[SI-LIST] Re: Pulse current handling capability of PCB
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Jack Olson <pcbjack@xxxxxxxxx>
- Date: Tue, 15 Sep 2009 08:18:39 -0700
Jack it boils down to: Maintaining a reasonable current to avoid
deplating, and keeping the copper from getting too hot too fast.
100W/sqin @ 1 oz is about 13C rise every 10ms. Up to about 1ms that
holds the temperature rise under a couple degrees C in a short time is
not a problem.
Steve.
Jack Olson wrote:
> I am only familiar with the IPC minimum recommendations
> and various articles in trade publications that refer to that.
> (so I've never seen that equation.)
> Where can I learn more about this specific subject?
> I mean, how did you derive that 100W/sqin for 20us?
>
> What if he had said 40us? 200us?
> What if he had said 10Hz? 100Hz?
>
> That's a subject I'd like to know more about...
>
> Jack
>
> .
> On Tue, Sep 15, 2009 at 7:50 AM, steve weir <weirsi@xxxxxxxxxx
> <mailto:weirsi@xxxxxxxxxx>> wrote:
>
> Assuming whatever is connecting to this is not limiting, then the rule
> of thumb is:
>
> Resistive loss density = I^2*0.5mW/( copper_weight * trace_width^2
> ) where:
>
> resistive loss density is W/sq in
> copper weight is in oz / sq ft.
> trace width is in inches
>
> For even something as short as 20us I would stay below 100W / sq in.
>
> Steve.
> Deepak V.L wrote:
> > Hi Havermann, Pls find the answers below
> >
> > -is this a periodic surge event (>1Hz) or will it just happen
> "once a day"?
> > It is not a periodic surge, It can happen only once when the
> system is
> > switched on.
> >
> > -is this surge current the only current on this trace?
> > Yes
> >
> > -are there other traces on the surrounding area that might
> coheat this
> > trace?
> > No
> >
> > -whats the copper weight?
> > 1 oz
> >
> > -on which layer of how many layers
> > The traces are in the external layers (dobulb sided board)
> >
> > Thanks,
> > Depak
> >
> >
> > ----- Original Message -----
> > From: "Havermann, Gert" <Gert.Havermann@xxxxxxxxxxx>
> > To: "Deepak V.L" <deepak.vl@xxxxxxxxxxxxxx
> <mailto:deepak.vl@xxxxxxxxxxxxxx>>; <si-list@xxxxxxxxxxxxx
> <mailto:si-list@xxxxxxxxxxxxx>>
> > Sent: Tuesday, September 15, 2009 5:46 PM
> > Subject: AW: [SI-LIST] Pulse current handling capability of PCB
> >
> >
> > Dear Deepak,
> >
> > This depends on many factors:
> > -is this a periodic surge event (>1Hz) or will it just happen
> "once a day"?
> > -is this surge current the only current on this trace?
> > -are there other traces on the surrounding area that might
> coheat this
> > trace?
> > -whats the copper weight?
> > -on which layer of how many layers
> >
> >
> >
> --------------------------------------------------------------------------
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> Gesellschaft:
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> > persönlich haftende Gesellschafterin: HARTING Electronics
> Management GmbH;
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> > -----Ursprüngliche Nachricht-----
> >
> > Von: si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>
> [mailto:si-list-bounce@xxxxxxxxxxxxx
> <mailto:si-list-bounce@xxxxxxxxxxxxx>] Im
> > Auftrag von Deepak V.L
> > Gesendet: Dienstag, 15. September 2009 13:51
> > An: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
> > Betreff: [SI-LIST] Pulse current handling capability of PCB
> >
> >
> > Dear Experts,
> > Could someone please guide me how to select a trace width for
> carrying a
> > 100A surge current for 20us over a PCB trace ?
> >
> >
> > Thanks in advance,
> > Deepak
>
>
--
Steve Weir
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