Material Selection and Laminate Design: Foundation of Rigid-Flex Synergy

· Substrate Adaptation: FR-4 (conventional scenarios), high Tg FR-4 (high-temperature scenarios, Tg≥170℃) or ceramic-filled materials (high-frequency scenarios) are used for rigid areas; polyimide (PI, temperature resistance 260℃) is preferred for flexible areas, polyester (PET, temperature resistance ≤150℃) for economical scenarios, and PTFE (dielectric constant ≤2.1) for high-frequency scenarios.

· Conductive Layer Selection: Rolled annealed (RA) copper foil (good ductility, bending resistance) is used for flexible areas, and electrodeposited (ED) copper foil (cost-controllable, suitable for static areas) for rigid areas. The copper foil thickness is 0.5-2 ounces (17-70μm), and 2-ounce thick copper is used for high-current areas.

· Adhesive and Lamination: Acrylic adhesive (good flexibility, temperature resistance 150℃) or epoxy adhesive (high temperature resistance 180℃, high rigidity) is selected, and adhesive-free laminates are used in high-end designs to reduce thickness; lamination configurations can be customized (2-layer rigid + 1-layer flexible, 4-layer rigid + 2-layer flexible, etc.), and the transition area requires continuous lamination design to avoid stress concentration.

Rigid-Flex Transition Area Process: Breaking Key Technical Difficulties

The transition area is the core of the process, requiring smooth connection between rigid and flexible parts

· Circuit design: 45° bevel or arc wiring is adopted to avoid right angles, and wires are perpendicular to the bending line, evenly distributed to reduce stress concentration;

· Edge treatment: Stress relief grooves are set to remove burrs and prevent circuit breakage during bending; 

· Reinforcement design: FR-4 or stainless steel stiffeners are pasted on the edge of the transition area to improve mechanical strength.