Steve wrote:
> --- In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@i...> wrote:
>
>>Steve wrote:
>>
>>>--- In Homebrew_PCBs@yahoogroups.com, Russell Shaw <rjshaw@i...> wrote:
>
>>>>Why do you need ∗any∗ coating on the pcb?
>>>
>>>Exposed conductors mean they are exposed to humid or dusty air, and
>>>the surface of the fiberglass substrate will build up contaminants and
>>>humidity.
>>
>>You could put the pcb in a sealed container with dry nitrogen
>>or normal air with moisture-absorbing gel.
>
> I was hoping for something that would allow repair and that would not
> require hermetically sealed pressure tested enclosures. Otherwise
> those are not bad suggestions.
>
> If you are wondering why I say pressure tested, the first time it
> ships by air it's got to stand more than a few PSI. That means a lid
> 2x4 inches at, say, 10psi air pressure in an unpressurized hold has to
> stand up to about 36 pounds forcing it open. I'm just shy of sea level.
With a couple of extra screws thru the center, the pressure would be
less problem.
On the next design, the high impedance circuit could be confined to
a small circuit board in a box, with a lead or pins plugging in to
the main pcb.