Improved Reliability and Mechanical Performance of Ag Microalloyed Sn58Bi Solder Alloys

Abstract

Ag microalloyed Sn58Bi has been investigated in this study as a Pb-free solder candidate to be used in modern electronics industry in order to cope with the increasing demands for low temperature soldering. Microstructural and mechanical properties of the eutectic Sn58Bi and microalloyed Sn57.6Bi0.4Ag solder alloys were compared. With the addition of Ag microalloy, the tensile strength was improved, and this was attributed to a combination of microstructure refinement and an Ag3Sn precipitation hardening mechanism. However, ductility was slightly deteriorated due to the brittle nature of the Ag3Sn intermetallic compounds (IMCs). Additionally, a board level reliability study of Ag microalloyed Sn58Bi solder joints produced utilizing a surface-mount technology (SMT) process, were assessed under accelerated temperature cycling (ATC) conditions. Results revealed that microalloyed Sn57.6Bi0.4Ag had a higher characteristic lifetime with a narrower failure distribution. This enhanced reliability corresponds with improved bulk mechanical properties. It is postulated that Ag3Sn IMCs are located at the Sn–Bi phase boundaries and suppress the solder microstructure from coarsening during the temperature cycling, hereby extending the time to failure.

Temperature‐dependent fatigue modelling of a novel Ni, Bi and Sb containing Sn‐3.8Ag‐0.7Cu lead‐free solder alloy

“…Over the past 10 years, there have been a remarkable number of lead-free solders created, such as SnAg, SnAgCu, SnCu, SnZn and SnZnBi. [3][4][5] However, in severe conditions with high operating temperatures, the properties of the solders are likely to decline over long term use due to aging effects. Thus, up to now, several strategies have been implemented to meet the requirements during long-term service and to preserve the material properties.…”

“…It is essential now to improve the new generations of lead‐free solders by conferring to them enhanced fatigue resistance. Over the past 10 years, there have been a remarkable number of lead‐free solders created, such as SnAg, SnAgCu, SnCu, SnZn and SnZnBi 3–5 . However, in severe conditions with high operating temperatures, the properties of the solders are likely to decline over long term use due to aging effects.…”

Analysis of Sn-Bi Solders: X-ray Micro Computed Tomography Imaging and Microstructure Characterization in Relation to Properties and Liquid Phase Healing Potential

“…The effect of In addition in Sn-Bi alloys on melting point and mechanical properties was shown by Wu et al [ 8 ] and microstructural effects due to Cu and Ag additions were investigated by Silva et al [ 9 ]. A strengthening effect of Ag addition to Sn-Bi alloys was reported by Ren et al [ 10 ]. Elastic properties and their temperature-dependence were investigated by means of pulse echo overlap method [ 12 ], ultrasonic transmission [ 15 , 16 ] and nano-indentation [ 3 , 17 ].…”

“…Recently, low melting point solders gained interest in the research community, where the Sn-Bi system is a promising candidate for soldering of temperature-sensitive components [ 2 ]. Studies investigated Sn-Bi alloys with respect to alloying elements [ 8 , 9 , 10 ], thermal parameters [ 11 ], magnetic stirring [ 12 ] and directional solidification [ 13 , 14 ]. The effect of In addition in Sn-Bi alloys on melting point and mechanical properties was shown by Wu et al [ 8 ] and microstructural effects due to Cu and Ag additions were investigated by Silva et al [ 9 ].…”

The Use of IR Soldering Stations in the Process of Disassembling in BGA Packaging

“…the occurrence of whiskers (threaded hair shapes up to 5ʅm in diameter and several millimeters long), short circuits caused by connecting several leads of the element with the solder metal as a result of the soldering process, and also due to human fault: incorrect selection of the soldering profile, which affects the quality of the connection, or a rapid increase in temperature, which, combined with moisture, leads to the formation of bubbles on the packaging (i.e. steam and other gases trapped in the packaging walls are the cause of delamination and cracking) [3][4][5]14].…”