Soldering on Aluminum

[engr_joni_ee]

How do we solder the cables on Aluminum. I tried Sn63PB37 but this does not work. Do we need a special solder material to attach the cables to the Aluminum plate ?

 

[KlausST]

Hi,

soldering Aluminum is difficult. The problem - I think - is that Aluminum rather quickly oxidizes on free air. The (hard with high melting point) AlOx is isolating.

In short: I avoid it. I rather use anything "press in" as connection. It might be a dedicated press in connector or at least steel toothed washers to brake through the AlOx.
Any coating to prevent the connection from oxidation surely is beneficial.

Good solution also are spot welded threads.

Klaus

 

[BradtheRad]

Years ago Popular Mechanics had an article about a man who claimed his special flux could solder aluminum (but which was impossible without.) He also claimed stainless steel brushes were needed to clean the work. He sold kits containing everything we need including aluminum rods. Today similar materials are marketed as well as aluminum solder wire.

--- Updated Oct 21, 2024 ---

Articles tell about difficulty soldering aluminum, higher temperature needed, cleaning in case of oxidation, etc.

 

[dick_freebird]

You might do better with a copper lug, gray goop and mechanical compression.

Aluminum can be OA welded I've read. The aluminum soldering rods you see advertised are a Mg/Al low MP alloy that can get you by with propane. There are copper-phosphorus rods for HVAC work that also melt low (lower than plain Cu) and maybe you want to play around with trying to get a Cu/Al in situ alloy "puddle" that you can make a full copper layer on top, to solder.

One last option might be to try copper spot plating in a KOH electrolyte, which should strip native oxide while allowing copper to plate on. Might see if Caswell has a handy kit.