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DESCRIPTION JP2006095167

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DESCRIPTION JP2006095167
The present invention provides a highly reliable ultrasonic probe with small variations in
sensitivity. A piezoelectric element, a first acoustic matching layer made of solid inorganic
material provided on one surface of the piezoelectric element, and a density of 6.5 g provided on
the first acoustic matching layer And a second acoustic matching layer made of a mixture of 1030 vol% of oxide powder dispersed in 10 cm / cm or more in the organic resin, and the
piezoelectric element, the first acoustic matching layer, and the second acoustic matching An
ultrasonic probe, wherein a plurality of laminates including layers are arranged in a onedimensional or two-dimensional array on the acoustic backing material. [Selected figure] Figure 1
Ultrasound probe
[0001]
The present invention relates to ultrasound probes.
[0002]
In the field of medical ultrasonic diagnostic equipment and nondestructive testing equipment, in
order to image the internal state of an object, ultrasonic waves are directed to the object and
reflections from interfaces of different acoustic impedances on the object An ultrasound probe is
used to receive the echo.
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In particular, the ultrasonic probe of the medical ultrasonic diagnostic apparatus is an array type
in which a large number of strip-shaped piezoelectric transducers are arrayed, and an ultrasonic
beam is electronically controlled to obtain a high-resolution tomogram in real time. it can.
[0003]
A general ultrasonic probe has a piezoelectric element having electrodes formed on both sides of
a piezoelectric body, a backing material provided on the lower surface of the piezoelectric
element, and an acoustic matching layer formed on the upper surface of the piezoelectric
element. The element and the acoustic matching layer have an arrayed structure. Usually, an
acoustic lens is formed on the acoustic matching layer. In addition, a pair of electrodes formed on
both sides of the piezoelectric body is connected to a flexible printed circuit board (FPC), and is
connected to the diagnostic device via a cable.
[0004]
The piezoelectric element is used as an ultrasonic wave transmitting and receiving element. The
backing material is used to absorb unwanted ultrasonic waves emitted to the back of the
piezoelectric element. The acoustic matching layer is used to increase the transmission and
reception efficiency of ultrasonic waves by matching the acoustic impedance of the piezoelectric
body and the human body. Therefore, the acoustic impedance value of the acoustic matching
layer is set to a value between the piezoelectric body (20 to 30 Mrayls) and the human body (1.5
Mrayls). When a plurality of acoustic matching layers are used, the acoustic impedance value of
each layer is set to be gradually smaller toward the human body. The reason for arraying the
acoustic matching layer together with the piezoelectric element is to suppress coupling with the
adjacent channel. The arrangement pitch of the array probes is as narrow as about 0.1 to 0.2
mm. The acoustic lens plays a role of focusing the ultrasonic wave when transmitting and
receiving the ultrasonic wave.
[0005]
Here, an ultrasonic probe used to diagnose the heart, liver, etc. of the human body requires a
resonance frequency of about 2 to 5 MHz. In addition, an ultrasound probe used to diagnose a
carotid artery or the like which is shallower than this requires a higher resonance frequency. The
piezoelectric body vibrates in the thickness direction, but in order to obtain a high resonance
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frequency, it is necessary to reduce the thickness in the vibration direction of the piezoelectric
body. Furthermore, the width of the piezoelectric body in the arrangement direction needs to be
set to 60% or less of the thickness in order to suppress the occurrence of unnecessary vibration.
[0006]
As the piezoelectric body, a lead zirconate titanate (PZT) -based piezoelectric ceramic having a
high electromechanical coupling coefficient k33 'of about 70% and high conversion efficiency
from electrical signal to mechanical vibration is conventionally used. ing. Also, in recent years, for
example, an electromechanical coupling constant k33 'of about 80, such as Pb ((Zn1 / 3Nb2 / 3)
0.91Ti0.09) O3 piezoelectric single crystal composed of a solid solution of lead zinc niobate and
lead titanate, is about 80 Piezoelectric materials having a very high efficiency of more than 10%
have been developed, and their application to ultrasonic probes is being studied.
[0007]
As an acoustic matching layer formed on the upper surface of a piezoelectric element, one in
which metal particles such as W are dispersed in an organic resin is known in order to efficiently
perform the input and output of ultrasonic waves to a human body. Further, in recent years, an
acoustic matching layer in which zinc oxide particles are dispersed in an organic resin has been
proposed (see Patent Document 1).
[0008]
However, when an ultrasonic probe is manufactured using the above-mentioned acoustic
matching layer, there are the following problems. In the case of using an acoustic matching layer
in which metal particles are dispersed in an organic resin, it is necessary to cut a metal that is
high in toughness and difficult to cut, so that the deterioration of the blade is remarkable during
array processing by dicing. When processing is continued with a deteriorated blade, chipping and
cracking occur in the piezoelectric body that is simultaneously cut. The chipping or crack
generated in the piezoelectric material causes the variation in capacitance of the element, and the
variation in capacitance is directly linked to the variation in sensitivity of the ultrasonic probe,
and the quality of the image is degraded.
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[0009]
On the other hand, in an acoustic matching layer in which zinc oxide particles are dispersed in an
organic resin, since the density of zinc oxide is low, it is necessary to increase the amount of zinc
oxide to be dispersed to obtain a required acoustic impedance value. If the amount of dispersion
increases, the amount of resin existing between adjacent oxide particles decreases, and the
adhesion between the particles decreases. For this reason, there is a problem that the grain is
extremely dropped in the array processing by dicing, and the fine processing can not be
performed accurately. In addition, although the acoustic matching layer may be used by metal
plating over its entire circumference, the adhesion with metal plating may be insufficient and
part of the electrode may peel off during array processing by dicing. was there. Since the
electrode on the acoustic matching layer side of the piezoelectric body is connected to the
ground plate through the electrode formed in the acoustic matching layer, the peeling of the
electrode causes a disconnection defect. In addition, disconnection may occur during actual use.
Unexamined-Japanese-Patent No. 2004-104629
[0010]
An object of the present invention is to provide a highly reliable ultrasonic probe with small
variations in sensitivity.
[0011]
An ultrasonic probe according to one aspect of the present invention includes a piezoelectric
element, a first acoustic matching layer formed of a solid inorganic substance provided on one
surface of the piezoelectric element, and the first acoustic matching layer. And a second acoustic
matching layer formed of a mixture obtained by dispersing 10 to 30 vol% of an oxide powder
having a density of 6.5 g / cm <3> or more provided on the organic resin. Do.
[0012]
According to the present invention, it is possible to provide a highly reliable ultrasonic probe
with small variations in sensitivity.
[0013]
Hereinafter, an ultrasound probe according to an embodiment of the present invention will be
described with reference to the drawings.
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FIG. 1 is a partially broken perspective view showing an ultrasonic probe according to an
embodiment of the present invention.
As shown in FIG. 1, in the ultrasonic probe according to the embodiment of the present invention,
the acoustic backing material 2, the piezoelectric body 1 provided on the acoustic backing
material 2, and the piezoelectric body 1 face the acoustic backing material 2 The second
electrode 4 provided on the first surface, the first electrode 5 provided on the second surface
opposite to the first surface of the piezoelectric body 1, and the first electrode 5 And a second
acoustic matching layer 3b provided on the first acoustic matching layer 3a.
Here, in the ultrasonic probe according to the embodiment of the present invention, the first
acoustic matching layer 3a is formed of a solid inorganic substance, and the second acoustic
matching layer 3b has an organic resin density of 6.5 g / cm <3>. It is formed of a material
containing 10 to 30 vol% of the above oxide powder. The acoustic impedance of the second
acoustic matching layer 3b is smaller than the acoustic impedance of the first acoustic matching
layer 3a. A laminated body in which a piezoelectric element including the first electrode 5 and
the second electrode 4 and the piezoelectric body 1 sandwiched therebetween, the first acoustic
matching layer 3a, and the second acoustic matching layer 3b is provided. , And divided into a
plurality and arranged in an array. In addition, although the acoustic lens 8 is provided on the
2nd acoustic matching layer 3b in FIG. 1, it is not limited to this. For example, the acoustic
matching layer may have a three-layer or four-layer structure. By setting the acoustic impedance
value of the acoustic matching layer between the acoustic impedance of the piezoelectric body
(20 to 30 Mrayls) and that of the human body (1.5 Mrayls) and gradually approaching the value
of the human body, the transmission / reception efficiency of ultrasonic waves is further
increased. improves. Further, in the case where the laminate in which the piezoelectric element,
the first acoustic matching layer 3a, and the second acoustic matching layer 3b are stacked is
arranged in a two-dimensional array, the resolution or the The sensitivity can be significantly
improved.
[0014]
In the ultrasonic probe according to the embodiment of the present invention, the first acoustic
matching layer 3a in contact with the piezoelectric element is made of a solid inorganic
substance, and the second acoustic matching layer 3b has an organic resin density of 6.5 g / cm
<3. > It is formed of a material in which 10 to 30 vol% of the above oxide powder is dispersed. By
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providing a plurality of acoustic matching layers, the acoustic impedance can be matched and the
transmission / reception efficiency of ultrasonic waves can be improved. In addition, by using the
above-described materials for the first and second acoustic matching layers 3a and 3b, it is
possible to suppress chipping and cracking of the piezoelectric body during array processing by
dicing and to reduce variations in element capacitance. Variations in the sensitivity of the
acoustic probe can be reduced.
[0015]
In the embodiment of the present invention, the solid inorganic substance used for the first
acoustic matching layer acts as a support plate of the piezoelectric body at the time of array
processing, and serves to suppress the blurring of the blade. Solid inorganic substances used for
the first acoustic matching layer include ceramics containing SiO2, MgO and Al2O3, ceramics
containing Si3 N4, AlN, Al2 O3 and ZrO2, ceramics containing calcium silicate and lithium
aluminosilicate, fluorine phlogopite ceramics, hexagonal crystals There are boron nitride
ceramics and the like. One or more selected from these can be used. Moreover, you may add an
additional element to these. Among them, ceramics containing SiO2, MgO and Al2O3 are
particularly excellent in processability, less damage to single crystals at the time of dicing, and
high in strength, so that the mechanical strength of the ultrasonic probe can be improved.
[0016]
The reason for defining the density and the dispersion amount of the oxide powder used for the
second acoustic matching layer in the embodiment of the present invention will be described.
When an oxide powder having a density of less than 6.5 g / cm <3> is to be filled, it is necessary
to increase the amount of oxide powder dispersed in order to achieve the desired acoustic
impedance as the second acoustic matching layer. If the amount of oxide powder dispersed in the
resin increases, the amount of resin existing between adjacent oxide powders decreases, and the
adhesion between the powder particles decreases, and oxidation occurs during polishing and
dicing. Product powder will be shattered. When the grain formation occurs, it is difficult to obtain
the dimensional accuracy, and in addition, there is a problem that the strength is extremely
reduced when microfabricated. Even if the density of the oxide powder is 6.5 g / cm <3> or more,
the same problem occurs unfavorably if the dispersed amount exceeds 30 vol%. In addition, when
the dispersion amount is less than 10 vol% and exceeds 30 vol%, the acoustic impedance for the
second acoustic matching layer is deviated from the desired acoustic impedance, which causes a
problem that the transmission and reception efficiency of ultrasonic waves is lowered.
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[0017]
In the ultrasonic probe according to the embodiment of the present invention, a material
containing 10 to 30 vol% of oxide powder of a perovskite structure containing 50% or more of
PbO and 1% or more of Nb2O5 in an organic resin as a second acoustic matching layer It is
preferable to use By dispersing the oxide powder of the perovskite structure containing 50% or
more of PbO and 1% or more of Nb2O5 in the organic resin, the oxide powder can be uniformly
dispersed, and the particle size reduction during array processing by dicing can be achieved. It
can be deterred. Furthermore, the oxide powder of the above-mentioned perovskite structure
contains the composition used also for the raw material of the piezoelectric body, and when the
second acoustic matching layer is metal-plated, the adhesion to the metal plating can be
improved. . Therefore, electrode peeling at the time of array processing can be suppressed.
[0018]
The ultrasonic probe according to the embodiment of the present invention uses, as the second
acoustic matching layer, a material containing 10 to 30 vol% of at least one selected from the
group consisting of CeO 2, Pr 2 O 3, Nd 2 O 3, Yb 2 O 3 and Lu 2 O 3 as an organic resin. Is
preferred. By dispersing the above-mentioned oxide powder in an organic resin, it becomes
possible to disperse the oxide powder uniformly, and it is possible to suppress the particle
shedding at the time of array processing by dicing.
[0019]
As described above, the second acoustic matching layer in the ultrasonic probe according to the
embodiment of the present invention can finish fine processing with high accuracy, because the
oxide powder dispersed in the resin at the time of array processing is significantly reduced. it
can. In addition, since the second acoustic matching layer has very good adhesion to metal (Au,
Ni) plating, electrode peeling during array processing can be suppressed, and conduction failure
of the element can be suppressed.
[0020]
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In the embodiment of the present invention, as the piezoelectric material, for example, Pb (B11-x,
Tix) O3 (wherein the value of x is 0.3 ≦ x ≦ 0.6, and B1 is selected from Zr, Sn and Hf). Or a
single crystal material having a composition represented by By using a piezoelectric body made
of such a solid solution type single crystal, the speed of sound can be made slower compared to a
piezoelectric body made of a piezoelectric ceramic, so a highly sensitive ultrasonic probe can be
obtained. In the above general formula, when x is less than 0.3, the Curie temperature of the
piezoelectric single crystal is lowered, and there is a possibility that depolarization occurs at the
time of cutting of the piezoelectric single crystal. On the other hand, when x exceeds 0.6, not only
a large electromechanical coupling coefficient can not be obtained, but also the matching of the
electrical impedance may be difficult when performing transmission and reception due to a
decrease in dielectric constant.
[0021]
In the embodiment of the present invention, as a piezoelectric material, Pb (B1, B2) 1-xTixO3
(wherein the value of x is 0.04 ≦ x ≦ 0.55, and B1 is Zn, Mg, Ni, Sc, A single crystal material
having a composition represented by at least one selected from the group consisting of In and Yb
and at least one selected from the group consisting of Nb and Ta may be used. By using a
piezoelectric body made of such a solid solution type single crystal, a high coupling coefficient
and a slow sound velocity can be realized compared to a piezoelectric body made of a
piezoelectric ceramic, so it is possible to obtain a highly sensitive ultrasonic probe. . In the above
general formula, when x is less than 0.04, the Curie temperature of the piezoelectric single
crystal is lowered, and there is a possibility that depolarization occurs when the piezoelectric
single crystal is cut. On the other hand, when x exceeds 0.55, not only a large electromechanical
coupling coefficient can not be obtained, but there is also a possibility that the matching of the
electrical impedance becomes difficult when transmitting and receiving due to the decrease of
the dielectric constant.
[0022]
Since these single crystal materials have higher piezoelectric properties than conventional
piezoelectric ceramics, they can be expected to improve the performance of ultrasonic probes
when applied to ultrasonic probes, but their mechanical strength is low. And chipping may cause
sensitivity variations. However, by using an acoustic matching layer containing the abovedescribed material, it is possible to suppress cracks and chipping during dicing, and it is possible
to produce a highly sensitive, wide-band single-crystal probe with small sensitivity variation and
high reliability.
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[0023]
The ultrasound probe according to the embodiment of the present invention can be used as
follows. As shown in FIG. 2, the first electrode 5 is connected to the ground plate 7, and the
second electrode 4 is connected to a not-shown ultrasonic diagnostic apparatus through a
flexible printed circuit board (FPC) 6. By applying a drive signal voltage from the ultrasonic
diagnostic apparatus to the piezoelectric body 1, the piezoelectric body 1 is vibrated and an
ultrasonic wave is transmitted from the acoustic lens 8 side. In addition, at the time of reception,
the ultrasonic wave received from the acoustic lens 8 is converted into an electric signal by the
piezoelectric body 1, and the received signal of each channel is delayed as desired by the beam
former in the ultrasonic diagnosis system. The phasing addition is performed by the middle
adder. After that, when measuring the fundamental wave, it passes through the fundamental
wave pass type filter in the ultrasonic diagnostic apparatus, and when measuring the second
harmonic, the high pass which removes the fundamental wave component in the ultrasonic
diagnostic apparatus Through a type filter, it visualizes with the monitor which is not illustrated.
[0024]
Next, a method of producing an ultrasonic probe according to an embodiment of the present
invention will be described. The manufacturing method of the piezoelectric ceramic used as a
piezoelectric material is demonstrated. Here, a method of producing a solid solution ceramic of
lead zirconate-lead titanate will be described. After using PbO, ZrO2, and TiO2 chemically high
purity as starting materials and correcting their purity, weigh them so that lead zirconate (PZ)
and lead titanate (PT) have a desired molar ratio, Pure water is added to this powder, and mixing
is carried out for a desired time by, for example, a ball mill containing ZrO 2 balls. After removing
the water content of the obtained mixture, the mixture is sufficiently ground by a grinder such as,
for example, a lai-kray machine. 5% by weight of polyvinyl alcohol is added to the pulverized
powder, mixed and granulated, and then pressed and molded with a mold. The molded body is
put in a magnesia sheath, degreased at 500 ° C., and fired at a desired temperature to obtain a
sintered body. After the sintered body is polished and processed, a conductive film is deposited
by sputtering, and the first electrode 5 and the second electrode 5 are respectively formed on the
ultrasonic transmitting and receiving surface of the piezoelectric body 1 and the surface opposite
to the transmitting and receiving surface by selective etching technology. To form a piezoelectric
element.
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[0025]
When a piezoelectric single crystal is used as the piezoelectric body, the piezoelectric single
crystal is manufactured according to the following procedure. Here, a method for producing a
solid solution single crystal of lead zinc niobate-lead titanate will be described. Using PbO, ZnO,
Nb2O5, and TiO2 which have high purity chemically as starting materials, after correcting the
purity of these, weighing so that zinc niobate (PZN) and lead titanate (PT) have desired molar
ratio And add PbO as a flux. Pure water is added to this powder, and mixing is carried out for a
desired time by, for example, a ball mill containing ZrO 2 balls. After removing the water content
of the obtained mixture, the mixture is sufficiently pulverized by, for example, a pulverizer such
as a lai-kai machine, and further placed in a rubber-type container, and a rubber press is
performed at a desired pressure. The solid removed from the rubber mold is placed in a
container of the desired volume, for example made of platinum, and melted at the desired
temperature. After cooling, the solid container is sealed, for example with a platinum lid, and the
container is placed at the center of the electric furnace. The temperature is raised to a
temperature higher than the melting temperature, gradually cooled to near the melting
temperature at a desired temperature lowering rate, and then cooled to room temperature.
Thereafter, nitric acid having a desired concentration is added to the vessel, and the vessel is
boiled to take out a solid solution single crystal, thereby obtaining a piezoelectric single crystal.
Here, single crystal growth by the flux method has been described. For example, a single crystal
manufactured by the Bridgman method, Kilopohrs method, hydrothermal growth method, TSSG
(Top Seeded Solution Growth) method, SSCG (Solid-State Single Crystal Growth) method, etc.
Crystalline materials can also be used. Here, although lead zinc niobate-lead titanate is mentioned
as an example, solid solution piezoelectric single crystals containing lead titanate obtained by
replacing the starting materials ZnO and Nb 2 O 5 with other elements can also be produced. .
After polishing and processing the obtained single crystal, a conductive film is deposited by
sputtering, and the first electrode 5 and the surface opposite to the ultrasonic transmitting and
receiving surface and the transmitting and receiving surface of the piezoelectric body 1 are
respectively selected by selective etching technology. The second electrode 4 is formed to obtain
a piezoelectric element.
[0026]
Next, a method of manufacturing an ultrasonic probe according to an embodiment of the present
invention will be described. Here, the case where a piezoelectric ceramic is used as the
piezoelectric body will be described.
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[0027]
The first acoustic matching layer 3a, on the entire surface of which a conductive layer (not
shown) made of metal or the like is formed by plating or the like, is adhered to the first electrode
5 side of the produced piezoelectric element by, for example, an epoxy adhesive. The first
acoustic matching layer 3a is formed of a solid inorganic substance. Similarly, a second acoustic
matching layer having a conductive layer (not shown) formed on the entire surface is bonded to
the first acoustic matching layer 3a. The second acoustic matching layer 3 b is formed of a
material containing 10 to 30 vol% of oxide powder having a density of 6.5 g / cm <3> or more in
an organic resin. The acoustic impedance of the second acoustic matching layer is made smaller
than the acoustic impedance of the first acoustic matching layer 3a in order to achieve acoustic
impedance matching with the object. Next, the FPC 6 having a plurality of conductor layers
(cables) 6a on the insulating layer 6b is adhered to the second electrode 4 side of the
piezoelectric element by using, for example, an epoxy adhesive. Thereafter, these are adhered
onto the acoustic backing material 2 so that the FPC 6 is in contact with the acoustic backing
material 2. By cutting a plurality of times from the acoustic matching layer to the FPC 6 using a
blade, a laminate of the piezoelectric element and the acoustic matching layer is arranged in an
array on the acoustic backing material 2 and separated from each other. Next, on the second
acoustic matching layer 3b, the ground plate 7 having the conductive layer 7a plated on the
insulating layer 7b is adhered, for example, with an epoxy adhesive. Further, the third acoustic
matching layer 3c is adhered to the earth plate 7 with an organic adhesive, and the acoustic lens
8 is formed thereon to obtain an ultrasonic probe.
[0028]
Even when a piezoelectric single crystal is used as the piezoelectric body, an ultrasonic probe can
be obtained by the same method. When the crystal system of the piezoelectric single crystal used
as the piezoelectric body 1 is rhombohedral or pseudo cubic, it is preferable that the ultrasonic
wave transmitting / receiving surface on the side of the first electrode 5 is a (001) plane. Such a
piezoelectric body 1 is produced by cutting out perpendicularly to the [001] axis (C axis) of the
piezoelectric single crystal.
[0029]
The first electrode 5 and the second electrode 4 are formed of, for example, a two-layer
conductive film of Ti / Au, Ni / Au or Cr / Au, or silver baking including glass frit. Although the
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two-layer structure and the three-layer structure are shown as the acoustic matching layer, a
multilayer structure of more than two layers may be used. The ground plate 7 adheres the
conductive layer to the sputtered second acoustic matching layer 3b, but does not have to adhere
to the entire second acoustic matching layer 3b, and may adhere only to both ends. Also, the
ground plate 7 may be bonded to the first acoustic matching layer 3a.
[0030]
EXAMPLES The present invention will be described in more detail based on examples given
below, but the invention is not meant to be limited by these.
[0031]
Example 1 Using PbO, ZrO2, and TiO2 having high purity chemically as starting materials and
correcting their purity, the molar ratio of lead zirconate (PZ) to lead titanate (PT) is 53: 47. The
powder was weighed so that pure water was added to the powder, and mixed for a desired time
by, for example, a ball mill containing ZrO 2 balls.
After removing the water content of the obtained mixture, it was sufficiently pulverized by a
pulverizer such as, for example, a lycai machine. 5% by weight of polyvinyl alcohol is added to
the pulverized powder, mixed and granulated, and then pressed and molded with a mold. The
molded body was put in a magnesia sheath, degreased at 500 ° C., and fired at 1250 ° C. to
obtain a sintered body.
[0032]
The sintered body is polished and processed into a piezoelectric body of 30 mm × 20 mm × 0.4
mm in size, and then a first electrode and a second electrode made of Cr / Au are formed by a
sputtering method to form a piezoelectric element And An electric field of 3 kV / mm was applied
to the piezoelectric element to perform polarization treatment. The acoustic impedance of this
piezoelectric element was 30 Mrayls.
[0033]
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On the first electrode side of this piezoelectric element, a Cr / Au electrode is formed on the
entire surface by sputtering, and an acoustic impedance is 13 Mrayls of a first acoustic matching
layer made of a ceramic containing SiO2, MgO and Al2O3 as an epoxy adhesive Glued. A Cr / Au
electrode is sputtered on a flat plate obtained by polishing and processing an epoxy resin in
which 10 vol% of cerium oxide (CeO 2) powder (density: 7.65 g / cm 3) is dispersed on the first
acoustic matching layer. A second acoustic matching layer formed on the entire surface by an
adhesive method was adhered with an epoxy adhesive. The acoustic impedance of the second
acoustic matching layer was 5 Mrayls. Thereafter, an FPC having a conductive layer made of Cu
on the second electrode side of the piezoelectric element and an acoustic backing material were
sequentially bonded with an epoxy adhesive.
[0034]
Next, the laminate of the piezoelectric element and the acoustic matching layer was cut into an
array at a pitch of 200 μm by a dicing saw having a blade with a thickness of 50 μm. After that,
a ground plate made of Au is bonded to the entire second acoustic matching layer with an epoxy
adhesive, and a third acoustic matching layer made of a polyethylene sheet on the ground plate
and having an acoustic impedance of 2 Mrayls is used as an epoxy adhesive. Glued. An acoustic
lens made of silicone rubber was bonded onto the third acoustic matching layer with a silicone
adhesive.
[0035]
When the capacitance of the piezoelectric of the completed ultrasonic probe was measured at 1
kHz from the end of the FPC, the average value of the 100 channels of piezoelectric arranged in
one ultrasonic probe is 90 pF, and the variation is 10% or less And was a good value. After that, a
coaxial cable with a capacitance of 110 pF / m and a length of 2 m was connected to the FPC and
connected to the diagnostic device to evaluate the ultrasonic probe characteristics. The variation
in sensitivity between them is as small as 15% or less.
[0036]
(Example 2) Oxide powder (density: 7.90 g / cm) containing PbO: 65 wt%, ZrO2: 20 wt%, TiO2:
10 wt%, MgO, 1 wt%, Nb2O 5: 4 wt% as a second acoustic matching layer The epoxy resin which
disperse | distributed 20 wt% of <3> was grind | polished and shape | molded, and what formed
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Cr / Au electrode by the sputtering method in the outer peripheral whole surface was used. The
second acoustic impedance was 5 Mrayls. An ultrasonic probe was produced in the same manner
as in Example 1 except for the second acoustic matching layer. When the capacitance of the
piezoelectric body of the ultrasonic probe completed in the same manner as in Example 1 was
measured at 1 kHz from the end of the FPC, the average value of 100 channels of piezoelectric
bodies included in one ultrasonic probe is 90 pF, which is uneven Was a good value of 8% or less.
In addition, when the ultrasonic probe characteristics were evaluated in the same manner as in
Example 1, the sensitivity was wide, and the sensitivity variation between channels was as very
small as 10% or less.
[0037]
Example 3 First, lead indium niobate Pb (In1 / 2Nb1 / 2) O3 (PIN), lead magnesium niobate Pb
(Mg1 / 3Nb2 / 3) O3 (PMN), and lead titanate PbTiO3 (PT). Mixed powder of 0.16 Pb (In1 /
2Nb1 / 2) O3-0.51 Pb (Mg1 / 3 Nb2 / 3) O3-0.33 PbTiO3 (PIMNT 16/51/33) weighed to have a
molar ratio of 16:51:33 , PbO used as a flux, and B2O3 are put in a 200 cc platinum container so
that the molar ratio of PIMNT16 / 51/33: PbO: B2O3 = 50: 40: 10 is raised to 1250 ° C. and
dissolved After cooling to room temperature, a solid solution piezoelectric single crystal was
grown. Thereafter, using a Laue camera, the orientation of the <001> axis of this piezoelectric
single crystal is determined, and the wafer is cut perpendicularly to this axis by a cutter to obtain
a wafer having a thickness of 600 μm. The cut piezoelectric single crystal is polished to a
thickness of 350 μm to form a 30 mm × 20 mm × 0.4 mm piezoelectric body, and then a first
electrode and a second electrode made of Cr / Au are formed by sputtering. As a piezoelectric
element. An electric field of 1 kV / mm was applied to the piezoelectric element to perform
polarization treatment. The acoustic impedance of this piezoelectric element was 25 Mrayls.
[0038]
Thereafter, in the same manner as in Example 2, an ultrasonic probe was produced. The
capacitance of the piezoelectric body of the ultrasonic probe completed in the same manner as in
Example 1 was measured at 1 kHz from the end of the FPC, and the average value of 100
channels of piezoelectric bodies included in one ultrasonic probe was 80 pF. Was a good value of
15% or less. In addition, when the ultrasonic probe characteristics were evaluated in the same
manner as in Example 1, the sensitivity was wide, and the sensitivity variation between channels
was as very small as 10% or less.
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[0039]
Example 4 In the same manner as in Example 3, a solid solution single crystal composed of lead
stannate PbSnO 3 (PSn) and lead titanate PbTiO 3 (PT) was obtained. Thereafter, in the same
manner as in Example 2, an ultrasonic probe was produced. When the capacitance of the
piezoelectric body of the ultrasonic probe completed in the same manner as in Example 1 was
measured at 1 kHz from the end of the FPC, the average value of 100 channels of piezoelectric
bodies included in one ultrasonic probe is 85 pF, which is uneven Was a good value of 14% or
less. In addition, when the ultrasonic probe characteristics were evaluated in the same manner as
in Example 1, the sensitivity was wide, and the sensitivity variation between channels was as very
small as 10% or less.
[0040]
Comparative Example 1 An ultrasonic probe was produced in the same manner as in Example 1
except that the method of producing the first and second acoustic matching layers was changed
to the following method.
[0041]
The first acoustic matching layer is a flat plate obtained by polishing and processing an epoxy
resin in which 40 wt% of tungsten metal powder is dispersed, and a Cr / Au electrode is formed
on the entire surface by a sputtering method.
The acoustic impedance of the first acoustic matching layer was 13 Mrayls. The first acoustic
matching layer was adhered to the first electrode side of the piezoelectric element with an epoxy
adhesive. An epoxy resin in which 60 vol% of zinc oxide (ZnO) or silica (SiO 2) powder (density:
5.60 g / cm <3> and 2.65 g / cm <3>) is dispersed on the first acoustic matching layer A second
acoustic matching layer, in which a Cr / Au electrode was formed on the entire surface by a
sputtering method, was bonded to a flat plate which had been polished and profiled with an
epoxy adhesive. The acoustic impedance of the second acoustic matching layer was 5 Mrayls.
[0042]
When the capacitance of the piezoelectric body of the ultrasonic probe completed in the same
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manner as in Example 1 was measured at 1 kHz from the end of the FPC, the average value of
100 channels of piezoelectric bodies included in one ultrasonic probe is 90 pF, which is uneven
Was as large as 20% or more. In addition, it included three conduction failure channels. This is
because the metal powder is dispersed in the first acoustic matching layer, so the load on the
blade during array processing is large and the blade gradually deteriorates. When cutting is
performed using a blade with reduced machinability, chipping and cracking of the piezoelectric
body occur to cause variation in capacity. Further, since the second acoustic matching layer
contains 30 vol% or more of the oxide powder, the adhesion between adjacent particles is
reduced and the particles fall off during array processing. A part of the electrode may peel off as
the particles fall off, which may cause disconnection. Further, when the ultrasonic probe
characteristics were evaluated in the same manner as in Example 1, although the channels
having high sensitivity and wide band were observed in some places, the sensitivity variation
between channels was very large at 25% or more. Such variation in sensitivity between channels
adversely affects the image quality of the tomogram displayed on the diagnostic device.
[0043]
Comparative Example 2 An ultrasonic probe was produced in the same manner as in Example 1
except that the method for producing the second acoustic matching layer was changed to the
following method.
[0044]
On the first electrode side of the piezoelectric element, a Cr / Au electrode is formed on the
entire surface by sputtering method, and an acoustic impedance is 13Mrayls of a first acoustic
matching layer made of ceramic containing SiO2, MgO and Al2O3 using an epoxy adhesive.
Glued.
The first acoustic matching layer is a flat plate obtained by polishing and processing an epoxy
resin in which 60 vol% of zinc oxide (ZnO) or silica (SiO 2) powder is dispersed, and a Cr / Au
electrode is formed on the entire surface by sputtering. The two acoustic matching layers were
bonded with an epoxy adhesive. The acoustic impedance of the second acoustic matching layer
was 5 Mrayls.
[0045]
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When the capacitance of the piezoelectric body of the ultrasonic probe completed in the same
manner as in Example 1 was measured at 1 kHz from the end of the FPC, the average value of
100 channels of piezoelectric bodies of one ultrasonic probe is 90 pF Was as large as 15% or
more. In addition, it included one conduction failure channel. This is because the second acoustic
matching layer contains 30 vol% or more of the oxide powder, so the adhesion between adjacent
particles is reduced and the particles fall off during array processing. A part of the electrode
peels off as the grains fall off, which causes a break. Further, when the ultrasonic probe
characteristics were evaluated in the same manner as in Example 1, although the channels
having high sensitivity and wide band were seen in some places, the sensitivity variation between
channels was very large at 20% or more. Such variation in sensitivity between channels adversely
affects the image quality of the tomogram displayed on the diagnostic device.
[0046]
Fifth Embodiment Next, an ultrasonic diagnostic apparatus using the ultrasonic probe of the first
embodiment will be described with reference to FIG. A medical ultrasonic diagnostic apparatus or
ultrasonic image inspection apparatus that transmits an ultrasonic signal to an object, receives a
reflected signal (echo signal) from the object, and forms an image of the object, as shown in FIG.
An array-type ultrasonic probe 10 having an ultrasonic signal transmitting / receiving function
as shown in FIG. 1 is mainly used. The ultrasonic probe 10 is connected to an ultrasonic probe
control unit 15 via a cable 11. In addition, a screen 16 is provided on the main body.
[0047]
The perspective view explaining the ultrasonic probe concerning the embodiment of the present
invention. BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing explaining the ultrasound
probe which concerns on embodiment of this invention. The schematic diagram which shows the
ultrasound diagnosing device of Example 5 of this invention.
Explanation of sign
[0048]
DESCRIPTION OF SYMBOLS 1 ... Piezoelectric body, 2 ... acoustic backing material, 3a ... 1st
acoustic matching layer, 3b ... 2nd acoustic matching layer, 3c ... 3rd acoustic matching layer, 3 ...
acoustic matching layer, 4 ... 2nd electrode , 5: first electrode 6a: conductive layer 6b: insulating
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layer 6: flexible printed wiring board 7a: conductive layer 7b: insulating layer 7: earth plate 8:
acoustic lens 10: ultrasonic probe , 11: cable, 15: ultrasonic probe control unit, 16: screen.
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