粗化LED晶片之封裝結構研究提升發光效率

LED在應用中，為達到接近原有光源的亮度要求，通常採取以「量」取勝的設計方式，但因使用大量的LED需要較大的單位面積，也會有開路或色不均的情況發生，因此LED發光效率逐年的提高，為各LED廠每年開發研究的技術課題。本文中研究透過封裝材料的設計與改變，提升單一LED的發光效率。當中選取： (1)相同功率但正面出光與側面出光比例不同的晶片 (2)碗杯角度分別為12度、45度、60度的三種導電支架 (3)折射率為1.41與1.54的封裝膠材，了解不同的封裝方式，光線由晶片經過折射、反射與全反射所得到的出光比例。實驗結果比較之下，晶片的影響只些微提高3~5%，封裝膠則有2~3%的增益，支架可有效提升2~18%的發光效率。在市場競爭下須考慮價格、功能、操作性、信賴度等LED的重要特性，開發LED產品優先找出最佳的碗杯角度為評估LED亮度的一項重點。

關鍵字

晶片；導電支架；封裝膠；發光效率

並列摘要

In the LED applications, in order to reach the luminance requirements of original light source, people usually use "large quantity to win" design rule, but that will require a larger product area. Using a large number of LEDs will lead to open-circuits or color unevenness. The LED luminous efficiency improves year by year, and it becomes an important technical issue of LED foundry development every year. In this thesis the design and change of packaging materials to enhance the single LED luminous efficiency were studied. The following topics were selected: (1) With same power, but the chips emitting top and side light in different ratios, (2) Three lead frames with different bowl cup angles of 12 degrees, 45 degrees, 60 degrees, respectively, (3) Encapsulation glues with refractive index of 1.41 and 1.54, respectively. From the study of above three package methods we can understand the light extracting effects in the LED chips after light refraction, reflection and total reflection in the package. From the comparisons of the experimental results, the effects of chip types were only 3 to 5% slightly increased, the encapsulation glues resulted in 2 to 3% of gain, and the lead frame can effectively enhance the luminous efficiency of 2 ~ 18%. For the competition in the market, many issues should be considered such as: price, functionality, operability, reliability and other important feature. For the assessment of LED products, the first priority will be to find the optimum bowl cup angle in order to obtain high brightness LEDs.