Thermal test dies are among the major tools used in package thermal design qualification. They are usually simple chips, containing heaters and temperature sensors. The sensors measure the temperature on the chip surface as a result of the steady state powering or the time dependence of the temperature increase or decrease in case of transient qualification. From these data, … [Read more...]
The thermal conductivity of fluids
About 10-15 years ago, fluids, either directly (mainly Fluorocarbons), or indirectly (cold plates flushed with water) cooled the majority of mainframe computers. Nowadays, the expected increase in heat flux density causes a renewed interest in either passive or active liquid cooling, because the limits of air cooling come within reach. Other practical applications in which … [Read more...]
Determining the junction temperature in a semiconductor package, part III the use of the junction-to-board thermal characterization parameter
In recent issues, this column has dealt with the use of a number of thermal metrics to calculate the junction temperature of integrated circuits under various conditions. These metrics explored were JA, JC, and JT. To summarize the uses of these metrics: JA represents the junction-to-air thermal resistance for a package tested in an industry-standard test environment. It is … [Read more...]
How Thermal Conductivity Relates to Electrical Conductivity
Because the accurate determination of thermal conductivity is a demanding task (often not recognized by either designers or vendors), methods, based on the measurement of another physical property that is uniquely coupled to thermal conductivity, are very challenging. One such method is based on the so-called Wiedemann-Franz Law, which links the thermal conductivity to the … [Read more...]
Low Noise Axial Fan Applications
There are three basics to creating low-noise axial fan applications: airflow path design initial fan design analysis and correction of specific acoustical responses in the physical model Each is important and contributes to the overall sound levels of the program. Figure 1. Representative flow-versus-pressure characteristic of system air path.A flow-versus-pressure … [Read more...]
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