UC Spark

Dr Ee-Hua Wong

Mechanical Engineering

Phone: +64 3 364 2987 ext. 7348
 Office: Civil/Mechanical Engineering 513

Fields of Research

  • Structural Integrity and Reliability - Design & Analysis
  • Wind and marine Renewable Energy - Innovative Solutions & Analysis
  • Microelectronics Packaging - Reliability Analysis & Design

Researcher Summary

Application of mechanics, computational modeling/simulation, materials, etc. to enhance the structural integrity and durability of engineering system/components/elements/materials.


Development of FAILURE/LIFE PREDICTION models for Engineering Materials (metals/polymers/composites) subject to complex Failure Drivers (mechanical, temperature, moisture, electrical, etc) supported by:

1. Multi-Physics Modeling that includes
  * Structural Analysis: fracture, impact, shock and vibration; and
  * Diffusion analysis: heat transfer, moisture diffusion, electro-migration; and
  * Coupled field analysis: thermo-mechanical, hygro-mechanical, chemical-mechanical, electro-mechanical; etc;

2. Materials Characterization that includes
  * Mechanical characterization: multi-axes, rate/environmental-dependent constitutive properties; and
  * Physical characterization: moisture diffusion, hygroscopic swelling, chemical cure shrinkage, etc; and

3. Accelerated Testing Methodology
* Development of test methodology that reduce test duration (by factor of 10 or 100)  while duplicating the physics of failure.


Successful applications of the above methodologies to defense, microelectronics, and energy industries.

Subject Area: Disciplines

Research Projects

Research Groups

Future Research

  • High strain rate loading; e.g. drop-impact of portable electronic devices
  • Fibre Reinforced Plastic Composites: Development of Multi-Dimension Failure Model
  • Wind and Marine Renewable Energy: Aero-Hydro-Structural Analysis
  • Accelerated test methodology
  • Wind and Marine Renewable Energy: Development of Innovative Solutions

Key Methodologies

  • Failure-Fault Analysis and Design to Remedy
  • Life Prediction and Development of Predictive Failure Model
  • Development of Accelerated Stress Test Methodology
  • Finite Element Analysis - Structure and Multi-Physics
  • Materials Characterization - Mechanical and Physical Properties

Prizes and Awards

  • Outstanding Paper Award: “A Study of Component-Level Measure of Board-Level Drop Impact Reliability by Ball Impact Test”, Proc. 3rd IMPACT/10th EMAP Joint Conference, 2008, pp. 107-112. (2008)
  • Outstanding Technical Paper Award: “Comprehensive treatment of moisture induced failure in IC packaging”, Proc. 3rd Int. Electron. Manuf. Technol., Japan, 1999, pp. 176-181. (1999)

Publications

(Selected outputs for last six years)

Intellectual Property
  • Tsai, K.T., Wong, E.H. and Rajoo, R. (2010) Micro-impact testing apparatus. Patent No. EP1846746, Europe.
  • Wong, E.H., Rajoo, R. and Lim, S.S. (2009) Method for forming and releasing interconnects. Patent No. 20090091025, USA.
  • Wong, E.H. and Seah, S.K.W. (2009) Method for forming interconnects. Patent No. 20090078745, USA.
  • Tsai, K.T., Wong, E.H. and Rajoo, R. (2009) Micro-impact testing apparatus. Patent No. 7500378, USA.
  • Wong, E.H., Seah, S.K.W. and Rajoo, R. (2008) Bend Testing Apparatus and Method of Carrying out the Same. Patent No. 7464606, USA.
  • Wong, E.H., Rajoo, R., Wong, W.K. and Iyer, M.K. (2007) Method and device to elongate a solder joint. Patent No. 7178711, USA.
Journal Article
  • Caers, J.F.J.M., Zhao, X.J., Wong, E.H., Seah, S.K.W., Selvanayagam, C.S., van Driel, W.D., Owens, N., Leoni, M., Tan, L.C., Eu, P.L., Lai, Y-S. and Yeh, C-L. (2010) A Study of Crack Propagation in Pb-free Solder Joints. IEEE Transactions on Electronics Packaging Manufacturing 33(2): 84-90. http://dx.doi.org/10.1109/TEPM.2009.2039710.
  • Wong, E.H., Seah, S.K.W., van Driel, W.D., Caers, J.F.J.M., Owens, N. and Lai, Y-S. (2009) Advances in the drop-impact reliability of solder joints for mobile applications. Microelectronics and Reliability 49(2): 139-149. http://dx.doi.org/10.1016/j.microrel.2008.12.001.
  • Wong, E.H., Mai, Y.W. and Woo, M. (2009) Analytical Solution for the Damped-Dynamics of Printed Circuit Board and Applied to Study the Effects of Distorted Half-Sine Support Excitation. IEEE Transactions on Advanced Packaging 32(2): 536-545. http://dx.doi.org/10.1109/TADVP.2009.2014737.
  • Wong, E.H., Lim, K.M. and Mai, Y-W. (2009) Analytical Solutions for PCB Assembly Subjected to Mismatched Thermal Expansion. IEEE Transactions on Advanced Packaging 32(3): 602-611. http://dx.doi.org/10.1109/TADVP.2009.2025222.
  • Wong, E.H. and Wong, C.K. (2009) Approximate solutions for the stresses in the solder joints of a printed circuit board subjected to mechanical bending. International Journal of Mechanical Sciences 51(2): 152-158. http://dx.doi.org/10.1016/j.ijmecsci.2008.12.003.
  • Wong, E.H., Seah, S.K.W., Selvanayagam, C.S., Rajoo, R., van Driel, W.D., Caers, J.F.J.M., Zhao, X.J., Owens, N., Leoni, M., Tan, L.C., Lai, Y-S. and Yeh, C-L. (2009) High-Speed Cyclic Bend Tests and Board-Level Drop Tests for Evaluating the Robustness of Solder Joints in Printed Circuit Board Assemblies. Journal of Electronic Materials 38(6): 884-895. http://dx.doi.org/10.1007/s11664-008-0610-5.
  • Wong, E.H. and Lim, T.B. (2008) A More Comprehensive Solution for Tri-Material Layers Subjected to Thermal Stress. IEEE Transactions on Components and Packaging Technologies 31(1): 54-64. http://dx.doi.org/10.1109/TCAPT.2007.906730.
  • Wong, E.H., Rajoo, R., Seah, S.K.W., Selvanayagam, C.S., van Driel, W.D., Caers, J.F.J.M., Zhao, X.J., Owens, N., Tan, L.C., Leoni, M., Eu, P.L., Lai, Y-S. and Yeh, C-L. (2008) Correlation studies for component level ball impact shear test and board level drop test. Microelectronics and Reliability 48(7): 1069-1078. http://dx.doi.org/10.1016/j.microrel.2008.04.008.
  • Rajoo, R., Lim, S.S., Wong, E.H., Hnin, W.Y., Seah, S.K.W., Tay, A.A.O., Iyer, M. and Tummala, R.R. (2008) Development of Stretch Solder Interconnections for Wafer Level Packaging. IEEE Transactions on Advanced Packaging 31(2): 377-385. http://dx.doi.org/10.1109/TADVP.2008.923390.
  • Zhang, G-J., Zhang, G., Chua, J.H., Chee, R-E., Wong, E.H., Agarwal, A., Buddharaju, K.D., Singh, N., Gao, Z. and Balasubramanian, N. (2008) DNA Sensing by Silicon Nanowire: Charge Layer Distance Dependence. Nano Letters 8(4): 1066 1070. http://dx.doi.org/10.1021/nl072991l.
  • Zhang, X., Wong, E.H., Rajoo, R., Iyer, M.K., Caers, J.F.J.M. and Zhao, X.J. (2008) Integrated Process-Aging Modeling Methodology for Flip Chip on Flex Interconnections With Nonconductive Adhesives. IEEE Transactions on Advanced Packaging 31(4): 882-889. http://dx.doi.org/10.1109/TADVP.2008.2005022.
  • Wong, E.H., Selvanayagam, C.S., Seah, S.K.W., van Driel, W.D., Caers, J.F.J.M., Zhao, X.J., Owens, N., Tan, L.C., Frear, D.R., Leoni, M., Lai, Y-S. and Yeh, C-L. (2008) Stress-strain characteristics of tin-based solder alloys at medium strain rate. Materials Letters 62(17-18): 3031–3034. http://dx.doi.org/10.1016/j.matlet.2008.01.101.
  • Wong, E.H., Selvanayagam, C.S., Seah, S.K.W., van Driel, W.D., Caers, J.F.J.M., Zhao, X.J., Owens, N., Tan, L.C., Frear, D.R., Leoni, M., Lai, Y-S. and Yeh, C-L. (2008) Stress-Strain Characteristics of Tin-Based Solder Alloys for Drop-Impact Modelling. Journal of Electronic Materials 37(6): 829-836. http://dx.doi.org/10.1007/s11664-008-0403-x.
  • Wong, E.H. and Wong, C.K. (2008) Tri-Layer Structures Subjected to Combined Temperature and Mechanical Loadings. IEEE Transactions on Components and Packaging Technologies 31(4): 790-800. http://dx.doi.org/10.1109/TCAPT.2008.2001196.
  • Wong, E.H., Mai, Y-W., Seah, S.K.W., Lim, K-M. and Lim, T.B. (2007) Analytical Solutions for Interconnect Stress in Board Level Drop Impact. IEEE Transactions on Advanced Packaging 30(4): 654–664. http://dx.doi.org/10.1109/TADVP.2007.898599.
  • Yu, H., Mhaisalkar, S.G. and Wong, E.H. (2007) Evolution of Contact Resistance during the Bonding Process of NCA Flip-Chip Interconnections. Journal of Electronic Materials 36(12): 1719-1723. http://dx.doi.org/10.1007/s11664-007-0257-7.
Conference Contribution - Paper in published proceedings
  • Zhao, X.J., Caers, J.F.J.M., Wong, E.H., Seah, S.K.W., v.Driel, W.D., Owen, N. and Lai, Y-S. (2009) Frequency dependent S-N curves for predicting drop impact robustness of Pb-free solder interconnects. San Diego, CA, USA: 59th Electronic Components & Technology Conference (ECTC), 26-29 May 2009. In Proceedings of 59th Electronic Components & Technology Conference 93-99. http://dx.doi.org/10.1109/ECTC.2009.5074002.
  • Seah, S.K.W., Wong, E.H., Selvanayagam, C.S., Caers, J.F.J.M., van Driel, W.D., Owens, N. and Lai, Y-S. (2008) A Comprehensive Test Method for Bridging the Gap between Product and Board Level Drop Tests. Singapore: 10th Electronics Packaging Technology Conference (EPTC 2008), 9-12 Dec 2008. In Proceedings of 10th Electronics Packaging Technology Conference (EPTC 2008) 1102-1107. http://dx.doi.org/10.1109/EPTC.2008.4763576.
  • Lai, Y-S., Wong, E.H., Rajoo, R., Seah, S.K.W., Selvanayagam, C.S., van Driel, W.D., Caers, J.F.J.M., Zhao, X.J., Owens, N., Tan, L.C., Leoni, M. and Eu, P.L. (2008) A Study of Component-Level Measure of Board-Level Drop Impact Reliability by Ball Impact Test. Taipei, Taiwan: 3rd International Microsystems, Packaging, Assembly & Circuits Technology Conference (IMPACT/10th EMAP Joint Conference), 22-24 Oct 2008. In Proceedings of 3rd International Microsystems, Packaging, Assembly & Circuits Technology Conference (IMPACT 2008) 57-62. http://dx.doi.org/10.1109/IMPACT.2008.4783807.
  • Caers, J.F.J., Wong, E.H., Seah, S.K.W., Zhao, X.J., Selvanayagam, C.S., van Driel, W.D., Owens, N., Leoni, M., Tan, L.C., Eu, P.L., Lai, Y-S. and Yeh, C-L. (2008) A study of crack propagation in Pb-free solder joints under drop impact. Lake Buena Vista, FL, USA: 58th Electronics Components & Technology Conference (ECTC 2008), 27-30 May 2008. 1166-1172. http://dx.doi.org/10.1109/ECTC.2008.4550123.
  • Wang, J., Seah, S.K.W., Wong, E.H. and Cadge, D. (2008) Fracture Mechanics Study of Fatigue Crack Growth in Solder Joints Under Drop Impact. Lake Buena Vista, FL, USA: 58th Electronics Components & Technology Conference (ECTC 2008), 27-30 May 2008. 1601-1605.
  • Wong, E.H., Seah, S.K.W., van Driel, W.D., Caers, J.F.J.M., Owens, N. and Lai, Y-S. (2008) Recent advances in drop-impact reliability. Freiburg, Germany: 9th IEEE EuroSimE International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, 21-23 Apr 2008. In Proceedings 1-9.
  • Owens, N., Wong, E.H., Seah, S.K.W., Selvanayagam, C.S., Rajoo, R., van Driel, W.D., Caers, J.F.J.M., Zhao, X.J., Tan, L.C., Leoni, M., Eu, P.L., Lai, Y-S. and Yeh, C-L. (2008) Second Level Interconnect Mechanical Robustness. Fountain Hills, AZ, USA: 4th International Conference & Exhibition on Device Packaging, 17-20 Mar 2008.
  • Zhao, X.J., Caers, J.F.J.M., de Vries, J.W.C., Wong, E.H. and Rajoo, R. (2007) A Component Level Test Method for Evaluating the Resistance of Pb-free BGA Solder Joints to Brittle Fracture under Shock Impact. Reno, NV, USA: 57th Electronic Components & Technology Conference (ECTC'07), 29 May-1 Jun 2007. In Proceedings of 57th Electronic Components & Technology Conference 1522-1529.
  • Woo, M.S.S. and Wong, E.H. (2007) Analytical Solution of the Dynamic Response of Printed Circuit Board to Support Excitation. Singapore: 9th Electronic Packaging Technology Conference (EPTC 2007), 10-12 Dec 2007. In Proceedings Electronics Packaging Technology Conference 2007 386-390. http://dx.doi.org/10.1109/EPTC.2007.4469786.
  • Selvanayagam, C.S., Wong, E.H., Seah, S.K.W., van Driel, W.D., Caers, J.F.J., Zhao, X.J., Owens, N., Tan, L.C., Frear, D.R., Leoni, M., Lai, Y-S. and Yeh, C-L. (2007) Constitutive Properties of Bulk Solder at ‘Drop-Impact’ Strain Rates. Singapore: 9th Electronic Packaging Technology Conference (EPTC 2007), 10-12 Dec 2007. In Proceedings Electronics Packaging Technology Conference 2007 360-364. http://dx.doi.org/10.1109/EPTC.2007.4469817.