Strain gauge

Abstract

To provide a strain gauge which is usable for balance application.SOLUTION: A strain gauge has a resin base material having flexibility, and a resistor formed of a film containing Cr, CrN and Cr2 N on the base material, in which a film thickness of the resistor is 100 nm or more and 700 nm or less.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] There is known a strain gauge that has a resistor on a substrate and is attached to an object to be measured to detect the characteristics of the object to be measured. Strain gauges are used as sensors, for example, for detecting the strain of a material or for detecting the ambient temperature (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-221696 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, strain gauges are sometimes used as scales in addition to sensors, and in such cases they must meet stricter creep standards than those for sensors, so there are cases where strain gauges that can be used for sensors cannot be used for scales.

[0005] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a strain gauge that can be used for weighing purposes. [Means for solving the problem]

[0006] This strain gauge has a flexible resin substrate and a resistor formed on the substrate from a film containing Cr, CrN, and Cr2N, and the thickness of the resistor is 100 nm or more and 700 nm or less. Effect of the Invention

[0007] According to the disclosed technique, a strain gauge that can be used for weighing purposes can be provided. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view illustrating the strain gauge according to the first embodiment. [Diagram 2] 1 is a cross-sectional view (part 1) illustrating a strain gauge according to a first embodiment. FIG. [Diagram 3] 4 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. FIG. [Figure 4] FIG. 2 is a diagram illustrating a method for measuring the amount of creep and the amount of creep recovery. [Diagram 5] FIG. 1 shows the results of Example 1. [Figure 6] FIG. 1 shows the results of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated explanations may be omitted.

[0010] First embodiment Fig. 1 is a plan view illustrating the strain gauge according to the first embodiment. Fig. 2 is a cross-sectional view illustrating the strain gauge according to the first embodiment, showing a cross section along line AA in Fig. 1. Referring to Fig. 1 and Fig. 2, the strain gauge 1 has a substrate 10, a resistor 30, and a terminal portion 41.

[0011] In this embodiment, for convenience, in the strain gauge 1, the side of the substrate 10 on which the resistor 30 is provided is referred to as the upper side or one side, and the side on which the resistor 30 is not provided is referred to as the lower side or the other side. Also, the surface on which the resistor 30 is provided in each portion is referred to as the one side or upper surface, and the surface on which the resistor 30 is not provided is referred to as the other side or lower surface. However, the strain gauge 1 can be used upside down or placed at any angle. Also, the planar view refers to the object being viewed from the normal direction of the upper surface 10a of the substrate 10, and the 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 resistor 30 and the like. The thickness of the substrate 10 is not particularly limited and can be appropriately selected depending on the purpose, but can be, for example, about 5 μm to 500 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.

[0015] The resistor 30 is a thin film formed in a predetermined pattern on the substrate 10, and is a sensing part that generates a resistance change when strained. The resistor 30 may be formed directly on the upper surface 10a of the substrate 10, or may be formed on the upper surface 10a of the substrate 10 via another layer. For convenience, the resistor 30 is shown in FIG. 1 with a matte pattern.

[0016] The resistor 30 can be made of, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 30 can be made of 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).

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

[0018] For example, when the resistor 30 is a Cr mixed phase film, the stability of the gauge characteristics can be improved by making α-Cr (alpha chromium) which is a stable crystal phase the main component. Furthermore, by making the resistor 30 mainly of α-Cr, the gauge factor of the strain gauge 1 can be 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C. Here, the main component means that the target substance accounts for 50% by weight or more of the total substance constituting the resistor, but from the viewpoint of improving the gauge characteristics, the resistor 30 preferably contains 80% by weight or more of α-Cr, and 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).

[0019] When the resistor 30 is a Cr mixed-phase film, the Cr mixed-phase film preferably contains 20% by weight or less of CrN and Cr2N. By containing 20% ​​by weight or less of CrN and Cr2N in the Cr mixed-phase film, a decrease in the gauge factor can be suppressed.

[0020] In addition, the ratio of Cr2N in CrN and Cr2N is preferably 80% by weight or more and less than 90% by weight, and more preferably 90% by weight or more and less than 95% by weight. When the ratio of Cr2N in CrN and Cr2N is 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more significant due to the Cr2N having semiconductor properties. Furthermore, by reducing the formation of ceramics, brittle fracture is reduced.

[0021] On the other hand, if a small amount of N2 or atomic N is mixed into the film, it will escape from the film due to the external environment (for example, a high temperature environment), causing a change in the film stress.By creating chemically stable CrN, it is possible to obtain a stable strain gauge without generating the unstable N mentioned above.

[0022] The terminal portions 41 extend from both ends of the resistor 30 and are formed in a substantially rectangular shape wider than the resistor 30 in a plan view. The terminal portions 41 are a pair of electrodes for outputting a change in resistance value of the resistor 30 caused by strain to the outside, and for example, a lead wire for external connection is joined to the terminal portions 41. For example, the resistor 30 extends from one of the terminal portions 41 while folding back in a zigzag manner and is connected to the other terminal portion 41. The upper surface of the terminal portion 41 may be covered with a metal having better solderability than the terminal portion 41. Although the resistor 30 and the terminal portion 41 are denoted by different reference numerals for convenience, the two can be integrally formed from the same material in the same process.

[0023] A cover layer 60 (insulating resin layer) may be provided on the upper surface 10a of the base material 10 so as to cover the resistor 30 and expose the terminal portion 41. By providing the cover layer 60, mechanical damage to the resistor 30 can be prevented. Furthermore, by providing the cover layer 60, the resistor 30 can be protected from moisture and the like. The cover layer 60 may be provided so as to cover the entire portion except for the terminal portion 41.

[0024] The cover layer 60 can be formed from an insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, composite resin (e.g., silicone resin, polyolefin resin), etc. The cover layer 60 may contain a filler or a pigment. There is no particular limit to the thickness of the cover layer 60 and it can be appropriately selected depending on the purpose, but it can be, for example, about 2 μm to 30 μm.

[0025] Here, a suitable film thickness of the resistor 30 will be described. When the strain gauge 1 is used for a sensor, the film thickness of the resistor 30 is not particularly limited and can be appropriately selected depending on the purpose, and can be, for example, about 50 nm to 2000 nm. In particular, a film thickness of 100 nm or more is preferable in that the crystallinity of the crystals constituting the resistor 30 (for example, the crystallinity of α-Cr) is improved, and a film thickness of 1000 nm or less is even more preferable in that cracks in the film and warping from the substrate 10 caused by internal stress of the film constituting the resistor 30 can be reduced.

[0026] On the other hand, when the strain gauge 1 is used for weighing purposes, it is necessary to satisfy standards related to creep, such as precision class C1 based on OIML R60 (hereinafter referred to as C1 standard) and precision class C2 based on OIML R60 (hereinafter referred to as C2 standard).

[0027] The C1 standard requires the creep amount and creep recovery amount to be within ±0.0735%. The C2 standard requires the creep amount and creep recovery amount to be within ±0.0368%. If the strain gauge 1 is used for sensor applications, the standard for the creep amount and creep recovery amount is approximately ±0.5%.

[0028] After extensive research, the inventors discovered that creep is highly dependent on the film thickness of resistor 30, and that in order to satisfy the C1 and C2 standards, it is necessary to narrow the film thickness of resistor 30 to a narrower range within the above-mentioned range of 50 nm to 2000 nm.

[0029] Specifically, taking into consideration the film thickness that improves the crystallinity of the crystals constituting resistor 30 as described above, it is preferable to set the film thickness of resistor 30 to 100 nm or more and 700 nm or less in order to satisfy the C1 standard.

[0030] To satisfy the C2 standard, it is preferable that the film thickness of resistor 30 is 150 nm or more and 500 nm or less. Furthermore, to reliably satisfy the C2 standard, and allow for a 50% margin (i.e., to satisfy half the value of the C2 standard), it is preferable that the film thickness of resistor 30 is 250 nm or more and 400 nm or less.

[0031] Furthermore, according to the inventors' investigations, creep also depends on the film thickness of the substrate 10, although not as much as on the film thickness of the resistor 30. Therefore, by setting the film thickness of the resistor 30 in the above range and further narrowing the film thickness of the substrate 10 within the above range of 5 μm to 500 μm, the amount of creep and the amount of creep recovery can be further reduced.

[0032] Specifically, in order to satisfy the C1 standard, the thickness of the substrate 10 is preferably 5 μm or more and 130 μm or less, and in order to satisfy the C2 standard, the thickness of the substrate 10 is preferably 5 μm or more and 100 μm or less.

[0033] In either case, the effect of improving the insulation property described above can be obtained by setting the lower limit of the film thickness of the substrate 10 to 10 μm or more. That is, taking into consideration the securing of insulation property, the film thickness of the substrate 10 is preferably set to 10 μm or more and 130 μm or less in order to satisfy the C1 standard, and the film thickness of the substrate 10 is preferably set to 10 μm or more and 100 μm or less in order to satisfy the C2 standard.

[0034] Furthermore, in order to reliably satisfy the C2 standard, allowing for a 50% margin (that is, to satisfy half the value of the C2 standard), the film thickness of the base material 10 is preferably set to 30 μm or more and 70 μm or less.

[0035] In this way, the strain gauge 1 can be used for weighing purposes by specifying the film thickness of the resistor 30 more strictly than before. Also, the strain gauge 1 can be used for weighing purposes with a sufficient margin by specifying the film thickness of the resistor 30 more strictly than before and further specifying the film thickness of the substrate 10 more strictly than before. However, the strain gauge 1 may also be used for sensor purposes.

[0036] To manufacture the strain gauge 1, first, a base material 10 is prepared, and a metal layer (for convenience, referred to as metal layer A) is formed on the upper surface 10a of the base material 10. The metal layer A is a layer that is finally patterned to become the resistor 30 and the terminal portion 41. Therefore, the material and thickness of the metal layer A are the same as the material and thickness of the resistor 30 and the terminal portion 41 described above.

[0037] The metal layer A can be formed by, for example, a magnetron sputtering method using a target made of a raw material capable of forming the metal layer A. The metal layer A may be formed by a reactive sputtering method, a vapor deposition method, an arc ion plating method, a pulsed laser deposition method, or the like instead of the magnetron sputtering method.

[0038] From the viewpoint of stabilizing the gauge characteristics, it is preferable to vacuum-deposit a functional layer of a predetermined thickness as a base layer on the upper surface 10a of the base material 10 by, for example, conventional sputtering, before depositing the metal layer A.

[0039] 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 metal layer A (resistor 30). The functional layer preferably further has a function of preventing oxidation of the metal layer A due to oxygen and moisture contained in the base material 10, and a function of improving adhesion between the base material 10 and the metal layer A. The functional layer may further have other functions.

[0040] Since the insulating resin film that constitutes the substrate 10 contains oxygen and moisture, it is effective for the functional layer to have the function of preventing oxidation of the metal layer A, particularly when the metal layer A contains Cr, since Cr forms a self-oxidized film.

[0041] 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 layer, the metal layer A (resistor 30), 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), and the like can be used. Examples of the metal include one or more metals selected from the group consisting of ruthenium (Ru), 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.

[0042] Examples of the alloy include FeCr, TiAl, FeNi, NiCr, CrCu, etc. Examples of the compound include TiN, TaN, Si3N4, TiO2, Ta2O5, SiO2, etc.

[0043] When the functional layer is made of a conductive material such as a metal or alloy, the thickness of the functional layer is preferably 1 / 20 or less of the thickness of the resistor. In this range, the crystal growth of α-Cr can be promoted, and a part of the current flowing through the resistor can be prevented from flowing through the functional layer, which reduces the detection sensitivity of strain.

[0044] When the functional layer is made of a conductive material such as a metal or alloy, the thickness of the functional layer is preferably 1 / 50 or less of the thickness of the resistor. In this range, the crystal growth of α-Cr can be promoted, and the strain detection sensitivity can be further prevented from being reduced due to a part of the current flowing through the resistor flowing through the functional layer.

[0045] When the functional layer is made of a conductive material such as a metal or alloy, the thickness of the functional layer is more preferably 1 / 100 or less of the thickness of the resistor, which can further prevent a part of the current flowing through the resistor from flowing through the functional layer, thereby preventing a decrease in the strain detection sensitivity.

[0046] When the functional layer is made of an insulating material such as an oxide or a nitride, the thickness of the functional layer is preferably 1 nm to 1 μm, which can promote the crystal growth of α-Cr and can be easily formed without cracking the functional layer.

[0047] When the functional layer is made of an insulating material such as an oxide or nitride, the thickness of the functional layer is preferably 1 nm to 0.8 μm, which can promote the crystal growth of α-Cr and can be easily formed without cracking the functional layer.

[0048] When the functional layer is made of an insulating material such as an oxide or nitride, the thickness of the functional layer is more preferably 1 nm to 0.5 μm, which can promote the crystal growth of α-Cr and can be more easily formed without cracking the functional layer.

[0049] The planar shape of the functional layer is patterned to be substantially the same as the planar shape of the resistor shown in FIG. 1, for example. However, the planar shape of the functional layer is not limited to being substantially the same as the planar shape of the resistor. When the functional layer is made of an insulating material, it does not have to be patterned to be the same as the planar shape of the resistor. In this case, the functional layer may be formed in a solid shape at least in the region where the resistor is formed. Alternatively, the functional layer may be formed in a solid shape on the entire upper surface of the substrate 10.

[0050] Furthermore, when the functional layer is made of an insulating material, the functional layer is formed relatively thick, at a thickness of 50 nm to 1 μm, and formed in a solid form, so that the thickness and surface area of ​​the functional layer are increased, and the heat generated by the resistor can be dissipated to the substrate 10. As a result, the deterioration of the measurement accuracy of the strain gauge 1 due to self-heating of the resistor can be suppressed.

[0051] The functional layer can be formed in vacuum by conventional sputtering, for example, using a raw material capable of forming the functional layer as a target 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, so that the amount of the functional layer formed can be minimized and the effect of improving adhesion can be obtained.

[0052] 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 a 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.

[0053] There are no particular restrictions on the combination of the material of the functional layer and the material of the metal layer A and can be selected appropriately depending on the purpose. For example, it is possible to use Ti for the functional layer and form a Cr mixed phase film with α-Cr (alpha chromium) as the main component for the metal layer A.

[0054] In this case, for example, the metal layer A 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 A 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. In this case, the ratio of CrN and Cr2N contained in the Cr mixed phase film, and the ratio of Cr2N in CrN and Cr2N can be adjusted by changing the amount and pressure of the nitrogen gas introduced (nitrogen partial pressure) or by adjusting the heating temperature by providing a heating process.

[0055] In these methods, the growth surface of the Cr mixed-phase film is determined by the functional layer made of Ti, and a Cr mixed-phase film containing α-Cr, which has a stable crystal structure, as a main component, can be formed. Furthermore, the Ti constituting the functional layer is diffused into the Cr mixed-phase film, thereby improving the gauge characteristics. For example, the gauge factor of the strain gauge 1 can be set to 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be set within the range of -1000 ppm / °C to +1000 ppm / °C. When the functional layer is made of Ti, the Cr mixed-phase film may contain Ti and TiN (titanium nitride).

[0056] When the metal layer A is a Cr mixed phase film, the functional layer made of Ti has all of the following functions: promoting the crystal growth of the metal layer A, preventing oxidation of the metal layer A due to oxygen and moisture contained in the base material 10, and improving the adhesion between the base material 10 and the metal layer A. The same applies when Ta, Si, Al, or Fe is used as the functional layer instead of Ti.

[0057] 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 crystal phase. As a result, it is possible to improve the stability of the gauge characteristics of the strain gauge 1. In addition, the material constituting the functional layer diffuses into the metal layer A, thereby improving the gauge characteristics of the strain gauge 1.

[0058] Next, the metal layer A is patterned by photolithography to form the resistor element 30 and the terminal portion 41 having the planar shape shown in FIG.

[0059] After forming the resistor 30 and the terminal portion 41, a cover layer 60 that covers the resistor 30 and exposes the terminal portion 41 is provided on the upper surface 10a of the substrate 10 as necessary, thereby completing the strain gauge 1. The cover layer 60 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 30 and expose the terminal portion 41, and then heating and curing the film. The cover layer 60 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 30 and expose the terminal portion 41, and then heating and curing the resin.

[0060] When a functional layer is provided on the upper surface 10a of the substrate 10 as an underlayer for the resistor 30 and the terminal portion 41, the strain gauge 1 has a cross-sectional shape as shown in Fig. 3. The layer indicated by reference numeral 20 is the functional layer. When the functional layer 20 is provided, the planar shape of the strain gauge 1 is, for example, the same as that shown in Fig. 1. However, as described above, the functional layer 20 may be formed solidly on a part or all of the upper surface of the substrate 10.

[0061] [Example 1] In Example 1, a suitable film thickness of the resistor 30 for reducing the amount of creep and the amount of creep recovery was investigated. Specifically, a plurality of strain gauges 1 with different film thicknesses of the resistor 30 were produced, and each strain gauge 1 was attached to a strain generating body made of SUS304, and the amount of creep and the amount of creep recovery were measured. Note that a polyimide resin film with a film thickness of 25 μm was used as the substrate 10.

[0062] The amount of creep and the amount of creep recovery are amounts that change over time as the amount of elastic deformation (amount of strain) of the surface of the strain gauge 1 on which the resistor 30 is provided changes, and therefore can be measured by monitoring the strain voltage calculated based on the output between a pair of terminal parts 41. A detailed description will be given with reference to FIG.

[0063] Fig. 4 is a diagram for explaining the method of measuring the creep amount and the creep recovery amount, in which the horizontal axis represents time and the vertical axis represents strain voltage [mV].

[0064] First, 10 seconds after turning on the power to the measuring device, a 150% load is applied to the strain gauge 1 attached to the flexure body for 10 seconds, and then the load is removed. After 20 minutes have passed since the load was removed, a 100% load is applied to the strain gauge 1 attached to the flexure body for 20 minutes, and then the load is removed. Then, wait for 20 minutes to pass after the load is removed.

[0065] The strain voltage changes, for example, as shown in Figure 4. In Figure 4, the absolute value B of the difference in strain voltage between 20 minutes after the 150% load is removed and immediately after the 100% load is applied is measured. Also, the absolute value ΔA of the difference in strain voltage between immediately after the 100% load is applied and 20 minutes after the 100% load started to be applied is measured. At this time, ΔA / B is the amount of creep. Next, the absolute value ΔC of the difference in strain voltage between immediately after the 100% load is removed and 20 minutes after the 100% load is removed is measured. At this time, ΔC / B is the amount of creep recovery.

[0066] It should be noted that a 100% load is 3 kg, and a 150% load is 1.5 times the 100% load.

[0067] FIG. 5 is a diagram showing the results of Example 1, and summarizes the results of measuring the creep amount and creep recovery amount of a plurality of strain gauges 1 with different film thicknesses of resistors 30 using the measuring method of FIG.

[0068] As shown in Fig. 5, if the thickness of resistor 30 is 700 nm or less, the creep amount and creep recovery amount of the C1 standard can be satisfied. Considering that the crystallinity of the crystals constituting resistor 30 is improved when the thickness of resistor 30 is 100 nm or more as described above, it is preferable to set the thickness of resistor 30 to 100 nm or more and 700 nm or less in order to satisfy the C1 standard.

[0069] 5, if the thickness of resistor 30 is 150 nm or more and 500 nm or less, the creep amount and creep recovery amount of the C2 standard can be satisfied. Furthermore, in order to reliably satisfy the C2 standard, allowing for a 50% margin (i.e., to satisfy half the value of the C2 standard), it is preferable that the thickness of resistor 30 be 250 nm or more and 400 nm or less.

[0070] [Example 2] In Example 2, a suitable film thickness of the substrate 10 for reducing the amount of creep and the amount of creep recovery was investigated. Specifically, a plurality of strain gauges 1 with different film thicknesses of the substrate 10 were produced, and each strain gauge 1 was attached to a strain generating body made of SUS304, and the amount of creep and the amount of creep recovery were measured. Note that a Cr mixed phase film with a film thickness of 220 nm was used as the resistor 30.

[0071] FIG. 6 is a diagram showing the results of Example 2, and summarizes the results of measuring the creep amount and creep recovery amount of a plurality of strain gauges 1 with different film thicknesses of the substrate 10 using the measuring method of FIG.

[0072] 6, if the thickness of the substrate 10 is 5 μm or more and 130 μm or less, the creep amount and creep recovery amount of the C1 standard can be satisfied. Considering that the insulation property is good when the thickness of the substrate 10 is 10 μm or more as described above, it can be said that the thickness of the substrate 10 is preferably 10 μm or more and 130 μm or less in order to satisfy the C1 standard.

[0073] 6, if the thickness of the substrate 10 is 5 μm or more and 100 μm or less, the creep amount and creep recovery amount of the C2 standard can be satisfied. Considering that the insulation property is good when the thickness of the substrate 10 is 10 μm or more as described above, it is preferable to set the thickness of the substrate 10 to 10 μm or less in order to satisfy the C2 standard.

[0074] Furthermore, in order to reliably satisfy the C2 standard, allowing for a 50% margin (that is, to satisfy half the value of the C2 standard), the film thickness of the base material 10 is preferably set to 30 μm or more and 70 μm or less.

[0075] Although the preferred embodiments have been described in detail above, 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. [Explanation of symbols]

[0076] 1 strain gauge, 10 substrate, 10a upper surface, 20 functional layer, 30 resistor, 41 terminal portion, 60 cover layer

Claims

[Claim 1] A flexible resin base material; On the substrate, Cr, CrN, and Cr ２ A resistor formed from a film containing N, The film thickness of the resistor is 100 nm or more and 700 nm or less.

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