Abstract
During a solder reflow process, IC components deform under a rather excessive temperature loading. A too high warpage at temperatures above solder melting can cause either that the joints in the corner are not soldered to the PCB pads or that the solder joints are shorted due to strong compression of the corner joints. In this work, the warpage of a 35 by 35 mm2 large PBGA package has been measured during a temperature profile, which is similar to a lead-free soldering process. It was found that the warpage becomes very high when the applied temperature is above the glass transition temperature of the overmould material. At that moment, there exists a very large CTE mismatch between the overmould and the BT laminate. The warpage measurements have been successfully verified by Finite Element Modelling, at least when the right material properties are used. This proves that modelling can be used as an estimator of warpage for packages. Also the impact of initial moisture uptake has been experimentally investigated, and it was shown that it has a dominant effect on its warpage behaviour. Finally, a FEM-based parametric study shows the impact of several design parameters.
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References
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Acknowledgments
The authors would like to thank Rafael De Weerdt, Veerle Simons, Myriam Vandepeer, Mario Gonzalez, Daniel Vanderstraeten, Guy Brizar and Eddy Blansaer for their support in the measurements and FEM simulations. The work has been supported by the IWT (institute for support of scientific research in Flanders).
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© 2011 Springer-Verlag London Limited
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Vandevelde, B. (2011). Excessive Warpage of Large Packages During Reflow Soldering. In: Grossmann, G., Zardini, C. (eds) The ELFNET Book on Failure Mechanisms, Testing Methods, and Quality Issues of Lead-Free Solder Interconnects. Springer, London. https://doi.org/10.1007/978-0-85729-236-0_13
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DOI: https://doi.org/10.1007/978-0-85729-236-0_13
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