‘Effects of Minor Alloying Additions on the Properties and Reliability of Pb‐Free Solders and Joints’

Abstract

Since July, 2006, following the EUs RoHS legislation, the consumer electronics industry has been offering 'green' products by eliminating Pb-containing solders and other toxic materials. This transition has been relatively smooth, because the reliability requirements are less stringent. However, the Pb-free transition for high-performance electronic systems (such as servers and telecommunication) is still on-going due to their rigorous reliability requirements. For example, the research and development efforts to implement Pb-free flipchip interconnections for high-end applications are still very active.In this chapter, the recent progress in Pb-free solder development, especially minor alloy additions to Sn-rich solders is reviewed in light of improving various physical, mechanical, metallurgical or electrical properties of solder joints. The topics to be discussed include those such as control of undercooling, microstructure, interfacial reactions, or void formation, as well as enhancing impact resistance, electromigration, and other mechanical properties.

Systematic investigation of Sn-Ag and Sn-Cu modified by minor alloying element of titanium

“…However, Ti addition seems not to be so effective for hindering the formation of Cu 3 Sn. In the case of Sn-Cu-Ti solders reacted with Ni, the interfacial IMC, (Cu,Ni) 6 Sn 5 , is also found to be impeded comparing to the case without Ti addition. When Sn-Ag-Ti solders undergo a reflow process on Ni, Ni 3 Sn 4 forms at the interface as a layer of equilibrium IMC and Ti addition unexpectedly accelerate the formation of Ni 3 Sn 4 .…”

“…According to previous reports, many of transition metals could be candidates for minor alloying elements due to their high reactivity, such as Ag, Co, Cu, Fe, Mn, Ni, Ti, Zn and others [1][2][3][4][5][6][7][8][11][12][13][14][15][16]. Among them, Ti addition was reported to enhance both drop-impact performances and thermal-creep property [7].…”

“…The selection of new solder materials has been an important topic in order to enhance the reliability of Pb-free solder joints. In the past few years, numerous studies have been conducted on the beneficial effects of minor alloying elements, including Co, Cu, Fe, Ni, Zn and others, into Sn-rich Pb-free solders [1][2][3][4][5][6]. Only recently have Liu et al.…”