10 Jun
2009
10 Jun
'09
6 p.m.
Allison wrote:
Its rare to see the top epoxy pop off but it happens. usually the part
either fails
or is most often thermally intermittent.
TMK, only Fairchild made those packages, although they had JEDEC numbers
(TO-105 and TO-106).
I kind of liked them somehow, perhaps a nostalgia thing. (Never seen them fail
mechanically, myself.) In all sorts of commercial equipment around the mid-60's
to 70's. 2N3638 was very popular.
FYI: Older DEC machines like straight-8 and friends
used a lot fo the ceramic
epoxy parts similar to the 2n3638 and 2n3563.
Those are ceramic headers with
a block of epoxy covering the die and are prone to popping the epoxy and the
symptom works when cold or mechanically intermittent.
Is that visually apparent, or is that an internal fault? If I
identified a bad transistor and removed it from a FLIP-CHIP, would it
be difficult to set up something with an oscilloscope to watch some
output then tap on the transistor to watch the trace "change" to
verify mechanical fragility?