Multi layer Flex PCB

A multi-layer flex PCB is a circuit board made of alternating single-sided or double-sided circuits. It combines the flexibility of a flex PCB with the high-density circuit capabilities of a multi-layer PCB. The layers are connected by conductive holes (common conductive holes include through holes, blind holes, and buried holes).
During the entire production process, multiple layers can be laminated together continuously or discontinuously. As shown in our picture, there are soft parts and rigid parts on a multi-layer flexible PCB, which are all determined by your design.

Stack-up

Multilayer flexible circuit boards can be composed of several single sided flex PCBs, several double sided flex PCBs, or a mixture of single layers and double layers. When we say how many layers a circuit board has, we are referring to the number of conductive layers. So below is the stackup diagram for a 4 layer flex PCB.

Stack-up of multi layer flex PCB

Benefits

High circuit density: Suitable for complex systems that require high circuit integration.
Stronger electrical performance: The multilayer structure of a flexible circuit can reduce electromagnetic interference (EMI) and crosstalk, and provide stable signal transmission.
Smaller size: Since circuits can be done on multiple layers, the product size can be reduced, which is suitable for miniaturized design.
Strong reliability: Suitable for harsh environmental conditions, such as aerospace and automotive electronics.

Applications

Multilayer flex PCB are an effective solution when faced with the following design challenges: unavoidable crossovers, specific impedance requirements, crosstalk elimination, additional shielding, and high component density.

Aerospace: Due to its excellent performance and reliability, it is suitable for aerospace equipment and instruments.
High-frequency communication: Such as in high-frequency circuits like 5G base stations and radar systems.
Industrial control: Works well in factory automation and robot control systems, etc.
Medical equipment: Perfect for modern medical devices that need compact and trustworthy circuits.

Advanced Features

High-speed signal transmission: Suitable for high-speed data transmission applications, reducing delays and signal attenuation.
High-temperature resistance: Multilayer for flexible circuit design provides better thermal management capabilities and can withstand higher operating temperatures.
Precise interlayer connection: Use microvia or blind hole technology to achieve efficient connection between different layers and improve overall performance.