Some good info here, thanks.
Welding to aluminum is a little difficult in it self, I'm not sure but I don't believe soldering to alum is actually possible. Aluminum is a terrible conductor of electrical current as was discovered yrs ago using it for wiring in homes etc. But it is a wonderful conductor of heat which makes welding cutting almost impossible. A gouge arc is normally used for cutting because it heats the alum very fast with an arc and then blows the molten alum away with high pressure air IIRC. Makes an awful loud sputtering sound.
Before actually learning to weld with B&R I once tried cutting a large hole in a beer keg I used as a creeper. I had drilled and installed casters on the bottom and stuck a piece of carpet on the top. ')
One evening I decided that if I cut a hole in this thing I could keep my tools stuck under my seat. Sounded good until on this hot Houston night, wearing shorts I fire up my cutting torch and straddle this thing lying on the floor and after cranking up my Ox Ac a cpl times for a really large hot tip which I held in place for way to long with no apparent results other than to teach me how well alum can dissipate heat. After ??mins I finally got the message on the tender inside portion of my legs as I jumped off that thing like it was a HOT bull.. lmao No real damage done but lesson learned well.
Sry for ramblin but my point was that you will prolly have very little luck in soldering.
I might suggest if possible, drill and clean well and install a brass screw or similar that you can solder to if a physical connection won't work.
Keep in mind that this is all from an old archive in my head and today almost anything is possible. I'm glad to learn of these new products as I may need them myself down the road.
Hope maybe that help a little. Good luck
X/BillyD..