FPCB (Flex PCB) Types of Flex Plus
Flex PCB or FPCB (Flexible Printed Circuit Board) is an innovative solution made from flexible and bendable materials, offering exceptional electrical performance and mechanical flexibility. This makes them especially ideal for space-constrained electronic designs. Due to their bendability and ability to adapt to complex 3D structures, Flex PCB has become a key element in modern electronics manufacturing. They are widely used in various electronic devices where flexibility is required, and there are several types of Flex circuit boards, each designed for specific constructions and applications. Here are some common types.
Printing circuits on Thermoplastic Polyurethane material
TPU is a versatile material known for its flexibility, durability, and chemical resistance, making it suitable for various industries, especially commonly used in the medical industry.
Special Specs of Flex Plus
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FPCB Size: Maiximum up to 250 * 2000 mm
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Thickness: 0.05 ~ 1mm
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Minimum Pitch: 0.08
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Circuit trace width 0.05mm, gap 0.05mm
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Circuits Conductive Material: Silver Paste
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Finishing: TPU for isolation cover
Single sided FPCB is the most basic type of flexible circuit. This type of FPCB has conductive traces on only one side of the flexible substrate. It is the most demanded type of flex PCB.
Special Specs of Flex Plus
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FPCB Size: Maiximum up to 500 * 4000 mm
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Thickness: 0.05 ~ 1mm
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Minimum Pitch: 0.08
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circuit trace width 0.05mm, gap 0.05mm
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Material: PI, PET, PEN
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Finishing: Ni/Au, Sn. Sn/Cu, OSP
Multilayer flexible printed circuit combine several single-sided or double-sided circuits with complex interconnect, shielding, and/or surface mount technologies in a multilayer design. They are used for more complex and dense circuits. The number of conductor layers in a multilayer flexible circuit is not only fixed. However, the actual application scenario should be considered in the design, including package size, number of layers and flexibility.
Special Specs of Flex Plus
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Layers: up to 6 Layers
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Maximum size: 250 * 800 mm
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Minimum Hole size: Laser 0.07mm ; CNC 0.15mm
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Trace Width & Gaps:
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Inner trace: 0.05 mm, 0.05 mm Outer trace: 0.075 mm, 0.075 mm
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Alignment: 0.075 mm
The conductive copper foil of double-sided FPCB exist on both sides of the polyimide. In most cases, two layers of copper are electrically connected by drilling small holes in the copper circuit and separating the dielectric. Then copper is plated on these holes to establish a connection between them. This allows for more complex circuit designs.
Special Specs of Flex Plus
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Minimum Hole Size: CNC0.1mm , Laser0.05mm
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Maximum Size: 250 * 800 mm Minimum Pitch: 0.1 mm
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Circuit trace width 0.05mm, gap 0.05mm
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Impedance Types of DS Flex PCB:
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Coverlay (Yellow, white, other color customizable)
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PSR (Yellow, Green, White) , Combination of Coverlay + PSR
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Impedance control: ±10%
Rigid-Flex PCB contain flexible and rigid areas, combining the advantages of flex PCB and rigid PCBs. This allows for cost-effective, customized solutions for equipment manufacturers. Flexible substrates can be used to connect two rigid areas without the use of plugs and cables. In this way, it is possible to maintain a short signaling pathway while taking miniaturization a step further. Moreover, the connection is also significantly stronger and more able to withstand mechanical stress.
Special Specs of Flex Plus
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Layers: Maximum 8 layers
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2-6 layers for regular production
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Structures:
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1. Rigid-Flex-Rigid: 4-8 layers
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2. Flex-Rigid-Flex: 3-6 layers
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3. Flex-Rigid: 2-4 Layers
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Solder Pads align accuracy: 0.1mm
Sculptured Flex PCB
These FPCBs have a unique construction where the conductor traces are selectively thinned or thickened to accommodate specific mechanical or electrical requirements.
The common sculptured flexible circuit has pins, which are made into through-hole connectors. The sculptured terminal pins are built-in and extend beyond the boundaries of the polyimide substrate. These pins are inserted into a series of holes on the Flex PCB and then soldered. This circuit design can also be soldered onto a series of surface mount pads. Usually, it is chosen to eliminate the need and cost of ZIF connectors.
Special Specs of Flex Plus
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FPCB Size: Maiximum up to 250*1500 mm
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Thickness: 1oz ~ 8oz
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Staggered Etchback: various thickness on each part
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Material: PI, PET, PEN
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Finishing: Ni/Au, Sn. Sn/Cu, OSP
Metal-clad FPCB
In this type, a layer of metal, such as copper, is applied to the flexible substrate to enhance its conductivity.
Adhesiveless FPCB
These FPCBs do not use adhesive materials between the layers, making them more suitable for high-temperature applications.
Coverlay Flex PCB
Coverlay is a protective layer added to an FPCB to insulate and protect the conductive traces from environmental factors.
Terminology of FPCBs
Staggered Etchback / Step Etchback
In the context of Rigid Flex PCB manufacturing, "staggered etchback" or "step etchback" refers to a process used to create controlled depth variations in the copper traces or conductive layers of a Rigid-Flex circuit board.
This process involves selectively etching away portions of the conductive layers to achieve different copper thicknesses at different locations on the board.
The purpose of staggered etchback is to optimize the flexibility and bending characteristics of the Rigid-Flex PCB. By varying the copper thickness, the board can have different degrees of flexibility in different regions, allowing it to bend and conform to the desired shape without compromising the electrical performance or mechanical integrity.
Staggered etchback is an essential technique in the fabrication of Rigid-flex circuit board, as it enables the board to accommodate the varying mechanical requirements and fit into complex geometries, common in applications such as aerospace, medical devices, and other electronics where space and weight constraints are critical.