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Subject: Re: Surface finish for space

Date: 05/02/00 at 12:30 AM
Posted by: John W. Childers
E-mail: jwchilders@goldengategraphics.com
Message Posted:

In Reply to: Surface finish for space posted by Brendon Parise on 05/01/00 at 10:32 PM:

Off and on over the years we've designed some boards for space exploration experiments conducted by CU/LASP (http://lasp.colorado.edu/) I can't answer your question on surface finishes, but could shed some light on out-gassing and another subject: vibration. I've also queried CU/LASP and invited them to respond.

OUT-GASSING:

For boards to be exposed to the vacuum of outer space, CU/LASP had us leave off all solder mask and silkscreen. Those boards were reflow finished (tin-lead plate), as that was quite a few years ago.

For boards going up in the space shuttle and not exposed to vacuum, out-gassing was not a consideration and so silkscreen and solder mask were allowed.

VIBRATION:

The intense vibration associated with rocket launched space vehicles can crack the plating in the vias (feed-thoughs) in printed circuit boards, thus causing opens. For the space exploration experiments (not space shuttle) CU/LASP had us make the vias large enough to feed wires through them, and make sure there were no vias underneath components. Assembly techinicians at CU/LASP would then stuff the vias with bare wires and solder both ends. This made feed-throughs that remain reliable under extreme vibration.

For the more recent space shuttle boards, we weren't required to do this, and I'm not sure why, as that is also a high vibration environment.


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