Synthesis and characterization of bulk nanostructured copper for nano wafer level packaging

Abstract

In the present study, nano size pure copper powder with grain size approximately 48nm and 78nm and micron size copper powder with grain size in nano meter range were uniaxially die compacted at room temperature at pressures ranging from 0.25GPa to 1.00GPa. The selection of pressure range was made based on the ability of Si wafer to withstand the pressure without experiencing mechanical damage and was based on literature search. The cold compacted copper compacts were subsequently sintered at 200a?| C for 2 hours under inert argon atmosphere. The primary objective of this investigation was to optimize the compaction pressure so as to get suitable properties of nanostructured copper for potential application as electronic packaging material. Results of characterization studies revealed that increasing the compaction pressure followed by low temperature sintering can refine the grain size, reduce the porosity and increase the hardness of the resultant compacts. The microhardness obtained was found to be comparatively superior than the one published for samples synthesized using inert gas deposition coupled with in-situ compaction, solution phase synthesis and plasma pressure compaction. Particular emphasis was placed to correlate the effect of variation in compaction load/pressure with the microstructual evolution and mechanical characteristics of the sintered samples.