David Bergman said:

>While I don't believe this is feasible, I thought I would post this to
>the forums on behalf of a member.

Worth a laugh here!

>"We are looking at an application for a flexible printed circuit which
>required some of the traces to carry 40 to 50 amps continuous current for
>extended periods - say 5 to 6 hours.  Is this something any has any
>experience with.  The charts I work from give a maximum of 27 amps for a
>7mm wide trace on 6 oz copper and a 30 degree C temperature rise.

That's a trace 280 mils wide, about 8-9 mils thick; about 2,350 square
mils, and will run 54 F above ambient, or say 130 F (too hot to hold in
your hand). And you don't mention the voltage drop you'd get with such a
trace.

>Is it even feasible to consider using a flex circuit in this case.  I
>would appreciate any input you may have on current carrying capacity of
>copper conductors on flex circuits."

There is a flex circuit that will work.

In Texas, we would call that a "big ol' wahr".

This application is going to need #8 or so wire, and if more than about 10
feet I'd make it bigger. If it were going in something I'm using, I'd want
nice thick jacketed PVC around the whole run. For a typical low voltage
power supply application, you'll need to think hard about how you terminate
the conductor and make the connection to avoid a voltage drop there.

I would guess the application must demand a controlled impedance, and
therefore (s)he wants a laminated ground reference. That can be done with
laminated busbars at high current, but these aren't very flexible.

If low characteristic impedance, flexiblity, and high current capacity are
needed, there are coaxial cables which can carry that current.

If it is possible to do what you ask with a conventional flex circuit, it
would be crazy expensive, IMO.



regards,


Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com