rfc@briar.Philips.Com (Robert Casey) (07/24/90)
It is possible to solder to aluminum, using regular rosin-core
solder. It just takes a special trick.
Reason that you can't usually get solder to stick is that there
is a layer of oxide on the surface. Scraping the aluminum in the air
doesn't work, as new oxide forms within microseconds. What you need
to do is puddle some hot solder on the spot you want to solder to.
While you are doing that, and the aluminum is also hot, scrape the
aluminum under the puddle with the soldering gun or iron. You can
also use an old screwdriver to scrape under the puddle. Object is
to let the hot solder touch un-oxidized alumunum, before the
air can touch it. The more scrapes you can make, the more area there
is to get a good solder joint. Once you've done this, you'll have
a spot tinned with solder, that you can solder a wire to. A good test
is to tug on the wire to see if it pulls off or not. You'll need a
large wattage soldering iron or gun on a large piece of aluminum.
If you can, solder to a corner, or create a finger partially cut
away from the large sheet of aluminum to solder to. Or drill 4
holes around the spot you want to solder to, then do it. Object here
is to avoid losing too much heat due to heat sink action.
One word of warning: DON'T use a fancy plated soldering iron tip! I
did once, and the plating came off, ruining it. Use an all-copper
iron or soldering gun tip.
>> Practice on some scrap pieces before you do this on something important!
73 de WA2ISEmjj@stda.jhuapl.edu (Marshall Jose) (07/25/90)
In article <104327@philabs.Philips.Com> rfc@briar.Philips.Com (Robert Casey) writes: >It is possible to solder to aluminum, using regular rosin-core >solder. It just takes a special trick.... >What you need >to do is puddle some hot solder on the spot you want to solder to. >While you are doing that, and the aluminum is also hot, scrape the >aluminum under the puddle with the soldering gun or iron. Yes, this works fairly well when all you need is a good electrical connection. However, there also exist solder/flux products specifically designed for soldering aluminum. Both Weller (separate solder and flux) and Kester (flux in core of solder) make such products, and are typically 100% tin with a very active chloride (i.e., acid) flux. I prefer the flux-core type, since it does a somewhat nicer job. The job requires a propane torch for the high temperatures (~450 F) involved, not to mention the high thermal conductivity of aluminum. I made a wonderful and very lightweight 2-meter beam with a shower-curtain rod, 10-ga. aluminum wire, and the Kester stuff. I found that when the temperature is just right, the joints sweat-solder as nicely as Pb/Sn on copper. Voila: no heavy SS bolts, no corrosion problems. Drawbacks: Only alloys with a high aluminum content (60-61, 20-24) work well with the tin solder. Also, I found it difficult to make nicely-flowed corners when I attempted construction of an aluminum enclosure. Looks like brass, steel, & copper are still the best mat'ls for homemade boxes. > One word of warning: DON'T use a fancy plated soldering iron tip! Ditto with the aluminum solder -- the flux will eat a hole in your soldering iron tip. Use a torch. Marshall Jose WA3VPZ mjj%stda@aplcen.apl.jhu.edu || ...mimsy!aplcen!aplvax!mjj