JPH06249606A - Strain sensor - Google Patents

Abstract

PURPOSE:To improve the performance and mass-productivity of a strain sensor by forming the pattern of a strain resistance material after forming an electrically insulating thin film having a special material constitution on the surface of a substrate. CONSTITUTION:An electrically insulating thin film is formed of a multiplayered film of a composite material of aluminum oxide and aluminum nitride and a silicon oxide layer. It is preferable to use a metallic substrate for the substrate of the thin film. The composite material is formed by performing sputtering in an inert gas atmosphere containing nitrogen by using, for example, an aluminum oxide target. The silicon oxide layer is formed by a CVD method by using, for example, a silicon compound. After forming the thin film electric resistor in such a way, a metallic thin film is formed on the terminal section of the electric resistor for fitting lead wires.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a strain sensor, and more particularly to a thin film strain sensor which is attached to a mechanical part or the like to detect the amount of strain generated during use thereof.

[0002]

2. Description of the Related Art It is known to use strain sensors to detect the amount of strain that mechanical parts generate during use.
Such mechanical parts may be installed in a narrow space, or the operating environment may differ significantly from the indoor environment.Therefore, there is a demand for a small and highly reliable strain sensor that can be used in such cases. It is rare.

As a strain sensor which meets such a demand, for example, a silicon oxide film is vapor-deposited on a metal strain body, and a resistive material mainly containing Ni and Cr is vapor-deposited to form a thin film resistor. Further, one end of the thin film resistor is formed. A strain gauge in which terminals for lead connection are vapor-deposited has been proposed (JP-A-48-309).
55), and forming an insulating film of alumina or the like on the surface of the article, forming a pattern of the strain sensing resistance material on it, and forming conductive means for electrically connecting this pattern, and forming an insulating film on these. A coated thin film strain gauge has also been proposed (JP-A-53-44052).

[0004]

Since such a strain sensor is normally fixed and used on the surface of a metal mechanical part or the like, a metal is usually used as a substrate material of the sensor. . When the measurement is required especially under a severe environment such as high temperature, the conventional strain sensor has a problem that the insulation between the substrate and the resistor is insufficient. However, if the insulating film provided on the substrate is formed thick in order to improve the insulating property, the strain sensor becomes thick and large as a whole, and the advantage of using the thin film sensor is lost. In addition, the conventional thin film strain sensor has a large variation in insulation performance, and there is a problem in that many products become defective during manufacturing.

Therefore, according to the present invention, by providing an insulating film having a small thickness and excellent in insulating property between the substrate and the resistor,
The object is to provide a thin strain sensor having high performance, high reliability, and suitable for mass production.

[0006]

The above object of the present invention is to:
A strain sensor comprising an electric insulator thin film and a strain sensing electric resistor thin film laminated on a substrate, and a metal thin film electrode further laminated on an electrode portion of the strain sensing electric resistor thin film, wherein This is achieved by a strain sensor characterized in that the insulating thin film is formed of a laminated film of a composite layer of aluminum oxide and aluminum nitride and a silicon oxide layer.

As the base material used in the strain sensor of the present invention, a metal base material is preferably used because it is possible to arbitrarily select a means for fixing it to the surface of a mechanical part or the like, but it is not particularly limited. .

Further, in the strain sensor of the present invention, the electric insulator thin film provided on the substrate is formed of a laminated film of a composite layer of aluminum oxide and aluminum nitride and a silicon oxide layer. Such a composite layer of aluminum oxide and aluminum nitride can be obtained by, for example, using an aluminum oxide target and performing sputtering film formation in an atmosphere of an inert gas such as argon containing nitrogen.

A silicon oxide layer is laminated on such a composite layer, and such a silicon oxide layer is formed by, for example, a CVD method using a silicon compound or by applying a silicate compound coating material. Can be obtained by The laminate film of the composite layer of aluminum oxide and aluminum nitride and the silicon oxide layer thus obtained may be used as it is as an electrical insulator thin film, but a composite layer may be further laminated thereon or a composite layer. It may be used as an electrical insulator thin film having a multi-layered structure by alternately laminating and silicon oxide layers.

The strain sensing electric resistor thin film used in the strain sensor of the present invention is made of a conventionally known platinum-based, nickel-chromium-based or silicon-based electrical resistance material by a method such as vapor deposition or sputtering, or by printing. It can be obtained by forming a film in accordance with a pattern according to the purpose of use, etc., but is not particularly limited.

In the strain sensor of the present invention, a thin metal film for attaching a lead wire is laminated and formed on the terminal portion of the thin film electric resistor thus formed. In addition to this, a coating may be provided on its surface to protect it from the external atmosphere. Such a protective coating has not only oxidation resistance and corrosion resistance but also electric insulation and electromagnetic shielding. If it is one, it is more preferable.

[0012]

The strain sensor of the present invention is thin and hardly changes the outer surface shape at the mounting position when it is fixed on the surface of a machine part or the like. Then, an electric current is applied to the attached strain sensor from an external power source through the terminal section to the electrical resistor, and the resistance of the electrical resistor of the strain sensor undergoes the same amount of strain as the strain generated on the surface of the mechanical component. Is compared with the resistance value of the comparative resistor to detect distortion,
Accurate measurement of the amount of strain can be performed without impairing the stress-strain characteristics of attached mechanical parts.

[0013]

【Example】

(Comparative Example 1) A substrate made of a chromium / nickel heat-resistant steel plate having a thickness of about 3 mm and having a polished surface was mounted in an RF sputtering apparatus, and argon and oxygen of about 10% were simultaneously introduced to adjust the pressure to about 10. RF sputtering film formation was performed on a heated substrate while maintaining the temperature at 10 ^-2 Torr, and a thickness of about 2 μm was applied on the substrate.
An alumina insulating film of mm × 20 mm was formed.

Next, a resist film having a resistance pattern is formed on the alumina insulating film, and a nickel-chromium (80/20) alloy film having a thickness of 0.1 μm is formed by RF.
After the sputtering film formation, a resist film having an open electrode pattern was formed on the electrode portions extending from both ends and the central portion of the resistor film, and the platinum electrode layer was formed by RF sputtering. After that, the resist film is peeled off, and the platinum electrode is placed on the electrode.
A comparative strain sensor A having a chrome resistor pattern was made.

(Comparative Example 2) In the same manner as in Comparative Example 1, an alumina layer having a thickness of about 2 μm was formed on a substrate, a coating material containing a siloxane ester as a main component was applied, and a thermal decomposition treatment was performed in an electric furnace. A silicon oxide layer having a thickness of about 0.1 μm was laminated. On the laminated insulating film of the alumina layer and the silicon oxide layer thus formed, a nickel-chromium resistor pattern in which a platinum electrode layer was provided on the electrode portion was formed in the same manner as in Comparative Example 1, and was used for comparison. A strain sensor B was created.

Example 1 A composite layer of aluminum oxide and aluminum nitride having a thickness of about 2 μm was formed on a substrate in the same manner as in Comparative Example 1 except that nitrogen was added to the atmospheric gas instead of oxygen. Then, a silicon oxide layer having a thickness of about 0.1 μm was laminated thereon in the same manner as in Comparative Example 2. Then, in the same manner as in Comparative Example 1, a resistor pattern having an electrode layer provided on the above laminated insulating film was formed to prepare a strain sensor C of the present invention.

(Test Example) Non-defective rate test Insulation resistance was measured by applying a DC voltage of 10 V between the substrate and the electrode for each of the above 100 strain sensors, and the insulation resistance value was 2000 MΩ or more at room temperature. The ratio of certain products was determined and shown in Table 1 as the non-defective product ratio (%).

Withstand voltage test In addition, with respect to each strain sensor that passed the above-mentioned non-defective rate test, the applied voltage was gradually increased to measure the change in the insulation resistance, and the voltage at which the insulation resistance value was 1000 MΩ or less was obtained to obtain the withstand voltage. (V), and the range of the variation is also shown in Table 1.

Temperature characteristic test Further, with respect to each strain sensor which passed the above non-defective rate test, the environmental temperature at the time of measuring the insulation resistance was changed to examine the change of the insulation resistance value at DC 10V, and the temperature at which the insulation resistance value dropped to 500 MΩ. The results obtained are also shown in Table 1.

[0020]

[Table 1] ────────────────────────────────── Strain sensor Good product rate (%) Withstand voltage (V ) Temperature characteristics (℃) ────────────────────────────────── A ^* 10 10 〜 30 200 〜 250 B ^* 27 20 to 30 250 to 300 C 73 50 to 60 300 to 350 ─────────────────────────────────── *: Comparative example

[0021]

The strain sensor of the present invention comprises an electrical insulator thin film of a special material structure provided on the surface of a substrate and a pattern of a strain resistance material formed thereon. Not only is the insulating property remarkably excellent as compared with the thin film-provided one, but also the reliability is high and a strain sensor of uniform quality can be efficiently produced.

Claims (1)

[Claims] 1. A strain formed by laminating an electric insulator thin film and a strain sensing electric resistor thin film on a substrate, and further laminating a metal thin film electrode on an electrode portion of the strain sensing electric resistor thin film. In the sensor, the strain sensor, wherein the electrical insulator thin film is formed of a laminate film of a composite layer of aluminum oxide and aluminum nitride and a silicon oxide layer.