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

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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.