
Let's Talk About Capacitor Failure - blakespot
https://bytecellar.com/2019/04/07/lets-talk-about-capacitor-failure/
======
laydn
If you want your aluminum capacitors to fail less often:

\- If you are designing the PCB and not repairing, keep them as far away from
heat sources as possible. If you're repairing a PCB and the caps are near heat
sources, consider isolating them with thermal material

\- Use the highest temperature rating capacitor that you can find, if cost is
not a concern.

\- Most caps now have a lifetime rating such as (4000 hrs in 85C). This
lifetime also has built-in ripple current assumptions, but for a first order
approximation, consider using the "longest rated at highest temperature" cap,
if cost is not a concern.

\- Again, as a very rough guideline, use the highest voltage rated capacitor
that you can find for your target rail. This is an approximation, because your
second goal should be to generally keep the ESR (equivalent series resistance)
low, and as the voltage rating increases, so does ESR. Commercial products
tend to choose the voltage rating around 1.2x - 1.5x target voltage. Most
industrial products that I've seen target a minimum of 2x.

~~~
wang_li
>consider isolating them with thermal material

This only slows down the transfer of heat, both in and out. I'd be surprised
if anything useful would come of this as eventually the cap is going to
achieve equilibrium with the environment, or if you wrap it up in a small
coat, it will take longer to transfer heat out of the cap than normal and run
hot.

~~~
robocat
Think a linear wall of isolation, so the capacitor can still dissipate heat to
the air.

A jacket around the capacitor would be a bad idea, especially since capacitors
can generate heat internally, and heat is what we don't want!

~~~
magicalhippo
Their lifetime is also non-linear with respect to ambient temperature. A 10 C
reduction[1] in ambient temperature roughly doubles the lifetime.

So shielding the capacitor from heat can be very beneficial, even if it's just
a few degrees.

[1]: www.rubycon.co.jp/en/products/alumi/pdf/life.pdf

------
ReC757
I remember many years ago a bad batch of dell small form factor machines that
constantly failed to popped capacitors. It would always be near the power
supply where the heat was greatest. I guess in that certain area the
capacitors were outside of their operating range...

Nevertheless, as a bored 16 year old, I enjoyed ripping apart all the machines
and calling the higher level support lines to order replacement motherboards.

As time went on, they took my word on if a machine had failed due to this
specific issue. I really enjoyed the responsibility and trust. Since I could
fix the machines faster than Dells support turnaround, I just asked them to
send the parts.

After about the hundredth machine, I never wanted to seat a processor again.
This was back when processors had hundreds of fragile pins too!

It’s likely that those experiences really pushed me towards software
development instead of IT. Good times...

~~~
rolleiflex
> After about the hundredth machine, I never wanted to seat a processor again.
> This was back when processors had hundreds of fragile pins too!

They still have hundreds of fragile pins. I just bent a few on an AMD Ryzen 7
that got popped out of its socket due to too weak a socket clamp while
removing the fan.

You know the saying - ‘The future is already here, it’s just unevenly
distributed.’ Turns out, it applies to the past, too.

~~~
jdsully
Intel went to LGA where we the pins are on the motherboard. In my experience
they are much less likely to be damaged there as they get protection from the
socket.

I’m not sure why AMD stuck with PGA.

~~~
paulmd
Lower cost, and some people are really attached to it because it's easier to
repair pins if they get bent. You can straighten out PGA pins with a razor
blade or a mechanical pencil pretty easily, LGA pins are... "challenging". It
can be done but it's not easy.

(also, to be blunt, AMD processors undergo such extreme depreciation that
they're practically disposable. After two years, AMD's flagship 1800X
processor has lost 2/3 of its value, a nice high-end mobo like a C6H is
literally more valuable than the flagship processor you had put on it. So it
makes sense to have the processor be the one with the easy-to-damage
sacrificial part on it. Intel it's the other way around, the processors are
expensive and your mobo is probably the cheaper part to replace if needed.)

~~~
jdsully
WOW you aren't kidding. First gen Threadrippers are _cheap_ now.

~~~
paulmd
I've seen the 1950X as low as $450 at Microcenter. TR4 motherboards are quite
expensive, but right now the Taichi is around $260 after rebate at Newegg.
Note that not all of the motherboards are designed to handle the higher-TDP
2970WX/2990WX, if you think that's an upgrade you'd make then look for one
with a beefier VRM. Also, the cheaper ones lack 10 GbE or some other higher-
end features.

You can also find the 1700 as low as $130 if you watch around. Needless to
say, if you have any batch-processing type tasks that don't need AVX2, that's
a hell of a deal too.

------
ahoka
[https://en.wikipedia.org/wiki/Capacitor_plague](https://en.wikipedia.org/wiki/Capacitor_plague)

A story of industrial espionage, betrayal and an incomplete electrolyte
formula.

~~~
hinkley
This page doesn't talk about it, but what I recall is that the stage was set
for this by a move away from a fire retardant (containing bromine) that was
linked to developmental disorders. To eliminate the fire retardant, they also
moved to a new capacitor chemistry.

That would represent a pretty big spike in demand from manufacturers. New
product, possibly new partnerships.

~~~
jandrese
That would be interesting because it would represent a second case of a safety
oriented change causing a significant reduction in product quality in as many
years. The other being the switch to RoHS lead free solder that caused a great
many BGA failures for companies like nVidia.

~~~
blattimwind
The failure in implementing lead-free strategies is really interesting,
because the _sole reason_ lead was put into electronics solder was that it
prevented the tin whisker growth pure tin solder or silver solder experienced.

So some odd-seventy-eighty years later people remove the lead and substitute
it with "straight nothin'" and are subsequently surprised they get tin
whiskers again?! WTF?

~~~
fake-name
Lead is added to solder because it lowers the melting point. It forms a
eutectic alloy.

Tin whiskers has nothing to do with it.

~~~
ddeck
_> Tin whiskers has nothing to do with it._

This is not accurate. Tin whiskers are a well-known problem resulting from
pure tin coatings (although the mechanism is not well understood) and lead has
historically been added to mitigate their growth (among other benefits).

From Wikipedia:

 _" Traditionally, lead was added to slow down whisker growth in tin-based
solders."_ [0]

From NASA:

 _" No single mitigation technique provides effective protection against
whisker formation except the addition of 3% or more of Pb by weight"_ [1]

 _" Suggestions for Reducing Risk of Tin Whisker Induced Failures...1. Avoid
the use of PURE TIN plated components if possible...Alloys of tin and lead are
generally considered to be acceptable where the alloy contains a minimum of 3%
lead by weight...Although some experimenters have reported whisker growth from
tin-lead alloys, such whiskers have also been reported to be dramatically
smaller than those from pure tin plated surfaces and are believed to
sufficiently small so as not to pose a significant risk for the geometries of
today's microelectronics."_ [2]

[0]
[https://en.wikipedia.org/wiki/Whisker_(metallurgy)](https://en.wikipedia.org/wiki/Whisker_\(metallurgy\))

[1]
[https://nepp.nasa.gov/whisker/reference/tech_papers/2011-kos...](https://nepp.nasa.gov/whisker/reference/tech_papers/2011-kostic-
Pb-free.pdf)

[2]
[https://nepp.nasa.gov/whisker/background/index.htm](https://nepp.nasa.gov/whisker/background/index.htm)

------
syntaxing
As others has mentioned, an ESR is the way go for capacitor diagnosis. Usually
you can find the capacitor by determining the symptoms. For instance, if the
power indicator turns on then off, it's probably near the power supply and
filter circuit. That being said, it can get super dangerous repairing old
vintage machines since there can be a huge ass capacitor upstream you do not
notice. Always discharge your capacitors before you work on them!!

~~~
kevin42
The ESR meter is like magic!

I have fixed a ton of discarded electronics by replacing bad capacitors I
found with my ESR meter. Several years back I bought a whole lot of broken
test equipment dirt cheap and fixed about 75% of it and resold for a nice
profit. Almost everything was fixed with new capacitors.

A few years back my oven died suddenly. I popped open the cover and went
through all the electrolytics with my ESR meter and found a bad one. I had
exactly that value in my parts bin, replaced it and the oven worked like new.
The total cost of the repair was less than $1.

~~~
Scoundreller
Any recommended ESR meters?

~~~
syntaxing
The blue ESR meter is pretty famous [1].

[1] [https://anatekinstruments.com/products/fully-assembled-
anate...](https://anatekinstruments.com/products/fully-assembled-anatek-blue-
esr-meter-besr)

------
cellularmitosis
While the limited lifespan of electrolytics is well known, I'm very curious as
to the lifespan of the humble yet ubiquitous 0.1uF ceramic disc capacitor.
There must be billions of these little buggers in digital electronics, and
I've never seen one go bad from age.

This site claims "For X7R and X5R the loss is calculated at -2.5% per decade
hour and for Y5V it is -7% per decade hour."
[https://www.johansondielectrics.com/ceramic-capacitor-
aging-...](https://www.johansondielectrics.com/ceramic-capacitor-aging-made-
simple) but that seems very pessimistic.

Interestingly, they also claim the ageing of ceramic caps can be reset by
baking them at 150C for a couple of hours. Many electronics board could
survive this, which seems to imply that a digital board which used exclusively
ceramic caps could in theory last ~forever (> 1 human lifetime).

~~~
Jeema101
I can tell you that most vintage radio and audio guys generally don't bother
replacing ceramic capacitors even on 70-80+ year old equipment, so my guess
would be 'a long time'.

~~~
Gibbon1
Most of the time the failure mode is excessive leakage. Which often doesn't
cause problems. And ceramic and tantalum capacitors tend to heal if running at
more than a few volts. I found a cap on battery backed up memory array that
was sucking about 50uA. Putting 5V across it 'fixed it'

------
zepearl
Is it true that japanese capacitors are the best?

Example ( [https://www.hardwaresecrets.com/how-to-identify-japanese-
ele...](https://www.hardwaresecrets.com/how-to-identify-japanese-electrolytic-
capacitors/) ):

> _Japanese capacitors are notoriously known by their above-the-average
> quality (good electrolyte and good sealing),_

Last year I had to buy a new power supply for my PC and some producers
mentioned explicitly that they were using japanese capacitors and I just
passively accepted it in the same style as "swiss watch"/"french
champagne"/"italian pasta"/"german car" (now excluding exhaust system, hehe)
,therefore intrinsecally referring to good quality, but I always wondered
"why?".

And if it's true that the "best" capacitors are made in japan, is there any
special reason (historical, social, because of source materials, etc...) for
that or is it just semi-random (e.g. many japanese that were picky discovered
that producing high-quality capacitors was just their perfect meaning of life
and therefore covered a previously ignored slice of the market)?

Thx :)

~~~
syntaxing
Good quality is directly correlated to good QC (quality control).
Manufacturing engineers spend a lot of time to define the process. There are
different methods such as six sigma (and the associated continue process
improvement) to control and detect the rejects. However, to get there requires
a lot of upfront cost and manpower which is why it costs more for better
quality parts.

~~~
zepearl
Thx (didn't know about "six sigma")

Do you think that maybe the japanese mentality is more "fit" to achieve such
precise/high-quality processes and QC than other people/nations/etc... in the
area of capacitors?

EDIT:

> _Lean management and Six Sigma are two concepts which share similar
> methodologies and tools. Both programs are Japanese-influenced,..._ (
> [https://en.wikipedia.org/wiki/Six_Sigma](https://en.wikipedia.org/wiki/Six_Sigma)
> )

Puah, really, never heard about this stuff - but isn't japanese mgmt structure
famous for being complicated (or is maybe just the "formality" of the mgmt
being very complicated for europeans?)?

~~~
syntaxing
Where something is made definitely effects the quality. The cultural effect
has a play in the equation but it's also the available resources. An assembly
line tends to be similar to a clock. Any piece that breaks in the chain can
cause the quality to suffer. Therefore, you need workers who can handle the
system and also be "trainable" to grow a product.

As others has mentioned, a lot these techniques stem from Demings. Most agree
that he had a huge role from transforming the quality of product manufactured
in Japan (synonymous to China today) to the top tier quality they can produce
now.

People study for years to be able to be good at root cause analysis and
assembly process management. To get a good assembly line processing requires
on honing in the details. For instance, the location of the workers relative
to each other, where they hand off the parts in the line, and also the
location and type of tools can easily effect your reject rate.

------
arcticbull
Part 2 re: Tantalum capacitors always being leaded parts isn't accurate, there
are lots of SMT tantalum capacitors. Due to it's status as a conflict
material, though, and it's unique extra-fiery failure mode when you exceed
it's ratings, I tend to stick with other low-ESR chemistries like aluminum
polymer electrolytic, ceramic or niobium oxide (much more stable - 95% less
likely to catch fire and non-conflict, similar performance).

~~~
xondono
The commenters point is that even typical SMT tantalums have leads:

\- A/B/C/.. type cases have tiny leads going outwards

\- more modern cases have metal sheet like leads bent down and inwards.

The thing is that tantalums capacity density is hard to beat, specially if you
are cost-restricted (those polymers are pricey).

There’s also a lot of research from NASA about the safety of tantalums, and
they actually think they’re fairly safe provided you don’t expose them to
voltage ripple (so don’t place them on SMPS)

~~~
blattimwind
> There’s also a lot of research from NASA about the safety of tantalums, and
> they actually think they’re fairly safe provided you don’t expose them to
> voltage ripple (so don’t place them on SMPS)

Besides even the shortest over-voltage incidents, Tantalums also don't like
high current pulses. Low-ESR power sources with quick ramp ups are a no-no.

~~~
xondono
Yes, I read a lot about tantalums and their failure modes some years ago
because we wanted to set some kind of use policy for our own products.

After a lot of research and testing we ended up forbidding the use of
tantalums in our designs and taking the cost hit whenever density was an
issue.

It’s a drastic measure but I think it was the right call, our products were a
perfect mixture of all the things that tantalums don’t support well.

------
jimnotgym
I have seen a few electrolytics fail with a bulged top in switching power
supplies and valve amplifiers, and once on a graphics card.

If you want to see how your old cap is doing

1) learn the safe way to discharge them 2) use an ESR meter to test them in
circuit. As to the correct ESR, compare a new cap to the one in circuit.

~~~
holy_city
>learn the safe way to discharge them

According to one electronics professor (prefaced this with "do not do this at
home") - all you have to do is short the leads with a screwdriver.

Or really use a resistor and some alligator clips. Of course a screwdriver is
easier to handle without touching the leads than those tiny alligator clips...

~~~
52-6F-62
Similar experience in film/tv industrial lighting ballasts and heads. Had old
techs evangelize that kind of thing. A lot of wacky people in that field.

I wouldn’t trust a screwdriver to be safe enough in many of those cases. Some
of the caps in those things are _massive_ and hold a charge for ages.

I almost killed myself on one thinking there’s no way there would be any
charge left after years being stored in an old uninsulated tractor trailer
outside. Boy was I wrong.

We were demoing some old ballasts—essentially crumpling them before recycling
to prevent raiders from seizing the equipment (it happened).

Well one coincidentally-aligned swing of the sledge caved the steel chassis in
just enough to short a monster cap. The thing exploded on contact. Thankfully
those old steel ballasts were tanks and nothing happened. I was sure glad I
was insulated at that moment.

Kids, am I right? ;P

Just want to second what others are saying: don’t toy with those things, and
don’t make uninformed assumptions!

~~~
trhway
>don’t toy with those things

on a much smaller scale - in about 3rd grade at one point we had that game
that took off like epidemic in our school and fortunately subsided quickly too
- shocking each other (today you'd call it "tazering":), in an open fight kind
of like 2 scorpions or sneaking upon, with the capacitors, wall socket charged
(220v in USSR) and if i remember correctly of 10-200mkF (like an 1in thick
cylinder or a block up to half Rubik cube size). The shock was profound to say
the least and according to some literature seems to be crossing into
accidentally deadly territory in unfortunate circumstances. Fortunately no
injuries/deaths happened. Happy childhood in USSR :) - many things from our
childhood one just cant do today anywhere.

~~~
MertsA
One thing that makes that capacitor prank significantly safer is that the
terminals are so close together so the actual current path through the victim
is very unlikely to send any significant current through their heart. Still
possible if they touched one terminal to their hand and the other terminal
landed on their body or if the victim got one terminal and the prankster
accidentally touched the other.

~~~
trhway
yes. Never thought about it. Frequently there were wires attached so that the
wires would stick out of your hand like 2-8in toward your opponent. Still
usually both ends would touch about the same locality on the body.

------
lgleason
Electrolytic capacitors, even high quality ones, will eventually dry out and
fail. The older the capacitor, the more likely this is to happen....sometimes
they will last longer even with lots of use but..........

~~~
cellularmitosis
> The older the capacitor, the more likely this is to happen

The funny thing is that due to this capacitor plague of the early 2000's,
capacitors which are even older than this have a better survival rate. The
plot of failure likelihood over time would be something like a line with a
weird bulge in the middle.

------
crashbunny
Only slightly relevant to the topic, there was a capacitor failure in Sydney
in 2004 that stopped trains on 6 lines during the morning commute causing
100,000 passengers to be stranded and unable to get to work. Like all complex
failures, there was more than one contributing factor, but if the capacitor
didn't fail the trains wouldn't have stopped.
[https://spectrum.ieee.org/riskfactor/computing/it/two-
capaci...](https://spectrum.ieee.org/riskfactor/computing/it/two-capacitors-
and-poor-software-design-cause-of-major-nsw-rail-outage-last-month)

------
sevensor
I recommend reading the massively informative comments section.

------
mrguyorama
I have seen an (anecdotal) large amount of capacitors failing in consumer
televisions. I recently replaced one in a friend's TV. These capacitors are
supposed to have rated lifetimes of roughly the lifetime of the TV, so why are
they failing in normal use? Is there another Dell situation, where a big batch
had slight issues?

~~~
jaclaz
>I have seen an (anecdotal) large amount of capacitors failing in consumer
televisions. I recently replaced one in a friend's TV. These capacitors are
supposed to have rated lifetimes of roughly the lifetime of the TV, so why are
they failing in normal use?

The point IMHO revolves around "What is the expected lifetime of a TV
(nowadays)?"

More anecdata, I own a "large" 32" Sony Trinitron that is incredibly heavy and
that works just fine (touch wood) since 2002 or so.

I also had a smaller Mivar that lasted more than 30 years (if I recall
correctly 32 years 1984-2016).

More recently (like 2013 or 2014) I procured for a friend's project a number
(20) of (admittedly el-cheapo) Hi-Sense 32" LCD's, 3 or 4 failed in about 25
months (or one month beyond the 24 months covered by warranty) and 2 failed
within warranty period (but the importer/assistance center closed before that
anyway), of these most were capacitors related issues (one was simply a cold
solder joint). But - besides the repaired ones - the remaining 13 or 14 still
work just fine.

~~~
blakespot
My 50-inch Pioneer PDP-5060 plasma (720p) lasted from late 2005 to 2014. I
felt that was a short lifespan. I replaced it with one of the last plasmas
sold, a 51-inch Samsung, and after four years a vertical line appeared. Now
there are two. It is failing. That seems short to me. (OP)

------
grawprog
The weirdest capacitor failure i've experienced was after a single speck of
dust ended up inside the control panel of one the CNC machines at work. It
landed directly on a capacitor that was part of a circuit for the backup
emergency stop system. The system refused to power on because it believed the
emergency stop was tripped.

We ended up bypassing the circuit itself directly in electrical cabinet until
we got an electrician in who found the problem capacitor. Luckily the actual
e-stop still worked, this was a backup e-stop, I guess, I'm still not entirely
sure. We ended up having to replace the entire CNC controller for the machine.

------
tyingq
I didn't see it in the article, but one way I'm used to finding bad
electrolytic caps that don't "look bad" is to smell them. I imagine there's
not a 100% correlation, but the ones I'm used to smell like fish when they
leaked.

No replacement for real testing/troubleshooting, but it was a good quick/dirty
test when I used to repair microwave transmitters for a living. Also got a lot
of curious looks while sniffing suspect boards :)

------
mikestew
I'm sure many factors go into the life span of a capacitor. The fix for old VW
dashboard clocks (at least in our '81 Vanagon): replace the two capacitors.
Now, our VW is 37 years old, but it seems to me a _clock_ should be a pretty
low-stress environment. Or maybe I'm wrong, I dunno. Why are 40 year old
computers still running on original caps, but a 12VDC clock fails in about the
same timespan?

~~~
jackhack
Auto power environments are actually very rough -- 30% (or more!) swings in V+
a nominal 12V system, noise injected by the points opening/closing and the
30,000V coil generating a spark, the old mechanical-switch voltage regulators
causing a giant surge, etc. Honestly, it's kind of amazing anything lasts in
that world.

I go through an in-dash CD player every few years.

(source: restored loads of aircooled VWs over the years.)

~~~
neuralRiot
Don't forget temperatures that can esily go from -20 to 140f, condensation,
dust, vibration, chemicals.

------
londons_explore
Capacitors fail either open or short.

Failing open will pretty much always not damage any other circuitry.

Failing short will _usually_ not damage other circuitry, since usually a fuse
will blow or the power supply refuse to start.

For the above reasons, I wouldn't preemptively change capacitors. From an
effort point of view, changing them in the unlikely event of a failure is far
less than changing them all 'just because'.

------
johnnycab
This is one of the major reasons, where so many decent electronics are being
consigned to the scrap-heap due to the most innocuous reasons and there are
avenues available to bring them back to life.

[https://www.avforums.com/threads/yamaha-rxv1700-power-
proble...](https://www.avforums.com/threads/yamaha-rxv1700-power-
problem.1533016/)

~~~
megous
Maybe. Personally, I try to replace caps, when possible, but oftent times I
find that real failure is corrosion of the board, I can do nothing about.

------
nathanvanfleet
I thought this was well known, but maybe just a rumor. But my understanding is
that at one point someone who worked for a capacitor company stole the formula
for making electrolytic capacitors and started their own company.
Unfortunately they didn't quite get it right, and they had what was called
"capacitor plague."

------
x0
Only time I've seen capacitor failure impact a system is on an old (Win XP)
motherboard I got recently, most of the aluminium caps near the RAM slots are
leaking, and only 1 of 4 slots work.

Oh and there was also the 33uf capacitor I put in backwards across 12VDC.
Venting failed, and now there's a dent in my ceiling.

------
metaphor
> _I can’t say for sure that I have ever seen an example of a capacitor
> failure utterly destroying a system._

I suspect the author has never encountered the imbalance failure mode of
matched-pair capacitors used in high-power weapon systems.

------
c0deR3D
Sometimes, a capacitor's failure also cause invisible damage to other ICs,
it's pretty annoying since some ICs can't just use volt-meter to check if it
is still functional.

~~~
jandrese
One of the things I hate most about electrolytic caps is the failure mode that
drips corrosive liquid over your PCB. Not only does it fail, it makes sure to
take the rest of the board with it.

------
ncmncm
This is a treasure hoard. So much accumulated experience on offer, just for
the time it takes to read it.

------
eltoozero
Tempest 3000 eh? I build Zarjaz Rotary controllers for that thing if you’re
interested. ;)

Funny story actually...

~~~
blakespot
Sounds like you saw my blog post elsewhere on the site about Tempest 3000, so
you surely saw my rotary. I can't recall...do I have a Zarjaz? Maybe an Opal.
Hmmmm. Nice game. Rotary or nothing!

