电镀铜薄膜疲劳性能与寿命预测

Tension-tension Fatigue Properties and Life Prediction of Electroplated Copper Films

利用MMT-11N微机械疲劳试验系统对11.5μm厚无基体支持的电镀铜薄膜试件的拉伸疲劳特性进行了试验研究。试件采用准LIGA工艺制作。试验在室温条件下进行,采用载荷控制、脉动循环加载,载荷频率为20Hz,得到了铜薄膜光滑试件和缺口试件的S-N曲线,根据传统宏观疲劳理论确定了铜薄膜循环应力—应变曲线和应变—寿命曲线。利用修正局部应力—应变法对缺口试件的疲劳寿命进行了预测,预测寿命与试验寿命误差在3.2倍因子之内,预测结果较好地符合试验结果。试验表明,取半寿命周期的迟滞回线作为稳定迟滞回线在微机械疲劳中仍是可信的,局部应力—应变法亦可应用于微机电系统疲劳寿命预测,宏观疲劳理论在一定程度上也适合于描述微机械疲劳。

Tensile fatigue properties of notched and smooth specimens for free-standing electroplated copper films with 11.5 lain thickness are studied. The tests are completed by using MMT-11N micro mechanical fatigue testing system. The specimens are fabricated with LIGA-like technology. The tests are carried out at room temperature under tension-tension cyclic loading with 20 Hz load frequency. S-N curve, cyclic σ-N curve and ε-N curve are obtained. Based on the modified local stress-strain approach, fatigue lives of notched specimens are predicted. The results agree well with the experimental fatigue lives. It proves that the hysteresis loop on half of the life cycle can be still used as stable hysteresis loop in micro mechanical fatigue, and the local stress-strain approach can be applied in life prediction of MEMS fatigue, thus the traditional fatigue research methods are also suitable for description of MEMS fatigue in a certain extent.