After reflow, a technician takes the board and manually solders any PTH (plated through-hole) components. In a larger production facility, the soldering of through-hole components may be done using a technique known as wave soldering, where the board is passed over a standing wave of molten solder, which adheres to component leads and any exposed metal on the board.
Because of the high mix of different designs and quantities at SparkFun, we’ve found it’s easier to push as much as possible to SMD (surface mount devices) and hand solder any PTH components. We use the Hakko FX-888D soldering iron on the production floor. They work fabulously, but the lower cost Atten 937b is great for entry level soldering.