doug smith wrote:
>
> Scott,
> You need to specify which layers are planes and traces,
>
> Example:
> L1 s
> L2 p
> L3 s
>
> etc...
> Regards,
> Doug
>
> >>> Scott Decker <[log in to unmask]@yusa.com> 02/05 9:26 AM >>>
> Hi All
> I have a question / problem....
>   I recently used the Impedance calculator on IPC WEB site and
> found a very interesting problem. On one occasion a few weeks
> ago, I used the calculator to do a quick stackup for a board I'm
> working on. The results were fine and were used as a baseline
> for the FAB shop to find me the values they use. I was just showing
> another designer here this neat calculator and changed the values
> I used to the values that the FAB shop gave me. Guess What....
> The calculator came back with an un-balanced impedance value!
> This is a very strange problem. I put in a balanced stackup
> and the values for impedance were different from the top to the
> bottom by 5 ohms. Sure you say, that's the 10% but, why are the
> numbers different? Maybe some of you out their can try these numbers.
> First. 6 Layer Board.
> .5 oz on both outside layers and 1 oz on all inside signals and planes.
> .005" traces on all layers
> Dielectric thickness as follows:
>     6.5
>     10
>     18
>     10
>     6.5
> Er value of 4.2
> OK now you have the numbers, the impedance should be around 72 ohms.
> But Wait! The values I got were 77 72 72 72...... What Gives?
>
> Any Comments???
> I already herd that it's because the UV rays from the sun were hitting
> the top of the board more, but I don't think that's true....(:-}
>
> --
> Scott Decker
> Senior PCB Designer
>
> AKA: PadMasterson
> E-Mail: [log in to unmask]
> -----------------------------------------------------------------
>
>    ^
>   ^^^    Praegitzer Design - A Division of Praegitzer Industries
>  ^^^^^   7245 N.W. Evergreen Pkwy, Suite 100, Hillsboro, OR 97124
> ^^^^^^^  Phone #: (503) 531-2050 Ext. 1820  Fax #: (503) 531-2051
>             Check out our WEB site at http://www.pii.com
> -----------------------------------------------------------------
Doug,
 I didn't' say it specifically, but the calculator on the site comes up
with the stackup I had and is the only one that can be used in this
case.
It should be:
S1
P1
S2
S3
P2
S1
Later

--
Scott Decker
Senior PCB Designer

AKA: PadMasterson
E-Mail: [log in to unmask]
-----------------------------------------------------------------

   ^
  ^^^    Praegitzer Design - A Division of Praegitzer Industries
 ^^^^^   7245 N.W. Evergreen Pkwy, Suite 100, Hillsboro, OR 97124
^^^^^^^  Phone #: (503) 531-2050 Ext. 1820  Fax #: (503) 531-2051
            Check out our WEB site at http://www.pii.com
-----------------------------------------------------------------

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