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JPH10170487

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DESCRIPTION JPH10170487
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic probe used in an ultrasonic flaw detector and a method of manufacturing the same.
[0002]
2. Description of the Related Art FIG. 3 shows how to take out the conventional upper and lower
electrodes. After bonding at normal temperature (low temperature), the upper electrode 5 is
drawn the lead wire 17 from the joined damper material (lead) 10 by the conductive resin 11.
Further, the lower electrode 3 directly leads the lead wire 12 from the lower electrode of the
piezoelectric element 4 by the conductive resin 11.
[0003]
FIG. 4 is a cross-sectional view of the completed ultrasonic probe in which the assembly shown in
FIG. In FIG. 4, when the lead wire 12 is drawn from the lower electrode 3 via the conductive resin
11, the lead wire 12 uses a thin wire in consideration of the performance of the probe, and the
area of the conductive resin 11 The ratio (area of conductive resin / area of piezoelectric
element) is made as small as possible. Accordingly, the lower electrode 3 and the lead wire 12
may be peeled off in the manufacturing process of housing the assembly shown in FIG. 3 in the
case 8. There is also a limit to reducing the area ratio of the conductive resin 11 in order to avoid
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peeling of the lead wire 12.
[0004]
Therefore, in the case of the conventional ultrasonic probe as shown in FIG. 3 and FIG. 4, not only
the efficiency of the manufacturing operation is poor, but also the conductive resin is partially
located on the front surface of the piezoelectric element. There is a problem in performance.
[0005]
Accordingly, an object of the present invention is to provide an ultrasonic probe capable of stably
connecting the GND (ground) wire from the lower electrode and having good manufacturing
efficiency and performance, and a method of manufacturing the same. It is to provide.
[0006]
[Means for Solving the Problems] The above object is to fix the room temperature bonded
piezoelectric element and the damper material in a case and fix them, and insert metal powder
such as tungsten into thermoplastic resin for acoustic lens in advance. The lower electrode and
the case are conducted by pouring the metal on the lower electrode side and then placing it on a
rotating table and rotating it at high speed, and arranging metal powder such as tungsten by the
centrifugal force due to the specific gravity on the outer periphery of the acoustic lens. To be
achieved.
[0007]
In addition, metal powder such as tungsten for conduction is arranged on the outer periphery of
the acoustic lens, so the influence on the front side radiation of the ultrasonic wave is reduced as
compared with the prior art, and the performance is improved.
[0008]
DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a cross-sectional view of an
ultrasonic probe according to the present invention.
Similar to the conventional ultrasonic probe shown in FIG. 3 and FIG. 4, the upper electrode 5
and the lower electrode 3 are joined to the piezoelectric element 4.
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An assembly of the piezoelectric element and the upper and lower electrodes forms an ultrasonic
transducer 2.
The piezoelectric element 4 is made of, for example, PbTiO 3 or the like.
The lower electrode and the upper electrode are both made of chromium, gold or the like. The
damper material 10 is bonded to the ultrasonic transducer 2 at normal temperature (low
temperature), and the outer peripheral surface is covered with the insulating layer 7 to be
insulated. The damper material is made of, for example, metallic lead. The insulating layer 7 can
be made of, for example, an epoxy resin. The assembly covered with the insulating layer 7 is
housed in a metal case 8. The insulating layer 7 insulates the damper material 10 from the metal
case 8. One end of the case 8 protrudes beyond the lower electrode 3, and the acoustic lens 6 is
disposed in a recess formed by the protrusion.
[0009]
Unlike the conventional ultrasonic probe shown in FIG. 3 and FIG. 4, in the ultrasonic probe of
the present invention, the conduction between the lower electrode 3 and the case 8 is not in the
lead wire but in the acoustic lens 6 Made by the lump of the metal powder 1 The lump of the
metal powder 1 is disposed along the lower outer end edge in the acoustic lens 6 to electrically
connect the lower electrode 3 and the metal case 8. The electric signal source 9 is connected to
the metal case 8 and the damper material 10 by lead wires 16 and 17 and conductive resins 11
and 18, respectively.
[0010]
FIG. 2 is a schematic sectional view showing a method of manufacturing an ultrasonic probe
according to the present invention. The ultrasonic transducer 2 is joined at room temperature to
the damper material 10, covered with the insulating layer 7, housed in a metal case 8, fixed with
an adhesive, and then fixed to the rotary table 14. Thereafter, a resin in which a conductive metal
powder 1 such as tungsten is blended in advance into a thermoplastic resin for an acoustic lens
is poured into the case from the lower electrode 3 side. Then, the case 8 is rotated at high speed
by the rotating table 14. As a result, the conductive metal powder 1 in the resin for the acoustic
lens 6 is arranged along the outer peripheral edge of the case 8 at the lower part in the acoustic
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lens 6 by the centrifugal force. Thereby, the lower electrode 3 and the metal case 8 are
conducted.
[0011]
Thereafter, the steel ball 13 is bonded to the upper end of the case 8 with the resin 15, and the
thermoplastic resin for the acoustic lens 6 is solidified to form the acoustic lens 6. The diameter
of the steel ball 13 is not particularly limited. The diameter of the steel ball 13 is naturally
restricted by the design curvature of the acoustic lens 6. As long as the design curvature of the
acoustic lens 6 can be formed, not only the steel ball but any arbitrary member can be used.
[0012]
Thermoplastic resins for the acoustic lens 6 are well known to those skilled in the art. For
example, epoxy-based thermoplastic resins can be suitably used. For example, the thermoplastic
resin is poured in a molten state from a suitable applicator into the case and cured at 20 ° C to
100 ° C. The conductive metal compounded in the thermoplastic resin is, for example, tungsten,
nickel, gold, copper, silver or alloys thereof. The conductive metal is preferably mixed in powder
form in the thermoplastic resin. The particle size of the conductive metal powder 1 is not
particularly limited, but generally, it is preferably 6 μm or less (in the case of 25 MHz). When
the particle size of the conductive metal powder is more than 6 μm, the volume is increased and
it appears on the end face of the concave surface of the lens, and it is not preferable because it is
corroded when it comes in contact with water. Although the compounding quantity of the
electroconductive metal powder in the thermoplastic resin for acoustic lenses is not specifically
limited, Generally, it is preferable to exist in the range of 50 wt%-60 wt%. If the compounding
amount of the conductive metal powder is less than 50 wt%, there is a possibility that sufficient
conduction between the lower electrode and the metal case can not be secured. On the other
hand, when the compounding amount of the conductive metal powder is more than 60 wt%, a
part of the piezoelectric element 4 is covered, which is not preferable because the sound field is
disturbed upon transmission of the ultrasonic wave.
[0013]
As described above, since the thermoplastic resin is poured into the case in a molten state, the
case 8 is rotated at a high speed before the resin loses fluidity, and the conductive metal powder
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is moved to the lower portion of the case 8 by the action of centrifugal force. It must be arranged
along the inner wall. The rotation speed of the case 8 by the rotation table 14 is not particularly
limited, but in general, it is preferably in the range of 1000 rpm to 1500 rpm. If the rotation
speed is less than 1000 rpm, only insufficient centrifugal force can be obtained to align the
conductive metal powder in the thermoplastic resin for an acoustic lens along the inner
peripheral edge of the case 8. On the other hand, if the rotational speed is more than 1,500 rpm,
the acoustic lens thermoplastic resin itself may be released to the outside of the case 8. The case
8 can also be rotated with the steel ball 13 placed on the upper end of the case 8.
[0014]
As described above, according to the present invention, since the lower electrode 3 and the metal
case 8 are connected by the conductive metal in the thermoplastic resin for an acoustic lens, the
lower electrode 3 and the metal are made of metal. Not only the conduction with the case 8 is
stabilized, but also the manufacturing efficiency is greatly improved since no lead wire is used.
Further, since the area ratio of the conductive metal in the thermoplastic resin for acoustic lens
on the surface of the lower electrode can also be reduced, a stable sound field can be easily
obtained by connecting to the electric signal source 9 in water. .
[0015]
Brief description of the drawings
[0016]
1 is a schematic cross-sectional view of the ultrasonic probe of the present invention.
[0017]
2 is a schematic sectional view showing a method of manufacturing the ultrasonic probe of the
present invention shown in FIG.
[0018]
3 is a schematic sectional view showing a bonded assembly of the ultrasonic transducer and the
damper material in the conventional ultrasonic probe.
[0019]
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4 is a schematic cross-sectional view of a conventional ultrasound probe having the assembly
shown in FIG.
[0020]
Explanation of sign
[0021]
DESCRIPTION OF SYMBOLS 1 electroconductive metal powder lump 2 ultrasonic transducer 3
lower electrode 4 piezoelectric element 5 upper electrode 6 acoustic lens 7 insulating layer 8
metal case 9 electric signal source 10 damper material 11, 12, 18, electroconductive resin 13
steel ball 14 rotation 16, 17 lead wire
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