Funny, the simplest thing to do there, and relatively cheap, is to lacquer the whole device after it's soldered. This is done on military grade hardware - or even tougher conformal coating.
This is a deceptively complex topic (as I learned over the years). For example, a whisker that does not penetrate the coating will either buckle and curl-up under the film or grow laterally under it. With fine pitch components having pin-to-pin gaps in the range of 0.25 mm, a short between pins can happen in just a few weeks.
Conformal coating is useful for other reasons, but, ultimately, it isn’t a solution for tin whiskers.
Back in the day I even looked into using specially formulated epoxy encasement. What starts happening there is that the coefficient of thermal expansion differential between The epoxy, board and components can cause all kinds of failures...and it still does not stop tin whisker growth or buckling.
I might be diving into some industrial work soon that does not benefit from RoHS exemptions in this domain. This is one of the important cards in my kanban board...likely a rabbit hole that will not be pleasant to navigate.
I took a quick look myself. Here's a note from Maxim with interesting data:
https://www.maximintegrated.com/en/design/technical-document...
I've used pretty much all the conformal coatings they list in this article. What they don't go into is buckling under the coating, which can short adjacent pins in fine pitch chips.
I truly hate this problem. I has wasted more of my time over the years than anything else. RoHS is, in my opinion, a very misguided directive. It's a perfect example of when politics gets ahead of reason and fear-mongering wins over science. If we are not careful we are on track to do something similar with climate change.
That helps avoid tin whiskers, but those aren't the only problem with lead free solder. It doesn't flow as easily as tin-lead, so dry joints are more common. It's relatively brittle, so it's more susceptible to vibration and thermal fatigue. Melting point is higher so components are more likely to be damaged during soldering.
Military hardware is exempt from RoHS for good reason.