应力和应力梯度对锡镀层晶须生长影响的临界评价
Critical Evaluation of Relative Importance of Stress and Stress Gradient in Whisker Growth in Tin Coatings
摘要：
在这里，我们研究的作用，应力状态和应力梯度的晶须生长锡镀层电沉积在黄铜。Sn涂层中的体应力使用基于激光光学的曲率设置进行测量，而掠射角X射线衍射被用来量化的表面应力，这也允许研究的晶须生长的面外应力梯度的作用。Sn涂层中的体应力和表面应力都随着时间的推移而演变，其中两者在沉积后立即是压缩的，并且此后当体应力单调地变得更压缩并且随后随着室温下的老化而饱和时，Sn涂层的表面附近的应力随着老化而不断地变得更拉伸。这些相反的体应力和表面应力的演变行为很容易建立一个负的平面外应力梯度，所需的自发生长的晶须。面外应力梯度的重要性也被验证通过外部施加广泛不同的应力状态和应力梯度的Sn涂层使用3点弯曲装置。结果表明，在外加拉伸应力作用下，晶须在涂层中生长较多，但负面外应力梯度较高。结果最终表明，与仅自然（即，应力的符号和大小）。
英文摘要：
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.
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