FreeLists / si-list / [SI-LIST] PCI-E, Zdiff and Er

[Roy M <roymesi@xxxxxxxxx>]

Hi Everyone,
I'm designing a PCI-E board and trying to figure out what the Er (dielectric
constant) should be in order to achieve the 5-5-5 width-space demand for
PCI-E and the Zdiff=100ohm (i found out that 5-5-5 is the demand for PCI-E
traces - could anyone confirm that???).
i tried to find in the internet something related to Er for PCI-E but
couldn't find anything. I did find though that the standard width of the add
on card is 63mil (1.6mm), but regarding the Er - zippo.
 What kind of substrate is better to achieve the 5-5-5? (i mean FR4 of Er=
4.2 or maybe something else...)
Maybe somone here designed other space-width ratio and achieved
Zdiff=100ohm? because i didn't succeed... what i got for Er=3.8 was 4-8-4
and not 5-5-5
  Thanks,
Roy
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