Process parameter optimization of selective soldering

The topic of this paper refers to selective miniwave soldering. Experiments with a commercially available machine were made to determine the optimal values of the soldering parameters. The experiments were designed with choosing a multilayered, FR4-type, mixed assembly printed circuit board (PCB), and a plug connector, with 112 pins, arrayed in five rows. During soldering, the solder miniwave was moved along the pin rows, and the challenge was to avoid solder bridges between the pins with small pitch, while obtaining perfect and void-free joints. It was found that the proper settings of preheating could significantly decrease the number of defects, and the solder bridging could be eliminated by using the machine's wave-lowering (pull-down) function at the end of the pin rows.