[SI-LIST] Re: Pulse current handling capability of PCB
- From: steve weir <weirsi@xxxxxxxxxx>
- To: Jack Olson <pcbjack@xxxxxxxxx>
- Date: Tue, 15 Sep 2009 08:24:01 -0700
The equation is just a derivation from the material properties:
1oz Cu 1.3mils thick.
pCu = 0.68E-6 Ohms / " = 0.5mOhms*oz / square
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> 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>; <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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>>> -----Ursprüngliche Nachricht-----
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>>> Von: 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
>>> 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
>>>
>>
>
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