Copper film insulates the wires from interference which would create noise in the output sound.
Electric Guitar
I assembled a Fender Stratocaster by ordering the bespoke body, neck, and necessary parts. I learned how pickups work (they are essentially analog sensors), soldered them to the potentiometers and switches which control the guitar's output, shielded the important signals with copper film, and fastened everything together after drilling some holes. Plays beautifully on my amplifier!
