But as can be expected with any conversion to new technology, especially with the expected life of a typical major household appliance, the proving ground is pretty rigorous. Polyester films ranging from 2 to 10 mil have been the primary choice as substrate, but other materials are usable. These materials include Polyimides and Polyetherimides that offer higher temperature at a price premium. Typical trace resistance of silver conductive ink is 2.5 ohm for a 1-in. Recently developed high-conductivity inks can reduce this value by as much as 50 percent.
Resistance varies inversely as line width increases.
The variability of the resistance is wider than that of copper. This means that the designer cannot easily substitute PTF for copper in applications requiring high current or controlled impedances. But, PTF is perfectly acceptable for signal circuit applications. With the proper materials and equipment today's screen printing process is capable of printing this pitch in volume production. Six layer circuits, including shield and ground, have been produced in high volume.