Introduction After selecting or designing a heat sink based upon a given air velocity orvolumetric flow rate through the fins, the thermal designer needs to determinethe total amount of flow which must be delivered in the duct or card passagecontaining the module w with heat sink. As shown in Figure 1, some of the flowwill go around or bypass the heat sink. In fact, depending … [Read more...]
Calculating interface resistance
Figure 1. Ceramic Package - Aluminum Heat SinkAssembly Introduction The exposed surface area of many of today's high powered electronic packagesis no longer sufficient for the removal of the heat generated during normaloperation. Heat sinks are a commonly-used, low cost means of increasing theeffective surface area for dissipating heat by means of convective air cooling.While … [Read more...]
Forced convection cooling of airborne electronics
Figure 1. AFT description Fin pitch = 25.01 per in = 985 per mPlate spacing, b = 0.200 in = 5.08 x 10-3 m Fin Length = 0.111 in = 2.8 x 10-3 m Flow passage hydraulic diameter 4rh = 0.004905 ft = 1.50 x 10-3 m Fin metal thickness = 0.004 in = 0.102 x 10-3 m Total heat transfer area/volume between plates, ß = 719.4 ft2 / ft3 = 2,360 m2 / m3 Fin area / total area = … [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...]
Electrical temperature measurement using semiconductors
Introduction Semiconductor junctions offer many useful properties including inherentcharacteristics which are well suited to temperature measurement. Within theelectronics cooling arena, these properties form the basis for "theelectrical method of junction temperature measurement" and are used formeasurement of junction temperatures within operating semiconductor devices. They … [Read more...]
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