| 摘要 |
PURPOSE: A Sn-Zn based unleaded solder with reduced oxidation of zinc is provided to manufacture unleaded solder capable of preventing zinc oxidation, a demerit of Sn-Zn based alloy as containing a large amount of inexpensive Zn in Sn, during casting and soldering to reduce production cost of solder. CONSTITUTION: The Sn-Zn based unleaded solder comprises 75.2 to 89.5 wt.% of Sn, 10 to 20 wt.% of Zn, 0.2 to 2 wt.% of In, 0.1 to 2 wt.% of Sb, 0.1 to 0.8 wt.% of Bi and 0.1 to 1.0 wt.% of master alloy of Cu-P, wherein loss of In is increased since oxidation of In is promoted as the addition amount of In is being increased although In is added to Sn-Zn based alloy to improve fusion point and wettability, content of In is limited to 2 wt.% or less considering demerit that an inert atmosphere is required, and In is expensive, it is possible to obtain increasing effect of solder speed by limiting the maximum addition amount of Sb to 2 wt.%, thereby narrowing the temperature range of solid-liquid coexistence to shorten solidification time during soldering as minimizing the production amount of Sb3Zn since intermetallic compound with Zn is inevitable although the temperature range of solid-liquid coexistence is narrowed when Sb is added to the Sn-Zn based alloy, the maximum addition amount of Bi is limited to 0.8 wt.% since 1 wt.% or more of Bi widens the temperature range of solid-liquid coexistence of Sn-Zn based solder although fusion point of the solder is lowered when Bi is added to the Sn-Zn based solder, content of P in the master alloy is set to 10 wt.% since P is lost due to severe vaporization of P, and it is impossible to manufacture an alloy to which P of a target composition is added, and the amount of the master alloy of Cu-P added to the Sn-Zn based solder is limited to the maximum 1 wt.% to avoid that 1% or more Cu is added for the total Sn-Zn based solder alloy amount since increase of fusion point of the Sn-Zn based solder is critically influenced by increase of Cu.
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