Tin whiskers and other packaging problems

[ppppenguin]

I've had TO18 transistors suffer an open circuit on occasion. From dim and distant memory they were mainly 2N706 ued on ex BBC video distribution amplifiers. I used to look after a lot of these and it was virtually a stock fault, after the electrolytics. There was often a bit of corrosion so I suspect it was damp storage in a previous life. Except that TO18 packages are meant to be watertight even if not fully hermetic.