Abstract
A methodology of modelling thermal contact resistance in thermo-fluid analysis software is
developed to estimate power device´s temperature, the most important value in thermal
management of automobile power supply, with accuracy.
To reduce thermal contact resistance of power device, silicon rubber sheet is used for
insulation. Rubber sheet can´t fill air gap in contact surface completely, so contact pressure
has a big influence on thermal contact resistance. The thermal contact resistance was
modelled by three steps; 1) Obtain the contact pressure profile by contact simulation, 2)
Calculate thermal contact resistance from empirical formula, 3) Fill the contact surface with
250 small plate objects, and change its thermal conductance by importing thermal contact
resistance table.
Contact region was tested by impact paper. The reacted area was wider than simulation result
in some points, but it agreed on the whole. The difference seems to be caused by the
unevenness of the package surface. The developed thermal contact resistance model was
applied to the prediction of the power device temperature of DC-DC converter. Even though
there were some differences in contact area, predicted chip and cupper flange temperature
agreed well with measurement.
Keywords - thermal simulation, contact resistance, contact pressure, power devices,
power supply