錫銅銲料與鎳基材之銲接反應研究：介金屬化合物的剝離防治、織構控制以及成長改質

Abstract

綜觀現今國際電子構裝領域，三維立體構裝之趨勢儼然已成為微電子產業發展之目標。而在眾多三維立體構裝的技術中，又以使用微米級銲點的晶片接合法最廣為人所使用。然而由於微米級銲點內部的介金屬化合物所佔之比例往往隨著元件操作溫度或時間增加而巨幅提升甚至完全佔滿，因此銲點的特性將不再受銲料所主導乃改由介金屬化合物所決定。故系統性地研究銲接反應內部介金屬化合物之相關性質便成為刻不容緩的議題。本論文即針對常用的Sn-Cu銲料及Ni表面處理層之銲接反應及其介金屬化合物(Cu,Ni)6Sn5進行基礎研究型的漸進式探討。探討的目標由被動避險至主動改質可分為三大階段：一、探求避免界面介金屬化合物剝離發生之方法。二、控制界面介金屬化合物之生長形貌。三、積極調整銲料成分以求銲料穩定化並改質介金屬化合物之成長速率。有鑑於此，本論文具體提出三大相對應之代表性議題：一、探討困擾產業界已久的界面(Cu,Ni)6Sn5之大規模剝離現象(Massive Spalling)之發生機制及實際應用的避免方法。二、研究Sn-Cu/Ni界面反應中所生成的(Cu,Ni)6Sn5與其Ni基材之方向性關係，並提出可供預測該系統中介金屬化合物生長方向之判斷準則。三、微量添加過渡金屬元素Ti於銲料中，以期對於介金屬化合物、銲接界面反應及銲料本質特徵進行改質。研究結果指出：一、界面(Cu,Ni)6Sn5的大規模剝離現象主要是受到熱力學上的平衡相轉變過程所驅動。二、界面(Cu,Ni)6Sn5與Ni基材存在一明確之從優取向生長關係，此關係可決定銲接反應中界面(Cu,Ni)6Sn5的生成方向，並可有效預測其反應後之生長織構(Texture)。三、微添加Ti元素於銲料中，可大幅降低其凝結過程之過冷度(Undercooling)，並在長時間熱處理過程中可穩定銲料內部之Sn晶粒組織；而微添加Ti元素對於不同的界面介金屬化合物之成長亦存在不同的影響。本論文對於所研究之議題，除了實驗佐證與結果探討外，亦將力求建立學理量化準則以供參酌引用。

In the field of modern electronic packaging, the three-dimensional integrated circuit (3D IC) packaging has become essential for the microelectronics industry. Under the continuing development of 3D IC packaging, solder micro bumping is regarded as the most accepted solution for executing the chip-to-chip bonding technology. Nevertheless, in solder micro bumping, the volume ratio of intermetallic compound(s) to solder could be very high. In fact, in many scenarios, solder is completely consumed and the joints are entirely made up of intermetallics immediately after assembly. Under such a condition, the mechanical properties of a solder joint will be no longer dominated by the properties of solder, but by those of the intermetallics. This dissertation therefore investigates the very common scenario between Sn-Cu solder and Ni substrate from three objectives regarding intermetallics: (1) to avoid the spalling of interfacial intermetallics, (2) to control the growth morphology of intermetallics, and (3) to modify solder composition and formation of intermetallics. Three corresponding issues are specifically proposed, among them are (1) uncovering the driving force for massive spalling phenomenon in Sn-Cu/Ni system, (2) studying the orientation relationship between intermetallics and substrate in Sn-Cu/Ni soldering reaction, and (3) investigating the effects of minor Ti addition on selected soldering systems and intermetallics. The results unequivocally show that (1) the massive spalling phenomenon of interfacial (Cu,Ni)6Sn5 was mainly driven by a shifting of the equilibrium phase in thermodynamics, (2) a pronounced preferred orientation relationship between (Cu,Ni)6Sn5 and Ni was identified, and it could be used to predict the growth texture of (Cu,Ni)6Sn5 in the future, and (3) Ti addition could effectively reduce the undercooling as well as have the microstructure of Sn stabilized against extreme aging conditions; Ti addition was found to influence the formations of different intermetallics as well. In addition to experimental evidence and data analysis, this dissertation also strives for quantitatively proposing theoretical regulations for reference.