Screen and stencil printed graphene heat spreaders on printed circuit boards for lowering of light emitting diode temperatures

Abstract

Continuously higher integration levels in (opto-)electronics require new solutions and materials for thermal management of excess heat. Here we investigate the integration of graphene-based heat spreader films with printed circuit board (PCB) assembled, high-power light emitting diodes (LEDs), as used in modern automotive lighting, using industrially highly scalable screen printing and stencil printing of the graphene-based films. We compare screen/stencil printing of graphene heat spreaders on the PCBs from archetypical water- and ester-based inks and characterize the resulting graphene heat spreaders with respect to printing fidelity and resolution, film microstructure, electrical and thermal properties and their performance in lowering LED temperatures during LED operation. Importantly, we use only comparatively low graphene film curing temperatures (150 °C) that are compatible with industrial PCB/surface-mounted-device (SMD) LED integration processes. We find that screen-printed, ester-based graphene heat spreaders result in a modest reduction of LED temperature during operation of on average − 2 K with a maximum reduction of −4 K. Generally, our work establishes the feasibility of scalable screen and stencil printing for integration of graphene films with state-of-the-art PCB/SMD assemblies.