Enhanced heat transfer by room temperature deposition of AlN film on aluminum for a light emitting diode package

Heat transfer is crucial to the fabrication of high efficiency light emitting diode (LED) packages. The effectiveness of the heat transfer depends on the package materials and design. This paper presents an application of high thermal conductivity aluminum nitride (AlN) films to replace low thermal conductivity epoxy resin or alumina substrates. The AlN film was directly deposited on an aluminum plate which enabled the removal of thermal interface materials (TIM) such as the adhesive thermal bonding sheets that are used in conventional metal printed circuit board (PCB)-based LED packaging process. A fully dense AlN ceramic film was successfully deposited at room temperature using the aerosol deposition method. The thermal resistance, a parameter of the heat transfer characteristic of an LED package, was measured using a thermal transient tester. The results showed that the thermal resistance of the LED package mounted on the AlN thick film was 28.5 K/W, while an LED package mounted on a conventional epoxy-based metal PCB and a PCB with thermal vias were 47.2 K/W and 36.5 K/W, respectively. This indicates that an aerosol-deposited AlN-based LED package exhibits greatly enhanced heat transfer compared to the conventional metal PCB.