Yuichi Uchida

CO2 laser drilling of printed wiring boards and development of in-process monitoring system

In this paper, CO2 laser drilling process for printed wiring board and the application to the in-process monitoring of the via hole quality are described. The process of CO2 laser drilling was investigated on the basis of high speed photograph, the light emission and thermal conduction. It was found that the temperature of the decomposed epoxy resin suddenly increased when the smear thickness become less than 2μm. Based on this analysis, a simple in-process monitoring technique was developed to estimate the smear feature by detecting the light emission using a photo sensor. The removing process of the smear by KrF excimer laser was also investigated on the basis of the spectrum of the light emission and the reflected excimer laser. The electric contact was accomplished by excimer laser removal the smear.