液态Sn-Cu钎料的黏滞性与润湿行为研究

Viscosities and wetting behaviors of Sn-Cu solders

金属熔体的黏度和表面张力都是与液态结构相关的敏感物理性质,且存在一定的相互关系.对于微电子封装材料而言,黏度和表面张力均是影响其工艺性能的重要参量.本文利用回转振动式高温熔体黏度仪测量了Sn-xCu(x=0.7,1.5,2)钎料熔体在不同温度下的黏度值,发现在一定温度范围内钎料熔体的黏度值存在突变,可划分为低温区和高温区.在各温区内,黏温关系很好地符合Arrhenius方程,在此基础上讨论了液态钎料的结构特征和演变规律.同时,利用黏度值计算了液态Sn-xCu钎料在相应温度下的表面张力,并通过Sn-xCu钎料在Cu基板上的润湿铺展实验对计算结果进行验证.结果显示,润湿角和扩展率的测试结果与表面张力的计算结果具有很好的一致性,表明通过熔体黏度值来计算锡基二元无铅钎料合金表面张力并评估其润湿性能的方法是可行的.

The viscosity and surface tension of metal melt are all sensitive physical properties that relate to the liquid structure and also have a certain correlation between them. For electronic packaging materials, both viscosities and surface tensions are very important parameters affecting the processing properties. In this study, the viscosities of Sn-xCu （x = 0.7, 1.5, 2） solder melts are measured by using a torsional oscillation high-temperature viscometer. Abrupt change in viscosity occurrs in a certain range of temperature. The temperature range can accordingly be divided into a low temperature zone and a high temperature zone. The relationship between viscosity and temperature can fit to the Arrhenius equation very well in each temperature zone. The structure characteristics and evolutions of the liquid solders are then discussed. Meanwhile, the surface tensions of the Sn-xCu solders are calculated according to the viscosity values at the corresponding temperatures. The test results of the wetting angle and the spreading rate are in good agreement with the calculations, indicating that the method of using the viscosity values to calculate the surface tensions of binary lead-free solder alloys and evaluate their wettabilities is feasible.