| 摘要 |
<p>A lead-free solder material, which is a Sn-Ag binary alloy comprising Al incorporated therein and thereby having a fine structure induced, through simultaneous and many engined crystal formation, by a coagulation accompanied with heterogeneous nucleation. A first embodiment, wherein 0.1 to 5 wt % of Ag is incorporated into an alloy containing 0.1 to 5 wt % of Al and the balanced amount of Sn; a second embodiment, which further contains 0.1 to 3 wt % of Cu, and 40 to 60 wt % of Bi or 40 to 50 wt % of In, in addition to the first embodiment; and a third embodiment which further contains, in addition to the first embodiment, 0.1 to 5 wt % of Cu and 0.1 to 5 wt % of one or more elements selected from among In, Bi, Ni, Au, Sb, Zn, Mg, La and Ce. In the structure of Fig 1 (a) according to the invention, it is observed that fine primary β-Sn crystals are formed and gaps between them are filled by a fine eutectic crystalline structure, whereas, in the structure of Fig 1 (b) or (c) of an comparative example containing no Al, rough primary β-Sn crystals account for the major part of the visual field. The lead-free solder material allows the formation of a fine primary β-Sn crystals, which results in the formation of a fine coagulated structure being independent of the cooling rate during implementation and the reduction in the amount of Ag used.</p> |
