Clarifications of FPC
According to the combination of base material and copper foil, flexible circuit board can be divided into two types: flexible board with adhesive and flexible board without adhesive. The price of non-adhesive flexible PCB is much higher than that of adhesive flexible PCB, but its flexibility, bonding force between copper foil and substrate and flatness of solder are also better than that of adhesive flexible PCB. So it is only used in the high demand situations, such as the: COF (CHIP ON FLEX, flexible board with bare chip, the high flatness of the pad) and so on. Because its price is high, most of the flexible PCBs used in the market are still adhesive flexible circuit board. Because the flexible circuit board is mainly used in the situation where bending is required, if the design or process is not reasonable, it is easy to produce micro-cracks, welding and other defects.
Economy of using FPC
If the circuit design is relatively simple, the total volume is small, and the space is suitable, the traditional internal connection is much cheaper. Flexible circuits are a good design option if the circuit is complex, processes many signals or has special electrical or mechanical requirements. When the size and performance of applications exceed the capacity of rigid circuits, flexible assembly is the most economical. A 12mil pad with a 5mil through hole and a flexible circuit with 3mil lines and spacing can be fabricated on a thin film. Therefore, it is more reliable to mount the chip directly on the film. There is no flame retardant that could be an ion source. These films may be protective and solidified at higher temperatures to obtain higher glass transition temperatures. Flexible materials are less costly than rigid materials because they are free of connectors.
FPC Case: Double Sided Flexible Circuit Board FPC with Immersion Gold
(FPC’s are custom-made products, the picture and parameters shown are just for reference)
General description
This is a type of flexible circuit for the application of Wireless Router. It’s a double sided FPC at 0.3mm thick. The base laminate is using from Shengyi. 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 |
2 |
| Board Type |
Flexible circuits |
| Board Thickness |
0.30mm |
| Board Material |
Polyimide (PI) 25µm |
| Board Material Supplier |
Shengyi |
| Tg Value of Board Material |
60℃ |
| |
| PTH Cu thickness |
≥20 µm |
| Inner Iayer Cu thicknes |
N/A |
| Surface Cu thickness |
35um |
| |
| Coverlay Colour |
Yellow |
| Number of Coverlay |
2 |
| Thickness of Coverlay |
25 µm |
| Stiffener Material |
NO |
| Stiffener Thickness |
N/A |
| |
| Type of Silkscreen Ink |
NO |
| Supplier of Silkscreen |
N/A |
| Color of Silkscreen |
N/A |
| Number of Silkscreen |
N/A |
| |
| Peeling test of Coverlay |
No peelable |
| Legend Adhesion |
3M 90℃ No peeling after Min. 3 times test |
| |
| Surface Finish |
Immersion Gold |
| Thickness of Nickle/Gold |
Au: 0.03µm(Min.); Ni 2-4µm |
| RoHS Required |
Yes |
| Famability |
94-V0 |
| |
| 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
Controllability of electrical parameter design
The end can be whole soldered
Material optionality
Low cost
Continuity of processing
Diversified shipping method
Engineering design prevents problems from occurring in pre production.
Application
Laser head FPC, medical equipment controller, Tablet antenna soft board
Quality Policy
Bicheng has developed series of management procedures and approaches to assure that PCBs are in compliance with the customers' requirements, inclusive of selection of the vendors, work in progress (WIP) inspection, outgoing delivery inspection and customer service etc.
Evaluation and Audit of Suppliers
Suppliers have to be evaluated by Bicheng. In addition, Bicheng will appraise and rank suppliers every year to guarantee the materials supplied are meeting Bicheng’s requirements. Furthermore, Bicheng continuously develop suppliers and supervise them to improve their quality and environment management basing on the systems of ISO9001 & ISO14001.
Contract Evaluation
Bicheng shall review and verify customer's requirements to make sure that we have the capability to satisfy customers' requirements including specifications, delivery and other demands prior to accepting an order.
Making, audit and control of manufacturing data.
When customers' design data and specifications are provided to our market department, Bicheng has to verify all the requirements. Then, convert the design data into manufacturing data by CAM. Finally, a manufacturing instruction (MI) is generated according to the real manufacturing process and technologies for manufacturing department as the basis for actual fabrication. MI must be reviewed by independent engineers and QA engineers before issue.
Incoming Material Quality Control
All materials have to be inspected before warehousing. We established a series of strict inspection procedure and instruction to control the incoming materials. Furthermore, various precise inspecting instruments and apparatus guarantee the capability to judge the material good or not. We issue material with first in first out principle, and give out “alarm” for the material that will reach the shelf life to ensure the materials are used up before expiry.
Control of Production Process
Right manufacturing instruction (MI), comprehensive equipment management and maintenance and process control, strict WIP inspection and monitoring as well as working instruction, all those make the whole fabrication process totally controlled.
Final Control and Inspection
All PCBs have to be gone through the open and short test as well as visual inspection after passed the specified physical tests. We own various advanced test equipment including customized, probe flying test machines to guarantee that each PCB is 100% tested.
Product Delivery Audit
We set up a dedicated FQA department to inspect the PCB products according to the customer's specifications and requirements by sampling. Qualified PCBs are going to be packed.
FQA also has to carry out a 100% audit of the warehouse packing and shipping products, including product number, customer number, product quantity, shipping address and so on prior to shipment.
Customer Service
We sets up a professional customer service team to proactively communicate with customers and timely deal with the customers' feedbacks. We highly focus on customers' needs and to understand customers’ demands, timely to adjust the policy of customer service and PCB product requirements.
