Miner’s rule assumes that damage in solder interconnects accumulates linearly under cyclic loading and is independent of the load sequence. Under these constraints, damage is equivalent to cycle ratio, defined as the ratio of the applied cycles to the cycles to failure for the specific cyclic loading condition. Due to these inherent assumptions, Miner’s rule can inaccurately estimate solder interconnect life under sequential loading conditions. A nonlinear damage model with load-dependent damage exponents would take into account the effect of loading sequence under sequential loading conditions. In the nonlinear damage model, damage is related to cycle ratio using a power law relationship with a load-dependent damage exponent. This paper presents an experimental approach to determine the load-dependent exponents under three load levels. Load drop in the specimens, as a result of cyclic loading induced changes, is used as the criterion for the damage state. The tests consisted of a series of constant amplitude (standalone) and blocks of sequential variable amplitude cyclic shear tests in a thermo-mechanical micro-scale analyzer. The load-dependent damage exponents were developed for SAC305 (96.5%Sn + 3.0%Ag + 0.5Cu) solder. The result of the study can be used for SAC305 damage accumulation model formulation. Further, the experimental approach can be used to generate additional fatigue data under variable amplitude loads.

中文翻译：

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确定连续循环载荷下SnAgCu焊料损伤曲线的实验方法

迈纳定律假设，在周期性负载下，焊料互连中的损坏会线性累积，并且与负载顺序无关。在这些约束条件下，损坏等效于循环比率，定义为特定循环载荷条件下所应用的循环与失效循环之间的比率。由于这些固有的假设，Miner规则可能会不正确地估计连续加载条件下的焊料互连寿命。具有取决于载荷的损伤指数的非线性损伤模型将考虑顺序载荷条件下载荷顺序的影响。在非线性损伤模型中，使用幂律关系和与载荷相关的损伤指数来将损伤与循环比相关。本文提出了一种确定三种负荷水平下与负荷有关的指数的实验方法。由于周期性荷载引起的变化，试样的荷载下降被用作破坏状态的判据。这些测试由一系列恒定振幅（独立）和在热机械微型分析仪中进行的连续可变振幅循环剪切试验块组成。针对SAC305（96.5％Sn + 3.0％Ag + 0.5Cu）焊料开发了与负载有关的破坏指数。研究结果可用于SAC305损伤累积模型的制定。此外，实验方法可用于在可变振幅负载下生成其他疲劳数据。这些测试由一系列恒定振幅（独立）和在热机械微型分析仪中进行的连续可变振幅循环剪切试验块组成。针对SAC305（96.5％Sn + 3.0％Ag + 0.5Cu）焊料开发了与负载有关的破坏指数。研究结果可用于SAC305损伤累积模型的制定。此外，实验方法可用于在可变振幅负载下生成其他疲劳数据。这些测试由一系列恒定振幅（独立）和在热机械微型分析仪中进行的连续可变振幅循环剪切试验块组成。针对SAC305（96.5％Sn + 3.0％Ag + 0.5Cu）焊料开发了与负载有关的破坏指数。研究结果可用于SAC305损伤累积模型的制定。此外，实验方法可用于在可变振幅负载下生成其他疲劳数据。