Thermal Design Studies of a High-Current Transistor Package

Low-cost high-current transistor packages with continuous current capacities up to 200 A are being introduced by semiconductor component manufacturers to serve the motor control market and potential markets in electric vehicle and power conditioning. Adequate thermal performance under steady-state and transient surge power dissipation is a key to the success of this product. Extensive experimental (parametric electrical, IR thermal imaging, and IR radiometric measurements), caiculational and computer modeling studies have been performed in the development of packages with excellent thermal performance. Studies of steady-state heat dissipation up to 500 W revealed a value of 0.28°C/W for
\theta
jA. This is quite adequate for the recently introduced packages with current capacities in the range of 50-200 A. Performance under a nonrepetitive power surge (100 kW amplitude, 5 µs width) has been addressed extensively. It is estimated that the peak temperature could reach 320°C for a 100-A package dissipating about 200 W of heat in an ambient of 20°C. The product is rated to meet up to 100 such nonrepetitive overstressing surges during its lifetime.