JP6830585B1 - Stress impedance sensor element and stress impedance sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stress impedance sensor element and a stress impedance sensor which have a strain gauge portion which can be easily attached to a minute object to be tested and have high sensitivity and small size. SOLUTION: The strain gauge ratio of the stress impedance sensor can be secured at 2000 or more by increasing the diameter of the magnetostrictive wire of the stress impedance sensor element to 5 to 18 μm and increasing the pulse frequency to 100 to 500 MHz. The length of the SI element is 0.06 to 5.5 mm, and a small stress impedance sensor having an excellent strain gauge ratio can be obtained. [Selection diagram] Fig. 1

Description

The present invention relates to a stress impedance sensor element and a stress impedance sensor that detect ultra-weak stress of ultra-small size.

The stress impedance sensor (hereinafter referred to as SI sensor) is disclosed in Patent Document 1 and Patent Document 2. Here, the stress impedance is a phenomenon in which the impedance of a magnetostrictive wire changes according to the amount of strain when strain is applied to an amorphous magnetostrictive wire (hereinafter referred to as a magnetostrictive wire), and a large impedance change occurs with a slight strain. High-sensitivity strain gauges have been developed.

The sensitivity evaluation of the SI sensor is evaluated by the strain gauge ratio G. It can be calculated with G = (dR / R) / (dL / L). L is the length of the stress detector, dL is the elongation, R is the electrical resistance of the detector, and dR is the amount of change in electrical resistance. The strain gauge ratio of a commercially available metal foil strain gauge is about 2, and the strain gauge ratio of a semiconductor strain gauge having high detection power is about 50 to 200.

In Patent Document 1 (Example 1), the magnetostrictive wire as a stress detector is a ferromagnetic linear metal body of an amorphous Fe-based alloy, having a diameter of 125 μm and a length of 200 mm (distance between terminals 150 mm). A distortion gauge ratio of about 63 is obtained at an excitation frequency of 10 MHz.
On the other hand, in Patent Document 2 (Example 1), the magnetostrictive wire, which is a stress detector, is a negative magnetostrictive Co-based amorphous wire, having a diameter of 30 μm, a length of 20 mm, an excitation frequency of 20 MHz, and a strain gauge ratio of 1286. Has been obtained. This is 6.5 times higher than the semiconductor strain gauge.

Further, according to Non-Patent Document 1 , a strain gauge ratio of 1524 is obtained when the wire diameter is 30 μm, the length is 30 mm , the excitation frequency is 20 MHz, and the current strength is 20 mA.
According to Non-Patent Document 2 (FIG. 2), it is reported that a strain gauge ratio of about 2000 can be obtained when the element length is 4 mm and the width is 2 mm, the excitation frequency is 15 MHz, and the current strength is 9.5 mA. ing.
According to Non-Patent Document 3 (Table 1), as a high-sensitivity strain gauge sensor comparable to an SI sensor, there are about 1000 spin MEMS type sensors having a size of about 5 mm square. According to Non-Patent Document 4, the latest report is made that the magnetostrictive material is changed to Fe amorphous alloy to realize a strain gauge ratio of 5000 in the MEMS type.

Among these, the present invention focuses on a stress impedance sensor having excellent sensitivity and suitable for miniaturization, and preferably has a length of 5 mm or less used for an in-vivo medical device such as a catheter using a stress impedance sensor element. Aims at the development of an ultra-compact and highly sensitive stress sensor of 1 mm or less. However, it is difficult to attach the magnetic wire of the existing product to the test piece of the SI sensor, and it has not been put into practical use. Furthermore, if the length of the element is shortened, the strain gauge ratio will decrease, so it is necessary to develop a new technology to achieve both miniaturization and high sensitivity.
In addition, the detector of the SI sensor is affected by the external magnetic field as well as the stress. When the external magnetic field is small, the effect is negligible. However, when the external magnetic field is larger than the geomagnetism, the SI sensor cannot ignore the influence of the external magnetic field. Therefore, it is necessary to develop a technology for magnetic shield as well as a technology for achieving both miniaturization and a high strain gauge ratio.

Japanese Patent Application Laid-Open No. 8-128904 JP-A-10-170355

Shinrei 萍 et al .: Japan Society for Applied Magnetics 22, 677-680 (1998) Hideya Yamadera et al .: Toyota Central R & D Labs. R & D Review, 3, 2, p51-56 (2001.6) Yokogawa Technical Report, 60, 1, p43-47 (2017) EE Times September 3, 2019 News

Based on the above background, the present invention has been made in order to realize miniaturization, high sensitivity, and measures against external magnetic fields.
The first problem is that the length of the stress impedance sensor element (hereinafter referred to as SI element) constituting the stress impedance sensor is 5.5 mm or less, preferably the element length is 1.4 mm or less, and the amorphous magnetostrictive wire. (Hereinafter referred to as magnetostrictive wire), the length is 1 mm or less, the width of the SI element is 0.20 mm or less, preferably 0.1 mm or less, and the thickness is 0.25 mm or less, preferably 0.20 mm or less. It is to aim.
The second problem is to aim for a strain gauge ratio of 2000 or more for the SI sensor in order to detect minute stresses in terms of sensitivity. At the same time, it is to improve high sensitivity and miniaturization at the same time.
The third problem is to develop a flexible type SI element that can be easily attached to the test piece.
The fourth issue is to develop a technique for eliminating the influence of the external magnetic field on the SI sensor.

The present inventor has diligently studied various factors affecting the strain gauge ratio.
As a result, as shown in FIG. 1, when the diameter of the magnetostrictive wire (denoted as wire diameter) is changed from 30 μm to 10 μm, the optimum frequency increases from 20 MHz to 200 MHz, and the strain gauge ratio at the optimum frequency is tripled. It was found that a reasonably high strain gauge factor was obtained and that it increased in proportion to the square root of the frequency.

As shown in FIG. 2, it was found that the strain gauge ratio strongly depends on the ratio of the length L of the magnetostrictive wire to the cross-sectional area S of the magnetostrictive wire, that is, the aspect ratio (L / S). It was found that the smaller the diameter of the magnetostrictive wire, the shorter the length of the element.
When the diameter of the magnetostrictive wire is 30 μm and the length is 20 mm for the SI element, the gauge ratio is about 1000, but when the length is shortened to 2 mm, the gauge ratio is drastically reduced to about 100. On the other hand, when the diameter of the magnetostrictive wire of the SI element was 10 μm and the lengths were 1 mm, 2 mm and 4 mm, the strain gauge ratio was about 1100, about 2300 and about 4500.

Based on the above findings, the present invention has devised a structure in which the SI element can be easily attached to the test piece.
On a flexible substrate, a substrate surface provided with an amorphous magnetostrictive wire (hereinafter referred to as a magnetostrictive wire) which is a stress detector and magnetostrictive wire electrodes at both ends of the magnetostrictive wire is fixed to the surface of the test piece with an adhesive. This is an SI element capable of measuring the surface stress of the test piece.
Further, in this element, the magnetostrictive wire is installed along the groove on the surface of the substrate in an insulated state from the substrate, and the magnetostrictive wire diameter may be embedded in the groove, or a part thereof is not embedded in the groove and the substrate is not embedded. A convex portion may be formed on the surface. Further, the magnetostrictive wires may be aligned along the mark lines with the grooves on the substrate as linear marks and fixed with an adhesive.

Since this element is formed on a flexible substrate, it can be easily fixed to the surface of the test object with an adhesive. The change in impedance generated in the magnetostrictive wire can be measured by an external electronic circuit through the magnetostrictive wire electrode. All wiring paths are insulated.

The manufacturing method of this device will be described.
Wiring patterns of a large number of elements are formed on the surface side of a flexible substrate having a predetermined size in consideration of the size of the element in the vertical and horizontal directions. A resist is applied to the surface side, a guide groove for aligning the magnetostrictive wire is formed therein, and a curing treatment is performed to solidify. After that, the magnetostrictive wires are aligned along the grooves and fixed with resin. The resin completely covers the magnetostrictive wire to ensure insulation. Finally, it is separated and used. The magnetostrictive wire may be embedded in the groove, or a part of the magnetostrictive wire may protrude. Further, the magnetostrictive wire may be aligned on the substrate surface by using the groove as a simple alignment line.
Further, on the back surface side, as many output electrodes as the number of elements are attached, and they are connected to the magnetostrictive wire electrodes on the front surface by via holes. It is also possible to connect to an external electronic circuit from the output electrode on the back surface side.

When measuring the stress applied to a small probe on the tip of a medical device such as a catheter, for example, the stress applied to a probe with a diameter of 0.3 mm is measured by installing SI elements on the four surfaces of the probe. When measuring, an SI element having a size of 2.0 mm or less in length, 0.2 mm or less in width, and 0.15 mm or less in thickness is desirable.

Since the magnetostrictive wire has a very small diameter of 18 μm or less, the thickness of the flexible substrate can be reduced to 0.05 mm to 0.15 mm, and as a result, the thickness of the entire SI element is 0.05 to 0.25 mm. can do. The electrode preferably has a diameter of about 0.04 to 0.10 mm. This is because the smaller the diameter of the electrode pad, the more preferable, but the smaller the diameter, the more difficult it is to join the electrode on the signal wiring.

In this element, the magnetic strain wire is made of an amorphous material with a glass coating having a diameter of 5 to 18 μm, and the magnetic strain wire electrode removes the glass coating on the upper surface of the magnetic strain wire to form a magnetic strain wire electrode with a metal vapor deposition film. It is an SI element which connects.
When the glass-coated wire is fixed to the test piece, the insulation is ensured and there is no risk of short circuit. However, it is necessary to remove the glass on the upper surface side of the wire from the electrode terminal portion, form the wire terminal on the wire surface with a metal vapor deposition film, and at the same time connect the wire terminal to the electrode terminal.
Nude amorphous magnetostrictive wires that are not glass-coated can also be applied, but they must be resin-coated or resin-coated after being attached to a flexible substrate to ensure insulation.

Further, when the external magnetic field is more than twice as large as the geomagnetism, the SI element detects the influence of the magnetic field having a magnitude that cannot be ignored at the same time as the stress. It has been found that by arranging a magnetic thin film having a shape of a square ring and having a thickness of about 2 μm to 10 μm on the surface of the device substrate so as to surround the magnetostrictive wire, it is possible to magnetically shield and remove the influence of an external magnetic field. The material of the magnetic thin film may be any material as long as it has a shielding function such as permalloy.
In order to realize a better magnetic shield, it is possible to add a magnetostrictive wire to a square ring and an elliptical ring similar to a square ring, and to make it into a wrapping shape that surrounds it from the top, bottom, left, and right. , A square ring magnetic thin film is most suitable.

Next, a stress impedance sensor using an SI element (hereinafter referred to as an SI sensor) was devised.
The SI sensor changes depending on the test piece that measures the stress load state, the magnetostrictive wire and the magnetostrictive wire attached to it, and the oscillation circuit that applies a high-frequency current or pulse current to the magnetostrictive wire and the stress applied to the test piece. The magnetostrictive wire is equipped with a signal processing circuit unit that detects the impedance of the magnetostrictive wire, and based on the above new findings, the magnetostrictive wire, which is a stress detection unit, has a diameter of 18 μm or less and a length of 5 mm or less, and energizes the magnetostrictive wire . By setting the frequency of the high-frequency current or pulse current to 100 to 500 MHz and the strength of the current to 50 mA or more, it is possible to output an output voltage proportional to the amount of distortion, and a gauge ratio of 2000 or more can be secured.

As the SI sensor circuit, a circuit that measures the element signal with an impedance analyzer circuit in the case of high-frequency current (Patent Document 1) is adopted, or in the case of pulse current, the peak value of the pulse signal waveform emitted by the wire. A circuit for holding a sample (Patent Document 1) and the like are widely used, and any of these circuits can be used as the circuit of the present invention.
However, since a high frequency of 200 MHz is used, it is preferable to use a pulse current as shown in the electronic circuit of FIG. 3 in consideration of power consumption.

The electronic circuit (FIG. 3) consists of a pulse oscillator, an element using magnetostrictive wires, a high-speed electronic switch, a peak hold circuit, and an amplifier. The peak voltage of the pulse waveform voltage corresponding to the impedance change amount of the magnetically distorted wire is detected by a high-speed electronic switch, the voltage is held by the peak hold circuit, and the output voltage is obtained by the amplifier. In sample holding, the peak voltage of the pulse signal waveform is detected by setting the peak value of the pulse signal waveform to 0.2 nsec or less by shortening the opening / closing time as much as possible with a high-speed switch.
The SI sensor that combines this element and the electronic circuit has a strain gauge ratio of 2000 or more.

The stress impedance sensor element and the stress impedance sensor can be easily attached to the test piece with a small size and high sensitivity. Moreover, the strain gauge ratio is about 40 times higher than that of a normal semiconductor strain gauge, and has a strain gauge ratio of 2000 or more, which makes it possible to detect minute strain or stress, and is a medical device. It is expected to be applied in the field of.

It is a figure which shows the influence of a frequency on a strain gauge ratio. It is a figure which shows the influence of the aspect ratio L / S on the strain gauge ratio. It is a figure of the electronic circuit of this invention. It is a top view which shows the SI element of this invention. It is sectional drawing of A1-A2 line of the SI element of this invention. It is a top view of the SI element which uses two magnetostrictive wires of this invention. It is a top view of the SI element magnetically shielded by the permalloy of this invention. It is sectional drawing of the B1-B2 line of the SI element magnetically shielded by the permalloy of this invention. It is sectional drawing of the C1-C2 line of the SI element magnetically shielded by the permalloy of this invention.

The stress impedance sensor element of the present invention includes a flexible substrate having flexibility, an amorphous magnetostrictive wire arranged on the flexible substrate, and an amorphous magnetostrictive wire electrode formed of two metal vapor deposition films . The length is 0.6 to 5.5 mm, and the amorphous magnetostrictive wire has a diameter of 5 to 18 μm and a length of 0.5 to 5.0 mm.
Further, it is preferably arranged in a groove formed in the amorphous substrate and covered with an insulating resin.

The change in impedance generated in the amorphous magnetostrictive wire (hereinafter referred to as the magnetostrictive wire) can be measured by an external electronic circuit by the lead wires from the magnetostrictive wire electrodes at both ends of the magnetostrictive wire.
Further, since the SI element is composed of a flexible substrate having flexibility, it can be easily fixed with an adhesive regardless of the shape of the surface of the test object. Further, since the magnetostrictive wire, which is a stress detector, is arranged on the surface of the SI element, it can directly contact the test piece and directly convert the strain of the test piece into the strain of the magnetostrictive wire.

The details will be described below.
<Amorphous magnetostrictive wire>
In order to detect minute stress, the smaller the diameter (cross-sectional area S) of the magnetostrictive wire, the higher the strain gauge ratio. Therefore, the diameter is set to 5 to 18 μm. The length (L) of the magnetostrictive wire is set to 0.05 to 5 mm to reduce the size of the element.
As the aspect ratio L / S increases from FIG. 1, the strain gauge ratio increases. Therefore, the diameter and length of the magnetostrictive wire are determined according to the specific application.
The material may be a Co-based amorphous magnetostrictive wire or an Fe-based amorphous magnetostrictive wire.
Further, as the amorphous magnetostrictive wire, a glass-coated or resin-coated or naked amorphous magnetostrictive wire having a diameter of 5 to 18 μm can be applied.

Further, the magnetostrictive wire is arranged in a groove and coated with a resin having an insulating property.
If the substrate does not have or is insufficient in insulating performance, it is necessary to secure the insulating property by applying an insulating material to the groove of the substrate, vapor deposition, etc. before arranging the magnetostrictive wire in the groove.
Further, a resist layer having an insulating property may be provided on the surface of the substrate, and a groove may be provided in the resist layer integrated with the substrate to arrange the magnetostrictive wire.
After arranging the magnetostrictive wire in the groove, the groove is filled with resin and the periphery of the magnetostrictive wire is also covered with resin.
All wiring paths are insulated.

<Structure of SI element>
An example of the structure of the SI element is shown in FIG.
In the SI element 1 shown in FIG. 4, the magnetostrictive wire 13 is arranged in the groove 12 provided on the substrate 11, and the magnetostrictive wire electrode 161 from the magnetostrictive wire terminals 14 at both ends of the magnetostrictive wire 13 via the connection wiring 15. It is connected to 162. FIG. 5 is a cross-sectional view taken along the line A1-A2 of FIG.
The SI element 1 is a substrate in which a resist layer 11R is provided on the substrate 11, and a groove 12 is provided in the resist layer 11R.
Further, FIG. 6 shows an SI element 1A using two magnetostrictive wires 13. By shortening the length of the magnetostrictive wire 13 and using two of them, the same sensitivity as in the case of one long magnetostrictive wire 13 can be obtained while reducing the size of the SI element 1A.

<Flexible board>
The substrate on which the magnetostrictive wire and the magnetostrictive wire electrode, which are stress detectors, are arranged is a flexible substrate that has flexibility so that the amorphous magnetostrictive wire attached to the test piece for measuring the stress load state can detect minute stress. Consists of.
Further, since the magnetostrictive wire is arranged on the flexible substrate, the surface of the substrate can be flexibly and easily fixed with an adhesive according to the surface shape of the test piece. It is most suitable not only for the flat surface of the test piece, but also for the rounded R surface of a cylinder.

<Magnetorstrictive wire electrode>
The amount of change in impedance generated in the magnetostrictive wire is transmitted from the magnetostrictive wire to the external electronic circuit by direct wiring (lead wire) from the magnetostrictive wire electrodes formed at both ends of the magnetostrictive wire. Therefore, it is composed of two magnetostrictive wire electrodes.
Further, as illustrated in FIGS. 4 and 5, magnetic strain wire terminals are provided at both ends of the magnetostrictive wire, and if necessary, a magnetostrictive wire electrode is provided via a connection wiring, and external electrons are provided by wiring from the magnetostrictive wire electrode. You may tell the circuit. Therefore, it is composed of two magnetostrictive wire terminals and two magnetostrictive wire electrodes, and if necessary, two or three connecting wirings that connect the magnetostrictive wire terminals and the magnetostrictive wire electrodes.

The size of the electrode is preferably 0.04 mm × 0.04 mm to 0.1 mm × 0.1 mm or 0.04 φmm to 0.1 φ mm. This is because the smaller the size of the electrode pad, the more preferable it is, but the smaller the size, the more difficult it is to join the electrode on the signal wiring.

In the case of an amorphous magnetostrictive wire with a glass coating, both ends of the magnetostrictive wire are removed from the glass coating on the upper surface of the magnetostrictive wire to form a magnetostrictive wire terminal with a metal vapor deposition film, and the magnetostrictive wire terminal and the magnetostrictive wire electrode are connected. ..
The magnetostrictive wire with a glass coating can ensure insulation when it is placed in a groove or fixed to a test object, so that there is no risk of a short circuit.

<Arrangement relationship between flexible substrate and magnetic wire>
A groove (guide groove) for arranging the magnetostrictive wire is formed on the flexible substrate, the magnetostrictive wire is arranged in the groove, and the magnetostrictive wire is bonded with a resin. As a result, the magnetostrictive wire can be reliably fixed to the substrate.
An insulating resist layer capable of forming a groove may be provided on the substrate (the surface of the substrate), and a groove may be formed in the resist layer. It is a resist-coated substrate and is a substrate in a broad sense.
The relationship between the groove depth and the magnetostrictive wire is that even if the upper part of the magnetostrictive wire diameter is the same as or buried in the substrate surface, or if a part of the magnetostrictive wire diameter forms a protrusion from the substrate surface. Good. Since a part of the diameter of the magnetostrictive wire protrudes from the groove to form a convex portion, the contact between the test piece and the magnetostrictive wire can be made closer.
The upper part or the convex part of the magnetostrictive wire is coated with an insulating resin. This is to ensure the insulating property when the surface of the substrate is fixed to the surface of the test piece with an adhesive.

<Element size>
The size of the SI element is 0.6 to 5.5 mm in length, 0.05 to 0.25 mm in width, and 0.05 to 0.25 mm in thickness. A small element can be obtained.
Preferably, the length is 0.6 to 1.2 mm, the width is 0.05 to 0.20 mm, and the thickness is 0.05 to 0.15 mm. Thereby , the stress applied to the wire having a diameter of 0.3 mm at the tip of the catheter can be measured.

<Magnetic thin film>
The shape of the magnetic thin film surrounding the magnetostrictive wire is a square ring shape or a ring shape, and the ring is surrounded by a magnetic thin film having a width of 20 μm to 50 μm and a thickness of about 2 μm to 20 μm, and has a magnetic shielding function. The material of the magnetic thin film may be any material as long as it has a shielding function such as permalloy. In order to realize a better magnetic shield, it is possible to add a magnetostrictive wire to the square ring and make it into a bag shape that surrounds it from the top, bottom, left, and right, but considering economic efficiency, the square ring magnetic thin film is the most suitable. is there.

The stress impedance sensor of the present invention comprises a stress impedance sensor element and an electronic circuit.
The stress impedance sensor element uses the SI element described above, and the electronic circuit includes a pulse oscillator that energizes an amorphous magnetostrictive wire with a high-frequency current or pulse current having a frequency of 100 to 500 MHz, a high-speed electronic switch, a peak hold circuit, and an amplifier. It has. The electronic circuit detects the peak voltage of the pulse waveform voltage corresponding to the impedance change amount of the amorphous magnetic strain wire by a high-speed electronic switch with an opening / closing time of 0.2 nsec or less.

<Electronic circuit>
The electronic circuit consists of a pulse oscillator, a high-speed electronic switch, a peak hold circuit and an amplifier.
First, the frequency of the high frequency current or pulse current energized from the pulse oscillator is 100 to 500 MHz. This is because when the diameter of the magnetic wire is reduced to 5 to 18 μm, the strain gauge ratio can be improved by using a high frequency.

As the electronic circuit of the SI sensor, a circuit (Patent Document 1) for measuring the element signal with an impedance analyzer circuit is used in the case of high-frequency current, and the peak of the pulse signal waveform transmitted by the magnetic wire in the case of pulse current. A circuit that holds a sample of a value (Patent Document 2) and the like are known, but both can be used as the electronic circuit of the present invention.
However, since a high frequency of 100 MHz to 500 MHz is used, it is preferable to use a pulse current in consideration of power consumption.
The electronic circuit (FIG. 3) consists of a pulse oscillator, an element using an amorphous magnetostrictive wire, a high-speed electronic switch, a peak hold circuit, and an amplifier. The peak voltage of the pulse waveform voltage corresponding to the impedance change amount of the magnetically distorted wire is detected by a high-speed electronic switch, the voltage is held by the peak hold circuit, and the output voltage is obtained by the amplifier. In sample holding, it is preferable to detect the peak voltage by setting the peak value of the pulse signal waveform to 0.2 nsec or less by shortening the opening / closing time as much as possible with a high-speed switch.

<SI sensor and test object>
Since the SI element of this SI sensor is arranged on a flexible substrate having flexibility, it can be easily fixed to the surface of the test object with an adhesive. Further, since the magnetostrictive wire, which is a stress detector, is arranged on the surface of the SI element, it is possible to directly contact the test piece and convert the strain of the test piece into the strain of the magnetostrictive wire .
The change in impedance generated in the magnetostrictive wire can be measured by an external electronic circuit through the magnetostrictive wire electrode.

By appropriately combining the aspect ratio of the amorphous magnetostrictive wire, which is a stress detector (L / S consisting of L having a length of 0.5 to 5.0 mm and S having a diameter of 5 to 18 μm), and a frequency of 100 to 500 MHz. A high strain gauge ratio of 2000 or more can be obtained.

According to the present invention, the stress impedance sensor can be miniaturized and highly sensitive, and the strain of the subject is directly converted into the strain of the magnetostrictive wire by being attached in contact with an arbitrary surface of the subject to be accurate. Distortion can be measured.
This SI sensor having the above configuration is a high-performance sensor that can output an output voltage proportional to the amount of strain of the magnetic wire, is compact, and has a strain gauge ratio of 2000 or more. Furthermore, it is a highly reliable sensor that eliminates the influence of the external magnetic field, which has been a drawback of conventional SI sensors.

Hereinafter, examples will be described with reference to the drawings.
[Example 1]
In the first embodiment, the stress impedance sensor element will be described with reference to FIGS. 7 to 9.
7 is a plan view, FIG. 8 is a sectional view taken along line B1-B2 of FIG. 7, and FIG. 9 is a sectional view taken along line C1-C2 of FIG.

A resist layer 11R having a length of 5.00 mm, a width of 0.20 mm, and a thickness of 10 μm is formed on the substrate 11 having a length of 5.25 mm.
A groove 12 having a width of 20 μm and a depth of 8 μm is formed in the resist layer 11R, and a magnetostrictive wire 13 having a diameter of 10 μm and a length of 4.6 mm is arranged. The magnetostrictive wire 13 is fixed to the groove 12 by the resin 17 and is insulated.
Magnetostrictive wire terminals 14 are arranged at both ends of the magnetostrictive wire 13, and are attached to the magnetostrictive wire output electrode 161 and the magnetostrictive wire GND electrode at one end of the substrate 11 (the right end in FIG. 7) via the connection wiring 15, respectively. It is connected.

The periphery of the magnetostrictive wire 13 is magnetically shielded by a square ring permalloy 11P having a width of 20 μm together with the magnetostrictive wire terminal 14 of the magnetostrictive wire 13. The thickness of the permalloy 11P is 20 μm on one side of the square ring intersecting with the connection wiring 14 (the side of the B1-B2 line in FIG. 7) and 20 μm on the other three sides.
Here, the permalloy 11P of the SI element 1B, the magnetostrictive wire terminal 14, the connecting wiring 15, the magnetostrictive wire electrodes (161 and 162) and the like are insulated with resin.

The performance of the SI element 1 was measured in an environment of a geomagnetic magnetic field using the electronic circuit used in the second embodiment. An adhesive was fixed to the cantilever of the SI element, a high-frequency current having an excitation frequency of 200 MHz and a current intensity of 80 mA was applied thereto, and the voltage between both ends of the magnetostrictive wire was measured. Stress was applied to the cantilever, and the stress dependence of the SI element was confirmed.
Next, the test was conducted by changing the external magnetic field from 0 to 300 G. As a result, the output corresponding to the stress could be obtained. The effect of the magnetic field was 1% or less, which was a negligible level. Further, a strain gauge ratio of 5200 was obtained.

On the other hand, when the magnetic shield by permalloy is not performed (there is no permalloy 11P of the square ring in FIG. 7), the output error increases with the increase of the external magnetic field, and 20% / full scale at 300G. There was an error in. Further, at this time, the strain gauge ratio was greatly reduced to about 500, and was greatly affected by the external magnetic field.

[Example 2]
The stress impedance sensor of the second embodiment is a combination of the SI element used in the first embodiment and the following electronic circuit.

The electronic circuit 2 of the SI sensor includes a pulse oscillator 21, an electronic switch 22 that turns on and off pulse energization, an SI element 23, and a peak hold circuit 26 that detects the peak value of the pulse voltage waveform generated by the SI element 23. In the case of a pulse current, the peak hold circuit 26 that sample-holds the peak value of the pulse signal waveform emitted by the magnetic wire includes a high-speed electronic switch 24 and a capacitor 25.
The frequency of the pulse current was 200 MHz, the strength of the current was 100 mA, and the high-speed electronic switch 22 controlled the pulse period to 1 MHz. In the sample hold, the peak value of the pulse signal waveform was set to 0.1 nsec by the high-speed switch 24, and the peak voltage was detected.
The peak-held voltage is amplified by the amplifier 27 and output as an output voltage. The output voltage is proportional to the stress applied to the test piece.

As a result of adhering this example to the test piece and applying stress for measurement, the same result as in Example 1 could be obtained.

[Example 3]
Example 3 relates to a stress impedance sensor that aims to apply stress to a wire having a diameter of 0.3 mm at the tip of a catheter, and applies an SI element to a test piece having a diameter of 0.3 mm by attaching an SI element with an adhesive. It was measured. The magnetostrictive wire , which is a stress detector, has a very small length of 1.8 mm and a diameter of 10 μm, which makes it possible to further reduce the size of the SI element. The size of the SI element is 2.0 mm in length, 0.12 mm in width, and 0.15 mm in thickness. The size of the electrode was 0.04 mm × 0.04 mm.
Since the diameter of the magnetostrictive wire was set to 10 μm, the pulse frequency was set to 200 MHz and the current strength was set to 80 mA. Despite the miniaturization, a strain gauge ratio of 2050 has been obtained.

As described above, since the SI sensor of the present invention is extremely small and has high sensitivity, it is suitable for application to in-vivo medical devices such as catheters.

1: Stress impedance sensor element (SI element)
11: Flexible substrate (board), 11R: Resist layer, 11P: Permalloy, 12: Groove, 13: Magnetostrictive wire, 14: Magnetostrictive wire terminal, 15: Connection wiring, 161: Magnetostrictive wire output electrode, 162: Magnetostrictive wire GND electrode , 17: Resin (insulating resin)
1A: SI element (two magnetostrictive wires)
31: Substrate, 32: Groove, 33: Magnetostrictive wire, 34: Magnetostrictive wire terminal, 35: Connection wiring, 36 (361, 362): Magnetostrictive wire electrode
1B: SI element (with magnetic film)
31: Substrate, 31R: Resist layer, 31P: Permalloy, 32: Groove, 33: Magnetostrictive wire, 34: Magnetostrictive wire terminal, 35: Connection wiring, 36 (361, 362): Magnetostrictive wire electrode,
37: Resin 2: Electronic circuit 21: Pulse oscillator, 22: Electronic switch, 23: SI element, 24: High-speed electronic switch,
25: Capacitor, 26: Peak hold circuit, 27: Amplifier

Claims (8)

In a stress impedance sensor element composed of a flexible substrate having flexibility, an amorphous magnetostrictive wire arranged on the flexible substrate, and an amorphous magnetostrictive wire electrode formed of two metal vapor deposition films .
The flexible substrate has a length of 0.6 to 5.5 mm.
The amorphous magnetostrictive wire is a stress impedance sensor element having a diameter of 5 to 18 μm and a length of 0.5 to 5.0 mm.
In a stress impedance sensor consisting of a stress impedance sensor element and an electronic circuit,
The stress impedance sensor element is a flexible substrate having a length of 0.6 to 5.5 mm, a diameter of 5 to 18 μm arranged in a groove formed in the flexible substrate, and a length of 0. It comprises an amorphous magnetostrictive wire made of 5 to 5.0 mm and coated with an insulating resin and an amorphous magnetostrictive wire electrode formed of two metal vapor deposition films .
The electronic circuit is a stress impedance sensor including a pulse oscillator that energizes the amorphous magnetic strain wire with a high-frequency current or a pulse current having a frequency of 100 to 500 MHz, a high-speed electronic switch, a peak hold circuit, and an amplifier.
In claim 2,
A stress impedance sensor in which the amorphous magnetostrictive wire is arranged in a groove formed in the substrate and is coated with an insulating resin. In claim 2 or 3,
The amorphous magnetostrictive wire is a stress impedance sensor characterized in that a part of the diameter of the amorphous magnetostrictive wire is formed as a convex portion on the surface of a substrate without being embedded in the groove. In any one of claims 2 to 4 ,
The amorphous magnetostrictive wire is made of an amorphous magnetostrictive wire having a glass coating having a diameter of 5 to 18 μm, and both ends of the amorphous magnetostrictive wire are formed by removing the glass coating on the upper surface of the amorphous magnetostrictive wire and forming an amorphous magnetostrictive wire terminal with a metal vapor deposition film. A stress impedance sensor characterized by forming the above and connecting the amorphous magnetostrictive wire terminal and the amorphous magnetostrictive wire electrode.
In any one of claims 2 to 5,
The amorphous magnetostrictive wire is a stress impedance sensor characterized in that it is surrounded by a magnetic thin film having a square ring or an elliptical ring. In any one of claims 2 to 6,
The stress impedance sensor element has a length of 0.6 to 5.5 mm and a width of 0.05 to 0.25 mm.
A stress impedance sensor having a thickness of 0.05 to 0.25 mm. In any one of claims 2 to 7,
The electronic circuit is a stress impedance sensor characterized in that a peak voltage of a pulse waveform voltage corresponding to an impedance change amount of the amorphous magnetostrictive wire is detected by the high-speed electronic switch with an opening / closing time of 0.2 nsec or less.

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