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Old 06-05-2010, 08:09 PM   #1
mjk
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Default What about all these SMD capacitors with no marking?

Am I missing something here or what?
How does one replace a capacitor that can't be identified?

I suppose that with a new board, you could unsolder each one of them and test it it with a MFD meter and then re-solder them. But, you can't tell what the voltage rating was.

Isn't this making us a throw away society even more?
Isn't this wasting National or World resources?

If the SMD resistor manufactures can label their parts, why can't the SMD capacitor manufactures do the same? Or maybe, require a schematic of any electronic item being purchased?

What are we going to do about this?
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Old 06-05-2010, 11:12 PM   #2
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Default Re: What about all these SMD capacitors with no marking?

I have no idea what you are talking about. I have never seen a motherboard capacitor that did not have a marking on it to its size (weather it be correct or not). some are not as obvious as others but are still there. so what exactly are you talking about? Can you give us an example of these caps that do not have any markings? I would like to see them..
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Old 06-06-2010, 10:04 AM   #3
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Default Re: What about all these SMD capacitors with no marking?

probably referring to ceramics.
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Old 06-07-2010, 03:42 AM   #4
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Default Re: What about all these SMD capacitors with no marking?

Quote:
Originally Posted by mjk
...If the SMD resistor manufactures can label their parts, why can't the SMD capacitor manufactures do the same?...
This is something I have often wondered. The only thing I can think of, is that it costs extra to laser print a capacitor, but then they do it to all resistors...

This used to be a big problem at my place of work, when the "pick & place" machine was accidentally loaded with the wrong capacitors. Without any markings on the SMD ceramic capacitors, there was no obvious way of knowing what was causing the fault on the boards.
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Old 06-07-2010, 04:01 AM   #5
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Default Re: What about all these SMD capacitors with no marking?

Quote:
Originally Posted by kaniki
I have no idea what you are talking about. I have never seen a motherboard capacitor that did not have a marking on it to its size (weather it be correct or not). some are not as obvious as others but are still there. so what exactly are you talking about? Can you give us an example of these caps that do not have any markings? I would like to see them..
Look at any SMD circuit board, & you will see many capacitors without markings. They are usually brown (but sometimes grey) small, rectangular components.
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Old 06-07-2010, 01:06 PM   #6
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Default Re: What about all these SMD capacitors with no marking?

Ok you are right. I was thinking about standard size caps.. not the mini ones like those..
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Old 03-04-2018, 05:30 AM   #7
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Default Re: What about all these SMD capacitors with no marking?

Quote:
Originally Posted by kaniki View Post
I have no idea what you are talking about. I have never seen a motherboard capacitor that did not have a marking on it to its size (weather it be correct or not). some are not as obvious as others but are still there. so what exactly are you talking about? Can you give us an example of these caps that do not have any markings? I would like to see them..
looks like you are living in the right place lol but the question remains why is it so?
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Old 04-14-2018, 07:03 PM   #8
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Default Re: What about all these SMD capacitors with no marking?

somewhere I did see a data sheet on these, it goes by size and shape. there is a card you can buy that has them all on and you put the one you have on the card and match it to the size and shape on the card. i have one some were.
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Old 04-14-2018, 08:53 PM   #9
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Default Re: What about all these SMD capacitors with no marking?

SMD ceramic capacitors are apparently rather sensitive to heat and physical stress, perhaps trying to label them brings a high probability of damage.
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Old 04-15-2018, 06:03 AM   #10
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Default Re: What about all these SMD capacitors with no marking?

Simply too little space to print series, capacitance and voltage.

In a large majority, they're decoupling capacitors ... 10nf 47nf, 100nf and voltage rating of 10..25v, maybe even less than 10v for <0402 footprints

In other places they're used in RC or other combinations for timing (on oscillators, switching regulators, micros etc) or for feedback or low pass/high pass filters or for other such purposes, so the values could be quite exact like let's say 270pF ... where would you fit .271 or something like that in a 0402 footprint?

And in some cases, the exact series of the capacitor does matter a lot die to voltage bias, or microphonics for example... See https://www.maximintegrated.com/en/a...ex.mvp/id/5527

Even if you'd have series you'd also need to have the voltage rating as maybe they use a 50v rated ceramic where they could have used a 16v one, for the reasons above..
It's better to look in service manuals for this info instead of the tiny capacitor..
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Old 04-15-2018, 08:40 AM   #11
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Default Re: What about all these SMD capacitors with no marking?

Quote:
Originally Posted by rgreair View Post
somewhere I did see a data sheet on these, it goes by size and shape. there is a card you can buy that has them all on and you put the one you have on the card and match it to the size and shape on the card. i have one some were.
The size of the SMD components is determined by the series number (0402, 1206, 2010 etc.) which indicates the package dimensions, so the value cannot be determined by size & shape alone, as there would be many different values in that series.
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Old 04-15-2018, 09:21 AM   #12
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Default Re: What about all these SMD capacitors with no marking?

Quote:
Originally Posted by mariushm View Post
...And in some cases, the exact series of the capacitor does matter a lot die to voltage bias, or microphonics for example... See https://www.maximintegrated.com/en/a...ex.mvp/id/5527 ...
Interesting article.

I never realised how drastically their capacitance could plummet with just a few volts of bias!
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Old 04-15-2018, 09:23 AM   #13
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Default Re: What about all these SMD capacitors with no marking?

It's a conspiracy so that designers makes it harder to find replacements!

It may very well be due to the fragility of the MLCCs and the fact that their value doesn't matter way too much. The print size can't be a problem because resistors are printed just fine.

Because capacitance and voltage both influence MLCC size I wish they would at least print one of these, then the other can be estimated by volume *sigh*
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Old 04-15-2018, 09:44 AM   #14
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Default Re: What about all these SMD capacitors with no marking?

if you guys wanna learn more

for ex same capacitance, voltage rating but could be different construction techniques to tackle some problems in some markets

EEVblog #1037 - Solving Ceramic Capacitor Cracking
https://www.youtube.com/watch?v=QgKY5QWehME

Dave demonstrates various practical PCB and component selection solutions and techniques to prevent flex stress cracking of Multi Layer Ceramic Capacitors (MLCC) on PCB's and preventing your product from catching on fire!

EEVblog #859 - Bypass Capacitor Tutorial
https://www.youtube.com/watch?v=BcJ6UdDx1vg&t=16s


EEVblog #626 - Ceramic Capacitor Voltage Dependency
https://www.youtube.com/watch?v=2MQyQUkwmMk
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Old 04-18-2018, 02:39 AM   #15
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Default Re: What about all these SMD capacitors with no marking?

you sometimes have to find the design sheet and go digging for the circuit to get the info
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