Electronic components aging

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

Reply to
Piotr Wyderski
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On a sunny day (Tue, 15 Oct 2013 12:50:39 +0200) it happened Piotr Wyderski wrote in :

[Tin] whiskers old AF118?, but never had problem with modern stuff.

FLASH memory WILL fail, if you use it or not. (Cosmic rays, leakage, migration of atoms in silicon, what not. I have noticed FLASH corruption. Same for EPROMs (anybody still uses those?) and EEPROM, optical media.

With ever smaller, like 14 micron etc, technology chips, these things will cause errors too.

LEDs degrade, high power ones maybe faster (flurescent layer in white ones maybe even more). Displays degrade, OLED will live rather short, expect color tracking errors in OLEDs that use different color material for differrent color pixels, the white ones with filters will do better.

Batteries, if you cannot get them anymore it could mean the end of your gadget, Often not user replacable...

Standards, change al the time, today's stuff may not work at all with stuff 10 years in the future (connectors, protocols, encryption, I have seen it all).

I think the idea is that people should buy new stuff as often as possible, things should stop working and be un-reparable 1 day after the minimum legal required guarantee ends. This is all so we designers have work, and can design ever more new crap.

Housings, will be designed bio-degradable, no kidding the plastic of my Creative Labs mp3 player is falling apart already, wonder where they got that bad pastic from..

The list is much longer, but hey, this should get you started.

Legal: Your design can no longer be used, it uses more than 10 uW in standby, etc etc.. hehe ;-)

Reply to
Jan Panteltje

Optocouplers

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Boris
Reply to
Boris Mohar

With the best will in the world, there is no electronics based technology that will last that long. It is hard enough doing designs that are required to have a life of 20 or 25 years with minimal (no) maintenance. After that time the equipment is replaced in major refurbishment programmes.

Any component that relies on the long term stabiliity of chemistry will degrade and fail eventually. Even in the mechanical world metals like Iron and Stainless Steel will change over time.

Only in software can you achieve really long lifetimes (if you are careful about your design) but then what would you have left to run it on?

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Paul E Bennett

Piotr Wyderski schrieb:

Hello,

they are almost immortal if there are no fast and frequent and large temperature changes and if oxygen has no access.

Bye

Reply to
Uwe Hercksen

Connectors & IC sockets.

Relays.

Reply to
Glenn B

One way of examining this is to look for cards returning from systems replaced by modern systems.

Look for the date codes (YYWW) for the youngest chip on the card to get some idea when the card was made.

While it might be hard to get such information from companies active in the industrial technology field for decades, you might be convinced them to use allow such figures "how good devices we are (still ??) making" to be published.

Reply to
upsidedown

Large soldered connections on PCBs. Things like high current transformer tags and automotive-grade interconnectors. The pads always seem to develop circular cracks and go intermittently O/C.

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Reply to
Adrian Tuddenham

Should last a long time if the LED current is kept low. Integrated current and high temperature degrade the LED. Design for degraded CTR, too.

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John Larkin                  Highland Technology Inc 
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Reply to
John Larkin

Keep power dissipation and currents low in semiconductors. Current causes electromigration. Heat wrecks everything. Use copper pours to keep temps down.

Keep PCBs cool and heat-sink parts like FPGAs to power pours.

Derate resistor power dissipation, and use copper-pour heat sinks. Use resistors in parallel to spread out heat. That minimizes FR4 degradation from resistor heat. For power, use wirewound resistors spaced away from the PCB.

Use stainless hardware, so fasteners don't rust. FR4 will cold-flow under pressure, so don't do things like bolt lugs to boards.

Avoid fans, and assume dust.

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

If you have to use aluminum electrolytics, derate voltage and overkill on capacitance, and buy good ones. Keep them cool.

Beware of fuse fatigue. Don't trust surface-mount polyfuses to work anywhere near specs.

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John Larkin                  Highland Technology Inc 
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Reply to
John Larkin

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.

Reply to
edward.ming.lee

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.

Reply to
RobertMacy

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

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Phil Hobbs

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

Reply to
edward.ming.lee

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).

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).

Pretty reliable, not as good as unstressed resistors.

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.

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.

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.

Probably, but less so.

RoHS solder probably doesn't help.

Solder joints can be bad, can get cracked etc.

What does failure of conformal coating look like?

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.

Reply to
Spehro Pefhany

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

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John Larkin                  Highland Technology Inc 
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Reply to
John Larkin

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?

Reply to
RobertMacy

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

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John Larkin         Highland Technology, Inc 

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Reply to
John Larkin

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

Reply to
Spehro Pefhany

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

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Tim Williams

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