Evolution of microstructure and effects on crack formation of Sn3.0Ag0.5Cu/Cu solder joints under accelerated thermal cycling. (5th April 2019)

• Record Type: Journal Article
• Authors: Yang, Linmei; Shi, Xuefeng; Quan, Shanyu
• Is Part Of: Materials research express. Volume 6:Number 7(2019)
• Publication Date: 2019-04-05
• Subjects: lead-free solder -- solder joints -- microstructures -- thermal cycling; Materials science -- Research -- Periodicals; Materials science -- Periodicals; 620.11
• DOI: 10.1088/2053-1591/ab1334
• Languages: English
• ISSNs: 2053-1591

Abstract

Abstract: Microstructure evolution of Sn3.0Ag0.5Cu/Cu solder joint and their effects on crack formation were investigated under accelerated thermal cycling. Isothermal aging experiments show that the thickness of interfacial compounds layer was proportional to the square root of aging time. A few large Ag3 Sn compounds were observed along solder/interfacial compounds layer even into the interfacial Cu6 Sn5 compounds layer after a long aging time. The accelerated thermal cycling tests were carried out for the solder joints with different microstructure. Experimental results showed that crack formation mechanism was greatly dependent on the microstructures of solder joint. For as-reflowed joint, stress concentration mainly appeared the grain boundaries of β -Sn due to the anisotropy of thermal expansion coefficients. The movements of dislocations were hindered by pinning on the fine Ag3 Sn precipitates. Microcracks initiated and propagated in β -Sn. However, with the increase of volume fraction of interfacial intermetallics compounds layer and the disappearance of Ag3 Sn cellular structure, brittle fracture occurred in the coarsened Cu6 Sn5 compounds layer.