Laser soldering and inspection of fine pitch electronic components

The increasing miniaturisation of integrated circuits has resulted in devices with lead spacings as small as 0.008 ''. Laser soldering has the potential to overcome many of the problems encountered with these devices by conventional soldering technologies. Nd:YAG laser soldering of a 224-lead ceramic chip onto a FR4 circuit board is described, using experimental design to optimise the laser parameters for soldering. In order to improve solder joint quality and repeatability, a rigorous thermal analysis is undertaken using a finite element model to investigate the temperature rise variations between the joints. Thermocouple measurements are made in real time of the laser soldering process to confirm the finite element model predictions.