Double Sided Assembled Flexible Printed Circuit Built On Polyimide With 90 OHM Impedance Control for Automobile Sensors
(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

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 17 years of PCB experience;

Applications
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

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 μm.

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 μm.

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.