The Technical Data column of the previous issue discussed the concept of thermal diffusivity. It makes sense to discuss in this issue a related topic: thermal effusivity. While thermal diffusivity, a, is defined as the ratio between the thermal conductivity, k, and the volumetric thermal capacity, ρcp, the effusivity, e, is related to their product, as follows: It is … [Read more...]
A Practical Implementation Of Silicon Microchannel Coolers
Introduction More than twenty-five years ago, Tuckerman and Pease first described the use of silicon microchannel cooling for very high power densities [1]. However, the coolers could not be fabricated easily and pressure drops were very high. As chip power densities are now increasing beyond air cooling limits, a variety of liquid cooling methods are being investigated. Due to … [Read more...]
Thermal Strain in Semiconductor Packages, Part II
Introduction This Calculation Corner continues Part I, published in the previous issue [1]. Part I described the construction of a typical flip-chip package configuration for high-power chips, consisting of a laminate assembly of materials adhesively bonded together and having different Coefficients of Thermal Expansion (CTE). The process of bonding these different materials … [Read more...]
Advanced Cooling Using Meso-Scale Evaporative Cold Plates
Introduction Thermal management of servers and communications equipment has become significantly more challenging over the past several years. As is well known, processor powers have increased to 150 W or more and are projected to continue to rise, despite the move to multi-core designs (and the huge investment in software that this entails) [1]. Rack-level functional density … [Read more...]
Electronics Cooling At Higher Pressures … a Positive Displacement Pump Solution
Introduction Many liquid cooling solutions in use today employ cooling system devices that result in system pressure drops limited to <0.5 bar (7.25 psi), which allows these systems to fit within the limits of centrifugal pumps. The evolution of alternative cooling devices has brought about pressure drop requirements >1.0 bar (14.50 psi) in some cases [1]. These higher … [Read more...]
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