Engineering review
The fabrication data is reviewed against the proposed construction, materials, tolerances and acceptance requirements. Clarifications should be closed before tooling and material release. Freeze the revision and retain a record of approved changes.
Circuit formation and lamination
Copper patterns, flexible substructures and rigid sections are produced using the process sequence required by the design. Registration, material handling and controlled bonding are especially important around transitions. The detailed route varies with via structure and stackup.
Drilling, plating and protection
Holes and interconnections are formed and metallized as required, while coverlay and solder mask protect designated regions. Surface finish is applied to exposed features. The process plan should account for the compatibility of materials and treatments.
Profile, inspect and test
The outline and flexible openings are completed, then the board is checked against the released requirements. Optical inspection, electrical testing and agreed dimensional or coupon measurements address different defect classes. Delivery documentation should identify the tested revision and lot.
Plan for assembly
Handling supports, temporary carriers and packing affect flexible circuits after fabrication. Discuss these requirements early so a board that passes fabrication inspection can be assembled without avoidable damage.