Per Viklund wrote:
>
> Yes please!
> Me too.
>
> There got to be some simplified equations one can use.
> I've heard about some freeware/shareware but these must be based upon
> some equations.
> Anybody got them?
>
> Regards
>
> Per Viklund
> DDE Sverige AB
>
> Clint Cote wrote:
> >
> > I'm looking for a way to capture what-if calculations for trace width/temp rise
> > above ambient for internal/external layers. I know about the charts in
> > IPC-D-275 but I'm looking for a spread sheet or stand alone app. that I can
> > print the results from. I don't have the time to build it my self and I would
> > appreciate help from anyone that might have a solution.
> >
> > Thanks
> > =============================================================
> > Clint Cote GE Fanuc Automation
> > PCB Designer PO Box 8106, Mail stop D-40
> > Phone: (804) 978-5946 Charlottesville, VA 22906
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> >
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Ya'll need to subscribe to Technet.
Ralph Hersey wrote:
>
> A formula for generating the chart was recently presented at IPCWorks
> '97 "Emperical equation for sizing copper PWB traces" by John McHardy
> and Mehendra Gandhi, Hughes Aircraft, technical paper SO6-2-1, and is
> in the form of I = k (T^0.44) (A^0.725)
>
> Where:
> I is current in amps.
>
> k is a constant = 0.048 for "external", and 0.024 for "internal"
> conductive patterns.
>
> T is the thermal rise above ambient in deg. C
>
> A is the area is in sq.mils. (as in inches).
>
> For outer layers, the model is very close to the MIL-STD-275 charts,
> it is more conservative at 100 deg C above ambient ~28 A for the
> model -vs- ~33 A for -275.
>
> In talking with John at IPCWorks '97, we discussed the variation
> between the model and the -275 charts, in particulat the inner layer
> model. There is also some deviations for inner layers, at 10 deg C,
> the model is more agressive (greater current) than -275 above about
> 5 A and 500 sq.mils. We agreed that "we as an industry" needs to
> conduct a study to determine what the real world really is and what
> the model should be.
>
> At ~ 700 sq.mils. the current for -275 is ~ 6 A, where the model is
> ~6.5 A. For other internal thermal rises, there is good agreement.
> Ralph Hersey
>
> Ralph Hersey & Associates
> 3885 Mills Way
> Livermore, CA 94550-3319
> PHN: 510.454.9805
> FAX: 510.454.9805
> e-mail: [log in to unmask]
>
coming soon to my web page.
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