JP2001083030A - Electrostatic capacity type pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To downsize a sensor and lower the cost by a method wherein the pressure is transmitted via bellows made of a metal serving as both a sealed plate of floating capacitance and a sealing cap. SOLUTION: A sensor chip 34 is constituted by a silicon substrate 32 forming a diaphragm part 35 and a glass substrate 33 forming a fixed electrode 37 and is disposed in a case 43, and bellows 32 made of a metal such as stainless, for example, are seal-adhered to this case 43. When a pressure is applied on the bellows 32, a pressure is applied to the diaphragm part 35 via an air, and the diaphragm part 35 constituting a movable electrode is deformed in correspondence to a pressure difference between the above pressure and the interior of a cavity part 36, and a gap between the diaphragm part 35 and a fixed electrode 37 changes, and an electrostatic capacity changes by changes of a gap width. As there is a constant correlation between the pressure and the gap, the electrostatic capacity is detected, thereby detecting the pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance type pressure sensor having a sensor chip in which an electrode portion formed on one substrate and a diaphragm portion formed on the other substrate face each other via a cavity. About.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view of an example using a capacitance type pressure sensor as a water level sensor, FIG. 4 is an external perspective view of an example of a capacitance type pressure sensor, and FIG. Sectional drawing of an example of a capacitance type pressure sensor (BB 'of FIG. 4)
Is shown.

As shown in FIG. 3, when a capacitance type pressure sensor is used as a water level sensor, a capacitance type pressure sensor 12 is provided on the bottom surface of a container 11 so that water having a size corresponding to the amount of water is supplied. The pressure applied to the container bottom is detected by a capacitance type pressure sensor, and the pressure is converted to a water level to measure the water level.

As shown in FIGS. 4 and 5, in the capacitance type pressure sensor, a fixed electrode 18 is formed on a glass substrate 14 as a first substrate, and silicon as a second substrate is
3, a diaphragm portion 16 that is deformed in response to pressure is formed.

[0005] The silicon substrate 13 and the glass substrate 14
A part thereof is joined, whereby a cavity 17 is formed below the diaphragm 16. The silicon substrate 13 and the glass substrate 14 constitute a sensor chip 15, and the sensor chip 15
Is adhered on the case 24 by the glass substrate 14.

Further, a glass substrate 14 constituting the sensor chip 15 and a case 24 on which the sensor chip 15 is disposed
Are formed with through holes 21 and 22 for introducing atmospheric pressure or for introducing a pressure to be compared with the measured pressure.

[0007] A lead terminal 25 integrally formed at the time of molding is arranged in the case 24, and the lead terminal 25 and the fixed electrode 18 are electrically connected by a lead wire 20.

The sensor chip 15 has a horizontal hole (not shown).
Is provided, whereby the fixed electrode 18 is electrically drawn to the outside.

In order to isolate the cavity 17 from the area outside the sensor chip, the lateral hole is sealed with a sealant 19.
Then, the sensor chip 15 is covered with a perforated shield plate 26 so that pressure is transmitted to the case 24, and silicone oil 27 is introduced into the case 2 to introduce a measured pressure.
4 and sealed with the cap 23 of the molding material on which the film 28 is stretched by ultrasonic welding.

In the silicon substrate 13, a concave portion (having a depth of 10 μm or less) for forming the cavity 17 is formed by etching in advance.

The sensor chip is formed by integrating the silicon substrate 13 and the glass substrate 14 by anodic bonding, and then etching the silicon substrate 13 to form the silicon substrate 13.
The diaphragm portion 16 is formed on the substrate to complete it.

The above-described steps are performed in a state of a wafer in which a plurality of sensor chips are arranged in a plane in order to simultaneously produce a plurality of sensor chips for mass production.

After the etching (diaphragm formation), washing with water and drying in a vacuum oven are repeated to sufficiently clean the inside of the cavity, and a wafer in which a plurality of sensor chips are connected in a plane is pasted on an adhesive resin sheet and diced. To separate each sensor chip.

Further, after dicing, washing and drying are performed to complete a sensor chip.

In the capacitance type pressure sensor shown in FIG. 5, when a pressure is applied to the membrane 28, a pressure is applied to the diaphragm 16 via the silicon oil, and the diaphragm 16 is movable according to the magnitude of the pressure difference from the pressure in the cavity. Diaphragm part 16 constituting an electrode
Is deformed.

The deformation of the diaphragm 16 changes the gap between the diaphragm 16 and the fixed electrode 18.

Here, the diaphragm 16 and the fixed electrode 1
8 has a relationship of c = ξ (A / d). In addition,
c is the capacitance, ξ is the dielectric constant of air, A is the electrode area, and d is the gap width between the electrodes.

Therefore, the capacitance changes due to the change in the gap width. Further, since there is a certain correlation between the pressure and the gap, it is necessary to know the pressure by detecting the capacitance. Can be.

[0019]

As described above, when a capacitance type pressure sensor is used as the water level sensor, the pressure to be measured is transmitted to the diaphragm portion of the sensor chip via the silicone oil through the membrane and sensed. Let me. However, in the conventional capacitance type pressure sensor, a shield plate is required through silicone oil or so as to cover the sensor chip, and there is a problem that the size and size are complicated and the price is high.

The present invention has been made in order to solve such problems, and it is an object of the present invention to provide a compact and inexpensive capacitive pressure sensor.

[0021]

According to the present invention, there is provided a first substrate on which an electrode portion is formed, and a second substrate on which a diaphragm portion deformed in response to pressure is formed. In an electrostatic capacitance type pressure sensor including a sensor chip in which the first and second substrates are bonded so that the electrode portion faces each other via a hollow portion, pressure is transmitted through a bellows. This is a capacitance type pressure sensor.

Further, the present invention is the above-mentioned electrostatic capacitance type pressure sensor, wherein the bellows also serves as a shield plate of a floating capacitance and a sealing cap.

Further, the present invention is the above-mentioned capacitance type pressure sensor, wherein the bellows is made of metal.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a capacitance type pressure sensor according to the present invention in which a bellows also has a shielding function will be described with reference to FIGS.

FIG. 1 shows an external perspective view of an example of a capacitance type pressure sensor in which the bellows of the present invention also has a shielding function, and FIG. 2 shows a stainless steel bellows of the present invention also having a shielding function. FIG. 2 shows a cross-sectional view (AA ′ of FIG. 1) of an example of a capacitance type pressure sensor.

The basic structure is the same as that of the conventional capacitance type pressure sensor shown in FIG.

In this embodiment, as shown in FIGS. 1 and 2, a stainless steel bellows 42 is sealingly bonded to a case 43.

When pressure is applied to the bellows 42, pressure is applied to the diaphragm 35 via air, and the diaphragm 35 constituting the movable electrode is deformed according to the magnitude of the pressure difference from the pressure in the cavity.

Therefore, the capacitance changes due to the change in the gap width, and since there is a certain correlation between the pressure and the gap, the pressure can be known by detecting the capacitance. .

In this embodiment, stainless steel is used as the material of the bellows. However, if a metal having good electric conductivity is used, the present invention is not limited to this. Any material may be used.

Further, in the present embodiment, the inside sealed with stainless steel bellows is air, but it goes without saying that a pressure transmission medium such as silicone oil may be sealed as in the conventional case.

[0032]

According to the present invention, by transmitting the pressure by the stainless steel bellows, it is possible to provide a small and inexpensive capacitive pressure sensor in which the bellows also has a shielding function.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing an example of a capacitance type pressure sensor in which a bellows of the present invention also has a shielding function.

FIG. 2 is an AA sectional view of FIG. 1 showing an example of a capacitance type pressure sensor in which the bellows of the present invention also has a shielding function.

FIG. 3 is a sectional view showing an example in which a capacitance type pressure sensor is used as a water level sensor.

FIG. 4 is an external perspective view showing an example using a capacitance type pressure sensor.

FIG. 5 shows an example using a capacitance type pressure sensor.
BB sectional drawing of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Container 12 Capacitance type pressure sensor 13 Silicon substrate 15 Sensor chip 16 Diaphragm part 17 Hollow part 18 Fixed electrode 19 Sealant 20 Lead wire 21 Through hole 22 Through hole 23 Cap 24 Case 25 Lead terminal 26 Shield plate 27 Silicone oil 28 film 31 capacitance type pressure sensor 32 silicon substrate 33 glass substrate 34 sensor chip 35 diaphragm portion 36 cavity portion 37 fixed electrode 38 sealing material 39 lead wire 40 through hole 41 through hole 42 bellows 43 case 44 lead terminal

Claims (3)

[Claims] A first substrate on which an electrode portion is formed; and a second substrate on which a diaphragm portion that is deformed in response to pressure is formed, wherein the diaphragm portion and the electrode portion form a hollow portion. The first and the second so as to face each other
A pressure sensor having a sensor chip joined to a substrate and transmitting pressure via a bellows. 2. The capacitance-type pressure sensor according to claim 1, wherein the bellows serves as both a shield plate for a floating capacitance and a sealing cap. 3. The capacitance type pressure sensor according to claim 1, wherein the bellows is made of metal.