ABSTRACT
Manufacturers of microelectronic devices often specify supply voltage limits and threshold values for power dissipation, junction temperature, frequency, and output current. This chapter presents an overview of the practice of derating and then provides a science-based method for establishing effective design and operating profiles for microelectronic devices. The reliability of electronic systems is believed to be very sensitive to component derating and exactly how the derating is applied. Guidelines for derating of devices have emphasized lowering the steady state operating temperature. Localized temperature gradients can exist in the chip metallization, chip, substrate, and package case, due to variations in the conductivities of material produced by defects in the form of voids or cracks. The locations of maximum temperature gradients in chip metallization are sites for mass transfer mechanisms, including electromigration. Thermal-stress derating guidelines rule out the option of reliable system designs at higher temperatures.
