I have a situation where I need to run several parallel traces,
all carrying 5amps simultaneously.
They are run side by side in batches of 3-4 (20 in all)

I remember hearing that the IPC chart tested external traces
and doubled the requirement for internal, so if I use a 40mil
trace for 5amps (2oz), an 80mil would suffice for internal.
I've since heard (from Jouppi?) that this internal number
is over-rated. Is that true?

If I use Doug Brook's PCBTEMP calculator (http://ultracad.com)
and type in my 2oz, 40mil, external trace I get a 16 degree rise,
which is fine. but when I switch to INTERNAL, with 80mil I get
a 29 degree rise. not acceptable.

SO MY QUESTION IS:
If the internal IPC chart was over-rated, why am I getting a
higher temp in the PCBTEMP calculator for internals?

I must have heard it wrong about the IPC charts?

Also, for any of you working with power out there, I'm concerned
that these calculators are thinking of a SINGLE trace around
a bunch of normal traces. How much different are my results
going to be if I am running LOTS of 5amp traces side by side?
I don't have access to ThermalMan or HavardThermal (or any
other tools except PCBTEMP)

hot and bothered,
Jack

---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------