Strain gauge

Abstract

To suppress decrease in measurement precision in a strain gauge having a resistance adjustment part.SOLUTION: A strain gauge includes a base material, and a resistor formed on an upper surface of the base material. The resistor includes a sensing resistance part, a resistance adjustment part, a first connection part, and a second connection part. The sensing resistance part forms a predetermined repetition pattern including multiple thin and long parts placed side by side with a longitudinal direction in a first direction, and a folded part for connecting edges of adjacent thin and long parts from among the multiple thin and long parts while being staggered and for connecting the respective thin and long parts in series. The resistance adjustment part is connected in parallel with the sensing resistance part via the first connection part and the second connection part. The resistance adjustment part includes multiple trim resistors. The resistance adjustment part, the first connection part, and the second connection part are disposed in positions that differ from an area in which the predetermined repetition pattern is formed, and that pass a center of the area and do not cross a straight line that is parallel with the first direction on the upper surface.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, a strain gauge that is attached to a measurement object and used is known. On the base material of the strain gauge, for example, a resistor is formed in a predetermined pattern such as a zigzag shape. In addition, the strain gauge may be provided with a resistance adjustment unit that is a resistor for trimming. The resistance adjustment unit is arranged, for example, near the center of the strain gauge surrounded by the predetermined pattern (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the resistance adjustment unit tends to have a complicated pattern in design, and the resistance adjustment unit may receive strain in a different direction component or strain of a different magnitude from the resistor that functions as the original sensing unit. In this case, due to the presence of the resistance adjustment unit, noise will be included in the output value of the strain gauge. That is, when a resistance adjustment unit is provided, while the resistance adjustment becomes easy, there is a risk that the measurement accuracy of the strain gauge will decrease.

[0005] The present invention has been made in view of the above points, and an object thereof is to suppress a decrease in measurement accuracy in a strain gauge having a resistance adjustment unit.

Means for Solving the Problems

[0006] A strain gauge according to an embodiment of the present disclosure includes a base material, a resistor formed on an upper surface of the base material,First electrode and second electrode, The resistor comprises a sensitive resistance portion, a resistance adjustment portion, a first connection portion, and a second connection portion, the sensitive resistance portion forming a predetermined repeating pattern including a plurality of elongated portions arranged side by side with their longitudinal direction facing a first direction, and folded portions connecting the ends of adjacent elongated portions in an alternating manner to connect each of the elongated portions in series, the resistance adjustment portion being connected in parallel with the sensitive resistance portion via the first connection portion and the second connection portion, the resistance adjustment portion including a plurality of trim resistors, and the resistance adjustment portion, the first connection portion, and the second connection portion being positioned on the upper surface at a location different from the region where the predetermined repeating pattern is formed, and at a location that does not intersect a straight line passing through the center of the region and parallel to the first direction. The first electrode is electrically connected to one end of the sensitive resistance portion and positioned not to intersect the straight line, the second electrode is electrically connected to the other end of the sensitive resistance portion and positioned not to intersect the straight line, in a second direction perpendicular to the first direction, on the opposite side of the straight line from the region where the first electrode is located, and all of the resistance adjustment portion, the first connection portion, and the second connection portion are located on the same side with respect to the straight line as one of the first electrode and the second electrode in the second direction, and on the upper surface, all of the resistance adjustment portion is located on the opposite side of the region where the repeating pattern is formed from one of the first electrode and the second electrode, which is located on the same side with respect to the straight line, on the opposite side of the region where the repeating pattern is formed. . [Effects of the Invention]

[0007] According to the disclosed technology, a strain gauge having a resistance adjustment section can suppress a decrease in measurement accuracy. [Brief explanation of the drawing]

[0008] [Figure 1] This is a plan view illustrating a strain gauge according to the first embodiment. [Figure 2] This is a cross-sectional view (part 1) illustrating a strain gauge according to the first embodiment. [Figure 3] Figure 1 is a magnified view of the vicinity of the resistance adjustment section. [Figure 4] This is a partially enlarged view (part 1) showing a modified configuration of the connection position between the resistance adjustment section and the resistor. [Figure 5] This is a magnified view (part 2) showing a modified configuration of the connection position between the resistance adjustment section and the resistor. [Figure 6] This is a cross-sectional view (part 2) illustrating a strain gauge according to the first embodiment. [Figure 7] This is a plan view illustrating a strain gauge according to a modified example of the first embodiment. [Figure 8] Figure 7 is a magnified view of the vicinity of the resistance adjustment section shown in Figure 7. [Figure 9] Figure 8 is a partially enlarged view showing an example where the resistance adjustment section and θ1 are different. [Modes for carrying out the invention]

[0009] The embodiments for carrying out the invention will be described below with reference to the drawings. In each drawing, identical components may be denoted by the same reference numeral. In each drawing, mutually orthogonal X, Y, and Z directions may be defined. In this case, in the X direction, the starting point (root) of the arrow may be referred to as the X- side, and the ending point (arrowhead) of the arrow may be referred to as the X+ side. The same applies to the Y and Z directions. In addition, in the description of each drawing, the description of components that are the same as those already 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 line AA in Figure 1.

[0011] Referring to Figures 1 and 2, the strain gauge 1 comprises a base material 10, a first wiring 41, a second wiring 42, a first electrode 51, a second electrode 52, and a resistor 100. The resistor 100 includes a sensitive resistance section 30, a resistance adjustment section 60, a first connection section 71, and a second connection section 72. First, we will describe in detail each part that constitutes the strain gauge 1.

[0012] In this embodiment, for convenience, in the strain gauge 1, the side where the resistor 100 of the base material 10 is provided is referred to as the "upper side", and the side where the resistor 100 is not provided is referred to as the "lower side". Also, the surface located on the upper side of each part is referred to as the "upper surface", and the surface located on the lower side of each part is referred to as the "lower surface". However, the strain gauge 1 can also be used in an upside-down state. Also, the strain gauge 1 can be arranged at an arbitrary angle. Also, the plan view means viewing the object in the normal direction from the upper side to the lower side with respect to the upper surface 10a of the base material 10. And the planar shape refers to the shape of the object when viewed in the normal direction.

[0013] The base material 10 is a member serving as a base layer for forming the resistor 100 and the like. The base material 10 has flexibility. A strain generating body may be joined to the lower surface of the base material 10 via an adhesive layer or the like. The thickness of the base material 10 is not particularly limited and may be appropriately determined according to the use purpose of the strain gauge 1 and the like. For example, the thickness of the base material 10 may be about 5 μm to 500 μm. In view of the strain transmission from the surface of the strain generating body to the sensing part and the dimensional stability against environmental changes, the thickness of the base material 10 is preferably within the range of 5 μm to 200 μm. Also, from the viewpoint of insulation, the thickness of the base material 10 is preferably 10 μm or more.

[0014] The base material 10 is formed from an insulating resin film such as a PI (polyimide) resin, an epoxy resin, a PEEK (polyether ether ketone) resin, a PEN (polyethylene naphthalate) resin, a PET (polyethylene terephthalate) resin, a PPS (polyphenylene sulfide) resin, an LCP (liquid crystal polymer) resin, or a polyolefin resin. Note that a film refers to a member having a thickness of about 500 μm or less and having flexibility.

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

[0016] Examples of materials other than the resin of the base material 10 include crystalline materials such as SiO2, ZrO2 (including YSZ), Si, Si2N3, Al2O3 (including sapphire), ZnO, perovskite-based ceramics (CaTiO3, BaTiO3), etc. In addition to the aforementioned crystalline materials, amorphous glass or the like may also be used as the material of the base material 10. Further, metals such as aluminum, aluminum alloy (duralumin), and titanium may be used as the material of the base material 10. When using a metal, an insulating film is provided on the metal base material 10.

[0017] The resistor 100 is a thin film formed on the upper side of the base material 10. Among the resistor 100, the sensing resistance portion 30 is a sensing portion that receives the strain in the direction component to be detected in the strain gauge 1 and causes a resistance change. The sensing resistance portion 30 includes a plurality of elongated portions 31, a plurality of folded portions 32, a first wiring connection portion 33, and a second wiring connection portion 34. In the example of FIG. 1, 28 elongated portions 31 are provided. Also, 13 folded portions 32 are provided on the X- side of the elongated portions 31, and 14 folded portions 32 are provided on the X+ side of the elongated portions 31.

[0018] In the sensing resistance portion 30, the plurality of elongated portions 31 are juxtaposed with their longitudinal directions facing the first direction (the X direction in the example of FIG. 1). And the plurality of folded portions 32 connect the ends of the adjacent elongated portions 31 among the plurality of elongated portions 31 alternately to connect each elongated portion 31 in series. Thereby, the sensing resistance portion 30 forms a repeating pattern that folds back in a zigzag as a whole.

[0019] In the sensing resistance portion 30, the end portion on the X- side of the elongated portion 31 located on the most Y+ side is connected to the first wiring 41 via the first wiring connection portion 33. Also, the end portion on the X- side of the elongated portion 31 located on the most Y- side is connected to the second wiring 42 via the second wiring connection portion 34. The longitudinal direction of the plurality of elongated portions 31 is the grid direction (the X direction in the example of FIG. 1), and the direction perpendicular to the grid direction is the grid width direction (the Y direction in the example of FIG. 1).

[0020] The first wiring connection section 33 connects the elongated section 31 located at one end in the Y direction (closest to Y+) to the first wiring 41. The second wiring connection section 34 connects the elongated section 31 located at the other end in the Y direction (closest to Y-) to the second wiring 42.

[0021] The resistor 100 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 100 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).

[0022] Here, a Cr multiphase film is a film in which Cr, CrN, and Cr2N are mixed together. The Cr multiphase film may contain unavoidable impurities such as chromium oxide.

[0023] The thickness of the resistor 100 is not particularly limited and may be determined appropriately depending on the intended use of the strain gauge 1. For example, the thickness of the resistor 100 may be approximately 0.05 μm to 2 μm. In particular, when the thickness of the resistor 100 is 0.1 μm or more, the crystallinity of the crystal constituting the resistor 100 (for example, the crystallinity of α-Cr) is improved. Also, when the thickness of the resistor 100 is 1 μm or less, (i) cracks in the film and (ii) warping of the film from the substrate 10, caused by internal stress in the film constituting the resistor 100, are reduced.

[0024] Considering the need to minimize lateral sensitivity and prevent wire breakage, the width of the resistor 100 is preferably 10 μm or more and 100 μm or less. More specifically, the width of the resistor 100 is preferably 10 μm or more and 70 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0025] For example, if the resistor 100 is a Cr multiphase film, the stability of the gauge characteristics can be improved by making α-Cr (alpha-chromium), a stable crystalline phase, the main component. Also, for example, if the resistor 100 is a Cr multiphase film, by making α-Cr the main component of the resistor 100, the gauge factor of strain gauge 1 can be set to 10 or higher, and the gauge factor temperature coefficient TCS and resistance temperature coefficient TCR can be set within the range of -1000 ppm / ℃ to +1000 ppm / ℃. Here, "main component" means a component that accounts for 50% by weight or more of the total material constituting the resistor. From the viewpoint of improving gauge characteristics, it is preferable that the resistor 100 contains 80% by weight or more of α-Cr. Furthermore, from the same viewpoint, it is even more preferable that the resistor 100 contains 90% by weight or more of α-Cr. Note that α-Cr is Cr with a bcc structure (body-centered cubic lattice structure).

[0026] Furthermore, if the resistor 100 is a Cr multiphase film, it is preferable that the amount of CrN and Cr2N contained in the Cr multiphase film be 20% by weight or less. By having CrN and Cr2N contained in the Cr multiphase film be 20% by weight or less, the decrease in the gauge factor of the strain gauge 1 can be suppressed.

[0027] Furthermore, in the Cr multiphase film, it is preferable that the ratio of CrN to Cr2N is such that the proportion of Cr2N is 80% or more and less than 90% by weight relative to the total weight of CrN and Cr2N. More preferably, the ratio is such that the proportion of Cr2N is 90% or more and less than 95% by weight relative to the total weight of CrN and Cr2N. Cr2N has semiconducting properties. Therefore, by setting the proportion of Cr2N to 90% or more and less than 95% by weight as described above, the decrease in TCR (negative TCR) becomes even more pronounced. Moreover, by setting the proportion of Cr2N to 90% or more and less than 95% by weight as described above, the ceramicization of the resistor 100 is reduced, making brittle fracture of the resistor 100 less likely to occur.

[0028] On the other hand, CrN also has the advantage of being chemically stable. By including more CrN in the Cr multiphase film, the possibility of unstable nitrogen generation can be reduced, thus enabling the creation of a stable strain gauge. Here, "unstable nitrogen" refers to trace amounts of N2 or atomic nitrogen that may be present in the Cr multiphase film. These unstable nitrogen atoms may escape from the film depending on the external environment (e.g., high temperature environment). When unstable nitrogen atoms escape from the film, the film stress of the Cr multiphase film may change.

[0029] The first wiring 41 and the second wiring 42 are formed on the substrate 10. The first wiring 41 electrically connects the first wiring connection portion 33 of the sensing resistance portion 30 to the first electrode 51. The second wiring 42 electrically connects the second wiring connection portion 34 of the sensing resistance portion 30 to the second electrode 52. In the example shown in Figure 1, the width of the first wiring 41 is narrower on the side of the first wiring connection portion 33 and wider towards the side of the first electrode 51, but this is just an example, and for example, the width of the first wiring 41 may be constant. The same applies to the second wiring 42.

[0030] The first electrode 51 and the second electrode 52 are formed on the substrate 10. The first electrode 51 is electrically connected to one end of the sensitive resistance portion 30 via the first wiring 41. The second electrode 52 is electrically connected to the other end of the sensitive resistance portion 30 via the second wiring 42. In a plan view, the first electrode 51 and the second electrode 52 are wider than the sensitive resistance portion 30, the first wiring 41, and the second wiring 42, and are formed in a substantially rectangular shape. The first electrode 51 and the second electrode 52 are a pair of electrodes for outputting to the outside the change in the resistance value of the sensitive resistance portion 30 caused by strain. For example, lead wires for external connection are joined to the first electrode 51 and the second electrode 52. A metal layer with low resistance, such as copper, or a metal layer with good solderability, such as gold, may be laminated on the upper surfaces of the first electrode 51 and the second electrode 52.

[0031] Although the sensing resistance section 30, the first wiring 41, the second wiring 42, the first electrode 51, and the second electrode 52 are given different reference numerals for convenience, they can be integrally formed from the same material in the same process.

[0032] The resistance adjustment section 60, the first connection section 71, and the second connection section 72 are formed on the base material 10. The resistance adjustment section 60 is a conductor pattern for adjusting the resistance value of the sensitive resistance section 30. The resistance adjustment section 60 is electrically connected in parallel with the sensitive resistance section 30 via the first connection section 71 and the second connection section 72. The resistance adjustment section 60, the first connection section 71, and the second connection section 72 will be described in detail below with reference to Figure 3, in addition to Figures 1 and 2.

[0033] Figure 3 is a magnified view of the vicinity of the resistance adjustment section shown in Figure 1. As shown in Figure 3, the resistance adjustment section 60 includes grid resistors R1, R2, R3, R4, R5, and R6, and trim resistors Ra, Rb, Rc, Rd, and Re. The grid resistors R1 to R6 have different resistance values. Also, the trim resistors Ra to Re have different resistance values. Furthermore, the resistance adjustment section 60 includes a first connection section 71, a second connection section 72, and connection sections x1, x2, x3, x4, x5, x6, and x7 that connect two or more of the grid resistors and / or trim resistors. Thus, the resistance adjustment section 60 includes multiple grid resistors and multiple trim resistors. Note that the number of grid resistors and trim resistors in the resistance adjustment section 60, and the way in which the grid resistors and trim resistors are connected, are not limited to the example in Figure 3.

[0034] The first connection part 71 connects one folded portion 32 of the sensing resistance part 30 to the connecting portion x1. The grid resistor R1 connects connecting portion x1 to connecting portion x2. The grid resistor R2 connects connecting portion x2 to connecting portion x3. The grid resistor R3 connects connecting portion x3 to connecting portion x4. The grid resistor R4 connects connecting portion x4 to connecting portion x5. The grid resistor R5 connects connecting portion x5 to connecting portion x6. The grid resistor R6 connects connecting portion x6 to connecting portion x7. The second connection part 72 connects connecting portion x7 to the second wiring connection part 34 of the sensing resistance part 30. The trim resistor Ra connects connecting portion x1 to connecting portion x3. The trim resistor Rb connects connecting portion x2 to connecting portion x4. The trim resistor Rc connects connecting portion x3 to connecting portion x5. Trim resistor Rd connects connector x4 and connector x6. Trim resistor Re connects connector x5 and connector x7.

[0035] Specifically, the grid resistors R1 to R6 and the connecting parts x1 to x7 are connected in series between the first connection part 71 and the second connection part 72. The trim resistor Ra is connected in parallel to the series circuit including the adjacent grid resistors R1 and R2. The trim resistor Rb is connected in parallel to the series circuit including the adjacent grid resistors R2 and R3. The trim resistor Rc is connected in parallel to the series circuit including the adjacent grid resistors R3 and R4. The trim resistor Rd is connected in parallel to the series circuit including the adjacent grid resistors R4 and R5. The trim resistor Re is connected in parallel to the series circuit including the adjacent grid resistors R5 and R6.

[0036] By cutting the trim resistors Ra~Re using laser trimming or the like, the resistance value of the resistance adjustment unit 60 connected between the first connection part 71 and the second connection part 72 can be adjusted. In other words, since the resistance adjustment unit 60 is connected in parallel with the sensitive resistance unit 30, the resistance value of the sensitive resistance unit 30 connected between the first electrode 51 and the second electrode 52 can be adjusted.

[0037] There are 32 ways to disconnect the trim resistors: (1) none of the trim resistors Ra to Re are disconnected, (2) one of the trim resistors Ra to Re is disconnected, (3) two of the trim resistors Ra to Re are disconnected, (4) three of the trim resistors Ra to Re are disconnected, (5) four of the trim resistors Ra to Re are disconnected, or (6) all of the trim resistors Ra to Re are disconnected.

[0038] In Figure 1, the region S shown by the rectangular dashed line represents the region on the substrate 10 where the repeating pattern of the sensitive resistance portion 30 is formed. The straight line L0 shown by the dashed line represents a straight line that bisects region S in the grid width direction. That is, the straight line L0 passes through the center of region S and is parallel to the first direction (the X direction in the example of Figure 1), which is the longitudinal direction of the elongated portion 31. The resistance adjustment portion 60, the first connection portion 71, and the second connection portion 72 are located outside region S (i.e., in a position different from the repeating pattern of the sensitive resistance portion 30) and do not intersect the straight line L0.

[0039] Here, in Figure 3, the folded portion 32 located on the X-side of the elongated portion 31 that is closest to the Y-side will be referred to as the "first folded portion 32," and the folded portion 32 adjacent to the Y+ side of the first folded portion 32 will be referred to as the "second folded portion 32." Similarly thereafter, the nth folded portion 32 located on the Y+ side will be referred to as the "nth folded portion 32." In this example in Figure 3, the first connection portion 71 is connected to the second folded portion 32, and the second connection portion 72 is connected to the second wiring connection portion 34.

[0040] Thus, the first connection portion 71 may be connected to one of the folded portions 32 located on the X-side of the elongated portion 31, and the second connection portion 72 may be connected to the second wiring connection portion 34. Furthermore, the sensing resistance portion 30 may include one or more folded portions 32 on the side of the second connection portion 72 rather than the folded portion 32 connected to the first connection portion 71. For example, in Figure 3, the first connection portion 71 may be connected to the third folded portion 32 or the fourth folded portion 32.

[0041] A cover layer (insulating resin layer) may be provided on the strain gauge 1. The cover layer is provided on the upper surface 10a of the base material 10, for example, to cover the sensing resistance part 30, the first wiring 41, and the second wiring 42, while exposing the first electrode 51 and the second electrode 52. 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, polyolefin resin). The cover layer may also contain fillers and pigments. The thickness of the cover layer is not particularly limited and can be appropriately selected according to the purpose. For example, the thickness of the cover layer can be about 2 μm to 30 μm. By providing a cover layer, mechanical damage to the sensing resistance part 30, the first wiring 41, and the second wiring 42 can be suppressed. In addition, by providing a cover layer, the sensing resistance part 30, the first wiring 41, and the second wiring 42 can be protected from moisture, etc.

[0042] In the resistance adjustment section 60 of the strain gauge 1, the grid resistors R1 to R6 and trim resistors Ra to Re, which have different lengths, form a complex pattern. Therefore, the resistance adjustment section 60 is susceptible to strain in a different direction and of a different magnitude than the sensing resistance section 30, which has a simple repeating pattern. The strain experienced by the resistance adjustment section 60 also affects the resistance value output from the strain gauge 1. Therefore, the strain experienced by the resistance adjustment section 60 can become a noise component in relation to the strain experienced by the sensing resistance section 30. From the standpoint of the detection accuracy of the strain gauge 1, it is desirable that the resistance adjustment section 60 be designed to minimize resistance changes caused by strain with directional and / or magnitude components that could become noise.

[0043] It is desirable that the strain gauge 1 be attached to the strain generating body such that the center of region S approximately coincides with the position where the greatest strain occurs in the strain generating body, and the longitudinal direction of the elongated portion 31 is approximately parallel to the strain direction of the strain generating body. When the strain gauge 1 is attached to the strain generating body in this manner, the strain gauge 1 can receive the greatest strain at a position near the straight line L0 in Figure 1.

[0044] Therefore, in the strain gauge 1, the resistance adjustment unit 60 and the first and second connection units 71 and 72 that connect the resistance adjustment unit 60 to the sensing resistance unit 30 are positioned (i) outside the region S and (ii) not intersecting with the straight line L0 (i.e., the center line in the grid width direction of the sensing resistance unit 30). This arrangement allows the resistance adjustment unit 60 to be positioned away from the straight line L0, which is the location where the strain gauge 1 experiences the greatest strain. As a result, the strain gauge 1 can reduce the amount of strain detected by the resistance adjustment unit 60. In other words, the strain gauge 1 can suppress a decrease in strain measurement accuracy caused by the resistance adjustment unit 60. To further enhance the effect of suppressing the amount of strain detected by the resistance adjustment unit 60, it is preferable to position the resistance adjustment unit 60 as far away from the straight line L0 as possible in the Y direction.

[0045] Furthermore, the position of the resistance adjustment section 60 on the upper surface 10a of the strain gauge 1 may be as follows. For example, the position of the resistance adjustment section 60 in the X direction may be on the same side as the first electrode 51 and / or the second electrode 52 with respect to region S. Alternatively, for example, the position of the resistance adjustment section 60 in the X direction may be on the opposite side of region S from the first electrode 51 and / or the second electrode 52, as shown in the example in Figure 1. With the latter arrangement, the resistance adjustment section 60 can be positioned further away from the straight line L0 in the Y direction, thereby increasing the effect of suppressing the amount of strain detected by the resistance adjustment section 60. In addition, with this arrangement, when soldering lead wires etc. to the first electrode 51 and the second electrode 52, it is possible to suppress solder from adhering to the resistance adjustment section 60 and affecting the resistance value of the grid resistor.

[0046] Furthermore, in strain gauge 1, one resistance adjustment section 60 includes multiple trim resistors. This makes it easier to position the entire resistance adjustment section 60 away from the straight line L0 in the Y direction, compared to, for example, connecting one trim resistor between each of the adjacent folded sections 32.

[0047] Furthermore, the widths of the grid resistors R1 to R6 may be the same as or narrower than the width of the elongated portion 31 of the sensing resistance section 30, but they may also be wider than the width of the elongated portion 31 of the sensing resistance section 30. By making the width of one or more of the grid resistors R1 to R6 wider than the width of the elongated portion 31 of the sensing resistance section 30, the amount of strain detected by the resistance adjustment section 60 can be further suppressed. The widths of all grid resistors R1 to R6 may also be wider than the width of the elongated portion 31 of the sensing resistance section 30. This further suppresses the amount of strain detected by the resistance adjustment section 60.

[0048] In the example shown in Figure 3, the second connection part 72 was connected to the second wiring connection part 34, but as shown in Figure 4, the second connection part 72 may also be connected to the second wiring 42. Alternatively, the second connection part 72 may be connected to both the second wiring 42 and the second wiring connection part 34. In other words, the second connection part 72 may be connected to the second wiring connection part 34 and / or the second wiring 42. In these cases as well, the resistance adjustment unit 60 will be connected in parallel with the sensitive resistance unit 30 via the first connection part 71 and the second connection part 72.

[0049] Furthermore, as shown in Figure 5, the resistance adjustment unit 60 may be configured to be connected to a certain folded portion 32 via a first connection portion 71, and to a different folded portion 32 via a second connection portion 72. In other words, the first connection portion 71 and the second connection portion 72 may each be connected to different folded portions 32. In this case, the sensing resistance unit 30 may have one or more folded portions 32 sandwiched between the folded portion 32 to which the first connection portion 71 is connected and the folded portion 32 to which the second connection portion 72 is connected.

[0050] Furthermore, in Figure 1, the resistance adjustment section 60, the first connection section 71, and the second connection section 72 may be positioned on the Y+ side of the straight line L0. In this case, for example, the first connection section 71 may be connected to the first wiring connection section 33 and / or the first wiring 41, and the second connection section 72 may be connected to the 10th folded section 32, the 11th folded section 32, etc. Alternatively, the first connection section 71 and the second connection section 72 may be connected to two different folded sections 32 positioned on the Y+ side of the straight line L0. In this case, the sensing resistance section 30 may include one or more folded sections 32 between the two folded sections 32 connected to the first connection section 71 and the second connection section 72.

[0051] Furthermore, the first connection part 71 and the second connection part 72 may be connected to different positions in the X direction of the first wiring 41 on the Y+ side of the first wiring 41. Also, the first connection part 71 and the second connection part 72 may be connected to different positions in the X direction of the second wiring 42 on the Y- side of the second wiring 42. In these cases as well, the resistance adjustment part 60 will be connected in parallel with the sensitive resistance part 30 via the first connection part 71 and the second connection part 72.

[0052] [Method of manufacturing strain gauges] In the strain gauge 1 according to this embodiment, a sensing resistance section 30, a first wiring 41, a second wiring 42, a first electrode 51, a second electrode 52, a resistance adjustment section 60, a first connection section 71, and a second connection section 72 are formed on the base material 10. Note that another layer (such as a functional layer described later) may be formed between the base material 10 and the layers of these components.

[0053] 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 form the sensing resistance part 30, the first wiring 41, the second wiring 42, the first electrode 51, the second electrode 52, the resistance adjustment part 60, the first connection part 71, and the second connection part 72. Therefore, the material and thickness of metal layer A are the same as the material and thickness of the sensing resistance part 30, etc., as described above.

[0054] 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.

[0055] 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.

[0056] 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 (sensitive resistance portion 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.

[0057] The insulating resin film constituting the base material 10 may contain oxygen and moisture, and Cr may form an oxidized film. Therefore, especially when metal layer A contains Cr, it is preferable to form a functional layer that has the function of preventing oxidation of metal layer A.

[0058] 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 fabricated. As a result, the stability of the gauge characteristics in 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 in the strain gauge 1.

[0059] Next, the metal layer A is patterned by photolithography to form the planar shape of the sensing resistance section 30, the first wiring 41, the second wiring 42, the first electrode 51, the second electrode 52, the resistance adjustment section 60, the first connection section 71, and the second connection section 72 shown in Figure 1. The planar shape of the strain gauge 1 when a functional layer is provided may be the same as in Figure 1, for example. Figure 6 is a cross-sectional view (part 2) illustrating a strain gauge according to the first embodiment. Figure 6 shows the cross-sectional shape of the strain gauge 1 when a functional layer 20 is provided as a base layer for the sensing resistance section 30, etc.

[0060] The planar shape of the functional layer 20 may be patterned to be substantially the same as the planar shape of, for example, the sensitive resistance portion 30. However, the planar shapes of the functional layer 20 and the sensitive resistance portion 30 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 a different shape from the planar shape of the sensitive resistance portion 30. In this case, the functional layer 20 may be formed as a solid block in the region where the sensitive resistance portion 30 is formed. Alternatively, the functional layer 20 may be formed as a solid block over the entire upper surface 10a of the base material 10.

[0061] After forming the sensing resistance portion 30, etc., a cover layer may be formed on the upper surface 10a of the base material 10. The cover layer covers, for example, the sensing resistance portion 30, the first wiring 41, and the second wiring 42, but the first electrode 51 and the second electrode 52 may be exposed from the cover layer. For example, a semi-cured thermosetting insulating resin film is laminated to the upper surface 10a of the base material 10 so as to cover the sensing resistance portion 30, the first wiring 41, and the second wiring 42, while exposing the first electrode 51 and the second electrode 52. The cover layer can then be formed by heating and curing the insulating resin film. The strain gauge 1 is completed by the above steps.

[0062] <Variations of the first embodiment> In a modified example of the first embodiment, the angle between the elongated portion of the resistor and the grid resistor of the resistance adjustment portion is shown to be different from that of the first embodiment. In the modified example of the first embodiment, descriptions of components that are the same as those described in the previously described embodiment may be omitted.

[0063] Figure 7 is a plan view illustrating a modified strain gauge according to the first embodiment. Figure 8 is a partially enlarged view of the vicinity of the resistance adjustment section shown in Figure 7. Referring to Figures 7 and 8, the angle between the elongated portion 31 of the sensing resistance section 30 and the grid resistances R1 to R6 of the resistance adjustment section 60 differs in strain gauge 1 shown in Figure 1.

[0064] In other words, in strain gauge 1 shown in Figure 1, the angle between the elongated portion 31 of the sensing resistance section 30 and the grid resistors R1 to R6 of the resistance adjustment section 60 was 0 degrees. In contrast, in strain gauge 1A, the longitudinal direction of the grid resistors R1 to R6 is inclined with respect to the first direction, which is the longitudinal direction of the elongated portion 31.

[0065] Specifically, as shown in Figure 8, in strain gauge 1A, the angle θ1 between the elongated portion 31 of the sensing resistance section 30 and the grid resistance R1 of the resistance adjustment section 60 is 45 degrees. Since the grid resistances R2 to R6 are arranged parallel to the grid resistance R1, the angle between the elongated portion 31 of the sensing resistance section 30 and the grid resistances R2 to R6 of the resistance adjustment section 60 is also 45 degrees. In Figure 8, X1 represents a straight line parallel to the X-axis, i.e., a straight line parallel to the elongated portion 31 of the sensing resistance section 30. Also, L1 represents a straight line parallel to the grid resistance R1.

[0066] The angle between X1 and L1 is defined as the absolute value of the smaller of the two angles obtained by rotating the radial vector clockwise and counterclockwise, with X1 as the initial line (0 degrees). Therefore, the angle between X1 and L1 will always fall within the range of 0 degrees to 90 degrees. In other words, in the example in Figure 8, the angle between X1 and L1 is 45 degrees, not 135 degrees.

[0067] In this way, by setting the angle between the elongated portion 31 of the sensing resistance section 30 and the grid resistors R1 to R6 of the resistance adjustment section 60 to 45 degrees, the resistance adjustment section 60 becomes even less able to detect strain in the linear L0 direction. As a result, the strain gauge 1A can detect the strain generated in the strain-generating body with greater accuracy using the sensing resistance section 30 compared to the strain gauge 1.

[0068] Figure 9 is a partially enlarged view showing an example where the resistance adjustment section shown in Figure 8 differs from θ1. In the strain gauge 1B shown in Figure 9, θ1 is set to 90 degrees. That is, in the strain gauge 1B, the longitudinal direction of the grid resistances R1 to R6 is perpendicular to the first direction, which is the longitudinal direction of the elongated section 31.

[0069] Thus, the angle between the grid resistors R1 to R6 of the resistance adjustment unit 60 and the elongated portion 31 of the sensing resistance unit 30 is not limited to 45 degrees as shown in Figure 8, but can be between 10 degrees and 90 degrees. The angle between the elongated portion 31 of the sensing resistance unit 30 and the grid resistors R1 to R6 of the resistance adjustment unit 60 is preferably between 45 degrees and less than 60 degrees, more preferably between 60 degrees and less than 75 degrees, and particularly preferably between 75 degrees and 90 degrees. The closer the angle between the elongated portion 31 of the sensing resistance unit 30 and the grid resistors R1 to R6 of the resistance adjustment unit 60 is to 90 degrees, the more the strain detected by the resistance adjustment unit 60 can be suppressed.

[0070] Preferred embodiments have been described in detail above. However, the strain gauges according to this disclosure are not limited to the embodiments and modifications described above. For example, various modifications and substitutions can be made to the strain gauges according to the embodiments described above without departing from the scope described in the claims. [Explanation of Symbols]

[0071] 1,1A,1B Strain gauge, 10 Base material, 10a Top surface, 20 Functional layer, 30 Sensing resistance section, 31 Elongated section, 32 Folded section, 33 First wiring connection section, 34 Second wiring connection section, 41 First wiring, 42 Second wiring, 51 First electrode, 52 Second electrode, 60 Resistance adjustment section, 71 First connection section, 72 Second connection section, 100 Resistor, R1~R6 Grid resistor, Ra~Re Trim resistor, x1~x7 Connecting section

Claims

1. Substrate and A resistor formed on the upper surface of the substrate, It has a first electrode and a second electrode, The resistor includes a sensitive resistance section, a resistance adjustment section, a first connection section, and a second connection section. The sensing resistance portion forms a predetermined repeating pattern including a plurality of elongated portions arranged side by side with their longitudinal direction facing a first direction, and folded portions that connect the ends of adjacent elongated portions in an alternating manner to connect each of the elongated portions in series. The resistance adjustment unit is connected in parallel with the sensing resistance unit via the first connection unit and the second connection unit. The aforementioned resistance adjustment section includes a plurality of trim resistors, The resistance adjustment unit, the first connection unit, and the second connection unit are arranged on the upper surface at a position different from the region where the predetermined repeating pattern is formed, and at a position that does not intersect with a straight line passing through the center of the region and parallel to the first direction. The first electrode is electrically connected to one end of the sensitive resistance portion and is positioned so as not to intersect with the straight line. The second electrode is electrically connected to the other end of the sensing resistance portion and is positioned in a location that does not intersect the straight line, and in a second direction perpendicular to the first direction, in a region opposite to the region where the first electrode is located across the straight line. All of the resistance adjustment section, the first connection section, and the second connection section are located on the same side with respect to the straight line as one of the first electrode and the second electrode in the second direction. A strain gauge in which, on the upper surface, the entirety of the resistance adjustment section is positioned on the opposite side of the region where the repeating pattern is formed, with respect to the straight line, one of the first electrode and the second electrode located on the same side.

2. The one end and the other end of the sensing resistance portion are, respectively, the ends of the sensing resistance portion in the second direction. The first electrode is connected to one end of the sensitive resistance section via the first wiring, The second electrode is connected to the other end of the sensing resistance section via the second wiring. The aforementioned sensitive resistance section is A first wiring connection portion that connects the elongated portion located on one end to the first wiring, A second wiring connection portion connects the elongated portion located on the other end side to the second wiring, Includes, One of the first connection portion and the second connection portion is connected to a wiring and / or a wiring connection portion connected to the first wiring, the second wiring, the first wiring connection portion, and the second wiring connection portion, which are located on the same side as the entirety of the resistance adjustment portion with respect to the straight line, The strain gauge according to claim 1, wherein the other of the first connection portion and the second connection portion is connected to one of the folded portions.

3. The strain gauge according to claim 1, wherein the first connection portion and the second connection portion are each connected to different folded portions.

4. The resistance adjustment unit includes a plurality of grid resistors connected in series, The strain gauge according to any one of claims 1 to 3, wherein each of the trim resistors is connected in parallel to a series circuit including two adjacent grid resistors.

5. The strain gauge according to claim 4, wherein the longitudinal direction of each of the grid resistors is inclined with respect to the first direction.

6. The strain gauge according to claim 5, wherein the angle between the grid resistance and the elongated portion is 10 degrees or more and 90 degrees or less.

7. The strain gauge according to any one of claims 4 to 6, wherein the width of one or more of the plurality of grid resistors is wider than the width of the elongated portion.

8. The resistor is made of Cr, CrN, and Cr ２ A strain gauge according to any one of claims 1 to 7, formed from a film containing N.

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