In response to Professor Plumbridge's contribution on tin pest, David Douthit has inquired further. I have forwarded his posting to Plumbridge, but I'll take a stab with my own answers, too.

1. The low-temperature (non-metallic) form of tin can be converted to the high (metallic) form by heating, but the damage is irreversible.
2. The tin pest phenomenon has not yet been studied long enough to allow charting. "Long enough" means decades, not months. Even slower than whiskers.
3. Similarly, predicting when (or if) a solder connection will fail due to tin pest is only a dream.

In fact, one question that I'd like to see addressed is the effect of size. Perhaps nucleation of tin pest is less likely for a tiny piece of tin (or high-tin alloy). By analogy, tiny droplets of liquid water are much easier to undercool without converting to ice (even to -40°C) than are larger volumes. The smaller surface area reduces the probability of nucleation.

Gordon Davy
Baltimore, MD
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410-993-7399



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