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DESCRIPTION JP2001025091

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DESCRIPTION JP2001025091
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a 13 composite piezoelectric vibrator plate useful for producing an ultrasonic probe and a method
for producing the same.
[0002]
2. Description of the Related Art A 1-3 composite piezoelectric vibrator plate is a 1-3 composite
piezoelectric body having a structure in which a one-dimensional thin rod of piezoelectric
ceramic is embedded in a three-dimensional matrix of a polymer material. The electrodes are
formed on the upper and lower surfaces of the first and second composite piezoelectric
members, and the first and third composite piezoelectric vibrator plates are manufactured by
polarization processing of the first and third composite piezoelectric members. As a piezoelectric
vibrator having a high electro-mechanical coupling coefficient and a low acoustic impedance, the
piezoelectric vibrator has a high electro-mechanical coupling coefficient since it is configured by
combining a piezoelectric ceramic having a high electro-mechanical coupling coefficient and a
polymer material having a low acoustic impedance. It is known that it is useful in preparation of
an ultrasound probe.
[0003]
An ultrasonic probe using the above 1-3 composite piezoelectric transducer plate converts an
electric pulse into an ultrasonic wave and converts an ultrasonic pulse into an electric signal as
shown in FIG. 3 and FIG. 1-3 complex piezoelectric vibrator plate 1 for conversion, an acoustic
matching layer 9 for efficiently emitting ultrasonic waves with a short waveform to the human
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body, and sound on the back surface of the 1-3 complex piezoelectric vibrator plate 1 It is
composed of a packing material 8 which performs a damping action and an acoustic lens 10 for
focusing an ultrasonic beam.
[0004]
That is, as shown in FIG. 3, the ultrasonic probe has a ground on the electrodes 4 of the 1-3
composite piezoelectric vibrator plate 1 in which the electrodes 4 are formed on the upper and
lower surfaces of the 1-3 composite piezoelectric body 2. As shown in FIG. 4, the lead frame 6
and the signal lead frame 7 are electrically bonded by the bonding material 5, disposed on the
packing 8, and the acoustic matching layer 9 is bonded on the electrode 4 on the upper surface.
The slices are cut at a fixed width, resin is injected into the cuts, and the acoustic lens 10 is
attached to the top of the whole.
However, in FIG. 4, illustration of the bonding material 5 is omitted in order to avoid
complication.
[0005]
However, although the above 1-3 composite piezoelectric vibrator plate has the above-mentioned
excellent characteristics, it has a matrix structure of a polymer material, so the heat resistance is
poor, and therefore, In the case of the assembly to the ultrasonic probe manufactured by
requiring the above-mentioned complicated processes, it had the following problems.
[0006]
The electrodes of the 1-3 composite piezoelectric vibrator plate are formed of gold or the like by
a sputtering method which is relatively resistant to heat, and are themselves expensive.
In the case of a piezoelectric vibrator plate made of ordinary piezoelectric ceramics, the
electrodes are excellent in heat resistance when the electrodes of the 1-3 composite piezoelectric
body are electrically connected to the ground lead frame or the signal lead frame. It can be made
of silver by the baking method, which makes it possible to perform electrical bonding with a
solder with strong bonding strength, but in the case of a 1-3 composite piezoelectric vibrator
plate, the heat resistance of the polymer material is poor Therefore, solder can not be used, and a
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conductive adhesive that cures at a low temperature has to be used.
However, since the conductive adhesive has a low bonding strength, a defect such as peeling of a
bonding portion is likely to occur at the time of slice cutting in a later step.
[0007]
The present invention solves the problems in the prior art as described above, and makes the
ultrasonic probe using the 1-3 composite piezoelectric transducer plate more reliable, reliable,
and less expensive. An object is to provide a 1-3 composite piezoelectric vibrator plate that can
be manufactured.
[0008]
SUMMARY OF THE INVENTION The present invention is directed to a 1-3 composite
piezoelectric comprising a 1-3 composite piezoelectric comprising a piezoelectric ceramic and a
polymer material, and electrodes formed on the upper and lower surfaces thereof. In the vibrator
plate, by forming a nickel layer as the electrode, bonding with the solder of the ground lead
frame or the signal lead frame to the electrode is enabled, and the above problem is solved.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION The thickness of the nickel layer as the
electrode is preferably 1 to 8 μm.
If the thickness of the nickel layer is less than 1 μm, solder corrosion (a phenomenon in which
the nickel layer melts into the solder) may occur, or a problem may occur in solderability
(solubility by solder) such as poor solder wettability. If the thickness of the nickel layer exceeds 8
μm, the solderability does not change, but it becomes easy to peel off.
[0010]
Here, the 1-3 composite piezoelectric vibrator plate of the present invention in which the
electrode is formed of a nickel layer will be described based on FIG. It comprises the body 2 and
electrodes 4 formed on the upper and lower surfaces thereof.
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The 1-3 composite piezoelectric body 2 is not shown in FIG. 1, but a one-dimensional thin rod of
piezoelectric ceramic (this thin rod may have any shape such as a prismatic column shape or a
cylindrical shape, etc.) The electrode 4 is configured to be embedded in a three-dimensional
matrix of the material (however, the upper surface of the piezoelectric ceramic is often not
embedded), and the electrode 4 is formed of a nickel layer.
[0011]
Furthermore, in the present invention, nickel layers are formed on the upper surface and the
lower surface of the 1-3 composite piezoelectric body, and silver is formed on the nickel layers,
except when the electrode is made of only the nickel layer as described above. Solder wettability
is further improved by forming a layer of tin or tin-lead alloy and forming the electrode with a
nickel layer and a layer of silver, tin or tin-lead alloy formed on the nickel layer be able to. As a
result, it becomes possible to shorten the heating time of the solder, reduce the damage of the
polymer part of the 1-3 composite piezoelectric body, and make it possible to perform the
bonding by the solder more strongly, etc. Therefore, this form is particularly preferable as the 13 composite piezoelectric vibrator plate of the present invention.
[0012]
Here, FIG. 2 shows a 1-3 composite piezoelectric vibrator plate in which the electrode is
composed of a nickel layer and a layer of silver, tin or tin-lead alloy formed on the nickel layer as
described above. In this preferred embodiment, the 1-3 composite piezoelectric oscillator plate 1
is formed on the 1-3 composite piezoelectric body 2, the nickel layer 4a formed on the upper and
lower surfaces thereof, and the nickel layer 4a. And an electrode 4 comprising a layer 4b of
silver, tin or tin-lead alloy.
[0013]
In the above preferred embodiment, the thickness of the nickel layer is 0.5 to 4 μm, the
thickness of the layer of silver, tin or tin-lead alloy is 0.5 to 5 μm, and the thickness of the nickel
layer and silver, tin or It is preferable that the sum with the thickness of the tin-lead alloy layer is
1 to 8 μm.
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If the thickness of the nickel layer is less than 0.5 μm, peeling is likely to occur after soldering.
In addition, when the thickness of the silver, tin or tin-lead alloy layer is less than 0.5 μm, the
improvement of the solder wettability can not be expected so much. Furthermore, if the nickel
layer exceeds 4 μm, the silver, tin or tin-lead alloy layer exceeds 5 μm, and the sum of the
nickel layer thickness and the silver, tin or tin-lead alloy layer thickness is 8 μm. In the case of
exceeding, it is not possible to expect improvement in solderability with increase in thickness,
and it becomes easy to peel off.
[0014]
In forming the nickel layer, the nickel composite layer can be formed at low cost by subjecting
the 1-3 composite piezoelectric body to electroless plating of nickel.
[0015]
In addition, a layer of silver, tin or tin-lead alloy can be formed by electroplating the electrolessplated 1-3 composite piezoelectric of nickel with silver, tin or tin-lead alloy. It can be formed on a
layer.
[0016]
In the present invention, as piezoelectric ceramics which constitute the 1-3 composite
piezoelectric body together with a polymer material, for example, lead zirconate titanate (PZT)
type, lead titanate type, barium titanate type, bismuth titanate, etc. Piezoelectric ceramics can be
used, but in particular, those based on PZT (that is, lead zirconate titanate but hereinafter
simplified and shown as “PZT based”) have high electromechanical coupling coefficient and It
is preferable from having a dielectric constant.
Moreover, as a polymeric material, a polyurethane resin, an epoxy resin, a silicone resin, an
acrylic resin etc. can be used, for example, According to a use, it can select and use from a soft
thing to a hard thing.
[0017]
The 1-3 composite piezoelectric material used in the present invention is not particularly limited
as long as it is composed of a piezoelectric ceramic and a polymer material, and, for example, the
conventional composition having a constant volume fraction of the piezoelectric ceramic It may
be a 1-3 composite piezoelectric material, or it may be a 1-3 composite piezoelectric material in
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which the volume fraction of the piezoelectric ceramic changes in the slice direction (the slice
direction at the time of ultrasonic probe production).
[0018]
EXAMPLES The present invention will be more specifically described by way of examples.
However, the present invention is not limited to these examples.
[0019]
Example 1 Using a dicing machine, grooves having a width of 30 μm were formed at intervals of
50 μm in the direction perpendicular to the slice direction on a PZT-based piezoelectric ceramic
plate.
[0020]
Next, an epoxy resin is poured into the grooves and vacuum degassing is carried out. After curing
the epoxy resin, grooves 30 μm wide are formed at intervals of 50 μm in the slice direction.
Thereafter, an epoxy resin was poured into the groove, and after vacuum degassing, the epoxy
resin was cured.
[0021]
The upper surface and the lower surface of this piezoelectric ceramic-polymer composite are
lapped with a double-sided lapping machine, and a thin rod of PZT-based piezoelectric ceramic
having one unit of 50 μm × 50 μm × 380 μm (in this example, a rectangular column
However, the shape thereof is not limited), and an epoxy resin is surrounded by a 30 μm width
to obtain a 1-3 μ composite piezoelectric material with a thickness of 380 μm.
[0022]
The 1-3 composite piezoelectric body is subjected to electroless plating of nickel, and the plating
time is controlled to obtain nickel layers of various thicknesses shown in Tables 1 and 2 on the
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surface of the 1-3 composite piezoelectric body. It formed.
[0023]
The above electroless plating treatment of nickel is carried out using a commercially available
phosphorus-based nickel plating solution [Nimden LPX (product side) manufactured by Uemura
Kogyo Co., Ltd.] after chemical pretreatment according to a conventional method. It carried out
on the conditions of 90 degreeC of bath temperatures.
However, the time was variously changed according to the plating thickness to be obtained.
[0024]
Next, electroplating of silver, tin or tin-lead alloy is performed to form a layer of silver, tin or tinlead alloy, and the plating time is controlled as shown in Tables 1-2. Layers of silver, tin or tinlead alloy of various thicknesses shown were formed.
The above silver electroplating process is performed by strike plating according to a
conventional method using a commercially available cyanation bath (Algna ET (trade name)
manufactured by Degussa Japan Co., Ltd.), and then the cathode current density is 1 A / dm 2 at
room temperature. The electroplating process of tin is carried out by preparing a sulfuric acid
bath containing 20 g / L (but "liter", the same shall apply hereinafter) of sulfuric acid, 40 g / L of
sulfuric acid and 25 g / L of cresol sulfonic acid at room temperature. Under the conditions of a
cathode current density of 1A / dm.sup.2, and electroplating of a tin-lead alloy is carried out
using a borofluorine containing 40 g / L of stannous, 15 g / L of lead, 100 g / L of free
borofluoric acid and 5 g / L of formalin. An acid bath was prepared and run at room temperature
under conditions of 3 A / dm 2 cathodic current density.
However, in each electroplating process, the time was variously changed according to the plating
thickness to be obtained.
[0025]
Then, the side plating layer (in this case, a nickel layer formed by electroless plating of nickel, or
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a nickel layer and silver, tin or tin formed by electroplating on the nickel layer) Removing the
lead alloy layer), leaving a plated layer only on the upper and lower surfaces of the 1-3
composite piezoelectric body, applying a direct current voltage between the upper and lower
electrodes of the plated layer to form a 1-3 composite piezoelectric body The 1-3 composite
piezoelectric vibrator plate was obtained by performing the polarization process of
[0026]
The 1-3 composite piezoelectric oscillator plate is pre-soldered at a soldering iron temperature of
250 ° C. using a solder of # KR-1960A (trade name) manufactured by Nippon Alumit Co., Ltd.
Connect a ground lead frame and a signal lead frame to the above electrodes with solder, and
examine solder wettability by observing the appearance after pre-soldering, and pull the lead
frame for solder peelability. It investigated by.
The results are shown in Tables 1 and 2 by the items of "appearance" and "peelability".
[0027]
The evaluation results are shown symbolically in Tables 1 and 2. The relationship between the
symbols and the evaluation is as follows.
[0028]
Appearance: ◎: very good :: good ×: not good enough for practical use
[0029]
Peeling property of solder: :: It indicates that the peeling surface is a surface that has broken the
1-3 composite piezoelectric material.
X: It shows that the peeling surface is a boundary surface of a 1-3 composite piezoelectric
material and an electrode, or is an electrode surface.
[0030]
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[Table 1]
[0031]
[Table 2]
[0032]
As apparent from the results shown in Tables 1 and 2, Samples Nos. 2 to 5, 7 to 11 and 14 to 21
belonging to the present invention have good solderability, and soldering is also possible. No
damage to the polymer material of the 1-3 composite piezoelectric body, that is, warping,
deformation, etc. was observed at all.
[0033]
As described above, according to the present invention, it is possible to provide a 1-3 composite
piezoelectric vibrator plate in which bonding of the lead frame to the electrode can be performed
by solder, thereby, It has become possible to produce ultrasonic probes with high reliability and
at low cost.
[0034]
Brief description of the drawings
[0035]
1 is a cross-sectional view schematically showing an example of a 1-3 composite piezoelectric
vibrator plate of the present invention.
[0036]
2 is a cross-sectional view schematically showing another example of the 1-3 composite
piezoelectric vibrator plate of the present invention.
[0037]
FIG. 3 is a cross-sectional view schematically showing the ultrasonic probe in a state before
attaching the acoustic lens in a slicing direction.
[0038]
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4 is a perspective view schematically showing an ultrasound probe.
[0039]
Explanation of sign
[0040]
1 1-3 composite piezoelectric vibrator plate 2 1-3 composite piezoelectric body 4 electrode 4 a
nickel layer 4 b layer of silver, tin or tin-lead alloy 5 bonding material 6 ground lead frame 7
signal lead frame 8 packing material 9 acoustic matching layer 10 acoustic lens
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