Strain gauge and strain sensor

Abstract

Provided is a strain gauge that has: a resin substrate, a resistor disposed on one side of the substrate, a first metal layer disposed on the other side of the substrate, and a first ceramic layer disposed on the side of the first metal layer opposite the substrate.

Description

Strain gauges, strain sensors

[0001] This invention relates to strain gauges and strain sensors.

[0002] A strain gauge is known that is attached to an object to be measured to detect its strain. The strain gauge includes a resistor that detects strain. The resistor is arranged on a resin substrate, for example (see, for example, Patent Document 1).

[0003] Japanese Patent Publication No. 2016-74934

[0004] Resin substrates are susceptible to dimensional changes due to moisture absorption and release, and these dimensional changes result in apparent strain. This apparent strain is superimposed on the strain of the object being measured, which should be detected by the resistor, becoming a noise component and thus reducing the accuracy of strain measurement. Therefore, improved moisture resistance is required in strain gauges to suppress the decrease in measurement accuracy.

[0005] This disclosure aims to improve the moisture resistance of strain gauges.

[0006] A strain gauge according to one embodiment of the present disclosure comprises a resin substrate, a resistor disposed on one side of the substrate, a first metal layer disposed on the other side of the substrate, and a first ceramic layer disposed on the side of the first metal layer opposite to the substrate.

[0007] According to this disclosure, the moisture resistance of strain gauges can be improved.

[0008] This is a plan view illustrating a strain gauge according to the first embodiment. This is a cross-sectional view (1) illustrating a strain gauge according to the first embodiment. This is a cross-sectional view (2) illustrating a strain gauge according to the first embodiment. This is a cross-sectional view illustrating a strain gauge according to the second embodiment. This is a cross-sectional view illustrating a strain gauge according to a modified example 1 of the second embodiment. This is a cross-sectional view illustrating a strain gauge according to the third embodiment. This is a cross-sectional view illustrating a strain gauge according to the fourth embodiment. This is a cross-sectional view illustrating a strain gauge according to the fifth embodiment. This is a cross-sectional view illustrating a strain gauge according to the sixth embodiment. This is a cross-sectional view illustrating a strain gauge according to the seventh embodiment.

[0009] The embodiments for carrying out the invention will be described below with reference to the drawings. In each drawing, the same components may be denoted by the same reference numeral. Also, in the description of each drawing, the description of components that have already been described may be omitted.

[0010] <First Embodiment> Figure 1 is a plan view illustrating a strain gauge according to the first embodiment. Figure 2 is a cross-sectional view (part 1) illustrating a strain gauge according to the first embodiment, showing a cross-section along the line A-A in Figure 1. In Figures 1 and 2 and subsequent drawings, a strain generating body 110 on which the strain gauge 1 is arranged is also shown as necessary.

[0011] Referring to Figures 1 and 2, the strain gauge 1 comprises a base material 10, a resistor 30, wiring 40, an electrode 50, a metal layer 61, a ceramic layer 62, and an adhesive layer 120. The adhesive layer 120 can be provided as needed. The strain gauge 1 is placed on the strain generating body 110. In this specification, a unit including one or more strain gauges 1 and a strain generating body 110 is also referred to as a "strain sensor". First, the parts constituting the strain gauge 1 will be described in detail.

[0012] In each embodiment, including this embodiment, for convenience, the side of the strain gauge that is in the same direction as the side on which the resistor 30 is provided when viewed from the base material 10 is referred to as the "upper side," and the side that is in the same direction as the side on which the resistor 30 is not provided when viewed from the base material 10 is referred to as the "lower side." For example, in the strain gauge 1 of Figure 1, the upper side is the positive Z-axis direction side, and the lower side is the negative Z-axis direction side. Also, the surface located above each part of the strain gauge according to each embodiment is referred to as the "upper surface," and the surface located below each part is referred to as the "lower surface." However, these definitions of upper and lower are for convenience only, and the strain gauge according to each embodiment can also be used upside down. Also, the strain gauge can be positioned at any angle. Furthermore, a plan view refers to viewing the object in the direction normal to the upper surface 10a of the base material 10 from the upper side to the lower side. And the planar shape refers to the shape of the object when viewed in the aforementioned normal direction.

[0013] The base material 10 is a component that serves as a base layer for forming the resistor 30, etc. In this specification, when it is stated that one component is "formed" on another component, unless otherwise specified, this includes both directly forming the other component on the component and indirectly forming it via other components. Similarly, when it is stated in this specification that another component is "placed" on a component, unless otherwise specified, this includes both directly placing the other component on the component and placing it via other components. The base material 10 is flexible. The thickness of the base material 10 is not particularly limited and may be appropriately determined according to the intended use of the strain gauge 1, etc. For example, the thickness of the base material 10 may be about 5 μm to 500 μm. However, from the viewpoint of strain transmission from the first main surface 110a of the strain generating body 110 to the resistor 30 which is the sensing part, and dimensional stability against environmental changes, the thickness of the base material 10 is preferably in the range of 5 μm to 200 μm. Furthermore, from the standpoint of insulation, it is preferable that the thickness of the substrate 10 be 10 μm or more.

[0014] The base material 10 is made of resin. The base material 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, LCP (liquid crystal polymer) resin, or polyolefin resin. The term "film" refers to a flexible material with a thickness of approximately 500 μm or less.

[0015] When the base material 10 is formed from an insulating resin film, the insulating resin film may contain fillers, impurities, etc. For example, the base material 10 may be formed from an insulating resin film containing fillers such as silica or alumina.

[0016] The resistor 30 is located on one side of the substrate 10. The resistor 30 is a thin film formed in a predetermined pattern. In the strain gauge 1, the resistor 30 is a sensitive part that receives strain and causes a change in resistance. The resistor 30 may be placed directly on the upper surface 10a of the substrate 10, or it may be placed on the upper surface 10a of the substrate 10 via another layer. In Figure 1, for convenience, the resistor 30 is shown with a dense, textured pattern.

[0017] The resistor 30 has a structure in which multiple elongated sections are arranged at predetermined intervals with their longitudinal directions aligned in the same direction (the direction of the A-A line in the example of Figure 1), and the ends of adjacent elongated sections are connected alternately, so that the whole structure is folded in a zigzag pattern. The longitudinal direction of the multiple elongated sections becomes the grid direction, and the direction perpendicular to the grid direction becomes the grid width direction (the direction perpendicular to the A-A line in the example of Figure 1).

[0018] The two elongated portions located on the outermost side in the grid width direction have one end in the longitudinal direction bent in the grid width direction, and each end 30e of the resistor 30 in the grid width direction １ and 30e ２ This forms the respective ends 30e of the resistor 30 in the grid width direction. １ and 30e ２ The resistor is electrically connected to the electrode 50 via the wiring 40. In other words, the wiring 40 is connected to each end 30e in the grid width direction of the resistor 30. １ and 30e ２ Each electrode 50 is electrically connected to it.

[0019] The resistor 30 can be formed from, for example, a material containing Cr (chromium), a material containing Ni (nickel), or a material containing both Cr and Ni. That is, the resistor 30 can be formed from a material containing at least one of Cr and Ni. An example of a material containing Cr is a Cr multiphase film. An example of a material containing Ni is Cu-Ni (copper nickel). An example of a material containing both Cr and Ni is Ni-Cr (nickel chromium).

[0020] Here, a Cr multiphase film is defined as a film of Cr, CrN, and Cr ２It is a film in which N etc. are in a mixed phase. The Cr mixed-phase film may contain inevitable impurities such as chromium oxide.

[0021] The thickness of the resistor 30 is not particularly limited and may be appropriately determined according to the purpose of use of the strain gauge 1 etc. For example, the thickness of the resistor 30 may be about 0.05 μm to 2 μm. In particular, when the thickness of the resistor 30 is 0.1 μm or more, the crystallinity of the crystal constituting the resistor 30 (for example, the crystallinity of α-Cr) is improved. Also, when the thickness of the resistor 30 is 1 μm or less, (i) cracks in the film and (ii) warpage from the film base material 10 due to internal stress of the film constituting the resistor 30 are reduced.

[0022] Considering making it difficult to generate transverse sensitivity and taking measures against disconnection, the width of the resistor 30 is preferably 10 μm or more and 100 μm or less. Further, the width of the resistor 30 is preferably 10 μm or more and 70 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0023] For example, when the resistor 3 is a Cr mixed-phase film, the stability of the gauge characteristics can be improved by making α-Cr (alpha chromium), which is a stable crystal phase, the main component. Also, for example, when the resistor 30 is a Cr mixed-phase film, by making the resistor 30 mainly composed of α-Cr, the gauge factor of the strain gauge 1 can be 10 or more, and the gauge factor temperature coefficient TCS and the resistance temperature coefficient TCR can be within the range of -1000 ppm / °C to +1000 ppm / °C. Here, "main component" means a component that occupies 50% by weight or more of all substances constituting the resistor. From the viewpoint of improving the gauge characteristics, it is preferable that the resistor 30 contains 80% by weight or more of α-Cr. Further, from the same viewpoint, it is more preferable that the resistor 30 contains 90% by weight or more of α-Cr. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0024] Also, when the resistor 30 is a Cr mixed-phase film, CrN and Cr contained in the Cr mixed-phase film ２ N is preferably 20% by weight or less. By CrN and Cr contained in the Cr mixed-phase film ２ N being 20% by weight or less, a decrease in the gauge factor of the strain gauge 1 can be suppressed.

[0025] Furthermore, CrN and Cr in Cr multiphase films ２ The ratio with N is CrN and Cr ２ For the total weight of N, Cr ２ It is preferable that the proportion of N be 80% by weight or more and less than 90% by weight. Furthermore, the ratio of CrN to Cr ２ For the total weight of N, Cr ２ It is more preferable that the proportion of N be between 90% and 95% by weight. ２ N has semiconductor properties. Therefore, as mentioned above, Cr ２ By setting the proportion of N to 90% by weight or more and less than 95% by weight, the decrease in TCR (negative TCR) becomes even more pronounced. Furthermore, the aforementioned Cr ２ By setting the proportion of N to 90% by weight or more and less than 95% by weight, the ceramicization of the resistor 30 can be reduced, making the resistor 30 less susceptible to brittle fracture.

[0026] On the other hand, CrN has the advantage of being chemically stable. By including more CrN in the Cr multiphase film, the possibility of unstable N being generated can be reduced, thus enabling the creation of a stable strain gauge. Here, "unstable N" refers to trace amounts of N that may be present in the Cr multiphase film. ２ Alternatively, it refers to atomic nitrogen. These unstable nitrogen atoms can escape from the membrane depending on the external environment (e.g., high temperature). When unstable nitrogen atoms escape from the membrane, the membrane stress of the Cr multiphase film can change.

[0027] In strain gauge 1, using a Cr multiphase film as the material for the resistor 30 makes it possible to achieve both high sensitivity and miniaturization. For example, while the output of a conventional strain gauge was about 0.04 mV / 2V, using a Cr multiphase film as the material for the resistor 30 makes it possible to obtain an output of 0.3 mV / 2V or higher. Furthermore, while the size (gauge length × gauge width) of a conventional strain gauge was about 3 mm × 3 mm, using a Cr multiphase film as the material for the resistor 30 makes it possible to miniaturize the size (gauge length × gauge width) to about 0.3 mm × 0.3 mm.

[0028] The wiring 40 is provided on the base material 10. The wiring 40 is electrically connected to the resistor 30 and the electrode 50. The wiring 40 is not limited to being linear and can be in any pattern. Also, the wiring 40 can have any width and any length. In Figure 1, for convenience, the wiring 40 is shown with a matte pattern that is less dense than the resistor 30. The wiring 40 may have a multilayer structure. For example, the wiring 40 can have a structure in which a metal layer made of a material with lower resistance than the lower layer is laminated on top of a lower metal layer.

[0029] The electrode 50 is provided on the substrate 10. The electrode 50 is electrically connected to the resistor 30 via the wiring 40. In a plan view, the electrode 50 is wider than the wiring 40 and is formed in a substantially rectangular shape. The electrode 50 is a pair of electrodes for outputting to the outside the change in the resistance value of the resistor 30 caused by strain. For example, lead wires for external connection are joined to the electrode 50. The electrode 50 may have a multilayer structure. For example, the electrode 50 can have a structure in which a metal layer made of a material with lower resistance than the lower layer and / or a metal layer made of a material with good solderability are laminated on top of a lower metal layer. For convenience, the resistor 30, wiring 40 and electrode 50 are given different reference numerals, but both can be formed integrally from the same material in the same process. In Figure 1, for convenience, the electrode 50 is shown with a textured pattern of the same density as the wiring 40.

[0030] The metal layer 61 can be placed on the other side of the base material 10. In the example shown in Figure 2, the metal layer 61 is placed on the lower surface 10b of the base material 10. The metal layer 61 is a protective layer that protects the base material 10 and the resistor 30, etc., placed on the base material 10. The metal layer 61 may be placed on a part of the lower surface 10b of the base material 10, but to enhance its protective effect, it is preferable to place it on the entire lower surface 10b of the base material 10.

[0031] Generally, resins have the property of absorbing and releasing moisture. Therefore, when detecting the strain of the strained body 110 in the strain gauge 1, if the base material 10 absorbs or releases moisture, the base material 10 expands and contracts, resulting in strain. The strain caused by the absorption or release of moisture by the base material 10 becomes a noise component with respect to the strain of the strained body 110 to be detected, thus reducing the measurement accuracy of the strain gauge 1.

[0032] In the strain gauge 1, by arranging the metal layer 61 on the lower surface 10b of the base material 10, it is possible to suppress the base material 10 from absorbing and releasing moisture from the lower surface 10b. Therefore, the moisture resistance of the strain gauge 1 can be improved. As a result, in the strain gauge 1, even in strain measurement in a high-humidity environment, the noise component caused by humidity is reduced, so that the strain of the strained body 110 can be accurately measured.

[0033] Also, electrical noise (such as noise caused by static electricity) superimposed on the resistor 30 reduces the measurement accuracy of the strain gauge 1. By arranging the metal layer 61 on the lower surface 10b of the base material 10, the electrical noise superimposed on the resistor 30 can be reduced. As a result, in the strain gauge 1, even in strain measurement in an environment with a lot of electrical noise, the electrical noise component is reduced, so that the strain of the strained body 110 can be accurately measured.

[0034] In particular, a highly sensitive strain gauge with a gauge factor of 10 or more using a Cr mixed-phase film is likely to generate noise components due to the influence of humidity, static electricity, etc., so the measurement accuracy of the strain gauge 1 is likely to decrease. Therefore, in the highly sensitive strain gauge 1 with a gauge factor of 10 or more using a Cr mixed-phase film, the effect of arranging the metal layer 61 is particularly remarkable.

[0035] In addition, by arranging the metal layer 61 on the lower surface 10b of the base material 10, effects such as preventing the charging of the base material 10 and equalizing the heat distribution of the strain gauge 1 can also be obtained.

[0036] Examples of materials for the metal layer 61 include alloys of any of the following metals: Cu, Ni, Al, Ag, Au, Pt, Pd, Sn, Cr, etc. A multilayer film formed by appropriately stacking any of these metals or alloys may be used as the metal layer 61. The same material as the resistor 30 (for example, a Cr multiphase film) may be used as the material for the metal layer 61.

[0037] The thickness of the metal layer 61 can be, for example, 0.001 μm or more and 5 μm or less. By setting the thickness of the metal layer 61 to 0.001 μm or more, sufficient moisture-proofing and noise reduction effects can be obtained. By setting the thickness of the metal layer 61 to 5 μm or less, the flexibility of the substrate 10 can be maintained, and as a result, a decrease in gauge modulus can be suppressed. Furthermore, by setting the thickness of the metal layer 61 to 5 μm or less, the metal layer 61 can be easily formed without cracking. For example, when an aluminum thin film is used as the metal layer 61, a metal layer 61 with a thickness of approximately 0.03 μm or more and 0.1 μm or less can be formed. Also, when a nickel thin film is used as the metal layer 61, a metal layer 61 with a thickness of approximately 0.002 μm or more and 3 μm or less can be realized. Furthermore, the elastic modulus of the metal layer 61 is, for example, approximately 50 GPa or more and 500 GPa or less.

[0038] The ceramic layer 62 can be positioned on the opposite side of the metal layer 61 from the base material 10. "Opposite side from the base material 10" means the side opposite to where the base material 10 is located. In the example shown in Figure 2, the ceramic layer 62 is positioned on the underside of the metal layer 61. The ceramic layer 62 is insulating. Together with the metal layer 61, the ceramic layer 62 forms a protective layer. While the ceramic layer 62 may be positioned on a portion of the underside of the metal layer 61, it is preferable to position it across the entire underside of the metal layer 61 to enhance its protective effect.

[0039] In strain gauge 1, by making the protective layer a laminated structure of a metal layer 61 and a ceramic layer 62, moisture absorption and release from the base material 10 from the lower surface 10b can be further suppressed compared to when the protective layer is composed of only a metal layer 61. Therefore, the moisture resistance of strain gauge 1 can be further improved. In addition, by using ceramics as the material laminated on the metal layer 61 and providing a ceramic layer 62, there is an advantage in that the heat resistance is improved compared to when a general resin or the like is laminated on the metal layer 61.

[0040] For example, the material for the ceramic layer 62 is SiO ２ , ZrO ２ (Including YSZ), Si, Si ２ N ３ Al ２ O ３ (Including sapphire), ZnO, perovskite ceramics (CaTiO) ３ , BaTiO ３ Examples include:

[0041] The thickness of the ceramic layer 62 can be, for example, 0.001 μm or more and 5 μm or less. By making the thickness of the ceramic layer 62 0.001 μm or more, a sufficient moisture-proof effect can be obtained. By making the thickness of the ceramic layer 62 5 μm or less, the flexibility of the substrate 10 can be maintained, and as a result, the decrease in gauge factor can be suppressed. For example, as the material of the ceramic layer 62, SiO ２ When using this method, a ceramic layer 62 with a thickness of approximately 0.01 μm to 0.5 μm can be realized. Furthermore, the elastic modulus of the ceramic layer 62 is, for example, approximately 50 GPa to 500 GPa.

[0042] The side of the ceramic layer 62 opposite to the substrate 10 can be bonded to the first main surface 110a of the strain-generating body 110 via the adhesive layer 120. In the example shown in Figure 2, the lower surface of the ceramic layer 62 is bonded to the first main surface 110a of the strain-generating body 110 via the adhesive layer 120.

[0043] The strain generating body 110 is a member that generates strain when subjected to a load. The strain generating body 110 is, for example, rectangular in shape in plan view. The outer peripheral region of the first main surface 110a of the strain generating body 110 is, for example, exposed in an annular shape on the outside of the base material 10 in plan view. As the material of the strain generating body 110, for example, SUS (stainless steel), copper, aluminum, etc. can be used. The strain generating body 110 can be formed, for example, by a press working method. Inorganic materials such as ceramics may also be used as the material of the strain generating body 110.

[0044] The adhesive layer 120 is not particularly limited as long as it is made of a material that has the function of bonding the first main surface 110a of the strain-generating body 110 to the lower surface of the ceramic layer 62. For example, the adhesive layer 120 may be a layer formed by using epoxy resin, modified epoxy resin, silicone resin, modified silicone resin, urethane resin, modified urethane resin, etc., to bond the ceramic layer 62 to the strain-generating body 110. Alternatively, the adhesive layer 120 may be a layer such as a bonding sheet used to bond the ceramic layer 62 to the strain-generating body 110. If the adhesive layer 120 is a bonding sheet layer, the adhesive layer 120 may include not only an adhesive but also an intermediate layer containing glass and / or resin, etc. The thickness of the adhesive layer 120 is not particularly limited. For example, the thickness of the adhesive layer 120 can be about 0.1 μm to 50 μm.

[0045] [Manufacturing Method of Strain Gauge 1] In the strain gauge 1 according to this embodiment, a resistor 30, wiring 40, and electrodes 50 are formed on the upper surface 10a of the base material 10. Another layer (such as a functional layer described later) may be formed between the upper surface 10a of the base material 10 and the layers of these components. A metal layer 61 and a ceramic layer 62 are formed on the lower surface 10b of the base material 10. If necessary, the lower surface of the ceramic layer 62 is bonded to the first main surface 110a of the strain generating body 110 by an adhesive layer 120.

[0046] The manufacturing method of the strain gauge 1 is described below. To manufacture the strain gauge 1, first, a 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. Metal layer A is the layer that will ultimately be patterned to become the resistor 30, wiring 40, and electrode 50. Therefore, the material and thickness of metal layer A are the same as those of the resistor 30, wiring 40, and electrode 50 described above.

[0047] Metal layer A can be deposited, for example, by a magnetron sputtering method targeting a raw material capable of forming metal layer A. Alternatively, metal layer A may be deposited using reactive sputtering, evaporation, arc ion plating, or pulsed laser deposition instead of magnetron sputtering.

[0048] Next, the metal layer 61 and the ceramic layer 62 are sequentially laminated on the lower surface 10b of the substrate 10. The metal layer 61 and the ceramic layer 62 can be formed, for example, by magnetron sputtering. Instead of magnetron sputtering, any of the above-mentioned film formation methods exemplified as methods for forming the metal layer A may be used to form the metal layer 61 and the ceramic layer 62.

[0049] Next, the metal layer A is patterned using a well-known photolithography method into a planar shape similar to the resistor 30, wiring 40, and electrode 50 in Figure 1. At this time, since the ceramic layer 62 is present beneath the metal layer 61, etching of the metal layer 61 by the etching solution used for patterning can be prevented. In other words, the ceramic layer 62 also functions as an etching barrier layer for the metal layer 61.

[0050] Alternatively, a base layer may be formed on the upper surface 10a of the substrate 10 before forming the metal layer A. For example, a functional layer of a predetermined thickness may be vacuum-deposited on the upper surface 10a of the substrate 10 by conventional sputtering. By providing a base layer in this way, the gauge characteristics of the strain gauge 1 can be stabilized.

[0051] In this application, the functional layer refers to a layer that has the function of promoting crystal growth of at least the upper metal layer A (resistor 30). Preferably, the functional layer further has the function of preventing oxidation of the metal layer A by oxygen or moisture contained in the substrate 10, and / or the function of improving the adhesion between the substrate 10 and the metal layer A. The functional layer may further have other functions.

[0052] The insulating resin film constituting the base material 10 may contain oxygen and moisture, and Cr may form an oxidized film. Therefore, especially when the metal layer A contains Cr, it is preferable to form a functional layer that has the function of preventing oxidation of the metal layer A.

[0053] In this way, by providing a functional layer beneath the metal layer A, crystal growth in the metal layer A can be promoted, and a metal layer A consisting of a stable crystalline phase can be produced. As a result, the stability of the gauge characteristics of the strain gauge 1 is improved. Furthermore, the diffusion of the material constituting the functional layer into the metal layer A improves the gauge characteristics of the strain gauge 1.

[0054] 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 these metals, or a compound of any of these metals.

[0055] Figure 3 is a cross-sectional view (part 2) illustrating a strain gauge according to the first embodiment. Figure 3 shows the cross-sectional shape of the strain gauge 1 when a functional layer 20 is provided as a base layer for the resistor 30, wiring 40, and electrode 50.

[0056] The planar shape of the functional layer 20 may be patterned to be substantially the same as the planar shapes of the resistor 30, wiring 40, and electrodes 50. However, the planar shapes of the functional layer 20 and the resistor 30, wiring 40, and electrodes 50 do not have to be substantially the same. For example, if the functional layer 20 is formed from an insulating material, the functional layer 20 may be patterned to be different from the planar shapes of the resistor 30, wiring 40, and electrodes 50. In this case, the functional layer 20 may be formed as a solid layer over the region where the resistor 30, wiring 40, and electrodes 50 are formed. Alternatively, the functional layer 20 may be formed as a solid layer over the entire upper surface of the substrate 10.

[0057] Through the above process, the strain gauge 1 is completed. If necessary, a strain sensor may be manufactured by bonding the lower surface of the ceramic layer 62 of one or more strain gauges 1 to the first main surface 110a of the strain generating body 110 with the adhesive layer 120.

[0058] <Second Embodiment> The second embodiment shows an example of a strain gauge in which the position of the protective layer differs from that of the first embodiment. In the second embodiment, the description of components identical to those described in the previously described embodiments may be omitted. Similarly, in each subsequent embodiment, the description of components identical to those described in the previously described embodiments will not be repeated.

[0059] Figure 4 is a cross-sectional view illustrating a strain gauge according to the second embodiment. Referring to Figure 4, the strain gauge 2 includes a base material 10, a resistor 30, wiring 40, an electrode 50, a metal layer 71, a ceramic layer 72, an adhesive layer 73, a metal layer 74, a resin layer 75, and an adhesive layer 120. The adhesive layers 73 and 120 can be provided as needed. Although the wiring 40 is not shown in Figure 4, it can be placed in the same position as in Figure 1. The same applies to the following figures.

[0060] In other words, strain gauge 2 has a structure in which the metal layer 61 and ceramic layer 62 are removed from strain gauge 1, and a metal layer 71, ceramic layer 72, adhesive layer 73, metal layer 74, and resin layer 75 are added. The other side of the base material 10 can be bonded to the first main surface 110a of the strain generating body 110, for example, via the adhesive layer 120. In the example of Figure 4, the lower surface 10b of the base material 10 is bonded to the first main surface 110a of the strain generating body 110 via the adhesive layer 120.

[0061] The metal layer 71 can be placed on one side of the base material 10. In the example shown in Figure 4, the metal layer 71 is placed on the upper surface 10a of the base material 10. That is, the metal layer 71 is placed on the upper side of the base material 10 when viewed from the entire strain gauge 2. The metal layer 71 is a protective layer that protects the base material 10 and the resistor 30 etc. placed on it. The metal layer 71 may be placed on a part of the upper surface 10a of the base material 10, but in order to enhance its effectiveness as a protective layer, it is preferable to place it on the entire upper surface 10a of the base material 10.

[0062] In strain gauge 2, by placing a metal layer 71 on the upper surface 10a of the base material 10, moisture absorption and release from the upper surface 10a of the base material 10 can be suppressed. Therefore, the moisture resistance of strain gauge 2 can be improved. As a result, even when measuring strain in a high-humidity environment, noise components caused by humidity are reduced in strain gauge 2, so the strain of the strain generating body 110 can be measured with high accuracy.

[0063] Furthermore, by placing the metal layer 71 on the upper surface 10a of the base material 10, electrical noise superimposed on the resistor 30 can be reduced. As a result, the strain gauge 2 can accurately measure the strain of the strain generating body 110 because the electrical noise component is reduced even when measuring strain in an environment with a lot of electrical noise.

[0064] In particular, highly sensitive strain gauges with a gauge factor of 10 or higher using a Cr multiphase film are prone to noise components being generated due to the effects of humidity and static electricity, which can easily reduce the measurement accuracy of the strain gauge 2. Therefore, the effect of placing a metal layer 71 is especially significant in highly sensitive strain gauges 2 with a gauge factor of 10 or higher using a Cr multiphase film.

[0065] Furthermore, by placing the metal layer 71 on the upper surface 10a of the base material 10, it is possible to prevent static charge buildup on the base material 10 and to equalize the heat distribution of the strain gauge 2.

[0066] The material of the metal layer 71 can be appropriately selected from the materials exemplified for the material of the metal layer 61. The thickness of the metal layer 71 can be within the same range as that of the metal layer 61. The elastic modulus of the metal layer 71 is also within the same range as that of the metal layer 61. The metal layer 71 can be formed using the various film formation methods exemplified for the metal layer 61. The material, thickness, elastic modulus, and other physical properties of the metal layer 61 and the metal layer 71 may be different or the same.

[0067] The ceramic layer 72 can be positioned on the opposite side of the metal layer 71 from the base material 10. That is, the ceramic layer 72 is positioned above the metal layer 71 when viewed from the entire strain gauge 2. In the example in Figure 4, the ceramic layer 72 is positioned on the upper surface of the metal layer 71. The ceramic layer 72 is insulating. The ceramic layer 72, together with the metal layer 71, constitutes a protective layer. The ceramic layer 72 may be positioned on a part of the upper surface of the metal layer 71, but to enhance its protective effect, it is preferable to position it on the entire upper surface of the metal layer 71.

[0068] The material of the ceramic layer 72 can be appropriately selected from the materials exemplified for the ceramic layer 62. The thickness of the ceramic layer 72 can be within the same range as that of the ceramic layer 62. The elastic modulus of the ceramic layer 72 is also within the same range as that of the ceramic layer 62. The ceramic layer 72 can be formed using the various film deposition methods exemplified for the ceramic layer 62. The material, thickness, elastic modulus, and other physical properties of the ceramic layer 62 and the ceramic layer 72 may be different or the same.

[0069] In strain gauge 2, by making the protective layer a laminated structure of a metal layer 71 and a ceramic layer 72, moisture absorption and release from the upper surface 10a of the base material 10 can be further suppressed compared to the case where the protective layer is composed of only a metal layer 71. Therefore, the moisture resistance of strain gauge 2 can be further improved. In addition, in strain gauge 2, by arranging an insulating ceramic layer 72 between the metal layer 71 and the resistor 30, wiring 40, and electrode 50, short circuits between the metal layer 71 and the resistor 30, wiring 40, and electrode 50 can be prevented.

[0070] The resistor 30, wiring 40, and electrode 50 can be positioned on the opposite side of the ceramic layer 72 from the base material 10. That is, the resistor 30, wiring 40, and electrode 50 are positioned on the upper side of the ceramic layer 72 when viewed from the entire strain gauge 2. In the example in Figure 4, the resistor 30, wiring 40, and electrode 50 are positioned on the upper surface of the ceramic layer 72. The aforementioned functional layer may be placed between the resistor 30, wiring 40, and electrode 50 of the strain gauge 2 and the ceramic layer 72.

[0071] The metal layer 74 is positioned on the opposite side of the ceramic layer 72 from the substrate 10 and can cover the resistor 30. In the example shown in Figure 4, the adhesive layer 73 is positioned on the upper surface of the ceramic layer 72, and the metal layer 74 is positioned on the upper surface of the adhesive layer 73. The metal layer 74 is bonded to the upper surface of the ceramic layer 72 by the adhesive layer 73 and indirectly covers the resistor 30, wiring 40, and electrode 50 via the adhesive layer 73. That is, the metal layer 74 is positioned above the ceramic layer 72 and the resistor 30 (and wiring 40) when viewed from the entire strain gauge 2 and covers at least the upper side of the resistor (and wiring 40). The material of the adhesive layer 73 can be appropriately selected from the materials exemplified as the material of the adhesive layer 120, as an insulating material.

[0072] The metal layer 74 is a protective layer that protects the substrate 10 and the resistor 30 placed thereon. The metal layer 74 may be placed together with the adhesive layer 73 on a part of the upper surface of the ceramic layer 72, but in order to enhance its protective effect, it is preferable to place it together with the adhesive layer 73 on the entire exposed portion of the upper surface of the ceramic layer 72 and the resistor 30.

[0073] The material of the metal layer 74 can be appropriately selected from the materials exemplified for the metal layer 61. The thickness of the metal layer 74 can be within the same range as that of the metal layers 61 and 71. The elastic modulus of the metal layer 71 is also within the same range as that of the metal layer 61. By arranging the metal layer 71 and the ceramic layer 72 on the upper surface 10a of the substrate 10, and further arranging the metal layer 74 that covers the resistor 30 via the adhesive layer 73, the moisture-proof effect and noise reduction effect can be further enhanced. Note that the materials, thickness, elastic modulus, and other physical properties of the metal layers 61 and 71 and the metal layer 74 may be different or the same.

[0074] The resin layer 75 can be positioned on the opposite side of the metal layer 74 from the base material 10. That is, the resin layer 75 is positioned above the metal layer 74 when viewed from the entire strain gauge 2. In the example in Figure 4, the resin layer 75 is positioned on the upper surface of the metal layer 74. The resin layer 75 can prevent corrosion and scratches of the metal layer 74. The resin layer 75 may be positioned on a part of the upper surface of the metal layer 74, but to enhance the protective effect of the metal layer 74, it is preferable to position it on the entire upper surface of the metal layer 74.

[0075] Examples of materials for the resin layer 75 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 thickness of the resin layer 75 can be, for example, about 2 μm to 50 μm. The material of the resin layer 75 may be the same as or different from the material of the base material 10.

[0076] To arrange the adhesive layer 73, the metal layer 74, and the resin layer 75, for example, a film is prepared in which the resin layer 75 is laminated on one side of the metal layer 74 and the adhesive layer 73 is laminated on the other side of the metal layer 74. Then, with the adhesive layer 73 facing the resistor 30, the wiring 40, and the electrode 50, the film is attached to the upper surface of the ceramic layer 72.

[0077] Alternatively, a film may be prepared in which a resin layer 75 is laminated on one side of a metal layer 74. In this case, an uncured adhesive, which will become an adhesive layer 73, is applied to the upper surface of the ceramic layer 72 so as to cover the resistor 30, wiring 40, and electrode 50. Then, with the metal layer 74 facing the adhesive, the film is placed on top of the adhesive, and the adhesive is cured to form the adhesive layer 73.

[0078] Alternatively, a first film may be prepared in which an adhesive layer 73 is laminated on one side of the metal layer 74, and a second film may be prepared in which an adhesive layer is laminated on one side of the resin layer 75. In this case, the first film is attached to the upper surface of the ceramic layer 72 with the adhesive layer 73 facing the resistor 30, wiring 40, and electrode 50. Furthermore, the second film is attached to the upper surface of the metal layer 74 with the adhesive layer facing the metal layer 74.

[0079] Furthermore, the adhesive layer 73, the metal layer 74, and the resin layer 75 are provided with openings 73x that expose at least a portion of the electrode 50. Lead wires are connected to the electrode 50 exposed within the openings 73x, for example, by solder.

[0080] Figure 5 is a cross-sectional view illustrating a strain gauge according to Modification 1 of the second embodiment. Referring to Figure 5, in strain gauge 2A, the adhesive layer 73, metal layer 74, and resin layer 75 extend from the upper surface 10a of the base material 10 to the side surface of the base material 10. The adhesive layer 73, metal layer 74, and resin layer 75 cover the respective side surfaces of the ceramic layer 72, metal layer 71, and base material 10. It is preferable that the adhesive layer 73, metal layer 74, and resin layer 75, which are positioned on the side surface of the base material 10, reach the first main surface 110a of the strain generating body 110. That is, it is preferable that there are no portions exposed from the laminated structure of the adhesive layer 73, metal layer 74, and resin layer 75 on the respective side surfaces of the ceramic layer 72, metal layer 71, and base material 10.

[0081] In this way, the metal layer 74 covers the upper surface 10a and side surfaces of the substrate 10 via the adhesive layer 73, thereby suppressing moisture absorption and release from the upper surface 10a and side surfaces of the substrate 10, and thus the moisture resistance of the strain gauge 2A can be further improved compared to the strain gauge 2.

[0082] <Third Embodiment> The third embodiment shows an example of a strain gauge in which a protective layer is added compared to the first embodiment.

[0083] Figure 6 is a cross-sectional view illustrating a strain gauge according to the third embodiment. Referring to Figure 6, the strain gauge 3 is obtained by adding an adhesive layer 73, a metal layer 74, and a resin layer 75 similar to those of the strain gauge 2A shown in Figure 5 to the strain gauge 1 shown in Figure 2, etc.

[0084] The metal layer 74 is positioned on one side of the substrate 10 via the adhesive layer 73, and the resistor 30 can be covered via the adhesive layer 73. In the example shown in Figure 6, the adhesive layer 73, the metal layer 74, and the resin layer 75 cover the upper surface 10a of the substrate 10, and further extend from the upper surface 10a to the side surface of the substrate 10, covering the respective side surfaces of the substrate 10, the metal layer 61, and the ceramic layer 62.

[0085] In this way, the metal layer 74 covers the upper surface 10a and side surfaces of the substrate 10 via the adhesive layer 73, thereby suppressing moisture absorption and release from the upper surface 10a and side surfaces of the substrate 10, and thus further improving the moisture resistance of the strain gauge 3 compared to the strain gauge 1.

[0086] Furthermore, the strain gauge 3 may have a structure in which the side surface of the base material 10 is exposed from the metal layer 74, similar to the strain gauge 2 shown in Figure 4. That is, in the strain gauge 3, the metal layer 74 may be placed only on the upper surface 10a of the base material 10 via the adhesive layer 73. In this case, since the metal layer 74 covers the upper surface 10a of the base material 10 via the adhesive layer 73, moisture absorption and release from the upper surface 10a of the base material 10 can be suppressed, and the moisture resistance of the strain gauge 3 can be further improved compared to the strain gauge 1.

[0087] <Fourth Embodiment> The fourth embodiment shows another example of a strain gauge in which a protective layer is added compared to the first embodiment.

[0088] Figure 7 is a cross-sectional view illustrating a strain gauge according to the fourth embodiment. Referring to Figure 7, the strain gauge 4 is obtained by adding the metal layer 71 and ceramic layer 72 shown in Figure 4 as protective layers to the strain gauge 1 shown in Figure 2, etc. In other words, in addition to the configuration of the strain gauge 1, the strain gauge 4 has a metal layer 71 arranged on the side of the upper surface 10a of the base material 10, and a ceramic layer 72 arranged on the opposite side of the metal layer 71 from the base material 10. In the strain gauge 4, the resistor 30 is arranged on the opposite side of the ceramic layer 72 from the base material 10.

[0089] In this way, by covering the upper surface 10a of the substrate 10 with the metal layer 71 and the ceramic layer 72, moisture absorption and release from the upper surface 10a of the substrate 10 can be suppressed, thereby further improving the moisture resistance of the strain gauge 4 compared to the strain gauge 1.

[0090] <Fifth Embodiment> The fifth embodiment shows an example of a strain gauge in which an additional protective layer is added compared to the fourth embodiment.

[0091] Figure 8 is a cross-sectional view illustrating a strain gauge according to the fifth embodiment. Referring to Figure 8, the strain gauge 5 is obtained by adding an adhesive layer 73, a metal layer 74, and a resin layer 75 similar to those of the strain gauge 2A shown in Figure 5 to the strain gauge 4 shown in Figure 7. In other words, the strain gauge 5 is a combination of the configuration of the strain gauge 1 shown in Figure 2, etc., and the configuration of the strain gauge 2A shown in Figure 5. In the example of Figure 8, the adhesive layer 73, the metal layer 74, and the resin layer 75 cover the upper surface of the ceramic layer 72 and further extend from the upper surface 10a of the base material 10 to the side surface of the base material 10, covering the respective side surfaces of the ceramic layer 72, the metal layer 71, the base material 10, the metal layer 61, and the ceramic layer 62.

[0092] In this way, the metal layer 74 covers the upper surface 10a and side surfaces of the substrate 10 via the adhesive layer 73, thereby suppressing moisture absorption and release from the upper surface 10a and side surfaces of the substrate 10, and thus the moisture resistance of the strain gauge 5 can be further improved compared to the strain gauge 4.

[0093] Furthermore, the strain gauge 5 may have a structure in which the side surface of the base material 10 is exposed from the metal layer 74, similar to the strain gauge 2 shown in Figure 4. That is, in the strain gauge 5, the metal layer 74 may be placed only on the upper surface 10a of the base material 10 via the adhesive layer 73. In this case, since the metal layer 74 covers the upper surface 10a of the base material 10 via the adhesive layer 73, moisture absorption and release from the upper surface 10a of the base material 10 can be suppressed, and the moisture resistance of the strain gauge 5 can be further improved compared to the strain gauge 4.

[0094] <Sixth Embodiment> In the sixth embodiment, an example of a strain gauge is shown in which the metal layers 61 and 71 are not provided in the strain gauge 4 of the fourth embodiment.

[0095] Figure 9 is a cross-sectional view illustrating a strain gauge 6 according to the sixth embodiment. Referring to Figure 9, the strain gauge 6 has a configuration in which the metal layers 61 and 71 are removed from the strain gauge 4 shown in Figure 7. That is, the strain gauge 6 has a base material 10, a ceramic layer 72 (third ceramic layer) disposed on one side of the base material 10, a resistor 30 disposed on the opposite side of the ceramic layer 72 from the base material 10, and a ceramic layer 62 (fourth ceramic layer) disposed on the other side of the base material 10.

[0096] In this way, by covering both the upper and lower surfaces of the substrate 10 with ceramic layers 62 and 72, moisture absorption and release from the upper and lower surfaces of the substrate 10 can be suppressed, thereby improving the moisture resistance of the strain gauge.

[0097] Furthermore, the sides of the base material 10 may be covered with the ceramic layers 62 and / or 72. By covering the sides of the base material 10 with the ceramic layers 62 and / or 72, moisture absorption and release from the sides of the base material 10 can be suppressed, thereby further improving the moisture resistance of the strain gauge.

[0098] <Seventh Embodiment> The seventh embodiment shows an example of a strain gauge in which a protective layer is added to that of the sixth embodiment. However, the protective layer in this embodiment differs from the protective layer shown in the fifth embodiment and the like in that it has a ceramic layer and a resin layer.

[0099] Figure 10 is a cross-sectional view illustrating a strain gauge 7 according to the seventh embodiment. Referring to Figure 10, the strain gauge 7 is the strain gauge 6 shown in Figure 9 with the addition of an adhesive layer 73, a ceramic layer 76, and a resin layer 75. The adhesive layer 73 and the resin layer 75 may be made of the same materials and have the same configuration as the strain gauge 2A shown in Figure 5. The ceramic layer 76 (fifth ceramic layer) has the same configuration as the metal layer 74 shown in Figure 5, except that the material of the metal layer 74 is changed from metal to ceramic. The material of the ceramic layer 76 may be selected from the same materials as the ceramic layers 62 and 72. The thickness of the ceramic layer 76 can be within the same range as the ceramic layers 62 and 72. The elastic modulus of the ceramic layer 76 is also within the same range as the ceramic layers 62 and 72. The ceramic layer 76 can be arranged using the various film deposition methods exemplified for the ceramic layers 62 and 72. Furthermore, the materials, thickness, elastic modulus, and other physical properties of the ceramic layer 76, the ceramic layer 62, and the ceramic layer 72 may be different or the same.

[0100] The strain gauge 7, in addition to the configuration of the strain gauge 6, includes a ceramic layer 76 positioned on one side of the base material 10 and covering the resistor 30, and a resin layer 75 positioned on the opposite side of the ceramic layer 76 from the base material 10. The ceramic layer 76 extends from one side of the base material 10 to the side surface of the base material 10, covering the sides of the base material 10, the ceramic layer 62, and the ceramic layer 72.

[0101] Furthermore, the strain gauge 7 may have a configuration in which the metal layer 74 of the strain gauge 2 shown in Figure 4 is replaced with a ceramic layer 76, that is, a structure in which the side surface of the base material 10 is exposed from the ceramic layer 76. In other words, in the strain gauge 7, the ceramic layer 76 may be placed only on the upper surface 10a of the base material 10 via an adhesive layer 73. In this case, by covering the upper surface 10a of the base material 10 with the ceramic layer 76 via the adhesive layer 73, moisture absorption and release from the upper surface 10a of the base material 10 can be suppressed.

[0102] <Modification 1> The strain gauge according to this disclosure may be configured by removing the ceramic layer 62 or the ceramic layer 72 from the strain gauge 6 shown in the sixth embodiment or the strain gauge 7 shown in the seventh embodiment. That is, the ceramic layer may be placed on either one side or the other side of the base material 10. By placing the ceramic layer on either the upper or lower side of the base material 10 in this way, the number of layers of the strain gauge can be reduced compared to the case where ceramic layers are placed on both sides, while suppressing moisture absorption and release of the base material 10 to some extent. In other words, a strain gauge can be realized that balances the simplification of the manufacturing process with the effect of preventing moisture absorption and release.

[0103] <Modification 2> The protective layer (protective layer including the ceramic layer 76) shown in the seventh embodiment may be implemented in combination with the strain gauge 1 according to the first embodiment, rather than the strain gauge 6 according to the sixth embodiment. In this case as well, it is possible to suppress moisture absorption and release from the upper surface 10a of the substrate 10.

[0104] Furthermore, the strain gauge 7 may be a strain gauge obtained by adding the protective layer shown in Figure 4 or Figure 5 to the strain gauge 6 according to the sixth embodiment. When a metal layer 74 (fourth metal layer) is used, similar to the case of the ceramic layer 76, moisture absorption and release from the upper surface 10a of the substrate 10 can be suppressed. Alternatively, the strain gauge 7 may include both the metal layer 74 and the ceramic layer 76 as protective layers. In this case, the order in which the metal layer 74 and the ceramic layer 76 are laminated does not matter, as long as the resistor 30, wiring 40, and electrode 50 are insulated from the metal layer 74 and the ceramic layer 76 by means of an adhesive layer 73 or the like.

[0105] Although preferred embodiments have been described in detail above, the strain gauge according to the present invention is not limited to the embodiments described above, and can be realized by making various modifications and substitutions to the embodiments described above without departing from the scope of the claims.

[0106] This international application claims priority based on Japanese Patent Application No. 2024-197399, filed on 12 November 2024, and the entire contents of Japanese Patent Application No. 2024-197399 are incorporated herein by reference.

[0107] 1, 2, 2A, 3, 4, 5, 6, 7 Strain gauge, 10 Base material, 10a Top surface, 10b Bottom surface, 20 Functional layer, 30 Resistor, 40 Wiring, 50 Electrode, 61, 71, 74 Metal layer, 62, 72, 76 Ceramic layer, 73, 120 Adhesive layer, 75 Resin layer, 110 Strain generating body, 110a First main surface

Claims

1. A strain gauge comprising: a resin substrate; a resistor disposed on one side of the substrate; a first metal layer disposed on the other side of the substrate; and a first ceramic layer disposed on the side of the first metal layer opposite to the substrate.

2. The strain gauge according to claim 1, comprising: a second metal layer disposed on one side of the substrate and covering the resistor; and a resin layer disposed on the opposite side of the second metal layer from the substrate.

3. The strain gauge according to claim 2, wherein the second metal layer extends from one side of the substrate to the side surface of the substrate, covering each of the sides of the substrate, the first metal layer, and the first ceramic layer.

4. The strain gauge according to claim 1, comprising a third metal layer disposed on one side of the substrate and a second ceramic layer disposed on the opposite side of the third metal layer from the substrate, wherein the resistor is disposed on the opposite side of the second ceramic layer from the substrate.

5. The strain gauge according to claim 4, comprising: a second metal layer disposed on the opposite side of the second ceramic layer from the substrate and covering the resistor; and a resin layer disposed on the opposite side of the second metal layer from the substrate.

6. The strain gauge according to claim 5, wherein the second metal layer and the resin layer extend from one side of the substrate to the side surface of the substrate, covering each of the sides of the second ceramic layer, the third metal layer, the substrate, the first metal layer, and the first ceramic layer.

7. A strain gauge comprising a flexible substrate, a third ceramic layer disposed on one side of the substrate, and a resistor disposed on the opposite side of the third ceramic layer from the substrate.

8. The strain gauge according to claim 7, further comprising a fourth ceramic layer disposed on the other side of the base material.

9. A strain gauge comprising a flexible substrate, a resistor disposed on one side of the substrate, and a fourth ceramic layer disposed on the other side of the substrate.

10. The strain gauge according to claim 9, comprising a third ceramic layer disposed on one side of the substrate, wherein the resistor is disposed on the side of the third ceramic layer opposite to the substrate.

11. A strain gauge according to any one of claims 7 to 10, comprising: a fourth metal layer disposed on one side of the substrate and covering the resistor; and a resin layer disposed on the opposite side of the fourth metal layer from the substrate.

12. A strain gauge according to claim 8 or 10, comprising: a fourth metal layer disposed on one side of the substrate and covering the resistor; and a resin layer disposed on the opposite side of the fourth metal layer from the substrate, wherein the fourth metal layer extends from one side of the substrate to the side surface of the substrate and covers each of the sides of the substrate, the third ceramic layer, and the fourth ceramic layer.

13. A strain gauge according to any one of claims 1, 4, or 7 to 10, comprising: a fifth ceramic layer disposed on one side of the substrate and covering the resistor; and a resin layer disposed on the opposite side of the fifth ceramic layer from the substrate.

14. A strain gauge according to claim 8 or 10, comprising: a fifth ceramic layer disposed on one side of the substrate and covering the resistor; and a resin layer disposed on the opposite side of the fifth ceramic layer from the substrate, wherein the fifth ceramic layer extends from one side of the substrate to the side surface of the substrate and covers each of the sides of the substrate, the third ceramic layer, and the fourth ceramic layer.

15. A strain sensor comprising a strain gauge according to any one of claims 1 to 6, and a strain-generating body having a first main surface, wherein the surface of the first ceramic layer opposite to the substrate is bonded to the first main surface.

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