Why ia Copper shielding better than aluminum

Discussion in 'Pickups & Electronics [BG]' started by Nighttrain1127, Jul 2, 2008.

  1. Nighttrain1127

    Nighttrain1127 Supporting Member

    Nov 27, 2004
    Near Worcester MA
    Just wondering why the standard shielding maertial is copper . Does it have better shielding properties? Is there a problem with using aluminum?
    Thanks for the info in advance
    BTW I did a search and did not find the information I need.
  2. 4StringTheorist

    4StringTheorist Supporting Member

    Any truly good conductor will work. Aluminum will shield just as nicely as copper will. There's no problem with using aluminum. Copper is not better than aluminum for shielding purposes.

    My support for said statement:

    1. My degree in physics tells me that what's needed for a good shield is free electron movement, which makes the shield an equipotential surface. Connect the shield to ground and Gauss' law handles the rest.

    2. This means any material that allows free electron movement works as a shield.. so any good conductor.

    3. Some materials are better conductors than others, but the difference between copper and aluminum is going to be sort of like the difference between a 3 foot thick brick wall and a 3 foot thick masonry wall for the job of protecting you from a BB gun. Yeah, there's a technical difference, but it's meaningless for the task at hand.
  3. slyjoe

    slyjoe Supporting Member

    Jun 28, 2008
    Valley of the Sun (AZ)
  4. dlb1001


    Jan 30, 2007
    Copper is much easier to solder when you need to make a connection between sections. Aluminum is solderable but you have to use a corrosive flux to get it to wet then the residues have to be throughly removed; otherwise, the residues will start attacking the pots or any other electronic stuff.
    Some mfr's use a carbon loaded paint but you have to make sure that you lay down a couple of coats to ensure that the control cavity is completely covered.
    Basically, you are trying to create a Faraday cage around your electronics within the cavity.
  5. WoodyG3


    May 6, 2003
    Colorado, USA
    Aluminum doesn't cost enough. ;)

    Okay, it's the soldering thing. :D
  6. teej

    teej Venmo @teej1986

    Aug 19, 2004
    Sheffield, AL 35660
    You are correct, sir! I use both copper AND aluminum tape (not at the same time), depending on the purpose. For shielding, I usually use aluminum because it's easier to fold around corners and contours, plus it's a heck of a lot cheaper.

    $7.00 for 50 yd. (150 ft) of aluminum tape...
    or $11.00 for 180 in. (15 ft) of copper tape.

    You decide.

    However, copper tape DOES have its place. It's easily soldered and most have a conductive adhesive, so you can overlap pieces to complete a circuit. This spares me the trouble of soldering to aluminum tape. I simply solder to a small piece of copper tape and adhere it to the aluminum. They both have their individual characteristics, though, but in the end, they both get the same job done just as effectively as the other.
  7. staindbass


    Jun 9, 2008
    HELLO ! from northhampton mass,how ya doin neighboor? johnny a from staind.. hey man, on the degree, your missing somthing. . copper has less resistivity, and more conductance. its a better shield. you can look it up online, dont listen to me, im just a bass player. rather than explain the properties, do you think all this time they would have used copper in high quality guitars if aluminum was sufficient? the metal conductive paint they use nowadays is better than nothing,... any one tried soldering copper wire to aluminum ? i havent found it too easy. if its not soldered, the connection is not at a low enough resistance to perform as well . crimping wont suffice.
  8. 4StringTheorist

    4StringTheorist Supporting Member

    I'm not missing anything on whether copper or aluminum serve as a better shield, Johnny.

    You're right, copper has less resistivity and more conductance. This is because the two are inverse of each other. A good resistor is a bad conductor and vice versa. Sort of like saying Bob has more tallness and less shortness than Jim. The two properties (tallness and shortness) are just the inverse of each other. Same thing with conductivity and resistivity.

    While I admitted that there is a conductivity difference between aluminum and copper, for the purposes of shielding a bass guitar, that difference is going to have absolutely no impact on how well shielded the instrument ends up.

    As other people in this thread have mentioned, there's a definite advantage to copper in terms of soldering. I hadn't known about the need for corrosive flux when soldering with aluminum. If anything explains the popularity of copper as an instrument shield it's these ease of use issues. Aluminum would be cheaper in terms of parts cost, but copper looks like it is the cheaper alternative in terms of labor and instrument longevity.
  9. slyjoe

    slyjoe Supporting Member

    Jun 28, 2008
    Valley of the Sun (AZ)
    Also, remember aluminum wiring in houses? Where the aluminum met the copper fixtures there can be a galvanic effect (which corrodes the connection). Don't know if this was dependent on the current though, which in a bass wouldn't matter. Unless you are getting real dangerous :)
  10. Nighttrain1127

    Nighttrain1127 Supporting Member

    Nov 27, 2004
    Near Worcester MA
    Thanks for all the info I guess copper is the easiest and least harmful way to go. TB is a great source of info thanks again
  11. Buster666


    Nov 29, 2008
    What would Faraday do?
    Faraday found that by wrapping a copper wire around a cardboard tube and passing a current thru the wire, he could influence the current by moving a magnet near it. Electro-magnetic Induction! I question whether aluminium wire would work as well.
    BTW, later James Clerk Maxwell formalized Faraday's work with the mathematical formulas, discovering that this was all about waves! And that it was all light, and that the speed of light was constant, everywhere. Even near a black hole or Dark Star. So if you buy Dark Star pickups for your bass, even if you are so unfortunate as to fall into a black hole we will still be able to hear your awesome bass solo, given that your instrument cord is long enough to reach back to your amp. I saw Phil demonstrate this at a Dead show in '67 when LSD was still legal.
  12. stflbn


    May 10, 2007
    :: LoL at all the physics nerds slapping their brains against each others ::

    Regardless of any price difference I just use Copper tape and am always happy with the results, and have been for 30+ years.

    Sometimes saving some $$ can be quickly over-ridden by problems... and honestly, who REALLY needs 50 yards of aluminum tape???

  13. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    There are two kinds of common interference, from electrical fields and magnetic fields (even though they are two aspects of the same phenomena, and you cant have one without the other).

    So another aspect is that copper is more transparent to magnetic fields than aluminum. Aluminum is a nonmagnetic material, but it's very easy to induce eddy currents and circulating fields in it. These fields have magnetic properties, and can be as effective as steel in blocking other magnetic fields.

    I use brass mesh for shielding in my pickups. It's an effective Faraday cage and doesn't kill the tone like a metal cover would.

    For general shielding I mostly use copper foil, but I also use aluminum. If you are using aluminum foil or tape, you can stick some conductive adhesive copper foil to it and solder to that.

    I avoid that carbon conductive paint. It's not thick enough and too resistive. The silver or nickel paint is better, but I stick with copper foil.
  14. derelicte


    Dec 25, 2007
    for the same reason that clay dot inlays sound better than other dots imho asaik my .02
  15. Galvanic effect depends only on the materials involved, not the current.
    Might be mildly temperature dependent though...
  16. Don't forget that shielding is to keep out RFI (radio frequency interference) In the electronics world, almost all equipment cases are made from aluminium, and aluminium sheet is used to separate rfi sensitive areas from rfi sources. In theory then, I suppose it should be as effective as a shield in guitars, but I expect the "solderability" issue has made copper more popular.
  17. Buster666


    Nov 29, 2008
    Eddy Currents!?!
    Point well taken, opening up another can of worms. Some of the high end audio companies that make phono preamps, etc, are eskewing the use of steel and aluminum and making chassis out of exotic wood or composites to reduce the eddy currents.
  18. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    It's the same thing with pickups. Any metal parts on the pickups are prone to eddy currents. This is why a non ferrous metal cover on the pickup changes the tone.

    50 years ago they seemed more preoccupied with shielding... you saw guitars with metal pick guards and stuff, and then you have the metal covers over the pickups as on Fender instruments.
  19. Subscribed.

    I just used copper with what I assume is conductive adhesive to shield the cavity on a project bass I work on, next thing is to shield the pup slots and then I'll probably not even notice any difference in the end anyway...


  20. Jim C

    Jim C I believe in the trilogy; Fender, Stingray, + G&L Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Here is the bottom line from a guy who worked on RF shielded room design for the DoD.

    Different materials offer better attenuation characteristics depending on frequency. Let's assume the RF frequency range is huge and we are look at 10 Kilotherts to 10 Gigohertz.

    This would include the "H" field (magnetic), "E" field, and microwave region

    For magnetic field attenutaion the material MUST be feros meaning some iron content; the most practical is cold rolled steel
    For higher frequencies copper is better partly due to material characteristics but also due to the ability to have a low impedence connection on overlap conditions.

    3M makes some of the best copper tape (available at mcmastercarr.com) and is also available with conductive adhesive. We did not find any appreciable difference with cond. adhesive so long as the overlap joints were clean and burnished.

    Also did some research on conductive paint (years ago) and was not very impressed with the results other than easier to apply and the only partical way for manufacturing due to the amount of time to tape correctly