Journal
MICROELECTRONICS RELIABILITY
Volume 54, Issue 8, Pages 1583-1591Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.microrel.2014.03.007
Keywords
Lead-free solder; Solder bump; Impact test; Joint strength; Fracture morphology; Isothermal aging
Funding
- education project for universities in Jiangsu Province [12KJB460003]
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In order to investigate the fracture behavior of Sn-3.0Ag-0.5Cu solder bump, solder balls with the diameter of 0.76 mm were soldered on Cu pad in this study, then high speed impact test and static shear test of solder bumps were carried out to measure the joint strength of the soldering interface. The effect of isothermal aging on joint strength as well as fracture behavior of solder bumps was investigated, and the composition of the fracture surface was identified by means of EPMA. The results indicate that the fracture is inside the bulk solder in low speed shear test regardless of the aging effect, thus the maximum load reflects the solder strength rather than the interfacial strength. It is also found that under 1 m/s impact loading, the crack initiation position is changed from solder/Cu6Sn5 interface to Cu3Sn/Cu interface after long time isothermal aging, and the fracture occurs inside the bulk solder accompanying with intermetallic compound in both of the as-soldered and aged joints. The thickened multiple IMC layers during isothermal aging account for the degraded impact resistance, and the change of the solder matrix is another factor for reduced impact resistance owing to Sn residue on the fracture surface. (C) 2014 Elsevier Ltd. All rights reserved.
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