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

Wojciech_Babij@UB.com
Wed, 17 Sep 1997 08:53:49 -0400

To get the proper impedance on your signal layers you could play with t=
he
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
decoupling.

Wojciech Babij
NEWBRIDGE

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.

=

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(a=
t
least 3 times), which in turn will result in large differences of th=
e
trace's characteristic impedance between first signal layer and secon=
d
, 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
> -----????-----
> ???: John Lin - TAO [SMTP:LinJohn@mail.dec.com]
> ????: 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,
>
> JOHNLIN
> CAE Engineer of EDA Department
> Digital Equipment Corp. Taiwan Branch
> Email: Linjohn@mail.dec.com
> TEL: 1-886-3-3900000 ext. 2565
>
>

=