Influence of temperature control limits on passively cooled computing system performance
Passively-cooled electronic systems such as tablet computers and cell phones commonly are thermally limited by the allowable touch temperature of their surfaces. These systems typically cannot cool maximum processor power in steady state and simultaneously meet surface temperature restrictions. The primary surface temperature control method for thin mobile devices is to limit power, typically resulting in lower computing performance. Improved thermal designs allow higher power dissipation and therefore increased computing performance. Thermal and mechanical design engineers typically operate in terms of temperature for a given power, and this is not usually translated to computing performance. It can be difficult to justify a better thermal design if it is not quantified in its utility to the user. This paper quantifies the tradeoffs between thermal solution performance/temperature control limits and computing performance for two tablet computers and one cell phone that all use the same type of SoC processor.
Thermal Performance Comparison of Advanced 3D Packaging Concepts for Logic and Memory Integration in Mobile Cooling Conditions
In this paper, we present the assessment of the thermal performance of four different 3D packaging concepts for the integration of logic and memory in a generic 5” mobile device: package-on-package (PoP), 3D stacked die in BGA package, Si interposer in BGA package and a reconstructed wafer level chip scale package (RWL-CSP) interposer. The thermal performance is compared using an experimentally validated conduction model. The simulation study for the evaluation of different system level cooling solutions for all four packages show that spreading the heat close to the heat source (in the package) is more efficient than the system level spreading.
Thermal management challenges in the passive cooling of handheld devices
This study explores the limits of cooling for handheld devices based on both testing and simulation under various conditions and provides guidelines for maximizing the amount of power that can be dissipated in these small form-factor devices. The factors affecting the maximum possible power dissipation are the available surface area and surface finishes, selection of the outer shell materials, thermal interface materials, heat spreaders and air gaps. In most cases, the limiting factor in the thermal design of these devices is not the temperatures of the internal components but the temperature of the external surfaces since these are in direct contact with the skin of the user. There have been studies that address the maximum allowable comfortable touch temperature of a handheld device. This study presents methods for maximizing the internal power dissipation of these devices while limiting the touch temperatures to the maximum comfortable limits.