A low-loss interface between a mm-wave integrated circuit and a waveguide comprises a surface having a contact location for said integrated circuit and a waveguide location for fixing a waveguide thereon; a transmission line extending along said surface from said contact location to the waveguide location and extending into the waveguide location as a waveguide feed; and a connection bump on a surface of the mm-wave integrated circuit. The mm-wave integrated circuit RFIC is connected to the surface at the contact location through the connection bump, such as to connect a signal output of the RFIC to the transmission line, thereby providing said low loss interface.