[PCB_FORUM] Re: How-to? [Impedance]

Have your fabricator work a stack up for you for a 50 ohm base board (if the 
majority, if not all of your nets are 50 ohms) with 5 mils as your 50 ohm wire 
width. this will eliminate the need to neck down at all.

________________________________

From: icu-pcb-forum-bounce@xxxxxxxxxxxxx 
[mailto:icu-pcb-forum-bounce@xxxxxxxxxxxxx] On Behalf Of William Billereau
Sent: Thursday, July 27, 2006 1:19 PM
To: icu-pcb-forum@xxxxxxxxxxxxx
Subject: [PCB_FORUM] How-to? [Impedance]


Hello All.
 
We are actually fighting with impedances!
all:all:50 ohm:5%
 
Allegro routes with an autocalculated line width of 5.68mils.
This is not possible to route inside the BGA which has an area with minimum 
line width set to 5 mils.
small lenght routed with 5mils have impedance DRCs.
 
I try to route them without the area using neck mode. The neck mode off the 
line is still 5mils. It does not switch again to 5.68mils...
but it is not even a solution because the neck has also DRCs.. grrrrr.
 
How do you generally proceed in such cases?
 
Thanks in advance!
 
    William.
 
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| Billereau William | PCB Designer |
| | Tel: (+4122) 76 73403 |
| CERN TS/DEM | william.billereau@xxxxxxx |
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