Sensor module

Abstract

To provide a sensor module comprising a strain gauge that functions as a humidity sensor.SOLUTION: A sensor module provided herein includes a support body and a first strain gauge comprising a first substrate made of resin and a first resistor formed on a first surface of the first substrate, where a second surface, different from the first surface, of the first substrate is fixed to the support body and at least a portion of the first surface is exposed or covered with a moisture-permeable layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a sensor module. [Background technology]

[0002] Conventionally, strain gauges that are attached to an object to be measured have been known. For example, strain gauges are sometimes used as sensors that detect strain in materials or sensors that detect ambient temperature (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-221696 Summary of the Invention [Problem to be solved by the invention]

[0004] There is also a demand for using strain gauges as sensors for detecting humidity.

[0005] The present invention has been made in view of the above points, and has an object to provide a sensor module having a strain gauge that functions as a humidity sensor. [Means for solving the problem]

[0006] A sensor module according to one embodiment of the present disclosure includes a support and a first strain gauge, the first strain gauge including a first substrate made of resin and a first resistor formed on a first surface of the first substrate, a second surface of the first substrate different from the first surface being fixed to the support, and at least a portion of the first surface being exposed or coated with a moisture-permeable layer. [Effects of the Invention]

[0007] According to the disclosed technology, it is possible to provide a sensor module having a strain gauge that functions as a humidity sensor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view illustrating the sensor module according to the first embodiment. [Figure 2] 1 is a cross-sectional view illustrating a sensor module according to a first embodiment. [Figure 3] These are the measurement results of Experiment 1. [Figure 4] Measurement results (part 1) of Experiment 2. [Figure 5] Measurement results (part 2) of Experiment 2. [Figure 6] Measurement results (part 1) of Experiment 3. [Figure 7] Measurement results (part 2) of Experiment 3. [Figure 8] 10A and 10B are diagrams illustrating the presence or absence of a sealing portion. [Figure 9] FIG. 2 is a plan view illustrating the strain gauge according to the first embodiment. [Figure 10] 1 is a cross-sectional view (part 1) illustrating a strain gauge according to a first embodiment. FIG. [Figure 11] FIG. 2 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. [Figure 12] FIG. 10 is a plan view illustrating a sensor module according to a first modification of the first embodiment. [Figure 13] FIG. 4 is a plan view showing another example of the sensor module according to the first embodiment. [Figure 14] 10A and 10B are a plan view and a cross-sectional view showing an example of a detection element included in a strain gauge according to a second embodiment. [Figure 15] 10A to 10C are a perspective view, a plan view, and a cross-sectional view showing an example of a detection element included in a strain gauge according to a third embodiment. [Figure 16] 10A to 10C are a perspective view, a plan view, and a cross-sectional view showing another example of a detection element included in a strain gauge according to the third embodiment. [Figure 17] 10A and 10B are a perspective view, a plan view, and a cross-sectional view showing still another example of a detection element included in a strain gauge according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the invention will be described with reference to the drawings. In each drawing, the same components may be assigned the same reference numerals. Furthermore, in each drawing, mutually orthogonal X, Y, and Z directions may be defined. In this case, in the X direction, the starting point (base) side of the arrow may be referred to as the X- side, and the ending point (arrowhead) side of the arrow may be referred to as the X+ side. The same applies to the Y and Z directions. Furthermore, in the description of each drawing, a description of components that are the same as components already described may be omitted.

[0010] First Embodiment [Sensor module] Fig. 1 is a plan view illustrating a sensor module according to the first embodiment, and Fig. 2 is a cross-sectional view illustrating the sensor module according to the first embodiment, taken along line AA in Fig. 1.

[0011] 1 and 2, the sensor module 1 mainly includes a strain element 10, strain gauges 100A (second strain gauge) and 100B (first strain gauge), and a sealing portion 200.

[0012] The flexure body 10 is a member that generates strain when subjected to a load. The flexure body 10 also serves as a support for supporting strain gauges 100A and 100B, which will be described later. The flexure body 10 is, for example, rectangular. Materials that can be used for the flexure body 10 include, for example, stainless steel (SUS), copper, and aluminum. The flexure body 10 is, for example, flat, and can be formed by a press working method or the like. The material for the flexure body 10 may also be an inorganic material such as ceramic.

[0013] The strain generating body 10 includes a sensitive region 11 and insensitive regions 12 and 13. The sensitive region 11 is an area used for detecting strain, and is designed to have a relatively low rigidity so that strain is easily generated when a load is applied. In contrast, the insensitive regions 12 and 13 are areas not used for detecting strain, and are designed to have a lower strain detection sensitivity than the sensitive region 11. There are no particular limitations on the configuration that realizes the difference in strain detection sensitivity between the sensitive region and the insensitive regions. For example, in this embodiment, the insensitive regions 12 and 13 are designed to have a higher rigidity than the sensitive region 11. This makes it possible to make the strain detection sensitivity of the insensitive regions 12 and 13 lower than that of the sensitive region 11.

[0014] As an example, in the sensor module 1, the rigidity is adjusted so that when the rated load of the sensor module 1 is applied to the center of the sensitive area 11, the amount of strain measured at the centers of the insensitive areas 12 and 13 is less than 1 / 4 of the amount of strain measured at the center of the sensitive area 11.

[0015] In this way, when the strain detection sensitivity is varied depending on the rigidity, it is more preferable to adjust the rigidity so that when the rated load of the sensor module 1 is applied to the center of the sensitive area 11, for example, the amount of strain measured at the centers of the insensitive areas 12 and 13 is 1 / 5 or less of the amount of strain measured at the center of the sensitive area 11, and it is even more preferable to adjust the rigidity so that it is 1 / 10 or less.

[0016] In this embodiment, as an example, the insensitive region 12 is formed thicker than the sensitive region 11, thereby making the rigidity of the insensitive region 12 higher than that of the sensitive region 11. However, the method of changing the rigidity of the sensitive region 11 and the insensitive regions 12 and 13 is not limited to changing their thicknesses. For example, the flexure body 10 may have a slit formed in a portion of a uniformly thick flexure body. In this case, the region near the slit becomes the sensitive region with relatively low rigidity, and the region farther from the slit becomes the insensitive region with relatively high rigidity. The flexure body 10 may also have a structure including a peripheral portion and a beam portion. In this case, the beam portion becomes the sensitive region with relatively low rigidity, and the peripheral portion becomes the insensitive region with relatively high rigidity. Specifically, the flexure body 10 may have a ring-shaped peripheral portion formed around the outer periphery of the uniformly thick flexure body and a beam portion formed to bridge the inside of the ring-shaped peripheral portion. The shape of the beam portion is not particularly limited, and for example, the beam portion may have a cross shape passing through the center of the ring.

[0017] In this embodiment, an insensitive area 12 is provided on the X- side of the sensitive area 11, and an insensitive area 13 is provided on the X+ side. The thickness t1 of the sensitive area 11 and the thickness t2 of the insensitive areas 12 and 13 are selected appropriately depending on the desired difference in rigidity between the two. Note that the sensitive area 11 and the insensitive area 12 may be provided in the flexure body 10, but the insensitive area 13 may not be provided. In other words, it is sufficient that the flexure body 10 has at least one sensitive area and one insensitive area.

[0018] The strain gauge 100A includes a substrate 110A, a resistor 130 formed on the upper surface of the substrate 110A, and a pair of electrodes 150. The strain gauge 100B includes a substrate 110B, a resistor 130 formed on the upper surface 110s of the substrate 110B, and a pair of electrodes 150. The strain gauges 100A and 100B may be strain gauges of the same specifications except for the substrates, or may be strain gauges of different specifications having a configuration described below. The substrate 110B is made of resin, but the substrate 110A may be made of resin or metal, etc. External connection wiring 180, such as lead wires or flexible substrates, is joined to the electrodes 150 of the strain gauges 100A and 100B by soldering or the like.

[0019] The strain gauge 100A is disposed in the sensitive region 11 on the upper surface 10m side of the flexure body 10. Specifically, a lower surface 110n of a substrate 110A of the strain gauge 100A is bonded to the sensitive region 11 by an adhesive layer 30. The strain gauge 100B is disposed in the insensitive region 12 on the upper surface 10m side of the flexure body 10. Specifically, a lower surface 110t of the substrate 110B of the strain gauge 100B is bonded to the insensitive region 12 by an adhesive layer 30.

[0020] The adhesive layer 30 is not particularly limited as long as it is a material that functions to bond the flexure element 10 and the strain gauges 100A and 100B together. For example, epoxy resin, modified epoxy resin, silicone resin, modified silicone resin, urethane resin, modified urethane resin, etc. can be used for the adhesive layer 30. A bonding sheet or the like can also be used for the adhesive layer 30. The thickness of the adhesive layer 30 is not particularly limited. For example, the thickness of the adhesive layer 30 can be approximately 0.1 μm to 50 μm.

[0021] The strain gauge 100A according to this embodiment is sealed by a sealing portion 200. The sealing portion 200 may be made of a material such as a thermosetting resin. Examples of thermosetting resins include urethane resin, epoxy resin, and silicone resin. The sealing portion 200 may be formed by a potting technique in which a liquid resin is applied to cover the strain gauge 100A and then thermally cured.

[0022] The sealing by the sealing unit 200 is performed after the external connection wiring 180 is joined to the electrode 150 of the strain gauge 100A. Therefore, the sealing unit 200 covers the entire strain gauge 100A, including the joint between the electrode 150 and the external connection wiring 180, as well as the sensitive area 11 located around the strain gauge 100A. By providing the sealing unit 200, the weather resistance of the joint between the electrode 150 and the external connection wiring 180 and the strain gauge 100A can be improved. The sealing unit 200 is not an essential component of the strain gauge 100A. For example, the strain gauge 100A may not be provided with the sealing unit 200 for various reasons, such as the structure of the flexure element 10 or the required specifications of the strain gauge 100A.

[0023] When strain occurs in the sensitive region 11, the strain gauge 100A arranged in the sensitive region 11 can detect the strain caused by the stress applied to the sensitive region 11 based on a change in the resistance value of the resistor 130. On the other hand, since the insensitive region 12 has higher rigidity than the sensitive region 11, the stress applied to the sensitive region 11 is not easily transmitted to the insensitive region 12. Therefore, the strain gauge 100B arranged in the insensitive region 12 detects little or no strain caused by the stress applied to the sensitive region 11.

[0024] The strain gauge 100B arranged in the dead area 12 is not sealed by a sealing portion. The strain gauge 100B arranged in the dead area 12 can detect the humidity around the sensor module 1. This will be described in detail below.

[0025] Generally, resins have the property of absorbing and releasing moisture, so when a strain gauge with a resistor attached to a resin substrate is attached to a flexural element to detect the strain of the flexural element, the detected value of the resistor is affected not only by the strain of the flexural element, but also by the strain caused by the moisture absorption or release of the substrate. The change in strain caused by the moisture absorption and release of the substrate is not the strain that is being detected (i.e., the strain transmitted to the flexural element). Therefore, the strain that occurs in the resin substrate becomes a noise component in a normal strain gauge.

[0026] However, the inventors thought that if the strain caused by moisture absorption and desorption of the substrate could be adequately detected, it might be possible to use a strain gauge as a humidity sensor, and therefore conducted the following experiment.

[0027] (Experiment 1) First, a resin film to be used as the substrate for the strain gauge was prepared. The prepared resin film was a polyimide film with a rectangular planar shape and a thickness of 25 μm. Next, this resin film was placed in an environmental test chamber. The temperature and humidity inside the environmental test chamber were then changed in a predetermined stepwise manner, and the change in length of the resin film was measured. The change in length was measured by clamping both ends of two opposing sides of the four sides of the resin film in a plan view, and measuring the change in length in the direction perpendicular to the clamped sides.

[0028] Figure 3 shows the measurement results of Experiment 1. In Figure 3, line (1) indicates temperature (°C), line (2) indicates humidity (RH%), and line (3) indicates the change in length of the resin film (%). The horizontal axis represents time, with one division representing 200 minutes, for a total of 1000 minutes.

[0029] As shown by line (1), the temperature was constant during the test. Also, as shown by line (2), the humidity was changed in stages over 1000 minutes, and even at the peak of the highest humidity, the humidity was not saturated. Under these conditions, as shown by line (3), the change in length of the resin film increased or decreased slightly depending on the humidity. These results show that the resin film that forms the base material of the strain gauge expands or contracts slightly due to moisture absorption.

[0030] (Experiment 2) First, a sensor module was prepared by bonding a strain gauge to a strain body. In the prepared sensor module, the strain body was made of a structural material such as stainless steel or aluminum alloy. The substrate of the strain gauge was a 25 μm thick polyimide film with a rectangular planar shape. The resistor material formed on the substrate was a Cr mixed phase film. Note that the strain gauge used in Experiment 2 was not sealed. Next, this sensor module was placed in an environmental test chamber. The temperature and humidity inside the environmental test chamber were changed in stages as preset, and the output value of the strain gauge was measured.

[0031] Figures 4 and 5 show the measurement results of Experiment 2. In Figure 4, line (1) indicates temperature (°C), and line (3) indicates the strain gauge output value (mV / V). In Figure 5, line (2) indicates humidity (°C), and line (3) indicates the strain gauge output value (mV / V). In Figures 4 and 5, the horizontal axis represents time, with one division representing 120 minutes, for a total of 600 minutes.

[0032] As shown by line (1) in Figure 4, the temperature remained almost constant during the test. Also, as shown by line (2) in Figure 5, the humidity was changed in stages from 40% to 85% over a period of 72 minutes, and the humidity was not saturated even at the peak. Under these conditions, as shown by lines (3) in Figures 4 and 5, the strain gauge output value increased and decreased in accordance with the humidity. Also, the increase and decrease in the strain gauge output value was gradual, just like the change in humidity.

[0033] In Figure 3 of Experiment 1, the strain gauge output value increases or decreases gradually as the humidity increases or decreases at each stage of the humidity change. In contrast, in Figure 5 of Experiment 2, the strain gauge output value increases or decreases rapidly to more than 90% of the peak output value at each stage, approximately 72 / 6 to 72 / 5 minutes after the humidity change. From these results, it can be said that by bonding the strain gauge to the flexure element, it is possible to detect strain due to moisture absorption with good response, which was only slight when the strain gauge was not bonded to the flexure element.

[0034] (Experiment 3) Experiment 3 was conducted under the same conditions as Experiment 2, except that the strain gauge was sealed with a sealing material. The sealing material was epoxy resin or silicone resin, and the entire strain gauge used in Experiment 3 was sealed using a potting technique. Figures 6 and 7 show the measurement results of Experiment 3. In Figure 6, line (1) represents temperature (°C), and line (3) represents the strain gauge output value (mV / V). In Figure 7, line (2) represents humidity (°C), and line (3) represents the strain gauge output value (mV / V). In Figures 6 and 7, the horizontal axis represents time, with one division representing 120 minutes, for a total of 600 minutes. Comparing Figures 6 and 7 with Figures 4 and 5, it can be seen that when the strain gauge was sealed, the humidity response of the strain gauge decreased and it almost stopped responding to humidity.

[0035] (Summary of Experiments 1-3) As described above, when a strain gauge is bonded to a flexural element, it becomes possible to detect with good responsiveness the expansion and contraction caused by moisture absorption and release of the resin film that serves as the base material of the strain gauge. Specifically, by fixing the bottom surface of the base resin film to the flexural element via an adhesive layer, the humidity responsiveness is reduced by at least 67 to 83 times. The mechanism behind this is thought to be as follows:

[0036] That is, when the bottom surface of the resin film is fixed to the flexure element, moisture absorption from the bottom side of the resin film decreases. Therefore, it is presumed that the difference in moisture absorption between the top surface (resistance element side) and the bottom surface (flexure element side) of the resin film increases strain, thereby improving humidity responsiveness. Furthermore, if the strain gauge is sealed with a sealing section so that the top surface of the resin film is not exposed at all, humidity responsiveness becomes almost zero. This is presumed to be because moisture absorption from the top surface of the resin film decreases, and the difference in moisture absorption between the top and bottom surfaces of the resin film is almost eliminated. Furthermore, it is presumed that another factor contributing to this improvement is that when the entire strain gauge is sealed with a sealing section, the resin film, which serves as the base material, is constrained to the flexure element via the sealing section, suppressing the expansion and contraction of the resistor due to moisture absorption and release of the resin film.

[0037] When using a strain gauge as a humidity sensor, it is preferable that it does not detect other strains as noise. For example, it is preferable that a strain gauge used as a humidity sensor is stress-insensitive and temperature-insensitive. Regarding stress, the strain gauge can be made stress-insensitive by adhering it to the insensitive area of ​​the strain-generating body. Regarding temperature, the strain gauge can be made temperature-insensitive by using a strain gauge with a TCR near zero.

[0038] As a humidity sensor, it is preferable to use a strain gauge with a TCR in the range of -200 ppm / °C to +200 ppm / °C, more preferably a strain gauge with a TCR in the range of -100 ppm / °C to +100 ppm / °C, and even more preferably a strain gauge with a TCR in the range of -50 ppm / °C to +50 ppm / °C.

[0039] From the above, in a strain gauge using a resin substrate, by fixing the lower surface of the substrate to the insensitive region of the strain generator and exposing at least a portion of the upper surface of the substrate, the substrate absorbs or releases moisture from the exposed portion. Therefore, it can be said that this strain gauge can be used as a humidity sensor. Alternatively, instead of exposing at least a portion of the upper surface of the substrate, the upper surface of the substrate may be covered with a moisture-permeable layer. In this case, too, it can be said that this strain gauge can be used as a humidity sensor because the substrate absorbs or releases moisture through the moisture-permeable layer.

[0040] When measuring strain and humidity simultaneously, as shown in Figures 1 and 2, strain gauge 100A attached to sensitive region 11 of one strain element 10 can function as a strain sensor, and strain gauge 100B attached to insensitive region 12 can function as a humidity sensor. With this configuration, humidity can be measured at approximately the same position when measuring strain on an object.

[0041] Furthermore, a strain gauge 100A that is not intended to measure humidity may be sealed with a sealing portion 200 as in the sensor module 1 shown in Figures 1 and 2, or may not be sealed with a sealing portion 200 as in the sensor module 1A shown in Figure 8. Note that, in a strain gauge 100A that functions as a strain sensor, it is preferable to provide a sealing portion 200 when measurement errors due to humidity become a problem.

[0042] Next, details of the strain gauges that can be used in the sensor modules 1 and 1A will be described.

[0043] [Strain gauge 100B] Fig. 9 is a plan view illustrating the strain gauge according to the first embodiment. Fig. 10 is a cross-sectional view (part 1) illustrating the strain gauge according to the first embodiment, showing a cross section along line BB in Fig. 9.

[0044] 9 and 10, the strain gauge 100B has a substrate 110B, a resistor 130, wiring 140, electrodes 150, and a cover layer 160. The cover layer 160 is not an essential component. For convenience, only the outer edge of the cover layer 160 is shown by a dashed line in FIGS. 9 and 10. First, each component of the strain gauge 100B will be described in detail.

[0045] In this embodiment, for convenience, the side of the strain gauge 100B on which the resistor 130 of the substrate 110B is provided is referred to as the "upper side," and the side on which the resistor 130 is not provided is referred to as the "lower side." Furthermore, the surface located on the upper side of each portion is referred to as the "upper surface," and the surface located on the lower side of each portion is referred to as the "lower surface." However, the strain gauge 100B can also be used upside down. The strain gauge 100B can also be positioned at any angle. Furthermore, a planar view refers to viewing an object in a normal direction from above to below the upper surface 110s of the substrate 110B. Furthermore, a planar shape refers to the shape of the object when viewed in the normal direction.

[0046] The substrate 110B is a member that serves as a base layer for forming the resistor 130 and the like. The substrate 110B is flexible. There are no particular limitations on the thickness of the substrate 110B, and it may be determined appropriately depending on the intended use of the strain gauge 100B, etc. For example, the thickness of the substrate 110B may be approximately 5 μm to 500 μm. From the standpoint of strain transmission from the upper surface 10m of the strain generator 10 to the sensing part and dimensional stability against environmental changes, the thickness of the substrate 110B is preferably within the range of 5 μm to 200 μm. From the standpoint of insulation, the thickness of the substrate 110B is preferably 10 μm or more.

[0047] The base material 110B is formed from an insulating resin film such as PI (polyimide) resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, LCP (liquid crystal polymer) resin, polyolefin resin, etc. The film refers to a flexible member having a thickness of about 500 μm or less.

[0048] When the base material 110B is formed from an insulating resin film, the insulating resin film may contain fillers, impurities, etc. For example, the base material 110B may be formed from an insulating resin film containing fillers such as silica or alumina.

[0049] In addition, for strain gauge 100B used to detect humidity, a base material made of resin is used as base material 110B.

[0050] The resistor 130 is a thin film formed in a predetermined pattern on the upper side of the substrate 110B. In the strain gauge 100B, the resistor 130 is a sensing element that generates a resistance change when strain is applied. The resistor 130 may be formed directly on the upper surface 110s of the substrate 110B, or may be formed on the upper surface 110s of the substrate 110B via another layer. For convenience, in FIG. 9, the resistor 130 is shown with a dense matte pattern. The shapes and sizes of the resistor 130 in each strain gauge shown in FIGS. 1 and 2 and FIGS. 8 to 12 are merely examples, and the resistor 130 of the strain gauge 100B is not limited to the examples shown. An example of the shape of the resistor 130 of the strain gauge 100B will be described below.

[0051] Resistor 130 has a structure in which multiple elongated portions are arranged at predetermined intervals with their longitudinal directions in the same direction (X direction in the example of FIG. 9), and the ends of adjacent elongated portions are alternately connected, resulting in a zigzag folded structure as a whole. The longitudinal direction of the multiple elongated portions is the grid direction, and the direction perpendicular to the grid direction is the grid width direction (Y direction in the example of FIG. 9).

[0052] In the resistor 130, the X- side end of the elongated portion located closest to the Y+ side bends in the Y+ direction and reaches one end 130e1 of the resistor 130 in the grid width direction. In addition, the X- side end of the elongated portion located closest to the Y- side bends in the Y- direction and reaches the other end 130e2 of the resistor 130 in the grid direction. Each of the ends 130e1 and 130e2 is electrically connected to the electrode 150 via the wiring 140. In other words, the wiring 140 electrically connects each of the ends 130e1 and 130e2 of the resistor 130 in the grid width direction to each of the electrodes 150.

[0053] The resistor 130 can be formed from, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 130 can be formed from a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr mixed phase film. An example of a material containing Ni is Cu-Ni (copper-nickel). An example of a material containing both Cr and Ni is Ni-Cr (nickel-chromium).

[0054] Here, the Cr mixed phase film is a film in which Cr, CrN, Cr2N, etc. are mixed together. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

[0055] The thickness of the resistor 130 is not particularly limited and may be determined appropriately depending on the intended use of the strain gauge 100B, etc. For example, the thickness of the resistor 130 may be approximately 0.05 μm to 2 μm. In particular, when the thickness of the resistor 130 is 0.1 μm or more, the crystallinity of the crystals constituting the resistor 130 (e.g., the crystallinity of α-Cr) is improved. Furthermore, when the thickness of the resistor 130 is 1 μm or less, (i) cracks in the film and (ii) warpage of the film from the substrate 110B caused by internal stress of the film constituting the resistor 130 are reduced.

[0056] Considering the need to prevent lateral sensitivity and to prevent disconnection, the width of resistor 130 is preferably 10 μm to 100 μm. Furthermore, the width of resistor 130 is preferably 10 μm to 70 μm, and more preferably 10 μm to 50 μm.

[0057] For example, when the resistor 130 is a Cr mixed-phase film, the stability of the gauge characteristics can be improved by using α-Cr (alpha chromium), which has a stable crystalline phase, as the main component. For example, when the resistor 130 is a Cr mixed-phase film, the resistor 130 can have an α-Cr main component, thereby enabling the gauge factor of the strain gauge 100B to be 10 or more, and the gauge factor temperature coefficient TCS and the temperature coefficient of resistance TCR to be within the range of −1000 ppm / °C to +1000 ppm / °C. Here, the term “main component” refers to a component that accounts for 50% by weight or more of the total material constituting the resistor. From the viewpoint of improving the gauge characteristics, the resistor 130 preferably contains 80% by weight or more of α-Cr. Furthermore, from the same viewpoint, the resistor 130 more preferably contains 90% by weight or more of α-Cr. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0058] Furthermore, when the resistor 130 is a Cr mixed phase film, the Cr mixed phase film preferably contains 20 wt % or less of CrN and Cr2N. By containing 20 wt % or less of CrN and Cr2N in the Cr mixed phase film, a decrease in the gauge factor of the strain gauge 100B can be suppressed.

[0059] Furthermore, the ratio of CrN to Cr2N in the Cr mixed phase film is preferably 80 wt% or more but less than 90 wt% of the total weight of CrN and Cr2N. More preferably, the ratio is 90 wt% or more but less than 95 wt% of the total weight of CrN and Cr2N. Cr2N has semiconducting properties. Therefore, by setting the Cr2N ratio to 90 wt% or more but less than 95 wt%, the decrease in TCR (negative TCR) becomes even more pronounced. Furthermore, by setting the Cr2N ratio to 90 wt% or more but less than 95 wt%, the resistor 130 is less likely to become ceramic, making it less susceptible to brittle fracture.

[0060] On the other hand, CrN has the advantage of being chemically stable. By including more CrN in the Cr mixed-phase film, the possibility of unstable N being generated can be reduced, resulting in a stable strain gauge. Here, "unstable N" refers to trace amounts of N2 or atomic N that can exist in the Cr mixed-phase film. This unstable N can escape from the film depending on the external environment (e.g., high-temperature environment). When unstable N escapes from the film, the film stress of the Cr mixed-phase film can change.

[0061] In strain gauge 100B, high sensitivity and miniaturization can be achieved when a Cr mixed-phase film is used as the material for resistor 130. For example, while the output of a conventional strain gauge was approximately 0.04 mV / 2 V, an output of 0.3 mV / 2 V or more can be obtained when a Cr mixed-phase film is used as the material for resistor 130. Furthermore, while the size (gauge length × gauge width) of a conventional strain gauge was approximately 3 mm × 3 mm, when a Cr mixed-phase film is used as the material for resistor 130, the size (gauge length × gauge width) can be reduced to approximately 0.3 mm × 0.3 mm.

[0062] The wiring 140 is provided on the base material 110B. The wiring 140 is electrically connected to the resistor 130 and the electrode 150. The wiring 140 is not limited to being linear and can have any pattern. The wiring 140 can have any width and any length. For convenience, in FIG. 9, the wiring 140 is shown with a matte pattern that is less dense than the resistor 130.

[0063] The electrode 150 is provided on the substrate 110B. The electrode 150 is electrically connected to the resistor 130 via the wiring 140. In a plan view, the electrode 150 is formed in a generally rectangular shape, wider than the wiring 140. The electrodes 150 are a pair of electrodes for outputting a change in the resistance value of the resistor 130 caused by strain to the outside. For example, a lead wire for external connection is joined to the electrode 150. A low-resistance metal layer such as copper or a metal layer with good solderability such as gold may be laminated on the upper surface of the electrode 150. Although the resistor 130, wiring 140, and electrode 150 are denoted by different reference numerals for convenience, they can be integrally formed from the same material in the same process. Note that in FIG. 9, the electrode 150 is depicted with a matte pattern of the same density as the wiring 140 for convenience.

[0064] The cover layer 160 (protective layer) is provided on the upper surface 110s of the base material 110B as needed, covering the resistor 130 and the wiring 140 and exposing the electrodes 150. The cover layer 160 is also provided so as to expose at least a portion of the upper surface 110s of the base material 110B. Alternatively, the cover layer 160 is made of a moisture-permeable material. The thickness of the cover layer 160 is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness of the cover layer 160 can be approximately 2 μm to 30 μm. By providing the cover layer 160, it is possible to prevent mechanical damage to the resistor 130.

[0065] [Manufacturing method for strain gauge 100B] In the strain gauge 100B according to this embodiment, a resistor 130, wiring 140, electrodes 150, and a cover layer 160 are formed on a substrate 110B. Note that another layer (such as a functional layer described below) may be formed between the substrate 110B and these component layers.

[0066] A method for manufacturing the strain gauge 100B will now be described. To manufacture the strain gauge 100B, first, a base material 110B is prepared, and a metal layer (for convenience, referred to as metal layer A) is formed on the upper surface 110s of the base material 110B. Metal layer A is a layer that will ultimately be patterned to become resistor 130, wiring 140, and electrode 150. Therefore, the material and thickness of metal layer A are the same as those of resistor 130, wiring 140, and electrode 150 described above.

[0067] The metal layer A can be formed by, for example, magnetron sputtering using a target made of a material capable of forming the metal layer A. Instead of magnetron sputtering, the metal layer A may be formed by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like. After the metal layer A is formed on the upper surface 110s of the base material 110B, the metal layer A is patterned by a well-known photolithography method into a planar shape similar to that of the resistor 130, the wiring 140, and the electrode 150 in FIG. 9 .

[0068] Alternatively, a base layer may be formed on the upper surface 110s of the base material 110B before the metal layer A is formed. For example, a functional layer having a predetermined thickness may be vacuum-deposited on the upper surface 110s of the base material 110B by conventional sputtering. By providing a base layer in this manner, the gauge characteristics of the strain gauge 100B can be stabilized.

[0069] In this application, the functional layer refers to a layer having the function of promoting the crystal growth of at least the upper layer, metal layer A (resistor 130). The functional layer preferably also has the function of preventing oxidation of metal layer A due to oxygen or moisture contained in base material 110B and / or the function of improving adhesion between base material 110B and metal layer A. The functional layer may also have other functions.

[0070] The insulating resin film constituting the base material 110B may contain oxygen and moisture, and Cr may form a self-oxidized film. Therefore, when the metal layer A contains Cr, it is preferable to form a functional layer having the function of preventing oxidation of the metal layer A.

[0071] In this way, by providing a functional layer below the metal layer A, it is possible to promote crystal growth in the metal layer A, and to produce a metal layer A consisting of a stable crystalline phase. As a result, the stability of the gauge characteristics of the strain gauge 100B is improved. Furthermore, the material constituting the functional layer diffuses into the metal layer A, thereby improving the gauge characteristics of the strain gauge 100B.

[0072] Examples of materials for the functional layer include one or more metals selected from the group consisting of Cr (chromium), Ti (titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C (carbon), Zn (zinc), Cu (copper), Bi (bismuth), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os (osmium), Ir (iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), and Al (aluminum), an alloy of any of the metals in this group, or a compound of any of the metals in this group.

[0073] 11 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. Fig. 11 shows the cross-sectional shape of a strain gauge 100B when a functional layer 120 is provided as an underlying layer for the resistor 130, the wiring 140, and the electrode 150.

[0074] The planar shape of the functional layer 120 may be patterned to be substantially the same as the planar shapes of the resistor 130, the wiring 140, and the electrodes 150, for example. However, the planar shapes of the functional layer 120, the resistor 130, the wiring 140, and the electrodes 150 do not have to be substantially the same. For example, when the functional layer 120 is formed from an insulating material, the functional layer 120 may be patterned to be different from the planar shapes of the resistor 130, the wiring 140, and the electrodes 150. In this case, the functional layer 120 may be formed solidly in the region where the resistor 130, the wiring 140, and the electrodes 150 are formed. The functional layer 120 is provided so as to expose at least a portion of the upper surface 110s of the substrate 110B.

[0075] After forming the resistor 130, the wiring 140, and the electrodes 150, a cover layer 160 is formed on the upper surface 110s of the base material 110B as needed. The cover layer 160 covers the resistor 130 and the wiring 140, but the electrodes 150 may be exposed from the cover layer 160. For example, the cover layer 160 can be formed by laminating a semi-cured thermosetting insulating resin film on the upper surface 110s of the base material 110B so as to cover the resistor 130 and the wiring 140 and expose the electrodes 150, and then heating and curing the insulating resin film. Through the above steps, the strain gauge 100B is completed.

[0076] The above has described strain gauge 100B in detail. On the other hand, strain gauge 100A may have the following differences from strain gauge 100B.

[0077] For example, the substrate 110A may or may not be made of resin. Examples of materials other than resin for the substrate 110A include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, and perovskite ceramics (CaTiO3, BaTiO3). In addition to the crystalline materials described above, amorphous glass or the like may also be used as the material for the substrate 110A. Metals such as aluminum, aluminum alloys (duralumin), and titanium may also be used as the material for the substrate 110A. When a metal substrate 110A is used, an insulating film is provided to cover the upper surface 110m.

[0078] Furthermore, the sizes of the various parts of strain gauge 100A and strain gauge 100B may or may not be the same. For example, the size of substrate 110A and the size of substrate 110B in a plan view may be different. The thickness of substrate 110A and the thickness of substrate 110B may be different. The pattern shape and material of resistor 130 may be different between strain gauge 100A and strain gauge 100B.

[0079] In the strain gauge 100A, the functional layer 120 may be formed solidly over the entire upper surface 110s of the substrate 110B. One of the strain gauges 100A and 100B may have a cover layer 160, while the other may not. When the strain gauge 100A is provided with a cover layer 160, the cover layer 160 may be provided to cover the entire upper surface 110s of the substrate 110B, as long as at least a portion of the electrode 150 is exposed. The strain gauge 100A may be sealed with a sealing unit 200. Examples of materials for the cover layer 160 include insulating resins such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, and composite resins (e.g., silicone resin and polyolefin resin). The cover layer 160 may contain a filler or a pigment. The cover layer 160 of the strain gauge 100B is preferably made of a moisture-permeable material and structure. Furthermore, the cover layer 160 of the strain gauge 100B is preferably provided so as to minimize the interference with strain caused by moisture absorption and release of the substrate 110B. For example, the cover layer 160 of the strain gauge 100B is preferably provided so as to expose at least a portion of the upper surface of the substrate 110B. Meanwhile, the cover layer 160 of the strain gauge 100A is not limited in material and structure to those of the cover layer of the strain gauge 100B, and the material and structure can be selected appropriately depending on the application and required specifications of the strain gauge 100A.

[0080] <Modification 1 of the First Embodiment> The grid directions of strain gauge 100A and strain gauge 100B may be different. A first modification of the first embodiment will be described below. Note that in the first modification of the first embodiment, descriptions of components that are the same as those in the previously described embodiments may be omitted.

[0081] FIG. 12 is a plan view illustrating a sensor module according to a first modification of the first embodiment. In the example of FIG. 12, in the sensor module 1B, the grid direction of the resistor 130 of the strain gauge 100B is offset by 90 degrees from the grid direction of the resistor 130 of the strain gauge 100A. Thus, in the sensor module 1B, the strain gauges 100A and 100B are arranged so that the grid direction of the strain gauge 100A and the grid direction of the strain gauge 100B are oriented in different directions. With this arrangement, when the grid direction of the strain gauge 100A is aligned with the direction of stress applied to the flexural element 10, the grid direction of the strain gauge 100B is offset from the direction of the stress, making it even more difficult for the strain gauge 100B to detect strain. In other words, noise components can be reduced when the strain gauge 100B detects strain in a substrate due to humidity. Arranging the strain gauges 100A and 100B in this manner is particularly effective when the difference in strain detection sensitivity between the sensitive area and the insensitive area of ​​the strain generating element is relatively small across the entire sensor module.

[0082] It is preferable that the grid direction of the resistor of strain gauge 100B is shifted by about 90 degrees from the grid direction of the resistor of strain gauge 100A, but if the two are non-parallel, this has a certain effect in making it more difficult for strain gauge 100B to detect strain.

[0083] In the above-described first embodiment and its modified examples, examples of sensor modules including strain gauge 100A and strain gauge 100B have been shown. However, in the sensor module according to the present invention, strain gauge 100A is not an essential component. In other words, the sensor module according to the present invention may include only strain gauge 100B.

[0084] Fig. 13 shows an example of a sensor module 2 that includes only a strain gauge 100B. As shown in Fig. 13, the sensor module 2 mainly includes a strain element 10A and a strain gauge 100B, but does not include a strain gauge 100A.

[0085] The flexure body 10A has a first region 12A and a second region 12B. The first region 12A is a region having strain detection sensitivity comparable to that of the insensitive region 12 of the flexure body 10 of the sensor module 1 shown in FIG. 1 etc. For example, the first region 12A may be a high-rigidity region. The second region 12B is a region having higher strain detection sensitivity than the first region 12A. For example, the second region 12B may be a low-rigidity region. The flexure body 10A does not have to have the second region 12B. That is, the entire flexure body 10A may be a region having strain detection sensitivity comparable to that of the first region 12A, i.e., the insensitive region 12 of the flexure body 10. That is, the flexure body 10A may have a uniform strain detection sensitivity. In this case, the flexure body 10A is a member that does not easily transmit strain, and therefore can be said to simply be a "support for supporting the strain gauge 100B."

[0086] The strain gauge 100B is disposed in the first region 12A on the upper surface 10m side of the flexure element 10A. Specifically, the lower surface of the base material 110B of the strain gauge 100B is bonded to the first region 12A by an adhesive layer. The strain gauge 100B is not sealed by a sealing portion. At least a portion of the upper surface of the base material 110B of the strain gauge 100B is exposed or is covered with a moisture-permeable layer. This allows the resin base material 110B to absorb and release moisture.

[0087] In this way, the strain gauge 100B is bonded to the first region 12A, which has high rigidity, and the substrate 110B can absorb and release moisture. Therefore, the strain gauge 100B can function as a humidity sensor. In other words, the sensor module 2 can be used as a sensor that detects only humidity.

[0088] Second Embodiment In the above-described embodiment and its modified examples, the strain gauge 100A (second strain gauge) and the strain gauge 100B (first strain gauge) according to the present disclosure are strain gauges using resistors. That is, in the above-described embodiment, the strain gauges 100A and 100B according to the present disclosure are metal strain gauges of an electrical resistance type. However, the strain gauges 100A and 100B according to the present disclosure are not limited to metal strain gauges. For example, the strain gauges 100A and 100B according to the present disclosure may be strain gauges that detect magnetic changes caused by strain in a strain-generating body (or a structure equivalent to the strain-generating body) using a detection element included in the strain gauge.

[0089] Specifically, the strain gauges 100A and 100B according to the present disclosure may be strain gauges including a detection element that utilizes the Villari phenomenon (described later). Alternatively, the strain gauges 100A and 100B according to the present disclosure may be strain gauges including a detection element having a magnetic tunnel junction (described later) structure. In the second embodiment, a strain gauge including a detection element that utilizes the Villari phenomenon will be described. In the third embodiment, a strain gauge including a detection element having a magnetic tunnel junction structure will be described.

[0090] In each embodiment of this specification, components having similar functions are given similar names and numbers, and descriptions will not be repeated. Furthermore, in each drawing (drawings from FIG. 14 onward) relating to each subsequent embodiment, the directions of the x-axis, y-axis, and z-axis will be redefined for description. That is, the x-, y-, and z-axes shown in FIG. 14 and subsequent drawings are intended solely for describing the structure of the detection element and do not indicate the orientation of the detection element within the overall sensor module shown in FIGS. 1 to 13. The various detection elements described below can be arranged on the substrate with their orientation appropriately determined depending on the direction of strain to be detected. In addition, in the following description, the positive direction of the z-axis will be referred to as "upper" and the negative direction of the z-axis will be referred to as "lower." That is, in the following description, "upper side" refers to the positive side of the z-axis, and "upper surface" refers to the surface on the positive side of the z-axis. Furthermore, "lower side" refers to the negative side of the z-axis, and "lower surface" refers to the surface on the negative side of the z-axis.

[0091] FIG. 14 is a diagram illustrating an example of a detection element 300 included in a strain gauge according to the second embodiment. FIG. 14(a) is a plan view of the detection element 300 when viewed from the positive to the negative direction of the z-axis (i.e., from the top to the bottom). FIG. 14(b) is a cross-sectional view of the detection element 300 shown in FIG. 14(a) taken along line α-α'. Note that FIGS. 14(a) and 14(b) do not illustrate wiring extending from the detection element 300. However, the detection element 300 may be connected to wiring that connects a drive coil 320 (described later) to a power source and wiring that transmits a current detected by a sensing coil 380.

[0092] As shown in FIG. 14(a), the detection element 300 includes a drive coil 320, a sense coil 380, and a base layer 310. The base layer 310 is a layer that serves as the core of the drive coil 320 and the sense coil 380. The sense coil 380 is a coil that detects the intensity of magnetization of the base layer 310 (more precisely, a base metal 370, described below). The drive coil 320 is a coil that generates a magnetic field. The detection element 300 has a double structure in which the sense coil 380 is wound on the inside and the drive coil 320 is wound on the outside, with the base layer 310 as the core. Note that the materials for the drive coil 320 and the sense coil 380 are preferably conductive metals such as Cu, Ag, Al, and Au, or alloys of these metals. The number of turns and cross-sectional area of ​​the drive coil 320 and the sense coil 380 may be appropriately designed depending on the strain detection sensitivity required for the detection element 300.

[0093] As will be described in detail later, when stress is applied to the base layer 310, the strength of magnetization changes in a base metal 370 (described later) included in the base layer 310. The detection element 300 can determine the strength of the stress (i.e., the degree of strain) applied to the base layer 310 by detecting this change in the strength of magnetization with the sensing coil 380.

[0094] The configuration of the detection element 300 will be further described with reference to the cross-sectional view of Figure 14(b). In Figure 14(b), the drive coil 320, the sensing coil 380, and the three insulating layers 340, 350, and 360 are each formed to surround the base metal 370, which is the core material. In other words, layers with the same component number in Figure 14(b) are connected to surround the base metal 370.

[0095] The base metal 370 is a member that serves as the core material for the various coils and insulating layers. The base metal 370 may be, for example, a substantially flat metal plate. The base metal 370 is covered and surrounded by the insulating layer 360. The base metal 370 is preferably made of a soft magnetic material, such as an Fe-Si-Al alloy such as sendust, or an Ni-Fe alloy such as permalloy. As shown in FIG. 14(b), the aforementioned base layer 310 is made of this base metal 370 and the insulating layer 360.

[0096] An insulating layer 350 is formed on the outside of insulating layer 360 so as to surround insulating layer 360. An insulating layer 340 is further formed on the outside of insulating layer 350. Insulating layer 350 is a layer that includes sensing coil 380, and is a layer in which gaps between sensing coil 380 are filled with an insulating material. Insulating layer 340 is a layer that includes drive coil 320, and is a layer in which gaps between drive coil 320 are filled with an insulating material. Insulating layers 340, 350, and 360 are preferably made of a dry film that is not affected by the magnetic field or a cured resist such as photosensitive polyimide.

[0097] As shown in FIG. 14(b), one surface of the detection element 300 may be attached to a substrate 110. The substrate 110 is a member that fixes the detection element 300. For example, the substrate 110 may be a flexible substrate made of a plastic film or the like. The detection element 300 is attached to the flexure element 10 or 10A via the substrate 110. The detection element 300 may be a detection element that is flat or thin film-shaped as a whole. If the detection element 300 is flat or thin film-shaped, the detection element 300 can be more easily attached to the substrate 110. The substrate 110 is not an essential component of the detection element 300. For example, the detection element 300 may not be provided with the substrate 110, and the lower surface of the detection element 300 may be directly attached to the flexure element 10 or 10A.

[0098] The flexure bodies 10 and 10A according to this embodiment may basically have the same configuration and material as the flexure bodies 10 and 10A according to the first embodiment and the modified example of the first embodiment. However, in this embodiment, it is more preferable that the flexure bodies 10 and 10A be made of a non-magnetic material. The flexure bodies 10 and 10A according to this embodiment can be made of, for example, non-magnetic stainless steel.

[0099] Next, the principle of detecting strain using the detection element 300 will be outlined. The detection element 300 includes a base metal 370, which is a magnetic material. When an alternating current is supplied from a power source to the drive coil 320, the drive coil 320 generates an alternating magnetic field around it. This generates a magnetic field, and the base metal 370 is magnetized. When the flexure element 10 or 10A deforms in this state, strain occurs. The strain is transmitted through the substrate 110, and stress is applied to the base metal 370. Note that if the detection element 300 is attached to the flexure element 10 or 10A without the substrate 110, stress is transmitted directly from the flexure element 10 or 10A to the base metal 370 (and the insulating layers 340-360 covering it).

[0100] When stress is applied to the base metal 370, the magnetic permeability of the base metal 370 changes in response to the stress. Therefore, the magnetization strength (degree of magnetization) of the base metal 370 changes. This phenomenon, in which the magnetic permeability and magnetization strength of a magnetic body change when stress is applied to the magnetic body, is called the "Villari phenomenon." According to the configuration of the detection element 300, an AC voltage corresponding to the magnetization strength of the base metal 370 is induced in the sensing coil 380, which serves as a pickup coil. Therefore, based on the principle of the Villari phenomenon, the stress applied to the base metal 370 can be calculated from the value of this AC voltage. The degree of strain of the strain-generating body 10 or 10A can then be determined from the calculated stress. When the detection element 300 has the shape shown in FIGS. 14(a) and 14(b), the grid direction of the detection element 300 is the same as the α-α' direction in FIG. 14(a). Based on the principle described above, the detection element 300 can detect strain in the strain-generating bodies 10 and 10A. That is, the sensing element 300 functions as a sensing element of a strain gauge.

[0101] It is desirable that the drive coil 320 be wound as uniformly as possible around the outside of the sensing coil 380 and over the entire area where the sensing coil 380 is present. This allows an alternating magnetic field to be applied more uniformly to the entire area of ​​the base metal 370 where the sensing coil 380 is present. This allows for more precise detection of changes in the magnetization strength of the base metal 370 due to the Villari phenomenon. This improves the performance of the detection element 300.

[0102] Furthermore, insulating layer 360 may be formed on only part of base metal 370 rather than the entirety of base metal 370. For example, a configuration may be adopted in which the regions of base metal 370 where sensing coil 380 and drive coil 320 are wound are covered with insulating layer 360, insulating layer 350 including sensing coil 380 is then covered from above insulating layer 360, and insulating layer 340 including drive coil 320 is further covered from above insulating layer 350.

[0103] 14(b), both ends of the base metal 370 in the x direction do not have to be covered with the insulating layer 360.

[0104] In the sensor modules 1, 1A, 1B, and 2 according to this embodiment, when the flexure element 10 or 10A is deformed (i.e., strain occurs in the flexure element), the substrate 110 of the strain gauge (or the detection element 300 itself) is strained. The detection element 300 can detect the magnetic change caused by this strain based on the principle of the Villari phenomenon described above.

[0105] The strain gauge including the detection element 300 according to this embodiment can be arranged on the flexure bodies 10 and 10A in any of the arrangement patterns shown in the first embodiment and the modified example of the first embodiment. That is, the detection element 300 according to this embodiment can be used to detect strain in the flexure bodies 10 and 10A in the same way as when an electrical resistance type strain gauge is used. Therefore, the strain gauge according to this embodiment has the same effects as the strain gauges 100A and 100B according to the first embodiment and the modified example of the first embodiment.

[0106] Third Embodiment FIG. 15 is a diagram showing a detection element 500, which is an example of a detection element included in a strain gauge according to the third embodiment. FIG. 16 is a diagram showing a detection element 600, which is another example of a detection element according to the third embodiment. FIG. 17 is a diagram showing a detection element 700, which is yet another example of a detection element according to the third embodiment. (a) of FIGS. 15 to 17 are perspective views of the detection elements 500, 600, and 700, respectively. (b) of FIGS. 15 to 17 are plan views of the detection elements 500, 600, and 700, respectively, when viewed from the positive direction to the negative direction of the z-axis. (c) of FIGS. 15 to 17 are cross-sectional views of the detection elements 500, 600, and 700, taken along a plane parallel to the zx plane. Note that wiring extending from the detection elements is not shown in any of FIGS. 15 to 17. However, these detection elements 500, 600, and 700 may be connected to a wiring that connects the upstream electrode 510 to a power source, and a wiring that connects the downstream electrode 520 to a power source, which will be described later.

[0107] 15 to 17(a), the detection elements 500, 600, and 700 include an upstream electrode 510, a downstream electrode 520, a magnetic film 530, and an insulating film 540. As shown in the figures, the insulating film 540 is sandwiched between the magnetic films 530. A magnetic tunnel junction is formed by the magnetic film 530 and the insulating film 540. In other words, the detection elements 500, 600, and 700 have a structure in which electrodes are connected to a magnetic tunnel junction structure.

[0108] The lower surfaces of the detection elements 500, 600, and 700 may be attached to a substrate similar to the substrate 110 according to the first embodiment and the modified example of the first embodiment. The detection element 500 may then be attached to the flexure element 10 or 10A via the substrate. The detection elements 500, 600, and 700 may also be flat-plate or thin-film detection elements as a whole. When the detection elements 500, 600, and 700 are flat-plate or thin-film shaped, the detection elements 500, 600, and 700 can be more easily attached to the substrate, the flexure element 10, or 10A. For example, the lower surfaces of the detection elements 500, 600, and 700 may be directly attached to the flexure element 10 or 10A.

[0109] The magnetic film 530 is a magnetic nano-thin film. The insulating film 540 is a nano-thin film made of an insulator. There are no particular limitations on the materials for the magnetic film 530 and the insulating film 540, as long as a magnetic tunnel junction structure can be formed. For example, the magnetic film 530 can be made of cobalt-iron-boron, or a 3d transition metal ferromagnetic material such as Fe, Co, or Ni, or an alloy containing any of these. The insulating film 540 can be made of silicon oxide, silicon nitride, aluminum oxide, magnesium oxide, or the like.

[0110] The upstream electrode 510 and the downstream electrode 520 are electrodes for applying a voltage to the magnetic tunnel junction structure. In the examples of FIGS. 15 to 17, a current flows from the upstream electrode 510 to the downstream electrode 520. For example, in the case of FIG. 15(c), when a voltage is applied between the upstream electrode 510 and the downstream electrode 520, electrons flow from the upper magnetic film 530 (on the positive z-axis side) across the insulating film 540 to the lower magnetic film 530 (on the negative z-axis side). This is a phenomenon known as the "tunnel effect," and the electrical resistance experienced when electrons pass through the insulating film 540 is known as the "tunnel resistance." In the examples of FIGS. 15 to 17, the junctions of the electrodes have ends processed to prevent current from short-circuiting the magnetic tunnel junction structure.

[0111] When strain is applied to the detection element 500 via the substrate 110 or the like, a magnetic change occurs in the tunnel junction structure. More specifically, the magnetization directions of the upper and lower magnetic films 530 are misaligned. When the magnetization directions of the upper and lower magnetic films 530 are misaligned in this way, the tunnel resistance increases compared to when the magnetization directions are parallel (tunnel magnetoresistance effect). Therefore, in the detection element 500 having the above-mentioned configuration, the current flowing between the electrodes decreases depending on the magnitude of strain in the detection element 500 (more precisely, the magnetic tunnel junction portion). In other words, as the strain increases, the electrical resistance increases. In this way, the detection element 500 can detect strain based on the current value relative to the applied voltage. Therefore, by attaching the detection element 500 to the strain-generating body 10 or 10A, the strain applied to the strain-generating body 10 or 10A can be measured.

[0112] The detection element having a magnetic tunnel junction structure is not limited to the example shown in FIG. 15. For example, detection elements 600 and 700 shown in FIGS. 16 and 17 can also be used. Both the detection element 600 shown in FIG. 16 and the detection element 700 shown in FIG. 17 are configured with an upstream electrode 510, a downstream electrode 520, a magnetic film 530, and an insulating film 540, and the principle of detecting strain using this configuration is similar to that of the detection element 500. The basic operation of the detection elements 600 and 700 is also similar to that of the detection element 500. The grid directions of the detection elements 500, 600, and 700 correspond to the x-axis direction (the positive direction of the x-axis and the negative direction of the x-axis) in FIGS. 15 to 17, respectively. As shown in FIG. 16, the detection element 600 has a structure in which the upper magnetic film 530 and the lower magnetic film 530 are partially connected. That is, a magnetic tunnel junction structure is formed only in a partial region of the magnetic film 530, and the tunnel magnetoresistance effect occurs in this structure. On the other hand, the detection element 700 shown in Fig. 17 is attached to the base material 110 via a substrate 710. As shown in Figs. 15 to 17, the design of the detection element may be changed as appropriate depending on the required size, durability, magnitude of stress to be detected, and the like, as long as it does not deviate from the above-mentioned principles.

[0113] The flexure bodies 10 and 10A according to this embodiment may basically have the same configuration and material as the flexure bodies 10 and 10A according to the first embodiment. However, in this embodiment, it is more preferable that the flexure bodies 10 and 10A be made of a nonmagnetic material. The flexure bodies 10 and 10A according to this embodiment may be made of, for example, nonmagnetic stainless steel. The entire detection elements 500, 600, and 700 may have a substantially flat plate shape, such as a film type. This allows the detection element 500 to be easily attached to the flexure bodies 10 and 10A. The detection elements 500, 600, and 700 may also have a structure for applying a weak magnetic field to the structural components of the magnetic tunnel junction, such as the drive coil. Applying a magnetic field to the structural components of the magnetic tunnel junction allows for more stable measurement of the tunnel magnetoresistance effect, thereby enabling stable strain detection.

[0114] Furthermore, the terms "upstream electrode" and "downstream electrode" in detection elements 500, 600, and 700 are used for convenience, and the direction of current flow may be reversed. That is, detection elements 500, 600, and 700 shown in Figures 15 to 17 may be designed so that current flows from downstream electrode 520 to upstream electrode 510.

[0115] In the sensor modules 1, 1A, 1B, and 2 according to the present embodiment, when the flexure element 10 or 10A is deformed (i.e., strain occurs in the flexure element), the substrate of the strain gauge (or the detection element 500, 600, or 700 itself) is strained. The detection element 500, 600, or 700 can detect the magnetic change caused by this strain based on the principle of the tunneling magnetoresistance effect described above.

[0116] Strain gauges including the detection elements 500, 600, and 700 according to this embodiment can be arranged on the flexure bodies 10 and 10A in any of the arrangement patterns shown in the first embodiment and the modified example of the first embodiment. That is, using the detection elements 500, 600, and 700 according to this embodiment, strain in the flexure bodies 10 and 10A can be detected in the same way as when an electrical resistance type strain gauge is used. Therefore, the strain gauges according to this embodiment have the same effects as the strain gauges 100A and 100B according to the first embodiment and the modified example of the first embodiment.

[0117] Preferred embodiments and the like have been described in detail above. However, the sensor module according to the present disclosure is not limited to the above-described embodiments and modifications. For example, various modifications and substitutions can be made to the sensor module according to the above-described embodiments and the like without departing from the scope of the claims. For example, a strain gauge including the detection element 300 according to the second embodiment or the detection elements 500, 600, or 700 according to the third embodiment, which is disposed in the sensitive region 11 (or second region 12B) of the strain generating body 10 (or 10A), may be sealed with the sealing portion 200 described in the first embodiment. [Explanation of symbols]

[0118] 1, 1A, 1B, 2 sensor module, 10, 10A strain element, 10m upper surface, 11 sensitive area, 12, 13 insensitive area, 12A first area, 12B second area, 30 adhesive layer, 100A, 100B strain gauge, 110A, 110B substrate, 110m, 110s upper surface, 110n, 110t lower surface, 120 functional layer, 130 resistor, 130e1, 130e2 termination, 140 wiring, 150 electrode, 160 cover layer, 200 sealing portion, 300, 500, 600, 700 detection element, 310 base layer, 320 drive coil, 340, 350, 360 insulating layer, 370 base metal, 380 sensing coil, 510 Upstream electrode, 520 downstream electrode, 530 magnetic film, 540 insulating film, 710 substrate

Claims

1. a support and a first strain gauge; The first strain gauge comprises: a first base material made of resin; a first resistor formed on a first surface of the first substrate, a second surface of the first substrate, the second surface being different from the first surface, is fixed to the support; At least a portion of the first surface of the sensor module is exposed or is covered with a moisture-permeable layer.

2. The sensor module of claim 1 , wherein the first strain gauge functions as a humidity sensor.

3. the support body includes a sensitive region that is distorted by stress and an insensitive region that has lower sensitivity to strain than the sensitive region; The sensor module according to claim 1 , wherein the second surface of the first substrate is fixed to the insensitive region.

4. a second strain gauge; The second strain gauge comprises: A second substrate; a second resistor formed on the first surface of the second substrate, The sensor module according to claim 3 , wherein a second surface of the second substrate, which is different from the first surface, is fixed to the sensitive region.

5. The sensor module according to claim 4 , further comprising a sealing portion that covers both the entire second strain gauge and the sensitive region located around the second strain gauge.

6. The sensor module according to claim 4 , wherein a grid direction of the first resistor is non-parallel to a grid direction of the second resistor.

7. The second resistor is made of Cr, CrN, and Cr ２ The sensor module according to claim 4 , which is formed from a film containing N.

8. The first resistor is made of Cr, CrN, and Cr ２ The sensor module according to claim 1 or 2, which is formed from a film containing N.

9. a support and a first strain gauge; The first strain gauge comprises: a first base material made of resin; a detection element formed on a first surface of the first substrate, a second surface of the first substrate, the second surface being different from the first surface, is fixed to the support; At least a portion of the first surface of the sensor module is exposed or is covered with a moisture-permeable layer.

10. The sensor module of claim 9 , wherein the first strain gauge functions as a humidity sensor.

11. the support body includes a sensitive region that is distorted by stress and an insensitive region that has lower sensitivity to strain than the sensitive region; The sensor module according to claim 9 , wherein the second surface of the first substrate is fixed to the insensitive region.

12. a second strain gauge; The second strain gauge comprises: A second substrate; a detection element formed on the first surface of the second substrate, The sensor module according to claim 11 , wherein a second surface of the second substrate, which is different from the first surface, is fixed to the sensitive region.

13. The sensor module according to claim 12 , further comprising a sealing portion that covers both the entire second strain gauge and the sensitive region located around the second strain gauge.

14. The sensor module according to claim 12 , wherein the grid direction of the first strain gauge is non-parallel to the grid direction of the second strain gauge.

15. The sensor module according to claim 9 , wherein the detection element detects a magnetic change caused by deformation of the support body.

16. the detection element includes a magnetic material, 16. The sensor module according to claim 15, wherein the detection element detects a change in intensity of magnetization of the magnetic body when pressure is applied to the magnetic body due to deformation of the support body.

17. the detection element includes a magnetic tunnel junction structure in which an insulating film is sandwiched between magnetic films, The sensor module according to claim 15 , wherein the detection element detects a magnetic change generated in the structure due to deformation of the support.

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