JPH08159905A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE: To obtain a semiconductor pressure sensor which is of a simple structure and a low-cost, whose characteristic is not sacrificed and which is improved so as to effectively prevent the destruction of a diaphragm part with reference to an excessive pressure from the outside. CONSTITUTION: The semiconductor pressure sensor is constituted of a semiconductor-pressure-sensor element 1, a pedestal 2 to which the element is attached, a housing 3 in which the semiconductor-pressure-sensor element 1 and the pedestal 2 are housed, pressure introduction ports 4, 5 which are attached to the housing 3, and a leak valve 6 which is installed at the sidewall of the pressure introduction port 5. The leak valve 6 is constituted in such a way that a valve body 8 which is fixed to the free end of a plate spring 9 is pressed to an opening 7 formed in the sidewall of the pressure introduction port 5 and that the opening 7 is closed elastically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor pressure sensor.

[0002]

2. Description of the Related Art In a semiconductor pressure sensor, a piezoresistor is formed on a silicon single crystal wafer, and a diaphragm portion is provided by anisotropically etching the back surface of the piezoresistor. When the diaphragm portion is deformed by pressure, the resistance of the piezoresistor is reduced. Is changed, the principle is that an electric signal corresponding to the pressure can be obtained.

By the way, since the diaphragm portion of this semiconductor pressure sensor is as thin as a few μm to a few tens of μm, if the pressure from the outside is too large, the deformation becomes too large and it may be damaged. Therefore, conventionally, measures are taken such as attaching a stopper to the element itself or thickening the diaphragm portion.

[0004]

However, if the diaphragm portion is made thicker as in the conventional case, the characteristics as a pressure sensor are impaired, and provision of a stopper having a complicated structure leads to an increase in cost. Therefore, in the conventional case, there is a problem that there is a limit in improving the breakdown voltage of the diaphragm part in terms of cost and characteristics.

In view of the above, the present invention has a simple structure at a low cost and does not sacrifice the characteristics of the pressure sensor, and at the same time, the diaphragm portion is protected against an excessive pressure from the outside. It is an object of the present invention to provide a semiconductor pressure sensor improved so as to effectively prevent destruction.

[0006]

To achieve the above object, in a semiconductor pressure sensor according to the present invention, a semiconductor pressure sensor element, a pressure introducing member for guiding pressure to the semiconductor pressure sensor element, and the pressure introducing member. It is characterized in that it is provided with a leak valve which is opened in response to an excessive pressure.

The above-mentioned leak valve may be composed of a valve body that closes an opening provided in the pressure introducing member and a spring member that supports the valve body.

Further, the above leak valve may be constituted by a plug body which closes an opening provided in the pressure introducing member and which escapes from the opening by the pressure when an excessive pressure is applied.

[0009]

A leak valve is provided in the pressure introducing member for guiding the pressure to the semiconductor pressure sensor element. This leak valve
When overpressure is applied, it is configured to open in response to the pressure. Therefore, when an excessive pressure is applied, the leak valve opens and the pressure can be released. As a result, it is possible to prevent an excessive pressure from being applied to the semiconductor pressure sensor element and protect it from damage. Since the pressure introducing member is provided with the leak valve, the structure is simple and the manufacturing cost does not increase.

The leak valve may have a structure in which the valve body is elastically held by a spring member, and the valve body is pressed against an opening provided in the pressure introducing member to be closed. In this case, the spring member is deformed by an excessive pressure, the valve body is retracted from the state of being pressed against the opening and the opening is opened, and the excessive pressure can be released. When the leak valve has such a structure, the structure is very simple.

Further, when the leak valve is composed of a plug,
When excessive pressure is applied, the stopper escapes from the state where the opening is closed and moves to the state where the opening is opened. Therefore, excessive pressure can be released. In the case of a leak valve having such a configuration, the opening remains open even when the pressure returns to a normal value, so it is necessary to separately attach the plug body, but since it only needs to be done once, it is possible to handle excessive pressure. It is effective when it is desired to protect it, and has an advantage that the cost can be reduced because the structure is extremely simple.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, a semiconductor pressure sensor element 1 has a piezoresistor formed in a diaphragm portion, and has a diameter of 10 mm to 2 as a whole.
It has a cylindrical shape of about 0 mm. This semiconductor pressure sensor element 1 is mounted on a pedestal 2. The semiconductor pressure sensor element 1 and the pedestal 2 are housed in a housing 3 made of metal or the like. The housing 3 is provided with pressure inlets 4 and 5 for introducing an external pressure to (the diaphragm portion of) the semiconductor pressure sensor element 1.
These pressure introduction ports 4 and 5 are made of, for example, metal pipes.

The pressure introducing port 5 has a side wall,
A leak valve 6 is provided. That is, the pressure introducing port 5
An opening 7 for leak is formed on the side wall of the valve 7, and the opening 7 is closed by the valve element 8. This valve body 8 is attached to the other end side of a leaf spring 9 whose one end is fixed to the side wall of the pressure introducing port 5 and is pressed in the direction of the opening 7 by the elasticity of the leaf spring 9, so that the opening 7 is closed. I have to.

The opening 7 may have a diameter of about 1 mm, and the valve body 8 is made of rubber, plastic, metal or the like. The leaf spring 9 is made of metal such as phosphor bronze.

In the semiconductor pressure sensor thus constructed, when the pressure introduced from the pressure introducing port 5 is within the normal range, the pressure applied to the valve body 8 of the opening 7 is elastic by the leaf spring 9. Since it is smaller than the above, the opening 7 is blocked by the valve body 8 as shown in FIG. Therefore, the pressure introduced from the pressure introducing port 5 is guided to the semiconductor pressure sensor element 1 on the pedestal 2 and the normal pressure sensing operation is performed, as shown by the arrow.

On the other hand, when the pressure introduced from the pressure introduction port 5 exceeds the normal range and becomes abnormally large, and the diaphragm portion of the semiconductor pressure sensor element 1 is destroyed, Since the pressure is also applied to the valve body 8 closing the opening 7, the force pushing the valve body 8 is applied to the leaf spring 9
2 is larger than the elasticity of the opening 7, and the opening 7 opens as shown in FIG. As a result, this excessive pressure escapes from the opened opening 7 as indicated by the arrow, and it is possible to prevent the excessive pressure from being applied to the diaphragm portion of the semiconductor pressure sensor element 1 as it is, and protect it from damage.
In this case, the pressure at which the leak valve 6 opens (opening pressure) is determined by changing the thickness of the leaf spring 9 to adjust its elasticity or changing the size of the opening 7.

When the excessive pressure disappears and the normal pressure is restored, the elasticity of the leaf spring 9 causes the valve body 8 to close the opening 7 again as shown in FIG. Therefore, the pressure introduced from the pressure introduction port 5 is directly guided to the semiconductor pressure sensor element 1,
Normal pressure sensing operation is performed.

The leak valve 6 is not provided only in the pressure introducing port 5, but may be provided in any place as long as it is a member for guiding the pressure to the semiconductor pressure sensor element 1. For example, if pressure is introduced from the pressure inlet 4 as shown in FIG. 3, a leak valve 6 may be provided on the side wall of the housing 3. This is because, in this case, the housing 3 serves as a member that guides pressure to the semiconductor pressure sensor element 1.

Further, the structure of the leak valve itself is not limited to the above. For example, it may be configured as shown in FIG. 4 or may be configured as shown in FIG. In FIG. 4, the leaf spring 11 itself is configured as a valve body that closes the leak opening 7 without providing the valve body 8 as a separate member as in FIGS. 1 and 3. The leaf spring 11 can be made of a metal such as phosphor bronze, and has a portion that functions as a valve body that closes the opening 7 as a free end and is fixed to the side wall on the opposite side (lower end in the figure). When the pressure is within the normal range, the opening 7 is closed by the leaf spring 11 as shown in FIG. 4A, but when the pressure becomes excessive, the leaf spring is closed as shown in FIG. 4B. One end of 11 is pushed by the portion of opening 7
Can be opened to release excessive pressure.

The leak valve shown in FIG. 5 has a simpler structure. In FIG. 5, the leak opening 7 is simply covered with the plug 12. The plug 12 can be made of rubber, plastic, metal, or the like, and is fitted in the leak opening 7 to close the opening 7. Under normal pressure, the opening 7 is blocked by the plug 12 as shown in FIG. 5A, but when excessive pressure is applied, the plug 12 is pushed out of this opening 7 and escapes as shown by the arrow. To do. for that reason,
The opening 7 is in an open state, and excessive pressure is released.
In this case, since the opening 7 remains open even when the pressure returns to the original normal range, the pressure to be detected is not directly guided to the semiconductor pressure sensor element, and it is not possible to return to the normal pressure sensing operation. Therefore, it is a one-time protection operation and cannot be used thereafter. However, once the plug body 12 is attached again, the normal pressure sensing operation can be performed, so that it is suitable for applications where such attachment work is not a concern. It can be said that it was.

In the case of the leak valve having the structure as shown in FIG. 5, the valve 12 is opened by being pushed by the pressure so that the stopper 12 escapes from the opening 7. Therefore, the stopper 12 is opened.
The strength of attachment of the valve to the opening 7 determines the pressure at which the valve opens. Therefore, depending on the material of the plug body 12, the relationship between the size of the plug body 12 and the size of the opening 7, the angle of the taper surface provided in the opening 7, and the like, it is adjusted how much overpressure the protective action is performed. can do.

Looking at an actual semiconductor pressure sensor,
For example, in a semiconductor pressure sensor for detecting a low pressure region where an output of about 70 millivolts can be obtained at a pressure of 70 grams / square centimeter, the thickness of the diaphragm portion is ten and several μ.
The breakdown voltage is about 4 to 5 kilograms / square centimeter, and if the thickness of the diaphragm part is increased to improve this breakdown voltage, the sensitivity will decrease, but this semiconductor pressure sensor has 3 kilograms / square centimeter. By providing a leak valve that opens about a centimeter, it is possible to improve the breakdown voltage without increasing the thickness of the diaphragm portion, that is, while keeping the sensitivity as it is.

On the contrary, if the breakdown withstand voltage is about the same, the sensitivity can be improved. For example the actual 5
A semiconductor pressure sensor for detecting a high pressure of about 0 kilograms / square centimeter needs a breakdown withstand voltage of about 100 kilograms / square centimeter, and it is necessary to increase the thickness of the diaphragm portion accordingly. As a result, the output voltage becomes about a dozen millivolts. In the case of such a semiconductor pressure sensor for high pressure region detection, 7
If a leak valve that opens at about 5 kilograms / square centimeter is provided, the diaphragm portion can be made thinner, and thereby the output voltage can be raised to about several tens of millivolts and the sensitivity can be improved.

As described above, according to the detected pressure range of each of the various semiconductor pressure sensors, various means such as changing the thickness of the leaf spring or changing the size of the pressure releasing opening can be used for the leak valve. By determining the opening pressure, it is possible to increase the pressure detection sensitivity while providing the breakdown withstanding pressure according to the detection pressure range.

[0025]

As described above, according to the embodiment,
According to the semiconductor pressure sensor of the present invention, an extremely simple structure in which a leak valve is provided in the pressure introducing member can release an excessive pressure and protect the semiconductor pressure sensor element from breakage. Therefore, avoid sacrificing sensitivity by thickening the diaphragm part of the semiconductor pressure sensor element,
The breakdown voltage can be improved without changing the sensitivity, or the sensitivity can be improved if the breakdown voltage is the same.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a semiconductor pressure sensor according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing the same embodiment at an excessive pressure.

FIG. 3 is a schematic cross-sectional view of a modified example.

FIG. 4 is a schematic cross-sectional view of another modification.

FIG. 5 is a schematic sectional view of still another modification.

[Explanation of symbols]

 1 Semiconductor Pressure Sensor Element 2 Pedestal 3 Housing 4 and 5 Pressure Inlet 6 Leak Valve 7 Leak Open 8 Valve Disc 9 and 11 Leaf Spring 12 Plug

Claims (3)

[Claims] 1. A semiconductor comprising: a semiconductor pressure sensor element; a pressure introducing member for introducing pressure to the semiconductor pressure sensor element; and a leak valve provided in the pressure introducing member and opening according to an excessive pressure. Pressure sensor. 2. The semiconductor pressure sensor according to claim 1, wherein the leak valve includes a valve body that closes an opening provided in the pressure introducing member and a spring member that supports the valve body. 3. The semiconductor pressure according to claim 1, wherein the leak valve comprises a plug body that closes an opening provided in the pressure introducing member and that escapes from the opening due to the pressure when an excessive pressure is applied. Sensor.