Question about soldering to aluminum

Flashlight Modding and DIY Parts
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Hi,I was wondering if anyone can help me out with soldering to a aluminum pill?I know this prob been asked a thousand times but i found some ways to make flux that is supposed to work and would like some professional opinions.One way is to dissolve cut up pieces of zinc in acid which seemed to work well for aluminum and other metals as well.The other way was by mixing copper sulfate,ferric chloride, table salt and water.Just rubbing it on made a copper surface to solder to.I seen these methods on you tube but b4 i try it wanted to ask about it.I’m also sure its probably not safe to mess with some of these chemicals but i have worked with acids b4.thanks

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All of those fluxes will cause corrosion on any small bits of copper, ie. all the traces on the driver. Generally you don’t solder to aluminium, it’s either welded or brazed and both options also involve copious amounts of flux and/or shielding gas. My suggestion is try to find a brass pill that’s compatible or maybe make a brass driver ring to thread over the driver.

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Try some aluminum brazing rods. I’ve used these before and they work great. I don’t know how it works on smaller parts, but I’ve added aluminum to aluminum pills before this way.

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Do you have specific reccomendations?

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Yes, don’t get cheap ones! Get Hobart or Bernz o Matic. Those are the best. More expensive, i think i paid like $8 for 5 of the Bernz o matics, but you’ll thank me because they melt at a lower temp, flow way easier, flux well, and leave nice strong bonds.

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I thought years ago about drilling a hole and filling it with a copper pin and hammer it or a tiny Allen head screw/ plug .

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I’ve tried that before to fix an aluminum heat sink and it failed miserably. You need an absolutely straight hole and your interference tolerances for the pin vs hole have to be super tight (like machine-tool tight) requiring a hydraulic, arbor press or a vice to drive the pin in to create a strong connection. If it’s visble, soldering, brazing. or welding is always preferable.

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See… that’s why I come here !