Wed Mar 22 21:06:22 CST 2023
FPC, Flexible Printed Circuit, also known as flexible PCB, is a thin insulating polymer film with a conductive circuit pattern printed on it, usually with a thin polymer coating to protect the circuit.
FPC is made of flexible copper laminate as the substrate of a circuit board, as a signal transmission medium used in the connection of electronic products.
Small devices such as notebooks and digital cameras, due to the small size of space, so will use flexible circuit boards, FPC is characterized by high circuit density, can be bent, folded, wound, in a narrow space to move at will, heat dissipation is also good.
FPC is best suited for data transmission cables between moving parts and motherboards, board-to-board, and miniaturized electrical equipment.
FPC has the characteristics of high density of wiring assembly, good bending, light weight, flexible process, etc. It meets the requirements of downstream electronics industry of intelligence, portability and thinness, and the usage in the field of vehicle is increasing, and the application scope covers lights, display modules, BMS/VCU/MCU three power control systems, sensors, advanced auxiliary systems and other related scenes.
Benefit from the development of the consumer electronics industry, consumer electronics FPC in the expansion of the docking station and USB4 series above see many applications, forgetting the product board end Type-C interface is mostly mounted on the hard board or a combination of hard and soft board, the traditional hard board does not have flexibility, inconvenient to use; while the combination of hard and soft board although both the carrying capacity of the hard board and soft board flexibility, but its production process is complex, requiring both FPC production equipment and PCB production equipment, production difficulties, yield rate is only about 70%, material waste, long production cycle, expensive.
FPC structure
In the consumer electronics, FPC will be increasingly used compared to the PCB hard board, FPC has many excellent features:
1. Can be bent, coiled, folded, allowing designers to move freely according to the space layout requirements and expansion.
2. High assembly density, can greatly reduce the volume and weight of electronic products; suitable for electronic products to high density, miniaturization, high reliability direction. Therefore, FPC has been widely used in aerospace, military, mobile communications, notebook computers, computer peripherals, PDA, digital cameras and other fields or products.
3. It can reduce electromagnetic and radio frequency interference; It is easy to realize automation and improve production efficiency.
4. FPC also has the advantages of good heat dissipation and solderability, easy assembly, low overall cost, etc. The combination of soft and hard design also makes up to some extent for the slight shortage of the flexible substrate in terms of component carrying capacity.
The above advantages make the application of FPC is expanding. At present, FPC material and process cost is still relatively high, the future with the maturity of the process and market increment, there will be good performance!
Generally, FPC are made through a photolithographic technology sheet by sheet. Recently, a more advanced way to produce FPC is RTR (roll to roll) lamination.
1. Shearing:
To optimize the material utilization, cut the material as working size for different design and layout concern.
2. CNC (computer numerical control) drilling:
To fit customers’ design and process demand, drill different holes on boards, such as alignment holes, testing vias, components holes, etc.
3. Plating through hole:
Since both the top and bottom layer are not conductive, plate copper on the hole-wall after drilling to realize pattern connection between layers. This process applies to the making of double-sided flexible boards.
4. Dry film lamination:
To create an etching resist layer, pass pre-treated boards through hot roller to laminate dry film on it.
5. Exposure:
Transfer the designed circuit pattern image to dry film laminated on the foil to create an exposure area.
6. Development:
Cast UV (ultraviolet) light on the dry film, the dry film on the exposure area will be polymerized and hardened, and the dry film on non-exposure area can be removed and expose copper.
7. Etching:
After development, non-exposure area will be moved away by chemical reaction and the protected area will be remained.
8. Stripping:
After etching, remove the dry film covering the circuit pattern and make pattern exposed.
9. AOI (automated optical inspection):
Use AOI tester to check the quality of circuit.
10. Coverlay pre-lamination:
The board will be covered with insulating layer called ‘coverlay’ to protect the circuit.
11. Hot press:
The board with coverlay pass through hot press machine to form adhesion between copper and coverlay.
12. Metal finish:
Coat the bonding area with nickel or gold to protect and keep the terminator’s function.
13. Screen printing:
If there’re needs to print visible information like logos or numbers onto the boards, silk screening will be applied.
14. Test:
Carry out electrical and functional test to detect the defects of finished circuits.
RTR is a new generation of FPC production method.
The main feature of RTR method is that it can complete the whole front process, from drilling to hot press, of all the FPC at the same time.
Therefore, once the RTR method reaches its stable capacity, the production efficiency will have a great enhancement.
Given the advantage of the RTR method, many manufacturers has made investments to equip RTR production line.
We HornmicLink are capable of developing and producing USB-C cables with FPC for you.
By HornmicLink_Henry @230322 21:15