Study on local recrystallization and damage mode of Lead-free BGA solder joint

Xu, Xing; Chen, Gaiqing; Cheng, M. D.

doi:10.1109/icept.2014.6922672

Cited by 1 publication

(1 citation statement)

References 11 publications

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“…The created dislocations during indentation are therefore likely to be blocked by these IMCs and a higher hardness is obtained. This observation is also consistent with the study conducted by Arfaei et al, Chen et al and Xu et al on SAC305 solder joints [6,22,23]. It is also noteworthy that the SAC305 macrograins hardness does not exhibit large differences according to the crystallographic orientation.…”

Section: Nanoindentation Testssupporting

confidence: 92%

Microstructural evolutions of Sn-3.0Ag-0.5Cu solder joints during thermal cycling

Libot

Alexis

Dalverny

et al. 2018

Microelectronics Reliability

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Temperature-induced solder joint fatigue is a main reliability concern for aerospace and military industries whose electronic equipment used in the field is required to remain functional under harsh loadings. Due to the RoHS directive which eventually will prevent lead from being utilized in electronic systems, there is a need for a better understanding of lead-free thermomechanical behavior when subjected to temperature variations. As solder joints mechanical properties are dependent of their microstructural characteristics, developing accurate solder joint fatigue models means to correctly capture the microstructural changes that undergo the solder alloy during thermal cycling. This study reports the Sn3.0Ag0.5Cu (SAC305) solder joints microstructural evolution during damaging temperature cycles. Electron BackScatter Diffraction (EBSD) analysis was conducted to assess the SAC305 microstructure corresponding to a specific damage level. Investigated microstructural features included the β-Sn grain size and crystallographic orientation, as well as the grain boundary misorientation and Ag 3 Sn intermetallic compound (IMC) size. As-reflowed and damaged components were also mechanically characterized using nanoindentation technique. The microstructural analysis of SAC305 solder joints prior to thermal cycling showed a highly textured microstructure characteristic of hexa-cyclic twinning with two β-Sn morphologies consisting of preferentially orientated macrograins known as Kara's beach ball, along with smaller interlaced grains. The main observation is that recrystallization systematically occurred in SAC305 solder joints during thermal cycling, creating a high population of misoriented grain boundaries leading to intergranular crack initiation and propagation in the high strain regions. The recrystallization process is accompanied with a progressive loss of crystallographic texture and twinning structure. Ag 3 Sn IMCs coalescence is another strong indicator of SAC305 solder damage since the bigger and more spaced the IMCs are the less dislocation pinning can prevent recrystallization from occurring.

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Section: Nanoindentation Testssupporting

confidence: 92%