銀相較於金有低成本及導電性佳的優點，機械性質也與金相近，因此在封裝產業有取代金線的潛力，但純銀線與鋁墊進行打線接合時易產生硬脆的介金屬化合物進而導致元件失效。本研究材料為Ø 20μm純銀線與添加2wt.% Pd的銀鈀合金線。首先，藉由線材退火前後的微觀組織、機械性質選定適當退火條件，再做放電結球後的微觀組織及機械性質的探討。最終選取as-received純銀線與退火275℃的銀鈀合金線，經打線接合後通電，觀察通電前後接合界面強度的變化與介金屬化合物生長情形。
as-received純銀線與銀鈀合金線經275℃、325℃、375℃持溫30分鐘的退火處理後，純銀線與銀鈀線硬度分別下降至0.3~0.37GPa與 0.74~0.77GPa。由於純銀線退火後強度太低，故在放電結球實驗使用as-received純銀線，銀鈀線用275℃的退火線，as-received銀鈀線在此階段實驗與275℃退火線做結球後的組織與機械性質比較。
經放電結球後，純銀線球部組織為柱狀晶，as-received銀鈀線為樹枝狀的柱狀晶。相較於as-received銀鈀線，275℃退火線球部組織有較多比例的樹枝狀晶。受到放電產生的熱影響，純銀線熱影響區晶粒粗大化現象較銀鈀合金線顯著；機械性質方面，銀鈀線結球後的UTS、YS、EL都比純銀線高。打線接合方面，線材與鋁基板接合後經拉伸測試，通電前，Ag-2Pd(275℃)的平均斷裂強度(7.7gf)高於純銀線(6.9gf)。經直流電0.4A通電0.5hr、1hr、2hr，純銀線與Ag-2Pd(275℃)斷裂強度皆下降，斷裂位置集中在線材上，與鋁基板無界面剝離的現象(即lift-off)。推測此原因為通電產生大量的焦耳熱，使接合後的線材晶粒成長為等徑晶，造成線材強度弱化。經通電5hr，純銀線與鋁基板的接合界面產生許多裂紋，Ag-2Pd(275℃)仍與鋁基板有良好且平整的接合界面；經通電24hr，純銀線與鋁基板發生lift-off，Ag-2Pd (275℃)與鋁基板仍保有良好接合界面。

In the packaging industry, Ag wire has the potential to replace Au wire due to its superior electrical properties, lower cost and similar mechanical properties compared with Au. When Ag wire bonds to Al pad, the growing and brittle Ag-Al intermetallic compounds (IMCs) will cause the failure of electronic components. In this study, the experimental materials are pure Ag wire and Ag-2Pd alloy wire. First, the appropriate annealing conditions were selected by the microstructure and mechanical properties of wires before and after annealing, and then the microstructure and mechanical properties after EFO process were investigated. Ultimately, the as-received Ag wire and Ag-2Pd wire annealed at 275℃ were selected to bond with Al pad and then the DC current was applied in order to discuss the variations of bonding interfacial strength and IMCs growth.
After as-received pure Ag and Ag-2Pd wires annealed at 275℃, 325℃, 375℃ for 30 minutes, the nano-hardness of pure Ag decreased to 0.3~0.37GPa, and that of Ag-2Pd decreased to 0.74~0.77GPa. Because the nano-hardness of annealing Ag wire was too low, the as-received Ag wire was used in the EFO process, while the Ag-2Pd wire annealed at 275℃ was selected. In this process, as-received Ag-2Pd wire was compared with Ag-2Pd wire annealed at 275℃ for their microstructure and mechanical properties.
After EFO process, the FAB of Ag wire was columnar grains, while the Ag-2Pd wire was dendritic columnar grains. Compared with Ag-2Pd wire, there were more dendrites in the FAB of Ag-2Pd(275℃). Due to the heat effects after EFO process, the grains of Ag wire in HAZ were coarser than those of Ag-2Pd and Ag-2Pd(275℃) wires. About mechanical properties, the UTS, YS and EL of Ag-2Pd and Ag-2Pd(275℃) wires were higher than those of Ag wire after EFO process. About wire bonding process, before electrical current test, the average bonding strength of Ag-2Pd(275℃) wire (7.7gf) is stronger than that of Ag wire (6.9gf); after applying 0.4A DC current to the bonding interface for 0.5hr, 1hr and 2hr, the bonding strength of two wires decreased, and the lift-off on bonding interface of those wires didn’t occur because the electrical current induced a lot of heat into wires, the grains of wire grew up and formed into equal-diameter grains. Those equal-diameter grains caused the weakening of wires, so the fracture sites occurred on the wires.
After applying 0.4A DC current to the bonding interface for 5hr, there were many cracks at the Ag-Al interface, but the Ag-2Pd(275℃) wire still had a good and flat bonding interface with Al pad; after electrical current test for 24hr, the lift-off occurred at Ag-Al interface, but the Ag-2Pd(275℃) wire still had a good bonding interface with Al pad.

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