[SI-LIST] Core or prepreg between signal and plane layers
- From: Johan Lans <johan.lans@xxxxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Fri, 19 Oct 2012 18:52:46 +0200
Hi
I'm working on a 16 layer board for video processing. There will be 100
Ohm differential pairs for 3Gbit digital video signals. Stackup is signal
on top layer, 2nd layer power, 3rd gnd, 4th signal, 5th signal, 6th power,
7th gnd and so on.
The manufacturer of the board wants to put prepreg between lyr 1 and 2, 3
and 4 etc and core between 2 and 3, 4 and 5 etc. A collegue of mine claims
that this stackup will give a less uniform impedance of the diff pairs,
since the distance from signal to plane layer will vary more due to the
initial softness of the prepreg. The manufacturer will produce a board with
core between signal and plane for a higher price, since layers registration
will be more difficult. Does anyone know how much this effect matters, and
if it's worth the money to get the more difficult to produce board?
/Johan
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