Conductivity improvement of microstructures made by nano-size-silver filled formulations

The most important problems connected with R&D work for microelectronic industry are miniaturization all electronic devices and ready equipment. This trend has no other options especially on the telecommunication, computers, advanced microelectronics and military fields. Those current trends are giving quite new requirements for all R&D teams, especially those, which are creating new technology, new materials and production methods. Right now is generally well known that Ink-Jet technology offers very new possibilities for production much better packaging circuits. Also is clear that for this purpose is a wide selection of several type materials with different functions (conductance, resistance, etc.). Of course Ink Jet method creates many new requirements not only for technology and production equipment, but mostly for materials which will be used. As example dispensing speed is as high as up to 2000 dots/sec, and such dispensing parameters create quite strong limitations connected with properties of dispensed medium - especially viscosity which should be less than 60 mPas. During each "shoot" very high acceleration is created up to 105 g. Within a few microseconds drop velocity variation up to 10 m/s occurs. This phenomenon requires the highest uniformity for dispensed medium. The Ink-Jet technology is used year by year wider for microelectronic packaging [1,2] and areas for printing very low pitch matrix (e.g. very fine pitch paths, antennas) seem to be extremely attractive. But there are special demands for ink-jet printing materials. The most important, as we've mentioned, is very low viscosity value and especially highly homogenous structure (like molecular fluid parameters) to avoid sedimentation and separation during dispensing process. Additionally, for electrical conductivity of printed structure, the liquid has to contain a number of percentage conductive filler with nano-sized dimension to avoid the printing nozzle blocking. The nano-size silver seems to be one of the best candidates for this purpose, especially when it's particle size dimensions will be less than 10 nm. It is important to remember, that silver atom size has diameter 0.28 nm, so such a small filler particle is comparable with size of binder fluid molecule. This is classical situation when formula will has stable properties.