SMD Capacitor Codes !

[engsamara]

Hi All,

I was Wondering If There Is A Code For Reading The SMD Capacitors Values 
I Searched about that !
But, there are some negative info about that 

Is there any code for them, especially Aluminum Electrolytic SMD ?!

Regards,
Arein

[pickit2]

A good start is here...

http://www.marsport.org.uk/smd/mainframe.htm

But there is no substitute for a meter...

[engsamara]

I Had A Look At The Website !

But Seems There Is No Rule For SMD Capacitors

Thanks

[pickit2]

In the real world, most SMD are not marked, they are supplied to OEM in reels of devices, or on tape.
if your lucky the device will have a house code, if your repairing a board, you can make an educated guess the value by where in the circuit, the device is.
don't forget capacitors have a wide tolerance so the guess work is ok, in most cases.

[h0nk]

Hello engsamara,

this one is from the ARRL-handbook chapter 22 in the case You really find a marked SMD capacitor.

As pickkit says, they are very rare.


Best Regards

[Parmin]

Capacitors are used for a few main purposes.
If you can figure out the purpose of the capacitor you can guess the value.
The difficult ones to guess are tuning capacitor where it needed to be of exact value.
The rest of them due to the nature of capacitor tolerance, it is possible to replace with similar decade rating based on their size and purpose.
In digital machines generally the capacitors are either decoupling (10n - 47n), coupling (100n) , snubbers (100p - 1n) or power conditioning (larger ones).

[Elmer]

Pickit is right ceramics aren't marked, but electrolytics (and tantalums) usually are. Three digits, where the last digit denotes zeroes to add, to get the value in picofarads. eg: 223=22000pF=22nF, 224=220000pF=220nF and so on.

[fpgaguy]

I have 0201, 0402, 0805's MLCC's on boards ... typically 1000's of them and I've never seen a marking of any kind on MLCC

If it's bypass you can usually guess it's 90% chance to be 0.1, but I use 1.0, 2.2, 0.22, 0.1, 0.01 and 0.001 depending on frequency of expected noise - but if you are repairing something it will probably not matter what you put back in


_but_ if you are in a feedback loop of a DCDC power supply or in PLL filter - then could be anything really

[keram]

Hello,
I can confirm, that there is no rules.
From my near 30 year experience I know that each manufacturer of capacitors provides its own rules for marking if applicable.
Especially you can buy capacitor engineering kits are they are most often marked if they are expensive.
e.g. for ATP porcelain capacitors you can orcder laser making option (http://www.atceramics.com/UserFiles/100b.pdf).
The same could be available for other suppliers.
Generally, small and cheap parts are not marked.
Aluminum, tantal, mika, foil are typoically marked but because they are marked without laser the package size must be big enough for it.