Derating by at least 2:1, better 3:1, seems safe. I have blown them up downstream of an LM1117, which can peak at about 1.2 amps.
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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
Only if leaded and mounted according to NASA - leads having graceful hook-like "loops" to relieve stress. Then wrapped around turret for mechanical reliability, and as a final step soldered for electrical reliability. Oh, yes..100 percent test values BEFORE using as you might find the one in a million that is almost shorted or crystallized to high value, or the one in ten thousand (or less) that was improperly binned.
Same gotchas.
Same gotchas.
Except Tants have a poor life that gets worse as temperature goes up. I would not recommend them for 50 year service; maybe 10 year service..
I know of the old wet can 'lytics that lasted on the average of 10-15 years,with maybe 10 percent lasting to 20 years WITHOUT electrolyte replacement. And this is in "typical" home environment,some areas in the US hotter than others. The problem with the "dry" 'lytics is there is no liquid electrolyte that can be replaced. The Sprague TE series seems to be the exception, lasting over 20 years with no apparent change (typical home environment).
Excellent; have seen no problems up to and including 200C. Around 210C or so, then something goes irrevocably sour. This info is not to be confused with usability,only as an indicator of possible reliability.
In the 70's or so, at (the original) Fairchild, they were making power transistors in the TO-3 package for hi-rel, and the Army told them to STOP plugging them into a test fixture as that decreased the reliability by at least an order of magnitude. The problem was, "merely" pluggint them in added stress to the leads,creating microcracks in the glass-to-kovar interface. So,extend that to anything that adds stress in lead=to=package interface.
*Temperature* cycling causes problems, most especially in vias, metal-glass-conductor (metal or doped silicon); due exclusively to the large difference in the coefficient of expansion.
There were attempts to glop silicone on top of a chip before encapsulation to reduce bondwire stresses..successful in that regard,but too much damn moisture got encapsulated with the glop.
Agree. Know noting about BGA issues.
X,Y,Z coefficients of expansion are all different and are grossly different that any parts you may encounter. Here is where the NASA stress-relief techniques come in handy. PCB vias should, in my opinion, be as large as one can get away with; none of this 14 mil-in-thick PCB. 20 mil is OK even at 200C.
I may have been the only vender that was RoHS compatible at least a year before the EU made an un-avoidable rule. One has no choice if one wishes to guarantee (essentially) PCBs up to
204C.. silver bearing solder is the lowest temperature must. I am totally against the SAC crap, despite the reasons behind the use. Multicore makes Savbit, a tin-lead solder alloyed with a small amount of copper - to eliminate the pitting of soldering bits (irons to us USians) due to copper in the production bits alloying out and into the solder. There is NO SUCH "CONCERN" WRT reflow soldering! The added copper decreases the reliability of the solder connection. With regard to silver-bearing solder, the same can be said about SAC crap.
Maybe..with great care and atmospheric controls (NO moisture), baking of units beforehand, etc.
Review NASA specs WRT nicking of wire during stripping.
I think they may the first to admit that they did not think the Voyagers would be operating for so long. It is one thing for the systems to last a long time, but a completely different thing if you are asked to make sure it will keep going.
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Indeed. Some people are afraid of electrolytic capacitors, but the wear-out mechanisms are well known and the lifetime can be very long if you treat i t as you should. The thermal cycle effects which is one of the major root c auses for failures are low due to mechanical reliefs in the packages used
Ceramic capacitors, that is used instead of electrolytic capacitors since t hey are thought to have better reliability, have horrible thermal cycling s pecs (at least for SMD types)
We used the JPL Derating guidelines (Jet Propulsion Laboratory, which later became a subdivision of NASA).
The idea of course is to keep the subjected stimuli well below the ratings of the device. The stimuli is calculated from what is expected and any shor t time overload condition. Normally maximum 60% of the ratings for voltage, current and power.
Reduced length document:
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When the basics is covered, the surroundings of the device is handled. In p rinciple any device is scrutinized for any failure and a DFMEA analysis is done to make sure what kind of propagation a single error has. The errors i s not just from components FIT, emvironment influences etc, but also from c osmic raditation. So a SEU (Single Event Upset) is also analyzed. For examp le, for ICs which has not passed the nessesary radiation limnits, the devic e is surround with components to protect it from the SEU and to reset it af ter the SEU
Any device has a FIT number, not only the Space rated parts, which can be f ound for most devices digging deeper in the manufactor tests reports. The F IT is normally deduces from accelerated thermal cycling tests.
As for the special RAD hard devices, that is used for Space designs, the di es are AFAIR special dies, used only for Space, with extensive testing on a ll important parameters
So any device is considered to be failure prone, and to increase availabili ty figures, redundant circuits are used, either fully redundant or partiall y redundant with voting systems
The trend recently has been to try to use non-RAD HARD components for space flight, to see if it is possible to save costs with possibly lower reliabi lity.
s of the device. The stimuli is calculated from what is expected and any sh ort time overload condition. Normally maximum 60% of the ratings for voltag e, current and power.
principle any device is scrutinized for any failure and a DFMEA analysis i s done to make sure what kind of propagation a single error has. The errors is not just from components FIT, emvironment influences etc, but also from cosmic raditation. So a SEU (Single Event Upset) is also analyzed. For exa mple, for ICs which has not passed the nessesary radiation limnits, the dev ice is surround with components to protect it from the SEU and to reset it after the SEU
found for most devices digging deeper in the manufactor tests reports. The FIT is normally deduces from accelerated thermal cycling tests.
dies are AFAIR special dies, used only for Space, with extensive testing on all important parameters
lity figures, redundant circuits are used, either fully redundant or partia lly redundant with voting systems
ce flight, to see if it is possible to save costs with possibly lower relia bility.
For practical design, important items to consider apart from other mentione d in the thread is the difference in thermal expansion coefficients from co mponents to the PCB. So for long reliability designs, placing ceramics on a FR4 substrate is not always optimal
Leadfree solder may also not be optimal, although I think the discussion of reliability of leadfree versus leaded designs have not ended
I mean to keep junction temperatures as low as possible if you want max MTBF. Operating "within ratings" (at max specified Tj) isn't good for reliability.
--
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
The graph at the end indicates that reducing the stress ratio (as defined there), provides an increase in reliability, but not a dramatic one. One could suspect that what that graph is really showing is that the the higher the stress ratio, the more quickly a latent fault becomes manifest, rather than that the stress itself causes the fault.
I have a digital clock I made 40 years ago. It has a flaky connection somewhere, but still works. I have a stereo amp I made even longer ago that still works.
I have thought about a similar problem from time to time, except that I was thinking of designing something for maybe 1000 years or more of storage followed by being expected to operate. I assumed that the whole equipment should be hermetically encapsulated and put somewhere cool, so I'm only thinking about inherent aging.
I think larger geometry chips may well be ok (provided they don't rely on stored charge like EPROMS and FLASH). (Also I think the patterns of metal in a chip that is passivated with oxide might well be visible after many thousands of years, and be a fairly dense and long-lasting way to store information. Because consumer chips also get made in very high volumes and end up discarded in landfils all over the world I expect that it will be possible to find be copies of a few on-chip inductors that I designed even after a very long time.)
My guess is that film capacitors like polypropylene might do alright for a long time.
I have observed high-K ceramic caps that have lost quite a lot of capacitance even after a few years but they could be restored by reheating when they are re-soldered, (which I consider cheating in this context, unless the equipment can do that itself).
Even for much shorter periods, batteries seem to be one of the worst causes of permanent damage due to electrolyte escaping, though I haven't seen a lithium coin cell leak so far.
Electrolytic caps seem to be able to last many decades if the equipment is turned on often enough to keep the dielectric formed. If the equipment is just stored for decades with no power applied then the dielectric degrades and if power is then applied suddenly they fail due to overheating, or if they are used in a low current circuit the leakage just makes it not work (maybe only temporarily). Even when the electrolytics are kept formed, it is also necessary to plan for the ESR to increase and the capacitance to decrease, otherwise the circuit will not last long.
I recall reading that inductors (chokes) used to be connected such that the fine wire was more negative than the iron core, rather than the other way around, so that any moisture didn't cause electrolytic corrosion of the thin wire if there were cracks in the enamel.
I have seen neodymium magnets which didn't last long (plating fell off and magnet turned to powder) though I have seen others that didn't have that problem.
I suspect that hermetic metal can tantalum capacitors have different reliability from the dipped style and perhaps the surface mount ones are different again. I have had a dipped tantalum cap go short circuit in an always-on battery charger application (trickle charger fed from a large series resistor) where I don't think it was ever subjected to high dv/dt.
Desinging in redundancy would help a lot, and if the redundant copies are different and each avoid using a different type/brand of component, that might help against the difficulty of predicting failure mechanisms.
I found this project slightly interesting, though I wouldn't have done it the same way:
I don't know about the dry type (being mil spec, hopefully their failure modes are well understood and controlled), but there is also a wet type (which also has very low leakage, once stabilized).
Can you talk to the electronics in our Hammond organ about that? It is
53 years old now and no signs of fatigure. First set of tubes. Then there is the Sachsenwerk radio from 1939. When I donated it to a museum a couple of years ago it ran just fine and likely still does.
Depends on how well the components are built they can easily outlast humans. I have a radio with the first "IC" in there from the roaring
20's. Last time I fired it up was over 15 years ago but it worked:
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You can still buy it used:
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Or look at the DC-3. It's still hauling lots of freight and passengers. These old airplanes are used for hard jobs, I think this one was built in 1937:
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My dad's old IBM 5100 from the mid-70's is still there :-)
Mosfets have a threshold voltage shift related to how many times they are switched. The rule of thumb is your chip should be able to last 10 years at the maximum clock frequency. But of course, this isn't hard and fast or even written down.
Basically a logic circuit will still work if the fet threshold voltage changes over time. But if there is some critical timing and the fet threshold voltage got larger, it will have less drive and thus the chip becomes slower.
The threshold shift effect has been around since the 1um days. I believe it is related to hot carriers. All sorts of foo was created over the years to keep this problem tolerable.
Try looking at some serious long term infrastructure systems. There is plenty of SCADA that has already lasted as much as 60 years or more. Lots more in heavy industries (refining, major metal mills, chemical plants, water treatment, wastewater treatment, etc.,) where replacement costs get really really big.
But Space has severe thermal management issues, it is a really good insulator after all. Also contact erosion is a major player in relay life, the design has to control that or the system dies early. I know i did some testing of relays for space use.
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