Flexible PCB -Flexible Printed Circuits are made of thin dielectric substrate & high ductility metal foil, flexible pcb can be bent or folded and used in static and dynamic applications.
Do you know why the fpc need to add the stiffener?
Flexible-only PCBs can withstand fewer components than rigid-flex. The rigid part of rigid-flex can also be as complex as a traditional rigid Circuit Board. Stiffeners are occasionally laminated the same time as the coverlay.
When we need to add the Stiffeners ?
Components are near or in an active, or dynamic, flex zone
Component size and weight will import stress onto the flex
A large number of SMT pads make planarity critical
Connectors that require repeated insertions or assemblies require a stiffener, or something to help alleviate the stress of pads.
When we don’t suggest to to add the Stiffeners ?
Small “static” components do not exert a large amount of strain on the flexible of the PCB.There are no components in the flex region.
How to choose the FPC stiffener?
As we all know, the Stiffeners are typically made of FR4, PI(Kapton), stainless and alumimum stiffener.Then how we we too choose the right stiffener?
PI is often used when the end of the flex must be thickened and inserted into a ZIF connector. However, the use of Kapton(PI) requires a separate lamination cycle. For golden area, we will be need to add the PI stiffener to meet the total thickness 0.2mm, 0.3mm or 0.5mm.
FR4 stiffener can be done within the same lamination cycle. FR4 stiffener usually added for the USB connector area.
Stainless stiffener is not easy to transformation. And it has the good hardness. And it can play a conductive and inductive role.
Aluminum stiffener has the best heat disspation effect, because it usually need to openning a tooling to cut the alumunum stiffener outline, then the cost is the highest.