JPH06100444B2 - Strain sensor manufacturing method - Google Patents

Description

Detailed Description of the Invention a. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a strain sensor for measuring strain (stress), force, pressure and the like.

B. 2. Description of the Related Art Conventionally, a band-shaped or flat-plate-shaped gauge material is adhered to the surface of a substrate, electrodes are attached to the surface, and the electrical property of the gauge material changes due to deformation of the substrate itself or the material to which the substrate is adhered, that is, a conductive substance. Strain sensors that measure the amount of strain by measuring changes in electrical resistance and changes in electrical properties of ceramic materials are often used, but recently, in this type of strain sensor, an insulating layer is provided on the substrate, and A thin layer of a gauge material is formed on the surface by vapor deposition or the like, and the thin layer is trimmed and shaped.

That is, as shown in FIG. 4, an insulating layer (2) is provided on a substrate (1), a gauge material (3) is formed on the surface thereof by vapor deposition or the like, and an electrode (4) is provided and trimmed. . In this case, both an inorganic substance and an organic substance are used as the insulating layer (2).

C. Problems to be Solved by the Invention However, in the conventional strain sensor, when the insulating layer (2) is made of an inorganic substance, there is a high possibility of causing insulation failure between the substrate and the gauge material due to the presence of pinholes or the like. , In order to prevent insulation failure, the thickness of the insulation layer must be increased, but if the thickness is increased, the insulation layer is likely to crack due to the deformation of the substrate, which may cause a decrease in life due to insulation failure or corrosion. Become. On the other hand, when the insulating layer (2) is made of an organic material, it has essentially low heat resistance, and especially when the thin layer of the gauge material is trimmed by the laser method, the insulating layer is cut or damaged at the same time. There is a problem that insulation failure may occur in some parts.

D. Means for Solving the Problems In the strain sensor having the above structure, the present invention directly forms a first insulating layer of an inorganic material having high heat resistance on a substrate,
Further, a second insulating layer made of an organic material, which is elastic and hard to generate cracks and pinholes, is directly formed thereon. In this manufacturing method, a thin layer of a gauge material is directly formed on the surface by vapor deposition or the like, electrodes are attached, and trimming is performed to eliminate the drawbacks of conventional products.

That is, as shown in FIG. 1, a first insulating layer (2) made of an inorganic material is directly formed on the surface of a deformable substrate (1), and a second insulating layer (5) made of an organic material is directly formed on the surface. To do. The gauge material (3) is directly formed on the surface by a method such as vapor deposition, and the electrode (4) is attached and trimmed.

According to this manufacturing method, even if there is a pinhole or the like in the first insulating layer, insulation is always maintained by the second insulating layer, and thus insulation failure between the gauge material and the substrate does not occur. Even if laser trimming is performed, the first insulating layer has the necessary heat resistance,
Does not cause insulation failure. Further, even if a crack occurs during film formation in the first insulating layer, which is a layer of an inorganic material, the second insulating layer is an organic material, so that insulation failure can be prevented.

By the way, since the gauge material is made of an inorganic material, if the adhesiveness between the gauge material and the second insulating layer made of an organic material is poor, the surface of the second insulating layer should be further improved in order to improve the adhesiveness. The third insulating layer made of an inorganic material may be formed. This is because the gauge material made of an inorganic substance generally has good adhesion to the insulating layer made of an inorganic substance. However, since the third insulating layer is merely for improving the adhesiveness and adhesion between the second insulating layer and the gauge material, the third insulating layer may have a small film thickness.

E. Example 1 As shown in the cross section in FIG. ₂ , Al ₂ O _{3 is} formed on the surface of the upper thin wall of the pressure sensor main body (6) having a hollow inside, a thin wall on the upper side, and a screw on the lower side. A first insulating layer (2) was provided, a second insulating layer (5) made of phenolic resin was formed on the first insulating layer (2), and a NiCr conductive thin film (gauge material) (3) was deposited thereon. An electrode is formed by depositing Ni on this conductive thin film, and then the resistance value of the conductive thin film is adjusted by laser trimming. In this structure, when a fluid is introduced into the hollow portion, strain occurs in the thin wall portion. Since strain changes the electrical resistance of the gauge material, this change can be measured to measure the fluid pressure.

In the present embodiment, when the gauge material is laser-trimmed, the heat resistance of the inorganic first insulating layer does not impair the electrical insulation between the substrate and the gauge material, and the first insulating layer alone causes pinholes. Sufficient insulation could be obtained by providing the second insulating layer even when insulation failure occurred.

Example 2 As shown in the cross section in FIG. 3, on a metal substrate (1)
A first insulating layer (2) of SiO ₂ was provided, a second insulating layer (5) of polyamide resin was formed thereon, and a conductive thin film (gauge material) (3) was vapor-deposited thereon. Next, after depositing the electrode (4), the conductive thin film (3) was laser-trimmed to adjust the resistance value.

The force (weight) (F) was measured by the amount of deformation of the substrate by supporting one end of the substrate and applying a force to the other end. In this case also, insulation failure due to laser trimming did not occur, and the insulation was good even after repeated measurements, and reliable measurement was possible.

F. EFFECTS OF THE INVENTION The present invention provides a strain sensor in which an electrode is provided after vapor deposition of a conductive thin film on a surface of a substrate, and the conductive thin film is trimmed to measure the strain amount of the substrate by a change in electric resistance of the thin film. The first insulating layer made of an inorganic material is directly formed, the second insulating layer made of an organic material is directly formed on the first insulating layer, the conductive material (gauge material) is vapor-deposited on the first insulating layer, and the electrodes are provided before trimming. Therefore, insulation failure due to pinholes in the first insulating layer can be compensated for at low cost, and the heat resistance of the first insulating layer does not damage the insulator due to local heating during trimming. When the insulation layer is made of an inorganic substance only, the thermal conductivity of the insulation layer is high and the heat during soldering escapes to the substrate, but since there is an insulation layer of an organic substance, it is easy to solder the electrode at room temperature. There are advantages. Further, even if the substrate is repeatedly subjected to strain and cracks are generated in the first insulating layer, the second insulating layer made of an organic material has elasticity, and thus insulation failure does not occur. That is, the method of manufacturing the sensor of the present invention is an effective method having various characteristics such as a pressure sensor and other strain detection type strain sensors, which has a good yield in manufacturing and a long life.

[Brief description of drawings]

1 is a partial sectional view of a strain sensor according to the present invention, FIG. 2 is a sectional view of a fluid pressure sensor using the strain sensor of the present invention, and FIG. 3 is a sectional view of a strain sensor of the present invention which is also used for force measurement. Is. FIG. 4 is a sectional view of a conventional strain sensor. (1) ... Substrate, (2) ... First insulating layer, (3) ... Conductive thin film, (4) ... Electrode, (5) ... Second insulating layer (organic substance), (6) ...... Pressure sensor body, (F) …… Force.

Claims (2)

[Claims] 1. A strain sensor for measuring strain by providing an insulating layer on a surface of a substrate, depositing a gauge material on the insulating layer, and measuring strain due to a change in electrical characteristics of the gauge material due to strain of the substrate. The first insulating layer is directly formed, the second insulating layer made of an organic material is directly formed on the upper surface of the first insulating layer, the gauge material is directly formed on the insulating layer by vapor deposition, and the resistance is adjusted by trimming. And a method of manufacturing a strain sensor. 2. The method of manufacturing a strain sensor according to claim 1, further comprising forming a third insulating layer of a thin inorganic material on the second insulating layer.