Flexible PCB introduction to products

The FPCB is also called the flexible printed circuit board, forming a flex pcb and rigid pcb material qualities of contrast, in today's electronic products design, has become quite common mixed use of felx and rigid interoperability of elasticity, from the Angle of the materials, process and key components are discussed, at the same time show that fpcb board use restrictions.

Material characteristics of flexible pcb 

Flexible pcb features in addition to the material is soft, there are light weight, the configuration is very thin/light structure, materials by repeated bending can not appear hard PCB insulation material fracture condition, soft plastic and flex board base material and wire laying, let soft board cannot respond to high current flow, voltage, and so on used in high power electronic circuits can hardly see flex pcb board design, but rather in the small current, low power, consumer electronics, soft plate usage is quite large.

Because flex pcb cost is still the key materials of PI, unit cost is higher, so in the product design, not usually used in flex pcb as the main carrier, but locally applied need on the key design of "flexible" features, such as digital camera's electronic flex board application of the zoom lens, or drive a read flex materials of electronic circuit, are in electronic components or functional module must run, rigid circuit board material is unsalvageable, a design instance of flex circuit board, it is now being used in Consumer electronics, Communication, Medical, Electrical Motor, Electronic Connector etc...   

In addition to the main material characteristics, the structural composition of FPCB substrate is also a key. FPCB is the covering film (upper layer) as the insulation and protection material, and the insulation substrate, calendering copper foil and follow-on agent in it constitute the whole FPCB. FPCB substrate material with insulation characteristics, generally used polyester (PET), polyamide (PI) two materials, PET or PI each has its own advantages/disadvantages.

FPCB is used in many products, but basically only lead lines, printed circuits, connectors and multifunctional integrated systems.According to the function, it can be divided into space design, change its shape, folding, bending design group, and FPCB design can be used to prevent the problem of electrostatic interference of electronic equipment.And the use of soft circuit board, without considering the cost, so that the quality of production directly on the soft board structure, not only the design volume is relatively small, the volume of the overall product can also be greatly reduced due to the characteristics of the plate.

The structure of FPCB substrate is quite simple. It mainly consists of the protective layer on top and the conductor layer in the middle. When mass production is carried out, the soft particle path plate can be matched with the positioning hole for the production process alignment and post-processing.As for the use of FPCB, the shape of the plate can be changed according to the space needs, or the folding form can be used, and as long as the multi-layer structure is designed in the form of anti-EMI and electrostatic barrier, the flexible circuit board can also achieve efficient EMI problem improvement design.

On the key circuit of the circuit board, the top superstructure of FPCB is Copper, including Ra (Rolled Annealed Copper) and Ed (Electro Deposited). The manufacturing cost of Ed Copper is quite low, but the material is easy to fracture or fault.RA (Rolled Annealed Copper) has high production cost, but its softness performance is better. Therefore, most of the flexible circuit boards used in high deflection state are made of RA materials.

As for FPCB to forming, need through the agent will then different layers of Adhesive coating, rolling copper, base material, the use of the general agents (Adhesive), Acrylic (Acrylic), Epoxy resin (Mo Epoxy) two categories is given priority to, the heat resistance of Epoxy resin is lower than the force that press a gram, is mainly used for people's livelihood mainly household goods, and the force that press a gram although the advantages of high heat resistance and high strength then, but its poor electrical insulation, and in the FPCB production structure, the thickness of the thickness of the adhesives total 20 ~ 40 microns (microns).

In the process of FPCB, will first make the copper foil and substrate, truncation processing take again after perforation, electroplating operations, generally in the FPCB hole location in advance, after the completion of photoresist coating processing, coating finish for FPCB exposure imaging procedures, namely in advance will be etched lines for processing, complete exposure imaging processing after solvent etching, etching at this time to a certain degree to conduction line after forming, surface is washed to remove the solvent and then to use adhesive evenly coated with etching at the grass-roots FPCB copper foil surface is successful, then cover attached with processing.

The FPCB has roughly 80% complete, at this time we must also for FPCB join points, such as increase the guide hole welding processing, then carries on the FPCB shape processing, after using the laser cutting specific appearance, for example, if the FPCB for flex and rigid composite plate, or need welded processing and function module, at this time for the secondary processing, or match reinforcement plate processing design, reinforcement and integrated design can be used to improve material performance for highly flexural applications.