JP2015051174

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DESCRIPTION JP2015051174
The present invention provides a probe or the like capable of suppressing positional deviation
between an acoustic lens and a capacitive transducer. A probe includes a transducer including an
element and a lead-out electrode of the element, a flexible wiring board including a wire
electrically connected to the lead-out electrode, and a stepped portion provided on the element.
An acoustic lens 104 is included. The acoustic lens 104 abuts on the end of the flexible wiring
substrate 103 at the stepped portion and is fixed. [Selected figure] Figure 1
Probe
[0001]
The present invention relates to a probe including a capacitive transducer or the like used as a
photoacoustic probe or the like used in an ultrasonic diagnostic apparatus or the like, and an
object information acquiring apparatus using the same.
[0002]
One of the ultrasonic diagnostic apparatuses uses a photoacoustic wave.
The photoacoustic wave is, for example, an ultrasonic wave generated when a pulse laser
(electromagnetic wave) irradiated from the outside of the body is absorbed by a tissue in the
body. Since photoacoustic waves are generated in specific tissues in the body, imaging of body
tissues using information on photoacoustic waves is possible. Sound waves, ultrasonic waves,
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photoacoustic waves and the like are called acoustic waves, but in the present specification, they
may be represented by ultrasonic waves.
[0003]
A probe can be used to detect ultrasound generated in the body. An ultrasound transducer is
disposed within the probe to convert the ultrasound into electrical signals. Conventionally,
ultrasonic transducers that use the piezoelectric effect have been used, but in recent years,
research and development of capacitance type is also active. A capacitive transducer includes, for
example, a cell composed of two electrodes provided so as to sandwich a substantially vacuummaintained space called a cavity, and includes one or more elements composed of one or more
cells. . One of the two electrodes is fixed to the membrane, and the vibrating membrane
configured in this way is vibratably held. When the vibrating film vibrates due to ultrasonic
waves and the distance between the two electrodes changes, a change in capacitance occurs.
When a voltage is applied between the two electrodes, a change in capacitance can be extracted
as a current signal. This is the principle of the ultrasonic wave receiving operation. Also, the
voltage applied between the two electrodes causes electrostatic attraction between the two
electrodes. The vibrating film can be vibrated by temporally changing the magnitude of the
applied voltage. This is the principle of the ultrasonic wave transmission operation. Among
capacitance type transducers, one manufactured by applying semiconductor microfabrication
technology is called a CMUT (Capasitive-Micromachined-Ultrasonic-Transducer). A probe in
which a plurality of capacitive transducers (i.e., the cells or elements) are arranged at high
density is suitable for achieving high image quality, which is a need for ultrasonic diagnostic
equipment.
[0004]
In the technical field as described above, a probe in which an acoustic lens is disposed on an
ultrasonic transducer has been proposed (see Patent Document 1). In addition, in a probe having
an acoustic lens, there is a probe in which an anisotropic conductive adhesive or the like and an
ultrasonic transducer are electrically connected (see Patent Document 2).
[0005]
Patent Document 1: Japanese Patent Application Publication No. 2008-119318 Patent Document
2: International Publication No. 2008/114582
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[0006]
In the probe, the acoustic lens is preferably fixed without displacement from the capacitive
transducer (i.e., cell or element).
However, the acoustic lens often uses a soft member such as silicone rubber, and even if the
acoustic lens is positioned by one portion, the other portion may be misaligned. An object of this
invention is to provide the probe etc. by which position shift with an acoustic lens and an
electrostatic capacitance type transducer was suppressed in view of the above-mentioned subject.
[0007]
The probe of the present invention is an acoustic transducer having a stepped portion provided
on an element, a transducer including the element and the lead-out electrode of the element, a
flexible wiring board including the wiring electrically connected to the lead-out electrode, and the
element. And a lens. The acoustic lens is abutted against the end of the flexible wiring board at
the stepped portion and fixed.
[0008]
In the probe of the present invention, since the acoustic lens is abutted against the end of the
flexible wiring board at the stepped portion and fixed, positional deviation between the acoustic
lens and the capacitive transducer is suppressed.
[0009]
BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing explaining one Embodiment of this
invention.
The top view explaining one embodiment of the present invention. Sectional drawing explaining
other embodiment of this invention. The figure which shows the example of a capacitive
transducer. BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram which shows the
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example of the information acquisition apparatus containing the probe of this invention.
[0010]
In the probe according to the present invention, an acoustic lens provided on an element of a
capacitive transducer or the like has a stepped portion including an L-shaped portion and the like
defined by two surfaces, and the flexible portion is flexible at the stepped portion. It abuts on the
end of the wiring board and is fixed. Although the embodiments and examples of the present
invention will be described based on such a concept, the present invention is not limited to these
embodiments and examples, and various modifications and changes are possible within the scope
of the gist of the present invention. is there.
[0011]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings. FIG. 1 is a cross-sectional view for explaining a first embodiment of the present
invention. In the substrate 100, elements (elements) 101 including a plurality of cells are onedimensionally or two-dimensionally arranged. In this embodiment, as shown in FIG. 2 which is a
top view, the elements 101 are arranged in one dimension (vertical direction in FIG. 2). The
takeout electrode 102 of the element 101 is disposed at the edge on the substrate 100. A flexible
wiring substrate 103 including a wire electrically connected to the lead-out electrode 102 is
disposed at the periphery of the substrate 100. In the present embodiment, the flexible wiring
substrate 103 is disposed on the left and right sides of the substrate 100 in a bent state. For
example, an anisotropic conductive film (ACF) 106 is used to connect the lead-out electrode 102
and the flexible wiring substrate 103, but the connection method is not limited to this as long as
connection can be made to a low resistance. When an anisotropic conductive film is used, the
level difference of the level difference portion can be reduced.
[0012]
An acoustic lens 104 having a stepped portion is disposed on the element 101. Here, the stepped
portion has an L-shaped portion defined by two planes extending at right angles to each other.
The acoustic lens 104 is in contact with the end of the flexible wiring substrate 103, and the
acoustic lens is fixed to the substrate 100 using an adhesive 105 or the like. More specifically,
the side surface of the end portion of the wiring substrate 103 abuts on one surface (surface
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extending vertically in FIG. 1) of the L-shaped portion of the step portion, and the upper surface
of the end portion of the wiring substrate 103 is the L shape of the step portion It is in contact
with the other surface of the protuberance (surface extending in the left and right direction in
FIG. 1). Such a butting structure is established on at least one of the left and right sides of the
view of the acoustic lens 104 to fix the acoustic lens.
[0013]
FIG. 2 is a top plan view of the above structure. Here, an example is shown in which the lead-out
electrodes 102 are alternately arranged in the left and right, but the lead-out electrodes 102 may
be arranged in only one of the left and right. At that time, the abutment structure is present only
on either the left or the right. Therefore, the position of the stepped portion on the other side of
the acoustic lens 104 is restricted by, for example, the end of the case or the like. Alternatively,
the other side of the acoustic lens 104 may have no stepped portion and may be a simple side
surface, and the side surface may be restricted in position by an end portion such as a case.
[0014]
Next, the reason why the positional deviation between the acoustic lens and the capacitive
transducer is suppressed in the present embodiment will be described. The positioning accuracy
at the time of connecting the flexible wiring substrate 103 to the extraction electrode 102 can be
made sufficiently small, and can be fixed, for example, with an accuracy of 100 micrometers or
less using the alignment mark. Further, each of the lead-out electrode 102 and the element 101
is a pattern in a substrate manufactured by a semiconductor process, and the positional deviation
is small. Therefore, the flexible wiring substrate 103 can be fixed to the element 101 with high
accuracy, and the acoustic lens 104 abutted against the flexible wiring substrate 103 is also fixed
to the element 101 with high accuracy. Is possible.
[0015]
In the present embodiment, the positioning accuracy can be improved by abutting the acoustic
lens 104 in the vicinity of the capacitive transducer. For example, compared with the case where
the acoustic lens is fitted on the outer side (side surface) of the substrate as in the technique of
Patent Document 1, the method of determining the position of the acoustic lens at a position near
the transducer Can be reduced to improve the positioning accuracy. On the other hand, in order
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to miniaturize the probe, it is preferable to minimize a member for fixing the acoustic lens. As in
the present invention, by using a flexible wiring substrate necessary for transmission or
reception for positioning of an acoustic lens, it is possible to provide a compact probe.
[0016]
As described above, the stepped portion of the acoustic lens which strikes the flexible wiring
substrate may be one or plural. The positioning accuracy can be improved as long as the
direction of abutment is any one or more of left, right, front, back, top and bottom, and it is not
limited to any one direction. Further, the entire surface of the step portion of the acoustic lens
does not have to abut the flexible wiring board, as long as at least two or more points are
abutted. In the probe of the present embodiment as described above, since the acoustic lens is
abutted against the end of the flexible wiring board at the stepped portion and fixed, positional
deviation between the acoustic lens and the transducer is suppressed.
[0017]
The above configuration can be understood as the following structure. That is, the projection of
the acoustic lens is fitted so that the substrate is rectangular and the recess formed by the
substrate and the end of the flexible wiring substrate disposed on at least one pair of opposing
sides of the substrate is fitted It is a probe that is arranged and the bottom of the protrusion is
glued to the substrate. Such a configuration is preferable because positioning and adhesion of the
acoustic lens can be performed easily and reliably.
[0018]
The following configuration can also be made. That is, the protrusion of the anisotropic
conductive film may be such that the protrusion of the anisotropic conductive film which may
occur when bonding the substrate and the flexible wiring substrate does not prevent the butt
between the flexible wiring substrate and the acoustic lens. The acoustic lens is provided with a
recess (see FIG. 3) for receiving the part. For example, a mode is conceivable in which the
stepped portion of the acoustic lens is an L-shaped portion having an obtuse angle as shown in
FIG. In this way, it is possible to prevent the protrusion of the anisotropic conductive film from
entering the recess formed by the stepped portion and the end of the flexible wiring board,
thereby preventing the abutment of the flexible wiring board and the acoustic lens. The decrease
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in the positioning accuracy of the acoustic lens can be suppressed. Such a recess is preferably
provided at the end of the acoustic lens, but the substrate 100 may be provided with a groove or
the like that is a recess for receiving the protruding portion of the anisotropic conductive film. Of
course, the position and shape of the recess are not limited to these. As described above, in the
present example, the recess of the anisotropic conductive film generated when bonding the
substrate and the flexible wiring substrate is formed by the step portion and the end of the
flexible wiring substrate, and the substrate The acoustic lens is mounted so as to come to the
formed recess or the like.
[0019]
Further, the above-described apparatus can be manufactured by, for example, a manufacturing
method including the following steps. First, the lead-out electrodes of the element are electrically
connected to the corresponding wires of the flexible wiring substrate via an anisotropic
conductive film or the like, and an adhesive is applied on the transducers of the substrate. Next,
the acoustic lens is positioned by fitting the protrusion of the acoustic lens (that is, the portion
defined by the step) into the recess formed by the end of the flexible wiring substrate and the
substrate, thereby positioning the acoustic lens. Contact the acoustic lens. Then, by applying
pressure to the acoustic lens and the substrate and heating while pressing both, the acoustic lens
is bonded onto the transducer.
[0020]
Next, a capacitive transducer, which is an example of a transducer used in the present invention,
will be described. FIG. 4 shows an example of a capacitive transducer having an element
including a plurality of cells. 4 (a) shows a top view, and FIG. 4 (b) is a cross-sectional view taken
along line A-B of FIG. 4 (a). The present transducer has a plurality of elements 8 (corresponding
to the element 101 in FIG. 2) having the cell structure 7. Although four elements 8 each have
nine cells 7 in FIG. 4, any number of elements may be included as long as each element 8
includes one or more cells. The arrangement form of the cells in the element 101 of FIG. 2 and
the arrangement form of the cells 7 in the element 8 of FIG. 4 do not necessarily match.
[0021]
In the cell 7 of this example, as shown in FIG. 4B, the substrate 1 (corresponding to the substrate
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100 in FIG. 1), the first electrode 2, the insulating film 3 on the first electrode 2, and the
insulating film 3 A vibrating membrane 4 vibratably supported via a gap 5 (a gap or the like) and
a second electrode 6 on the vibrating membrane 4 are provided. The substrate 1 is made of Si,
but an insulating substrate such as glass may be used. The first electrode 2 is formed of a metal
thin film such as titanium or aluminum. When the substrate 1 is formed of low-resistance silicon,
it may be used as the first electrode 2 itself. The insulating film 3 can be formed by depositing a
thin film such as silicon oxide. The vibrating membrane 4 and the vibrating membrane
supporting portion which is a portion for supporting the vibrating membrane 4 are formed by
depositing a thin film such as silicon nitride. The second electrode 6 can be made of a metal thin
film such as titanium or aluminum. The vibrating film of the membrane portion made of a silicon
nitride film or a single crystal silicon film and the second electrode portion can be taken together
as a vibrating film. As described above, in this example, the element includes at least one cell
having a structure in which a vibrating membrane including one of two electrodes provided with
a gap in between is vibratably supported.
[0022]
The drive principle of the transducer of this example will be described. Since the cell is formed of
the first electrode 2 and the vibrating film provided across the gap 5, in order to receive the
acoustic wave, a DC voltage is applied to the first electrode 2 or the second electrode 6. Apply.
This bias voltage is applied from the voltage application means. When an acoustic wave is
received, the vibrating film vibrates due to the acoustic wave and the distance (height) of the gap
changes, so the capacitance between the electrodes changes. An acoustic wave can be detected
by detecting this capacitance change from the first electrode 2 or the second electrode 6. The
received signal due to such capacitance change is sent to the amplifier circuit. The element can
also transmit an acoustic wave by applying an AC voltage to the first electrode 2 or the second
electrode 6 to vibrate the diaphragm. A transmission signal of such an alternating voltage is
transmitted from the transmission / reception circuit to the element 8.
[0023]
In the present embodiment, the surface of the acoustic lens 104 has a wedge shape and extends
in the direction perpendicular to the paper surface of FIG. Therefore, the beam of the acoustic
wave is narrowed by the power of the curvature of the acoustic lens 104 in the left-right
direction of FIG. In the direction perpendicular to the paper surface of FIG. 1, since the acoustic
lens 104 has no power, a beamforming transmission / reception technique is taken. In this
method, a limited set of a limited number of elements of the total number of transmittable
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channels is sequentially delayed in the vertical direction of the drawing sheet, and one beam is
formed and scanned. It is possible to obtain the information of the ultrasonic wave of the subject
in the direction. After forming one beam in the 1D or 2D array of elements and acquiring
information on the ultrasonic wave of the subject in the beam direction, the beam direction is
further shifted by one element, in the row or column direction, Get sound wave information. By
sequentially performing this operation and combining information, an image called, for example,
a B (Brightness) mode image is created. In the ultrasound transmission / reception system that
performs this operation, the elements and circuits of the channel used for beamforming transmit
and receive signals, but the elements and circuits not used are not transmit and receive signals.
Of course, depending on the required function, the surface of the acoustic lens 104 can have
other shapes, such as a spherical shape.
[0024]
Example 1 A more specific example 1 will be shown below. In this embodiment, a plurality of
capacitance type transducers and extraction electrodes are fabricated on a silicon wafer by a
semiconductor process. From the silicon wafer, the substrate is cut into 50 mm long and 10 mm
wide. The elements 101 are arranged one-dimensionally in the longitudinal direction, and the
extraction electrodes 102 are disposed on the left or right of the respective capacitive
transducers.
[0025]
This will be described with reference to FIG. The flexible wiring substrate 103 is a copper wiring
with a thickness of 10 μm, and the upper and lower sides of the flexible wiring substrate 103
are insulated with polyimide of 50 μm except for a place connected to the lead-out electrode
102. After applying the anisotropic conductive film 106 on the lead-out electrode 102 disposed
around the substrate 100 and aligning the flexible wiring board 103 thereon, the flexible wiring
board is pressed and fixed from above. Thereafter, the anisotropic conductive film is thermally
cured at 80 ° C. to bond the lead-out electrode 102 and the wiring of the flexible wiring
substrate 103. The flexible wiring substrate is bonded to the left and right sides of the substrate
100. As a result of measuring the positional deviation of each of the lead-out electrode 102 and
the wiring of the flexible wiring substrate 103 after bonding, the positional deviation in the
vertical direction (the extending direction of the wiring) is 50 μm at maximum, The
misalignment in the in-plane direction is at most 20 μm.
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[0026]
The acoustic lens 104 is made of silicone, and the lower portion has a convex 100 μm step, and
the upper portion has a lens shape with a radius of curvature of 14 mm. After applying an
adhesive 105 with a thickness of 20 μm on the capacitance type transducer, insert the stepped
portion which is the convex of the acoustic lens 104 between the left and right flexible wiring
boards 103, and one side of the flexible wiring board 103 and the acoustic The lens 104 is
abutted and fixed. While applying pressure from above the acoustic lens 104, the adhesive 105
is thermally cured at 80 ° C. to adhere the acoustic lens 104 to the substrate 100.
[0027]
In the probe thus produced, cross sections are cut out at five locations, and the central axis of the
acoustic lens 104 (extending in the direction perpendicular to the plane of the drawing of FIG. 1)
and the central axis of the capacitive transducer (vertical to the plane of the drawing of FIG.
Deviation from the direction) was measured. As a result, the positional deviation between the
acoustic lens and the capacitive transducer was at most 20 μm. Although the above is an
embodiment in which the elements 101 of the capacitive transducer are one-dimensionally
arranged, the positioning and fixing may be similarly performed even when the capacitive
transducers are two-dimensionally arranged. It is possible.
[0028]
(Other Embodiments) The above-mentioned capacitance type transducer can be applied to an
object information acquiring apparatus such as an ultrasonic diagnostic apparatus. Acoustic wave
from the subject is received by the transducer, and the output electrical signal is used to acquire
subject information reflecting the optical characteristic value of the subject such as light
absorption coefficient, and subject information reflecting the difference in acoustic impedance it
can.
[0029]
More specifically, an example of the information acquisition apparatus irradiates a subject with
light (electromagnetic wave including visible light and infrared light). As a result, photoacoustic
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waves generated at a plurality of positions (portions) in the subject are received, and a
characteristic distribution indicating the distribution of the characteristic information
respectively corresponding to the plurality of positions in the subject is obtained. The
characteristic information acquired by the photoacoustic wave indicates the characteristic
information related to light absorption, and the initial sound pressure of the photoacoustic wave
generated by the light irradiation, or the light energy absorption density derived from the initial
sound pressure, the absorption coefficient And the characteristic information reflecting the
concentration of the substance that constitutes the tissue. The concentration of the substance is,
for example, oxygen saturation, total hemoglobin concentration, oxyhemoglobin or
deoxyhemoglobin concentration, and the like. In addition, the information acquisition apparatus
can also be used for diagnosis of malignant tumors and vascular diseases of humans and animals,
and follow-up of chemical treatment. Therefore, as a subject, diagnostic objects such as the
breast, neck, and abdomen of a living body, specifically, a human or an animal are assumed. The
light absorber inside the subject represents a tissue having a relatively high absorption
coefficient inside the subject. For example, when a part of the human body is a subject, there are
oxyhemoglobin or deoxyhemoglobin, a blood vessel containing a large amount of them, a tumor
containing a large amount of new blood vessels, a plaque on a carotid artery wall, and the like.
Furthermore, molecular probes that bind specifically to malignant tumors and the like by using
gold particles and graphite, and capsules that transmit drugs also serve as light absorbers.
[0030]
In addition to the reception of the photoacoustic wave, the ultrasonic wave transmitted from the
probe including the transducer receives the reflected wave due to the ultrasonic echo reflected in
the subject, thereby acquiring the distribution regarding the acoustic characteristic in the subject
You can also The distribution relating to the acoustic characteristics includes a distribution
reflecting the difference in acoustic impedance of the tissue inside the subject.
[0031]
FIG. 5A shows an information acquisition apparatus using the photoacoustic effect. The pulsed
light oscillated by the light source 2010 is irradiated to the subject 2014 via the optical member
2012 such as a lens, a mirror, and an optical fiber. The light absorber 2016 inside the object
2014 absorbs the energy of the pulsed light and generates a photoacoustic wave 2018 which is
an acoustic wave. The transducer 2020 of the present invention in the probe unit 2022 receives
the photoacoustic wave 2018, converts it into an electrical signal, and outputs it to the front end
circuit of the probe unit. The front end circuit performs signal processing such as a preamplifier
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and sends it to the signal processing unit 2024 of the main unit via the connection unit. The
signal processing unit 2024 performs signal processing such as A / D conversion and
amplification on the input electrical signal, and outputs the processed signal to the data
processing unit 2026 of the main unit. The data processing unit 2026 acquires object
information (characteristic information reflecting the optical characteristic value of the object
such as a light absorption coefficient) as image data using the input signal. Here, the signal
processing unit 2024 and the data processing unit 2026 are collectively referred to as a
processing unit. The display unit 2028 displays an image based on the image data input from the
data processing unit 2026. The probe portion 2022 and the main body portion may be
integrated.
[0032]
FIG. 5B shows an information acquisition apparatus such as an ultrasonic echo diagnostic
apparatus using reflection of acoustic waves. The acoustic wave transmitted from the transducer
2120 of the present invention in the probe portion 2122 to the subject 2114 is reflected by the
reflector 2116. The transducer 2120 receives the reflected acoustic wave (reflected wave) 2118,
converts it into an electrical signal, and outputs it to the front end circuit in the probe unit. The
front end circuit performs signal processing such as a preamplifier and sends it to the signal
processing unit 2124 of the main unit via the connection unit. The signal processing unit 2124
performs signal processing such as A / D conversion and amplification on the input electrical
signal, and outputs the processed signal to the data processing unit 2126 of the main unit. The
data processing unit 2126 acquires object information (characteristic information reflecting a
difference in acoustic impedance) as image data using the input signal. Here, the signal
processing unit 2124 and the data processing unit 2126 are also referred to as a processing unit.
The display unit 2128 displays an image based on the image data input from the data processing
unit 2126. Here too, the probe portion 2122 and the main body portion can be integrated.
[0033]
The probe unit may be one that scans mechanically, or one that is moved by a user such as a
doctor or an engineer with respect to a subject (hand-held type). Moreover, in the case of the
apparatus using a reflected wave like FIG.5 (b), you may provide the probe which transmits an
acoustic wave separately from the probe to receive. Furthermore, the apparatus has both the
functions of the apparatus shown in FIGS. 5A and 5B, object information reflecting the optical
characteristic value of the object, and object information reflecting the difference in acoustic
impedance. , And may be acquired. In this case, the transducer 2020 in FIG. 5A may transmit not
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only the photoacoustic wave but also the acoustic wave and the reflected wave.
[0034]
100 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · flexible wiring board, 104 · · · acoustic lens, 105 ·
· adhesive, 106 · · anisotropic conductive film
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