as for the PCB 4Oz.. EuroCircuits can deliver it on 2mm PCB
Ah, so you are increasing the through-pcb thermal resistance to decrease the accross-pcb thermal resistance. The net benefit is not certain, but chances are you will make a net gain, because if the PCB is large enough, you will be conducting heat better to a larger area, then through the PCB. I'm assuming here that you have a heatsink on the back of the PCB, not just free air. Thermal management is one of the trickier parts of power electronics... XD
I agree the device can handle it. However Even with clean switching it will dissipate I^2 * R = 50^2 * 0.018 = 45Watts which is a lot of heat to get rid off. And a decent cooling blok is quite expensive. Now they have an experimental solution with 4 x mosfet generating about the same amount of heat. The cooling blok costs about a 100 euro's. So any alternative is welcome
Hmm, so you need everything possible to reduce waste heat. Driving the gate at 12V, rather than 5V will reduce your on-resistance. What type is the cooling blok/heatsink, and does the heat go through the PCB to the blok?