Lead-Free Electronic Solders for Severe Service Conditions

Electronic solder joints present in modern microelectronics encounter several severe simultaneous fields during service. Severe fluctuations in temperatures causing thermomechanical fatigue, high current density causing electromigration, and mechanical stresses, encountered during service significantly affect the reliability of the electronic interconnects. In addition to their individual influences, synergistic interactions between them play significant roles. In tin based electronics, whisker growth and tin-pest resulting from phase transformation are also becoming long-term reliability concerns. Current focus of the project is to develop a fundamental understanding of these issues by carrying out detailed studies on microstructural evolution and its influence on the life of the electronic solder joints. The main aim of the project is to develop suitable models for reliability predictions, and arrive at appropriate solutions to combat such problems.

Polymer Composites with Low CTE Particulate Fillers

Significant thermal stresses due to coefficient of thermal expansion (CTE) mismatch develop between the electronic components and the polymeric substrates used in microelectronic circuit boards. In order to improve the reliability of the microelectronic products it is essential to reduce the CTE of the polymeric circuit boards. Role of low and negative CTE particulate reinforcements on reducing the CTE of epoxy matrices is being studied.

Reviewed Journal Publications

Lee, A.; Subramanian, K. N. "Development of Nano-Composite Lead-Free Electronic Solders," of Electronic Materials, 34 (11) 1399-1407 (2005).

Subramanian, K. N. "A Parametric Approach for Assessment of Thermomechanical Fatigue Performance of Sn-based Solder Joints," Journal of Electronic Materials 34 (10), 1313-1317, (2005).

Guo, F.; Lee, J. G.; Hogan, T. P.; Subramanian, K. N. "Electrical Conductivity Changes in Bulk Sn, and Eutectic Sn-Ag in Bulk and in Joints, from Aging and Thermal Shock," Journal of Materials Research 20(2), 364-374, (2005).

Rhee, H.; Subramanian, K. N.; Lee, A. "Role of Imposed Cyclic Straining on the Stress Relaxation Behavior of Eutectic Sn-3.5Ag Solder Joints," Journal of Materials Science: Materials in Electronics 16, 169-176, (2005).

Lee, J. G.; Subramanian, K. N. "Microstructural Features Contributing to Enhanced Behavior of Sn-Ag Based Solder Joints," Soldering and Surface Mount Technology 17(1), 33-39, (2005).

Sonje, P.U.; Subramanian, K.N.; Lee. A. "Characterization of Polymeric Composites with Low CTE Ceramic Particulate Filler," J. of Adv. Materials 36, 22, (2004).

Guo, F.; Lee, J.; Subramanian, K. N. "Solders Strengthened with Nickel Particles - an Overview," Advanced Materials and Processes, 162 (8), 81-81, (2004).

Subramanian, K. N.; Lee, J. G. "Effect of Anisotropy of Tin on Thermomechanical Behavior of Solder Joints," Journal of Materials Science: Materials in Electronics, 15, 235-240, (2004).

Telang, A. U.; Bieler, T. R.; Lucas, J. P.; Suburamanian, K. N.; Lehman, L. P.; Xing, Y.; Cotts, E. J. "Grain-boundary Character and Grain Growth in Bulk Tin and Bulk Lead-Free Solder Alloys," Journal of Electronic Materials 33 (12), 1412-1423, (2004).

Telang, A.U.; Bieler, T.R.; Lucas, J.P.; Subramanian, K.N.; Lehman, L.P.; Xing, Y.; Cotts, E.J. "Grain-Boundary Character and Grain Growth in Bulk Tin and Bulk Lead-Free Solder Alloys," J. Electronic Materials 33, 1412, (2004).

Telang, A.U.; Bieler, T.R.; Lucas, J.P.; Subramanian, K.N.; Lehman, L.P.; Xing, Y.; Cotts, E.J. "Grain Boundary Character and Grain Growth in Bulk Tin and Bulk Lead-free Solder Alloys," J Electronic Materials 33(12), 1412-1423, (2004).

Rhee, H.; Subramanian, K.N.; Lee, A.; Lee, J.G. "Mechanical Characterization of Sn-3.5Ag Solder Joints at Various Temperatures", Soldering and Surf. Mount Tech. 15, 21, (2003).

Guo, F.; Choi, S.; Subramanian, K. N.; Bieler, T. R.; Lucas, J. P.; Achari, A.; Paruchuri, M. "Evaluation of Creep Behavior of Near Eutectic Sn-Ag Solders Containing Small Amount of Alloy Additions," Materials Science and Engineering A351/1-2, 190-199, (2003).

Lucas, J. P.; Rhee, H.; Guo, F.; Subramanian, K. N. "Nanoindentation Mechanical Properties of Intermetallic Compounds Formed Pb-Free Sn-Ag Solder Joints," Journal of Electronic Materials 32(12), 1375-1383, (2003)

Lucas, J.P.; Rhee, H.; Guo F.; Subramanian K.N. "Mechanical Properties of Intermetallic Compound Associated with Pb-Free Solder Joints Using Nanoindentation," J. Electronic Materials 32, 1375-1383 (2003).

Telang, A. U.; Bieler, T. R.; Mason, D. E.; Subramanian, K. N. "Comparisons of Experimental and Computed Crystal Rotations due to Slip in Crept and Thermomechanically Fatigued Dual Shear Eutectic Sn-Ag Solder Joints," Journal of Electronic Materials 32(12), 1455-1462, (2003).

Rhee, H.; Subramanian, K. N. "Effects of Prestrain, Rate of Prestrain, and Temperature on the Stress-Relaxation Behavior of Eutectic Sn-3.5Ag Solder Joints," Journal of Electronic Materials 32(11), 1310-1316, (2003).

Rhee, H.; Guo, F.; Lee, J. G.; Chen, K. C.; Subramanian, K. N. "Effects of Intermetallic Morphology at the Metallic Particle/Solder Interface on Mechanical Properties of Sn-Ag-Based Solder Joints," Journal of Electronic Materials 32(11), 1257-1264, (2003).

Lee, J. G.; Chen, K. C.; Subramanian, K. N. "Formation and Growth of Intermetallics around Metallic Particles in Eutectic Sn-Ag Solder," Journal of Electronic Materials 32(11), 1240-1248, (2003).

Subramanian, K. N.; Lee, J. G. "Physical Metallurgy in Lead-Free Electronic Solder Development," Journal of Metals 55(5), 26-32, (2003).

Lee, J. G.; Subramanian, K. N. "Effect of Dwell Times on Themomechanical Fatigue Behavior of Sn-Ag Based Solder Joints," Journal of Electronic Materials, 32(6), 523-530, (2003).

Guo, F.; Lee, J. G.; Subramanian, K. N. "Creep Behavior of Composite Lead-Free Electronic Solder Joints," Soldering and Surface Mount Technology 15(1), 39-42, (2003).

Ferguson, K. J.; Telang, A.; Lee, J. G.; Subramanian, K. N. "Microstructural Effects on the Behavior of Sn-Ag Solder Joints under Repeated Reverse Stressing," Journal of Materials Science: Materials in Electronics 14, 157-164, (2003).

Books, Chapters, Monographs

Subramanian, K. N.; Choi, S.; Guo, F. "High-Temperature Lead-Free Solders with Dispersoids," Puttlitz/Handbook of Lead (Pb) - Free Technology for Microelectronic Assembly, Chapter 10, 301-330 (2004).

Conference Proceedings

Lee, J. G.; Guo, F.; Subramanian, K. N. "Thermomechanical Fatigue Behavior on Pb-Free Automotive Electronic Solders," SAE 2003 World Congress, Detroit, MI, March 3-6, 2003, SAE Paper Number 2003-01-0621, (2003).

Other Works

Prepared and submitted the Annual Report for "Modeling of Microstructure Evolution and Thermomechanical Fatigue in Lead-Free Solder Joints" to National Science Foundation, (2003).