Abstract: This paper introduces a versatile and robust packaged GM pressure sensor suitable for mass production by using silicon pressure resistance sensors fabricated by MEMS (micro electro mechanical systems) technology combined with intelligent integrated signal conditioning technology. Temperature calibration of the sensor's zero and full scale through intelligent conditioning technology enables high-accuracy measurements over a wide temperature range and is suitable for mass production.
0 Preface
The continuous improvement of today's car performance is due to the continuous development of automotive electronics. A representative core component is the sensor. The sensor converts various physical signals into electrical signals to transmit the specific state of the vehicle to the electronic control unit for vehicle control. As a key component of automotive electronics, today's electronic technology is booming. In the 2000 automotive electronics technology review, Fleming, the US automotive sensor authority, pointed out the bright future of MEMS technology in the field of automotive sensors. A diffusion silicon pressure sensor based on MEMS technology and intelligent signal conditioning is designed to cope with the pressure detection of automotive pressure systems.
1 sensor principle and package design
In order to convert the pressure signal into an electrical signal, the strain principle is applied, and the Wheatstone detection bridge is fabricated on the single crystal silicon wafer by MEMS technology. The monocrystalline silicon wafer is made into a sensitive component that integrates stress sensitivity and power conversion. As shown in Figure 1.
Figure 1 sensitive components
When the silicon chip is subjected to external stress, the bridge arm resistance of the silicon strain bridge will change, generally in the Wheatstone bridge detection mode. as shown in picture 2.
Figure 2 Wheatstone Bridge
Its output voltage is expressed as vo = KAR / R (Rl = such as = R3 = R4, ΔR1 = ΔR3 = ΔR2 = ΔR4).
Since the change in resistance is directly related to the stress P, then:
Where: Vo is the output voltage, mV; S is the sensitivity, mV/V/Pa; P is the external force or stress, Pa; VB is the bridge pressure, VOS is the zero output, mV.
A single silicon chip can only perform signal conversion independently as part of a detection unit, so a specific package must be available for pressure detection. The silicon chip of Figure 2 is electrostatically sealed with a PYREX glass ring.
The PYREX glass ring acts as a mechanically fixed support elastic sensor for the silicon chip and insulates the silicon chip from the package, while the hole of the PYREX glass ring just becomes the reference pressure cavity and electrode lead cavity of the sensor. Its structure is shown in Figure 3.
Figure 3 sensitive component package
The sensitive core of Figure 3 is sealed onto the metal threaded base to form a pressure-measuring front end, as shown in Figure 4.
Figure 4 installable pressure measurement front end
This packaging technology can carry a pressure of at least 15 MPa and can withstand a pressure of 100 MPa if specially treated.
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