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A reaction study of sulfur vapors with pure silver and silver-indium solid solutions as a new anti-tarnishing test method

  • Author(s): Fu, Shao-Wei
  • Advisor(s): Lee, Chin C
  • et al.

In electronic packaging, silver tarnishing is a critical issue since the corrosive gases could penetrate into the gas-permeable epoxy molding compounds and tarnish the silver-based bonding components [1]. The generated silver sulfide after silver tarnishing reduces the electric conductivity and mechanically reduces the bonding reliability [2]. Hence, to improve the reliability of Ag-based bonding systems in the packaging industry, it is critical to develop an effective method of enhancing the Ag anti-tarnishing property. In Ag-based system, Ag-In alloys were proposed as the promising interconnection material for electronics packaging due to its great bonding ability and superior intrinsic mechanical properties [3]. In this paper, remarkable improvement in the anti-tarnishing property of Ag-In solid solution alloys has been revealed. A brief summary of preparation of the homogeneous Ag-In solid solution phase is illustrated. The crystallographic structure and chemical composition of the Ag-xIn alloys are identified by using X-ray diffraction (XRD) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX). In the following sections, quantitative results of the anti-tarnishing property of Ag-In solid solution alloys are exhibited and discussed with pure silver samples in comparison. According to experimental results, the reaction rates between silver and sulfur gases are greatly suppressed in Ag-In alloys. As a result, Ag-In solid solution alloys exhibit excellent anti-tarnishing property, offering an alternative Ag-based bonding material in the future applications in electronic packaging.

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