Progress and Perspective of Near-Ultraviolet and Deep-Ultraviolet Light-Emitting Diode Packaging Technologies

Abstract

Ultraviolet light-emitting diodes (UV-LEDs) have drawn considerable attention in environment, life science, and industry fields, such as the applications of near UV-LEDs in resin curing, illumination, and identification, and deep UV-LEDs in disinfection, medical treatment, and biochemical inspection. However, due to the limitation of packaging technology, UV-LED devices exhibit low light efficiency and poor reliability compared with visible LEDs. The organic encapsulation materials are prone to UV aging, thermal degradation, and nonairtightness, which significantly reduce the performances of UV-LEDs. In order to solve this issue, UV-LED packaging technology has been proposed for UV-LED devices instead of conventional LED packaging. In this review, we investigated in detail the overview and challenges of near-ultraviolet light-emitting diodes (NUV-LED)/deep-ultraviolet light-emitting diodes (DUV-LED) packaging. For the packaging of UV-LEDs, all inorganic encapsulation materials, hermetic packaging structures with low-temperature bonding, reduced reflection losses, UV stable and transparent materials, and effective thermal management are key progresses to enhance the light efficiency and reliability of UV-LEDs. In addition, the summary and perspectives of NUV-LED/DUV-LED packaging were introduced and discussed.

Epoxy Molding Compound Lead Frames With Silicone Resin for Encapsulating AlGaN-Based UVB Light-Emitting Diodes

“…Therefore, to improve the reliability of UVB-LEDs, the mainstream design for packaging has involved flipping the LED chip bonded onto the AlN-based LFs and using an attached quartz glass as a hermetic cover. This kind of packaging structure for DUV-LEDs comes, however, with higher materials costs, severely decreased light extraction, and limited optical performance [17][18][19][20]. Some DUV-transparent encapsulation materials have been proposed to ameliorate these drawbacks such as sol−gel methyl siloxane hybrid material, fluorine resins, and liquid packaging structure.…”

Recent Advances in Packaging Technologies of AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes

“…These two technologies can both bond the deep UV LED chip on the sapphire lenses directly at room temperature, which improves the LEE significantly by reducing the interfaces. The [104,105] experimental results show that, under 350 mA forward current, the output power of the 255 and 280 nm LED increased by 2.8-and 2.3-fold, reaching 73.6 and 153 mW, respectively.…”

“…However, aluminum shows a very high reflectivity (>90%) in deep UV region which is suitable for making the deep UV sub-mounts. [105,[113][114][115] Kuo et al of National Chiao Tung University proposed an aluminum-based sidewall reflector to enhance the LEE of AlGaN-based deep UV LED, as a result the output power increases by 18.38%. [116] The hollow packaging structure is also called inorganic packaging structure due to avoiding the high energy UV light emitting to the organic adhesive directly.…”

“…[153] As we all know that one of another main concerns for LEDs is their junction temperature and thermal stability. As depicted in studies, [105,154,155] the thermal effect is a key issue which affects the performance of the LED devices. However, AlGaN-based deep UV μLED as a novel technology, relative researches on it are very limited.…”

“…The low LEE of the AlGaN‐based deep UV LED devices in packaging level is mainly due to Fresnel reflection loss, total internal reflection (TIR) loss, and UV‐absorbing by packaging materials. [ 17,34,104,105 ] Figure shows the typical light propagation of packaged AlGaN‐based deep UV LED device. The packaged device typically consisted of a ceramic sub‐mount, an AlGaN‐based deep UV LED chip, and a quartz glass.…”