Phase structure and cyclic deformation in eutectic tin-lead alloy: A numerical analysis

Citation
Yl. Shen et al., Phase structure and cyclic deformation in eutectic tin-lead alloy: A numerical analysis, J ELEC PACK, 123(1), 2001, pp. 74-78
Citations number
15
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Mechanical Engineering
Journal title
JOURNAL OF ELECTRONIC PACKAGING
ISSN journal
1043-7398 → ACNP
Volume
123
Issue
1
Year of publication
2001
Pages
74 - 78
Database
ISI
SICI code
1043-7398(200103)123:1<74:PSACDI>2.0.ZU;2-6
Abstract
This study is devoted to providing a mechanistic rationale of coarsening in duced failure in solder alloys during thermomechanical fatigue. Micromechan ical modeling of cyclic deformation of eutectic tin-lead alloy was undertak en using the finite element method. The models consist of regularly arrange d tin-rich and lead-rich phases, simulating the lammellar array and colony structure in a typical eutectic system. A fine structure and a coarse struc ture, bearing the same phase fraction but different in the aspect ratio of each lead-rich layer and in the number of lead-rich layers in each colony, are utilized for representing the microstructure before and after coarsenin g, respectively. Both phases are treated as elastic-plastic solids with the ir respective properties. For simplicity the creep effect is ignored withou t compromising the main objective of this study. Cyclic lending under pure shear and unilaxial conditions is modeled It is found that both the fine an d coarse structures exhibit essentially the same macroscopic stress-strain response. The coarse structure, however, shows a greater maximum effective plastic strain on a local scale throughout the deformation, The numerical r esult implies that, in a solder joint, a locally coarsened region may not b e mechanically weaker than its surrounding, but it is subject to early dama ge initiation due to accumulated plasticity. Other implications regarding s older alloy failure and micromechanical modeling of two-phase materials are discussed.