JP2023071473A - strain gauge - Google Patents

Abstract

To provide a strain gauge whose creep characteristics have been improved.SOLUTION: A strain gage includes: a substrate, a resistor formed of a film containing Cr, CrN, and Cr2 N on the substrate: and an insulating resin layer formed on the substrate and covering the resistor. A groove which is open to the upper surface side and not open to the lateral side is provided in the insulating resin layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to strain gauges.

A strain gauge is known that has a resistor on a base material, is attached to an object to be measured, and detects the characteristics of the object to be measured. BACKGROUND ART Strain gauges are used, for example, as sensors that detect strain in materials and sensors that detect ambient temperature (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2001-221696

In addition to being used for sensors, strain gauges are sometimes used for scales. Whether the strain gauge is used as a sensor or as a scale, the creep property is important. When the strain gauge is used as a scale, it must satisfy particularly stringent creep property standards.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a strain gauge with improved creep characteristics.

The present strain gauge comprises a substrate, a resistor formed on the substrate from a film containing Cr, CrN, and _Cr2N , and an insulating resin layer formed on the substrate and covering the resistor. , and the insulating resin layer is provided with a groove that opens on the upper surface side and does not open on the side surface side.

According to the disclosed technique, a strain gauge with improved creep characteristics can be provided.

1 is a plan view illustrating a strain gauge according to a first embodiment; FIG. 1 is a cross-sectional view (part 1) illustrating a strain gauge according to a first embodiment; FIG. It is a figure explaining the measuring method of the amount of creeps, and the amount of creep recovery. It is a figure which shows the study result of the amount of creeps, and the amount of creep recovery. FIG. 2 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment; FIG. 4 is a plan view illustrating a strain gauge according to Modification 1 of the first embodiment; FIG. 4 is a cross-sectional view (part 1) illustrating a strain gauge according to Modification 1 of the first embodiment; FIG. 11 is a cross-sectional view (Part 2) illustrating a strain gauge according to Modification 2 of the first embodiment;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First embodiment>
1 is a plan view illustrating a strain gauge according to a first embodiment; FIG. 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 and 2, the strain gauge 1 has a substrate 10, a resistor 30, wirings 40, electrodes 50, and a cover layer 60. As shown in FIG.

In this embodiment, for the sake of convenience, in the strain gauge 1, the side of the substrate 10 on which the resistor 30 is provided is the upper side or one side, and the side on which the resistor 30 is not provided is the lower side or the other side. and Also, the surface on which the resistor 30 of each part is provided is defined as one surface or upper surface, and the surface on which the resistor 30 is not provided is defined as the other surface or lower surface. However, the strain gauge 1 can be used upside down or arranged at any angle. Further, the term "planar view" refers to viewing an object from the direction normal to the upper surface 10a of the substrate 10, and the term "planar shape" refers to the shape of the object viewed from the direction normal to the upper surface 10a of the substrate 10. and

The base material 10 is a member that serves as a base layer for forming the resistor 30 and the like, and has flexibility. The thickness of the base material 10 is not particularly limited, and can be appropriately selected according to the purpose. In particular, when the thickness of the base material 10 is 5 μm to 200 μm, the transmission of strain from the surface of the strain generating body bonded to the lower surface of the base material 10 via an adhesive layer or the like, and the dimensional stability against the environment. The thickness is preferably 10 μm or more, and more preferable from the viewpoint of insulation.

The substrate 10 is made of, for example, PI (polyimide) resin, epoxy resin, PEEK (polyetheretherketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, LCP (liquid crystal It can be formed from an insulating resin film such as polymer) resin, polyolefin resin, or the like. Note that the film refers to a flexible member having a thickness of about 500 μm or less.

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 substrate 10 may be formed from, for example, an insulating resin film containing a filler such as silica or alumina.

Materials other than the resin of the base material 10 include, for example, SiO ₂ , ZrO ₂ (including YSZ), Si, Si ₂ N ₃ , Al ₂ O ₃ (including sapphire), ZnO, perovskite ceramics (CaTiO ₃ , BaTiO ₃ ) and other crystalline materials, as well as amorphous glass and the like. Also, as the material of the base material 10, a metal such as aluminum, an aluminum alloy (duralumin), or titanium may be used. In this case, for example, an insulating film is formed on the base material 10 made of metal.

The resistor 30 is a thin film formed in a predetermined pattern on the substrate 10, and is a sensing part that undergoes a change in resistance when subjected to strain. The resistor 30 may be formed directly on the top surface 10a of the base material 10, or may be formed on the top surface 10a of the base material 10 via another layer.

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. Materials containing Cr include, for example, a Cr mixed phase film. Materials containing Ni include, for example, Cu—Ni (copper nickel). Materials containing both Cr and Ni include, for example, Ni—Cr (nickel chromium).

Here, the Cr mixed phase film is a film in which Cr, CrN, Cr ₂ N, or the like is mixed. The Cr mixed phase film may contain unavoidable impurities such as chromium oxide.

The thickness of the resistor 30 is not particularly limited, and can be appropriately selected according to the purpose. In particular, when the thickness of the resistor 30 is 0.1 μm or more, the crystallinity of the crystal (for example, the crystallinity of α-Cr) forming the resistor 30 is preferably improved. It is further preferable in that cracks in the film caused by internal stress of the film constituting the film 30 and warping from the base material 10 can be reduced.

For example, when the resistor 30 is a Cr mixed phase film, the stability of gauge characteristics can be improved by using α-Cr (alpha chromium), which is a stable crystal phase, as the main component. In addition, since the resistor 30 is mainly composed of α-Cr, the gauge factor of the strain gauge 1 is 10 or more, and the temperature coefficient of gauge factor TCS and the temperature coefficient of resistance TCR are within the range of -1000 ppm/°C to +1000 ppm/°C. can be Here, the term "main component" means that the target material accounts for 50% by weight or more of all the materials constituting the resistor. It preferably contains 90% by weight or more, more preferably 90% by weight or more. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

Moreover, when the resistor 30 is a Cr mixed phase film, the content of CrN and Cr ₂ N contained in the Cr mixed phase film is preferably 20% by weight or less. When CrN and Cr ₂ N contained in the Cr mixed phase film are 20% by weight or less, a decrease in gauge factor can be suppressed.

Also, the ratio of Cr ₂ N in CrN and Cr ₂ N is preferably 80% by weight or more and less than 90% by weight, more preferably 90% by weight or more and less than 95% by weight. When the ratio of Cr ₂ N in CrN and Cr ₂ N is 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more pronounced due to Cr ₂ N having semiconducting properties. . Furthermore, by reducing ceramicization, brittle fracture is reduced.

On the other hand, when a small amount of N ₂ or atomic N is mixed in the film and is present, they escape from the film due to the external environment (for example, high temperature environment), causing a change in film stress. By creating chemically stable CrN, a stable strain gauge can be obtained without generating unstable N.

The electrode 50 is electrically connected to both ends of the resistor 30 via the wiring 40, and is formed in a substantially rectangular shape wider than the resistor 30 and the wiring 40 in plan view. Note that the wiring 40 may be wider than the resistor 30 . The electrodes 50 are a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 30 caused by strain, and are connected to, for example, lead wires for external connection. The resistor 30 , for example, extends from one side of the electrode 50 through the wiring 40 while folding in a zigzag manner, and reaches the other side of the electrode 50 through the wiring 40 . A metal layer with low resistance such as copper may be laminated on the upper surface of the wiring 40 . A metal layer with low resistance such as copper or a metal layer with good solderability such as gold may be laminated on the upper surface of the electrode 50 . Although the resistor 30, the wiring 40, and the electrode 50 are denoted by different symbols for convenience, they can be integrally formed from the same material in the same process.

A cover layer 60 (insulating resin layer) is provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the wiring 40 and expose the electrodes 50 . The cover layer 60 can be made of insulating resin such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, composite resin (eg, silicone resin, polyolefin resin). The cover layer 60 may contain fillers or pigments. The thickness of the cover layer 60 is not particularly limited, and can be appropriately selected according to the purpose.

By providing the cover layer 60, it is possible to prevent the resistor 30 and the wiring 40 from being mechanically damaged. Also, by providing the cover layer 60, the resistor 30 and the wiring 40 can be protected from moisture and the like.

The cover layer 60 is provided with a plurality of grooves 60x that open on the upper surface side of the cover layer 60 . The groove 60x is provided so as to penetrate the cover layer 60 and expose the upper surface 10a of the base material 10 . The inner side surface of the groove 60x is formed by the cover layer 60, and the bottom surface of the groove 60x is formed by the upper surface 10a of the substrate 10. As shown in FIG. Note that the groove 60x does not open on the side surface of the cover layer 60 . The strength of the cover layer 60 can be maintained by not opening the grooves 60x on the side surfaces of the cover layer 60 .

The resistor 30 is composed of a plurality of elongated portions having substantially the same length, which are arranged at predetermined intervals with their longitudinal directions directed in the same direction (direction perpendicular to line AA in FIG. 1), and the ends of the adjacent elongated portions are aligned. It is a structure in which the parts are connected in order and folded back in a zigzag as a whole. The longitudinal direction of the plurality of elongated portions is the grid direction.

In the example of FIG. 1, in plan view, the grooves 60x are elongated portions arranged in all regions between the adjacent elongated portions of the cover layer 60 and on both outer sides of the resistor 30 in the direction orthogonal to the grid direction. It is arranged along the elongated portion in the region outside the portion. In addition, grooves 60x may be arranged as necessary in the outer regions of the elongated portions arranged on both outer sides of the resistor 30 in the direction perpendicular to the grid direction. The groove 60x preferably has a length that faces substantially the entire longitudinal direction of each elongated portion. The inner surfaces of groove 60x preferably do not reach the sides of resistor 30, but may do so if desired. The technical significance of the grooves 60x will be described later.

[Reduction of creep]
When using the strain gauge 1 for weighing applications, it is necessary to satisfy the standard for creep. Standards related to creep include, for example, accuracy grade C1 based on OIML R60 (hereinafter referred to as C1 standard) and accuracy grade C2 based on OIML R60 (hereinafter referred to as C2 standard).

The C1 standard requires that the creep amount and creep recovery amount be ±0.0735% or less. In addition, the C2 standard requires that the amount of creep and the amount of creep recovery be ±0.0368% or less. When the strain gauge 1 is used as a sensor, the standard for creep amount and creep recovery amount is about ±0.5%.

The creep properties of strain gauges are affected by the viscoelasticity of the constituent materials. In general, metal materials, which are elastic materials, do not creep, but creep occurs in resins, which are viscous materials. Since the strain gauge 1 is provided with the cover layer 60 made of resin, the viscosity of the cover layer 60 cannot be ignored.

As a result of intensive studies by the inventors, the creep value depends on the value of L/(L+S), where L is the line of the resistor 30 and S is the space. We have come to the conclusion that this is preferable. Here, the line L of the resistor 30 is the width of one elongated portion forming the resistor 30 in the direction orthogonal to the grid direction (the direction of line AA in FIG. 1). Also, the space S is the width of the cover layer 60 in the direction perpendicular to the grid direction (in the direction of line AA in FIG. 1) between adjacent strips.

The amount of creep and the amount of creep recovery are amounts in which the amount of elastic deformation (amount of strain) of the surface on which the resistor 30 is provided in the strain gauge 1 changes over time. can be measured by monitoring the strain voltage calculated by A detailed description will be given with reference to FIG.

FIG. 3 is a diagram illustrating a method of measuring the creep amount and the creep recovery amount. In FIG. 3, the horizontal axis is time, and the vertical axis is strain voltage [mV].

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 strain generating body for 10 seconds, and then the load is removed. When 20 minutes have passed after the unloading, a 100% load is applied to the strain gauge 1 attached to the strain generating body for 20 minutes, and then the load is unloaded. Then, wait for 20 minutes after unloading.

The strain voltage changes, for example, as shown in FIG. In FIG. 3, the absolute value B of the strain voltage difference is measured 20 minutes after the 150% load is removed and immediately after the 100% load is applied. In addition, the absolute value ΔA of the difference in strain voltage immediately after application of 100% load and 20 minutes after the start of application of 100% load is measured. At this time, ΔA/B is the amount of creep. Next, the absolute value ΔC of the difference in strain voltage 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.

The 100% load is 3 kg, and the 150% load is 1.5 times the 100% load.

FIG. 4 is a diagram showing the study results of the creep amount and the creep recovery amount. The creep amount and the creep recovery amount of a plurality of strain gauges 1 with different values of L/(L+S) were measured by the measurement method shown in FIG. This is a summary of the results. Specifically, the amount of creep and the amount of creep recovery were measured by attaching each strain gauge 1 onto a strain-generating body made of SUS304. As the substrate 10, a polyimide resin film having a thickness of 25 μm was used. A Cr mixed phase film was used for the resistor 30 . As the cover layer 60, a polyimide resin film having a thickness of 15 μm was used.

As shown in FIG. 4, as L/(L+S) increases, the amount of creep and the amount of creep recovery decrease. For example, if L/(L+S) is 96.5% or more, the C1 standard creep amount and creep recovery amount can be satisfied. Also, when L/(L+S) is 98.5% or more, the C2 standard creep amount and creep recovery amount can be satisfied. That is, by controlling L/(L+S) within a predetermined range, the amount of creep and the amount of creep recovery are improved, so the strain gauge 1 can be used for weighing applications. Also, L/(L+S) may be controlled to some extent, and other creep countermeasures may be used in combination to satisfy the standard regarding creep. Of course, the strain gauge 1 may also be used for sensor applications.

L/(L+S) can be increased by increasing the width of each elongated portion of the resistor 30 and narrowing the interval between adjacent elongated portions. As shown in FIG. 1, the space S can also be increased by providing a groove 60x in the cover layer 60 to reduce the space S. That is, by providing the grooves 60x along the elongated portions in the regions between the adjacent elongated portions of the cover layer 60, L/(L+S) is increased, so that the viscosity of the cover layer 60 can be reduced and the creep properties can be improved.

In addition, in the case of a highly sensitive strain gauge with a gauge factor of 10 or more (for example, when a Cr mixed phase film is used for the resistor 30), it is sensitive to the influence of material properties due to its high sensitivity, and the creep characteristics are also remarkable. may decrease. Therefore, in a highly sensitive strain gauge having a gauge factor of 10 or more, it is extremely important to control L/(L+S) within a predetermined range to improve creep characteristics.

[Manufacturing method of strain gauge]
In order to manufacture the strain gauge 1 , first, the base material 10 is prepared, and a metal layer (referred to as metal layer A for convenience) is formed on the upper surface 10 a of the base material 10 . The metal layer A is a layer that is finally patterned to become the resistor 30 , the wiring 40 and the electrode 50 . Therefore, the material and thickness of the metal layer A are the same as those of the resistor 30, the wiring 40, and the electrode 50 described above.

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

From the viewpoint of stabilizing the gauge characteristics, before forming the metal layer A, a functional layer having a predetermined thickness is vacuum-formed on the upper surface 10a of the substrate 10 as a base layer by conventional sputtering, for example. is preferred.

In the present application, the functional layer refers to a layer having a function of promoting crystal growth of at least the upper 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 also have other functions.

Since the insulating resin film that constitutes the base material 10 contains oxygen and moisture, especially when the metal layer A contains Cr, Cr forms a self-oxidizing film. Being prepared helps.

The material of the functional layer is not particularly limited as long as it has a function of promoting the crystal growth of at least the upper metal layer A (resistor 30), and can be appropriately selected according to the purpose. Chromium), Ti (titanium), V (vanadium), Nb (niobium), Ta (tantalum), Ni (nickel), Y (yttrium), Zr (zirconium), Hf (hafnium), Si (silicon), C ( carbon), Zn (zinc), Cu (copper), Bi (bismuth), Fe (iron), Mo (molybdenum), W (tungsten), Ru (ruthenium), Rh (rhodium), Re (rhenium), Os ( osmium), Ir (iridium), Pt (platinum), Pd (palladium), Ag (silver), Au (gold), Co (cobalt), Mn (manganese), Al (aluminum) 1 selected from the group consisting of Metal or metals, alloys of any of this group of metals, or compounds of any of this group of metals.

Examples of the above alloy include FeCr, TiAl, FeNi, NiCr, CrCu, and the like. Examples of _the above compounds include TiN, TaN _{, Si3N4} , _TiO2 , _Ta2O5 , _SiO2 and the like.

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. Within this range, it is possible to promote the crystal growth of α-Cr, and to prevent a part of the current flowing through the resistor from flowing through the functional layer, thereby preventing a decrease in strain detection sensitivity.

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. Within this range, it is possible to promote the crystal growth of α-Cr, and further prevent the deterioration of the strain detection sensitivity due to part of the current flowing through the resistor flowing through the functional layer.

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. Within such a range, it is possible to further prevent a decrease in strain detection sensitivity due to part of the current flowing through the resistor flowing through the functional layer.

When the functional layer is made of an insulating material such as oxide or nitride, the thickness of the functional layer is preferably 1 nm to 1 μm. Within such a range, the crystal growth of α-Cr can be promoted, and the film can be easily formed without causing cracks in the functional layer.

When the functional layer is made of an insulating material such as oxide or nitride, the thickness of the functional layer is more preferably 1 nm to 0.8 μm. Within such a range, the crystal growth of α-Cr can be promoted, and the functional layer can be formed more easily without cracks.

When the functional layer is made of an insulating material such as oxide or nitride, the thickness of the functional layer is more preferably 1 nm to 0.5 μm. Within such a range, the crystal growth of α-Cr can be promoted, and the functional layer can be formed more easily without cracks.

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. If the functional layer is made of an insulating material, it may not be patterned in the same planar shape as the resistor. In this case, the functional layer may be solidly formed at least in the region where the resistor is formed. Alternatively, the functional layer may be formed all over the top surface of the substrate 10 .

Further, when the functional layer is formed of an insulating material, the thickness and surface area of the functional layer can be increased by forming the functional layer relatively thickly, such that the thickness is 50 nm or more and 1 μm or less, and by forming the functional layer in a solid shape. Since the resistance increases, the heat generated by the resistor can be dissipated to the base material 10 side. As a result, in the strain gauge 1, deterioration in measurement accuracy due to self-heating of the resistor can be suppressed.

The functional layer can be formed, for example, by conventional sputtering using a raw material capable of forming the functional layer as a target and introducing Ar (argon) gas into the chamber in a vacuum. By using the conventional sputtering method, the functional layer is formed while etching the upper surface 10a of the base material 10 with Ar. Therefore, the amount of film formation of the functional layer can be minimized and an effect of improving adhesion can be obtained.

However, this is an example of the method of forming the functional layer, and the functional layer may be formed by another method. For example, before forming the functional layer, the upper surface 10a of the substrate 10 is activated by a plasma treatment using Ar or the like to obtain an effect of improving adhesion, and then the functional layer is vacuum-formed by magnetron sputtering. You may use the method to do.

The combination of the material of the functional layer and the material of the metal layer A is not particularly limited and can be appropriately selected according to the purpose. It is possible to form a Cr mixed phase film as a main component.

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 the chamber. Alternatively, the metal layer A may be formed by reactive sputtering using pure Cr as a target, introducing an appropriate amount of nitrogen gas into the chamber together with Ar gas. At this time, by changing the introduction amount and pressure (nitrogen partial pressure) of nitrogen gas and adjusting the heating temperature by providing a heating process, the ratio of CrN and _Cr N contained in the Cr mixed phase film, and CrN and Cr The proportion of _Cr2N in _2N can be adjusted.

In these methods, the growth surface of the Cr mixed phase film is defined 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. In addition, the diffusion of Ti constituting the functional layer into the Cr mixed phase film improves the gauge characteristics. For example, the gauge factor of the strain gauge 1 can be 10 or more, and the temperature coefficient of gauge factor TCS and the temperature coefficient of resistance 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 or TiN (titanium nitride).

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

In this way, by providing the functional layer under the metal layer A, the crystal growth of the metal layer A can be promoted, and the metal layer A having a stable crystal phase can be produced. As a result, in the strain gauge 1, the stability of gauge characteristics can be improved. Further, by diffusing the material forming the functional layer into the metal layer A, the gauge characteristics of the strain gauge 1 can be improved.

Next, the metal layer A is patterned by photolithography to form the planar resistor 30, the wiring 40, and the electrode 50 shown in FIG.

After that, the strain gauge 1 is completed by providing a cover layer 60 having grooves 60x covering the resistors 30 and the wirings 40 and exposing the electrodes 50 on the upper surface 10a of the base material 10 .

In order to form the cover layer 60 having the grooves 60x, for example, a semi-cured thermosetting insulating resin is applied to the upper surface 10a of the base material 10 so as to cover the resistors 30 and the wirings 40 and expose the electrodes 50. After laminating the film, the insulating resin film is heated and cured. Then, for example, the cover layer 60 is irradiated with a laser beam to form a groove 60x.

When a functional layer is provided on the upper surface 10a of the substrate 10 as a base layer for the resistor 30, the wiring 40, and the electrodes 50, the strain gauge 1 has a cross-sectional shape shown in FIG. A layer indicated by reference numeral 20 is a functional layer. The planar shape of the strain gauge 1 when the functional layer 20 is provided is, for example, the same as that shown in FIG. However, as described above, the functional layer 20 may be formed solidly on part or all of the upper surface of the base material 10 .

<Modification 1 of the first embodiment>
Modification 1 of the first embodiment shows an example in which the number and shape of grooves formed in the cover layer are different. In addition, in Modification 1 of the first embodiment, the description of the same components as those of the already described embodiment may be omitted.

FIG. 6 is a plan view illustrating a strain gauge according to Modification 1 of the first embodiment. FIG. 7 is a cross-sectional view illustrating a strain gauge according to Modification 1 of the first embodiment, showing a cross section along line BB of FIG. Referring to FIGS. 6 and 7, the strain gauge 1A differs from the strain gauge 1 (see FIG. 1, etc.) in that one groove 60x is formed in the cover layer 60. FIG. In plan view, the grooves 60x are arranged along the elongated portions in one region of the cover layer 60 between adjacent elongated portions. In plan view, the grooves 60x may be arranged in any one or more regions between the adjacent elongated portions of the cover layer 60 along the elongated portions.

As mentioned above, by increasing the value of L/(L+S), the strain gauge can be used for weighing applications. However, even if the strain gauge is not used for weighing purposes, it may be desirable to reduce the amount of creep and the amount of creep recovery to some extent. In such a case, one or more grooves 60 x may be formed in the cover layer 60 . The number of grooves 60x can be appropriately determined according to the desired values of creep amount and creep recovery amount.

By thus forming one or more grooves 60x in the cover layer 60, the viscosity of the cover layer 60 can be reduced, thereby improving creep characteristics.

As shown in FIG. 8, the grooves 60x do not have to penetrate the cover layer 60. FIG. In the example of FIG. 8, the inner side surface and the bottom surface of the groove 60x are formed of the cover layer 60. In the example of FIG. In the case of FIG. 8 as well, the viscosity of the cover layer 60 can be reduced, so the creep characteristics can be improved.

The groove 60x does not have to penetrate the cover layer 60 when the strain gauge 1 shown in FIG.

Although the preferred embodiments and the like have been described in detail above, the present invention is not limited to the above-described embodiments and the like, and various modifications and substitutions can be made to the above-described embodiments and the like without departing from the scope of the claims. can be added.

Reference Signs List 1, 1A strain gauge, 10 substrate, 10a upper surface, 20 functional layer, 30 resistor, 40 wiring, 50 electrode, 60 cover layer, 60x groove

Claims (7)

a base material;
a resistor formed from a film containing Cr, CrN, and _Cr2N on the substrate;
an insulating resin layer formed on the base material and covering the resistor,
The strain gauge, wherein the insulating resin layer is provided with a groove that opens on the upper surface side and does not open on the side surface side. The resistor has a structure in which a plurality of elongated portions are arranged at predetermined intervals with the longitudinal direction directed in the same direction, and the ends of the adjacent elongated portions are connected in order and folded in a zigzag as a whole,
2. The groove according to claim 1, wherein said grooves are arranged along said elongated portions in any one or more regions between said adjacent elongated portions of said insulating resin layer in plan view. strain gauge. In a plan view, the grooves cover all regions of the insulating resin layer between the adjacent elongated portions and the elongated portions arranged on both outer sides of the resistor in the direction orthogonal to the grid direction. 3. A strain gauge according to claim 2, arranged along the elongated portion in an outer region. The strain gauge according to any one of claims 1 to 3, wherein the groove is provided so as to expose the upper surface of the base material. 5. The method of claim 1, wherein L/(L+S) is 96.5% or more, where L is the line of the resistor and S is the space of the resistor in the direction perpendicular to the grid direction of the resistor. A strain gauge according to any one of the paragraphs. 5. L/(L+S) is 98.5% or more, where L is the line of the resistor and S is the space of the resistor in the direction orthogonal to the grid direction of the resistor. A strain gauge according to any one of the paragraphs. 7. The strain gauge according to any one of claims 1 to 6, having a gauge factor of 10 or more.

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