How is their rated current measured, i think if a transistor can do 5 amps at 60 volts it should be able to do 25 amps at 12v, am i wrong?
Not necessarily, depends on the silicon design. Current density a big factor in
transistor, whether or not the junction can handle that much current. Same is
true for bond wires and pads, what they were designed for.
And as prior discussion safe area considerations, both thermal and electrical.
Regards, Dana.