title: White thin-film flip-chip LEDs with uniform color temperature using laser lift-off and conformal phosphor coating technologies.
abstract: We fabricated a phosphor-conversion white light emitting diode (PC-WLED) using a thin-film flip-chip GaN LED with a roughened u-GaN surface (TFFC-SR-LED) that emits blue light at 450 nm wavelength with a conformal phosphor coating that converts the blue light into yellow light. It was found that the TFFC-SR-LED with the thin-film substrate removal process and surface roughening exhibits a power enhancement of 16.1% when compared with the TFFC-LED without a sapphire substrate. When a TFFC-SR-LED with phosphors on a Cu-metal packaging-base (TFFC-SR-Cu-WLED) was operated at a forward-bias current of 350 mA, luminous flux and luminous efficacy were increased by 17.8 and 11.9%, compared to a TFFC-SR-LED on a Cup-shaped packaging-base (TFFC-SR-Cup-WLED). The angular correlated color temperature (CCT) deviation of a TFFC-SR-Cu-WLED reaches 77 K in the range of -70° to + 70° when the average CCT of white LEDs is around 4300 K. Consequently, the TFFC-SR-LED in a conformal coating phosphor structure on a Cu packaging-base could not only increase the luminous flux output, but also improve the angular-dependent CCT uniformity, thereby reducing the yellow ring effect.
authors.forename: Huan-Ting
authors.initials: HT
authors.lastname: Lin
authors.forename: Ching-Ho
authors.initials: CH
authors.lastname: Tien
authors.forename: Chen-Peng
authors.initials: CP
authors.lastname: Hsu
authors.forename: Ray-Hua
authors.initials: RH
authors.lastname: Horng
mesh_terms: D003116:Color; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005708:Gallium / Q000737:chemistry*; D007834:Lasers; D008029:Lighting / Q000295:instrumentation*; D008567:Membranes, Artificial; D012666:Semiconductors; D013696:Temperature
chemical_list: D008567:Membranes, Artificial; C473348:gallium nitride; D005708:Gallium