本實驗所探討之SAC305無鉛銲錫合金為Sn-3.0Ag-0.5Cu的三元合金，其熔點為217 C。由於電子產品的可靠度與銲點與基板界面的介金屬化合物 (Intermetallic compound, IMCs)的機械性質有關，且文獻指出拉球測試(Ball Pull test)中，垂直於界面拉伸方向的應力是造成銲點破壞的主因。因此本實驗以接近熔點的210 C、改變不同界面IMCs成長處理時間 (5、7.5、9、10、15、20hrs)，進行SAC305/Cu之固態擴散接合；以拉伸試驗量測錫銅界面的接合強度 (Adhesive strength, )，並在拉伸試驗前後，以SEM及EDS進行SAC305無鉛銲錫合金與金屬銅基材之界面和破壞面的組織分析及觀察。其中由EDS及X-ray結果可以得知錫銅介面形成的介金屬化合物為Cu6Sn5、Cu3Sn；從SEM觀察得知IMCs的整體厚度、Cu6Sn5層及Cu3Sn層厚度並未隨著IMCs成長處理之時間增加而增加。
拉伸試驗後，由SEM觀察錫銅破壞界面的縱剖面，發現破壞路徑大多行經Cu6Sn5層，少數發生在Cu3Sn層及Cu3Sn/Cu界面處。隨著210℃的IMC成長處理時間增加(5、7.5、9、10、15、20hrs)，拉伸試驗結果依據接合強度之高低分佈可分成三區：第一區的5hrs條件下，接合強度低於5MPa，應為IMCs成長不足使接合不完全；第二區為7.5 hrs、9 hrs、10 hrs等條件，此區相較其他條件有較高的接合強度，平均接合強度為20MPa左右，配合5 hrs、7.5 hrs、9 hrs、10 hrs之破壞面表面觀察結果，發現當破壞路徑經過Cu6Sn5層比例增加時，拉伸強度也跟著增加。韋伯解析結果顯示隨著IMCs成長處理的時間增加，特徵接合強度下降，數據分佈變廣；第三區之15 hrs、20 hrs條件的平均接合強度皆小於3MPa。比較5hrs、7.5hrs、15hrs錫銅界面之EPMA分析結果，Ag3Sn生成於Cu6Sn5層接近SAC305處，且其含量隨著IMC成長處理時間增加，可能是使界面接合強度於下降的因素之一 。

The formation of intermetallic compounds (IMCs) helps to provide good metallurgical bonding between solders and substrate in the microelectronic packing applications. Previous reports pointed out that the tensile stress is a main cause induces the fracture of solder joints during the Ball Pull tests. Owing to the above-mentioned reasons, this study attempts to find out an optimal interfacial IMCs growing condition between SAC305 and copper substrate through performing the solid-state bonding process with 210C IMCs growth treatments and different time (5, 7.5, 9, 10, 15, 20 hrs). The variation of interfacial adhesion strength, bonding reliability and failure behaviors were examined. Tensile tests were applied to measure the interfacial adhesive strength of SAC305/Cu bonding.
The tensile test results have obvious difference with different IMCs growth treatment time. With 7.5~10 hrs IMCs growth treatment, average adhesive strength are around 20MPa and much higher than others. Besides, the results of Weibull analysis of 7.5, 9, 10 hrs show the adhesive strength and the bonding reliability are decreased with increasing heating time, and 7.5 hrs specimens has the highest characteristic strength of SAC305/Cu interfacial bonding, less data fluctuation and a left-shift wear-out failure model of increasing failure rate (IFR). As the result, the optimal IMCs growing condition is 7.5 hrs.
From the cross-sectional observation of SEM and Weibull model, the cracks propagate through the Cu6Sn5 IMCs layer can help reliability and adhesive strength increase. Besides, according to the results of EPMA analysis, the forming of Ag3Sn at the interface of SAC305/Cu is propagate with IMCs growth treatment time and it may be one of the reasons that average adhesive strength is decease with IMCs growth treatment time.

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