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PCB Stiffeners For Flexible Circuit Board (FPC)

Flexible circuit boards are a popular printed circuit board. Flexible PCBs allow you to assemble product circuits when the design of some products does not allow rigid PCB boards. Therefore, they are invaluable for many electronic applications.

FPC may be too flexible and may not stiffen where stiffness is required. We created PCB stiffeners for these situations. In terms of flexible circuits, stiffeners are a common and important requirement in many designs. They provide mechanical functionality to the flexible area rather than part of the electrical requirements of the entire part.

Demand for flexible PCBs is increasing in all business sectors due to particularly strong demand in the medical, military and industrial markets. Because these components are typically very small, we can be used with a variety of high-mix, low-capacity flexible PCB orders to meet technical and volume requirements. We have a very strong team to support the different volume needs of different industries.

Flexible PCB stiffener requirements fall in the following usage categories:

(source from https://www.epectec.com/flex/flex-circuit-stiffeners.html)

Component / Connector Stiffeners
Creates a localized rigid area where components / connectors are attached.
Protects solder joints by preventing bending of the flex in component area.

fpc stiffeners

ZIF Stiffeners
Localized thickness increase at contact fingers to meet specific ZIF connector specifications.

flexible pcb stiffeners

Localized Bend Constraints
Restrict bend area(s) to specific location(s) in a flex design to either facilitate final assembly, achieve specific bend requirement(s) or other end use requirement.

Stiffener Materials for Flexible PCB

The stiffener is usually made of FR-4 or Kapton.

The most common material used for stiffeners in flexible PCB designs is FR4, ranging in thickness from 0.008" to 0.059". The most common thickness is 0.020", 0.031", 0.039" or 0.059". The general rule is to use the thickest ribs, designed to allow a maximum of 0.059", which replicates the traditional rigid printed circuit board.

Kapton or Polyimide is used to increase the thickness of the ZIF connector contact fingers and provide support for them. It allows for tight tolerances in bending thickness and component contours at the contacts, depending on the connector specifications. Typically, in the finger area, the bend thickness tolerance is +/- 0.002" and the profile width is +/- 0.003". Polyimide is also used to limit the bending ability of specific areas to facilitate installation in final assembly, to enhance mounting hole locations, and to provide additional wear resistance in the presence of wear problems.

Additional Stiffener Materials

In some flexible circuit designs, alternative materials such as stainless steel or aluminum can be used. These are typically used for applications that require heat dissipation or increased stiffness, but can significantly increase the cost of the part and should only be used when needed.

PCB Stiffeners Usages
* Strengthen any specific area of the board of directors.
* Maintain proper thickness in the flexible circuit.
* Support for PCB components and connectors.
* Restrict flexible parts to the area they should be.
* In order to better handle thin boards.
* Keep certain areas of the flexible circuit flat and stable.
* Meet the ZIF connector specifications.
* Increase the bending radius of the circuit at the intersection of the rigid and curved portions. This will avoid stress on the flexible part during multiple bending operations.
* Connectors that require repeated insertion or assembly require stiffeners or help to relieve pad pressure.
* Component size and weight will introduce stress into the curved part

Basically, when you need a rigid area in a flexible circuit, you can use stiffeners, perhaps to protect the components or connectors that are connected there. This does not bend the circuit and protect the integrity of the solder joints.

If you don't know how the PCB reinforced board works for your flexible board, or if you can use the PCB reinforced board in a variety of ways, JY engineer will be happy to discuss it with you. Our experts can detail the rib itself and discuss alternatives for flexible boards that use ribs effectively.


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