JPH08136379A - Thin film gauge pressure sensor - Google Patents

Abstract

PURPOSE: To prevent a strain gauge bridge circuit from touching a swelling part of an insulating film generated at an outer peripheral part of a diaphragm when the strain gauge bridge circuit is formed on the insulating film made of an organic material on the surface of the diaphragm. CONSTITUTION: An R-shaped part 11 of a predetermined radius of curvature is formed at a boundary part between a strain part 1b and a cylindrical part 1a of a diaphragm 1 at the side where the pressure acts to the diaphragm 1. A part where the maximum extension stress acts to the diaphragm 1 is moved towards the center of the diaphragm 1, and consequently the position where a strain gauge bridge circuit 3 is formed on the diaphragm 1 is brought closer to the center of the diaphragm 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film gauge pressure gauge for detecting the pressure acting on a diaphragm having a strain gauge bridge circuit formed on its surface, from the amount of strain of the diaphragm.

[0002]

2. Description of the Related Art Conventionally, there are various types of thin film gauge pressure gauges in which a strain gauge bridge circuit is formed on the surface of a diaphragm. For example, as disclosed in JP-A-57-196127, a diaphragm is disclosed. There is a device in which an insulating film is formed on the surface of and the strain gauge bridge circuit is formed on the insulating film.

[0003]

When the insulating film on the surface of the diaphragm is formed of an organic material, the insulating film is formed by coating with a spinner or a dip.
This insulating film is in a raised state on the outer peripheral portion of the diaphragm. Further, if a strain gauge pattern is formed on this raised portion, there is a drawback that peeling easily occurs.

Further, if an attempt is made to form a zero balance adjustment pattern, a zero correction pattern, and a span temperature correction pattern on a diaphragm together with a strain gauge pattern, it is necessary to form these zero balance adjustment patterns and the like outside the strain gauge pattern. Then, it is easily peeled off because it is applied to the raised portion of the insulating film.

If the diameter of the diaphragm is increased, the strain gauge bridge circuit can be formed without hitting the raised portion of the insulating film, but in that case, the thin film gauge pressure gauge cannot be downsized.

Therefore, according to the present invention, the respective patterns forming the strain gauge bridge circuit are formed close to the center of the diaphragm so that the strain gauge bridge circuit is not applied to the raised portion of the insulating film formed on the outer peripheral portion of the diaphragm. Provided is a thin film gauge pressure gauge capable of preventing the strain gauge bridge circuit from peeling off from the insulating film when the strain gauge bridge circuit is applied to a raised portion of the insulating film.

[0007]

According to the first aspect of the present invention,
A diaphragm with a thin plate strained portion is provided at one end of the tubular portion, an insulating film made of an organic material is formed on the surface of the diaphragm, and a strain gauge pattern and a zero balance adjustment pattern are formed on the insulating film with a metal material. A strain gauge bridge circuit having a zero point temperature correction pattern and a span temperature correction pattern is formed, and in a thin film gauge pressure gauge having a protective film formed on the insulating film to cover the strain gauge bridge circuit, a pressure is applied to the diaphragm. An R-shaped portion having a predetermined radius of curvature is formed at a boundary portion between the strained portion and the tubular portion on the side on which is operated.

[0008]

In the invention described in claim 1, it is possible to move the portion on the diaphragm where the maximum tensile stress acts to the center side of the diaphragm. Therefore, when the strain gauge pattern is formed on the diaphragm, the tensile stress is applied to the diaphragm. The strain gauge pattern for detection can be formed closer to the center side of the diaphragm, and along with this, each pattern such as the zero balance adjustment pattern and the zero point temperature correction pattern arranged outside the strain gauge pattern can also be formed. Can be formed closer to the center side of the diaphragm.Therefore, peeling of the strain gauge bridge circuit caused by the strain gauge bridge circuit being applied to the raised portion of the insulating film on the outer peripheral portion of the diaphragm can reduce the diameter of the diaphragm. It can be prevented without increasing the size, and the strain gauge bridge circuit itself becomes smaller. It is possible to reduce the variation in the film characteristics that form the respective patterns of the eye strain gauge bridge circuit.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a thin film gauge pressure gauge. This thin film gauge pressure gauge has a diaphragm 1 formed of a metal material such as duralumin, aluminum or stainless steel, and an organic material such as a polyimide resin on the surface of the diaphragm 1. An insulating film 2 is formed, a strain gauge bridge circuit 3 is formed on the insulating film 2, and a protective film 4 covering the strain gauge bridge circuit 3 is formed on the insulating film 2 with an organic material such as a polyimide resin. It was done.

Now, a procedure for forming the strain gauge bridge circuit 3 will be described. The strain gauge bridge circuit 3 includes strain gauge patterns 5a to 5d, zero balance adjustment patterns 6a and 6b, span temperature correction pattern 7, zero point temperature correction patterns 8a and 8b, and lead wiring patterns 9a to 9f. And lead terminals 10a-10
It consists of d and. First, the surface of the diaphragm 1 is coated with a viscous liquid organic material by a spinner or a dip to form an insulating film 2, and then a NiCrSi layer, a Ti layer and a Cu layer are sequentially laminated by a thin film technique. Then, the strain gauge patterns 5a to 5d and the zero balance adjustment pattern 6 are formed on the NiCrSi layer by the etching technique.
a, 6b are formed, a span temperature correction pattern 7 and zero point temperature correction patterns 8a, 8b are formed on the Ti layer, and C
Lead wiring patterns 9a to 9f and lead terminals 10 on the u layer
a to 10d are formed.

Next, as shown in FIG. 2, the diaphragm 1 has a thin plate-shaped strained portion 1b at one end of a cylindrical tubular portion 1a.
The diameter of the tubular portion 1a (outer diameter of the diaphragm 1) is 20 mm, and the diameter of the strained portion 1b is 8 mm.
Is. Then, an R-shaped portion 11 having a predetermined radius of curvature is formed at the boundary portion between the strained portion 1b and the tubular portion 1a on the side where the pressure acts on the diaphragm 1.

Since the insulating film 2 is formed by coating a viscous liquid organic material with a spinner or a dip, as shown in FIG. 2, the outer peripheral side of the diaphragm 1 is raised and laminated on it. Ni
The CrSi layer, the Ti layer, and the Cu layer are in a raised state. The size at which this swelling occurs varies depending on the outer diameter of the diaphragm 1.
It is 3 mm, and is about 3 mm when the outer diameter of the diaphragm 1 is 20 mm as in this embodiment.

In such a structure, first, an outline of pressure detection by the thin film gauge pressure gauge will be described.
When the pressure of the fluid to be detected acts on the diaphragm 1 as shown in FIG. 2, the strain portion 1b is strained upward, and the strain gauge patterns 5a to 5d are also strained accordingly, and the electrical resistance is changed. To do. Then, the pressure is detected by detecting the change in the electric resistance with an external circuit (not shown) connected to the lead terminals 10a to 10d.

Next, the positions where the strain gauge patterns 5a to 5d are formed need to be the portions of the diaphragm 1 to which the most stress is applied. Therefore, the result of stress distribution analysis on the surface of the diaphragm 1 performed using an idea (structure analysis software) with the radius of curvature of the R-shaped portion 11 as a parameter will be described based on the graph of FIG. The radius of curvature of the R-shaped portion 11 is 0.2 mm, 0.4 mm, and 1.
The outer diameter of the diaphragm 1 was 20 mm, and the diameter of the strained portion 1b was 8 mm. As can be seen from this analysis result, the location where the maximum extension stress is applied is near the center of the diaphragm 1, but the location where the maximum compression stress is applied is the center of the diaphragm 1 as the radius of curvature increases. You can see that it moves to the side.

Therefore, when the strain gauge patterns 5a to 5d are formed on the diaphragm 1, it is the same that the strain gauge patterns 5c and 5d for detecting the extension stress are formed at the center of the diaphragm 1, but the R shape is formed. The strain gauge patterns 5a and 5b for detecting the compressive stress as the radius of curvature of the portion 11 is increased can be formed close to the center of the diaphragm 1. Then, the zero point balance adjustment patterns 6a and 6b, the span temperature correction pattern 7, the zero point temperature correction patterns 8a and 8b, and the lead wiring pattern 9 arranged outside the strain gauge patterns 5a to 5d.
a-9f and lead terminals 10a-10d are also diaphragms 1.
Can be formed closer to the center side. Therefore, the strain gauge bridge circuit 3 formed on the diaphragm 1 does not overlap the raised portion of the insulating film 2 on the outer peripheral portion of the diaphragm 1, and the strain gauge bridge circuit 3
It is possible to prevent the peeling from the insulating film 2 which may be caused by the swelling of the insulating film 2.

Specifically, the diameter of the diaphragm 1 is set to 20.
mm, the diameter of the strained portion 1b is 8 mm, and the dimension of the raised portion of the insulating film 2 is 3 mm, the strain gauge bridge circuit 3
The effective radius that can form the circle is 7 mm. When the radius of curvature of the R-shaped portion 11 is 0.2 mm, the location where the maximum compressive stress is applied is approximately 4.2 mm from the center of the diaphragm 1, and when the radius of curvature is 1 mm, it is approximately 3.5 mm.
When comparing these two, the diaphragm 1
Move about 0.7 mm to the center side of. Therefore, when the effective radius is 7 mm, the strain gauge patterns 5a and 5b can be formed by moving by 0.7 mm, so that the strain gauge bridge circuit 3 is not applied to the raised portion of the insulating film 2 and the strain gauge bridge 5 is formed. It is extremely effective in preventing peeling of the circuit 3.

Further, the strain gauge patterns 5a and 5b are formed close to the center of the diaphragm 1 and the zero point balance adjustment patterns 6a and 6b and the zero point temperature correction patterns 8a and 8b arranged around the strain gauge patterns 5a and 5b are also included in the diaphragm 1.
The strain gauge bridge circuit 3 can be downsized as a whole by forming the strain gauge bridge circuit 3 closer to the center side, and the downsizing of the strain gauge bridge circuit 3 reduces variations in the film characteristics of each pattern.

[0018]

As described above, according to the first aspect of the present invention, the R-shaped portion having a predetermined radius of curvature is formed at the boundary between the strained portion and the cylindrical portion on the side where the pressure acts on the diaphragm. It is possible to move the point where the maximum extension stress acts on the diaphragm to the center of the diaphragm.
Therefore, when the strain gauge pattern is formed on the diaphragm, the strain gauge pattern for detecting the extension stress can be formed closer to the center side of the diaphragm, and along with this, the zero strain gauge arranged on the outside of the strain gauge pattern can be formed. Each pattern such as the balance adjustment pattern and the zero point temperature correction pattern can also be formed close to the center of the diaphragm. Therefore, the strain gauge bridge circuit is applied to the raised portion of the insulating film formed on the outer peripheral portion of the diaphragm. The strain gauge bridge circuit can be prevented from peeling from the insulating film without increasing the diameter of the diaphragm, and the strain gauge bridge circuit itself can be miniaturized. It is possible to reduce the variation in the film characteristics of each pattern forming the.

[Brief description of drawings]

FIG. 1 is a plan view of a thin film gauge pressure gauge showing an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional front view showing a state in which an insulating layer, a NiCrSi layer, a Ti layer, and a Cu layer are laminated on the surface of a diaphragm.

FIG. 3 is a graph showing the results of stress distribution analysis on the surface of the diaphragm performed using the radius of curvature of the R-shaped portion as a parameter.

[Explanation of symbols]

 1 Diaphragm 1a Cylindrical part 1b Strain part 2 Insulation film 3 Strain gauge bridge circuit 4 Protective film 5a-5d Strain gauge pattern 6a, 6b Zero balance adjustment pattern 8a, 8b Zero point temperature correction pattern 7 Span temperature correction pattern 11 R shape part

Claims (1)

[Claims] 1. A diaphragm in which a thin plate-shaped strained portion is formed is provided at one end of a tubular portion, an insulating film made of an organic material is formed on the surface of the diaphragm, and a strain gauge pattern made of a metal material is formed on the insulating film. In a thin film gauge pressure gauge, a strain gauge bridge circuit having a zero balance adjustment pattern, a zero point temperature correction pattern, and a span temperature correction pattern is formed, and a protective film covering the strain gauge bridge circuit is formed on the insulating film. A thin film gauge pressure gauge, characterized in that an R-shaped portion having a predetermined radius of curvature is formed at a boundary portion between the strained portion and the cylindrical portion on the side where pressure acts on the diaphragm.