外文翻譯--- 大功率白光led封裝工藝技術與研制

1、<p><b>　　附錄A</b></p><p>　　Research&Fabrication of Packaging Technology for High Power White LED</p><p>　　Comparing with the traditional incandescent and fluorescent lighting

2、, the high Power white LED has many significant incomparable advantages such as energy saving, envirorunental protection, long life and so on. It represents the development direction of green lighting, and is moving into

3、 the field of lighting rapidly. From the packaging technology of 1 W high-bower white LED, the cost and performance of several methods were analyzed and compared for white light LED. Based on this, using the“blue</p&g

4、t;<p>　　Introduction</p><p>　　LED use semiconductor chips of solid as light emitting materials, the use of electric light-emitting. As a light source, LED's advantages is in energy saving, envir

5、onmental protection and long-lived three aspects. LED does not depend on heating filament to light-emitting, energy conversion efficiency is very high, in theory only 10% of the energy consumption of incandescent. compa

6、red with fluorescent, LED can be up to 50% of the energy saving effect. Special survey showed that the annual elec</p><p>　　White LED production method</p><p>　　At present, the way to product wh

7、ite light with LED chips show in the table1.</p><p>　　Tab.1 Preparation principle of“blue chip&YAG phosphor"</p><p>　　As a result of "blue light chips + YAG phosphor " have a

8、 white LED production method of the lowest cost, practicality's characteristic has become the mainstream products on the market. Therefore, the experiment chosen this method to product white LED.</p><p

9、>　　Key processes and technical measures Compared with the ordinary white-light LED, the high-power (W-class power) white LED has a higher power and more heat, therefore, in the packaging process, be considered ligh

10、t, electricity, heat and other factors.</p><p>　　Flip-chip technology Installed in the traditional way of LED chip package, because of P-type doped GaN difficulties, the current widely used in the prepar

11、ation of P-type GaN metal transparent electrodes on the ways in which even the spread of current in order to achieve the purpose of light-emitting uniformity. P-type GaN on the transparent electrode metal to absorb 30% t

12、o 40% of a light, while n-type electrode and the lead will block some of the revealing light, which severely affect the ch</p><p>　　This experiment, to take advanced flip chip (flip-chip) technology, through

13、 the P-chip and n very very bottom of the production of ultrasonic gold wire leads to solder joint as the electrode structure and the outside of the Si chip on the production floor gold lead, to overcome the above-mentio

14、ned LED chips are mounted in a light efficiency and the shortcomings of current constraints; chip PN junction from the heat generated by gold wire solder through a direct transfer to the Si substrate and h</p><

15、;p>　　Optical design techniques</p><p>　　1. To improve the refractive index</p><p>　　High-power white light LED chip refractive index of n = 2-4, much higher than the lens plays a role in the

16、refractive index of packaging materials (generally of the refractive index of epoxy resin at about 1.4-1.5). Therefore, when the light after the chip packaging materials, in a total reflection from the interface effect o

17、ccurred, resulting in about 50% of the light reflection back to the chip itself, can not be effectively exported to become ultra-high brightness LED chips from low light eff</p><p>　　2. Optimization of spher

18、ical optical lens</p><p>　　High-power LED devices at the top of the spherical lens design, LED light to improve the efficiency of market applications, also plays an important role. In the lens materials, sel

19、ect a high transmittance of the glass or acrylic and other synthetic materials to improve light efficiency; applications in the market, according to lighting differences in optical design of the needs of the market deman

20、d for the company's largest spherical lens structure basis, taking into account a variety of other l</p><p>　　The production process and analyzes finally</p><p>　　Split ---- Blue light chip

21、testing----The blue light chip sticks the piece----The vacuum dries----Eutectic welds----Wire solder YGA luminous powder----Vacuum drying----Point scattering medicinal preparation----Vacuum drying----Fills the rubber----

22、Vacuum drying----Drawing of patterns----Partly cuts----Test---All cuts---Long roasts---Separation---Packing---Warehousing Based on the above technology means 1w completed the development of high-power white LED to wo

23、rk with a advanced company, 1W hi</p><p>　　Tab.2 Comparison of measurement results with similar foreign products搜索</p><p>　　Although high efficiency white light LED develops successfully, but to

24、 achieve and surpass the international advanced level, and realizes the batched production, but also has the following question to need to solve: </p><p>　　a. color uniformity is not high</p><p>

25、;　　This experiment selects “the blue light chip +YAG luminous powder” to have the white light LED manufacture method, because of using the manual spot rubber, will cause the luminous powder to be uneven distribution inev

26、itably, causes in various directions, the yellow light colour blending allocated proportion not to be inconsistent blue, thus t influencing product's illumination luster and the uniformity, The white light color temp

27、erature change fluctuation which send out by it will be big, initia</p><p>　　b. color rendering property index is insufficient </p><p>　　The development of high-power white light LED products is

28、 the ultimate goal for general lighting, and therefore the color index is very important evaluation. This experiment using blue, yellow blending methods produce white LED, so the performance of red is bad, causing part o

29、f the spectrum is not continuous, the spectrum can not be part of reflection to the human eye, which will feel the objects in the human eye color distortion. At present, the insider has been trying to use ultra-violet li

30、ght</p><p>　　Coclusion In brief, high-power white light LED package is a multi-disciplinary involved, such as optical, electrical, thermal, materials and other study. From a certain perspective, high-po

31、wer white light LED package is not only a manufacturing technology, but also a constant innovation in the development of basic sciences. The need for good packaging technology of optical, electrical, thermal, materials a

32、nd other physical nature of the understanding and use of the package to be introduced </p><p><b>　　附錄B </b></p><p>　　大功率白光LED封裝工藝技術與研制</p><p>　　與傳統(tǒng)的白熾燈、熒光燈照明相比，由于大功率白光LE

33、D具有顯著的節(jié)能、環(huán)保、使用壽命長等一系列不可比擬的優(yōu)勢，代表著新型綠色、環(huán)保照明的發(fā)展方向，正迅速進軍照明領域。從1W大功率白光LED的封裝工藝技術出發(fā)，在分析比較了幾種產(chǎn)生白光LED方法的成本、性能的基礎上，最終選取性價比相對較高的“藍光芯片+YAG熒光粉”產(chǎn)生白光LED的制作方法。實踐證明，在提高大功率白光LED發(fā)光效率、均勻性和穩(wěn)定性等方面，還需要進一步開發(fā)新材料，采用新工藝。</p><p><b

34、>　　引言</b></p><p>　　LED是利用固體半導體芯片作為發(fā)光材料，采用電場發(fā)光。作為光源，LED優(yōu)勢體現(xiàn)在節(jié)能、環(huán)保和長壽命三個方面。LED不依靠燈絲發(fā)熱來發(fā)光，能量轉(zhuǎn)化效率非常高，理論上只需要白熾燈10%的能耗，相比熒光燈，LED也可以達到50%的節(jié)能效果。專項調(diào)查表明，我國照明用電每年在3000億度以上，用LED取代全部白熾燈或部分取代熒光燈，可節(jié)省1/3的照明用電，意味著節(jié)約

35、1000億度，相當于一個總投資超過2000億三峽工程全年的發(fā)電量。用LED替代熒光燈，避免熒光燈竹破裂溢出汞的一次污染，而且制造LED的廢棄底板(鋁基覆銅板)可以回收重復利用。LED采用固體封裝，結(jié)構(gòu)牢固，壽命可達h。此外，LED還具有工作電壓低、耗電量小、光效高、響應時間極短(ns級)、光色純、重量輕、體積小等一系列特性，發(fā)展突飛猛進，尤其是大功率高亮度白光LED的發(fā)明，被業(yè)界稱為繼取火照明、愛迪生發(fā)明電燈之后的“照明領域的第三次革命

36、”。</p><p>　　白光LED的制作方法 </p><p>　　目前，用LED芯片產(chǎn)生白光的方法見表(1)</p><p>　　由于“藍光芯片+YAG熒光粉”產(chǎn)生白光LED的制作方法，其成本最低，實用性強，已經(jīng)成為目前市場產(chǎn)品的主流。因此，本實驗選用該方法制作白光LED。</p><p>　　表1白光LED產(chǎn)生方法的比較</p&g

37、t;<p><b>　　關鍵工藝及技術措施</b></p><p>　　相對于普通白光LED而言，大功率(W級功率)白光LED具有更高的功率和更大的發(fā)熱量，因此，在封裝過程中，需要綜合考慮光、電、熱等多方面因素。</p><p><b>　　倒裝芯片技術</b></p><p>　　在傳統(tǒng)的正裝LED芯片封裝

38、方式中，由于P型GaN摻雜困難，當前普遍采用在P型GaN上制備金屬透明電極的方法，使電流均勻擴散，以達到發(fā)光均勻性的目的。P型GaN上的金屬透明電極要吸收30%-40%的光，同時H型電極和引線也會遮擋部分光線的透出，這嚴重地影響著LED芯片的出光效率。在制造過程中，為改善出光效率，普遍采取減薄金屬透明電極的方法，這樣反過來又限制了電流在H型GaN表面的均勻擴散，影響了產(chǎn)品的可靠性，制約著LED芯片的工作電流。</p>&l

39、t;p>　　同時，這種正裝結(jié)構(gòu)的PN結(jié)熱量通過藍寶石襯底導出，藍寶石的導熱系數(shù)為35 W/ (mK)(比金屬層要差)，熱阻較大，導致竹芯溫度上升，從而影響器件的各項性能。</p><p>　　本實驗中，采取先進的flip chip(倒裝芯片)技術，通過在芯片的P極和n極下方制作超聲波金絲球焊點作為電極的引出結(jié)構(gòu)，并在芯片外側(cè)的Si底板上制作金絲引線，克服了上述正裝LED芯片在出光效率與電流制約方面的缺點;從

40、芯片PN結(jié)產(chǎn)生的熱量通過金絲球焊點，直接傳導至Si基板和熱沉，其傳熱效果遠優(yōu)于正裝藍寶石的散熱結(jié)構(gòu)；flip chip的金絲球焊結(jié)構(gòu)縮短了導線路徑，避免了在傳統(tǒng)正裝芯片結(jié)構(gòu)中因?qū)Ь€路徑較長而產(chǎn)生的高熱現(xiàn)象；同時，在Si基板上制作反向偏置的PN結(jié)，實現(xiàn)Si基板與Cu熱沉之間的電隔離;從而提高了LED產(chǎn)品壽命，使封裝的可靠性得到極大提升。</p><p><b>　　光學設計技術</b><

41、/p><p><b>　　1. 折射率的改善</b></p><p>　　大功率白光LED的芯片折射率n= 2-4，遠高于起著透鏡作用的封裝材料的折射率(一般環(huán)氧樹脂的折射率約在1.4-1.5)。因此，當芯片發(fā)出的光經(jīng)過封裝材料時，在一者界面處發(fā)生全反射效應，造成約50%的光線反射回芯片內(nèi)部，無法有效導出，成為超高亮度LED芯片取光效率很低的根本原因。如何將內(nèi)部不同材料間

42、折射、反射消耗掉的光能加以利用，是設計出光系統(tǒng)的關鍵。</p><p>　　因此，在采取倒裝芯片技術提高出光效率的同時，還通過在芯片發(fā)光層與Si底板之間增加反射層、對芯片側(cè)面的熱沉進行鏡面加工等方法，增加器件的發(fā)光率。此外，在倒裝芯片的藍寶石襯底與環(huán)氧樹脂結(jié)合面之間，增加一層Si膠材料作為緩沖層，減少因熱膨脹應力作用而引起的脫層現(xiàn)象，以改善芯片出光的折射率和提高產(chǎn)品可靠性。</p><p>

43、;　　2. 球形透鏡的光學優(yōu)化</p><p>　　大功率LED器件頂部的球形透鏡設計，在提高LED出光效率、實現(xiàn)市場應用方面，同樣起著十分重要的作用。在透鏡材料方面，選取高透光的玻璃或亞克力等合成材料，以提高出光效率;在市場應用方面，根據(jù)照明器具光學設計的差異化需求，公司以市場需求量最大的球形透鏡結(jié)構(gòu)為基礎，兼顧其他多種透鏡設計結(jié)構(gòu)。</p><p><b>　　熱學封裝技術&

44、lt;/b></p><p>　　散熱對于功率型LED器件是至關重要的，如果不能將電流產(chǎn)生的熱量及時的散出，保持PN結(jié)的結(jié)溫在允許范圍內(nèi)，將無法獲得穩(wěn)定的光輸出和維持正常的器件壽命。通常用的散熱材料中，盡管Ag的導熱率最好，但由于成本較高，不適宜作通用型散熱器。而Cu的導熱率比較接近Ag,且成本比Ag低。Al的導熱率雖然低于Cu，但其綜合成本最低，有利于大規(guī)模制造。</p><p>

45、　　經(jīng)過反復實驗對比，采取的做法是:連接芯片部分采用Cu基或Ag基作熱沉，再將該熱沉連接在A1基散熱器，將熱量散出(風冷或熱傳導方式)。</p><p>　　這種做法的優(yōu)點是:充分考慮散熱器性能價格比，將不同特點的散熱器結(jié)合在一起做到高效散熱，并目成本控制合理化。</p><p>　　此外，連接Cu基熱沉與芯片之間的材料選擇也是十分重要的，普通LED常用銀膠作為連接材料。但由于Ag膠的熱阻

46、高，導熱系數(shù)在10-25 W/ (mK)，采用Ag膠為連接材料，就等于人為地在芯片與熱沉之間加上了一層熱阻。</p><p>　　為此，引入新的固品工藝，即共品焊接技術:以Sn片焊接作為品粒與熱沉之間連接材料。Sn的導熱系數(shù)為67 W/(mK)，其散熱效果與物理特性遠優(yōu)于Ag膠，因此取得了較為理想的導熱效果(熱阻系數(shù)約為16 C/ W)。</p><p><b>　　制作工藝及結(jié)

47、果分析</b></p><p>　　裂片----藍光芯片測試----藍光芯片粘片----真空烘----共晶焊----焊線一點YGA熒光粉----真空烘干----點散射劑----真空烘干----灌膠----真空烘干----脫模----半切----測試---全切---長烤---分選---包裝---入庫。</p><p>　　本文基于以上工藝技術手段完成了1w大功率白光LED的研制工

48、作，通過與某知名公司1W大功率白光LED封裝產(chǎn)品的參數(shù)性能相比較，本實驗所研制的1w大功率白光LED產(chǎn)品，其發(fā)光效率接近國外的同類產(chǎn)品。</p><p>　　具體測試結(jié)果如表2所示。</p><p>　　表2 測試結(jié)果與國外同類產(chǎn)品對比</p><p>　　雖然大功率白光LED研制成功，但是要達到和超過國際先進水平，并實現(xiàn)批量化生產(chǎn)，還有以下問題需要解決:</

49、p><p><b>　　色度均勻性不高</b></p><p>　　本實驗選用“藍光芯片+YAG熒光粉”產(chǎn)生白光LED的制作方法，由于采用手工點膠，不可避免地會造成熒光粉的分布不均，使得在各方向的藍、黃光混色配比不一致，從而影響產(chǎn)品的發(fā)光色澤與均勻性，其發(fā)出的白光色溫變化起伏較大，引發(fā)所謂的光斑效應。色度均勻性的提高還有賴于新技術手段的開發(fā)。</p><

50、;p><b>　　顯色性指數(shù)不足</b></p><p>　　大功率白光LED產(chǎn)品發(fā)展的終極目標是用作一般照明燈具，因而顯色性指數(shù)是非常重要的評估指標。本實驗采用藍、黃混色產(chǎn)生白光的方法，因此對紅色的表現(xiàn)能力較差，造成部分光譜的不連續(xù)，該部分光譜不能被反射到人眼，從而人眼會感覺到物體顏色的失真。目前，業(yè)界己經(jīng)在嘗試用紫外光芯片搭配RGB熒光粉，來彌補現(xiàn)有白光LED紅色表現(xiàn)能力不足的缺陷

51、，但是由于紫外光能量強，極易破壞許多封裝材料，如當環(huán)氧樹脂受紫外光長期照射時，其結(jié)構(gòu)在含氧的環(huán)境下很容易斷鍵劣化，產(chǎn)生發(fā)色機團，導致封裝材料黃變，進而大幅影響白光LED亮度與白色均一性。因此，開發(fā)抗紫外光的透明性封裝材料成為提高顯色指數(shù)一致性的新挑戰(zhàn)。</p><p><b>　　結(jié)語</b></p><p>　　總之，大功率白光LED封裝是一個涉及到多學科，如光學、