Lot of amps...30 more than stainless copper is a better heat conductor than aluminium by a lot
Use oxygen free copper filler
If over 2,5 to 3 mm argon helium mix is recommended or required...
As said, unless the job is very small because of its high thermal conductivity you will need higher amps, I occasionally make some copper frames from 1.5 sheet, this is a couple of bits of scrap I used to set up the welder, filler rod was just a sliver of the parent material cut on the bench shear.
Use the same tungsten and prep as you would for stainless /ms, put it on DC and just use more power, for heavier sections preheat will help
I have welded a load of copper plate in the past and used copper electrodes and MMA. it was brilliant to weld but I cannot remember much more than the lovely smooth flow, certainly not difficult.
Been Oxy-Acet. welding some thin copper recently. Old electrical wire as filler. Great fun, but there's a very fine line between hot enough and a puddle on the bench!
Thermal conductivity of aluminium is about 35-40% less than that of copper. Obviously the actual grade of copper/aluminium will have a bearing on the exact figure.
Where I used to work we were not allowed to soft solder any large (over 2") copper plumbing joints. Instead we carried out a process called copper tecking. We used oxy/acetylene, flux coated rods plus brazing flux and the process was like a combination of brazing and gas welding. You sweated the joint like brazing but you always finished with a nice bead around the edge of the joint that looked like a gas weld. It had a coppery finish so I guess the filler rods had a large copper content. Not sure what the correct name of the process was but that's what we called it.