熔融Sn-3.0Ag-0.5Cu在倾斜铜基板上表面形貌的模拟

通过润湿性实验,借助有限元软件Surface Evolver模拟研究了在490 K温度下熔融态的无铅焊料Sn-3.0Ag-0.5Cu在倾斜铜基板上的铺展行为及界面特性.根据经验方程拟合熔滴侧面轮廓曲线并获得三相点处的接触角大小.经计算发现,在基板的倾斜角度较小时,三相接触线几乎不发生移动,三相接触线的后三相点沿基板向前移动,前三相点保持不动,相应地,前进角逐渐增大并达到最大值.随着基板倾斜角度的继续增大,前三相点开始向前移动,导致前进角逐渐减小,最终熔滴从基板上滑落.通过模拟铺展过程表征了接触角的滞后现象;通过SEM及EDS手段分析界面微观结构,说明了在润湿过程中发生了界面化学反应,确定了金属间化合物Cu6Sn5生成并呈扇贝形分布.

Simulation analysis on the surface morphology of Sn-3.0Ag-0.5Cu melting on the inclined Cu substrate

To investigate interface properties of molten Sn-3.0Ag-0.5Cu solder melting on the inclined Cu substrate, numerical simulation is carried out by Surface Evolver at 490 K with wetting experiments. Profile curves of the droplets are fitted with empirical equation, which are proposed to obtain preferable contact angles. According to the experimental results, it is indicated that the contact line hardly moves at the very beginning and the rear point of triple line moves forward along the substrate subsequently, but the front point of triple line is still pinned on the substrate. Correspondingly,the advancing contact angle gradually increases to the peak value. When the inclined angle of the substrate continues to increase, the advancing contact angle decreases along with the front point of triple line moving forward, and finally the drop slides down from the substrate. In this paper, contact angle hysteresis is characterized by the numerical simulation. Furthermore, the interface microstructure is observed by means of SEM and EDS. It is illustrated that the interfacial chemical reaction happens in the wetting process which determines the formation of intermetallic Cu6Sn5 that distributes as the scallop shape.