The microstructure and performance of micro drills coated with Cr, Cr(2)N, and CrWCN thin films for applying to drill the PCB (printed circuit board) at high rpm (400 krpm) were systematically investigated by means of AFM, TEM, nano indentation and scratch test in this study. The results of properties evaluation for these coatings on the tungsten drill samples revealed that the doping of W accompanied with pursing C(2)H(2) gas on the Cr(2)N coating effectively increases the hardness of Cr(2)N film from 8 GPa to 25 GPa and decreases the frictional coefficient from 0.35 to 0.25. In addition, when these three thin films were applied on the on-line test of drilling the PCB for 24,000 holes, the CrWCN thin film shows the best wear resistance among these three thin films, presenting the minimum flank wear and 4-5 times longer tool life than the uncoated samples. Therefore, the CrWCN thin film is suggested to be a prominent material for protective coatings according to its excellent wear resistance and adhesive capability. (C) 2009 Elsevier B.V. All rights reserved.