JP2007104208A - Method for manufacturing acoustic matching layer used for ultrasonic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for simply and inexpensively manufacturing individual acoustic matching layers used for an ultrasonic sensor regardless of the structure of the ultrasonic sensor. <P>SOLUTION: The method for manufacturing acoustic matching layers used for an ultrasonic sensor includes a process in which a plurality of recesses (11a) are formed on the surface of a resin layer (11), and a hard layer (12) made of ceramic or metal is formed with an aerosol deposition method so as to fill the recesses (11a). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement in a method for manufacturing an acoustic matching layer used in an ultrasonic sensor.

  Some ultrasonic sensors include a transmitter / receiver including a piezoelectric element. Here, the “piezoelectric element” is one in which thin-film electrodes are formed on both surfaces of a piezoelectric body polarized in the thickness direction. When transmission is performed, the piezoelectric body is vibrated by applying a signal voltage between both electrodes. As a result, ultrasonic waves are radiated from the surface of the piezoelectric body. Conversely, at the time of reception, the piezoelectric body vibrates by applying ultrasonic waves to the surface of the piezoelectric body, and as a result, an electrical signal is output between both electrodes. As a typical example of such a piezoelectric body, PZT (lead zirconate titanate) is often used.

  In general, a substance has its own acoustic impedance, so that a piezoelectric body also has its own acoustic impedance, and gases and liquids that are the medium through which ultrasonic waves propagate also have their own acoustic impedance. Here, it is difficult to efficiently transmit ultrasonic waves (or acoustic energy) between substances having significantly different acoustic impedances. Therefore, by providing an acoustic matching layer having an acoustic impedance of an intermediate size between the piezoelectric body and the ultrasonic propagation medium between them, the transmission of ultrasonic waves between the piezoelectric body and the medium is efficient. You can do well.

  4 to 6, IEEE ULTRASONICS SYPOSIUM, 2001, pp. The manufacturing method of the ultrasonic sensor including the acoustic matching layer disclosed in 1031-1034 is illustrated in a schematic perspective view.

  In FIG. 4, for example, a piezoelectric ceramic substrate 1 having a diameter of 30 mm and a thickness of 1 mm is diced to form a plurality of piezoelectric material quadrangular columns 1a arranged in a matrix. The pitch, interval, and height of these piezoelectric material square pillars 1a are, for example, 210 μm, 60 μm, and 500 μm, respectively.

  In FIG. 5, which is an enlarged partial perspective view compared to FIG. 4, for example, by performing second dicing to form a plurality of V-shaped grooves orthogonal to each other using a blade having a taper angle of 30 degrees. The piezoelectric material quadrangular pyramid 1b is formed on the piezoelectric material quadrangular column 1a. Thereafter, grooves having a width of 60 μm existing between the piezoelectric material rectangular columns 1 a adjacent to each other are filled with the insulating polymer material 2.

  In FIG. 6, for example, a Cr—Au electrode film 3 is formed on the surface of the piezoelectric material quadrangular pyramid portion 1 b by vapor deposition. Thereafter, the electrode film 3 is filled with a conductive composite resin 4 containing a conductive epoxy resin and tungsten powder. That is, the Cr—Au electrode film 3 and the conductive composite resin 4 function as a common electrode for the plurality of piezoelectric material square pillars 1a. Thereafter, the substrate portion 1 remaining at the bottom of the piezoelectric material quadrangular column 1a is removed, and the respective piezoelectric material quadrangular columns 1a are separated. An ultrasonic sensor can be obtained by forming individual electrode films on the bottom surface of each piezoelectric material quadrangular column 1a.

In the ultrasonic sensor of FIG. 6 obtained in this way, the quadrangular pyramid portion 1b of the piezoelectric body and the composite resin 4 function as an acoustic matching layer. In the acoustic matching layers 1b and 4, the conductive composite resin 4 has an acoustic impedance close to that of the ultrasonic propagation medium (gas or liquid). On the other hand, the quadrangular pyramid portion 1b of the piezoelectric body has a horizontal cross-sectional area that increases as it approaches the quadrangular prism 1a of the piezoelectric body. Accordingly, in the acoustic matching layers 1b and 4, the total acoustic impedance continuously changes from the upper surface to the lower surface, and the acoustic energy is efficiently transmitted from the ultrasonic wave propagation medium to the quadrangular prism 1a of the piezoelectric body. be able to.
2001, IEEE ULTRASONICS SYPOSIUM, pp. 1031-1034

  As described above, the acoustic matching layers 1b and 4 in Non-Patent Document 1 are formed integrally with the piezoelectric column 1a. Therefore, the acoustic matching layers 1b and 4 cannot be manufactured individually with the ultrasonic sensor, and lack flexibility in manufacturing the acoustic matching layer.

  In addition, since the piezoelectric column 1a is formed by dicing, it is limited to a square column. Accordingly, the piezoelectric pyramid portion 1b formed by further dicing on the piezoelectric column 1a is also limited to a quadrangular pyramid shape. The intervals between the quadrangular pyramids 1b of the piezoelectric bodies are also limited to the same intervals as the intervals between the piezoelectric columns 1a.

  On the other hand, it is desirable that the acoustic matching layer can be individually designed and manufactured regardless of the structure of the ultrasonic sensor. Then, the degree of freedom in designing the acoustic matching layer is expanded, and the manufacturing process can be simplified and the cost can be reduced.

  Accordingly, an object of the present invention is to provide a method capable of individually and easily manufacturing an acoustic matching layer at a low cost regardless of the structure of the ultrasonic sensor.

  The method for manufacturing an acoustic matching layer for an ultrasonic sensor according to the present invention includes a step of forming a plurality of recesses on the surface of a resin layer and forming a hard layer made of ceramic or metal by an aerosol deposition method so as to fill the recesses. It is characterized by including.

  In addition, it is preferable that the cross-sectional area of the recessed part of a resin layer is changing continuously in the thickness direction of the resin layer. Further, the concave portion of the resin layer can be preferably formed in the shape of a cone, a triangular pyramid, a polygonal pyramid, or a V-shaped groove. Furthermore, the concave portion of the resin layer can be preferably formed by using any one of hot embossing, ultraviolet curing mold, thermosetting mold, micro drill, laser ablation, or synchrotron radiation ablation.

  Moreover, it is preferable that the nanoparticle which has a particle size of 100 nm or less is used as a fine powder raw material used when forming a hard layer by the aerosol deposition method. As the material for the hard layer, alumina, zirconia, tungsten, or molybdenum can be preferably selected.

  According to the present invention as described above, the acoustic matching layer can be individually and easily manufactured at a low cost regardless of the structure of the ultrasonic sensor.

  1 and 2, a manufacturing process of an acoustic matching layer for an ultrasonic sensor according to an embodiment of the present invention is illustrated in schematic cross-sectional views.

  In FIG. 1, first, a resin layer 11 having a plurality of recesses 11a is formed. These recesses 11a in the resin layer 11 have a cross-sectional area that continuously changes in the depth direction of the resin layer. As the shape of the concave portion 11a having a transverse area that continuously changes in the depth direction of the resin layer, for example, a shape such as a cone, a triangular pyramid, a polygonal pyramid, or a V-shaped groove can be preferably employed.

  The resin layer 11 having the concave portions 11a is formed by, for example, using a mold having a plurality of cone-shaped convex portions formed by machining or the like, hot embossing the resin layer, or UV (ultraviolet) curable resin mold. Or it can manufacture simply and at low cost by performing a thermosetting resin mold.

  In addition, the resin layer 11 having the recesses 11a can be easily and inexpensively manufactured by performing mechanical processing with a micro drill on the flat resin layer or laser ablation or synchrotron radiation ablation together with a mask having a predetermined pattern. can do.

  Next, as shown in FIG. 2, a hard layer 12 made of ceramic or metal is formed so as to fill a plurality of recesses 11 a in the resin layer 11. As a material of such a hard layer 12, for example, ceramics such as alumina and zirconia, or metals such as tungsten and molybdenum can be preferably employed.

  Here, these materials for the hard layer 12 have a very high melting point, and even if sintered to form the hard layer 12, a very high sintering temperature is required. Can't withstand

  FIG. 3 is a schematic block diagram illustrating a high-speed injection molding (aero deposition) apparatus that can be preferably used to form the hard layer 12 made of such a high-melting-point material. The aero deposition apparatus includes a decompression chamber 21, and the decompression chamber 21 can be exhausted by a vacuum pump (not shown) connected to an exhaust port 21a. A movable stage 22 is provided inside the decompression chamber 21. The movable stage 22 can move in the vertical and horizontal directions (XY directions) and rotate (θ movement) in a horizontal plane. The resin layer 11 is mounted on the movable stage 22 with the plurality of recesses 11a facing downward.

  Outside the decompression chamber 21, an aerosolization chamber 23 and a high-pressure gas cylinder 24 connected thereto are provided. The aerosolization chamber 23 is placed on a stirring table 25 for stirring, and the bottom of the aerosolization chamber 23 is loaded with a ceramic or metal fine powder raw material 23a. The aerosolization chamber 23 is provided in the decompression chamber 21 and connected to the nozzle 26.

  High-pressure gas is injected from the high-pressure cylinder 24 through the valve 27 and the gas pipe 28 into the fine powder raw material 23 a in the aerosolization chamber 23. As such a high-pressure gas, for example, air, nitrogen gas, argon gas or the like can be preferably used.

  When the high pressure gas is injected into the fine powder raw material 23a, the aerosolization chamber 23 is vibrated by the agitating vibration table 25, and the fine powder raw material 23a is aerosolized by the action of the vibration and the high pressure gas injected. The aerosolized fine powder raw material is sent to the nozzle 26 via the valve 29 and the aerosol transport pipe 30.

  A movable shutter or mask 31 is provided between the nozzle 26 and the movable stage 22, and the start and stop of aerosol injection onto the resin layer 11 can be reliably controlled by the shutter 31.

  In the aerosol deposition apparatus shown in FIG. 3, the hard layer 12 can be formed by causing the aerosolized fine powder material to collide with the resin layer 11 at high speed from the nozzle 26 with a high-pressure carrier gas. That is, the fine powder raw material colliding with the resin layer 11 at a high speed can be formed into a dense film by colliding and crushing those fine powders. At this time, in order to form a dense hard layer 12 with few pores (pores), the particle diameter of the fine powder raw material is preferably as small as possible, and it is preferable to use nanoparticles having a particle diameter of about 100 nm or less.

  Further, if the nanoparticles are used as the fine powder raw material 23a, the aerosolization in the aerosol generation chamber 23 can be easily and completely performed. The aerosol is transported through the valve 29 and the aerosol transport pipe 30, and further from the nozzle 26. Injection can be performed smoothly.

  As described above, by using the aerosol deposition apparatus as shown in FIG. 3, the hard layer 12 for embedding the plurality of recesses 11a in the resin layer 11 can be formed easily and at low cost. An acoustic matching layer for an acoustic wave sensor can be manufactured and provided simply and at low cost.

  According to the present invention as described above, the acoustic matching layer can be individually and simply manufactured at low cost regardless of the structure of the ultrasonic sensor.

It is typical sectional drawing illustrating the manufacturing method of the acoustic matching layer for ultrasonic sensors by one Embodiment of this invention. It is typical sectional drawing which shows the acoustic matching layer for ultrasonic sensors obtained through the process of FIG. FIG. 3 is a schematic block diagram illustrating an aerosol deposition apparatus that can be preferably used to manufacture the acoustic matching layer for an ultrasonic sensor of FIG. 2. It is a typical perspective view illustrating the manufacturing method of the ultrasonic sensor by a prior art. FIG. 5 is a schematic perspective view illustrating a process following FIG. 4. FIG. 6 is a schematic perspective view illustrating the process following FIG. 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Piezoelectric substrate, 1a Piezoelectric quadratic column, 1b Piezoelectric quadrangular pyramid part, 2 Insulating polymer, 3 Cr-Au electrode film, 4 Conductive composite resin, 11 Resin layer, 11a Recess, 12 From ceramic or metal Hard layer, 21 Decompression chamber, 21a Exhaust port, 22 Movable stage, 23 Aerosolization chamber, 23a Fine powder raw material, 24 High pressure gas cylinder, 25 Stirring shaking table, 26 Nozzle, 27 Valve, 28 High pressure gas transport pipe, 29 Valve , 30 aerosol transport tube, 31 shutter.

Claims (7)

Forming a plurality of recesses on the surface of the resin layer;
A method for producing an acoustic matching layer for an ultrasonic sensor, comprising: forming a hard layer made of ceramic or metal by an aerosol deposition method so as to fill the plurality of recesses.   2. The method of manufacturing an acoustic matching layer for an ultrasonic sensor according to claim 1, wherein the cross-sectional area of the recess continuously changes in the thickness direction of the resin layer.   The method for manufacturing an acoustic matching layer for an ultrasonic sensor according to claim 2, wherein the recess has a shape of a cone, a triangular pyramid, a polygonal pyramid, or a V-shaped groove.   4. The concave portion of the resin layer is formed by any one of hot embossing, ultraviolet curing mold, thermosetting mold, micro drill, laser ablation, or synchrotron radiation ablation. The manufacturing method of the acoustic matching layer for ultrasonic sensors as described in 2.   The ultrasonic wave according to any one of claims 1 to 4, wherein nanoparticles having a particle size of 100 nm or less are used as a fine powder raw material used when the hard layer is formed by an aerosol deposition method. A method for producing an acoustic matching layer for a sensor.   The method for producing an acoustic matching layer for an ultrasonic sensor according to claim 1, wherein alumina, zirconia, tungsten, or molybdenum is selected as the material of the hard layer.   An acoustic matching layer for an ultrasonic sensor, which is manufactured by the method according to claim 1.

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