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September 2012

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TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
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Fri, 7 Sep 2012 08:36:45 -0700
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Hi Pete,

Thanks for your response.  My post was somewhat confusing, as by OSP over 
Immersion Silver I actually meant to use Semblant SPF or SCI for corrosion 
protection.  I was advised by a member to re-post it with correction. 

I really wanted to know if Immersion Silver can be selectively applied to 
certain part of circuit, which I know now is not correct.  Rest of the 
board will still have solder mask, so SPF or SCI can be applied only to 
the part of the circuit with no solder mask.

I have been adjusting trace impedance to take in to account the solder 
mask effect.  However it still produces non-uniform impedance due to 
uneven application of solder mask. 



Regards
Ravinder Ajmani
HGST, a Western Digital company
[log in to unmask]
 

5601 Great Oaks Pkwy. 
San Jose, CA 95119-1003
www.hgst.com




Pete <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
09/07/2012 06:21 AM
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Pete    <[log in to unmask]>


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Re: [TN] PCB Fab process






Ravinder,

If you are using both Immersion silver and OSP, I believe that the 
Immersion Silver will be the replacement for the HASL, OSP can be applied 
selectively (not the entire board).  But neither provide good long term 
corrosion protection over traces.  If you must route high speed traces on 
outer layers, consider adjusting the trace width of the high speed traces 
to account for a solder mask cover.

You may want to subscribe to the Designer's council listserver for more 
advice on PCB design questions.

Pete



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