FreeLists / si-list / [SI-LIST] Re: Via-In-Pad or Via-Next-To-Pad - which is best?

[Ray Anderson <Raymond.Anderson@xxxxxxx>]

I'd say the via-in-pad arrangement has the minimum
inductance of the two geometries you have described. 
The enclosed current loop will have a smaller area 
compared to the escaped via arrangement.

The inductance contributed by different diameter vias
is miniscule compared to the first order effects of
different loop areas.

-Ray Anderson

Sun Microsystems.

>
>
>Which has the minuimum inductance for a decoupling cap:
>
>1.  Blind via-in-pad with via diameter of 0.15mm finished, 
>    extending from layers 1 to 5 in a 6-layer board, OR
>    
>2.  Tracking to an immediately-adjacent 0.7mm pad, 0.3mm 
>    finished blind via,extending from layers 1 to 5 in a 6-layer 
>    board?
>    
>Many thanks,
>    
>-- 
>JP Nicholls  /  jpnicholls@xxxxxxxx

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