Dielectric Printed Circuit Board Planar Thermosyphon

It is well established that prolonged operation at high junction temperatures reduces the lifetime of LEDs, significantly undermining one of the main benefits of LED lighting systems. Despite advances in LED device technology, a significant fraction of the electrical energy input is wasted as heat. Inadequate removal of this heat results in poor optical performance and sort lifespan of LED lighting systems. The proposed Passive Heat Spreader significantly enhances lateral heat spreading and also decreases the overall thermal resistance versus current printed circuit board thermal management solutions. An added benefit of the design is that it also promotes a lower cost and less complex chip package by eliminating the need for an electrically isolated thermal pad. In Phase I, a prototype Passive Heat Spreader has been modeled, fabricated and tested. Overall, the results show that an 85% reduction in thermal resistance can be obtained with a high purity water based passive heat spreader when compared to state of the art metal core printed circuit boards. Reliability testing also showed positive results. In Phase II, efforts will be focus on developing the passive heat spreader thermal solution for a targeted application. A number of issues will be addressed to bring the Technology Readiness Level to level 7, including life and reliability issues, performance related issues, cost issues and optical performance issues. Most importantly, the effort includes optical and thermal testing of the passive heat spreader in an LED system. Commercial Applications and Other Benefits: Artificial lighting represents a large percentage of energy consumption across various sectors: residential, commercial, and industrial. In recent years the solid state lighting industry has become an economically viable alternative to incandescent and fluorescent lighting. Of the three, it offers the potential for longest lifetimes and highest efficacy without the inclusion of hazardous materials like mercury. These factors support the DOE decision to develop a multi-year road map, whose goal is to ensure and accelerate the development and deployment of LED lighting products. Thermal management has been identified as a critical obstacle along this road map, which the proposed dielectric planar thermosyphon seeks to address; and it will enable the development of the solid state lighting industry.