Subject: temperature rise on a trace
   Date: Wed, 16 Dec 1998 09:11:02 -0600
   From: [log in to unmask]
     To: [log in to unmask]


This comes from any undergrad heat transfer book.

Assuming worst case, no heat lost to air or conducted away through the epoxy of
the board, then

Temp rise = (Power x time)/(mass of copper trace x specific heat of copper)

Power = current^2 x resistance of trace

density of copper is 8954 kg/m^3

specific heat of copper is 383 J/kg C

You can figure it out from here.

Tony Kordyban
Tellabs Operations


(For more info on things like this, check out my book "Hot Air Rises and Heat
Sinks:  Everything You Know About Cooling Electronics Is Wrong", available from
ASME Press, or amazon.com)


Hiteshew, Michael wrote:
>
> Hi,
>         I have a little physics problem maybe someone can help me with. I'm
> looking
> for an equation to solve for the temperature rise in a trace with a given
> amperage over
> a given period of time. Here's the problem:
>         A copper (inner layer) trace will have 6 amps on it (under short
> circuit conditions)
> for a maximum of 128 microseconds. For a given trace width and length, I can
> calculate
> the DC resistance. What I can't calculate is the temperature rise on that
> trace over that
> time. Obviously, I need to know this to ensure I don't approach the fusing
> temperature
> of the copper.
>         I'll turn this into a science project if I have to, but I'm
> wondering if anyone has
> this equation at their fingertips. Thanks in advance if you do.
>
>  Michael Hiteshew
>  Lockheed Martin Launching Systems
>  [log in to unmask]
>  (410) 682-1259
>
>

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
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
################################################################