Shield the entire pick guard?

[DrVenkman]

I'm getting ready to do my first shielding job, and have a question on doing the pickguard. Should I entirely cover the back of the pickguard with my foil, or should I only do the parts that match up with parts of the body that are shielded (pickup and control cavities, and routes for wiring)?

I can't see any benefit to doing the whole thing, but then again I'm not an electrical engineer so I'm asking the experts here.

And a separate question: is there any harm to mixing aluminum and copper foil when shielding? This is purely academic as I'll be using copper throughout but I was curious. Here's why I was thinking of this.

Ideally for the pickguard you want a single sheet of foil to do the shielding, because it's easier and avoids dealing with any joints in the shielding. Copper foil is relatively expensive and isn't available everywhere. Aluminum foil is relatively cheap and easy to find. Pull some off the roll, use some spray adhesive to hold it in place, and you're good to go. On the flip side, in the body cavities you need to use multiple pieces to fit all the cavities, and they should ideally be soldered at at the joints (even if the tape has conductive adhesive), and copper is a heck of a lot easier to solder than aluminum. Plus if you're going to solder it anyway you can use slug tape, which is way cheaper than special purpose shielding tape.

The potential problem is where the aluminum on the pick guard meets the copper on the body. Is there any issue with using two different metals in this fashion?

[Turnaround]

There is no benefit from shielding the entire pickguard. Essentially you are trying to create a grounded conductive box around the electronic components. Try to create a complete box - no gaps. And be sure it is grounded.

There will be no issue with using aluminum foil on the pickguard. To ensure that the foil on the pickguard gets properly grounded, extend the foil inside the cavity up over the edge of the cavity until it covers one screw hole from the pickguard - just a little foil tab will do. That way when you screw down the pickguard the screw pressure will ensure a good contact between cavity and pickguard. As a bonus you will be able to check your grounding with a multi-meter after assembly - from the screw at the foil tab to the bridge or the body of the output jack.

[DrVenkman]

That's what I thought, but it's nice to have confirmation. Thanks.

[tstone]

There can be a galvanic action between copper and aluminum which causes the aluminum to be eaten away where the two dissimilar materials are in contact. But this is normally not an issue unless you are in an extremely humid tropical environment.