臺灣博碩士論文加值系統

本實驗針對新型高溫無鉛銲料Bi-Ag合金塊材與銲點之顯微組織與機械性質相關性進行探討。研究項目包括Ag含量與應變速率對塊材拉伸特性影響、Bi-Ag合金與常用基材Cu、Ni銲點組織、介面反應物奈米壓痕測試以及高溫時效前後銲點拉伸破壞行為等。
Bi-Ag合金具非平衡共晶凝固組織，於共晶成份組織中可觀察到初晶相(Ag)、共晶組織(Bi-Ag共晶) 以及亞共晶相 (Bi) 並存。實驗結果指出隨著Ag含量增加，有助於提升Bi-Ag合金的拉伸強度。延伸率以Bi-11Ag最佳、pure Bi次之，以Bi-2.5Ag最差。研判共晶組織中細小具方向性排列之Ag顆粒易引發裂縫串聯傳播，導致Bi-2.5Ag較差的延性。過共晶Bi-11Ag合金組織中出現大量初晶Ag，可減緩應力集中，阻礙裂縫傳播，有效改善於較高應變速率下之脆性問題。
Bi-Ag與Cu基材反應介面並未生成金屬間化合物，而以形成Cu晶界溝槽(grain boundary grooving)做為機械鍵結。接合狀態之銲點拉伸強度與Pb-5Sn/Cu相當。較高的Ag含量加深溝槽深度，有助於穩定拉伸性質。經高溫時效之Bi-Ag/Cu銲點雖因溝槽深度變淺強度略為降低，但仍具相當的可靠度。反觀Pb-5Sn/Cu因Cu3Sn厚度明顯增加，以及可能伴隨生成的Kirkendall voids，造成接合強度大幅下降。
Bi-Ag與Ni反應介面產生金屬間化合物NiBi3及NiBi，NiBi之硬度與彈性模數較NiBi3高上許多(NiBi：硬度1.55GPa、模數為39.28；NiBi3硬度7.23GPa、模數132.7GPa)，於接合狀態主要生成相為NiBi3。高溫時效過程中NiBi3及NiBi因基材與銲料間互擴散而成長，但各別之厚度及成長速率受銲料中富Ag相(尤其是初晶Ag)影響相當大，其中Bi-2.5Ag/Ni之NiBi3經時效30天異常增厚至80

The study investigated and clarified the relationship between microstructure and mechanical properties of Bi-Ag high temperature Pb-free solders, in the form of bulk material or joints with Cu and Ni. Several subjects were studied systematically, including the effect of Ag content and strain rate on the tensile properties of bulk Bi-Ag alloys, interfacial reaction between Bi-Ag solders and the substrates, the nanoindentation analysis of the reaction layers thus formed, as well as the influence of thermal aging on the tensile fracture behavior of solder joints.
As for the bulk materials, the microstructure of Bi-Ag alloys exhibited a non-equilibrium eutectic solidification feature showing that together with the primary Ag, Bi-Ag eutectics and the pro-eutectic Bi co-existed in the solidified structure. Experimental results show that the tensile strength increased with a raised Ag content and the elongation in the decreasing order was Bi-11Ag, pure Bi and Bi-2.5Ag. It could be deduced that crack might propagate through the fine, oriented eutectic Ag particles easily and consequently the Bi-2.5Ag alloy possessed poor ductility. In contrast, the massive primary Ag which has the ability to retard strain localization and stunt crack growth is probably responsible for the superior ductility of the Bi-11Ag sample at high deformation rates.
Without forming intermetallic compounds (IMC), the molten solder grooved and further penetrated along grain boundaries (GBs) of the Cu substrate. It was also demonstrated that the grooved grain boundaries played the role in interfacial bonding for the Bi-Ag/Cu joints and provided a comparable joint strength to that of the Pb-5Sn/Cu. An increase in Ag content was able to enhance GB grooving and thus a concentrated joint tensile strength could be obtained. The interface between Bi-Ag and Cu became smooth and the GB grooves was suppressed to a certain extent when suffering thermal aging. However, unlike the degraded strength of Pb-5Sn/Cu joints with the thickened Cu3Sn and accompanying Kirkendall voids, an acceptable joint strength still remained for thermal aged Bi-Ag/Cu joints.
NiBi and NiBi3 could be observed at the Bi-Ag/Ni interface, however, in the as-jointed state the NiBi located between NiBi3 and the Ni substrate was almost undetectable. According to the nanoindentation results, the hardness and elastic modulus of NiBi are substantially greater than that of NiBi3. During thermal aging, the NiBi3 and NiBi became thickened through the interdiffusion between Ni and Bi and remarkably the thickness of NiBi3 reached 80

中文摘要……………………………………………………I
英文摘要…………………………………………………IIl
總目錄………………………………………………………V
表目錄........................................VII
圖目錄……………………………………………………IX

第一章 前言………………………………………………………1
第二章 文獻回顧…………………………………………………3
第三章 實驗方法…………………………………………………21
第四章 實驗結果與討論…………………………………………27
第五章 結論..........................................67
參考資料.............................................69

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