Why can copper foil and aluminum foil shield electromagnetic signals?
In addition because the copper or aluminum oxidation caused by the contact resistance increases, the long-term use of suggestions for tinned copper foil, shielding effectiveness after 2 years will not fall too much. I have a new measurement of shielding effectiveness of copper foil and tinned copper foil at the beginning are basically the same, 114dB (copper 1GHZ) and 112dB (tinned copper 1GHZ). The shielding effectiveness of one year after the 84dB (copper 1GHZ) and 110dB (tinned copper 1GHZ). The effect is really bad.
Therefore, they usually back conductive adhesive, otherwise shielding effectiveness is very poor, under normal circumstances, with conductive adhesive copper foil / aluminum foil can reach more than 90dB, with flying conductive adhesive only about 40dB
Copper foil and aluminum foil can shield electromagnetic signals because they form a closed shielding chamber with the surrounding metal. Aluminum foil or copper foil and metal form continuous conduction
