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Grogster

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Posted: 11:48pm 23 Feb 2013

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SMD resistors are labeled - such as 103(10k), but so far as I have found, NO SMD ceramic caps are marked - NONE of them. They are all the same brown colour, albeit different shades of brown from different manufactures, and also physically taller caps in any standard size, but I have never come across any that are labeled with the capacitance such as 104(100n) or 105(1uF).

How come?

Smoke makes things work. When the smoke gets out, it stops!

MOBI
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Joined: 02/12/2012
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Posted: 02:32pm 24 Feb 2013

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Hi Graeme,

Like you, I have wondered the same thing. I (probably like you) googled for the reason. None given. I did find recurringly, the statement that SMT Caps are generally not labelled.

A few sites suggested a good capacitance meter. That is what I use.

I guess that the most SMT caps we use in digital configurations will be of the VDD decoupling type and so will be around 104.

Mind you, some of the SMTs are so tiny, I doubt if one could read the markings even with good eyes and a maggie.

David M.

Grogster

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Posted: 03:17pm 24 Feb 2013

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I agree on the smaller ones! :D

Let me amend the details to why don't they label 0805/0806/1210 etc - the bigger of the SMD caps.

It's not really a problem - I just make sure I put the SMD caps I buy into partitioned and labeled fishing tackle boxes when I get them, to avoid any confusion, but I have often wondered why they are not marked like the resistors are.

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Warpspeed
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Joined: 09/08/2007
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Posted: 03:28pm 06 Mar 2013

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Probably because the capacitance value is only one part of identifying a capacitor.
You might also be interested in knowing the dialectic type and voltage rating if ever one needs replacing.

Resistors are easy, the resistance value and physical size tells you everything.

In todays throw away world, very few surface mount boards are ever repaired.
I did this myself for a while, but without a circuit, and with multilayer boards, and not being able to identify components, it is a very difficult time consuming task.

Usually it is cheaper for a manufacturer to just replace whole boards than to try to fix them. The whole board then becomes one replaceable component.

If you are going to do that, there is no need to identify anything, and the whole board can be covered in a conformal coating, so you cannot even see individual components or probe the ends.
Individual capacitors and resistors become just anonymous bumps in the coating.

Cheers, �Tony.

Grogster

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Posted: 09:51pm 06 Mar 2013

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[quote]Probably because the capacitance value is only one part of identifying a capacitor.
You might also be interested in knowing the dialectic type and voltage rating if ever one needs replacing.[/quote]

Good point.

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Downwind

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Posted: 02:06am 07 Mar 2013

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Still i think a capacitance value on the chip would be a great advantage, on average a certain package will often fall into a particular category, so some basic information on the chip value would be a good start.

Pete.

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