臺灣博碩士論文加值系統

高功率發光二極體(High-power light-emitting diode, HP-LED)因具有高發光率、省電、無汞、壽命長等優勢，逐漸取代市面上傳統的白熾燈泡成為固態照明的主流。目前LED的輸入電功率僅有一半左右轉換為光能，其餘則轉換成熱能，若未能適時將熱移除，勢必影響二極體元件的發光強度與壽命。以傳統水平結構GaN型LED為例，熱能大部分藉傳導方式由晶片背面，經接合之固晶材料(die-bonding materials)以及印刷電路板、散熱鰭片等路徑排出，因此，散熱儼然成為LED製程相當重要的課題。
其中固晶材料直接與LED晶片接合是散熱排除的第一道途徑，由於製程成本考量，傳統封裝廠常以銀膠或高分子膠等作為LED的固晶材料，但隨著發光效率的需求提升，其輸入功率也同步提高，由於較低的熱傳導係數無法及時將高功率LED所產生的熱導出，使得LED晶片內部結點溫度過高，造成LED壽命衰減。因此，散熱特性優秀的金屬類銲料近年來發展相當迅速，傳統在封裝產業上，錫鉛銲料由於其熔點低(183℃)，在電子產業中被廣泛使用，然而，鉛會嚴重影響人類的中樞神經，製程廢棄物亦會汙染環境，歐盟也於2006年發布RoHs指令禁止電子產品含有鉛物質，取而代之的材料種類繁多，常見如錫膏如(SnAgCu合金)、錫鉍銲膏(SnBi合金)與金錫銲料(Au-20%Sn合金)等作為替代的固晶材料，但因Au-20%Sn合金與SnAgCu合金熔點較高(280、220℃↑)，為使其熔化，固晶製程的溫度必須提升至銲料熔點之上，可能造成模組熱應力問題以及製程成本提高。
本研究接續先期研究所開發出的新型低溫金屬固晶接合製程，將鉍/錫分別鍍於以銅鍍錫為表面金屬層之商用散熱基板，再以低溫熱壓方式使錫鉍原子藉由交互擴散達成共晶組成，使界面發生液-固反應完成固晶接合，爾後以長效熱處理與高溫信賴性測試分析此低溫固晶製程對於LED的微結構變化、固晶接附力、光特性與熱特性之影響。

The high-power light-emitting diodes substitute traditional incandescent gradually because of their high luminous efficiency, electricity saving, mercury less and longer life time. Currently, only half of the input power transforms into light for light emitting diodes operation, the rest half transforms into heat. If heat cannot be dissipated timely, the luminous intensity and life time of LEDs decrease. For GaN-based LEDs, heat dissipates from LED backside, die-bonding materials, MCPCB, and heat sink. Thus, heat dissipation technology is very important in LED fabrication.
Die attach adhesive (DAA) is the first path for LED heat dissipation. Considering the fabricate cost, silver paste or epoxy paste are usually used for the die-bonding process. In order to reach the requirement of increasing luminous efficiency, the input power needs to be increase. However, those DAAs have low thermal conductivity which can’t dissipate heat immediately. The increasing of junction temperature will decrease LED life time. In packaging fabrication, electronic industry used Pb-Sn solder because of its low melting point (~183℃). However, metallic Pb affects the central nervous system of human body and also contaminates the environments. In 2006, European Union unit defined a rule (RoHs) which mentioned that Pb cannot be used in the electronics products. Therefore, some replacement materials about Sn-Ag-Cu, Sn-Bi or Au-Sn solder come out in these several years. However, some of them have a high melt point which increases manufacture cost or is harmful to thermal stress issue.
This study follows a previous research in our laboratory which developed a new low-temperature die-bonding structure fabrication. A trilayer of Sn/Bi/Sn was deposited on a MCPCB substrate as the die-bonding material for a LED die. The eutectic Sn/Bi system melts at a lower eutectic temperature (138℃) by using a facile thermocompression process, and accomplished the die bonding via liquid/solid reactions. Meanwhile, the microstructure, adhesives shear strength, optical and thermal properties will be the main points in this investigation.

目錄
致謝 i
中文摘要 ii
Abstract iii
目錄 iv
圖目錄 vi
表目錄 ix
第一章 前 言 1
第二章 文獻回顧 2
(一) 高功率發光二極體之原理與發展趨勢 2
2.1.1 發光二極體之發光原理與製程 2
2.1.2 發光二極體之發展與課題 4
(二) 高功率發光二極體固晶製程與分析 18
2.2.1 發光二極體構裝介紹 18
2.2.2 界面反應 20
2.2.3 熱學量測分析儀之原理 25
2.2.4 機械性質分析簡介 27
第三章 實驗方法 31
(一) 高功率發光二極體之固晶材料開發與分析 31
3.1.1 固晶材料之製備與樣品製作 31
3.1.2 發光二極體之特性分析方法 35
3.1.3 發光二極體之固晶機械性質分析方法 36
(二) 高功率發光二極體之固晶界面反應 36
3.2.1 發光二極體固晶過程之液/固反應 36
3.2.1 發光二極體封裝完成後之固/固反應 41
3.2.2 發光二極體之金相樣品之製備與分析 41
第四章 結果與討論 43
(一) 高功率發光二極體之固晶材料與界面分析 43
4.1.1 固晶材料微結構分析 43
4.1.2 固晶材料熱處理微結構分析 46
(二) 高功率發光二極體之固晶材料與界面分析 49
4.2.1 固晶材料對LED之表面溫度分析 49
4.2.2 固晶材料對LED之熱暫態特性分析 52
4.2.3 固晶材料對LED之光衰特性分析 54
(三) 高功率發光二極體之機械性質分析 55
第五章 結論 64
(一) 實驗結論 64
(二) 未來展望 65
第六章 參考文獻 66

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