The growth of eutectic colonies in Sn–Cu, Sn–Zn and Sn–Ag–Cu eutectic alloys has already been reported in the literature. However, relationships between this kind of microstructure and mechanical properties remain undetermined for solders. The use of water-cooled copper (Cu) and AISI 1020 low-C steel molds and the eutectic Sn-9 wt.%Zn alloy make it possible to address this matter. The samples grown in the Cu mold demonstrated higher solidification rates than those developed in the low-C steel mold. Overall, the microstructure is constituted by Zn-lamellae embedded in a Sn-rich matrix. The Zn lamellae are not only uneven in thickness but also irregularly perforated. Due to Cu dissolution into the alloy, a small fraction of Cu₅Zn₈ intermetallic particles formed during solidification of the Sn-9 wt.%Zn alloy in the Cu mold. The contamination with Cu appears to be responsible for the improvement in the distribution of Zn-lamellae. The decrease in spacing between broken lamellae measured from SEM images, as well as a higher number of Zn particles per area, explain such occurrence. Ductility and tensile strength of different samples could allow the establishment of relationships among properties vs. eutectic colony spacing. For the Cu mold, the motion of Cu towards the alloy as well as higher solidification rates, allowed microstructures to be formed combining 60% of strain to fracture and 52 MPa of ultimate tensile strength. These achievements are mainly due to the finest spacings of both the eutectic colony (λχ = 36 μm) and the Zn lamellae (λ_L=0.9 μm), besides homogeneous distribution of Cu across the resulting microstructure.

Sn-Cu，Sn-Zn和Sn-Ag-Cu共晶合金中共晶菌落的生长已有文献报道。但是，对于焊料，这种微观结构和机械性能之间的关系仍然不确定。使用水冷铜（Cu）和AISI 1020低碳钢模具以及低共熔Sn-9 wt。％Zn合金可以解决此问题。与低碳钢模具相比，在铜模具中生长的样品具有更高的凝固速率。总体而言，微观结构由嵌入富Sn的基质中的Zn薄片构成。锌薄片不仅厚度不均匀，而且不规则地穿孔。由于铜溶解到合金中，所以一小部分的Cu ₅ Zn ₈在Cu模具中凝固Sn-9 wt。％Zn合金过程中形成的金属间化合物颗粒。铜的污染似乎是造成锌薄片分布改善的原因。由SEM图像测得的断裂薄片之间的间距减小，以及每面积Zn颗粒数量增加，可以解释这种情况。延展性和不同样品的抗张强度可能允许属性之间建立关系的对比共晶菌落间距。对于铜模具，铜向合金的运动以及较高的凝固速率，使得结合形成60％的微结构成为可能断裂应变和52 MPa的极限抗拉强度。这些成就，主要是由于两者共晶菌落（λχ= 36μm）和锌薄片（的最好的间距λ_大号= 0。 9微米），除了在整个所得微铜的均匀分布。