Strain gauge and method for manufacturing strain gauge

Abstract

To provide a strain gauge which can suppress breakage of a conductor.SOLUTION: The strain gauge includes: a base material 10 with flexibility; a resistor 20 formed on the base material 10; and an electrode 30 electrically connected to the resistor 20. The electrode 30 includes: a first metal layer 40 formed of the same material as the material of the resistor 20; a second metal layer 50 formed on the first metal layer 40, the second metal layer being formed of a material different from the material of the first metal layer 40; and a breakage suppression unit 60 in which the first metal layer 40 and the second metal layer 50 are not formed. The breakage suppression unit 60 is formed along the external edge of a part of the second metal layer 50 in plane vision.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to strain gauges and methods of manufacturing strain gauges. [Background technology]

[0002] Patent Document 1 discloses a strain gauge having a flexible substrate, a resistor formed on the substrate, and a pair of electrodes formed on the substrate and electrically connected to the resistor via wiring. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-008026 Summary of the Invention [Problem to be solved by the invention]

[0004] If stress is concentrated in one part of the strain gauge, the conductor on the substrate may break.

[0005] The present disclosure provides a strain gauge capable of suppressing conductor breakage, and a method for manufacturing the strain gauge. [Means for solving the problem]

[0006] A strain gauge according to one embodiment of the present disclosure comprises a flexible substrate, a resistor formed on the substrate, and an electrode electrically connected to the resistor, the electrode having a first metal layer made of the same material as the resistor, a second metal layer formed on the first metal layer and made of a material different from the first metal layer, and a breakage suppression portion in which the first metal layer and the second metal layer are not formed, the breakage suppression portion being formed along a portion of the outer edge of the second metal layer in a plan view. Effect of the Invention

[0007] The present disclosure can provide a strain gauge capable of suppressing conductor breakage, and a method for manufacturing the strain gauge. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view illustrating the strain gauge according to the first embodiment. [Diagram 2] 2 is an enlarged plan view illustrating a main part in FIG. 1. [Diagram 3] 3 is a cross-sectional view illustrating a cross section taken along line III-III in FIG. 2. [Figure 4] FIG. 11 is an enlarged plan view illustrating a main part of a strain gauge according to a second embodiment. [Diagram 5] FIG. 11 is an enlarged plan view illustrating a main part of a strain gauge according to a third embodiment. [Figure 6] FIG. 13 is a plan view illustrating a strain gauge according to a fourth embodiment. [Figure 7] 7 is an enlarged plan view illustrating a main part in FIG. 6. FIG. [Figure 8] FIG. 13 is a plan view illustrating a strain gauge according to a fifth embodiment. [Figure 9] 9 is an enlarged plan view illustrating a main part in FIG. 8. FIG. [Figure 10] 1 is a cross-sectional view illustrating a cross section of a strain gauge according to a first embodiment. [Figure 11] 4 is a cross-sectional view illustrating a cross section of a strain gauge before a breakage suppression portion is formed. FIG. [Figure 12] 6 is a cross-sectional view illustrating a cross section of a strain gauge according to a second embodiment. FIG. [Figure 13] 13 is a cross-sectional view illustrating a cross section of a strain gauge according to a third embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0010] In the directions of parallel, right-angle, orthogonal, horizontal, vertical, up-down, left-right, front-back, etc., deviations are permitted to the extent that they do not impair the effects of the embodiment. The shape of the corners is not limited to right angles and may be rounded. Parallel, right-angle, orthogonal, horizontal, and vertical may include approximately parallel, approximately right-angle, approximately orthogonal, approximately horizontal, and approximately vertical, respectively.

[0011] For example, "approximately parallel" means that even if two lines or two surfaces are not completely parallel to each other, they can be treated as being parallel to each other as long as it is within the range of manufacturing tolerance. As with "approximately parallel," "approximately right angle," "approximately perpendicular," "approximately horizontal," and "approximately vertical" are also intended to correspond to the respective terms as long as the relative positional relationship between the two lines or two surfaces is within the range of manufacturing tolerance.

[0012] [Strain gauge 100 according to the first embodiment] A strain gauge 100 according to a first embodiment will be described with reference to Figs. 1 to 3. The strain gauge 100 is an example of a strain gauge according to the present disclosure. Fig. 1 is a plan view illustrating the strain gauge 100 according to the first embodiment. Fig. 2 is a plan view illustrating an enlarged view of a main part in Fig. 1. Fig. 3 is a cross-sectional view illustrating a cross section along line III-III in Fig. 2.

[0013] For ease of explanation, an XYZ orthogonal coordinate system consisting of an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other may be set in the drawings. Note that this coordinate system is defined for the purpose of explanation, and does not limit the posture of the strain gauge 100 according to this embodiment.

[0014] In the description of the embodiment, the terms X-axis direction, Y-axis direction, and Z-axis direction are used. The X-axis direction includes the positive X-axis direction and the negative X-axis direction. The Y-axis direction includes the positive Y-axis direction and the negative Y-axis direction. The Z-axis direction includes the positive Z-axis direction and the negative Z-axis direction. The positive Z-axis direction is defined as the top, and the negative Z-axis direction is defined as the bottom. For example, as shown in FIG. 3, the side on which the substrate 10 is disposed is defined as the bottom. In using the strain gauge 100, the arrangement of the strain gauge 100 is not limited, and for example, the substrate 10 may be disposed on the top side, and the second metal layer 50 may be disposed on the bottom side.

[0015] The strain gauge 100 includes a substrate 10, a resistor 20, and an electrode 30. The resistor 20 and the electrode 30 are formed on the substrate 10. The resistor 20 and the electrode 30 are electrically connected. The strain gauge 100 may include a cover layer 102. The cover layer 102 is indicated by a dashed line in FIG. 1.

[0016] [Base material 10] The substrate 10 is, for example, adhered to the upper surface of the flexure body. An adhesive layer is formed between the flexure body and the substrate 10. The substrate 10 is flexible. The substrate 10 is, for example, plate-shaped. The thickness direction of the substrate 10 is along the Z-axis direction. The substrate 10 has a predetermined thickness in the Z-axis direction. As shown in FIG. 3, the substrate 10 has an upper surface 11 and a lower surface 12 that face each other in the Z-axis direction.

[0017] The substrate 10 is a base member for forming the resistor 20, the electrodes 30, etc. The thickness of the substrate 10 is not particularly limited and may be appropriately determined depending on the intended use of the strain gauge 100, etc. For example, the thickness of the substrate 10 may be about 5 μm to 500 μm. From the viewpoint of the transferability of strain from the strain generating body to the sensing part and the dimensional stability against environmental changes, the thickness of the substrate 10 is preferably within the range of 5 μm to 200 μm. From the viewpoint of insulation, the thickness of the substrate 10 is preferably 10 μm or more.

[0018] The substrate 10 is formed from an insulating resin film such as PI (polyimide) resin, epoxy resin, PEEK (polyether ether ketone) resin, PEN (polyethylene naphthalate) resin, PET (polyethylene terephthalate) resin, PPS (polyphenylene sulfide) resin, polyolefin resin, etc. The film refers to a flexible member having a thickness of about 500 μm or less.

[0019] When the substrate 10 is formed from an insulating resin film, the insulating resin film may contain a filler, impurities, etc. For example, the substrate 10 may be formed from an insulating resin film containing a filler such as silica or alumina.

[0020] Examples of materials other than resin for the substrate 10 include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, and perovskite ceramics (CaTiO3, BaTiO3). In addition to the above-mentioned crystalline materials, amorphous glass or the like may be used as the material for the substrate 10. Metals such as aluminum, aluminum alloy (duralumin), and titanium may also be used as the material for the substrate 10. When a metal substrate 10 is used, an insulating film is provided so as to cover the upper surface 11.

[0021] [Resistor 20] The resistor 20 has a grid portion. The resistor 20 may include a plurality of grid portions. The resistor 20 is a sensitive portion of the strain gauge 100.

[0022] The resistor 20 is a thin film formed in a predetermined pattern on the substrate 10. In the strain gauge 100, the resistor 20 is a sensing part that receives strain and produces a resistance change. The resistor 20 may be formed directly on the upper surface 11 of the substrate 10, or may be formed on the upper surface 11 of the substrate 10 via another layer.

[0023] [Materials for resistor 20] The resistor 20 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 20 can be made of a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr mixed phase film. An example of a material containing Ni is Cu-Ni (copper nickel). An example of a material containing both Cr and Ni is Ni-Cr (nickel chromium).

[0024] Here, the Cr mixed phase film is a film in which Cr, CrN, Cr2N, etc. are mixed. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

[0025] [Thickness of resistor 20] The thickness of the resistor 20 is not particularly limited and may be appropriately determined depending on the intended use of the strain gauge 100. For example, the thickness of the resistor 20 may be about 0.05 μm to 2 μm. In particular, when the thickness of the resistor 20 is 0.1 μm or more, the crystallinity of the crystals constituting the resistor 20 (for example, the crystallinity of α-Cr) is improved. Furthermore, when the thickness of the resistor 20 is 1 μm or less, (i) cracks in the film and (ii) warping of the film from the substrate 10 caused by the internal stress of the film constituting the resistor 20 are reduced.

[0026] [Width of resistor 20] The width of resistor 20 can be optimized for required specifications such as resistance value and lateral sensitivity, and can be set to, for example, about 10 μm to 100 μm while taking into consideration measures against disconnection. The width of resistor 20 is the width intersecting the longitudinal direction of resistor 20.

[0027] [20 Resistor Crystals] For example, when the resistor 20 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, for example, when the resistor 20 is a Cr mixed-phase film, the resistor 20 uses α-Cr as the main component, so that the gauge factor of the strain gauge 100 can be 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be in the range of -1000 ppm / °C to +1000 ppm / °C. Here, the "main component" means a component that occupies 50% by weight or more of the total material constituting the resistor. From the viewpoint of improving the gauge characteristics, the resistor 20 preferably contains 80% by weight or more of α-Cr. Furthermore, from the same viewpoint, the resistor 20 more preferably contains 90% by weight or more of α-Cr. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0028] In addition, when the resistor 20 is a Cr mixed-phase film, the Cr mixed-phase film preferably contains 20% by weight or less of CrN and Cr2N. By containing 20% ​​by weight or less of CrN and Cr2N in the Cr mixed-phase film, a decrease in the gauge factor of the strain gauge 100 can be suppressed.

[0029] In addition, the ratio of CrN and Cr2N in the Cr mixed phase film is preferably such that the ratio of Cr2N is 80% by weight or more and less than 90% by weight with respect to the total weight of CrN and Cr2N. More specifically, the ratio is more preferably such that the ratio of Cr2N is 90% by weight or more and less than 95% by weight with respect to the total weight of CrN and Cr2N. Cr2N has semiconductor properties. Therefore, by setting the ratio of Cr2N to 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes more significant. Furthermore, by setting the ratio of Cr2N to 90% by weight or more and less than 95% by weight, the resistor 20 is less likely to become ceramic, and the resistor 20 is less likely to be brittle fractured.

[0030] On the other hand, CrN has the advantage of being chemically stable. By including more CrN in the Cr mixed-phase film, the possibility of unstable N being generated can be reduced, resulting in a stable strain gauge. Here, "unstable N" refers to trace amounts of N2 or atomic N that may be present in the Cr mixed-phase film. This unstable N may escape to the outside of the film depending on the external environment (e.g., high-temperature environment). When unstable N escapes to the outside of the film, the film stress of the Cr mixed-phase film may change.

[0031] The resistor 20 includes a plurality of elongated portions 20a. The longitudinal direction of the elongated portions 20a is, for example, along the X-axis direction. The elongated portions 20a are formed at a predetermined interval in the Y-axis direction. The ends of adjacent elongated portions 20a are connected in a staggered manner. That is, the resistor 20 has a structure in which it is folded back in a zigzag pattern as a whole. The elongated portions 20a are connected in series.

[0032] The longitudinal direction of the multiple elongated portions 20a is the grid direction. The direction perpendicular to the grid direction is the grid width direction. The grid direction is the X-axis direction, and the grid width direction is the Y-axis direction. Note that the grid direction and the grid width direction are not limited to this, and the grid direction may be the Y-axis direction, and the grid width direction may be the X-axis direction.

[0033] [Electrode 30] The strain gauge 100 includes a pair of electrodes 30. The pair of electrodes 30 are electrically connected to both ends of the resistor 20. The electrodes 30 may be, for example, teardrop-shaped in a plan view. The electrode 30 includes, for example, a first portion 30a that is triangular and a second portion 30b that is semicircular. The first portion 30a is disposed closer to the resistor 20 than the second portion 30b.

[0034] The electrode 30 is an electrode for outputting a change in resistance value caused in the resistor 20 due to strain to the outside. For example, a lead wire for external connection is joined to the electrode 30. Each electrode 30 is formed on the substrate 10. For example, the electrode 30 may be substantially circular or substantially rectangular in a plan view. The electrode 30 may have a shape having different widths in the longitudinal direction of the electrode 30. A wiring may be formed between the electrode 30 and the resistor 20. A portion of the electrode 30 closer to the resistor 20 may be referred to as a wiring.

[0035] [First metal layer 40] 1 to 3, the electrode 30 has a first metal layer 40 and a second metal layer 50. The first metal layer 40 is made of the same material as the resistor 20. Although the resistor 20 and the first metal layer 40 are given different reference numerals for convenience, they can be integrally formed from the same material in the same process. Therefore, the resistor 20 and the first metal layer 40 have approximately the same thickness.

[0036] [Second metal layer 50] The second metal layer 50 is formed from a material different from the first metal layer 40. The second metal layer 50 may be formed from a material having a lower resistance than the resistor 20 and the first metal layer 40. The second metal layer 50 may also be formed from a material having better solder wettability than the first metal layer 40.

[0037] The material of the second metal layer 50 may be a material having a lower resistance than the resistor 20. The material of the second metal layer 50 is not particularly limited and can be appropriately selected depending on the purpose. For example, when the resistor 20 is a Cr mixed phase film, the material of the second metal layer 50 may be Cu, Ni, Al, Ag, Au, Pt, etc., or an alloy of any of these metals, a compound of any of these metals, or a laminated film in which any of these metals, alloys, and compounds are appropriately laminated. The thickness of the second metal layer 50 is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness of the second metal layer 50 may be about 3 μm to 5 μm.

[0038] The material of the second metal layer 50 may be formed from a material having better solder wettability than the first metal layer 40. For example, when the material of the first metal layer 40 is a Cr mixed phase film, the material of the second metal layer 50 may be Cu, Ni, Sn, or Zn. When the material of the second metal layer 50 is Cu, the first metal layer 40 can prevent solder erosion and improve solder wettability. There is no particular limit to the thickness of the second metal layer 50, and it can be appropriately selected depending on the purpose. The thickness of the second metal layer may be, for example, about 3 μm or more and 5 μm or less.

[0039] The material of the second metal layer 50 may be formed from a material having a lower gauge factor than the first metal layer 40. For example, when the first metal layer 40 is a Cr mixed-phase film, the material of the second metal layer 50 may be Cu, Ni, Al, Ag, Au, Pt, or the like, or an alloy of any of these metals, a compound of any of these metals, or a laminated film in which any of these metals, alloys, or compounds are appropriately laminated. The Cr mixed-phase film may be, for example, a film in which Cr, CrN, Cr2N, or the like is mixed.

[0040] The material of the second metal layer 50 may be formed from a material having a higher thermal conductivity than the first metal layer 40. For example, when the first metal layer 40 is a Cr mixed phase film, the material of the second metal layer 50 may be C, Al, Si, Au, Ag, Cu, Pd, Pt, Sn, Pb, In, Ga, Ge, a transition metal, a rare earth, or an alloy of any of these metals, or an oxide, nitride, or compound of any of these materials. The second metal layer 50 may be a laminated film in which any of these materials, alloys, oxides, nitrides, or compounds are appropriately laminated. The material of the second metal layer 50 may be a material having a higher electrical conductivity than the first metal layer 40.

[0041] For example, when the first metal layer 40 is a Cr mixed phase film, the thermal conductivity of Cr contained in the first metal layer 40 is about 96.5 W / m·K. In contrast, the thermal conductivity of gold is about 319 W / m·K. The thermal conductivity of silver is about 428 W / m·K. The thermal conductivity of copper is about 403 W / m·K.

[0042] The material of the second metal layer 50 may be a material having a lower elastic modulus than the first metal layer 40 .

[0043] The second metal layer 50 is formed so as to cover a portion of the upper surface of the first metal layer 40. In a plan view, the outer edge of the second metal layer 50 is formed inside the outer edge of the first metal layer 40. In other words, the outer edge of the first metal layer 40 is formed outside the outer edge of the second metal layer 50 in a plan view. The outer edge means an end. The area of ​​the second metal layer 50 is smaller than the area of ​​the first metal layer 40.

[0044] One or more other metal layers may be laminated on the upper surface of the second metal layer 50. For example, a gold layer may be laminated on the upper surface of the second metal layer 50, which is a copper layer. Alternatively, a palladium layer and a gold layer may be laminated in this order on the upper surface of the second metal layer 50, which is a copper layer.

[0045] [Breakage prevention portion 60] As shown in FIG. 2 and FIG. 3, the strain gauge 100 is formed with a breakage suppression portion 60. The electrode 30 includes the breakage suppression portion 60. The breakage suppression portion 60 is a portion where the first metal layer 40 and the second metal layer 50 are not formed. The breakage suppression portion 60 is formed along a part of the outer edge 50a of the second metal layer 50 in a plan view. The outer edge 50a may be a side surface of the second metal layer 50. The side surface may be a surface along the Z axis. The outer edge may be an edge that forms an outline in a plan view. The plan view is a view along the thickness direction of the second metal layer 50, that is, a view of the second metal layer 50 in the Z axis direction. In a plan view, the breakage suppression portion 60 is formed between the first metal layer 40 and the second metal layer 50.

[0046] The breakage suppression portion 60 is formed in a linear shape in a plan view. The breakage suppression portion 60 is formed by removing the first metal layer 40. The breakage suppression portion 60 may be formed by removing the first metal layer 40 and the second metal layer 50.

[0047] The breakage suppression portion 60 has a predetermined width. The width is along a direction intersecting the longitudinal direction. As shown in FIG. 3, the width direction of the breakage suppression portion 60 may be the X-axis direction. The breakage suppression portion 60 may be a portion in which the first metal layer 40 has been removed and only the substrate 10 remains. In the portion in which the breakage suppression portion 60 is formed, the first metal layers 40 are separated from each other in the width direction of the breakage suppression portion 60. The first metal layers 40 are formed on both sides of the breakage suppression portion 60. A portion of the first metal layer 40 is divided at the breakage suppression portion 60.

[0048] The breakage suppression portion 60 is formed, for example, by laser processing. For example, the breakage suppression portion 60 can be formed by irradiating a laser onto a portion where the first metal layer 40 is formed to remove the first metal layer 40. For example, the breakage suppression portion 60 may be formed by irradiating a laser onto a portion where the first metal layer 40 and the second metal layer 50 are formed to remove the first metal layer 40 and the second metal layer 50.

[0049] 2, the breakage suppression portion 60 may include a portion formed between the resistor 20 and the second metal layer 50 in a plan view. As shown in Fig. 3, a cavity C may be formed in the breakage suppression portion 60. By irradiating with a laser, only the first metal layer 40 is removed, and the portion from which the first metal layer 40 has been removed becomes the cavity C.

[0050] At least a portion of the first metal layer 40 on the resistor 20 side is exposed from the second metal layer 50 in a plan view. The "resistor side" may be the side closer to the resistor 20. "Exposed from the second metal layer" may mean not being covered by the second metal layer 50.

[0051] The outer edge 60a of the breakage suppression portion 60 is formed to overlap with a part of the inner edge 40a of the first metal layer 40 or the outer edge 50a of the second metal layer 50 in a plan view. As shown in Figures 2 and 3, the outer edge 60a of the breakage suppression portion 60 includes the inner edge 40a of the first metal layer 40. The inner edge 40a of the first metal layer 40 forms the outer edge of the breakage suppression portion 60.

[0052] [Acute angle 51] 2, the second metal layer 50 has an acute angle portion 51 that forms an acute angle in a plan view. The breakage suppression portion 60 is formed following an outer edge 50a of the acute angle portion 51. The acute angle portion 51 may be a top portion. The breakage suppression portion 60 may include a portion formed between the resistor 20 and the acute angle portion 51 in the Y-axis direction.

[0053] [Cover layer 102] 1 and 3, the strain gauge 100 may include a cover layer 102. The cover layer 102 covers the resistor 20 and the electrode 30. The cover layer 102 is formed so as to expose a portion of the second metal layer 50 of the electrode 30. The cover layer 102 has an opening 102a that exposes a portion of the second metal layer 50. As shown in FIG. 3, the cavity C after the first metal layer 40 is removed is covered by the cover layer 102.

[0054] The strain gauge 100 is provided with the cover layer 102, thereby preventing mechanical damage and the like from occurring to the resistor 20 and the electrodes 30. The strain gauge 100 is provided with the cover layer 102, thereby protecting the resistor 20 and the electrodes 30 from moisture and the like. The cover layer 102 is formed so as to cover the entire second metal layer 50 except for a portion thereof.

[0055] Examples of materials for the cover layer 102 include insulating resins such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, and composite resins (e.g., silicone resin, polyolefin resin). The cover layer 102 may contain a filler or a pigment. The thickness of the cover layer 102 is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness of the cover layer 102 can be about 2 μm to 30 μm. By providing the cover layer 102, it is possible to prevent mechanical damage, etc., from occurring to the resistor 20. Furthermore, by providing the cover layer 102, it is possible to protect the resistor 20 from moisture, etc.

[0056] [Dummy wiring 80] The strain gauge 100 may also have dummy wiring 80 formed in the same manner as the electrode 30. The dummy wiring 80 has a first metal layer 81 and a second metal layer 82. The first metal layer 81 is formed together with the substrate 10 and the first metal layer 40. The second metal layer 82 is formed together with the second metal layer 50.

[0057] [Functions and Effects of the Strain Gauge 100 According to the First Embodiment] The strain gauge 100 according to the first embodiment includes a flexible substrate 10, a resistor 20 formed on the substrate 10, and an electrode 30 electrically connected to the resistor 20. The electrode 30 includes a first metal layer 40 made of the same material as the resistor 20, a second metal layer 50 formed on the first metal layer 40 and made of a material different from that of the first metal layer, and a breakage suppression portion 60 in which the first metal layer 40 and the second metal layer 50 are not formed. The breakage suppression portion 60 is formed along a part of an outer edge 50a of the second metal layer 50 in a plan view.

[0058] According to such a strain gauge 100, the breakage suppression portion 60 is formed along the outer edge 50a of the second metal layer 50, so that the substrate 10 is easily deformed, and stress concentration on the outer edge 50a of the second metal layer 50 can be alleviated. Stress concentration acting on the region of the second metal layer 50 adjacent to the breakage suppression portion 60 can be alleviated. Since the strain gauge 100 can alleviate stress concentration, breakage (damage) of the electrode 30, which is a conductor, can be suppressed. The strain gauge 100 can suppress the occurrence of cracks in the second metal layer 50. According to the strain gauge 100, it is possible to suppress the occurrence of cracks in the second metal layer 50, and it is possible to suppress a decrease in accuracy in strain detection. According to the strain gauge 100, it is possible to improve reliability.

[0059] In the strain gauge 100, at least a portion of the first metal layer 40 on the resistor 20 side is exposed from the second metal layer 50 in a plan view, the breakage suppression portion 60 is formed between the first metal layer 40 and the second metal layer 50 in a plan view, and the inner edge 40a of the first metal layer 40 forms the outer edge 60a of the breakage suppression portion 60. In the strain gauge 100, the outer edge 60a of the breakage suppression portion 60 is formed by the inner edge 40a of the first metal layer 40. Such a strain gauge 100 provides the same effects as those described above.

[0060] The breakage suppression portion 60 is formed in a linear shape in a plan view. Such a linear breakage suppression portion 60 can minimize the area of ​​the breakage suppression portion 60. Therefore, the effort required for processing the breakage suppression portion 60 can be minimized.

[0061] The strain gauge 100 further includes a cover layer 102 that covers at least a portion of the surfaces of the substrate 10, resistor 20, and electrodes 30. The strain gauge 100 having this configuration can suppress mechanical damage to the substrate 10, resistor 20, and electrodes 30 that are covered by the cover layer 102. The strain gauge 100 having this configuration can also protect the resistor 20 and electrodes 30 from moisture. As a result, the reliability of the strain gauge 100 can be improved.

[0062] In the strain gauge 100, the breakage suppression portion 60 is formed by removing a portion of the first metal layer 40 by laser processing. The breakage suppression portion 60 can be formed by irradiating a laser to remove the first metal layer 40. The laser light can remove only the first metal layer 40 from above the resin cover layer 102. As shown in the second embodiment, when the laser light is irradiated to the portion where the second metal layer 50 is formed on the first metal layer 40, the first metal layer 40 and the second metal layer 50 are removed. The laser light can pass through the resin cover 102 and remove the first metal layer 40 and the second metal layer covered by the resin cover 102. Since the laser light can remove only the metallic resistor 20, the resistor 20 can be irradiated with the laser light from above the resin cover layer 102.

[0063] In the strain gauge 100, the second metal layer 50 has an acute angle portion 51 that forms an acute angle in a plan view, and the fracture suppression portion 60 is formed along the outer edge 50a of the acute angle portion 51. With this type of strain gauge 100, by forming the fracture suppression portion 60 along the acute angle portion 51 where stress concentration is likely to occur, it is possible to alleviate stress concentration at the acute angle portion 51. With this type of strain gauge 100, it is possible to suppress the occurrence of cracks at the acute angle portion 51.

[0064] Moreover, in the strain gauge 100, the breakage suppression portion 60 is formed between the resistor 20 and the second metal layer 50 in a plan view. With such a strain gauge 100, the breakage suppression portion 60 is formed along the second metal layer 50 at a position close to the resistor 20. This makes it possible to reduce stress concentration in the second metal layer 50 at a position close to the resistor 20. With such a strain gauge 100, it is possible to suppress the occurrence of cracks in the second metal layer 50 at a position close to the resistor 20.

[0065] In the strain gauge 100, the first metal layer 40 may contain chromium nitride, and the second metal layer 50 may contain copper. With such a strain gauge 100, by forming copper, which has better solder wettability than chromium nitride, on the chromium nitride, it is possible to prevent solder erosion and improve the solder wettability.

[0066] [Manufacturing method of strain gauge 100] Next, a method for manufacturing the strain gauge 100 according to this embodiment will be described. To manufacture the strain gauge 100, first, a base material 10 is prepared.

[0067] Next, a metal layer A is formed on the upper surface 11 of the substrate 10. Here, for convenience, it is referred to as metal layer A. The metal layer A is a layer that is finally patterned to become the resistor 20, the first metal layer 40, and the first metal layer 81. The material and thickness of the metal layer A are the same as the material and thickness of the resistor 20 and the first metal layer 40 described above.

[0068] The metal layer A can be formed by, for example, magnetron sputtering using a target made of a raw material capable of forming the metal layer A. Instead of magnetron sputtering, the metal layer A may be formed by reactive sputtering, vapor deposition, arc ion plating, pulsed laser deposition, or the like. After the metal layer A is formed on the upper surface 11 of the substrate 10, the metal layer A is patterned by a well-known photolithography method into a planar shape similar to the resistor 20, the first metal layer 40, the first metal layer 81, and the like in FIG.

[0069] Alternatively, a base layer may be formed on the upper surface 11 of the substrate 10, and then the metal layer A may be formed. For example, a functional layer having a predetermined thickness may be vacuum-formed by conventional sputtering on the upper surface 11 of the substrate 10. By providing a base layer in this manner, the gauge characteristics of the strain gauge 100 can be stabilized.

[0070] In this specification, the functional layer refers to a layer having a function of promoting the crystal growth of at least the upper layer, the metal layer A (resistor 20). The functional layer preferably further has a function of preventing oxidation of the metal layer A due to oxygen or moisture contained in the substrate 10, and / or a function of improving adhesion between the substrate 10 and the metal layer A. The functional layer may further have other functions.

[0071] The insulating resin film constituting the substrate 10 may contain oxygen and moisture, and Cr may form a self-oxidized film. Therefore, particularly when the metal layer A contains Cr, it is preferable to form a functional layer having a function of preventing the oxidation of the metal layer A.

[0072] In this way, by providing a functional layer below the metal layer A, it is possible to promote crystal growth of the metal layer A, and to fabricate a metal layer A consisting of a stable crystal phase. As a result, the stability of the gauge characteristics of the strain gauge 100 is improved. In addition, the material constituting the functional layer diffuses into the metal layer A, thereby improving the gauge characteristics of the strain gauge 100.

[0073] Examples of materials for the functional layer include one or more metals selected from the group consisting of 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), and Al (aluminum), an alloy of any of the metals in this group, or a compound of any of the metals in this group.

[0074] The planar shape of the functional layer may be patterned to be substantially the same as the planar shapes of the substrate 10, the first metal layer 40, and the first metal layer 81 shown in FIG. 1. However, the planar shapes of the functional layer, the resistor 20, the first metal layer 40, and the first metal layer 81 may not be substantially the same. For example, when the functional layer is made of an insulating material, the functional layer may be patterned to a shape different from the planar shapes of the resistor 20, the first metal layer 40, and the first metal layer 81. In this case, the functional layer may be formed in a solid shape in the region where the resistor 20, the first metal layer 40, and the first metal layer 81 are formed, for example. Alternatively, the functional layer may be formed in a solid shape on the entire upper surface 11 of the substrate 10.

[0075] Next, a second metal layer 50 and a second metal layer 82 are formed on the upper surface of the metal layer A. Specifically, the second metal layer 50 is formed on the upper surface of the first metal layer 40, and the second metal layer 82 is formed on the upper surface of the first metal layer 81. The second metal layer 50 and the second metal layer 82 can be formed by, for example, a semi-additive method.

[0076] Next, the breakage suppression portion 60 is formed. As shown in Fig. 2 and Fig. 3, the breakage suppression portion 60 can be formed by irradiating a laser along the outer edge 50a of the second metal layer 50. For example, the breakage suppression portion 60 can be formed by irradiating a laser onto the surface of a portion of the first metal layer 40 adjacent to the second metal layer 50 to remove the first metal layer 40.

[0077] Thereafter, a cover layer 102 is provided on the upper surface 11 of the substrate 10 as necessary. The cover layer 102 is formed so as to cover the resistor 20, the electrode 30, and the dummy wiring 80. The cover layer 102 is formed so as to expose a part of the second metal layer 50. The cover layer 102 can be produced, for example, by laminating a semi-cured thermosetting insulating resin film on the upper surface 11 of the substrate 10 so as to expose a part of the second metal layer 50, and then heating and curing the film. The cover layer 102 may also be produced by applying a liquid or paste-like thermosetting insulating resin to the upper surface 11 of the substrate 10, and then heating and curing the resin. The opening 102a that exposes a part of the second metal layer 50 of the electrode 30 can be formed, for example, by a photolithography method.

[0078] When the cover layer 102 is formed, after the cover layer 102 is formed, a laser is irradiated from above the cover layer 102 to remove the first metal layer 40 .

[0079] [Carbide layer 70 of strain gauge 100 according to the first embodiment] Next, the carbonized layer 70 of the strain gauge 100 according to the first embodiment will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view illustrating a cross section of the strain gauge 100 according to the first embodiment. As shown in Fig. 10, the carbonized layer 70 is formed on the surface of the breakage suppression section 60. The carbonized layer 70 may be continuous along the longitudinal direction of the breakage suppression section 60.

[0080] The surface of the breakage suppression portion 60F is the surface after the first metal layer 40 has been removed. The carbonized layer 70 is formed, for example, after irradiation with a laser. The carbonized layer 70 is a layer in which the resin constituting the base material 10 has been carbonized by the thermal energy of the laser light. The carbonized layer 70 is formed in a shallow region on the upper surface 11 side of the base material 10. The carbonized layer 70 is visually recognized as being, for example, a dark color (black, brown, etc.). The cavity C in contact with the carbonized layer 70 is a portion in which the first metal layer 40 and the second metal layer 50 are absent. In the Z-axis direction, the cavity C is formed between the carbonized layer 70 and the cover layer 102.

[0081] Fig. 11 is a cross-sectional view illustrating a cross section of the strain gauge 101 before the breakage suppression portion 60 is formed. In Fig. 11, an area B1 to be irradiated with a laser is indicated by a dashed line. In the area B1, the first metal layer 40 is formed, but the second metal layer 50 is not formed. By irradiating the area B1 with a laser, the first metal layer 40 in the area B1 is removed, and a cavity C as shown in Fig. 10 is formed. This cavity C is the breakage suppression portion 60.

[0082] 10, the breakage suppression portion 60 is formed in an area defined by the carbonized layer 70, the cover layer 102, and the first metal layer 40. The inner edge 40a of the first metal layer 60 forms the outer edge 60a of the breakage suppression portion 60. The inner edge 40a is an edge within the first metal layer 40 that is formed after the laser is irradiated.

[0083] [Strain gauge 100B according to the second embodiment] Next, a strain gauge 100B according to a second embodiment will be described with reference to Fig. 4. Fig. 4 is a plan view illustrating an enlarged view of a main part of the strain gauge 100B according to the second embodiment. The strain gauge 100B according to the second embodiment shown in Fig. 4 differs from the strain gauge 100 according to the first embodiment shown in Fig. 2 in that the position where the breakage suppression portion 60B is formed is different from the breakage suppression portion 60 in plan view. Note that in the description of the second embodiment, the same description as in the first embodiment may be omitted.

[0084] The breakage suppression portion 60B is formed at the acute angle portion 51 of the second metal layer 50. The breakage suppression portion 60B is formed along a part of the outer edge 50a of the second metal layer 50, and also along a part of the outer edge 50b before processing of the second metal layer 50. In a plan view, the breakage suppression portion 60 is formed inside the outer edge 50b before processing. In a plan view, the outer edge 50b is the boundary between the first metal layer 40 and the second metal layer 50 before processing of the breakage suppression portion 60B.

[0085] The strain gauge 100B according to the second embodiment has the same effect as the strain gauge 100. The laminated second metal layer 50 and first metal layer 40 are irradiated with a laser to remove the second metal layer 50 and the first metal layer 40, thereby forming the breakage suppression portion 60B. The breakage suppression portion 60B can be formed by removing the second metal layer 50 and the first metal layer 40 from the top. The cross section of the breakage suppression portion 60B is substantially the same as the cross section of the breakage suppression portion 60 shown in FIG. 3.

[0086] [Laser irradiation position and carbonized layer] Fig. 12 is a cross-sectional view illustrating a cross section of a strain gauge 100B according to the second embodiment. Fig. 12(a) is a cross-sectional view illustrating a cross section of a strain gauge 101B before a breakage prevention portion 60B is formed. Fig. 12(b) is a cross-sectional view illustrating a cross section of a strain gauge 100B after a laser is irradiated to form a breakage prevention portion 60B.

[0087] 12(a), the outer edge 50b before the laser irradiation is present at a position that is the boundary of the area B3. The first metal layer 40 and the second metal layer 50 are present within the area B3 to be irradiated with the laser. In the area B2, the cover layer 102 is formed on the second metal layer 50. The cover layer 102 includes a surface that contacts the outer edge 50b of the second metal layer 50 before the laser irradiation.

[0088] The laser is irradiated into the area B3 to form the breakage suppression portion 60B shown in Fig. 12(b). By irradiating the area B3 with the laser, the first metal layer 40 and the second metal layer 50 in the area B3 are removed. The breakage suppression portion 60B is a region where the first metal layer 40 and the second metal layer 50 have been removed.

[0089] After the laser is irradiated and the first metal layer 40 and the second metal layer 50 are removed, a carbonized layer 70 is formed on the substrate 10. The cavity C adjacent to the carbonized layer 70 is a portion where the first metal layer 40 and the second metal layer 50 are absent, and is a breakage suppression portion 60B.

[0090] As shown in FIG. 12(b), the breakage suppression portion 60B is formed in an area defined by the carbonized layer 70, the cover layer 102, the first metal layer 40, and the second metal layer 50. The inner edge 40a of the first metal layer 40 forms the outer edge 60a of the breakage suppression portion 60B. The inner edge 40a is an edge within the first metal layer 40 formed after the laser irradiation. The outer edge 50a of the second metal layer 50 includes the outer edge formed after the laser irradiation. The outer edge 60a of the breakage suppression portion 60B includes the inner edge 40a and the outer edge 50a formed after the laser irradiation.

[0091] [Strain gauge 100C according to the third embodiment] Next, a strain gauge 100C according to a third embodiment will be described with reference to Fig. 5. Fig. 5 is a plan view illustrating an enlarged view of a main part of the strain gauge 100C according to the third embodiment. The strain gauge 100C according to the third embodiment shown in Fig. 5 differs from the strain gauge 100 according to the first embodiment shown in Fig. 2 in that the position where the breakage suppression portion 60C is formed is different from the breakage suppression portion 60 in plan view. Note that in the description of the third embodiment, the same description as in the first and second embodiments may be omitted.

[0092] The breakage suppression portion 60C is formed at the acute angle portion 51 of the second metal layer 50. The breakage suppression portion 60C is formed along a part of the outer edge 50a of the second metal layer 50, and also along a part of the outer edge 50b before processing of the second metal layer 50. In a plan view, the breakage suppression portion 60C is formed on both sides of the outer edge 50b before processing. The breakage suppression portion 60C is formed on the outer side and the inner side of the outer edge 50b. In a plan view, the breakage suppression portion 60C is formed so as to straddle the outer edge 50b, which is the boundary before processing of the breakage suppression portion 60C.

[0093] The strain gauge 100C according to the third embodiment has the same effect as the above-mentioned strain gauge 100. The breakage suppression portion 60C can be formed by irradiating a laser along a part of the outer edge 50b that is the boundary between the first metal layer 40 and the second metal layer 50 to remove the first metal layer 40 and the second metal layer 50. The cross section of the breakage suppression portion 60B is substantially the same as the cross section of the breakage suppression portion 60 shown in FIG.

[0094] [Laser irradiation position and carbonized layer] Fig. 13 is a cross-sectional view illustrating a cross section of a strain gauge 100C according to a third embodiment. Fig. 13(a) is a cross-sectional view illustrating a cross section of a strain gauge 101C before a breakage prevention portion 60C is formed. Fig. 13(b) is a cross-sectional view illustrating a cross section of a strain gauge 100C after a laser is irradiated to form a breakage prevention portion 60C.

[0095] As shown in FIG. 13(a), the outer edge 50b before the laser irradiation exists within the range B2. Within the range B2 irradiated with the laser, there exists a region where the second metal layer 50 is not laminated on the first metal layer 40, and a region where the second metal layer 50 is laminated on the first metal layer 40. The outer side of the outer edge 50b of the second metal layer 50 is the region where the second metal layer 50 is not laminated, and the inner side of the outer edge 50b is the region where the second metal layer 50 is laminated on the first metal layer 40. The cover layer 102 is formed on the first metal layer 40 and the second metal layer 50. The cover layer 102 includes a surface that contacts the outer edge 50b of the second metal layer 50 before the laser irradiation.

[0096] The laser is irradiated into the area B2 to form the breakage suppression portion 60C shown in FIG. 13(b). By irradiating the area B2 with the laser, the first metal layer 40 and the second metal layer 50 in the area B2 are removed. In the area where the second metal layer 50 is laminated on the first metal layer 40, the first metal layer 40 and the second metal layer 50 are removed. The breakage suppression portion 60C is formed so as to straddle the outer edge 50b before processing. The breakage suppression portion 60C includes an area where only the first metal layer 40 is removed and an area where the first metal layer 40 and the second metal layer 50 are removed.

[0097] After the laser is irradiated and the first metal layer 40 and the second metal layer 50 are removed, a carbonized layer 70 is formed on the substrate 10. The cavity C adjacent to the carbonized layer 70 is a portion where the first metal layer 40 and the second metal layer 50 are absent, and is a breakage suppression portion 60C.

[0098] As shown in FIG. 13(b), the breakage suppression portion 60C is formed in an area defined by the carbonized layer 70, the cover layer 102, the first metal layer 40, and the second metal layer 50. The inner edge 40a of the first metal layer 60F forms the outer edge 60a of the breakage suppression portion 60C. The inner edge 40a is an edge within the first metal layer 40 formed after the laser irradiation. The outer edge 50a of the second metal layer 50 includes the outer edge formed after the laser irradiation. The outer edge 60a of the breakage suppression portion 60C includes the inner edge 40a and the outer edge 50a formed after the laser irradiation.

[0099] [Strain gauge 100D according to the fourth embodiment] Next, a strain gauge 100D according to a fourth embodiment will be described with reference to Figs. 6 and 7. Fig. 6 is a plan view illustrating the strain gauge 100D according to the fourth embodiment. Fig. 7 is a plan view illustrating an enlarged view of a main part in Fig. 6. The strain gauge 100D according to the fourth embodiment shown in Figs. 6 and 7 differs from the strain gauge 100 according to the first embodiment shown in Figs. 1 and 2 in that the arrangement of the second metal layer 50B of the electrode 30B is different from the second metal layer 50 of the electrode 30, and the arrangement of the breakage suppression portion 60D is different from the breakage suppression portion 60. In the description of the fourth embodiment, the same description as in the first to third embodiments may be omitted.

[0100] The strain gauge 100D includes an electrode 30B. The electrode 30B has a first metal layer 40 and a second metal layer 50B. The second metal layer 50B is formed to have a circular shape in a plan view.

[0101] In the strain gauge 100D, the breakage suppression portion 60D is formed along a part of the outer edge 50a of the second metal layer 50B. The breakage suppression portion 60D is formed in a curved shape. The breakage suppression portion 60D may be curved along an arc, for example. The breakage suppression portion 60D may be formed along a semicircle of the circular second metal layer 50B. In a plan view, the breakage suppression portion 60D is formed at a position closer to the resistor 20 with respect to the second metal layer 50B. The breakage suppression portion 60D may have a length equal to or less than half the circumference of the circle, or may have a length equal to or more than half the circumference. The breakage suppression portion 60D may be formed at a position farther from the resistor 20 with respect to the second metal layer 50B. In addition, the shape of the second metal layer 50B is not limited to a circle, and may be, for example, an ellipse.

[0102] The strain gauge 100D according to the fourth embodiment has the same effect as the strain gauge 100. The breakage suppression portion 60D can be formed by irradiating a laser along a part of the outer edge 50a that is the boundary between the first metal layer 40 and the second metal layer 50B and removing the first metal layer 40. The cross section of the breakage suppression portion 60B is substantially the same as the cross section of the breakage suppression portion 60 shown in FIG. 3. The breakage suppression portion 60D may be formed so as to straddle the outer edge 50a before processing, or may be formed inside the outer edge 50a before processing.

[0103] The radius of curvature of the breakage suppression portion 60D is larger than the radius of curvature of the breakage suppression portion 60. The breakage suppression portion 60D is formed at a position farther away from the resistor 20 than the breakage suppression portion 60. This can further reduce stress concentration in the second metal layer 50B. In the strain gauge 100D, the occurrence of cracks in the second metal layer 50B can be suppressed.

[0104] [Strain gauge 100E according to the fifth embodiment] Next, a strain gauge 100E according to a fifth embodiment will be described with reference to Figs. 8 and 9. Fig. 8 is a plan view illustrating the strain gauge 100E according to the fifth embodiment. Fig. 9 is a plan view illustrating an enlarged view of a main part in Fig. 8. The strain gauge 100E according to the fifth embodiment shown in Figs. 8 and 9 differs from the strain gauge 100 according to the first embodiment shown in Figs. 1 and 2 in that the arrangement of the electrode 30C is different from that of the electrode 30, and that the arrangement of the breakage suppression portion 60E is different from that of the breakage suppression portion 60. In the description of the fifth embodiment, the same description as that of the first to fourth embodiments may be omitted.

[0105] The strain gauge 100E includes an electrode 30C. The electrode 30C has a first metal layer 40C and a second metal layer 50C. The electrode 30C includes a first portion 30a and a second portion 30b. The first portion 30a is disposed closer to the resistor 20 than the second portion 30b. The second portion 30b is disposed farther from the resistor 20 than the first portion 30a. The first portion 30a and the second portion 30b are adjacent to each other in the X-axis direction.

[0106] As shown in FIG. 9, the outer edge 50a of the second metal layer 50C includes outer edges 50c to 50e. The outer edge 50c is a portion that extends linearly along the Y-axis direction. The outer edge 50d is a portion that curves from the end of the linear outer edge 50c that is closer to the resistor 20 and extends in the X-axis direction. The outer edge 50c includes a curved portion and a straight portion. The outer edge 50e is a portion that curves from the end of the linear outer edge 50c that is farther from the resistor 20 and extends in the X-axis direction. The outer edge 50e may include a curved portion and a straight portion.

[0107] In the strain gauge 100E, a breakage suppression portion 60E is formed along a part of the outer edges 50c-50e, which are a part of the outer edge 50a of the second metal layer 50. The breakage suppression portion 60E includes a straight portion and a curved portion. The breakage suppression portion 60E is disposed outside the outer edges 50c-50e in a plan view. The breakage suppression portion 60E may be disposed inside the outer edges 50c-50e before processing the breakage suppression portion 60E, or may be formed on both sides of the outer edges 50c-50e.

[0108] The breakage suppression portion 60E may include a portion disposed between the resistor 20 and the second metal layer 50 in a plan view. The breakage suppression portion 60E may be formed in the first portion 30a closer to the resistor 20, and may not be formed in the second portion 30b farther from the resistor 20. The breakage suppression portion 60E may be formed in the second portion 30b.

[0109] The strain gauge 100E according to the fifth embodiment has the same effect as the above-mentioned strain gauge 100. The breakage suppression portion 60E can be formed by irradiating a laser along a portion of the outer edges 50c-50e that are the boundary between the first metal layer 40C and the second metal layer 50C to remove the first metal layer 40. The cross section of the breakage suppression portion 60E is substantially the same as the cross section of the breakage suppression portion 60 shown in FIG.

[0110] It should be noted that the embodiments disclosed herein are illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.

[0111] In the above embodiment, the first metal layer 40 is removed from the breakage suppression portion 60 as shown in FIG. 3 , but as a reference embodiment, the first metal layer 40 may be thinly formed on the upper surface 11 of the substrate 10. The breakage suppression portion 60 may have a first metal layer 40 that is thinner than a portion adjacent to the breakage suppression portion 60.

[0112] Furthermore, the thickness of the base material 10 in the breakage suppression section 60 may be the same as or thinner than the portion adjacent to the breakage suppression section 60.

[0113] Moreover, the wall surfaces on both sides of the breakage suppression portion 60 may be surfaces along the Z-axis direction, or may be inclined surfaces inclined with respect to the Z-axis direction.

[0114] In the method for manufacturing the strain gauge 100, the step of forming the breakage suppression portion 60 may further include a step of forming the cover layer 102. The step of forming the breakage suppression portion 60 is performed after the step of forming the cover layer 102, and a laser is irradiated from above the cover layer 102 to remove at least the first metal layer 40. "Removing at least the first metal layer" may mean removing a portion where only the first metal layer 40 is formed, or may mean removing the first metal layer 40 and the second metal layer 50 in a portion where the second metal layer 50 is laminated on the first metal layer 40. [Explanation of symbols]

[0115] 100, 100B, 100C, 100D, 100E... strain gauge, 10... substrate, 20... resistor, 30, 30B, 30C... electrode, 40, 40C... first metal layer, 40a... inner edge of first metal layer, 50, 50B, 50C... second metal layer, 50a to 50e... outer edge of second metal layer, 51... acute angle portion, 60, 60B, 60C, 60D, 60E, 60F... fracture suppression portion, 70... carbonized layer, 102... cover layer, C... cavity, X... X-axis direction, Y... Y-axis direction, Z... Z-axis direction

Claims

1. A flexible substrate; A resistor formed on the substrate; an electrode electrically connected to the resistor; The electrode is a first metal layer made of the same material as the resistor; a second metal layer formed on the first metal layer and made of a material different from that of the first metal layer; a breakage suppression portion in which the first metal layer and the second metal layer are not formed, A strain gauge, wherein the breakage suppression portion is formed along an outer edge of a portion of the second metal layer in a plan view.

2. At least a portion of the first metal layer on the resistor side is exposed from the second metal layer in a plan view; The breakage suppression portion is formed between the first metal layer and the second metal layer in a plan view, The strain gauge of claim 1 , wherein an inner edge of the first metal layer forms an outer edge of the break restraint.

3. The strain gauge according to claim 1 , wherein the breakage prevention portion is formed in a linear shape in a plan view.

4. The strain gauge according to any one of claims 1 to 3, further comprising a cover layer covering the surfaces of the substrate, the resistor, and at least a portion of the electrodes.

5. The strain gauge according to any one of claims 1 to 4, wherein a carbonized layer is formed on a surface of the substrate in the breakage prevention portion.

6. The strain gauge according to claim 5 , wherein the breakage suppression portion is formed in an area defined by the carbonized layer, the cover layer, and the first metal layer.

7. The strain gauge according to claim 5 , wherein the breakage suppression portion is formed in an area defined by the carbonized layer, the cover layer, the first metal layer, and the second metal layer.

8. The strain gauge according to claim 1 , wherein the breakage suppression portion is formed between the resistor and the second metal layer in a plan view.

9. The strain gauge according to any one of claims 1 to 8, wherein the second metal layer is formed from a material having better solder wettability than the first metal layer.

10. the first metal layer comprises chromium nitride; The strain gauge according to any one of claims 1 to 9, wherein the second metal layer comprises copper.

11. the second metal layer has an acute angle portion that forms an acute angle in a plan view, The strain gauge according to any one of claims 1 to 10, wherein the breakage suppression portion is formed along an outer edge of the acute angle portion.

12. A method for manufacturing a strain gauge comprising a resistor formed on a flexible substrate and an electrode electrically connected to the resistor, the method comprising the steps of: forming the resistor and the electrodes, each made of a first metal layer, on the substrate; forming a second metal layer on the electrode, the second metal layer being made of a material different from the first metal layer; and forming a breakage suppression portion, in a plan view, along an outer edge of a portion of the second metal layer, where the first metal layer and the second metal layer are not formed.

13. The method for manufacturing a strain gauge according to claim 12 , wherein in the step of forming the breakage suppression portion, at least the first metal layer is removed by laser processing.

14. forming a cover layer that covers at least a portion of the surfaces of the substrate, the resistor, and the electrodes; 14. The method for manufacturing a strain gauge according to claim 12 or 13, wherein the step of forming the breakage suppression portion is performed after the step of forming the cover layer, and a laser is irradiated from above the cover layer to remove at least the first metal layer.

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