Multilayer Flexible Printed Circuit (FPC) Multi-layer Flexible PCB Board
(FPC’s are custom-made products, the picture and parameters shown are just for reference)
General description
This type of flexible circuit is 4-layer structure built on polyimide (PI) for the application of wireless router, 1oz copper each layer. The base laminate is from Shengyi. Coated by yellow covering layer, immersion gold is plated on pads. A connector is designed at both ends. It’s fabricated per IPC 6012 Class 2 using supplied Gerber data.
Parameter and data sheet
| Size of Flexible PCB | 300.5X 25.5mm |
| Number of Layers | 4 |
| Board Type | Flexible circuits |
| Board Thickness | 0.30mm |
| Board Material | Polyimide (PI) 25µm |
| Board Material Supplier | Shengyi |
| Tg Value of Board Material | 60℃ |
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| PTH Cu thickness | ≥20 µm |
| Inner Iayer Cu thicknes | 35 µm |
| Surface Cu thickness | 35 µm |
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| Coverlay Colour | Yellow |
| Number of Coverlay | 2 |
| Thickness of Coverlay | 25 µm |
| Stiffener Material | NO |
| Stiffener Thickness | N/A |
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| Type of Silkscreen Ink | NO |
| Supplier of Silkscreen | N/A |
| Color of Silkscreen | N/A |
| Number of Silkscreen | N/A |
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| Peeling test of Coverlay | No peelable |
| Legend Adhesion | 3M 90℃ No peeling after Min. 3 times test |
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| Surface Finish | Immersion Gold |
| Thickness of Nickle/Gold | Au: 0.03µm(Min.); Ni 2-4µm |
| RoHS Required | Yes |
| Famability | 94-V0 |
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| Thermal Shock Test | Pass, -25℃±125℃, 1000 cycles. |
| Thermal Stress | Pass, 300±5℃,10 seconds, 3 cycles. No delamination, no blistering. |
| Function | 100% Pass electrical test |
| Workmanship | Compliance with IPC-A-600H & IPC-6013C Class 2 |
Features and benefits
Excellent flexibility
Reducing the volume
Weight reduction
Consistency of assembly
Increased reliability
Material optionality
Low cost
Continuity of processing
Diversified shipping method
Engineering design prevents problems from occurring in pre production.
Applications
Laser head FPC, medical equipment controller, Tablet antenna soft board
Multilayer Flexible Circuits
For the most part, manufacture of multilayer flexible circuits is based upon processes of single sided flexible PCB and double sided PTH flexible PCB. Both types evolve from the conventional covercoated double-sided flexible circuits that are bonded together. For a number of reasons, it is not recommended to combine too many flexible circuits into a multilayer flexible circuit.
Materials and Thicknesses of Multilayer FPC
It is common practice to use the materials listed below.
Dielectric Substrates
50 µm (2 mil) polyimide because of its higher stability and easier handling compared with 25 µm (1 mil) polyimide.
Copper Foil
35 µm (1 oz.) copper foil, provided this thickness is compatible with the current carrying requirements of the finished circuit.
Covercoat
25 µm (1 mil) polyimide for a 35 µm (1.4 mil) thick copper foil, since it ensures a better encapsulation of the conductors than a 50 µm (2 mil) polyimide.
25 µm (1 mil) acrylic adhesive for achieving a good encapsulation and a low-flow lamination. Too much acrylic adhesive leads to reliability problems, e.g. barrel cracks, foil cracks, and a too deep etchback.
Outer Layers
Outer layers should not be provided with any circuitry (conductors) on the bonding side because of the risk of air entrapment at the interface.
Bonding Materials
When using covercoated flexible circuits as inner layers, the circuits and the rigid parts are bonded together by means of sheet adhesives.
Processes
A simplified flow diagram is shown below.
More Displays of Multi-layer FPC
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Multilayer Flexible Printed Circuit (FPC) Multi-layer Flexible PCB Board Images
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