本研究主旨在探討Sn-3.5Ag與Sn-3.5Ag-0.5Cu兩款電子構裝用無鉛銲錫之機械性質及潛變行為，並與目前工業上常用的Sn-37Pb銲錫做比較，以了解未來運用無鉛銲錫替代傳統含鉛銲錫之可行性。此外，亦利用掃描式電子顯微鏡(SEM)來觀察此兩款無鉛銲錫及傳統錫鉛銲錫之潛變破壞特徵。 實驗結果顯示，此兩款無鉛銲錫之抗拉強度及抗潛變能力在室溫及90oC之間皆會隨著溫度的提昇而降低。在室溫下，Sn-3.5Ag-0.5Cu合金有最高的抗拉強度，Sn-3.5Ag合金次之，Sn-37Pb合金最低。另外，在相同的測試溫度下，由於Sn-3.5Ag-0.5Cu合金有較Sn-3.5Ag合金均勻之共晶相及數量較多之介金屬顆粒，因此可以發現Sn-3.5Ag-0.5Cu比Sn-3.5Ag合金有較高之抗拉強度與潛變強度。Sn-37Pb合金在潛變實驗中所表現之超塑性行為經推測主要是由於高溫環境、擠製製程與低施加應力所造成。最後，藉由排除第三階段潛變及破斷位置的影響，發現利用Monkman-Grant關係式來描述此三款銲錫之潛變行為有相當不錯的結果。此外，本文也利用Larson-Miller關係式來整合潛變壽命、外加應力與溫度之間關係，分析結果顯示Larson-Miller關係式對此兩款無鉛銲錫的潛變壽命也有相當不錯的描述。 由SEM觀察得知，在相同溫度之下，潛變之破斷表面可以發現數量比拉伸破斷面多之較大孔洞。此外，在兩款無鉛銲錫中可發現微小孔洞會成核在晶界面與（或）介金屬界面，而此兩者的差異主要受到實驗溫度的不同所影響。此兩款無鉛銲錫在不同溫度下之孔洞形成位置似乎與不同之應力指數及其對應之潛變機制有一定程度的關聯性。 The purpose of this study is to investigate the mechanical properties and creep behavior of Sn-3.5Ag and Sn-3.5Ag-0.5Cu lead-free solders. These properties were compared with those of conventional Sn-37Pb solder to evaluate the feasibility of using lead-free solders to replace the Pb-contained ones in the future. Fractography analysis with scanning electronic microscopy (SEM) was conducted to determine the creep fracture mechanisms for the given three solders. Experimental results show that the ultimate tensile strength (UTS) and creep resistance were decreased with increasing temperature from room temperature (RT) to 90oC for each given lead-free solder. At RT, Sn-3.5Ag-0.5Cu alloy had the highest tensile and creep strength followed by Sn-3.5Ag alloy, and then the Sn-37Pb alloy. Due to a more uniform distribution of eutectic phases and a larger fraction of IMCs, the Sn-3.5Ag-0.5Cu alloy had greater UTS and creep strength than did the eutectic Sn-3.5Ag solder at each testing temperature. The superplasticity behavior in the Sn-37Pb solder at RT was associated with a high homologous temperature, extruding process, and low stress levels. By neglecting the effects of tertiary creep and failure position of specimen, the creep behavior of the given three alloys could be well described by the Monkman-Grant rule. Larson-Miller relationship was also applied and showed good results in correlating the creep rupture time, applied stress and temperature for the given two lead-free solders. From SEM observations, it could be found that the creep fracture surfaces had more larger microvoids than did the tensile ones at a given temperature. In addition, microvoids were found to nucleate in grain boundaries and/or matrix/intermetallic interfaces (MIIs) for the two lead-free solders at different temperatures. The variation of stress exponent n and corresponding creep mechanism with testing temperature for the given two lead-free solders seemed to be related to the difference in nucleation site of microvoid at different testing temperatures.
