JP2815279B2 - pressure sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure sensor for detecting a pressure of a fluid to be measured, and more particularly to a capacitance type pressure sensor for detecting a pressure by utilizing a change in capacitance between opposed electrodes. About.

[0002]

2. Description of the Related Art FIG. 15 shows a conventional general pressure conversion element 900 used for a capacitance type pressure sensor (see Japanese Patent Publication No. 60-34687, etc .; first conventional example). The pressure conversion element 900 includes a thick substrate 901 and a thin diaphragm 902 that is deformed by the pressure of the measurement fluid, and these substrates 901 and the diaphragm 902 are connected to each other by a ring-shaped joint.
903 are arranged in parallel with each other at a predetermined interval. Opposite surfaces 904, 905 of substrate 901 and diaphragm 902
A space 906 is formed therebetween so as to be surrounded by the joint 903. A substantially circular electrode 91 is provided on the facing surface 904 of the substrate 901.
On the other hand, a substantially circular electrode 911 having the same size as the electrode 910 is provided on the facing surface 905 of the diaphragm 902, and a capacitor 912 having a capacitance C is formed by the facing electrodes 910 and 911. I have. Also, the diaphragm
The surface of 902 opposite to the facing surface 905 is a pressure receiving surface 907 to which the pressure of the measurement fluid is applied.

[0003] A conductive path 913 for taking out the electrode extending toward the outer end is formed continuously at one portion of the outer edge of the electrode 910, while one portion of the outer edge of the electrode 911 is formed at the outer end. A conductive path 914 for extracting an electrode extending toward the electrode is formed continuously. The dotted line in the figure indicates the state of the lines of electric force generated between the electrodes 910 and 911. The lines of electric force are straight near the center of each electrode 910, 911, but near the outer edge of each electrode 910, 911, each conductive path 913, 914.
And the joint 903 is disturbed.

In such a first conventional example, the space 90
Then, the atmosphere or the like is led to 6 to make it a reference pressure, while the pressure of the measurement fluid is applied from the pressure receiving surface 907, and the diaphragm 902 is deflected by these differential pressures. And this diaphragm 902
The pressure between the electrodes 910 and 911 changes along with the deflection of the electrode 910, and the pressure of the measurement fluid is detected by using the change in the capacitance C of the capacitor 912. In some cases, absolute pressure measurement is performed with the space 906 as a vacuum.

FIG. 16 shows a pressure conversion element 800 which is another conventional example obtained by improving the general pressure conversion element 900 shown in the first conventional example (see Japanese Patent Application Laid-Open No. 60-56233). A second conventional example). The hatching in FIGS. 16B and 16C does not show a cross section, but is shown for easy understanding in description. The pressure conversion element 800 is configured in the same manner as in the first conventional example, and a thick substrate 801 and a thin diaphragm 802 are arranged at predetermined intervals in parallel with each other via a ring-shaped joint 803. ing. Between opposing surfaces 804 and 805 of the substrate 801 and the diaphragm 802,
A space 806 is formed so as to be surrounded by the joint 803. A substantially circular electrode 810 is provided on the facing surface 804 of the substrate 801.
A ring-shaped (C-shaped) electrode 811 which is arranged so as to surround the outside of the substantially circular electrode 810 and has a part thereof cut off.
And the opposite surface 805 of the diaphragm 802
Is provided with a substantially circular electrode 812 having the same outer diameter as that of the outer electrode 811. A capacitor 814 having a capacitance C1 is formed by these opposed electrodes 810 and 812.
Are formed, and a capacitor 815 having a capacitance C2 is formed by the electrode 811 and the electrode 812. Also, the diaphragm
The surface opposite to the facing surface 805 of 802 is a pressure receiving surface 807 to which the pressure of the measurement fluid is applied.

At one location of the outer edge of the electrode 810, a conductive path 816 for extracting an electrode, which passes through the cut portion of the electrode 811 and extends toward the outer end, is formed continuously.
A conductive path 817 for taking out an electrode extending toward the outer end is continuously formed at one position of the outer edge of the substrate. on the other hand,
At one location on the outer edge of the electrode 812, a conductive path 818 for extracting an electrode extending toward the outer end is continuously formed. Further, the substrate 801 has a through hole 819 communicating the space 806 with the outside, and the atmosphere serving as a reference pressure is introduced into the space 806 from the through hole 819.

In the second conventional example, the atmosphere is guided to the space 806 as a reference pressure, as in the first conventional example.
On the other hand, the pressure of the measurement fluid is applied from the pressure receiving surface 807, and the diaphragm 802 is bent by these differential pressures. And
The pressure between the electrodes 810 and 812 and the distance between the electrodes 811 and 812 change with the flexure of the diaphragm 802, and the pressure of the measurement fluid is detected by using the change in the capacitances C1 and C2 of the capacitors 814 and 815. According to the second conventional example, the capacitances C1 and C2 of the capacitors 814 and 815 are
806 is affected by changes in the dielectric constant ε due to changes in humidity, temperature, etc.
By detecting C1 / C2, this effect can be corrected and pressure measurement can be performed. That is, each capacitor 814,815
If the distance between the electrodes is D1, D2 and the electrode area is S1, S2, C1 / C2 = (ε × S1 / D1) / (ε × S2 / D2) = (S1 × D2)
/ (S2 × D1), and the dielectric constant ε is canceled, so that the pressure measurement can be performed by correcting the influence of the change in the dielectric constant ε.

[0008]

However, in the above-mentioned first conventional example shown in FIG. 15, when the pressure of the measurement fluid is detected by the gauge pressure, the atmosphere must be introduced into the space 906. Since the permittivity of the atmosphere in the space 906 changes under the influence of changes in the temperature and humidity of the atmosphere, the capacitance C of the capacitor 912 changes, so that accurate pressure detection can be performed. There was a problem that it was not possible.
In addition, the electrodes 910, 911
Since the insulation resistance between them also changes, there is a problem that accurate pressure cannot be detected even by this.

As shown by the broken lines in FIG.
The lines of electric force generated near the outer edges of 910 and 911 are swelling outward, and the permittivity due to changes in the temperature and humidity of the materials of the substrate 901, the diaphragm 902, and the joint 903 disposed in the swelling portion outside , The capacitance C of the capacitor 912 changes. Also, when an object 920 having an extremely different dielectric constant approaches the diaphragm 902, the lines of electric force swell toward the object 920 and the capacitance C
Are affected by this. In addition, conductive paths for taking out electrodes
Since the 913 and 914 are provided so as to protrude outward from the outer edges of the electrodes 910 and 911, the lines of electric force also swell outward, and the capacitance C is affected by this, and accurate pressure detection can be performed. There was a problem that it was not possible.

In the second conventional example shown in FIG.
Divide the electrode on the side of the substrate 801 into two capacitors 814 and 81
5 (Capacitance C1, C2) is formed. By detecting C1 / C2 by a measurement circuit (not shown), the influence of the change in the dielectric constant ε due to the change in humidity, temperature, etc. in the space 806 is corrected. The pressure of the measurement fluid can be detected. However, the outer electrode 811 on the substrate 801 side and the electrode on the diaphragm 802 side
The lines of electric force generated between the first and second conductive lines 812 and 812 are disturbed by the influence of the conductive paths 817 and 818 and the joint 803 for taking out the electrodes. The capacitor 815 is affected by the change in the dielectric constant of the material of the substrate 801
However, there is a problem that the electrostatic capacitance C2 changes, which makes it impossible to accurately detect the pressure.

The outer electrode 811 on the side of the substrate 801 is formed in a ring shape (C-shape) in which a part is cut to pass through the conductive path 816 of the central electrode 810. However, since the capacitance C2 of the capacitor 815 is affected by the terminal effect, there is a problem that accurate pressure cannot be detected. Further, the electrode 811 is formed in such a partially cut ring-like shape as a conductive path projecting outward.
817 and a substantially circular electrode 810, 812
However, these have shapes in which conductive paths 816 and 818 protrude outward, respectively, and are not simple shapes, so that there is a problem that the manufacturing process becomes complicated.

An object of the present invention is to provide a pressure sensor which can accurately measure pressure and is easy to manufacture.

[0013]

SUMMARY OF THE INVENTION The object of the present invention is to divide the electrodes on the substrate side into a plurality of parts and to simplify these electrodes to achieve the above object. Specifically, the present invention includes a thick-walled substrate and a thin-walled elastic diaphragm that is disposed opposite to the substrate at a predetermined interval, and faces each of the opposing surfaces of the substrate and the elastic diaphragm. An electrode is provided, which is a pressure sensor that detects a pressure applied to the elastic diaphragm by a change in capacitance between the electrodes, wherein the electrode on the substrate side among the electrodes is divided into a plurality, and the divided substrate side Are sequentially arranged so as to surround the inner electrode. Of the divided electrodes on the substrate side, the electrodes except for the central electrode are respectively
Is formed in a closed loop with a constant width, most outer electrode is maintained at ground or a predetermined constant voltage, elastic die of the electrode
The electrode on the diaphragm side is formed in a solid substantially circular shape, and the
From the outer edge of the outermost electrode on the substrate side over the entire circumference
Also has an outer edge located on the outside, the electrode of the substrate
On the surface opposite to the surface provided with
An electrode terminal for the electrode on the system side is provided.
The outer edge of the electrode on the conductive diaphragm side is
It is characterized in that conduction is made through a conduction portion of the through hole .

Here, the electrode on the substrate side is divided into three parts,
It is desirable that the center electrode of the three divided electrodes is formed in a solid circular shape without a central portion, and the remaining two electrodes are formed in a closed annular shape. Also,
Connect the conducting part and outer edge of the through hole to one end of the through hole.
Conducted by conductive paste inserted from the side, the substrate
The joint provided between the elastic diaphragm and
A space where part of the edge is exposed and communicates with the through hole
It is possible to fill this space with conductive paste
desirable.

[0015]

In the present invention as described above, the pressure of the measurement fluid is applied to the elastic diaphragm to bend it, and the change in the capacitance accompanying the change in the distance between the opposed electrodes at this time is grasped. Detect pressure. At this time, the outermost electrode among the plurality of divided electrodes on the substrate side is grounded, for example, and is not used for measurement. Therefore, only the lines of electric force between the grounded electrode on the substrate side and the electrode on the elastic diaphragm side bulge outward, and the capacitance is affected by the surrounding materials, and the substrate side used for measurement is The lines of electric force between the remaining electrodes and the electrodes on the elastic diaphragm side are formed substantially straight, and the capacitance is not affected by the surrounding materials. For this reason, even if the temperature and humidity of the surrounding materials such as the substrate, the elastic diaphragm and their joints change, and the dielectric constant changes, the measurement is not affected and accurate measurement is performed. In addition, in a plurality of capacitors formed by the remaining electrodes excluding the outermost electrode on the substrate side, that is, the electrodes used for measurement and the electrodes on the elastic diaphragm side, the ratio or the sum of the capacitance of each capacitor is measured by the measurement circuit. By detecting the ratio of the difference between the substrate and the elastic diaphragm, the effect of the change in the dielectric constant of the atmosphere in the space between the substrate and the elastic diaphragm is corrected.In addition to the measurement that eliminates the influence of the surrounding material due to the grounding described above, More accurate measurement is performed.

Further, of the plurality of divided electrodes on the substrate side, the electrodes except for the central electrode are each formed in a closed annular shape having a fixed width, and project outwardly as in the first and second conventional examples described above. Since the shape does not have a portion to be cut or a cut portion, the influence of the terminal effect described above is reduced, and the measurement accuracy is improved. In addition, because of such a simple electrode shape, the manufacturing process is simplified. And
When the electrode on the elastic diaphragm side is formed in a solid and substantially circular shape
In both cases, the outermost electrode on the substrate side
An outer edge located further outside than the outer edge is provided.
The electrode terminals for the electrodes of the elastic diaphragm on the back of the substrate.
When pulled out to the outer edge corresponding to the substrate
It is sufficient to provide a through hole at the position, and take the electrode terminal
It is easy to pull out.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 6 show a capacitance type pressure conversion element 10 according to a first embodiment of the present invention. In FIG. 1, a pressure conversion element 10 is mounted inside a pressure sensor (not shown), and converts the pressure into an electrical output signal in order to detect the pressure of the measurement fluid. The pressure transducer 10 has a main body 10A having a flat cylindrical outer shape, and the main body 10A includes a ceramic thick substrate 11 and a ceramic thin diaphragm 12 which is deformed by the pressure of a measurement fluid. The substrate 11 and the diaphragm 12 are arranged at predetermined intervals in parallel with each other via a joint 20. A space 30 is formed between the opposing surfaces 13 and 14 of the substrate 11 and the diaphragm 12 so as to be surrounded by the ring-shaped joint 20.

As shown in FIG. 2, the opposite surface 13 of the substrate 11 has a solid circular central electrode 31 with a central portion not missing.
Each ring-shaped reference electrode 32 and shield electrode 33
Are provided, while a common electrode 34 having a solid circular shape is provided on the facing surface 14 of the diaphragm 12. FIG. 2 is a diagram of the state where the substrate 11 and the diaphragm 12 are viewed from the opposing surfaces 13 and 14, respectively (the bonding portion 20 is not formed). The hatching in the figure does not show a cross section, but is shown for easy understanding in description, and the same applies to hatching in FIGS. 3A and 9 described later. On the opposing surface 13 of the substrate 11,
The center electrode 31 is formed in a solid circular shape and has a reference electrode
Reference numeral 32 denotes an annular shape (ring shape) closed so as to surround the central electrode 31.
Further, a shield electrode 33 is formed on the outside thereof in a closed annular shape (ring shape) so as to surround the reference electrode 32. The distance S1 between the center electrode 31 and the reference electrode 32 and the distance S2 between the reference electrode 32 and the shield electrode 33 are, for example, about 500 μm, respectively. On the facing surface 14 of the diaphragm 12, the common electrode 34
Is formed in a solid circle and its outer diameter DC is the shield electrode
A portion of the common electrode 34 outside the outer edge of the shield electrode 33 is larger than the outer diameter DS of the common electrode 34, and serves as an outer edge portion 38 for forming an electrode terminal described later. Also,
Outside the shield electrode 33 on the opposing surface 13 of the substrate 11, a connection terminal 39 electrically connected to the outer edge portion 38 of the common electrode 34 is formed of a conductive material such as silver-palladium paste.

Returning to FIG. 1, the space is defined by these electrodes.
A total of three capacitors are formed using the atmosphere in 30 as a dielectric. That is, the capacitor 35 having the capacitance CM and the reference electrode 32
The common electrode 34 forms a capacitor 36 having a capacitance CR, and the shield electrode 33 and the common electrode 34 form a capacitor 37 having a capacitance CS. The distance T between the electrodes of each of the capacitors 35, 36, and 37 is determined by the thickness of the joint 20, and in a state where no pressure acts on the diaphragm 12,
For example, it is about 50 μm. The surface of the diaphragm 12 opposite to the facing surface 14 is a pressure receiving surface 16 to which the pressure of the measurement fluid is applied. The pressure conversion element 10 is configured to control the pressure of the measurement fluid acting on the pressure receiving surface 16 of the diaphragm 12 and the space 30.
The diaphragm 12 bends due to the pressure difference from the internal atmospheric pressure, and the distance between the electrodes of the capacitors 35, 36, and 37 changes from its initial value T, and accordingly, the capacitances CM, CR, and CS change. This is used to detect the pressure of the measurement fluid.

A one-chip IC 60 is mounted on the back surface 15 of the substrate 11 (the surface opposite to the opposing surface 13). This one-chip IC 60 has a C-MOS
ASIC (custom IC), each capacitance CM, C
Measurement circuit 65 for measuring changes in R and CS (see FIG. 5 described later)
Built-in. An electrode pattern 40 for directly mounting the one-chip IC 60 is formed on the rear surface 15 of the substrate 11 by printing. 3A and 3B show a detailed configuration of the electrode pattern 40. FIG. 3A shows a state before the one-chip IC 60 is mounted, and FIG. 3B shows a state after the one-chip IC 60 is mounted. . The electrode pattern 40 includes a circuit path 63A formed in a ring shape on the outer edge of the back surface 15 of the substrate 11, and an electrode for the shield electrode 33 on the substrate 11 side is provided on the inner protruding portion on the right side of the circuit path 63A in the drawing. Terminal 43 is formed in an electrically conductive state. On the other hand, inside the circuit path 63A, the central electrode 31 on the substrate 11, the electrode terminals 41 and 42 for the reference electrode 32, and the common electrode 34 on the diaphragm 12 side.
Electrode terminals 44 are formed in the form of spots, and these electrode terminals 41, 42, 44 form key-shaped circuit paths 61, 62, 64, respectively.
Guided to the position of the foot (pin). At this time, the common electrode
A circuit path 63B is provided at predetermined intervals around the electrode terminal 44 for 34 and the circuit path 64.
Is connected to the inside of the left side portion of the ring-shaped circuit path 63A in the figure and is integrated with the circuit path 63A. Further, the circuit path 63B is arranged so as to pass through the position of the foot of the one-chip IC 60 located on both sides of the tip of the circuit path 64, and is connected to the ground terminal of the one-chip IC 60. Each of the circuit paths 63A and 63B electrically connected to the electrode terminal 43 for the shield electrode 33 is grounded. Therefore, a circuit path 61 including the electrode terminal 41 for the center electrode 31 and a circuit path 62 including the electrode terminal 42 for the reference electrode 32
And a circuit path 64 including the electrode terminal 44 for the common electrode 34,
They are arranged so as to be isolated from each other by circuit paths 63A and 63B as ground electrodes. Therefore, it is possible to reduce the influence of an increase in leakage current due to a decrease in insulation resistance therebetween.

As shown in FIG. 1, each of the electrode terminals 41, 42, 43, and 44 has a conductive portion 51, formed in an electrode hole 45, 46, 47, 48 provided to penetrate the substrate 11, respectively. 52, 53, 54
As a result, it is electrically connected to the connection terminal 39 which is electrically connected to the center electrode 31, the reference electrode 32, the shield electrode 33, and the common electrode 34, respectively. At this time, each conducting part 51, 52, 53, 54
Are provided on the inner wall surface of each of the electrode holes 45, 46, 47, and 48, and a through hole is formed at the center of each hole. Of these, the through holes of the electrode holes 48 are closed by the conductive paste 25 described later, but the remaining electrode holes 45, 46,
At least one of the forty-seven through holes is open at the entrance on both sides, so that the outside atmosphere can be guided to the space 30.

FIG. 4 shows a detailed cross section of the joint 20. The bonding portion 20 is formed of an overcoat glass 21 that is disposed in close contact with the substrate 11 so as to cover the outer peripheral side of the shield electrode 33.
And a ring-shaped high melting point glass 22 provided between the overcoat glass 21 and the diaphragm 12 to adjust the distance between the overcoat glass 21 and the diaphragm 12 and functioning as a spacer, and between the overcoat glass 21 and the diaphragm 12 And a low-melting glass 23 disposed around the inner and outer peripheral sides of the high-melting glass 22. The overcoat glass 21 is provided to increase the edge distance between the shield electrode 33 and the common electrode 34 and increase the edge resistance.
The high-melting glass 22 is made of crystallized glass or the like, and is provided so as to maintain a predetermined distance between the substrate 11 and the diaphragm 12, that is, a distance T between the electrodes by adjusting the thickness thereof. Changing the pressure range generally involves changing the diaphragm 12
The thickness can be changed by adjusting the thickness T of the high-melting glass 22. The low-melting glass 23 is an amorphous glass or the like, and a space 24 is provided in a part thereof. In this space 24, a conductive paste 25 for conducting the outer edge portion 38 of the common electrode 34 and the connection terminal 39 is inserted, and the space 24 prevents the conductive paste 25 from protruding when the conductive paste 25 is inserted in a manufacturing process described later. The space 30 is separated from the space 30 by a low-melting glass 23. As a result, the common electrode 34 has its outer edge 38
Thus, the conductive paste 25, the connection terminals 39, and the conductive portions 54 are connected to the electrode terminals 44 on the rear surface 15 of the substrate 11 in this order. A part of the space 24 into which the conductive paste 25 is inserted is also formed at a position corresponding to the overcoat glass 21.
Such a space 24 may be provided in the high melting point glass 22 depending on the arrangement of the high melting point glass 22.

FIG. 5 shows a measuring circuit 65 built in the one-chip IC 60. In FIG. 5, the measuring circuit 65
The circuit 70 is a circuit means for obtaining an output signal related to the ratio of the sum and difference of the capacitances CM and CR of the capacitors 35 and 36 in the main body 10A of the pressure transducer 10 as described in detail below. A zero-point adjusting circuit 71 which is a zero-point adjusting means for adjusting a zero point of an output signal of the measuring circuit 65; a pressure of a measuring fluid to be added to the diaphragm 12 of the main body 10A; A span adjusting circuit 72 which is a span adjusting means for adjusting a magnitude relationship (span) between a range of an input-side pressure and a range of an output-side output signal in relation to an output signal of the measuring circuit 65; And a linearity correction circuit 73 as linearity correction means for correcting the linearity of the relationship between the output signal and the output signal.

The circuit 70 includes an operational amplifier 83, and the output terminal of the span adjustment circuit 72 and the output signal of the linearity correction circuit 73 are input to the minus terminal of the operational amplifier 83. The output side of the operational amplifier 83 is directly connected to one terminal of the switch 75, and is also connected to one terminal of the switch 74 via the operational amplifier 84. Each of these switches
The common terminals 75 and 74 are connected to the center electrode 31 and the reference electrode 32, which are one electrode of the capacitors 35 and 36, respectively. The common electrode 34, which is the other electrode of each of the capacitors 35 and 36, is connected to the minus terminal of the operational amplifier 85 via a switch 76, and the output side of the operational amplifier 85 is common to the other terminals of the switches 75 and 74. Connected to the negative terminal of the operational amplifier 86. A capacitor 77 for data hold (details will be described later) is provided between the output side of the operational amplifier 85 and the minus terminal.
(Capacitance C0). The output signal of the zero point adjustment circuit 71 is input to the minus terminal of the operational amplifier 86. The output side of the operational amplifier 86 is connected to the output terminal 78 and output to the linearity correction circuit 73. The signal is fed back. In addition,
The plus terminals of the operational amplifiers 83 to 86 are respectively grounded.

The zero point adjustment circuit 71, the span adjustment circuit 72, and the linearity correction circuit 73 are each composed of a plurality of Zeners connected in parallel to a digital / analog converter 80 (DAC).
By having a zap diode 81 (indicated by n in FIG. 5) and trimming them by the required number of bits,
The output signal can be adjusted according to each function.

In FIG. 5, the circuit 70 comprises three switches
74, 75, and 76, which are switched between a dotted line and a solid line in the figure. First, switch 74, 7
5 and 76 are indicated by dotted lines.
The output voltage VI of the operational amplifier 83 and the output voltage −VI of the operational amplifier 84 are applied to 5, 36, and the charges QM and QR corresponding to the respective capacitances CM and CR are QM = −CM × VI and QR = CR × Stored by VI. Here, as a specific example of the voltage, the capacitance, etc., the voltage VI is about 2.5 V (2 × VI = 5 V).
CR is, for example, 30 pF, and the capacitance CM of the capacitor 35 generally changes by about 6 to 8 pF due to the bending of the diaphragm 12,
On the other hand, the capacitance CR of the capacitor 36 changes by 1 to 2 pF,
The difference between the two capacitances is about 5-6pF. Next, when the switches 74, 75, and 76 are in the solid line state, the difference ΔQ between the charges QM and QR stored in the capacitors 35 and 36 moves to the capacitor 77 having the capacitance C0. At this time, if QR> QM, the voltage VX of each of the capacitors 35 and 36 is balanced in the state of the following equation. VX = (QR−ΔQ) / CR = (QM + ΔQ) / CM From this, ΔQ = (CM × QR−CR × QM) / (CR + CM) is obtained. Therefore, the operation of the operational amplifier
The output voltage VO of 85 is: VO = VX = (QR−ΔQ) / CR = [CR × VI − {(CM × QR−CR × QM) / (CR + CM)}] / CR = [CR × VI − ｛( CM × CR × VI + CR × CM × VI) / (CR + CM)｝] / CR = {(CR−CM) / (CR + CM)} × VI, and the sum and difference of the capacitances CM and CR of the capacitors 35 and 36 An output signal related to the ratio can be obtained.

In the first embodiment, the pressure of the measurement fluid is detected as follows. First, at the same time that the pressure of the measurement fluid is applied to the pressure receiving surface 16 of the diaphragm 12, the atmosphere is introduced into the space 30 through at least one of the through holes formed in the electrode holes 45, 46, 47, and the space 30 is introduced. The inside is set to the atmospheric pressure. At this time, the diaphragm 12 bends due to the pressure difference between the pressure receiving surface 16 side and the space 30 side. Usually space
It bends to the 30 side, but to the opposite side when the pressure of the measurement fluid is negative (atmospheric pressure or lower). Next, a change in each capacitance CM, CR due to a change in the distance between the electrodes of each of the capacitors 35, 36 due to the deflection of the diaphragm 12 is captured by the measurement circuit 65, and the capacitance CM, CR of each of the capacitors 35, 36 is captured. To obtain an output signal related to the ratio of the sum to the difference. Then, by calibrating the relationship between the output signal and the pressure in advance, the pressure of the measurement fluid corresponding to the detected output signal is obtained.

Hereinafter, the pressure transducer 10 according to the first embodiment will be described.
An example of a method for manufacturing the device will be described. First, in the manufacturing process (1), the substrate 11 and the diaphragm 12 are processed and formed by using an appropriate material, for example, alumina ceramics. Alumina (Al ₂ O ₃ ) is a typical fine ceramic material, has a high melting point, is hard, and has excellent electrical insulation. Substrate 11
The thickness of the diaphragm 12 is usually about 4 mm, and the thickness of the diaphragm 12 varies depending on the pressure range of the pressure to be measured, the relationship with the effective diameter of the diaphragm 12, and the like.
It is about.

Next, in the manufacturing process (2), each electrode and the joint 20 are printed and fired on the substrate 11 and the diaphragm 12. This printing and firing can all be performed using a hybrid IC (HIC) manufacturing technique and manufacturing machine. In the manufacturing process (2A), the center electrode 3 is arranged on the front surface (opposing surface 13) of the substrate 11 in an arrangement as shown in FIG.
1. The three electrodes of the reference electrode 32 and the shield electrode 33 and the connection terminal 39 are screen-printed. The printing material is silver palladium paste, etc.
Bake at a temperature of about 900 ° C. Baking thickness is 5 ~ 10μ
m. At this time, each of the electrode holes 45 to 48 is suctioned using the vacuum of the vacuum chuck, and the silver palladium paste being printed is transmitted through the inner wall surface so that each of the electrode holes 45 to 48 is sucked.
Pour into 48. In the manufacturing process (2B), the substrate 11
The electrode pattern 40 including the respective electrode terminals 41 to 44 is screen-printed on the back surface (back surface 15) of FIG. The printing material is the same silver palladium paste as in the manufacturing step (2A), and the firing method and firing thickness are the same as in the manufacturing step (2A). Also in this case, the manufacturing process (2A)
Similarly to the above, each of the electrode holes 45 to 48 is suctioned using the vacuum of the vacuum chuck, and the silver palladium paste being printed is poured into each of the electrode holes 45 to 48 so as to be transmitted along the inner wall surface. As shown in the cross section of FIG. 6, conductive portions 51 to 54 are respectively formed on the inner surfaces of the electrode holes 45 to 48 by pouring by vacuum suction from the facing surface 13 side and the back surface 15 side. A through hole is formed. Further, of the through holes formed in these electrode holes 45 to 48, the electrode hole 48 for the common electrode 34 is formed on one side by the conductive paste 25 (see FIG. 4) inserted in the manufacturing step (4) described later. Is closed, but the other central electrode 31, reference electrode 32,
At least one of the electrode holes 45 to 47 for the shield electrode 33 is opened on both sides as a low-pressure port for guiding the atmosphere into the space 30.

In the manufacturing process (2C), the overcoat glass 21 is printed on the facing surface 13 of the substrate 11 in the arrangement shown in FIGS. The printing material is passivation glass or the like, and is fired in a continuous furnace at a temperature of about 700 to 900 ° C.
The fired thickness is about 20 to 28 μm. Manufacturing process (2D)
In the above, a high melting point glass 22 functioning as a spacer is placed on the overcoat glass 21 (arrangement shown in FIGS. 1 and 4).
Print. The printing material is a glass paste, which is fired in a continuous furnace at a temperature of about 700 to 900 ° C. The calcined thickness is about 20 to 50 μm, but this thickness varies depending on the range of the pressure sensor. In the manufacturing process (2E), the manufacturing process (2D)
In the arrangement surrounding the inside and the outside of the high melting point glass 22 printed in the above, in other words, in the arrangement straddling both sides of the high melting point glass 22 (the arrangement shown in FIGS. 1 and 4), the low melting point glass 23 for joining is used.
Print and dry. At this time, printing is performed with a mask excluding this portion so that the space 24 is formed at a position corresponding to the electrode hole 48 at the same time. The printing material is a glass paste, and the dry thickness is about 20 to 50 μm, but this thickness varies depending on the measurement range of the pressure sensor.

On the other hand, in the manufacturing process (2F), a circular common electrode as shown in FIG.
Print 34. The printing material is, for example, a gold resinate, which is fired at a temperature of about 700 to 900 ° C. in a continuous furnace.
The calcined thickness is about 0.5 to 1 μm. Manufacturing process (2
In G), the same material as the low-melting glass 23 for bonding printed in the manufacturing step (2E) is printed on the facing surface 14 of the diaphragm 12 in the arrangement shown in FIGS. The dry thickness is about 20 to 50 μm, but depends on the measurement range of the pressure sensor. The low-melting glass 23 has a greatly reduced thickness after baking compared to its dry thickness due to baking in the next manufacturing step (3). In addition, printing of the low-melting glass 23 in one of the manufacturing process (2E) and the manufacturing process (2G) is omitted, and the low-melting glass 23 is printed on only one of the substrate 11 side and the diaphragm 12 side to perform bonding. In some cases,
In short, the low-melting glass 23 is printed on at least one side so as to have the cross-sectional arrangement shape shown in FIG. 4 after firing in the next manufacturing step (3).

Subsequently, in the manufacturing process (3), each facing surface 1
The substrate 11 and the diaphragm 12 are combined so that the substrates 3 and 14 face each other, and the low-melting glass 23 is baked to join them. The firing temperature is about 600-700 ° C. After that, the manufacturing process (4)
Then, a conductive paste 25 ( see FIG. 4 ) is applied to the space 24 through a through hole formed in the electrode hole 48 and attached to the tip of a thin line and the like. Conduction with the provided electrode terminal 44 is performed. The firing is usually performed at a temperature of 600 ° C. or less. Finally, the manufacturing process (5)
At a position where one end of each of the circuit paths 61 to 64 on the back surface 15 of the substrate 11 is concentrated, that is, at a position corresponding to the position of the foot of the one-chip IC 60, a measurement circuit 65 inside the one-chip IC 60 is provided.
Are mounted by soldering, and the one-chip IC 60 is mounted thereon.

According to the first embodiment, the following effects can be obtained. That is, the electrode on the substrate 11 side is
1, since the reference electrode 32 and the shield electrode 33 are divided into three, the influence of the ceramics, which is the material of the substrate 11 near the bonding portion 20, and the low melting point glass 23 forming the bonding portion 20, etc. Side condenser 37 (capacitance CS)
Only the inner capacitors 35, 36 (capacitance
CM, CR) may not be affected by these. That is, due to the presence of the joint portion 20, the electric lines of force connecting the shield electrode 33 and the common electrode 34 are formed so as to bulge outward, and the capacitance CS changes in the dielectric constant due to a change in humidity of the ceramics, the low melting point glass 23, and the like. On the other hand, the lines of electric force connecting the central electrode 31 and the reference electrode 32 to the common electrode 34 become normal in a substantially straight manner in the space 30, and the capacitances CM and CR are It will be affected only by the dielectric constant of the atmosphere. For this reason, the outermost, that is, the shield electrode 33 on the side of the joint 20 is not used for measurement but is used for grounding, and measurement is performed using the central electrode 31 and the reference electrode 32 on the inner side. Measurement can be performed accurately without being affected by the glass 23 and the like.

As shown in FIG. 5, the voltage V at the output terminal 78 is given by the circuit 70 as V は VO = ｛(CR-CM) / (CR +
CM)｝ × VI, and the capacitance C of each capacitor 35, 36
Since an output signal related to the ratio of the sum and difference of M and CR can be obtained, the dielectric constant of the atmosphere in the space 30 changes under the influence of temperature, humidity, etc., and accordingly, the capacitance CM, Even if CR changes, this effect can be corrected, and the measurement accuracy can be further improved in addition to the effect provided by providing the shield electrode 33 described above. That is, the capacitance C
M and CR represent the electrode area AM and AR, and the distance between the electrodes DM and
Assuming that DR and its change amount are DMP and DRP (DMP> DRP), CM = ε × AM / (DM−DMP) and CR = ε × AR / (DR−DRP), where the dielectric constant ε is Even if it changes under the influence of the temperature, humidity, etc. of the atmosphere in the space 30, since the voltage V of the output terminal 78 is the ratio of the sum and difference of the capacitances CM and CR, this effect is canceled. be able to.

Further, since the center electrode 31 is formed in a circular shape, and the reference electrode 32 and the shield electrode 33 are formed in a closed annular shape, it can be easily manufactured. Furthermore, since the common electrode 34 is formed in a circular shape, the substrate 11 and the diaphragm
Since the joining operation can be performed without considering its direction when joining with 12, the manufacturing can be facilitated. The outer edge 38 of the circular common electrode 34
Is located outside the outer edge of the outermost shield electrode 33 on the substrate 11 side, so that the electrode terminal 44 for the common electrode 34 on the back surface 15 of the substrate 11 can be easily taken out. can do.

Further, since the shield electrode 33 is provided, when the humidity as the humidity increases, the ceramics as the material of the substrate 11 and the edge resistance of the low-melting glass 23 and the like forming the joint 20 are reduced. Leakage current (leakage current) flowing from the electrode 32 to the common electrode 34 can be absorbed by the shield electrode 33. Since the shield electrode 33 is not used for measurement, the effect of humidity on measurement can be reduced by providing the shield electrode 33 after all.

The joining portion 20 has a high-melting glass 22 functioning as a spacer, and a low-melting glass 23 for joining is disposed around the high-melting glass 22. By adjusting, the substrate 11 and the diaphragm
12, the distance T between the electrodes can be easily set to a parallel and predetermined distance. In addition, joint 20
Has an overcoat glass 21, which increases the edge distance between the shield electrode 33 and the common electrode 34 and increases the edge resistance, so that the leakage current between them can be reduced. Then, by printing this overcoat glass 21 so as to cover not only a part of the shield electrode 33 but also the central electrode 31 and the reference electrode 32, when the diaphragm 12 is over-deformed, these electrodes and the common electrode 34 Can be prevented from being short-circuited. Also,
The overcoat glass 21 covers a part of the shield electrode 33 and a part of the reference electrode 32 side is directly exposed to the atmosphere in the space 30, so that when a leakage current is generated from the reference electrode 32, it is easily absorbed. It has become. For this reason, the bonding portion 20 by the shield electrode 33 described above is used.
The effect of preventing a leakage current from the reference electrode 32 to the common electrode 34 along the edge surface of the semiconductor device can be improved. Further, since the space 24 is provided in advance in the low-melting glass 23 and the overcoat glass 21, the inconvenience that the conductive paste 25 for taking out the common electrode 34 from outside is inserted into the space 30 is prevented beforehand. can do.

In the electrode pattern 40 provided on the back surface 15 of the substrate 11, the circuit paths 63A and 63B conducted to the electrode terminal 43 for the shield electrode 33 are connected to the electrode terminal for the common electrode 34.
A circuit path 62 including an electrode terminal 41 for the center electrode 31 and a circuit path 62 including an electrode terminal 42 for the reference electrode 32, and an electrode for the common electrode 34 are arranged so as to surround a circuit path 64 including 44. The circuit path 64 including the terminal 44 is in a state of being separated from each other by circuit paths 63A and 63B as ground electrodes. For this reason, when the humidity of the atmosphere in contact with the electrode pattern 40 increases, the circuit path 61 for the center electrode 31
And common electrode from circuit path 62 for reference electrode 32
The leakage current to the circuit path 64 for 34 can be absorbed by the circuit paths 63A and 63B for the shield electrode 33, and accurate measurement can be performed.

The arrangement of the electrode pattern 40 reduces the influence of changes in atmospheric humidity, thereby obtaining a large change in capacitance such that the influence of leakage current is negligible. Can be prevented from becoming large. Furthermore, it is not necessary to seal the atmosphere in contact with the electrode pattern 40 in order to reduce the influence of a change in humidity as in the related art, so that the number of sealing parts and sealing steps can be reduced, so that the cost can be reduced. Since no space is required for sealing, the pressure sensor can be downsized from this point as well. Then, except for at least one of the through holes formed in the electrode holes 45, 46, and 47, which are low-pressure ports, the rear surface of the substrate 11 covers the electrode pattern 40.
By applying a process of so-called potting for dropping and closing a molten resin or the like on the 15, it can be used even in a severe environment. A polyurethane resin or the like can be used as the potting material. Further, since the arrangement of the electrode patterns 40 can reduce the influence of the disturbance as described above, a weak current can be detected. For this reason, the amplification sensitivity of the amplification element can be increased, and the pressure conversion element 10 can have a very small capacity, so that the pressure sensor can be downsized.

Further, a passage (low-pressure port) for guiding the atmosphere serving as a reference pressure for measurement into the space 30 is ensured by using the through holes formed in the electrode holes 45, 46, 47, so that the substrate
A low-pressure port can be secured only in the manufacturing steps (2A) and (2B) in which the electrode pattern 40 on the back surface 15 side of the 11 and the respective electrodes on the opposing surface 13 are conducted. The manufacturing process can be omitted.

Further, the measuring circuit 65 is entirely a one-chip IC.
60, and put this one-chip IC 60 on the back of the substrate 11.
Since it is directly mounted on the electrode pattern 40 on 15, compared to the case where a measurement circuit composed of many components is mounted on a printed circuit board etc. provided as a separate member as in the conventional example,
It is possible to reduce the number of components constituting the measurement circuit and to omit components such as a printed circuit board on which the components are mounted,
The number of parts can be reduced. For this reason, the number of mounting steps of components and a printed circuit board and the like constituting these measuring circuits is reduced, so that the manufacturing process can be simplified, and the installation space for the printed circuit board and the like can be omitted, so that the pressure sensor can be downsized. be able to.

The electrode pattern 40 on the back surface 15 side of the substrate 11
The central electrode 31, the reference electrode 32, the shield electrode 33, and the connection terminal 39 on the side of the facing surface 13 are all printed with a low-viscosity silver-palladium paste with good viscosity, so that conduction between them is ensured. It can be carried out. The inconvenience that occurs in the conduction between the gold resinate and the silver palladium paste, which is generally performed as a combination of these materials, that is, the different materials are in contact with each other because the thickness after firing of the gold resinate is thin. To eliminate the inconvenience of the so-called gold side erosion phenomenon, in which the gold resinate on one side diffuses into the silver-palladium paste on the other side and disappears, causing a conduction failure. Can be. Further, the electrode pattern 40 on the back surface 15 side of the substrate 11, the central electrode 31, the reference electrode 32, the shield electrode 33 on the facing surface 13 side,
And printing both sides with the connection terminal 39 with gold resinate,
When the through-hole processing of each of the electrode holes 45 to 48 is performed, the printed amount of the conductive portions 51 to 54 becomes extremely small because the gold resinate is finished thinly, and poor conduction may occur. In the through-hole treatment with silver-palladium paste, such inconvenience does not occur,
Conduction can be reliably performed.

FIGS. 7 and 8 show a capacitive pressure transducer 100 according to a second embodiment of the present invention. The configuration, operation, and the like of the pressure conversion element 100 are substantially the same as those of the above-described first embodiment except for the measurement circuit built in the one-chip IC, and the manufacturing method is also the same. Therefore, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described. FIG. 7 shows the main body 10A of the pressure transducer 100.
And the condensers 35, 36,
Measuring circuit 165 to measure changes in capacitance CM, CR, CS of 37
FIG. 8 shows the measurement principle. On the back surface 15 of the substrate 11, the same electrode pattern 40 as that of the first embodiment shown in FIG. 3A is formed, and a one-chip IC 160 incorporating a measuring circuit 165 in the electrode pattern 40 is formed. Is directly mounted.

7 and 8, the measuring circuit 165 includes an oscillator (AC power supply) 170. The voltage from the oscillator 170 is passed through operational amplifiers 171 and 172 as a correct positive / inverted signal as a capacitor 35 (capacitance CM). condenser
36 (capacitance CR). At this time, a condenser
The voltages VM and VR generated between the electrodes 35 and 36 are
The values satisfy dVM / dt = IM / CM and dVR / dt = IR / CR, and the currents IM and IR flowing through the capacitors 35 and 36 are values proportional to the respective capacitances CM and CR. The signal applied by the oscillator 170 may be a sine wave or a triangular wave. As a result, the operational amplifier
A current I proportional to the difference between the capacitances of the capacitors 35 and 36 (CM-CR) flows through the input terminal 174 of the 173. Therefore, the capacitances CM and CR are set to be substantially equal, and the amounts of change ΔCM and ΔCR of the capacitances CM and CR according to the deflection of the diaphragm 12 due to the pressure of the measurement fluid are set so that ΔCM> ΔCR. By arranging the condensers 35 and 36, that is, the condenser 35 is disposed on the central side where the amount of deflection of the diaphragm 12 is large.
By disposing the (capacitance CM), an output signal as a function of the pressure of the measurement fluid acting on the pressure receiving surface 16 of the diaphragm 12 can be obtained at the output terminal 175 of the operational amplifier 173.

The dotted lines in FIG. 7 indicate the lines of electric force running between the electrodes, and the lines of electric force in such a state are formed while reversing the direction at a constant period according to the signal of the oscillator 170. It has become. Electrode terminal 43 for shield electrode 33
The circuit paths 63A and 63B (see FIG. 3) which are electrically connected to the circuit path 64 are disposed so as to surround the circuit path 64 including the electrode terminal 44 for the common electrode 34 (corresponding to the dotted line in FIG. 8), and the buffer paths from the ground terminals 176 and 177 Connected to element 178 and grounded. These ground terminals 176 and 177 are connected to the input terminal 174 of the operational amplifier 173.
And the signal application terminals 179, 18 from the operational amplifiers 171, 172
It is arranged to be separated from 0.

According to the second embodiment, effects such as high-precision measurement and downsizing of the pressure sensor can be obtained in substantially the same manner as in the first embodiment. In the second embodiment, the difference between the capacitances of the capacitors 35 and 36 (CM-CR)
Since the output is detected as above, it is not possible to avoid the influence of a change in the dielectric constant due to a change in the temperature or humidity of the atmosphere in the space 30 as in the first embodiment described above, but since the shield electrode 33 is provided, As in the case of the embodiment, the influence of the ceramics, the low-melting glass 23 and the like can be avoided. In the second embodiment, each of the above effects can be realized with a simpler circuit than in the first embodiment.

FIGS. 9 to 11 show a capacitance type pressure conversion element 200 according to a third embodiment of the present invention.
The pressure transducer 200 has substantially the same configuration, operation, and the like as those of the above-described first and second embodiments, except for a measurement circuit built in the one-chip IC and an electrode pattern on the back surface of the substrate. Are the same. Therefore, the same portions are denoted by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described. FIG. 9 shows the detailed configuration of the electrode pattern 240 of the pressure transducer 200. FIG. 10 shows the main body 10A of the pressure transducer 200 and the capacitors 35, 36, 37 formed in the main body 10A. The state of connection with the measuring circuit 265 for measuring changes in the capacitances CM, CR, and CS of FIG.
FIG. 11 shows the measurement principle.

In FIG. 9, the substrate 11 of the pressure transducer 200
An electrode pattern 240 different from those of the first embodiment and the second embodiment is provided on the back surface 15 of the first embodiment, and the one-chip IC 260 is directly mounted on the electrode pattern 240. Reference numeral 9 denotes a state before the one-chip IC 260 is mounted. Electrode pattern 24 of the third embodiment
0 denotes the respective electrode terminals 41, 4 for the center electrode 31, the reference electrode 32, the shield electrode 33, and the common electrode 34 at the same positions as the electrode patterns 40 (see FIG. 3) of the first and second embodiments.
2, 43, 44, of which electrode terminals 41, 42, 4
The key-shaped circuit paths 261, 262, 264 guided to the positions of the feet (pins) of the one-chip IC 260 from 4 also have the same arrangement shape as the circuit paths 61, 62, 64 of the first and second embodiments. Further, the circuit path 263A which is electrically connected to the electrode terminal 43 and is formed in a ring shape on the outer edge of the back surface 15 of the substrate 11 is also the first,
It has the same arrangement shape as the circuit path 63A of the second embodiment. However, the electrode pattern 240 of the third embodiment has a circuit path 263B having a different arrangement shape from the circuit path 63B of the electrode pattern 40 of the first and second embodiments. That is, the circuit path of the electrode pattern 40 of the first and second embodiments
63B is connected to the inside of the left side of FIG. 3 of the ring-shaped circuit path 63A and is arranged so as to surround the electrode terminal 44 for the common electrode 34 and the circuit path 64. The circuit path 263B of the example electrode pattern 240 is connected to the inside protruding portion of the ring-shaped circuit path 263A on the right side in FIG. 9 and includes the electrode terminal 41 for the center electrode 31.
The circuit paths 262 including the electrode terminals 42 for the reference electrode 32 are separately arranged at predetermined intervals. Also, this circuit path 263B
26, 262, 264, which pass through the position of the foot of the one-chip IC 260, which is alternately disposed,
7,278,279. Each circuit path 26 electrically connected to the electrode terminal 43 for these shield electrodes 33
3A and 263B are grounded. Therefore, the common electrode 34
The circuit path 264 including the electrode terminal 44 for the central electrode 31 and the circuit path 261 including the electrode terminal 41 for the center electrode 31 and the reference electrode
The circuit path 262 including the electrode terminal 42 for 32 is arranged so as to be isolated from each other by circuit paths 263A and 263B as ground electrodes. Therefore, it is possible to reduce the influence of an increase in leakage current due to a decrease in insulation resistance therebetween.

10 and 11, the measuring circuit 265 according to the third embodiment is different from the measuring circuit 16 of the second embodiment.
Unlike FIG. 5, power is applied from the common electrode 34 side. The measuring circuit 265 includes an oscillator (AC power supply) 270, and the signal of the oscillator 270 is converted to a capacitor 35 (capacitance CM),
A current is applied to the capacitor 36 (capacitance CR) from the common electrode 34 by exciting them. At this time, currents IM and IR proportional to the capacitances CM and CR flow through the input terminals 271,272. The input signals are amplified by operational amplifiers 273 and 274, respectively, and the difference is calculated by a calculation circuit 275 and output to an output terminal 276. Thus, an output signal can be obtained at the output terminal 276 as a function of the pressure of the measurement fluid acting on the pressure receiving surface 16 of the diaphragm 12. Note that the oscillator 270
May be a sine wave or a triangular wave. Here, as an example of specific numerical values,
When the specification of the pressure sensor is about 0 to 2000 mmH ₂ O, an AC signal is applied from the oscillator 270 and each capacitance is
Assuming that CM and CR are, for example, 30 pF, the capacitance CM of the capacitor 35 normally changes by about 6 to 8 pF due to the bending of the diaphragm 12, while the capacitance CR of the capacitor 36 is 1 to 2 pF.
F, and the difference between the two capacitances is about 5 to 6 pF.

The dotted lines in FIG. 10 indicate the lines of electric force running between the electrodes, and the lines of electric force in such a state are formed while reversing the direction at a constant period according to the signal of the oscillator 270. It has become. Electrode terminal 43 of shield electrode 33
The circuit paths 263A and 263B (see FIG. 9) which are electrically connected to the circuit paths 261A and 263B separately surround the circuit path 261 including the electrode terminal 41 for the center electrode 31 and the circuit path 262 including the electrode terminal 42 for the reference electrode 32, respectively. It is arranged (corresponding to the dotted line in FIG. 11), and is connected to the buffer element 280 from the grounding terminals 277, 278, 279 and is grounded. These grounding terminals 277,27
8,279 are arranged so as to separate the signal application terminal 281 from the oscillator 270 and the input terminals 271 and 272 to the operational amplifiers 273 and 274, respectively. Therefore, it is possible to reduce the influence of an increase in leakage current due to a decrease in insulation resistance therebetween.

According to the third embodiment, effects such as high-precision measurement and downsizing of the pressure sensor can be obtained in substantially the same manner as in the first and second embodiments. Further, in the third embodiment, the output is detected by taking the difference between the currents IM and IR by the arithmetic circuit 275. Therefore, the dielectric circuit caused by the temperature change or humidity change of the atmosphere in the space 30 as in the first embodiment described above. Although the influence of the rate change cannot be avoided, the influence of the ceramics, the low melting point glass 23, and the like can be avoided as in the first embodiment because the shield electrode 33 is provided. In the third embodiment, each of the above effects can be realized with a simpler circuit than in the first embodiment.

It should be noted that the present invention is not limited to the above embodiments, but includes other configurations that can achieve the object of the present invention. For example, the following modifications are also included in the present invention. . That is, in each of the above embodiments, the central electrode 31 on the substrate 11 side is formed in a circular shape, but is not limited to this shape. For example, as shown in FIG. A similar closed annular (ring-shaped) electrode 90 may be used, or FIG.
May be a polygonal electrode 91 such as a square,
In short, a simple shape having little influence of the terminal effect may be used. Then, a closed annular electrode 90 as shown in FIG.
By doing so, a low-pressure port 92 for guiding the atmosphere into the space 30 can be formed inside. The hatching in FIGS. 12 and 13 does not show a cross section, but is shown for easy understanding in description. Accordingly, the reference electrode 32 and the shield electrode 33 need not be formed in an annular shape, but may be, for example, polygonal annular electrodes 93 and 94 such as a square as shown in FIG. What is necessary is just to be a closed ring.

Further, in each of the above embodiments, the diaphragm
The common electrode 34 on the 12 side is formed in a circular shape, but is not limited to a circular shape, and may be, for example, a polygonal shape close to a circle. In short, the outer edge of the common electrode 34 is a shield on the substrate 11 side. It is sufficient that the electrode 33 is located outside the entire periphery of the outer periphery of the electrode 33.

In each of the above embodiments, the central electrode 31, the reference electrode 32 and the shield electrode 33 are formed on the substrate 11 side, but four or more electrodes may be formed. For example, center electrode 31 and reference electrode
Further, an electrode which is maintained at a predetermined constant voltage or ground, which corresponds to a shield electrode, may be further provided between the first and second electrodes.

Further, in the first embodiment, the measuring circuit 65
Thus, an output signal related to the ratio (CR−CM) / (CR + CM) of the sum and difference of the capacitances CM and CR of the capacitors 35 and 36 can be obtained. In the third embodiment, the measurement circuits 165 and 265 are configured to obtain output signals proportional to the difference (CM-CR) between the capacitances CM and CR of the capacitors 35 and 36, respectively. , CR ratio CM / CR may be obtained, and in this case as well, the effects of changes in the temperature, humidity, etc. of the atmosphere in the space 30 are corrected as in the first embodiment. Measurement can be performed. For example, a measurement circuit 96 having switches 95A, 95B, 95C as shown in FIG. 14 is provided, and by switching these switches 95A, 95B, 95C, the output related to the ratio CR / CM of the capacitances CM, CR. Signal output terminal 97
Can be obtained. In this case, switch 95A is
Switch 95B is closed and switch 95C
Is opened, and electric charges are stored in the capacitors CM and CR. On the other hand, when the switch 95A is connected to the ground side, the switch 95B is opened and the switch 95C is closed, and a required charge is sampled and held in the capacitor 99.

The method of forming the electrodes 31 to 34 and the bonding portions 20
The formation method and the like need not be the method shown in the manufacturing process of each of the above-described embodiments.For example, each of the electrodes 31 to 34 is not screen-printed, but is plated, etched, by other means usually used such as sputtering. It may be formed. Further, the thickness of the substrate 11 and the diaphragm 12 of the present invention, and the thickness of each electrode 31
-34 thickness, inter-electrode distance, capacitance CM, CR, CS of each capacitor 35-37, numerical values such as specifications of pressure sensors, etc. are not limited to the numerical values specifically described in each of the above embodiments. Instead, it may be appropriately determined according to the measurement target, the measurement environment, and the like.

In each of the above embodiments, the space 30 is set to the atmospheric pressure, and the pressure of the measurement fluid is detected as a gauge pressure. The pressure difference between the pressure in the space 30 and the pressure applied to the pressure receiving surface 16 may be detected. Further, the measurement fluid (fluid acting on the pressure receiving surface 16) to be measured by the pressure sensor incorporating the pressure conversion element 10 of the present invention may be a liquid or a gas.

[0058]

As described above, according to the present invention, the electrode on the substrate is divided into a plurality of electrodes, and the outermost electrode among the divided electrodes on the substrate is grounded or maintained at a predetermined constant voltage. Since it is not used for measurement, it can accurately measure pressure without being affected by changes in temperature, humidity, etc. of surrounding objects.In addition, all electrodes on the board except the center electrode are closed. Since it has a simple electrode shape formed in an annular shape, there is an effect that the manufacturing process can be simplified.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is an exploded view of the first embodiment.

FIG. 3 is a configuration diagram showing an electrode pattern on the back surface of the first embodiment.

FIG. 4 is a sectional view showing a main part of the first embodiment.

FIG. 5 is a configuration diagram showing a measurement circuit of the first embodiment.

FIG. 6 is a sectional view showing another main part of the first embodiment.

FIG. 7 is a configuration diagram showing a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of a measurement circuit according to a second embodiment.

FIG. 9 is a configuration diagram showing an electrode pattern on the back surface according to the third embodiment of the present invention.

FIG. 10 is a configuration diagram showing a third embodiment.

FIG. 11 is an explanatory diagram of a measurement circuit according to a third embodiment.

FIG. 12 is a schematic configuration diagram showing a modification of the present invention.

FIG. 13 is a schematic configuration diagram showing another modified example of the present invention.

FIG. 14 is a schematic explanatory view showing still another modified example of the present invention.

FIG. 15 is a sectional view showing a first conventional example.

FIG. 16 is a configuration diagram showing a second conventional example.

[Explanation of symbols]

 10,100,200 Pressure transducer 11 Substrate 12 Diaphragm 20 Joint 31 Center electrode 32 Reference electrode 33 Shield electrode 34 Common electrode 35 Capacitor (capacitance CM) 36 Capacitor (capacitance CR) 37 Capacitor (capacitance CS) 38 Outer edge 44 Electrode terminal for common electrode 40,240 Electrode pattern 60,160,260 One-chip IC 65,165,265,96 Measurement circuit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Fujito Tanaka Nagano Prefecture, Tobu-cho, Ogata-gun, Oaza 5463 (9) Inventor Kenji Nagasawa Kenji Nagasawa 160-5 Ueda, Ueda-shi, Nagano Prefecture (56) References JP-A-50-3385 (JP, A) JP-A-4-20830 (JP, A) Tokuhyo Hei 3-504161 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01L 9/12

Claims (3)

(57) [Claims] 1. A semiconductor device comprising: a thick substrate; and a thin elastic diaphragm opposed to the substrate at a predetermined interval.
An electrode is provided on each of the opposing surfaces of the substrate and the elastic diaphragm, and is a pressure sensor that detects a pressure applied to the elastic diaphragm by a change in capacitance between the electrodes. The electrode on the side is divided into a plurality of parts, and the divided electrodes on the substrate side are sequentially arranged so as to surround the inner electrodes. Of the electrodes on the divided substrate side, the electrodes except for the central electrode are respectively is formed in a closed loop with a constant width, most outer electrode is maintained at ground or a predetermined constant voltage, substantially circular elastic diaphragm-side electrode of the solid of the electrode
Formed on the substrate side over the entire circumference.
Outer electrode located further outside than the outer edge of the outer electrode
Having an edge portion, the surface of the substrate opposite to the surface on which the electrodes are provided,
An electrode terminal for the electrode on the elastic diaphragm side is provided.
Electrode terminal and the outer edge of the electrode on the elastic diaphragm side
Through the conductive portion of the through hole penetrating the substrate
A pressure sensor characterized by being electrically connected . 2. The pressure sensor according to claim 1, wherein the electrode on the substrate side is divided into three, and a central electrode among the three divided electrodes is formed in a solid circular shape without a central portion missing. A pressure sensor, wherein the remaining two electrodes are formed in a closed annular shape. 3. The pressure sensor according to claim 1, wherein the conductive portion of the through hole and the outer edge portion are electrically connected to each other by a conductive paste inserted from one end of the through hole. The joint provided between the elastic diaphragm and the elastic diaphragm is provided with a space where a part of the outer edge is exposed and communicates with the through hole, and that the space is filled with the conductive paste. Features pressure sensor.