本研究的主旨是將鋅添加至銅金屬墊層以改善銲料接合的可靠度。實驗的設計是以純錫為銲料與不同鋅濃度的銅鋅基材做接合，其中鋅濃度分別為15以及30 wt.%，形成Sn/Cu-xZn之銲接系統。此Sn/Cu-xZn銲接系統迴銲於250 ℃ 2分鐘後，再經過150℃，10、20以及40天的熱處理。當Zn含量在Sn/Cu-xZn系統中從15 wt.%增加至30 wt.%時，Cu3Sn與Cu6Sn5將分別地被抑制。此外，沒有任何Kirkendall孔洞生成於Sn與Cu-Zn的界面之間。經過40天熱處理後，不同的多層介金屬相，[Cu6Sn5/Cu3Sn/Cu(Zn)] 與 [Cu6Sn5/Cu(Zn,Sn)/CuZn]分別生成於 Sn/Cu-15Zn 與 Sn/Cu-30Zn 系統之界面。 Sn/Cu-Zn 銲接系統中相的生長機制可藉由場發式電子微探儀 (FE-EPMA) 精確的定量分析，進而搭配 Sn-Cu-Zn 三元相圖得到完整的解釋。
在純錫與銅鋅合金固態反應的過程中， Cu(Zn,Sn) 與 CuZn 相依序生成在 Cu-Sn 化合物下方。在熱處理的過程中，當鋅在 Cu6Sn5 內的增加至飽和濃度時， Cu(Zn,Sn) 會析出於Cu6Sn5的內部，而使得 Cu6(Sn,Zn)5 轉變成 CuZn 相。這樣的 Cu6(Sn,Zn)5 與 CuZn 間相轉變機制與接合界面上 Kirkendall 孔洞的抑制有很明顯的關係。
在純錫與不同銅鋅基材間液態反應的過程中， Cu6Sn5是主要且共同的界面生成物。經過 250 oC 迴銲後， Sn/Cu-30Zn 界面上的 Cu6Sn5 的形貌呈現出具有多刻面的柱狀結構，且沿著特定方向成長。另一方面，圓球形與扇貝狀的 Cu6Sn5 分別生成於 Sn/Cu-15Zn 與 Sn/Cu 的接合界面處。鋅含量不同造成 Cu6Sn5 形貌差異的現象可藉由Jackson’s parameter (α) 來解釋。隨著鋅含量在Cu6(Sn,Zn)5 化合物中增加， Cu6(Sn,Zn)5 的生成能變化也相對提升。此外，整體介金屬化合物的平均生成厚度隨著鋅含量在銅鋅基板中增加而減少。根據這些研究結果可以得知銅鋅合金是個具有潛力的金屬墊層材料。

Zn addition to Cu under bump metallurgy (UBM) in the solder joint was the subject of this study. An alternative design was carried out to fabricate pure Sn as the solder and Cu-xZn (x=15 and 30 wt.%) as the UBM to form the reaction couple. As Zn increased from 15 to 30 wt.% in Sn/Cu-Zn system, the growth of both Cu3Sn and Cu6Sn5 could be suppressed. Besides, no Kirkendall void was observed at the interface in both Sn/Cu-Zn couples during heat treatment. After 40-day aging, different multilayered phases of [Cu6Sn5/Cu3Sn/Cu(Zn)] and [Cu6Sn5/Cu(Zn,Sn)/CuZn] formed at the interface of [Sn/Cu-15Zn] and [Sn/Cu-30Zn], respectively. Intermetallic compounds (IMCs) growth mechanism during aging was discussed and proposed on the basis of the composition variation in the joint assembly with the aid of electron microscopic characterization and Sn-Cu-Zn ternary phase diagram. According to these analyses of interfacial morphology and IMCs formation in Sn/Cu-Zn system, Cu-Zn may be a potential UBM for retarding the Cu pad consumption in solder joints.
In the solid reaction of pure Sn solder and Cu-Zn alloy, Cu(Zn,Sn) and CuZn phases were formed adjacent to the Cu-Sn compounds in sequence. In this study, Cu(Zn,Sn) phase was precipitated inside Cu6Sn5 as the accumulation of Zn atoms in Cu6Sn5 reached the saturated concentration. Finally, Cu(Zn,Sn) phase would transform into the CuZn phase during annealing. The growth mechanism of CuZn phase was related to the suppression of the Kirkendall voids formation at the interface.
In the liquid reaction of pure Sn on the different Cu-xZn (x= 0, 15 and 30 wt.%) substrates, Cu6Sn5 was the dominating product at each interface. After reflow at 250 oC, the Cu6Sn5 morphology was faceted pillar in the Sn/Cu-30Zn system and it grew along the specific direction with the extended wetting time. On the other hand, round and scallop-like Cu6Sn5 were formed in the Sn/Cu-15Zn and Sn/Cu systems, respectively. The phenomenon can be explained by Jackson’s parameter, which was used to correlate the morphology variation with the formation enthalpy. It was noted that the higher Zn concentration in the Cu6Sn5 led to the larger energy change in Cu6(Sn,Zn)5 formation. Moreover, the average thickness of total IMCs grew slowly as the Zn content in Cu-Zn substrate increased.

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