FYI
Steve Rose
PCB Design Engineer
Corning Incorporated
SP-DV-01-MOD 1 #8
Corning NY 14831
Phone: 607 974-1791
Fax: 607 974-1844
Email: [log in to unmask]
> ----------
> From: Greg Bordash[SMTP:[log in to unmask]]
> Reply To: DesignerCouncil E-Mail Forum.;Greg Bordash
> Sent: Friday, February 05, 1999 1:47 PM
> To: [log in to unmask]
> Subject: Re: [DC] ? Impedance Calculator at IPC's WEB site.
>
> Scott & the DC,
>
> I too have found a similar problem with the Impedance Calculator in Pads
> PowerPCB ver.2.1. I've noticed that the calculated value DOES NOT
> change
> when you change the thickness of the copper. It does not matter what the
> layer stackup is or what board type, 4L, 6L etc ...
>
> Another possible problem is that the final value is about 5-6 ohms higher
> than the calculators on the IPC & AUTOMATA web sites. So much for your
> 10%
> budget. It's amazing how much time is needed/wasted to check & re-check
> something as simple as this. Especially when you have to account for
> added
> copper plating thickness' and reduced track width due to the etching
> process.
>
> The question is .. What do you believe and if you do are you right ?
> If anyone knows the right answer to this one inquiring minds want to know.
>
>
> PS. Off on a tangent - Does anyone know how to remove coloured pencil
> marks
> off this small digitizing light table. It's really a pain in the neck.
> :)
>
> And by the way its -2 C and sunny here in Toronto.
>
> Regards, Greg.
>
> Gregory E. Bordash,
> Team Leader, PCB CAD Group
> ATI Technologies Inc.,
> 33 Commerce Valley Drive East,
> Thornhill, Ontario, Canada, L3T 7N6
> Phone:(905) 882-2600 ext: 8370, Fax: (905) 882-9339
> Email: [log in to unmask]
>
>
> > ----------
> > From: Scott Decker[SMTP:[log in to unmask]]
> > Reply To: DesignerCouncil E-Mail Forum.;Scott Decker
> > Sent: Friday, February 05, 1999 12:27 PM
> > To: [log in to unmask]
> > Subject: [DC] ? Impedance Calculator at IPC's WEB site.
> >
> > 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
> > -----------------------------------------------------------------
> >
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> following text in the body:
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> For technical support contact Hugo Scaramuzza at [log in to unmask] or
> 847-509-9700 ext.312
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To unsubscribe: SIGNOFF DesignerCouncil
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
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