Corrosion Science and Technology

The Corrosion Science Society of Korea (한국부식방식학회)
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Effects of Ag and Cu Additions on the Electrochemical Migration Susceptibility of Pb-free Solders in Na2SO4 Solution

  • Yoo, Y.R. (School of Advanced Materials Engineering, Andong National University) ;
  • Nam, H.S. (School of Advanced Materials Engineering, Andong National University) ;
  • Jung, J.Y. (School of Advanced Materials Engineering, Andong National University) ;
  • Lee, S.B. (School of Materials Science and Engineering, Seoul National University) ;
  • Park, Y.B. (School of Advanced Materials Engineering, Andong National University) ;
  • Joo, Y.C. (School of Materials Science and Engineering, Seoul National University) ;
  • Kim, Y.S. (School of Advanced Materials Engineering, Andong National University)
  • Published : 2007.04.01
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Abstract

The smaller size and higher integration of advanced electronic package systems result in severe electrochemical reliability issues in microelectronic packaging due to higher electric field under high temperature and humidity conditions. Under these harsh conditions, electronic components respond to applied voltages by electrochemical ionization of metal and the formation of a filament, which leads to short-circuit failure of an electronic component, which is termed electrochemical migration. This work aims to evaluate electrochemical migration susceptibility of the pure Sn, Sn-3.5Ag, Sn-3.0Ag-0.5Cu solder alloys in $Na_{2}SO_{4}$. The water drop test was performed to understand the failure mechanism in a pad patterned solder alloy. The polarization test and anodic dissolution test were performed, and ionic species and concentration were analyzed. Ag and Cu additions increased the time to failure of Pb-free solder in 0.001 wt% $Na_{2}SO_{4}$ solution at room temperature and the dendrite was mainly composed of Sn regardless of the solders. In the case of SnAg solders, when Ag and Cu added to the solders, Ag and Cu improved the passivation behavior and pitting corrosion resistance and formed inert intermetallic compounds and thus the dissolution of Ag and Cu was suppressed; only Sn was dissolved. If ionic species is mainly Sn ion, dissolution content than cathodic deposition efficiency will affect the composition of the dendrite. Therefore, Ag and Cu additions improve the electrochemical migration resistance of SnAg and SnAgCu solders.

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References

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