Compensating technique of field-distorting error for the CO2 laser galvanometric scanning drilling machines

Laser galvanometric scanning system has been widely used in the laser drilling machines to form the microvias of high-density interconnected printed circuit boards (HDI PCBs). Although the galvanometric scanning system can increase the speed and efficiency of laser drilling process, it is usually associated with a field distortion error. The investigation discusses the field distortion error of a laser scanning system based on a CO2 laser drilling machine and provides a method for correcting this distortion error. The field distortion error is a random error in the laser galvanometric scanning system. This irregular error is usually corrected using pre-compensation methods that apply an error function. The paper gives a pre-compensation technique to correct the distortion error of scanning image, which using the two-dimensional (2D) Lagrangian polynomials modified the control commands of the galvanometric scanning system. The results in this study indicate that the compensation method effectively amended the field distortion and increased the accuracy of the positioning of the holes that were drilled using a laser galvanometric scanning drilling machine. The positioning errors of drilling holes have reduced from +/- 0.3 to +/- 0.05mm after error compensation. This pre-compensation method could be widely adopted in all galvanometric scanning system, such as pre-objective and post-objective scanning system. (c) 2006 Elsevier Ltd. All rights reserved.