目前高功率的覆晶式(Flip-Chip) GaN LED 在照明光源的運用為一重要趨勢。相較於正面發光的傳統wire-bonding 方式，Flip-chip LED 提供較好的散熱系統，所產生的熱可由下方面積的p-type 銲料凸塊所導開。經由本實驗室FIB(Focus Ion Beam)的觀察， 目前Lumileds 所使用的凸塊為錫鉛合金， 但未來無鉛銲料的使用勢在必行。無鉛銲料的製程和結構如何影響LED 歐姆接觸行為及散熱效率，是一個非常重要的問題。本計劃第一年將就此一問題，規劃並加以解決，其進行方式如下：(1)研究界面反應及迴銲溫度對於整體金屬墊層的電性及光反射率的影響、(2)以FIB 與TEM 觀察各功能金屬層間交互擴散及反應行為對於整個金屬化層的電性及光反射率的影響。本計畫的第二年將進一步開發高散熱效率的金凸塊及覆晶接合，金凸塊的最佳大小及尺寸將利用電腦熱流模擬所取得。在這年度的下半段運用預購買的覆晶鍵合機開發覆晶封裝製程。而在第三年將運用電腦熱流模擬設計一適當的銅散墊片尺寸， 運用In 鍵合Si submount 與銅散墊片。再進行整體LED 覆晶封裝L-I 曲線的量測。最後我們會建立模擬以描述散熱效率(熱流模擬)與發光效率(L-I 曲線)的關係。藉由本計劃的進行可將總體package 的thermal resistance 由300K/W降至15K/W 以下。使得以無鉛覆晶封裝LED 之發光效率提升， 以達成照明光源之目的。本計畫除了上述之目標之外， 將就一些關鍵的技術作深入的學術研究。 Nowadays, high-power LED is replacing all kinds of lighting devices. Comparing to the traditional wire-bonding LED packing, flip chip assembly provides a better heat dissipation system. Therefore, it has been reported that LED in flip-chip packing has better lighting efficiency than in other packaging methods. We have found that the flip-chip bumps developed by Lumileds LED are SnPb solder bumps. Yet, as we know, Pb-free solder bump has been a 「must」 in the opto-electronic industry due to the environmental and humane health issues. How the process of Pb-free solder affects the lighting performance of LED is a very important issue. In the first year of this project, we will study the effect of interface reaction between Pb-free solder and metallization on the behavior of Ohmic contact and light reflectivity of the GaN/metallization interface. In the second years, we will design a new Au bump, which will provide better heat dissipation and promote better lighting effeciency. In the third year, using computer simulation to design the optimum size and shape of Cu heat spreader. Then, using In bonding to bond Si submount with Cu heat spreader. We believe that In bonding will reduce thermal resistance of entire LED flip-chip structure. At final, we will build a model to explain the relationship between LED heat dissipation efficiency and lighting efficiency. 研究期間：9608 ~ 9707
