Why don't they mark SMD caps? - Page 2

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Re: Why don't they mark SMD caps?



Quoted text here. Click to load it

They'd also be a little hard to solder in. ;-)

Cheers!
Rich


Re: Why don't they mark SMD caps?



"David L. Jones" wrote:
Quoted text here. Click to load it


   Most of what we used were marked with a two character code.  The
cheaper suppliers were unmarked.  I have a javascript I wrote to let
production workers ID SMD caps.  Of course we were building equipment
for NASA, NOAA, the ESA and military, so they didn't mind the fraction
of a cent more per cap to pay for markings.

   I'll try to upload the zipped script files if you'd like to see them.


--
You can't have a sense of humor, if you have no sense!

Re: Why don't they mark SMD caps?


On Thu, 23 Jul 2009 10:58:49 -0400, "Michael A. Terrell"

Quoted text here. Click to load it


  Caps with markings did NOT have a higher price schedule, dipshit.

Re: Why don't they mark SMD caps?


On Thu, 23 Jul 2009 10:58:49 -0400, "Michael A. Terrell"

Quoted text here. Click to load it

  Wrong again.  Markings fell out of vogue as part size decreased to the
point where it was labor intensive to even examine the marking.

Re: Why don't they mark SMD caps?


On Thu, 23 Jul 2009 17:47:08 -0700, Archimedes' Lever

Quoted text here. Click to load it

Then why are they still there on resistors of the same size, DimBulb?

Re: Why don't they mark SMD caps?



Quoted text here. Click to load it


  Because resistors are fired glazed parts to seal the resistance medium
from moisture, and that can have legible letters included.  If chip caps
had an outer glaze or epoxy slab on them, lettering could easily be
added.  The industry has found better performance from uncoated MCCs, and
fire glazing is out of the question as the layer terminations are
thermally sensitive.

 The chip cap markings, even on the larger form factor parts, was a very
fuzzy, out of focus character set, beneath the actual first surface of
the mlcc.  Maybe laser etched or it is a very very thin ink.  Some were
surface marked, but most were submerged. On a smaller form factor, that
becomes very hard to see, and adds labor to inspect via the marking, and
it does become harder to manufacture as well, causing more fab failures
before they even get going.

  Visual comparison with the reel is the most common and preferred method
for already installed parts. Visual comparison and testing for loose
parts.  Some can be ID'd by their 'color', which *can* indicate substrate
choice,which should be easy to note on the reel info label.  When certain
caps are a buck each (microwave SMD chip caps), and others are fractions
of a penny (El Cheapo Browno), one wants to be sure that one places the
right part in the right locations.

Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

What labour ?

geoff



Re: Why don't they mark SMD caps?



Quoted text here. Click to load it
  Now, in the modern facility, post assembly inspection doesn't really
even happen any more as it relates to part values.  Most post reflow
inspection is for locating any tombstoned or pad shifted parts.

  BGA requires X-ray to inspect.

  There was a time, however, when a post process inspector would actually
examine the discreet parts on an assembly, and verify the value of parts.
This was particularly true of a first article assembly, prior to a
production run.

  Now that form factors are so small, actual part value verification on
assemblies is rare.  It is also more difficult. Even with the
magnification aids.

  And the likelihood that a test or repair technician would know how to
read a chip cap with anything other than a meter is very, very close to
nil.

Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

Why do resistors of the same size still commonly have the markings then?
It's not about the size, we are talking 1206/0805 and other large sizes
here.
Markings on these size caps are not common (some would say rare), and it's
*always* been that way.
The question is why?...

Dave.

--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
We've slightly trimmed the long signature. Click to see the full one.
Re: Why don't they mark SMD caps?



Quoted text here. Click to load it

  It maybe has "always been that way" with el cheapo brands, but I used
to do pre-reflow inspection (post pick and place), and have loaded the
cassettes into the picker placer, and have loaded the reels into the
cassettes and have programmed the PCB into it... yada yada yada...

  I have seen a lot of caps that were marked, so you are either using
cheap parts and always have, or your "always has" only amounts to a year
or two, since they now seldom do it.

Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

Can you poin us at not-so-cheap marked SMD capacitors so I would always use
those in my projects? I don't care if they twice the price of those unmarked
cheap ones...

---
******************************************************************
*  KSI@home    KOI8 Net  < >  The impossible we do immediately.  *
We've slightly trimmed the long signature. Click to see the full one.
Re: Why don't they mark SMD caps?



wrote:
Quoted text here. Click to load it

Well, looking at some bog-standard 0805 0.1 uF 16V ceramic caps
available from Digikey, only Kemet mentions even optional marking (as E
noted above). No mention at all, that I saw, in the datasheets for
Panasonic or Murata or Yageo or Johanson. Must be that those are all "el
cheapo" brands, I suppose.

--
Rich Webb     Norfolk, VA

Re: Why don't they mark SMD caps?



Quoted text here. Click to load it

  I like obsolete marking systems.

http://my.execpc.com/~endlr/markings.html

Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

Money.

It's way too expensive to mark teeny tiny little parts that nobody's
ever going to look at anyway - the reels are clearly marked, and they're
loaded into the stuffing machine, and that's the last human interaction
the parts will ever see.

If you're hand-prototyping, you'd either have to mark them yourself
or mark the tape carrier or bin or envelope where you're keeping them.

Hope This Helps!
Rich


Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

I learned how to solder the little resistors, and that requires the microscope.
They still look small. The iron looks like a bat and the tweezers a claw, and
the little resistor looks like a speck.

I would need a stronger scope to read any lettering on it.
Some larger parts have little two letter codes on them and I don't even want to
know what they mean.

greg

Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

Then why do they mark the exact same size resistors?
Resistors are generally cheaper than caps, so it would make more sense not
to mark the resistors to increase the margin, so it would be the other way
around, if that's the real reason.

Dave.

--
---------------------------------------------
Check out my Electronics Engineering Video Blog & Podcast:
We've slightly trimmed the long signature. Click to see the full one.
Re: Why don't they mark SMD caps?



Quoted text here. Click to load it
  SMD resistors get a ceramic glaze coating over the applied resistance
medium.  It gets fired on.  The lettering is usually fired glaze as well.
The resistance medium is hygroscopic, so they have to seal it up.

  multilayer chip caps CANNOT be fired in an oven that way.  They barely
make it through the reflow process.

Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

No. They _DO_ mark resistors and resistors are generally even cheaper than
capacitors.

---
******************************************************************
*  KSI@home    KOI8 Net  < >  The impossible we do immediately.  *
We've slightly trimmed the long signature. Click to see the full one.
Re: Why don't they mark SMD caps?



Quoted text here. Click to load it

  Learn to read, ditz!  Nobody was talking about resistors.  Christ! That
is even obvious from the title!

Re: Why don't they mark SMD caps?


Quoted text here. Click to load it

Umm, yes it's about resistors too, it was mentioned in my very first post.
My original question is why don't they mark SMD capacitors, when it's very
common to mark the same size SMD resistors.
So Sergey's remark is perfectly valid. It's common to mark cheap resistors,
but it's not common to mark more expensive capacitors of the same size -
why?
It's clearly not about cost, as Rich mentioned.
I'm assuming the reason is technical/process related, and not historical
etc, but I'm not sure, so that's why I  asked.

Dave.

--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
We've slightly trimmed the long signature. Click to see the full one.

Site Timeline