The three basic modes of how heat generated at the chip surface dissipates to the ambient environment are conduction, convection, and radiation, and are described below:
Conduction: Heat transfer occurs due to direct contact of matter. The fundamental relationship that governs the conduction mode of heat transfer is described in Equation 1. The dx distance is shown in Figure 1.
Rearranging Equation 1 above provides a relationship between thermal resistance and the factors affecting it (see Equation 2).
Convection: Heat transfer between a solid and nearby fluid in motion. The basic relationship for heat transfer by convection has the same form as that for conduction as described in Equation 3 (Newton's law of cooling).
Rearranging Equation 3 using a similar approach to that of heat transfer by conduction describes the relationship between thermal resistance and the factors affecting it (Equation 4).
Radiation: Heat transfer through vacuum. The presence of a medium is not required and heat transfer can happen through empty space.
Refer to application note AN-842 for more details. For other question note addressed by the Knowledge Base, please submit a technical support request.


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AN-842 Thermal Considerations in Package Design and Selection Application Note PDF 495 KB