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.
Parametric thermal modeling of heat transfer in handheld electronic devices
The dimensions and power dissipation information of various commercial handheld electronics were collected to find benchmarking size and power ranges. The relationship between device size parameter, defined as total volume divided by external surface area, and the power dissipation was determined. Three dimensional finite element models were used to model the conduction, natural convection, and surface-to-surface radiation phenomena inside of the devices. Simulations were performed of four designs of handheld mockups with three boundary conditions on the enclosure modeling the device operating in free air, handheld, and in a clothing pocket. Various combinations of external case and circuit board conductivity were modeled. The ratio between the thermal resistance internal to the device and the resistance from the case surface to the ambient were also determined.