JP2014110601A - Ultrasonic vibrator unit and process of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an array vibrator by cutting a vibrator blank bonded to a circuit board with a cutting tool.SOLUTION: Grooves 38 are formed at a vibrator bonding plane 36 of a circuit board 16. A vibrator blank containing a layer of a piezoelectric element material is bonded to the vibrator bonding plane 36. The vibrator blank is cut with a cutting tool at positions of the grooves 38 and individual vibrators 12 are cut out to produce an array vibrator 14. With the grooves 38 being formed in advance, the cutting tool is capable of cutting the vibrator blank without contacting a hard-to-cut circuit board 16.

Description

  The present invention relates to an ultrasonic transducer unit having an array transducer used for an ultrasonic probe, and a method for manufacturing the same.

  Ultrasound diagnostic apparatuses are used in the medical field. The ultrasonic diagnostic apparatus is an apparatus that transmits / receives ultrasonic waves to / from a living body and forms an ultrasonic image based on a reception signal obtained thereby. Ultrasonic wave transmission / reception with respect to a living body is executed by an ultrasonic probe (probe). The probe includes a vibrator including a piezoelectric element, and ultrasonic waves are transmitted and received by driving the vibrator. A probe having an array transducer composed of a large number of individual transducers is known. In this probe, the transmission / reception direction and focal point of the ultrasonic beam can be changed by controlling the phase for driving each transducer. Further, the beam can be scanned by continuously changing the transmission / reception direction.

  In order to improve the resolution of an acquired image and to obtain information in a three-dimensional space, it is required to configure an array transducer from a larger number of individual transducers. On the other hand, there is a demand for miniaturization of the probe. Accordingly, an array transducer in which a large number of individual transducers are arranged at high density is required.

  An array transducer is manufactured by joining a material (hereinafter referred to as a transducer blank) on a substrate having an electronic circuit for driving the array transducer, cutting and dividing the material, and cutting out a large number of individual transducers. be able to. Japanese Patent Application Laid-Open No. H10-228561 discloses a technique of cutting an individual vibrator by cutting it using a dicing saw so as to leave a part of the bottom of the vibrator blank, and then burning the remaining part using a laser. (See paragraph 0021).

Japanese translation of PCT publication No. 2005-507581

In the method described in Patent Document 1, it is necessary to prepare a laser processing machine for manufacturing the array vibrator, and the equipment becomes large. On the other hand, when the vibrator blank is cut using only a dicing saw, the cutting depth is made deeper than the thickness of the vibrator blank and the substrate surface is cut at the same time to ensure cutting, that is, to eliminate uncut residue. There is a need to. However, in this case, since the cutting depth is deep, there is a problem that the cutting fluid is not sufficiently supplied and cooling is difficult. Moreover, the board | substrate provided with the electronic circuit may be a material with a low heat transfer rate, and there exists a problem that cutting will become difficult if cutting fluid is not fully supplied as mentioned above.
It is an object of the present invention to reliably cut a vibrator blank by processing using a cutting tool such as a dicing saw when an array vibrator is manufactured on a substrate provided with an electric circuit.

  In the manufacturing method of the ultrasonic vibration unit including the array vibrator of the present invention, a vibrator blank having a layer of a piezoelectric element material is joined to a circuit board surface provided with a groove, and after joining, a groove on the circuit board surface is joined. The transducer blank is cut using a cutting tool in accordance with the position of the substrate and divided into individual transducers to form an array transducer. In addition, a cutting tool refers to the tool which scrapes material from a workpiece | work by contacting a workpiece | work.

  Since the groove is already formed in the circuit board when the vibrator blank is cut, the contact of the cutting tool with the circuit board is prevented or reduced, and the processing becomes easy.

  The thickness of the cutting blade used when cutting the vibrator blank can be made thinner than the width of the groove provided on the circuit board surface. Thereby, it can prevent more reliably that a cutting blade contacts a circuit board.

  Further, the groove can be formed on the surface of the circuit board by cutting, and the thickness of the grooving blade used when cutting the groove can be made larger than the thickness of the cutting blade used when cutting the vibrator blank. . Thereby, a groove having a width wider than the thickness of the cutting blade can be formed by one grooving.

  Furthermore, when cutting the vibrator blank, the cutting blade can enter the groove on the surface of the circuit board. Thereby, the vibrator blank can be surely cut.

  Furthermore, when the vibrator blank is bonded, the groove on the surface of the circuit board can be filled with an adhesive used for bonding. The groove can be filled at the same time as joining, and the work is simplified. Further, when the thickness of the cutting blade is thinner than the width of the groove, the adhesive in the groove is involved in the bonding of the circuit board and the individual vibrator, and these can be bonded more reliably.

  An ultrasonic transducer unit according to another aspect of the present invention includes a circuit board having a groove formed on a surface thereof, and an array vibrator bonded to the circuit board surface having the groove formed thereon. The individual vibrators to be configured are provided corresponding to the sections divided by the grooves on the circuit board, and the width of the grooves formed on the circuit board is made wider than the interval between the individual vibrators provided on both sides of the groove. ing.

  Further, the groove provided in the circuit board can be filled with an adhesive used for joining the circuit board and the array transducer.

In a preferred aspect of the method for manufacturing an ultrasonic transducer unit, the transducer blank further includes a layer of an acoustic matching layer material. Furthermore, the vibrator blank can further include a layer of a resonant layer material.
Furthermore, in another preferable aspect, the vibrator blank having a plurality of material layers is joined to the circuit board after these layers are joined and integrated.
Furthermore, in another preferable aspect, a step of filling a space between the individual vibrators constituting the array vibrator with a filling agent is included.
Furthermore, in another preferable aspect, after the step of filling the plugging agent, the step of adhering a ground electrode common to the individual vibrator to the surface of the array vibrator opposite to the face facing the circuit board is provided. included.
Furthermore, in a preferable aspect, the step of adhering a protective layer for protecting the array transducer to the array transducer to which the ground electrode is adhered is included.

  According to the present invention, it is possible to easily cut a vibrator blank using a cutting tool.

It is a perspective view which shows schematic structure of the ultrasonic transducer | vibrator unit of this embodiment. It is a perspective view explaining 1 process of the manufacturing process of an ultrasonic transducer | vibrator unit, and is a figure which shows a circuit board. It is a perspective view explaining one process of the manufacturing process of an ultrasonic transducer | vibrator unit, and is a figure which shows the circuit board in which the groove | channel was formed. It is a figure which shows the external appearance of a dicing saw. It is a perspective view explaining one process of the manufacturing process of an ultrasonic transducer | vibrator unit, and is a figure which shows the state by which the transducer blank was joined to the circuit board. It is a perspective view explaining one process of the manufacturing process of an ultrasonic transducer | vibrator unit, and is a figure which shows the state by which the transducer blank was cut | disconnected and the array transducer | vibrator was formed. FIG. 7 is a longitudinal sectional view of the array transducer shown in FIG. 6. It is a perspective view explaining 1 process of the manufacturing process of an ultrasonic transducer | vibrator unit, and is a figure which shows the state which filled the space | interval with the individual oscillator.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a completed state of the ultrasonic transducer unit 10 of the present embodiment. The ultrasonic transducer unit 10 transmits and receives ultrasonic waves upward in FIG. In the following description, terms indicating the upper and lower relationships such as “upper” and “lower surface” are limited to the upper and lower in the figure, and do not indicate the upper and lower relationships in the usage mode. The ultrasonic transducer unit 10 includes a two-dimensional array transducer 14 in which individual transducers 12 are arranged vertically and horizontally. The array transducer 14 shown in the figure has the same number of transducers 12 arranged vertically and horizontally, and is configured in a substantially square shape as a whole. Further, in the figure, for the sake of explanation, the number of the individual vibrators 12 is 25 in a 5 × 5 arrangement, but the actual array vibrator 14 has a remarkably large number of, for example, several thousand individual vibrators. 12 is provided. In this configuration, the ultrasonic beam can be scanned in two intersecting directions. A three-dimensional ultrasonic image representing the three-dimensional space can be formed from the data in the three-dimensional space captured by scanning in two directions. An ultrasonic image in an arbitrary cross section can also be formed from this data. The array transducer may be a one-dimensional array in which the individual transducers 12 are linearly arranged in a line. Further, it may be a substantially rectangular array in which different numbers of individual vibrators 12 are arranged in the vertical direction and the horizontal direction.

  The ultrasonic transducer unit 10 includes a circuit board 16 including an electronic circuit that drives the array transducer 14 and a protective layer 18 that covers and protects the array transducer 14. In the case of this unit 10, the circuit board 16 includes an electronic circuit board 20 on which an electronic circuit is formed, and a relay board 22 having a wiring or a circuit connecting the electronic circuit and the individual vibrator 12. The relay board 22 may have a function of switching the connection between the terminal on the electronic circuit and the individual vibrator 12. The array vibrator 14 is smaller than the circuit board 16, and a part of the surface (the vibrator joint surface 36) of the circuit board 16 to which the array vibrator 14 is joined is exposed without being covered by the array vibrator 14.

  The individual vibrator 12 includes a vibration element 26 including a piezoelectric element 24 and a matching layer 28. The vibration element 26 may be configured by only the piezoelectric element 24, or may be configured by combining the piezoelectric element 24 and the resonance layer 30. The resonance layer 30 is disposed on the back side of the piezoelectric element 24, that is, on the opposite side to the direction in which ultrasonic waves are transmitted and received. The resonance layer 30 has an acoustic impedance higher than that of the piezoelectric element 24, forms a hard back layer, and the piezoelectric element 24 and the resonance layer 30 are integrated to transmit and receive ultrasonic waves. . The acoustic impedances of the piezoelectric element 24 and the resonance layer 30 are, for example, about 30 MRayls and 70 to 100 MRayls, respectively. The material of the resonance layer 30 is, for example, a super hard material that is a composite of cobalt, zirconia, and the like and a tungsten compound. The resonant layer 30 resonates with the piezoelectric element 24 and serves to efficiently transmit ultrasonic waves toward the living body. In this case, the piezoelectric element 24 is adjusted to a thickness of approximately one quarter (λ / 4) with respect to the wavelength λ of the ultrasonic wave having a frequency to be used.

  The matching layer 28 is a layer for reducing acoustic impedance from the piezoelectric element 24 to the living body stepwise to acoustically match the piezoelectric element 24 and the living body. The matching layer 28 may be composed of only one layer, but may include a plurality of layers in order to reduce the acoustic impedance as smoothly as possible. In the example shown in the figure, the first matching layer 28A and the second matching layer 28B are composed of two layers. The material of the matching layer 28 is a resin, for example, an epoxy resin.

  A ground electrode 32 common to the individual vibrators 12 is bonded to the surface of the individual vibrator 12 facing the protective layer 18. The matching layer 28 has conductivity, and electrically connects the ground electrode 32 and the vibration element 26. The matching layer 28 can be made of carbon, carbon, graphite, or a resin mixed with a conductive filler in order to have conductivity. On the other hand, an electrode pad 34 (see FIG. 2) formed on the surface of the circuit board 16 is connected to the surface of the individual vibrator 12 facing the circuit board 16. In the aspect in which the vibration element 26 is constituted only by the piezoelectric element 24, the electrode pad 34 is directly connected. When the vibration element 26 includes the resonance layer 30, the resonance layer 30 is made conductive, and the piezoelectric element 24 and the electrode pad 34 are electrically connected.

  Next, a method for manufacturing the ultrasonic transducer unit 10 will be described. FIG. 2 shows the circuit board 16. The circuit board 16 is made of low temperature co-fired ceramics (LTCC). Low-temperature co-fired ceramics have a lower thermal conductivity than other ceramic materials, have a high temperature during cutting, and are prone to deformation and breakage of the cutting tool. Therefore, when cutting low-temperature co-fired ceramics, it is necessary to sufficiently supply the cutting fluid and cool it, and to increase the rigidity of the cutting tool so that the tool does not deform.

  An electrode pad 34 is formed on a surface 36 of the circuit board 16 to which the array transducer 14 is bonded later (hereinafter referred to as a transducer bonding surface 36). The electrode pad 34 is electrically connected to an electronic circuit formed in the circuit board 16.

  FIG. 3 is a view showing a state in which a groove is cut on the surface of the circuit board 16. Grooves 38 are formed vertically and horizontally on the vibrator bonding surface 36 of the circuit board 16. The groove 38 is formed so as to pass between the electrode pads 34. This groove is indicated by reference numeral 38a in the figure. The groove 38 is also formed so as to surround the entirety of the plurality of electrode pads 34. This groove is indicated by reference numeral 38b in the drawing. As a result, one electrode pad 34 is arranged in one section 39 surrounded by the groove 38 and not divided by the groove 38.

  The groove 38 is processed using a cutting tool, for example, a dicing saw. A schematic configuration of the dicing saw 40 is shown in FIG. The dicing saw 40 has an annular plate-shaped dicing blade 42 (hereinafter referred to as a blade 42) and a flange 44 that supports the blade 42, and is rotationally driven by a transmission shaft 46. As will be described later, in this embodiment, a dicing saw for forming the groove 38 in the circuit board 16 and a dicing saw for forming the individual vibrator 12 are used. In order to distinguish these, the former will be described using reference numeral 40A and the latter using reference numeral 40B. The amount by which the blade 42 protrudes from the flange 44, that is, the difference between the radii of the blade 42 and the flange 44 is referred to as the blade protrusion amount h. As shown in FIG. 3, the width of the groove 38 is w and the depth is d. By setting the thickness t of the blade 42 to w, a groove having a width w can be formed by one cutting. The groove width w and the groove depth d can be set to 0.04 to 0.1 mm and 0.05 to 0.3 mm, for example.

  As will be described later, the groove 38 is provided for the purpose of making a relief of the dicing saw 40B when the individual vibrator 12 is cut out, and the groove depth d may be shallow. Therefore, the cutting fluid can be supplied to the portion of the circuit board 16 where the dicing saw 40A is cutting, and the circuit board 16 and the blade 42 can be prevented from being insufficiently cooled. Further, the cutting amount h of the dicing saw 40A can be reduced, the rigidity of the blade 42 is increased, and the deformation thereof is suppressed. Further, since the groove 38 can be processed while the electrode pad 34 is visible, the groove can be reliably formed at a predetermined position. That is, the electrode pad 34 can be prevented from being scraped.

  FIG. 5 is a view showing a state in which the vibrator blank 48 is bonded to the circuit board 16 in which the groove 38 is formed. After the groove 38 is cut, the transducer blank 48 that is the material of the array transducer 14 is bonded to the transducer bonding surface 36. The vibrator blank 48 includes a vibration element material 50 that is later divided to be the vibration element 26 and a matching layer material 52 that is similarly divided to be the matching layer 28. The vibration element material 50 includes a piezoelectric element material 54 that becomes the piezoelectric element 24. When the vibration element 26 includes the piezoelectric element 24 and the resonance layer 30, the vibration element material 50 includes a resonance layer material 56 that becomes the resonance layer 30. The number of matching layer materials 52 is the same as the number of matching layers 28. Each material forms a layer, and is laminated to form the vibrator blank 48 and then bonded onto the circuit board 16. Alternatively, the layers may be sequentially stacked on the circuit board 16.

  The material constituting each layer may have an electrode layer over the entire surface facing the adjacent material. The electrode layer is made of gold, silver, or other metal having good conductivity. As a method for forming the electrode layer, plating, vapor deposition, ion plating, sputtering, baking, chemical vapor deposition (CVD), or the like can be employed. Further, an electrode layer similar to the above electrode layer can be provided on the surface of the vibrator blank 48 facing the circuit board 16, that is, the entire lower surface of the vibration element material 50. Similarly, an electrode layer similar to the above electrode layer can be provided on the entire surface of the vibrator blank 48 facing the protective layer 18.

  The circuit board 16 and the vibrator blank 48 are joined using a non-conductive adhesive. As the adhesive, for example, an epoxy adhesive, a urethane adhesive, a cyanoacrylate adhesive, or the like can be used. When the circuit board 16 and the vibrator blank 48 are bonded, the groove 38 can be filled with an adhesive. Since the adhesive filled in the groove 38 is thicker than the portion other than the groove 38, it contributes to firmly joining the circuit board 16 and the vibrator blank 48.

  FIG. 6 is a diagram showing a state in which the vibrator blank 48 is cut and divided to form individual vibrators 12. The vibrator blank 48 is cut by a cutting tool, for example, a dicing saw 40B, at the position of the groove 38 already formed on the surface of the circuit board 16. By cutting, the individual vibrator 12 in which the vibration element 26 and the matching layer 28 are stacked is cut out. One individual vibrator 12 may be formed for one section 39. In this case, one individual vibrator 12 is connected to one electrode pad. Since the groove 38 can be visually recognized when the vibrator blank 48 is cut, it can be cut according to the position of the groove 38. Thus, the transducer blank 48 is cut at the position of the groove 38 so that the transducer blank 48 is separated into the individual transducers 12 and the array transducer 14 is formed. By cutting the vibrator blank 48 at the position of the groove 38 or along the groove 38, the individual vibrator 12 can be formed corresponding to the position of the electrode pad 34. Without the groove 38, when the vibrator blank 48 is cut, there is no target, and the processing reliability is reduced as compared with the case where the groove 38 is present.

  The cutting of the vibrator blank 48 is performed deeper than the thickness of the vibrator blank 48. That is, the cutting depth is obtained by adding a certain amount α to the thickness of the vibrator blank 48. α is a value capable of reliably separating the individual vibrators 12 from each other, and is a value smaller than the depth d of the groove 38. For example, if the depth d of the groove 38 is 0.15 mm, α can be set to 0.12 mm. By cutting deeper than the thickness of the vibrator blank 48, the groove is formed again in the adhesive 58 filling the groove 38. This groove is referred to as a re-formed groove 60. Further, when an electrode layer is formed on the surface of the vibrator blank 48 facing the circuit board 16, the electrode layer can be reliably cut by cutting deeper than the thickness of the vibrator blank 48. On the other hand, due to the thickness of the vibrator blank 48, it is difficult to supply the cutting fluid to a deep position when the vibrator blank 48 is cut, and it is necessary to increase the amount h of the dicing saw 40B. These are disadvantageous factors related to cutting because of insufficient cooling capacity and reduced rigidity of the dicing saw 40B. However, since the dicing saw 40B does not cut the circuit board 16 made of a material that is difficult to cut, the necessary cooling can be performed even if the amount of cutting fluid supplied is small.

  The blade thickness t of the dicing saw 40B used for the vibrator blank 48 can be made smaller than the width of the groove 38. If the width w of the groove 38 is 0.04 to 0.1 mm, for example, it can be 0.02 mm. From the description order, the blade thickness t of the dicing saw 40B is described as being determined from the width of the groove 38. However, in the general design process, the interval between the adjacent individual vibrators 12 is determined first. . Therefore, in practice, the thickness t of the blade 42 of the dicing saw 40B is first determined, and the width w of the groove 38 is determined accordingly. Further, as for the depth d of the groove 38, in practice, α that can reliably separate the individual vibrators 12 is determined first, and the depth of the groove 38 is determined in accordance with this.

  FIG. 7 is a longitudinal sectional view of FIG. The groove 38 is formed wider than the interval between the individual vibrators 12 positioned on both sides of the groove 38, and also exists in a part below the individual vibrator 12. An adhesive 58 is in contact with the lower surface of the individual vibrator 12 facing the groove 38. Even in a portion other than the portion facing the groove 38, the individual vibrator 12 and the circuit board 16 are bonded by the adhesive 58, but the thickness of the layer of the adhesive 58 formed in this portion is thin. On the other hand, the thickness of the layer of the adhesive 58 in the groove 38 is thick and can be bonded more strongly. Thereby, the individual vibrator 12 is more firmly bonded to the circuit board 16, and for example, peeling due to the force from the dicing saw 40B received during cutting can be prevented.

  FIG. 8 is a diagram illustrating a state in which a gap between adjacent individual vibrators 12 is clogged. A gap between the individual vibrators 12 is filled with a filling agent 62. As the plugging agent 62, an adhesive such as an epoxy-based adhesive, a urethane-based adhesive, or a silicone-based adhesive can be used, and an adhesive mixed with a filler can also be used. As the plugging agent 62, the same one as the adhesive 58 may be used. Further, the filling agent 62 may be filled in the re-forming groove 60.

  Finally, the ground electrode 32 common to the plurality of individual vibrators 12 is formed on the upper surface of the array vibrator 14, and the protective layer 18 is further formed. As a result, the ultrasonic transducer unit 10 shown in FIG. 1 is completed. The process of forming the ground electrode 32 and the protective layer 18 can be performed simultaneously with the clogging process which is the previous process. For example, when the protective layer 18 having the ground electrode 32 formed on the surface facing the array transducer 14 is prepared and bonded to the array transducer 14, clogging is also performed using an adhesive used for the bonding. Like that.

  The protective layer 18 may have a shape other than the flat plate shape shown in FIG. For example, a cap shape having an edge covering the entire side surface or a part of the array transducer 14 can be used. Further, the upper surface of the protective layer 18 may be a curved surface, particularly a convex surface.

  10 ultrasonic transducer units, 12 transducers, 14 array transducers, 16 circuit boards, 20 electronic circuit boards, 22 relay boards, 24 piezoelectric elements, 26 vibration elements, 28 matching layers, 30 resonance layers, 34 electrode pads, 36 transducer interface, 38 groove, 48 transducer blank, 50 transducer element material, 52 matching layer material, 54 piezoelectric element material, 56 resonance layer material.

Claims (7)

A method of manufacturing an ultrasonic transducer unit having an array transducer,
Bonding a vibrator blank having a layer of piezoelectric element material to a circuit board surface on which grooves are formed;
Cutting the vibrator blank using a cutting tool in accordance with the position of the groove on the circuit board surface to form an array vibrator;
A method for manufacturing an ultrasonic transducer unit, comprising:   2. The method of manufacturing an ultrasonic transducer unit according to claim 1, wherein the thickness of the cutting blade for cutting the transducer blank is thinner than the width of the groove cut on the surface of the circuit board. Method. It is a manufacturing method of the ultrasonic transducer unit according to claim 1,
And further comprising the step of forming grooves on the surface of the circuit board by cutting,
The method of manufacturing an ultrasonic transducer unit, wherein a thickness of the grooving blade for cutting the groove is thicker than a thickness of the cutting blade for cutting the transducer blank.   The method of manufacturing an ultrasonic transducer unit according to claim 2 or 3, wherein when the transducer blank is cut, the cutting blade is inserted into a groove on the surface of the circuit board.   5. The method for manufacturing an ultrasonic transducer unit according to claim 1, wherein in the step of bonding the transducer blank, the groove on the surface of the circuit board is filled with an adhesive used for bonding. Manufacturing method of ultrasonic transducer unit. A circuit board with grooves formed on the surface;
An array transducer which is composed of individual transducers provided corresponding to the sections divided by the grooves of the circuit board, and which is bonded to the surface of the circuit board on which the grooves are formed;
Including
The width of the groove formed in the circuit board is wider than the interval between the individual vibrators provided on both sides of the groove,
Ultrasonic transducer unit.   8. The ultrasonic transducer unit according to claim 7, wherein the groove formed in the circuit board is filled with an adhesive used for joining the circuit board and the array transducer.

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