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 ??

Thanks for the time to answer this question.

Ed Angell

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 ??

snipped

I've no hard data, but I sure think it's the way to bet.

The thermal expansion/contraction of repeated on-off cycles, tending to
make something "crack", coupled with the fact that chemical reactions
take place faster at higher temperatures, would make me think that lower
temperatures would make for longer life.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"

There is a rule of thumb, that an increase of 10 degrees C, halves the
life. To determine the mean time to failure, they generally run
accelerated life tests by testing at elevated temperatures.

That said, it may not make any significant difference to you. Back in
the 60's the better transistors had a mean time to failure of about
1500 years ( based obviously on accelerated life tests ). If your
triacs had a mean time to failure of 1500 years based on a junction
temperature of say 30 degrees C, then running them at a junction
temperature of 70 degrees might reduce the mtf to 90 years. Just
remember the temp limit is the junction temp, not the ambient temp.

Dan

"Ed Angell" edangellatcomcastdotnet wrote in message
...
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 ??

I can't give you a scientific answer, but I used to run thousands of
triacs in outdoor traffic control boxes in south Florida. We seldom had a
failure that could not be explained by lightning or a short circuit.

Vaughn

On Wed, 9 Feb 2005 08:21:33 -0800, the renowned "Ed Angell"
edangellatcomcastdotnet 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 ??

Proabably. Running right at the limits will shorten the life. But
thermal cycling can really kill power semiconductors, especially the
cheap-a** TO-220 type. The bond between die and leadframe/heatsink
fails, causing the semiconductor die itself to overheat. I've seen
failures in the range of xE4 cycles where x is a single digit.

Also, if the die is already very hot, a surge of current that it might
otherwise survive can heat the die enough to destroy it.


Thanks for the time to answer this question.

Ed Angell



Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Dan, would you please contact me off the NG ??
Thanks,
Ed Angell

wrote in message
ups.com...
There is a rule of thumb, that an increase of 10 degrees C, halves the
life. To determine the mean time to failure, they generally run
accelerated life tests by testing at elevated temperatures.

That said, it may not make any significant difference to you. Back in
the 60's the better transistors had a mean time to failure of about
1500 years ( based obviously on accelerated life tests ). If your
triacs had a mean time to failure of 1500 years based on a junction
temperature of say 30 degrees C, then running them at a junction
temperature of 70 degrees might reduce the mtf to 90 years. Just
remember the temp limit is the junction temp, not the ambient temp.

Dan

Jeff Wisnia wrote:
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 ??

I think it is the internal temp of transistors etc that kills them.
External temp is an indirect measure.

So 'peak' internal temp kills em. average prolly don't care.

On Wed, 09 Feb 2005 17:01:14 GMT, "Vaughn Simon"
wrote:


"Ed Angell" edangellatcomcastdotnet wrote in message
...
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 ??

I can't give you a scientific answer, but I used to run thousands of
triacs in outdoor traffic control boxes in south Florida. We seldom had a
failure that could not be explained by lightning or a short circuit.

Triacs used in traffic control loadswitchs are very conservatively
applied, or at least they were in the '70s. Lamp loads are tough
because of the arc that occurs when a lamp burns out. Most of the
triacs were at least 20 amp parts and some were bigger.

Lightning in South Florida was a problem. We got some controllers
back from Dade County that looked like they'd been dipped in a
volcano! I think some of the 8-phase dual-ring controllers I
designed back then are still in service in MN.

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.

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.

--
The instructions said to use Windows 98 or better, so I installed RedHat.

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.

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.



My brain is swiss cheese these days but if I remember correctly, aren't
Triacs and SCRs a device such that the higher the temp, the lower the
internal resistance? I seem to remember something about people putting
them in parallel and a vicious cycle starting where one would conduct a
higher percentage of the load, heat a little more and drop internal
resistance, therefore heat more until it blows.

Just curoius...one of these days I have to switch an inductive load on a
forging machine somehow. Output is about 6000 amps at 3 volts. Makes
the theoretical (no loss) input about 75 amps at 240 V. The problem is
that things are so highly inductive, any digital switching would have to
be far greater than the 75 amp rating. That gets spendy. If you could
gang the darned things, the cost would be MUCH better.

Any ideas on a cheap but digitally controlled solution? In the old
days, one might use mercury relays. Regular relays will fry and lock.
Of course there are ways to suck up the initial inductive load but I'd
rather keep things simple.


Koz

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.

On Wed, 09 Feb 2005 14:20:55 -0800, Koz
wrote:



Just curoius...one of these days I have to switch an inductive load on a
forging machine somehow. Output is about 6000 amps at 3 volts. Makes
the theoretical (no loss) input about 75 amps at 240 V. The problem is
that things are so highly inductive, any digital switching would have to
be far greater than the 75 amp rating. That gets spendy. If you could
gang the darned things, the cost would be MUCH better.

Any ideas on a cheap but digitally controlled solution? In the old
days, one might use mercury relays. Regular relays will fry and lock.
Of course there are ways to suck up the initial inductive load but I'd
rather keep things simple.

Inductive loads don't have an initial current surge. The problem is
a voltage surge when you try to turn them off, unless you turn them
off at an instant when current is passing thru zero. Back-to-back
SCR's inherently do this and are suitable for switching inductive AC
loads. You can buy these as "solid state switch" modules. These
guys have modules with ratings up to 125 amps and 660 VAC:
http://www.crouzet-usa.com/catalog/gordos/gnssr.pdf

"Koz" wrote in message
...
|
| Just curoius...one of these days I have to switch an inductive load on a
| forging machine somehow. Output is about 6000 amps at 3 volts. Makes
| the theoretical (no loss) input about 75 amps at 240 V. The problem is
| that things are so highly inductive, any digital switching would have to
| be far greater than the 75 amp rating. That gets spendy. If you could
| gang the darned things, the cost would be MUCH better.
|
| Any ideas on a cheap but digitally controlled solution? In the old
| days, one might use mercury relays. Regular relays will fry and lock.
| Of course there are ways to suck up the initial inductive load but I'd
| rather keep things simple.
|
|
| Koz

I've seen "hockey puck" IGBT's and SCR's in the several thousand amp
range. Haven't seen much on ebay but there are on the surplus market.
Several hundred bucks a pop, compared to several thousand bucks a pop new.
IIRC, the voltage range was in the thousands, though, and wouldn't know what
the forward drop would be.
There are lighter duty devices ranging from minimal amperage to several
hundred. Look for IGBT and SCR's on ebay. To switch AC fully with SCR's
you need two back to back, which is essentially what a TRIAC is.

On Wed, 09 Feb 2005 14:39:57 -0800, Jim Stewart wrote:

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.

As far as I know the characteristics of materials hasn't recently,
although manufacturing processes have. Modern parts are better but the
effects of temperature on material migration is solely a materials
property. Testing that I was involved in some 15 years ago showed
measureable changes in device characteristics after relatively short runs
at the upper limit for a number of devices. Extrapolating that out results
in the prediction of earlier failure as compared to the same device
running at the lower end of the temperature range.

I used to have a number of papers from other studies done on a wide
variety of devices that supports what physics says should happen.

That's not to say that the manufacture's data is wrong. Many devices have
a published lifetime vs temperature spec and on average those devices will
run according to that curve. But that wasn't the question the OP asked.

--
The instructions said to use Windows 98 or better, so I installed RedHat.

In article ,
Jeff Wisnia wrote:
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 ??

snipped

I've no hard data, but I sure think it's the way to bet.

The thermal expansion/contraction of repeated on-off cycles, tending to
make something "crack", coupled with the fact that chemical reactions
take place faster at higher temperatures, would make me think that lower
temperatures would make for longer life.

In particular, there are existing cracks in chips resulting from
the dicing process (breaking apart the silicon wafer into all the
individual chips).

If the crack is curved so it points back to the edge -- no
problems. However, if it is pointed towards the active area, then it
will grow with repeated temperature cycling (note that staying warm is
better than shooting up and down frequently). The action is like that of
a crack in your windshield. It may sit there all summer as a nice short
little crack, but once winter comes, and you start blowing heated air on
a frozen windshield, that crack will grow.

One of the things which makes transistors and ICs made to mil
specs so expensive relative to commercial ones is that each chip is
microscopically examined, and those with cracks which are pointing
towards an active area are rejected (perhaps to wind up in commercial
chips with the same basic part number.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

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 ??

Thanks for the time to answer this question.

Ed Angell


Warm is ok. Make sure the heat sink is kept clean and if air was supplied,
the air source clean also.

Hot is not ok.

Martin

--
Martin Eastburn, Barbara Eastburn
@ home at Lion's Lair with our computer
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

In article , DoN. Nichols says...

The thermal expansion/contraction of repeated on-off cycles, tending to
make something "crack", coupled with the fact that chemical reactions
take place faster at higher temperatures, would make me think that lower
temperatures would make for longer life.

In particular, there are existing cracks in chips resulting from
the dicing process (breaking apart the silicon wafer into all the
individual chips).

Another issue is that the die are typically wire-bonded to the
head it is on. The bonding wires are relatively fragile and
the bond between the die metalization and the wire itself is
a source of failure. Again this is exacerbated by thermal
cycling issues.

When I wire bond stuff, I use a puff of gas from a hand-held
gun to apply force to the bonds. Any ones that are weak will
detach at this point and ones that pass this test will not
fail under repeated thermal cycling.

Many commercial ICs have the bonds encapsulated - but the combination
of Si die, aluminum wire, and polymer goop never have exactly the
same thermal expansion.

Jim

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

Jim Levie wrote:

On Wed, 09 Feb 2005 14:39:57 -0800, Jim Stewart wrote:


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.


As far as I know the characteristics of materials hasn't recently,
although manufacturing processes have. Modern parts are better but the
effects of temperature on material migration is solely a materials
property. Testing that I was involved in some 15 years ago showed
measureable changes in device characteristics after relatively short runs
at the upper limit for a number of devices. Extrapolating that out results
in the prediction of earlier failure as compared to the same device
running at the lower end of the temperature range.

I used to have a number of papers from other studies done on a wide
variety of devices that supports what physics says should happen.

That's not to say that the manufacture's data is wrong. Many devices have
a published lifetime vs temperature spec and on average those devices will
run according to that curve. But that wasn't the question the OP asked.

I went back and reread your post and I don't
disagree in principle. The failure rate may
indeed be exponential with temperature. The
*practical* issue is "where are we on the knee
of the curve"? If, at 80 deg c, we are still
way down on the flat part of the curve, the
temperature effects on reliability are very
small-to-nonexistant. I maintain that this
is the case with modern power semiconductors
in decent metal-and-glass packages, operated
within their specifications.

I would have no problem designing, selling, and
standing behind a warranty on a product whose
parts are operating within the manufacturer's
specifications, even if it meant running a power
semiconductor at 80 or 100 deg C, as long as
I knew that worst-case, the value would never
be exceeded.

On Thu, 10 Feb 2005 10:34:32 -0800, the renowned Jim Stewart
wrote:

I would have no problem designing, selling, and
standing behind a warranty on a product whose
parts are operating within the manufacturer's
specifications, even if it meant running a power
semiconductor at 80 or 100 deg C, as long as
I knew that worst-case, the value would never
be exceeded.

Triacs don't tend to have very good reliability in a fairly large
class of applications. The temperature is but a small factor (in a
decent design). Bigger factors (aside from the thermal cycling that I
already mentioned) are current and voltage surges. Ordinary fuses are
not fast enough to protect fragile semicondutors the way they are
often derated (eg. using a 10A or 8A triac at 5A). Ordinary MOVs may
be not sufficient to clamp voltage transients at non-damaging levels,
unles the semiconductors are rated at much higher than normal voltage.
They are really quite delicate compared to a hefty contact, and what's
often worse, they typically fail "on". Without massive overrating (eg.
using a 40A/1000V triac at 4A/240V, which costs a lot more money) it
may not be possible to protect them adequately at all.

It would be nice if a semiconductor manufacturer were to address the
issue by coming out with relatively inexpensive, yet rugged large-die
parts in low-cost packaging, but it's not happened yet that I know of.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

I know I vastly oversimplified things in my reply. If you want to
learn a lot more google on Arrhenius.

Dan
Jim Stewart wrote:
Jim Levie wrote:

On Wed, 09 Feb 2005 14:39:57 -0800, Jim Stewart wrote:


I think that you've oversimplifed the situation.

I went back and reread your post and I don't
disagree in principle. The failure rate may
indeed be exponential with temperature. The
*practical* issue is "where are we on the knee
of the curve"? If, at 80 deg c, we are still
way down on the flat part of the curve, the
temperature effects on reliability are very
small-to-nonexistant. I maintain that this
is the case with modern power semiconductors
in decent metal-and-glass packages, operated
within their specifications.

I would have no problem designing, selling, and
standing behind a warranty on a product whose
parts are operating within the manufacturer's
specifications, even if it meant running a power
semiconductor at 80 or 100 deg C, as long as
I knew that worst-case, the value would never
be exceeded.

wrote:
I know I vastly oversimplified things in my reply. If you want to
learn a lot more google on Arrhenius.

I'm aware of Arrhenius.


Dan
Jim Stewart wrote:

Jim Levie wrote:


On Wed, 09 Feb 2005 14:39:57 -0800, Jim Stewart wrote:



I think that you've oversimplifed the situation.

I went back and reread your post and I don't
disagree in principle. The failure rate may
indeed be exponential with temperature. The
*practical* issue is "where are we on the knee
of the curve"? If, at 80 deg c, we are still
way down on the flat part of the curve, the
temperature effects on reliability are very
small-to-nonexistant. I maintain that this
is the case with modern power semiconductors
in decent metal-and-glass packages, operated
within their specifications.

I would have no problem designing, selling, and
standing behind a warranty on a product whose
parts are operating within the manufacturer's
specifications, even if it meant running a power
semiconductor at 80 or 100 deg C, as long as
I knew that worst-case, the value would never
be exceeded.

On Thu, 10 Feb 2005 10:34:32 -0800, Jim Stewart wrote:
I went back and reread your post and I don't
disagree in principle. The failure rate may
indeed be exponential with temperature. The
*practical* issue is "where are we on the knee
of the curve"? If, at 80 deg c, we are still
way down on the flat part of the curve, the
temperature effects on reliability are very
small-to-nonexistant. I maintain that this
is the case with modern power semiconductors
in decent metal-and-glass packages, operated
within their specifications.

Yeah, the question is what the vendor's data specs are. Some vendors
publish lifetime vs temperature data on their parts that will tell you
right off if your design is in a safe area. Now if the vendors specs on
lifetime were for 20C and the part had a max temp rating of 100C you could
run into a lifetime issue running at 80-90C continuously. It just all
tempeds on how the vendor has rated/tested the part.

--
The instructions said to use Windows 98 or better, so I installed RedHat.