As the backing material 92, it is preferable to use the same member as the ultrasonic transducer or a material having an acoustic impedance substantially equal to that of the FPC 91 to reduce acoustic reflection at the FPC 91. Further, as the backing material 92, a material having a small pressure change and high pressure resistance is preferable in order to suppress a manufacturing error in a subsequent process. Further, a plurality of members are laminated in the thickness direction to form the backing material 92, that is, a laminated backing having a layer having a layer for adjusting acoustic performance as an upper layer, and a material having a high heat resistance with little heat change. By forming the material, it is possible to suppress manufacturing errors and obtain good acoustic characteristics.

  Next, as shown in FIG. 3A, the vibrator plate 90 is cut along the row direction to a depth of at least half or more of the thickness, and the vibrator plate 90 is equal to the number of vibrators in the column direction at the time of completion. (Here, it is divided into two for convenience). Needless to say, when the vibrator plate 90 can be divided without dividing the signal line, the vibrator plate 90 may be completely separated and cut to the FPC 91. A groove 93 formed by cutting is filled with a non-conductive and curable filler 94 as shown in FIG. As the material of the filler 94, a resin having a small acoustic coupling between adjacent elements and a high mechanical strength is employed. After filling with the filler 94, as shown in FIG. 3C, an Au thin film as a common ground electrode 95 is formed on the entire front surface (ultrasonic radiation surface) of the vibrator plate 90 by, for example, sputtering.

  On the common ground electrode 95, an acoustic matching layer 96 is mounted as shown in FIG. Subsequently, as shown in FIG. 4B, the piezoelectric vibrator dividing grooves 97 are formed along the column direction by cutting at a depth reaching at least the FPC 91 and the backing material 92 from the acoustic matching layer 96 through the vibrator plate 90. Then, the acoustic matching layer 96 and the vibrator plate 90 are divided into the number of vibrators in the row direction at the time of completion (here, three for convenience). Since this division is performed in the above-described wiring pattern non-formation region, the wiring pattern is not divided. Of the plurality of grooves 97, some of the grooves 97 are connected to the above-described through holes.

  And after forming the slit 98 for folding FPC91 by cutting as shown to Fig.5 (a), the whole is forcedly curved. Here, the slit 98 is a groove extending from the end portion of the FPC 91 to the through hole 100 and completely separates the FPC 91. Then, as shown in FIG. 5B, the FPC 91 is divided for each slit 98, and the signal extraction surface of the divided FPC 91 is folded in the direction of wrapping the backing material 92 at the position of the through hole 100.

  As described above, it is possible to form a two-dimensional array ultrasonic transducer (convex probe) in which a plurality of ultrasonic transducers are arranged in a curved surface and the ultrasonic wave transmitting / receiving surface has a convex shape.

  Conventionally, when the wiring pattern is formed radially (not shown) and the wiring pattern interval in the vicinity of the transducer plate 90 is very narrow, the slit 98 cannot be formed to a position close to the side surface of the transducer plate 90. For this reason, the FPC 91 cannot be folded at this position, but in this embodiment, the FPC 91 is close to the side surface of the vibrator plate 90 only by connecting the slit 98 to the through-hole 100 formed in advance. Can be folded in position. Therefore, since the end portion of the FPC 91 does not extremely protrude from the side surface of the vibrator plate 90, the storage capacity of the transducer can be improved.

  (Second Embodiment) In the first embodiment, the folding of the FPC (flexible printed circuit board) has been described. Subsequently, in the second embodiment, specific examples of conductor exposed portions, wiring patterns, etc. of the FPC will be described. To do.

  FIG. 6 is a cross-sectional view of an FPC according to the second embodiment of the present invention. The FPC of this embodiment is characterized by having a plurality of conductive layers and electrical insulating layers that are alternately stacked. That is, as shown in FIG. 6, a plurality of conductor layers 20 (two layers in this case) and electrical insulating layers 21 are alternately stacked, and the individual conductor layers are electrically connected through the through holes 22. Yes. The number of conductor layers 20 is not limited to two, and the number of layers may be further increased.

  In a state where the plurality of conductor exposed portions provided dispersed in the FPC and the electrodes on the back surfaces of the plurality of ultrasonic transducers provided on the transducer plate (not shown) are electrically connected, The vibrator plate is bonded via an electrically insulating resin.

  FIG. 6A shows an example in which a conductor exposed portion 23 is formed at the same position as the through hole 22 connecting the conductor layers. FIG. 6B shows the through hole 22 connecting the conductor layers. Examples in which the conductor exposed portions 23 are formed at different positions are respectively shown.

  In the example shown in FIG. 6A, an exposed hole (through hole) 22 reaching the surface of the lower conductor layer 20 is formed in the electrically insulating layer 21 made of polyimide, and a conductive material is filled in the exposed hole. Then, a protruding portion (bump) protruding from the surface of the electrical insulating layer is formed thereon, and this is used as a conductor exposed portion 23. The conductor exposed portion 23 protrudes from the FPC surface. In the example of FIG. 6A, the formation of the conductor exposed portion and the electrical connection between the conductor layers can be realized at the same position, so that the space efficiency in the FPC is excellent.

  Further, in the example shown in FIG. 6B, the through hole 22 and the conductor exposed portion 23 are formed as in FIG. 6A, but the through hole 22 and the conductor exposed portion 23 are formed at positions separated from each other. Therefore, in terms of space efficiency, it is inferior to the example of FIG. 6A, but on the other hand, it has the advantage of easy manufacture.

  FIGS. 7 and 8 are diagrams showing wiring patterns in the FPC having the conductor exposed portions shown in FIGS. 6A and 6B. FIG. 7 shows the wiring pattern shown in FIG. The layer structure as in a) is applied. FIG. 8 shows a case where a layer structure as shown in FIG. 6B is applied to the wiring pattern shown in FIG.

  According to FIG. 7, the repeat pitch in the row direction can be reduced by passing a part of the wiring pattern through a conductor layer different from the conductor layer on which another pattern is formed. Alternatively, the number of conductor exposed portions in the column direction can be increased (corresponding to increasing the number of wiring patterns). Therefore, the transducer array pitch in the row direction can be reduced, and the number of transducer arrays in the column direction can be increased.

  Further, according to FIG. 8, by passing a part of the wiring pattern through a conductor layer different from the conductor layer on which other patterns are formed, the conductor exposed portions can be separated without increasing the repeat pitch in the row direction. Can be connected in common. Accordingly, the drive electrodes of the transducers at symmetrical positions in the column direction can be commonly connected without increasing the transducer arrangement pitch in the row direction, and a complicated wiring pattern can be formed. The present invention is not limited to the above-described embodiment, and can be implemented with various modifications.

It is a figure which shows the structure of the two-dimensional array ultrasonic transducer which concerns on 1st Embodiment of this invention, Comprising: The figure (a) is a top view, The figure (b) is sectional drawing. The perspective view for demonstrating the manufacturing method of the two-dimensional array ultrasonic transducer which concerns on 1st Embodiment of this invention. The perspective view for demonstrating the manufacturing method of the two-dimensional array ultrasonic transducer which concerns on 1st Embodiment of this invention. The perspective view for demonstrating the manufacturing method of the two-dimensional array ultrasonic transducer which concerns on 1st Embodiment of this invention. The perspective view for demonstrating the manufacturing method of the two-dimensional array ultrasonic transducer which concerns on 1st Embodiment of this invention. Sectional drawing of FPC which concerns on 2nd Embodiment of this invention. The figure which shows the wiring pattern in FPC which has the conductor exposed part which concerns on 2nd Embodiment of this invention. The figure which shows the wiring pattern in FPC which has the conductor exposed part which concerns on 2nd Embodiment of this invention. The figure for demonstrating the manufacturing method of the ultrasonic transducer which concerns on a prior art example. The figure for demonstrating the manufacturing method of the ultrasonic transducer which concerns on a prior art example. The figure for demonstrating the manufacturing method of the ultrasonic transducer which concerns on a prior art example. The figure which shows the case where a slit can be formed to the vicinity of a piezoelectric plate in the ultrasonic transducer which concerns on a prior art example. The figure which shows the case where a slit cannot be formed to the vicinity of a piezoelectric plate in the ultrasonic transducer which concerns on a prior art example. The figure which shows the wiring pattern and structure of the printed wiring board of the ultrasonic transducer which concerns on a prior art example. The figure which shows the wiring pattern and structure of the printed wiring board of the ultrasonic transducer which concerns on a prior art example. The figure which shows the cross section of the conductor exposed part of the printed wiring board of the ultrasonic transducer which concerns on a prior art example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Piezoelectric vibrator board, 2 ... Wiring pattern, 3 ... FPC (flexible printed circuit board), 4 ... Through-hole, 5 ... Slit.

Claims (9)

A plurality of conductor exposed portions provided dispersed on the printed wiring board and electrodes on the back surfaces of the plurality of ultrasonic vibrators provided on the vibrator plate are electrically connected, and the printed wiring board has a predetermined In the ultrasonic transducer in which the conductive layer according to the wiring pattern, and the electrically insulating layer provided on the electrically conductive layer, the exposed hole reaching the electrically conductive layer from the electrically insulating layer is provided on the exposed conductor portion.
The ultrasonic transducer according to claim 1, wherein the printed wiring board has a plurality of conductive layers and electrical insulating layers that are alternately stacked.   The ultrasonic transducer according to claim 1, wherein the plurality of conductive layers are electrically connected through a through hole.   The ultrasonic transducer according to claim 2, wherein a conductor exposed portion is formed at the position of the through hole.   The ultrasonic transducer according to claim 1, wherein the conductor exposed portion protrudes from the surface of the printed wiring board.   The ultrasonic transducer according to claim 1, wherein the exposed hole is filled with a conductive material.   The printed wiring in a state where the plurality of conductor exposed portions provided dispersedly on the printed wiring board and the electrodes on the back surfaces of the plurality of ultrasonic vibrators provided on the vibrator plate are electrically connected. 2. The ultrasonic transducer according to claim 1, wherein the plate and the vibrator plate are bonded through an electrically insulating resin.   The ultrasonic transducer according to claim 1, wherein the plurality of conductor exposed portions are commonly connected by the same conductive layer.   The ultrasonic transducer according to claim 1, wherein the printed wiring board is a flexible printed wiring board.   The ultrasonic transducer according to claim 1, wherein the conductor exposed portion and the ultrasonic transducer are two-dimensionally inserted.

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