| Summary: | 碩士 === 國立成功大學 === 工程科學系碩博士班 === 95 === In order to find stress-strain-damage behavior of solder ball by using solder joint specimen, this thesis defined, at first, the stiffness of material testing system, whose value could be determined from the slope of linear range of loading or unloading of the load-displacement hysteresis loop. Within this range, the solder joints behaved linear elastic with Young’s modulus and shear modulus of bulk material. As a result, the (elastic) stiffness of solder joint specimen under proportional displacement path (Φ) could be determined. Employing the series combination of spring for material testing system, the stiffness of grips could be calculated, whose value was fixed under its corresponding proportional displacement path. Consequently, the load-displacement hysteresis loop of solder joint specimen could be constructed.
In this paper, isothermal undamage simple shear test data of solder joint specimen having 9 Sn/3.5Ag/0.75Cu balls were used as a base to determine the kernel function of endochronic viscoplasticity and the material function in the intrinsic time measure whose values were increased from Φ=90° to 0° but decreased as increased of the effective inelastic strain amplitude. Based on these, the isotropic endochronic viscoplasticity with cyclic damage under various proportional displacement path was used to compute load-displacement hysteresis loops. The computational results were in excellent agreement with data. According to Lee’s evolution equation of cyclic damage and the small increase in effective inelastic strain amplitude with increasing cyclic number, the relationship between damage factor D and the cyclic number N could be derived: , here was increased both from Φ=90° to 0° and the increase of effective inelastic strain amplitude. But the trend of was reversed. Usage of data of D vs. N curves and load-displacement hysteresis loops of various Φ, critical values of damage factor could be determined, 0.4<Dc<0.5 and its value was indepent of Φ.
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