As complexity increases and dies and packages become even larger, temperature gradients also increase, leading to problems with thermal mismatch. Hence, thermomechanical analysis grows in importance. Apart from the temperature differences, the most important parameter describing thermally induced stress is the coefficient of thermal expansion (CTE, or °), expressed in units of … [Read more...]
A practical formula for air-cooled boards in ventilated enclosures
Fig. 1 - Ventilated cabinet Introduction Natural air convection is commonly applied as a cooling technique for electronic equipment of moderate power density such as telecommunication boxes. The main advantage of natural convection isits intrinsic reliability, because air movement is generated simply bydensity gradients, if an external body force field exists. However, due … [Read more...]
Thermal resistance: an oxymoron?
Introduction Dark light, deafening silence, cruel kindness, living dead, fuzzy logic,honest politics. The adjectives seem to contradict the substantives; such afigure of speech is called an oxymoron. It will be argued within this articlethat 'thermal resistance' is also a serious candidate for this category, atleast if the concept is being applied without realizing the … [Read more...]
Thermal Conductivity
For most calculations regarding the thermal analysis of electronic systems, thermal conductivities of solid materials are required. It is felt that many designers would welcome a comprehensive list showing these values for certain classes of objects, such as PCB materials, leadframes, molding compounds, alloys etc.. This issue starts with 45 leadframe materials, the data for … [Read more...]
Packaging: designing for thermal performance
Figure 1. Various leadframe and BGA packages Introduction The well-established trend within the electronics industry to provide everincreasing computing power at less cost seems to defy the laws of economics.However, this industry has not been able to suspend the laws of physics. Eachcalculation by each of the millions of transistors in the modern personalcomputer is … [Read more...]
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