Carbon nanotubes on flattened tin alloy spheres in a Ball Grid Array (BGA) for cold cathode applications

Carbon Nanotube (CNT) is an excellent field emission source, and is widely explored in applications like sensors, AFM probes, cathodes for Carbon Nanotube Field Emission Display (CNT-FED), and cathodes for microwave device. The requirements on field emission characteristics for these applications vary, but it is often necessary to attach CNT onto a metal electrode surface. When CNT is grown directly on a metal surface by conventional CVD processes, the poor adhesion of CNT to the metal surface and, in some cases, low electrical conductivity leave room for improvements. We hot-bond CVD grown CNT with Ball Grid Array (BGA) of 0.5 mm diameter Tin alloy (Sn63/Pb37) spheres placed in pre-designated positions on a metal surface to form a cold cathode for microwave device applications. The forming temperature is about 200degC. This method not only provides an easy way to make CNT-metal cathode, it also greatly improve the field emission characteristics of the original CNT. The turn on electric field (at J= 1 muA/cm²) is 1.56 V/mum with the field enhancement factor beta reaching 2203. The DeltaJ/DeltaE is around 1.09 M.