Details of LED structure

白光發光二極體可依照其製作所使用的物質分為有機發光二極體、與無機發光二極體。目前市場主要半導體白光光源主要有以下三種方式：

White LED is categorized into organic LED and non-organic LED based on its manufacturing components. Currently, the 3 types of semiconductor white LED in the market are:

以紅、藍、綠三色發光二極體晶粒組成白光發光模組，具有高發光效率、高演色性優點，但同時也因不同顏色晶粒磊晶材料不同，連帶使電壓特性也隨之不同。因此使得成本偏高、控制線路設計複雜且混光不易。

The white LED module that is based on the use of red, blue and green tri-color LED chips has the advantages of high luminous efficacy and high color rendition. However, these chips employed different epitaxial materials to produce different color, resulting in their current-voltage characteristics variant. This leads to high cost, complicates circuit design and also makes color mixing difficult.

而由日亞化學所提出，以藍光發光二極體激發黃色YAG螢光粉產生白光發光二極體，則為目前市場主流方式。日本日亞化學所研發出的白光發光二極體，其結構為在藍光發光二極體晶片的外圍填充混有黃光YAG螢光粉的光學膠，此藍光發光二極體晶片所發出藍光之波長約為400～530nm，利用藍光發光二極體晶片所發出的光線激發黃光螢光粉產生黃色光。但同時也會有部份的藍色光發射出來，此部份藍色光配合上螢光粉所發出之黃色光，即形成藍黃混合之二波長的白光。然而，此種利用藍光發光二極體晶片與黃光螢光粉組合而成之白光發光二極體，有下列數種缺點：

However, by Nichia Corporation, using blue LED to stimulate yellow YAG phosphor powder to manufacture white LED is presently the most popular method in the market. The white LED developed by Nichia Corporation is structured by encapsulating blue LED chip within YAG phosphor powder and optical adhesive mixture. The blue LED chip emits blue light at wavelength of 400 ~ 530nm, part of the light stimulates the yellow YAG phosphor and produce yellow light, the other part of blue light transmits out from the phosphor’s yellow light, and the combination of blue light and yellow light forms the white light. However, white LED that makes use of combining blue LED and yellow light phosphor has the following disadvantages:

至於以紫外光發光二極體激發透明光學膠中含均勻混有一定比例之藍色、綠色、紅色螢光粉，激發後可得到三波長之白光。三波長白光發光二極體具有高演色性優點，但卻有發光效率不足缺點。

As for using UV LED to stimulate the optical adhesive that contains a certain ratio of blue, green and red phosphor powders, the stimulation generates three wavelengths of white light. This triple wavelengths white LED have the advantage of high color rendering capability, but also have the disadvantage of poor luminous efficacy.

不論白光LED是以紫外光、或藍光晶片與螢光粉搭配而成，其共同缺點為發光亮度不足與均勻度控制不易。目前工業界以增加透光度或從晶粒導出更多可用發光量，來解決發光二極體亮度不足之問題。例如使用透明導電材料以增加晶粒的出光量、改變晶粒磊晶或電極結構設計以便汲取出更多可用發光量。另外當使用紫外光LED作激發白光之光源時，因紫外光的波長越短時對人眼的傷害愈大，因此必須將紫外光阻絕於白光LED結構內。要改善以上問題，一方面需提高螢光粉的白光轉換效率與阻絕紫外光外漏，另方面是希望在改進螢光發光量的同時亦可改善發光均勻度。

Regardless of whether the phosphor-based white LED uses blue LED chip or UV LED chip as its light source, the disadvantages are insufficient luminous flux and difficulty in controlling uniformity.

Currently, LED industry resolve the luminous flux issue by increasing the transmittance or extracting more luminous flux from the chips. For example, using transparent conductive material to increase the luminous flux that chip generates and changing chip’s epitaxial structure or LED electrode design to gain higher light extraction efficiency. Also, when using UV LED as light source for stimulation, the shorter the UV wavelength, the more harm it causes to the human eye. Hence, the UV has to be detained within the white LED structure. To address the above issues, increasing the UV conversion rate by phosphor powder and blocking the leakage of UV are required. In improving the phosphor's luminous flux, it is also intended that uniformity can be improved at the same time.

《圖一 Japan Nichia's patented white LED concept》

Improve LED luminous Efficacy through Packaging

為改善上述缺點，在美國專利第5,962,971號使用紫外光濾波器（UV filter）作為發光二極體螢光粉層光出射面的封裝。此方式除可增加螢光粉層的發光均勻度外，並可吸收阻絕發光二極體晶片所發出之紫外光對人眼的傷害。另外在飛利浦所申請的美國專利第5,813,753號，是在紫外光/藍光發光二極體晶片的發光面上，鍍上一層短波穿透濾波器（short wave pass filter），以增加發光晶片之紫外光出射量與發光二極體發光面之可見光(螢光)反射量。另一方面，在紫外光/藍光發光二極體之前端出射面以可見光穿透濾波器（long wave pass filter）作封裝，亦可增加可見光的穿透率。

In order to counter the above deficiency, a UV filter is employed as the packaging of phosphor layer emission exit, as patented in US Patent 5,962,971. This method not only improves the uniformity of phosphors luminosity, it also absorbs and blocks the UV emitted from LED chip which will cause harm to the human eye. Also, in Philips' US Patent 5,813,753, the light emitting surface of UV / blue LED chip is coated with a layer of short wave pass filter to increase the chip’s UV emission and increase chip’s reflectivity of visible light (phosphors). On the other hand, using a long wave pass filter as packaging of UV/blue LED front side emission exit can improve the visible light transmittance.

《圖二 Concept of White LED through UV Excitation》

Increase Light Extraction Efficiency and Reduce Heat Resistance

由於高亮度LED的應用面不斷擴大，如液晶電視、手機、PDA、以及照明領域等，所以各色LED晶片輸入功率的不斷提高，對封裝技術主要除封裝結構要有高的取光效率（extraction efficiency）外，另一重要關鍵技術是降低熱阻，才能使光輸出功率穩定、壽命增加和提高可靠性。LED發光層所用的磊晶材料採用MOCVD技術和量子井（Quantum Well；QW）結構，使其提高其內量子效率。但由於內全反射（Total Internal Reflection；TIR）原因，使得晶片的光汲取效率過低並產生發熱現象。傳統的LED封裝結構，一般是用膠或銀膠將LED晶片黏貼在導線架的反射杯中或SMD基座上，再由金或鋁線焊線機完成LED元件的內外連接正負極後，用環氧樹脂封裝而成。若採用傳統式的LED封裝形式其程序雖然簡單，但其熱阻高達250℃/W～300℃/W。LED將會因為散熱不良而導致晶片溫度迅速上升和環氧樹脂變質，進而造成LED元件的加速老化到失去發光功能，且因為持續的熱量累積所產生的發光效率降低，並將加速LED元件本身增溫，增溫效應形成應力造成結構不良而燒毀。

As the applications of high brightness LED continues expand, such as LCD TV, mobile phones and lighting etc., the input power of various colored LED chips continues to increase. In order to stabilize the power of optical output, increase the life span and improve the reliability, not only does the package structure must have high light extraction efficiency, reducing heat resistance is also an important key technology to package technology. The use of epitaxial material that employed quantum well structure and MOCVD technology for LED light emitting layer increases its internal quantum efficiency. However, due to the total internal reflection, the chip’s light extraction efficiency becomes too low and causes the chip to overheat. In traditional LED packaging, adhesive or silver epoxy is used to mount the LED chip onto the reflection cavity of lead frame or SMD substrate, and then connect the anode and cathode of LED chip to their corresponding leads with gold/aluminum bound wire by using the wire bounder, and finally packaged with epoxy. Though the procedure of traditional LED packaging is simple, the heat resistance can be up to 250℃/W ~ 300℃/W. As such, the bad cooling will cause the temperature of the chip to rise and the epoxy to deteriorate, which accelerates the LED degrading and losing its light emitting ability. The reducing of light luminous efficacy caused by continued accumulation of heat, accelerates the increase of LED temperature and the effect of increasing temperature creates stress to LED structure, causing it to burn.

因此，現有的新型LED的設計採用了覆晶（flip-chip）結構來提高晶片的光汲取效率，並改善晶片的散熱特性以降低熱阻。另一方面也有利用增大LED晶片面積，提高工作電流來增加LED的光電轉換效率，以獲得較大的發光量。除了LED晶片外，白光LED的螢光粉材料與微光學設計技術也具舉足輕重且關鍵的封裝技術。如何進行整體發光二極體結構的二次光學設計以配合材料特性以提高元件的發光效率為目前熱門研究方向，例如晶粒內部結構設計反射功能並配合外加的反射器與特殊微光學透鏡結構提升 LED發光效率。另一方面，改進螢光粉的成份以增加螢光轉換效率，亦為世界各大光電半導體廠與照明大廠兵家必爭的一塊大餅。

Hence, the new LED design uses flip-chip packaging to increase the chip's light extraction efficiency, and improves the chip's cooling ability to reduce heat resistance. Other than that, using bigger LED chip surface and increasing working current improve the conversion efficacy, hence gaining higher luminous flux. Besides the LED chip, other key packaging techniques are the materials of the phosphors used in white LED and micro-optic design techniques.

The current popular research direction is how to make a secondary optical design on the overall LED structure, together with the materials' characteristics, to improve the LED's luminous efficacy. For example, by designing the chip internal structure with reflective capability and together with external reflector and special micro-optical lens structure, the LED’s luminous efficacy will be increased. On the other hand, improving the components of the phosphors for higher phosphor conversion efficiency is a competitive market for the optoelectronic semiconductor and lighting manufacturers in the world.

Taiwan's LED Packaging Suppliers' Customer Details

Taiwan's LED Packaging Industry Market Status

LED packaging revenue for August increases by 8.7% which exceeds that of chip industry, which is 5.2%

據產業研究機構LEDinside資料統計，8月台灣上市上櫃LED廠商營收總額共新台幣64.11億元，月增率7.2％，其中封裝廠月成長8.7％，優於晶粒廠的5.2％。

LED晶粒廠8月營收總額27.57億元，較7月成長5.2％，年成長達14％；LED封裝廠商8月營收約36.54億元，較7月成長8.7％。

Based on statistics by industry research agency LEDinside, August total revenue for Taiwan's listed LED companies was 64.11 billion NTD, an increase of 7.2% from previous month. Packaging industry rose by 8.7%, which is more than that of the chip industry's 5.2%. LED chip industry's August revenue was 27.57 million NTD, an increase of 5.2% from July's revenue. Its yearly growth is 14%. LED packaging industry's August revenue was 36.54 billion NTD, an increase of 8.7% from July's revenue.

觀察下游LED封裝部分，8月份整體營收36.54億元，月增率8.7％，年增率4.4％。封裝廠產值超越去年同期水準。如封裝廠商億光8月營收約11.17億元，創下歷史新高。

We can see that LED packaging industry's August total revenue was 36.54 billion NTD, an increase of 8.7% from previous month, and its yearly growth is 4.4%. Packaging industry's output exceeded that of last year's same period. Everlight's August revenue set a record high of about 11.17 billion NTD.

April 2009 LED Packaging Industry's Revenue Ranking

(Domination: NTD million)

Q4 Demand for LED chip is still high, packaging industry suffers

LEDinside調查，由於高亮度藍光晶片迄今仍供不應求，預估藍光LED晶粒訂單可望旺到10月份，部份廠商接單能見度甚至達年底。至於LED封裝廠則因中小尺寸背光需求漸入淡季、大尺寸背光恐面臨客戶調節庫存，第四季業績動能可能會受到衝擊。

From LEDinside's survey, high brightness blue LED chip is in short supply, and it is estimated that the order will continue to increase till October. Some suppliers' orders have even last till year end. As for LED packaging industry, because small and medium size backlight demand decreases due to off season, and adjustment of inventory of large size backlight, Q4's performance may suffer.

LEDinside指出，觀察近期LED市場下游LED封裝廠，據調查，目前廠商的訂單能見度，大多僅達9月底。LEDinside表示，主因是第四季以後傳統淡季來臨，包括中小尺吋的手機背光源等等應用產品需求，將隨著手機的出貨淡季來臨而逐漸下滑。大尺寸背光部分則因第三季LED供給吃緊，面板廠有超額下單（over booking）的現象。預料在第四季面板需求下滑後，面板廠商也將開始調節手中的LED庫存。這些因素都將影響部分LED封裝廠今年第四季的營收成長動能。

LEDinside points out with respect to LED's lower stream market, LED packaging industry's order will last till September at most. The main reason is the off-season after the fourth quarter, which includes the lower demand of small and medium size mobile phone backlight due to the off-season of mobile phones. The supply shock of LED in the third quarter causes overbooking of large size backlight by the panel supplier. It is expected that in the fourth quarter when the demand of panel declines, panel supplier may start to adjust their LED inventory. These factors will affect some of the LED packaging suppliers' fourth quarter revenue growth.

個別廠商來看，封裝廠億光8月份營收約11.17億元，也創歷史新高，月增17.2％、年增9.5％。主要係受惠於中大尺寸背光源和智慧型手機應用比重提升。東貝由於長期佈局於背光領域，直接受惠於中大尺寸背光需求，營收續創歷史新高，8月營收達4.24億元，月增5.5％，相較去年同期成長40％。而手機應用比重較高的宏齊，在白牌手機需求出籠下，8月營收達2.62億元，月增7.1％，下半年新產品導入下，營收仍有成長空間。佰鴻也因打入中大尺寸背光源供應鍊，8月份營收創新高4.33億元，月增25.7％、年增22％。

Looking at the individual packaging suppliers, Everlight's August revenue set a record high of 11.17 billion NTD, an increase of 17.2% from the previous month, and its yearly growth is 9.5%. This is mainly due to increase in usage of medium and large size backlight and smart phones. Unity Opto's revenue set a record of 4.24 billion NTD in August, an increase of 5.5% from previous month, mainly due the demand in medium and large size backlight. Compared to the same period last year, its growth has increased by 40%. Bright LED, whose market is mainly in the mobile phone, with the increase in white-box cell phone, its August revenue reached 2.62 billion NTD, an increase of 7.1%. With the launch of new products in the second half of the year, there is still room of increase of revenue. Bright, with its market in medium and large size backlight supply, reached a record revenue of 4.33 billion NTD in August, an increase of 25.7% from previous month. Its yearly growth is 22%.

Bright's EPS this year is nearly 1.5 NTD and continues to expand its SMD capacity in the following year.

LED封裝廠佰鴻，2009年第三季受惠於紅外線產品和SMD型LED封裝產品訂單顯著升溫，平均產能利用率提高至近90％水位，不僅營收成長，毛利率和獲利也可望大幅好轉。法人估佰鴻今年第三季營收將較上季成長25％～30％，毛利率將回升到20％以上。另方面，因應TV背光源業務也逐漸展開，佰鴻也預計，將於明年持續擴充SMD型LED封裝產能，明年資本支出可能超過5億元。

In 2009 third quarter, due to the increase in order of infrared products and SMD LED packaging, Bright's average capacity utilization reached nearly 90%. Not only revenue increased, gross margin and net profit will also significantly improve. It is expected that Bright's revenue will increase by 25% to 30% as compared to the last quarter, and its gross margin will return to above 20%. On the other hand, with the expansion into TV backlight business, Bright expects that next year, with the continued expansion of SMD LED packaging capacity, its capital expenditure may exceed 5 billion NTD.

目前可見光LED產品（包含一般LED產品、各類高亮度LED產品等等）佔佰鴻營收比重達55％～60％，不可見光（紅外線LED）產品營收佔比約40％～45％。受惠於個別客戶需求增溫，佰鴻今年第三季紅外線產品營收，較上季大增70％，紅外線產品之產能利用率也達到近乎滿載。至於可見光LED方面，SMD型LED產品則因NB背光源和手機背光源出貨穩定成長，第三季平均產能利用率也持續升高到90％水位。

Currently, visible LED products (including general LED product and other high brightness LED product, etc.) contributes to 55% to 60% of Bright's revenue while invisible (infrared LED) LED products contributes to 40% to 50% of the revenue. With the increase of customers' demand, Bright's third quarter revenue for infrared products greatly increases by 70%, and its capacity utilization is almost full. As for visible LED, due to the stable growth of NB backlight and mobile phone backlight, third quarter's SMD LED average capacity utilization also reaches a high rate of 90%.

佰鴻預期，9月份營收會比8月份更好。主因是大尺寸背光源業務持續成長，另外中國大陸LED路燈標案也將於近期內加速釋出。法人估佰鴻今年9月份營收可望持穩於4億元高檔，第三季合併營收估達12～13億元，季增25％～30％左右。

Bright expects that September's revenue will be much better than August's, the main reason being the continued growth of large size backlight industry. Also, China's LED street light tender will be released soon. It is expected that Bright's September revenue this year will reach a steady high of 4 billion NTD.

由於佰鴻第三季平均產能利用率大幅提升，毛利率可望回升到20％以上，加上費用支出和業外損失減少，法人估佰鴻第三季單季獲利有機會挑戰1.8～2億元。

Because Bright's third quarter average capacity utilization significantly improves, gross profit margin is expected to return to above 20%. Besides, with the decrease in expenses and non-operating loss, there is a chance that Bright's third quarter net profit will reach 1.8 to 2 billion NTD.

由於佰鴻正積極擴張電視背光源產品業務，初步已打入韓系客戶電視背光源供應鏈，接下來佰鴻還會持續開發台灣和中國大陸等地TV系統廠商的訂單，未來規劃將持續擴充SMD型LED產能，明年資本支出預估將超過5億元。

As Bright is actively expanding into TV backlight product industry, it has preliminarily penetrated into Korean consumer TV backlight supply chain. Next, Bright will continue to cater to Taiwan's and China's TV system suppliers' order. In the future, it will continue to expand the SMD LED capacity. Next year's capital expenditure is expected to exceed 5 billion NTD.

Taiwan Oasis awarded Hong Kong LED Technology Tender

根據中國東莞市發展利用市場工作領導小組，今年8月份所發布的「2009年粵港關鍵領域重點突破項目」中的東莞專項招標揭標公告，台灣LED封裝廠李洲科技表示，旗下轉投資的東莞李洲電子科技，成為這次台資企業中唯一的得標廠商。得標項目包括LED照明燈具散熱技術，以及光效能提升研究和產業化計劃。東莞市政府不僅將提供經費獎助，未來得標廠商在爭取公共部門標案時，也將有優先權。東莞李洲所開發的LED照明產品、LED路燈，也都將於今年第四季陸續上市。

According to the Dongguan tender result announcement in the August issue of “2009 Guangdong-Hongkong Key Domain Breakthrough Project of China” published by China Dongguan City's market leading group, Taiwan's LED packaging supplier Oasis said that its Dongguan Oasistek is the only company among the Taiwan-funded companies awarded the tender. The awarded tender items include LED lighting thermal technology as well as study of optical performance improvement and industrialization project. Not only will Dongguan city government provides grant funding, winning tenderers will be given priority when tendering for public sector's tenders in the future. Dongguan Oasistek's products such as LED lighting fixtures and LED street lights will be launched in the fourth quarter this year.

李洲科技董事長李明順說，李洲科技在東莞市的電子信息技術投標項目取得第一回合勝利，是通過重重嚴格的檢驗。以市場對路燈使用壽命長效期的要求，李洲的產品主要係在亮度、散熱及光學設計方面勝出。目前東莞李洲與大陸各省都已展開接洽、合作，其中，東莞和河南地區，可望最先繳出成績。

Oasistek's chairman, Lee, Ming-Shun said, Oasistek in winning the Dongguan's electronic and information technology tender, went through numerous stringent examinations. Oasis' winning points are on the products' brightness, thermal and optical design, which caters to the market's demand for long operating life street lights. Oasistek has started to contact and cooperate with various Mainland provinces, and the first result is expected to be seen in Dongguan Henan.

李洲近來積極朝照明市場佈局。目前在東莞廠區已開始著手建置LED路燈示範工程，除了達到節能目標，同時也供外界進行產品檢視。在上游LED晶粒垂直整合部分，李洲轉投資的洲磊科技已與旭晶光科技進行整合，未來將加強開發高亮度LED晶粒產品。下游應用則透過轉投資的東莞李洲，同步朝LED路燈、崁燈、燈管、檯燈、汽車照明及模組等等各項應用發展。

Recently, Oasis has been working towards the lighting fixtures market. Currently, Dongguan plant is working on its LED street lights demonstration project. Besides targeting for energy saving, it also opens its doors to the public for product examination. In terms of upper stream LED chip vertical integration, Oasis' UniLite and LuxtalTek is in the integration process, and will work towards producing high brightness LED chip products. In terms of lower stream supply, Dongguan's Oasis will work towards producing LED street lights, down lights, lamps, table lamps, automotive lighting and modules etc.

儘管目前李洲主要營收來源仍以LED顯示看板應用為主，佔營收比重約達60～70％， SMD表面黏著型LED產品營收佔比約10％，燈泡型LED產品營收佔比約10％，LED照明系統模組產品，合計營收佔比仍低於10％。不過，李洲強調，照明應用是LED業者下一步勢必要走的路，明年來自照明應用的營收貢獻，就會較顯著的增長。

Even though 60% to 70% of Oasis' revenue is from LED display board usage, 10% from SMD surface mount LED products, 10% from bulb-type LED products and 10% from LED lighting module, Oasis emphasizes that lighting applications is the next step for LED industry. In the year to come, revenue from lighting applications will significantly increase.

Conclusion

LED已逐漸普及成為日常生活常用的電子元件。目前全球LED發展趨勢以白光LED與高亮度LED為主要發展方向，在環保需求與高價能源時代來臨的今天，白光LED因省電與輕薄短小特性，並可應需求製作成大尺寸陣列發光模組等而在照明領域成為明日之星。因此若能取代現有照明光源技術，將可為全球能源產業帶來新一波產業革命和文明發展。而各種封裝技術不斷推陳出新，也將為LED提供更好的發光效率。現階段無論從光、機、電、熱等方面探討白光發光二極體都是可以發揮的領域，其未來發展影響非常深遠，值得各界持續投注心力。

LED has gradually become our daily common household electrical components. Currently, the global LED development is heading towards white LED and high-power LED. In today's environment friendly requirements and high cost energy resource environment, white LED with its energy-saving and thin short and small attributes, and its ability to be made into large LED display modules, has made its name as the star of the lighting domain. Hence, if it can replace the current lighting technology, it will bring a new wave of industry revolution and civilization development to the global energy industry. Also, the innovative packaging technology will lead to better LED luminous efficacy. At the present stage, optics, mechanical, electrical science and thermal science are areas to be explored in the study of white LED. It will have a deep influence on the future development; hence the continued effort is much worth.