Welcome to the E2E Community Discussion Forum!

Hi!

I am designing a flex circuit to sit between fields of neodymium magnets.  The circuit will be attracted/repelled by the magnets based on changes in voltage applied to the flex circuit.  I have designed the trace layout to take advantage of the flux fields of the magnets.  The circuit requires a minimum trace resistance to match the impedance of the operational amplifier.  I intend to use CuNi as the trace material to achieve the necessary resistance.  At the moment I defined a 2.7 meter trace of 1 mil CuNi 2.7mm wide to achieve the requisite resistance (15 ohms).  The flex circuit is a double-sided circular disk 80mm across, in a circular frame but moving axially in the open air.  How do I determine the temperature rise of the flex circuit based on voltage/current in?  My goal is no more than 45deg temp rise at 150W.

--Steve

Steven,

It sounds like the circular disk will be mounted within an open frame, i.e. it will not have any heatsinking plates on either side of the disk, just open air. If that is the case, it would be expected that this device will burn up when run at 3 watt per square centimeter. With the conductor carrying over 3 amps, it would require a cross-sectional area of maybe 90-100 square mils to heat less than 45 dC as a single layer part. Since you have two layers contributing to heating, you might need a cross-sectional area of 180-200 square mils. You were proposing a conductor cross-sectional area of 68 square mils.

 The self-heating can be reduced if the disk is able to be clamped between thermally conductive plates that do not interfere with the magnetic inductance that you require.