JPS60195402A - Strain gauge - Google Patents

Abstract

PURPOSE:To increase a gauge coefficient, and also to manufacture easily the titled strain gauge by constituting the gauge by forming an amorphous semiconductor film on a flexible substrate. CONSTITUTION:A metallic electrode 2 consisting of Ni, etc. is formed by means of vapor-deposition of an electron beam, etc., on a high polymer film substrate 1 of about 40-120mum thick consisting of polyimide, etc. Subsequently, an amorphous silicon film 3 is formed linearly, for instance, to a size of about 0.1X1mm. by a glow discharge decomposition method, and an epoxy phenol compound paint is applied in a shape of a pattern onto the film 3, by which a light shielding protective film 4 of about 10mum thick is formed. In this way, a gauge coefficient can be set to scores of times of a metallic strain coefficient.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical field to which the invention pertains) The present invention relates to a strain gauge that measures the amount of strain from changes in electrical resistance.

(Prior art and its problems) Conventional strain gauges are wire gauges in which electrical resistance wires such as nichrome wires and manganin wires with a diameter of about 10 μrrL are bent and pasted in a zigzag pattern on paper or felt. In order to flow, 0u-N with a thickness of several μm is coated on a polymer film made of polyimide, phester, and phenol resin.
There is a foil gauge in which i-alloy is pasted and etched in a zigzag pattern with a width of several tens of micrometers. The gauge coefficient of these strain gauges is 2 to 3, and in order to increase the sensitivity various complicated measures must be taken, which makes them expensive. There is also a problem with reliability because thin wires or thin foil are attached using adhesive. In addition, there are products that use semiconductor chips instead of metal, and the gauge factor is improved by 10 to 50 times, but there are only 5 semiconductor chips, and it is extremely difficult to attach thin chips with good reproducibility. . Furthermore, since the resistance change of a strain gauge changes depending on the direction of strain and the angle it makes, when measuring strain distribution within a large area, it is necessary to install a large number of gauges aligned in a predetermined direction. Requires effort.

(Objective of the Invention) The present invention eliminates the drawbacks of the conventional strain gauges described above, has a large gauge coefficient, is easy to manufacture, and can be formed on a large-area substrate by aligning a large number of strain gauges. The purpose is to provide strain gauges.

(Summary of the Invention) The strain gauge according to the present invention achieves the above object by being composed of an amorphous semiconductor film formed on a flexible substrate. It is effective to use amorphous silicon (hereinafter referred to as α-81), particularly a microcrystalline S1 film.

(Embodiment of the Invention) FIGS. 1(α) and (A) show an embodiment of the present invention, in which Ni, Or, stainless steel.

T1 or Ni-0r, Ml-Or-Au, Ti
-Al-0u.

Metal electrodes 2 made of a laminated layer of TI-p, 1-N1, etc. are formed by electron beam evaporation or sputtering evaporation at intervals of, for example, 1 ms. Such an electrode pattern can be formed by placing a metal mask on the polymer film 1 during vapor deposition, or by photolithography after full-surface vapor deposition. Next, the α-81 film 3 is formed in a linear shape, for example, with dimensions of 0.1 rrbm XI Bm, by a glow discharge decomposition method.

The α-81 film is produced by a known method using silane gas diluted 10 to 30 times with hydrogen and applying a high frequency electric field in a vacuum of 1 to 1 O Torr. α-81 membrane 3 p
Diborane gas is added to the silane gas to form a mold, and phosphine gas is added to the silane gas to form an n-type. The substrate temperature is 150
It is preferable to keep it at ~3000. As the high frequency power is increased, microcrystalline grains with a size of 150 to 20 OA grow into the film, forming a microcrystalline film. P-type that is not microcrystallized.

3 In the case of n-type α-81, the electrical conductivity is 10 to 10 (ΩCm), but in the case of microcrystalline film, it is 1 to 10 (ΩCm-)
becomes. Therefore, by using a microcrystalline film with a thickness of 200 OA,
Obtain a resistance of 00 kΩ. When 81F gas is used instead of silane gas (stHa), a highly conductive film can be obtained by diluting it approximately 10 times with hydrogen, but this film also has a microcrystalline structure.

In order to protect α-51113, a phenolic paint or phenolic paint is applied in a pattern by a method such as printing, and a light-shielding protective film 4 having a thickness of about 10 μm is coated. FIG. 2 shows another embodiment in which a thin metal plate 5 made of stainless steel or the like is used and an insulating resin layer 6 made of polyimide or the like is applied thereon to form a substrate.

These strain gauges are used by pasting the substrate 1 or 5 onto the object to be measured with an adhesive.

The characteristics of this thin film strain gauge are shown in FIGS. 3(α) to (C). Figures (α) and (A) show strain ε and resistance change rate △R
/H relationship. Figure (α) is for a p-type S1 thin film, and Figure (b) is for an n-type S1 thin film, and △R/R changes in proportion to the gauge coefficient. Different values are shown depending on the angle θ between the horizontal direction and the strain direction. Line 31 is for θ = 0, that is, when the gauge is placed in the direction of strain, line 32 is for θ = 90°, that is, when the gauge is placed transverse to the strain, and line 33 is for θ = 45°. This is the case. FIG. 3(C) shows the angular dependence of the gauge coefficient on strain, where the line 34 is the p-type and the line 35 is the p-type.

FIG. 4 is a plan view of another embodiment of the strain gauge. In this case, three metal electrodes 2 are formed on a polymer film substrate 1, and p-type machine crystallized α-81 films 7 and 8 are provided at right angles to each other. The width and length of the α-8i films 7 and 8 are the same. The protective film 4 covering it also shields light. Now, assuming that the resistance of the α-81 film 7 is R1, the resistance of the α-81 film is R8, and a strain ε forming an angle θ when viewed from the length direction of the α-81 film 7 is applied, R, :R, .・k(T)f1+α(θ)ε)R,=R&
It can be written as 0-k(T) (1+α(9♂-θ)ε1. However, RTor R80 is the value of the unstrained α-81 films 7 and 8 at the reference temperature, and k(T) is the value. It is a coefficient that indicates the temperature characteristics of
, ΔR,=R++ok (T)α(90−θ)e. As a result, a quantity with no temperature dependence is obtained. R10/
If R20 is measured at the reference temperature when there is no strain,
Since this is a quantity that has no temperature dependence, there is no need to worry about errors due to temperature. Also, if the size and shape of the resistance part of the strain gauge are almost the same, R70/R8° will be approximately 1
becomes. Figure 5 shows α(θ)-α in the p-type α-81 film.
The angle dependence of the value of (90-θ) is shown. It can be seen that the sensitivity is amplified compared to FIG. 3(c).

This makes it possible to detect the amount of strain and the direction of strain. Since the patterning of the α-81 film 7.8 shown in FIG. 4 is performed by photoetching, it is easy to form it accurately and the accuracy of strain measurement is improved. (L-8i
It goes without saying that the films 7 and 8 do not necessarily need to be formed at right angles, but data analysis and calculations become somewhat complicated.

In the embodiment shown in FIG. 6, two small metal electrodes 2 and one large metal electrode 21 are provided, and two microcrystallized α
-81 films 9 and 10 are formed in parallel. The film 9 is a p-type α-81 film, and the film 10 is an n-type α-81 film. In this case, assuming that the resistance of the membrane 9 is H and the resistance of the membrane 110 is Rlo, the same as in FIG. 4 is obtained. R90+”to
o is the resistance of the membranes 9 and 10 at a certain temperature when no strain ε is applied. By measuring this amount, temperature dependence can be eliminated.

FIG. 7 shows the relationship between αp(θ)-αn(θ) and angle θ.

In the embodiment shown in FIG. 8, four metal electrodes 2 are provided, and the α-8
1 film 11.12.13.14 and the diagonal α-
81 thin film 15 is formed. Membrane 11゜12.13.
14 does not necessarily have to form a square, but the membrane 11
, 13 and membranes 12, 14 are preferably parallel. Although not shown, a light-shielding protective film is coated as in the other embodiments. FIG. 9 is a circuit diagram explaining the operation of this strain gauge, in which a voltage is applied from a power source 16 to cause a current to flow through each thin film resistor. The resistances of thin films 11, 12, 13, and 14.15 are respectively "l + R2l R3+ R4r R
5, the voltage (■) that appears across the thin film 15 is the product of the output voltage of the power supply 16 (E) and three of these for both the numerator and denominator, so there is no error in ■ due to temperature fluctuations. .

Rlo l”201 Rso 1 R40t-R+
+ Rt + Rs l Assuming the value of R4 without strain at the reference temperature, when membranes 1 and 3 and membrane 2゜4 form a right angle, R, = R, o (l + α (θ) εj R32R30f1 + α ( θ)ε” Ftt=F'to (l+α(9011-〇)ε)R,
= R4(, (l+α(90″-〇)ε).Here, RIR3R2R4: Rlo R3(1(1+2α(
θ)ε)−R20R40(1+2α(90°−〇)ε
J and R7゜R8゜" If formed to become R2OR40, R+ Rs Rt R4 = 2 Rho Rs
o (α(θ)-α(90'-〇))ε(ol), so "In2" and "In4" are terms proportional to the strain ε, and the measurement of the voltage V is independent of temperature fluctuations and can be performed with high precision. Strain can be measured.The variation due to distortion in R8 to R3 is at most a few tenths of a percent, so the errors caused by each term in the denominator and R5 in the numerator are not a problem.The voltage ■ is amplified by the amplifier 17. and conversion to strain values is also performed.

Since the resistive thin films 11 and 13, 12 and 14 are parallel to each other, each changes with the same rate of change in strain. Therefore, the voltage V is a value obtained by amplifying the strain in the form of a difference in rate of change, which is convenient for highly accurate measurement of minute strain. Thin film 11
, 12.13.14 is p-type α-81 or n-type α-8
1, or the thin films 11, 13, 12, and 14 may be made of α-81 of different conductivity types.

(Effects of the Invention) The present invention provides an amorphous semiconductor film such as an α-EN thin film or a microcrystalline α-811 film that can be formed even on a flexible substrate made of a polymer film by low-temperature vapor phase growth. 10) By constructing a strain gauge from a thin film, a highly sensitive strain gauge having a gauge factor several tens of times higher than that of a metal strain gauge can be obtained. Moreover, a gauge resistor of any shape can be easily formed using a photoetching method, and the cost is low and the reliability is very high. In addition, it has become extremely easy to manufacture a matrix in which a large number of strain gauges are arranged in the same direction for measuring strain distribution in a wide area.

[Brief explanation of the drawing]

Figure 1 shows one embodiment of the present invention, where figure (α) is a plan view and figure (α) is a plan view.
b) is a sectional view taken along the line A-A in figure (α), FIG. 2 is a sectional view corresponding to FIG. 1 (cL) of another embodiment, and FIG. 3 is a sectional view corresponding to FIG. Figure 2 shows the characteristics of the embodiment, Figure (α) shows the resistance change rate and strain diagram for the p-type α-81, which is an angle dependence diagram of the characteristics, and Figure 6 is a plan view of a further different embodiment. , FIG. 7 is an angular dependence diagram of its characteristics, FIG. 8 is a plan view of yet another embodiment, and FIG. 9 is its measurement circuit diagram. 1: Polymer film substrate, 2.21: Metal electrode, 5: Metal thin plate, 6: Polymer film, 3. '7.8.9.10.11゜12, 13.14.15: α-81 thin film. , -01X8/8 →θ Fig. 5 Fig. 7M 13 Fig. 8 Fig. 9 = 11-

Claims (1)

[Claims] l) A strain gauge comprising an amorphous semiconductor film formed on a flexible substrate. 2. The strain gauge according to claim 1, wherein the amorphous semiconductor is amorphous silicon. 3) The strain gauge according to claim 2, wherein the amorphous silicon is fine-grained amorphous silicon. 4) In the gauge according to any one of claims 1 to 3, it is provided that the amorphous semiconductor film is a p-type semiconductor film and an n-type semiconductor film arranged in parallel on the same substrate. Characteristic strain gauge.