【作者】 白宁；

【导师】 陈旭；

【作者基本信息】 天津大学 ， 化工过程机械， 2008， 博士

【摘要】 随着环保呼声的高涨和越来越多禁止在电子产品中使用含铅钎料的法案的出台,无铅钎料在微电子封装工业中全面代替有铅钎料已经是大势所趋。焊点的可靠性对整个集成电路封装的可靠性甚至电路本身性能的可靠性都有着重要的意义。然而在当前,由于无铅钎料本身还处于发展的初期,学术界对无铅钎料进行的力学性能研究相对匮乏。在这种背景下,对无铅钎料的力学性能进行全面的试验和理论研究是很有必要的。本文选用Sn-0.7Cu和Sn-3Ag-0.5Cu两种目前使用最广泛,也是最具发展前景的无铅钎料作为研究对象。使用实验室自主研发的能够进行小型试件多轴复杂加载试验的微型材料试验机,对上述两种钎料进行了多种温度和应变率下的单轴拉伸、蠕变、应变率跳跃、应力跳跃等简单试验,以及单轴棘轮,循环扭转,多轴棘轮,多轴复杂路径加载等复杂的循环本构试验。用Anand、Bodner-Partom、SVBO、McDowell等四种本构模型对两种试验材料的单轴拉伸曲线进行了模拟,在此基础上讨论了这几种模型对无铅焊锡钎料的适用性。在若干组不同温度和应变率的单轴拉伸试验现象的基础上,用饱和应力归一化的概念将不同条件下的单轴拉伸试验曲线统一了起来,提出了无背应力概念的统一型本构模型——模型I。发现单轴棘轮试验曲线加载卸载段的不对称性,现有的四种本构模型以及模型I都无法解释这种现象。在模型I的基础上提出了有背应力概念的统一型本构模型——模型II。该模型采用类似于McDowell模型的两个背应力分量,并对其中的短程背应力引入了类似于“屈服面”的“加载面”概念。这一模型成功地模拟了棘轮试验中滞环的不对称现象,并对复杂路径加载等试验作出了成功的模拟,同时又保持了模型I预测简单试验的良好功能。更多还原

【Abstract】 In electronic packaging industry, with the rising of environment protection requirement and the appearance of more and more laws forbidding the use of lead-containing solder, it is a trend to replace the traditional lead-containing solder by lead-free solder. The reliability of solder joint greatly affects the reliability of IC packaging, even the performance of the circuit. However, because the lead-free solder is in its early stage of development, the research on mechanical properties of lead-free solders is relatively simple and little. Due to the situation mentioned above, it is necessary to perform experimental and theoretical research on mechanical properties of lead-free solders.Two types of lead-free solders, Sn-0.7Cu and Sn-3Ag-0.5Cu, which will be potential solders to be widely used in electronic packaging, are studied. Uniaxial tensile test, creep test, strain rate jump test, stress jump test, and complicated tests, such as uniaxial ratcheting test, uniaxial cyclic torsional test, multiaxial ratcheting test, multiaxial test with complex path, were conducted on the two types of lead-free solders under several conditions with different strain rates and temperatures. All the tests were carried out on a minitype tension-torsional testing machine, developed by ourself, which can provide complex loading tests on mini specimen.Anand model, Bodner-Partom model, SVBO model and McDowell model were adopted to simulate the uniaxial tensile tests of the lead-free solders, the applicability of the four models to lead-free solders were discussed based on the simulation results. Based on several uniaxial tensile tests with different strain rates and temperatures, the stress and strain were mormalized by saturation stress. The uniaxial tensile test curves showed unified stress-strain curves for all the tests. A unified constitutive model without back stress concept, model I was constructed.Loading/unloading asymmetry, which could not be explained by the four discussed models and model I, was observed in uniaxial ratcheting tests. A new unified model with back stress concept, model II was proposed. Two back stress components were employed by model II, just like the case of McDowell model. In addition, model II introduced a concept of“loading surface”similar with“yield surface”. The model simulated the loading/unloading asymmetry phenomenon in uniaxial ratcheting tests successfully and presented good predictions to complex loading path tests. Model II kept the ability of model I to simulate uniaxial tensile tests.更多还原