Jong-Woo Shin

T-jet: a novel thermal inkjet printhead with monolithically fabricated nozzle plate on SOI wafer

A novel thermal inkjet printhead with monolithically fabricated nickel nozzle plate on SOI wafer has been proposed for the first time. A chamber and a restrictor are implemented on the 40 /spl mu/m thick top-silicon layer, and a nozzle plate covering heater layers are monolithically fabricated on them. Unlike the general back-shooters, the inkjet printhead reported here is a kind of back-shooter, which has a chamber and a restrictor with arbitrary shape by utilizing the silicon dioxide etch-stop layers in the bottom and sidewalls of chamber. Moreover, nozzle plating mold process, followed by placing the chamber underneath the heater layer, is performed on a planar surface, resulting in more uniform and reliable control of nozzle size. The new design was applied for monochrome inkjet printhead, which has 56 nozzles in 2 columns with real 600NPI(nozzle per inch), and showed good performances such as a drop velocity of 12 m/s, a drop volume of 30 pl, and a maximum firing frequency of 12 kHz for single nozzle ejection. From nozzle by nozzle inspection, we observed the uniformity variation of less than 4% in drop speed as well as drop volume. The monolithic fabrication process resulted in a good uniformity and is expected to have superior manufacturing yield to the nozzle assembly process.

Investigation of reliability problems in thermal inkjet printhead

This paper presents a failure analysis result for enhancing the reliability of thermal inkjet printhead. A novel inkjet printhead is fabricated using MEMS process, and we analyze the failure mechanism of inkjet head based on detailed experimental observations. The design modification of micro heater to avoid an early stage of failure yields the reliability enhancement of printhead.

Failure mechanisms in thermal inkjet printhead analyzed by experiments and numerical simulation

This paper presents a failure analysis result for enhancing the reliability of thermal inkjet printhead. A novel inkjet printhead is fabricated using MEMS process, and we analyze the failure mechanism of inkjet head based on detailed experimental observations and numerical simulations. The failures presented in this work showed three primary factors influencing the failure modes and lifetime of printhead; bubble cavitation damage, thermal fatigue, and electromigration of heater. The design modification of micro heater to avoid an early stage of failure by electromigration yields the reliability enhancement of thermal inkjet printhead.

Firing frequency improvement of back shooting inkjet printhead by thermal management

This paper presents a firing frequency improvement of a backshooter type inkjet printhead, DomeJet, with an optimized thermal design. DomeJet is a thermally driven monolithic inkjet printhead that consists of dome-shaped ink chambers and omega-shaped heaters over the chambers. As the firing frequency increases, the residual heat accumulated in heater layer causes unstable droplet ejection. In a roofshooter architecture printhead, a silicon substrate with a layer of silicon dioxide between the substrate and the heater is an excellent thermal reservoir. Compared to a roofshooter, a backshooter type head has disadvantage in heat release since the heater is confined to a thin film which has low thermal conductivity. In this study, two models are proposed. Model I has an aluminum metal layer over the heater that forms heat passage to the substrate, and Model II has thick nickel nozzle plate in contact with the metal layer to enhance heat dissipation capability. The result gives a head being operated at a frequency of 40 kHz.