What are the pitfalls of soldering a board with a heating element from a 3d printer?

Question

3D printers

All the time I solder smd components with a hairdryer and solder paste, which must first be warmed up so that it spreads over the pads in a dosed manner. what problems can arise with the board itself if it is placed on a heating element from a 3d printer, for example, mk2b? taking into account the fact that it is possible to control the heating temperature through the controller
And is it possible to heat this element so that the flux evaporates and a clear solder is formed without damaging the chips on the board and frizz?

Answer 1

the paste does not "spread" during heating, the correct application is determined only by its amount for each particular pad.
the flux should not evaporate "separately" - its task is to spread and remove oxides exactly during the melting and the actual soldering process. if everything is warmed up too early, then a variant is possible when the active fraction drains / evaporates and only liquefied feces remain in the form of tin gruel. You can estimate the "correct" heating time by taking the average of the soldering thermal profiles for any SMD components.
similarly with the fiberglass itself - simple options are not intended for constant background heating. +135 or +150 degrees mentioned in places is not the operating temperature, but the border at which deterioration and deterioration of resins is already guaranteed. it's just that these deteriorations fit into the guests / ipc standards