Table 1. Dynamic Viscosity Values for Various Gases and Liquids When we look at a fluid parcel subject to a velocity gradient in the direction perpendicular to the direction of the flow, we observe that this fluid parcel deforms. This type of deformation is called shear. The ability to withstand shear is a material property called the dynamic viscosity m. The viscosity … [Read more...]
Moisture permeation in electronics
Environmental control for electronic packages and enclosures often involves understanding and managing moisture concentration. Excessive moisture combined with processing temperatures can cause damage. High humidity levels have other potentially harmful effects such as corrosion. Since the movement of heat and moisture are similar (i.e., diffusive), thermal engineers may be … [Read more...]
Thermal conductivity of common alloys in electronics packaging
Thermal conductivity of common alloys in electronics packaging Jim Wilson, Associate Technical Editor Property Thermal Conductivity (W/mK) @25°C CTE (ppm/°C) @25°C Copper 395 17.1 Aluminum 200 23.5 CuMo 160-185 7.0-9.0 CuW 180-220 6.5-8.5 Kovar 17 5.9 Alloy42 12-15 4-6 Invar + … [Read more...]
Thermal Challenges In LED Cooling
Introduction During the last ten years, developments in LED semiconductors have led to an important change in LED applications from that of luminous indicator to that of illuminator. With LEDs now advancing into several lighting fields, LEDs have become one of the standard methods of producing light, joining more traditional sources such as incandescent, fluorescent and … [Read more...]
Packaging Challenges For High Heat Flux Devices
Introduction It comes as no surprise to anyone in our industry that device power levels are increasing to support customer expectations of ever greater functionality and performance. The greatest thermal challenges in computing occur in the packaging of processors. This results not only from the fact that processors typically have the largest overall power dissipation in a … [Read more...]
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