FPC-PCB Circuit Boards: Flexible in Spatial Layout, Leading the New Trend of Circuits

FPC is a kind of flexible circuit board with high circuit density, light weight, thin thickness and excellent bending performance.

FPC is made from flexible raw materials such as polyimide (PI) or polyethylene terephthalate (PET).  It can be freely bent, wound and folded, can withstand millions of dynamic bends without damaging the conductors, can be arranged arbitrarily according to the requirements of spatial layout, and can move and expand freely in three-dimensional space, thus realizing the integration of PCB assembly and conductor connection.  

FPC also has the advantages of good heat dissipation, good solderability, easy assembly and low overall cost.  It is widely used in fields or products such as aerospace, medical equipment, mobile communications, notebook computers, computer peripheral equipment, PDAs, automotive electronics and so on.

I. What are the differences between PCB and FPC?

1. PCBs are made through printing technology, so they are called Printed Circuit Boards. FPCs are also made by printing, so FPCs are also Printed Circuit Boards. Printed Circuit Boards include rigid PCBs and flexible PCBs. However, we are accustomed to referring to rigid PCBs as PCBs and flexible PCBs as FPCs or FPCBs.

2. The space utilization rates are different. The common space expansion solutions for PCBs are to use slots and interface cards. As long as FPCs adopt the transfer pipeline design, similar structures can be made, and they have greater flexibility in terms of direction design.

3. The two have different characteristics. FPCs usually use PI (Polyimide) or PET (Polyethylene Terephthalate) as the base substrates and can be freely bent or flexed. PCBs are usually made of FR4, ceramics, Teflon and metals and cannot be bent or flexed.

4. The two have different uses. FPCs are used for connections that require repeated bending and some small components. PCBs are usually used in places where bending is not required and relatively high hardness is needed.

II. How to Manufacture Flexible PCBs?

1. Manufacturing Technology for Double-Layer Flexible PCBs

Cutting - Drilling - PTH (Plated Through Hole) - Electroplating - Pretreatment - Dry Film Lamination - Alignment - Exposure - Development - Pattern Electroplating - Film Removal - Pretreatment - Dry Film Lamination - Alignment and Exposure - Development - Etching - Film Removal - Surface Treatment - Coverlay Lamination - Pressing - Curing - Nickel Deposition - Legend Printing - Cutting - Electrical Measurement - Punching - Final Inspection - Packaging - Shipping.

2. Manufacturing Technology for Single-Layer Flexible PCBs

Cutting - Drilling - Dry Film Lamination - Alignment - Exposure - Development - Etching - Stripping - Surface Treatment - Coverlay Lamination - Pressing - Curing - Surface Treatment and Nickel/Gold Deposition - Legend Printing - Shearing - Electrical Measurement - Punching - Final Inspection - Packaging - Shipping.  

III. Two Key Issues in Manufacturing Flexible PCBs

1. How to Solder FPC onto PCB?

Soldering a flexible PCB requires the use of FPC connectors to connect with the PCB. As a result, rigid - flexible PCBs or rigid - flexible combined PCBs come into being. This can save the cost of soldering FPCs to PCBs and FPC connectors, and also has better space utilization and more stable performance.

Sometimes, for soldering FPCs, because they are too soft, we need to design a reinforcement for them. FPC reinforcements are usually made of Altium flexible PCBs.

2. How to Clean Flexible PCBs?

The ion - cleaning flexible PCB machine can solve the problems of poor hydrophilicity and poor copper - plating adhesion of FPCs. The poor hydrophilicity of the flexible PCB material PI is the fundamental cause that affects the reliability of copper plating. The surface treatment of the PI substrate by the plasma - cleaning machine can effectively improve the hydrophilicity of PI.