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...]
Thermal Strain In Semiconductor Packages, Part I
Introduction Silicon became the semiconductor of choice for ICs because of its electrical properties, not because of its mechanical properties. In the earliest days of ICs when chips were small and power levels were low, the mechanical properties of silicon were of little consequence. However, for some time, the opposite situation has been the norm. Now, there are much larger … [Read more...]
About viscosity
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...]
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