Thermal enhancement of optical-thermal-electrical isolation package structure for UVA LEDs

Abstract

As one of the most important heat transfer channels for ultraviolet radiation-A light-emitting diodes (UVA LEDs), the substrate often simultaneously undertakes the tasks of electrical connection and UV reflection as well, which makes the optical, thermal and electrical performance mutually constrained, resulting in poor heat dissipation and light output efficiency. In order to suppress the constraint relationship between these factors, the printed-circuit-board copper heat sink composite substrate (PCCS) was assembled by adhesion and pressure implantation, and UVA LEDs with optical-thermal-electrical isolation packaging structure were prepared. The light, electricity, and heat in this structure flow in their respective pathways, greatly reducing the mutual influence. Compared with commercial Al2O3 -Ceramic devices, under the driving current of 1000 mA and testing conditions of 25 ℃, the junction temperature of PCCS devices decreased by 13.3 ℃, and the thermal resistance decreased by 5 K/W with a higher stable-transient ratio. At 25 ℃, the lifespan of PCCS devices is 20 % longer than that of Al2O3-Ceramic devices. The above results indicate that the optical-thermal-electrical isolation packaging structure effectively solves the problem of reduced light output efficiency caused by heat accumulation through reasonable separation of the pathways, resulting in significant application potential in improving the luminous efficiency and reliability of UVA LED devices.