The family of laminates under the name FR-4 by the NEMA (National Electrical Manufacturers Association, USA) classification. These are the most common materials for the single sided, double sided and multilayer printed circuit boards with strict requirements for mechanical strength. FR-4 is a composite material based on woven glass-epoxy compounds. As a rule, laminate has a matte yellow color, green color of the PCB gives it a solder mask which is applied to the surface. Flammability rating is UL94-V0.

Depending on the properties and applications, FR-4 laminates are divided into the following subclasses:

standard, with a glass transition temperature T_g of ~ 130°C, with UV blocking or without it. The most common and widely used type, at the same time, the cheapest of FR-4;

with a higher glass transition temperature, T_g ~ 170°C - 180°C, compatible with the lead free reflow technology;

halogen-free, compatible with the lead free reflow technology;