A Study on the Vibration Fracture Characteristics of Sn-Ag Lead-Free Solders

• Main Authors: Tsuey-Mei In, 殷翠梅
• Other Authors: Truan-Sheng Lui
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/82491583605147097377

碩士 === 國立成功大學 === 材料科學及工程學系 === 89 === Sn-Pb solders have been widely used in electronic components. However, during application, resonant vibration fatigue may occur and cause failure. Pb would make damage to the environment and hazard human''s health so that the usage inhibition of Pb is necessary. Therefore, the exploration of the Sn-Ag solders'' resonant vibration fatigue characteristics is essential. This research has two aspects, one is the solidification rate, putting Sn-3.5wt%Ag alloy on the gypsum-mold and graphite-mold. And the other is Ag content, with 3.5Ag, 4.4Ag, 5.5Ag, and 6.0Ag, and graphite-mold is used. To sum up the abovementioned results about Sn-Ag alloy, the practicability of replacing Sn-Pb solder about the resonant vibration fatigue characteristics will be evaluated. Experimental results indicate that the deflection amplitude in resonance can be classified into three stages as a function of vibration cycle during resonant test. In stageⅠ, the deflection amplitude increases with increasing number of vibration cycles. And the deflection amplitude maintains a constant in stageⅡ. The deflection amplitude decrease with increasing vibration cycles in stage Ⅲ. The critical crack length for the onset of this final stage is a function of solidification rate or Ag content. Moreover striated deformation occurred in all Sn-Ag test specimens. In view of the solidification rate effect, the deflection of gypsum-mold specimen is lower then graphite-mold specimen because of the bigger damping capacity. In gypsum-mold specimen that actually promotes the crack propagation rate, due to the micro-cracks could be introduced by the onset striated deformation. But gypsum-mold specimen has bigger crack tortuosity then graphite-mold specimen so that it has better crack resistance. The change of Ag contents dose not have apparent influence on the tensile strength and elongation. The deflection amplitude will decrease with increasing the number of Ag3Sn particles, which results in the increase of resonant vibration life and improves crack resistance. In the observation of crack paths, primary Sn-rich phase and eutectic Sn-rich phase are continually each other. To compare the D-N curve (Deflection vs. Cyclic number curve) between Sn-Pb and Sn-Ag solders under the identical vibration push force, Sn-3.5Ag solder possess lower deflection amplitude and better vibration fracture resistance and fatigue life than Sn-Pb solders. The tensile strength and elongation of Sn-3.5wt%Ag is satisfied with our application requirement. So that Sn-3.5Ag will substitute for Sn-40Pb in the future. 英文摘要..........................................................................................................Ⅲ 總目錄..............................................................................................................Ⅴ 表目錄..............................................................................................................Ⅶ 圖目錄................................................................................................................1 第二章 文獻回顧.............................................................................................5 2-1 銲錫的歷史........................................................................................5 2-2 Sn-Ag系銲錫特性與Sn-Pb銲錫比較.............................................10 2-3 共振特性............................................................................................13 2-3-1 共振頻率...................................................................................13 2-3-2 試片偏移量與振動次數之關係（D-N曲線）...................14 2-4 裂縫傳播行為...................................................................................16 第三章 實驗方法............................................................................................24 3-1 實驗材料與熔煉...............................................................................24 3-2 金相觀察............................................................................................25 3-3 硬度試驗............................................................................................25 3-4 拉伸試驗............................................................................................25 3-5 共振疲勞試驗...................................................................................26 第四章 實驗結果............................................................................................35 4-1 金相組織之觀察..............................................................................35 4-1-1 凝固速率與微觀組織之關係...............................................35 4-1-2 Ag含量與顯微組織之關係...................................................36 4-2 微觀組織與拉伸機械性質間之關係.............................................38 4-2-1 不同凝固速率與硬度、拉伸性質之關係..........................38 4-2-2 不同Ag含量與硬度、拉伸性質之關係..............................39 4-3 共振試驗............................................................................................39 4-3-1 不同的凝固速率與振動破壞特性間之關係......................39 4-3-2 不同的Ag含量與振動破壞特性間之關係..........................42 4-3-3 試片末端偏移量固定時之振動疲勞檢討...........................44 第五章 討論.......................................................................................................76 5-1 凝固速率、Ag3Sn與初始偏移量的影響......................................76 5-2 影響裂紋傳播路徑的因素..............................................................77 5-3 取代有鉛銲錫之無鉛銲錫設計.....................................................79 第六章 結論.......................................................................................................88 參考文獻............................................................................................................90