Investigation of ink-jet printing of self-assembled monolayers for copper circuit patterning

The aim of this study is to investigate the feasibility of depositing a self-assembled monolayer (SAM) coating using ink-jet printing, which can subsequently be used to pattern copper tracks on a printed circuit board (PCB). Such a technique could allow the rapid modification of interconnection layouts using computer aided design, and so aid prototype production and the manufacture of low-medium volume products. The study describes the adaptation of an existing solution based method for SAM formation on copper, to an ink-jet printing process. The challenges posed by the formulation of an ink possessing specific fluid properties, and the need to control the substrate wettability are discussed. Subsequently, using micro-liter scale droplet trials, the ability of deposited SAM layers to act as plating/etching resists is investigated. In addition, a novel patterning strategy is demonstrated, utilizing the ability of SAM modified regions to locally enhance solder wetting. Finally, the ink jet printing of an alkanethiol solution is demonstrated using a commercial print-head achieving 50 mum feature sizes.