Why don't they mark SMD caps?

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An interesting question was posted on another forum:
"can you get (ceramic) SMD caps (1206,0805 etc) with the values printed on
them?".

My first response was that I've very rarely seen this (like maybe once), and
while it is possible (see
http://www.synrad.com/search_apps/application_briefs/117-2.htm ), you
basically can't get labeled ones, they are almost always without markings.

It got me to thinking, why is it so?
My guess would be that it's due to the surface finish (or lack thereof) on
ceramic capacitors, and/or the delicate nature of their multi-layer
construction means they could be more easily damaged or properties altered
by the process.
As opposed to most SMD resistors that have a coating on them which would
allow for easy and accurate printing using various technologies.

Any know the real reason(s) why ceramic SMD caps don't have markings?

Dave.
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Re: Why don't they mark SMD caps?


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   Ahh..the caps could likewise be coated (and AFAIK they .are. coated
prior to potting for leaded versions).
   Then, given that coating, they could be marked like the resistors you
mentioned.
   BUT..that was "never" done so it will not be done (gotta stay in that
rut...).

Re: Why don't they mark SMD caps?



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I doult very much any manufacter would coat SMD caps as it would increase
the height to capacitor sits above the board, increasing the mounted
inductance, a crital factor when designing high frequecny boards.
Manufactuers spend a lot of money trying to reduce this unwanted property.

see http://www.avx.co.il/docs/techinfo/licadesign.pdf
or
http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/D1A54E16FEC61B058525721E006EF53C /$file/Sun%20Paper%20on%20ESL%20&%20ESR.pdf
although these articles deal with via placement they discuss the need to
reduce the size of the loop that current flows in, a loop that would be
increased if a capacitor had an extra coating on it.



Re: Why don't they mark SMD caps?



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http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/D1A54E16FEC61B058525721E006EF53C /$file/Sun%20Paper%20on%20ESL%20&%20ESR.pdf
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Coating or encapsulation? Coating could be insignificantly thin.



Re: Why don't they mark SMD caps?



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http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/D1A54E16FEC61B058525721E006EF53C /$file/Sun%20Paper%20on%20ESL%20&%20ESR.pdf
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It might be possible but I can't think of any non-conductive material that
could be layered thin enough and still go through a wave solder machine.



Re: Why don't they mark SMD caps?


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Um, so what about the stuff they put on resistors?

Ink is incredibly thin stuff.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms



Re: Why don't they mark SMD caps?



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    I didn't think an ink would withstand the the temperature (thinking
along the lines of markings either being etchings or printed then
encapsulated) but I have found an ink that could withstand the temperature,
can even be used on ceramic materials, only problem is it has the be air
brush stenciled, manufacture states it's not suitable for stamp or roller
application.
    Okay so I've got no idea why such an ink isn't used to directly print to
the capacitor,

Shaun



Re: Why don't they mark SMD caps?



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 There are plenty of SMD chip cap makers that emblazon a value ID marking
on their caps.

  The fact is more likely that you are using a size of cap that does not
allow such a marking. I would say that 0805 is the smallest size I have
seen markings on.

Re: Why don't they mark SMD caps?


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Can you provide links?

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No, the original person who asked the question specifically stated sizes as
big as 1206.
So it has nothing to do with physical size.
Can't say I've seen the values ever printed on caps even larger than 1206.

The question is about whay it's common to mark SMD resistors, but not common
to mark SMD caps.

Dave.
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Re: Why don't they mark SMD caps?



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  Note the requisite that was declared. They are 0805 or larger.

  The absolute cheapest variety will not have them.  The higher end
varieties likely will.

 The customer pays for the cap substrate medium and its termination
method. The markings never were charged for from my recall.

Re: Why don't they mark SMD caps?


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Yep, that's fine, you don't expect them on smaller ones.

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Like I said, can you provide links?

Dave.

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Check out my Electronics Engineering Video Blog & Podcast:
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Re: Why don't they mark SMD caps?



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  I found AVX data sheets that show them (markings), butI would want to
see marking actually mentioned in the data before I post what I find.

Re: Why don't they mark SMD caps?


From "Ceramic Commercial-Off-The-Shelf Surface Mount Capacitors (COTS)" from
Kemet:


"Marking
These chips are supplied unmarked. If required, they can be laser-marked as
an extra cost option. Details on the
marking format are included in KEMET Surface Mount Catalog F3102."



Re: Why don't they mark SMD caps?



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 That is a KEMET  LASER MARKING option.

 Do you really think that all cap makers follow the same business model
as Kemet?

Re: Why don't they mark SMD caps?



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Come to think of it, wave solder is more of a through hole process.
The modern process is reflow.  Wave solder does not pay well with SMD
parts on both sides, reflow does.

Re: Why don't they mark SMD caps?



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  Originally, SMD parts were used along with thru hole. The "solder
side", as it was called, had thermal cure glue at all the SMD locations,
and the SMD parts get placed  with no solder paste at all, and then the
curing oven bakes them in place. Then the boards went to a push line or
auto-inserter and the thru hole parts get added, being careful with the
solder side attached-but-not-yet-soldered parts.  During wave solder, the
PCB gets passed over a flux bubbler.  Next thing you know, the thru hole
and the bottom side SMD parts are soldered.

Re: Why don't they mark SMD caps?


On Thu, 23 Jul 2009 06:43:12 -0500, "Tim Williams"

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  Not ink.  It is a baked on enamel.  Axial resistors get fired in an
oven after they are painted.  That is why the stripes hold there color
through thermal cycling.

Re: Why don't they mark SMD caps?



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 chip caps are bare.  That is why they are hygroscopic too.

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Bullshit, if you believe the jerks in this NG your business won't go very
far.  If the part is too small to label, then how can you label it?  That's
the real reason.  It's not because of it's too cheap.  Another wrong
interpretation of the Rednecks.


Re: Why don't they mark SMD caps?



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  You're a goddamned idiot. IF you had enough brains to read the ENTIRE
thread, you would know that we are talking about 0805 and larger form
factors.

  Since you are a total retard from the get go, however, you are clueless
every time you post.

  They do not do it because it saves several manufacturing process steps,
idiot.  THAT IS COST.  Go the fuck away, idiot.

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