The oven step that melts solder paste and bonds SMD parts to the PCB.
How it looks
Drawing: a process that happens at the assembler
A typical lead-free reflow profile: the board rides a conveyor through oven zones and its temperature follows this curve.
How it works
Where it fits
Comes right after pick-and-place; paste was printed through a stencil. Small batches can use a hot plate instead of an oven. Hidden joints like a BGA's are made here and cannot be touched up later.