KR20000072100A - Compact pressure sensor using diffuse thin film strain gauge - Google Patents

Abstract

PURPOSE: A small pressure sensor is provided to optimally design a sensing unit having an excellent sensitivity and an embedding type amplifier. CONSTITUTION: In a small pressure sensor by using a diffusive thin film type strain gauge(60), a sensing device is made up of a silicon single crystal of 4x3x1.7mm and a diaphragm deforming upon receiving pressure. A thin type semiconductor deformation rate gauge formed on a stainless diaphragm converts the pressure to an electric signal. An inputted power voltage is changed to a certain voltage in a power circuit. A bridge is supplied to the strain gauge through the power circuit. Herein, a pressure strain gauge generates an output voltage in proportion to the pressure.

Description

Compact Pressure Sensor Using Diffusion Thin Film Strain Gages {.}

The present invention is a thin-film electrical resistance strain gauge pressure sensor with excellent durability and reliability, and more specifically, with the development of thin film technology, it is possible to optimally determine the diaphragm gauge shape, the thickness and diameter of the diaphragm receiver plate, and the strain gauge. It consists of a Wheatstone bridge circuit to design a receiver having excellent sensitivity. The present invention also relates to the development of a thin film pressure sensor that can be actively used as an automatic control element by having environmental resistance and durability due to the design of an embedded amplifier.

In general, strain gages (strain gages) are used in the field of measurement of load, pressure, torque, and other actual stress as the use of the pressure drop effect that the resistance value changes as the strain is applied to the metal or semiconductor.

In addition, the pressure sensor is used to measure not only the hydraulic pressure of an automobile engine but also a high precision, especially for a wide range of pressures from low pressure to high pressure, such as general industrial pressure measurement.

The demand for sensors in each field is increasing rapidly as the electronic core technology, high function, and diversification of advanced core technologies are progressing all over the world, and according to the increase of sensor demand, developed countries have already classified the sensor technology development business into a high-tech business. In addition, by intensively supporting research and development, the technology level of sensors is further advanced, mass production is established, and low cost and miniaturization and smartization are realized.

According to this trend, the thin film type pressure sensor to be developed in the present invention is a method of integrating strain gauge Wheatstone bridge arrangement, deposition technology, and electronic technology for optimal design and excellent sensitivity of a receiver.

Therefore, the measurement accuracy is superior to that of the existing foil strain gauge and it is applicable to petrochemical industry and automobile industry.

As a result, when faced with the situation that domestic pressure sensor production technology remains at the basic level, the present invention provides not only domestic market protection but also unique design technology and manufacturing technology to enable export to foreign countries.

The conventional pressure sensor is an analog type, and its measuring accuracy is only 0.3%, so it is impossible to secure long-term stability and reliability for use in high pressure measurement.

Accordingly, the present invention has been made in view of the above-described conventional problems, and an object thereof is to provide an optimum design of a receiver having excellent sensitivity, an arrangement of a strain gage whistle bridge, and a design of an internal amplifier.

According to a feature of the present invention, the diaphragm strain gauge having a diaphragm pattern is directly bonded to a stainless steel diaphragm structure to change the pressure so that the optimal design and strain of the receiving part including the diaphragm under pressure are applied. Built-in amplifier design that integrates a gauge pressure sensor and a voltage amplifier.

1 is a cross-sectional view of a compact pressure sensor using a diffusion type thin film strain gauge of the present invention.

2 is a device design diagram of a compact pressure sensor using a diffusion type thin film strain gauge of the present invention;

Figure 3 is a pressure conversion block diagram of a compact pressure sensor using a diffusion thin film strain gauge of the present invention

4 is an arrangement of strain gauges of a compact pressure sensor using a diffusion type thin film strain gauge of the present invention.

5 is a circuit diagram of a built-in amplifier of a small pressure sensor using a diffusion thin film strain gauge of the present invention

<Explanation of symbols for the main parts of the drawings>

10: pressure introduction part 50: electrode contact part

20: strain diaphragm 60: strain gauge

30: Sio2 insulating film 70: protective film

40: Cu-Ni thin film

The pressure sensor using the thin-film strain gauge according to the present invention for achieving the above object is to develop a thin-film high-precision pressure sensor to deposit a constantan (Cu-Ni alloy) on the insulating film after depositing an insulating film (SiO ₂ ) on the stainless steel as a receiver .

Commonly used for remote control, automatic control, or pressure measurement is an electric resistance strain gauge type pressure sensor with excellent reconfiguration and reliability. In recent years, with the development of thin film technology, the diaphragm gauge shape is easily processed as required by the consumer, making it easier to design the pressure transducer and to have a better sensitivity than the conventional one.

It is difficult to determine the thickness and diameter of diaphragm receiving plate in addition to the diaphragm strain gauge in the design of the pressure-receiving part and structure. However, it is difficult to use the conventional method. Could get In addition, various coating works are performed to protect strain gauge circuits.

Constant diaphragm size and thin thickness increase pressure sensitivity but decrease the rated pressure range and maximum applied pressure. If the size of the piezoresistor on the diaphragm is large, the alignment between the resistor and the diaphragm is easy and the reproducibility is increased, but the pressure sensitivity is reduced.

On the other hand, four resistors are arranged in the form of a bridge in order to obtain a self-temperature compensation effect, and these resistors place the resistors within 50 µm from the edge of the diaphragm to facilitate double-sided matching.

Therefore, according to the above configuration, it is possible to produce a confinement part which is excellent up to a maximum measurement accuracy of 0.1% than the conventional one.

The built-in amplifier has an output of 0 ~ 5V so that it can be easily assembled for process control telemetry and central monitoring. In addition, the output of the Wheatstone Bridge circuit of the designed pressure-receiving section is set to OP Amp. The circuit design is designed to enable 100 times or more ultra-short amplification using a circuit and the like.

Therefore, by the above configuration, it can be widely used throughout the industry beyond the use of the conventional experimental measuring instrument.

EXAMPLE

Hereinafter, a preferred embodiment of the pressure sensor using the thin-film strain gauge according to the present invention constituting the configuration as follows.

1 is a cross-sectional view showing a structural diagram of a pressure sensor according to the present invention.

Figure 4 shows the arrangement of the strain gauges of the pressure sensor according to the present invention.

The receiver according to the present invention is made of a silicon single crystal having a size of about 4 × 3 × 1.7 mm, which is composed of a diaphragm 20 that deforms under pressure. It is selected in four places and becomes thermal diffusion (molecular bond). When an input is applied to the receiver, the resistance of the four places 60 increases and decreases, thereby obtaining a voltage signal proportional to the pressure change. However, this method requires a high-accuracy laser trimming of the thin film resistor to compensate for the temperature. The operating principle of the thin film type semiconductor pressure sensor is a thin film type semiconductor strain gauge formed on the stainless diaphragm phase 20 and receives the pressure to convert the pressure into an electrical signal. Thin-film strain gage is formed by inserting insulating film 30 on the surface of diaphragm, and two gauges are used for tensioning and two for compression. The strain is accurately detected. The strain element forms four sets of diaphragms and combines them into a Wheatstone bridge as shown in FIG. The grit G ₂ , G ₄ of the strain gauge produces a compressive strain, G ₁ , G ₃ generates a tensile strain, which is added to the Wheatstone bridge. In this way the pressure is converted from the strain gauge to the electrical output. That is, this is the same as G ₄ = Rg ₁ , G ₂ = Rg ₃ , G ₃ = Rg ₂ , and G ₁ = Rg ₄ in FIG. ₄ .

Four resistors were arranged in the form of a bridge in order to increase the pressure sensitivity and obtain a self-compensating effect. As the resistors 40 are located at the edges of the diaphragm, the pressure sensitivity is increased, but a matching error is likely to occur. Therefore, these resistors placed the resistors within 50 µm from the edge of the diaphragm to facilitate double-sided matching.

Diaphragm outer diameter 30mm, diaphragm inner diameter 2mm, diaphragm thickness 2.8mm, outer gauge width 3mm.

In the theoretical analysis, the thickness of diaphragm was the most influential factor in the strain generation of the pressure transducer.

5 is a circuit diagram of a built-in amplifier of a high-precision pressure sensor using a thin-film strain gauge of the present invention.

The input power supply voltage is stabilized and becomes a constant voltage in the power supply circuit, and the bridge is supplied to the strain gauge through the power supply circuit. At this time, the pressure strain gauge bonded to the receiver generates an output voltage proportional to the pressure. This voltage is amplified in the DC amplifier circuit and output from 0 to 5V from the voltage output circuit. After the heat treatment of the structural part of the pressure sensor, the stress concentration by machining was distributed. The pressure inlet was lengthened to measure the static pressure and assembled by screwing. In addition, an air leak hole was installed to facilitate the transmission of the measured fluid pressure.

As described above, the pressure sensor using the thin-film strain gauge according to the present invention has a wide range of pressure measurement ranges from low pressure to high pressure in an arrangement of a whistle bridge for optimal design and excellent sensitivity of the diaphragm self temperature compensation It is useful for high-precision pressure sensors such as general pressure measurement requiring precision, and the measurement accuracy is up to 0.1% or more. In addition, according to the design of the built-in amplifier, as shown in Figure 5 facilitated the automatic control throughout the industry.

With the development of high-precision pressure sensor, Korea's core technology can gain international competitiveness.

Claims (4)

The sensing element is made of silicon single crystal with a size of about 4 × 3 × 1.7mm, and the receiving part is composed of diaphragm that deforms under pressure. The input power supply voltage is stabilized and becomes constant voltage in the power supply circuit, and the bridge is supplied to the strain gauge through the power supply circuit. At this time, the pressure strain gauge attached to the receiver is a pressure sensor that generates an output voltage proportional to the pressure. A pressure sensor having a diaphragm outer diameter of 30 mm, a diaphragm inner diameter of 2 mm, a diaphragm thickness of 2.8 mm, and an outer gauge width of 3 mm selected in the method for selecting an optimum parameter. The diaphragm is formed of four pairs, and the combination is formed into a whistle bridge so that the grit G ₂ and G ₄ of the strain gauge generate a compressive strain, and G ₁ and G ₃ generate a tensile strain. Pressure sensor added to The pressure strain gauge adhered to the receiver produces an output voltage proportional to the pressure. Pressure sensor that amplifies this voltage in DC amplifier circuit and outputs 0 ~ 5V in voltage output circuit.