Thin film AC ZnSxSe1-x:Mn EL
Conventional ZnS:Mn electroluminescence (EL) device has a good level of brightness but needs a high operating voltage. The best way to lower the operating voltage seemed to be by reducing the band gap of the host material and to achieve this, ZnSe had been proposed before. However, our experiments showed that when the ZnSe:Mn EL was operated at low voltages the brightness level and contrast ratio decreased, due to the yellowish coloration of the ZnSe film. The authors have developed a host material which combines both advantages; the high brightness level of ZnS, and the low operating voltage of ZnSe. A material with a band gap between those of ZnS (3.7 eV) and ZnSe (2.7 eV) was tested. By coevaporation of ZnS and ZnSe, a solid solution ZnSxSe1-xwas found in an evaporated film. By measuring the absorption edge and using X-ray techniques, we found that the band gap varied in proportion to the concentration of selenium. A thin film of ZnS0.4Se0.6EL sandwiched between Y2O3insulating layers can operate at a low voltage (120 V) with a high level of brightness (>100 fL at 1 KHz), with a very small upward voltage shift (10 V) during aging.
ac electroluminescence in thin‐film ZnSe : Mn
ac electroluminescence from thin films of Mn‐doped ZnSe, sandwiched between two insulating films, shows a hysteresis in light output versus applied voltage, similar to that observed in ZnS : Mn. We also find that the threshold voltage for light emission is approximately a factor of 2 smaller for ZnSe structures than for similarly prepared ZnS structures of identical dimensions.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.