1. The minimum line/trace widths and thicknesses of the finished FPC wire shall be determined by the required current carrying capacity of the wire and the maximum allowable temperature rise.
2. The Minimum line width/space at BEST TECH currently is 2mil/2mil (0.05/0.05mm)
3. As for the circuits in the hollow zone of the single side double head and hollow board (Duall Access FPC) as well as double side hollow board are better designed to be wider for avoiding disconnection due to insufficient strength during the fabrication process.
Maximizing Line Widths
You can find some simple calculators to calculate the trace (conductor) width for circuit board:
The first thing to consider is the electrical characteristics. The line space on each layer should be as larger as possible to meet the requirement of the rated voltage between the wires. There is a table for your reference as below：