Materials and Society: Front Page
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JOM Examines Lead-Free Solder Reliability Issues
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By Lynne Robinson
Posted on:
6/3/2009 12:00:00 AM...
Reliability issues continue to pose challenges for those engineering lead-free solder packages. Materials issues directly related to solder joint reliability are explored in five papers in the June issue of JOM. As Kejun Zeng wrote in his commentary to the topic, “Investigation of the dependence of properties of bulk solder alloys on compositions and processes can, of course, greatly help reliability engineering of solder joints. However, because of the strong effect of the interface between solder and soldered metal on the reliability of fine pitch solder joints, research of bulk solders is not enough to answer all the questions. The influences of composition and microstructure of solder joints on the reliability of bond interface should also be studied.”
The papers comprising JOM’s Lead-Free Solder technical emphasis are:
“Microstructural Coarsening in Sn-Ag-based Solders and Its Effects
on Mechanical Properties”
I. Dutta, P. Kumar, and G. Subbarayan
Microelectronic solders based on Sn-Ag alloys are susceptible to microstructural changes during storage or service, resulting in evolution of joint properties which can affect reliability and performance over time. The authors summarize their research in characterization of microstructural coarsening in Sn-Ag based solders and examine the impact that this has on mechanical properties and reliability of solder joints.
“Lead-free Solders with Rare Earth Additions”
Fu Guo, Mengke Zhao, Zhidong Xia, Yongping Lei, Xiaoyan Li, and Yaowu Shi
This research summary discusses employing rare earths (RE) as alloying elements in an effort to improve the comprehensive properties, such as wettability, microstructural stability, creep resistance, and mechanical strength and integrity, of lead-free solders. The authors present fabrication techniques for RE-containing solders, as well as analyze the effects of RE element addition on certain lead-free solder alloys.
“Cracking and Phase Stability in Reaction Layers between Sn-Cu-Ni Solders and Cu Substrates”
K. Nogita, C.M. Gourlay, and T. Nishimura
This paper reports experimental data showing that Ni-bearing solder systematically exhibited significantly fewer cracks in the interfacial intermetallic compound layer. The authors also conclude that the material at the solder joint is more thermally stable than Ni-free Sn-Cu alloys.
“Surface Oxidation of Molten Sn(Ag, Ni, In, Cu) Alloys”
Y.Y. Lee, H.W. Tseng, Y.H. Hsiao, and C.Y. Liu
In summarizing studies of the surface oxidations of molten Sn(Ag, Ni, In, Cu) alloys, the authors conclude that the microstructure (phase and density) of the surface oxide layer is the key factor for surface oxidation formation. They also found that the microstructure of the Sn surface oxide layer is highly influenced by the additives in the solder alloys.
“A Corrosion Investigation of Solder Candidates for High-Temperature Applications”
Vivek Chidambaram, John Hald, Rajan Ambat, and Jesper Hattel
The authors report on a corrosion investigation of potential lead-free solder candidates for high-temperature applications. They found that, among the two primary candidate alloys for high-temperature solders, Au-Sn-based candidate alloys close to the eutectic composition are more corrosion resistant than Au-Ge-based ones. The paper also provides an overview of corrosion-related problems that need to be investigated before substituting high-Pb solders with Au-Sn-based ones.
TMS members and JOM subscribers can read this month’s full collection papers by accessing this link. For additional news and research information on lead-free solders, visit the Lead-Free Solder digital resource center in the Materials and Society community of Materials Technology@TMS.
Lynne Robinson is the news and feature writer for Materials Technology@TMS.
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