以加速壽命模型評估晶圓級晶片尺寸封裝體在熱循環下之疲勞壽命

Investigation of Fatigue Life of Wafer-Level Chip-Scale Packages under Thermal Cycling Conditions by Acceleration Models

邱柏倫(Po-Lun Chou)

指導教授 ： 吳文方

國立臺灣大學/工學院/機械工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.01302

摘要

現今輕薄型電子產品當道，晶圓級封裝(Wafer-Level Chip-Scale Packages, WLCSP)的產品需求益趨增加，而業界為快速回應市場需求，常壓縮電子產品開發時程，藉由加速壽命試驗，快速取得產品壽命資訊。觀察此些試驗結果，即便在同一測試環境下，封裝體壽命往往具有相當的離散性，並非如多數研究所得結果為一定値。為使模擬分析反應並呈現試驗或實測結果，本研究以有限元素法為分析工具，探討一晶圓級封裝體在業界常用熱循環試驗規範下，因參數變異對其壽命分佈的影響，並藉分析所得之壽命，建構晶圓級封裝體之壽命預估模型。本研究分為三部份，在第一部份方面，本研究選擇一特定晶圓級封裝體，針對其材料與尺寸參數，設定合理的變異，進行力學分析與熱疲勞壽命計算，以探討參數變異對封裝體壽命之影響；在第二部份方面，本研究選擇數個加速壽命模型，針對封裝體在不同測試環境下壽命分佈的模擬結果，以迴歸分析求取模型參數，並探討各模型之優劣，最後選擇較適當的Norris–Landzberg模型來描述加速壽命試驗結果，並分析預估誤差，制定進一步的分析策略；在最後一部份，本研究除增加壽命預估模型參數，以增進預估準確度外，也進行熱循環參數對封裝體壽命的敏感度分析，並配合熱機械疲勞特性，提出壽命預估模型的改善方案。本研究分析結果顯示，熱循環參數中的最高溫度對晶圓級封裝體壽命影響最劇，在JEDEC所述各熱循環試驗條件下，如果選擇最高溫度110℃者為區分試驗條件並搭配Norris-Landzberg加速壽命模型預估封裝體壽命，其平均預估誤僅在1.59%之內。

關鍵字

晶圓級封裝 ； 有限元素法 ； 參數變異性 ； 加速壽命模型 ； 熱疲勞壽命

並列摘要

Wafer-Level Chip-Scale Packages (WLCSP) have become more and more popular due to their light-weights and small sizes. To reduce time-to-market of a product as well as its development cost, the electronics industry often employs accelerated tests to find the life of the product. It appears that test outcome of the product’s life is not determin-istic but a random variable following a certain probability distribution. Therefore, in the present study, a finite element analysis taking uncertainty into consideration of a WLCSP subjected to various JEDEC prescribed thermal cyclic loading conditions is performed. A life prediction model of the WLCSP is constructed based on the analytical result. The study is divided into three parts. In the first part, a few parameters involved in the package size, material property are assumed random to account for their uncer-tainties. In particular, the influence of these uncertainties on fatigue life of the package is investigated. In the second part of the study, nonlinear regression analyses are carried out to find parametric values of several acceleration models. The Norris-Landzberg model is selected after comparing its performance with those of others. In the last part, in addition to parameters of the prediction model, thermal mechanical fatigue properties are taken into account and sensitivity analysis is performed for improvement of the pre-diction accuracy. The final result of the present study indicates the maximum value of the cycling temperature has great impact on life prediction of the WLCSP. In particular, for the studied WLCSP, the maximum temperature of 110℃ is suggested to be selected for dividing all JEDEC prescribed thermal cycling conditions into two groups when predicting lives of the package subjected to different conditions. The prediction errors are found to be within 1.59% by doing so.

並列關鍵字

Wafer-Level Chip-Scale Package (WLCSP) ； Finite Element Analysis ； Uncertainty ； Acceleration Model ； Thermal Fatigue Life

參考文獻

44. 許登凱，電子封裝體受熱循環應力之疲勞壽命分析與可靠度研究，國立台灣大學機械工程研究所碩士論文，民國97年。

3. J. H. Lau and S. W. R. Lee, “Effects of microvia build-up layers on the solder joint reliability of a wafer level chip scale package (WLCSP),” Proceedings of the 51st Electronic Components and Technology Conference, pp. 1207-1215, 2001.

4. D. H. Kim, P. Elenius and S. Barrett, “Solder joint reliability and characteristics of deformation and crack growth of Sn-Ag-Cu versus eutectic Sn-Pb on a WLP in a thermal cycling test,” IEEE Transactions on Electronics Packaging Manufacturing, Vol. 25, No. 2, pp. 84-90, 2002.

5. G. Gustafsson, I. Guven, V. Kradinov and E. Madenci, “Finite element modeling of BGA packages for life prediction,” Proceedings of the 50th Electronic Components and Technology Conference, pp. 1059-1063, 2000.

6. H. C. Cheng, C. Y. Yu and W. H. Chen, “An effective thermal-mechanical modeling methodology for large-scale area array typed packages,” Computer Modeling in Engineering and Sciences, Vol. 7, pp. 1-17, 2005.