After the components have been mounted and the populated PCB is tested, conformal coating is used, which is basically a guy with a tin of goo and a brush. The goo is generously brushed over the all the components and the entire pcb. Once hardened, it is designed to prevent outgassing and provide some resistance to vibration shock.
Actually, here is the way I learned it...
I was told that conformal coating's main function was to prevent shorts by floating debris. It covers all contacts, conductors, everything.. Think of all the tiny flakes of aluminum about the size of a grain of salt, that start floaing all over the place once you vibrate and/or reach zero G... falling between the pins of modern IC's.. Conformal coating prevents that.
They told me that it does not prevent outgassing. (or at least it does not count as a method to reduce outgassing). I agree on vibration and shock, but over here, that process (uses the same material, just denser) is called "staking". It globs things like capacitors with tiny wires to the board... This is one step then before the "coating"...
Also, resistors are soldered to the board with a smooth bend in the lead so that on thermal expansion and contraction, the leads can bend without stressing the part. Just lots and lots of deails... Etc.
Bob WB4APR