strain gauge

Abstract

To provide a strain gauge capable of increasing a resistance value of a resistor while suppressing an increase in an area of a base material.SOLUTION: Strain gauges (1, 1A, or 1B) each comprise a base material (10), an insulation layer (40) formed on the base material (10), and a resistor (30) formed so as to spirally surround the insulation layer (40).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a strain gauge. [Background technology]

[0002] Conventionally, strain gauges that are attached to an object to be measured have been known. For example, strain gauges are sometimes used as sensors that detect strain in materials or sensors that detect ambient temperature (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-221696 Summary of the Invention [Problem to be solved by the invention]

[0004] A strain gauge has a resistor on a substrate. It is preferable that the resistance value of this resistor is adjustable. For example, increasing the length of the resistor in a strain gauge can increase the resistance value. However, increasing the length of the resistor requires increasing the area of ​​the substrate on which the resistor is mounted. Therefore, when manufacturing a strain gauge with a high resistance value, the strain gauge tends to become larger.

[0005] The present invention has been made in view of the above points, and has as its object to increase the resistance value of a resistor in a strain gauge while suppressing an increase in the area of ​​the substrate. [Means for solving the problem]

[0006] A strain gauge according to an embodiment of the present disclosure includes a substrate, an insulating layer formed on the substrate, and a resistor formed so as to spirally surround the insulating layer. The resistor includes a plurality of first resistance portions and a plurality of second resistance portions, and the first resistance portions, the insulating layer, and the second resistance portions are laminated in this order on the base material, both ends of the first resistance portions are exposed from the insulating layer, and the first resistance portions are electrically connected to the second resistance portions at the ends without the insulating layer being interposed therebetween, thereby forming the resistor in the spiral shape. . [Effects of the Invention]

[0007] According to the disclosed technology, in a strain gauge, the resistance value of the resistor can be increased while suppressing an increase in the area of ​​the substrate. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view illustrating the strain gauge according to the first embodiment. [Figure 2] 1 is a cross-sectional view (part 1) illustrating a strain gauge according to a first embodiment. FIG. [Figure 3] FIG. 2 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view (part 3) illustrating the strain gauge according to the first embodiment. [Figure 5] FIG. 2 is a plan view illustrating a strain gauge according to a first modified example of the first embodiment. [Figure 6] FIG. 10 is a plan view illustrating a strain gauge according to a second modification of the first embodiment. [Figure 7] FIG. 7 is a diagram showing an example of adjustment of the strain gauge shown in FIG. 6. [Figure 8] FIG. 10 is a partially enlarged plan view (part 1) showing another example of the resistance adjusting region. [Figure 9] FIG. 10 is a partially enlarged plan view (part 2) showing another example of the resistance adjusting region. [Figure 10] FIG. 10 is a partially enlarged plan view (part 3) showing another example of the resistance adjusting region. [Figure 11] FIG. 10 is a partially enlarged plan view (part 4) showing another example of the resistance adjusting region. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the invention will be described with reference to the drawings. In each drawing, the same components may be assigned the same reference numerals. In addition, in the description of each drawing, the description of the same components as those already described may be omitted.

[0010] First Embodiment Fig. 1 is a plan view illustrating a strain gauge according to the first embodiment. Fig. 2 is a cross-sectional view (part 1) illustrating the strain gauge according to the first embodiment, showing a cross section along line A-A' in Fig. 1. Fig. 3 is a cross-sectional view (part 2) illustrating the strain gauge according to the first embodiment, showing a cross section along line B-B' in Fig. 1.

[0011] 1 to 3, the strain gauge 1 has a substrate 10, a resistor 30, an insulating layer 40, and electrodes 50. In the strain gauge 1 according to this embodiment, the resistor 30 is formed so as to spirally surround the insulating layer 40 formed on the substrate 10. First, each part constituting the strain gauge 1 will be described in detail.

[0012] In this embodiment, for convenience, the side of the strain gauge 1 on which the resistor 30 of the substrate 10 is provided is referred to as the "upper side," and the side on which the resistor 30 is not provided is referred to as the "lower side." The surface located on the upper side of each portion is referred to as the "upper surface," and the surface located on the lower side of each portion is referred to as the "lower surface." However, the strain gauge 1 can also be used upside down. The strain gauge 1 can also be positioned at any angle. A planar view refers to viewing an object in a normal direction from above to below the upper surface 10a of the substrate 10. A planar shape refers to the shape of the object when viewed in the normal direction.

[0013] The substrate 10 is a member that serves as a base layer for forming the resistor 30 and the like. The substrate 10 is flexible. A flexure element may be bonded to the lower surface of the substrate 10 via an adhesive layer or the like. The thickness of the substrate 10 is not particularly limited and may be determined appropriately depending on the intended use of the strain gauge 1, etc. For example, the thickness of the substrate 10 may be approximately 5 μm to 500 μm. From the standpoint of strain transmission from the surface of the flexure element to the sensing part and dimensional stability against environmental changes, the thickness of the substrate 10 is preferably within the range of 5 μm to 200 μm. From the standpoint of insulation, the thickness of the substrate 10 is preferably 10 μm or more.

[0014] 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, LCP (liquid crystal polymer) resin, polyolefin resin, etc. The film refers to a flexible member having a thickness of about 500 μm or less.

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

[0016] Materials other than resin for the substrate 10 include, for example, crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, and perovskite ceramics (CaTiO3, BaTiO3). In addition to the crystalline materials described above, amorphous glass or the like may also be used as the material for the substrate 10. Metals such as aluminum, aluminum alloys (duralumin), and titanium may also be used as the material for the substrate 10. When a metal is used, an insulating film is provided on the metallic substrate 10.

[0017] The resistor 30 is a thin film formed in a predetermined pattern on the upper side of the substrate 10. In the strain gauge 1, the resistor 30 is a sensing part that receives strain and generates a resistance change. For convenience, the resistor 30 is shown in FIG. 1 with a matte finish. The detailed structure of the resistor 30 will be described later.

[0018] 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 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).

[0019] Here, the Cr mixed phase film is a film in which Cr, CrN, Cr2N, etc. are mixed together. The Cr mixed phase film may contain inevitable impurities such as chromium oxide.

[0020] The thickness of the resistor 30 is not particularly limited and may be determined appropriately depending on the intended use of the strain gauge 1, etc. For example, the thickness of the resistor 30 may be approximately 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 crystals constituting the resistor 30 (for example, the crystallinity of α-Cr) is improved. Furthermore, when the thickness of the resistor 30 is 1 μm or less, (i) cracks in the film and (ii) warping of the film from the substrate 10 caused by internal stress of the film constituting the resistor 30 are reduced.

[0021] Considering the need to reduce lateral sensitivity and to prevent disconnection, the width of resistor 30 is preferably 10 μm to 100 μm. Furthermore, the width of resistor 30 is preferably 10 μm to 70 μm, and more preferably 10 μm to 50 μm. In resistor 30, the width of first resistive portion 31 and the width of second resistive portion 32, which will be described later, may be the same or different.

[0022] For example, when the resistor 30 is a Cr mixed-phase film, the stability of the gauge characteristics can be improved by using α-Cr (alpha chromium), which has a stable crystalline phase, as the main component. Furthermore, when the resistor 30 is a Cr mixed-phase film, the resistor 30 can have an α-Cr main component, thereby enabling the gauge factor of the strain gauge 1 to be 10 or more, and the temperature coefficient of gauge factor (TCS) and the temperature coefficient of resistance (TCR) to be within the range of −1000 ppm / °C to +1000 ppm / °C. Here, the term “main component” refers to a component that accounts for 50% by weight or more of the total material constituting the resistor. From the viewpoint of improving the gauge characteristics, the resistor 30 preferably contains 80% by weight or more of α-Cr. Furthermore, from the same viewpoint, the resistor 30 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).

[0023] Furthermore, when the resistor 30 is a Cr mixed phase film, the Cr mixed phase film preferably contains 20 wt % or less of CrN and Cr2N, which can suppress a decrease in the gauge factor of the strain gauge 1.

[0024] Furthermore, the ratio of CrN to Cr2N in the Cr mixed phase film is preferably 80 wt% or more but less than 90 wt% of the total weight of CrN and Cr2N. More preferably, the ratio is 90 wt% or more but less than 95 wt% of the total weight of CrN and Cr2N. Cr2N has semiconducting properties. Therefore, by setting the Cr2N ratio to 90 wt% or more but less than 95 wt%, the decrease in TCR (negative TCR) becomes even more pronounced. Furthermore, by setting the Cr2N ratio to 90 wt% or more but less than 95 wt%, the ceramicization of the resistor 30 can be reduced. Therefore, the resistor 30 is less susceptible to brittle fracture.

[0025] On the other hand, CrN also has the advantage of being chemically stable. By including more CrN in the Cr mixed-phase film, the possibility of unstable N occurring can be reduced, resulting in a stable strain gauge. Here, "unstable N" refers to trace amounts of N2 or atomic N that can exist within the Cr mixed-phase film. This unstable N can escape from the film depending on the external environment (e.g., high-temperature environment). When unstable N escapes from the film, the film stress of the Cr mixed-phase film can change.

[0026] The electrodes 50 are electrically connected to both ends of the resistor 30. In plan view, the electrodes 50 are formed in a generally rectangular shape, wider than the resistor 30. The electrodes 50 are a pair of electrodes for outputting changes in the resistance value of the resistor 30 caused by strain to the outside. Lead wires for external connection, for example, are joined to the electrodes 50. A low-resistance metal layer, such as copper, or a highly solderable metal layer, such as gold, may be laminated on the upper surface of the electrode 50. Although the resistor 30 and the electrodes 50 are denoted by different reference numerals for convenience, they can be integrally formed using the same material in the same process. Connections, which are wiring with a predetermined pattern, may be provided between both ends of the resistor 30 and each electrode 50. Hereinafter, for convenience, the electrode 50 located on side B in FIG. 1 will be referred to as the "starting electrode 50," and the electrode 50 located on side B' in FIG. 1 will be referred to as the "ending electrode 50." However, the starting and ending ends of the electrodes 50 may be reversed.

[0027] [Details of Resistor 30] The resistor 30 includes a plurality of first resistive portions 31 that form a lower layer and a plurality of second resistive portions 32 that form an upper layer, with an insulating layer 40 sandwiched between them. Each of the first resistive portions 31 is elongated and slender, and is arranged side by side on the substrate 10 at a predetermined interval, with its longitudinal direction directed in a first direction (the direction from arrow A to arrow A' in FIG. 1). The first resistive portions 31 are substantially parallel to each other. The first resistive portions 31 may be formed directly on the upper surface 10a of the substrate 10, or may be formed on the upper surface 10a of the substrate 10 via another layer. The longitudinal direction of each of the first resistive portions 31 corresponds to the grid direction (the direction from arrow A to arrow A' in FIG. 1), and the direction perpendicular to the grid direction corresponds to the grid width direction (the direction from arrow B to arrow B' in FIG. 1).

[0028] An insulating layer 40 is formed on the substrate 10, covering a portion of each first resistor portion 31 and exposing both ends. In other words, each first resistor portion 31 is covered by the insulating layer 40 except for both ends. The insulating layer 40 is an interlayer insulating layer that insulates the lower and upper layers of the resistor 30. The material of the insulating layer 40 can be appropriately selected from, for example, the resins exemplified as materials for the substrate 10. The thickness of the insulating layer 40 is not particularly limited as long as it is thick enough to insulate the lower and upper layers of the insulating layer 40. For example, the thickness of the insulating layer 40 can be 10 μm or more.

[0029] Each second resistor 32 includes a first portion 32a, two second portions 32b, and two third portions 32c. The first portion 32a is a portion of the second resistor 32 that is formed on the upper surface 40a of the insulating layer 40. The first portions 32a are arranged side by side at a predetermined interval with their longitudinal directions facing the second direction. Here, the "second direction" refers to a direction that is inclined with respect to the first direction (the direction from arrow A to arrow A' in FIG. 1). The first portions 32a are substantially parallel to each other. That is, the first portions 32a are inclined with respect to the first resistor 31.

[0030] Each second portion 32b is a portion of the second resistor portion 32 formed on a side surface of the insulating layer 40. Each third portion 32c is a portion of the second resistor portion 32 laminated on an end of the first resistor portion 31. One end of each second portion 32b is connected to the first portion 32a, and the other end is connected to the third portion 32c. In other words, the third portion 32c is electrically connected to the first portion 32a via the second portion 32b. Each third portion 32c is electrically connected to an end of the first resistor portion 31. However, one third portion 32c of the second resistor portion 32 that serves as the starting or ending end of the resistor 30 is laminated on a connection portion rather than an end of the first resistor portion 31, and is electrically connected to the connection portion. For example, in FIG. 1, the end of the resistor 30 is the second resistor portion 32. In this case, as shown in the figure, one third portion 32c of the terminal second resistor portion 32 is stacked on and conductive with the end portion of the first resistor portion 31, and the other third portion 32c is stacked on and conductive with the connection portion. The second resistor portion 32 may be formed directly on the upper surface 40a or the side surface of the insulating layer 40, or may be formed on the upper surface 40a or the side surface of the insulating layer 40 via another layer.

[0031] Each second resistor portion 32 may not include the third portion 32c. In this case, the first resistor portion 31 and the lower end of the second portion 32b of the second resistor portion 32 are directly connected. In this case, the second portion 32b of the second resistor portion 32 at the start or end of the resistor 30 is directly connected to the connecting portion. The second portion 32b does not have to be formed on the side surface of the insulating layer 40. For example, the second portion 32b may be a via wiring that penetrates the insulating layer 40 and connects the first portion 32a and the third portion 32c. Alternatively, the third portion 32c may not be provided, and the second portion 32b, which is a via wiring, may directly electrically connect the first portion 32a and the first resistor portion 31. In this case, the end of the first resistor portion 31 does not have to be exposed from the insulating layer 40.

[0032] As shown in FIGS. 1 to 4 , in a layer in which the first resistor sections 31 are formed, a certain first resistor section 31 is adjacent to at least one of the other first resistor sections 31. A certain second resistor section 32 connects adjacent first resistor sections 31 in series among the multiple first resistor sections 31. The connection relationship between the first resistor sections 31 and the second resistor sections 32 will be described below. In the following description, the first resistor section 31 located closest to the B side in FIG. 1 will be referred to as the “first first resistor section 31,” and the first resistor section 31 located next to the B side will be referred to as the “second first resistor section 31.” Similarly, the first resistor section 31 located n-th closest to the B side will be referred to as the “n-th first resistor section 31.” Furthermore, the second resistor section 32 located closest to the B side in FIG. 1 will be referred to as the “first second resistor section 32,” and the second resistor section 32 located next to the B side will be referred to as the “second second resistor section 32.” Similarly, the second resistor section 32 located n-th on the B side will be referred to as the "n-th second resistor section 32."

[0033] In the example of FIG. 1 , in the layer in which the first resistor portions 31 are formed, the first first resistor portion 31 is adjacent to the second first resistor portion 31. Furthermore, the second first resistor portion 31 is adjacent to the first first resistor portion 31 and the third first resistor portion 31. In the example of FIG. 1 , the starting electrode 50 and the end portion on the A side of the first first resistor portion 31 are connected via a connection portion. Furthermore, the end portion on the A' side of the first first resistor portion 31 and the end portion on the A side of the second first resistor portion 31 are connected in series by the first second resistor portion 32. Furthermore, the end portion on the A' side of the second first resistor portion 31 and the end portion on the A side of the third first resistor portion 31 are connected in series by the second second resistor portion 32.

[0034] Similar connections are repeated thereafter. Then, the sixth second resistor portion 32 in FIG. 1 (i.e., the terminal second resistor portion 32) is connected to the terminal electrode 50 via a connection portion. In this manner, in the strain gauge 1 according to this embodiment, the ends of adjacent first resistor portions 31 in the layer in which the first resistor portions 31 are formed are alternately connected by the second resistor portions 32. As a result, one spiral resistor 30 is formed between the two electrodes 50.

[0035] Thus, the strain gauge 1 has a substrate 10, an insulating layer 40 formed on the substrate 10, and a resistor 30 formed in a spiral shape by electrically connecting a portion located between the substrate 10 and the insulating layer 40 (in this embodiment, the first resistive portion 31) and a portion located on the opposite side of the insulating layer 40 from the substrate 10 (in this embodiment, the first portion 32a of the second resistive portion 32).

[0036] By forming the resistor 30 in a spiral shape, it is possible to increase the length of the resistor 30 without increasing the area of ​​the upper surface 10a of the substrate 10. As a result, the strain gauge 1 according to this embodiment can have a higher resistance value of the resistor 30 than a conventional strain gauge having a substrate of the same size. In other words, according to this embodiment, the resistance value of the resistor 30 can be increased while suppressing an increase in the area of ​​the substrate 10 of the strain gauge 1. Furthermore, by increasing the resistance value of the resistor 30, the range of choices for the resistance value of the resistor 30 at the design stage of the strain gauge 1 is expanded. Therefore, according to this embodiment, a strain gauge with a high degree of freedom in designing the resistance value at the manufacturing stage can be realized.

[0037] Two or more insulating layers may be laminated on the substrate. In this case, resistors are formed on the upper and / or lower sides of the multiple insulating layers, and by connecting them, the entire resistor is formed in a spiral shape. For example, assume that two insulating layers are laminated on the substrate. In this case, a second insulating layer is formed on the second resistor section, and a resistor (e.g., a third resistor section) is also formed on the second insulating layer. Then, by connecting the starting electrode to the first first resistor section to the first second resistor section to the first third resistor section to the second first resistor section to the second second resistor section to the second third resistor section, ..., the nth first resistor section to the nth second resistor section to the nth third resistor section to the n+1th first resistor section to the end electrode in series, the number of turns of the spiral can be increased even when using a substrate of the same size. This allows the resistor length to be longer in the strain gauge, thereby increasing the resistance value of the resistor.

[0038] The strain gauge 1 may be provided with a cover layer (insulating resin layer). The cover layer is provided on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the insulating layer 40 and expose the electrodes 50. Examples of materials for the cover layer include insulating resins such as PI resin, epoxy resin, PEEK resin, PEN resin, PET resin, PPS resin, and composite resins (e.g., silicone resin and polyolefin resin). The cover layer may contain a filler or a pigment. The thickness of the cover layer is not particularly limited and can be appropriately selected depending on the purpose. For example, the thickness of the cover layer may be approximately 2 μm to 30 μm. By providing the cover layer, mechanical damage to the resistor 30 can be suppressed. Furthermore, by providing the cover layer, the resistor 30 can be protected from moisture and the like.

[0039] [Strain gauge manufacturing method] The strain gauge 1 according to this embodiment is formed by laminating a plurality of first resistance portions 31, an insulating layer 40, and a plurality of second resistance portions in this order on a substrate 10. Note that another layer (such as a functional layer, which will be described later) may be formed between these layers of components. A method for manufacturing the strain gauge 1 will now be described. To manufacture the strain gauge 1, first, the substrate 10 is prepared, and a metal layer (for convenience, referred to as metal layer A) is formed on the upper surface 10a of the substrate 10. Metal layer A is a layer that will ultimately be patterned to become the first resistance portions 31 and electrodes 50. Therefore, the material and thickness of metal layer A are the same as those of the first resistance portions 31 and electrodes 50 described above.

[0040] 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.

[0041] Alternatively, a base layer may be formed on the upper surface 10a of the substrate 10 before the metal layer A is formed. For example, a functional layer having 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 manner, the gauge characteristics of the strain gauge 1 can be stabilized.

[0042] In the present application, the functional layer refers to a layer having the function of promoting the crystal growth of at least the upper layer, metal layer A (resistor 30). The functional layer preferably also has the function of preventing oxidation of metal layer A due to oxygen or moisture contained in substrate 10 and / or the function of improving adhesion between substrate 10 and metal layer A. The functional layer may also have other functions.

[0043] The insulating resin film constituting the substrate 10 may contain oxygen and moisture, and Cr may form a self-oxidized film. Therefore, when the metal layer A contains Cr, it is preferable to form a functional layer having a function of preventing oxidation of the metal layer A.

[0044] In this way, by providing a functional layer below the metal layer A, it is possible to promote crystal growth in the metal layer A, and to produce a metal layer A consisting of a stable crystalline phase. As a result, the stability of the gauge characteristics of the strain gauge 1 is improved. Furthermore, the material constituting the functional layer diffuses into the metal layer A, thereby improving the gauge characteristics of the strain gauge 1.

[0045] Next, the metal layer A is patterned by photolithography to form the first resistor portion 31 and the two electrodes 50 having the planar shape shown in Fig. 1. When the functional layer is provided, the planar shape of the strain gauge 1 may be the same as that shown in Fig. 1, for example.

[0046] After the first resistor portions 31 and the electrodes 50 are formed, the insulating layer 40 is formed on the substrate 10. At this time, the insulating layer 40 is formed so as to expose both end portions of each of the first resistor portions 31 and cover the entire surface other than the end portions. For example, the insulating layer 40 can be formed by laminating a semi-cured thermosetting insulating resin film on the upper surface 10a of the substrate 10 so as to expose both end portions of each of the first resistor portions 31 and cover the entire surface other than the end portions, and then heating and curing the insulating resin film.

[0047] Next, the second resistor 32 is formed, including a first portion 32a, two second portions 32b, and two third portions 32c. The second resistor 32 can be formed by the same method as the first resistor 31 and the electrode 50. As with the first resistor 31, a functional layer is preferably vacuum-deposited as a base layer for the second resistor 32. FIG. 4 is a cross-sectional view (part 3) illustrating a strain gauge according to the first embodiment. FIG. 4 shows the cross-sectional shape of the strain gauge 1 when a functional layer 20a is provided as a base layer for the first resistor 31 and the electrode 50, and a functional layer 20b is provided as a base layer for the first portion 32a of the second resistor 32.

[0048] The planar shape of the functional layer 20a may be patterned to be substantially the same as the planar shape of the first resistor portion 31, for example. The planar shape of the functional layer 20b may be patterned to be substantially the same as the planar shape of the second resistor portion 32, for example. However, the planar shapes of the functional layer 20a and the first resistor portion 31, and the planar shapes of the functional layer 20b and the second resistor portion 32 do not have to be substantially the same. For example, if the functional layer 20a is made of an insulating material, the functional layer 20a may be patterned to be different from the planar shape of the first resistor portion 31. In this case, the functional layer 20a may be formed in a solid shape in the region where the first resistor portion 31 is formed, for example. Alternatively, the functional layer 20a may be formed in a solid shape over the entire upper surface of the substrate 10. The same applies to the relationship between the functional layer 20b and the second resistor portion 32. Note that only one of the functional layers 20a and 20b may be provided.

[0049] The first portion 32a is formed on the upper surface 40a of the insulating layer 40. Each of the second portions 32b is formed on a side surface of the insulating layer 40, and one end is connected to the first portion 32a. Each of the third portions 32c is laminated on both ends of the first resistor portion 31 exposed from the insulating layer 40, and is connected to the other end of the second portion 32b. Each of the third portions 32c is electrically connected to the ends of the first resistor portion 31 exposed from the insulating layer 40 or to the connection portions.

[0050] After forming the second resistor portion 32, a cover layer may be formed on the upper surface 10a of the substrate 10. The cover layer covers the resistor 30 and the insulating layer 40, but the electrodes 50 may be exposed from the cover layer. For example, the cover layer can be formed by laminating a semi-cured thermosetting insulating resin film on the upper surface 10a of the substrate 10 so as to cover the resistor 30 and the insulating layer 40 and expose the electrodes 50, and then heating and curing the insulating resin film. Through the above steps, the strain gauge 1 is completed.

[0051] <Modification 1 of the First Embodiment> In the first modification of the first embodiment, an example is shown in which the width of at least a part of the second resistor portion 32 is different from the width of the first resistor portion 31. Note that in the first modification of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0052] Fig. 5 is a plan view illustrating a strain gauge according to Modification 1 of the first embodiment. Referring to Fig. 5, the strain gauge 1A differs from the strain gauge 1 shown in Fig. 1 in that the width (i.e., thickness) of the second resistance portion 32 is wider than the width of the first resistance portion 31.

[0053] As shown in FIG. 5 , the width of each second resistor portion 32 may be wider than the width of the first resistor portion 31. In the example of FIG. 5 , the width of each portion of each second resistor portion 32 is wider than the width of the first resistor portion 31. That is, the widths of the first portion 32a, the second portion 32b, and the third portion 32c are all wider than the width of the first resistor portion 31. Note that when the width of the third portion 32c is wider than the width of the first resistor portion 31, the third portion 32c may be formed to cover the upper surface and both side surfaces of the first resistor portion 31 exposed from the insulating layer 40. Furthermore, the width of a portion of the second resistor portion 32 may be different from the width of the first resistor portion 31. For example, the first resistor portion 31 and the second resistor portion 32 may be formed so that the width of the first portion 32a, which is the main portion having the largest area in the second resistor portion 32, is wider than the width of the first resistor portion 31.

[0054] In this way, the width of part or all of the second resistor portion 32 may be made wider than the width of the first resistor portion 31. Conversely, the width of part or all of the second resistor portion 32 may be made narrower than the width of the first resistor portion 31.

[0055] As shown in FIG. 5, when the width of each portion of the second resistor portion 32 is made wider than the width of the first resistor portion 31, the resistance value of the strain gauge 1A can be lowered compared to when the width of each portion is the same as the width of the first resistor portion 31. Furthermore, when the width of each portion of the second resistor portion 32 is made narrower than the width of the first resistor portion 31, the resistance value of the strain gauge 1A can be increased compared to when the width of each portion is the same as the width of the first resistor portion 31. Thus, by forming the resistor 30 in a spiral shape and further forming the first resistor portion 31 and the second resistor portion 32 with different widths, the range of resistance value options for the resistor 30 can be further widened during the design stage. This improves the design freedom of the strain gauge 1A.

[0056] <Modification 2 of the First Embodiment> In the second modification of the first embodiment, an example is shown in which the first portion 32a of the second resistor 32 has a resistance adjustment region. Note that in the second modification of the first embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0057] Fig. 6 is a plan view illustrating a strain gauge according to Modification 2 of the first embodiment. Referring to Fig. 6, strain gauge 1B differs from strain gauge 1 in Fig. 1 and strain gauge 1A in Fig. 5 in that a resistance adjustment region E is provided in first portion 32a of second resistance portion 32.

[0058] Like the strain gauges 1 and 1A, the strain gauge 1B also has the first resistor portions 31 arranged side by side at a predetermined interval on the substrate 10 with their longitudinal directions facing the first direction. However, unlike the strain gauges 1 and 1A, a resistance adjustment region E is provided in a part of the first portion 32a. When the resistance adjustment region E is provided, the shape and dimensions, such as width, of the first portion 32a are not particularly limited. For example, in the example of FIG. 6, the first portion 32a includes a portion extending in the first direction and a portion extending in a direction inclined with respect to the first direction. The resistance adjustment region E is provided in the portion extending in a direction inclined with respect to the first direction.

[0059] In the resistance adjustment region E, the first portion 32a has two patterns arranged approximately parallel to each other and connected in parallel. By cutting one of the parallel patterns in the resistance adjustment region E with a laser or the like, the resistance value of the resistor 30 can be increased. Therefore, by cutting the resistance adjustment region E after forming the strain gauge 1B, the resistance of the resistor 30 can be adjusted later to a higher value. Figure 7 is a diagram showing an example of adjustment of the strain gauge shown in Figure 6. In the example of Figure 7, one of the parallel patterns is cut in the two resistance adjustment regions E indicated by arrows C.

[0060] 6 and 7, a resistance adjustment region E is provided in each first portion 32a, allowing for fine-tuned resistance adjustment. However, it is not essential to provide a resistance adjustment region E in each first portion 32a, and it is sufficient to provide a resistance adjustment region E in one or more first portions 32a depending on the required specifications.

[0061] Furthermore, for example, when the second resistance portion 32 includes a portion that is parallel to the first resistance portion 31, as in the strain gauge 1B shown in Figures 6 and 7, the detection sensitivity of the first resistance portion 31 in the longitudinal direction can be improved.

[0062] 8 is a partially enlarged plan view (part 1) showing another example of the resistance adjustment region. As shown in FIG. 8, in the resistance adjustment region E, the first portion 32a may include three patterns arranged substantially parallel to each other and connected in parallel. Alternatively, in the resistance adjustment region E, the first portion 32a may include four or more patterns arranged substantially parallel to each other and connected in parallel. That is, the resistance adjustment region E may include two or more patterns connected in parallel. The more patterns connected in parallel, the more precisely the resistance value can be adjusted.

[0063] FIG. 9 is a partially enlarged plan view (part 2) showing another example of the resistance adjustment region. As in the example shown in FIG. 9, the resistance adjustment region E may be an area widened for resistance adjustment, rather than a branched pattern. The resistance value of the resistor 30 can be increased by removing a portion of the widened area using a laser or the like to reduce the area of ​​the conductor. For example, the resistance value of the resistor 30 can be adjusted to a higher value by removing the triangular area F shown by the dashed line in FIG. 9.

[0064] FIG. 10 is a partially enlarged plan view (part 3) showing another example of the resistance adjustment region. As shown in FIG. 10, the resistance adjustment region E may include a pattern formed by hollowing out a portion of the first portion 32a. In the example shown in FIG. 10, the first portion 32a has two patterns arranged substantially parallel to each other and connected in parallel. In this case, too, the resistance value of the resistor 30 can be adjusted to a higher value by cutting one of the parallel patterns with a laser or the like. Note that the parallel patterns may have different thicknesses. When the parallel patterns have different thicknesses, cutting the thicker one results in a larger change in resistance value. Therefore, in this case, the amount of change in resistance can be adjusted depending on which of the parallel patterns is cut.

[0065] FIG. 11 is a partially enlarged plan view (part 4) showing another example of the resistance adjustment region. As shown in FIG. 11, the resistance adjustment region E may include a pattern G1 that branches outward from a constant-width region of the first portion 32a to form a loop. In this case, the resistance value of the resistor 30 can be adjusted to a higher value by cutting the pattern G1 with a laser or the like. Because the pattern G1 is parallel to the first portion 32a, the change in the resistance value due to cutting the pattern G1 is small. In other words, cutting the pattern G1 allows for fine adjustment of the resistance value. The resistance value of the resistor 30 can also be adjusted to a higher value by cutting the unbranched pattern G2 with a laser or the like instead of the pattern G1. Furthermore, even if neither the pattern G1 nor the pattern G2 is cut, the presence of the pattern G1 increases the number of sensitive parts of the strain gauge 1B compared to a case where the pattern G1 is not cut (e.g., the strain gauge 1 shown in FIG. 1). The change in the resistance value is greater when the pattern G2 is cut than when the pattern G1 is cut. Therefore, when the strain gauge 1B has the resistance adjustment region E shown in FIG. 11, the amount of change in resistance can be adjusted depending on whether the pattern G1 or the pattern G2 is cut.

[0066] As described above, there are various patterns for adjusting the resistance value of the resistor 30 in the resistance adjustment region E, which can be appropriately selected or combined as needed. The shape, size, and number of the resistance adjustment region E may be appropriately determined depending on the application, such as when it is desired to more easily calculate the resistance value, when it is desired to perform resistance adjustment with greater accuracy, and / or when it is desired to more easily cut the resistance adjustment pattern.

[0067] As in the example of FIG. 9 of the second modified example of the first embodiment, for example, in the strain gauge 1 shown in FIG. 1 or the strain gauge 1A shown in FIG. 5, a part of the first portion 32a of the second resistance portion 32 may be made into a resistance adjustment region, and the resistance value of the resistor 30 may be adjusted to a higher value by cutting a part of the pattern of the resistance adjustment region with a laser or the like to reduce the area of ​​the conductor.

[0068] In this way, by providing the resistance adjustment region, it is possible to adjust the resistance value of the resistor 30 after forming the resistor 30. Therefore, it is possible to correct the variation in the resistance value of each strain gauge and obtain the desired resistance value.

[0069] The preferred embodiments and the like have been described in detail above. However, the strain gauge according to the present disclosure is not limited to the above-described embodiments and modifications. For example, the strain gauge 1A of Modification 1 may be provided with a resistance adjustment region E as in Modification 2. In this way, when implementing the present disclosure, various modifications and substitutions can be made without departing from the scope of the claims. [Explanation of symbols]

[0070] 1, 1A, 1B strain gauge, 10 substrate, 10a, 40a upper surface, 20a, 20b functional layer, 30 resistor, 31 first resistor portion, 32 second resistor portion, 32a first portion, 32b second portion, 32c third portion, 40 insulating layer, 50 electrode

Claims

1. A substrate; an insulating layer formed on the substrate; a resistor formed so as to spirally surround the insulating layer, the resistor includes a plurality of first resistor portions and a plurality of second resistor portions, a plurality of the first resistance portions, the insulating layer, and a plurality of the second resistance portions are stacked in this order on the base material; both ends of the plurality of first resistor portions are exposed from the insulating layer; a plurality of first resistance portions electrically connected to a plurality of second resistance portions at the end portions without an insulating layer therebetween, thereby forming the resistor in the spiral shape;

2. the plurality of first resistor portions are arranged side by side on the substrate; the plurality of second resistor portions include portions juxtaposed on the insulating layer; 2. The strain gauge according to claim 1, wherein the ends of adjacent first resistor portions among the plurality of first resistor portions are alternately connected by the second resistor portion to form the spiral resistor.

3. 3. The strain gauge according to claim 2, wherein the second resistor portion includes a first portion formed on the insulating layer and a second portion electrically connecting the first portion and the first resistor portion.

4. the second resistor portion further includes a third portion stacked on the end portion of the first resistor portion, The strain gauge according to claim 3 , wherein the third portion is electrically connected to the first portion via the second portion.

5. The first resistor portions are arranged side by side at predetermined intervals with their longitudinal directions directed in a first direction, 5. The strain gauge according to claim 3, wherein the first portions of each of the second resistors are arranged side by side at predetermined intervals with their longitudinal directions directed in a second direction inclined with respect to the first direction.

6. The first resistor portions are arranged side by side at predetermined intervals with their longitudinal directions directed in a first direction, 5. The strain gauge according to claim 3, wherein the first portion of at least one of the second resistors includes a portion extending in the first direction and a portion extending in a direction inclined relative to the first direction.

7. The strain gauge according to claim 3 , wherein the first portion of the second resistor has a resistance adjustment region.

8. The strain gauge according to claim 7 , wherein the resistance adjustment region includes two or more patterns connected in parallel.

9. 9. The strain gauge according to claim 2, wherein a width of at least a portion of the second resistor portion is different from a width of the first resistor portion.

10. The resistor is made of Cr, CrN, and Cr ２ The strain gauge according to claim 1 , which is formed from a film containing N.

Images