Cr - Si Thin Film Preparation And Development Of Ultrahigh Pressure Sensor

Diesel engine electronically controlled high pressure common rail fuel injection system comprises an electric control system and a fuel supply system. And the electronic control system consists of sensors, electronic control unit (ECU) and actuator. The rail sensor are the core part of common rail system, while the pressure sensor is the core one in many sensors. The diesel engine with common rail technology of Bosch company is advanced in the world, the fourth generation of electronic fuel injection pressure fuel injection system is developing. It is required pressure sensor works in about200MPa common rail oil pressure, so the researching of the ultra-high pressure sensor has a very important significance.Alloy thin film piezoresistive sensor is selected as rail pressure sensor in this paper, and the sensitive unit of pressure sensor is Cr-Si-Ni-Ti piezoresistive film. Cr-Si piezoresistive films were prepared on Al2O3ceramic substrates by magnetron sputtering. The effects of sputtering parameters and annealing on electrical properties of the piezoresistive films were investigated. The results reveal that the optimal sputtering parameters are sputtering pressure being2Pa, RF sputtering power being150W, target-substrate distance being7cm, sputtering time being50minute. The thin film deposited at room temperature is amorphous, then annealing at different temperatures, with the annealing temperatures increasing, Temperature coefficient of resistance (TCR) of the films increase steeply, the gauge factor increases at first and then goes down with, the room temperature resistivity of the film decrease steeply, the microstructure of the flims annealed at temperature lower than600℃are also amorphous. The good properties of the thin flim, such as the TCR of-1.1ppm/℃and GF of2.2, and electrical resistivity of0.662Ω·cm are obtained when the films is annealed at300℃. Excellent performance of the sensitive film as a material foundation for ultra-high pressure sensor research.Ultra-high pressure sensor prepared by sputtering and photolithography stripping process, using electronic beam evaporation deposited about10μm SiO2insulating layer on the surface of cylindrical stainless steel, then use the magnetron sputtering deposited about450nm graphical Cr-Si-Ni-Ti sensitive film on the insulating layer, and then deposited about200nm graphical gold electrode on the sensitive film, final deposited about500nm graphical SiNx protective film. The author has already sent three batch of more than20samples to DIAS automotive electronic system company limited of Shanghai Automotive Industry Corporation for evaluation test.