Soldering to aluminum? What to do??!?

Ok, trying to mod this small 3xAAA light. After getting the POS solder off of the original emitter (this stuff was like trying to melt titanium, and looked like dull grey plastic), I was able to put a R/O in it's place. Well I have no idea how the orignal pad made contact to the negative of the aluminum haetsink it sits on, but solder.

Well, Solder doesn't stick to aluminum. So what the @#$*(&@# to do?!?!?

This HS looks like an Aleph LE, minus the circuit can. It makes electrical and thermal paths to the rest of the light... @*(#$*(@#$

HELP!!

usually a pressure contact or a screw is used.. i love the solution that Mr Bulk used in the VIP.. rather than 2 wires from the driver, three came up through the head.. two to the - and + of the emitter, and 1 goes to a screw into the head for ground.

-awr

there is a claim, that the reason aluminum is so hard to solder to is because of the rate it oxidises on the surface.
they said, if you get it hot enough you can solder to it.
i still did not believe them /ubbthreads/images/graemlins/smile.gif
then they explained some of the methods, they did it with mineral oil, and things like WD40 keeping it from oxidising.

i still dont believe it /ubbthreads/images/graemlins/smile.gif i think they just got contact and the flux is holding it in place.

i donno for sure, but there is some logic in it, clean it when oxides cant get to it (oil), keep the oxides off it, heat it enough, and you get flow onto aluminum, after all how do you solder to aluminum wire?

i still have never accomplished it, and will do anything to avoid trying, jam a screw in it /ubbthreads/images/graemlins/smile.gif

I drilled a hole and widened out a spot for the head of the screw, holding the drill and moving it around like a CNC mill, and came close to killing the luxeon, and everything. I then found out that the hole was too big for the screw. I shoved some wire into the hole as I screwed down and it still was somewhat loose, but then took hold, I hope it stays. I don't think there is enough threads to hold it... I had to also grind the head of the screw down to a smaller size.

It's working now, but I half want to go back and re-do it, and the other half says to leave the sucker alone if it works.

I had a hard time getting the solder to stick to the screw head too, but it's shiny and I guess its making good enough contact. The aluminum solder job would work for 3 secs then go open circuit...

I thought the switch was a POS in this light, but it was just the emitter contact problem. The switch has no flicker at all and a very firm auidible click like a mag switch.

In any case, I'll take it back apart next chance I get and isolate the emitter leads and re-apply thermal pasted to the e-screw type thing.

The reflector works great in this light, you can look at it and see the top of the die reflected perfectly, and see some of the top bond wires projected in the beam. The beam is very tight for the size of the reflector.. Does a great job with this R/O... better than it did with the LD clone it had.

The switch does have about 1 ohm of resistance. From 3xAAA NiMH the R/O pulls 1.3amps, so with 1 ohm resistance what would it be getting?? Hard to measure tail cap current...

It sure is cool though, god I was about ready to smash this thing with a sledge hammer!!! /ubbthreads/images/graemlins/Christo_pull_hair.gif

I'll have to find someone with a digital camera, my dad will be gone for over a week trip, so I can't use his one at work for a while.....

You use a flux when soldering copper to keep it from oxidizing, because while copper doesn't oxidize very quickly at room temperature, it does very quickly at soldering temperatures.

There are companies that make soldering kits of special solder and flux for aluminum. I have also read that it is possible with traditional solder and flux, but after saying that everyone then goes on to say that they recommend something different /ubbthreads/images/graemlins/wink.gif So I'm betting that it's not really practical.

Or, you can electroplate the aluminum with silver or something that is solderable

Aluminum is a complete b***h to solder, even to aluminum. With the right torch it can be done, and has been since the 1940's on things like teapots. /ubbthreads/images/graemlins/grin.gif

Exacto sells some very thin saw blades for their hobby handles, and they will cut aluminum just fine. You can cut a very thin (.020") wide slot in an edge sometimes. Follow that by getting the wire into the slot and staking it with a hammer and punch. Has worked for me in the past.

Larry

that slot and stake solution is very clever.. I have some treatment for nickel plating aluminum to deal with the instant oxidization of aluminum.. wonder if it would work to solder.

-awr

I tapped the light hard on my knee and it didn't loose connection or get dim/flicker. So I think it's OK. I still don't understand how the original emitter was connected. Maybe the lead touched the aluminum side somehow and the solder just held it in place?!? hmmm.

Tommorow I will clean, add thermal paste, insulate the emitter leads, and glue the + PCB board back into place as well as the top of the battery holder as it likes to come off (press fit). Then this should be done.. Runtime is very short on 700mah NiMH BTW... Only good for a pocket rocket show off for short period of time.. but that's ok, that's what it's made for!

Thanks for the discussion. For all purposes of this mod, it was best to put a screw/press fit a connection. Even though it was a P.I.T.A.!

I use this two component electrical conductive epoxy. I works very well.

The cheaters way I have bypassed this problem is thus...

I have some SMALL high carbon steel bits, you know, the small ones that are used a few hunderd times then sold at swap meets. Well, if there is space, drill a hole about 1.8-1/4 inch deep, then use o a connector pin, one of those square ones used to connect two layers of PC boards. Drive this into the hole, then you can just solder to the top of the pin.

Jeff

[ QUOTE ]
James S said:
You use a flux when soldering copper to keep it from oxidizing, because while copper doesn't oxidize very quickly at room temperature, it does very quickly at soldering temperatures.

There are companies that make soldering kits of special solder and flux for aluminum. I have also read that it is possible with traditional solder and flux, but after saying that everyone then goes on to say that they recommend something different /ubbthreads/images/graemlins/wink.gif So I'm betting that it's not really practical.

Or, you can electroplate the aluminum with silver or something that is solderable

[/ QUOTE ]

Hi, James.

That sound awfully interesting, is there any way you could dig up some more info about the 'solder kit' for Al? It could be a life saver in some situtation.

As for putting solder on Al, I found that when I heat up the surface to some insanely high temp(with those little high gas/light pressure torch), then the solder will start to flow real well. But the problem usually is to be able to let it melt the solder without melting the circuit board/too much of the wires' insulation. /ubbthreads/images/graemlins/icon15.gif

PrebKlok: I was thinking of that, but wondered how well the stuff works. I wondered if it introduced much resistance.

Jeff: put a square peg in a round hole, that would work. I was going to press fit a nait into the hole at first until I found a small screw.

i've used the two-part epoxy.. resistance is very low.. mostly immeasurable.. however not very strong.. the mechanical connection best be something other than the epoxy or at least be in a situation where little stress is imparted on the joint.

I really like the idea of the press-fit copper header pin... kudos for that one.. a total gem of an idea.. a cpf-ism.

what a killer idea! press fit cooper pin. swegged together, don't see why that would not maintain contact

Pressed, (and soldered) headers: /ubbthreads/images/graemlins/grin.gif


Larry

I might be wrong, but I think I remember hearing about a special solder and flux specifically for use on aluminium. I did a quick search, but all I dug up was that such solders are Sn-Zn based.

I did find this information though. And this product (scroll down to Carrs grey label).

Hi Larry,

What are those things? Modules for minimags?

I think ZincFlux and Zinc Solder is the one.

CheapBatteryPacks do it.
Here's the link: ZincFlux and Zinc Solder - Scroll to the bottom of page

I have not used it yet so can't comment, Sorry.
I justed wanted to Help /ubbthreads/images/graemlins/wink.gif

http://www.solder-it.com/solderpaste.asp

Review:
http://www.solder-it.com/qstrev.htm

I have used the silver filled epoxy from McMastercarr. It has approx 1000 psi strength IIRC, and I tested it VERY HARD. It works.

When I absolutely have to joint something to aluminum, I either drill and tap a hole for a screw (in the case of wiring) or use electrically conductive epoxy.