Experimental and Numerical Studies of the Thermal Hinge in a Notebook Computer

Abstract

The power of semiconductor chips, especially the CPU chip used in the notebook computer, is increasing nowadays while the size of the computer box is decreasing. To cope with this ever-increasing heat load within the notebook computer, many design engineers tend to use bigger heat sinks and fans. However, these approaches add weight, acoustic noise, and power consumption to the computer, none of which is desirable. A method of transferring heat from a CPU chip to the backside of the liquid-crystal display (LCD) and letting heat dissipate into the surroundings has been explored before. This is sometimes called the thermal hinge method since heat is transferred across the hinge of a notebook computer. In this paper, the structure of a new thermal hinge and its thermal performance will be revealed. This new thermal hinge has two main parts: one is the base, which is stationary and which has a heat pipe connected to a metal plate on top of a CPU chip, and the other is the rotational part, which is mounted on the LCD cover with a heat pipe connected to a heat spreader. The base is supported by a set of springs to ensure that the base is always in good thermal contact with the rotational part of the hinge. This spring-loaded thermal hinge using an aluminum heat spreader on a plastic LCD cover was built and tested and the results were compared with a numerical model that was constructed using a commercially available CFD code. The results from the experiments and numerical modeling agree reasonably well. Because of this, the numerical model has been used to optimize the hinge structure. The effects of the size, thickness, and materials of the heat spreader as well as the materials of the LCD cover on the hinge thermal performance have been studied and will be discussed.