On Correlation Between Melt Structural States Of SnAg(Cu) Solders And Their So Lidification & Wettability

It has become an inevitable trend at home and abroad that lead-free solders were used in electronics, information and other fields. But research on lead-free solders mainly concentrated in component selection, as well as the effect of trace element on various properties. Preparation conditions of lead-free solders were less concerned about. While liquid-solid hereditary about structure had long been noted in material production and research practice.As the breakthrough point, TI-LLST was focused on the relevance of SnAg(Cu) melt structure with solidification structure and wettability. The main contents, achievement and innovation were summarized as follows:Temperature dependence of electrical resistivities of liquid Sn-Ag (Cu) lead-free alloys with different components was surveyed by the resistivity experiments. Different characteristics and patterns of abnormal changes along with various alloys were found onρ-T curves. And the changes indicated that there were reversible and irreversible structural transition in alloy melts, reversible one was related with the chemical short-range order, and irreversible one with topological short-range order.Refined eutectic solidification structure might result from irreversible post-transition melt. This might be due to smaller clusters hindering nucleation in the melt, resulting in lower supercooling degree and higher nucleation rate.The solder obtained from irreversible post-transition melt had advantages in brazing over conventional prepared solders, rapid spreading, thin and leveled IMC layer, as well as insensitivity of the layer to brazing temperature and time. These advantages might be owing to that faster melting, lower melt viscosity of new solder that favorable for spreading, and smaller size of the clusters lead to slower growth of compound layer.Perspection from melt structure to explore a new preparation process of lead-free solder is obvious technological innovation. This breakthrough point is more conducive to search for its intrinsic physical nature...