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.
Package thermal challenges due to changing mobile system form factors
Mobile platforms have driven semiconductor package form factors from several times the die area to sizes approaching die size. To make matters even more challenging, the package thickness, traditionally on the order of 1–3 mm, has been reduced to thicknesses less than 0.40 mm. In mobile applications, it is size that drives package design. There has been a price paid for the package shrinkage in terms of its thermal performance. Copper, previously used for power and ground planes, and multiple layers of traces, has been replaced with extremely fine traces built in fewer layers. The body size previously used to promote the spreading of heat from the die is now left with two options for heat flow: either out the top (immediately above the die) or through the bottom (below the die) of the package. Improvements to the chip architecture in terms of power efficiency is one of the few remaining options for thermal enhancement at the package-level. Further thermal enhancement should focus on the system level, as this is where the greatest opportunities exist. While many papers have focused on the thermal challenges associated with the system-level, few have translated these constraints to challenges at the package level. This study investigates the historical evolution of mobile platforms and their impact on packaging thermal challenges. Metrics for evaluating the optimization of packages for the mobile space will also be discussed.
Japanese women marriage migrants today : negotiating gender, identity and community in search of a new lifestyle in Western Sydney
...................................................................................................................... vi CHAPTER 1. LIFESTYLE MIGRANT, CONSEQUENT SETTLER AND MARRIAGE MIGRANT ............................................................................................. 7 1.