JPH0282103A - Gauge base incorporated with reinforcing material for strain gauge and its manufacture - Google Patents

Abstract

PURPOSE:To improve the heat resistance, moisture proof, and fatigue life by mixing insulating superfines of an insulating material with a specific resin material and forming an extremely thin film of a base material uniformly. CONSTITUTION:The gauge base 1 is manufactured by mixing insulating superfines of silicon nitride as the insulating material with epoxy resin liquid as a reinforcing material. Further, resistance foil 2 which constitutes a grid is packed in the shaped base 1 and etched by photoetching. Then, a gauge lead 5 is fixed to a gauge tab 4 by spot welding. Then the resistance value of the grid is measured and classified, a laminate film 6 is cut, and the top surface 1a of the base 1 is covered to finish the strain gauge. Consequently, the heat resistance, moisture proof, and fatigue life can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a reinforcing gauge base for a strain gauge and a method for manufacturing the same, and more particularly to a reinforcing gauge base for a strain gauge and a method for manufacturing the same.

A strain gauge made of the above-mentioned base material, in which a sensing part made of a resistive material or a semiconductor material is formed on one surface of the base material, and the other surface is attached to an object to be measured to detect the strain generated in the object to be measured. The present invention relates to a base and a method for manufacturing the same.

[Conventional technology]

In general, a foil strain gauge is composed of a gauge base, a strain sensitive section formed of a resistive material or a semiconductor material on the surface of the gauge base, and a laminate film or the like that covers this strain sensitive section. Conventionally, a commercially available so-called insulating film in which an epoxy resin, a phenol epoxy resin, and a polyimide resin are formed into a film shape has been used as a base material for the gauge base.

In addition, when such a commercially available product is not used, the base material is impregnated with a resin and then formed into a film. In other words, paper, glass paper, asbestos paper, etc. are used as the base material, liquid epoxy resin, phenol resin, phenol epoxy resin, silicone resin, etc. are used as the resin, and the base material is immersed in the resin liquid. There is a manufacturing method in which the resin is removed from the resin liquid after a predetermined period of time and formed into a film by heating, pressurizing, etc. [Problems to be solved by the invention] Generally, The conditions required for the gauge base of a strain gauge (hereinafter referred to as "gauge base conditions") include the following.

(a) The shrinkage rate during curing is small.

(b) It has a large hardening coefficient.

(c) There should be no cracking, warping, twisting, etc. after curing.

(d) Strength is sufficient against temperature, humidity, and strain values.

(e) No hygroscopicity.

(f) Having a high pain limit.

(g) Maintain high electrical insulation against temperature and humidity.

(h) Must be chemical resistant.

Although the gauge-based conditions are 1 or more, electrical insulation and creep properties are particularly required compared to general insulating films. In other words, it is rather suitable that there is no creep not only at room temperature but also at the limit of the operating temperature range, and that creep occurs rapidly when the temperature limit is exceeded. It is also desirable to have high hardness and maintain the elastic modulus up to the temperature limit.

Now, in conventional gauge bases, when using the above-mentioned commercially available insulating films, there has been a problem that there are few that satisfy the dimensions (particularly thickness) and the above-mentioned conditions for the gauge base. In other words, the thinner the gauge base is, the less the rheological influence of the plastic (resin), the better the strain transmission, and the less creep occurs, but conventionally there was only a thick insulating film of about 20 μm. Therefore, strain gauges using such insulating films as gauge bases are hard and do not conform to the shape of the object to be measured, making it difficult to handle when bonding the strain gauge to the object to be measured, and the so-called flexible strain gauges. There was a problem with poor stability.

On the other hand, conventional gauge-based manufacturing methods not only have the problem of low impregnation of the resin into the base material, making it difficult for the resin to soak uniformly into the base material, but also air bubbles. Ta. The presence of such impregnated bubbles causes problems such as deterioration of strain transmission, unstable strain gauge output, and creep. In addition, the bubble portion receives concentrated stress and residual strain, which deteriorates the durability (for example, fatigue limit) of the strain gauge. Furthermore, since moisture in the air gets mixed into the bubble portion, there are problems in that the temperature resistance deteriorates and the insulation properties of the strain gauge deteriorate.

Furthermore, due to the difference in physical constants such as longitudinal elastic modulus (Young's modulus), linear expansion coefficient, and heat transfer coefficient between the gauge base and the foil material forming the strain sensing part, the foil material and the gauge base are lined (backing). As a result, the strain gauge curls so that the foil side is convex and the side of the gauge base to which the foil material is not attached is concave. sensory part)
There was a problem in that the manufacturing yield was lowered due to the occurrence of defects in accutance and defective appearance.

In addition, such curled strain gauges may cause uneven pressure when bonded, and air bubbles may easily enter the adhesive (bonding surface), resulting in deterioration of the strain gauge's characteristics, lowering its fatigue limit, and increasing the risk of creep. There is a problem in that this leads to an increase in mechanical hysteresis and electrical connection failure.

The present invention has been made in view of the above circumstances.

The aim is that by forming it into an ultra-thin film, it will not only significantly improve adhesiveness and strain transmission properties, but also dramatically improve heat resistance, moisture resistance, and fatigue life. Manufacture of a reinforcing material-containing gauge base for a strain gauge, which provides a reinforcing material-containing gauge base for a strain gauge that can improve various properties of the gauge, and also enables easy manufacturing and processing of the gauge base, which is uniform and extremely thinner than conventional gauge bases. The purpose is to provide a method.

[Means and Method for Solving the Problems] In order to achieve the above-mentioned objects, the present invention provides a base material in which a sensing portion made of a resistive material or a semiconductor material is formed on one surface of the base material, and a sensing portion made of a resistive material or a semiconductor material is formed on the other surface of the base material. A gauge base made of the above-mentioned base material of a strain gauge attached to a material to detect strain generated in the object to be measured includes a predetermined resin material and ultrafine insulating powder made of an insulating material, and the above-mentioned insulating The reinforcing material-containing gauge base of the strain gauge according to the present invention is characterized in that the base material is formed into a uniform and extremely thin film by mixing powder into the resin material. Ultrafine insulating powder made of insulating material is mixed into a specified resin material and adjusted by stirring, mixing, and pulverizing.
A feature of the present invention is that the adjusted resin material is applied to a mold release material to form the base material in the form of a uniform and extremely thin film.

[For production]

In the gauge base with reinforced material constructed as above, the resin material is strengthened by insulating powder, the Young's modulus of the base material is increased, the strain transmission effect is enhanced, the mechanical strength is increased, and the fatigue life is long. This increases heat resistance. Since it is formed extremely thin, it conforms well to the shape of the object to be measured, improving adhesion. Furthermore, since it is formed uniformly, no bubbles are generated, and moisture resistance is improved.

In addition, since it is reinforced by insulating powder and is extremely thin, curling properties are improved and manufacturing yield is improved.

In addition, as a manufacturing method, the resin itself is mixed with insulating powder and adjusted to form a film, so it is easy to obtain an ultra-thin shape, and because it is adjusted by stirring, mixing, and pulverizing, a uniform base material can be obtained. can be easily obtained.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 and FIG. 2 are a central vertical cross-sectional view and a plan view, respectively, showing a state in which a reinforcing material-containing gauge base of a strain gauge according to the present invention is adhered to the surface of a cover 8111 with an adhesive.

In FIGS. 1 and 2, 1 is a reinforcing material-containing gauge base (hereinafter simply referred to as "gauge base J") of the strain gauge according to the present invention, and 1a and 1b are upper surfaces of the base gauge 1. 2 is a resistance foil formed on the upper surface 18 of the base 1 by rolling or by vapor deposition or sputtering, and 3 is a resistance foil formed by photo-etching the resistance foil 2. 4 is a gauge tab formed at both ends of the grid 3 at the same time as the grid 3; 5 is a gauge tab 4 having one end spot welded or soldered, etc.; 6 is a laminate film that covers the grid 3 and gauge tab 4 and the upper surface la side of the gauge base 1 that attaches and supports them for moisture proofing and damage prevention; 7 is an adhesive for strain gauge; 8
is an object to be measured to which the lower surface 1b of the gauge base 1 is adhered by the adhesive 7.

Note that the strain gauge 9 is composed of the gauge base 1, the grid 3, the gauge tab 4, the gauge lead 5, and the laminate film 6.

3 and 4 are a longitudinal sectional view and a plan view showing the configuration of a wheeler used in the method for manufacturing a gauge base according to the present invention.

In FIGS. 3 and 4, 10 is an opening 10 at the upper end.
a is a cylindrical cover having a bottom portion 10b at the lower end, and 11 is a flat upper surface 11b supported by a rotatable shaft 11a protruding from the bottom fob at approximately the center of the cover 10.
12 is a release material set on the upper surface 11b of the rotary plate 11, 13.13a, 13
b is a resin liquid as an adjusted resin material, of which 1
3 is the resin liquid in a state where it has been dropped onto the mold release material 12, 13b is in the state where it is being dropped, and 13a is the resin liquid in the state where it is stored in the container 14 in which it is dropped. Note that the shaft 11a is configured to be rotationally driven by a prime mover (not shown).

FIG. 5 is a characteristic diagram comparing and showing the characteristics of the strain gauge 9 of this embodiment and a conventional strain gauge (not shown).

Figures 6 to 8 are graphs showing the characteristic tests of this example. Figure 6 is the fatigue life test, Figure 7 is the creep test, and Figure 8 is the graph showing the characteristic tests of this example.
The figure shows a mechanical hysteresis test.

First, a method of manufacturing the gauge base 1 of this embodiment shown in FIGS. 1 and 2 will be described.

A reinforcing material in the form of ultrafine particulate (0.1 μm or less) insulating powder made of silicon nitride as an insulating material is mixed into an epoxy resin liquid as a resin material, and then chemically and mechanically treated by stirring, mixing, and pulverizing. I do.

Note that a kneader, a ball mill, etc. are used for this treatment.

The resin liquid adjusted in this way, that is, the adjusted resin liquid, is applied to a mold release material made of, for example, a polyester film with a thickness of 25 to 50 μrn, dried and baked, and the mold release material is removed to form a gauge. The base is made. For this operation (processing), for example, the wheeler shown in FIGS. 3 and 4 is used.

That is, the mold release material 12 is set on the upper surface 11b of the rotary plate 11 of the wheeler, and an amount of resin liquid 13 corresponding to the area of the gauge base to be formed is dropped onto the mold release material 12, and then the rotary plate 11 is is rotated for a predetermined time while maintaining a predetermined rotation speed.

By this rotation, the resin liquid 13 is spread and coated on the mold release material 12 in the form of a film.

In this state, take out the mold release material 12 from the wheeler,
Dry and bake in a constant temperature bath, etc. After baking as described above, the mold release material is removed to produce a gauge base.

Next, the manufacturing process of the strain gauge 9 shown in FIGS. 1 and 2 will be explained.

First, the gauge base 1 manufactured as described above is cut into a desired shape. On the other hand, the foil material of the resistance foil constituting the grid 3 is inspected, cut into a predetermined shape, and heat-treated. This resistance foil is lined with a shaped gauge base, and then photo-etched.
Etching, then shape inspection, cutting, resistance, 11
The gauge lead 5 thus processed is attached to the gauge tab 4 by spot welding or soldering. and.

The resistance value of the grid 3 is measured and classified, and the laminate film 6 is cut and then the upper surface la side of the gauge base 1 is covered to finish.

Next, the characteristics of this embodiment will be explained based on FIG. 5 while comparing them with those of the conventional type.

First, the fatigue life of characteristic item 1 is improved by more than twice. still,
The fatigue life measurement conditions are as shown in Fig. 6 at room temperature, where a strain of ±1500 x 10-' is applied alternately, and whether or not the life has been reached is determined by monitoring the output of the strain gauge 9. Zero points without strain, TEN corresponding to a strain of +1500X10-' and COM corresponding to a strain of -1500XIO-', respectively 100XIO-'
It is determined that the life has been reached when either one of the following phenomena occurs: a change of A, 8 or more corresponding to the strain, or a spike noise appears in the output of the strain gauge 9.

The strain limit (elongation property) of property item 2 is improved by a little less than twice.

The measurement conditions at this time were such that the strain gauge 9 was pulled at room temperature until the resistance wire 2 peeled off or the grid 3 broke.

The heat resistance of characteristic item 3 is the heat resistance as a strain gauge, and there was an improvement of 80°C.

Adhesiveness of characteristic item 4 was evaluated by attaching gauge base 1 to the test piece with adhesive and evaluating the shear strength during tensile shearing in accordance with JIS K6851 r Adhesive Tensile Shear Bonding Strength Test Method. Improved by 2 times.

Characteristic item 5, creep, is measured at a constant room temperature and a constant load (±10
The results of measuring the change in the output of the strain gauge 9 over time by applying a strain of 0OXIO''.

As shown in Figure 7, in one measurement example, 4.5με in one hour.
The final measurement (test) results showed a two-fold improvement.

The moisture resistance of property item 6 is determined by exposing the strain gauge 9 attached to the test piece to an atmosphere of 20°C and 62% RH and 45°C and 90% RH, and repeating 20 cycles. As a result of measuring the zero drift of the strain gauge 9, it was improved by two times.

The insulation resistance of characteristic item 7 is the DC voltage 5 between the measured object (conductor) 8 and the gauge lead 5 after the test of characteristic item 6 above.
As a result of measurement with 0V applied, the improvement was 2X107 times.

Characteristic item 8, the minimum radius of curvature, is used to test the flexibility of the strain gauge.
This refers to the minimum radius of curvature that can be attached to a strain gauge, and as a result of comparative measurements using a strain gauge with a gauge length of 1 m, it was improved by over 1.5 times.

The thickness of the gauge base 1 in characteristic item 9 could be reduced by half.

Drift in characteristic item 10 means the drift when installed on a curved surface, and the temperature of the test specimen at 80" C1 is 1! r
= 10 mm, test time was 24 hours, and the change in the zero point over time was measured with no stress on the test specimen, and the results showed a three-fold improvement.

The Young's modulus of the gauge base 1 of characteristic item 11 is.

It was improved by 2.5 times. The linear expansion coefficient of characteristic item 12 was improved by a little less than 4 times to 5 times.

Heat transfer coefficient of characteristic item 13 (unit: 10-'cal/
5ec-CIIl/°C-all) was improved by a little more than 2.5 times.

Broadly interpreted, the mechanical hysteresis in characteristic item 14 also means the strain transfer effect, and as shown in Figure 8, the load increase/decrease cycle when a mechanical strain εm=±3000×10−' strain 7 is applied. As a result of measuring the maximum values Ml and M2, the results were 1.4.

In this way, the gauge base of this embodiment is extremely thin at 15 μm, which is half that of the conventional one, and is uniformly formed.
It has the advantage of having a large Young's modulus and a high strain transmission effect. Furthermore, since it is uniform, there are no air bubbles mixed in.
It has the advantages of excellent moisture resistance, improved mechanical strength, and long fatigue life.

Further, by incorporating the reinforcing material, there is an advantage that not only the heat resistance of the gauge base 1 but also the strain gauge 9 is improved, the wettability is improved, and the adhesiveness is improved.

Furthermore, since it is extremely thin, has a small coefficient of linear expansion, and has a Young's modulus close to that of the object to be measured 8, it has the advantage of improved curling properties, improved manufacturing yield, and improved workability of bonding.

It should be noted that the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the spirit thereof.

For example, the resin liquid in the examples is not limited to epoxy resin, and any one of other phenol resins, phenol epoxy resins, and silicone resins may be used.

Further, the reinforcing material is not limited to silicon nitride, and any one of alumina, silica, and boron may be used.

Furthermore, the grid 3 is not limited to being composed of the resistance foil 2;
It may also be made of semiconductor material.

〔Effect of the invention〕

As detailed above, according to the present invention, the gauge base can be formed into an ultra-thin film shape, the linear expansion coefficient is small, the heat transfer coefficient is large, and the adhesiveness and strain transferability are excellent. It is possible to provide a reinforcing material-containing gauge base for strain gauges that can dramatically improve heat resistance, moisture resistance, and fatigue life, thereby greatly improving various properties of strain gauges, and is also uniform and ultra-thin. It is possible to provide a manufacturing method that allows the above-mentioned gauge base to be easily manufactured and processed.

[Brief explanation of drawings]

1 and 2 are a central vertical sectional view and a plan view, respectively, showing a reinforcing material-containing gauge base according to the present invention adhered to a measured object with an adhesive, and FIGS. 3 and 4 are
The figures are a vertical cross-sectional view and a plan view showing the configuration of a wheeler used in the method for manufacturing a gauge base according to the present invention, and FIG. 5 shows a strain gauge to which this embodiment is applied and a conventional strain gauge (not shown). ) characteristic diagram comparing and showing the characteristics of
Figures 8 to 8 are graphs showing the results of characteristic tests of strain gauges to which the two embodiments were applied. Of these, Figure 6 is a fatigue life test, Figure 7 is a creep test, and Figure 8 is a mechanical test. Hysteresis tests are shown respectively. 1... Gauge base with reinforcing material (gauge base) 2... Resistance foil, 6... Lamiho 1-film, 7...
Adhesive, 9...Strain gauge, 11... Rotating plate, 13... Resin liquid. ... Grid, 8 ... Measurement object, 10 ... Cover 12 ... Release material,

Claims (4)

[Claims] (1) The above-mentioned base material of a strain gauge in which a sensing part made of a resistive material or a semiconductor material is formed on one surface of the base material, and the other surface is attached to an object to be measured to detect the strain generated in the object to be measured. The gauge base comprises a predetermined resin material and ultrafine insulating powder made of an insulating material, and the insulating powder is mixed into the resin material to form the base material into a uniform and extremely thin film. A gauge base containing a reinforcing material for a strain gauge, characterized in that it is configured to form a strain gauge. (2) A reinforcing material-containing gauge base for a strain gauge according to claim 1, wherein the resin material is made of any one of epoxy resin, phenol resin, phenol epoxy resin, and silicone resin. (3) A reinforcing material-containing gauge base for a strain gauge according to claim 1, wherein the insulating material is made of any one of alumina, silica, boron, and silicon nitride. (4) The above-mentioned base material of a strain gauge in which a sensing part made of a resistive material or a semiconductor material is formed on one surface of the base material, and the other surface is attached to an object to be measured to detect the strain generated in the object to be measured. In the gauge base manufacturing method, which involves mixing ultrafine insulating powder made of an insulating material into a predetermined resin material and adjusting it by stirring, mixing, and pulverizing, the adjusted resin material is applied to a mold release material. A method for producing a reinforcing material-containing gauge base for a strain gauge, comprising: forming the base material in the form of a uniform and extremely thin film.