Direct-Write Process for UV-Curable Epoxy Materials by Inkjet Technology
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Direct-Write Process for UV-Curable Epoxy Materials by Inkjet Technology W. Voit a,b, K.V. Rao b and W. Zapka a XaarJet AB, SE-175 26 Järfälla, Sweden b Engineering Materials Physics Division, Royal Institute of Technology (KTH), SE-100 44 Stockholm, Sweden
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ABSTRACT We demonstrate drop-on-demand inkjet printing technique to be a high throughput method for the patterned deposition of UV-curable epoxy materials. Different multi-nozzle printheads have been used to produce epoxy droplets with controlled volume in the range from 15 to 180 pl, and to apply the droplets with high placement accuracy. For a large dot grid pattern, which was printed by addressing 126 individual ink channels, standard deviations of σx = 2.3 µm and σy = 2.6 µm have been achieved for the error in dot placement. The deposited epoxy dots were found to form planar convex lenses with a focal length of 142 µm. In addition, we have successfully printed magnetic nanoparticles in a carrier fluid with the drop-on-demand printheads, as a step towards the production of composites. INTRODUCTION The ability of inkjet techniques to deposit a large variety of different materials, including polymers, material-precursors or dispersions of nanoparticles in fluidic media, makes it a highly flexible process for direct-write applications. The inkjet process is an additive non-contact method, and can be applied even on surfaces with pronounced topography. In particular multi-nozzle drop-on-demand inkjet printheads enable the deposition of patterned layers at a rate of several tens of cm2 per second. The versatility of this technique has been demonstrated for the production of different structures and devices in ceramic, electronic and MEMS applications [1-3]. Epoxy materials have been deposited before for applications in MEMS packaging and optics, but by using inkjet devices that are based on a single channel actuation [4]. We have recently reported the dispensing of epoxy materials for bonding applications using a multi-nozzle piezoelectric inkjet printhead [5]. In this paper we describe the dot diameters achievable for epoxy materials with the present day inkjet printing capabilities, their placement accuracy and their surface profiles. In addition, we present attempts to print geometric patterns with magnetic inks, indicating the potential of drop-on-demand inkjet printing for future applications in micro-manufacturing, specifically the printing of nanosized solid particles of ceramic, electrically conductive or magnetic materials for the production of complex hybrid devices. EXPERIMENTAL DETAILS OF THE INKJET DEPOSITION METHOD Piezoelectric drop-on-demand inkjet printheads from Xaar have been used in the experimental work presented herein to deposit epoxy materials onto different substrates. The mode of operation of these printheads is based on the generation of an acoustic wave within a small actuator channel due to an appropriate movement of the channel walls. This acoustic wave
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creates the ejection of a single ink droplet through a well
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