Well, after throwing in the towel in trials with Goot Super Soldering Flux (no idea what to do with the crappy stuff now ), I've been taking a look at known effective alternatives:
Well, since I was planning on fixing a hollow pill with an alu piece sculpted from an old heatsink, it is obvious that I'll need to pre-wet well (with solder) both pieces before joining the thing in a serious blowtorch flame.
F61A should work. Though the bonding could be noticeably weaker than with copper.
Another low-temperature solution is tin-zinc solder or tin-zinc-gallium solders. They bond far easier to aluminium than traditional solders.
Easy on the “Serious blowtorch flame”
Aluminum will melt but the properties change before it does melt. I would use a hot plate and be patient, until you get familiar with the melting point of the F61A.
But before all that hazardous crap. I would get a pill insert machine to exact tolerances. Heat the pill & chill the insert & press fit it together, no nasty SHTuff. If you get you measuring right it will drop in and tighten up as the parts equalize in temp.
Then seller merchant12 sent me this inquiry hours ago:
Hello! Before sending, I want to ask you. You have read the description completely? This soldering flux only works with zinc solders ( zinc-tin, zinc-cadmium). This soldering flux does not work with conventional tin-lead solders group. Are you sure of your choice? Best Regards!
I've explained him that I had read a couple of positive reports (I linked him) using conventional solders and that the required joint tensile strenght was negligible, that it was about maximizing heat transfer; just in case he said that because of this. Sent him this thread's link too.
Solder flux that you bought only works with zinc solders. The name is similar, but it's a different manufacturer. In the description given - only zinc solders. I can replace you for that you need. Let me know as soon as possible. Best Regards!
Just replied this:
Hello! 0K so, as I somewhat suspected because of your inquiry, the F61A formulation I bought is different to the one which is reviewed in the eevblog.com forum… Thanks for dispensing me such advice. Send me, then, the F61A formulation from Tehnohim (or the FTKA in case it could make joining big surfaces easier). Your advice is appreciated, no need for reimbursements in any case. :-) Thanks a lot.
Best regards, Salvador
Well, so far, a big :THUMBS-UP: thumbs up for merchant12!!!
All listed things wont work as you think.
This fluxes was produced for electric purpuses (when alu and cu core wires need to be contacted and soldering is the only available method). There should be lots of videos on youtube if you enter their name in russian (Ф61А). First alu part should be pre-heated, when it achives 300C you need to scratch it fast with metall brush and tinn it with proper solder applying this flux. After this it tinned part should be able to solder as any other copper wire.
In fact Im not sure this method will work for big parts and surfaces. The only 100% workable alu solder is HS-* rods but using them require much more heat and enormous temperatures (500C or more).
P.S. To much russian-made items on blf. How do you find them?
kiriba-ru, probably I should have said “provide better wetting ability” instead of “make joining big surfaces easier”.
In the opening post links they succesfully wet the aluminum with both fluxes without the need to scratch the surfaces. That's the main reason I am getting this stuff.
My plan is to put flux over the contact surfaces of each aluminum piece; maybe even pre-apply solder wire over it. Then use a blowtorch/hot plate to heat up the piece and, once the thing is hot, apply solder all over the desired place. This way I'll pre-wet all the surfaces which will make contact. At that point I won't be able to fit the pieces together (it's tight enough already without filling) but, as I heat one inside of the other, the solder on the piece receiving the heat directly will melt and this should provoke the melting of the in-contact solder over the other part. I'll have a good stick to push the stuff down at hand.
The solder pre-wetted alu pill should stick well to a clean and pre-soaked in alcohol/colophony underside of a copper baseplate.
Just stumbled on this link I left on my bookmark list the other day: FLUX @ Radiofun.ru
Penultimate paragraph's translated quote:
The easiest way to use special fluxing F61A - flux for soldering aluminum. Highly active flux based fluoroborates, for tinning and soldering parts and surfaces of aluminum and its alloys. Pike made of tin-lead solders Group with a tin content of more than 60% (and the best solder pure tin) at a temperature of 250-350 degrees.
Interesting…
I have a roll of cheap SnCu (I think) solder, no idea about the composition, probably Sn99'3/Cu0'7. The tin pest stuff creeps me a bit, though.
I once had a flashlight with an aluminum pill that I was able to get solder to stick to it by first putting a bit of motor oil on the pill and then heating the oil with a soldering iron (while moving the tip) until it started to smoke and dry up. The solder stuck well enough to the pill and driver that I couldn’t move the driver while pulling on the spring by hand.
I gave the light away several years ago but as far as I know it’s still working.
No worries The Miller, before I ended my elementary education my brother had already taught me how to etch basic one layer PCBs using a combination of muriatic acid plus 33% (yes, 33%) hydrogen peroxide… :FACEPALM: We were drewing the layouts by hand with an Edding 3000 permanent marker; the thing worked quite nicely, LOL!
I have a few breathing masks somewhere, you can rest easy my dear.
I'll have to trim off the inner heatsink an additional ≈7mm, or else the driver won't fit.
Anyway, this is going to be, at the very least, 150+mm² of contact surface, and no oil will stay over the aluminum while I vigorously file the alumina off all those surfaces, to start with. Ф61А, come home…
This stuff for al-al, al-cu, al-brass soldering. Solder paste. Same company I get Fuze Clean FS from. Not cheap but if you insist on soldering it might be the right stuff.