On the possibility of microwelding with laser beams^asterisk

We define microwelds as having fusion zone dimensions of <100 μm. At such small dimensions the required laser irradiance to produce melting is at or above conventional estimates of the irradiance required to produce drilling. The question thus arises if such small microwelds can be made via laser processes. A theoretical criterion defining the threshold pulse energy and beam intensity required for melt displacement (necessary for penetration-mode welding or drilling) is proposed. The results of numerical simulation present dependences of the threshold pulse energy and beam intensity as functions of laser pulse duration and beam radius. Experimental verification of the proposed criterion is described and a comparison of theoretical predictions and measurements is presented.