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It has been found (from missions like the Long Duration Exposure Facility, LDEF) that some metals, especially tin and cadmium in solders, used in space-electronics assemblies, form crystal whiskers over time, which lead to short circuits in the circuitry when the whiskers reach other components or tracks.

What mitigation procedures are in place to prevent whisker growth?

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    $\begingroup$ ...other than epoxy? $\endgroup$
    – SF.
    Commented Feb 8, 2016 at 2:03
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    $\begingroup$ I don't have an answer, but NASA has quite a bit of information on the topic at nepp.nasa.gov/whisker $\endgroup$
    – Tristan
    Commented Mar 20, 2017 at 21:43
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    $\begingroup$ @Tristan the CSA has a bit of information as well: youtu.be/94-puZit3DA $\endgroup$
    – uhoh
    Commented Mar 21, 2017 at 3:12

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Often, electrical systems prone to whisker growth are coated with a 2-3 millimeter layer of polymer (called a conformal coat); this not only prevents growth of whiskers, but also prevents any loose electrical contacts from creating short circuits. There are many benefits that are associated with doing this. Another likely cause of crystalline whisker growth may be residual stress of the circuit after the solder has been electroplated; thus, several strategies, such as using dip-soldering, or hot-oil reflow, are used to release the tension.

One of the better strategies for mitigating tin-whisker growth, however, is to simply avoid tin-zinc solders; this, however, may not be the most viable option as replacements aren't exactly the same.

More detail can be found on this site.

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    $\begingroup$ Conformal coating provide tons of other advantages though, like resistance to atomic oxygen in orbit and water vapor before launch. $\endgroup$
    – Schlusstein
    Commented Mar 22, 2017 at 0:33
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    $\begingroup$ @rebeccazh If you can find the time to add some links confirming these methods are actually used to prevent whisker growth, this could be a good answer. Please consider editing. Welcome to the site $\endgroup$
    – OrangePeel52
    Commented Mar 22, 2017 at 13:55
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    $\begingroup$ To reiterate the last point, often another mitigation is simply to not use these materials. For instance, device legs will often be de-tinned. $\endgroup$
    – Paul Norridge
    Commented Mar 22, 2017 at 21:26
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Conformal coatings mostly, just like on Earth. A thin polymer layer impedes problematic whiskers principally by confining them to the inside of the coating.

Theses links confirm that NASA has a large interest in the study of conformal coatings and likes to use them. The first one includes pictures of whiskers that formed under coatings towards the end. https://nepp.nasa.gov/whisker/reference/tech_papers/2006-Woodrow-Conformal-Coating-PartII.pdf
This is a presentation about from NASA about the hazards of whiskers and how they are mitigated.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070021449.pdf
This one just lists some companies that NASA uses for confomal coatings. Possibly of interest.
http://blog.paryleneconformalcoating.com/blog/nasa-conformal-coating-companies

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    $\begingroup$ +1 for research, but please note that link-only answers are discouraged, partly due to link-rot risks. (Example of answer recently deleted for this reason and the explanation) You're probably partially covered here by adding several, and ones that have managed to stay alive for a decade. But if you can include a bit of relevant information in the form of block quotes or images, that would greatly improve the quality of your answer. $\endgroup$
    – uhoh
    Commented Mar 21, 2017 at 3:58
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    $\begingroup$ This could be a good answer if some explanation and excerpts from the links were added. Please consider expanding this answer. $\endgroup$
    – OrangePeel52
    Commented Mar 22, 2017 at 13:57

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