Strain gauge

Abstract

To provide a strain gauge which can measure unknown strains in a main strain direction, without considering bonding accuracy.SOLUTION: A strain gauge includes a resin flexible base material, and a resistor, wherein the resistor includes a first functional layer formed from metal, an alloy or a metallic compound directly on one surface of the base material, a first resistance part which is formed from a film containing Cr, CrN and Cr2N and contains α-Cr as a main component, directly on one surface of the first functional layer, a second functional layer formed from metal, an alloy or a metallic compound directly on the other surface of the base material, and a second resistance part which is formed from a film containing Cr, CrN and Cr2N and contains α-Cr as a main component, directly on one surface of the second functional layer, wherein the first functional layer and the second functional layer have a function for promoting crystal growth of α-Cr and film-forming the film containing α-Cr as a main component, and the first resistance part and the second resistance part are arranged so that the grid directions cross each other in plan view.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] A strain gauge that is attached to a measurement object to detect the strain of the measurement object is known. The strain gauge includes a resistor that detects strain, and as the material of the resistor, for example, a material containing Cr (chromium) or Ni (nickel) is used. Further, the resistor is formed on a base material made of, for example, an insulating resin (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, there is a method of measuring strain with an unknown principal strain direction by shifting the grid directions of two strain gauges by a desired angle (for example, 90 degrees or 45 degrees) and attaching them to a measurement object. In this method, since two strain gauges are bonded together, the bonding accuracy is poor and it is difficult to bond them at a desired angle. As a result, accurate strain measurement could not be performed.

[0005] The present invention has been made in view of the above points, and an object thereof is to provide a strain gauge capable of measuring strain with an unknown principal strain direction without considering the bonding accuracy.

Means for Solving the Problems

[0006] This strain gauge comprises a flexible resin base material and a resistor, the resistor having a first functional layer formed directly on one surface of the base material from a metal, alloy, or metal compound, a first resistive portion mainly composed of α-Cr formed directly on one surface of the first functional layer from a film containing Cr, CrN, and Cr2N, a second functional layer formed directly on the other surface of the base material from a metal, alloy, or metal compound, and one surface of the second functional layer directly containing Cr, CrN, and Cr2N The first functional layer and the second functional layer include a second resistive layer mainly composed of α-Cr, formed from a film, the first functional layer and the second functional layer have the function of promoting the crystal growth of α-Cr and forming a film mainly composed of α-Cr, the thickness of the first resistive layer and the second resistive layer is 0.05 μm or more and 2 μm or less, the thickness of the first functional layer and the second functional layer is 1 nm or more and 100 nm or less, and the first resistive layer and the second resistive layer are arranged so that their grid directions intersect in a plan view. [Effects of the Invention]

[0007] According to the disclosed technology, a strain gauge capable of measuring strain with an unknown principal strain direction can be provided without considering bonding accuracy. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view illustrating a strain gauge according to the first embodiment. [Figure 2] This is a plan view illustrating the pattern of the resistance portion 31 in a strain gauge according to the first embodiment. [Figure 3] This is a cross-sectional view (part 1) illustrating a strain gauge according to the first embodiment. [Figure 4] This is a cross-sectional view (part 2) illustrating a strain gauge according to the first embodiment. [Figure 5] This figure illustrates the manufacturing process of a strain gauge according to the first embodiment. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the invention will be described below with reference to the drawings. In each drawing, the same reference numerals are used for identical components, and redundant explanations may be omitted.

[0010] <First Embodiment> Figure 1 is a plan view illustrating a strain gauge according to the first embodiment. Figure 2 is a plan view illustrating the pattern of the resistance portion 31 in the strain gauge according to the first embodiment. Figure 3 is a cross-sectional view illustrating a strain gauge according to the first embodiment, showing a cross section along line AA in Figures 1 and 2. Figure 4 is a cross-sectional view illustrating a strain gauge according to the first embodiment, showing a cross section along line BB in Figures 1 and 2. Referring to Figures 1 to 4, the strain gauge 1 includes a base material 10, a resistor 30 (resistance portions 31 and 32), terminal portions 41 and 42, and cover layers 61 and 62.

[0011] In this embodiment, for convenience, the side of the strain gauge 1 on which the resistance portion 32 is provided is referred to as the upper side or one side, and the side on which the resistance portion 31 is provided is referred to as the lower side or the other side. Furthermore, the surface on which the resistance portion 32 is provided in each part is referred to as one surface or the upper surface, and the surface on which the resistance portion 31 is provided is referred to as the other surface or the lower surface. However, the strain gauge 1 can be used upside down or positioned at any angle. Moreover, a plan view refers to viewing the object from the direction normal to the upper surface 10a of the base material 10, and a planar shape refers to the shape of the object when viewed from the direction normal to the upper surface 10a of the base material 10.

[0012] The substrate 10 is a base layer component for forming the resistor 30 and the like, and is flexible. The thickness of the substrate 10 is not particularly limited and can be appropriately selected depending on the purpose, but for example, it can be about 5 μm to 500 μm. In particular, a substrate thickness of 5 μm to 200 μm is preferable because it can reduce the strain sensitivity error of the resistive parts 31 and 32.

[0013] The base material 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, or polyolefin resin. The term "film" refers to a flexible material with a thickness of approximately 500 μm or less.

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

[0015] The resistor 30 is formed on the substrate 10 and is a sensitive part that undergoes a change in resistance when subjected to strain. The resistor 30 includes resistive parts 31 and 32 laminated via the substrate 10. In other words, the resistor 30 is a collective term for the resistive parts 31 and 32, and is referred to as the resistor 30 when there is no need to distinguish between the resistive parts 31 and 32. For convenience, in Figures 1 and 2, the resistive parts 31 and 32 are shown with a textured surface.

[0016] The resistive portion 31 is a thin film formed in a predetermined pattern on the lower surface 10b side of the substrate 10. The resistive portion 31 may be formed directly on the lower surface 10b side of the substrate 10, or it may be formed on the lower surface 10b side of the substrate 10 via another layer.

[0017] Pads 31A for receiving vias are formed at both ends of the resistor 31. The pads 31A extend from both ends of the resistor 31 and, in a plan view, are wider than the resistor 31 and are formed in a roughly rectangular shape.

[0018] The resistive portion 32 is a thin film formed in a predetermined pattern on the upper surface 10a side of the substrate 10. The resistive portion 32 may be formed directly on the upper surface 10a of the substrate 10, or it may be formed on the upper surface 10a of the substrate 10 via another layer.

[0019] The resistance part 32 is arranged such that, in plan view, the grid direction intersects with the grid direction of the resistance part 31. Here, "intersects" means that the grid direction of the resistance part 32 and the grid direction of the resistance part 31 are not parallel in plan view.

[0020] In plan view, the grid direction of the resistance part 32 is, for example, 90 degrees (orthogonal) with respect to the grid direction of the resistance part 31. However, this is just an example, and the grid direction of the resistance part 32 may be 45 degrees with respect to the grid direction of the resistance part 31 in plan view, or other angles may also be possible.

[0021] The resistor 30 (resistance parts 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 resistor 30 can be formed from a material containing at least one of Cr and Ni. Examples of the material containing Cr include, for example, a Cr mixed-phase film. Examples of the material containing Ni include, for example, Ni-Cu (nickel copper). Examples of the material containing both Cr and Ni include, for example, Ni-Cr (nickel chromium).

[0022] Here, the Cr mixed-phase film is a film in which Cr, CrN, Cr2N, etc. are in a mixed phase. The Cr mixed-phase film may contain unavoidable impurities such as chromium oxide.

[0023] The thickness of the resistor 30 is not particularly limited and can be appropriately selected according to the purpose. For example, it can be set to about 0.05 μm to 2 μm. In particular, when the thickness of the resistor 30 is 0.1 μm or more, it is preferable in terms of improving the crystallinity of the crystals constituting the resistor 30 (for example, the crystallinity of α-Cr), and when it is 1 μm or less, it is more preferable in terms of reducing film cracks caused by internal stress of the film constituting the resistor 30 and warping from the base material 10.

[0024] For example, if the resistor 30 is a Cr multiphase film, the stability of the gauge characteristics can be improved by making α-Cr (alpha-chromium), a stable crystalline phase, the main component. Furthermore, by making α-Cr the main component of the resistor 30, the gauge factor of strain gauge 1 can be set to 10 or higher, and the temperature coefficient of gauge factor TCS and the temperature coefficient of resistance TCR can be set within the range of -1000 ppm / ℃ to +1000 ppm / ℃. Here, "main component" means that the substance in question accounts for 50% or more by mass of the total substances constituting the resistor, but from the viewpoint of improving gauge characteristics, it is preferable that the resistor 30 contains 80% by weight or more of α-Cr. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0025] The terminal portions 41 and 42 are formed on the base material 10. The terminal portions 41 and 42 may be formed directly on the upper surface 10a of the base material 10, or they may be formed on the upper surface 10a of the base material 10 via another layer.

[0026] The terminal section 41 is a pair of electrodes for outputting to the outside the change in resistance value of the resistance section 31 caused by strain, and for example, an external connection lead wire is attached to it.

[0027] One end of the terminal portion 41 is electrically connected to one end of the pad 31A exposed within the via hole 10x, via the via hole 10x that penetrates the base material 10. One end of the terminal portion 41 is formed continuously from the upper surface 10a of the base material 10 to the side wall of the via hole 10x and the upper surface of one end of the pad 31A exposed within the via hole 10x, and is electrically connected to one end of the pad 31A.

[0028] A recess 10y is formed within the via hole 10x by the side wall of one via hole 10x of the terminal portion 41 and the portion formed on one upper surface of the pad 31A exposed within the via hole 10x. However, one side of the terminal portion 41 may be filled with via hole 10x (and the recess 10y may not be formed).

[0029] Furthermore, the other end of the terminal portion 41 is electrically connected to the other end of the pad 31A exposed within the via hole 10x, via the via hole 10x that penetrates the base material 10. The other end of the terminal portion 41 is formed, for example, continuously from the upper surface 10a of the base material 10 to the side wall of the via hole 10x and the upper surface of the other end of the pad 31A exposed within the via hole 10x, and is electrically connected to the other end of the pad 31A.

[0030] A recess 10y is formed within the via hole 10x by the side wall of the other via hole 10x of the terminal portion 41 and the portion formed on the other upper surface of the pad 31A that is exposed within the via hole 10x. However, the other terminal portion 41 may be filled with via hole 10x (the recess 10y may not be formed).

[0031] In a plan view, the terminal portion 41 is wider than the resistor portion 31 and is formed in a roughly rectangular shape, with the resistor portion 31 extending between one end of the terminal portion 41 and the other end of the terminal portion 41, folding back and forth in a zigzag pattern. The upper surface of the terminal portion 41 may be covered with a metal that has better solderability than the terminal portion 41.

[0032] The terminal portion 42 extends from both ends of the resistor portion 32 and, in a plan view, is wider than the resistor portion 32 and is formed in a substantially rectangular shape. The terminal portion 42 is a pair of electrodes for outputting to the outside the change in the resistance value of the resistor portion 32 caused by strain, and for example, lead wires for external connection are joined to it. The resistor portion 32 extends from one terminal portion 42 in a zigzag pattern and is connected to the other terminal portion 42. The upper surface of the terminal portion 42 may be covered with a metal that has better solderability than the terminal portion 42.

[0033] Although the resistor 32 and terminals 41 and 42 are given different reference numerals for convenience, both can be formed integrally from the same material in the same process.

[0034] The cover layer 61 is an insulating resin layer provided on the upper surface 10a of the base material 10 so as to cover the resistor portion 32 and expose the terminal portions 41 and 42. By providing the cover layer 61, mechanical damage to the resistor portion 32 can be prevented. In addition, by providing the cover layer 61, the resistor portion 32 can be protected from moisture and other elements. The cover layer 61 may be provided so as to cover the entire portion excluding the terminal portions 41 and 42.

[0035] The cover layer 62 is an insulating resin layer provided on the lower surface 10b of the base material 10 so as to cover the resistor 31 and the pad 31A. By providing the cover layer 62, mechanical damage to the resistor 31 and the pad 31A can be prevented. In addition, by providing the cover layer 62, the resistor 31 and the pad 31A can be protected from moisture and other elements.

[0036] The cover layers 61 and 62 can be formed from insulating resins such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, and composite resins (e.g., silicone resin, polyolefin resin). The cover layers 61 and 62 may contain fillers and pigments. The thickness of the cover layers 61 and 62 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 for the cover layer 62 is preferable in terms of strain transmission from the surface of the strain-generating body joined to the lower surface of the cover layer 62 via an adhesive layer, etc., and dimensional stability against the environment, and a thickness of 10 μm or more is even more preferable in terms of insulation. Note that the cover layer 61 and the cover layer 62 may be formed from different materials, or they may be formed with different thicknesses.

[0037] Figure 5 is a diagram illustrating the manufacturing process of a strain gauge according to the first embodiment, and shows a cross-section corresponding to Figure 4.

[0038] To manufacture the strain gauge 1, first, in the process shown in Figure 5(a), a base material 10 is prepared, and a metal layer 310 is formed on the entire lower surface 10b of the base material 10, which will ultimately be patterned to form the resistance portion 31 and the pad 31A. The material and thickness of the metal layer 310 are the same as those of the resistor 30 (resistance portion 31) described above.

[0039] The metal layer 310 can be formed, for example, by depositing it using a magnetron sputtering method targeting a raw material capable of forming the metal layer 310. Alternatively, the metal layer 310 may be deposited using reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or other methods instead of magnetron sputtering.

[0040] From the viewpoint of stabilizing the gauge characteristics, it is preferable to vacuum-deposit a functional layer with a thickness of approximately 1 nm to 100 nm on the lower surface 10b of the substrate 10 as an underlayer, for example, by conventional sputtering, before depositing the metal layer 310.

[0041] In this application, the functional layer refers to a layer that has the function of promoting crystal growth in the upper resistive layer (the patterned metal layer 310). Preferably, the functional layer further has the function of preventing oxidation of the upper resistive layer by oxygen and moisture contained in the substrate 10, etc., and the function of improving the adhesion between the substrate 10, etc. and the upper resistive layer. The functional layer may further have other functions.

[0042] Since the insulating resin film that makes up the base material 10 contains oxygen and moisture, and especially when the upper layer, which is the resistive layer, contains Cr, Cr forms an oxidized film, it is effective for the functional layer to have a function that prevents oxidation of the upper layer, which is the resistive layer.

[0043] The material of the functional layer is not particularly limited as long as it has the function of promoting crystal growth in at least the upper layer, the resistive layer, and can be appropriately selected according to the purpose. Examples include 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 F. Examples include one or more metals selected from the group consisting of e (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 these metals, or a compound of any of these metals.

[0044] Examples of the alloys mentioned above include FeCr, TiAl, FeNi, NiCr, and CrCu. Examples of the compounds mentioned above include TiN, TaN, Si3N4, TiO2, Ta2O5, and SiO2.

[0045] The functional layer can be deposited using a conventional sputtering method, for example, by targeting a raw material capable of forming a functional layer and introducing Ar (argon) gas into a chamber. By using the conventional sputtering method, the functional layer is deposited while etching the lower surface 10b of the substrate 10 with Ar, thus minimizing the amount of functional layer deposited and achieving improved adhesion.

[0046] However, this is just one example of a method for forming a functional layer, and the functional layer may be formed by other methods. For example, the lower surface 10b of the substrate 10 may be activated by plasma treatment using Ar or the like before forming the functional layer to improve adhesion, and then the functional layer may be formed in a vacuum by magnetron sputtering.

[0047] There are no particular restrictions on the combination of materials for the functional layer and the resistive layer on top, and they can be appropriately selected according to the purpose. For example, it is possible to use Ti as the functional layer and deposit a Cr multiphase film mainly composed of α-Cr (alpha-chromium) as the resistive layer on top.

[0048] In this case, for example, the resistive layer (the upper layer) can be deposited by magnetron sputtering with Ar gas introduced into the chamber, using a raw material capable of forming a Cr multiphase film as the target. Alternatively, the resistive layer (the upper layer) may be deposited by reactive sputtering with pure Cr as the target, using a reactive sputtering method with an appropriate amount of nitrogen gas introduced into the chamber along with Ar gas.

[0049] In these methods, a functional layer made of Ti dictates the growth surface of the Cr multiphase film, enabling the formation of a Cr multiphase film primarily composed of α-Cr, which has a stable crystalline structure. Furthermore, the diffusion of Ti constituting the functional layer into the Cr multiphase film improves the gauge characteristics. For example, the gauge factor of strain gauge 1 can be set to 10 or higher, and the gauge factor temperature coefficient TCS and resistance temperature coefficient TCR can be set within the range of -1000 ppm / °C to +1000 ppm / °C. Note that when the functional layer is formed from Ti, the Cr multiphase film may contain Ti or TiN (titanium nitride).

[0050] Furthermore, when the upper resistive layer is a Cr multiphase film, the functional layer made of Ti has all of the following functions: promoting crystal growth in the upper resistive layer, preventing oxidation of the upper resistive layer by oxygen and moisture contained in the substrate 10, and improving adhesion between the substrate 10 and the upper resistive layer. The same applies when Ta, Si, Al, or Fe are used instead of Ti as the functional layer.

[0051] In this way, by providing a functional layer beneath the resistive layer, it becomes possible to promote crystal growth in the upper resistive layer, thereby enabling the fabrication of a resistive layer consisting of a stable crystalline phase. As a result, the stability of the gauge characteristics of the strain gauge 1 can be improved. Furthermore, the diffusion of the material constituting the functional layer into the upper resistive layer can improve the gauge characteristics of the strain gauge 1.

[0052] Next, in the process shown in Figure 4(b), via holes 10x are formed that penetrate the substrate 10 and expose the upper surface of the metal layer 310. The via holes 10x can be formed, for example, by a laser processing method. The via holes 10x are formed on the region where the metal layer 310 is patterned to become the pad 31A.

[0053] Next, in the process shown in Figure 4(c), a metal layer 320 is formed over the entire upper surface 10a of the substrate 10, which will ultimately be patterned to form the resistor portion 32 and the terminal portions 41 and 42. The metal layer 320 is formed continuously from the upper surface 10a of the substrate 10 to the side walls of the via holes 10x and the upper surface of the metal layer 310 exposed inside the via holes 10x, and is electrically connected to the metal layer 310.

[0054] A recess 10y is formed within the via hole 10x by the portion of the metal layer 320 formed on the side wall of the via hole 10x and on the upper surface of the metal layer 310 exposed within the via hole 10x. However, the metal layer 310 may fill the via hole 10x (it does not need to form the recess 10y).

[0055] The material and thickness of the metal layer 320 can be the same as, for example, the metal layer 310. The metal layer 320 can be formed by, for example, the same method as the metal layer 310. For the same reasons as the metal layer 310, it is preferable to vacuum-deposit a functional layer with a thickness of about 1 nm to 100 nm on the upper surface 10a of the substrate 10 as a base layer, for example by conventional sputtering, before depositing the metal layer 320.

[0056] Next, in the process shown in Figure 4(d), the functional layer and metal layer 310 formed on the lower surface 10b of the substrate 10, and the functional layer and metal layer 320 formed on the upper surface 10a of the substrate 10 are patterned by photolithography. As a result, the resistor portion 31 and pad 31A with the shape shown in Figure 2 are formed on the lower surface 10b of the substrate 10, and the resistor portion 32 and terminal portions 41 and 42 with the shape shown in Figure 1 are formed on the upper surface 10a of the substrate 10. By simultaneously patterning the metal layer 310 and the metal layer 320 by photolithography, the relative positional accuracy of the resistor portion 31 and the resistor portion 32 can be improved.

[0057] After the process shown in Figure 4(d), a cover layer 61 is formed on the upper surface 10a of the base material 10, covering the resistor 32 and exposing the terminals 41 and 42. Additionally, a cover layer 62 is formed on the lower surface 10b of the base material 10, covering the resistor 31 and the pad 31A. The materials and thicknesses of the cover layers 61 and 62 are as described above.

[0058] The cover layer 61 can be manufactured, for example, by laminating a semi-cured thermosetting insulating resin film onto the upper surface 10a of the base material 10 so as to cover the resistance portion 32 and expose the terminal portions 41 and 42, and then heating and curing it. Alternatively, the cover layer 61 may be manufactured by applying a liquid or paste-like thermosetting insulating resin to the upper surface 10a of the base material 10 so as to cover the resistance portion 32 and expose the terminal portions 41 and 42, and then heating and curing it. The cover layer 62 can be manufactured in the same manner as the cover layer 61. Through the above steps, the strain gauge 1 is completed.

[0059] Thus, in strain gauge 1, a resistance portion 31 is formed on the lower surface 10b of the base material 10, and a resistance portion 32 is formed on the upper surface 10a of the base material 10, with the grid directions of the resistance portion 31 and the resistance portion 32 intersecting. Furthermore, the resistance portion 31 and the resistance portion 32 can be formed by simultaneously patterning metal layers formed on both sides of the base material 10 using photolithography. As a result, it is possible to improve the relative positional accuracy of the resistance portion 31 and the resistance portion 32, and a strain gauge can be realized in which the grid directions of the resistance portion 31 and the resistance portion 32 intersect with a desired value with high accuracy. Consequently, it is possible to measure strain with an unknown principal strain direction without considering bonding accuracy.

[0060] Furthermore, the strain gauge 1 has a laminated structure in which the top and bottom of the base material 10 are approximately symmetrical. That is, the resistance portion 31 and the cover layer 62 are laminated on the lower surface 10b side of the base material 10, and the resistance portion 32 and the cover layer 61 are laminated on the upper surface 10a side of the base material 10. This structure makes it possible to reduce the warping that occurs in the strain gauge 1.

[0061] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. [Explanation of symbols]

[0062] 1 Strain gauge, 10 Base material, 10a Top surface, 10b Bottom surface, 10x Via hole, 10y Recess, 30 Resistor, 31, 32 Resistor section, 41, 42 Terminal section, 61, 62 Cover layer

Claims

1. A flexible resin base material, It has a resistor, The resistor comprises a first functional layer formed directly on one surface of the substrate from a metal, alloy, or metal compound, and Cr, CrN, and Cr ２ A first resistive layer mainly composed of α-Cr, formed from a film containing N, a second functional layer formed directly on the other surface of the substrate from a metal, alloy, or metal compound, and Cr, CrN, and Cr ２ It includes a second resistive portion mainly composed of α-Cr, formed from a film containing N, The first functional layer and the second functional layer have the function of promoting the crystal growth of α-Cr and forming a film mainly composed of α-Cr. The thickness of the first resistor and the second resistor is 0.05 μm or more and 2 μm or less. The thickness of the first functional layer and the second functional layer is 1 nm or more and 100 nm or less. The strain gauge is arranged such that the first resistance section and the second resistance section intersect in a plan view of the grid.

2. It has a first electrode electrically connected to the first resistor and a second electrode electrically connected to the second resistor, The strain gauge according to claim 1, wherein the first electrode and the second electrode are formed on one side of the substrate.

3. The second electrode is electrically connected to a pad extending from the end of the second resistive portion via a via hole provided in the substrate. The strain gauge according to claim 2, wherein the second electrode is formed continuously from one side of the substrate to the side wall of the via hole and the surface of the pad exposed within the via hole, and a recess is formed within the via hole.

4. A first insulating resin layer covering the first resistive portion is formed on one side of the substrate. The strain gauge according to any one of claims 1 to 3, wherein a second insulating resin layer covering the second resistive portion is formed on the other side of the base material.

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