🚀 go-pugleaf

"Robert Baer" <robertbaer@localnet.com> wrote in message 
news:ttqdnac-5O96jPXXnZ2dnUVZ_sidnZ2d@posted.localnet...
> David L. Jones wrote:
>> An interesting question was posted on another forum:
>> "can you get (ceramic) SMD caps (1206,0805 etc) with the values printed 
>> on them?".
>>
>> My first response was that I've very rarely seen this (like maybe once), 
>> and while it is possible (see 
>> http://www.synrad.com/search_apps/application_briefs/117-2.htm), you 
>> basically can't get labeled ones, they are almost always without 
>> markings.
>>
>> It got me to thinking, why is it so?
>> My guess would be that it's due to the surface finish (or lack thereof) 
>> on ceramic capacitors, and/or the delicate nature of their multi-layer 
>> construction means they could be more easily damaged or properties 
>> altered by the process.
>> As opposed to most SMD resistors that have a coating on them which would 
>> allow for easy and accurate printing using various technologies.
>>
>> Any know the real reason(s) why ceramic SMD caps don't have markings?
>>
>> Dave.
>   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 http://www.avx.co.il/docs/techinfo/licadesign.pdf
or 
http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/D1A54E16FEC61B058525721E006EF53C/$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.