[Elecraft] CK722 transistor

[Alan Bloom]

John Adams-2 wrote:
> 
> I peeled the blue metal cover off and some gooey stuff, and there was a
> smaller, silver metal cased transistor inside. 

I think the gooey stuff was heat sink compound.   Before the planar
process was invented for making transistors and ICs, the junctions were
formed by diffusing dopants from opposite sides of the semiconductor
chip.  That is, the chip itself was the base and the collector and
emitter were diffused in from opposite sides.

The chip was suspended inside the case in "mid air", held up by the
three leads.  Since air is a lousy thermal conductor, they would fill up
the inside of the case with heat sink compound to conduct the heat from
the chip to the case.

With modern transistors, both the emitter and base are diffused from the
same side so the chip can be laid flat on the case header.  (That's why
the collector is almost always connected to the case of a metal-can
transistor.)  Among other advantages, that method gives excellent
thermal conduction to the case.

Al N1AL