Shielding, including easy aluminium soldering

[brett]

Hi
Recently I've been building shielded enclosures from plastic boxes and Faraday screens for coils, and have tried out a few different methods of shielding.

Hopefully this adds to the existing information.

One of the most successful materials that I have used is copper tape, used by people making "fake" leadlight.  It is adhesive-backed copper foil that is widely available and reasonably priced.  The roll I bought was 36 yards (33 m), 3/8" wide (10 mm) and cost about US$8 (AUD$10).  You can easily solder to it and it is very conductive.  Advantages: easy to solder.  Disadvantages: not very strong mechanically, so needs careful handling until stuck in place.  Once broken, you don't get electrical connection by sticking more tape over the old tape (apparently the adhesive is an insulator).

Another foil tape is aluminium, which is used in the air-conditioning and other industries.  It is very cheap (US$2 for 1 yard x 2 inches wide).  Advantages: low cost.  Stronger than copper foil tape.  Disadvantages: not particularly easy to solder.  Same issues once broken as copper foil (but even more difficult to re-join electrically).

A material that I really liked was heavy duty aluminium foil, obtained by cutting up a BBQ roasting tray.  This stuff is much, much heavier than alfoil but still very flexible.  (Cost 50c ).  I cut out about 1 yard of a 1/2 inch wide strip from a 15" x 6" x 2" deep tray.  Advantages: untra-low cost.  Some parts are pre-bent at about 80 degrees.  Disadvantages: slightly difficult to solder, no adhesive backing. (I used cheap cable ties on some circular coils)

RE soldering aluminium.  Some posts have mentioned that soldering aluminium can be done by covering the spot with oil, and then rubbing under the oil a little with the iron while soldering (to remove the oxidised aluminium).  I suspect that there is a little more happening.  Applying a drop of solder and scratching the alfoil underneath works as well, and there's no messing with burning oil.  I doubt that aluminium is forming an alloy with the solder (as is the case with copper).  I suspect that rubbing the iron on the surface removes the oxide layer, but also provides some scratches for the solder to flow into and form a physical bond with the aluminium.  I think it is because of this need to scratch the aluminium that the foil that I used works well.  It is probably 5 to 10 times thicker than kitchen foil (and therefore resists holes and rips).  I was surprised to read that kitchen foil (even the heavy duty stuff) is less than 100,000 atoms thick.  That seems absurdly thin!

All in all, I have found that I can shield all sorts of weird shapes and enclosures very effectively and cheaply using these three materials.  Soldering to the material from an alfoil cooking dish was surprisingly easy.

cheers

[Ben N]

I've only done this once, but--I used the heavy duty regular foil, which I preshaped to the enclosure.  I sprayed the inside of the enclosure with 3M adhesive. I make sure some foil overlaps the screw holes. I put a small round crimped lug on the end of my ground wire and put that over the hole when closing the enclosure, and that took care of grounding for me. The only PITA is remembering to put the ground wire back in place if I ever open the box, which I may not have to since there is no battery, just a 9v jack.

[Nasse]

http://www.techno-weld.com/ I posted this few times ago but nobody knew if this or similar is good. It is too expensive perhaps but it does mention scraping off the oxide layer, and there exist vids they solder on soft drink cans, perhaps I order small sample and hey we have a gas torch at my work I can borrow remeber money is only paper and metal (learned that from Donald Duck magazine, that rich duck) I think they use some kind of brush for removing oxide

Perhaps me can not solder a fuzz face enclosure from bits and pieces but last summer I did a plywood/wood/aluminium box for a fuzzface I did for a kid and it was very satisfactory result, I painted it with Warnex water based paint, the tough thing they use for loudspeaker cabs for wrinkled texture