Symposium: Solidification Modeling and Microstructure Formation: In Honor of Prof. John Hunt

Metallurgical and Materials Transactions A

, Volume 38, Issue 7, pp 1530-1538

First online:

Solidification Condition Effects on Microstructures and Creep Resistance of Sn-3.8Ag-0.7Cu Lead-Free Solder

  • J. LiangAffiliated withEMC Corp.Chongqing University
  • , N. DariavachAffiliated withEMC Corp. Email author 
  • , D. ShangguanAffiliated withFlextronics

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Metallurgical, mechanical, and environmental factors all affect service reliability of lead-free solder joints and are under extensive study for preparation of the transition from Sn-Pb eutectic soldering to lead-free soldering in the electronic industry. However, there is a general lack of understanding about the effects of solidification conditions on the microstructures and mechanical behavior of lead-free solder alloys, particularly on the long-term reliability. This study attempts to examine the creep resistance of the Sn-Ag-Cu eutectic alloy (Sn-3.8Ag-0.7Cu, SAC387) with a variety of solidification conditions with cooling rates ranging from 0.3 °C/s to 17 °C/s. Results indicate that solidification conditions have a major influence on the creep resistance of SAC387 alloy; up to two orders of magnitude change in the steady-state creep rates were observed at low stress levels. An understanding of the mechanical property change with microstructures, which are determined by the solidification conditions, should shed some light on the fundamental deformation and fracture mechanisms of lead-free solder alloys and can provide valuable information for long-term reliability assessment of lead-free solder interconnections.