本研究發展出一套可模擬銲錫接點在迴 銲過程流動行為的程式，利用此程式可以模 擬無荷重銲錫接點在改變銲錫體積、錫墊形 狀與尺寸、基板潤濕性等參數的形狀變化，
並可計算出銲錫接點的站立高度與最大寬 度，與實驗結果比較可得到良好的吻合。另 外本研究也使用軟體Surface Evolver 來模擬 荷重銲錫接點的形狀變化，討論的影響參數 有銲錫體積、元件重量、元件尺寸、錫墊與 元件形狀的改變等等，並與實驗結果比較，
亦得到良好的準確性。
由模擬結果與實驗驗證可得到以下的結論：
1. 無荷重銲錫接點型態變化：
在相同的錫墊上，銲錫體積與站立高 度、最大寬度、接觸角皆呈正比。若錫墊尺 寸不同，放置在錫墊尺寸較小上的銲錫有較 高的站立高度。若錫墊形狀不同，放置在圓 形錫墊的銲錫站立高度略高於正方形錫墊，
但彼此差異不大。改變基板潤濕性，發現基 板潤濕性較差的銲錫隆點有較低的站立高度 和較大的最大寬度。觀察錫墊配置與最大可 能銲錫體積量的關係，由模擬結果得知錫墊 低於周圍綠漆的設計較錫墊高於周圍綠漆的 設計能獲得較大的最大可能銲錫體積。
2. 荷重銲錫接點型態變化：
在放置相同元件的條件下，錫墊面積越 大則站立高度越低。銲錫體積量則與站立高 度成正比，且體積量增加對銲錫站立高度有 顯著的影響。比起銲錫體積的影響，元件重 量對銲錫站立高度的影響不大。而元件尺寸 與銲錫接點站立高度成反比。改變元件與錫 墊形狀，發現圓形元件放置在圓形錫墊上有
最高的銲錫站立高度，而正方形元件放置在 正方形錫墊上有最低 銲錫站立高度。
七、成果自評
本研究為三年期的研究計畫，研究進度 均能幾近目標。實驗部分，對於銲錫的凝固 行為能充分的了解，熱物性質與顯微組織更 有深入之研究，將來若是使用此銲錫材料，
在使用上增加其可靠度；模擬部分，銲錫接 點的型態變化於電子構裝上能作有效的預 測，迴銲過程中錫球內部流場變化，包括溫 度、壓力及速度，對於迴銲過程中能有更充 分掌握；此外，模擬及實驗能互相作驗證得 到令人滿意的結果。上述之結果，均在本計 畫有相關的論文發表於國際期刊及會議。
附錄
Materials Science & Engineering A, 413-414 (2005) 312-316.
Solidification behavior of Sn-9Zn-xAg Lead-free Solder Alloys
Ying-Ling Tsai and Weng-Sing Hwang*
Department of Materials Science and Engi-neering,National Cheng Kung University,
Tainan, Taiwan
Abstract
Solidification behaviors of Sn-9Zn-xAg lead-free solder alloys, which vary with Ag content, are examined by using scanning elec-tron microscopy, elecelec-tron probe microanalysis, X-ray analysis, computer aided-cooling curve analysis and differential scanning calorimetry.
The backscattered images and X-ray diffraction patterns indicate that with the addition of silver two intermetallic compounds; γ-Ag5Zn8 and ε-AgZn3, form in the expense of zinc phase. The solid fraction versus temperature relationship and microstructure analysis show that Sn-Zn eutectic structures appear following the forma-tion of primary tin. It is concluded in this study
that the complicated solidification process of Sn-9Zn-xAg alloys can be described as L(liquid)
→ L + γ-Ag5Zn8 → L + γ-Ag5Zn8 + ε-AgZn3 → L + γ-Ag5Zn8 + ε-AgZn3 + β-Sn → γ-Ag5Zn8 + ε-AgZn3 + β-Sn + eutectic (Sn + Zn).
Keywords: lead-free solder alloy, solidification, intermetallic compound
Materials Transactions, Vol.47 No.04 (2006) pp.1186-1192 © 2006 The Japan Institute of Metals
The Simulation of Shape Evolution of Solder Joints During Reflow Process and Its
Experi-mental Validation
Ya-Yun Chou1, Hung-Ju Chang1, Jer-Haur Kuo1 and Weng-Sing Hwang1,2
1 Department of Materials Science and Engi-neering, National Cheng Kung University,
Tainan, Taiwan, R.O. China
2 Metal Industries Research and Development Centre, Kaohsiung, Taiwan, R.O. China
Abstract
A three-dimensional computer aided analysis system has been developed in this study based on fluid dynamics to simulate the shape evolution of solder joints during the re-flow process.
The solution of velocity and pressure fields is based on SOLA (SOLution Algorithm) scheme, and the method to construct the inter-face and the transportation of volume fractions of liquid in the cells are coupled with PLIC (Piecewise Linear Interface Calculation) and VOF (Volume of Fluid) technologies. In order to consider the effect of surface tension on a fluid surface, the CSF (Continuum Surface Force) model is employed.
The simulated results are compared with experimental measurements and good consis-tency is observed. Furthermore, the simulated results can reveal the evolution of the molten solder from its initial state to the equilibrium state. It is also capable of analyzing the over-flow conditions when the amount of solder de-posit is too much to be constrained in the sol-der pad, which is not achievable by the
en-ergy-based technique such as Surface Evolver.
Keywords: mathematical modeling, solder joint, reflow process, Surface Evolver
Conference Program IMAPS-Taiwan 2006 Technical Symposium
Effects of Al Addition on the Microstructure and Solidification of the Sn - 8.5Zn - 0.5Ag -
0.1Ga - xAl Lead-free Solder Alloys
Chi-Wei Chou1∗, Ming-Hsiu Tsai1, Hao-Long Chen2, Weng-Sing Hwang1
1. National Cheng Kung University, 2. Kao Yuan University.
∗No.1, Ta-Hsueh Road, Tainan 701, Taiwan.
Tel: +886-6-275-7575-62963, Fax:
+886-6-234-4393 and E-mail:
Abstract
The microstructure and solidification of Sn-8.5Zn-0.5Ag-0.1Ga-xAl lead-free solder al-loys, where x varies between 0.01 and 3.0 wt.%, were examined by using X-ray analysis, scan-ning electron microscopy, energy dispersive spectrometer, differential scanning calorimetry and computer aided-cooling curve analysis.
The Ga is uniformly distributed in the Sn-matrix, Al combines with Ag and Zn to form an Al-Ag compound and Al-Zn (Al-rich) phase, and Ag combines with Zn to form Ag-Zn com-pound. The DSC profiles of Sn-8.5Zn-0.5Ag-0.1Ga-xAl alloys show that a large endothermic peak and finite tail-off were observed with proceeding small for each solder alloy. The results indicate that the Al contents varied from 0.01 wt.% to 2.0 wt.%, and the
melting point of the Sn-8.5Zn-0.5Ag-0.1Ga-xAl solder alloys decreased from 197.9 to 195.5℃, because the Ag-Zn intermetallic compounds decreased and the Ag-Al increased in the alloys.
The pasty ranges of the alloys, measured by heating curves, increase from 7.8 to 9.4℃ and that measured by cooling curves, increase from 2.7 to 3.7℃. The solid fractions versus tem-perature relationship curve and transition temperatures of these solders upon cooling were identified with cooling curves as well as with differential scanning calorimetry.
Keywords: Lead-free, solder, alloy, solidifica-tion, microstructure, computer aided-cooling curve analysis
誌謝
本 研 究 承 蒙 國 科 會 經 費 之 資 助 NSC94-2216-E-006-009，在此謹以誌謝。
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