Mike,

Sorry to have to say this but putting 50 amps through a backplane is a
lousy idea, whoever thought of it needs to consider far more practical
solutions such as copper bussbars or wires.  You will be having way
too much IR (voltage) drop and God Forbid if you get a short, the IR
heating will peel that trace right off the laminate (the epoxy will
fry).

Hardly a safe method, IMNSHO.

I assume you need to get power to a bunch of connectors on boards
being plugged into the backplane?  One way to do it is to put Phoenix
Contact screw terminal blocks adjacent to the backplane connectors and
wire to them with whatever guage wire the amps flowing call for.

Bob


----- Original Message -----
From: DeVita, Mike <[log in to unmask]>
To: <[log in to unmask]>
Sent: December 21, 1999 9:58 AM
Subject: [DC] Plating limitations


: Happy Holidays,
: I am working on a backplane design that requires the ability to
handle up to
: 50Amps. This brings to mind alot of questions.
:
: To handle that kind of current I need a trace with a width no less
than .82"
: with 2oz material, or  .55" with 3oz material, with a 20 degree C
: temperature rise.
:
: 1) What are the ramifications of using 2 or 3oz copper current
carrying
: external layers and 1 oz for internal signal layers ie warping,
cost,
: manufacturability, hole plating issues.
:
: 2) If I use the 2 external layers as planes with 1 or 1.5oz copper,
I can
: double the heat disipation area (roughly) and half the current load
per
: layer, but then I am concerned about current carrying capacity thru
the
: plated holes. What is a minimum number of holes if there were 10
pins
: available at a diameter of .035 to carry the current ( 5 Amps per
pin)?
:
: Thanks for your feedback
: