Research on Strength Evaluation of Electronic Packages and Materials

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The research has been performed to develop methods for integrity assessment of electronic packages. The main results are summarized as follows :1. Methods have been developed and verified for evaluation of creep rupture strength of solder and fatigue strength against tension-compression, torsional and impact loadings. Also fatigue characteristics of copper have been successfully analyzed.2. Methods for nondestructive evaluation of mechanical properties and adhesive strength have been developed for thin films. Also fatigue characteristics of the thin films have been revealed based on developing a new testing method.3. Formation of a polymer injection weld and its effect on mechanical properties have been disclosed. Also internal stress which occurs in the curing process has been estimated analytically.4. Irradiation conditions of YAG laser have been found for the change in color of plastic IC package.5. A method has been developed to increase number of cycles to failure of flexible printed circuits.6. A new method for life design and testing has been proposed on the basis of the reliability engineering approach.7. A new method has been developed to evaluate accurately the delayed fracture behavior of an optical glass fiber, based on crack measurement.8. A numerical method for analyzing thermal stress of IC package has been developed. Also delamination and fracture caused. in mounting process of plastic LSI packages have been analyzed. Moreover, a method for evaluating the thermal fatigue life in microelectronic conductor and a model for the conductor failure due to stress migration have been proposed.9. Singular stress fields near a corner of jointed dissimilar materials have been analyzed.10. New techniques using infrared thermography and ultrasonics have been developed and verified for inspection of delamination.