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3D integration results from the ever demanding trend towards smaller and lower -profile , lighter and lower cost packaged devices requires further package miniaturization . With the present System -on -chip (SOC ) technology reaching its limitation in terms of functionality and cost , effort are being concentrated on exploring the third dimension , i .e . 3D integration . It provides a volumetric packaging solution for higher integration and performance and results in size and weight reduction . Approaches to achieve 3D integration are die and wafer stacking . A key technology to realize the potential of stacking is implementation of vertical electrical interconnects between die and wafer stacks .
This thesis discusses the approach to form vertical interconnects between wafer stacks through solder reflow . It elaborates the fabrication process for formation of electrical interconnects and wafer bonding using photosensitive Benzocyclobutene (BCB ) . Profiler results of solder reflow are also included . Die level bonding for die stacking is also discussed . Bonding is achieved using a fluxless soldering and electrical interconnections between dies are formed through thermo -compression bonding . Two different solder compositions were used and bonding results are discussed . Furthermore , low frequency and high frequency analysis of interconnects are done to select the correct dimension for interconnects specific to the application . |
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