溫度效應對FCBGA在彎曲試驗下之疲勞壽命的影響

Thermal Effects on the Fatigue Life of FCBGA Component under Cyclic Bend Test

陳淑鈴(Shu-Ling Chen)

指導教授 ： 陳永樹

元智大學/工程學院/機械工程學系/碩士(2007年)

摘要

本研究主要在探討溫度效應對覆晶球柵陣列構裝(Flip Chip Ball Grid Array, FCBGA)元件可靠度之影響進行研究。研究方式係以四點彎曲測試，分別對FCBGA元件在25℃、75℃以及100℃之條件下，進行循環彎曲試測，以期了解構裝內部錫球在溫度效應下之疲勞壽命。在四點彎曲測試中，採用具有Daisy Chain的FCBGA做為測試樣品，Daisy Chain將FCBGA內部的每個錫球串聯成電路，在進行四點彎曲測試時，同步擷取Daisy Chain的電阻訊號，據以判定元件是否失效，並透過光學顯微鏡觀察錫球之失效模式。此外，同時利用有限元素分析，模擬FCBGA元件在不同溫度下之四點彎曲測試時錫球之受力情況，並由模擬結果計算角落錫球於循環彎曲測試之塑性應變區間，配合疲勞壽命公式，估算錫球之疲勞壽命。所得之理論計算壽命值再與實驗壽命值比較，探討溫度效應對元件可靠度之影響。
研究發現元件壽命會隨著溫度上升而下降，而錫球發生疲勞破壞的位置在於錫球與電路板接合界面上。此外，在有限元素分析中，先後選用四分之一及切片模型進行分析，以進一步探討不同分析模型對疲勞壽命預估之準確度的影響，比較之後發現以四分之一模型所得之結果較為準確。綜合言之，本研究對於FCBGA構裝元件於溫度效應下之可靠度，提供一個有效的評估模式，將可提供設計者於產品設計時的參考，以期達到在設計階段即可掌握元件之可靠度。

關鍵字

彎曲測試 ； 疲勞壽命 ； 覆晶式球柵陣列構裝 ； 有限元素分析

並列摘要

In this study, the temperature effect on the reliability of the Flip Chip Ball Grid Array (FCBGA) component is investigated through combining experiment, finite element analysis (FEA) and the theoretical fatigue life calculation. The four-point bend test is conducted for the fatigue life of the FCBGA at various evaluated temperatures, namely 25℃, 75℃ and 100℃. During the tests, the daisy chain circuits, which link up all the solder balls of the component in series connection with certain initial resistance, are used for the checking up of the component failure. The surge in the resistance of the circuits are used as indices for the solder ball’s failure and the corresponding test cycle is then regarded as the fatigue life of the test component. After the tests, the failure mode analysis is introduced to observe the failure mechanism of the solder balls.
For the finite element analysis, it is employed to simulate the FCBGA component when subjected to a cyclic bending load under specified temperatures. The resulted strains at the corner solder ball can then be used to estimate the fatigue life with the theoretical fatigue life model. The influence of the temperature effect on the reliability of component can be examined further by comparing the estimated fatigue life with the experimental fatigue life.
It is found that the life of the FCBGA component at higher temperatures is less than that at lower temperatures. The failure locations are all observed to occur at the interface between bulk solder and printed circuit board. Besides, the accuracy of the fatigue life prediction with the quarter and the sliced finite element models is also examined. It indicates that the former is more accurate than the later in predicting the fatigue life. To summarize, the investigation offers an efficient way to evaluate the temperature effect on the reliability of the FCBGA component. It can provide the designer to have idea of the component life so that the reliability can be improved right at the design stage.

並列關鍵字

Bend Test ； Fatigue Life ； FCBGA ； FEA.

參考文獻

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