What is the difference between silver flex circuits and copper flex circuit?

Silver flex circuits were developed as a lower-cost option to copper flex circuits. Silver conductive ink is screen-printed onto a heat stabilized polyester film. 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. 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 less expensive than Kapton copper flex. However a copper flex circuit may be more suitable for dense circuit arrays or in certain environmental conditions.