Papers by Author: Lin Wang

Abstract: High voltage 4H-SiC Ti Schottky junction barrier schottky (JBS) diode with breakdown voltage of 1700 V and forward current of 5 A has been fabricated. A low reverse leakage current below 3.8×10^-5 A/cm² at the bias voltage of -1700 V has been obtained. The forward on-state current was 5 A at V_F = 1.7 V and 15.8 A at V_F = 3 V. The active area is 1.5 mm × 1.5 mm. The turn-on voltage is about 0.9 V. The on-state resistance is 3.08 mΩ·cm². The doping and thickness of the N-type drift layer and the device structure have been performed by numerical simulations. The SiC JBS devices have been fabricated and the processes were in detail. The die was assembled in a TO-220 package. The thickness of the N- epilayer is 17 µm, and the doping concentration is 3.2 × 10¹⁵ cm⁻³. The number of floating guard p-rings was chosen to be 25, the distance between the rings was chosen to be 0.7 µm ~ 1.3 µm and the width of the p-rings is 2.5 µm. We use the PECVD Si_xN_y/SiO₂ as the passivation dielectric and a non photosensitive polyamide as the passivation in the end. The reverse recovery current I_r was 1.26A and the reverse recovery time T_rr was 26ns when the diode was switched from 5A forward current to a reverse voltage of 700V. The reverse recovery electric charge Q_rr of 16nC was obtained.

Abstract: A heated sprue device for ceramic injection moulding was used to research the defects in injection-moulded technical ceramics. By use of the heated sprue device, the problem of sprue solidification was resolved and the density of the injection moulding specimens was increased while the defects eliminated. The influence of the processing parameters on the defects of the injection molding specimens was investigated in detail by X-ray radiography camera and photograph. It turns that the sprue solidification time has much influence on the defects in injection-moulded technical ceramics. Reasons causing the results above were also analyzed. Based on the research, bars of 20mm in diameter without macroscopic defects and turbine blade of fine property with Si3N4/SiC(w) materials were prepared by injection moulding.

Abstract: According to the heat transmission theory, in the aid of computer, the temperature distribution in the cylinder cavity was calculated. The temperature of the mould has much influence on the time for the injection material’s temperature of the cavity center to drop to the injection material softening temperature. The influence of the processing parameters on the density of the injection molding specimens was also investigated. It turns that the injection molding specimens’ density changes little with the increase of injection temperature and pressure, but changes a lot with the increase of holding pressure time.