Hi Jimmy,

I would like to help analyze the copper thickness issue with you but first I
would need to know more about the specifics of the design...

Here are a few questions that come to mind...

What was the width of the trace(s)?
How long were the traces?
Did you pass the traces from one side of the board to another or an internal
plane using multiple vias?
Were the traces external or internal to the board structure?
Were they under a solder mask?
What was the board material type and stack up?
What was the temperature ambient that the board was being spec'd to survive
in?
Were there planes in the board?
Are there other heat producing devices pumping heat into the board near the
traces?
What is nature of the heat conduction path to the ambient air?

Thermal rise of the high amperage traces and voltage drop across them needs
to be looked at as a system issue... there are many factors that can affect
the results...

Mike Jouppi's Thermal Man's website is a terrific source for more accurate
calculations, but that doesn't mean that you should not build some 'extra
headroom' in your designs to cover for worst case situations... In fact the
IPC charts that were developed for the Military back in MIL-STD-275 were
designed with that headroom in them... de-rated by at least 50%, so they
made designs more robust... and thus more survivable under extreme
conditions.

Send me some more specifics and we can think about the failure issues and
come up with a solution... I have design boards for 2500 Watt switcher power
supplies and RF power amplifiers so I may be able to lend a little insight
into the problem if I can get a little more info to fill in the gaps.


Best regards,

Bill Brooks - KG6VVP
PCB Design Engineer, C.I.D.+, C.I.I.
Tel: (760)597-1500 Ext 3772 Fax: (760)597-1510
Datron World Communications, Inc.
_______________________________________
San Diego Chapter of the IPC Designers Council
Communications Officer, Web Manager
http://dcchapters.ipc.org/SanDiego/
http://pcbwizards.com

-----Original Message-----
From: Jimmy Blier - Paradox [mailto:[log in to unmask]]
Sent: Wednesday, April 19, 2006 11:44 AM
To: [log in to unmask]
Subject: [DC] The capacity of electric plating to carry current

Hi everyone,

I'm facing a dilemma regarding the capacity of electric plating to carry
high currents.

We made a PCB that had to handle a current of 30 amps.

We made some calculations and figured that we needed 3 once copper thickness
to achieve the requirements.

The PCB manufacture didn't have in stock the required thickness, so they
proposed to use a PCB 2 once thick and simply electro plate the missing
once.

Since we were short in time we agreed to the proposal.

The results we got are completely off the track according to what we
expected.

What could be responsible for this?

Does electric plating has the same current capacity or does it differ from
the plain old copper on the PCB?

Or could this be the result of a calculation error from our part?

If so can anyone tell me were I can find more accurate charts and data to
establish what need for this high current design?

Cheers,

--

Jimmy Blier
Senior PCB designer
Paradox Security Systems Ltd.
780 Industrial Blvd.
St-Eustache, Quebec, Canada J7R 5V3
Phone : 450.491.7444 Fax : 450.491.3454
<mailto:[log in to unmask]>
<http://www.paradox.ca/>

----------------------------------------------------------------------------
-----
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
---------------------------------------------------------------------------------