以數值分析來研究覆晶銲點之電遷移現象｜國立中央大學博碩士論文系統

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研究生：	陳欣楷 Hsin-kai Chen
論文名稱：	以數值分析來研究覆晶銲點之電遷移現象 Numerical Analysis on the Electromigration in Electrical Packages
指導教授：	高振宏 C Robert Kao 鄭紹良 Shao-Liang Cheng
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 化學工程與材料工程學系 Department of Chemical & Materials Engineering
畢業學年度：	95
語文別：	中文
論文頁數：	85
中文關鍵詞：	焦耳熱、電流密度、模擬、電遷移、孔洞發展、覆晶
外文關鍵詞：	Joule heating, current density, flip chip, simulation, void propagation, electromigration
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本篇論文是利用有限元素法，透過電腦模擬，分別改變下列三種參數條件：通入電流、環境溫度、網格大小，藉由分析電流密度與環境溫度在不同網格密度下，隨著輸入電流增加的變化及分佈，來探討覆晶銲點之敏感度，並於不同環境溫度與網格密度條件下，找出臨界輸入電流值；並預測在高電流密度之條件下，孔洞生長的可能路徑。
模擬結果顯示：Al導線之中間點的溫度最高，電子流從Al導線進入UBM之處使UBM靠近陰極的邊緣有相當高的電流密度聚集，銲錫嵌入IMC的邊緣處也有很高的電流密度和溫度，這兩區都是關鍵易產生缺陷之處！。相同網格密度、環境溫度，輸入不同電流下，當輸入電流越大，電阻增加越多，焦耳熱的效應更劇烈，溫度上升越高！而電阻即使考慮TCR，焦耳熱的效應中還是以電流大小為主。在高電流密度的條件下，過了潛伏期之後，孔洞最初會在銲料電流密度最大的地方成核，然後開始沿著IMC與銲錫的接面，對應Al導線前緣進入pad的區域擴散，接著往陽極端發展，當孔洞發展至整個截面的99.9％時，銲錫接點產生的焦耳熱會使銲錫達到熔點，覆晶銲點也因此失效。此外，並分析材料熱傳導能力差異及熱源位置對散熱之影響。

In this study, the finite element method is used to analyze flip chip solder joints under electromigration. Current input, environment temperature and element size are the three important factors for such electromigration simulation. We will discuss the sensitivity of flip chip solder joints under electromigration by analyzing current density distribution and temperature distribution under different current input and element size. We will also determine the critical current input for different environment temperature and element size. In addition, we investigate the void propagation in the case of high current input. It is found that the maximum temperature is within the Al trace. The location where electrons enter UBM from Al trace exist rather high current density. The solder next to the IMC also exist rather high current density and temperature. These two locations are both important and easily be damaged. For the same element size and environment temperature, resistance will increase much more when current input increases, and the effect of Joule heating will be more severe. Even though we consider temperature coefficient of resistance, current input is the major factor for the effect of Joule heating. For void nucleation and propagation issue, we use simulation to predict the path which void may propagate, and analyze the effect of Joule heating. In the case of high current input, void nucleation begins at the maximum current density region after incubation time, and then spreads along the contact area of IMC and solder. When 99.9% of the contact window is covered by the void, solder will reach its melting point and then fail by the effect of Joule heating. Furthermore, we will also analysis the influence of heat dissipation by heat conduction ability and location of heat source.

中文摘要……………………………………………………………… .I
英文摘要……………………………………………………………… II
誌謝……………………………………………………………………III
目錄……………………………………………………………………IV
圖目錄………………………………………………………………....VI
表目錄……………………………………………………………...…VIII
第一章 電遷移簡介及文獻回顧............................................................1
1 電遷移原理及動力學表示式………………………………...1
2 擴散機制……………………………………………………...5
3 電流叢集效應與孔洞生成發展……………………………...6
4 焦耳熱效應………………………………………………… .11
5 覆晶銲點之電遷移現象…………………………………… .11
6 通電下之電流密度及熱通量分布…………………………. 15
7 研究動機……………………………………………………. 22
第二章 研究方法介紹……………………………………….………..24
1 有限元素法及軟體介紹……………………………………..24
2 模擬分析程序………………………………………………..25
2.1 定義元素及材料性質………………………….……..25
2.2 建立幾何模型……………………………..………….25
2.3 建立網格……………….……………………………..26
2.4 施加負載及邊界條件………………………………...26
2.5 計算求解 …………………………………...………..27
2.6 後處理…………………………………………...……27
3 理論基礎與方程式…………………………………………..27
3.1電傳導 …………………………………………..……27
3.2 熱傳導………………………………………..………29
3.3 熱對流………………………………………..………30
3.4 熱輻射…………………………………….……….....32
3.5 電熱轉換……………………………………………..32
第三章 模擬及實驗設計……………………………………………..33
1 通電散熱實驗設計………………………………………….33
2 模擬幾何尺寸及材料性質………………………………….33
3 基本假設…………………………………………………….37
4網格設定……………………………………………………..38
5負載設定及邊界條件………………………………………..39
5.1 電熱耦合分析………………………………………..39
5.2 孔洞發展分析………………………………………..39
第四章 模擬及實驗結果與討論……………………………………..41
1 通電散熱實驗結果與討論………………………………….41
2 電熱耦合分析……………………………………………….44
2.1 網格大小影響分析……………………………………44
2.2 輸入電流大小影響分析………………………………47
2.3 環境溫度大小影響分析………………………………49
2.4 模型之電流密度與溫度結果分析……………………49
3 孔洞發展分析……………………………………………….54
4 焦耳熱與散熱分析…………………………………….……64
第五章 結論…………………………………………………………..71
參考文獻…………………………………………………………..72

                                

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