Localized etching of an insulator film coated on a copper wire using an atmospheric-pressure microplasma jet

Atmospheric-pressure microplasma jets (AP mu PJs) of Ar and Ar/O-2 gases were generated from the tip of a stainless steel surgical needle having outer and inner diameters of 0.4 and 0.2 mm, respectively, with a rf excitation of 13.56 MHz. The steel needle functions both as a powered electrode and a gas nozzle. The operating power is 1.2-6 W and the corresponding peak-to-peak voltage Vp.p. is about 1.5 kV. The AP mu PJ was applied to the localized etching of a polyamide-imide insulator film (thickness of 10 mu m) of a copper winding wire of 90 mu m diameter. The insulator film around the copper wire was completely removed by the irradiated plasma from a certain direction without fusing the wire. The removal time under the Ar AP mu PJ irradiation was only 3 s at a rf power of 4 W. Fluorescence microscopy and scanning electron microscope images reveal that good selectivity of the insulator film to the copper wire was achieved. In the case of Ar/O-2 AP mu PJ irradiation with an O-2 concentration of 10% or more, the removed copper surface was converted to copper monoxide CuO. (c) 2007 American Institute of Physics.