Why don't they mark SMD caps?

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...).

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

or $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.

$file/Sun%20Paper%20on%20ESL%20&%20ESR.pdf

Coating or encapsulation? Coating could be insignificantly thin.

$file/Sun%20Paper%20on%20ESL%20&%20ESR.pdf

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.

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

Ink is incredibly thin stuff.

Tim

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Website: http://webpages.charter.net/dawill/tmoranwms

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

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

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.

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.

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!

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

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

Cheers! Rich

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

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.

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Can you provide links?

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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Check out my Electronics Engineering Video Blog & Podcast:
http://www.alternatezone.com/eevblog/

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

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

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

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