JPH03200036A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To reduce contact area with a stem and to stabilize these sensor also at temperature changing by using a spacer which possesses a thermal expansion coefficient approximate to a silicone diaphragm chip. CONSTITUTION:A fluid pressure from a manifold inlet hole is impressed upon a diaphragm 28a through a tube for introducing pressure 23, a through hole 12a of a stem 12, a through-hole 27c of a spacer 27 and a through hole 30a of a pedestal 30. On the other hand, an air pressure is impressed upon a diaphragm 29a through a tube for introducing pressure 24, respective through-holes 12b, 27d and 31a of the stem 12 and the spacer 27 and the pedestal 31. Accordingly, the fluid pressure and the air pressure introduced through the tubes 23 and 24 distort the diaphragms 28a and 29a respectively and distortion changes the resistance value of Wheatstone bridge resistance formed on the surface of the diaphragms 28a and 29. The change is processed at the arithmetic circuit of a circuit board 32 and the fluid pressure and the air pressure indicated with the absolute pressures from lead pins 14 and 15 are outputted simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor pressure sensor used to detect intake air pressure, atmospheric pressure, exhaust pressure, etc. of an internal combustion engine installed in an automobile or the like.

(Conventional technology) In recent years, with social demands such as fuel savings and exhaust gas regulations for automobiles, various sensors have been used to control the engine's electronic fuel injection 1 ignition timing and exhaust gas recirculation amount using a microcomputer. I have started to do this.

In the electronic control of this engine, it is extremely important to accurately detect the absolute pressure in the atmosphere and in the manifold, and a highly reliable pressure sensor is required, and various improved pressure sensors have been proposed accordingly. There is.

A conventional pressure sensor of this type will be explained with reference to FIG.

The figure is a cross-sectional view of a conventional semiconductor pressure sensor, in which a stem 1 with a stepped portion 1a on one periphery has a through hole 1b communicating with a pressure introduction pipe 2 fixed to the lower surface by brazing etc., and a lead pin 3 inserted therein. Two small through holes IC are provided. The lead pin 3 inserted into the small through hole IC is fixed by hermetically sealing the gap between it and the small through hole 1c using glass 4.

A silicon diaphragm chip 5, which is provided with a diaphragm 5a having a Wheatstone bridge resistance for pressure detection formed on its surface, is fixed to the center of the upper surface of the stem 1 with an adhesive 6, and has a through hole 7a in the center communicating with the diaphragm 5a. It is fixed on a pedestal 7 on which a pedestal 7 is formed. In addition,
The above pedestal 7 is.

A material having a thermal expansion coefficient similar to that of the silicon diaphragm chip 5 is used, and a circumferential groove 7b is provided to relieve thermal stress from the stem 1. Further, the bridge electrode (not shown) of the Wheatstone bridge resistor is connected to the lead pin 3 by a conductive wire 8 (1).

A bottomed cylindrical cap 9 fixed to the stepped portion 1a of the stem 1 covers the silicon diaphragm chip 5 and the pedestal 7 to form a vacuum chamber 11, and is sealed with solder 10 at the center of the upper surface. A sealing hole 9a is provided.

A method of assembling the semiconductor pressure sensor configured as described above will be explained.

First, the pressure introduction pipe 2 is brazed to the stem 1, and then the lead pin 3 is inserted into the small through hole IC and fixed with the glass 4. On the other hand, the silicon diaphragm chip 5 is fixed on the pedestal 7. Next, the pedestal 7 is attached to the center of the upper surface of the stem 1 using adhesive 6, and then the bridge electrode and the tip of the lead pin 3 are attached. Connect with wire 80
Next, the cap 9 is sealed to the stepped portion 1a of the stem 1 by pressure contact or welding, leaving the sealing hole 9a as it is.

Next, the cap 9 is placed in a vacuum, the air inside the cap 9 is removed, and at the same time, the sealing hole 9a is sealed using the solder 10.

A vacuum chamber 11 is formed.

In the semiconductor pressure sensor assembled in this way, the diaphragm 5a of the silicon diaphragm chip 5 is housed in the vacuum chamber 11.

Using this vacuum pressure as a reference pressure, the absolute pressure of the fluid introduced by the pressure introduction pipe 2 can be measured.

(Problems to be Solved by the Invention) However, with the above configuration, basically only one absolute pressure can be measured with one sensor, and the heat applied to the silicon diaphragm chip 5 from the stem 1 via the pedestal 7 Since the influence of stress is large and this distorts the silicon diaphragm chip 5, the value of the Wheatstone bridge resistance formed in the diaphragm 5a varies depending on the temperature, which causes a problem that the pressure detection characteristics are unstable.

This problem is mainly caused by the silicon diaphragm chip 5.
．． This is due to the difference in coefficient of thermal expansion between the stem 19, the pedestal 7, and the adhesive 6.

For this reason, as mentioned above, the pedestal 7 is made of a material with a coefficient of thermal expansion similar to that of the silicon diaphragm chip 5, and the thickness of the pedestal 7 is increased, or the circumferential groove 7b is provided. There was a problem that not only the workability of the pedestal 7 was reduced and the cost of II construction was increased, but also the reliability was reduced.

The present invention solves the above problems, and provides a semiconductor pressure sensor that is capable of simultaneously detecting at least two absolute pressures with one sensor, has a simple structure, is highly reliable, and has stable characteristics. It is.

(Means for Solving the Problems) In order to solve the above problems, the present invention has a thermal expansion coefficient similar to that of a silicon diaphragm chip, which has recesses for mounting at least two pedestals each having a silicon diaphragm chip fixed thereto. a spacer having a spacer, a stem integrally formed with a recess to which the spacer is adhered and a recess to which a plurality of lead pins are glass-sealed, and a through hole in the stem that communicates with the diaphragm of the silicon diaphragm chip, It consists of a pressure introduction pipe connected through a filter and a circuit board that processes the detected resistance value. A cap hermetically bonded to the stem forms a sealed chamber that covers the silicon diaphragm and circuit board. is the reference pressure section by vacuum or gas filling.

(Function) With the above configuration, pressures at at least two places, such as atmospheric pressure and intake manifold pressure, can be measured simultaneously, and in the case of vacuum, the absolute pressure is measured directly, and in the case of gas filling, the pressure is corrected by the circuit. Output as an absolute pressure value. Further, since the pedestal and spacer have a coefficient of thermal expansion similar to that of the silicon diaphragm chip, the influence of thermal stress from the stem is eliminated, and variations in resistance value due to thermal stress are eliminated.

Furthermore, since a filter is built into the upper part of the pressure introduction pipe, it can be used as a pressure transducer that can be attached directly to the pressure introduction hose.

(Example) An example of the present invention is shown in FIGS. 1(a), (b), and (c).
, (d) and (e).

Figure 1 (a), (b), (c), (d) and (
e) is a plan sectional view of a semiconductor pressure sensor according to the invention, respectively;

They are a front sectional view, a side sectional view seen from the left, a side sectional view seen from the right, and a main part front sectional view. In the figure, a rectangular stem 12 formed by press-molding a metal plate has a recess 12c and a recess 12c with two through holes 12a and 12b formed at the bottom.
A recess 12d is provided in which the lead pins 13.14.1.5 and 16 of the book are hermetically fixed by the glass 17. Note that the number of recesses 12d is not one as shown in FIG. 1(d), but may be four independent recesses for each lead pin 13, 14, 15, and 16.

Lead pin 13 is for power supply, lead pin 14 and 1
5 is for output, and lead pin 16 is for ground, and is connected to the inner diameter electrode portions (not shown) of feedthrough capacitors 18, 19, 20 and 21, respectively, by soldering or the like. Also 1 feedthrough capacitor 18.19.20 and 2]
The outer diameter electrode portion (not shown) is connected to the connection band 22 by soldering, and is further fixed and electrically connected to the stem 12. The lower surface of the recess 12c of the stem 12 communicates with the five through holes 12a and 12b.

Pressure introduction pipes 23 and 24 are passed through filters 25 and 26, respectively, by means such as welding.

Airtightly connected.

The spacer 27 is airtightly joined to the concave portion 12c of the stem 12, and pedestals 30 and 31 having silicon diaphragm chips 28 and 29 fixed thereto are hermetically fixed at locations corresponding to the through holes 12a and 12b, respectively. Storage recesses 27a and 27b are formed, and through holes 27e and 27d communicating with the above-mentioned through holes 12a and 12b are provided at the center of the bottom surface thereof. Note that diaphragms 28a and 29a having Wheatstone bridge resistors (not shown) formed on their surfaces are formed at the centers of the silicon diaphragm chips 28 and 29, respectively. Moreover, the above-mentioned pedestals 30 and 31 are connected to the through-hole 12 of the above-mentioned stem 12 and spacer 27, respectively.
Through holes 30a and 31a are provided which communicate with a and 27C1 and 12b and 27d, respectively, and are configured so that the pressure of the fluid introduced by pressure introduction pipes 23 and 24 can be applied to diaphragms 28a and 29a. .

The circuit board 32 is formed with an arithmetic circuit that calculates the absolute pressure value from the resistance value output from the Wheatstone bridge.
It is positioned by the positioning protrusion 27e formed on the spacer 27 and the positioning hole 32a of the circuit board 32 that fits therein, and is attached to the spacer 27, and the input terminal part of the above-mentioned arithmetic circuit and the above-mentioned silicon diaphragm Chip 2
8 and the bridge electrode of the Wheatstone bridge resistor on 29 are connected by a conductive wire 33, and further,
The power input terminal section, output terminal section, and ground terminal section are electrically connected to the glue dowels 13, 14, 15, and 16.

A hat-shaped cap 34 airtightly fixed to the peripheral edge 12e of the stem 12 by welding or the like is an airtight chamber 3 that covers the silicon diaphragm chips 28 and 29 and one circuit board 32.
form 5. Further, a gas filling pipe 36 is attached to a corner of the stem 12.

A method of assembling the semiconductor pressure sensor configured in this way will be explained.

First, the spacer 27 is airtightly joined to the concave portion 12c of the stem 12, and then four screws are attached to the concave portion 12d.
4, 15 and 16 are inserted and hermetically fixed with glass 17.

Next, the through hole 12a is inserted into the lower surface of the recess 12c of the stem 12.
and 12b are installed so as to be covered with filters 25 and 26, respectively, and the pressure introduction pipes 23 and 24 are
Then, feedthrough capacitors 18, 19, 20 and 21 are inserted into the glued pins 13, 14, 15 and 16, respectively, and the connection band 22 is fixed by welding or the like.
After fixing, the inner and outer electrodes (both not shown), the lead pins 13, 14, 15, 16, and the connection band 22 are connected by soldering. On the other hand, silicon diaphragm chips 28 and 29 are fixed to the upper surfaces of two pedestals 30 and 31, respectively.

Next, after the pedestals 30 and 31 to which the silicon diaphragm chips 28 and 29 are bonded are hermetically fitted into the storage recesses 27a and 27b of the spacer 27, the circuit board 32 is positioned and also mounted on the spacer 27, and the wires 33
Connect electrically.

Next, the cap 34 is hermetically sealed to the peripheral edge 12e of the stem 12 by means of pressure contact, welding, or the like. that time.

If the airtight connection is made in a vacuum, the airtight chamber 3 inside the cap 34 will be formed.
5, a vacuum chamber is formed and the reference pressure becomes 0, and then when a reference pressure gas is filled from the gas filling pipe 36, a certain reference pressure is created.

If formed from a vacuum chamber, the measured pressure will be absolute pressure,
Once the reference pressure is created by filling in the gas, it is corrected to absolute pressure by the circuit board 32, so that it is output as absolute pressure in any case.

Next, a pressure measurement method and operation will be described using, for example, a case where the intake air pressure of an internal combustion engine is measured using the semiconductor pressure sensor configured as described above.

One pressure introduction pipe 23 is connected to an intake hole of an intake manifold of an internal combustion engine. At this time, the other pressure introduction pipe 24 is left open. When the internal combustion engine starts operating, fluid pressure from the manifold intake hole is applied to the pressure introduction pipe 23. The voltage is applied to the diaphragm 28a through the through hole 12a of the stem 12, the through hole 27c of the spacer 27, and the through hole 30a of the pedestal 30. On the other hand, atmospheric pressure is detected through the pressure introduction pipe 24° stem 12. Spacer 27
and the through hole 12b of the pedestal 31.

27'd and 31a to the diaphragm 29a.

Therefore, the fluid pressure and atmospheric pressure introduced through the pressure introduction pipes 23 and 24 are applied to the diaphragm 2, respectively.
8a and 29a, and this distortion causes diaphragm 2
The resistance values of the Wheatstone bridge resistors for pressure detection formed on the surfaces of 8a and 29a are changed. The change in the bridge resistance value described above is processed by the arithmetic circuit of the fifth circuit board 32, and the fluid pressure and atmospheric pressure expressed in absolute pressure are simultaneously output from the lead pins 14 and 15.

Note that since the spacer 27 and the pedestals 30 and 31 are made of a material that has a coefficient of thermal expansion similar to that of the silicon diaphragm chips 28 and 29, the thermal stress that occurs between the stem 12 and the spacer 27 when the temperature changes is absorbed by the silicon diaphragm chips 28 and 29. 29, there is no difference in fluctuation due to thermal stress in the Wheatstone bridge resistance system formed on the diaphragms 28a and 29a, and the characteristics of the semiconductor pressure sensor are stabilized. In addition, since the pressure introduction pipe 23 is equipped with a filter 25,
Since it can be connected directly to the intake hole of the internal combustion engine and also has a built-in circuit board 32 to function as a pressure transducer, the number of parts is reduced, installation is simplified, costs are reduced, and reliability is improved.

(Effects of the Invention) As described above, according to the present invention, two pressures can be measured simultaneously in absolute pressure.

In addition, by using a spacer with a coefficient of thermal expansion similar to that of a silicon diaphragm chip, and by forming a pedestal storage recess to reduce the contact area with the stem, it is highly reliable and has stable characteristics even when temperature changes. A semiconductor pressure sensor is obtained. In addition, by using a spacer with a thermal expansion coefficient similar to that of the silicon diaphragm chip, there is no need to construct the stem with an expensive material that has a thermal expansion coefficient similar to that of the silicon diaphragm chip. By forming the concave portion, the glass hermetic sealing portion can be integrated with the stem, and the cost of the stem can be significantly reduced. Since the spacer can be press-molded, it can be manufactured at extremely low cost. In addition, the circuit board can be mounted with a wide bonding area.

The circuit board will not break due to impact caused by dropping. Furthermore, the use of a connecting band facilitates soldering between the feedthrough capacitor and the stay 11, which have a large difference in heat capacity.

Furthermore, since it has a built-in circuit board, it can be used as a pressure transducer.

Since it can be directly connected to the intake pressure hole of an internal combustion engine, the number of parts is reduced and one assembly is simple, reducing costs and improving reliability.

[Brief explanation of drawings]

FIG. 1(a) is a plan sectional view of a semiconductor pressure sensor according to the present invention, and FIGS. 1(b), (C) and (d) are (a)
Front and side sectional views cut along the X-X line, Y-Y line, and 2-2 line in the figure and drawn using the triangulation method, Figure (e) is a front sectional view of the main part, and Figure 2 is the conventional FIG. 2 is a cross-sectional view of a semiconductor pressure sensor. 1.12...Stem, 1a...Step, lb
. 7a, 12a, 12b, 27e, 27d, 3
0a, 31a = through hole, le... small through hole,
2,23.24...Pipe for pressure introduction, 3
, 13, 14, 15° 1G...Lead pin, 4. I
7...Glass, 5, 28.29...Silicon diaphragm chip, 5a, 28a, 29a・
...Diaphragm, 6..Adhesive, 7,30.31.
...Pedestal, lb circumferential groove, 8,33...Wire,
9, 34... Cap, 9a... Sealing hole,
10...Solder, 11...Vacuum chamber, 12c,
12d... recess,] 2e-periphery, 18.19.
20.21... Feedthrough capacitor, 22... Connection band, 25.26... Filter, 27e... Spacer, 27a. 27b...Storage recess, 27e...Positioning protrusion, 32...Circuit board, 32a...Positioning hole,
35...airtight chamber, 36...vibrator for gas filling. Figure 1(a)

Claims (4)

[Claims] (1) A pedestal having a through hole communicating with the pressure-sensitive diaphragm to which a semiconductor single-crystal chip forming a pressure-sensitive diaphragm is fixed, and having a thermal expansion coefficient similar to that of the semiconductor single-crystal chip; and a stem hermetically sealed with a through hole that communicates with the through hole, and a plurality of lead pins that input and output from the pressure sensitive diaphragm, and a stem that communicates with the through hole of the stem in an airtight manner. A semiconductor pressure sensor comprising a pressure introduction pipe bonded to the stem, and a cap that is hermetically fitted to the stem to form an airtight chamber covering the semiconductor single crystal chip, and use this airtight chamber as a vacuum chamber or a reference pressure chamber. , at least two pedestals each having the above-mentioned semiconductor single-crystal chip fixed thereto are hermetically joined to the stem via a spacer, filters are installed between the stems and the pressure introduction pipes, and the above-mentioned air A semiconductor pressure sensor characterized in that a circuit board having a calculation circuit for calculating absolute pressure is built in a closed room, and feedthrough capacitors are attached to each of the lead pins. (2) The semiconductor pressure sensor according to claim (1), wherein the pedestal and spacer are made of a material having a thermal expansion coefficient similar to that of a semiconductor single crystal chip. (3) The semiconductor pressure sensor according to claim (1), wherein the circuit board is attached to a spacer having a coefficient of thermal expansion approximate to that of a semiconductor single crystal chip. (4) Claim (1) characterized in that one electrode of the feedthrough capacitor is connected to the stem via a connection band.
) semiconductor pressure sensor described.