Strain gauges, sensor modules

Abstract

To provide a strain gauge that can improve the efficiency of attachment work to a strain generating body. [Solution] This strain gauge has a flexible resin substrate, a functional layer formed directly on one side of the substrate from a metal, alloy, or metal compound, and a plurality of resistors whose main component is α-Cr and formed from a film containing Cr, CrN, and Cr2N directly on one side of the functional layer, wherein the functional layer has the function of promoting crystal growth of the α-Cr and forming a film whose main component is α-Cr, each of the plurality of resistors has a thickness of 0.05 μm or more and 2 μm or less, the thickness of the functional layer is 1 nm or more and 100 nm or less, and the plurality of resistors includes two resistors arranged so as to be positioned opposite each other across the flexure element when the substrate is attached to the flexure element.

Description

[Technical Field]

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

[0002] There is known a strain gauge that is attached to a measurement object to detect strain of the measurement object. The strain gauge has a resistor that detects strain, and the resistor is made of a material containing, for example, chromium (Cr) or nickel (Ni). Also, for example, one resistor is formed on one surface of a substrate made of insulating resin (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-74934 Summary of the Invention [Problem to be solved by the invention]

[0004] In some cases, multiple strain gauges each equipped with a single resistor are prepared and attached to different surfaces of a strain generating body to measure strain. In this case, attaching the individual strain gauges to the different surfaces of the strain generating body takes time, and therefore improvements in work efficiency are needed.

[0005] The present invention has been made in view of the above points, and has an object to provide a strain gauge that can be attached to a strain generating element more efficiently. [Means for solving the problem]

[0006] This strain gauge comprises a flexible resin substrate, a functional layer formed directly on one side of the substrate from a metal, alloy, or metal compound, and a plurality of resistors whose main component is α-Cr and formed from a film containing Cr, CrN, and CrN directly on one side of the functional layer, wherein the functional layer has the function of promoting crystal growth of the α-Cr and forming the film whose main component is α-Cr, each of the plurality of resistors has a thickness of 0.05 μm or more and 2 μm or less, the functional layer has a thickness of 1 nm or more and 100 nm or less, and the plurality of resistors includes two resistors arranged so as to be positioned opposite each other across the flexure element when the substrate is attached to the flexure element. [Effects of the Invention]

[0007] According to the disclosed technology, it is possible to provide a strain gauge that can be attached to a strain-generating body more efficiently. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a plan view illustrating a strain gauge according to a first embodiment. [Figure 2] 1 is a cross-sectional view illustrating a strain gauge according to a first embodiment. [Figure 3] 1 is a perspective view illustrating a sensor module according to a first embodiment. [Figure 4] 1 is a cross-sectional view illustrating a sensor module according to a first embodiment. [Figure 5] FIG. 2 is a plan view illustrating a strain gauge according to a first modified example of the first embodiment. [Figure 6] FIG. 10 is a perspective view illustrating a sensor module according to a first modified example of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes the preferred embodiments of the present invention with reference to the accompanying drawings. In the drawings, the same components are designated by the same reference numerals, and redundant explanations may be omitted.

[0010] First Embodiment Fig. 1 is a plan view illustrating a strain gauge according to a first embodiment. Fig. 2 is a cross-sectional view illustrating the strain gauge according to the first embodiment, taken along line AA in Fig. 1. Referring to Figs. 1 and 2, the strain gauge 1 has a substrate 10, resistors 31 and 32, wiring patterns 41 and 42, and terminal portions 51 and 52.

[0011] In this embodiment, for convenience, the side of the strain gauge 1 on which the resistors 31 and 32 of the substrate 10 are provided is referred to as the upper side or one side, and the side on which the resistors 31 and 32 are not provided is referred to as the lower side or the other side. Furthermore, the side on which the resistors 31 and 32 of each portion are provided is referred to as the one side or upper side, and the side on which the resistors 31 and 32 are not provided is referred to as the other side or lower side. However, the strain gauge 1 can be used upside down or positioned at any angle. Furthermore, a planar view refers to viewing the object from the normal direction of the upper surface 10a of the substrate 10, and a planar shape refers to the shape of the object viewed from the normal direction of the upper surface 10a of the substrate 10.

[0012] The substrate 10 is a flexible member that serves as a base layer for forming the resistors 31 and 32, etc. In this embodiment, the planar shape of the substrate 10 is a rectangular shape. There are no particular restrictions on the thickness of the substrate 10 and it can be selected appropriately depending on the purpose, but it can be, for example, about 5 μm to 1000 μm. In particular, a thickness of 5 μm to 200 μm is preferable in terms of the transferability of strain from the surface of the strain generator bonded to the lower surface of the substrate 10 via an adhesive layer or the like and dimensional stability against the environment, and a thickness of 10 μm or more is even more preferable in terms of insulation.

[0013] The substrate 10 can be formed from an insulating resin film such as PI (polyimide) resin, epoxy resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, polyolefin resin, etc. The film refers to a flexible member having a thickness of about 500 μm or less.

[0014] Here, "formed from an insulating resin film" does not prevent the base material 10 from containing fillers, impurities, etc. in the insulating resin film. The base material 10 may be formed from an insulating resin film containing fillers such as silica or alumina, for example.

[0015] The resistors 31 and 32 are formed on the substrate 10 and are sensing parts that undergo a resistance change when strain is applied. The resistors 31 and 32 can be arranged on the substrate 10 with their grid directions facing in the same direction, for example. For convenience, the resistors 31 and 32 are shown in a matte finish in FIG. 1.

[0016] The resistors 31 and 32 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 resistors 31 and 32 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 Ni-Cu (nickel copper). An example of a material containing both Cr and Ni is Ni-Cr (nickel chromium).

[0017] Here, the Cr mixed phase film is a film containing a mixture of Cr, CrN, Cr2N, etc. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

[0018] The thickness of the resistors 31 and 32 is not particularly limited and can be appropriately selected depending on the purpose, but can be, for example, about 0.05 μm to 2 μm. In particular, a thickness of 0.1 μm or more for the resistors 31 and 32 is preferable because it improves the crystallinity of the crystals constituting the resistors 31 and 32 (for example, the crystallinity of α-Cr), and a thickness of 1 μm or less is even more preferable because it reduces cracks in the film constituting the resistors 31 and 32 and warpage from the substrate 10 caused by internal stress in the film.

[0019] For example, when the resistors 31 and 32 are Cr mixed-phase films, 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. Furthermore, by using α-Cr as the main component of the resistors 31 and 32, the gauge factor of the strain gauge 1 can be 10 or more, and the temperature coefficient of gauge factor (TCS) and temperature coefficient of resistance (TCR) can be within the range of −1000 ppm / °C to +1000 ppm / °C. Here, “main component” means that the target substance accounts for 50 mass% or more of all materials constituting the resistor. From the viewpoint of improving the gauge characteristics, however, it is preferable that the resistors 31 and 32 contain α-Cr at 80 wt% or more. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0020] The terminal portions 51 extend from both ends of the resistor 31 via the wiring pattern 41 and are formed in a generally rectangular shape wider than the resistor 31 in a plan view. The terminal portions 51 are a pair of electrodes for outputting a change in the resistance value of the resistor 31 caused by strain to the outside, and are connected to, for example, lead wires for external connection. The resistor 31 extends, for example, from one of the terminal portions 51 via the wiring pattern 41 while folding back in a zigzag pattern and is connected to the other terminal portion 51 via the wiring pattern 41.

[0021] The terminal portions 52 extend from both ends of the resistor 32 via the wiring pattern 42 and are formed in a generally rectangular shape in plan view, wider than the resistor 32. The terminal portions 52 are a pair of electrodes for outputting a change in the resistance value of the resistor 32 caused by strain to the outside, and are connected to, for example, lead wires for external connection. The resistor 32 extends, for example, from one of the terminal portions 52 via the wiring pattern 42 while folding back in a zigzag pattern and is connected to the other terminal portion 52 via the wiring pattern 42.

[0022] The upper surfaces of the terminal portions 51 and 52 may be covered with a metal having better solderability than the terminal portions 51 and 52. Although the resistors 31 and 32, the wiring patterns 41 and 42, and the terminal portions 51 and 52 are given different reference numerals for convenience, they can be integrally formed from the same material in the same process.

[0023] A cover layer 61 (insulating resin layer) may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 31 and expose the terminal portion 51. By providing the cover layer 61, it is possible to prevent mechanical damage to the resistor 31. Furthermore, by providing the cover layer 61, it is possible to protect the resistor 31 from moisture and the like. Note that the cover layer 61 may be provided so as to cover a wider area excluding the terminal portion 51.

[0024] A cover layer 62 (insulating resin layer) may be provided on the upper surface 10a of the substrate 10 so as to cover the resistor 32 and expose the terminal portion 52. By providing the cover layer 62, it is possible to prevent mechanical damage to the resistor 32. Furthermore, by providing the cover layer 62, it is possible to protect the resistor 32 from moisture and the like. Note that the cover layer 62 may be provided so as to cover a wider area excluding the terminal portion 52.

[0025] The cover layers 61 and 62 can be formed from an insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, or composite resin (e.g., silicone resin or polyolefin resin). The cover layers 61 and 62 may contain a filler or a pigment. There are no particular restrictions on the thickness of the cover layers 61 and 62 and the thickness can be appropriately selected depending on the purpose, but it can be, for example, about 2 μm to 30 μm.

[0026] Fig. 3 is a perspective view illustrating the sensor module according to the first embodiment. Fig. 4 is a cross-sectional view illustrating the sensor module according to the first embodiment, showing a vertical cross section along line BB in Fig. 3. For convenience, the dimensional ratios of the components are changed between Fig. 2 and Fig. 4.

[0027] 1 to 4, the substrate 10 of the strain gauge 1 has a first region E1 that can be attached to the first surface S1 of the strain element 110, and a second region E2 and a third region E3 that can be attached to the second surface S2 and the third surface S3 that are adjacent to the first surface S1 of the strain element 110 and face each other.

[0028] In the strain gauge 1, the terminal portions 51 and 52 that serve as electrodes are arranged in the first region E1. In the strain gauge 1, the resistor 31 is arranged in the second region E2, and the resistor 32 is arranged in the third region E3. In the strain gauge 1, the resistors 31 and 32 are arranged so as to be positioned opposite each other with the strain element 110 in between when the substrate 10 is attached to the strain element 110.

[0029] The sensor module 5 has a strain gauge 1, a flexure body 110, and an adhesive layer 120. In the sensor module 5, the base material 10 is fixed to the surface of the flexure body 110 via the adhesive layer 120. More specifically, the first region E1 of the base material 10 is fixed to the first surface S1 of the flexure body 110 via the adhesive layer 120, the second region E2 is fixed to the second surface S2 via the adhesive layer 120, and the third region E3 is fixed to the third surface S3 via the adhesive layer 120.

[0030] That is, in the sensor module 5, the terminal portions 51 and 52 that serve as electrodes are arranged on the first surface S1 of the flexure body 110, the resistor 31 is arranged on the second surface S2 of the flexure body 110, and the resistor 32 is arranged on the third surface S3 of the flexure body 110. The resistor 31 arranged on the second surface S2 and the resistor 32 arranged on the third surface S3 face each other with the flexure body 110 in between.

[0031] 1 to 4, the terminal portions 51 and 52 are arranged in the first region E1, but the present invention is not limited to this, and the terminal portion 51 may be arranged in the second region E2, and the terminal portion 52 may be arranged in the third region E3. However, in terms of improving workability, it is preferable to arrange the terminal portions 51 and 52 in the first region E1. By arranging the terminal portions 51 and 52 in the first region E1, the terminal portions 51 and 52 can be connected to lead wires or the like only on the same surface (first surface S1) of the sensor module 5.

[0032] The strain gauge 1 detects the strain generated in the strain element 110 as a change in the resistance of the resistors 31 and 32. The strain element 110 is made of a metal such as Fe, SUS (stainless steel), or Al, or a resin such as PEEK, and is deformed (generates strain) in response to an applied force.

[0033] The adhesive layer 120 is not particularly limited and can be selected appropriately depending on the purpose as long as it has the function of bonding the strain gauge 1 and the flexure element 110 together, and can be made of, for example, epoxy resin, modified epoxy resin, silicone resin, modified silicone resin, urethane resin, modified urethane resin, etc. Materials such as bonding sheets can also be used. The thickness of the adhesive layer 120 is not particularly limited and can be selected appropriately depending on the purpose, and can be, for example, about 0.1 μm to 50 μm.

[0034] To manufacture the strain gauge 1, first, a substrate 10 is prepared, and a metal layer (for convenience, referred to as metal layer 300) is formed on the entire upper surface 10a of the substrate 10. The metal layer 300 will eventually be patterned to become the resistors 31 and 32, the wiring patterns 41 and 42, and the terminal portions 51 and 52. The material and thickness of the metal layer 300 are the same as those of the resistors 31 and 32, the wiring patterns 41 and 42, and the terminal portions 51 and 52 described above.

[0035] The metal layer 300 can be formed by, for example, magnetron sputtering using a target made of a raw material capable of forming the metal layer 300. Instead of magnetron sputtering, the metal layer 300 may be formed by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like.

[0036] From the viewpoint of stabilizing the gauge characteristics, it is preferable to vacuum-deposit a functional layer having a thickness of about 1 nm to 100 nm on the upper surface 10a of the substrate 10 as a base layer by, for example, conventional sputtering before depositing the metal layer 300.

[0037] In the present application, the functional layer refers to a layer having a function of promoting the crystal growth of at least the upper layer, the resistors 31 and 32 (patterned metal layer 300). The functional layer preferably also has a function of preventing oxidation of the resistors 31 and 32 due to oxygen and moisture contained in the substrate 10, and a function of improving adhesion between the substrate 10 and the resistors 31 and 32. The functional layer may also have other functions.

[0038] The insulating resin film that constitutes the substrate 10 contains oxygen and moisture, and since Cr forms a self-oxidized film, particularly when the resistors 31 and 32 contain Cr, it is effective for the functional layer to have the function of preventing oxidation of the resistors 31 and 32.

[0039] The material of the functional layer is not particularly limited as long as it has the function of promoting the crystal growth of at least the upper layers, the resistors 31 and 32, and can be appropriately selected depending on the purpose. For example, 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), or an alloy of any of the metals in this group, or a compound of any of the metals in this group.

[0040] Examples of the alloys include FeCr, TiAl, FeNi, NiCr, CrCu, etc. Examples of the compounds include TiN, TaN, Si3N4, TiO2, Ta2O5, SiO2, etc.

[0041] The functional layer can be formed in vacuum by conventional sputtering, for example, using a target made of a material capable of forming the functional layer and introducing Ar (argon) gas into a chamber. By using conventional sputtering, the functional layer is formed while etching the upper surface 10a of the substrate 10 with Ar, thereby minimizing the amount of the functional layer formed and achieving an improvement in adhesion.

[0042] However, this is just one example of a method for forming the functional layer, and the functional layer may be formed by other methods. For example, a method may be used in which the upper surface 10a of the substrate 10 is activated by plasma treatment using Ar or the like before forming the functional layer, thereby improving adhesion, and then the functional layer is vacuum-formed by magnetron sputtering.

[0043] There are no particular restrictions on the combination of the material of the functional layer and the material of the metal layer 300 that will become the resistors 31 and 32, etc., and it can be selected appropriately depending on the purpose. For example, it is possible to use Ti as the functional layer and form a Cr mixed phase film with α-Cr (alpha chromium) as the main component as the metal layer 300.

[0044] In this case, for example, the metal layer 300 can be formed by magnetron sputtering using a raw material capable of forming a Cr mixed phase film as a target and introducing Ar gas into a chamber. Alternatively, the metal layer 300 can be formed by reactive sputtering using pure Cr as a target and introducing an appropriate amount of nitrogen gas together with Ar gas into a chamber.

[0045] In these methods, the Ti functional layer defines the growth plane of the Cr mixed-phase film, allowing the formation of a Cr mixed-phase film primarily composed of α-Cr, which has a stable crystal structure. Furthermore, the Ti constituting the functional layer diffuses into the Cr mixed-phase film, improving the gauge characteristics. For example, the gauge factor of the strain gauge 1 can be set to 10 or more, and the temperature coefficient of gauge factor (TCS) and temperature coefficient of resistance (TCR) can be set within the ranges of -1000 ppm / °C to +1000 ppm / °C. When the functional layer is made of Ti, the Cr mixed-phase film may contain Ti or TiN (titanium nitride).

[0046] When the resistors 31 and 32 are Cr mixed phase films, the functional layer made of Ti has all of the following functions: promoting the crystal growth of the resistors 31 and 32; preventing the resistors 31 and 32 from being oxidized by oxygen and moisture contained in the substrate 10; and improving the adhesion between the substrate 10 and the resistors 31 and 32. The same applies when Ta, Si, Al, or Fe is used as the functional layer instead of Ti.

[0047] In this way, by providing a functional layer below the resistors 31 and 32, it is possible to promote the crystal growth of the resistors 31 and 32, and to produce resistors 31 and 32 consisting of a stable crystalline phase. As a result, it is possible to improve the stability of the gauge characteristics of the strain gauge 1. Furthermore, by diffusing the material constituting the functional layer into the resistors 31 and 32, it is possible to improve the gauge characteristics of the strain gauge 1.

[0048] After the functional layer and metal layer 300 are formed over the entire upper surface 10a of the base material 10, the functional layer and metal layer 300 formed on the upper surface 10a of the base material 10 are patterned by photolithography into the shape shown in Fig. 1. This forms resistors 31 and 32, wiring patterns 41 and 42, and terminal portions 51 and 52.

[0049] After forming the resistors 31 and 32, the wiring patterns 41 and 42, and the terminal portions 51 and 52, a cover layer 61 that covers the resistor 31 and exposes the terminal portion 51 and a cover layer 62 that covers the resistor 32 and exposes the terminal portion 52 are provided on the upper surface 10a of the substrate 10 as needed, thereby completing the strain gauge 1. The cover layers 61 and 62 can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 10a of the substrate 10 so as to cover the resistor 31 and expose the terminal portion 51 and to cover the resistor 32 and expose the terminal portion 52, and then heating and curing the film. The cover layers 61 and 62 may also be produced by applying a liquid or paste-like thermosetting insulating resin to the upper surface 10a of the substrate 10 so as to cover the resistor 31 and expose the terminal portion 51 and to cover the resistor 32 and expose the terminal portion 52, and then heating and curing the film.

[0050] To manufacture the sensor module 5, after the strain gauge 1 is fabricated, the base material 10 of the strain gauge 1 is attached to the flexure element 110. Specifically, for example, one of the above materials that will become the adhesive layer 120 is applied to the lower surface of the base material 10 and / or the surface of the flexure element 110 (predetermined areas of the first surface S1, the second surface S2, and the third surface S3). Then, the lower surface of the base material 10 is made to face the surface of the flexure element 110, and the strain gauge 1 is placed on the flexure element 110 with the applied material sandwiched between them. Alternatively, a bonding sheet may be sandwiched between the flexure element 110 and the base material 10.

[0051] Next, the strain gauge 1 is heated to a predetermined temperature while being pressed against the flexure element 110, and the applied material is cured to form the adhesive layer 120. This bonds the surface of the flexure element 110 and the underside of the substrate 10 via the adhesive layer 120, completing the sensor module 5. The sensor module 5 can be used to measure, for example, load, pressure, torque, acceleration, etc.

[0052] In this way, in the sensor module 5, the resistors 31 and 32 are arranged at positions facing each other with the strain body 110 in between. Therefore, for example, when bending stress occurs with the second surface S2 of the strain body 110 on the tensile side and the third surface S3 on the compressive side, the output of the terminal portion 51 connected to the resistor 31 arranged on the second surface S2 and the output of the terminal portion 52 connected to the resistor 32 arranged on the third surface S3 have the same absolute value but opposite signs. As a result, the detection sensitivity can be improved when strain detection is performed by connecting the outputs of the terminal portions 51 and 52 to a Wheatstone bridge.

[0053] Furthermore, by using one strain gauge 1 on which multiple resistors are patterned, the efficiency of the attachment work can be improved compared to when multiple strain gauges are used and attached individually to the strain element 110. Furthermore, by using the strain gauge 1, the number of parts of the sensor module 5 can be reduced compared to when multiple strain gauges are used and attached individually to the strain element 110, and the reliability of the sensor module 5 can be improved.

[0054] <Modification 1 of the First Embodiment> In the first modification of the first embodiment, an example of a strain gauge and a sensor module having four resistors is shown. Note that in the first modification of the first embodiment, the description of the same components as those in the previously described embodiments may be omitted.

[0055] Fig. 5 is a plan view illustrating a strain gauge according to Modification 1 of the first embodiment. Fig. 6 is a perspective view illustrating a sensor module according to Modification 1 of the first embodiment. Note that the cross-sectional shapes of the strain gauge and the sensor module according to Modification 1 of the first embodiment are the same as those in Figs. 2 and 4, and therefore are not shown.

[0056] 5, strain gauge 1A has a substrate 10X having a cross-shaped planar shape. On substrate 10X, resistor 31, wiring pattern 41, terminal portion 51, resistor 32, wiring pattern 42, and terminal portion 52 are provided in the same arrangement as on strain gauge 1. Furthermore, on substrate 10X, resistor 33, wiring pattern 43, terminal portion 53, resistor 34, wiring pattern 44, and terminal portion 54 are provided.

[0057] The resistors 33 and 34 are formed on the substrate 10X and are sensing elements that undergo a resistance change when strained. The resistors 33 and 34 can be arranged on the substrate 10X with the grid direction facing the same direction. The resistors 33 and 34 and the resistors 31 and 32 can be arranged on the substrate 10X with the grid direction facing perpendicularly to each other. The material and thickness of the substrate 10X and the resistors 33 and 34 can be the same as those of the substrate 10X and the resistors 31 and 32, for example. Note that in FIG. 5, the resistors 31, 32, 33, and 34 are shown with a matte finish for convenience.

[0058] The terminal portions 53 extend from both ends of the resistor 33 via the wiring pattern 43 and are formed in a generally rectangular shape in plan view, wider than the resistor 33. The terminal portions 53 are a pair of electrodes for outputting a change in the resistance value of the resistor 33 caused by strain to the outside, and are connected to, for example, lead wires for external connection. The resistor 33 extends, for example, from one of the terminal portions 53 via the wiring pattern 43 while folding back in a zigzag pattern and is connected to the other terminal portion 53 via the wiring pattern 43.

[0059] The terminal portions 54 extend from both ends of the resistor 34 via the wiring pattern 44 and are formed in a generally rectangular shape in plan view, wider than the resistor 34. The terminal portions 54 are a pair of electrodes for outputting a change in the resistance value of the resistor 34 caused by strain to the outside, and are joined to, for example, lead wires for external connection. The resistor 34 extends, for example, from one of the terminal portions 54 via the wiring pattern 44 while folding back in a zigzag pattern and is connected to the other terminal portion 54 via the wiring pattern 44.

[0060] The upper surfaces of the terminal portions 53 and 54 may be covered with a metal having better solderability than the terminal portions 53 and 54. Although the resistors 31, 32, 33, and 34, the wiring patterns 41, 42, 43, and 44, and the terminal portions 51, 52, 53, and 54 are given different reference numerals for convenience, they can be integrally formed from the same material in the same process.

[0061] A cover layer 63 (insulating resin layer) may be provided on the upper surface 10a of the substrate 10X so as to cover the resistor 33 and expose the terminal portion 53. By providing the cover layer 63, it is possible to prevent mechanical damage to the resistor 33. Furthermore, by providing the cover layer 63, it is possible to protect the resistor 33 from moisture and the like. Note that the cover layer 63 may be provided so as to cover a wider area excluding the terminal portion 53.

[0062] A cover layer 64 (insulating resin layer) may be provided on the upper surface 10a of the substrate 10X so as to cover the resistor 34 and expose the terminal portion 54. By providing the cover layer 64, mechanical damage to the resistor 34 can be prevented. Furthermore, by providing the cover layer 64, the resistor 34 can be protected from moisture and the like. Note that the cover layer 64 may be provided so as to cover a wider area excluding the terminal portion 54. The material and thickness of the cover layers 63 and 64 may be the same as those of the cover layers 61 and 62, for example.

[0063] 5 and 6, the substrate 10X of the strain gauge 1A has a first region E1 that can be attached to the first surface S1 of the flexure element 110, a second region E2 and a third region E3 that can be attached to the second surface S2 and the third surface S3 that are adjacent to the first surface S1 of the flexure element 110 and face each other, and a fourth region E4 and a fifth region E5 that can be attached to the fourth surface S4 and the fifth surface S5 that are adjacent to the first surface S1 of the flexure element 110 and face each other.

[0064] In the strain gauge 1A, terminal portions 51, 52, 53, and 54, which serve as electrodes, are arranged in a first region E1. In the strain gauge 1A, the resistor 31 is arranged in a second region E2, the resistor 32 is arranged in a third region E3, the resistor 33 is arranged in a fourth region E4, and the resistor 34 is arranged in a fifth region E5. In the strain gauge 1A, the resistors 31 and 32 are arranged so as to be positioned opposite each other across the flexure element 110 when the substrate 10X is attached to the flexure element 110, and the resistors 33 and 34 are arranged so as to be positioned opposite each other across the flexure element 110 when the substrate 10X is attached to the flexure element 110.

[0065] The sensor module 5A has a strain gauge 1A, a flexure body 110, and an adhesive layer 120. In the sensor module 5A, the base material 10X is fixed to the surface of the flexure body 110 via the adhesive layer 120. More specifically, the first region E1 of the base material 10X is fixed to the first surface S1 of the flexure body 110 via the adhesive layer 120, the second region E2 is fixed to the second surface S2 via the adhesive layer 120, the third region E3 is fixed to the third surface S3 via the adhesive layer 120, the fourth region E4 is fixed to the fourth surface S4 via the adhesive layer 120, and the fifth region E5 is fixed to the fifth surface S5 via the adhesive layer 120.

[0066] That is, in the sensor module 5A, the terminal portions 51, 52, 53, and 54 that serve as electrodes are arranged on the first surface S1 of the flexure body 110, the resistor 31 is arranged on the second surface S2 of the flexure body 110, the resistor 32 is arranged on the third surface S3 of the flexure body 110, the resistor 33 is arranged on the fourth surface S4 of the flexure body 110, and the resistor 34 is arranged on the fifth surface S5 of the flexure body 110. The resistor 31 arranged on the second surface S2 and the resistor 32 arranged on the third surface S3 face each other with the flexure body 110 in between. Furthermore, the resistor 33 arranged on the fourth surface S4 and the resistor 34 arranged on the fifth surface S5 face each other with the flexure body 110 in between.

[0067] In this way, in the sensor module 5A, the resistors 31 and 32 are arranged in positions facing each other with the strain body 110 in between. Therefore, for example, when bending stress occurs with the second surface S2 of the strain body 110 on the tensile side and the third surface S3 on the compressive side, the output of the terminal portion 51 connected to the resistor 31 arranged on the second surface S2 and the output of the terminal portion 52 connected to the resistor 32 arranged on the third surface S3 have the same absolute value but opposite signs. As a result, the detection sensitivity can be improved when strain detection is performed by connecting the outputs of the terminal portions 51 and 52 to a Wheatstone bridge.

[0068] Similarly, in the sensor module 5A, the resistors 33 and 34 are arranged at positions facing each other across the strain body 110. Therefore, for example, when bending stress occurs with the fourth surface S4 of the strain body 110 being the tensile side and the fifth surface S5 being the compressive side, the output of the terminal portion 53 connected to the resistor 33 arranged on the fourth surface S4 and the output of the terminal portion 54 connected to the resistor 34 arranged on the fifth surface S5 will have the same absolute value but opposite signs. As a result, the detection sensitivity can be improved when strain detection is performed by connecting the outputs of the terminal portions 53 and 54 to a Wheatstone bridge.

[0069] Furthermore, by using one strain gauge 1A on which multiple resistors are patterned, the efficiency of the attachment work can be improved compared to when multiple strain gauges are used and attached individually to the strain element 110. Furthermore, by using the strain gauge 1A, it is possible to reduce the number of components of the sensor module 5A compared to when multiple strain gauges are used and attached individually to the strain element 110, and the reliability of the sensor module 5A can be improved.

[0070] The above describes in detail preferred embodiments, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0071] For example, the first embodiment shows an example of a strain gauge having two resistors, and the first modification of the first embodiment shows an example of a strain gauge having four resistors. However, the strain gauge according to the present invention may have any number of resistors as long as it includes at least two resistors that are positioned so as to be opposite each other across the strain element when the substrate is attached to the strain element.

[0072] Furthermore, the first embodiment has been described as an example of a strain gauge having a substrate with a rectangular planar shape, and Modification 1 of the first embodiment has been described as an example of a strain gauge having a substrate with a cross planar shape. However, the strain gauge according to the present invention may have any planar shape for the substrate, as long as it includes at least two resistors arranged so as to be positioned opposite each other across the flexure element when the substrate is attached to the flexure element. Therefore, the planar shape is not limited to simple shapes such as a rectangular or cross shape, and more complex planar shapes may be used to match the shape of the flexure element. [Explanation of symbols]

[0073] 1, 1A strain gauge, 5, 5A sensor module, 10, 10X substrate, 10a upper surface, 31, 32, 33, 34 resistor, 41, 42, 43, 44 wiring pattern, 51, 52, 53, 54 terminal portion, 61, 62, 63, 64 cover layer, 110 strain element, 120 adhesive layer

Claims

1. a flexible resin substrate; a functional layer formed directly on one surface of the substrate from a metal, alloy, or metal compound; Cr, CrN, and Cr are directly applied to one surface of the functional layer. ２ a plurality of resistors formed from a film containing N and containing α-Cr as a main component; the functional layer has a function of promoting crystal growth of the α-Cr and forming a film containing the α-Cr as a main component; the thickness of each of the plurality of resistors is 0.05 μm or more and 2 μm or less; The thickness of the functional layer is 1 nm or more and 100 nm or less, The plurality of resistors are strain gauges including two resistors arranged so as to be opposite each other across the strain element when the base material is attached to the strain element.

2. the base material includes a first region that can be attached to a first surface of the strain generating body, and a second region and a third region that can be attached to a second surface and a third surface that are adjacent to the first surface and opposed to each other, 2. The strain gauge according to claim 1, wherein one of the two resistors is disposed in the second region, and the other of the two resistors is disposed in the third region.

3. a first electrode electrically connected to one of the two resistors and a second electrode electrically connected to the other of the two resistors; The strain gauge according to claim 2 , wherein the first electrode and the second electrode are disposed in the first region.

4. 4. The strain gauge according to claim 1, wherein the two resistors are arranged on the substrate with their grid directions facing in the same direction.

5. 5. The strain gauge according to claim 1, further comprising an insulating resin layer that covers at least one of the plurality of resistors.

6. A strain gauge according to any one of claims 1 to 5; the strain element to which the base material is attached, The sensor module has the two resistors disposed at positions facing each other with the strain-generating element interposed therebetween.

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