WeberChuang@via.com.tw on 09/17/97 07:57:53 AM
To: LinJohn@mail.dec.com, si-list@silab.Eng.Sun.COM
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:LinJohn@mail.dec.com]
> ????: 1997?9?17? ?? 02:45
> ???: 'SI_LIST'
> ??: [SI-LIST] : stackup impedance.
> Does anybody have idea about how to calculate the impedance of
> stackup with following structures.
> S-S-G-P-S-S ( 6 layers).
> 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: Linjohn@mail.dec.com
> TEL: 1-886-3-3900000 ext. 2565