臺灣博碩士論文加值系統

本實驗研究以脈衝式YAG雷射（Pulse YAG Laser）進行共晶錫球（Eutectic Solder Ball）在銅銲墊上之無助銲劑迴銲接合（Fluxless Reflow Soldering），以了解雷射功率、脈衝寬度與迴銲次數等製程條件對銲點外觀形貌、微觀結構與接合強度之影響。實驗結果顯示，雷射迴銲所形成之銲點高寬比低於傳統迴銲之銲點，在較低功率及較大脈衝寬度（即較長的加熱時間）的迴銲條件下可得到較平整的銲點外觀、較均勻之微觀結構及較佳之接合強度。掃描式電子顯微鏡（Scanning Electron Microscopy，SEM）之觀察發現銲點與基板界面的介金屬層（Intermetallic Compound，IMC）以厚度小於１μm的Cu6Sn5相為主；隨著雷射功率的增加，其IMC逐漸轉以棒狀或樹枝狀沿冷卻方向成長；經多次雷射脈衝迴銲的銲點內則會出現棒狀的Cu3Sn相。推力測試（Shear Test）對接合強度之測試顯示，脈衝雷射銲點可達到的平均剪力約9.6 Nt/mm2，為工業標準的1.8倍，破斷面的觀察發現其有效銲點皆因錫球受剪應力破裂（Ball Shear），表面呈現韌性破斷（Ductile Fracture），符合JEDEC所制定 BGA推球規範之破裂模式一型態；而不良銲點則皆因錫球與銲墊間缺乏完整之潤濕（即規範之破裂模式三型態），且破斷面隨潤濕程度及受熱均勻程度的影響呈現數種不同的形貌，實驗分析結果顯示銅/銲錫界面的潤濕狀況及雷射光束入射的相對位置為影響此一無助銲劑迴銲接合良率的主因。

This work studied the fluxless reflow soldering of eutectic solder ball on copper (Cu) pad utilizing pulse YAG laser. The effects of soldering conditions including laser power density, pulse width (i.e., the irradiation time) and reflow times on the morphology, microstructure and shear strength of solder joint were investigated. The experimental results revealed that the solder joints exhibit better shape and bonding strength when they were soldered at the conditions of lower power density and larger pulse width. The observation using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) revealed that the layer-like intermetallic compound (IMC) is mainly Cu6Sn5 phase of thickness less than 1 μm. With the increase of power density, the morphology of IMCs became rod-like or dendrites and the IMCs grew along the cooling direction. For the solder joints subjected to multiple laser pulse soldering, the rod-like Cu3Sn phase was observed. Shear test was adopted to evaluate the bonding strength of laser-soldered joints. The joints exhibited the average shear strength of 9.6 Nt/mm2, about 1.8 times over than the industry standards (5.40 Nt/mm2). The cross-sectional morphology observation indicated that all successful joints fractured inside the solder joints due to shear force and the ductile fracture feature fitted to the fracture mode #1 of JEDEC shear test standard. As to the unsuccessful joints, they failed due to incomplete wetting that fitted to the fracture mode #3 of JEDEC standard. The morphology of fracture surfaces varied according to the degree of wetting of solder on Cu pad and the mount of heat absorbed during soldering. The analytical results indicated that the wetting behaviors of solder on Cu pad and the relative position of the incident laser beams are the two major factors affecting the yield of the fluxless reflow soldering utilizing pulse YAG laser.

摘 要 i
Abstract ii
誌 謝 iv
目 錄 vi
圖目錄 viii
表目錄 x
第一章 前 言 1
2.1. 元件與電路板的組裝技術 3
2.2. 選擇性銲接技術 5
2.3. 雷射選擇性迴銲 8
2.4. 雷射迴銲技術研究之回顧 10
2.5. 介金屬化合物之形成 12
2.5.1. 傳統迴銲技術 13
2.5.2. 雷射迴銲技術 13
2.7. 研究動機 15
第三章 實驗方法 18
3.1. 實驗方法 18
3.1.1. 銲點製備 18
3.1.2. 銲點界面分析 20
3.1.3. 銲點接合強度分析 20
3.2. 實驗設備 20
3.2.1. NEWPORT LW4200 型雷射銲接系統 20
3.2.2. 推球系統 21
第四章 結果與討論 22
4.1. 雷射迴銲條件對銲點外觀與內部形貌的影響 22
4.1.1. 脈衝寬度 22
4.1.2. 雷射功率 22
4.1.3. 迴銲次數 24
4.2. 界面介金屬化合物（IMC）形貌之觀察 25
4.2.1. 傳統迴銲 25
4.2.2. 一次迴銲之界面形貌 25
4.2.3. 二次迴銲之微觀結構 29
4.3. 推力試驗 31
4.3.1. 推力試驗結果 32
4.3.2. 推力試驗破斷面觀察 36
4.3.2.1. 有效銲點一之破斷面觀察 36
4.3.2.2. 不良銲點之破斷面觀察 38
第五章 結 論 43
第六章 未來研究與展望 45
附錄 46
參考文獻 47


圖目錄
圖2-1. 電子封裝的層次區分[3]。 10
圖2-2. PTH與SMT之接合方式：（a）PTH；（b）SMT[3]。 10
圖2-3. 波銲程序示意圖[3]。 10
圖2-4. Drag Soldering 及 Dip Soldering。（a）Drag Soldering之單一噴嘴及（b）Dip Soldering特製噴嘴板[6]。 10
圖2-5. 感應式加熱法示意圖 [7]。 10
圖2-6. Panasonic Soft Beam系統示意圖 10
圖2-7. 可程式控制之雷射迴銲系統 10
圖2-8. UV雷射光從玻璃背面加熱錫球示意圖 10
圖2-9. 脈衝式雷射加熱後之錫球外觀 10
圖2.10. 錫-銅相圖[31]。 10
圖2-11. 錫球推力測試法示意圖[32]。 10
圖2-12. 六種破裂模式[32]。 10
圖2-13. 銲接的兩種型態。 10
圖3-1. 實驗流程 10
圖3-2 多次脈衝加熱式意圖。 10
圖3-3. Newport LW4200 型雷射銲接系統。 10
圖4-1. 不同迴銲時間的銲點外觀 10
圖4-2. 不同的迴銲功率的銲點外觀 10
圖4-3. 200 V-7 msec-2.0 J，二次迴銲的銲點。 10
圖4-4. 錫球置於銅墊上經260°C，10分鐘後所得的界面結構。 10
圖4-5. 不同的脈衝寬度之銲點界面形貌 10
圖4-6. 205 V-10 msec-2.8 J銲點之界面形貌 10
圖4-7.（a）210 V-10 msec-3.2 J與（b）220 V-10 msec-3.9 J之銲點之界面形貌 10
圖4-8. 220 V-10 msec-3.9 J之銲點微觀結構 10
圖4-9. （a）215 V-10 msec-3.5 J之銲點微觀結構 10
圖4-10.（a）220 V-10 msec-3.9 J之銲點微觀結構；（b）為（a）圖圈起處之放大。 10
圖4-11. （a）200 V-7 msec-2.0 J，兩次脈衝銲點微觀結構，圈起處為裂縫。（b）為（a）圖界面處之放大。 10
圖4-12. （a）200 V-10 msec-4.8 J，二次迴銲之銲點斷面形貌及（b）圈起處之EDX成分分析。 10
圖4-13.（a）200 V-10 msec-7.2 J，三次迴銲銲點之破斷表面形貌及（b）橫截面形貌。 10
圖4-14. （a）200 V-7 msec-2.0 J，一次迴銲，（b）200 V-10 msec-2.4 J，一次迴銲及（c）200 V-7 msec-2.0 J，兩次迴銲之銲點推力強度分佈圖。 10
圖4-15.（a）200 V-7 msec-2.0 J，一次迴銲；（b）200 V-10 msec-2.4 J，一次迴銲與（c）200 V-7 msec-2.0 J，二次迴銲有效銲點發生韌性斷裂之銲點橫截面形貌。 10
圖4-16. 各雷射迴銲條件下有效銲點之斷裂表面 10
圖4-17. 不良銲點的斷裂之五種表面型態 10
圖4-18. 各雷射迴銲條件下不良銲點常見的破斷面 10


表目錄
表 2-1. 材料對YAG雷射光的吸收效率[15]。 10
表 3-1. 雷射迴銲實驗參數表（離焦距離 = 1.5 mm）。 10
表 4-1. 不同的迴銲功率的銲點高度與寬度。 10
表 4-2. 圖4.5之界面IMC成分EDX分析結果。 10
表 4-3. 200 V-10 msec-7.2 J，三次迴銲截面觀察的EDX成分分析 10
表 4-4（a）. 200 V-7 msec-2.0 J，一次迴銲之銲點推力測試結果 10
表 4-4（b）. 200 V-10 msec-2.4 J，一次迴銲之銲點推力測試結果 10
表 4-4（c）. 200 V-7 msec-2.0 J，兩次迴銲之銲點推力測試結果 10
表 4-5. 破裂模式一之推力強度分析結果。 10

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