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|Attaching Small Devices Using Aerosol Jet Deposition|
|Keywords: Aerosol Jet, surface mount devices, die attach|
|Attaching Small Devices Using Aerosol Jet Deposition Kurt Christenson,* David Sessoms and Mike Renn Optomec, St. Paul, Minnesota, USA The trend towards smaller devices is challenging the limits of current die-attach technology. The pads on a 01005 passive package (400 x 200 um) are typically 100 by 160 um and are spaced 200 um apart. Aerosol Jet® technology has the capability of printing such small patterns with the required resolution and placement accuracy. In Aerosol Jet processing, an ink is atomized to form a mist of approximately 3 um diameter droplets, which are aerodynamically focused on to a substrate forming features with minimum dimensions of approximately 10 um. The deposition tip has a stand-off distance of approximately three millimeters and is well suited to deposition on fully 3D parts. Conductive traces or contact pads can be formed with nanoparticle or microflake metal inks. Silver is typically used due to its high electrical conductivity and lack of an insulating oxide. Ten-nanometer scale nanoparticles of silver sinter in the range of 100-200° C, allowing the formation of conductors on low-temperature substrates. Flake-based inks typically contain a polymer that crosslinks in the same temperature range. The polymer shrinks on curing, holding the flakes in contact and providing adhesion to the substrate. Beyond component attach, deposited conductors are typically used to form conductive traces, bond pads and antennas. Dielectrics can be deposited to form crossovers in complex wiring patterns or as an overcoat to protect the traces. Adhesives can be deposited for attaching components and UV-cure polymers can be used to form micro-mechanical structures. This work describes the results of using the Aerosol Jet process to deposit a flake-based conductive ink to attach small passive and active components. The results include visual analysis of the attached parts along with those of shear strength and electrical conductivity testing of the bonds. Substrates include glass (for visual analysis), copper PCBs, gold, and Aerosol-Jet printed patterns on ceramics. Results indicate that Aerosol-Jet deposited wiring, contact pads, and component attach can satisfy mil-spec requirements for as-manufactured performance. Environmental and life time testing are planned and initial results will be presented. *Corresponding author: kchristenson (at) Optomec.com|
|Kurt Christenson, Senior Scientist
St. Paul, MN