PCB - Flex-pcb

Baselectron produces single and double layer flex-pcb for various applications
Material to produce them is polyimide (for example Dupont kapton)
In Flex-pcb, solder mask is usually substituted from a coverlay (polyimide sheet) but it is also possible to use common solder mask (green, white, black, blue, red or yellow)

Note:
The printed circuits are also called differently depending on their characteristics, for example:

Single sided
Monolayer and Single side are different ways to identify a printed circuit with a single side or with a single layer of tracks.

Double sided
Double side and bilayer there are different ways to identify a printed circuit with dual sides or with the tracks on both surfaces.

Multilayer
Multilayer MLB are the names that are used to identify multilayer printed circuits with additional layers of internal tracks.

Solder
Solder resist or solder mask is what is called the usually green protective layer that limits the welding to only the pads and also leaves the comb connectors and mechanical contacts uncovered, it is often shortened to solder.