Laser Drilling of Very Small Electronic Via Holes in Common Circuit Board Materials

As microelectronics continue to shrink, it is becoming increasingly difficult and expensive to mechanically drill very small via holes (<0·010 in.). Using lasers and optical technology, it is possible to drill any material. Thin circuit board materials of various compositions were investigated as candidates for laser drilling using a 100 watt CO2 laser. Laser variables were pulse frequency, duty cycle, and number of pulses (total energy delivered). Delivered energy seems to be the most critical parameter, and the optimal holes were drilled within a narrow energy band, although there was much data scatter. The best laser drilled holes were of lower quality than that obtainable with mechanical drilling. Photographs of the best holes in all materials are included.