Journal ArticleDOI
Lead-free Solders in Microelectronics
Mulugeta Abtew,Guna S Selvaduray +1 more
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TLDR
The most widely used Pb-free solders have the eutectic composition as mentioned in this paper, which has been identified as a major factor affecting alloy selection, since this will have a major impact on the other polymeric materials used in microelectronic assembly and encapsulation.Abstract:
Practically all microelectronic assemblies in use today utilize Pb–Sn solders for interconnection. With the advent of chip scale packaging technologies, the usage of solder connections has increased. The most widely used Pb–Sn solder has the eutectic composition. Emerging environmental regulations worldwide, most notably in Europe and Japan, have targeted the elimination of Pb usage in electronic assemblies, due to the inherent toxicity of Pb. This has made the search for suitable “Pb-free” solders an important issue for microelectronics assembly. Approximately 70 Pb-free solder alloy compositions have been proposed thus far. There is a general lack of engineering information, and there is also significant disparity in the information available on these alloys. The issues involved can be divided into two broad categories: manufacturing and reliability/performance. A major factor affecting alloy selection is the melting point of the alloy, since this will have a major impact on the other polymeric materials used in microelectronic assembly and encapsulation. Other important manufacturing issues are cost, availability, and wetting characteristics. Reliability related properties include mechanical strength, fatigue resistance, coefficient of thermal expansion and intermetallic compound formation. The data available in the open literature have been reviewed and are summarized in this paper. Where data were not available, such as for corrosion and oxidation resistance, chemical thermodynamics was used to develop this information. While a formal alloy selection decision analysis methodology has not been developed, less formal approaches indicate that Sn-rich alloys will be the Pb-free solder alloys of choice, with three to four alloys being identified for each of the different applications. Research on this topic continues at the present time at a vigorous pace, in view of the imminence of the issue.read more
Citations
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Journal ArticleDOI
Effect of cooling rate on the room-temperature impression: creep of lead-free Sn–9Zn and Sn–8Zn–3Bi solders
TL;DR: In this paper, the influence of cooling rate on the creep behavior of Sn-9%Zn and Sn-8% Zn-3%Bi solder alloys was studied by impression testing.
Journal ArticleDOI
Growth of intermetallic compounds in the Sn-9Zn/Cu joint
C. S. Lee,Fuh-Sheng Shieu +1 more
TL;DR: In this article, the authors studied the microstructure of the Sn-9Zn/Cu joint in soldering at temperatures ranging from 230°C to 270°C, and showed that the growth of the mechanism of intermetallic compound (IMC) formation is controlled by ripening.
Journal ArticleDOI
Fabrication of Sn-Ag/CeO 2 Electro-Composite Solder by Pulse Electrodeposition
TL;DR: In this article, the SnAg/CeO2 nanocomposite solders have been pulse electrodeposited from an aqueous citrate bath containing varying concentrations of CeO2 nanopowders (1 to 30 g/L).
Journal ArticleDOI
Complex eutectic growth and Bi precipitation in ternary Sn-Bi-Cu and Sn-Bi-Ag alloys
TL;DR: In this paper, the eutectic growth and precipitation of Bi within the β-Sn dendritic matrix have been characterized with emphasis on both eUTectic growing and precipitation.
Journal ArticleDOI
Fracture mechanism and strength-influencing factors of Cu/Sn-4Ag solder joints aged for different times
Qingke Zhang,Z.F. Zhang +1 more
TL;DR: In this article, the tensile properties and fracture mechanisms of Cu/Sn-4Ag solder joints aged at 180°C for different times were investigated at the strain rates of 1.25−×−10−4−s−1 and 1.5−×-10−1−s −1, respectively.
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