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DESCRIPTION JP2009258077

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DESCRIPTION JP2009258077
PROBLEM TO BE SOLVED: To manufacture an acoustic emission sensor, a cooling device, and an
acoustic emission sensor having a very low noise characteristic even when cooling or heating, in
which a piezoelectric element and a conductive case are mounted using a fluid material. I will
provide a. A conductive case having a piezoelectric element formed by sandwiching a
piezoelectric body between a pair of electrodes, and having an output terminal, and the
piezoelectric element are mounted using a flowable material. [Selected figure] Figure 1
Acoustic emission sensor, cooling device and method of manufacturing acoustic emission sensor
[0001]
The present invention relates to an acoustic emission sensor, and in particular, an acoustic
emission sensor, a cooling device, and a piezoelectric element and a conductive case mounted
using a flowable material, which enable extremely low noise characteristics. The present
invention relates to a method of manufacturing an acoustic emission sensor.
[0002]
In order to realize the miniaturization and speeding up of semiconductor devices, it is extremely
important to reduce the capacitance between interconnections, and the development of devices
using low dielectric constant insulating films is rapidly advanced.
[0003]
However, devices using low dielectric constant insulating films are pointed out that adhesion is
insufficient at the interface between the low dielectric constant insulating film and other
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materials, and interface peeling is likely to occur. Development of accurate peeling strength
evaluation technology is desired.
[0004]
As a method for evaluating the adhesion of thin films, a method called m-ELT (modified Edge Liftoff Test) has been widely used in recent years (E. O. Shaffer II, Designing Reliable Polymer
Coatings, Polymer Engineering and Science, Vol 36, p 2375 (1996)).
[0005]
In the above method, after the sample is applied and cured with an epoxy resin, the sample is
cooled, and a peeling force is applied to the end face of the thin film due to the internal stress of
the resin generated by the cooling, and the peeling is promoted.
[0006]
Under the present circumstances, the internal stress ((sigma) 0) of resin can be derived | led-out
from the temperature which the thin film peeled by measuring beforehand the relationship
between the internal stress of resin, and temperature.
[0007]
Furthermore, assuming that the energy released at the time of peeling is approximately equal to
the energy stored in the resin layer, the stress strength applied to the thin film if the thickness (h)
of the resin layer is sufficiently larger than the thickness of the thin film Intensity = Kapp) is
derived by the following equation (1).
Kapp = σ0 · (h / 2) 1/2 (1)
[0008]
This method is characterized in that the test can be carried out relatively easily, and the peel
strength of the thin film can be quantified.
[0009]
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However, in the measurement method according to the m-ELT method described above, since the
determination at the time of peeling of the thin film is performed by visual observation, it is
difficult to accurately determine the temperature at the moment when peeling occurs. There is a
problem that the variation is large.
Therefore, it is difficult to obtain high quantitative accuracy by this method.
[0010]
On the other hand, for the purpose of reducing the variation in the peeling temperature judgment
as described above and deriving the peeling strength of the thin film with high accuracy, a
method of performing peeling detection using an acoustic emission sensor has been proposed
(E.g., Patent Document 1).
According to this method, the acoustic emission signal, that is, the elastic wave which is a part of
the energy released as the thin film is separated can be detected with high accuracy by the
acoustic emission signal detection means. It is possible to derive the thin film peeling strength
with high accuracy as compared with.
[0011]
The method associated with the above method is now disclosed using FIG.
[0012]
FIG. 5 shows an example of the structure of a general piezoelectric acoustic emission sensor, in
which a piezoelectric element consisting of a piezoelectric body and a pair of electrodes is
mounted in a conductive case having an output terminal. It has a structure.
[0013]
FIG. 5A shows an example in which the piezoelectric element and the conductive case are fixed
by an adhesive.
[0014]
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FIG. 5B is an example in which the entire piezoelectric element is fixed by sealing with a resin so
that the piezoelectric element and the conductive case are in close contact.
[0015]
In FIG. 5C, one electrode of the piezoelectric element is only in contact with the conductive case,
but the piezoelectric element is fixed by inserting a spacer between the other electrode and the
conductive case Example.
[0016]
As described above, in a general piezoelectric acoustic emission sensor, the piezoelectric element
is sufficiently fixed using an adhesive, a resin, a spacer or the like so as not to drop out of the
conductive case.
[0017]
Further, in a general piezoelectric acoustic emission sensor, a working temperature range is
defined, and use within that temperature range is recommended.
This operating temperature range is determined not only by the operating temperature of the
piezoelectric body itself, but also by considering the heat resistant temperature of the abovementioned adhesive, resin, spacer and the like.
[0018]
On the other hand, considering the temperature dependency of each material constituting the
sensor, each material has its own coefficient of thermal expansion, and when the entire sensor is
cooled or heated, the coefficient of thermal expansion of each material There is a possibility that
a slight strain occurs due to the difference of and the piezoelectric body is detected as an elastic
wave.
[0019]
For example, in the process of cooling the entire sensor, a minute strain is generated at the
interface between the piezoelectric element or the conductive case and the adhesive due to the
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difference in the thermal expansion coefficient of the respective materials, and detected as an
elastic wave by the piezoelectric body Be done.
The elastic wave is generated inside the sensor, that is, a noise component of the sensor itself.
[0020]
However, as a general usage form of an acoustic emission sensor, the entire sample on which the
sensor is mounted is cooled or heated to a certain temperature, and the measurement is
performed in a stable temperature state. The distortion was relaxed and stable, and noise was not
a problem.
JP, 2008-134088, A
[0021]
However, as described above, in a general piezoelectric acoustic emission sensor, a piezoelectric
element or a conductive case and a material for fixing the piezoelectric element to the conductive
case in the process of cooling or heating, for example, an adhesive At the interface between the
resin, the spacer, and the like, there is a problem that noise is generated due to the difference in
the thermal expansion coefficient of the respective materials.
[0022]
For this reason, in the conventional acoustic emission sensor, when used for evaluating the
adhesion of a thin film, noise is generated inside the sensor during the cooling process, and it
becomes difficult to determine the peeling temperature with high accuracy.
[0023]
SUMMARY OF THE INVENTION It is an object of the present invention to provide an acoustic
emission sensor, a cooling device, and a method of manufacturing the acoustic emission sensor,
which have very low noise characteristics even during cooling or heating.
[0024]
In order to achieve the above object, a first acoustic emission sensor according to the present
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invention comprises a piezoelectric element formed by sandwiching a piezoelectric body between
a pair of electrodes, a conductive case having an output terminal, and the piezoelectric element.
The device is characterized in that it is mounted using a flowable material.
[0025]
A first cooling device according to the present invention includes a temperature detector, and is
further characterized in that the acoustic emission sensor of the present invention is mounted.
[0026]
In a first method of manufacturing an acoustic emission sensor according to the present
invention, a step of forming a piezoelectric element by sandwiching a first piezoelectric member
between a pair of electrodes, a conductive case having an output terminal, and the piezoelectric
element And a mounting step of mounting using a flowable material.
[0027]
According to the present invention, an acoustic emission sensor having extremely low noise
characteristics becomes possible even during cooling or heating, and when used for thin film
peeling detection, acoustic emission can be judged with high accuracy. A method of
manufacturing a sensor, a cooling device and an acoustic emission sensor can be provided.
[0028]
The present invention achieves what is described below.
[0029]
In an acoustic emission sensor in which a piezoelectric element including a piezoelectric body
and a pair of electrodes is mounted in a conductive case having an output terminal, the
piezoelectric element and the conductive case are mounted using a fluid material. To provide an
acoustic emission sensor characterized by
[0030]
According to this sensor, since the piezoelectric element is not completely fixed as in the prior art
by being attached to the conductive case using a fluid material, in the process of cooling or
heating, the piezoelectric element or the conductive case Since distortion does not occur with the
flowable resin and noise does not occur, the problem of high-accuracy determination of the
separation temperature can be solved when this sensor is used for detection of separation of a
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thin film.
[0031]
Further, it is desirable that the piezoelectric element be mounted using a fluid material so that
one electrode of the piezoelectric element is connected to the output terminal of the conductive
case and the other electrode is disposed adjacent to the conductive case.
By connecting and arranging in this manner, the conductive case can sufficiently perform the
electrical shielding effect, and the reduction of noise enables highly accurate measurement.
[0032]
Here, the flowable material may be flowable within the working temperature range of the sensor
and not solidify, and may not flow and solidify outside the use temperature range.
[0033]
Preferably, the flowable material is added such that the piezoelectric element and the conductive
case are disposed adjacent to each other.
In this case, the flowable material may be added so as to connect a part of the piezoelectric
element and a part of the conductive case, or may be added so as to cover the entire piezoelectric
element.
[0034]
Furthermore, the flowable material in the present invention may be disposed between the
piezoelectric element and the conductive case.
[0035]
Hereinafter, preferred or best modes for carrying out the present invention will be described.
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The following embodiment is an example, is not limited to this, and can be modified or changed
within the range which can be easily conceived by those skilled in the art.
[0036]
1 to 3 show an example of the structure of an acoustic emission sensor according to the present
invention.
[0037]
The piezoelectric element 1 includes a piezoelectric body 11 and a pair of electrodes (electrodes
12 and 13), and is attached to the conductive case 31 using a fluid material 21.
The conductive case 31 has an output terminal 32 and is connected to the electrode 12 using a
lead 33.
[0038]
The flowable material 21 is a material that is fluid and does not solidify within the expected
operating temperature range of the acoustic emission sensor, and is non-flowable and solidifies
outside the operating temperature range. May be
[0039]
Moreover, although a material having viscosity is desirable so that the piezoelectric element 1
does not come off the conductive case 31, the flowable material 21 is not particularly limited by
the viscosity.
For example, a grease is used as the flowable material 21. The material is not particularly limited
to the grease as long as it has the above-mentioned characteristics.
[0040]
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For example, as shown in FIG. 1, the piezoelectric element 1 is disposed adjacent to the
conductive case 31 and attached using the flowable material 21.
[0041]
By arranging the electrode 13 of the piezoelectric element 1 so as to be adjacent to the
conductive case 31, the conductive case 31 can sufficiently perform the electrical shielding
effect, and the noise can be reduced, so that highly accurate measurement can be performed. It
becomes possible.
The flowable material 21 is attached by adding so as to connect a part between the side surface
of the piezoelectric element 1 and the bottom surface of the conductive case 31.
[0042]
Alternatively, as shown in FIG. 2, the entire piezoelectric element 1 may be attached by covering
it with the flowable material 21.
[0043]
Alternatively, the flowable material 21 may be attached by connecting the piezoelectric element
1 and the conductive case 31 as shown in FIG. 3, for example.
In this case, in order to enhance the electrical shielding effect by the conductive case 31, the
flowable material 21 preferably has conductivity, but the flowability material 21 is not
particularly limited by the conductivity.
[0044]
Next, the manufacturing process of the acoustic emission sensor of the present invention having
the above-mentioned configuration and the one in which the thin film peeling detection is carried
out by actually using the acoustic emission sensor of the present invention will be shown.
[0045]
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First, in the present embodiment, piezoelectric elements were used in which electrode plates
were attached to the upper and lower surfaces of a cylindrical piezoelectric body having a
diameter of 5 mm and a height of 3 mm.
The piezoelectric material used was PZT (lead zirconate titanate).
[0046]
Next, install the piezoelectric element on the bottom of the stainless steel case with the output
terminal and add grease so as to connect the side of the piezoelectric element and the bottom of
the case, so that the piezoelectric element does not fall off. did.
Here, the stainless steel case has a structure in which the upper surface can be opened and
closed, so that the piezoelectric element can be easily attached.
[0047]
Moreover, the grease was used for low temperature lubrication, and used as a grease which had
low temperature fluidity to -60 ° C and was not frozen.
Next, the upper electrode of the piezoelectric element and the output terminal were connected by
a lead wire, and finally the upper surface of the stainless steel case was closed to obtain an
acoustic emission sensor.
[0048]
The following is an example in which thin film peeling was detected using the acoustic emission
sensor of the present invention.
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This will be described below with reference to the drawings.
[0049]
FIG. 4 shows an outline of a thin film peeling strength measuring apparatus.
The acoustic emission sensor 51 of the present invention is attached to the sample 60 and is
used to detect an acoustic emission signal generated from the sample 60.
[0050]
The thin film peeling strength measuring apparatus has an acoustic emission sensor 51, a
cooling device 71 for cooling the sample 60, and a temperature detector 72 for detecting a
cooling temperature, and the sample 60 is attached with the acoustic emission sensor 51. It is
held and cooled in the cooling device 71 in the closed state.
[0051]
The sample 60 is prepared by forming the resin 63 on the thin film 62 side of the substrate 61
on which the thin film 62 is stacked.
The thin film 62 may be formed on the substrate 61 as a plurality of layers.
In this case, peeling of the thin film 62 occurs at the weakest interface of the plurality of layers.
[0052]
When the sample 60 is cooled, the resin 63 starts thermal contraction and an internal stress
corresponding to the cooling temperature is generated.
A peeling force is generated on the end face of the thin film 62 due to the internal stress
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generation of the resin 63 due to the cooling, and the thin film 62 is peeled off.
An acoustic emission signal generated as the thin film 62 peels is detected by an acoustic
emission sensor 51.
[0053]
The sample was specifically produced by the following method.
[0054]
First, 600 nm thick silicon dioxide, 30 nm thick nitrogen-doped silicon carbide, 120 nm thick low
dielectric insulating film, and 600 nm thick silicon dioxide were sequentially stacked on a 775
μm thick silicon substrate.
It is known that the low dielectric constant insulating film has lower adhesion than silicon dioxide
conventionally used as the insulating film.
[0055]
Next, an epoxy resin is applied on the outermost surface silicon dioxide and adjusted with a jig
such as a squeegee so that the thickness is almost uniformly 120 μm, and then it is heated at
120 ° C. for 10 minutes in an oven. Hardening treatment was performed.
Finally, it was made into the sample of peeling strength measurement by cutting out to 10 mm
square by dicing.
Further, for comparison, a sample in which only a silicon substrate was cut into 10 mm square
was also prepared.
[0056]
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Next, an acoustic emission sensor was fixed to the silicon substrate side of the sample with
grease.
The signal from the acoustic emission sensor was amplified by an amplifier via a coaxial cable
and set to be recorded by a recording device.
[0057]
A sample equipped with an acoustic emission sensor was placed in a cooling device equipped
with a temperature controller, the temperature was reduced from room temperature at -2 ° C /
min, and the generated acoustic emission signal was detected by a thermocouple Recorded with
temperature.
[0058]
First, as a result of measuring a sample of only a silicon substrate prepared for comparison by
the above method, no acoustic emission signal is detected even if the temperature is lowered to 60 ° C, and noise is generated inside the sensor in the cooling process. Can be confirmed.
[0059]
Next, as a result of reducing the sample prepared for thin film peeling strength measurement to 60 degreeC, the acoustic emission signal was detected in -30 degreeC vicinity.
[0060]
At this time, when the sample is confirmed from the observation window provided in the cooling
device, the peeling of the thin film can be confirmed, and it can be understood that the acoustic
emission signal corresponds to the peeling of the thin film.
[0061]
From this, it is understood that, when the acoustic emission sensor of the present invention is
used, no noise is generated even in the cooling process, and therefore peeling of the thin film can
be detected by the acoustic emission signal without visual observation.
[0062]
Next, another embodiment of the acoustic emission sensor of the present invention will be
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described.
[0063]
As the piezoelectric element, one having an electrode plate attached to the upper and lower
surfaces of a cylindrical piezoelectric body (PZT) with a diameter of 5 mm and a height of 3 mm,
as in the above-described embodiment was used.
Next, a stainless steel case having an output terminal and a piezoelectric element are mounted
using grease for low temperature lubrication as in the above embodiment, but two types of
acoustic emission sensors are manufactured by changing the mounting method. Made.
[0064]
First, in the first acoustic emission sensor, the piezoelectric element is placed on the bottom of a
stainless steel case having an output terminal, and grease is added to cover the entire
piezoelectric element so that the piezoelectric element does not fall off. Semi-fixed.
[0065]
Furthermore, the second acoustic emission sensor applies a thin layer of grease to the bottom of
a stainless steel case having an output terminal, and places the piezoelectric element on top of it,
so that the piezoelectric element does not fall off in a semi-fixed state And
[0066]
Next, peeling detection of the thin film was performed using the two types of acoustic emission
sensors.
Peeling detection was performed using the thin film peeling strength measuring apparatus of
FIG. 4 using the method similar to the said Example.
[0067]
First, as a result of measuring each of the samples of only the silicon substrate prepared for
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comparison using the above two types of acoustic emission sensors, the acoustic emission signal
is detected even if the temperature is lowered to -60 ° C. In the cooling process, it can be
confirmed that no noise is generated inside the sensor.
[0068]
Next, as a result of measuring the sample prepared for thin film peeling strength measurement to
-60 ° C. using the above two types of acoustic emission sensors, an acoustic emission signal is
obtained around -30 ° C. was detected.
[0069]
At this time, when the sample is confirmed from the observation window provided in the cooling
device, the peeling of the thin film can be confirmed, and it can be understood that the acoustic
emission signal corresponds to the peeling of the thin film.
[0070]
As described above, when the acoustic emission sensor according to the present invention is
used, noise does not occur in the cooling process, and when used for thin film peeling detection,
highly accurate judgment of the peeling temperature becomes possible.
[0071]
In the present embodiment, an example in the cooling process has been described, but it is easily
understood that by making the flowable material into a material having fluidity on the high
temperature side, an acoustic emission sensor which does not generate noise in the heating
process is easily realized. it can.
[0072]
Furthermore, although the example used in the detection of thin film peeling has been described
in the present embodiment, it can be easily understood that the present invention can be widely
applied to the detection of an acoustic emission signal at the time of cooling or heating.
[0073]
It is a 1st figure which shows the acoustic emission sensor of embodiment of this invention.
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It is a 2nd figure which shows the acoustic emission sensor of embodiment of this invention.
It is a 3rd figure which shows the acoustic emission sensor of embodiment of this invention.
It is a figure which shows the thin film peeling strength measuring apparatus in the Example of
this invention.
It is a figure which shows the conventional acoustic emission sensor.
Explanation of sign
[0074]
Reference Signs List 1 piezoelectric element 11 piezoelectric body 12, 13 electrode 21 flowable
material 31 conductive case 32 output terminal 33 lead wire 41 adhesive 42 resin 43 spacer 51
acoustic emission sensor 60 sample 61 substrate 62 thin film 63 resin 71 cooling device 72
temperature Detector
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