臺灣博碩士論文加值系統

近幾年來，Pd金屬薄膜廣泛被應用於Au/Pd/Ni(P) (ENEPIG) 三層結構的表面處理層中，以避免 Au/Ni(P) (ENIG) 雙層結構處理層最為人詬病的黑墊問題 (black pad)。在與銲料進行銲接反應時，表層的Au、Pd鍍層會快速的溶入銲料合金中，而底部的Ni(P)層則緊接著與含有不同Pd(或Au)濃度的銲料進行界面反應。銲料中Pd濃度的高低，主要係由不同Pd鍍層的厚度與銲點尺寸來決定。隨著電子產業的發展，單位尺寸下元件的功能不斷增，則銲點的尺寸勢必將不斷的縮小且數量不斷的增加。由於銲料體積與尺寸是成三次方關係，而Pd金屬主要來源的銲墊表面積則是與尺寸成平方關係，所以在尺寸縮小的同時，即使是使用相同厚度的Pd金屬鍍層，但所產生的Pd濃度卻會大幅的提高。而本研究第一部分實驗利用自行配置不同Pd
濃度的銲料，與電鍍Ni銲墊進行界面反應，結果發現，界面反應的產物對Pd濃度非常敏感，當Pd濃度較低時(低於 0.05 wt.% )，介面的產物只有一層連續的Ni3Sn4，而當Pd濃度些微上升至0.1 wt.%時，除了連續的Ni3Sn4之外，還有許多不連續的介金屬在界面生成，經由EBSD與EPMA的驗證，此不連續的產物為base on PdSn4結構的(Pd,Ni)Sn4，而當鈀濃度高於0.2 wt.%時，此(Pd,Ni)Sn4則在Ni3Sn4上形成緻密的連續層，藉由高速推球的所測得的界面性質結果顯示，當界面形成(Pd,Ni)Sn4/Ni3Sn4雙層結構時會大幅降低銲點的機械強度。
而本研究第二部分更進一步利用業界慣用的Sn3Ag0.5Cu銲料合金融入不同濃度的Pd來與電鍍Ni銲墊來進行反應。結果顯示，當Pd濃度高於0.3 wt.%時，(Pd,Ni)Sn4 亦開始在界面形成，且銲點的機械性質隨之下降。此外本研究亦發現銲點中Cu金屬的存在能有效抑制(Pd,Ni)Sn4在界面形成連續層，避免銲點界面的脆性斷裂發生。因此，可避免隨Pd濃度提升所造成的Pd-embrittlememt 現象。

The Pd concentration effect on the interfacial reaction of the Ni/Sn-xPd (x = 0.05 – 1 wt.%) and Ni/Sn3Ag0.5Cu–xPd alloys (x = 0 – 1 wt.%) system were investigated in this study. We found that a slight variation in the Pd concentration produced a completely different reaction product(s) in spite of only a 0.05 wt.% difference. For the case in Ni/Sn-xPd reactions, when the Pd concentration was high (more than 0.2 wt.%), a Pd-Ni-Sn layer over Ni3Sn4 was created. The Pd-Ni-Sn was identified to be the PdSn4-based structure through electron backscattered diffraction (EBSD) analysis. In contrast, the Ni3Sn4 replaced the (Pd,Ni)Sn4 when the Pd concentration was below 0.05 wt.%. A Pd-Ni-Sn isotherm simulated by the CALPHAD method was utilized to rationalize the above transition. Additionally, the mechanical reliability in response of the interfacial microstructure was evaluated through a high-speed-ball-shear (HSBS) test. The correlation of the interfacial strength with various Pd concentrations will be established in this study. The interfacial reaction between Ni and Sn3Ag0.5Cu–xPd alloys (x = 0 – 1 wt.%) at 250oC and the mechanical reliability of the solder joints were investigated in this study. For the case in Ni/Sn3Ag0.5Cu–xPd reactions, when x was low (≤ 0.2 wt.%), the reaction product at the Ni/SnAgCu–xPd interface was a layer of (Cu,Ni)6Sn5. An increase of x to 0.3 wt.% produced one additional (Pd,Ni)Sn4 compound that was discontinuously scattered above the (Cu,Ni)6Sn5. When x was relatively high (0.5 wt.% – 1 wt.%), a dual layer of (Pd,Ni)Sn4–(Cu,Ni)6Sn5 developed with the reaction time. The results of HSBS test showed that the mechanical strengths of the Ni/Sn3Ag0.5Cu–xPd joints also degrade with increasing x, especially when x reached a high level equal to or greater than 0.3 wt.%. This degradation corresponded to the growth of (Pd,Ni)Sn4 at the interface, and joints easily failed along the boundaries of solder/(Pd,Ni)Sn4 and (Pd,Ni)Sn4/(Cu,Ni)6Sn5 in the HSBS test. The (Pd,Ni)Sn4–induced joint failure (Pd–embrittlement) was alleviated by doping the solder with an appropriate amount of Cu. When the Cu concentration increased to 1 wt.% and the Pd concentration did not exceed 0.5 wt.%, the growth of (Pd,Ni)Sn4 could be thoroughly inhibited, thereby avoiding the occurrence of the Pd–embrittlement in solder joints.

Chinese Abstract i
English Abstract iii
Contents v
List of Tables vi
List of Figures vii
Chapter 1 Introduction 1
1.1 Electroless Nickel/Immersion Gold (ENIG) 1
1.2 Challenges and issues of ENIG 1
1.3 Electroless Nickel/Electroless Palladium/Immersion Gold
(ENEPIG) 5
1.4 The objective of this study 7
Chapter 2 Literature review 10
2.1 The Au concentration effect 10
2.2 The Zn concentration effect 12
2.3 The Cu concentration effect 16
Chapter 3 Experimental procedures 20
Chapter 4 Results 24
4.1 Low-Pd concentration cases in Sn-xPd/Ni system 24
4.2 High-Pd concentration cases in Sn-xPd/Ni system 30
4.3 High speed ball shear test results of Sn-xPd/Ni interfaces 33
4.4 Interfacial microstructures in Sn3Ag0.5Cu-xPd/Ni system 37
4.5 High speed ball shear test results of Sn3Ag0.5Pd-xPd/Ni interfaces 43
Chapter 5 Discussions 51
5.1 Low-Pd concentration cases in Sn-xPd/Ni system 51
5.2 High-Pd concentration cases in Sn-xPd/Ni system 56
5.3 Interfacial results in Sn3Ag0.5Cu-xPd/Ni system 60
Chapter 6 Conclusions 64
References 66

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