Thermal Simulations of a UV LED module with nanosilver sintered die attach process on graphene-coated copper substrates

Abstract

The industrial market has been growing for high-power ultraviolet (UV) LEDs in curing, water purifying, and other applications that required high light output. As a rule of thumb, LED lumen output usually drops 0.3–0.5% for each 1°C increase in temperature while operating within the typical working temperature range. Such requirements for high-power UV LED modules indicate that innovative materials and processes for module packaging are needed to reduce thermal conductivity and to ensure high reliability.In this work, UVA (wavelengths between 365–405nm) LEDs were chosen, since the increasing usage in curing equipment for drying paints, adhesives, and other curable materials. In order to reduce the thermal conductivity of UVA LED packages, a high power UV Chip on Board (COB) based LED module was simulated. Compared with traditional modules using silver-filled adhesive and metal-core printed circuit boards(MCPCB) substrate, the novel high power UV COB based module was using nano-silver material for die attach process. Such silver sintering method is emerging for high power electronics applications. Such substrate is then sintered on copper heatsink which is covered by a thin layer of graphene, for better thermal management. Such novel structure was investigated using ABAQUS software and the Heat Transfer Module. The simulation is intended to first check how much thermal conductivity reduce caused by nanosilver sinter die attach process. Secondly, the simulation will also investigate the graphene influence on the copper heatsink. Results from the simulation will show the typical structural function of a 200W LED module with reduced thermal resistance up to 7%. The module temperature with edge-to-center temperature difference will also be checked as a standard to compare the heat dissipation capacity. Besides, the simulation will provide temperatures in various parts of the LED module in steady-state conditions, as an indication for reliability.