Printed circuit boards are generally made with one of two materials (there are others), either a paper epoxy (FR-3) or a fiberglass epoxy (FR-4). There are others, but these are most common.
Paper epoxy (FR-3) has a lower temperature tolerance, is not as mechanically stable, can be burnt easily, and is constructed of paper and epoxy holding it together. You see it in a lot of commercial (expensive or not...) equipment. It is mostly brown...
Hello-- Older imported electronics used a phenolic-based laminate-- typically medium to dark brown and liable to losing its traces when the repairer applied too much heat. Oh, and when overheated it smelled like warm horse s*it.
