Heat Generation and Dissipation
The adverse impact of temperature on device/material reliability has been emphasized often in this book. The degradation rate for most devices/materials tends to accelerate exponentially with increasing temperature. Therefore, for reliability reasons, lower temperature device operation is usually preferred. However, many devices (both electrical and mechanical) can generate significant amounts of heat as they are being operated. Once device operation begins, the rate of increase in temperature of the device/material will depend upon on the heat generation within the device, the heat capacity of the materials, and the heat dissipation from the device to the heat sink (which is often the ambient). Elevated device temperature during operation (versus the ambient temperature) creates a thermal gradient which serves to drive heat flow from the device. In thermal equilibrium the heat dissipation from the device will just match the heat generation within the device. Managing device heat dissipation may require a significant engineering effort—but the improvements in reliability can be worth the effort.
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