Printed Silver Micro-pillars Embedded in a Phase Change Material Matrix for Thermal Management Applications

This work demonstrates printed silver micro-pillars embedded in a phase change material (PCM) matrix as an alternative to traditional thermal management approaches in applications where a high degree of heat dissipation is needed for short periods of time. The silver micro-pillars are needed to provide an increased thermal conductivity compared to that of the PCM alone. For a demonstration device, an ultra violet light emitting diode (UVLED) was chosen and operated at high power. The UVLED was mounted on a PCB with its thermal pad coinciding with a thru-hole in the PCB that provides access for aerosol-jet printing of silver micro-pillars directly on the thermal pad. The thru-hole that encloses the micro-pillars was then filled with a PCM (paraffin wax) with a high latent heat of fusion (173.6 J/g) and with a melting temperature of ~56 °C. The opening of the thru-hole at the back of the PCB was sealed with a thin Cu foil glued to the back Cu cladding using a flexible adhesive. Two cases of PCM-based thermal management for the UVLED were compared: 1) using the PCM only and 2) the PCM with printed micro-pillars. The UVLEDs were operated in pulsed mode using the maximum current specified by the manufacturer to generate the greatest amount of heat. The emitted light intensity, power dissipation and temperature of the UVLED were monitored while the maximum current was applied. It was demonstrated that the printed micro-pillars with a PCM provided the best thermal management for the UVLED compared to the PCM only.