| The Sn-Pb solder with low melting point, high strength and good technics is the source of electronic industrial production. It contains mainly Sn, Pb and little other metal elements. Among them, Pb is toxic and harmful to people's health if contacting it long term. With the strengthen of people's consciousness for protecting the environment, the voice of forbidden the usage of solder containing Pb element is higher and higher. The main countries in the world have enacted laws to restrict or forbid the use of solder containing Pb. So it has practical significance to research the Pb-free solder for replacing the conventional Sn-Pb solder in the 21th century. The research of Pb-free solder has become a focus in soldering industry from the 1990's. There are many alloys system have been exploited so far, mainly including Sn-Ag, Sn-Cu, Sn-Bi, Sn-Zn binary system and Sn-Ag-Cu, Sn-Ag-Bi, Sn-Zn-Bi, Sn-Zn-Ag ternary system. Among them, the Sn-Zn system Pb-free solder is a kind of new alloy system developed in recent years, and has the merit of enough source, low price, near melting temperature compared with Sn-Pb eutectic solder, so has been regarded as an important alloy system to replace the Sn-Pb solder. Due to it has some natural shortcomings such as poor soldering technics, low resistance to corrosion and oxidation for its joint, little research has carried through at home and abroad. So the paper aims at Sn-Zn alloy system, studies many performance of it and the influence of adding other metal elements. The test result indicates that the Sn-Zn eutectic alloy has good characteristics in general compared with other componential alloys. The Sn-Zn eutectic structure consists of alternating Sn-rich and needle shape Zn rich phase, and its wettability is poor, mechanical properties is good compared with Sn-Pb solder. With adding appropriate amount of Bi, the melting temperature of the Sn-Zn system declines,... |
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