Tin whiskers and other packaging problems

[Pat Pending]

So what was wrong with Lockfits that isn't a problem with the smaller TO92 

Later ones weren't so bad. But the earlier ones had no provision for bonding the quite large surface area of the leadouts to the packaging, was molded in two seperate opperations, was made from a hygroscopic plastic, and the transistor chip and interconnections were completely inbedded in the case material. The TO-92's had smaller (mostly) round leadouts that were sintered to provide bonding to the epoxy, were made from a more resin rich epoxy and were encapsulated in one opperation with a "void" for the silicon to live in. the lockfit was designed to provide the consumer electronics industry with a cheap easy to use package that would simplify assembly and speed up production, which it did, but the packaging was just that, cheap. BTW the ones in old hybrid TVs hardly ever used to fail, the valves kept them warm and dry! And post 75 were the improved ones. TFK Types were the ones to have, they hardly ever failed.
The gent I was talking to said that Mullard only ever made one good transistor package the glass SO2. Regards. Andy.