Double layer FPC

Double layer FPC

With two layers of conductive traces, double layer FPCs offer higher routing density, enabling the integration of more electronic components. This results in improved functionality and expanded capabilities of electronic devices. As a leading flexible PCB supplier, Sienta can provide double sided flexible circuit board within 3-5 working days. And also support flexible PCB assembly service including components sourcing. With a growing demand for flexible circuit boards, Sienta are ready to take on any challenge and deliver top-quality products at competitive prices!.

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Double layer FPC

Capabilities Of Double layer FPC

Item Finished Cu Thickness Min.Trace Width Min.Trace Spacing(mil)
Circuit 12-18um 2mil 2mil
18-35um 3mil 3mil
35-50um 4mil 4mil
50-70um 6mil 6mil
Surface Treatment Thickness
(HASL) only for rigid flexible PCB Sn: 2um-40um
(HASL L/F) only for rigid flexible PCB Sn: 2um-40um
ENEPIG Ni: 1.0um-6.0um Pd: 0.10um Au: 0.10um
Hard gold plating Ni: 1.0um-6.0um Au:0.02um-2um
Soft gold plating Ni: 1.0um-6.0um Au:0.02um-1um
ENIG Ni: 120-200U” Au: 2-4U”
Immersion silver Ag: ≥0.4um
Tin plating 2um-15um

A double-layer FPC typically consists of the following key elements:

a. Raw material: The base material usually made of flexible materials like polyimide (PI) or polyethylene terephthalate (PET), which provides the FPC with its flexibility.

b. Conductive Layers: Two layers of copper or other conductive materials are bonded to the base material. These layers serve as the conductive lines for electrical signals.

c. Insulating Layer: An insulating layer or dielectric material is placed between the two conductive layers to prevent electrical short circuits and provide mechanical support.


Double-layer FPCs offer several advantages:

a. Enhanced Circuit Density: With two conductive layers, designers can create more complex and denser circuit patterns, which can be crucial in applications with space constraints.

b. Improved Signal Integrity: Double-layer FPCs can effectively route and shield signals, minimizing crosstalk and interference between adjacent traces.

c. Design Flexibility: The dual layers allow for different routing configurations, including interconnections and the ability to accommodate both surface mount and through-hole components.

d. Reliability: The insulating layer between the conductive layers ensures reliable electrical isolation and prevents short circuits.

Manufacturing Process

The manufacturing process of double-layer FPCs is similar to that of single-layer FPCs with an additional layer of copper and insulation. It involves steps such as material preparation, drilling holes, copper etching, lamination, shape and testing. The key difference is in the careful alignment and bonding of the two conductive layers with the insulating layer sandwiched in between.


Double-layer flexible circuits are used in various industries and applications, including:

a. Consumer Electronics: They are found in smartphones, laptops, cameras, and other portable devices to accommodate complex interconnections and slim designs.

b. Automotive: Double-layer FPCs are used in vehicle infotainment systems, dashboard displays, sensors, and control modules.

c. Medical Devices: In applications like medical imaging equipment, patient monitoring devices, and diagnostic instruments.

d. Aerospace and Defense: Used in avionics, radar systems, and communication devices.

e. Industrial Equipment: Double-layer FPCs can be found in control systems, industrial automation, and robotics.

f. Telecommunications: They are used in network infrastructure, routers, and communication equipment.

Design Considerations

Designing a double-layer FPC requires careful consideration of factors such as the stack-up, routing, and material selection to ensure that the circuit functions reliably and can be manufactured effectively. Designers must also consider the flexibility and bending requirements of the FPC, as well as thermal and environmental conditions in the application.

Double-layer FPCs are an excellent choice when more complex circuitry and a higher level of interconnectivity are needed in a flexible and space-efficient package. Their use is widespread in industries where compact and reliable flexible circuit solutions are required.

Benefits of Double layer FPC

  • Compact Design

    By utilizing both sides of the flexible substrate, double layer FPCs can accommodate a higher density of components and interconnects, enabling more compact designs.

  • Increased Routing Options

    Double layer FPCs allows designers to optimize signal paths, minimize crosstalk, and reduce electromagnetic interference (EMI) between traces.

  • Improved Signal Integrity

    Double layer FPCs allowing for dedicated ground and power planes on separate layers,which helps to reduce noise and interference, enhancing the overall performance and reliability of the circuit.

  • Flexibility and Reliability

    Double layer FPCs retain the flexibility and bendability characteristic of FPCs. The use of flexible materials enables them to conform to non-planar surfaces or fit into tight spaces.

  • Weight and Space Savings

    Compared to rigid PCBs, double layer FPCs are typically lighter and more compact.

  • Cost-effectiveness

    The elimination of connectors and reduced assembly steps due to the flexible nature of FPCs can lead to lower overall production costs.


  • Q What is your MOQ(Minimum Order Quantity)?

    We have no MOQ limited.Sample and mass production all can support.

  • Q What is needed for quotation?

    FPC&rigid-flex PCB&PCB:Quantity, Gerber file and Technical requirements(material,surface finish treatment, copper thickness,board thickness ,...)
    PCBA:PCB information, BOM list

  • Q Can you manufacture my PCB from a picture?

    No, we cannot accept BMP, GIF, TIFF, or JPG pictures as the manufacturing file.If you do not have gerber file, you can send us sample to copy it.

  • Q Are my files safe?

    We ensure complete safety and security of your files and protect our customers' intellectual property throughout the entire process. Any documents provided by our customers are kept strictly confidential and are never shared with any third parties.

  • Q How long will it take to receive my quotation?

    We will respond your quotation within 24 hours to the quotation requests.

  • Q How can I pay?

    We accept payments by PayPal, cash, bank transfer (T/T),WU,Alipay. If need other payment method please contact us (

  • Q What's your transport method?

    We use UPS, FedEx, or DHL to ship the boards. If you have your own freight forwarding company, we can also work with them.

  • Q Do you offer free sample?

    We can offer samples, but you must pay for them first. If you go ahead with mass production later on, the cost of the samples will be deducted.We look forward to establishing a long-term business relationship with you!

  • Q What is your standard lead time?

    As FPC&PCB belong to customized products,generally it is 3-7 days for samples and 10-20 days for mass products.The actual delivery date according to difficulty of the products, the quantity and etc.Please contact us to get different product lead time.

  • Q How do you control the product quality?

    We adhere to strict quality control standards set by ISO 9001, ISO 14001, IATF 16949, and SGS. All boards undergo 100% testing and we offer a range of inspection options including visual, X-ray, AOI, and ICT/FCT.

  • Q How many layer can you produce for flexible PCB?

    For FPC, we can produce from 1 layer to 8 layers.

  • Q How many layer can you produce for Rigid flexible PCB?

    For Rigid flexible PCB board, we can produce from 2 layer to 8 layers.

  • Q Which surface treatment can you produce for FPC, PCB and rigid flexi PCB?

    We can produce Immersion gold, immersion silver, OSP, hot air Levelling(L/F), Gold plating,ENIPIG, Immersion tin and etc.

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