[amsat-bb] Re: Space Grade Soldering ?
bruninga at usna.edu
Tue Jan 29 15:50:51 PST 2008
> 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
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
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