Thermal measurements and modelling of electronic packages
Yang, Li Yu
Date of Issue1997
School of Mechanical and Aerospace Engineering
In this study, thermal characterization experiments were carried out under natural and forced cooling conditions for three kinds of TAB packages with and without die attach and heat sink. Both the electrical test method and infrared imaging techniques were used to investigate the junction temperatures and thermal resistances of the TAB packages under steady state and transient conditions. The steady state experimental results revealed that the chip power dissipation, die attach, package layout, air velocity and environmental conditions have some effects on the thermal performance of TAB packages. The junction temperature was found to increase linearly with chip power dissipation and decrease with the air velocity. The increase of air velocity will significantly reduce the junction to ambient thermal resistance and case to ambient thermal resistance, but has negligible effect on the junction to case thermal resistance. In contrast, the junction to case thermal resistance depends significantly on the chip power dissipation of the TAB packages. However, the case to ambient thermal resistance was found to be independent of the chip power dissipation. The addition of die attach and thermal vias results in a reduction of about 6°C for the junction temperature and 7°CAV for the junction to ambient thermal resistance at chip power dissipation of 0.9 W and still air conditions. By using a pin fin heat sink array attached to the bottom side of the thermal vias on the PCB, maximum reductions in the junction temperature of about 5°C and 6°C/W for the junction to ambient thermal resistance 0Ja, respectively were achieved. At an air velocity of 2 m/s, a junction to ambient thermal resistance of 55 °C/W can be achieved by the TAB package with die attach, thermal vias and heat sink. In addition, environmental condition also affects the thermal performance of the TAB packages. With the increase of ambient temperature, the junction to ambient thermal resistance decreases.
Nanyang Technological University