Strain gauge

Abstract

In a strain gauge having a resistor formed on a flexible substrate, an electrode structure is realized that ensures reliable bonding with the workpiece even when miniaturized. [Solution] The device comprises a flexible resin substrate 10, a functional layer formed directly from a metal, alloy, or metal compound on one surface of the substrate, a resistor 30 mainly composed of α-Cr formed directly from a film containing Cr, CrN, and Cr2N on one surface of the functional layer, and a pair of electrodes 41 electrically connected to the resistor. The thickness of the resistor is 0.05 μm or more and 2 μm or less. Each electrode includes a plurality of first patterns arranged side by side at predetermined intervals and electrically connected to each other. Between opposing electrodes, a plurality of second patterns are arranged with the longitudinal direction in the same direction as the plurality of first patterns. The spacing between adjacent first patterns, the spacing between adjacent second patterns, and the spacing between adjacent first patterns and second patterns are the same.

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. Also, for example, both ends of the resistor are used as electrodes, and an external connection lead wire or the like is joined to the electrodes by solder, enabling signal input / output with an electronic component (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] However, when the strain gauge is miniaturized, the size of the electrode also becomes smaller accordingly, making it difficult to connect to a lead wire or the like using solder. Therefore, in recent years, a method of joining a miniaturized electrode to a flexible substrate or the like using a joining material other than solder (for example, an anisotropic conductive film) has been attempted, and it is required to ensure the joining reliability between the miniaturized electrode and the object to be joined.

[0005] The present invention has been made in view of the above points, and an object of the present invention is to realize an electrode structure that can ensure the joining reliability with an object to be joined even when miniaturized in a strain gauge having a resistor formed on a flexible substrate.

Means for Solving the Problems

[0006] This strain gauge comprises a flexible resin substrate, a functional layer formed directly on one surface of the substrate from a metal, alloy, or metal compound, a resistor mainly composed of α-Cr formed directly on one surface of the functional layer from a film containing Cr, CrN, and Cr2N, and a pair of electrodes electrically connected to the resistor. The functional layer has the function of promoting the crystal growth of α-Cr and forming a film mainly composed of α-Cr. The thickness of the resistor is 0.05 μm to 2 μm, and the thickness of the functional layer is 1 nm to 100 nm. Each electrode includes a plurality of first patterns arranged side by side at predetermined intervals and electrically connected to each other. Between opposing electrodes, a plurality of second patterns are arranged with the longitudinal direction in the same direction as the plurality of first patterns. The spacing between adjacent first patterns, the spacing between adjacent second patterns, and the spacing between adjacent first patterns and second patterns are the same. [Effects of the Invention]

[0007] According to the disclosed technology, in a strain gauge having a resistor formed on a flexible substrate, it is possible to realize an electrode structure that ensures reliable bonding with the workpiece even when miniaturized. [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 cross-sectional view illustrating a strain gauge according to the first embodiment. [Figure 3] This is a plan view illustrating a strain gauge according to a modified example 1 of the first embodiment. [Figure 4] This is a plan view illustrating a strain gauge according to a modified example 2 of the first embodiment. [Figure 5] This is a plan view illustrating a strain gauge according to a second 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 cross-sectional view illustrating a strain gauge according to the first embodiment, showing a cross-section along line AA in Figure 1. Referring to Figures 1 and 2, the strain gauge 1 includes a base material 10, a resistor 30, a terminal portion 41, and a dummy pattern 45.

[0011] In this embodiment, for convenience, the side of the base material 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. Furthermore, the surface on which the resistor 30 is provided at each part is referred to as one surface or the upper surface, and the surface on which the resistor 30 is not 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, "plan view" refers to viewing the object from the direction normal to the upper surface 10a of the base material 10, and "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 base material 10 is a member that serves as a base layer for forming the resistor 30, etc., and is flexible. The thickness of the base material 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 thickness of 5 μm to 200 μm of the base material 10 is preferable in terms of the transmission of strain from the surface of the strain-generating body joined to the lower surface of the base material 10 via an adhesive layer, etc., and dimensional stability against the environment, and a thickness of 10 μm or more is even preferable in terms of insulation.

[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 a thin film formed on the substrate 10 in a predetermined pattern, and is a sensitive part that undergoes a change in resistance when strained. The resistor 30 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. For convenience, in Figure 1, the resistor 30 is shown with a textured surface.

[0016] The resistor 30 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. An example of a material containing Cr is a Cr multiphase 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, a Cr multiphase film is a film in which Cr, CrN, Cr2N, etc., are mixed. The Cr multiphase film may contain unavoidable impurities such as chromium oxide.

[0018] The thickness of the resistor 30 is not particularly limited and can be appropriately selected according to the purpose. For example, it can be 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 crystal 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.

[0019] For example, when the resistor 30 is a Cr mixed-phase film, the stability of the gauge characteristics can be improved by using α-Cr (alpha chromium), which is a stable crystal phase, as the main component. Also, when the resistor 30 has α-Cr as the main component, 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 within the range of -1000 ppm / °C to +1000 ppm / °C. Here, the main component means that the target substance occupies 50 mass% or more of all the substances constituting the resistor. From the viewpoint of improving the gauge characteristics, the resistor 30 preferably contains 80 wt% or more of α-Cr. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0020] The terminal portions 41 are electrically connected to both ends of the resistor 30. The terminal portions 41 are a pair of electrodes for outputting the change in the resistance value of the resistor 30 caused by strain to the outside. For example, a flexible substrate for external connection or the like is joined via an anisotropic conductive film (ACF). The resistor 30 is, for example, connected to the other terminal portion 41 while extending in a zigzag manner from one of the terminal portions 41.

[0021] Each terminal portion 41 includes a plurality of patterns 41a arranged in the Y direction at a predetermined interval with the X direction as the longitudinal direction, and a pattern 41b with the Y direction as the longitudinal direction. Each pattern 41a is electrically connected to each other via the pattern 41b.

[0022] One end of each pattern 41a is connected to one longitudinal side of pattern 41b, and the other end of each pattern 41a is open. The width of pattern 41a is arbitrary, but can be made narrower than the width of the resistor 30, for example.

[0023] One end of pattern 41b is connected to the end of resistor 30. However, it is not necessary for one end of pattern 41b to be connected to the end of resistor 30; it is sufficient for it to be connected to the end of resistor 30 at any point on pattern 41b. For example, the other end of pattern 41b may be connected to the end of resistor 30, or it may be connected to the end of resistor 30 at any point between the two ends of pattern 41b. The width of pattern 41b is arbitrary, but for example, it can be formed to be narrower than the width of resistor 30.

[0024] Between opposing terminal portions 41 arranged in the Y direction, multiple electrically floating dummy patterns 45 are arranged side by side in the Y direction at predetermined intervals, with the X direction as the longitudinal direction.

[0025] More specifically, a plurality of dummy patterns 45 are arranged between the plurality of patterns 41a constituting one terminal section 41 and the plurality of patterns 41a constituting the other terminal section 41, with their longitudinal directions aligned in the same direction as the patterns 41a. The longitudinal directions of the patterns 41a and dummy patterns 45 can be, for example, parallel to the grid direction of the resistor 30, but are not limited to this. The width of the dummy patterns 45 is the same as the width of the patterns 41a.

[0026] Multiple dummy patterns 45 are arranged at regular intervals in the Y direction together with multiple patterns 41a constituting one terminal section 41 and multiple patterns 41a constituting the other terminal section 41. That is, the spacing between adjacent patterns 41a, the spacing between adjacent dummy patterns 45, and the spacing between adjacent patterns 41a and dummy patterns 45 are equal. Also, the width of the patterns 41a and the spacing between the patterns 41a may be different. It is desirable to set the spacing between the patterns 41a to 0.5 to 1.5 times the width of the patterns 41a in order to achieve uniform heat and pressure distribution. It is desirable to set the spacing between the patterns 41a to 1 time the width of the patterns 41a in order to achieve even more uniform heat and pressure distribution.

[0027] Although the resistor 30, terminal portion 41, and dummy pattern 45 are given different reference numerals for convenience, they can all be formed integrally from the same material in the same process.

[0028] 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 and the dummy pattern 45. Providing the cover layer 60 prevents mechanical damage to the resistor 30. In addition, providing the cover layer 60 protects the resistor 30 from moisture and other elements. The cover layer 60 may be provided so as to cover the entire portion excluding the terminal portion 41 and the dummy pattern 45.

[0029] 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, or composite resin (e.g., silicone resin, polyolefin resin). The cover layer 60 may contain fillers or pigments. There are no particular restrictions on the thickness of the cover layer 60, and it can be appropriately selected depending on the purpose, but for example, it can be about 2 μm to 30 μm.

[0030] To manufacture the strain gauge 1, first, a base material 10 is prepared, and a resistor 30, terminal portion 41, and dummy pattern 45 in the planar shape shown in Figure 1 are formed on the upper surface 10a of the base material 10. The material and thickness of the resistor 30, terminal portion 41, and dummy pattern 45 are as described above. The resistor 30, terminal portion 41, and dummy pattern 45 can be formed integrally from the same material.

[0031] The resistor 30, terminal portion 41, and dummy pattern 45 can be formed, for example, by depositing a film using a magnetron sputtering method targeting a raw material capable of forming the resistor 30, terminal portion 41, and dummy pattern 45, and then patterning it by photolithography. The resistor 30, terminal portion 41, and dummy pattern 45 may also be deposited using reactive sputtering, evaporation, arc ion plating, pulsed laser deposition, or the like, instead of magnetron sputtering.

[0032] 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 upper surface 10a of the substrate 10 as an underlayer, for example by conventional sputtering, before depositing the resistor 30, terminal portion 41, and dummy pattern 45. The functional layer is then patterned with the resistor 30, terminal portion 41, and dummy pattern 45 together with the resistor 30, terminal portion 41, and dummy pattern 45 into the planar shape shown in Figure 1 by photolithography after the resistor 30, terminal portion 41, and dummy pattern 45 have been formed on the entire upper surface of the functional layer.

[0033] In this application, the functional layer refers to a layer that has the function of promoting crystal growth of the resistor 30, which is at least the upper layer. Preferably, the functional layer also has the function of preventing oxidation of the resistor 30 by oxygen and moisture contained in the substrate 10, and the function of improving the adhesion between the substrate 10 and the resistor 30. The functional layer may also have other functions.

[0034] Since the insulating resin film that makes up the base material 10 contains oxygen and moisture, and especially when the resistor 30 contains Cr, the Cr forms an oxidized film, it is effective for the functional layer to have a function that prevents oxidation of the resistor 30.

[0035] The material of the functional layer is not particularly limited as long as it is a material that has the function of promoting crystal growth of the upper layer resistor 30, and can be appropriately selected according to the purpose, but 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), Examples include one or more metals selected from the group consisting of 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 these metals, or a compound of any of these metals.

[0036] 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.

[0037] 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 upper surface 10a of the substrate 10 with Ar, thus minimizing the amount of functional layer deposited and achieving improved adhesion.

[0038] 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 upper surface 10a 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.

[0039] There are no particular restrictions on the combination of materials for the functional layer, the resistor 30, the terminal portion 41, and the dummy pattern 45, 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 resistor 30, the terminal portion 41, and the dummy pattern 45.

[0040] In this case, for example, the resistor 30, terminal portion 41, and dummy pattern 45 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 resistor 30, terminal portion 41, and dummy pattern 45 may be deposited by reactive sputtering with pure Cr as the target, using a suitable amount of nitrogen gas introduced into the chamber along with Ar gas.

[0041] 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).

[0042] Furthermore, when the resistor 30 is a Cr multiphase film, the functional layer made of Ti has all of the following functions: promoting crystal growth of the resistor 30, preventing oxidation of the resistor 30 by oxygen and moisture contained in the substrate 10, and improving the adhesion between the substrate 10 and the resistor 30. The same applies when Ta, Si, Al, or Fe are used instead of Ti as the functional layer.

[0043] In this way, by providing a functional layer beneath the resistor 30, it becomes possible to promote crystal growth in the resistor 30, and a resistor 30 consisting of a stable crystalline phase can be fabricated. As a result, the stability of the gauge characteristics in the strain gauge 1 can be improved. Furthermore, the diffusion of the material constituting the functional layer into the resistor 30 can improve the gauge characteristics in the strain gauge 1.

[0044] After forming the resistor 30, terminal portion 41, and dummy pattern 45, the strain gauge 1 is completed by providing a cover layer 60 on the upper surface 10a of the base material 10, if necessary, which covers the resistor 30 and exposes the terminal portion 41 and dummy pattern 45. The cover layer 60 can be made, 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 resistor 30 and expose the terminal portion 41 and dummy pattern 45, and then heating and curing it. Alternatively, the cover layer 60 may be made 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 resistor 30 and expose the terminal portion 41 and dummy pattern 45, and then heating and curing it.

[0045] Thus, in the strain gauge 1, a plurality of dummy patterns 45 are arranged between a pair of terminal portions 41 that serve as electrodes. The plurality of dummy patterns 45 are arranged at regular intervals in a predetermined direction, with their longitudinal directions aligned, together with the plurality of patterns 41a that constitute one terminal portion 41 and the plurality of patterns 41a that constitute the other terminal portion 41. Furthermore, the width of the dummy patterns 45 is the same as the width of the patterns 41a.

[0046] This allows for the uniform application of heat and pressure to the anisotropic conductive film when a flexible substrate or the like is placed on a pair of terminal portions 41 and a dummy pattern 45 via an anisotropic conductive film, and when the pair of terminal portions 41 is joined to the flexible substrate or the like via the anisotropic conductive film. As a result, the reliability of the joint when joining the pair of terminal portions 41 to the flexible substrate or the like via the anisotropic conductive film can be improved.

[0047] Furthermore, leaving at least one end of each pattern 41a open is preferable because it provides a way for excess anisotropic conductive film to escape when pressure is applied to the anisotropic conductive film.

[0048] Furthermore, when the width of pattern 41a and the width of dummy pattern 45 are the same, and the spacing between adjacent patterns 41a, adjacent dummy patterns 45, and adjacent patterns 41a and dummy patterns 45 are the same, it is possible to apply heat and pressure most uniformly to the anisotropic conductive film. Therefore, this configuration is the best, but a certain effect can be obtained even if all of these requirements are not met.

[0049] In other words, each terminal portion 41 includes a plurality of patterns 41a arranged side by side at predetermined intervals and electrically connected to each other, and a plurality of dummy patterns 45 are arranged between opposing terminal portions 41 with their longitudinal directions in the same direction as the patterns 41a. This provides a certain effect of improving the bonding reliability when bonding a pair of terminal portions 41 to a flexible substrate or the like via an anisotropic conductive film. The same applies to subsequent embodiments.

[0050] <Modification 1 of the first embodiment> Modification 1 of the first embodiment shows an example of a strain gauge with a different electrode pattern from that of the first embodiment. In Modification 1 of the first embodiment, descriptions of components that are the same as those described in the previously described embodiment may be omitted.

[0051] Figure 3 is a plan view illustrating a strain gauge according to modification 1 of the first embodiment. Referring to Figure 3, strain gauge 1A differs from strain gauge 1 (see Figures 1, 2, etc.) in that the terminal portion 41 and dummy pattern 45 are replaced by terminal portion 42 and dummy pattern 46.

[0052] The terminal portion 42 is electrically connected to both ends of the resistor 30. The terminal portion 42 is a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 30 caused by strain, and for example, a flexible substrate for external connection is bonded to it via an anisotropic conductive film. The resistor 30 extends from one terminal portion 42 in a zigzag pattern and is connected to the other terminal portion 42.

[0053] Each terminal section 42 is composed of a plurality of patterns 42a arranged side by side in the Y direction at predetermined intervals with the X direction as the longitudinal direction, and a pattern 42b with the Y direction as the longitudinal direction. Each pattern 42a is electrically connected to each other via the pattern 42b.

[0054] The approximate center of each pattern 42a is connected to pattern 42b. One end of the outermost pattern 42a is connected to the end of the resistor 30, while one end of each other pattern 42a is open. The other ends of all patterns 42a are also open. The width of pattern 42a is narrower than the width of the resistor 30. The width of pattern 42b is arbitrary, but may be narrower than the width of the resistor 30.

[0055] However, it is not necessary for one end of the outermost pattern 42a to be connected to the end of the resistor 30; it is sufficient for one end of any pattern 42a to be connected to the end of the resistor 30. For example, one end of the innermost pattern 42a (on the dummy pattern 46 side) may be connected to the end of the resistor 30, or one end of any pattern 42a located between the outermost and innermost may be connected to the end of the resistor 30.

[0056] Note that the pattern 42b of terminal section 42 is the same as the pattern 41b of terminal section 41, but its position has been moved from the innermost part in the X direction (towards the resistor 30) to the center. Its function of electrically connecting multiple patterns arranged side by side in the Y direction is the same. The pattern 42b of terminal section 42 may be provided at any position between the innermost part in the X direction (towards the resistor 30) and the outermost part (opposite side from the resistor 30). Alternatively, the pattern 42b of terminal section 42 may be provided at the outermost part in the X direction (opposite side from the resistor 30).

[0057] Between opposing terminal portions 42 arranged in the Y direction, a plurality of electrically floating dummy patterns 46 are arranged side by side in the Y direction at predetermined intervals, with the X direction as the longitudinal direction.

[0058] More specifically, a plurality of dummy patterns 46 are arranged between the plurality of patterns 42a constituting one terminal section 42 and the plurality of patterns 42a constituting the other terminal section 42, with their longitudinal directions aligned in the same direction as the patterns 42a. The longitudinal directions of the patterns 42a and the dummy patterns 46 can be, for example, parallel to the grid direction of the resistor 30, but are not limited to this. The width of the dummy patterns 46 is the same as the width of the patterns 42a.

[0059] Multiple dummy patterns 46 are arranged at regular intervals in the Y direction together with multiple patterns 42a that constitute one terminal section 42 and multiple patterns 42a that constitute the other terminal section 42. That is, the spacing between adjacent patterns 42a is equal to the spacing between adjacent dummy patterns 46, and the spacing between adjacent patterns 42a and dummy patterns 46 is equal to the spacing between adjacent patterns 42a and dummy patterns 46.

[0060] Although the resistor 30, terminal portion 42, and dummy pattern 46 are given different reference numerals for convenience, they can be formed integrally from the same material in the same process.

[0061] Thus, in the strain gauge 1A, a plurality of dummy patterns 46 are arranged between a pair of terminal portions 42 that serve as electrodes. The plurality of dummy patterns 46 are arranged at regular intervals in a predetermined direction, with their longitudinal directions aligned, together with the plurality of patterns 42a that constitute one terminal portion 42 and the plurality of patterns 42a that constitute the other terminal portion 42. Furthermore, the width of the dummy patterns 46 is the same as the width of the patterns 42a.

[0062] This makes it possible to improve the bonding reliability when bonding a pair of terminal portions 42 and a flexible substrate or the like via an anisotropic conductive film, similar to the first embodiment.

[0063] <Modification 2 of the first embodiment> Modification 2 of the first embodiment shows another example of a strain gauge with a different electrode pattern from that of the first embodiment. In Modification 2 of the first embodiment, descriptions of components that are the same as those described in the previously described embodiment may be omitted.

[0064] Figure 4 is a plan view illustrating a strain gauge according to a modification 2 of the first embodiment. Referring to Figure 4, strain gauge 1B differs from strain gauge 1 (see Figures 1, 2, etc.) in that the terminal portion 41 and dummy pattern 45 are replaced by terminal portion 43 and dummy pattern 47.

[0065] The terminal portion 43 is electrically connected to both ends of the resistor 30. The terminal portion 43 is a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 30 caused by strain, and for example, a flexible substrate for external connection is bonded to it via an anisotropic conductive film. The resistor 30 extends from one terminal portion 43 in a zigzag pattern and is connected to the other terminal portion 43.

[0066] Each terminal section 43 is composed of a plurality of patterns 43a arranged side by side in the X direction at predetermined intervals with the Y direction as its longitudinal direction, and a pattern 43b with the X direction as its longitudinal direction. Each pattern 43a is electrically connected to one another via the pattern 43b.

[0067] One end of each pattern 43a is connected to one longitudinal side of pattern 43b, and the other end of each pattern 43a is open. The width of pattern 43a is narrower than the width of resistor 30.

[0068] One end of pattern 43b is connected to the end of the resistor 30. However, it is not necessary for one end of pattern 43b to be connected to the end of the resistor 30; it may be connected to the end of the resistor 30 at any position on the innermost (resistor 30 side) pattern 43a. The width of pattern 43b is arbitrary, but it can be formed to be narrower than the width of the resistor 30, for example.

[0069] Between opposing terminal portions 43 arranged in the Y direction, multiple electrically floating dummy patterns 47 are arranged side by side in the X direction at predetermined intervals, with the Y direction as the longitudinal direction.

[0070] More specifically, a plurality of dummy patterns 47 are arranged between the opposing ends of the plurality of patterns 43a constituting one terminal portion 43 and the plurality of patterns 43a constituting the other terminal portion 43, with their longitudinal directions aligned in the same direction as the patterns 43a. The longitudinal directions of the patterns 43a and dummy patterns 47 can be, for example, perpendicular to the grid direction of the resistor 30, but are not limited to this. The width of the dummy patterns 47 is the same as the width of the patterns 43a.

[0071] Multiple sets of one pattern 43a and one dummy pattern 47 constituting one terminal section 43, and one pattern 43a constituting the other terminal section 43, arranged in a line in the Y direction so as not to touch each other, are arranged in rows at predetermined intervals in the X direction. In other words, the spacing between adjacent sets is equal.

[0072] Although the resistor 30, terminal portion 43, and dummy pattern 47 are given different reference numerals for convenience, they can be formed integrally from the same material in the same process.

[0073] Thus, in the strain gauge 1B, multiple dummy patterns 47 are arranged between a pair of terminal portions 43 that serve as electrodes. The multiple dummy patterns 47 are arranged at regular intervals in a predetermined direction, with their longitudinal directions aligned, together with the multiple patterns 43a that make up one terminal portion 43 and the multiple patterns 43a that make up the other terminal portion 43. The width of the dummy patterns 47 is the same as the width of the patterns 43a.

[0074] This improves the bonding reliability when joining a pair of terminal portions 43 and a flexible substrate or the like via an anisotropic conductive film, similar to the first embodiment.

[0075] <Second Embodiment> The second embodiment shows another example of a strain gauge with a different electrode pattern from that of the first embodiment. In the second embodiment, descriptions of components that are the same as those described in the previously described embodiments may be omitted.

[0076] Figure 5 is a plan view illustrating a strain gauge according to the second embodiment. Referring to Figure 5, strain gauge 2 differs from strain gauge 1 (see Figures 1 and 2, etc.) in that terminal portion 41 is replaced by terminal portion 44. Note that strain gauge 2 does not have a dummy pattern.

[0077] The terminal portion 44 is electrically connected to both ends of the resistor 30. The terminal portion 44 is a pair of electrodes for outputting the change in the resistance value of the resistor 30 caused by strain to the outside, and for example, a flexible substrate for external connection is bonded to it via an anisotropic conductive film.

[0078] Each terminal section 44 is composed of a plurality of patterns 44a arranged side by side in the Y direction at predetermined intervals with the X direction as the longitudinal direction, and a pattern 44b with the Y direction as the longitudinal direction. Each pattern 44a is electrically connected to each other via the pattern 44b.

[0079] One end of each pattern 44a is connected to one side of the longitudinal direction of pattern 44b, and the other end of each pattern 44a is open. The width of pattern 44a is formed to be the same as the width of resistor 30.

[0080] One end of pattern 44b is connected to the end of resistor 30. The width of pattern 44b is arbitrary, but for example, it can be formed to be the same as the width of resistor 30.

[0081] Between opposing terminal portions 44 arranged in the Y direction, resistors 30 are arranged with the X direction as the grid direction and patterned in a zigzag pattern at predetermined intervals.

[0082] More specifically, a resistor 30 is positioned between the multiple patterns 44a constituting one terminal section 44 and the multiple patterns 44a constituting the other terminal section 44, with the grid direction oriented in the same direction as the longitudinal direction of the patterns 44a.

[0083] The resistor 30 is arranged in the Y direction at regular intervals, with multiple patterns 44a constituting one terminal portion 44 and multiple patterns 44a constituting the other terminal portion 44, all oriented in the same longitudinal direction. That is, the spacing between adjacent patterns 44a is equal to the spacing between adjacent patterns constituting the resistor 30, and the spacing between adjacent patterns 44a and patterns constituting the resistor 30 is equal to the spacing between adjacent patterns 44a and patterns constituting the resistor 30.

[0084] Although the resistor 30 and the terminal portion 44 are given different reference numerals for convenience, they can be formed integrally from the same material in the same process.

[0085] Thus, in the strain gauge 2, a zigzag patterned resistor 30 is arranged between a pair of terminal portions 44 that serve as electrodes. The zigzag patterned resistor 30, together with the multiple patterns 44a constituting one terminal portion 44 and the multiple patterns 44a constituting the other terminal portion 44, are arranged at regular intervals in a predetermined direction with their longitudinal directions aligned. Furthermore, the width of the resistor 30 is the same as the width of the patterns 44a.

[0086] This improves the bonding reliability when bonding a pair of terminal portions 44 to a flexible substrate or the like via an anisotropic conductive film, similar to the first embodiment.

[0087] Furthermore, in strain gauge 2, since the density of the resistor 30 and the terminal portion 44 is substantially uniform, it is easier to form the resistor 30 and the terminal portion 44 by etching compared to strain gauges 1, 1A, and 1B, where the density of the resistor and the terminal portion is not uniform.

[0088] 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.

[0089] For example, the above embodiments and modifications described improved bonding reliability when joining a pair of terminals to a flexible substrate via an anisotropic conductive film, but the electrode structure according to the present invention also produces similar effects when using anisotropic conductive paste (ACP). [Explanation of symbols]

[0090] 1, 1A, 1B, 2 Strain gauges, 10 Substrate, 10a Top surface, 30 Resistor, 41, 42, 43, 44 Terminal section, 41a, 41b, 42a, 42b, 43a, 43b, 44a, 44b Pattern, 60 Cover layer

Claims

1. A flexible resin base material, A functional layer formed directly from a metal, alloy, or metal compound is provided on one side of the aforementioned substrate. On one side of the functional layer, Cr, CrN, and Cr ２ A resistor mainly composed of α-Cr, formed from a film containing N, The resistor comprises a pair of electrodes electrically connected to it, The functional layer has the function of promoting the crystal growth of α-Cr and forming a film mainly composed of α-Cr. The thickness of the resistor 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. Each of the electrodes includes a plurality of first patterns that are arranged side by side at predetermined intervals and electrically connected to one another. Between the opposing electrodes, a plurality of first patterns and a plurality of second patterns oriented in the same longitudinal direction are arranged. A strain gauge in which the spacing between adjacent first patterns, the spacing between adjacent second patterns, and the spacing between adjacent first and second patterns are the same.

2. The strain gauge according to claim 1, wherein the width of the first pattern and the width of the second pattern are the same.

3. The strain gauge according to claim 2, wherein the spacing between the first patterns is 0.5 to 1.5 times the width of the first pattern.

4. The strain gauge according to any one of claims 1 to 3, wherein the plurality of the second patterns are electrically floating dummy patterns.

5. The strain gauge according to any one of claims 1 to 3, wherein the plurality of the second patterns are zigzag patterns constituting the resistor.

6. The strain gauge according to claim 4 or 5, wherein a plurality of second patterns are arranged between a plurality of first patterns constituting one electrode and a plurality of first patterns constituting the other electrode, with the second patterns facing each other and oriented in the same longitudinal direction as the first patterns.

7. The strain gauge according to any one of claims 4 to 6, wherein the longitudinal directions of the first pattern and the second pattern are parallel to the grid direction of the resistor.

8. A strain gauge according to any one of claims 2 to 4, wherein a plurality of second patterns are arranged between the opposing ends of a plurality of first patterns constituting one electrode and a plurality of first patterns constituting the other electrode, and the second patterns are oriented in the same longitudinal direction as the first patterns.

9. The strain gauge according to claim 8, wherein the longitudinal directions of the first pattern and the second pattern are perpendicular to the grid direction of the resistor.

Images