From Package to System Thermal Characterization and Design of High Power 2.5-D IC

The 2.5-D semiconductor package is the most popular package structure for high end applications. In this study, for thermal enhancement of a 2.5-D package, several thermal solutions such as lid attachment, fin heat sink, and fan-cooled heat sink with or without embedded heat pipe are considered in thermal simulation and measurement analysis of a 2.5-D thermal test vehicle with multi chips on interposer. All the designs rely on 6L printed circuit board to maximize power dissipation. The heat sink is mounted on top of the package to minimize thermal resistance. Anodized aluminum extrusion fin heat sink is used for low power condition (12 W) while fan-cooled heat sink is used for input power above 60 W to reduce heat accumulation. An interesting observation is that there is no significant difference of thermal enhancement in high power (168 W) thermal measurement between heat sink with or without the heat pipe. However, thermal simulation results indicate that this case has a noticeable thermal enhancement, as a decrease of about 8 °C was observed in the junction temperature. Thus, the heat sink performance has been verified by Q_max measurement. In addition, the thermal interface material coverage issues were considered while examining high power thermal performance by simulating two different reducing volume conditions, namely, void dispersion and volume shrinkage. The results indicate that the shrinkage is a major factor to be considered for all the simulation conditions.