[AR] Re: LEO radiation shielding
- From: Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Thu, 05 Dec 2019 22:23:43 +0100
Am 05.12.2019 um 21:25 schrieb Allen Newcomb:
Avoid ball grid array packages. You'll have thousands of thermal cycles
and the solder balls will crack first, sometimes in less than a year.
Besides, the balls are almost always no-lead nowadays.
( MPAe people had a procedure to leach off the "wrong" coating
and the reapply a solder coat with the "proper" alloy.)
That also goes for LCC ( as in Leadless Chip Carrier ) packages.
They have no "give".
Ceramic Quad Flat Package have elastic leads and a heavy package.
Glue the case to PCB other wise you will get fatique breaks
at the package/pin interface.
( we had that as a fault for "early" Rosetta hardware after accel table
tests :-)
you get obscure errors as the breaks tend to touch and give
contact but show microfonic behaviour.
check: take a needle and scratch along the legs of a side.
the good ones "pling", the broken legs sound different "flat".
Uwe
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