*gasp* Useful EDN article on tantalum caps
Phil Hobbs
http://www.edn.com/article/509092-What_a_cap_astrophe_.php
Now that there's this existence proof, maybe there'll be a bit
more...perhaps someone will write them another useful article, e.g. a
compendium of all two-transistor circuits.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
John Larkin
<pcdhSpamM...@electrooptical.net> wrote:
>Stupid title, but actual useful info on tantalum cap behaviour:
>
>http://www.edn.com/article/509092-What_a_cap_astrophe_.php
>
>Now that there's this existence proof, maybe there'll be a bit
>more...perhaps someone will write them another useful article, e.g. a
>compendium of all two-transistor circuits.
>
>Cheers
>
>Phil Hobbs
Tantalums fail from excess current, namely dV/dt. MnO2 is an oxidizer
and tantalum is a fuel, and only a tiny ignition source sets it off.
They are fine for current-limited applications but firebombs if used
to bypass power rails. Derate them 3:1 on voltage if you must use them
as power bypasses. Better yet use aluminums, polymer aluminums for
wide-temperature appls
John
Phil Hobbs
The interesting thing in the article is that soldering makes large tants
vulnerable to overvoltage failure well below their rating, and that they
can be reconditioned (and made much more reliable) by putting a current
limit on the power supply. That's more useful for repairs or fixing
problems with a shipping product than for new designs, admittedly.
Still, I thought it was kind of cool, and remarkable for being in EDN!
John Larkin
<pcdhSpamM...@electrooptical.net> wrote:
Serious non-commercial technical content is a good thing for EDN to do
now and then!
But tantalums are incredibly erratic, which is why different people
form different theories about their failure mechanisms. My worst
experience was with thru-hole gumdrops, hand soldered, which hadn't
been exposed to much heat. I think I still have a few thousand around
in a box somewhere.
I sometimes use tantalums as switching or linear reg output filters,
because the ESRs are often right and aluminums don't work cold. But I
try to limit dV/dT and derate about 3:1 on voltage.
The manufacturers mostly try to hide the failure mechanisms. One tant
maker recommends that they *always* be voltage derated 2:1. So why do
they call it a 25 volt cap is it's only safe to use at 12.5? Grrrrr.
ftp://jjlarkin.lmi.net/P14_reg.gif
C1 is a tantalum, and C40 limits its dV/dT.
I *have* exploded tantalums on the outputs of LM1117s.
John
Jim Yanik
news:4C091ABE...@electrooptical.net:
TEKTRONIX used tantalums for many years in their scopes,and the failures
were not objectionably high. Usage was mostly on power rails,BTW.
--
Jim Yanik
jyanik
at
localnet
dot com
lang...@fonz.dk
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Fri, 04 Jun 2010 09:47:43 -0400, Phil Hobbs
>
yeh luckly I were glasses, I have a scratch one glass from an
exploding tant
on the output of a switching regulator
-Lasse
Mycelium
>
>TEKTRONIX used tantalums for many years in their scopes,and the failures
>were not objectionably high. Usage was mostly on power rails,BTW.
Yeah, except that they also used mostly mil spec components and
production methodologies back then as well, and one (an engineer) could
rely on the fact that they had been thoroughly conditioned before use on
the production line.
A hermetically sealed mil EL cap has a shelf life of decades. A COTS
EL cap does not. There are several mechanisms that are/were in place
during their manufacture to ensure that reliability level on those
specialized caps, even though they differ little at the
physical/electrical level... ie they are both paste laminated foil
roll-ups.
Capt. Cave Man
>
>yeh luckly I were glasses, I have a scratch one glass from an
>exploding tant
>on the output of a switching regulator
>
>-Lasse
Gaze at circuits that you just 'fixed' as you re-energize them often,
do ya? (you likely cause their failure with poor solder technique)
I tend to gaze at the input current numbers. I do not have such
catastrophic failures often, as with proper bench technique, the failure
modes can almost always be spotted prior to any such actual event occurs.
John Larkin
Wet-slugs don't detonate like MnO2 dry tantalums. The MIL CLR-types
are very reliable. They have silver cases, so have gotten expensive.
I don't think these are roll-ups. They are a sintered tantalum slug
floating in a conductive paste, in a silver can. The semi-liquid paste
must put the fires out.
John
Paul Hovnanian P.E.
> On 6/4/2010 10:04 AM, John Larkin wrote:
>> On Fri, 04 Jun 2010 09:47:43 -0400, Phil Hobbs
>> <pcdhSpamM...@electrooptical.net> wrote:
>>
>>> Stupid title, but actual useful info on tantalum cap behaviour:
>>>
>>> http://www.edn.com/article/509092-What_a_cap_astrophe_.php
>>>
>>> Now that there's this existence proof, maybe there'll be a bit
>>> more...perhaps someone will write them another useful article, e.g. a
>>> compendium of all two-transistor circuits.
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>> Tantalums fail from excess current, namely dV/dt. MnO2 is an oxidizer
>> and tantalum is a fuel, and only a tiny ignition source sets it off.
>> They are fine for current-limited applications but firebombs if used
>> to bypass power rails. Derate them 3:1 on voltage if you must use them
>> as power bypasses. Better yet use aluminums, polymer aluminums for
>> wide-temperature appls
>>
>> John
>>
>
> The interesting thing in the article is that soldering makes large tants
> vulnerable to overvoltage failure well below their rating, and that they
> can be reconditioned (and made much more reliable) by putting a current
> limit on the power supply. That's more useful for repairs or fixing
> problems with a shipping product than for new designs, admittedly.
> Still, I thought it was kind of cool, and remarkable for being in EDN!
That might make a good argument for a properly thought out burn in
procedure. There's too much pressure from management to just build it and
ship it (airplanes included).
--
Paul Hovnanian pa...@hovnanian.com
----------------------------------------------------------------------
Have gnu, will travel.
cassiope
> Phil Hobbs <pcdhSpamMeSensel...@electrooptical.net> wrote innews:4C091ABE...@electrooptical.net:
>
>
>
> > On 6/4/2010 10:04 AM, John Larkin wrote:
> >> On Fri, 04 Jun 2010 09:47:43 -0400, Phil Hobbs
In the late '70s Tek decreed that its design engineers should
only use tantalums with explicit series resistance (3ohms/volt IIRC),
and
enforced it with the design review process. Direct power supply
bypassing
was a no-no. This was after a lawsuit stemming from a fire started by
a Tek
product took out a large mobile lab. I think it was around that time
that Tek
also got much more serious about ensuring that connector bodies were
flame retardant, and started worrying about their switch cams with all
its
flammable delrin.
Maybe the rate of failure was not "objectionably high", but when the
consequences
can be serious (as with the tantalum self-immolation, or with a
certain current
oil leak), you have to consider implications beyond your own immediate
product.
-former Tek design engineer
Joerg
> Stupid title, but actual useful info on tantalum cap behaviour:
>
> http://www.edn.com/article/509092-What_a_cap_astrophe_.php
>
> Now that there's this existence proof, maybe there'll be a bit
> more...perhaps someone will write them another useful article, e.g. a
> compendium of all two-transistor circuits.
>
They could have reduced the text body to eight letters:
*PHUT* ... *BANG*
:-)
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
John Larkin
We've had tantalums fail months or years after a product was shipped.
On one of our VME modules, which we do burn in, well over half the
field failures were tantalum caps. Field MTBF increased by about 3:1
when we fixed that problem.
This is more an engineering issue than a test/burnin thing. Dry
tantalums have to be designed in very carefully, and the manufacturers
mostly don't want to tell you what's safe or not safe.
John
Joerg
Sounds just like LDOs :-)
John Larkin
wrote:
Lots of LDOs need tantalum output caps to be stable. It's a
conspiracy.
John
Glenn Gundlach
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Fri, 04 Jun 2010 13:25:20 -0700, Joerg <inva...@invalid.invalid>
> wrote:
>
>
>
> >John Larkin wrote:
> >> On Fri, 04 Jun 2010 09:53:36 -0700, "Paul Hovnanian P.E."
> >> <p...@hovnanian.com> wrote:
>
> >>> Phil Hobbs wrote:
>
> >>>> On 6/4/2010 10:04 AM, John Larkin wrote:
> >>>>> On Fri, 04 Jun 2010 09:47:43 -0400, Phil Hobbs
How do polymer caps stack up?
G²
John Larkin
>G�
Assuming that's a serious question, and not a terrible pun, they're
great, but ESR is so low that some LDOs won't like them.
They don't flame like tantalums, don't freeze like aluminums, and I'm
not sure about long-term reliability.
John
George Herold
Can't you add a bit of R?
George H.
>
> They don't flame like tantalums, don't freeze like aluminums, and I'm
> not sure about long-term reliability.
>
> John- Hide quoted text -
>
> - Show quoted text -
Michael A. Terrell
L is better for tantalums.
--
Anyone wanting to run for any political office in the US should have to
have a DD214, and a honorable discharge.
Joerg
Z is even better. I'd like one more hour of Z but I have to service the
pellet stove today ...
Archimedes' Lever
wrote:
>Z is even better. I'd like one more hour of Z but I have to service the
>pellet stove today ...
I could do that in my Z. :-)
k...@att.bizzzzzzzzzzzz
IBM used kabillions of the things for direct power rail bypassing, as well.
The problems were mainly because it was almost impossible to guarantee they
were stuffed the right way. They came up with all sorts of schemes, including
integrated fuses in the package, to solve the problem. Last I knew, they
still use tons of them (and run around in a panic when the global supply of
tantalum dries up, as it does every decade or so).
I still use tantalums (Aluminums, yuck!) for bulk capacitance. The only
problem we're having with them is T0 shorts on 220uF 16V caps. Some circuits
have a 10 or 25ohm 0603 series resistor and it takes that out.
k...@att.bizzzzzzzzzzzz
Phut - *BANG*! Yeah, sorta. ;-)
k...@att.bizzzzzzzzzzzz
Pellet stove? It'll be 90F today, and humid (T-boomers soon).
Joerg
> On Sat, 05 Jun 2010 09:05:19 -0700, Joerg <inv...@invalid.invalid> wrote:
>
>> Michael A. Terrell wrote:
>>> George Herold wrote:
>>>> On Jun 4, 7:22 pm, John Larkin
>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>> On Fri, 4 Jun 2010 16:15:49 -0700 (PDT), Glenn Gundlach
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> <stratu...@yahoo.com> wrote:
>>>>>> On Jun 4, 2:10 pm, John Larkin
[...]
>>>>>> How do polymer caps stack up?
>>>>>> G
>>>>> Assuming that's a serious question, and not a terrible pun, they're
>>>>> great, but ESR is so low that some LDOs won't like them.
>>>> Can't you add a bit of R?
>>>
>>> L is better for tantalums.
>>>
>> Z is even better. I'd like one more hour of Z but I have to service the
>> pellet stove today ...
>
> Pellet stove? It'll be 90F today, and humid (T-boomers soon).
We had to heat until end of May. Global warming, you know :-)
Pellet stove is done, now it's the wood stove. Way easier, piece of
cake. Then comes my all time favorite honey-do job, cleaning the ash
vacuum <cough, cough>.
Mycelium
I split off talking about ELs in the same breath. Sorry you missed it.
Mycelium
wrote:
Cool first hand info and response.
k...@att.bizzzzzzzzzzzz
>k...@att.bizzzzzzzzzzzz wrote:
>> On Sat, 05 Jun 2010 09:05:19 -0700, Joerg <inv...@invalid.invalid> wrote:
>>
>>> Michael A. Terrell wrote:
>>>> George Herold wrote:
>>>>> On Jun 4, 7:22 pm, John Larkin
>>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>>> On Fri, 4 Jun 2010 16:15:49 -0700 (PDT), Glenn Gundlach
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> <stratu...@yahoo.com> wrote:
>>>>>>> On Jun 4, 2:10 pm, John Larkin
>
>[...]
>
>>>>>>> How do polymer caps stack up?
>>>>>>> G
>>>>>> Assuming that's a serious question, and not a terrible pun, they're
>>>>>> great, but ESR is so low that some LDOs won't like them.
>>>>> Can't you add a bit of R?
>>>>
>>>> L is better for tantalums.
>>>>
>>> Z is even better. I'd like one more hour of Z but I have to service the
>>> pellet stove today ...
>>
>> Pellet stove? It'll be 90F today, and humid (T-boomers soon).
>
>
>We had to heat until end of May. Global warming, you know :-)
Yeah, tell me about it. I've been running the AC since the middle of April
(both on this weekend). I never used to run the AC until July. ;-)
>Pellet stove is done, now it's the wood stove. Way easier, piece of
>cake. Then comes my all time favorite honey-do job, cleaning the ash
>vacuum <cough, cough>.
No ashes here; gas logs.
John Larkin
wrote:
>k...@att.bizzzzzzzzzzzz wrote:
>> On Sat, 05 Jun 2010 09:05:19 -0700, Joerg <inv...@invalid.invalid> wrote:
>>
>>> Michael A. Terrell wrote:
>>>> George Herold wrote:
>>>>> On Jun 4, 7:22 pm, John Larkin
>>>>> <jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
>>>>>> On Fri, 4 Jun 2010 16:15:49 -0700 (PDT), Glenn Gundlach
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> <stratu...@yahoo.com> wrote:
>>>>>>> On Jun 4, 2:10 pm, John Larkin
>
>[...]
>
>>>>>>> How do polymer caps stack up?
>>>>>>> G
>>>>>> Assuming that's a serious question, and not a terrible pun, they're
>>>>>> great, but ESR is so low that some LDOs won't like them.
>>>>> Can't you add a bit of R?
>>>>
>>>> L is better for tantalums.
>>>>
>>> Z is even better. I'd like one more hour of Z but I have to service the
>>> pellet stove today ...
>>
>> Pellet stove? It'll be 90F today, and humid (T-boomers soon).
>
>
>We had to heat until end of May. Global warming, you know :-)
We have the heat on now. All year, in fact. Quite a change from New
Orleans.
John
Michael A. Terrell
John Larkin wrote:
>
> We have the heat on now. All year, in fact. Quite a change from New
> Orleans.
It's ironic that heating oil washes up on the beach where you don't
need it. :(
Mycelium
John Larkin
<myce...@thematrixattheendofthemushroomstem.org> wrote:
$88 each. Cool.
John
Mycelium
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:
>$88 each. Cool.
So, you can read ads and do math. Me too.
Mycelium
Made in the USA for the use of USA customers only.
Keep a hard working US cap maker employed today, buy Evans' capacitors!
JosephKK
I kind of have to agree, i haven't seen or heard of much stuff that
useful in EDN for over 40 years. Of course i have not been a subscriber
for over 25 years over the lack of content.