評估電子構裝可靠度，為電子構裝產業之重要課題，其中負責電性連結之錫球強度，對產品的好壞具有決定性之影響力。若焊錫界面黏著強度不足，在遭受溫度或外力負載時所發生之脫層破壞，將嚴重影響構裝體之可靠度。本研究引用破壞力學觀念，以數值模擬方法，評估構裝中焊墊與錫球間因迴焊缺失所形成之裂縫，當受到溫度循環作用時，裂縫尖端應力強度因子及應變能密度因子之變化趨勢。
本模擬在封裝尺寸上，分別採用傳統塑性球柵陣列之大型封膠構裝，並與晶片級尺寸之塑性球柵陣列小型封膠構裝模型做比較。另外在錫球材料方面，傳統上所使用之含鉛錫球中鉛的成分，會對環境及人體健康造成危害，各先進國家莫不積極尋找無鉛之替代性材料。因此本文在兩種尺寸之構裝模型上，分別採用含鉛材料及未來勢必使用之無鉛材料錫球，以黏塑性質理論加以分析，比較各裂縫應力強度因子之趨勢變化，以探討上述模型存有裂縫時之壽命差異。
經研究後發現，當錫球含有介面裂縫時，銲錫採用無鉛合金之應力強度因子，較含鉛合金材料為高。但隨循環次數的變化趨勢而言，含鉛材料之應變能密度因子斜率較大，上升較快。另外，在封裝尺寸上，大封膠構裝模型之裂縫所造成的破壞情形較為嚴重。

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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