Rectifier diode is a kind of device changing AC to DC and has anode and cathode two sides, widely applicable in fields of high power drive, high power rectifiers, non-conotrollable and half-controllable rectifiers. The disc type rectifier diode is characterized by high mean current, low forward voltage drop and double-side cooling, matching with various air-cooling or water-cooling radiators. At present, the high power diode is up to 10000A and voltage can reach 8500V. The stud type, hermetic metal cases with glass and ceramic insulators, is a kind of device changing AC to DC and has anode and cathode two sides, widely applicable in fields of battery chargers, converters, power supplies, welding machines & motor controls etc. The stud type rectifier diodes are mainly improved from I.R & Semikron and apart from them, the Russian-style diodes, avalanche diodes are developed successfully,too. The metal stud structure and ceramic-metal stud structure both are available and characterized by high surge current capability. Its current is up to 500A.