版權所有 翻印必究 Creep of Thermally Aged SnAgCu-Solder Joints S. Wiese, M. Roellig, K.-J. Wolter Dresden University of Technology, Electronic Packaging Laboratory, Germany TU Dresden, Fak. Ed, IAVT, D Dresden /4/281 STUT 太陽能材料與模組實驗室 日 期： 指導老師：林 克 默 、 黃 文 勇 學 生：陳 立 偉

版權所有 翻印必究 Outline 1.Introduction 2.Experiments on Bulk Samples 3.Experiments on PCB Samples 4.Experiments on Flip-Chip Joints 5.Comparison between different specimen types 6.Conclusions 2015/4/282 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Introduction In order to characterise the mechanical behaviour of SnAgCu solders, there have been a myriad of creep tests conducted on bulk solder specimens. Performing these tests is not complicated and the results are easy to interpret. These smaller test vehicles do not necessarily represent the physics found in real solder joints because they are manufactured differently than solder joints in electronic packages. 2015/4/283 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Investigations by Stormswold [1] showed the dependence of creep resistance on the volume fraction of Ag in SnAg solders and the cooling rate during solidification Yan et al. [2] showed the influence of the soldering process on the mechanical properties Berck et al. [3] proved the existence of the Orowan bowing as a basic deformation mechanism Kerr and Chawla [4] proved the existence of nanometer-sized precipitates as the major obstacles for dislocation movement in SnAgCu solders. 2015/4/284 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 the creep research activities on the Sn-Ag-Cu system into two branches. The first branch follows the idea of a double power creep law, which has broad fundamental aspects of material physics. The other branch prefers a sinh creep law, which has no physical basis but fits well into several FEM codes 2015/4/285 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 The research presented in this paper follows the first branch and focuses on the physics behind the measured creep deformations. The major goal is to correlate detected deformation kinetics with processes and operating conditions that can be found in typical environments for electronic packages. 2015/4/286 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 another question concerning the decline of creep resistance over time is when the solder is exposed to higher temperatures. To address these issues an experimental method was chosen that is based on investigations on different specimen types. 2015/4/287 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Experiments on Bulk Samples Figure 1: Design and microstructure (SnAgCu) of bulk specimen; Load frame for creep tests on bulk specimens 2015/4/288 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Figure 2: Creep data for bulk specimens SnAg3.5SnAg3.8Cu /4/289 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Experiments on PCB Samples Figure3: Design and microstructure (SnAgCu) of PCB specimen; Test fmture for creep tests on PCB specimens 2015/4/2810 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Figure 4: Creep data for PCB specimens 2015/4/2811 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 The results of the creep experiments on PCB samples is shown in diagrams in Figure 4. The steady state creep rate is plotted versus the applied stress. The upper diagram shows the results for SnAg3.5 solder. The creep data indicates a simple power law behaviour. 2015/4/2812 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 However, it needs to be assumed that in both, a low stress behaviour might not have been detected because the creep rates that were achieved during the creep tests were too high. The lower diagram shows the results for SnAg3.8Cu0.7 solder. The data indicates a double power law creep behaviour. No difference could be found between as-cast specimens and thermally stored specimens. 2015/4/2813 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Experiments on Flip-Chip Joints Figure 5: Design and microshucture (SnAgCu, stored 24W125 ℃ ) of flip chip specimen 2015/4/2814 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Figure 6: Test setup for experiments on flip-chip joints 2015/4/2815 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Figure 7: Creep data for flip-chip joints 2015/4/2816 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 In order to compare the creep behaviour between different specimen types, the raw creep data was fit using Equation /4/2817 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 2015/4/2818 STUT 太陽能材料與模組實驗室

版權所有 翻印必究 Conclusions 實驗的結果表示，短時間的焊條儲熱現象明顯， 但使用更長時間的再儲熱，並不會改變焊條的 潛熱現象。 實驗結果發現銅、金，金屬間化合物能明顯加 強 SnAg 焊料和 SnAgCu 焊料。然而，最終強化效 果取決於焊料種類，所以其強度優於小體積的 倒晶接合。 2015/4/2819 STUT 太陽能材料與模組實驗室