JPH06160221A - Wiring pattern of strain sensor - Google Patents

Abstract

PURPOSE:To obtain the wiring pattern of a strain sensor for relaxing the process control for a strain gauge formation position. CONSTITUTION:Strain gauges 14 and 16 for detecting compression distortion and gauges 18 and 20 for detecting pull distortion are laid out at radius positions (a) and (b) where the absolute values of compression distortion and pull distortion are equal and both change rates are equal. Therefore, when the positions for forming the strain gauges 14 and 18 or 16 and 20 deviate, the fluctuations of the compression distortion and pull distortion caused by the deviation are nearly equal if the deviation is equal to or less than a certain level, thus preventing the balance of wheatstone bridge circuit which is constituted by the gauges from being affected greatly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiring pattern of a strain sensor applied to a pressure sensor, an acceleration sensor or the like.

[0002]

2. Description of the Related Art When a fluid stress acts on the entire area of a diaphragm (diaphragm) of an elastic body, the membrane is deformed in proportion to this stress. At this time, by attaching a strain gauge to the diaphragm and detecting the strain, the stress acting on the elastic body can be detected from the relationship between the stress and the strain. Therefore, conventionally, in pressure sensors and the like, a diaphragm strain sensor in which a strain gauge is attached to a diaphragm has been used.

However, since semiconductor precision processing technology has been developed since then, a diaphragm type strain sensor in which a diaphragm is formed by etching a silicon single crystal plate, and impurities are selectively diffused into the diaphragm to use a part of the surface of the diaphragm as a strain gauge is considered as a pressure sensor. Developed for sensors.

FIG. 4 shows an example of wiring on the circular diaphragm 100 which constitutes a pressure sensor. The circular diaphragm 100 is formed to have a predetermined thickness, for example, by removing the back surface side of the central portion of the silicon single crystal plate 200 having a predetermined thickness by etching. The circular diaphragm 100 is shown in FIG.
When a uniformly distributed load (for example, hydraulic pressure) is applied to the entire surface of the silicon single crystal plate 200 from the rear side of the sheet of FIG. Strain gauges 102 and 104 are formed, and the first and second strain gauges 102 and 104 for detecting the compressive strain are generated at radial positions where a compressive strain whose absolute value is substantially equal to the tensile strain generated at the position where the strain gauges 102 and 104 are formed. Third and fourth strain gauges 106 and 108 are formed. Between the first and second strain gauges 102 and 104 for detecting tensile strain and the third and fourth strain gauges 106 and 108 for detecting compressive strain, wirings 110, 112 and 114 made of a metal vapor deposition film are provided. ，
A Wheatstone bridge circuit is formed by connecting as shown in FIG. Therefore, compressive strain and tensile strain, that is, the strain gauges 106 and 108 for detecting compressive strain.
Is a plus output terminal (+), which is determined by the resistance values of the strain gauges 102 and 104 for detecting tensile strain after the change.
Is detected as the potential difference between the negative output terminal (-).

A compressive strain detecting strain gauge and a tensile strain detecting strain gauge are respectively arranged on the upper and lower surfaces of a pair of cantilevers constituting the acceleration sensor, and a Wheatstone bridge circuit is constituted by these strain gauges. Also, similarly to the above, the voltage determined depending on the resistance value after the change between the strain gauge for detecting the compression strain and the strain gauge for detecting the tensile strain is detected as the potential difference.

[0006]

In the conventional wiring pattern on the diaphragm, the first and second strain gauges 102 and 104 for detecting tensile strain and the third and fourth strain gauges for detecting compressive strain are provided. Since the strain gauges 106 and 108 of No. 1 were formed at positions where only the absolute values of the tensile strain and the compressive strain are equal, the circular diaphragm 10
They are often formed in different directions when viewed from the center point O of 0 (directions substantially orthogonal to each other in FIG. 4), and the rate of change in tensile strain and compressive strain at the position where these gauges are formed is not considered. . Therefore, the positions of the first and second strain gauges 102 and 104 for detecting tensile strain and the positions of the third and fourth strain gauges 106 and 108 for detecting compressive strain are slightly different from the initially planned positions. As a result, the Wheatstone bridge circuit is out of balance, and an error is likely to occur, which makes the process control for the formation position of the strain gauge complicated and difficult.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a wiring pattern of a strain sensor which can ease process control for a strain gauge forming position.

[0008]

A wiring pattern of a strain sensor according to the present invention is a strain sensor for detecting a resistance value of a strain gauge generated according to a tensile strain and a compressive strain generated in a strain gauge arranging member elastically deformed by an external force. And a strain gauge for compressive strain detection arranged in a compressive strain generation region of the strain gauge disposing member, and a change rate of compressive strain and a change in tensile strain at an arrangement position of the strain gauge for compressive strain detection. A strain gauge for tensile strain detection arranged in a tensile strain generation region of the strain gauge arranging member having an equal rate,
Have at least one set.

[0009]

According to the above configuration, when a Wheatstone bridge circuit is configured to include the compressive strain detecting strain gauge and the tensile strain detecting strain gauge, the compressive strain detecting strain gauge and the tensile strain detecting strain gauge are provided. Are placed at positions where the strain gauge placement members have the same rate of change in compressive strain and tensile strain, and if the placement positions of these strain gauges are misaligned, the misalignment is not greater than a certain size. The change amounts of the compressive strain and the tensile strain caused by are substantially the same, and the balance of the Wheatstone bridge circuit is not significantly affected.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows a wiring pattern of a diaphragm strain sensor according to an embodiment of the present invention.

In this figure, a circular diaphragm 10 serving as a strain gauge arranging member is formed to have a predetermined thickness by etching a back surface side of a central portion of a silicon single crystal plate 12 having a predetermined thickness into a substantially cylindrical shape by etching. There is. Circular diaphragm 1
Above 0, a first strain gauge 14 and a second strain gauge 16 are formed in a circular arc shape so as to face each other at a position of a radius a from the center point O. Further, on the circular diaphragm 10, at a position with a radius b from the center point O, a third strain gauge 14 is formed in the same direction as the first strain gauge 14 when viewed from the center point O.
The fourth strain gauge 20 is formed in an arc shape in the same direction as the second strain gauge 16 when viewed from the center point O. These first to fourth strain gauges 14, 16, 18 and 20 are formed of, for example, a p-type high resistance layer in which a small amount of p-type impurities are diffused, and are the same when the circular diaphragm 10 is not strained. It is formed to have a resistance value.

Further, on the circular diaphragm 10, between the first strain gauge 14 and the third strain gauge 18, between the third strain gauge 18 and the second strain gauge 16, and between the second strain gauge 18 and the second strain gauge 16. The first wiring 22 and the second wiring 22 which electrically connect between the strain gauge 16 and the fourth strain gauge 20 and between the fourth strain gauge 20 and the first strain gauge 14, respectively.
The wiring 24, the third wiring 26, and the fourth wiring 28 are formed of a metal vapor deposition film. Circumferential portions 22A, 2 of the first to fourth wirings 22, 24, 26, 28
4A, 26A, and 28A are formed at positions of radius c from the center point O.

FIG. 2 shows an arbitrary radius of circumferential strain generated in the plane when a uniformly distributed load (for example, hydraulic pressure) is applied to the entire surface of the silicon single crystal plate 12 from the rear side of the paper surface of FIG. The top distribution is shown. In FIG. 2, the horizontal axis X represents the radius, and the vertical axis Y represents the strain (compressive strain is positive, tensile strain is negative). In this figure, the compressive strain is maximum at the center point O, and the tensile strain is maximum at a point near the outer diameter of the circular diaphragm 10 (a position slightly closer to the center side). If the tensile strain is −A at a point of radius b near the point where the tensile strain takes the maximum value, and the radius of the point at which a compressive strain A having the same absolute value is generated is a, the radius is in the middle. At the point of radius c, the tensile strain and the compressive strain are balanced and the strain becomes zero.

In the present embodiment, as shown in FIG. 1, the first and second strain gauges 14 and 16 are arranged at a portion having a radius a for detecting compressive strain, and the third portion has a third portion at a portion having a radius b. The fourth strain gauges 18 and 20 are arranged to detect tensile strain. Further, the circumferential portions 22A, 24A, 26A, 28A of the above-mentioned first to fourth wirings 22, 24, 26, 28 are arranged in the radius c portion. A power supply terminal (V), a ground terminal (G), a positive output terminal (+), and a negative output terminal (-) are provided between the strain gauges, respectively, as shown in FIG. A Wheatstone bridge circuit 30 shown in 3 is formed.

Therefore, when, for example, hydraulic pressure is applied to the entire surface of the silicon single crystal plate 12, the resistance values of the first strain gauge 14 and the third strain gauge 18 forming a pair with the first strain gauge 14 after the change, and The voltage determined according to the changed resistance value of the second strain gauge 16 and the fourth strain gauge 20 forming the set is detected as a potential difference between the positive output terminal (+) and the negative output terminal (-). To be done. The pressure can be obtained from the relationship between stress and strain based on the detected potential difference.

Here, the strain gauges forming a pair, for example, the first and third strain gauges 14 and 18 are on the straight line connecting the center point O and these strain gauges 14 and 18, and only a predetermined amount β. Consider a case where the circular diaphragm 10 is formed at a position displaced to the outer peripheral side. In the case of this embodiment, since the first and third strain gauges 14 and 18 are formed in the same direction when viewed from the center point O, as shown in FIG. 2, the radius (a
There is always an allowable deviation amount β such that the absolute value of the strain amount (A−α) at the point of + β) and the strain amount − (A−α) at the point of the radius (b + β) are equal to each other. If the strain gauge forming position is deviated within the range, the balance of the Wheatstone bridge circuit 30 is not lost, and the output characteristic is not deteriorated by this. This also applies to the case where the formation positions of the second and fourth strain gauges forming the pair mutually deviate.

Therefore, the displacement of the disposition position of the strain gauge is zero.
Since it is acceptable within the range of to β, the process control of the strain gauge forming position can be relaxed.

The first to fourth wirings 22, 24,
Circumferential portions 22A, 24A, 26A, 2 of 26, 28
Since 8A is theoretically arranged in the radius portion where the strain is zero, the resistance value does not change in this portion, and the wiring 2
Most of the compressive strain and the tensile strain generated in the radial portions 2, 24, 26, 28 cancel each other out, resulting in the wiring 2
The influence of the change in the resistance value of 2, 24, 26, 28 is very small.

In the above embodiments, the wiring pattern of the strain sensor for the pressure sensor using the circular diaphragm as the strain gauge arranging member has been exemplified, but the present invention is not limited to this, and the acceleration sensor may be used. It can also be applied when forming a strain gauge on the cantilever that constitutes it.

In the above embodiment, the semiconductor gauge is used as the strain gauge for detection. However, the present invention is not limited to this, and includes the case of using a metal thin film gauge or the like. .

[0022]

As described above, according to the present invention,
Since the strain gauge for detecting the compressive strain and the strain gauge for detecting the tensile strain are arranged at the positions where the rate of change of the compressive strain and the tensile strain of the strain gauge arranging member are the same, if these are within a predetermined range, these Even if the formation position of the strain gauge is deviated, the amount of change in strain is substantially the same, and the balance of the Wheatstone bridge circuit including them is not significantly affected. Therefore, since there is a certain degree of tolerance for the displacement of the strain gauges, there is an unprecedented excellent effect that the process control for the strain gauge formation positions can be relaxed.

[Brief description of drawings]

FIG. 1 is a schematic front view showing a wiring pattern according to an embodiment of the present invention.

FIG. 2 is a diagram showing a distribution of strain when a uniformly distributed load such as hydraulic pressure is applied to the silicon single crystal plate of FIG.

3 is a diagram showing a Wheatstone bridge circuit configured by the wiring pattern of FIG.

FIG. 4 is a schematic front view showing a conventional wiring pattern.

[Explanation of symbols]

10 Circular Diaphragm (Strain Gage Arrangement Member) 14 First Strain Gage (Strain Gage for Compressive Strain Detection) 16 Second Strain Gage (Strain Gage for Compressive Strain Detection) 18 Third Strain Gage (Tensile Strain Detection) Strain gauge) 20th strain gauge (strain gauge for detecting tensile strain)

Claims (1)

[Claims] 1. A wiring pattern of a strain sensor for detecting a resistance value of a strain gauge generated according to tensile strain and compression strain generated in a strain gauge arrangement member elastically deformed by an external force, wherein the strain gauge arrangement member is compressed. A strain gauge for compressive strain detection arranged in the strain generation region, and a tensile strain generation region of the strain gauge arrangement member in which the rate of change in compressive strain and the rate of change in tensile strain at the arrangement position of the strain gauge for detecting compression strain are equal. A strain sensor wiring pattern having at least one set of a strain gauge for detecting tensile strain arranged in the.