JPH03200035A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To stabilize the sensor also at temperature changing by using a pedestal and a stem which posses a thermal expansion coefficient approximate to a silicone diaphragm chip. CONSTITUTION:At least two pedestals 14 and 15 on which the chips 12 and 13 are fixed are provided on a stem 16 which possesses a thermal expansion coefficient approximate to silicone diaphragm chip 12 and 13. Then, by using the chips 12 and 13, the pedestals 14 and 15 and the stem 16 compatibly thermal stress from the stem 16 is removed and a sensor which possesses a stable property is obtained. Besides, since filters 28 and 29 are equipped to tubes for introducing pressure 26 and 27, it can be fitted directly to the inlet hole and so on of an internal combustion engine, and moreover, since a circuit board 30 which forms an operation circuit to calculate an absolute pressure is built in, it can be used as a pressure transducer.

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.

(Prior technology) In recent years, with social demands such as fuel savings and exhaust gas regulations for automobiles, various sensors have been used to control engine electronic fuel injection, ignition timing, and exhaust gas recirculation amount using microcomputers. 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 1c are provided. The lead pin 3 inserted into the small through hole 1c is fixed by hermetically sealing the gap with the small through hole 1c using glass 4.

A silicon diaphragm chip 5 provided with a diaphragm 5a having a Wheatstone bridge resistor for pressure detection formed on its surface is fixed on a pedestal 7 having a through hole 7a fixed with an adhesive 6 at the center of the upper surface of the stem 1 described above. There is.

The pedestal 7 is made of a material having a coefficient of thermal expansion similar to that of the silicon diaphragm chip 5, and is provided with a circumferential groove 7b for relieving thermal stress from the stem 1. In addition, the bridge electrode (not shown) of the above Wheatstone bridge resistor is connected to the above lead pin 3.
and is connected by a conductive wire 8.

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, 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, after brazing the pressure introducing pipe 2 to the stem 1, the lead pin 3 is inserted into the small through hole 1c and fixed with the glass 4. On the other hand, the silicon diaphragm chip 5 is fixed on the pedestal 7. Next, the above-described pedestal 7 is attached to the center of the upper surface of the stem 1 using an adhesive 6, and then the bridge electrode and the tip of the lead pin 3 are connected with a wire 8.

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, and the air inside the cap 9 is removed, and at the same time, the sealing hole 9a is sealed using the solder 10 to form a vacuum chamber 11.

In the semiconductor pressure sensor assembled in this manner, the diaphragm 5a of the silicon diaphragm chip 5 is housed in the vacuum chamber 11, and the pressure introduction pipe 2 uses this vacuum pressure as a reference pressure to control the fluid introduced. Absolute pressure 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 thermal stress exerted on the silicon diaphragm chip 5 from the stem 1 via the pedestal 7 This has a large influence on the silicon diaphragm chip 5, which causes the value of the Wheatstone bridge resistance formed on the diaphragm 5a to vary depending on the temperature.
Therefore, there was a problem that the pressure detection characteristics were not stable.

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 thermal expansion coefficient 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 is a problem that not only the workability of the pedestal 7 is lowered and the manufacturing cost is increased, but also the reliability is lowered.

The present invention solves the above problems, and provides a semiconductor pressure sensor that can detect at least two absolute pressures simultaneously with - sensors, has a simple structure, is highly reliable, and has stable characteristics. It is something.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention includes at least two pedestals each having a silicon diaphragm chip fixed to each stem having a thermal expansion coefficient similar to that of the silicon diaphragm chip. A recess is provided for hermetically sealing a plurality of lead pins using glass, and a filter is installed between the stem and the pressure introducing pipe, and the stem is airtightly joined to the recess. The airtight chamber thus formed is kept at a vacuum or reference pressure, and a circuit board for absolute collapse calculation is built therein, and a feedthrough capacitor inserted through the lead pin is mounted therein.

(Function) The above configuration not only makes it possible to simultaneously measure absolute pressures at two or more locations with one semiconductor pressure sensor, but also enables the use of a pedestal with a thermal expansion coefficient similar to that of a silicon diaphragm chip. By using a stem in combination, the influence of thermal stress from the stem is eliminated, and a semiconductor pressure sensor having stable characteristics can be obtained. In addition, since the pressure introduction pipe is equipped with a filter, it can be directly attached to the intake hole of an internal combustion engine, etc. Furthermore, it has a built-in circuit board with a calculation circuit that calculates the absolute pressure.
Can be used as a pressure transducer.

(Example) An example of the present invention will be described with reference to FIG. Figure 1 (a
), (b), (c) and (d) are a plan sectional view, a front sectional view, a side sectional view seen from the left side, and a side sectional view seen from the right side of a semiconductor pressure sensor according to the present invention.

In the same figure, diaphragms L2a and 13a have Wheatstone bridge resistances (not shown) formed on their surfaces.
The silicon diaphragm chips 12 and 13 having a coefficient of thermal expansion similar to that of the silicon diaphragm chips 12 and 13 are respectively fixed to the upper end surfaces of two cylindrical pedestals 14 and 15 having a coefficient of thermal expansion similar to that of the silicon diaphragm chips 12 and 13. but,
It communicates with the diaphragms 12a and 13a of the silicon diaphragm chips 12 and 13 fixed thereto. The above silicon diaphragm chips 12 and 13
The stem 16, which is press-molded from a metal plate having a thermal expansion coefficient similar to the above, has a circular recess 16c and a circular recess 16c with through holes 16a and 1.6b in the center, respectively, which airtightly fix the two pedestals 14 and 15. 16d and the four lead pins 17, 18, 19 and 20 respectively on the glass 21.
Four open cylindrical parts 16e, 16f, 16 sealed with
There are four rectangular parts 16i formed with g and 16h.

In addition, the lead pin 17 is i11! Lead pins 18 and 19 are for output, lead pin 20 is for ground, and feedthrough capacitors 22, 23, and 24 are inserted through each of them.
and 25 are attached so that their outer diameter parts fit into the tips of the open cylindrical part of the stem 16], 6e, 16f, 1.6g and 16h, and the inner diameter electrode part and the outer diameter side electrode (both not shown) by soldering.

The lead pins 17, 18, 19 and 20 are connected to the open cylindrical portions 16e, 16f, 16g and ], 6h of the stem 16, respectively.

Further, the bottoms of the circular recesses 16c and 16d of the stem 16 have through holes 16a and 16b, respectively, and through holes 14a and 1 of the two pedestals 14 and 15, respectively.
The pedestals 14 and I5 are hermetically fixed so that the pedestals 5a are electrically conductive, and furthermore, two pressure introduction pipes 26 and 27 are connected to the filters 28 and 2, respectively, on the lower surface thereof.
9, and are airtightly joined by welding or the like. Thereby, the fluid introduced from the two pressure introduction pipes 26 and 27 can apply fluid pressure to the diaphragms 12a and 13a of the silicon diaphragm chips 12 and 13, respectively, via the filters 28 and 29.

An arithmetic circuit (not shown) for calculating the absolute pressure is formed on the surface, and through holes are formed through which the two pedestals 4 and 15 and the four rieto pins 17, 1, 8, 19 and 20 are inserted, respectively. The provided circuit board 30 is mounted on the shelf-like portion of the stem 16, and is connected to the arithmetic circuit and the diaphragm 12a.
and the output end of the Wheatstone bridge resistor on 13a and the lead pin], 7.18.19 and the end of 20 are electrically connected by conductive wires 31, respectively.

A rectangular cap 32 airtightly adhered to the peripheral edge 16j of the stem 16 by welding or the like covers the silicon diaphragm chips 12 and 13 and the circuit board 30 to form an airtight chamber 33, and allows a vacuum chamber or gas to be formed. It is used as an enclosed reference pressure chamber. The gas-filled pipe 34 provided at the corner of the stem 16 is used to remove air from the airtight chamber 33 or to insert gas at a standard pressure.

To assemble the semiconductor pressure sensor configured in this way,
First, after sealing the lead pins 17, 18, 19 and 20 to the stem 16 with glass 21, the filters 28 and 2
9, while fixing the pressure introducing vibrator 26 and z7 by means such as welding,
24 and 25 lead pins 17.18.19 and 2
0, and its inner diameter electrode and outer diameter electrode (both not shown) are connected to lead pins 17, 18, 19 and 20, respectively.
and opening 1 of stem 16] Cylindrical portions 16e, 16f, 16
g and +6h, respectively, by means such as soldering.

Next, the pedestals 14 and 15 to which the silicon diaphragm chips 12 and 13 are fixed, respectively, are hermetically joined to the bottom surfaces of the circular recesses 16c and 16d of the stem 16, and the subsequent circuit board 30 is attached, and then electrically connected with the wire 31. Connect to.

Next, the cap 32 is hermetically sealed to the peripheral edge 16j of the stem 16 by means of pressure contact, welding, or the like. At that time, if the cap 32 is hermetically sealed in a vacuum, a vacuum chamber with a reference pressure of 0 will be formed in the airtight chamber 33, and if gas at a reference pressure is then filled from the gas-filled vibrator 34, the airtight chamber 33 will have a certain reference pressure. is formed. If a vacuum chamber is formed, the measured pressure becomes absolute pressure, and if a reference pressure is formed by gas filling, the circuit board 3
0, it is converted to absolute pressure, and in either case, the output is absolute pressure.

Next, a pressure measurement method and operation will be described, taking as an example a case in which the intake air pressure of an internal combustion engine is determined by the semiconductor pressure sensor configured as described above.

Internal combustion g? 11s! To the intake hole of the + intake manifold,
One of the pressure introduction pipes 26 of the semiconductor pressure sensor is directly connected and attached. At this time, the other pressure introduction pipe 27 is left open. When the internal combustion engine starts operating, fluid pressure from the intake hole of the manifold flows into the pressure introduction pipe 26. The voltage is applied to the diaphragm 12a through the through hole 16a of the stem 16*through the through hole 14a of the pedestal 14. On the other hand, the atmospheric pressure is the pressure introduction pipe 27. The voltage is applied to the diaphragm 13a through the through holes 16b and 15a of the stem 16 and the base 15.

Therefore, the fluid pressure and atmospheric pressure introduced through the 5 pressure introduction pipes 26 and 27 are applied to the diaphragm 1
2a and 13a, and this distortion causes diaphragm 1
The resistance value of the Wheatstone bridge resistor for pressure detection formed on the surfaces of 2a and 13a is changed.

The change in the bridge resistance value indicated by l- is calculated by calculation 1 [! of the circuit board 30]. ? The fluid pressure expressed in absolute pressure and the atmospheric pressure are simultaneously output from the lead pins 18 and 19.

In addition, since the stem 16 and the pedestals fi14 and 15 are made of a material that has a coefficient of thermal expansion similar to that of the silicon diaphragm chips 12 and 13, the stem 11 and the pedestal 7, which are affected by temperature changes in the conventional example, are Since the influence of thermal stress generated during this period is removed, the output characteristics of the pressure sensor are stabilized.

Further, since the pressure introduction pipe 26 is equipped with a filter 28, it can be directly connected to the intake hole of the internal combustion engine, and since it has a built-in circuit board 30 and functions as a pressure transducer, parts inspection can be reduced.

Installation is simplified and costs are reduced, while reliability is improved.

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

Further, since the pedestal and stem have a coefficient of thermal expansion similar to that of a silicon diaphragm chip, a highly reliable semiconductor pressure sensor with stable characteristics even when the temperature changes can be obtained.

In addition, since the pressure introduction pipe has a built-in filter, it can be connected directly to the intake hole of the internal combustion engine, and since it has a built-in circuit board, it works as a pressure transducer, reducing the need to inspect parts when measuring pressure. , a semiconductor pressure sensor that is easy to install and inexpensive can be obtained.

[Brief explanation of drawings]

FIG. 1(a) is a plan sectional view of a semiconductor pressure sensor according to the present invention, and FIG. 1(b), (c) and (d) are (a)
) Lines X-X, Y-Y@ and 2-2IIi! Front cross-sectional view and side cross-sectional view cut at
The figure is a sectional view of a conventional semiconductor pressure sensor. 1.16...Stem, 1a...Step, lb. 7a, 14a, 15a, 1.6a, i6b...
-H through hole, 1c...small through hole, 2, 26.27.
・Pressure introduction pipe, 3.17.18.19.20
...Lietbin, 4.21...Glass, 5,12
゜1:3...Silicon diaphragm chip, 5a. 1.2i, 13a...diaphragm, 6...adhesive, 7, I/I, 15...pedestal, 7b...
Circumferential groove, 8゜31...Wire, 9.32...
Cap, 9a...1 sealing hole, 10...solder, 11...vacuum chamber, 16c, 16d-four circular parts,
16e, 16f, 16H. 16h...opening cylindrical part, 16i...rectangular recessed part,
16j...periphery, 22.23.24.25...
Feedthrough capacitor, 28.29...filter, 30
...Circuit board, 33...Airtight chamber, 34...Gas-filled pipe.

Claims (2)

[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 bonded pressure introduction pipe and a cap that is hermetically fitted to the stem to form an airtight chamber covering the semiconductor single crystal chip, and to use the airtight chamber as a vacuum chamber or a reference pressure chamber, Using a stem having a coefficient of thermal expansion similar to that of a semiconductor single crystal chip, at least two pedestals each having a pressure-sensitive diaphragm formed thereon are hermetically connected, and between the stem and a pressure introduction pipe communicating with each pressure-sensitive diaphragm. Attach a filter to the
A semiconductor pressure sensor characterized by having a built-in circuit board for calculating absolute pressure inside an airtight chamber. (2) The semiconductor pressure sensor according to claim (1), wherein the circuit board is mounted on the stem having a coefficient of thermal expansion similar to that of the circuit board.