On A Reliability Evaluation Method for Electronic Devices Considering Thermal Stress Generated by the Manufacturing Process Based on Super Imposed Method

塑料薄膜上的微电子电路被认为是未来的信息通信设备之一。为了实现这一目标，本研究的目的是建立一种多尺度的数值分析和实验方法来测量薄膜的机械性能与制造过程中产生的残余应力，器件的可靠性评估的一个重要点是了解在施加载荷下作用在结构上的应力状态和损伤模式的机理。研制了一种新的激光显微镜疲劳试验装置。本文通过静态试验和疲劳试验，对电器基板用塑料薄膜-机织物复合材料在载荷作用下的损伤发展机理进行了原位观察，针对疲劳试验结果分散性大的问题，提出了用统计方法确定疲劳强度的设计方法。设计裕度可以由失效概率和置信水平决定，并考虑小样本的影响。该方法可以确定具有裕度的应力水平。在此基础上，发展了一种多尺度数值方法--叠加法，用于分析考虑热应力影响的局部应力状态和整体变形行为。与传统方法相比，该方法在精度和计算量方面具有上级的特点.结果表明，所提出的数值和实验方法是非常有用的电子器件的可靠性和寿命评估。

A micro-electronic circuit on a plastic film has been expected as one of the future information-communication devices. In order to realize, the aims of this study are to establish a multi-scale numerical analysis and an experimental method for the measurement of the mechanical properties of the film with the residual stress generated by the manufacturing process.An important point for evaluation of reliability of the devices is to comprehend the stress state acted on the structure under applied load and the mechanism of the damage mode. New fatigue testing apparatus to detect the damage using a laser microscope had been developed. The mechanism of damage development of the plastic film and woven fabric composites for the substrate of the electric devices under load had been investigated with In-situ observation during the static test and fatigue test.Since the experimental results of fatigue test show large scatter, the statistical method was proposed in order to decide the fatigue strength for design. The design margin can be decided by the probability of failure and confidence level considering an effect of small samples. The stress level with a margin can be decided by the proposed method. Furthermore, the super impose method, which is one of the multi-scale numerical methods, had been developed in order to analyze the local stress conditions and behavior of the global deformation considering an effect of the thermal stress. The proposed procedure has superior properties about accuracy and computational cost than the traditional method. It is revealed that the proposed numerical and experimental methods are very useful for the reliability and lifetime evaluations for the electronic devices.