JPS5975676A - Distortion sensor - Google Patents

Abstract

PURPOSE:To obtain the distortion sensor of high degree of accuracy and high reliability at low cost by a method wherein an insulating resin layer, a resistive layer having Ni, Cr and Si as main ingredients, a resistive layer having Ti as a main ingredient, and a conductive layer having Cu as a main ingredient are formed by lamination on a beam material successively, and the prescribed pattern is formed by performing a photoetching. CONSTITUTION:After the pattern forming surface of the beam body 1 has been flattened by polishing and cleaned, polyimide resin is uniformly applied on the pattern forming surface. Subsequently, the above is hardened by heating and an insulating resin layer 14 consisting of polyimide resin is formed. Then, the first resistive layer 15 is obtained by forming an Ni-Cr-Si layer on the insulating resin layer 14 by performing a sputtering, a Ti film layer is formed as the second resistive layer 16, and a Cu film layer is formed on said Ti film layer as a conductive layer 17. After the prescribed pattern has been formed on the above laminated body, the pattern as shown in the diagram (a) is obtained by performing an etching on the Cu, Ti and Ni-Cr-Si located on the region other than the pattern above-mentioned. Subsequently, the pattern as shown in the diagram (b) is obtained by performing an etching on strain gage resistive bodies 8a- 8d and the Cu layer of the upper layer of a temperature sensor 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a strain sensor used, for example, in an electronic scale.

[Technical background of the invention and its problems] In conventional strain sensors formed using thin film resistors, NiCr or NiCr cermet is used as the strain gauge resistor, and the insulating layer between the strain gauge and the beam body is is SjO+
Inorganic oxide layers such as Ta 205 and Ta 205 are used.

In this case, the temperature coefficient of resistance of the strain gauge resistor must be made as small as possible in order to reduce temperature drift at the zero point, but NiCr and NiCr cermet have a strong dependence on the degree of vacuum during film formation, so the temperature coefficient It is not easy to reduce the variation in Furthermore, when the above-mentioned inorganic oxide is used as the insulating layer, the beam body surface is susceptible to scratches and vinyl pole carvings, and insulation defects are likely to occur. When used as a strain sensor, f
) Ta2O! Since materials such as i have poor flexibility, cracks are likely to occur when a large impact is applied to the beam body. Furthermore, although Au is used as the conductor layer, it is expensive.

[Object of the Invention] The present invention was made in view of the above points, and an object of the present invention is to obtain a highly accurate, highly reliable, and inexpensive strain sensor.

[Summary of the invention]

The present invention includes an insulating resin layer, NiCrSi k, on the beam body.
A first resistance layer containing T1 as the main component, a second resistance layer containing T1 as the main component, and a conductor layer containing Cu' as the main component are sequentially laminated, and a predetermined pattern is formed by photo-etching. It is suitable for strain sensors in terms of the combination of characteristics, and it is made so that pattern formation is easy.

[Embodiments of the invention]

An embodiment of the present invention will be described based on the drawings.

First of all, Figure 1 does not show the trajectory of the strain sensor; it is a beam body (made by machining duralumin, 5O8630, etc.).
1) is connected by the groove (2) and has a thin deformed part (3).
Holes (5) (6'l) forming (4) are formed.

A strain sensor circuit (7) is installed on the top surface of the beam body (1).
is patterned 9, and the strain gauge resistor (8
cL) (8/') (80) (8d) is the thin deformed part (3)
(4) Provided above.

Further, (9) is a temperature sensor, which is a resistor that compensates for changes in the amount of deformation of the beam body (1) due to temperature. These strain gauge resistors (8a) (8A) (8G) (8d
) and temperature sensor (9) are connected to each other by a lead pattern ←O) to form a strain sensor circuit as shown in FIG.

Further, a hole Qz for attachment to the base αJ is formed in the beam body (1), and a hole α3 to which a metal fitting to which a load is applied is connected is formed on the tip side. Figure @3 shows the state of deformation when a load is applied. Now, when a load W is applied, the beam body (1) deforms, and the strain gauge resistor (8cL) (84) undergoes tensile υ Upon receiving strain, the strain gauge resistors (8L-) (8d) receive compressive strain, their respective resistance values change, and an output voltage is generated in the strain sensor circuit.

The formation of the strain sensor circuit will now be explained with reference to FIGS. 4 to 6. First, the pattern forming surface of the beam body (1) was polished flat and cleaned, and then
A varnish-like polyimide resin having a viscosity of 100 ml is applied dropwise and the beam body (1) is rotated by a spinner at a rotational speed of about 160 rpm to uniformly apply the polyimide resin to the surface on which the polyimide pattern is formed. After that, after drying at 100℃ for 1 hour,
By heating and curing at 00° C. for 1 hour, an insulating resin layer made of polyimide resin with a thickness of 4 μm is formed. Then, by sputtering, a 100 mm thick NiCrSi layer (Ni; 70.Cr
:20. Si'IO) is formed to form the first resistance layer α9. Furthermore, a Ti film layer with a thickness of 1 μm is formed as a second resistance layer (te, and a conductor layer α7 on the surface of the Ti film layer with a thickness of 2 μm).
Form a u film layer. FIG. 4 shows the laminate thus obtained. Here, for the sputtering thread, the initial vacuum level is 6 x 1O-6 Torr, and the argon partial pressure is Phr.
= 4 x 1O-3 Torr, and use I) O'FN source for sputtering output.

A predetermined pattern is obtained by photo-etching the laminate thus formed. Sunzu, its 5
After forming a predetermined pattern with photoresist as shown in rv ta+, cu in the area other than this pattern part.

Etching is performed using Ti and NiCrSi f etchants to obtain a pattern as shown. Here, the polyimide resin layer 1, that is, the absolute resin layer α→ is exposed in the area other than the pattern portion. Here is the last NiC
In etching the rSi layer, a ferric fluoride hydroxide etchant is used, and polyimide resin is not attacked by this etchant and is therefore ideal.

Incidentally, in the case of a 5iOz layer, which is a known insulating layer, C cannot be used because of the corrosion caused by ferric fluoride hydroxide.

Subsequently, as shown in FIG. 5, the upper layer 61 of the strain gauge resistors (8a) (84) (8c) (8ii) and the S temperature sensor (9) was etched using a Cu etchant. We get a pattern like .This gives us a pattern like
The Ti film is exposed at necessary locations on the pattern. In this case, the etchant for Cu is ferric chloride, and since this etchant does not corrode the υTi film, selective etching as described above is possible, and this film configuration is convenient. be. In this process, the temperature sensor (19) is completed.Furthermore, as shown in the to5 diagram fGl, the strain gauge resistor (8 cL) (8 lines (s)
c) By etching the Ti layer laminated in (sd) with a Ti etchant, the first resistance layer oF9 made of NiCrSi is exposed, and the strain sensor circuit is completed. Here, the Ti film is etched by 7H of hydrofluoric acid.
This etchant makes NiCrSi
The film is not eroded and the selective etching described above becomes possible. FIG. 6 shows a sectional view along the line X of FIG. 5 (,).

As shown in Fig. 6, the lead no. turn 00 layer is N.
It is a laminate of iCrSi/Ti/Cu, and the temperature sensor (9) is made of NiCrSi/TiO,) rRI
H body, strain gauge resistor (8tL) (8'+
4) (8c) (8d) are composed only of NiCrSi layers.

Therefore, according to this embodiment, the first resistance layer 09 made of the NiCrSi layer has a large specific resistance of about 200 μΩα.
And the temperature coefficient of resistance is several ppm/1? : Because it is small,
Strain gauge resistor (8eL) (84) (8c)
' (8d) is suitable. Furthermore, during sputtering formation, there is little dependence on formation conditions such as degree of vacuum, argon partial pressure, sputtering speed, etc., so manufacturing is easy.

In addition, the temperature coefficient of resistance of the T1 film is 3000 when the film thickness is 1μ.
Since the temperature is as large as ppm/°C, it is suitable as a temperature sensor (9).

Moreover, Cu has a small resistivity (2 to 3 x to-
'Ωcrn), it is possible to solder the lead wires even after the pattern is formed, it is inexpensive, and it is suitable as the lead pattern α1. In the end, polyimide resin layer/NiCr5i layer ZTi layer Z
According to the film structure of the Cu layer, it is suitable as a strain sensor due to its characteristics, and since it is easy to form a pattern by selective etching, it is also suitable as a strain sensor from this point of view.

In this example, polyimide resin was used as the insulating resin layer Q, but cyclized polybutadiene rubber may also be used. First, the pattern forming surface of the beam body (1) is polished smooth and cleaned, and then a face-shaped cyclized polybutadiene rubber whose viscosity is adjusted to 300 ep is dropped, and the beam body (1) is spun with a spinner. The cyclized polybutadiene rubber is uniformly applied to the pattern forming surface by rotating at a rotation speed of 160 rpm.

Then, after evaporating the solvent for 30 minutes at 80°C,
By heating and curing for 1 hour, a cyclized polybutadiene rubber film having a thickness of 4 μm was formed. Next, as in the case of polyimide resin, after forming the first and second resistance layers α→a0 and the conductor layer αη by sputtering, a predetermined pattern is formed by photoetching. In this case as well, the cyclized polybutadiene rubber film is not corroded by the etchant during etching.

By the way, in order to reduce the resistance value of the lead pattern αQ, it is possible to increase the pattern width or increase the film thickness. In this case, when the pattern area is limited, such as in a small strain sensor, it is necessary to increase the film thickness of the lead pattern. However, if the thickness of the Cu layer as an auxiliary conductive layer is made to be 3 to 5 microns, for example, problems during film formation are accumulated and phenomena such as peeling often occur. On the other hand, Au and AI can be used as conductor layer materials with low distortion.
! is known, but Au is expensive and Al cannot be soldered. In such a case, the conductor layer (17
) is AI! -1+ using a Cu layer is fine. For example, insulating resin layer H-4μ, NiCrSi layer=0.14
．． After forming a Ti layer with a thickness of ip, an At layer with a thickness of 5μ, and a Cu layer with a thickness of 1μ, a predetermined pattern was obtained by selective etching using the process described above. Of course, a thick film without distortion is achieved by the AJ layer, and soldering is ensured by the presence of the Cu layer. In this case, AI! A phosphoric acid-acetic acid based etchant is used as the etchant, which enables selective etching without corroding the Ti film. Note that such a four-layer stacked structure NiCrS
i/TI/Aj? /Cu has good adhesion between the films when they are all successively laminated in the same vacuum chamber without breaking the vacuum, but Ni(:rsi / Ti /
Al! After stacking them continuously in the same vacuum chamber, they are taken out from the vacuum chamber and AI! When a C11 layer is laminated on the layer, Al
It was found that poor adhesion easily occurs between the film and the Cu film. On the other hand, when several hundred Ni or Ti films were formed before laminating the Cu film and the Cu film was laminated, good adhesion was obtained. Therefore, if all layers are not formed in the same vacuum chamber, Ni
A layer configuration of CrSi/'l'i/Ae/Ni/cu or NiCrSi/Ti/A/'/Ti/Cu is desirable.

〔Effect of the invention〕

As described above, the present invention provides an insulating resin layer on the beam body, N
i(:r) A first resistance layer containing Si as a main component, a second resistance layer containing Ti as a main component, and a conductor layer containing Cu as a main component.
Since the layers are sequentially laminated and a predetermined pattern is formed by photo-etching, it is suitable for strain sensors due to the characteristics based on the combination of these layers.The pattern formation is also easy, so it can be used with high precision. It is possible to provide a highly reliable and inexpensive product.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; FIG. 1 is a perspective view, FIG. 2 is a circuit diagram, FIG. 3 is a side view in an operating state, FIG. 4 is a longitudinal side view showing the gist, and FIG. Figures (a1 to (-1) are plan views showing the photoetching process, Figure 6 is Figure 5 (
It is a sectional view taken along the line xx' of C1. DESCRIPTION OF SYMBOLS 1... Beam body, 14... Insulating resin layer, 15...
・First resistance layer, 16...Second resistance layer, 17...Conductor layer], 3 Tori no LL Imo 5 Kobo BO is 51υ

Claims (1)

[Claims] 1. An insulating resin layer, a first resistance layer mainly composed of NiCrSi, a second resistance layer mainly composed of Ti, and a conductor layer mainly composed of Cu are sequentially laminated on the beam body. A strain sensor characterized in that a predetermined pattern is formed by photoetching. 2. The strain sensor according to claim 1, wherein the insulating 4ml fat layer is formed of polyimide resin. 3. The strain sensor of claim 1ii4, item 1, wherein the insulating resin layer is formed of cyclized polybutadiene rubber.