Abstract
摘要:目前以錫為基材(Sn-based)的無鉛銲料已是國際間各大電子公司所採用之主要電子銲料,然而隨著產品使用經驗的增加,發現此一系列的銲料在提昇可靠度方面,仍有進一步改善的空間,而其中又發現以銲點的界面反應對於可靠度的影響最為直接。近年來國際間許多研究團隊,嘗試在銲料中添加微量的合金元素,來抑制Cu3Sn 介金屬的生長並進一步減少伴隨Cu3Sn 生成的Kirkendall voids 數目,以提昇銲點的性能及可靠度。因為目前已有文獻證實,Kirkendall voids 的生成確實會造成銲點可靠度的降低。
本研究團隊在添加微量合金元素研究方面,曾進行過添加Ni、Fe、Co 等研究,並獲得顯著的成果。在2002 年本研究團隊首次發現添加微量Ni 元素能有效的抑制SnAg 及SnAgCu銲料與Cu 反應時界面Cu3Sn 的生長。後續研究更發現添加微量Fe 或Co 元素也有相同之效果,並首次証實元素添加量即使小到100 ppm (0.01 wt.%) 仍有效果。國際上進行添加微量合金元素的研究所採用的合金包含有Ni、Fe、Co、Mn、Ge、Ti、Si、Cr 以及Zn,其中又以添加微量Zn 元素的研究最為大家所重視。因為已有文獻報導添加Zn 能有效的改善銲料的機械性質,但是關於添加Zn 對界面反應的影響仍尚未有完整的探討。本研究團隊在2006 年首次提出銲料中添加Zn 的濃度會對於界面反應產生非常大的影響,更於2008 年初步的證實添加Zn濃度的效果受銲料體積效應的影響,如此的研究成果也吸引著積極從事無鉛銲料研發的CPU連接器大廠--嘉澤端子的重視,加上本研究團隊在添加微量合金元素研究以及銲料體積效應研究上豐富的經驗以及成熟的技術,因此促成了此產學合作計畫的提出。
本計畫的目標是深入的了解,在工業界實際使用的銲料體積下,元素的添加對無鉛銲料與Cu 反應所產生之影響。本研究除了將對現象作一完整觀察與描述外,並將對其機制作深入探討。嘉澤端子將提供工業界在無鉛銲料開發的實務經驗,並結合本研究團隊在添加Zn元素研究的學術理論成果。本計畫目標完成後,將可提供嘉澤端子在無鉛銲料開發上的銲料選擇,也可提供本研究團隊建立不同體積下、不同Zn 添加元素濃度下,介金屬生長的動力學與擴散動力學資料,為本團隊在無鉛銲料領域的研究奠立更完整的理論研究基礎。
Abstract: The Sn-based family of lead-free solders has firmly established itself as the leading replacement for the eutectic PbSn solder for electronic applications. However, recent studies revealed several reliability issues associated with this solder family. One of the critical issues is the formation of Kirkendall voids when soldered with Cu substrate. Excessive Kirkendall void formation increases the potential for brittle interfacial fracture. At this stage, main research efforts to reduce this potential formation of Kirkendall voids for reliability improvement are focused on adding minor alloy elements. For example, Ni, Fe, Co, Mn, Ge, Ti, Si, Cr and Zn had been evaluated for their potential for suppressing the void coalescence during the reactions between solders and Cu substrate. The most noteworthy alloying element is Zn.
Adding a small amount of Zn has the added benefits of improving the creep resistance of the solder, and inhibiting the formation of large Ag3Sn plates that have a week interfacial strength with solder. All these experimental observations point to the conclusion that Zn is a very promising alloying element for Sn-based solders. Nevertheless, the ideal amount of Zn addition has not been identified. In fact, the efforts of different levels of Zn alloying on the interfacial reactions are not well characterized at all. In 2006, our research group first showed that the reaction between Zn-doped Sn-based solders and Cu substrates displays a very strong Zn concentration sensitivity. Moreover, our recent studies also point out the effect of Zn concentration on interfacial reactions is related to the solder volume. These results had been noticed by the leading company in manufacturing CPU socket, LOTES. They are very interested in the benefits of Zn addition and want to understand the capability of Zn addition in real solder joint application. With our group experienced studies of minor alloy additions (Ni, Fe, Co) and solder volume effect, it is proposed to study the effects of Zn addition on the interfacial reactions.
The key objective of this study is to examine the effects of Zn addition on the interfacial reactions between the lead-free solders and the Cu substrate under real solder joint size, and to understand the fundamental mechanisms for such effects. The objective is to be achieved in one year. The effects of different levels Zn addition on the interfacial reaction during the reflow will be investigated under real solder joint scale. The accomplishment of the stated objective of this study will provide LOTES the detailed fundamental kinetic data that are critical in designing more reliable electronic products. Moreover, understanding of Zn effects on interfacial reactions and volume effect on Zn addition will enrich the knowledge of lead-free solders development in our research group.
Keyword(s)
銲料
Zn 合金添加
柯氏孔洞
界面反應
體積效應
lead-free solder
Zn addition
interfacial reaction
Kirkendall void
volume effect