| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 93 === In electronic packaging industry, it’s an important issue to estimate the reliability of the package. The strength of solder joint can influence the performance of products effectively. While the adhesive strength is not strong enough, the delamination may occur due to the severe temperature change or external load on the interface, which results in decreasing the reliability of the products. The study uses the concept of fracture mechanics and numerical simulation method to estimate the stress intensity factor and strain energy density factor around the crack tip due to the failure of reflow.
The simulation includes two types of model, PBGA assembly and PBGA chip-scale package. Two kinds of material, lead-free solder and lead solder, are used to make the comparison. Since lead solder would cause the damage to the human body and the environmental pollution, lead-free solder becomes the trend in the future. The theory of viscoplasticity is applied to analyze the tendency of stress intensity factor and the difference of the life-cycle between the above models is discussed in detail.
In conclusion, while the crack occurs at the interface of solder ball, the stress intensity factor of lead-free solder is higher. But, the strain energy density factor of lead–free solder joint is found to increase monotonously as increasing of thermal cycles. Furthermore, the crack of PBGA assembly would make the fracture become worse.
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