Interesting post by Utima Thule at DIYaudio:
http://www.diyaudio.com/forums/soli...ng-mt200-power-transistors-2.html#post5333091
"Just IMHO I don't miss the MT200 packages.
One can get roughly 6 pcs of equivalent TO-3P devices for the same price as 4 pcs of MT200, inside it the silicon substrate is still attached onto a TO-3P metal base which in turn is attached to a larger MT200 base, paying ~2 €$£ more for extra metal and plastic huh?
Borrowing a picture from this link:
2SA1215 2SC2921, identify genuine and fake
View attachment 1115295 View attachment 1115296
What I think is going on here is that by probably soldering the TO-3P metal base to a larger
metal base with 2 screws there is good thermal conductivity to the larger base which provides
more area to the insulator with 2 screws for better contact for lower overall thermal resistance.
It would be very interesting to find out if there are types that employ the same die, perhaps have a cross reference table.
People have probably seen where a bar is used over single screw packages to provide more
even pressure for lower thermal resistance. Two screws from the MT200 mount could be used
with a bar or channel to provide pressure on a replacement TO-3P device.