Electronic components aging

> 
> Avoid all-silicon current paths, and don't make direct connection between
> silicon and the outside world.

That means one thing: Plain Old Relays.  How long can sealed relays be expected to last, if we only fire it up occasionally?  Perhaps one in weeks.

On Tue, 15 Oct 2013 09:14:23 -0700, <edward.ming.lee@gmail.com> wrote:

>
>>
>> Avoid all-silicon current paths, and don't make direct connection  
>> between
>> silicon and the outside world.
>
> That means one thing: Plain Old Relays.  How long can sealed relays be  
> expected to last, if we only fire it up occasionally?  Perhaps one in  
> weeks.


Would designers of those Jupiter/Staurn satellites, etc jump in here? Give  
back to the community. Their stuff works ten years and upwords of 25  
years. Be great if they wrote a little history of the 'battles' one must  
embark on and the design philosophy required to overcome THOSE reliability  
obstacles.

On 10/15/2013 12:14 PM, edward.ming.lee@gmail.com wrote:
>
>>
>> Avoid all-silicon current paths, and don't make direct connection between
>> silicon and the outside world.
>
> That means one thing: Plain Old Relays.  How long can sealed relays be expected to last, if we only fire it up occasionally?  Perhaps one in weeks.
>

Nah, it's okay if you use protection on the I/O connectors, e.g. a 
series resistor and reverse-biased diodes to the supplies.  (Extra 
points for splitting the resistor and connectiong the diodes to the 
middle.)

Another good piece of JL advice is to consider using a couple of 
inverse-series depletion MOSFETs in place of the outermost resistor if 
you need it to be really bulletproof, e.g. a microammeter that will 
survive connection to the mains indefinitely.

Cheers

Phil Hobbs

-- 
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

> Would designers of those Jupiter/Staurn satellites, etc jump in here? Give  
> back to the community. Their stuff works ten years and upwords of 25  
> years. Be great if they wrote a little history of the 'battles' one must  
> embark on and the design philosophy required to overcome THOSE reliability  
> obstacles.

But they don't have the same enemies: Air and Water.  Space might be easier to deal with than mother Earth.

On Tue, 15 Oct 2013 12:50:39 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

>Speaking of high reliability... I think that it is often
>a somewhat neglected issue, so I start this thread as a
>mean to collect *practical* observations for people who
>care about long MTBF. In other words, "if I had to build
>a device which should last 50 years, I would... what?"

Be careful about using terms like MTBF unless you know the actual
definitions. Often it applies only to the bottom of the bathtub curve,
so infantile failures and wear-out are not considered. IOW, a part
with a 20 year MTBF could legitimately wear out in a few years (if it
even lasts the first month).  

>Resistors (if not overloaded): immortal

Not my experience. Resistors that get warm and resistors that are
stressed by high voltages (especially large DC voltage) often die
early. Surge damage (often limits are not specified) can occur on
stuff connected to the outside world (eg. induced currents from
lightning strikes). 

Resistors run at < 10% of rating and low voltage can pretty much be
ignored, IME. 

Trimpots and trimcaps are pretty good too (unless abused).

>Ceramic capacitors: as above

Pretty reliable, not as good as unstressed resistors. 

>Tantalum/nobium caps: ?

Don't know. The niobium oxide ones are claimed to use the new "no
burn" technology so presumably they'll spontaneously burst into flames
less frequently. 

>Electrolytic caps: disaster area

Expect to replace them after 5 years to 50 years, depending on how
much heat they see (internal and external) and other factors. But
they're quite _reliable_, they just have a limited and fairly
predictable life, like electromechanical relays. It's pretty much
impossible to make a mains-powered device of any usefulness without
electrolytic caps, and there is a lot of experience with their
reliability- eg. my HP 333A distortion meter is loaded with them
(maybe 50+) and it still works fine after maybe 40-45 years. 

Lack of electrolytic caps can lead to extreme design choices that may
negatively affect reliability. 

Inductors made from fine copper wire can be unreliable. 

>Transistors, diodes and ICs: the silicon die should not
>degrade, but how about the endurance of the resin?

If they're stressed, they can die early, sometimes very early.
Moisture can hurt them. Temperature cycling can make them die very
early- some early SSRs would die in months from thermal cycling if you
ran them at the worst-case duty cycle. Power semiconductors are almost
always stressed and can die early or later from thermal cycling. Parts
run at too high internal current densities can die from
electromigration, especially if hot. Radiation can kill them or cause
degradation or latch-up. Sometimes they're damaged in assembly and
expire later.  

LEDs and optocoupler LEDs degrade, especially if run hot and/or near
their current limits. I would guess photodiodes with plastic lenses
degrade if exposed to UV. Switches wear out, relays wear out. 


>At least some early Polish ICs had problems here:
>the thermal coefficient of the casing was not well-matched
>and power cycling finally broke the bonding wires.
>There were some moisture absorbtion problems, too.
>Is it still an issue?

Probably, but less so. 

>BGA: it can be expected that thermal cycling will
>eventually destroy the balls, as there are no "springs"
>to absorb thermal stresses. Gull wings are much better here.

RoHS solder probably doesn't help. 

>FR4: ?

Solder joints can be bad, can get cracked etc. 

>Soldering: the EU has done a lot in order to make
>the newer devices not very reliable as a consequence
>of the RoHS directive. I see nothing wrong with the
>old SnPb joints, the old boards look healthy.
>
>Conformal coating: ?

What does failure of conformal coating look like? 

>Wires: ?

Need to be treated carefully to avoid fatigue failures due to
vibration or other flexing, but very reliable if properly used. Crimp
connections are usually quite good if done right. 

Sensors are frequently a problem, mostly due to their operating
environment. 

Connectors, due to corrosion and abuse. Especially if they're soldered
to a board (and especially^2 if they're SMT and not mechanically
isolated from abuse). 

Anything on a panel or connected to the outside world in any way is an
opportunity for idiot-proofing to be tested. 


>Please add your comments.
>
>	Best regards, Piotr

On Tue, 15 Oct 2013 12:42:34 -0400, Spehro Pefhany
<speffSNIP@interlogDOTyou.knowwhat> wrote:

>On Tue, 15 Oct 2013 12:50:39 +0200, Piotr Wyderski
><peter.pan@neverland.mil> wrote:
>
>>Speaking of high reliability... I think that it is often
>>a somewhat neglected issue, so I start this thread as a
>>mean to collect *practical* observations for people who
>>care about long MTBF. In other words, "if I had to build
>>a device which should last 50 years, I would... what?"
>
>Be careful about using terms like MTBF unless you know the actual
>definitions. Often it applies only to the bottom of the bathtub curve,
>so infantile failures and wear-out are not considered. IOW, a part
>with a 20 year MTBF could legitimately wear out in a few years (if it
>even lasts the first month).  
>
>>Resistors (if not overloaded): immortal
>
>Not my experience. Resistors that get warm and resistors that are
>stressed by high voltages (especially large DC voltage) often die
>early. Surge damage (often limits are not specified) can occur on
>stuff connected to the outside world (eg. induced currents from
>lightning strikes). 
>
>Resistors run at < 10% of rating and low voltage can pretty much be
>ignored, IME. 
>
>Trimpots and trimcaps are pretty good too (unless abused).
>
>>Ceramic capacitors: as above
>
>Pretty reliable, not as good as unstressed resistors. 
>
>>Tantalum/nobium caps: ?
>
>Don't know. The niobium oxide ones are claimed to use the new "no
>burn" technology so presumably they'll spontaneously burst into flames
>less frequently. 

MnO2 tantalums are fine as long as peak current (ie, dv/dt) is limited. So,
don't use them to bypass power rails.


-- 

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

On Tue, 15 Oct 2013 09:34:27 -0700, <edward.ming.lee@gmail.com> wrote:

>
>> Would designers of those Jupiter/Staurn satellites, etc jump in here?  
>> Give
>> back to the community. Their stuff works ten years and upwords of 25
>> years. Be great if they wrote a little history of the 'battles' one must
>> embark on and the design philosophy required to overcome THOSE  
>> reliability
>> obstacles.
>
> But they don't have the same enemies: Air and Water.  Space might be  
> easier to deal with than mother Earth.
>


they do have vibration, extreme temperature ranges, many temperature  
cyclings, and probably radiation hardening [which can be considered simply  
as accelerated testing on earth?]

probably no water, smog, or dust though. Remember all those plastic IC's  
that died when shipped from Silicon Valley in the north flown down to Los  
Angeles in the south and the packages 'sucked' in smog during pressure  
change from descent of the airline carrier. Later the smog simply 'ate'  
the IC's up. Were those Fairchild's or National's first attempts at  
plastic packaging?

On Tue, 15 Oct 2013 09:14:23 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

>
>> 
>> Avoid all-silicon current paths, and don't make direct connection between
>> silicon and the outside world.
>
>That means one thing: Plain Old Relays.  How long can sealed relays be expected to last, if we only fire it up occasionally?  Perhaps one in weeks.

We've used zillions (well, maybe 20,000) Fujitsu sealed DPDT telecom
type relays, as cal bus and range switches. They are very reliable.


-- 

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation

On Tue, 15 Oct 2013 09:44:18 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>
>>Don't know. The niobium oxide ones are claimed to use the new "no
>>burn" technology so presumably they'll spontaneously burst into flames
>>less frequently. 
>
>MnO2 tantalums are fine as long as peak current (ie, dv/dt) is limited. So,
>don't use them to bypass power rails.

They're okay for bypassing power rails if you have a local regulator
that limits current (and if you derate the voltage). 

My opinion on capacitors:
- Definitely avoid electrolytics
- Tantalums are, at *best*, dubious.
- Ceramics don't die, but they do vary with temp, voltage and age.

I have some old equipment with them and none are toast (my Tek 475, 
whereas the electrolytics are all dried up), but that's just one case.

The main hazards are excessive voltage, and current spikes; they will be 
more reliable under conditions where this is controlled.  For instance, 
using 16 to 25V rated caps on a 5V rail, and supplying each subcircuit 
from a current limiter (since a small bypass cap looks like a grain of 
sand against a heavy source, even if that source is current limited). 
Tantalums have also been made with internal fuses: of course, you need to 
accommodate failure in your design, which begs the question, why did you 
bother installing it in the first place?

- Ceramics are more-or-less forever, but they do change.  A typical X7R 
(and I won't even consider any worse grade) is +/-10% at room temperature, 
but can be -20% at rated temperature (I think??) and -50% at rated 
voltage.  The derating is therefore similar to tantalums: pick 3x more 
voltage rating than you need.  High-Q ceramics also age, where the value 
simply drops over time, while under polarization I think.  I forget if 
this is included in the rated tolerance, or if it's additional as well. 
(Drops of -50% aren't uncommon, but I don't recall if that's Z5U or what.) 
So the challenge is, desigining your circuit to accommodate a wide range 
of capacitance while meeting guaranteed performance.

Gold standard would be using C0G where possible (essentially an ideal 
capacitor at most frequencies, and AFAIK, stable under all conditions), of 
course, these are bulky and expensive.  Definitely worth considering for 
the smaller timing and signal filtering components (say, anything up to 
10n, maybe even 100n).

- Resistors: carbon composition can age a bit, especially under heavy 
load, but with those pretty much history these days, that's not a problem. 
:)  I don't know of any issues otherwise.  General advice applies, don't 
overheat them (as much for their own sake as for the sake of stuff 
nearby).

- Generic silicon thoughts: I don't know that modern molding materials 
(i.e., since, say, the 60s or 70s?) are a problem (at least over here? 
:) ).  Plenty of equipment survives from those days, including power 
amplifiers, for instance, that see wide temperature swings.

- BGAs: I don't think these are actually a big problem.  If leaded solder 
is used (reball if necessary?), cracking balls isn't a problem.  The chip 
can also be underfilled with resin, encapsulating the balls and gluing the 
chip down.  Pains could also be taken to minimize flexural stress on the 
chip and board (a good idea around any large or brittle device), say with 
stiffening frames or strategic routes through the board.

With the amount of consumer stuff since RoHS, you'd think we'd have seen a 
lot more examples of tin whiskers -- apparently it was all hot air, and 
the processes turned out much more reliable than anyone expected.  Yes 
there have been notorious cases of cracked balls: Xbox's Red Ring of Death 
for one, but that's a thermal issue at its root.  It's characteristic of 
the process, but not one that is commonly seen under normal operation (of 
suitable vibration and temperature conditions).

I also heard QFPs can be more failure prone, I guess because they have so 
damn many leads and not much solder to hold them down?  Only example I 
have is a computer from 1987, which contains PLCC and TQFP gate arrays, 
but old logic like that never sees strain or temperature cycling, so it's 
a bad example.

- Wiring -- do what the aerospace people do: use teflon wire, and lots of 
ties.  I suppose I wouldn't mind PVC wire myself, but it probably will go 
brittle after long enough.  Of course, you can't clamp or pull teflon too 
tightly either, because it cold-flows!  Vibration and stress is the killer 
on connections, so keeping all that neatly secured will go a long way.

Now, all of that said -- plenty of consumer electronics have demonstrated 
a life time over half a century, at not much above ambient temperature --  
but guaranteeing an MTBF of the same isn't so easy.  The best approach is 
going to be finding mil-spec components, ceramic body packages where 
possible, and doing what the avionics people do, massive loads of ceramics 
to replace electrolytics.  Gold plated everything is quite typical.  Mil 
spec doesn't seem to have any problems with FR4 (heck, even old consumer 
phenolic from the toob days remains mostly intact, and there's no kidding 
about temperature cycling there).  Controlling temperature is the other 
killer; excessive heatsinking isn't a bad thing!

Tim

-- 
Seven Transistor Labs
Electrical Engineering Consultation
Website: http://seventransistorlabs.com

"Piotr Wyderski" <peter.pan@neverland.mil> wrote in message 
news:l3j6m1$nkp$1@node2.news.atman.pl...
> Speaking of high reliability... I think that it is often
> a somewhat neglected issue, so I start this thread as a
> mean to collect *practical* observations for people who
> care about long MTBF. In other words, "if I had to build
> a device which should last 50 years, I would... what?"
>
> Resistors (if not overloaded): immortal
>
> Ceramic capacitors: as above
> Tantalum/nobium caps: ?
>
> Electrolytic caps: disaster area
>
> Transistors, diodes and ICs: the silicon die should not
> degrade, but how about the endurance of the resin?
> At least some early Polish ICs had problems here:
> the thermal coefficient of the casing was not well-matched
> and power cycling finally broke the bonding wires.
> There were some moisture absorbtion problems, too.
> Is it still an issue?
>
> BGA: it can be expected that thermal cycling will
> eventually destroy the balls, as there are no "springs"
> to absorb thermal stresses. Gull wings are much better here.
>
> FR4: ?
>
> Soldering: the EU has done a lot in order to make
> the newer devices not very reliable as a consequence
> of the RoHS directive. I see nothing wrong with the
> old SnPb joints, the old boards look healthy.
>
> Conformal coating: ?
>
> Wires: ?
>
> Please add your comments.
>
> Best regards, Piotr