A corrosion investigation of solder candidates for high-temperature applications

Abstract

How would you……describe the overall signifi cance of this paper? Potential lead-free solder candidates for high-temperature applications that were determined by using computational thermodynamics were assessed from the corrosion perspective. This work reveals 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 the Au-Gebased ones.…describe this work to a materials science and engineering professional with no experience in your technical specialty? The solder candidates that could adhere to the solidifi cation criterion required for replacing the high-leadcontaining solders were investigated from the corrosion perspective. An overview of corrosion-related problems that have to be thoroughly investigated before substituting the currently used one has been reported. …describe this work to a layperson?A drive for miniaturization, multiplicity of materials, and globalization has resulted in corrosion being a signifi cant issue in the complex electronic packaging systems that are being developed. The possible corrosion scenario for the promising lead-free solder candidates in such packaging for high-temperature applications has been investigated in this work.The step-soldering approach is being employed in the multi-chip module technology. High-lead-containing alloys are among the solders currently being used in this approach. Au-Sn and Au-Ge based candidate alloys have been proposed as alternative solders for this application. In this work, a corrosion investigation was carried out on potential ternary lead-free candidate alloys based on these binary alloys for high-temperature applications. These promising ternary candidate alloys were determined by the CALPHAD approach based on the solidifi cation criterion and the nature of the phases predicted in the bulk solder. This work reveals that the Au-Sn-based candidate alloys close to the eutectic composition (20 wt.% Sn) are more corrosion resistant than the Au-Ge-based ones.

Development of Au–Ge based candidate alloys as an alternative to high-lead content solders

“…Usually, non-metal impurities pop up during the sphere forming process and it is necessary to clean the metal sphere. Normally it is done by washing it by ethanol followed by drying [15]. The solder sphere is remelted a couple of times for homogenization.…”

“…These ternary combinations were then optimized for a narrow solidification range since a narrow solidification range is commercially preferred for facilitating rapid production, efficient process control, preventing the movement of components during solidification and for minimizing segregation during solidification [4,5]. Phases predicted in the bulk solder for these optimized ternary combinations at 150 and 200 • C are shown in Table 1.…”

“…The eutectic melting temperature of the Au-Ge (28 at.% Ge) composition is 360 • C. It slightly deviates from the permissible liquidus temperature. Phase-equilibria calculation shows that the addition of a low melting point metal such as In or Sb or Sn decreases the melting point of this alloy below 350 • C [5]. Thus, the effect of these low melting point metals on the Au-Ge eutectic with respect to microstructure and its corresponding mechanical properties has been investigated in this work.…”

“…Among the cheaper alternatives being proposed, Zn-Al based alloys have several limitations since Zn is highly corrosive while Al possesses a high natural radius of curvature (R) that would hamper the drive for miniaturization. The continuing miniaturization of components in the microelectronics industry places ever increasing demands upon solder alloys to be designed for low R values in order to prevent bridging between contacts as the pitch between contacts keeps getting smaller and smaller during the miniaturization drive [5].…”

Corrosion resistance of Pb-free and novel nano-composite solders in electronic packaging

“…Especially, advanced packaging technologies make the solder alloy susceptible to corrosion problems [41]. Thus, in the electronics industry, corrosion has become a significant factor in recent years because of the extremely complex systems that have been developed and the increasing demand on their reliability [42,43]. For example, using Cu and Sn metals allows fine-pitch interconnections to be fabricated at relatively low cost.…”