Flexible keyboards typically have both circuits manufactured from polyester. They can be low profile (1.0mm) with all switches and connections screen printed on to heat stabilised polyester, this is then laminated to an engineered switch spacer and finally profiled to the customers specifications, and adhered directly to the final product.
MacDermid Autotype offer a range of heat stabilized polyester films suitable for screen printing with conductive, graphite and dielectric inks. For further details please see the product information section on Autostat.
Link to MacDermid Autotype Autostat films
Link to MacDermid Autotype Screen Films
Link to MacDermid Autotype Screen Emulsions
Link to MacDermid Autotype Screen Chemicals