[time-nuts] Space stuff (was: The ultraAtomic clock for home)

[Attila Kinali]

On Fri, 7 Apr 2017 21:30:18 -0700
jimlux <jimlux at earthlink.net> wrote:

> > No doubt.  I suspect also that space flight hardware doesn't use blobs
> > on plain FR4.  While one problem with the blob technique is the
> > permeability of the blob material, another is the permeability of the
> > substrate -- and FR4 is pretty bad in this regard.
> 
> We fly a fair amount of FR4 - sure, we might do some coupons or get 
> source traceability. And it depends on the mission - a billion dollar 
> mission to Europa is different than others.

Yes, it depends a lot on what the project is about. We have done a
project where whe choose PCBs from Eurocircuits because they offered
better quality over price than some space qualified manufacturer
and the mission was not critical (only flying up a space station.
If it breaks, you can send up a replacement part). Even a lot of
the chips on the board were just industrial grade plastic packages.

On others, any plastic was a total no go (optics in space, aka any
outgasing will condensate on the lens) and everything had to be
super-duper-space-quality (aka a simple 2N2222 suddenly costs 100€
or more and comes with a few binders full of documentation.. not
to forget the ITAR declaration).

Also, which techniques can be used in a specific mission highly depend
on the contractor who does the assembly. Some have no problem with
BGA packages, while others aren't going to solder any package where
they cannot visually inspect every solder joint (e.g. like QFN).

				Attila Kinali

-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
                 -- Miss Matheson, The Diamond Age, Neil Stephenson