- 學位論文
添加鍺對於含稀土錫銀銅銲錫之特性影響研究
The Effect of Germanium Additions on the Properties of SnAgCu-RE Solder
摘要
錫銀銅(Sn-Ag-Cu)三元合金已被評估為最有潛力取代傳統錫鉛共晶(Sn-37Pb)合金而成為主流的無鉛銲錫，但因其相較於傳統錫鉛共晶銲錫合金仍有著熔點過高、潤濕性較差等數項缺點，故許多研究嘗試於錫銀銅銲錫合金中添加稀土元素以進行改質處理。研究結果已證實於銲錫合金中添加稀土元素可有效提高機械強度及提升物理特性。然而本研究室(國立台灣大學材料所莊東漢教授所主持之電子構裝實驗室)於西元2006年首度發現在銲錫合金內添加稀土元素將引發錫鬚異常快速的成長，其成長速率在室溫可達8.6 Angstrom/Sec，遠高於文獻上過去有關錫鬚研究的成長速率(0.01 Angstrom/Sec∼0.1 Angstrom/Sec)，此種異常成長的錫鬚將有可能造成電子接點短路而產生嚴重的可靠度問題。經研究指出因添加稀土元素所產生的錫鬚異常成長主要是由於銲錫合金內部的稀土介金屬化合物氧化所導致，故本研究嘗試於含稀土之錫銀銅銲錫合金中添加具有顯著抗氧化能力的鍺元素，並針對其抑制錫鬚生成的效果、物理性質與機械性質的變化進行廣泛的的討論，且同時對於各種添加鍺元素的含稀土之錫銀銅無鉛銲錫的球格陣列構裝接點其界面反應與機械強度進行全面性的整理。 實驗結果指出於Sn3Ag0.5Cu0.5RE銲錫合金中添加0.5wt.%以上的鍺元素時，在稀土介金屬化合物周圍與銲錫合金基地中將可觀察到明顯的「含鍺相」出現；不僅如此，於Sn3Ag0.5Cu0.5Ce銲錫合金中添加0.5wt.%以上的鍺元素可有效的抑制室溫中的錫鬚成長與高溫(150℃)中的錫堆出現，但於Sn3Ag0.5Cu0.5La銲錫合金中則其效果並不明顯；推測此與於含稀土之錫銀銅銲錫合金中添加鍺元素可有效降低稀土介金屬化合物CeSn3的氧化速率，但對LaSn3則無明顯的影響有密切的關係。此外添加適量的鍺元素亦可提升Sn3Ag0.5Cu0.5RE銲錫合金本身與電子構裝接點中大部分的機械性質(如：抗拉強度、維克式微硬度等)，但若鍺元素添加量過多時，則反而會使其機械強度及潤濕性質大幅下降。
並列摘要
Ternary Sn-Ag-Cu alloys have been recommended as potential candidates to replace the eutectic Sn-37Pb alloy as a major Pb-free solder. Due to the higher melting temperature and poorer wettability of the Sn-Ag-Cu solder, many researchers have tried to improve these properties by adding rare earth elements into the Sn-Ag-Cu solder. The studies on adding rare earth elements into Sn-Ag-Cu solder indicate that the mechanical strength and physical properties are, indeed, improved. However, as our laboratory was the first to discover, the phenomenon of amazingly rapid growth of tin whiskers on the surface of solder alloys containing rare earth elements is another problem that needs to be solved. The growth rate at room temperature can reach 8.6 Angstrom/Sec, which is much higher than the values reported in the literature (0.01 Angstrom/Sec~0.1 Angstrom/Sec). It is known that tin whiskers can cause short circuits in solder joints and lead to serious problems with reliability. Our studies of Sn-Ag-Cu-RE solder indicate that “Rare Element Intermetallic Compound” (RE-IMC) oxidation causes that abnormal tin whisker growth, so we added Germanium (Ge), which effectively prevents the surface oxidation of the solder into the Sn-Ag-Cu-RE solder, and observed its effects on the tin whisker growth, physical properties, and mechanical strength. The results of our experiments indicate that a “Ge-Containing Phase” (GCP) exists around the “Rare-Earth Intermetallic Compound” (RE-IMC) and in the matrix of the solder when Germanium addition is greater than 0.5wt.% in Sn-Ag-Cu-RE. The tin whisker growth behaviors resulting from the RE-IMC depend on the amount of Germanium addition in Sn3Ag0.5Cu0.5Ce solder. When the amount of Germanium addition in Sn3Ag0.5Cu0.5Ce solder is greater than 0.5wt.%, the growth of tin whiskers at room temperature, and that of hillocks at high temperature (150℃), can be inhibited. However, the influence of adding Germanium into the Sn3Ag0.5Cu0.5La solder is not significant. The reason why adding Germanium can inhibit tin whisker and hillock growth is that the rate of CeSn3 oxidation in Sn-Ag-Cu-Ce is decreased, but the rate of LaSn3 oxidation in Sn-Ag-Cu-La system is not changed significantly. Furthermore, the addition of a suitable amount of Germanium in Sn3Ag0.5Cu0.5RE solder can improve a lot of mechanical properties of alloy and solder joint (for example: ultimate tensile strength, Vickers microhardness), but excessive addition of Germanium causes a significant degradation of the mechanical strength and wettability.