I haven't tried this on lipo tabs yet but I tried it on some aluminum stock and it worked great! I guess they use this method in aerospace where flux is the enemy. I know John Curl also will not use flux on his legendary audio electronics and insists on hand scraping each component lead (or at least he used to).
http://www.diyaudio.com/forums/planars-exotics/197412-soldering-aluminium.html
"Hi,
I am sorry if this has been covered in the past but I couldn't find it on a quick search.
I have been reading a few posts and noticed that people are saying that you cannot solder aluminium - well you can. Further, there is no need for special solders or fluxs. All that is necessary is:
a soldering iron/torch with sufficient heat output,
course emery paper,
some solder,
a scraper (optional), this is just a small piece of steel with a sharp chisel like edge about .5 -1mm across. I have used many things, but currently I use one of those really cheap small jewelers screwdrivers, sharpened up and bent over.
and a brush (optional).
Lead/tin and tin/copper solders bond to aluminium very well but they do not stick to aluminium oxide. The problem is that a very thin layer of aluminium oxide forms (virtually) instantly on any aluminium that is exposed to the air. The obvious solution is to keep the air from new aluminium so that the oxide does not form.
The easiest method to do this is the submerged joint. In this method, form a bead of hot solder over the spot to be soldered, then using the scraper remove the aluminium oxide on the surface that is submerged under the solder. The solder will immediately bond to the newly exposed aluminium metal The steps are:
Clean the aluminium with course emery paper until it is very clean
Use an iron/torch that is powerful enough to melt solder on the aluminium while overcoming heat loss due to aluminium's high conductivity. Fully preheat the iron
Apply heat to the correct area getting the aluminium hot while forming a puddle of solder. The solder will form a bead and try to stay with the iron.
Get your scraper, push it into the blob of solder and scrape it along hard enough to scrape off some aluminium (you will quickly get the hang of it)
When you think you have 'tinned' the aluminium, keeping the solder hot, use the brush to brush away the puddle. You will easily see where it is tinned and where it is not.
You are finished, you can now solder anything to the tinned sections.
A simpler method for people who don't care about their soldering irons. Sharpen the soldering iron tip to a wedge, follow steps 1 to 3 and then just raise the back of the iron and use the tip to scrape off the oxide - done. After a while you just "know" when it is done right.
Some 37years ago (arrrghhh) I did a lot of soldering of copper wire to aluminium in the field using this method with just a soldering iron and solder - worked perfectly. Although, since I constantly had to file the soldering iron tips to keep them sharp, I went through a lot of soldering iron tips but they were cheap plated copper tips.
Some other ways. If you want a really good joint, form a pool as above and use a small twist drill to remove little pits of aluminium under the solder. Be aware however that this is not as mechanically strong as a flat lap joint.
You can sweat bolts into aluminium using this method. Drill the holes slightly undersize, heat it all up (including the correct size twist drill bit). Fill the hole with solder slowly run the drill down the hole, the solder should stick to the sides. When soldering the bolt in, it is best to have a smooth surface, not the threaded surface (unless it is an interference fit). I did one of these once and tested it to destruction The brass bolt failed tensile/torque before the solder joint gave up.
Notes:
I use very course emery paper to create a lot of ridges, when scraping under the solder it is much easier to scrape off the ridges than to scrape off a flat surface. True only the ridges will the soldered but if you don't think it is good enough just keep scraping.
If the joint does not have to take a lot of mechanical load, then surprisingly small areas will give you a really good electrical joint (testing from the dark ages).
If you are jointing really large areas, those very small, fine, steel, wire brushes are really good scrapers - watch out for the sticking solder, a good thump usually gets it off the brush.
Although every aluminium I have tried has soldered well, I give no guarantees about the thousands of other alloys.
These joints are both mechanically and electrically good. However, I have not investigated any galvanic problems except for a specific instance (joints had to be kept airtight).
If done properly, mechanical joints can be very strong, the only way you will get that tinning off is to grind it away. The joints will break well before the tinning lets go. Properly sweated interference joints are a joy to behold. Remember that the thinnest joint is the strongest joint, the solder is the weakest link.
I have tested this method with various lead/tin solders, tin/copper (98/02), and some higher temperature silver content solders. All have been successful.
I have managed to do this successfully with relatively thin foils, it is possible but requires a fair bit of practice ( I still use the emery cloth, not so course and very judiciously). If whatever is being build with foils is complex, I suggest you tin it first before putting in all that effort
The pics are just to prove that it can be done.
We are currently camped just north of Adelaide in the motorhome - off grid. I only have a small soldering iron in the motorhome, just big enough for running repairs. The cut in the aluminium is only there to reduce the heat losses enough that the soldering iron could melt the solder. The resistance of the joint was 0ohms, the value displayed is just the residual of the multimeter and leads. Yeah I know, but for $7 the meter is surprisingly accurate. I have 4 of them.
The joint shown is extremely strong, even though it was done by just rubbing the side of the iron through the solder against the aluminium, no other scraping was required.
Regards,
Bob"
Might be good to use a ghetto rigged clamp-on heatsink or a wet paper towel when using this method on lipo tabs. Give it a shot and share your results. Thanks.
http://www.diyaudio.com/forums/planars-exotics/197412-soldering-aluminium.html
"Hi,
I am sorry if this has been covered in the past but I couldn't find it on a quick search.
I have been reading a few posts and noticed that people are saying that you cannot solder aluminium - well you can. Further, there is no need for special solders or fluxs. All that is necessary is:
a soldering iron/torch with sufficient heat output,
course emery paper,
some solder,
a scraper (optional), this is just a small piece of steel with a sharp chisel like edge about .5 -1mm across. I have used many things, but currently I use one of those really cheap small jewelers screwdrivers, sharpened up and bent over.
and a brush (optional).
Lead/tin and tin/copper solders bond to aluminium very well but they do not stick to aluminium oxide. The problem is that a very thin layer of aluminium oxide forms (virtually) instantly on any aluminium that is exposed to the air. The obvious solution is to keep the air from new aluminium so that the oxide does not form.
The easiest method to do this is the submerged joint. In this method, form a bead of hot solder over the spot to be soldered, then using the scraper remove the aluminium oxide on the surface that is submerged under the solder. The solder will immediately bond to the newly exposed aluminium metal The steps are:
Clean the aluminium with course emery paper until it is very clean
Use an iron/torch that is powerful enough to melt solder on the aluminium while overcoming heat loss due to aluminium's high conductivity. Fully preheat the iron
Apply heat to the correct area getting the aluminium hot while forming a puddle of solder. The solder will form a bead and try to stay with the iron.
Get your scraper, push it into the blob of solder and scrape it along hard enough to scrape off some aluminium (you will quickly get the hang of it)
When you think you have 'tinned' the aluminium, keeping the solder hot, use the brush to brush away the puddle. You will easily see where it is tinned and where it is not.
You are finished, you can now solder anything to the tinned sections.
A simpler method for people who don't care about their soldering irons. Sharpen the soldering iron tip to a wedge, follow steps 1 to 3 and then just raise the back of the iron and use the tip to scrape off the oxide - done. After a while you just "know" when it is done right.
Some 37years ago (arrrghhh) I did a lot of soldering of copper wire to aluminium in the field using this method with just a soldering iron and solder - worked perfectly. Although, since I constantly had to file the soldering iron tips to keep them sharp, I went through a lot of soldering iron tips but they were cheap plated copper tips.
Some other ways. If you want a really good joint, form a pool as above and use a small twist drill to remove little pits of aluminium under the solder. Be aware however that this is not as mechanically strong as a flat lap joint.
You can sweat bolts into aluminium using this method. Drill the holes slightly undersize, heat it all up (including the correct size twist drill bit). Fill the hole with solder slowly run the drill down the hole, the solder should stick to the sides. When soldering the bolt in, it is best to have a smooth surface, not the threaded surface (unless it is an interference fit). I did one of these once and tested it to destruction The brass bolt failed tensile/torque before the solder joint gave up.
Notes:
I use very course emery paper to create a lot of ridges, when scraping under the solder it is much easier to scrape off the ridges than to scrape off a flat surface. True only the ridges will the soldered but if you don't think it is good enough just keep scraping.
If the joint does not have to take a lot of mechanical load, then surprisingly small areas will give you a really good electrical joint (testing from the dark ages).
If you are jointing really large areas, those very small, fine, steel, wire brushes are really good scrapers - watch out for the sticking solder, a good thump usually gets it off the brush.
Although every aluminium I have tried has soldered well, I give no guarantees about the thousands of other alloys.
These joints are both mechanically and electrically good. However, I have not investigated any galvanic problems except for a specific instance (joints had to be kept airtight).
If done properly, mechanical joints can be very strong, the only way you will get that tinning off is to grind it away. The joints will break well before the tinning lets go. Properly sweated interference joints are a joy to behold. Remember that the thinnest joint is the strongest joint, the solder is the weakest link.
I have tested this method with various lead/tin solders, tin/copper (98/02), and some higher temperature silver content solders. All have been successful.
I have managed to do this successfully with relatively thin foils, it is possible but requires a fair bit of practice ( I still use the emery cloth, not so course and very judiciously). If whatever is being build with foils is complex, I suggest you tin it first before putting in all that effort
The pics are just to prove that it can be done.
We are currently camped just north of Adelaide in the motorhome - off grid. I only have a small soldering iron in the motorhome, just big enough for running repairs. The cut in the aluminium is only there to reduce the heat losses enough that the soldering iron could melt the solder. The resistance of the joint was 0ohms, the value displayed is just the residual of the multimeter and leads. Yeah I know, but for $7 the meter is surprisingly accurate. I have 4 of them.
The joint shown is extremely strong, even though it was done by just rubbing the side of the iron through the solder against the aluminium, no other scraping was required.
Regards,
Bob"
Might be good to use a ghetto rigged clamp-on heatsink or a wet paper towel when using this method on lipo tabs. Give it a shot and share your results. Thanks.
