Situ tailoring of material properties in 3D printed electronics

#This invention relates to the field of additive printing.

#There is a growing need for advanced metallization techniques for 3D interconnects in through silicon via (TSV) and 3D integration in integrated circuit (IC) packaging. There is also a demand for printing conductive patterns including printed circuit boards, interconnects, bumps in a range of substrates with varying glass transition temperature and outgassing properties.

#Flexible electronics, displays and wearable monitoring technologies require printing of conducting materials including conducting organics and/or metal coatings and interconnects on flexible and non-traditional substrates like plastics, cellulose, polymers, textiles where the conventional techniques for metallization are difficult to apply

#FIG. 1A shows the schematic of the plasma jet printer system with provisions for the addition of various process gases to tailor the material properties of the nanoparticle/microparticle in the plasma jet printer. Various process gases including helium, argon, hydrogen, nitrogen, carbon dioxide, oxygen, methane, alkane, alkene, silane, carbon tetra fluoride, sulfur hexafluoride, etc., can be used on their own or with appropriate mixture to suit various requirements.

#FIG. 1B shows the schematic of an alternate embodiment of the invention with provisions for the addition of various process gases to tailor the material properties of the nanoparticle/microparticle in the plasma jet printer. Various process gases including helium, argon, hydrogen, nitrogen, carbon dioxide, oxygen, methane, alkane, alkene, silane, carbon tetra fluoride, sulfur hexafluoride, etc., can be used on their own or with appropriate mixture to suit various requirements.

#FIG. 2 shows through silicon via (TSV) copper fill using plasma processing. Copper filling by conventional physical vapor deposition copper filling results in void as shown in FIG. 2. Plasma jet printed copper fill has the potential to fill the via without any voids as shown in FIG. 3.

#FIG. 1 shows the schematic of the plasma jet printer system with provisions for the addition of various process gases to tailor the material properties of the nanoparticle/microparticle in the plasma jet printer. Various process gases including helium, argon, hydrogen, nitrogen, carbon dioxide, oxygen, methane, alkane, alkene, silane, carbon tetra fluoride, sulfur hexafluoride, etc., can be used on their own or with appropriate mixture to suit the need. Nanoparticle/microparticle colloid input. FIG. 1 shows the following elements: Nanoparticle/microparticle colloid input 1 Gas supply line for in situ processing 2 Gas supply line for in situ processing 3 Manifold for controlling the gas flow to the plasma jet nozzle 4 Plasma jet printer nozzle 5 Nanoparticle/microparticle colloid 6 in the plasma jet printer nozzle prior to exposure to plasma jet with particle size and shape same as the input colloid Nanoparticle/microparticle 7 in the plasma jet with physical, chemical and electronic characteristics controlled by the input gas, applied voltage, nanoparticle/microparticle concentration and plasma process parameters Metal electrodes 8 of the plasma jet connected to high voltage power supply for creating the plasma discharge Nanoparticle/microparticle 9 exiting the plasma jet nozzle with tailored characteristics determined by the plasma process parameters

#The plasma jet printer consists of a tube 10 made of any one or more of the following: silicon, silicon wafer, quartz, glass, ceramic, plastic, machinable ceramic, glass reinforced epoxy, polyimide, polyetheretherketone, fluoropolymer, aluminum, or any other dielectric material. The tube also contains two metal electrodes 8 connected to high voltage power supply for creating a plasma discharge in the plasma jet chamber. The high voltage power supply can be any one of the following AC, DC, radio frequency, pulsed power supply. The nozzle 5, through which the material to be deposited is focused to the substrate, can be part of this tube with one end of the tube being the nozzle for printing and another end for receiving the particle to be coated. Alternatively the nozzle, through which the material to be printed is focused to the substrate, can also be a separate component from the tube and connected to the tube to focus the plasma jet. The nozzle could be replaced without having to change the tube and electrode assembly.

#FIG. 1b shows the schematic of the plasma jet printer system with provision 12 to introduce reactive and/or non reactive gases through an outer nozzle 11 with wherein the material in aerosol meets with the gas from outer nozzle at the exit of the inner nozzle. This will enable surface modification of the material while retaining the bulk properties of the nano materials. Also, the secondary gas supply through the outer nozzle 11 can be used for post treatment without having to use an additional plasma jet printer for treatment. The secondary gas supply through the outer nozzle can also be used to sustain the plasma and for focused printing, while the inner nozzle carries the materials to be printed. This can help in increasing the momentum of the particles to get a highly directional printing.