This material type denotes a class of flame resistant and flame retardant composite materials – also called laminates or thermosetting polymers – consisting of epoxy resin and glass fibre fabric.
The acronym FR stands for flame retardant and satisfies the requirements of UL94-V0.
Among others FR-4 is used as non-conductive base material for electric circuit boards, and it is one of the most common materials used in this area of application.
Compared to similar composite materials it has better tracking resistance and lower water absorption.
Another advantage of FR-4 is the good adhesion properties of the material, which ensure that copper circuit path structures applied to the base material last a long time.