Tin whiskers and other packaging problems

[ppppenguin]

I don't have the reference to hand but there was an interesting failure mode in line output transistors such as the BU105. You had to control the switch off very carefully to avoid SOAR problems. If you switched them off too quickly there was a problem that I don't remember very clearly. I think it was excess carriers trapped in the very large collector region. If you switched them too slowly then you got the usual SOAR problems.