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  • 學位論文

溫度循環負載作用之無鉛化封裝的可靠度評估

Investigations on the Reliability Assessment of Lead-Free Packages Subjected to Temperature Cyclic Loading

指導教授 : 鍾文仁
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摘要


電子微系統封裝中,傳統錫鉛Sn-Pb與無鉛化錫球在材料性質與製程參數上有相當明顯的差異,就以Sn-Ag/Sn-Ag-Cu之二元及三元合金來說,其熔點比Sn-Pb高出30℃,這些都依序會導致在塑性及潛變行為上很大的分歧。因而本文首先使用田口法針對晶圓級晶片尺寸封裝(WLCSP)之三種無鉛銲料(96.5Sn-3.5Ag、95.5Sn-3.8Ag-0.7Cu及95.5Sn-3.9Ag-0.6Cu)分別在PCB上對溫度循環負載的效應;利用 直交表配合升溫率、高溫恆溫溫度、低溫恆溫溫度、高溫恆溫時間及低溫恆溫時間等五個溫度負載參數,進行剪潛應變、剪塑性應變及剪塑性-潛應變行為之三個實驗分析。分析結果顯示,在這三種實驗結果發現測試因子中:(1)溫度範圍的大小對剪應變範圍的效應與影響是最大的;(2)在剪潛應變的實驗中,高溫溫度影響最大而低溫溫度次之;剪塑性應變與剪塑性-潛應變兩個實驗分析中,皆是低溫溫度影響最大而高溫溫度次之。 接著,使用63Sn-37Pb錫鉛銲料及96.5Sn-3.5Ag、95.5Sn-3.8Ag-0.7Cu兩種無鉛銲料,分別在四種不同的溫度循環負載作用下,進行彈性-塑性-潛變之熱機械行為的比較;研究結果可知:(1)在這三種合金銲料中,其等效塑性應變範圍的大小依序分別為96.5Sn-3.5Ag、95.5Sn-3.8Ag-0.7Cu及63Sn-37Pb;(2)而96.5Sn-3.5Ag最能防止潛變;(3)在每種溫度負載中,95.5Sn-3.8Ag-0.7Cu之彈性-塑性-潛變的熱機械行為比96.5Sn-3.5Ag相近於63Sn-37Pb錫鉛銲料;(4)在這個部分的探討分析中,影響晶圓級晶片尺寸封裝之錫球組合在PCB上的可靠度效應最大的也是溫度範圍。

並列摘要


There are clear differences between the microstructures of classical Sn-Pb solder and the new lead-free solders in material properties and processing parameters in the electronic packages. For example, the melting point of Sn-Ag/Sn-Ag-Cu solders is higher than that of Sn-Pb solders by 30℃ in particular. These in turn lead to significant divergences in plastic and creep behaviors. In this study, the effects of the temperature cyclic loading on the three lead-free solder joints of 96.5Sn-3.5Ag, 95.5Sn-3.8Ag-0.7Cu, and 95.5Sn-3.9Ag-0.6Cu bumped wafer level chip scale package (WLCSP) on printed circuit board (PCB) assemblies are investigated by Taguchi method. The orthogonal arrays of is applied to examine the shear strain effects of solder joints under five temperature loading parameters of the temperature ramp rate, the high and low dwelling temperatures, and the dwelling time of both high and low temperatures by means of three simulated analyses of creep, plastic, and plastic-creep behavior on the WLCSP assemblies. It is found that, (1) The range of temperature loading is the most significant factor on the effects of shear strain range from these analyses; (2) The effect of high dwelling temperature on the shear strain range is larger than that of low dwelling temperature in creep analysis, while the effect of high dwelling temperature on the shear strain range is smaller than that of low dwelling temperature in both plastic and plastic-creep analyses. Secondly, the elastic-plastic-creep behaviors of the 96.5Sn-3.5Ag and 95.5Sn-3.8Ag-0.7Cu lead-free solders with the classical 63Sn-37Pb solder are subjected to four different temperature cycle tests and then investigated by finite element analysis. It can be seen that, (1) The equivalent plastic strain range of 96.5Sn-3.5Ag solder is larger than that of 63Sn-37Pb and 95.5Sn-3.8Ag-0.7Cu solders, and the equivalent plastic strain range of 95.5Sn-3.8Ag-0.7Cu is slight higher than that of 63Sn-37Pb solder; (2) The 96.5Sn-3.5Ag solder alloy can sustain more creep than others; (3) The elastic-plastic-creep behaviors of the 95.5Sn-3.8Ag-0.7Cu solder in each temperature loading is more consistent with the 63Sn-37Pb solder than that of 96.5Sn-3.5Ag solder;(4) From a point of view in which investigates the elastic-plastic-creep behaviors to these three solder alloys in detail, the range of the temperature loading is also the most important factor to the reliability of the solder bumped WLCSP on PCB assemblies.

參考文獻


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