Like any other SEMI standards, SEMI F47 is not a legal requirement, but required by most semiconductor manufacturers such as Intel, TI, IBM, Samsung etc. around the world. Every new semiconductor manufacturing tool that enters a SEMI Fab has to comply with the SEMI F47 Voltage Sag requirements. It is used both for semiconductor equipment, and for components and subsystems within semiconductor equipment. Enforcement is entirely customer-driven; the procurement agents of semiconductor equipment know the economic consequences of sag-induced failures, and generally refuse to pay for new equipment that fails the SEMI F47 immunity requirement. More and more tool manufacturers require the same from their component suppliers (power supplies, vacuum pumps, HF generators etc.). SEMI F47 Testing and Certification is usually an essential part of any tool purchase specification.