JP2002354591

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DESCRIPTION JP2002354591
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
array-type ultrasound probe (array-type probe) in the technical field of industry, and more
particularly to a method of deriving an earth wire.
[0002]
BACKGROUND OF THE INVENTION Arrayed probes are used, for example, as ultrasonic wave
transmission / reception sources in medical ultrasound diagnostic devices. Usually, a plurality of
piezoelectric elements are aligned and electronically driven in sectors or in a linear manner to
obtain a tomographic image.
[0003]
(An example of prior art) FIGS. 4 and 5 are views of an arrayed probe for explaining an example
of the prior art, FIG. 4 is a side sectional view, and FIG. 5 is a plan view. The arrayed probe is
formed by arranging a plurality of piezoelectric elements 2 having upper and lower surface
electrodes 1 (ab) on a backing material 3. An acoustic matching layer 4 is formed in the central
region of the piezoelectric element 2 to match the acoustic impedance with the living body.
Usually, after the piezoelectric plate is fixed on the backing material 3 and the continuous
acoustic matching layer is laminated, the piezoelectric plate 2 and the acoustic matching layer 4
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are cut and divided.
[0004]
Then, lead wires 5 (ab) are connected to the surfaces of both end portions by solder, and the
upper surface electrodes 1 a are connected in common to make a ground potential. Thereafter, a
filler (not shown) is embedded between the piezoelectric elements 2 and the acoustic matching
layer 4. In each lower surface electrode 1b, metal foils 6 for leading out the electrodes are
connected in a staggered manner at both end portions, and a drive voltage is applied.
[0005]
[Problems to be Solved by the Invention] (Problems of the Prior Art) However, in the array type
probe of the above configuration, when connecting the lead wire to the upper surface electrode
1a of the piezoelectric element 2, the upper surface electrode 1a is heated by the heat of the
solder. There is a problem of peeling (so-called solder corrosion). For example, when the
adhesion strength of the electrode is small as in the case of a composite piezoelectric material,
this becomes a particularly significant problem. In addition, there is a problem of thermal
damage in which the piezoelectricity of the piezoelectric element 2 is impaired by the heat of the
solder.
[0006]
For this reason, for example, use of the conductive adhesive 7 was considered instead of the
solder. However, in this case, there is a problem that the conductive adhesive 7 intrudes into the
groove between the piezoelectric elements 2 to electrically connect the upper and lower surface
electrodes 1 (ab) (FIG. 6). In the case of solder, it does not intrude into the part without the
electrode.
[0007]
In addition, it is also conceivable to connect the lead wires 5 (ab) after embedding the filler in the
groove between the piezoelectric elements 2, but in this case, the filler adheres to the surfaces of
both ends of the piezoelectric element 2. There was a problem of impairing the electrical
continuity.
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[0008]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an arrayed
probe in which thermal damage to the top electrode and the piezoelectric element is prevented.
[0009]
SUMMARY OF THE INVENTION According to the present invention, a metal foil is bonded to the
end surface of a piezoelectric element by a conductive adhesive, and lead wires are commonly
connected to the metal foil as a basic solution. .
[0010]
In the present invention, metal foils are bonded to the end surface of the piezoelectric element
with a conductive adhesive to commonly connect the lead wires.
Thus, the conductive adhesive blocks the heat of the solder and reduces the heat transfer to the
top electrode and the piezoelectric element.
In addition, since the electrodes of the piezoelectric element are not directly soldered, no solder
corrosion occurs.
Hereinafter, one embodiment of the present invention will be described.
[0011]
1 and 2 are views of an array-type probe for explaining an embodiment of the present invention,
FIG. 1 is a side sectional view, and FIG. 2 is a partial front sectional view. The description of the
same parts as in the prior art example is simplified or omitted. In the array type probe, as
described above, the plurality of piezoelectric elements 2 having the upper and lower surface
electrodes 1 (ab) are aligned on the backing material 3, and the acoustic matching layer 4 is
formed in the central region. The metal foils 6 for leading out the electrodes are connected in a
staggered manner at both ends.
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[0012]
Then, in this embodiment, after the piezoelectric plate and the continuous acoustic matching
layer 4 are fixed on the backing material 3, the continuous metal foil is fixed to the surface of
both end portions of the top electrode 1 a by the conductive adhesive 7. Next, the metal foil and
the conductive adhesive 7 are cut together with the piezoelectric plate and the continuous
acoustic matching layer to obtain the metal foil 8 fixed by the individual piezoelectric elements 2,
the acoustic matching layer 4 and the conductive adhesive 7. Then, lead wires 5 (ab) are
connected in common to both ends of the upper surface electrode 1a by solder (not shown), and
set to the ground potential. Then, a filler (not shown) is embedded between the grooves.
[0013]
With such a configuration, the conductive adhesive 7 and the metal foil 8 are interposed between
the upper surface electrode 1 a of the piezoelectric element 2 and the solder. Therefore, the
solder is not in direct contact with the upper surface electrode 1 a and the heat of the solder is
absorbed and cut off by the resin component (heat capacity) of the conductive adhesive 7. This
prevents electrode peeling without causing solder corrosion. Then, the heat transfer to the
piezoelectric element 2 is reduced to maintain the piezoelectricity favorably. From these things,
the heat damage of the upper surface electrode 1a and the piezoelectric element 2 by solder heat
is prevented.
[0014]
[Second Embodiment] FIG. 3 is a side sectional view of an array type probe for explaining another
embodiment of the present invention. The description of the same parts as those of the previous
embodiment will be omitted. In this embodiment, the metal foil 8 is connected by the conductive
adhesive 7 so as to protrude from both ends of the piezoelectric element 2. An insulating
adhesive 9 is provided on the lower surface of the protrusion of the metal foil 8 to fix the
protrusion. Then, lead wires 5 (ab) are connected on the protruding portions by a conductive
adhesive (not shown), and the upper surface electrodes 1 a are electrically connected in common.
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[0015]
In such a case, since the lead wire 5 (ab) is connected on the protrusion of the metal foil 8, the
conductive adhesive does not intrude between the grooves of each piezoelectric element 2. And
since it connects by a conductive adhesive, it can join at low temperature rather than a solder.
Therefore, the thermal damage to the upper surface electrode 1a and the piezoelectric element 2
can be further reduced.
[0016]
Not only the conductive adhesive but also solder may be used for connection. Even in this case,
since the lead wire 5 (ab) is detached from the top electrode 1a and connected, and the heat
capacity of the insulating adhesive 9 is also added to prevent heat transfer, it is possible to
further reduce the thermal damage.
[0017]
[Other Matters] In the above embodiments, the lead wires 5 (ab) are disposed on the surfaces of
both ends of the piezoelectric element 2, but they may be surfaces of one end. In this case, the
acoustic matching layer 4 can be formed on the entire surface except for the one end surface. In
addition, although the lower surface electrode 1b is led out in a zigzag form from both ends by
the metal foil 6, it may be derived only from one end. Although the piezoelectric elements 2 are
arranged on a plane, those arranged on a curved surface can also be applied.
[0018]
According to the present invention, since the metal foil is bonded to the end surface of the
piezoelectric element by the conductive adhesive and the lead wire is commonly connected to the
metal foil, thermal damage to the upper surface electrode and the piezoelectric element is
prevented. An array type probe can be provided.
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