Low-cost fabrication of printed electronics devices through continuous wave laser-induced forward transfer

Laser induced forward transfer (LIFT) is a direct-writing technique that allows printing inks from a liquid film in a similar way to inkjet printing but with fewer limitations concerning ink viscosity and loading particle size. In this work we prove that liquid inks can be printed through LIFT by using continuous wave (CW) instead of pulsed lasers, which allows a substantial reduction in the cost of the printing system. Through the fabrication of a functional circuit on both rigid and flexible substrates (plastic and paper) we provide a proof-of-concept that demonstrates the versatility of the technique for printed electronics applications

Laser-induced forward transfer for printed electronics applications

Laser-induced forward transfer (LIFT) is a printing technique based on the action of a laser pulse that is focused on a thin film of a precursor ink for getting the transfer of a droplet onto a receiver substrate. The experiments presented in this article aim to demonstrate the ability of LIFT to produce electronic circuits on paper, a substrate that is flexible, cheap and recyclable. Tests were conducted in order to study the printing of conductive tracks with an Ag ink. The printing of a suspension of carbon nanofibers (CNFs) was also studied in order to demonstrate the ability of LIFT for printing inks with particles with some microns in size that provoke inkjet nozzles to clog. As a proof-of-concept of the LIFT possibilities, both inks were used to print entirely by LIFT a functional humidity sensor on a piece of paper. All the LIFT experiments were performed with a Nd:YAG laser that delivers pulses of a few hundreds of ns in an attempt to approach the technique to laser systems that are already introduced in many production lines for marking and labeling

Development and optimization of inkjet printing based technologies for hybrid printed circuit boards

[eng] The main goal of this doctoral thesis is the development and optimization of inkjet- based technologies for hybrid electronic circuits manufacturing, as well contribute on the development of the incoming low cost electronics. Regarding that, a novel solution for connecting regular SMDs and standard silicon SMD packages by inkjet printing is proposed. The novel connecting method allows the assembling at very low temperatures, and thus assures the compatibility with the incoming substrates. Electrical contact resistance and shear strength measurements performed by silver nanoparticle- based ink are comparable to benchmark connecting materials. In sum up, flexible hybrid circuit is successfully manufactured by silver nanoparticle-based ink on paper, where different SMDs size-shaped are assembled demonstrating the reliability and feasibility of the proposed method. Another objective of the work is to apply and adapt the print-on-slope technique to assemble directly the silicon dies on PCB, proposing a novel strategy to overcome the drawbacks of the wire bonding in the Conductive AFM measurements. Then, a novel setup for conductive AFM mode 2D materials characterization was manufactured. The 2D connection on ramp-shape terminations gives a better functionality than current wire bonding connections. The AFM tip moves over the silicon die without physical obstruction, giving a unique solution at this novel method to characterize the material degradation. In the field of multilayer hybrid PCB manufacturing, the goal is to prove the potentiality of different metal-insulator-metal structures inkjet-printed and evaluate their reliability and the electrical performance for low cost multilayer circuit based on paper substrate. In the light of the results, heterogeneous structures combining inorganic and organic dielectric material, where PVP fills the inorganic cracks and voids, possess a similar and outstanding feasibility in both paper and glass substrate without short-circuits. The greatest achievement of this work is the development and optimization of a novel capillarity-assisted SMD assembling method for the manufacturing of hybrid circuits inkjet-printed. In addition, taking advantage of print-on-slope technique, direct assembling of silicon die integrated circuits to PCB is successfully applied. Moreover, heterogeneous structures inkjet-printed open new solutions for multilayer hybrid circuits.[cat] L’objectiu principal d’aquesta tesi doctoral és el desenvolupament i l’optimització de tecnologies basades en injecció de tinta per a la fabricació de circuits electrònics híbrids, així com contribuir al desenvolupament de l’electrònica de baix cost. Es proposa una nova solució per connectar els dispositius de muntatge superficial (SMDs) mitjançant impressió de tinta amb càrrega de nanopartícules de plata. El nou mètode de soldadura permet fer la connexió a temperatures molt baixes i, per tant, assegura la compatibilitat amb els substrats tèrmicament menys resistents. Les mesures elèctriques de resistència de contacte i les mesures mecàniques de resistència de cisalla obtingudes són comparables a als obtinguts amb materials de connexió convencionals. En definitiva, s’ha aconseguit fabricar circuits hídrids flexibles amb èxit mitjançant tinta basada en nanopartícules de plata sobre paper, on diferents dimensions de SMDs han estat soldats, la qual cosa demostra la fiabilitat i la viabilitat del mètode proposat. Un altre dels objectius del treball és aplicar i adaptar la tècnica d'impressió mitjançant rampes per muntar directament microelectrònica sobre circuits impresos. Mitjançant aquesta tècnica, s’han superat els inconvenients provocats per les unions de fil d’or al realitzar mesures conductives mitjançant AFM. Així, s’ha utilitzat una nova estratègia per a la caracterització de materials 2D mitjançant la tècnica de CAFM. Les connexions 2D proporcionen una millor funcionalitat que les connexions actuals mitjançant fils. De fet, la punta AFM es mou sobre la mostra de silici sense obstrucció física, donant una solució única en aquest mètode per caracteritzar la degradació del material. En el camp de la fabricació de PCB híbrida multicapa, l'objectiu és provar la potencialitat de diferents estructures metall-aïllant-metall impreses mitjançant inkjet i avaluar la seva fiabilitat i les propietats elèctriques per a un circuit multicapa de baix cost basat en substrat de paper. A la vista dels resultats, les estructures heterogènies que combinen material dielèctric inorgànic i orgànic, on el PVP omple les esquerdes i els buits de les capes de material inorgànic, presenten unes bones prestacions elèctriques i tenen una viabilitat similar tant en paper com en substrat de vidre sense curtcircuits. La fita més rellevant d’aquest treball és el desenvolupament i l’optimització d’un nou mètode de soldadura de SMDs mitjançant inkjet i assistit per capil·laritat. Aprofitant la tècnica d'impressió sobre rampes, s’ha aconseguit muntar directament circuits integrats de silici sobre PCBs. A més, les estructures heterogènies impreses per injecció de tinta obren noves solucions per a circuits híbrids multicapa