KCS

We introduce a low-melting-point Sn-P-F-O component type of glass for use as a light-emitting diode (LED) encapsulant which allows processing at a low sintering temperature and in less time (less than 300 °C; one minute) with a typical sintering process. To confirm that the obtained glass materials are chemically bonded, FT-IR, XPS, and EDX analyses demonstrate good interlinkages among the Sn-P-F-O composition. Moreover, physical surveys of the glass encapsulant are evaluated in comparison with Si resin through physical analyses specifically involving the thermal conductivity, actual operating temperature in a chip-on-board (COB) LED, and optical transmittance when exposed to long-term heat radiation. We also fabricate on-chip COB-type pc-WLEDs using green (BaSr)₂SiO₄:Eu²⁺ and red (SrCa)AlSiN₃:Eu²⁺ dual-phase phosphors with low-sintering-temperature Sn-P-F-O glass frit. The optical properties of these fabricated single-package WLEDs showed feasible luminous efficacy rates (71.7 – 85.4 lm/W) with external quantum efficiency levels of 26.9 – 32.4%, excellent color rendering indexes (CRIs) (94 – 97), and high special CRIs for strong red (R₉, 87 – 99) in a correlated color temperature range of 2700 to 10000 K. In addition, we confirmed the good thermal stability of these glass encapsulant on-chip type COB pc-WLEDs compared to that of the Si encapsulant on-chip type by taking current dependence (up to an applied current of 300 mA) and long-term operating measurements (~200 hrs).