RU2536100C1 - Bonded semiconductor resistive strain gauge - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: bonded resistive strain gauge includes a polymer substrate, and a carrier from thin metal foil in the form of rectangular platforms connected with a strip. A separating dielectric film is made on the carrier and repeats its shape and dimensions. The resistive strain gauge also includes a strain-sensitive film from polycrystalline samarium monosulphide and two metal-film platforms. Each metal-film platform is located on the separating dielectric film and represents a rectangular platform with a projection in the form of a strip; length of each strip provides for their mutual overlap in the central part of the resistive strain gauge, and the strain-sensitive film is made in the form of a strip located between ends of projections of metal-film platforms in their overlap zone.

EFFECT: invention allows reducing electrical resistance of a resistive strain gauge by providing high strain sensitivity at small sizes and by supplying current normally to the plane of the strain-sensitive strip which is located between projections of metal films in their mutual overlap zone.

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Description

The invention relates to measuring technique and can be used both in strength tests to determine the stress state of structures, and as a sensitive element in sensors of mechanical quantities (force, pressure, weight, displacement, etc.).

Known strain gauge (SU 1717946, G01B 7/16, 7/18, publ. 07.03.1992) containing a strain-sensitive strip of samarium monosulfide, pads and a dielectric substrate of silicate glass.

The disadvantage of this solution is the limited scope: determination of the stress state inside the mass of concrete or other hardening materials.

Known glued semiconductor strain gauge containing a polymer substrate, a strain-sensitive film and metal contacts at the ends of the strain-sensitive film (D.T. Ankudinov, K. N. Mamaev. Low-base resistance strain sensors, Mechanical Engineering, 1968, pp. 47-50).

Strain-sensitive film made of bismuth has a low strain-sensitivity.

The closest technical solution is a glued semiconductor strain gauge containing a polymer substrate, a metal foil carrier made in it in the form of rectangular pads connected by a strip, formed on the other side of the carrier in shape and size, a separation dielectric film, and a strain-sensitive polycrystalline film samarium monosulfide and two metal-film sites (patent No. 2463687 from 06.23.2011, publ. 10.10.2012). In this design, the strain-sensitive film also repeats the shape and size of the carrier. An unshunted section of the strain-sensitive film is left between the contact metal-film pads and current flows along the strip of the strain-sensitive film along it.

The disadvantage of the prototype is too high resistance, which is difficult to reconcile with the input characteristics of the strain gauge.

The invention is aimed at achieving a technical result, which consists in obtaining a strain gauge with high strain sensitivity and relatively low electrical resistance at small sizes.

Below, when disclosing the invention and considering its specific implementation, other types of achieved technical result will be named.

To achieve the specified technical result in the proposed stick-on semiconductor strain gauge, as well as in the prototype, containing a polymer substrate, a metal foil carrier is made on it in the form of rectangular pads connected by a strip, formed on the other side of the carrier in shape and size, the dielectric separating it a film, as well as a strain-sensitive film made of polycrystalline samarium monosulfide and two metal-film pads, in contrast to the prototype each the metal film pad is located on the separating dielectric film and is a rectangular pad with a strip-shaped protrusion, the length of each strip ensuring their mutual overlap in the central part of the strain gauge, and the strain-sensitive film is made in the form of a strip located between the ends of the protrusions of the metal film pads in the area of their overlap .

Unlike all known strain gauges in which current flows along a strain gauge strip between contact pads (metal films), in the proposed technical solution it passes along the normal to the plane of the strip, which is located between the protrusions of the metal films, in the zone of their mutual overlap, which allows you to reduce its electrical resistance, while maintaining a high strain sensitivity at small sizes.

The invention is illustrated by drawings, where:

figure 1 - glued semiconductor strain gauge in plan;

figure 2 is a longitudinal section of a strain gauge;

figure 3 - the direction of the passing current in the prototype;

figure 4 - direction of the passing current in the present invention.

The proposed glued strain gauge comprises a polymer substrate 1, a carrier 2 made on it of thin (e.g., 0.01 mm) metal (e.g., constantan) foil in the form of rectangular pads connected by a strip (dumbbell shape). A separating dielectric film 3 is repeated on the carrier 2 in shape and size. The strain gauge also contains a strain-sensitive film 4 of polycrystalline samarium monosulfide and two metal-film pads 5 (contact pads). Each metal-film pad 5 is located on the separating dielectric film 3 and is a rectangular platform with a protrusion in the form of a strip 6, the length of each strip 6 ensures their mutual overlap in the central part of the strain gauge, and the strain-sensitive film 4 is made in the form of a strip located between the ends of the protrusions 6 of the metal film 5 sites in the area of their overlap.

The proposed strain gauge works as follows.

The strain gauge works as well as the prototype; according to the appropriate technology, it is glued to the surface of the part under study. Under mechanical forces, the part is deformed (stretched or compressed), and the strain gauge glued onto the part is stretched or compressed by ΔL, obtaining a relative deformation Δ / L, which in turn leads to a relative change in the resistance (ΔR / R) of the strain gauge. Values ΔL / L and ΔR / R are interconnected through the coefficient of strain sensitivity:

ΔR / R = KΔL / L,

where K is the coefficient of strain sensitivity;

ΔL / L is the relative deformation;

ΔR / R is the relative change in resistance.

The proposed strain gauge differs from the known only extremely low electrical resistance due to the very small semiconductor length and significant cross-section.

Figure 4 and 5 shows the direction of current flow in the prototype (figure 4) and the proposed strain gauge (figure 5). For comparison, we take two equally sized sensitive elements 0.3 × 0.3 × 0.0005.

R = ρL / bh

The resistance R is proportional to the resistivity ρ, the length of the conductor L (conductor size in the direction of current flow) and inversely proportional to the cross section b · h, where b is the width of the conductor, h is the thickness of the conductor.

We take the resistivity of the sensitive elements of the prototype and the proposed strain gauge equal. Then the length of the conductor in the prototype is 0.3 mm, and in the proposed invention 0.0005 mm, that is, 600 times less. The cross-section of the prototype 0.3 × 0.0005 = 0.00015 mm ² , and the proposed invention 0.3 × 0.3 = 0.09 mm ² , that is, 60 times larger, and in general 60 × 60 = 36000, that is, all things being equal, the resistance of the proposed strain gauge will be 36000 times less than the prototype. This allows one to choose such dusting (deposition) modes of a polycrystalline film of samarium monosulfide at which it has maximum sensitivity.

Thus, the proposed design of a glued semiconductor strain gauge allows to reduce its electrical resistance, providing high strain sensitivity at small sizes, by redirecting the current normal to the plane of the strain gauge strip, which is located between the protrusions of the metal films, in the area of their mutual overlap.

Claims (1)

A glued semiconductor strain gauge containing a polymer substrate, a metal foil carrier made in it in the form of rectangular pads connected by a strip, formed on the other side of the carrier in shape and size, a separation dielectric film, and a strain-sensitive film made of polycrystalline samarium monosulfide and two metal film site, characterized in that each metal film site is located on a separation dielectric film and yaet a rectangular pad with a projection in the form of strips, the length of each strip ensures their mutual overlap in the central part of the strain gauge and strain-gauge film is formed as a strip located between the ends of the projections metalloplenochnyh sites in the area of their overlap.

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