How is FPC made?

FPC is also called flexible circuit board and soft board. It has the characteristics of high wiring density, light weight and thin thickness. It is a highly reliable and excellent flexible printed circuit board; it is widely used in consumer electronic terminal products , Such as smart phones, tablet computers, personal medical devices, etc.
 
What materials does FPC consist of?
FPC is made up of flexible substrate (PI/PET), copper foil (Cu) and adhesive (AD) bonded together, and then combined with cover film (Coverlay) and reinforcing material (Stiffener).
1. Copper
The materials are divided into rolled copper (Rolled Anneal Copper Foil) and electrodeposited copper (Electrode-posited Copper Foil). In terms of characteristics, rolled copper has better mechanical properties. When flexibility is required, most of them use rolled copper. The thickness is divided into four types: 1/3OZ, 1/2OZ, 1OZ, and 2OZ.
2. Substrate
There are two kinds of substrates: PI (Polyamide) and PET (Polyester). The price of PI is higher, but its flame resistance is better, and the price of PET is lower, but it is not heat resistant. Therefore, if there is a need for welding, most of them are made of PI. Generally, there are three kinds of thickness: 1/2mil, 1mil and 2mil.
3. Adhesive
Generally, there are two types of adhesives: Acrylic (acrylic glue) and Epoxy (epoxy glue). Epoxy glue is most commonly used. The thickness can be 0.4-2mil, and 0.72mil thick glue is generally used.
4. Coverlay
The cover film is composed of "substrate + glue", and its substrate is divided into two types: PI and PET. The thickness is from 0.5-1.4mil.
5. Stiffener
(1) Function: In order to weld the parts in the local area of ​​the soft board, increase the reinforcement material for installation and compensate the thickness of the soft board.
(2) Material: PI/PET/FR4/SUS.
(3) Combination method: PSA (Pressure Sensitive Adhesive): pressure sensitive (such as 3M series);
(4) Thermal Set: thermosetting type (bonding strength, solvent resistance, heat resistance, creep resistance)
 
In PCB manufacturing, FPC is a special process, with certain technical thresholds and manufacturing difficulties. Some PCB factories either find it troublesome to produce, or feel that the number of customers produced is small, which makes them reluctant to do it, or do less. POE can be used as FPC technology to meet customers' various PCB proofing needs.