近十年來由於電子商品的市場需求日增，而商品為了朝向輕薄短小的世界潮流，對於電子材料的品質，要求更高的水準，於是許多關於這方面的研究也越來越多；而由於二元合金固化是生產電子材料上，最主要的製程，並且在未來的電子材料及航空工業的需求上，如矽晶圓、氣渦輪葉片，都需要更高的產品品質；如何改良製程獲得高品質的原材，就變的更重要了。然而，在合金固化的過程中，流體的傳遞現象，對於材料的結構及機械性質影響很大，再加上晶體成長過程中還有許多不同形態的缺陷需要去克服，所以合金固化一直受到學術界廣泛的研究。
而利用單向固化製程，固化合金可以得到晶格排列較整齊以及較佳的機械性質，如較佳的強度；但單向固化製程中，仍然會有缺陷的發生，降低了固化合金的機械性質。而這些缺陷常發生在固化合金中的固液接觸面上，所以我們可以合理的推測，固化時固液介面的形狀改變會對產品的品質有很大的影響，如晶體中差排密度及析出物破裂的形成，均與固液介面的穩定性有關。為了改善這種缺陷的情況，本文將針對合金固化時，研究固液介面的變化情形，並嘗試改變固化系統的參數，分析對固液介面形態不穩定(morphological instability)的影響。
本文模擬鉛-錫合金單向固化的流場，並假設本系統的單向固化流場作濃度週期性調變，利用解析解的方法，探討這種情況下系統的基態流場的變化，藉此了解此基態流場的特性；接著再對此基態流場作線性穩定分析，來探討固液介面的形態不穩定，並討論系統在濃度週期性調變下特定的變動頻率 值及變動振幅δ值大小，對系統同步及次調和兩種形態不穩定模態之影響。

In the process of producing electronic products, solidification is one of the most important processes. For the requirement of future electronic material and air industry, such as silicon wafer and turbine, both request better quality manufacturing process. How to improve the manufacturing process effectively has become more significant. In this paper, we analyzed the alteration of the interface in the process of solidification. After that, we changed the parameters of solidification to see if it takes place in the effect of morphological instability.
We simulated the directional solidification process of Pb-Sn alloy by assuming the modulation of the concentration and temperature in flow field. To understand the characteristics of basic state, we investigated the changes of basic state in this situation by the analytic solution. The two morphological instability modes, synchronous and subharmonic modes, were then investigated by linear stability analysis under specific frequency and amplitude.

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