Abstract
Lumen output and efficacy of high-power LEDs have crossed 200 lm/W, and the application of LEDs is growing beyond illumination into other areas like horticulture, UV-C LEDs for disinfection, and health-centric lighting where controlling parameters like the shift in wavelength, Color Rendering Index (CRI), etc. are important. Whether delivering high light output or controlled spectral designs for specific applications, thermal management of LEDs to lower the junction temperature is vital as it directly impacts the intended performance. The packaging substrate on which the LED is mounted plays a critical role in controlling the junction temperature. In this study, a thin film amorphous silicon (a-Si) dielectric coating on an aluminum (a-Si/Al) substrate followed by a 300 nm thick copper trace pattern for LED attachment using magnetron sputtering Physical Vapor Deposition (PVD) process has been carried out. Three other Packaging material substrates of FR4, Metal Core PCB (MCPCB), and Silicon using undoped Silicon wafer were fabricated, and a Nano-ceramic on Aluminum substrate was also procured for comparative Transient Thermal analysis study using Luxeon-Rebel Cool White LED. The Thermal resistance from the LED junction to the bottom of the a-Si/Al packaging substrate attached to the liquid temperature-controlled heat sink measured at 700 mA driving current, as per industry standard JEDEC 51–14 method, was 8.77 °C/W. Compared to this Thermal resistance value of a-Si/Al substrate, the thermal resistance of Silicon substrate, Nanoceramic on Aluminum, MCPCB, and FR4-based packaging substrates were 3.19%, 55.53%, 180.73%, and 405% higher with the corresponding Thermal resistance values of 9.05 °C/W, 13.64 °C/W, 24.62 °C/W and 44.34 °C/W respectively. Light Lumen output measurements for the substrates with the lowest and the highest thermal resistance, namely the (a-Si/Al) and FR4 substrates were also measured and the light output efficacy of the (a-Si/Al) substrate was 9.46% higher than the FR4 substrate. Also, the light output drop of the (a-Si/Al) substrate was only 1.66% compared against 10.66% for the FR4 substrate after 30 min of testing under no heatsink attachment conditions. Thus, the a-Si thin film-coated Aluminum as the LED packaging substrate can help lower the junction temperature with low thermal resistance and improve the color quality, efficacy, lumen depreciation, and reliability.
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References
Titkov E et al (2014) Temperature-dependent internal quantum efficiency of blue high-brightness light-emitting diodes. IEEE J Quantum Electron 50(11):911–920
Ryu GH, Ryu HY (2015) Analysis of the temperature dependence of phosphor conversion efficiency in white light-emitting diodes. J Opt Soc Korea 19(3):311–316. https://doi.org/10.3807/JOSK.2015.19.3.311
Park JH, Lee JW, Kim DY, Cho J, Schubert EF, Kim J, Lee J et al (2016) Variation of the external quantum efficiency with temperature and current density in red, blue, and deep ultraviolet light-emitting diodes. J Appl Phys 119:023101
Wilcoxon R (2017) Does a 10°C Increase in Temperature Really Reduce the Life of Electronics by Half? https://www.electronics-cooling.com/2017/08/10c-increase-temperature-really-reduce-life-electronics-half/. Accessed 18 Aug 2017
Dai Q, Schubert MF, Kim MH, Kim JK, Schubert EF, Koleske DD, Crawford MH, Lee SR, Fischer AJ, Thaler G et al (2009) Internal quantum efficiency and nonradiative recombination coefficient of GaInN/GaN multiple quantum wells with different dislocation densities. Appl Phys Lett 94:111109
Kumar A, Yadav RP et al (2017) Structural study of aluminum nitride thin film grown by radio frequency sputtering technique. International Conference on Computer, Communications, and Electronics (Comptelix). https://doi.org/10.1109/COMPTELIX.2017.8004027
Hahn BD, Kim Y, Ahn CW, Choi JJ et al (2016) Fabrication and characterization of aluminum nitride thick film coated on aluminum substrate for heat dissipation. Ceram Int 42(16) https://doi.org/10.1016/j.ceramint.2016.08.128
Ong ZY et al (2015) Thermal performance of high power LED on boron doped aluminum nitride thin film coated copper substrates. J Sci Res Rep 5(2):109–119. https://doi.org/10.9734/JSRR/2015/14232
Shanmugan S, Mutharasu D (2014) Thermal transient analysis of high-power green LED fixed on BN coated Al substrates as heatsink. IEEE Trans Electron Devices 61(9):3213–3216. https://doi.org/10.1109/TED.2014.2327211
Mutharasu D, Shanmugan S, Anithambigai P, Ong ZY (2013) Performance testing of 3-W LED mounted on ZnO thin film coated Al as heat sink using dual interface method. Electron Devices, IEEE Trans 60(7):2290–2295. https://doi.org/10.1109/TED.2013.2261856
Idris MS et al (2020) Performance of 9.0 W light-emitting diode on various layers of magnesium oxide thin film thermal interface material. Appl Phy A 126:646. https://doi.org/10.1007/s00339-020-03820-y
Bellanger P, Maurice C, Minj A, Roques S (2015) Understanding phenomena of thin silicon film crystallization on aluminium substrates. Energy Procedia 84:156–164
Braun JL, Baker CH et al (2016) Size effects on the thermal conductivity of amorphous silicon thin films. Phys Rev B 93:140201(R)
Acknowledgements
The first author would like to acknowledge the support from CMTI Labs Bangalore in preparing Silicon substrates.
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The authors did not receive support from any organization for the submitted work. No funding was received to assist with the preparation of this manuscript. No funding was received for conducting this study.
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Conceptualization, Material preparation, Measurements, analysis and manuscript preparation by the First Author, Natarajan V. Chidambaram; Review of Manuscript, editing, suggestions by the Second Author, Jayalakshmi R.; Thin Film Lab, Raman lab identification by the Third Author, Ramachandran C.S. ; Silicon substrate lab coordination by the Fourth Author, Ramachandra C.
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Appendices
Appendix A
1.1 Thin Film Amorphous Silicon on Aluminum Deposition Process
Started with 2-inch × 2-inch and 1-inch × 1-inch 6061-T6 Aluminum plates, as shown in Fig. 14 and following the steps described.
1.2 Polishing and Cleaning of the Aluminum plate Top side
The aluminum plate was polished, planarized, and cleaned for the a-Si PVD process.
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a)
Polished by # 320 Ultra Fine sandpapers
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b)
Polished by 1000 sandpapers
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c)
Polished by 4000 sandpapers
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d)
Polished by 1 um Polishing suspension
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e)
Polished by 0.05 um Polishing suspension
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f)
The samples were washed with soap water
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g)
The samples were carefully cleaned by IPA
1.3 Amorphous Si deposition Process
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1.
Amorphous Si was deposited by magnetron sputtering:
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a)
Sputter deposition rate is first measured from a test sample, and the deposition thickness is measured by an ellipsometer.
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b)
The deposition rate of 0.65 nm/sec was obtained
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c)
Every 250 s will cool down the targets for 4 min
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d)
Overall, 123 cycles were used for 2 um thickness Si deposition for 21 h
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a)
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2.
2 um Amorphous Silicon thickness was obtained.
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3.
Initially, the Silicon film had some peeling.
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4.
Added the Ti layer
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5.
Successful amorphous Silicon with 2 um thickness was obtained
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6.
The silicon coating electrical insulation from the Aluminum, measured by multi-meter > 2Mohm
1.4 Copper Trace Pattern Deposition for LED Attachment
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1.
Cu was deposited by magnetron sputtering:
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a)
Sputter deposition rate is first measured from a test sample, and the deposition thickness was measured by ellipsometer, and transmittance.
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b)
The deposition rate of 2 nm/sec was obtained
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c)
300 nm Cu was deposited in the trace pattern on top of a-Si/Al
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a)
Appendix B
2.1 Silicon Substrate Fabrication
Started with a 4-inch undoped Silicon wafer, as shown in Fig. 15.
The process involves 20 nm Ti deposition on the wafer, followed by 50 nm Au and Copper plating, followed by Au and Ti etching in non-patterned area to leave the copper LED trace pattern on the silicon wafer, as shown in Fig. 16.
The Full wafer is then cut into individual Silicon Substrate as shown in Fig. 17.
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Chidambaram, N.V., Jayalakshmi, R., Ramachandran, C.S. et al. A Comparative Thermal and Lumen Performance Study of Thin-film Amorphous Silicon Dielectric Coating on Aluminum as an LED Packaging Substrate. Silicon 16, 4831–4841 (2024). https://doi.org/10.1007/s12633-024-03043-3
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DOI: https://doi.org/10.1007/s12633-024-03043-3