Selective soldering pallets allow the soldering of plated through hole (PTH) components to dual sided mixed technology assemblies while protecting solder side surface mount devices (SMD). These pallets have machined pockets to clear for components and shield the heat and solder from thermally sensitive or non-glued parts.
In some cases, there can be as many as 5 or more different depths of component pockets on the same pallet. The solder apertures are the areas that will expose your PTH leads to solder.
These apertures have a wall that presses against the circuit board to control the area that is exposed to the solder. Machined into the fixture are a series of details cut into the bottom surface that are engineered to promote solder flow to all the PTH areas.
Although this type of fixture solves many problems it’s very important that the PCB layout follows guidelines to allow adequate space between the PTH and surface mounted devices when selective soldering is being considered.