Jim Levie wrote:

On Wed, 09 Feb 2005 08:21:33 -0800, Ed Angell wrote:


Sorry for the OT post, but I don't know a better group of knowledgeable
folks to ask.

As long as a triac is run within it's published temperature limits, is there
any shortening of their life due to running warm ??


Yes. The lifetime of a semiconductor device is directly related to its
operating (junction) temperature. The cause of eventual failure (assuming
operation within the envelope) is a result of migration of material
within the junction, which is exponential with temperature as I recall.

I think that you've oversimplifed the situation. I don't
think you will find much difference in lifetimes between
a semiconductor running at 20 deg C and one running at
80 deg C. Not today with modern parts. As long as the
part is working with within it's current and voltage
safe operating area and within it's temperature range,
you should not expect more failures than if it were
running at 20 deg C.

Bob Pease, probably the world's greatest authority on
analog IC design wrote some good stuff on this subject
years ago. Unfortunately, I can't find it on the web.
As best as I can recall, his position was that the
standard lifetime derating curves for temperature
that the military and aerospace companies use were
in error and lifetime stays pretty much linear until
you exceed a certain temp.

Take the temperature above the specifications and all
bets are off. As another poster suggested, I suspect
extreme temperature cycling with plastic packages will
reduce lifetimes as well.

Whether the reduction in lifetime is of concern depends on how hot the
device runs, how close to rated limits it is used, and what transients it
will be exposed to.