These IGBT's would be mounted on a water cooled copper plate.
Reference: RWMA - Resistance Welding Manual 4th Edition
IGBT’S are the switching devices in inverter controls. They handle large amounts of power during resistance welding and can heat up. Yes, they must be cooled. They are normally mounted on a water cooled plate to remove the heat. IGBT's are indirectly cooled with this mounting system.