# [SI-LIST] : ¦^ĀŠ : [SI-LIST] : stackup impedance.

Weber Chuang ([email protected])
Wed, 17 Sep 1997 14:57:53 +0800

Hi,

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(at
least 3 times), which in turn will result in large differences of =
the
trace's characteristic impedance between first signal layer and =
second
, 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.

regards
weber =20
=20
> =B1H=A5=F3=AA=CC: John Lin - TAO [SMTP:[email protected]]
> =B6=C7=B0e=AE=C9=B6=A1: 1997=A6~9=A4=EB17=A4=E9 =A4U=A4=C8 02:45
> =A6=AC=A5=F3=AA=CC: 'SI_LIST'
> =A5D=A6=AE: [SI-LIST] : stackup impedance.
>=20
> Hi,
> Does anybody have idea about how to calculate the impedance of
> stackup with following structures.
>=20
> S-S-G-P-S-S ( 6 layers).
>=20
> and
>=20
> G-S-S-S-S-P (6 layers).
>=20
> I checked books and tried to find equations to calculate impedance.=20
> However, I cannot find any.
>=20
>=20
> Best Regards,
>=20
> JOHNLIN
> CAE Engineer of EDA Department
> Digital Equipment Corp. Taiwan Branch
> Email: [email protected]
> TEL: 1-886-3-3900000 ext. 2565
>=20
>=20