Since the edges of the traces slope down somewhat, due to the etching
process, I would prefer one trace with twice the single width over 2
traces set apart.
If inductance is a topic, as ist sometimes is with high currents, and I
remember it correctly, L will also be less for a single trace twice as
wide compared to two traces of a single width.
But to answer your original question, I would check number 2). The wider
the better. The charts predict a temperature rise based on thickness and
width. From an ambient point of view, two traces that are close together
can be seen as one, the width of which is the sum of the individual
widths, multiplied with a factor <1 e.g. 0.75.
Cheers,
Volkmar
Volkmar Huss, C.I.D.
Prettl Elektronik Luebeck GmbH
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Jack
Olson
Sent: Thursday, May 10, 2007 4:54 PM
To: [log in to unmask]
Subject: Re: [DC] Current vs. Temperature (IPC vs. PCBTEMP)
Thanks for explaining to everyone how unique my "challenge"
is, but I would think others have faced similar situations.
I'm not really asking anyone to solve my problem for me, and it this
unique application doesn't really warrant buying and learning a thermal
simulator, but it just makes me wonder how other people treat the
problem.
Many people I'm sure have multiple currents on a board.
(I don't think ALL of us are doing 2.5V digital designs)
If you assume the chart or calculator is for a single trace, and you
have TWO traces, do you:
1) use the single trace values?
2) increase the width a little?
3) try to leave space between them?
4) simulate it?
So its kind of a POLL.
What do YOU do?
just curious,
Jack
On 5/9/07, Brooks,Bill <[log in to unmask]> wrote:
>
> Generally most boards do not have the same conditions that Jack is
> describing to the group. This is a specialized application and I would
> recommend doing a thermal model of the board before making any
> assumptions.
> We use a program called ICEPACK
>
> (http://www.ansys.com/products/icepak/default.asp )
>
> along with our Solidworks 3D model of the board assembly which is a
> direct output from the Altium Designer board design program and we can
> plug thermal temp and conductivity values into the board assembly and
> predict what the temps will be at any given ambient in any enclosure
> we design.
>
> The challenge facing Jack is predicting what the total load of heat
> will raise the temperature to hoping of course that it does not exceed
> the Tg of the board material.
>
>
> Bill Brooks
> PCB Design Engineer, C.I.D.+
> Tel: (760)597-1500 Fax: (760)597-1510
> Datron World Communications, Inc.
> Vista, California
>
>
> ----------------------------------------------------------------------
> ----------- 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=4.3.16for additional
> information, or contact Keach Sasamori at [log in to unmask] or
> 847-615-7100 ext.2815
>
> ----------------------------------------------------------------------
> -----------
>
------------------------------------------------------------------------
---------
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
------------------------------------------------------------------------
---------
---------------------------------------------------------------------------------
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
---------------------------------------------------------------------------------
|
