4 Layer Flex PCBs

Yes, flex PCBs can absolutely be multilayer. SFX PCB manufactures multilayer flexible circuits with up to 8 layers on polyimide substrates, supporting advanced features like laser drilling down to 4mil, impedance control of ±10%, and inner layer line widths as fine as 2.5mil/2.5mil for high-density designs.

4 layer flex PCBs are primarily built on polyimide (PI) substrates, which offer excellent thermal stability, flexibility, and electrical performance. SFX PCB also supports DuPont films and polyester materials with adhesive or non-adhesive constructions, depending on application requirements such as temperature range and mechanical flexibility demands.

SFX PCB offers a comprehensive range of surface finishes including ENIG (Electroless Nickel Immersion Gold), OSP, HASL, Immersion Silver, Immersion Tin, ENEPIG, Soft Gold, and hard Gold Plating. The choice of finish depends on solderability requirements, shelf life, application environment, and whether the board is used in high-wear connector areas.

4 layer flex PCBs are used across aerospace, defense, medical devices, automotive systems, industrial automation, telecommunications, and consumer electronics. Their ability to bend, fold, and fit into complex three-dimensional enclosures makes them ideal for hearing aids, X-ray equipment, avionics, radar systems, ABS controllers, and wearable technology.

SFX PCB's flexible PCBs are manufactured under ISO 9001:2015 and ISO 14001:2015 quality management systems. Multilayer rigid-flex products meet IPC Class II standards. All boards undergo two-factor quality control combining visual and optical inspection, along with electrical testing, impedance testing, and solderability testing prior to shipment.

In low-volume production, SFX PCB achieves laser drilling down to 4mil, inner layer line width/space of 2.5mil/2.5mil, outer layer line width/space of 3mil/3mil, and BGA pitch as fine as 0.15mm. Board outline tolerance is held to ±0.025mm, enabling highly precise, dense circuit designs for miniaturized electronic products.