Components of a flexible circuit
A flexible circuit consists of copper foil, dielectric substrate+ coverlay and adhesive.
Copper foil is available in two different types of copper: ED Copper and RA copper.

ED copper is an electro-deposited (ED) copper foil produced in the same way as the copper
Foil used for rigid printed circuit boards. this also means that the copper is " treated", i.e., it
Has a slightly rough surface on one side, which ensures a better adhesion when the copper
Foil is bonded to the base material.
RA copper is a rolled and annealed copper foil produced from electrolytically deposited cathode
Copper, which is melted and cast into ingots. the ingots are first hot-rolled to a certain size and
Milled on all surfaces. the copper is then cold-rolled and annealed, until the desired thickness is
Obtained.
Copper foil is available in thickness of 12, 18, 35 and 70 m.

the most common available for dielectric substrate and coverlay is polyimide films. this material
Can also be used as coverlay. Polyimide is best suited for flexible circuits because of its
Characteristics as stated below:
     High temperature resistance allows soldering operations without damaging the flexible
    circuits
     Very good electrical properties
     Good chemical resistance
Polyimide is available in thicknesses of 12.5, 20, 25 and 50 m.

Base laminates for rigid printed circuit boards are copper foils laminated together with the
Base materials, the adhesive coming from the prepreg material during lamination. Contrary
to this is the flexible circuit where the lamination of the copper foil to the film material is
Achieved by means of an adhesive system. It is necessary to distinguish between two main
Systems of adhesive, namely thermoplastic and thermoset adhesives. The choice is dictated
Partly by the processing, and partly by the application of the finished flexible circuit.



FPC Case: Double Sided Flexible PCB Built on Polyimide
with 90 OHM Impedance Control
(Flexible printed circuits are custom-made products, the picture and parameters shown are
Just for reference)

General description
this is a type of flexible printed circuits built on polyimide substrate with connectors assembled
for the application of USB wireless. the base material is double layer adhesive RA Copper 35um
on polyimide 25um thick. It has 90 Ohm differential impedance with 4.7mil track and 7.9mil
Track seperation. There're 2 thickness on the head stiffener, one for 0.3mm FR-4 and one for
0.8mm FR-4 to support the connectors. Whole flex has no silkscreen, but with yellow coverlay
and immersion gold on pads. the base material is from Shengyi SF202, entire board supplying
Single up. They're fabricated per IPC 6012 Class 2 using supplied Gerber data. Every 80 pieces
Are packed for shipment. 

Parameter and data sheet

PCB Size:	120 x 95mm = 1 PCS
Number of Layers	2 layers
Board Type	Flexbile cirucit
Board Thickness	0.2mm +/-10%
Board Material	Double layer adhesive RA Copper 35um, Polyimide 25um
Board Material Supplier	Shengyi
Tg Value of Board Material	60
PTH Cu thickness	20 um
Inner Iayer Cu thicknes	N/A
Surface Cu thickness	35 um (1oz)
Coverlay Colour	Yellow
Number of Coverlay	2
Thickness of Coverlay	25 um
Stiffener	0.3mm FR4+pure glue 0.8mm FR4+pure glue
Type of Silkscreen Ink	N/A
Supplier of Silkscreen	N/A
Color of Silkscreen	N/A
Number of Silkscreen	N/A
Minimum via (mm)	0.3
Minimum Trace (mil)	4.7
Minimum Gap(mil)	7.9
Impedance Control	90 Ohm differential impedance with 4.7mil track and 7.9mil strak seperation
Surface Finish	Immersion Gold
RoHS Required	Yes
Famability	94-V0
Thermal Shock Test	Pass, -25125, 1000 cycles.
Thermal Stress	Pass, 3005,10 seconds, 3 cycles. No delamination, No blistering.
Function	100% Pass electrical test
Workmanship	Compliance with IPC-A-600H & IPC-6013C Class 2
Type of artwork to be supplied	Email file, Gerber RS-274-X, PCBDOC etc
Service area	Worldwide, Globally.

Features and benefits
Excellent flexibility;
Reducing the volume;
Weight reduction;
High solderability, no stressing of circuit boards and less contamination of PCB surface;
Quick and on-time delivery;
16000 square meter workshop;
on-time service;
More than 15 years of PCB experience;


Application
Industrial control temperature controller, Automobile sensor flex board, LED display,
Tablet PC module, laser head FPC, mobile phone built-in antenna FPC, contact belt
of inkjet printer


FPC


Flying probe test