Strain gauge, strain measuring device, and strain measuring method

Abstract

To provide strain gauges that can improve practicality. [Solution] The nanogranular structure film constituting the resistor 2 formed on one main surface of the substrate 1 of the strain gauge is a general formula L 100-a-b-c M a F b O c It has a composition represented by (L: one or more metallic elements selected from Fe, Co, Ni, Pt, Au, Ag, and Cu; M: one or more elements selected from Li, Mg, Al, Ca, Sr, Ba, Gd, and Y; F: fluorine; O: oxygen; 40.0 ≤ a + b + c ≤ 63.0). It is composed of a nanogranular structure film in which metallic particles Q1 with an average particle size of 1.0 to 5.0 nm, represented by L, are distributed in an insulating matrix Q2 consisting of fluoride or fluoride and oxide of M.

Description

Technical Field

[0001] The present invention relates to a technique for measuring the strain of an object.

Background Art

[0002] It has been reported that, in response to the deformation of a nanogranular structure film in which metal particles of nanometer size are dispersed in a fluoride matrix, the distance between the metal particles changes and the electrical conductivity of the nanogranular structure film changes (see, for example, Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the above phenomenon occurs at an extremely low temperature close to the liquid helium temperature, it is difficult to put into practical use products or the like using this phenomenon.

[0005] Therefore, an object of the present invention is to provide a strain gauge that can improve practicality.

Means for Solving the Problems

[0006] The strain gauge of the present invention is A strain gauge comprising a substrate and a resistor formed on the surface of the substrate, The aforementioned resistor is, General formula L 100-a-b-c M a F b O c The material has a composition represented by (L: one or more metal elements selected from Fe, Co, Ni, Pt, Au, Ag, and Cu; M: one or more elements selected from Li, Mg, Al, Ca, Sr, Ba, Gd, and Y; F: fluorine; O: oxygen; 40 ≤ a + b + c ≤ 63), and is composed of a nanogranular structure film in which metal particles with an average particle size of 1.0 to 5.0 nm represented by L are distributed in an insulating matrix of fluoride or fluoride and oxide of M.

[0007] (Effects of the invention) According to the strain gauge of the present invention, the deformation of the nanogranular structure film constituting the resistor changes the spacing between the metal particles constituting the nanogranular structure film. This changes the thickness of the tunnel barrier between the particles (granules), and thus changes the electrical conductivity. As a result, the electrical resistivity of the entire film increases, and a high electrical resistivity comparable to that of the low-temperature region described in Non-Patent Document 1 is achieved even at room temperature. Furthermore, even at room temperature, electrical conductivity due to high-order tunneling as described in Non-Patent Document 2 is realized, improving the gauge factor of the strain gauge and, consequently, its practicality.

[0008] The effect of the present invention is that, since tunnel conduction based on a nanogranular structure is essential, by having a crystallinity of 20% or more of the insulating matrix, it is possible to ensure that the band gap of the material constituting the insulating matrix forming the tunnel barrier is a value sufficient for insulation (5 eV or more).

[0009] In nanogranular structures, there are regions where physical properties such as electrical conductivity change discontinuously. This region is the percolation threshold, defined by the percolation theory in Non-Patent Document 3. In nanogranular structures, at the percolation threshold, the granules in the nanogranular structure change from an isolated state to a continuous state due to contact or other factors. This structural change causes the electrical conductivity to change from tunnel conduction to metallic conduction. In the region near the percolation threshold, when particles do not contact each other and maintain tunnel conduction, an extremely thin tunnel barrier is formed. The thinning of the tunnel barrier increases tunnel establishment, leading to an increase in tunnel conduction phenomena, including high-order tunneling. [Brief explanation of the drawing]

[0010] [Figure 1] Diagram illustrating the configuration of a strain gauge as one embodiment of the present invention. [Figure 2] An explanatory diagram of the microstructure of a resistor. [Figure 3] An explanatory diagram relating the relationship between the atomic ratio a+b+c of the resistor of the present invention and the gauge ratio of the strain gauge. [Figure 4] An explanatory diagram illustrating the relationship between the atomic ratio a+b+c of the resistor of the present invention and the temperature dependence of the gauge ratio of the strain gauge. [Figure 5A] An explanatory diagram regarding the temperature dependence of the gauge factor in one embodiment. [Figure 5B] A diagram illustrating the temperature dependence of the gauge factor in other embodiments. [Modes for carrying out the invention]

[0011] A strain gauge, as shown in Figure 1 as an embodiment of the present invention, comprises a substrate 1 and a resistor 2.

[0012] The substrate 1 is made of an insulating material with flexibility such as glass, quartz glass, a Si wafer with an oxidized surface, or a flexible resin, and is formed, for example, in a substantially rectangular plate shape. Further, the substrate 1 may be made of metal, and an insulating thin film such as polyimide, an oxide such as Al2O3, a fluoride such as MgF2, or an epoxy resin may be formed on at least one main surface thereof. On one main surface of the substrate 1, a reference mark 12 (such as a center mark) that serves as a target for the position and orientation of the strain gauge (resistor 2) is provided.

[0013] The resistor 2 is formed on one main surface of the substrate 1 and is composed of a nanogranular structure film or a nanogranular thin film having a predetermined gauge pattern. For example, as shown in FIG. 1, the resistor 2 includes a plurality of straight portions 21 that extend substantially linearly in the longitudinal direction of the substrate 1 while being folded at the distal folding tab 22 and the proximal folding tab 24 from one gauge tab 20 to the other gauge tab 20. Each of a pair of gauge leads 4 is connected to each of the pair of gauge tabs 20. The gauge pattern of the resistor 2 may be variously changed.

[0014] As schematically shown in FIG. 2, the resistor 2 is composed of a nanogranular structure film in which metal particles Q1 of nanometer size are arranged substantially uniformly dispersed in an insulating matrix Q2. The thickness of the nanogranular structure film is, for example, 0.1 to 10.0 μm.

[0015] The nanogranular structure film has the general formula L 100-a-b-c M a F b O c(L: One or more metal elements selected from Fe, Co, Ni, Pt, Au, Ag, and Cu; M: One or more elements selected from Li, Mg, Al, Ca, Sr, Ba, Gd, and Y; F: Fluorine; O: Oxygen. It has a composition represented by 40.0 ≦ a + b + c ≦ 63.0. The metal particles Q1 have an average particle size of 1.0 to 5.0 nm and are distributed in an insulating matrix Q2 composed of a fluoride of M or a fluoride and an oxide. The elements of L and M are selected by a combination that forms a nanogranular structure in which the metal particles Q1 mainly consist of L and the insulating matrix mainly consists of M, F, and O. For example, 12.0 ≦ a ≦ 22.0, 17.0 ≦ b ≦ 46.0, and 0 ≦ c ≦ 1.0. Also, it is preferable that the crystallinity of the insulating matrix Q2 is 20% or more.

[0016] An insulating protective layer or a protective film (e.g., SiO2, Al2O3, etc.) may be provided on one main surface of the substrate 1 so as to cover the resistor 2.

[0017] (Manufacturing method) The resistor 2 constituting the strain gauge is formed on one main surface of the substrate 1 using a sputtering method or an RF sputtering film-forming apparatus. A target of at least one non-magnetic metal element among Fe, Co, Ni, Pt, Au, Ag, and Cu and a target of a fluoride (or a fluoride and an oxide) of one or more elements selected from Li, Mg, Al, Ca, Sr, Ba, Gd, and Y are sputtered simultaneously. The composition of the resistor 2 is adjusted by the ratio of the area, the number, etc. of Fe, Co, Ni, Pt, Au, Ag, or Cu chips arranged on the target facing the substrate 1. Thereby, a nanogranular structure film in which metal particles of nanometer size are dispersed in a matrix composed of a fluoride is obtained.

[0018] For sputter deposition, Ar gas or a mixed gas of Ar and O2 (0.1-10%) is used. Film thickness is controlled by adjusting the deposition time, resulting in a film thickness of approximately 0.3-5.0 [μm]. To control the crystallinity of resistor 2, the substrate temperature is controlled to any temperature within the ranges of 200-600 [°C], 250-550 [°C], or 300-500 [°C], the sputtering pressure during deposition is controlled to 1-60 [mTorr], and the sputtering power is adjusted within the range of 50-350 [W]. Furthermore, since the crystallinity of resistor 2 is known to vary depending on its composition, the substrate temperature, deposition pressure, and sputtering power may be controlled according to the composition.

[0019] (Examples) A nanogranular thin film was deposited on a substrate by simultaneously sputtering a Co target (76 mm in diameter) and a BaF2 powder sintering target (76 mm in diameter) using an RF sputtering apparatus. Corning-XG glass with dimensions of 50 × 50 mm and a thickness of 0.5 mm was used as the substrate, and the substrate temperature during deposition was adjusted to 300°C using a lamp heating method. The strain gauge of Example 1 was fabricated using the nanogranular thin film thus obtained. Similarly, according to the above embodiment, the temperature, pressure, power, etc. were adjusted accordingly, and in particular, the substrate temperature was controlled to be within the range of 200 to 500°C before the nanogranular thin film was deposited, and the strain gauges of Examples 2 to 23 were fabricated using these films.

[0020] (Comparative example) Comparative examples 1 and 2, each having a nanogranular thin film with the composition shown in Table 1, were fabricated under the same conditions as in the examples.

[0021] Table 1 summarizes the composition of the nanogranular thin films constituting the strain gauges for Examples 1-23 and Comparative Examples 1-2, the gauge factor of the strain gauges, the degree of crystallinity determined from the X-ray diffraction results of the insulating matrix Q2, the temperature change rate of the gauge factor from 0 to 50°C, and the substrate temperature during film formation. Note that the substrate temperature during film formation is measured using a lamp heating method, so an error of up to ±10% may occur. In XRD, it is possible to calculate the degree of crystallinity by performing profile fitting within a certain range around the main peak of the fluoride or fluoride oxide constituting the insulating matrix Q2. However, in nanogranular structures, because they are nanometer-sized microstructures, the presence of microcrystalline phases can broaden the XRD peaks, making it difficult to distinguish them from amorphous phases. Therefore, even if the degree of crystallinity of the insulating matrix Q2 based on XRD is measured to be 70% for a certain sample, the degree of crystallinity of the insulating matrix Q2 for samples produced under the same manufacturing conditions may be measured to be 80%-90% or even 85%-95%.

[0022] [Table 1]

[0023] Figure 3 shows the correlation between a+b+c, which represents the composition of the nanogranular thin films constituting the strain gauges of Examples 1 to 23, and the gauge factor at room temperature, as indicated by the circled numbers corresponding to each example. Figure 3 also shows the correlation for the strain gauges of Comparative Examples 1 and 2, as indicated by the black circles corresponding to each comparative example. From Table 1 and Figure 3, it can be seen that the gauge factors of the strain gauges of Examples 4, 5, 9, 10, 13, 16, 20, and 22 are 15 or higher, which is higher than the gauge factors of the strain gauges of the other examples. The crystallinity of the nanogranular thin films constituting the strain gauges of Examples 4, 5, 9, 10, 13, 16, 20, and 22 falls within the range of 38% to 64%, and a+b+c falls within the range of 50.1% to 59.1%. In Examples 4, 13, 16, 20, and 22, where L is one or more magnetic metal elements selected from Fe, Co, and Ni, the crystallinity of the nanogranular thin films constituting the strain gauges falls within the range of 38% to 64%, and a+b+c falls within the range of 50.1% to 59.1%. In Examples 5, 9, and 10, where L is one or more non-magnetic metal elements selected from Pt, Au, Ag, and Cu, the crystallinity of the nanogranular thin films constituting the strain gauges falls within the range of 41% to 61%, and a+b+c falls within the range of 53.9% to 56.5%.

[0024] Figure 4 shows the correlation between a+b+c, which represents the composition of the nanogranular thin films constituting the strain gauges of Examples 1 to 23, and the temperature change rate of the gauge fraction from 0°C to 50°C, as indicated by the circled numbers corresponding to each example. From Table 1 and Figure 4, it can be seen that the temperature change rate of the gauge fraction of the strain gauges of Examples 1, 2, 4, 5, 6, 8, 9, 10, 13, 16, 17, 18, 20, 22, and 23 is less than 1000 ppm / °C, which is lower compared to the strain gauges of the other examples. The crystallinity of the nanogranular thin films constituting the strain gauges of Examples 1, 2, 4, 5, 6, 8, 9, 10, 13, 16, 17, 18, 20, and 22 falls within the range of 38% to 64%, and a+b+c falls within the range of 50.1% to 59.1%. In Examples 1, 2, 4, 13, 16, 17, 20, and 22, where L is one or more magnetic metal elements selected from Fe, Co, and Ni, the crystallinity of the nanogranular thin films constituting the strain gauges falls within the range of 38% to 64%, and a+b+c falls within the range of 50.1% to 59.1%. In Examples 5, 6, 8, 9, 10, and 18, where L is one or more non-magnetic metal elements selected from Pt, Au, Ag, and Cu, the crystallinity of the nanogranular thin films constituting the strain gauges falls within the range of 41% to 61%, and a+b+c falls within the range of 54.5% to 58.1%.

[0025] Figures 5A and 5B show the temperature dependence of the gauge fraction of the strain gauges from Example 10 and Example 5 when placed in a temperature environment of -50°C to 50°C, respectively. [Explanation of Symbols]

[0026] 1... Circuit board 12...Standard mark 2. Resistor 20... Gauge Tab 21‥Straight line part 22. Distal folded tab 24... Proximal wrap tab 4. Gauge Lead Q1‥Metal particles Q2... Insulating matrix.

Claims

1. A strain gauge comprising a substrate and a resistor formed on the surface of the substrate, The resistor is of general formula L 100-a-b-c M a F b O c A strain gauge having a composition represented by (L: one or more metallic elements selected from Fe, Co, Ni, Pt, Au, Ag, and Cu; M: one or more elements selected from Li, Mg, Al, Ca, Sr, Ba, Gd, and Y; F: fluorine; O: oxygen; 40.0 ≤ a + b + c ≤ 63.0), and composed of a nanogranular structure film in which metallic particles with an average particle size of 1.0 to 5.0 nm represented by L are distributed in an insulating matrix of fluoride or fluoride and oxide of M.

2. In the strain gauge according to claim 1, A strain gauge having a crystallinity of 20% or more in the insulating matrix.

3. In the strain gauge according to claim 2, A strain gauge in which the degree of crystallinity of the insulating matrix is ​​in the range of 24% to 64%.

4. In the strain gauge according to claim 3, L is one or more magnetic metal elements selected from Fe, Co, and Ni. The degree of crystallinity of the insulating matrix is ​​in the range of 38% to 64%. a+b+c is a strain gauge that falls within the range of 50.1% to 59.1%.

5. In the strain gauge according to claim 3, L is one or more nonmagnetic metallic elements selected from Pt, Au, Ag, and Cu. The degree of crystallinity of the insulating matrix is ​​in the range of 41% to 61%. a+b+c is a strain gauge that falls within the range of 54.5% to 58.1%.

6. In the strain gauge according to claim 1, A strain gauge in which the change in gauge factor over a temperature range of 0 to 50°C is ±1500 ppm / °C or less.

7. A strain measuring device comprising: a strain gauge according to any one of claims 1 to 6; a circuit component constituting a bridge circuit including the strain gauge; and a magnet for applying a magnetic field to the strain gauge.

8. A strain measurement method comprising the steps of: attaching a strain gauge according to any one of claims 1 to 6 to an object; applying a magnetic field to the strain gauge using a magnet; and detecting the strain pattern in the object according to a change in the electrical resistance of the strain gauge.

Images