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To maintain the best possible thermal environment in electronic packages, the engineer must establish the most efficient path for heat transfer from the electronic devices to an external cooling agent. The path is typically subdivided into internal and external components, representing, respectively, heat transfer by conduction through different materials and interfaces separating the devices from the package surface and heat transfer by convection from the surface to the coolant. Depending on the scale and speed of the electronic circuits, as well as on constraints imposed by nonthermal considerations, the coolant may be a gas or a liquid and heat transfer may be by natural, forced, or mixed convection or, in the case of a liquid, by pool or forced convection boiling. In this paper a comprehensive review of convection cooling options is provided.

Laser-assisted machining (LAM) of silicon nitride Si3N4 is evaluated for its potential to become an economically viable process in fabricating precision ceramic parts. On-line measurements of cutting force and workpiece temperature are performed, and tool wear and surface integrity are examined. Tool wear characteristics are determined as a function of workpiece temperature, which is measured on-line using a laser pyrometer. Tool wear/failure mechanisms are characterized using optical microscopy, while application of scanning electron microscopy to heated and machined surfaces, as well as to chips, is used to infer material removal mechanisms and the extent of damage caused by LAM. The sub-surface damage of parts produced by LAM is compared with that of typical ground parts.