Thermal Transients in Electronic Packages

The use of a transient analysis to accurately characterize the operating temperature of electronic modules should result in lower temperature estimates. This will reflect increases in both the reliability estimates and the performance specifications. An accurate cooling analysis would also enhance the projected product life or reduce the system cooling requirements. Simplified expressions have been obtained for the calculation of chip and module thermal transients which, when superimposed, characterize the total package time/temperature response. Empirical data demonstrate the validity of the assumptions used to obtain these expressions. The thermal time constants are also presented in graphical form using parameters easily obtainable by the design engineer (e.g., cooling air velocity, steadystate temperature differences, and module location) so that order of magnitude assessments can be made.