Corrosion resistant thermal ink jet print cartridge and method of manufacturing same

Abstract

A thin film structure is fabricated using photolithographic techniques and includes a plurality of substrates defining a resistor film, a conductor film and a passivation layer. The resistor film is etched to provide a plurality of individual heaters. The conductor film is etched to provide a plurality of conductive traces. At least one passivation layer covers the conductor film. A plurality of electrical contact pads are also formed that extend through etched holes in the passivation layer so that the electrical contact pads make electrical contact with the conductive traces. A nozzle plate is attached to the thin film structure. The nozzle plate has a plurality of individual nozzle orifices and also defines a plurality of corresponding ejection cavities for receiving ink from an ink reservoir via capillary action. The ejection cavities are each aligned with a corresponding one of the heaters for thermally ejecting ink through the orifices onto an adjacent print medium, The thin film structure and the attached nozzle plate are mounted to a housing that includes the ink reservoir. A mixture of a volatile liquid carrier and at least one corrosion inhibitor is sprayed onto the portion of the thin film structure having the plurality of electrical contact pads. The mixture has a very low surface tension so that the mixture will wick into any minute crevices around the perimeters of the electrical contact pads. The liquid carrier is evaporated by passing the assembled print cartridge through an oven so that the corrosion inhibitor will hermetically seal the crevices. Moisture is thereby prevented from entering the minute crevices and causing corrosion that would otherwise lead to operational failures of the print cartridge.