Development of Zr-Ti-N Coatings for Micro Drills for Machining of PCBs

Abstract

A group of Zr-Ti-N coatings was prepared and studied to access their potential as a protective layer for micro drills to obtain cutting tool wear improvement. The coatings were grown using an industrial-scale four-target closed-field unbalanced magnetron sputtering ion plating system, employing one Ti and three Zr targets working in residual N2 atmosphere. To achieve Zr-Ti-N coatings with varying Ti doping content, the current applied to the Ti target was subjected to change from 0A to 3.6A while those to the Zr targets were kept constant. The coatings were characterized using GDOES, XRD, SEM, Vickers microhardness tester, scratch tester and Rockwell C indentation tester. Evaluation of wear improvement by Zr-Ti-N coatings for microdrills was conducted by machining of FR4 print circuit boards. It was found that the coatings with 16.5 at.% Ti doping content showed the highest microhardness and wear improvement for microdrills. Wear of microdrills with this coating could be reduced by a factor of two as compared with traditional TiN coated ones.