论文标题
对压力和应力梯度在罐装涂层中的晶须生长中的相对重要性的批判性评估
Critical Evaluation of Relative Importance of Stress and Stress Gradient in Whisker Growth in Tin Coatings
论文作者
论文摘要
在这里，我们研究了应力状态和应激梯度在黄铜电沉积中晶须涂层中的作用。使用基于激光 - 透视的曲率设置测量了SN涂层中的大量应力，而瞥见角度X射线衍射来量化表面应力。这也允许研究平面外应力梯度在晶须生长中的作用。 SN涂层中的体积应力和表面应力随时间而演变，在沉积后立即压缩，然后单调的散装应力变得更加压缩，随后在室温下与衰老饱和，SN涂层表面附近的压力不断地变得更加拉伸。这些散装和表面应力的相反的进化行为很容易确定晶须自发生长所需的平面外应力梯度。面外应力梯度的重要性也通过使用3点弯曲设备在SN涂层中施加了广泛不同的应力状态和应力梯度来验证。始终观察到，在外部拉伸应力下涂料中的晶须生长更多，但是，平面外应力梯度较高。结果最终表明了平面外应力梯度在晶须生长上的关键作用，而仅与应力的性质（即符号和幅度）相比。
Here, we study the role of stress state and stress gradient in whisker growth in Sn coatings electrodeposited on brass. The bulk stress in Sn coatings was measured using a laser-optics based curvature setup, whereas glancing angle X-ray diffraction was employed to quantify the surface stress; this also allowed studying role of out-of-plane stress gradient in whisker growth. Both bulk stress and surface stress in Sn coating evolved with time, wherein both were compressive immediately after the deposition, and thereafter while the bulk stress monotonically became more compressive and subsequently saturated with aging at room temperature, the stress near the surface of the Sn coating continually became more tensile with aging. These opposing evolutionary behaviors of bulk and surface stresses readily established a negative out-of-plane stress gradient, required for spontaneous growth of whiskers. The importance of out-of-plane stress gradient was also validated by externally imposing widely different stress states and stress gradients in Sn coatings using a 3-point bending apparatus. It was consistently observed that whisker growth was more in the coatings under external tensile stress, however, with higher negative out-of-plane stress gradient. The results conclusively indicate the critical role of negative out-of-plane stress gradient on whisker growth, as compared to only the nature (i.e., sign and magnitude) of stress.
