Silicon/water vapor chamber as heat spreaders for microelectronic packages

A numerical study is performed to characterize the thermal and mechanical performances of silicon/water vapor chambers as heat spreaders for electronics cooling applications and to compare their performance against Cu heat spreaders. 2D flow and energy equations are solved in the vapor and liquid regions, along with conduction in the wall. An equilibrium model for heat transfer and a Brinkman-Forchheimer extended Darcy model for fluid flow are solved in the wick region. In addition to thermal modeling, FEA is also performed to study the impact of the proposed design on die stresses. The study shows that this system can match or thermally perform better than a more standard Cu spreader while also reducing the compressive stress in the Si by as much as 96%. Analysis shows that there are two main factors contributing towards the reduction of stress in the Si die, namely, the better CTE match between the Si die and the Si heat spreader and higher compliance (less stiffness) of the vapor chamber compared to standard heat spreaders. Thus Si vapor chambers provide a good design alternative to a standard Cu heat spreader without compromising on the reliability and performance of the Si.