thermal impedance, junction-to-reference point (Z_θJX)

The transient thermal impedance from the junction to a reference point. For a specified power pulse duration, Z_θJX is given by

Z_θJX = (T_Jf - T_Ji - ΔT_X) / P_H

where

T_Jf is the junction temperature at the end of the power pulse;

T_Ji is the junction temperature before the start of the power pulse;

ΔT_X is the change in reference point temperature during the heating pulse. For short heating pulses, e.g., during die attach evaluation, this term is normally negligible;

P_H is the magnitude of the heating power pulse applied to the device under test, i.e., the product of I_H and V_H.

References