Re: [SI-LIST] : (unknown chars) : [SI-LIST] : stackup impedance.

[email protected]
Wed, 17 Sep 1997 08:53:49 -0400

To get the proper impedance on your signal layers you could play with t=
width of the traces (ie different of width on layer 1 and 2). Putting
ground and power layer as close as possible together gives you good

Wojciech Babij

[email protected] on 09/17/97 07:57:53 AM

To: [email protected], [email protected]
cc: (bcc: Wojciech Babij/UB Networks)
Subject: [SI-LIST] : ?? : [SI-LIST] : stackup impedance.


For S-S-G-P-S-S stackup, to avoid crosstalk, the distance
between first signal layer and second must be much larger than the
distance between second signal layer and power or ground plane(a=
least 3 times), which in turn will result in large differences of th=
trace's characteristic impedance between first signal layer and secon=
, not good for signal. Is there any special reason to arrange the
stackup in such manners? However, for the signal layer that is close=

to the plane, formula for embeded microstrip might still work, for the=

top or bottom layer, it will vary according to the neighboring trace in=

the second and third signal layer accordingly. We have tried such
stackup, lots of troubles.
> -----????-----
> ???: John Lin - TAO [SMTP:[email protected]]
> ????: 1997?9?17? ?? 02:45
> ???: 'SI_LIST'
> ??: [SI-LIST] : stackup impedance.
> Hi,
> Does anybody have idea about how to calculate the impedance of
> stackup with following structures.
> S-S-G-P-S-S ( 6 layers).
> and
> G-S-S-S-S-P (6 layers).
> I checked books and tried to find equations to calculate impedance.
> However, I cannot find any.
> Best Regards,
> CAE Engineer of EDA Department
> Digital Equipment Corp. Taiwan Branch
> Email: [email protected]
> TEL: 1-886-3-3900000 ext. 2565