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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
