Inkjet printing is a technique based on the deposition of small drops of liquid on precise locations on a substrate to build a pattern. It is a promising and attractive technique, as it is cost-saving, non-contact, modular and scalable, and a wide variety of materials can be printed with little to no waste. In this work, two polymeric inks have been studied, characterized, and inkjet printed, with the final goal of employing these results to print a vibration damping layer on a Micro-Electro-Mechanical-Systems (MEMS) device. This work demonstrated the possibility of employing diluted solution to print complex patterns on two substrates, namely planar silicon and silicon nitride. The inkjet printing process of the two different inks, a modified acrylate and an acrylated polyurethane, has been studied and characterized. The inks have been tested to optimize jetting, and different waveforms have been tuned to fit the ink properties. The behavior of the ink droplets impinging on the substrate has also been evaluated. Simple squared bumps first, and final MEMS pattern later, have been printed and analyzed by means of cross-sectional profilometry and Atomic Force Microscopy. The typical inkjet challenges have been evidenced in this work, such as poor walls verticality, low layer thickness, pattern broadening, coffee ring effect and lateral ink accumulation. These issues have been addressed throughout the work, and some solutions have been proposed. To address the coffee ring and accumulation issues, a mixed solvent solution has been introduced, which reduced the problem when printing at room temperature. Pattern broadening has been effectively reduced by attempting a step reticulation approach that strongly limited redissolution of already deposited layers, resulting in improved walls verticality and thickness. Both inks have been successfully employed to inkjet print the final MEMS pattern on both substrates without evident differences between the two, implying that no major inhomogeneity problems should arise when printing on the patterned MEMS wafer.
La stampa a getto di inchiostro è una tecnologia basata sulla deposizione di piccole gocce in posizioni precise su di un substrato. La sua peculiarità risiede nell'essere una tecnologia economica, senza contatto, modulare e scalabile, che permette la stampa di una grande varietà di materiali con scarti limitati. In questo studio due inchiostri polimerici sono stati studiati, caratterizzati e stampati a getto, con l’obiettivo finale di utilizzare i risultati ottenuti per stampare un film adatto a smorzare le vibrazioni su un dispositivo MEMS (Micro-Electro-Mechanical-Systems). Durante questo lavoro sono state utilizzate soluzioni diluite per stampare pattern su due substrati, silicio planare e silicio nitruro. Il processo di stampa per i due inchiostri, un acrilato e un poliuretano acrilato, è stato analizzato, gli inchiostri sono stati ottimizzati per il getto e diverse forme d’onda sono state adattate agli inchiostri. Il comportamento delle gocce sui substrati è stato inoltre analizzato. Gli inchiostri sono stati usati inizialmente per la stampa di semplici quadrati, per arrivare al pattern finale in seguito. La relativa analisi è stata eseguita tramite profilometria e microscopia a forza atomica (AFM). Le tipiche problematiche relative alla stampa a getto d’inchiostro sono state evidenziate in questo lavoro, come la scarsa verticalità delle pareti, i bassi spessori, l’allargamento del pattern, l’effetto “coffee ring”, e l’accumulo laterale di inchiostro, e alcune soluzioni sono state proposte. Per il problema di accumulo, è stato proposto l’utilizzo di una soluzione contenente due solventi, la quale ha ridotto questo fenomeno durante la stampa a temperatura ambiente. L’allargamento del pattern è stato ridotto tramite una reticolazione a step che ha limitato la ridissoluzione degli strati già deposti, migliorando anche la verticalità e lo spessore del film. Entrambi gli inchiostri sono stati usati per stampare il pattern finale sui due substrati senza mostrare evidenti differenze tra i due, implicando la probabile assenza di problematiche legate all’inomogeneità durante la stampa sul MEMS.
Inkjet printing of polymeric inks for pattern manufacturing
Caporaso, Maria Teresa
2020/2021
Abstract
Inkjet printing is a technique based on the deposition of small drops of liquid on precise locations on a substrate to build a pattern. It is a promising and attractive technique, as it is cost-saving, non-contact, modular and scalable, and a wide variety of materials can be printed with little to no waste. In this work, two polymeric inks have been studied, characterized, and inkjet printed, with the final goal of employing these results to print a vibration damping layer on a Micro-Electro-Mechanical-Systems (MEMS) device. This work demonstrated the possibility of employing diluted solution to print complex patterns on two substrates, namely planar silicon and silicon nitride. The inkjet printing process of the two different inks, a modified acrylate and an acrylated polyurethane, has been studied and characterized. The inks have been tested to optimize jetting, and different waveforms have been tuned to fit the ink properties. The behavior of the ink droplets impinging on the substrate has also been evaluated. Simple squared bumps first, and final MEMS pattern later, have been printed and analyzed by means of cross-sectional profilometry and Atomic Force Microscopy. The typical inkjet challenges have been evidenced in this work, such as poor walls verticality, low layer thickness, pattern broadening, coffee ring effect and lateral ink accumulation. These issues have been addressed throughout the work, and some solutions have been proposed. To address the coffee ring and accumulation issues, a mixed solvent solution has been introduced, which reduced the problem when printing at room temperature. Pattern broadening has been effectively reduced by attempting a step reticulation approach that strongly limited redissolution of already deposited layers, resulting in improved walls verticality and thickness. Both inks have been successfully employed to inkjet print the final MEMS pattern on both substrates without evident differences between the two, implying that no major inhomogeneity problems should arise when printing on the patterned MEMS wafer.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/179548