From GameWatcher: “Far Cry New Dawn is, unlike its predecessors, a bit of an RPG-lite experience, and with that territory comes the need to farm various materials to craft better weaponry.
Far Cry New Dawn Circuit Boards are one of the most important rare resources, and you need them for virtually any high-end weapon worth a damn. These firearms will be key for your completion of late-game missions, so you’d do well to stock up on Circuit Boards in advance.”
Source: N4G PC Far Cry: New Dawn Circuit Boards – How to Get High-End Weapons