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...]
Reliability Testing Of Thermal Greases
Introduction Thermal Interface Materials (TIMs) play a key role in the thermal management of electronic systems by providing a path of low thermal resistance between the heat generating devices and the heat spreader/sink. Typical TIM solutions include adhesives, greases, gels, phase change materials, pads, and solder alloys. Most TIMs consist of a polymer matrix, such as an … [Read more...]
Thermal Effusivity
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...]
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...]
Thermal Diffusivity
Thermal diffusivity is a measure of the transient thermal response of a material to a change in temperature and the term thermal diffusivity (α) is defined asα= k/(ρ x cp) where αis the thermal diffusivity (m2/sec) k is the thermal conductivity (W/m-K) ρ is the density (kg/m3) cp is the heat capacity (J/kg-K) It should be noted that each of these quantities can … [Read more...]
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