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Flexible Printed Circuit Board, FPC Double-sided Board

End product: mobile phone, iPAD, intelligent wearable device, industrial control, video recorder, calculator, drone, vehicle, medical equipment, etc

Max number of layers: 16L

Substrate type: Polymide, LCP, PET

Substrate brand: Shengyi, Lianmao, Taihong, Xinyang, Xingao, Panasonic, Dupont, Jiujiang

Stiffener type: FR4, PO, PET, Steel sheet, Al sheet, PSA, Nylon

Surface finish: ENIG, ENEPIG, OSP, Gold electroplating, Gold electroplating + ENIG, Gold electroplating + OSP, Immersion Ag

    Definition of FPC(see figure 1 for details)


    1.FPC—Flexible Printed Circuit, a highly reliable and flexible printed circuit made by etching onto copper foil using polyester film or polyimide as the substrate to form a circuit.  

    2.Product Characteristics : ① Small size and light weight : meeting the needs of high-density, miniaturization, lightweight, thinness and high reliability development directions; ② High flexibility : can move and expand freely in 3D space, achieving integrated component assembly and wire connection. 

    FPC classification +FPC basic materials (see figure 2 for details)

    According to the number of conductive layers, it can be divided into single-sided board, double-sided board and multi-layer board.

    Single-sided board : conductor on one side only.
    Double-sided board : there’re 2 conductors on both sides, and to establish electrical connection between 2 conductors with through hole (via) as a bridge. A through hole is a small copper plated hole on the hole wall that can be connected to the circuits on both sides.
    •Multi-layer board : contains 3 or more layers of conductors, with more precise layout. 
    •Except single-sided board, the number of layers of rigid board is generally even, such as 2, 4, 6, 8 layers, mainly because the odd layer stacking structure is asymmetric and prone to board warping. On the other hand, flexible PCB is different as there’s no problem of warping, so 3-layer, 5-layer, etc. are common. 


    Copper foil is devided into Electro-Deposited copper(ED Copper) and Rolled Annealed copper(RA Copper) 

    Comparison between RA copper and ED copper 
    Cost high low
    Flexibility good poor
    Purity 99.90% 99.80%
    Microscopic structure sheet-like columnar

    So the application of dynamic bending must use RA copper, such as the connection plate for folding/sliding phones and the expansion&contraction parts of digital cameras. In addition to its price advantage, ED copper is also more suitable for the production of micro circuits due to its colomnar structure. 

    Adhesive Substrate  Adhesiveless Substrate
    0.5mil 12um 1/3OZ 0.5mil 1/3OZ
    13um 0.5OZ 0.5OZ
    1mil 13um 0.5OZ 1mil 1/3OZ
    20um 1OZ 0.5OZ

    Conventional Substrate Configuration

    The commonly used thickness specifications for the base copper of soft boards include 1/3oz, 0.5oz, 1oz and other thickness specifications. Unconventional copper thicknesses include 1/4oz, 3/4oz and 2oz, etc.


    Camera, video camera, CD-ROM, DVD, hard drive, laptop, telephone, mobile phone, printer, fax machine, TV, medical equipment, automotive electronics, aerospace and industrial control, new energy products.