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Although lead free soldering has been the main stream of industry since 2006, with the replacement of eutectic SnPb system by SnAgCu system, the development of drop-in lead-free alternatives for high melting high lead solder alloys is still far from mature. BiAg alloy exhibits acceptable bulk strength but very poor ductility and wetting, therefore is not acceptable as an option. In current work, a...
Lead free soldering has been the main stream of industry since 2006, with eutectic SnPb system phased out by SnAgCu system. However, development of lead-free alternatives for high melting high lead solder alloys is still struggling, thus hampering the completion of full lead-free conversion. BiAg alloy exhibits acceptable bulk strength but very poor ductility and wetting on copper, therefore is not...
Bi element addition effects on Sn-0.3Ag-0.7Cu low-Ag solder properties are studied in this work. Solder alloy with different Bi adding amount, Sn-0.3Ag-0.7Cu-XBi (X = 0, 1.0, 3.0, 4.5), were fabricated. The melting point, wettability, and strength tests were carried out to find the effects of Bi addition on current low-Ag solder. Thermal aging of the solder interconnects with different Bi addition...
A new structural effect that was developed based on the concepts of the cantilever beams has been proposed in order to illustrate the measurement divergence of nanoindentation test for Cu6Sn5 IMCs. Cu6Sn5 IMCs were fabricated in Sn3.5Ag/Cu solder joints by wetting reaction at 250°C and subsequent thermal aging, and measured by nanoindentation. In this study, the extra displacement created by the cantilever-like...
Sn-Ag-Cu (SAC) and Sn-Ag alloys are considered to be the most promising Pb-free solders for electronics applications. The properties of these solders can be improved by the addition of minor alloying elements to control the intermetallic compounds (IMCs) that are formed during soldering and high temperature storage/cycling. Additional alloying elements into the solder alloys change the solidification...
The excessive growth of intermetallic compound (IMC) and the formation of microvoids in the interface between Sn-Ag-Cu (SAC) solder and Cu substrate have been a serious problem which may degrade the solder joints reliability. Recently, a new Cu-Zn alloy solder wetting layer for the Pb-free solders has been developed to reduce the IMC growth rate. In this paper, the kinetics of IMC growth and the shear...
Gradually diminishing solderability and potential risk of whisker growth are two major concerns in using immersion tin as a final finish for printed wiring boards. Both phenomena are attributable to the spontaneous formation of intermetallic compounds (IMC) of Cu6Sn5 and Cu3Sn between the tin coating and copper substrate. The formation of IMC consumes the free tin in the coating that is essential...
The microstructures of SnBi/Cu interconnect after reflow and its evolution during solid-state aging at 393 K were investigated using transmission electron microscopy (TEM). It was found that after reflow there were two kinds of intermetallic compounds (IMCs) - Cu6Sn5 and Cu3Sn in solder joint. Above these IMC layers there was a Bi-rich layer which consisted of discontinuous Bi particles. During solid...
We recently developed Cu-Zn alloy wetting layer for the SAC solder balls to improve the reliability. In this paper, IMC formation and solder joint reliability have been investigated in the solder joint between SAC solder balls and Cu-Zn alloy pads, and Cu pads were also used as a reference. Sn-4.0Ag-0.5 Cu solder balls were used and the substrates were Cu and 80 wt% Cu-20 wt% Zn pads which were defined...
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