Re: DeSoldering 4 layer pcbs

[TQuiroz]

I usually use a heat gun, but how to use it will depend whether I want to save the component, the board, or both. If the board is multilayer and must be saved, I suggest preheating it at about 50C for a whole day. This will remove any moisture that FR-4 substrates tend to absorb when not used for long periods. Otherwise, suddenly heating the board will cause the moisture trapped in the inner FR-4 layers to expand rapidly, risking damaging the inner copper traces and vias. This is very obvious when inspecting the vias with a good magnifier. In a damaged board, the walls of the "barrel" in a via will be cracked.
If I only care about the component, then concentrating the heat on it will eventually remove it. Works like a charm. Components such as plastic connectors will require close monitoring, applying the heat on the solder side.
For smaller components such as surface mount parts I suggest a small butane torch.
My two cents.

Tony