Application of Spark Sintering to Preparation of Zn-50Sn-Al2O3/Cu Joints for AC-Low Voltage Fuse Elements Without Lead

摘要

After the casting and cold drawing of fuse alloys, the joint between fuse alloys and Cu has been soldered using their parts for fabrication of AC-low voltage elements used in electric power line, which means to complex fabrication processes. As case study for the power saving, the Zn-50mass% Sn-8vol% Al2O3 and Cu was directly joined using their powders by spark sintering, for development of Pb-free fuse elements, which led to the keep of initial microstructural state because of the un-melting without soldering. The sintering of their powders showed a low sinter-ability because of the large difference in their melting points, which meant the difficulty in application of spark sintering to the fabrication of their joints. However, the joints of Zn-Sn-Al2O3 fuse alloy and Cu connectors were prepared successfully by controlling the maximum holding temperature of 433-473 K. The joints were sintered at the solid state of 433 K, showed a little of reaction area at the interface between the fuse alloy and Cu. In contrast, the joints with high relative density which were sintered at the liquid state, showed much amount of reaction area at the interface. The temperature dependence of specific resistivity, thermal conductivity and specific heat was measured for electrical and thermal calculations. The joint sintered at the solid state showed the close values in their properties to the solidified alloy as the reference. Both the melt and un-melt down performance for AC-low voltage fuse elements could be satisfied on the joints of fuse alloy and Cu sintered at the solid state, which resulted in the same performance shown in the standard alloys by complex fabrication processes consisting of casting and soldering as previously manufacturing method.