JPH0749278A - Pressure sensor - Google Patents

Abstract

PURPOSE:To provide a pressure sensor compact and high in reliability at a low cost. CONSTITUTION:An upper board 13 provided with a protruding part 13a is provided with a hole part 16 and a wiring pattern 19 formed thereon. An intermediate board 14 is provided with a cutout part 17 from the end part of a protruding part 14a. The protruding part 15a of a lower board 15 and the protruding part 14a of the intermediate board 14 are overlapped to laminate the lower board 15 to the lower face of the intermediate board 15. The protruding part 14a and the protruding part 13a, and the end part 17a of the cutout part 17 and the hole part 16 are respectively overlapped to laminate the upper board 13 on the upper face of the intermediate board 14, thus forming a circuit board 3, and a pressure lead-in passage 11 disposed parallel to the circuit board 3 is formed at the circuit board 3. An IC chip 2a and CR chip parts 2b are mounted on the wiring pattern 19 to form a signal processing circuit 2. A pressure sensor chip 1 is further mounted on the circuit board 3, in correspondence with the opening position of the pressure lead-in passage 11, to prepare a pressure sensor A.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to pressure sensors. Specifically, it relates to a pressure sensor that measures the pressure of a fluid such as air.

[0002]

2. Description of the Related Art Conventionally, as a pressure sensor modularized by combining a semiconductor pressure sensor chip and a signal processing circuit, for example, a pressure sensor chip is directly mounted on a package board which also serves as a circuit board or through a pedestal. There is a mounted one (Japanese Patent Laid-Open No. 1-185424,
JP-A-1-165437 and JP-A-55-116252.
(See the official gazette). However, in these pressure sensors, a pressure introducing component such as a pipe for guiding pressure to the pressure sensor must be attached to the pressure sensor, so that the pressure sensor becomes large and costly, and the reliability is poor. was there.

In addition, a fixed electrode is directly formed on a package substrate on which a signal processing circuit is mounted, and a diaphragm chip having a movable electrode is opposed to the fixed electrode and bonded to the package substrate to reduce the electrostatic size. There is a capacitive pressure sensor ("AN ULTRAMINIATURECMOS PRESSURE SENSOR FO
RA MULTIPLEXED CARDIOVASCULAR CATHETER "Transduce
rs'91 Proceedings A13.4, p1018-1020, 1991). However, with this pressure sensor, if a differential pressure type structure is used,
When introducing pressure to the capacity forming chamber formed by the diaphragm chip and the package substrate, the pressure introducing component must be attached to the diaphragm chip, at which time the stress on the diaphragm chip adversely affects the pressure sensor,
Further, there is a problem that the cost is high and the manufacturing process is complicated. Further, in the case of the absolute pressure type structure, the wiring for pulling out the fixed electrode causes unevenness on the package substrate, and a gap is created between the diaphragm chip and the package substrate. There was a problem that it was inferior.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the drawbacks of the above conventional examples, and an object of the present invention is to provide a compact and highly reliable pressure sensor at low cost. It is in.

[0005]

According to a first pressure sensor of the present invention, a hole is opened inside the substrate from a side surface of the substrate to an upper surface of the substrate, a pressure sensor chip is mounted on the substrate, and the hole is inserted through the hole. The pressure is introduced into the pressure sensor chip.

Further, in the second pressure sensor of the present invention, the support substrate elastically supporting the detecting portion is joined to the circuit board on which the signal processing circuit is mounted or the pedestal on the circuit board,
In a pressure sensor in which a fixed electrode is provided on the circuit board or the pedestal so as to face a movable electrode provided in the detection unit, the circuit board and the pedestal from the side surface of the circuit board to the upper surface of the pedestal. A hole is opened inside the pedestal, pressure is introduced into the detection unit through the hole, and a conductive thin film part connected to the fixed electrode is provided in at least a part of the hole, and the conductive thin film part is provided. It is characterized in that the signal processing circuit is electrically connected by bypassing a joining portion between the support substrate and the circuit substrate or the pedestal.

[0007]

In the first pressure sensor of the present invention, the pressure is introduced into the inside of the substrate on which the pressure sensor chip is mounted from the hole opened from the side surface of the substrate to the upper surface of the substrate.

Further, in the second pressure sensor of the present invention, pressure is applied from the hole portion provided inside the circuit board and the pedestal on which the fixed electrodes are formed from the side surface of the circuit board to the upper surface of the circuit board or the pedestal. It is planned to be introduced.

Therefore, in the pressure sensor of the present invention,
Since the substrate and the pressure introducing means are integrally configured, it is not necessary to attach the pressure introducing component, the pressure sensor can be downsized, the cost can be reduced, and the reliability can be improved.

Further, in the second pressure sensor of the present invention, the conductive thin film portion for connecting to the fixed electrode is provided in at least a part of the hole opened from the side surface of the circuit board to the upper surface of the circuit board or the pedestal, Since the conductive thin film portion and the signal processing circuit are electrically connected to each other by bypassing the joining portion between the supporting substrate and the circuit board or the pedestal, the supporting substrate and the circuit board or the pedestal can be joined without a gap. Therefore, the airtightness of the pressure sensor can be increased, the alignment accuracy at the time of joining the support substrates can be increased, and the reliability of the pressure sensor can be further improved.

[0011]

1 (a) is an internal plan view of a pressure sensor A according to an embodiment of the present invention, and FIG. 1 (b) is a sectional view thereof.
The pressure sensor A includes a pressure sensor chip 1 and an IC chip 2a.
Parts such as chip capacitors, chip capacitors and chip resistors 2
It is composed of a signal processing circuit 2 including b and the like, a circuit board 3, an input / output terminal 4 and the like, and is covered with a case 5. The pressure sensor chip 1 is mounted on the circuit board 3 together with the signal processing circuit 2, and the sensor signal of the pressure sensor chip 1 is connected to the signal processing circuit 2 from the electrode lead-out pad 30 on the frame 6 and is used as an input / output terminal. 4 can be taken out to the outside.

In the pressure sensor chip 1, a silicon cover 8 is placed on the upper surface of a silicon frame 6 in which a thin film diaphragm 7 is elastically supported on the entire surface of a rectangular frame, and a silicon cover 8 is placed around the cover 8. The parts are joined to the frame 6 by a low temperature joining technique or the like. A movable electrode is provided on the upper surface of the diaphragm 7, and a fixed electrode is provided on the inner surface of the cover 8 with a minute gap from the movable electrode to form a capacitor between both electrodes.

On the side surface of the circuit board 3, a square rod-shaped introduction pipe 9 is provided integrally with the circuit board 3, so that a tube 10 from a pressure source can be easily connected. A pressure introducing path 11 for introducing pressure to the pressure sensor chip 1 passes through the inside of the circuit board 3 from the introducing pipe 9 on the side surface of the circuit board 3, and is opened on the upper surface of the circuit board 3.

FIG. 2 is an exploded perspective view of the circuit board 3.
The circuit board 3 has the same shape, that is, the upper board 13 and the intermediate board 1.
4, the lower substrate 15 is formed by stacking three substrates. Each substrate 13, 14, 15 has a convex portion 13a,
The convex portion 14a and the convex portion 15a are provided, and the upper substrate 13 is provided with a hole 16 and the intermediate substrate 14 is provided with a notch 17 from the end of the convex portion 14a. Intermediate board 1
On the lower surface of 4, the lower substrate 15 is overlapped with the convex portions 14a and the convex portions 15a aligned with each other.
a and the convex portion 13a are aligned with each other, and the hole portion 16 and the end portion 17a of the cutout portion 17 are aligned with each other so that the intermediate substrate 1
The upper substrate 13 and the lower substrate 15 are adhered to the upper and lower surfaces of the No. 4 substrate. In this way, the circuit board 3 in which the introduction pipe 9 is integrated is produced, and the pressure introduction path 11 is provided inside the circuit board 3 in parallel with the circuit board 3 by the notch 17 and the hole 16. be able to. Further, the wiring pattern 19 is provided on the upper surface of the upper substrate 13, and the IC chip 2a
The signal processing circuit 2 can be formed by mounting the chip component 2b.

When the pressure P is applied from the tube 10, however, the pressure P passes through the pressure introducing passage 11 and is introduced into the pressure sensor chip 1 through the opening on the upper surface of the circuit board 3. When the pressure P is introduced, the diaphragm 7 is displaced according to the magnitude of the introduced pressure P, and the magnitude of the electrostatic capacitance C of the capacitor changes. This change in the capacitance C is detected by the signal processing circuit 2 connected to the pressure sensor chip 1,
The magnitude of the pressure P applied to the pressure sensor A can be known.

With such a structure, the pressure P
Since it is not necessary to separately attach a component such as a pipe for introducing the pressure sensor, the manufacturing process of the pressure sensor A can be simplified, and the manufacturing cost of the pressure sensor A can be reduced. Moreover, since the pressure sensor chip 1 is directly mounted on the circuit board 3 which also serves as a package board, the pressure sensor A can be downsized and the reliability can be improved.

FIGS. 3A and 3B show a pressure sensor B which is another embodiment of the present invention. As shown in FIG. 3, the pressure sensor B has a resin portion 20 formed of a moisture resistant resin over substantially the entire circumference of the circuit board 3. In addition, a resist coat (not shown) is formed on both sides of each of the three upper substrates 13, the intermediate substrate 14, and the lower substrate 15 which form the circuit substrate 3, except for the portion of the upper substrate 13 on which the wiring pattern 19 is formed. ) Has been applied. Since the surface of the circuit board 3 is rough, it is most likely to absorb moisture. By sealing this portion with a moisture resistant resin, the circuit board 3 can be prevented from absorbing moisture. Further, since the surface of each of the three substrates 13, 14 and 15 constituting the circuit board 3 is coated with a resist, the dielectric constants of the introduced air, the frame 6 and the like are changed by the moisture absorption of the circuit board 3. There is nothing to do. Further, the gap between the upper substrate 13 and the intermediate substrate 14 and the intermediate substrate 1
Since the pressure of air or the like does not escape from the gap between the lower substrate 4 and the lower substrate 15 or the moisture does not permeate, the pressure P introduced into the pressure sensor B can be accurately measured.

FIG. 4 shows a pressure sensor C which is still another embodiment. 4A is a partially cutaway plan view of the pressure sensor C, and FIG. 4B is a partially cutaway sectional view thereof,
The pressure sensor C is composed of a frame 21, a signal processing circuit 2, a circuit board 3, and the like.

The pressure sensor C has a frame 21 in which a thin-film diaphragm 23 is elastically supported on the entire surface of a rectangular frame on the circuit board 3. A support frame 24 is formed by plating Au on the circuit board 3,
The periphery of the frame 21 is Au-Si eutectic bonded on the support frame 24. Frame 21 and diaphragm 23
Is integrally formed from a single crystal silicon wafer by a semiconductor manufacturing technique, and a movable electrode 25 is formed on the inner surface of the diaphragm 23. A fixed electrode 26 is formed on the upper surface of the circuit board 3 so as to face the movable electrode 25 and forms a capacitor with a minute gap. The accuracy of the gap can be improved by bonding the frame 21 onto the support frame 24 by Au-Si eutectic bonding.

Like the first embodiment, the circuit board 3 is made by laminating three boards, an upper board 13, an intermediate board 14 and a lower board 15, and the upper board 13 has a hole 1
6 is provided, the pressure introduction path 11 is formed by the notch 17 provided in the intermediate substrate 14, and the pressure can be introduced into the diaphragm 23 from the hole 16 provided in the upper substrate 13. .

Further, another hole portion 27 is provided in the upper substrate 13, and the hole portion 16 forming the pressure introducing path 11 and the regions including the inner peripheral surfaces of the two hole portions 16 and 27 are respectively formed. The conductive thin film portions 28a and 28b are provided to form through holes. A connection portion 29 that connects the thin film portion 28a and the thin film portion 28b is provided on the back surface of the upper substrate 13. The fixed electrode 26 has two thin film portions 28a, 2
Al and the like are vapor-deposited together with 8b and the connecting portion 29 to be integrally formed, and the thin film portion 28b is connected to one end 31 of the signal processing circuit 2 formed on the surface of the upper substrate 13. Thus, the fixed electrode 26 is connected to the end 3 of the signal processing circuit 2.
1, the movable electrode 25 is electrically connected from the electrode lead-out pad 30 on the frame 21 to another end 32 of the signal processing circuit 2 by a bonding wire 33.

When pressure is applied to the pressure sensor C, the diaphragm 23 is displaced, changing the electrostatic capacitance of the capacitor. This change in capacitance is detected by the signal processing circuit 2, and the magnitude of the applied pressure can be known.

In this pressure sensor C, the fixed electrode 2
Since 6 is directly formed on the circuit board 3, the cover 8
Can be eliminated. Further, since it is not necessary to join the frame 21 and the cover 8, the manufacturing process can be simplified and the cost of the pressure sensor C can be reduced.
Moreover, since the fixed electrode 26 on the circuit board 3 is connected to the signal processing circuit 2 from the hole 16 through the inside of the circuit board 3, the frame 21 and the circuit board 3 can be bonded together without a gap.

FIGS. 5A and 5B show a pressure sensor D which is still another embodiment of the present invention. A lead-out portion 34 is formed on the joint surface of the frame 21 so as to have conductivity by injecting impurities at a high concentration, and the movable electrode 2 of the diaphragm 23 is formed.
5 is electrically connected. The support frame 24 is formed on the circuit board 3 by Au plating.
Is connected to the signal processing circuit 2. The pressure sensor D is
The frame 21 is formed on the support frame 24 by Au-Si eutectic bonding. By electrically connecting the movable electrode 25 to the signal processing circuit 2 via the lead-out portion 34 and the support frame 24 in this manner, connection by a bonding wire is unnecessary, and further, the manufacturing process of the pressure sensor D is performed. It can be simplified.

FIGS. 6A and 6B show a pressure sensor E which is another embodiment. Frame 21 of pressure sensor E
Is stacked on the glass substrate 35 having the same thermal expansion as that of silicon, and the peripheral portion of the frame 21 is bonded to the glass substrate 35 by an anodic bonding method or the like. The fixed electrode 26 is provided on the upper surface of the glass substrate 35 so as to face the movable electrode 25. In addition, the glass substrate 35 has holes 16 in the circuit board 3.
The introduction port 36 is opened in accordance with the position of, and the pressure from the pressure introduction passage 11 is applied to the diaphragm 23 via the introduction port 36.

A conductive thin film portion 37 is provided from the inner peripheral surface of the inlet 36 to the back surface of the glass substrate 35, and the thin film portion 37 is formed integrally with the fixed electrode 26 by vapor deposition of Al or the like. A support frame 24 is formed on the circuit board 3 by Au plating and is connected to the signal processing circuit 2. The glass substrate 35 is bonded onto the support frame 24 by soldering, and the fixed electrode 26 is electrically connected to the signal processing circuit 2 via the thin film portion 37 and the support frame 24. On the other hand, the movable electrode 25 of the diaphragm 23 is connected to the signal processing circuit 2 by the bonding wire 33 from the electrode lead-out pad 30 of the frame 21.

As described above, if the glass substrate 35 having the same coefficient of thermal expansion as that of silicon is sandwiched between the circuit board 3 and the frame 21, it is possible to reduce distortion when the frame 21 is mounted. The temperature characteristics of the sensor E can be improved.

[0028]

According to the first pressure sensor of the present invention,
Pressure is introduced from the side surface of the substrate on which the pressure sensor chip is mounted to the upper surface of the substrate through a hole opened.

Further, in the second pressure sensor of the present invention, pressure is introduced into the inside of the circuit board on which the fixed electrodes are formed from the side hole of the circuit board to the upper surface of the circuit board or the pedestal. I have decided.

Therefore, in the pressure sensor of the present invention,
Since it is not necessary to attach a pressure introducing component, the pressure sensor can be downsized, the cost can be reduced, and the reliability can be improved.

Further, in the second pressure sensor of the present invention, since the support substrate and the circuit board can be joined together without a gap,
It is possible to improve the airtightness of the pressure sensor, the alignment accuracy at the time of joining, and further improve the reliability.

[Brief description of drawings]

FIG. 1A is an internal plan view of a pressure sensor according to an embodiment of the present invention, and FIG. 1B is a sectional view thereof.

FIG. 2 is an exploded perspective view of a circuit board that constitutes the above pressure sensor.

3A is an internal plan view of a pressure sensor according to another embodiment of the present invention, and FIG. 3B is a sectional view thereof.

FIG. 4A is a partially cutaway plan view of a pressure sensor according to still another embodiment of the present invention, and FIG. 4B is a partially cutaway sectional view thereof.

5A is a partially cutaway plan view of a pressure sensor according to still another embodiment of the present invention, and FIG. 5B is a partially cutaway sectional view thereof.

6A is a partially cutaway plan view of a pressure sensor according to yet another embodiment of the present invention, and FIG. 6B is a partially cutaway sectional view thereof.

[Explanation of symbols]

 3 circuit board 6 frame 11 pressure introduction path 17 notch portion 19 wiring pattern 20 resin portion 21 frame 24 support frame 26 fixed electrode 28a, 28b thin film portion 34 lead portion 35 glass substrate

Claims (2)

[Claims] 1. A hole is opened inside the substrate from a side surface of the substrate to an upper surface of the substrate, a pressure sensor chip is mounted on the substrate, and pressure is introduced into the pressure sensor chip through the hole. Pressure sensor. 2. A support substrate that elastically supports the detection unit is bonded to a circuit board on which a signal processing circuit is mounted or a pedestal on the circuit board, and is opposed to a movable electrode provided in the detection unit. In a pressure sensor provided with a fixed electrode on a circuit board or on the pedestal, a hole is opened inside the circuit board and the pedestal from a side surface of the circuit board to an upper surface of the circuit board or the pedestal, and the hole portion A pressure is introduced into the detection unit via a conductive thin film portion connected to the fixed electrode in at least a part of the hole, and the conductive thin film portion and the signal processing circuit are connected to the support substrate and the circuit board. Alternatively, the pressure sensor is characterized in that it is electrically connected by bypassing the joint with the pedestal.