WO2024029538A1 - ひずみゲージ - Google Patents

ひずみゲージ Download PDF

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Publication number
WO2024029538A1
WO2024029538A1 PCT/JP2023/028168 JP2023028168W WO2024029538A1 WO 2024029538 A1 WO2024029538 A1 WO 2024029538A1 JP 2023028168 W JP2023028168 W JP 2023028168W WO 2024029538 A1 WO2024029538 A1 WO 2024029538A1
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Prior art keywords
resistor
strain
gauge
strain gauge
line width
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
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PCT/JP2023/028168
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English (en)
French (fr)
Japanese (ja)
Inventor
慎也 戸田
寿昭 浅川
厚 北村
真一 丹羽
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MinebeaMitsumi Inc
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MinebeaMitsumi Inc
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Application filed by MinebeaMitsumi Inc filed Critical MinebeaMitsumi Inc
Priority to CN202380056014.2A priority Critical patent/CN119604738A/zh
Priority to US19/099,904 priority patent/US20260036474A1/en
Priority to EP23850092.0A priority patent/EP4567370A1/en
Publication of WO2024029538A1 publication Critical patent/WO2024029538A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/16—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge
    • G01B7/18—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance
    • G01B7/20—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring the deformation in a solid, e.g. by resistance strain gauge using change in resistance formed by printed-circuit technique
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/20—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
    • G01L1/22—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges
    • G01L1/2287—Measuring force or stress, in general by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress using resistance strain gauges constructional details of the strain gauges

Definitions

  • the present invention relates to a strain gauge.
  • strain gauges that are used by being attached to an object to be measured have been known.
  • the gauge factor of a strain gauge is usually about 2, but some strain gauges equipped with a resistor whose main component is Cr have a gauge factor of about 10 (for example, see Patent Document 1).
  • the gauge factor is large, but if the lateral sensitivity ratio, which is the ratio of lateral sensitivity to longitudinal sensitivity, is large, a detection error will occur. Therefore, there is a need for a strain gauge that has a higher gauge factor than the conventional gauge factor (about 2) and a lower transverse sensitivity ratio.
  • the present invention has been made in view of the above points, and aims to provide a strain gauge that has a higher gauge factor and a lower transverse sensitivity ratio than conventional ones.
  • a strain gauge includes a base material and a resistor formed on the base material, the resistor is made of a material containing Cr as a main component, and has lateral sensitivity.
  • FIG. 2 is a plan view illustrating a strain gauge according to the first embodiment.
  • FIG. 2 is a cross-sectional view (part 1) illustrating the strain gauge according to the first embodiment.
  • FIG. 2 is a cross-sectional view (Part 2) illustrating the strain gauge according to the first embodiment. It is a figure explaining a lateral sensitivity ratio.
  • FIG. 2 is a diagram (part 1) showing the study results of Example 1.
  • FIG. 2 is a diagram (part 2) showing the study results of Example 1;
  • FIG. 3 is a diagram (Part 3) showing the study results of Example 1;
  • FIG. 4 is a diagram (part 4) showing the study results of Example 1;
  • FIG. 5 is a diagram (part 5) showing the study results of Example 1;
  • FIG. 7 is a diagram showing the study results of Example 2.
  • FIG. 1 is a plan view illustrating a strain gauge according to a first embodiment.
  • FIG. 2 is a cross-sectional view (part 1) illustrating the strain gauge according to the first embodiment, and shows a cross section taken along line AA in FIG.
  • the strain gauge 1 includes a base material 10, a resistor 30, wiring 40, an electrode 50, and a cover layer 60.
  • the cover layer 60 can be provided as necessary. Note that in FIGS. 1 and 2, only the outer edge of the cover layer 60 is shown with a broken line for convenience. First, each part constituting the strain gauge 1 will be explained in detail.
  • the strain gauge 1 the side of the base material 10 where the resistor 30 is provided is referred to as the "upper side", and the side where the resistor 30 is not provided is referred to as the "lower side”. .
  • the surface located above each part is referred to as the "upper surface”, and the surface located below each part is referred to as the "lower surface”.
  • the strain gauge 1 can also be used upside down.
  • the strain gauge 1 can also be arranged at any angle.
  • planar view refers to viewing the object in the normal direction from the upper side to the lower side with respect to the upper surface 10a of the base material 10.
  • the planar shape refers to the shape of the object when viewed in the normal direction.
  • the base material 10 is a member that becomes a base layer for forming the resistor 30 and the like.
  • the base material 10 has flexibility.
  • the thickness of the base material 10 is not particularly limited, and may be determined as appropriate depending on the intended use of the strain gauge 1.
  • the thickness of the base material 10 may be about 5 ⁇ m to 500 ⁇ m.
  • a strain-generating body may be bonded to the lower surface side of the strain gauge 1 via an adhesive layer or the like.
  • the thickness of the base material 10 is preferably within the range of 5 ⁇ m to 200 ⁇ m. .
  • the thickness of the base material 10 is preferably 10 ⁇ m or more.
  • the base material 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, or LCP (liquid crystal) resin. It is formed from an insulating resin film such as polymer) resin or polyolefin resin. Note that the film refers to a member having a thickness of approximately 500 ⁇ m or less and having flexibility.
  • the insulating resin film may contain fillers, impurities, and the like.
  • the base material 10 may be formed from an insulating resin film containing filler such as silica or alumina.
  • Examples of materials other than resin for the base material 10 include SiO 2 , ZrO 2 (including YSZ), Si, Si 2 N 3 , Al 2 O 3 (including sapphire), ZnO, perovskite ceramics (CaTiO 3 , Examples include crystalline materials such as BaTiO 3 ). Further, in addition to the above-mentioned crystalline materials, amorphous glass or the like may be used as the material of the base material 10. Further, as the material of the base material 10, metals such as aluminum, aluminum alloy (duralumin), stainless steel, titanium, etc. may be used. When using metal, an insulating film is provided to cover the upper and lower surfaces of the metal base material 10.
  • the resistor 30 is a thin film formed in a predetermined pattern on the upper side of the base material 10.
  • the resistor 30 is a sensing portion that receives strain and causes a change in resistance.
  • the resistor 30 may be formed directly on the upper surface 10a of the base material 10, or may be formed on the upper surface 10a of the base material 10 via another layer.
  • the resistor 30 is shown in a dense satin pattern for convenience.
  • the resistor 30 includes a plurality of elongated portions and a plurality of folded portions.
  • the plurality of elongated portions are arranged side by side with their longitudinal directions facing in the same direction.
  • the plurality of folded portions alternately connect the ends of adjacent elongated portions among the plurality of elongated portions to connect the respective elongated portions in series.
  • the resistor 30 has a structure that is folded back in a zigzag pattern as a whole.
  • the longitudinal direction of the plurality of elongated portions is the grid direction, and the direction perpendicular to the grid direction is the grid width direction.
  • One end portion in the longitudinal direction of the two elongated portions located at the outermost sides in the grid width direction is bent in the grid width direction to form respective terminal ends 30e 1 and 30e 2 of the resistor 30 in the grid width direction.
  • Each terminal end 30e 1 and 30e 2 of the resistor 30 in the grid width direction is electrically connected to an electrode 50 via a wiring 40.
  • the wiring 40 electrically connects each terminal end 30e 1 and 30e 2 of the resistor 30 in the grid width direction to each electrode 50.
  • the gauge factor is preferably 5 or more.
  • the gauge factor of the strain gauge 1 does not depend on the line width W of the resistor 30.
  • the gauge factor does not depend on the line width W of the resistor 30 means that the difference between the maximum value and the minimum value of the gauge factor in the range of the line width W of the resistor 30 from 0.1 ⁇ m to 70 ⁇ m is 2 or less.
  • the lateral sensitivity ratio of the strain gauge 1 has a positive correlation with the logarithm of the line width W of the resistor 30, and becomes lower as the line width W of the resistor is narrower.
  • the gauge factor of the strain gauge 1 does not depend on the film thickness T of the resistor 30.
  • the term “gauge factor does not depend on the film thickness T of the resistor 30” means that the difference between the maximum value and the minimum value of the gauge factor in the range where the film thickness T of the resistor 30 is 30 nm or more and 800 nm or less is 2 or less. Refers to the case. Further, the lateral sensitivity ratio of the strain gauge 1 has a negative correlation with the film thickness T of the resistor 30, and becomes lower as the film thickness T of the resistor 30 becomes thicker.
  • the value of the lateral sensitivity ratio of the strain gauge 1 changes under the influence of both the line width W and the film thickness T of the resistor 30. Note that the definition of the lateral sensitivity ratio and the relationship between the line width W and film thickness T of the resistor 30 and the gauge factor and lateral sensitivity ratio will be described in detail separately.
  • the strain limit has a negative correlation with the film thickness T of the resistor 30, and becomes lower as the film thickness T of the resistor 30 becomes thicker.
  • the strain limit is the value of mechanical strain at which cracks or wire breaks begin to occur when strain is applied to the strain gauge. Note that the relationship between the film thickness T of the resistor 30 and the strain limit will be described in detail separately.
  • the resistor 30 can be formed from a material containing Cr (chromium) as a main component, for example.
  • the term "main component" refers to a component that accounts for 50% by weight or more of all materials constituting the resistor 30.
  • An example of a material containing Cr as a main component is a Cr mixed phase film.
  • the Cr mixed phase film is a film in which Cr, CrN, Cr 2 N, etc. are mixed in phase.
  • the Cr mixed phase film may contain inevitable impurities such as chromium oxide.
  • the stability of the gauge characteristics can be improved by using ⁇ -Cr (alpha chromium), which is a stable crystalline phase, as the main component.
  • ⁇ -Cr alpha chromium
  • the resistor 30 has ⁇ -Cr as its main component, so that the gauge factor of the strain gauge 1 is 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR are can be within the range of -1000ppm/°C to +1000ppm/°C.
  • the resistor 30 contains 80% by weight or more of ⁇ -Cr.
  • the resistor 30 contains 90% by weight or more of ⁇ -Cr.
  • ⁇ -Cr is Cr having a bcc structure (body-centered cubic lattice structure).
  • the resistor 30 is a Cr mixed phase film
  • the content of CrN and Cr 2 N in the Cr mixed phase film is 20% by weight or less.
  • the Cr mixed phase film contains 20% by weight or less of CrN and Cr 2 N, a decrease in the gauge factor of the strain gauge 1 can be suppressed.
  • the ratio of CrN and Cr 2 N in the Cr mixed phase film is preferably such that the ratio of Cr 2 N is 80% by weight or more and less than 90% by weight with respect to the total weight of CrN and Cr 2N . . More preferably, the ratio is such that the proportion of Cr 2 N is 90% by weight or more and less than 95% by weight with respect to the total weight of CrN and Cr 2N .
  • Cr 2 N has semiconductor properties. Therefore, by setting the above-mentioned proportion of Cr 2 N to 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more remarkable. Further, by setting the above-mentioned proportion of Cr 2 N to 90% by weight or more and less than 95% by weight, it is possible to reduce the ceramic resistance of the resistor 30 and make brittle fracture of the resistor 30 less likely to occur.
  • CrN has the advantage of being chemically stable. By including a larger amount of CrN in the Cr multiphase film, it is possible to reduce the possibility of unstable N being generated, thereby making it possible to obtain a stable strain gauge.
  • "unstable N” means a trace amount of N 2 or atomic N that may exist in the Cr multiphase film. Depending on the external environment (for example, high temperature environment), these unstable N may escape out of the membrane. When unstable N escapes from the film, the film stress of the Cr multiphase film may change.
  • the strain gauge 1 when a Cr mixed phase film is used as the material for the resistor 30, higher sensitivity and smaller size can be achieved.
  • the output variation of a conventional strain gauge is about 0.04 mV/2V
  • the output variation is 0.3 mV/2V or more.
  • the size of a conventional strain gauge is approximately 3 mm x 3 mm
  • the size when a Cr mixed phase film is used as the material for the resistor 30 is approximately 3 mm x 3 mm. Width) can be downsized to approximately 0.3 mm x 0.3 mm.
  • the wiring 40 is provided on the base material 10.
  • the wiring 40 has one end electrically connected to both ends of the resistor 30, and the other end electrically connected to the electrode 50.
  • the wiring 40 is not limited to a straight line, and may have any pattern. Further, the wiring 40 can have any width and any length. Note that in FIG. 1, for convenience, the wiring 40 is shown in a matte pattern with a lower density than the resistor 30.
  • the electrode 50 is provided on the base material 10.
  • the electrode 50 is electrically connected to the resistor 30 via the wiring 40.
  • the electrode 50 is formed in a substantially rectangular shape with a wider width than the wiring 40 in plan view.
  • the electrodes 50 are a pair of electrodes for outputting to the outside a change in resistance value of the resistor 30 caused by strain.
  • a lead wire for external connection is connected to the electrode 50.
  • 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.
  • the resistor 30, the wiring 40, and the electrode 50 are given different symbols for convenience, they can be integrally formed using the same material in the same process. Note that in FIG. 1, for convenience, the electrode 50 is shown in a satin pattern with the same density as the wiring 40.
  • the cover layer 60 is provided on the upper surface 10a of the base material 10, if necessary, so as to cover the resistor 30 and the wiring 40 and expose the electrode 50.
  • the material of the cover layer 60 include insulating resins such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, and composite resin (eg, silicone resin, polyolefin resin).
  • the cover layer 60 may contain filler or pigment.
  • the thickness of the cover layer 60 is not particularly limited, and can be appropriately selected depending on the purpose. For example, the thickness of the cover layer 60 can be about 2 ⁇ m to 30 ⁇ m.
  • strain gauge manufacturing method In the strain gauge 1 according to the present embodiment, the resistor 30, the wiring 40, the electrode 50, and the cover layer 60 are formed on the base material 10. Note that another layer (such as a functional layer to be described later) may be formed between the base material 10 and the layers of these members.
  • the base material 10 is prepared, and a metal layer (for convenience, referred to as metal layer A) is formed on the upper surface 10a of the base material 10.
  • the metal layer A is a layer that is finally patterned to become the resistor 30, 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 and the like 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 using reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like instead of magnetron sputtering.
  • the thickness of the metal layer A can be adjusted to a desired value.
  • the metal layer A is patterned into a planar shape similar to the resistor 30, wiring 40, and electrode 50 in FIG. 1 by a well-known photolithography method.
  • the line width of the resistor 30 can be adjusted to a desired value.
  • the resistor 30 includes a plurality of elongated portions arranged in parallel, and a folded portion that alternately connects the ends of adjacent elongated portions among the plurality of elongated portions and connects the respective elongated portions in series.
  • the configuration includes
  • the metal layer A may be formed after forming a base layer on the upper surface 10a of the base material 10.
  • a functional layer having a predetermined thickness may be formed in vacuum on the upper surface 10a of the base material 10 by conventional sputtering.
  • the functional layer refers to a layer that has a function of promoting crystal growth of at least the upper metal layer A (resistor 30).
  • the functional layer further has a function of preventing oxidation of the metal layer A due to oxygen or moisture contained in the base material 10, and/or a function of improving the adhesion between the base material 10 and the metal layer A. is preferred.
  • the functional layer may further include other functions.
  • the insulating resin film constituting the base material 10 may contain oxygen and moisture, and Cr may form a self-oxidation film. Therefore, especially when the metal layer A contains Cr, it is preferable to form a functional layer having a function of preventing the metal layer A from being oxidized.
  • Examples of materials for the functional layer 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), 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), an alloy of any metal in this group, or a compound of any metal in this group.
  • FIG. 3 is a cross-sectional view (Part 2) illustrating the strain gauge according to the first embodiment.
  • Part 2 shows a cross-sectional shape of the strain gauge 1 in which the functional layer 20 is provided as a base layer for the resistor 30, the wiring 40, and the electrode 50.
  • the planar shape of the functional layer 20 may be patterned to be approximately the same as the planar shape of the resistor 30, the wiring 40, and the electrode 50, for example.
  • the planar shapes of the functional layer 20, the resistor 30, the wiring 40, and the electrode 50 do not have to be substantially the same.
  • the functional layer 20 when the functional layer 20 is formed of an insulating material, the functional layer 20 may be patterned into a shape different from the planar shape of the resistor 30, the wiring 40, and the electrode 50.
  • the functional layer 20 may be formed in a solid manner, for example, in a region where the resistor 30, the wiring 40, and the electrode 50 are formed.
  • the functional layer 20 may be formed in a solid manner over the entire upper surface of the base material 10.
  • a cover layer 60 is formed on the upper surface 10a of the base material 10, if necessary. Although the cover layer 60 covers the resistor 30 and the wiring 40, the electrode 50 may be exposed from the cover layer 60.
  • a semi-cured thermosetting insulating resin film is laminated on the upper surface 10a of the base material 10 so as to cover the resistor 30 and wiring 40 and expose the electrode 50, and then the insulating resin film is laminated.
  • the cover layer 60 can be formed by heating and curing. Through the above steps, the strain gauge 1 is completed.
  • FIG. 4 is a diagram illustrating the lateral sensitivity ratio.
  • axis M indicates the direction in which strain is desired to be measured.
  • a strain gauge 1A whose grid direction is oriented in the direction of the axis M, and a strain gauge 1B whose grid direction is oriented perpendicular to the axis M are attached to the strain body 100.
  • the x-axis, y-axis, and z-axis in FIG. 4 indicate axes that are orthogonal to each other.
  • Axis M is parallel to the y-axis
  • the direction perpendicular to axis M is parallel to the x-axis.
  • equation (3) the lateral sensitivity ratio K defined by the ratio of the lateral sensitivity F t to the vertical sensitivity F a is expressed by equation (3).
  • ⁇ y is the strain generated in the direction of the axis M
  • ⁇ x is the strain generated in the direction perpendicular to the axis M.
  • RA is the resistance value of the resistor of the strain gauge 1A when no strain is generated.
  • R B is the resistance value of the resistor of the strain gauge 1B when no strain is generated.
  • ⁇ R A is a change in resistance value that occurs in the resistor of the strain gauge 1A when strains ⁇ x and ⁇ y occur.
  • ⁇ R B is a change in resistance value that occurs in the resistor of the strain gauge 1B when strains ⁇ x and ⁇ y occur.
  • the amount of output change is about 0.10 mV/V.
  • the lateral sensitivity ratio is 70% or less and the gauge factor is 5 or more.
  • the lateral sensitivity ratio is more preferably 50% or less, even more preferably 40% or less, and particularly preferably 30% or less.
  • the gauge factor is more preferably 8 or more, more preferably 11 or more, and particularly preferably 14 or more. The smaller the lateral sensitivity ratio and the larger the gauge factor, the larger the amount of output change when a bridge circuit is formed using strain gauges.
  • Example 1 (Relationship between line width of resistor, lateral sensitivity ratio and gauge factor) The inventors produced a strain gauge sample and investigated the relationship between the line width of the resistor, the lateral sensitivity ratio, and the gauge factor.
  • a Ti film with a thickness of 3 nm was vacuum-formed as a functional layer 20 by conventional sputtering on the upper surface 10a of a base material 10 made of polyimide resin with a thickness of 25 ⁇ m.
  • a Cr mixed phase film having a thickness of 200 nm was formed as a resistor 30, wiring 40, and electrode 50 over the entire upper surface of the functional layer 20 by magnetron sputtering.
  • the functional layer 20, the resistor 30, the wiring 40, and the electrode 50 were patterned by photolithography as shown in FIG. 1, and a strain gauge sample was produced. This sample was patterned so that the line width W of the resistor 30 was 500 ⁇ m.
  • strain gauge samples were prepared by patterning the resistors 30 so that the line widths W were 200 ⁇ m, 100 ⁇ m, 50 ⁇ m, 40 ⁇ m, 20 ⁇ m, 10 ⁇ m, and 5 ⁇ m, respectively. Then, the lateral sensitivity ratio and gauge factor of each sample of the strain gauge were measured in a 20° C. environment, and are summarized in FIG.
  • the gauge factor of the manufactured sample does not depend on the line width W of the resistor 30.
  • the difference between the maximum value and the minimum value of the gauge factor when the line width W of the resistor 30 changes is about 1.5.
  • the lateral sensitivity ratio has a positive correlation with the logarithm of the line width W of the resistor 30, and becomes lower as the line width of the resistor 30 becomes narrower.
  • FIG. 6 shows the relationship between the line width of the resistor, the lateral sensitivity ratio, and the gauge factor when a sample having a gauge factor of about 9 was prepared using the same method.
  • the gauge factor does not depend on the line width W of the resistor 30, whereas the lateral sensitivity ratio has a positive correlation with the logarithm of the line width W of the resistor 30. The narrower the area, the lower the area. Although not shown, other samples with a gauge factor of 5 or more exhibit similar characteristics.
  • FIG. 7 is a diagram showing the relationship between the line width of the resistor, the lateral sensitivity ratio, and the amount of change in the output of the strain gauge.
  • Figure 7 shows the relationship between the line width, the lateral sensitivity ratio, and the amount of change in the output of the strain gauge, which was experimentally determined by the inventors for a strain gauge with a gauge factor of 5 and a strain gauge with a gauge factor of 15. .
  • FIG. 7 also shows the amount of change in output of a commercially available strain gauge with a gauge factor of 2 as a comparative example. Note that the amount of output change shown in FIG. 7 is the amount of output change when a bridge circuit is formed using a strain gauge.
  • the gauge factor is 5 and the lateral sensitivity ratio is 70% or more, it is possible to obtain an amount of output change that is equal to or greater than that of a commercially available strain gauge.
  • the lateral sensitivity ratio can be set to 70% or less.
  • the line width By setting the line width to 70 ⁇ m or less, it is possible to realize a strain gauge with an output variation equal to or greater than that of commercially available strain gauges. For example, by setting the line width of the resistor 30 to 70 ⁇ m so that the lateral sensitivity ratio is 70% and the gauge factor is 15, it is possible to realize a strain gauge with an output change that is about three times that of commercially available strain gauges. .
  • the lateral sensitivity ratio is more preferably 50% or less, even more preferably 40% or less, and particularly preferably 30% or less. From FIG. 5, by setting the line width W of the resistor 30 to 20 ⁇ m or less, the lateral sensitivity ratio can be made 50% or less. Furthermore, from FIG. 5, by setting the line width W of the resistor 30 to 10 ⁇ m or less, the lateral sensitivity ratio can be made 40% or less. Further, from FIG. 5, by setting the line width W of the resistor 30 to 5 ⁇ m or less, the lateral sensitivity ratio can be made 30% or less.
  • the gauge factor in order to obtain an output change equal to or higher than that of a commercially available strain gauge, the gauge factor should be 5 or more, but the gauge factor of each sample using a Cr mixed phase film for the resistor 30 is 14 or more. , and a sufficiently large value is obtained. Note that even when a Cr mixed phase film is used for the resistor 30, the gauge factor can be adjusted to various values of 5 or more by changing the content of ⁇ -Cr in the resistor 30. Further, by using a Cr mixed phase film for the resistor 30 and increasing the crystallinity of ⁇ -Cr, the gauge factor can be set to about 5 or more and 10 or less.
  • the resistor 30 is formed from a material containing Cr as a main component, has a gauge factor of 5 or more, is independent of the line width of the resistor 30, and has a lateral sensitivity ratio of the line width of the resistor 30. It is possible to realize a strain gauge that has a positive correlation with the logarithm and becomes lower as the line width of the resistor 30 becomes narrower. Such characteristics can be achieved at least when the line width of the resistor 30 is within the range of 0.1 ⁇ m or more and 70 ⁇ m.
  • a Ti film with a thickness of 3 nm was vacuum-formed as a functional layer 20 by conventional sputtering on the upper surface 10a of a base material 10 made of polyimide resin with a thickness of 25 ⁇ m.
  • a Cr mixed phase film having a thickness of 800 nm was formed as a resistor 30, wiring 40, and electrode 50 over the entire upper surface of the functional layer 20 by magnetron sputtering.
  • the functional layer 20, the resistor 30, the wiring 40, and the electrode 50 were patterned by photolithography as shown in FIG. 1, and a strain gauge sample was produced. Note that the patterning was performed so that the line width W of the resistor 30 was 50 ⁇ m.
  • strain gauge samples were prepared in which the film thicknesses T of the resistors 30 were formed to be 500 nm, 200 nm, 100 nm, 50 nm, and 30 nm, respectively. Then, the lateral sensitivity ratio and gauge factor of each sample of the strain gauge were measured in a 20° C. environment, and are summarized in FIG. 8.
  • the gauge factor of the prepared sample does not depend on the film thickness T of the resistor 30.
  • the difference between the maximum value and the minimum value of the gauge factor when the film thickness T of the resistor 30 changes is about 1.5.
  • the lateral sensitivity ratio has a negative correlation with the film thickness T of the resistor 30, and it is recognized that the value of the lateral sensitivity ratio tends to decrease as the film thickness T of the resistor 30 increases.
  • gauge factor is about 15 in FIG. 8, it has been confirmed that samples with various gauge factors of 5 or more also exhibit characteristics similar to those in FIG. 8, although illustrations are omitted.
  • the lateral sensitivity ratio is 70% or less, an output change equal to or greater than that of a commercially available strain gauge can be obtained, but from FIG. 8, the film thickness T of the resistor 30 should be 200 nm or more. Accordingly, the lateral sensitivity ratio can be made 70% or less. In other words, it is possible to realize a strain gauge in which the film thickness of the resistor 30 is 200 nm or more so that the transverse sensitivity ratio is 70% or less and the gauge factor is 5 or more.
  • the gauge factor in order to obtain an output change equal to or higher than that of a commercially available strain gauge, the gauge factor should be 5 or more, but the gauge factor of each sample using a Cr mixed phase film for the resistor 30 is 14 or more. , and a sufficiently large value is obtained. Note that even when a Cr mixed phase film is used for the resistor 30, the gauge factor can be adjusted to various values of 5 or more by changing the content of ⁇ -Cr in the resistor 30. Further, by using a Cr mixed phase film for the resistor 30 and increasing the crystallinity of ⁇ -Cr, the gauge factor can be set to about 5 or more and 10 or less.
  • the resistor 30 is formed from a material containing Cr as a main component, has a gauge factor of 5 or more, is independent of the film thickness of the resistor 30, and has a lateral sensitivity ratio that is equal to the film thickness of the resistor 30. It is possible to realize a strain gauge that has a negative correlation and becomes lower as the film thickness of the resistor 30 becomes thicker.
  • the above experiment shows that when the film thickness T of the resistor 30 is 200 nm, the line width W of the resistor 30 should be 70 ⁇ m or less in order to make the lateral sensitivity ratio 70% or less. Ta. Furthermore, the above experiment shows that when the line width W of the resistor 30 is 50 ⁇ m, the film thickness T of the resistor 30 should be set to 200 nm or more in order to make the lateral sensitivity ratio 70% or less. Ta.
  • the lateral sensitivity ratio of the strain gauge 1 changes due to the influence of both the line width W and film thickness T of the resistor 30, It is also possible to reduce the lateral sensitivity ratio to 70% or less over a wide range. That is, even if the line width W of the resistor 30 is thicker than 70 ⁇ m, the lateral sensitivity ratio can be made 70% or less by adjusting the film thickness T to an appropriate value. Similarly, even if the film thickness T of the resistor 30 is thinner than 200 nm, the lateral sensitivity ratio can be made 70% or less by adjusting the line width W to an appropriate value.
  • FIG. 9 is a contour map showing the lateral sensitivity ratio with respect to line width and film thickness, and summarizes the experimental results conducted by the inventors.
  • 0% ⁇ lateral sensitivity ratio ⁇ 70% in the first region indicated by the high-density dot pattern, 0% ⁇ lateral sensitivity ratio ⁇ 70%.
  • a strain gauge is used in which the line width W and film thickness T of the resistor 30 satisfy the above equation (1) so that the lateral sensitivity ratio is 70% or less and the gauge factor is 5 or more. realizable.
  • the lateral sensitivity ratio can be made to be 70% or less, almost independent of the film thickness T.
  • a gauge factor of 5 or more can be obtained by using other materials instead of the Cr mixed phase film.
  • materials that can obtain a gauge factor of 5 or more include Ge, Pt, Si, Ni, Cu, C, Ti, Cr, or materials containing these. Specifically, they include Cr-N, Ge, Ge-In, Ge-Ga, Ge-P, Pt, Pt-In, Cu, Ni-C, Si, Ti-C-O, and the like. Further, by adjusting the line width W and/or film thickness T of the resistor 30 using these materials, a desired lateral sensitivity ratio can be obtained.
  • the line width W and film thickness T of the resistor 30 satisfy the above equation (1) so that the lateral sensitivity ratio is 70% or less and the gauge factor is 5 or more. It is possible to realize a strain gauge that is said to be Further, the gauge factor is 5 or more and does not depend on the line width of the resistor 30, and the lateral sensitivity ratio has a positive correlation with the logarithm of the line width of the resistor 30, and the narrower the line width of the resistor 30, the more the line width of the resistor 30 is narrower. It is possible to realize a strain gauge with a lower strain rate.
  • the resistor 30 is formed from these materials, the gauge factor is 5 or more, it does not depend on the film thickness of the resistor 30, and the lateral sensitivity ratio has a negative correlation with the film thickness of the resistor 30. The thicker the film thickness of the resistor 30, the lower the strain gauge can be realized.
  • Example 2 The inventors fabricated a plurality of strain gauge samples for each film thickness with the same specifications as those used in Example 1, "Relationship between resistor film thickness, lateral sensitivity ratio, and gauge factor.” We investigated the relationship between body membrane thickness and strain limit. However, the film thicknesses of the resistors were 1100 nm, 800 nm, 500 nm, 200 nm, 100 nm, 50 nm, and 30 nm. Note that although the line width of the resistor was constant at 50 ⁇ m, the strain limit does not substantially depend on the line width of the resistor.
  • FIG. 10 is a diagram showing the study results of Example 2, in which the minimum value of the strain limit for each film thickness in a plurality of strain gauge samples is plotted.
  • the strain limit has a negative correlation with the film thickness T of the resistor 30, and it is recognized that the value of the strain limit tends to decrease as the film thickness T of the resistor 30 increases.
  • the film thickness T of the resistor 30 is in the range of 30 nm or more and 200 nm or less, the strain limit value decreases significantly.
  • the film thickness T of the resistor 30 exceeds 200 nm, the strain limit value gradually decreases.
  • the film thickness T of the resistor 30 is preferably 800 nm or less so that the strain limit is 6000 ⁇ 10 ⁇ 6 or more.
  • the strain gauge 1 is attached to the strain body and expands and contracts to follow the movement of the strain body, thereby detecting the amount of strain in the strain body. Therefore, in order to detect a larger amount of strain, the strain gauge 1 itself must not be damaged (broken wire, etc.) during the expansion and contraction process, and a higher strain limit is required. In the strain gauge 1, by setting the film thickness T of the resistor 30 to 800 nm or less, it is possible to improve the strain limit.
  • the film thickness T is more preferably 600 nm or less, even more preferably 400 nm or less, and particularly preferably 200 nm or less.
  • the strain limit can be significantly improved, and by setting the film thickness T to 100 nm or less, the strain limit can be further improved.
  • the lateral sensitivity ratio can be made 70% or less by adjusting the line width W. For example, by setting the line width W of the resistor 30 to 40 ⁇ m or less and the film thickness T to 200 nm or less, the lateral sensitivity ratio can be made 70% or less, and the strain limit can be significantly improved. .
  • the same characteristics as in FIG. 10 can be obtained by using other materials instead of the Cr mixed phase film.
  • Other materials include Ge, Pt, Si, Ni, Cu, C, Ti, Cr, or materials containing these. Specifically, they include Cr-N, Ge, Ge-In, Ge-Ga, Ge-P, Pt, Pt-In, Cu, Ni-C, Si, Ti-C-O, and the like.
  • Suitable range of film thickness T of resistor 30 From the results of Example 2, focusing on the strain limit, it is preferable that the film thickness T of the resistor 30 is 800 nm or less so that the strain limit is 6000 ⁇ 10 ⁇ 6 or more. Therefore, when the results of Example 2 are taken into consideration with the results of Example 1, the resistor 30 is adjusted so that the lateral sensitivity ratio is 70% or less and the gauge factor is 5 or more within the range where the film thickness T is 800 nm or less. It can be said that it is preferable that the line width W and the film thickness T satisfy the above formula (1).
  • a strain gauge is constructed in which the line width W and film thickness T of the resistor 30 are adjusted so that the lateral sensitivity ratio is 70% or less, the gauge factor is 5 or more, and the strain limit is 6000 ⁇ 10 -6 or more. realizable. With this strain gauge, it is possible to improve the accuracy of strain detection and to detect a larger amount of strain.
  • the strain limit may be less than 6000 ⁇ 10 ⁇ 6 , so it is not essential that the film thickness T of the resistor 30 be 800 nm or less.
  • strain gauge according to the present disclosure is not limited to the embodiments, modifications, etc. described above.
  • various modifications and substitutions can be made to the strain gauges according to the above-described embodiments without departing from the scope of the claims.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
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