JPH0894468A - Capacitive pressure sensor - Google Patents

Abstract

PURPOSE: To obtain a capacitive pressure sensor which is not susceptible to stray capacity and external field and can detect the pressure accurately. CONSTITUTION: The capacitive pressure sensor comprises a sensor chip 15. The sensor chip 15 comprises a silicon substrate 11 provided with an electrode part 16 and a glass substrate 12 provided with a diaphragm part 13 which is deformed depending on the pressure. The diaphragm part 13 and the electrode part 16 are disposed oppositely through a gap and the silicon substrate 11 is bonded to the glass substrate 12. The pressure sensor detects the pressure based on the variation of capacitance between the diaphragm part 13 and the electrode part 16 due to variation in the width of the gap caused by the pressure being applied to the diaphragm part 13. The sensor chip 15 is mounted on a shield member, also serves as a lead terminal 31, disposed in a sealed housing.

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, and in particular, electrodes are formed on a silicon substrate and a glass substrate respectively, and the electrode surfaces are opposed to each other to bond the silicon substrate and the glass substrate. The present invention relates to a capacitance type pressure sensor.

[0002]

2. Description of the Related Art Generally, a pressure sensor shown in FIG. 2 is known as this type of capacitance type pressure sensor. The pressure sensor shown in FIG. 2 is a capacitance type pressure sensor, in which a silicon substrate 11 is formed with a diaphragm portion 13 that deforms in response to pressure, and a fixed electrode 16 is formed on a glass substrate 12.
Are formed. Silicon substrate 11 and glass substrate 12
And are joined at a part of them, and
A cavity portion 14 is formed below the diaphragm portion 13. The silicon substrate 11 and the glass substrate 12 form a sensor chip 15, and the sensor chip 15 is bonded to the pedestal 23 by the glass substrate 12. Further, the glass substrate 12 forming the sensor chip 15 and the pedestal 23 on which the sensor chip 15 is arranged
There are formed passages 19 and 20 for introducing atmospheric pressure or for introducing a pressure to be compared with the measured pressure. Pedestal 2
3, lead terminals 24, which are formed together at the time of molding, are arranged.
And are electrically connected by a lead wire 18.

The sensor chip 15 is provided with a lateral hole, by which the fixed electrode 16 is drawn out. After that, the lateral hole is sealed with a sealant 17 in order to separate the cavity 14 from the area outside the sensor chip. Then, the pedestal 23 and the cap 22 of the molding material as the cover member provided with the passage 21 for introducing the measured pressure are sealed by ultrasonic welding.

In the illustrated capacitance type pressure sensor, when pressure is applied to the diaphragm portion 13, the diaphragm portion 13 is deformed according to the magnitude of the pressure. The deformation of the diaphragm portion 13 changes the gap between the diaphragm portion 13 and the fixed electrode 16. Here, between the diaphragm portion 13 and the fixed electrode 16, c = ξ (A /
There is a relationship of d). Note that c is capacitance, ξ is the dielectric constant of air, A is the electrode area, and d is the interelectrode gap width.

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

[0006]

However, in the above-mentioned conventional capacitance type pressure sensor, the capacitance which changes depending on the pressure to be detected is as small as 1 to 2 pF and is easily affected by the stray capacitance. It was impossible to detect an accurate pressure because the influence other than the pressure to be applied was large. Moreover, even if the measurement position of the pressure sensor is changed, the electric field in the outside world changes and the detected pressure also changes.

Therefore, a technical object of the present invention is to provide an electrostatic capacitance type pressure sensor which is not easily affected by stray capacitance and external electric field and which can perform accurate pressure detection.

[0008]

According to the present invention, the diaphragm portion has a first substrate on which an electrode portion is formed and a second substrate on which a diaphragm portion that deforms in response to pressure is formed. And a gap between the electrodes according to pressure applied to the diaphragm portion, the sensor chip being joined to the first and second substrates so that the electrodes and the electrode portion are opposed to each other with a gap therebetween. In a capacitance type pressure sensor in which the pressure is detected by changing the width and changing the capacitance between the diaphragm portion and the electrode portion due to the change in the gap width, It is arranged on the shield material that also serves as the lead terminal in the stationary housing. Further, there is obtained an electrostatic capacitance type pressure sensor characterized in that the sensor chip is three-dimensionally covered with a shield material in a sealed casing, and the shield material is also used as a lead terminal.

[0009]

In the present invention, the sensor chip is three-dimensionally covered with the shield material in the sealed casing, and the lead material also serves as the shield material. As described above, by covering the sensor chip three-dimensionally with the shield material in the sealed casing, it is not affected by shielding the stray capacitance and the external electric field, and accurate pressure detection can be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a capacitance type pressure sensor according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an example of the outline of the capacitance type pressure sensor of the present invention. As shown in FIG. 1, a pressure sensor for measurement includes a silicon substrate 11 having a diaphragm portion 13 forming a movable electrode that is deformed by a pressure to be measured and a cavity portion 14 provided below the diaphragm portion 13, and a fixed electrode 1.
6, and a sensor chip 15 composed of a glass substrate 12 for introducing atmospheric pressure or a hole 19 for introducing a pressure to be compared with the measured pressure. A lateral hole is formed in the sensor chip between the silicon substrate 11 and the glass substrate 12 in order to pull out the fixed electrode 16. The fixed hole 1 is formed by the lateral hole of the sensor chip 15.
6 is drawn out. Then, in order to isolate the cavity 14 and the area outside the sensor chip, the lateral holes are used as the sealant 1.
It is sealed by 7. The sensor chip 15 is bonded onto the lead terminal 31 which also serves as a shield material. The lead terminal 24 and the fixed electrode 16 are electrically connected by a lead wire 18. Sensor chip 15
Is three-dimensionally covered by a shield material in the sealed casing, and the lead terminal 31 also serves as the shield material. The lead terminal 31 and the lead terminal 31 which also serves as a shield material are formed together with the pedestal 23 molded by a molding material. The lead terminal 31 also serving as the shield material is
Grounded on a circuit board (not shown). The pedestal 23 and the molding material cap 22 as a cover member having the pressure introducing hole 21 for introducing the measured pressure are sealed by ultrasonic welding.

The operation of the capacitance type pressure sensor according to the embodiment of the present invention is the same as that of the conventional one, so the description thereof will be omitted. However, the capacitance type pressure sensor according to the embodiment of the present invention will not be described. By three-dimensionally covering the sensor chip 15 with the shield material in the sealed casing, it is not affected by shielding the stray capacitance and the external electric field, and accurate pressure detection can be performed.

[0013]

As described above, according to the present invention, the sensor chip is three-dimensionally covered by the shield material in the sealed casing, and the lead terminal also serves as the shield material. As described above, according to the present invention, the sensor chip is three-dimensionally covered by the shield material in the sealed casing, so that the stray capacitance and the external electric field are not affected by shielding, and accurate pressure detection is performed. It is possible to provide an electrostatic capacitance type pressure sensor capable of doing so.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an outline of a capacitance type pressure sensor of the present invention.

FIG. 2 is a cross-sectional view showing an example of an outline of a conventional capacitance type pressure sensor.

[Explanation of symbols]

 11 Silicon Substrate 12 Glass Substrate 13 Diaphragm Part 14 Cavity Part 15 Sensor Chip 16 Fixed Electrode 17 Sealing Material 18 Lead Wire 19 Through Hole 20 Through Hole 21 Pressure Introducing Hole 22 Cap Part 23 Pedestal 24 Lead Terminal 31 Also as a Shielding Material Existing lead terminal

Claims (2)

[Claims] 1. A first substrate on which an electrode portion is formed and a second substrate on which a diaphragm portion that deforms in response to pressure is formed, and a gap is formed between the diaphragm portion and the electrode portion. A sensor chip bonded to the first and second substrates so as to face each other,
The gap width of the gap is changed according to the pressure applied to the diaphragm portion, and the pressure is detected by the change of the electrostatic capacitance between the diaphragm portion and the electrode portion due to the change of the gap width. A capacitance type pressure sensor, wherein the sensor chip is arranged on a shield material also serving as a lead terminal in a sealed casing. 2. The capacitance type pressure sensor according to claim 1, wherein the sensor chip is three-dimensionally covered with a shield material in a sealed casing, and the lead terminal also serves as the shield material.