These heaters allow the user to have the rework area at a higher temperature than the remainder of the PCB thereby reducing the likelihood of board warpage during the process of reflow. A typical lead-free, hot air source thermal profile is seen below.
First, the bottom side heating begins to warm up the board with one temperature (typically 160 or 170C) being in the rework location and another, typically 150 C, being at other areas of the board. During the time this temperature is applied to the bottom side of the board the nozzle temperature begins to climb during the “ramp” period of the reflow profile.