Next-generation Packaging Enabled by an Engineered Copper Nanomaterial

Abstract

Current and next-generation high power devices require a new set of materials with higher electrical and thermal conductivity to efficiently spread and remove increased waste heat. Kuprion's ActiveCopper technology enables the formation of bulk copper joints at typical soldering temperatures, yet the resulting interconnects are stable up to 500°C or more. This technology has been developed for a number of applications including die attach, thermal vias, and a replacement for WCu heat spreaders. Die attach materials can be dispensed, screened, or stenciled like traditional solder pastes followed by a solder-like thermal profile in a reflow oven under an inert atmosphere. Sintering can be achieved with or without pressure. Thermal vias are generated by stenciling an ActiveCopper paste directly into open circuit board cavities up to 4 mm in diameter followed by hot pressing under conditions similar to those used for traditional PCB manufacture. The resulting copper vias have thermal conductivity up to 330 W/mK, are solder compatible with or without further surface finish, and show excellent bonding to electroplated copper on the via sidewalls. Near net shape heat spreaders akin to WCu or AlSiC can also be generated via hot pressing or injection molding. The CTE of vias and spreaders can be tuned by adjusting the formulation of the original paste. ActiveCopper technology enables the design of all-Copper systems that can handle the increased thermal demands of next-generation electronics while avoiding failure modes attributed to intermetallic formation. Copper also presents an advantage over silver-based systems which show increased migration, dendritic growth, and voiding under higher thermal and electrical loads.