11 Jul
2005
11 Jul
'05
12:50 p.m.
>>>> "Tony" == Tony Duell <ard
at p850ug1.demon.co.uk> writes:
> I have cleaned them with board cleaner and checked
the switches
> for operation. Some of the IC pins are getting rusty. Are the IC's
> sealed very well or can moisture get in the chips
Tony> In theory they're hermetically sealed, in practice it is
Tony> possible for contaminants to get into plastic packages
Tony> (particularly).
Plastic packages are NOT hermetically sealed, which is why
metal/ceramic packages are the traditional package for Milspec
applications. I'm not sure if they still are always used there, but
certainly you're unlikely to find plastic packages in, say,
spaceflight applications. Plastic keeps crud out quite well, and
casual exposure to moisture shouldn't be any problem. After all, PCBs
are washed after assembly to take off the flux. But hermetic -- no.
paul