新型高溫無鉛銲料的材料性質與界面反應之研究

Abstract

歐盟於2006年7月1日開始實行了危害物質限用指令(ROHS, Restriction of Hazardous Substance)，此一法令限制了包含”鉛”等六種有害物質添加在電子產品之中，其中對於微電子封裝產業影響最大的就是含鉛銲料的禁止使用，目前各大工業聯盟以及廠商皆已使用無鉛銲料取代錫鉛銲料。而使用在儲存陣列、伺服系統、晶片接合、LED封裝以及覆晶封裝等屬於特殊用途的高溫高鉛銲料則因為其高可靠性，而可以使用到2010年。隨著時間逐步接近，關於此高溫銲料的無鉛候選材料仍然是將來需要解決的議題。 本研究依據二元相圖的固液相線區間選擇了四種可能的二元合金進行研究，分別是Bi-2.8Se、Bi-2.8Mn、Bi-1.8Mg以及Mg-51.3Zn四種二元合金，並將此四種合金銲料以DSC分析、維克氏硬度量測以及潤濕測試，並將銲料與Cu片做液態及固態反應。研究成果顯示此四種銲料的固液相線溫度區間在260oC~420oC之間，Mg-51.3Zn的硬度是Au-20Sn的0.7倍，Bi-2.8Se、Bi-2.8Mn及Bi-1.8Mg的硬度皆比Sn-10Sb銲料還低。Bi-2.8Mn潤濕性優於Bi-2.8Se，但兩者與Pb-10Sn以及Sn-3Ag-0.5Cu相比仍然有一些差距。 而在界面反應的情形，Bi-2.8Se與Cu基板反應並不會在界面上形成介金屬，只會在銲料生成塊狀的Cu2Se介金屬。時效時間達到2000小時後，Bi-2.8Se/Cu界面產生氧化情形。Bi-2.8Mn與Cu基板反應在界面上升成兩層介金屬，分別是Bi4Cu4Mn3以及BiMn溶Cu，當試片於200oC時效時，界面上轉變為Bi4Cu4Mn3單一層介金屬，而時效後的界面介金屬並不會因為時效時間拉長而有明顯的增厚。Bi-1.8Mg與Cu反應在銲料中發現了針狀Bi-Cu相，此相沒有在相圖中觀察到，需要藉由TEM獲知更多的訊息。

After 1 July 2006, the RoHS banned the use of Lead (Pb) and several other materials contained in electronic products. However, RoHS guidelines exempt the use of Pb internal to (at the first-level interconnect) flip-chip packages until 2010. A suitable Pb-free alternative to replace high Pb solder( e.g., 95Pb-5Sn, with a melting range from 308oC to 312oC) has not been found and the pressure to move to lead free will continue for the entire industry. In this study, three Bi-based solders, Bi-2.8Se, Bi-2.8Mn and Bi-1.8Mg, were used to observed the melting range, hardness and wetting behavior. Moreover, the interfacial reaction between Bi-based solders and Cu were also observed. Our result shows that the hardness of these three Bi-based solders are lower than Sn-10Sb. And the wetting behavior are worse than Pb-10Sn and Sn-3Ag-0.5Cu. There are no intermetallic compounds formation at Bi-1.8Mg/Cu and Bi-2.8Se/Cu interface. In addition, Se would encourage the consumption of Cu. Finally, two intermetallics, Bi4Cu4Mn3 and BiMn(Cu), formed between Bi-2.8Mn and Cu after reaction.