Microelectronic corrosion solder

The improvement of existing materials as well as the development of new materials is often based on the use of a chemical reaction in which a solid reacts with another solid, a liquid or a gas to form a solid product (an intermetallic, a silicide, an oxide, a salt, etc) at the interface between initial substances. Therefore, kinetics of solid-state formation of chemical compound layers are of interest not only to chemists (researchers and technologists) but also to metal and solid-state physicists, materials scientists, metallurgists, specialists in the field of corrosion, protective coating, welding, soldering and microelectronics. 

The diversity of materials, drive toward miniaturization, and globalization have significantly contributed to the corrosion of microelectronic devices [37]. However, the key point is that solder joints are often exposed to corrosive environments that can accelerate the corrosion process. Although corrosion resistance is an important parameter in choosing solder alloys, the corrosion behavior of Sn-Pb solder joints was rarely of interest because the oxide that forms on the tin-lead alloy is relatively stable. Mori et al. showed that both Pb-rich and Sn-rich phases dissolve when the Sn-Pb solder alloy is immersed in corrosive solution, and the corrosion rate is slower than that of the Sn-Ag solder [38, 39]. Compared to traditional Sn-Pb solders, Sn-Ag-Cu solders are easily corroded in corrosive environments due to their special structures (as shown in Fig. 3). The presence of AgsSn in Sn-Ag-Cu solders accelerates the dissolution of tin from the solder matrix into a corrosive medium... 

Corrosion of solder alloys, in the presence of a suitable electrolyte can occur either due to the potential difference between the major phases in the alloy or galvanic coupling between one or more phases of the alloy and other parts of the microelectronics device. Some metals that are frequently used in microelectronics are Cu, Au, Ag, Ni and Pd. The standard emf for these metals and metals used in solder alloys are listed in Table 3 [4]. Especially, advanced packaging technologies make the solder alloy susceptible to corrosion problems... 

L.J. Turbini, M.S. Ramanachalam, R. Saied, B. Smith, and V. Yelander, A Corrosion Test for Characterizing Solder Flux Residues, Proceedings of Pan Pacific Microelectronics Symposium, 1996, p 201-203... 

Microelectronic solder joints are subjected to a number of failure mechanisms such as thermal cycle cracking, electromigration, thermomigration, corrosion, etc. Any new solder alloy must satisfy all of these requirements simultaneously. Power cycle testing stresses an assembly in a manner that closely repUcates actual appUcation use conditions. 

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