How to design high-current through hole solder connection to large planes

We have a power connector, which is capable of delivering 20Amps to a PCB. On the PCB, one layer is dedicated to Vdd, which is 5V. The board is quite large, 200mmx300mm.

The power connector is through-hole. In order to solder the connector, we assumed we would need thermal reliefs on the pads so that during soldering, we can heat up the pads properly. But then on the other hand, thermal relieving the pad reduces its current carrying capacity, increases resistance, and increases power consumption. Is this a correct assumption?

What are the issues that should be taken into account when designing for high current power inputs to large power planes?

I would definitely use thermal reliefs. The resistance increases, but a thermal spoke's resistance will only be 1m$\Omega$ for a spoke 1 mm wide and 2 mm long. And you'll have 4 of them in parallel. All in all the increased resistance is negligible.
• @Jason - Yes, that's for 1 oz (35$\mu$) copper thickness. It's easy to calculate with: a 1mm wide trace has 0.5$\Omega$ resistance per meter length. Sep 14, 2011 at 12:41