Influence of latent heat released from solder joints II: PCB deformation during reflow and pad cratering defects
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This work is focused on the deformation of FR4 laminate, a material used to form many basic components of electronic assemblies, during the reflow process. The thermal expansion of FR4 was assessed from room temperature up to 250 °C. The dilatation characteristics of the laminate were found to be highly anisotropic in three directions. Special attention was paid to the irreversible changes in the laminate after the first thermal cycle, and the results were used to analyze the effects of latent heat on the deformation of FR4 during reflow. The latent heat released during solidification of a solder joint heats not only the joint but also its surrounding, leading to localized expansion of all materials around the joint and potentially causing pad cratering. Thermal expansion measurements demonstrated that the coefficient of thermal expansion (CTE) of the FR4 laminate in the z direction was at least 10 times that of the adjacent materials in the electronics assembly. This large difference in the CTE leads to residual strains in the assembly. An analysis of this problem is presented, and a model for the effect of latent heat on the FR4 deformation is proposed.
KeywordsResidual Stress PCBs Latent Heat Solder Joint Thermal Cycle
This work was performed at the Magnetism and Low Temperature Laboratories (http://mltl.eu/) as part of the Czech Research Infrastructures Program (LM 2,011,025). Support was also received from the Grant Agency of the Czech Technical University in Prague (Grant No. SGS15/196/OHK3/3T/13).
- 5.R. Osiroff, D.P.H. Hasselman, J. Compos. Mater. 25, 1588 (1991)Google Scholar
- 9.P. Geng, T. Bandorawalla, S. Cho, H. Hsiao, J. Kuchy, G. Long, R. Martinson, A. Mcallister, M. Mello, K. Meyyappan, R. Williams, L. Zhu, in Proceedings of the 56th Electronic Components and Technology Conference (2006)Google Scholar
- 12.M. Placek, K. Dusek, J. Urbanek, in Proceedings of the 2014 37th International Spring Seminar on Electronics Technology ISSE (2014), pp. 193–197Google Scholar
- 16.A. Geczy, L. Tersztyanszky, B. Illes, A. Kemler, and A. Szabo, in Design and Technology in Electronic Packaging SIITME, 2013 IEEE 19th International Symposium for Design and Technology (2013), pp. 65–68Google Scholar
- 18.K. Dušek, A. Rudajevová, M. Plaček, J. Mater. Sci. Mater. Electron. 27, 543 (2015)Google Scholar
- 20.A. Rudajevova, K. Dusek, Kov. Mater. Met. Mater. 50, 295 (2012)Google Scholar
- 22.H. Ma, W. Xie, G. Subbarayan, K.-C. Liu, in IEEE 61st Electronic Components and Technology Conference (ECTC) (2011), pp. 979–983Google Scholar
- 23.M. Mukadam, G. Long, P. Butler, V. Vasudevan, in Proceedings of SMTA International (2005), pp. 324–329Google Scholar
- 25.K. Newman, in International Conference on Thermal, Mechanical and Multi-physics Simulation and Experiments in Microelectronics and Microsystems. 2008 EuroSimE 2008 (2008), pp. 1–15Google Scholar