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Title: Study of self-alignment of μBGA packages
Authors: Hung, K.C.
Chan, Y.C.
Tu, P.L.
Ong, H.C.
Webb, D. Patrick
Lai, J.K.L.
Keywords: Gas flow effect
BGA package
Issue Date: 2000
Publisher: © IEEE
Citation: HUNG, K.C. ... et al, 2000. Study of self-alignment of μBGA packages. IEEE Transactions on Advanced Packaging, 23 (4), pp. 631- 636
Abstract: In this paper, a detailed study of the self-alignment of BGA packages is presented. Complete self-alignment can be achieved even for a misalignment of the package of larger than 50% off the test board pad centres. A small residual displacement of the package from perfect alignment after reflow is observed. The reason for this displacement is the action of gas flow viscous drag on the package during reflow. The use of eutectic SnPb solder paste slightly reduces self-aligning ability, due to the increase in the solder volume, which reduces the restoring force. Exposure of the solder paste to a 25 C and 85% RH humidity environment also has a detrimental effect on the self-alignment of the BGA package, due to solvent evaporation and moisture absorption in the paste causing solderability degradation. The self-alignment of the package is also affected when there is slow spreading of molten solder on the pad surface. This is attributed to the reduction of restoring force due to the decrease in effective wetting surface area of the board pad.
Description: This article was published in the journal, IEEE Transactions on Advanced Packaging [© IEEE] and is also available at: http://ieeexplore.ieee.org Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
Version: Published
DOI: 10.1109/6040.883752
URI: https://dspace.lboro.ac.uk/2134/4105
ISSN: 1521–3323
Appears in Collections:Published Articles (Mechanical, Electrical and Manufacturing Engineering)

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