Choose the construction around the motion
Single-sided, double-sided and multilayer flexible circuits solve different routing problems. Additional conductive and dielectric layers increase routing capacity but also change thickness and stiffness. First establish whether the circuit is a static interconnect, an installation fold or a repeated-motion component.
Stiffeners support local functions
A stiffener can support a connector, contact tail or component mounting area. It is a local mechanical reinforcement, and should not be confused with an electrically interconnected rigid region in a rigid-flex construction. Specify the stiffener material, thickness, adhesive and location in the fabrication drawing.
Coverlay and exposed pads
Coverlay protects copper in flexible regions. Its openings, registration allowance and adhesive flow must be considered when defining small pads and fine-pitch connectors. Ask the fabricator to review the opening geometry and the transition between protected routing and exposed contact areas.
Release checklist
Supply the flex outline, material stack, contact orientation, insertion thickness, bend envelope, copper requirements and any shielding. Confirm how the circuit will be supported during assembly and handling. Review the complete dimensional tolerance stack for mating connectors rather than specifying nominal thickness alone.