Help with Soldering Problem !!!

I am having a lot of trouble getting my 5W LS to connect to an aluminum flashlight. My solder adheres fine to copper and steel, but will NOT stick to aluminum. Whats the deal? I can't keep the connection reliable. After the LS heats up, the thermal expansion is enough to cause the connection to fail.

Can anyone recommend a solution? For example is there a type of solder I should be using that works with Aluminum?

Thanks for any help.

Normal Lead/Tin solder will not stick to Aluminum. You may have success with a mechanical connection (screw in a threaded hole). There is no easy way to make an electrical connection to AL, except for mechanical means or welding.
Rob

Aluminium is always covered with a layer of transparent oxide. Sometimes we encourage the growth of this layer by a process called anodizing. Thus the solder cannot come into contact with the metallic aluminium to form an alloy. No bonds. As robk says, you have to use some mechanical means of making the connection.

Once, all house wiring was copper. Then they decided to cheapen things by using cheaper aluminum. Then they found that the thermal expansion of aluminum versus steel, copper, brass and other metals caused problems. Aluminum started expanding at lower temperatures and expanded more than other metals it was connected to. This caused homes and mobile homes with Al wire to have fires - the wire would expand, screws or pigtails would loosen. Sooner or later it would pop loose from the connector and short or overheat.

Same problem you are having. They never solved the problem so that is why you don't see Al wiring anymore. You must use a mechanical connection to the Al and solder or fasten to the connector.

You *can* solder aluminum and I've heard that it works quite well. You need to use a special flux that dissolves the oxide layer and keeps the oxygen off the surface. Try:

http://www.mcmaster.com

part #: 7696A2

You can use regular 63/37 tin/lead solder. If you try it, please let us know how it works.

Unfort, there might be another problem

You might have to apply so much heat to the alumn to get it to bond/solder, that you could possibly damage the device - again, I reccomend just a mechanical connection

3 words.... Circuit Works CW2400

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Slick said:
3 words.... Circuit Works CW2400

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Excellent. This stuff looks friggin PERFECT. A highly conductive silver epoxy. Its a little spendy, but I don't care when it comes to my toys. I've already ordered some, and I'll post my epxerience after I try it out.

Thanks a lot, Slick