- 學位論文
鍍鎳處理對無鉛銲錫銲點機械性質與組織之影響研究
Mechanical Properties and Microstructure Evolution of Lead Free Solder on Ni-based Barrier Coatings
摘要
本文主要探討不同鍍鎳處理應用於組裝製程中，與Sn-Ag-Cu系無鉛銲料接合之機械性質與界面之微結構的影響。本研究以方型之純銅塊作不同鍍鎳處理，鍍鎳方式包括了電鍍鎳、常用於UBM (Under bump metal)中之濺鍍鎳-釩與目前主要應用於BGA銲墊之無電鍍鎳-磷，與Sn-3.0 wt% Ag-0.5 wt% Cu (SAC305)錫膏進行迴銲，接合後的試片再以150℃進行24、48、96、240、480與720小時的時效處理，最後以剪切測試分析銲點可靠度，與金相觀察其界面介金屬化合物以及其破斷失效原因。 研究中發現不同鎳鍍膜與SAC305錫膏進行迴銲反應後，銲錫處之生成相皆相同，包括了β-Sn與Cu6Sn5和Ag3Sn的析出物，而界面處則產生出不同的IMC層，無電鍍鎳-磷系統生成(Cu,Ni)6Sn5、(Ni,Cu)3Sn4及Ni3P之富磷層；鎳-釩生成(Cu,Ni)6Sn5和Ni-Sn-Cu-V四元介穩相；電鍍鎳系統則是生成(Cu,Ni)6Sn5與(Ni,Cu)3Sn4。經時效處理後IMC層也出現不同的變化。而各鍍膜的反應消耗速度以電鍍鎳層最為快速，於96小時後便已經反應完畢，失去阻障效果；其中以鎳-釩鍍膜阻障效率最高，由於其IMC層含有Ni-Sn-Cu-V四元介穩相，與150 ℃下會發生Up-hill diffusion，因此界面處IMC層不易靠原子擴散而成長。 在銲點的機械性質部分，在迴銲過後發現鎳-釩系統強度較不足的原因在於鍍膜與銅基板間並無良好的接合強度，因此提前發生破裂，而無電鍍鎳-磷與電鍍鎳系統則能夠使破斷發生於銲錫本身，具有一定的剪切強度。經時效處理後，各系統皆逐漸由銲錫處的延性破斷轉為IMC層間的脆性破斷，無電鍍鎳-磷系統於240小時後轉變為銲錫與(Cu,Ni)6Sn5間之破斷，而後破裂則出現於(Ni,Cu)3Sn4與富磷層間；鎳-釩系統則於480小時後破裂方式為(Cu,Ni)6Sn5與Ni-Sn-Cu-V層間破壞；電鍍鎳系統脆性破斷是先發生於銲錫與(Cu,Ni)6Sn5之間，而後轉為Cu6Sn5和Cu3Sn層間破斷。在720小時後之可靠度方面，以無電鍍鎳-磷保持最佳強度，電鍍鎳次之，而以鎳-釩表現最差。
並列摘要
This work studied the reliability variation and the microstructure evolution of the interfacial intermetallic compounds (IMCs) layer formed between different Ni-based barrier coatings, electroplating Ni, sputtering Ni-V and electroless Ni-P, solder with Sn-3.0 wt% Ag-0.5 wt% Cu during 150 ℃ aging. The interfacial morphologies for the joints were investigated by using the field emission scanning electron microscope with EDS, and their reliability was analysis by shear strength test. It is the same that β-Sn matrix precipitate with Cu6Sn5 and Ag3Sn phases were formed at solder side after SAC305 solder paste reacted with these Ni coatings, but different IMC layers were formed at interface: (Cu,Ni)6Sn5, (Ni,Cu)3Sn4 and Ni3P for Ni-P system; (Cu,Ni)6Sn5 and Ni-Sn-Cu-V for Ni-V system; (Cu,Ni)6Sn5 and (Ni,Cu)3Sn4 for electroplating Ni system. Those IMC layers also transform to different phases during aging. After 96 hours aging, electroplating Ni coating could not lessen the high-speed diffusion between Sn and Cu atoms due to it consumed to grow the IMC layer. The most effective barrier layer of the three is Ni-V coating. It is because there is up-hill diffusion at 150 ℃ between Ni-Sn-Cu-V and (Cu,Ni)6Sn5 phase cause the IMCs hard to grow up. The normal shear fracture mode after soldering should be break at solder bulk, like the cases in Ni-P and electroplating Ni systems in the study. The shear strength of Ni-V system is lower than others due to the bonding strength between Ni-V coating and copper substrate is not enough. The fracture mode transfer from ductile bulk-fracture to brittle interface-fracture. Ni-P system turns to break between solder and (Cu,Ni)6Sn5 after 240 hours, (Ni,Cu)3Sn4 and P-rich layer after 480 hours. Rapture was found between (Cu,Ni)6Sn5 and Ni-Sn-Cu-V after 480 hours for Ni-V system. The electroplating Ni fractured between solder and (Cu,Ni)6Sn5 before 480 hours, fractured between (Cu,Ni)6Sn5 and Cu3Sn after then. Overall, Ni-P system performs the best reliability after 720 hours aging.