Flexible Printed Circuit Board, often called FPC, is a kind of circuit board with high reliability and good flexibility using polyimide as the substrate. It has the features of lightness, thinness,softness,and flexibility.
In order to facilitate the subsequent soldering and overall assembly, we sometimes need to intensify some certain areas of the flex PCBs, to reduce the flexibility and give the board enough support to stand the components during assembly. The common method of strengthening a FPC is to add a stiffener, a kind of hard material applied for the intensified area; Apart from supporting components, Stiffeners can also play a role in heat dissipation, and some stiffeners with special design can be used as assembly helpers as well.
One thing needs to be mentioned is that:stiffener provides mechanical function for the flexible area and is not part of the electrical schematic of the design.
When the stiffener is used to create a localized rigid area in the flex circuit where components are installed, the stiffener material can be chosen based on the design and final product demand(quality, heat dissipation,cost,flexibility,etc). The typical FPC stiffener material can be stainless steel,PI,and FR4，and there’re also a variety of thicknesses available for options.
Stiffener adhesive:
The adhesives used for laminating the FPC substrate can also be used as stiffener adhesives.Besides,pressure sensitive adhesive(PSA) is one of most used adhesive as well.To decide which adhesive to be used is based on the specific demand.