銲錫在電子產品中被拿來廣泛使用，且因為用來當作接點其失效將嚴重影響電子產品壽命，在環保意識抬頭下，使用無鉛銲錫來取代錫鉛銲錫成為國際間的主流。但因無鉛銲錫是可靠度並未完成建立，故其可靠度為一重要研究課題，本文以銲錫受到潛變及循環負載下作為研究重點，本文將重點放在錫銀銲錫Sn2.4Ag合金之潛變及循環負載行為。
本論文主旨在建構一具有移動硬化效應之錫銀Sn2.4Ag合金黏塑性材料本構模型。利用狀態變數來描述微結構變化並做為建構黏塑型模型之主軸，以背應力當成狀態變數，藉以讓模型具有移動硬化效應。配合錫銀Sn2.4Ag之潛變實驗及定應變率實驗在各種溫度實驗結果之曲線擬合。並且利用此黏塑性本構模型來模擬數種循環負載下與最廣泛使用之Anand黏塑性本構模型作為比較。
比對結果可發現，錫銀銲錫Sn2.4Ag 具有強烈的移動硬化效應，故本文建構之黏塑性模型比起等向性硬化的Anand黏塑性本構模型更能表現出材料實際之非線型潛變行為。

Solder is used extensively in electronic devices for electrical interconnection. As a result of the drive for environmental protection, the toxic lead-bearing solder is being replaced with lead-free solder. A critical issue of the lead-free conversion is that reliability information of electronic components and systems using lead-free solder is scarce due to the limited experiences with these new alloys. Under typical temperature cycling conditions, thermomechanical stress-induced solder fatigue cracking is the dominant failure mode in electronic systems. In order to accurately model solder damage under the cyclic loading condition, it is important to characterize the inelastic behavior of solder under cyclic loading condition.
In this research the viscoplastic behavior of Sn2.4Ag is considered by using a state variable approach. The most popular viscoplastic model used for considering solder constitutive behavior is the Anand model. The main drawback of the Anand model is that only the isotropic hardening effect is considered, but not the kinematic hardening. In order to overcome this issue, a Chaboche viscoplastic model that considers the kinematic hardening behavior is applied to model the Sn2.4Ag constitutive behavior. The model constants are determined from curve fitting constant strain rate and creep experimental results. A numerical model based on the Chaboche model is applied to simulate several load histories and compared to experimental results and other numerical results obtained from Anand model. It is observed that the Chaboche model could properly describe the transient creep response when the applied load jumps or reverses.

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