Millimetre-wave pin diodes have been developed for the first time in a flipchip structure, to achieve repeatability in the device features. GaAs flipchip pin diodes were manufactured on a semi-insulating substrate, and bondpads were located on mesas to minimise the parasitic elements. A waveguide switch with two biased diodes has shown, in the 94 GHz window, less than 1 dB of insertion loss, greater than 30 dB of isolation, and a switching time lower than 10 nS.<<ETX>>