JP2583137B2 - Semiconductor pressure sensor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor pressure sensor used for detecting an intake air pressure, an atmospheric pressure, an exhaust, or the like of an internal combustion engine mounted on an automobile or the like.

(Prior Art) In recent years, in response to social demands such as fuel saving of automobiles and emission control, various sensors are used to control electronic fuel injection of an engine by a microcomputer, ignition timing and exhaust gas recirculation amount. I started to do it.

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

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

FIG. 1 is a cross-sectional view of a conventional semiconductor pressure sensor, in which a stem 1 having a stepped portion 1a on its periphery is inserted through a through hole 1b communicating with a pressure introducing pipe fixed to the lower surface by brazing or the like, and a lead pin 3. Two small through holes 1c are provided.
The lead pins 3 inserted into the small through-holes 1c are hermetically sealed using glass 4 and fixed to the small through-holes 1c.

A silicon diaphragm chip 5 provided with a diaphragm 5a having a Wheatstone bridge resistor for pressure detection formed on the surface thereof is fixed to the center of the upper surface of the stem 1 with an adhesive 6, and has a central portion communicating with the diaphragm 5a. Hole 7a
Are fixed on the pedestal 7 on which is formed. The pedestal 7 is made of a material having a thermal expansion coefficient similar to that of the silicon diaphragm chip 5, and has a circumferential groove 7b for relaxing thermal stress from the stem 1. A bridge electrode (not shown) of the Wheatstone bridge resistor is connected to the lead pin 3 by a conductive wire 8.

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

A method of assembling the semiconductor pressure sensor thus configured will be described.

First, after brazing the pressure introducing pipe 2 to the stem 1, the lead pin 3 is inserted into the small through hole 1 c and fixed with the glass 4. On the other hand, the silicon diaphragm chip 5 is fixed on the base 7. Next, the 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 by a wire 8.
Next, the cap 9 is sealed to the step 1a of the stem 1 by pressing or welding while leaving the sealing hole 9a as it is. Next, the vacuum chamber 11 is formed by evacuating the air inside the cap 9 while evacuating the cap 9 and sealing the sealing hole 9 a with the solder 10.

The semiconductor pressure sensor assembled in this way is
Since the diaphragm 5a of the silicon diaphragm chip 5 is housed in the vacuum chamber 11, the absolute pressure of the fluid introduced by the pressure introducing pipe 2 can be measured using this vacuum pressure as a reference pressure.

(Problems to be Solved by the Invention) However, in the above configuration, basically, only one absolute pressure can be measured by one sensor, and heat applied to the silicon diaphragm chip 5 from the stem 1 via the pedestal 7 can be measured. Since the influence of the stress is large and this distorts the silicon diaphragm chip 5, the value of the Wheatstone bridge resistance formed on the diaphragm 5a fluctuates depending on the temperature, and there is a problem that the pressure detection characteristics are not stable. This problem is mainly attributable to the difference in the thermal expansion coefficients of the silicon diaphragm chip 5, the stem 1, the pedestal 7, and the adhesive 6.

Therefore, as described above, the pedestal 7 is made of a material having a thermal expansion coefficient similar to that of the silicon diaphragm chip 5,
Although the thickness of the pedestal 7 is increased or the circumferential groove 7b is provided, this not only lowers the workability of the pedestal 7, increases the manufacturing cost, but also lowers the reliability. Was.

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

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

(Operation) With the above configuration, at least two pressures, such as the atmospheric pressure and the intake manifold pressure, can be measured at the same time. In the case of a vacuum, the absolute pressure is directly corrected. It is output as a pressure value. Further, since the pedestal and the spacer have a thermal expansion coefficient similar to that of the silicon diaphragm chip, the influence of the thermal stress from the stem is eliminated, and the variation in the resistance value due to the thermal stress is eliminated. Further, since the filter is built in the upper part of the pressure introducing pipe, it can be used as a pressure transducer which can be directly bonded to the pressure introducing hose.

(Example) FIGS. 1 (a), (b), (c), and (c) show an embodiment of the present invention.
This will be described with reference to (d) and (e).

FIGS. 1 (a), (b), (c), (d) and (e)
1 is a plan sectional view, a front sectional view, a side sectional view as viewed from the left, a side sectional view as viewed from the right, and a front sectional view of a main part of a semiconductor pressure sensor according to the present invention. In the figure,
A rectangular stem 12 formed by pressing a metal plate has a concave portion 12c having two through holes 12a and 12b formed at the bottom and a concave portion in which four lead pins 13, 14, 15 and 16 are hermetically fixed by glass 17. 12d is provided. The recess 12d is
As shown in FIG. 1 (d), each lead pin 13, 14,
There may be four independent recesses for each of 15 and 16. The lead pin 13 is for power supply, the lead pins 14 and 15 are for output, and the lead pin 16 is for ground. The lead pins 13 are connected to the inner diameter electrodes (not shown) of the feedthrough capacitors 18, 19, 20 and 21 by soldering or the like. I have. The outer diameter electrodes (not shown) of the feedthrough capacitors 18, 19, 20 and 21 are connected to the connection band 22 by soldering, and are further fixed to the stem 12 and electrically connected thereto. Recess 12c of stem 12
The pressure introduction pipes 23 and 24 are connected to the lower surfaces of the filters 25 and 24, respectively, so as to communicate with the through holes 12a and 12b.
It is airtightly joined by means such as welding through 26.

The spacer 27 airtightly joined to the concave portion 12c of the stem 12 is provided at a position corresponding to the through holes 12a and 12b,
Storage recesses 27a and 27b to which the pedestals 30 and 31 to which the silicon diaphragm chips 28 and 29 are fixed are fixed airtightly are formed, and through holes 27c and 27d communicating with the through holes 12a and 12b are provided at the center of the bottom surface. Have been. The above-mentioned silicon diaphragm chip 28 and
At the center of 29, diaphragms 28a and 29a each having a Wheatstone bridge resistor (not shown) formed on the surface are formed. Further, the pedestals 30 and 31 are connected to the through holes 12a and 2a of the stem 12 and the spacer 27, respectively.
7c, and through holes 30a and 31a communicating with 12b and 27d, respectively, are provided, and pressure introduction pipes 23 and 24 are provided.
Is applied to the diaphragms 28a and 29a.

The circuit board 32 on which the arithmetic circuit for calculating the absolute pressure value from the resistance value output by the Wheatstone bridge is formed,
The positioning protrusions 27e formed on the spacer 27 and the positioning holes 32a of the circuit board 32 fitted to the positioning protrusions 27e are mounted on the spacer 27, and the input terminals of the arithmetic circuit and the silicon diaphragm are mounted on the spacer 27. The bridge electrodes of the Wheatstone bridge resistors on the chips 28 and 29 are connected by a conductive wire 33, and further, a power input terminal section,
An output terminal section and a ground terminal section, and the aforementioned lead pins 13, 1
4, 15 and 16 are electrically connected.

A hat-shaped cap 34 hermetically fixed to the peripheral portion 12e of the stem 12 by welding or the like forms an airtight chamber 35 that covers the silicon diaphragm chips 28 and 29 and the circuit board 32. In addition, in the corner of the stem 12 above, a gas filling pipe
36 is installed.

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

First, the spacer 27 is airtightly joined to the recess 12c of the stem 12, and the four lead pins 13, 14, 15, and 1 are further fitted to the recess 12d.
6 is passed through and glass 17 is airtightly fixed. Next, on the lower surface of the concave portion 12c of the stem 12, the through holes 12a and 12b are attached so as to be covered with filters 25 and 26, respectively, and the pressure introducing pipes 23 and 24 are fixed by welding or the like, and subsequently,
After penetrating capacitors 18, 19, 20 and 21 are inserted through the above lead pins 13, 14, 15 and 16, respectively, and fixed with a connection band 22, the inner and outer electrodes (both not shown) of the same,
The above lead pins 13 are connected to the connection bands 14, 15, 16 and the connection band 22 by soldering. On the other hand, a silicon diaphragm chip is provided on the upper surface of the two pedestals 30 and 31, respectively.
Secure 28 and 29.

Next, after the pedestals 30 and 31 to which the silicon diaphragm chips 28 and 29 have been bonded are air-tightly bonded to the storage recesses 27a and 27b of the spacer 27, the circuit board 32 is positioned and mounted on the spacer 27 again, and the wires 33 are electrically connected. Connection.

Next, the cap 34 is hermetically joined to the peripheral portion 12e of the stem 12 by means such as pressure welding or welding. At this time, if the airtight joining is performed in a vacuum, the airtight chamber 35 inside the cap 34 is formed with a vacuum chamber to have a reference pressure of 0, and then the gas filled pipe is formed.
If a gas for the reference pressure is filled from 36, a certain reference pressure will be formed.

If the measurement pressure is formed from the vacuum chamber, the measured pressure becomes an absolute pressure. If the reference pressure by gas filling is formed, the measured pressure is corrected to the absolute pressure by the circuit board 32. In any case, the absolute pressure is output.

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

One pressure introduction pipe 23 is connected to an intake hole of an intake manifold of the internal combustion engine. At this time, the other pressure introduction pipe 24 is left open. When the internal combustion engine starts operating, the fluid pressure from the manifold intake hole passes through the pressure introducing pipe 23, 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, and the diaphragm 28
applied to a. On the other hand, the atmospheric pressure is the pressure introduction pipe 24,
The voltage is applied to the diaphragm 29a through the stem 12, the spacer 27, and the through holes 12b, 27d and 31a of the pedestal 31.

Therefore, the fluid pressure and the atmospheric pressure introduced through the pressure introducing pipes 23 and 24 are respectively changed by the diaphragm 28a.
And 29a, distorting the diaphragm 28a and
The resistance value of the Wheatstone bridge resistor for pressure detection formed on the surface of 29a is changed. The change in the bridge resistance value is processed by the arithmetic circuit of the circuit board 32, and the fluid pressure and the atmospheric pressure expressed in absolute pressure are simultaneously output from the lead pins 14 and 15.

Since the spacer 27 and the pedestals 30 and 31 are made of a material having a thermal expansion coefficient similar to that of the silicon diaphragm chips 28 and 29, the stem 12 and the
Since the thermal stress generated therebetween does not affect the silicon diaphragm chips 28 and 29, the diaphragm 28
The fluctuation difference due to the thermal stress of the Wheatstone bridge resistance system formed at a and 29a is eliminated, and the characteristics of the semiconductor pressure sensor are stabilized. In addition, the pressure introduction pipe 23 has a filter
25, which can be directly connected to the intake hole of the internal combustion engine, and has a built-in circuit board 32 that acts as a pressure transducer, reducing the number of parts, simplifying installation and reducing costs, The performance is improved.

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

In addition, by using a spacer with a thermal expansion coefficient similar to that of the silicon diaphragm chip, and by forming a pedestal storage recess, the contact area with the stem has been reduced,
A highly reliable semiconductor pressure sensor having stable characteristics even when the temperature changes can be obtained. In addition, by using a spacer having a thermal expansion coefficient similar to that of the silicon diaphragm chip, it is not necessary to configure the stem with an expensive material having a thermal expansion coefficient similar to that of the silicon diaphragm chip, and furthermore, the airtight joint with the lead pin can be formed. By forming the recess, the glass hermetic sealing portion can be integrally formed with the stem, and the cost of the stem can be greatly reduced. Since the spacer can be press-molded, it can be manufactured at extremely low cost. Further, since the circuit board can be mounted with a large bonding area, the circuit board does not break due to an impact due to a drop or the like. Further, the use of the connection band facilitates the soldering between the through capacitor and the stem having a large difference in heat capacity. Furthermore, since the circuit board is incorporated, it can be used as a pressure transducer and can be directly connected to the intake pressure hole of the internal combustion engine, so that the number of parts is reduced, the assembly is simple, the cost is reduced, and the reliability is improved.

[Brief description of the drawings]

FIG. 1 (a) is a cross-sectional plan view of a semiconductor pressure sensor according to the present invention, and FIGS. 1 (b), (c) and (d) are lines XX, YY and Z in FIG. FIG. 3 (e) is a front cross-sectional view of a main part, and FIG. 2 is a cross-sectional view of a conventional semiconductor pressure sensor. 1,12… Stem, 1a… Step, 1b, 7a, 12a, 12b, 27c, 27d, 30a,
31a: Through hole, 1c: Small through hole, 2, 23, 24: Pressure introducing pipe, 3, 13, 14, 15, 16 ... Lead pin, 4, 17: Glass, 5, 28,
29: Silicon diaphragm chip, 5a, 28a, 29a: Diaphragm, 6: Adhesive, 7, 30, 31: Pedestal, 7b: Circumferential groove, 8,3
3… Wire, 9,34… Cap, 9a… Sealing hole, 10… Solder, 11… Vacuum chamber, 12c, 12d… Recess, 12e… Peripheral part, 18,19,
20, 21 ... feedthrough capacitor, 22 ... connection band, 25, 26 ... filter, 27e ... spacer, 27a, 27b ... storage recess, 27e ... positioning projection, 32 ... circuit board, 32a ... positioning hole, 35 ...
Airtight room, 36 ... gas filling pipe.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-432 (JP, A) JP-A 64-61638 (JP, A) JP-A 54-123077 (JP, A) 122537 (JP, U) Japanese Utility Model Showa 63-97833 (JP, U) Japanese Utility Model Showa 62-192234 (JP, U)

Claims (4)

(57) [Claims] A pedestal having a thermal expansion coefficient similar to that of said semiconductor single crystal chip, wherein said pedestal is provided with a through hole communicating with said pressure sensitive diaphragm, said semiconductor single crystal chip having a pressure sensitive diaphragm formed thereon being fixed thereto. The base is hermetically bonded, a through-hole communicating with the through-hole is provided, and a plurality of lead pins that input and output to and from the pressure-sensitive diaphragm are hermetically sealed to the stem, and communicate with the through-hole of the stem. A pressure-introducing pipe air-tightly bonded to the stem and a cap that is air-tightly bonded to the stem to form an air-tight chamber that covers the semiconductor single crystal chip, and uses the air-tight chamber as a vacuum chamber or a reference pressure chamber. In the sensor, at least two pedestals each having the semiconductor single crystal chip fixed thereto are hermetically bonded to a stem via a spacer,
A filter was mounted between the stem and the pressure introducing pipe, a circuit board having an arithmetic circuit for calculating the absolute pressure was built in the airtight chamber, and a feedthrough capacitor was mounted on each of the lead pins. Characteristic semiconductor pressure sensor. 2. The semiconductor pressure sensor according to claim 1, wherein the pedestal and the spacer are formed of a material having a thermal expansion coefficient similar to that of the semiconductor single crystal chip. 3. The semiconductor pressure sensor according to claim 1, wherein said circuit board is mounted on a spacer having a thermal expansion coefficient similar to that of a semiconductor single crystal chip. 4. The semiconductor pressure sensor according to claim 1, wherein one electrode of said feedthrough capacitor is connected to a stem via a connection band.