OPTIMIZATION OF HEAT SINK DESIGN WITH FOCUS ON TRANSIENT THERMAL RESPONSE

摘要

Transient heat flow in the heat sink base is modeled assuming hemispherical expansion of isotherms, and a closed form formula for temporal thermal resistance is derived. The objective of the study is to optimize the thickness of the heat sink base on a given mass for energy efficient design. Since the state-of-art VLSI generates a variety of temporal heat in short and long time duration, it is important and effective to model the solution of thermal response as an explicit and simple formula of time function. Stepwise input of heat from the heat source that spreads to a wider area rectangular heat sink base is used for model verification. The model assumes constant airflow though the fins. Numerical analysis was conducted to validate the model for a wide range of time scale, and the results were referred to explicate the modes of temperature propagation. The analytical model based on the stepwise input is extended to general time function of heat input based on the comparison. On the basis of the analytical model, the geometry of the base is discussed for a given mass. Various ratio of footprint to thickness is studied over the wide range of time response. It was found that the optimum shape for steady-state is also effective for dynamic. In addition, a recommendation was made for a small time response.