Abstract: There is disclosed a light-emitting device assembly use in a large-sized printhead. The assembly includes a number of insulating substrates including first and second substrates. A conducting layer is formed on each substrate. A conductive adhesive layer is formed on the conducting layer. The conducting layer on the first substrate extends close to the abutting end of this substrate. The conducting layer on the second substrate is set back a first distance from the abutting end of the second substrate. Light-emitting devices are disposed in the vicinity of the abutting end of the conducting layer on the second substrate. Light-emitting devices on the first substrate are made to protrude a second distance greater than the first distance from the abutting end of the first substrate. The light-emitting array protruding from the first substrate is made to bear against the light-emitting device array set back from the abutting end of the second substrate.