在本論文研究中，我們提出一個具有前瞻性的策略:利用光學同調斷層掃描技術來決定發光二極體封裝膠的熱膨脹係數。由於發光二極體的封裝膠與封裝材料的膨脹係數不匹配，在高電流注入情況下，晶片裡封裝膠嚴重的熱膨脹勢必會造成發光二極體元件的失效。因此一項能迅速且精確地評估發光二極體晶片封裝膠的熱膨脹係數技術是需要的。光學同調斷層掃描具有非侵入性、高速以及高解析的特性，以至於可以直接、未破壞性地透過光學同調斷層掃描系統重建二維和三維影像來評估發光二極體晶片封裝膠橫截面影像的高度變化。另一方面，通過順向電壓法與紅外線熱影像法可以得知注射電流與發光二極體溫度之間的重要關係。經過分析與比較，利用順向電壓法與紅外線熱影像法得到發光二極體晶片封裝膠（聚苯乙烯）之熱膨脹係數分別是16.5×10-5 /℃與51.64×10-5 /℃。這說明了利用順向電壓法得到發光二極體的溫度更接近晶片封裝膠的外在環境溫度，因此與之前文獻結果相比，我們提出的方法更能準確地評估晶片封裝膠的熱膨脹係數數值。最重要的是，我們相信我們提出的方法不僅可以提高發光二極體晶片封裝膠的熱膨脹係數數值的準確性，還能提供比傳統檢測器—熱機械分析儀具非破壞性且更有效率的檢測方法。

In this study, we proposed a promising strategy by using the optical coherence tomography (OCT) technology to determine the coefficient of thermal expansion (CTE) for an encapsulant light-emitting diodes (LED) chip. Under a high current injection condition, a serious thermal expansion within the encapsulant LED chip, due mainly to the large CTE mismatch between epoxy glue and epitaxial materials, will inevitably cause a device failure. Therefore, an effective and accurate estimation of CTE for an encapsulant LED chip is required. The OCT has non-invasive, high-speed and high-resolution properties, so that a direct and undestroyed evaluation for the height variation of cross-sectional images of the encapsulant LED chip is feasible through the reconstructed two- and three-dimensional images of OCT system. On the other hand, the important correlation between the LED temperatures with injected currents is obtained through both forward-voltage dropping and infrared thermography methods. As a result, the CTE values of epoxy glue (polystyrene) are 16.5×10−5/℃ and 51.64×10−5/℃ for the OCT system associated with forward-voltage dropping and infrared thermography methods, respectively. It suggest the LED temperature derived by the forward-voltage dropping method is more closed to the atmosphere temperature of epoxy glue of LED chip, so that can provide a much accurate estimation of CTE value as compared to previously published results. Most importantly, we believe our proposed method can not only improve the accuracy to estimate the CTE value of encapsulant LED chips, but provide a non-destructive and efficient way over the traditional inspection method by the thermal mechanical analyzer.

[1] W. M. Rohsenow, J. P. Hartnett, and E. N. Ganicang, Handbook of heat transfer fundamentals (2nd edition), New York, McGraw-Hill Book, 1985, chap. 4,pp.164
[2] L. Kim, G. W. Lee, W. J. Hwang, J. S. Yang, and M. W. Shin, “Thermal analysis and design of GaN-based LEDs for high power applications,” phys. stat. sol. (c), vol. 0,no.7,pp.2261-2264,2003
[3] H. I. Abdelkader, H. H. Hausien and J. D. Martin, “Temperature rise and thermal rise-time measurements of a semiconductor laser diode, ” Rev.Sci.lnstrum.vol.63,np.3,pp.2004-2007,1992
[4] P. W. Epperlein and G. L. Bona, “Influence of the vertical structure on the mirror facet temperatures of visible GaInP quantum well lasers,” Appl. Phys. Lett., vol.62,no.24,pp.3074-3076,1993.
[5] Karim, “Measurement of junction temperature of a semiconductor laser diode,” Proceedings of INMIC,pp.659-662, 2004.
[6] W. J. Hwang, T. H. Lee, L. Kim and M. W. Shin, “Determination of junction temperature and thermal resistance in the GaN-based LEDs using direct temperature measurement,” phys. stat. sol. (c),vol. 1, no. 10, pp.2429-2432, 2004.
[7] Y. Xi and E. F. Schubert, “Junction–temperature measurement in GaN ultraviolet light-emitting diodes using diode forward voltage method,” Appl. Phys. Lett. vol.85,no.12,pp 2163-2165 ,2004.
[8] Y. Xi, J.-Q. Xi, Th. Gessmann, J. M. Shah, J. K. Kim, E. F. Schubert, A. J. Fischer, M. H. Crawford, K. H. A. Bogart, and A. A. Allerman, “Junction and carrier temperature measurements in deep-ultraviolet light-emitting diodes using three different methods,” Appl. Phys. Lett. vol.86,p. 031907, 2005.
[9] Yangang Xi, Thomas Gessmann, Jingqun Xi, Jong Kyu Kim, Jay M. Shah, E. Fred Schubert, Arthur J. Fischer, Mary H. Crawford, Katherine H. A. Bogart and Andrew A. Allerman, “Junction Temperature in Ultraviolet Light- Emitting Diodes,”J.J.Appl. Phys., vol.44,no.10,pp.7260-7266,2005.
[10] S. Chhajed, Y. Xi, Th. Gessmanna, J.-Q. Xi, J. M. Shah, J. K. Kim, and E. F. Schubert, “Junction temperature in light-emitting diodes assessed by different methods,”Proc. SPIE Int. Soc. Opt. Eng.,vol.5739,pp.16-24, Mar.2005.
[11] F. Wall, P. S. Martin, and G. Harbers, “High power LED package Requirment,” Proc. SPIE 5187, 85-92 (2004).
[12] D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, et al., "Optical coherence tomography," Science, vol. 254, pp. 1178-1181, 1991.
[13] R. C. Youngquist, S. Carr, and D. E. Davies, "Optical coherence-domain reflectometry: a new optical evaluation technique," Optics Letters, vol. 12, pp. 158-160, 1987.
[14] X. Clivaz, R. Novàk, H. Gilgen, F. Marquis-Weible, and R. Salathé, "High-resolution reflectometry in biological tissues," Optics Letters, vol. 17, pp. 4-6, 1992.
[15] J. Schmitt, A. Knüttel, and R. Bonner, "Measurement of optical properties of biological tissues by low-coherence reflectometry," Applied Optics, vol. 32, pp. 6032-6042, 1993.
[16] B. Hochheimer, G. Lutty, and S. D’Anna, "Ocular fluorescein phototoxicity," Applied optics, vol. 26, pp. 1473-1479, 1987.
[17] Tomasz Bajraszewski, Maciej Wojtkowski, Maciej Szkulmowski, Anna Szkulmowska, Robert Huber, and Andrzej Kowalczyk, “Improved spectral optical coherence tomography using optical frequency comb,” Opt. Express 16, pp. 4163-4176 , 2008.
[18] S. R. Chinn, E. A. Swanson, and J. G. Fujimoto, “Optical coherence tomography using a frequency-tunable optical source,” Opt. Lett. 22, pp. 340-342 , 1997.
[19] S. R. Chinn, E. A. Swanson, and J. G. Fujimoto, “Optical coherence tomography using a frequency-tunable optical source,” Opt. Lett. 22, pp. 340-342 , 1997.
[20] B. Golubovic, B. E. Bouma, G. J. Tearney, and J. G. Fujimoto, “Optical frequency-domain reflectometry using rapid wavelength tuning of a Cr4+:forsterite laser,” Opt. Lett. 22, pp. 1704-1706 , 1997.
[21] W. Y. Oh, S. H. Yun, G. J. Tearney, and B. E. Bouma, “115 kHz tuning repetition rate ultrahigh-speed velength-swept semiconductor laser,” Opt. Lett. 30, pp. 3159-3161, 2005.
[22] R. Leitgeb, C. Hitzenberger, and Adolf Fercher,“Performance of fourier domain vs. time domain optical coherence tomography,” Opt. Express 11, pp. 889-894 , 2003.
[23] J. M. Schmitt, S. L. Lee, “An Optical Coherence Microscope with Enhabced Resolving Power in thick tissue,” Opt. Commun, Vol. 142, pp.203 (1997).
[24] H. L. Jin, M. T. Tsai,2012. “Differentiation of oral precancerous tissues based on the analyses of optical scattering property,”
[25] J. Millman and C. Halkias, Integrated Electronics (McGraw–Hill, New York, 1972).
[26] Y. Xi and E. F. Schubert, “Junction–temperature measurement in GaN ultraviolet light-emitting diodes using diode forward voltage method,” Appl. Phys. Lett. vol.85,no.12,pp 2163-2165 ,2004.
[27] 管鴻、許進明，「減碳科技:LED及OLED照明」，科學發展，第483期，2013，第48-53頁。
[28] 中華民國光電學會，「led工程師基礎概念與應用」，五南出版社，2012，第47~48頁。
[29] http://www.renishaw.com/en/raman-bands-explained--25808
[30] 教學手冊留存-劉悟慢-熱像儀簡要操作方法
[31] Moon-Hwan Chang, Diganta Das, and Michael Pecht, “Junction Temperature Characterization of High Power Light Emitting Diodes,”