JPH07318582A - Acceleration sensor - Google Patents

Abstract

PURPOSE:To provide an acceleration sensor which is manufactured in a small size. CONSTITUTION:A cylindrical sensor mount 3 is placed and fixed onto a printed circuit board 2 of an acceleration sensor 1. A sensor ship 5 is laid out in the sensor mount 3 and silicone gel 8 of a proper density is contained. The sensor chip 5 is a monolithic semiconductor chip where a diffusion strain gauge 5b and an amplifier 5c are set on the upper surface. The diffusion strain gauge 5b is formed at a thin part 5 of the sensor chip 5. When an acceleration is applied to the acceleration sensor 1, the sensor chip 5 receives pressure via the silicon gel 8 inside the sensor mount 3. The diffusion strain gauge 5b senses the distortion at a thin part 5a and outputs an electrical signal in response to the pressure. The amplifier 5c amplifies the electrical signal from the diffusion strain gauge 5b and outputs the amplified detection voltage to the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acceleration sensor.

[0002]

2. Description of the Related Art Conventionally, an acceleration sensor for detecting acceleration by detecting a pressure change has been used. The present applicant has already proposed and applied for such an acceleration sensor. FIG. 4A shows a partially cutaway perspective view of the acceleration sensor 50. Further, FIG. 4B shows a cross-sectional view of the acceleration sensor 50 of FIG.

A cylindrical sensor mount 3 is mounted and fixed on the circuit board 2. A vent hole 4 is provided in a central portion of the circuit board 2 surrounded by the sensor mount 3. A C-type diaphragm-type semiconductor pressure-sensitive sensor chip (hereinafter, simply referred to as a sensor chip) 5 is mounted in the sensor mount 3 so as to close the ventilation hole 4.

The sensor chip 5 has a rectangular parallelepiped shape in which the bottom is hollowed out in a trapezoidal shape, and the hollowed out portion is a thin portion 5a. A diffusion strain gauge 5b made of a silicon semiconductor (PN junction element) is formed on the thin portion 5a, and the strain in the thin portion 5a (that is, the pressure applied to the thin portion 5a) is sensed and An electric signal corresponding to the pressure is output as a detection signal. The hollowed-out portion below the thin portion 5 a of the sensor chip 5 is open to the outside air through the ventilation hole 4.

The sensor chip 5 is electrically connected to the printed pattern 7 formed on the circuit board 2 via the bonding wire 6. Further, a silicon gel 8 having an appropriate density is housed in the sensor mount 3 so as to cover the sensor chip 5.

An amplifier 9 is provided on the circuit board 2. The amplifier 9 is housed in a general surface mount type package, and is electrically connected to the print pattern 7. Further, an external terminal 11 is electrically connected to the amplifier 9 via a print pattern 10. Amplifier 9
Is designed to input a detection signal from the sensor chip 5, amplify and process the detection signal, and output it to the outside through the print pattern 10 and the external terminal 11.

When acceleration is applied to the acceleration sensor 50 thus constructed, the sensor chip 5 immediately receives pressure through the silicon gel 8 inside the sensor mount 3. Then, the thin portion 5a of the sensor chip 5 bends and vibrates. At this time, since the hollowed-out portion of the sensor chip 5 is open to the outside air through the ventilation hole 4,
Even if the volume of the hollow portion changes due to bending and vibration of the thin portion 5a, no pressure is applied from the hollow portion to the thin portion 5a side. The diffusion strain gauge 5b formed on the thin portion 5a senses bending and vibration of the thin portion 5a,
An electric signal corresponding to the bending of the thin portion 5a and the distortion due to vibration (that is, the pressure applied to the thin portion 5a) is output as a detection signal.

That is, the detection signal of the diffusion strain gauge 5b (sensor chip 5) corresponds to the acceleration applied to the acceleration sensor 50. The detection signal of the sensor chip 5 is the bonding wire 6 and the print pattern 7.
Is output to the amplifier 9 via. Further, the detection signal is amplified by the amplifier 9 and output to the outside via the print pattern 10 and the external terminal 11.

[0009]

There is a demand for miniaturization of the acceleration sensor 50 as described above, but in recent years, the demand level has been increasing. However, since the circuit board 2 needs an area for mounting the amplifier 9 in addition to an area for mounting and fixing the sensor mount 3, the area of the circuit board 2 cannot be reduced, and the acceleration is increased. This has hindered the miniaturization of the sensor 50.

The present invention has been made to solve the above problems, and an object thereof is to provide an acceleration sensor which can be miniaturized.

[0011]

According to a first aspect of the present invention, there is provided a case, an acceleration transmission medium housed in the case, an acceleration applied from the outside, the acceleration transmission medium being disposed in the case. A pressure sensitive element integrally formed with a piezoelectric transducer for detecting the acceleration detected through a medium and converting the detected acceleration into an electric signal; and an amplifying element for amplifying the electric signal from the piezoelectric transducer. Use as a summary.

The invention according to a second aspect is characterized in that the pressure-sensitive element is a monolithic type in which the piezoelectric transducer and the amplifying element are simultaneously formed on a semiconductor chip. A third aspect of the invention is summarized as the pressure-sensitive element is a hybrid type in which at least one of the piezoelectric converter and the amplification element is arranged on a semiconductor chip.

[0013]

Therefore, according to the first aspect of the present invention, the pressure-sensitive element is a piezoelectric element that detects an externally applied acceleration through the acceleration transmission medium and converts the detected acceleration into an electric signal. The transducer and the amplification element that amplifies the electric signal from the piezoelectric transducer are integrally formed.

According to the second aspect of the present invention, the pressure-sensitive element is a monolithic type, and since the piezoelectric transducer and the amplification element are simultaneously formed on the semiconductor chip, an increase in manufacturing steps is suppressed. be able to.

According to the third aspect of the invention, the pressure sensitive element is a hybrid type, and at least one of the piezoelectric converter and the amplifying element is arranged on the semiconductor chip. As for the arrangement, a piezoelectric transducer is formed on a semiconductor chip, and another semiconductor chip having an amplifying element formed thereon is bonded to the semiconductor chip to form a pressure sensitive element. Further, an amplifying element is formed on the semiconductor chip, and another semiconductor chip having a piezoelectric converter formed thereon is bonded to the semiconductor chip to form a pressure sensitive element. Further, on the sensor chip, a semiconductor chip having a piezoelectric transducer formed thereon and a semiconductor chip having an amplification element formed thereon are bonded together to form a pressure sensitive element. With these configurations, the combination of the piezoelectric converter and the amplification element is optional.

[0016]

【Example】

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, the same components as those of the conventional structure are designated by the same reference numerals and detailed description thereof will be omitted. FIG. 1A shows a partially cutaway perspective view of the acceleration sensor 1 of this embodiment. In addition, in FIG.
The sectional view on the AA line of (a) is shown.

The sensor chip 5 is a monolithic semiconductor chip in which a diffusion strain gauge 5b and an amplifier 5c are simultaneously formed on the upper surface thereof. Therefore, the sensor chip 5
The manufacturing process of 1 does not increase significantly compared with the manufacturing process of the conventional sensor chip 5. The amplifier 5c has the same function as the conventional amplifier 9, amplifies the detection signal output from the diffusion strain gauge 5b, and outputs the detection signal to the outside via the bonding wire 6, the print pattern 7, and the external terminal 11. To do.

FIG. 2 shows an equivalent circuit of the sensor chip 5. The diffusion strain gauge 5b of the sensor chip 5 is composed of strain resistors R1 to R4 connected in a bridge. The power supply voltage Vcc is applied to the node between the strain resistors R1 and R2, and the node between the strain resistors R3 and R4 is grounded. The node between the strain resistors R2 and R4 and the strain resistors R1 and R4
A node between the nodes 3 and 3 is connected to the amplifier 5c. The amplifier 5c has a voltage of the node of the distortion resistors R2 and R4 and a resistor R1,
The detection voltage V is amplified by amplifying the difference with the voltage of the node between R3.
Output as _OUT .

When pressure is applied to the sensor chip 5, the resistance values of the strain resistors R1 to R4 change, and a detection signal corresponding to the pressure applied to the diffusion strain gauge 5b is output. Amplifier 5
c amplifies the detection signal and outputs it as a detection voltage V _OUT .

As described above, according to this embodiment, the amplifier 5c is simultaneously formed on the sensor chip 5 together with the diffusion strain gauge 5b, and the detection signal output from the diffusion strain gauge 5b is generated by the amplifier 5c. It was amplified and output to the outside.

As a result, since it is not necessary to provide only the sensor chip 5 and the amplifier 9 on the circuit board 2, the area of the circuit board 2 can be made smaller than in the conventional case, and the acceleration sensor 1 can be miniaturized. can do. Further, since the diffusion strain gauge 5b and the amplifier 5c are integrally formed on the sensor chip 5 and the conventional work of mounting the amplifier 9 on the circuit board 2 is not required, the manufacturing cost can be reduced accordingly. (Second Embodiment) Next, a second embodiment of the present invention will be described with reference to the drawings.

In this embodiment, the same components as those in the first embodiment are designated by the same reference numerals and detailed description thereof will be omitted. FIG. 3A shows an acceleration sensor 20 of this embodiment.
The partially cutaway perspective view of FIG. In addition, in FIG.
The BB sectional drawing of (a) is shown.

A substrate 21 of the acceleration sensor 20 has a commercially available metal package (for example, TO standardized by JEDEC).
-3, TO-5, etc.) are used. An external terminal 22 penetrates through the substrate 21, and the external terminal 22 is insulated and fixed to the substrate 21 by a glass hermetic seal 23. An amplifier 5c is integrally formed with the diffusion strain gauge 5b on the sensor chip 5 provided on the substrate 21 as in the first embodiment. The external terminal 22 is electrically connected to the sensor chip 5 by the bonding wire 6.

The upper end of the sensor mount 3 mounted and fixed on the substrate 21 is covered with a cap 24 to prevent dust and dirt from entering the silicon gel 8. Cap 24
A ventilation hole 25 is provided in the approximate center of the silicone gel 8
Is exposed to the outside air through the ventilation hole 25.

As described above, according to this embodiment, since the sensor chip 5 can be mounted on the substrate 21 of the commercially available package, the acceleration sensor 20 can be downsized as in the first embodiment. Further, since the substrate 21 is a commercially available package, when the acceleration sensor 20 is used, the acceleration sensor 20 can be attached by using a commercially available socket corresponding to the package, as in a normal electronic component. Can handle.

The present invention can be embodied as follows. 1) The mass of the silicon gel 8 is adjusted by diffusing particles of an appropriate material (metal, ceramics, synthetic resin, etc.) having an appropriate mass into the silicon gel 8 to adjust the detection sensitivity of the acceleration sensor 1. To do.

2) The sensor chip 5 may have any shape as long as it is a diaphragm type, and may have an E-shaped cross section, for example. 3) The upper end of the sensor mount 3 of the first embodiment is covered with the cap 24 as in the second embodiment. With this configuration, it is possible to prevent dust and dirt from entering the silicon gel 8 as in the embodiment.

4) In each of the above embodiments, the sensor chip 5 is a hybrid type semiconductor chip. That is, the diffusion strain gauge 5b is formed on the semiconductor chip, and another semiconductor chip having the amplifier 5c formed thereon is bonded to the semiconductor chip to form the sensor chip 5. Further, the amplifier 5c is built in the semiconductor chip, and another semiconductor chip having the diffusion strain gauge 5b formed thereon is bonded to the semiconductor chip to form the sensor chip 5. Further, on the sensor chip 5, a semiconductor chip having a diffusion strain gauge 5b and a semiconductor chip having an amplifier 5c are bonded and configured. With these configurations, the combination of the diffusion strain gauge 5b and the amplifier 5c becomes optional.

Although the respective embodiments of the present invention have been described above, technical ideas other than the claims which can be understood from the respective embodiments will be described below together with their effects. B) In the acceleration sensor according to claim 1, the case 3 is mounted and fixed on the substrate 2, and the substrate 2 has a plurality of external terminals 11 for outputting the electric signal amplified by the amplifying element 5c to the outside. Acceleration sensor provided with. With this configuration, the acceleration sensor can be easily connected.

(B) In the acceleration sensor according to claim 1, the case 3 is mounted and fixed on the substrate 21, and the substrate 21 penetrates the substrate 21 and the insulator 23.
A plurality of external terminals 2 that are fixed to the substrate 21 by means of and output the electric signal amplified by the amplifying element 5c to the outside.
An acceleration sensor provided with 2. With this configuration, the same effect as the above-mentioned a) can be obtained.

In the present specification, members relating to the constitution of the invention are defined as follows. a) A piezoelectric transducer is an element that senses bending and a signal and outputs an electric signal according to the distortion due to the bending and vibration, and includes a bulk element and a piezoelectric element in addition to a diffusion strain gauge.

B) The pressure-sensitive element is an element for detecting an applied pressure and converting the pressure into an electric signal, and in addition to a C-type diaphragm type semiconductor pressure-sensitive sensor chip, a diaphragm using a thin film gauge. Type sensor chips and diaphragm type capacitive pressure sensitive sensor chips are also included.

C) The acceleration transmission medium means a gel composition, and in addition to silicon gel, polymer gel containing one material selected from the group consisting of polyvinyl alcohol, polyurethane, polyether and polyester as a main component. It also includes an acrylic acid derivative and the like.

[0035]

As described in detail above, according to the present invention, it is possible to provide an acceleration sensor which can be miniaturized.

[Brief description of drawings]

1A is a partially cutaway perspective view of an acceleration sensor according to a first embodiment of the present invention, and FIG. 1B is a sectional view taken along line AA of FIG.

FIG. 2 is a block circuit diagram of an acceleration sensor according to the first embodiment.

3A is a partially cutaway perspective view of the acceleration sensor of the second embodiment, and FIG. 3B is a sectional view taken along line BB of FIG.

4A is a partially cutaway perspective view showing a conventional acceleration sensor, and FIG. 4B is a sectional view taken along the line D-D of FIG. 4A.

[Explanation of symbols]

2 ... Circuit board as substrate, 3 ... Sensor mount as case, 8 ... Silicon gel as acceleration transmission medium,
5 ... Diaphragm type semiconductor pressure sensitive sensor chip as pressure sensitive element, 5b ... Diffusion strain gauge as piezoelectric transducer, 5c
... amplifier as amplification element, 11 ... external terminal, 21 ... substrate, 22 ... external terminal, 23 ... glass hermetic seal as insulator.

Front page continuation (72) Inventor Kenichi Kinoshita No. 1 Noda, Toyota, Oguchi-machi, Niwa-gun, Aichi Prefecture Tokai Rika Electric Co., Ltd.

Claims (3)

[Claims] 1. A case (3), an acceleration transmission medium (8) housed in the case (3), and the case (3).
A piezoelectric transducer (5b) which is arranged inside and which detects an externally applied acceleration through the acceleration transmission medium (8) and converts the detected acceleration into an electric signal, and the piezoelectric transducer (5b). An acceleration sensor comprising: a pressure-sensitive element (5) integrally formed with an amplification element (5c) for amplifying the electric signal of. 2. The acceleration sensor according to claim 1, wherein the pressure sensitive element (5) is a monolithic type in which the piezoelectric transducer (5b) and the amplification element (5c) are built on a semiconductor chip. 3. The acceleration according to claim 1, wherein the pressure sensitive element (5) is a hybrid type in which at least one of the piezoelectric transducer (5b) and the amplification element (5c) is arranged on a semiconductor chip. Sensor.