🚀 go-pugleaf

"Dennis" <dennis@nowhere.com> wrote in message 
news:4a683e83$0$9756$5a62ac22@per-qv1-newsreader-01.iinet.net.au...
>
> "Shaun" <not.today@go.away.au> wrote in message 
> news:4a68395a$0$3253$afc38c87@news.optusnet.com.au...
>>
>> "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.
>>
>>
>
> Coating or encapsulation? Coating could be insignificantly thin.
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.