Papers by Author: Yan Fu Yan

Abstract: Zn20Sn6Cu solder with the melting point of 382°C has good mechanical properties and low cost. Therefore it is considered as an ideal high-temperature lead-free solder. However, its physical properties and spreading properties are poor. In this paper a new solder was made by adding trace LaNd into Zn20Sn6Cu alloy to improve the performance. The effect of the content of LaNd on physical properties and weld ability of Zn20Sn6Cu solder was investigated. The experimental results showed that the effect of the content of LaNd on the melting point of Zn20Sn6Cu solder was not obvious and the liquid-solid temperature range of the Zn20Sn6Cu solder increased with the increasing of the content of LaNd (less than 0.5 wt.%). When RE content was 0.1 wt.%, the liquid-solid temperature range of Zn20Sn6Cu0.1RE was only 13.3°C. The resistivity of the novel solders increased with the increasing of the content of LaNd. When LaNd is higher than 0.3 wt%, the resistivity of the novel solder sharply increased. The spreading performance of the new solder alloy was improved obviously by adding trace LaNd into Zn20Sn6Cu solder. When the content of LaNd was 0.1 wt%, the spreading area of Zn20Sn6Cu0.1LaNd solder reached to the maximum value of 32.5% bigger than that of the matrix solder, which mainly related to the formation of the new CuZn₅ and Cu₅Zn₈ phases as well as the intermetallic compounds between the solder and the substrate. Therefore, considering the physical properties and spreading properties of the novel solders, the best content of LaNd is about 0.1 wt.%.

Abstract: Bi5Sb8Sn solder alloy is the most promising alternative to existing high-Pb solder as high-temperature lead-free soft solder alloy series whose melting point is about 264°C and have better conductivity and mechanical properties, but its wettability need to be improved. In this paper a novel Bi5Sb8SnLaNd quaternary alloy have been developed by adding a small amount of mixed rare earth LaNd elements into Bi5Sb8Sn solder alloy to improve the technological properties of Bi5Sb8Sn alloys. The experimental results showed that adding 0.1～0.3wt.% LaNd into Bi5Sb8Sn solder alloy made the melting point changed slightly, but resulted in the wettability of the solder alloy significant improvement. Compared with the matrix of Bi5Sb8Sn, the spreading area of solder alloy was about 20% bigger when the content of LaNd is 0.1wt.%. With increasing the content of rare earth LaNd, the spreading area of solder alloy decreased, but it was still higher than that of the matrix of Bi5Sb8Sn. This may be mainly attributed to the formation of new phases with rare earth and the thickness of the substrate intermetallic compounds in the Bi5Sb8Sn solder alloy.

Abstract: By alloying principle, a novel quaternary high-temperature lead-free solder was formed by adding trace Sn into Bi5Sb2Cu. The influences of trace Sn on the microstructure and mechanical properties of the novel solder alloy were systematically investigated. Results show that the new phases â-SnSb and mesh Sb2Sn3 are formed and dispersed in the novel solder, whose dispersion strengthening make the tensile strength and shear strength of the new solder alloy increase. When Sn is less than 8 wt%, the tensile strength and the shear strength of the new solder increase with the increasing of content of Sn. When Sn is 8wt%, the tensile strength and shear strength is respectively 52.79MPa and 17.00MPa, which is respectively improved about 90.6% and 64 wt.% compared to the matrix solder. When Sn is 10wt.%, the mechanical properties of the solder take a decrease trend, but they are still better than those of the matrix solder.

Abstract: The effects of Ni on the properties of the Sn-2.5Ag-0.7Cu-0.1Re solder alloy and its creep properties of solder joints are researched. The results show that with adding 0.05wt% Ni in the Sn-2.5Ag-0.7Cu-0.1Re solder alloy, the elongation can be sharply improved without decreasing its tensile strength and it is 1.4 times higher than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. Accordingly the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints is the longest, which is 13.3 times longer than that of Sn-2.5Ag-0.7Cu-0.1Re and is also longer than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. In the same environmental conditions, the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints can sharply decrease with increasing the temperature and stress.

Abstract: Particle-enhanced is the way to improve properties of solder alloys. In the present work, the influence of Ag particle-enhanced on the wettability and creep rupture life of 99.3Sn0.7Cu eutectic solder with Ag content of 1vol% to 10vol% were investigated. It was indicated that the wettability of the composite solders could be improved by adding minute amount of Ag particles. With increasing the amount of Ag particles, the spreading areas of the composite solders increased when Ag was below 5vol%. When Ag was above 5vol%, the spreading areas started decreasing. When Ag content was up to 10vol%, the wettability of the composite solder sharply deteriorated. In addition, the creep rupture lives of the composite solders were longer than that of 99.3Sn0.7Cu eutectic solder at the same condition. When Ag content was 5vol%, the creep rupture life of the composite solder was the longest among the investigated composite solders and about 23 times of that of 99.3Sn0.7Cu eutectic solder.

Abstract: It is a difficult subject to develop the high temperature solder with thewhose melting point is within 250～450°C in solder field. Bi5Sb solder alloy whosewith the melting point of about is about 280°C is limited for itshas bad solderability and mechanical properties. In the present work, the new BiSbCu ternary alloy wasis preparformed by adding different contents of Cu to Bi5Sb solder alloy to improve its solderability and mechanical properties. Results showed that the effect of adding 0.5～5.0％Cu into Bi-5Sb on the melting point of Bi5Sb solder alloy wais not distinct , but its solderability and mechanical properties weare markedly improved. Compared to the matrix of Bi5Sb, the spreading area of solder alloy wais about 57.8% largbigger and the tensile strength wais about 212.4% highbigger when the content of Cu wais 1.5wt.%. Analysis of tThe microstructure showeds that the needle-like Cu2Sb gradually becaomes shorter and dense along with the increasing of the content of Cu, which can effectaffected the properties of the solder alloy.