JPH04204128A - Stress sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To block the growing and expansion of the peeling of an insulating film which is formed in a cutting step and to improve operating reliability as a sensor by forming a step part at the periphery of the thin plate piece wherein a part which acts as a stress sensor is formed. CONSTITUTION:A step part is provided at the entire periphery or at a part of the periphery of a thin plate piece 1 wherein a strain detecting part comprising strain gages 5 and electrode wirings 6 is formed. An insulating film 4 is formed on the entire upper surface of this pattern and rigidly fixed to the thin plate piece 1. In the fabricating method of this sensor, the plate piece is cut with a cutter 13 after the formation of the insulating film 4. At first, a cutting groove 12 is formed, and the groove part is cut by the cutter 13. Thus, the step part is formed in the thin plate piece 1. Cracks and peeling parts are formed at the edges of the cut part. These parts are formed at the lower surface of the step and are not expanded to the upper surface of the step. The sensor can be readily fabricated by simply forming the groove 12 in the thin plate piece 1. Thus, the sensor having the high operation reliability, from which the effect of the peeling is removed, can be fabricated at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stress sensor and a method for manufacturing the same, and particularly to a stress sensor that measures stress generated in a structural member of a civil engineering/construction machine or the resulting strain generated in the member. The present invention also relates to a stress sensor used to measure stress in various other mechanical members, and a method for manufacturing the same.

[Conventional technology]

Types of stress sensors include, for example, pressure sensors, strain sensors, torque sensors, and load sensors. Among these stress sensors, a relatively well-known pressure sensor will be described below as an example.

FIG. 7 shows a longitudinal sectional view of a typical conventional pressure sensor.

In FIG. 7, 1 is a thin plate piece, which has the function of deforming in response to pressure. A cylindrical member 2 is fixed to the lower part of the thin plate piece 1 in the figure. One end of the cylindrical member 2 is fixed to the periphery of the lower surface of the thin plate piece 1 to support the thin plate piece 1. la and 2a are joint surfaces between the thin plate piece 1 and the cylindrical member 2, respectively. Since the peripheral portion of the thin plate piece 1 is supported by the cylindrical member 2, only the central portion thereof can move while being constrained by the peripheral portion. The center portion of the thin plate piece 1 is a strain-generating portion, and the lower surface thereof is a pressure-receiving surface. When pressure is applied to the pressure receiving surface by fluid etc., the thin plate piece 1
causes distortion. Arrow 3 in the figure means pressure.

On the other hand, an insulating film 4 is first formed on the surface of the thin plate piece 1 opposite to the pressure-receiving surface, and furthermore, a semiconductor strain gauge 5 and an electrode wiring 6 are formed on the upper surface of the insulating film 4. This electrode wiring 6
is for connecting the semiconductor strain gauge 5 to other external electric circuit parts.

The conventional method for manufacturing a pressure sensor having the above configuration is as follows:
As shown in FIGS.

7 is a metal thin plate base material, which has a fairly large area. Later, this thin plate base material 7 is cut into pieces to produce the above-mentioned thin plate pieces 1. An insulating film 4 is formed on the upper surface of the thin plate base material 7. This insulating film 4 includes Sin, , SiC,
A plug 7 of SiNx or the like is formed by a film forming method such as CVD or sputtering. Furthermore, 8 is a polycrystalline silicon thin film for making a strain gauge, and is formed on the entire upper surface of the insulating film 4. Next, the polycrystalline silicon thin film 8 is formed into a pattern of a plurality of strain gauges 5 by photolithography. Reference numeral 6 denotes electrode wiring, which is formed of Au, Kl, etc. by vacuum evaporation and sputtering.

FIG. 13 shows a cutting process for removing the thin plate piece 1 that functions as a stress sensor. In this cutting process, the insulating film 4 and the thin plate base material 7 are cut by the cutter 9 of the dicing machine for each set consisting of a predetermined number of semiconductor strain gauges 5 and electrode wiring 6, and the above-mentioned thin plate pieces 1 are cut out. A large number of thin plate pieces 1 are made from a single thin plate base material 7. Next, as a final step, if the cylindrical member 2 is joined to a predetermined location on the lower surface of the thin plate piece 1,
Complete. As the bonding means, for example, a method is used in which an insert member 10 made of aluminum or the like is applied to the bonding surface 2a, the two are brought into close contact with each other, and annealing is performed at a temperature of 550° C. or higher for a predetermined period of time.

[Problem to be solved by the invention]

In the conventional stress sensor manufacturing method described above, a large number of strain gauges and electrode wirings are fabricated on a large-area thin plate base material 7 using semiconductor manufacturing technology and film forming technology, and then the thin plate base material 7 is
By cutting the insulating film 4 formed on the upper surface and the thin plate base material 7 together, a large number of thin plate pieces 1 can be obtained, thereby enabling mass production.

However, in the conventional manufacturing process, the cutter 9 cuts the insulating film 4.
Since there is a step of cutting the thin plate base material 7 on which a Cracks occur in the insulating film 4, or peeling occurs between the insulating film 4 and the thin plate base material near the edge of the cut location. If such peeling exists, the peeled part will grow while the thin film piece 1 is used as a pressure receiving part of a pressure sensor for a long period of time, and eventually the lower part of the strain gauge and electrode wiring will also be peeled off. There is also a risk that the pressure sensor may lose its function.

An object of the present invention is to provide a stress sensor whose manufacturing process includes a cutting process, in which the peeled part of the insulating film that occurs in the cutting process is formed as a small part, and the peeled part then grows to the lower part of the insulating film of a strain gauge, etc. An object of the present invention is to provide a stress sensor that has a structure that prevents this from occurring and thereby performs stable sensing operation over a long period of time, and to provide a manufacturing method that can easily produce a stress sensor having such characteristics at a low cost. be.

[Means to solve the problem]

The stress sensor according to the present invention connects an insulating film formed on one side of a thin plate piece having a pressure receiving part, a strain gauge formed on this insulating film, and this strain gauge to an external electric circuit part. A stress sensor is formed by cutting out a thin plate piece from a large area monolithic thin plate base material on which an insulating film, a strain gauge, and an electrode wiring are formed,
It is characterized in that the thin plate piece has a stepped portion at its periphery.

The stress sensor according to the present invention is characterized in that, in the above configuration, the step portion is a step between a location where the strain gauge is formed and a location where cutting is performed.

The stress sensor according to the present invention is characterized in that in each of the above configurations, a cylindrical member is fixed to the pressure receiving surface side of the thin plate piece.

The stress sensor according to the present invention is characterized in that in each of the above configurations, the strain gauge is a semiconductor strain gauge.

A method for manufacturing a stress sensor according to the present invention includes forming a groove in a thin plate base material, forming an insulating film on the surface of the thin plate base material on which the groove is formed,
Strain gauges and electrode wiring are formed in each of a plurality of regions surrounded by grooves on the insulating film, and the thin plate base material is cut along the grooves with a cutting tool having a width smaller than the width of the grooves.
The present invention is characterized in that a plurality of thin plate pieces for stress sensors are made.

A method for manufacturing a stress sensor according to the present invention is characterized in that the strain gauge is a semiconductor strain gauge in the aforementioned manufacturing method.

[Effect]

In the stress sensor according to the present invention, a stepped portion is formed on the entire periphery or a partial edge of a thin plate piece on which a strain detection section consisting of a strain gauge or an electrode wiring is formed, and in this form, a stepped portion is formed on the entire upper surface of the thin plate piece. The insulating film is firmly attached to the thin plate piece. This stress sensor manufacturing method includes a step of forming an insulating film and then cutting it with a cutter, but by forming a groove for the cutting part and cutting the groove part,
A step is formed in each cut out thin plate piece. Although cracks and peeling are formed at the edges of the cut portions, since they are on the lower surface of the step, the peeling and the like do not extend to the upper surface of the step. That is, by providing a stepped portion between the location to be cut and the location where the strain detection portion is formed, it is possible to block the influence of peeling caused by cutting.

With the method for manufacturing a stress sensor according to the present invention, a stress sensor having the above-described characteristics can be easily formed. In other words, at an early stage before forming an insulating film, grooves are formed in the shape of a lattice on the surface of the thin plate base material from which the thin plate pieces are cut out, and then the insulation is formed by applying conventional semiconductor technology and film formation technology. A thin plate piece having a portion functioning as a stress sensor can be taken out by forming a film and a strain detecting portion and then cutting along a groove.

〔Example〕

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

FIG. 1 is a longitudinal sectional view showing the features of the stress sensor according to the present invention, and FIGS. 2 to 6 are diagrams showing the manufacturing process of the stress sensor according to the present invention. In this embodiment, an example of a pressure sensor will be described in the same way as in the case of the prior art.

Regarding the illustrated example according to this embodiment, the same elements as described in the conventional pressure sensor will be described with the same reference numerals.

In FIG. 1, numeral 1 is a metal thin plate piece that has a pressure receiving function and deforms in response to pressure, and 2 is a cylindrical member attached to the lower periphery of the thin plate piece 1. The thin plate piece 1 has a planar rectangular shape. The cylindrical member 2 is made of metal such as 5US630 in a cylindrical shape, and supports the thin plate piece 1 which is easily deformed. In this structure, the peripheral portion of the thin plate piece 1 is fixed, and only the central portion thereof is deformed. The lower surface of the central portion becomes the pressure receiving surface. The central portion of the thin plate piece 1 functions as a strain-generating portion when pressure is applied in the direction of the arrow 3 in the figure. The thin plate piece 1 is actually 5US
630 etc., and its thickness is 0.2-2Il1
It is m. The thin plate piece 1 and the cylindrical member 2 are bonded together using a diffusion bonding method or a method using an adhesive, as in the case of the prior art.

A step 11 is formed on the entire peripheral edge (or a part thereof) of the thin plate piece 1 . This step 11 is a part of a groove on a lattice formed in the thin plate base material in order to cut out the thin plate piece 1 from the thin plate base material as described later.

An insulating film 4 is formed on the upper surface of the thin plate piece 1.

The material of this insulating film 4 is as explained in the prior art section. The function of the insulating film 4 is to maintain electrical insulation between the strain detection section formed thereon and the thin plate piece 1. This insulating film 4 is formed over the entire upper surface of the thin plate piece 1, and at the same time is also formed over the entire surface of the portion where the step 11 is formed. However, the insulating film layer on the vertical wall of the step 11 is thinner, and the thickness of the insulating film on the upper surface (upper step surface) of the step 11 and the lower surface (lower step surface) are
The thickness of the insulating film is almost the same. Also, step 11
Regarding the insulating film on the lower surface of the insulating film 4, peeling occurs between the insulating film 4 and the thin plate piece 1. However, this peeling does not extend to the upper surface of the step of the thin plate piece 1 because the vertical wall surface of the step 11 exists in the middle thereof. Especially when looking at the entire thin plate piece 1,
The insulating film 4 covers the high portion of the thin plate piece 1 in a cap-like manner, and since the vertical wall portion of the step 11 has a rough surface, it is firmly bonded to the insulating film 4 due to its fine irregularities. As a result, if there is a risk that the peeling will expand, it has the effect of preventing the expansion.

Further, on the insulating film 4, a semiconductor strain gauge 5 and a required number of electrode wirings 6 as electrical connection lines are formed.

Next, a method of manufacturing the pressure sensor described above will be explained with reference to FIGS. 2 to 6.

In the manufacturing method according to this embodiment, first, a metal thin plate base material 7 from which a large number of the thin plate pieces 1 are cut out is prepared (FIG. 2). Therefore, the material and thickness of the thin plate base material 7 are the same as those of the thin plate piece 1. Next, linear cutting grooves 12 for taking out a large number of thin plate pieces 1 from the thin plate base material 7 are formed in, for example, a grid pattern (FIG. 3). Various methods can be considered for forming the grooves 12. In this embodiment, the width 11 is 0.2 to 3II by using, for example, a guiding tool.
A groove I is formed. Further, the depth of the groove 12 is not particularly limited, but it is preferably about 80 to 90% of the thickness of the thin plate base material 7. FIG. 4 shows that an insulating film 4 is formed on the upper surface of a thin plate base material 7, and a set of a semiconductor strain gauge 5 and an electrode wiring 6 for forming a strain detection section is further formed on the surface of a predetermined region corresponding to each thin plate piece 1. be done. The method of forming the insulating film 4, strain gauge 5, and electrode wiring 6 is the same as in the case of the prior art described above. That is, the insulating film 4 is 5in2. SiC, SiNx, etc. are formed by a film forming method such as plasma CVD or sputtering, the strain gauge 5 is formed by a photolithography method after forming a polycrystalline silicon thin film on the entire upper surface of the insulating film 4, and the electrode wiring 6 is formed by a photolithography method. , Au, Aj! etc. are formed by vacuum evaporation method and sputtering method.

In the manufacturing method of this embodiment, the insulating film 4 is formed on the entire upper surface of the thin plate base material 7, and as a result, the insulating film 4 is also formed in the grooves 12. The thickness of the insulating film 4 is approximately 1 to 20 μm on the planar surface. Furthermore, although the vertical wall surface forming the trench 12 is exaggerated in the illustrated example, in reality, due to the film formation technology used to form the insulating film, its thickness is smaller than that of the flat surface such as the bottom surface of the trench. It is relatively thin.

The step shown in FIG. 5 is a cutting step for removing the thin plate piece 1 serving as a pressure sensor from the thin plate base material 7 on which the strain detection section is formed. In this cutting process, the width of the groove 12!
Cutting is performed along the groove 12 using a disc-shaped cutter 13 having a width smaller than that of the cutter 13 . In this cutting step, peeling occurs in the insulating film 4 formed at the cut portion, that is, the bottom portion of the groove 12, along the edges of the cut. This peeled portion is small in area. Further, regarding the external appearance of the planar rectangular thin plate piece 1 cut out from the thin plate base material 7 by the cutter 13, a step 11 is formed on the entire periphery or some local edges as shown in the figure. The part where the peeling occurs is the lower side of the step 11, and the peeling does not extend to the upper side.

FIG. 6 is the final step, and shows the step of joining the thin plate piece 1 and the cylindrical member 2. The bonding method is similar to the conventional method described above, and diffusion bonding or an adhesive is used. In the case of diffusion bonding, an insert material 10 such as aluminum laminate is applied to the joint surface 2a of the cylindrical member 2, and is brought into close contact with the joint surface 1a of the thin plate piece 1. Thereafter, it is heated at a required temperature of 550° C. or higher for a certain period of time. In the adhesive method, adhesive is applied to the joint surface of the cylindrical member 2,
It is brought into close contact with the bonding surface of the thin plate piece 1 and heated for a certain period of time at a temperature required for the adhesive to be effective.

A pressure sensor is formed as described above. In this pressure sensor, the step 11 is formed on the periphery, so even if peeling or cracking occurs during the cutting process, the peeling will stop at the bottom surface of the step, and the strain detection section will not work properly. It does not grow and expand to the upper side of the formed step. Also, the shape of the step 11 and the insulating film 4 covering it
Due to this bonding relationship, the insulating film 4 is firmly bonded to the surface of the thin plate piece 1, further preventing the insulating film 4 from peeling and expanding.

In the above embodiments, the pressure sensor was mainly described, but the structure and manufacturing method according to the present invention can be applied to other single-boat fishing force sensors such as strain sensors. Further, as a method for forming the groove 12, it is also possible to use a mold or the like.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, since the stepped portion is formed at the periphery of the thin plate piece on which the portion functioning as the stress sensor is formed, the stepped portion is formed in the cutting step of the method for manufacturing the thin plate piece unit. The presence of the step prevents the growth and expansion of the peeling of the insulating film, which prevents the peeling from propagating to the insulating film portion below the strain gauge and electrode wiring, improving the operational reliability of the sensor. Further, according to the present invention relating to the manufacturing method, the stress sensor having the above-mentioned characteristics can be easily manufactured by simply forming a predetermined groove on the surface of a thin plate base material, and the effects of peeling can be eliminated at low cost. A stress sensor with high operational reliability can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the stress sensor according to the present invention, and FIG.
FIG. 6 is a process diagram showing a method of manufacturing a stress sensor according to the present invention, FIG. 7 is a longitudinal cross-sectional view of a conventional stress sensor, and FIGS. 8 to 14 are process diagrams of a conventional manufacturing method. [Explanation of symbols] 1...Thin plate piece 2...φ/cylindrical member 4...Insulating film 5...Strain gauge 6...Electrode wiring 7... Thin plate base material 8... Polycrystalline silicon thin film 9.13... Rumor cutter 10... Insert member 11... Step 12... Groove

Claims (6)

[Claims] (1) An insulating film formed on one side of a thin plate having a pressure receiving part, a strain gauge formed on this insulating film, and electrode wiring for connecting this strain gauge to an external electric circuit part. In a stress sensor in which the thin plate piece is cut out from a large area monolithic thin plate base material on which the insulating film, the strain gauge, and the electrode wiring are formed, a periphery of the thin plate piece has a A stress sensor characterized by having a stepped portion. (2) The stress sensor according to claim 1, wherein the step portion is a step between a portion where the strain gauge is formed and a portion where cutting is performed. (3) The stress sensor according to claim 1 or 2, characterized in that a cylindrical member is fixed to the pressure receiving surface side of the thin plate piece. (4) The stress sensor according to any one of claims 1 to 3, wherein the strain gauge is a semiconductor strain gauge. (5) forming a groove in a thin plate base material, forming an insulating film on the surface of the thin plate base material on which the groove is formed, and forming a strain gauge on each of a plurality of regions surrounded by the grooves on the insulating film; and electrode wiring, and cutting the thin plate substrate along the groove with a cutting tool having a width smaller than the width of the groove;
A method for manufacturing a stress sensor, characterized in that a plurality of thin plate pieces for stress sensors are manufactured. (6) In the method for manufacturing a stress sensor according to claim 5,
A method of manufacturing a stress sensor, wherein the strain gauge is a semiconductor strain gauge.