錫銀銅合金添加Ce無鉛銲錫球格陣列構裝之動態疲勞可靠度評估

Dynamic Fatigue Life Evaluation of Ce Doped Sn-Ag-Cu Solder Ball Grid Array Packages

鄭智元(Chih-Yuan Cheng)

指導教授 ： 莊東漢

國立臺灣大學/工學院/材料科學與工程學研究所/博士(2009年)

https://doi.org/10.6342/NTU.2009.00029

摘要

無鉛銲錫添加稀土元素已被廣泛證實可以改善其熔點、潤溼性、強度、延展性、抗潛變性及耐振動破裂性，然而目前大多數添加稀土無鉛銲錫的性能研究均集中在塊材材料(bulk material)的基本特性分析，有關實際電子構裝接點的可靠度評估幾乎未見到任何報導。針對電子產品的應用需求，本研究將利用動態疲勞試驗方法有系統地探討Sn-3Ag-0.5Cu、Sn-3Ag-0.5Cu-0.05Ce、Sn-3Ag-0.5Cu-0.5Ce、Sn-3Ag-0.5Cu-0.5Ce-0.2Zn及Sn-1Ag-0.5Cu-0.06Ni-0.01Ge之銲錫球格陣列構裝（Ball Grid Array Packages）的可靠度，同時搭配有限元素分析方法評估電子構裝銲錫接點之受力行為及可靠度壽命。BGA構裝試片之基板(substrate)的銅銲墊將分別採用無電鍍鎳金(ENIG)、浸錫(ImSn)、有機保銲膜(OSP)及無電鍍鎳鈀金(ENEPIG)等四種不同表面處理與採用無電鍍鎳金(ENIG)表面處理的印刷電路板(PCB)來進行試片組裝。
研究結果顯示：在四種不同表面處理的比較上除了ImSn外，其餘三種Sn-3Ag-0.5Cu銲錫接點的可靠度壽命皆高於Sn-3Ag-0.5Cu-0.05Ce，整體比較結果顯示兩者銲錫接點的可靠度壽命差異性不大，有別於添加稀土合金塊材其各項機械性質明顯高於未添加的結果。另外，結合熱因子動態疲勞試驗結果顯示試驗溫度越低，可靠度壽命越高，且Sn-3Ag-0.5Cu銲錫接點在所有試驗溫度條件下其可靠度壽命皆高於Sn-1Ag-0.5Cu-0.06Ni-0.01Ge，但後者表現出較佳的高溫疲勞特性。最後在Sn-3Ag-0.5Cu-0.5Ce及Sn-3Ag-0.5Cu-0.5Ce-0.2Zn銲錫合金接點可靠度的比較結果得知，雖然添加Zn可抑制因添加稀土元素Ce造成的錫鬚快速生長，但添加Zn後會使得銲錫接點整體的可靠度稍微下降。

關鍵字

無鉛銲錫 ； 稀土元素 ； 有限元素分析 ； 動態疲勞試驗 ； 可靠度評估

並列摘要

Pb-free solders added with rare earth elements have been widely verified to be able to improve their melting temperature, wettability, strength, ductility, creep resistance. However, most studies for the performance of rare earth doped solders are concerned with the analyses of their basic materials characteristics. The evaluation of reliability for real electronic packaging joints are scarcely reported. Aiming at the application requirements of electronic products, this project will systematically investigate the reliability of BGA packages by dynamic fatigue life test method with Sn-3Ag-0.5Cu, Sn-3Ag-0.5Cu-0.05Ce, Sn-3Ag-0.5Cu-0.5Ce, Sn-3Ag-0.5Cu-0.5Ce-0.2Zn and Sn-1Ag-0.5Cu-0.06Ni-0.01Ge solder materials. Finite element analysis was also used to estimate the stress concentration phenomenon and probable failure location. The surface finishes for Cu pads on BT substrates include ENIG, ImSn, OSP and NiPdAu. Both the traditional and Halogen-free substrates are employed for FR-4 PCB.
The results show that the Sn-3Ag-0.5Cu-0.05Ce solder joints have similar fatigue lives as the undoped Sn-3Ag-0.5Cu specimens in spite of the various surface finishes such as ENIG, NiPdAu, ImSn and OSP. Dynamic fatigue life tests with thermal effect indicate that lower temperature, higher reliability, and Sn-3Ag-0.5Cu solder has higher fatigue life than Sn-1Ag-0.5Cu-0.06Ni-0.01Ge in all test conditions, but Sn-1Ag-0.5Cu-0.06Ni-0.01Ge has better high temperature fatigue resistance. The results also imply that although adding the Zn elements in the Ce doped solders can inhibit the occurrence of rapid whisker growth, but it cannot assure the improvement of fatigue reliability of its solder joints in real packages.

並列關鍵字

Pb-free solders ； Rare earth elements ； Finite element analysis ； dynamic fatigue life test ； Reliability evaluation.

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