An Investigation of Reliability of High Density Electronic Package-to-Board Interconnections from the Perspective of Solder Joint Metallurgy

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2010-12-13
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76 + app. 60
Report series / Helsinki University of Technology. Laboratory of Electronics Production Technology, 14
The integration and miniaturization trend of the electronic packaging leads to much finer pitch of the device and package lead terminations. Several reliability concerns and issues that were previously not encountered are now surfacing. The objective of this thesis work is to investigate the reliability of the package-to-board interconnection from the perspective of solder joint metallurgy. It was carried out with several advanced packages such as CSP, WLCSP and leadless ceramic packages on organic laminate PWBs using tin-silver-copper based interconnection materials. The assemblies were subjected to several loading conditions and levels such as thermal, mechanical, and environmental stresses. As expected, the board level reliability (BLR) of electronic assemblies strongly depended on microstructure and morphology of the solder joints. Dispersion strengthening effect of the intermetallic compounds (IMCs), coarsening of the IMC particles, strain rate hardening, solder fatigue, and recrystallization of Sn grains in the highly stressed areas were observed. These were found to directly impact Pb-free solder joint reliability. Appropriate thermal aging can improve joint reliability up to 50% due to coarsening of the IMC particles. In addition, other factors such as dissolution of metals, interfacial reactions, IMC spalling, and cross interaction of surface materials on the two sides of the joints were also observed and discussed. The effects can be expressed as a series of interactive relationships: materials (pad surface materials and solder alloy composition) and/or soldering process lead to microstructure change in bulk solder and/or at interface, which in turn leads to joint reliability variation.
Supervising professor
Paulasto-Kröckel, Mervi
Thesis advisor
Kivilahti, Jorma
electronic packaging, solder joint metallurgy, board level reliability, intermetallic compounds
Other note
  • [Publication 1]: Weiqun Peng and Marco Elisio Marques. 2007. Effect of thermal aging on drop performance of chip scale packages with SnAgCu solder joints on Cu pads. Journal of Electronic Materials, volume 36, number 12, pages 1679-1690.
  • [Publication 2]: Weiqun Peng, Eduardo Monlevade, and Marco E. Marques. 2007. Effect of thermal aging on the interfacial structure of SnAgCu solder joints on Cu. Microelectronics Reliability, volume 47, number 12, pages 2161-2168.
  • [Publication 3]: Eduardo Franco de Monlevade and Weiqun Peng. 2007. Failure mechanisms and crack propagation paths in thermally aged Pb-free solder interconnects. Journal of Electronic Materials, volume 36, number 7, pages 783-797.
  • [Publication 4]: Weiqun Peng, Steve Dunford, Puligandla Viswanadham, and Stephen Quander. 2003. Microstructural and performance implications of gold in Sn-Ag-Cu-Sb interconnections. In: Proceedings of the 53rd Electronic Components and Technology Conference (ECTC 2003). New Orleans, Louisiana, USA. 27-30 May 2003. IEEE. Pages 809-815. ISBN 0-7803-7991-5.
  • [Publication 5]: Weiqun Peng. 2009. An investigation of Sn pest in pure Sn and Sn-based solders. Microelectronics Reliability, volume 49, number 1, pages 86-91.
  • [Publication 6]: Jianjun Wang, Weiqun Peng, and Wei Ren. 2006. Power Amplifier (PA) transistors fatigue life prediction under thermo-mechanical cyclic loading. In: Proceedings of the 7th International Conference on Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-Systems (EuroSimE 2006). Como, Italy. 23-26 April 2006. IEEE. Pages 1-8. ISBN 1-4244-0276-X.