A fabrication method achieves bump bonds (to connect two electronic devices) with a pitch of less than 20 μm using UV-curable conductive epoxy resin cured with an array of nano-LEDs. Nano-LEDs are devices with sizes less than or equal to 5 μm, typically arranged in an array. After deposition of the uncured conductive epoxy layer, the nano-LED array enables a fast curing of the bumps with high spatial resolution. Next, the uncured resin is washed off and the chips are assembled, before final thermal curing takes place.