Development of bulk nanostructured copper with superior hardness for use as an interconnect material in electronic packaging

Abstract

In this study, nano size pure copper powders (particle size: 78-nm) were compacted in a die, in a uniaxial direction, at room temperature at pressures ranging from 0.25 GPa to 1.00 GPa. The selection of pressure range was based on an ability of silicon (Si) wafer to withstand the pressure without experiencing mechanical damage. The cold compacted copper compacts were then sintered at 200°C for 2 hours in an atmosphere of argon. The primary purpose of the study was to optimize the compaction pressure so as to get a suitable combination of properties for the nanostructured copper for application as electronic packaging material. Results of characterization studies revealed that cold compaction followed by low temperature sintering exerted a profound influence on grain size, porosity and hardness of the consolidated compact. The microhardness of the consolidated compact was found to be superior than the hardness of samples synthesized using techniques of inert gas deposition coupled with in-situ compaction, solution phase synthesis and plasma pressure compaction. The influence of variation in compaction pressure on microstructural development and mechanical properties (hardness) of the sintered samples is presented and discussed.