| AVS 60th International Symposium and Exhibition | |
| MEMS and NEMS | Tuesday Sessions |
| Session MN-TuP |
| Session: | MEMS and NEMS Poster Session |
| Presenter: | N. Oraon, International Institute of Information Technology, India |
| Authors: | N. Oraon, International Institute of Information Technology, India J.C. Lusth, The University of Alabama S.L. Burkett, The University of Alabama M. Rao, International Institute of Information Technology, India |
| Correspondent: | Click to Email |
Solder based self assembled (SBSA) structures are formed by transforming 2D patterns to 3D structures. SBSA processing involves conventional lithography, metal deposition, and etching methods in addition to dip soldering and solder reflow. The processing involves free metals around a fixed metal, when reflowed; the free metal pattern is rotated towards the fixed metal pattern till the solder reaches minimum surface energy. In previous work, we investigated two types of soldering: face and edge-soldered SBSA structures. The 3D structure produces an excess solder when the amount of the solder deposited is more than the 3D volume. The excess solder which is measured from the top of the metal structure to the top of the solder in face-soldered SBSA structures is known as solder standoff height (SSH). SSH is envisioned as being useful as a solder bump that could be used to stack hybrid layers in 3D integration schemes. Experimentally, SSH was found to be heat resistant. The simulation study we performed reflects the effect of processing parameters such as gap-size between metal patterns, solder thickness, and solder coverage on the formation of 3D structures. Formation of 3D structures is influenced by the tilt of free metal towards the fixed metal. Hence tilt angle is considered as one of the output parameters. The processing parameters are analyzed for truncated square pyramid (TSP) and open cube (OC) structures using an open source simulation tool, Surface Evolver.
Surface Evolver is an interactive program for the study of surfaces shaped by surface tension. Simulation results show that as the gap size decreases, the minimum solder energy is attained at lower tilt angles for face-soldered TSP and OC structures. Edge-soldered OC structures follow a similar trend. The tilt angle remains constant for a range of gap sizes for edge-soldered TSP structures. Varying solder thickness varies the minimum energy tilt angle for face-soldered structures. For edge-soldered structures, tilt angle remains constant irrespective of solder thickness. Optimum tilt angle remains constant for solder coverage of 70 % and higher in both TSP and OC structures.