Silver flex circuits were developed as a lower-cost option to copper circuits. Silver conductive ink is screen-printed onto a heat stabilized polyester film therefore the term "additive process". Silver ink traces are more flexible than solid copper traces. Copper flex circuits begin with a solid copper film laminated onto a polyester or polyimide (Kapton) film that is then chemically etched away to leave copper traces. Because of the chemicals involved, the manufacture of copper etched circuitry is not as environmentally friendly as screen-printing silver traces.
A rule of thumb is a silver flex circuit can be used with applications of 1 watt or less and has higher resistance than a copper flex circuit. A copper flex circuit can handle higher amps and voltage than a silver flex circuit and has lower resistance.
Due to the low cost of the polyester base material and applying silver only where it is required, the silver flex is considerably less expensive than Kapton copper flex.
Components can be soldered onto copper flex circuits. Components cannot be soldered onto silver flex circuitry and are attached with conductive adhesive.
Copper flex allows a minimum of 0.5mm pitch. Silver flex allows a minimum of 1.0mm pitch.