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
Introduction 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 … [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...]
- « Previous Page
- 1
- …
- 65
- 66
- 67
- 68
- 69
- …
- 86
- Next Page »
