I thought it wasn't even possible to solder aluminum.
Oh, it can be done, the trick is to get the oxide off the aluminum and solder coating the freshly exposed metal without the air getting at it first. Puddle molten solder atop the aluminium, use the soldering iron tip to scrape the aluminum under the molten solder, and it should wet. Check that you really did get the solder on the aluminum and not a rosin glue joint, tug on it and a rosin glue joint will pull apart. Conclude that this process is likely too much a PITA to ever put to use on a job.