An investigation on micro-via drilling on ceramic substrates by a picosecond laser

Special ceramics are getting more attention as substrate materials for IC packaging, LED packaging and PC board. Certain ceramic materials have high mechanical strength, low thermal expansion, high electric barrier and high thermal conductivity. These properties are idea for devices pf designated purpose such as high power IC, LED and fast communication IC. For these applications via holes for signal and power connection are necessary. As the devices are miniaturized the sizes of via holes are forced to be reduced even down to tens of micrometers, thus, the drilling task can only be performed by laser. However, the ceramics are brittle and during the laser machining process the thermal stress and shock may easily cause defect in the heat affected zone. Also the debris generated in the thermal fusion-solidation process deteriorate the integrity of the via hole such as the in-out diameter, taper angle and roughness around the via. There is a trade-off between machining efficiency and quality has to be tuned. In this paper we apply a 12 picosecond 1033 nm wavelength laser to study the photo material interaction for drilling micro via in three thin plates of AlN, Al2O3 and Fe2O3 ceramic. AlN and Al2O3 are good heat dissipation material and Fe2O3 is idea for electronic noise immunity. A detail report of the results including machining parameters and inspection of via holes will be presented.